Pressure detection device

Abstract

To suppress accuracy deterioration in detection of a detection target signal by reducing vibration of a pressure sensing device at a frequency close to a frequency of the signal based on changes in pressure to be sensed.SOLUTION: A pressure sensing device is provided, comprising a piezoelectric element 41 for sensing changes in pressure, a conducting member 47 for transmitting an electrical signal from the piezoelectric element 41, a cylindrical tip outer housing 31 for accommodating the conducting member 47 therein, and a swaged portion P formed by applying pressure from a side of the tip outer housing 31 to the conducting member 47 to serve as vibration suppression means for suppressing vibration of the conducting member 47 at a specific frequency.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a pressure detection device.

Background Art

[0002] As a pressure detection device for detecting the pressure in a combustion chamber of an internal combustion engine or the like, a device using a detection element such as a piezoelectric element has been proposed.

[0003] Patent Document 1 describes a pressure detection device including a piezoelectric element, a conductive member that conducts an electrical signal from the piezoelectric element, a cylindrical first housing member that houses the conductive member inside, and a conductive and cylindrical second housing member that covers the conductive member and the first housing member.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When an impact is applied to the pressure detection device from the outside, vibrations such as natural frequencies corresponding to, for example, the axial length may occur in the conductive member and the housing member. When these vibrations are transmitted to the piezoelectric element, noise corresponding to the vibrations occurs in the output of the piezoelectric element. And when the frequency of the signal based on the pressure change to be detected by the pressure detection device is close to this natural frequency, there is a possibility of causing a decrease in the detection accuracy of the signal based on the pressure change to be detected.

[0006] An object of the present invention is to suppress a decrease in the detection accuracy of a signal to be detected by reducing vibrations of the pressure detection device caused by a frequency close to the frequency of the signal based on the pressure change to be detected.

Means for Solving the Problems

[0007] The pressure detection device of the present invention for achieving the above object includes a detection element that detects a change in pressure, a conductive member that conducts an electrical signal from the detection element, a cylindrical housing that houses the conductive member therein, and vibration suppression means that is formed by applying pressure to the conductive member from the housing side and suppresses vibration of the conductive member at a specific frequency. Here, the vibration suppression means may be means for adjusting the natural frequency of the conductive member to a value outside a predetermined frequency range. Further, the housing may be configured to include a cylindrical first housing that houses the conductive member therein, and a cylindrical second housing that houses the conductive member and the first housing therein. Further, the housing may be configured to further include a cylindrical third housing that houses the conductive member, the first housing, and the second housing therein. Further, at least a part between the conductive member and the housing may be filled with a filler. Also, the vibration suppression means may be means for fixing the conductive member and the housing at a specific position in the axial direction. Also, the vibration suppression means may be a caulked portion formed by caulking from the outside of the housing. From another perspective, the pressure detection device of the present invention includes a detection element that detects a change in pressure, a conductive member that conducts an electrical signal from the detection element, and a cylindrical housing that houses the conductive member therein, and has a caulked portion that caulks the housing and the conductive member. Here, a member having insulating properties may be interposed between the housing and the conductive member in the caulked portion, and the housing and the conductive member may be insulated. Further, the caulked portion may be formed by a force directed toward the center of a cross section substantially perpendicular to the axis at a specific position in the axial direction of the housing and the conductive member, and the housing and the conductive member may be caulked from a plurality of directions of the cross section.

Advantages of the Invention

[0008] According to the present invention, it is possible to reduce the vibration of the pressure detection device at a frequency close to the frequency of the signal based on the pressure change to be detected, and suppress a decrease in the detection accuracy of the signal to be detected.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. [Configuration of Pressure Detection System] 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 in 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 90 that electrically connects the pressure detection device 20 and the control device 100.

[0011] Here, the internal combustion engine 10 for which pressure is to be detected includes a cylinder block 11 having a cylinder formed therein, a piston 12 that reciprocates within the cylinder, and a cylinder head 13 fastened to the cylinder block 11 and configured to form a combustion chamber C together with the piston 12 and the like. Further, a communication hole 13a that communicates the combustion chamber C with the outside is provided in the cylinder head 13. Then, the tip side of the pressure detection device 20 is inserted into this communication hole 13a, and the pressure detection device 20 is fixed to the cylinder head 13, thereby attaching the pressure detection device 20 to the internal combustion engine 10. Here, the cylinder block 11, the piston 12, and the cylinder head 13 that constitute the internal combustion engine 10 are made of a conductive metal material such as cast iron or aluminum.

[0012] [Configuration of Pressure Detection Device] FIG. 2 is a side view of the pressure detection device 20. Further, FIG. 3 is a cross-sectional view taken along line III-III of the pressure detection device 20 shown in FIG. 2. Furthermore, FIG. 4 is an enlarged cross-sectional view of region IV of the pressure detection device 20 shown in FIG. 3. Note that FIG. 4 also shows the main part of the cylinder head 13 to which the pressure detection device 20 is to be attached.

[0013] The pressure detection device 20 has a housing portion 30 that is cylindrical as a whole and is provided to be exposed to the outside, a detection mechanism portion 40 that includes various mechanisms for detecting pressure, is almost entirely housed inside the housing portion 30, and is provided so that a part thereof is exposed to the outside, a seal portion 70 attached to the outer peripheral surface of the housing portion 30, and a buffer member 80 attached to one end side of the housing portion 30 (the left side of the housing portion 30 in FIG. 2). The pressure detection device 20 is attached to the internal combustion engine 10 shown in FIG. 1 such that the left side (the buffer member 80 side) in FIG. 2 faces the combustion chamber C (the lower side in FIG. 1) and the right side (the connection cable 90 side) in FIG. 2 faces the outside (the upper side in FIG. 1). In the following description, in FIG. 2, the side facing left in the figure is referred to as the "tip side" of the pressure detection device 20, and the side facing right in the figure is referred to as the "rear end side" of the pressure detection device 20. Also, in the following description, the center line direction of the pressure detection device 20 indicated by a one-dot chain line in FIG. 2 and the like is simply referred to as the "center line direction". Here, in the present embodiment, the "tip side" corresponds to the "one end side", and the "rear end side" corresponds to the "other end side".

[0014] (Configuration of the housing portion) The housing portion 30 as an example of the body portion includes a tip external housing 31, a diaphragm head 32 attached to the tip side of the tip external housing 31, an intermediate external housing 33 attached to the rear end side of the tip external housing 31, and a rear end external housing 34 attached to the rear end side of the intermediate external housing 33. The housing portion 30 further includes a first internal housing 35 attached inside the tip external housing 31 and on the rear end side of the diaphragm head 32, and a second internal housing 36 attached inside the tip external housing 31 and on the rear end side of the first internal housing 35.

[0015] 〔Tip external housing〕 The tip outer housing 31 is a member having a hollow structure and presenting a cylindrical shape as a whole. The tip outer housing 31 is an example of a housing and an example of a third housing. The tip outer housing 31 is made of a metallic material such as stainless steel that has conductivity and high heat resistance and acid resistance. Examples of such a metallic material include SUS630 known as a precipitation hardening type stainless steel and SUH660 known as an austenitic heat resistant steel (heat resistant alloy). However, various other metals or various alloys (various stainless steels, various heat resistant steels or various heat resistant alloys) etc. can be adopted as long as they satisfy the required characteristics. Also, as shown in FIG. 2, a caulking portion P is formed at an appropriate position in the middle of the center line direction on the tip outer housing 31.

[0016] 〔Diaphragm Head〕 The diaphragm head 32 as an example of a pressure receiving portion is a member presenting a disc shape as a whole. The diaphragm head 32 is made of a metallic material such as stainless steel that has conductivity and high heat resistance and acid resistance. Examples of such a metallic material include SUS630 known as a precipitation hardening type stainless steel and SUH660 known as an austenitic heat resistant steel (heat resistant alloy). However, various other metals or various alloys (various stainless steels, various heat resistant steels or various heat resistant alloys etc.) can be adopted as long as they satisfy the required characteristics. In this example, the diaphragm head 32 is made of the same material (for example, SUS630) as the tip outer housing 31.

[0017] As shown particularly in FIG. 4, the diaphragm head 32 has a pressure receiving surface (front surface) 32a that is formed with a central recess 32b in the central part on the tip side and receives pressure by being exposed to the outside (combustion chamber C side). Further, the diaphragm head 32 has a rear surface annular recess 32c formed by annularly notching the rear surface on the back side of the pressure receiving surface 32a, and as a result of the existence of the rear surface annular recess 32c, a rear surface central protrusion 32d that protrudes from the central part of the pressure receiving surface 32a (the formation site of the front surface central recess 32b) toward the rear end side. Furthermore, the diaphragm head 32 has a rear surface annular flat part 32e formed by annularly notching the peripheral part on the rear surface of the pressure receiving surface 32a, and as a result of the existence of the rear surface annular recess 32c and the rear surface annular flat part 32e, a rear surface annular protrusion 32f that protrudes from around the rear surface central protrusion 32d toward the rear end side. Moreover, as a result of providing the concave pressure receiving surface 32a, the diaphragm head 32 has a front surface annular protrusion 32g that protrudes from the entire peripheral edge of the pressure receiving surface 32a toward the tip side. This front surface annular protrusion 32g is located on the opposite side (front side) of the rear surface annular flat part 32e. Incidentally, from another perspective, the tip side of the diaphragm head 32 can be regarded as having a front surface annular protrusion 32g and a pressure receiving surface 32a formed by notching the central part thereof in a circular shape, and a front surface central recess 32b formed by further notching the central part of the pressure receiving surface 32a.

[0018] The diaphragm head 32 is provided so as to close the opening on the tip side of the tip outer housing 31. More specifically, the tip side of the tip outer housing 31 abuts against the rear surface annular flat part 32e of the diaphragm head 32. And laser welding is performed over the entire circumference of the outer peripheral surface at the boundary between the diaphragm head 32 and the tip outer housing 31.

[0019] Here, in the diaphragm head 32 of the present embodiment, the periphery of the thinnest rear surface annular recess 32c expands and contracts in response to an external force, so that it functions as a spring. And the diaphragm head 32 vibrates in accordance with the pressure (external pressure) received from the combustion chamber C or the like.

[0020] 〔Intermediate outer housing〕 The intermediate outer housing 33 is a member having a hollow structure and presenting a cylindrical shape as a whole. The intermediate outer housing 33 is made of a metallic material such as stainless steel that has conductivity and high heat resistance and acid resistance. As such a metallic material, for example, SUS430LX known as ferritic stainless steel can be exemplified. However, as long as the required properties are satisfied, various other metals or various alloys (various stainless steels, various heat-resistant steels, or various heat-resistant alloys) can be adopted. In this example, the intermediate outer housing 33 is made of a material (for example, SUS430LX) different from that of the tip outer housing 31.

[0021] The tip side of the intermediate outer housing 33 is fitted into the rear end side of the tip outer housing 31. And laser welding is performed over the entire circumference of the outer peripheral surface at the boundary between the intermediate outer housing 33 and the tip outer housing 31.

[0022] 〔Rear end outer housing〕 The rear end outer housing 34 is a member having a hollow structure and presenting a cylindrical shape as a whole. The rear end outer housing 34 is made of a metallic material such as stainless steel that has conductivity and high heat resistance and acid resistance. As such a metallic material, for example, SUS430LX known as ferritic stainless steel can be exemplified. However, as long as the required properties are satisfied, various other metals or various alloys (various stainless steels, various heat-resistant steels, or various heat-resistant alloys, etc.) can be adopted. In this example, the rear end outer housing 34 is made of the same material (for example, SUS430LX) as that of the intermediate outer housing 33.

[0023] The tip side of the rear end outer housing 34 is fitted into the rear end side of the intermediate outer housing 33. And laser welding is performed over the entire circumference of the outer peripheral surface at the boundary between the rear end outer housing 34 and the intermediate outer housing 33.

[0024] 〔First inner housing〕 The first inner housing 35 is a member having a hollow structure and presenting a cylindrical shape as a whole. The first inner housing 35 is made of a metal material such as stainless steel that has conductivity and high heat resistance and acid resistance. Examples of such metal materials include SUS630 known as a precipitation hardening type stainless steel and SUH660 known as an austenitic heat-resistant steel (heat-resistant alloy). However, various other metals or various alloys (various stainless steels, various heat-resistant steels, or various heat-resistant alloys, etc.) can be adopted as long as they satisfy the required properties. In this example, the first inner housing 35 is made of the same material (for example, SUS630) as the diaphragm head 32. Also, the first inner housing 35 and the diaphragm head 32 may be made of different materials.

[0025] The tip side of the first inner housing 35 abuts against the rear end side of the diaphragm head 32. More specifically, the surface located on the tip side of the first inner housing 35 abuts against the surface on the rear end side of the rear surface annular convex portion 32f of the diaphragm head 32. At this time, a partial region on the tip side of the first inner housing 35 is located inside the rear surface annular concave portion 32c of the diaphragm head 32. And at the boundary portion between the first inner housing 35 and the diaphragm head 32, laser welding is performed over the entire circumference of the outer peripheral surface.

[0026] 〔Second Inner Housing〕 The second inner housing 36 is a member having a hollow structure and presenting a cylindrical shape as a whole. The second inner housing 36 is made of a metal material such as stainless steel that has conductivity and high heat resistance and acid resistance. Examples of such metal materials include SUS630 known as a precipitation hardening type stainless steel and SUH660 known as an austenitic heat-resistant steel (heat-resistant alloy). However, various other metals or various alloys (various stainless steels, various heat-resistant steels, or various heat-resistant alloys, etc.) can be adopted as long as they satisfy the required properties. In this example, the second inner housing 36 is made of the same material (for example, SUS630) as the first inner housing 35.

[0027] The tip side of the second inner housing 36 is configured to be housed inside the rear end side of the first inner housing 35. Further, the surface on the tip side of the second inner housing 36 abuts against the surface on the rear end side of the second insulating member 52 (details will be described later). At this time, the rear end side of the second inner housing 36 is exposed to the rear end side of the first inner housing 35. And, laser welding is performed over the entire circumference of the outer peripheral surface at the boundary between the second inner housing 36 and the first inner housing 35.

[0028] (Configuration of the detection mechanism section) The detection mechanism section 40 includes a piezoelectric element 41, a tip electrode member 42, a tip insulating member 43, a rear end electrode member 44, and a rear end insulating member 45. Further, the detection mechanism section 40 includes a first coil spring 46, a conductive member 47, a holding member 48, a pressing member 49, and an insulating tube 50. Furthermore, the detection mechanism section 40 includes a first insulating member 51, a second insulating member 52, a support member 53, and a second coil spring 54. Furthermore, the detection mechanism section 40 includes a first housing member 55, a pressing member 551, a second housing member 56, a circuit built-in member 57, a connecting member 58, a closing member 59, and a third insulating member 60.

[0029] [Piezoelectric element] The piezoelectric element 41 is a member having a generally cylindrical shape as a whole. The piezoelectric element 41 includes a piezoelectric body that exhibits a piezoelectric action of the longitudinal piezoelectric effect. The piezoelectric element 41 is disposed inside the tip outer housing 31 (and the first inner housing 35). The piezoelectric element 41 is an example of a detection element.

[0030] Here, the longitudinal piezoelectric effect means that when an external force is applied to the stress application axis in the same direction as the charge generation axis of the piezoelectric body, charges are generated on the surface of the piezoelectric body in the direction of the charge generation axis. Therefore, in this example, in response to a change in pressure along the center line direction, signals (charge signals) due to the generated charges are output to the surface on the tip side and the surface on the rear end side of the piezoelectric element 41.

[0031] Next, the case where the transverse piezoelectric effect is utilized in the piezoelectric element 41 will be exemplified. The transverse piezoelectric effect means that when an external force is applied to the stress application axis located at a position orthogonal to the charge generation axis of the piezoelectric body, charges are generated on the surface of the piezoelectric body in the direction of the charge generation axis. A plurality of piezoelectric bodies thinly formed in a thin plate shape may be laminated, and by laminating in this way, the charges generated in the piezoelectric body can be efficiently collected to increase the sensitivity of the sensor. 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 both the longitudinal piezoelectric effect and the transverse piezoelectric effect. Further, as the piezoelectric body used in the piezoelectric element 41, it is preferable to use a single crystal (inorganic single crystal) composed of the above-described inorganic material, and particularly preferably a langasite-based single crystal.

[0032] 〔Tip electrode member〕 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 conductivity and high heat resistance. Examples of such a metal material include SUS630 known as a precipitation hardening type stainless steel and SUH660 known as an austenitic heat resistant steel (heat resistant alloy). However, as long as the required characteristics are satisfied, various other metals or various alloys (various stainless steels, various heat resistant steels, or various heat resistant alloys, etc.) can be adopted. In this example, the tip electrode member 42 is made of the same material (for example, SUS630) as the diaphragm head 32. The tip electrode member 42 is disposed inside the tip outer housing 31 and on the tip side of the piezoelectric element 41, and the surface on the rear end side of the tip electrode member 42 is in contact with the surface on the tip side of the piezoelectric element 41. In this example, the tip side surface, the rear end side surface, and the outer peripheral surface of the tip electrode member 42 are not particularly plated with gold or the like, and the base metal of the metal material constituting the tip electrode material is exposed as it is.

[0033] 〔Tip insulating member〕 The tip insulating member 43 is a member having a cylindrical shape as a whole. The tip insulating member 43 is made of a ceramic material such as alumina that has insulating properties and high heat resistance. The tip insulating member 43 is disposed inside the tip outer housing 31 and on the tip side of the tip electrode member 42, and the surface on the rear end side of the tip insulating member 43 is in contact with the surface on the tip side of the tip electrode member 42. On the other hand, the surface on the tip side of the tip insulating member 43 is in contact with the surface on the rear end side of the central convex portion 32d provided on the diaphragm head 32.

[0034] 〔Rear-end electrode member〕 The rear-end electrode member 44 is a member having a cylindrical shape as a whole. The rear-end electrode member 44 is made of a metal material such as stainless steel that has conductivity and high heat resistance. Examples of such a metal material include SUS630 known as a precipitation-hardening type stainless steel and SUH660 known as an austenitic heat-resistant steel (heat-resistant alloy). However, as long as the required characteristics are satisfied, various other metals or various alloys (various stainless steels, various heat-resistant steels, or various heat-resistant alloys, etc.) can be adopted. In this example, the rear-end electrode member 44 is made of the same material (for example, SUS630) as the tip electrode member 42. The rear-end electrode member 44 is disposed inside the tip outer housing 31 and on the rear end side of the piezoelectric element 41, and the surface on the tip side of the rear-end electrode member 44 is in contact with the surface on the rear end side of the piezoelectric element 41. In this example, the rear end side surface and the outer peripheral surface of the rear-end electrode member 44 are gold-plated. On the other hand, the surface on the tip side of the rear-end electrode member 44, that is, the surface in contact with the rear end side of the piezoelectric element 41, is not particularly gold-plated or the like, and the base metal of the metal material constituting the rear-end electrode member 44 is exposed as it is.

[0035] 〔Rear-end insulating member〕 The rear-end insulating member 45 is a member having a hollow structure and presenting an annular (cylindrical) shape as a whole. The rear-end insulating member 45 is made of a ceramic material such as alumina that has insulation properties and high heat resistance. The rear-end insulating member 45 is disposed inside the tip external housing 31 and on the rear-end side of the rear-end electrode member 44, and the surface on the tip side of the rear-end insulating member 45 is in contact with the surface on the rear-end side of the rear-end electrode member 44. In this example, the rear-end insulating member 45 is made of the same material (for example, alumina ceramics) as the tip insulating member 43.

[0036] 〔First Coil Spring〕 The first coil spring 46 is a member presenting a spiral shape as a whole and is configured to expand and contract in the center line direction. The first coil spring 46 is made of a metal material such as phosphor bronze that has conductivity and high heat resistance, and its surface is gold-plated. The first coil spring 46 is disposed inside the tip external housing 31. More specifically, the tip side of the first coil spring 46 is disposed inside the through-hole provided in the rear-end insulating member 45, and its tip is in contact with the surface on the rear-end side of the rear-end electrode member 44. On the other hand, the rear-end side of the first coil spring 46 protrudes beyond the rear-end side of the rear-end insulating member 45. A coil spring having a relatively large spring constant is used for the first coil spring 46. More specifically, the first coil spring 46 has a firmness such that the vibration of the conductive member 47 inserted into the rear-end side as described later is transmitted to the rear-end electrode member 44 located on the tip side.

[0037] 〔Conductive Member〕 The conductive member 47 is a rod-shaped member as a whole. The conductive member 47 is made of a metal material such as brass having electrical conductivity, and its surface is gold-plated. The conductive member 47 has a tip rod-shaped portion 471 located at the most tip side, an intermediate rod-shaped portion 472 located at the rear end side of the tip rod-shaped portion 471, and a rear rod-shaped portion 473 located at the rear end side of the intermediate rod-shaped portion 472. In the conductive member 47, the outer diameters of the tip rod-shaped portion 471, the intermediate rod-shaped portion 472, and the rear rod-shaped portion 473 increase in this order. The conductive member 47 is disposed inside the tip external housing 31. More specifically, the tip side of the conductive member 47, i.e., the tip side of the tip rod-shaped portion 471, is inserted into the rear end side of the first coil spring 46 and disposed inside the rear insulating member 45. However, unlike the first coil spring 46, the tip of the tip rod-shaped portion 471 does not contact the surface on the rear end side of the rear end electrode member 44. At this time, the rear end of the first coil spring 46 abuts against the boundary portion (step portion) between the tip rod-shaped portion 471 and the intermediate rod-shaped portion 472 of the conductive member 47. In this example, the first coil spring 46 and the conductive member 47 are joined and integrated by laser welding. Through the above procedure, the first coil spring 46 is sandwiched between the rear end electrode member 44 and the conductive member 47 and is compressed in the center line direction. Meanwhile, the intermediate rod-shaped portion 472 and the rear end rod-shaped portion 473 of the conductive member 47 protrude toward the rear end side of the rear end insulating member 45.

[0038] [Holding member] The holding member 48 is a member having a hollow structure and presenting a cylindrical shape as a whole. The holding member 48 is an example of a housing and an example of a first housing. The holding member 48 is made of a synthetic resin material such as insulating PPS (Polyphenylenesulfide) or PPT (Polypropylene Terephthalate). The holding member 48 has a tip portion located at the most distal end side, an intermediate portion located at the rear end side of the tip portion, and a rear end portion located at the rear end side of the intermediate portion. In the holding member 48, the outer diameter increases in the order of the tip portion, the intermediate portion, and the rear end portion. The holding member 48 is arranged to straddle the inside of the tip outer housing 31 and the inside of the intermediate outer housing 33. And, the above-mentioned conductive member 47 is accommodated and held inside the holding member 48. More specifically, the holding member 48 houses the rear end side of the conductive member 47, that is, the rear end side of the rear end rod-shaped portion 473, inside. By the above procedure, among the conductive member 47, the tip rod-shaped portion 471 and the intermediate rod-shaped portion 472, and the tip side of the rear end rod-shaped portion 473 protrude to the tip side of the holding member 48. On the other hand, a recess is formed at the rear end of the holding member 48, extending from the rear end side toward the tip side. Also, the conductive member 47 and the holding member 48 are integrated by press-fitting (snug fitting).

[0039] 〔Pressing Member〕 The pressing member 49 is a member having a hollow structure (through hole) and presenting a cylindrical shape as a whole. The pressing member 49 is made of a metal material such as stainless steel that has conductivity and high heat resistance. Examples of such a metal material include SUS630 known as a precipitation hardening type stainless steel and SUH660 known as an austenitic heat-resistant steel (heat-resistant alloy). However, as long as it satisfies the required characteristics, various other metals or various alloys (various stainless steels, various heat-resistant steels, or various heat-resistant alloys, etc.) can be adopted. In this example, the pressing member 49 is made of the same material (for example, SUS630) as the diaphragm head 32. The pressing member 49 is arranged inside the tip outer housing 31 and straddles the inside of the first inner housing 35 and the inside of the second inner housing 36.

[0040] Inside the through-hole provided in the pressing member 49, a piezoelectric element 41, a tip electrode member 42, a rear-end electrode member 44, a rear-end insulating member 45, a first coil spring 46, etc. are accommodated. And, the inner side on the tip side and the surface on the rear-end side of the through-hole provided in the pressing member 49 are in contact with the surface on the tip side of the tip electrode member 42. Further, a tip insulating member 43 is disposed at the opening on the tip side of the through-hole provided in the pressing member 49.

[0041] Here, the pressing member 49 of the present embodiment functions as a spring by the side portion on the tip side, which is the thinnest, expanding and contracting in response to an external force. And, the pressing member 49 applies a preload to the piezoelectric element 41 together with a support member 53 or the like.

[0042] 〔Insulating Tube〕 The insulating tube 50 is a member having a hollow structure with two openings provided along the center line direction and presenting a cylindrical shape as a whole. Further, the insulating tube 50 of the present embodiment is composed of a material having insulating properties. And, the insulating tube 50 of the present embodiment has a function of integrating (modularizing) these together with itself by accommodating and fixing the tip electrode member 42, the piezoelectric element 41, the rear-end electrode member 44, and the rear-end insulating member 45 inside itself while being in contact with them in order from the tip side.

[0043] Here, as the material constituting the insulating tube 50, various materials can be selected regardless of whether they are organic or inorganic as long as they have insulating properties, but from the viewpoint of facilitating modularization, it is desirable to use an organic material having heat shrinkability (for example, a synthetic resin material), that is, a heat shrinkable tube.

[0044] The insulating tube 50 is disposed inside the tip outer housing 31 and inside the pressing member 49. The surface on the tip side of the insulating tube 50 faces the inner side on the tip side and the surface on the rear end side of the through hole provided in the pressing member 49 with a gap therebetween. Inside the insulating tube 50, the rear end side of the tip electrode member 42, the piezoelectric element 41, the rear end electrode member 44, and the tip side of the rear end insulating member 45 are accommodated. In other words, the tip side of the tip electrode member 42 protrudes beyond the tip of the insulating tube 50, and the rear end side of the rear end insulating member 45 protrudes beyond the rear end of the insulating tube 50.

[0045] 〔First Insulating Member〕 The first insulating member 51 is a member having an overall annular shape. The first insulating member 51 is made of a ceramic material such as alumina that has insulating properties and high heat resistance. The first insulating member 51 is disposed inside the tip outer housing 31, inside the first inner housing 35, and outside the pressing member 49. The surface on the tip side of the first insulating member 51 contacts the surface on the rear end side of the stepped portion provided inside the first inner housing 35, and the surface on the rear end side of the first insulating member 51 contacts the surface on the tip side of the protrusion (rib) provided over the entire outer peripheral surface of the pressing member 49. In this example, the first insulating member 51 is made of the same material (for example, alumina ceramics) as the rear end insulating member 45.

[0046] 〔Second Insulating Member〕 The second insulating member 52 is a member that generally has an annular shape. Similar to the first insulating member 51, the second insulating member 52 is made of a ceramic material such as alumina that has insulation properties and high heat resistance. The second insulating member 52 is disposed inside the distal end outer housing 31, inside the first inner housing 35, and outside the pressurizing member 49. Also, the second insulating member 52 is disposed on the rear end side of the first insulating member 51. Then, the surface on the distal end side of the second insulating member 52 contacts the surface on the rear end side of the protrusions (ribs) provided over the entire circumference on the outer peripheral surface of the pressurizing member 49, and the surface on the rear end side of the second insulating member 52 contacts the surface on the distal end side of the second inner housing 36. In the present embodiment, the second insulating member 52 having the same dimensions as the first insulating member 51 is used. Also, in this example, the second insulating member 52 is made of the same material (for example, alumina ceramics) as the first insulating member 51.

[0047] 〔Supporting member〕 The support member 53 is a member having a hollow structure and generally presenting a cylindrical shape as a whole. The support member 53 is made of a metallic material such as stainless steel that has conductivity and high heat resistance. Examples of such metallic materials include SUS630 known as a precipitation-hardening type stainless steel, and SUH660 known as an austenitic heat-resistant steel (heat-resistant alloy). However, various other metals or various alloys (various stainless steels, various heat-resistant steels, or various heat-resistant alloys, etc.) can be adopted as long as they satisfy the required characteristics. In this example, the support member 53 is made of the same material (e.g., SUS630) as the pressurizing member 49. The support member 53 is inside the distal end outer housing 31, and its distal end side is disposed inside the pressurizing member 49. However, the rear end side of the support member 53 protrudes from the rear end of the pressurizing member 49. And the surface on the distal end side of the support member 53 is in contact with the surface on the rear end side of the rear end insulating member 45. Also, laser welding is performed over the entire outer peripheral surface at the boundary between the support member 53 and the pressurizing member 49. Inside the support member 53, the rear end side of the first coil spring 46 and the distal end sides of the conductive member 47 and the holding member 48 are accommodated. The inner diameter of the support member 53 is larger than the outer diameter of the holding member 48. For this reason, the inner peripheral surface of the support member 53 and the outer peripheral surface of the holding member 48 face each other with a gap therebetween and are not in direct contact.

[0048] 〔Second Coil Spring〕 The second coil spring 54 is a member having a spiral shape as a whole and is configured to expand and contract in the center line direction. The second coil spring 54 is made of a metal material such as phosphor bronze that has conductivity and high heat resistance, and its surface is gold-plated. In this example, the second coil spring 54 is made of the same material (for example, phosphor bronze) as the first coil spring 46. The second coil spring 54 is disposed inside the distal end outer housing 31. More specifically, the distal end side of the second coil spring 54 is disposed on the rear end side of the support member 53 and outside the outer peripheral surface, and its distal end is in contact with the surface on the rear end side of the pressing member 49. Inside the second coil spring 54, the conductive member 47, the holding member 48, the support member 53, and the distal end side of the first housing member 55 are disposed. A coil spring having a spring constant smaller than that of the first coil spring 46 is used for the second coil spring 54.

[0049] 〔First housing member〕 The first housing member 55 is a member having a hollow structure and presenting a cylindrical shape as a whole. The first housing member 55 is an example of a housing and an example of a second housing. The first housing member 55 is made of a metal material such as copper or stainless steel that has conductivity, and its surface is gold-plated.

[0050] The first housing member 55 is disposed inside the distal end outer housing 31. More specifically, the distal end side of the first housing member 55 faces the rear end side of the support member 53, and the second coil spring 54 faces outside its outer peripheral surface. And the rear end of the second coil spring 54 abuts against the surface on the distal end side of the stepped portion on the distal end side of the first housing member 55. By the above procedure, the second coil spring 54 is sandwiched between the pressing member 49 and the first housing member 55 and is in a compressed state in the center line direction. The distal ends of the conductive member 47 and the holding member 48 are accommodated inside the through hole provided in the first housing member 55.

[0051] The outer diameter of the first housing member 55 is smaller than the inner diameter of the tip external housing 31. Therefore, the outer peripheral surface of the first housing member 55 and the inner peripheral surface of the tip external housing 31 face each other through a gap and are not in direct contact. In addition, the inner diameter of the first housing member 55 is larger than the outer diameter of the support member 53 and the outer diameter of the holding member 48. Therefore, the inner peripheral surface of the first housing member 55 and the outer peripheral surface of the support member 53, and the inner peripheral surface of the first housing member 55 and the outer peripheral surface of the holding member 48 face each other through a gap and are not in direct contact.

[0052] The pressing member 551 is a member having a cylindrical shape as a whole. The pressing member 551 is provided on the outer peripheral surface of the first housing member 55 at a position corresponding to the crimped portion P of the tip external housing 31, over the entire circumference of the first housing member 55. The pressing member 551 has a length along the center line direction that corresponds to at least the range where pressure is applied to form the crimped portion P in the tip external housing 31. At the position where the pressing member 551 is provided, the inner diameter of the pressing member 551 is approximately equal to the outer diameter of the first housing member 55, and the outer diameter is approximately equal to the inner diameter of the tip external housing 31. Therefore, the inner peripheral surface of the pressing member 551 contacts the outer peripheral surface of the first housing member 55, and the outer peripheral surface contacts the inner peripheral surface of the tip external housing 31. The pressing member 551 is attached, for example, by inserting the first housing member 55 from the tip side into the cylindrically molded pressing member 551, or by filling a space between the first housing member 55 and the tip external housing 31 with resin. The pressing member 551 is an example of a filler.

[0053] The pressing member 551 is a member for holding the first housing member 55 evenly along the circumferential direction by receiving pressure applied to the tip external housing 31 at the crimping portion P. In addition, by interposing the pressing member 551 between the first housing member 55 and the tip external housing 31, insulation between the first housing member 55 and the tip external housing 31 in the electrical connection structure described below is maintained. The pressing member 551 is formed of a material such as resin or rubber that has insulation properties and heat resistance. As an example, the pressing member 551 may be formed using Teflon (registered trademark) (polytetrafluoroethylene (PTFE)).

[0054] As an example other than the above-mentioned pressing member 551 made of resin or rubber, the filler may be aluminum oxide powder (hereinafter referred to as "alumina powder") or zirconium oxide powder (hereinafter referred to as "zirconia powder"), which have excellent insulating properties and heat resistance. In this case, the alumina powder or zirconia powder is, for example, a fine powder with a particle size of about 1 μm, which is filled in the space between the outer circumferential surface of the first housing member 55 and the inner circumferential surface of the tip external housing 31, and flows in the space filled with the alumina powder or zirconia powder when pressure is applied to the tip external housing 31 at the crimping part P, thereby maintaining the insulation between the first housing member 55 and the tip external housing 31 in the electrical connection structure described later.

[0055] [Second storage member] The second housing member 56 is a hollow member having a cylindrical shape as a whole. Like the first housing member 55, the second housing member 56 is made of a metal material such as brass or stainless steel having electrical conductivity, and its surface is gold plated.

[0056] The second housing member 56 is disposed across the inside of the tip outer housing 31 and the inside of the intermediate outer housing 33. More specifically, the tip side of the second housing member 56 is housed within the first housing member 55. Further, the intermediate portion and the rear end portion of the holding member 48 are housed inside the through hole provided in the second housing member 56. The first housing member 55 and the second housing member 56 are integrated by press-fitting (tight fitting) and laser welding.

[0057] 〔Circuit Built-in Member〕 As particularly shown in FIG. 3, the circuit built-in member 57 includes a circuit board 571 that performs various processes using an electronic circuit on an electrical signal generated by weak charges output by the piezoelectric element 41, and a sealing portion 572 that seals the circuit board 571 by housing the circuit board 571 therein. The circuit built-in member 57 is inside the intermediate outer housing 33, and is disposed inside the second housing member 56 in almost the entire area except for a part of the rear end side. In particular, the entire area of the circuit board 571 is disposed inside the second housing member 56. Further, the tip side of the circuit built-in member 57 is fitted into a recess provided on the rear end side of the holding member 48. A metal plate (electrode terminal) provided on the tip side of the circuit built-in member 57 is in contact with the rear end side of the conductive member 47. Also, a metal plate (electrode terminal) provided on the outer peripheral surface of the circuit built-in member 57 is in contact with the inner peripheral surface of the second housing member 56.

[0058] 〔Connection Member〕 The connecting member 58 is a member having a columnar shape as a whole. The connecting member 58 includes a base material made of a synthetic resin material such as insulating PPS or PPT, and wirings and terminals made of a metal material such as conductive copper. The connecting member 58 is arranged so as to straddle the inside of the intermediate outer housing 33 and the inside of the rear end outer housing 34. Note that, among the connecting member 58, the portion (outer peripheral surface) facing the intermediate outer housing 33 or the rear end outer housing 34 is made of a synthetic resin material, and the metal material is not exposed at this portion. The rear end side of the circuit built-in member 57 faces the front end side of the connecting member 58, and a metal plate (electrode terminal) provided on the circuit built-in member 57 is fitted into the terminal provided on the connecting member 58. Further, the front end sides of the respective conductor portions exposed on the power line 91, the signal line 92, and the ground line 93 constituting the connection cable 90 are inserted into the rear end side of the connecting member 58. The intermediate outer housing 33 and the connecting member 58 are integrated by press fitting (tight fitting).

[0059] 〔Blocking member〕 The blocking member 59 is a member having a columnar shape as a whole. However, three through holes are formed in the blocking member 59 along the center line direction. The blocking member 59 is made of an insulating rubber material. The front end side of the blocking member 59 is arranged inside the rear end outer housing 34, and the rear end side thereof protrudes outside the rear end of the rear end outer housing 34. The front end side of the blocking member 59 faces the rear end side of the connecting member 58. Further, the above-described power line 91, signal line 92, and ground line 93 are inserted into the three through holes provided in the blocking member 59. The rear end outer housing 34 and the blocking member 59 are integrated by press fitting (tight fitting).

[0060] 〔Third insulating member〕 The third insulating member 60 is a member having a hollow structure and presenting a cylindrical shape as a whole. However, the third insulating member 60 has a structure in which a cylindrical portion provided on the front end side and an annular portion provided on the rear end side are integrated. The third insulating member 60 is composed of a synthetic resin material such as PPS having insulating properties. The third insulating member 60 is arranged so as to straddle the inside of the front end outer casing 31 and the inside of the intermediate outer casing 33. More specifically, the front end side of the third insulating member 60 is arranged inside the front end outer casing 31, and the rear end side of the third insulating member 60 is arranged inside the intermediate outer casing 33. And, the outer peripheral surface of the cylindrical portion of the third insulating member 60 faces the inner peripheral surface of the rear end side of the front end outer casing 31. Also, the front end side surface of the annular portion of the third insulating member 60 is in contact with the rear end side surface of the front end outer casing 31. On the other hand, the inner peripheral surface of the cylindrical portion of the third insulating member 60 faces the outer peripheral surface of the first accommodating member 55 and the outer peripheral surface of the second accommodating member 56. Also, the rear end side surface of the annular portion of the third insulating member 60 is in contact with the second accommodating member 56.

[0061] (Configuration of the seal part) As particularly shown in FIGS. 2 and 3, the seal part 70 includes a first seal member 71 located relatively on the front end side and a second seal member 72 located relatively on the rear end side.

[0062] 〔First seal member〕 The first seal member 71 is a member presenting an annular shape as a whole, and in this example, it is composed of a square ring having a square cross section. The first seal member 71 is composed of a copper material with high heat resistance and acid resistance and having tin plating on the surface. And, the first seal member 71 is attached to the outer peripheral surface of the front end outer casing 31 constituting the casing part 30. When the pressure detection device 20 is attached to the cylinder head 13 with the first seal member 71 attached, the outer peripheral surface of the front end outer casing 31 at the position where the first seal member 71 is attached faces the outer surface of the cylinder head 13 with the first seal member 71 interposed therebetween.

[0063] [Second Sealing Member] The second sealing member 72 is a member having an annular shape as a whole. In this example, it is composed of an O-ring having a circular cross-section. The second sealing member 72 is composed of a synthetic rubber material such as fluororubber having high mechanical resilience. And the second sealing member 72 is attached to the outer peripheral surface of the rear end outer casing 34 that constitutes the casing part 30. This second sealing member 72 serves as a sealing member to prevent water or the like from entering from the outside of the internal combustion engine 10, and also serves as a vibration-proof member to prevent the pressure detection device 20 from vibrating due to vibrations during the operation of the internal combustion engine 10 or the mounting environment and colliding with the inner surface of the communication hole 13a in the cylinder head 13. Therefore, among the materials having high mechanical resilience, a fluororubber material having particularly high heat resistance of resilience and a long service life of the vibration suppression function is suitable for the second sealing member 72.

[0064] (Configuration of Buffer Member) The buffer member 80 as an example of the temperature reduction part is disposed at the tip of the pressure detection device 20 as shown in FIGS. 2, 3, etc.

[0065] The buffer member 80 is a member having a disk shape as a whole. This buffer member 80 has a cylindrical shape. A through hole penetrating from the front end side surface to the rear end side surface is formed in the buffer member 80.

[0066] The buffer member 80 is composed of a metal material (super heat-resistant alloy) having conductivity and higher heat resistance than the diaphragm head 32. As such a metal material, for example, an iron-based alloy system can be exemplified, and a kind of gamma prime precipitation-strengthened super heat-resistant alloy can be given. However, as long as the required characteristics are satisfied, various other super heat-resistant alloys can be adopted. And as the usable super heat-resistant alloys, matrix-strengthened super heat-resistant alloys, carbide precipitation-strengthened super heat-resistant alloys, and gamma prime precipitation-strengthened super heat-resistant alloys can be mentioned. Note that the usable super heat-resistant alloys may be any of an iron-based alloy system, a nickel-based alloy system, and a cobalt alloy system.

[0067] [Relationship between the buffer mechanism section and the diaphragm head] Further, in the present embodiment, the rear end side of the buffer member 80 and the surface annular convex portion 32g in the diaphragm head 32 are abutted against each other, and laser welding is performed over the entire circumference of the outer peripheral surface to integrate them. Therefore, in this example, the diaphragm head 32 and the buffer member 80 are fixed (welded) in a state of being in contact with each other. However, the flat portion provided on the rear end side of the buffer member 80 and the pressure receiving surface 32a and the surface central concave portion 32b provided on the front end side of the diaphragm head 32 face each other with a space therebetween (see also FIG. 4).

[0068] And in a state where the pressure detection device 20 is attached to the cylinder head 13, the front end side of the buffer member 80 is adapted to abut against a stepped portion 13b provided in the communication hole 13a (see FIG. 4). Also, in a state where the pressure detection device 20 is attached to the cylinder head 13, the side wall portion of the buffer member 80 is in contact with the inner wall of the communication hole 13a.

[0069] [Control of noise based on vibration] Here, consider the vibration generated in the pressure detection device 20. When the pressure detection device 20 receives an external impact, vibration may occur in the tip external housing 31, which is a long member, and the members inside it. Here, for the purpose of considering the problems when vibration occurs, a configuration is assumed in which the pressing member 551 is not provided between the tip external housing 31 and the first housing member 55.

[0070] Among the first housing member 55, the conductive member 47, and the holding member 48 housed in the tip external housing 31, the conductive member 47 and the holding member 48 are integrated by press-fitting (clearance fitting), but there is a gap between the holding member 48 and the first housing member 55. In other words, the conductive member 47 and the holding member 48 are not supported except at the portions where they contact other members at both ends. Also, when the pressing member 551 is not provided, there is a gap between the first housing member 55 and the tip external housing 31. For this reason, the first housing member 55 is also not supported except at the portions where it contacts other members at both ends.

[0071] Since the first housing member 55, the conductive member 47, and the holding member 48 are long, they have a low natural frequency and resonance may occur due to vibration. When this vibration is transmitted through each member of the pressure detection device 20 and reaches the piezoelectric element 41, the piezoelectric element 41 detects the pressure change due to the vibration and outputs a charge signal (noise). Here, when the above natural frequency is close to the vibration frequency of the signal to be detected by the pressure detection device 20, it may cause a decrease in the detection accuracy of the signal.

[0072] (Vibration transmission path) As a specific vibration transmission path, for example, the following paths are assumed. · First, a path in which the vibration of the conductive member 47 and the holding member 48 is transmitted from the tip rod-shaped portion 471 of the conductive member 47 to the rear-end electrode member 44 via the first coil spring 46 and presses the piezoelectric element 41 (hereinafter referred to as the "first transmission path") is conceivable. · Also, a path in which the vibration of the first housing member 55 is transmitted to the rear-end electrode member 44 via the second coil spring 54, the support member 53, and the rear-end insulating member 45 and presses the piezoelectric element 41 (hereinafter referred to as the "second transmission path") is conceivable. · When a protrusion that contacts the inner wall of the first housing member 55 is provided on the outer periphery of the holding member 48 to support the holding member 48, the vibration of the conductive member 47 and the holding member 48 is also transmitted to the first housing member 55 via the protrusion and is added to the vibration propagating through the second transmission path. · Also, a path in which the vibration of the conductive member 47 and the holding member 48 is transmitted to the support member 53 when the holding member 48 collides with the inner wall of the support member 53, and further transmitted to the rear-end electrode member 44 via the rear-end insulating member 45 and presses the piezoelectric element 41 (hereinafter referred to as the "third transmission path") is conceivable. · In addition, various vibrations derived from the internal combustion engine 10 may be applied to the entire pressure detection device 20 and may be mixed in from the middle of these paths.

[0073] Of these paths, it is assumed that the vibration transmitted by the first transmission path has the greatest influence on the output of the piezoelectric element 41. The pressure detection device 20 of the present embodiment has vibration suppression means for suppressing vibration having a natural frequency close to the frequency of the signal to be detected with respect to the vibration of the conductive member 47 and the holding member 48.

[0074] (Vibration suppression means) In the present embodiment, the purpose of the vibration suppression means is to avoid the natural frequencies of the conductive member 47 and the holding member 48 from becoming close to the frequency of the signal to be detected, rather than reducing the vibration of the conductive member 47 and the holding member 48 themselves. This purpose is achieved, for example, by excluding the natural frequencies of the conductive member 47 and the holding member 48 from the range of natural frequencies that the pressure detection device 20 can detect. Also, it may be achieved by excluding the natural frequencies of the conductive member 47 and the holding member 48 from a predetermined frequency range within the range of natural frequencies that the pressure detection device 20 can detect, for example, from 1 to 2 kHz, which is a typical abnormal combustion vibration frequency of an internal combustion engine. Therefore, in the present embodiment, as the vibration suppression means, means for preventing vibration is provided at an appropriate position in the center line direction of the conductive member 47 and the holding member 48. Thereby, the natural frequencies of the conductive member 47 and the holding member 48 are controlled.

[0075] As a specific vibration suppression means, a caulking portion P is formed on the tip external housing 31. By caulking the tip external housing 31, the tip external housing 31 is deformed and the internal first housing member 55 is pressed and deformed. Then, the deformed first housing member 55 presses and fixes the conductive member 47 and the holding member 48. Thereby, the vibration of the first housing member 55, the conductive member 47, and the holding member 48 is suppressed at the position where the caulking portion P is formed. Also, since a fulcrum can be formed in the middle (the caulked position) in the center line direction of the first housing member 55, the conductive member 47, and the holding member 48, the natural frequencies of the tip side and the rear end side of the caulking portion P of these members become higher.

[0076] In the above description, it has been described that the caulked and deformed tip outer housing 31 presses the first housing member 55. On the other hand, in order to maintain the electrical connection structure described later, the pressure detection device 20 of the present embodiment needs to maintain a state where the tip outer housing 31 and the first housing member 55 do not come into contact with each other. Therefore, in the present embodiment, a pressing member 551 is interposed between the tip outer housing 31 and the first housing member 55 at the position where the caulking portion P of the tip outer housing 31 is formed, so that the tip outer housing 31 and the first housing member 55 do not directly contact each other. Further, by providing the pressing member 551 between the tip outer housing 31 and the first housing member 55, variations in the force with which the tip outer housing 31 deformed by caulking presses the holding member 48 are suppressed.

[0077] The caulking portion P does not necessarily need to be provided over the entire circumference of the tip outer housing 31. Specifically, for example, the caulking portion P may be formed by applying pressure to three or four points in the circumferential direction of the tip outer housing 31 by so-called three-point caulking or four-point caulking. However, it is necessary to avoid bias in the pressure from a specific direction intersecting the center line direction and deformation such that the tip outer housing 31 bends with respect to the center line direction. Further, in the examples shown in FIGS. 2 and 3, the caulking portion P is provided only at one location in the middle along the center line direction of the tip outer housing 31, but caulking portions may be provided at a plurality of locations in the center line direction.

[0078] Further, the position of the caulking portion P can be determined according to the natural vibration frequency etc. of the first housing member 55, the conductive member 47, and the holding member 48 after the caulking portion P is formed on the tip outer housing 31. For example, the ratio of the length on the tip side to the length on the rear end side with respect to the caulking portion P of the tip outer housing 31 may be 1:1 or 1:2. Further, the caulking portion P is formed at a position where it does not become difficult to attach to the communication hole 13a of the cylinder head 13 of the internal combustion engine 10 according to the shape of the tip outer housing 31.

[0079] [Configuration of the connection cable] As shown particularly in FIGS. 2 and 3, the connection cable 90 includes twisted power lines 91, signal lines 92, and ground lines 93, and a covering member (not shown) that covers the outer peripheries of these power lines 91, signal lines 92, and ground lines 93. Here, each of the power lines 91, signal lines 92, and ground lines 93 has a conductor portion composed of a tinned soft copper stranded wire and an insulating portion composed of polyethylene (cross-linked polyethylene) or the like formed by strengthening a cross-linked structure using an electron beam or the like and covering the outer periphery of the conductor portion to insulate it. Further, the covering member is composed of a rubber material or a resin material having insulating properties. Note that, if necessary, a shielding body for shielding the power lines 91, signal lines 92, and ground lines 93 may be provided in the connection cable 90.

[0080] [Electrical connection structure in pressure detection device] Here, the electrical connection structure in the pressure detection device 20 will be described. [Positive path] In the pressure detection device 20, the end face (positive electrode) on the rear end side of the piezoelectric element 41 is electrically connected to the rear end electrode member 44, the first coil spring 46, and the conductive member 47. Further, the conductive member 47 is electrically connected to an input signal terminal provided on the circuit built-in member 57. Hereinafter, the electrical path from the end face on the rear end side of the piezoelectric element 41 to the input signal terminal of the circuit board 571 via the rear end electrode member 44, the first coil spring 46, and the conductive member 47 will be referred to as the 'positive path'.

[0081] [Negative path] On the other hand, in the pressure detection device 20, the end face (negative electrode) on the front end side of the piezoelectric element 41 is electrically connected to the front end electrode member 42, the pressurizing member 49, and the support member 53. Further, the pressurizing member 49 is electrically connected to an input ground terminal provided on the second coil spring 54, the first housing member 55, the second housing member 56, and the circuit built-in member 57. Hereinafter, the electrical path from the end face on the front end side of the piezoelectric element 41 to the input ground terminal of the circuit board 571 via the front end electrode member 42, the pressurizing member 49, the support member 53, the second coil spring 54, the first housing member 55, and the second housing member 56 will be referred to as the 'negative path'.

[0082] (Housing path) On the other hand, in the pressure detection device 20, the diaphragm head 32 is electrically connected to the front-end outer housing 31, the intermediate outer housing 33, and the rear-end outer housing 34. Further, the diaphragm head 32 is electrically connected to the first inner housing 35 and the second inner housing 36. Furthermore, the diaphragm head 32 is electrically connected to the buffer member 80. Hereinafter, the electrical path from the second inner housing 36 to the first inner housing 35, the diaphragm head 32, the front-end outer housing 31, the intermediate outer housing 33, and the rear-end outer housing 34, and from the diaphragm head 32 to the buffer member 80 is referred to as the 'housing path'. When the pressure detection device 20 is attached to the cylinder head 13 of the internal combustion engine 10 shown in FIG. 1, for example, male threads (not shown) provided on the front-end outer housing 31, the diaphragm head 32, and the buffer member 80 contact female threads (not shown) provided on the inner peripheral surface of the communication hole 13a, and for example, the surface wall portion 814 of the buffer member 80 contacts the stepped portion 13b provided in the communication hole 13a. At this time, the cylinder head 13 (and the cylinder block 11) and the housing path are at substantially the same electric potential.

[0083] (Relationship between the positive path and the negative path) Here, in the pressure detection device 20 of the present embodiment, the negative path exists outside the positive path. In other words, the positive path is accommodated inside the negative path. The positive path and the negative path are electrically insulated by the rear-end insulating member 45, the holding member 48, the insulating tube 50, and the air gap formed between both paths.

[0084] (Relationship between the negative path and the housing path) Also, in the pressure detection device 20, the housing path exists outside the negative path. In other words, the negative path is accommodated inside the housing path. The negative path and the housing path are electrically insulated by the front-end insulating member 43, the first insulating member 51, the second insulating member 52, the third insulating member 60, and the air gap formed between both paths.

[0085] (Relationship between the housing path and the positive path) Furthermore, in the pressure detection device 20, as a result, a housing path exists outside the positive path. In other words, the positive path is accommodated inside the housing path. And as described above, since the positive path and the negative path are electrically insulated from each other, and the negative path and the housing path are electrically insulated from each other, the housing path and the positive path are electrically insulated from each other.

[0086] [Mounting Procedure for Pressure Detection Device for Internal Combustion Engine] Here, the mounting procedure for the pressure detection device 20 on the internal combustion engine 10 will be described. First, the pressure detection device 20 is arranged so that its tip side, i.e., the side of the buffer member 80, faces the communication hole 13a provided in the cylinder head 13 of the internal combustion engine 10 from the outside of the internal combustion engine 10. Subsequently, the tip side of the pressure detection device 20 is inserted into the communication hole 13a.

[0087] Then, the pressure detection device 20 is rotated clockwise with respect to the axial direction with respect to the cylinder head 13 of the internal combustion engine 10. This operation is preferably performed via a torque wrench. Along with this, the female thread provided on the inner peripheral surface of the communication hole 13a in the cylinder head 13 meshes with the male thread provided on the outer peripheral surfaces of the tip external housing 31, the diaphragm head 32, and the buffer member 80 in the pressure detection device 20, and the pressure detection device 20 is screwed into the cylinder head 13. As a result, the buffer member 80 provided on the tip side of the pressure detection device 20 moves toward the combustion chamber C provided in the internal combustion engine 10.

[0088] Also, with such screwing, among the buffer members 80 provided in the pressure detection device 20, the surface on the tip side of the surface wall portion 814 provided in the buffer member 80 abuts against the surface on the rear end side of the step portion 13b provided in the communication hole 13a of the cylinder head 13 in the internal combustion engine 10. Along with this, the pressure detection device 20 basically reaches a state where it cannot be screwed in further, but by further tightening using a torque wrench, an axial force (fastening axial force) predetermined along the axial direction is applied to the pressure detection device 20 and the cylinder head 13. As described above, the attachment of the pressure detection device 20 to the internal combustion engine 10, in other words, the fastening of the pressure detection device 20 to the cylinder head 13 is completed.

[0089] [Pressure detection operation by pressure detection device] Subsequently, 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 32a of the diaphragm head 32. Here, in the pressure detection device 20 of the present embodiment, a buffer member 80 is provided on the tip side of the diaphragm head 32, and the combustion gas (an example of a fluid) generated in the combustion chamber C reaches the pressure receiving surface 32a of the diaphragm head 32 after passing through the nine through holes 816 provided in the buffer member 80. In other words, the buffer member 80 receives the combustion gas, and the temperature of the combustion gas is lowered as it flows through the through holes 816, and the combustion gas with the lowered temperature is supplied to the diaphragm head 32.

[0090] Then, in the diaphragm head 32, the pressure received by the pressure receiving surface 32a is transmitted to the back surface central convex portion 32d on the back side, and further transmitted from the back surface central convex portion 32d to the tip electrode member 42 via the tip insulating member 43. The pressure transmitted to the tip electrode member 42 acts on the piezoelectric element 41 sandwiched between the tip electrode member 42 and the rear end electrode member 44. In the piezoelectric element 41, charges corresponding to the received pressure are generated. The charges generated in the piezoelectric element 41 are supplied as charge signals to the circuit board 571 via the positive path and the negative path. The charge signal supplied to the circuit board 571 is output as an output signal after various processes are performed by a processing circuit (not shown) mounted on the circuit board 571. Then, the output signal output from the circuit board 571 is transmitted to the control device 100 via the connection member 58 and the connection cable 90.

[0091] In the case of the present embodiment, the combustion gas generated in the combustion chamber C is deprived of heat by the buffer member 80 while passing through the nine through-holes 816 provided in the buffer member 80. For this reason, the temperature of the combustion gas after passing through the buffer member 80 is lower than that of the combustion gas before passing through. As a result, in the present embodiment, by providing the buffer member 80 in the pressure detection device 20, the temperature of the combustion gas reaching the pressure receiving surface 32a of the diaphragm head 32 can be reduced by, for example, 100°C or more compared to the case where the buffer member 80 is not provided.

[0092] For example, when the temperature of the combustion gas generated in the combustion chamber C is very high, if this high-temperature combustion gas is directly applied to the pressure receiving surface 32a of the diaphragm head 32, there is a concern that the diaphragm head 32 will be overheated by the high-temperature combustion gas, and as a result, thermal degradation will occur in the diaphragm head 32. In the case of SUS630 or SUH660 used as the raw material of the diaphragm head 32 in the present embodiment, if it is used for a long time in an environment where the temperature of the combustion gas hitting the diaphragm head 32 exceeds, for example, 700°C, the strength of the diaphragm head 32 itself will gradually decrease.

[0093] On the other hand, in the present embodiment, as described above, the combustion gas hits the diaphragm head 32 in a state where the temperature is lowered by the buffer member 80 provided on the tip side of the diaphragm head 32. Thereby, it is possible to suppress a decrease in the strength of the diaphragm head 32 from a long-term perspective.

[0094] [Other configurations of the pressure detection device] In the present embodiment, in order to suppress the influence of noise caused by the vibration of a long member in the pressure detection device 20 on the signal to be detected, vibration suppression means for controlling the natural frequency of such a member is provided. Further, in the above embodiment, a pressure detection device 20 having a structure in which a positive path and a negative path are provided inside the device as electrical paths and a housing path passing through the housing portion 30 (hereinafter referred to as an "internal insulation structure") has been described as an example. Here, the above problems also occur in a pressure detection device having no internal insulation structure (hereinafter, such a structure is referred to as a "non-internal insulation structure"), and the vibration suppression means of the present embodiment can be applied. Hereinafter, a pressure detection device having a non-internal insulation structure will be described, and the application of the vibration suppression means to such a pressure detection device will be described.

[0095] FIG. 5 is a cross-sectional view of a pressure detection device having a non-internal insulation structure. FIG. 6 is an enlarged view of the V region of the pressure detection device shown in FIG. 5.

[0096] [Configuration of the pressure detection device] The pressure detection device A5 includes a sensor unit A100 having a piezoelectric element A10 that converts the pressure in the combustion chamber C into an electrical signal, a signal processing unit A200 that processes the electrical signal from the sensor unit A100, and a holding member A300 that holds the signal processing unit A200. When this pressure detection device A5 is attached to the cylinder head 13, it is inserted into the communication hole 13a formed in the cylinder head 13 first from the side of the diaphragm head A40 of the sensor unit A100 to be described later. In the following description, the left side of FIG. 5 is the tip side of the pressure detection device A5, and the right side is the rear end side of the pressure detection device A5.

[0097] (Configuration of the sensor unit) The sensor unit A100 includes a piezoelectric element A10 that converts the received pressure into an electrical signal, and a housing unit A30 that is cylindrical and has a cylindrical hole formed therein for housing the piezoelectric element A10 and the like. Hereinafter, the direction of the center line of the cylindrical hole formed in the housing unit A30 will be simply referred to as the center line direction.

[0098] Further, the sensor unit A100 includes a diaphragm head A40 provided so as to close the opening on the tip side of the housing unit A30 and on which the pressure in the combustion chamber C acts, a tip electrode member A50 provided between the diaphragm head A40 and the piezoelectric element A10, and a rear end electrode member A55 disposed on the side opposite to the tip electrode member A50 with respect to the piezoelectric element A10. The sensor unit A100 also includes an insulating ring A60 made of alumina ceramic that electrically insulates the rear end electrode member A55, a support member A65 provided on the rear end side of the insulating ring A60 and supporting the end of a covering member A23 (to be described later) of the signal processing unit A200, and a coil spring A70 interposed between the rear end electrode member A55 and a conductive member A22 (to be described later).

[0099] 〔Housing Unit〕 As shown in FIG. 6, the housing unit A30 has a first housing unit A31 provided on the tip side and a second housing unit A32 provided on the rear end side. The first housing unit A31 is a cylindrical member. The second housing unit A32 is a cylindrical member as shown in FIG. 5. The tip end portion of the second housing unit A32 is fitted (press-fitted) into the rear end portion of the first housing unit A31 with a tight fit. The housing unit A30 corresponds to the tip outer housing 31 of the pressure detection device 20 described with reference to FIGS. 2 to 4, and a caulking portion P is formed at an appropriate position in the middle of the center line direction. More specifically, the caulking portion P is provided at a position in the housing unit A30 corresponding to the first convex portion A251 of a conductive member covering portion A231 (to be described later). The second housing unit A32 is an example of a housing and an example of a second housing.

[0100] 〔Tip Electrode Member〕 The tip electrode member A50 is a columnar member. By the outer peripheral surface of the tip electrode member A50 contacting the inner peripheral surface of the first housing portion A31 and the end surface on the tip side contacting the diaphragm head A40, the tip portion of the piezoelectric element A10 is electrically connected to the housing portion A30.

[0101] 〔Rear end electrode member〕 The rear end electrode member A55 is a columnar member. On the end surface on the rear end side of the rear end electrode member A55, a columnar protruding portion A55a protruding toward the rear end side from this end surface is provided. The outer diameter of the protruding portion A55a is smaller than the inner diameter of the insulating ring A60. The length of the protruding portion A55a is longer than the width (length in the center line direction) of the insulating ring A60, and the tip of the protruding portion A55a is exposed from the insulating ring A60. There is a gap between the outer peripheral surface of the rear end electrode member A55 and the inner peripheral surface of the first housing portion A31.

[0102] 〔Insulating ring〕 The insulating ring A60 is a cylindrical member formed of alumina ceramics or the like. The inner diameter (the hole diameter at the center) is slightly larger than the outer diameter of the base end portion of the protruding portion A55a of the rear end electrode member A55, and the outer diameter is substantially equal to the inner diameter of the first housing portion A31.

[0103] 〔Support member〕 The support member A65 is a tubular member. The protruding portion A55a of the rear end electrode member A55 is exposed through the insulating ring A60 to the inside of the support member A65. The inner diameter of the support member A65 is larger than the outer diameter of the tip portion of the conductive member A22 of the signal processing unit A200 described later. Also, the inner diameter of the support member A65 is smaller than the outer diameter of the tip side end portion of the covering member A23 of the signal processing unit A200 described later, and this covering member A23 is press-fitted into the inner wall of the support member A65 with a tight fit. Thereby, the support member A65 functions as a member that supports the end portion of the covering member A23.

[0104] 〔Coil spring〕 The coil spring A70 is a spiral spring member that expands and contracts in the center line direction. The tip of the protruding portion A55a of the rear end electrode member A55 is inserted into the coil spring A70 from the tip side. Further, the coil spring A70 is inserted into the insertion hole A22a of the conductive member A22 described later. The length of the coil spring A70 is set to a length that can be interposed in a compressed state between the rear end electrode member A55 and the conductive member A22. As the material of the coil spring A70, an alloy with high elasticity and excellent durability, heat resistance, corrosion resistance, etc. may be used. Further, it is advisable to apply gold plating to the surface of the coil spring A70 to enhance electrical conduction. The coil spring A70 corresponds to the first coil spring 46 of the pressure detection device 20 described with reference to FIGS. 2 to 4, and has a hardness such that the vibration of the conductive member A22 is transmitted to the rear end electrode member A55 via the protruding portion A55a.

[0105] (Configuration of signal processing unit) As shown in FIG. 5, the signal processing unit A200 includes a circuit board unit A21 that at least amplifies an electrical signal, which is a weak charge obtained from the piezoelectric element A10 of the sensor unit A100, a rod-shaped conductive member A22 that guides the charge generated in the piezoelectric element A10 to the circuit board unit A21, a covering member A23 that covers the circuit board unit A21, the conductive member A22, etc., and an O-ring A26 that seals the circuit board unit A21, etc.

[0106] 〔Circuit board unit〕 The circuit board unit A21 has a mounting board A210 on which electronic components and the like constituting a circuit for amplifying the weak charge obtained from the piezoelectric element A10 of the sensor unit A100 are mounted. Input pins for electrically connecting to the conductive member A22 and output pins for electrically connecting to a control device for input pins for grounding are connected to the mounting board A210.

[0107] 〔Conductive member〕 The conductive member A22 is a rod-shaped member, and an insertion hole A22a into which the tip of the protruding portion A55a of the rear end electrode member A55 is inserted is formed at the tip portion. The rear end portion of the conductive member A22 is electrically connected to the mounting board A210 of the circuit board unit A21.

[0108] 〔Cover member〕 The cover member A23 has a conductive member covering portion A231 that covers the outer periphery of the conductive member A22, and a substrate covering portion A232 that covers the side and bottom surfaces of the mounting substrate A210 of the circuit board portion A21. The cover member A23 is formed of an insulating material such as resin.

[0109] 〔Conductive member covering portion〕 The conductive member covering portion A231 is a long cylindrical member, and the tip of the conductive member covering portion A231 is fitted (press-fitted) into the inner wall of the support member A65 by a snap fit. The conductive member covering portion A231 corresponds to the holding member 48 of the pressure detection device 20 described with reference to FIGS. 2 to 4 and is integrated with the conductive member A22 accommodated therein. The conductive member covering portion A231 is an example of a housing and an example of a first housing.

[0110] The conductive member covering portion A231 has a first convex portion A251 provided near the tip and a second convex portion A252 provided near the rear end. In this example, a plurality (for example, 4) of the first convex portions A251 and the second convex portions A252 are provided at regular intervals along the circumferential direction on the outer peripheral surface of the conductive member covering portion A231.

[0111] 〔First convex portion and second convex portion〕 The first convex portion A251 and the second convex portion A252 are in contact with the inner peripheral surface of the second housing portion A32. As a result, the conductive member covering portion A231 is supported by the second housing portion A32. Here, the first convex portion A251 is provided near the tip of the conductive member covering portion A231 and the second convex portion A252 is provided near the rear end, but in order to control the natural vibration frequency of the conductive member A22 and the conductive member covering portion A231 to a desired vibration frequency, it may be provided at an intermediate position in the center line direction of the conductive member covering portion A231.

[0112] (Configuration of holding member) The holding member A300 is a thin-walled cylindrical member. The holding member A300 is attached to the second housing part A32 while holding the signal processing part A200. Thereby, the holding member A300 suppresses the movement of the signal processing part A200 with respect to the housing part A30.

[0113] (Vibration control means) In the pressure detection device A5 having a non-internal insulation structure, the conductive member A22 and the conductive member coating part A231 are long members, and similar to the pressure detection device 20 of the internal insulation structure described with reference to FIGS. 2 to 4, vibrations with a low natural frequency may occur. Then, the vibrations generated in the conductive member A22 and the conductive member coating part A231 are transmitted from the protruding part A55a of the rear end electrode member A55 to the rear end electrode member A55 via the coil spring A70, and pressurize the piezoelectric element A10. Further, the vibrations generated in the conductive member A22 and the conductive member coating part A231 are transmitted to the rear end electrode member A55 via the support member A65 and the insulating ring A60, and pressurize the piezoelectric element A10. For this reason, the same problems as those described for the pressure detection device 20 of the internal insulation structure may occur.

[0114] Therefore, a caulking portion P was provided on the second housing portion A32 to control the natural frequencies of the conductive member A22 and the conductive member coating portion A231. As shown in FIGS. 5 and 6, the caulking portion P is provided at a position corresponding to the first convex portion A251 of the conductive member coating portion A231. Then, the deformed second housing portion A32 formed by the caulking portion P presses and fixes the conductive member coating portion A231 and the conductive member A22 via the first convex portion A251 that contacts the inner peripheral surface of the second housing portion A32. As a result, the vibration of the conductive member coating portion A231 and the conductive member A22 is suppressed at the position where the caulking portion P is formed, and the vibration frequencies on the tip side and the rear end side of the caulking portion P increase. The natural frequencies of the conductive member A22 and the conductive member coating portion A231 can be controlled to a desired vibration frequency when the first convex portion A251 and the second convex portion A252 contact the inner peripheral surface of the second housing portion A32. However, when the conductive member coating portion A231 is molded from resin, there is a concern that the conductive member coating portion A231 may soften when the operating environment temperature of the pressure detection device 20 is high, reducing the vibration suppression effect. However, by providing the caulking portion P that applies pressure to the conductive member A22 from the outside of the second housing portion A32, the natural frequencies of the conductive member A22 and the conductive member coating portion A231 can be controlled to a desired vibration frequency and the vibration can be reliably suppressed.

[0115] Here, the caulking portion P was provided at a position corresponding to the first convex portion A251 of the conductive member coating portion A231 in the second housing portion A32. On the other hand, a member as an example of a filling member that presses the conductive member coating portion A231 may be interposed between the second housing portion A32 and the conductive member coating portion A231, and the caulking portion P may be provided at a position corresponding to this member. As the filling member, a member having an overall cylindrical shape similar to the pressing member 551 in the previous embodiment, alumina powder, or zirconia powder can also be applied. Further, the caulking portion P may be provided at a plurality of locations along the center line direction of the second housing portion A32.

[0116] The caulking portion P does not necessarily have to be provided over the entire circumference of the second housing portion A32, and it may be formed by so-called three-point caulking or four-point caulking. However, it is necessary to avoid a bias in the pressure from a specific direction intersecting the center line direction and prevent the second housing portion A32 from deforming so as to bend with respect to the center line direction.

[0117] [Others] As described above, the present embodiment has been explained, but the technical scope of the present invention is not limited to the above embodiment. For example, in the present embodiment, in the pressure detection device 20 with an internal insulation structure, a pressing member 551 is provided between the tip external housing 31 and the first housing member 55, but a pressing member may also be interposed between the first housing member 55 and the holding member 48.

[0118] Also, in the present embodiment, the configuration in which the caulking portion P is provided on the tip external housing 31 of the pressure detection device 20 with an internal insulation structure and the second housing portion A32 of the pressure detection device A5 with a non-internal insulation structure as vibration suppression means has been described, but it is not limited to this. The vibration suppression means only needs to be able to control so that the natural frequencies in the pressure detection devices 20 and A5 do not approach a specific vibration frequency of the detection target. For example, the space between the tip external housing 31 and the first housing member 55 in the pressure detection device 20, or the space between the second housing portion A32 and the conductive member covering portion A231 in the pressure detection device A5, may be filled with parts such as resin or rubber, or the members may be fixed by partially filling an adhesive. By such an arrangement of parts and the adhesive, the movement of the first housing member 55 and the conductive member covering portion A231 is obstructed, thereby changing the vibration of these members and avoiding the natural frequency approaching a specific vibration frequency of the detection target. In addition, various changes and alternative configurations that do not depart from the scope of the technical idea of the present invention are included in the present invention.

Explanation of Reference Numerals

[0119] 1…Pressure detection system, 10…Internal combustion engine, 11…Cylinder block, 12…Piston, 13…Cylinder head, 13a…Communication hole, 20…Pressure detection device, 30…Housing part, 31…Tip outer housing, 41…Piezoelectric element, 44…Rear end electrode member, 45…Rear end insulating member, 46…First coil spring, 47…Conductive member, 48…Holding member, 53…Supporting member, 54…Second coil spring, 55…First housing member, 551…Pressing member, A5…Pressure detection device, A10…Piezoelectric element, A22…Conductive member, A30…Housing part, A31…First housing part, A32…Second housing part, A50…Tip electrode member, A55…Rear end electrode member, A60…Insulating ring, A65…Supporting member, A70…Coil spring, A231…Conductive member coating part, A251…First convex part, P…Caulking part

Claims

1. A detection element for detecting a change in pressure, A conductive member for conducting an electrical signal from the detection element, A cylindrical first housing for housing the conductive member therein, A convex portion provided on an outer peripheral surface of the first housing, A cylindrical second housing for housing the conductive member and the first housing therein, Vibration suppression means that is formed by applying pressure from the second housing side at a position corresponding to the position where the convex portion of the first housing is provided with respect to the conductive member, and suppresses vibration of the conductive member at a specific frequency, A pressure detection device, characterized by comprising the above.

2. The pressure detection device according to claim 1, wherein the vibration suppression means is means for adjusting the natural frequency of the conductive member to a value outside a predetermined frequency range that causes noise in the output of the detection element.

3. The pressure detection device according to claim 1 or claim 2, characterized in that at least a part between the conductive member and the first housing is filled with a filler.

4. The pressure detection device according to claim 1 or claim 2, wherein the vibration suppression means is means for fixing the conductive member, the first housing, and the second housing at the position where the convex portion of the first housing in the axial direction is provided.

5. The pressure detection device according to claim 4, wherein the vibration suppression means is a caulked portion formed by caulking from the outside of the second housing.

6. A detection element for detecting a change in pressure, A conductive member for conducting an electrical signal from the detection element, A cylindrical first housing for housing the conductive member therein, A convex portion provided on an outer peripheral surface of the first housing, A cylindrical second housing for housing the conductive member and the first housing therein, and A pressure detection device, characterized by having a caulked portion that caulks the second housing, the first housing, and the conductive member at a position corresponding to the position where the convex portion of the first housing is provided.

7. The pressure detection device according to claim 6, characterized in that a member having insulating properties is interposed between the first housing and the conductive member in the caulked portion, and the first housing and the conductive member are insulated from each other.

8. The caulked portion is formed by a force directed toward the center direction of a cross section substantially orthogonal to the axis at a position corresponding to the position where the convex portion of the first housing is provided in the axial direction of the first housing, the second housing, and the conductive member, and the first housing, the second housing, and the conductive member are caulked from a plurality of directions of the cross section. The pressure detection device according to claim 6, characterized in that.

9. The pressure detection device according to claim 6, further comprising a cylindrical third housing that houses the conductive member, the first housing, and the second housing therein.

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