JP2013213834A

JP2013213834A - Air flow rate measuring apparatus

Info

Publication number: JP2013213834A
Application number: JP2013147507A
Authority: JP
Inventors: Yasushi Kono; 泰河野; Junzo Yamaguchi; 順三山口
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2013-07-16
Filing date: 2013-07-16
Publication date: 2013-10-17

Abstract

PROBLEM TO BE SOLVED: To improve detection accuracy of an air flow rate by setting a sheet resistance of a lead section 43 lower than a sheet resistance of a temperature measuring section 8 without increasing a cost in a detection unit of an air flow rate measuring apparatus.SOLUTION: An impurity density of the lead section 43 is enhanced more than the impurity density of the temperature measuring section 8, such that the sheet resistance of the lead section 43 is set lower than the sheet resistance of the temperature measuring section 8. This configuration can negligibly minimize a voltage drop in the lead section 43 compared with a voltage drop in the temperature measuring section 8 so as to improve sensibility of the temperature measuring section 8 with respect to a flow rate signal, thus improving the detection accuracy of the air flow rate. Providing a difference in the impurity densities between the temperature measuring section 8 and the lead section 43 can be implemented without increasing the cost. However, the impurity density of a specific range 51 of the lead section 43 that is continuously extended from the temperature measuring section 8 is set similar to that of the temperature measuring section 8.

Description

本発明は、流路を通過する空気の流量（以下、空気流量と略して呼ぶことがある。）を測定する空気流量測定装置に関する。 The present invention relates to an air flow rate measuring apparatus that measures a flow rate of air passing through a flow path (hereinafter, sometimes abbreviated as “air flow rate”).

従来から、例えば、車両の内燃機関に吸入される空気の流量（以下、吸気量と呼ぶことがある。）の測定には、空気流量として質量流量を直接的に測定できる利点から、熱式の空気流量測定装置が用いられている。
この熱式の空気流量測定装置の検出部は、通電により発熱する発熱部と、発熱部から空気を介して熱的影響を受けることで、空気流量相当の電気信号（以下、流量信号と略して呼ぶ。）を発生する測温部とを有し、流量信号は、所定の制御回路により処理されてエンジン等を制御する電子制御装置（ＥＣＵ）に出力される。 Conventionally, for example, in the measurement of the flow rate of air sucked into an internal combustion engine of a vehicle (hereinafter sometimes referred to as an intake air amount), the thermal flow rate can be directly measured from the advantage that the mass flow rate can be directly measured. An air flow measuring device is used.
The detection unit of this thermal air flow rate measuring device has a heat generating part that generates heat when energized, and an electrical signal equivalent to the air flow rate (hereinafter abbreviated as a flow rate signal) by receiving heat from the heat generating part via air. The flow rate signal is processed by a predetermined control circuit and output to an electronic control unit (ECU) that controls the engine and the like.

また、検出部は、流量信号を制御回路に出力するための測温部用電極、測温部用電極と測温部とを導通させる測温部用リード部、発熱部に通電するための発熱部用電極、および発熱部用電極と発熱部とを導通させる発熱部用リード部を有し、検出部側の測温部用、発
熱部用電極が、それぞれ制御回路側の測温部用、発熱部用電極とボンディングワイヤ等により接続されている。
ところで、車両に用いられる空気流量測定装置では、エンジン制御における制御性向上の観点から、様々な改善策が検討されている。 The detection unit includes a temperature measuring unit electrode for outputting a flow rate signal to the control circuit, a temperature measuring unit lead unit for connecting the temperature measuring unit electrode and the temperature measuring unit, and a heat generating unit for energizing the heating unit. And a heating part lead for conducting the heating part electrode and the heating part, and the heating part electrode for the detection part and the heating part electrode for the temperature measuring part on the control circuit side, It is connected to the heating part electrode by a bonding wire or the like.
By the way, in the air flow measuring device used for a vehicle, various improvement measures are examined from the viewpoint of improving controllability in engine control.

例えば、特許文献１は、空気の流れ方向において、発熱部や測温部が成形されるメンブレンの幅、発熱部の幅、および測温部の幅を数値的に限定することで、応答性向上、測定レンジ拡大、および、発熱部の経時的な抵抗変動の抑制等を図っている。
また、特許文献２は、発熱部のシート抵抗を発熱部用リード部のシート抵抗の５倍以上に設定することで、発熱部用リード部の発熱による時間的遅れを解消して応答性向上を図っている。 For example, Patent Document 1 improves responsiveness by numerically limiting the width of the membrane in which the heat generating unit and the temperature measuring unit are formed, the width of the heat generating unit, and the width of the temperature measuring unit in the air flow direction. In addition, the measurement range is expanded and the resistance variation with time of the heat generating part is suppressed.
Further, Patent Document 2 sets the sheet resistance of the heat generating part to 5 times or more of the sheet resistance of the heat generating part lead part, thereby eliminating the time delay due to heat generation of the heat generating part lead part and improving the responsiveness. I am trying.

また、特許文献３は、発熱部および測温部を多結晶ケイ素の半導体膜で設けるとともに、発熱部の不純物濃度を測温部の不純物濃度よりも大きく設定することで、発熱部のシート抵抗を下げて発熱部を発熱させるための駆動電圧を低減したり、測温部の抵抗温度係数を大きくして測定感度を高めたりしている。
さらに、特許文献４は、発熱部を単結晶ケイ素の半導体膜で設けるとともに、発熱部の不純物濃度を所定値未満に数値的に限定することで、発熱部の経時的な抵抗変動の抑制を図っている。 Further, Patent Document 3 provides a heat generating portion and a temperature measuring portion made of a polycrystalline silicon semiconductor film, and sets the impurity concentration of the heat generating portion to be larger than the impurity concentration of the temperature measuring portion, thereby reducing the sheet resistance of the heat generating portion. The drive voltage for lowering the heat generation part to reduce the heat is reduced, or the resistance temperature coefficient of the temperature measurement part is increased to increase the measurement sensitivity.
Further, Patent Document 4 provides a heat generating portion made of a single crystal silicon semiconductor film and numerically limits the impurity concentration of the heat generating portion to a value lower than a predetermined value, thereby suppressing resistance variation with time of the heat generating portion. ing.

ところで、検出部から得られる流量信号は、ボンディングワイヤ、および検出部側、制御回路側の測温部用電極を介して制御回路に入力され、制御回路で処理された後にＥＣＵに出力される。このため、流量信号には、測温部における電圧降下に基づく信号部分以外に、測温部用リード部における電圧降下に基づく信号部分が含まれている。 By the way, the flow rate signal obtained from the detection unit is input to the control circuit via the bonding wire and the temperature measurement unit electrodes on the detection unit side and the control circuit side, and is processed by the control circuit and then output to the ECU. For this reason, the flow rate signal includes a signal portion based on the voltage drop in the temperature measuring lead portion in addition to the signal portion based on the voltage drop in the temperature measuring portion.

この結果、流量信号に対する測温部の感度は、測温部用リード部における電圧降下の影響を受けるので、測温部用リード部のシート抵抗が大きく、測温部用リード部における電圧降下が測温部における電圧降下に比べて無視できないほどに有意な数値になってしまうと、空気流量の検出精度が低下してしまう。 As a result, the sensitivity of the temperature measuring unit with respect to the flow rate signal is affected by the voltage drop in the temperature measuring unit lead, so the sheet resistance of the temperature measuring unit lead is large, and the voltage drop in the temperature measuring unit lead is small. If the value becomes so significant that it cannot be ignored compared to the voltage drop in the temperature measuring section, the detection accuracy of the air flow rate is lowered.

なお、特許文献１には、測温部を単結晶ケイ素の半導体膜で設け、測温部用リード部を単結晶ケイ素の半導体膜とアルミニウムや金等の金属膜との多層膜で設ける構成が開示されている。この構成によれば、金属膜を含む多層膜とすることでシート抵抗は下がるものの、多層膜化することによるコストアップや、半導体膜と金属膜との分離の虞に起因する信頼性低下等の問題がある。 Patent Document 1 has a configuration in which the temperature measuring unit is provided with a single crystal silicon semiconductor film, and the temperature measuring lead portion is provided with a multilayer film of a single crystal silicon semiconductor film and a metal film such as aluminum or gold. It is disclosed. According to this configuration, although the sheet resistance is reduced by using a multilayer film including a metal film, the cost increases due to the multilayer film, and the reliability decreases due to the risk of separation between the semiconductor film and the metal film. There's a problem.

また、特許文献２では、発熱部のシート抵抗を発熱部用リード部のシート抵抗の５倍以上に設定するために、発熱部用リード部の幅を広げたり、発熱部用リード部を２段階で成膜して厚みを増したり、発熱部用リード部を少なくとも２種類の金属膜を成膜することで設けたりしているが、いずれの方法もコストアップになってしまう。 Further, in Patent Document 2, in order to set the sheet resistance of the heat generating part to 5 times or more of the sheet resistance of the heat generating part lead part, the width of the heat generating part lead part is increased, or the heat generating part lead part is provided in two stages. In this method, the thickness is increased by forming a film or the lead part for the heat generating part is provided by forming at least two kinds of metal films. However, both methods increase the cost.

特開２００２−４８６１６号公報JP 2002-48616 A 特開平８−３１３３１８号公報JP-A-8-313318 特開平１１−８３５８０号公報JP 11-83580 A 特開２００８−１９２８３９号公報JP 2008-192839 A

本発明は、上記の問題点を解決するためになされたものであり、その目的は、空気流量測定装置の検出部において、コストアップすることなく、測温部用リード部のシート抵抗を測温部のシート抵抗よりも低く設定して空気流量の検出精度を高めることにある。 The present invention has been made in order to solve the above-described problems, and an object of the present invention is to measure the sheet resistance of the lead part for the temperature measuring part without increasing the cost in the detecting part of the air flow measuring device. This is to increase the detection accuracy of the air flow rate by setting it lower than the sheet resistance of the part.

〔請求項１の手段〕
請求項１に記載の空気流量測定装置は、空気流量相当の電気信号（流量信号）を発生する検出部を備え、流量信号を所定の制御回路により処理して出力する。また、検出部は、通電により発熱する発熱部と、発熱部から空気を介して熱的影響を受けることで、流量信号を発生する測温部と、流量信号を制御回路に出力するための電極（測温部用電極）と、測温部用電極と測温部とを導通させるリード部（測温部用リード部）とを有する。 [Means of Claim 1]
The air flow rate measuring device according to claim 1 includes a detection unit that generates an electric signal (flow rate signal) corresponding to the air flow rate, and processes and outputs the flow rate signal by a predetermined control circuit. In addition, the detection unit includes a heating unit that generates heat when energized, a temperature measurement unit that generates a flow signal by being thermally affected by air from the heating unit, and an electrode for outputting the flow signal to the control circuit. (Temperature measuring part electrode) and a lead part (temperature measuring part lead part) for conducting the temperature measuring part electrode and the temperature measuring part.

そして、発熱部、測温部および測温部用リード部は、半導体基板の表面に設けられた電気絶縁膜上に成形され、測温部および測温部用リード部はケイ素の半導体膜として成形され、測温部用リード部は測温部よりも不純物濃度が高い。
そして、半導体基板は表面と裏面との間を貫通する空洞を有し、電気絶縁膜の一部は空洞を覆うメンブレンをなし、測温部用リード部の内、測温部から連続する部分は、発熱部および測温部とともにメンブレン上に成形されている。
そして、測温部用リード部の内、メンブレン上に形成される部分には、測温部から連続して不純物濃度が測温部と同等の範囲が存在する。
なお、かかる範囲とは、測温部から連続して線幅が徐々に広がっていき広がり終わるまでの領域である。 The heat generating part, the temperature measuring part and the lead part for the temperature measuring part are formed on an electric insulating film provided on the surface of the semiconductor substrate, and the temperature measuring part and the lead part for the temperature measuring part are formed as a silicon semiconductor film. In addition, the temperature measuring lead part has a higher impurity concentration than the temperature measuring part.
And the semiconductor substrate has a cavity penetrating between the front surface and the back surface, a part of the electrical insulating film forms a membrane that covers the cavity, and the portion that continues from the temperature measuring portion of the lead portion for the temperature measuring portion is It is molded on the membrane together with the heat generating part and the temperature measuring part.
And in the part formed on a membrane among the lead parts for temperature measuring parts, the range where impurity concentration is equivalent to a temperature measuring part exists continuously from a temperature measuring part.
In addition, this range is an area | region until a line width is gradually expanded from the temperature measurement part, and it complete | finishes it.

これにより、測温部用リード部のシート抵抗を測温部のシート抵抗よりも低く設定することができる。また、測温部と測温部用リード部との間で不純物濃度に差を設けることは、コストアップすることなく実施できる。
したがって、空気流量測定装置の検出部において、コストアップすることなく、測温部用リード部のシート抵抗を測温部のシート抵抗よりも低く設定して流量信号に対する測温部の感度を高め、空気流量の検出精度を高めることができる。
測温部用リード部の内、メンブレン上に形成される部分に、測温部から連続して不純物濃度が測温部と同等の範囲を設けることで、測温部用リード部におけるシート抵抗の経時的な変化を抑制することができる。 Thereby, the sheet resistance of the lead part for temperature measuring parts can be set lower than the sheet resistance of the temperature measuring part. In addition, providing a difference in impurity concentration between the temperature measuring unit and the temperature measuring unit lead unit can be performed without increasing the cost.
Therefore, in the detection part of the air flow rate measuring device, without increasing the cost, the sheet resistance of the temperature measuring part lead part is set lower than the sheet resistance of the temperature measuring part to increase the sensitivity of the temperature measuring part to the flow signal, The detection accuracy of the air flow rate can be increased.
Of the temperature measurement lead part, the sheet resistance in the temperature measurement lead part can be reduced by providing an area where the impurity concentration is the same as that of the temperature measurement part. Changes over time can be suppressed.

〔請求項２の手段〕
請求項２に記載の空気流量測定装置によれば、測温部および測温部用リード部をなすケイ素は単結晶である。
ケイ素の半導体膜は、不純物濃度が大きくなると経時的な抵抗変動の割合（抵抗変化率）が大きくなり、多結晶ケイ素の方が単結晶ケイ素よりも抵抗変化率が大きくなる。よって、測温部および測温部用リード部を単結晶ケイ素の半導体膜とすることで、経時的な測定誤差の増加を抑えることができる。 [Means of claim 2]
According to the air flow rate measuring device of the second aspect, the silicon forming the temperature measuring unit and the temperature measuring unit lead is a single crystal.
As the impurity concentration of a silicon semiconductor film increases, the rate of change in resistance over time (resistance change rate) increases, and the resistance change rate of polycrystalline silicon is higher than that of single crystal silicon. Therefore, by making the temperature measuring part and the temperature measuring part lead part a single crystal silicon semiconductor film, an increase in measurement error over time can be suppressed.

〔請求項３の手段〕
請求項３に記載の空気流量測定装置によれば、測温部は、空気の流れる方向に関して、発熱部の上流側に設けられる上流側測温部、および発熱部の下流側に設けられる下流側測温部を含んでおり、流量信号は、上流側測温部と下流側測温部との温度差に基づいて生じる。
これにより、順方向の空気流量ばかりでなく逆方向の空気流量をも測定できるので、例えば、吸気量を測定する場合のように脈動が生じる場合にも高精度に空気流量を測定できる。 [Means of claim 3]
According to the air flow rate measuring device according to claim 3, the temperature measuring unit has an upstream temperature measuring unit provided on the upstream side of the heat generating unit and a downstream side provided on the downstream side of the heat generating unit with respect to the air flow direction. A temperature measurement unit is included, and the flow rate signal is generated based on a temperature difference between the upstream temperature measurement unit and the downstream temperature measurement unit.
As a result, not only the forward air flow rate but also the reverse air flow rate can be measured, so that the air flow rate can be measured with high accuracy even when pulsation occurs, for example, when the intake air amount is measured.

〔請求項４の手段〕
請求項４に記載の空気流量測定装置によれば、検出部は、発熱部および測温部とは別に設けられて発熱部と所定の温度相関にある傍熱部を有し、発熱部への通電は、傍熱部の温度に応じて制御される。
これにより、発熱部への通電制御は、傍熱部の温度を利用して実行されるので、発熱部のシート抵抗がジュール熱により経時的に変動しても、測定精度を低下させることなく維持することができる。 [Means of claim 4]
According to the air flow rate measuring device of the fourth aspect, the detection unit is provided separately from the heat generation unit and the temperature measurement unit, and has a side heating unit that has a predetermined temperature correlation with the heat generation unit. Energization is controlled according to the temperature of the indirectly heated portion.
As a result, the energization control of the heat generating part is performed using the temperature of the indirectly heated part, so even if the sheet resistance of the heat generating part fluctuates over time due to Joule heat, it is maintained without reducing the measurement accuracy. can do.

〔請求項５の手段〕
請求項５に記載の空気流量測定装置によれば、発熱部はケイ素の半導体膜として設けられ、発熱部は測温部よりも不純物濃度が高い。
これにより、発熱部のシート抵抗を下げることができるので、発熱部を目標温度まで昇温するための駆動電圧を低減することができる。 [Means of claim 5]
According to the air flow rate measuring device of the fifth aspect, the heat generating part is provided as a silicon semiconductor film, and the heat generating part has a higher impurity concentration than the temperature measuring part.
Thereby, since the sheet resistance of the heat generating part can be lowered, the driving voltage for raising the temperature of the heat generating part to the target temperature can be reduced.

空気流量測定装置の流路構成図である（実施例１）。It is a flow-path block diagram of an air flow measuring device (Example 1). （ａ）は検出部、制御回路および保持部材の配置を示す部分平面図であり、（ｂ）は検出部、制御回路および保持部材の配置を示す部分断面図である（実施例１）。(A) is a partial top view which shows arrangement | positioning of a detection part, a control circuit, and a holding member, (b) is a fragmentary sectional view which shows arrangement | positioning of a detection part, a control circuit, and a holding member (Example 1). 検出部の積層状態を示す部分断面図である（実施例１）。(Example 1) which is a fragmentary sectional view which shows the lamination | stacking state of a detection part. （ａ）は発熱部への通電を制御するための回路構成を示す回路構成図であり、（ｂ）は流量信号を出力するための回路構成を示す回路構成図である（実施例１）。(A) is a circuit block diagram which shows the circuit structure for controlling electricity supply to a heat-emitting part, (b) is a circuit block diagram which shows the circuit structure for outputting a flow signal (Example 1). メンブレン上における発熱部および測温部の配置を示す平面図である（実施例１）。(Example 1) which is a top view which shows arrangement | positioning of the heat generating part and temperature measuring part on a membrane. （ａ）は発熱部によりメンブレン上に形成される温度分布を示す分布図であり、（ｂ）はメンブレン上における発熱部および測温部の配置を示す断面図である（実施例１）。(A) is a distribution diagram which shows the temperature distribution formed on a membrane by a heat generating part, (b) is sectional drawing which shows arrangement | positioning of the heat generating part and temperature measuring part on a membrane (Example 1). 下流側測温部と上流側測温部との温度差ΔＴと、空気流量との相関を示す相関図である（実施例１）。(Example 1) which is a correlation diagram which shows the correlation with temperature difference (DELTA) T of a downstream temperature measuring part and an upstream temperature measuring part, and an air flow rate. 不純物濃度と抵抗率との相関を示す相関図である（実施例１）。FIG. 3 is a correlation diagram showing the correlation between impurity concentration and resistivity (Example 1). 不純物濃度と抵抗変化率との相関を示す相関図である（実施例１）。It is a correlation diagram which shows the correlation with impurity concentration and resistance change rate (Example 1). メンブレン上における発熱部、測温部および傍熱部の配置を示す平面図である（実施例２）。(Example 2) which is a top view which shows arrangement | positioning of the heat-emitting part on a membrane, a temperature measurement part, and a side heat part. 発熱部への通電を制御するための回路構成を示す回路構成図である（実施例２）。(Example 2) which is a circuit block diagram which shows the circuit structure for controlling electricity supply to a heat-emitting part. 不純物濃度と抵抗温度係数との相関を示す相関図である（実施例２）。It is a correlation diagram which shows the correlation with an impurity concentration and a resistance temperature coefficient (Example 2).

実施形態１の空気流量測定装置は、空気流量相当の電気信号（流量信号）を発生する検出部を備え、流量信号を所定の制御回路により処理して出力する。また、検出部は、通電により発熱する発熱部と、発熱部から空気を介して熱的影響を受けることで、流量信号を発生する測温部と、流量信号を制御回路に出力するための電極（測温部用電極）と、測温部用電極と測温部とを導通させるリード部（測温部用リード部）とを有する。 The air flow rate measuring apparatus according to the first embodiment includes a detection unit that generates an electric signal (flow rate signal) corresponding to an air flow rate, and processes and outputs the flow rate signal by a predetermined control circuit. In addition, the detection unit includes a heating unit that generates heat when energized, a temperature measurement unit that generates a flow signal by being thermally affected by air from the heating unit, and an electrode for outputting the flow signal to the control circuit. (Temperature measuring part electrode) and a lead part (temperature measuring part lead part) for conducting the temperature measuring part electrode and the temperature measuring part.

そして、発熱部、測温部および測温部用リード部は、半導体基板の表面に設けられた電気絶縁膜上に成形され、測温部および測温部用リード部はケイ素の半導体膜として成形され、測温部用リード部は測温部よりも不純物濃度が高い。 The heat generating part, the temperature measuring part and the lead part for the temperature measuring part are formed on an electric insulating film provided on the surface of the semiconductor substrate, and the temperature measuring part and the lead part for the temperature measuring part are formed as a silicon semiconductor film. In addition, the temperature measuring lead part has a higher impurity concentration than the temperature measuring part.

また、半導体基板は表面と裏面との間を貫通する空洞を有し、電気絶縁膜の一部は空洞を覆うメンブレンをなしている。そして、測温部用リード部の内、測温部から連続する部分は、発熱部および測温部とともにメンブレン上に成形されている。
また、測温部および測温部用リード部をなすケイ素は単結晶である。 The semiconductor substrate has a cavity penetrating between the front surface and the back surface, and a part of the electric insulating film forms a membrane covering the cavity. And the part continuing from a temperature measurement part among the lead parts for temperature measurement parts is shape | molded on the membrane with the heat generating part and the temperature measurement part.
Silicon forming the temperature measuring section and the lead section for the temperature measuring section is a single crystal.

さらに、測温部は、空気の流れる方向に関して、発熱部の上流側に設けられる上流側測温部、および発熱部の下流側に設けられる下流側測温部を含んでおり、流量信号は、上流側測温部と下流側測温部との温度差に基づいて生じる。
また、発熱部はケイ素の半導体膜として設けられ、発熱部は測温部よりも不純物濃度が高い。 Further, the temperature measuring unit includes an upstream temperature measuring unit provided on the upstream side of the heat generating unit and a downstream temperature measuring unit provided on the downstream side of the heat generating unit with respect to the direction of air flow, It occurs based on the temperature difference between the upstream temperature measuring unit and the downstream temperature measuring unit.
The heat generating part is provided as a silicon semiconductor film, and the heat generating part has a higher impurity concentration than the temperature measuring part.

実施形態２の空気流量測定装置によれば、検出部は、発熱部および測温部とは別に設けられて発熱部と所定の温度相関にある傍熱部を有し、発熱部への通電は、傍熱部の温度に応じて制御される。 According to the air flow rate measurement device of the second embodiment, the detection unit is provided separately from the heat generation unit and the temperature measurement unit, and has a side heating unit that has a predetermined temperature correlation with the heat generation unit. It is controlled according to the temperature of the indirectly heated part.

〔実施例１の構成〕
実施例１の空気流量測定装置１の構成を、図面を用いて説明する。
空気流量測定装置１は、例えば、図１に示すように、車両の内燃機関に吸入される空気の通路２に突出するように配されて空気流量を測定するために用いられており、空気との伝熱を利用することで空気流量として質量流量を直接的に測定できるものである。 [Configuration of Example 1]
The structure of the air flow rate measuring apparatus 1 of Example 1 is demonstrated using drawing.
For example, as shown in FIG. 1, the air flow rate measuring device 1 is arranged so as to protrude into a passage 2 of air sucked into an internal combustion engine of a vehicle and is used for measuring an air flow rate. By using this heat transfer, the mass flow rate can be directly measured as the air flow rate.

また、空気流量測定装置１は、通路２を流れる空気の一部をバイパスさせるバイパス流路３を形成しており、バイパス流路３に、空気流量相当の電気信号（流量信号）を発生する検出部４を備える。そして、空気流量測定装置１は、検出部４から得られる流量信号を所定の制御回路５により処理する（図２（ａ）参照）。また、制御回路５により処理された流量信号は、内燃機関を制御するための電子制御装置（ＥＣＵ：図示せず）に入力され、ＥＣＵは、この流量信号に基づいて吸気量を把握するとともに、吸気量に基づく燃料噴射制御等の各種の制御処理を実行する。 Further, the air flow rate measuring device 1 forms a bypass flow path 3 that bypasses a part of the air flowing through the passage 2, and detects that an electric signal (flow signal) corresponding to the air flow rate is generated in the bypass flow path 3. Part 4 is provided. And the air flow rate measuring apparatus 1 processes the flow rate signal obtained from the detection part 4 by the predetermined | prescribed control circuit 5 (refer Fig.2 (a)). The flow rate signal processed by the control circuit 5 is input to an electronic control unit (ECU: not shown) for controlling the internal combustion engine, and the ECU grasps the intake air amount based on the flow rate signal, Various control processes such as fuel injection control based on the intake air amount are executed.

検出部４は、後記する発熱部７や測温部８等が表面に成形された半導体基板９、半導体基板９を保持する保持部材１０等からなり（図２（ａ）、（ｂ）参照）、バイパス流路３に突出するように配されている。ここで、半導体基板９の表面は、図３に示すように、電気絶縁膜１１により覆われている。また、半導体基板９には、表面と裏面との間を貫通する空洞１２が設けられており、電気絶縁膜１１の一部は空洞１２を覆うメンブレン１３をなしている。そして、発熱部７や測温部８は、メンブレン１３上に配置されている。 The detection unit 4 includes a semiconductor substrate 9 having a heat generation unit 7, a temperature measurement unit 8 and the like, which will be described later, formed on the surface thereof, a holding member 10 that holds the semiconductor substrate 9, and the like (see FIGS. 2A and 2B). , And is arranged so as to protrude into the bypass flow path 3. Here, the surface of the semiconductor substrate 9 is covered with an electrical insulating film 11 as shown in FIG. In addition, the semiconductor substrate 9 is provided with a cavity 12 penetrating between the front surface and the back surface, and a part of the electric insulating film 11 forms a membrane 13 that covers the cavity 12. The heat generating unit 7 and the temperature measuring unit 8 are disposed on the membrane 13.

発熱部７は、通電により発熱するように設けられており、空気の温度を検出する空気温検出部１６、固定抵抗１７、１８とともに、発熱部７の温度を制御するためのブリッジ回路１９を形成している（図４（ａ）参照）。また、発熱部７と固定抵抗１７との接続点の電位を示す端子２０、および空気温検出部１６と固定抵抗１８との接続点の電位を示す端子２１は、比較器２２の入力端に接続され、比較器２２は、端子２０、２１間の電位差に応じた電気信号を出力する。 The heat generating unit 7 is provided to generate heat when energized, and forms a bridge circuit 19 for controlling the temperature of the heat generating unit 7 together with an air temperature detecting unit 16 for detecting the temperature of the air and fixed resistors 17 and 18. (See FIG. 4A). A terminal 20 indicating the potential of the connection point between the heat generating unit 7 and the fixed resistor 17 and a terminal 21 indicating the potential of the connection point between the air temperature detecting unit 16 and the fixed resistor 18 are connected to the input terminal of the comparator 22. The comparator 22 outputs an electrical signal corresponding to the potential difference between the terminals 20 and 21.

なお、ブリッジ回路１９では、端子２０、２１以外に、発熱部７の高電位側と空気温検出部１６の高電位側との接続点の電位を示す端子２３、および、固定抵抗１７の低電位側と固定抵抗１８の低電位側との接続点の電位を示す端子２４が設けられている。 In the bridge circuit 19, in addition to the terminals 20 and 21, the terminal 23 indicating the potential of the connection point between the high potential side of the heat generating unit 7 and the high potential side of the air temperature detecting unit 16, and the low potential of the fixed resistor 17. A terminal 24 is provided which indicates the potential at the connection point between this side and the low potential side of the fixed resistor 18.

また、比較器２２から出力される電気信号は、電源２５から発熱部７への通電をオンオフするスイッチング素子２６に入力され、発熱部７は、比較器２２から出力される電気信号によりスイッチング素子２６が作動することで通電を受ける。
以上の構成により、発熱部７の温度は、空気の温度（つまり、空気温検出部１６の温度）よりも一定の温度差だけ高くなるように制御される。 The electrical signal output from the comparator 22 is input to the switching element 26 that turns on and off the power supply from the power supply 25 to the heating unit 7, and the heating unit 7 receives the switching element 26 by the electrical signal output from the comparator 22. Is energized by operating.
With the above configuration, the temperature of the heat generating unit 7 is controlled to be higher than the temperature of the air (that is, the temperature of the air temperature detecting unit 16) by a certain temperature difference.

なお、空気温検出部１６、固定抵抗１７、１８はメンブレン１３以外の半導体基板９上に電気絶縁膜１１を介して設けられている。また、比較器２２やスイッチング素子２６は、制御回路５の一部として設けられている。 The air temperature detection unit 16 and the fixed resistors 17 and 18 are provided on the semiconductor substrate 9 other than the membrane 13 via the electrical insulating film 11. Further, the comparator 22 and the switching element 26 are provided as a part of the control circuit 5.

測温部８は、発熱部７から空気を介して熱的影響を受けることで流量信号を発生するものであり、バイパス流路３における空気の流れる方向に関して、図５に示すように、発熱部７の上流側に設けられる第１、第２上流側測温部２９、３０、および発熱部７の下流側に設けられる第１、第２下流側測温部３１、３２からなる。ここで、発熱部７、第１、第２上流側測温部２９、３０、および第１、第２下流側測温部３１、３２は、上流側から下流側に向かって、第１上流側測温部２９、第２上流側測温部３０、発熱部７、第２下流側測温部３２、第１下流側測温部３１の順に、メンブレン１３上に並んでいる。 The temperature measuring unit 8 generates a flow rate signal by being thermally influenced by the heat from the heat generating unit 7, and as shown in FIG. 7, the first and second upstream temperature measuring sections 29 and 30 provided on the upstream side of the heater 7, and the first and second downstream temperature measuring sections 31 and 32 provided on the downstream side of the heat generating section 7. Here, the heat generating unit 7, the first and second upstream temperature measuring units 29 and 30, and the first and second downstream temperature measuring units 31 and 32 are arranged on the first upstream side from the upstream side toward the downstream side. The temperature measuring unit 29, the second upstream side temperature measuring unit 30, the heat generating unit 7, the second downstream side temperature measuring unit 32, and the first downstream side temperature measuring unit 31 are arranged on the membrane 13 in this order.

また、第１、第２上流側測温部２９、３０、および第１、第２下流側測温部３１、３２は、流量信号を出力するためのブリッジ回路３３を形成している（図４（ｂ）参照）。そして、第１上流側測温部２９と第１下流側測温部３１との接続点の電位を示す端子３４、および第２下流側測温部３２と第２上流側測温部３０との接続点の電位を示す端子３５は、増幅器３６の入力端に接続され、増幅器３６は、端子３４、３５間の電位差に応じた電気信号を流量信号として出力する。 Moreover, the 1st, 2nd upstream temperature measuring parts 29 and 30 and the 1st, 2nd downstream temperature measuring parts 31 and 32 form the bridge circuit 33 for outputting a flow signal (FIG. 4). (See (b)). And the terminal 34 which shows the electric potential of the connection point of the 1st upstream temperature measuring part 29 and the 1st downstream temperature measuring part 31, and the 2nd downstream temperature measuring part 32 and the 2nd upstream temperature measuring part 30 A terminal 35 indicating the potential of the connection point is connected to the input terminal of the amplifier 36, and the amplifier 36 outputs an electrical signal corresponding to the potential difference between the terminals 34 and 35 as a flow rate signal.

なお、ブリッジ回路３３では、端子３４、３５以外に、第１上流側測温部２９の高電位側と第２下流側測温部３２の高電位側との接続点の電位を示す端子３７、および、第１下流側測温部３１の低電位側と第２上流側測温部３０の低電位側との接続点の電位を示す端子３８が設けられている。 In the bridge circuit 33, in addition to the terminals 34 and 35, a terminal 37 that indicates the potential at the connection point between the high potential side of the first upstream temperature measuring unit 29 and the high potential side of the second downstream temperature measuring unit 32, In addition, a terminal 38 indicating a potential at a connection point between the low potential side of the first downstream side temperature measuring unit 31 and the low potential side of the second upstream side temperature measuring unit 30 is provided.

ここで、流量信号は、第１、第２上流側測温部２９、３０と第１、第２下流側測温部３１、３２との温度差に基づいて生じる。
すなわち、図６に示すように、バイパス流路３に空気が流れていない場合、発熱部７と空気との伝熱により、発熱部７の上、下流側には均等に熱が伝達されて発熱部７の位置を中心として上、下流側に対称な温度分布が形成される。 Here, the flow rate signal is generated based on a temperature difference between the first and second upstream temperature measuring units 29 and 30 and the first and second downstream temperature measuring units 31 and 32.
That is, as shown in FIG. 6, when air is not flowing through the bypass flow path 3, heat is evenly transmitted above and downstream of the heat generating portion 7 due to heat transfer between the heat generating portion 7 and the air. A symmetrical temperature distribution is formed on the upstream side and the downstream side with respect to the position of the portion 7.

そして、バイパス流路３において上流側から下流側に向かう順方向の空気の流れが生じた場合、発熱部７の上流側では伝熱量が下がって下流側では伝熱量が上がるので、温度分布が下流側に偏って第１、第２上流側測温部２９、３０と第１、第２下流側測温部３１、３２との間に温度差ΔＴが生じる。そして、温度差ΔＴは、図７に示すように、空気流量に応じて変化するため、端子３４、３５間の電位差は空気流量に応じた値となり、増幅器３６から出力される電気信号は空気流量相当の電気信号（流量信号）となる。 When a forward air flow from the upstream side to the downstream side occurs in the bypass flow path 3, the heat transfer amount decreases on the upstream side of the heat generating portion 7, and the heat transfer amount increases on the downstream side. A temperature difference ΔT is generated between the first and second upstream temperature measuring units 29 and 30 and the first and second downstream temperature measuring units 31 and 32. Since the temperature difference ΔT changes according to the air flow rate as shown in FIG. 7, the potential difference between the terminals 34 and 35 becomes a value according to the air flow rate, and the electric signal output from the amplifier 36 is the air flow rate. It becomes a considerable electric signal (flow rate signal).

なお、増幅器３６から出力された流量信号は、制御回路５において、Ａ／Ｄ変換された後、ＤＳＰ（デジタルシグナルプロセッサの略）より処理され、さらにＤＳＰから出力されたデジタル値が周波数に変換されて（つまりＤ／Ｆ変換されて）、ＥＣＵに出力される（図４（ｂ）参照）。また、増幅器３６は、制御回路５の一部として設けられている。 The flow rate signal output from the amplifier 36 is A / D converted in the control circuit 5 and then processed by a DSP (abbreviation of digital signal processor), and the digital value output from the DSP is converted into a frequency. (Ie, D / F converted) and output to the ECU (see FIG. 4B). The amplifier 36 is provided as a part of the control circuit 5.

ところで、制御回路５は、発熱部７や測温部８等が設けられた半導体基板９とは別の半導体基板４１上に設けられている（図２（ｂ）参照）。このため、発熱部７と比較器２２やスイッチング素子２６との間、第１、第２上流側測温部２９、３０および第１、第２下流側測温部３１、３２と増幅器３６の間は、以下に説明するリード部４２、４３、後記する検出部４側の電極、ボンディングワイヤ４４、および制御回路５側の電極（図示せず）等を介して電気的に接続されている。 By the way, the control circuit 5 is provided on a semiconductor substrate 41 different from the semiconductor substrate 9 provided with the heat generating unit 7, the temperature measuring unit 8, and the like (see FIG. 2B). Therefore, between the heat generating unit 7 and the comparator 22 and the switching element 26, between the first and second upstream temperature measuring units 29 and 30, and the first and second downstream temperature measuring units 31 and 32 and the amplifier 36. Are electrically connected via lead portions 42 and 43 described below, electrodes on the detection portion 4 side described later, bonding wires 44, electrodes on the control circuit 5 side (not shown), and the like.

すなわち、端子２０、２１、２３、２４は、発熱部７の温度を制御する電気信号を検出部４と制御回路５との間で入出力するための検出部４側の電極として構成されている（以下、端子２０、２１、２３、２４を、それぞれ電極２０、２１、２３、２４と呼ぶ。）。そして、発熱部７と電極２０、２３との間は、電気配線としてのリード部４２により導通し、電極２０、２３は、制御回路５側の電極とボンディングワイヤ４４により導通している（図２（ｂ）、図３、図４（ａ）参照）。 That is, the terminals 20, 21, 23, 24 are configured as electrodes on the detection unit 4 side for inputting / outputting an electric signal for controlling the temperature of the heat generation unit 7 between the detection unit 4 and the control circuit 5. (Hereinafter, the terminals 20, 21, 23, and 24 are referred to as electrodes 20, 21, 23, and 24, respectively). The heat generating portion 7 and the electrodes 20 and 23 are electrically connected by a lead portion 42 as electric wiring, and the electrodes 20 and 23 are electrically connected by an electrode on the control circuit 5 side and a bonding wire 44 (FIG. 2). (See (b), FIG. 3, and FIG. 4 (a)).

また、端子３４、３５、３７、３８は、流量信号を制御回路５に出力するための検出部４側の電極として構成されている（以下、端子３４、３５、３７、３８を、それぞれ電極３４、３５、３７、３８と呼ぶ。）。そして、第１上流側測温部２９および第１下流側測温部３１と電極３４との間、ならびに、第２上流側測温部３０および第２下流側測温部３２と電極３５との間は、電気配線としてのリード部４３により導通し、電極３４、３５は、制御回路５側の電極とボンディングワイヤ４４により導通している（図２（ｂ）、図３、図４（ｂ）参照）。 The terminals 34, 35, 37, and 38 are configured as electrodes on the detection unit 4 side for outputting a flow rate signal to the control circuit 5 (hereinafter, the terminals 34, 35, 37, and 38 are respectively electrodes 34. , 35, 37, and 38). And between the 1st upstream side temperature measuring part 29 and the 1st downstream side temperature measuring part 31, and the electrode 34, the 2nd upstream side temperature measuring part 30, the 2nd downstream side temperature measuring part 32, and the electrode 35 The electrodes 34 and 35 are electrically connected to the electrodes on the control circuit 5 side by the bonding wires 44 (FIGS. 2B, 3 and 4B). reference).

リード部４２、４３は、半導体基板９の表面において電気絶縁膜１１上に成形されている（図３参照）。そして、リード部４２、４３の内、発熱部７および測温部８からそれぞれ連続する部分４６、４７は、発熱部７および測温部８とともにメンブレン１３上に成形されている（図５参照）。そして、発熱部７、測温部８およびリード部４２、４３は、電気絶縁膜４８により覆われ、さらに保護膜４９により覆われて保護されている（図３参照）。 The lead portions 42 and 43 are formed on the electrical insulating film 11 on the surface of the semiconductor substrate 9 (see FIG. 3). Of the lead portions 42 and 43, portions 46 and 47 that are continuous from the heat generating portion 7 and the temperature measuring portion 8 are formed on the membrane 13 together with the heat generating portion 7 and the temperature measuring portion 8 (see FIG. 5). . The heat generating unit 7, the temperature measuring unit 8, and the lead units 42 and 43 are covered with an electrical insulating film 48 and further protected with a protective film 49 (see FIG. 3).

また、発熱部７、測温部８およびリード部４２、４３は、単結晶ケイ素の半導体膜として設けられ、発熱部７は測温部８よりも不純物濃度が高く、リード部４３は測温部８よりも不純物濃度が高い。ここで、不純物濃度と抵抗率との間には、図８に示すような相関があるので、不純物濃度が上がると抵抗率が下がる。このため、発熱部７は測温部８よりもシート抵抗が小さく、リード部４３は測温部８よりもシート抵抗が小さい。なお、不純物とは、リン、ボロン等である。 Further, the heat generating unit 7, the temperature measuring unit 8 and the lead units 42 and 43 are provided as a semiconductor film of single crystal silicon, the heat generating unit 7 has a higher impurity concentration than the temperature measuring unit 8, and the lead unit 43 is a temperature measuring unit. The impurity concentration is higher than 8. Here, since there is a correlation as shown in FIG. 8 between the impurity concentration and the resistivity, the resistivity decreases as the impurity concentration increases. Therefore, the heat generating unit 7 has a sheet resistance smaller than that of the temperature measuring unit 8, and the lead unit 43 has a sheet resistance smaller than that of the temperature measuring unit 8. The impurities are phosphorus, boron and the like.

〔実施例１の効果〕
実施例１の空気流量測定装置１によれば、測温部８およびリード部４３はケイ素の半導体膜として設けられ、リード部４３は測温部８よりも不純物濃度が高い。
ここで、検出部４から得られる流量信号は、検出部４側の電極３４、３５、ボンディングワイヤ４４、および制御回路５側の電極を介して制御回路５に入力される。このため、流量信号には、測温部８における電圧降下に基づく信号部分以外に、リード部４３における電圧降下に基づく信号部分が含まれている。 [Effect of Example 1]
According to the air flow rate measuring apparatus 1 of the first embodiment, the temperature measuring unit 8 and the lead unit 43 are provided as a silicon semiconductor film, and the lead unit 43 has a higher impurity concentration than the temperature measuring unit 8.
Here, the flow rate signal obtained from the detection unit 4 is input to the control circuit 5 via the electrodes 34 and 35 on the detection unit 4 side, the bonding wire 44, and the electrode on the control circuit 5 side. For this reason, the flow rate signal includes a signal portion based on the voltage drop in the lead portion 43 in addition to the signal portion based on the voltage drop in the temperature measuring portion 8.

この結果、流量信号に対する測温部８の感度は、リード部４３における電圧降下の影響を受けるので、リード部４３のシート抵抗が大きく、リード部４３における電圧降下が測温部８における電圧降下に比べて無視できないほどに有意な数値になってしまうと、空気流量の検出精度が低下してしまう。 As a result, the sensitivity of the temperature measuring unit 8 with respect to the flow rate signal is affected by the voltage drop in the lead part 43, so that the sheet resistance of the lead part 43 is large, and the voltage drop in the lead part 43 becomes the voltage drop in the temperature measuring part 8. If the value becomes so significant that it cannot be ignored, the detection accuracy of the air flow rate is lowered.

そこで、リード部４３の不純物濃度を測温部８の不純物濃度よりも高めて、リード部４３のシート抵抗を測温部８のシート抵抗よりも低く設定する。これにより、リード部４３における電圧降下を測温部８における電圧降下に比べて無視できる程度に小さくして、流量信号に対する測温部８の感度を高めることができるので、空気流量の検出精度を高めることができる。 Therefore, the impurity concentration of the lead part 43 is set higher than the impurity concentration of the temperature measuring part 8, and the sheet resistance of the lead part 43 is set lower than the sheet resistance of the temperature measuring part 8. As a result, the voltage drop in the lead part 43 can be made negligibly small compared to the voltage drop in the temperature measuring part 8, and the sensitivity of the temperature measuring part 8 with respect to the flow rate signal can be increased. Can be increased.

また、測温部８とリード部４３との間で不純物濃度に差を設けることは、コストアップすることなく実施できる。したがって、空気流量測定装置１の検出部４において、コストアップすることなく、リード部４３のシート抵抗を測温部８のシート抵抗よりも低く設定して空気流量の検出精度を高めることができる。 In addition, providing a difference in impurity concentration between the temperature measuring unit 8 and the lead unit 43 can be performed without increasing the cost. Therefore, in the detection part 4 of the air flow rate measuring device 1, the sheet resistance of the lead part 43 can be set lower than the sheet resistance of the temperature measurement part 8 without increasing the cost, and the detection accuracy of the air flow rate can be increased.

また、半導体基板９は表面と裏面との間を貫通する空洞１２を有し、電気絶縁膜１１の一部は空洞１２を覆うメンブレン１３をなしている。そして、リード部４３の内、測温部８から連続する部分４７は、発熱部７および測温部８とともにメンブレン１３上に成形されている。 Further, the semiconductor substrate 9 has a cavity 12 that penetrates between the front surface and the back surface, and a part of the electrical insulating film 11 forms a membrane 13 that covers the cavity 12. Of the lead portion 43, a portion 47 continuing from the temperature measuring portion 8 is formed on the membrane 13 together with the heat generating portion 7 and the temperature measuring portion 8.

これにより、部分４７を含む全てのリード部４３に関して、シート抵抗を測温部８よりも低く設定することができる。
また、ケイ素の半導体膜は、図９に示すように、不純物濃度が大きくなると経時的な抵抗変動の割合（抵抗変化率）が大きくなる。よって、部分４７の内、測温部８から連続するさらに小さい範囲５１、換言すれば、測温部８から連続して線幅が徐々に広がっていき広がり終わるまでの領域（図５参照）では、発熱部７からの伝熱により温度が上昇するので、不純物濃度が高いとシート抵抗が経時的に変化して測定誤差が生じてしまう。 Accordingly, the sheet resistance can be set lower than that of the temperature measuring unit 8 with respect to all the lead parts 43 including the part 47.
Further, as shown in FIG. 9, in the silicon semiconductor film, the rate of resistance variation with time (resistance change rate) increases as the impurity concentration increases. Therefore, in the portion 47, the smaller range 51 continuous from the temperature measuring unit 8, in other words, the region from the temperature measuring unit 8 until the line width gradually increases and ends (see FIG. 5). Since the temperature rises due to heat transfer from the heat generating portion 7, if the impurity concentration is high, the sheet resistance changes with time and a measurement error occurs.

そこで、範囲５１に関しては、不純物濃度を測温部８と同等にしてシート抵抗を測温部８と同じになるように設定する。
なお、範囲５１の境界線（図５参照）は、実際に温度が上昇するか否かを測定して決定される。また、図９に示す抵抗変化率は、リンを不純物として、３１０℃の温度条件で通電開始から１０００時間経過後の測定結果である。 Therefore, for the range 51, the impurity concentration is set to be equal to that of the temperature measuring unit 8, and the sheet resistance is set to be the same as that of the temperature measuring unit 8.
Note that the boundary line of the range 51 (see FIG. 5) is determined by measuring whether or not the temperature actually increases. Moreover, the resistance change rate shown in FIG. 9 is a measurement result after elapse of 1000 hours from the start of energization under the temperature condition of 310 ° C. with phosphorus as an impurity.

また、測温部８およびリード部４３をなすケイ素は単結晶である。
ケイ素の半導体膜は、多結晶ケイ素の方が単結晶ケイ素よりも抵抗変化率が大きくなる（図９参照）。よって、測温部８およびリード部４３を単結晶ケイ素の半導体膜とすることで、経時的な測定誤差の増加を抑えることができる。 The silicon forming the temperature measuring unit 8 and the lead unit 43 is a single crystal.
In the silicon semiconductor film, polycrystalline silicon has a higher resistance change rate than single-crystal silicon (see FIG. 9). Therefore, by using the temperature measuring portion 8 and the lead portion 43 as single crystal silicon semiconductor films, an increase in measurement error over time can be suppressed.

また、測温部８は、空気の流れる方向に関して、発熱部７の上流側に設けられる第１、第２上流側測温部２９、３０、および発熱部７の下流側に設けられる第１、第２下流側測温部３１、３２を含んでおり、流量信号は、第１、第２上流側測温部２９、３０と第１、第２下流側測温部３１、３２との温度差に基づいて生じる。
これにより、順方向の空気流量ばかりでなく逆方向の空気流量をも測定できるので、例えば、吸気量を測定する場合のように脈動が生じる場合にも高精度に空気流量を測定できる。 In addition, the temperature measuring unit 8 includes first and second upstream temperature measuring units 29 and 30 provided on the upstream side of the heat generating unit 7 and a first provided on the downstream side of the heat generating unit 7 with respect to the air flow direction. The second downstream temperature measuring units 31 and 32 are included, and the flow rate signal is a temperature difference between the first and second upstream temperature measuring units 29 and 30 and the first and second downstream temperature measuring units 31 and 32. Arise based on.
As a result, not only the forward air flow rate but also the reverse air flow rate can be measured, so that the air flow rate can be measured with high accuracy even when pulsation occurs, for example, when the intake air amount is measured.

また、発熱部７はケイ素の半導体膜として設けられ、発熱部７は測温部８よりも不純物濃度が高い。
これにより、発熱部７のシート抵抗を下げることができるので、発熱部７を目標温度まで昇温するための駆動電圧を低減することができる。 The heat generating part 7 is provided as a silicon semiconductor film, and the heat generating part 7 has a higher impurity concentration than the temperature measuring part 8.
Thereby, since the sheet resistance of the heat generating part 7 can be lowered, the drive voltage for raising the temperature of the heat generating part 7 to the target temperature can be reduced.

〔実施例２〕
実施例２の空気流量測定装置１によれば、図１０に示すように、発熱部７および測温部８とは別に、発熱部７と所定の温度相関にある傍熱部５３がメンブレン１３上に設けられている。そして、発熱部７への通電は、傍熱部５３の温度に応じて制御される。 [Example 2]
According to the air flow rate measuring apparatus 1 of the second embodiment, as shown in FIG. 10, apart from the heat generating part 7 and the temperature measuring part 8, the side heat part 53 having a predetermined temperature correlation with the heat generating part 7 is provided on the membrane 13. Is provided. The energization of the heat generating unit 7 is controlled according to the temperature of the indirectly heated unit 53.

すなわち、実施例２のブリッジ回路１９は、図１１に示すように、傍熱部５３、空気温検出部１６、固定抵抗５４、５５により設けられている。また、傍熱部５３と固定抵抗５４との接続点の電位を示す端子５６、および空気温検出部１６と固定抵抗５５との接続点の電位を示す端子５７は、比較器２２の入力端に接続され、比較器２２は、端子５６、５７間の電位差に応じた電気信号を出力する。 That is, the bridge circuit 19 according to the second embodiment is provided with an indirectly heated portion 53, an air temperature detecting portion 16, and fixed resistors 54 and 55 as shown in FIG. A terminal 56 indicating the potential at the connection point between the indirectly heated portion 53 and the fixed resistor 54 and a terminal 57 indicating the potential at the connection point between the air temperature detection unit 16 and the fixed resistance 55 are connected to the input terminal of the comparator 22. The comparator 22 is connected and outputs an electrical signal corresponding to the potential difference between the terminals 56 and 57.

また、実施例２のブリッジ回路１９では、端子５６、５７以外に、傍熱部５３の低電位側と空気温検出部１６の低電位側との接続点の電位を示す端子５８、および、固定抵抗５４の高電位側と固定抵抗５５の高電位側との接続点の電位を示す端子５９が設けられている。さらに、発熱部７は、端子５８の低電位側に設けられる。 Further, in the bridge circuit 19 of the second embodiment, in addition to the terminals 56 and 57, a terminal 58 that indicates the potential of the connection point between the low potential side of the indirectly heated portion 53 and the low potential side of the air temperature detecting portion 16, and a fixed A terminal 59 indicating the potential at the connection point between the high potential side of the resistor 54 and the high potential side of the fixed resistor 55 is provided. Further, the heat generating portion 7 is provided on the low potential side of the terminal 58.

そして、スイッチング素子２６は、比較器２２から出力される電気信号により、電源２５から発熱部７およびブリッジ回路１９への通電をオンオフする。
このような構成により、傍熱部５３の温度が空気の温度（つまり、空気温検出部１６の温度）よりも一定の温度差だけ高くなるように、発熱部７への通電が制御される。
なお、固定抵抗５４、５５はメンブレン１３以外の半導体基板９上に電気絶縁膜１１を介して設けられている。 Then, the switching element 26 turns on and off the energization from the power source 25 to the heat generating unit 7 and the bridge circuit 19 by the electric signal output from the comparator 22.
With such a configuration, energization to the heat generating unit 7 is controlled such that the temperature of the indirectly heated unit 53 is higher than the temperature of the air (that is, the temperature of the air temperature detecting unit 16) by a certain temperature difference.
The fixed resistors 54 and 55 are provided on the semiconductor substrate 9 other than the membrane 13 via the electrical insulating film 11.

以上により、発熱部７への通電制御は、傍熱部５３の温度を利用して実行されるので、発熱部７のシート抵抗がジュール熱により経時的に変動しても、測定精度を低下させることなく維持することができる。 As described above, the energization control to the heat generating portion 7 is performed using the temperature of the indirectly heated portion 53, so that the measurement accuracy is lowered even if the sheet resistance of the heat generating portion 7 varies with time due to Joule heat. Can be maintained without.

また、実施例２の空気流量測定装置１においても、発熱部７の不純物濃度を高めることにより、発熱部７の昇温のための駆動電圧の低減が図られているが、傍熱部５３の温度に応じて発熱部７への通電を制御するので、発熱部７において不純物濃度を高めても発熱部７への通電制御に何ら問題は生じない。 Also in the air flow rate measuring device 1 of the second embodiment, the drive voltage for increasing the temperature of the heat generating part 7 is reduced by increasing the impurity concentration of the heat generating part 7. Since energization to the heat generating part 7 is controlled according to the temperature, no problem occurs in energization control to the heat generating part 7 even if the impurity concentration is increased in the heat generating part 7.

すなわち、不純物濃度を高めていくと、図９の単結晶ケイ素の相関線および図１２の相関線に示すように、不純物濃度の数値が１×１０２０ｃｍ−３を超えると抵抗変化率が上昇したり、抵抗温度係数が低下したりするので、発熱部７においても１×１０２０ｃｍ−３を超えるように不純物濃度を高めると、抵抗温度係数が低下したり、抵抗変化率が上昇したりしてしまう。 That is, as the impurity concentration is increased, the resistance change rate increases when the value of the impurity concentration exceeds 1 × 10 20 cm −3 as shown in the correlation line of single crystal silicon in FIG. 9 and the correlation line in FIG. Since the temperature coefficient of resistance decreases, if the impurity concentration is increased so as to exceed 1 × 10 20 cm −3 even in the heat generating portion 7, the temperature coefficient of resistance decreases or the rate of change in resistance increases.

しかし、実施例２の空気流量測定装置１によれば、発熱部７への通電制御は、発熱部７自体の温度に応じて行われるのではなく傍熱部５３の温度に応じて行われる。このため、発熱部７自体の抵抗温度係数や抵抗変化率に関わりなく発熱部７への通電を制御できるので、発熱部７において不純物濃度を高めても、何ら問題なく発熱部７への通電を制御できる。 However, according to the air flow rate measuring device 1 of the second embodiment, the energization control to the heat generating unit 7 is performed not according to the temperature of the heat generating unit 7 itself but according to the temperature of the side heat unit 53. For this reason, since the power supply to the heat generating part 7 can be controlled regardless of the resistance temperature coefficient and the resistance change rate of the heat generating part 7 itself, even if the impurity concentration is increased in the heat generating part 7, the power supply to the heat generating part 7 can be performed without any problem. Can be controlled.

〔変形例〕
空気流量測定装置１の態様は、実施例１、２に限定されず種々の変形例を考えることができる。例えば、実施例１、２の空気流量測定装置１によれば、発熱部７、測温部８およびリード部４２、４３は、単結晶ケイ素の半導体膜として設けられていたが、多結晶ケイ素の半導体膜として設けてもよい。 [Modification]
The aspect of the air flow rate measuring device 1 is not limited to the first and second embodiments, and various modifications can be considered. For example, according to the air flow rate measuring device 1 of the first and second embodiments, the heat generating unit 7, the temperature measuring unit 8, and the lead units 42 and 43 are provided as single-crystal silicon semiconductor films. It may be provided as a semiconductor film.

さらに、実施例１、２の空気流量測定装置１は、車両の内燃機関への吸気量を測定するために用いられていたが、空気流量測定装置１の使用用途は、このような吸気量の測定に限定されず、様々な流路を通過する空気流量の測定に用いることができる。 Furthermore, the air flow rate measuring device 1 of the first and second embodiments has been used to measure the intake air amount to the internal combustion engine of the vehicle. However, the usage of the air flow rate measuring device 1 is such an intake air amount. It is not limited to measurement, but can be used to measure the flow rate of air passing through various channels.

１空気流量測定装置
４検出部
５制御回路
７発熱部
８測温部
９半導体基板
１１電気絶縁膜
１２空洞
１３メンブレン
２１電極
２９第１上流側測温部（上流側測温部）
３０第２上流側測温部（上流側測温部）
３１第１下流側測温部（下流側測温部）
３２第２下流側測温部（下流側測温部）
４３リード部
４７部分（測温部から連続する部分）
５１範囲（線幅が徐々に広がっていき広がり終わるまでの領域）
５３傍熱部 DESCRIPTION OF SYMBOLS 1 Air flow measuring device 4 Detection part 5 Control circuit 7 Heat generation part 8 Temperature measurement part 9 Semiconductor substrate 11 Electrical insulating film 12 Cavity 13 Membrane 21 Electrode 29 1st upstream temperature measurement part (upstream temperature measurement part)
30 Second upstream temperature sensor (upstream temperature sensor)
31 1st downstream temperature measuring part (downstream temperature measuring part)
32 Second downstream side temperature measuring unit (downstream side temperature measuring unit)
43 Lead 47 part (continuous part from temperature measuring part)
51 range (area until the line width gradually increases and ends)
53 Side heat section

Claims

In an air flow rate measuring apparatus that includes a detection unit that generates an electrical signal equivalent to an air flow rate, and that processes and outputs the electrical signal equivalent to the air flow rate by a predetermined control circuit,
The detection unit includes a heating unit that generates heat when energized
A temperature measuring unit that generates an electrical signal corresponding to the air flow rate by receiving a thermal influence from the heat generating unit via air;
An electrode for outputting an electrical signal corresponding to the air flow rate to the control circuit;
It has a lead part that conducts this electrode and the temperature measuring part,
The heat generating part, the temperature measuring part and the lead part are molded on an electric insulating film provided on the surface of a semiconductor substrate,
The temperature measuring part and the lead part are formed as a silicon semiconductor film, and the lead part has a higher impurity concentration than the temperature measuring part,
The semiconductor substrate has a cavity penetrating between the front surface and the back surface, and a part of the electrical insulating film forms a membrane covering the cavity,
Of the lead part, the part continuing from the temperature measuring part is molded on the membrane together with the heat generating part and the temperature measuring part,
Of the lead portion, a portion formed on the membrane has a range in which the impurity concentration is equivalent to the temperature measuring portion continuously from the temperature measuring portion,
Such a range is an area from the temperature measuring section to the area where the line width gradually spreads and finishes spreading.

The air flow rate measuring device according to claim 1,
2. The air flow rate measuring apparatus according to claim 1, wherein silicon forming the temperature measuring part and the lead part is a single crystal.

In the air flow rate measuring device according to claim 1 or 2,
The temperature measuring unit includes an upstream temperature measuring unit provided on the upstream side of the heat generating unit and a downstream temperature measuring unit provided on the downstream side of the heat generating unit with respect to the air flow direction,
The air flow rate measuring apparatus according to claim 1, wherein the electrical signal corresponding to the air flow rate is generated based on a temperature difference between the upstream temperature measuring unit and the downstream temperature measuring unit.

In the air flow rate measuring device according to any one of claims 1 to 3,
The detection unit is provided separately from the heating unit and the temperature measurement unit, and has a side heating unit that has a predetermined temperature correlation with the heating unit,
Energization to the heat generating part is controlled according to the temperature of the indirectly heated part.

In the air flow measuring device according to any one of claims 1 to 4,
The air flow measuring device according to claim 1, wherein the heat generating portion is provided as a silicon semiconductor film, and the heat generating portion has a higher impurity concentration than the temperature measuring portion.