JPH0223070A - Linear type ultrasonic motor - Google Patents

Abstract

PURPOSE:To prevent a reflected wave from generating by integrally providing a damper having a larger loss coefficient than that of a driving side member to one longitudinal end of the member. CONSTITUTION:A longitudinal elastic element 10 is formed of brass having 0.0003 of loss coefficient to become a driving side member. An ultrasonic vibrator 12 is secured along the longitudinal direction of the element 10, and a plurality of sets of the vibrators 12 each having, for example, 8 piezoelectric elements 14 are provided. Further, a driven side member 30 is pressed by a pressing unit to the opposite face of the element 10 to the vibrator 12 to be brought into pressure contact therewith and to be longitudinally movable. A pair of dampers 32 are integrally secured to both longitudinal ends of the element 10. As the damper 32 an Mu-Cu alloy having larger loss coefficient (0.05) than that of the brass is employed. Thus, the structure of a motor is simplified in small size.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a linear ultrasonic motor.

BACKGROUND ART A driven member is pressed against a linear part of an oval ring-shaped driving member, and elastic waves generated in the driving member move the driven member along the longitudinal direction of the linear part. A relatively driven linear ultrasonic motor (hereinafter referred to as a first linear ultrasonic motor) has been considered.

Furthermore, as described in, for example, JP-A-62-77071-A and JP-A-62-77072, a movable body or a magnet ( A linear ultrasonic motor (hereinafter referred to as a linear ultrasonic motor) that presses a driven member (corresponding to the driven member) and drives the driven member relatively in a direction perpendicular to the axis of the driving member using elastic waves generated in the driving member. , a second linear ultrasonic motor) is being considered.

For example, as described in Proceedings of the Acoustical Society of Japan, October 1988, p. 627 and 184 of ``Piezoelectric/Electrostrictive Actuators'' (Morikita Publishing), one of the vibrators can be used to drive a rod-shaped member. A slider that generates an elastic wave by vibrating one end (corresponding to a side member), and receives the elastic wave propagating through the rod-shaped member by the other vibrator, and is pressed against the rod-shaped member by the elastic wave. A linear ultrasonic motor (hereinafter referred to as a third linear ultrasonic motor) that relatively drives a rod-shaped member (corresponding to a driven member) along the longitudinal force and direction of a rod-shaped member has been considered.

Problems to be Solved by the Invention However, in the first linear type ultrasonic motor, the shapes of the elastic waves generated in the straight part and the semicircular part of the drive side member are different, and scattering and reflection of the elastic waves occur, resulting in a uniform Since it is difficult to obtain a strong elastic wave, it is difficult to stably drive the driven member, and since the driving member is ring-shaped, it is inevitable that the linear ultrasonic motor will be relatively large.

On the other hand, in the second linear ultrasonic motor,
Since the driving side member has a cylindrical shape, uniform elastic waves can be obtained, but a sufficient contact area between the driving side member and the driven side member cannot be obtained, making it difficult to obtain a sufficient driving force.

In addition, in the third linear type ultrasonic motor, the structure of the linear type ultrasonic motor is relatively complicated due to the need to match both vibrators in order to obtain suitable elastic waves. At the same time, it is inevitable that the linear ultrasonic motor will be relatively large.

The present invention has been made against the background of the above-mentioned circumstances, and its purpose is to provide a relatively simple structure that can obtain suitable elastic waves and ensure a relatively large driving force. Another object of the present invention is to provide a small linear ultrasonic motor.

Means for Solving the Problems In order to achieve the above object, the present invention includes a driving side member having a longitudinal shape and a driven side member that is brought into pressure contact with the driving side member. A linear type ultrasonic motor in which a driven side member is relatively driven along the longitudinal direction of the driving side member by the generated elastic waves, the linear ultrasonic motor comprising: (a) fixed to the driving side member; an ultrasonic vibrator that generates the elastic wave in the driving side member;
) A vibration damper having a loss coefficient larger than the loss coefficient of the drive side member and integrally provided at at least one end in the longitudinal direction of the drive side member.

Operation and Effects of the Invention According to the linear ultrasonic motor configured as described above,
An ultrasonic vibrator fixed to the drive side member generates an elastic wave in the drive side member, and the driven side member is relatively driven along the longitudinal direction of the drive side member by the elastic wave. At this time, at least one end in the longitudinal direction of the drive side member has a loss coefficient larger than the loss coefficient (the ratio of the thermal energy generated by one vibration of the vibration system to the vibration energy possessed by the vibration system) of the drive side member. Since the vibration damper having a loss coefficient is integrally provided, the elastic wave can be attenuated in the vibration damper, and reflected waves can be suitably prevented from being generated at the end of the driving side member. . As a result, suitable elastic waves can always be formed, and the driven member can be stably driven by the elastic waves. Moreover, since a linear type ultrasonic motor is constructed by fixing an ultrasonic vibrator to a longitudinal drive side member and integrally providing a damper at the end of the drive side member, the linear type ultrasonic motor is The structure of the sonic motor can be made relatively simple, and the linear ultrasonic motor can be made relatively small. Moreover, since the driving side member has a longitudinal shape, a sufficient contact area with the driven side member can be ensured, and a relatively large driving force can be ensured.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

In FIG. 1, 10 is a longitudinal elastic body,
In this embodiment, for example, the loss coefficient is O, OOO3.
Made of brass with This loss coefficient is expressed as the ratio of the thermal energy generated by one vibration of the vibration system to the vibration energy possessed by the vibration system, and is a coefficient that indicates the vibration characteristics (damping force) of the vibration system. It is. The elastic body 10 is
This corresponds to the driving side member of this embodiment, and an ultrasonic vibrator 12 is fixed to the lower surface of the elastic body 10 in FIG. 1 along the longitudinal direction of the elastic body 10. This ultrasonic transducer 12 is, for example, 8
The piezoelectric element 14 is configured to have a plurality of sets each including a set of piezoelectric elements 14. Note that each group is configured similarly to each other, so
The following description will be made regarding only one set of eight piezoelectric elements 14.

The eight piezoelectric elements 14 are divided into two parts, a first part 16 and a second part 18 of four adjacent to each other, each of which is fixed to the elastic body 10 via a small electrode 20.
The first portion 16 and the second portion 18 are spaced apart by a distance corresponding to, for example, 1/4 of the wavelength of a composite elastic wave, which will be described later. First part 16 and second part 18
Each piezoelectric element 14 is manufactured by applying a DC electric field to a ferroelectric crystal to perform polarization treatment, and the polarization direction is in the thickness direction (as shown by the arrow in FIG. 2).
They are arranged so as to be alternately reversed in the vertical direction (in the figure). A common large electrode 22 is fixed to the surface of each piezoelectric element 14 of the first part 16 opposite to the small electrode 20 side, and a large electrode 24 is similarly fixed to each piezoelectric element 14 of the second part 18. It is fixed. A high frequency voltage of a predetermined frequency is applied between the large electrode 22, 24 and each small electrode 20 from a high frequency power source 26 via the elastic body 10. This predetermined frequency is determined by the piezoelectric element 12 and the elastic body 1.
This frequency is approximately equal to the natural frequency of 0. Second part 18
A 90° phase shifter is provided between the side large electrode 24 and the high frequency power source 26, and the piezoelectric element 14 of the second portion 18
A high frequency voltage having a phase shift of 90° is applied to the piezoelectric element 14 of the first portion 16 .

On the surface of the elastic body 10 opposite to the ultrasonic transducer 12 side,
As shown in FIG. 1, a driven side member 30 is pressed by a pressing device such as a spring (not shown) and brought into pressure contact, and this driven side member 30 is movable in the longitudinal direction of the elastic body 10. A pair of damping bodies 32 are integrally fixed to both ends of the elastic body 10 in the longitudinal direction by adhesive or the like. The vibration damping body 32 is made of, for example, a Mn-Cu alloy having a larger loss coefficient (for example, about 0.05) than the brass, and the length of the elastic body 1O of the vibration damping body 32 in the longitudinal direction is , is preferably made longer than the wavelength of a composite elastic wave (for example, about four times the wavelength of a composite elastic wave, which will be described later).

For example, in the pair of damping bodies 32, the elastic body 1
0 is fixed to a fixed base (not shown).

In the linear ultrasonic motor configured as described above, when the high frequency voltage is applied to the ultrasonic vibrator 12, each piezoelectric element 14 expands and contracts alternately in the longitudinal direction of the elastic body 10. , the parts corresponding to the first part 16 and the second part 18 of the elastic body 10 together with the piezoelectric element 14 are deflected and vibrated in the vertical direction in FIGS. Two elastic waves (so-called standing waves) whose positions and phases are shifted by 90° are generated on the opposite surface. In this case, if we focus on the − point of the composite elastic wave (so-called traveling wave), which is a combination of both elastic waves, we can see that it is making an elliptical motion rotating in one direction, as is well known, and the ellipse of this composite elastic wave The driven side member 30 that is pressed against the surface of the elastic body 10 as it moves moves against the elastic body lO.
will be relatively driven along the longitudinal direction. Note that the driving direction of the driven member 30 can be changed by reversing the polarity of the high frequency voltage. and,
During such driving, it is preferable that reflected waves are generated at both ends of the elastic body 10 because the elastic waves are attenuated by the dampers 32 provided at both ends of the elastic body 10. be stopped. This is considered to be because vibrational energy is converted into thermal energy in the damper 32.

As a result, in this embodiment, a suitable composite elastic wave is always formed, and the driven member 30 is stably driven by the composite elastic wave. Moreover, a linear ultrasonic motor is constructed by fixing an ultrasonic vibrator 12 to a longitudinal elastic body 10 along the longitudinal direction and fixing damping bodies 32 to both ends of the elastic body 1o. Therefore, while the linear ultrasonic motor has a relatively hour wheel structure and is relatively small, the elastic body 1
0 has a longitudinal shape, a sufficient contact area with the driven member 30 is ensured, and a relatively large driving force can be ensured.

Further, according to this embodiment, the ultrasonic transducer 12 is
0, the amplitude of the composite elastic wave can be made uniform over the entire length of the elastic body 10 in the longitudinal direction, and the elastic body IO can be driven over the entire length of the elastic body 10 in the longitudinal direction. It has the advantage of keeping the force constant.

In addition, in the above-mentioned embodiment, the ultrasonic transducer 12 is the elastic body 1
Although the elastic body 10 is provided over substantially the entire length in the longitudinal direction of the elastic body 10, it may be provided only in a part of the longitudinal direction of the elastic body 10.

Further, in the above-mentioned embodiment, the damper 32 is made of a Mn-Cu alloy, but it is not necessarily made of a Mg-0.6% Zr alloy, for example.

The splitting body can also be made of 12% chromium copper, graphite cast iron, or the like.

Furthermore, in the above-mentioned embodiment, the damping bodies 32 are provided at both longitudinal ends of the elastic body 10, but even if the damping bodies are provided only at one longitudinal end of the drive side member. It is possible to obtain the effects of the present invention.

Further, in the above-described embodiment, the vibration damping bodies 32 are provided on both end faces facing the longitudinal direction of the elastic body 10, but it is not necessary to configure them in this way. For example, as shown in FIG. The damping bodies 34 may be provided on the side surfaces parallel to the longitudinal direction of both ends of the elastic body 10 in the longitudinal direction. Even in this case, it is possible to obtain some of the effects of the present invention.

In addition, various changes may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an outline of the linear ultrasonic motor of the present invention. FIG. 2 is a front view showing an enlarged main part of FIG. 1. FIG. 3 is a diagram showing another example of the present invention,
2 is a diagram corresponding to FIG. 1. FIG. 10: Elastic body (driving side member) 12: Ultrasonic transducer 30: Driven side member 32.34: Vibration damping body Fig. 1

Claims (1)

[Scope of Claims] The driving side member has a longitudinal shape and the driven side member is brought into pressure contact with the driving side member, and the driven side member is moved by the elastic waves generated in the driving side member. A linear ultrasonic motor of a type that is relatively driven along the longitudinal direction of a driving side member, and an ultrasonic vibrator that is fixed to the driving side member and generates the elastic wave in the driving side member. , a linear type ultrasonic wave characterized by including a vibration damper having a loss coefficient larger than the loss coefficient of the driving side member and integrally provided at at least one end in the longitudinal direction of the driving side member. motor.