JPH03123088A - Solid-state actuator - Google Patents

Abstract

PURPOSE:To decrease not only an electrical field applied to a solid-state element in intensity but also a source voltage and to enable the element to generate a large distortion by a method wherein two or more solid-state elements possessing a piezoelectric longitudinal effect are laminated to form a laminated oscillator, the solid-state elements are connected in series to a power supply, and the laminated oscillator is joined to an elastic plate in a thicknesswise direction. CONSTITUTION:A pair of laminated oscillators 10 are used to constitute a unimorph type solid-state actuator. Inner electrodes are provided for solid-state elements 1, which are laminated, burned, and cut. Conductors 21 and 22 are joined as electrodes to the crosswise end faces of the laminated oscillator 10 as shown by a double dotted chain line. As the conductors 21 and 22 are connected in parallel, the solid-state elements 1 can be enhanced in electrical field intensity with a low drive voltage. The laminated oscillator 10 is joined to an elastic plate 4 with a adhesive agent in a thicknesswise direction. When a voltage is applied, a distortion of expansion or contraction is generated in the solid-state elements 1 corresponding to the directions of the polarization axes of the elements 1 and the electrical field applied to them, and the laminated oscillator 10 is able to produce a large distortion.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a solid-state actuator for positioning optical disks, magnetic disks, etc. at high speed and with high precision.

(Prior art) Lead titanate derconate ceramics (PZT) have conventionally been used as one of the solid-state elements that convert mechanical signals and electrical signals.
), and research is underway in ultrasonic engineering with the aim of increasing the output as a vibrating body and miniaturizing it as a delay element.

On the other hand, in the field of recent semiconductor manufacturing equipment, information equipment such as optical disks and magnetic disks, and the field of precision processing technology, research on improving the precision of positioning technology is active. Of these,
Solid-state actuators that utilize piezoelectric (electrostrictive) effects have recently attracted attention because they have features such as being able to perform minute positioning on the submicron order simply by controlling voltage.

The piezoelectric body used as a drive source for the solid-state actuator is divided into two types: a piezoelectric longitudinal effect type and a piezoelectric transverse effect type.

In the former case, strain or force in a direction parallel to the polarization axis of the ceramic is used. Although the amount of displacement that can be generated is small, the generated force is large and its response is fast. In the latter case, strain or force in a direction perpendicular to the polarization axis of the ceramic is used. The bimorph type, which has developed the use of this lateral effect, generates a small force but can obtain a relatively large displacement.

When using the above piezoelectric body as a solid actuator,
The piezoelectric longitudinal effect type has large piezoelectric constant d, piezoelectric constant g, and electromechanical coupling coefficient, and is the most effective. but,
Actuators that utilize the piezoelectric longitudinal effect generally have fairly high mechanical impedance, and therefore require an impedance matching mechanism tailored to the applied equipment, making the mechanism more complex.

On the other hand, bimorph actuators that utilize piezoelectric transverse effects have a considerably smaller electromechanical coupling coefficient;
The impedance matching mechanism as described above is unnecessary, the mechanism is simple, and the value of use is high.

Figure 4 is a diagram showing the operation of the above actuator, Figure 4 (
A) is an operation diagram of an actuator using piezoelectric longitudinal effect,
FIG. 4(B) is an operation diagram of an actuator using the piezoelectric transverse effect.

In FIG. 4(A), in the case of the piezoelectric longitudinal effect, the solid-state element 1
Both surfaces are made into electrode surfaces 8 using a good conductor such as gold or silver, and a polarization axis is formed in the direction shown by arrow P in the figure perpendicular to the picture electrode surface 8. Then, when a voltage (2) is applied from the voltage VjJA 13 to the solid-state element 1 via the lead wire 23, a force or displacement is generated in the direction shown by the arrow Q, which can be utilized.

That is, the input energy to the solid-state element 1 is W,=C,
V, l"/2 The strain energy stored per unit volume of the solid element 1 is W, -S z"72 S 33 The electric capacity is expressed as Cs = ab ε33" / 1. However, ε33T: stress is Dielectric constant S in the polarization axis direction for a constant case:
++E: Elastic compliance in the polarization axis direction when the electric field strength is constant S3: Strain in the polarization axis direction. At this time, the efficiency is ζs=W/W.

=S 22/ S zzEC3V 3”=Ss”/ab
ff 333Eεs3'' E32 Here, the electric field strength is E3 = V3 /1.

On the other hand, in the case of the piezoelectric transverse effect in FIG. 4(B), when the voltage V1 is applied from the power source 13, the input energy to the solid-state element 1 is Wll=C,V,''/2 of the solid-state element 1. The strain energy stored per unit volume is: W inertia -3+"/2s The electric capacity is expressed as C,1=616 s, l"/a. However, ε33T: direction of polarization axis when stress is constant dielectric constant S1 of
．． E: Elastic compliance in the direction perpendicular to the polarization axis when the electric field strength is constant Sl: Strain in the direction perpendicular to the polarization axis. At this time, the efficiency is ζ, = W/W.

= SI"/ S 11' C1V 1"-3+"/
a bj2 S++' esyding E,! Here, the electric field strength is E+=V+/a.

Comparing the efficiency ζ3 of the piezoelectric longitudinal effect and the efficiency ζ1 of the piezoelectric transverse effect, ζ3/ζ,=s,-(S3E,)''/s33E(31E3)''.

Here, to simplify the calculation, a=b=l.

Let E+=E, l. From each constant when the solid-state element 1 is composed of the above-mentioned PZT, S, "= 533):/ (1,2 to 1.5) S, ≧
(2-2.5) S.

Therefore, ζ3/ζ1 is ζ3/gu, = (2~2.5)2/(1,2~1.5)
-2.7 to 4.2, and using the vertical effect is several times more efficient than using the horizontal effect. Calculatedly, the reason why the strain S3 in the direction of the polarization axis is 2 to 2.5 times the strain SI in the direction perpendicular to the polarization axis is because the piezoelectric strain constant d in each direction is dss≧(2 to 2.5) d
This is because there is a relationship of 31.

When the strain of the solid-state element 1 is directly taken out to the outside and used as an actuator, the solid-state element 1 is normally placed under a high electric field exceeding ν/mm, and a general-purpose power source is used. In order to be placed under such a high electric field strength, the distance between the electrodes of the solid state element 1 itself must be at least about 0.2 to 0.3 mm. In other words, unless the solid-state device 1 is fired to a thickness of about 0.2 to 0.3+++ m, it is practically impossible to place it under an electric field exceeding 1 kv/mm. In a bimorph type actuator that utilizes a piezoelectric transverse effect, strain in the longitudinal direction (direction perpendicular to the polarization axis) of the solid-state element 1 having a thickness of about 0.2 to 0.311II11 is utilized in its construction. Therefore, by increasing the length in the longitudinal direction, it is possible to obtain a displacement of several tens of millimeters in practice, and this type of actuator can be manufactured easily.

On the other hand, when the longitudinal effect is used, the energy efficiency is better than when the lateral effect is used, but as described above, the solid-state element 1 must be made thinner. However, if the solid-state element 1 is thin, the amount of energy that the solid-state element 1 itself can hold will be smaller in proportion to its volume, so the amount of work that the solid-state element 1 can do to the outside will also be smaller, and in the end it will be difficult to use the actuator for practical use. It is almost impossible to obtain this with a single structure as shown in FIG. 4(A).

Therefore, multilayer actuators manufactured by applying manufacturing techniques for multilayer wiring boards, chip capacitors, etc. have been provided.

FIG. 5 is a perspective view of the laminated actuator.

In the figure, a solid-state element 1 laminated in a thin plate shape is connected to a conductor 21.
．． It is electrically connected in parallel to the power supply 13 via 22, etc., and the driving voltage is lowered to utilize the mechanical displacement obtained in series in the direction indicated by the arrow Q.

Since each solid-state element l is fired to a thickness of about 0.2 to 0.3 cylinders, each can be heated to about 1kv with a low power supply voltage.
When about 50 sheets are laminated, a displacement of about 5 μm can be obtained with a power supply voltage of 100 ν.

(Problem to be Solved by the Invention) However, in the solid actuator having the above configuration, the solid element 1 is formed by mixing smoky ceramic powder, a binder, a plasticizer, a solvent, etc., and is fired to form a film. There are countless bores. Therefore, the dielectric strength voltage of the solid-state element 1 is influenced by the size and number of the bores, and cannot be made higher than the dielectric strength voltage of air.

When dielectric breakdown occurs in the solid-state element 1 due to the bore, the broken part becomes carbonized and short-circuits the pole faces 8 of both types, so that it no longer functions as an actuator.

The present invention solves the problems of the conventional solid-state actuators described above, and provides a solid-state actuator that can lower the strength of the electric field applied to the solid-state element, lower the power supply voltage, and generate large strain. purpose.

(Means for solving the problem) For this purpose, in the solid actuator of the present invention,
A laminated vibrating body is formed by laminating a plurality of solid elements that utilize the piezoelectric longitudinal effect, each solid element is connected in parallel to a power source, and the laminated vibrating body is bonded to an elastic plate in its thickness direction.

In addition, the laminated vibrating body has two bonding surfaces extending in the thickness direction.
The solid-state elements may be coupled to a power source so that positive strain is generated in one laminated vibrating body and negative strain is generated in the other laminated vibrating body.

(Function) According to the present invention, a laminated vibrating body is formed by laminating a plurality of solid elements using the piezoelectric longitudinal effect as described above, each solid element is connected in parallel to a power source, and the laminated vibrating body is Since the body is joined to the elastic plate in the thickness direction, the strain generated in each solid element can be applied to the elastic plate to obtain a large displacement.

In addition, the laminated vibrating body has two bonding surfaces extending in the thickness direction.
If each solid-state element is connected to a power source in such a way that positive strain is generated in one laminated vibrating body and negative strain is generated in the other laminated vibrating body, the strain caused by each laminated vibrating body can be amplified. can.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the solid actuator of the present invention, FIG. 1(A) is a perspective view thereof, FIG. 1(B) is a sectional view thereof,
FIG. 1(C) is a diagram of the same bending state.

In the figure, a unimorph solid actuator is formed using a set of laminated vibrating bodies 10. As described above, the solid element 1 is formed by mixing the roasted ceramic powder, binder plasticizer, solvent, etc. and forming a film. and,
After the internal electrodes are printed, the solid-state device 1 is laminated, fired, and cut. The laminated vibrating body 10 is electrode-bonded by conductors 21 and 22 on both sides in the width direction indicated by two-dot chain lines. As described above, since the conductors 2L22 are connected in parallel, it is possible to increase the electric field strength of each solid-state element 1 with a low driving voltage.

The laminated vibrating body 10 having the above structure is bonded to an elastic plate 4 with an adhesive 3 in its thickness direction to form a unimorph solid actuator. When a voltage is applied, expansion/contraction strain occurs depending on the direction of the polarization axis of each solid-state element 1 and the direction of its electric field, and the laminated vibrating body 10 can generate large strain with a low driving voltage.

Adhesive 3 bonding the laminated vibrating body 10 and the elastic plate 4
If the thickness of the adhesive layer 3 is smaller than that of the laminated vibrating body 10 and the elastic plate 4, the shear deformation of the adhesive layer 3 can be ignored.
The strain generated in the solid element 1 and the elastic plate 4 is continuously and temporarily distributed in the thickness direction of the solid actuator.
As shown in Figure (C), the solid actuator bends with a certain curvature.

FIG. 2 is a diagram showing a second embodiment of the solid actuator of the present invention, FIG. 2(A) is a perspective view thereof, FIG. It is a bending state diagram.

In the figure, a bimorph solid actuator is formed using two sets of laminated vibrating bodies 10L102.

In this case, each of the laminated vibrating bodies 101 and 102 is constructed by laminating solid elements 1, and is coupled by a coupling surface 5 extending in the thickness direction. Then, one laminated vibrating body 10
The electrode surfaces of each of the solid-state elements 1 of one layered vibrating body 102 and each of the solid-state elements 1 of the other layered vibrating body 102 are shifted by half a pitch from each other.

That is, the electrode surfaces are a-a and bb, and each solid-state element 1
If the polarization axis direction P is taken from the electrode plane b-b to the electrode plane a-a direction, since the individual solid-state elements 1 are shifted by half a pitch as described above, the electrode plane a-a between each solid-state element 1 is , b-b
This means that there is an electrical short circuit. The appearance is 2 in the diagram.
The electrodes are connected to each other by conductors 21 and 22 in the area surrounded by the dashed dotted line.

When a voltage is applied to the solid-state actuator, the strains of both the laminated vibrating bodies 101 and 102 have opposite signs, so that it is possible to excite the bending motion as shown in FIG. 2(C).

FIG. 3 is a diagram showing a third embodiment of the solid state actuator of the present invention, FIG. 3(A) is a perspective view thereof, FIG. 3(B) is a sectional view thereof, and FIG. 3(C) is a bent view thereof. FIG.

In the figure, unlike the example in FIG. 2, the solid elements 1 of the two laminated vibrators 101 and 102 are not electrically short-circuited by shifting the solid elements 1 by half a pitch, but are electrically connected by connecting means 23. short-circuited. In terms of operation, as in the example shown in Fig. 2, when a voltage is applied to the solid actuator, the strains in both the laminated vibrators 101 and 102 have opposite signs, so the actuator makes a bending motion as shown in Fig. 3 (C). excite.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As described above in detail, according to the present invention, a plurality of collective elements using the piezoelectric longitudinal effect are stacked to form a 34-layered vibrating body, and each solid-state element is connected in parallel to the power source. The laminated vibrating body is connected to an elastic plate in its thickness direction, or two sets of laminated vibrating bodies are connected by a bonding surface extending in the thickness direction, so that a positive strain is applied to one laminated vibrating body, and a positive strain is applied to the other laminated vibrating body. Each solid-state element is connected to a power source so that negative strain is generated in the laminated vibrating body.

Therefore, it is possible to provide an actuator with energy efficiency several times higher than that of conventional unimorph or bimorph solid state actuators that utilize piezoelectric transverse effects. It is possible to drive with voltage, and a general-purpose power source can be used.

Furthermore, in conventional actuators that utilize piezoelectric longitudinal effects, the mechanical impedance is quite high, and it is necessary to prepare an impedance matching mechanism compatible with the applied equipment, which makes the mechanism complicated. In solid state actuators, an impedance matching mechanism is not required and the mechanism is simple.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the solid actuator of the present invention, FIG. 1(A) is a perspective view thereof, FIG. 1(B) is a sectional view thereof,
FIG. 1(C) is a bending state diagram of the same, FIG. 2 is a diagram showing a second embodiment of the solid state actuator of the present invention, FIG. 2(8) is a perspective view of the same, and FIG. 2(B) is a diagram of the same. A sectional view, FIG. 2(C) is a bending state diagram of the same, FIG. 3 is a diagram showing a third embodiment of the solid actuator of the present invention, FIG. 3(A) is a perspective view of the same, and FIG. ) is the same sectional view, Figure 3 (C) is the same bending state diagram, Figure 4
The figure shows the operation of the actuator, Figure 4 (A) shows the operation of the actuator using the piezoelectric longitudinal effect, and Figure 4 (A) shows the operation of the actuator using the piezoelectric longitudinal effect.
B) is an operation diagram of an actuator using piezoelectric transverse effect;
FIG. 5 is a perspective view of a laminated actuator. DESCRIPTION OF SYMBOLS 1... Solid-state element, 8... Electrode surface, 13... Power supply,
2L22...Conductor, 23...Lead wire, 101,1
02...Laminated vibrating body.

Claims (2)

[Claims] (1) (a) Form a laminated vibrating body by laminating a plurality of solid-state elements that utilize the piezoelectric longitudinal effect, (b) Connect each solid-state element in parallel to a power source, (c) Connect the laminated vibrating body to its A solid actuator characterized by being joined to an elastic plate in the thickness direction. (2) (a) Two sets of the laminated vibrating bodies are connected by a coupling surface extending in the thickness direction, and (b) positive strain is generated in one laminated vibrating body and negative strain is generated in the other laminated vibrating body. 2. The solid state actuator according to claim 1, wherein each solid state element is connected to a power source in such a manner.