JPH01315280A - Method of driving ultrasonic motor and vibrator for the motor - Google Patents

Abstract

PURPOSE:To obtain a reduced thickness and a high driving force by mounting a piezoelectric actuator at the other free end of an elastic plate secured at its one side end. CONSTITUTION:An ultrasonic motor is composed of a stainless steel elastic plate 21, a piezoelectric ceramic plate 22, electrodes 23, a piezoelectric actuator 24, and a Teflon sheet 25, and the plate 21 is clamped with bolts 28 at stainless steel jigs 26, 27. When an AC electric field of 25kHz is applied from a seizure electrode 23 to the plate 22, an AC electric field in which its phase is advanced at 90 deg. is applied to the actuator 24, and a stainless steel roller 29 is brought into pressure contact with the top of the actuator 24, the roller 29 is rotated in a direction of the arrow 201. Thus, when the volume of the ceramics is equal as compared with the ultrasonic motor using a longitudinal bending multiplex mode vibrator, higher maximum speed and starting driving force are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a motor that utilizes ultrasonic vibration energy.

(Prior technology) Conventionally, as an ultrasonic motor, a piezoelectric ceramic plate is bonded to one side of an elastic plate, and the two resonance frequencies of longitudinal vibration in the longitudinal direction and bending vibration in the width direction are made to match or approach each other, and an electric field of a frequency near the two resonance frequencies is generated. A standing wave ultrasonic motor has been proposed that utilizes a vibrator (hereinafter referred to as a longitudinal-flexural multimode vibrator) that excites the two vibrations in a degenerate state by applying the above-described vibrations to a piezoelectric body. This will be explained below with reference to the drawings.

First, FIG. 5 shows an example of a longitudinal-flexural multimode vibrator.

This is a vibrator that excites first-order longitudinal vibration in the length direction and first-order bending vibration in the width direction in a degenerate state. FIG. 5(a) is a front view, and FIG. 5(C) is a side view.

Metal electrode films 53 are provided on both upper and lower surfaces of a piezoelectric ceramic plate 52 that is uniformly polarized in the thickness direction, and are bonded to the bottom surface of an elastic plate 51. At this time, the elastic plate 51 and the piezoelectric ceramic plate 52 are dimensioned so that the resonant frequencies of the first-order longitudinal vibration mode in the length direction and the first-order bending vibration mode in the width direction match. 2 between the metal electrodes of such a vibrator
By applying an AC voltage equal to the resonance frequency of the two vibration modes, a standing wave having an amplitude displacement distribution shown in FIGS. 5(b) and 5(d) is excited. Here, 54 in FIG. 5(b) indicates a displacement distribution of first-order longitudinal vibration in the length direction, and 55 in FIG. 5(d) indicates a displacement distribution of first-order bending vibration in the width direction. In this way, the longitudinal-flexural multimode vibrator uses two different vibration modes in a degenerate manner.

(Problems to be Solved by the Invention) The standing wave type ultrasonic motor using the above-mentioned vibrator has higher speed and driving force than the conventional ultrasonic motor using traveling waves, and the driving method By devising the shape of the elastic plate, even higher speeds and higher driving forces are possible.

In addition, because it is necessary to match the resonant frequencies of multiple modes, longitudinal vibration in the longitudinal direction and bending vibration in the width direction, there is a small degree of freedom when designing the vibrator. Spurious vibrations caused by multiple high-order longitudinal bending vibrations occur near the directional longitudinal vibration mode, and it is extremely difficult to suppress these spurious vibrations. Therefore, there was a drawback that it was difficult to drive in a self-excited manner.

(Means for Solving the Problems) The present invention has an elastic plate fixed at one end, and an elastic plate at a position where the other free end contacts the main surface of the elastic plate so as to be able to slide sideways. The present invention provides a vibrator for an ultrasonic motor characterized by installing a piezoelectric actuator that is displaced in the thickness direction, and a method for driving an ultrasonic motor using this vibrator.

(Function) FIG. 1(a) is a side view of an example of the basic configuration of a vibrator in the present invention. This will be explained below with reference to the drawings.

A piezoelectric body 12 is provided on the main surface of the elastic plate 11, and an end portion 15 is fixed. Further, there is a piezoelectric body 13 fixed to another member at the lower part of the free end, and the piezoelectric body 13
A slidable sheet 14 is placed on the elastic plate 11, and the slidable sheet 14 contacts the elastic plate 11. In such a vibrator, when an alternating current electric field equal to the resonant frequency of the first mode of longitudinal longitudinal vibration of the elastic body 11 is applied to the piezoelectric body 12,
A vibration 16 with a large amplitude in the X-axis direction is generated in the elastic plate 11. The distribution of displacement in the X-axis direction is shown in FIG. 1(b). As can be seen from FIG. 1(b) 19, the vibration amplitude is highest near the free end of the elastic body. Further, when an alternating current electric field is applied to the piezoelectric body 13 located at the lower part of the free end of the elastic plate 11, the upper part of the piezoelectric body vibrates in biaxial directions as shown in FIG. 1(a) 17. This vibration 17 is transmitted to the elastic plate 11 through the sheet 14. As a result, an elliptical motion 18, which is a combination of the vibrations 16 and 17, can be obtained at the free end of the elastic plate 11.

In conventional longitudinal-flexural multimode vibrators, it is necessary to match the resonance frequencies of two types of vibration modes, and these resonance frequencies largely depend on the shape of the vibrator. Therefore, in order to match the resonance frequencies of two different vibration modes,
Not only are strict dimensions required for the vibrator, but there are also strict requirements regarding the material constants of the materials that make up the vibrator.

Therefore, when actually manufacturing the longitudinal-flexural multimode vibrator, it is essential to adjust the frequencies of the two vibration modes. On the other hand, according to the method of the present invention, there is only one type of vibration mode in the resonant state, so the degree of freedom in size is much greater. Furthermore, since spurious vibrations are essentially low, self-oscillation is facilitated in the used resonance mode.

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

FIG. 2 is a diagram showing one embodiment of the ultrasonic motor of the present invention. In Figure 2, 21 is a stainless steel elastic plate, 22
23 is a piezoelectric ceramic plate, 23 is a silver baked electrode, 24 is a piezoelectric actuator, 25 is a Teflon sheet, and the elastic plate 21 is fixed to stainless steel jigs 26 and 27 by bolts 28. The dimensions of the vibrator are as follows: elastic plate 21
has a length of 80 mm, a width of 15 mm, and a thickness of 3 mm, and a portion of 30 mm in length is fixed to jigs 26 and 27.

Furthermore, the piezoelectric ceramic plate 22 has a length of 25 mm and a width of 15 mm.
, the thickness is 1 mm, and the piezoelectric actuator 23 is 10 mm cubic. In this vibrator, the resonance frequency of the first mode of longitudinal longitudinal vibration of the elastic plate 21 is 25 kHz.

Baking is performed from the electrode 23 to the piezoelectric ceramic plate 22 at 25kHz.
An alternating current electric field with a phase lead of 90° is applied to the piezoelectric actuator 24, and a stainless steel roller 29 of 10 k is applied above the piezoelectric actuator 24.
When pressed with gf, the roller 29 rotated in the direction of the arrow 201. Compared to an ultrasonic motor using a longitudinal-flexural multimode vibrator, when the volume of the piezoelectric ceramic is equal,
Approximately 1.5 times the maximum speed and approximately twice the starting driving force were obtained.

In FIG. 3, a piezoelectric ceramic plate 31 is also installed on the upper surface of the elastic plate 21 of the vibrator shown in FIG. As a result, the upper and lower surfaces of the elastic plate 21 are symmetrical, so that the frequency of 20 to 30 kHz is
It was possible to reduce the spurious vibration of bending vibration within the range of about 20 dB.

FIG. 4 shows one embodiment of the sheet feeder, in which a rubber roller 41 is placed above the roller 29 in FIG. 2, and a paper 43 is inserted between the two rollers 29 and 41. be. The rubber roller 41 was pressed against the paper 43 and the stainless steel roller 29 with a force of 3 kgf, and the stainless steel roller 29 was pressed against the elastic plate 11 with a force of 10 kgf. As a result, the maximum speed is approximately 1.3 times higher and the maximum speed is approximately 2.5 times higher than that of a sheet feeder that uses longitudinal-bending multiple modes.
Eight times the starting driving force was obtained.

(Effects of the Invention) As described above, according to the present invention, it is possible to realize a thin, high-driving-power motor that utilizes ultrasonic energy.
It has the advantage of allowing devices to be made ultra-thin, and has great industrial value.

[Brief explanation of the drawing]

FIG. 1(a) is a basic configuration diagram of the vibrator of the present invention.
b) is a displacement distribution diagram, Figures 2, 3, and 4 are embodiment configuration diagrams, Figures 5 (a) and (C) are basic configuration diagrams of a conventional vibrator, and Figure 5 (b) , (d) is a displacement distribution diagram. In the figure, 11, 21.51 are elastic plates, 12.13 are piezoelectric bodies, 14.25 are sliding sheets, 15 are fixed surfaces, 1
6.17.18 is the vibration direction, 19, 54.55 is the displacement distribution, 22.31.52 is the piezoelectric ceramic plate, 24 is the piezoelectric actuator, 23, 32.53 is the silver baking electrode,
26 and 27 are support jigs, 28 are bolts, 29 and 41 are rollers, 201 and 42 are the rotational directions of the rollers, 43 is thin paper, and 44 is the direction in which the paper travels.

Claims (1)

[Scope of Claims] (1.) Resonant vibration of the first mode of longitudinal longitudinal vibration of an elastic plate with one end fixed and the other free, and the other main surface of the elastic plate in a sideways sliding state. The ultrasonic device is characterized by rotating a roller disposed in contact with the elastic plate by combining vibration in a non-resonant state that is displaced in the thickness direction of the elastic plate by a piezoelectric body disposed so as to be in contact with an end region of the elastic plate. How to drive a sonic motor. (2.) An elastic plate with one end fixed, and a displacement in the thickness direction of the elastic plate at a position where it contacts the vicinity of the other end of the main surface of the elastic plate in a state where it can skid sideways at the other end. A vibrator for an ultrasonic motor, characterized by being equipped with a piezoelectric actuator.