JPH05267741A - Piezoelectric actuator - Google Patents

Abstract

(57) [Abstract] [Purpose] A piezoelectric actuator using a bimorph plate formed by stacking piezoelectric plates with different polarization directions.
An object of the present invention is to provide a piezoelectric actuator that can be driven in an axial direction or a circumferential direction. A bimorph region 4 in which the polarization of the piezoelectric plate and the polarization of a polarization inversion layer 3 formed on one side of the piezoelectric plate point in opposite directions.
And an actuator body 6 in which an uninverted region 5 made of a piezoelectric plate whose polarization points in the same thickness direction is integrated,
Independent electrodes 71 and 72 are provided for the bimorph region 4 and the non-inverted region 5.
Configure on both sides of the.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator which can be driven in two axial directions by using a bimorph plate formed by superposing piezoelectric plates having different polarization directions.

Since piezoelectric actuators can be made smaller and lighter and do not emit sound, their application to optical switches and the like is being studied. For example, an optical switch is constructed by fixing one optical fiber on a piezoelectric actuator and two optical fibers on a fixing base.

That is, the end face of the optical fiber on the piezoelectric actuator is made to face the end face of one of the optical fibers on the fixed base, and when the piezoelectric actuator is driven, it is made to face the end face of the other optical fiber. You can switch the route.

However, the optical axes of the optical fibers facing each other may be displaced before and after the driving of the piezoelectric actuator due to temperature changes and the like. The light path can be switched by an actuator in one axis direction, but an actuator that can be driven in two axis directions is required to correct the optical axis.

Further, since the piezoelectric actuator is small and lightweight, it is being considered to be incorporated in the lens barrel of the lens for fine adjustment of the focus. However, in order to finely adjust the focus built into the lens barrel, an actuator that can be driven in the circumferential direction is required.

However, in the conventional piezoelectric actuator,
It is necessary to combine two in order to drive in the axial direction, and there is no advantage that the size and weight can be reduced. Therefore, there is a demand for the development of a piezoelectric actuator that can be driven biaxially or circumferentially by one unit.

[0007]

2. Description of the Related Art FIG. 4 is a side sectional view showing a conventional piezoelectric actuator. FIG. 4 (a) shows a laminated piezoelectric actuator that utilizes the piezoelectric vertical effect and includes a plurality of piezoelectric plates 1 and electrodes 2.
Are alternately laminated, and the electrodes 2 stacked via the piezoelectric plate 1 are connected so that driving voltages having different polarities are alternately applied in parallel.

On the other hand, the piezoelectric plates 1 sandwiched by the electrodes 2 are arranged so that their polarizations alternately point in opposite directions as indicated by arrows, and when a drive voltage is applied to the electrodes 2, they correspond to their polarities. Then, each piezoelectric plate 1 expands and contracts in the thickness direction, and the height of the actuator changes.

FIG. 4B shows a piezoelectric actuator using a bimorph plate, which is sandwiched between electrodes 2
Two piezoelectric plates 1 having one piezoelectric plate 1 and sandwiched between electrodes 2
Are stacked so that their respective polarizations point in opposite directions as indicated by arrows.

When a drive voltage is applied between the electrodes 2, one piezoelectric plate 1 expands according to the polarity of the drive voltage, but the other piezoelectric plate 1 contracts, and the free end of the bimorph plate whose one end is fixed is fixed. It moves upward or downward in the figure depending on the polarity of the applied drive voltage.

[0011]

However, all of the conventional piezoelectric actuators shown in FIG. 4 can be driven in one axis direction but cannot be driven in two axis directions. As a result, there is a problem in that two piezoelectric actuators are required for driving in the biaxial directions, which is against the reduction in size and weight.

An object of the present invention is to provide a piezoelectric actuator which can be driven biaxially or circumferentially by itself.

[0013]

FIG. 1 is a perspective view showing an actuator according to the present invention. Note that the same object is denoted by the same symbol throughout the drawings.

The above problem is caused by the polarization of the piezoelectric plate and the bimorph region 4 in which the polarization of the polarization inversion layer 3 formed on one side of the piezoelectric plate points in the opposite direction, and the non-inversion region composed of the piezoelectric plate in which the polarization points in the same thickness direction. This is achieved by the piezoelectric actuator of the present invention having an actuator body 6 in which 5 are integrated, and having independent electrodes 71 and 72 on both sides of the bimorph region 4 and the non-inverted region 5.

[0015]

In FIG. 1, the bimorph region in which the polarization of the piezoelectric plate and the polarization of the polarization inversion layer formed on one side of the piezoelectric plate point in opposite directions and the non-inverted region of the piezoelectric plate in which the polarization points in the same thickness direction are integrated. Has an actuator body that is
The piezoelectric actuator of the present invention, which has independent electrodes on both sides of the bimorph region and the non-inverted region, has a structure in which a driving voltage is applied to the electrodes in the bimorph region to move the free end in the thickness direction of the actuator body and A drive voltage can be applied to the electrodes in the region to move the free end in the length direction of the actuator body. That is, a single piezoelectric actuator that can be driven in two axial directions or in a circumferential direction can be realized.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 2 is a perspective view showing a modified example of the actuator according to the present invention, and FIG. 3 is a view for explaining the pyroelectric phenomenon.

In the actuator according to the present invention shown in FIG. 1, one end of an actuator body 6 made of LiNbO ₃ has a base 8
The bimorph region 4 formed on the free end side of the actuator body 6 is integrated with the non-inverted region 5 on the fixed end side.

In the bimorph region 4, a film of, for example, Ti is deposited on the surface of the actuator body 6 and heat-treated near the Curie point, so that the polarization direction is inverted to the middle of the thickness of the actuator body 6 as shown by the arrow. The polarization inversion layer 3 is formed.

Even if the entire actuator body 6 is heat-treated in the vicinity of the Curie point when the polarization inversion layer 3 of the bimorph region 4 is formed, in the non-inversion region 5 where the surface of the actuator body 6 is not coated with a film such as Ti. Polarization inversion layer 3
Is not formed.

Bimorph region 4 of actuator body 6
Independent electrodes 71 and 72 are formed on both surfaces of the non-inversion region 5 and the non-inversion region 5, respectively, and a drive voltage can be applied to the electrodes 71 and 72 from the outside through lead wires (not shown). ing.

As described above, the bimorph region in which the polarization of the piezoelectric plate and the polarization of the polarization inversion layer formed on one side of the piezoelectric plate point in opposite directions and the non-inverted region of the piezoelectric plate in which polarization points in the same thickness direction are integrated. A piezoelectric actuator of the present invention, which has an actuator body made into a matrix and has independent electrodes on both sides of a bimorph region and a non-inverted region, has a free end of the actuator body with a drive voltage applied to the electrode in the bimorph region. It is possible to move the free end in the length direction of the actuator main body while moving the actuator in the thickness direction and applying a drive voltage to the electrode in the non-inversion region. That is, a single piezoelectric actuator that can be driven in two axial directions or in a circumferential direction can be realized.

A piezoelectric actuator using a bimorph plate can displace the free end in any direction by switching the polarity of the drive voltage, and by changing the applied drive voltage, the amount of displacement at the free end can be adjusted freely. It is possible to control.

However, since it is necessary to apply a relatively high driving voltage between the electrodes, it is not suitable for, for example, a camera which is usually driven with a low voltage. Therefore, it is desired to realize a piezoelectric actuator that can be driven by applying a relatively low voltage even when driving only in one axis direction.

A modified example of the actuator according to the present invention shown in FIG. 2 uses a piezoelectric plate made of pyroelectric material such as LiNbO ₃ , LiTaO ₃ , and utilizes the pyroelectric effect of generating a relatively high voltage when heated. Has realized an actuator that can be driven at a low voltage.

That is, in FIG. 2, a modification of the present invention is LiNb.
One end of the actuator body 6 made of O ₃ is fixed to the base 8, and the bimorph region 4 formed on the free end side of the actuator body 6 is integrated with the non-inverted region 5 on the fixed end side.

In the bimorph region 4, a film of, for example, Ti is deposited on the surface of the actuator body 6 and heat-treated near the Curie point, so that the polarization direction is reversed to the middle of the thickness of the actuator body 6 as shown by the arrow. The polarization inversion layer 3 is formed.

An electrode 73 made of NiCr or the like for electrically connecting the bimorph region 4 and the non-inverted region 5 is provided on one surface of the actuator body 6, and a bimorph region 4 made of an ordinary conductive material is provided on the opposite surface. It comprises an electrode 74 which electrically connects the non-inverted regions 5.

The electrode 73 made of a thin film of NiCr or the like is used as a heating element in the non-inverted region 5 and a slit 75 is provided to increase the resistance value. By applying a driving voltage to both ends of the electrode 73 divided by the slit 75, the electrode 73 generates heat and the non-inverted region 5 is heated.

Pyroelectric materials such as LiNbO ₃ and LiTaO ₃ have a pyroelectric effect in which electric charges are generated when the temperature changes and a potential difference is generated between the two surfaces. As shown in Fig. 3 (a), when the temperature of the pyroelectric body is stable, the polarization of the pyroelectric body and the external floating charge are balanced and the potential difference cannot be detected.

However, if the temperature of the pyroelectric body changes, it is
As shown in (b), the polarization of the pyroelectric material fluctuates and the equilibrium state with the external stray charges is lost, and extra charges are generated. There is a large potential difference between them.

In the modification of the present invention, the electrodes formed on both sides of the bimorph region 4 are electrically connected to the electrodes on both sides of the non-inversion region 5, and the non-inversion region 5 is formed by the pyroelectric effect.
The electric charges generated on the both sides are collected by the electrodes on both sides thereof and applied to both sides of the bimorph region 4.

As described above, the bimorph region in which the polarization of the piezoelectric plate and the polarization of the polarization inversion layer formed on one side of the piezoelectric plate point in opposite directions, and the non-inverted region of the piezoelectric plate in which polarization points in the same thickness direction are integrated. The actuator body has an actuator body made of a conductive material, and an electrode made of a resistance material for electrically connecting the bimorph region and the non-inverted region and an electrode made of a conductive material for electrically connecting the bimorph region and the non-inverted region. The modified example of the piezoelectric actuator according to the present invention, which is formed on each of the two surfaces, can realize a piezoelectric actuator that can be driven by applying a relatively low voltage.

[0033]

As described above, according to the present invention, one piezoelectric actuator that can be driven biaxially or circumferentially,
Also, it is possible to provide a piezoelectric actuator that can be driven by applying a relatively low voltage.

[Brief description of drawings]

FIG. 1 is a perspective view showing an actuator according to the present invention.

FIG. 2 is a perspective view showing a modified example of the actuator according to the present invention.

FIG. 3 is a diagram for explaining a pyroelectric phenomenon.

FIG. 4 is a side sectional view showing a conventional piezoelectric actuator.

[Explanation of symbols]

 3 polarization inversion layer 4 bimorph region 5 non-inversion region 6 actuator body 8 base 71, 72, 73, 74 electrode 75 slit

Claims (3)

[Claims] 1. A bimorph region (4) in which the polarization of a piezoelectric plate and the polarization of a polarization inversion layer (3) formed on one side of the piezoelectric plate point in opposite directions, and a piezoelectric plate in which the polarization points in the same thickness direction. Actuator body with integrated unreversed area (5)
(6) having independent electrodes (71, 72) in the bimorph region
A piezoelectric actuator comprising: (4) and the non-inverted region (5) on both sides. 2. A bimorph region (4) in which the polarization of the piezoelectric plate and the polarization of a polarization inversion layer (3) formed on one side of the piezoelectric plate are in opposite directions, and a piezoelectric plate in which the polarization is in the same thickness direction. Actuator body with integrated unreversed area (5)
(6), which is made of a resistance material and electrically connects the bimorph region (4) and the non-inversion region (5), and an electrode (73) made of a conductive material and the bimorph region (4) and the non-inversion region (5). Inversion area (5)
The electrode (74) for electrically connecting
A piezoelectric actuator characterized in that it is formed on both sides of (6). 3. The piezoelectric plate according to claim 1, wherein the piezoelectric plate is LiNbO ₃ , Li
A piezoelectric actuator characterized by being TaO ₃ or another pyroelectric material.