[Meter Patent] Thermal Air Flow Meter
There is no limit to creativity, and the instrument is invented. Today we introduce a patent for the invention of a national invention - a thermal air flow meter. The patent was filed by Hitachi Automotive Systems Co., Ltd. and was issued an authorization notice on November 16, 2018.
Description
The present invention relates to a thermal air flow meter including a sensor component including a sensor chip including a flow rate detecting unit and an LSI for processing a signal detected by a flow rate detecting unit.
Background of the invention
Schematic diagram of the deformation pattern of the sensor component
The thermal air flow meter that measures the gas flow rate includes a flow rate detecting unit that measures the flow rate, and measures the flow rate of the gas by performing heat transfer between the flow rate detecting unit and the gas to be measured. The flow measured by the thermal air flow meter is widely used as an important control parameter in a variety of devices. Thermal air flow meters are characterized by the ability to measure gas flow, such as mass flow, with relatively high precision compared to other types of flow meters.
However, it is desirable to further improve the accuracy of gas flow measurement. For example, in a vehicle equipped with an internal combustion engine, the expectation of saving fuel costs and the expectation of exhaust gas purification are very high. In response to these expectations, it is sought to measure the amount of intake air which is a main parameter of the internal combustion engine with high precision. The thermal air flow meter that measures the intake air introduced into the internal combustion engine includes a sub passage that takes in a part of the intake air amount and a flow rate detecting unit that is disposed in the sub passage, and the flow rate detecting unit performs heat between the gas to be measured and the gas to be measured. The state of the gas to be measured flowing through the sub-passage is measured, and a power signal indicating the amount of intake air introduced into the internal combustion engine is output. Such a technique is disclosed, for example, in Japanese Laid-Open Patent Publication No. 2011-252796 (Patent Document 1).
The air flow measuring device according to Patent Document 1 includes a casing that forms an internal flow path through which the taken in air flows, a sensor chip disposed in the secondary flow path, and a circuit chip that processes a power signal generated by the sensor chip, and the sensor The chip and the circuit chip are assembled as a sensor component that becomes a structural component (paragraphs 0027, 0031). The casing has a hole in which the sensor member is fitted, and two abutting faces that face each of the two abutting faces provided on the sensor member are provided on the surface on which the hole is formed (paragraph 0033). On the face on which the hole is formed, a rib is provided on the face other than the two abutting faces, and the sensor member is press-fitted into the hole by being crimped to the tip end of the rib, and is fixed in the case (paragraph 0034). Thereby, the transmission of the linear expansion is interrupted between the sensor member and the case, and the stress caused by the difference in the linear expansion does not act on the sensor chip or the circuit chip, and the variation of the resistance of the sensor chip or the component of the circuit chip is suppressed (summary) ).
Summary of the invention
SUMMARY OF THE INVENTION Problems to be Solved by the Invention In order to measure the flow rate of air with high precision by a thermal air flow meter, it is desired to position the sub-passage on a thermal air flow meter for measuring the flow rate of air flowing through the main passage. The flow rate detecting unit is fixed and accurately measures the flow rate detected by the flow rate detecting unit.
In the technique described in Patent Document 1, a case having an internal flow path through which a hole for inserting a sensor member is opened is formed of a resin, and a flow rate detecting unit sensor member is manufactured differently from the case, and secondly, it is internally The hole of the flow path is inserted into the state of the sensor member, and the sensor member is fixed in the case. The elastic adhesive is filled in the gap between the hole opened to the internal flow path and the sensor chip, and the gap between the sensor member and the embedded portion in the case, and the mutual linear expansion coefficient difference is absorbed by the elastic force of the adhesive.
Further, in order to reduce the deviation of the position and angle between the sensor member and the sub-passage provided on the casing, the sensor member (especially the flow detecting portion) is accurately positioned with respect to the sub-passage (internal flow path), and the casing It is effective to fix the sensor component including the flow rate detecting portion at the same time.
However, in this case, the thermal stress generated in the resistance in the LSI: Large Scale Integration is higher than that in the case of using the adhesive due to the difference in linear expansion coefficient between the sensor member and the case. The problem of reduced measurement accuracy.
An object of the present invention is to provide a thermal air flow meter which has high measurement accuracy by ensuring high positioning accuracy of a flow rate detecting portion and reducing the influence of thermal stress generated by resistance in an LSI.
In order to achieve the above object, a thermal air flow meter according to the present invention includes a sensor unit in which a circuit portion including a resistor and a flow rate detecting portion are molded and exposed so that at least a part of the flow rate detecting portion is exposed. a case in which the flow rate detecting unit is disposed in the sub-passage and accommodates the sensor member, and the sensor member is molded by the first resin and the second resin molded by the second resin is formed. In the flowmeter, the sensor member includes a resin structure in which the second resin that forms the casing is fixed to the casing, and a tensile stress is generated in a direction parallel to a surface of the sensor member that is exposed to the flow rate detecting portion.
In this case, when the resistance arrangement surface side of the circuit portion (LSI) is the surface, the volume ratio of the case resin formed on the back surface side of the sensor member and covering the sensor member can be formed on the surface side of the sensor member, and the cover sensor can be formed. The box resin of the part is bulky. Alternatively, when the resistance arrangement surface side of the LSI is the surface side, the relationship between the thickness t1 of the sensor member resin formed on the surface side of the LSI and the thickness t2 of the sensor member resin formed on the back surface side of the LSI may be t1.
According to the present invention, when the sensor member is fixed at the same time as the molding of the casing, stress generated on the LSI can be reduced, so that high positioning accuracy and high measurement accuracy of the flow rate detecting portion can be obtained. Thermal air flow meter.
For further information, please download the full specification of the patent.
To read : [MeterPatent]Self-correctingConductivityFlowmeter
There is no limit to creativity, and the instrument is invented. Today we introduce a patent for the invention of a national invention - a thermal air flow meter. The patent was filed by Hitachi Automotive Systems Co., Ltd. and was issued an authorization notice on November 16, 2018.
Description
The present invention relates to a thermal air flow meter including a sensor component including a sensor chip including a flow rate detecting unit and an LSI for processing a signal detected by a flow rate detecting unit.
Background of the invention
Schematic diagram of the deformation pattern of the sensor component
The thermal air flow meter that measures the gas flow rate includes a flow rate detecting unit that measures the flow rate, and measures the flow rate of the gas by performing heat transfer between the flow rate detecting unit and the gas to be measured. The flow measured by the thermal air flow meter is widely used as an important control parameter in a variety of devices. Thermal air flow meters are characterized by the ability to measure gas flow, such as mass flow, with relatively high precision compared to other types of flow meters.
However, it is desirable to further improve the accuracy of gas flow measurement. For example, in a vehicle equipped with an internal combustion engine, the expectation of saving fuel costs and the expectation of exhaust gas purification are very high. In response to these expectations, it is sought to measure the amount of intake air which is a main parameter of the internal combustion engine with high precision. The thermal air flow meter that measures the intake air introduced into the internal combustion engine includes a sub passage that takes in a part of the intake air amount and a flow rate detecting unit that is disposed in the sub passage, and the flow rate detecting unit performs heat between the gas to be measured and the gas to be measured. The state of the gas to be measured flowing through the sub-passage is measured, and a power signal indicating the amount of intake air introduced into the internal combustion engine is output. Such a technique is disclosed, for example, in Japanese Laid-Open Patent Publication No. 2011-252796 (Patent Document 1).
The air flow measuring device according to Patent Document 1 includes a casing that forms an internal flow path through which the taken in air flows, a sensor chip disposed in the secondary flow path, and a circuit chip that processes a power signal generated by the sensor chip, and the sensor The chip and the circuit chip are assembled as a sensor component that becomes a structural component (paragraphs 0027, 0031). The casing has a hole in which the sensor member is fitted, and two abutting faces that face each of the two abutting faces provided on the sensor member are provided on the surface on which the hole is formed (paragraph 0033). On the face on which the hole is formed, a rib is provided on the face other than the two abutting faces, and the sensor member is press-fitted into the hole by being crimped to the tip end of the rib, and is fixed in the case (paragraph 0034). Thereby, the transmission of the linear expansion is interrupted between the sensor member and the case, and the stress caused by the difference in the linear expansion does not act on the sensor chip or the circuit chip, and the variation of the resistance of the sensor chip or the component of the circuit chip is suppressed (summary) ).
Summary of the invention
SUMMARY OF THE INVENTION Problems to be Solved by the Invention In order to measure the flow rate of air with high precision by a thermal air flow meter, it is desired to position the sub-passage on a thermal air flow meter for measuring the flow rate of air flowing through the main passage. The flow rate detecting unit is fixed and accurately measures the flow rate detected by the flow rate detecting unit.
In the technique described in Patent Document 1, a case having an internal flow path through which a hole for inserting a sensor member is opened is formed of a resin, and a flow rate detecting unit sensor member is manufactured differently from the case, and secondly, it is internally The hole of the flow path is inserted into the state of the sensor member, and the sensor member is fixed in the case. The elastic adhesive is filled in the gap between the hole opened to the internal flow path and the sensor chip, and the gap between the sensor member and the embedded portion in the case, and the mutual linear expansion coefficient difference is absorbed by the elastic force of the adhesive.
Further, in order to reduce the deviation of the position and angle between the sensor member and the sub-passage provided on the casing, the sensor member (especially the flow detecting portion) is accurately positioned with respect to the sub-passage (internal flow path), and the casing It is effective to fix the sensor component including the flow rate detecting portion at the same time.
However, in this case, the thermal stress generated in the resistance in the LSI: Large Scale Integration is higher than that in the case of using the adhesive due to the difference in linear expansion coefficient between the sensor member and the case. The problem of reduced measurement accuracy.
An object of the present invention is to provide a thermal air flow meter which has high measurement accuracy by ensuring high positioning accuracy of a flow rate detecting portion and reducing the influence of thermal stress generated by resistance in an LSI.
In order to achieve the above object, a thermal air flow meter according to the present invention includes a sensor unit in which a circuit portion including a resistor and a flow rate detecting portion are molded and exposed so that at least a part of the flow rate detecting portion is exposed. a case in which the flow rate detecting unit is disposed in the sub-passage and accommodates the sensor member, and the sensor member is molded by the first resin and the second resin molded by the second resin is formed. In the flowmeter, the sensor member includes a resin structure in which the second resin that forms the casing is fixed to the casing, and a tensile stress is generated in a direction parallel to a surface of the sensor member that is exposed to the flow rate detecting portion.
In this case, when the resistance arrangement surface side of the circuit portion (LSI) is the surface, the volume ratio of the case resin formed on the back surface side of the sensor member and covering the sensor member can be formed on the surface side of the sensor member, and the cover sensor can be formed. The box resin of the part is bulky. Alternatively, when the resistance arrangement surface side of the LSI is the surface side, the relationship between the thickness t1 of the sensor member resin formed on the surface side of the LSI and the thickness t2 of the sensor member resin formed on the back surface side of the LSI may be t1.
According to the present invention, when the sensor member is fixed at the same time as the molding of the casing, stress generated on the LSI can be reduced, so that high positioning accuracy and high measurement accuracy of the flow rate detecting portion can be obtained. Thermal air flow meter.
For further information, please download the full specification of the patent.
To read : [MeterPatent]Self-correctingConductivityFlowmeter
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