JPH044772A - ultrasonic motor - Google Patents

Abstract

PURPOSE:To make an efficient and stable motion possible by setting the width of a mounting end arranged in the direction of wavelength of the bending oscillation of a longitudinal oscillator to 1/3 wavelength and less of a bending oscillator. CONSTITUTION:The width B at a mounting end in the direction of wavelength of bending oscillation of longitudinal oscillators 3, 4 mounted on a bending oscillator 1, which generates a standing-wave bending oscillation and comprising a piezoelectric ele-ment 6 stuck to an elastic body 7, is set to 1/3 or less of the wavelength lambda of the bending oscillator 1. When longitudinal oscillators 3, 4 of such dimensions are used, the bending oscillation of the bending oscillator 1 is no longer prevented and the elliptic oscillation at the tips of the longitudinal oscillators 3, 4 is generated efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic motor, and more particularly, to an improvement in an ultrasonic motor that generates a driving force for a moving body using ultrasonic vibrations.

[Prior Art] The present applicant previously filed an application (Japanese Patent Application No. 1-195767) regarding an ultrasonic motor using a piezoelectric element.

This ultrasonic motor consists of a plate-shaped or rod-shaped elastic body and a piezoelectric element fixed to the elastic body, and is a bending vibrator that generates standing wave type bending vibration by applying an alternating voltage to the piezoelectric element. and is provided on the surface of the elastic body on the nodal line of the bending vibration, is swung about the nodal line by the bending vibration, and expands and contracts in the amplitude direction of the bending vibration by applying an alternating voltage. a vertical vibrator, and a movable body that is pressed against the tip surface of the vertical vibrator, and expands and contracts the vertical vibrator in synchronization with the bending vibration, thereby reducing the bending vibrator and the longitudinal vibrator. The moving object is moved relative to the vehicle.

Next, an example of the configuration of this ultrasonic motor will be explained in a little more detail with reference to FIG. The base ends of vertical vibrators 3 and 4 formed by laminating a plurality of piezoelectric element plates polarized in the thickness direction are bonded to the vertical vibrators 3 and 4.
4 to the sliding surface 8 a J of the linear rail 8:
The structure is configured such that they are brought into pressure contact with each other by pressure adjustment springs 15 in orthogonal directions, and by applying an alternating current voltage to the piezoelectric element 6 and the piezoelectric element of the vertical vibrator, respectively, the bending vibrator 1 is caused to generate bending vibration. The vertical vibrator is expanded and contracted in synchronization with the bending vibration, and the movable body is moved relative to the bending vibrator 1 and the longitudinal vibrators 3 and 4.

[Problems to be Solved by the Invention] However, in the ultrasonic motor configured as described above, depending on the shape of the vertical vibrator provided on the nodal line of the bending vibrator, the vertical vibrator may become a bending vibrator. The problem was that the bending vibration of the motor was inhibited, and the motor hardly moved.

That is, when a vertical vibrator is adhesively fixed onto a boiled bending vibrator, the bending vibrator becomes difficult to bend due to the rigidity of the vertical vibrator. Regarding this flexibility, the wider the width of the base end of the vertical vibrator, the more pronounced the influence of the rigidity of the vertical vibrator becomes, which impedes the bending of the flexural vibrator and adversely affects the vibration amplitude. It turns out.

In addition, the neutral axis 0 (see Figure 1) of the bending vibrator 1 is moved to the side where the longitudinal vibrators 3 and 4 are bonded, causing an internal loss of the bending vibrator, and furthermore, the vibration mode of the bending vibration Not only will this affect the vibration, but the position of the nodes in the vibration will also shift, and the elliptical locus of the tip of the vertical vibrator will also be affected.

In addition, it is difficult to manufacture the above-mentioned vertical vibrator with a width of 0.5 mi + width or less, and even if it were manufactured, the amplitude at the tip of the vertical vibrator would be 14 m1, considering that the driving frequency is 50 KHz. The acceleration of is 1×10 m/s2,
In other words, the force is as large as 10,000 times the gravitational acceleration, and a bending force is also applied to the longitudinal oscillator, so considering the rigidity of the longitudinal oscillator, it will bend easily and
Durability is lost. Further, since the input power to the vertical vibrator cannot be large, the amplitude cannot be maintained and the efficiency deteriorates, so a vertical vibrator having a width of 0.5 gn or less is not suitable.

Therefore, an object of the present invention is to eliminate the above-mentioned problems, and to enable efficient and stable operation by extracting sufficient driving force from the longitudinal oscillator without inhibiting the flexural vibration of the flexural oscillator. We are in providing ultrasonic motors.

1. Means and operation for solving the problem] As the concept is shown in FIG. 1, the ultrasonic motor according to the present invention includes a bending vibrator 1 that generates a standing wave type bending vibration, and the bending vibrator. In an ultrasonic motor equipped with vertical vibrators 3 and 4 made of laminated piezoelectric elements that expand and contract in the thickness direction provided on nodes la of 1 and a movable body that is pressed against the end surface of the vertical vibrators,
The width B of the mounting base end in the wavelength direction of the bending vibration of the longitudinal vibrators 3 and 4 attached to the bending vibrator 1 made by adhering the piezoelectric element 6 to the elastic body 7 is defined as 1 of the wavelength λ of the bending vibrator 1. /3 or less.

By using the longitudinal vibrator 3.4 having such dimensions, the bending vibration of the bending vibrator is not hindered, and elliptical vibration is efficiently generated at the tip of the longitudinal vibrator.

[Implementation example] Hereinafter, the present invention will be explained with reference to illustrated embodiments.

Figures 2 to 4 show an embodiment of the present invention, and this embodiment is based on Japanese Patent Application No. 1-195, which was previously proposed by the applicant.
The present invention is applied to an ultrasonic motor having a basic structure of the linear type disclosed in No. 76.7.

The bending vibrator 1 is made of stainless steel, brass, or phosphor bronze.

Piezoelectric elements 6 arranged in the ratio shown in FIG. 6 are integrally bonded to the lower surface of an elastic body 7 made of aluminum or the like. By arranging the piezoelectric element 6 in this manner, third-order bending vibration with both ends free can be excited most efficiently, and in this case, a vibration node 1a is created at a position as shown in FIG. From the position of the node 1a of this bending vibrator 1, that is, from both sides of the elastic body 7 in the left and right longitudinal direction (0,0944+o,2614)
The first piezoelectric element plate is formed by laminating a plurality of piezoelectric element plates polarized in the thickness direction as shown in FIGS.
．． Second vertical vibrators 3 and 4 are bonded together, and the end faces of the vertical vibrators 3 and 4 are pressed in a direction perpendicular to the sliding surface 8a of the linear rail 8.

At the position of each node 1a of this bending vibrator 1, four support bins 10a, 1 are provided on both widthwise sides of the elastic body.
0b, 10c, and 10d are attached. Figure 7 (
A) and (B) are side views of the driver 2 (see Figure 2);
FIG. 3 is a front view of the driving body 2, in which an elastic body 7. Piezoelectric element 6
．． 1st. Second longitudinal vibrator 3.4.4 support bins 10a
, 10b, 10c.

10d. Note that the arrow in the figure indicates the polarization direction.

4 protruding from the side of the elastic body 7 forming the driving body 2
Support bins 10a, 10b, 10c.

10d is formed of a short cylindrical body so as not to impede the minute rotational reciprocating motion of the node caused by bending vibration, and
As shown in FIG. 4, it is supported by a support 12 fixed to a support mounting plate 11. The upper surface of this support stand 12 has V-shaped grooves for receiving the support bottles 10a to 10d, respectively.

A hole is provided in the center of the support mounting plate 11 through which the tip of the support bolt 18 passes. In addition, the pressure adjustment spring 15 and the spring pressure adjustment nut 17 guided by the upper and lower spring holders 14 and 16 are attached to the bolt 18.
The upper tip of the bolt 18 is fitted into a hole in the center of the support mounting plate 11. Since this spring pressure adjusting nut 17 is engaged with the threaded portion of the bolt 18, by turning this spring pressure adjusting nut 17, the pressure adjusting spring 15 can be adjusted to move upward in the figure. Then, the support base mounting plate 11 moves upward, and the ends of each of the vertical vibrators 3 and 4 attached to the moving body are
It comes into pressure contact with the sliding surface 8a of the linear rail 8.

A thread is cut in the center of the lower plate 19, and the lower part of the bolt 18 is screwed into the lower plate 19.

The lower part of the bolt 18 is in the shape of a disc, and since it touches the lower surface of this disc or the upper surface of the lower plate 19, the bolt 18
is fixed with no play. And linear rail 8
A rotatable wheel 22 attached to the shaft 23 by a bearing 26 is mounted on the sliding surface 8b.

The upper plate 21 and the lower plate 19 are fixed by left and right side plates 20, and the upper plate 21. The lower plate 192 and both side plates 2° are formed of a rigid body. As shown in FIGS. 2 and 4, a shaft 23 through which the wheels 22 pass is fixed above the center of both side plates 20. One mounting plate guide rod 25 is embedded in each side of the support base mounting plate 11 on the front side and the back side in FIG. It is designed to be guided by a groove 24 bored in the vertical direction. This prevents the support mounting plate 11, which moves up and down when adjusting the contact pressure between the linear rail sliding surface 8a and the vertical vibrators 3 and 4, from wobbling.

To drive the ultrasonic motor configured in this way, as shown in FIG. It is sufficient to apply sinusoidal voltages from an AC power source P with a phase shift of 90 degrees. When a voltage is applied, the bending vibrator 1 generates a standing wave type bending vibration, and also expands and contracts in synchronization with the vertical vibrator 3.4. By generating elliptical vibrations on the end faces, it is possible to move the rails 8 (see FIGS. 2 to 4) that are in pressure contact with the end faces of the vertical vibrators 3 and 4.

Next, in the linear ultrasonic motor having the above configuration, the width B of the mounting base end in the wavelength direction of the bending vibration of the longitudinal vibrators 3 and 4 will be explained. First, the total length of the bending vibrator 1 is
For example, the impedance curve of a flexural oscillator having a width B at the base end of the attachment of various longitudinal oscillators to a flexural oscillator is measured for a linear motor driven in a tertiary flexural mode with both ends free at 27.9a+m. .

Note that the height T of each vertical vibrator measured was constant, and the width B of the base end attached to the bending vibrator was 1 mm, 3
mg, 5m11. 6mm, 7mm, 8m
It is m. Then, Qm representing the sharpness of vibration is determined from an impedance curve measured for a vibrator having the above valley width B as a characteristic of the motor.

This Qm is the reciprocal of the vibration loss coefficient, that is, the reciprocal of the proportion of vibration loss energy inside the material, and a larger Qm indicates a smaller vibration loss.

FIG. 8 is a diagram showing the Qm value at the time of bending resonance with respect to the width B of each of the above-mentioned mounting base ends. As can be seen from this figure, when the width B is 6.7.8 mm, the Qm value is small. This means that the width B of the base end of the longitudinal vibrator is 6InI
If it is more than n, the loss of bending vibration when bending the bending vibrator becomes large, indicating that the characteristics as a motor deteriorate.

That is, when expressed in relation to the wavelength λ of the vibration of the bending vibrator, the width B of the base end of the longitudinal vibrator is ⅓ or less.

Furthermore, although the above measurements were performed using a third-order bending mode vibrator with both ends free, it is also possible to use a second-order or first-order bending mode vibrator with both ends free, or a bending vibrator supported at one end or both ends. Of course.

In order to obtain such a stable, high-output linear ultrasonic motor, the width B of the mounting base end in the wavelength direction of the bending vibration should be 1/3 or less of the wavelength λ of the bending vibrator. Become.

9 to 11 show a driving body 2 consisting of a bending vibrator 1 and longitudinal vibrators 3 and 4 in an ultrasonic motor according to the present invention.
This figure shows a modification example of each.

In the driving body 2 in the embodiment, the longitudinal vibrator 3,
No. 4 was a prismatic type in which the overall width and the width B of the mounting base end were formed to be the same, but this does not need to be a prismatic type. That is, as shown in the driving body 2A of FIG. 9, the vertical vibrators 3A and 4A are formed by stacking piezoelectric elements in a T-shape, and the vertical vibrators 3A and 4A are connected to the bending vibrator IA. The width B of the attachment base end is configured to be λ/3 or less. Even if the longitudinal oscillators 3A and 4A are configured in this manner, a highly efficient motor can be provided.

In addition, in the examples described so far, the vertical vibrators 3, 4.3A, and 4A are adhesively fixed on the plane of the bending vibrator on a flat plate, but this is as shown in the drive body 2B in FIG. A T-shaped base 7a is placed on the nodal line of the bending vibrator 1 made of the elastic body 7 made of metal and the piezoelectric element 6, so that the width Bo of the fixed part is 173λ or less.

7b is integrally molded with the elastic body 7, and this base 7a.

The wide vertical vibrators 3B and 4B may be adhesively fixed to the upper surface of the vibrator 7b, respectively.

With this configuration, the T-shaped base 7a of the elastic body 7,
Since the portion 7b is made of the same metal as the elastic body made of phosphor bronze, brass, stainless steel, aluminum, etc., it is stronger than the piezoelectric element. It is possible to reduce the vibration loss of the flexural vibrator 1 and increase the vibration generation force of the vertical vibrator by fixing the wide vertical vibrator to the T-shaped base by adhesively fixing the wide vertical vibrator to the T-shaped base. This makes it possible to supply highly efficient motors.

Furthermore, the width B is formed as shown in FIG. 10 above. If cut grooves 7C are bored in the elastic body 7 on both sides of the bases 7a and 7b having fixed parts as shown in FIG.
Since the fixed portions of the vertical vibrators 3B and 4B approach the neutral axis 0 of the bending vibrator 1 by the depth of the cut groove 7C, it is possible to supply a thinner and smaller ultrasonic motor.

[Effects of the Invention] As described above, according to the present invention, the width of the mounting base end in the wavelength direction of the bending vibration of the longitudinal vibrator in the ultrasonic motor is
Since it was set to 1/3 wavelength or less of the bending vibrator,
Even if the shape of the bending vibrator and the vibration mode used are determined based on its function as a motor actuator,
If the above width is satisfied, the device operates with high efficiency and stable driving force.

Therefore, depending on the shape of the vertical oscillator installed on the nodal line of the flexural oscillator, the vertical oscillator may obstruct the flexural vibration of the flexural oscillator, causing the motor to stop moving. Ultrasonic motor can be provided.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the concept of the present invention, FIG. 2 is a side sectional view of an ultrasonic motor showing an embodiment of the present invention, and FIGS. 3 and 4 are diagrams showing the ultrasonic motor shown in FIG. A front view and a perspective view of the sonic motor, FIG. 5 is an electric circuit diagram when applying an AC drive voltage to the piezoelectric element of the bending vibrator and the piezoelectric element of the vertical vibrator in the ultrasonic motor, and FIG. , a line diagram showing the third-order bending vibration state excited by the bending vibrator in the ultrasonic motor shown in FIG. 2 above, and FIGS. The side view and front view of the body.
Diagrams showing Qm values during bending resonance for
FIG. 1 is a side view showing a modification of the driving body in the ultrasonic motor. 1...Bending vibrator 1a...
...Node 3.4...Longitudinal vibrator 6...Piezoelectric element 7...Elastic body

Claims (2)

[Claims] (1) A bending vibrator consisting of a plate-shaped or rod-shaped elastic body and a piezoelectric element fixed to the elastic body, which generates standing wave type bending vibration by applying an alternating voltage to the piezoelectric element; Longitudinal vibration that is provided on the surface of the elastic body on the nodal line of the bending vibration, is oscillated about the nodal line by the bending vibration, and expands and contracts in the amplitude direction of the bending vibration when an alternating current voltage is applied. and a movable body that is pressed against the tip end surface of the vertical vibrator, and expands and contracts the vertical vibrator in synchronization with the bending vibration, thereby making it possible for the bending vibrator and the longitudinal vibrator to In an ultrasonic motor that relatively moves a movable body, the width of the base end of the longitudinal vibrator fixed to the elastic body is
An ultrasonic motor characterized in that the wavelength of the bending vibration is one-third or less of the wavelength λ. (2) The ultrasonic motor according to claim 1, wherein the longitudinal vibrator is composed of piezoelectric elements laminated in the thickness direction of the elastic body.