JPH06213438A - Piezoelectric igniter - Google Patents

Abstract

PURPOSE:To set a voltage generated from a piezoelectric element substantially to a constant highest voltage irrespective of a temperature and to prevent deterioration of it. CONSTITUTION:Initial strains of a housing 4, pressure generating means 3 and a piezoelectric element 2 based on a temperature change are regulated by a temperature compensating member 6 thereby to set an initial pressure to be received by the element 2 within an initial pressure setting range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ignition device for igniting an internal combustion engine by utilizing a high voltage generated by a piezoelectric body, and more particularly, to make the voltage generated by the piezoelectric body constant regardless of temperature. The present invention relates to a piezoelectric ignition device capable of

[0002]

2. Description of the Related Art FIG. 2 is a sectional view showing the structure of a conventional piezoelectric ignition device, and FIG. 3 is a time chart showing the voltage of the main part of the piezoelectric ignition device. A conventional piezoelectric ignition device is connected to a spark plug 1 and converts a strain energy into an electric energy to generate a voltage, and a piezoelectric body 2 adjacent to the piezoelectric body 2, which converts the electric energy into a strain energy to generate a pressure. And a housing for fixing and holding the piezoelectric actuator 3 and the piezoelectric body 2 so that the strain is regulated to generate a pressure and the pressure is applied to the piezoelectric body 2. 4, a drive circuit 5 for applying a voltage as electric energy to the piezoelectric actuator 3 is connected to the piezoelectric actuator 3.

The piezoelectric body 2 uses the principle that when a piezoelectric element such as PZT (lead zirconate titanate) receives a pressure, it generates a voltage by generating a polarization charge, and is applied. A voltage represented by the following equation is generated with respect to the pressure F.

V = gLF / S

Here, g is the voltage output constant, L is the length of the piezoelectric body, and S is the cross-sectional area of the piezoelectric body. In FIG. 2, two such piezoelectric bodies 2 are used facing each other, and these facing surfaces 2a
Is provided with an electrode 2b connected to the spark plug 1 so that an electric charge (negative electric charge) of the same sign is generated, and the end surface 2c on the opposite side of the electrode 2b is the ground electrode side.

The piezoelectric actuator 3 has a laminated structure in which a plurality of thin piezoelectric elements 3a are electrically provided in parallel with each other with electrodes 3b arranged alternately in positive and negative, and is applied to one piezoelectric element. All piezoelectric elements 3 depending on
a generates the same strain (elongation or contraction), and the strain is regulated by the housing 4 and the piezoelectric body 2 so that a large pressure is applied to the piezoelectric body 2. At both ends of the piezoelectric actuator 3, a metal body 3c is provided which serves as a ground electrode and protects a plurality of thin piezoelectric elements 3a.

As shown in FIG. 3, the drive circuit 5 generates an actuator drive pulse (A) for driving the piezoelectric actuator 3 to generate a high voltage in the piezoelectric body 2. The actuator drive pulse (A) is generated in synchronization with the falling edge of a rectangular ignition signal (not shown). The piezoelectric actuator 3 driven by this actuator drive pulse (A) causes the piezoelectric body 2 to generate a high-voltage piezoelectric output voltage (B), which causes the spark plug 1 to spark.

The housing 4 has a cylindrical outer shape and has a hole 4a provided along the central axis thereof. After the piezoelectric body 2 and the piezoelectric actuator 3 are inserted into the hole 4a sequentially,
The metal body 3c forming the rear end portion of the piezoelectric actuator 3 is pressed and supported and fixed by the fixing screw 4b. With the configuration described above, the piezoelectric actuator 3 has its distortion regulated by the fixing screw 4b of the housing 4 and the piezoelectric body 2, and the generated pressure can be applied to the piezoelectric body 2.

By the way, when the piezoelectric actuator 3 and the piezoelectric body 2 are pressed and supported as described above, an initial pressure is applied to the piezoelectric body 2. FIG. 4 is a diagram showing the relationship between the initial pressure and the output voltage of the piezoelectric body 2. As can be seen from this figure, the output voltage of the piezoelectric body 2 has a constant relationship with the initial pressure, and when the initial pressure is within a certain range, the output voltage becomes maximum, and the piezoelectric ignition device can be efficiently used. be able to. Further, if the initial pressure is set to exceed this range, the piezoelectric body 2 will be deteriorated. Therefore, conventionally, the above-mentioned pressure range is set as the initial pressure setting range, and the piezoelectric actuator 3 and the piezoelectric body 2 are set to the housing 4.
At the time of mounting the piezoelectric actuator 2, the piezoelectric actuator 3 is pressed and supported and fixedly held so that the initial pressure applied to the piezoelectric body 2 is within the above-mentioned initial pressure setting range.

[0010]

By the way, in the conventional piezoelectric ignition device, the housing 4, the piezoelectric actuator 3, and the piezoelectric body 2 have different coefficients of thermal expansion, and they are provided without consideration. Has been. Therefore, when the ambient temperature of the piezoelectric igniter changes, the housing 4, the piezoelectric actuator 3, and the piezoelectric body 2 respectively expand or contract due to the temperature change, and the initial strain of the piezoelectric body 2 that is restricted is restricted. That is, the initial pressure received by the piezoelectric body 2 changes and deviates from the above-mentioned initial pressure setting range. As a result, the piezoelectric body output generated at the time of ignition by the piezoelectric body 2 decreases, and reliable ignition cannot be performed, Body 2
There was a problem that it deteriorated.

The present invention has been made to solve the above-mentioned problems, and the voltage generated by the piezoelectric body can be set to a substantially constant maximum voltage regardless of temperature, and its deterioration can be prevented. The purpose is to obtain a piezoelectric igniter that can.

[0012]

SUMMARY OF THE INVENTION A piezoelectric ignition device according to the present invention has a pressure generating means for generating a pressure by controlling a strain generated by receiving a voltage, and a high pressure receiving a pressure by the pressure generating means. A housing for fixing and holding the pressure generating means and the piezoelectric body so that the piezoelectric body for generating the voltage and the strain of the pressure generating means are regulated to generate the pressure and the pressure is applied to the piezoelectric body. And a temperature compensating member which is provided in the housing and makes the initial pressure applied to the piezoelectric body constant regardless of the temperature.

[0013]

In the piezoelectric ignition device according to the present invention, the initial distortion of the housing, the pressure generating means, and the piezoelectric body due to the temperature change is adjusted by the temperature compensating member so that the piezoelectric body receives the initial strain even if the temperature changes. The pressure can be kept within the initial pressure setting range.

[0014]

【Example】

Example 1. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional configuration diagram showing a piezoelectric ignition device according to the present invention. In the figure, the same symbols as those in FIG. 2 indicate the same components as those in FIG. In this embodiment, the temperature compensation member 6 is provided between the back wall 4c of the hole 4a of the housing 4 and the back end 2c-1 of the piezoelectric body 2. For the temperature compensating member 6, duralumin having a coefficient of thermal expansion β (= 23 × 10 ⁻⁶ ) is used for iron having a coefficient of thermal expansion α (= 11 × 10 ⁻⁶ ) of the housing 4.

With the above configuration, the temperature compensating member 6 expands and contracts in response to expansion and contraction of the housing 4 due to temperature changes, and as a result, the initial pressure applied to the piezoelectric body 2 can be made substantially constant. Therefore, the initial pressure can be kept within the initial pressure setting range shown in FIG. 4 regardless of the change in ambient temperature.

In this embodiment, the piezoelectric actuator 3 constitutes the pressure generating means of the present invention.

[0017]

As is apparent from the above structure, according to the piezoelectric ignition device of the present invention, the pressure generating means for generating the pressure by restricting the strain generated by receiving the voltage, and the pressure generating means. And a piezoelectric body that generates a high voltage by receiving pressure from the pressure generating means, and that generates pressure by regulating the strain of the pressure generating means and that this pressure is applied to the piezoelectric body. Since a housing for fixedly holding and a temperature compensating member provided on the housing for making the initial pressure applied to the piezoelectric body constant irrespective of the temperature, the piezoelectric body receives the initial pressure even if a temperature change occurs. The pressure can be kept within the initial pressure setting range, and therefore, the voltage generated by the piezoelectric body can be set to a substantially constant maximum voltage regardless of the temperature, and its deterioration can be prevented. .

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional configuration diagram showing a configuration of a conventional piezoelectric ignition device.

FIG. 3 is a time chart showing a voltage of a main part of a conventional piezoelectric ignition device.

FIG. 4 is a diagram showing an initial pressure and an output voltage of a piezoelectric body.

[Explanation of symbols]

 2 Piezoelectric body 3 Piezoelectric actuator 4 Housing 6 Temperature compensation member

Claims (1)

[Claims] 1. A pressure generating means for generating a pressure by restricting strain generated by receiving a voltage, a piezoelectric body for generating a high voltage by receiving a pressure by the pressure generating means, and a pressure generating means for the pressure generating means. A casing for fixing and holding the pressure generating means and the piezoelectric body so that the strain is regulated to generate the pressure and the pressure is applied to the piezoelectric body, and the casing is provided in the casing and is applied to the piezoelectric body. A piezoelectric ignition device, comprising: a temperature compensating member that keeps the initial pressure constant regardless of the temperature.