JPH01315275A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To obtain a reduced thickness and a high driving force by employing a longitudinal vibrator in which piezoelectric ceramic plates of lateral effect adhere to the vicinities of both ends of an elastic plate secured at its both ends, and the piezoelectric ceramic plates. CONSTITUTION:Both ends of an elastic plate 11 are secured, and piezoelectric ceramics 12 so adhere to the vicinity of the stationary end of the plate 11 as to be symmetrical with respect to the longitudinal direction of the plate 11. The ceramics 12 having lateral effect adhere to the front and rear faces of the plate 11, and are driven in resonance in revere phases A, B as a pair to form a primary resonance mode longitudinally of the plate 11. Further, second piezoelectric ceramics 13 adhere to the center of the plate 11. A vibration of lateral direction (bending direction) of the plate 11 is applied thereto, combined with the previous vibration to form an elliptical motion. Thus, a roller 21 is brought into pressure contact with the vibrator by a spring or the like to be rotated. As a result, a large torque is obtained at the roller 21.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an ultrasonic motor that utilizes ultrasonic vibration, and more particularly to a motor that has the function of moving a flexible sheet such as paper.

(Prior art) Conventionally, input/output devices such as printers, facsimiles, and copiers, as well as printing devices, use electromagnetic motors as a drive source to feed and run recording paper, transmitting the motion to rollers, and connecting the rollers and paper. The paper is fed using friction. However, in this type of system, the shape of the motor and rollers is thick compared to the thickness of the paper being run (-1), and the structure is complicated due to the large number of parts such as gears and other deceleration means.
The device was large. Therefore, recently, an ultrasonic motor shown in FIG. 5 has been proposed as a small and thin paper feeding motor. FIG. 5 shows a vibrator that excites primary longitudinal vibration in the longitudinal direction and primary bending vibration in the width direction in a degenerate state, with (a) being a front view and (C) being a side view. In FIG. 5, a piezoelectric ceramic plate 52 as a vibration source is bonded to the bottom surface of an elastic plate 51, and the elastic plate 51 and piezoelectric ceramic plate 52 resonate in a longitudinal vibration mode in the length direction and a bending vibration mode in the width direction. The dimensions are such that the frequencies match. By exciting two such vibrators at the resonant frequencies of the two vibration modes, the results shown in Figures 5(b) and (d) are obtained.
A standing wave with an amplitude displacement distribution expressed by is generated. Here, FIG. 5(b) shows the displacement distribution 53 of the first-order longitudinal vibration in the longitudinal direction.
, (d) shows the displacement distribution 54 of the first-order bending vibration in the width direction. In this way, a method has been used in which the vertical and horizontal resonances of the piezoelectric ceramic plate 52 cause elliptic motion as the movement of mass points on the surface of the elastic plate 51.

(Problems to be Solved by the Invention) The above-mentioned ultrasonic motor has a simple structure and has the advantage of being a low-cost motor, but it has multiple modes of longitudinal vibration in the length direction and bending vibration in the width direction. Since it is necessary to match the resonant frequencies, it is difficult to design the shape, and in actual driving, it is difficult to control because multiple high-order vibrations are likely to be included.

(Means for Solving the Problems) The present invention has a configuration in which transverse effect piezoelectric ceramic plates are joined near both ends of an elastic plate whose both ends are fixed, and the piezoelectric ceramic plates on the front and back sides are connected to voltages of the same phase. The vertical vibrator vibrates in the longitudinal direction of the elastic plate by driving the piezoelectric ceramic plates at both ends with voltages with opposite phases, and vibrates with a phase difference of 90 degrees from the vertical vibrator. , a piezoelectric ceramic plate whose vibration acts perpendicularly to the central portion of the longitudinal vibration.

(Function) As is well known, an ultrasonic motor uses a piezoelectric ceramic vibrator or the like to cause elliptical motion as a mass point movement on the surface of an elastic body, and the mouth and tail pressed against the elastic body undergo elliptical motion. It rotates due to the force of.

In the present invention, both ends of the elastic plate in the longitudinal direction, that is, in the vertical direction, are fixed, and a piezoelectric ceramic plate for longitudinal excitation is joined. The piezoelectric ceramic plates are bonded to the front and back surfaces, and are bonded near the fixed ends of both ends of the elastic plate so as to be symmetrical in the longitudinal direction.

The piezoelectric ceramic plates on the front and back sides are excited in the same phase,
Further, each of the piezoelectric ceramic plates at both ends is excited with opposite phases to generate the -th order longitudinal vibration mode.

Furthermore, a piezoelectric ceramic plate for bending vibration is provided at the center of the elastic plate, which vibrates in the lateral direction of the elastic plate, that is, in the bending direction, with a phase difference of 90 degrees in response to the longitudinal vibration of the elastic plate. In the vibrator configured in this manner, an elliptical motion occurs on the elastic plate due to the combination of vertical and bending vibrations, and when the roller is pressed against the elastic plate, the roller rotates. Further, in this configuration, by sandwiching a flexible sheet such as paper between the roller and the elastic plate, the roller can be rotated to perform a paper feeding operation.

(Example) The present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of the present invention, with FIG. 1(a) being a schematic top view for explaining the principle and operation, and FIG. 1(b) being a front view. In FIG. 1, both ends of an elastic plate 11 are fixed, and piezoelectric ceramics 12 are bonded near the fixed ends so as to be symmetrical with respect to the longitudinal direction of the elastic plate 11.

The piezoelectric ceramics 12 having a transverse effect are bonded to the front and back surfaces of the elastic plate 11. By forming such a pair of piezoelectric ceramics 12 on the back surface and driving the piezoelectric ceramics 12 at both ends resonantly with mutually opposite phases A and B,
A first-order resonance mode is formed in the longitudinal direction of the elastic plate 11, that is, in the vertical direction. Therefore, this piezoelectric ceramic is hereinafter referred to as the first piezoelectric ceramic 12. In order to prevent this vibration, a second piezoelectric ceramic 13 is further connected to the center of the elastic plate 11. The second piezoelectric ceramic, Cus 13
gives vibration to the elastic plate 11 in the lateral direction, that is, in the bending direction, and the vibration is applied to the first piezoelectric ceramic plate 12 at 90°
It is driven with a phase difference of degrees. At this time, a combined elliptical motion is formed in the center of the elastic plate.

FIG. 2 shows one embodiment of a rotating motor, in which a roller 21 is mounted on the vibrator shown in FIG.
(not shown) for rotation. The roller 21 rotates due to the elliptical motion generated by the first and second piezoelectric ceramics 12,13. Since the second piezoelectric ceramic 13 can have greater rigidity than conventional piezoelectric ceramics, the pressing force of the roller 21 can be increased and a large rotational torque can be obtained.

FIG. 3 shows one embodiment of a traveling mechanism for a flexible sheet such as paper, in which the paper 31 sandwiched between the roller 21 and the elastic plate 11 shown in FIG. The vehicle travels on the guide 32. Since the present invention provides a high rotational torque, a high propulsion traveling mechanism can be obtained even when feeding paper. In the present invention, since the longitudinal vibration and bending vibration of the elastic plate are driven separately, there is an effect that forward/reverse rotation, start/stop of rotation, etc. can be easily controlled by controlling the operation of the second piezoelectric ceramic. Further, since the present invention uses a vibrator using a flat elastic plate, it is possible to obtain a small, particularly thin motor, and there is an effect that a thin printer and facsimile machine can be obtained.

FIG. 4 shows a second embodiment of the present invention, in which a second piezoelectric ceramic 13 is placed on the center of the elastic plate 11. In this example as well, the second piezoelectric ceramic 13
The combination of vertical and horizontal vibrations produces elliptical motion, allowing it to operate as a motor.

(Effects of the Invention) In the present invention, since the first-order longitudinal vibration of the elastic plate whose both ends are fixed is used, the influence of the vibration component in the width direction of the elastic plate is small, and the operation is stable.

Further, since the transverse vibration is driven independently of the longitudinal vibration, the design of the vibrator is easy, and a reliable motor vibrator can be obtained. In addition, since the rigidity of the piezoelectric ceramic for transverse vibration can be increased, the pressing force of the roller as an output end can also be increased, and a large rotational torque can be obtained. Therefore, according to the present invention, it is possible to obtain a thin, high-drive motor that utilizes ultrasonic energy, which has the effect of making paper feeding mechanisms of printers, facsimile machines, etc. thinner.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of a vibrator which is a first embodiment of the present invention, FIG. 2 is a diagram showing an embodiment as a motor, and FIG. 3 is a diagram showing an embodiment of a traveling mechanism for a seat etc. FIG. 4 is a basic configuration diagram of the second vibrator of the present invention, and FIG. 5 is a diagram showing a conventional example. Each symbol in the figure indicates the following content. DESCRIPTION OF SYMBOLS 11... Elastic plate, 12... First piezoelectric ceramics, 13... Second piezoelectric ceramics, 21... Roller, 31... Paper, 32... Guide, 51... Elasticity Plate, 52... Piezoelectric ceramics, 5
3... Vertical displacement distribution, 54... Lateral displacement distribution.

Claims (1)

[Claims] Transverse-effect piezoelectric ceramic plates are bonded to the front and back surfaces near both ends of an elastic plate whose both ends are fixed, and a vertical vibrator vibrates in the longitudinal direction of the elastic plate, and a vertical vibrator is placed in contact with the central part of the elastic plate to vibrate the vibration. and a piezoelectric ceramic that acts perpendicularly to the longitudinal vibration.