JPH0477554B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an ultrasonic motor, and more particularly to an ultrasonic motor that generates traveling elastic waves in an elastic vibrator and drives a moving body using the traveling elastic waves.

(Prior Art) An ultrasonic motor includes, for example, a fixed body and a moving body, and at least one of the fixed body and the moving body includes at least one vibrator driven by a plurality of electrostrictive elements, and the ultrasonic motor includes at least one vibrator driven by a plurality of electrostrictive elements. The extraction lead of the electrostrictive element is connected to a driving power source, the fixed body and the movable body press each other at at least one point on the surface of the vibrator to transmit torque, and the ultrasonic electric energy applied to the electrostrictive element is converted into mechanical vibration. This is a device that converts the mechanical vibration energy into energy and converts the mechanical vibration energy into unidirectional movement of a moving body, and this type of device has already been disclosed in Japanese Patent Application Laid-Open No. 52-29192.

In particular, here, a surface acoustic wave is used as the mechanical vibration energy, and the moving body is frictionally driven by the elastic wave, and at this time, a standing wave is generated by the vibration of at least one electrostrictive element. The following describes a motor configured to allow

FIG. 1 shows the driving principle of this type of motor, where 1 is a moving body and 2 is an elastic vibrator. The X-axis indicates the traveling direction of a surface wave occurring on the surface of the vibrator 2, and the Z-axis is its normal direction.

When the elastic vibrator 2 is vibrated by an electrostrictive element (not shown), a surface acoustic wave is generated and propagates on the surface of the vibrator. This elastic wave is a surface wave with longitudinal waves and transverse waves, and the motion of the mass point is vibration that describes an elliptical orbit. Focusing on mass point A, it is performing an elliptical motion with a longitudinal amplitude u and a lateral amplitude w, and if the traveling direction of the surface wave is the +X direction, the elliptical motion is rotating counterclockwise. This surface wave has a peak A for each wavelength,
A′..., whose apex velocity is only the X component, and V=2πfu (where f is the frequency). Therefore, when the surface of the movable body 1 is brought into pressure contact with this surface, the surface of the movable body contacts only the vertices A, A'..., so the movable body 1 moves in the direction of arrow N due to the frictional force between it and the vibrator 2. It will be driven by

The moving speed of the moving body 1 in the direction of arrow N is proportional to the frequency f. Furthermore, since frictional drive is performed by pressurized contact, it depends not only on the vertical oscillation width u but also on the lateral oscillation width w. That is, the moving speed of the moving body 1 is proportional to the size of the elliptical motion, and the larger the elliptical motion, the higher the speed.
Therefore, the speed of the moving body is proportional to the voltage applied to the electrostrictive element.

FIG. 2 shows the principle for generating surface waves in the elastic vibrator 2 shown in FIG. 1. 3a
and 3b are electrostrictive elements, such as PzT, attached to the elastic vibrator 2 at intervals such that elastic waves can be obtained most efficiently from the resonance frequency of the elastic vibrator 2, and 3a is an electrostrictive element such as PzT. , 3b are connected to line B. 4 is a power source for driving this motor,
A voltage of V=Vosin〓t is supplied, and as is clear from the figure, a voltage of V=Vosin〓t is applied to line A. A voltage of V=Vosin (〓t±π/2) is applied to the line B by the 90° phase shifter 5. + and - are switched depending on the moving direction of the moving object. i.e. 90°
The moving direction of the moving object differs depending on whether the phase shifter 5 shifts the phase by +90° or by -90°.

(a) to (d) show the vibration state of the vibrator 2 depending on time, (a) is t = 2nπ/ω, and (b) is t = π/2ω + 2nπ/
ω, (c) is the state of tπ/ω+2nπ/ω, and (d) is the state of t3π/2ω+2nπ/ω.

Although the elastic wave propagates to the right in FIG. 2, any mass point on the drive surface of the vibrator 2 performs an elliptical motion in the counterclockwise direction. Therefore, the moving body (not shown) that is pressed against the drive surface moves to the left.

FIG. 3 shows a conventional example of an ultrasonic motor constructed based on the principle explained above. In the figure, 6 is a rotating body, and 7 is a friction body (for example, rubber).
These are then glued together to form an integral structure. 8 is a vibrator, 9 is a vibration absorbing member, and these are the holder 1
Attached to 0. The rotating body 6 is connected to a vibrator 8 via a friction body 7 by a pressure regulating spring 11 and a pressure regulating nut 12.
is brought into contact with moderate pressure. By generating a traveling elastic wave on the front surface 8a of the vibrator 8 through an electrostrictive element (not shown) fixed to the back surface thereof,
The rotor 6 is driven. The vibration absorbing member 9 is made of a material that absorbs vibrations, such as felt, so that there is no adverse effect due to vibrations between the vibrator 8 and the holder 10.

In the conventional ultrasonic motor described above, since it is necessary to bring the rotating body 6 and the vibrator 8 into pressure contact due to its principle, mechanical means such as a spring 11 is used to bring about the pressure contact. Therefore, as shown in Figure 3,
When the spring 11 and the rotating body 6 come into contact with each other, the rotating body 6
This obstructs the rotation of the motor and reduces the efficiency of the motor.

Moreover, it is mechanically complicated, which hinders miniaturization.

(Objective) It is an object of the present invention to provide a novel ultrasonic motor that eliminates the drawbacks of the conventional examples described above, has excellent drive efficiency, has a simple structure, and does not require complicated adjustments.

(Embodiment) Fig. 4 shows an embodiment of the present invention. In the figure, 13 is a rotating body, 14 is a permanent magnet, and 5 is a friction body, and these elements 13, 14, and 15 are bonded. It is an integrated structure. 16 is a vibrator, 17 is a vibration absorbing member, and these elements 16 and 17 are bonded and attached to a holder 18. Holder 1
8 is made of magnetic material.

The rotating body 13 is a magnetic holder 18 of a permanent magnet 14.
The vibrator 16 is brought into pressure contact with the vibrator 16 by the adhesive force caused by the magnetic force. The rotor 13 is driven by generating traveling elastic waves on the front surface 16a of the vibrator 16 through an electrostrictive element (not shown) fixed to the back surface 16b.

FIG. 5 shows another embodiment of the present invention,
In the figure, permanent magnets 21 and 22 are arranged so as to repel each other in the plane direction. 23 is a rotating body, 2
4 is a friction body, and these elements 22, 23, and 24 are bonded to form an integral structure. 25 is a vibrator,
26 is a vibration absorbing member, which is attached to the lower holder 27. A permanent magnet 21 is attached to the upper holder shown at 20. Upper holder 20 and lower holder 2
7 are connected by screws 19a, 19b, and 19c to form an ultrasonic motor. Here, the magnets 21 and 22 are not in contact with each other and repel each other due to magnetic force. The rotating body 23 and the vibrator 25 are magnets 2
1 and 22 are brought into contact under appropriate pressure due to the repulsive force due to mutual magnetic force. The rotating body 23 is driven by generating traveling elastic waves on the front surface 25a of the vibrator 25 through an electrostrictive element (not shown) fixed to the back surface thereof.

Especially in the case of such a donut-shaped motor, conventionally, pressure cannot be applied to the rotating body by mechanical pressure means (springs, etc.) near the center of rotation, so there is no pressure between the pressure means and the rotating body. However, according to this embodiment, such driving loss is eliminated.

In the above two embodiments, a rotary type motor has been described, but a structure that uses magnetic force to pressurize the vibrator and the moving body is equally effective even in a linear type motor.

(Effects) As explained above, according to the present invention, an elastic traveling wave is generated in an elastic vibrator, and an ultrasonic motor that drives a moving body as a driven body is used, thereby pressurizing the vibrator and the moving body. Since the contact is made using the magnetic force from the magnetic force generation mechanism, the elastic vibrator and the moving body as the driven body come into contact with only the necessary pressure, eliminating the need for the conventional application of force that would interfere with the drive of the moving body as the driven body. There is no mechanical contact between the pressure means and the moving body as a driven body, and the driving efficiency of the motor is dramatically improved. In particular, with a donut-shaped motor, applying pressure closer to the center of rotation would reduce loss due to contact, but due to the donut shape, this cannot be done.
Although the loss is extremely large, since there is no contact between the pressurizing means and the moving body, the driving efficiency of the motor is dramatically improved.

In addition, the structure for applying pressure can be extremely simplified and downsized because it only requires a set of mechanisms that attract or repel magnetically, and it also has many advantages, such as eliminating the need for complicated adjustments. You will be able to get it. Note that 16 or 25 constitutes an elastic vibrator, 13, 15 or 23, 24 constitutes a driven body, and 14, 18 or 21, 22 constitutes a magnetic force generating mechanism.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the principle of an ultrasonic motor that uses surface acoustic waves of an elastic vibrator, Figure 2 is an explanatory diagram of the driving method of an ultrasonic motor, and Figure 3 is an exploded view of a conventional example of an ultrasonic motor. FIG. 4 is an exploded perspective view of one embodiment of the ultrasonic motor according to the present invention, and FIG. 5 is an exploded perspective view of another embodiment of the present invention. 13;23... moving body (rotating body), 16;25
... Vibrator, 15; 24 ... Friction body, 15; 2
1, 22...Permanent magnet, 18...Magnetic holder.

Claims (1)

[Claims] 1. Elastic vibrator 16; 25 and driven body 13, 1
5; 23, 24; and a magnetic force generating mechanism 14, 18; 21, 22, wherein the driven bodies 13, 15; 23, 24 are in contact with the elastic vibrator 16; is driven, and the driven bodies 13, 15; 23, 24
and the elastic vibrator 16; 25 are brought into pressure contact with each other by magnetic force from the magnetic force generating mechanisms 14, 18; 21, 22.