JP7166897B2 - pressure detector - Google Patents

Description

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

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

For example, in Patent Document 1, a conductive cylindrical first housing, a diaphragm attached to the front end side of the first housing, and a diaphragm arranged in the first housing on the rear end side of the diaphragm, acting through the diaphragm a piezoelectric element for detecting the pressure applied, a first electrode provided between the diaphragm and the piezoelectric element in the first housing and in contact with both of them, and a piezoelectric element at the rear end side of the piezoelectric element in the first housing. A second electrode portion provided in contact with the element, and a rod-shaped conductive member electrically connected to the second electrode portion on the rear end side of the second electrode portion and transmitting an output signal from the piezoelectric element. The first electrode portion, the piezoelectric element, and the second electrode portion are housed inside and electrically connected to the first electrode portion. a second housing that partially surrounds the conductive member with a gap therebetween and is electrically connected to the second housing and accommodated in the first housing; and between the second housing and the accommodating member. A pressure sensing device is described with a coil spring disposed and electrically connecting the two.

JP 2017-173122 A

A conventional pressure sensing device includes a conductive member connected to one pole side of a piezoelectric element and a second housing partially surrounding the conductive member and connected to the other pole side of the piezoelectric element. It is housed inside the first housing with a gap. Here, when an external impact is applied to the pressure detection device, the distance (the size of the gap) between the second housing and the conductive member and the distance between the second housing and the first housing, which is a conductor, change. Subject to change. In particular, since one end of the second housing in the conventional pressure detection device is supported by the coil spring, the distance between these members is likely to change. A change in the distance between the members results in a change in the capacitance between the members, generating pulse-like noise between the members and possibly impairing the reliability of the output signal of the pressure detection device.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable pressure detection device.

a pressure detection element that outputs an electrical signal corresponding to pressure received from the outside; a conductive member that conducts the electrical signal from the pressure detection element; a first housing member that houses the conductive member; a conductive second housing member arranged to cover at least a part of the member and the first housing member; and a housing for housing, wherein the conductive member and the second housing member are electrically insulated, wherein a convex portion is provided on an outer peripheral surface of the first housing member, and the The pressure detection device is such that the second housing member is supported by the first housing member by the convex portion coming into contact with the inner peripheral surface of the second housing member.

In such a pressure detection device, one end of the second housing member may be elastically supported within the housing, and the other end may be rigidly supported.

Further, a conductive inner housing that accommodates the pressure detection element and is disposed inside the housing and electrically connected to the pressure detection element is provided, and the inner housing and the second housing are provided. The member may be an electrically connected pressure sensing device.

Furthermore, the internal housing and the second housing member may be connected by a coil spring.

Further, the pressure detection device may have an insulating member disposed between the housing and the inner housing so that the housing and the inner housing are electrically insulated from each other.

According to the present invention, it is possible to provide a highly reliable pressure detection device.

1 is a schematic configuration diagram of a pressure detection system 1 according to an embodiment; FIG. 1 is a cross-sectional view of a pressure detection device according to an embodiment; FIG. 2 is an enlarged cross-sectional view of the tip side of the pressure detection device according to the embodiment; FIG. 3 is an enlarged cross-sectional view of an intermediate portion of the pressure detection device according to the embodiment; FIG. It is a perspective view of a holding member according to the embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[Configuration of pressure detection system]
FIG. 1 is a schematic configuration diagram of a pressure detection system 1 according to an embodiment. The pressure detection system 1 includes a pressure detection device 20 that detects the pressure (combustion pressure) in the combustion chamber C in the internal combustion engine 10, and supplies power to the pressure detection device 20, and based on the pressure detected by the pressure detection device 20, A control device 80 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 are provided.

Here, an internal combustion engine 10 whose pressure is to be detected includes a cylinder block 11 in which cylinders are formed, pistons 12 that reciprocate within the cylinders, pistons 12 fastened to the cylinder block 11, and a combustion chamber C It has a cylinder head 13 that configures. Further, the cylinder head 13 is provided with a mounting hole 13a that communicates the combustion chamber C with the outside. The pressure detection device 20 is attached to the internal combustion engine 10 by inserting and fixing the pressure detection device 20 into the attachment hole 13a. Here, the cylinder block 11, the piston 12, and the cylinder head 13 that constitute the internal combustion engine 10 are made of a conductive metal material such as cast iron or aluminum.

[Configuration of Pressure Detector]
FIG. 2 is a cross-sectional view of the pressure detection device 20. As shown in FIG. FIG. 3 is an enlarged sectional view of the tip side of the pressure detection device 20. As shown in FIG. FIG. 4 is an enlarged cross-sectional view of an intermediate portion of the pressure detection device 20. As shown in FIG. FIG. 5 is a perspective view of a holding member.

The pressure detection device 20 of the present embodiment includes a casing portion 30 exposed to the outside and various mechanisms for detecting pressure, and is substantially entirely housed in the casing portion 30 and partially (connection mechanism described later). The member 54) has a detection mechanism portion 40 provided so as to be exposed to the outside, and a seal portion 70 attached to the outer peripheral surface of the housing portion 30. As shown in FIG. 2, the left side of the internal combustion engine 10 shown in FIG. is mounted so that the right side (the part where the detection mechanism part 40 is exposed) faces the outside (upward in FIG. 1). Also, in this state, the seal portion 70 is positioned inside the mounting hole 13 a provided in the cylinder head 13 . In the following description, in FIG. 2 , the left side of the pressure detection device 20 is referred to as the “front end side”, and the right side of the pressure detection device 20 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 detection device 20 indicated by the one-dot chain line in FIG. 2 is simply referred to as the direction of the center line.

[Configuration of housing]
The housing part 30 as an example of the housing includes a distal housing 31, a diaphragm 32 attached to the distal side of the distal housing 31, and a rear end attached to the rear end side of the distal housing 31. A side housing 33 is provided.

(Tip side housing)
The distal 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 electrical conductivity and high heat resistance and acid resistance.

The distal housing 31 has a first distal housing 311 relatively located on the distal side and a second distal housing 312 relatively located on the rear end side. Here, in the tip end side housing 31, the outer peripheral surface on the rear end side of the first tip end side housing 311 and the inner peripheral surface on the tip end side of the second tip end side housing 312 are laser-welded so that both It is configured to integrate the Then, the diaphragm 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 attached to the rear end side of the second front end side housing 312 by fitting. be done.

Here, the outer peripheral surface of the first tip end housing 311 is provided with a concave portion 311a for mounting a first seal member 71 (details of which will be described later) that constitutes the seal portion 70 . In addition, inside the first tip side housing 311, there is a portion set to a first diameter on the tip side and a portion set to a second diameter larger than the first diameter on the rear end side. An inner stepped portion 311b is provided at the boundary between these two portions to connect them.

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

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

The diaphragm 32 has a recessed portion 32b formed in the central portion on the tip end side, and is exposed to the outside (combustion chamber C side) to receive pressure, a pressure receiving surface (surface) 32a, and a back side of the pressure receiving surface 32a. A concave portion 32c provided by annularly notching the rear surface of the pressure receiving surface 32c, and a convex portion 32d projecting from the central portion of the pressure receiving surface 32a (where the concave portion 32b is formed) to the rear end side as a result of the existence of the concave portion 32c. have. This diaphragm 32 is provided so as to block the opening on the distal end side of the first distal housing 311 . A boundary portion between the diaphragm 32 and the first tip end side housing 311 is laser-welded along the entire circumference of the outer peripheral surface.

(Rear end housing)
The rear end housing 33 is a member having a hollow structure and having a tubular shape as a whole. The rear end side housing 33 is made of a metal material such as stainless steel that has electrical 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 housing 33 is positioned outside the internal combustion engine 10, and therefore has higher heat resistance and acid resistance than the front housing 31. Low material can be used.

The rear-end housing 33 has a first rear-end housing 331 positioned relatively on the front end side and a second rear-end housing 332 positioned relatively on the rear end side. Here, in the rear end side housing 33, by fitting the outer peripheral surface of the front end side of the second rear end side housing 332 into the inner peripheral surface of the rear end side of the first rear end side housing 331, the two are separated. It is configured to integrate. 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 connection member 54 (details of which will be described later) is attached to the rear end side of 332 by fitting.

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

(Piezoelectric element)
A piezoelectric element 41 as an example of a pressure detection element is a member having a cylindrical shape as a whole. The piezoelectric element 41 comprises a piezoelectric body exhibiting piezoelectric action of piezoelectric longitudinal effect. The piezoelectric longitudinal effect means that when an external force is applied to the stress application axis in the same direction as the charge generation axis of the piezoelectric body, charges are generated on the surface of the piezoelectric body in the charge generation axis direction. The piezoelectric element 41 is arranged inside the distal housing 31 and on the rear end side of the diaphragm 32 . The piezoelectric element 41 is accommodated in the tip 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 a pressure member 49 provided inside the distal end side housing 31 and inside an element ring 60 provided inside this pressure member 49. . Also, the outer diameter of the piezoelectric element 41 is slightly smaller than the inner diameter of the element ring 60 that accommodates the piezoelectric element 41 therein. The tip side surface of the piezoelectric element 41 is in contact with the rear end side surface of the tip electrode member 42 . On the other hand, the rear end side surface of the piezoelectric element 41 is in contact with the front end side surface of the first rear end electrode member 43 . Also, the outer peripheral surface of the piezoelectric element 41 faces the inner peripheral surface of the element ring 60 . Thus, by providing the element ring 60 between the inner peripheral surface of the pressure member 49 and the outer peripheral surface of the piezoelectric element 41, the pressure member 49 and the piezoelectric element 41 do not come into direct contact with each other.

Next, the case where the piezoelectric element 41 utilizes the piezoelectric lateral effect will be exemplified. The piezoelectric transverse effect means that when an external force is applied to a stress application axis positioned perpendicular to the charge generation axis of the piezoelectric body, charges are generated on the surface of the piezoelectric body in the direction of the charge generation axis. A plurality of thin plate-shaped piezoelectric bodies may be laminated. By laminating in this way, electric charges generated in the piezoelectric bodies can be efficiently collected and the sensitivity of the sensor can be increased. Examples of piezoelectric materials that can be used in the piezoelectric element 41 include langasite crystals (langasite, langatite, langanite, LTGA) having piezoelectric longitudinal and piezoelectric effects, crystal, gallium phosphate, and the like. can do. In the piezoelectric element 41 of this embodiment, LTGA single crystal is used as the piezoelectric material.

(Tip electrode member)
The tip electrode member 42 is a member having a cylindrical shape as a whole. The tip electrode member 42 is made of a metal material such as stainless steel, which has electrical conductivity and high heat resistance. Insulating coating 42a is formed on the central portion of the front end side surface of tip electrode member 42 by coating a ceramic material exhibiting insulating properties, such as alumina and zirconia. Here, the insulating coating 42a has, for example, a circular shape, and its diameter is larger than the diameter of the projection 32d provided on the back surface of the diaphragm 32. smaller than the diameter of the opening.

The tip electrode member 42 is arranged inside a pressure member 49 provided inside the tip side housing 31 . The tip electrode member 42 is arranged on the rear end side of the diaphragm 32 and on the tip side of the piezoelectric element 41 . However, unlike the piezoelectric element 41 described above, the tip electrode member 42 is not accommodated within the element ring 60 . Also, the outer diameter of the tip electrode member 42 is slightly smaller than the inner diameter of the pressure member 49 that accommodates the tip electrode member 42 therein. Then, of the front end side surface of the tip electrode member 42 , the central region where the insulating coating 42 a is provided is in contact with the rear end side surface of the projection 32 d provided on the back surface of the diaphragm 32 . . In addition, of the front end side surface of the tip electrode member 42 , the peripheral area where the insulating coating 42 a is not provided is in contact with the back side surface of the opening provided at the front end side of the pressure member 49 . . On the other hand, the rear end side surface of the tip electrode member 42 is in contact with the tip side surface of the piezoelectric element 41 . Also, the outer peripheral surface of the tip electrode member 42 faces the inner peripheral surface of the pressure member 49 .

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

The first rear end electrode member 43 is arranged inside a pressure member 49 provided inside the front end housing 31 . The first rear end electrode member 43 is arranged on the rear end side of the piezoelectric element 41 and on the front end side of the second rear end electrode member 44 . Here, the first rear end electrode member 43 is arranged inside the element ring 60 provided inside the pressure member 49 . Also, 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 slightly smaller than the inner diameter of the element ring 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 rear end side surface of the first rear end electrode member 43 is in contact with the front end side surface of the second rear end electrode member 44 . Also, the outer peripheral surface of the first rear end electrode member 43 faces the inner peripheral surface of the element ring 60 . Thus, by providing the element ring 60 between the inner peripheral surface of the pressure member 49 and the outer peripheral surface of the first rear end electrode member 43, the pressure member 49 and the first rear end electrode member 43 are No direct contact.

(Second rear end electrode member)
The second rear end electrode member 44 is a member having a top shape as a whole and a T-shaped cross section. The second rear end electrode member 44 is made of a metal material such as stainless steel, which has electrical conductivity and high heat resistance. The second rear end electrode member 44 includes a disk-shaped main body portion 44a located on the front end side, and a cylindrical main body portion 44a extending from the central portion of the rear end side surface of the main body portion 44a toward the rear end side. It has a projecting first projection 44b and a columnar second projection 44c projecting from the rear end of the first projection 44b toward the rear end. Here, the diameter of the first convex portion 44b is smaller than the diameter of the 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 a pressure member 49 provided inside the front end housing 31 . Here, the tip side of the body portion 44 a of the second rear end electrode member 44 is arranged inside the element ring 60 provided inside the pressure member 49 . On the other hand, the portion of the second rear end electrode member 44 that is closer to the rear end than the second rear end electrode member 44 is arranged outside the element ring 60 . The outer diameter of the body portion 44 a of the second rear end electrode member 44 is substantially the same as the outer diameter of the piezoelectric element 41 and slightly smaller than the inner diameter of the element ring 60 . The surface of the main body portion 44 a of the second rear end electrode member 44 on the front end side is in contact with the surface of the first rear end electrode member 43 on the rear end side. On the other hand, the rear end side surface of the main body portion 44 a is in contact with the front end side surface of the insulating ring 45 . The outer peripheral surface of the first protrusion 44b of the second rear end electrode member 44 is in contact with the inner peripheral surface of the insulating ring 45 at the tip side thereof, and the inner peripheral surface of the support member 50 at the rear end side with a gap therebetween. are confronted with. 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 with a gap therebetween, and the first coil spring 46 mounted on the outer peripheral surface It is in contact with the conducting member 47 via the contact. Thus, by providing the element ring 60, the 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 rear end electrode member 44 are separated from each other. It does not come into direct contact with the end electrode member 44 . Further, by providing a 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 do not come into direct contact with each other. .

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

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

(first coil spring)
The first coil spring 46 is a member having a spiral shape as a whole and expands and contracts in the direction of the center line. The first coil spring 46 is made of a metal material such as a Ni—Co alloy or stainless steel, which has electrical conductivity and is higher in electrical conductivity than the distal end side housing 31 .

The first coil spring 46 is provided inside the distal end side housing 31 and arranged inside the pressure member 49 and inside the support member 50 . The first coil spring 46 is arranged on the rear end side of the second rear end electrode member 44 and on the front end side of the conducting member 47, and is welded or adhered to the second rear end side electrode member 44 and the conducting member 47. are joined by That is, the first coil spring 46 is arranged across the second rear end electrode member 44 and the conductive member 47 . Here, the tip side of the first coil spring 46 is wound around the second convex portion 44 c of the second rear end electrode member 44 , and the rear end side of the first coil spring 46 is provided on the tip side of the conductive member 47 . It is inserted into the tip side concave portion 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 concave portion 47 a of the conductive member 47 . As a result, the tip of the first coil spring 46 hits the boundary (step) between the first projection 44b and the second projection 44c of the second rear end electrode member 44, and the tip of the first coil spring 46 is in contact with the outer peripheral surface of the second protrusion 44 c of the second rear end electrode member 44 . On the other hand, the rear end of the first coil spring 46 abuts against the bottom of the tip-side recess 47 a of the transmission member 47 , and the rear end of the first coil spring 46 contacts the inner peripheral surface of the tip-side recess 47 a of the transmission member 47 . are in contact with Also, the outer periphery of the first coil spring 46 faces the inner peripheral surface of the support member 50 with a gap therebetween. By providing a 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 as an example of the conductive member is a member having a bar shape as a whole. The conductive member 47 is made of a conductive metal material such as phosphor bronze, and its surface is plated with gold. The transmission member 47 is provided with the above-described tip-side concave portion 47a at its tip, and has a rear-end side recess 47a at its rear end, which has a diameter smaller than that of the central portion in the center line direction and protrudes toward the rear end side. A convex portion 47b is provided.

The conducting member 47 is provided inside the front end housing 31, and almost all parts thereof except for the front end portion and the rear end portion (rear end convex portion 47b) are arranged inside the holding member 48. there is Further, the front end side of the transmission member 47 is inside the pressure member 49, the rear end side of the transmission member 47 is inside the housing member 52, and the intermediate portion between the front end side and the rear end side is the second coil spring. 51, respectively. The conductive member 47 is arranged on the rear end side of the first coil spring 46 and on the front end side of the circuit board 53 . The conducting member 47 is arranged so as to pass through a through hole provided in the holding member 48 along the centerline direction. The outer diameter of the distal end portion of the conductive member 47 (the portion not covered by the holding member 48 ) is larger than the inner diameter of the holding member 48 and smaller than the inner diameter of the supporting member 50 . Furthermore, the outer diameter of the rear end portion (rear end-side protrusion 47 b ) of the transmission member 47 is approximately the same as the inner width of the holding portion provided in the holding member 48 . Furthermore, the outer diameter of the central portion of the transmission member 47 in the centerline 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 side concave portion 47 a of the transmission member 47 , so that the first coil spring 46 is in contact with the rear end side. On the other hand, the rear-end-side convex portion 47b of the conducting member 47 is fitted in a holding portion provided on the holding member 48. As shown in FIG. Further, the outer peripheral surface of the distal end portion of the conductive member 47 faces the inner peripheral surface of the support member 50 with a gap therebetween. Furthermore, the outer peripheral surface of the central portion of the transmission member 47 in the center line direction faces the second coil spring 51 via the holding member 48 and the gap. Furthermore, the outer peripheral surface of the rear end portion of the transmission member 47 faces the outer peripheral surface of the housing member 52 via the gap and the holding member 48 . Thus, by providing a gap and holding member 48 between the inner peripheral surface of supporting member 50 and the outer peripheral surface of conducting member 47, supporting member 50 and conducting member 47 do not come into direct contact with each other. Further, by providing a gap and holding member 48 between the inner peripheral surface of second coil spring 51 and the outer peripheral surface of conducting member 47, second coil spring 51 and conducting member 47 do not come into direct contact with each other. Furthermore, by providing a gap between the inner peripheral surface of the housing member 52 and the outer peripheral surface of the conducting member 47, the housing member 52 and the conducting member 47 do not come into direct contact with each other.

(Holding member)
The holding member 48 as an example of the first housing member is a tubular member. The holding member 48 includes a front end side cylinder portion 48a located on the front end side of the holding member 48, an intermediate cylinder portion 48b located in the middle portion, and a first rear end cylinder portion 48c located on the rear end side of the intermediate cylinder portion 48b. , and a second rear end side tubular portion 48d located on the rear end side of the first rear end side tubular portion 48c. The outer diameter of the tip side tubular portion 48a is smaller than the inner diameter of the support member 50, the outer diameter of the intermediate tubular portion 48b is larger than that of the tip side tubular portion 48a, and the outer diameter of the first rear end side tubular portion 48c is larger than the intermediate tubular portion 48b. , and the outer diameter of the second rear end side tubular portion 48d is larger than the outer diameter of the first rear end side tubular portion 48c. Further, the outer diameters of the intermediate tubular portion 48b, the first rear end side tubular portion 48c, and the second rear end side tubular portion 48d are smaller than the inner diameter of the housing member 52 at these portions.

A convex portion 48e that protrudes toward the outer circumference of the intermediate tubular portion 48b is provided on the outer peripheral portion of the intermediate tubular portion 48b. Four projections 48e are provided at intervals of 90 degrees along the circumferential direction on the outer peripheral surface of the intermediate cylindrical portion 48b at positions where the length ratio between the front end side and the rear end side in the center line direction is 1:2. The outer diameter of the intermediate cylindrical portion 48b including the convex portion 48e is set to be the same as or slightly larger than the inner diameter of the housing member 52 at the portion where the convex portion 48e is provided. The convex portion 48e is configured as a convex portion having a flat surface whose height from the outer peripheral surface of the intermediate cylindrical portion 48b is substantially constant.

The first rear end cylinder portion 48c and the second rear end cylinder portion 48d serve as holding portions for fitting and holding the circuit board 53. A cutout portion 48f is formed by cutting a portion of the cylindrical portion across the portion 48d in the center line direction.

The outer peripheral surface of the tip end side cylindrical portion 48a of the holding member 48 faces the inner peripheral surface of the support member 50 and the inner peripheral surface of the second coil spring 51 with a gap therebetween. Further, the outer peripheral surfaces of the first rear end side tubular portion 48c and the second rear end side tubular portion 48d, which are the portions of the intermediate tubular portion 48b excluding the convex portion 48e, face the inner peripheral surface of the housing member 52 with a gap therebetween. The convex portion 48e of the intermediate cylindrical portion 48b is in contact with the inner peripheral surface of the housing member 52 by inserting the holding member 48 into the housing member 52 by press fitting.

Since the holding member 48 is structurally provided with fine details (for example, a convex portion 48e) and the pressure detecting device 20 is used in a high-temperature environment such as the internal combustion engine 10, strength and heat resistance are required. In view of this, it is composed of a synthetic resin material such as PPS (GF40) or PBT (GF40) in which 40% glass frit is filled in polyphenylene sulfide or polybutylene terephthalate having insulating properties. A transmission member 47 is accommodated in the tubular holding member 48, and the rear end portion of the holding member 48 (more specifically, the first rear end side tubular portion 48c and the second rear end side tubular portion 48d) is provided with a conductive member 47. The circuit board 53 is held by the cutout portion 48 f ), and the circuit board 53 is attached to the transmission member 47 . In this way, the holding member 48 restricts the relative movement between the conducting member 47 and the housing member 52 by means of the convex portion 48e, holds the distance between the conducting member 47 and the housing member 52 at a predetermined distance, and has the notch. The portion 48f has a function of holding the conductive member 47 and the circuit board 53. As shown in FIG.

Such a holding member 48 is provided across the inside of the front end side housing 31 and the inside of the rear end side housing 33 . In addition, the front end side cylinder portion 48a of the holding member 48 is inside the pressure member 49 and the second coil spring 51, the intermediate cylinder portion 48b, the first rear end side cylinder portion 48c, and the second rear end side cylinder portion 48d are the housing members. 52, respectively. The holding member 48 is arranged on the rear end side of the insulating ring 45 and on the front end side of the connecting member 54 .

(Pressure member)
The pressure member 49, which is an example of the internal housing, 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 electrical conductivity and high heat resistance.

The pressurizing member 49 of the present embodiment includes a distal cylindrical portion 491 located on the most distal side and having an opening at the distal end, and an intermediate cylindrical portion disposed on the rear end side of the distal cylindrical portion 491. 492 and a rear end tubular portion 493 located on the rear end side of the intermediate tubular portion 492 and on the rearmost side. In this pressurizing member 49, the outer diameter of the intermediate tubular portion 492 is larger than that of the distal tubular portion 491 and the rear tubular portion 493, and the outer diameter of the rear tubular portion 493 is larger than that of the distal tubular portion 491. diameter is larger. The pressurizing member 49 has a front end stepped portion 49b that connects the front end tubular portion 491 and the intermediate tubular portion 492 at the boundary portion, and a boundary portion between the intermediate tubular portion 492 and the rear end tubular portion 493. and a rear end stepped portion 49c connecting the two. Note that the inner diameters of the pressure members 49 are the same except for the opening provided at the tip. Therefore, in the pressurizing member 49 , the thickness of the intermediate tubular portion 492 is larger than that of the rear end tubular portion 493 , and the thickness of the rear end tubular portion 493 is larger than that of the tip tubular portion 491 . is larger than the wall thickness of Therefore, in the pressure member 49, the intermediate tubular portion 492 is the least flexible, while the tip tubular portion 491 is the most flexible (easily functioning as a spring).

In addition, in the pressure member 49, the outer peripheral surfaces of the tip cylindrical portion 491, the tip stepped portion 49b, the intermediate tubular portion 492, and the rear stepped portion 49c are coated with insulating ceramics, such as alumina and zirconia. An insulating film 49a formed by coating material is continuously formed.

The pressurizing member 49 is provided inside the housing 31 on the distal end side so that the distal cylindrical portion 491 is on the distal end side. Inside the pressing member 49 are the piezoelectric element 41 , the tip electrode member 42 , the first rear electrode member 43 , the second rear electrode member 44 , the insulating ring 45 , the tip side of the support member 50 , the element ring 60 , the second electrode member 44 . 1 coil spring 46, the tip side of the transmission member 47, and the tip side of the holding member 48 are accommodated. The pressure member 49 is arranged on the rear end side of the diaphragm 32 and on the front end side of the housing member 52 . Further, the outer diameter of the pressure member 49 differs between the tip tubular portion 491, the intermediate tubular portion 492, and the rear tubular portion 493, but is smaller than the inner diameter of the tip side housing 31 at all positions. Furthermore, the inner diameter of the pressurizing member 49 is such that it is is slightly larger than the outer diameter of the support member 50 , and the portion facing the support member 50 has substantially the same outer diameter as the support member 50 .

Here, between the outer peripheral surface of the rear end cylindrical portion 493 provided on the rear end side of the pressure member 49 and the inner peripheral surface on the rear end side of the first front end side housing 311, the abutment pipe 57 is provided. are placed.

A surface of the pressure member 49 on the front end side of the front end tubular portion 491 (surface on the front side of the opening) faces the concave portion 32c of the diaphragm 32 with a gap therebetween. On the other hand, the rear end side of the rear end tubular portion 493 faces the first insulating member 61 with a gap therebetween. In addition, the outer peripheral surface of the distal end cylindrical portion 491 faces the inner peripheral surface of the first distal end side housing 311 via a gap. Furthermore, the outer peripheral surfaces of the front end stepped portion 49b, the intermediate cylindrical portion 492, and the rear end stepped portion 49c are in contact with the insulating coating 49a and face the inner peripheral surface of the first front end housing 311 via the insulating coating 49a. is doing. Furthermore, the outer peripheral surface of the rear end tubular portion 493 faces the inner peripheral surface of the abutting pipe 57 via a gap. Thus, by providing the gap and the insulating film 49a between the outer peripheral surface of the pressure member 49 and the inner peripheral surface of the first tip end side housing 311 and the inner peripheral surface of the abutment pipe 57, the pressure member 49, the first tip housing 311 and the abutment pipe 57 do not come into direct contact with each other.

(support member)
The support member 50 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 electrical conductivity and high heat resistance.

The support member 50 is provided inside the tip side housing 31 , and the tip side is positioned inside the pressure member 49 and the rear end side is positioned outside the pressure member 49 . Further, the support member 50 has therein the rear end side of the second rear end electrode member 44 (the first convex portion 44b and the second convex portion 44c), the first coil spring 46, the tip side of the conductive member 47, and the holding member. 48 is accommodated. The support member 50 is arranged on the rear end side of the insulating ring 45 and on the front end side of the housing member 52 . Also, the outer diameter of the support member 50 is substantially the same as the inner diameter of the first pressure member 37 . Further, the inner diameter of the support member 50 varies 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 . It is larger than the outer diameter of the first coil spring 46 at the portion facing the conductive member 47, larger than the outer diameter of the conductive member 47 at the portion facing the holding member 48, and the outer diameter of the holding member 48 at the portion facing the holding member 48. bigger than The tip side surface of the support member 50 (the surface on the front side of the opening) is in contact with the rear end side surface of the insulating ring 45 . On the other hand, the rear end side surface of the support member 50 faces the housing member 52 with a gap therebetween. Further, the tip 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 side of the second coil spring 51 . there is Here, 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 this portion are laser-welded over the entire circumference to form a second welded portion 59, thereby forming the pressure member. 49 and the support member 50 are joined and fixed. On the other hand, the inner peripheral surface of the supporting member 50 faces the second rear end electrode member 44, the first coil spring 46, the conducting member 47 and the holding member 48 with a gap therebetween. Thus, by providing a gap between the inner peripheral surface of the support member 50 and the second rear end electrode member 44, the first coil spring 46, the conductive member 47 and the holding member 48, the support member 50 and the second The second rear end electrode member 44, the first coil spring 46, the conducting member 47 and the holding member 48 are not in direct contact with each other.

(Second coil spring)
The second coil spring 51 is a member having a spiral shape as a whole and expands and contracts in the direction of the center line. The second coil spring 51 is made of a metal material such as stainless steel, which has electrical conductivity and high heat resistance.

The second coil spring 51 is provided inside the tip-side housing 31 , the tip side thereof is located on the rear end side and outside of the support member 50 and is joined thereto, and the rear end side thereof is the tip side of the housing member 52 . And it is located outside and joined. That is, the second coil spring 51 is arranged across the support member 50 and the housing member 52 . In addition, the outer diameter of the second coil spring 51 is smaller than the inner diameter of the distal housing 31 (more specifically, the second distal housing 312). Furthermore, the inner diameter of the second coil spring 51 is slightly smaller than the outer diameter of the support member 50 on the rear end side and the outer diameter of the housing member 52 on the front end side. The outer periphery of the second coil spring 51 faces the inner peripheral surface of the distal housing 31 with a gap therebetween. By providing a gap between the outer periphery of the second coil spring 51 and the inner peripheral surface of the distal housing 31 in this manner, the second coil spring 51 and the distal housing 31 do not come into direct contact with each other.

(Accommodating member)
The housing member 52 as an example of the second housing member is a member having a tubular shape as a whole. The housing member 52 is made of a metal material such as brass or stainless steel, which has electrical conductivity and is higher in electrical conductivity than the distal housing 31. The surface of the housing member 52 is plated with gold.

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

The housing member 52 is provided so that the first tubular portion 521 is on the distal end side, straddling the interior of the distal housing 31 and the interior of the rear housing 33 . Inside the accommodating member 52, the rear end side of the conducting member 47, the rear end side of the holding member 48, the circuit board 53, and the ground plate 55 are accommodated. The housing member 52 is arranged on the rear end side of the support member 50 and on the front end side of the connection member 54 . In addition, although the outer diameter of the housing member 52 differs among the first tubular portion 521, the second tubular portion 522, the third tubular portion 523, and the fourth tubular portion 524, all the positions are 31 and the inner diameter of the rear end housing 33 . Furthermore, although the inner diameter of the housing 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, each member accommodated therein can be accommodated. , and is large enough to be placed.

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

A surface of the housing member 52 on the front end side of the first cylindrical portion 521 (surface on the front side of the opening) faces the rear end side surface of the support member 50 with a gap therebetween. Also, 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 circuit board 53 . In addition, the outer peripheral surfaces of the first cylindrical portion 521 and the first stepped portion 52a face the inner peripheral surface of the second tip end side housing 312 via a gap. Furthermore, the outer peripheral surface of the second cylindrical portion 522 faces the inner peripheral surface of the second tip end side housing 312 via the gap and the first insulating member 61 . Furthermore, the second stepped portion 52b faces the inner peripheral surface of the second tip end side housing 312 with the first insulating member 61 interposed therebetween. In addition, the outer peripheral surface of the third tubular portion 523 faces the inner peripheral surface of the second tip end side housing 312 via the gap and the second insulating member 62 . Furthermore, the outer peripheral surface of the third stepped portion 52c faces the inner peripheral surface of the second tip end side housing 312 with the second insulating member 62 interposed therebetween. The outer peripheral surface of the fourth cylindrical portion 524 faces the inner peripheral surface of the second front end side housing 312 through the gap, and the first rear end side housing through the gap and the third insulating member 63 . It faces the inner peripheral surface of the body 331 . In this way, between the outer peripheral surface of the housing member 52 and the second front end housing 312 and the first rear end housing 331, the gap, the first insulating member 61, the second insulating member 62 and the third insulating member are formed. By providing the member 63, the housing member 52, the second front end side housing 312 and the first rear end side housing 331 do not come into direct contact with each other. In addition, the inner peripheral surface of the first cylindrical portion 521 of the housing member 52 faces the holding member 48 with a gap therebetween. In addition, the inner peripheral surface of the second tubular portion 522 faces the outer peripheral surface of the holding member 48 with a gap except for the portion where the protrusion 48e of the holding member 48 is located, and the portion where the protrusion 48e is located faces the outer peripheral surface of the holding member 48. is in contact with the projection 48e.

The housing member 52 is elastically supported inside the distal housing 31 by the contact of the first stepped portion 52a with the second coil spring 51 on the distal end side thereof, and the second stepped portion 52b and the second stepped portion 52b on the rear end side. The third stepped portion 53b and the fourth cylindrical portion 524 face the second front end side housing 312 and the first rear end side housing 331 via the first insulating member 61, the second insulating member 62 and the third insulating member 63. The rear end portion of the fourth tubular portion 524 is rigidly supported inside the rear end housing 33 by facing the connection member fixed to the rear end housing 33 . Further, the housing member 52 supports the outer peripheral surface of the holding member 48 inside thereof by the second tubular portion 522 coming into contact with the convex portion 48 e of the holding member 48 .

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

The circuit board 53 includes an integration circuit that integrates an input signal (charge signal) input from the piezoelectric element 41 and converts it into a voltage signal, and an amplifier that amplifies the voltage signal input from the integration circuit and outputs it as an output signal. A circuit and a power supply circuit that powers elements such as operational amplifiers that constitute the integrating circuit and the amplifying circuit are mounted (all not shown).

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

The connection member 54 has its front end side located inside the second rear end side housing 332 and its rear end side 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 housing 332 inside the second rear end housing 332 .

The outer diameter of the tubular portion located on the distal 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 connection member 54 is substantially the same as the outer diameter of the second rear end side housing 332 . Also, the tip side of the connection member 54 faces the inner peripheral surface of the second rear end side housing 332 via a gap or an O-ring 56 .

(ground plate)
The ground plate 55 is a strip-shaped member as a whole. The ground plate 55 is made of a conductive metal material such as phosphor bronze, and its surface is plated with gold.

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

(O-ring)
The O-ring 56 is an annular member as a whole. The O-ring 56 is made of a synthetic resin such as polytetrafluoroethylene (PTFE) or a fluororubber such as vinylidene fluoride fluororubber (FKM), which has high heat resistance, moisture permeability resistance, and acid resistance as well as insulating properties. made up of materials.

The O-ring 56 is attached to the outer peripheral surface of the connection member 54, and when the connection member 54 is attached to the second rear end side housing 332, the outer peripheral surface of the connection member 54 and the second rear end side housing are separated from each other. 332 and the inner peripheral surface thereof.

(butting pipe)
The abutting pipe 57, which is 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 having electrical conductivity and high heat resistance.

The abutting pipe 57 is arranged inside the first tip end side housing 311 in the region where the first tip end side housing 311 and the second tip end side housing 312 overlap in the tip end side housing 31 . ing. The abutting pipe 57 is located on the rear end side of the intermediate cylindrical portion 492 of the pressure member 49 and on the front end side of the first insulating member 61 . In addition, the outer diameter of the impingement pipe 57 is substantially the same as the inner diameter of the rear end side of the first distal end housing 311 that accommodates the impingement pipe 57 . On the other hand, the inner diameter of the abutment pipe 57 is larger than the outer diameter of the rear end tubular portion 493 of the pressure member 49 . The front end side surface of the abutment pipe 57 is in contact with the rear end stepped portion 49c of the pressure member 49 (the surface on which the insulating coating 49a is formed). On the other hand, the rear end side surface of the abutting pipe 57 faces the front end side surface of the first insulating member 61 via a gap. Further, the outer peripheral surface of the abutting pipe 57 is in contact with the inner peripheral surface of the first distal end side housing 311 on the rear end side. Here, the first welded portion 58 obtained by laser-welding the inner peripheral surface of the rear end side of the first distal end side housing 311 and the outer peripheral surface of the abutment pipe 57 facing this portion over the entire circumference. , 1, the housing 311 on the front end side and the abutting pipe 57 are joined and fixed. On the other hand, the inner peripheral surface of the abutment pipe 57 faces the outer peripheral surface of the rear end tubular portion 493 of the pressure member 49 with a gap therebetween. Thus, by providing the insulating film 49a and the gap between the rear end step portion 49b and the rear end cylindrical portion 493 of the pressure member 49 and the abutment pipe 57, the abutment pipe 57 and the pressure member 49 is not in direct contact.

(First welded part)
The first welded portion 58 is a portion formed by laser-welding the inner peripheral surface of the first tip end side housing 311 on the rear end side and the outer peripheral surface of the abutment pipe 57 over a circumference.

(Second 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 the entire circumference.

(element ring)
The element ring 60 is a member having a cylindrical shape as a whole. The element ring 60 is made of an insulating synthetic resin material such as fluorine-based resin. This element ring 60 is arranged inside a pressure member 49 provided inside the distal end side housing 31 . Inside the element ring 60, the tip end sides of the body portions 44a of the piezoelectric element 41, the first rear electrode member 43, and the second rear electrode member 44 are accommodated. The element ring 60 is positioned on the rear end side of the tip electrode member 42 and on the tip side of the insulating ring 45 . Also, the outer diameter of the element ring 60 is slightly smaller than the inner diameter of the pressure member 49 . Furthermore, the inner diameter of the element ring 60 is slightly larger than the outer diameters of the body portions 44 a of the piezoelectric element 41 , the first rear electrode member 43 , and the second rear electrode member 44 . The tip side of the element ring 60 faces the rear end side surface of the tip electrode member 42 . On the other hand, the rear end side of the element ring 60 faces the front end side surface of the insulating ring 45 . Also, the outer peripheral surface of the element ring 60 faces the inner peripheral surface of the pressure member 49 . Furthermore, the inner peripheral surface of the element ring 60 faces the outer peripheral surface of the main body portion 44 a of the piezoelectric element 41 , the first rear end electrode member 43 and the second rear end electrode member 44 . In this manner, the element ring 60 and the gap formed by the element ring 60 are provided between the pressure member 49 and the main body portion 44 a of the piezoelectric element 41 , the first rear electrode member 43 , and the second rear electrode member 44 . Therefore, the pressure member 49 does not come into direct contact with the first rear end electrode member 43 and the second rear end electrode member 44 .

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

The first insulating member 61 is arranged inside the distal housing 31 . The first insulating member 61 is arranged outside the second tubular portion 522 and the second stepped portion 52b of the housing member 52 . In addition, the outer diameter of the first insulating member 61 is slightly smaller than the inner diameter of the second distal housing 312 at the corresponding portion, and the inner diameter of the first insulating member 61 is smaller than the outer diameter of the housing member 52 at the corresponding portion. is also slightly larger. The outer peripheral surface of the first insulating member 61 is in contact with the second distal housing 312 , and the inner peripheral surface of the first insulating member 61 is in contact with the housing member 52 .

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

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

By providing the gap, the first insulating member 61 and the second insulating member 62 between the distal housing 31 (second distal housing 312) and the housing member 52, the distal housing 31 and the housing 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 having insulating properties and high heat resistance.

The third insulating member 63 is arranged inside the rear end side housing 33 and at a position closer to the rear end than the second insulating member 62 . The third insulating member 63 is positioned outside the fourth cylindrical portion 524 of the housing member 52 . The outer diameter of the third insulating member 63 is substantially the same as the inner diameter of the first rear end housing 331, and the inner diameter of the third insulating member 63 is the outer diameter of the fourth cylindrical portion 524 of the housing member 52. bigger than The outer peripheral surface of the third insulating member 63 is in contact with the inner peripheral surface of the first rear end side housing 331 , and the inner peripheral surface of the third insulating member 63 has a portion of the inner peripheral surface on the distal end side that extends from the accommodating member 52 . , and the others face the housing member 52 through a gap.

[Structure of seal part]
The seal portion 70 has a first seal member 71 relatively located on the front end side and a second seal member 72 relatively located on the rear end side. When the pressure detection device 20 is attached to the internal combustion engine 10, the first sealing member 71 and the second sealing member 72 abut against the inner peripheral surface of the mounting hole 13a (see FIG. 1) provided in the cylinder head 13. . The sealing portion 70 mainly has a function of sealing the combustion gas in the combustion chamber C with the first sealing portion 71 , and the second sealing member 72 prevents the pressure detection device 20 from vibrating together with the first sealing member 71 . In addition, it has a function of preventing water or the like from entering the mounting hole 13a from the outside of the cylinder head 13. As shown in FIG.

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

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

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

The second seal member 72 is fitted into a recess 312 a provided on the outer peripheral surface of the second tip end housing 312 . Its inner diameter is slightly smaller than the outer diameter of the recess 312a, and its outer diameter is slightly larger than the inner diameter of the mounting hole 13a. In the present embodiment, the second sealing member 72 is arranged on the tip side of the second tip end side housing 312 (see FIG. 2), but the tip side of the rib portion 312b that protrudes outward, that is, the cylinder It may be arranged at the rear end portion of the mounting hole 13a of the head 13. In this case, it is possible to effectively prevent water or the like from entering the mounting hole 13a from the outside.

[Electrical Connection Structure in Pressure Detector]
Here, the electrical connection structure in the pressure detection device 20 will be described.

(positive path)
In the pressure detection device 20, the end face (positive electrode) on the rear end side of the piezoelectric element 41 includes a first rear end electrode member 43 made of metal, a second rear end electrode member 44 made of metal, and a first coil spring made of metal. It is electrically connected to a conductive member 47 made of metal via 46 . The conductive member 47 made of metal is electrically connected to an input terminal (not shown) provided on the circuit board 53 via the holding portion, wiring, and terminals made of metal provided on the holding member 48 . be. Below, from the surface of the rear end side of the piezoelectric element 41, through the first rear end electrode member 43, the second rear end electrode member 44, the first coil spring 46, the conductive member 47, and the holding member 48, to the circuit board 53 The electrical path leading to is referred to as the "positive path".

(negative path)
On the other hand, in the pressure detection device 20, the end face (negative electrode) on the tip side of the piezoelectric element 41 includes a tip electrode member 42 made of metal, a pressure member 49 made of metal, and a support member 50 made of metal (second welded portion). 59), a second coil spring 51 made of metal, a housing member 52 made of metal, and a ground plate 55 made of metal, and a ground terminal (not shown) provided on the circuit board 53. It is connected. In the following, an electrical connection from the tip side surface of the piezoelectric element 41 to the circuit board 53 via the tip electrode member 42, the pressure member 49, the support member 50, the second coil spring 51, the housing member 52 and the ground plate 55 will be described. is called a "negative path".

(Chassis path)
On the other hand, in the pressure detection device 20, the metal diaphragm 32 is connected to the metal rear end side via the metal tip end side housing 31 (the first tip end side housing 311 and the second tip end side housing 312). It is electrically connected to the housing 33 (the first rear housing 331 and the second rear housing 332). Further, in the pressure detection device 20, the metal first distal end side housing 311 is electrically connected to the metal impinging pipe 57 (first weld portion 58). An electrical path from the diaphragm 32 to the rear end side housing 33 and the abutment pipe 57 via the front end side housing 31 is hereinafter referred to as a "housing path".

(Relationship between positive route and negative route)
Here, in the pressure detection device 20 of the present embodiment, the negative path exists outside the positive path. In other words, the positive path is contained within the negative path. The positive path and the negative path are electrically insulated by the element ring 60, the insulating ring 45, the holding member 48 and the air gap formed between both paths. Here, in the present embodiment, the negative path is an example of the first electrical path, and the positive path is an example of the second electrical path.

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

(Relationship between housing path and positive path)
In this pressure detection 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. As described above, the positive path and the negative path are electrically insulated, and the negative path and the housing path are electrically insulated. are electrically insulated.

(others)
Here, the housing part 30 constituting the housing path is a part of the pressure detection device 20 that is exposed to the outside. It has become. On the other hand, each member that constitutes the positive path and the negative path is a part of the pressure detection device 20 that is housed inside the casing 30 . For this reason, each member constituting the positive path and the negative path is preferably made of a material having higher conductivity than each member constituting the housing path (housing section 30). Each member constituting the housing 30) is preferably made of a material having higher acid resistance than each member constituting the positive path and the negative path.

[Pressure detection operation by pressure detection device]
Now, the pressure detection operation by the pressure detection device 20 will be described.
When the internal combustion engine 10 is operating, the pressure (combustion pressure) generated within the combustion chamber C is applied to the pressure receiving surface 32a of the diaphragm 32 . In the diaphragm 32, the pressure received by the pressure receiving surface 32a is transmitted to the convex portion 32d on the back side, and further transmitted from the convex portion 32d to the tip electrode member 42 via the insulating coating 42a. The pressure transmitted to the tip end electrode member 42 acts on the piezoelectric element 41 sandwiched between the tip end electrode member 42 and the first rear end electrode member 43, and the piezoelectric element 41 generates an electric charge corresponding to the received pressure. occur. The charge generated in the piezoelectric element 41 is supplied as a charge signal to an input signal terminal (not shown) of the circuit board 53 via a positive path. The charge signal supplied to the circuit board 53 is subjected to various processes in the circuit mounted on the circuit board 53, and is made into an output signal. 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. FIG.

[Effects of this embodiment]
In the pressure detection device 20 of the present embodiment, a protrusion 48e is provided on the outer peripheral surface of the holding member 48 that accommodates the conductive member 47 therein, and the conductive member 47 is accommodated by contacting the inner peripheral surface of the accommodating member 52 that covers the holding member 48. The holding member 48 is supported by the member 52 (in other words, the housing member 52 is supported by the holding member 48). As a result, even if an impact or the like is applied to the pressure detection device 20 from the outside, it is possible to suppress the deflection of the housing member 52 due to the vibration caused by the impact or the like, and the vibration between the housing member 52 and the conductive member 47 can be suppressed. It is now possible to hold relative positions in a preset positional relationship. As a result, noise caused by changes in the relative positional relationship between the housing member 52 and the conducting member 47 can be prevented. In addition, the pressure detection device 20 in the present embodiment has a configuration in which one end of the housing member 48 is supported by the second coil spring 51, but when one end of the housing member 52 is elastically supported in this manner, the effect is particularly remarkable. It is.

Further, in the pressure detection device 20 of the present embodiment, the convex portion 48e is provided at a position where the length ratio between the front end side and the rear end side of the holding member 48 in the center line direction is 1:2. The holding member 48 is supported (the housing member 52 is supported by the holding member 48). In the present embodiment, the position of the protrusion 48e that intermediately supports the holding member 48 (the position at which the holding member 48 is intermediately supported) is the position where the primary natural frequency of the holding member 48 including the transmission member 47 is high. have set. As a result, it becomes possible to separate the natural frequency of the holding member 48 including the conductive member 47 from the vibration range assumed in the environment where the pressure detection device 20 is used, and suppress the resonance of the holding member 48 and the like. can be done.

[others]
In the present embodiment, the outer peripheral surface of the holding member 48 surrounded by the housing member 52 is provided with four protrusions 48e in the circumferential direction, but the present invention is not limited to this. For example, the interval at which the convex portions 48e are provided in the circumferential direction may be smaller than 90 degrees, or may be larger than 90 degrees. Further, in the present embodiment, the convex portion 48e is partially provided at a position where the length ratio in the center line direction between the front end side and the rear end side of the intermediate cylindrical portion 48b in the holding member 48 is 1:2. However, it may be provided at a position where the length ratio between the front end side and the rear end side of the intermediate cylindrical portion 48b in the center line direction is 1:1, or at another position. It is preferable that the holding member 48 is provided at a position where the natural vibration of the holding member 48 is high. Alternatively, the projection 48e may extend from the front end side of the holding member 48 to the rear end side. Furthermore, a plurality of protrusions 48 e may be arranged side by side in the center line direction of the holding member 48 . Furthermore, the convex portion 48e in the present embodiment is configured as a convex portion having a flat surface whose height from the outer peripheral surface of the holding member 48 is substantially constant. It is also possible to adopt a configuration including a slanted surface that gradually becomes higher.

1 Pressure detection system 10 Internal combustion engine 11 Cylinder block 12 Piston 13 Cylinder head 13a Mounting hole 20 Pressure detection device 30 Case part 31 Tip side case 311 First tip side case 311a Recess 311b Inner stepped part 312 Second tip side case Body 312a Concave portion 312b Rib portion 32 Diaphragm 32a Pressure receiving surface (surface)
32b concave portion 32c concave portion 32d convex portion 33 rear end housing 331 first rear end housing 332 second rear end housing 40 detection mechanism section 41 piezoelectric element 42 tip electrode member 42a insulation film 43 first rear end electrode member 44 Second rear end electrode member 44a Main body portion 44b First protrusion 44c Second protrusion 45 Insulation ring 46 First coil spring 47 Conductive member 47a Tip side recess 47b Rear end side protrusion 48 Holding member 48a Tip side cylindrical portion 48b Intermediate Tubular portion 48c First rear tubular portion 48d Second rear tubular portion 48e Projection 48f Notch 49 Pressure member 49a Insulating coating 491 Tip tubular portion 492 Intermediate tubular portion 493 Rear tubular portion 49b Tip step Part 49c Rear end stepped portion 50 Supporting member 51 Second coil spring 52 Housing member 521 First tubular portion 522 Second tubular portion 523 Third tubular portion 524 Fourth tubular portion 52a First stepped portion 52b Second stepped portion 52c Third stepped portion 53 Circuit board 54 Connection member 54a Board-side connector 54b Cable-side connector 55 Ground plate 56 O-ring 57 Abutment pipe 58 First welded portion 59 Second welded portion 60 Element ring 61 First insulating member 62 Second Insulating member 63 Third insulating member 70 Sealing member 71 First sealing member 72 Second sealing member 80 Control device 90 Connection cable 120 Pressure detector 220 Pressure detector

Claims (5)

a pressure detection element that outputs an electrical signal corresponding to the pressure received from the outside;
a conductive member that conducts the electrical signal from the pressure sensing element;
a first housing member housing the conductive member therein;
a conductive second housing member arranged to cover at least a portion of the conductive member and the first housing member;
a housing that internally houses the pressure detection element, the conductive member, the first housing member, and the second housing member;
In the pressure detection device in which the conductive member and the second housing member are electrically insulated,
A convex portion is provided on the outer peripheral surface of the first housing member, and the second housing member is supported by the first housing member by contacting the convex portion with the inner peripheral surface of the second housing member. ,
The pressure detection device , wherein the inner peripheral surface of the tip of the second housing member faces the first housing member with a gap therebetween. 2. The pressure detection device according to claim 1, wherein one end of said second housing member is elastically supported within said housing, and the other end is rigidly supported. a conductive internal housing that accommodates the pressure sensing element therein and is disposed inside the housing and electrically connected to the pressure sensing element;
2. The pressure detection device according to claim 1, wherein the inner housing and the second housing member are electrically connected. 4. The pressure detection device according to claim 3 , wherein the inner housing and the second housing member are connected by a coil spring. 5. The pressure detection device according to claim 4, wherein an insulating member is arranged between the housing and the internal housing to electrically insulate the housing and the internal housing.

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