Physical quantity detection device

Abstract

Provided is a physical quantity detection device (20) that can be disposed in a main flow path (22a) in which a to-be-measured gas (2) flows in one direction, the physical quantity detection device (20) comprising: a circuit chamber (135a) for accommodating a circuit board (300); an inflow port (220) that communicates the circuit chamber (135a) with the main flow path (22a) and that causes the to-be-measured gas (2) flowing through the main flow path (22a) to flow into the circuit chamber (135a); an outflow port (170) that communicates the circuit chamber (135a) with the main flow path (22a) and causes the to-be-measured the gas (2) in the circuit chamber (135a) to flow out to the main flow path (22a); and a sensor (322) disposed inside of the circuit chamber (135a) such that at least a portion of the to-be-measured gas (2) flowing from the inflow port (220) to the outflow port (170) is located in a path (2a).

Description

[Technical field]

[0001] The present invention relates to a physical quantity detection device. [Background technology]

[0002] There is known a physical quantity detection device that is disposed in the intake passage of an engine and measures and detects physical quantities such as flow rate, temperature, humidity, etc. of a gas to be measured (e.g., air) that is taken in. For example, Patent Document 1 discloses a physical quantity detection device (air flow measurement device) in which a bypass flow passage that takes in part of the air flowing inside a duct and a sub-bypass flow passage that is branched off from the bypass flow passage and takes in part of the air flowing through the bypass flow passage are formed in a housing, and various sensors (e.g., a flow rate sensor, an intake air temperature sensor, a humidity sensor) are disposed in the sub-bypass flow passage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-87254 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for miniaturization of physical quantity detection devices, and it is becoming necessary to reduce the space required for arranging sensors in the sub-bypass flow paths within a housing and to reduce the number of sensors arranged in the sub-bypass flow paths. An object of the present invention is to provide a compact physical quantity detection device. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention provides a physical quantity detection device that can be arranged in a main flow path through which a measurement target gas flows in one direction, the physical quantity detection device including: a circuit chamber that accommodates a circuit board; an inlet hole that communicates the main flow path with the circuit chamber and allows the measurement target gas flowing through the main flow path to flow into the circuit chamber; an outlet hole that communicates the main flow path with the circuit chamber and allows the measurement target gas in the circuit chamber to flow out to the main flow path; and a sensor arranged in the circuit chamber so that at least a part of the sensor is located on a path of the measurement target gas flowing from the inlet hole to the outlet hole. When the physical quantity detection device is disposed in the main flow path, the upstream side and the downstream side are defined based on a flow of the measurement target gas flowing in one direction through the main flow path, and the inlet hole is located downstream of the outlet hole. . Effect of the Invention

[0006] According to the present invention, since the sensor is provided in the circuit chamber, the physical quantity detection device can be made compact. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of an internal combustion engine control system using a physical quantity detection device according to a first embodiment. [Diagram 2] FIG. 1 is a front view of a physical quantity detection device according to a first embodiment. [Diagram 3] FIG. 2 is a right side view of the physical quantity detection device according to the first embodiment. [Figure 4] FIG. 2 is a left side view of the physical quantity detection device according to the first embodiment. [Diagram 5] FIG. 2 is a rear view of the physical quantity detection device according to the first embodiment. [Figure 6] 1 is a plan view of a physical quantity detection device according to a first embodiment. FIG. [Figure 7] FIG. 2 is a bottom view of the physical quantity detection device according to the first embodiment. [Figure 8] 1 is a left side view of the physical quantity detection device according to the first embodiment, with a cover removed from a housing. FIG. [Figure 9]2 is a front view of a surface of a cover detached from a housing, the surface facing the housing, in the physical quantity detection device according to the first embodiment. FIG. [Figure 10] FIG. 5 is a perspective view of the cross section AA of FIG. [Figure 11] FIG. 11 is a view taken along the arrow B in FIG. [Figure 12] FIG. 11 is a view taken along the arrow B in FIG. [Figure 13] 5 is a cross-sectional view taken along CC in FIG. 4. [Figure 14] 5 is a cross-sectional view taken along CC in FIG. 4. [Figure 15] FIG. 11 is an analytical diagram showing the behavior of a measurement target gas that flows in from an inlet in a physical quantity detection device according to a comparative example in which an inlet is disposed upstream of the inlet of the present invention. [Figure 16] 4 is an analytical diagram showing the behavior of a measurement target gas that has flowed in through an inlet of the physical quantity detection device according to the first embodiment. FIG. [Figure 17] 5 is a cross-sectional view taken along line CC of FIG. 4 of the physical quantity detection device according to the second embodiment. FIG. [Figure 18] 5 is a cross-sectional view taken along line CC of FIG. 4 of a physical quantity detection device according to a third embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the configuration and operation of the physical quantity detection device according to the first to third embodiments of the present invention will be described with reference to the drawings. Note that the same reference numerals denote the same parts in each drawing.

[0009] (First embodiment) 1 is a schematic diagram of an internal combustion engine control system using a physical quantity detection device according to the first embodiment. The internal combustion engine control system 1 is a control system for an internal combustion engine in which air, which is a measurement target gas 2, is sucked in through an air cleaner 21 based on the operation of an internal combustion engine 10 equipped with an engine cylinder 11 and an engine piston 12.

[0010] The measurement target gas 2 sucked in through an air cleaner 21 is guided to a combustion chamber 11 a of an engine cylinder 11 via an intake body 22 , a throttle body 23 , and an intake manifold 24 .

[0011] The measurement gas 2 introduced into the combustion chamber 11a has a physical quantity detected by a physical quantity detection device 20 in the main flow passage 22a, and is mixed with fuel supplied from a fuel injection valve 14 based on the physical quantity, forming an air-fuel mixture, which is then introduced into the combustion chamber 11a.

[0012] The air-fuel mixture introduced into the combustion chamber 11a combusts explosively and generates mechanical energy due to spark ignition from the spark plug 13. The gas after combustion is then introduced into the exhaust pipe 16a through the exhaust valve 16 and is exhausted from the exhaust pipe 16a as exhaust gas 3 to the outside of the vehicle.

[0013] The flow rate of the measurement gas 2 introduced into the combustion chamber 11a is controlled by a throttle valve 25 whose opening changes based on the operation of the accelerator pedal. Also, the fuel supply amount is controlled based on the flow rate of the measurement gas 2 introduced into the combustion chamber 11a. Therefore, the driver can change the opening of the throttle valve 25 by operating the accelerator pedal, control the flow rate of the measurement gas 2 introduced into the combustion chamber 11a, and change the mechanical energy generated in the internal combustion engine.

[0014] The physical quantity detection device 20 is a device that detects physical quantities such as the flow rate, temperature, humidity, and pressure of the measured gas 2 that is taken in from the air cleaner 21 and flows through the main flow path 22a (in this embodiment, the flow path inside the intake body 22), and inputs these physical quantities to the control device 4 as electrical signals.

[0015] Furthermore, the throttle angle sensor 26 is a sensor that detects the opening degree of the throttle valve 25 and inputs the same as an electric signal to the control device 4. Furthermore, the rotation angle sensor 17 is a sensor that inputs detection values ​​as an electric signal to the control device 4 in order to detect the positions and states of the engine piston 12, intake valve 15, and exhaust valve 16 of the internal combustion engine, and the rotation speed of the internal combustion engine. Furthermore, the oxygen sensor 28 is a sensor that inputs detection values ​​as an electric signal to the control device 4 in order to detect the mixture ratio state of the fuel amount and the air amount from the state of the exhaust gas 3.

[0016] The control device 4 is a device that calculates the fuel injection amount and ignition timing based on the detection values ​​of the physical quantity detection device 20, the throttle angle sensor 26, the rotation angle sensor 17, and the oxygen sensor 28. The amount of fuel supplied from the fuel injection valve 14 and the ignition timing at which the ignition is performed by the spark plug 13 are controlled based on the calculation results of the control device 4. Furthermore, in order to control the rotation speed of the internal combustion engine in an idle operating state, the control device 4 controls the amount of air bypassing the throttle valve 25 when the internal combustion engine is in an idle operating state by the idle air control valve 27. Therefore, the fuel supply amount and ignition timing, which are the main control amounts of the internal combustion engine, are calculated based on the detection values ​​of the physical quantity detection device 20.

[0017] FIG. 2 is a front view of the physical quantity detection device 20 according to this embodiment. FIG. 3 is a right side view of the physical quantity detection device 20 according to this embodiment. FIG. 4 is a left side view of the physical quantity detection device according to this embodiment. FIG. 5 is a rear view of the physical quantity detection device according to this embodiment. FIG. 6 is a plan view of the physical quantity detection device according to this embodiment. FIG. 7 is a bottom view of the physical quantity detection device according to this embodiment. Note that, hereinafter, the measurement gas 2 flows through the main flow path 22a in one direction indicated by an arrow, and the upstream side and downstream side will be described based on the direction of the arrow.

[0018] The physical quantity detection device 20 has a flange portion 111 which is a part for fixing to the intake body 22, a connector portion 112 which is a part for electrically connecting to an external device, and a measurement portion 113 which is a part for measuring the physical quantity of the measured gas 2.

[0019] 6 and 7, a pair of fixing holes 141 are provided at diagonally opposite corners of the flange portion 111. A through hole 142 is provided at the center of the fixing hole portion 141, and the physical quantity detection device 20 is fixed to the intake body 22 by a screw inserted into the through hole 142.

[0020] 5, the connector portion 112 is provided on the upper portion of the flange portion 111, and includes, for example, a plurality of (four in this embodiment) external input / output terminals 147 and a correction terminal 148. The plurality of external input / output terminals 147 include a terminal for outputting physical quantities such as flow rate and temperature that are measurement results of the physical quantity detection device 20, and a power supply terminal for supplying DC power for operating the physical quantity detection device 20. The correction terminal 148 is a terminal used for storing a correction value in the physical quantity detection device 20. The correction terminal 148 has a shape that does not interfere with the connection of the external input / output terminal 147. For example, the correction terminal 148 is shorter than the external input / output terminal 147, and is designed not to interfere with the connection of the external input / output terminal 147.

[0021] The measuring part 113 is provided at the lower part of the flange part 111, and has a wide left side surface 121 and a right side surface 122, and a narrow front surface 123, a back surface 124, and a bottom surface 125. The measuring part 113 is inserted into the main flow path 22a from a through hole provided in the intake body 22 and disposed in the main flow path 22a. The measuring part 113 fixed in the main flow path 22a is disposed with the left side surface 121 and the right side surface 122 aligned with the direction in which the measurement target gas 2 flows, the front surface 123 on the upstream side, and the back surface 124 on the downstream side with respect to the main flow path 22a.

[0022] As shown in FIG. 2, the front surface 123 of the measuring unit 113 is provided with a sub-passage inlet 131 on the bottom surface 125 side. Also, as shown in FIG. 5, the rear surface 124 of the measuring unit 113 is provided with a first outlet 132 on the bottom surface 125 side, and a second outlet 133 is provided immediately above the first outlet 132. The combined opening area of ​​the first outlet 132 and the second outlet 133 is larger than the opening area of ​​the sub-passage inlet 131. This can prevent the measurement target gas 2 from accumulating in the measuring unit 113. Also, since the opening area of ​​the first outlet 132 is smaller than the opening area of ​​the second outlet 133, it can prevent the measurement target gas 2 flowing in from the sub-passage inlet 131 from flowing out only from the first outlet 132 and not from the second outlet 133.

[0023] The measurement target gas 2 flowing near the center of the intake body 22 is taken in from the sub-passage inlet 131 to the sub-passage 134, and is discharged from the first outlet 132 and the second outlet 133 to the main passage 22a. At this time, since the sub-passage inlet 131 is provided on the bottom surface 125 side, the physical quantity detection device 20 can measure the physical quantity of the measurement target gas 2 flowing in a portion away from the intake body 22. This makes it possible to suppress a decrease in measurement accuracy due to the influence of heat radiation from the main passage 22a, etc.

[0024] 2 to 5, the distance between the left side surface 121 and the right side surface 122 is shorter than the distance between the front surface 123 and the rear surface 124. This allows the physical quantity detection device 20 to suppress the resistance force caused by the measurement gas 2.

[0025] 8 is a left side view of the physical quantity detection device 20 according to this embodiment with the cover 200 removed from the housing 100. As shown in Fig. 8, the housing 100 is provided with a sub-flow path groove 150 that connects the sub-flow path inlet 131, the first outlet 132, and the second outlet 133, and a recess 135 that accommodates the circuit board 300 and is fixed to a bottom surface 135b (see Fig. 13 described later).

[0026] The sub-flow groove 150 is a groove for passing the measurement target gas 2 through the measuring unit 113 to detect a physical quantity. The sub-flow groove 150 includes a first sub-flow groove 151 that communicates between the sub-flow inlet 131 and the first outlet 132, and a second sub-flow groove 152 that branches off from the first sub-flow groove 151, makes an upward detour, and then bends downward to communicate with the second outlet 133.

[0027] The recess 135 is a recess provided in a region above the sub-flow path inlet 131 and in front of the second sub-flow path groove 152 in the housing 100. A circuit board 300 electrically connected to an external input / output terminal by, for example, a bonding pad and a bonding wire is fixed to a bottom surface 135b of the recess 135.

[0028] Fig. 9 is a front view of the surface of the cover 200 facing the housing 100 when removed from the housing 100 in the physical quantity detection device 20 according to this embodiment. The cover 200 is a member that closes the opening 101 (see Fig. 8) of the housing 100, and is formed of, for example, a flat plate. As shown in Fig. 9, the cover 200 is provided with ribs 211-217 that are protrusions protruding from an inner surface 201 toward the opposing housing 100, and an inlet hole 220, which will be described later.

[0029] The ribs 211-217 are inserted into recessed grooves 161-167 (see FIG. 8) provided in the peripheral wall 126 that surrounds the sub-flow passage groove 150 and the recess 135 of the housing 100 and separates the inside from the outside of the housing 100, and are adhered thereto with an adhesive. In this way, the cover 200 is fixed to the housing 100. Note that the cover 200 can also be fixed to the housing 100 without providing the ribs 211-217 on the cover 200. In this case, the recessed grooves 161-167 are not provided in the peripheral wall 126 of the housing 100, and for example, the tip of the peripheral wall 126 is adhered to the inner surface 201 of the cover 200, thereby fixing the cover 200 to the housing 100.

[0030] By attaching the cover 200 to the housing 100, the sub-flow passage groove 150 of the housing 100 forms the sub-flow passage 134. In addition, the first sub-flow passage groove 151 and the second sub-flow passage groove 152 provided in the sub-flow passage groove 150 form the first sub-flow passage 134a and the second sub-flow passage 134b, respectively.

[0031] The first sub-channel 134a is a channel that communicates the sub-channel inlet 131 and the first outlet 132, and takes in the measurement target gas 2 flowing through the main channel 22a from the sub-channel inlet 131, passes it through, and returns it from the first outlet 132 to the main channel 22a.

[0032] The second sub-channel 134b is a channel that communicates between the first sub-channel 134a and the second outlet 133, takes in the measurement target gas 2 flowing through the first sub-channel 134a, passes it through, and returns it to the main channel 22a from the second outlet 133. The second sub-channel 134b is provided with an outward channel portion 134c that branches off midway through the first sub-channel 134a and extends upward toward the flange portion 111, and a return channel portion 134d that makes a U-turn above the measuring portion 113, extends downward toward the tip side, and communicates with the second outlet 133.

[0033] A flow sensor (flow rate detection unit) 311 is disposed in the forward flow path portion 134c of the second sub-flow path 134b. The second sub-flow path 134b is bypassed upward, then makes a U-turn and communicates with the second outlet 133 below, so that the flow path is long and it is possible to suppress the influence of the pulsation of the measurement target gas 2 on the flow rate sensor 311. The flow rate sensor 311 is provided at a tip portion of a chip package 310 fixed to the circuit board 300, which protrudes into the second sub-flow path groove 152.

[0034] Furthermore, by attaching the cover 200 to the housing 100, the recess 135 of the housing 100 forms a circuit chamber 135a together with the cover 200. The circuit chamber 135a accommodates the circuit board 300, which is fixed to the bottom surface 135b of the recess 135, by covering the circuit board 300 with the cover 200. Sensors 322, such as a pressure sensor, a temperature sensor, and a humidity sensor, are mounted on the circuit board 300 accommodated in the circuit chamber 135a.

[0035] The circuit chamber 135a is provided with an inlet 220 and an outlet 170 for passing the measurement target gas 2 flowing through the main flow path 22a in the circuit chamber 135a in order to detect the physical quantity of the measurement target gas 2 by a sensor 322 arranged in the circuit chamber 135a.

[0036] The inlet hole 220 is a hole that communicates the main flow path 22a and the circuit chamber 135a and allows the measurement target gas 2 flowing through the main flow path 22a to flow into the circuit chamber 135a. In this embodiment, the inlet hole 220 is provided in the left side surface 121 (i.e., the cover 200) of the measurement unit 113. The inlet hole 220 may be provided in the right side surface 122 (i.e., the housing 100) of the measurement unit 113.

[0037] The outflow hole 170 is a hole that communicates the main flow path 22a and the circuit chamber 135a and allows the measurement gas 2 in the circuit chamber 135a to flow into the main flow path 22a. In this embodiment, the outflow hole 170 is provided in the right side surface 122 of the measurement unit 113 (i.e., the housing 100). The outflow hole 170 may be provided in the left side surface 121 of the measurement unit 113 (i.e., the cover 200).

[0038] 8, the sensor 322 is disposed in the circuit chamber 135a so that at least a part of the sensor 322 is located on the path 2a of the measurement target gas 2 flowing from the inlet 220 to the outlet 170. The sensor 322 is preferably disposed at a position away from the peripheral wall 126 in the circuit chamber 135a.

[0039] In this embodiment, the sensor 322 is preferably a humidity sensor. The humidity sensor is attached to the circuit board 300 so that at least a portion of the humidity sensor is located on the path 2a. Therefore, the physical quantity detection device 20 can detect the humidity of the measurement target gas 2 flowing through the path 2a. For accurate detection, it is preferable to use a capacitance type sensor as the humidity sensor. Note that a resistance type sensor may be used to reduce costs.

[0040] In addition, in a state where the physical quantity detection device 20 is disposed in the main flow path 22a, when the upstream side and the downstream side are defined based on the flow of the measurement target gas 2 flowing in one direction through the main flow path 22a, it is preferable that the inlet hole 220 is located downstream of the outlet hole 170 as shown in FIG. 8.

[0041] Fig. 10 is a perspective view of the cross section taken along the line AA in Fig. 4. As shown in Fig. 10, the outflow hole 170 is preferably provided in a protrusion 171 protruding from a side wall 100a of the housing 100 covering the circuit chamber 135a from the main flow path 22a side to the main flow path 22a. When the outflow hole 170 is provided in the protrusion 171 in this manner, separation of the measurement gas 2 occurs near the outflow hole 170, lowering the pressure near the outflow hole 170 below the pressure near the inflow hole 220. This makes it easier for the measurement gas 2 in the circuit chamber 135a to flow from the inflow hole 220 located on the downstream side of the main flow path 22a toward the outflow hole 170 located on the upstream side.

[0042] 11 and 12 are views taken along the line B in FIG. 10, and FIGS. 13 and 14 are cross-sectional views taken along the line CC in FIG. 4. When the inlet 220 is viewed from the main flow path 22a side (the B side in FIG. 10), the physical quantity detection device 20 is preferably configured such that a portion (most downstream portion) 221 located at the most downstream side of the inlet 220 has any of the characteristics shown in FIGS. 11 and 12. That is, as shown in FIG. 11, the most downstream portion 221 is preferably located at the same position as the downstream wall surface (downstream wall surface) 126a that forms the circuit chamber 135a. Alternatively, as shown in FIG. 12, the most downstream portion 221 is preferably located downstream of the downstream wall surface 126a. Note that, when the inlet 220 has the above-mentioned characteristics, the inlet 220 is not limited to being located at the downstream side of the outlet 170.

[0043] In particular, when the physical quantity detection device 20 is viewed from the main flow path 22a side (side B in FIG. 10), it is preferable that the wall surface 126a of the circuit chamber is visible on the downstream side inside the inlet 220 as shown in FIG. 12. It is also preferable that the wall surface 126a of the circuit chamber has at least one protrusion 126b on the downstream side inside the inlet 220.

[0044] 13 and 14, in the physical quantity detection device 20, it is preferable that the wall surface 126a of the circuit chamber 135a covers a downstream portion 222a of the outlet 222 of the inlet 220. Note that it is sufficient that the wall surface 126a covers the downstream portion 222a of the outlet 222 of the inlet 220. Therefore, as shown in Fig. 13, the wall surface 126a may extend to the bottom surface 135b, and as shown in Fig. 14, a wall surface 126c provided on the lower part of the wall surface 126a on the downstream side of the wall surface 126a may extend to the bottom surface 135b.

[0045] [effect] In this embodiment, the sensor 322 is provided so that at least a part of it is located on the path of the measurement target gas 2 flowing from the inlet 220 to the outlet 170 in the circuit chamber 135a. That is, the measurement space of the sensor 322, which was previously provided in the second sub-channel 134b, is provided in the circuit chamber 135a. This makes it possible to reduce the size of the second sub-channel 134b, and therefore the physical quantity detection device 20.

[0046] Furthermore, by positioning a part of the sensor 322 on the path 2a of the measurement target gas 2, the measurement target gas 2 can be actively caused to flow near the sensor 322, thereby promoting replacement of the measurement target gas 2 and ensuring the responsiveness of the sensor 322. For example, when a humidity sensor is used as the sensor 322, replacement of the measurement target gas 2 near the humidity sensor is promoted, so that the humidity of the measurement target gas 2 can be detected with good responsiveness.

[0047] In addition, in the physical quantity detection device 20 of this embodiment, when the upstream side and the downstream side are defined based on the flow of the measurement target gas 2 flowing in one direction in the main flow channel 22a, it is preferable that the inlet hole 220 is located downstream of the outlet hole 170. When the inlet hole 220 and the outlet hole 170 are arranged in this way, the measurement target gas 2 in the circuit chamber 135a flows in the opposite direction from the downstream side to the upstream side with respect to the flow direction of the measurement target gas 2 flowing in the main flow channel 22a. In other words, the measurement target gas 2 flowing in the main flow channel 22a enters the circuit chamber 135a from the inlet hole 220 and makes a U-turn before flowing. By intentionally obstructing the smooth flow of the measurement target gas 2 by making a U-turn in this way, it is possible to suppress the intrusion of foreign matter (e.g., water) into the circuit chamber 135a (that is, most foreign matter in the main flow channel 22a flows toward the downstream side due to inertia without entering the circuit chamber 135a from the inlet hole 220), and the amount of foreign matter reaching the sensor 322 can be reduced. Although the flow velocity of the measurement gas 2 in the circuit chamber 135a is slower than the flow velocity in the main flow path 22a, the response time of the humidity sensor does not depend much on the flow velocity, so there is no problem with the responsiveness even if the flow velocity becomes slower.

[0048] On the upstream side of the left side surface 121 and the right side surface 122 of the physical quantity detection device 20, a vortex tends to be generated due to the collision of the measurement target gas 2 with the front surface 123, and foreign matter tends to adhere to the upstream side of the left side surface 121 and the right side surface 122 of the physical quantity detection device 20. However, by arranging the inlet 220 on the downstream side of the left side surface 121 or the right side surface 122 of the physical quantity detection device 20 as described above, the inlet 220 can be moved away from the upstream side where foreign matter adheres, and the amount of foreign matter reaching the sensor 322 can be reduced.

[0049] Fig. 15 is an analytical diagram showing the behavior of the measurement target gas 2 flowing in from the inlet 1220 in a physical quantity detection device according to a comparative example in which the inlet 1220 is arranged upstream of the inlet 220 of the present invention. Also, Fig. 16 is an analytical diagram showing the behavior of the measurement target gas 2 flowing in from the inlet 220 in the physical quantity detection device 20 according to the present embodiment.

[0050] In the inlet 1220 of the physical quantity detection device according to the comparative example, a portion (most downstream portion) 1221 located on the most downstream side is located upstream of a downstream wall surface (downstream wall surface) 126a forming the circuit chamber 135a. In this case, the flow path width of the measurement target gas 2 is suddenly expanded when it reaches the circuit chamber 135a from the inlet 1220. For example, the flow path of the measurement target gas 2 has a shape of a so-called expanding pipe, and the measurement target gas 2 discharged from the outlet 1222 of the inlet 1220 forms a vortex 2b as shown in FIG. 15. The vortex 2b causes turbulence in the flow of the measurement target gas 2 in the circuit chamber 135a, so that foreign matter is likely to remain in the circuit chamber 135a, and the foreign matter is likely to reach the sensor 322.

[0051] To address this issue, in this embodiment, when the inlet 220 is viewed from the main flow path 22a side, as shown in Fig. 11, the most downstream portion 221 is preferably located at the same position as the downstream wall surface (downstream wall surface) 126a forming the circuit chamber 135a, or as shown in Fig. 12, the most downstream portion 221 is preferably located downstream of the downstream wall surface 126a. In this case, since the downstream wall surface 126a functions as a throttle of the flow path of the measurement target gas 2, the flow velocity of the measurement target gas 2 flowing into the circuit chamber 135a increases as shown in Fig. 16, and the generation of the vortex 2b can be suppressed. As a result, the measurement target gas 2 in the circuit chamber 135a can be actively discharged toward the outlet hole 170, so that the retention of foreign matter in the circuit chamber 135a is suppressed, and the foreign matter can be suppressed from reaching the sensor 322.

[0052] In particular, when the physical quantity detection device 20 is viewed from the main flow path 22a side (side B in FIG. 10), it is preferable that the wall surface 126a of the circuit chamber is visible on the downstream side inside the inflow hole 220 as shown in FIG. 12. It is also preferable that the wall surface 126a of the circuit chamber has at least one convex portion 126b on the downstream side inside the inflow hole 220. Thereby, the convex portion 126b of the downstream wall surface 126a functions as a throttle of the flow path of the measurement target gas 2, and the flow velocity of the measurement target gas 2 flowing into the circuit chamber 135a is further increased, and the generation of the vortex 2b can be suppressed. In addition, since the measurement target gas 2 in the circuit chamber 135a can be actively discharged toward the outflow hole 170, the retention of foreign matter in the circuit chamber 135a is suppressed, and the foreign matter can be suppressed from reaching the sensor 322.

[0053] The measurement target gas 2 may contain water as a foreign matter. When the inventors analyzed the behavior of the water inside the circuit chamber 135a, they found that the water gathers on the peripheral wall 126 of the circuit chamber 135a. When the sensor 322 is disposed at a position away from the peripheral wall 126 inside the circuit chamber 135a as in this embodiment, water is less likely to reach the sensor 322, so that the physical quantity of the measurement target gas 2 can be easily detected accurately.

[0054] Second embodiment Fig. 17 is a CC cross-sectional view of the physical quantity detection device according to the second embodiment of the present invention shown in Fig. 4. The physical quantity detection device according to this embodiment differs from the physical quantity detection device 20 according to the first embodiment in the following points. That is, a downstream wall surface 2126a forming the circuit chamber 2135a is inclined so as to form an obtuse angle θ with a bottom surface 2135b of the circuit chamber 2135a, and when the inlet hole 220 is viewed from the main flow path side (side B), a portion (most downstream part) 221 located on the most downstream side of the inlet hole 220 is located downstream of an intersection line 2126b between the downstream wall surface 2126a and the bottom surface 2135b of the circuit chamber 2135a.

[0055] [effect] Since the downstream wall surface 2126a of this embodiment functions as a throttle of the flow path of the measured gas 2 like the downstream wall surface 126a of the first embodiment, the flow velocity of the measured gas 2 flowing into the circuit chamber 2135a increases, and the generation of the vortex 2b can be suppressed. As a result, the measured gas 2 in the circuit chamber 2135a can be actively discharged toward the outflow hole 170, so that the retention of foreign matter in the circuit chamber 2135a is suppressed, and the foreign matter can be suppressed from reaching the sensor 322.

[0056] Third embodiment 18 is a cross-sectional view of the physical quantity detection device according to the third embodiment of the present invention taken along the CC line shown in FIG. 4. The physical quantity detection device according to this embodiment is different from the physical quantity detection device according to the second embodiment in the following respects. That is, the physical quantity detection device according to this embodiment includes a convex portion 3126d having an end face 3126c located downstream of the intersection line 3126b. In other words, when the inlet 220 is viewed from the main flow path side (side B), the wall surface 3126a of the circuit chamber 3135a seen on the downstream side inside the inlet 220 has a plurality of convex portions (in this embodiment, convex portions 3126d, 3126e) in the height direction of the wall surface 3126a, and the convex portion whose end face is located most upstream among the plurality of convex portions is the convex portion 3126e closest to the bottom surface 3135b of the circuit chamber 3125a.

[0057] [effect] Since the downstream wall surface 3126a functions as a throttle of the flow path of the measurement target gas 2 like the downstream wall surface 126a in the first embodiment, the flow velocity of the measurement target gas 2 flowing into the circuit chamber 3135a increases, and the generation of the vortex 2b can be suppressed. As a result, the measurement target gas 2 in the circuit chamber 3135a can be actively discharged toward the outflow hole 170, so that the retention of foreign matter in the circuit chamber 3135a is suppressed, and the foreign matter can be suppressed from reaching the sensor 322.

[0058] The present invention is not limited to the above-described embodiment, and includes various modified examples. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to those including all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0059] 2...measured gas, 2a...path, 2b...vortex, 20...physical quantity detection device, 22a...main flow path, 100...housing, 113...measurement section, 126...peripheral wall, 126a, 2126a, 3126a...downstream wall surface, 135a, 2135a, 3135a...circuit chamber, 135b, 2135b, 3135b...bottom surface, 170...outlet hole, 171...projection, 200...cover, 220...inlet hole, 221...most downstream portion, 222...outlet, 300...circuit board, 322...sensor, 2126b, 3126b...intersection line, 3126c...end surface, 3126d, 3126e...projection

Claims

1. A physical quantity detection device that can be arranged in a main flow path through which a measurement target gas flows in one direction, a circuit chamber for accommodating a circuit board; an inlet hole that communicates the main flow path with the circuit chamber and allows the measurement target gas flowing through the main flow path to flow into the circuit chamber; an outflow hole that communicates the main flow path with the circuit chamber and through which the measurement target gas in the circuit chamber flows out to the main flow path; a sensor disposed in the circuit chamber so as to be at least partially located on a path of the measurement target gas flowing from the inlet to the outlet, In a state where the physical quantity detection device is disposed in the main flow path, When the upstream side and the downstream side are defined based on the flow of the measurement target gas flowing in one direction through the main flow path, The physical quantity detection device, wherein the inlet hole is located downstream of the outlet hole.

2. The physical quantity detection device according to claim 1 , In a state where the physical quantity detection device is disposed in the main flow path, When the upstream side and the downstream side are defined based on the flow of the measurement target gas flowing in one direction through the main flow path, a downstream wall surface that forms the circuit chamber, and a downstream side wall surface that forms the circuit chamber.

3. The physical quantity detection device according to claim 1 , The physical quantity detection device, wherein the sensor is disposed at a position away from a peripheral wall of the circuit chamber.

4. The physical quantity detection device according to claim 1 , a downstream wall surface that defines the circuit chamber is inclined to form an obtuse angle with a bottom surface of the circuit chamber; a downstream wall surface forming the circuit chamber and a bottom surface of the circuit chamber, the downstream wall surface being positioned downstream of the intersection line between the downstream wall surface forming the circuit chamber and a bottom surface of the circuit chamber, when the inlet hole is viewed from the main flow path side.

5. The physical quantity detection device according to claim 4, a downstream wall surface forming the circuit chamber is provided with a convex portion having an end surface located downstream of the intersection line when the inlet hole is viewed from the main flow path side.

6. The physical quantity detection device according to claim 1 , A physical quantity detection device, characterized in that, when the inlet is viewed from the main flow path side, a wall surface of the circuit chamber is visible on the downstream side inside the inlet.

7. The physical quantity detection device according to claim 6 , A physical quantity detection device, characterized in that a wall surface of the circuit chamber seen from the inside of the inlet on the downstream side has at least one convex portion.

8. The physical quantity detection device according to claim 6 , a wall surface of the circuit chamber seen from the downstream side inside the inlet has a plurality of protrusions in a height direction of the wall surface, The physical quantity detection device, wherein the convex portion having an end face located furthest upstream among the plurality of convex portions is the convex portion closest to a bottom surface of the circuit chamber.

9. The physical quantity detection device according to claim 6 , A physical quantity detection device, characterized in that a wall surface of the circuit chamber covers a portion of the downstream side of the outlet of the inlet.

10. The physical quantity detection device according to claim 1 , The physical quantity detection device, wherein the outflow hole is provided in a protrusion that protrudes into the main flow path from a side wall that covers the circuit chamber from the main flow path side.

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