JP5279667B2 - Thermal air flow sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal air flow rate sensor of high accuracy, high reliability, and low cost. <P>SOLUTION: The thermal air flow rate sensor includes: a flow rate sensor element 4 for measuring air flow rate; an environmental sensor element 5 for measuring at least one of temperature, pressure and humidity of air flow; a sub passage 7 in which the flow rate sensor element 4 is arranged; and a housing 15 that has the sub passage 7 and is arranged in the main air flow 3. The center side of the main air flow 3 than the sub passage 7 in which the flow rate sensor element 4 is arranged includes a measuring chamber 10 that is separated from the sub passage 7 and stores the environmental sensor element 5 communicating with the main air flow 3. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a thermal air flow sensor for measuring an air flow rate, for example, a thermal type sensor having a flow rate sensor for measuring an air flow rate of air sucked into an internal combustion engine and an environmental sensor for measuring environmental characteristics of the air. The present invention relates to an air flow sensor.

  2. Description of the Related Art Conventionally, a thermal type air flow sensor that is provided in an electronically controlled fuel injection device of an internal combustion engine such as an automobile and measures an intake air amount has become mainstream because a mass air amount can be directly detected. Among these, a thermal air flow sensor manufactured by a semiconductor micromachining technique and its sensor element have been attracting attention because they can be reduced in cost and can be driven with low power.

  In recent internal combustion engines, more advanced engine control is required in order to reduce fuel consumption, and environmental parameters such as intake air temperature, pressure, and humidity can be measured with high accuracy as well as intake air amount. It has been demanded. These measurement signals such as the intake air amount, temperature, pressure, and humidity are important data related to the combustion process, and are used for calculating the fuel injection time and the like.

  As described above, for example, the following patent documents 1 and 2 exist as prior art documents of a thermal air flow sensor having an environmental sensor for measuring the intake air amount, temperature, pressure, humidity, and the like.

Japanese Patent No. 3335860 Special table 2001-509854 gazette

  In the conventional example of Patent Document 1 (Japanese Patent No. 3335860), a thermal air flow sensor having a humidity sensor that measures the humidity of intake air is disclosed as an environmental sensor. The humidity sensor element has a sensor element structure integrally formed on the flow rate sensor element and the semiconductor substrate by micromachining technology.

  As shown in FIG. 6 of Patent Document 1, in the conventional mounting structure, the humidity sensor element is covered with a protective body so as not to be directly affected by the air flow. A vent hole with a small dimension to reach the humidity sensor element in the protective body is formed.

  In the conventional example configured in this way, the humidity sensor element is prevented from being directly exposed to the air flow, so even when mounted in the intake passage of an internal combustion engine such as an automobile, from the viewpoint of dust prevention and the like. It has a desirable configuration.

  However, the humidity sensor element is located closer to the pipe wall (passage wall) of the intake passage (main passage) than the sub-passage in which the flow rate sensor element is disposed, and due to the temperature rise of an internal combustion engine such as an automobile Since heat of the tube wall is conducted to the humidity sensor element and is also affected by the heat of the heater of the flow sensor element, there is a problem that adversely affects humidity measurement accuracy.

  On the other hand, in the conventional example of Patent Document 2 (Japanese Patent Publication No. 2001-509854), a humidity sensor that measures the humidity of intake air as an environmental sensor and a thermal air flow sensor that has a pressure sensor that measures pressure are disclosed. Yes.

  As shown in FIG. 1 of Patent Document 2, in the conventional mounting structure, as in Patent Document 1, the humidity sensor has a pipe wall of the intake passage (main passage) rather than the sub-passage in which the flow sensor element is arranged. It is the structure located in the place near (passage wall). Therefore, similarly to Patent Document 1, heat from the pipe wall of the intake passage is conducted to the humidity sensor element due to a temperature rise of an internal combustion engine such as an automobile, which has a problem of adversely affecting humidity measurement accuracy.

  Moreover, in FIG. 2 of patent document 2, it has the structure where a flow sensor element and a pressure sensor element are integrally formed on a semiconductor substrate, and are arrange | positioned in a subchannel | path. In such a configuration, since the pressure sensor element is directly exposed to the air flow, there are problems in terms of pressure measurement accuracy and dust prevention.

  Furthermore, in FIG. 3 of Patent Document 2, a humidity sensor for humidity detection is installed in the intake passage separately from the air flow rate sensor, which increases the number of parts, increases the number of assembly steps, and increases the manufacturing cost. not enough.

  The object of the present invention is to solve the problems of the above-described conventional example, and to provide a thermal air having a low-cost and high-precision environmental sensor that is not affected by the heat of the pipe wall of the intake passage due to the temperature rise of an internal combustion engine such as an automobile It is to provide a flow sensor.

  The thermal air flow sensor of the present invention that solves the above problems includes a housing disposed in a main passage, a sub-passage that is formed in the housing and through which a part of the air flowing in the main passage passes, A measurement chamber that is formed in the housing and communicates with at least one of the main passage and the sub-passage, a flow rate sensor element that is disposed in the sub-passage and measures the air flow rate of air passing through the sub-passage, An environmental sensor element that is housed in the measurement chamber and measures at least one of temperature, pressure, and humidity of air in the measurement chamber, wherein the measurement chamber is more than the sub-passage. It is characterized by being disposed on the center side of the passage away from the passage wall of the main passage.

  According to the present invention, since the measurement chamber for storing the environment sensor element is disposed on the center side of the passage farther from the passage wall of the main passage than the sub passage, the environment sensor element is affected by the heat from the passage wall. Can be suppressed. Therefore, for example, it is possible to provide a thermal air flow sensor having a highly accurate environmental sensor that is not affected by the heat of the pipe wall of the intake passage due to the temperature rise of the internal combustion engine.

  The housing has a first communication hole that communicates between the main passage and the measurement chamber, and the first communication hole passes through the main passage in the main passage. It is good also as a structure opened to the housing outer wall surface of the said housing extended along the flow direction of the air to do.

  Therefore, air can be taken into the measurement chamber from the main passage through the first communication hole. And since the 1st communicating hole is opening in the housing outer wall surface of the housing extended along the flow direction of the air which passes the inside of a main passage, when taking in air from a main passage to a measurement chamber, Can prevent foreign matter such as dust contained in the gas from flowing into the first communication hole, and protect the environmental sensor element housed in the measurement chamber from foreign matter such as dust. Therefore, a thermal air flow sensor having a highly reliable environmental sensor can be provided.

  Further, the first communication hole may be configured to open into a recessed portion provided in the outer wall surface of the housing, or may be configured to open toward the downstream side of the main passage. And the 1st communicating hole is good also as a structure each drilled and formed in a pair of wall part arranged mutually opposing which forms the measurement chamber of the housing. According to these configurations, it is possible to further suppress foreign matters such as dust from flowing into the first communication hole, and it is possible to provide a thermal air flow sensor having a highly reliable environmental sensor.

  The housing may have a second communication hole that communicates between the sub-passage and the measurement chamber. According to this configuration, a thermal air flow sensor having a highly accurate and highly reliable environmental sensor can be provided.

  Further, by adopting a configuration in which the flow sensor element and the environment sensor element are mounted and integrated on a common support substrate, a thermal air flow sensor having a highly accurate environmental sensor can be provided at a low cost.

  In addition to the flow sensor element and the environmental sensor element, the common support substrate is mounted with a signal processing circuit for processing an output signal of each sensor element, and connects each sensor element to the signal processing circuit. By providing the electrical wiring layer, it is possible to provide a thermal air flow sensor having a highly accurate environmental sensor at low cost.

  In addition, the common support substrate is provided with a recess for housing the flow rate sensor element, and the surface of the flow rate sensor element is disposed in the recess so as not to protrude from the surface of the common support substrate. A thermal air flow sensor having an environmental sensor can be provided.

  Further, since the environmental sensor element includes at least one of a pressure sensor element, a humidity sensor element, and a temperature sensor element, a thermal air flow sensor having a highly accurate environmental sensor can be provided at low cost.

  Further, the flow sensor element and the environmental sensor element are sensor elements formed on a semiconductor substrate by a micromachining technique, thereby providing a thermal air flow sensor having a highly accurate environmental sensor at low cost.

  In addition, the flow rate sensor element and the environmental sensor element are sensor elements integrally formed on a common semiconductor substrate by micromachining technology, so that a thermal air flow sensor having a highly accurate environmental sensor at low cost. Can provide.

  According to the present invention, since the measurement chamber for storing the environment sensor element is disposed on the center side of the passage farther from the passage wall of the main passage than the sub passage, the environment sensor element is affected by the heat from the passage wall. Can be suppressed. Therefore, for example, it is possible to provide a thermal air flow sensor having a highly accurate, reliable, and low-cost environmental sensor that is not affected by the heat of the pipe wall of the intake passage due to the temperature rise of the internal combustion engine.

1 is a longitudinal sectional view of a thermal air flow sensor having an environmental sensor showing an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line A-A ′ of FIG. 1. The detailed top view of the common support substrate 6. FIG. FIG. 3 is a detailed cross-sectional view of a common support substrate 6. The detailed sectional view of common support board 6 of the 2nd example. The detailed top view of the common support substrate 6 of a 3rd Example. The detailed top view of the common support substrate 6 of a 4th Example. The longitudinal cross-sectional view of the thermal type air flow sensor which has an environmental sensor which shows a 5th Example. B-B 'sectional drawing of FIG. Detailed sectional drawing of the communicating hole 16a of a 6th Example. The detailed sectional view of communication hole 16a of the 7th example. Detailed sectional drawing explaining the 8th Example.

Embodiments according to the present invention will be described below in detail with reference to the drawings.
[Example 1]
FIG. 1 is a longitudinal sectional view of a thermal air flow sensor having an environmental sensor showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA ′ of FIG. A module housing 15 of a thermal air flow sensor 1 having an environmental sensor is mounted via a module flange 12 in an intake passage (main passage) 2 of an internal combustion engine such as an automobile.

  A sub-passage 7 (7a, 7b) is formed at the tip of the module housing 15 so that a part of the air flowing in the intake passage 2 passes, and the flow rate sensor element 4 is installed in the sub-passage 7b. Has been. In addition, a measurement chamber 10 in which the environmental sensor element 5 is housed is installed in the module housing 15 on the center side of the intake passage 2 of the sub passage 7b where the flow sensor element 4 is installed. That is, the measurement chamber 10 is disposed on the center side of the passage farther from the passage wall of the intake passage 2 than the sub-passage 7.

  The flow sensor element 4 and the environment sensor element 5 are installed inside the module housing 15, are integrally mounted on the common support substrate 6 together with the signal processing circuit 11, and are electrically connected. It is electrically connected to the outside through a connector terminal 14 in the connector 13.

  The sub-passage 7 is opened in parallel to the sub-passage inlet 8 that opens perpendicularly to the main airflow 3 that is the flow of air flowing inside the intake passage 2, and the main airflow 3 that flows inside the intake passage 2. A sub-passage outlet 9 is provided. Further, the straight portion 7a of the sub passage 7 of the inlet portion 8 is deviated by 180 ° by a continuous curved surface at the bottom, and the flow sensor element 4 is installed in the straight portion 7b of the sub passage 7. ing.

  According to this structure, foreign matter such as dust that has entered along with the main air flow 3 from the intake passage 2 into the sub passage 7 is caused by the inertial force due to its own speed and mass, so-called inertia effect. Therefore, the air intake passage 2 is re-introduced from the sub-passage outlet 9 without colliding with the flow sensor element 4 installed substantially near the center of the sub-passage 7b. Is discharged.

  As shown in FIG. 2, the flow rate sensor element 4 is disposed in a recess 19 provided in the common support substrate 6 sandwiched between the upper and lower module housings 15a and 15b. It is installed so that it does not protrude from the surface. If the flow sensor element 4 protrudes from the surface of the common support substrate 6, the air flow cannot be accurately measured due to the turbulent influence of the air flow in the sub-passage 7b, and the impact risk of foreign matter such as entering dust is high. Become.

  The environmental sensor element 5 is installed in the distal end portion of the common support substrate 6 and is housed in a measurement chamber 10 constituted by upper and lower module housings 15 a and 15 b that are separated from the auxiliary passage 7. The measurement chamber 10 is provided with communication holes (first communication holes) 16 a and 16 b that communicate with the intake passage 2. The communication holes 16 a and 16 b are provided so as to open in parallel with the main air flow 3 passing through the intake passage 2.

  Specifically, the communication holes 16 a and 16 b are formed by being drilled in a pair of wall portions arranged opposite to each other of the module housings 15 a and 15 b forming the measurement chamber 10. And it opens to the housing outer wall surfaces 15c and 15d of the module housing 15 extended along the flow direction of the main air flow 3.

  As described above, the communication holes 16a and 16b are configured to open in the direction parallel to the main air flow 3, so that the risk of impact of dust and the like in the main air flow 3 can be reduced, and the communication holes 16a and 16b can be reduced. The new main air flow 3 can be directly flowed into the measurement chamber 10 at a low speed by using the generated negative pressure, and the measurement by the environment sensor element 5 can be executed accurately.

  The negative pressure generated in the communication holes 16a and 16b can be optimally set according to the size and installation position of the communication holes 16a and 16b. By setting the sizes of the communication holes 16a and 16b asymmetrically, a negative pressure difference is generated in the communication holes 16a and 16b, and the direction and flow rate of the new main air flow 3 flowing into the measurement chamber 10 can be controlled. it can.

  2, the module housing 15 may be provided with a communication hole (second communication hole) 16c that communicates between the sub-passage 7 and the measurement chamber 10, and the communication holes 16a, 16b A negative pressure difference is generated between the communication hole 16c and the direction and flow rate of the new main air flow 3 flowing into the measurement chamber 10 can be controlled. Further, only one of the communication holes 16a and 16b may be used, or only the communication hole 16c may be used.

  In addition, when an environment of an internal combustion engine such as an automobile is assumed, it is necessary to ensure reliability in consideration of raindrops and freezing. The size of the communication holes 16a and 16b needs to be set to an appropriate size considering the above raindrops and freezing.

  If the size of the communication holes 16 a and 16 b is too small, raindrops will block the communication hole due to surface tension, and the new main air flow 3 flowing into the measurement chamber 10 will be hindered. In addition, there is a possibility of freezing in winter, and it is necessary to secure a certain size as the size of the communication holes 16a and 16b in order to prevent raindrops and freezing.

On the other hand, if the communication holes 16a and 16b are too large, dust or the like contained in the main air flow 3 may flow into the measurement chamber 10 and directly hit the environmental sensor element 5 to be damaged. It is necessary to set the communication hole of an appropriate size to prevent dust. Further, when the amount of the new main air flow 3 flowing into the measurement chamber 10 is increased, it is necessary to provide a plurality of communication holes of an appropriate size for preventing dust.
As described above, by appropriately setting the sizes of the communication holes 16a and 16b and the number of communication holes, an appropriate negative pressure difference in the communication holes can be set, and a new main air flow 3 flowing into the measurement chamber 10 can be set. Direction and flow rate can be controlled.

  In addition, since accurate measurement becomes impossible if moisture stays in the measurement chamber 10, in addition to the communication holes 16a and 16b, another communication hole is used for excretion of moisture to the main air flow 3 side or the sub-passage 7 side. It is also possible to form (discharge holes) in the measurement chamber 10.

  In addition, since the environmental sensor element 5 is installed at the tip of the common support substrate 6 and accommodated in the measurement chamber 10 isolated from the sub-passage 7, the environmental sensor element 5 is not affected by the air flow. In addition, since the environmental sensor element 5 is arranged closer to the center of the main air flow 3 than the sub passage 7b in which the flow sensor element 4 is arranged, a cooling effect by the sub passage 7b can be expected. The thermal effect of the pipe wall of the intake passage 2 due to the temperature rise of the internal combustion engine is reduced, and a thermal air flow sensor having a highly accurate environmental sensor can be realized.

  3 and 4 are a detailed plan view and a cross-sectional view of the common support substrate 6. The common support substrate 6 is composed of ceramic laminated substrates 6a, 6b, and 6c. The flow sensor element 4 is bonded and fixed to the recess 19 formed in the common support substrate 6 with an adhesive or the like. The environmental sensor element 5 is also bonded and fixed to the tip of the common support substrate 6 with an adhesive or the like. The environmental sensor element 5 and the flow rate sensor element 4 are wire-bonded by the connection terminal 17a and the gold wire 18a, and are electrically connected to the signal processing circuit 11 by the wiring layer 20 formed on the ceramic laminated substrates 6a, 6b, and 6c.

  Further, the output signals of the environment sensor element 5 and the flow sensor element 4 are subjected to processing such as appropriate correction in the signal processing circuit 11, and then connected to the wiring layer 20, the connection terminal 17b and the gold wire 18b by wire bonding. It is output to the outside through the terminal 14.

  The flow sensor element 4 has at least a heater formed on a diaphragm made of an electrically insulating film by anisotropic etching from the lower surface of a semiconductor substrate such as silicon. The temperature of the heater is controlled by flowing a heating current so as to be a predetermined temperature, and the air flow rate is detected from the heating current or the temperature difference between the temperature sensors arranged upstream and downstream of the heater.

  The environmental sensor element 5 includes a humidity sensor element 5a, a pressure sensor element 5b, and a temperature sensor element 5c, which are also formed on a semiconductor substrate such as silicon. These sensor elements are integrally formed on a common semiconductor substrate by semiconductor micromachining technology.

  As the humidity sensor element 5a, for example, an element similar to the humidity sensor element described in Patent Document 1 which is a conventional example is used, but another type of humidity sensor element may be applied. Further, the pressure sensor element 5b has a configuration in which pressure applied to a silicon diaphragm formed by anisotropic etching from the lower surface of a semiconductor substrate such as silicon is detected by a piezoresistive effect formed on the diaphragm, or a capacitance. It is the structure detected by. The temperature sensor element 5c is configured to detect from a temperature change of a resistor made of polysilicon, metal, or the like formed on a semiconductor substrate.

  In the thermal air flow sensor having the environment sensor of the present invention configured as described above, the air flow rate is controlled by the flow sensor element 4 formed in the sub passage 7b, and the humidity sensor of the environment sensor element 5 housed in the measurement chamber 10 is used. From the element 5a, the pressure sensor element 5b and the temperature sensor element 5c, the environmental parameters of the humidity, pressure and temperature of the main air flow 3 are detected with high reliability and high accuracy.

  Further, by adopting alumina or a composite material of alumina and glass as the ceramic material of the common support substrate 6, the thermal conductivity can be reduced, and the heat of the pipe wall of the intake passage 2 due to the temperature rise of the internal combustion engine such as an automobile. The influence can be reduced.

  Furthermore, since the ceramic multilayer substrates 6a, 6b, and 6c are configured, wiring patterns such as printing can be formed on the front and back surfaces of the multilayer substrate, and through holes partially formed between the multilayer substrates can be formed. In addition, it is possible to reduce the size and to reduce the cost by integrally forming the electric parts.

[Example 2]
FIG. 5 shows a cross-sectional view of the common support substrate 6 of the thermal air flow sensor having the environmental sensor according to the second embodiment of the present invention.

  The difference from the first embodiment shown in FIG. 4 is that the concave portion 21 is provided in the common support substrate 6 composed of the ceramic laminated substrates 6a, 6b and 6c.

  The concave portion 21 prevents the thermal effect of the pipe wall of the intake passage 2 and the thermal effect from the flow rate sensor element 4 on which the heater is formed due to a temperature rise of an internal combustion engine such as an automobile, on the environment sensor element 5. By providing the recess 21 having the thermal insulation effect, the thermal effect is further reduced by the first embodiment, and the environmental parameters of the humidity, pressure and temperature of the main air flow 3 are detected with higher accuracy.

[Example 3]
In FIG. 6, the top view of the common support substrate 6 of the thermal type air flow sensor which has an environmental sensor which is a 3rd Example of this invention is shown.

  Unlike the first embodiment shown in FIG. 3, the humidity sensor element 5a, the pressure sensor element 5b, and the temperature sensor element 5c of the environmental sensor element 5 are formed on different semiconductor substrates such as silicon. That is. Thus, by forming sensor elements on separate semiconductor substrates, there is an advantage that an optimum sensor structure and manufacturing process can be selected for each of the humidity sensor element 5a, the pressure sensor element 5b, and the temperature sensor element 5c.

  Further, as the humidity sensor element 5a, a humidity sensor system in which a moisture sensitive film is formed on a ceramic substrate not using a semiconductor substrate to detect electric resistance and capacitance, and as the temperature sensor element 5c, a bulk type sensor such as a thermistor is used. It is possible to use a chip resistor or a printed resistor printed on the ceramic support substrate 6. Similarly, various structures can be applied to the pressure sensor element 5b.

  Further, depending on the system configuration, not all of the humidity sensor element 5a, the pressure sensor element 5b, and the temperature sensor element 5c are adopted, but one or two sensor elements are selected and adopted as necessary. It is also possible to do.

[Example 4]
In FIG. 7, the top view of the common support substrate 6 of the thermal type air flow sensor which has an environmental sensor which is the 4th Example of this invention is shown.

  The difference from the first embodiment shown in FIG. 3 is that the humidity sensor element 5a, the pressure sensor element 5b and the temperature sensor element 5c of the flow sensor element 4 and the environmental sensor element 5 are arranged on a common semiconductor substrate 22 such as silicon. Is formed integrally. As described above, the flow sensor element 4 and the environment sensor element 5 are integrally formed on the semiconductor substrate 22, thereby reducing the cost by reducing the number of components.

[Example 5]
FIG. 8 is a longitudinal sectional view of a thermal air flow sensor having an environmental sensor according to a fifth embodiment of the present invention, and FIG. 9 is a sectional view taken along the line BB ′ of FIG.

  What is different from the first embodiment shown in FIG. 1 and FIG. In the first embodiment, the straight portion 7a of the sub-passage 7 has a so-called high dust-proof inertia effect that bypasses the straight portion 7b by a continuous curved surface at the bottom and reaches the straight portion 7b. In contrast, in this embodiment, a straight pipe configuration is used. The main air flow 3 enters the sub-passage 7 having a straight pipe structure from the inlet 8 and reaches the intake passage 2 from the outlet 9.

  Such a configuration is a problem in terms of reliability in measuring the air flow rate of an internal combustion engine of an automobile, but it is a gas flow rate detection in which foreign matter such as dust used in industrial or semiconductor manufacturing is controlled. Is applicable. Compared to the sub-passage 7 of the first embodiment, the cost is reduced because it is a simple sub-passage.

[Example 6]
FIG. 10 is a detailed cross-sectional view of the communication hole 16a of the thermal air flow sensor having the environmental sensor according to the sixth embodiment of the present invention.

  In the embodiment shown in part C of FIGS. 2 and 9, the communication hole 16 a is opened in a flat upper housing 15 b that forms the measurement chamber 10 in which the environmental sensor element 5 is accommodated, parallel to the main air flow 3. It was configured in a straight line. On the other hand, in this embodiment, as shown in FIG. 10, a recess 24 is provided in the housing outer wall surface 15 d of the upper housing 15 b, and the communication hole 16 a is formed in the recess 24.

  In this manner, by providing the recess 24, the opening of the communication hole 16a becomes a shadow with respect to the direction in which the foreign matter 23 such as dust contained in the main air flow 3 travels. Can reduce the risk of entering the measurement chamber 10. As a result, it is possible to prevent destruction due to the collision of the foreign matter 23 such as dust entering the environmental sensor element 5 and to realize a thermal air flow sensor having a more reliable environmental sensor. In addition, the same structure as the communication hole 16a is formed symmetrically on the communication hole 16b side.

[Example 7]
FIG. 11 is a detailed cross-sectional view of the communication hole 16a of the thermal air flow sensor having the environmental sensor according to the seventh embodiment of the present invention.

  In this embodiment, a bent portion 25 extending in the downstream direction of the main air flow 3 is provided in the communication hole 16a of the recess 24 of the upper housing 15b. In this manner, by providing the bent portion 25 in the communication hole 16a, the communication hole 16a opens toward the downstream direction of the main air flow 3, and it is possible to further prevent entry of the foreign matter 23 such as dust. It becomes.

[Example 8]
FIG. 12 is a detailed sectional view of a thermal air flow sensor having an environmental sensor according to the eighth embodiment of the present invention.

  In this embodiment, an opening means 26 such as a mesh or a filter is provided in place of the communication hole 16a of the recess 24 of the upper housing 15b. Even with such a configuration, entry of foreign matter 23 such as dust can be prevented.

  In the communication hole 16 and the opening means 26 such as a mesh or a filter in the above embodiment, regarding the size of the hole, the number of holes, etc., the expected flow range of the main air flow 3 and the size of the foreign matter 23 such as dust. , And can be appropriately selected according to the amount.

1 Thermal air flow sensor 2 Intake passage (main passage)
2a passage wall 3 main air flow 4 flow rate sensor element 5 environment sensor elements 6, 6a, 6b, 6c common support substrates 7, 7a, 7b sub-passage 8 inlet 9 outlet 10 measurement chamber 11 signal processing circuit 12 module flange 13 connector 14 connector Terminals 15, 15a, 15b Housing 15c, 15d Housing outer wall surfaces 16a, 16b Communication hole (first communication hole)
16c communication hole (second communication hole)
25 Communication holes 17a, 17b Connection terminals 18a, 18b Gold wires 19, 21 Recess 20 Wiring part 22 Semiconductor substrate 23 Foreign matter such as dust 24 Depression part 26 Opening means

Claims (12)

A housing disposed in the main passage;
A sub-passage formed in the housing and through which a part of the air flowing in the main passage passes;
A measurement chamber formed in the housing and communicating with at least one of the main passage and the sub-passage;
A flow rate sensor element that is disposed in the sub-passage and measures an air flow rate of air passing through the sub-passage;
An environmental sensor element that is housed in the measurement chamber and measures at least one of temperature, pressure, and humidity of the air in the measurement chamber;
At least the measurement chamber is spaced from the passage wall of the main passage and is disposed in a space in the housing from the center side of the main passage relative to the sub passage, and at least one of the main passage and the sub passage A thermal air flow sensor characterized in that it communicates with the air through a communication hole . The communication hole has a first communicating hole communicating between said main passage and said measuring chamber,
The first communicating holes, according to claim 1, characterized in that the opening in the housing outer wall surface of the housing extending along the flow direction of air passing through the main passage by the main passage Thermal air flow sensor.   3. The thermal air flow sensor according to claim 2, wherein the first communication hole opens into a hollow portion provided in the outer wall surface of the housing. 4. The thermal air flow sensor according to claim 3, wherein the first communication hole opens toward the downstream side of the main passage in the hollow portion .   The said 1st communicating hole is each drilled and formed in a pair of wall part mutually opposingly arranged which forms the said measurement chamber of the said housing, The any one of Claim 2 to 4 characterized by the above-mentioned. The thermal air flow sensor according to claim 1. The communication hole, the thermal according to any one of the preceding claims 2, characterized in that it has a second communication hole communicating between the auxiliary passage and the measurement chamber Air flow sensor.   The thermal air flow sensor according to any one of claims 1 to 6, wherein the flow sensor element and the environmental sensor element are mounted and integrated on a common support substrate.   In addition to the flow rate sensor element and the environmental sensor element, a signal processing circuit for processing an output signal of each sensor element is mounted on the common support substrate, and electrical wiring for connecting each sensor element to the signal processing circuit The thermal air flow sensor according to claim 7, further comprising a layer.   The common support substrate is provided with a recess for accommodating the flow sensor element, and the surface of the flow sensor element is disposed in the recess so as not to protrude from the surface of the common support substrate. The thermal air flow sensor according to 7 or 8.   The thermal air flow sensor according to any one of claims 1 to 9, wherein the environmental sensor element includes at least one of a pressure sensor element, a humidity sensor element, and a temperature sensor element.   The thermal air flow rate according to any one of claims 1 to 10, wherein the flow sensor element and the environmental sensor element are sensor elements formed on a semiconductor substrate by a micromachining technique. Sensor.   12. The sensor element according to claim 1, wherein the flow sensor element and the environment sensor element are sensor elements integrally formed on a common semiconductor substrate by a micromachining technique. Thermal air flow sensor.

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