JPH06213119A - Piezoelectric ignition device - Google Patents

Abstract

PURPOSE:To secure ignition and improve reliability of ignition time by generating pressure by ignition signals, generating high voltage by the pressure, increasing battery voltage by the ignition signal to charge battery, and superimposing the charged voltage on the high voltage. CONSTITUTION:When an ignition signal generator 7 outputs an ignition signal, a drive circuit 5 synchronously outputs actuator drive pulses to a piezoelectric ignition section 6. Thus, a piezoelectric actuator generates high pressure in synchronization with the ignition signals and makes piezoelectric body in the piezoelectric ignition section 6 generate high voltage. Also, the ignition signal is inputted in a DC/DC converter 8 to increase battery voltage as negative voltage, and the increased voltage charges a capacitor 10. The charged voltage is superimposed on output voltage of piezoelectric body in the piezoelectric ignition section 6 via a diode 9 and applied to an ignition plug 1 as ignition plug applied voltage.

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 in particular, it is possible to secure discharge energy and improve reliability of ignition timing. The present invention relates to a piezoelectric ignition device capable of

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing the structure of a conventional piezoelectric ignition device in a partial section, and FIG. 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. A piezoelectric actuator 3 for generating a voltage, a housing 4 for fixedly supporting the piezoelectric body 2 and the piezoelectric actuator 3, and a drive circuit 5 connected to the piezoelectric actuator 3 for applying a voltage as electric energy to the piezoelectric actuator 3. The piezoelectric body 2 and the piezoelectric actuator 3 are configured as a piezoelectric ignition unit 6 in the housing 4.

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. 3, two such piezoelectric bodies 2 are used facing each other, and these facing surfaces 2a are used.
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 the applied voltage
a generates the same strain (elongation or contraction), and this strain is limited 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.

The drive circuit 5 drives the piezoelectric actuator 3 to generate an actuator drive pulse for generating a high voltage in the piezoelectric body 2. As shown in FIG. 4, this actuator drive pulse is generated in synchronization with the falling edge of the rectangular ignition signal (A). The piezoelectric actuator 3 driven by this actuator drive pulse (B) causes the piezoelectric body 2 to generate a high-voltage piezoelectric output voltage (C), 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 of the piezoelectric actuator 3 is supported and fixed by the fixing screw 4b.

[0009]

However, the discharge by the piezoelectric body 2 is capacitive discharge, the discharge energy is small, and the discharge time is short. Therefore, it is not possible to perform sufficient ignition only with such discharge energy,
Therefore, in the past, a DC voltage of several Kv has been superimposed to supplement this discharge energy.
If such a DC voltage is constantly applied to the ignition plug 1, there is a risk that ignition will be performed at a timing other than the ignition timing by the ignition signal, and there is a problem that reliability of the ignition timing is impaired.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to secure discharge energy and perform reliable ignition, and also to improve reliability of ignition timing. The purpose is to get the device.

[0011]

A piezoelectric ignition device according to the present invention comprises a pressure generating means for generating a pressure based on an ignition signal, and a piezoelectric body for generating a high voltage by receiving pressure from the pressure generating means. Boosting means for boosting the battery voltage in synchronization with the ignition signal, charging means for charging the battery voltage boosted by the boosting means, and charging voltage charged by the charging means are generated by the piezoelectric body. And a voltage superimposing means for superimposing the high voltage.

[0012]

When the pressure generating means generates pressure on the basis of the ignition signal, the piezoelectric body receives stress to generate polarized charge, thereby generating a high voltage. This high voltage is superposed on the battery voltage which is boosted by the boosting means and further charged by the charging means, becomes sufficient discharge energy, and is applied to the spark plug.

[0013]

【Example】

Example 1. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a piezoelectric ignition device according to the present invention, and FIG. 2 is a time chart showing a voltage of a main part of the piezoelectric ignition device. As shown in FIG. 1, the piezoelectric ignition device of the present invention includes an ignition signal generator 7 for generating an ignition signal, a drive circuit 5 connected to the ignition signal generator 7, and a drive circuit 5 connected to the drive circuit 5. The piezoelectric ignition unit 6, the DC / DC converter 8 connected to the ignition signal generator 7, and the DC / DC converter 8 side between the output side of the piezoelectric ignition unit 6 and the output side of the DC / DC converter 8. And a capacitor 10 connected between the cathode of the diode 9 and the ground.
The ignition plug 1 is connected to the output side of the piezoelectric ignition unit 6. As shown in FIG. 3, the piezoelectric ignition unit 6 is composed of a piezoelectric body 2, a piezoelectric actuator 3, and a housing 5 supporting these.

With the above construction, when the ignition signal generator 7 generates the ignition signal (A) as shown in FIG. 2, the drive circuit 5 outputs the actuator drive pulse (B) shown in FIG. 4 in synchronization with this. The piezoelectric actuator 3 which outputs to the piezoelectric ignition unit 6 and receives this drive pulse (B) generates a large pressure in synchronization with the ignition signal. This pressure is applied to the piezoelectric body 2 of the piezoelectric ignition unit 6, and the piezoelectric body 2 generates a high voltage as the piezoelectric body output voltage (C).

On the other hand, DC / DC receiving the ignition signal (A)
The converter 8 boosts a battery (not shown) voltage as a negative voltage in synchronization with this ignition signal, and the boosted voltage is charged in the capacitor 10 as a capacitor charging voltage (D). Then, the piezoelectric output voltage (C) and the capacitor charging voltage (D) are superimposed via the diode 9 and applied to the ignition plug 1 as the ignition plug application voltage (E).

The ignition plug applied voltage (E) is at a high voltage for a long time as compared with the piezoelectric output voltage (C) shown in FIG. 3, and a large discharge power can be given to the ignition plug 1. As well as being able to perform reliable ignition, the timing of applying a high voltage to the spark plug 1 is synchronized with the ignition signal, so that discharge may be performed at a timing other than the ignition timing as in the conventional case. To be prevented.

In the above configuration, the ignition signal generator 7,
The drive circuit 5 and the piezoelectric actuator 5 compose pressure generating means in the present invention, the DC / DC converter 8 composes boosting means in the invention, the capacitor 10 composes charging means in the invention, the diode 9 and the capacitor. Reference numeral 10 constitutes the voltage superimposing means in the present invention.

[0018]

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 based on the ignition signal and the high voltage generated by the pressure generated by the pressure generating means are generated. The generated piezoelectric body, boosting means for boosting the battery voltage in synchronization with the ignition signal, charging means for charging the battery voltage boosted by the boosting means, and charging voltage charged by the charging means Since the voltage superimposing means for superimposing the high voltage generated by the piezoelectric body is provided, discharge energy can be secured, reliable ignition can be performed, and reliability of ignition timing can be enhanced. Play.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a time chart showing a voltage of a main part of the first embodiment.

FIG. 3 is a configuration diagram showing a configuration of a conventional piezoelectric ignition device in a partial cross section.

FIG. 4 is a time chart showing a voltage of a main part of a conventional piezoelectric ignition device.

[Explanation of symbols]

 2 Piezoelectric body 3 Piezoelectric actuator 5 Drive circuit 6 Piezoelectric ignition unit 8 DC / DC converter 9 Diode 10 Capacitor

Claims (1)

[Claims] 1. A pressure generating means for generating a pressure based on an ignition signal, a piezoelectric body for generating a high voltage in response to the pressure generated by the pressure generating means, and a booster for boosting a battery voltage in synchronization with the ignition signal. Means, charging means for charging the battery voltage boosted by the boosting means, and voltage superposition means for superposing the charging voltage charged by the charging means on the high voltage generated by the piezoelectric body. A piezoelectric ignition device characterized by the above.