JPH0323550Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The present invention is a signal output system that detects pressure changes in the cylinder of an internal combustion engine due to fuel injection, combustion, knocking, etc., which is caused by compressive strain of a piezoelectric element plate. This invention relates to a pressure sensor that detects pressure.

<Prior art> As this type of pressure sensor, laminated members such as a piezoelectric element plate and a pressure transmission rod are housed in a stacked manner in a mounting hole of a mounting bracket to be installed in the cylinder of an internal combustion engine. The sensing end protrudes from the mounting bracket, and the sensing end is connected to a metal diaphragm that covers the tip of the mounting bracket, and pressure fluctuations acting on the sensing end of the pressure transmission rod cause compressive strain in the piezoelectric element plate. There is a device that generates a charge and extracts it as an output signal to detect the pressure fluctuation.

<Problems to be solved by the invention> By the way, as shown in FIG. 3, in the case of a laminate a consisting of a conventional laminate member b such as a piezoelectric element plate and a pressure transmission rod, it is difficult to process and form the laminate member b. Since there is a limit to the degree of flatness and orthogonality of the laminated surface f, it is not necessarily uniform. For this reason, as exaggeratedly shown in the figure, uneven contact occurs between each laminated member b, and the pressure on the piezoelectric element plate is uneven, resulting in variations in characteristics and defects due to uneven pressure, reducing durability. This was the cause of such problems.

The present invention aims to eliminate the above drawbacks.

<Means for Solving the Problems> In the pressure sensor having the above-mentioned basic configuration, the present invention applies low-temperature wax to the required laminated surfaces of laminated members such as piezoelectric element plates and pressure transmission rods, and A laminate is formed by later applying heat treatment and integrating the materials.
The laminate is housed in the mounting hole.

Examples of low-temperature wax include solder and silver wax.

<Function> The laminated members are bonded together through low-temperature wax. Therefore, even if the laminated surfaces of the laminated members have poor flatness or orthogonality, they can be laminated densely. Therefore, pressure on the piezoelectric element plate acts evenly over its entire surface.

<Example> FIG. 1 shows an embodiment of the present invention.

A cylindrical mounting bracket 1, which has a threaded portion 2 for screwing into a cylinder block on its narrow circumferential surface, has a through hole 3 in its center that extends in the longitudinal direction and extends to its tip. . The through hole 3 has
The inner cylinder 4 is open at the lower end and has an insertion hole 5 for the lead wire x formed at the upper end. A female screw 6 is formed on the inner peripheral surface of the lower part of the inner cylinder 4. In addition, a mounting collar 7 is formed on the lower circumferential surface of the inner cylinder 4.
By welding the mounting collar 7 to the lower end of the mounting bracket 1, the inner cylinder 4 is partially fixed to the mounting bracket 1. Note that this fixing is performed after the laminate 8 and the like, which will be described later, are attached.

The inside of the inner tube 4 constitutes a mounting hole, and a laminate 8, which is a main part of the present invention, is housed in the mounting hole on the side of the inner section 4a.

The laminate 8 includes an insulator 9, a packing 10, a spacer 11, an annular conductive cylinder piece 12, a terminal plate 13,
It consists of a plate-shaped piezoelectric element plate 14 made of a material such as PZT with electrodes formed on the upper and lower main surfaces, a terminal plate 15, and a pressure transmission rod 16 arranged in a laminated manner, and the area around the connecting part is heated. It is covered with a shrink tube 17. The laminate 8 is made up of the heat shrinkable tube 17
It is insulated from the inner cylinder 4 by. Further, the laminate 8
Inside, a connection path z is formed on the terminal board 13, and within the connection path z, a lead wire x is connected to a connection rising tongue piece 13a formed on the terminal board 13.

The lead wire x is pulled out to the outside of the connection path z and connected to the cable y, and the piezoelectric element plate 1
The upper surface electrode 4 is electrically connected to the cable y.

The laminate 8 having the above structure, as shown in FIG.
Low-temperature wax such as silver wax is applied to the laminated surface f of each laminated member such as the piezoelectric element plate 14, and each member is bonded, and then heat treated to solidify and integrate into a laminated form. It is something.

At this time, the laminated surface f of the alumina-based member
The laminated surface f of the piezoelectric element plate 14 is subjected to a sputter electrode formation of molybdenum metal or electroless plating of nickel. Also, at this time, the piezoelectric element plate 14 is made of lithium niobate (Tc=1200
The use of single crystals such as lithium tantalate (Tc = 700°C), quartz (Tc = 500°C), etc. is effective because it allows the use of wax materials in the high temperature range.

The pressure transmitting rod 16 of the laminated body 8 has a detection end having a smaller diameter from the center, and an abutment jaw surface 18 is formed at the stepped portion between the top and the smaller diameter portion.

After the laminate 8 is attached to the inner cylinder 4, the inner cylinder 4 is provided with the following:
A cylindrical screw 19 is screwed along the female screw 6. In the tightened state, the upper end of the cylindrical screw 19 is pressed against the abutment jaw surface 18 side of the pressure transmission rod 16 via the annular packing, and each laminated member inside the inner cylinder 4 is pressed against the inner surface 4a. pressed to the side. Further, in this state, the pressure transmission rod 16 passes through the cylindrical screw 19 and projects its sensing end further downward than the inside of the inner cylinder 4. A rising side wall 21 is provided at the lower end.
Diaphragm 2 which is externally fitted and fixed to the lower end of mounting bracket 1
0 is concatenated.

The pressure sensor having the above configuration includes a mounting bracket 1.
The screw portion 2 of the cylinder block is attached to the cylinder block, and the mounting bracket 1 is mounted with the tip thereof exposed inside the cylinder. When pressure fluctuation occurs in the cylinder in this installed state, pressure acts on the sensing end of the pressure transmission rod 16. Therefore, due to the pressure, the piezoelectric element plate 1
4 is compressed toward the inner surface 4a, and an electric charge is generated due to the compressive strain. This charge is taken out as a voltage via the lead wire x and the cable y.

In the above embodiment, the present invention is applied to a case where the inner cylinder 4 is used and the inside of the cylinder is used as the mounting hole. The laminate 8 may be inserted into the mounting hole.

<Effects of the invention> As mentioned above, in the present invention, since low-temperature wax is supplied to the laminated surface f of each laminated member to laminate the laminated members, the problem arises due to the limit of the molding accuracy of each member. Gaps between the laminated surfaces are filled, mismatches such as uneven contact are eliminated, and the pressure from the pressure transmission rod acts evenly on the piezoelectric element plate, making it possible to obtain stable output characteristics. Furthermore, since each member is joined face-to-face, there is no damage to the member due to uneven pressure, and there are excellent effects such as improved durability.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional side view of one embodiment of the present invention;
The figure is a longitudinal sectional side view of the laminate 8, and FIG. 3 is a longitudinal sectional side view of the laminate a having a conventional structure. 1; mounting bracket, 8; laminate, 11; piezoelectric element plate, 16; pressure transmission rod, 17; heat shrink tube,
20; diaphragm, f; laminated surface, g; low temperature wax,
x; Lead wire.

Claims (1)

[Scope of Claim for Utility Model Registration] A piezoelectric element plate, a pressure transmission rod, etc. are housed in a stacked manner in a mounting hole of a mounting bracket to be attached to a cylinder of an internal combustion engine, and the sensing end of the pressure transmission rod is connected from the mounting bracket. In the case where the detection end is connected to a metal diaphragm that covers the tip of the mounting bracket, low-temperature wax is applied to the required laminated surfaces of the piezoelectric element plate, pressure transmission rod, etc., and heat treatment is performed after the lamination. A pressure sensor for an internal combustion engine, characterized in that a laminate is formed by integrating the laminate, and the laminate is housed in the mounting hole.