JP5293278B2 - Thermal flow meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air flow meter capable of improving the accuracy of flow rate detection by reducing stress generated in a sensor substrate 9 and reducing an influence of the strain of a diaphragm 9a to a resistor. <P>SOLUTION: A sensor 3 for measuring the amount of air intake is integrally composed as a sensor subassembly where a sensor chip 10 and a circuit section 11 are mounted to a common sensor base material 12, and fixed by making the sensor base material 12 adhere to a sensor housing 2 with an adhesive 14. In the sensor base material 12, mainly the back of a circuit mount 12b is adhered and the back of a chip mount 12a is not adhered except one portion. More specifically, one edge side of the sensor base material 12 including a region where a diaphragm 9a of a sensor substrate 9 is projected at the sensor mount 12a is not adhered to the sensor housing 2, thus reducing stress (stress generated by a difference in thermal expansion between the sensor housing 2 and the sensor substrate 9, packaging stress in assembly, or the like) generated in the sensor substrate 9. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a thermal type flow meter in which a heating resistor is disposed on a diaphragm provided on a sensor substrate, and a gas flow rate is measured based on a temperature distribution generated by the heat generated by the heating resistor.

  2. Description of the Related Art Conventionally, a thermal flow meter that measures an intake air amount of an automobile engine is known. In this thermal type flow meter, for example, as shown in FIG. 6B, a sensor in which a heating resistor and a flow rate detection resistor (not shown) are formed on the surface of a diaphragm 110 provided on the sensor substrate 100. A chip 120 and a circuit unit 130 (see FIG. 6A) for detecting the intake air amount based on the resistance value of the flow rate detection resistor that changes according to the temperature distribution generated by the heat generation of the heating resistor, In some cases, the circuit unit 130 and the sensor chip 120 are mounted on a common sensor base material 140 and configured as a sensor subassembly 150 as shown in FIG. The sensor subassembly 150 is built in a sensor housing 170 that forms a bypass passage 160 for taking a part of intake air, and the entire back surface of the sensor base material 140 is covered with an adhesive 180 as shown in FIG. It is fixed to the sensor housing 170.

However, in the above configuration, a stress due to a difference in thermal expansion between the sensor housing 170 that is resin-molded and the sensor substrate 100 that is a semiconductor such as silicon, a mounting stress during assembly, and the like are generated in the sensor substrate 100. It has been found that the sensor substrate 100 (particularly, the diaphragm 110) is distorted by the stress, so that the resistance value of the resistor formed on the diaphragm 110 changes and affects the flow rate detection accuracy.
Therefore, Patent Document 1 proposes a configuration in which stress generated in the sensor substrate 100 is relaxed by forming stress relaxation grooves in the sensor substrate 100.

JP 2007-24589 A

However, in the conventional technique described in Patent Document 1, the stress itself generated in the sensor substrate 100 cannot be reduced, and the influence of distortion remains, so there is a limit to improving the flow rate detection accuracy. Further, since the stress relaxation grooves are formed in the sensor substrate 100, the manufacturing process of the sensor substrate 100 becomes complicated, and there is a problem that the cost increases. In addition, the stress relaxation grooves are formed to reduce the strength of the sensor substrate, and the sensor chip 120 may be destroyed by dust or the like flying with air.
The present invention has been made based on the above circumstances, and its purpose is to reduce the stress generated in the sensor substrate and reduce the influence of the distortion of the diaphragm on the resistor, thereby improving the flow rate detection accuracy. It is to provide a flow meter.

(Invention of Claim 1)
The present invention relates to a sensor housing that forms a bypass passage for taking in a part of gas, a sensor chip in which a heating resistor and a flow rate detection resistor are arranged on the surface of a diaphragm provided on the sensor substrate, and a heating temperature of the heating resistor. And a circuit unit for detecting the flow rate of the gas flowing through the bypass passage based on the resistance value of the flow rate detection resistor that changes according to the temperature distribution generated by the heat generation of the heating resistor, and a sensor chip, A thermal flow meter in which a circuit unit is mounted on a common sensor base material and configured as a sensor subassembly, and the sensor base material is fixed to the sensor housing by an adhesive, and the sensor base material has one end A chip mounting portion for mounting the sensor chip on the side, and a circuit mounting portion for mounting the circuit portion on the other end side from the chip mounting portion, and a sensor by an adhesive. Includes an area not fixed to the housing, the area when calling a non-adhesive portion, the entire chip mounting portion, and the one end including a mounting range of the circuit portion of the circuit mounting portion included in the non-adhesive portion It is characterized by.

According to said structure, compared with the case where the whole surface of a sensor base material is adhere | attached and fixed to a sensor housing, the whole chip | tip mounting part including the area | region where a bonding area is small and a diaphragm is projected, and a circuit mounting part Since one end side including the mounting range of the circuit part is not bonded to the sensor housing, stress generated in the sensor board (stress due to thermal expansion difference between the sensor housing and the sensor board, mounting stress during assembly, etc.) Can be reduced. As a result, the distortion of the sensor substrate can be suppressed, and the stress transmission to the resistor (heating resistor and flow rate detection resistor) on the diaphragm provided on the sensor substrate can be reduced, so that the temperature characteristics of the resistor greatly change. No, flow rate detection accuracy can be improved.
Further, according to the present invention, since it is not necessary to process the stress relaxation groove disclosed in Patent Document 1 into the sensor substrate, the manufacturing process of the sensor substrate is not complicated, the cost can be reduced, and the sensor It does not reduce the strength of the substrate.

Further, according to the present invention , the sensor base material is an adhesive portion in which an end portion of the circuit mounting portion on the other end side from the non-adhesive portion is fixed to the sensor housing by an adhesive, and the adhesive portion is It is characterized in that at least both the front surface and the back surface of the sensor base material are bonded to the sensor housing.
For example, compared with the case where only the back surface of the sensor base material is bonded to the sensor housing, since the bias of the generated stress becomes smaller when at least both the back surface and the front surface of the sensor base material are bonded, it occurs on the sensor substrate. Stress can be further reduced.

In addition, since the entire chip mounting portion and one end side including the mounting range of the circuit portion of the circuit mounting portion are included in the non-bonding portion, the area of the bonding portion is limited and the sensor subassembly is reduced. Although it is disadvantageous for securely and firmly fixing , in the present invention , since at least the back surface and the front surface of the sensor base material are bonded together, the sensor subassembly can be more securely fixed.
In the present invention, not only the back surface and the front surface of the sensor base material (the end portion of the circuit mounting portion) but also the entire circumference of the sensor base material (the end portion of the circuit mounting portion) can be bonded to the sensor housing.

(Invention of Claim 2 )
The thermal flow meter according to claim 1 is characterized in that the sensor housing is provided with a guide portion for positioning one end side of the sensor base material.
In the sensor subassembly of the present invention, the entire back surface of the sensor base material is not bonded to the sensor housing, the bonding area is smaller than the conventional one, and the sensor chip mounting side has a non-bonded portion. For this reason, it is desirable to position one end side of the sensor base material having the chip mounting portion by some means. On the other hand, in the present invention, since one end side of the sensor base material can be positioned by the guide portion provided in the sensor housing, the displacement of the sensor chip mounted on the sensor base material can be prevented, and the flow rate can be detected with high accuracy. It can be carried out.
In the present invention, for example, the side surface of the sensor base material can be brought into contact with the guide portion of the sensor housing, but the side surface of the sensor base material cannot be brought into direct contact with the guide portion. When the location where the guide portion is provided on the sensor housing is limited, for example, a configuration may be adopted in which convex portions are provided on both side surfaces of the sensor base material and the convex portions are restrained by the guide portions.

(Invention of Claim 3 )
The thermal flow meter according to claim 1 or 2, wherein the circuit unit includes a circuit board on which a plurality of circuit elements are mounted, and the circuit board is used as a sensor base material.
In the present invention, by using a circuit board on which a plurality of circuit elements are mounted as a sensor base material, it is not necessary to use a dedicated sensor base material different from the circuit board, so the number of parts can be reduced, and Costs can be reduced by simplifying the configuration.

(A) The top view which shows the sensor part of an air flow meter, (b) It is sectional drawing which shows the attachment state of a sensor chip (Example 1). It is sectional drawing which shows the state which attached the air flow meter to the intake duct. (Example 2) which is a top view which shows the sensor part of an air flow meter. (A) The top view which shows the sensor part of an air flow meter, (b) It is AA sectional drawing of the same figure (a) (Example 3). (A) The top view which shows the sensor part of an air flow meter, (b) It is BB sectional drawing of the same figure (a) (Example 4). (A) The top view which shows the sensor part of an air flow meter, (b) It is sectional drawing which shows the attachment state of a sensor chip (prior art).

The best mode for carrying out the present invention will be described in detail by the following examples (Examples 1 to 4 and modifications) .
However, in each of the above embodiments, Examples 1 and 2 show reference examples to which the present invention is not applied, whereas Examples 3 and 4 and the modified examples are specific examples to which the present invention is applied. Is shown. In each embodiment, an example of an air flow meter that measures the intake air amount of an automobile engine will be described as an example of a thermal flow meter.

The airflow meter 1 shown in FIGS. 1 and 2 will be described as Example 1. FIG.
The air flow meter 1 of the present embodiment includes a sensor housing 2 and a sensor unit 3.
As shown in FIG. 2, the sensor housing 2 is detachably inserted into the intake duct 4 from an attachment hole formed in the intake duct 4, and is hermetically sealed with an O-ring 5 between the attachment hole. . The intake duct 4 forms part of an intake passage connected to an intake port (not shown) of the engine. For example, an outlet pipe of an air cleaner arranged at the uppermost stream of the intake passage, or this An intake pipe connected to the downstream side of the outlet pipe.

In the sensor housing 2, a bypass passage that takes in the air that flows from the right side (air cleaner side) to the left side (engine side) in the intake duct 4 shown in FIG. 2, that is, a part of the air sucked into the engine. Is formed. The bypass passage is formed by a main passage 6 through which air flows approximately linearly between the inlet 6a and the outlet 6b, and a sub-passage 7 that takes in part of the air flowing through the main passage 6. The sub-passage 7 is branched from the middle of the main passage 6 and leads to an outlet 7a different from the main passage 6. The sub-passage 7 is formed to have a passage length longer than that of the main passage 6, and the flow direction changes greatly in the middle of the passage. Has a part.
The sensor housing 2 is integrally provided with a connector 8 for electrical connection with an ECU (electronic control unit) that controls the operating state of the engine.

As shown in FIG. 1B, the sensor unit 3 includes a sensor chip 10 in which a heating resistor and a flow rate detection resistor (both not shown) are formed on the surface of a diaphragm 9a provided on a sensor substrate 9 such as silicon. And the flow rate of the air flowing through the bypass passage (sub-passage 7) based on the resistance value of the flow rate detection resistor that changes according to the temperature distribution generated by the heat generation of the heating resistor, while controlling the heating temperature of the heating resistor. And a circuit unit 11 (see FIG. 1A).
The sensor chip 10 and the circuit unit 11 are mounted on a common sensor base material 12 and integrally formed as a sensor subassembly. As shown in FIG. 1B, an electrode (not shown) of the sensor chip 10 and The lead frame 11a of the circuit unit 11 is electrically connected by wire bonding. Note that the sensor chip 10 illustrated in FIG. 1B is an enlarged cross-sectional view of the sensor chip 10 illustrated in FIG.

The sensor base material 12 is formed, for example, in a substantially plate shape by a resin material, and as shown in FIG. 1A, a chip mounting portion 12a for mounting the sensor chip 10 on one end side, and other than the chip mounting portion 12a. A circuit mounting portion 12b for mounting the circuit portion 11 is provided on the end side. In addition, the low floor surface 12c which formed the height lower than the circumference | surroundings (it was dug down) is formed in the center part of the circuit mounting part 12b, and the circuit part 11 is mounted in this low floor surface 12c.
As shown in FIG. 1B, the sensor chip 10 has the back surface of the sensor substrate 9 fixed to the surface of the chip mounting portion 12a with an adhesive 13. However, the entire surface of the sensor substrate 9 is not bonded, and only the electrode side (upper side of the sensor chip 10 shown in FIG. 1B) is bonded from the portion where the diaphragm 9a is provided.
The circuit unit 11 is configured, for example, by mounting a plurality of circuit elements on a circuit board, and is mounted on the low floor 12c of the circuit mounting unit 12b and resin-molded.

In the sensor unit 3 (sensor subassembly) of the present embodiment, the back surface of the sensor base material 12 is fixed to the sensor housing 2 by the adhesive 14, and the sensor chip 10 has a flow of air flowing through the sub passage 7 as shown in FIG. Exposed to the flow. However, the sensor base material 12 does not mean that the entire back surface of the chip mounting portion 12a and the circuit mounting portion 12b are bonded, but has a region that is not fixed to the sensor housing 2 by the adhesive 14.
Here, when the sensor base material 12 is fixed to the sensor housing 2 by the adhesive 14, an area where the sensor base material 12 is fixed to the sensor housing 2 is called an adhesive part, and an unbonded area is called a non-adhesive part. As shown in FIG. 5, at least one end side of the sensor base material 12 including a region where the diaphragm 9a of the sensor substrate 9 is projected in the chip mounting portion 12a is included in the non-bonded portion. Specifically, as shown in FIG. 1 (a), the hatched area (the entire circuit mounting portion 12b and a part of the chip mounting portion 12a) is an adhesive portion, and hatching is applied. A non-adhesive portion is a range that is not present (substantially the entire chip mounting portion 12a excluding a part included in the adhesive portion).

(Operation and Effect of Example 1)
In the sensor unit 3 of the present embodiment, the sensor chip 10 and the circuit unit 11 are mounted on a common sensor base material 12 and are integrally formed as a sensor subassembly. The sensor base material 12 is attached to the sensor housing 2 by an adhesive 14. Glued and fixed. Here, the sensor base material 12 is mainly bonded to the back surface of the circuit mounting portion 12b, and the back surface of the chip mounting portion 12a is not bonded except for a part thereof. That is, one end side of the sensor base material 12 including a region where the diaphragm 9 a of the sensor substrate 9 is projected on the chip mounting portion 12 a is not bonded to the sensor housing 2.

According to the above configuration, compared with the conventional configuration shown in FIG. 6, that is, when the entire back surface of the sensor base material 140 is bonded to the sensor housing 170, the stress generated in the sensor substrate 9, for example, the sensor housing 2. It is possible to reduce the stress due to the difference in thermal expansion between the sensor board 9 and the sensor substrate 9, the mounting stress during assembly, and the like. As a result, distortion of the sensor substrate 9 can be suppressed, and stress transmission to the resistors (heating resistors and flow rate detection resistors) formed on the surface of the diaphragm 9a can be reduced, so that the temperature characteristics of the resistors greatly change. The flow rate detection accuracy can be improved.
Further, in this embodiment, since it is not necessary to process the stress relaxation groove disclosed in Patent Document 1 into the sensor substrate 9, the manufacturing process of the sensor substrate 9 is not complicated, the cost can be reduced, and The strength of the sensor substrate 9 is not reduced.

FIG. 3 is a plan view illustrating the sensor unit 3 of the air flow meter 1 according to the second embodiment.
The second embodiment is an example in which the range in which the sensor base material 12 is bonded to the sensor housing 2 is limited to a part of the circuit mounting portion 12b. That is, the non-bonded portion of the sensor base material 12 is expanded to one end side including the entire chip mounting portion 12a and the mounting range of the circuit portion 11 (the range indicated by the broken line in the drawing) of the circuit mounting portion 12b. . In other words, only the end portion of the circuit mounting portion 12b that is the portion farthest from the sensor chip 10 (the region hatched with a two-dot chain line in the figure) is an adhesive portion, and the adhesive portion includes the circuit portion 11. The mounting range is not included. Thereby, compared with the structure of Example 1, since the area of the adhesion part of the sensor base material 12 can be made small and the adhesion part can be set in the place farthest from the sensor chip 10, it occurs in the sensor substrate 9. The stress to be applied can be further reduced, and the effect of suppressing the influence of distortion on the diaphragm 9a is also increased.

FIG. 4A is a plan view illustrating the sensor unit 3 of the air flow meter 1 according to the third embodiment.
In the third embodiment, as in the second embodiment, the bonding portion of the sensor base material 12 is the end of the circuit mounting portion 12b farthest from the sensor chip 10 [FIG. 4 (a) is hatched with a two-dot chain line. This is an example in which the entire circumference of the sensor base material 12 is fixed to the sensor housing 2 with the adhesive 14 as shown in FIG.
In the third embodiment, since the entire circumference of the sensor base material 12 is bonded and fixed to the sensor housing 2, it occurs when compared with the configuration in which only the back surface of the sensor base material 12 described in the second embodiment is bonded to the sensor housing 2. Since the stress bias is reduced, the stress generated in the sensor substrate 9 can be further reduced.

In the configuration of the second embodiment, the bonding portion of the sensor base material 12 is set at the end of the circuit mounting portion 12b farthest from the sensor chip 10 and the area of the bonding portion is small. This is disadvantageous for securing securely and firmly. On the other hand, in the third embodiment, even if the bonding portion of the sensor base material 12 is set at the end of the circuit mounting portion 12b farthest from the sensor chip 10, the entire circumference of the sensor base material 12 is covered with the sensor housing 2. Therefore, the sensor unit 3 can be more reliably fixed as compared with the second embodiment.
In Example 3, instead of the entire circumference of the sensor base material 12, for example, the back surface and the surface of the sensor base material 12 may be bonded to the sensor housing 2.

FIG. 5A is a plan view illustrating the sensor unit 3 of the air flow meter 1 according to the fourth embodiment.
As shown in FIG. 5, the fourth embodiment is an example in which a pair of guide portions 15 are provided in the sensor housing 2 and one end side of the sensor base material 12 is positioned by the guide portions 15.
In the sensor unit 3 described in the first to third embodiments, the entire back surface of the sensor base material 12 is not bonded to the sensor housing 2, and in particular, the back surface of the chip mounting unit 12 a on which the sensor chip 10 is mounted is not. Since it is an adhesive portion and is not attached to the sensor housing 2, it is desirable to position one end side of the sensor base material 12 having the chip mounting portion 12a by some means.

Therefore, in the fourth embodiment, as shown in FIG. 5 (b), guide portions 16 are provided on the sensor housing 2 by providing positioning projections 16 on both sides of the sensor base material 12 forming the chip mounting portion 12a. The one end side of the sensor base material 12 is positioned by restraining the convex portion 16 by 15. As an example of the guide portion 15 provided in the sensor housing 2, for example, as shown in FIG. 5A, the chip mounting portion 12a of the sensor base material 12 is opposed to the chip mounting portion 12a so as to face both left and right sides of the drawing. And has a predetermined length in the vertical direction in the figure, and a slit-like groove is formed extending in the vertical direction in the figure.
On the other hand, the convex portions 16 provided on the sensor base material 12 form taper portions on both sides of the chip mounting portion 12a where the thickness of the sensor base material 12 (dimension in the vertical direction in the drawing) gradually decreases, and the end surfaces of the taper portions Is provided in a shape that can be fitted in the groove of the guide portion 15.

The above positioning structure is suitable, for example, for an air flow meter 1 of the type in which the sensor unit 3 is inserted (slotted in) into the sensor housing 2 from the upper side to the lower side in FIG. That is, when the sensor portion 3 is slotted into the sensor housing 2, the convex portion 16 provided on the sensor base material 12 is fitted into the groove formed by the guide portion 15, so that the sensor base material 12 Positioning is performed by restraining movement in the plate thickness direction and the left-right direction. Thereby, since the position shift of the sensor chip 10 mounted on the sensor base material 12 can be prevented, the flow rate can be detected with high accuracy.
In the fourth embodiment, an example in which the sensor base material 12 is provided with the convex portion 16 and the convex portion 16 is restrained by the guide portion 15 provided in the sensor housing 2 has been described. A configuration in which the side surfaces of the sensor base material 12 (for example, both side surfaces of the chip mounting portion 12a) are brought into contact with the guide portions 15 of the sensor housing 2 without positioning the protrusions 16 may be employed.

(Modification)
In the above-described Examples 1 to 4, the example in which the sensor chip 10 and the circuit unit 11 are mounted on the common sensor base material 12 is described, but the circuit board used for the circuit unit 11 is replaced with the sensor base material 12. It can also be used. That is, the circuit board may be extended to provide the chip mounting portion 12a, and the sensor chip 10 may be mounted on the chip mounting portion 12a. In this case, by using the circuit board as the sensor base material 12, it is not necessary to use the dedicated sensor base material 12 separately from the circuit board, so that the number of parts can be reduced and the cost can be reduced by simplifying the configuration. Is also possible.

DESCRIPTION OF SYMBOLS 1 Air flow meter 2 Sensor housing 3 Sensor part (sensor subassembly)
6 Main passage (bypass passage)
7 Sub passage (bypass passage)
9 Sensor board 9a Diaphragm 10 Sensor chip 11 Circuit part 12a Chip mounting part 12b Circuit mounting part 15 Guide part

Claims (3)

A sensor housing that forms a bypass passage for taking in part of the gas;
A sensor chip in which a heating resistor and a flow rate detection resistor are arranged on the surface of a diaphragm provided on the sensor substrate;
The heating temperature of the heating resistor is controlled, and the flow rate of the gas flowing through the bypass passage is detected based on the resistance value of the flow rate detection resistor that changes according to the temperature distribution generated by the heating of the heating resistor. A circuit part,
A thermal flow meter in which the sensor chip and the circuit unit are mounted on a common sensor base material and configured as a sensor subassembly, and the sensor base material is fixed to the sensor housing by an adhesive. ,
The sensor base material has a chip mounting portion for mounting the sensor chip on one end side, and a circuit mounting portion for mounting the circuit portion on the other end side from the chip mounting portion, and the sensor by an adhesive. When there is a region not fixed to the housing and the region is called a non-adhesive portion, the entire chip mounting portion and one end side including the mounting range of the circuit portion among the circuit mounting portions are the non-adhesive Included in the
The sensor base material is an adhesive part in which an end of the circuit mounting part which is the other end side from the non-adhesive part is fixed to the sensor housing by an adhesive, and the adhesive part is the sensor base material A thermal flow meter characterized in that at least both of the front and back surfaces are bonded to the sensor housing . In the thermal type flow meter according to claim 1,
A thermal flow meter , wherein the sensor housing is provided with a guide portion for positioning one end side of the sensor base material . In the thermal type flow meter according to claim 1 or 2,
The circuit unit includes a circuit board on which a plurality of circuit elements are mounted, and the circuit board is used as the sensor base material .

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