JPH0197177A - Supersonic motor - Google Patents

Abstract

PURPOSE:To improve durability and to stabilize operation, by driving a longitudinally bending standing wave in a resilient plate. CONSTITUTION:A multi-mode vibration chip having a trapezoidal cross-section to be employed in a supersonic paper feed motor is provided with a resilient body 11 made of stainless steel and formed such that the central section is two times as thick as the end section. A PZT piezoelectric ceramic board 12 and a silver baked electrode 13 are adhered to the resilient body 11. When compared with a vibration chip employing a uniform resilient board, the vibration chip having central section two times as thick as the lateral end section provides a uniform distribution of vibration at a portion where the piezoelectric ceramic board 11 is adhered. Furthermore, a roller is pressure contacted, thus enabling stable paper feed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a motor using ultrasonic vibration energy, particularly an ultrasonic motor for paper feeding.

(Prior Art) Conventionally, an ultrasonic motor for paper feeding is configured to excite a traveling wave in an elastic body and move a moving body placed on the surface of the elastic body through frictional force. In this case, in order to obtain a traveling wave, special consideration had to be given to preventing reflected waves and energy return. In response, an ultrasonic motor for paper feeding using standing waves has been proposed, which actively utilizes the unique resonance state of an elastic body. Compared to an ultrasonic motor for paper feeding that uses traveling waves, the ultrasonic motor has the advantages of high energy conversion efficiency and essentially large amount of vibration energy. As an ultrasonic motor using standing waves, an ultrasonic motor for paper feeding has been proposed that uses a multi-mode vibrator that utilizes longitudinal vibration and width bending (flexural) vibration of an elastic plate. As shown in Figure 2, this ultrasonic motor utilizes longitudinal vibration in the longitudinal direction and bending vibration in the width direction of a rectangular plate, and the resonance frequency of the longitudinal vibration in the longitudinal direction and the resonance frequency of the bending vibration in the width direction are mutually different. set to approach. FIG. 2(a) is a plan view of the multimode vibrator, FIG. 2(b) is a front view, and FIG. 2(c) is a side view. In the figure, 21 is an elastic flat plate made of fiber-reinforced plastic, metal plate, fiber-reinforced metal, etc., and 22 is P
A ZT-based piezoelectric ceramic plate 23 is an electrode formed on the front and back surfaces of the piezoelectric ceramic plate. The piezoelectric ceramic plate 22 is polarized in the thickness direction, and the piezoelectric ceramic plate 22 and the elastic flat plate 21 are firmly bonded with solder or epoxy adhesive.

Next, the operating principle of this paper feed ultrasonic motor using a vertical bending multi-mode vibrator will be explained. When an alternating current voltage is applied to the piezoelectric ceramic plate 22 from the electric terminals 24 and 25, mechanical vibration is excited through the electromechanical coupling coefficient 31. When the piezoelectric ceramic plate 22 is extended in the longitudinal direction, the same piezoelectric ceramic plate 2
2 shrinks in the width direction.

On the other hand, when the piezoelectric ceramic plate 22 contracts in the longitudinal direction,
Conversely, it will stretch in the width direction. Therefore, since the piezoelectric ceramic plate 22 is firmly bonded to the elastic flat plate 21, the resonance frequency fL1 of the longitudinal vibration mode of the multimode vibrator composed of the piezoelectric ceramic plate 22 and the elastic plate 21 is , 1 and the resonance frequency fB1 of the bending vibration mode related to the width direction. When w are made coincident or sufficiently close to each other, when longitudinal vibration is excited as shown by the arrow in FIG. 2(a), at the same time, as shown by the dotted line in FIG. 2(e), the piezoelectric ceramic plate 22 Since the width dimension changes, bending vibration is excited. Resonant frequency fL1. l and fB
Since l and w match or are very close to each other, when the longitudinal vibration resonance frequency fL1,1 is excited, the width bending vibration is also forcibly excited. Moreover, at the same time, regarding the elongation vibration of the piezoelectric ceramic plate, since the elastic flat plate is not piezoelectrically active, length bending vibration is also excited. In this case, length bending vibration is not a natural resonant mode. The displacement related to longitudinal vibration in length is ξLl,1, and the displacement related to bending vibration in width is ξBl,w,
Let ξB and L be displacements related to length bending vibration. Here L
1 and B1 mean longitudinal and bending first-order natural resonance modes, respectively. The vibration modes of this longitudinal bending multimode vibrator are shown in FIGS. 3(a) to 3(d). In FIG. 3, numeral 31 indicates an elastic flat plate. In FIGS. 2 and 3, L, W and T indicate the length, width and thickness of the vibrator, respectively.

When using this multimode vibrator as an ultrasonic motor for paper feeding, for example, Fig. 4 (a), (b), (c
), the roller 4 is placed on the surface of the multimode vibrator 41.
By pressing 6, it can be easily used as a paper feeding ultrasonic motor. Here, 42 is a piezoelectric ceramic plate,
43 is an electrode, and 44.45 is a terminal. That is, at the pressure contact surface that is pressed against the multimode vibrator surface by the roller, the bending vibration displacement uB and the longitudinal vibration displacement uL are orthogonal to each other and synchronized, as shown in FIG. 4, so that the roller 46 and the vibrator As soon as paper 47 is inserted between 41, it can be moved in the direction indicated by the arrow.

(Problems to be Solved by the Invention) For practical use, an ultrasonic motor for paper feeding using a flat multi-mode vibrator having a uniform thickness requires a certain width dimension W. Since the resonant frequency of bending vibration is approximately proportional to the plate thickness, W can be increased by increasing the plate thickness, but in this case, the volume of the elastic flat plate becomes considerably larger than the volume of the PZT plate, and the vertical There was a drawback that the displacement of vibration and bending vibration became small.

In addition, in a flat plate multi-mode vibrator with a thickness like -, the strain related to the width bending vibration mode is concentrated in the widthwise central part where the PZT-based piezoelectric ceramic plate is bonded, and for this reason, when driven at high power, There was a problem in that the adhesive portion between the elastic plate 21 and the piezoelectric ceramic plate 22 shown in FIG. 2 peeled off. Furthermore, when using this multimode vibrator as an ultrasonic motor for paper feeding, since the displacement regarding the width bending vibration mode is not uniform at the part where the vibrator can be taken out using a roller or the like, that is, the central part of the width dimension, The paper feed speed and paper feed propulsion force were unstable. An object of the present invention is to provide an ultrasonic motor that is thin, operates stably, and is capable of high-power operation by improving such a conventional vertical bending multimode vibrator.

(Means for Solving the Problems) The present invention provides an ultrasonic motor using a longitudinal bending multi-mode vibrator that operates with first-order longitudinal longitudinal vibration and first-order width bending vibration. A multi-mode vibrator is used in which an elastic body is thicker at the center than at the ends, and a piezoelectric ceramic plate is bonded to the width center of the elastic body.

(Function) The vertical bending multi-mode vibrator according to the present invention, in which the width center portion is at least twice as thick as the width end portions, has stress related to the width bending vibration mode in the width center portion to which the piezoelectric ceramic plate is bonded. concentration is small, and a practically sufficient width W can be achieved relative to the length L. Further, the displacement of the width bending vibrator becomes almost uniform in the portion where the roller for extracting vibration energy or the elastic piece with a small sliding friction coefficient comes into pressure contact with the present multimode vibrator. Furthermore, there is less concentration of stress related to width bending vibration in the area where the piezoelectric ceramic plate is bonded, and high power driving is possible. Therefore, the ultrasonic motor according to the present invention is thin and capable of stably moving a film-like moving object such as paper, and is also capable of high-power operation.

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

FIG. 1 shows a multimode vibrator 11 having a trapezoidal cross section and used in an ultrasonic motor for paper feeding according to the present invention. The same figure (a
) shows a plan view, figure (b) shows a front view, and figure (c) shows a side view. In the figure, reference numeral 11 is an elastic body made of stainless steel, and the center part is twice as thick as the end parts. 12 is PZT
The piezoelectric ceramic plate 13 is a silver baked electrode, and in the same figure, L, W and T are the length, width and thickness dimensions of the multimode vibrator, respectively. Further, T1 indicates the thickness of the elastic body, and T2 indicates the thickness of the piezoelectric ceramic plate. The dimensions of the vibrator are W=21mm, T1=1.5mm, T2=0.5m
m, L=105 mm. In this resonator, fLl
, 1=fB1. w=25kHz. Similarly, T1=
A multimode oscillator with a rectangular cross section that operates with length longitudinal vibration and width bending vibration at 25 kHz was fabricated with 1.5 mm 1 T2 = 0.5 mm. fLl,1=fB1. w=2
The dimensions when obtaining 5kHz are L=107mm, W=
It was 18.5 mm. As shown in FIG. 5(a), the displacement distribution of the width bending vibration mode was observed by irradiating the longitudinal bending multimode vibrator according to the present invention with laser light from the direction of the arrow (laser holography method). 51 is an elastic flat plate, 52 is a piezoelectric ceramic plate, and 53 is an electric plate. As a result, as shown by the solid line in FIG. 5(b), the vibration displacement of the portion to which the PZT-based piezoelectric ceramic plate was bonded was almost uniform. On the other hand, the displacement distribution of a multimode vibrator using a stainless steel elastic body having a uniform thickness was observed as shown by the dotted line. Therefore, the vibrator according to the present invention in which the width center portion is twice or more thicker than the width end portions,
Compared to a vibrator using a uniform flat elastic plate, an average vibration distribution is obtained in the area where the piezoelectric ceramic plate is bonded. Next, using the produced vibrator, a paper feeding experiment was carried out by pressing a roller at the central part in the width direction and at a part 3 cm from the end in the length direction. At this time,
When an AC voltage of 70 (V) and 25 kHz was applied, stable paper feeding was achieved and a paper feeding speed of 45 cm/see was obtained. Also, the durability was sufficient. Note that the vertical bending vibrator for an ultrasonic paper feed motor according to the present invention does not need to have a trapezoidal cross-sectional shape, and the width center portion of the elastic plate is 2 mm wider than the width end portion of the elastic plate.
It is effective if the thickness is at least twice as thick.For example, it goes without saying that a vibrator having a convex cross-sectional shape as shown in FIG. 6 is also effective.

(Effects of the Invention) According to the present invention, by driving a standing wave of vertical bending in an elastic flat plate, it is possible to realize a motor suitable for thin paper feeding that has excellent durability and can operate stably. .

[Brief explanation of the drawing]

Figures 1 (a), (b), and (c) are diagrams showing examples of the ultrasonic motor of the present invention, and Figures 2 (a), (b), and (c).
Figures 3(a) to 3(d) show a conventional ultrasonic motor.
is a diagram showing the vibration modes of a longitudinal bending multimode oscillator, 4th
The figure shows an example of a paper-feeding ultrasonic motor equipped with rollers, Figure 5 shows the method and results of observing the relative displacement distribution of the width bending vibration mode using the laser holography method, and Figure 6 shows the method of observing the relative displacement distribution of the width bending vibration mode using the laser holography method. A diagram showing another example. In these figures, 11.
21.31.41.51 is an elastic flat plate, 12.22.42
．． 52 is a piezoelectric ceramic plate, 13.23.43.53 is an electrode, 14.15.24.25.44.45 is a voltage terminal, and 46 is a roller.

Claims (1)

[Claims] In an ultrasonic motor as a driving source, a longitudinal bending multi-mode vibrator operating in a first-order longitudinal vibration mode and a first-order width bending vibration mode is used as an elastic body of the vibrator, compared to the end portion in the width direction. An ultrasonic motor characterized in that an elastic body is made thicker at the center of the width, and a piezoelectric ceramic plate is bonded to the center of the elastic body in the width direction.