Detection device for a physical quantity

Abstract

A physical quantity detection device configured to detect a physical quantity of a target gas flowing in a main passage, the physical quantity detection device comprising: a housing arranged in the main passage; a sub-passage arranged in the housing; a flow rate detection unit arranged in the sub-passage; a circuit unit electrically connected to the flow rate detection unit; and a circuit chamber arranged in the housing that accommodates the circuit unit.and a first inlet passage having one end open to the subpassage and the other end open to the circuit chamber to connect the subpassage and the circuit chamber, and configured to introduce pressure of the target gas from the subpassage into the circuit chamber, the flow rate sensing unit comprising: a diaphragm with a diaphragm front surface exposed to the subpassage and a diaphragm rear surface exposed to a closed chamber separate from the subpassage;and a second inlet passage with one end open to the circuit chamber and the other end open to the closed chamber to connect the circuit chamber and the closed chamber, configured to introduce the pressure of the target gas from the circuit chamber into the closed chamber, and the circuit chamber having at least one or more projections arranged opposite an opening to which the other end of the first inlet passage is open.

Description

Technical area

[0001] The present invention relates to a detection device for a physical quantity, which is designed to detect a physical quantity of, for example, intake air in an internal combustion engine. State of the art

[0002] PTL 1 discloses a structure of an airflow rate measuring device comprising a bypass flow path that receives a portion of the air flowing through a main flow path in a duct, a sub-bypass flow path that branches off from the bypass flow path and receives a portion of the air flowing through the bypass flow path, and a sensor installed in the sub-bypass flow path. The sensor comprises a diaphragm for detecting a flow rate, and the diaphragm comprises a front element surface exposed to the sub-bypass flow path and a rear element surface exposed to a closed chamber that communicates with a circuit chamber via a vent hole. List of oppositions patent literature

[0003] PTL 1: JP 2020-34508 A Summary of the invention: Technical problem

[0004] A physical quantity sensing device is required to accurately measure a flow rate signal, even when used in different types of internal combustion engines. It has been found that in an internal combustion engine, a turbocharger mounted downstream of the physical quantity sensing device generates sound pressure that affects the flow rate characteristic of the device. The turbocharger induces a sound pressure resonance phenomenon on the front and rear surfaces of the diaphragm element, which influences the flow rate characteristic and ultimately leads to an error in flow rate measurement. In the conventional configuration described above, i.e.,In a configuration that contains only one connecting passage between the subpass or main passage and the ventilation hole of the sensing device for a physical quantity, the sound pressure can cause an error in the sensing of the flow rate.

[0005] One object of the present invention is to provide a detection device for a physical quantity which is designed to reduce the influence of the resonance phenomenon of sound pressure on the flow rate characteristic. Solution to the problem

[0006] To achieve this objective, the present invention provides a physical quantity detection device configured to detect a physical quantity of a target gas flowing in a main passage, wherein the physical quantity detection device comprises: a housing located in the main passage; a subpassage arranged within the housing; a flow rate measurement unit located in the underpass; a circuit unit that is electrically connected to the flow rate detection unit; a circuit chamber arranged in the housing, in which the circuit unit is housed, and a first pressure introduction passage having an end open to the underpass and an end open to the circuit chamber to establish a connection between the underpass and the circuit chamber, and configured to introduce the pressure of the target gas from the underpass into the circuit chamber.

[0007] The flow rate sensing unit comprises: a diaphragm with a diaphragm front surface exposed to the underpass and a diaphragm rear surface exposed to a closed chamber separate from the underpass; and a second pressure introduction passage having an end open to the circuit chamber and an end open to the closed chamber to connect the circuit chamber and the closed chamber, and configured to introduce the pressure of the target gas from the circuit chamber into the closed chamber, and the circuit chamber has at least one or more projections arranged opposite an opening to which the other end of the first pressure introduction passage is open. Advantageous effects of the invention

[0008] The present invention provides a detection device for a physical quantity which is designed to reduce the influence of a resonance phenomenon of sound pressure on the flow rate characteristic.

[0009] Further features of the present invention will become apparent from the present descriptions and the accompanying drawings. Problems, configurations, and effects beyond those described above are clarified below in descriptions of embodiments. List of characters [ Fig. Figure 1 is a system diagram showing an embodiment in which a detection device for a physical quantity according to the present invention is used in an internal combustion engine control system. [ Fig. 2] Fig. Figure 2 is a front view of the detection device for a physical quantity. [ Fig. 3] Fig. Figure 3 is a view showing a state in which a cover is removed from a housing of the sensing device for a physical quantity. [ Fig. 4] Fig. Figure 4 is a perspective view showing a back surface of the cover. [ Fig. 5] Fig. Figure 5 is a cross-sectional view of the cover and housing in Fig. 2, taken along a plane perpendicular to a connecting surface of the cover and the housing. [ Fig. 6] Fig. Figure 6 is a cross-sectional view along line VI-VI in Fig. 5. [ Fig. 7] Fig. Figure 7 is a cross-sectional view of a chip enclosure. [ Fig. 8] Fig. Figure 8 is an enlarged view of a main part in Fig. 5. [ Fig. 9] Fig. Figure 9 is a cross-sectional view along line VIII-VIII in Fig. 5. [ Fig. 10] Fig. 10 is an enlarged view of a main part in Fig. 9. [ Fig. 11] Fig. Figure 11 is a diagram illustrating a difference between the physical quantity detection device according to the present invention and a physical quantity detection device according to a comparative example. [ Fig. 12] Fig. Figure 12 is a diagram to describe a difference in the results of measured sound pressures between the present invention and the comparison example. [ Fig. 13] Fig. Figure 13 is a diagram describing a modification of a first embodiment. Description of the embodiments

[0010] One embodiment of the present invention, described below (hereinafter referred to as an embodiment), solves various problems as a specific product. In particular, it solves various problems when used as a detection device designed to detect a physical quantity of the intake air of a vehicle and exhibits various effects. One of the various problems solved by the following embodiments has been described above under the technical problem that the present invention is intended to solve, and one of the various effects achieved by the following embodiments has been described above under the advantageous effects of the present invention. Various problems that the following embodiments are intended to solve and various effects that the following embodiments are intended to achieve are clarified in the descriptions of the following embodiments.The problems and effects described below (as the problems and effects that the following embodiments are intended to solve and achieve) therefore include, in addition to the technical problems and advantageous effects of the present invention described above, further content.

[0011] In the following embodiments, the same reference numerals denote the same configuration, even in different FIGS, and thus the same functions and effects are achieved. Previously described configurations are identified by the same reference numerals, and a detailed description may be omitted. <Erste Ausführungsform>

[0012] Fig. Figure 1 is a system diagram showing an embodiment in which a detection device for a physical quantity according to the present invention is used in an internal combustion engine system 1 with electronic fuel injection.

[0013] The physical quantity sensing device of this embodiment is used in the internal combustion engine system 1 for a motor vehicle. The internal combustion engine system 1 comprises an engine 2 together with a turbocharger 15, a main passage 22, and an exhaust passage 9. The main passage 22 comprises, in upstream order, an air cleaner 4, a physical quantity sensing device 20, an intercooler 6, a throttle valve 7, and an intake manifold 8; and the exhaust passage 9 comprises an exhaust catalyst 10. The intake manifold 8 is equipped with a thermal humidity measuring device 11, an intake pressure sensor 12, and an intake air temperature sensor 13 and measures the humidity, pressure, and temperature of the intake air introduced into the engine 2.

[0014] The physical quantity sensing device 20 detects any physical quantity, such as flow rate, temperature, humidity, and pressure, of target gases drawn in as intake air by the air cleaner 4 and flowing through the main passage 22. The physical quantity detected by the physical quantity sensing device 20 is converted into an electrical signal and fed to a control device (an electronic control unit (ECU)). The control device uses the physical quantity of the intake air as an output from the physical quantity sensing device 20 to calculate a fuel injection quantity or an ignition timing of the engine 2.

[0015] Fig. Figure 2 is a front view of the detection device for a physical quantity.

[0016] The detection device for a physical quantity 20 is used in a state in which it is inserted into the main passage 22 through a mounting opening arranged in a passage wall of the main passage 22 and is attached to the main passage 22. The detection device for a physical quantity 20 contains a housing within the main passage 22 through which the target gas flows. The housing of the detection device for a physical quantity 20 comprises a housing 100 and a cover 200 attached to the housing 100. The housing 100 is manufactured, for example, by injection molding a plastic material. The cover 200 is formed, for example, from a plate-shaped part made of a metal material or the plastic material, and in this embodiment from an injection-molded part made of an aluminum alloy or the plastic material.

[0017] The housing 100 comprises a flange 111 for attaching the sensing device for a physical quantity 20 to the main passage 22, a connector 112 extending from the flange 111 to be led out of an inlet body for electrical connection with an external device, and a measuring unit 113 extending from the flange 111 to protrude towards a center of the main passage 22.

[0018] The measuring unit 113 has a thin and elongated shape, extending straight from the flange 111, and comprises a front surface 121 and a back surface 122, each as a broad surface, as well as a side surface 123 and a side surface 124 as a pair of narrow side surfaces. In the detection device for a physical quantity 20, which is attached to the main passage 22, the measuring unit 113 projects from an inner wall of the main passage 22 towards the center of the main passage 22. The front surface 121 and the back surface 122 are arranged parallel to each other along a central axis of the main passage 22. The narrow side surfaces 123 and 124 of the measuring unit 113, as a pair of narrow side surfaces, are arranged opposite each other.The side surface 123 is arranged on one side longitudinally upstream of the measuring unit 113 in the main passage 22, and the side surface 124 is arranged on the other side transversely downstream of the measuring unit 113 in the main passage 22. The measuring unit 113 has a lower surface 125 at its distal end, with the detection device for a physical quantity 20 attached to the main passage 22.

[0019] In the measuring unit 113, side surface 123 has a sub-passage inlet 131, and side surface 124 has a first outlet 132 and a second outlet 133. The sub-passage inlet 131, the first outlet 132, and the second outlet 133 are located near the distal end of the measuring unit 113, which extends from the flange 111 toward the center of the main passage 22. The sensing device for a physical quantity 20 comprises the measuring unit 113, which extends orthogonally to a centerline of the main passage 22, but each of the side surfaces 123 and 124 has a narrow width. With this configuration, the sensing device for a physical quantity 20 maintains a lower fluid resistance for the target gas.

[0020] Fig. Figure 3 is a view illustrating a state in which the cover is removed from the housing of the sensing device for a physical quantity; Fig. 4 is a rear view of the cover; and Fig. Figure 5 is a cross-sectional view of the cover and housing in Fig. 2, which is recorded along a plane perpendicular to a connecting surface of the cover and the housing. It should be noted that in the following descriptions, the longitudinal direction of the measuring unit 113, in which the measuring unit 113 extends from the flange 111, can be referred to as the Z-axis, the transverse direction of the measuring unit 113, in which the measuring unit 113 extends from the lower passage inlet 131 to the first outlet 132, can be referred to as the X-axis, and the thickness direction of the measuring unit 113, in which the measuring unit 113 extends from the front surface 121 to the rear surface 122, can be referred to as the Y-axis.

[0021] The measuring unit 113 of the housing 100 contains a flow rate sensor 411 as a flow rate detection element, an intake air temperature sensor 321, and a humidity sensor 322. The flow rate sensor 411 is located in the center of a sub-passage 134. The flow rate sensor 411 detects the flow rate of the target gas flowing through the main passage. The intake air temperature sensor 321 is located in the center of a temperature detection passage 136, which is open at one end near the sub-passage inlet 131 on the side surface 123 and at the other end to both the front surface 121 and the rear surface 122 of the measuring unit 113. The intake air temperature sensor 321 detects the temperature of the target gases flowing through the main passage. The humidity sensor 322 is arranged in a humidity measuring chamber 137 of the measuring unit 113.The humidity sensor 322 measures the humidity of the target gas taken into the humidity measuring chamber 137 through a window 138 which is open towards the back surface of the measuring unit 113.

[0022] The measuring unit 113 houses the subpassage 134 and a circuit chamber 135 for receiving a circuit plate 300. The circuit chamber 135 and the subpassage 134 are covered and closed by the cover 200 attached to the front surface 121 of the measuring unit 113.

[0023] The cover 200 has the shape of a flat plate to cover the front surface 121 of the measuring unit 113. As in Fig. As shown in Figure 4, the cover 200 has a rib 221 on its back surface. The rib 221 is formed along a section of the cover 200 connected to the measuring unit 113. As shown in Fig. As shown in Figure 5, the measuring unit 113 has a recessed groove 141 on its front surface 121, and the rib 221 is to be inserted into the recessed groove 141. After the rib 221 has been inserted into the recessed groove 141 of the measuring unit 113, the cover 200 is glued onto the measuring unit 113 with an adhesive.

[0024] The circuit chamber 135 is arranged on one side in the direction of the X-axis (closer to the side surface 123), i.e., upstream in the flow direction of the target gas in the main passage 22. The sub-passage 134 is arranged above a region located closer to the distal end (closer to the underside 125) of the measuring unit 113 in the Z-axis direction with respect to the circuit chamber 135, and above a region located closer to the other side in the X-axis direction (closer to the side surface 124), i.e., downstream in the flow direction of the target gas in the main passage 22 with respect to the circuit chamber 135.

[0025] The subpassage 134 comprises a first subpassage A and a second subpassage B, which branches off midway from the first subpassage A. The first subpassage A extends along the X-axis direction of the measuring unit 113 between the subpassage inlet 131, which is open to the side surface 123 on one side of the measuring unit 113, and the first outlet 132, which is open to the side surface 124 on the other side of the measuring unit 113. The first subpassage A comprises a flow path that extends along the flow direction of the target gas in the main passage 22 from the subpassage inlet 131 to the first outlet 132. The first subpassage A receives the target gas flowing through the subpassage inlet 131 and into the main passage 22, and then returns the target gas to the main passage 22 through the first outlet 132.The first subpassage A is formed when a first subpassage groove embedded in the front surface of the measuring unit 113 is covered by an area 201 of the cover 200.

[0026] The second subpassage B branches off in the middle of the first subpassage A, bends towards a proximal end (the flange) of the measuring unit 113, and extends in the direction of the Z-axis of the measuring unit 113. Then, at the proximal end of the measuring unit 113, the second subpassage B bends towards the other side (side surface 124) of the measuring unit 113 in the direction of the X-axis of the measuring unit 113, returns to the distal end of the measuring unit 113, and again extends in the direction of the Z-axis of the measuring unit 113. Before the first outlet 132, the second subpassage B bends towards the other side (side surface 124) of the measuring unit 113 in the X-axis direction and transitions into the second outlet 133, which is open towards the side surface 124 of the measuring unit 113. The second outlet 133 is located downstream of the main passage in the direction of flow of the target gas being measured in the main passage 22.The second outlet 133 has an opening area that is essentially the same as or slightly larger than that of the first outlet 132, and is located closer to the proximal end in the longitudinal direction of the measuring unit 113 with respect to the first outlet 132.

[0027] The second subpassage B comprises a flow path that moves back and forth along the Z-axis direction of the measuring unit 113. The second subpassage B includes a forward passage region B1, which branches off at the middle of the first subpassage A and extends towards the proximal end of the measuring unit 113 (away from the first subpassage A), and a reverse passage region B2, which extends from near the proximal end of the measuring unit 113 (one end of a separation passage segment), where the second subpassage B reverses direction, towards the distal end of the measuring unit 113 (towards the first subpassage A). The return passage area B2 comprises a flow path connected to the second outlet 133, which is positioned downstream in the direction of flow of the target gas in the main passage 22 with respect to the lower passage inlet 131 and is open downstream in the direction of flow of the target gas.The second subpassage B allows the target gas, which was diverted from the first subpassage A to flow into it, to flow through the second outlet 133 and then back into the main passage 22. The second subpassage B is formed when a second subpassage groove 152, recessed in the front surface of the measuring unit 113, is covered by a region 202 of the cover 200.

[0028] In the middle of the second subpassage B, a first inlet passage 161 is arranged to introduce the pressure of the target gas from the second subpassage B into the circuit chamber 135. The first inlet passage 161 has one end open to the second subpassage B and one end open to the circuit chamber 135, connecting the second subpassage B and the circuit chamber 135. The first inlet passage 161 includes an inlet access 162, which is open to the second subpassage B. The inlet access 162 is offset outwards from a side wall of the second subpassage B.

[0029] The inlet 162 of the second subpassage B is arranged in a folding region in which the second subpassage B is folded back from the forward passage region B1 to the return passage region B2, specifically in a curved region on an outer, semicircularly curved side surface, the curved region being closer to the return passage region B2 than the upper part of the folding region. The first inlet 161 extends along the Z-axis direction of the measuring unit 113 from the inlet 162 to the proximal end of the measuring unit 113, is substantially L-shaped towards the side surface 123 of the measuring unit 113 to extend along the X-axis direction, and continues to an opening 163 that is open to the circuit chamber 135.

[0030] The flow rate sensor (a flow rate sensing unit) 411 is located in the middle of the forward passage section B1 of the second subpass B. The inlet port 162 is located downstream of the flow rate sensor 411 in the second subpass B in the direction of flow of the target gas. The flow rate sensor 411 is arranged in a sensor assembly 400, and the sensor assembly 400 is mounted on the circuit board 300.

[0031] Circuit components, such as the sensor assembly 400, a pressure sensor 320, the intake air temperature sensor 321, and the humidity sensor 322, are mounted on a front mounting surface of the circuit board 300; and circuit components, such as a chip resistor and a chip capacitor (not shown), are mounted on a rear mounting surface. The circuit board 300 is arranged inside the measuring unit 113, extending longitudinally from the proximal end to the distal end of the measuring unit 113 and transversely from the side surface 123 to the side surface 124 of the measuring unit 113.

[0032] The circuit board 300 comprises a base body 301 in the circuit chamber 135, together with a first projection 302 in the temperature sensing passage 136, a second projection 303 in the humidity sensing chamber 137, and a third projection 304 in the forward passage area B1 of the second subpassage B. The first projection 302, the second projection 303, and the third projection 304 extend from the base body 301 at the same surface level as each other. The intake air temperature sensor 321 is attached to the distal end of the first projection 302, and the humidity sensor 322 is attached to the second projection 303. The third projection 304 is located opposite the sensor assembly 400 in the forward passage area B1 of the second subpassage B. The third projection 304 of the circuit plate 300 closes an open section of a recessed groove 404 of the sensor assembly 400 to form a first passage section D1.Furthermore, a second passage area D2 is formed between the third projection 304 of the circuit plate 300 and a bottom wall surface 152a of the second underpass groove 152.

[0033] The sensor assembly 400 comprises a support 401, the proximal end of which is attached to the circuit plate 300 in the circuit chamber 135 and the distal end of which projects into the second subpass groove 152. The flow rate sensor 411 is located at the distal end of the support 401. The flow rate sensor 411 is supported by the sensor assembly 400 to be exposed to the forward passage area B1 of the second subpass B. The flow rate sensor 411 is positioned at a constant distance from the circuit plate 300, which projects from the circuit chamber 135, and measures the flow rate of the target gases flowing through the second subpass B.

[0034] Fig. Figure 7 is an enlarged view of the sensor setup 400 in Fig. 6. The sensor assembly 400 is a plastic housing in which the flow rate sensor 411, an LSI 412, and a leadframe 413 are encapsulated with plastic. The flow rate sensor 411 and the LSI 412 are mounted on a surface of the leadframe 413. The sensor assembly 400 is formed when the flow rate sensor 411 is sealed with plastic, leaving a diaphragm of the flow rate sensor 411 exposed.

[0035] The sensor assembly 400 comprises the carrier 401, which is molded from plastic and has a flat, plate-like shape with a predetermined thickness. In the sensor assembly 400, the carrier 401 includes a proximal end 401A, which is located in the circuit chamber 135, and a distal end 401B of the carrier 401, which projects into the second underpass groove 152. The sensor assembly 400 is electrically connected to the circuit plate 300 and mechanically secured by a mounting section.

[0036] The recessed groove 404 is located at the distal end of the carrier 401. At the distal end of the carrier 401, the recessed groove 404 extends along a width direction of the distal end of the carrier 401, and the flow rate sensor 411 is positioned so that it is exposed at an intermediate position in the direction in which the recessed groove 404 extends. The flow rate sensor 411 comprises a sensor element 405 with a membrane structure. The sensor element 405 of the flow rate sensor 411 comprises the membrane with a membrane front surface 411a that is exposed to the forward passage region B1 of the second subpassage B, and with a membrane rear surface 411b that is exposed to a closed chamber 421 that is separated from the subpassage 134.

[0037] A heating element is arranged on the membrane front surface 411a, and a pair of electrical resistors are positioned between the heating element and a spaced distance apart. Air flows through the flow rate sensor 411, passing over the membrane front surface 411a and being heated by the heater. The heat distribution changes according to the airflow, and the electrical resistance changes accordingly. The flow rate sensor 411 measures the flow rate of the target gas based on this change in electrical resistance.

[0038] The enclosed chamber 421 is arranged within the sensor element 405 of the flow rate sensor 411. The sensor element 405 is attached to one surface of the conductor frame 413; and the enclosed chamber 421 is sealed by a polyimide band 414, which is attached to the other surface of the conductor frame 413, and comprises an enclosed space that is separated from the external environment.

[0039] The sensor assembly 400 has a ventilation passage 422, one end of which is open to the circuit chamber 135 and the other end of which is open to the closed chamber 421, thus establishing a connection between the circuit chamber 135 and the closed chamber 421. On the other surface of the conductor frame 413, a recessed groove extends continuously between an opening hole 423 and the closed chamber 421. On the other surface of the conductor frame 413, the sheet-shaped polyimide strip 414 is attached to seal an open section of the recessed groove, and the ventilation passage 422 comprises an end open to the closed chamber 421 and an end extending through to the opening hole 423. The ventilation passage 422 connects the closed chamber 421, to which the membrane rear surface 411b is open, and the circuit chamber 135.The ventilation passage 422 corresponds to a second inlet passage, which is configured to introduce the pressure of the measuring target gas from the circuit chamber 135 into the closed chamber 421.

[0040] Fig. Figure 8 is an enlarged view of a main part of Fig. 5, Fig. Figure 9 is a cross-sectional view along line VIII-VIII of Fig. 5, and Fig. 10 is an enlarged view of a main part of Fig. 9.

[0041] The circuit chamber 135 comprises at least one or more projections 210 arranged opposite the opening 163 of the first inlet passage 161. The one or more projections 210 comprise a plurality of projections and recesses. The one or more projections 210 are integrally formed with the cover 200. The one or more projections 210 are arranged at a predetermined distance from a side wall of the circuit chamber 135 and from the circuit plate 300, such that the target gas flows through the first inlet passage 161 to flow between the second sub-passage B and the circuit chamber 135.

[0042] For example, in Fig. 4 and Fig. As shown in Figure 9, the one or more projections 210 comprise a first projection 211 and a second projection 212. The first projection 211 is located opposite the opening 163 of the first inlet passage 161 in the circuit chamber 135; and the second projection 212 is located away from the opening 163 of the first inlet passage 161, with the first projection 211 positioned between the second projection 212 and the opening 163. The first projection 211 is formed in a rectangular parallelepiped shape with a length W1 that is substantially equal to the opening width W0 of the opening 163, and is located opposite and above the opening width W0 of the opening 163. The second projection 212 is cuboid in shape with a length W2 that is greater than the opening width W0 of the opening 163, and is aligned parallel to the first projection 211.

[0043] As in Fig. As shown in Figure 10, the one or more projections 210 have a space S1 formed between a distal end of the first projection 211 and the main body 301 of the circuit plate 300, a space S2 formed between the first projection 211 and the second projection 212, and a space S3 formed between a distal end of the second projection 212 and the main body 301 of the circuit plate 300. Space S1 is closer to the opening 163 of the first inlet passage 161 with respect to space S2 and is narrower (has a smaller cross-sectional area) than space S2; and space S2 is farther from the opening 163 of the first inlet passage 161 with respect to space S1 and is wider (has a larger cross-sectional area) than space S1 (S1 < S2). In relation to room S2 and room S3, room S3 is narrower than room S2.

[0044] Fig. Figure 11 is a diagram to describe a difference between the physical quantity detection device of the present invention and a physical quantity detection device of a comparison example. Fig. 11 (1) illustrates a structure in the comparative example in which one or more projections 210 are not included; Fig. 11 (2) illustrates a structure in the present invention in which one or more projections 210 are included; and Fig. 11 (3) is a diagram describing a relationship between sound pressure and distance to a measuring point in a case where these protrusions are included and in a case where the protrusions are not included.

[0045] In this embodiment, the turbocharger 15 is arranged downstream of the detection device for a physical quantity 20 and generates a sound wave that is intended to travel from the second sub-passage B through the first inlet passage 161 to the circuit chamber 135.

[0046] As in Fig. As shown in Figure 11 (1), in the comparative example, a sound wave SW, which has entered the circuit chamber 135 through the opening 163 of the first inlet passage 161, encounters no obstacle and thus travels with barely damped sound pressure into the depth of the circuit chamber 135. In the sensor setup 400, the sound wave SW then passes from the opening 423 through the ventilation passage 422 into the closed chamber 421, to which the diaphragm's rear surface is exposed. Here, resonances of the sound pressure can occur on the element's front surface and the element's rear surface of the diaphragm, and a thermoacoustic phenomenon can generate heat convection, which causes a change in the temperature distribution of the heater on the diaphragm and ultimately an error in the detection of the flow rate.

[0047] On the other hand, as in Fig. Figure 11 (2) shows that, in the present invention, the sound wave SW, after entering the circuit chamber 135 through the opening 163 of the first inlet passage 161, is blocked by one or more projections 210 and therefore cannot travel in a straight line. The sound pressure of the sound wave SW is thereby diffracted and attenuated, thus becoming smaller. As e.g. in Fig. As shown in Figure 11 (3), the sound pressure in the structure containing the projections is lower than in the structure not containing the projections.

[0048] When the sound wave SW, which entered the circuit chamber 135 through the opening 163 of the first inlet passage 161, travels from chamber S1 to chamber S2, where the cross-sectional area increases, the fluid flowing through it is stretched, leading to a decrease in the fluid's velocity and pressure. As a result, less energy passes through chamber S3, and the remaining energy is reflected back into chamber S2 and attenuated there. The sound wave is reflected at a point where the impedance changes rapidly (rises or falls rapidly), and thus at an inlet between chamber S2 and chamber S1 and at an outlet between chamber S2 and chamber S3. The reflected sound wave causes interference in chambers S1, S2, and S3. This dissipates the energy of the sound wave, resulting in a lower sound pressure level.

[0049] In this configuration, the sound pressure in the second subpassage B is actively damped, and the sound wave is less likely to maintain a high energy level when transmitted to the closed chamber 421. Furthermore, in this configuration, the resonance of the sound pressure on the element's front and rear surfaces of the diaphragm is less prone, resulting in higher accuracy in flow rate detection.

[0050] Fig. Figure 12 is a diagram describing a result of the sound pressure measured in the present invention and the comparative example. As a difference in sound pressure measured near a predetermined frequency, the result in the comparison example shows a maximum sound pressure of 28 dB, while the result according to the present invention shows a maximum sound pressure of 25 dB. It is therefore understood that with the detection device for a physical quantity according to the present invention, the sound pressure is reduced and thus improved compared to the comparison example.

[0051] Fig. 13 is a diagram showing a modification of this embodiment accordingly Fig. 8 shows.

[0052] In this modification, the one or more projections 210 comprise a plurality of third projections 213. Each of the multiple third projections 213 is rod-shaped and is arranged opposite the opening 163 of the first inlet passage 161 in the circuit chamber 135. The multiple third projections 213 are arranged over a length corresponding to the opening width W0 of the opening 163 and are zigzagged at a predetermined distance from one another. The multiple third projections 213 are arranged at the predetermined distance sufficient to block the sound wave SW that has entered the circuit chamber 135 through the opening 163 of the first inlet passage 161, thus preventing the sound wave SW from traveling in a straight line.

[0053] In this modification, similar to the previous embodiments, the sound pressure in the second subpassage B is actively damped, and the sound wave is less likely to retain its high energy level when transmitted to the closed chamber 421. Furthermore, in this configuration, the sound pressure resonance is less prone to occurring on the front and rear surfaces of the diaphragm element, resulting in increased accuracy in flow rate detection. The number of the multiple third projections 213 can be varied to adjust the sound pressure damping as desired.

[0054] With regard to the embodiments described above, the present invention is not limited thereto. Accordingly, it is readily understood that any modification, addition, or deletion of a configuration of each unit, appropriately made in accordance with the present invention, naturally falls within the scope of the claims of the present invention. For example, the detailed description of each of the configurations in the foregoing embodiments is in every respect to be regarded as merely illustrative for convenience of description and is therefore not limiting. Furthermore, a configuration of one embodiment may be partially replaced by a configuration of other embodiments and / or additionally comprise a configuration of other embodiments.Furthermore, any addition, removal, and replacement of other configurations can be performed partially on, from, and with a configuration in any embodiment. Reference symbol list 15 turbochargers 20 Detection device for a physical quantity 100 cases 200 Cover (housing) 134 Underpass 135 Circuit chamber 161 first introductory passage 162 Introductory Access 163 Opening 210 lead 211 first lead 212 second lead 213 third lead 300 Circuit board (circuit unit) 400 sensor structure 411 Flow rate sensor (flow rate detection unit) 411a Membrane front surface 411b Membrane back surface 422 Ventilation passage B second underpass B1 Forward Passage Area B2 Return passage area

Claims

[1] A physical quantity detection device configured to detect a physical quantity of a target gas flowing in a main passage, the physical quantity detection device comprising: a housing arranged in the main passage; a sub-passage arranged in the housing; a flow rate sensing unit arranged in the sub-passage; a circuit unit electrically connected to the flow rate sensing unit; a circuit chamber arranged in the housing and accommodating the circuit unit; and a first inlet passage having one end open to the sub-passage and the other end open to the circuit chamber to connect the sub-passage and the circuit chamber, and configured to introduce pressure of the target gas from the sub-passage into the circuit chamber, wherein The flow rate sensing unit comprises: a diaphragm with a diaphragm front surface exposed to the underpass and a diaphragm rear surface exposed to a closed chamber separate from the underpass; and a second inlet passage with one end open to the circuit chamber and the other end open to the closed chamber to connect the circuit chamber and the closed chamber, and configured to introduce the pressure of the target gas from the circuit chamber into the closed chamber, and the circuit chamber has at least one or more projections arranged opposite an opening to which the other end of the first inlet passage is open. [2] Detection device for a physical quantity according to claim 1, wherein the at least one or more projections comprise a first projection which is arranged opposite the opening and a second projection which is arranged away from the opening, wherein the first projection is arranged between the opening and the second projection. [3] Detection device for a physical quantity according to claim 2, wherein the first projection has a length equal to the width of the opening and is positioned opposite and above the width of the opening, and the second projection has a length that is greater than the width of the opening, and is arranged and aligned parallel to the first projection. [4] Detection device for a physical quantity according to claim 1, wherein the at least one or more projections comprise a plurality of third projections, each of the third projections having a rod shape. [5] Detection device for a physical quantity according to claim 4, wherein the multiple third projections are arranged over a length corresponding to an opening width of the opening and are distributed in a zigzag pattern at a predetermined distance from each other. [6] Detection device for a physical quantity according to claim 1, wherein the first inlet passage has an inlet access which is arranged offset outwards from a side wall of the underpass. [7] Detection device for a physical quantity according to claim 6, wherein the underpass has a forward passage area extending to one side in a predetermined axial direction, and a return passage area extending from one end of the forward passage area, where the underpass reverses direction, to the other side in the axial direction, and the inlet access is arranged in a folding area in which the underpass is folded back from the forward passage area to the return passage area, in a curvature area on an outer semicircularly curved side surface, wherein the curvature area is closer to the return passage area with respect to a vertex of the folding area. [8] Detection device for a physical quantity according to claim 7, wherein the flow rate detection unit is configured to detect a flow rate of the target gas and is located in the underpass, and The inlet access is arranged downstream in the flow direction of the target gas in the underpass with respect to the flow rate detection unit. [9] Detection device for a physical quantity according to claim 8, wherein the flow rate detection unit is arranged in the forward passage area of ​​the underpass.