JP5145990B2 - Air flow sensor - Google Patents

Description

  The present invention relates to an air flow sensor that detects an air flow rate, and more particularly to an air flow sensor that is suitable for detecting an intake air amount to an internal combustion engine.

  Conventionally, as shown in FIG. 10A, the air flow sensor 100 is provided with an insulating film 101 provided in a plane substantially parallel to the direction of air flow, and provided on the surface 102 of the insulating film 101 by energization. A heat generating resistor 103 that generates heat, is provided on the surface 102 on the downstream side of the heat generating resistor 103, has a resistance value that changes according to the temperature, and includes downstream detection resistors 104 and 105 (for example, , See Patent Document 1).

  The air flow rate sensor 100 forms a temperature distribution along the air flow direction on the surface 102 by heating the heating resistor 103, and based on this temperature distribution, a detection difference is detected between the upper and downstream detection resistors 104 and 105. And an air flow rate in a predetermined air flow path is detected according to the detection difference.

  That is, according to the air flow rate sensor 100, the temperature distribution as shown in FIG. 10B is formed on the fixed axis X on the surface 102, for example, by the heat generated by the heating resistor 103. As a result, a temperature difference δ is generated between the portion X1 of the upstream detection resistor 104 that intersects the fixed axis X and the portion X2 of the downstream detection resistor 105 that intersects the fixed axis X. Then, a detection difference Δ between the upstream and downstream detection resistors 104 and 105 is obtained as a numerical value corresponding to a numerical value obtained by averaging such a difference δ in the longitudinal direction in the figure, and the air flow rate is determined based on the detection difference Δ. Detected.

  Here, the air flow sensor 100 shown in FIG. 10 (a) is a one-side drawer type in which both the positive and negative terminals 106, 107 of the heating resistor 103 are formed on one end side in the longitudinal direction. As shown in FIG. 11, a plus-side terminal 106 is formed on one end side in the longitudinal direction and a minus-side terminal 107 is formed on the other end side in the longitudinal direction. There is a double-sided drawer type.

  Also in this double-drawing type air flow sensor 100, a temperature distribution similar to that in FIG. 10B is formed in the direction of air flow to generate a difference δ, and the difference δ is averaged in the longitudinal direction in the figure. As a corresponding numerical value, a detection difference Δ between the upper and downstream detection resistors 104 and 105 is obtained, and the air flow rate is detected based on the detection difference Δ.

  In the following description, an extremely simplified wiring pattern is used as the one-sided and double-sided heating resistor 103 for simplification of description. That is, as the one-side drawing-type heat generating resistor 103, a wiring pattern having a folded portion 110 whose energization direction is folded back in a substantially U shape is taken up (see FIG. 10A). As an example, a wiring pattern having two folded portions 110 will be described (see FIG. 11).

  In addition, even when both the positive side and negative side terminals 106 and 107 are formed on the other end side in the longitudinal direction, the one side pull-out type, and the negative side terminal 107 is formed on one end side in the longitudinal direction, The case where the positive terminal 106 is formed on the other end side in the longitudinal direction is also a double-sided drawer type.

  By the way, the detection accuracy of the air flow sensor 100 is the extent to which the range in which the temperature distribution along the direction of the air flow is clearly formed, such as the fixed axis X, can be drawn in the longitudinal direction. It depends. That is, the wider the range in the longitudinal direction in which the difference δ can be clearly obtained, the higher the detection difference Δ can be obtained, and the higher the detection accuracy of the air flow sensor 100 can be.

  Therefore, when the longitudinal range in which the difference δ can be clearly obtained is defined as the high accuracy detection region, the high accuracy detection region is provided in the longitudinal direction as long as possible from the viewpoint of improving the detection accuracy of the air flow sensor 100. preferable.

  Here, regarding the one-side pull-out type air flow sensor 100, when the high-precision detection region is considered as a range in which, for example, air moving between the upper and lower detection resistors 104 and 105 can pass through at least one resistance wiring, The accuracy detection area is a range A shown in FIG. Further, regarding the double-drawing type air flow rate sensor 100, a high-precision detection region is considered as a range in which, for example, air moving between the upper and downstream detection resistors 104 and 105 can pass through at least two resistance wires. The detection area is a range B shown in FIG.

However, the longer the high-precision detection region such as the ranges A and B is lengthened in the longitudinal direction, the longer the resistance wiring of the heating resistor 103 becomes and the higher the resistance value of the heating resistor 103 becomes. For this reason, if priority is given to improving detection accuracy and the high-precision detection region is lengthened in the longitudinal direction, the power consumption of the air flow sensor 100 increases and the voltage applied to the heating resistor 103 increases.
Japanese Patent Laid-Open No. 10-253414

  The present invention has been made to solve the above problems, and its purpose is to detect the voltage applied to the heating resistor without reducing the detection accuracy or without increasing the voltage applied to the heating resistor. An object of the present invention is to provide an air flow sensor capable of increasing accuracy.

[Means of Claim 1]
The air flow rate sensor according to claim 1 is provided with an insulating film provided in a plane substantially parallel to the direction of air flow, a heating resistor provided on the surface of the insulating film and generating heat when energized, and a heating resistance on the surface of the insulating film. An upstream detection resistor provided on the upstream side, the resistance value of which varies depending on the temperature, and a downstream detection resistor provided on the downstream side of the heating resistor on the surface of the insulating film, the resistance value of which varies depending on the temperature. A temperature distribution along the direction of air flow is formed on the surface of the insulating film by heating the heating resistor, and a detection difference is generated between the upstream detection resistor and the downstream detection resistor based on the temperature distribution. The air flow rate is detected according to the difference.

When a direction parallel to the surface of the insulating film and perpendicular to the air flow direction is defined as a longitudinal direction, the heating resistor is provided with a folded portion where the energization direction is folded back in a substantially U shape. The folded portion includes a first linear portion that is energized from one end in the longitudinal direction toward the other end, a second linear portion that is energized from the other end in the longitudinal direction toward the other end, and the first linear portion. a connecting portion for connecting the other end of the edge and the second linear portion, possess a extended portion extending to the other end in the longitudinal direction from the connection portion, the connection portion and the extending portion, of the surface of the insulating film It is provided only within the range where the back surface is a thin film so as to be exposed to the air.

  As a result, the extended portion does not contribute to an increase in the resistance value of the heat generating resistor (that is, an increase in the voltage applied to the heat generating resistor), but becomes a high temperature due to heat conduction, thereby contributing to the formation of a highly accurate detection region. Therefore, while maintaining the longitudinal length of the high-precision detection region, the resistance value of the heating resistor is lowered or the longitudinal length of the high-precision detection region is extended while maintaining the resistance value of the heating resistor. Can be. As a result, the applied voltage to the heating resistor can be reduced without reducing the detection accuracy, or the detection accuracy can be increased without increasing the applied voltage to the heating resistor.

[Means of claim 2]
According to the air flow rate sensor of the second aspect, the folded portion has a first straight portion that is energized from one end in the longitudinal direction toward the other end, and a second straight line that is energized from the other end in the longitudinal direction toward the one end. A connecting portion that connects the other end of the first straight portion and the other end of the second straight portion, and a bridge that bridges the first straight portion and the second straight portion on one end side in the longitudinal direction from the connecting portion. possess a section, connecting and bridge, among the surface of the insulating film, the back side is provided only within the range in which a thin film so as to be exposed to the air.

  Thereby, since a bridge | crosslinking part forms a parallel connection with a connection part, the folding part which has a bridge | crosslinking part reduces the applied voltage to a heat-generation resistance rather than the folding part which does not have a bridge | crosslinking part. For this reason, similarly to the means of claim 1, it is possible to reduce the applied voltage to the heating resistor without lowering the detection accuracy, or to increase the detection accuracy without increasing the applied voltage to the heating resistor.

The air flow sensor of the best mode 1 includes an insulating film provided in a plane substantially parallel to the direction of air flow, a heating resistor provided on the surface of the insulating film and generating heat when energized, and a heating resistor on the surface of the insulating film. An upstream detection resistor whose resistance value changes according to the temperature, and a downstream detection resistor which is provided downstream of the heat generation resistor on the surface of the insulating film and whose resistance value changes according to the temperature. By forming a temperature distribution along the direction of the air flow on the surface of the insulating film by heating the heating resistor, a detection difference is generated between the upstream detection resistor and the downstream detection resistor based on the temperature distribution, The air flow rate is detected according to the detection difference.

When a direction parallel to the surface of the insulating film and perpendicular to the air flow direction is defined as a longitudinal direction, the heating resistor is provided with a folded portion where the energization direction is folded back in a substantially U shape. The folded portion includes a first linear portion that is energized from one end in the longitudinal direction toward the other end, a second linear portion that is energized from the other end in the longitudinal direction toward the other end, and the first linear portion. a connecting portion for connecting the other end of the edge and the second linear portion, possess a extended portion extending to the other end in the longitudinal direction from the connection portion, the connection portion and the extending portion, of the surface of the insulating film It is provided only within the range where the back surface is a thin film so as to be exposed to the air.

According to the air flow sensor of the best mode 2, the folded portion has a first straight portion that is energized from one end in the longitudinal direction toward the other end and a second linear portion that is energized from the other end in the longitudinal direction toward the one end. The straight portion, the connecting portion that connects the other end of the first straight portion and the other end of the second straight portion, and the first straight portion and the second straight portion are bridged on one end side in the longitudinal direction from the connecting portion. and a bridge portion possess, connections and cross section of the surface of the insulating film, the back side is provided only within the range in which a thin film so as to be exposed to the air.

[Configuration of Example 1]
The structure of the air flow sensor 1 of Example 1 is demonstrated using FIG. 1, FIG.
The air flow sensor 1 is, for example, an air flow meter that is disposed in a body (not shown) formed in a flow path so as to take in a part of intake air from the air cleaner toward the engine and release it, and measures an intake air amount. Configure. The air flow rate sensor 1 detects the air flow rate using heat transfer with the air flow taken into the body.

  That is, the air flow sensor 1 includes an insulating film 2 provided in a planar shape substantially parallel to the direction of air flow taken into the body, and a heating resistor 4 provided on the surface 3 of the insulating film 2 and generating heat by energization. The upstream detection resistor 5 provided on the upstream side of the heat generating resistor 4 on the surface 3 and the resistance value changes in accordance with its own temperature, and provided on the downstream side of the heat generating resistor 4 on the surface 3 depending on its own temperature. And a downstream detection resistor 6 whose resistance value changes.

The air flow sensor 1 forms a temperature distribution along the air flow direction on the surface 3 of the insulating film 2 by heating the heating resistor 4, and the upstream side detection resistor 5 and the downstream side detection resistor 6 based on the temperature distribution. causing a detection difference delta between, detects the air flow rate in accordance with the detected difference delta.
In the following description, a direction parallel to the surface 3 and perpendicular to the air flow direction is defined as a longitudinal direction (see FIG. 2A).

  As shown in FIG. 1, the insulating film 2 is provided on a silicon substrate 9, and the silicon substrate 9 is exposed to the flow path on the surface 3 side on which the heat generating resistor 4 and the upstream and downstream detection resistors 5 and 6 are formed. It is formed to do. The surface 3 is covered with a protective film 11 for protecting the heating resistor 4 and the upper and downstream detection resistors 5 and 6.

  As shown in FIG. 2A, the heating resistor 4 is formed from a single resistor, and has two terminals 13 and 14 on the surface 3 on the plus side and the minus side. The terminals 13 and 14 are both formed on one end side in the longitudinal direction. That is, the air flow rate sensor 1 is a one-side drawer type in which the terminals 13 and 14 of the heating resistor 4 are formed only on one side in the longitudinal direction.

The upper and downstream detection resistors 5 and 6 are provided in parallel to each other in the longitudinal direction.
The upstream detection resistor 5 is formed of a resistor 16 on the side of the heating resistor 4 (hereinafter referred to as the heating element side) and a resistor 17 on the opposite side of the heating resistor 4 (hereinafter referred to as the counter heating element side). The resistor 16 has two terminals 18 and 19 formed on the other end side in the longitudinal direction. The resistor 16 has two turns on one end side in the longitudinal direction and has one turn on the other end side. Yes. The resistor 17 has two terminals 20 and 21 formed at one end in the longitudinal direction, has two turns at the other end in the longitudinal direction, and has one turn at one end. .

  Further, the downstream detection resistor 6 is also formed of a resistor 24 on the heating element side and a resistor 25 on the counter heating element side, and the resistor 24 has the same configuration as the resistor 16. It has the same configuration as the body 17.

  With the above configuration, in the air flow sensor 1, due to the heat generated by the heat generating resistor 4, for example, a temperature distribution as shown in FIG. As a result, a temperature difference δ is generated between the portion X1 of the upstream detection resistor 5 intersecting the fixed axis X and the portion X2 of the downstream detection resistor 6 intersecting the fixed axis X. Then, a detection difference Δ between the upstream and downstream detection resistors 5 and 6 is obtained as a numerical value corresponding to a numerical value obtained by averaging such a difference δ in the longitudinal direction of the drawing, and the air flow rate is determined based on the detection difference Δ. Detected.

[Features of Example 1]
Features of the air flow rate sensor 1 according to the first embodiment will be described with reference to FIG.
The heating resistor 4 according to the first embodiment is provided as one folded portion 27 in which the energization direction is folded in a substantially U shape. The folded portion 27 includes a first straight portion 28 that is energized from one end in the longitudinal direction toward the other end, a second straight portion 29 that is energized from the other end in the longitudinal direction toward the other end, and a first straight line. possess a connecting portion 30 that connects the other end and the other end of the second straight portion 29 of the part 28, and two extending portions 31 from the connecting portion 30 extends to the other end in the longitudinal direction, the connecting portion 30 And the extension part 31 is provided only in the range which is a thin film so that the back surface side may be exposed to air among the surface 3.

  Here, the detection accuracy of the air flow sensor 1 is such that the range in which the axis where the temperature distribution along the direction of the air flow is clearly formed, such as the fixed axis X, can be drawn extends in the longitudinal direction. Depends on. That is, the wider the range in the longitudinal direction in which the difference δ can be clearly obtained, the higher the detection difference Δ can be obtained, and the higher the detection accuracy of the air flow sensor 1 can be.

  Therefore, if the longitudinal range in which the difference δ can be clearly obtained is defined as the high accuracy detection region, the high accuracy detection region is provided in the longitudinal direction as long as possible from the viewpoint of improving the detection accuracy of the air flow sensor 1. preferable. Then, regarding the one-side-drawn type air flow sensor 1, when considering the high-precision detection region as a range in which, for example, the air moving between the upper and downstream detection resistors 5 and 6 can pass through at least one resistance wiring, The detection region is a range α in the longitudinal direction between the folding of the upper and downstream detection resistors 5 and 6 on one end side and the other end of the extending portion 31.

  That is, although the extended portion 31 does not contribute to an increase in the resistance value of the heat generating resistor 4 (that is, an increase in the voltage applied to the heat generating resistor 4), the extension portion 31 becomes high temperature due to the heat conduction of the resistance wiring. Contribute to. That is, the folded portion 27 including the extended portion 31 forms the high accuracy detection region as a range α longer in the longitudinal direction than the range α1 of the high accuracy detection region formed by the folded portion 27 not including the extended portion 31. .

[Effect of Example 1]
According to the air flow sensor 1 of the first embodiment, the heating resistor 4 is energized from the first linear portion 28 that is energized from one end in the longitudinal direction to the other end, and from the other end in the longitudinal direction to the one end. The second straight portion 29, the connection portion 30 connecting the other end of the first straight portion 28 and the other end of the second straight portion 29, and two extensions extending from the connection portion 30 to the other end in the longitudinal direction Part 31 is provided. Moreover, the connection part 30 and the extension part 31 are provided only in the range used as the thin film so that the back surface side may be exposed to air among the surface 3. FIG.
As a result, the extending portion 31 does not contribute to an increase in the resistance value of the heating resistor 4 (that is, an increase in the voltage applied to the heating resistor 4), but becomes high temperature due to the heat conduction of the resistance wiring. Contributes to formation.

  For this reason, for example, while shortening the length of the folding | returning part 27 other than the extended part 31 in the longitudinal direction, and adding the extended part 31, heating resistance 4 is maintained, maintaining the length of a highly accurate detection area | region. The resistance value can be lowered. As a result, the voltage applied to the heating resistor 4 can be reduced without reducing the detection accuracy. Moreover, while maintaining the length of the folding | returning part 27 other than the extended part 31 in the longitudinal direction, by adding the extended part 31, the length of a highly accurate detection area | region is maintained, maintaining the resistance value of the heating resistor 4. FIG. Can be extended. As a result, the detection accuracy can be increased without increasing the voltage applied to the heating resistor 4.

According to the air flow rate sensor 1 of the second embodiment, the heating resistor 4 bridges the first straight portion 28 and the second straight portion 29 on one end side in the longitudinal direction from the connecting portion 30 as shown in FIG. the bridge portion 34 is closed, the connecting portion 30 and the bridge portion 34, of the surface 3, the back side is provided only within a range that is a thin film so as to be exposed to the air.
As a result, the bridging portion 34 forms a parallel connection with the connecting portion 30, so that the voltage to be applied to the heat generating resistor 4 is lower than when the bridging portion 34 is not provided. The high-precision detection region is a longitudinal range β between the folding of one end of the upper and downstream detection resistors 5 and 6 and the other end of the connection portion 30.

  For this reason, for example, while maintaining the length of the folded portion 27 in the longitudinal direction and adding the bridging portion 34, the voltage applied to the heating resistor 4 is reduced while maintaining the length of the high-precision detection region. be able to. As a result, the voltage applied to the heating resistor 4 can be reduced without reducing the detection accuracy. Further, by extending the length of the folded portion 27 in the longitudinal direction according to the reduction width of the voltage applied to the heating resistor 4 by setting the bridging portion 34, the applied voltage to the heating resistor 4 can be increased without increasing the length. The accuracy detection area can be extended. As a result, the detection accuracy can be increased without increasing the voltage applied to the heating resistor 4.

  According to the air flow rate sensor 1 of the third embodiment, as shown in FIG. 4, the terminal 13 of the heating resistor 4 is formed on one end side in the longitudinal direction, and the terminal 14 is formed on the other end side in the longitudinal direction. That is, the air flow sensor 1 is a double-sided drawer type in which the terminals 13 and 14 are formed separately at both ends in the longitudinal direction.

  The heating resistor 4 has a wiring pattern so as to form two folded portions 35 and 36. That is, the folded portions 35 and 36 have the first straight portions 37 and 38, the second straight portions 39 and 40, and the connecting portions 41 and 42, respectively, and the second straight portions 39 of the folded portion 35 are folded. It is provided so as to coincide with the first straight part 38 of the part 36. The heating resistor 4 has an extending portion 43 extending from the connecting portion 41 to the other end side in the longitudinal direction, and an extending portion 44 extending from the connecting portion 42 to the one end side in the longitudinal direction.

  Here, regarding the double-drawing type air flow sensor 1, if the high-precision detection region is considered as a range in which air moving between the upper and downstream detection resistors 5, 6 can pass through at least two resistance wires, for example, The accuracy detection region is a longitudinal range γ between one end of the extended portion 44 and the other end of the extended portion 43.

  That is, the folded portions 35 and 36 including the extended portions 43 and 44 are longer in the longitudinal direction than the range γ1 of the high-precision detection region formed by the folded portions 35 and 36 not including the extended portions 43 and 44. A high-precision detection region is formed.

  As shown in FIG. 5, the air flow rate sensor 1 of the fourth embodiment is also a double-sided drawer type, and the folded portions 35 and 36 are bridge portions 48 that bridge the first straight portion 37 and the second straight portion 39, respectively. The first straight portion 38 and the second straight portion 40 have a cross-linking portion 49 that cross-links. The high-precision detection region is a longitudinal range ε between one end of the connection portion 36 and the other end of the connection portion 41.

[Modification]
The heating resistor 4 of the first embodiment is provided with two extending portions 31, and the heating resistor 4 of the third embodiment is provided with two extending portions 43 and 44. The number is not limited. For example, the number of installations may be four as shown in FIG. Moreover, the shape of the extension part is not limited to the rectangular shape bordered by a straight line as in the first and third embodiments, and may have a border by a curved line, for example. Moreover, when providing a some extension part, you may change a shape for every extension part.

  The heating resistor 4 of the second embodiment is provided with one bridging portion 34 in one folded portion 27, and the heating resistor 4 of the fourth embodiment has 1 in each of the two folded portions 35 and 36. Although the individual bridging portions 48 and 49 are provided, the number of bridging portions installed per folded portion and the total number of bridging portions are not limited.

For example, the number of installations may be three as shown in FIG. 7, and the number of installations may be four as shown in FIG. As shown in FIG. 9, for example, a bridging portion may be provided on one end side with respect to the folding, and when a plurality of bridging portions are provided, the shape may be changed for each bridging portion.
Furthermore, as shown in FIGS. 7 to 9, both the extending portion and the bridging portion may be provided in the heating resistor 4.

  Further, with respect to the air flow rate sensor 1 having a wiring pattern of the heating resistor 4 that is more complicated than those of the first to fourth embodiments, by providing an extending portion or a bridging portion, an applied voltage to the heating resistor 4 can be applied without lowering the detection accuracy. It is possible to reduce the detection accuracy or increase the detection accuracy without increasing the voltage applied to the heating resistor 4. In addition, as the air flow sensor 1 in which the wiring pattern of the heating resistor 4 is more complicated than those of the first to fourth embodiments, for example, two or more folded portions are formed in the case of one-side drawer, or the folded portion is in the case of both-side drawer. There may be mentioned those in which three or more are formed, and furthermore, there may be mentioned those in which the heating resistor 4 is composed of two or more resistors.

(Example 1) which is a cross-sectional block diagram of an air flow sensor. (A) is a top view of an air flow sensor, (b) is a distribution map which shows temperature distribution along the direction of an air flow (Example 1). (Example 2) which is a top view of an air flow sensor. (Example 3) which is a top view of an air flow sensor. (Example 4) which is a top view of an air flow sensor. It is a top view of an air flow rate sensor (modification example). It is a top view of an air flow rate sensor (modification example). It is a top view of an air flow rate sensor (modification example). It is a top view of an air flow rate sensor (modification example). (A) is a top view of an air flow sensor, (b) is a distribution map which shows temperature distribution along the direction of an air flow (conventional example). It is a top view of an air flow sensor (conventional example).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air flow sensor 2 Insulating film 3 Surface 4 Heat generation resistance 5 Upstream detection resistance 6 Downstream detection resistance 27, 35, 36 Folding part 28, 37, 38 1st linear part 29, 39, 40 2nd linear part 30, 41 , 42 Connecting portions 31, 43, 44 Extension portions 34, 48, 49 Bridge portion Δ Detection difference δ Difference

Claims (2)

An insulating film provided in a planar shape substantially parallel to the direction of air flow;
A heating resistor provided on the surface of the insulating film and generating heat when energized;
An upstream detection resistor provided on the upstream side of the heat generating resistor on the surface of the insulating film, the resistance value of which varies with temperature;
A downstream detection resistor provided on the downstream side of the heating resistor on the surface of the insulating film, the resistance value of which varies with temperature,
Due to the heating of the heating resistor, a temperature distribution along the direction of air flow is formed on the surface of the insulating film, and a detection difference is generated between the upstream detection resistor and the downstream detection resistor based on the temperature distribution. In the air flow rate sensor that detects the air flow rate according to the detection difference,
When the direction parallel to the surface of the insulating film and perpendicular to the direction of airflow is defined as the longitudinal direction,
The heating resistor is provided with a folded portion where the energization direction is folded back into a substantially U shape,
The folded portion includes a first linear portion that is energized from one end to the other end in the longitudinal direction, a second linear portion that is energized from the other end in the longitudinal direction to the one end, and the first linear portion. It possesses a connecting portion for connecting the other ends of the of the second linear portion, and a extending portion extending from the connecting portion to the other end of the longitudinal,
The air flow sensor according to claim 1, wherein the connecting portion and the extending portion are provided only within a range where the back surface of the insulating film is a thin film so that the back surface is exposed to the air. An insulating film provided in a planar shape substantially parallel to the direction of air flow;
A heating resistor provided on the surface of the insulating film and generating heat when energized;
An upstream detection resistor provided on the upstream side of the heat generating resistor on the surface of the insulating film, the resistance value of which varies with temperature;
A downstream detection resistor provided on the downstream side of the heating resistor on the surface of the insulating film, the resistance value of which varies with temperature,
Due to the heating of the heating resistor, a temperature distribution along the direction of air flow is formed on the surface of the insulating film, and a detection difference is generated between the upstream detection resistor and the downstream detection resistor based on the temperature distribution. In the air flow rate sensor that detects the air flow rate according to the detection difference,
When the direction parallel to the surface of the insulating film and perpendicular to the direction of airflow is defined as the longitudinal direction,
The heating resistor is provided with a folded portion where the energization direction is folded back into a substantially U shape,
The folded portion includes a first straight portion energized from one end to the other end in the longitudinal direction, a second straight portion energized from the other end in the longitudinal direction to the one end, and the first straight portion. A connecting portion that connects the other end of the second straight portion and the other end of the second straight portion, and a bridging portion that bridges the first straight portion and the second straight portion on one end side in the longitudinal direction from the connecting portion. I have a,
The air flow sensor according to claim 1, wherein the connecting portion and the bridging portion are provided only within a range in which the back surface of the insulating film is a thin film so that the back surface is exposed to the air.

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