JP6845756B2 - Pressure detector - Google Patents

Description

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

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

For example, Patent Document 1 describes a tubular housing, a diaphragm attached to the front end side of the housing, a piezoelectric element arranged on the rear end side of the diaphragm in the housing and detecting a pressure acting through the diaphragm, and a housing. A first electrode portion provided in contact between the diaphragm and the piezoelectric element in contact with both of them, and a second electrode portion provided in contact with the piezoelectric element on the rear end side of the piezoelectric element in the housing. An insulating ring provided in contact with the second electrode on the rear end side of the second electrode portion in the housing, a support member provided in contact with the insulating ring on the rear end side of the insulating ring in the housing, and a housing. Inside itself, the first electrode portion, the piezoelectric element, the second electrode portion, the insulating ring and the support member are housed, and the support member is pressed so as to pressurize the first electrode portion in the axial direction of the housing. A pressure detecting device including a pressurizing member that applies a load to the piezoelectric element by being fixed is described.

Japanese Unexamined Patent Publication No. 2013-205307

Here, if noise enters from the outside to the inside of the pressure detection device, the noise will be superimposed on the output from the detection element. When noise is superimposed in this way, the error in the detected pressure becomes large.
Further, in this type of pressure detecting device, a predetermined load is applied to the detecting element. However, if the detection element is not sufficiently positioned with respect to the housing of the pressure detection device, the load applied to the detection element fluctuates, and the error in the detected pressure becomes large.
An object of the present invention is to suppress the superposition of external noise on the output from the detection element and to suppress the fluctuation of the load applied to the detection element.

The pressure detection device of the present invention includes a detection element for detecting a change in pressure, a first housing having conductivity and accommodating the detection element inside, and the first housing having conductivity and said first housing. An insulating film having a second housing to be housed inside, formed in at least one of the first housing or the second housing, and electrically insulating the first housing and the second housing. It is characterized by having.
Further, the insulating film may be made of a material having a coefficient of thermal expansion equivalent to or close to that of the material constituting the first housing or the second housing.
Further, the insulating film may be characterized in that the first housing or the second housing is coated with a stainless steel paint.
Further, the first housing is attached to the tip side of the second housing by applying a load to the detection element by sandwiching the detection element from the front end side and the rear end side of the first housing. A deformable member that deforms in response to external pressure, and a pressure that is insulating and is provided between the deformable member and the detection element inside the second housing and acts on the deformable member. An insulating transmission member that transmits the above to the detection element, and a fixing member that fixes the first housing to the second housing in a state of being electrically insulated from the deforming member and the second housing. It can be characterized by including.
Further, the first housing has a tubular shape and has a protruding portion protruding outward on the outer peripheral surface, and the fixing member is connected to the inner peripheral surface of the second housing via the insulating member. By sandwiching the protruding portion between them, the first housing can be fixed to the second housing.
Further, the first housing is arranged outside the detection element, is electrically connected to the tip side of the detection element, and is electrically insulated from the rear end side of the detection element, so that the tip of the detection element is electrically insulated. The first applying member that applies a load from the side and the first applying member that is provided on the rear end side of the first applying member, is electrically connected to the first applying member, and is electrically insulated from the detection element. It can be characterized by having a second imparting member that applies a load from the rear end side of the detection element by being fixed to the imparting member.
Further, the first housing includes a conductive member that is housed inside the first housing and is electrically connected to the rear end side of the detection element to conduct a detection signal output by the detection element. One housing can be characterized by being electrically connected to the tip end side of the detection element and electrically insulated from the conduction member to serve as a ground for the detection element.

According to the present invention, it is possible to suppress the superposition of external noise on the output from the detection element and to suppress the fluctuation of the load applied to the detection element.

It is a schematic block diagram of the pressure detection system which concerns on embodiment. It is a side view of the pressure detection device. It is sectional drawing (III-III sectional view of FIG. 2) of the pressure detection apparatus. It is an enlarged cross-sectional view of the tip side of a pressure detection device. It is a perspective view of a pressurizing member. It is a perspective view of the accommodating member.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[Pressure detection system configuration]
FIG. 1 is a schematic configuration diagram of the pressure detection system 1 according to the embodiment.
The pressure detection system 1 supplies power to the pressure detection device 20 for detecting the pressure (combustion pressure) in the combustion chamber C in the internal combustion engine 10 and the pressure detection device 20, and is based on the pressure detected by the pressure detection device 20. It includes a control device 80 that controls the operation of the internal combustion engine 10, and a connection cable 90 that electrically connects the pressure detection device 20 and the control device 80.

Here, the internal combustion engine 10 whose pressure is to be detected includes a cylinder block 11 in which a cylinder is formed, a piston 12 that reciprocates in the cylinder, and a combustion chamber C that is fastened to the cylinder block 11 together with the piston 12 and the like. It has a cylinder head 13 constituting the above. Further, the cylinder head 13 is provided with a communication hole 13a for communicating the combustion chamber C and the outside. Then, the tip side of the pressure detection device 20 is inserted into the communication hole 13a, and the rib portion 312b (see FIG. 2 described later) provided in the pressure detection device 20 is fixed to the cylinder head 13 to fix the internal combustion engine. A pressure detection device 20 is attached to the 10. 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 side view of the pressure detecting device 20. FIG. 3 is a cross-sectional view of the pressure detection device 20 (cross-sectional view of III-III in FIG. 2). FIG. 4 is an enlarged cross-sectional view of the tip end side of the pressure detection device 20.

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

[Configuration of housing]
The housing portion 30 includes a front end side housing 31, a diaphragm head 32 attached to the front end side of the front end side housing 31, and a rear end side housing 33 attached to the rear end side of the front end side housing 31. It has. Here, in the present embodiment, the front end side housing 31 and the rear end side housing 33 function as an example of the housing, and the diaphragm head 32 functions as an example of the deformable member.

(Tip side housing)
The tip-side housing 31 is a member having a hollow structure and having a tubular shape as a whole. The tip-side housing 31 is made of a metal material such as stainless steel, which has conductivity and high heat resistance and acid resistance.

The front end side housing 31 has a first front end side housing 311 relatively located on the front end side and a second front end side housing 312 relatively located on the rear end side. Here, in the front end side housing 31, both are formed by laser welding the outer peripheral surface on the rear end side of the first front end side housing 311 and the inner peripheral surface on the front end side of the second front end side housing 312. It is configured to integrate. The diaphragm head 32 is attached to the front end side of the first front end side housing 311 by laser welding, and the rear end side housing 33 is fitted to the rear end side of the second front end side housing 312. It is attached.

Here, a recess 311a for mounting the first seal member 71 (details will be described later) constituting the seal portion 70 is provided on the outer peripheral surface of the first front end side housing 311. Further, inside the first front end side housing 311, there are a portion set to a first diameter on the front end side and a portion set to a second diameter larger than the first diameter on the rear end side. It exists, and an inner step portion 311b connecting the two parts is provided at the boundary between the two parts.

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

(Diaphragm head)
The diaphragm head 32 is a member having a disk shape as a whole. The diaphragm head 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 head 32 and the tip-side housing 31 are made of the same material.

The diaphragm head 32 has a recess 32b formed in the central portion on the tip side, and a pressure receiving surface (surface) 32a that receives pressure by being exposed to the outside (combustion chamber C side) and a back side of the pressure receiving surface 32a. A concave portion 32c provided by cutting out the back surface in an annular shape, and a convex portion 32d protruding toward the rear end side from the central portion (the forming portion of the concave portion 32b) of the pressure receiving surface 32a as a result of the presence of the concave portion 32c. have. The diaphragm head 32 is provided so as to close the opening on the distal end side of the first distal end side housing 311. Then, laser welding is performed on the boundary portion between the diaphragm head 32 and the first distal end side housing 311 over the entire outer peripheral surface.

(Rear end side housing)
The rear end side housing 33 is a member having a hollow structure and exhibiting a tubular 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 attached to the internal combustion engine 10, the rear end side housing 33 is located outside the internal combustion engine 10, and therefore has higher heat resistance and acid resistance than the above-mentioned front end side housing 31. Low materials can be used.

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

[Configuration of detection mechanism]
The detection mechanism unit 40 includes a piezoelectric element 41, a front end electrode member 42, a first rear end electrode member 43, and a second rear end electrode member 44. Further, the detection mechanism unit 40 includes an insulating ring 45, a first coil spring 46, a conduction member 47, and a holding member 48. Further, the detection mechanism unit 40 includes a pressurizing member 49, a support member 50, a second coil spring 51, and an accommodating member 52. Furthermore, the detection mechanism unit 40 includes a circuit board 53, a connecting member 54, a ground plate 55, and an O-ring 56. Further, the detection mechanism unit 40 includes a butt pipe 57. The detection mechanism unit 40 includes an insulating pipe 60, a first insulating member 61, a second insulating member 62, and a third insulating member 63. Here, in the present embodiment, the pressurizing member 49 and the supporting member 50 function as an example of the imparting member, and the first rear end electrode member 43 and the second rear end electrode member 44 are the second transmission member. It functions as an example.

(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 that exhibits a piezoelectric action of a piezoelectric vertical effect. The piezoelectric longitudinal effect means that when an external force is applied to a stress application shaft in the same direction as the charge generation axis of the piezoelectric body, a charge is generated on the surface of the piezoelectric body in the charge generation axis direction. The piezoelectric element 41 is located inside the front end side housing 31 and is arranged on the rear end side of the diaphragm head 32. The piezoelectric element 41 is housed in the front end side housing 31 so that the center line direction is the direction of the stress application axis. Here, the piezoelectric element 41 is arranged inside the pressurizing member 49 provided inside the tip-side housing 31, and inside the insulating pipe 60 provided inside the pressurizing member 49. .. Further, the outer diameter of the piezoelectric element 41 is slightly smaller than the inner diameter of the insulating pipe 60 accommodating the piezoelectric element 41 inside. The front end side surface of the piezoelectric element 41 is in contact with the rear end side surface of the front end 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. By providing the insulating pipe 60 between the inner peripheral surface of the pressurizing member 49 and the outer peripheral surface of the piezoelectric element 41 in this way, the pressurizing member 49 and the piezoelectric element 41 do not come into direct contact with each other.

Next, a case where the piezoelectric lateral effect is used for the piezoelectric element 41 will be illustrated. 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, a charge is generated on the surface of the piezoelectric body in the direction of the charge generation axis. A plurality of piezoelectric bodies formed thinly in the shape of a thin plate may be laminated, and by laminating in this way, the electric charge generated in the piezoelectric body can be efficiently collected to increase the sensitivity of the sensor. Examples of the piezoelectric material that can be used in the piezoelectric element 41 include langasite crystals (langasite, langateite, langanite, LTGA) having a piezoelectric longitudinal effect and a piezoelectric lateral 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, which has both conductivity and high heat resistance. Further, an insulating film 42a coated with a stainless paint exhibiting insulating properties is formed at the central portion of the front end electrode member 42 on the front end side surface. Here, the insulating film 42a as an example of the insulating transmission portion has a circular shape, for example, and its diameter is larger than the diameter of the convex portion 32d provided on the back surface of the diaphragm head 32, and is pressurized. It is smaller than the diameter of the opening provided on the tip end side of the member 49.

The tip electrode member 42 is arranged inside a pressurizing member 49 provided inside the tip side housing 31. The tip electrode member 42 is arranged on the rear end side of the diaphragm head 32 and on the tip 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. Further, the outer diameter of the tip electrode member 42 is slightly smaller than the inner diameter of the pressurizing member 49 accommodating the tip electrode member 42 inside. Then, of the front end side surface of the tip electrode member 42, the central region where the insulating film 42a is provided comes into contact with the rear end side surface of the convex portion 32d provided on the back surface of the diaphragm head 32. There is. Further, of the surface on the tip side of the tip electrode member 42, the peripheral region where the insulating film 42a is not provided is in contact with the surface on the back side of the opening provided on the tip side of the pressurizing member 49. .. On the other hand, the rear end side surface of the tip electrode member 42 is in contact with the front end side surface of the piezoelectric element 41. The outer peripheral surface of the tip electrode member 42 faces the inner peripheral surface of the pressurizing member 49.

Here, in the present embodiment, the insulating film 42a is formed by coating with a stainless steel paint, but a material other than the stainless steel paint, for example, SiO ₂ , polyimide, ceramics, or the like may be coated. However, the insulating film 42a is a material having insulating properties and high heat resistance, and having a coefficient of thermal expansion equivalent to or close to that of the material constituting the diaphragm head 32 and the tip electrode member 42 in contact with the insulating film 42a. It is preferable to configure it. This is to prevent peeling, breakage, and destruction of the insulating film 42a caused by the difference in the coefficient of thermal expansion between the insulating film 42a and the diaphragm head 32 and the tip electrode member 42 that come into contact with the insulating film 42a. In the present embodiment, since the diaphragm head 32 and the tip electrode member 42 are made of a metal material such as stainless steel, the insulating film 42a is made of stainless steel paint.
Further, the insulating film 42a coated with the stainless steel paint can be formed by applying the stainless steel paint diluted with thinner, toluene, xylene or the like by an electrostatic spray method, a spray method, a dip method or the like. The insulating film 42a formed of the stainless steel paint has better coverage for the coated member (here, the tip electrode member 42) as compared with materials such as _{SiO 2, polyimide, and ceramics, and can be obtained by changing the dilution amount of the paint.} The resistance value can be adjusted, and it is easy to form a thick film. The insulating film 42a preferably has a film thickness of 1 μm or more and a resistance value of 10 kΩ or more in order to ensure insulating properties. If the thickness of the insulating film 42a is insufficient, dielectric breakdown may occur in the insulating film 42a due to noise such as a surge. However, it is possible to improve the dielectric breakdown strength by making the insulating film 42a a thick film. Is.

(1st 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, high heat resistance, and a small thermal expansion difference from the piezoelectric element 41.

The first rear end electrode member 43 is arranged inside the pressurizing member 49 provided inside the front end side housing 31. The first rear end electrode member 43 is located on the rear end side of the piezoelectric element 41 and is arranged on the front end side of the second rear end electrode member 44. Here, the first rear end electrode member 43 is arranged inside the insulating pipe 60 provided inside the pressurizing 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 front end side surface of the first rear end electrode member 43 is in contact with the rear end side surface 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 surface on the front end side of the second rear end electrode member 44. The outer peripheral surface of the first rear end electrode member 43 faces the inner peripheral surface of the insulating pipe 60. In this way, by providing the insulating pipe 60 between the inner peripheral surface of the pressurizing member 49 and the outer peripheral surface of the first rear end electrode member 43, the pressurizing member 49 and the first rear end electrode member 43 can be made to work. Do not contact directly.

(Second rear end electrode member)
The second rear end electrode member 44 is a member that 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, which has conductivity and high heat resistance. The second rear end electrode member 44 has a disk shape and is located on the front end side of the main body portion 44a, and has a columnar shape and is on the rear end side surface of the main body portion 44a from the central portion toward the rear end side. It includes a first convex portion 44b that protrudes, and a second convex portion 44c that has a columnar shape and protrudes further toward the rear end side from the rear end of the first convex portion 44b. Here, the diameter of the first convex portion 44b is smaller than the diameter of the main body portion 44a, and the diameter of the second convex portion 44c is smaller than the diameter of the first convex portion 44b.

The second rear end electrode member 44 is arranged inside the pressurizing member 49 provided inside the front end side housing 31. Here, the tip end side of the main body portion 44a of the second rear end electrode member 44 is arranged inside the insulating pipe 60 provided inside the pressurizing member 49. On the other hand, the portion of the second rear end electrode member 44 that is on the rear end side of the second rear end electrode member 44 is arranged outside the insulating pipe 60. Further, the outer diameter of the main body portion 44a 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 front end side surface of the main body 44a of the second rear end electrode member 44 is in contact with the rear end side surface of the first rear end electrode member 43. On the other hand, the surface on the rear end side of the main body 44a is in contact with the surface on the front end side of the insulating ring 45. Further, the outer peripheral surface of the first convex portion 44b of the second rear end electrode member 44 has its front end side in contact with the inner peripheral surface of the insulating ring 45, and its rear end side is the inner circumference of the support member 50 via an air gap. Facing the 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 mounted on the outer peripheral surface. Is in contact with the conducting member 47 via. In this way, by providing the insulating pipe 60, the air gap, and the insulating ring 45 between the inner peripheral surface of the pressure member 49 and the outer peripheral surface of the second rear end electrode member 44, the pressure member 49 and the second It does not come into direct contact with 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 that exhibits an annular shape as a whole. The insulating ring 45 is made of a ceramic material such as alumina, which has insulating properties and high heat resistance.

The insulating ring 45 is arranged inside a pressurizing member 49 provided inside the front end side housing 31. The insulating ring 45 is located on the rear end side of the main body portion 44a of 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 arranged inside the through hole provided in the insulating ring 45. Further, the outer diameter of the insulating ring 45 is slightly smaller than the inner diameter of the pressurizing 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 convex portion 44b in the second rear end electrode member 44. The surface of the insulating ring 45 on the front end side is in contact with the surface of the second rear end electrode member 44 on the rear end side of the main body portion 44a. On the other hand, the surface on the rear end side of the insulating ring 45 is in contact with the surface on the front end side of the support member 50. The outer peripheral surface of the insulating ring 45 faces the inner peripheral surface of the pressurizing 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 that exhibits 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, which has conductivity and is more conductive than the front end side housing 31, and its surface is gold-plated.

The first coil spring 46 is provided inside the tip-side housing 31, and is arranged inside the pressurizing member 49 and inside the support member 50. The first coil spring 46 is located on the rear end side of the second rear end electrode member 44 and on the front end side of the conduction member 47. That is, the first coil spring 46 is arranged so as to straddle the second rear end electrode member 44 and the conduction member 47. Here, the tip 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 tip end side of the conduction member 47. It is inserted into the tip-side recess 47a. The inner diameter of the first coil spring 46 is larger than the outer diameter of the second convex portion 44c of the second rear end electrode member 44 and smaller than the inner diameter of the first convex portion 44b. On the other hand, the outer diameter of the first coil spring 46 is smaller than the inner diameter of the tip-side recess 47a in the conduction member 47. As a result, the tip of the first coil spring 46 abuts on the boundary (step portion) between the first convex portion 44b and the second convex portion 44c in the second rear end electrode member 44, and is on the tip 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 on the bottom of the distal end side recess 47a of the conductive member 47, and the rear end side of the first coil spring 46 is the inner peripheral surface of the distal end side recess 47a of the conductive member 47. Is in contact with. The outer circumference of the first coil spring 46 faces the inner peripheral surface of the support member 50 via an air gap. By providing an air gap between the inner peripheral surface of the support member 50 and the first coil spring 46 in this way, the support member 50 and the first coil spring 46 do not come into direct contact with each other.

(Conduction 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 gold-plated. The conduction member 47 is provided with the above-mentioned tip side recess 47a at the tip thereof, and at the rear end, the rear end side having a diameter smaller than the central portion in the center line direction and projecting toward the rear end side. A convex portion 47b is provided.

The conduction member 47 is provided inside the front end side housing 31, and almost all parts except the front end portion and the rear end portion (rear end side convex portion 47b) are arranged inside the holding member 48. There is. Further, the tip side of the conduction member 47 is inside the pressurizing member 49, the rear end side of the conduction member 47 is inside the accommodating member 52, and the intermediate portion located between the tip side and the rear end side is the second coil spring. It is located inside 51, respectively. The conduction member 47 is located on the rear end side of the first coil spring 46 and on the front end side of the circuit board 53. The conduction member 47 is arranged so as to penetrate a through hole provided in the holding member 48 along the center line direction. The outer diameter of the tip end portion (the portion not covered by the holding member 48) of the conducting member 47 is larger than the inner diameter of the holding member 48 and smaller than the inner diameter of the supporting member 50. Further, the outer diameter of the rear end portion (rear end side convex portion 47b) of the conduction 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 central portion of the conducting member 47 in the center line direction is substantially the same as the inner diameter of the holding member 48. Then, the rear end side of the first coil spring 46 is inserted into the tip end side recess 47a of the conduction 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 conduction member 47 is fitted in the holding portion provided on the holding member 48. Further, the outer peripheral surface of the tip 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 of the central portion of the conduction member 47 in the center line direction 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 accommodating member 52 via the air gap and the holding member 48. 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 in this way, the support member 50 and the conductive member 47 do not come into direct contact with each other. 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 come into direct contact with each other. Further, by providing an air gap between the inner peripheral surface of the accommodating member 52 and the outer peripheral surface of the conducting member 47, the accommodating member 52 and the conducting member 47 do not come into direct contact with each other.

(Holding member)
The holding member 48 is a member in which a tubular portion located on the front end side and a plate-shaped portion located on the rear end side are integrated. The holding member 48 comprises a base material made of a synthetic resin material such as PPT (Polypropylene Terephthalate) having insulating properties, and wiring and terminals made of a metal material such as copper having conductivity. Includes. The conductive member 47 is housed in the tubular portion located on the tip end side of the holding member 48, and the circuit board 53 is mounted on the 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 conduction member 47 and the circuit board 53.

Of the holding member 48, a portion (outer peripheral surface) facing the support member 50, the second coil spring 51, and the accommodating member 52 is made of a synthetic resin material so that the metal material is not exposed to this portion. .. Further, of the holding member 48, a portion (inner peripheral surface) facing the intermediate portion located between the front end portion and the rear end portion of the conduction member 47 is also made of a synthetic resin material, and a metal is formed in this portion. The material is not exposed. Further, on the rear end side of the tubular portion of the holding member 48, a holding portion made of a metal material is provided to fit and hold the rear end side convex portion 47b of the conduction member 47. A wiring for electrically connecting to a signal input terminal (not shown) of the circuit board 53 is attached to this holding portion.

The holding member 48 is provided so as to straddle the inside of the front end side housing 31 and the inside of the rear end side housing 33. Further, the tip end side of the holding member 48 is inside the pressurizing member 49, the rear end side of the conduction member 47 is inside the accommodating member 52, and the intermediate portion located between the tip end side and the rear end side is the second coil spring. It is located inside 51, respectively. The holding member 48 is located on the rear end side of the insulating ring 45 and on the front end side of the connecting member 54.

The outer diameter of the tubular portion located on the tip 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 accommodated in this portion. It is smaller than the inner diameter of the member 52. Further, the outer peripheral surface of the holding member 48 on the tip end side of the tubular portion 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 of the holding member 48 on the rear end side of the tubular portion and the outer peripheral surface of the plate-shaped portion come into contact with the inner peripheral surface of the accommodating member 52 or the inner peripheral surface of the accommodating member 52 via an air gap. Facing the face.

(Pressurized member)
The pressurizing member 49 as an example of the first applying member is a member having a tubular shape as a whole. The pressure member 49 is made of a metal material such as stainless steel, which has conductivity and high heat resistance.

FIG. 5 is a perspective view of the pressurizing member 49. Hereinafter, the configuration of the pressurizing member 49 will be described with reference to FIG. In FIG. 5, the lower left side in the figure is the front end side, and the upper right side in the figure is the rear end side.

The pressurizing member 49 of the present embodiment has a tip tubular portion 491 located on the most tip side and having an opening at the tip, and an intermediate tubular portion arranged on the rear end side of the tip tubular portion 491. It includes a 492 and a rear end tubular portion 493 which is located on the rear end side of the intermediate tubular portion 492 and is located on the rearmost end side. In this pressurizing member 49, the outer diameter of the intermediate tubular portion 492 is larger than that of the tip tubular portion 491 and the rear end tubular portion 493, and the outer diameter of the rear end tubular portion 493 is larger than that of the tip tubular portion 491. The diameter is large. The pressure member 49 is formed by a tip step portion 49b connecting the tip 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. Further, a rear end step portion 49c for connecting the two is further provided. The inner diameter of the pressurizing member 49 is the same except for the opening provided at the tip. Therefore, in the pressurizing member 49, the wall thickness of the intermediate tubular portion 492 is larger than the wall thickness of the rear end tubular portion 493, and the wall thickness of the rear end tubular portion 493 is the tip tubular portion 491. It is larger than the wall thickness of. Therefore, in the pressure member 49, the intermediate tubular portion 492 is the most difficult to bend, while the tip tubular portion 491 is the most flexible (easily functions as a spring). Here, in the present embodiment, the tip step portion 49b, the intermediate tubular portion 492, and the rear end step portion 49c function as an example of the protruding portion.

Further, among the pressure members 49, an insulating film 49a formed by coating an insulating stainless steel material is continuously formed on the outer peripheral surfaces of the tip step portion 49b, the intermediate tubular portion 492, and the rear end step portion 49c. It is formed (see FIG. 4). Here, in the present embodiment, the insulating film 49a functions as an example of the insulating portion.

The pressurizing member 49 is provided inside the tip side housing 31 so that the tip tubular portion 491 is on the tip side. Inside the pressurizing member 49, the piezoelectric element 41, the tip electrode member 42, the first rear end electrode member 43, the second rear end electrode member 44, the insulating ring 45, the tip side of the support member 50, the insulating pipe 60, and the first 1 The coil spring 46, the tip end side of the conduction member 47, and the tip end side of the holding member 48 are housed. The pressurizing member 49 is located on the rear end side of the diaphragm head 32 and on the front end side of the accommodating member 52. Further, the outer diameter of the pressure member 49 is different between the tip tubular portion 491, the intermediate tubular portion 492, and the rear end tubular portion 493, but is smaller than the inner diameter of the front end side housing 31 at all positions. Further, the inner diameter of the pressurizing member 49 is set at a portion facing the front electrode member 42 and the insulating pipe 60 (piezoelectric element 41, first rear end electrode member 43, second rear end electrode member 44, insulating ring 45). It 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 the portion facing the support member 50.

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

The front end side surface (front surface side surface of the opening) of the tip tubular portion 491 of the pressurizing member 49 faces the recess 32c of the diaphragm head 32 via an air gap. On the other hand, the rear end side of the rear end tubular portion 493 faces the first insulating member 61 via an air gap. Further, the outer peripheral surface of the tip tubular portion 491 faces the inner peripheral surface of the first tip side housing 311 via an air gap. Further, the outer peripheral surfaces of the tip step portion 49b, the intermediate tubular portion 492, and the rear end step portion 49c come into contact with the insulating film 49a and face the inner peripheral surface of the first tip side housing 311 via the insulating film 49a. are 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. In this way, by providing an air gap and an insulating film 49a between the outer peripheral surface of the pressurizing member 49, the inner peripheral surface of the first distal end side housing 311 and the inner peripheral surface of the abutting pipe 57, pressurization is performed. The member 49, the first distal end side housing 311 and the abutting pipe 57 do not come into direct contact with each other.

Here, in the present embodiment, the insulating film 49a is formed by coating with a stainless steel paint, but a material other than the stainless steel paint, for example, SiO ₂ , polyimide, ceramics, or the like may be coated. However, for the same reason as the insulating film 42a, the insulating film 49a is preferably made of a material having a coefficient of thermal expansion equivalent to or close to that of the material constituting the pressure member 49 and the first distal end side housing 311. In the present embodiment, since the pressure member 49 and the first distal end side housing 311 are made of a metal material such as stainless steel, the insulating film 49a is made of stainless steel paint. Further, the insulating film 42a coated with the stainless steel paint can be formed by applying the stainless steel paint diluted with thinner, toluene, xylene or the like by an electrostatic spray method, a spray method, a dip method or the like. The insulating film 49a formed of the stainless steel paint has better coverage for the coated member (here, the pressure member 49) as compared with materials such as _{SiO 2, polyimide, and ceramics, and can be obtained by changing the dilution amount of the paint.} The resistance value can be adjusted, and it is easy to form a thick film. The insulating film 49a preferably has a film thickness of 1 μm or more and a resistance value of 10 kΩ or more in order to ensure insulating properties. By making the insulating film 49a a thick film, it is possible to improve the dielectric breakdown strength.

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

The support member 50 is provided inside the front end side housing 31, and the front end side thereof is located inside the pressurizing member 49 and the rear end side is located outside the pressurizing member 49. Further, inside the support member 50, the rear end side (first convex portion 44b and second convex portion 44c) of the second rear end electrode member 44, the first coil spring 46, the tip side of the conduction member 47, and the holding member It houses the tip side of 48. The support member 50 is located on the rear end side of the insulating ring 45 and on the front end side of the accommodating member 52. Further, the outer diameter of the support member 50 is substantially the same as the inner diameter of the first pressurizing 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 the portion facing the second rear end electrode member 44, and is larger than the outer diameter of the first coil spring 46. The outer diameter of the first coil spring 46 is larger than the outer diameter of the first coil spring 46, the outer diameter of the conductive member 47 is larger than the outer diameter of the conductive member 47, and the outer diameter of the holding member 48 is larger than 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 accommodating member 52 via an air gap. Further, the tip end side of the outer peripheral surface of the support member 50 is in contact with the inner peripheral surface of the pressure member 49, and the rear end side of the outer peripheral surface of the support member 50 is in contact with the tip end side of the second coil spring 51. There is. Here, the pressure member is formed by the second welded portion 59 obtained by laser welding the inner peripheral surface of the pressure member 49 on the rear end side and the outer peripheral surface of the support member 50 facing the portion by laser welding over one circumference. The 49 and the support 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 conduction member 47, and the holding member 48 via the air gap. In this way, by providing an 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 conduction member 47, and the holding member 48, the support member 50 and the support member 50 can be separated. The second rear end electrode member 44, the first coil spring 46, the conduction member 47, and the holding member 48 do not come into direct contact with each other.

(2nd coil spring)
The second coil spring 51 is a member that exhibits 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 both conductivity and high heat resistance, and its surface is gold-plated. As described above, in the present embodiment, the materials of the first coil spring 46 and the second coil spring 51 are different.

The second coil spring 51 is provided inside the front end side housing 31, and the front end side thereof is on the rear end side and the outside of the support member 50, and the rear end side is on the front end side and the outside of the accommodating member 52, respectively. positioned. That is, the second coil spring 51 is arranged so as to straddle the support member 50 and the accommodating member 52. Further, the outer diameter of the second coil spring 51 is smaller than the inner diameter of the tip side housing 31 (more specifically, the second tip side housing 312). Further, the inner diameter of the second coil spring 51 is slightly smaller than the outer diameter on the rear end side of the support member 50 and the outer diameter on the front end side of the accommodating member 52. The outer circumference of the second coil spring 51 faces the inner peripheral surface of the front end side housing 31 via an air gap. By providing an air gap between the outer circumference of the second coil spring 51 and the inner peripheral surface of the tip-side housing 31 in this way, the second coil spring 51 and the tip-side housing 31 do not come into direct contact with each other. ..

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

FIG. 6 is a perspective view of the accommodating member 52. Hereinafter, the configuration of the accommodating member 52 will be described with reference to FIG. Also in FIG. 6, the lower left side in the figure is the front end side, and the upper right side in the figure is the rear end side.

The accommodating member 52 of the present embodiment has a first tubular portion 521 located on the most distal end side and having an opening at the distal end, and a second tubular portion arranged on the rear end side of the first tubular portion 521. The shape portion 522, the third tubular portion 523 arranged on the rear end side of the second tubular portion 522, and the fourth tubular portion 524 arranged on the rear end side of the third tubular portion 523 are provided. ing. The outer diameter of the accommodating member 52 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, the diameter of the accommodating member 52 increases stepwise (4 steps) from the front end side to the rear end side. The accommodating member 52 includes a first step portion 52a that connects the first tubular portion 521 and the second tubular portion 522 at a boundary portion, and a second tubular portion 522 and a third tubular portion 523. A second step portion 52b that connects the two at the boundary portion of the above, and a third step portion 52c that connects the two at the boundary portion between the third tubular portion 523 and the fourth tubular portion 524 are further provided. Unlike the pressurizing member 49 described above, the accommodating member 52 has a wall thickness set to a constant size regardless of the position in the center line direction. Therefore, in the pressure member 49, the inner diameter is increased 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 accommodating member 52 is provided so as to straddle the inside of the front end side housing 31 and the inside of the rear end side housing 33 so that the first tubular portion 521 is on the front end side. Inside the accommodating member 52, the rear end side of the conduction member 47, the rear end side of the holding member 48, the circuit board 53, and the grounding plate 55 are accommodated. The accommodating member 52 is located on the rear end side of the support member 50 and on the front end side of the connecting member 54. Further, the outer diameter of the accommodating member 52 differs between the first tubular portion 521, the second tubular portion 522, the third tubular portion 523, and the fourth tubular portion 524, but the front end side housing is provided at all positions. It is smaller than the inner diameter of 31 and the rear end side housing 33. Further, the inner diameter of the accommodating 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 is outside each member accommodated inside. Larger than the diameter.

Here, the first insulating member 61 is arranged between the rear end side and the second step portion 52b of the second tubular portion 522 of the accommodating member 52 and the inner peripheral surface of the second tip side housing 312. ing. Further, a second insulating member 62 is arranged between the rear end side and the third step portion 52c of the third tubular portion 523 of the accommodating member 52 and the inner peripheral surface of the second tip side housing 312. There is. Further, a third insulating member 63 is arranged between the fourth tubular portion 524 of the accommodating member 52 and the first rear end side housing 331.

The front end side surface (front surface side surface of the opening) of the first tubular portion 521 of the accommodating member 52 faces the rear end side surface of the support member 50 via an air gap. Further, 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. Further, the outer peripheral surfaces of the first tubular portion 521 and the first stepped portion 52a face the inner peripheral surface of the second tip-side housing 312 via an air gap. Further, the outer peripheral surface of the second tubular portion 522 faces the inner peripheral surface of the second distal end side housing 312 via the air gap and the first insulating member 61. Furthermore, the second step portion 52b faces the inner peripheral surface of the second tip-side housing 312 via the first insulating member 61. Further, the outer peripheral surface of the third tubular portion 523 faces the inner peripheral surface of the second distal end side housing 312 via an air gap and a second insulating member 62. Further, the outer peripheral surface of the third step portion 52c faces the inner peripheral surface of the second tip side housing 312 via the second insulating member 62. The outer peripheral surface of the fourth tubular portion 524 faces the inner peripheral surface of the second front end side housing 312 via the air gap, and the first rear end is interposed via the air gap and the third insulating member 63. It faces the inner peripheral surface of the side housing 331. As described above, the air gap, the first insulating member 61, the second insulating member 62, and the third insulating member 62 are between the outer peripheral surface of the accommodating member 52 and the second front end side housing 312 and the first rear end side housing 331. By providing the insulating member 63, the accommodating member 52 and the second front end side housing 312 and the first rear end side housing 331 do not come into direct contact with each other.

(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 due to a weak electric charge output by the piezoelectric element 41 according to the received pressure, and is composed of a so-called printed wiring board. The circuit board 53 is provided so as to straddle the inside of the front end side housing 31 and the inside of the rear end side housing 33. Further, the circuit board 53 is arranged on the rear end side of the conduction member 47 and on the front end side of the connection member 54. Further, the circuit board 53 is mounted on the holding member 48, and the entire circuit board 53 is arranged inside the accommodating member 52.

The circuit board 53 has an amplifier circuit that integrates an input signal (charge signal) input from the piezoelectric element 41 and converts it into a voltage signal, and an amplifier that amplifies the voltage signal input from the integrating circuit into an output signal. A circuit and a power supply circuit that serves as a power source for elements such as operational amplifiers that constitute these integrator circuits and amplifier circuits are mounted (all not shown).

(Connecting member)
The connecting member 54 is a member having a columnar shape as a whole. The connecting member 54 includes a base material made of a synthetic resin material such as PPT having insulating properties, wiring and terminals made of a metal material such as copper having conductivity, and the like. However, the 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. .. Further, the rear end side of the connecting member 54 is provided with an opening having a concave shape and opening toward the rear end side. A substrate-side connector 54a that projects toward the distal end and is electrically connected to the circuit board 53 is provided on the distal end side of the connecting member 54. On the other hand, on the rear end side of the connection member 54, inside the opening, a cable side connector 54b to be connected to the connection cable 90 shown in FIG. 1 is provided while projecting toward the rear end side. Has been done. Further, a recess is provided on the outer peripheral surface of the connecting member 54 on the tip end side over the entire circumference, and an O-ring 56 is attached to the recess.

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

The outer diameter of the tubular portion located on the front end side of the connecting 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 tubular portion located on the rear end side of the connecting member 54 is substantially the same as the outer diameter of the second rear end side housing 332. Further, the tip end side of the connecting 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 gold-plated.

The ground plate 55 is provided so as to straddle the inside of the front end side housing 31 and the inside of the rear end side housing 33, and the tip thereof is inside the accommodating member 52 and is located above the circuit board 53. The rear end protrudes toward the rear end side from the rear end of the accommodating member 52. The tip end side of the grounding plate 55 is electrically connected to the grounding terminal (not shown) of the circuit board 53, and the rear end side of the grounding plate 55 is the inner circumference of the fourth tubular portion 524 of the accommodating member 52. It is electrically connected to the surface.

(O-ring)
The O-ring 56 is a member that exhibits an annular shape as a whole. The O-ring 56 is made of a synthetic resin material such as PTFE (Polytetrafluoroethylen), which has insulating properties and high heat resistance, moisture permeability resistance, 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 side housing 332, the outer peripheral surface of the connecting member 54 and the second rear end side housing It is sandwiched between the inner peripheral surface of 332.

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

The abutting pipe 57 is located inside the region where the first tip-side housing 311 and the second tip-side housing 312 overlap in the tip-side housing 31, and is arranged inside the first tip-side housing 311. ing. The abutting pipe 57 is located on the rear end side of the intermediate tubular portion 492 of the pressurizing member 49 and on the tip end side of the first insulating member 61. Further, the outer diameter of the abutting pipe 57 is substantially the same as the inner diameter of the rear end side of the first front end side housing 311 accommodating the abutting pipe 57. On the other hand, the inner diameter of the abutting pipe 57 is larger than the outer diameter of the rear end tubular portion 493 of the pressurizing member 49. The surface of the abutting pipe 57 on the tip end side is in contact with the rear end step portion 49c (the surface on which the insulating film 49a is formed) of the pressurizing 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. Further, the outer peripheral surface of the abutting pipe 57 is in contact with the inner peripheral surface on the rear end side of the first front end side housing 311. Here, the inner peripheral surface on the rear end side of the first front end side housing 311 and the outer peripheral surface of the abutting pipe 57 facing this portion are laser-welded over one circumference by the first welded portion 58. 1. The tip side housing 311 and the abutting pipe 57 are joined and fixed. On the other hand, the inner peripheral surface of the abutting pipe 57 faces the outer peripheral surface of the rear end tubular portion 493 of the pressurizing member 49 via an air gap. In this way, by providing the insulating film 49a and the air gap between the rear end stepped portion 49b and the rear end tubular portion 493 of the pressurizing member 49 and the abutting pipe 57, the abutting pipe 57 and the abutting pipe 57 are pressurized. It does not come into direct contact with the member 49.

(1st weld)
The first welded portion 58 is a portion formed 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 abutting pipe 57 over one circumference.

(2nd weld)
The second welded portion 59 is a portion formed by laser welding the inner peripheral surface of the pressure member 49 on the rear end side 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 a synthetic resin material such as LCP (Liquid Crystal Polymer) having insulating properties. The insulating pipe 60 is arranged inside a pressurizing member 49 provided inside the tip-side housing 31. Inside the insulating pipe 60, the front end side of the main body 44a of the piezoelectric element 41, the first rear end electrode member 43, and the second rear end electrode member 44 is housed. The insulating pipe 60 is located on the rear end side of the tip electrode member 42 and on the tip side of the insulating ring 45. Further, the outer diameter of the insulating pipe 60 is slightly smaller than the inner diameter of the pressurizing member 49. Further, the inner diameter of the insulating pipe 60 is slightly larger than the outer diameter of the main body 44a of the piezoelectric element 41, the first rear end electrode member 43, and the second rear end electrode member 44. The tip end side of the insulating pipe 60 faces the rear end side surface of the tip electrode member 42. On the other hand, the rear end side of the insulating pipe 60 faces the front end side surface of the insulating ring 45. The outer peripheral surface of the insulating pipe 60 faces the inner peripheral surface of the pressurizing member 49. Further, the inner peripheral surface of the insulating pipe 60 faces the outer peripheral surface 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. In this way, an air gap is provided by the insulating pipe 60 and the insulating pipe 60 between the pressure member 49 and 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. As a result, the pressurizing member 49, the first rear end electrode member 43, and the second rear end electrode member 44 do not come into direct contact with each other.

(First insulating member)
The first insulating member 61 is a member having a tubular shape on the front end side and an annular shape on the rear end side. The first insulating member 61 is made of a ceramic material such as alumina, which has insulating properties and high heat resistance.

The first insulating member 61 is arranged inside the tip-side housing 31. The first insulating member 61 is arranged outside the second tubular portion 522 and the second stepped portion 52b (see FIG. 6) of the accommodating member 52. Further, the outer diameter of the first insulating member 61 is slightly smaller than the inner diameter of the second distal end side housing 312 of the corresponding portion, and the inner diameter of the first insulating member 61 is smaller than the outer diameter of the accommodating member 52 of the corresponding portion. Is also slightly larger. The outer peripheral surface of the first insulating member 61 is in contact with the second tip-side housing 312, and the inner peripheral surface of the first insulating member 61 is in contact with the accommodating member 52.

(Second insulating member)
The second insulating member 62 is a member that exhibits an annular shape as a whole. The second insulating member 62 is made of a ceramic material such as alumina, which has insulating properties and high heat resistance.

The second insulating member 62 is arranged at a position inside the front end side housing 31 and on the rear end side of the first insulating member 61. The second insulating member 62 is arranged outside the third tubular portion 523 and the third stepped portion 52c (see FIG. 6) of the accommodating member 52. Further, the outer diameter of the second insulating member 62 is slightly smaller than the inner diameter of the second distal end side housing 312 of the corresponding portion, and the inner diameter of the second insulating member 62 is smaller than the outer diameter of the accommodating member 52 of the corresponding portion. Is also slightly larger. The outer peripheral surface of the second insulating member 62 is in contact with the second tip-side housing 312, and the inner peripheral surface of the second insulating member 62 is in contact with the accommodating member 52.

In this way, by providing the air gap, the first insulating member 61, and the second insulating member 62 between the tip side housing 31 (second tip side housing 312) and the accommodating member 52, the tip side housing The 31 and the accommodating member 52 do not come into direct contact with each other.

(Third insulating member)
The third insulating member 63 is a member having a tubular shape as a whole. The third insulating member 63 is made of a ceramic material such as alumina, which has insulating properties and high heat resistance.

The third insulating member 63 is arranged at a position inside the rear end side housing 33 and on the rear end side of the second insulating member 62. The third insulating member 63 is located outside the fourth tubular portion 524 of the accommodating member 52. Further, the outer diameter of the third insulating member 63 is substantially the same as the inner diameter of the first rear end side housing 331, and the inner diameter of the third insulating member 63 is the outer diameter of the fourth tubular portion 524 of the accommodating 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 a part of the inner peripheral surface of the third insulating member 63 on the tip side is the accommodating member 52. And the others confront the accommodating member 52 via the air gap.

[Structure of seal part]
The seal portion 70 has a first seal member 71 that is relatively located on the front end side and a second seal member 72 that is relatively located on the rear end side. In the state where the pressure detection device 20 is attached to the internal combustion engine 10, the first seal member 71 and the second seal member 72 abut on the inner peripheral surface of the communication hole 13a (see FIG. 1) provided in the cylinder head 13. ..

(1st seal member)
The first seal member 71 is a member having a hollow structure and exhibiting a tubular shape as a whole. The first sealing member 71 is made of a synthetic resin material such as PTFE, which has insulating properties and high heat resistance and acid resistance.

The first seal member 71 is fitted in a recess 311a provided on the outer peripheral surface of the first front end side housing 311. The inner diameter thereof is slightly smaller than the outer diameter of the recess 311a, and the outer diameter thereof is slightly larger than the inner diameter of the communication hole 13a.

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

The second seal member 72 is fitted in a recess 312a provided on the outer peripheral surface of the second tip-side housing 312. The inner diameter thereof is slightly smaller than the outer diameter of the recess 312a, and the outer diameter thereof is slightly larger than the inner diameter of the communication hole 13a.

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

(Positive route)
In the pressure detection device 20, the end face (positive electrode) on the rear end side of the piezoelectric element 41 is a metal first rear end electrode member 43, a metal second rear end electrode member 44, and a metal first coil spring. It is electrically connected to the metal conductive member 47 via the 46. The metal conducting 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. To. In the following, from the surface on the rear end side of the piezoelectric element 41, the circuit board 53 is connected to the circuit board 53 via the first rear end electrode member 43, the second rear end electrode member 44, the first coil spring 46, the conduction member 47, and the holding member 48. The electrical path leading to it is called the "positive path".

(Negative route)
On the other hand, in the pressure detection device 20, the end face (negative electrode) on the tip end side of the piezoelectric element 41 is a metal tip electrode member 42, a metal pressure member 49, and a metal support member 50 (second welded portion). 59), a second coil spring 51 made of metal, a metal accommodating member 52, and a metal grounding plate 55, and electrically connected to a grounding terminal (not shown) provided on the circuit board 53. It is connected. In the following, electrical from the front end side surface of the piezoelectric element 41 to the circuit board 53 via the tip electrode member 42, the pressurizing member 49, the support member 50, the second coil spring 51, the accommodating member 52, and the grounding plate 55. The path is called a "negative path".

(Case route)
On the other hand, in the pressure detection device 20, the metal diaphragm head 32 is a metal rear end via a metal tip side housing 31 (first tip side housing 311 and second tip side housing 312). It is electrically connected to the side housing 33 (the first rear end side housing 331 and the second rear end side housing 332). Further, in the pressure detecting device 20, the metal first tip side housing 311 is electrically connected to the metal abutting pipe 57 (first welded portion 58). Hereinafter, the electrical path from the diaphragm head 32 to the rear end side housing 33 and the abutting pipe 57 via the front end side housing 31 will be 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 contained 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 housing route)
Further, in the pressure detecting device 20, the housing path exists outside the negative path. In other words, a negative path is housed inside the housing path. The negative path and the housing path are the insulating film 42a provided on the tip electrode member 42, the insulating film 49a provided on the pressure member 49, the first insulating member 61, the second insulating member 62, and the third. It is electrically insulated by the insulating member 63 and an air gap formed between the two paths.

(Relationship between chassis path and positive path)
Then, in the pressure detecting device 20, as a result, the housing path exists outside the positive path. In other words, the positive path is housed inside the housing path. Then, as described above, the positive path and the negative path are electrically insulated, and the negative path and the housing path are electrically insulated, so that the housing path and the positive path are electrically insulated. And are electrically insulated.

(Other)
Here, the housing portion 30 constituting the housing path is a portion exposed to the outside in the pressure detecting device 20, and in particular, the diaphragm head 32 faces the combustion chamber C whose acidity increases with combustion. It is a part. On the other hand, each member constituting the positive path and the negative path is a portion housed in the housing portion 30 in the pressure detecting device 20. Therefore, it is preferable that each member constituting the positive path and the negative path is made of a material having higher conductivity than each member constituting the housing path (housing portion 30), and the housing path (housing path (housing portion 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.

[Assembly procedure of pressure detector]
Next, the assembly procedure of the pressure detection device 20 used in the present embodiment will be described.

First, the front end side of the first front end side housing 311 and the back surface side (convex portion 32d side) of the diaphragm head 32 are opposed to each other and abutted against each other. Then, in this state, laser welding is performed around the boundary between the first tip-side housing 311 and the diaphragm head 32.

Next, the pressurizing member 49 is inserted into the first front end side housing 311 in the structure including the first front end side housing 311 and the diaphragm head 32 from the rear end side with the tip tubular portion 491 as the front end side. To do. At this time, the pressurizing member 49 is inserted until the tip step portion 49b provided on the outer peripheral surface of the pressurizing member 49 abuts on the inner step portion 311b provided on the inner peripheral surface of the first tip side housing 311. Do. Along with this, the insulating film 49a provided on the outer peripheral surface of the tip step portion 49b of the pressure member 49 and the intermediate tubular portion 492 comes into contact with the inner peripheral surface of the first tip side housing 311. Further, the convex portion 32d of the diaphragm head 32 is inserted into the opening provided on the tip end side of the tip tubular portion 491 of the pressurizing member 49.

Subsequently, the abutting pipe 57 is inserted from the rear end side between the inner peripheral surface of the first front end side housing 311 and the outer peripheral surface of the rear end tubular portion 493 of the pressurizing member 49. At this time, the abutting pipe 57 is inserted until the tip end side of the abutting pipe 57 abuts on the rear end step portion 49c provided on the pressurizing member 49. Along with this, the insulating film 49a provided on the rear end step portion 49c of the pressurizing member 49 comes into contact with the tip end side of the abutting pipe 57.

In this state, the rear end side of the first front end side housing 311 and the abutting pipe 57 are laser welded over one circumference to form the first welded portion 58. At this time, the intermediate tubular portion 492 of the pressurizing member 49 is sandwiched between the inner step portion 311b of the first distal end side housing 311 and the tip end side of the abutting pipe 57, so that the pressurizing member 49 becomes It is fixed to the first tip side housing 311. As a result, the pressurizing member 49 is positioned with respect to the first distal end side housing 311 and the diaphragm head 32.

Next, in the pressurizing member 49 in the structure including the first distal end side housing 311 and the diaphragm head 32, the pressurizing member 49 and the abutting pipe 57, from the rear end side, the tip electrode member 42, the insulating pipe 60, The piezoelectric element 41, the first rear end electrode member 43, the second rear end electrode member 44, the insulating ring 45, and the support member 50 are inserted in this order. When the tip electrode member 42 is inserted into the pressurizing member 49, the surface on which the insulating film 42a is formed is set as the tip side. Further, when the second rear end electrode member 44 is inserted into the pressurizing member 49, the main body portion 44a is on the front end side and the second convex portion 44c is on the rear end side. At this time, the insulating film 42a provided on the tip end side of the tip electrode member 42 housed in the pressurizing member 49 comes into contact with the convex portion 32d provided on the rear end side of the diaphragm head 32. Further, inside the insulating pipe 60, the front end side of the main body 44a of the piezoelectric element 41, the first rear end electrode member 43, and the second rear end electrode member 44 is arranged. Further, the first convex portion 44b and the second convex portion 44c of the second rear end electrode member 44 are exposed to the inside of the tip side of the support member 50 through the holes provided in the insulating ring 45.

In this state, the position of the support member 50 in the center line direction is adjusted with respect to the pressure member 49, and the load (preload) applied to the piezoelectric element 41 via the pressure member 49 and the support member 50 is adjusted.

Then, after the position adjustment of the support member 50 with respect to the pressure member 49 in the center line direction is completed, the rear end side of the pressure member 49 and the support member 50 are laser-welded over one circumference to form the second welded portion 59. To do. At this time, the front end side of the piezoelectric element 41 is added via the front end electrode member 42, and the rear end side is added via the first rear end electrode member 43, the second rear end electrode member 44, the insulating ring 45, and the support member 50. It is fixed to the pressure member 49. Further, in this state, the pressurizing member 49 is already fixed to the first front end side housing 311 and the diaphragm head 32. Therefore, the piezoelectric element 41 housed in the pressurizing member 49 is fixed to the diaphragm head 32 in a state where a predetermined preload is applied. As a result, the pressurizing member 49, the supporting member 50, and the piezoelectric element 41 are positioned with respect to the first distal end side housing 311 and the diaphragm head 32.

Subsequently, the first coil spring 46 is inserted from the rear end side into the support member 50 in the structure to which the support member 50 is attached, and the second rear end electrode member exposed to the inside of the front end side of the support member 50. It is attached to the second convex portion 44c of 44. Further, the second coil spring 51 is inserted and mounted on the rear end side of the support member 50 in the above structure from the rear end side. Further, the second front end side housing 312 is screwed and attached to the first front end side housing 311 in the above structure from the rear end side. Furthermore, the first insulating member 61 and the second insulating member 62 are inserted into the second front end side housing 312 from the rear end side in this order. Along with this, the first insulating member 61 is positioned by abutting the step portion provided on the tip side in the second tip side housing 312, and the second insulating member 62 is positioned in the second tip side housing 312. It is positioned by hitting a step portion provided on the rear end side.

On the other hand, in a process different from the assembly of the structure, the conduction member 47 is inserted into the tip end side of the holding member 48 from the tip end side. Further, a circuit board 53 including a ground plate 55 is attached to the rear end side of the holding member 48. At this time, the rear end side convex portion 47b of the conduction member 47 attached to the holding member 48 and the circuit board 53 are electrically connected. Then, the holding member 48 on which the conduction member 47 and the circuit board 53 (ground plate 55) are mounted is inserted into the accommodating member 52 from the rear end side with the conduction member 47 as the front end side. At this time, the holding member 48 is held until the boundary between the tubular portion and the plate-shaped portion (the tip end side of the plate-shaped portion) abuts against the inner peripheral surface of the second stepped portion 52b provided on the accommodating member 52. Insert 48. Along with this, the tip end side of the tubular portion of the holding member 48 and the tip end side (tip side recess 47a) of the conduction member 47 exposed from the tubular portion of the holding member 48 are closer to the tip side than the first tubular portion 521. Protrude. Further, the inner peripheral surface of the accommodating member 52 and the rear end side of the grounding plate 55 come into contact with each other.

Then, an accommodating member including a conduction member 47, a circuit board 53 (ground plate 55), and a holding member 48 from the rear end side in the second front end side housing 312 in the structure to which the second insulating member 62 is attached. 52 is inserted with the first tubular portion 521 as the tip end side. At this time, until the second step portion 52b provided on the accommodating member 52 abuts on the first insulating member 61 installed in the second tip-side housing 312 (the third step portion 52c provided on the accommodating member 52). However, the accommodating member 52 is inserted until it hits the second insulating member 62 installed in the second distal end side housing 312). Along with this, the rear end side of the second tubular portion 522 and the outer peripheral surface of the second step portion 52b of the accommodating member 52 come into contact with the inner peripheral surface and the rear end side surface of the first insulating member 61. Further, the rear end side of the third tubular portion 523 and the outer peripheral surface of the third step portion 52c of the accommodating member 52 come into contact with the inner peripheral surface and the rear end side surface of the second insulating member 62. On the other hand, the rear end side of the first coil spring 46 is inserted into the tip end side recess 47a of the conduction member 47, and the rear end side of the first coil spring 46 abuts against the bottom of the tip end side recess 47a. Further, the first tubular portion 521 of the accommodating member 52 is inserted into the rear end side of the second coil spring 51, and the rear end of the second coil spring 51 abuts on the first step portion 52a of the accommodating member 52. As a result, the first coil spring 46 and the second coil spring 51 are in a state of being compressed in the center line direction as compared with before the accommodating member 52 is inserted into the structure.

Subsequently, the first rear end side housing 331 and the third insulating member 63 are inserted and attached to the second front end side housing 312 in the structure to which the accommodating member 52 is attached from the rear end side. As a result, the outer peripheral surface of the fourth tubular portion 524 of the accommodating member 52 comes into contact with the inner peripheral surface of the third insulating member 63. Further, the second rear end side housing 332 is inserted into the first rear end side housing 331 from the rear end side.

Then, with respect to the second rear end side housing 332 in the structure to which the second rear end side housing 332 is attached, a connecting member 54 having an O-ring 56 mounted on the outer peripheral surface is attached to the substrate side from the rear end side. Insert the connector 54a with the tip side as the tip side. At this time, the O-ring 56 mounted on the connecting member 54 enters the inside of the second rear end side housing 332 and comes into contact with the second rear end side housing 332. Further, the circuit board 53 and the board-side connector 54a provided on the connecting member 54 are electrically connected.

Finally, the first seal member 71 is attached to the recess 311a of the first front end side housing 311 in the structure to which the connecting member 54 is attached, and the second seal is attached to the recess 312a of the second front end side housing 312. The member 72 is attached.
As described above, the assembly of the pressure detection device 20 is completed.

[Pressure detection operation by pressure detection device]
Then, 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. In the diaphragm head 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. Then, 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, and the piezoelectric element 41 receives an electric charge according to the received pressure. Occurs. The electric charge generated in the piezoelectric element 41 is supplied as an input signal terminal (not shown) charge signal of the circuit board 53 via a positive path. The charge signal supplied to the circuit board 53 is converted into an output signal by performing various processes in the circuit mounted on the circuit board 53. Then, 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.

[Effect of this embodiment]
In the pressure detection device 20 of the present embodiment, the piezoelectric element 41 is sandwiched between the pressure member 49 and the support member 50 by fixing the positional relationship between the pressure member 49 and the support member 50 in the center line direction. , A predetermined load is applied to the piezoelectric element 41. Then, in a state where the pressurizing member 49 accommodating the piezoelectric element 41 is brought into contact with the inner peripheral surface of the tip side housing 31 via the insulating film 49a, the tip side housing is used by using the abutting pipe 57. The pressurizing member 49 was fixed to 31. As a result, the pressurizing member 49 and the tip side housing 31 are electrically insulated, and the load fluctuates on the housing portion 30 (tip side housing 31) via the pressurizing member 49 and the support member 50. The piezoelectric element 41 can be fixed in a suppressed state.

Further, in the pressure detecting device 20 of the present embodiment, the insulating film 42a is provided on the tip side of the tip electrode member 42 existing between the piezoelectric element 41 and the diaphragm head 32. As a result, the tip electrode member 42 and the diaphragm head 32 can be electrically insulated.

Here, in the present embodiment, the above-mentioned tip electrode member 42 and the pressurizing member 49 also have a configuration that also serves as a negative path for the piezoelectric element 41. The path can be electrically isolated from the housing path including the distal housing 31 and the diaphragm head 32.

The pressure detection device 20 of the present embodiment is attached to the internal combustion engine 10, and when the internal combustion engine 10 is mounted on an automobile, noise having a frequency on the order of kHz generated by a cracker, a headlight, a wiper, or the like (hereinafter referred to as Then, it is called low frequency noise) enters the cylinder head 13 of the internal combustion engine 10. In the present embodiment, since the housing portion 30 made of metal in the pressure detection device 20 is attached to the cylinder head 13 made of metal, the low frequency noise that has entered the cylinder head 13 is generated. , It also propagates to the housing 30 of the pressure detection device 20.

Here, in the pressure detection device 20 of the present embodiment, the housing path including the housing portion 30 and the positive path and the negative path from the piezoelectric element 41 to the circuit board 53 are electrically insulated. There is. Therefore, the low frequency noise propagated from the cylinder head 13 to the housing portion 30 of the pressure detection device 20 is less likely to be transmitted to the circuit board 53 via the pressurizing member 49, the support member 50, the conduction member 47, and the like. As a result, the fluctuation (fluctuation) of the potential in the circuit board 53 due to the low frequency noise is suppressed, and the fluctuation (fluctuation) of the output signal output from the circuit board 53 to the outside (control device 80, etc.) is suppressed. Can be reduced.

Further, when the internal combustion engine 10 is mounted on an automobile, radio waves having a frequency on the order of MHz, which are usually used in mobile phones, radios, televisions, and the like, fly around the automobile. When this radio wave is applied to the conduction member 47 provided in the pressure detection device 20, noise having a frequency on the order of MHz (hereinafter referred to as high frequency noise) is transmitted to the circuit board 53.

Here, in the pressure detection device 20 of the present embodiment, the pressure member 49 and the support member 50 are used to cover the conduction member 47. Therefore, the radio waves radiated to the pressure detection device 20 from the outside are blocked by the pressure member 49 and the support member 50, and are difficult to be transmitted to the conduction member 47. As a result, the fluctuation (fluctuation) of the potential in the circuit board 53 due to the high frequency noise is suppressed, and it is possible to reduce the fluctuation (fluctuation) of the output signal output from the circuit board 53 to the outside. Become.

Further, in the present embodiment, the circuit board 53 is covered with the metal accommodating member 52. Therefore, the radio wave radiated to the pressure detection device 20 from the outside is blocked by the accommodating member 52, and it becomes difficult to reach the circuit board 53. As a result, the fluctuation (fluctuation) of the potential in the circuit board 53 caused by the high frequency noise is suppressed, and the fluctuation (fluctuation) of the output signal output from the circuit board 53 to the outside can be further reduced. It will be possible.

[Other]
In the present embodiment, by providing the insulating film 42a on the tip side of the tip electrode member 42, the tip electrode member 42 forming the negative path and the diaphragm head 32 forming the housing path are electrically insulated. I tried to do it, but it is not limited to this. For example, an insulating plate made of a ceramic material such as alumina, which has insulating properties and high heat resistance, may be arranged between the tip electrode member 42 and the diaphragm head 32.

Further, in the present embodiment, a negative path is configured by providing an insulating film 49a on a part of the outer peripheral surface of the pressure member 49 (intermediate tubular portion 492, tip step portion 49b and rear end step portion 49c). The pressurizing member 49 and the first distal end side housing 311 and the abutting pipe 57 constituting the housing path are electrically insulated, but the present invention is not limited to this. For example, an insulating ring made of a ceramic material such as alumina, which has insulating properties and high heat resistance, may be arranged between the pressurizing member 49, the first tip-side housing 311 and the abutting pipe 57, or an air gap may be provided. It does not matter if it is formed.

Further, in the present embodiment, between the rear end side and the second step portion 52b of the second tubular portion 522 of the accommodating member 52 and the inner peripheral surface of the second distal end side housing 312, the third accommodating member 52 has a third. Between the rear end side of the tubular portion 523 and the third stepped portion 52c and the inner peripheral surface of the second tip side housing 312, the fourth tubular portion 524 and the first rear end side housing 331 of the accommodating member 52. By arranging the first insulating member 61, the second insulating member 62, and the third insulating member 63, respectively, the accommodating member 52 that constitutes a negative path and the tip-side housing that constitutes the housing path. The 31 and the rear end side housing 33 are electrically insulated, but the present invention is not limited to this. For example, an insulating film formed by coating a part of the outer peripheral surface of the accommodating member 52 with a stainless material exhibiting insulating properties may be formed, or between the accommodating member 52 and the front end side housing 31 and the rear end side housing 33. An air gap may be formed.

Further, in the present embodiment, the first tip side housing 311 and the abutting pipe 57 are fixed by using the first welded portion 58, but the present invention is not limited to this, and for example, both are screwed in. It may be fixed by. Furthermore, in the present embodiment, the pressure member 49 and the support member 50 are fixed by using the second welded portion 59, but the present invention is not limited to this, and for example, both are fixed by screwing or the like. It doesn't matter if you do.

Further, in the present embodiment, the first rear end electrode member 43 and the second rear end electrode member 44 are arranged as separate members, but the present invention is not limited to this, and for example, the first rear end electrode member. The 43 and the second rear end electrode member 44 may be replaced with one member and arranged.

Further, in the present embodiment, the tip electrode member 42 is not housed in the insulating pipe 60, but the present invention is not limited to this, and the tip electrode member 42 may be housed in the insulating pipe 60. It doesn't matter.

Furthermore, in the present embodiment, the case where the piezoelectric element 41 is used as the pressure detecting element in the pressure detecting device 20 has been described as an example, but the present invention is not limited to this, and for example, a strain gauge or a separation is used. An electrode or the like may be used.

1 ... Pressure detection system, 10 ... Internal engine, 20 ... Pressure detection device, 30 ... Housing part, 31 ... Front end side housing, 32 ... Diaphragm head, 33 ... Rear end side housing, 40 ... Detection mechanism part, 41 ... Piezoelectric element, 42 ... Tip electrode member, 42a ... Insulation film, 43 ... First rear end electrode member, 44 ... Second rear end electrode member, 45 ... Insulation ring, 46 ... First coil spring, 47 ... Conduction member, 48 ... Holding member, 49 ... Pressurizing member, 49a ... Insulating film, 50 ... Support member, 51 ... Second coil spring, 52 ... Accommodating member, 53 ... Circuit board, 54 ... Connecting member, 55 ... Ground plate, 56 ... O ring , 57 ... abutment pipe, 58 ... first welded part, 59 ... second welded part, 60 ... insulated pipe, 61 ... first insulating member, 62 ... second insulating member, 63 ... third insulating member, 70 ... seal Part, 71 ... 1st seal member, 72 ... 2nd seal member, 80 ... control device, 90 ... connection cable

Claims (6)

A detection element that detects changes in pressure and
A first housing having conductivity and accommodating the detection element inside,
It is provided with a second housing having conductivity and accommodating the first housing inside.
An insulating film formed on at least one of the first housing or the second housing and electrically insulating the first housing and the second housing is provided .
The first housing applies a load to the detection element by sandwiching the detection element from the front end side and the rear end side of the first housing.
A deforming member attached to the tip side of the second housing and deformed by receiving external pressure, and
An insulating transmission member having an insulating property and provided between the deformable member and the detection element inside the second housing and transmitting the pressure acting on the deformable member to the detection element.
A fixing member that fixes the first housing to the second housing in a state of being electrically insulated from the deforming member and the second housing.
A pressure detector comprising: The pressure detecting device according to claim 1, wherein the insulating film is made of a material having a coefficient of thermal expansion equivalent to or similar to that of the material constituting the first housing or the second housing. The pressure detecting device according to claim 1 or 2, wherein the insulating film is an insulating film obtained by coating the first housing or the second housing with a stainless paint. The first housing has a tubular shape and is provided with a protruding portion protruding outward on the outer peripheral surface.
The fixing member is characterized in that the first housing is fixed to the second housing by sandwiching the protruding portion between the fixing member and the inner peripheral surface of the second housing via the insulating film. The pressure detecting device according to any one of claims 1 to 3. The first housing is
A first application that is arranged outside the detection element, is electrically connected to the front end side of the detection element, is electrically insulated from the rear end side of the detection element, and applies a load from the front end side of the detection element. Members and
The detection element is provided on the rear end side of the first granting member, is electrically connected to the first granting member, is electrically insulated from the detection element, and is fixed to the first granting member. The pressure detecting device according to any one of claims 1 to 3, further comprising a second applying member that applies a load from the rear end side. A conductive member that is housed inside the first housing and electrically connected to the rear end side of the detection element to conduct a detection signal output by the detection element is further included.
Claims 1 to 1, wherein the first housing becomes a ground of the detection element by being electrically connected to the tip end side of the detection element and electrically insulated from the conduction member . The pressure detection device according to any one of 3.

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