JPH02151283A - Ultrasonic linear motor - Google Patents

Abstract

PURPOSE:To reduce the thickness and the size of an ultrasonic linear motor by approaching the resonance points of a bending mode and a longitudinal mode of a square rodlike base provided integrally with a driver to each other to generate a composite resonance, and moving a slider. CONSTITUTION:The length and thickness sizes of a base 1 are made to have dimensional relationship for simultaneously generating modes. When a voltage is applied to piezoelectric elements 3a-3d, the base 1 is excited to simultaneously generate two modes, thereby performing a composite resonance. Since the polarizable polarities of right and left piezoelectric elements are opposite to each other, it operates to elongate a left half longitudinally and to contract a right half, thereby performing a vibration of a secondary longitudinal mode.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an ultrasonic linear motor,
In particular, the present invention relates to an ultrasonic linear motor that operates as a -axis actuator by applying an electric signal in the ultrasonic range to a piezoelectric element.

[Conventional technology]

Conventionally, this type of ultrasonic linear motor has been proposed by this inventor (Utility Application No. 161013/1982), and to explain this with reference to FIG. Two drivers (12a) and (12b) are provided protruding from the negative side of the base (11).

Moreover, two piezoelectric elements (13a) and (13b) for bending mode are mounted on the base body (11), and drive elements (12a) and (12
A piezoelectric element (14) is provided on each side of b). (15) are mounting holes, (A 1 ), (A2),
(B1), (B2), and (B) are terminals of connection leads of each piezoelectric element, and (FB) is a feedback terminal.

In the ultrasonic unit configured as above, when voltage in the ultrasonic range is applied between terminals (A1) and (B), the base (
11) and the driver elements (12a) and (12b) are bent as shown by the - dotted chain line, and the driver element (12a) kicks out the slider pressed against the driver element in the direction of the arrow (M). When a voltage e is applied to the terminals (A1) and (B), the ultrasonic unit bends as shown by the broken line, and the driver (
12b) kicks out the slider in the direction of arrow (M).

When the above voltage is applied to the terminals (A2) and (B), the polarization of the piezoelectric elements (13a) and (13b) is opposite, so the operation is reversed, and the slider moves in the direction of the arrow (N). driven to.

In this way, the slider, which is the driven body, can be arbitrarily given linear movement in opposite directions.

[Problem to be solved by the invention]

The conventional ultrasonic linear motor as described above has a drive element (1
Since it is necessary to provide the piezoelectric element (14) also in 2a) and (12b), the height of the ultrasonic unit increases, making it difficult to make it thinner, and there are many places where the piezoelectric element is pasted. There were problems such as complicated manufacturing work.

This invention attempts to solve the above problems, and aims to provide an ultrasonic linear motor that can integrate the drive element and the motor body to make it extremely thin and also achieve miniaturization. That is.

[Means to solve the problem]

In the ultrasonic linear motor according to the present invention, two groups of piezoelectric elements each consisting of a plurality of piezoelectric elements are alternately fixed on opposing surfaces of a rectangular bar-shaped base made of an elastic body, and a plurality of piezoelectric elements are provided integrally with the base. The drive element is installed at a location where the displacement of both the length and bending vibration modes of the base body is large. Each group of piezoelectric elements is
Simultaneously generate longitudinal vibration and bending vibration in the base in a single group.

[Effect]

In this invention, the vibration mode of the base body is determined by the arrangement of the piezoelectric elements, and the moving direction of the slider, which is always in pressure contact with the driver, is determined by switching the piezoelectric element groups.

Furthermore, since the length and bending vibrations of the base are excited by one group of piezoelectric elements, there are always two terminals during operation (during energization).

【Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6. In Figures 1 to 4, a base body (1) made of an elastic rectangular bar has drive elements (2a), (2b), and (2c) integrally protruding from its upper surface (la) at the center and at both ends. It is set up. In addition, the upper and lower surfaces (1a) of the base (1)
(1b) includes the first group of piezoelectric elements (3a), (3b), and
c) (3d) are fixed alternately up and down, and the second group of piezoelectric elements (4a), (4b), (4c), and (4d) face each of the first group of piezoelectric elements (3a) to (3d). The upper and lower parts are fixed alternately. The polarization of these piezoelectric elements is determined by the polarization of the substrate (
1) The piezoelectric elements located on the left and right sides of the center have opposite polarities. (5) shows the dividing line of the electrodes on one piezoelectric plate, but each piezoelectric plate may be separate.

Generally, conductive metal is suitable as the elastic material forming the base (1). In particular, when a wide operating temperature range is required as an ultrasonic linear motor, a piezoelectric material made of ceramic with a coefficient of thermal expansion is suitable. It is desirable that the elastic loss be close to that of the element, and under conditions of use with large amplitudes, it is desirable to have a small elastic loss in order to reduce heat generation.

Note that the electrodes and connection leads provided on the piezoelectric element are not illustrated.

Next, the operation will be explained. Figures 5 and 6 show the base (1
), FIG. 5 shows the bending fifth harmonic mode, and FIG. 6 shows the length second harmonic mode.

Now, if the length and thickness of the base body (1) are set in such a way that the modes shown in Figures 5 and 6 occur simultaneously, and voltage is applied to the piezoelectric elements (3a) to (3d), , the base body (1) is excited and generates the above two modes simultaneously to perform complex resonance. To explain the behavior during this time in more detail, the first group of piezoelectric elements (3a) to (3d),
The second group of piezoelectric elements (4a) to (4d) are responsible for moving the slider in the left and right directions, and the polarization of the piezoelectric elements is opposite in the left half and right half from the center. Therefore, when voltage is applied to the piezoelectric elements of the first group, the piezoelectric elements (3a) to (
3d) and match the polarity so as to generate the mode shown in Fig. 5.
The substrate (1) is excited in the next layer mode. In addition, since the polarization polarities of the left and right piezoelectric elements are opposite to each other, the left half acts to extend in the length direction and the right half to contract, as shown in Figure 6, causing vibration in the second length mode. It will be accompanied.

Therefore, the point (Pl) on the driver (2a) is lifted upward by the bending mode, and is pressed against the slider more than ever before, and moves to the right in FIG. 6 by the length mode, so the point The slider above (p+) moves to the right. At this time, the respective points (pg) (p, ) of the drive elements (2b) (2c) are located below due to the bending mode, so they are in a non-contact state with the slider, resulting in a missed swing. Then, in the next half cycle, the behavior shown in Figures 5 and 6 is reversed, and now the point (
While P2) and (Pl) are in contact with the slider,
In FIG. 6, each arrow is reversed and points to the right, so the slider moves to the right.

Thus, the points (PI') and (pg) (Pl)
kicks the slider to the right, working alternately in half cycles.

It is easy to see that the movement of the slider to the left is achieved by switching the voltage application to the second group of piezoelectric elements (4a) to (4d). That is, the mode shown in FIG. 6 remains the same, and only the mode shown in FIG. 5 is reversed.

When one of the terminals of the piezoelectric elements in the first group and the second group is working, the other is in an open state, and when the amplitude is large, a considerable voltage is generated on the open side, so this has an adverse effect. In order to eliminate this problem, it is conceivable to short-circuit idle terminals each time they are switched. In that case, it goes without saying that the dimensions of the base body (1) are set slightly different, and the node positions of the base body (1) are set as shown in FIG. 6 (N1
) and (N2) are roughly common, and the general method is to use this point to assemble and fix. The fixing means is, for example, a point (Nl)CNt on the above-mentioned node.
) and remove it by welding a support rod to it, which also serves as the body ground wire.

When pressing the slider against the drive elements (2a) to (2C), make sure that even pressure is applied at all times by rollers and springs.
And set it up so that it can be moved smoothly. At this time,
Adding a taper like an abacus ball to the rollers to also serve as a guide to prevent lateral slippage will save on parts.

As described above, by first determining the dimensional relationship of the base (1), arbitrary linear reciprocating movement of the slider can be achieved by driving either the left or right piezoelectric element, thereby eliminating troublesome adjustments during assembly. Since there is no need for a drive circuit, phase adjustment, etc., both the device configuration and operation are significantly simplified.

The oscillation circuit that serves as the power source is generally an automatic oscillation circuit that detects the impedance of the ultrasonic unit when it resonates and uses an automatic tracking method. A signal may also be extracted.

Since each piezoelectric element is placed in each abdomen of the bending mode, the generation of vibration modes other than this becomes very weak, and therefore automatic oscillation is performed stably.

Since this also aligns the polarity of the length mode, stable oscillation can be achieved as well.

The idea of this invention is to combine the bending mode and the length mode, so the mutual usage modes are not limited to the above embodiments, but when the size is large and the power is large, a combination with a higher order mode is established. The range of designs is further expanded.

The slider and the ultrasonic unit move relative to each other, and either side may be moved.

Furthermore, it is easily possible to incorporate encoder means for position detection into both the guide rail and the motor.

(Effects of the Invention) As is clear from the above description, the present invention produces complex resonance by bringing mutual resonance points of the bending mode and the length mode close to each other in a rectangular bar-shaped base body integrally provided with a driver. Since the slider is moved by moving the slider, it has an extremely simple structure.
Thinner and smaller size can be achieved without adjustment and at low cost.

...Second group of piezoelectric elements.

Claims (1)

[Claims] An ultrasonic signal is applied to each group of the first and second groups of piezoelectric elements in which a plurality of piezoelectric elements are fixed alternately in the length direction on the upper and lower surfaces. a rectangular bar-shaped base made of an elastic body that is simultaneously excited with vibration and bending vibration, and a position near a position on one surface of the base where the displacement amount of vibration modes of both the longitudinal vibration and the bending vibration is large; An ultrasonic linear motor comprising a plurality of integrally protruding drive elements, the moving direction of a slider pressed against the drive elements being selected by switching signal application to the first and second groups of piezoelectric elements. .