JP2020056610A - Pressure detector - Google Patents

Abstract

To provide a pressure detector having small thermal effects.SOLUTION: The pressure detector comprises: a pressure detection element 41 for detecting a change of pressure of a pressure medium; a cylindrical housing 311 for accommodating the pressure detection element 41 inside; a diaphragm 32 attached to one end of the housing 311, for receiving the pressure of the pressure medium; and an annular seal member 71 attached to the outer circumference of the housing 311, for airtightly sealing between the housing 311 and a fitting hole for fitting a pressure detector 20 by being compressed therebetween. A housing 311 tip part that is a portion of the housing 311 on the end side from a reference position in the axial direction of the housing 311 at which the pressure received from the seal member 71 compressed between the housing 311 and the fitting hole is highest and a housing 311 rear end part that is a portion of the housing 311 closer to the other end side than the reference position where the axial length of the housing 311 is equal to the housing 311 tip part are substantially equal in rigidity.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a pressure detection device that detects pressure using a detection element.

  2. Description of the Related Art As a pressure detecting device for detecting a pressure in a combustion chamber of an internal combustion engine or the like, an apparatus using a detecting element such as a piezoelectric element has been proposed.

  As an example of the pressure detection device, a cylindrical housing, a diaphragm attached to the front end side of the housing, a piezoelectric element arranged at the rear end side of the diaphragm in the housing, and detecting a pressure acting via the diaphragm, and a housing There is a pressure detecting device provided with a pressure transmitting member that contacts between the diaphragm and the pressure-sensitive element in the inside thereof and transmits the deflection of the diaphragm to the pressure-sensitive element. It is known that when such a pressure detecting device is used in a high-temperature environment such as an internal combustion engine, the surface of the diaphragm is bent by heat, and the output of the pressure detecting device is affected. In order to suppress the influence of bending due to heat, for example, Patent Document 1 proposes a pressure detecting device having a depression on the surface of a diaphragm. Patent Document 2 discloses a pressure detection device that includes a seal member that surrounds an outer surface of a housing (sensor body) and seals a space between the pressure detection device and a mounting hole (accommodation opening) of an internal combustion engine. ing.

JP-A-7-19981 JP 2010-91563 A

  A cylindrical housing, a diaphragm attached to a front end side of the housing, a piezoelectric element arranged at a rear end side of the diaphragm in the housing, and detecting a pressure acting through the diaphragm, and a diaphragm and a pressure-sensitive element in the housing In a pressure detecting device provided with a pressure transmitting member that abuts both of them and transmits the deflection of the diaphragm to the pressure-sensitive element, the surface of the diaphragm is bent by heat and affects the output of the pressure detecting device as described above. However, as a cause thereof, it is considered that the expansion and contraction of the cylindrical housing due to heat and the expansion and contraction of the sealing member surrounding the outer surface of the housing are considered.

  The expansion and contraction of the housing can be reduced by minimizing the difference in thermal expansion between each member accommodated in the housing and the housing as much as possible. However, for the sealing member, PTFE (Polytetrafluoroethylene: polytetrafluoroethylene) is used. ) Is often used, and since a metal material such as stainless steel is used for the housing, it is difficult to set a small difference in thermal expansion.

  In addition, the seal member surrounding the outer surface of the housing is mounted in a state of being sandwiched between the mounting hole for mounting the pressure detection device and the housing of the pressure detection device in order to seal between the two. Therefore, the pressure detection device receives pressure from the seal member in the radial direction of the housing, and the housing is in a state where the housing is tightened in the radial direction by the seal member. At this time, when the housing and the seal member receive heat, the seal member and the housing expand, the pressure received by the housing from the seal member increases, and the housing is radially inward (inside of the housing) by being tightened from the seal member. Distorted. Accordingly, the portion of the housing sandwiching the seal member is distorted radially outward. Due to the distortion of the housing, the surface of the diaphragm attached to the front end of the housing is extended in the radial direction, and the center of the diaphragm is distorted toward the front end in the axial direction (the side opposite to the side on which the pressure detection element is disposed), and pressure detection The output of the device will decrease (the pressure on the pressure sensing element will decrease). At this time, it is not enough to simply provide a depression in the diaphragm, and it is required to reduce the thermal effect in a pressure detection device in which the outer surface of the housing is surrounded by a seal member.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a pressure detecting device having a small thermal effect.

  A pressure detection device that is attached to a mounting hole of a container containing a pressure medium and detects a pressure of the pressure medium, wherein the pressure detection element that detects a change in pressure of the pressure medium and the pressure detection element are housed therein. A cylindrical housing, a diaphragm attached to one end of the housing, for receiving pressure of the pressure medium, attached to an outer periphery of the housing, and compressed between the housing and the mounting hole; An annular sealing member that hermetically seals between the two, and at a position where the pressure received from the sealing member compressed between the housing and the mounting hole is highest in the axial direction of the housing. A housing tip that is a part of the housing on one end side from a certain reference position, and an axial length of the housing is equal to the housing tip, and the housing is located on the other end side from the reference position. The rear end of the housing, which is the part, is rigid Substantially be a pressure detecting apparatus according to claim equal.

  The pressure detection device may further include a rigidity adjusting element for reducing or increasing the rigidity of the housing front end or the housing rear end at one of the housing front end and the housing rear end. Good.

  The rigidity adjusting element may be a pressure detecting device that is a thin portion provided at a part of the front end portion of the housing or a rear end portion of the housing.

  ADVANTAGE OF THE INVENTION According to this invention, the pressure detection apparatus with a small heat influence can be provided.

1 is a schematic configuration diagram of a pressure detection system 1 according to an embodiment. It is a sectional view of a pressure detector concerning an embodiment. It is an expanded sectional view of the tip side of the pressure detecting device concerning an embodiment. FIG. 4 is a diagram illustrating a pressure detection device of Comparative Example 1. FIG. 9 is a diagram illustrating a pressure detection device of Comparative Example 2.

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 the embodiment. The pressure detection system 1 detects a pressure (combustion pressure) in a combustion chamber C of the internal combustion engine 10, and supplies power to the pressure detection device 20 and, based on the pressure detected by the pressure detection device 20. A control device 80 for controlling the operation of the internal combustion engine 10 and a connection cable 90 for electrically connecting the pressure detection device 20 and the control device 80 are provided.

  Here, the internal combustion engine 10 whose pressure is to be detected includes a cylinder block 11 having a cylinder formed therein, a piston 12 reciprocating in the cylinder, a combustion chamber C which is fastened to the cylinder block 11 and the piston 12 and the like. And a cylinder head 13. The cylinder head 13 is provided with a mounting hole 13a for communicating the combustion chamber C with the outside. The pressure detection device 20 is attached to the internal combustion engine 10 by inserting and fixing the pressure detection device 20 into the attachment hole 13a. Here, the cylinder block 11, the piston 12, and the cylinder head 13 constituting the internal combustion engine 10 are made of a conductive metal material such as cast iron or aluminum.

[Configuration of pressure detector]
FIG. 2 is a cross-sectional view of the pressure detection device 20. FIG. 3 is an enlarged sectional view of the distal end side of the pressure detection device 20.

  The pressure detection device 20 according to the present embodiment includes a housing 30 exposed to the outside and various mechanisms for detecting pressure, and is substantially entirely housed in the housing 30 and partially (connection described later). It has a detection mechanism section 40 provided so that the member 54) is exposed to the outside, and a seal section 70 attached to the outer peripheral surface of the housing section 30. The pressure detecting device 20 is different from the internal combustion engine 10 shown in FIG. 1 in that the left side in FIG. 2 (the portion where the housing 30 is exposed) faces the combustion chamber C (the lower side in FIG. 1). Is attached so that the right side (the part where the detection mechanism 40 is exposed) faces the outside (upward in FIG. 1). In this state, the seal 70 is located inside the mounting hole 13 a provided in the cylinder head 13. In the following description, in FIG. 2, the side facing the left in the figure is referred to as the “front end side” of the pressure detection device 20, and the side facing the right in the drawing is referred to as the “rear end side” of the pressure detection device 20. Further, in the following description, the center line direction of the pressure detecting device 20 indicated by a dashed line in FIG. 2 is simply referred to as the center line direction.

[Configuration of housing unit]
The housing unit 30 includes a front housing 31, a diaphragm 32 attached to the front end of the front housing 31, and a rear housing 33 attached to the rear end of the front housing 31. Have.

(Front side housing)
The distal end side housing 31 is a member having a hollow structure and presenting a cylindrical shape as a whole. The front end side housing 31 is made of a metal material such as stainless steel having conductivity and high heat resistance and acid resistance.

  The front end housing 31 includes a first front end housing 311 located relatively on the front end side, and a second front end housing 312 located relatively on the rear end side. Here, in the distal end housing 31, the outer peripheral surface on the rear end side of the first distal end housing 311 and the inner peripheral surface on the distal end side of the second distal end housing 312 are laser-welded, so that both are formed. Are integrated. The diaphragm 32 is attached to the distal end side of the first distal end housing 311 by laser welding, and the rear end housing 33 is attached to the rear end side of the second distal end housing 312 by fitting. Can be

  Here, a concave portion 311 a for mounting a first seal member 71 (which will be described in detail later) constituting the seal portion 70 is provided on the outer peripheral surface of the first front end side housing 311. Further, the concave portion 311a is provided with a convex portion 311c having a large diameter at a central portion in the center line direction of the concave portion 311a and having the central portion as an apex and decreasing in diameter toward the front end side and the rear end side of the concave portion 311a. . Further, inside the first front end side housing 311, a part set to a first diameter on the front end side, and a part set to a second diameter larger than the first diameter on the rear end side. An inner step 311b is provided at the boundary between these two parts to connect them. The first distal end housing 311 has a portion from a vertex of the convex portion 311c in the concave portion 311a to a distal end portion of the first distal end housing 311 (joining portion with the diaphragm 32) from a vertex of the convex portion 311c. And the rigidity between the portion from the vertex of the convex portion 311c to the rear end side, and the length from the vertex of the convex portion 311c to the front end portion of the first front side housing 311 in the center line direction is equal. They are set to be almost equal.

  In the pressure detection device 20 according to the present embodiment, by adjusting the thickness of the first distal end housing 311, the distance from the top of the convex portion 311 c to the distal end of the first distal end housing 311 is adjusted. Rigidity between the part and the part from the vertex of the convex part 311c to the rear end side, and the part from the vertex of the convex part 311c to the front end part of the first front side housing 311 in the center line direction is equal. Are configured to be equal. As another method for equalizing the rigidity, for example, as a rigidity adjusting element, at least one of the inner peripheral surface and the outer peripheral surface of the first distal housing 311 has a thin wall formed of an annular groove or a groove in the center line direction. It is also possible to provide a part partially. In addition to the grooves, at least one of the inner peripheral surface and the outer peripheral surface of the first distal end side housing 311 may be partially provided with a thick portion formed of a convex portion.

  On the other hand, on the outer peripheral surface of the second front end side housing 312, a concave portion 312a for mounting a second seal member 72 (which will be described later in detail) constituting the seal portion 70 together with the first seal member 71 is provided. . Further, a ring-shaped rib portion 312b protruding outward is provided on the outer peripheral surface of the second front end side housing 312 on the rear end side of the concave portion 312a. The rib portion 312b is used for fixing the pressure detecting device 20 to the internal combustion engine 10 (more specifically, the cylinder head 13).

(Diaphragm)
The diaphragm 32 is a member having a disk shape as a whole. The diaphragm 32 is made of a metal material such as stainless steel, which has conductivity and high heat resistance and acid resistance. In particular, in this example, the diaphragm 32 and the front end side housing 31 are made of the same material.

  The diaphragm 32 has a concave portion 32b formed in a central portion on the distal end side, a pressure receiving surface (front surface) 32a that receives pressure by being exposed to the outside (the combustion chamber C side), and a back side of the pressure receiving surface 32a. A concave portion 32c provided by notching the rear surface annularly, and a convex portion 32d projecting rearward from a central portion (a portion where the concave portion 32b is formed) of the pressure receiving surface 32a due to the presence of the concave portion 32c. Have. The diaphragm 32 is provided so as to close an opening on the distal end side of the first distal end housing 311. The boundary between the diaphragm 32 and the first tip side housing 311 is subjected to laser welding over the entire outer peripheral surface.

(Rear end side housing)
The rear end side housing 33 is a member having a hollow structure and presenting a cylindrical shape as a whole. The rear end side housing 33 is made of a metal material such as stainless steel, which has conductivity and high heat resistance and acid resistance. However, when the pressure detection device 20 is mounted on the internal combustion engine 10, the rear end housing 33 is located outside the internal combustion engine 10, so that the rear end housing 33 has higher heat resistance and acid resistance than the front end housing 31 described above. Lower materials can be used.

  The rear-end-side housing 33 has a first rear-end-side housing 331 located relatively on the front end side, and a second rear-end-side housing 332 located relatively on the rear end side. Here, in the rear end side housing 33, the outer peripheral surface on the front end side of the second rear end side housing 332 is fitted into the inner peripheral surface on the rear end side of the first rear end side housing 331, so that both are fitted. It is configured to be integrated. The front-end housing 31 (more specifically, the second front-end housing 312) is attached to the front-end side of the first rear-end housing 331 by fitting, and the second rear-end housing 311 is fitted. A connection member 54 (to be described in detail later) is attached to the rear end side of 332 by fitting.

[Configuration of detection mechanism]
The detection mechanism 40 includes a piezoelectric element 41, a front electrode member 42, a first rear electrode member 43, and a second rear electrode member 44. The detection mechanism 40 includes an insulating ring 45, a first coil spring 46, a conductive member 47, and a holding member 48. Further, the detection mechanism section 40 includes a pressing member 49, a supporting member 50, a second coil spring 51, and a housing member 52. Furthermore, the detection mechanism unit 40 includes a circuit board 53, a connection member 54, a ground plate 55, and an O-ring 56. Further, the detection mechanism section 40 includes an abutment pipe 57. The detection mechanism section 40 includes an insulating pipe 60, a first insulating member 61, a second insulating member 62, and a third insulating member 63.

(Piezoelectric element)
The piezoelectric element 41 as an example of the detection element is a member having a columnar shape as a whole. The piezoelectric element 41 includes a piezoelectric body exhibiting a piezoelectric effect of a piezoelectric longitudinal effect. The piezoelectric longitudinal effect means that when an external force is applied to a 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. The piezoelectric element 41 is disposed inside the front end housing 31 and on the rear end side of the diaphragm 32. The piezoelectric element 41 is accommodated in the distal end side housing 31 such that the center line direction is the direction of the stress application axis. Here, the piezoelectric element 41 is disposed inside the pressure member 49 provided inside the distal end side housing 31 and inside the insulating pipe 60 provided inside the pressure member 49. . The outer diameter of the piezoelectric element 41 is slightly smaller than the inner diameter of the insulating pipe 60 that houses the piezoelectric element 41 therein. The front surface of the piezoelectric element 41 is in contact with the rear surface of the front electrode member 42. On the other hand, the surface on the rear end side of the piezoelectric element 41 is in contact with the surface on the front end side of the first rear end electrode member 43. The outer peripheral surface of the piezoelectric element 41 faces the inner peripheral surface of the insulating pipe 60. Thus, by providing the insulating pipe 60 between the inner peripheral surface of the pressing member 49 and the outer peripheral surface of the piezoelectric element 41, the pressing member 49 and the piezoelectric element 41 do not directly contact.

  Next, an example in which the piezoelectric lateral effect is used for the piezoelectric element 41 will be described. The piezoelectric lateral effect means that when an external force is applied to a 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 thin-film-shaped piezoelectric bodies may be laminated, and by laminating in such a manner, electric charges generated in the piezoelectric bodies can be efficiently collected and the sensitivity of the sensor can be increased. Examples of the piezoelectric body usable in the piezoelectric element 41 include the use of a langasite-based crystal (langasite, langatate, langanite, LTGA) having a piezoelectric longitudinal effect and a piezoelectric transverse effect, quartz, gallium phosphate, and the like. can do. In the piezoelectric element 41 of the present embodiment, an LTGA single crystal is used as the piezoelectric body.

(Tip electrode member)
The tip electrode member 42 as an example of the first transmission member is a member having a columnar 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. An insulating film 42a formed by coating a ceramic material having an insulating property, such as alumina or zirconia, is formed in a central portion of a surface on the distal end side of the distal electrode member 42. Here, the insulating film 42a as an example of the insulating transmission part has, for example, a circular shape, and the diameter thereof is larger than the diameter of the convex part 32d provided on the back surface of the diaphragm 32. 49 is smaller than the diameter of the opening provided on the tip side.

  The tip electrode member 42 is arranged inside a pressing member 49 provided inside the tip side housing 31. The tip electrode member 42 is disposed on the rear end side of the diaphragm 32 and on the front end side of the piezoelectric element 41. However, unlike the piezoelectric element 41 described above, the tip electrode member 42 is not housed in the insulating pipe 60. The outer diameter of the tip electrode member 42 is slightly smaller than the inner diameter of the pressing member 49 that houses the tip electrode member 42 therein. And, of the surface on the distal end side of the distal electrode member 42, the central region where the insulating film 42a is provided is in contact with the rear end surface of the convex portion 32d provided on the back surface of the diaphragm 32. . Further, of the surface on the distal end side of the distal end electrode member 42, the peripheral region where the insulating film 42 a is not provided is in contact with the surface on the back side of the opening provided on the distal end side of the pressing member 49. . On the other hand, the surface on the rear end side of the tip electrode member 42 is in contact with the surface on the front end side of the piezoelectric element 41. The outer peripheral surface of the tip electrode member 42 faces the inner peripheral surface of the pressing member 49.

(First rear end electrode member)
The first rear end electrode member 43 is a member having a disk shape as a whole. The first rear end electrode member 43 is made of a metal material such as stainless steel which has conductivity and high heat resistance and has a small difference in thermal expansion from the piezoelectric element 41.

  The first rear end electrode member 43 is disposed inside a pressure member 49 provided inside the front end side housing 31. The first rear end electrode member 43 is arranged on the rear end side of the piezoelectric element 41 and on the front end side of the second rear end electrode member 44. Here, the first rear end electrode member 43 is disposed inside an insulating pipe 60 provided inside the pressing member 49. Further, the outer diameter of the first rear end electrode member 43 is substantially the same as the outer diameter of the piezoelectric element 41, and is slightly smaller than the inner diameter of the insulating pipe 60. The surface on the front end side of the first rear end electrode member 43 is in contact with the surface on the rear end side of the piezoelectric element 41. On the other hand, the surface on the rear end side of the first rear end electrode member 43 is in contact with the front end side surface of the second rear end electrode member 44. Further, the outer peripheral surface of the first rear end electrode member 43 faces the inner peripheral surface of the insulating pipe 60. By providing the insulating pipe 60 between the inner peripheral surface of the pressing member 49 and the outer peripheral surface of the first rear end electrode member 43, the pressing member 49 and the first rear end electrode member 43 Do not touch directly.

(2nd rear end electrode member)
The second rear end electrode member 44 has a top shape as a whole and has a T-shaped cross section. The second rear end electrode member 44 is made of a metal material such as stainless steel having conductivity and high heat resistance. The second rear end electrode member 44 has a disk-shaped main body portion 44a located on the front end side, and has a columnar shape and has a rear end side surface from the central portion on the rear end side surface of the main body portion 44a. The protruding portion includes a first protruding portion 44b that protrudes, and a second protruding portion 44c having a columnar shape and protruding further from the rear end of the first protruding portion 44b toward the rear end side. Here, the diameter of the first protrusion 44b is smaller than the diameter of the main body 44a, and the diameter of the second protrusion 44c is smaller than the diameter of the first protrusion 44b.

  The second rear end electrode member 44 is disposed inside a pressing member 49 provided inside the front end side housing 31. Here, the front end side of the main body portion 44 a in the second rear end electrode member 44 is disposed inside an insulating pipe 60 provided inside the pressing member 49. On the other hand, a portion on the rear end side of the second rear end electrode member 44 is disposed outside the insulating pipe 60. Further, the outer diameter of the main body portion 44 a of the second rear end electrode member 44 is substantially the same as the outer diameter of the piezoelectric element 41, and is slightly smaller than the inner diameter of the insulating pipe 60. The surface of the second rear end electrode member 44 on the front end side of the main body portion 44a is in contact with the surface of the first rear end electrode member 43 on the rear end side. On the other hand, the surface on the rear end side of the main body portion 44a is in contact with the surface on the front end side of the insulating ring 45. The outer peripheral surface of the first convex portion 44b of the second rear end electrode member 44 has its distal end side in contact with the inner peripheral surface of the insulating ring 45, and its rear end side has an inner peripheral surface of the support member 50 via an air gap. Face to face. Further, the outer peripheral surface of the second convex portion 44c of the second rear end electrode member 44 faces the inner peripheral surface of the support member 50 via an air gap, and the first coil spring 46 attached to the outer peripheral surface. Is in contact with the conductive member 47 through the contact. Thus, by providing the insulating pipe 60, the air gap, and the insulating ring 45 between the inner peripheral surface of the pressing member 49 and the outer peripheral surface of the second rear end electrode member 44, the pressing member 49 and the second It does not directly contact the rear end electrode member 44. Further, by providing an air gap between the inner peripheral surface of the support member 50 and the outer peripheral surface of the second rear end electrode member 44, the support member 50 and the second rear end electrode member 44 are in direct contact with each other. do not do.

(Insulation ring)
The insulating ring 45 is a member having a ring shape as a whole. The insulating ring 45 is made of a ceramic material such as alumina having an insulating property and a high heat resistance.

  The insulating ring 45 is disposed inside a pressing member 49 provided inside the distal end side housing 31. The insulating ring 45 is located on the rear end side of the main body portion 44 a in the second rear end electrode member 44 and on the front end side of the support member 50. Here, the first convex portion 44b of the second rear end electrode member 44 is disposed inside the through hole provided in the insulating ring 45. The outer diameter of the insulating ring 45 is slightly smaller than the inner diameter of the pressing member 49. Further, the inner diameter of the through hole of the insulating ring 45 is slightly larger than the outer diameter of the first protrusion 44 b of the second rear end electrode member 44. The front surface of the insulating ring 45 is in contact with the rear surface of the main body 44 a of the second rear electrode member 44. On the other hand, the rear end surface of the insulating ring 45 is in contact with the front end surface of the support member 50. Further, the outer peripheral surface of the insulating ring 45 faces the inner peripheral surface of the pressing member 49. Further, the inner peripheral surface of the insulating ring 45 faces the outer peripheral surface of the first convex portion 44b of the second rear end electrode member 44.

(1st coil spring)
The first coil spring 46 is a member having a spiral shape as a whole, and expands and contracts in the center line direction. The first coil spring 46 is made of a metal material such as brass having conductivity and higher conductivity than the distal end side housing 31, and its surface is plated with gold.

  The first coil spring 46 is provided inside the distal end side housing 31, and is arranged inside the pressing member 49 and inside the supporting member 50. The first coil spring 46 is disposed on the rear end side of the second rear end electrode member 44 and on the front end side of the conductive member 47. That is, the first coil spring 46 is disposed so as to straddle the second rear end electrode member 44 and the conductive member 47. Here, the front end side of the first coil spring 46 is wound around the second convex portion 44c of the second rear end electrode member 44, and the rear end side of the first coil spring 46 is provided on the front end side of the conduction member 47. Is inserted into the formed front-side concave portion 47a. The inner diameter of the first coil spring 46 is larger than the outer diameter of the second protrusion 44c of the second rear end electrode member 44 and smaller than the inner diameter of the first protrusion 44b. On the other hand, the outer diameter of the first coil spring 46 is smaller than the inner diameter of the front-side concave portion 47 a of the conductive member 47. As a result, the distal end of the first coil spring 46 abuts on the boundary (step) between the first convex portion 44b and the second convex portion 44c in the second rear end electrode member 44, and the distal end side of the first coil spring 46. Is in contact with the outer peripheral surface of the second convex portion 44c of the second rear end electrode member 44. On the other hand, the rear end of the first coil spring 46 abuts against the bottom of the distal recess 47a of the conductive member 47, and the rear end of the first coil spring 46 is the inner peripheral surface of the distal recess 47a of the conductive member 47. Is in contact with The outer periphery of the first coil spring 46 faces the inner peripheral surface of the support member 50 via an air gap. As described above, by providing the air gap between the inner peripheral surface of the support member 50 and the first coil spring 46, the support member 50 and the first coil spring 46 do not directly contact.

(Conductive member)
The conductive member 47 is a member having a rod shape as a whole. The conductive member 47 is made of a conductive metal material such as brass, and its surface is plated with gold. The front end of the conductive member 47 is provided with the above-described front-side concave portion 47a. The rear end of the conductive member 47 has a diameter smaller than that of the center in the center line direction and projects toward the rear end. The projection 47b is provided.

  The conductive member 47 is provided inside the front end housing 31, and almost all portions except for the front end portion and the rear end portion (the rear end side convex portion 47 b) are arranged inside the holding member 48. I have. The front end of the conductive member 47 is inside the pressurizing member 49, the rear end of the conductive member 47 is inside the housing member 52, and the intermediate portion located between the front end and the rear end is a second coil spring. 51, respectively. The conduction member 47 is disposed on the rear end side of the first coil spring 46 and on the front end side of the circuit board 53. The conductive member 47 is disposed so as to pass through a through hole provided in the holding member 48 along the center line direction. The outer diameter of the tip of the conductive member 47 (the portion not covered by the holding member 48) is larger than the inner diameter of the holding member 48 and smaller than the inner diameter of the support member 50. Further, the outer diameter of the rear end portion (the rear end side convex portion 47b) of the conductive member 47 is substantially the same as the inner width of the holding portion provided on the holding member 48. Furthermore, the outer diameter of the center of the conductive member 47 in the center line direction is substantially the same as the inner diameter of the holding member 48. The rear end of the first coil spring 46 is inserted into the front-side concave portion 47 a of the conductive member 47, so that the first coil spring 46 is in contact with the first coil spring 46. On the other hand, the rear end side convex portion 47b of the conductive member 47 is fitted into a holding portion provided on the holding member 48. Further, the outer peripheral surface of the distal end portion of the conductive member 47 faces the inner peripheral surface of the support member 50 via an air gap. Further, the outer peripheral surface at the center in the center line direction of the conductive member 47 faces the second coil spring 51 via the holding member 48 and the air gap. Furthermore, the outer peripheral surface of the rear end portion of the conductive member 47 faces the outer peripheral surface of the housing member 52 via the air gap and the holding member 48. Thus, by providing the air gap and the holding member 48 between the inner peripheral surface of the support member 50 and the outer peripheral surface of the conductive member 47, the support member 50 and the conductive member 47 do not directly contact. Further, by providing the air gap and the holding member 48 between the inner peripheral surface of the second coil spring 51 and the outer peripheral surface of the conductive member 47, the second coil spring 51 and the conductive member 47 do not directly contact. Furthermore, by providing an air gap between the inner peripheral surface of the housing member 52 and the outer peripheral surface of the conductive member 47, the housing member 52 and the conductive member 47 do not directly contact.

(Holding member)
The holding member 48 is a member formed by integrating a cylindrical portion located on the front end side and a plate-shaped portion located on the rear end side. The holding member 48 includes a base made of a synthetic resin material such as PPT (polypropylene terephthalate) having an insulating property, and a wiring and a terminal made of a metal material such as a conductive copper. Contains. A conductive member 47 is accommodated in a cylindrical portion located on the front end side of the holding member 48, and a circuit board 53 is mounted on a plate-shaped portion located on the rear end side of the holding member 48. As described above, the holding member 48 has a function of holding the conductive member 47 and the circuit board 53.

  A portion (outer peripheral surface) of the holding member 48 facing the support member 50, the second coil spring 51, and the housing member 52 is made of a synthetic resin material, so that the metal material is not exposed to this portion. . Further, a portion (inner peripheral surface) of the holding member 48 facing the intermediate portion located between the front end portion and the rear end portion of the conductive member 47 is also made of a synthetic resin material. The material is not exposed. At the rear end side of the cylindrical portion of the holding member 48, a holding portion which is made of a metal material and which fits and holds the rear end side projection 47b of the conductive member 47 is provided. Wiring for electrically connecting to a signal input terminal (not shown) of the circuit board 53 is attached to this holding unit.

  The holding member 48 is provided across the inside of the front end housing 31 and the inside of the rear end housing 33. The front end side of the holding member 48 is inside the pressure member 49, the rear end side of the conduction member 47 is inside the housing member 52, and the intermediate portion located between the front end side and the rear end side is a second coil spring. 51, respectively. The holding member 48 is disposed on the rear end side of the insulating ring 45 and on the front end side of the connection member 54.

  The outer diameter of the cylindrical portion located on the distal end side of the holding member 48 is smaller than the inner diameter of the support member 50, and the outer diameter of the plate-shaped portion located on the rear end side of the covering member is equal to the outer diameter of the housing. It is smaller than the inner diameter of the member 52. Further, the outer peripheral surface on the distal end side of the cylindrical portion of the holding member 48 faces the inner peripheral surface of the support member 50 and the inner peripheral surface of the second coil spring 51 via an air gap. Further, the outer peripheral surface on the rear end side of the cylindrical portion of the holding member 48 and the outer peripheral surface of the plate-shaped portion are in contact with the inner peripheral surface of the housing member 52 or through the air gap. Face to face.

(Pressing member)
The pressing member 49 as an example of the first applying member is a member having a cylindrical shape as a whole. The pressure member 49 is made of a metal material such as stainless steel having conductivity and high heat resistance.

  The pressing member 49 according to the present embodiment includes a distal end tubular portion 491 that is located at the most distal end side and has an opening at the distal end, and an intermediate tubular portion that is disposed at the rear end side of the distal end tubular portion 491. 492, and a rear end tubular portion 493 located at the rear end side of the intermediate tubular portion 492 and located at the rearmost end side. In the pressing member 49, the outer diameter of the intermediate tubular portion 492 is larger than that of the front tubular portion 491 and the rear tubular portion 493, and the outer diameter of the rear tubular portion 493 is larger than that of the front tubular portion 491. The diameter is increasing. The pressing member 49 includes a stepped portion 49b connecting the front end tubular portion 491 and the intermediate tubular portion 492 at a boundary portion between the front end tubular portion 491 and the intermediate tubular portion 492, and a boundary portion between the intermediate tubular portion 492 and the rear end tubular portion 493. And a rear end step portion 49c connecting the both. The inner diameter of the pressing member 49 is the same size except for an opening provided at the tip. For this reason, in the pressing member 49, the thickness of the intermediate cylindrical portion 492 is larger than the thickness of the rear end cylindrical portion 493, and the thickness of the rear end cylindrical portion 493 is larger than the front end cylindrical portion 491. Is larger than the wall thickness. Therefore, in the pressing member 49, the intermediate cylindrical portion 492 is most difficult to bend, while the distal cylindrical portion 491 is most easily bent (easy to function as a spring).

  Further, the outer peripheral surfaces of the front step portion 49b, the intermediate tubular portion 492, and the rear step portion 49c of the pressing member 49 are coated with a ceramic material having an insulating property, such as alumina and zirconia, etc. The insulating film 49a is formed continuously.

  The pressure member 49 is provided inside the front end housing 31 so that the front end tubular portion 491 is on the front end side. Inside the pressure member 49, the piezoelectric element 41, the front electrode member 42, the first rear end electrode member 43, the second rear end electrode member 44, the insulating ring 45, the front end side of the support member 50, the insulating pipe 60, One coil spring 46, the distal end side of the conductive member 47 and the distal end side of the holding member 48 are housed. The pressing member 49 is arranged on the rear end side of the diaphragm 32 and on the front end side of the housing member 52. Further, the outer diameter of the pressure member 49 is different between the front cylindrical portion 491, the intermediate cylindrical portion 492, and the rear cylindrical portion 493, but is smaller than the inner diameter of the front housing 31 at all positions. Further, the inner diameter of the pressing member 49 is set at a position facing the front end electrode member 42 and the insulating pipe 60 (the piezoelectric element 41, the first rear end electrode member 43, the second rear end electrode member 44, and the insulating ring 45). Is slightly larger than the outer diameter of the support member 50, and is substantially the same as the outer diameter of the support member 50 at a portion facing the support member 50.

  Here, an abutting pipe 57 is provided between the outer peripheral surface of the rear end cylindrical portion 493 provided on the rear end side of the pressing member 49 and the inner peripheral surface of the rear end side of the first front end housing 311. Is arranged.

  Further, a surface on the distal end side of the distal end cylindrical portion 491 (the surface on the front side of the opening) of the pressing member 49 faces the concave portion 32c of the diaphragm 32 via an air gap. On the other hand, the rear end side of the rear end cylindrical portion 493 faces the first insulating member 61 via an air gap. Further, the outer peripheral surface of the distal end tubular portion 491 faces the inner peripheral surface of the first distal end side housing 311 via an air gap. Further, the outer peripheral surfaces of the front step portion 49b, the intermediate cylindrical portion 492, and the rear step portion 49c are in contact with the insulating film 49a and face the inner peripheral surface of the first front housing 311 via the insulating film 49a. doing. Furthermore, the outer peripheral surface of the rear end tubular portion 493 faces the inner peripheral surface of the abutting pipe 57 via an air gap. As described above, by providing the air gap and the insulating film 49a between the outer peripheral surface of the pressurizing member 49 and the inner peripheral surface of the first tip side housing 311 and the inner peripheral surface of the butting pipe 57, the pressurization is performed. The member 49 does not directly contact the first tip side housing 311 and the butting pipe 57.

(Support member)
The support member 50 as an example of the second applying member is a member having a cylindrical shape as a whole. The support member 50 is made of a metal material such as stainless steel having conductivity and high heat resistance.

  The support member 50 is provided inside the front end housing 31, and its front end is located inside the pressing member 49, and its rear end is located outside the pressing member 49. The support member 50 has a rear end side of the second rear end electrode member 44 (the first convex portion 44b and the second convex portion 44c), a first coil spring 46, a front end side of the conductive member 47, and a holding member. 48 are accommodated. The support member 50 is disposed on the rear end side of the insulating ring 45 and on the front end side of the housing member 52. The outer diameter of the support member 50 is substantially the same as the inner diameter of the first pressing member 37. Further, the inner diameter of the support member 50 differs depending on the position in the center line direction, but is larger than the outer diameter of the second rear end electrode member 44 at a portion facing the second rear end electrode member 44, and The portion facing the first coil spring 46 is larger than the outer diameter of the first coil spring 46, the portion facing the conductive member 47 is larger than the outer diameter of the conductive member 47, and the portion facing the holding member 48 is the outer diameter of the holding member 48. Greater than. The surface on the front end side of the support member 50 (the surface on the front side of the opening) is in contact with the surface on the rear end side of the insulating ring 45. On the other hand, the surface on the rear end side of the support member 50 faces the housing member 52 via an air gap. The distal end of the outer peripheral surface of the support member 50 is in contact with the inner peripheral surface of the pressing member 49, and the rear end of the outer peripheral surface of the support member 50 is in contact with the distal end of the second coil spring 51. I have. Here, the inner peripheral surface of the rear end side of the pressing member 49 and the outer peripheral surface of the supporting member 50 facing this portion are formed by the second welded portion 59 obtained by laser welding over the entire circumference. 49 and the supporting member 50 are joined and fixed. On the other hand, the inner peripheral surface of the support member 50 faces the second rear end electrode member 44, the first coil spring 46, the conductive member 47, and the holding member 48 via an air gap. Thus, by providing the air gap between the inner peripheral surface of the support member 50 and the second rear end electrode member 44, the first coil spring 46, the conductive member 47, and the holding member 48, the support member 50 The second rear end electrode member 44, the first coil spring 46, the conduction member 47, and the holding member 48 do not directly contact.

(Second coil spring)
The second coil spring 51 is a member having a spiral shape as a whole, and expands and contracts in the center line direction. The second coil spring 51 is made of a metal material such as stainless steel which has conductivity and high heat resistance, and its surface is plated with gold. As described above, in the present embodiment, the first coil spring 46 and the second coil spring 51 are made of different materials.

  The second coil spring 51 is provided inside the front end side housing 31, and the front end side is on the rear end side and outside of the support member 50, and the rear end side is on the front end side and outside of the housing member 52, respectively. positioned. That is, the second coil spring 51 is disposed so as to straddle the support member 50 and the housing member 52. The outer diameter of the second coil spring 51 is smaller than the inner diameter of the distal end housing 31 (more specifically, the second distal end housing 312). Further, the inner diameter of the second coil spring 51 is slightly smaller than the outer diameter of the support member 50 on the rear end side and the outer diameter of the housing member 52 on the distal end side. The outer periphery of the second coil spring 51 faces the inner peripheral surface of the distal end side housing 31 via an air gap. As described above, by providing the air gap between the outer periphery of the second coil spring 51 and the inner peripheral surface of the distal housing 31, the second coil spring 51 does not directly contact the distal housing 31. .

(Accommodation member)
The housing member 52 is a member having a cylindrical shape as a whole. The housing member 52 is made of a metal material such as brass or stainless steel, which has conductivity and is more conductive than the distal end side housing 31, and its surface is gold-plated.

  The housing member 52 according to the present embodiment includes a first cylindrical portion 521 located at the most distal end and having an opening at the distal end, and a second cylindrical portion disposed at the rear end side of the first cylindrical portion 521. A cylindrical portion 522, a third cylindrical portion 523 disposed on the rear end side of the second cylindrical portion 522, and a fourth cylindrical portion 524 disposed on the rear end side of the third cylindrical portion 523. ing. In this housing member 52, the outer diameter increases in the order of the first tubular portion 521, the second tubular portion 522, the third tubular portion 523, and the fourth tubular portion 524. That is, in the housing member 52, the diameter increases stepwise (four steps) from the front end side to the rear end side. The housing member 52 includes a first step portion 52a connecting the first tubular portion 521 and the second tubular portion 522 at a boundary portion thereof, a second tubular portion 522, and a third tubular portion 523. And a third step 52c connecting the two at the boundary between the third tubular portion 523 and the fourth tubular portion 524. Note that, unlike the above-described pressurizing member 49, the thickness of the housing member 52 is set to a constant size regardless of the position in the center line direction. For this reason, in the pressing member 49, the inner diameter increases in the order of the first tubular portion 521, the second tubular portion 522, the third tubular portion 523, and the fourth tubular portion 524.

  The housing member 52 is provided such that the first tubular portion 521 is on the front end side across the inside of the front end housing 31 and the inside of the rear end housing 33. Inside the housing member 52, the rear end side of the conductive member 47, the rear end side of the holding member 48, the circuit board 53 and the ground plate 55 are housed. The housing member 52 is disposed on the rear end side of the support member 50 and on the front end side of the connection member 54. Further, the outer diameter of the housing member 52 is different between the first tubular portion 521, the second tubular portion 522, the third tubular portion 523, and the fourth tubular portion 524, but the distal end housing is located at all positions. 31 and the inner diameter of the rear end side housing 33. Further, the inner diameter of the housing member 52 is also different between the first tubular portion 521, the second tubular portion 522, the third tubular portion 523, and the fourth tubular portion 524, but the outer diameter of each member housed inside is different. Larger than the diameter.

  Here, the first insulating member 61 is disposed between the rear end side of the second cylindrical portion 522 and the second step portion 52 b of the housing member 52 and the inner peripheral surface of the second front end side housing 312. ing. A second insulating member 62 is disposed between the rear end side of the third cylindrical portion 523 and the third step portion 52 c of the housing member 52 and the inner peripheral surface of the second front end side housing 312. I have. Further, a third insulating member 63 is disposed between the fourth cylindrical portion 524 of the housing member 52 and the first rear end side housing 331.

  The surface on the front end side of the first tubular portion 521 (the surface on the front side of the opening) in the housing member 52 faces the rear end side surface of the support member 50 via an air gap. The first tubular portion 521 is in contact with the second coil spring 51. On the other hand, the rear end side of the fourth tubular portion 524 faces the holding member 48. The outer peripheral surfaces of the first cylindrical portion 521 and the first step portion 52a are opposed to the inner peripheral surface of the second front end housing 312 via an air gap. Further, the outer peripheral surface of the second cylindrical portion 522 faces the inner peripheral surface of the second front end side housing 312 via the air gap and the first insulating member 61. Furthermore, the second step portion 52 b is opposed to the inner peripheral surface of the second distal end housing 312 via the first insulating member 61. The outer peripheral surface of the third cylindrical portion 523 faces the inner peripheral surface of the second front end side housing 312 via the air gap and the second insulating member 62. Further, the outer peripheral surface of the third step portion 52c is opposed to the inner peripheral surface of the second front end housing 312 via the second insulating member 62. The outer peripheral surface of the fourth cylindrical portion 524 faces the inner peripheral surface of the second front end housing 312 via the air gap, and the first rear end via the air gap and the third insulating member 63. It faces the inner peripheral surface of the side housing 331. Thus, the air gap, the first insulating member 61, the second insulating member 62, and the third By providing the insulating member 63, the housing member 52 does not directly contact the second front end side housing 312 and the first rear end side housing 331.

(Circuit board)
The circuit board 53 is a member having a rectangular plate shape as a whole. The circuit board 53 performs various processes using an electric circuit on an electric signal based on a weak electric charge output from the piezoelectric element 41 in accordance with the received pressure, and is configured by a so-called printed wiring board. The circuit board 53 is provided across the inside of the front end housing 31 and the inside of the rear end housing 33. Further, the circuit board 53 is disposed on the rear end side of the conductive member 47 and on the distal end side of the connection member 54. Further, the circuit board 53 is mounted on the holding member 48 and is entirely disposed inside the housing member 52.

  The circuit board 53 includes an integration circuit that integrates an input signal (charge signal) input from the piezoelectric element 41 and converts the signal into a voltage signal, and an amplification circuit that amplifies a voltage signal input from the integration circuit to output an output signal. A circuit and a power supply circuit serving as a power supply for elements such as an operational amplifier constituting the integration circuit and the amplification circuit are mounted (all not shown).

(Connecting member)
The connection member 54 is a member having a columnar shape as a whole. The connection member 54 includes a base made of a synthetic resin material such as PPT having an insulating property, and wirings and terminals made of a metal material having a conductive property such as copper. However, a portion (outer peripheral surface) of the connecting member 54 that contacts or faces the second rear end side housing 332 is made of a synthetic resin material, so that the metal material is not exposed to this portion. . An opening having a concave shape and opening toward the rear end is provided on the rear end of the connection member 54. A board-side connector 54 a that protrudes toward the tip side and is electrically connected to the circuit board 53 is provided on the distal end side of the connection member 54. On the other hand, a cable-side connector 54b to be connected to the connection cable 90 shown in FIG. Have been. In addition, a concave portion is provided on the outer peripheral surface on the distal end side of the connection member 54 over one circumference, and an O-ring 56 is attached to the concave portion.

  The connection member 54 has a front end located inside the second rear end housing 332 and a rear end located outside the second rear end housing 332. The O-ring 56 attached to the outer peripheral surface of the connection member 54 is in contact with the inner peripheral surface of the second rear end housing 332 inside the second rear end housing 332.

  The outer diameter of the cylindrical portion located on the distal end side of the connection member 54 is smaller than the inner diameter of the second rear end side housing 332. On the other hand, the outer diameter of the cylindrical portion located on the rear end side of the connection member 54 is substantially the same as the outer diameter of the second rear end side housing 332. The distal end side of the connection member 54 faces the inner peripheral surface of the second rear end side housing 332 via an air gap or an O-ring 56.

(Ground plate)
The ground plate 55 is a member having a band shape as a whole. The ground plate 55 is made of a conductive metal material such as phosphor bronze, and its surface is plated with gold.

  The grounding plate 55 is provided across the inside of the front end side housing 31 and the inside of the rear end side housing 33, and its front end is located inside the housing member 52 and above the circuit board 53. The rear end protrudes more rearward than the rear end of the housing member 52. The front end of the ground plate 55 is electrically connected to a ground terminal (not shown) of the circuit board 53, and the rear end of the ground plate 55 is connected to the inner periphery of the fourth tubular portion 524 of the housing member 52. It is electrically connected to the surface.

(O-ring)
The O-ring 56 is a member having a ring shape as a whole. The O-ring 56 is made of a synthetic resin material such as PTFE which has insulating properties and high heat resistance, moisture permeability and acid resistance.

  The O-ring 56 is attached to the outer peripheral surface of the connecting member 54, and when the connecting member 54 is attached to the second rear end housing 332, the outer peripheral surface of the connecting member 54 and the second rear end housing 332 between the inner peripheral surface and the inner peripheral surface.

(Butting pipe)
The butting pipe 57 as an example of the fixing member is a member having a cylindrical shape as a whole. The butting pipe 57 is made of a metal material such as stainless steel which has conductivity and high heat resistance.

  The butting pipe 57 is disposed inside the region where the first distal housing 311 and the second distal housing 312 overlap in the distal housing 31 and inside the first distal housing 311. ing. The butting pipe 57 is located on the rear end side of the intermediate tubular portion 492 of the pressing member 49 and on the front end side of the first insulating member 61. The outer diameter of the butting pipe 57 is substantially the same as the inner diameter of the rear end of the first front housing 311 that houses the butting pipe 57. On the other hand, the inner diameter of the butting pipe 57 is larger than the outer diameter of the rear end cylindrical portion 493 of the pressing member 49. The front end surface of the butting pipe 57 is in contact with the rear end step 49 c (the surface on which the insulating film 49 a is formed) of the pressing member 49. On the other hand, the surface on the rear end side of the abutting pipe 57 faces the surface on the front end side of the first insulating member 61 via an air gap. The outer peripheral surface of the butting pipe 57 is in contact with the inner peripheral surface of the rear end side of the first front end housing 311. Here, the first welded portion 58 obtained by laser welding the inner peripheral surface on the rear end side of the first front end side housing 311 and the outer peripheral surface of the butting pipe 57 facing this part over one circumference. The front end housing 311 and the butting pipe 57 are joined and fixed. On the other hand, the inner peripheral surface of the butting pipe 57 is opposed to the outer peripheral surface of the rear end cylindrical portion 493 of the pressing member 49 via the air gap. As described above, by providing the insulating film 49a and the air gap between the rear end step 49b and the rear end cylindrical portion 493 of the pressing member 49 and the butting pipe 57, the pressing pipe 57 is pressurized. It does not directly contact the member 49.

(First weld)
The first welded portion 58 is a portion formed by laser welding the inner peripheral surface of the rear end side of the first front end side housing 311 and the outer peripheral surface of the butting pipe 57 over one circumference.

(Second weld)
The second welded portion 59 is a portion formed by laser welding the inner peripheral surface on the rear end side of the pressing member 49 and the outer peripheral surface of the support member 50 over one circumference.

(Insulated pipe)
The insulating pipe 60 is a member having a cylindrical shape as a whole. The insulating pipe 60 is made of an insulating synthetic resin material such as LCP (Liquid Crystal Polymer). This insulating pipe 60 is arranged inside a pressure member 49 provided inside the distal end side housing 31. The distal end side of the main body portion 44a of the piezoelectric element 41, the first rear end electrode member 43, and the second rear end electrode member 44 is housed inside the insulating pipe 60. The insulating pipe 60 is located on the rear end side of the distal end electrode member 42 and on the distal end side of the insulating ring 45. The outer diameter of the insulating pipe 60 is slightly smaller than the inner diameter of the pressing member 49. Further, the inner diameter of the insulating pipe 60 is slightly larger than the respective outer diameters of the main body portion 44 a of the piezoelectric element 41, the first rear end electrode member 43, and the second rear end electrode member 44. The front end of the insulating pipe 60 faces the rear end surface of the front electrode member 42. On the other hand, the rear end side of the insulating pipe 60 faces the surface on the front end side of the insulating ring 45. Further, the outer peripheral surface of the insulating pipe 60 faces the inner peripheral surface of the pressing member 49. Further, the inner peripheral surface of the insulating pipe 60 faces the outer peripheral surface of the main body portion 44 a of the piezoelectric element 41, the first rear end electrode member 43, and the second rear end electrode member 44. Thus, the insulating pipe 60 and the air gap formed by the insulating pipe 60 are provided between the pressing member 49 and the main body 44a of the piezoelectric element 41, the first rear end electrode member 43, and the second rear end electrode member 44. Thus, the pressing member 49 does not directly contact the first rear end electrode member 43 and the second rear end electrode member 44.

(First insulating member)
The first insulating member 61 is a member having a cylindrical shape on the front end side and an annular shape on the rear end side. The first insulating member 61 is formed of a ceramic material such as alumina having an insulating property and a high heat resistance.

  This first insulating member 61 is disposed inside the front end side housing 31. The first insulating member 61 is disposed outside the second cylindrical portion 522 and the second step portion 52b in the housing member 52. Further, the outer diameter of the first insulating member 61 is slightly smaller than the inner diameter of the second front end side housing 312 of the corresponding part, and the inner diameter of the first insulating member 61 is smaller than the outer diameter of the housing member 52 of the corresponding part. Is also slightly larger. Then, the outer peripheral surface of the first insulating member 61 is in contact with the second front end side housing 312, and the inner peripheral surface of the first insulating member 61 is in contact with the housing member 52.

(Second insulating member)
The second insulating member 62 is a member having a ring shape as a whole. The second insulating member 62 is made of a ceramic material such as alumina having an insulating property and high heat resistance.

  The second insulating member 62 is disposed inside the front end housing 31 at a position closer to the rear end than the first insulating member 61 is. The second insulating member 62 is disposed outside the third cylindrical portion 523 and the third step portion 52c in the housing member 52. Further, the outer diameter of the second insulating member 62 is slightly smaller than the inner diameter of the second distal end housing 312 at the corresponding portion, and the inner diameter of the second insulating member 62 is smaller than the outer diameter of the housing member 52 at the corresponding portion. Is also slightly larger. The outer peripheral surface of the second insulating member 62 is in contact with the second front end side housing 312, and the inner peripheral surface of the second insulating member 62 is in contact with the housing member 52.

  Thus, by providing the air gap, the first insulating member 61 and the second insulating member 62 between the distal end housing 31 (second distal end housing 312) and the housing member 52, the distal end housing is provided. 31 and the housing member 52 do not directly contact.

(Third insulating member)
The third insulating member 63 is a member having a cylindrical shape as a whole. The third insulating member 63 is made of a ceramic material such as alumina having an insulating property and a high heat resistance.

  The third insulating member 63 is disposed inside the rear end housing 33 at a position closer to the rear end than the second insulating member 62 is. The third insulating member 63 is located outside the fourth tubular portion 524 in the housing member 52. The outer diameter of the third insulating member 63 is substantially the same as the inner diameter of the first rear end housing 331, and the inner diameter of the third insulating member 63 is the outer diameter of the fourth tubular portion 524 of the housing member 52. Greater than. The outer peripheral surface of the third insulating member 63 is in contact with the inner peripheral surface of the first rear end side housing 331, and the inner peripheral surface of the third insulating member 63 has a part on the front end side that is the housing member 52. The other faces the housing member 52 via the air gap.

[Structure of seal part]
The seal portion 70 has 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. In a state where the pressure detecting device 20 is attached to the internal combustion engine 10, the first seal member 71 and the second seal member 72 abut against an inner peripheral surface of an attachment hole 13a (see FIG. 1) provided in the cylinder head 13. .

(First seal member)
The first seal member 71 is a member having a hollow structure and presenting a cylindrical shape as a whole. The first seal member 71 is made of a synthetic resin material such as PTFE that has insulating properties and high heat resistance and acid resistance.

  The first seal member 71 is fitted in a concave portion 311 a provided on the outer peripheral surface of the first front end side housing 311. The inner diameter is slightly smaller than the outer diameter of the central portion where the diameter of the convex portion 311c of the concave portion 311a is the largest, and the outer diameter is slightly larger than the inner diameter of the mounting hole 13a. In a state where the first seal member 71 is fitted in the concave portion 311a and the pressure detecting device 20 is mounted in the mounting hole 13a, the first distal end side housing is located at a central portion where the diameter of the convex portion 311c of the concave portion 311a is maximum. The pressure that the body 311 receives from the first seal member 71 is the highest.

(Second seal member)
The second seal member 72 is a member having a ring shape as a whole, and uses an O-ring here. The second seal member 72 is also made of a synthetic resin material such as PTFE that has insulating properties and high heat resistance and acid resistance.

  The second seal member 72 is fitted in a concave portion 312 a provided on the outer peripheral surface of the second front end side housing 312. The inner diameter is slightly smaller than the outer diameter of the recess 312a, and the outer diameter is slightly larger than the inner diameter of the mounting hole 13a.

[Electrical connection structure in pressure detector]
Here, an electrical connection structure in the pressure detection device 20 will be described.

(Positive path)
In the pressure detection device 20, the rear end surface (positive electrode) of the piezoelectric element 41 has a first rear electrode member 43 made of metal, a second rear electrode member 44 made of metal, and a first coil spring made of metal. 46, it is electrically connected to a conductive member 47 made of metal. The metal conductive member 47 is electrically connected to an input terminal (not shown) provided on the circuit board 53 via a metal holding portion, wiring, and terminals provided on the holding member 48. You. In the following, a circuit board 53 is provided from the rear end side surface of the piezoelectric element 41 via a first rear end electrode member 43, a second rear end electrode member 44, a first coil spring 46, a conductive member 47, and a holding member 48. The electrical path leading to is called a “positive path”.

(Negative path)
On the other hand, in the pressure detecting device 20, the end surface (negative electrode) on the tip end side of the piezoelectric element 41 has a metal tip electrode member 42, a metal pressing member 49, and a metal supporting member 50 (second welding portion). 59), a second coil spring 51 made of metal, a housing member 52 made of metal, and a ground plate 55 made of metal, and electrically connected to a ground terminal (not shown) provided on the circuit board 53. It is connected. In the following, an electrical connection from the surface on the distal end side of the piezoelectric element 41 to the circuit board 53 via the distal electrode member 42, the pressing member 49, the support member 50, the second coil spring 51, the housing member 52, and the ground plate 55 Is called a “negative path”.

(Housing route)
On the other hand, in the pressure detecting device 20, the metal diaphragm 32 is connected to the metal rear end side via the metal front end housing 31 (the first front end housing 311 and the second front end housing 312). The housing 33 is electrically connected to the first rear end housing 331 and the second rear end housing 332. Further, in the pressure detecting device 20, the metal first tip side housing 311 is electrically connected to the metal butting pipe 57 (the first welded portion 58). Hereinafter, an electrical path from the diaphragm 32 to the rear end housing 33 and the abutting pipe 57 via the front end housing 31 is referred to as a “housing path”.

(Relationship between positive and negative paths)
Here, in the pressure detection device 20 of the present embodiment, a 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 insulating pipe 60, the insulating ring 45, the holding member 48, and the air gap formed between the two paths. Here, in the present embodiment, the negative path is an example of the first electric path, and the positive path is an example of the second electric path.

(Relationship between negative route and case route)
Further, in the pressure detecting device 20, the casing path exists outside the negative path. In other words, a negative path is accommodated inside the case path. The negative path and the housing path are defined by an insulating film 42a provided on the tip electrode member 42, an insulating film 49a provided on the pressing member 49, a first insulating member 61, a second insulating member 62, and a third It is electrically insulated by an insulating member 63 and an air gap formed between both paths.

(Relationship between chassis path and positive path)
As a result, in the pressure detecting device 20, the casing path exists outside the positive path. In other words, the positive path is accommodated inside the case path. As described above, the positive path and the negative path are electrically insulated, and the negative path and the housing path are electrically insulated. Are electrically insulated.

(Other)
Here, the casing portion 30 that constitutes the casing path is a portion that is exposed to the outside in the pressure detection device 20, and in particular, the diaphragm 32 is a portion that faces the combustion chamber C whose acidity increases with combustion. It has become. On the other hand, each member constituting the positive path and the negative path is a part of the pressure detection device 20 that is accommodated in the housing 30. For this reason, it is preferable that each member forming the positive path and the negative path is made of a material having higher conductivity than each member forming the housing path (the housing unit 30). It is preferable that each member constituting the housing portion 30) is made of a material having higher acid resistance than each member constituting the positive path and the negative path.

[Pressure detection operation by pressure detector]
Now, 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 32. In the diaphragm 32, the pressure received by the pressure receiving surface 32a is transmitted to the convex portion 32d on the back side, and further transmitted from the convex portion 32d to the tip electrode member 42 via the insulating film 42a. The pressure transmitted to the tip electrode member 42 acts on the piezoelectric element 41 sandwiched between the tip electrode member 42 and the first rear end electrode member 43. In the piezoelectric element 41, electric charges corresponding to the received pressure are generated. Occurs. The charge generated in the piezoelectric element 41 is supplied as a charge signal of an input signal terminal (not shown) of the circuit board 53 via a positive path. The charge signal supplied to the circuit board 53 is subjected to various processes by a circuit mounted on the circuit board 53 to be an output signal. The output signal output from the circuit board 53 is transmitted to the outside (here, the connection cable 90 and the control device 80) via the connection member 54.

[Effects of the present embodiment]
In the pressure detection device 20 of the present embodiment, in the first distal end housing 311 to which the first seal member 71 is attached, a position where the pressure received by the first distal end housing 311 from the first seal member 71 becomes maximum ( In the present embodiment, a portion from the vertex of the convex portion 311c to the distal end portion of the first distal housing 311 at the center of the concave portion 311a and the vertex of the convex portion 311c, and the convex portion 311c So that the rigidity with the portion from the vertex of the convex portion 311c to the portion on the center line direction from the vertex of the convex portion 311c to the distal end of the first distal housing 311 is substantially equal. did. This makes it possible to suppress the influence of distortion caused by heat in the pressure detecting device 20 to a small extent.

  Next, the result of comparing and evaluating the pressure detecting device 20 according to the present embodiment with other pressure detecting devices will be described. FIG. 4 is a diagram showing a comparative example showing another pressure detecting device. FIG. 4A shows a pressure detecting device 120 of Comparative Example 1, and FIG. 4B shows a pressure detecting device 220 of Comparative Example 2. . The pressure detecting device 120 and the pressure detecting device 220 are different from the pressure detecting device 20 only in the shape of the first front end side housing, and the common parts and members are denoted by the same reference numerals. Is omitted.

  The pressure detection device 120 is a pressure detection device including the first front end housing 1311 having a thicker rear end side of the first front end housing 311 in the pressure detection device 20. In other words, the front end side of the first front end side housing 1311 (specifically, the front end side of the concave portion 311a from the convex portion 311c and the portion up to the joint surface with the diaphragm 32) (specifically, The rigidity of the convex portion 311c from the convex portion 311c to the distal end side of the concave portion 311a and the rear end side of the convex portion 311c having the same length as the joint surface with the diaphragm 32) is increased.

  The pressure detecting device 220 is a pressure detecting device including a first distal end housing 2331 in which the thickness of the distal end side of the first distal end housing 311 in the pressure detecting device 20 is increased. In other words, the front end side of the first front end side housing 2311 (specifically, the front end side from the convex portion 311c of the concave portion 311a and the portion up to the joint surface with the diaphragm 32) (specifically, The rigidity of the rear end portion of the convex portion 311c which is equal to the length from the convex portion 311c of the concave portion 311a to the joint surface with the diaphragm 32 is reduced.

  The inventor attached these pressure detecting devices 20, 120, and 220 to an engine tester, measured the output of the pressure detecting device, and evaluated the thermal influence of the pressure detecting device. The evaluation was performed on the pressure detection devices 20, 120, and 220 under exactly the same conditions. In addition, as a comparison target of this evaluation, a hydraulic high cycle test machine with the pressure detection devices 20, 120, and 220 attached was used as a reference. The hydraulic high-cycle tester is a test that is less affected by heat because the pressure test is performed with the pressure detection device exposed to oil. As a result of the test using the hydraulic high cycle tester, the outputs of the pressure detecting devices 20, 120, and 220 are almost the same, and the output is set to 100%, and the evaluation results will be described below.

  Table 1 shows the output of the pressure detecting device in the eight samples used in the present evaluation.

  Samples S1 to S3 shown in Table 1 are pressure detecting devices 20, samples S4 to S6 are pressure detecting devices 120, and samples S7 to S8 are pressure detecting devices 220, and their outputs are evaluated. In addition, the sample S1-S8 used the sample different from the sample used for the hydraulic high cycle test machine.

  From the evaluation results, it is understood that the outputs of the samples S1 to S3 are almost 100%, and the influence of heat is small. Samples S4 to S6 have an output of about 95%, which indicates that the output is reduced due to the influence of heat. Samples S7 to S8 have an output of about 102%, which indicates that the output has increased due to the influence of heat.

  According to the above results, the pressure detection device 20 has the least influence of heat, and making the rigidity of the casing on the front end side and the rear end side of the seal member substantially equal reduces the influence by the heat of the pressure detection device. It turns out to be effective.

  In the present embodiment, the concave portion 311a of the first distal end side housing 311 is provided with the convex portion 311c, but is not limited to this. For example, a concave portion 311a having a flat bottom without the convex portion 311c may be used. In that case, the first front end side housing 311 receives uniform pressure from the first seal member 71 over the entire concave portion 311a. In such a case, the central portion receiving the pressure from the first seal member 71 is used. Is the location where the pressure received by the first tip housing 311 from the first seal member 71 is the highest. In other words, in the case where the convex portion 311c is not provided in the concave portion 311a in the present embodiment, the distal end side and the rear end side of the first distal end housing 311 are referred to with respect to the center of the concave portion 311a in the center line direction. What is necessary is just to set rigidity.

DESCRIPTION OF SYMBOLS 1 Pressure detection system 10 Internal combustion engine 11 Cylinder block 12 Piston 13 Cylinder head 13a Mounting hole 20 Pressure detection device 30 Housing 31 Front end housing 311 First front end housing 311a Concave portion 311b Inner step 312 Second front end housing Body 312a Recess 312b Rib 32 Diaphragm 32a Pressure receiving surface (surface)
32b concave portion 32c concave portion 32d convex portion 33 rear end side housing 331 first rear end side housing 332 second rear end side housing 40 detection mechanism section 41 piezoelectric element 42 front electrode member 42a insulating film 43 first rear end electrode member 44 second rear end electrode member 44a main body portion 44b first convex portion 44c second convex portion 45 insulating ring 46 first coil spring 47 conductive member 47a distal end concave portion 47b rear end convex portion 48 holding member 49 pressing member 49a insulating film 491 Front end tubular portion 492 Intermediate tubular portion 493 Rear end tubular portion 49b Front end stepped portion 49c Rear end stepped portion 50 Support member 51 Second coil spring 52 Housing member 521 First tubular portion 522 Second tubular portion 523 Third Cylindrical part 524 Fourth cylindrical part 52a First step 52b Second step 52c Third step 53 Circuit board 54 Connecting member 54a Board-side connector 54b Cable-side connector 5 Ground plate 56 O-ring 57 Butt pipe 58 First weld 59 Second weld 60 Insulation pipe 61 First insulation member 62 Second insulation member 63 Third insulation member 70 Seal member 71 First seal member 72 Second seal member 80 control device 90 connection cable 120 pressure detection device 220 pressure detection device

Claims (3)

In a pressure detection device that is attached to the attachment hole of the container containing the pressure medium and detects the pressure of the pressure medium,
A pressure detecting element for detecting a change in pressure of the pressure medium,
A cylindrical housing that houses the pressure detection element therein;
A diaphragm attached to one end of the housing and receiving pressure of the pressure medium,
An annular sealing member attached to the outer periphery of the housing and compressed between the housing and the mounting hole to hermetically seal between the two;
A housing that is a part of the housing on one end side from a reference position where a pressure received from the sealing member compressed between the housing and the mounting hole is the highest in the axial direction of the housing. It is assumed that the front end portion has the same axial length as the housing front end portion, and the housing rear end portion, which is a portion of the housing at the other end side from the reference position, has substantially the same rigidity. Characteristic pressure detecting device.   2. A stiffness adjusting element for reducing or increasing the rigidity of the front end of the housing or the rear end of the housing, at one of the front end of the housing and the rear end of the housing. 3. The pressure detecting device according to 1.   The pressure detecting device according to claim 2, wherein the rigidity adjusting element is a thin portion provided at a part of a front end portion of the housing or a rear end portion of the housing.

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