JPH11219773A - Manufacture of spark plug and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably and efficiently adjust dimensions of a spark gap even if a deformation resistance of a grounding electrode varies among individual bodies of spark plugs. SOLUTION: A die 5 applies a processing in a direction to reduce a spark gap (g) to a grounding electrode W2 of a work W, Plural dies 5 having different finishing positions of processing, i.e., different sizes A are prepared, and an interval of the spark gap (g) is gradually reduced by applying the dies one by one to the grounding electrode W2 starting from one with a bigger A. The first die 5 applies the processing to W2 , and an interval of the spark gap (g) is then measured with a processing load removed. If the measured value is bigger than a target value, further processing is applied by using the next die 5 with the finishing position of processing located closer to the center electrode W1 side, and the processing and measurement of the spark gap (g) interval are repeated until the measured value reaches the target value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a center electrode disposed in an insulator, and a ground electrode facing the center electrode, wherein a center electrode is provided between the center electrode and the ground electrode and between the center electrode and the ground electrode. The present invention relates to a method and an apparatus for adjusting a spark gap interval of a spark gap of a spark plug in which a spark gap is formed at least in between.

[0002]

2. Description of the Related Art For example, among spark plugs of a so-called parallel electrode type, in which a tip end surface of a center electrode and a side surface of a ground electrode are substantially parallel to each other, a spark plug having a particularly small spark gap tolerance width or a spark plug originally having a small spark gap width. Conventionally, in the manufacture of a pole type spark plug, in order to secure a spark gap tolerance, the gap has been often adjusted manually. However, it is needless to say that manual adjustment of the spark gap interval is extremely inefficient and requires skill. Therefore, in order to automate such spark gap interval adjustment, Japanese Patent No. 2636814 discloses that
While pressing the outer surface of the ground electrode with a press punch, the spark gap interval is monitored in real time by image analysis,
A method of adjusting the pressing force so as to obtain a target spark gap interval is disclosed. Also, a method has been proposed in which a predetermined impact working pressure is repeatedly applied to the ground electrode by a hammering mechanism such as an air hammer (for example, Japanese Patent Application Laid-Open No. 8-1).
No. 53566).

[0003]

However, monitoring the spark gap interval while pressing the outer surface of the ground electrode,
The method of adjusting the pressing force has a drawback that the amount of elastic return of the ground electrode when the pressing is released is not always constant within the lot of the spark plug to be processed, and the obtained spark gap interval tends to vary. On the other hand, in the method using hammering, the impact position of the hammer on the ground electrode tends to change as the bending deformation of the ground electrode progresses. As a result, there is a problem that the deformation behavior of the ground electrode is not stable, and the spark gap interval finally obtained tends to vary.

Further, in the above-mentioned conventional technique by hammering, the same number of hits is set uniformly if the spark gap interval measured before the hit is the same. However, in general, when adjusting the spark gap of a large number of spark plugs, the deformation resistance to bending of the ground electrode generally varies between individual plugs. For example, spark plugs of the same standard have the same conditions (number of times). Even if you add hammering,
The same amount of deformation is not always obtained. Therefore, if the number of hammering times is determined uniformly according to the spark gap interval, the deformation proceeds too much and the spark gap interval becomes too narrow due to the variation in the deformation resistance of the ground electrode, or conversely, the deformation becomes insufficient and the spark gap becomes insufficient. Inconveniences such as an excessively large gap interval are liable to occur, and all of them have a problem of leading to a failure.

Here, for example, when the spark gap interval is larger than the target value, it is relatively easy to correct by adding hammering, but when the spark gap interval falls below the target value, the hammering method cannot be used. Therefore, the correction becomes very troublesome, and in some cases, the correction becomes impossible. In order to prevent such a situation, it is conceivable to perform hammering in a small number of times while monitoring the spark gap interval frequently, but this greatly reduces the efficiency of the spark gap adjustment step. Would be.

According to the present invention, even if the deformation resistance of the ground electrode varies among the individual spark plugs, the spark gap size can be adjusted reliably and efficiently, and the production efficiency and the yield of the spark plug are improved. It is an object of the present invention to provide a manufacturing method and an apparatus which can contribute to the above.

[0007]

The method of the present invention comprises a center electrode disposed in an insulator, and a ground electrode facing the center electrode. The present invention relates to a method for manufacturing a spark plug in which spark gaps having a predetermined interval are formed between at least one of the gaps and between the insulator and the ground electrode, and has the following features to solve the above-mentioned problems. That is, by bringing the working portion of the mold into contact with the ground electrode, and in that state, moving the mold relative to the ground electrode until the working portion reaches a predetermined working end position. Processing for reducing the spark gap is performed on the ground electrode. A plurality of molds are prepared, and in the direction of forming the spark gap, when a virtual reference position is set on the opposite side of the center electrode with respect to the ground electrode with respect to the spark plug to be processed, the plurality of molds are , The distance d from the reference position to the machining end position
Are different from each other and are applied to the ground electrode in ascending order of the distance d, thereby gradually reducing the spark gap interval. Then, the ground electrode is processed by a mold having a predetermined processing end position, and after the processing, the spark gap interval is measured in a state where the processing load by the mold is released, and the measured value is a target value. If it is larger than this, further processing is performed by using the next mold, and the processing and the measurement of the spark gap interval are repeated until the measured value reaches the target value.

Further, the device of the present invention has a center electrode disposed in an insulator, and a ground electrode facing the center electrode, and a space between the center electrode and the ground electrode and between the insulator and the ground electrode. A spark plug manufacturing apparatus in which spark gaps at predetermined intervals are formed in at least one of the spark plugs has the following characteristics. That is, a processing apparatus and a spark gap interval measuring mechanism for measuring a spark gap interval of the spark plug to be processed are provided. The processing device is configured to bring the processing action portion of the mold into contact with the ground electrode, and in that state, move the die relative to the ground electrode until the processing action portion reaches a predetermined processing end position. As a result, a process for reducing the spark gap is performed on the ground electrode. A plurality of molds are prepared, and in the direction of forming the spark gap, when a virtual reference position is set on the opposite side of the center electrode with respect to the ground electrode with respect to the spark plug to be processed, the plurality of molds are The distance d from the reference position to the processing end position is different from each other, and the spark gap interval is gradually reduced by applying the distance d to the ground electrode in ascending order. Then, the ground electrode is processed by a mold having a predetermined processing end position, and after the processing, the spark gap interval is measured in a state where the processing load by the mold is released. If the value is larger than the value, further processing is performed by using the next mold, and the processing and the measurement of the spark gap interval are repeated until the measured value reaches the target value.

[0009] In the method or apparatus according to the present invention,
A state in which a plurality of dies having different processing end positions are sequentially applied to the ground electrode, so that the processing for reducing / adjusting the spark gap interval is performed stepwise, and the processing load is released each time processing at each step is completed. , The spark gap interval is confirmed by measurement, and processing is terminated when the measured spark gap interval reaches a target value. Therefore, even if the amount of elastic return after processing of the ground electrode varies, the spark gap interval after the elastic recovery is confirmed, and if it is insufficient, additional processing may be performed. Therefore, the spark gap interval can be reliably adjusted to a target value. In addition, since the hammering, in which the impact position on the ground electrode is easy to change, is not used, and a mold with a fixed processing end position is used, the amount of processing in each processing step can be precisely controlled, and the deformation of the ground electrode Resistant to variations in resistance. In addition, a situation in which the spark gap interval is excessively reduced and correction is difficult or impossible is unlikely to occur. From these facts, it is possible to efficiently and accurately adjust the spark gap interval of the spark plug, which can contribute to improvement in manufacturing efficiency and yield.

In the spark plug to be processed, the direction in which the spark gap is formed by the mold may be, for example, a direction along the axis of the metal shell and toward the base end of the center electrode (ie, the axial direction). This is suitable for manufacturing a parallel electrode type spark plug described later. On the other hand, in a plane orthogonal to the axis of the center electrode, the direction may be a direction toward the axis of the center electrode (so-called radial direction). This is suitable for manufacturing a multipolar spark plug described later. Here, the direction in which the spark gap is formed and the direction in which the mold moves need not necessarily match.

In the above method or apparatus, the mold is
It is possible to approach / separate from the ground electrode in the axial direction of the metal shell. In this case, the processing action portion contacts the outer surface of the bent portion of the ground electrode, thereby moving the processing displacement component in the y direction along the axis of the metal shell and toward the base end of the center electrode, and also the axis of the ground electrode. A processing displacement component in the x direction orthogonal to the y direction and toward the tip end of the ground electrode in a plane including the same can be generated with respect to the ground electrode. However, the side where the spark gap is located in the axial direction of the center electrode is the front end side, and the opposite side is the rear end side. According to this method, for example, as shown slightly exaggeratedly in FIG. 3 (a), the inner edge of the tip of the projecting portion of the mold becomes the working portion (5a) and is formed on the outer surface of the bent portion of the ground electrode (W2). By contact, the ground electrode (W2) is pushed by the working portion (5a) not only in the above-mentioned y direction (that is, the moving direction of the mold) but also in a direction x orthogonal to this direction. (Α in the y direction and β in the x direction).

[0012] For example, as shown in FIG. 3 (b), such a mold is placed between an inner side surface of the ground electrode (W2) bent sideways and a front end surface of the center electrode (W1). When applied to a spark plug in which a spark gap (g) is formed (a so-called parallel electrode type spark plug), the spark gap interval can be adjusted using the processing displacement α in the y direction. On the other hand, as shown in FIG. 3C, a ground electrode (W2) is provided on the side surface of the center electrode (W1) such as a multipolar spark plug.
In the spark plug of the type in which the spark gap (g) is formed with the front end faces facing each other, the spark gap interval can be adjusted using the processing displacement β in the x direction. in this way,
One type of mold has an advantage that it can be applied to a plurality of types of spark plugs having different spark gap formation modes.

Next, a mold receiving portion is formed at a predetermined position of the spark plug to be processed or at a predetermined position of a plug support for supporting the spark plug to be processed. Can be formed. In this case, when the mold relatively approaches the spark plug to be processed, the positioning contact portion contacts the mold receiving portion, whereby the working portion of the mold is positioned at the machining end position. You can do so. Further, by changing the dimensions of the mold from the positioning contact portion to the working portion, it is possible to adjust the machining end positions of the molds to be different from each other. According to this, the processing contact portion formed on the mold is brought into contact with the mold receiving portion formed on the spark plug to be processed or the plug support, so that the working portion of the mold is at the processing end position. It will be positioned. That is, the processing end position is determined by the dimensions of the die, and even if the absolute position of the spark plug to be processed slightly changes, the processing end position relative to the processed spark plug does not change. As a result, variations in the processing amount are less likely to occur, and the accuracy of adjusting the spark gap interval can be further improved.

The spark plug to be processed has one end coupled to the front end surface of the metal shell, and the other end side bent back to the center electrode side to form a bent portion. When the mold is used to approach or separate from the ground electrode in the axial direction of the metal shell, the following modes are possible. That is, the mold receiving portion of the spark plug to be processed is formed on the metal shell or a plug support that supports the spark plug to be processed in the metal shell.
In addition, the mold has a main body that is located on the side of the metal shell at a position corresponding to the ground electrode and extends in the axial direction of the metal shell, and when the mold approaches the ground electrode, The rear end of the main body portion serves as a positioning contact portion and comes into contact with the mold receiving portion, while a protruding portion protruding toward the ground electrode is formed on the front end side of the main body portion. As a result, the inner edge of the tip of the protruding portion comes into contact with the outer surface of the bent portion of the ground electrode as a working portion. By doing so, similarly to the above, it is possible to cause processing displacement in the two directions of x and y, and it is possible to cope with a plurality of types of spark plugs having different spark gap formation modes. . For example, when a spark plug to be processed is used in which a flange-shaped gasket receiving portion is formed along the circumferential direction at a position separated by a predetermined length in the axial direction from the leading end edge on the outer peripheral surface of the metal shell. The gasket receiving portion can be used as the mold receiving portion.

Next, in the method of the present invention, an image of the spark gap forming portion formed by the ground electrode and the center electrode is photographed, and the spark gap interval is measured based on the photographed image. it can. In this case, the device of the present invention includes, as a spark gap interval measuring mechanism, an image capturing device that captures an image of a spark gap forming portion formed by the ground electrode and the center electrode, and a spark based on the captured image. And a measurement analysis means for measuring the gap interval. By the image processing, the spark gap interval of the spark plug to be processed can be accurately measured, and the adjustment accuracy of the spark gap interval can be improved.

The apparatus of the present invention can be provided with a to-be-processed spark plug transport mechanism for intermittently transporting the to-be-processed spark plug along a predetermined transport path. In this case, a plurality of molds each having a different machining end position, and a plurality of unit machining devices including a mold drive mechanism for relatively moving the mold closer to and away from the ground electrode of the spark plug to be processed,
A spark gap interval measuring mechanism provided in association with each unit processing device, and a spark plug to be processed (hereinafter, a passing spark plug which is also provided in association with each unit processing device and whose spark gap interval reaches a target value) ) From the transport path may be arranged at a plurality of predetermined intervals along the transport path in the order in which the distance d of the mold is gradually increased. According to this, stepwise bending of the ground electrode can be performed in parallel on a plurality of spark plugs to be sequentially conveyed, and thus the spark plug gap adjusting process of the spark plug according to the present invention can be performed extremely. It can be performed efficiently. In this case, in each set, the unit processing device, the spark gap interval measuring mechanism, and the discharging mechanism are arranged at substantially equal intervals in this order from the upstream side in the transport direction of the spark plug to be processed, and the position of each device or mechanism. If the processing, spark gap interval measurement and discharge of the passed spark plug are performed sequentially while repeating intermittent stop at
The spark gap interval adjustment processing can be performed more efficiently.

[0017]

Embodiments of the present invention will be described below with reference to embodiments shown in the drawings. 1A and 1B are a plan view and a side view conceptually showing one embodiment of a spark plug manufacturing apparatus (hereinafter, simply referred to as a manufacturing apparatus) of the present invention. The manufacturing apparatus 1 includes a linear conveyor 300 as a transport unit that intermittently transports a to-be-processed spark plug (hereinafter, also referred to as a workpiece) W along a linear transport path C, and along the transport path C. , A process implementation unit for adjusting the spark gap interval of the work W, that is, a work loading mechanism 11 as a spark plug loading mechanism to be processed, a ground electrode alignment mechanism 12 for positioning a ground electrode of the work W at a predetermined position, and photographing / analysis for preparation Unit 13
(Measuring mechanism for spark gap before bending), rejected product discharging mechanism (A) 14, a plurality of spark gap adjusting units (10 sets in this embodiment) (I) to (X), and rejected product discharging mechanism (B) ) 2
1 are arranged in this order from the upstream side in the transport direction.
Each of the spark gap adjusting units (I) to (X) includes a mold bending machine (unit processing device) 15, a photographing / analyzing unit 16 (spark gap interval measuring mechanism), and an acceptable product discharging mechanism 17 (discharging mechanism). And these are arranged in this order along the transport path C. In addition, the arrangement interval of each process execution unit is adjusted so that it is an integral multiple of the distance δ in units of a certain distance δ along the transport path C.

In the linear conveyor 300, a carrier 302 on which a work W is detachably mounted is attached to a chain 301 as a circulating member at predetermined intervals. Then, the chain 301 is connected to the servo motor 2
4 intermittently drives the carrier 302, that is, the work W, intermittently by the unit of the distance δ along a predetermined linear path.

As shown in FIGS. 2A and 4A,
The workpiece W includes a cylindrical metal shell W3, an insulator W4 fitted inside the metal shell W3 such that the front end and the rear end protrude, and a center electrode W inserted in the axial direction of the insulator W4.
1, and a ground electrode W2, one end of which is connected to the metal shell W3 by welding or the like and the other end side is bent back to the side, and the side surface is arranged so as to face the tip of the center electrode W1.
Etc. are provided. The opposing portion between the center electrode W1 and the ground electrode W2 is used as a firing portion, and the opposing direction (the center electrode W2)
A gap formed between 1 and the axial direction of the metal shell W3) is a spark gap g. In the axial direction O of the center electrode W3, the side where the spark gap g is located is the front end side, and the opposite side is the rear end side.

The metal shell W3 is formed in a cylindrical shape from a metal such as low carbon steel, and constitutes a housing of the spark plug W to be processed.
A screw portion W5 for attaching the plug W to an engine block (not shown) is formed. A gasket receiving portion W6 is formed on the outer peripheral surface of the metal shell W3 so as to protrude in a flange shape along the circumferential direction adjacent to the base end side (rear end side) of the screw portion W5 in the axial direction. Is formed. A tool engaging portion W7 having a hexagonal axial cross-sectional shape is formed on the rear side of the gasket receiving portion W6 so as to protrude outward.

On the other hand, a cylindrical work holder 23 having an open upper end is integrally mounted on the upper surface of each carrier 302. The work W is removably inserted into the work holder 23 from the rear end side, and the rear end edge of the tool engagement portion W7 is supported from below by the peripheral edge of the opening of the work holder 23. The sheet is conveyed together with the carrier 302 in a state where the gap g side is up.

The work carrying mechanism 11, the rejected product discharging mechanism (A) 14, the rejected product discharging mechanism (B) 21 and the accepted product discharging mechanism 17 shown in FIG.
Is, for example, as shown in FIG.
A work supply unit or a work discharge unit (provided at a position J in the figure) set to the side in the transport direction C of FIG.
It is constituted as a transfer mechanism for transferring the work W between the work holder 23 positioned in the carry-in or discharge mechanism. The transfer mechanism 35 includes a chuck hand mechanism 36 held up and down by an air cylinder 37, and an advance / retreat drive mechanism 39 for driving the chuck hand mechanism 36 forward / backward by an air cylinder 38 or the like. The chuck hand mechanism 36 is driven to open and close by an air cylinder or the like (not shown). The chuck hand mechanism 36 is lowered by the air cylinder 37 to hold the work W, and then moved up and down by the air cylinder 38 to move to the transfer destination. Then, it is lowered again to release the holding of the work W, and the transfer is completed.
Then, in the case of loading the work, the work W is received by the work supply unit, transferred to the work holder 23 of the linear conveyor 300, and mounted thereon. On the other hand, in the case of discharging the work, the work W is extracted from the work holder 23, transferred to a work discharge section (for example, a work collection box or a shooter) and discharged.

FIG. 6 conceptually shows a configuration example of the ground electrode alignment mechanism 4. The ground electrode alignment mechanism 4 is capable of approaching / separating from the tip of the work (spark plug) W in the axial direction, and is rotated by a motor 151 or the like at a predetermined angle (one rotation in this embodiment) around the axis. It has a rotating member 150 provided rotatably intermittently, and a groove 152 having a width, length, and depth corresponding to the ground electrode W2 of the work W is formed on the bottom surface of the rotating member 150. It is formed so as to be cut in the radial direction from the outer peripheral surface.

When the work W is carried into the ground electrode alignment mechanism 4, the rotating member 150 falls to the tip of the work W. At this time, the direction of the groove 152 of the rotating member 150 is along the transport path C (FIG. 1), and its open side edge is
It is located on the arrangement side of a mold 5 (FIG. 4) described later, in this embodiment, on the upstream side in the transport direction C. Then, at the time of being brought into the ground electrode alignment mechanism 4, the ground electrode W
Since the position of 2 is indefinite, even if the rotating member 150 falls, in many cases, the groove 152 does not fit with the ground electrode W2, and the rotating member 150
It will be on top.

Next, the motor 151 operates and the rotating member 1
50 rotates around the axis while sliding on the ground electrode W2 on the bottom surface. The ground electrode W2 has a groove 15 during its rotation.
2 and thereafter, the work W rotates together with the rotating member 150. Then, the rotation member 150 stops rotating when it makes one rotation from the initial position. This allows
The ground electrode W2 is positioned in the direction along the transport direction C. The driving unit of the rotating member 150 may be configured by a rotary actuator using air or hydraulic pressure.

Next, as shown in FIG. 7, each of the preparation photographing / analyzing unit 13 and the photographing / analyzing unit 16 (FIG. 1) includes a photographing camera 40 and an analyzing section (measurement / analysis means) ) 110. Camera 40
Is configured as a CCD camera having, for example, a two-dimensional CCD sensor as an image detection unit, and is held at a predetermined height by a frame or the like (not shown) so that the work W carried into the photographing / analysis unit 13 is The ignition portion formed by the center electrode W1 and the ground electrode W2 and the spark gap g are photographed from the side. Note that the photographing optical system of each photographing camera 40 is preferably configured by a telecentric optical system so that a change in image size due to defocus is reduced. FIG. 16 schematically shows an example of the photographed image.

FIGS. 2A and 2B schematically show an example of a mold bending machine (hereinafter, simply referred to as a machine) 15. The work W is carried into the processing machine 15 by the linear conveyor 300, and is positioned at a predetermined processing position. The processing machine 15 has a total of four columns 51 erected at predetermined intervals in front and rear on both sides in the transport direction of the linear conveyor 300, and a support plate 52 is attached to the upper ends of the columns 51, The machine frame of the processing machine 15 is formed. On the upper surface of the support plate 52, a cylinder 53 (a mold driving mechanism) driven by pneumatic or hydraulic pressure is provided.
Is attached, and a piston rod 54 extending downward through the support plate 52 is moved up and down. The mold holder 5 is provided on the lower end surface of the piston rod 54.
The mold 5 for bending the ground electrode is mounted on the mold holder 55 in a detachable manner with bolts 56 and the like. On the other hand, below the carrier 302 positioned at the processing position, a receiving punch 57 that comes into contact with the lower surface of the carrier 302 and receives the processing force of the mold 5 is arranged to be able to move up and down. Receiving punch 57
Retreats downward while the carrier 302 is moving, and rises during processing to contact the lower surface of the carrier 302. However,
When the interference between the moving carrier 302 and the receiving punch 57 does not matter, the vertical position of the receiving punch 57 may be fixed.

The work W is placed on the ground electrode alignment mechanism 4 (FIG. 6).
As a result, the ground electrode W2 is aligned in the transport direction C and its front end face is directed downstream in the transport direction C, and is positioned in the processing machine 15. By extending the piston rod 54 by the cylinder 53, the mold 5 approaches and separates from the ground electrode W2 from above in the axial direction of the metal shell W3.

As shown in FIG. 4A, the mold 5 has a main body 5b which is located on the side of the metal shell W3 at a position corresponding to the ground electrode W2 and extends in the axial direction of the metal shell W3. At the same time, when the mold 5 approaches the ground electrode W2 side, the lower end surface 5d (rear end: positioning contact portion) of the main body 5b and the upper surface (mold receiving portion) W6a of the gasket receiving portion W6. It comes into contact. A protruding portion 5 protruding toward the ground electrode W2 is provided on the tip end side of the main body 5b.
a is formed, and a predetermined amount of radius (for example, about 2 to 10 mm) is applied to the edge on the inner edge side of the tip. The rounded portion becomes the working portion 5c, and the mold 5 descends to come into contact with the ground electrode W2, and the ground electrode W2 is subjected to a bending process in a direction in which the spark gap g is reduced.

When the mold 5 approaches the work W from above, the working portion 5c contacts the ground electrode W2 at a certain position. In this state, when the mold 5 is further lowered to a position corresponding to the gasket receiving portion W6, bending of the ground electrode W2 by the working portion 5c proceeds. When the main body 5b comes into contact with the gasket receiving portion W6, the working portion 5c is at the working end position PF, where bending to the ground electrode W2 is also finished. As shown in FIG. 4B, the upper end surface 23a of the work holder 23 projects outward from the outer peripheral edge of the tool engaging portion W7 of the metal shell W3 to form a mold receiving portion, and the main body portion is formed. The rear end face (positioning contact portion) of 5b may be brought into contact therewith.

As shown in FIG. 3A, the working portion 5c
Is in contact with the outer surface of the bent portion of the ground electrode W2, and along the axis O of the metal shell W3 and toward the base end of the center electrode W1 in the y-direction, a processing displacement component α in the plane including the axis of the ground electrode W2. The processing displacement component β in the x direction orthogonal to the y direction and toward the tip end of the ground electrode W2 is
2 against. In the work W of FIG. 1, as shown in FIG. 3B, a spark gap g is formed between the inner surface of the ground electrode W2 bent sideways and the front surface of the center electrode W1. Since the spark gaps are formed, the spark gaps g are formed in the y direction, and the intervals thereof are adjusted using the corresponding machining displacement α.

The outline of the method for adjusting the spark gap interval of the spark plug by the manufacturing apparatus 1 will be described below with reference to FIG. First, the work W mounted on the carrier 302 of the linear conveyor 300 is photographed by the preparation photographing / analysis unit 13 by the work loading mechanism 11 of FIG. 1, and an image of the ignition portion is photographed. Initial value (hereinafter referred to as spark gap initial value) g
0 is measured. Based on the initial value g0, it is determined whether or not the spark gap of the workpiece W can be adjusted. If not, the workpiece W is removed from the linear conveyor 300 by the rejected product discharging mechanism (A) 14. On the other hand, when it is determined that the adjustment is possible, the spark gap adjustment is sequentially performed by the subsequent spark gap adjustment units (I) to (X).

In the mold bending machine 15 of each spark gap adjusting unit, the upper limit position of the drive stroke of the piston rod 54 in FIG. 2 is adjusted to be the same, while the main body of the mold 5 is adjusted as shown in FIG. The dimensions A from the lower end face position of the portion 5b to the working portion 5c are all different values, and are arranged in descending order of the value of A from the upstream side of the transport path C (FIG. 1). In the present embodiment, the most upstream processing machine 1
5 is set to A0 (mm), and thereafter, the dimension A is set so as to decrease by 0.01 mm (therefore, the mold 5 of the processing machine 15 on the most downstream side has the dimension A = A0).
−0.09 mm). In this case, as shown in FIG. 4A, when a virtual reference position PB with respect to the workpiece W is set on the opposite side of the center electrode W1 with respect to the ground electrode W2 in the direction of forming the spark gap g. When the value of A increases, the distance d from the reference position PB to the machining end position PF decreases. Therefore, it can be said that the respective die bending machines 15 are arranged in the order in which the distance d is sequentially increased.

The work W is placed on the linear conveyor 300.
Is carried to the mold bending machine 15 of the first spark gap adjusting unit (I), where it is bent by the mold 5 of A = A0. Next, the mold 5 is retracted to release the processing load, and is carried to the photographing / analysis unit 16 (FIG. 1) to measure the spark gap interval again. Then, if the spark gap interval has reached the target value, it is determined that the work has passed, and the passed work discharge mechanism 17 of the unit discharges and collects the passed work. On the other hand, if the measured value of the spark gap interval has not reached the target value, the same is sent to the subsequent spark gap adjusting unit and the same process is repeated. In this case, the dimension A of the mold is reduced by 0.01 mm each time the spark gap adjusting unit is shifted to the one stage downstream, and the processing end position PF in FIG. Approaching. When the spark gap interval reaches a target value in a certain spark gap adjusting unit, the processing is discontinued in that unit, and the passed work W is discharged and collected. In the final spark gap adjustment unit (X),
The work W determined to be rejected because the spark gap interval does not fall within the target value range is discharged and collected by the rejected product discharge mechanism (B) 21 in FIG.

For example, the ground electrode W2 may have variations in the deformation resistance and the amount of elastic return (spring back) after processing among the workpieces. However, in the above method, the processing of the ground electrode W2 is performed stepwise in units of 0.01 mm, and the spark gap interval after elastic recovery is confirmed by image analysis every time the processing of one step is completed. Is designed to perform additional processing by a subsequent spark gap adjusting unit. Therefore, the spark gap interval can be reliably adjusted to the target value. Also,
Since the hammering in which the hitting position with respect to the ground electrode W2 is easy to change is not used, and the mold 5 having the determined processing end position according to the dimension A is used, it is possible to precisely control the processing amount in each processing step. Therefore, the resistance to deformation of the ground electrode W2 is hardly affected.

Hereinafter, an example of an operation sequence of the manufacturing apparatus 1 will be described. FIG. 9 shows the main control unit 10 of the manufacturing apparatus 1.
FIG. 3 is a block diagram illustrating an electrical configuration of a peripheral device 0 and its surroundings. The main control unit 100 includes a microprocessor including an I / O port 101 and a CPU 102, a ROM 103, a RAM 104, and the like connected thereto.
103 stores a main control program 103a. The drive unit 2c of the linear conveyor 300 (FIG. 1) is connected to the I / O port 101. The drive section 2c includes a servo drive unit 2a, the above-described servo motor 24 for driving the conveyor connected thereto, and an angle sensor 2b such as a rotary encoder for detecting the rotational angle position of the servo motor 24. It is configured.
In addition, the I / O port 101 includes the above-described process execution units, namely, the work loading mechanism 11, the ground electrode alignment mechanism 12, the preparation photographing / analysis unit 13, and the rejected product discharging mechanism (A) 1.
4. Spark gap adjusting units (I) to (X) (including mold bending machine 15, photographing / analyzing unit 16, and acceptable product discharging mechanism 17, respectively) and reject product discharging mechanism (B) 21
Is connected.

Further, to the I / O port 101 are connected a storage device 105 composed of a hard disk device and the like, and an input unit 106 composed of a keyboard or a mouse. The storage device 105 stores, for each type of spark plug for which the spark gap interval is to be adjusted, a plug part number as information for specifying the type, a value of the target spark gap interval, and the like. Used and used. On the other hand, the RAM 104
In addition to functioning as a work area 104a, it is used as a memory for storing various measured values described later, a storage area for control flags, and the like.

Next, the electrical configuration of the preparation photographing / analyzing unit 13 and the photographing / analyzing unit 16 are exactly the same. FIG. 10 is a block diagram showing one example (hereinafter, a representative example will be described with the photographing / analysis unit 16).
The photographing / analyzing unit 16 is configured such that the analyzing unit 110
O port 111 and CPU 112 and RO connected thereto
The microprocessor 113 includes a microprocessor including an M113 and a RAM 114, and the ROM 113 stores an image analysis program 113a. RAM 114 is
It functions as a work area for the CPU 112. Also, I
The I / O port 111 has a camera 40 (two-dimensional CCD).
Sensor 115 and a sensor controller 116 for converting the sensor output into a two-dimensional digital image signal).

FIG. 11 is a block diagram showing an example of an electrical configuration of the die bending machine 15. As shown in FIG. Mold bending machine 15
Means that the control unit 120 includes an I / O port 121 and a CPU 122, a ROM 123, and a RAM 12 connected thereto.
The control program 123a is stored in the ROM 123. A cylinder 53 (FIG. 2B) for driving the above-described mold 5 is connected to the I / O port 121 via a cylinder driving unit 53a. RAM12
Reference numeral 4 functions as a work area for the CPU 122.

FIG. 12 shows the transfer mechanism 35 included in the work loading mechanism 11, the rejected product discharging mechanism (A) 14, and the rejecting mechanism (B) 21.
FIG. 6 is a block diagram illustrating an example of an electrical configuration of FIG. The transfer mechanism 35 is such that the control unit 130 controls the I / O port 131
And the CPU 132, ROM 133 and R connected thereto.
The operation mechanism 135 including the chuck hand mechanism 36, the air cylinder 37, the air cylinder 38, and the like in FIG. 5 is connected to the microprocessor 134. The ROM 133 stores a control program 133a, and the RAM 134 functions as a work area for the CPU 132.

Hereinafter, the operation of the manufacturing apparatus 1 will be described. First, FIG. 13 shows a flow of the drive processing program MP1 of the linear conveyor 300 by the main control unit 100 in FIG. In the step of M101, each process execution part of FIG. 9, that is, the work loading mechanism 11, the ground electrode alignment mechanism 1
2. Preparation / analysis unit 13 for rejected products
(A) 14, spark gap adjusting units (I) to (X) (mold bending machine 15, photographing / analyzing unit 16,
Passed product discharge mechanism 17) and rejected product discharge mechanism
(B) An activation signal is transmitted to 21. In response to this, the control programs are simultaneously activated on the respective process execution units (the analysis unit 110 and the control units 120 and 130 in FIGS. 10, 11 and 12). As described later, these control programs are executed each time the processing is completed.
To return a completion signal. On the other hand, the program MP1 turns on the process end flag (formed in the RAM 104 of FIG. 9) every time these completion signals are received (M102 to M109, M1101 to M1).
206, M118, M119). In the case where another process (not shown) is present, a similar flag is provided, and is turned on each time a completion signal is received. Then, if all the flags are turned on in M120, the linear conveyor 300 (FIG. 1) is driven by a certain distance δ, and the flags are reset. Thereby, each work W is simultaneously carried to the next process position and stopped. Next, in M125, a new start signal is transmitted to each step execution unit, and the process returns to M102 to repeat the same processing.

In response to the start signal, the control program at each process execution section is executed in parallel for a plurality of works W held at each process execution position (FIG. 1). Less than,
In order to facilitate understanding, the flow of processing of each program will be described using flowcharts as appropriate according to the execution order when focusing on one work W. First, as shown in FIG. 18, in the work W loading process (LP2) by the work loading mechanism 11, the presence or absence of the work W to be loaded is checked by a sensor (not shown) or the like (L201). Work loading mechanism 11 performs a loading operation (L204:
In this process, L202 and L203 are skipped).
Thereby, a new work W is mounted on the work holder 23 (FIG. 2). When the operation is completed, a completion signal is transmitted (L205).

The work W, which has been subjected to preliminary bending with respect to the ground electrode W2, is carried into the linear conveyor 300. FIG. 14 conceptually illustrates the preliminary bending step. As shown in FIG. 14A, the ground electrode W2 of the work W has a shape extending straight in the axial direction of the metal shell W3 before the preliminary bending. First, the rough bending spacer 250 (the upper surface is an inclined surface) is brought into contact with the front end surface of the center electrode W1.
By pressing the roller 251 of the roller pusher 252 from the side, the ground electrode W2 is bent to a position where it hits the upper surface of the coarse bending spacer 250.
As a result, a temporary gap g 'is formed between the side surface of the ground electrode W2 and the front end surface of the center electrode W1 so that the coarse bending spacer 250
Corresponding to the upper surface of the ground electrode W2. Next, the coarse bending spacer 25
Spark gap initial value g to extract 0 and obtain instead
A finishing spacer 253 having a thickness corresponding to 0 (set to be larger than the final spark gap interval target value) is inserted. In this state, the preliminary bending is completed by pressing the ground electrode W2 against the finishing spacer 253 by the bending punch 254, and a spark gap g having an initial value g0 is formed between the ground electrode W2 and the center electrode W1. You.

The work W carried into the linear conveyor 300 is conveyed to the ground electrode alignment mechanism 4 shown in FIG. 1, and the alignment processing of the ground electrode W2 already described with reference to FIG. 6 is performed. Then, it is further transported to the next position, and the process of measuring the spark gap initial value g0 by the photographing / analysis unit 13 for preparation is performed. The flow of the control program LP1 for measuring the spark gap interval is as shown in FIG. That is, upon receiving the activation signal (L101), the image of the firing portion of the work W is photographed by the photographing camera 40 of FIG. 7 (L102).
As a result, as shown in FIG. 16, the ground electrode W2 and the center electrode W1 produce an image due to light and darkness between the background and the background, and the image data is captured via the I / O port 111. It is. Next, the image data is binarized (L103), and from the image, an edge K1 on the ground electrode side facing the spark gap g and an edge K2 on the center electrode side as well.
Are determined (L104, L105).

Next, the origin O '(0,0) is set at one end (left end in this embodiment) of the edge K2 on the center electrode side (L106), and the scan position X (x, y) is set. The origin O 'is set (L107). Then, a reference line V passing through the scan position X and orthogonal to the edge K2 is generated (L108), the coordinates of the intersection P with the edge K1 on the ground electrode side are determined (L109), and the spark gap interval is determined by the line segment XP.
(L110: However, when no intersection P occurs, the calculation and storage of the spark gap interval are not performed). Next, a new reference line V is generated by increasing the x coordinate of the scan position X by a fixed amount Δx (L111, L112), and the process returns to L109 to return to the edge K1.
Is calculated and stored in the same manner as described above. Then, the processing of L109 to L112 is repeated until the intersection with K1 does not occur, and the smallest one of the measured spark gap intervals is the measured value of the spark gap interval gn (in this case, the spark gap initial value g0).
And transmits it to the main control unit 100 (FIG. 9) (L
111-L115).

The main controller 100 (FIG. 9) receives this, and the process proceeds to the spark gap initial value determination processing MP2 in FIG. First, the spark gap interval measurement value gn is received from the preparation photographing / analysis unit 13 (M201), and gn is g ′.
min to g'max (where g'min is the initial lower limit allowable value,
It is checked whether g'max is within the range of an initial upper limit allowable value, g'min <g'max (M202, M203). If the measured value of the spark gap interval gn falls within this range, it is determined that adjustment to the spark gap interval target value is possible, and the rejected product discharge mechanism (A) 14 (FIG. 1) on the downstream side is determined. , A non-operation command signal for commanding non-operation of the work, and an operation command signal to the mold bending machine 15 (FIG. 1) of the spark gap adjusting unit (I) (M204, M205). On the other hand, gn is g'min
If it is out of the range of ~ g'max, it is judged as a rejected product, and an operation command signal is transmitted to the rejected product discharging mechanism (A) 14 (FIG. 1). On the other hand, the carrier 302 of the linear conveyor 300 from which the work W has been discharged is further conveyed to the downstream side in an empty state. Not to do
A non-operation command signal for the workpiece W is transmitted to all the process execution units downstream of the rejected product discharge mechanism (A) 14 (M206, M207).

Next, the transfer mechanism 35 of the rejected product discharge mechanism (A) 14 is controlled by the same flow as LP2 in FIG. Then, upon receiving an operation command signal from the main control unit 100 (FIG. 9) in L203, the transfer mechanism 35 is operated in L204, and the rejected work W is discharged from the linear conveyor 300 (FIG. 1). On the other hand, if a non-operation command signal is received in L202, L204 is skipped and the transfer mechanism 35
Does not work. In any case, a completion signal is finally transmitted to the main control unit 100 (FIG. 9) in L205.

FIG. 19 shows an operation control program LP3 of the die bending machine 15. That is, L
When an operation command signal is received from the main control unit 100 (FIG. 9) at 302, the mold driving cylinder 53 of FIG. 2 is operated at L303, and the ground electrode W2 of the work W is bent by the mold 5. On the other hand, when a non-operation command signal is received in L301, L303 is skipped and the cylinder 53 does not operate. In any case, a completion signal is finally transmitted to the main control unit 100 in L304.

Returning to FIG. 1, the spark gap adjusting unit
The workpiece W subjected to bending by the mold bending machine 15 in (I) and the spark gap interval has been adjusted is conveyed to the photographing / analysis unit 16 and subjected to exactly the same flow as LP1 in FIG. Is performed, and the measured value gn is transmitted to the main control unit 100 (FIG. 9).

The main controller 100 receives this, and the spark gap determination processing MP4 shown in FIG. 20 is performed. Here, the measured value gn is received in M401, and it is checked whether or not gn is smaller than the target value gp (that is, whether or not the spark gap interval has reached the target value gp) (M402). If the measured value of the spark gap interval gn is larger than the target value gp, it is determined that further processing is necessary, and a non-operation is commanded to the acceptable product discharging mechanism 17 (FIG. 1) in the spark gap adjusting unit. An operation command signal is transmitted to the mold bending machine 15 (FIG. 1) of the spark gap adjusting unit (in this case (II)) (M403, M40).
4). On the other hand, when gn ≦ gp, an operation command signal is transmitted to the accepted product discharging mechanism 17 (FIG. 1) in the spark gap adjusting unit, and all the process execution units downstream of the accepted product discharging mechanism 17 are sent. Then, a non-operation command signal for the work W is transmitted (M405, M406).

As described above, in the spark gap adjusting units (I) to (IX) of FIG. 1, the mold bending machine 15 operates according to LP3 of FIG. 19 only when an operation command signal is received from the main control unit 100 side. The photographing and analyzing unit 16 is shown in FIG.
20. The main control unit 100 performs the spark gap determination processing MP4 of FIG. 20 for the measured value gn of the spark gap interval. If gn ≦ gp, the bending process is completed by the spark gap adjusting unit, and the workpiece W is discharged and collected by the accepted product discharging mechanism 17 (FIG. 1). If gn> gp, the next spark gap is adjusted. The same process is repeated after being carried to the adjustment unit.

The work W transported to the last spark gap adjusting unit (X) without being discharged halfway is bent by the mold bending machine 15 to form the ground electrode W2, photographed and analyzed. The measurement of the spark gap interval by the unit 16 is performed in the same manner, while the main control unit 1
On the 00 side, the spark gap final determination process MP5 of FIG. 21 is executed. Here, first, the measured value gn is gmin to gma
It is checked whether or not x (where gmin is a final lower limit allowable value, gmax is a final upper limit allowable value and gmin <gmax) (M502, M503). If the measured value of the spark gap interval gn falls within this range, it is determined to be acceptable, and an operation command signal for the workpiece is sent to the next acceptable product discharging mechanism 17 (FIG. 1), and the unacceptable product is also sent. Discharge mechanism
(B) The non-operation command signal is transmitted to 21 (M5
04, M505). On the other hand, if gn is out of the range of gmin to gmax, it is judged as a rejected product, and the non-operation command signal for the workpiece is sent to the accepted product discharging mechanism 17 (FIG. 1). B) An operation command signal is transmitted to 21 (M504, M505). And
Upon receiving the operation command signal, the accepted product discharging mechanism 17 ejects and collects the passed work W, and the rejected product discharging mechanism (B)
Reference numeral 21 discharges and collects the failed work W.

As shown in FIG. 22, the manufacturing apparatus 1 has a spark gap g, such as a multipolar spark plug, in which the tip of the ground electrode W2 faces the side of the center electrode W1 and the spark gap g is formed. The same applies to plugs.
In this case, as shown in FIGS. 3A and 3C, the interval of the spark gap g is adjusted using the above-described machining displacement β in the x direction. In this case, the preparatory photography shown in FIG.
Analysis unit 13 or each spark gap adjustment unit
The photographing / analyzing unit 16 of (I) to (X), as shown in FIG. 23B, controls the photographing camera 40 so as to photograph the ignition portion of the work W from the tip side of the center electrode W1. Deploy.

The program for measuring the spark gap interval in this case is, for example, LP5 in FIG. First, an image of the spark gap portion of the workpiece W is captured by the capturing camera 40 (L502). As a result, FIG.
As shown in (b), the portion of the ground electrode W2 and the center electrode W1
The image data with the portion is taken in via the I / O port 111. Next, the image data is binarized (L50
3), as shown in FIG. 23A, the outer shape of the center electrode W1 is approximated by a three-point circle, and its radius r0 and the coordinates of the center O (x0, y
0) is obtained (L504, L505). Note that the three-point approximation for obtaining r0 and O may be repeated a plurality of times while changing the positions of the three points, and an average value thereof may be employed in order to improve accuracy.

Next, as shown in FIG. 23 (b), a reference line L passing through the center O at the reference angle position θ0 is generated for the approximate circle, and the coordinates of the intersection P with the inner edge Q of the end face of the ground electrode W2 are generated. , The spark gap interval g is determined as the difference between r0 and the line segment OP, and this difference is stored (L506 to L508:
However, when the intersection P does not occur, the spark gap interval g
Is not calculated or stored). Next, a new reference line L 'is generated by increasing the angular position by a fixed minute angle [Delta] [theta], and an intersection with Q is calculated to similarly calculate and store the spark gap interval g (L509 to L513). This is repeated until the point of intersection with Q no longer occurs, and the smallest one of the measured g's is determined as the spark gap interval measurement value gn and transmitted to the main control unit 100 (FIG. 9) (L511 to L511).
515).

In the embodiment described above, each mold 5 of the mold bending machine 15 has a gasket receiving portion W6 of the work W as shown in FIGS. 4 (a) and 4 (b).
The rear end face 5d of the main body portion 5b as a positioning contact portion is brought into contact with a mold receiving portion such as the workpiece holder 23 or the like, and a dimension A from the rear end face 5d to the working portion 5c is measured.
Was changed to adjust the machining end position PF.
However, the dimension of the mold 5 may be fixed, and the processing end position PF may be adjusted by changing the arrangement height of the cylinder 53 with respect to the workpiece W or the expansion / contraction stroke of the piston rod 54, for example.

[Brief description of the drawings]

FIG. 1 is a plan view and a side view showing an embodiment of an apparatus for producing a spark gap of a spark plug according to the present invention.

FIG. 2 is a front view and a plan view schematically showing a die-type bending machine;

FIG. 3 is a diagram illustrating the operation of a mold.

FIG. 4 is a front sectional view showing a method of using a mold together with a modified example.

FIG. 5 is an explanatory view of a transfer mechanism.

FIG. 6 is a conceptual diagram showing a ground electrode alignment mechanism together with its operation.

FIG. 7 is a conceptual diagram of an imaging / analysis unit.

FIG. 8 is a process explanatory diagram of the spark gap interval adjusting method of the present invention.

FIG. 9 is a block diagram showing an electrical configuration of a main control unit.

FIG. 10 is a block diagram showing an electrical configuration of the imaging / analysis unit.

FIG. 11 is a block diagram showing an electrical configuration of a control unit of the die bending machine.

FIG. 12 is a block diagram showing an electrical configuration of a control unit of the transfer mechanism.

FIG. 13 is a flowchart showing a flow of a linear conveyor driving process of the main control unit.

FIG. 14 is an explanatory diagram of a preliminary bending step of the ground electrode.

FIG. 15 is a flowchart showing the flow of a spark gap interval measurement process.

FIG. 16 is a schematic diagram showing an example of an image used for measuring a spark gap interval.

FIG. 17 is a flowchart showing a flow of a spark gap interval initial value determination process of the main control unit.

FIG. 18 is a flowchart showing the flow of the operation of the transfer mechanism.

FIG. 19 is a flowchart showing a flow of operation of the die bending machine.

FIG. 20 is a flowchart illustrating a flow of a spark gap interval determination process of the main control unit.

FIG. 21 is a flowchart showing a flow of a spark gap interval final determination process of the main control unit.

FIG. 22 is an explanatory view showing another example of the spark plug to be processed, together with a method of applying a mold to the ground electrode.

FIG. 23 is an explanatory diagram showing an example of image processing in measuring the spark gap interval.

FIG. 24 is a flowchart showing the flow of the spark gap interval measurement process.

[Description of Signs] 1 Spark Gap Spacing Gap Manufacturing Device C Transport Path W Spark Plug to Be Treated W1 Center Electrode O Center Axis W2 Grounding Electrode W3 Metal Body W4 Insulator W6 Gasket Receiver (Mold Receiver) Reference Signs List 5 Mold 5a Projection 5b Body 5c Working part 5d Rear end face of body (positioning contact part) PB Reference position PF Finishing position 15 Mold bending machine (machining device, unit machining device) 16 Photographing / analysis Unit (spark gap interval measurement mechanism) 17 Accepted product discharge mechanism (discharge mechanism) 40 Photographing camera (image photographing device) 53 Cylinder (die driving mechanism) 110 Analysis unit (measurement / analysis means) 300 Linear conveyor (conveying spark plug to be processed) mechanism)

Claims (9)

[Claims] A center electrode disposed in an insulator; and a ground electrode facing the center electrode, wherein a center electrode is provided between the center electrode and the ground electrode and between the insulator and the ground electrode. A method for manufacturing a spark plug in which spark gaps at predetermined intervals are formed in at least one of the above, wherein a working part of a mold is brought into contact with the ground electrode, and in that state, the working part is predetermined. By moving the mold relative to the ground electrode until the processing end position is reached, processing is performed on the ground electrode in a direction in which the spark gap is reduced, and a plurality of molds are prepared. In a direction in which the spark gap is formed, when a virtual reference position is set on the opposite side to the center electrode with respect to the ground electrode with respect to the spark plug to be processed, the plurality of molds are formed. Are different from each other in the distance d from the reference position to the processing end position, and the distance d
By applying to the ground electrode in ascending order, the spark gap interval is gradually reduced, and the ground electrode is processed by a mold having a predetermined processing end position, After the processing, the spark gap interval is measured in a state where the processing load by the mold is released, and when the measured value is larger than the target value, further processing is performed by using the next mold. And a process of repeating the processing and the measurement of the spark gap interval until the measured value reaches the target value. 2. A spark plug according to claim 1, wherein a side where the spark gap is located in the axial direction of the center electrode is a front end side, and a side opposite to the rear end side is a rear end side. While having a metal shell, the ground electrode has one end coupled to the tip end surface of the metal shell, and the other end side is bent back to the side toward the center electrode to form a bent portion. In addition, the mold is arranged to approach and separate from the ground electrode in the axial direction of the metal shell, and the working portion contacts the outer surface of the bent portion of the ground electrode, A processing displacement component in the y direction along the axis of the metal shell and toward the base end of the center electrode, and also orthogonal to the y direction in a plane including the axis of the ground electrode, and on the tip side of the ground electrode. Opposite And x direction of the processing displacement component method of manufacturing a spark plug according to claim 1, wherein those raised against the ground electrode. 3. A mold receiving portion is formed at a predetermined position of the spark plug to be processed or at a predetermined position of a plug support for supporting the spark plug to be processed, while the die receiving portion is formed at the mold. A positioning contact portion corresponding to the mold is formed. When the mold relatively approaches the spark plug to be processed, the positioning contact portion abuts on the mold receiving portion. The machining action portion is positioned at the machining end position, and by changing a mold dimension from the positioning contact portion to the machining action portion, the machining end position of each mold is changed. The spark plug manufacturing method according to claim 1, wherein the spark plugs are adjusted to be different from each other. 4. A spark plug according to claim 1, wherein a side where the spark gap is located in the axial direction of the center electrode is a front end side, and a side opposite to the front end is a rear end side. While having a metal shell, the ground electrode has one end coupled to the tip end surface of the metal shell, and the other end side is bent back to the side toward the center electrode to form a bent portion. The mold is arranged to approach / separate from the ground electrode in the axial direction of the metal shell, and the mold receiving portion is configured to hold the spark plug to be processed in the metal shell or the metal shell. The plug is formed on the supporting plug, and the mold has a main body that is located on a side of the metal shell at a position corresponding to the ground electrode and extends in an axial direction of the metal shell. When the mold approaches the ground electrode side, the rear end of the main body portion serves as the positioning contact portion and abuts on the mold receiving portion. 4. The spark plug according to claim 3, wherein a protrusion protruding toward the ground electrode is formed, and an inner edge of a tip of the protrusion contacts the outer surface of the bent portion of the ground electrode as the working portion. Production method. 5. An outer peripheral surface of the metal shell is formed with a flange-shaped gasket receiving portion along a circumferential direction at a position away from the leading edge by a predetermined length in the axial direction. The method for manufacturing a spark plug according to claim 4, wherein a gasket receiving portion is the mold receiving portion. 6. An image of a spark gap forming portion formed by the ground electrode and the center electrode, and the spark gap interval is measured based on the captured image. 2. The method for manufacturing a spark plug according to item 1. 7. A center electrode disposed in an insulator, and a ground electrode facing the center electrode, between the center electrode and the ground electrode and between the insulator and the ground electrode. A spark plug manufacturing apparatus in which a spark gap at a predetermined interval is formed in at least one of the spark plugs, wherein a working part of a mold is brought into contact with the ground electrode, and in that state, the working part is predetermined. By moving the mold relative to the ground electrode until the processing end position is reached, processing is performed on the ground electrode in a direction in which the spark gap is reduced, and a direction in which the spark gap is formed. In the above, when a virtual reference position is set on the opposite side of the center electrode across the ground electrode with respect to the spark plug to be processed, the plurality of dies are
The distance d from the reference position to the processing end position is different from each other, and the spark gap interval is reduced stepwise by applying the distance d to the ground electrode in ascending order. A processing device; and a spark gap interval measuring mechanism for measuring the spark gap interval of the spark plug to be processed, wherein the ground electrode is processed by a mold having a predetermined processing end position, and after the processing, In, the spark gap interval is measured in a state where the processing load by the mold is released, and when the measured value is larger than the target value, the processing is further performed by using the next mold, The processing and the measurement of the spark gap interval are repeated until the measured value reaches the target value. Plug of manufacturing equipment. 8. An image capturing apparatus for capturing an image of a spark gap forming section formed by the ground electrode and the center electrode, wherein the spark gap measuring mechanism includes: The apparatus for manufacturing a spark plug according to claim 7, further comprising a measurement analysis means for measuring an interval. 9. A spark plug transport mechanism for intermittently transporting the spark plug to be processed along a predetermined transport path is provided, and the dies having different machining end positions, and the dies are mounted on the dies. A plurality of unit processing devices including a mold driving mechanism for relatively approaching / separating the ground electrode of the processing spark plug, and the spark gap interval measurement mechanism provided along with each of the unit processing devices; Similarly, a set of a discharge mechanism that is provided along with each unit processing device and discharges the processed spark plug whose spark gap interval has reached the target value from the transfer path is sequentially provided with the distance d of the mold. 9. The spark plug manufacturing apparatus according to claim 7, wherein a plurality of spark plugs are arranged at predetermined intervals along the transport path in an increasing order.