JPS6331479A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To prevent a stator temperature from rising by providing cooling blades in an air gap between opposed rotor and stator. CONSTITUTION:Piezoelectric units 2 and 3 are bonded to the bottom of an elastic unit 1, and a ringlike projection 1a is formed on the upper surface to form a stator 4. This stator 4 is fixedly bonded to a stationary base 5 in sector circle, and the rotational shaft 7a of a rotor 7 is engaged through a bearing 9 with the center. A vent hole 12 is formed in the rotor 7, a wear resistant lining material 6 is further bonded, and contacted with the projection 1a of the stator 4. In this case, radial cooling blades 8 are formed on the rotor end face in an air gap between opposed stator 4 and rotor 7. Thus, when the rotor 7 is driven, the blades 8 simultaneously perform a cooling function. As a result, it can prevent the stator temperature of the motor from rising to reduce the output of the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an ultrasonic motor that generates driving force using electro-mechanical conversion means such as a piezoelectric body.

2. Description of the Related Art Conventionally, an ultrasonic motor using this type of piezoelectric electro-mechanical conversion means has a configuration as shown in FIG. ing. That is, it includes a stator formed by stacking two circular piezoelectric bodies 2 and 3 and a circular elastic body 1 in the thickness direction, and a circular rotor 7 that makes surface contact with the stator. It has a ring-shaped protrusion 1a for applying energy, and by applying electrical signals out of phase with each other to the piezoelectric bodies 2 and 3, rotational force is obtained.

Problems to be Solved by the Invention Since the ultrasonic motor configured in this way has a large energy density stored per unit volume, it can be smaller than a conventional electromagnetic motor to obtain the same output. It has the advantage of However, at present, the motor efficiency is about 45%, and about half of the motor's human power is lost, which increases the temperature rise of the above-mentioned small ultrasonic motor. Ultrasonic motor is
It is most efficient when driven at a certain resonant frequency determined by the stator shape and material (density, Young's modulus), etc. However, due to the temperature rise mentioned above, this drive frequency changes, resulting in However, there was a problem in that the motor output decreased.

Therefore, the present invention aims to suppress the stator temperature rise due to the loss as much as possible by the means described later, to reduce the change in the drive frequency (and to prevent the motor output from decreasing).

Means for Solving the Problem As a means, a cooling means such as a radial cooling grating is provided on the end face of the rotor in the gap where the stator and rotor of the ultrasonic motor face each other, or on the rotor shaft. .

In this construction, the cooling shaft is integrated with the rotor, so that the cooling shaft exhibits its cooling ability at the same time as power is supplied to the motor and the rotor is driven. Therefore, it is possible to prevent the stator temperature of the motor from rising, to reduce the temperature change in the drive frequency, and to reduce the reduction in motor output. Furthermore, when the input power to the ultrasonic motor is increased, the motor rotational speed also increases, so that the cooling effect due to the cooling force increases, and the temperature rise is suppressed within a certain range.

Embodiments Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. FIG. 1 shows a first embodiment.

1 is an elastic body, for example, a metal such as iron and stainless steel.

A piezoelectric body 2 and a piezoelectric body 3 are firmly bonded to the bottom surface of the elastic body 1 with a resin adhesive. Further, a ring-shaped protrusion 1a is provided on the upper surface of the elastic body 1, and the structure is such that the range of mechanical strain can be expanded and output can be effectively extracted. These constitute the stator 4. Note that the circular piezoelectric bodies 2 and 3 are each polarized in the circumferential direction with n polarization (n: an even number) alternately as a positive pole and a negative pole. The piezoelectric body 2 and the piezoelectric body 3 are mechanically joined with a phase difference of π/2 (electrical angle). (-The polarization width is assumed to be π in electrical angle.) A lead wire (not shown) is attached to the body 3 so that a voltage can be applied.

The stator 4 is adhesively fixed to a fixing base 5 at knots. A bearing 9 is provided at the center of the stator 4, into which the rotating shaft 7a of the rotor 7 is fitted. On the other hand, a wear-resistant lining material 6 is adhered to the rotor 7 provided with the through hole 12 so as to come into contact with the ring-shaped protrusion 1a of the stator 4 described above. Also, the tip of the rotating shaft 7a is threaded, and the lining material 6
The structure is such that the ring-shaped protrusion 1a contacts with an appropriate load and is tightened with a spring washer 10 and a nut 11 so as to be pressurized. Further, radial cooling holes 8 are formed on the end face of the rotor in the gap where the stator 4 and the rotor 7 face each other.

The operation of the ultrasonic motor equipped with the cooling means configured as described above will be explained.

The ultrasonic motor is driven at a certain resonant frequency, which is determined by the shape and material (density, Young's modulus) of the stator. Now, when the two-phase AC voltages with resonant frequencies different in phase by π/2 are applied to the piezoelectric bodies 2 and 3, the stator 4 generates progressive mechanical strain waves. Therefore, the rotor 7, which is in pressure contact with the stator 4, contacts only at the peak of the wave (contact at n/2 points), and is sent at the wave peak speed in the opposite direction to the direction of travel of the wave, It rotates around the rotor shaft 7a. Therefore, the radial cooling blade 8 provided on the end face of the rotor in the gap where the stator 4 and the rotor 7 face each other also rotates, and the ventilation holes 12 of the rotor are used as air inlets to supply air to the two sides of the stator 4. It works by forcibly blowing air to cool the stator and prevent the stator temperature from rising by 1'' due to loss.

Incidentally, since the protrusion 1a provided on the stator is a protrusion with a slit, the cooling blade 8 (: therefore, it is sent,
The warm air that has cooled the stator is forced out through this groove, so no heat is trapped in the void. When the temperature rise of the stator is suppressed in this way, the change in drive frequency due to temperature is also suppressed, and it becomes possible to reduce the reduction in the output of the motor.

In FIG. 1, eight radial cooling holes 8 are provided, but the invention is not limited to this. Although the cooling vane S has a linear shape in the radial direction, it is not limited to this. (For example, the cooling blade S has a linear shape in the circumferential direction.) (always arranged side by side).Also, the rotor's ventilation hole 1
2 is not limited to eight.

FIG. 2 shows another embodiment of the invention. The configuration of the ultrasonic motor is almost the same as the first embodiment, but
Cooling vents 8 for blowing air to the stator are provided radially on the rotor shaft 7a via bosses 13, instead of on the end face of the rotor as described above. The operation is similar to that described in the first embodiment. In addition, in FIG. 2, the radial cooling blades 8 are as follows:
Although eight are provided, the number is not limited to this number.

Further, although the cooling blade has an M-line shape in the radial direction, it is not limited to this, and various shapes such as a circular arc shape can be considered to increase the air volume. The number of ventilation holes 12 is not limited to eight either.

(Clearly, the present invention has a stator composed of an elastic body and a piezoelectric body for exciting the elastic body, and a rotor that is brought into pressure contact with the stator under a certain appropriate load.) In the ultrasonic motor configured, a cooling means such as a cooling mechanism is provided in a gap where the rotor and stator face each other so as to cool the motor, and when power is supplied to the motor and the rotor is driven, By blowing air using the cooling force, it is possible to prevent the temperature of the motor stator from rising, to reduce changes in the drive frequency due to temperature, and to reduce the reduction in motor output.

[Brief explanation of the drawing]

FIG. 1 is a top view and a front sectional view of an ultrasonic motor equipped with a cooling means according to a first embodiment of the present invention, and FIG. 2 is a top view and a front sectional view of an ultrasonic motor equipped with a cooling means according to a second embodiment of the present invention. 3 is a top view and a front sectional view, and FIG. 3 is an exploded perspective view of a conventional ultrasonic motor. 1...Elastic body, 2.3...Piezoelectric body, 4
...Stator, 7...Rotor, 7a.
... Rotating shaft, 8, 14 ... Cooling shaft. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1
7-loaf 8-;
12-m-ventilation/friend 12.
14-11 Lingke F Criminal Aid Diagram 3

Claims (3)

[Claims] (1) A stator comprising an elastic body and a piezoelectric body that excites the elastic body, and a rotor that is brought into pressure contact with the stator under a certain appropriate load, and a gap portion where the rotor and the stator face each other. Ultrasonic motor equipped with cooling means. (2) The ultrasonic motor according to claim 1, wherein the cooling means is configured by providing cooling vanes radially on the end face of the rotor in the gap where the rotor and the stator face each other. (3) The ultrasonic motor according to claim 1, wherein the cooling means is constructed by providing cooling holes radially on the rotor shaft of the rotor.