JPH0732611B2 - Ultrasonic motor oscillator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a motor using ultrasonic vibration energy.

(Prior Art) As an ultrasonic paper feed motor, a piezoelectric ceramic plate is contacted with one surface of a conventional elastic plate to match or approach the two resonance frequencies of the longitudinal longitudinal vibration and the width bending vibration, and An ultrasonic motor using a vibrator (hereinafter referred to as a longitudinal bending multimode vibrator) that excites the two vibrations in a degenerate state by applying an electric field to a piezoelectric body has been proposed. Hereinafter, description will be given with reference to the drawings.

First, an example of the longitudinal bending multimode oscillator is shown in FIG. This is a vibrator that excites the primary longitudinal vibration in the length direction and the primary bending vibration in the width direction in a degenerate state. FIG. 4 (a) is a front view and FIG. 4 (c) is a side view. A metal electrode film 43 is formed on both upper and lower surfaces of a piezoelectric ceramic plate 42 uniformly polarized in the thickness direction.
Is provided and attached to the bottom surface of the elastic plate 41. At this time, the elastic plate 41 and the piezoelectric ceramic plate 42 are dimensioned so that the resonance frequencies of the primary longitudinal vibration mode in the length direction and the primary bending vibration mode in the width direction match. By applying an AC piezoelectric having a resonance frequency of two vibration modes between the metal electrodes of such a vibrator, as shown in FIG.
A standing wave having an amplitude displacement distribution represented by (d) is excited. Here, 44 in FIG. 4 (b) shows the displacement distribution of the primary longitudinal vibration in the length direction, and 45 in FIG. 4 (d) shows the displacement distribution of the primary bending vibration in the width direction. As described above, the longitudinal bending multimode oscillator is used by degenerating two different vibration modes.

(Problems to be Solved by the Invention) The ultrasonic motor using the above-mentioned vibrator has a large speed and driving force as compared with the ultrasonic motor using the conventional traveling wave, and the shape of the elastic plate is devised. It is possible to further increase the speed and driving force by making the

However, when the piezoelectric ceramic plate expands and contracts piezoelectrically during high-power excitation, a displacement stress is applied to the adhesive surface, and the piezoelectric body is easily peeled off.

In addition, since it is necessary to match the resonance frequencies of multiple modes of length longitudinal vibration and width bending vibration, the degree of freedom when designing a vibrator is small, and the longitudinal longitudinal vibration that is the resonance mode actually used is It was extremely difficult to suppress these spurious vibrations due to the occurrence of spurious vibrations due to multiple high-order length bending vibrations near the mode. Therefore, there is a drawback that it is difficult to drive by self-excitation.

(Means for Solving the Problems) According to the present invention, elastic plates are added to both ends of a piezoelectric ceramic plate to which a static compressive stress bias is applied. An elastic body having a mass distribution in the direction different from that of the elastic plate is provided so as to be integrated with the elastic plate, and the elastic body converts vibration in the longitudinal direction of the elastic plate into vibration in the thickness direction. Is a vibrator for an ultrasonic motor characterized by a structure capable of generating elliptical vibration, which is a combination of the above vibrations.

(Operation) By configuring the vibrator as described above, a high speed and high driving force ultrasonic motor can be realized. Hereinafter, description will be given with reference to the drawings.

FIG. 1 is a side view of the basic configuration of a vibrator according to the present invention. A piezoelectric ceramic plate 12 is inserted between elastic plates 11, and an elastic body 13 is provided at the end of the elastic plate. Where the elastic plate
11 and the center of gravity 14 of the piezoelectric ceramic plate 12 and the center of gravity 15 of the elastic body 13.
It is an important point that the respective z-coordinate values are different, that is, the mass distribution in the thickness direction is different.

When an AC electric field is applied to the piezoelectric ceramic plate 12 in such a vibrator, the vibrator repeats expansion and contraction in the x-axis direction as indicated by arrow 16, and this becomes longitudinal vibration. This longitudinal vibration is generated by the elastic plate 11
Is transmitted from the elastic body 13 to the elastic body 13, but since the elastic body 13 has its center of gravity located above the elastic plate 11, the vibration 16 to z in the x-axis direction
An axial vibration component 17 is generated. As a result, elliptical vibration 18 can be obtained on the upper surface of the elastic body 13.

As shown in FIG. 4, the conventional longitudinal bending multimode oscillator has a structure in which the piezoelectric ceramic plate 42 is attached to the bottom surface of the elastic plate 41, so that a displacement stress is applied to the adhesive surface between the elastic plate 41 and the electrode 43. Join. Therefore, the piezoelectric ceramic plate 42 is easily peeled off when the vibrator is vibrated with a large power. However, when the method of the present invention is used, since the contact surface between the piezoelectric ceramic plate 12 and the elastic plate 11 is perpendicular to the vibration direction 16, there is room for structural displacement between the elastic body 11 and the piezoelectric ceramic plate 12 to occur. There is no. Therefore, the piezoelectric ceramic plate 12 is less likely to be peeled off, and it is possible to vibrate with a larger power.

In the conventional longitudinal bending multimode oscillator, it is necessary to match the resonance frequencies of two kinds of vibration modes, and these resonance frequencies greatly depend on the shape of the oscillator. Therefore, in order to match the resonance frequencies of two different vibration modes, not only strict dimensions are required for the oscillator, but also strict requirements are imposed on the material constants of the materials forming the oscillator. Therefore, when actually manufacturing the above-mentioned longitudinal bending multimode oscillator, frequency adjustment of two vibration modes was indispensable. On the other hand, according to the method of the present invention,
Since only one type of vibration mode is used, the degree of freedom of dimension becomes much larger. Also, since spurious vibrations are essentially small, self-sustained pulsation becomes easy in the resonance mode used.

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

2 (a) and 2 (b) are views showing one embodiment of the ultrasonic motor of the present invention. FIG. 2 (a) is a side view of the ultrasonic motor for a sheet feeder, and FIG. 2 (b). [Fig. 4] is a plan view of a vibrator. 21, 24 are elastic plates and elastic bodies made of stainless steel, 22 is a PZT piezoelectric ceramic plate, and 23 is a silver baking electrode. The size of the vibrator is 93 mm long, 20 mm wide, and 5 mm thick for the main body (elastic plate 21-piezoelectric ceramic plate 22-elastic plate 21), and the elastic body 24 is 15 mm long, 20 mm wide, and 8 mm thick. The plate 22 has a length of 50 mm, a width of 20 mm, and a thickness of 5 mm, and FIG. 2 (a)
Medium a = 3 mm, b = 5 mm, and a bolt with a diameter of 3 mm 25
A static compressive stress bias was applied to the piezoelectric ceramic plate 22 by. Here, the bolt is screwed into a stainless elastic body. This bias applying method is not limited to the bolt. The resonance frequency of longitudinal vibration in this oscillator is 25 kHz.

A thin paper 27 was placed on the elastic body 24, a stainless steel roller 26 having a width of 10 mm and a diameter of 15 mm was placed at a position 10 mm from the end surface of the elastic body, and the paper 27 was pressed by the roller 26. When an alternating electric field of 25 kHz was applied from the baking electrode 23 to the piezoelectric ceramic plate 22, the roller 26 rotated in the direction of arrow 28, and the paper 27 proceeded in the direction of arrow 29. In the case of an ultrasonic motor for a sheet feeder using a conventional vertical bending multimode oscillator as shown in FIG. 4, peeling of the piezoelectric ceramic plate 42 occurred at about 1/3 of the oscillator when the input power was 10 W or more. However, in the case of the vibrator of FIG. 2, the piezoelectric ceramic plate 22 did not peel even with an input power of 25 W. It is possible to vibrate with such a large power, and as a result, it is about 1.
A maximum speed of 5 times and a starting drive force of about 2.5 times were obtained.

FIG. 3 is one of the embodiments of the rotary type motor, in which the roller 36 is directly rotated by the elastic plate 34 except for the paper of FIG. When the roller pressure contact force is 1.0 kg, it is about 1.
8 times more starting torque was obtained.

(Effects of the Invention) As described above, according to the present invention, it is possible to realize a thin motor having a high driving force using ultrasonic energy, and it is possible to achieve an ultrathin paper feeding mechanism for a printer, a facsimile, or the like. And has a great industrial value.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a vibrator of the present invention, FIGS. 2 and 3 are configuration diagrams of an embodiment, and FIGS. 4 (a) and 4 (c) are basic configuration diagrams of a conventional vibrator, FIG. (B) and (d) are displacement distribution maps. In the figure, 11,21,31,41 are elastic plates, 12 is a piezoelectric body, 13,24,34 are elastic bodies, 14 is the center of gravity of the elastic plate 11 and the piezoelectric body 12, 15 is the center of gravity of the elastic body 13, and 16 is the center of gravity. X-axis vibration, 17 z-axis vibration, 18 elliptical vibration, 22, 32, 42 piezoelectric ceramic plates, 23, 33, 43 silver baking electrodes, 25, 35 Tightening bolts, 26 and 36 are rollers, 27 is thin paper, 28 and 37 are roller rotation directions, 29 is paper traveling direction, and 44 and 45 are displacement distributions, respectively.

Front page continuation (72) Inventor Sadayuki Takahashi 5-33-1 Shiba, Minato-ku, Tokyo NEC Corporation Stock company (72) Inventor Tadaho Uchikawa 5-33-1, Shiba, Minato-ku, Tokyo NEC Corporation In the company

Claims (1)

[Claims] 1. A first and a second elastic plate are added to both ends of a piezoelectric ceramic plate to which a static compressive stress bias is applied. The first elastic plate has a first elastic plate at an end or in the vicinity thereof. The elastic plate is formed into an asymmetric shape in the thickness direction, and the elastic body that generates elliptical vibration, which is a combination of these two kinds of vibrations, is integrated by converting the vibration in the longitudinal direction of the elastic plate into the vibration in the thickness direction. A transducer for an ultrasonic motor, which is characterized in that