JPH0313839B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to an ultrasonic motor using a piezoelectric vibrator.

[Technical background of the invention and its problems] Ultrasonic motors can be roughly divided into those that perform linear motion (linear type) and those that perform rotary motion (rotary type). The configuration of the linear type is shown in Fig. 9. When the piezoelectric vibrator 1 vibrates the elastic vibrator 2 as shown in the figure, an elastic wave 3 is generated in the elastic vibrator 2 and propagates on the surface of the elastic vibrator 2 in the direction of the arrow. At this time, the elastic wave 3 at the mass point on the surface of the elastic vibrating body 2 is performing an elliptical motion 4 having longitudinal and transverse amplitudes as shown in FIG. It's rotating. This elastic wave 3
has an apex 5 for each wavelength, and when the sliding body 6 is brought into pressure contact with the elastic vibrating body 2, the sliding body 6 contacts the elastic vibrating body 2 only at the apex 5 of the elastic wave, so due to the elliptic motion 4. It obtains a frictional force and moves in the direction of arrow B, that is, in the opposite direction to the propagation direction of the elastic wave 3. In addition,
Reference numeral 7 indicates a friction material for efficiently transmitting the elastic waves 3 to the sliding body 6. Usually, in a linear ultrasonic motor based on the principle shown in FIG. 10, the piezoelectric vibrator 1 is made of piezoelectric ceramic such as BaTiO ₃ or PZT, and the elastic vibrator 2 is made of metal or plastic.

The ultrasonic motor, whose exploded view is shown in FIG. 11 and front view shown in _FIG . A voltage of V ₀ sinωt is supplied to the piezoelectric vibrator 11b, and the phase is changed by 90 degrees from V _1. V ₂ =
V ₀ cosωt, the piezoelectric vibrator 11c has a further 90° phase change V ₃ = -V ₀ sinωt, the piezoelectric vibrator 11d has a 1
The sliding body 1 is brought into pressurized contact with the elastic vibrating body 12 by applying a voltage V ₄ =-V ₀ cosωt with a phase change of 90° from 1c to drive each piezoelectric vibrator.
6 will perform a rotational movement.

In such a linear type or rotary type ultrasonic motor, a metal having a high Young's modulus is often used for the elastic vibrating bodies 2 and 12 in order to increase the propagation efficiency of elastic waves. However, if, for example, metal is used for the sliding bodies 6 and 16 and it is brought into direct contact with the elastic vibrating bodies 2 and 12 to obtain driving force, the vibrations and frictional force of the elastic waves will turn into noise and heat, making it impractical. However, when a vibration isolating material is used to eliminate the noise, there is a problem in that the vibration isolating material absorbs the vibrations of the elastic waves and the frictional force, making it impossible to obtain sufficient driving force.

[Object of the invention] The present invention provides a friction material that is brought into pressure contact with an elastic vibrating body and has a hardness change in the depth direction perpendicular to the contact surface with the elastic vibrating body. It is possible to provide an ultrasonic motor that is high-speed, produces little friction noise, and has excellent durability.

[Summary of the Invention] An ultrasonic motor according to the present invention includes an elastic vibrator including a piezoelectric vibrator, and a friction material brought into pressure contact with the elastic vibrator, and drives the piezoelectric vibrator. In an ultrasonic motor that induces elastic waves on the elastic vibrating body to cause linear or rotational movement of the friction material or the elastic vibrating body itself, the friction material is moved in a depth direction perpendicular to a contact surface with the elastic vibrating body. stepped,
It is characterized by having a hardness change consisting of a gradient or a combination thereof.

[Embodiments of the Invention] Example 1 An example of a rotary ultrasonic motor will be described. As shown in the front sectional view in Fig. 1 and the exploded view in Fig. 2, the shaft 21 is used to transmit the driving force to the outside.
For the sliding body 22 that is integrated with the sliding body 22, metal is generally used in consideration of rigidity, durability, workability, etc. for those that require a large torque. In addition, an elastic vibrating body 24 (outer diameter 60 mm, inner diameter 50 mm) is attached to the sliding body 22 and comes into contact with it via an integrated friction material 23.
is made of metal such as duralumin, and a piezoelectric vibrator 25 (made of PZT) is attached to the elastic vibrator 24. The friction material 23 has a thickness of, for example, 1 mm, and its hardness changes with a gradient in the depth direction perpendicular to the contact surface with the elastic vibrating body, that is, in the thickness direction, as shown by curve A in FIG. . The hardness shown in Figure 3 is the spring type hardness type A (JIS A) specified in JIS K 6301, and the code B indicates hardness 99,
Code C indicates a reference example with hardness of 87. An absorber 2 disposed in contact with the piezoelectric vibrator 25
6 is for preventing the vibration of the piezoelectric vibrator 25 from being transmitted to the case 27, the sealing lid 28, etc. In addition,
29 and 30 are bearings, 31 is a mounting base, and 32 is a spring. An ultrasonic motor as shown in FIG. 1 is manufactured using a friction material 23 having hardness of curves A, B, and C shown in FIG. FIG. 4 shows the rotational speed of the sliding body 22 with respect to the input voltage of the ultrasonic motor, FIG. 5 shows the torque characteristics, and FIG. 6 shows the noise characteristics. In the embodiment, in order to maintain the initial characteristics of the ultrasonic motor, a depth of 0.2 mm from the surface in contact with the elastic vibrating body 24 is made to have a constant hardness so that it can withstand long-term use.

As is clear from FIGS. 4 to 6, in the ultrasonic motor according to the present invention, conventional symbols B and C
It has improved characteristics such as rotation speed, torque, and noise compared to the conventional ultrasonic motor, making it possible to provide an ultrasonic motor that is quiet, high speed, and has large torque. In particular, noise and speed or torque have a contradictory relationship, and in order to achieve high speeds, it is better to have a high hardness for the friction material 23, etc., but increasing the hardness tends to increase noise. The present invention has solved this problem.

Example 2 An ultrasonic motor similar to that of Example 1 was manufactured using a friction material having hardness (coded as D) as shown in FIG. 7, and its characteristics were measured. The results are shown in FIGS. 4 to 6 above. Almost the same values as curve A shown could be obtained. The hardness shown in Figure 7 is based on the Rockwell hardness R scale (H _R R) specified in JIS K 7202.
was used. Furthermore, in order to improve the adhesion with the sliding body 22 shown in FIGS. 1 and 2, it is also effective to use a coupling material in the contact area with the sliding body 22 to match the coefficient of thermal expansion. . In addition,
As shown in FIG. 8, friction materials having various hardness changes as shown by symbols E, F, and G (all on the Rockwell hardness R scale) may be used.

Example 3 Furthermore, as in Example 2, the friction material 7 of the linear ultrasonic motor shown in FIG. 9 was given a hardness difference in the depth direction, that is, in the direction perpendicular to the sliding surface as shown in FIG. When using a device with
The thrust results shown in FIGS. 13 and 14 were obtained. A curve C shown by a dotted line in FIGS. 13 and 14 is the conventional friction material shown in FIG.

In Examples 1 and 3, it has been described that the sliding bodies are rotated or linearly moved, but similar effects can be obtained by using an ultrasonic motor that uses these sliding bodies as fixed bodies and operates the elastic vibrating body itself.

In addition, in the above embodiment, a configuration in which a friction material was interposed between an elastic vibrating body and a sliding body was described;
A similar effect can be obtained by using the contact portion of the sliding body itself with the elastic vibrating body as a friction material and having a hardness change in the depth direction.

[Effects of the Invention] According to the present invention, it is possible to provide an ultrasonic motor having characteristics such as low noise, high speed, and large torque. I was able to resolve the drawbacks of the contradictory relationship.

[Brief explanation of drawings]

1 to 8 show an embodiment of the rotary ultrasonic motor according to the present invention, FIG. 1 is a front cross-sectional view showing the configuration of the ultrasonic motor, and FIG. 2 is an ultrasonic motor shown in FIG. An exploded view of the motor, Figure 3 is a curve diagram showing the hardness of the friction material, Figure 4 is a curve diagram showing the rotation speed of the sliding body with respect to the input voltage of the ultrasonic motor, and Figure 5 is a curve diagram showing the rotation speed of the sliding body with respect to the input voltage. Figure 6 is a curve diagram showing the torque characteristics, Figure 6 is a curve diagram showing the noise generated with respect to input voltage, Figure 7 is a curve diagram showing other examples of the hardness of friction materials, Figure 8 is the same hardness of friction materials, etc. 9 is a configuration diagram of a linear ultrasonic motor, FIG. 10 is an explanatory diagram showing the operating principle of an ultrasonic motor, and FIG. 11 is a conventional rotary ultrasonic motor. Fig. 12 is a front view of the main parts of the ultrasonic motor shown in Fig. 11, Fig. 13 is a curve diagram showing the speed of the sliding body with respect to input voltage, and Fig. 14 is an exploded view showing the main parts of the motor. FIG. 3 is a curve diagram showing thrust versus voltage. 22...Sliding body, 23...Friction material, 24...Elastic vibrator, 25...Piezoelectric vibrator, 27...Case, 28...Sealing lid.

Claims (1)

[Claims] 1 An elastic vibrating body including a piezoelectric vibrator and a friction material brought into pressure contact with the elastic vibrating body, driving the piezoelectric vibrating body to induce an elastic wave on the elastic vibrating body to In an ultrasonic motor that linearly or rotationally moves a friction material or an elastic vibrating body itself, the friction material exhibits a hardness change in the depth direction perpendicular to the contact surface with the elastic vibrating body in a stepwise manner, a gradient, or a combination thereof. An ultrasonic motor comprising: