JPS6222029A - Notking sensor for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve workability and reliability by calcining the resistance for lowering the impedance of piezoelectric ceramics in the piezoelectric ceramics themselves and forming these in a body and eliminating the external fitting work of the resistance. CONSTITUTION:Filmy electrodes 31a and 31b are formed by applying, for instance, silver paste to both end faces of the cylindrical piezoelectric ceramics 3 and calcining these. Then, at the same time, the resistance 32 for lowering the impedance of the piezoelectric ceramics 3 is formed filmily by applying the resistance paste, for instance, paste-shaped cermet to the resistance and burning it in a state to connect the electrodes 31a and 31b. As a result, the workability is improved eliminating the external fitting work of the resistance with the inferior fitting workability and the control side is made easy and the reliability is improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a knocking sensor that is attached to an engine body (cylinder block, etc.) to detect vibrations in order to detect knocking in the combustion chamber of an internal combustion engine. .

<Prior Art> Examples of conventional knocking sensors include those shown in FIGS. 2 and 3.

To explain this, a pair of piezoelectric ceramics 3 with an electrode plate 2 sandwiched between them are placed at the bottom of a bottomed cylindrical housing 1.
A weight 4 for applying stress to the piezoelectric ceramic 3 due to vibration acceleration is fixed by tightening with a bolt 5. 6 is an insulator, and 7 is an electrode plate on the ground side.

A terminal 9 is attached to the opening of the housing 1 by caulking the edge of the opening to take out the electrical signal generated in the piezoelectric ceramic 3 from the output side electrode plate 2 via the lead wire 8. The connector 10 with the connector 10 is installed. 11 is a disc spring, and 12 is a heat-shrinkable insulating tube.

Such a knocking sensor is attached to a cylinder block or the like using a threaded portion 13 provided in a housing 1, and upon receiving the vibration, generates an electric signal in a piezoelectric ceramic 3 corresponding to the vibration acceleration, and this electric signal is transmitted to an external control unit. This control unit is designed to detect knocking vibrations (see Japanese Utility Model Application Publication No. 180427/1983).

Incidentally, such an abnormal state of the knocking sensor is expected to include disconnection of the output signal line such as the lead wire 8 from the piezoelectric ceramic 3, a short circuit of the signal line to the ground side, a short circuit to the power supply side, etc.

For this reason, a resistor is connected in parallel between the electrodes of the piezoelectric ceramic, which has infinite impedance in terms of direct current, and the voltage drop across the resistor is used to equivalently lower the direct current impedance of the piezoelectric ceramic, thereby preventing abnormalities. A device that can be detected has been proposed (see Japanese Utility Model Application Publication No. 58-26631).

That is, as shown in FIGS. 2 and 3, a resistor 14 is installed between the output side electrode plate 2 and the ground side electrode plate 7, and the circuit is as shown in FIG. 4. .

In this way, referring to FIG. 4, first, if the signal line S is normal, the output voltage V to the control unit side will be the voltage of the power supply ■. is divided by the resistor 15 and the resistor 14 to obtain a voltage v1. Next, when the signal vAS is disconnected, the output voltage V becomes the voltage v0 of the power supply. Further, when the signal line S is short-circuited to the power supply side or the ground side, the output voltage V becomes vo or zero, respectively. Therefore, all abnormalities can be detected at level 1.

<Problems to be Solved by the Invention> However, when a resistor is installed inside the sensor in order to reduce the impedance of the piezoelectric ceramic for the purpose of abnormality detection, conventionally the resistor was installed between the electrode plates. However, the workability was very poor (mainly because soldering is work, there was a problem in that it was difficult to manage the quality of the joints).

In view of these conventional problems, the present invention integrates a resistor for reducing the impedance of the piezoelectric ceramic into the piezoelectric ceramic, thereby improving workability, reliability, layout, etc. during assembly. The purpose is to achieve this goal.

<Means for Solving the Problems> In order to achieve the above object, the present invention fires electrodes on both end faces of a piezoelectric ceramic, and also fires a resistor in the form of connecting the electrodes on both end faces to the side faces of the piezoelectric ceramic. It is configured to do this.

<Function> In the above configuration, a resistor for reducing the impedance can be integrated into the piezoelectric ceramic, and workability can be improved by eliminating the need to attach an external resistor.
It is possible to improve reliability, improve layout, and reduce costs.

<Example>゛ An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows a piezoelectric ceramic according to the present invention.
For example, silver paste or nickel paste is applied to both end faces of the cylindrical piezoelectric ceramic 3 and fired to form the film-like electrodes 318.31b. At the same time, a resistive paste, such as a paste-like cermet (a mixture of metal and ceramic) is applied to a part of the side surface of the piezoelectric ceramic 3 to connect the electrodes 31a and 31b on both end surfaces.
By coating and firing, a film-like resistor 32 is formed.

If two such piezoelectric ceramics 3 are used and assembled as shown in FIG. 2, the circuit will be equivalent to that shown in FIG. 4 without using the external resistor 14, and functionally it will be the same as the conventional one. Since the same performance as that of 14 is obtained, and the external resistor 14 is eliminated, the installation work can be eliminated, workability is improved, reliability is improved, the layout can be simplified, and costs can be reduced. Further, since the external resistor 14 is not required, the shape of the electrode plate 2.7 can be simplified, and the electrode plate 7 on the ground side can also be omitted.

Although the example in which two piezoelectric ceramics 3 are used has been described above, it is also possible to use only one piezoelectric ceramic 3.

Furthermore, even when two resistors are used, at least one of them may be made of a piezoelectric ceramic with a fired resistor 32 as shown in FIG.

<Effects of the Invention> As explained above, according to the present invention, since the impedance lowering resistor of the piezoelectric ceramic is fired into the piezoelectric ceramic itself, an external resistor is eliminated, and the work of attaching the resistor can be eliminated. This not only improves performance, but also improves reliability, improves layout, and reduces costs.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a piezoelectric ceramic showing an embodiment of the present invention, and FIG. 2 is a sectional view of a knocking sensor showing a conventional example.
FIG. 3 is a sectional view taken along line mm in FIG. 2, and FIG. 4 is a circuit diagram of the knocking sensor. 1... Housing 2... Electrode plate 3... Piezoelectric ceramic 4... Weight 31a, 31b
...Electrode 32...Resistance patent applicant Japan Electronics Co., Ltd. Agent Patent attorney Fujio Sasashima Figure 1 1b Figure 2

Claims (1)

[Claims] A piezoelectric ceramic and a weight for applying stress to the piezoelectric ceramic by vibration acceleration are fastened and fixed to the bottom of a bottomed cylindrical housing that is attached to the engine body, and knock vibration is generated from the electric signal generated in the piezoelectric ceramic. A knocking sensor for an internal combustion engine that detects
A knocking device for internal combustion engines in which a resistor is connected in parallel between the electrodes of a piezoelectric ceramic, and the electrodes are fired on both end faces of the piezoelectric ceramic, and the resistor is fired with the electrodes on both end faces connected to the sides of the piezoelectric ceramic. sensor.