JPS6311073A - Vibrating wave motor - Google Patents

Abstract

PURPOSE:To improve the yielding force and speed, by specifying a bar vibrating body with multiple lugs for a vibrating substance, and by setting the natural frequency of transverse vibration of this lug higher than the vibration frequency of a motor. CONSTITUTION:A vibrating wave motor is composed of a group of piezoelectric elements 1, an elastic body 21 as a vibrating substance, a moving body 3, a supporting vibration absorber 4 and an anchor body 5. By the travelling vibrating wave of a group of piezoelectric elements 1, etc. the moving body 3 coming into contact with the elastic body 21 is forced to move in the direction of an arrow A or in the reverse direction. At this moment, multiple lugs 21A extended from the bottom of the elastic body 21 are provided in the whole circuit of the elastic body 21. The form of the lug 21A is selected so that the natural frequency of the transverse vibration of the beam of this lug 21A may become higher than the vibrating frequency of the motor. Thus, the travelling wave is not disturbed and its yielding force is not reduced even if the length 1 of the lug 21A is elongated and the pressure W to apply is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a vibration wave motor driven by progressive vibration waves, and particularly to the structure of its vibrator.

(Prior art) A vibration wave motor uses, for example, the vibration motion generated when a frequency voltage is applied to a piezoelectric vibrator as a driving force.
Compared to conventional electromagnetic motors, they do not require windings, so they have a simpler and smaller structure, and have the advantage of being able to provide torque even when rotating at low speeds, and have attracted attention in recent years.

A method for transmitting the displacement of a vibrating body to a moving body in such a vibration wave motor is disclosed in Japanese Patent Application Laid-open No. 178988/1988;
Methods such as those disclosed in Japanese Patent Application Laid-Open No. 59-201685 have been proposed.

FIG. 1 is a diagram illustrating the outline of the configuration of such a conventional example,
FIG. 2 explains its operating principle.

1 is a piezoelectric element group as an electro-mechanical conversion element, 2 is an elastic body as a vibrating body, 3 is a moving body, 4 is a vibration absorbing material for support,
5 is a fixed body. For example, as shown in the plan view of FIG. 3, piezoelectric element group l has sector-shaped parts indicated by dotted lines (+) and (-).
As shown by the symbol, it is polarized in the thickness direction.

An AC voltage v==vosinωt is applied from a power source (not shown) to the piezoelectric element group forming the A phase represented by 1a, and the piezoelectric elements forming the B phase represented by 1b located at a position shifted by λ/4 in phase are applied. By applying V=±VO cos ωt to the element group, a progressive bending surface wave (that is, a progressive vibration wave) is generated in the elastic body 2 joined to the piezoelectric element group 1. As a result, the movable body 3 in contact with the elastic body 2 is moved in the direction of arrow A or the opposite direction.

The elastic body 2 is provided with a protrusion 2A that increases the amplitude of the progressive bending surface wave. Incidentally, the magnification rate of the swing width is determined by the length 1 of the protrusion 2A (see FIG. 1).

The movable body 3 presses into contact with the elastic body 2 with a pressure W (see FIG. 1), and moves at a speed U due to the frictional force with the elastic body 2. The vibrating body made up of the piezoelectric element group 1 and the elastic body 2 is supported by a vibration absorbing material 4 such as felt, and has a structure in which vibrations are not transmitted to the fixed body 5.

In the above configuration, the speed U of the moving body 3 can be increased by increasing the length l of the two protrusions.
If the length l of the protrusion 2A is made too long in order to raise the elastic body 2, the natural frequency of the transverse vibration of the protrusion 2A becomes too low than the frequency (drive frequency) of the frequency voltage for driving the motor, and the movement of the elastic body 2 is reduced. There is a problem in that most of the waves are absorbed by the friction surface, and the generated force P determined by the friction coefficient μ of the friction surface and the pressing force W (p=μW) is not generated.

On the other hand, if the pressing force W is increased, the pressing force concentrates on the bottom of the projection 2A, causing a problem that the traveling waves generated in the elastic body 2 are obstructed.

(Objective) An object of the present invention is to provide a vibration wave motor that eliminates the drawbacks of the conventional motor and improves the generated force and speed at the same time. The present invention will be explained in detail below using the drawings.

FIG. 4 is a configuration diagram of a main part of an embodiment of the present invention, where 21 is an elastic body as a vibrating body, 21A is a plurality of nine protrusions extending from the bottom of the elastic body 21, and the protrusions 21A are shown in FIG. Furthermore, the fifth
(The figure shows only a part of the protrusion 21A) As shown, the elastic body 21
It is located all around the area.

The protrusion 21A has a bottom surface 21a as a fixed end and a top surface 21b as a fixed end.
The natural frequency ω1 of the transverse vibration of the beam when is the free end is
It is formed into a shape that is higher than the driving frequency of the motor. Note that ω1 is E...Young's modulus, ρ...density, A...protrusion 21
The cross-sectional area when the cross-sectional area from the top to the bottom of A is averaged,
(2) Represented by the second moment of area of the protrusion, and l...The length from the bottom surface to the top surface of the protrusion 21A.

Further, the area of the bottom portion 21a of the protrusion 21A is formed larger than the area of the top portion 21b in order to reduce the surface pressure applied to the bottom portion.

In the fourth illustrated embodiment, elements having the same functions as those of the first illustrated element are given the same reference numerals and their explanations will be omitted. The operating principle of the vibration wave motor according to the above configuration is the same as that of the above-mentioned Japanese Patent Application Laid-Open No. 59-201685, so a description thereof will be omitted.

In this embodiment, since the shape of the protrusion 21A is as described above, even if the length of the protrusion 1 is increased and the pressing force W is increased, the traveling wave will not be hindered, and the generated force P will be small. There's nothing wrong with that. Therefore, a desired speed can be obtained and, at the same time, a large generated force can be obtained.

Further, the angle θ (see FIG. 4) between the side surface of the protrusion 21A and the friction surface of the movable body 3 is formed to be smaller than 90°. Therefore, this embodiment has the effect that the protrusion 21A can be easily formed by molding such as forging (casting).

6 to 8 are main part configuration diagrams of other embodiments of the vibration wave motor according to the present invention, showing only the elastic body. 2
2, 23, and 24 are elastic bodies 22A and 23A that are similar to the elastic bodies shown in the fourth figure but differ only in shape.

24A is a protrusion. The direction of travel of the traveling wave is indicated by arrow A.

The basic characteristics are the same as those of the elastic body 21 and projection 21A shown in the fourth figure. In the sixth illustrated embodiment, the protrusion 22A is attached to the bottom 22a.
The cross-sectional area is reduced in multiple steps (two steps in FIG. 6) between the top part 22b and the top part 22b, and FIG.
The angle θ is 90° between the bottom 23a and the top 23b.
Figure 8 shows the side surface changed from around 90° to around 90' or less.

Further, even with protrusion shapes other than those described above, the same effect can be produced as long as the bottom area of the protrusion is larger than the top area.

As described above, in the present invention, the vibrating body is a rod-shaped vibrating body having a plurality of protrusions, and the shape of the protrusions is formed so that the natural frequency of the transverse vibration of the protrusions is higher than the driving frequency of the motor. It is possible to obtain both force and desired speed.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of main parts of a conventional vibration wave motor, Fig. 2 is an explanatory diagram of the operation of the motor shown in the first drawing, Fig. 3 is a layout diagram of the piezoelectric element group of the motor shown in the first drawing, and Fig. 4 is the invention of the present invention. FIG. 5 is a perspective view of the vibrating body of the motor shown in FIG. 4, and FIGS. 6 to 8 are main parts of other embodiments of the vibration wave motor according to the present invention. FIG. In the figure, 21, 22. 23. 24...Elastic body, 2L
A, 22A, 23A, 24A...Protrusions.

Claims (3)

[Claims] (1) In a vibration wave motor that generates progressive vibration waves in a vibrating body by applying a frequency voltage to an electro-mechanical conversion element, and uses the vibration waves to frictionally drive a moving body that contacts a contact portion of the vibrating body. , the vibrating body is a rod-shaped vibrating body having a plurality of protrusions on the side in contact with the movable body, and the shape is such that the natural frequency of the bending vibration of the protrusions is higher than the frequency of the frequency voltage. Features a vibration wave motor. (2) The vibration wave motor according to claim (1), wherein the top area of the protrusion is smaller than the bottom area. (3) The angle between the side surface of the protrusion and the movable body is 90
The vibration wave motor according to claim (1), characterized in that the vibration wave motor is smaller than .degree.