JP6499601B2 - Detection device and detection system - Google Patents

Description

  The present invention relates to a detection device and a detection system for detecting a physical quantity.

  For example, in a device such as an automobile having an internal combustion engine, a plurality of detection devices that detect pressure, temperature, and the like are mounted in the device. Based on the detection results of these detection devices, a control device called an ECU (Engine Control Unit) controls the operation of the internal combustion engine.

  For example, in Patent Literature 1, a piezoelectric element for detecting pressure and a processing circuit for processing a detection signal of the piezoelectric element are incorporated in a metal casing (housing), and the casing and the ground of the processing circuit are incorporated. A pressure detection device in which is electrically connected is described. Patent Document 1 describes that the casing of the pressure detection device is attached to the cylinder head (made of metal) of the internal combustion engine so that the casing and the cylinder head are attached in an electrically connected state. Yes. Further, Patent Document 1 discloses a pressure detection device and a control device that performs control based on an output signal output from a processing circuit of the pressure detection device, an electric wire for supplying power from the control device to the pressure detection device, a pressure It is described that an electric wire for sending a signal from the detection device to the control device and an electric wire for sharing the ground between the control device and the pressure detection device are used. Furthermore, Patent Document 1 describes that the ground of the control device and the cylinder head of the internal combustion engine are connected to a cylinder block (made of metal) that constitutes the internal combustion engine together with the cylinder head and also functions as a grounding body. ing. Therefore, the ground of the processing circuit of the pressure detection device in Patent Document 1 is connected to the cylinder block via the housing and the cylinder head, and is connected to the cylinder block via the electric wire and the control device.

JP 2013-156171 A

Here, by attaching a housing (conductor) electrically connected to the ground of the processing circuit in the detection device to a mounted body (for example, a cylinder block) made of a conductor, the housing and the mounted body When a configuration is adopted in which the mounting body is further grounded and the mounted body is grounded, noise may enter the processing circuit from the mounted body through the housing. In addition, when such a configuration is employed, noise may enter the processing circuit due to radio waves or the like irradiated from the outside of the housing. Such noise can cause malfunction of the processing circuit.
An object of this invention is to reduce the noise which penetrates into the processing circuit of a detection apparatus from the outside.

The detection device of the present invention includes a detection element that detects a change in a physical quantity, a processing circuit that performs electrical processing on a detection signal output from the detection element, and has at least a part of the processing circuit that has conductivity. A conductive member arranged to cover and connected to the ground of the processing circuit;
A casing that houses the detection element, the processing circuit, and the conductive member and is electrically insulated from the detection element, the processing circuit, and the conductive member; a ground of the processing circuit ; and the conductive member And a direct current suppression unit that is connected while suppressing current flow .
Here, the ground of the processing circuit and the ground of the detection element are electrically connected, and the conductive member may be disposed so as to cover the processing circuit and the detection element .
From another point of view, the detection device of the present invention has a detection element that detects a change in physical quantity, a processing circuit that electrically processes a detection signal output from the detection element, and conductivity. And a first housing that is disposed so as to accommodate at least a part of the processing circuit and is connected to a ground of the processing circuit, and a second housing that has conductivity and accommodates the first housing. An insulating member that is insulated and disposed between the first housing and the second housing and electrically insulates the first housing from the second housing , The second casing has higher conductivity than the first casing, and the first casing has higher acid resistance than the second casing .
Also, disposed between the detection element and the second housing may further include other insulating member for electrically insulating the said second housing and the detection element.
Furthermore, from another viewpoint, the detection system of the present invention has a detection element that detects a change in physical quantity, a processing circuit that electrically processes a detection signal output from the detection element, and conductivity. And a conductive member arranged to cover at least a part of the processing circuit and connected to the ground of the processing circuit, the detection element, the processing circuit, and the conductive member, and the detection element and the processing circuit And a casing that is electrically insulated from the conductive member and in contact with a grounded conductor, the ground of the processing circuit, and the conductive member while suppressing the application of direct current a detection device comprising a DC suppression unit for connecting a supply line for supplying a power supply voltage to the processing circuit, a transmission line for transmitting an output signal output from the processing circuit, the conductive portion Or connected to the detection device via a ground line for connecting to the ground of the processing circuit, and connected to the conductor in a system different from the system via the ground wire, And a supply / processing device that supplies the power supply voltage and processes the output signal input from the detection device.
Furthermore, from another viewpoint, the detection system of the present invention has a detection element that detects a change in physical quantity, a processing circuit that electrically processes a detection signal output from the detection element, and a conductivity. And a first housing that is arranged to accommodate at least a part of the processing circuit and is connected to the ground of the processing circuit, and has conductivity and accommodates the first housing, and is grounded. A second housing that is mounted in contact with the conductive body, and is disposed between the first housing and the second housing that have insulation properties, and the first housing and the second housing electrically saw including an insulating member for insulating the housing, the second housing has high conductivity than that of the first housing, the first housing the acid resistance than the second housing a high detection device, a supply line for supplying a power supply voltage to the processing circuit, output from the processing circuit Connected to the detection device via a transmission line for transmitting an output signal to be transmitted and a ground line for connecting to the ground of the first casing or the processing circuit, and via the ground line A supply / processing device that is connected to the conductor in a system different from the system, supplies the power supply voltage to the detection device, and processes the output signal input from the detection device.

  According to the present invention, it is possible to reduce noise that enters the processing circuit of the detection apparatus from the outside.

It is a schematic block diagram of the pressure detection system which concerns on embodiment. It is a perspective view of a pressure detection apparatus. It is sectional drawing (III-III sectional drawing of FIG. 2) of a pressure detection apparatus. It is an expanded sectional view of the tip side of a pressure detection device. It is a schematic block diagram of the circuit board provided in the pressure detection apparatus. It is a block diagram of a control apparatus. It is sectional drawing of a connection cable. It is a figure for demonstrating the electrical connection structure of a pressure detection system. It is a figure for demonstrating the 1st modification of the electrical connection structure of a pressure detection system. It is a figure for demonstrating the 2nd modification of the electrical connection structure of a pressure detection system. It is a figure for demonstrating the 3rd modification of the electrical connection structure of a pressure detection system.

Embodiments of the present invention will be described below 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 detects the pressure (combustion pressure) in the combustion chamber C in the internal combustion engine 10, and supplies power to the pressure detection device 20 and based on the pressure detected by the pressure detection device 20. A control device 80 that controls the operation of the internal combustion engine 10 and a connection cable 90 that electrically connects the pressure detection device 20 and the control device 80 are provided.

  Here, the internal combustion engine 10 to be subjected to pressure detection includes a cylinder block 11 in which a cylinder is formed, a piston 12 that reciprocates in the cylinder, and a combustion chamber C that is fastened to the cylinder block 11 together with the piston 12 and the like. The cylinder head 13 is configured. Further, the cylinder head 13 is provided with a communication hole 13a that allows the combustion chamber C to communicate with the outside. A female screw (not shown) is formed inside the communication hole 13a, and a male screw (not shown) formed on the outer peripheral surface of the pressure detection device 20 is screwed into the internal combustion engine 10 to detect pressure. The apparatus 20 is attached. Note that seal members (not shown) are provided on both ends of the communication hole 13a so as to maintain airtightness in the combustion chamber C interposed between the cylinder head 13 and the pressure detection device 20. Yes.

[Configuration of pressure detector]
FIG. 2 is a perspective view of the pressure detection device 20. FIG. 3 is a cross-sectional view of the pressure detection device 20 (III-III cross-sectional view of FIG. 2). Further, FIG. 4 is an enlarged cross-sectional view of the front end side of the pressure detection device 20.

  A pressure detection device 20 as an example of a detection device includes a detection unit 30 that detects pressure as an example of a physical quantity, and a processing unit 50 that performs various processes on an electrical signal obtained when the detection unit 30 detects pressure. have. The pressure detection device 20 is configured so that the detection unit 30 faces the combustion chamber C (downward in FIG. 1) and the processing unit 50 faces outside (upward in FIG. 1) with respect to the internal combustion engine 10 shown in FIG. It is attached. In the following description, in FIG. 2, the side toward the lower left in the figure (the detection unit 30 side) is referred to as the “tip side” of the pressure detection device 20, and the side toward the upper right in the figure (the processing unit 50 side) This is referred to as the “rear end side” of the detection device 20. In the following description, the center line direction of the pressure detection device 20 indicated by a one-dot chain line in FIG. 2 is simply referred to as a center line direction.

[Configuration of detector]
The detection unit 30 includes a front end side case 31 fitted to the front end side of a rear end side case 51 (details will be described later) provided in the processing unit 50, and a diaphragm attached to the front end side of the front end side case 31. And a head 32.

  Among these, the front end side housing | casing 31 is a member which has a hollow structure and exhibits a cylindrical shape as a whole. The distal end side casing 31 is made of a metal material such as stainless steel having conductivity and high acid resistance. The distal end side casing 31 includes a first distal end side casing 311 positioned relatively on the distal end side and a second distal end side casing 312 positioned relatively on the rear end side. Here, in the distal end side casing 31, both the outer peripheral surface on the rear end side of the first distal end side casing 311 and the inner peripheral surface on the distal end side of the second distal end side casing 312 are laser-welded. Is configured to be integrated. The diaphragm head 32 is attached to the front end side of the first front end side housing 311 by laser welding, and the rear end side case 51 is fitted to the rear end side of the second front end side case 312 by fitting. It is attached. A male screw meshing with a female screw (not shown) provided on the inner peripheral surface of the communication hole 13a (see FIG. 1) of the cylinder head 13 is provided on the outer peripheral surface of the center portion in the center line direction of the second tip side housing 312. (Not shown) is formed.

  On the other hand, the diaphragm head 32 is a member having a disk shape as a whole. The diaphragm head 32 is made of a metal material such as stainless steel having conductivity and high heat resistance and acid resistance. In particular, in this example, the diaphragm head 32 and the distal end side casing 31 are made of the same material. The diaphragm head 32 is a recess provided by annularly cutting a pressure receiving surface (front surface) 32a that receives pressure by being exposed to the outside (combustion chamber C side) and a back surface that is the back side of the pressure receiving surface 32a. Due to the presence of the concave portion 32b, there is a convex portion 32c that protrudes from the center of the back surface of the pressure receiving surface 32a toward the rear end side. The diaphragm head 32 is provided so as to close the opening on the distal end side of the first distal end side housing 311. Laser welding is performed on the boundary between the diaphragm head 32 and the first distal end side housing 311 over the entire circumference of the outer peripheral surface.

  In addition, the detection unit 30 is disposed (accommodated) inside the front end side housing 31, and includes the piezoelectric element 33, the insulating plate 34, the front end electrode member 35, the rear end electrode member 36, the first pressurizing member 37, and the second The pressure member 38, the support member 39, the insulating pipe 40, the first insulating ring 41, the second insulating ring 42, the third insulating ring 43, the fourth insulating ring 44, and the fifth insulating ring 45 are further provided.

  The piezoelectric element 33 as an example of the detection element is a member having a cylindrical shape as a whole. The piezoelectric element 33 includes a piezoelectric body that exhibits the piezoelectric action of the piezoelectric longitudinal effect. The piezoelectric longitudinal effect means that when an external force is applied to the stress application axis in the same direction as the charge generation axis of the piezoelectric body, charges are generated on the surface of the piezoelectric body in the charge generation axis direction. The piezoelectric element 33 is disposed inside the front end side casing 31 and on the rear end side of the diaphragm head 32. The piezoelectric element 33 is accommodated in the distal end side casing 31 so that the center line direction is the direction of the stress application axis. Here, the piezoelectric element 33 is inside the first pressurizing member 37 provided inside the distal end side housing 31 and inside the insulating pipe 40 provided inside the first pressurizing member 37. Has been placed. The outer diameter of the piezoelectric element 33 is slightly smaller than the inner diameter of the insulating pipe 40 that accommodates the piezoelectric element 33 therein. The front surface of the piezoelectric element 33 is in contact with the rear surface of the front electrode member 35. On the other hand, the rear end surface of the piezoelectric element 33 is in contact with the front end surface of the rear end electrode member 36. Further, the outer peripheral surface of the piezoelectric element 33 faces the inner peripheral surface of the insulating pipe 40. Thus, by providing the insulating pipe 40 between the inner peripheral surface of the first pressure member 37 and the outer peripheral surface of the piezoelectric element 33, the first pressure member 37 and the piezoelectric element 33 are in direct contact with each other. do not do.

  Next, a case where the piezoelectric lateral effect is used for the piezoelectric element 33 will be exemplified. The piezoelectric lateral effect means that when an external force is applied to a stress application axis at a position orthogonal to the charge generation axis of the piezoelectric body, charges are generated on the surface of the piezoelectric body in the direction of the charge generation axis. A plurality of thinly formed piezoelectric bodies may be laminated, and by laminating in this way, the charge generated in the piezoelectric bodies can be efficiently collected to increase the sensitivity of the sensor. Examples of the piezoelectric material that can be used in the piezoelectric element 33 include the use of a langasite crystal (a langasite, langagate, langanite, LGTA) having a piezoelectric longitudinal effect and a piezoelectric transverse effect, crystal, gallium phosphate, or the like. can do. In the piezoelectric element 33 of the present embodiment, a langasite single crystal is used as the piezoelectric body.

  The insulating plate 34 as an example of another insulating member is a member having a disk shape as a whole. The insulating plate 34 is made of a ceramic material such as alumina that has insulating properties and high heat resistance. The insulating plate 34 is disposed at a position that closes the opening existing on the distal end side of the first pressure member 37 provided in the distal end side housing 31. The insulating plate 34 is disposed on the rear end side of the diaphragm head 32 and on the front end side of the front end electrode member 35. In addition, the outer diameter of the insulating plate 34 is slightly smaller than the inner diameter of the opening provided on the distal end side of the first pressure member 37 and slightly larger than the outer diameter of the convex portion 32 c of the diaphragm head 32. The front end surface of the insulating plate 34 is in contact with the convex portion 32 c of the diaphragm head 32. On the other hand, the rear end surface of the insulating plate 34 is in contact with the front end surface of the front electrode member 35. The outer peripheral surface of the insulating plate 34 is opposed to the inner peripheral surface of the opening provided on the tip side of the first pressure member 37.

  The tip electrode member 35 is a member having a cylindrical shape as a whole. The tip electrode member 35 is made of a metal material such as stainless steel having conductivity and high heat resistance. The tip electrode member 35 is disposed inside a first pressure member 37 provided in the tip side casing 31. However, unlike the piezoelectric element 33 described above, the tip electrode member 35 is not accommodated in the insulating pipe 40. The front electrode member 35 is disposed on the rear end side of the insulating plate 34 and on the front end side of the piezoelectric element 33. Further, the outer diameter of the tip electrode member 35 is slightly smaller than the inner diameter of the first pressure member 37 that accommodates the tip electrode member 35 therein. The front end surface of the front electrode member 35 is in contact with the rear end surface of the insulating plate 34 and the back surface of the opening provided on the front end side of the first pressure member 37. On the other hand, the rear end surface of the front electrode member 35 is in contact with the front end surface of the piezoelectric element 33. Further, the outer peripheral surface of the tip electrode member 35 faces the inner peripheral surface of the first pressure member 37.

  The rear end electrode member 36 is a member having a cylindrical shape as a whole. The rear end electrode member 36 is made of a metal material such as stainless steel having conductivity and high heat resistance. The rear end electrode member 36 is disposed inside a first pressure member 37 provided inside the front end side casing 31. Here, the front end side of the rear end electrode member 36 is disposed inside the insulating pipe 40 provided inside the first pressurizing member 37. On the other hand, the rear end side of the rear end electrode member 36 is disposed outside the insulating pipe 40. A counterbore 36a for inserting the front end side of the second pressure member 38 is formed at the center of the rear end surface of the rear end electrode member 36. Further, the outer diameter of the rear end electrode member 36 is substantially the same as the outer diameter of the piezoelectric element 33 and is slightly smaller than the inner diameter of the insulating pipe 40. The front end side surface of the rear end electrode member 36 is in contact with the rear end side surface of the piezoelectric element 33. On the other hand, the rear end surface of the rear end electrode member 36 is in contact with the front end surface of the first insulating ring 41, and the bottom surface of the counterbore 36a provided on the rear end side of the rear end electrode member 36 is It is in contact with the tip side of the second pressure member 38. Further, the distal end side of the outer peripheral surface of the rear end electrode member 36 faces the inner peripheral surface of the insulating pipe 40. On the other hand, the rear end side of the outer peripheral surface of the rear end electrode member 36 faces the inner peripheral surface of the first pressurizing member 37 through the air gap. Thus, by providing the insulating pipe 40 and the air gap between the inner peripheral surface of the first pressure member 37 and the outer peripheral surface of the rear end electrode member 36, the first pressure member 37 and the rear end electrode member are provided. 36 is not in direct contact.

  The first pressure member 37 is a member that exhibits a tubular shape as a whole. The first pressure member 37 is made of a metal material such as stainless steel having conductivity and high heat resistance. The first pressurizing member 37 is provided inside the distal end side casing 31, and an insulating plate 34 is disposed so as to close the opening provided on the distal end side thereof, and the piezoelectric element 33, The front end electrode member 35, the rear end electrode member 36, the second pressure member 38, the front end side of the support member 39, the insulating pipe 40, and the first insulating ring 41 are accommodated. The first pressurizing member 37 is disposed on the rear end side of the diaphragm head 32 and on the front end side of a buffer member 55 (details will be described later) constituting the processing unit 50. Further, the outer diameter of the first pressure member 37 varies depending on the position in the center line direction, but is smaller than the inner diameter of the distal end side casing 31 (more specifically, the first distal end side casing 311) at all positions. . Further, the inner diameter of the first pressurizing member 37 is outside of the insulating plate 34, the tip electrode member 35, the insulating pipe 40 (piezoelectric element 33, the rear end electrode member 36) and the first insulating ring 41. It is larger than the diameter and slightly smaller than the outer diameter of the support member 39 at the part facing the support member 39. Here, between the outer peripheral surface on the rear end side of the first pressure member 37 and the inner peripheral surface on the rear end side of the first front end side housing 311, the second insulation is located at a position relatively on the front end side. Third insulating rings 43 are arranged at positions where the ring 42 is relatively on the rear end side. The front-side surface of the first pressure member 37 (the surface on the front side of the opening) is opposed to the recess 32 b provided on the rear end side of the diaphragm head 32. On the other hand, the rear end side of the first pressure member 37 is in contact with the front end side of the buffer member 55. Further, the rear end side of the outer peripheral surface of the first pressure member 37 is in contact with the inner peripheral surface of the second insulating ring 42, and the rear end side thereof faces the third insulating ring 43 through an air gap. Yes. Further, the distal end side of the outer peripheral surface of the first pressure member 37 is opposed to the inner peripheral surface of the first distal end side housing 311 through an air gap. Thus, an air gap is formed by the recess 32b between the front-side surface of the first pressure member 37 and the back surface of the diaphragm head 32, and the outer peripheral surface of the first pressure member 37 and the front-side housing are provided. By providing the second insulating ring 42 between the inner peripheral surface of the first front end side housing 311 of 31, the front end side housing 31, the diaphragm head 32, and the first pressure member 37 are directly Do not touch. In contrast, the inner peripheral surface of the first pressure member 37 is in direct contact with the outer peripheral surfaces of the tip electrode member 35, the insulating pipe 40, the first insulating ring 41, and the support member 39. Further, the inner peripheral surface of the first pressure member 37 is not in direct contact with the outer peripheral surfaces of the piezoelectric element 33 and the rear end electrode member 36.

  The second pressurizing member 38 is a spiral member as a whole, and is a coil spring that expands and contracts in the center line direction. The second pressure member 38 is made of a metal material such as brass having conductivity and higher conductivity than the distal end side housing 31. The second pressurizing member 38 is inside the first pressurizing member 37 provided inside the distal end side housing 31 and inside the first pressurizing member 37 and the first insulating member 39. It is arranged so as to pass through the ring 41 and reach the counterbore 36 a of the rear end electrode member 36. The second pressurizing member 38 is disposed on the rear end side of the rear end electrode member 36 and on the front end side of a conductive member 53 (details will be described later) provided in the processing unit 50. Further, the outer diameter of the second pressure member 38 is the inner diameter of the opening provided on the front end side of the support member 39, the inner diameter of the through hole provided in the first insulating ring 41, and the rear end electrode member 36. It is smaller than the inner diameter of the counterbore 36a. Furthermore, the inner diameter of the second pressurizing member 38 is larger than the outer diameter of the tip side convex portion 53 a (details will be described later) provided on the tip side of the conductive member 53. The distal end side of the second pressure member 38 is in contact with the rear end electrode member 36 by being inserted into the counterbore 36 a of the rear end electrode member 36. On the other hand, the rear end side of the second pressurizing member 38 is in contact with the conductive member 53 by inserting the leading end side convex portion 53 a of the conductive member 53. Further, the front end side of the outer peripheral surface of the second pressure member 38 faces the inner peripheral surface of the counterbore hole 36 a of the rear end electrode member 36 and the inner peripheral surface of the through hole of the first insulating ring 41. Furthermore, the rear end side of the outer peripheral surface of the second pressure member 38 faces the inner peripheral surface of the support member 39 through an air gap. As described above, by providing the air gap between the inner peripheral surface of the support member 39 and the second pressure member 38, the support member 39 and the second pressure member 38 are not in direct contact with each other.

  The support member 39 is a member having a cylindrical shape as a whole. The support member 39 is made of a metal material such as stainless steel having conductivity and high heat resistance. The support member 39 is provided inside the front end side casing 31, and the front end side is located inside the first pressure member 37 and the rear end side is located outside the first pressure member 37. ing. The support member 39 accommodates the rear end side of the second pressurizing member 38 therein, and the front ends of the conductive member 53 and the covering member 54 (details will be described later) located on the front end side of the processing unit 50. Accommodates the side. The support member 39 is disposed on the rear end side of the first insulating ring 41 and on the front end side of a housing member 56 (details will be described later) constituting the processing unit 50. The outer diameter of the support member 39 is slightly larger than the inner diameter of the first pressure member 37. Further, the inner diameter of the support member 39 differs depending on the position in the center line direction, but is larger than the outer diameter of the conductive member 53 and the covering member 54 provided in the processing unit 50 at all positions. The front end side surface (surface on the front side of the opening) of the support member 39 is in contact with the rear end side surface of the first insulating ring 41. On the other hand, the rear end surface of the support member 39 faces the covering member 54 through an air gap. Further, the outer peripheral surface of the support member 39 is in contact with the inner peripheral surface of the first pressure member 37. Furthermore, the inner peripheral surface of the support member 39 is opposed to the second pressure member 38, the conductive member 53, and the covering member 54 through an air gap. Thus, by providing an air gap between the inner peripheral surface of the support member 39 and the second pressure member 38, the conductive member 53, and the covering member 54, the support member 39 and the second pressure member 38, The conductive member 53 and the covering member 54 are not in direct contact.

  The insulating pipe 40 is a member having a cylindrical shape as a whole. The insulating pipe 40 is made of a synthetic resin material such as LCP (Liquid Crystal Polymer) having insulating properties. The insulating pipe 40 is disposed inside the first pressurizing member 37 provided inside the distal end side housing 31. The insulating pipe 40 accommodates the piezoelectric element 33 and the front end side of the rear end electrode member 36 therein. The insulating pipe 40 is arranged on the rear end side of the front electrode member 35 and on the front end side of the first insulating ring 41. Further, the outer diameter of the insulating pipe 40 is slightly smaller than the inner diameter of the first pressure member 37. Further, the inner diameter of the insulating pipe 40 is slightly larger than the outer diameter of each of the piezoelectric element 33 and the rear end electrode member 36. The distal end side of the insulating pipe 40 faces the rear end surface of the distal electrode member 35. On the other hand, the rear end side of the insulating pipe 40 faces the surface on the front end side of the first insulating ring 41. Further, the outer peripheral surface of the insulating pipe 40 is opposed to the inner peripheral surface of the first pressure member 37. Further, the inner peripheral surface of the insulating pipe 40 faces the outer peripheral surface of the piezoelectric element 33 and the outer peripheral surface of the rear end electrode member 36. Thus, by providing the air gap by the insulating pipe 40 and the insulating pipe 40 between the first pressure member 37 and the piezoelectric element 33 and the rear end electrode member 36, the first pressure member 37 and the piezoelectric element 33 are provided. And it does not contact the rear end electrode member 36 directly.

  The first insulating ring 41 is a member having an annular shape as a whole. The first insulating ring 41 is made of a ceramic material such as alumina that has insulating properties and high heat resistance. The first insulating ring 41 is disposed inside a first pressurizing member 37 provided inside the distal end side casing 31. A through hole penetrating the first insulating ring 41 along the center line direction is formed at the center of the first insulating ring 41. The outer diameter of the first insulating ring 41 is slightly smaller than the inner diameter of the first pressure member 37. Further, the inner diameter of the through hole of the first insulating ring 41 is slightly larger than the outer diameter of the second pressure member 38. The front surface of the first insulating ring 41 is in contact with the rear surface of the rear electrode member 36. On the other hand, the rear end surface of the first insulating ring 41 is in contact with the front end surface of the support member 39. Further, the outer peripheral surface of the first insulating ring 41 is opposed to the inner peripheral surface of the first pressure member 37. Further, the inner peripheral surface of the first insulating ring 41 is opposed to the outer periphery of the second pressure member 38.

  The second insulating ring 42 is a member having an annular shape as a whole. The second insulating ring 42 is made of a ceramic material such as alumina that has insulating properties and high heat resistance. The second insulating ring 42 is disposed inside the distal end side housing 31 and on the rear end side and outside of the first pressure member 37. A through-hole penetrating the second insulating ring 42 along the center line direction is formed at the center of the second insulating ring 42. Further, the outer diameter of the second insulating ring 42 is slightly larger than the inner diameter of the distal end side casing 31 (more specifically, the first distal end side casing 311). Further, the inner diameter of the second insulating ring 42 is slightly smaller than the outer diameter of the first pressure member 37. The front-side surface of the second insulating ring 42 is in contact with the rear-side surface of the protruding portion that protrudes outward from the outer peripheral surface of the first pressure member 37. On the other hand, the rear end surface of the second insulating ring 42 is in contact with the front end surface of the third insulating ring 43. Further, the outer peripheral surface of the second insulating ring 42 is in contact with the inner peripheral surface of the distal end side housing 31. Further, the inner peripheral surface of the second insulating ring 42 is in contact with the outer peripheral surface of the first pressure member 37.

  The third insulating ring 43 is a member having an annular shape as a whole. The third insulating ring 43 is made of a ceramic material such as alumina that has insulating properties and high heat resistance. The third insulating ring 43 is disposed inside the distal end side housing 31 and outside the first pressure member 37. A through-hole penetrating the third insulating ring 43 along the center line direction is formed at the center of the third insulating ring 43. Further, the outer diameter of the third insulating ring 43 is slightly larger than the inner diameter of the distal end side casing 31 (more specifically, the first distal end side casing 311). Further, the inner diameter of the third insulating ring 43 is larger than the outer diameter of the first pressure member 37 and larger than the inner diameter of the second insulating ring 42. The front end surface of the third insulating ring 43 is in contact with the rear end surface of the second insulating ring 42. On the other hand, the rear end surface of the third insulating ring 43 is opposed to the air gap provided on the rear end side. Further, the outer peripheral surface of the third insulating ring 43 is in contact with the inner peripheral surface of the distal end side housing 31. Furthermore, the inner peripheral surface of the third insulating ring 43 is opposed to the outer peripheral surface of the first pressure member 37 through an air gap.

  The fourth insulating ring 44 as an example of an insulating member is a member having an annular shape as a whole. The fourth insulating ring 44 is made of a ceramic material such as alumina that has insulating properties and high heat resistance. The fourth insulating ring 44 is inside the distal end side casing 31 (more specifically, the second distal end side casing 312), and is an accommodation member 56 (details will be described later) provided in the processing unit 50. It is arranged on the rear end side and outside. A through-hole penetrating the fourth insulating ring 44 along the center line direction is formed at the center of the fourth insulating ring 44. Further, the outer diameter of the fourth insulating ring 44 is slightly larger than the inner diameter of the distal end side housing 31. Further, the inner diameter of the fourth insulating ring 44 is slightly smaller than the outer diameter of the housing member 56. The front end surface of the fourth insulating ring 44 is in contact with the inner peripheral surface of the front end housing 31. On the other hand, the rear end surface of the fourth insulating ring 44 is in contact with the outer peripheral surface of the housing member 56. Further, the outer peripheral surface of the fourth insulating ring 44 is in contact with the inner peripheral surface of the distal end side housing 31. Further, the inner peripheral surface of the fourth insulating ring 44 is in contact with the outer peripheral surface of the housing member 56.

  The fifth insulating ring 45 as an example of the insulating member is a member having an annular shape as a whole. The fifth insulating ring 45 is made of a ceramic material such as alumina that has insulating properties and high heat resistance. The fifth insulating ring 45 is inside the front end side casing 31 (more specifically, the second front end side casing 312), and is an accommodation member 56 (details will be described later) provided in the processing unit 50. Arranged outside. A through-hole penetrating the fifth insulating ring 45 is formed in the central portion of the fifth insulating ring 45 along the center line direction. Further, the outer diameter of the fifth insulating ring 45 is slightly larger than the inner diameter of the distal end side casing 31. Further, the inner diameter of the fifth insulating ring 45 is slightly smaller than the outer diameter of the housing member 56. The front end surface of the fifth insulating ring 45 is in contact with the inner peripheral surface of the front end housing 31. On the other hand, the rear end surface of the fifth insulating ring 45 is in contact with the outer peripheral surface of the housing member 56. Further, the outer peripheral surface of the fifth insulating ring 45 is in contact with the inner peripheral surface of the distal end side housing 31. Further, the inner peripheral surface of the fifth insulating ring 45 is in contact with the outer peripheral surface of the housing member 56.

  Thus, by providing the 4th insulating ring 44 and the 5th insulating ring 45 between the front end side housing | casing 31 and the accommodating member 56 which comprises the process part 50, the front end side housing | casing 31 and the accommodating member 56 are provided. Is not in direct contact.

[Configuration of processing section]
The processing unit 50 includes a rear end side casing 51 that fits on the rear end side of the front end side casing 31 (specifically, the second front end side casing 312), and a front end side of the rear end side casing 51. A connecting member that is accommodated in the rear end side, and that the rear end side is exposed to the outside of the rear end side of the rear end side casing 51 and is a connection target of the connection cable 90 (see FIG. 1). 52.

  Among these, the rear end side housing | casing 51 is a member which has a hollow structure and exhibits a cylindrical shape as a whole. The rear end side casing 51 is made of a metal material such as stainless steel having conductivity and high acid resistance. The rear end side of the rear end side casing 51 is attached with the rear end side of the front end side casing 31 (specifically, the second front end side casing 311) by fitting, The connecting member 52 is attached by fitting.

  On the other hand, the connection member 52 is a member having a columnar shape as a whole. The connecting member 52 includes a base material made of a synthetic resin material such as PPT (Polypropylene Terephthalate) having insulation properties, and wiring and terminals made of a metal material such as copper having conductivity. Contains. However, a portion (outer peripheral surface) of the connecting member 52 that contacts the above-described rear end side casing 51 is made of a synthetic resin material, and the metal material is not exposed to this portion (not contacted with the connecting member 52). It is like that. In addition, a first board side terminal 521, a second board side terminal 522, and a third board side terminal 523, each of which serves as an electrical connection terminal, are provided on the tip side of the connection member 52 so as to protrude toward the tip side. It has been. On the other hand, on the rear end side of the connection member 52, an opening 520 having a recessed shape and opening toward the rear end side is formed. And in the opening part 520, the 1st connection terminal 52a, the 2nd connection terminal 52b, and the 3rd connection terminal 52c used as the connection object of the connection cable 90 (refer FIG. 1) protrude toward the rear end side. Is provided. Here, the first board side terminal 521 is electrically connected to the first connection terminal 52a, the second board side terminal 522 is electrically connected to the second connection terminal 52b, and the third board side terminal 523 is electrically connected to the third connection terminal 52c. Has been.

  Further, the processing unit 50 is disposed (accommodated) inside the front end side casing 31 and / or the rear end side casing 51, and includes a conductive member 53, a covering member 54, a buffer member 55, a storage member 56, and a circuit board 57. And a holding member 58.

  The conductive member 53 is a member having a rod shape as a whole. The conductive member 53 is made of a metal material such as brass having conductivity. The conductive member 53 is provided with a tip-side convex portion 53a having a diameter smaller than that of the center portion in the center line direction at the tip, and a rear end having a diameter smaller than that of the center portion in the center line direction. A side convex portion 53b is provided. The conductive member 53 is provided inside the front end side housing 31, the front end side is inside the first pressure member 37, the rear end side is inside the housing member 56, and the front end side and the rear end side The intermediate portions located between the two are located inside the buffer member 55. The conductive member 53 is disposed on the rear end side of the second pressure member 38 and on the front end side of the circuit board 57. In addition, the outer diameter of the convex portion 53 a on the front end side of the conductive member 53 is slightly larger than the inner diameter of the second pressure member 38. Further, the outer diameter of the rear end convex portion 53 b of the conductive member 53 is substantially the same as the inner width of a rear end holding portion 54 a (details will be described later) provided on the covering member 54. Furthermore, the outer diameter of the central portion in the center line direction of the conductive member 53 is substantially the same as the inner diameter of the covering member 54. The conductive member 53 is disposed so as to pass through a through hole provided in the covering member 54 along the center line direction, and the front-end-side convex portion 53a protrudes to the front end side from the front end of the covering member 54, and the rear end The side convex portion 53 b protrudes to the rear end side from the concave portion provided on the rear end side of the covering member 54. And the front end side convex part 53a of the conduction member 53 is contacting the 2nd pressurization member 38 by being inserted inside the 2nd pressurization member 38. As shown in FIG. On the other hand, the rear end convex portion 53 b of the conductive member 53 is fitted into a rear end holding portion 54 a provided on the covering member 54. Further, the outer peripheral surface of the central portion in the center line direction of the conductive member 53 is in contact with the inner peripheral surface of the covering member 54.

  The covering member 54 is a member having a tubular shape as a whole. The covering member 54 includes a base material made of a synthetic resin material such as PPT having insulation properties, and wiring and terminals made of a metal material such as copper having conductivity. However, a portion (outer peripheral surface) of the covering member 54 that faces the support member 39, the buffer member 55, and the housing member 56 is made of a synthetic resin material so that the metal material is not exposed to this portion. Yes. Further, a rear end holding portion 54 a that is made of a metal material and that fits and holds the rear end convex portion 53 b of the conductive member 53 is provided on the rear end side of the covering member 54. The covering member 54 is provided inside the front end side housing 31, the front end side is inside the first pressurizing member 37, the end side is inside the accommodating member 56, and the front end side and the rear end The intermediate part located between the two sides is located inside the buffer member 55. The covering member 54 is disposed on the rear end side of the second pressure member 38 and on the front end side of the circuit board 57. The outer peripheral surface of the covering member 54 has a shape in which the outer diameter increases stepwise from the front end side toward the rear end side. A through-hole penetrating the covering member 54 is formed in the central portion of the covering member 54 along the center line direction. Further, the outer diameter on the front end side of the covering member 54 is smaller than the inner diameter of the support member 39, and the outer diameter on the rear end side of the covering member 54 is smaller than the inner diameter of the housing member 56. Further, the inner diameter of the covering member 54 is substantially the same as the outer diameter of the central portion of the conductive member 53 in the center line direction. And the front-end | tip of the coating | coated member 54 is provided in the front-end | tip side of the conduction member 53, and is contacting the rear end of the bulging part whose outer diameter is a little thicker than the center part in the center line direction. On the other hand, the rear end of the covering member 54 is in contact with the front end of the circuit board 57. Further, the outer peripheral surface of the covering member 54 is opposed to the inner peripheral surface of the support member 39 through an air gap. Further, the inner peripheral surface of the covering member 54 is in contact with the conductive member 53.

  The buffer member 55 is a spiral member as a whole, and is a coil spring that expands and contracts in the direction of the center line. The buffer member 55 is made of a metallic material such as brass having conductivity. The buffer member 55 is provided inside the front end side housing 31, and the front end side thereof is located outside the first pressurizing member 37, and the rear end side thereof is located outside the accommodating member 56. That is, the buffer member 55 is disposed across the first pressure member 37 and the housing member 56. Further, the outer diameter of the buffer member 55 is smaller than the inner diameter of the distal end side casing 31 (specifically, the second distal end side casing 312). Further, the inner diameter of the buffer member 55 is slightly smaller than the outer diameter of the rear end of the first pressure member 37 and the outer diameter of the front end side of the housing member 56. The outer periphery of the buffer member 55 is opposed to the distal end side casing 31 through an air gap. On the other hand, the inner periphery on the front end side of the buffer member 55 is in contact with the outer peripheral surface on the rear end side of the first pressure member 37, and the inner periphery on the rear end side of the buffer member 55 is the outer periphery on the front end side of the housing member 56. In contact with the surface. Thus, by providing an air gap between the outer periphery of the buffer member 55 and the inner peripheral surface of the front end side housing 31, the buffer member 55 and the front end side housing 31 are not in direct contact.

  The housing member 56 as an example of the conductive member or the first housing is a member that has a tubular shape as a whole. The housing member 56 is made of a metallic material such as brass having conductivity. The housing member 56 is provided across the inside of the front end side casing 31 and the inside of the rear end side casing 51. The housing member 56 is disposed on the rear end side of the first pressure member 37 and on the front end side of the connection member 52. The outer peripheral surface and inner peripheral surface of the housing member 56 have a shape in which the outer diameter and inner diameter increase stepwise from the front end side toward the rear end side. A through-hole penetrating the housing member 56 along the center line direction is formed in the central portion of the housing member 56. Further, the outer diameter on the front end side of the housing member 56 is smaller than the inner diameter of the front end side housing 31, and the outer diameter on the rear end side of the housing member 56 is smaller than the inner diameter of the rear end side housing 51. Here, between the outer peripheral surface of the housing member 56 and the inner peripheral surface of the front end side housing 31, the fourth insulating ring 44 is located on the relatively front end side, and the rear end side portion. The fifth insulating rings 45 are arranged respectively. Further, the inner diameter on the front end side of the housing member 56 is larger than the outer diameter of the covering member 54, and the inner diameter on the rear end side of the housing member 56 is slightly smaller than the outer diameter of the holding member 58. The inner diameter of the intermediate portion located between the rear end side and the rear end side is slightly larger than the outer diameter of the circuit board 57. The front end side of the housing member 56 is in contact with the rear end side of the buffer member 55. On the other hand, the rear end side of the housing member 56 is opposed to the connection member 52 through an air gap. Further, the outer peripheral surface on the front end side of the housing member 56 faces the front end side housing 31 through the fourth insulating ring 44, the fifth insulating ring 45, and an air gap formed by these, and the rear end of the housing member 56 The outer peripheral surface on the side faces the rear end side casing 51 through an air gap.

  The circuit board 57 is a member having a rectangular plate shape as a whole. The circuit board 57 performs various processes using an electric circuit on an electric signal (charge signal: an example of a detection signal) due to a weak charge output from the piezoelectric element 33 in accordance with the received pressure. It is comprised by the printed wiring board. The circuit board 57 is provided across the inside of the front end side casing 31 and the inside of the rear end side casing 51. The circuit board 57 is disposed on the rear end side of the conductive member 53 and the covering member 54 and on the front end side of the connection member 52. Further, the entire circuit board 57 is disposed inside the accommodating member 56, and the circuit board 57 is disposed between the outer peripheral surface on the rear end side of the circuit board 57 and the inner peripheral surface on the rear end side of the accommodating member 56. A holding member 58 is provided. On the rear end side of the circuit board 57, a power receiving terminal 57c, an output signal terminal 57d, and an output ground to be connected to the first board side terminal 521, the second board side terminal 522, and the third board side terminal 523 described above. A terminal 57e is provided. Here, the power receiving terminal 57c is electrically connected to the first board side terminal 521, the output signal terminal 57d is electrically connected to the second board side terminal 522, and the output ground terminal 57e is electrically connected to the third board side terminal 523. Although details will be described later, the power receiving terminal 57c is used to supply power to the circuit board 57, the output signal terminal 57d is used to output a signal from the circuit board 57, and the output ground terminal 57e is grounded to the circuit board 57. Used for. Details of the circuit board 57 will be described later.

  The holding member 58 is a member having a cylindrical shape as a whole. The holding member 58 includes a base material made of a synthetic resin material such as PPT having an insulating property, and wirings made of a metal material such as conductive copper. The holding member 58 extends over the inside of the front end side housing 31 and the inside of the rear end side housing 51, and is provided at a position inside the housing member 56 and outside the circuit board 57. The holding member 58 is disposed on the rear end side of the fifth insulating ring 45 and on the front end side of the connection member 52. A through-hole penetrating the holding member 58 along the center line direction is formed in the central portion of the holding member 58. The outer diameter of the holding member 58 is slightly larger than the inner diameter on the rear end side of the housing member 56. Further, the inner diameter of the holding member 58 on the tip side is slightly smaller than the outer diameter of the circuit board 57. The outer peripheral surface of the holding member 58 is in contact with the inner peripheral surface on the rear end side of the housing member 56. On the other hand, the inner peripheral surface on the front end side of the holding member 58 is in contact with the outer peripheral surface on the rear end side of the circuit board 57. Here, the wiring provided on the holding member 58 contacts the inner peripheral surface of the housing member 56 on the outer peripheral surface thereof, and is connected to an input ground terminal 57b (details will be described later) of the circuit board 57 on the inner peripheral surface. The

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

  In the pressure detection device 20, the end surface (positive electrode) on the rear end side of the piezoelectric element 33 is electrically connected to the metal rear end electrode member 36, and the rear end electrode member 36 is a metal second pressurizing member. It is connected to a metallic conductive member 53 via a (coil spring) 38. The metal conductive member 53 is electrically connected to the metal rear end holding portion 54a of the covering member 54 basically composed of an insulator, and the rear end holding portion 54a is connected to the circuit board 57. Is electrically connected to an input signal terminal 57a (see FIG. 5 described later). In the following, the surface of the piezoelectric element 33 from the rear end side reaches the input signal terminal 57a of the circuit board 57 via the rear end electrode member 36, the second pressure member 38, the conductive member 53, and the rear end holding portion 54a. The electrical path is referred to as a “positive path”.

  On the other hand, in the pressure detection device 20, the end face (negative electrode) on the tip side of the piezoelectric element 33 is electrically connected to a metal tip electrode member 35, and the tip electrode member 35 is a metal first pressurizing member 37. The metal buffer member 55 is electrically connected via (and the metal support member 39). The metal buffer member 55 is electrically connected to a metal housing member 56, and the housing member 56 is basically connected to a metal wiring provided on a holding member 58 formed of an insulator. Thus, it is electrically connected to an input ground terminal 57b (see FIG. 5 described later) provided on the circuit board 57. In the following description, the circuit board 57 is connected to the tip electrode member 35, the first pressure member 37 (support member 39), the buffer member 55, the housing member 56, and the holding member 58 from the tip side surface of the piezoelectric element 33. The electrical path to the input ground terminal 57b is referred to as a “negative path”.

  On the other hand, in the pressure detection device 20, the metal front end side casing 31 (the first front end side casing 311 and the second front end side casing 312) is made of the metal diaphragm head 32 and the metal rear end side casing. 51 is electrically connected. Hereinafter, an electrical path from the diaphragm head 32 through the front end side casing 31 to the rear end side casing 52 is referred to as a “casing path”.

  Thus, in the pressure detection device 20 of the present embodiment, a negative path exists outside the positive path. The positive path and the negative path are electrically insulated by the insulating pipe 40, the first insulating ring 41, the covering member 54, and an air gap formed by these.

  Moreover, in this pressure detection apparatus 20, the housing | casing path | route exists in the outer side of a negative path | route. The negative path and the casing path are electrically connected by an insulating plate 34, a second insulating ring 42, a third insulating ring 43, a fourth insulating ring 44, a fifth insulating ring 45, and an air gap formed by these. Is electrically insulated.

  In the pressure detection device 20, the positive path and the negative path are electrically insulated, and the negative path and the casing path are electrically insulated, so that the positive path and the casing are electrically insulated. The path is electrically insulated.

  In the following description, the front end side housing 31, the diaphragm head 32, and the rear end side housing 51 may be collectively referred to as “housing 60” (an example of the second housing) (FIG. 2 and FIG. 2). (See FIGS. 8 to 11 described later). In the following description, the tip electrode member 35, the first pressure member 37, the support member 39, the buffer member 55, and the housing member 56 may be collectively referred to as a “shielding body 70” (FIGS. 8 to 9). 11).

  Here, the housing 60 is a part exposed to the outside in the pressure detection device 20, and in particular, the diaphragm head 32 is a part facing the combustion chamber C where the acidity increases with combustion. On the other hand, the shielding body 70 is a part accommodated in the inside of the housing 60 in the pressure detection device 20, and is also a part that forms a negative path in this example. For this reason, the shielding body 70 is preferably made of a material having higher acid resistance than the housing 60, and the housing 60 is preferably made of a material having higher conductivity than the shielding body 70.

[Configuration of circuit board]
FIG. 5 is a schematic configuration diagram of the circuit board 57 provided in the pressure detection device 20.
The circuit board 57 includes a printed wiring board 571 on which wiring (circuit pattern) for mounting one or a plurality of electronic components (circuit elements) is formed, and a processing circuit 572 mounted on the printed wiring board 571. ing.

  In this embodiment, a so-called glass epoxy substrate based on a glass cloth base epoxy resin is used as the printed wiring board 571. The circuit board 57 is provided with an input signal terminal 57a, an input ground terminal 57b, a power receiving terminal 57c, an output signal terminal 57d, and an output ground terminal 57e as input / output terminals.

  Here, a positive path in the pressure detection device 20 is connected to the input signal terminal 57a, and a negative path in the pressure detection device 20 is connected to the input ground terminal 57b. On the other hand, the first board side terminal 521 is connected to the power receiving terminal 57c, the second board side terminal 522 is connected to the output signal terminal 57d, and the third board side terminal 523 is connected to the output ground terminal 57e ( (See FIG. 3). In the circuit board 57, an input ground terminal 57b and an output ground terminal 57e are connected.

  The processing circuit 572 also integrates the charge signal input from the piezoelectric element 10 via the input signal terminal 57a and converts it into a voltage signal, and amplifies the converted voltage signal to output the output signal terminal. And an amplifier circuit 572b for outputting to 57d. Here, the power supply voltage for operating these is supplied to the integrating circuit 572a and the amplifier circuit 572b via the power receiving terminal 57c. The grounds of the integrating circuit 572a and the amplifying circuit 572b are connected to the input ground terminal 57b and the output ground terminal 57e. In this example, the processing circuit 572 is configured by a so-called integrated circuit (IC).

[Pressure detection operation by pressure detector]
Now, the pressure detection operation by the pressure detection device 20 will be described.
When the internal combustion engine 10 is operating, the pressure (combustion pressure) generated in the combustion chamber C is applied to the pressure receiving surface 32 a of the diaphragm head 32. In the diaphragm head 32, the pressure received by the pressure receiving surface 32 a is transmitted to the convex portion 32 c on the back side, and further transmitted from the convex portion 32 c to the insulating plate 34. The pressure transmitted to the insulating plate 34 is transmitted to the tip electrode member 35, thereby acting on the piezoelectric element 33 sandwiched between the tip electrode member 35 and the rear end electrode member 36. Electric charges are generated according to the pressure received. The charge generated in the piezoelectric element 33 is transferred to the input signal terminal 57a of the circuit board 57 via the positive path, that is, the rear end electrode member 36, the second pressure member 38, the conductive member 53, and the rear end holding portion 54a. Supplied as The charge signal supplied to the circuit board 57 is converted into a voltage signal by integration processing by the integration circuit 572a, and further output by being amplified by the amplification circuit 572b. Then, the output signal output from the amplifier circuit 572b is externally (here, from the output signal terminal 57d of the circuit board 57 via the second board side terminal 522 and the second connection terminal 52b provided in the connection member 52. It is transmitted to the transmission line 92 of the connection cable 90 and the control device 80).

[Configuration of control device]
FIG. 6 is a block diagram of the control device 80.
The control device 80 as an example of the supply / processing device includes a power supply unit that generates a power supply voltage for the pressure detection device 20 by reducing a voltage (for example, + 12V) supplied from a battery (not shown) to about 5V. 81, an ECU (Engine Control Unit) 82 that controls the operation of the internal combustion engine 10 based on an output signal input from the pressure detection device 20, and a device housing 83 that accommodates the power supply unit 81 and the ECU 82 therein. It has. The ECU 82 is configured by a so-called one-chip microcomputer, and temporarily executes an MPU (Micro-processing unit) that performs various arithmetic processes, a ROM (Read Only Memory) that stores a program executed by the MPU, and a program executed by the MPU. A RAM (Random Access Memory) or the like for storing generated data is incorporated.

  In addition, the control device 80 includes a power transmission terminal 80 a that transmits the power supply voltage from the power supply unit 81 toward the pressure detection device 20, a reception terminal 80 b that receives an output signal from the pressure detection device 20, and the pressure detection device 20. And a ground terminal 80c for common ground potential. In this example, each ground of the power supply unit 81 and the ECU 82 is connected to the ground terminal 80 c, and the ground terminal 80 c is also connected to the apparatus housing 83.

[Connection cable configuration]
FIG. 7 is a cross-sectional view of the connection cable 90.
The connection cable 90 includes a supply line 91, a transmission line 92, a ground line 93, a drain wire 94, a shielding part 95, and a braided part 96. The supply line 91, the transmission line 92, and the ground line 93 are each composed of a conductor portion made of a tinned annealed copper stranded wire, an insulating portion that is made of silicon rubber or the like and that covers and insulates the outer periphery of the conductor portion. And have.

  The transmission line 92 and the ground line 93 are paired. The drain wire 94 is composed of a tin-plated annealed copper stranded wire or the like, and is vertically attached (or wound) to the paired transmission line 92 and grounding wire 93. The shielding part 95 is configured by winding an aluminum mylar tape or copper foil having aluminum deposited on one side of a PET tape around the transmission line 92, the ground line 93 and the drain wire 94. The braided portion 96 is configured by weaving cotton yarn, silk yarn, or the like. The braided portion 96 covers the supply line 91, the transmission line 92, the ground line 93, and the drain wire 94 that are integrated by the shielding portion 95. It is integrated. Here, the braided part 96 may be configured to cover only the shielding part 95 (the transmission line 92 and the ground line 93), and the supply line 91 may exist as a single line (separate).

  One end of the supply line 91 is connected to a power receiving terminal 57 c provided on the circuit board 57, and the other end of the supply line 91 is connected to a power transmission terminal 80 a provided on the control device 80. One end of the transmission line 92 is connected to an output signal terminal 57 d provided on the circuit board 57, and the other end of the transmission line 92 is connected to a reception terminal 80 b provided on the control device 80. Further, one end of the ground line 93 is connected to an output ground terminal 57 e provided on the circuit board 57, and the other end of the ground line 93 is connected to a ground terminal 80 c provided on the control device 80.

[Electric connection structure of pressure detection system]
FIG. 8 is a diagram for explaining an electrical connection structure of the pressure detection system 1 according to the present embodiment. FIG. 8 also shows a battery 100 mounted on an automobile or the like together with the internal combustion engine 10 (the same applies to FIGS. 9 to 11 described later).

First, the connection relationship inside the pressure detection device 20 will be described.
In the pressure detection device 20, the rear end side, that is, the positive electrode side of the piezoelectric element 33 is connected to the input signal terminal 57a of the circuit board 57 via a positive path, and the front end side, that is, the negative electrode side of the piezoelectric element 33 is negative. The circuit board 57 is connected to the input ground terminal 57b via the path. In the circuit board 57, each of the input signal terminal 57a, the input ground terminal 57b, the power receiving terminal 57c, the output signal terminal 57d, and the output ground terminal 57e is connected to the processing circuit 572.

  Further, in the pressure detection device 20, an output ground terminal 57 e (may be the input ground terminal 57 b) provided on the circuit board 57 is connected to a shielding body 70 including a housing member 56 that houses the circuit board 57 therein. . And in the pressure detection apparatus 20, the shielding body 70 and the housing | casing 60 which accommodates the shielding body 70 in the inside are in the insulated state.

Next, the connection relationship inside the control device 80 will be described.
In control device 80, the output side of power supply unit 81 is connected to power transmission terminal 80a, and the input side of ECU 82 is connected to reception terminal 80b. In the control device 80, the power supply unit 81 and the grant side of the ECU 82 are connected to the ground terminal 80c and the device housing 83.

Next, the connection relationship between the pressure detection device 20 and the internal combustion engine 10 will be described.
In the present embodiment, as described with reference to FIG. 1, the internal combustion engine 10 is screwed into the cylinder head 13 (more specifically, the communication hole 13 a) provided in the internal combustion engine 10. The pressure detection device 20 is attached to. For this reason, the housing | casing 60 (1st front end side housing | casing 311) which comprises the pressure detection apparatus 20 is connected to the internal combustion engine 10 (cylinder head 13).

Further, the connection relationship between the internal combustion engine 10 and the control device 80 and the battery 100 will be described.
The positive electrode 101 of the battery 100 is connected to a power supply unit 81 provided in the control device 80. On the other hand, the negative electrode 102 (an example of a conductor) of the battery 100 is connected to the internal combustion engine 10 and the device casing 83 of the control device 80. Further, the negative electrode 102 of the battery 100 is connected (grounded) to the body of the automobile.

Furthermore, the connection relationship among the pressure detection device 20, the internal combustion engine 10, the connection cable 90, and the control device 80 will be described.
First, the supply line 91 constituting the connection cable 90 has one end connected to the power receiving terminal 57c provided on the circuit board 57 of the pressure detection device 20, and the other end connected to the power transmission terminal 80a provided on the control device 80. Is done. Further, the transmission line 92 constituting the connection cable 90 has one end connected to the output signal terminal 57d provided on the circuit board 57 of the pressure detection device 20, and the other end connected to the reception terminal 80b provided on the control device 80, respectively. Connected. Further, the ground wire 93 constituting the connection cable 90 has one end connected to the output ground terminal 57e provided on the circuit board 57 of the pressure detection device 20, and the other end connected to the ground terminal 80c provided on the control device 80. Connected. Furthermore, the drain wire 94 constituting the connection cable 90 and in contact with the shielding portion 95 has one end connected to the internal combustion engine 10 and the other end connected to the device casing 83 of the control device 80. Thus, the drain wire 94 provided in the connection cable 90 is grounded at both ends.

In addition, although description was abbreviate | omitted here, the connection cable 90 is actually connected with the circuit board 57 via the connection member 52 provided in the pressure detection apparatus 20 (refer FIG. 3).
Therefore, in practice, one end of the supply line 91 is connected to the first connection terminal 52 a of the connection member 52, and is connected to the power reception terminal 57 c of the circuit board 57 via the first substrate side terminal 521 of the connection member 52. In practice, one end of the transmission line 92 is connected to the second connection terminal 52 b of the connection member 52, and is connected to the output signal terminal 57 d of the circuit board 57 via the second substrate side terminal 522 of the connection member 52. Further, actually, one end of the ground wire 93 is connected to the second connection terminal 52 b of the connection member 52, and is connected to the output signal terminal 57 d of the circuit board 57 via the second substrate side terminal 522 of the connection member 52.

  In the pressure detection device 20 of the pressure detection system 1 of the present embodiment, the housing 60 that houses the piezoelectric element 33, the circuit board 57, the shielding body 70, and the like is disposed inside the negative electrode of the battery 100 via the internal combustion engine 10. 102 (grounded). On the other hand, inside the housing 60, the piezoelectric element 33 and the circuit board 57 are housed inside to electrically shield them from the outside, and also function as a grounding system for the piezoelectric element 33 and the circuit board 57. The shielding body 70 to be connected is connected (grounded) to the negative electrode 102 of the battery 100 via the connection cable 90 (ground line 93) and the control device 80. In the pressure detection device 20, the casing 60 and the shielding body 70 are insulated.

  The pressure detection device 20 of the present embodiment is attached to an internal combustion engine 10, and when the internal combustion engine 10 is mounted on an automobile, noise having a frequency on the order of kHz (hereinafter referred to as “kHz”) generated by a horn, a headlight, a wiper, or the like. Is referred to as low-frequency noise) enters the cylinder head 13 of the internal combustion engine 10. And in this Embodiment, since the housing | casing 60 comprised with the metal among the pressure detection apparatuses 20 is attached to the cylinder head 13 comprised with the metal, the low frequency noise which penetrate | invaded the cylinder head 13 is the following. It also propagates to the housing 60 of the pressure detection device 20.

  Here, in the pressure detection device 20 of the present embodiment, the housing 60 and the positive and negative paths from the piezoelectric element 33 to the circuit board 57 are electrically insulated. For this reason, the low frequency noise propagated from the cylinder head 13 to the housing 60 of the pressure detection device 20 is not easily transmitted to the circuit board 57. As a result, the fluctuation (fluctuation) of the ground potential in the circuit board 57 due to the low frequency noise is suppressed, and the fluctuation (fluctuation) of the output signal output from the circuit board 57 can be reduced. Become.

  Further, when the internal combustion engine 10 of the present embodiment is mounted on an automobile, radio waves with a frequency on the order of MHz, which are usually used in mobile phones, radios, televisions, etc., fly around the automobile. When this radio wave is applied to the circuit board 57 provided in the pressure detection device 20, noise with a frequency on the order of MHz (hereinafter referred to as high frequency noise) is generated on the circuit board 57.

  Here, in the present embodiment, the circuit board 57 is covered (accommodated) using the metal accommodating member 56 constituting the shielding body 70. For this reason, the radio wave irradiated to the pressure detection device 20 from the outside is blocked by the shielding body 70 including the housing member 56, and is difficult to reach the circuit board 57. As a result, the fluctuation (fluctuation) of the ground potential in the circuit board 57 due to the high frequency noise is suppressed, and the fluctuation (fluctuation) of the output signal output from the circuit board 57 can be reduced. .

  In the present embodiment, since the shielding body 70 also serves as a negative path, the configuration of the pressure detection device 20 is simplified compared to the case where the shielding body 70 and the negative path are provided separately. can do.

[First Modification of Electrical Connection Structure of Pressure Detection System]
FIG. 9 is a diagram for explaining a first modification of the electrical connection structure of the pressure detection system 1.
In the example shown in FIG. 9, the connection relationship inside the pressure detection device 20, the connection relationship inside the control device 80, the connection relationship between the pressure detection device 20 and the internal combustion engine 10, and the internal combustion engine 10 and the control device 80, The connection relationship with the battery 100 is the same as that described with reference to FIG.

  However, in the example shown in FIG. 9, the connection cable 90 does not include the ground wire 93, and one end of the drain wire 94 provided on the connection cable 90 is not the internal combustion engine 10 but the circuit board 57 in the pressure detection device 20. The point connected to the output ground terminal 57e and the point that the other end of the drain wire 94 is connected to the ground terminal 80c of the control device 80 instead of the device housing 83 of the control device 80 are shown in FIG. Different from the example shown.

  Also in the pressure detection system 1 shown in FIG. 9, similarly to the case shown in FIG. 8, the fluctuation (variation) of the output signal due to the intrusion of the low frequency noise and the high frequency noise from the outside to the circuit board 57 is reduced. It becomes possible to make it. In particular, in the example shown in FIG. 9, the potential of the shielding portion 95 connected (contacted) with the drain wire 94 in the connection cable 90 is the potential of the shielding body 70 provided in the pressure detection device 20 (the ground potential of the pressure detection device 20). ). For this reason, as shown in FIG. 8, by connecting one end of the drain wire 94 to the internal combustion engine 10, the potential of the shielding portion 95 is made common with the potential of the internal combustion engine 10 where low frequency noise may exist. Thus, low-frequency noise is hardly superimposed on the output signal in the transmission line 92.

  In addition, the pressure detection system 1 shown in FIG. 9 has an advantage that the number of core wires constituting the connection cable 90 can be reduced (3 wires → 2 wires) as compared with the configuration shown in FIG.

[Second Modification of Electrical Connection Structure of Pressure Detection System]
FIG. 10 is a diagram for explaining a second modification of the electrical connection structure of the pressure detection system 1.
In the example shown in FIG. 10, the connection relationship inside the pressure detection device 20, the connection relationship inside the control device 80, the connection relationship between the pressure detection device 20 and the internal combustion engine 10, and the internal combustion engine 10 and the control device 80, The connection relationship with the battery 100 is the same as that described with reference to FIG.

  However, in the example shown in FIG. 10, one end of the drain wire 94 provided in the connection cable 90 is connected to the shielding body 70 in the pressure detection device 20 instead of the internal combustion engine 10. Is different.

  Also in the pressure detection system 1 shown in FIG. 10, similarly to the case shown in FIG. 8, the fluctuation (variation) of the output signal caused by the low frequency noise and the high frequency noise entering the circuit board 57 from the outside is reduced. It becomes possible to make it. In particular, in the example shown in FIG. 10, the potential of the shielding portion 95 connected (contacted) with the drain wire 94 in the connection cable 90 is the potential of the shielding body 70 provided in the pressure detection device 20 (the ground potential of the pressure detection device 20). ). For this reason, as shown in FIG. 8, by connecting one end of the drain wire 94 to the internal combustion engine 10, the potential of the shielding portion 95 is made common with the potential of the internal combustion engine 10 where low frequency noise may exist. Thus, low-frequency noise is hardly superimposed on the output signal in the transmission line 92.

  Further, in the pressure detection system 1 shown in FIG. 10, compared to the configuration shown in FIG. 8, there are two ground systems (a ground line 93 and a drain wire 94) that connect the pressure detection device 20 and the control device 80. Therefore, even if one of the ground wire 93 and the drain wire 94 is disconnected, the common ground of the pressure detection device 20 and the control device 80 can be maintained in the remaining wires. This makes it possible to increase system redundancy.

[Third Modification of Electrical Connection Structure of Pressure Detection System]
FIG. 11 is a diagram for explaining a third modification of the electrical connection structure of the pressure detection system 1.
In the example shown in FIG. 11, the connection relationship within each device and between each device is basically the same as that described in FIG.

  However, in the example illustrated in FIG. 11, the pressure detection device 20 further includes a capacitor 573 (an example of a direct current suppression unit) connected to the output ground terminal 57 e and the shielding body 70, as illustrated in FIG. 10. Different from the example. In this example, the capacitor 573 is attached to the circuit board 57, but it may be attached to a part different from the circuit board 57.

  Also in the pressure detection system 1 shown in FIG. 11, as in the case shown in FIG. 8, the fluctuation (variation) of the output signal caused by the intrusion of the low frequency noise and the high frequency noise from the outside to the circuit board 57 is reduced. It becomes possible to make it. Further, in the pressure detection system 1 shown in FIG. 11, as in the case shown in FIG. 10, the potential of the shielding portion 95 connected (contacted) with the drain wire 94 in the connection cable 90 is changed to the shielding provided in the pressure detection device 20. It can be made common with the potential of the body 70 (the ground potential of the pressure detection device 20). For this reason, as shown in FIG. 8, by connecting one end of the drain wire 94 to the internal combustion engine 10, the potential of the shielding portion 95 is made common with the potential of the internal combustion engine 10 where low frequency noise may exist. Thus, low-frequency noise is hardly superimposed on the output signal in the transmission line 92.

  Further, as described above, in the pressure detection system 1 shown in FIG. 10, since there are two ground systems (the ground wire 93 and the drain wire 94) that connect the pressure detection device 20 and the control device 80, one of them is disconnected. Even in the state, common ground can be maintained by using other lines. However, even if the ground wire 93 is disconnected, for example, a current flows through the supply line 91 and the drain wire 94, so that it is impossible to detect that the ground wire 93 is disconnected. On the other hand, in the example shown in FIG. 11, in the pressure detection device 20, the shielding body 70 and the output ground terminal 57 e to which one end of the ground wire 93 is connected are connected via a capacitor 573. In this manner, when a DC voltage is applied between the power transmission terminal 80a and the ground terminal 80c in the control device 80 under a situation where the ground line 93 is not disconnected, the supply line 91 and the ground A direct current flows through the line 93. On the other hand, when a DC voltage is applied between the power transmission terminal 80a and the ground terminal 80c in the situation where the ground line 93 is disconnected, the disconnected ground line 93 is connected to the ground line 93. DC current does not flow, and since the capacitor 573 is present, no DC current flows through the drain wire 94 that is not disconnected. Therefore, when the pressure detection device 20 is provided with the capacitor 573, it is possible to detect the disconnection of the ground wire 93 depending on whether or not a direct current is applied.

  Further, in the example shown in FIG. 11, there are two grounding systems (grounding wire 93 and drain wire 94) that connect the pressure detection device 20 and the control device 80 as in the case shown in FIG. 10. For this reason, even when the ground wire 93 and the drain wire 94 are disconnected, the common ground can be maintained in the remaining wires, and the redundancy of the system can be increased.

  Here, in the example shown in FIG. 11, the capacitor 573 is used as the direct current suppression unit. However, the present invention is not limited to this. For example, a diode having the cathode on the output ground terminal 57 e side may be used.

[Others]
In the present embodiment, the casing 60 of the pressure detection device 20 is made of a conductive metal material. You may make it comprise with material. In this case, it is not necessary to insulate the housing 60 and the shielding body 70 via various insulating members (the insulating plate 34, the fourth insulating ring 44, and the fifth insulating ring 45) and the air gap.

  Further, in the present embodiment, the shielding element 70 covers (accommodates) the piezoelectric element 33, the positive path, and the circuit board 57, but covers (accommodates) at least a part of the circuit board 57. If so, an effect of reducing noise is produced compared to a case where the circuit board 57 is not covered (not accommodated).

  Here, in the present embodiment, the circuit board 57 is covered (accommodated) using the cylindrical accommodating member 56, but the present invention is not limited to this, and the accommodating member 56 is, for example, a metal A metal braid or the like braided may be used.

  Furthermore, in the present embodiment, the drain wire 94 provided in the connection cable 90 is grounded at both ends, but the present invention is not limited to this and may be grounded at one end. However, when the drain wire 94 is grounded at both ends, it is easier to suppress intrusion of noise into the circuit board 57 than when the drain wire 94 is grounded at one end.

  Furthermore, in the present embodiment, the pressure detection device 20 that detects the combustion pressure of the internal combustion engine 10 using the piezoelectric element 33 has been described as an example, but the present invention is not limited to this. For example, you may apply to the detection apparatus which detects various physical quantities, such as temperature, humidity, or a flow volume.

DESCRIPTION OF SYMBOLS 1 ... Pressure detection system, 10 ... Internal combustion engine, 20 ... Pressure detection apparatus, 30 ... Detection part, 31 ... Front end side housing | casing 32 ... Diaphragm head, 33 ... Piezoelectric element, 34 ... Insulating plate, 35 ... End electrode member, 36 ... rear end electrode member, 37 ... first pressure member, 38 ... second pressure member, 39 ... support member, 40 ... insulating pipe, 41 ... first insulating ring, 42 ... second insulating ring, 43 ... third Insulating ring, 44 ... 4th insulating ring, 45 ... 5th insulating ring, 50 ... processing part, 51 ... rear end side housing, 52 ... connecting member, 53 ... conducting member, 54 ... covering member, 55 ... buffer member, 56 ... Housing member, 57 ... Circuit board, 58 ... Holding member, 60 ... Housing, 70 ... Shielding body, 80 ... Control device, 81 ... Power supply unit, 82 ... ECU (Engine Control Unit), 83 ... Device housing, 90 ... Connection cable, 100 ... Battery

Claims (6)

A detecting element for detecting a change in physical quantity;
A processing circuit for performing electrical processing on a detection signal output from the detection element;
A conductive member that is electrically conductive and is disposed so as to cover at least a part of the processing circuit, and is connected to the ground of the processing circuit;
A housing that houses the detection element, the processing circuit, and the conductive member, and is electrically insulated from the detection element, the processing circuit, and the conductive member ;
A detection apparatus comprising: a direct current suppression unit that connects a ground of the processing circuit and the conductive member while suppressing energization of direct current . The ground of the processing circuit and the ground of the detection element are electrically connected,
The detection device according to claim 1, wherein the conductive member is disposed so as to cover the processing circuit and the detection element. A detecting element for detecting a change in physical quantity;
A processing circuit for performing electrical processing on a detection signal output from the detection element;
A first housing that is electrically conductive and is disposed to accommodate at least a portion of the processing circuit and is connected to a ground of the processing circuit;
A second housing having electrical conductivity and containing the first housing;
Disposed between and has an insulating property of the first housing and the second housing, and a electrically insulating insulating member and said first casing and said second casing,
The detection apparatus, wherein the second casing has higher conductivity than the first casing, and the first casing has higher acid resistance than the second casing . 4. The detection according to claim 3 , further comprising another insulating member that is disposed between the second housing and the detection element and electrically insulates the second housing from the detection element. 5. apparatus. A detection element that detects a change in physical quantity; a processing circuit that electrically processes a detection signal output from the detection element; and a conductive circuit that is disposed so as to cover at least a part of the processing circuit. A conductive member connected to the ground of the processing circuit, the detection element, the processing circuit, and the conductive member are accommodated, and electrically insulated from the detection element, the processing circuit, and the conductive member, and grounded A detection device including a casing mounted in contact with a conductor , a direct current suppression unit that connects the ground of the processing circuit and the conductive member while suppressing energization of direct current ;
A supply line for supplying a power supply voltage to the processing circuit, a transmission line for transmitting an output signal output from the processing circuit, and a ground line for connecting to the conductive member or the ground of the processing circuit And connected to the conductor in a system different from the system via the ground line, and supplies the power supply voltage to the detection device and is input from the detection device. And a supply / processing device for processing the output signal. A detection element that detects a change in physical quantity, a processing circuit that performs electrical processing on a detection signal output from the detection element, and is arranged to have conductivity and accommodate at least a part of the processing circuit; A first housing connected to the ground of the processing circuit; a second housing that is conductive and contains the first housing; and is mounted in contact with a grounded conductor; is disposed between the insulating and has and the first housing and the second housing, viewed including an insulating member for electrically insulating the said first casing and said second casing, the A second housing having a higher conductivity than the first housing, the first housing having a higher acid resistance than the second housing ;
A supply line for supplying a power supply voltage to the processing circuit; a transmission line for transmitting an output signal output from the processing circuit; and the ground for the first casing or the processing circuit. Connected to the detection device via a ground line and connected to the conductor in a system different from the system via the ground wire, supplying the power supply voltage to the detection device and from the detection device A detection system including a supply / processing device for processing an input output signal.

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