JP2023049395A - Pressure sensing device - Google Patents

Abstract

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

Description

The present invention relates to a pressure sensing device.

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.

Patent Document 1 discloses a piezoelectric element, a conductive member that conducts an electric signal from the piezoelectric element, a cylindrical first housing member that houses the conductive member therein, and a conductive member that covers the conductive member and the first housing member. and a cylindrical second housing member.

JP 2020-85864 A

When an impact is applied to the pressure detection device from the outside, the conductive member and the housing member may vibrate, for example, at a natural frequency depending on the length in the axial direction. When these vibrations are transmitted to the piezoelectric element, noise corresponding to the vibration is generated in the output of the piezoelectric element. If the frequency of the signal based on the pressure change to be detected by the pressure detection device is close to this natural frequency, there is a possibility that the detection accuracy of the signal based on the pressure change to be detected will be lowered.

SUMMARY OF THE INVENTION An object of the present invention is to suppress deterioration in detection accuracy of a signal to be detected by reducing vibration of a pressure detection device at a frequency close to that of a signal based on a pressure change to be detected.

A pressure detection device according to the present invention for achieving the above object comprises a detection element for detecting a change in pressure, a conductive member for conducting an electrical signal from the detection element, and a cylindrical housing for accommodating the conductive member. and a vibration suppression means formed by applying pressure to the transmission member from the housing side and suppressing vibration of the transmission member at a specific frequency.
Here, the vibration suppression means may be means for adjusting the natural frequency of the transmission member to a value outside a predetermined frequency range.
Further, the housing includes a tubular first housing that houses the conductive member therein, and a tubular second housing that houses the conductive member and the first housing therein. It is good as
Further, the housing may further include a cylindrical third housing that accommodates the conductive member, the first housing, and the second housing therein.
Further, at least a portion between the conductive member and the housing may be filled with a filler.
Further, the vibration suppression means may be means for fixing the transmission member and the housing at a specific position in the axial direction.
Further, the vibration suppressing means may be a crimped portion formed by crimping the housing from the outside.
Viewed from another point of view, the pressure detection device of the present invention comprises a detection element for detecting a change in pressure, a conducting member for conducting an electric signal from the detecting element, and a cylinder housing the conducting member inside. and a crimped portion for crimping the casing and the conductive member.
Here, an insulating member may be interposed between the housing and the conductive member in the crimped portion, so that the housing and the conductive member are insulated.
Further, the crimped portion is formed at a specific position in the axial direction of the housing and the transmission member by a force directed toward the center of a cross section substantially orthogonal to the axis, and is applied from a plurality of directions of the cross section to the housing and the transmission member. The conductive member may be crimped.

According to the present invention, it is possible to reduce the vibration of the pressure detection device due to the frequency close to the frequency of the signal based on the pressure change to be detected, and suppress the deterioration of the detection accuracy of the signal to be detected.

1 is a schematic configuration diagram of a pressure detection system according to an embodiment; FIG. FIG. 2 is a side view of a pressure sensing device with an internal insulation structure; 3 is a cross-sectional view of the pressure detection device shown in FIG. 2 taken along line III-III. FIG. 4 is an enlarged view of the IV region of the pressure detection device shown in FIG. 3; FIG. 1 is a cross-sectional view of a non-internally insulated pressure sensing device; FIG. FIG. 6 is an enlarged view of a V region portion of the pressure detection device shown in FIG. 5;

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 100 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 100 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 communication 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 the tip side of the pressure detection device 20 into the communication hole 13 a and fixing the pressure detection device 20 to the cylinder head 13 . 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 side view of the pressure detection device 20. FIG. 3 is a cross-sectional view of the pressure detection device 20 shown in FIG. 2 taken along line III-III. Furthermore, FIG. 4 is an enlarged cross-sectional view of the IV region of the pressure detection device 20 shown in FIG. 4 also shows a main part of the cylinder head 13 to which the pressure detection device 20 is attached.

The pressure detection device 20 includes a housing portion 30 which has a cylindrical shape as a whole and is provided so as to be exposed to the outside, and various mechanisms for detecting pressure. A detection mechanism portion 40 provided so as to be partially exposed to the outside, a seal portion 70 attached to the outer peripheral surface of the housing portion 30, and one end side of the housing portion 30 (in FIG. 2, the housing portion 30 ) and a cushioning member 80 attached to the left side of the 2 faces the combustion chamber C (lower side in FIG. 1), and the right side in FIG. 90 side) faces the outside (upward in FIG. 1). 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 . In addition, 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. Here, in the present embodiment, the "front end side" corresponds to the "one end side", and the "rear end side" corresponds to the "other end side".

(Structure of housing)
The housing part 30 as an example of the body part includes a distal end external housing 31, a diaphragm head 32 attached to the distal end side of the distal external housing 31, and an intermediate part attached to the rear end side of the distal external housing 31. An outer housing 33 and a rear end outer housing 34 attached to the rear end side of the intermediate outer housing 33 are provided. The housing part 30 includes a first inner housing 35 attached to the rear end side of the diaphragm head 32 inside the tip outer housing 31, and a first inner housing 35 inside the tip outer housing 31 and attached to the rear end side of the diaphragm head 32. A second internal housing 36 attached to the rear end side of the housing 35 is further provided.

[Tip external housing]
The distal end outer housing 31 is a member having a hollow structure and having a tubular shape as a whole. The tip external housing 31 is an example of a housing, and is an example of a third housing. The distal end outer housing 31 is made of a metal material such as stainless steel having electrical conductivity and high heat resistance and acid resistance. Examples of such a metal material include SUS630 known as precipitation hardening stainless steel and SUH660 known as austenitic heat resistant steel (heat resistant alloy). However, other various metals or alloys (various stainless steels, various heat-resistant steels, or various heat-resistant alloys) can be used as long as they satisfy the required properties. In addition, as shown in FIG. 2, the distal end outer housing 31 is formed with a crimped portion P at an appropriate position in the middle of the center line direction.

[Diaphragm head]
The diaphragm head 32, which is an example of a pressure receiving portion, 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 is electrically conductive and has high heat resistance and acid resistance. Examples of such a metal material include SUS630 known as precipitation hardening stainless steel and SUH660 known as austenitic heat resistant steel (heat resistant alloy). However, other various metals or alloys (various stainless steels, various heat-resistant steels, various heat-resistant alloys, etc.) can be employed as long as they satisfy the required properties. In this example, the diaphragm head 32 is made of the same material as the distal end outer housing 31 (for example, SUS630).

As shown particularly in FIG. 4, the diaphragm head 32 has a surface central concave portion 32b formed in the central portion on the tip end side, and a pressure receiving surface (surface) that receives pressure by being exposed to the outside (combustion chamber C side). 32a. In addition, the diaphragm head 32 has a back surface annular recess 32c formed by annularly notching the back surface of the pressure receiving surface 32a, and the presence of the back surface annular recess 32c. It has a rear central convex portion 32d that protrudes toward the rear end side from the formation portion of the central concave portion 32b on the front surface. Furthermore, the diaphragm head 32 has a back surface annular flat portion 32e formed by annularly notching the peripheral portion of the back surface of the pressure receiving surface 32a, and the back surface annular recess 32c and the back surface annular flat portion 32e. It has an annular rear convex portion 32f that protrudes from the periphery of the central convex portion 32d to the rear end side. Furthermore, the diaphragm head 32 has a surface annular convex portion 32g that protrudes from the entire peripheral edge of the pressure receiving surface 32a to the tip side as a result of providing the concave pressure receiving surface 32a. The front annular convex portion 32g is located on the opposite side (front side) of the back annular flat portion 32e. From another point of view, the front end side of the diaphragm head 32 includes a surface annular convex portion 32g and a pressure receiving surface 32a formed by circularly notching the central portion of the diaphragm head 32, and a central portion of the pressure receiving surface 32a. can also be regarded as having a surface central recess 32b formed by further notching the .

The diaphragm head 32 is provided so as to block the opening of the distal end outer housing 31 on the distal end side. More specifically, the distal end side of the distal end external housing 31 abuts against the rear annular flat portion 32 e of the diaphragm head 32 . A boundary between the diaphragm head 32 and the distal end outer housing 31 is laser-welded along the outer peripheral surface thereof.

Here, the diaphragm head 32 of the present embodiment functions as a spring by expanding and contracting the periphery of the thinnest annular concave portion 32c in response to an external force. The diaphragm head 32 vibrates according to the pressure (external pressure) received from the combustion chamber C or the like.

[Intermediate external housing]
The intermediate outer housing 33 is a member having a hollow structure and having a tubular shape as a whole. The intermediate outer housing 33 is made of a metal material such as stainless steel that has electrical conductivity and high heat resistance and acid resistance. As such a metal material, for example, SUS430LX known as ferritic stainless steel can be exemplified. However, other various metals or alloys (various stainless steels, various heat-resistant steels, or various heat-resistant alloys) can be used as long as they satisfy the required properties. In this example, the intermediate outer housing 33 is made of a material different from that of the tip outer housing 31 (for example, SUS430LX).

The distal end side of the intermediate external housing 33 is fitted into the rear end side of the distal external housing 31 . The boundary between the intermediate outer housing 33 and the distal end outer housing 31 is laser-welded along the outer peripheral surface thereof.

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

The front end side of the rear end outer housing 34 is fitted into the rear end side of the intermediate outer housing 33 . A boundary portion between the rear end outer housing 34 and the intermediate outer housing 33 is laser-welded along the outer peripheral surface thereof.

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

The front end side of the first internal housing 35 abuts the rear end side of the diaphragm head 32 . More specifically, the front end surface of the first internal housing 35 abuts against the rear end surface of the rear annular convex portion 32 f of the diaphragm head 32 . At this time, a portion of the front end side of the first inner housing 35 is positioned inside the rear annular concave portion 32 c of the diaphragm head 32 . The boundary between the first inner housing 35 and the diaphragm head 32 is laser-welded along the outer peripheral surface.

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

The front end side of the second internal housing 36 is accommodated inside the rear end side of the first internal housing 35 . In addition, the front end side surface of the second internal housing 36 abuts the rear end side surface of the second insulating member 52 (details will be described later). At this time, the rear end side of the second internal housing 36 is exposed to the rear end side of the first internal housing 35 . A boundary portion between the second internal housing 36 and the first internal housing 35 is laser-welded along the outer peripheral surface thereof.

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

〔Piezoelectric element〕
The piezoelectric element 41 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 element 41 is arranged inside the tip outer housing 31 (and the first inner housing 35). The piezoelectric element 41 is an example of a detection element.

Here, 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. Therefore, in this example, a signal (charge signal) due to the generated charge is output to the front end side surface and the rear end side surface of the piezoelectric element 41 according to the change in pressure along the center line direction. Become.

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. As the piezoelectric material used in the piezoelectric element 41, a single crystal (inorganic single crystal) made of the inorganic material described above is preferably used, and it is particularly desirable to use a langasite-based single crystal.

[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. Examples of such a metal material include SUS630 known as precipitation hardening stainless steel and SUH660 known as austenitic heat resistant steel (heat resistant alloy). However, other various metals or alloys (various stainless steels, various heat-resistant steels, various heat-resistant alloys, etc.) can be employed as long as they satisfy the required properties. In this example, the tip electrode member 42 is made of the same material as the diaphragm head 32 (for example, SUS630). The tip electrode member 42 is arranged inside the tip external housing 31 and on the tip side of the piezoelectric element 41 so that the rear end side surface of the tip electrode member 42 contacts the tip side surface of the piezoelectric element 41 . It has become. In this example, the front end side surface, the rear end side surface, and the outer peripheral surface of the tip electrode member 42 are not particularly plated with gold or the like, and the background of the metal material constituting the tip electrode material is exposed as it is. ing.

[Insulating material at the tip]
The tip insulating member 43 is a member having a cylindrical shape as a whole. The tip insulating member 43 is made of a ceramic material such as alumina having insulating properties and high heat resistance. The tip insulating member 43 is arranged inside the tip external housing 31 and on the tip side of the tip electrode member 42 , and the rear end side surface of the tip insulating member 43 contacts the tip side surface of the tip electrode member 42 . It is designed to On the other hand, the tip-side surface of the tip insulating member 43 contacts the rear-end-side surface of the rear surface central protrusion 32 d provided on the diaphragm head 32 .

[Rear end electrode member]
The rear end electrode member 44 is a member having a cylindrical shape as a whole. The rear end electrode member 44 is made of a metal material such as stainless steel having electrical conductivity and high heat resistance. Examples of such a metal material include SUS630 known as precipitation hardening stainless steel and SUH660 known as austenitic heat resistant steel (heat resistant alloy). However, other various metals or alloys (various stainless steels, various heat-resistant steels, various heat-resistant alloys, etc.) can be employed as long as they satisfy the required properties. In this example, the rear end electrode member 44 is made of the same material as the tip electrode member 42 (for example, SUS630). The rear end electrode member 44 is arranged inside the front end external housing 31 and on the rear end side of the piezoelectric element 41 , and the front end side surface of the rear end electrode member 44 is aligned with the rear end side surface of the piezoelectric element 41 . come into contact. In this example, the rear end side surface and the outer peripheral surface of the rear end electrode member 44 are plated with gold. On the other hand, the surface of the rear end electrode member 44 on the front end side, that is, the surface in contact with the rear end side of the piezoelectric element 41 is not particularly plated with gold or the like. The skin is exposed as it is.

[Rear end insulating member]
The rear end insulating member 45 is a member having a hollow structure and presenting an annular (cylindrical) shape as a whole. The rear end insulating member 45 is made of a ceramic material such as alumina having insulating properties and high heat resistance. The rear end insulating member 45 is arranged inside the distal end external housing 31 and on the rear end side of the rear end electrode member 44 , and the surface of the rear end insulating member 45 on the front end side faces the rear end of the rear end electrode member 44 . It is designed to come into contact with the side surface. In this example, the rear end insulating member 45 is made of the same material as the front end insulating member 43 (for example, alumina ceramics).

[First coil spring]
The first coil spring 46 is a member having a spiral shape as a whole, and is adapted to expand and contract in the centerline direction. The first coil spring 46 is made of a metal material, such as phosphor bronze, which has electrical conductivity and high heat resistance, and the surface thereof is plated with gold. The first coil spring 46 is arranged inside the tip outer housing 31 . More specifically, the tip side of the first coil spring 46 is arranged inside the through hole provided in the rear end insulating member 45 , and the tip thereof is located on the rear end side surface of the rear end electrode member 44 . is made to come into contact with On the other hand, the rear end side of the first coil spring 46 protrudes toward the rear end side of the rear end insulating member 45 . A coil spring having a somewhat large spring constant is used for the first coil spring 46 . More specifically, the first coil spring 46 has hardness to the extent that the vibration of the conductive member 47 inserted on the rear end side is transmitted to the rear end electrode member 44 located on the front end side, as will be described later.

[Transmission member]
The conducting member 47 is a member having a bar shape as a whole. The conductive member 47 is made of a conductive metal material such as brass, and its surface is plated with gold. The transmission member 47 includes a distal rod-shaped portion 471 located on the most distal side, an intermediate rod-shaped portion 472 located on the rear end side of the distal rod-shaped portion 471, and a rear rod-shaped portion 473 located on the rear end side of the intermediate rod-shaped portion 472. and Moreover, in the transmission member 47, the outer diameters of the front end rod-shaped portion 471, the intermediate rod-shaped portion 472, and the rear end rod-shaped portion 473 are increased in this order. The conducting member 47 is located inside the distal outer housing 31 . More specifically, the distal end side of the conductive member 47 , that is, the distal end side of the distal rod-shaped portion 471 is inserted into the rear end side of the first coil spring 46 and arranged inside the rear end insulating member 45 . However, unlike the first coil spring 46 , the tip of the tip rod-shaped portion 471 does not contact the rear-end-side surface of the rear-end electrode member 44 . At this time, the rear end of the first coil spring 46 abuts the boundary (step) between the tip rod-shaped portion 471 and the intermediate rod-shaped portion 472 of the transmission member 47 . In this example, the first coil spring 46 and the conductive member 47 are joined by laser welding and integrated. Through the above procedure, the first coil spring 46 is sandwiched between the rear end electrode member 44 and the conductive member 47 and is compressed in the centerline direction. On the other hand, the intermediate rod-shaped portion 472 and the rear rod-shaped portion 473 of the transmission member 47 protrude toward the rear end of the rear insulation member 45 .

[Holding member]
The holding member 48 is a member having a hollow structure and having a tubular shape as a whole. The holding member 48 is an example of a housing and an example of a first housing. The holding member 48 is made of an insulating synthetic resin material such as PPS (Polyphenylenesulfide) or PPT (Polypropylene Terephthalate). The holding member 48 has a distal end portion located on the most distal side, an intermediate portion located on the rear end side of the distal end portion, and a rear end portion located on the rear end side of the intermediate portion. The outer diameter of the holding member 48 increases in the order of the distal end, the intermediate portion, and the rear end. The holding member 48 is arranged across the inner side of the distal outer housing 31 and the inner side of the intermediate outer housing 33 . The conducting member 47 is accommodated and held inside the holding member 48 . More specifically, the holding member 48 accommodates the rear end side of the transmission member 47 , that is, the rear end side of the rear end rod-shaped portion 473 . By the above procedure, of the transmission member 47 , the tip rod-shaped portion 471 , the intermediate rod-shaped portion 472 , and the tip side of the rear-end rod-shaped portion 473 protrude toward the tip side of the holding member 48 . On the other hand, the rear end of the holding member 48 is formed with a recess extending from the rear end side to the front end side. Further, the transmission member 47 and the holding member 48 are integrated by press fitting (clearance fit).

[Pressure member]
The pressure member 49 is a member having a hollow structure (through hole) and 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. Examples of such a metal material include SUS630 known as precipitation hardening stainless steel and SUH660 known as austenitic heat resistant steel (heat resistant alloy). However, other various metals or alloys (various stainless steels, various heat-resistant steels, various heat-resistant alloys, etc.) can be employed as long as they satisfy the required properties. In this example, the pressure member 49 is made of the same material as the diaphragm head 32 (for example, SUS630). The pressurizing member 49 is arranged inside the tip outer housing 31 and straddling the inside of the first inner housing 35 and the inside of the second inner housing 36 .

The piezoelectric element 41, the tip electrode member 42, the rear end electrode member 44, the rear end insulating member 45, the first coil spring 46, and the like are accommodated inside the through hole provided in the pressure member 49. FIG. The inner and rear end surfaces of the through hole provided in the pressure member 49 are in contact with the front end surface of the tip electrode member 42 . In addition, the tip insulating member 43 is arranged in the opening on the tip side of the through hole provided in the pressure member 49 .

Here, the pressure member 49 of the present embodiment functions as a spring by expanding and contracting the thinnest tip side portion according to an external force. The pressure member 49 applies a preload to the piezoelectric element 41 together with the support member 53 and the like.

[Insulation tube]
The insulating tube 50 is a member having a hollow structure with two openings provided along the centerline direction and having a tubular shape as a whole. Moreover, the insulating tube 50 of the present embodiment is made of an insulating material. The insulating tube 50 of the present embodiment accommodates the tip electrode member 42, the piezoelectric element 41, the rear end electrode member 44, and the rear end insulating member 45 in order from the tip side, and fixes them in contact with each other. By doing so, it has the function of integrating (modularizing) these together with itself.

Here, the material constituting the insulating tube 50 may be selected from various organic or inorganic materials as long as they have insulating properties. It is desirable to use a shrinkable organic material (for example, a synthetic resin material), that is, a heat-shrinkable tube.

The insulating tube 50 is arranged inside the distal end outer housing 31 and inside the pressure member 49 . The front end side surface of the insulating tube 50 faces the inner and rear end side surfaces on the front end side of the through hole provided in the pressure member 49 with a gap therebetween. Inside the insulating tube 50, the rear end side of the front end electrode member 42, the piezoelectric element 41 and the rear end electrode member 44, and the front end side of the rear end insulating member 45 are accommodated. In other words, the distal end side of the distal electrode member 42 protrudes further to the distal side than the distal end of the insulating tube 50 , and the rear end side of the rear end insulating member 45 protrudes further to the rear end side than the rear end of the insulating tube 50 . Protruding.

[First insulating member]
The first insulating member 51 is a member having an annular shape as a whole. The first insulating member 51 is made of a ceramic material such as alumina having insulating properties and high heat resistance. The first insulating member 51 is arranged inside the tip outer housing 31 , inside the first inner housing 35 and outside the pressure member 49 . The front end side surface of the first insulating member 51 is in contact with the rear end side surface of the stepped portion provided inside the first internal housing 35, and the rear end side surface of the first insulating member 51 is in contact with the rear end side surface. , and contact with the front end side surface of a projection (rib) provided on the entire outer peripheral surface of the pressure member 49 . In this example, the first insulating member 51 is made of the same material as the rear end insulating member 45 (for example, alumina ceramics).

[Second insulating member]
The second insulating member 52 is a member having an annular shape as a whole. Like the first insulating member 51, the second insulating member 52 is made of a ceramic material such as alumina that has insulating properties and high heat resistance. The second insulating member 52 is arranged inside the tip outer housing 31 , inside the first inner housing 35 and outside the pressure member 49 . Also, the second insulating member 52 is arranged on the rear end side of the first insulating member 51 . Then, the front end side surface of the second insulating member 52 comes into contact with the rear end side surface of the projection (rib) provided on the entire outer peripheral surface of the pressure member 49 , and the rear end of the second insulating member 52 The side surface is adapted to contact the tip side surface of the second internal housing 36 . In this embodiment, as the second insulating member 52, one having the same dimensions as the first insulating member 51 is used. Also, in this example, the second insulating member 52 is made of the same material as the first insulating member 51 (for example, alumina ceramics).

[Support member]
The support member 53 is a member having a hollow structure and having a tubular shape as a whole. The support member 53 is made of a metal material such as stainless steel, which has electrical conductivity and high heat resistance. Examples of such a metal material include SUS630 known as precipitation hardening stainless steel and SUH660 known as austenitic heat resistant steel (heat resistant alloy). However, other various metals or alloys (various stainless steels, various heat-resistant steels, various heat-resistant alloys, etc.) can be employed as long as they satisfy the required properties. In this example, the support member 53 is made of the same material as the pressure member 49 (for example, SUS630). The support member 53 is arranged inside the distal end outer housing 31 and the distal end side thereof is disposed inside the pressure member 49 . However, the rear end side of the support member 53 protrudes from the rear end of the pressure member 49 . The front end side surface of the support member 53 is in contact with the rear end side surface of the rear end insulating member 45 . In addition, the boundary between the support member 53 and the pressure member 49 is laser-welded along the outer peripheral surface. The support member 53 accommodates the rear end side of the first coil spring 46 and the tip sides of the transmission member 47 and the holding member 48 . The inner diameter of the support member 53 is larger than the outer diameter of the holding member 48 . Therefore, the inner peripheral surface of the support member 53 and the outer peripheral surface of the holding member 48 face each other with a gap therebetween and are not in direct contact with each other.

[Second coil spring]
The second coil spring 54 is a member having a helical shape as a whole and expands and contracts in the direction of the center line. The second coil spring 54 is made of a metallic material, such as phosphor bronze, which has electrical conductivity and high heat resistance, and its surface is plated with gold. In this example, the second coil spring 54 is made of the same material as the first coil spring 46 (for example, phosphor bronze). The second coil spring 54 is arranged inside the distal end outer housing 31 . More specifically, the tip side of the second coil spring 54 is arranged on the rear end side and outside the outer peripheral surface of the support member 53 , and the tip comes into contact with the rear end side surface of the pressure member 49 . It is designed to Inside the second coil spring 54, the conducting member 47, the holding member 48, the supporting member 53, and the distal end side of the first accommodating member 55 are arranged. A coil spring having a spring constant smaller than that of the first coil spring 46 is used for the second coil spring 54 .

[First housing member]
The first housing member 55 is a member having a hollow structure and having a tubular shape as a whole. The first housing member 55 is an example of a housing and an example of a second housing. The first housing member 55 is made of a conductive metal material such as brass or stainless steel, and its surface is plated with gold.

The first housing member 55 is arranged inside the distal end outer housing 31 . More specifically, the distal end side of the first housing member 55 faces the rear end side of the support member 53, and the second coil spring 54 faces the outer peripheral surface thereof. The rear end of the second coil spring 54 abuts against the front end side surface of the front end side stepped portion of the first housing member 55 . Through the above procedure, the second coil spring 54 is sandwiched between the pressing member 49 and the first housing member 55, and is compressed in the centerline direction. The distal end portions of the conducting member 47 and the holding member 48 are accommodated inside the through hole provided in the first accommodating member 55 .

The outer diameter of the first housing member 55 is smaller than the inner diameter of the tip outer housing 31 . Therefore, the outer peripheral surface of the first housing member 55 and the inner peripheral surface of the distal end external housing 31 face each other with a gap therebetween and are not in direct contact with each other. Also, the inner diameter of the first housing member 55 is larger than the outer diameter of the support member 53 and the outer diameter of the holding member 48 . For this reason, the inner peripheral surface of the first housing member 55 and the outer peripheral surface of the support member 53, and the inner peripheral surface of the first housing member 55 and the outer peripheral surface of the holding member 48 face each other with a gap therebetween, and are in direct contact. not.

The pressing member 551 is a member having a tubular shape as a whole. The pressing member 551 is provided on the outer peripheral surface of the first housing member 55 and at least at a position corresponding to the crimped portion P of the distal end outer housing 31 over the entire circumference of the first housing member 55 . The pressing member 551 has a length corresponding to at least a range in which pressure is applied to form the crimped portion P on the tip outer housing 31 along the centerline direction. At the position where the pressing member 551 is provided, the inner diameter of the pressing member 551 is substantially equal to the outer diameter of the first housing member 55 , and the outer diameter is substantially equal to the inner diameter of the distal end outer housing 31 . Therefore, the inner peripheral surface of the pressing member 551 contacts the outer peripheral surface of the first housing member 55 , and the outer peripheral surface contacts the inner peripheral surface of the tip outer housing 31 . The pressing member 551 is formed by, for example, inserting the first housing member 55 from the distal end side into the pressing member 551 formed in a cylindrical shape, or by filling the space between the first housing member 55 and the distal end external housing 31 with resin. It can be attached by The pressing member 551 is an example of a filler.

The pressing member 551 is a member for receiving pressure applied to the distal end outer housing 31 at the crimped portion P and pressing the first housing member 55 uniformly along the circumferential direction. In addition, by interposing the pressing member 551 between the first housing member 55 and the distal end outer housing 31, insulation between the first housing member 55 and the distal end outer housing 31 in the electrical connection structure described later can be achieved. Retains gender. The pressing member 551 is made of a material such as resin, rubber, or the like, which has insulation and heat resistance. As an example, the pressing member 551 may be formed using Teflon (registered trademark) (polytetrafluoroethylene (PTFE)).

As another example of the holding member 551 made of resin or rubber, the filler may be aluminum oxide powder (hereinafter referred to as “alumina powder”) or zirconium oxide powder (hereinafter referred to as “zirconia powder”), which has excellent insulation and heat resistance. ”) is fine. In this case, the alumina powder or zirconia powder is, for example, a fine powder with a particle size of about 1 μm, and is filled in the space between the outer peripheral surface of the first housing member 55 and the inner peripheral surface of the tip outer housing 31, At the crimped portion P, pressure is applied to the tip outer housing 31, and the alumina powder or the zirconia powder flows in the space filled with the first housing member 55 and the tip exterior in the electrical connection structure described later. Insulation with the housing 31 is maintained.

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

The second housing member 56 is arranged across the inner side of the tip outer housing 31 and the inner side of the intermediate outer housing 33 . More specifically, the distal end side of the second housing member 56 is housed inside the first housing member 55 . In addition, the intermediate portion and the rear end portion of the holding member 48 are accommodated inside the through hole provided in the second accommodating member 56 . The first housing member 55 and the second housing member 56 are integrated by press fitting (tight fit) and laser welding.

[Component with built-in circuit]
As shown particularly in FIG. 3, the circuit-incorporating member 57 accommodates therein a circuit board 571 that performs various processing using an electronic circuit on an electrical signal of weak electric charge output from the piezoelectric element 41, and the circuit board 571. A sealing portion 572 for sealing the circuit board 571 is provided. The circuit-incorporating member 57 is arranged inside the intermediate external housing 33 and almost entirely inside the second accommodating member 56 except for a part on the rear end side. In particular, the circuit board 571 is entirely arranged inside the second housing member 56 . Further, the tip side of the circuit-incorporating member 57 is fitted into a concave portion provided on the rear end side of the holding member 48 . A metal plate (electrode terminal) provided on the front end side of the circuit-incorporating member 57 contacts the rear end side of the conductive member 47 . A metal plate (electrode terminal) provided on the outer peripheral surface of the circuit-incorporating member 57 is in contact with the inner peripheral surface of the second housing member 56 .

[Connection member]
The connection member 58 is a member having a columnar shape as a whole. The connection member 58 includes a base material made of an insulating synthetic resin material such as PPS or PPT, and wires and terminals made of a conductive metal material such as copper. The connection member 58 is arranged across the inner side of the intermediate outer housing 33 and the inner side of the rear end outer housing 34 . A portion (peripheral surface) of the connection member 58 facing the intermediate outer housing 33 or the rear end outer housing 34 is made of a synthetic resin material, and the metal material is not exposed to this portion. there is The rear end side of the circuit-incorporating member 57 faces the front end side of the connecting member 58 , and the metal plate (electrode terminal) provided on the circuit-incorporating member 57 is fitted into the terminal provided on the connecting member 58 . It has become. In addition, the conductor portions exposed at the distal end sides of the power line 91, the signal line 92, and the ground line 93, which constitute the connection cable 90, are inserted into the rear end side of the connection member 58, respectively. The intermediate external housing 33 and the connection member 58 are integrated by press fitting (tight fit).

[Clogging member]
The closing member 59 is a member having a columnar shape as a whole. However, the closing member 59 is formed with three through holes along the centerline direction. The closing member 59 is made of an insulating rubber material. The blocking member 59 has its front end side disposed inside the rear end outer housing 34 and its rear end side protruding outside the rear end of the rear end outer housing 34 . The front end side of the blocking member 59 faces the rear end side of the connecting member 58 . Also, the power line 91 , the signal line 92 and the ground line 93 described above are inserted into the three through holes provided in the closing member 59 . The rear end outer housing 34 and the closing member 59 are integrated by press fitting (tight fit).

[Third insulating member]
The third insulating member 60 is a member having a hollow structure and having a tubular shape as a whole. However, the third insulating member 60 has a structure in which a cylindrical portion provided on the front end side and an annular portion provided on the rear end side are integrated. The third insulating member 60 is made of an insulating synthetic resin material such as PPS. The third insulating member 60 is arranged across the inner side of the tip outer housing 31 and the inner side of the intermediate outer housing 33 . More specifically, the distal end side of the third insulating member 60 is arranged inside the distal end outer housing 31, and the rear end side of the third insulating member 60 is arranged inside the intermediate outer housing 33. It is The outer peripheral surface of the cylindrical portion of the third insulating member 60 faces the inner peripheral surface of the distal end outer housing 31 on the rear end side. Further, the front end side surface of the annular portion of the third insulating member 60 contacts the rear end side surface of the front end external housing 31 . On the other hand, the inner peripheral surface of the cylindrical portion of the third insulating member 60 faces the outer peripheral surface of the first housing member 55 and the outer peripheral surface of the second housing member 56 . The rear end surface of the annular portion of the third insulating member 60 contacts the second housing member 56 .

(Structure of seal portion)
As shown particularly in FIGS. 2 and 3, the seal portion 70 includes 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. .

[First seal member]
The first seal member 71 is a member having an annular shape as a whole, and in this example, is configured by an angular ring having a square cross section. The first sealing member 71 is made of a tin-plated copper material having high heat resistance and acid resistance. The first sealing member 71 is attached to the outer peripheral surface of the tip outer housing 31 that constitutes the housing section 30 . When the pressure detection device 20 is attached to the cylinder head 13 with the first seal member 71 attached, the outer peripheral surface of the distal end outer housing 31 at the position where the first seal member 71 is attached is the first seal member 71. is opposed to the outer surface of the cylinder head 13 with the .

[Second sealing member]
The second seal member 72 is a member having an annular shape as a whole, and in this example, is configured by an O-ring having a circular cross section. The second seal member 72 is made of a synthetic rubber material such as fluororubber, which has high mechanical resilience. The second seal member 72 is attached to the outer peripheral surface of the rear end outer housing 34 that constitutes the housing section 30 . The second seal member 72 serves as a seal member that prevents water or the like from entering from the outside of the internal combustion engine 10, and also prevents the pressure detection device 20 from being damaged during operation of the internal combustion engine 10 or with vibrations in the installation environment. vibrates and collides with the inner surface of the communication hole 13 a in the cylinder head 13 . Therefore, for the second seal member 72, among materials with high mechanical resilience, a fluororubber material that has high resilience and heat resistance and a long-life vibration suppression function is particularly suitable.

(Structure of cushioning member)
A buffer member 80, which is an example of a temperature reducing section, is arranged at the tip of the pressure detection device 20 as shown in FIGS.

The cushioning member 80 is a member having a disc shape as a whole. The cushioning member 80 has a cylindrical shape. The cushioning member 80 is formed with a through hole penetrating from the surface on the front end side to the surface on the rear end side.

The cushioning member 80 is made of a metal material (super heat-resistant alloy) having electrical conductivity and higher heat resistance than the diaphragm head 32 . As such a metal material, for example, it is an iron-based alloy system, and one type of gamma prime precipitation-strengthened super heat-resistant alloy can be exemplified. However, various super heat-resistant alloys other than these can be employed as long as they satisfy the required properties. Examples of usable superalloys include matrix-strengthened superalloys, carbide precipitation-strengthened superalloys, and gamma-prime precipitation-strengthened superalloys. Any of iron-based alloys, nickel-based alloys, and cobalt alloys may be used as the super heat-resistant alloys that can be used.

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

When the pressure detection device 20 is attached to the cylinder head 13, the tip side of the cushioning member 80 abuts against the stepped portion 13b (see FIG. 4) provided in the communication hole 13a. Further, when the pressure detection device 20 is attached to the cylinder head 13, the side wall portion of the cushioning member 80 is in contact with the inner wall of the communication hole 13a.

[Control of noise based on vibration]
Now, consider the vibration that occurs in the pressure detection device 20 . When the pressure detection device 20 receives an external impact, vibration may occur in the distal end outer housing 31, which is an elongated member, and the members inside thereof. Here, in order to consider problems when vibration occurs, a configuration in which the pressing member 551 is not provided between the distal end outer housing 31 and the first housing member 55 is assumed.

Of the first housing member 55 , the transmission member 47 and the holding member 48 housed in the distal end outer housing 31 , the transmission member 47 and the holding member 48 are integrated by press fitting (clearance fit). and the first housing member 55 has a space therebetween. In other words, the conducting member 47 and the holding member 48 are not supported except at their ends where they come into contact with other members. Moreover, when the pressing member 551 is not provided, there is a gap between the first housing member 55 and the distal end outer housing 31 . For this reason, the first housing member 55 is also not supported except for the portions at both ends that come into contact with other members.

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

(Transmission path of vibration)
As a specific vibration transmission path, for example, the following path is assumed.
・First, the vibration of the conductive member 47 and the holding member 48 is transmitted from the distal end rod-shaped portion 471 of the conductive member 47 to the rear end electrode member 44 via the first coil spring 46, and pressurizes the piezoelectric element 41 (hereinafter referred to as the “second 1 transfer pathway”) is conceivable.
・Furthermore, the vibration of the first housing member 55 is transmitted to the rear end electrode member 44 via the second coil spring 54, the support member 53, and the rear end insulating member 45, and pressurizes the piezoelectric element 41 (hereinafter referred to as the "second transfer pathway”).
If a projection that contacts the inner wall of the first housing member 55 is provided on the outer periphery of the holding member 48 to support the holding member 48, the vibration of the transmission member 47 and the holding member 48 will also be transmitted through the projection. It is transmitted to the housing member 55 and joins the vibration propagating through the second transmission path.
・The vibration of the conductive member 47 and the holding member 48 is propagated to the supporting member 53 by the holding member 48 colliding with the inner wall of the supporting member 53, and further to the rear end electrode member 44 via the rear end insulating member 45. A path (hereinafter referred to as a “third transmission path”) that transmits pressure to the piezoelectric element 41 is conceivable.
- In addition, various vibrations originating from the internal combustion engine 10 are applied to the entire pressure detection device 20, and it is conceivable that the vibrations enter from the middle of these paths.

Among these paths, the vibration transmitted through the first transmission path is assumed to have the greatest influence on the output of the piezoelectric element 41 . The pressure detection device 20 of the present embodiment has vibration suppressing means for suppressing vibrations of the transmission member 47 and the holding member 48 at a natural frequency close to the frequency of the signal to be detected.

(Vibration suppression means)
In this embodiment, the vibration suppressing means does not reduce the vibration itself of the conductive member 47 and the holding member 48, but the natural frequency of the conductive member 47 and the holding member 48 is close to the frequency of the signal to be detected. The purpose is to avoid becoming a vibration frequency. This purpose is achieved, for example, by removing the natural frequencies of the conducting member 47 and the holding member 48 from the range of natural frequencies that the pressure detection device 20 can detect. Further, the natural vibration of the transmission member 47 and the holding member 48 is detected from a predetermined frequency range within the natural frequency range that can be detected by the pressure detection device 20, for example, 1 to 2 kHz, which is a typical abnormal combustion frequency of an internal combustion engine. It may be realized by removing the number. Therefore, in the present embodiment, means for preventing vibration is provided at an appropriate position in the direction of the center line of the transmission member 47 and the holding member 48 as the vibration suppressing means. Thereby, the natural frequencies of the transmission member 47 and the holding member 48 are controlled.

As a specific vibration suppressing means, a caulking portion P is formed on the tip outer housing 31 . By crimping the distal end outer housing 31, the distal outer housing 31 is deformed, and the first housing member 55 inside is pressed and deformed. Then, the deformed first housing member 55 presses and fixes the conductive member 47 and the holding member 48 . As a result, vibrations of the first housing member 55, the conducting member 47 and the holding member 48 are suppressed at the positions where the crimped portions P are formed. In addition, the first housing member 55, the transmission member 47, and the holding member 48 have fulcrums in the middle of the center line direction (crimped positions). The natural frequency of the side becomes higher.

In addition, in the above description, it has been described that the tip outer housing 31 deformed by crimping presses the first housing member 55 . On the other hand, in the pressure detection device 20 of the present embodiment, it is necessary to maintain a state in which the distal end outer housing 31 and the first housing member 55 are not in contact with each other in order to maintain an electrical connection structure, which will be described later. Therefore, in the present embodiment, a pressing member 551 is interposed between the distal end outer housing 31 and the first housing member 55 at the position where the crimped portion P of the distal end outer housing 31 is formed, so that the distal end outer housing 31 and the first housing member 55 are prevented from coming into direct contact with each other. In addition, by providing the pressing member 551 between the distal end outer housing 31 and the first housing member 55, variations in the force with which the distal outer housing 31 deformed by crimping presses the holding member 48 are suppressed. .

The crimped portion P does not necessarily have to be provided over the entire circumference of the tip outer housing 31 . Specifically, for example, the crimped portion P may be formed by applying pressure to three or four points in the circumferential direction of the distal end outer housing 31 by so-called three-point crimping or four-point crimping. However, it is necessary to avoid deforming the distal end outer housing 31 so as to bend with respect to the centerline direction due to biased pressure from a specific direction intersecting the centerline direction. In addition, in the examples shown in FIGS. 2 and 3, the crimped portion P is provided only at one midpoint along the centerline direction of the distal end outer housing 31, but the crimped portion P is provided at a plurality of locations along the centerline direction. You can set up a department.

Also, the position of the crimped portion P can be determined according to the natural frequencies of the first housing member 55 , the transmission member 47 and the holding member 48 after the crimped portion P is formed on the distal end outer housing 31 . For example, the ratio of the length of the distal end side to the crimped portion P of the distal end external housing 31 to the length of the rear end side may be 1:1 or 1:2. Moreover, the crimped portion P is formed at a position where it is not difficult to mount it to the communication hole 13a of the cylinder head 13 of the internal combustion engine 10 according to the shape of the distal end outer housing 31 .

[Configuration of connection cable]
2 and 3, the connection cable 90 includes a twisted power line 91, a signal line 92 and a ground line 93, and a sheath covering the power line 91, the signal line 92 and the ground line 93. a member (not shown). Here, the power supply line 91, the signal line 92, and the ground line 93 are each composed of a conductive portion composed of a tin-plated annealed copper twisted wire, and polyethylene (crosslinked polyethylene) or the like obtained by strengthening the crosslinked structure using an electron wire or the like. and an insulating portion that covers and insulates the outer periphery of the conductor portion. In addition, the covering member is made of an insulating rubber material or resin material. The connection cable 90 may be provided with a shield for shielding the power line 91, the signal line 92 and the ground line 93, if necessary.

[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 is electrically connected to the rear end electrode member 44 , the first coil spring 46 and the conducting member 47 . Also, the conductive member 47 is electrically connected to an input signal terminal provided in the circuit-incorporating member 57 . Hereinafter, an electrical path from the rear end side surface of the piezoelectric element 41 to the input signal terminal of the circuit board 571 via the rear end electrode member 44, the first coil spring 46 and the conductive member 47 will be referred to as a "positive route”.

(negative path)
On the other hand, in the pressure detection device 20 , the end face (negative electrode) of the piezoelectric element 41 on the tip side is electrically connected to the tip electrode member 42 , the pressure member 49 and the support member 53 . Also, the pressure member 49 is electrically connected to input ground terminals provided on the second coil spring 54 , the first housing member 55 , the second housing member 56 and the circuit-incorporating member 57 . In the following, the circuit board 571 will be described from the tip side surface of the piezoelectric element 41 via the tip electrode member 42 , the pressure member 49 , the support member 53 , the second coil spring 54 , the first accommodation member 55 and the second accommodation member 56 . is called the "negative path".

(Chassis path)
On the other hand, in the pressure detection device 20 , the diaphragm head 32 is electrically connected to the distal end outer housing 31 , the intermediate outer housing 33 and the rear end outer housing 34 . Also, the diaphragm head 32 is electrically connected to the first internal housing 35 and the second internal housing 36 . Furthermore, the diaphragm head 32 is electrically connected with the buffer member 80 . In the following, from the second inner housing 36 to the first inner housing 35, the diaphragm head 32, the front end outer housing 31, the intermediate outer housing 33 and the rear end outer housing 34, and from the diaphragm head 32 to the buffer member The electrical path leading to 80 is referred to as the "enclosure path". When the pressure detection device 20 is attached to the cylinder head 13 of the internal combustion engine 10 shown in FIG. A female thread (not shown) provided on the inner peripheral surface of the communication hole 13a is contacted, and the surface wall portion 814 of the cushioning member 80, for example, contacts the stepped portion 13b provided in the communication hole 13a. At this time, the cylinder head 13 (and the cylinder block 11) and the housing path have substantially the same potential.

(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 rear end insulating member 45, the holding member 48, the insulating tube 50, and an air gap formed between both paths.

(Relationship between negative path and housing path)
Further, in the 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 electrically insulated.

(Relationship between housing path and positive path)
Furthermore, in the pressure sensing device 20, there is a housing path outside the positive path as a result. 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. is electrically insulated.

[Procedure for installing the pressure detection device to the internal combustion engine]
Now, a procedure for attaching the pressure detection device 20 to the internal combustion engine 10 will be described.
First, the pressure detection device 20 is arranged in the communication hole 13a provided in the cylinder head 13 of the internal combustion engine 10 so that the front end side, that is, the buffer member 80 side thereof faces the internal combustion engine 10 from the outside. Subsequently, the tip side of the pressure detection device 20 is inserted into the communication hole 13a.

Then, the pressure detection device 20 is rotated clockwise with respect to the cylinder head 13 of the internal combustion engine 10 with respect to the axial direction. In addition, it is desirable to perform this operation via a torque wrench. Along with this, a female thread provided on the inner peripheral surface of the communication hole 13a in the cylinder head 13 and a male thread provided on the outer peripheral surfaces of the tip outer housing 31, the diaphragm head 32 and the buffer member 80 in the pressure detection device 20. are engaged with each other, and the pressure detection device 20 is screwed into the cylinder head 13 . As a result, the buffer member 80 provided on the tip side of the pressure detection device 20 moves toward the combustion chamber C provided in the internal combustion engine 10 .

As a result of such screwing, of the cushioning member 80 provided in the pressure detection device 20 , the surface on the front end side of the surface wall portion 814 provided in the cushioning member 80 is not communicated with the cylinder head 13 of the internal combustion engine 10 . It abuts against the surface on the rear end side of the stepped portion 13b provided in the hole 13a. As a result, the pressure detection device 20 is basically in a state where it cannot be screwed any further. A predetermined axial force (fastening axial force) is applied along the line. By the above, attachment of the pressure detection device 20 to the internal combustion engine 10, in other words, fastening of the pressure detection device 20 to the cylinder head 13 is completed.

[Pressure detection operation by pressure detection device]
Next, the pressure detection operation by the pressure detection device 20 will be described.
When the internal combustion engine 10 is operating, the pressure (combustion pressure) generated within the combustion chamber C is applied to the pressure receiving surface 32a of the diaphragm head 32 . Here, in the pressure detection device 20 of the present embodiment, the cushioning member 80 is provided on the tip side of the diaphragm head 32, and the combustion gas (an example of the fluid) generated in the combustion chamber C is transferred to the cushioning member 80. It reaches the pressure receiving surface 32 a of the diaphragm head 32 after passing through the provided nine through holes 816 . In other words, the cushioning member 80 receives the combustion gas, the combustion gas flows through the through-holes 816 to lower the temperature, and the temperature-lowered combustion gas is supplied to the diaphragm head 32 .

Then, in the diaphragm head 32, the pressure received by the pressure receiving surface 32a is transmitted to the back surface center convex portion 32d on the back side, and further transmitted from the back surface center convex portion 32d to the tip electrode member 42 via the tip insulating member 43. . The pressure transmitted to the tip electrode member 42 acts on the piezoelectric element 41 sandwiched between the tip electrode member 42 and the rear electrode member 44, and the piezoelectric element 41 generates an electric charge according to the received pressure. The charge generated in the piezoelectric element 41 is supplied as a charge signal to the circuit board 571 through the positive path and the negative path. The charge signal supplied to the circuit board 571 is subjected to various processes in a processing circuit (not shown) mounted on the circuit board 571 to be an output signal. An output signal output from the circuit board 571 is transmitted to the control device 100 via the connection member 58 and the connection cable 90 .

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

For example, when the temperature of the combustion gas generated in the combustion chamber C is extremely high, if this high-temperature combustion gas directly hits the pressure receiving surface 32a of the diaphragm head 32, the diaphragm head 32 is overheated by the high-temperature combustion gas, resulting in As a result, there is a concern that the diaphragm head 32 may deteriorate due to heat. In the case of SUS630 or SUH660, which is used as the raw material of the diaphragm head 32 in this embodiment, it may be used for a long time in an environment where the temperature of the combustion gas hitting the diaphragm head 32 exceeds, for example, 700°C. If there is, the strength of the diaphragm head 32 itself will gradually decrease.

In contrast, in the present embodiment, the combustion gas hits the diaphragm head 32 while the temperature is lowered by the cushioning member 80 provided on the tip side of the diaphragm head 32 as described above. As a result, deterioration in the strength of the diaphragm head 32 can be suppressed from a long-term perspective.

[Another configuration of the pressure detection device]
In this embodiment, in order to suppress the influence of noise due to vibration of long members in the pressure detection device 20 on signals to be detected, a vibration suppressing means for controlling the natural frequency of such members is provided. Further, in the above-described embodiment, a structure having a positive path and a negative path inside the device as electrical paths and a housing path passing through the housing section 30 (hereinafter referred to as "internal insulation structure") ) has been described as an example. Here, the above problem also occurs in a pressure detection device that does not have an internal insulating structure (such a structure is hereinafter referred to as a "non-internal insulating structure"), and the vibration suppressing means of the present embodiment can be applied. . Hereinafter, a pressure detection device having a non-internal insulation structure will be described, and application of vibration suppressing means to such a pressure detection device will be described.

FIG. 5 is a cross-sectional view of a non-internally insulated pressure sensing device. 6 is an enlarged view of the V region of the pressure detection device shown in FIG. 5. FIG.

[Configuration of Pressure Detector]
The pressure detection device A5 has a sensor portion A100 having a piezoelectric element A10 that converts the pressure in the combustion chamber C into an electric signal, a signal processing portion A200 that processes the electric signal from the sensor portion A100, and a signal processing portion A200. and a holding member A300. When mounting the pressure detection device A5 to the cylinder head 13, the later-described diaphragm head A40 of the sensor portion A100 is first inserted into the communication hole 13a formed in the cylinder head 13. As shown in FIG. In the following description, the left side of FIG. 5 is the front end side of the pressure detection device A5, and the right side is the rear end side of the pressure detection device A5.

(Configuration of sensor section)
The sensor unit A100 includes a piezoelectric element A10 that converts a received pressure into an electric signal, and a cylindrical casing A30 having a cylindrical hole for accommodating the piezoelectric element A10 and the like. ing. Hereinafter, the centerline direction of the cylindrical hole formed in the housing portion A30 is simply referred to as the centerline direction.

Further, the sensor part A100 is provided so as to close the opening on the tip end side of the housing part A30, and is between the diaphragm head A40 on which the pressure in the combustion chamber C acts, and the diaphragm head A40 and the piezoelectric element A10. and a rear electrode member A55 arranged on the opposite side of the piezoelectric element A10 from the tip electrode member A50. In addition, the sensor section A100 is provided with an insulating ring A60 made of alumina ceramic that electrically insulates the rear end electrode member A55, and a cover member A23, which will be described later, of the signal processing section A200. and a coil spring A70 interposed between the rear end electrode member A55 and a later-described conducting member A22.

[Case part]
As shown in FIG. 6, the housing part A30 has a first housing part A31 provided on the front end side and a second housing part A32 provided on the rear end side. The first housing part A31 is a cylindrical member. The second housing part A32 is a cylindrical member, as shown in FIG. The tip portion of the second housing portion A32 is fitted (press-fitted) to the rear end portion of the first housing portion A31 by interference fit. The housing part A30 corresponds to the distal end external housing 31 of the pressure detection device 20 described with reference to FIGS. More specifically, the crimped portion P is provided in the housing portion A30 at a position corresponding to a first convex portion A251 of a conductive member covering portion A231, which will be described later. The second housing part A32 is an example of a housing and an example of a second housing.

[Tip electrode member]
The tip electrode member A50 is a cylindrical member. The outer peripheral surface of the tip electrode member A50 is in contact with the inner peripheral surface of the first housing A31, and the end surface on the tip side is in contact with the diaphragm head A40. connected

[Rear end electrode member]
The rear end electrode member A55 is a cylindrical member. A columnar projecting portion A55a is provided on the end surface of the rear end electrode member A55 on the rear end side so as to project from the end surface toward the rear end side. The outer diameter of the projecting portion A55a is smaller than the inner diameter of the insulating ring A60. The length of the projecting portion A55a is longer than the width (the length in the direction of the center line) of the insulating ring A60, and the tip of the projecting portion A55a is exposed from the insulating ring A60. There is a gap between the outer peripheral surface of the rear end electrode member A55 and the inner peripheral surface of the first housing part A31.

[Insulation ring]
The insulating ring A60 is a cylindrical member made of alumina ceramics or the like. The diameter is substantially equal to the inner diameter of the first casing part A31.

[Support member]
The support member A65 is a cylindrical member. A protruding portion A55a of the rear end electrode member A55 is exposed to the inside of the support member A65 through the insulating ring A60. The inner diameter of the support member A65 is larger than the outer diameter of the tip portion of the transmission member A22 of the signal processing unit A200, which will be described later. The inner diameter of the support member A65 is smaller than the outer diameter of the tip end of the cover member A23 of the signal processing unit A200, which will be described later. . Thereby, the support member A65 functions as a member that supports the end portion of the cover member A23.

[Coil spring]
The coil spring A70 is a spiral spring member that expands and contracts in the centerline direction. The distal end portion of the projecting portion A55a of the rear electrode member A55 is inserted into the coil spring A70 from the distal end side. Also, the coil spring A70 is inserted into an insertion hole A22a of a conduction member A22, which will be described later. The length of the coil spring A70 is set to such a length that it can be interposed between the rear end electrode member A55 and the conductive member A22 in a compressed state. As the material of the coil spring A70, it is preferable to use an alloy having high elasticity and excellent durability, heat resistance, contact resistance, and the like. Also, the surface of the coil spring A70 may be plated with gold to enhance electrical conductivity. The coil spring A70 corresponds to the first coil spring 46 of the pressure detection device 20 described with reference to FIGS. It has a

(Configuration of signal processing section)
As shown in FIG. 5, the signal processing unit A200 includes a circuit board unit A21 that at least amplifies an electric signal, which is a weak electric charge obtained from the piezoelectric element A10 of the sensor unit A100, and a circuit board unit A21 that amplifies the electric signal generated in the piezoelectric element A10. A rod-shaped conductive member A22 leading to the substrate portion A21, a cover member A23 covering the circuit board portion A21, the conductive member A22, and the like, and an O-ring A26 sealing the circuit board portion A21 and the like are provided.

[Circuit board part]
The circuit board section A21 has a mounting board A210 on which electronic components and the like constituting a circuit for amplifying weak charges obtained from the piezoelectric element A10 of the sensor section A100 are mounted. The mounting board A210 is connected to an input pin for electrical connection with the conductive member A22 and an output pin for electrical connection with a grounding input pin control device.

[Transmission member]
The conductive member A22 is a rod-shaped member, and an insertion hole A22a is formed in the tip portion thereof into which the tip portion of the projecting portion A55a of the rear end electrode member A55 is inserted. A rear end portion of the conductive member A22 is electrically connected to the mounting substrate A210 of the circuit board portion A21.

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

[Conductive member covering part]
The conducting member covering portion A231 is an elongated cylindrical member, and the tip of the conducting member covering portion A231 is fitted (press-fitted) to the inner wall of the support member A65 by interference fit. The conductive member covering portion A231 corresponds to the holding member 48 of the pressure detection device 20 described with reference to FIGS. 2 to 4, and is integrated with the conductive member A22 housed inside. The conductive member covering portion A231 is an example of a housing and an example of a first housing.

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

[First Projection and Second Projection]
The first convex portion A251 and the second convex portion A252 abut against the inner peripheral surface of the second housing portion A32. As a result, the conductive member covering portion A231 is supported by the second housing portion A32. Here, the first convex portion A251 is provided near the tip of the conductive member covering portion A231, and the second convex portion A252 is provided near the rear end portion of the conductive member covering portion A231. In order to control the natural frequency to a desired frequency, it may be provided at an intermediate position in the direction of the center line of the conductive member covering portion A231.

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

(Vibration control means)
In the pressure detection device A5 with a non-internal insulation structure, the conductive member A22 and the conductive member cover A231 are long members, and are similar to the pressure detection device 20 with an internal insulation structure described with reference to FIGS. , vibration with a low natural frequency may occur. The vibration generated in the conductive member A22 and the conductive member covering portion A231 is transmitted from the projecting portion A55a of the rear end electrode member A55 to the rear end electrode member A55 via the coil spring A70, and pressurizes the piezoelectric element A10. Vibrations generated in the conductive member A22 and the conductive member covering portion A231 are transmitted to the rear end electrode member A55 via the support member A65 and the insulating ring A60, and pressurize the piezoelectric element A10. Therefore, problems similar to those described for the pressure detection device 20 having an internal insulation structure may arise.

Therefore, a crimped portion P is provided on the second housing portion A32 to control the natural frequencies of the conductive member A22 and the conductive member covering portion A231. As shown in FIGS. 5 and 6, the crimped portion P is provided at a position corresponding to the first convex portion A251 of the conductive member covering portion A231. Then, the second housing portion A32 deformed by the formation of the crimped portion P presses the conductive member covering portion A231 and the conductive member A22 via the first convex portion A251 that contacts the inner peripheral surface of the second housing portion A32. fixed. As a result, the vibration of the conductive member covering portion A231 and the conductive member A22 is suppressed at the position where the crimped portion P is formed, and the vibration frequencies of the front end side and the rear end side of the crimped portion P are increased. The natural frequency of the conductive member A22 and the conductive member covering portion A231 is controlled to a desired frequency by abutting the first convex portion A251 and the second convex portion A252 against the inner peripheral surface of the second casing portion A32. However, if the conductive member covering portion A231 is made of resin, the conductive member covering portion A231 may soften when the operating environment temperature of the pressure detection device 20 is high, and the vibration suppressing effect may be reduced. . However, by providing the conductive member A22 with the crimped portion P to which pressure is applied from the outside of the second housing portion A32, the natural frequency of the conductive member A22 and the conductive member covering portion A231 can be controlled to a desired frequency and reliably. vibration can be suppressed.

Here, the crimped portion P is provided in the second housing portion A32 at a position corresponding to the first convex portion A251 of the conductive member covering portion A231. On the other hand, a member as an example of a filling member that presses the conductive member covering portion A231 is interposed between the second housing portion A32 and the conductive member covering portion A231, and the caulking portion P is provided at a position corresponding to this member. You can set it. As the filling member, a member having a cylindrical shape as a whole, alumina powder, or zirconia powder can be applied as in the case of the pressing member 551 in the previous embodiment. Also, the crimped portion P may be provided at a plurality of locations along the center line direction of the second housing portion A32.

The crimped portion P does not necessarily have to be provided over the entire circumference of the second housing portion A32, and may be formed by so-called three-point crimping or four-point crimping. However, it is necessary to avoid deforming the second housing part A32 so as to bend with respect to the centerline direction due to biased pressure from a specific direction that intersects the centerline direction.

[others]
Although the present embodiment has been described above, the technical scope of the present invention is not limited to the above embodiment. For example, in the present embodiment, the pressing member 551 is provided between the distal end outer housing 31 and the first housing member 55 in the pressure detection device 20 having an internal insulation structure. You may interpose a holding member also between.

In addition, in the present embodiment, as vibration suppressing means, a crimped portion P is provided in the distal end external housing 31 of the pressure detection device 20 having an internal insulation structure and the second housing portion A32 of the pressure detection device A5 having a non-internal insulation structure. has been described, but it is not limited to this. The vibration suppressing means only needs to be able to control the natural frequency of the pressure detection device 20 and A5 so as not to approach the specific frequency to be detected. For example, resin The member may be fixed by filling it with parts such as , rubber, etc., or partially filling it with an adhesive. By preventing the movement of the first housing member 55 and the conductive member covering portion A231 by such arrangement of parts and the adhesive, the vibration of these members is changed, and the natural frequency becomes the specific frequency to be detected. You can avoid getting too close. In addition, the present invention includes various modifications and alternative configurations that do not depart from the scope of the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 1... Pressure detection system 10... Internal combustion engine 11... Cylinder block 12... Piston 13... Cylinder head 13a... Communication hole 20... Pressure detection device 30... Housing part 31... Tip external housing, 41 Piezoelectric element 44 Rear end electrode member 45 Rear end insulating member 46 First coil spring 47 Conductive member 48 Holding member 53 Support member 54 Second coil spring 55 First housing Members 551... Pressing member A5... Pressure detecting device A10... Piezoelectric element A22... Conductive member A30... Housing part A31... First housing part A32... Second housing part A50... Tip electrode member , A55... Rear end electrode member, A60... Insulating ring, A65... Supporting member, A70... Coil spring, A231... Conducting member covering part, A251... First convex part, P... Crimping part

Claims (12)

a sensing element that senses changes in pressure;
a conducting member that conducts an electrical signal from the sensing element;
a tubular housing that accommodates the conductive member therein;
vibration suppression means formed by applying pressure to the transmission member from the housing side and suppressing vibration of the transmission member at a specific frequency;
A pressure detection device comprising: 2. The pressure detection device according to claim 1, wherein said vibration suppression means is means for adjusting the natural frequency of said transmission member to a value outside a predetermined frequency range. The housing is
a cylindrical first housing that accommodates the conductive member therein;
a cylindrical second housing that accommodates the conductive member and the first housing therein;
The pressure detection device according to claim 1 or 2, characterized by comprising: 4. The pressure detection device according to claim 3, wherein the housing further includes a cylindrical third housing that accommodates the conductive member, the first housing, and the second housing therein. . 3. The pressure detection device according to claim 1, wherein at least a portion between said conductive member and said housing is filled with a filler. 3. The pressure detection device according to claim 1, wherein said vibration suppression means is means for fixing said transmission member and said housing at a specific position in the axial direction. 7. The pressure detecting device according to claim 6, wherein said vibration suppressing means is a crimped portion formed by crimping said housing from outside. a sensing element that senses changes in pressure;
a conducting member that conducts an electrical signal from the sensing element;
a cylindrical housing that accommodates the conductive member inside,
A pressure detection device, comprising a crimped portion for crimping the housing and the conductive member. 9. The pressure detection according to claim 8, wherein an insulating member is interposed between the casing and the conducting member in the crimped portion to insulate the casing and the conducting member. Device. The crimped portion is formed at a specific position in the axial direction of the housing and the transmission member by a force directed toward the center of a cross section substantially orthogonal to the axis, and the housing and the conduction member are formed from a plurality of directions of the cross section. 9. The pressure sensing device according to claim 8, wherein the members are crimped. The housing is
a cylindrical first housing that accommodates the conductive member therein;
a cylindrical second housing that accommodates the conductive member and the first housing therein;
9. The pressure detection device according to claim 8, comprising: 12. The pressure detection device according to claim 11, wherein the housing further comprises a cylindrical third housing that accommodates the conductive member, the first housing and the second housing therein. .

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