Pressure detection device

Abstract

To provide a pressure detecting device capable of performing measurement with high reliability.SOLUTION: A pressure detecting device 20 comprises: a housings 31, 32 having a pressure receiving part 32 which receives an external pressure; and a pressure detecting part which is housed inside the housing 31 and outputs an electric signal corresponding to the pressure received by the pressure receiving part 32, with the pressure receiving part 32 having a pressure receiving surface 32b for receiving the pressure and a transmission part 32a which is in contact with the pressure detecting part and transmits the pressure received by the pressure receiving part 32b to the pressure detecting part. An elastic member 90 having a through hole 90d is disposed between the pressure detecting part and the housing 31, 32, and the transmission part 32a is slidably inserted into the through hole 90d.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a pressure detection device, and more particularly to a device that is mounted in a combustion chamber of an internal combustion engine and is capable of detecting the pressure within the combustion chamber. [Background technology]

[0002] Conventionally, devices that use a pressure-sensitive element such as a piezoelectric element as a pressure detection section have been proposed as devices that are attached to an internal combustion engine and detect the pressure inside the combustion chamber. For example, a pressure detection device described in Patent Document 1 will be described.

[0003] The pressure detection section of the pressure detection device has electrode members provided on both end faces of the piezoelectric element, and the piezoelectric element is incorporated into the pressure detection device main body with a predetermined load applied by members such as the electrode members, an elastic member arranged between the housing section and the pressure detection section, and a diaphragm head. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-162376 A Summary of the Invention [Problem to be solved by the invention]

[0005] For example, the sensitivity of a pressure-sensitive element made of a piezoelectric crystal depends on the direction of the force acting on the pressure-sensitive element, and generally, in a pressure detection device, the crystal axis of the piezoelectric crystal is oriented so that the largest piezoelectric effect is obtained for pressure acting in a perpendicular direction on the pressure-receiving surface of the diaphragm head. Here, for example, when the pressure inside the combustion chamber of an internal combustion engine is measured using a pressure detection device, the pressure-receiving surface of the diaphragm head of the pressure detection device may be subjected to not only pressure acting in a vertical direction perpendicular to the pressure-receiving surface, but also pressure that is a composite of vertical and horizontal components. This horizontal component of pressure acting on the pressure-receiving surface may cause horizontal distortion in the diaphragm head, and this horizontal distortion of the diaphragm head may become a noise component in the force acting in the vertical direction that is originally intended to be measured by the pressure detection device, thereby reducing the reliability of the pressure detection device.

[0006] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a pressure detection device capable of performing highly reliable measurements. [Means for solving the problem]

[0007] The pressure detection device includes a housing having a pressure-receiving portion that receives pressure from the outside, and a pressure detection portion that is housed inside the housing and outputs an electrical signal corresponding to the pressure received by the pressure-receiving portion, the pressure-receiving portion has a pressure-receiving surface that receives the pressure, and a transmission portion that abuts against the pressure detection portion and transmits the pressure received at the pressure-receiving surface to the pressure detection portion, an elastic member having a through hole is arranged between the pressure detection portion and the housing, and the transmission portion is slidably inserted into the through hole. The transmission part may be loosely fitted into the through hole, and the transmission part and the through hole may be loosely fitted with a fit tolerance of 0.02 mm to 0.07 mm. The elastic member may be produced by pressing. Furthermore, the elastic member may have a bottom portion in which the through hole is provided, an elastic portion connected to the bottom portion, and a flange portion connected to the elastic portion, the housing may have a pressure-receiving member having the pressure-receiving portion and a housing member that houses the pressure detection portion, and the elastic member may be fixed to the housing by clamping the flange portion between the pressure-receiving member and the housing member. Effect of the Invention

[0008] According to the present invention, it is possible to provide a pressure detection device capable of performing highly reliable measurements. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of a pressure detection system according to an embodiment. [Diagram 2] FIG. [Diagram 3] 3 is a cross-sectional view (cross-sectional view taken along line AA in FIG. 2) of the pressure detection device. [Figure 4] 4 is an enlarged cross-sectional view of the tip side (area I in FIG. 3) of the pressure detection device. [Diagram 5] FIG. 2 is a diagram showing an elastic member provided in the pressure detection device, where (a) is a plan view and (b) is a cross-sectional view taken along the line AA of (a). [Figure 6] 4 is a cross-sectional view of an internal housing provided in the pressure detection device. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. [Pressure detection system configuration] FIG. 1 is a schematic configuration diagram of a pressure detection system 1 according to an embodiment. This pressure detection system 1 includes a pressure detection device 20 that detects the pressure (combustion pressure) in the combustion chamber C of the internal combustion engine 10, a control device 100 that supplies power to the pressure detection device 20 and controls the operation of the internal combustion engine 10 based on the pressure detected by the pressure detection device 20, and a connection cable 80 that electrically connects the pressure detection device 20 and the control device 100.

[0011] Here, the internal combustion engine 10, which is the target of pressure detection, has a cylinder block 11 in which a cylinder is formed, a piston 12 that reciprocates in the cylinder, and a cylinder head 13 that is fastened to the cylinder block 11 and forms a combustion chamber C together with the piston 12. The cylinder head 13 is provided with a communication hole 13a that communicates the combustion chamber C with the outside. A female screw (not shown) is provided inside the communication hole 13a. The pressure detection device 20 is attached to the internal combustion engine 10 by inserting the tip end of the pressure detection device 20 into the communication hole 13a and fixing the pressure detection device 20 to the cylinder head 13. More specifically, the pressure detection device 20 is attached by screwing a male screw provided on the tip end of the pressure detection device 20 into the female screw provided in the communication hole 13a. Here, the cylinder block 11, the piston 12, and the cylinder head 13 that constitute the internal combustion engine 10 are made of a metal material having electrical conductivity, such as cast iron or aluminum.

[0012] [Configuration of pressure detection device] Fig. 2 is a side view of the pressure detection device. Fig. 3 is a cross-sectional view (cross-sectional view taken along line AA in Fig. 2) of the pressure detection device 20. Fig. 4 is an enlarged cross-sectional view of the tip side (area I in Fig. 3) of the pressure detection device 20.

[0013] The pressure detection device 20 has a housing part 30 which is generally cylindrical and exposed to the outside, and a detection mechanism part 40 which includes various mechanisms for detecting pressure, is almost entirely housed inside the housing part 30, and is partially exposed to the outside, to which a connection cable 80 is connected. The pressure detection device 20 is attached to the internal combustion engine 10 shown in FIG. 1 so that the left side in FIG. 2 faces the combustion chamber C (the lower side in FIG. 1) and the right side in FIG. 2 faces the outside (the upper side in FIG. 1). In the following description, the side facing the left in FIG. 2 is referred to as the "front end side" of the pressure detection device 20, and the side facing the right in FIG. 2 is referred to as the "rear end side" of the pressure detection device 20. In the following description, the center line direction of the pressure detection device 20 shown by the dashed line in FIG. 2 is simply referred to as the "center line direction". In this embodiment, the "center line direction" is an example of the axial direction, the "tip side" is an example of one end side, and the "rear end side" is an example of the other end side.

[0014] [Housing configuration] The housing unit 30 includes a front external housing 31 and a diaphragm head 32 attached to the front side of the front external housing 31. The housing unit 30 also includes a first housing 33 attached to the rear end side of the diaphragm head 32 inside the front external housing 31. The housing unit 30 also includes a rear external housing 35 attached to the rear end side of the front external housing 31. In the housing unit 30, the front external housing 31, the diaphragm head 32, and the rear external housing 35 are exposed to the outside. In contrast, the first housing 33 is not exposed to the outside and is accommodated inside the front external housing 31.

[0015] [External housing at the tip] The tip external housing 31 is a member having a hollow structure and a cylindrical shape as a whole. The tip external housing 31 is made of a metal material such as stainless steel that is conductive and has high heat resistance and acid resistance. The tip external housing 31 has, from the tip side to the rear end side, a small diameter part 31a having the smallest outer diameter, a large diameter part 31b having the largest outer diameter, and a tapered medium diameter part 31c. A male thread 31d is provided on the outer peripheral surface of the tip side of the small diameter part 31a of the tip external housing 31.

[0016] [Diaphragm head] The diaphragm head 32, which is an example of a pressure-receiving member, is a member having a disk shape as a whole. The diaphragm head 32 is made of a metal material such as stainless steel that is conductive and has high heat resistance and acid resistance. The diaphragm head 32 is a member provided to close the openings on the tip side of the tip external housing 31 and the first housing 33, and has a pressure-receiving surface 32b that receives pressure from the outside and a convex portion 32a that protrudes from the rear end side of the pressure-receiving surface 32b and is a transmitting portion that transmits the pressure received by the pressure-receiving surface 32b to a pressure detection portion described later. The diaphragm head 32 is fixed to the elastic member 90 by laser welding the entire periphery of the boundary portion with the elastic member 90 described later.

[0017] [First cabinet] The first housing 33 is a member having a hollow structure and a cylindrical shape as a whole. The first housing 33 is made of a metal material such as stainless steel that is conductive and highly heat-resistant. FIG. 6 is a cross-sectional view of an internal housing provided in a pressure detection device. The first housing 33 has, from one end side to the other end side, a visor portion 33a protruding in a direction perpendicular to the center line direction of the first housing 33, a body portion 33b having an outer diameter smaller than that of the visor portion 33a, a small diameter portion 33c having an outer diameter smaller than that of the body portion 33b, and a tapered portion 33d having a tapered shape whose outer diameter increases from the small diameter portion 33c toward the other end side, and the body portion 33b and the small diameter portion 33c are connected by a step portion 33e having a surface perpendicular to the center line direction. Here, the distance (wall thickness) from the outer surface to the inner surface in the direction perpendicular to the outer surface in each part constituting the first housing 33 is almost uniform from the visor portion 33a to the tapered portion 33d.

[0018] The first housing 33 is provided so that the rear end surface of the overhanging portion 32a abuts against the front end side of the small diameter portion 31a of the front external housing 31, and the body portion 33b, the small diameter portion 33c, the tapered portion 33d, and the stepped portion 33e located on the rear end side of the overhanging portion 32a are housed inside the front external housing 31. The boundary between the first housing 33 and the front external housing 31 is laser welded around the entire periphery.

[0019] The first housing 33 can be formed by, for example, a press working method. A variety of characteristics, such as spring characteristics and hardness, can be obtained by selecting the material, plate thickness, and hardening conditions of the first housing 33, and by setting the processing conditions. For example, by molding the first housing 33 by a press working method using a transfer die, the first housing 33 can be formed in a large quantity with high precision and at high speed in a shape that is difficult to achieve by a cutting method. Furthermore, the press working method forms grain flows that follow the shape of the material of the first housing 33, so that a high-strength first housing 33 can be obtained.

[0020] [Rear end external housing] The rear end external housing 35 is a member having a hollow structure and a cylindrical shape as a whole. The rear end external housing 35 is made of a metal material such as stainless steel that is conductive and has high heat resistance and acid resistance. The rear end external housing 35 has a front end tapered portion 35a, a first cylindrical portion 35b, a second cylindrical portion 35c, a third cylindrical portion 35d, and a fourth cylindrical portion 35e from the front end side to the rear end side. Here, the front end tapered portion 35a is tapered in such a way that the outer diameter gradually decreases from the front end side end of the rear end external housing 35 to the rear end side, and the rear end side end is connected to the first cylindrical portion 35b. The first cylindrical portion 35b, the second cylindrical portion 35c, and the third cylindrical portion 35d have smaller outer diameters in this order, and between the first cylindrical portion 35b and the second cylindrical portion 35c, there is a step portion 35f having a surface perpendicular to the center line direction and connecting the first cylindrical portion 35b and the second cylindrical portion 35c. The fourth cylindrical portion 35e has an outer diameter larger than the adjacent third cylindrical portion 35d, and has an outer diameter between the second cylindrical portion 35c and the third cylindrical portion 35b. In the rear end external housing 35, the distance (wall thickness) from the outer surface to the inner surface at each portion in the direction perpendicular to the outer surface is almost uniform in the tip tapered portion 35a, the first cylindrical portion 35b, the second cylindrical portion 35c, and the step portion 35f. In contrast, the thicknesses of the third cylindrical portion 35d and the fourth cylindrical portion 35e are smaller than the thicknesses of the tip tapered portion 35a, the first cylindrical portion 35b, the second cylindrical portion 35c, and the step portion 35f.

[0021] The inside of the rear end external housing 35 on the front end side has a first inner diameter portion 35g which is the inner diameter portion of the front end taper portion 35a, a second inner diameter portion 35h which is the inner diameter portion of the first cylindrical portion 35b, and a third inner diameter portion 35i which is the inner diameter portion of the second cylindrical portion 35c to the third cylindrical portion 35d. The inner diameter of the first inner diameter portion 35g gradually decreases from the front end side and is connected to the second inner diameter portion 35h at the end on the rear end side. The inner diameters of the second inner diameter portion 35h and the third inner diameter portion 35i decrease in this order.

[0022] The rear external housing 35 is provided such that the medium diameter portion 31c of the front external housing 31 abuts against the first inner diameter portion 35g of the rear external housing 35. The boundary between the rear external housing 35 and the front external housing 31 is laser welded over the entire periphery.

[0023] It should be noted that each of the above-mentioned welded portions does not necessarily have to be formed over the entire circumference, and may be formed by spot welding in which a plurality of laser spots are formed.

[0024] [Detection mechanism configuration] The detection mechanism 40 can be broadly divided into a pressure detection section consisting of a piezoelectric element 41, a tip electrode member 42, a rear electrode member 43, an insulating member 44, and a coil spring 45, and a signal processing section consisting of a circuit-embedded member 46, a connecting member 47, and a blocking member 48.

[0025] [Piezoelectric element] The piezoelectric element 41 is a member having a cylindrical shape as a whole. The piezoelectric element 41 includes a piezoelectric body that exhibits a piezoelectric action of the piezoelectric longitudinal effect. The piezoelectric element 41 is disposed inside the tip external housing 31 (and the first housing 33).

[0026] Here, the piezoelectric longitudinal effect refers to the generation of electric charges on the surface of the piezoelectric body in the charge generation axis direction when an external force is applied to the stress application axis in the same direction as the charge generation axis of the piezoelectric body. Therefore, in this example, a signal due to the generated electric charges (charge signal: an example of an electric signal) is output on the front and rear end surfaces of the piezoelectric element 41 in response to the change in pressure along the center line direction.

[0027] Next, a case where the piezoelectric transverse effect is used in the piezoelectric element 41 will be illustrated. The piezoelectric transverse effect means that when an external force is applied to a stress application axis at a position perpendicular to the charge generation axis of the piezoelectric body, a charge is generated on the surface of the piezoelectric body in the charge generation axis direction. A plurality of thin piezoelectric bodies formed in a thin plate shape may be laminated, and by laminating them in this way, the charge generated in the piezoelectric body can be efficiently collected and the sensitivity of the sensor can be increased. Examples of piezoelectric bodies that can be used in the piezoelectric element 41 include Langasite-based crystals (Langasite, Langatate, Langanite, LTGA), quartz, and gallium phosphate, which have the piezoelectric longitudinal effect and the piezoelectric transverse effect. In addition, as the piezoelectric body used in the piezoelectric element 41, it is preferable to use a single crystal (inorganic single crystal) made of the above-mentioned inorganic material, and it is particularly preferable to use a Langasite-based single crystal.

[0028] [Tip electrode material] The tip electrode member 42 is a member having a cylindrical shape as a whole. The tip electrode member 42 is made of a metal material such as stainless steel that has electrical conductivity and high heat resistance. The tip electrode member 42 is disposed inside the tip external housing 31 (and the first housing 33) and on the tip side of the piezoelectric element 41, so that the rear end surface of the tip electrode member 42 comes into contact with the tip side surface of the piezoelectric element 41. In addition, the tip side surface of the tip electrode member 42 comes into contact with the rear end surface of the protrusion 32a of the diaphragm head 32. The outer diameter of the tip electrode member 42 is larger than the outer diameter of the piezoelectric element 41.

[0029] [Rear electrode part] The rear electrode member 43 is a member that has a top shape as a whole. More specifically, the rear electrode member 43 has a T-shaped cross section, and has a front end portion with a large outer diameter and a rear end portion with an outer diameter smaller than that of the front end portion. The rear electrode member 43 is made of a metal material such as stainless steel that has electrical conductivity and high heat resistance. The rear electrode member 43 is disposed inside the front external housing 31 (and the first housing 33), and the front end surface of the front end portion of the rear electrode member 43 is in contact with the rear end surface of the piezoelectric element 41. In addition, the outer diameter of the front end portion of the rear electrode member 43 is slightly larger than the outer diameter of the piezoelectric element 41, and the outer diameter of the rear end portion of the rear electrode member 43 is smaller than the outer diameter of the piezoelectric element 41.

[0030] [Insulating material] The insulating member 44 is a member having a hollow structure and exhibiting an annular (cylindrical) shape as a whole. The insulating member 44 is made of a ceramic material such as alumina, which has insulating properties and high heat resistance. The insulating member 44 is disposed inside the tip external housing 31 (and the first housing 33) and on the rear end side of the rear electrode member 43, so that the tip side surface of the insulating member 44 contacts the rear end side surface of the tip part of the rear electrode member 43. In addition, the rear end part of the rear electrode member 43 is inserted into the through hole provided in the insulating member 44. Furthermore, the rear end side surface of the insulating member 44 contacts the step part 33e of the first housing 33. As a result, the tip electrode member 42, the piezoelectric element 41, the rear electrode member 43 and the insulating member 44 are sandwiched and fixed between the diaphragm head 32 and the first housing 33 via the first housing 33. At this time, it is desirable that a gap exists between the outer peripheral surfaces of the front electrode member 42 , the piezoelectric element 41 , the rear electrode member 43 and the insulating member 44 and the inner peripheral surface of the first housing 33 .

[0031] [Elastic member] The elastic member 90 is a member for applying a certain stress to the piezoelectric element 41. The piezoelectric element 41 needs to be kept in a state where a predetermined load (preload) is applied in order to increase its sensitivity and linearity, and by incorporating this elastic member 90, a state where the action of the preload is maintained is realized. FIG. 5 shows the elastic member, (a) being a plan view, and (b) being an AA cross-sectional view of (a). The elastic member 90 is a member having a circular dish shape as a whole, and has a concave portion consisting of a bottom 90a having a flat surface and a side wall 90b standing vertically from the bottom 90a, and a flange 90c extending outward from the side wall 90b with a surface parallel to the bottom 90a. In addition, an opening 90d is provided in the center of the bottom 90a of the elastic member 90. The elastic member 90 is made of a metal material such as copper, stainless steel, or aluminum. Here, the elastic member 90 has elasticity against a force acting in a direction perpendicular to the flat surface of the bottom 90a. In this embodiment, the elastic force of the elastic member 90 is determined only by the Young's modulus of the side wall 90b, but a desired elastic modulus may be structurally obtained by, for example, inclining the side wall 90b with respect to the direction of the acting force.

[0032] The elastic member 90 is arranged in a layered manner in the first housing 33 together with the piezoelectric element 41, the front electrode member 42, the rear electrode member 43, and the insulating member 44, and constitutes one of the internal components of the first housing 33. Here, the elastic member 90 is arranged such that the rear end side surface (the side from which the side wall portion 90b extends) of the flange portion 90c abuts on the front end side surface of the visor portion 33a of the first housing 33. Also, the diaphragm head 32 abuts on the front end side surface of the flange portion 90c. The elastic member 90 is fixed to the first housing 33 and the diaphragm head 32 by laser welding over the entire periphery of the boundary portions between the elastic member 90 and the first housing 33 and the diaphragm head 32.

[0033] By providing the elastic member 90 with the flange 90c and clamping and fixing the flange 90c between the diaphragm head 32 and the first housing 33 in this manner, it is possible to increase the reliability of the fixing of the elastic member 90 compared to a case in which the elastic member 90 is disposed between the diaphragm head 90 and the pressure detection unit and fixed between them by only the elastic force. As a result, it is possible to reduce wear between the elastic member 90 and the member with which it comes into contact, which is caused by slight movement of the elastic member 90, etc.

[0034] The elastic member 90 is arranged in the pressure detection device 20 by arranging the insulating member 44 inside the first housing 33, and then accommodating the rear end electrode member 43, the piezoelectric element 41, and the tip electrode member 42. More specifically, the insulating member 44 is arranged so that the rear end side of the insulating member 44 abuts against the tip side of the step portion 33e inside the body portion 33b of the first housing 33, and the rear end electrode member 43, the piezoelectric element 41, and the tip electrode member 42 are arranged on the insulating member 44. Next, the elastic member 90 is arranged on the tip electrode member 42 and pressed in the axial direction of the first housing 33, so that a certain stress is applied to the elastic member 90 together with each of the laminated members, and the elastic member 90 is fixed to the first housing 33 in a compressed state. The compressed elastic member 90 applies a certain stress (predetermined load) to the piezoelectric element 41 by the action of its elastic force, and a state in which a certain preload is applied is maintained.

[0035] Here, the relationship between the elastic member 90 and the diaphragm head 32 will be described. As shown in FIG. 4, the elastic member 90 is disposed such that the rear end surface of the bottom portion 90a having the opening 90d abuts against the tip electrode member 42, and the tip end surface of the flange portion 90c abuts against the diaphragm head 32. The protruding portion 32a of the diaphragm head 32 is inserted into the opening 90d and directly abuts against the tip end surface of the tip electrode member 42. For this reason, the opening diameter of the opening 90d is formed to a size that allows the outer diameter of the protruding portion 32a to be inserted and allows the protruding portion 32a to slide relative to the opening 90d. In this embodiment, the protruding portion 32a of the diaphragm head 32 is clearance-fitted into the opening 90b of the elastic member 90. More specifically, the gap between the opening diameter of the opening 90b of the elastic member 90 and the outer diameter of the protruding portion 32a protruding from the diaphragm head 32 is set to a small value of 0.02 mm to 0.07 mm. As a result, when the diaphragm head 32 receives pressure from the outside, the movement of the protruding portion 32a of the diaphragm head 32 in a direction perpendicular to the center line direction is restricted by the opening 90d of the elastic member 90. Therefore, it is possible to suppress the force acting on the piezoelectric element 41 in a direction perpendicular to the center line direction, and it is possible to measure pressure with high reliability in the pressure detection device 20. Furthermore, in particular, in the piezoelectric element 41 made of a single crystal, there is a concern that the piezoelectric element 41 may be destroyed when pressure other than perpendicular is applied to the pressure receiving surface of the piezoelectric element 41 due to the anisotropy of the compressive strength due to the crystal axis direction, but it is also possible to suppress the destruction of the piezoelectric element 41.

[0036] The elastic member 90 can be formed, for example, by a press working method. A variety of characteristics, such as spring characteristics and hardness, can be obtained by selecting the material, plate thickness, and hardening conditions of the elastic member 90 and by setting the processing conditions. For example, by forming the elastic member 90 by a press working method using a transfer die, the elastic member 90 can be formed in a large quantity with high precision and high speed in a shape that is difficult to obtain by a cutting method. In addition, the press working method forms grain flows that follow the shape of the material of the elastic member 90, so that a high-strength elastic member 90 can be obtained. Furthermore, since high-strength and thinner parts can be connected to each other by welding, it is easy to form a complex shape that corresponds to the application of the pressure detection device 40.

[0037] [Coil spring] The coil spring 45 is a member having a helical shape as a whole, and expands and contracts in the direction of the center line. The coil spring 45 is made of a metal material such as phosphor bronze having electrical conductivity. The coil spring 45 is disposed inside the front external housing 31 (first housing 33) and straddles the inside of the insulating member 44. Therefore, the outer diameter of the coil spring 45 is smaller than the inner diameter of the through hole provided in the insulating member 44. The front end side of the coil spring 45 contacts the surface of the rear end side of the rear electrode member 43 inside the insulating member 44.

[0038] [Circuit-embedded components] The circuit-embedded member 46 includes a circuit board 50 that processes an electric signal generated by a weak charge output by the piezoelectric element 41, and a sealing portion 60 that houses the circuit board 50 and seals the circuit board 50. The circuit-embedded member 46 further includes an input signal electrode 71, an input ground electrode 72, a power-receiving electrode 73, an output signal electrode 74, and an output ground electrode 75 that are electrically connected to the circuit board 50. Here, the input signal electrode 71 is provided on the leading end side of the circuit board 50, and the input ground electrode 72, the power-receiving electrode 73, the output signal electrode 74, and the output ground electrode 75 are provided on the rear end side of the circuit board 50. Each of the input signal electrode 71 to the output ground electrode 75 has one end sealed in the sealing portion 60 and connected to the circuit board 50, while the other end is exposed to the outside without being covered by the sealing portion 60. The input signal electrode 71 to the output ground electrode 75 are each made of a plate-shaped metal material having electrical conductivity.

[0039] The input signal electrode 71 has a base 711 extending along the center line direction and connected to the circuit board 50, and a protruding portion 712 protruding from the tip side of the base 711. Here, the width of the protruding portion 712 (the length in the direction intersecting the center line direction) is narrower than the width of the base 711 and smaller than the inner diameter of the coil spring 45. The input signal electrode 71 has the entire protruding portion 712 and the tip side of the base 711 exposed without being covered by the sealing portion 60. This portion is inserted inside the first housing 33, and the rear end side of the coil spring 45 is wound around the protruding portion 712.

[0040] [Connection parts] The connection member 47 is a columnar member as a whole. The connection member 47 includes a base material made of an insulating synthetic resin material such as PPS or PPT, and wiring and terminals made of a conductive metal material such as copper. The connection member 47 is disposed inside the rear end external housing 35. The rear end side of the circuit-containing member 46 faces the front end side of the connection member 47, and the rear ends of the power receiving electrode 73, the output signal electrode 74, and the output ground electrode 75 provided on the circuit-containing member 46 are inserted into the front end side of the connection member 47.

[0041] [Blocking material] The blocking member 48 is a member having a columnar shape as a whole. However, the blocking member 48 has three through holes formed along the center line direction. The blocking member 48 is made of an insulating rubber material. The tip side of the blocking member 48 is disposed inside the rear end external housing 35, and the rear end side protrudes outward from the rear end of the rear end external housing 35. The tip side of the blocking member 48 faces the rear end side of the connection member 47. In addition, each electric wire (described in detail later) constituting the connection cable 80 is inserted into the three through holes provided in the blocking member 48. The outer diameter of the blocking member 48 is slightly larger than the inner diameter of the rear end side (second inner diameter portion 35g) of the rear end external housing 35, and the rear end external housing 35 and the blocking member 48 are integrated by press-fitting (tight fit).

[0042] [Connection cable configuration] The connection cable 80 includes a twisted power line 81, a signal line 82, and a ground line 83, a covering member 84 that covers the outer circumference of the power line 81, the signal line 82, and the ground line 83, and an inclusion 85 that fills the gap between the power line 81, the signal line 82, the ground line 83, and the covering member 84. The power line 81 is connected to the power receiving electrode 73, the signal line 82 to the output signal electrode 74, and the ground line 83 to the output ground electrode 75, via the connection member 47. Here, the power line 81, the signal line 82, and the ground line 83 each have a conductor portion made of tin-plated soft copper twisted wire, and an insulating portion made of polyethylene (cross-linked polyethylene) or the like whose cross-linked structure is reinforced by an electron beam or the like and that covers and insulates the outer circumference of the conductor portion. The covering member is made of an insulating rubber material or resin material. If necessary, the connection cable 80 may be provided with shields for shielding the power line 81, the signal line 82, and the ground line 83.

[0043] [Pressure detection operation by pressure detection device] Next, the pressure detection operation by the pressure detection device 20 will be described. When the internal combustion engine 10 is operating, the pressure (combustion pressure) generated in the combustion chamber C is applied to the pressure receiving surface 32b of the diaphragm head 32. In the diaphragm head 32, the pressure received by the pressure receiving surface 32b is transmitted to the front electrode member 42 via the protruding portion 32a. Then, the pressure transmitted to the front electrode member 42 acts on the piezoelectric element 41 sandwiched between the front electrode member 42 and the rear electrode member 43, and an electric charge corresponding to the received pressure is generated in the piezoelectric element 41. The electric charge signal generated in the piezoelectric element 41 is supplied as an electric charge signal to the circuit board 50 via the rear electrode member 43, the coil spring 44, and the input signal electrode 71. The electric charge signal supplied to the circuit board 50 is subjected to various processes in the processing circuit mounted on the circuit board 50 to become an output signal. Then, the output signal output from the output signal electrode 74 of the circuit board 50 is transmitted to the control device 100 via the connection member 47 and the connection cable 80, and is used for controlling the internal combustion engine 10. During this time, the processing circuit mounted on the circuit board 50 is supplied with a power supply voltage from the control device 100 via the power receiving electrode 73 and the input ground electrode 72. [Explanation of symbols]

[0044] 1...pressure detection system, 10...internal combustion engine, 20...pressure detection device, 30...housing portion, 31...front external housing, 32...diaphragm head, 33...first housing, 35...rear external housing, 40...detection mechanism portion, 41...piezoelectric element, 42...front electrode member, 43...rear electrode member, 44...insulating member, 45...coil spring, 46...circuit-embedded member, 47...connecting member, 48...blocking member, 50...circuit board, 71...input signal electrode, 72...input ground electrode, 73...power receiving electrode, 74...output signal electrode, 75...output ground electrode, 80...connecting cable, 81...power line, 82...signal line, 83...ground line, 84...covering member, 90...elastic member, 100...control device

Claims

1. A pressure detection device including a housing having a pressure receiving portion that receives pressure from the outside, and a pressure detection portion that is accommodated inside the housing and outputs an electrical signal corresponding to the pressure received by the pressure receiving portion, the pressure receiving portion has a pressure receiving surface that receives the pressure, and a transmission portion that abuts against the pressure detection portion and transmits the pressure received at the pressure receiving surface to the pressure detection portion, an elastic member having a through hole is disposed between the pressure detection unit and the housing; The transmission portion is slidably inserted into the through hole. A pressure detection device comprising:

2. 2. The pressure detection device according to claim 1, wherein the transmission portion is clearance-fitted into the through hole.

3. 3. The pressure detection device according to claim 2, wherein the transmission portion and the through hole have a slight fit with a fit tolerance of 0.02 mm to 0.07 mm.

4. 3. The pressure detection device according to claim 1, wherein the elastic member is produced by pressing.

5. the elastic member has a bottom portion in which the through hole is provided, an elastic portion connected to the bottom portion, and a flange portion connected to the elastic portion, the housing includes a pressure receiving member including the pressure receiving portion and a housing member that houses the pressure detection portion, 3. The pressure detection device according to claim 1, wherein the elastic member is fixed to the housing by sandwiching the flange between the pressure-receiving member and the housing member.

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