JPH01177878A - Oscillatory wave motor - Google Patents

Abstract

PURPOSE:To miniaturize the title motor, and to reduct cost thereof by forming a gradient inside the side face of an annular stator, exciting amplitude by vibrations in the radial direction of the stator and curved progressive waves having amplitude in the axial direction and combining the two amplitude. CONSTITUTION:An oscillatory wave motor is composed of a stator 1, a piezoelectric element 5, a rotor 9, a cushion 11, a box body 12, a thrust bearing 13, a spring 15, etc. When a gradient is shaped to one end face of an annular resonator constituted of an elastic body, in which both end faces of the stator 1 are formed on surfaces vertical to the axial direction, and curved oscillations having amplitude in the axial direction are excited from the underside of an annular elastic body, oscillations having amplitude in the direction vertical to the direction that curved oscillations are transmitted are excited, using the neutral plane of the elastic body as a boundary in said stator 1. Oscillations in the circumferential direction are acquired by oscillations in the radial direction and progressive waves having amplitude parallel with the axial direction, and the two oscillations are combined, thus driving the pressure-contacted rotor 9.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vibration wave motor, particularly an ultrasonic motor using ultrasonic vibration as a driving source.

(Prior art) In recent years, ultrasonic motors that obtain rotational or running motion by exciting ultrasonic vibrations using electromechanical coupling elements such as piezoelectric ceramics have become small-sized motors that can achieve high efficiency and high response characteristics. It is attracting attention as Regarding the motor using this ultrasonic wave, for example, "Nikkei Mechanical J (
It is explained in the February 28, 1983 issue and the September 23, 1985 issue). An example of a conventional ultrasonic motor and its principle will be described below with reference to the drawings.

The ultrasonic motor shown in Fig. 5 is a traveling wave rotation type or annular type, and has an annular elastic diaphragm (stator 1).
An annular piezoelectric element 5 having the same shape as the stator 1 is bonded to the back surface of the stator 1 and integrated. However, the thickness of the piezoelectric element 5 may not be the same as the thickness of the stator 1. As shown in FIG. 6, the piezoelectric element 5 has electrodes A and B.
The electrodes are divided into two electrode groups, and arranged so as to be shifted in the circumferential direction by hJ4 (λ is the wavelength of the natural vibration mode of the stator 1). In addition, the length of each electrode in the circumferential direction is set to 1/2 of λ, and the direction of polarization of each adjacent electrode is 6th.
Alternate in opposite directions as indicated by the 10- symbol in the tooth.

Then, by covering the surfaces of electrode groups A and H with conductive paint, etc., or connecting them with conductive wires, electrode groups A,
Each electrode in H is combined into one electrode. Then, the same annular moving body (rotor 9
) is pressed with a predetermined pressure by means such as a spring. The sliding surface of the rotor 9 is made of wear-resistant material.
For example, abrasion with the stator 1 is prevented by providing a lining surface 14 made of a composite plastic material containing aromatic polyamide fibers as a filler and a polyurethane resin as a matrix. Next, when alternating current voltages whose temporal phases are shifted by 90 degrees are applied to electrode groups A and B, each electrode alternately expands and contracts in the circumferential direction, and bending vibration occurs in the stator 1 due to the bimetallic effect. As a result, electrode 2 is shifted by 90 degrees in position and phase from electrode A and electrode B.
Two standing waves with wavelengths corresponding to the length of
These waves are combined to form a traveling wave. As shown in FIG. 7, when focusing on one point C on the surface of the stator 1, the traveling wave on the stator 1 traces an elliptical trajectory. Since the lining surface 14 is in contact with the apex of the traveling wave of the stator, the rotor 9 is moved by friction in the direction of the locus of the apex of the ellipse. The rotor 9 moves to the left, contrary to the direction of travel of the traveling wave. Therefore, the rotor 9 rotates opposite to the direction of travel of the traveling wave on the stator 1, its rotational speed is related to the speed of the elliptical trajectory, and the output torque is determined by the coefficient of friction between the stator 1 and the lining surface 14. . The rotor 9 is held in the radial direction by a radial bearing 16, and a thrust bearing 1
3 serves to maintain the shaft in the axial direction, and is attached to the housing 12 via these two bearings.

(Problems to be Solved by the Invention) Among annular vibration wave motors, a motor having a configuration in which the rotor and stator are in pressurized contact in a plane perpendicular to the axial direction is suitable for two types of load directions. It was necessary to use bearings. That is, in the above motor, if the coaxiality between the rotor and the stator is poor, the motor characteristics will deteriorate, so the radial bearing 16 that maintains the coaxiality between the rotor and the stator is
and a thrust for axial retention, which is the direction of the load due to pressurized contact between the rotor and stator.

A bearing 13 had to be used. This increases the number of component parts, which is a problem and hinders miniaturization and cost reduction.

In addition, in the case of an ultrasonic motor, the stator's natural frequency and the corresponding vibration mode excited by the electrodes of the piezoelectric element are determined at the time of design.
The stator itself has unique characteristics, and as shown in FIG. 10, the slope of the torque versus rotational speed characteristic curve does not depend on the input voltage.

Of course, when incorporating a motor into a device, it is possible to adjust the reduction ratio to exceed the characteristics of the motor, but in general, such adjustment is not possible with ultrasonic motors assuming that they are directly driven. Therefore, it is necessary to design according to the required performance of the equipment, which poses the problem of requiring a lot of work.

The purpose of the present invention is to obtain rotational driving force with a simple configuration that does not require radial bearings that perform radial holding.
Another object of the present invention is to provide a vibration wave motor in which the characteristics of torque and rotation speed can be arbitrarily set using the same stator.

(Means for Solving the Problems) The present invention converts an input electrical signal having a vibration waveform into mechanical vibration on one end surface of an annular stator made of an elastic body with both end surfaces perpendicular to the axial direction. A vibrator is glued to the inner or outer side of the annular stator, and the direction of b is the amplitude in the radial direction of the stator, and b is the amplitude in the radial direction of the stator. It is a vibration wave motor.

(Function) One end face of the annular resonator made of an elastic body with both end faces perpendicular to the axial direction is provided with a slope as shown in the cross-sectional view of FIG. When a bending vibration having an amplitude in the direction is excited from the lower surface of the annular elastic body, the stator 1 has an amplitude in the direction perpendicular to the direction in which the bending vibration is transmitted, that is, in the radial direction, with the neutral plane of the elastic body as a boundary. A vibration having the following values is excited. This is because the bending rigidity is different between the inside and outside of the stator, and when bending vibration is transmitted, the amount of expansion and contraction of the elastic body is different between the inside and outside of the stator, so the bending strain generated in the stator is caused by vibration having an amplitude in the radial direction. This is to become. Circumferential vibration is obtained by this radial vibration and a traveling wave having an amplitude parallel to the axial direction, and these two
By combining the two vibrations, the mass points on the inside or outside, excluding the intersection line between the side surface of the ring and the neutral plane, will vibrate with an elliptical orbit. Therefore, by bringing the rotor into pressure contact with the inside or outside of the stator, driving force in the rotational direction is obtained. The direction of rotation is opposite on the inside and outside of the ring, and opposite on the upper and lower sides of the neutral plane.

Note that the vibration that excites the above-mentioned radial vibration may be a standing wave instead of a traveling wave, but by using a traveling wave that has an amplitude parallel to the axial direction, the radial amplitude and circumferential vibration can be obtained at the same time. be able to.

The above vibration having an amplitude in the radial direction reverses its phase at the neutral plane of the elastic body, so the amplitude is zero at the neutral plane and increases as the distance from the neutral plane increases. Maximum at . Therefore, by changing the position of the rotor in pressure contact, the relationship between the torque and the rotational speed can be defined. In other words, when the pressure contact position of the rotor is close to the neutral plane, the slope of the torque approximation line with respect to the rotation speed becomes steep, giving a characteristic that prioritizes torque over the rotation speed. When the vehicle is away from the elevation, the slope of the rotational speed vs. torque approximation straight line becomes gentle, and a characteristic that prioritizes the rotational speed over the torque is obtained. Therefore, vibration wave motors with different characteristics can be obtained using the same stator.

By providing a slope at the part of the stator that contacts the rotor under pressure, the axial pressing force becomes a force perpendicular to the slope and a force parallel to the slope, depending on the magnitude of the slope. The component force perpendicular to the inclined surface becomes the pressing force between the rotor and the stator.

This pressurizing force acts on the surface of the stator which is vibrating along the elliptical orbit, and drives the rotor by friction in the direction of the locus at the apex of the ellipse among the vibrations depicting the elliptical orbit. At the same time, this pressing force serves to maintain rotation in the radial direction and to self-center. In order to utilize the vibration in the radial direction, as shown in the explanatory diagram of the amplitude component in FIG. 2(a), the amplitude in the axial direction is The magnitude of the slope is determined so that the component 23 perpendicular to the slope of the slope is small. That is, if the amplitude in the direction parallel to the axis of the stator is a and the amplitude in the radial direction is b, then the magnitude of the gradient is less than or equal to b/a. The magnitude of Taber here determines the ratio of inclination, as shown in the explanatory diagram of FIG. 2(b), and refers to a/13.

(Embodiment) FIG. 1(a) is a sectional view showing an embodiment of the present invention. In the figure, 1 is an annular stator made of an elastic material. An electric signal, for example, an electric signal having a frequency of 48 kHz is input to the piezoelectric element 5 having the electrode structure shown in the explanatory diagram of FIG. 6 to excite a bending traveling wave having an amplitude in the axial direction of the stator.

In this case, the shapes and dimensions of the stator 1 and the piezoelectric element 5 are predetermined so that their natural vibrations match the frequency of the intended input electrical signal. Also, the size of the slope is 3/8
is set to . As mentioned above, this satisfies the condition that the magnitude of the gradient is equal to or less than b/a, where a is the amplitude in the axial direction of the stator and b is the amplitude in the radial direction.

As for the piezoelectric element 5, a traveling wave is generated by inputting electric signals having vibration waveforms whose phases are different from each other by 90 degrees to the electrode group A and the electrode group B of the piezoelectric element shown in FIG. 6. The vibration in the axial direction of the stator caused by the traveling wave produces a vibration amplitude 6 in the circumferential direction of the stator on the inner and outer surfaces of the annular ring of the stator, as shown in FIGS. 3(a) and 3(b). At the same time, a vibration 7 having an amplitude in the radial direction as shown in the top view of FIG. 3(e) is generated. The shape of the annular stator 1 makes it easier to obtain the vibration amplitude 7 in the radial direction, so the ratio of the thickness in the axial direction of the stator to the width in the radial direction of the annular ring is preferably 0.5 to 3. The vibration amplitude 6 in the circumferential direction of Fig. 3(ω) due to the traveling wave and the radial vibration amplitude 7 of Fig. 3(C) are combined,
As shown in the top view of the stator in d), a vibration 8 having an elliptical orbit is generated on the side surface of the stator 1 excluding the intersection line with the neutral plane. Using the vibration 8 generated on the spiral slope of the outer side surface of the stator 1, the rotor 9 is moved as shown in the cross-sectional view of FIG.
By adopting a bone structure that pressurizes and contacts the side surfaces of the stator 1 excluding the neutral surface, the circumferential motion near the top and bottom of the elliptical orbit of the vibration 8 is converted into rotational motion of the rotor 9. For the portion of the rotor 9 that comes into contact with the stator 1, a material with excellent wear resistance, such as an aromatic polyamide synthetic resin, is used. Note that the rotational driving force is obtained by a shaft 10 provided on the rotor 9.

As shown in the cross-sectional view of FIG. 1(a), by making the shape of the stator 1 and the shape of the part of the rotor 9 that comes into pressurized contact with the stator 1 into shapes with the same gradient size, the bearing can be moved in the axial direction. It is sufficient to provide the thrust bearing 13 that bears the force, and a bearing that carries the load in the radial direction is unnecessary.

FIG. 4 is a sectional view showing another embodiment in which the positional relationship between the stator and rotor in FIG. 1(a) is changed.

According to this embodiment, the directions of the inner and outer elliptical orbits of the stator 1 are opposite in the portion that contacts the rotor 9, so the motor of FIG. The rotation direction is opposite to that of the motor configured as shown in FIG. 1(a). Note that the shape of the stator may be inclined on both the inner and outer sides, or may be inclined on one side as required.

Furthermore, as shown in the perspective view of FIG. 1(b), the stator 1 has a plurality of recesses 4 with an opening angle 2 of the inner edge of the stator ring of 4.1 degrees and an opening angle 3 of the outer edge of the stator ring of 1.9 degrees. They can also be provided at equal intervals. By providing such a concave portion, vibration in the radial direction is likely to occur.Furthermore, by changing the shape, the rotation speed can be changed.

Regarding the shape, there is an effect that the rotation speed increases as the opening angle 2 at the inner edge is larger than the opening angle 3 at the outer edge.

Note that any modification may be made without departing from the purpose; for example, the side surface of the recess 4 viewed from the top surface of the stator shown in FIG. 1('b) may be a curved surface, and the above implementation The examples do not limit the scope of the invention.

(Effects of the Invention) A vibration amplitude in the stator radial direction obtained by exciting a bending traveling wave having an amplitude in the axial direction of the stator in a stator having a slope on the inside or outside of the side surface of the annular stator; By combining the two amplitudes, the vibration amplitude in the circumferential direction obtained by exciting a bending traveling wave having an amplitude in the axial direction of According to the vibration wave motor which generates rotational torque by pressurizing the rotor into contact with the inclined surface of the side surface of the stator on the side where the open end of the recess is located from the intersection line between the neutral surface of the stator and the side surface of the stator, the rotor and Since the configuration with the stator is self-aligning,
This eliminates the need for bearings that carry loads in the radial direction, which has the effect of reducing the number of parts. Therefore, it is possible to achieve miniaturization and cost reduction, and even if the external shape of the stator is limited, the drive frequency does not deviate from the ultrasonic range. A motor can be realized.

[Brief explanation of the drawing]

FIG. 1(a) is a sectional view showing an embodiment of the present invention;
b) is a perspective view showing the stator of the embodiment of the present invention, FIGS. 2(a) and (b) are explanatory diagrams of the amplitude components of the present invention, and FIG.
a) to (d) are explanatory diagrams showing the state of vibration according to the present invention, and FIG. 4 is a cross-sectional view showing an embodiment of the vibration wave motor according to the present invention, in which the rotor is brought into pressure contact with the inside of the side surface of the stator. , FIG. 5 is a sectional view of a conventional annular motor, FIG. 6 is an explanatory diagram showing the polarization of a piezoelectric element bonded to the stator, and FIG. 7 is an explanatory diagram showing the state of vibration due to traveling waves.

Claims (1)

[Claims] A vibrator for converting an input electric signal having a vibration waveform into mechanical vibration is bonded to one end face of an annular stator made of an elastic body with both end faces perpendicular to the axial direction. α/β<b/a toward the inner or outer side surface of the annular stator opposite to the bonding surface of the vibrator (where α/β is the magnitude of the slope, and a is parallel to the axis of the annular stator) b is the amplitude in the radial direction of the stator, and b is the amplitude in the radial direction of the stator. vibration wave motor.