JPH01177877A - Oscillatory wave motor - Google Patents

Abstract

PURPOSE:To set torque and the number of revolution extending over a wide range by bringing the sliding surface of an annular rotor into pressure-contact with a stator side face within a range up to the crossover line of a stator neutral plane and a stator side face. CONSTITUTION:An oscillatory wave motor is composed of a stator 1, a piezoelectric element 5, a rotor 9, a cushion 11, a stator substrate 12, etc. When a plurality of. recessed sections 4, in which the angle 3 of aperture of the outer edge of the torus in the stator 1 is made the same as or smaller than the angle 2 of aperture of the inner edge of the torus, are formed and curved oscillations having amplitude in the axial direction of the recessed sections 4 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 the oscillations in the radial direction and progressive waves having amplitude in parallel with the axial direction. Accordingly, the rotor 9 is brought into pressure-contact with the inside or outside of the stator 1, thus obtaining driving force in the direction of rotation.

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. 7 is called a traveling wave rotation type or annular type.
) 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. 8, the electric element 5 has electrodes of the piezoelectric element A and H.
The electrodes are divided into two groups of electrodes, and arranged so as to be shifted by J4 (λ is the wavelength of the natural vibration mode of the stator 1) in the circumferential direction.

In addition, the circumferential length of each electrode is 172 of λ, and the polarization direction of each adjacent electrode is 8th.
Alternate them as shown by the + and - symbols in the figure. Then, by covering the surfaces of electrode groups A and B with conductive paint or the like or connecting them with conductive wires, the electrodes in electrode groups A and B are combined into one electrode.

And above the stator 1 is 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 provided with a lining surface 14 made of a wear-resistant material, for example, a composite plastic material with aromatic polyamide fiber as a filler and a polyurethane resin as a matrix.1. Prevents wear with the stator 1. 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. 9, the traveling wave on the stator 1 draws an elliptical locus when focusing on one point C on the surface of the stator 1. Since the lining surface 14 is in contact with the apex of the traveling wave of the stator, the rotor 9 can be moved by friction in the direction of the trajectory of the apex of the ellipse, so the rotor 9 is moved in the opposite direction to the traveling direction of the traveling wave. Go left. 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. .

(Problems to be Solved by the Invention) FIG. 10 shows a motor characteristic curve representing the relationship between the rotational speed and rotational torque of a conventional ultrasonic motor. This characteristic is similar to that of an electromagnetic DC motor, in that the lower the rotation speed, the greater the torque.

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, so the stator itself has unique characteristics and As shown in FIG. 10, the slope of the characteristic curve of torque versus rotational speed does not depend on the input voltage.

Of course, it is possible to change the characteristics of the motor by adjusting the reduction ratio when incorporating the motor into equipment, but in general,
Ultrasonic motors are premised on direct drive, and such adjustment is not possible. Therefore, it is necessary to design according to the required performance of the equipment, which poses a problem of requiring a lot of man-hours.

Further, by providing a plurality of recesses in the stator and changing the depth of the recesses, the amplitude of the stator can be changed and the rotation speed can be controlled. However, at the same time, the depth of the recess also changes the natural frequency of the stator. Therefore, the inner diameter of the stator,
Unless the outer diameter is corrected, the natural frequency of the stator may not be able to be set within the desired excitation frequency range. This is a limitation when designing the stator and is a problem with toroidal ultrasonic motors. Note that the desirable excitation frequency here is a frequency in the ultrasonic range ranging from 20 kHz, which exceeds the human audible range, to a frequency limited by the performance of the power source, for example, 200 kHz.

The object of the present invention is to be able to arbitrarily select torque and rotational speed characteristics using the same stator, and to prevent the drive frequency from deviating from the ultrasonic range even if the stator has a limited external shape. An object of the present invention is to provide a vibration wave motor whose rotation speed can be set.

(Means for solving the problem) A vibrator that converts an input electrical signal into mechanical vibration, which has a vibration waveform on one end face of a toroidal resonator made of an elastic body with both end faces perpendicular to the axial direction. In a vibration wave motor having a structure in which an annular stator and an annular rotor are brought into pressurized contact with each other, a plurality of recesses are provided on the other end surface of the annular resonator, and the recesses The opening angle of the outer edge is the same or smaller than the opening angle of the inner edge, and the line of intersection between the neutral plane of the stator and the side surface of the stator is greater than the line of intersection between the side surface of the stator and one end surface having the opening of the recess. A vibration wave motor characterized in that a sliding surface of the annular rotor, which has a sliding surface on the inner or outer side of the ring, comes into pressure contact with the stator side surface.

(Function) As shown in the top perspective view of the stator in FIG. 1(b), an opening angle of the inner edge of the ring is formed on one end surface of the annular resonator made of an elastic body with both end surfaces perpendicular to the axial direction. When a bending vibration having an amplitude in the axial direction of the stator 1 is excited from the lower surface of the annular elastic body to the stator 1 provided with a plurality of recesses 4 having the same or smaller opening angle 3 of the outer edge with respect to the stator 1, the stator 1
Vibration is excited that 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 the boundary. This is because in a stator provided with a plurality of recesses 4 having the characteristics described above, 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. This is because the bending strain that occurs in the radial direction causes vibrations that have an amplitude in the radial direction. Vibration in the circumferential direction is obtained by this radial direction vibration and a traveling wave having an amplitude parallel to the axial direction, and by combining these two vibrations, the intersection line between the side surface of the ring and the neutral plane is removed. The inner or outer mass points vibrate in 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 direction vibration may be a standing wave instead of a traveling wave, but by using a traveling wave with an amplitude parallel to the axial direction, radial direction vibration and circumferential direction 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 both torque and rotation 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 straight line with respect to the rotation speed becomes steep, resulting in a characteristic that prioritizes torque over the rotation speed. In this case, 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.

Furthermore, in the present invention, even when there are regulations regarding the dimensions of the stator,
By changing the shape of the recess 4, the rotation speed and torque can be changed.

That is, the larger the difference between the opening angle 2 at the inner edge and the opening angle 3 at the outer edge of the recess 4, the larger the difference in bending rigidity in the axial direction around the circumference between the inner and outer circumferences. Therefore, the magnitude of the vibration amplitude in the radial direction changes depending on the magnitude of the difference between the opening and opening angles, and therefore the rotation speed of the motor changes. Conventionally, the rotation speed of the motor was changed by changing the depth of the recess 4, but changing the depth of the recess 4 changes the natural frequency of the stator more than changing the difference in opening angle. . The range allowed for the natural frequency of the stator is limited to the ultrasonic frequency range of approximately 20 kHz to 200 kHz, and it is not desirable to greatly change the natural frequency. In this regard, in the present invention, since the difference between the opening angle 2 at the inner edge and the opening angle 3 at the outer edge of the recess 4 is changed, the effect on the resonance frequency of the stator is small and the effect is large.

(Embodiment) FIG. 1(a) is a perspective view showing an embodiment of the present invention, in which 1 is made of an elastic material such as phosphor bronze and has a thickness 5.
An electric signal, for example, an electric signal having a frequency of 44 kHz is input to the piezoelectric element 5, which is an annular stator with a diameter of 1.5 mm and has an electrode structure shown in the explanatory diagram of FIG. Excite a bending traveling wave with amplitude in the axial direction. As shown in the perspective view of FIG. 1(b), the stator 1 has a groove depth of 2.2 mm, an opening angle 2 of the inner edge of the stator ring of 4.5 degrees, and an opening angle 3 of the outer edge of the stator ring of 1.5 degrees. A plurality of concave portions 4 are provided at intervals. In this case stator 1
The shape and dimensions of the piezoelectric element 5 are predetermined so that its natural vibration matches the frequency of the target input electric signal (44 kHz in this case). Further, 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. 8. Then, due to the vibration in the axial direction of the stator due to the traveling wave, as shown in Fig. 2 (
As shown in the plan view of a) and the cross-sectional view of (b), the stator 1
Vibration amplitude 6 in the stator circumferential direction on the inner and outer surfaces of the ring
can be obtained. At the same time, a vibration 7 having an amplitude in the radial direction as shown in the plan view of FIG. 2(c) is generated. The shape of the annular stator 1 is preferably such that the ratio of the thickness in the axial direction of the stator to the width in the radial direction of the annular ring is 0.5 to 3 in order to facilitate obtaining the radial amplitude 7 described above. And Fig. 2 (
The combination of the circumferential vibration amplitude 6 in b) and the radial vibration amplitude 7 in FIG. A vibration 8 having an elliptical orbit is generated on the side surface excluding the light beam portion. The vibration 8 generated on the outer side surface of the stator 1 causes
As shown in the cross-sectional view, by adopting a structure in which the rotor 9 is brought into pressure contact with the side surface of the stator 1, the circumferential motion near the apex 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 that is highly wear-resistant, 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.

In addition, if a configuration is adopted in which the pressure contact position of the rotor 9 on the side surface of the stator 1 can be changed in FIG. 1(a), in the drooping characteristic of the vibration wave motor shown in FIG. It is possible to change the slope of the approximate straight line even if the stator is the same, and a motor that prioritizes rotation speed or torque can be realized using the same stator.

FIG. 3 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).

FIG. 4 shows another example of the opening angle of the recess 4 provided in the stator 1. FIG. Dimensions of stator 1, depth of recess 4,
The number is the same as that in Fig. 1(b), but the side surfaces of the recess 4 are parallel, and the opening angle 2 of the inner edge of the recess is 2.7.
degree, and the opening angle 3 of the outer edge is 2.0 degrees. Figure 1 (
In the embodiment of the recessed portion 4 shown in b) and the embodiment of the recessed portion 4 shown in FIG. Comparing the radial vibration 13 of the outer edge, the radial vibration of the recess shown in FIG. 1(b) has a smaller amplitude than the radial vibration of the recess shown in FIG. The motor having the recess shown in FIG. 4 has characteristics of low rotation and high torque.

Note that any modification may be made without departing from the purpose; for example, as shown in the perspective view of FIG. 6, the shape of the recess viewed from the top surface of the stator may be a part of an ellipse; The above examples do not limit the scope of the invention.

(Effect of the invention) A bending traveling wave having an amplitude in the axial direction of the stator is excited in a stator provided with a plurality of recesses in which the opening angle of the outer edge is the same or smaller than the opening angle of the inner edge of the annular resonator. By combining two amplitudes: the obtained vibration amplitude in the stator radial direction and the circumferential vibration amplitude obtained by exciting the stator with a bending traveling wave having an amplitude in the axial direction of the stator, the stator side surface and the neutral Elliptical vibration is excited on the stator side surface excluding the intersection line of the stator, and rotational torque is generated by pressurizing the rotor into contact with the stator side surface on the side where the open end of the recess is located from the intersection line of the stator neutral surface and the stator side surface. According to the vibration wave motor, by changing the pressure contact position of the rotor, it is possible to realize a vibration wave motor with characteristics that give priority to torque or rotation speed with the same stator. This has the effect that the difference between the opening angle of the inner edge and the opening angle of the outer edge becomes one of the geometrical and dimensional parameters that determine the rotation speed and torque characteristics of the vibration wave motor.

By adopting the configuration described above, it is possible to arbitrarily select the characteristics of torque and rotation speed with the same stator, and even if the external shape of the stator is limited, the driving frequency will not deviate from the ultrasonic range. It is possible to create a vibration wave motor whose torque and rotation speed can be set.

[Brief explanation of the drawing]

FIG. 1(a) is a sectional view showing the basic configuration of the present invention, FIG. 1(b) is a perspective view showing the features of the present invention, and FIGS. 2(a) to (
d) is an explanatory diagram showing the state of vibration according to the present invention; FIG. 3 is a sectional view showing an embodiment of the vibration wave motor according to the present invention in which a rotor is brought into pressure contact with the inside of the side surface of a stator;
The figure is a perspective view of the top surface of the stator showing one embodiment of the recess according to the present invention, FIG. 5 is an explanatory diagram showing the amplitude in the radial direction at the outer edge of the tip of the recess, and FIG. 7 is a cross-sectional view of a conventional annular motor, FIG. 8 is an explanatory diagram showing the polarization of a piezoelectric element bonded to the stator, and FIG. 9 is a diagram showing vibrations caused by traveling waves. FIG. 10 is an explanatory diagram showing the drooping characteristics of the motor. 1... Stator, 2... Opening angle at the inner edge of the recess, 3...
... Opening angle at the outer edge of the recess, 4... Recess, 5... Piezoelectric element, 6... Circumferential amplitude, 7... Radial amplitude, 8...
...Vibration that describes an elliptical orbit, 9...Rotor, 10...
, 11... Cushion, 12... Stator board, 1
3... Radial amplitude of the outer edge of the tip of the recess 1.14...
Lining, A, B... electrode group, C, D... one point on the stator surface.

Claims (1)

[Claims] an annular stator having a structure in which a vibrator for converting an input electric signal having a vibration waveform into mechanical vibration is bonded to one end surface of an annular resonator made of an elastic body having both end surfaces perpendicular to the axial direction; In a vibration wave motor configured to make pressurized contact with the annular rotor, a plurality of recesses are provided on the other end surface of the annular resonator, and the recesses have an opening angle of the outer edge with respect to an opening angle of the inner edge of the annular resonator. The angles are the same or smaller, and a circular ring is formed on the stator side surface from the intersection line between the one end surface having the opening of the recess and the stator side surface to the intersection line between the stator neutral plane and the stator side surface. A vibration wave motor characterized in that a sliding surface of the annular rotor, which has an inner or outer side surface as a sliding surface, is brought into pressure contact with the sliding surface of the annular rotor.