JP2590536B2 - Ultrasonic motor - Google Patents

Description

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

(Prior art) As an ultrasonic motor, a piezoelectric ceramic plate is adhered to one side of a conventional elastic plate, and the two resonance frequencies of the longitudinal vibration in the length direction and the bending vibration in the width direction are matched or approached. Is applied to a piezoelectric body to excite the two vibrations in a degenerate state (hereinafter, referred to as a vertical-bending multi-mode vibrator). This will be described below with reference to the drawings.

First, an example of a longitudinal-bending multimode vibrator is shown in FIG.
To (d). This vibrator 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. Metal electrode films 43 are provided on both upper and lower surfaces of a piezoelectric ceramic plate 42 uniformly polarized in the thickness direction, and the metal electrode films 43 are bonded to the bottom surface of the elastic plate 41. At this time, the elastic plate 41 and the piezoelectric ceramic plate 42 are dimensioned such that the resonance frequency 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 voltage equal to the resonance frequency of the two vibration modes between the metal electrodes of such a vibrator, a standing wave having an amplitude displacement distribution shown in FIGS. 4B and 4D is generated. Excited. Here, in FIG.
44 is the displacement distribution of the primary longitudinal vibration in the longitudinal direction, Fig. 4 (d)
Numeral 45 indicates the displacement distribution of the primary bending vibration in the width direction. As described above, the longitudinal-bending multi-mode vibrator uses two different vibration modes in a degenerate manner.

Further, the roller has a structure in which the roller is fixed to the housing 54 by a spring 52 via an elastic plate 41 and a silicon rubber 53 as shown in FIG.

(Problems to be Solved by the Invention) The standing wave type ultrasonic motor using the above-described vibrator has both a large speed and a large driving force as compared with a conventional ultrasonic motor using a traveling wave, and a driving method. By further devising the shape of the elastic plate, it is possible to further increase the speed and driving force.

In addition, since it is necessary to match the resonance frequencies of a plurality of modes, that is, longitudinal vibration in the longitudinal direction and bending vibration in the width direction, the degree of freedom in designing the vibrator is small, and the length is the length of the resonance mode actually used. Spurious vibrations due to a plurality of high-order longitudinal bending vibrations occurred near the longitudinal vibration mode, and it was extremely difficult to suppress these spurious vibrations.
Therefore, there is a drawback that it is difficult to drive in a self-excited manner.

Further, in order to increase the torque of the roller, it is necessary to press the roller against the vibrator. However, conventionally, as shown in FIG. Was. In this method, a force is applied to the housing so that the housing cannot be made thinner and lighter.If the housing is pressed with strong force, the silicon rubber 53 is deformed and the vibrator is tilted. When it is increased, the vibration amplitude becomes smaller.

(Means for Solving the Problems) According to the present invention, a non-resonant expandable and contractible multilayer ceramic actuator is adhered and fixed on a central main surface of a rectangular plate vibrator operating in a longitudinal longitudinal secondary mode. An ultrasonic motor is provided, in which a roller pressed against the actuator is rotated by a spring using a longitudinal vibration secondary mode of a rectangular vibrator and non-resonant vibration of a laminated actuator.

(Operation) FIGS. 1A and 1B are a side view and a displacement distribution diagram, respectively, of a basic configuration of an ultrasonic motor according to the present invention. Second
The figure is an enlarged view of the main part of FIG. This will be described below with reference to the drawings.

The rectangular plate vibrator 11 has a longitudinal longitudinal vibration secondary mode in a resonance state at a certain frequency. The displacement distribution at that time is shown in FIG. As can be seen from the displacement distribution 15, the maximum displacement is obtained at the center of the vibrator 11. The state of the vibration at the center is shown in FIGS. 2a and 2b. Since the actuator can be displaced in the directions shown in FIGS. 2c and 2d, if the electric field applied to the rectangular plate vibrator and the actuator is set to the same frequency and a and c and b and d occur simultaneously, the roller 13 Rotate in the direction of e. Conversely, if a and d and b and c occur simultaneously, the roller 13 rotates in the direction of f.

Since a spring is inserted between the rotation axis of the roller 13 and the rectangular plate vibrator 11, the roller 13 is statically pressed against the actuator. Here, the tension of the spring is perpendicular to the longitudinal direction, and since the equivalent stiffness in the a and b directions of the spring is small, the vibrations a and b are not reduced by the influence of the spring. Further, since the tension of the spring acts only between the rectangular flat plate vibrator 11 and the roller 13, the characteristics of the motor do not depend on the external housing.

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

FIG. 3 is a diagram showing one embodiment of the ultrasonic motor of the present invention. In FIG. 3, 31 is a rectangular plate made of stainless steel, 32
Is a piezoelectric actuator, 33 is a copper roller, 34 is a stainless steel spring, 35, 37, 38, and 39 are piezoelectric ceramic plates, and 36 is a baked silver electrode. The dimensions of the vibrator are as follows: rectangular flat plate 31 has length 160 mm, width 18 mm, thickness 3 mm, piezoelectric actuator 32 has
Each of the piezoelectric ceramics 35, 37, 38, and 39 has a length of 50 mm, a width of 18 mm, and a thickness of 0.5 mm, and has a polarization such that the ceramic plates 38 and 39 shrink when the ceramic plates 35 and 37 expand. It is arranged. Longitudinal longitudinal vibration 2
The resonance frequency of the next mode is 25 kHz. The spring 13 was adjusted so that the static tension became 10 kgf.

25KH from ceramic electrode 36 to ceramic plate 35, 37, 38, 39
When an AC electric field of z was applied and an AC electric field having the same frequency and a phase advance of 20 to 30 ° was applied to the actuator 32, the roller rotated in the direction of the arrow 301. When the volume of the ceramic is equal to that of the ultrasonic motor using the longitudinal-bending multi-mode vibrator, the maximum speed of about 1.5 times and the starting torque of about 3 times were obtained.

(Effects of the Invention) As described above, according to the present invention, it is possible to realize a thin and high driving force motor using ultrasonic energy.
It has the advantage of making devices and the like ultra-thin and lightweight, and has great industrial value.

[Brief description of the drawings]

1 (a) and 1 (b) are basic structural diagrams of a vibrator of the present invention,
FIG. 2 is an enlarged view of a main part, FIG. 3 is a configuration diagram of an embodiment, FIGS. 4 (a) and 4 (c) are basic configuration diagrams of a conventional vibrator, and FIGS. 4 (b) and 4 (d) are displacements. FIG. 5 is a distribution diagram showing a basic configuration of a conventional ultrasonic motor. In the figure, 11 and 41 are rectangular flat plates, 31 is a stainless steel rectangular flat plate,
12 is a piezoelectric actuator, 32 is a piezoelectric actuator, 1
3, 51 are rollers, 33 is a copper roller, 14, 52 are springs, 34 is a stainless steel spring, 15, 44, 45 are displacement distributions, 35, 37,
38, 39, and 42 are piezoelectric ceramic plates, 36 and 43 are silver-baked electrodes, 53 is silicon rubber, 54 is a housing, and 301 is the rotation direction of the roller.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Sadayuki Takahashi 5-33-1, Shiba, Minato-ku, Tokyo Inside NEC Corporation (72) Inventor Tadasuho 5-3-1, Shiba, Minato-ku, Tokyo NEC (56) References JP-A-63-59777 (JP, A)

Claims (1)

(57) [Claims] 1. A non-resonant, expandable and contractible multilayer ceramic actuator is fixedly arranged on a central main surface of a rectangular flat plate vibrator operating in a longitudinal longitudinal secondary mode in a longitudinal direction. An ultrasonic motor characterized in that a roller is provided with a pressure contact by a spring.