KR20080096265A - Piezoelectric element and piezoelectric actuator using the piezoelectric element - Google Patents

Abstract

The present invention relates to a piezoelectric element in which two vibration modes are generated by currents of the same frequency and a piezoelectric actuator using the piezoelectric element. The piezoelectric actuator includes a linear cantilever-shaped piezoelectric element that vibrates independently in a bending direction and a longitudinal direction when an electrical signal is input, a displacement expanding mechanism fixedly disposed on each surface of the piezoelectric element, and first and second fixing plates. . The piezoelectric element is configured such that the resonance mode of the bending vibration and the resonance mode of the longitudinal vibration are generated by the current of the same frequency.

According to the present invention, the piezoelectric actuator is designed such that the resonance mode of the longitudinal vibration and the resonance mode of the vibration in the bending direction are simultaneously generated by the current of the same frequency, thereby further expanding the displacement of the piezoelectric actuator. . In addition, this allows for faster and more accurate position control.

Description

Piezoelectric element and piezoelectric actuator using the piezoelectric element {Piezoelectric plate and Piezoelectric Actuator using the plate}

1 is a plan view showing a piezoelectric element of a conventional piezoelectric actuator.

2 (a) and 2 (b) are diagrams illustrating a secondary bending mode and a primary longitudinal vibration mode of vibration in a bending direction of a piezoelectric element of a piezoelectric actuator according to a first embodiment of the present invention, respectively.

3 and 4 are diagrams showing moving directions of application of current to a piezoelectric element of a piezoelectric actuator according to a first embodiment of the present invention;

5 is a perspective view of the piezoelectric actuator according to the first embodiment of the present invention as a whole;

6 (a) and 6 (b) are schematic diagrams illustrating a perspective view and an operation of the piezoelectric actuator according to the second embodiment of the present invention.

<Explanation of symbols on main parts of the drawings>

20, 40: piezo actuator

23, 43: piezoelectric element

25, 45: first ceramic tip

27, 47: second ceramic tip

48: third ceramic tip

31: first fixing plate

33: second fixing plate

41: moving plate

49: fixed plate

The present invention relates to a piezoelectric element and a piezoelectric actuator using the piezoelectric element, and more particularly, a piezoelectric element in which two resonance modes are generated by a current of the same frequency and a piezoelectric element further expanding vibration displacement by using the piezoelectric element. It relates to an actuator.

1 is a plan view showing a piezoelectric element of a conventional piezoelectric actuator.

Referring to FIG. 1, the conventional piezoelectric element 13 is configured in a rectangular parallelepiped form.

The piezoelectric element 13 has four polarization regions, that is, a first polarization region 13a, a second polarization region 13b, a third polarization region 13c, and a fourth polarization region 13d. The four polarization regions have the same polarization direction in the thickness direction. The four polarization regions 13a, 13b, 13c, and 13d have the same size and are arranged in two rows. The electrodes are formed on the four polarization regions 13a, 13b, 13c, and 13d, respectively.

The first polarization region 13a and the fourth polarization region 13d have the same polarization direction, and the second polarization region 13b and the third polarization region 13c are opposite to the first polarization region 13a. Direction of the polarization. The first polarization region 13a and the fourth polarization region 13d and the second polarization region 13b and the third polarization region 13c are connected by lead wires (not shown), respectively.

When a current is applied to the first polarization region 13a and the fourth polarization region 13d, a piezoelectric effect occurs in the first polarization region 13a and the fourth polarization region 13d, and conversely, the second polarization effect is generated. When a current is applied to the polarization region 13b and the third polarization region 13c, a piezoelectric effect occurs in the second polarization region 13b and the third polarization region 13c, so that the piezoelectric element 13 contracts. Will expand.

Piezoelectric actuators according to the prior art generally rely on a single resonant mode in many cases, or may not use structural vibration. The piezoelectric actuator according to the prior art has a problem that the displacement generated is small and the piezoelectric actuator cannot be accurately controlled.

An object of the present invention devised to solve the above problems of the prior art is to provide a piezoelectric element in which the resonance mode of the vibration in the bending direction and the vibration in the longitudinal direction is generated by the current of the same frequency.

Another object of the present invention is to further expand the vibration displacement by using the above-described piezoelectric element, thereby providing a piezoelectric actuator capable of quicker and more accurate position control.

Piezoelectric actuator according to a feature of the present invention for solving the above problems,

Piezoelectric element of linear cantilever shape of rectangular parallelepiped that vibrates independently in the bending direction and the longitudinal direction when an electrical signal is input,

A first displacement expanding mechanism fixedly mounted to left and right nodes of the secondary bending mode in which the vibration phases of the first surface of the piezoelectric element are the same;

A second displacement expanding mechanism fixedly mounted to a second surface opposite to the first surface of the piezoelectric element;

A first fixing plate connected to the first displacement expanding mechanism to provide a total stress;

A second fixing plate connected to the second displacement expanding mechanism to provide a total stress;

In the piezoelectric element, two resonance modes are generated by a current having the same frequency, and the two resonance modes are a resonance mode of bending direction vibration and a resonance mode of longitudinal vibration, and the resonance mode of bending direction vibration is secondary bending. Mode, the resonance mode of the longitudinal vibration is the primary longitudinal vibration mode.

The piezoelectric actuator having the above-mentioned characteristics is characterized in that the first and second displacement expanding mechanisms are ceramic tips.

The piezoelectric actuator having the above-mentioned characteristics is characterized in that the piezoelectric element is linearly moved if an electrical signal is input to the piezoelectric element.

On the other hand, the piezoelectric actuator according to another feature of the present invention,

Piezoelectric element of linear cantilever shape that vibrates independently in the bending direction and the longitudinal direction when an electrical signal is input,

A first displacement expanding mechanism fixedly disposed on the first surface of the piezoelectric element, the first displacement expanding mechanism being disposed at left and right nodes in which the phases of the vibration modes are the same;

A second displacement expanding mechanism fixedly disposed on a second surface opposite to the first surface of the piezoelectric element;

A moving plate movably connected to the first displacement expanding mechanism to provide total stress to the first displacement expanding mechanism;

A fixed plate fixedly connected to the second displacement expanding mechanism and the piezoelectric element to provide total stress to the second displacement expanding mechanism;

The piezoelectric element is characterized in that the two vibration modes are generated by the current of the same frequency,

In the piezoelectric actuator, if an electrical signal is applied to the piezoelectric element, an elliptic locus motion occurs in the first displacement expanding mechanism, and the moving plate moves linearly by an elliptical locus motion of the first displacement expanding mechanism. It is characterized by.

The piezoelectric element according to another feature of the present invention is formed in a rectangular parallelepiped shape having a predetermined length, thickness, and height, and is formed in a linear cantilever shape that vibrates independently in a bending direction and a longitudinal direction when an electrical signal is input from the outside.

By adjusting the length or adjusting the height and thickness, the two resonance modes are generated by the current of the same frequency,

The two resonance modes are the resonance mode of the bending vibration and the resonance mode of the longitudinal vibration.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First embodiment

2 (a) and 2 (b) are diagrams illustrating a secondary bending mode and a primary longitudinal vibration mode of vibration in the bending direction of the piezoelectric element of the piezoelectric actuator according to the first embodiment of the present invention, respectively. 4 is a view illustrating the moving directions of the piezoelectric actuator according to the first embodiment of the present invention applied to the piezoelectric element, Figure 5 is a view showing the piezoelectric actuator according to the first embodiment of the present invention as a whole One perspective view.

As shown in FIG. 5, the piezoelectric actuator 20 according to the first embodiment of the present invention is fixed to the piezoelectric element 23 and the upper surface of the piezoelectric element 23 so as to be symmetrically disposed left and right. First ceramic tips 25, a second ceramic tip 27 fixedly disposed at the center of the lower surface of the piezoelectric element 23, and a first fixing plate connected to the first ceramic tips 25 ( 31) and a second fixing plate 33 connected to the second ceramic tip 27.

As shown in FIGS. 3 and 4, the piezoelectric element 23 includes four polarization regions, that is, a first polarization region 23a, a second polarization region 23b, a third polarization region 23c, and a fourth polarization region 23. Polarization regions 23d are formed, and the four polarization regions have the same polarization direction in the thickness direction. The four polarization regions 23a, 23b, 23c, and 23d have the same size and are arranged in two rows. The electrodes are formed on the four polarization regions 23a, 23b, 23c, and 23d, respectively.

The first polarization region 23a and the fourth polarization region 23d have the same polarization direction, and the second polarization region 23b and the third polarization region 23c are opposite to the first polarization region 23a. It has a polarization direction of. The first polarization region 23a and the fourth polarization region 23d and the second polarization region 23b and the third polarization region 23c are connected by lead wires (not shown), respectively.

The piezoelectric element 23 has a linear cantilever-shaped cuboid shape having a predetermined length, thickness, and height, and vibrates independently in a bending direction and a longitudinal direction when an electrical signal is input from the outside. The piezoelectric element 23 is designed such that the two resonant modes are generated by the current of the same frequency by adjusting the length or adjusting the height and thickness, the two resonant modes being the resonant mode of the bending direction vibration and the longitudinal direction. It is preferable that it is a resonance mode of vibration. In particular, in the piezoelectric element, it is most preferable that the resonance mode of the bending vibration is the secondary bending mode, and the resonance mode of the longitudinal vibration is the primary longitudinal vibration mode.

When the cantilever-shaped piezoelectric element 23 is tuned to lengths of lengths, heights, and thicknesses of x, y, and z, all vibration modes are changed. Here, while setting appropriate lengths of x, y, and z, The frequencies of the first longitudinal vibration mode and the second bending mode described above are simulated in advance. This can be derived from the FEM analysis and also through experiments.

Due to this design, when the piezoelectric actuator 20 matches the frequency of the input current with one of the resonant frequencies of the structure, the piezoelectric actuator 20 has a mode shape corresponding to the frequency as shown in FIG. This corresponds to the primary bending mode, primary longitudinal vibration mode, etc.) and amplifies the larger displacement. It should be noted that these resonant modes are independent of each other, but because they have overlapping effects, when two resonant modes are generated at the same time, the amplification effect of the displacement is further increased.

Furthermore, when the resonance modes of the vibrations in the bending direction and the longitudinal vibration direction occur at the same time, as shown in FIG. 5, the position of the first ceramic tip 25 is determined.

3 and 4, an elliptic locus motion occurs in the first ceramic tip 25 and the second ceramic tip 27 attached to the piezoelectric element 23. The first ceramic tips 25 are respectively arranged at nodes where the vibration phases of the locus motion are the same.

Meanwhile, a first surface of the first fixing plate 31 is fixedly connected to the first ceramic tip 25, and a second surface opposite to the first surface of the first fixing plate 31 is connected to a spring. . Therefore, the first fixing plate is pre-loaded to the first ceramic tip 25 by the compression force of the spring or the like.

The first surface of the second fixing plate 33 is connected to the second ceramic tip 27, and the second surface opposite to the first surface of the second fixing plate is connected to a spring. Therefore, the second fixing plate is subjected to the total stress to the second ceramic tip 25 by the compressive force provided from the spring or the like.

In this case, the total stress is preferably generated using a compressive force of a spring (not shown) formed on the outer side of the first fixing plate 31 and the second fixing plate 33.

Hereinafter, the operation of the piezoelectric actuator 20 according to the first embodiment of the present invention having the above-described configuration will be described in detail.

When a current having a frequency set to the first polarization region 23a and the fourth polarization region 23d or the second polarization region 23b and the third polarization region 23c of the piezoelectric element 23 is applied, FIG. As shown in FIG. 3 or FIG. 4, the piezoelectric element 23 contracts and expands so that the piezoelectric element of the piezoelectric actuator 20 linearly moves left and right.

Meanwhile, as shown in FIG. 3, when the piezoelectric element 23 vibrates by inputting current into the first polarization region 23a and the fourth polarization region 23d, the first ceramic tip 25 may be vibrated. And the second ceramic tips 27 are compressed by the elastic force of the springs of the first and second fixing plates 31 and 33, respectively, so that the piezoelectric elements 23 directly linearly move to the right.

At this time, if the total stress by the spring, that is, the compressive force is too strong and greater than the force generated by the operation of the piezoelectric actuator 20, the piezoelectric element 23 is impossible to drive. In addition, if the compressive force is too weak, the transmission of the movement is not effectively achieved, it is not a continuous movement occurs a non-linear drive occurs.

Therefore, in order to design the piezoelectric actuator, it is necessary to adjust the prestress of the piezoelectric actuator 20 by adjusting the compression force of the spring connected to the first and the second fixing plate in advance.

On the contrary, as shown in FIG. 4, when a current is applied to the second polarization region 23b and the third polarization region 23c, the piezoelectric element 23 of the piezoelectric actuator 20 is moved to the left in the same principle. Linear movement.

Second embodiment

FIG. 6A is a perspective view illustrating a piezoelectric actuator according to a second embodiment of the present invention, and FIG. 6B is a conceptual diagram for explaining driving of the piezoelectric actuator. Hereinafter, the structure and operation of a piezoelectric actuator according to a second embodiment of the present invention will be described with reference to FIG. 6.

Referring to FIG. 6, the piezoelectric actuator 40 according to the second embodiment of the present invention may be fixed to the piezoelectric element 43 and the first ceramic tips respectively fixed to be symmetrical to the upper surface of the piezoelectric element 43. 45, a moving plate 41 connected to the first ceramic tips 45, a second ceramic tip 47 fixedly disposed at a lower center of the piezoelectric element 43, and the piezoelectric element 43. Third ceramic tips 48 fixedly disposed on the left and right sides thereof, and fixing plates 49 connected to the second and third ceramic tips to fix the piezoelectric elements.

The piezoelectric element 43 is configured in the same manner as the piezoelectric element 23 of the first embodiment of the present invention shown in Figs. 3 and 4, and the piezoelectric element 43 is fixed by the fixing plate 49. .

The moving plate 41 exerts a prestress with the first ceramic tip 45, and the fixed plate 49 is connected to the piezoelectric element by the second ceramic tip 47 and the third ceramic tip 48. 43), a total stress is applied to the piezoelectric element.

In this case, the total stress is preferably generated using a compressive force of a spring (not shown) formed on the outside of the movable plate 41 and the fixed plate 49.

Hereinafter, the operation of the piezoelectric actuator 40 according to the second embodiment having the above-described configuration will be described in detail.

When the current of the set frequency is applied to the piezoelectric actuator 40, the piezoelectric element 43 contracts and expands, and at the set frequency, two vibrations, namely, longitudinal and bending vibrations, occur simultaneously. At this time, the method of designing the structure of the piezoelectric element 43 so that each vibration mode of the piezoelectric element 43 becomes the primary longitudinal vibration mode and the secondary bending mode is the same as that of the first embodiment of the present invention. .

Referring to FIG. 6B, when the piezoelectric element 43 vibrates, the second ceramic tip 47 is compressed from below to above by the elastic force of the spring of the fixing plate 49. The first ceramic tip 41 fixed to the piezoelectric element 43 is vibrated. Then, the moving plate 41, which is a free end, is linearly moved from side to side by the elastic force of the spring compressed from the top to the bottom.

In this case, also in the piezoelectric actuator according to the second embodiment of the present invention, it is necessary to adjust the total stress of the piezoelectric actuator 40 by adjusting the compression force of the spring.

The piezoelectric actuator of the present invention configured as described above allows the resonance modes of the longitudinal vibration and the vibration in the bending direction to be generated by the current of the same frequency, thereby further expanding the displacement of the piezoelectric actuator, thereby making it faster and faster. The advantage is that accurate position control is possible.

In addition, the piezoelectric actuator of the present invention has an advantage that it can be applied to a linear position control motor by disposing a ceramic tip, which is a displacement expanding mechanism, at a node where the phase of the elliptical motion is the same.

In addition, the piezoelectric actuator of the present invention and its design method can be controlled more quickly and precisely by disposing a ceramic tip at each node of the secondary bending mode, so that the piezoelectric actuator can be applied to exposure of an atomic force microscope or a semiconductor process. There is an advantage to this.

In addition, the piezoelectric actuator of the present invention and a design method thereof have an advantage of constituting a faster and more accurate piezoelectric actuator by matching the secondary bending mode and the primary resonance mode among the resonance modes of the piezoelectric actuator.

Claims (11)

A piezoelectric element of linear cantilever shape that vibrates independently in a bending direction and a longitudinal direction when an electrical signal is input; A first displacement expanding mechanism fixedly disposed on the first surface of the piezoelectric element, the first displacement expanding mechanism being disposed at left and right nodes where the phases of the vibration modes are the same; A second displacement expanding mechanism fixedly disposed on a second surface opposite to the first surface of the piezoelectric element; A first fixing plate fixedly connected to the first displacement expanding mechanism to provide total stress to the first displacement expanding mechanism; A second fixing plate fixedly connected to the second displacement expanding mechanism to provide total stress to the second displacement expanding mechanism; And the piezoelectric element has two resonance modes generated by current of the same frequency. The piezoelectric actuator of claim 1, wherein the piezoelectric element linearly moves by a total stress provided to the first and second displacement expanding mechanisms when an electrical signal is applied to the piezoelectric element. Piezo actuator. A piezoelectric element of linear cantilever shape that vibrates independently in a bending direction and a longitudinal direction when an electrical signal is input; A first displacement expanding mechanism fixedly disposed on the first surface of the piezoelectric element, the first displacement expanding mechanism being disposed at left and right nodes where the phases of the vibration modes are the same; A second displacement expanding mechanism fixedly disposed on a second surface opposite to the first surface of the piezoelectric element; A moving plate movably connected to the first displacement expanding mechanism to provide total stress to the first displacement expanding mechanism; A fixed plate fixedly connected to the second displacement expanding mechanism and the piezoelectric element to provide total stress to the second displacement expanding mechanism; And the piezoelectric element has two resonance modes generated by current of the same frequency. The piezoelectric actuator of claim 3, wherein, when an electrical signal is applied to the piezoelectric element, an elliptic trajectory motion occurs in the first displacement expanding mechanism, and the elliptic trajectory motion of the first displacement expanding mechanism is performed. A piezoelectric actuator, characterized in that the moving plate moves linearly. The piezoelectric actuator according to any one of claims 1 to 4, wherein the two resonant modes of the piezoelectric element are a resonant mode of bending vibration and a resonant mode of longitudinal vibration. The piezoelectric actuator according to any one of claims 1 to 4, wherein the first and second displacement expanding mechanisms are ceramic chips. According to any one of claims 1 to 2, wherein the first fixing plate and the second fixing plate is characterized in that connected to the spring portion to the outside, the first and second fixing plate provided The stress is due to the elastic force of the spring portion, the piezoelectric actuator. According to any one of claims 3 to 4, The movable plate and the fixed plate is characterized in that connected to the spring portion to the outside, the total stress provided by the movable plate and the fixed plate is the spring portion A piezoelectric actuator characterized by the elastic force. The piezoelectric actuator according to any one of claims 1 to 4, wherein the piezoelectric element adjusts the length or thickness and height of the piezoelectric element so that the two vibration modes are generated by the current of the same frequency. . It has a predetermined length, thickness, and height, and when an electric signal is input from the outside, it is made of a linear cantilever shape that vibrates independently in the bending direction and the longitudinal direction. By adjusting the length or adjusting the height and thickness, two piezoelectric modes are generated by current of the same frequency. The piezoelectric element of claim 10, wherein the two resonance modes of the piezoelectric element are a resonance mode of bending direction vibration and a resonance mode of longitudinal vibration.

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