JPH03245778A - Piezoelectric actuator - Google Patents

Abstract

PURPOSE:To simplify the construction by using transversal effect laminated piezoelectric elements for one kind of vibrator elements arranged in two directions meeting at almost right angles to each other, and a longitudinal effect laminated piezoelectric element for the other. CONSTITUTION:A vibrator 11 with both arm sections 13a, 13b formed at its ends has a U-shaped construction, and both the arm sections 13a, 13b are composed of longitudinal effect laminated piezoelectric elements. The base section 15 with the arm sections 13a, 13b glued to it and held is composed of a transversal effect laminated piezoelectric element. A longitudinal effect laminated piezoelectric element 13 is an element of piezoelectric elements laminated through the medium of electrodes, and expands or contracts in the direction of lamination in proportion to applied voltage. Whereas, the transversal effect laminated piezoelectric element is an element which expands or contracts in the direction perpendicular to the laminated direction. As mentioned above, the vibrator 11 is merely composed of the transversal effect laminated piezoelectric element and longitudinal effect piezoelectric elements joined to one another.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric actuator driven by a piezoelectric element.

[Prior Art] Conventionally, there has been a piezoelectric actuator using a piezoelectric element as an excitation source, as shown in FIG. In the figure, 51 is a case containing a piezoelectric actuator, 53 is an elastic body rotatably supported by a rotating shaft 55 fixed to the case 51, and 55 is a movable element moved by this piezoelectric actuator. It is. Piezoelectric elements 57 and 59 are bonded to the upper surface and both side surfaces of the elastic body 53, and a contact portion 61 that contacts the movable element 55 is formed at the end thereof.

In the piezoelectric actuator configured in this way, when a voltage of a predetermined frequency is applied to the piezoelectric element 57.59 on the elastic body 53, the piezoelectric element 57.59 expands and contracts according to the frequency, causing the elastic body 53 to vibrate. . And elastic body 53
The contact portion 61 formed in the contact portion 61 vibrates in a substantially circular trajectory with the vibration of the elastic body 53, and the movable element 55 is moved due to contact resistance with the contact portion 61.

[Problems to be Solved by the Invention] However, in the piezoelectric actuator configured as described above, it is necessary to set the vibration frequency of the piezoelectric element to the resonance frequency of the elastic body. There were many points to consider in the design. Furthermore, the piezoelectric actuator constructed in this manner has a complicated structure and is relatively large, so that there are restrictions on the conditions under which it can be used.

The present invention has been made to solve the above-mentioned problems, and aims to reduce design considerations such as the resonance frequency of the elastic body and further simplify the structure.

[Means for Solving the Problems] In order to achieve this object, the piezoelectric actuator of the present invention has vibrators in two directions substantially perpendicular to each other, one of which is a transverse-motion stacked piezoelectric element, and the other is a longitudinal-effect piezoelectric element. It is an integrated layered piezoelectric element. Also, the thickness t per layer of the transverse motion integrated layered piezoelectric element
5μm<t<40μm.

[Function] In the piezoelectric actuator of the present invention having the above configuration,
When an AC voltage is applied to the transverse effect piezoelectric element and the longitudinal effect piezoelectric element, the transverse effect piezoelectric element expands and contracts in the horizontal direction with respect to the voltage application direction, and the longitudinal effect piezoelectric element expands and contracts in the vertical direction. The movable element is then driven in a predetermined direction by the combined vibration of these two piezoelectric elements.

[Example] Hereinafter, an example embodying the present invention will be described with reference to the drawings.

FIG. 1 shows a piezoelectric actuator of the present invention. Reference numeral 1 denotes a case that forms the outer frame of the piezoelectric actuator of the present invention, and this case 1 is provided with openings 3 and 5 on the left and right sides shown in the figure, and the piezoelectric actuator is inserted through the openings 3 and 5. A movable element 7, which is moved by a piezoelectric actuator, is movably inserted through the piezoelectric actuator. Inside the case 1, a rotating roller 9 for smoothly moving the movable element 7 is provided at a position in contact with the upper surface of the movable element 7, and a vibrator 1 which is a drive source of the piezoelectric actuator.
1 is built-in.

The vibrator 11 has a U-shape with both arm parts 13a and 13b formed at the ends thereof.

Reference numeral 13b is constituted by a vertically effecting laminated piezoelectric element, and the base 15 to which both arm portions 13a and 13b are bonded and held is constituted by a transversely acting laminated piezoelectric element. Further, the longitudinal effect integrated layered piezoelectric element 13 is a piezoelectric element in which piezoelectric elements are stacked via electrodes, and expands and contracts in the stacking direction according to the applied voltage, and the lateral effect integrated layered piezoelectric element 15 is , is a piezoelectric element that expands and contracts in a direction perpendicular to the stacking direction. This vibrator 11 is fixed to a holding rod 17 fixed to the case 1.

Next, the operation of the piezoelectric actuator configured in this way will be explained using FIG. 2. First, the left arm portion 1 of the vibrator 11
A voltage of a predetermined polarity is applied to a 3g piezoelectric element. Then, the arm portion 13a is extended toward the movable element 7, and the movable element 7 is held between the arm portion 13a and the rotating roller 9 (FIG. 2a).
. Next, while maintaining this state, when a voltage is applied to the piezoelectric element of the base 15, the base 15 is expanded, and the movable element 7 is relatively moved as the base 15 is expanded. Next, when the voltage applied to the arm 13a is stopped and a voltage is applied to the arm 13b, the arm 13a contracts to its original length and the arm 13b extends (FIG. 2b). When the voltage applied to the base 15 is stopped with the mover 7 being crimped by the arm 13b, the expanded base 15 is contracted to its original length.
As the base portion 15 contracts, the mover 7 is further relatively moved to the left. Then, the voltage application to the arm portion 13b is released,
When the above-described operation is repeated, the movable element 7 continuously moves relatively.

In addition, in order to relatively move the mover 7 to the right, the arm portion 13 is
It is sufficient to reverse the order of voltage application a, and the basic operation does not differ depending on the moving direction of the movable element 7.

Further, by reversing the polarity of the voltage applied to the piezoelectric element, the piezoelectric element can be contracted, and the movable element 7 may be moved by this contraction operation. Furthermore, if the polarity of the voltage applied to the base 15 is made reversible, the mover 17 can be expanded and contracted as piezoelectricity is applied.
The movement stroke of the movable element 17 can be increased.

On the other hand, the physical properties of the transverse effect laminated piezoelectric element are expressed by the following equation, where the length of the piezoelectric element is l, the amount of displacement of the length is Δ15, and the thickness is t.

Here, d31: piezoelectric constant [m/V1 M, 1: electrostrictive constant [m/V2 coE: electric field]. When used in a piezoelectric actuator, d3. =-160X
10-12 [m/V] M31- 2.41 X 10
-” [m/V2] Jl -34X10-' [
Mko is raised.

In addition, under these conditions, in order to drive the piezoelectric actuator at the fastest speed, the voltage applied to the piezoelectric element was experimentally 50
■(Effective value), 50KH2.

At this time, the moving speed of the mover is approximately 1.8 m/s. On the other hand, the moving speed of the movable element can be considered to be the rotational speed of a circular motion in which velocity components in two directions, elongating and contracting in the vertical direction and the horizontal direction, are combined. Then, the displacement amount Δl of the piezoelectric element
is considered to be the amplitude of a circular motion rotating with a period of 50KH2 and a speed in the connecting direction of 1.8m/s, and when substituted for V, we get 1.8m/s-2πX50X103Xrr-ffxlo
xlo-6, and the amplitude Δl of the piezoelectric element is 10 μm (effective value).

Therefore, by substituting each value into the formula (■), the thickness t of the piezoelectric element is 10X10-6--1.60X10-12X60,',
It becomes t-40Cμm. The thickness of each layer of the lateral effect stacked piezoelectric element must be 40 μm or less.

Furthermore, piezoelectric elements are manufactured by sintering ceramic powder, and as shown in FIG. 3, the powder is not sintered uniformly, resulting in gaps (voids) 19 between the powder. For this reason, if the distance between the electrode 21 and the electrode 21 is too narrow, the gap will affect the operation of the piezoelectric element, but if the distance is set to about 5 powders (5 μm) or more, the voltage element can be used without being affected by the gap. can do.

Therefore, if the thickness t of the lateral effect stacked piezoelectric element per layer is 5 μm<t<40 μm, the piezoelectric device can be used satisfactorily.

[Effects of the Invention] As is clear from the detailed description above, according to the present invention, an elastic body is not required for the vibrator of the piezoelectric actuator,
There is no need to consider the resonance frequency of the elastic body. Further, the structure of the vibrator is simple because it is only a transverse effect stacked piezoelectric element and a longitudinal effect stacked piezoelectric element joined together. In addition, the thickness t per layer of the transverse effect laminated piezoelectric element is 5 μm<t
Since it is <40 μm, the piezoelectric element can be used optimally.

[Brief explanation of drawings]

1 to 3 show embodiments embodying the present invention. FIG. 1 is a sectional view showing the inside of the piezoelectric actuator of the present invention, and FIG. 2 is a side view showing the operation of the piezoelectric actuator. , FIG. 3 is a micrograph showing the sintered state of a transverse effect laminated piezoelectric element, and FIG. 4 is a cross-sectional view showing the structure of a conventional piezoelectric actuator. In the figure, 1 is a case, 7 is a mover, 11 is a vibrator, 19 is a gap, and 21 is an electrode.

Claims (2)

[Claims] 1. A piezoelectric actuator comprising vibrators in two directions substantially perpendicular to each other, wherein one of the vibrators is a transverse effect stacked piezoelectric element and the other vibrator is a longitudinal effect stacked piezoelectric element. 2. In the piezoelectric actuator according to claim 1, the thickness t of each layer of the transverse effect laminated piezoelectric element is 5 μm<t<4.
A piezoelectric actuator characterized by having a thickness of 0 μm.