JPS63268476A - Oscillatory wave motor - Google Patents

Abstract

PURPOSE:To improve efficiency by bringing the wave number of oscillatory waves excited on the circumference of a ring-shaped vibrator and the number of grooves to specific relationship in the ring-shaped vibrator having a large number of the grooves in the radial direction. CONSTITUTION:A ring-shaped piezoelectric body 1 and a ring-shaped vibrator 2, to the whole circumference of which grooves 3 in the radial direction are notched and which consists of an elastic body, are joined with adhesives, etc., thus constituting an oscillatory wave motor together with a ring-shaped moving body. The piezoelectric body 1 has a large number of electrodes 1a partitioned by cut lines 1b, and each electrode 1a has length of lambda/2 (lambda represents a wavelength) and is formed in two groups (A and B phase) displaced in lambda/4. When AC voltage, phase of which is displaced at 90 deg. mutually, is applied to the electrodes in two groups of the A phase and B phase, bending oscillatory waves in a wavelength lambda proceeding in the circumferential direction of the vibrator 2 are generated in the vibrator 2. Accordingly, the ring-shaped moving body brought into contact with the vibrator 2 is friction-driven.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a so-called vibration wave motor that frictionally drives a moving body using progressive vibration waves generated in a vibrating body.

[Background of the invention] A vibration wave motor has a vibrating body made of an elastic material.
Alternately opposite polarity at wavelength pitch, and 174 between groups.
Two groups of electro-mechanical energy conversion elements (for example, piezoelectric elements, electrostrictive elements, magnetostrictive elements, etc., hereinafter referred to as piezoelectric elements) arranged so that there is a wavelength shift are bonded and fixed. AC voltage having a temporal phase difference of about 90° is applied to the groups (hereinafter referred to as A phase and B phase) to generate a progressive vibration wave in the vibrating body, thereby bringing the vibrating body into pressure contact. It is configured to frictionally drive a moving body that is moving.

In this vibration wave motor, when the AC voltage is applied to the piezoelectric element group to cause the vibrating body to resonate, each mass point on the vibrating body surface that is in contact with the moving body undergoes spheroidal motion, and this spheroidal motion causes the moving body to resonate. is friction driven. The radius of rotation of this spheroidal motion in the circumferential direction of the vibrating body is proportional to the distance from the neutral plane of the vibrating body (a surface to which no bending stress is applied) to the mass point on the vibrating body surface. The larger the distance, the greater the driving speed with the same amplitude. Therefore, in order to increase the driving speed with the same amplitude and increase efficiency, by carving grooves perpendicular to the traveling direction of the vibration waves on the surface of the vibrating body on the moving body side, the distance from the neutral plane of the vibrating body to the surface on the moving body side can be reduced. Enlarged, so-called grooved vibration wave motors are known.

However, if the number and position of these grooves are inappropriate, there will be a difference in the amplitude of the vibrations excited in the A phase and B phase, causing noise, or the position of the antinode of the excited vibration in the - phase may differ. The position of the excited vibration node of the other phase may shift, the characteristics may change depending on the driving direction of the moving object, or the resonance frequencies of the A phase and B phase may shift.
There were problems such as inability to drive efficiently.

[Object of the Invention] The object of the present invention is to eliminate the above-mentioned drawbacks of the grooved vibration wave motor, and to obtain a vibration wave motor which is more efficient and whose characteristics change less depending on the driving direction.

[Summary of the Invention] The present invention provides an electric-mechanical energy converting vibration element that is attached to a ring-shaped vibrating body that is bonded on one side and has a large number of radial grooves provided at equal intervals in the circumferential direction on the other side. - By applying an alternating current voltage to the mechanical energy conversion vibrating element, a ring-shaped moving body that is in pressurized contact with the other surface of the vibrating body is frictionally rotated without producing a bending vibration wave that advances in the circumferential direction. In a vibration wave motor configured to It is characterized by having the following.

[Embodiments of the Invention] In Fig. 1, 1 is a ring-shaped piezoelectric body, 2 is a ring-shaped stationary body made of an elastic body with radial grooves 3 carved on the entire circumference, and both are bonded with adhesive or the like. It is joined. The piezoelectric body has a large number of electrodes 1a separated by cuts 1b as shown in FIG. 2 when viewed from the bottom, and each electrode 1a has a length of λ/2 (λ is the wavelength). These electrodes 1a are arranged in two groups (
A phase and B phase), and these A phase.

There is a shift of λ/4 between the B phases. In each electrode section, the piezoelectric body 1 is polarized in the polarization directions shown by + and - in the figure. Two groups of electrodes, A phase and B phase, have a phase of 90° to each other.
When a shifted AC voltage is applied, a bending vibration wave of wavelength λ is generated in the vibrating body 2, which travels in the circumferential direction of the vibrating body 2. As a result, a ring-shaped moving body (not shown) that is in contact with the vibrating body 2 is frictionally driven. The circumference of the vibrating body 2 is an integral multiple (k times) of the wavelength λ, and in the case of FIG. 2, k=5. k is called the wave number of the vibration wave motor.

Figures 3(a) and (b) are for N=6 and N=8 respectively.
FIG. 3 is a partial side view of one wavelength of the vibrating body 2 having a relationship of k (N is the number of grooves 3, k is the wave number).

The vibrating body 2 has a small moment of inertia and low rigidity at the groove 3 portion. Therefore, it can be fully predicted that the vibration characteristics will change depending on the phase relationship between the groove 3 and the electrode 1a.

Assuming that the electrode 1a shown in FIGS. 3(a) and 3(b) is of phase A, in the antinode of the vibration excited in phase A, in FIG. High rigidity,
In the figure (b), it is low. Also, since the antinode of the vibration excited in the B phase is shifted by 90 degrees from the A phase, the antinode in Fig. 3 (
In both a) and (b), the rigidity of the vibrating body is low.

For the two types of vibrators shown in Figures 3(a) and (b), the amplitudes of the A-phase drive and B-phase drive were measured from point P to point Q at the same voltage. ), (b). For the vibrator with N=6, see Figure 4 (
As shown in a), the amplitude x1 in the A-phase drive was about 70% of the amplitude Xb in the B-phase drive, and there was also a difference of about 30% in input power. On the other hand, for the object to be photographed with N=8,
As shown in FIG. 4(b), there was no particular difference between the amplitude X in the A-phase drive and the amplitude X in the B-phase drive, and the input power was also almost the same. This effect can be expected not only when N=8k but also when N=4+nk (m is a natural number).

The above explanation is based on the case where the groove 3 is a rectangular groove, but
A similar effect can be obtained in the case of semicircular grooves, triangular grooves, etc., which have smoother circumferential rigidity changes.

As mentioned above, a vibrating body that satisfies N = 4mK (m is a natural number) has resonance when driven in either A or B phase because the groove position is in the same phase for both A and B phases. The frequency and resonance resistance are almost equal, allowing efficient driving. Furthermore, by aligning the cut 1b of the electrode with the groove 3, the position of the node moves <<, and a vibration wave motor with uniform characteristics can be obtained for either clockwise or counterclockwise drive. This is particularly effective when m is 1.2.

[Effects of the Invention] According to the present invention, since the position of the groove of the vibrating body is in the same phase with respect to both the A and B phases, there is no difference in the amplitude of vibration when driving either the A phase or the B phase. The antinode and node positions of the excited vibrations of each phase A and B do not deviate from each other, and the resonant frequency and resonant resistance are almost the same when driving either the A or B phase.
Efficient driving becomes possible. This can also be achieved by reducing changes in characteristics depending on the driving direction.

[Brief explanation of the drawing]

Figure 1 is a perspective view of the grooved vibrator, Figure 2 is a diagram showing the electrode pattern of the piezoelectric element, and Figures 3 (a) and (b) are each N=6.
FIGS. 4(a) and 4(b) are partial side views for one wavelength of the grooved vibrator that satisfies N=8k, and N=6 and N=6, respectively.
8 is a graph of amplitude measurement results in case No. 8. 1... Piezoelectric element, 1a... Electrode 1b...
Cut end of electrode 2... Vibrating body. Figure 1 Figure 2

Claims (2)

[Claims] (1) The electro-mechanical energy conversion vibration element is attached to a ring-shaped vibrating body having a plurality of radial grooves bonded on one side and provided at equal intervals in the circumferential direction on the other side. A vibration configured to generate a bending vibration wave traveling in the circumferential direction by applying an alternating current voltage to the element, and to frictionally rotate a ring-shaped moving body that is in pressurized contact with the other surface of the vibrating body. The wave motor is characterized by having a relationship of N: 4mK (m is a natural number) between the wave number k of the vibration wave excited on the circumference of the vibrating body and the number N of the grooves of the vibrating body. vibration wave motor. (2) The vibration wave motor according to claim (1), wherein the center of the groove of the vibrating body coincides with a cut in an electrode provided on the electric-energy conversion element.