JPS60219972A - Fine moving device utilizing laminated piezoelectric elements - Google Patents

Abstract

PURPOSE:To drive with a low voltage by employing a small-sized high performance laminated piezoelectric element for a clamping element. CONSTITUTION:Cylindrical piezoelectric elements 10, 11 having a shaft 9 and electrodes coated independently on the inner and outer peripheral surfaces and made of laminated piezoelectric elements engaged at an interval on the outer periphery of the shaft 9, holding members 12, 14 adhesively bonded to the outer peripheral surfaces of the elements 10, 11, and a hollow piezoelectric element 14 made of a laminated piezoelectric elements bonded at the end to the members 12, 13 are provided. Thus, when the clamping element having the same shape as the conventional clamping element is formed of the laminated piezoelectric elements, the performance of the same degree as the conventional clamping element can be obtained with the voltage of 1/10 of the conventional one.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an ultra-fine positioning device used for positioning optical equipment, controlling precision equipment, and the like.

(Prior art) As this type of fine movement device, US Patent No. 3902'08
Inchworm-type fine movement devices disclosed in No. 4 and No. 3902085 are well known and are in practical use. The configuration will be explained using the schematic diagram shown in FIG. In Figure 1, 1. 3. 4 is a cylindrical element made of piezoelectric material, and the inner and outer surfaces of each element are coated with electrodes. When the voltage applied to the element is increased or decreased through this electrode, element 1 expands and contracts in the axial direction, and elements 3 and 4 are clamping elements that expand and contract in the radial direction, and when they contract, they restrict the position of shaft 2. be able to. Numeral 6 is a clamp for storing and fixing the center element 1 via a holding member 7.

The coupling member 8 bridges the element 1 and the elements 3 and 4, and is adhesively fixed to each element. Bly Bz, BS is the power supply, 几1. R3 is a discharge resistor, Sly s2.
s is a switch. The fine movement device can be operated by the operation described below. First, after closing the switch S1 to the power supply side and restraining the shaft 2 with the clamp element 3,
Switch S is closed to the power supply side to increase the voltage of R3, extend element 1, and move shaft 2 to the left. Next, switch S is closed to the power supply side to restrain the shaft 7 with the clamp element 4, and then switch S1 is closed to the resistance side to restrain the shaft 2 by the clamp element 3, and then the voltage of E2 is decreased to restrain the shaft 7. 1 and move the shaft 2 to the left. By repeating each of the above steps, the shaft 2 will be sequentially moved to the left. On the other hand, movement in the right direction is possible by reversing the order of restraining the shaft by the clamp element 3 and restraining the shaft by the clamp element 4 among the operations described above. The two directions of movement described above can be used to set the load connected to the shaft part in the desired position.

In an actual device, the above-mentioned switches and control of voltage increase/decrease, etc. are performed using a computer or the like, and high-speed operation is also possible.

(Problems with the Prior Art) A problem in the development of the inchworm-type fine movement device having the above-mentioned configuration is the technical restriction in increasing the elongated weight of the piezoelectric material. Since the expansion/contraction rate of piezoelectric material is proportional to the electric field strength, if the thickness of the ceramic element is increased to increase the amount of expansion/contraction, a large voltage is required. Therefore, the dimensions of the piezoelectric element 3.4 are determined by taking into consideration the above-mentioned applied voltage, mechanical strength, ease of obtaining uniform engagement between the ceramic elements 3 and 4 and the shaft 2, and an inner diameter of 11 iui. , 60 for a ceramic element with a wall thickness of 1+w
By applying a voltage of about 0.5 μm, a change in the inner diameter of 2 to 3 μm was obtained. That is, in FIG. 1, when a voltage of about 600 mm is applied to the ceramic elements 3 and 4, the ceramic elements 3 and 4 contract in the radial direction and restrain the shaft. In that case 2-3
Since only μ is reduced, the tolerance for variations in the sizes of the ceramic elements 3, 4 and the shaft 2 is small, and manufacturing techniques such as processing and assembly to obtain uniform engagement between the ceramic elements 3, 4 and the shaft 2 are at their limits. There is something close to.

Next, focusing on the means for applying an electric field to the center element 1, electrodes are provided on the inner and outer circumferential surfaces of the cylindrical element, a voltage is applied in the thickness direction, and the center element 1 is expanded and contracted in the axial direction perpendicular to the direction of application. This is an attempt to make use of the transverse effect distortion of the element. In general, as a property of piezoelectric ceramics, under the same electric field strength, the relationship holds that the transverse effect strain is 1/2 of the longitudinal effect strain, and this is shown in Japanese Patent Laid-Open No. 49
-86816 is also described in detail. Therefore, using transverse effect strain requires twice as much electric field strength as using longitudinal effect strain, which is inefficient. It is also possible to configure electrodes 29 on both end faces of the cylindrical element and utilize longitudinal effect strain, but as mentioned earlier, the distance between both end faces is larger than the distance between the thick parts, so the same A much higher voltage is required to obtain the electric field strength. Therefore, the dimensions of the center element 1 are determined by taking into account mechanical strength, amount of expansion and contraction, etc. in addition to the applied voltage mentioned above. was applied to obtain a change in the amount of expansion and contraction of 2μ.

On the other hand, by further increasing the voltage applied to the ceramic element,
It is not preferable to increase the amount of expansion and contraction in order to operate the fine movement device at high speed. That is, as can be seen from the operating procedure of the fine movement device described above, in order to operate the fine movement device at high speed, it is necessary that the switch Sly Sats operates at high speed, and a transistor is used. Increasing the voltage applied to ceramic elements requires the development of transistors that operate isometrically at high voltages and at high speeds. Figures 3 (,) and (b) are structural diagrams of alloy junction transistors for power use, where 30 is an emitter;
1 is a collector, 32 is a base, and 33 is a semiconductor. Here, the current area of the emitter 30 and collector 31 is made as large as possible so that the current density does not become excessive. The faster the switching speed, the
Due to the skin effect, current only flows near the electrode surface, so it is necessary to further increase the surface area of the electrode.

Therefore, if the transistor has a high breakdown voltage, t'
! ! However, the surface area of the semiconductor and electrodes becomes larger, and the yield is lower than that of low-voltage products, making them more expensive.

There is also a method of dividing a high voltage using a plurality of low voltage transistors for switching, but this requires adjustment time to solve problems of delay and balance of each transistor. For the reasons mentioned above, increasing the voltage applied to the ceramic element to increase the amount of expansion and contraction is not desirable in order to achieve a fine movement device at higher speeds, and is a major obstacle in making inchworm-type motors cheaper and more compact. It becomes.

(Objective of the Invention) The present invention provides a fine movement device that employs laminated piezoelectric elements for the above-mentioned clamping element and center element, and can be driven at a low voltage.

(Structure of the Invention) In order to achieve the above object, the present invention includes a first cylindrical element that is composed of a laminated piezoelectric element exhibiting a piezoelectric inverse effect and is expandable and contractible in the axial direction, and an inner part of the first cylindrical element. a shaft movable within the cylinder of the first cylindrical element; connected to the first cylindrical element via a coupling member;
a second cylindrical element made of a laminated piezoelectric element capable of expanding and contracting in the radial direction to hold and fix the outer peripheral surface of the shaft; and means for applying an electric field within the second cylindrical element; A fine movement device using a laminated piezoelectric element is provided, comprising a housing connected to a first cylindrical element via a coupling member and housing and fixing the first cylindrical element. That is.

(Description of the structure of the invention) In order to achieve high strain generation through low voltage applied driving, electrodes are set on the front and back surfaces of the thin plate element in the thickness direction, and a voltage is applied in parallel to a large number of layers stacked and integrated. Laminated piezoelectric elements are well known and have been put into practical use, but they are known and have been put into practical use, increasing the field strength of the piezoelectric element even further by applying an electric field to the piezoelectric element, and producing high strain as a whole. Since this is not possible, a high driving voltage is still required. Since adhesive is used to laminate the thin plates, productivity is low and costs are high. Furthermore, due to the presence of the adhesive layer, uniform strain cannot be obtained as a pure piezoelectric element. Lack of reliability such as longevity. Further, due to its large size, etc., it was not fully satisfactory as an element for electronic parts. However, the ultra-small piezoelectric ceramic element introduced in the Technical Research Report of the Institute of Electronics and Communication Engineers (US83-8) uses the manufacturing technology of multilayer ceramic capacitors to integrate piezoelectric ceramic plates into one layer without using adhesives. This is an innovative laminated piezoelectric element that overcomes all of the above-mentioned drawbacks.The present invention utilizes this laminated piezoelectric element to provide a fine movement device that can be driven at low voltage.

(Example) Hereinafter, the present invention will be explained in detail based on an example of implementation. FIG. 4 is a schematic diagram of a fine movement device according to the present invention, FIG. 5 is a radial cross-sectional view, and FIG. 6 is a schematic diagram of a hollow laminated piezoelectric element used in the device of the present invention.

The embodiments of the present invention shown in FIGS. 4, 5, and 6 are as follows:-
A cylindrical piezoelectric element comprising a shaft 9 and a laminated piezoelectric element having electrodes independently attached to the inner and outer circumferential surfaces thereof and fitted at a distance from each other on the outer circumferential surface of the shaft. an element 10.11 and a holding member 12.13 adhesively fixed onto the outer peripheral surface of each of the cylindrical element 10.11;
A hollow piezoelectric element 14 consisting of a laminated piezoelectric element whose end portions are adhesively fixed to the holding member and held in a bridging manner between the holding members, and a housing 15 for storing and holding the hollow piezoelectric element an L-shaped rod member 19 that fits and guides a U-shaped notch provided on the guide portion side 18 whose one end is press-fitted into the housing part 5 and which is press-fitted and fixed to the end of the shaft 9. , a group of lead wires 20 for supplying voltage to the three piezoelectric elements, a cape A/21, a case 22, 23 which is connected to the housing 15, and a case 22, 23 which is press-fitted to one end of the shaft and has an object attached to one end. Rod-shaped member 2 having coupling means for holding
4.

Referring to FIG. 6, the hollow laminated piezoelectric element 10.11 has a large number of internal electrode layers 25 embedded inside the ceramic in a layered manner and exposed at the end face of the element. Since every other internal electrode layer is covered with an insulator 26 and external electrodes 27 and 28 are applied from above,
Each internal electrode layer will be electrically connected to each other in parallel. Furthermore, since these elements are polarized in the thickness direction, when a voltage is applied between the external electrodes, they expand in the thickness direction in proportion to the magnitude of the voltage. At this time, it contracts in the radial direction, and this radial contraction restrains the shaft.

Since the electrode spacing of the laminated piezoelectric element is 100μ, the applied voltage is 1 of 600V when using a conventional piezoelectric element with a thickness of 1n.
The same distortion factor can be obtained with a voltage of /10. Also, the mechanical strength and ease of achieving uniform engagement with the shaft are almost the same as with conventional elements. Therefore, if a clamp element having the same shape as a conventional clamp element is made of a laminated piezoelectric element, performance comparable to that of the conventional clamp element can be obtained with a voltage that is 1/10 of the conventional applied voltage. On the other hand, the shape of the center element is the same as the conventional one, with an inner diameter of 11 mm and 111 mm.
．． Although the wall thickness is 111mm and the length is 25.4mm, the electrode spacing of the laminated piezoelectric element is 100μ, and because it utilizes the longitudinal effect, it can expand and contract 12 times even if the applied voltage is reduced to 1/10. It has the advantage of operating at high speed when used as a shakutori shimushi type fine movement device.

In the fine movement device according to the present invention, since it is necessary to accurately produce extremely small displacements on the submicron level, members directly involved in movement, such as the shaft 9, the holding member 12.13, and the coupling member 16.17, are preferably piezoelectric. A ceramic material having a low thermal expansion coefficient equivalent to or similar to that of the element 14 and the laminated type 10.11 is preferable. In addition, since the three types of members mentioned above are in direct contact with the electrodes, at least their surfaces must be made of non-conductive material. Since it is a moving member, it is preferably made of the above-mentioned ceramic material. Cylindrical element 10
．． 11 returns to its original shape and dimensions when the voltage application is removed. When no voltage is applied, the distance between the shaft outer circumferential surface and the element inner circumferential surface should be set so that tj is zero fitting, taking into consideration the prevention of radial play and the grip force associated with the contraction of the element. Bye. Holding member 12a.

12b and 12c have a fan-like shape (see FIG. 5, 13 is the same), and are adhesively fixed on the outer circumferential surface of each of the cylindrical piezoelectric elements 10 and 11 at a distance of 120°, and Glue and hold at its ends. Coupling member 16.17
are respectively 1 on the outer circumferential surface of the piezoelectric element 14 at the center in the axial direction.
They are fixed with adhesive at a distance of 800 mm, and are positioned and fixed with adhesive at the shoulder of the step provided inside the housing 15. The rod-shaped member 24 has a coupling means with the object, and is preferably a metal member having a low coefficient of thermal expansion for the purpose of transmitting force to the object and positioning it. The L-shaped bar member 19 has a function of preventing rotation of the shaft 9.

The operation sequence of the fine movement device according to the present invention is the same as that described in the section of the prior art, and the switches S1+S2 in FIG.
and S, transistors with a withstand voltage of 70V are used and are controlled by a computer. In this example, the electrode spacing is 1
Although a laminated piezoelectric element with a diameter of 00μ was used, it is also possible to drive at an even lower voltage by using a laminated piezoelectric element with an even smaller electrode spacing.

(Effects of the Invention) As explained above, the present invention has a configuration in which a compact and high-performance laminated piezoelectric element is used as an element that performs a clamping action. (1) Low voltage drive and high speed are possible. .

(2) Multi-layered element of monolithic firing type, mass production possible.

Extremely reliable.

(3) For the above reasons, the device and drive circuit can be made smaller and more compact.

The economic, functional, and reliability ripple effects are enormous.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram to explain the inchworm-type fine movement device, Figure 2 is a perspective view of a telescopic element in the case where the vertical effect is not used in the conventional example, and Figure 3 is an alloy type junction transistor for electric power. , FIG. 4 is a side cutaway view of a fine movement device showing an embodiment of the present invention, FIG. 5 is a radial cross-sectional view, and FIG. 6 is a schematic cross-sectional view of a laminated piezoelectric element used in the present invention. It is a diagram. 1, 3.4... Cylindrical piezoelectric element 2, 9... Shaft 6.15... Housing 7, 16, 17... Coupling member 7, 8. 12.13... Holding member 10. 11.14...Hollow laminated piezoelectric element 20...
・Lead wire group 21... Cable 22. 23... Case 24... Rod-shaped member 25... Internal electrode layer 26
...Insulators 27, 28...External electrodes 29...Electrodes 30...Emitter 31...Collector 32...
・Base 33...Semiconductor Fig. 2 Fig. 3 j <b) Fig. 4') f Fig. 5 76 Fig. 5

Claims (1)

[Claims] A first cylindrical element capable of expanding and contracting in the axial direction, means for applying an electric field to the first cylindrical element, and a cylinder of the first cylindrical element a second cylindrical element that is connected to the first cylindrical element via a coupling member and that is capable of expanding and contracting in the radial direction to hold and fix the outer peripheral surface of the shaft; a cylindrical element, a means for applying an electric field within the second cylindrical element, connected to the first cylindrical element via a coupling member,
A fine movement device using a laminated piezoelectric element, comprising a housing for storing and fixing the first cylindrical element.