JPH06313746A - Pressure sensor - Google Patents

Abstract

PURPOSE:To prevent the disconnection of the signal output wire of a piezoelectric element by connecting the projecting edge of the conductive electrode rod of a relay electrode body mounted on a piezoelectric plate or a terminal plate connected to it to an external electrical path. CONSTITUTION:The title pressure sensor is mounted on a cylinder head, a piezoelectric element 11 is distorted due to pressure fluctuation generated inside, and then a signal voltage is generated and pressure fluctuation is detected. A relay electrode body 13 is mounted on the piezoelectric element 11 directly or is mounted on a terminal plate 12 electrically connected to it. The electrode body 13 consists of a cylindrical retention body 14 and a conductive electrode rod 15 and is constituted with the rod 15 press-fitted in an engagement hole at the center of the retention body 14. Then, the projecting edge of the electrode rod 15 is connected to an external electrical path via a lead wire 27. Since the electrode rod 15 is press-fit into the engagement hole, a full tensile strength can be attained, thus preventing them from being separated. Also, since the retention body 14 can be formed separately, the mounting surface can be fully flattened and electrical connection can be secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor for detecting a change in internal pressure of a cylinder of an internal combustion engine with a piezoelectric element.

[0002]

2. Description of the Related Art At least a piezoelectric element plate and a pressure transmission rod are housed inside a metal shell mounted on a cylinder of an internal combustion engine, and a detection end of the pressure transmission rod is projected from the metal shell, and the detection end is attached to the metal shell. A pressure sensor which is connected to a metal diaphragm covering the tip of the is known from Japanese Utility Model Publication No. 3-38675. This pressure sensor is mounted by mounting the screw part on the cylinder head and exposing the tip of the metal shell inside the cylinder. When pressure fluctuations occur in the cylinder in this mounted state, pressure acts on the tip of the pressure transmission rod via the diaphragm. Therefore, the piezoelectric element plate is compressed by the pressure, and the compression strain generates electric charges.

[0003]

As disclosed in Japanese Utility Model Laid-Open No. 63-78237, a terminal plate electrically connected to a rear surface electrode of a piezoelectric element plate is provided with two strips in the radial direction up to the center thereof. Cut the cutting lines and bend the insides of both the cutting lines almost vertically to project the connecting tongue pieces from the center of the terminal plate, and resistance-weld the lead wires to the rising tongue pieces. By doing so, the signal output generated in the piezoelectric element is taken out.

However, the tensile strength of the rising tongue is not sufficient, and therefore, when the lead wire is connected to the metal shell, a tensile force may be applied and the rising tongue may be broken to break the wire. It was

It is an object of the present invention to provide a pressure sensor provided with a connecting means which does not have such drawbacks.

[0006]

SUMMARY OF THE INVENTION According to the present invention, at least a mounting surface and an inner surface of a fitting hole are electrically conductive, and a conductive cylindrical holder is provided. A relay electrode body including a conductive electrode rod is mounted on the piezoelectric element plate or a terminal plate electrically connected to the piezoelectric element plate, and an electrical take-out end for connecting the protruding end of the conductive electrode rod to an external electric circuit. It is characterized by doing so.

[0007]

The conductive electrode rod is electrically connected to the electrode of the piezoelectric element plate through the conductive cylindrical holder. In this structure, since the conductive electrode rod is press-fitted into the fitting hole, sufficient tensile strength is achieved. Therefore, there is no separation when connecting a conducting member such as a lead wire to the electrode rod. Further, since the cylindrical holder is separately formed, it is possible to provide the mounting surface with flatness. Therefore, the electrical connection between the lead wire and the piezoelectric element plate is ensured through this relay electrode.

Further, it is possible to connect to the external electric circuit with a connector by utilizing the conductive electrode rod.

[0009]

FIG. 1 shows an example of a pressure sensor attached to a cylinder head to which the present invention is applied.

Reference numeral 1 denotes a metal shell having a bolt structure in which a male screw 2 to be screwed into a cylinder head is formed on the outer periphery of a lower end portion 1a, and a hexagonal portion 3 adapted to a tightening tool such as a spanner is formed on the outer periphery of the upper end portion 1b. The shaft hole 4 is formed in the inside. The shaft hole 4 penetrates the center of the metal shell 1 in the vertical direction, and is constituted by a small-diameter mounting hole 4a, a medium-diameter mounting hole 4b, and a large-diameter mounting hole 4c which are connected to each other.

A pressure transmitting rod 9 is inserted into the mounting hole 4a on the smaller diameter side, and its lower end is welded to a metal diaphragm 6 joined so as to hermetically seal the end face of the lower end 1a of the metal shell 1. There is. Further, a disc spring 7 is provided between the step portion of the mounting holes 4a, 4b of the metal shell 1 and the pressure transmission rod 9 so as to support the large diameter portion of the pressure transmission rod 9. It absorbs the strain caused by the difference in thermal expansion and the difference in heat transfer between the components, and the stress caused by the elongation due to the tightening torque in the male screw portion.

In the mounting hole 4b, a terminal plate 10, a piezoelectric element 11 having electrodes formed on the front and back surfaces, a terminal plate 12, a relay electrode body 13 and an abutting member 16 according to the present invention are sequentially laminated. To be done. These laminated bodies 8 are surrounded by an insulating pipe 18 and insulated from the metal shell 1. An electrode rod 15 is projected from the relay electrode body 13.

A spherical surface is formed at the upper end of the contact member 16. Further, a holding metal fitting 20 having a conical concave surface 21 that can uniformly contact the spherical surface of the contact member 16 is mounted in the large-diameter mounting hole 4c.

A hole is formed in the center of each of the abutting member 16 and the pressing member 20, and the electrode rod 15 of the relay electrode body 13 penetrates the hole in the assembled state. The electrode rod 15 is insulated from the holding metal fitting 20 by an insulating tube 22. Then, the cylindrical connecting end 28a formed on the lead wire 27 is externally fitted to the electrode rod 15 protruding from the pressing fitting 20 and joined by caulking or welding.

Further, the press fitting 20 is provided with the contact member 16
The lower peripheral surface is pressed against the conical surface of the
It is fixed to the step portion between b and the large-diameter mounting hole 4c by resistance welding.

On the other hand, a beak-shaped metal cap 33 is fitted in the mouth portion of the mounting hole 4c and is welded with argon. Inside the metal cap 33, a ceramic stopper 35 is provided.
The signal carrying cable 36 (external electric path) connected to an external device is inserted into the stopper 35, and the protruding end of the cable 36 is fitted with the cylindrical connecting end 28b formed at the upper end of the lead wire 27. Then, they are joined by crimping or welding. Then, the electrode rod 1 is connected via the lead wire 27.
5 and the cable 36 are connected, and the signal output of the piezoelectric element plate 11 can be taken out from the cable 36 to the outside.

The pressure sensor having such a structure is mounted by screwing it into a mounting screw hole of the cylinder head, and the piezoelectric element 11 is distorted by a pressure fluctuation generated in the cylinder during combustion or knocking, and the distortion causes a signal. A voltage is generated so that the pressure fluctuation can be detected.

Next, the structure of the relay electrode body 13 according to the main part of the present invention will be described.

As shown in FIGS. 2 and 3, the relay electrode body 13
Is composed of a cylindrical holder 14 made of a metal material and a conductive electrode rod 15, and the conductive electrode rod 15 is press-fitted (see FIG. 3) into a fitting hole 14a penetrating the center of the holder 14. To be done. In this case, the cylindrical holder 14 and the electrode rod 15 have substantially the same coefficient of thermal expansion and prevent loosening due to temperature change. When the cylindrical holder 14 is made of a metal material as described above, the abutting member 16 is made of alumina, in order to prevent electrical connection between the cylindrical holder 14 and the retainer 20. It is made of a ceramic material such as zirconia to achieve sufficient compressive strength and insulation. Further, the upper and lower surfaces of the cylindrical holder 14 and the lower surface of the contact member 16 are subjected to surface treatment such as lapping in order to prevent an unbalanced load on the piezoelectric element plate 11 so as to obtain flatness. To

Although it is possible to form the relay electrode body 13 integrally, it is possible to separate the relay electrode body 13 by the cylindrical holder 14 and the electrode rod 15 in this way. Since the cylindrical holder 14 has a simple shape, the molding accuracy can be improved and the upper and lower surfaces can be machined flat.

On the other hand, the cylindrical holder 14 includes the piezoelectric element plate 11 or the terminal plate 12 and the electrode rod 15 connected thereto.
And serves as a relay conductor for electrically connecting the mounting surface contacting at least the terminal plate 12 and the inner surface of the fitting hole 14a into which the electrode rod 15 is press-fitted. As long as it has sex,

Here, in FIGS. 4 and 5, the conductive cylindrical holding body 14 is made of a ceramic material as a base body to serve also as the abutting member 16, and the mounting surface thereof and the inner surface of the fitting hole 14a. A conductive layer 14b is formed by coating on the above to ensure conductivity. Then, the electrode rod 15 is press-fitted and connected to the conductive layer 14b, whereby the relay electrode body 13 is configured. In this structure, the conductive layer 14b is
Metallization with a noble metal such as platinum, gold, silver, palladium, nickel is suitable. For example, it can be formed by calcining a ceramic substrate, applying platinum paste, and calcining at 1500 ° C. When the cylindrical holder 14 is made of a ceramic material as described above, there are advantages that the heat resistance is good and the thermal expansion is small.

In the above structure, as shown in FIG.
A cylindrical connector 40 is interposed between the electrode rod 15 protruding upward from the holding metal fitting 20 and the protruding end of the signal carrying cable 36 from the stopper 35, and the upper end of the 40 is connected to the cable 36.
By externally fitting and caulking and further fitting the lower end of the 40 onto the electrode rod 15, the cable 36 and the electrode rod 15 can be electrically connected without using a lead wire. Therefore, there is an advantage that the wiring process is simplified and a disconnection accident at the time of connection or subsequent occurrence can be avoided and a stable electrical connection can be secured.

As shown in FIG. 6, 1 to 4 slits are formed in the lower end of the cylindrical connector 40 in the longitudinal direction so as to have elasticity in the radial direction and electrically connect to the electrode rod 15. May be.

[0025]

As described above, the present invention employs the relay electrode body 13 including the conductive cylindrical holder 14 and the conductive electrode rod 15 press-fitted into the fitting hole 14a. 13 is mounted on the piezoelectric element plate 11 directly or on the terminal plate 12 electrically connected thereto, and the projecting end of the conductive electrode rod 15 is connected to the external electric circuit. Therefore, the conductive electrode rod 15 is Since it is press-fitted into the fitting hole 14a, sufficient tensile strength is achieved, and there is no separation when connecting a conductive member such as a lead wire to the electrode rod 15. Further, since the cylindrical holding body 14 is separately formed, it is possible to provide a flatness on the mounting surface thereof. Therefore, the electrical connection between the external electric path and the piezoelectric element plate 11 can be achieved through the relay electrode 13. The connection will be secured. Furthermore, it becomes possible to apply a direct connector connection to the conductive electrode rod 15,
By omitting the lead wire connection, there are excellent effects such as easy connection processing.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a pressure sensor showing an embodiment of the present invention.

FIG. 2 is an exploded perspective view of a relay electrode body 13.

FIG. 3 is a vertical sectional side view showing a procedure for assembling the relay electrode body 13.

FIG. 4 is a vertical sectional side view showing a procedure for assembling a relay electrode body 13 having another configuration.

FIG. 5 is a vertical sectional side view of a pressure sensor according to another embodiment of the present invention.

FIG. 6 is a perspective view showing an example of a cylindrical connector 40.

[Explanation of reference numerals] 1 metal shell 9 pressure transmission rod 11 piezoelectric element 12 terminal plate 13 relay electrode body 14 cylindrical holder 14a fitting hole 14b conductive layer 15 electrode rod 16 abutting member 20 holding metal fitting 40 connector

Claims (2)

[Claims] 1. A metal shell mounted on a cylinder of an internal combustion engine, in which at least a piezoelectric element plate and a pressure transmission rod are housed, a detection end of the pressure transmission rod is projected from the metal shell, and the detection end is attached to the metal shell. In a pressure sensor that is connected to a metal diaphragm that covers the tip of, the conductive cylindrical holding body having at least the mounting surface and the inner surface of the fitting hole having conductivity, and the fitting hole penetrating to the center of the holding body. A relay electrode body consisting of a press-fitted conductive electrode rod is mounted on the piezoelectric element plate or a terminal plate electrically connected to the piezoelectric element plate, and an electrical connection for connecting the protruding end of the conductive electrode rod to an external electric circuit. A pressure sensor for an internal combustion engine, characterized in that the pressure sensor is used as a target take-out end. 2. The conductive cylindrical holder is formed by forming a base body of a ceramic material and coating a conductive layer on the mounting surface and the inner surface of the fitting hole. A pressure sensor for an internal combustion engine as described.