JP2004319335A

JP2004319335A - Method and device for manufacturing spark plug

Info

Publication number: JP2004319335A
Application number: JP2003113100A
Authority: JP
Inventors: Kenji Shimizu; 賢二志水
Original assignee: NGK Spark Plug Co Ltd
Current assignee: Niterra Co Ltd
Priority date: 2003-04-17
Filing date: 2003-04-17
Publication date: 2004-11-11
Anticipated expiration: 2023-04-17
Also published as: DE102004018272A1; FR2854000B1; FR2854000A1; JP4133537B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for manufacturing a spark plug capable of suppressing the dispersion in electric resistance value between spark plugs as much as possible. <P>SOLUTION: The top-side portion of each plug base structure 150 is concentrically fitted into and held by each retaining hole part 161 of a retaining plate 160 through each cylindrical receiving member 170. A receiving member 170 closer to the end part of the retaining plate 160 of the receiving members 170 has a heat capacity larger than a receiving member 170 closer to the center of the retaining member 160. According to this, at the time of heating in a heating chamber, the heat of the end part of the retaining plate 160 is absorbed by the end-side receiving member 170, and this heat amount absorbed is larger than that of the center-side receiving member 170. Therefore, the softening state of glass powder in the end-side plug base structure 150 is approximated to the softening state of glass powder in the center-side plug base structure 150. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、スパークプラグの製造方法及び製造装置に関するものである。
【０００２】
【従来の技術】
従来、スパークプラグの一例としては、いわゆる抵抗体入りスパークプラグが挙げられる。この抵抗体入りスパークプラグは、プラグ本体と、接地電極を有する固定用筒状金具とを備えている。当該抵抗体入りスパークプラグの製造方法としては、下記特許文献１に開示されたものがある。
【０００３】
この製造方法によれば、まず、筒状の絶縁部材と、この絶縁部材の先端側部位内に同軸的に嵌装した柱状の中心電極と、絶縁部材の基端側部位内に同軸的に挿入した端子金具と、絶縁部材内に端子金具と中心電極との間に積層状に設けた導電性ガラス粉末及び電気抵抗材料粉末（ガラス粉末を含む）からなる導電性ガラス粉末混合物とを備えた端子金具の押圧による圧入前の状態にあるプラグ本体（以下、プラグ基礎構造体という）を組み立てる。
【０００４】
しかして、このように組み立てたプラグ基礎構造体を加熱炉内に搬入して加熱した後当該加熱炉から搬出し、端子金具を絶縁部材の基端側部位内に押圧により圧入する。これにより、上述した導電性ガラス粉末混合物が端子金具と中心電極との間で加圧により圧縮され、両ガラスシール層の間に電気抵抗体を介在させてなる焼結導電体として焼結形成され、プラグ基礎構造体がプラグ本体として完成される。
【０００５】
ここで、当該製造方法において、プラグ基礎構造体の加熱炉内への搬入加熱及び端子金具の圧入は次のようにして行われる。上述したプラグ基礎構造体を複数準備し、これら各プラグ基礎構造体を保持板に保持する。この保持は、当該プラグ基礎構造体の各々を、その先端側部位にて、保持板の各保持孔部に軸方向に嵌装することで行われる。
【０００６】
このように保持した保持板を、当該各プラグ基礎構造体を上方へ延出させるように水平状に支持して加熱炉内に搬入して加熱する。然る後、保持板を、上述のようにプラグ基礎構造体の各々を保持したまま、加熱炉から搬出して、プレス装置により、当該各プラグ基礎構造体の端子金具を対応の絶縁部材の基端側部位内に押圧により圧入する。
【０００７】
【特許文献１】
特開平１１−２５１０３３号公報
【０００８】
【発明が解決しようとする課題】
ところで、上記製造方法において、上述のように焼結形成された焼結導電体の電気抵抗値は、上述した導電性ガラス粉末混合物の材料成分と当該材料成分の焼結形成密度によって特定される。また、一般に、抵抗体入りスパークプラグの電気抵抗値は、加熱炉内でのプラグ基礎構造体の加熱状況やこの加熱後端子金具圧入までの間のプラグ基礎構造体の冷却状態に大きく影響されるといわれる。
【０００９】
しかし、上述のように各プラグ基礎構造体を加熱炉内で加熱する場合、保持板も同様に加熱される。当該保持板は厚みと伝熱性を有することから、上記加熱の際、その熱エネルギーは、通常、当該保持板の中央側よりも端部側に多く作用する。従って、保持板の端部の受熱量は当該保持板の中央の受熱量よりも増大する。
【００１０】
このため、保持板の端部に沿い位置するプラグ基礎構造体（以下、端部側プラグ基礎構造体という）の受熱量も、保持板の端部の受熱量の増大に追随し、残りのプラグ基礎構造体（以下、中央側プラグ基礎構造体という）の受熱量よりも増大する。換言すれば、端部側プラグ基礎構造体内の導電性ガラス粉末混合物中のガラス粉末の軟化度合いが、上記中央側プラグ基礎構造体内の導電性ガラス粉末混合物中のガラス粉末の軟化度合いよりも高くなる。
【００１１】
従って、加熱炉から搬出した保持板の各プラグ基礎構造体において、上述のように端子金具を絶縁部材の基端側部位内に圧入する際、当該圧入による導電性ガラス粉末混合物に対する圧縮力は、上記中央側プラグ基礎構造体に対しては、上記端部側プラグ基礎構造体よりも相対的に弱く作用する。このため、上記中央側プラグ基礎構造体内の導電性ガラス粉末混合物の焼結形成密度は、上記端部側プラグ基礎構造体内の導電性ガラス粉末混合物の焼結形成密度よりも低下する。その結果、上記中央側プラグ基礎構造体内の焼結導電体の電気抵抗値は、上記端部側プラグ基礎構造体内の焼結導電体の電気抵抗値よりも大きくなる。
【００１２】
換言すれば、保持板に保持した各プラグ基礎構造体内の導電性ガラス粉末混合物の焼結形成密度は、受熱量の多い端部側プラグ基礎構造体よりも、受熱量の少ない中央側プラグ基礎構造体において低くなることで、上述のようにプラグ基礎構造体間の電気抵抗値のばらつきを生ずる。
【００１３】
以上のようなことから、抵抗体入りスパークプラグの電気抵抗値は、上に述べた加熱炉内でのプラグ基礎構造体の加熱状況や当該加熱後端子金具圧入までの間のプラグ基礎構造体の冷却状況のみで特定されるのではなく、上記加熱の際の保持板の端部側と中央側との受熱量の差によっても、変動し、その結果、各抵抗体入りスパークプラグ間で電気抵抗値が大きくばらつくことが分かった。
【００１４】
そこで、本発明は、以上のようなことに対処するため、スパークプラグ間の電気抵抗値のばらつきをできる限り抑制するようにしたスパークプラグの製造方法及び製造装置を提供することを目的とする。
【００１５】
【課題を解決するための手段】
上記課題の解決にあたり、本発明に係るスパークプラグの製造方法では、請求項１の記載によれば、中空状の絶縁部材（１１０）の先端側に軸方向に嵌装した中心電極（１２０）と、絶縁部材の基端側に軸方向に挿入した端子金具（１３０）と、中心電極と端子金具との間にて絶縁部材内に設けた導電性ガラス粉末混合物（１５１、１５３、１５４、１５５）とを備えるプラグ基礎構造体（１５０）を複数準備し、かつ、複数の保持孔部（１６１）を離散状に貫通形成してなる保持板（１６０）を準備する。
【００１６】
そして、複数のプラグ基礎構造体のうち保持板の端部に沿って位置するプラグ基礎構造体（以下、端部側プラグ基礎構造体という）を、その先端側にて、保持板よりも熱伝導率の低い伝熱材料からなる中空状の受け部材（１７０、１８０）（以下、端部側受け部材という）を通し、複数の保持孔部のうち保持板の端部に沿って位置する保持孔部（以下、端部側保持孔部という）に嵌装するとともに、残りのプラグ基礎構造体（以下、中央側プラグ基礎構造体という）をその先端側にて残りの保持孔部（以下、中央側保持孔部という）に直接嵌装することで、複数のプラグ基礎構造体を保持板により保持する。
【００１７】
ついで、複数のプラグ基礎構造体が保持板から上方へ延出するように当該保持板を支持した状態で、複数のプラグ基礎構造体を、その導電性ガラス粉末混合物中のガラス粉末が軟化するように、保持板及び端部側受け部材と共に加熱し、
この加熱後、複数のプラグ基礎構造体を保持した保持板を上記支持状態のまま外気中に搬送し、
複数のプラグ基礎構造体の各々の端子金具をその対応絶縁部材内に押圧により軸方向に圧入して、当該対応絶縁部材内の導電性ガラス粉末混合物を圧縮焼結させて焼結導電体（１４０）とすることで、複数のプラグ基礎構造体の各々をプラグ本体として形成するようにした。
【００１８】
これによれば、上述のように、端部側プラグ基礎構造体を、その先端側にて、保持板よりも熱伝導率の低い伝熱材料からなる端部側受け部材を通し、端部側保持孔部に嵌装するとともに、中央側プラグ基礎構造体をその先端側にて中央側保持孔部に直接嵌装することで、複数のプラグ基礎構造体を保持板により保持する。
【００１９】
このため、上記加熱の際に、保持板の端部の方が当該保持板の中央よりも受熱量が多く、端部側プラグ基礎構造体は速く加熱されていく。さらに、プラグ基礎構造体は互いに並んで保持板から上方へ延出されているので、端部側プラグ基礎構造体は、中央側プラグ基礎構造体に比べて、上記加熱により加熱された空気にあたり易く、加熱され易い。しかし、所定の熱容量をもつ端部側受け部材を備えることで、保持板の端部から端部側受け部材を介して端部側プラグ基礎構造体に伝わる熱の量は中央側プラグ基礎構造体に直接伝わる熱量に近づいていく。
【００２０】
また、上記加熱後、外気中に搬出された保持板のプラグ基礎構造体がその端子金具にて対応の絶縁部材内に押圧により圧入される過程においては、保持板の端部の方が当該保持板の中央よりも放熱量が多く端部側プラグ基礎構造体は速く冷却していく。その上、中央側プラグ基礎構造体相互間で保温効果が発生して、端部側プラグ基礎構造体は中央側プラグ基礎構造体よりも冷却され易い。しかし、所定の熱容量をもつ端部側受け部材を備えることで、端部側プラグ基礎構造体から端部側受け部材を介して保持板に伝わる熱の量は中央側プラグ基礎構造体から直接伝わる熱量に近づいていく。
【００２１】
従って、端部側プラグ基礎構造体内のガラス粉末の軟化度合いは、中央側プラグ基礎構造体内のガラス粉末の軟化度合いに近似して維持される。このため、端部側及び中央側の各プラグ基礎構造体の焼結導電体の焼結密度、即ち、電気抵抗値も互いに近似する。その結果、電気抵抗値のばらつきの少ない歩留まりの良好なスパークプラグとしての製造が可能となる。
【００２２】
なお、保持板は、四角形に限ることなく六角形等の多角形その他種々の形状であってもよいが、保持板の端部に沿って貫通形成してなる保持孔部（端部側保持孔部）は、格子状に保持孔部を貫通形成してなる例えば四角形の保持板をその上面からみたとき、当該保持板において、その四辺のいずれかの辺に沿って位置する各保持孔部の中心を通る線であって上記いずれかの辺に平行な線（平行中心線という）のうち、当該いずれかの辺に最も近い平行中心線を通る保持孔部に少なくとも相当する（後述する図８或いは図３１参照）。
【００２３】
また、本発明は、請求項２の記載によれば、請求項１に記載のスパークプラグの製造方法において、中央側プラグ基礎構造体をも、その先端側にて、保持板よりも熱伝導率の低い伝熱材料からなる他の中空状の受け部材（１７０、１８０）（以下、中央側受け部材という）を通し、上記対応中央側保持孔部に嵌装することで、保持板による上記保持を行う。
【００２４】
然る後、複数のプラグ基礎構造体の上方への延出を維持するように保持板を支持した状態で、上記加熱を、中央側受け部材をも含めて行う。ここで、端部側受け部材は、中央側受け部材よりも大きな熱容量を有するように形成されている。
【００２５】
これによれば、中央側プラグ基礎構造体も、その先端側にて、保持板よりも熱伝導率の低い伝熱材料からなる中央側受け部材を通し、中央側保持孔部に嵌装する。
【００２６】
このため、上記加熱の際に、保持板の端部の方が当該保持板の中央よりも受熱量が多く、端部側プラグ基礎構造体は速く加熱していく。さらに、プラグ基礎構造体は互いに並んで保持板から上方へ延出されているので、端部側プラグ基礎構造体は、中央側プラグ基礎構造体に比べて、上記加熱により加熱された空気にあたり易く、加熱され易い。しかし、中央側受け部材よりも大きな熱容量をもつ端部側受け部材を備えることで、保持板の端部から端部側受け部材を介して端部側プラグ基礎構造体に伝わる熱の量は保持板の中央から中央側受け部材を介して中央側プラグ基礎構造体に伝わる熱量に近づいていく。
【００２７】
また、外気中に搬出された保持板のプラグ基礎構造体がその端子金具にて対応の絶縁部材内に押圧により圧入される過程においては、保持板の端部の方が当該保持板の中央よりも放熱量が多く、端部側プラグ基礎構造体は速く冷却していく。その上、中央側プラグ基礎構造体相互間で保温効果が発生して、端部側プラグ基礎構造体は中央側プラグ基礎構造体よりも冷却され易い。しかし、中央側受け部材よりも大きな熱容量をもつ端部側受け部材を備えることで、端部側プラグ基礎構造体から端部側受け部材を介して保持板に伝わる熱の量は中央側プラグ基礎構造体から中央側受け部材を介して保持板に伝わる熱量に近づいていく。
【００２８】
従って、端部側プラグ基礎構造体内のガラス粉末の軟化度合いは、中央側プラグ基礎構造体内のガラス粉末の軟化度合いに近似して維持される。その結果、請求項１に記載の発明と同様に、電気抵抗値のばらつきの少ない歩留まりの良好なスパークプラグとしての製造が可能となる。
【００２９】
また、本発明は、請求項３の記載によれば、請求項２に記載のスパークプラグの製造方法とは、端部側受け部材が中央側受け部材よりも大きな熱容量を有するように形成されていることとは異なり、端部側受け部材の熱伝導率が中央側受け部材の熱伝導率よりも低くなっている点で相違する。
【００３０】
これによれば、上記加熱の際及びその後の外気中への搬送下では、端部側受け部材が中央側受け部材よりも熱伝導率において低いことが、端部側受け部材が中央側受け部材よりも熱容量において大きいことと同様の熱作用効果を発揮する。その結果、請求項３の記載の発明によっても、スパークプラグの電気抵抗値のばらつきの抑制の観点から請求項２に記載の発明と実質的に同様の作用効果を達成できる。
【００３１】
また、本発明は、請求項４の記載によれば、請求項３に記載のスパークプラグの製造方法において、端部側受け部材は、中央側受け部材よりも大きな熱容量を有するように形成されていることを特徴とする。
【００３２】
これによれば、上記加熱の際及びその後の外気中への搬送下では、端部側受け部材が中央側受け部材よりも大きな熱容量を有することが、端部側受け部材が中央側受け部材よりも熱伝導率において低いことと相乗的に作用し、熱作用効果をより一層向上させる。その結果、請求項４の記載の発明によれば、スパークプラグの電気抵抗値のばらつきの抑制の観点から請求項３に記載の発明の作用効果をより一層向上できる。
【００３３】
また、本発明は、請求項５の記載によれば、請求項１〜４のいずれか一つに記載のスパークプラグの製造方法において、受け部材は、それぞれ、上記対応プラグ基礎構造体の導電性ガラス粉末混合物に対する対応部位をも覆うように形成された筒状受け部材（１８０）であることを特徴とする。
【００３４】
これによれば、プラグ基礎構造体のうちその先端部から導電性ガラス粉末混合物の全体の周囲にかけて、対応の受け部材により覆われる。従って、上記加熱の際に、受け部材は、対応のプラグ基礎構造体内の導電性ガラス粉末混合物の全体に対し、相互間の保温効果を発揮する。よって、プラグ基礎構造体内のガラス粉末の軟化状態は、導電性ガラス粉末混合物の全体に亘り、良好に促進される。その結果、請求項１〜４のいずれか一つに記載の発明の作用効果をより一層向上できる。
【００３５】
また、本発明は、請求項６の記載によれば、請求項１〜５のいずれか一つに記載のスパークプラグの製造方法において、保持板は、端部側保持孔部よりも中央側部位にて、保持板の端部よりも小さな熱容量を有するように凹状に形成し小熱容量部位（１６４、１６５、１６６、１６９、１９５、１９６、１９７）として構成されていることを特徴とする。
【００３６】
これによれば、上記加熱の際、上記凹状に形成された小熱容量部位の受熱量は、当該凹状に形成された小熱容量部位のない保持板よりも、速く増大する。このため、上記凹状に形成された小熱容量部位から熱伝達を受ける中央側プラグ基礎構造体内のガラス粉末の軟化がより一層促進されて端部側プラグ基礎構造体内のガラス粉末の軟化状態により一層近似する。その結果、請求項１〜５のいずれか一つに記載の発明の作用効果をより一層向上できる。
【００３７】
なお、上記小熱容量部位の凹状の深さは、端部側プラグ基礎構造体と中央側プラグ基礎構造体との熱量が近づくように適宜設定されるものであり、さらには、上記小熱容量部位の凹状は貫通状であってもよい。
【００３８】
また、本発明は、請求項７の記載によれば、請求項１〜６のいずれか一つに記載のスパークプラグの製造方法において、保持板は、端部側保持孔部のうち互いに隣り合う保持孔部間にて、保温部材（１９０）を保持板の上方へ突出するように配設してなることを特徴とする。
【００３９】
これによれば、上記加熱の際、端部側保持孔部のうち互いに隣り合う保持孔部間に配設された保温部材にも保持板から熱が伝わる。よって、端部側プラグ基礎構造体の保持板からの受熱量がさらに抑制され、より一層、中央側プラグ基礎構造体の受熱量に近づいていく。また、上記加熱後外気中に搬出された保持板のプラグ基礎構造体がその端子金具にて対応の絶縁部材内に押圧により圧入される過程においては、保温部材と端部側プラグ基礎構造体との保温効果により、端部側プラグ基礎構造体の放熱量が、中央側プラグ基礎構造体の放熱量に、より一層、近づいていく。よって、中央側プラグ基礎構造体内のガラス粉末の軟化が端部側プラグ基礎構造体内のガラス粉末の軟化状態に近づいていく。その結果、請求項１〜６のいずれか一つに記載の発明の作用効果をより一層向上し得る。
【００４０】
また、本発明によれば、請求項８の記載によれば、請求項１〜７のいずれか一つに記載のスパークプラグの製造方法において、保持板は、その搬送方向或いはこの搬送方向に対する交叉方向に沿い前記保持孔部を形成して格子状に配置した四角形状の保持板であって、保持孔部のうち、上記搬送方向に対する直交方向の両端の一方に位置する保持孔部の中心と当該直交方向の両端の一方との間隔及び上記直交方向の両端の他方に位置する保持孔部の中心と当該直交方向の両端の他方との間隔は、最短距離にて隣り合う保持孔部の中心の間隔よりも広いことを特徴とする。
【００４１】
これによれば、保持板の上記直交方向の端部の熱が端部側プラグ基礎構造体に伝わりにくい。従って、当該端部側受け部材内のガラス粉末の軟化は進みにくい。このため、プラグ基礎構造体の電気抵抗値は、端部側プラグ基礎構造体の焼結導電体の焼結密度と中央側プラグ基礎構造体の焼結導電体の焼結密度との間のばらつきはさらに少なくなる。その結果、請求項１〜７のいずれか一つに記載の発明の作用効果をより一層向上できる。
【００４２】
また、本発明は、請求項９の記載によれば、請求項１〜８のいずれか一つに記載のスパークプラグの製造方法において、保持板において、保持孔部のうち最短距離にて隣り合う保持孔部は、その中心の間隔を同一にするように形成されていることを特徴とする。
【００４３】
これによれば、中央側プラグ基礎構造体間の相互の保温効果による中央側プラグ基礎構造体内のガラス粉末の軟化が、より一層、均一に達成され得る。その結果、請求項１〜８のいずれか一つに記載の発明の作用効果のより一層の向上に役立つ。
【００４４】
また、本発明は、請求項１０の記載によれば、請求項１〜９のいずれか一つに記載のスパークプラグの製造方法において、保持板を、複数、プラグ基礎構造体の上方への延出を維持するように支持して連続的に隙間なく上記搬送方向に並べて、上記加熱を行うようにした。
【００４５】
これによれば、上記加熱の際に、保持板間におけるプラグ基礎構造体の熱環境のばらつきを減少させることができ、その結果、連続する保持板のプラグ基礎構造体間の電気抵抗値のばらつきをも減少させることができる。
【００４６】
また、本発明は、請求項１１の記載によれば、請求項１０に記載のスパークプラグの製造方法において、保持板の保持孔部のうち上記搬送方向の後端側の保持孔部の中心と上記搬送方向に後続して並ぶ保持板の保持孔部のうち上記搬送方向の先端側の保持孔部の中心との間の間隔は、保持孔部のうち最短距離にて隣り合う保持孔部の中心の間隔と同一であることを特徴とする。
【００４７】
これによれば、後続保持板及びその受け部材並びにプラグ基礎構造体は、先行保持板及びその受け部材並びにプラグ基礎構造体と同様の受熱状態におかれる。このため、先行及び後続の両保持板間においても、プラグ基礎構造体の電気抵抗値のばらつきが、上述と同様に少なくなる。その結果、連続する保持板を、その受け部材及びプラグ基礎構造体と共に加熱しても、保持板に、プラグ基礎構造体の電気抵抗値がばらつくことがなく、連続する保持板に亘り、歩留まりのよいスパークプラグの製造が可能となる。その結果、請求項１０に記載の発明の作用効果をより一層向上できる。
【００４８】
また、本発明に係るスパークプラグの製造装置は、請求項１２の記載によれば、
加熱室（３１１）と、この加熱室内にてその入り口から出口にかけて水平方向に搬送可能に支持した加熱室用搬送機構（３２１）とを備える加熱装置（３００）と、
加熱室の出口から加熱室用搬送機構の搬送方向に向け水平方向に搬送可能に支持したプレス装置用搬送機構（４２０）を有するように加熱室の出口に配設されたプレス装置（４００）とを備える。
【００４９】
そして、中空状の絶縁部材（１１０）の先端側に軸方向に嵌装した中心電極（１２０）と、絶縁部材の基端側に軸方向に挿入した端子金具（１３０）と、中心電極と端子金具との間にて絶縁部材内に設けた導電性ガラス粉末混合物（１５１、１５３、１５４、１５５）とを備えるプラグ基礎構造体（１５０）を複数準備し、かつ、複数の保持孔部（１６１）を離散状に貫通形成してなる伝熱性保持板（１６０）を準備する。
【００５０】
しかして、複数のプラグ基礎構造体のうち保持板の端部に沿って位置するプラグ基礎構造体（以下、端部側プラグ基礎構造体という）を、その先端側にて、保持板よりも熱伝導率の低い伝熱材料からなる中空状の受け部材（１７０、１８０）（以下、端部側受け部材という）を通し、保持孔部のうち保持板の端部に沿って位置する保持孔部（以下、端部側保持孔部という）に嵌装するとともに、残りのプラグ基礎構造体（以下、中央側プラグ基礎構造体という）をその先端側にて残りの保持孔部（以下、中央側保持孔部という）に直接嵌装することで、複数のプラグ基礎構造体を保持板により保持する。
【００５１】
ついで、複数のプラグ基礎構造体が保持板から上方へ延出するように保持板を加熱室用搬送機構により支持して加熱室内に搬入し、
この加熱室内にて、複数のプラグ基礎構造体を、その導電性ガラス粉末混合物中のガラス粉末が軟化するように、保持板及び端部側受け部材と共に加熱し、
この加熱後、複数のプラグ基礎構造体を保持した保持板を、加熱室用搬送機構により加熱室の出口から搬出してプレス装置用搬送機構によりプレス装置内に搬入し、
このプレス装置により、複数のプラグ基礎構造体の各々の端子金具をその対応絶縁部材内に押圧により軸方向に圧入し、対応絶縁部材内の導電性ガラス粉末混合物を圧縮焼結させて焼結導電体（１４０）として形成することで、複数のプラグ基礎構造体の各々をプラグ本体として形成する。
【００５２】
これによれば、請求項１に記載の発明と同様の作用効果を達成し得るスパークプラグの製造装置を提供できる。
【００５３】
なお、各請求項１及び１２の記載において、「離散状」とは、格子状を含み、各保持孔部の保持板に対する形成が分散していることをいう。また、上記各手段の括弧内の符号は、後述する実施形態に記載の具体的手段との対応関係を示すものである。
【００５４】
【発明の実施の形態】
以下、本発明の各実施形態を図面に基づいて説明する。
（第１実施形態）
図１は、本発明の第１実施形態により製造される内燃機関用抵抗体入りスパークプラグの一例を示している。この抵抗体入りスパークプラグは、プラグ本体１００及び固定用筒状金具２００を備えている。
【００５５】
プラグ本体１００は、筒状絶縁部材１１０、柱状中心電極１２０及び柱状端子金具１３０を備えており、筒状絶縁部材１１０内には、段付き内孔１１１が、当該絶縁部材１１０と同軸的に貫通形成されている。ここで、当該段付き内孔１１１は、絶縁部材１１０の先端側部位（図１にて図示下側）にて小径部１１２を有し、絶縁部材１１０の基端側部位（図１にて図示上側）にて小径部１１２よりも径の大きい大径部１１３を有する。
【００５６】
柱状中心電極１２０は、絶縁部材１１０の小径部１１２内に同軸的に嵌装されており、この中心電極１２０は、その隆起状頭部１２１にて、大径部１１３内からその小径部１１２との境界段部に係合し、その先端部１２２にて、小径部１１２の先端から外方へ露呈している。
【００５７】
柱状端子金具１３０は、その段付きロッド部１３１にて、絶縁部材１１０の大径部１１３内にその先端側から軸方向に圧入されており、この端子金具１３０は、その端子部１３２にて、絶縁部材１１０の基端部１１４に着座している。
【００５８】
また、プラグ本体１００は、柱状焼結導電体１４０を備えており、この焼結導電体１４０は、絶縁部材１１０の大径部１１３内にて、中心電極１２０の頭部１２１と端子金具１３０の先端部１３３との間に介装されている。当該焼結導電体１４０は、ガラスシール層１４１（以下、先端側ガラスシール層１４１ともいう）、電気抵抗体１４２及びガラスシール層１４３（以下、基端側ガラスシール層１４３ともいう）でもって構成されている。先端側ガラスシール層１４１は、中心電極１２０の頭部１２１側に位置し、一方、基端側ガラスシール層１４３は、段付きロッド部１３１の先端部１３３側に位置している。また、電気抵抗体１４２は、両ガラスシール層１４１及び１４３の間に介在している。
【００５９】
但し、両ガラスシール層１４１、１４３は、共に、銅（Ｃｕ）や鉄（Ｆｅ）或いはこれらの合金等の金属粉末をガラス粉末に混合した混合物（以下、シール原料粉末混合物ともいう）を焼結した組成物（以下、焼結シール組成物ともいう）で構成されている。また、電気抵抗体１４２は、ガラス粉末を炭素粉末等の抵抗材料粉末に混合した物（以下、抵抗体原料粉末混合物ともいう）を焼結した組成物（以下、焼結抵抗体組成物ともいう）で構成されている。従って、上記両焼結シール組成物及び焼結抵抗体組成物でもって焼結導電体１４０を構成している。
【００６０】
なお、焼結導電体１４０のうち、両ガラスシール層１４１、１４３は、電気抵抗体１４２の介在のもとに、端子金具１３０の先端部１３３と中心電極１２０の頭部１２１との間の導通を確保し、電気抵抗体１４２は、電波ノイズの発生を低減させる役割を果たす。また、上記両シール原料粉末混合物及び抵抗体原料粉末混合物でもって導電性ガラス粉末混合物ともいう。
【００６１】
固定用筒状金具２００は、当該内燃機関のシリンダヘッド内に固定されるもので、この固定用筒状金具２００は、その金属筒体部２１０にて、絶縁部材１１０の先端側部位に外方から同軸的に嵌装されている。ここで、金属筒体部２１０の基端開口部２１１は、リング状の両パッキング２１２及び環状充填層２１３を介し絶縁部材１１０の軸方向中間部位に外方からカシメにより固着されている。
【００６２】
固定用筒状金具２００の接地電極２２０は、金属筒体部２１０の先端開口部２１４の一部からＬ字状に延出して、その延出端部２２１にて、中心電極１２０の先端部１２２に、空隙２２２を介し対向している。なお、接地電極２２０は、その基端部にて、金属筒体部２１０の先端開口部２１４の一部に溶接されている。
【００６３】
次に、上述のように構成した抵抗体入りスパークプラグを製造するための製造装置の一例について、図９〜図１５を参照して説明する。この製造装置は、図９にて示すごとく、加熱装置３００を備えており、この加熱装置３００は、図９及び図１０にて示すことく、加熱炉３１０を有している。この加熱炉３１０は、その内部に、略直方体形状の加熱室３１１を備えており、この加熱室３１１は、図９及び図１０にて示すごとく、加熱上室部３１２と、加熱下室部３１３とに、後述する保持板により上下に区画される。
【００６４】
当該加熱炉３１０は、図９にて示すごとく、複数のガスバーナ３１４及び複数のガスバーナ３１５を備えており、複数のガスバーナ３１４（以下、上側ガスバーナ３１４ともいう）は、加熱上室部３１２の上壁に沿い、図９にて図示左右方向（加熱炉３１０或いは加熱室３１１の前後方向に対応）に沿い配設されている。また、このような複数の上側ガスバーナ３１４の配設は、図１０にて示すごとく、加熱上室部３１２の上壁の図示左右方向中央にて上側ガスバーナ３１４を左右にに配列（本実施形態では３列に配列）することでなされている。このように配設した複数の上側ガスバーナ３１４は、その各配設位置から下方向にガスの燃焼による熱エネルギーを放出する。
【００６５】
一方、複数のガスバーナ３１５（以下、下側ガスバーナ３１５ともいう）は、加熱下室部３１３の底壁に沿い、図９にて図示左右方向（加熱炉３１０或いは加熱室３１１の前後方向に対応）に沿い、複数の上側ガスバーナ３１４に対向するように配設されている。また、このような複数の下側ガスバーナ３１５の配設は、図１０にて示すごとく、加熱下室部３１３の底壁の図示左右方向中央にて下側ガスバーナ３１５を左右に配列（本実施形態では５列に配列）することでなされている。なお、ガスバーナの配設数は、下側ガスバーナ３１５の方が上側ガスバーナ３１４よりも多くすることで、後述するプラグ基礎構造体内の先端側シール原料粉末混合物から軟化して、後述するプレスにて、中心電極１２０と端子金具１３０との間の電気的接続不良の発生を抑制する。
【００６６】
このように配設した複数の下側ガスバーナ３１５は、その各配設位置から上方向にガスの燃焼による熱エネルギーを放出する。なお、各ガスバーナ３１４、３１５は、ガス供給源（図示しない）から供給されるガスを燃焼させる。また、両上側排気孔３１６は、加熱上室部３１２の図１０にて図示左右側壁に貫通形成されて、加熱上室部３１２内から加熱炉３１０の外部への排気を行う。また、両下側排気孔３１６は、加熱下室部３１３の図１０にて図示左右側壁に貫通形成されて、加熱下室部３１３内から加熱炉３１０の外部への排気を行う。
【００６７】
また、当該加熱装置３００は、図１１〜図１３にて示すごとく、搬送装置３２０を備えている。この搬送装置３２０は、図１０にて示すように、左右両側の搬送コンベア３２１を有しており、これら搬送コンベア３２１は、加熱室３１１の図１０にて図示左右方向中央に対し互いに対称的な構成にて、加熱下室部３１３の左右両側内壁の各上端近傍部に配設されている。
【００６８】
そこで、右側搬送コンベア３２１を例にとりその構成について説明すると、この右側搬送コンベア３２１は、図１０にて示すごとく、加熱下室部３１３の右側内壁の上端近傍部に配設されている。当該右側搬送コンベア３２１は、図１０にて円３２２にて拡大して示すごとく、長手状支持バー３２３と、複数の搬送ローラ３２４（図１０では一つの搬送ローラ３２４のみを示す）とを備えている。
【００６９】
複数の搬送ローラ３２４は、図１０から分かるように、保持板（後述する）を支持しており、支持バー３２３は、当該保持板が左右方向（加熱室３１１の左右方向に相当）に動くことを抑制している。また、各左側搬送コンベア３２１は、その回転軸（図示しない）にて、加熱室３１１の前後方向に回転自在となっている。
【００７０】
一方、左側搬送コンベア３２１は、上述のように右側搬送コンベア３２１とは対称的な構成を有することから、この左側搬送コンベア３２１の各搬送ローラは、右側搬送コンベア３２１の各搬送ローラ３２４にそれぞれ対向して位置し、加熱下室部３１３の左側内壁の上端近傍部に配設した左側搬送コンベア３２１の支持バーでもって、右側搬送コンベア３２１と同様に前後方向に回転自在に支持されている。
【００７１】
また、搬送装置３２０は、図１１にて示すごとく、空圧や油圧等の流体圧またはモータ等の機械を利用するリニアアクチュエータ３２５を備えており、このリニアアクチュエータ３２５は、そのシリンダ３２６にて、加熱炉３１０において加熱室３１１の図１１にて図示右側壁に設けた支持穴部３１７内に支持されている。当該リニアアクチュエータ３２５は、板状押動部材３２７を備えており、この押動部材３２７は、シリンダ３２６内のピストン（図示しない）から延出するピストンロッド３２８の延出端部に同軸的に支持されている。
【００７２】
しかして、リニアアクチュエータ３２５では、押動部材３２７は、シリンダ３２６から図１１にて図示左方向（加熱室１１の前方方向）へ摺動するピストンロッド３２８により同一方向へ押動されて、加熱室３１１の搬入路３１８のうち両搬送コンベア３２１に対向する部位（以下、コンベア対向部位ともいう）内に向け前進する（図１２参照）。また、押動部材３２７は、シリンダ３２６内へのピストンロッド３２８の摺動に伴いこのピストンロッド３２８に引っ張られて搬入路３１８の上記対向部位内からシリンダ３２６側に後退する（図１３参照）。
【００７３】
ここで、上記ピストンは、シリンダ３２６の内部を両室に区画するように、シリンダ３２６内に同軸的にかつ摺動可能に嵌装されており、当該ピストンは、シリンダ３２６の両室の一方への流体圧供給源（図示しない）からの流体圧の圧送に伴い、シリンダ３２６内にて搬入路３１８の上記対向部位側へ摺動し、上記両室の他方への上記流体圧の圧送に伴い、シリンダ３２６内にて搬入路３１８の上記対向部位とは反対方向に摺動する。
【００７４】
また、搬入路３１８は、図１１にて示すごとく、加熱炉３１０において、加熱室３１１の図示右側にて両搬送コンベア３２１の長手方向に直交するように水平状に設けられている。また、この搬入路３１８は、その上記対向部位にて、加熱室３１１内にその入り口（加熱室３１１の図１１にて図示右端開口部）を介し開口するとともに、支持穴部３１７内にその内端部を介し開口している。なお、加熱室３１１の入り口は、加熱室３１１のうち両搬送コンベア３２１の各搬送ローラの軸の上側に形成されている。
【００７５】
また、加熱装置３００は、図９及び図１１にて示すごとく、板状シャッター３３０を備えており、このシャッター３３０は、加熱炉３１０において加熱室３１１の図９にて図示左側壁（加熱室３１１の前側壁）の外面に形成した凹所３１９内に、加熱室３１１の出口（加熱室３１１の図９にて図示左端開口部）を上下方向に開閉するように、収容されている。
【００７６】
しかして、シャッター３３０は、凹所３１９内にて上方へ変位して、加熱室３１１の出口を開く（図１２参照）。また、シャッター３３０は、凹所３１９内にて下方へ変位して、加熱上室部３１２の出口を閉じる（図１１及び図１３参照）。
【００７７】
また、当該製造装置は、図９にて示すごとく、プレス装置４００を備えており、このプレス装置４００は、加熱炉３１０に図９にて図示左側から併設されている。当該プレス装置４００は、図１５にて示すごとく、搬送装置４１０と、下ダイ４２０と、この下ダイ４２０の直上にて昇降可能に支持される上ダイ４３０とを備えている。
【００７８】
搬送装置４１０は、左右の両昇降部材４１１を有しており、これら両昇降部材４１１は、下ダイ４２０の図１５にて図示左右両壁４２１に沿い昇降可能に支持されている。また、当該搬送装置４１０は、搬送コンベア４１２を有しており、この搬送コンベア４１２は、図１４にて示すごとく、複数の昇降軸４１３と、複数の搬送ローラ４１４とにより構成されている。なお、搬送装置４１０は、シャッター３３０を介し加熱室３１１の出口に対向している。
【００７９】
複数の昇降軸４１３は、図１５にて例示するごとく、その各両端部にて、両昇降部材４１１により水平状に支持され、かつ、図１４にて示すごとく、両昇降軸４１１によりその図示左右方向に沿い、所定間隔にて配列支持されている。ここで、当該複数の昇降軸４１３は、下ダイ４２０の上面に形成した複数の横溝４２２（図１４にて図示上下方向溝４２２）内に昇降可能に位置している。
【００８０】
しかして、複数の昇降軸４１３は、両昇降部材４１１の昇降に伴い、複数の横溝４２２内にて昇降するようになっている。なお、複数の横溝４２２は、図１４にて図示左右方向には各昇降軸４１３と同様の所定間隔配列にて位置するように、図１４にて図示上下方向には互いに平行となるように、下ダイ４２０の上面に沿い形成されている。
【００８１】
複数の搬送ローラ４１４は、図１４から分かるように、複数の昇降軸４１２の各々に同数ずつ回転自在に支持されており、複数の昇降軸４１２に支持した各搬送ローラ４１４は、下ダイ４２０の上面に形成した複数の縦溝４２３（図１４にて図示左右方向溝４２３）内に、昇降軸４１２毎に、その軸方向に沿い所定軸方向間隔にて同軸的に支持されている。
【００８２】
ここで、複数の縦溝４２３は、複数の横溝４２２と十字状に交差するように、上記所定軸方向間隔と同一間隔にて、下ダイ４２０の上面に形成されている。従って、昇降軸４１２毎に、一昇降軸４１２に支持した各搬送ローラ４１４は、その対応の一縦溝４２３と上記一昇降軸４１２に対応の一横溝４２２との各交差部にて、上記対応の一縦溝４２３内に位置している（図１５参照）。
【００８３】
しかして、複数の搬送ローラ４１４は、複数の昇降軸４１３の昇降に伴い、複数の縦溝４２３内を昇降するようになっており、当該複数の搬送ローラ４１４は、その上昇により、その各上端部にて、下ダイ４２０の上面よりも上方へ突出する。また、当該複数の搬送ローラ４１４は、その下降により、その各上端部をも含めて、下ダイ４２０の上面よりも下方に位置するように、複数の横溝４２３内に収納される。
【００８４】
上ダイ４３０は、図１５にて示すごとく、ダイ本体４３１と、複数本（本実施形態では、６本×６本）のロッド４３２とを備えており、ダイ本体４３１は、油圧供給源（図示しない）からの油圧により昇降する。複数本のロッド４３２は、図１５にて図示左右方向に６本及び図示奥行き方向に６本配列されて、ダイ本体４３１の下面から下方に向け格子状に垂下している。このような各ロッド４３２の格子状配列は、後述する保持板１６０の各保持孔部１６１の格子状配列に対応する。ここで、各ロッド４３２は、その先端部にて、下ダイ４２０の上面のうち各縦溝４２３とこれに隣り合う各縦溝４２３との間の各上面部に対向するようになっている。
【００８５】
なお、当該製造装置では、加熱装置３００の両搬送コンベア３２１、リニアアクチュエータ３２５及びシャッター３３０並びにプレス装置４００の両昇降部材４１１及び上ダイ４３０等の各動作は、当該製造装置により上記抵抗体入りスパークプラグを後述するように製造するに際し、所定の順序にて、制御回路（図示しない）によりシーケンス制御されるようになっている。
【００８６】
以下、このように構成した当該製造装置による抵抗体入りスパークプラグの製造方法について説明する。最初に、端子金具１３０を押圧により圧入する前のプラグ本体１００の構成を、プラグ基礎構造体１５０（図６参照）として準備する。
【００８７】
具体的には、柱状中心電極１２０を、図２にて示すごとく、筒状絶縁部材１１０の小径部１１２内に大径部１１３を通し同軸的に嵌装する。ついで、ガラスシール層１４１を形成するための上記シール原料粉末混合物（以下、シール原料粉末混合物１５１ともいう）を、図３にて示すごとく、絶縁部材１１０の大径部１１３内に所定量供給する。
【００８８】
然る後、押さえ棒１５２を絶縁部材１１０の大径部１１３内に挿入し、図４にて示すごとく、当該押さえ棒１５２によりシール原料粉末混合物１５１を中心電極１２０の頭部１２１上に予備圧縮する。ついで、押さえ棒１５２を絶縁部材１１０から除いた状態で、電気抵抗体１４２を形成するための上記抵抗体原料粉末混合物（以下、抵抗体原料粉末混合物１５３ともいう）を、絶縁部材１１０の大径部１１３内に所定量供給する。そして、再び、押さえ棒１５２を絶縁部材１１０の大径部１１３内に挿入し、当該押さえ棒１５２により抵抗体原料粉末混合物１５３を予備圧縮済みのシール原料粉末混合物１５１上に予備圧縮する。
【００８９】
ついで、再び、押さえ棒１５２を絶縁部材１１０から除いた状態で、ガラスシール層１４３を形成するための上記シール原料粉末混合物（以下、シール原料粉末混合物１５４ともいう）を、図５にて示すごとく、絶縁部材１１０の大径部１１３内に所定量供給する。そして、押さえ棒１５２を絶縁部材１１０の大径部１１３内に挿入し、当該押さえ棒１５２によりシール原料粉末混合物１５４を予備圧縮済みの抵抗体原料粉末混合物１５３上に予備圧縮する（図５参照）。
【００９０】
その後、押さえ棒１５２を絶縁部材１１０から除いた状態で、端子金具１３０を、その段付きロッド部１３１にて、図６にて示すごとく、絶縁部材１１０の大径部１１３内に押圧することなく挿入する。現段階では、端子金具１３０の端子部１３２は、絶縁部材１１０の基端部１１４から離れて維持される。これにより、１個のプラグ基礎構造体１５０の準備が完了する（図６参照）。このようなプラグ基礎構造体１５０を３６個の複数倍準備する。
【００９１】
然る後、プラグ基礎構造体１５０を筒状受け部材１７０を介し四角形状の平板からなる保持板１６０に次のようにして保持する。ここで、保持板１６０及び受け部材１７０の構成について説明する。
【００９２】
保持板１６０は、図６〜図８から分かるように、複数個（例えば、３６個）の保持孔部１６１を有しており、これら各保持孔部１６１は、保持板１６０に、一行（図８にて左右方向に対応）あたり６個ずつ、一列（図８にて上下方向に対応）あたり６個ずつ、貫通形成されて、６行×６列の格子状に配置されている。但し、一行を構成する６個の保持孔部１６１のうち互いに隣り合う両保持孔部１６１の軸心間隔は、一列を構成する６個の保持孔部１６１のうち互いに隣り合う両保持孔部１６１の軸心間隔と同一である。
【００９３】
各保持孔部１６１は、それぞれ、図６及び図７にて示すごとく、大径部１６２及び小径部１６３を同軸的に備えて構成されている。各保持孔部１６１において、大径部１６２は、保持板１６０の表面１６４側に位置し、小径部１６３は、保持板１６０の裏面１６５側に位置している。
【００９４】
また、各保持孔部１６１のうち、保持板１６０の図８にて図示左右方向両端部及び図示上下方向両端部に沿って位置する保持孔部１６１（以下、端部側保持孔部１６１ともいう）は、共に、図７にて示すような同一断面形状を有する。また、これら端部側保持孔部１６１よりも保持板１６０の中央側に位置する保持孔部１６１（以下、中央側保持孔部１６１ともいう）は、共に、図６にて示すような同一断面形状を有する。
【００９５】
ここで、端部側保持孔部１６１の大径部１６２の内径は、図６及び図７にて示すごとく、中央側保持孔部１６１の大径部１６２の内径よりも大きく形成されているが、端部側保持孔部１６１の小径部１６３の内径は、中央側保持孔部１６１の小径部１６３の内径に等しい。このように構成した保持板１６０を、複数準備する。なお、保持板１６０は、耐熱性及び耐酸化性を有する金属材料（例えば、ステンレス鋼、インコネル或いはコバルト系の金属）で形成されている。
【００９６】
受け部材１７０は、図６及び図７にて示すごとく、中央側或いは端部側の保持孔部１６１の大径部１６２内に同軸的に嵌装されるもので、当該受け部材１７０は、保持板１６０よりも熱伝導率の低い材料（例えば、セラミック材料）で形成されている。以下、端部側保持孔部１６１の大径部１６２に嵌装される受け部材１７０を端部側受け部材１７０ともいい、中央側保持孔部１６１の大径部１６２に嵌装される受け部材１７０を中央側受け部材１７０ともいう。
【００９７】
端部側受け部材１７０は、その外周面にて端部側保持孔部１６１の大径部１６２の内周面に一様に当接するように、当該大径部１６２内に嵌合され、また、中央側受け部材１７０は、その外周面にて中央側保持孔部１６１の大径部１６２の内周面に一様に当接するように、当該大径部１６２内に嵌合される。従って、端部側受け部材１７０の肉厚は、中央側受け部材１７０の肉厚よりも厚く設定されている。また、当該端部側受け部材１７０及び中央側受け部材１７０の各内径は、共に同一であって、プラグ基礎構造体１５０の絶縁部材１１０のつば状環状部（以下、つば状環状部１１５ともいう）の外径よりも小さい。
【００９８】
このように構成した受け部材１７０は、保持板１６０の一枚あたり、端部側受け部材１７０を２０個ずつ、中央側受け部材１７０を１６個ずつ、準備したプラグ基礎構造体１５０の数に合わせて準備する。
【００９９】
然る後、準備した保持板１６０毎に、各中央側受け部材１７０を、図６にて例示するごとく、その先端部（以下、先端部１７２ともいう）から当該保持板１６０の各中央側保持孔部１６１の大径部１６２内に同軸的に嵌装する。また、各端部側受け部材１７０を、図７にて例示するごとく、先端部１７２から当該保持板１６０の各端部側保持孔部１６１の大径部１６２内に同軸的に嵌装する。これに伴い、各中央側及び端部側の受け部材１７０は、その先端部１７２にて、図６及び図７にて例示するごとく、大径部１６２の小径部１６３との境界である底面に着座する。このとき、各中央側及び端部側の受け部材１７０は、対応の各保持孔部１６１から外方へ延出している。
【０１００】
ついで、このように２０個の端部側受け部材１７０及び１６個の中央側受け部材１７０を嵌装した保持板１６０毎に、３６個のプラグ基礎構造体１５０の各々を、その先端部から、図６及び図７にて例示するごとく、当該保持板１６０の端部側及び中央側の各受け部材１７０内に嵌装する。これに伴い、各プラグ基礎構造体１５０は、そのつば状環状部１１５の下端面１１６にて、対応の受け部材１７０の基端面１７１上に着座する。
【０１０１】
これにより、各プラグ基礎構造体１５０は、対応の各受け部材１７０により図６及び図７にて例示するように保持される。このとき、各プラグ基礎構造体１５０のうちつば状環状部１１５よりも先端側部分は、対応の各受け部材１７０内にほぼ位置して、対応の各保持孔部１６１の小径部１６３内を臨んでいる（図６及び図７参照）。
【０１０２】
以上のようにして各受け部材１７０を介し各プラグ基礎構造体１５０を保持した各保持板１６０は、図９〜図１１から分かるように、各プラグ基礎構造体１５０を上方へ延出させ状態で、加熱炉３１０の搬入路３１８内に搬入されて、搬送装置３２０のリニアアクチュエータ３２５及び両搬送コンベア３２１により加熱上室部３１２内に順次搬送される。ついで、当該各保持板１６０は、加熱室３１１内にて各複数の上側ガスバーナ３１４及び下側ガスバーナ３１５により上下から加熱され、然る後、図１２〜図１４にて示すように、リニアアクチュエータ３２５及び両搬送コンベア３２１によりプレス装置４００内に順次搬送される。
【０１０３】
以下、このような各保持板１６０の搬入、加熱及び搬出の過程について詳細に説明する。上述のように受け部材１７０を介しプラグ基礎構造体１５０を保持した各保持板１６０が、複数、図１１にて示すごとく、加熱炉３１０の加熱上室部３１２内に順次搬入されると、当該各保持板１６０は、その各プラグ基礎構造体１５０を上方へ延出させるように両搬送コンベア３２１により水平状に支持されて、加熱上室部３１２内にて順次搬送される。
【０１０４】
そして、このように搬送された順序で、各プラグ基礎構造体１５０は、各保持板１６０及びその各受け部材１７０と共に、加熱室３１１内にて、各上側ガスバーナ３１４及び各下側ガスバーナ３１５のガスの燃焼エネルギーにより所定加熱条件のもとに加熱される。当該所定加熱条件は、所定加熱時間と所定加熱温度とからなるものである。これら所定加熱時間及び所定加熱温度は、プラグ基礎構造体１５０内の各シール原料粉末混合物１５１、１５４及び抵抗体原料粉末混合物１５３中の各ガラス粉末を軟化させるに適するように設定されている。
【０１０５】
例えば、上記所定加熱温度は、プラグ基礎構造体１５０内の各シール原料粉末混合物１５１、１５４及び抵抗体原料粉末混合物１５３中の各ガラス粉末の軟化点（ガラス軟化点）以上の所定加熱温度（例えば、９００℃〜１０００℃の範囲以内の温度）である。また、上記所定加熱時間は、当該ガラス粉末を上記所定加熱温度による加熱にて軟化させるに要する時間であって、保持板１６０の加熱上室部３１２内への搬送後当該加熱上室部３１２から搬出するまでの時間（例えば、８分〜２０分の範囲内の時間）に相当する。
【０１０６】
ここで、上述のように加熱上室部３１２内に搬入された保持板１６０の一つ（図１１にて図示左端側保持板１６０）を例にとり、この保持板１６０の各プラグ基礎構造体１５０、当該保持板１６０及びその各受け部材１７０に対する加熱工程について説明する。
【０１０７】
加熱上室部３１２内に搬入された保持板１６０の各プラグ基礎構造体１５０、当該保持板１６０及びその各受け部材１７０は、上側及び下側の各ガスバーナ３１４及び３１５のガスの燃焼エネルギーにより次のような状態で加熱される。
【０１０８】
即ち、上述のごとく、上側及び下側の各ガスバーナ３１４、３１５が、上記ガス供給源からのガスを燃焼させると、各上側ガスバーナ３１４はその各配設位置から下方向に燃焼エネルギーを放出し、一方、各下側ガスバーナ３１５は、その各配設位置から上方向に燃焼エネルギーを放出する。
【０１０９】
従って、各上側ガスバーナ３１４の燃焼エネルギーは、加熱上室部３１２内に輻射され輻射熱として伝達されるとともに主として当該加熱上室部３１２内にて空気の流れにのって対流し対流熱として伝達される。一方、各下側ガスバーナ３１５の放出加熱エネルギーは、加熱下室部３１３内に輻射され輻射熱として伝達されるとともに主として当該加熱下室部３１３内にて空気の流れにのって対流し対流熱として伝達される。
【０１１０】
これにより、各上側ガスバーナ３１４の燃焼エネルギーは加熱上室部３１２内に亘り均一に熱として伝達され、一方、各下側ガスバーナ３１５の燃焼エネルギーは加熱下室部３１３内に亘り均一に熱として伝達される。このような熱伝達下におかれた保持板１６０の各プラグ基礎構造体１５０への熱伝達は、上述の輻射及び対流による熱伝達でもって効率よく行われる。
【０１１１】
また、この熱伝達状態では、保持板１６０の各プラグ基礎構造体１５０は互いに並んで当該保持板１６０から上方へ延出しているため、加熱上室部３１２内の対流熱は、各プラグ基礎構造体１５０の間を通り伝達される。このため、当該各プラグ基礎構造体１５０のうち保持板１６０の中央側に位置するプラグ基礎構造体相互間で保温効果が発生する。従って、保持板１６０の中央側に位置するプラグ基礎構造体の相互間では上記熱伝達効率がより一層高められる。
【０１１２】
以上のような均一で効率のよい熱の伝達状態にあっても、本明細書の冒頭で述べたように、保持板１６０の端部の方が当該保持板１６０の中央よりも受熱量が多い。そして、端部側プラグ基礎構造体１５０は、中央側プラグ基礎構造体１５０に比べて、加熱炉３１０内において加熱された対流熱にあたり易く加熱され易い。しかし、本第１実施形態では、上述のごとく、保持板１６０においては、
端部側保持孔部１６１には、プラグ基礎構造体１５０が端部側受け部材１７０を介して嵌装され、中央側保持孔部１６１には、プラグ基礎構造体１５０が中央側受け部材１７０を介して嵌装されている。
【０１１３】
しかも、端部側受け部材１７０の肉厚の方が、上述のごとく、中央側受け部材１７０の肉厚よりも厚い。このため、端部側受け部材１７０の方が、中央側受け部材１７０よりも大きな熱容量を有する。従って、端部側受け部材１７０が吸収する熱の量の方が中央側受け部材１７０が吸収する熱の量よりも多くなる。
【０１１４】
よって、上述のように、保持板１６０の端部の方が当該保持板１６０の中央よりも受熱量が多くても、当該保持板１６０の端部から端部側受け部材１７０を介しプラグ基礎構造体１５０（以下、端部側プラグ基礎構造体１５０ともいう）に伝わる熱の量は、減少して、保持板１６０の中央から中央側受け部材１７０を介しプラグ基礎構造体１５０（以下、中央側プラグ基礎構造体１５０ともいう）に伝わる熱の量に近づいていく。このことは、端部側プラグ基礎構造体１５０の先端側部位の受熱量が中央側プラグ基礎構造体１５０の先端側部位の受熱量に近づいていくことを意味する。
【０１１５】
以上のような加熱状態にあっては、各プラグ基礎構造体１５０は上記所定加熱温度に向けて加熱され、当該各プラグ基礎構造体１５０内の各シール原料粉末混合物１５１、１５４及び抵抗体原料粉末混合物１５３中の各ガラス粉末が軟化されていく。しかも、上述のように端部側プラグ基礎構造体１５０の先端側部位の受熱量が中央側プラグ基礎構造体１５０の受熱量に近づいていくことから、上記各ガラス粉末の軟化状態は、端部側プラグ基礎構造体１５０と中央側プラグ基礎構造体１５０との間で近似していく状態になる。
【０１１６】
然る後、上記所定加熱時間が経過すると、加熱装置３００のシャッター３３０が図９にて図示上方へ開く。また、プレス装置４００の搬送装置４１０において、両昇降部材４１１が、図１５にて図示上方へ上昇し搬送コンベア４１２を上昇させる。このため、当該搬送コンベア４１２の各搬送ローラ４１４がその上端部にて下ダイ４２０の上面から突出する。
【０１１７】
これに伴い、搬送装置３２０のリニアアクチュエータ３２５が、上記流体圧供給源からの流体圧に基づき、ピストンロッド３２８により押動板３２７を押し出して、この押動板３２７により加熱室３１１の入り口の外側に位置する保持板１６０（図１１参照）を搬送方向（加熱室３１１の前後方向）に押動する。
【０１１８】
このため、上述した左端側保持板１６０が、図１２及び図１３にて示すように、加熱室３１１からプレス装置４００内に押し出される。その後、リニアアクチュエータ３２５の押動板３２７は図１３にて示すごとく図示右方へ戻り、搬入路３１８上の保持板１６０が加熱室３１１の入り口に対応する位置まで搬入される。
【０１１９】
上述のように加熱されてプレス装置４００内に押し出された保持板１６０は、リニアアクチュエータ３２５による押し出しのもと、その各プラグ基礎構造体１５０及び各受け部材１７０と共に、上述のように上昇した搬送コンベア４１２の各搬送ローラ４１４によりその回転に伴いプレス装置４００の下ダイ４２０の直上に搬送される（図１４参照）。これに伴い、両昇降部材４１１が下降し搬送コンベア４１２を降下させる。このため、当該搬送コンベア４１２の各搬送ローラ４１４が下ダイ４２０内に収納されて、保持板１６０がその裏面にて下ダイ４２０の上面に着座する。
【０１２０】
ついで、当該保持板１６０の各プラグ基礎構造体１５０では、その各端子金具１３０が、端子部１３２にて、上ダイ４３０の下降により各ロッド４３２により各絶縁部材１１０の基端部１１４に向けて下ダイ４２０の対応の各上記上面部上にて押圧される。これに伴い、各端子金具１３０の端子部１３２は、図１６にて例示するごとく、各絶縁部材１１０の各基端部１１４上に着座する。これにあわせて、各端子金具１３０の段付きロッド部１３１は、対応の各絶縁部材１１０の大径部１１３内に圧入され、その先端部により、当該大径部１１３内にて予備圧縮済みのシール原料粉末混合物１５４、抵抗体原料粉末混合物１５３及びシール原料粉末混合物１５１を、シール原料粉末混合物１５４からシール原料粉末混合物１５１にかけて対応の中心電極１２０の頭部１２１上に押圧する。
【０１２１】
以上のように、保持板１６０のプレス装置４００内への搬送後当該保持板１６０の各プラグ基礎構造体１５０がその端子金具１３０にて対応の絶縁部材１２０内に押圧により圧入される過程においては、保持板１６０の端部の方が保持板１６０の中央よりも放熱量が多く端部側プラグ基礎構造体１５０は速く冷却していく。その上、中央側プラグ基礎構造体１５０相互間で保温効果が発生して、端部側プラグ基礎構造体１５０は中央側プラグ基礎構造体１５０よりも冷却され易い。
【０１２２】
しかし、所定の熱容量をもつ端部側受け部材１７０を備えることで、端部側プラグ基礎構造体１５０から端部側受け部材１７０を介して保持板１６０に伝わる熱の量は減少し中央側プラグ基礎構造体１５０から保持板１６０に直接伝わる熱量に近づいていく。このため、各端部側プラグ基礎構造体１５０内のガラス粉末の軟化度合いは、各中央側プラグ基礎構造体１５０内の各ガラス粉末の軟化度合いに近似して維持される。
【０１２３】
よって、端部側及び中央側の各プラグ基礎構造体１５０のいずれにおいても、プラグ基礎構造体１５０毎には、シール原料粉末混合物１５４、抵抗体原料粉末混合物１５３及びシール原料粉末混合物１５１が、端子金具１３０による押圧でもって、均一な焼結密度にて、基端側ガラスシール層１４３、電気抵抗体１４２及び先端側ガラスシール層１４１からなる焼結導電体１４０として圧縮焼結される。また、端部側及び中央側の各プラグ基礎構造体１５０間では、上述のごとく、ガラス粉末の軟化度合いが近似しているため、端部側及び中央側の各プラグ基礎構造体１５０の焼結導電体１４０の焼結密度も互いに近似する。従って、端部側及び中央側の各プラグ基礎構造体１５０間の電気抵抗値のばらつきは非常に少なくなる。
【０１２４】
これにより、各プラグ基礎構造体１５０は相互に電気抵抗値（焼結導電体１４０の電気抵抗値）のばらつきの少ないプラグ本体１００として形成される。その結果、保持板１６０毎に、３６個のプラグ本体１００の各電気抵抗値は、ばらつくことなく、均質に確保され、歩留まりのよいプラグ本体１００の形成が可能となる。このようなプラグ本体１００の形成後は、プラグ本体１００に対し固定用筒状金具２００を組み付けることで、電気抵抗値のばらつきの少ない歩留まりの良好な抵抗体入りスパークプラグとしての製造が完了する。
（第２実施形態）
図１７は、本発明の第２実施形態の要部を示している。この第２実施形態では、各筒状受け部材１８０が、上記第１実施形態にて述べた各筒状受け部材１７０に代えて、図１７にて例示するごとく、採用されている。この第２実施形態においても、受け部材１８０には、上記第１実施形態にて述べた端部側及び中央側の各受け部材１７０にそれぞれ対応する端部側及び中央側の各受け部材１８０があるが、図１７は、中央側受け部材１８０を例示している。
【０１２５】
受け部材１８０は、端部側及び中央側の受け部材１７０のいずれであっても、プラグ基礎構造体１５０内の上記導電性ガラス粉末混合物（図１７にて符号１５５により示す）の全体を包囲するように、受け部材１７０よりも長い軸長を有している。また、受け部材１８０内には、段付き内孔１８１が同軸的に形成されており、この段付き内孔１８１は、プラグ基礎構造体１５０のつば状環状部１１５の外径よりも大きい内径を有する大径部１８２と、上記受け部材１７０の軸長及び内径を有する小径部１８３とを、上下に有する。また、段付き内孔１８１の大径部１８１の軸長は、受け部材１８０の軸長に合わせて長くしてある。なお、中央側及び端部側の各受け部材１８０のその他の構成は上記中央側及び端部側の各受け部材１７０とそれぞれ同様である。また、その他の構成は上記第１実施形態と同様である。
【０１２６】
このように構成した本第２実施形態では、各中央側受け部材１８０は、上記各中央側受け部材１７０と同様に、その小径部１８３側から上記第１実施形態にて述べた保持板１６０の各中央側保持孔部１６１内に図１７にて例示するごとく嵌装される。各端部側受け部材１８０は、上記各端部側受け部材１７０と同様に、その小径部１８３側から上記保持板１６０の各端部側保持孔部１６１内に嵌装される。
【０１２７】
また、上記第１実施形態にて述べた各プラグ基礎構造体１５０は、その先端側部位から、対応の各受け部材１８０内にその大径部１８２側から嵌装され、つば状環状部１１５の下端面１１６にて、大径部１８２の小径部１８３との境界底面に着座する。
【０１２８】
このような状態では、中央側及び端部側の各プラグ基礎構造体１５０のいずれであっても、各プラグ基礎構造体１５０のうちその先端部から導電性ガラス粉末混合物１５５の全体にかけて対応する軸方向対応部が、各対応の受け部材１８０により覆われる。
【０１２９】
従って、上述のように各受け部材１８０を介し各プラグ基礎構造体１５０を保持した保持板１６０が、上記第１実施形態にて述べたと同様に加熱室３１１内に搬送されて各プラグ基礎構造体１５０及び保持板１６０と共に加熱されると、各受け部材１８０は、その受熱量により、対応の各プラグ基礎構造体１５０内の導電性ガラス粉末混合物１５５の全体に対し上記相互間の保温効果を発揮する。
【０１３０】
ここで、受け部材１８０の軸長が受け部材１７０の軸長よりも長い分だけ、受け部材１８０の熱容量は、端部側及び中央側の各受け部材毎に、受け部材１７０よりも大きくなる。このため、各受け部材１８０の受熱量も、端部側及び中央側の各受け部材毎に、各対応の受け部材１７０の受熱量よりも多い。従って、導電性ガラス粉末混合物１５５の全体に対する上記相互間の保温効果は、上記第１実施形態に比べ、より一層向上する。その結果、各プラグ基礎構造体１５０内のガラス粉末の軟化状態は、導電性ガラス粉末混合物１５５の全体に亘り、良好に促進される。よって、焼結導電体１４０の焼結密度つまり電気抵抗値が、端部側及び中央側の各プラグ基礎構造体の双方において、より一層ばらつきなく確保され得る。
【０１３１】
また、本第２実施形態にて述べたように、上記受け部材１７０の軸長とは異なる軸長の受け部材を受け部材１８０として準備することで、プラグ基礎構造体１５０の軸長が上記第１実施形態と異なっていても、当該プラグ基礎構造体の保持板１６０の段付き内孔への保持が確実に行える。この意味では、種々の互いに軸長を異にする筒状受け部材を準備することで、各種の軸長のプラグ基礎構造体の保持板への保持が可能となる。その他の作用効果は、上記第１実施形態と同様である。
（第３実施形態）
図１８及び図１９は本発明の第３実施形態の要部を示している。この第３実施形態では、上記第１実施形態にて述べた保持板１６０において、各中央側保持孔部１６１のうち、図１９にて図示左右方向において互いに隣り合う各両中央側保持孔部１６１間には、貫通孔部１６６が図１８及び図１９にて示すごとく付加的に形成されている。各貫通孔部１６６は、図１８にて例示するように、小径部１６７及び大径部１６８を同軸的に上下に有し、それぞれ、保持板１６０の表面側と裏面側とを連通させている。その他の構成は上記第１実施形態と同様である。
【０１３２】
このように構成した本第３実施形態では、上述のように、各貫通孔部１６６が、各両隣接中央側保持孔部１６１間に形成されることで、中央側保持孔部１６１が格子状に位置する保持板１６０の中央の体積が減少する。このため、保持板１６０の中央の熱容量が、各貫通孔部１６６を設けない場合に比べて上記体積の減少分だけ小さくなる。このことは、本第３実施形態では、保持板１６０の中央が小熱容量部として形成されることを意味する。
【０１３３】
従って、上記第１実施形態と同様に、各受け部材１７０を介し各プラグ基礎構造体１５０を保持した保持板１６０が加熱室３１１内に搬送され、各受け部材１７０が、各プラグ基礎構造体１５０及び保持板１６０と共に加熱されると、保持板１６０の上記小熱容量部の受熱量は、上記第１実施形態にて述べた保持板１６０よりも、速く増大する。
【０１３４】
このため、各中央側受け部材１７０を介する上記小熱容量部から各中央側プラグ基礎構造体１５０の先端部位への伝熱が、上記第１実施形態に比べて、より一層促進されて、各中央側プラグ基礎構造体１５０内のガラス粉末の軟化がさらに進み各端部側プラグ基礎構造体１５０内のガラス粉末の軟化状態により一層近づく。その結果、焼結導電体１４０の焼結密度つまり電気抵抗値が、端部側及び中央側の各プラグ基礎構造体の双方において、より一層ばらつきなく確保され得る。その他の作用効果は上記第１実施形態と同様である。
（第４実施形態）
図２０及び図２１は、本発明の第４実施形態を示している。この第４実施形態では、複数の段付き円柱状保温部材１９０が付加的に採用されており、これら保温部材１９０は、図２１にて示すごとく、上記第１実施形態にて述べた保持板１６０（図８参照）において、その端部に沿うように、互いに隣り合う各端部側保持穴部１６１間にそれぞれ配設されている。
【０１３５】
各保温部材１９０は、図２０にて例示するごとく、それぞれ、円柱部１９１の軸方向中央につば状環状部１９２を形成して構成されている。当該各保温部材１９０は、図２０及び図２１から分かるように、円柱部１９１の下側部位にて、各貫通孔部１９９（後述する）内に同軸的に嵌装されて、環状部１９２にて、保持板１６０の表面１６４上に着座している。これにより、各円柱部１９１の上側部位は、保持板１６０の表面１６４から上方へ突出している。
【０１３６】
ここで、各貫通穴部１９９は、それぞれ、図２０にて例示するごとく、上記保持板１６０の互いに隣り合う各端部側保持孔部１６１の間に付加的に形成されている。なお、保温部材１９０は、金属材料やセラミック材料等の耐熱性のある材料でもって形成されている。
【０１３７】
また、本第４実施形態では、保持板１６０の板厚は、図２０にて例示するごとく、端部側保持孔部１６１の大径部１６２内に端部側受け部材１７０の全体を嵌装するようにしてある。また、保持板１６０の板厚は、図２０では図示されていないが、同様に、中央側保持孔部１６１内に中央側受け部材１７０の全体を嵌装するようにしてある。その他の構成は上記第３実施形態と同様である。
【０１３８】
このように構成した本第４実施形態では、上述のように、各貫通孔部１９９が、各両中央側保持孔部１６１間に形成されることで、上記加熱の際、端部側保持孔部１６１のうち互いに隣り合う保持孔部１６１間に配設された保温部材１９０にも保持板１６０から熱が伝わる。よって、端部側プラグ基礎構造体１５０の保持板１６０からの受熱量がさらに抑制され、より一層、中央側プラグ基礎構造体１５０の受熱量に近づいていく。
【０１３９】
また、加熱炉３１０から搬出された保持板１６０のプラグ基礎構造体１５０がその端子金具１３０にて対応の絶縁部材１１０内に押圧により圧入される過程においては、保温部材１９０が各両端部側保持孔部１６１間にて保持板１６０から上方へ突出することで、保温部材１９０と端部側プラグ基礎構造体１５０との保温効果により、端部側プラグ基礎構造体１５０の放熱量が、中央側プラグ基礎構造体１５０の放熱量により一層近づいていく。
【０１４０】
従って、本第４実施形態では、中央側プラグ基礎構造体１５０内のガラス粉末の軟化が端部側プラグ基礎構造体１５０内のガラス粉末の軟化状態により一層近づく。その結果、焼結導電体１４０の焼結密度つまり電気抵抗値が、端部側及び中央側の各プラグ基礎構造体の双方において、より一層ばらつきなく確保され得る。その他の作用効果は上記第１実施形態と同様である。
（第５実施形態）
図２２〜図２５は、本発明の第５実施形態の要部を示している。この第５実施形態では、上記第３実施形態にて述べた保持板１６０において、各貫通孔部１６６（図１８参照）に代えて、図２２〜図２５にて示すごとく、複数の円柱状凹部１６９が形成されている。当該各円柱状凹部１６９は、保持板１６０のすべての保持孔部１６１のうち、図２２及び図２４にて図示対角線方向において互いに隣り合う両保持孔部１６１毎に、両保持孔部１６１間の中央に、保持板１６０の裏面１６５側から形成されている。その他の構成は上記第３実施形態と同様である。
【０１４１】
このように構成した本第５実施形態では、上述のように、各凹部１６９が、各両隣接保持孔部１６１間の中央に形成されることで、保持板１６０のうち各端部側保持孔部１６１よりも中央側部位の体積を、当該保持板１６０の裏面側から減少させる。
【０１４２】
このため、保持板１６０の上記中央側部位の熱容量が、各凹部１６９を設けない場合に比べて上記体積の減少分だけ小さくなる。これにより、本第５実施形態では、保持板１６０の上記中央側部位が小熱容量部として形成されるが、この小熱容量部は、上記第３実施形態にいう小熱容量部よりも広い範囲に亘る。
【０１４３】
従って、上記第３実施形態と同様に、各受け部材１７０が、各プラグ基礎構造体１５０及び保持板１６０と共に加熱されると、保持板１６０の上記小熱容量部の受熱量は、上記第３実施形態にて述べた保持板１６０よりも、さらに速く増大する。
【０１４４】
これにより、各中央側受け部材１７０を介する上記小熱容量部から各中央側プラグ基礎構造体１５０の先端部位への伝熱が、より一層促進される。その結果、焼結導電体１４０の焼結密度つまり電気抵抗値が、端部側及び中央側の各プラグ基礎構造体の双方において、より一層ばらつきなく確保され得る。その他の作用効果は上記第３実施形態と同様である。
（第６実施形態）
図２６〜図２８は、本発明の第６実施形態の要部を示している。この第６実施形態では、上記第５実施形態にて述べた保持板１６０において、四角形状の凹所１９５が、各円柱状凹部１６９に代えて、図２７及び図２８にて示すごとく、形成されている。この凹所１９５は、保持板１６０の裏面１６５に形成されており、当該凹所１９５の内周壁は、保持板１６０の裏面１６５のうち、各端部側保持孔部１６１と、当該各端部側保持孔部１６１に隣接して位置する各中央側保持孔部１６１との間の中央を通り四角形状に構成されている。
【０１４５】
また、当該凹所１９５内には、各円筒部１９６が、図２８にて示すごとく、保持板１６０のうち各中央側保持孔部１６１の小径部１６３の軸を中心に形成されており、当該各円筒部１９６の外径は、対応の各中央側受け部材１７０の外径よりも大きくなっている。その他の構成は上記第５実施形態と同様である。
【０１４６】
このように構成した本第６実施形態では、上述のように、凹所１９５が、上述のように保持板１６０に四角形状に形成されることで、保持板１６０のうち各端部側保持孔部１６１よりも中央側部位の体積を、当該保持板１６０の裏面側から減少させる。
【０１４７】
これにより、本第６実施形態では、保持板１６０の上記中央側部位が小熱容量部位として形成されるが、この小熱容量部位は、上記第５実施形態にいう小熱容量部位よりも大きい。従って、本第６実施形態によれば、その小熱容量部位が、より一層大きな伝熱作用を発揮し、上記第５実施形態にて述べた電気抵抗値のばらつきがより一層抑制され得る。
（第７実施形態）
図２９は、本発明の第７実施形態の要部を示している。この第７実施形態では、上記第６実施形態にて述べた保持板１６０において、その裏面１６５側から、凹所１９７が、凹所１９５に代えて、形成されている。凹所１９７の内周壁は、上記凹所１９５の内周壁よりもさらに拡大されている。具体的には、凹所１９７の内周壁は、図２９にて示すごとく、各端部側保持孔部１６１の内周部のうち保持板１６０の中央側半周部まで拡大されている。
【０１４８】
これによれば、凹所１９７は、保持板１６０において上記第６実施形態にて述べた小熱容量部位よりもさらに広範囲に亘る小熱容量部を形成する。従って、より一層大きな伝熱作用を発揮して上記電気抵抗値のばらつきがより一層抑制され得ることで、上記第６実施形態にて述べた作用効果をより一層向上させる。
（第８実施形態）
図３０は、本発明の第８実施形態の要部を示している。この第８実施形態では、上記第７実施形態にて述べた保持板１６０において、上記凹所１９７に加え、各貫通孔部１９８が採用されている。各貫通孔部１９８は、図３２にて示すごとくく、凹所１９７内において、各中央側段付き内孔部１６１のうち、保持板１６０の図３０にて図示対角線方向に沿って互いに隣り合う両中央側段付き内孔部１６１毎に、両中央側段付き内孔部１６１の中央にて保持板１６０に貫通形成されている。
【０１４９】
これによれば、各貫通孔部１９８は、保持板１６０において上記第７実施形態にて述べた小熱容量部をさらに小さくした小熱容量部を形成する。従って、上記第７実施形態にて述べた作用効果をより一層向上させる。
（第９実施形態）
図３１は、本発明の第９実施形態の要部を示している。この第９実施形態では、上記第１実施形態にて述べた各保持孔部１６１は、図３１にて示すごとく、保持板１６０において、その図示上下方向に交叉する方向（例えば、４５°にて交叉する方向）に沿い形成されて格子状に配置されている。
【０１５０】
換言すれば、当該各保持孔部１６１は、互いに隣り合う４つずつでもって、保持板１６０の搬送方向（図３１にて図示上下方向）において、各菱形の４つの頂部に位置するように、保持板１６０に形成されている。但し、一つの菱形の各頂部に位置する各保持孔部１６１のうち、当該菱形の辺に沿って互いに隣り合う両頂部に位置する両保持孔部１６１の中心間隔（以下、辺方向間隔ともいう）は、共に同一である。
【０１５１】
ここで、互いに隣り合う両保持孔部１６１の中心間隔は、すべての保持孔部１６１に関し、同一に設定されている。また、各保持孔部１６１のうち保持板１６０の端部に沿って位置する各保持孔部は上記端部側保持孔部１６１を構成し、残りの各保持孔部１６１は上記中央側保持孔部１６１を構成する。
【０１５２】
また、各端部側保持孔部１６１のうち、図３１にて図示左端に位置する各端部側保持孔部１６１の中心と保持板１６０の左端との間の図示左右方向間隔及び図示右端に位置する各端部側保持孔部１６１の中心と保持板１６０の右端との間の図示左右方向間隔は、上記辺方向間隔よりも広い。これは、保持板１６０の端部のうち左右方向の端部でも、受熱量が、上述のごとく、当該保持板１６０の中央よりも多いことから、当該左右方向の端部の熱が、各端部側受け部材１７０及び各端部側プラグ基礎構造体１５０の先端側部位に伝わりにくいようにするためである。
【０１５３】
また、このように構成した保持板１６０が、複数、図３１にて示すごとく、搬送方向に連続して隣接する場合、先行の保持板１６０の搬送方向後端に位置する端部側保持孔部１６１と、当該先行保持板１６０に後続する保持板１６０の搬送方向先端に位置する端部側保持孔部１６１との間の中心間隔は、上記搬送方向において、後続保持板１６０（或いは、先行保持板１６０）の各保持孔部１６１のうち搬送方向に沿って隣り合う両端部側保持孔部１６１の中心間隔に等しくなっている。これは、加熱室３１１内での加熱の際に、保持板１６０毎のプラグ基礎構造体１５０への熱の影響を、連続する先行及び後続の両保持板１６０間においても、均一にするためである。その他の構成は上記第１実施形態と同様である。
【０１５４】
このように構成した本第９実施形態では、上記第１実施形態にて述べたと同様に、各プラグ基礎構造体１５０を各受け部材１７０を介し保持した各保持板１６０が、連続して順次加熱室３１１内に搬送されると、各プラグ基礎構造体１５０及び各受け部材１７０は、保持板１６０毎に、当該保持板１６０と共に加熱される。
【０１５５】
この加熱の際、上述のごとく、保持板１６０の左端に位置する各端部側保持孔部１６１の中心と保持板１６０との左端との間の左右方向間隔及び保持板１６０の右端に位置する各端部側保持孔部１６１の中心と保持板１６０との右端との間の左右方向間隔は、共に、上記辺方向間隔よりも広い。このため、保持板１６０の左右方向の端部の熱が、各端部側受け部材１７０の先端側部位及び各端部側プラグ基礎構造体１５０の先端側部位に伝わりにくい。
【０１５６】
従って、当該各端部側受け部材１７０内のガラス粉末の軟化は上記第１実施形態よりも進みにくい。このため、保持板１６０毎の各プラグ基礎構造体１５０では、端部側プラグ基礎構造体１５０の焼結導電体１４０の焼結密度（つまり、電気抵抗値）と中央側プラグ基礎構造体１５０の焼結導電体１４０の焼結密度（つまり、電気抵抗値）との間のばらつきが上記第１実施形態よりもさらに少なくなる。
【０１５７】
また、上述のごとく、先行の保持板１６０の搬送方向後端に位置する端部側保持孔部１６１と、当該先行保持板１６０に後続する保持板１６０の搬送方向先端に位置する端部側保持孔部１６１との間の中心間隔は、上記搬送方向において、先行保持板１６０の各保持孔部１６１のうち搬送方向に沿って隣り合う両端部側保持孔部１６１の中心間隔に等しい。
【０１５８】
従って、後続保持板１６０及びその各受け部材１７０並びに各プラグ基礎構造体１５０は、先行保持板１６０及びその各受け部材１７０並びに各プラグ基礎構造体１５０と同様の受熱状態におかれる。このため、先行及び後続の両保持板１６０間においても、各プラグ基礎構造体１５０の電気抵抗値のばらつきが、上述と同様に少なくなる。
【０１５９】
その結果、連続する保持板１６０を、その各受け部材１７０及び各プラグ基礎構造体１５０と共に加熱しても、保持板１６０毎に、プラグ基礎構造体１５０の電気抵抗値がばらつくことがなく、連続する各保持板１６０に亘り、歩留まりのよいプラグ本体１００の形成が可能となる。
（第１０実施形態）
図３２は、本発明の第１０実施形態の要部を示している。この第１０実施形態では、上記第１実施形態にて述べた搬送装置３２０において、リニアアクチュエータ３２５を廃止するとともに、保持板１６０を加熱装置３００に搬入する搬入装置５００を採用し、かつ、加熱室３１１の入り口側にもシャッター３３０を開閉可能に配設した構成となっている。
【０１６０】
搬入装置５００は、図３２にて示すごとく、互いに平行な両端部部材５０１と、複数のローラ５０２とを備えている。各ローラ５０２は、図３２にて示すごとく、両端部部材５０１間にこれら端部部材５０１に対し直交するように互いに間隔をおいて回転可能に支持されている。ここで、搬入装置５００は、各ローラ５０２を搬入路３１８の搬入方向に向けて当該搬入路３１８上に配置される（図３２参照）。また、当該搬入装置５００が搬入路３１８の加熱室３１２の入り口に対向する部位に位置したとき、この位置にて両端部部材５０１を静止状態に維持したまま、各ローラ５０２は両端部部材５０１間にて図３２にて図示右側方向へ回転するようになっている。その他の構成は上記第１実施形態と同様である。
【０１６１】
このように構成した本第１０実施形態において、各プラグ基礎構造体１５０を支持した保持板１６０を搬入装置５００上にのせて、当該搬入装置５００を、搬入路３１８に沿い図３２にて図示矢印方向に搬入する。そして、この搬入装置５００が加熱室３１２の入り口に対向する部位に達したとき、当該搬入装置５００の各ローラ５０２が両端部部材５０１間にて加熱室３１２方向に回転する。このとき、加熱室３１２の入り口側のシャッター３３０が開く。
【０１６２】
このため、保持板１６０は、搬入装置５００の各ローラ５０２によりその回転でもって加熱室３１２内に送り込まれる。その後、上記第１実施形態にて述べたと同様に、各プラグ基礎構造体１５０を支持した保持板１６０は、両搬送コンベア３２１により加熱室３１２内にて搬送され加熱される。
【０１６３】
以上のように、搬入装置５００を採用すれば、上記第１実施形態にて述べたリニアアクチュエータ３２５に依ることなく、各プラグ基礎構造体１５０を支持した保持板１６０を円滑に順次加熱室３１２内に搬入して加熱に付すことができる。その他の作用効果は上記第１実施形態と同様である。
【０１６４】
なお、本発明の実施にあたり、上記各実施形態に限ることなく、以下のような種々の変形例が挙げられる。
（１）保持板１６０には、保持孔部１６１に限ることなく、例えば、単なる貫通状保持孔部を形成するようにしてもよい。この場合には、受け部材１７０或いは１８０の上端に環状フランジを同軸的に設け、受け部材１７０或いは１８０をそのフランジにて上記貫通状保持孔部の上端部に着座させるようにして当該貫通状保持孔部に嵌装する。
（２）保持板１６０は、四角板形状に限ることなく、適宜な板形状をとり得る。ここで、保持板１６０は、伝熱性の他、耐熱性及び耐酸化性を有することが望ましい。
（３）受け部材１７０或いは１８０は、筒状に限ることなく、環状その他の中空状を有すればよい。
（４）受け部材１７０或いは１８０は、端部側受け部材のみとし、中央側受け部材を廃止してもよい。この場合には、各中央側プラグ基礎構造体１５０は、直接、保持板１６０の各中央側保持孔部１６１内に嵌装する。これによっても、上記第１実施形態と同様の作用効果を達成できる。
（５）抵抗体入りスパークプラグに限ることなく、抵抗体を有しないスパークプラグに本発明を適用してもよい。この場合には、プラグ基礎構造体内の導電性ガラス粉末混合物がシール原料粉末混合物１５１或いは１５４のみで構成される。
（６）加熱室３１１内のガスバーナは、下側ガスバーナのみで構成してもよい。また、加熱室３１１内の加熱源は、ガスバーナに限ることなく、例えば、電気ヒータであってもよく、さらには、ガスバーナと電気ヒータとを組み合わせたものであってもよい。
（７）搬送コンベア３２１、４２０は、上記実施形態にて述べた構成に限ることなく、保持板１６０を搬送方向に搬送できる構成であればどのような搬送機構であってもよい。
（８）絶縁部材１１０は筒状に限ることなく中空状であればよい。固定用端子金具２００の金属筒体部２１０は、筒体に限ることなく中空体であればよく、また、この中空体に軸方向に切り割りを形成したものでもよい。
（９）中心電極１２０及び端子金具１３０は、柱状に限ることなく、絶縁部材１１０内に挿入できる構成であれば必要に応じて適宜形状変更してもよい。
（１０）保温部材１９０は、円柱状に限ることなく、例えば、円柱部１９１の下側部位を貫通孔部１６８に嵌装させて着座する構成であれば、円柱部１９１の上側部位及びつば状環状部１９２の形状を適宜変更してもよい。
（１１）上記第１〜第１０の各実施形態を互いに適宜組み合わせれば、上述した電気抵抗値のばらつきの抑制をより一層向上させ得る。
【図面の簡単な説明】
【図１】本発明の第１実施形態にて製造される抵抗入りスパークプラグの一例を示す断面図である。
【図２】図１の抵抗体入りスパークプラグにおけるプラグ基礎構造体の組立工程を示す図である。
【図３】図１の抵抗体入りスパークプラグにおけるプラグ基礎構造体の組立工程を示す図である。
【図４】図１の抵抗体入りスパークプラグにおけるプラグ基礎構造体の組立工程を示す図である。
【図５】図１の抵抗体入りスパークプラグにおけるプラグ基礎構造体の組立工程を示す図である。
【図６】上記プラグ基礎構造体の断面図である。
【図７】上記プラグ基礎構造体の断面図である。
【図８】図６及び図７の保持板の平面図である。
【図９】上記第１実施形態における製造装置の図１０にて９−９線に沿う部分破断概略断面図である。
【図１０】図９にて１０−１０線に沿う拡大断面及び部分拡大断面を示す図である。
【図１１】図９にて１１−１１線に沿う要部拡大断面図である。
【図１２】図１１にてリニアアクチュエータの作動との関係で示す要部拡大断面図である。
【図１３】図１１にてリニアアクチュエータの作動との関係で示す要部拡大断面図である。
【図１４】図１２の要部拡大断面図である。
【図１５】図１２のプレス装置の部分破断断面図である。
【図１６】上記プラグ基礎構造体の端子金具圧入後の断面図である。
【図１７】本発明の第２実施形態の要部を示す拡大断面図である。
【図１８】本発明の第３実施形態の要部を示す断面図である。
【図１９】上記第３実施形態における保持板の平面図である。
【図２０】本発明の第４実施形態の要部を示す断面図である。
【図２１】上記第４実施形態における保持板の平面図である。
【図２２】本発明の第５実施形態における保持板の平面図である。
【図２３】図２２にて２３−２３線に沿う断面図である。
【図２４】上記第５実施形態における保持板の裏面図である。
【図２５】図２４にて２５−２５線に沿う断面図である。
【図２６】本発明の第６実施形態における保持板の平面図である。
【図２７】上記第６実施形態における保持板の裏面図である。
【図２８】図２６にて２８−２８線に沿う断面図である。
【図２９】本発明の第７実施形態の要部を示す裏面図である。
【図３０】本発明の第８実施形態の要部を示す裏面図である。
【図３１】本発明の第９実施形態の要部を示す平面図である。
【図３２】本発明の第１０実施形態の要部を示す断面図である。
【符号の説明】
１００…プラグ本体、１１０…絶縁部材、１２０…中心電極、
１３０…端子金具、１４０…焼結導電体、１５０…プラグ基礎構造体、
１５１、１５４…シール原料粉末混合物、１５３…抵抗体原料粉末混合物、
１５５…導電性ガラス粉末混合物、１６１…保持孔部、１６４…表面、
１６５…裏面、１６６、１６８…貫通孔部、１６９…凹部、
１７０、１８０…受け部材、１９０…保温部材、１９５、１９７…凹所、
１９６…円筒部、２２０…接地電極、３００…加熱装置、
３１１、３１２…加熱室、３２１、４２０…搬送コンベア、４００…プレス装置。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for manufacturing a spark plug.
[0002]
[Prior art]
Conventionally, as an example of a spark plug, there is a so-called resistor-containing spark plug. This spark plug including a resistor includes a plug body and a fixing tubular metal fitting having a ground electrode. As a method for manufacturing the spark plug including the resistor, there is one disclosed in Patent Document 1 below.
[0003]
According to this manufacturing method, first, a cylindrical insulating member, a column-shaped center electrode fitted coaxially in the distal end portion of the insulating member, and coaxially inserted in the proximal end portion of the insulating member. Provided with the above-mentioned terminal fitting and a conductive glass powder mixture comprising a conductive glass powder and an electric resistance material powder (including glass powder) provided in a laminated state between the terminal fitting and the center electrode in the insulating member. A plug body (hereinafter, referred to as a plug basic structure) in a state before press-fitting by pressing a metal fitting is assembled.
[0004]
Then, the plug substructure assembled in this manner is carried into a heating furnace and heated, then carried out of the heating furnace, and the terminal fitting is pressed into the base end portion of the insulating member by pressing. As a result, the above-described conductive glass powder mixture is compressed by pressure between the terminal fitting and the center electrode, and is sintered and formed as a sintered conductor having an electric resistor interposed between the two glass seal layers. The plug substructure is completed as a plug body.
[0005]
Here, in the manufacturing method, the carrying-in heating of the plug substructure into the heating furnace and the press-fitting of the terminal fittings are performed as follows. A plurality of plug substructures described above are prepared, and each of these plug substructures is held on a holding plate. This holding is performed by fitting each of the plug substructures in the holding hole portion of the holding plate in the axial direction at the front end portion thereof.
[0006]
The holding plate thus held is horizontally supported so that the plug substructures extend upward, and is carried into the heating furnace to be heated. Thereafter, the holding plate is carried out of the heating furnace while holding each of the plug substructures as described above, and the terminal fittings of each of the plug substructures are connected to the base of the corresponding insulating member by a press device. It is press-fitted into the end portion by pressing.
[0007]
[Patent Document 1]
JP 11-251033 A
[0008]
[Problems to be solved by the invention]
By the way, in the above manufacturing method, the electric resistance value of the sintered conductor formed by sintering as described above is specified by the material component of the conductive glass powder mixture and the sintering density of the material component. In general, the electric resistance value of a spark plug containing a resistor is greatly influenced by the heating state of the plug basic structure in the heating furnace and the cooling state of the plug basic structure until the terminal fitting is pressed after this heating. It is said that
[0009]
However, when each plug substructure is heated in a heating furnace as described above, the holding plate is also heated. Since the holding plate has a thickness and heat conductivity, the heat energy usually acts more on the end side than on the center side of the holding plate during the heating. Therefore, the amount of heat received at the end of the holding plate is greater than the amount of heat received at the center of the holding plate.
[0010]
Therefore, the amount of heat received by the plug substructure located along the end of the holding plate (hereinafter, referred to as an end plug substructure) also follows the increase in the amount of heat received at the end of the holding plate, and the remaining plugs It is larger than the amount of heat received by the foundation structure (hereinafter, referred to as the center plug foundation structure). In other words, the degree of softening of the glass powder in the conductive glass powder mixture in the end-side plug substructure is higher than the degree of softening of the glass powder in the conductive glass powder mixture in the center-side plug substructure. .
[0011]
Therefore, in each plug substructure of the holding plate carried out of the heating furnace, when the terminal fitting is pressed into the base end portion of the insulating member as described above, the compressive force on the conductive glass powder mixture by the press fitting is: It acts relatively weaker on the central plug substructure than on the end plug substructure. Therefore, the sintering density of the conductive glass powder mixture in the central plug substructure is lower than the sintering density of the conductive glass powder mixture in the end plug substructure. As a result, the electric resistance of the sintered conductor in the center plug substructure becomes larger than the electric resistance of the sintered conductor in the end plug substructure.
[0012]
In other words, the density of sintering of the conductive glass powder mixture in each plug substructure held by the holding plate is lower than that of the end plug substructure that receives more heat than the central plug substructure that receives less heat. The lowering in the body causes variations in electrical resistance between the plug substructures as described above.
[0013]
From the above, the electric resistance value of the spark plug containing the resistor is determined by the heating condition of the plug basic structure in the heating furnace described above and the plug basic structure during the heating up to the terminal fitting press-fitting. Not only specified by the cooling condition, but also by the difference in the amount of heat received between the end side and the center side of the holding plate at the time of the above heating, and as a result, the electric resistance between the spark plugs containing each resistor is changed. The values were found to vary greatly.
[0014]
In view of the above, an object of the present invention is to provide a method and an apparatus for manufacturing a spark plug in which variations in electric resistance between spark plugs are suppressed as much as possible.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, in the method for manufacturing a spark plug according to the present invention, according to the first aspect, the center electrode (120) fitted axially to the distal end side of the hollow insulating member (110) is provided. A terminal fitting (130) axially inserted on the base end side of the insulating member, and a conductive glass powder mixture (151, 153, 154, 155) provided in the insulating member between the center electrode and the terminal fitting. Are prepared, and a holding plate (160) is prepared by forming a plurality of holding holes (161) through the holes in a discrete manner.
[0016]
The plug substructure located along the end of the holding plate among the plurality of plug substructures (hereinafter referred to as an end plug substructure) is more thermally conductive at the tip end than the holding plate. A holding hole positioned along an end of the holding plate among the plurality of holding holes through a hollow receiving member (170, 180) (hereinafter, referred to as an end receiving member) made of a heat transfer material having a low rate. (Hereinafter, referred to as an end-side holding hole), and the remaining plug base structure (hereinafter, referred to as a center-side plug base structure) is attached to the remaining holding hole (hereinafter, referred to as a center) at its distal end. The plurality of plug substructures are held by the holding plate by directly fitting into the side holding holes.
[0017]
Then, with the plurality of plug substructures supporting the holding plate so as to extend upward from the holding plate, the plurality of plug substructures are softened so that the glass powder in the conductive glass powder mixture is softened. In addition, heated together with the holding plate and the end side receiving member,
After this heating, the holding plate holding the plurality of plug substructures is conveyed to the outside air in the above-mentioned supporting state,
The terminal fittings of each of the plurality of plug substructures are pressed into the corresponding insulating member in the axial direction by pressing, and the conductive glass powder mixture in the corresponding insulating member is compressed and sintered to form a sintered conductor (140). ), Each of the plurality of plug substructures is formed as a plug body.
[0018]
According to this, as described above, the end-side plug substructure is passed through the end-side receiving member made of a heat-transfer material having a lower thermal conductivity than the holding plate on the front end side, and The plurality of plug substructures are held by the holding plate by fitting the center plug substructure directly into the center side holding hole at the distal end thereof while being fitted into the holding hole.
[0019]
For this reason, at the time of the above-mentioned heating, the end of the holding plate receives a larger amount of heat than the center of the holding plate, and the end-side plug substructure is rapidly heated. Further, since the plug substructures extend upward from the holding plate side by side with each other, the end plug substructures are more likely to hit the air heated by the heating as compared with the center plug substructure. , Easy to heat. However, by providing the end-side receiving member having a predetermined heat capacity, the amount of heat transmitted from the end of the holding plate to the end-side plug basic structure via the end-side receiving member can be reduced. Approaching the amount of heat transmitted directly to
[0020]
Further, after the above-mentioned heating, in a process in which the plug substructure of the holding plate carried out into the outside air is pressed into the corresponding insulating member by the terminal fitting by pressing, the end of the holding plate is held by the holding member. More heat is dissipated than in the center of the plate, and the end plug substructure cools faster. In addition, a heat retention effect occurs between the central plug substructures, and the end plug substructures are more likely to be cooled than the central plug substructures. However, by providing the end receiving member having a predetermined heat capacity, the amount of heat transmitted from the end plug basic structure to the holding plate via the end receiving member is directly transmitted from the central plug basic structure. Approaching the calorific value.
[0021]
Therefore, the degree of softening of the glass powder in the end plug substructure is maintained close to the degree of softening of the glass powder in the center plug substructure. For this reason, the sintered densities of the sintered conductors of the plug substructures on the end and center sides, that is, the electric resistance values are also close to each other. As a result, it is possible to manufacture a spark plug having a small variation in electric resistance value and a good yield.
[0022]
The holding plate is not limited to a quadrangle but may be a polygon such as a hexagon or other various shapes. However, a holding hole formed through the end of the holding plate (an end side holding hole). ) Is, for example, a square holding plate formed by penetrating the holding holes in a lattice shape, when viewed from the upper surface, the holding plate has each holding hole located along any one of the four sides. Among the lines passing through the center and parallel to any one of the above sides (referred to as parallel center lines), they correspond at least to holding holes passing through the parallel center line closest to any one of the sides (see FIG. 8 described later). Alternatively, see FIG. 31).
[0023]
According to a second aspect of the present invention, in the method for manufacturing a spark plug according to the first aspect, the center-side plug substructure also has a thermal conductivity higher than that of the holding plate at the distal end side. The other holding member (170, 180) (hereinafter, referred to as a center side receiving member) made of a heat transfer material having a low heat transfer material is fitted into the corresponding center side holding hole portion, whereby the holding by the holding plate is performed. I do.
[0024]
Thereafter, with the holding plate being supported so as to maintain the upward extension of the plurality of plug substructures, the heating is performed including the center-side receiving member. Here, the end-side receiving member is formed so as to have a larger heat capacity than the central-side receiving member.
[0025]
According to this, the center-side plug substructure is also fitted in the center-side holding hole at the tip end side through the center-side receiving member made of a heat transfer material having a lower thermal conductivity than the holding plate.
[0026]
For this reason, at the time of the above-mentioned heating, the end part of the holding plate receives more heat than the center of the holding plate, and the end-side plug substructure heats up quickly. Further, since the plug substructures extend upward from the holding plate side by side with each other, the end plug substructures are more likely to hit the air heated by the heating as compared with the center plug substructure. , Easy to heat. However, by providing the end receiving member having a larger heat capacity than the center receiving member, the amount of heat transmitted from the end of the holding plate to the end plug substructure via the end receiving member is maintained. The amount of heat transmitted from the center of the plate to the central plug substructure via the central receiving member is approached.
[0027]
Further, in a process in which the plug base structure of the holding plate carried out into the outside air is pressed into the corresponding insulating member by the terminal fitting by pressing, the end of the holding plate is closer to the center of the holding plate. Also, the heat dissipation amount is large, and the end side plug substructure cools rapidly. In addition, a heat retention effect occurs between the central plug substructures, and the end plug substructures are more likely to be cooled than the central plug substructures. However, by providing the end-side receiving member having a larger heat capacity than the center-side receiving member, the amount of heat transmitted from the end-side plug base structure to the holding plate via the end-side receiving member is reduced. It approaches the amount of heat transmitted from the structure to the holding plate via the central receiving member.
[0028]
Therefore, the degree of softening of the glass powder in the end plug substructure is maintained close to the degree of softening of the glass powder in the center plug substructure. As a result, similarly to the first aspect of the invention, it is possible to manufacture a spark plug having a small variation in electric resistance value and a good yield.
[0029]
According to a third aspect of the present invention, there is provided a method of manufacturing a spark plug according to the second aspect, wherein the end-side receiving member is formed so as to have a larger heat capacity than the center-side receiving member. The difference is that the thermal conductivity of the end-side receiving member is lower than the thermal conductivity of the central-side receiving member.
[0030]
According to this, at the time of the heating and during the subsequent transfer to the outside air, the end-side receiving member has a lower thermal conductivity than the center-side receiving member. It exerts the same heat effect as having a larger heat capacity. As a result, according to the third aspect of the invention, substantially the same operation and effect as the second aspect of the invention can be achieved from the viewpoint of suppressing the variation in the electric resistance of the spark plug.
[0031]
According to a fourth aspect of the present invention, in the method for manufacturing a spark plug according to the third aspect, the end-side receiving member is formed so as to have a larger heat capacity than the center-side receiving member. It is characterized by having.
[0032]
According to this, at the time of the heating and during subsequent transportation to the outside air, the end-side receiving member has a larger heat capacity than the center-side receiving member, and the end-side receiving member has a larger heat capacity than the center-side receiving member. Also act synergistically with the low thermal conductivity to further enhance the thermal effect. As a result, according to the invention of the fourth aspect, the operation and effect of the invention of the third aspect can be further improved from the viewpoint of suppressing the variation of the electric resistance value of the spark plug.
[0033]
According to a fifth aspect of the present invention, in the method for manufacturing a spark plug according to any one of the first to fourth aspects, each of the receiving members has a conductive property of the corresponding plug substructure. It is characterized by being a cylindrical receiving member (180) formed so as to also cover the corresponding part for the glass powder mixture.
[0034]
According to this, from the tip of the plug substructure to the entire periphery of the conductive glass powder mixture, it is covered with the corresponding receiving member. Therefore, at the time of the above-mentioned heating, the receiving member exerts a mutual heat-retaining effect on the entire conductive glass powder mixture in the corresponding plug substructure. Therefore, the softened state of the glass powder in the plug substructure is favorably promoted throughout the conductive glass powder mixture. As a result, the operation and effect of the invention according to any one of claims 1 to 4 can be further improved.
[0035]
According to a sixth aspect of the present invention, in the method for manufacturing a spark plug according to any one of the first to fifth aspects, the holding plate is located at a position closer to the center than the end-side holding hole. , Is characterized in that it is formed in a concave shape so as to have a smaller heat capacity than the end of the holding plate and configured as small heat capacity portions (164, 165, 166, 169, 195, 196, 197).
[0036]
According to this, during the heating, the amount of heat received by the small heat capacity portion formed in the concave shape increases faster than that of the holding plate having no small heat capacity portion formed in the concave shape. Therefore, the softening of the glass powder in the central plug substructure receiving heat transfer from the small heat capacity portion formed in the concave shape is further promoted, and the glass powder in the end plug substructure is further approximated to the softened state. I do. As a result, the function and effect of the invention according to any one of claims 1 to 5 can be further improved.
[0037]
In addition, the concave depth of the small heat capacity portion is appropriately set so that the amount of heat between the end-side plug base structure and the center-side plug base structure approaches each other. The concave shape may be a penetrating shape.
[0038]
According to a seventh aspect of the present invention, in the method for manufacturing a spark plug according to any one of the first to sixth aspects, the holding plates are adjacent to each other in the end side holding holes. A heat retaining member (190) is provided between the holding holes so as to protrude above the holding plate.
[0039]
According to this, at the time of the above-mentioned heating, heat is transmitted from the holding plate also to the heat insulating member disposed between the adjacent holding holes in the end side holding holes. Therefore, the amount of heat received from the holding plate of the end-side plug basic structure is further suppressed, and the amount of heat received further approaches the amount of heat received by the central-side plug basic structure. Further, in a process in which the plug basic structure of the holding plate carried out into the outside air after the heating is pressed into the corresponding insulating member by the terminal fitting by pressing, the heat retaining member and the end side plug basic structure Due to the heat retention effect described above, the amount of heat radiation of the end-side plug substructure is even closer to the amount of heat radiation of the center-side plug substructure. Therefore, the softening of the glass powder in the central plug substructure approaches the softened state of the glass powder in the end plug substructure. As a result, the operation and effect of the invention according to any one of claims 1 to 6 can be further improved.
[0040]
Further, according to the present invention, according to the eighth aspect, in the method for manufacturing a spark plug according to any one of the first to seventh aspects, the holding plate has a crossing direction with respect to the conveyance direction or the conveyance direction. A rectangular holding plate formed with the holding holes along the direction and arranged in a lattice, and the center of the holding holes located at one of both ends of the holding holes in the direction orthogonal to the transport direction. The distance between one of the two ends in the orthogonal direction and the distance between the center of the holding hole located at the other of the two ends in the orthogonal direction and the other of the two ends in the orthogonal direction is the center of the holding hole adjacent to the shortest distance. It is wider than the interval.
[0041]
According to this, it is difficult for the heat at the end in the orthogonal direction of the holding plate to be transmitted to the end-side plug substructure. Therefore, the softening of the glass powder in the end-side receiving member does not easily progress. For this reason, the electrical resistance value of the plug substructure may vary between the sintered density of the sintered conductor of the end plug substructure and the sintered density of the sintered conductor of the center plug substructure. Is even less. As a result, the function and effect of the invention according to any one of claims 1 to 7 can be further improved.
[0042]
According to a ninth aspect of the present invention, in the method for manufacturing a spark plug according to any one of the first to eighth aspects, the holding plate is adjacent to the holding hole at the shortest distance. It is characterized in that the holding holes are formed so as to have the same center spacing.
[0043]
According to this, the softening of the glass powder in the central plug substructure due to the mutual heat retaining effect between the central plug substructures can be achieved more uniformly. As a result, the function and effect of the invention described in any one of claims 1 to 8 is further improved.
[0044]
According to a tenth aspect of the present invention, in the method for manufacturing a spark plug according to any one of the first to ninth aspects, a plurality of holding plates are extended upward of the plug basic structure. The heating was performed by supporting the sheet so as to maintain the protrusion and continuously arranging it in the transport direction without any gap.
[0045]
According to this, it is possible to reduce the variation in the thermal environment of the plug substructure between the holding plates during the heating, and as a result, the variation in the electric resistance value between the plug substructures of the continuous holding plates is reduced. Can also be reduced.
[0046]
According to the eleventh aspect of the present invention, in the spark plug manufacturing method according to the tenth aspect, the center of the holding hole on the rear end side in the transport direction among the holding holes of the holding plate. The interval between the center of the holding hole on the leading end side in the conveyance direction of the holding holes of the holding plate arranged in the conveyance direction following the conveyance direction is the distance between the holding holes adjacent to each other at the shortest distance among the holding holes. It is characterized in that it is the same as the center interval.
[0047]
According to this, the succeeding holding plate and its receiving member and the plug basic structure are placed in the same heat receiving state as the preceding holding plate and its receiving member and the plug basic structure. For this reason, even between the preceding and succeeding holding plates, the variation in the electric resistance value of the plug basic structure is reduced in the same manner as described above. As a result, even if the continuous holding plate is heated together with the receiving member and the plug substructure, the electric resistance value of the plug substructure does not vary in the holding plate, and the yield is reduced over the continuous holding plate. A good spark plug can be manufactured. As a result, the function and effect of the invention described in claim 10 can be further improved.
[0048]
According to a twelfth aspect of the spark plug manufacturing apparatus according to the present invention,
A heating device (300) including a heating chamber (311), and a heating-chamber transfer mechanism (321) supported in the heating chamber so as to be horizontally transferable from an entrance to an exit thereof;
A press device (400) disposed at the exit of the heating chamber so as to have a transport mechanism for a press device (420) supported so as to be capable of being transported in the horizontal direction from the exit of the heating chamber to the transport direction of the transport mechanism for the heating chamber; Is provided.
[0049]
A center electrode (120) fitted axially on the distal end side of the hollow insulating member (110); a terminal fitting (130) inserted axially on the base end side of the insulating member; A plurality of plug substructures (150) each including a conductive glass powder mixture (151, 153, 154, 155) provided in an insulating member between a metal fitting are prepared, and a plurality of holding holes (161) are prepared. ) Is prepared in a discrete manner to provide a heat conductive holding plate (160).
[0050]
Accordingly, of the plurality of plug substructures, the plug substructure located along the end of the holding plate (hereinafter, referred to as an end plug substructure) is heated more at the tip side than the holding plate. A holding hole located along the end of the holding plate among the holding holes, passing through hollow receiving members (170, 180) (hereinafter, referred to as end side receiving members) made of a heat conductive material having low conductivity. (Hereinafter, referred to as an end-side holding hole), and the remaining plug basic structure (hereinafter, referred to as a center-side plug basic structure) is attached to the remaining holding hole (hereinafter, referred to as a center side) at its distal end. The plurality of plug substructures are held by the holding plate by directly fitting into the holding holes.
[0051]
Next, the holding plate is supported by the heating chamber transfer mechanism so that the plurality of plug substructures extend upward from the holding plate, and is carried into the heating chamber.
In the heating chamber, the plurality of plug substructures are heated together with the holding plate and the end side receiving member so that the glass powder in the conductive glass powder mixture is softened,
After this heating, the holding plate holding the plurality of plug substructures is carried out from the exit of the heating chamber by the heating chamber transfer mechanism, and is carried into the press device by the press device transfer mechanism,
With this press device, each terminal fitting of the plurality of plug substructures is pressed into the corresponding insulating member in the axial direction by pressing, and the conductive glass powder mixture in the corresponding insulating member is compressed and sintered to form a sintered conductive material. By forming as a body (140), each of the plurality of plug substructures is formed as a plug body.
[0052]
According to this, it is possible to provide a spark plug manufacturing apparatus capable of achieving the same operation and effect as the invention described in claim 1.
[0053]
In the description of each of claims 1 and 12, the term "discrete" includes a lattice shape, and means that the formation of the holding holes on the holding plate is dispersed. Further, the reference numerals in parentheses of the above-mentioned units indicate the correspondence with specific units described in the embodiments described later.
[0054]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(1st Embodiment)
FIG. 1 shows an example of a spark plug with a resistor for an internal combustion engine manufactured according to a first embodiment of the present invention. The spark plug with a resistor includes a plug body 100 and a fixing cylindrical metal fitting 200.
[0055]
The plug body 100 includes a cylindrical insulating member 110, a columnar center electrode 120, and a columnar terminal fitting 130. In the cylindrical insulating member 110, a stepped inner hole 111 penetrates coaxially with the insulating member 110. Is formed. Here, the stepped inner hole 111 has a small-diameter portion 112 at a distal end portion (lower side in FIG. 1) of the insulating member 110 and a base end side portion (shown in FIG. 1) of the insulating member 110. On the upper side), a large diameter portion 113 having a larger diameter than the small diameter portion 112 is provided.
[0056]
The columnar center electrode 120 is coaxially fitted in the small diameter portion 112 of the insulating member 110, and the center electrode 120 is connected to the small diameter portion 112 from within the large diameter portion 113 at the raised head 121. And is exposed outward from the distal end of the small-diameter portion 112 at the distal end portion 122 thereof.
[0057]
The columnar terminal fitting 130 is axially press-fitted into the large-diameter portion 113 of the insulating member 110 from the tip side at the stepped rod portion 131, and the terminal fitting 130 is It is seated on the base end 114 of the insulating member 110.
[0058]
Further, the plug body 100 includes a columnar sintered conductor 140, and the sintered conductor 140 is provided between the head 121 of the center electrode 120 and the terminal fitting 130 within the large diameter portion 113 of the insulating member 110. It is interposed between the distal end portion 133. The sintered conductor 140 includes a glass seal layer 141 (hereinafter, also referred to as a distal glass seal layer 141), an electric resistor 142, and a glass seal layer 143 (hereinafter, also referred to as a proximal glass seal layer 143). Have been. The distal glass seal layer 141 is located on the head 121 side of the center electrode 120, while the proximal glass seal layer 143 is located on the distal end 133 side of the stepped rod 131. Further, the electric resistor 142 is interposed between the two glass seal layers 141 and 143.
[0059]
However, both of the glass seal layers 141 and 143 are formed by sintering a mixture obtained by mixing a metal powder such as copper (Cu), iron (Fe), or an alloy thereof with a glass powder (hereinafter, also referred to as a seal raw material powder mixture). (Hereinafter, also referred to as a sintered seal composition). The electric resistor 142 is a composition obtained by sintering a mixture of glass powder and a resistance material powder such as carbon powder (hereinafter also referred to as a resistor raw material powder mixture) (hereinafter also referred to as a sintered resistor composition). ). Therefore, the sintered conductor 140 is constituted by both the sintered seal composition and the sintered resistor composition.
[0060]
The two glass seal layers 141 and 143 of the sintered conductor 140 are electrically connected between the distal end 133 of the terminal fitting 130 and the head 121 of the center electrode 120 with the electric resistor 142 interposed therebetween. , And the electric resistor 142 plays a role in reducing the generation of radio noise. Further, the mixture of both seal raw material powder and the resistor raw material powder is also referred to as a conductive glass powder mixture.
[0061]
The fixing tubular member 200 is fixed inside the cylinder head of the internal combustion engine. The fixing tubular member 200 is attached to the distal end portion of the insulating member 110 by the metal tubular portion 210. From coaxially. Here, the base end opening 211 of the metal cylindrical body 210 is fixed to the axially intermediate portion of the insulating member 110 via both ring-shaped packings 212 and the annular filling layer 213 by caulking from the outside.
[0062]
The ground electrode 220 of the fixing cylindrical metal fitting 200 extends in an L-shape from a part of the distal end opening 214 of the metal cylindrical body 210, and has a distal end 122 of the center electrode 120 at the extended end 221. Are opposed to each other via a gap 222. In addition, the ground electrode 220 is welded at a base end thereof to a part of the distal end opening 214 of the metal cylindrical body 210.
[0063]
Next, an example of a manufacturing apparatus for manufacturing the spark plug with a resistor configured as described above will be described with reference to FIGS. This manufacturing apparatus is provided with a heating device 300 as shown in FIG. 9, and this heating device 300 has a heating furnace 310 as shown in FIG. 9 and FIG. The heating furnace 310 includes a substantially rectangular parallelepiped heating chamber 311 therein. As shown in FIGS. 9 and 10, the heating chamber 311 includes an upper heating chamber 312 and a lower heating chamber 313. In addition, it is vertically divided by a holding plate described later.
[0064]
As shown in FIG. 9, the heating furnace 310 includes a plurality of gas burners 314 and a plurality of gas burners 315, and the plurality of gas burners 314 (hereinafter, also referred to as an upper gas burner 314) includes an upper wall of the upper heating chamber 312. 9 are arranged along the left-right direction in FIG. 9 (corresponding to the front-rear direction of the heating furnace 310 or the heating chamber 311). In addition, as shown in FIG. 10, the upper gas burners 314 are arranged right and left at the center of the upper wall of the heating upper chamber portion 312 in the left-right direction as shown in FIG. (Arranged in three rows). The plurality of upper gas burners 314 arranged in this way emit heat energy from the combustion of gas downward from the respective arrangement positions.
[0065]
On the other hand, a plurality of gas burners 315 (hereinafter, also referred to as lower gas burners 315) are arranged along the bottom wall of the lower heating chamber 313, and are shown in FIG. Along with a plurality of upper gas burners 314. Further, as shown in FIG. 10, the lower gas burners 315 are arranged side by side at the center of the bottom wall of the heating lower chamber 313 in the left-right direction as shown in FIG. Are arranged in five rows). The number of gas burners provided is such that the lower gas burner 315 is softened from the tip side seal raw material mixture in the plug substructure described later by making it larger than the upper gas burner 314, and is pressed by a press described later. The occurrence of poor electrical connection between the center electrode 120 and the terminal fitting 130 is suppressed.
[0066]
The plurality of lower gas burners 315 disposed in this way emit heat energy from the combustion of gas upward from the respective disposed positions. The gas burners 314 and 315 burn gas supplied from a gas supply source (not shown). Further, both upper exhaust holes 316 are formed to penetrate the left and right side walls of the upper heating chamber 312 in FIG. 10 to exhaust air from inside the upper heating chamber 312 to the outside of the heating furnace 310. Further, both lower exhaust holes 316 are formed through the left and right side walls of the lower heating chamber 313 in FIG. 10 to exhaust air from inside the lower heating chamber 313 to the outside of the heating furnace 310.
[0067]
Further, the heating device 300 includes a transfer device 320 as shown in FIGS. 11 to 13. As shown in FIG. 10, the transport device 320 has transport conveyors 321 on both the left and right sides. These transport conveyors 321 are symmetrical with respect to the center of the heating chamber 311 in FIG. In the configuration, the heating lower chamber 313 is disposed near the upper end of each of the left and right inner walls.
[0068]
The configuration of the right conveyor 321 will be described with reference to the right conveyor 321 as an example. The right conveyor 321 is disposed near the upper end of the right inner wall of the lower heating chamber 313 as shown in FIG. The right transport conveyor 321 includes a longitudinal support bar 323 and a plurality of transport rollers 324 (only one transport roller 324 is shown in FIG. 10) as shown in an enlarged circle 322 in FIG. I have.
[0069]
As can be seen from FIG. 10, the plurality of transport rollers 324 support a holding plate (to be described later), and the support bar 323 moves the holding plate in the left-right direction (corresponding to the left-right direction of the heating chamber 311). Has been suppressed. Further, each left conveyor 321 is rotatable in the front-rear direction of the heating chamber 311 on its rotation axis (not shown).
[0070]
On the other hand, since the left conveyor 321 has a configuration symmetrical to the right conveyor 321 as described above, each conveyor roller of the left conveyor 321 faces each conveyor roller 324 of the right conveyor 321. As in the case of the right conveyor 321, it is rotatably supported by the support bar of the left conveyor 321 disposed near the upper end of the left inner wall of the lower heating chamber 313.
[0071]
Further, as shown in FIG. 11, the transfer device 320 includes a linear actuator 325 using a fluid pressure such as pneumatic pressure or hydraulic pressure, or a machine such as a motor. In the heating furnace 310, the heating chamber 311 is supported in a support hole 317 provided in a right side wall of the heating chamber 311 in FIG. The linear actuator 325 includes a plate-like pushing member 327. The pushing member 327 is coaxially supported by an extension end of a piston rod 328 extending from a piston (not shown) in the cylinder 326. Have been.
[0072]
In the linear actuator 325, the pushing member 327 is pushed in the same direction by the piston rod 328 that slides from the cylinder 326 to the left in FIG. 11 (to the front of the heating chamber 11) in FIG. The transport path 311 moves forward into a portion facing the two conveyors 321 (hereinafter, also referred to as a conveyor facing portion) (see FIG. 12). Further, the pushing member 327 is pulled by the piston rod 328 as the piston rod 328 slides into the cylinder 326, and retreats to the cylinder 326 side from within the above-mentioned opposed portion of the carry-in path 318 (see FIG. 13).
[0073]
Here, the piston is coaxially and slidably fitted in the cylinder 326 so as to partition the inside of the cylinder 326 into both chambers, and the piston is inserted into one of the two chambers of the cylinder 326. As the fluid pressure is supplied from a fluid pressure supply source (not shown), the cylinder slides in the cylinder 326 toward the opposite side of the carry-in path 318, and the fluid pressure is supplied to the other of the two chambers. , Slides in the cylinder 326 in the direction opposite to the above-described facing portion of the carry-in path 318.
[0074]
As shown in FIG. 11, the loading path 318 is provided horizontally in the heating furnace 310 so as to be orthogonal to the longitudinal direction of the two conveyors 321 on the right side of the heating chamber 311 in the drawing. In addition, the carry-in path 318 opens into the heating chamber 311 through the entrance thereof (the right end opening of the heating chamber 311 in FIG. 11 in FIG. 11) and the support hole 317 in the support hole 317. It is open through the end. The entrance of the heating chamber 311 is formed above the axis of each transport roller of both transport conveyors 321 in the heating chamber 311.
[0075]
9 and 11, the heating device 300 includes a plate-shaped shutter 330. The shutter 330 is provided on the left side wall (the heating chamber 311) of the heating chamber 311 in the heating furnace 310 in FIG. The outlet of the heating chamber 311 (the left end opening of the heating chamber 311 in FIG. 9) is housed in a recess 319 formed on the outer surface of the front wall of the heating chamber 311 so as to be opened and closed in the vertical direction.
[0076]
Thus, the shutter 330 is displaced upward in the recess 319 to open the outlet of the heating chamber 311 (see FIG. 12). Further, the shutter 330 is displaced downward in the recess 319 to close the outlet of the upper heating chamber 312 (see FIGS. 11 and 13).
[0077]
Further, as shown in FIG. 9, the manufacturing apparatus includes a press device 400, and the press device 400 is provided in the heating furnace 310 in addition to the left side in FIG. As shown in FIG. 15, the press device 400 includes a transfer device 410, a lower die 420, and an upper die 430 supported up and down immediately above the lower die 420.
[0078]
The transfer device 410 has left and right lifting members 411, which are supported so as to be able to move up and down along the left and right walls 421 of the lower die 420 in FIG. In addition, the transport device 410 has a transport conveyor 412, and the transport conveyor 412 includes a plurality of elevating shafts 413 and a plurality of transport rollers 414, as shown in FIG. Note that the transport device 410 faces the outlet of the heating chamber 311 via the shutter 330.
[0079]
The plurality of elevating shafts 413 are horizontally supported at both ends by both elevating members 411 as illustrated in FIG. 15, and as shown in FIG. It is arranged and supported at predetermined intervals along the direction. Here, the plurality of elevating shafts 413 are positioned so as to be able to ascend and descend in a plurality of lateral grooves 422 (vertical grooves 422 shown in FIG. 14) formed on the upper surface of the lower die 420.
[0080]
Thus, the plurality of elevating shafts 413 move up and down in the plurality of lateral grooves 422 as the two elevating members 411 move up and down. It should be noted that the plurality of lateral grooves 422 are positioned at the same predetermined interval arrangement as the lifting shafts 413 in the horizontal direction shown in FIG. 14 and are parallel to each other in the vertical direction shown in FIG. It is formed along the upper surface of the lower die 420.
[0081]
As can be seen from FIG. 14, the plurality of transport rollers 414 are rotatably supported on each of the plurality of elevating shafts 412 by the same number, and each transport roller 414 supported by the plurality of elevating shafts 412 is provided on the lower die 420. A plurality of vertical grooves 423 (horizontal direction grooves 423 in FIG. 14) formed on the upper surface are coaxially supported at predetermined axial intervals along the axial direction of each elevating shaft 412.
[0082]
Here, the plurality of vertical grooves 423 are formed on the upper surface of the lower die 420 at the same interval as the predetermined axial direction interval so as to cross the plurality of horizontal grooves 422 in a cross shape. Therefore, for each elevating shaft 412, each transport roller 414 supported by one elevating shaft 412 is provided at each intersection of one corresponding vertical groove 423 and one horizontal groove 422 corresponding to one elevating shaft 412. (See FIG. 15).
[0083]
The plurality of transport rollers 414 move up and down in the plurality of vertical grooves 423 as the plurality of elevating shafts 413 move up and down. The portion protrudes above the upper surface of the lower die 420. In addition, the plurality of transport rollers 414 are stored in the plurality of lateral grooves 423 so as to be located below the upper surface of the lower die 420, including the upper ends thereof, as a result of the lowering.
[0084]
As shown in FIG. 15, the upper die 430 includes a die body 431 and a plurality of (6 × 6 in this embodiment) rods 432. Up / down by hydraulic pressure from In FIG. 15, six rods 432 are arranged in the horizontal direction in the drawing and the six rods 432 in the depth direction in the drawing, and hang down from the lower surface of the die main body 431 in a lattice shape. Such a lattice arrangement of the rods 432 corresponds to a lattice arrangement of the holding holes 161 of the holding plate 160 described later. Here, each of the rods 432 has, at its distal end, opposed to each of the upper surfaces of the upper surface of the lower die 420 between the vertical grooves 423 and the adjacent vertical grooves 423.
[0085]
In the manufacturing apparatus, the operations of the two conveyors 321, the linear actuator 325 and the shutter 330 of the heating device 300, the two lifting members 411 and the upper die 430 of the press device 400, and the like are performed by the manufacturing device. When the plug is manufactured as described later, the plug is sequence-controlled by a control circuit (not shown) in a predetermined order.
[0086]
Hereinafter, a method of manufacturing a spark plug with a resistor by the manufacturing apparatus configured as described above will be described. First, the configuration of the plug body 100 before the terminal fitting 130 is press-fitted by pressing is prepared as a plug substructure 150 (see FIG. 6).
[0087]
Specifically, as shown in FIG. 2, the columnar center electrode 120 is coaxially fitted into the small-diameter portion 112 of the tubular insulating member 110 through the large-diameter portion 113. Next, as shown in FIG. 3, a predetermined amount of the above-mentioned sealing material powder mixture (hereinafter, also referred to as sealing material powder mixture 151) for forming the glass seal layer 141 is supplied into the large-diameter portion 113 of the insulating member 110. .
[0088]
Thereafter, the holding rod 152 is inserted into the large-diameter portion 113 of the insulating member 110, and the sealing raw material mixture 151 is pre-compressed onto the head 121 of the center electrode 120 by the holding rod 152 as shown in FIG. I do. Then, with the holding rod 152 removed from the insulating member 110, the above-mentioned resistor raw material powder mixture for forming the electric resistor 142 (hereinafter also referred to as the resistor raw material powder mixture 153) is supplied to the large diameter of the insulating member 110. A predetermined amount is supplied into the unit 113. Then, the pressing rod 152 is inserted into the large diameter portion 113 of the insulating member 110 again, and the resistor raw powder mixture 153 is pre-compressed onto the pre-compressed sealing raw material powder mixture 151 by the pressing rod 152.
[0089]
Next, with the holding rod 152 removed from the insulating member 110 again, the above-mentioned sealing material powder mixture (hereinafter, also referred to as a sealing material powder mixture 154) for forming the glass seal layer 143 is as shown in FIG. A predetermined amount is supplied into the large diameter portion 113 of the insulating member 110. Then, the holding rod 152 is inserted into the large diameter portion 113 of the insulating member 110, and the sealing raw powder mixture 154 is pre-compressed onto the pre-compressed resistor raw material powder mixture 153 by the pressing rod 152 (see FIG. 5). .
[0090]
Thereafter, with the holding rod 152 removed from the insulating member 110, the terminal fitting 130 is not pressed by the stepped rod portion 131 into the large diameter portion 113 of the insulating member 110 as shown in FIG. insert. At this stage, the terminal portion 132 of the terminal fitting 130 is maintained apart from the base end 114 of the insulating member 110. Thus, preparation of one plug substructure 150 is completed (see FIG. 6). A plurality of such 36 plug substructures 150 are prepared.
[0091]
Thereafter, the plug substructure 150 is held on the holding plate 160 made of a rectangular flat plate via the cylindrical receiving member 170 as follows. Here, the configuration of the holding plate 160 and the receiving member 170 will be described.
[0092]
As can be seen from FIGS. 6 to 8, the holding plate 160 has a plurality of (for example, 36) holding holes 161. 8 (corresponding to the left-right direction) and 6 per row (corresponding to the up-down direction in FIG. 8), and are arranged in a grid of 6 rows × 6 columns. However, the distance between the axial centers of the two holding holes 161 adjacent to each other among the six holding holes 161 forming one row is the same as the distance between the two holding holes 161 adjacent to each other among the six holding holes 161 forming one row. Is the same as the axial center distance.
[0093]
As shown in FIGS. 6 and 7, each holding hole 161 includes a large-diameter portion 162 and a small-diameter portion 163 coaxially. In each holding hole 161, the large diameter portion 162 is located on the front surface 164 side of the holding plate 160, and the small diameter portion 163 is located on the back surface 165 side of the holding plate 160.
[0094]
Further, of the holding holes 161, the holding holes 161 (hereinafter, also referred to as end-side holding holes 161) located along both ends in the left-right direction in the drawing and both ends in the up-down direction in the drawing of the holding plate 160 in FIG. 7) have the same cross-sectional shape as shown in FIG. Further, the holding holes 161 (hereinafter also referred to as the center holding holes 161) located closer to the center of the holding plate 160 than the end side holding holes 161 have the same cross section as shown in FIG. It has a shape.
[0095]
Here, as shown in FIGS. 6 and 7, the inner diameter of the large-diameter portion 162 of the end-side holding hole 161 is formed larger than the inner diameter of the large-diameter portion 162 of the center-side holding hole 161. The inner diameter of the small-diameter portion 163 of the end-side holding hole 161 is equal to the inner diameter of the small-diameter portion 163 of the center-side holding hole 161. A plurality of holding plates 160 configured as described above are prepared. The holding plate 160 is formed of a metal material having heat resistance and oxidation resistance (for example, stainless steel, Inconel, or a cobalt-based metal).
[0096]
As shown in FIGS. 6 and 7, the receiving member 170 is coaxially fitted into the large-diameter portion 162 of the holding hole 161 on the center side or the end side. It is formed of a material having a lower thermal conductivity than the plate 160 (for example, a ceramic material). Hereinafter, the receiving member 170 fitted to the large-diameter portion 162 of the end-side holding hole 161 is also referred to as an end-side receiving member 170, and the receiving member fitted to the large-diameter portion 162 of the center-side holding hole 161. 170 is also referred to as a center side receiving member 170.
[0097]
The end-side receiving member 170 is fitted into the large-diameter portion 162 so that the outer peripheral surface thereof uniformly contacts the inner peripheral surface of the large-diameter portion 162 of the end-side holding hole 161. The central receiving member 170 is fitted into the large-diameter portion 162 such that the outer peripheral surface thereof uniformly contacts the inner peripheral surface of the large-diameter portion 162 of the central holding hole 161. Therefore, the thickness of the end-side receiving member 170 is set to be larger than the thickness of the center-side receiving member 170. The inner diameters of the end-side receiving member 170 and the center-side receiving member 170 are the same, and the flange-shaped annular portion of the insulating member 110 of the plug basic structure 150 (hereinafter also referred to as the collar-shaped annular portion 115). ) Smaller than the outside diameter.
[0098]
The receiving member 170 configured as described above has 20 end-side receiving members 170 and 16 central-side receiving members 170 per one holding plate 160 in accordance with the number of prepared plug substructures 150. Prepare.
[0099]
Thereafter, for each prepared holding plate 160, as shown in FIG. 6, each center side receiving member 170 is moved from its front end (hereinafter also referred to as the front end 172) to each center side holding member 170. It fits coaxially in the large diameter portion 162 of the hole 161. 7, each end-side receiving member 170 is coaxially fitted into the large-diameter portion 162 of each end-side holding hole 161 of the holding plate 160 from the tip 172 as illustrated in FIG. Along with this, the receiving members 170 on the center side and the end side are disposed on the bottom surface which is the boundary between the large-diameter portion 162 and the small-diameter portion 163 at the distal end portion 172 as illustrated in FIGS. To sit down. At this time, the receiving members 170 on the center side and the end side extend outward from the corresponding holding holes 161.
[0100]
Next, for each holding plate 160 in which the twenty end-side receiving members 170 and the sixteen central-side receiving members 170 are fitted, 36 plug substructures 150 are respectively transferred from the distal ends thereof. As illustrated in FIGS. 6 and 7, the holding plate 160 is fitted into each of the receiving members 170 on the end side and the center side. Accordingly, each plug substructure 150 is seated on the base end surface 171 of the corresponding receiving member 170 at the lower end surface 116 of the collar-shaped annular portion 115.
[0101]
Thereby, each plug substructure 150 is held by the corresponding receiving member 170 as illustrated in FIGS. 6 and 7. At this time, a portion of each plug basic structure 150 closer to the distal end than the brim-shaped annular portion 115 is located substantially in each corresponding receiving member 170 and faces the inside of the small diameter portion 163 of each corresponding holding hole 161. (See FIGS. 6 and 7).
[0102]
As can be seen from FIGS. 9 to 11, each holding plate 160 holding each plug substructure 150 via each receiving member 170 as described above is in a state where each plug substructure 150 is extended upward. Are transported into the carry-in path 318 of the heating furnace 310, and are sequentially transported into the upper heating chamber 312 by the linear actuator 325 of the transport device 320 and the two transport conveyors 321. Then, each holding plate 160 is heated from above and below by a plurality of upper gas burners 314 and lower gas burners 315 in the heating chamber 311, and then, as shown in FIGS. Then, the sheets are sequentially conveyed into the press device 400 by the two conveyors 321.
[0103]
Hereinafter, the process of carrying in, heating, and carrying out each of the holding plates 160 will be described in detail. As described above, when a plurality of holding plates 160 holding the plug substructure 150 via the receiving members 170 are sequentially carried into the heating upper chamber 312 of the heating furnace 310 as shown in FIG. Each holding plate 160 is horizontally supported by the two conveyors 321 so that each plug substructure 150 extends upward, and is sequentially conveyed in the upper heating chamber 312.
[0104]
Then, in the order of being transported in this manner, each plug substructure 150, together with each holding plate 160 and its respective receiving member 170, in the heating chamber 311, the gas of each upper gas burner 314 and each lower gas burner 315. The fuel is heated under predetermined heating conditions by the combustion energy. The predetermined heating condition includes a predetermined heating time and a predetermined heating temperature. The predetermined heating time and the predetermined heating temperature are set so as to be suitable for softening each glass powder in each of the seal raw material powder mixtures 151 and 154 and the resistor raw material powder mixture 153 in the plug substructure 150.
[0105]
For example, the predetermined heating temperature is equal to or higher than the predetermined softening point (glass softening point) of each glass powder in each of the seal raw material powder mixtures 151 and 154 and the resistor raw material powder mixture 153 in the plug substructure 150. , 900 ° C. to 1000 ° C.). The predetermined heating time is a time required for softening the glass powder by heating at the predetermined heating temperature, and after the glass plate is conveyed into the heating upper chamber 312 of the holding plate 160, This corresponds to the time (for example, a time within a range of 8 minutes to 20 minutes) until the product is carried out.
[0106]
Here, as an example, one of the holding plates 160 (the left-hand side holding plate 160 shown in FIG. 11) carried into the heating upper chamber portion 312 is taken as an example, and each plug basic structure 150 of the holding plate 160 is taken as an example. The heating process for the holding plate 160 and each of the receiving members 170 will be described.
[0107]
Each plug substructure 150 of the holding plate 160 carried into the heating upper chamber portion 312, the holding plate 160 and the respective receiving members 170 thereof are subjected to the following combustion energy of the gas of the upper and lower gas burners 314 and 315. It is heated in such a state.
[0108]
That is, as described above, when the upper and lower gas burners 314 and 315 burn the gas from the gas supply source, the upper gas burners 314 emit combustion energy downward from their respective arrangement positions, On the other hand, each lower gas burner 315 emits combustion energy upward from each of the disposition positions.
[0109]
Therefore, the combustion energy of each upper gas burner 314 is radiated into the upper heating chamber 312 and transmitted as radiant heat, and at the same time, is convected along the flow of air mainly in the upper heating chamber 312 and is transmitted as convection heat. You. On the other hand, the heating energy released from each lower gas burner 315 is radiated into the lower heating chamber 313 and transmitted as radiant heat, and at the same time, convectively flows along the flow of air in the lower heating chamber 313 to generate convection heat. Is transmitted.
[0110]
Thus, the combustion energy of each upper gas burner 314 is uniformly transmitted as heat throughout the upper heating chamber 312, while the combustion energy of each lower gas burner 315 is uniformly transmitted as heat throughout the lower heating chamber 313. Is done. Heat transfer to each plug substructure 150 of the holding plate 160 placed under such heat transfer is efficiently performed by the above-described heat transfer by radiation and convection.
[0111]
Also, in this heat transfer state, the plug base structures 150 of the holding plate 160 extend upward from the holding plate 160 side by side, so that the convective heat in the heating upper chamber portion 312 is It is transmitted between the bodies 150. Therefore, a heat retaining effect is generated between the plug substructures located at the center side of the holding plate 160 among the plug substructures 150. Therefore, the heat transfer efficiency is further enhanced between the plug substructures located on the center side of the holding plate 160.
[0112]
Even in the uniform and efficient heat transfer state as described above, the end of the holding plate 160 receives more heat than the center of the holding plate 160, as described at the beginning of this specification. . Then, the end-side plug substructure 150 is more likely to hit the convection heat heated in the heating furnace 310 than the center-side plug substructure 150. However, in the first embodiment, as described above, in the holding plate 160,
The plug base structure 150 is fitted into the end holding hole 161 via the end receiving member 170, and the plug base structure 150 is fitted with the center receiving member 170 in the center holding hole 161. It is fitted through.
[0113]
Moreover, the thickness of the end-side receiving member 170 is larger than the thickness of the central-side receiving member 170 as described above. Therefore, the end-side receiving member 170 has a larger heat capacity than the central-side receiving member 170. Therefore, the amount of heat absorbed by the end-side receiving member 170 is larger than the amount of heat absorbed by the central-side receiving member 170.
[0114]
Therefore, as described above, even if the end of the holding plate 160 receives a larger amount of heat than the center of the holding plate 160, the plug base structure is connected to the end of the holding plate 160 via the end receiving member 170. The amount of heat transmitted to the body 150 (hereinafter, also referred to as the end-side plug substructure 150) is reduced, and the plug substructure 150 (hereinafter, center-side) is transferred from the center of the holding plate 160 via the center receiving member 170. (Also referred to as plug substructure 150). This means that the amount of heat received at the distal end portion of the end-side plug substructure 150 approaches the amount of heat received at the distal end portion of the central-side plug substructure 150.
[0115]
In the heating state as described above, each plug substructure 150 is heated toward the predetermined heating temperature, and each seal raw material powder mixture 151, 154 and resistor raw material powder in each plug substructure 150 is heated. Each glass powder in the mixture 153 is softened. Moreover, since the amount of heat received at the distal end portion of the end-side plug substructure 150 approaches the amount of heat received by the center-side plug substructure 150 as described above, the softened state of each of the glass powders is determined by the end portion. An approximate state is established between the side plug substructure 150 and the center plug substructure 150.
[0116]
Thereafter, when the predetermined heating time has elapsed, the shutter 330 of the heating device 300 is opened upward in FIG. 9. In the transfer device 410 of the press device 400, both lifting members 411 move upward in the drawing in FIG. 15 to raise the transfer conveyor 412. Therefore, each transport roller 414 of the transport conveyor 412 projects from the upper surface of the lower die 420 at its upper end.
[0117]
Along with this, the linear actuator 325 of the transfer device 320 pushes the pushing plate 327 by the piston rod 328 based on the fluid pressure from the fluid pressure supply source, and the pushing plate 327 causes the outside of the entrance of the heating chamber 311 to move. The holding plate 160 (see FIG. 11) located at the position (1) is pushed in the transport direction (the front-back direction of the heating chamber 311).
[0118]
For this reason, the left end holding plate 160 described above is pushed out of the heating chamber 311 into the press device 400 as shown in FIGS. Thereafter, the pushing plate 327 of the linear actuator 325 returns to the right in the drawing as shown in FIG. 13, and the holding plate 160 on the carrying path 318 is carried in to a position corresponding to the entrance of the heating chamber 311.
[0119]
The holding plate 160 heated and extruded into the press device 400 as described above, together with the respective plug substructures 150 and the respective receiving members 170 under the extrusion by the linear actuator 325, is transported upward as described above. With the rotation of each conveyor roller 414 of the conveyor 412, the press device 400 is conveyed directly above the lower die 420 of the press device 400 (see FIG. 14). Along with this, the two lifting members 411 move down to lower the conveyor 412. Therefore, each transport roller 414 of the transport conveyor 412 is stored in the lower die 420, and the holding plate 160 is seated on the upper surface of the lower die 420 on the back surface.
[0120]
Then, in each plug substructure 150 of the holding plate 160, each terminal fitting 130 is moved toward the base end 114 of each insulating member 110 by each rod 432 as the upper die 430 descends at the terminal portion 132. It is pressed on the corresponding upper surface of the lower die 420. Accordingly, the terminal portions 132 of the respective terminal fittings 130 are seated on the respective base end portions 114 of the respective insulating members 110 as illustrated in FIG. At the same time, the stepped rod portions 131 of the terminal fittings 130 are press-fitted into the large-diameter portions 113 of the corresponding insulating members 110, and the leading ends thereof are pre-compressed in the large-diameter portions 113. The seal material powder mixture 154, the resistor material powder mixture 153, and the seal material powder mixture 151 are pressed onto the corresponding head 121 of the center electrode 120 from the seal material powder mixture 154 to the seal material powder mixture 151.
[0121]
As described above, in the process in which each plug substructure 150 of the holding plate 160 is pressed into the corresponding insulating member 120 by the terminal fitting 130 after the conveyance of the holding plate 160 into the press device 400 by pressing. In addition, the end portion of the holding plate 160 has a larger amount of heat radiation than the center of the holding plate 160, and the end-side plug substructure 150 cools faster. In addition, a heat retention effect is generated between the center side plug substructures 150, and the end side plug substructures 150 are easier to cool than the center side plug substructures 150.
[0122]
However, by providing the end receiving member 170 having a predetermined heat capacity, the amount of heat transmitted from the end plug substructure 150 to the holding plate 160 via the end receiving member 170 is reduced, and the center plug It approaches the amount of heat transmitted directly from the substructure 150 to the holding plate 160. Therefore, the degree of softening of the glass powder in each end-side plug substructure 150 is maintained close to the degree of softening of each glass powder in each central-side plug substructure 150.
[0123]
Therefore, in each of the plug substructures 150 on the end side and the center side, the sealing raw material powder mixture 154, the resistor raw material powder mixture 153, and the seal raw material powder mixture 151 are provided for each plug substructure 150. By pressing with the metal fitting 130, the sintered body is compression-sintered at a uniform sintering density as a sintered conductor 140 composed of the base end glass seal layer 143, the electric resistor 142 and the front end glass seal layer 141. Further, since the degree of softening of the glass powder is similar between the plug substructures 150 on the end side and the center side as described above, the sintering of the plug substructures 150 on the end side and the center side is performed. The sintering densities of the conductors 140 are also close to each other. Accordingly, the variation in the electric resistance value between the plug substructures 150 on the end side and the center side is very small.
[0124]
As a result, each plug substructure 150 is formed as the plug main body 100 with little variation in electric resistance value (electrical resistance value of the sintered conductor 140). As a result, the electrical resistance values of the 36 plug bodies 100 for each holding plate 160 are uniformly maintained without variation, and the plug bodies 100 with good yield can be formed. After the formation of the plug main body 100, the fixing cylindrical metal fitting 200 is assembled to the plug main body 100, thereby completing the manufacture of the spark plug including the resistor with a small variation in electric resistance value and a good yield.
(2nd Embodiment)
FIG. 17 shows a main part of the second embodiment of the present invention. In the second embodiment, each cylindrical receiving member 180 is employed as illustrated in FIG. 17 instead of each cylindrical receiving member 170 described in the first embodiment. Also in the second embodiment, the receiving member 180 includes end-side and center-side receiving members 180 respectively corresponding to the end-side and center-side receiving members 170 described in the first embodiment. However, FIG. 17 illustrates the center receiving member 180.
[0125]
The receiving member 180 surrounds the entirety of the above-mentioned conductive glass powder mixture (indicated by reference numeral 155 in FIG. 17) in the plug substructure 150, regardless of whether the receiving member 170 is on the end side or the center side. Thus, it has a longer axial length than the receiving member 170. Further, a stepped inner hole 181 is formed coaxially in the receiving member 180, and the stepped inner hole 181 has an inner diameter larger than the outer diameter of the collar-shaped annular portion 115 of the plug substructure 150. A large diameter portion 182 and a small diameter portion 183 having the axial length and the inside diameter of the receiving member 170 are provided vertically. Further, the axial length of the large diameter portion 181 of the stepped inner hole 181 is made longer in accordance with the axial length of the receiving member 180. The other configurations of the receiving members 180 on the center side and the end portion are the same as those of the receiving members 170 on the center side and the end portion. Other configurations are the same as those of the first embodiment.
[0126]
In the second embodiment configured as described above, each of the center-side receiving members 180 is similar to each of the center-side receiving members 170, from the small-diameter portion 183 side of the holding plate 160 described in the first embodiment. Each center side holding hole 161 is fitted as illustrated in FIG. Each end-side receiving member 180 is fitted into each end-side holding hole 161 of the holding plate 160 from the small-diameter portion 183 side, similarly to each of the end-side receiving members 170.
[0127]
Further, each plug substructure 150 described in the first embodiment is fitted from its distal end portion into the corresponding receiving member 180 from its large diameter portion 182 side, and the At the lower end surface 116, it sits on the bottom of the boundary between the large diameter portion 182 and the small diameter portion 183.
[0128]
In such a state, in each of the plug substructures 150 on the center side and the end side, a corresponding shaft extends from the front end of each plug substructure 150 to the entire conductive glass powder mixture 155. The direction corresponding portion is covered by the corresponding receiving member 180.
[0129]
Therefore, as described above, the holding plate 160 holding the plug basic structures 150 via the receiving members 180 is conveyed into the heating chamber 311 in the same manner as described in the first embodiment, and the plug base structures 150 When heated together with the holding plate 150 and the holding plate 160, each receiving member 180 exerts the above-mentioned mutual heat-retaining effect on the entire conductive glass powder mixture 155 in the corresponding plug substructure 150 depending on the amount of heat received. I do.
[0130]
Here, as the axial length of the receiving member 180 is longer than the axial length of the receiving member 170, the heat capacity of the receiving member 180 is larger than the receiving member 170 for each of the end-side and center-side receiving members. Therefore, the amount of heat received by each of the receiving members 180 is greater than the amount of heat received by the corresponding receiving member 170 for each of the end members and the center member. Therefore, the mutual heat retaining effect on the entirety of the conductive glass powder mixture 155 is further improved as compared with the first embodiment. As a result, the softened state of the glass powder in each plug substructure 150 is favorably promoted throughout the conductive glass powder mixture 155. Therefore, the sintering density of the sintered conductor 140, that is, the electrical resistance value, can be ensured even more evenly in each of the plug substructures on the end side and the center side.
[0131]
In addition, as described in the second embodiment, by preparing the receiving member 180 having a different axial length from the axial length of the receiving member 170, the axial length of the plug basic structure 150 can be increased. Even if it is different from the first embodiment, it is possible to reliably hold the plug substructure in the stepped inner hole of the holding plate 160. In this sense, by preparing various cylindrical receiving members having different axial lengths from each other, it becomes possible to hold the plug substructures having various axial lengths to the holding plate. Other functions and effects are the same as those in the first embodiment.
(Third embodiment)
FIGS. 18 and 19 show a main part of a third embodiment of the present invention. In the third embodiment, in the holding plate 160 described in the first embodiment, of the center holding holes 161, both center holding holes 161 adjacent to each other in the left-right direction in FIG. Between them, a through-hole portion 166 is additionally formed as shown in FIGS. As illustrated in FIG. 18, each through-hole portion 166 has a small-diameter portion 167 and a large-diameter portion 168 coaxially above and below, and connects the front side and the rear side of the holding plate 160 to each other. . Other configurations are the same as those of the first embodiment.
[0132]
In the third embodiment configured as described above, as described above, each through-hole 166 is formed between each adjacent center-side holding hole 161 so that the center-side holding hole 161 is formed in a lattice shape. The volume at the center of the holding plate 160 located at the center position is reduced. For this reason, the heat capacity at the center of the holding plate 160 is reduced by the above-described reduction in volume as compared with the case where the respective through-hole portions 166 are not provided. This means that in the third embodiment, the center of the holding plate 160 is formed as a small heat capacity portion.
[0133]
Therefore, similarly to the first embodiment, the holding plate 160 holding each plug basic structure 150 via each receiving member 170 is transported into the heating chamber 311, and each receiving member 170 is connected to each plug basic structure 150. When heated together with the holding plate 160, the amount of heat received by the small heat capacity portion of the holding plate 160 increases faster than the holding plate 160 described in the first embodiment.
[0134]
For this reason, the heat transfer from the small heat capacity portion to the distal end portion of each central side plug substructure 150 via each central side receiving member 170 is further promoted as compared to the first embodiment, and each central side plug base structure 150 is further promoted. The softening of the glass powder in the side plug substructure 150 further progresses and approaches the softened state of the glass powder in each end plug substructure 150. As a result, the sintered density of the sintered conductor 140, that is, the electric resistance value, can be ensured even more uniformly on both the end side and the center side plug substructures. Other functions and effects are the same as those of the first embodiment.
(Fourth embodiment)
FIG. 20 and FIG. 21 show a fourth embodiment of the present invention. In the fourth embodiment, a plurality of stepped cylindrical heat insulating members 190 are additionally employed, and these heat insulating members 190 are, as shown in FIG. 21, the holding plate 160 described in the first embodiment. In FIG. 8 (see FIG. 8), they are arranged between the end side holding holes 161 adjacent to each other along the end.
[0135]
As illustrated in FIG. 20, each of the heat retaining members 190 is formed by forming a collar-shaped annular portion 192 at the axial center of the columnar portion 191. As can be seen from FIGS. 20 and 21, each of the heat retaining members 190 is coaxially fitted in each through-hole 199 (described later) at a lower portion of the columnar portion 191, and is fitted to the annular portion 192. And is seated on the surface 164 of the holding plate 160. Thus, the upper portion of each column 191 projects upward from the surface 164 of the holding plate 160.
[0136]
Here, each through-hole 199 is additionally formed between each adjacent end-side holding hole 161 of the holding plate 160 as illustrated in FIG. The heat retaining member 190 is formed of a heat-resistant material such as a metal material or a ceramic material.
[0137]
In the fourth embodiment, the thickness of the holding plate 160 is such that the entire end-side receiving member 170 is fitted into the large-diameter portion 162 of the end-side holding hole 161 as illustrated in FIG. I have to do it. Although the thickness of the holding plate 160 is not shown in FIG. 20, the whole of the central receiving member 170 is fitted in the central holding hole 161 in the same manner. Other configurations are the same as those of the third embodiment.
[0138]
In the fourth embodiment having the above-described configuration, as described above, the through-holes 199 are formed between the center-side holding holes 161 so that the end-side holding holes can be formed during the heating. Heat is also transmitted from the holding plate 160 to the heat retaining member 190 disposed between the adjacent holding holes 161 in the portion 161. Therefore, the amount of heat received from the holding plate 160 of the end-side plug substructure 150 is further suppressed, and the amount of heat received further approaches the amount of heat received by the center-side plug substructure 150.
[0139]
In the process in which the plug substructure 150 of the holding plate 160 carried out of the heating furnace 310 is pressed into the corresponding insulating member 110 by the terminal fitting 130 by pressing, the heat insulating member 190 is held at each end side. By protruding upward from the holding plate 160 between the holes 161, the heat release effect of the heat retaining member 190 and the end-side plug substructure 150 reduces the heat radiation amount of the end-side plug substructure 150 to the center side. The heat radiation amount of the plug substructure 150 is further approached.
[0140]
Therefore, in the fourth embodiment, the softening of the glass powder in the center-side plug substructure 150 is closer to the softening state of the glass powder in the end-side plug substructure 150. As a result, the sintered density of the sintered conductor 140, that is, the electric resistance value, can be ensured even more uniformly on both the end side and the center side plug substructures. Other functions and effects are the same as those of the first embodiment.
(Fifth embodiment)
22 to 25 show a main part of a fifth embodiment of the present invention. In the fifth embodiment, as shown in FIGS. 22 to 25, a plurality of cylindrical recesses are used in the holding plate 160 described in the third embodiment, instead of the through holes 166 (see FIG. 18). 169 are formed. Each of the cylindrical concave portions 169 is provided between the two holding holes 161 of the holding holes 161 adjacent to each other in the diagonal direction shown in FIGS. It is formed at the center from the back surface 165 side of the holding plate 160. Other configurations are the same as those of the third embodiment.
[0141]
In the fifth embodiment configured as described above, as described above, each recess 169 is formed at the center between each adjacent holding hole 161, and thus each end side holding hole of the holding plate 160 is formed. The volume of the portion on the center side of the portion 161 is reduced from the back side of the holding plate 160.
[0142]
Therefore, the heat capacity of the central portion of the holding plate 160 is reduced by the amount corresponding to the decrease in the volume as compared with the case where the concave portions 169 are not provided. Thus, in the fifth embodiment, the central portion of the holding plate 160 is formed as a small heat capacity portion. The small heat capacity portion extends over a wider range than the small heat capacity portion described in the third embodiment. .
[0143]
Therefore, similarly to the third embodiment, when each receiving member 170 is heated together with each plug substructure 150 and the holding plate 160, the amount of heat received by the small heat capacity portion of the holding plate 160 becomes equal to the third embodiment. It increases faster than the holding plate 160 described in the embodiment.
[0144]
Thereby, the heat transfer from the small heat capacity portion to the distal end portion of each central plug substructure 150 via each central receiving member 170 is further promoted. As a result, the sintered density of the sintered conductor 140, that is, the electric resistance value, can be ensured even more uniformly on both the end side and the center side plug substructures. Other functions and effects are the same as those of the third embodiment.
(Sixth embodiment)
26 to 28 show a main part of a sixth embodiment of the present invention. In the sixth embodiment, in the holding plate 160 described in the fifth embodiment, square recesses 195 are formed instead of the cylindrical recesses 169 as shown in FIGS. 27 and 28. ing. The recess 195 is formed on the back surface 165 of the holding plate 160, and the inner peripheral wall of the recess 195 is formed on the back surface 165 of the holding plate 160 by each end side holding hole 161 and each end portion It is formed in a square shape passing through the center between the central holding holes 161 located adjacent to the side holding holes 161.
[0145]
Further, in the recess 195, as shown in FIG. 28, each cylindrical portion 196 is formed around the axis of the small-diameter portion 163 of each central-side holding hole 161 in the holding plate 160. The outer diameter of each cylindrical portion 196 is larger than the outer diameter of each corresponding central receiving member 170. Other configurations are the same as those of the fifth embodiment.
[0146]
In the sixth embodiment configured as described above, as described above, the recess 195 is formed in the holding plate 160 in a rectangular shape as described above, so that each end side holding hole of the holding plate 160 is formed. The volume of the portion on the center side of the portion 161 is reduced from the back side of the holding plate 160.
[0147]
Thus, in the sixth embodiment, the central portion of the holding plate 160 is formed as a small heat capacity portion. The small heat capacity portion is larger than the small heat capacity portion described in the fifth embodiment. Therefore, according to the sixth embodiment, the small heat capacity portion exhibits a larger heat transfer effect, and the variation in the electric resistance value described in the fifth embodiment can be further suppressed.
(Seventh embodiment)
FIG. 29 shows a main part of the seventh embodiment of the present invention. In the seventh embodiment, in the holding plate 160 described in the sixth embodiment, the recess 197 is formed instead of the recess 195 from the back surface 165 side. The inner peripheral wall of the recess 197 is further enlarged than the inner peripheral wall of the recess 195. Specifically, as shown in FIG. 29, the inner peripheral wall of the concave portion 197 is enlarged to the central peripheral half of the holding plate 160 in the inner peripheral portion of each end side holding hole 161.
[0148]
According to this, the recess 197 forms a small heat capacity portion in the holding plate 160 over a wider range than the small heat capacity portion described in the sixth embodiment. Therefore, the variation in the electric resistance value can be further suppressed by exhibiting a larger heat transfer function, and the function and effect described in the sixth embodiment can be further improved.
(Eighth embodiment)
FIG. 30 shows a main part of an eighth embodiment of the present invention. In the eighth embodiment, in addition to the recess 197, each through-hole 198 is employed in the holding plate 160 described in the seventh embodiment. As shown in FIG. 32, the through holes 198 are adjacent to each other along the diagonal direction in FIG. 30 of the holding plate 160 of the center side stepped inner holes 161 in the recess 197. Each of the central stepped inner holes 161 is formed to penetrate the holding plate 160 at the center of both central stepped inner holes 161.
[0149]
According to this, each through-hole 198 forms a small heat capacity portion in the holding plate 160, which is smaller than the small heat capacity portion described in the seventh embodiment. Therefore, the functions and effects described in the seventh embodiment are further improved.
(Ninth embodiment)
FIG. 31 shows a main part of a ninth embodiment of the present invention. In the ninth embodiment, as shown in FIG. 31, each holding hole 161 described in the first embodiment is formed in the holding plate 160 in a direction intersecting the illustrated vertical direction (for example, at 45 °). (Intersecting direction) and are arranged in a grid pattern.
[0150]
In other words, each of the holding holes 161 has four adjacent to each other, and is positioned at the four apexes of each rhombus in the transport direction of the holding plate 160 (the vertical direction in FIG. 31). It is formed on the holding plate 160. However, among the holding holes 161 located at the tops of one rhombus, the center interval between the holding holes 161 located at both tops adjacent to each other along the side of the rhombus (hereinafter also referred to as the side direction interval). ) Are the same.
[0151]
Here, the center interval between the two holding holes 161 adjacent to each other is set to be the same for all the holding holes 161. Further, of the holding holes 161, each holding hole positioned along the end of the holding plate 160 constitutes the end-side holding hole 161, and the remaining holding holes 161 correspond to the center-side holding hole 161. The unit 161 is constituted.
[0152]
In addition, of the end side holding holes 161, the left and right distances between the center of each end side holding hole 161 located at the left end in FIG. 31 and the left end of the holding plate 160 and the right end in the drawing. The distance between the center of each of the end side holding holes 161 and the right end of the holding plate 160 in the illustrated left-right direction is wider than the above-described side direction distance. This is because, as described above, the amount of heat received at the left and right ends of the holding plate 160 is greater than the center of the holding plate 160 as described above. This is in order to make it difficult to transmit to the distal end portion of the unit-side receiving member 170 and the end-side plug substructure 150.
[0153]
When a plurality of the holding plates 160 configured as described above are continuously adjacent to each other in the transport direction as shown in FIG. 31, the end side holding hole located at the rear end of the preceding holding plate 160 in the transport direction. The center interval between the holding plate 160 and the end-side holding hole 161 located at the leading end of the holding plate 160 following the preceding holding plate 160 in the transfer direction is determined by the following holding plate 160 (or the previous holding plate) in the transfer direction. Each of the holding holes 161 of the plate 160) is equal to the center interval of the both end side holding holes 161 adjacent to each other along the transport direction. This is because, when heating in the heating chamber 311, the effect of heat on the plug substructure 150 for each holding plate 160 is made uniform even between both the preceding and succeeding holding plates 160. is there. Other configurations are the same as those of the first embodiment.
[0154]
In the ninth embodiment configured as described above, similarly to the first embodiment, the holding plates 160 holding the plug substructures 150 via the receiving members 170 are continuously heated sequentially. When transported into the chamber 311, each plug substructure 150 and each receiving member 170 are heated for each holding plate 160 together with the holding plate 160.
[0155]
At the time of this heating, as described above, the horizontal distance between the center of each end side holding hole 161 located on the left end of the holding plate 160 and the left end of the holding plate 160 and the right end of the holding plate 160 The left-right space between the center of each end-side holding hole 161 and the right end of the holding plate 160 is wider than the above-mentioned side-direction space. Therefore, heat at the left and right ends of the holding plate 160 is less likely to be transmitted to the distal end portions of the end receiving members 170 and the distal end portions of the end plug substructures 150.
[0156]
Therefore, the softening of the glass powder in each end side receiving member 170 is less likely to proceed than in the first embodiment. For this reason, in each plug substructure 150 for each holding plate 160, the sintered density (that is, the electric resistance value) of the sintered conductor 140 of the end plug substructure 150 and the central plug substructure 150 Variations between the sintered conductor 140 and the sintered density (that is, the electrical resistance value) are further reduced as compared with the first embodiment.
[0157]
Further, as described above, the end-side holding hole 161 located at the rear end of the preceding holding plate 160 in the conveyance direction, and the end-side holding hole located at the front end of the holding plate 160 following the preceding holding plate 160 in the conveyance direction. The center interval between the holes 161 is equal to the center interval between both end side holding holes 161 adjacent to each other along the conveyance direction among the holding holes 161 of the preceding holding plate 160 in the conveyance direction.
[0158]
Therefore, the succeeding holding plate 160 and its respective receiving members 170 and each plug basic structure 150 are placed in the same heat receiving state as the preceding holding plate 160 and its respective receiving members 170 and each plug basic structure 150. For this reason, even between the preceding and succeeding holding plates 160, the variation in the electric resistance value of each plug substructure 150 is reduced in the same manner as described above.
[0159]
As a result, even if the continuous holding plate 160 is heated together with the respective receiving members 170 and the respective plug substructures 150, the electrical resistance value of the plug substructure 150 does not vary for each holding plate 160, and The plug body 100 having a good yield can be formed over the holding plates 160 to be formed.
(Tenth embodiment)
FIG. 32 shows a main part of a tenth embodiment of the present invention. In the tenth embodiment, in the transfer device 320 described in the first embodiment, the linear actuator 325 is eliminated, and the carry-in device 500 for carrying the holding plate 160 into the heating device 300 is employed. A shutter 330 is also provided on the entrance side of 311 so as to be openable and closable.
[0160]
As shown in FIG. 32, the loading device 500 includes both end members 501 parallel to each other and a plurality of rollers 502. As shown in FIG. 32, the rollers 502 are rotatably supported between both end members 501 at intervals from each other so as to be orthogonal to the end members 501. Here, the carry-in device 500 is disposed on the carry-in path 318 with the rollers 502 facing the carry-in direction of the carry-in path 318 (see FIG. 32). Further, when the loading device 500 is located at a position facing the entrance of the heating chamber 312 of the loading path 318, the rollers 502 are connected between the both end members 501 while the both end members 501 are kept stationary at this position. At the right side in FIG. 32. Other configurations are the same as those of the first embodiment.
[0161]
In the tenth embodiment configured as above, the holding plate 160 supporting each plug substructure 150 is placed on the loading device 500, and the loading device 500 is moved along the loading path 318 in FIG. Carry in the direction. Then, when the carry-in device 500 reaches a portion facing the entrance of the heating chamber 312, each roller 502 of the carry-in device 500 rotates in the direction of the heating chamber 312 between both end members 501. At this time, the shutter 330 on the entrance side of the heating chamber 312 is opened.
[0162]
Therefore, the holding plate 160 is sent into the heating chamber 312 by the rotation of each roller 502 of the loading device 500. Thereafter, as described in the first embodiment, the holding plate 160 supporting each plug substructure 150 is transferred and heated in the heating chamber 312 by both transfer conveyors 321.
[0163]
As described above, if the loading device 500 is employed, the holding plate 160 supporting each plug substructure 150 can be smoothly and sequentially placed in the heating chamber 312 without depending on the linear actuator 325 described in the first embodiment. To be heated. Other functions and effects are the same as those of the first embodiment.
[0164]
In carrying out the present invention, the following various modifications can be given without being limited to the above embodiments.
(1) The holding plate 160 is not limited to the holding hole 161 and may be, for example, a simple through-hole. In this case, an annular flange is provided coaxially on the upper end of the receiving member 170 or 180, and the receiving member 170 or 180 is seated on the upper end of the through-hole by the flange. Fit into the hole.
(2) The holding plate 160 can take an appropriate plate shape without being limited to a square plate shape. Here, it is desirable that the holding plate 160 has heat resistance and oxidation resistance in addition to heat conductivity.
(3) The receiving member 170 or 180 is not limited to a cylindrical shape and may have an annular shape or another hollow shape.
(4) The receiving member 170 or 180 may include only the end-side receiving member, and the central-side receiving member may be omitted. In this case, each central-side plug substructure 150 is directly fitted into each central-side holding hole 161 of the holding plate 160. With this, the same operation and effect as those of the first embodiment can be achieved.
(5) The present invention may be applied to a spark plug having no resistor without being limited to the spark plug containing a resistor. In this case, the conductive glass powder mixture in the plug substructure is composed of only the sealing raw material powder mixture 151 or 154.
(6) The gas burner in the heating chamber 311 may be constituted by only the lower gas burner. The heating source in the heating chamber 311 is not limited to a gas burner, and may be, for example, an electric heater, or may be a combination of a gas burner and an electric heater.
(7) The transport conveyors 321 and 420 are not limited to the configuration described in the above embodiment, and may be any transport mechanism that can transport the holding plate 160 in the transport direction.
(8) The insulating member 110 is not limited to a cylindrical shape and may be a hollow shape. The metal cylindrical portion 210 of the fixing terminal fitting 200 is not limited to a cylindrical body, but may be a hollow body, or may be a hollow body formed by cutting in the axial direction.
(9) The shape of the center electrode 120 and the terminal fitting 130 is not limited to a columnar shape, and may be appropriately changed as necessary as long as it can be inserted into the insulating member 110.
(10) The heat retaining member 190 is not limited to the columnar shape. For example, if the lower portion of the columnar portion 191 is fitted into the through-hole portion 168 and seated, the upper portion of the columnar portion 191 and the brim-shaped portion are provided. The shape of the annular portion 192 may be appropriately changed.
(11) By appropriately combining the first to tenth embodiments, it is possible to further improve the suppression of the variation in the electric resistance value described above.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a spark plug with a resistor manufactured in a first embodiment of the present invention.
FIG. 2 is a view showing a process of assembling a plug basic structure in the spark plug with a resistor of FIG. 1;
FIG. 3 is a view showing an assembling process of a plug basic structure in the spark plug with a resistor of FIG. 1;
FIG. 4 is a view showing an assembling process of a plug basic structure in the spark plug with a resistor shown in FIG. 1;
5 is a view showing an assembling process of a plug basic structure in the spark plug with a resistor of FIG. 1;
FIG. 6 is a sectional view of the plug substructure.
FIG. 7 is a sectional view of the plug substructure.
FIG. 8 is a plan view of the holding plate of FIGS. 6 and 7;
FIG. 9 is a partially broken schematic sectional view of the manufacturing apparatus according to the first embodiment, taken along line 9-9 in FIG. 10;
FIG. 10 is an enlarged sectional view and a partially enlarged sectional view taken along line 10-10 in FIG. 9;
FIG. 11 is an enlarged sectional view of a main part along line 11-11 in FIG. 9;
FIG. 12 is an enlarged sectional view of a main part shown in FIG. 11 in relation to the operation of the linear actuator.
FIG. 13 is an enlarged sectional view of a main part shown in FIG. 11 in relation to the operation of the linear actuator.
FIG. 14 is an enlarged sectional view of a main part of FIG.
FIG. 15 is a partially broken sectional view of the press device of FIG.
FIG. 16 is a cross-sectional view of the plug basic structure after terminal fittings are press-fitted.
FIG. 17 is an enlarged sectional view illustrating a main part of a second embodiment of the present invention.
FIG. 18 is a sectional view showing a main part of a third embodiment of the present invention.
FIG. 19 is a plan view of a holding plate according to the third embodiment.
FIG. 20 is a cross-sectional view illustrating a main part of a fourth embodiment of the present invention.
FIG. 21 is a plan view of a holding plate according to the fourth embodiment.
FIG. 22 is a plan view of a holding plate according to a fifth embodiment of the present invention.
FIG. 23 is a sectional view taken along the line 23-23 in FIG.
FIG. 24 is a rear view of the holding plate according to the fifth embodiment.
FIG. 25 is a sectional view taken along line 25-25 in FIG. 24;
FIG. 26 is a plan view of a holding plate according to a sixth embodiment of the present invention.
FIG. 27 is a rear view of the holding plate in the sixth embodiment.
FIG. 28 is a sectional view taken along line 28-28 in FIG. 26;
FIG. 29 is a rear view showing a main part of a seventh embodiment of the present invention.
FIG. 30 is a rear view showing a main part of an eighth embodiment of the present invention.
FIG. 31 is a plan view showing a main part of a ninth embodiment of the present invention.
FIG. 32 is a sectional view showing a main part of a tenth embodiment of the present invention.
[Explanation of symbols]
100: plug body, 110: insulating member, 120: center electrode,
130 ... terminal fittings, 140 ... sintered conductor, 150 ... plug basic structure,
151, 154: seal raw material powder mixture, 153 ... resistor raw material powder mixture,
155: conductive glass powder mixture, 161: holding hole, 164: surface,
165: back surface, 166, 168: through hole portion, 169: concave portion,
170, 180: receiving member, 190: heat retaining member, 195, 197: recess,
196: cylindrical portion, 220: ground electrode, 300: heating device,
311, 312: heating chamber; 321, 420: transport conveyor; 400: press device.

Claims

In a method for manufacturing a spark plug including a plug body,
A center electrode axially fitted to the distal end side of the hollow insulating member; a terminal fitting axially inserted to the base end side of the insulating member; and the insulating member between the center electrode and the terminal fitting. Prepare a plurality of plug substructures comprising a conductive glass powder mixture provided in the member, and prepare a holding plate formed by forming a plurality of holding holes in a discrete manner,
Of the plurality of plug substructures, a plug substructure located along an end of the holding plate (hereinafter, referred to as an end plug substructure) is heated more at the tip side than the holding plate. Through a hollow receiving member (hereinafter, referred to as an end-side receiving member) made of a heat conductive material having a low conductivity, a holding hole portion (along an end portion of the holding plate) of the plurality of holding hole portions that is located along an end portion of the holding plate. Hereinafter, it is fitted into the end-side holding hole, and the remaining plug base structure (hereinafter, referred to as the center plug base structure) is held at the distal end side by the remaining holding hole (hereinafter, center-side holding). (Referred to as a hole), whereby the plurality of plug substructures are held by the holding plate,
With the plurality of plug substructures supporting the holding plate such that the plurality of plug substructures extend upward from the holding plate, the plurality of plug substructures is formed by the glass powder in the conductive glass powder mixture. Heated together with the holding plate and the end side receiving member so as to soften,
After this heating, the holding plate holding the plurality of plug substructures is conveyed to the outside air in the supporting state,
The terminal fittings of each of the plurality of plug substructures are pressed into the corresponding insulating member in the axial direction by pressing, and the conductive glass powder mixture in the corresponding insulating member is subjected to compression sintering to thereby obtain a sintered conductive material. A method of manufacturing a spark plug, wherein each of the plurality of plug substructures is formed as the plug main body.

The center-side plug substructure is also passed through another hollow receiving member (hereinafter, referred to as a center-side receiving member) made of a heat conductive material having a lower thermal conductivity than the holding plate on the distal end side, By being fitted in the corresponding central side holding hole, the holding by the holding plate is performed,
Thereafter, in a state where the holding plate is supported so as to maintain the plurality of plug substructures extending upward, the heating is performed including the center-side receiving member,
The method according to claim 1, wherein the end-side receiving member is formed to have a larger heat capacity than the center-side receiving member.

The center-side plug substructure is also passed through another hollow receiving member (hereinafter, referred to as a center-side receiving member) made of a heat conductive material having a lower thermal conductivity than the holding plate on the distal end side, By being fitted in the corresponding central side holding hole, the holding by the holding plate is performed,
Thereafter, in a state where the holding plate is supported so as to maintain the plurality of plug substructures extending upward, the heating is performed including the center-side receiving member,
The method of claim 1, wherein a thermal conductivity of the end-side receiving member is lower than a thermal conductivity of the center-side receiving member.

The method according to claim 3, wherein the end-side receiving member is formed to have a larger heat capacity than the center-side receiving member.

5. The receiving member according to claim 1, wherein each of the receiving members is a cylindrical receiving member formed so as to cover a portion of the corresponding plug substructure that corresponds to the conductive glass powder mixture. 6. 7. A method for manufacturing a spark plug according to any one of the above.

The holding plate is formed in a concave shape so as to have a smaller heat capacity than the end portion of the holding plate at a position on the center side of the end side holding hole, and is configured as a small heat capacity portion. The method for manufacturing a spark plug according to claim 1.

The said holding plate is arrange | positioned so that it may protrude above the said holding plate between the holding holes adjacent to each other among the said end part side holding holes, The said holding plate is characterized by the above-mentioned. 7. The method for manufacturing a spark plug according to any one of items 1 to 6.

The holding plate is a rectangular holding plate in which the holding holes are formed and arranged in a grid along the transport direction or a direction crossing the transport direction,
Among the holding holes, the distance between the center of the holding hole located at one of both ends in the direction orthogonal to the transport direction and one of both ends in the orthogonal direction, and the holding hole located at the other of both ends in the orthogonal direction. 8. The spark according to claim 1, wherein a distance between a center of the holding hole and the other of both ends in the orthogonal direction is wider than a distance between centers of adjacent holding holes at the shortest distance. Plug manufacturing method.

9. The holding plate according to claim 1, wherein the holding holes adjacent to each other at the shortest distance among the holding holes are formed to have the same center distance. 7. A method for manufacturing a spark plug according to any one of the above.

A plurality of said holding plates, supported so as to maintain the upward extension of each of the plug substructures, continuously arranged without gaps in the transport direction, and the heating was performed. 10. The method for manufacturing a spark plug according to any one of the above items 9.

Among the holding holes of the holding plate, the center of the holding hole on the rear end side in the conveyance direction and the holding hole of the front end in the conveyance direction among the holding holes of the holding plate that are arranged in the conveyance direction. The method for manufacturing a spark plug according to claim 10, wherein the distance between the center of the spark plug and the center of the holding hole is the same as the distance between the centers of the holding holes adjacent to each other at the shortest distance among the holding holes.

In a spark plug manufacturing apparatus including a plug body, a heating chamber, and a heating device including a heating chamber transport mechanism supported so that it can be transported in a horizontal direction from the entrance to the exit in the heating chamber,
A press device disposed at the exit of the heating chamber so as to have a transport mechanism for a press device supported so as to be capable of being transported in a horizontal direction from the exit of the heating chamber to the transport direction of the transport mechanism for the heating chamber. ,
A center electrode axially fitted to the distal end side of the hollow insulating member; a terminal fitting axially inserted to the base end side of the insulating member; and the insulating member between the center electrode and the terminal fitting. Prepare a plurality of plug substructures comprising a conductive glass powder mixture provided in the member, and prepare a holding plate formed by forming a plurality of holding holes in a discrete manner,
Of the plurality of plug substructures, a plug substructure located along an end of the holding plate (hereinafter, referred to as an end plug substructure) is heated more at the tip side than the holding plate. Through a hollow receiving member made of a heat conductive material having low conductivity (hereinafter, referred to as an end receiving member), a holding hole (hereinafter, referred to as an end) located along an end of the holding plate among the holding holes. At the same time, the remaining plug base structure (hereinafter, referred to as a center plug base structure) is fitted to the remaining holding hole (hereinafter, referred to as a center holding hole) at the distal end thereof. ), The plurality of plug substructures are held by the holding plate,
The plurality of plug substructures is carried into the heating chamber by supporting the holding plate by the heating chamber transport mechanism so that the plurality of plug substructures extend upward from the holding plate,
In the heating chamber, the plurality of plug substructures are heated together with the holding plate and the end-side receiving member so that the glass powder in the conductive glass powder mixture is softened,
After this heating, the holding plate holding the plurality of plug substructures is carried out from the outlet of the heating chamber by the heating chamber transfer mechanism, and is carried into the press device by the press device transfer mechanism,
With this pressing device, the terminal fittings of each of the plurality of plug substructures are pressed into the corresponding insulating member in the axial direction by pressing, and the conductive glass powder mixture in the corresponding insulating member is compression-sintered. A plurality of plug substructures each being formed as the plug body by forming the plug substructures as sintered conductors.