JPS61244079A - Apparatus for driving piezoelectric actuator - Google Patents

Abstract

PURPOSE:To avoid deterioration of characteristics caused by depolarization even if a high electric field is applied by a method wherein electrodes are provided on both sides of the polarizing direction of a piezoelectric slipping effect type actuator element and a DC source is connected so as to apply an electric field with the same direction as the polarization to the element. CONSTITUTION:Two terminals of a driving source 30 are connected to electrodes 22 and 23 formed on a piezoelectric slipping effect type actuator 11. An electric field formed between the electrodes 22 and 23 deforms the piezoelectric slipping effect type actuator 11 and creates a fine displacement. A subsidiary source 60 is a DC source for preventing depolarization and its two terminals are connected to electrodes 41 and 42 formed on the piezoelectric slipping effect type actuator 11 and an electric field formed between the electrodes 41 and 42 has the same direction as the polarization of the element. With this constitution, the depolarization of the element can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an actuator drive device using a piezoelectric solid effect.

[Technical background of the invention and its problems]

Actuators that utilize the piezoelectric effect are well known, and in recent years in particular have become smaller and lighter, consume less power, do not generate heat, and do not generate magnetic fields, so they have little effect on other electronic components. Another feature is that voltage control is easy.

For example, a laminated effect actuator in which a plurality of disc-shaped piezoelectric ceramic elements are laminated together and a field is applied to each element in the thickness direction KN to generate a minute displacement is used as an actuator for minute positioning in semiconductor manufacturing equipment. In addition to this, it is also used as a beam spot control element of a laser device. Further, actuators using piezoelectric transverse effects such as conimorph, bimorph, and multimorph, which are formed by laminating a plurality of rectangular piezoelectric plates, are also widely used. In other words, it is known that when two rectangular plate-shaped piezoelectric plates (t-2) are bonded together and an electric field is applied so that one plate expands and the other plate contracts, the rectangular plates bend in the longitudinal direction. Piezoelectric relays and auto-tracking actuators for helical scan video recorders that use such bending as an actuator are known.

On the other hand, the piezoelectric effect has a flattening effect in addition to the above-mentioned effects. The piezoelectric constant of the piezoelectric actuator, which determines the piezoelectric actuator's sensitivity (displacement amount/applied voltage), is thicker than that of the vertical effect type, and as an actuator that moves parallel on a plane, it has a higher piezoelectric constant than the vertical effect. It is expected to be used as a solid actuator because of its simple structure. This effect means that when a piezoelectric element is polarized and an electric field is applied in a direction perpendicular to the polarization direction, the piezoelectric element will be polarized in the same direction in the thickness direction (in this case, in the same direction as the applied electric field). The piezoelectric element deforms in this direction. FIG. 2 is a cross-sectional view of a piezoelectric element for explaining the Beshi effect of piezoelectricity. This causes deformation of the piezoelectric element. Figure (5) shows that the electric field between electrodes 20 and 21 is 1
□%, and Figure (B) shows the state of the element while an electric field is being applied, showing that the surface of the electrode 20 is moving relative to the surface of the electrode 210. In actuators using the piezoelectric vector effect.

The direction of the electric field during polarization is perpendicular to the polarization axis and the direction of the electric field when a small displacement occurs, so when a large electric field is applied,
There is a risk of depolarization. For example, in a piezoelectric Pesci effect actuator made of T-96 material manufactured by Toshiba Ceramics, when a DC or AC electric field of lkv/m is applied as a driving electric field, depolarization occurs after about 1° and the amount of displacement decreases. It has been confirmed that this decreases. This depolarization differs depending on conditions such as the coercive electric field voltage of the material used and the electric field applied during driving, but generally it uses the pinch piezoelectric effect and the horizontal effect, which tend to occur with materials with low coercive electric field voltage. Compared to actuators that use piezoelectric sliding, it is difficult to use them under high electric fields, and in the example of T-96 material mentioned above, an electric field of only about 100 m can be applied. Actuators that use piezoelectric effects have large limitations on the electric field that can be applied, making it difficult to generate large displacements, which is the original characteristic of actuators that use piezoelectric effects.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and it is an object of the present invention to provide a piezoelectric actuator drive device that eliminates any deterioration of characteristics due to depolarization even when applied with a large electric field.

[Summary of the invention]

The present invention provides an electrode on the end face of the piezoelectric solid-effect actuator element in a direction perpendicular to the direction of the driving electric field.
F. A piezoelectric actuator driving device characterized in that electrodes are provided on both end faces of the actuator element in the polarization direction, and a DC power source is connected to the electrodes so that an electric field in the same direction as that during polarization is applied to the electrodes.

A piezoelectric Bef effect type actuator is made of a single layer or a plurality of piezoelectric materials having a desired shape and made of a piezoelectric material subjected to a single polarization treatment. In general, piezoelectric materials used in piezoelectric solid-effect actuators have a piezoelectric constant d
For example, PZT (Pb(Zr,Ti)Os)-based two-component materials,
Pb(Yt/z, Nbx/z)03 (Pb, 5r
)TtOa PbZrO3 system, P b (Co 1/
2 t Wl/2 ) 03 P b (T j t
Z r ) 03 series, pb (Mg3A, Nb%) 03
Pb('r+, Zr)03 series Pb(Sb%,
Nb Rhino 03-P b (T' t zr) 03 series, P
b CZn5AtNb'pf) 03 series Pb (T
i, Zr) 03 series* P b (Zn%, Nbm Os
There are three-component materials such as P b (Lad, Nb%) 03 series and the like. In addition, compositions near the morphotropic phase transition exhibit good properties.

In general, when a large driving electric field is applied to a piezoelectric shear effect type actuator using a piezoelectric material, the piezoelectric constant dl that generates the shear effect of the piezoelectric material increases.
s and the coupling coefficient k15 decrease, and the amount of displacement to be generated becomes smaller. In other words, it is known that piezoelectricity decreases due to depolarization.

This has also been confirmed in the research conducted by the present inventors.

FIG. 3 shows the relationship between the piezoelectric constant of the element and the magnitude of the applied electric field when an alternating current electric field is applied to a piezoelectric solid effect type element made of T-96 material manufactured by Toshiba Ceramics.

In the figure, this characteristic is irreversible j), 1. The piezoelectric constant of the element to which an electric field of more than 0 kv/w is applied decreases by more than 60% of its initial value, and the characteristics do not recover even after the electric field is removed.As a method to suppress this depolarization, the polarization axis of the piezoelectric slip effect element It is possible to prevent depolarization by applying an electric field in the same direction as . Figure 1 shows an example of a piezoelectric solid-effect actuator that makes it possible to apply an electric field in the same direction as the polarization axis.The auxiliary power supply 60 is a DC power supply for preventing depolarization, and the electrodes 41 and 42 are connected to the elements. According to research by the present inventors, in the circuit configuration shown in FIG. 1, even if a large driving electric field is applied as shown in FIG. It was found that there was almost no deterioration of the piezoelectric constant of the element.

By using the driving method of the present invention as described above, a piezoelectric solid effect type actuator with a large displacement amount and excellent reliability can be realized.

[Embodiments of the invention]

Examples of the present invention will be described in detail below. FIG. 1 is a schematic diagram of a driving circuit for a piezoelectric Bayer effect actuator using the piezoelectric actuator driving method according to the present invention.

The drive power supply 30 consists of a function generator that generates a desired waveform and a DC amplifier with a maximum generated voltage of ±200V.The DC amplifier used in this example generates a voltage of DC to 5ooV (fxooV up to z). The two terminals of the drive power source 300 are connected to electrodes 22 and 23 formed on the piezoelectric solid effect actuator 11, and the electric field generated by these causes the piezoelectric slip effect actuator to deform and cause minute displacement. The auxiliary power source 60 is a DC power source for preventing depolarization.The two terminals of the auxiliary power source 60 are electrodes 41 and 42 formed on the piezoelectric solid effect actuator 11.
In order to prevent depolarization of the p1 element, the electric field due to K is applied in the same direction as the polarization direction of the element.

Here, the piezoelectric solid effect type actuator 11 is made of T-96 material manufactured by Toshiba Ceramics and is laminated with 5 m x 5 m x 0.2 ft.

Are the electrodes people? It is formed by vapor deposition. ±2oo to the piezoelectric actuator connected as described above.

When a voltage of 30 Hz was applied and the characteristics over time were investigated, no decrease in the amount of displacement was observed.

As described above, as a method for preventing deterioration due to depolarization in a piezoelectric slip effect type actuator, depolarization could be prevented by providing an electrode that coincides with the polarization axis of the actuator and further applying an electric field between the electrodes.

[Brief explanation of the drawing]

Fig. 1 is a basic principle diagram and a circuit diagram showing an embodiment for explaining the present invention in detail, Fig. 2 is a structural sectional view of a piezoelectric slip effect type actuator, and Figs. 3 and 4 are piezoelectric solid effect actuators. FIG. 3 is a characteristic diagram showing how the piezoelectric constant d15 of the element changes with respect to the applied electric field of the shaped actuator. 11...Piezoelectric SpeQ effect type actuator 30...
Drive power source 60... Auxiliary power source agent Patent attorney Kensuke Norichika (and one other person) Figure 1 Figure 2

Claims (1)

[Claims] A piezoelectric slip effect actuator, a pair of electrodes provided on an end face in the direction of the polarization axis of the piezoelectric slip effect actuator, and a DC power supply for applying a DC voltage in the same direction as the polarization direction to the electrodes. Features a piezoelectric actuator drive device.