JPH05236764A - Power supply for driving piezoelectric actuator - Google Patents

Abstract

PURPOSE:To provide a power supply for driving a piezoelectric actuator in which insulation resistance between internal electrodes can be prevented from lowering even when a voltage is applied on a piezoelectric actuator under high humidity environment. CONSTITUTION:In the power supply for driving a piezoelectric actuator to produce a displacement or generating force substantially proportional to the magnitude of applying voltage, an AC voltage component is superposed on a DC voltage component to produce the applying voltage wherein the AC voltage component is set lower than 1% of the DC voltage component while having magnitude proportional to that of the DC voltage component and the frequency of the AC voltage component is set higher than 20kHz.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator for converting electric energy into mechanical energy such as displacement or force.
The present invention relates to a power supply device for driving a computer.

[0002]

2. Description of the Related Art Conventionally, precision positioning devices and precision X-
As a Y-table actuator, a voice coil motor
Electromagnetic actuators such as motors and pulse motors have been used, but in recent years, piezoelectric actuators, which are superior to the electromagnetic actuators in terms of positioning accuracy, response speed, power consumption, etc., are being used. ..

Since this piezoelectric actuator can obtain a displacement amount or a generated force substantially proportional to the magnitude of the applied voltage, the magnitude of the output DC voltage is controlled as a power source device for driving the piezoelectric actuator. Those that can be used are generally used. Further, since the piezoelectric actuator is electrically regarded as a capacitance element, the voltage applied to the piezoelectric actuator causes the piezoelectric actuator to have a charge amount.
There is also used a power supply device capable of discharging the electric charge or returning the charge amount to the power supply side.

Piezoelectric actuators are roughly classified into two types, a laminated type and a bimorph type.

The laminated type piezoelectric actuator has a high displacement accuracy and a large generating force, and the bimorph type piezoelectric actuator has a large displacement amount. A laminated type is often used as an actuator for a precision positioning device and a precision XY table.

In the laminated piezoelectric actuator, piezoelectric ceramic plates and internal electrode plates are alternately laminated, external electrodes are arranged on both sides of these plates, and the external surfaces of these external electrodes are made of organic resin. It is covered with a film. A conventional power supply device for driving a piezoelectric actuator applies a DC voltage to an external electrode of the piezoelectric actuator.

[0007]

However, in the conventional power source device for driving the piezoelectric actuator, when a direct current voltage is applied to the laminated piezoelectric actuator for a long time in a high humidity environment, the piezoelectric actuator is not used. Even if the side surface of the actuator is covered with an organic resin film, it is difficult to prevent the intrusion of water into the piezoelectric actuator, so the insulation resistance between the internal electrodes is reduced, and it is extremely short. There is a problem of reaching.

It is presumed that the cause of this is a migration due to ionization of silver contained as a component of the internal electrode due to water permeating through the organic resin film of the exterior and adhering to the exposed surface of the internal electrode.

That is, in the positive electrode of the internal electrode exposed on the surface of the piezoelectric actuator, the reaction represented by the following chemical formula 1 proceeds.

[0010]

[Chemical 1]

At the negative electrode of the internal electrode exposed on the surface of the piezoelectric actuator, the reaction represented by the following chemical formula 2 proceeds.

[0012]

[Chemical 2]

As these reactions proceed, silver grows in a dendritic manner on the surface-exposed internal electrode portion on the negative side, and the substantial distance between the positive electrode and the negative electrode of the surface-exposed internal electrode is shortened. The insulation resistance between the electrodes decreases.

Therefore, a technical object of the present invention is to provide a piezoelectric actuator capable of preventing a decrease in insulation resistance between internal electrodes even when a voltage is applied to the piezoelectric actuator in a high humidity environment. It is to provide a power supply device for driving the motor.

[0015]

According to the present invention, in a power supply device for driving a piezoelectric actuator, which can obtain a displacement amount or a generated force substantially proportional to the magnitude of an applied voltage, the applied voltage is a DC voltage. An AC voltage component is superposed on the component, and the AC voltage component is 1% or less of the DC voltage component, has a magnitude proportional to the DC voltage component, and has a frequency of 20 KHz or more. A power supply device for driving the actuator is obtained.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

As shown in FIG. 1, a driving power supply device 1 of the present invention applies a voltage to a piezoelectric actuator 2. In this piezoelectric actuator 2, piezoelectric ceramic plates 21 and internal electrode plates 22 are alternately laminated, and external electrodes 23 are arranged on both sides of the piezoelectric ceramic plates 21 and internal electrode plates 22.
The outer surface of No. 3 is coated with an organic resin film 24. A glass insulating member 25 is inserted between every other joint between the piezoelectric ceramic plate 21 and the internal electrode plate 22 between the piezoelectric ceramic plate 21 and the internal electrode plate 22. The external electrode 23
Are connected to the output terminals of the driving power supply device 1 by the conductors 26, respectively.

The voltage applied to the piezoelectric actuator 2 of the driving power supply device 1 is obtained by superimposing an AC voltage component on a DC voltage component, and the AC voltage component is less than 1% of the DC voltage component and the DC voltage component is less than 1%. The size is proportional to the component, and the frequency is 20 KHz or higher.

When an AC voltage of a magnitude that does not cause polarization reversal is applied to the piezoelectric actuator 2, the relationship between the applied voltage and the displacement amount is not linear but has hysteresis as shown in FIG. That is, when an AC voltage is applied to the piezoelectric actuator 2, there is a loss of energy, and part of it is consumed as heat energy. The voltage applied to the piezoelectric actuator 2 of the driving power supply device 1 is
If the AC voltage component is superimposed on the DC voltage component,
The piezoelectric actuator 2 generates heat. When the piezoelectric actuator 2 generates heat and its temperature becomes slightly higher than the ambient temperature, it is possible to prevent the intrusion of water.

When an AC voltage is applied to the piezoelectric actuator 2, the piezoelectric actuator 2 vibrates almost in proportion to the magnitude of the voltage. However, if the AC voltage component is sufficiently smaller than the DC voltage component, the vibration does not hinder the function of the piezoelectric actuator 2.

Next, the experimental results for confirming the effect of the present invention will be described.

FIG. 3 shows an output waveform of the power supply device 1 for driving the piezoelectric actuator 2 according to the embodiment of the present invention. The output waveform shown in FIG. 3 is obtained by superimposing a DC voltage component of 100 V and an AC voltage component of 25 KHz at 0.2 V. For comparison, FIG. 4 shows an output waveform of a conventional power supply device for driving a piezoelectric actuator. The output waveform shown in FIG. 4 indicates a DC voltage of 100V.

The piezoelectric ceramic plate 21 has a cross section of 5 ×
A resin film 24 having a length of 5 mm and a length of 18 mm is used.
When a voltage having the output waveform shown in FIG. 3 is applied to the laminated piezoelectric actuator 2 formed of epoxy resin (experimental example of the present invention) and when a voltage having the output waveform shown in FIG. 4 is applied ( The results shown in Table 1 below were obtained in Comparative Example). It should be noted that each characteristic is measured 5 minutes after the temperature change stops after the application of the voltage and becomes a steady state, and the temperature is measured by adhering and fixing a thermocouple to the resin film 24 of the piezoelectric actuator 2. It was measured.

[0024]

[Table 1]

Further, the samples shown in Table 1 were subjected to long-term aging under the same conditions in a constant temperature and high humidity test tank under the environmental conditions of a temperature of 40 ° C. and a relative humidity of 90%. The results shown in are obtained.

[0026]

[Table 2]

From Table 1, by using the power supply device for driving the piezoelectric actuator of the present invention, the displacement amount is the same as that of the conventional example (comparative example), but the temperature of the piezoelectric actuator is 17 ° C. You can see that it is getting higher. As a result, as is clear from Table 2, by using the power supply device for driving the piezoelectric actuator of the present invention, the piezoelectric actuator was used for a long-term aging in a constant temperature and high humidity environment (comparative example). The failure rate is very small compared to the example) and the life is extended.

[0028]

According to the power supply device for driving a piezoelectric actuator of the present invention, even if a voltage is applied to the piezoelectric actuator in a high humidity environment and used, the insulation resistance between the internal electrodes is prevented from lowering. be able to.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram for explaining the present invention.

FIG. 3 is a diagram showing an output waveform in one embodiment of the present invention.

FIG. 4 is a diagram showing an example of output waveforms in a conventional power supply device for driving a piezoelectric actuator.

[Explanation of symbols]

 1 Power Supply Device for Driving 2 Piezoelectric Actuator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kyoshin Kanbara 6-3-20 Tsunashima East, Kohoku Ward, Yokohama City, Kanagawa Prefecture NF Co., Ltd. Circuit design block (72) Inventor Sadayuki Takahashi 5-7 Shiba, Minato-ku, Tokyo No. 1 within NEC Corporation

Claims (1)

[Claims] 1. In a power supply device for driving a piezoelectric actuator, which can obtain a displacement amount or a generated force substantially proportional to the magnitude of an applied voltage, the applied voltage has an alternating voltage component superimposed on a direct current voltage component. A power supply device for driving a piezoelectric actuator, wherein the AC voltage component is 1% or less of the DC voltage component, has a magnitude proportional to the DC voltage component, and has a frequency of 20 KHz or more.