PHYSICAL SIZE MEASURING DEVICE

Abstract

Device (20) for measuring a physical quantity of a fluid, the device for measuring a physical quantity comprising: a bypass flow channel (30) through which the fluid flows; a detection unit (50) having a physical quantity detection unit (22) configured to detect a physical quantity of the fluid in the bypass flow channel, and a detection terminal (52) electrically connected to the physical quantity detection unit; a housing (21) having a flow channel forming portion (61) having an insulating property and forming the bypass flow channel, and a terminal receiving portion (65) having an insulating property and receiving the detection terminal; and a grounding section (23d) connecting the section forming the flow channel to an earth (GND), where: a specific volume resistance of the section forming the flow channel in a range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm, and the terminal receiving section includes the following: an insulating portion (71c) configured to impart insulating properties to the terminal receiving portion, and a conductive portion (72c) provided in a mixed state in the insulating portion and having a conductivity such that the volume resistivity of the terminal receiving portion is smaller than the volume resistivity of the insulating portion, wherein the terminal receiving portion comprises: an outer layer (66) forming an outer surface (65a, 65b) of the terminal receiving portion, an inner layer (67) in which a content ratio of the conductive portion to the insulating portion is lower than that of the outer layer, and which is provided within the outer layer, with the sensing port located in the inner layer.

Description

Technical field

[0001] The present disclosure relates to a physical quantity measuring device or to a device for measuring a physical quantity. BACKGROUND

[0002] DE 10 2016 209 150 A1 discloses a sensor for determining at least one parameter of a fluid medium flowing through a measuring channel, in particular an intake air mass flow of an internal combustion engine. The sensor comprises a sensor housing, in particular a plug-in sensor that is inserted or can be inserted into a flow tube and in which a channel structure is formed that has the measuring channel, and at least one sensor chip arranged in the measuring channel for determining the parameter of the fluid medium. The sensor housing has an inlet into the channel structure, which faces the main flow direction of the fluid medium, and at least one outlet from the channel structure. The channel structure is delimited by wall sections. The wall sections have at least partially electrically insulating properties. Regions of the sensor housing that border the wall sections have electrically conductive properties.

[0003] JP 2003-269277 A discloses a housing body made of non-conductive resin for enclosing a filter element, which surrounds an outer periphery of a fuel pump. A distance between a housing of the fuel pump and an inner cylinder of the housing body is set to 1 mm or less. The inner cylinder surrounds 50% or more of an outer periphery of the housing. Despite the formation of the filter body made of non-conductive resin, an electrical charge on a filter unit moves to the fuel pump housing via the housing body by corona discharge. An expensive conductive resin and a grounding element are thus unnecessary.

[0004] DE 10 2014 218 579 A1 discloses a sensor arrangement for determining at least one parameter of a fluid medium flowing through a measuring channel, in particular an intake air mass flow of an internal combustion engine. The sensor arrangement comprises a sensor housing, in particular a plug-in sensor inserted or insertable into a flow tube, at least one sensor chip arranged in the measuring channel for determining the parameter of the fluid medium, and a plug part for electrically contacting the sensor chip. The plug part is arranged on the sensor housing. The sensor housing and the plug part are made of an electrically conductive plastic.

[0005] As a physical quantity measuring device of a fluid, for example, Patent Document 1 discloses a physical quantity measuring device that measures the flow rate of intake air drawn into an internal combustion engine. The physical quantity measuring device includes a curved passage through which the fluid flows and a flow measuring element provided in the curved passage. In Patent Document 1, when foreign matter such as dust enters the curved passage and collides with the flow measuring element along with the fluid, the flow measuring element may be damaged depending on the size and speed of the foreign matter.To counteract the above-mentioned disadvantage, an inner wall surface of the curved passage has a rough surface, causing the foreign matter entering the curved passage to collide with the rough surface and change the traveling direction, thereby reducing the speed and resulting in a reduction in kinetic energy. As described above, in Patent Document 1, even if the foreign matter collides with the flow measuring element, damage to the flow measuring element is prevented. Prior art documentPATENT DOCUMENT

[0006] Patent Document 1: Japanese Patent No. JP 4553898 B2

[0007] However, when the foreign matter enters the curved passage, if an electrical attraction force is generated between the foreign matter and a physical quantity detection unit such as the flow meter, the foreign matter tends to adhere to the physical quantity detection unit, raising concerns that the detection accuracy of the physical quantity may be reduced. For this reason, for example, as disclosed in Patent Document 1, if the speed of the foreign matter in the curved passage is reduced, it is considered that the foreign matter is more likely to adhere to the physical quantity detection unit, even if damage to the physical quantity detection unit caused by the collision of the foreign matter can be prevented. Summary

[0008] An object of the present invention is to provide a physical quantity measuring device capable of suppressing deterioration of the detection accuracy of the physical quantity detecting unit due to adhesion of foreign matter to the physical quantity detecting unit.

[0009] The object is achieved by the device having the features of claim 1. Further advantageous developments and embodiments of the invention are the subject of the subsequent claims.

[0010] To achieve the above-mentioned object, a first aspect of the present disclosure is a physical quantity measuring device that measures a physical quantity of a fluid. The physical quantity measuring device includes a bypass flow channel through which a fluid flows, a physical quantity detecting unit for detecting a physical quantity of the fluid in the bypass flow channel, a detecting unit having a detection terminal electrically connected to the physical quantity detecting unit, a housing having a flow channel forming portion having an insulating property and forming a bypass flow channel, a terminal accommodating portion having an insulating property and accommodating a detection terminal, and a grounding portion connecting the flow channel forming portion to a ground.The specific volume resistance of the section forming the flow channel is in the range of 1.0 × 10. 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm.

[0011] If the fluid flowing around the physical quantity measuring device contains foreign matter such as sand, which is easily positively charged, the foreign matter can easily become positively charged by approaching or touching the flow channel forming part or section of the physical quantity measuring device. Therefore, it is assumed that the flow channel forming section becomes slightly negatively charged. In this case, foreign matter is likely to adhere to the flow channel forming section. Since the negative charges charged in the flow channel forming section migrate to the physical quantity detecting unit, the physical quantity detecting unit also tends to be negatively charged. If foreign matter such asIf foreign matter, such as sand that is already positively charged, enters the bypass flow channel and approaches or touches the physical quantity detecting unit, an electrical attraction force is generated between the foreign matter and the physical quantity detecting unit, and the foreign matter can easily adhere to the physical quantity detecting unit.

[0012] On the other hand, according to the first aspect, the volume resistivity of the flow channel forming portion is in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm and less than 1.0 ×10 15 up to 10 16(1.0 × 10 to the 15th power to the 16th power) Ωcm, which is the volume resistivity of a general insulating material. With this configuration, when the flow channel forming part is negatively charged due to the approach or contact of foreign matter with the flow channel forming part, the voltage generated by the negative charge causes dielectric breakdown in the flow channel forming part to the ground through the grounding part. In this case, the negative charges charged in the physical quantity detection unit are also discharged to the ground via the flow channel forming part and the grounding part, so the charges in both the flow channel forming unit and the physical quantity detection unit are eliminated. For this reason, the adhesion of foreign matter to the flow channel forming section 61 and the physical quantity detection unit is made difficult.

[0013] A second aspect of the present disclosure is a physical quantity measuring device that measures a physical quantity of a fluid, including a housing forming a bypass flow channel through which the fluid flows, a physical quantity detecting unit that detects the physical quantity of the fluid in the bypass flow channel, and a grounding portion in which the housing is grounded. The volume resistivity of the housing is in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm.

[0014] Since the specific volume resistance of the casing forming the bypass flow channel is in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm, the second aspect has the same effect as the first aspect. Short description of the drawings

[0015] The above and other objects, features and advantages of the present disclosure will become apparent from the following detailed description with reference to the accompanying drawings.

[0016] It shows / It shows: Fig. 1 is a diagram showing a configuration of a combustion system according to a first embodiment; Fig. 2 is a front view of an air flow meter mounted on an inlet pipe; Fig. 3 a cross-sectional view along a line III-III in the Fig. 2; Fig. 4 is a front view showing a configuration of a sensor SA; Fig. 5 is a vertical cross-sectional view showing an internal configuration of the sensor SA; Fig. 6 is a diagram for explaining an arrangement of insulating and conductive portions or parts in a first flow channel element and a second flow channel element; Fig. 7 is a diagram for explaining an arrangement of insulating portions and conductive portions in a terminal receiving portion; Fig. 8 a diagram explaining the charging of foreign matter passing through an air filter; Fig. 9 is a diagram for explaining the dielectric breakdown occurring in the first flow channel element or the first flow channel element; Fig. 10 is a graph showing the relationship between a measurement error rate of the air flow meter and the volume resistivity of a housing; Fig. 11 is a diagram for explaining an arrangement of insulating portions and conductive portions in a terminal receiving part according to a second embodiment; and Fig. 12 is a diagram for explaining an insulating portion in a terminal receiving part according to a third embodiment. DETAILED DESCRIPTION

[0017] Hereinafter, a plurality of embodiments of the present disclosure will be described with reference to the drawings. Incidentally, the same reference numerals are assigned to the corresponding components in each embodiment, so that duplicate descriptions can be omitted. When only a part of the configuration is described in each embodiment, the above-described configuration of the other embodiments can be applied to the other parts of the configuration. Furthermore, not only the combinations of the configurations explicitly shown in the description of the respective embodiments but also the configurations of the plurality of embodiments can be partially combined even if the combinations are not explicitly shown, particularly if there is no problem in the combination.Unspecified combinations of the configurations described in the majority of embodiments and the modification examples are also listed in the following description. (First embodiment)

[0018] One in the Fig. The combustion system 10 shown in FIG. 1 includes an internal combustion engine 11 such as a gasoline engine, an intake passage 12, an exhaust passage 13, an air flow meter 20, and an ECU 15, and the combustion system 10 is mounted on, for example, a vehicle. The air flow meter 20 is located in the intake passage 12 and measures physical quantities such as a flow rate, a temperature, a humidity, and a pressure of the intake air supplied to the internal combustion engine 11. The air flow meter 20 corresponds to a "physical quantity measuring device" that measures a fluid such as the intake air. The intake air is a gas supplied to a combustion chamber 11a of the internal combustion engine 11. In the combustion chamber 11a, a mixture of the intake air and a fuel is ignited by a spark plug 17.

[0019] The ECU (Engine Control Unit) 15 is a control unit for controlling the operation of the combustion system 10. The ECU 15 is a computational processing circuit including a processor, a storage medium such as RAM, ROM, and flash memory, a microcomputer with an input / output unit, a power supply circuit, and the like. A sensor signal output from the air flow meter 20, a sensor signal output from a large number of vehicle-mounted sensors, and the like are input to the ECU 15. The ECU 15 uses the measurement results of the air flow meter 20 to perform engine control such as controlling a fuel injection amount and an EGR amount of an injector 16. The ECU 15 is a control unit that controls the operation of the internal combustion engine 11, and the combustion system 10 can be referred to as an engine control system. The ECU 15 corresponds to an external device.

[0020] The combustion system 10 includes a plurality of measurement units as on-board sensors. In addition to the air flow meter 20, the measurement units include a throttle sensor 18a, an intake pressure sensor 18b, a water temperature sensor 18c, a crank angle sensor 18d, an air-fuel ratio sensor 18e, a knock sensor 18f, a cam angle sensor 18g, and the like. Each of these measurement units is electrically connected to the ECU 15 and outputs a detection signal to the ECU 15.

[0021] The combustion system 10 includes an air cleaner 19 that cleans the intake air. The air cleaner 19 is provided at an upstream end of the intake passage 12. The air cleaner 19 includes an air filter 19a that removes foreign matter from the air drawn into the intake passage 12. The air filter 19a includes a mesh or the like that allows the intake air to pass through while trapping foreign matter, and is made of, for example, a synthetic resin material such as polyethylene.

[0022] The air flow meter 20 is located in the intake duct 12 on a downstream side of the air cleaner 19 and on an upstream side of the throttle valve to which the throttle position sensor 18a is attached. As shown in the Fig. 2 and Fig. As shown in Fig. 3, the air flow meter 20 is attached to an intake pipe 12a such as a duct, which forms the intake duct 12. The intake pipe 12a has an air flow meter insertion hole 12b as a through hole penetrating an outer peripheral portion of the intake pipe 12a. The air flow meter insertion port 12b is provided with an annular pipe flange 12c, and the pipe flange 12c is contained in the intake pipe 12a. The air flow meter 20 is inserted into the pipe flange 12c, and the air flow meter insertion port 12b is inserted into the intake duct 12, and in this inserted state, is attached to the intake pipe 12a and the pipe flange 12c.

[0023] In the present embodiment, a width direction X, a height direction Y, and a depth direction Z are defined for the air flow meter 20, wherein the directions X, Y, and Z are orthogonal to each other. The air flow meter 20 extends in the height direction Y, and the inlet duct 12 extends in the depth direction Z. As shown in FIG. 3, the air flow meter 20 has an inlet part 20a that enters the inlet duct 12 and a protruding part 20b that protrudes outward from the pipe flange 12c without entering the inlet duct 12. The inlet part 20a and the protruding part 20b are aligned in the height direction Y.The air flow meter 20 has a pair of end surfaces 20c and 20d arranged in the height direction Y. One end surface included in the incoming part 20a is referred to as the air flow meter tip end surface 20c, and the other end surface included in the protruding part 20b is referred to as the air flow meter base end surface 20d. The air flow meter tip end surface 20c and the air flow meter bottom end surface 20d are orthogonal to the height direction Y. Furthermore, the tip end surface of the pipe flange 12c is also orthogonal to the height direction Y.

[0024] As in the Fig. 2 to 5, the air flow meter 20 comprises a housing 21, a flow rate detecting unit 22 which detects the flow rate of the intake air, and an intake air temperature sensor 23 (see Fig. 4) which detects the temperature of the intake air. The housing 21 is made of a resin material or the like. The housing 21 of the air flow meter 20 is fixed to the intake pipe 12a so that the flow rate detecting unit 22 can come into contact with the intake air flowing through the intake passage 12. The housing 21 has a housing main body 24, a ring holding portion 25, a flange portion 27, and a connector portion 28. An O-ring 26 is attached to the ring holding portion 25.

[0025] The housing main body 24 is cylindrically shaped as a whole, and in the housing 21, the ring holding portion 25, the flange portion 27, and the connector portion 28 are integrally provided in the housing main body 24. The ring holding portion 25 is included in the input portion 20a, and the flange portion 27 and the connector portion 28 are included in the protruding portion 20b.

[0026] The ring holding part 25 is provided inside the pipe flange 12c and holds the O-ring 26 so that it is not displaced in the height direction Y. The O-ring 26 is a sealing member for sealing the intake passage 12 inside the pipe flange 12c and is in close contact with both an outer peripheral surface of the ring holding part 25 and an inner peripheral surface of the pipe flange 12c. A fastening hole, such as a screw hole, for attaching a fastening tool, such as a screw for attaching the air flow meter 20 to the intake pipe 12a is provided in the flange part 27. The connector part 28 is a protecting part that protects a plurality of connector terminals 28a electrically connected to the flow rate detecting unit 22. A plug part is connected to the connector part 28.The plug part is provided at the end of a connection line electrically connected to the ECU 15, and the plug part is mounted on the connector portion 28 so that the control unit 15 and the flow rate detection unit 22 are electrically connected.

[0027] The flow rate detection unit 22 is housed in the housing 21. On the other side, as shown in the Fig. 4, the intake air temperature sensor 23 is provided outside the housing 21. The intake air temperature sensor 23 includes a temperature sensing element 23a for detecting the temperature of the intake air, a pair of lead wires 23b extending from the temperature sensing element 23a, a signal terminal 23c for transmitting a detection signal, and a ground terminal 23d connected to a ground or ground GND (see Fig. 9). The temperature sensor element 23a is bridged by the lead wire pair 23b, with one of the two lead wires 23b being connected to the signal terminal 23c or the signal connection 23c and the other to the ground terminal 23d or the ground connection 23d. The temperature sensor element 23a is connected to the signal terminal 23c or the signal connection 23c and the ground terminal 23d or the ground connection 23d via the lead wire 23b.

[0028] The signal terminal 23c and the ground terminal 23d are each electrically connected to the connector terminal 28a. The plurality of connector terminals 28a includes a ground terminal that is grounded to the ground GND in a state where the plug part is mounted on the connector portion 28, and the ground terminal 23d is connected to the ground terminal so as to be grounded to the ground GND.

[0029] The housing 21 has a terminal support part 21a that supports the signal terminal 23c and the ground terminal 23d. The terminal support part 21a is formed by protruding an outer surface of the housing 21 outward. The signal terminal 23c and the ground terminal 23d are supported by the terminal support part 21a by penetrating into the interior of the terminal support part 21a. At least a part of the ground terminal 23d and the ground terminal 23d is exposed to the outside of the housing 21. Fig. 2, the flow rate detection unit 22 is not shown.

[0030] As in Fig. 3 and Fig. 5, the housing 21 forms a bypass flow passage 30 into which a portion of the intake air flowing through the intake passage 12 flows. The bypass flow passage 30 is disposed in the inlet part 20a of the air flow meter 20. The bypass flow passage 30 has a through flow passage 31 and a measuring flow passage 32, and the through flow passage 31 and the measuring flow passage 32 are formed in an interior of the housing 21. The intake passage 12 may be referred to as a main passage, and the bypass flow passage 30 may be referred to as a sub-passage.

[0031] The through-flow channel 31 penetrates the casing 21 in the depth direction Z. The through-flow channel 31 has an inflow port 33 as an upstream end and an outflow port 34 as a downstream end. The measurement flow channel 32 is a branch flow channel branching from an intermediate portion of the through-flow channel 31, and the flow rate detection unit 22 is provided in the measurement flow channel 32. The measurement flow channel 32 has a measurement inlet 35, which is an upstream end of the measurement flow channel 32, and a measurement outlet 36, which is a downstream end of the measurement flow channel 32. A portion where the measurement flow channel 32 branches from the through-flow channel 31 is a boundary between the through-flow channel 31 and the measurement flow channel 32, and the measurement inlet 35 is included in the boundary. The measuring input or inlet 35 corresponds to a branch input, and the measuring output or outlet 36 corresponds to a branch output.The boundary between the through flow channel 31 and the measuring flow channel 32 can also be referred to as the flow channel boundary.

[0032] The flow rate detection unit 22 is a thermal flow sensor with a heater. The flow rate detection unit 22 outputs a detection signal corresponding to a temperature change caused by heat generation of the heating element or heater. The flow rate detection unit 22 is a rectangular parallelepiped chip component, and the flow rate detection unit 22 may also be referred to as a sensor chip. The flow rate detection unit 22 corresponds to a "physical quantity detection unit" that detects the intake air flow rate as a physical fluid quantity. Furthermore, the flow rate detection unit 22 is not limited to a thermal flow rate sensor and may be a movable flap flow rate sensor, a Kalman vortex flow rate sensor, or the like.

[0033] The air flow meter 20 includes a sensor assembly including the flow rate detection unit 22, and the sensor assembly is referred to as the SA 50 sensor. The SA 50 sensor is housed within the housing 21 in a state where the flow rate detection unit 22 is exposed in the measurement flow channel 32. The SA 50 sensor may also be referred to as a measurement unit or a sensor package.

[0034] The SA 50 sensor has an inlet portion 50a that enters the measuring flow channel 32 and a protruding portion 50b that protrudes from the measuring flow channel 32 without entering the measuring flow channel 32. The inlet portion 50a and the protruding portion 50b are aligned in the height direction Y, and the flow rate detection unit 22 is contained in the inlet portion 50a.

[0035] The SA sensor 50 has an SA main body 51 with the flow rate detection unit 22 and a plurality of lead terminals 52 protruding from the SA main body 51. In the SA sensor 50, a detection result of the flow rate detection unit 22 is input to a processing unit, e.g., a circuit chip, and a processing result of the processing unit is output to the ECU 15 via the lead terminals 52. The SA main body 51 has the processing unit and a molded part that protects the processing unit and the like, and the lead terminal 52 is electrically connected to the flow rate detection unit 22 through the processing unit and the like within the molded part. A volume resistivity, that is, a resistance per unit volume of the molded part, is greater than 1.0 10 14(1.0 × 10 to the 14th power) Ωcm. The lead terminals 52 are made of a conductive material such as metal with conductivity, and a plurality of lead terminals 52 protrude from the SA main body 51. At least one of the lead terminals 52 is connected, together with the ground terminal 23d, to the ground terminal 28a in the connector terminals 28a. The sensor SA 50 corresponds to a "detection unit," and the lead terminal 52 corresponds to a "detection terminal."

[0036] The housing 21 is formed by the combination of a plurality of constituent members. As in Fig. As shown in FIGS. 2 to 5, the housing 21 includes, as a plurality of components, a flow passage forming portion 61, which is a component that forms the bypass flow passage 30, and a terminal receiving portion 65, which is a component that receives the guide terminals 52. The guide terminals 52 are also push-in terminals that are inserted into the terminal receiving portion 65.

[0037] The flow channel forming portion 61 and the terminal receiving portion 65 are arranged side by side in the height direction Y, and in the housing 21, most of the inlet part 20a is formed by the flow channel forming portion 61, and most of the protruding portion 20b is formed by the terminal receiving portion 65. The boundary between the flow channel forming portion 61 and the terminal receiving portion 65 extends in the direction perpendicular to the height direction Y and substantially coincides with the boundary between the inlet part 20a and the protruding portion 20b. The boundary between the flow channel forming portion 61 and the terminal receiving portion 65 may be located at a position deviating from the boundary between the inlet part 20a and the protruding portion 20b toward the air flow meter tip end surface 20c side or the air flow meter base 20d side.

[0038] The terminal receiving portion 65 houses the entire guide terminal 52. The guide terminal 52 is located closer to the air flow meter bottom surface 20d than the boundary between the flow channel forming portion and the terminal receiving portion. In the housing 21, the flange portion 27 and the connector portion 28 are included in the terminal receiving portion.

[0039] The flow channel forming section 61 is formed by the combination of a plurality of constituent elements and as these constituent elements, as shown in the Fig. 2, has a first flow channel element 62 and a second flow channel element 63. The first flow channel element 62 and the second flow channel element 63 are arranged side by side in the width direction X, and the boundary between these flow channel elements 62 and 63 extends in the direction perpendicular to the width direction X. Each of the first flow channel element 62 and the second flow channel element 63 is provided with a groove on the surface that overlaps each other, and the bypass flow channel 30 is formed by combining these grooves of the first and second flow channel elements 62 and 63. The flow channel forming portion 61 includes the bypass flow channel 30 and the ring holding part 25.

[0040] The first flow channel element 62 has a terminal support portion 21a or terminal support part 21a. Therefore, the first flow channel element 62 is grounded to the ground GND via the ground terminal 23d on the terminal support portion 21a or terminal support part 21a. The first flow channel part 62, the second flow channel part 63, and the terminal receiving portion 65 are connected to each other by a resin material or the like. Therefore, the second flow channel element 63 and the terminal receiving portion 65 are grounded to the ground GND via the ground terminal 23d through the first flow channel element 62. That is, the housing 21 is grounded to the ground GND via the ground terminal 23d. In this case, the ground terminal 23d corresponds to the "ground portion."

[0041] As in the Fig. 6 and the Fig. As shown in Figure 7, each of the flow channel members 62, 63 and the terminal receiving portion 65 is in a state where a plurality of conductive portions 72a, 72b, 72c having conductivity are mixed and dispersed in insulating portions 71a, 71b, 71c having insulating properties. The insulating portions 71a to 71c are formed from a resin material as an insulating material, and examples of the resin material are thermoplastic resins such as polybutylene terephthalate resin (PBT resin) and polyphenylene sulfide resin (PPS resin). The insulating portions 71a to 71c are reversibly solidified due to the properties of the thermoplastic resin. The conductive parts 72a to 72c may contain one type of thermoplastic resin or multiple types of thermoplastic resins.

[0042] The conductive parts 72a to 72c are formed from a carbon material as the conductive material, and examples of the carbon material include carbon powder, carbon fibers, nanocarbon, graphene, and carbon microparticles. The conductive parts 72a to 72c contain a plurality of selected elements from carbon powder, carbon fibers, nanocarbon, graphene, and carbon microparticles. Examples of nanocarbon include carbon nanotubes, carbon nanofibers, fullerenes, and so on.

[0043] Each specific volume resistance, ie the resistance per unit volume of the flow channel elements 62, 63 and the terminal receiving portion 65, is in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm or more and 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm or less. The volume resistivity of the insulating portions 71a to 71c is greater than 1.0 × 10 14(1.0 × 10 to the 14th power) Ωcm. Since the insulating portions 71a to 71c are mixed with the plurality of conductive portions 72a to 72c, the volume resistivity of each of the flow channel members 62 and 63 and the terminal receiving portion 65 is smaller than the volume resistivity of the insulating portions 71a to 71c. In the flow channel members 62, 63, and the terminal receiving portion 65, the insulating material constituting the insulating portions 71a to 71c is a main material, and the conductive material constituting the conductive portions 72a to 72c is an additive material added to the main material.

[0044] In the flow channel elements 62, 63 and the terminal receiving portion 65, the content rate and the content of the conductive portions 72a to 72c with respect to the insulating portions 71a to 71c are adjusted so that the volume resistivity becomes a value in the range of 1.0 × 10 11(1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power). Ωcm. Regarding the contents of the flow channel elements 62, 63 and that in the terminal receiving portion 65, the insulating portions 71a to 71c are larger than the conductive parts 72a to 72c. For example, the mass of the conductive parts 72a to 72c is in the range of 2% to 20% of the mass of the insulating portions 71a to 71c. In the present embodiment, the mass of the conductive parts 72a to 72c is set to about 12% of the mass of the insulating portions 71a to 71c.

[0045] As in the Fig. 6, in the flow channel elements 62 and 63, the conductive parts 72a and 72b are distributed throughout the insulating portions 71a and 71b. The flow channel elements 62, 63 have outer surfaces 62a, 63a and inner surfaces 62b, 63b enclosed in the outer surface of the casing 21, forming the bypass flow channel 30. The inner surface of the casing 21 is a molding surface forming the bypass flow channel 30, and the inner surfaces 62b and 63b of the flow channel elements 62 and 63 are included in the inner surface of the casing 21. The volume resistivity of each of the flow channel elements 62 and 63 is a value indicating a resistance between the outer surfaces 62a and 63a and the inner surfaces 62b and 63b. As a method for measuring the specific volume resistivity, there is a two-terminal method in which a current is passed between the outer surfaces 62a and 63a and the inner surfaces 62b and 63b.

[0046] As in the Fig. As shown in Figure 7, the terminal receiving portion 65 has an exposed surface 65a enclosed in the outer surface of the housing 21 and a connecting surface 65b connected to the flow channel members 62 and 63. The volume resistivity of the terminal receiving portion 65 is a value indicating a resistance between the exposed surface 65a and the connecting surface 65b and can be measured using the two-terminal method described above. The exposed surface 65a and the connecting surface 65b are included in the outer surface of the terminal receiving portion 65.

[0047] The terminal receiving portion 65 has an outer layer 66 forming the exposed surface 65a and the connecting surface 65b, and an inner layer 67 provided within the outer layer 66. The outer layer 66 extends along the outer surface of the terminal receiving portion 65 so as to cover the entire inner layer 67. In the terminal receiving portion 65, the content ratio of the conductive part 72c with respect to the insulating portion 71c in the outer layer 66 is higher than that in the inner layer 67. The inner layer 67 does not contain or slightly contains the conductive part 72c, and the volume resistivity of the inner layer 67 is higher than that of the outer layer 66.

[0048] Also in the housing 21, which is formed by assembling the flow channel elements 62, 63 and the terminal receiving portion 65, the specific volume resistivity, ie the resistance per unit volume, is in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14(1.0 × 10 to the 14th power) Ωcm. The volume resistivity of the housing 21 is a value indicating the resistance between the outer surface 62a of the first flow channel member 62 and the exposed surface 65a of the terminal receiving portion 65, and the resistance between the outer surface 62a of the second flow channel member 63 and the exposed surface 65a of the terminal accommodating portion 65. The volume resistivity can be measured using the two-terminal method described above. That is, the volume resistivity of the housing 21 is a value indicating the resistance between parts of the outer surface of the housing 21 that are separated from each other.

[0049] Furthermore, in the flow channel forming section 61, which is formed by joining the flow channel elements 62 and 63, the specific volume resistance, ie the resistance per unit volume, is in the range of 1.0 × 10 11(1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm. The flow resistivity of the flow channel forming portion 61 is a value indicating the resistance between the outer surface 62a of the first flow channel member 62 and the outer surface 62a of the second flow channel member 63, and is measured by the two-terminal method described above or the like. That is, the volume resistivity of the flow channel forming portion 61 is a value indicating the resistance between separate portions of the outer surface of the flow channel forming portion 61.

[0050] The lead terminal 52 of the sensor SA 50 is completely housed in the inner layer 67 of the terminal receiving portion 65 and does not protrude from the inner layer 67. As described above, the inner layer 67 in the terminal receiving portion 65 hardly contains the conductive part 72c, so that the insulation performance of the inner layer 67 is higher than that of the outer layer 66. Therefore, it is possible to prevent the lead terminal 52 from leaking into the terminal receiving portion 65. Fig. 7, the connector terminals 28a and the SA main body 51 are not shown.

[0051] The flow channel members 62, 63 and the terminal receiving portion 65 are manufactured by injecting a molten resin in a state where a conductive material is mixed with an insulating material from an injection molding machine into a molding device such as a mold. The speed of injecting the molten resin from the injection molding machine into the molding device is slower in the case of manufacturing the flow channel members 62, 63 than in the case of manufacturing the terminal receiving portion 65. As described above, the injection speed of the molten resin is relatively slow, so that the conductive material is easily distributed over the entire flow channel members 62 and 63. In addition, since the injection speed of the molten resin is relatively high in the case of manufacturing the terminal receiving portion 65, the conductive material is not distributed over the entire terminal receiving portion 65.Therefore, the conductive material of the outer layer 66 is biased to be larger than the conductive material of the inner layer 67. The first flow channel member 62, the second flow channel member 63, and the terminal receiving portion 65 are bonded together using a molten resin used for resin molding the flow channel members 62, 63 and the terminal receiving portion 65. For this reason, the conductive part is also mixed and dispersed at these bonded parts in the insulating portion.

[0052] In resin molding using the molding jig, a skin layer is formed by cooling and solidifying the molten resin in contact with the surface of the molding jig in the molten resin injected into the molding jig, and the molten resin within the skin layer is solidified at a later time than the skin layer to form a core layer. In the flow channel members 62 and 63 and the terminal receiving portion 65, the skin layer is likely to contain a large amount of conductive material. In the flow channel members 62 and 63, the skin layer and the core layer have the same conductive material content. On the other hand, in the terminal receiving portion 65, the content rate of the conductive part 72c in the skin layer is higher than in the core layer. In the terminal receiving portion, the skin layer is the outer layer 66, and the core layer is the inner layer 67.

[0053] If the foreign matter contained in the intake air is small enough to pass through the air cleaner 19a, the foreign matter passes through the air cleaner 19 and reaches the air flow meter 20. When the foreign matter comes into contact with the housing 21 of the air flow meter 20, the foreign matter and the housing 21 may be charged with static electricity by frictional charging or contact charging. When the foreign matter, which is more likely to be positively charged than the housing 21, comes into contact with the housing 21, this foreign matter becomes a positively charged positive foreign matter Fp, and a negative charge 75 is generated in the housing 21 (see Fig. 9). The negative charge 75 is located on the outer surface, such as the skin layer, and at a location close to the inner surface in the casing 21. When the foreign matter, which is likely to be positively charged, has already become the positive foreign matter Fp, the positive foreign matter Fp comes into contact with the casing 21, so that the positive foreign matter Fp continues to be positively charged and the casing 21 continues to be negatively charged. Therefore, the negative charge 75 increases.

[0054] Examples of foreign substances that tend to be positively charged include foreign substances containing glass components such as sand and dust. In the charging column, which indicates whether each substance is slightly positively or negatively charged, if the substance located at the position of the charging column that is more easily positively charged than the material forming the housing 21 is a foreign substance, the foreign substance is positively charged, and the housing 21 is slightly negatively charged.

[0055] As in the Fig. As shown in Figure 8, when the foreign matter F comes into contact with the air filter 19a while passing through the air filter 19a along with the intake air, the foreign matter F is more likely to be positively charged than the material of the air filter 19a in the charging column. As a result, it becomes positively charged and becomes a positive foreign matter Fp. In this case, the air filter 19a is negatively charged. It is also assumed that foreign matters that are slightly positively charged pass through the air filter 19 without being positively charged.

[0056] As in the Fig. 5, the positive foreign matter Fp that has passed through the air filter 19 reaches the air flow meter 20 and approaches the outer or inner surface of the housing 21. In this case, the positive foreign matter Fp is easily attracted by the negative electric charge 75 generated by contact with the housing 21 or already present, and therefore easily adheres to the outer surface 62a and the inner surface 62b of the housing 21. In the air flow meter 20, when the negative charge 75 in the housing 21 increases to a certain extent due to the repeated charging of the housing 21 by the foreign matter, the negative charge 75 easily diffuses from the housing 21 into the flow rate detection unit 22 of the sensor SA 50.When the flow rate detection unit 22 is negatively charged by the negative charge 75 that has moved to the flow rate detection unit 22, the positive foreign matter Fp that has entered the measurement flow channel 32 along with the intake air is electrically attracted to the negative charge 75 in the flow rate detection unit 22. As a result, the positive foreign matter Fp easily adheres to the flow rate detection unit 22. As described above, if the foreign matter adheres to the flow rate detection unit 22, there is a possibility that the detection accuracy of the flow rate detection unit 22 will be reduced due to the presence of the foreign matter.

[0057] Since the specific volume resistance of each of the flow channel elements 62 and 63 is a value in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14(1.0 × 10 to the 14th power) Ωcm, dielectric breakdown due to the negative charge 75 is relatively easy to occur in the present embodiment as described above.

[0058] For example, as in the Fig. 9, a plurality of negative charges 75 are accumulated in the conductive part 72X near the outer surface 62a, and a plurality of positive impurities Fp are electrically attracted by the negative charges 75. As a result, it is assumed that the majority of the positive impurities Fp adhere to the outer surface 62a of the first flow channel element 62. In this case, the first flow channel element 62 is in a negatively charged state due to static electricity, and the conductive part 72X is included in the skin layer of the first flow channel element 62. In the first flow channel element 62, the larger the number of negative charges 75 accumulated in the conductive part 72X, the higher the potential of the conductive part 72X on the negative side becomes.When the voltage becomes high to a certain extent due to this potential, the discharge Ed is generated between the conductive part 72X and the conductive part 72Y near the conductive part 72X.

[0059] When the discharge Ed occurs between the conductive portions 72X and 72Y, dielectric breakdown occurs in the portion between the conductive portions 72X and 72Y in the insulating portion 71a, and the negative charge 75 in the conductive portion 72X moves to the conductive portion 72Y. Since such discharge and dielectric breakdown occur at a plurality of locations in the path connecting the conductive portion 72X and the ground terminal 23d, the negative charge 75 accumulated in the conductive portion 72X is discharged to the ground GND via the plurality of conductive portions 72a and the ground terminal 23d. As described above, when the negative charges 75 that have electrically attracted the plurality of positive impurities Fp disappear from the conductive portion 72X, the positive impurities Fp easily separate from the outer surface 62a of the first flow channel member 62.Therefore, it is possible to suppress the generation of the negative charge 75 by negatively recharging the first flow channel element 62 by the influence of the positive impurity Fp in contact with the outer surface 62a.

[0060] A voltage of 0.1 kV to 10 kV is considered a voltage at which dielectric breakdown due to static electricity is likely to occur. The volume resistivity of the first flow channel element 62, in which dielectric breakdown is likely to occur, varies depending on the voltage generated by static electricity. For example, the higher the volume resistivity, the higher the voltage at which electrostatic breakdown is likely to occur. In particular, at a static electricity of 0.1 kV, when the volume resistivity is about 1.0 × 10 11(1.0 × 10 to the 11th power) Ωcm, a dielectric breakdown is relatively likely, and at a static electricity of 1 kV, when the volume resistivity is 1.0 × 1012 (1.0 × 10 to the 12th power) Ωcm, dielectric breakdown is relatively likely. In addition, at a static electricity of 10 kV, when the volume resistivity is about 1.0 × 1013 (1.0 × 10 to the 13th power) is Ωcm, dielectric breakdown is relatively likely. Therefore, in the vehicle-mounted air flow meter 20, a voltage value likely to be generated in the housing 21 due to static electricity is determined by a test or the like, and it is preferable to adjust the volume resistivity of the housing 21 at the time of manufacturing the air flow meter 20 based on the determined result.

[0061] In the Fig. 9, the ground terminal 23d is positioned near the inner surface 62b to illustrate the path through which the negative charge 75 travels, but as described above, the ground terminal 23d is actually positioned near the outer surface 62a.

[0062] Also, in the second flow channel element 63, when multiple negative charges 75 electrically attract the positive impurities Fp adhering to the outer surface 63a, discharge and dielectric breakdown are likely to occur at multiple locations along the path connecting the negative charges 75 and the ground terminal 23d. In this case, since the ground terminal 23d is not connected to the second flow channel element 63, the negative charge 75 accumulated in the second flow channel element 63 is discharged to the ground GND via the first flow channel element 62.

[0063] Also, in the outer layer 66 of the terminal receiving portion 65, when a plurality of negative charges 75 electrically attract the positive impurities Fp attached to the exposed surface 65a, discharge and dielectric breakdown are likely to occur at a plurality of locations in the path connecting the negative charges 75 and the ground terminal 23d. However, in the terminal receiving portion 65, discharge and dielectric breakdown are less likely to occur in the inner layer 67 because the conductive part 72c is hardly included in the inner layer 67. In addition, since the ground terminal 23d may not be provided in the terminal receiving portion 65, the negative charge 75 accumulated in the outer layer 66 of the terminal receiving portion 65 is discharged to the ground GND through the first flow channel member 62 and the second flow channel member 63 without passing through the inner layer 67.

[0064] Next, a relationship between the measurement accuracy of the air flow meter 20 and the volume resistivity of the housing 21 is described. Here, the measurement accuracy of the air flow meter 20 is used as an error rate with respect to the intake air quantity in the intake passage 12. The error rate is calculated as the ratio of the error magnitude of the measured value of the air flow meter 20 to the true value of the intake air quantity. As shown in the Fig. 10, is in the area where the volume resistivity of the housing 21 is 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm or less, the error rate of the measured value is sufficiently small. On the other hand, in the range where the volume resistivity of the package 21 is greater than 1.0 × 10 14(1.0 × 10 to the 14th power) Ωcm, the error rate of the measured value increases rapidly. As described above, in the test to detect the relationship between the volume resistivity of the housing 21 and the error rate of the measured value, test results were obtained that the detection accuracy of the flow rate detection unit 22 is improved by setting the volume resistivity of the housing 21 to a value of 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm or less.

[0065] Furthermore, in the configuration in which the volume resistivity of the flow channel elements 62 and 63, the terminal receiving portion 65, the flow channel forming portion and the housing 21 is less than 1.0 × 10 11(1.0 × 10 to the 11th power) Ωcm, discharge and dielectric breakdown are expected to occur even when the static electricity energy accumulated in the casing 21 is relatively small. With this configuration, the number of discharges and dielectric breakdowns occurring in the insulating portions 71a to 71c tends to increase excessively, and there is a concern that deterioration of the insulating portions 71a to 71c due to dielectric breakdown is likely to progress. On the other hand, the volume resistivity of the casing 21 and the like in the present embodiment is 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm or more. Therefore, excessive dielectric breakdown is unlikely to occur due to the charging of the case 21, and it is therefore possible to suppress deterioration of the insulating portions 71a to 71c due to the dielectric breakdown.

[0066] According to the present embodiment described above, the volume resistivity of the flow channel forming portion is a value in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14(1.0 × 10 to the 14th power) Ωcm. In this configuration, discharge and dielectric breakdown are relatively likely to occur due to the electric energy of the negative charges 75 accumulated in the flow channel forming portion 61, so the negative charges 75 can be easily discharged to the ground GND via the ground terminal 23d. In this case, even if the negative charges 75 accumulated in the flow channel forming portion 61 are diffused in the flow rate detection unit 22, the negative charges 75 accumulated in the flow rate detection unit 22 are also discharged to the ground GND via the flow channel forming portion 61.As described above, it is possible to prevent the detection accuracy of the flow rate detection unit 22 from decreasing due to the adhesion of foreign matter to the flow rate detection unit 22 because the foreign matter is less likely to adhere to the flow rate detection unit 22 by eliminating the negatively charged state of the flow channel forming portion 61 and the flow rate detection unit 22.

[0067] Furthermore, since the detection accuracy of the flow rate detection unit 22 is improved, the measurement result, which is the output of the air flow meter 20 at the input of the ECU 15, becomes stable. Therefore, in the configuration where the ECU 15 controls the output of the internal combustion engine 11 using the output of the air flow meter 20, as in the present embodiment, the output of the internal combustion engine 11 can be stabilized and improved by stabilizing the output of the air flow meter 20. Furthermore, the casing 21 and the flow rate detection unit 22 can be prevented from being contaminated by the adhesion of the positive foreign matter Fp to the casing 21 and the flow rate detection unit 22.In this case, it is possible to suppress the loss of intake air flow in the intake passage 12 due to the foreign matter adhering to the outer surface of the housing 21, so that the intake performance can be improved, and furthermore, it is possible to eliminate the adverse effect on other products such as the throttle position sensor 18a. Furthermore, in this case, since the smooth flow of intake air in the bypass flow passage 30 can be maintained due to the foreign matter adhering to the inner surface of the housing 21, the output stability of the air flow meter 20 can be increased.

[0068] According to the present embodiment, the volume resistivity of the terminal receiving portion 65 is a value in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14(1.0 × 10 to the 14th power) Ωcm. Therefore, even if the terminal receiving portion 65 is negatively charged, the negative charge 75 can be discharged to the ground GND due to dielectric breakdown, as in the case where the flow channel forming portion 61 is negatively charged. Therefore, it is possible to eliminate the state where the terminal receiving portion 65 and the flow rate detection unit 22 are negatively charged.

[0069] According to the present embodiment, the volume resistivity of the casing 21 is a value in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14(1.0 × 10 to the 14th power) Ωcm. Therefore, even if the housing 21 is negatively charged, the negative charge 75 can be discharged to the ground GND due to dielectric breakdown, as in the case where the flow channel forming portion 61 is negatively charged. Therefore, it is possible to eliminate the state where the housing 21 and the flow rate detection unit 22 are negatively charged.

[0070] According to the present embodiment, in the casing 21, the insulating portions 71a to 71c are mixed with the conductive portions 72a to 72c. In this configuration, when the negative charge 75 accumulates near the outer surface of the casing 21, dielectric breakdown occurs from the portion where the negative charge 75 accumulates to the nearby conductive portions 72a to 72c, allowing the negative charge 75 to move toward the ground terminal 23d. In this way, in the insulating portions 71a to 71c, dielectric breakdown occurs at a plurality of locations within a short distance from the part divided by the conductive portions 72a to 72c. Therefore, the negative charge 75 can reach the ground terminal 23d.Therefore, it is possible to realize a configuration in which the negative charge 75 accumulated in the housing 21 is easily discharged to ground GND due to the dielectric breakdown.

[0071] According to the present embodiment, the conductive parts 72a to 72c are formed by combining multiple types of carbon materials. Therefore, when the flow channel members 62, 63 and the terminal accommodating portion 65 are molded with the molten resin, the conductive material in the molten resin can be easily distributed throughout the insulating material. In this case, the conductive parts 72a to 72c can be arranged near the surface, such as the outer layer or skin layer of the flow channel members 62, 63 and the terminal accommodating portion 65, even if the flow channel members 62, 63 and the terminal accommodating portion 65 have a complicated shape. Therefore, the majority of negative charges 75 accumulated near the surface easily move to the nearby conductive parts 72a to 72c due to dielectric breakdown.As described above, the negative charge 75 can be efficiently discharged to ground GND by efficiently responding to the complicated product shape of the housing 21.

[0072] According to the present embodiment, the insulating portions 71a to 71c are made of a reversibly solidified thermoplastic resin. Therefore, when dielectric breakdown due to static electricity occurs in the flow channel members 62 and 63 and the terminal receiving portion 65, even if the insulating portions 71a to 71c melt at the location where the dielectric breakdown occurs, it is assumed that the melted portion will resolidify. In this case, it is assumed that the insulating portions 71a to 71c are unlikely to deteriorate due to the occurrence of dielectric breakdown.Therefore, it is possible to suppress the deterioration of the casing 21 due to the dielectric breakdown and at the same time realize the configuration in which the casing 21 and the flow rate detecting unit 22 are less likely to be charged by the dielectric breakdown.

[0073] According to the present embodiment, in the terminal receiving portion 65, the content ratio of the conductive part 72c of the inner layer 67 receiving the lead terminal 52 is lower than that of the outer layer 66. Therefore, when the terminal receiving portion 65 is negatively charged, the negative charge 75 can be discharged to the ground GND by causing dielectric breakdown in the outer layer 66. Moreover, the inner layer 67 can ensure insulation, so that leakage of the lead terminal 52 does not occur. For this reason, the detection accuracy of the flow rate detection unit 22 is prevented from being degraded by static electricity through the outer layer 66, so that it is possible to accurately exchange signals between the lead terminal 52 and the external device such as the ECU 15.

[0074] In the terminal receiving portion 65, the outer layer 66 and the inner layer 67 are integrally molded with a conventional molten resin. With this configuration, the various functions of electrically insulating the lead terminal 52 to enable electrical conduction and electrically conducting the terminal to prevent charging of the terminal can be realized by one type of molten resin, without using multiple types of molten resins. Therefore, it is possible to manufacture the terminal receiving portion with excellent structure and cost.

[0075] According to the present embodiment, the ground terminal 23d is exposed to the outside from the outer surface of the flow channel forming portion 61. With this configuration, when the flow channel forming portion 61 is negatively charged, the negative charge 75 can move near the outer surface of the flow channel forming portion 61 and reach the ground terminal 23d. In this case, since the negative charge 75 in the flow channel forming portion 61 can be discharged to the ground GND via both the internal path accompanied by dielectric breakdown and the external path extending along the outer surface, it is possible to more reliably suppress the negative charge of the flow channel forming portion 61.

[0076] According to the present embodiment, the volume resistivity of the flow channel forming portion 61 is a value indicating the resistance between the outer surfaces 62a and 63a and the inner surfaces 62b and 63b. Therefore, the volume resistivity of the flow channel forming portion is set to 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14(1.0 × 10 to the 14th power) Ωcm. Therefore, it is possible to control the ease of occurrence of the phenomenon that the negative charge 75 passes through the interior of the flow channel forming portion 61 and reaches the ground terminal 23d due to dielectric breakdown. Therefore, even if the ground terminal 23d is connected to only one of the outer surfaces 62a and 63a and the inner surfaces 62b and 63b in the flow channel forming portion 61, the negative charge 75 accumulated on the other side can reach the ground terminal 23d due to the occurrence of dielectric breakdown. (Second embodiment)

[0077] In the first embodiment, the inner layer 67 and the outer layer 66 are formed due to the uneven distribution of the insulating portion 71c in the terminal receiving portion 65. In the second embodiment, however, the insulating portion 71c is diffused throughout the terminal receiving portion 65, and the inner layer 67 and the outer layer 66 are not formed. In the present embodiment, the differences from the first embodiment will be mainly described.

[0078] As in the Fig. As shown in Fig. 11, in the terminal receiving portion 65, as in the case of the flow channel elements 62 and 63, the conductive part 72c is in a state of being diffused throughout the insulating portion 71c. In this configuration, the volume resistivity of the terminal receiving portion 65 is a value in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14(1.0 × 10 to the 14th power) Ωcm. In this case, in the terminal receiving part 65, although the conductive part 72c is provided around the lead terminal 52, the insulation breakdown of the insulating portion 71c is less likely to occur under a voltage applied to the lead terminal 52, so that leakage at the lead terminal 52 can be suppressed.

[0079] In the present embodiment, the injection speed of the molten resin from the injection molding machine into the molding device is slowed down to the same level as the injection speed of the molten resin when the flow channel members 62 and 63 are resin-molded when the terminal receiving portion 65 is resin-molded. In this case, the state in which the conductive material is easily mixed with all the molten resin injected into the molding device is easily maintained, so that the conductive part 72c easily diffuses into the entire insulating portion 71c. (Third embodiment)

[0080] In the first embodiment, the terminal receiving portion 65 includes the conductive part 72c, but in the third embodiment, the terminal receiving portion 65 does not include the conductive part 72c, as shown in Fig.12. In the present embodiment, the differences from the first embodiment will be described primarily.

[0081] Since the terminal receiving part 65 does not include the conductive part 72a, the volume resistivity of the terminal receiving part 65 is greater than 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm, as well as the volume resistivity of the insulating portion 71c. In this configuration, since the insulation of the leading terminal 52 is improved by the terminal receiving part 65, the accuracy of signal exchange between the leading terminal 52 and the ECU 15 can be further improved.

[0082] Although a plurality of embodiments according to the present disclosure have been described above, the present disclosure is not construed as being limited to the above-mentioned embodiments and can be applied to various embodiments and combinations within a scope that does not deviate from the spirit of the present disclosure. Modifications of the above-mentioned embodiments will be described.

[0083] As a first modification, the flow channel elements 62 and 63 may include an outer layer in which the conductive parts 72a and 72b are mixed in the insulating portions 71a and 71b, and an inner layer in which the content ratio of the conductive parts 72a and 72b to the insulating portions 71a and 71b is lower than in the outer layer. Even in this case, the volume resistivity of the flow channel elements 62 and 63 and the portion 61 forming the flow channel and the housing 21 is a value in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm.

[0084] As a second modification, in the terminal receiving portion 65, the outer layer 66 may be one layer thicker than the surface or skin layer. In this case, the outer layer 66 is formed by the skin layer and a part of the core layer. That is, even in the core layer, there is a region where a large part of the conductive part 72c is included in a part on the peripheral edge side, and this part forms the outer layer 66, while the remaining part forms the inner layer 67.

[0085] As a third modification, the flow channel forming portion 61 may be formed by a single member instead of assembling a plurality of members such as the flow channel members 62 and 63 to form the flow channel forming part 61. For example, the flow channel forming portion is integrally molded from resin. Since the volume resistivity of the flow channel forming portion 61 even in this configuration is a value in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm, the negative charge 75 accumulated in the flow channel forming part 61 is easily discharged to ground GND due to dielectric breakdown. Furthermore, in the flow channel forming portion, the conductive portion is mixed with the insulating portion, so dielectric breakdown is likely to occur in the insulating portion.

[0086] As a fourth modified example, the housing 21 may be formed by a single member instead of assembling a plurality of members such as the flow channel members 62 and 63 and the terminal receiving portion 65 to manufacture the housing 21. For example, the housing 21 is integrally molded with resin. Even in this configuration, since the volume resistivity of the housing 21 has a value in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm, the negative charge 75 accumulated in the housing 21 is easily discharged to ground GND due to the dielectric breakdown.

[0087] Furthermore, in the housing 21, the conductive part is mixed with the insulating portion, so that dielectric breakdown in the insulating portion is likely to occur.

[0088] As a fifth modification, the flow channel members 62 and 63 and the terminal receiving portion 65 do not include the conductive portions 72a to 72c in the insulating portions 71a to 71c. The volume resistivity of the insulating portions 71a to 71c is a value in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm. In this configuration, the volume resistivity of the insulating material forming the insulating portions 71a to 71c is a value in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm.

[0089] As a sixth modification, a thermosetting resin or the like may be used instead of the thermoplastic resin as the resin material constituting the insulating portions 71a to 71c. Further, a rubber material or the like may be used instead of the resin material as the insulating material constituting the insulating portions 71a to 71c.

[0090] As a seventh modification, only one type of carbon powder, carbon fiber, nanocarbon, graphene, and carbon microparticles may be used as the carbon material constituting the conductive parts 72a to 72c. Furthermore, a metal material such as aluminum may be used instead of the carbon material as the conductive material constituting the conductive parts 72a to 72c.

[0091] As an eighth modification, the volume resistivity of each member such as the flow channel members 62 and 63, the terminal receiving portion 65, the flow channel forming portion 61, and the housing 21 is calculated using a surface resistance which is the resistance per unit area of these members.

[0092] As a ninth modification, in the members such as the flow channel members 62 and 63, the terminal receiving portion 65, the flow channel forming portion 61, and the housing 21, the resistance value of the portion having the largest resistance value may be a value in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm. For example, in the case 21, the resistance value between the two furthest points is set to a value in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14(1.0 × 10 to the 14th power) Ωcm. Even with this configuration, if the housing 21 becomes charged by static electricity, it is possible to cause a dielectric breakdown by discharge within the housing 21 and discharge the negative charge 75 to ground GND.

[0093] As a tenth modification, in the measuring flow passage 32 through which a fluid such as intake air flows, a temperature sensor for detecting the temperature of the fluid, a humidity sensor for detecting the humidity of the fluid, a pressure sensor for detecting the pressure and the like may be provided as a physical quantity detecting unit such as the flow rate detecting unit 22.

[0094] As an eleventh modification, the bypass flow channel 30 may include only the measuring flow channel 32 of the through flow channel 31 and the measuring flow channel 32. For example, the measuring inlet 35 may be provided on the outer surface of the housing 21 instead of the inlet port 33.

[0095] As a twelfth modification, a plurality of grounding portions may be provided, such as the grounding terminal 23d attached to the housing 21. For example, a grounding portion is attached to each of the flow passage members 62, 63, and the terminal receiving portion 65. Furthermore, a plurality of grounding portions may be attached to at least one of the first flow passage member 62, the second flow passage member 63, and the terminal receiving portion 65. For example, in the first flow passage member 62, the grounding portion is individually attached to the outer surface 62a and the inner surface 62b.

Claims

[1] Device (20) for measuring a physical quantity of a fluid, the device for measuring a physical quantity comprising: a bypass flow channel (30) through which the fluid flows; a detection unit (50) having a physical quantity detection unit (22) configured to detect a physical quantity of the fluid in the bypass flow channel, and a detection terminal (52) electrically connected to the physical quantity detection unit; a housing (21) having a flow channel forming portion (61) having an insulating property and forming the bypass flow channel, and a terminal receiving portion (65) having an insulating property and receiving the detection terminal; and a grounding section (23d) connecting the section forming the flow channel to an earth (GND), where: a specific volume resistance of the section forming the flow channel in a range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm, and the terminal receiving section includes the following: an insulating portion (71c) configured to impart insulating properties to the terminal receiving portion, and a conductive portion (72c) provided in a mixed state in the insulating portion and having a conductivity such that the volume resistivity of the terminal receiving portion is smaller than the volume resistivity of the insulating portion, wherein the terminal receiving portion comprises: an outer layer (66) forming an outer surface (65a, 65b) of the terminal receiving portion, an inner layer (67) in which a content ratio of the conductive portion to the insulating portion is lower than that of the outer layer, and which is provided within the outer layer, with the sensing port located in the inner layer. [2] A physical quantity measuring device according to claim 1, wherein the flow channel forming portion comprises: an insulating portion (71a, 71b) configured to impart insulating properties to the flow channel forming portion; and a conductive portion (72a, 72b) provided in a mixed state with the insulating portion and having a conductivity such that the volume resistivity of the flow channel forming portion is smaller than that of the insulating portion. [3] The physical quantity measuring device according to claim 2, wherein the conductive portion contains at least one of the following: carbon powder, carbon fiber, nanocarbon, graphene, and carbon microparticles. [4] A physical quantity measuring device according to claim 2 or 3, wherein the insulating portion is made of thermoplastic resin. [5] A physical quantity measuring device according to any one of claims 1 to 4, wherein the volume resistivity of the terminal receiving portion is in the range of 1.0 × 10 11 (1.0 × 10 to the 11th power) Ωcm to 1.0 × 10 14 (1.0 × 10 to the 14th power) Ωcm. [6] A physical quantity measuring device according to any one of claims 1 to 5, wherein the grounding portion is exposed to the outside from the outer surface (62a) of the flow channel forming portion. [7] A physical quantity measuring device according to any one of claims 1 to 6, wherein the volume resistivity of the flow channel forming portion is a value indicating the resistance between the outer surface (62a, 63a) and the inner surface (62b, 63b) of the flow channel forming portion.

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