JPH0846261A - Multilayered piezoelectric actuator - Google Patents

Abstract

PURPOSE:To provide a multilayered piezoelectric actuator capable of highly precise positioning at a high speed. CONSTITUTION:When positioning is controlled at a position stretched by 10mum from a present position, a voltage is applied to a piezoelectric element 12 of a rough movement part 3, which is moved as far as a distance of 10+ or -0.1mum.. For the residual + or -0.1mum, a voltage is applied to a laminate 5 of a piezoelectric element 4 of a fine movement part 2, and position alignment is completed by movement of + or -0.005mum. By installing the fine movement part 2 and the rough movement part 3, high speed response and fine positioning are both satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric actuator composed of a coarse moving portion and a fine moving portion formed by a laminated body in which one or more piezoelectric elements are laminated.

[0002]

2. Description of the Related Art Piezo actuators have been conventionally used as high-precision positioning actuators. Since the effective stroke of the piezo actuator is extremely small, the resolution is inevitably low, and the resolution for a full stroke is about 1 to 0.1% at most. Therefore, as disclosed in Japanese Unexamined Patent Publication No. 5-160459, a coarse movement piezo actuator and a fine movement piezo actuator are stacked in series in the displacement direction to extend the effective stroke, and the resolution is up to 0.01%. Has improved.

[0003]

However, the above-mentioned fine movement piezo actuator not only has a small number of laminated layers but also has a small capacitance. Therefore, in order to drive this piezo actuator for fine movement, it is necessary to control an extremely small current, and there is a problem that the cost of the drive circuit becomes high. The present invention has been made in order to solve the above problems, focusing on the fact that the capacitance changes depending on the number of laminated piezoelectric elements and the plate thickness, and a piezoelectric element for fine movement that allows a large current to flow, and a small current. An object of the present invention is to provide a laminated piezoelectric actuator that can be positioned at high speed and with high accuracy by using an operating high speed piezoelectric element.

[0004]

In order to achieve the above object, a laminated piezoelectric actuator of the present invention according to claim 1 is a coarse movement part and a fine movement formed by a laminated body in which one or more piezoelectric elements are laminated. And a plate portion of the piezoelectric element forming the fine moving portion, the plate thickness of the piezoelectric element forming the fine moving portion is smaller than the plate thickness of the piezoelectric element forming the coarse moving portion. .

In order to achieve the above object, the invention according to claim 2 is a laminated piezoelectric actuator in which a coarse movement portion and a fine movement portion formed by a laminated body in which one or more piezoelectric elements are laminated are arranged in series. In the above, the fine movement part is composed of a plurality of units each having 2 ⁿ (n = 0, 1, ...) Number of piezoelectric elements, and the number of piezoelectric elements is different for each unit. And

In order to achieve the above object, the invention according to claim 3 is characterized in that, in the laminated piezoelectric actuator according to claim 2, each unit constituting the fine movement part is individually driven. To do.

In order to achieve the above object, the invention according to claim 4 forms a coarse moving portion and a fine moving portion by a laminated body in which one or more piezoelectric elements are laminated, and ends of the coarse moving portion in the laminating direction. The portion and the side portion orthogonal to the stacking direction of the fine movement portion are in contact with each other.

[0008]

According to the laminated piezoelectric actuator of the first aspect of the present invention, by making the plate thickness of the piezoelectric element forming the fine moving portion thinner than the plate thickness of the piezoelectric element forming the coarse moving portion, fine movement is achieved. The capacitance of each piezoelectric element forming the part is larger than the capacitance of the piezoelectric element forming the coarse movement part. Therefore, when the electric field strengths are made equal, the strain per piezoelectric element forming the fine moving part is smaller than the strain per piezoelectric element forming the coarse moving part, but The flowing current becomes equal. Therefore, by applying the same amount of current, it is possible to position a minute amount of displacement in the fine moving part and position a predetermined amount of displacement in the coarse moving part at high speed, which simplifies the configuration of the drive circuit and reduces the current. Control can be performed easily.

According to another aspect of the laminated piezoelectric actuator of the present invention, the number of piezoelectric elements is 2 ⁿ (n = 0,
1, 2, ...), and the number of piezoelectric elements is different for each unit. Therefore, the positioning of the minute displacement amount can be performed only by controlling the ON / OFF of each unit whose displacement amount is different stepwise.

According to the laminated piezoelectric actuator of the third aspect, each unit constituting the fine movement part is individually driven, so that the displacement amounts of the units which are different in stages are arbitrarily combined, By performing the on / off control, it is possible to improve the positioning accuracy of the minute displacement amount.

According to the laminated piezoelectric actuator of the fourth aspect, the end portion in the laminating direction of the coarse moving portion and the side portion of the fine moving portion orthogonal to the laminating direction are in contact with each other. The fine movement part driven by the application of the voltage can be displaced in the displacement amount defined by the Poisson's ratio and in the displacement direction of the coarse movement part, and the positioning accuracy of the minute displacement amount can be further improved.

[0012]

【Example】

(First Embodiment) A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view showing the structure of the laminated piezoelectric actuator according to this embodiment. The fine moving part 2 and the coarse moving part 3 are arranged in series between the insulating dummies 1a and 1b arranged at both ends with the insulating dummy 1c interposed therebetween. Insulation dummy 1a,
1b and 1c are insulators that prevent the voltage applied to the element from leaking to the outside, and are also interposed between the peripheral component and the element to protect the element. For this reason, the insulation dummies 1a, 1b, 1c have lead zirconate titanate (hereinafter referred to as P
ZT) or ceramics such as alumina,
The surface roughness and the flatness of both end surfaces are both finished with high precision.

The structure of the fine movement unit 2 will be described. Multiple PZ
A laminated body 5 is formed by laminating piezoelectric elements 4 such as T, and electrodes 6 are formed on both surfaces of the laminated body 5 with silver paste or the like (see FIG. 2). In order to electrically connect the piezoelectric elements 4 in parallel, external electrodes 7, 7 are formed on the side surface of the laminated body 5 so as to face each other in the radial direction with silver paste or the like. The (+) electrode plate 8 is provided between the insulating dummy 1 a and the laminated body 5, and
The (−) electrode plate 9 is disposed between the insulating dummy 1c and the insulating dummy 1c. The (+) electrode plate 8 and the (-) electrode plate 9 have a thickness of 0.0.
It is formed of a stainless thin plate or a copper thin plate of about 2 mm. The radial electrode pieces 8a and 9a are bent and overlapped with the external electrodes 7 and 7. Lead wires 10 and 11 are connected to the electrode pieces 8a and 9a, respectively.

The structure of the coarse moving unit 3 will be described. Fine movement part 2
The electrodes 13 are formed on both surfaces of the piezoelectric element 12 having a plate thickness that is at least twice the plate thickness of the piezoelectric element 4. The (+) electrode plate 14 is arranged between the insulating dummy 1c and the piezoelectric element 12, and the (-) electrode plate 15 is arranged between the laminated piezoelectric element 12 and the insulating dummy 1b. Since the plurality of stacked piezoelectric elements 12 are electrically connected in parallel, each piezoelectric element 12
The (+) electrode plate 14 and the (-) electrode plate 15 are alternately arranged between them. Each (+) electrode plate 14 and (-) electrode plate 15
The electrode pieces 14a and 15a facing each other in the radial direction.
Is formed, and is bent along the side surface of the piezoelectric element 12. Between each electrode piece 14a and each electrode piece 15a, side surface electrode plates 16 and 17 are spot-welded and connected in a bridge shape. Lead wires 18 and 19 are connected to the side surface electrode plates 16 and 17. Piezoelectric element 12, electrode 13,
The materials and compositions of the (+) electrode plate 14 and the (-) electrode plate 15 are the same as those of the fine movement part 2.

In order to control the minute displacement with high precision by the fine moving section 2, it is necessary to apply a minute current to the piezoelectric element 4, but in consideration of the leakage current in the switching element in the amplifier, as much as possible. It is preferable to use the piezoelectric element 4 through which an electric current flows. Moreover, the number of sheets may be small because it controls the minute displacement. However, when a piezoelectric element 12 having the same plate thickness as that of the coarse moving portion 3 is used, the flowing current is too small. For this reason, the laminated body 5 that constitutes the fine movement portion 2 is formed by laminating a plurality of piezoelectric elements 4 that are thinner than the piezoelectric elements 12 of the coarse movement portion 3. This increases the electrostatic capacity so that a large amount of current flows.

On the other hand, the high speed response of the piezoelectric actuator is
In reality, it is governed by the capacity of the power supply. As the capacitance of the piezoelectric actuator decreases, the current consumption decreases. Therefore, increase the thickness of the piezoelectric element to reduce the number of elements,
By reducing the capacitance, high-speed response can be secured even with a small current amplifier.

Therefore, in this embodiment, the plate thickness of one of the piezoelectric elements 4 constituting the laminated body 5 of the fine moving part 2 is the coarse moving part 3
The thickness is set to 1/2 or less of the plate thickness of the piezoelectric element 12.
As a result, the capacitance per piezoelectric element 4 is twice or more that of the piezoelectric element 12. Therefore, when the electric field strengths are made equal, the strain per piezoelectric element 4 is equal to or less than half the strain of the piezoelectric element 12, but the flowing currents are equal. Specifically, the plate thickness of the fine movement part 2 is 0.1.
10 piezoelectric elements 4 of mm are laminated to form a laminated body 5,
When an electric field strength of up to 1 kV / mm is applied, positioning can be performed with an accuracy of ± 0.005 μm (± 0.5%) for a displacement of 0 to 1 μm. Further, when 100 pieces of piezoelectric elements 12 having a plate thickness of 0.5 mm are laminated in the coarse movement part 3 and an electric field strength of up to 1 kV / mm is applied, ± 0.
Positioning with an accuracy of 1 μm (± 0.2%) can be performed in 1 ms using a 150 mA power supply.

When the laminated piezoelectric actuator having the above-mentioned structure is used to perform positioning control to a predetermined position, for example, when it is desired to extend the current position by 10 μm, a voltage is applied to the piezoelectric element 12 of the coarse movement part 3 to obtain 10 ± 0. Move to a distance of 1 μm. Subsequently, with respect to the remaining ± 0.1 μm, a voltage is applied to the laminated body 5 of the piezoelectric elements 4 of the fine movement part 2 to obtain ± 0.0 μm.
Position by moving by 05 μm. By providing the fine moving part 2 and the coarse moving part 3, both high-speed response and fine positioning can be provided. In the above embodiment, the fine movement unit 2
Although the plate thickness of the piezoelectric element 4 is set to 1/2 or less of the plate thickness of the piezoelectric element 12 of the coarse movement part 3, the invention is not limited to this.
It is apparent that the fine movement portion 2 can be finely positioned as compared with the coarse movement portion 3 by making the piezoelectric element 4 thinner than the piezoelectric element 12. Further, the laminated body 5 of the fine movement part 2 has the piezoelectric elements 4 laminated in order, but the (+) electrode plate 8 and the (−) electrode plate 9 are interposed between the laminated piezoelectric elements 4 as in the coarse movement portion 3. You may make it the structure sandwiched alternately.

(Second Embodiment) FIG. 3 is a schematic view showing the structure of a laminated piezoelectric actuator according to the second embodiment. A fine movement portion 22 and a coarse movement portion 23 are formed between the insulating dummies 1a and 1b at both ends. Piezoelectric element 24 used for fine movement section 22 and piezoelectric element 25 used for coarse movement section 23
In the same manner as in the first embodiment, electrodes are formed on both sides with silver paste or the like. The structure of the coarse moving portion 23 is also the same as that of the coarse moving portion 3 of the first embodiment. The fine movement unit 22 is a stack of three fine movement units 22a, 22b, 22c.

The fine movement units 22a to 22c have 2 ⁿ (n
= 0,1,2,) piezoelectric elements 24 are sandwiched between (+) electrode plates 26 (-) electrode plates 27 which are alternately arranged, and stacked, and each fine movement unit 22a to 22a.
The number of piezoelectric elements 24 in c is different. Then, the (+) electrode plate 26 of each of the fine movement units 22a to 22c.
To the individual amplifier circuits 30a-30
c is connected. Further, the piezoelectric element 25 of the coarse moving portion 23
The (+) electrode plate 31 between them is connected to the amplifier circuit 33 by a common lead wire 32. The (−) electrode plate 27 of the fine movement part 22 and the (−) electrode plate 34 of the coarse movement part 23 are grounded by a common lead wire 35.

When one piezoelectric element 24 is driven by applying a certain electric field strength, if the piezoelectric element 24 is displaced by 0.02 μm, each of the fine movement units 22a to 22c has an amplifier circuit 30a.
. To 30c, respectively, the fine movement unit 22a is 0 to 0.02 .mu.m, and the fine movement unit 22b is 0 to
0.04 μm, fine movement unit 22c is 0 to 0.08 μm
It can be displaced. Therefore, by any combination of the driven fine movement units 22a to 22c, 0 to 0.
A displacement of 14 μm can be controlled and positioned at a pitch of 0.02 μm. The coarse movement unit 23 having the same configuration as that of the first embodiment is
± 0.1 μm (± 0.2 μm) for displacement of 0 to 50 μm
%) Positioning can be performed. Fine movement part 22
By combining the coarse movement unit 23 and
Positioning can be performed in the range of m with an accuracy of 0.02 μm.

The piezoelectric elements 24 of the fine movement units 22a to 22c are individually turned on / off and driven for each unit, and it is not necessary to control a minute current.
There is no particular need to mention the plate thickness of. The laminated piezoelectric actuator of the second embodiment has the above-mentioned configuration, and has a full stroke of 120,000 to 1/10,
000 accuracy and high speed positioning.

(Third Embodiment) FIG. 4 is a principle view of a laminated piezoelectric actuator according to the third embodiment. Coarse movement part 33
At the end of the piezoelectric element 36 in the stacking direction, the fine movement part 32 is arranged via an insulating plate 37. The fine moving part 32 is in contact with the insulating plate 37 at a side part thereof that is orthogonal to the stacking direction of the piezoelectric elements 34. The direction in which the voltage is applied to the fine moving portion 32 and the coarse moving portion 33 is the stacking direction of the piezoelectric elements 34 and 36. The configurations of the fine moving portion 32 and the coarse moving portion 33 are the same as those of the first
The structure of the coarse moving unit 3 of the embodiment or the coarse moving unit 23 of the second embodiment can be used as it is.

Fine movement unit 32 driven by application of voltage
Can be displaced in the displacement direction of the coarse motion portion 33 by the displacement amount defined by the Poisson's ratio. Piezoelectric elements 34, 36 such as PZT
Since the Poisson's ratio (horizontal strain / vertical strain) is about 0.3, the resolution of the positioning of the minute displacement amount by the fine moving part 32 can be increased about 3 times as compared with the case of the first and second embodiments. it can. Fine moving parts 2 and 22 of the first and second embodiments
The piezoelectric elements 4 and 24 used in the above are circular, but may be square or polygonal as shown in FIG. However, it is preferable to use a polygonal shape other than a circular shape for the piezoelectric element of the third embodiment.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a structure of a laminated piezoelectric actuator of a first embodiment.

FIG. 2 is an exploded perspective view showing an outline of a laminated body that constitutes a fine movement unit.

FIG. 3 is a schematic view showing a structure of a laminated piezoelectric actuator of a second embodiment.

FIG. 4 is a principle diagram of a laminated piezoelectric actuator of a third embodiment.

FIG. 5 is a perspective view showing a modified example of the piezoelectric element used for the fine movement part.

[Explanation of symbols]

2 Fine movement part 3 Coarse movement part 4, 12, 24, 25, 3
4,36 Piezoelectric element 5 Laminated body 22a to 22c Fine movement unit 30a to 30c, 33 Amplifier circuit

Claims (4)

[Claims] 1. A laminated piezoelectric actuator in which a coarse movement portion and a fine movement portion formed by a laminated body in which one or more piezoelectric elements are laminated are arranged in series, and a plate of the piezoelectric element forming the fine movement portion. A laminated piezoelectric actuator having a thickness smaller than a plate thickness of the piezoelectric element forming the coarse movement portion. 2. A laminated piezoelectric actuator in which a coarse movement portion and a fine movement portion formed by a laminated body in which one or more piezoelectric elements are laminated are arranged in series, wherein the fine movement portion has 2 ⁿ piezoelectric elements. (N = 0,1,2 ...
..) consisting of multiple units
A laminated piezoelectric actuator characterized in that the number of piezoelectric elements is different for each unit. 3. The laminated piezoelectric actuator according to claim 2, wherein each unit that constitutes the fine movement unit is individually driven. 4. A coarse movement part and a fine movement part are formed by a laminated body in which one or more piezoelectric elements are laminated, and an end portion in the lamination direction of the coarse movement part and a side orthogonal to the lamination direction of the fine movement part. A laminated piezoelectric actuator, characterized in that it is in contact with a portion.