JP3214260B2 - Resonant drive type piezoelectric actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator, and more specifically, to a resonance-driven piezoelectric actuator driven at its resonance frequency to greatly improve displacement.

[0002]

2. Description of the Related Art In a conventional piezoelectric actuator, a metal electrode plate (internal electrode) is provided on the entire front and back surfaces of a piezoelectric body, and a piezoelectric body polarized in a thickness direction and a metal electrode plate are alternately stacked and integrated with an adhesive or the like. It has the structure which was done. Every other metal electrode plate is externally electrically connected in parallel outside, and the electrical terminals are taken out. When a voltage is applied to the electric terminal, the actuator is displaced in the polarization direction, and performs an expansion and contraction motion. However, in the actuator having such a structure, the displacement of the piezoelectric body in the radial direction (perpendicular to the polarization direction) is suppressed by the metal electrode plate, and the displacement cannot be sufficiently performed in the polarization direction. Was as small as about 0.01%. Therefore, a mechanism for increasing the displacement has been proposed (for example, Japanese Utility Model Laid-Open No. 4-26558).

[0003]

In the proposed mechanism for increasing the displacement of the piezoelectric actuator, a method using a lever, a method using frictional force, and a method using hydraulic pressure by a piston or the like are used. However, these methods have various problems. For example, in the method using a lever, the actuator itself becomes large,
In addition, the responsiveness is affected by the displacement magnifying mechanism, and the responsiveness which is the largest characteristic of the piezoelectric body is reduced. The method using the frictional force has a problem in durability due to wear of the frictional portion. The method using a piston requires a hydraulic chamber and a mechanism for homogenizing the pressure, resulting in an increase in size.

[0004] The present invention does not use a complicated mechanism,
It is an object of the present invention to provide a piezoelectric actuator with increased displacement.

[0005]

According to the present invention, there is provided a piezoelectric body having a polarization axis in a direction parallel to a side surface, and a pair of internal electrode plates provided on both end surfaces of the piezoelectric body perpendicular to the polarization axis. Wherein the outer diameter of the internal electrode plate is 20 to 50% of the outer diameter of the piezoelectric body.

According to the present invention, there is provided a piezoelectric body having a polarization axis in a direction parallel to a side surface, a pair of internal electrode plates provided on both end surfaces of the piezoelectric body perpendicular to the polarization axis, A resonance drive type piezoelectric actuator comprising a body and an elastic layer provided between the internal electrode plates, wherein the elastic layer has a thickness of 1 to 20 μm, and

(Equation 2) (Where λ is the resonance wavelength of the resonance driving type piezoelectric actuator, and n is a positive integer), and the resonance driving type piezoelectric actuator is provided.

Further, according to the present invention, a piezoelectric body having a polarization axis in a direction parallel to a side surface, a pair of internal electrode plates provided on both end surfaces of the piezoelectric body perpendicular to the polarization axis, and A resonance drive type piezoelectric actuator comprising a body and an elastic body layer provided between the internal electrode plates, wherein a connection between the internal electrode plate and the piezoelectric body is provided at a central portion of the elastic body, A resonance-driven piezoelectric actuator is provided, which is made of a conductor filled in a through hole having an outer diameter of 10 to 30% of the outer diameter of the internal electrode plate.

[0008]

According to the first aspect of the present invention, by setting the outer diameter of the internal electrode plate to 20 to 50% of the outer diameter of the piezoelectric body, a radial direction in which the center of the piezoelectric body becomes an antinode in a resonance mode is provided. In a resonance-driven piezoelectric actuator using a primary vibration mode (perpendicular to the polarization direction), the displacement of the piezoelectric body in the thickness direction (polarization direction) is improved without hindering radial vibration.

According to the second aspect of the present invention, by incorporating an elastic body having a specific thickness between the piezoelectric body and the internal electrode, the radial vibration of the piezoelectric body can be converted into a thickness direction.
The displacement of the piezoelectric body in the thickness direction is improved.

According to the third aspect of the present invention, the displacement is improved by incorporating an elastic body between the piezoelectric body and the internal electrode plate, and the elastic body is filled in a through hole having a specific outer diameter provided at a central portion of the elastic body. By connecting the internal electrode plate and the piezoelectric body with a conductor, poor conduction and breakage due to an impact load during driving are prevented.

[0011]

Supplementary Description of Means for Solving the Problems The piezoelectric material, internal electrode plate material and elastic material used in the present invention are not particularly limited, and various materials can be used. For example, PZT can be used as the piezoelectric material, SUS, Al, SK material or the like can be used as the internal electrode plate material, and rubber, silicon rubber, or the like can be used as the elastic material.

As in the present invention, in order to improve the displacement by using the radial primary vibration mode of the piezoelectric body as the resonance mode, the outer diameter of the internal electrode must be 20 to the outer diameter of the piezoelectric body.
It must be within 50%. If the outer diameter of the internal electrode is smaller than this range, the piezoelectric body may be broken, while if it is larger than this range, the radial displacement of the piezoelectric body is suppressed, and the desired effect cannot be obtained.

Further, by incorporating an elastic body between the piezoelectric body and the internal electrode, the radial vibration of the piezoelectric body can be converted to the thickness direction, and the displacement can be improved. However, since this effect uses the primary vibration mode in the radial direction of the piezoelectric body as the resonance mode as described above, it is necessary that the thickness of the elastic body be a predetermined dimension. That is,

(Equation 3) It is necessary that the thickness be represented by If the elastic body does not have the thickness represented by this formula, the energy of the resonance vibration is lost, and the displacement of the piezoelectric body cannot be improved. Specifically, for example, a driving frequency of 130 Hz and a resonance wavelength of 6.
In the case of 28μm, the thickness of the elastic body is 1.57 ± 1μm, 4.71 ±
1μm, 7.85 ± 1μm, 11.00 ± 1μm, 14.13 ± 1μ
m or 17.34 ± 1 μm. Further, this thickness must be in the range of 1 to 20 μm. If it is not within this range, the displacement may be reduced due to the buffering action of the elastic layer.

A conductor is used to connect the piezoelectric body and the internal electrode. The conductor has a Young's modulus lower than that of an elastic body incorporated between the piezoelectric body and the internal electrode, such as Ag, Cu, or the like.
It is preferable to use a metal paste containing Al, Au, or the like, or a metal such as Hg. The connection between the piezoelectric body and the internal electrode is made by the conductor filled in a through hole provided at the center of the elastic body. The outer diameter of the through hole is 10 to 30% of the outer diameter of the internal electrode plate. It is necessary to be. If the outer diameter of the through-hole is larger than this range, the vibration in the radial direction of the piezoelectric body is suppressed, so that the effect of improving the displacement cannot be obtained. If it is smaller than this range, a sufficient connection between the piezoelectric body and the internal electrode cannot be obtained.

[0015]

An embodiment of the present invention will be described below with reference to the drawings. First, the configuration of the resonance driving type piezoelectric actuator of this embodiment will be described with reference to FIG. This actuator comprises a plurality of piezoelectric bodies 1, elastic bodies 2 and internal electrode plates 3, and the internal electrode plates are connected to a drive power supply 4. As shown in FIG. 2, a through hole is provided at the center of the elastic body 2, and the through hole is filled with a conductor 5 that electrically connects the piezoelectric body and the internal electrode plate.

In this embodiment, Pb, Z
A PZT piezoelectric body manufactured by a predetermined method using a PZT piezoelectric material containing r, Ti and other trace elements was used. The elastic member 2 was formed by using silicon rubber, applying silicon rubber in a donut shape through a screen to the piezoelectric member 1, and drying the silicon rubber. The silver paste was filled in the central through-hole. SU as the internal electrode plate 3
Using S, silicon rubber was applied thereto in the same manner as described above, and after drying, silver paste was filled in the through holes. Next, silicon rubber was bonded, assembled into the structure shown in FIG. 1, and finally, the internal electrode plate was connected to manufacture the resonance drive type piezoelectric actuator of the present invention.

Example 1 By the above method, the outer diameter of the piezoelectric body 1 was 20 mm, the thickness of the elastic body 2 was 11 μm, the outer diameter of the internal electrode plate 3 was 10 mm, and the outer diameter of the through hole was 3 mm.
mm resonant drive type piezoelectric actuator (one piezoelectric body)
This actuator was driven at a driving voltage of 0 to 200 V, a load of 10 MPa, 20 MPa and 30 MPa while changing the driving frequency, and its displacement was measured. The result is shown in FIG. This actuator showed a large displacement of about 15 μm at the resonance point of about 130 KHz.

Example 2 An actuator was manufactured in the same manner as in Example 1 except that the outer diameter of the internal electrode plate 3 was changed, and this actuator was driven at a driving frequency of 130 KHz at a driving voltage of 100 V. The displacement was measured. The result is shown in FIG.
A large displacement was obtained when the outer diameter of the internal electrode plate was 20 to 50% of the outer diameter of the piezoelectric body.

Example 3 An actuator was manufactured in the same manner as in Example 1 except that the thickness of the elastic body 2 was changed, and this actuator was operated at a driving voltage of 100 V, a driving frequency of 130 KHz, and a wavelength of 6.
It was driven at 28 μm and its displacement was measured. The results are shown in Table 1 and FIG.

[0020]

[Table 1]

From these results, there is a relationship similar to a sine waveform between the thickness of the elastic body and the displacement, and the thickness of the elastic body corresponding to the top of the graph in FIG. 5 has a width of ± 1 μm. ,
Resonance wavelength of resonance driven piezoelectric actuator λ (6.28 μm)
Against

(Equation 4) Have a relationship.

Example 4 An actuator was manufactured by changing the outer diameter of the through-hole and the other conditions were the same as in Example 1 above, and the actuator was driven at a driving frequency of 130 KHz at a driving voltage of 100 V, and the displacement was changed. It was measured. The result is shown in FIG. The through hole, i.e., the outer diameter of the connection conductor is 10 to 50
Large displacements were obtained when the magnitude was%.

[0023]

According to the present invention, by setting the size of the internal electrode plate to 20 to 50% of the size of the piezoelectric body, an elastic body having a specific thickness is incorporated between the internal electrode plate and the piezoelectric body. Accordingly, the connection between the piezoelectric body and the internal electrode plate is made to have a specific size, thereby improving the displacement of the actuator.

By improving the displacement as described above, the driving voltage can be reduced to less than half of that of the conventional actuator, and the size of the power source can be reduced. Furthermore, by incorporating an elastic body, it is possible to prevent external shearing force applied to the piezoelectric body without suppressing radial distortion of the piezoelectric body. As a result, cracking of the piezoelectric body is prevented, and durability is improved. Will be increased.

[Brief description of the drawings]

FIG. 1 is a side view showing a resonance drive type piezoelectric actuator of the present invention.

FIG. 2 is a cross-sectional view of the resonance drive type piezoelectric actuator of FIG. 1 taken along line AA.

FIG. 3 is a graph showing the relationship between the displacement of the actuator of the present invention and the driving frequency in Example 1.

FIG. 4 is a graph showing the relationship between the displacement of the actuator of the present invention and the outer diameter of the internal electrode plate in Example 2.

FIG. 5 is a graph showing the relationship between the displacement of the actuator of the present invention and the thickness of the elastic body in the third embodiment.

FIG. 6 is a graph showing the relationship between the displacement of the actuator of the present invention and the outer diameter of a through hole in Example 4.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1: Piezoelectric body 2: Elastic body 3: Internal electrode 4: Drive power supply

Claims (3)

(57) [Claims] 1. A resonance-driven piezoelectric actuator comprising: a piezoelectric body having a polarization axis in a direction parallel to a side surface; and a pair of internal electrode plates provided on both end faces of the piezoelectric body perpendicular to the polarization axis. The resonance drive type piezoelectric actuator, wherein the outer diameter of the internal electrode plate is 20 to 50% of the outer diameter of the piezoelectric body. 2. A piezoelectric body having a polarization axis in a direction parallel to a side surface, a pair of internal electrode plates provided on both end surfaces of the piezoelectric body perpendicular to the polarization axis, and a portion between the piezoelectric body and the internal electrode plate. In the resonance drive type piezoelectric actuator comprising the elastic layer provided in the above, the elastic layer has a thickness of 1 to 20μ
m, and (Wherein, λ is the resonance wavelength of the resonance-driven piezoelectric actuator, and n is a positive integer). 3. A piezoelectric body having a polarization axis in a direction parallel to a side surface, a pair of internal electrode plates provided on both end surfaces of the piezoelectric body perpendicular to the polarization axis, and a portion between the piezoelectric body and the internal electrode plate. In the resonance drive type piezoelectric actuator comprising the elastic layer provided in the elastic body, the connection between the internal electrode plate and the piezoelectric body is provided at the center of the elastic body, and the outer diameter of the internal electrode plate is set to 10%. A resonant drive type piezoelectric actuator characterized by being made of a conductor filled in a through hole having an outer diameter of about 30%.