JPH04165969A - Disc type ultrasonic motor - Google Patents

Abstract

PURPOSE:To improve contacting state between an oscillator and a mover remarkably and to suppress noise in audible region by making a recess in an elastic body constituting the mover and forming a frictional member so that it covers at least the recess. CONSTITUTION:An annular recess 4 is made in an elastic body 1 on the side contacting with a protrusion on an oscillator and a mover 3 is constituted by applying a frictional member 2 onto the elastic body so that the frictional member 2 covers at least the recess 4. Unnecessary vibration due to fluctuation of amplitude between standing waves caused by areal shift or applying position shift from the oscillator having protrusion or theoretical radial inclination of oscillatory displacement are absorbed through surface correcting effect produced when the frictional member 2 on the recess 4 deforms along the distribution of oscillatory displacement. According to the constitution, allowance of flatness is enlarged and noise in audible region caused by beat components of driving frequency and unnecessary oscillation frequency due to restriction of machining or unnecessary oscillation can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a disk-type ultrasonic motor that generates driving force using elastic vibrations of a piezoelectric body.

Conventional technology: An ultrasonic motor motor that excites elastic vibrations in a vibrating body laminated with piezoelectric materials such as piezoelectric ceramics, and uses this as a driving source. For example, for driving in strong magnetic fields such as NMR (nuclear magnetic resonance apparatus). It is attracting attention as a motor.

Hereinafter, the conventional technology of a disc-type ultrasonic motor will be described in detail with reference to the drawings.

FIG. 6 is a cutaway perspective view of a disc-type ultrasonic motor excited in a vibration mode of second order in the radial direction, third order in the circumferential direction or higher;
The vibrating body 6 is constructed by bonding a disk-shaped piezoelectric body 9 to a disk-shaped elastic body 8. Projections 10 are provided on the vibrating body 6 in an annular shape at equal intervals. Numeral 11 is a friction material made of a wear-resistant material. Numeral 12 is an elastic body, which are pasted together to form the moving body 3. The movable body 3 is in pressure contact with the vibrating body 6 via the friction material 11. When an electric field is applied to the piezoelectric body 9, a traveling wave of bending vibration is excited in the circumferential direction of the vibrating body 6, thereby driving the movable body 3. 9. The arrow in the figure indicates the rotation direction of the moving body 3.

FIG. 7 shows an example of the electrode structure of the piezoelectric body 9 used in the disk type ultrasonic motor of FIG. In the figure, four elastic waves are excited in the circumferential direction. The electrodes are polarized in the order of +10-- as shown in the figure, and each electrode corresponds to a quarter wavelength (90 degrees). By connecting these electrodes in a ten-to-ten order, electrodes A and B, which are shifted by 90 degrees in position and phase, are constructed.

Piezoelectric body 9 of the disc type ultrasonic motor configured as above
V+ =Vex 5in(ωt) on electrodes A and B of
---(1) Va-Vθx cos(ωt)
---(2) However, ■11 = Instantaneous value of voltage ω: Angular frequency t: Application deviation of voltages V1 and ■2 expressed in time (for the astringent vibrator 6, ξ−ξe x (cos(ωt) x cos(kx)+
5in(ωt)x 5in(kx))−ξθx co
s(ωt-kx)' ---(3) where ξ: Amplitude value of bending vibration ξ9 = Instantaneous value of bending vibration k: Wave number (2π/λ) λ: Wavelength X: Progressing in the circumferential direction, expressed by position A traveling wave of bending vibration is excited.

Figure 8 shows point A on the surface of the vibrating body 6 moving in an ellipse with the long axis 2W and the short axis 2u due to the excitation of the traveling wave, and the movable body 3 placed under pressure on the vibrating body 3. It shows how, due to close contact, the waves move at a speed of V-ω×u in the direction opposite to the direction of wave propagation due to frictional force.

FIG. 9 shows the vibration displacement distribution in the radial direction when the secondary vibration mode is excited in a disk without the protrusion 10.

From the figure, there is a maximum point of vibrational displacement and an interior portion 13 (where no vibration occurs) in the radial direction of the disk. In the case of the second-order vibration mode in the radial direction, the main feature is that it can be supported and fixed with screws etc. inside the part.In the case of such a configuration, the lateral displacement U is used to improve the rotational speed of the motor. In order to enlarge the protrusion, which is difficult to machine, move the movable body 3 of the vibrating body 6 near the maximum point of vibration amplitude.
It is installed on the contact surface with the

Furthermore, since the driving source is frictional force, the plane precision (waviness, etc.) of the friction material provided on the moving body and the protrusion 10 in contact with it is an important factor for motor characteristics and noise in the audible range. ing.

Problems to be Solved by the Invention Conventional disc type ultrasonic motor Variations in mechanical strength and height of roots (
yo Resonant frequency shift, output torque, efficiency, drive electrode A,
This directly affects the motor characteristics, such as the generation of noise in the audible range due to the beat component between the frequency of unnecessary vibration and the drive frequency, which is caused by the difference in the area of B or the misalignment of the bonding of the piezoelectric body and the vibrating body with protrusions. is affecting. Therefore, there are problems in terms of machining time, machining accuracy, and cost due to improvements in planar accuracy.

It also improves the flatness accuracy of the vibrating body when it is stationary,
Even if we assume that the vibrating body itself vibrates ideally with the same amplitude between each standing wave and no unnecessary vibrations, it will have a vibration displacement distribution in the radial direction as shown in Figure 8, which is different from the actual vibrating body. It is impossible to obtain complete contact with the moving object.

Furthermore, the quality of contact poses a major problem in practical use as a motor, such as variations in motor characteristics and the source of noise.

Therefore, the present invention aims to provide a circular type ultrasonic motor that solves the above-mentioned conventional problems.

Means for Solving the ProblemMeans for solving the above problem (by forming a protrusion or a recess on the vibrating body, providing a recess on the elastic body constituting the movable body on the side that contacts the formed surface, and covering at least the recess. The movable body and vibrating body are constructed by pasting friction materials together.

Function: The disk-type ultrasonic motor of the present invention (main) has a concave portion in the elastic body constituting the movable body on the surface that comes into contact with the protrusion or concave portion of the vibrating body, and a friction material is pasted to at least cover the concave portion. By adopting the movable body configuration, when the pressing force of the protruding part of the vibrating body is applied to the friction material on the concave part, the surface correction effect that the friction material follows the surface of the protrusion due to deformation when both ends of the friction material are fixed is achieved. Contact between the vibrating body and the moving body can be easily ensured.

In addition, due to the surface correction structure described above, the absorption of unnecessary vibration components caused by the unbalance of the amplitude of each standing wave that generates elastic traveling waves prevents the generation of noise in the audible range, and provides stable motor characteristics with less variation. It is something that can be obtained.゛Examples The present invention will be described in detail below with reference to drawings of examples.

(First Embodiment) FIG. 1 is a cross-sectional view of a moving body in a first embodiment of the disc type ultrasonic motor of the present invention.

In the same figure, the elastic body 1 constitutes a disc-shaped moving body 3 together with a friction material 2, and an annular recess 4 is provided on the side of the elastic body 1 that contacts the protrusion of the vibrating body, A friction material 2 is bonded to an elastic body so as to at least cover the movable body 3.

A disk-type ultrasonic motor is constructed by pressurizing the movable body 3 (mi) having the above configuration with a vibrating body having protrusions through the friction material 2 in the same manner as in the case shown in FIG.

By making the moving body have the configuration of this embodiment, A in FIG.
When attaching the B electrode to a vibrating body that has an area misalignment or a protrusion, a concave portion 4 is provided to receive unnecessary vibration due to amplitude variation between each standing wave caused by positional misalignment and the tilt force of the radial vibration displacement that occurs in principle. As a result, the friction material 2 on the concave portion 4 deforms along the vibration displacement distribution, so that the vibration can be absorbed by the surface correction effect.

As a result, the allowable range for planar accuracy can be expanded, and it is possible to eliminate restrictions on machining and audible noise due to beat components of unnecessary vibration frequencies and drive frequencies due to unnecessary vibrations.

(Second Embodiment) FIG. 2 is a sectional view of a moving body in a second embodiment of the present invention, and FIG. 3 LL is a plan view and a sectional view of a vibrating body in this embodiment. Moreover, FIG. 4 shows a cross-sectional view of a state in which the moving body and the vibrating body are combined.

In FIG. 2, a moving body 3 (an elastic body 1 having a recess 4)
It is made up of a friction material 2 having a convex portion 5 that is bonded to the friction material 2.

In FIG. 3, a recess 7 is provided in the vibrating body 6 to increase frictional resistance.

q- The position of the convex portion 5 (relative to the concave portion 7 of the vibrating body 6 shown in FIG. 3) is provided at the position of the maximum displacement of vibration in the vibration mode of FIG. This has a great effect on determining the contact position with the body 3.

Shape of recess 7 (main Fig. 5 (aL (bL (c)
Various shapes can be considered, such as, but the shape is not limited to this. In addition, the shape of the concave portion 4 can be variously considered.
The shape shown in FIG. 5 or a tapered shape may be used as long as it has a surface correction effect or an effect of absorbing unnecessary vibrations, and is not limited to the shape of the above embodiment.

The disc type ultrasonic motor of this configuration (mainly basically a flat disc).The recess 7 may be slightly deeper than the amount of displacement of the vibrating body 6. Machining issues such as distortion that occurs when machining protrusions as in conventional examples (
(accuracy, cost, etc.) can be easily resolved.

In addition, since unnecessary vibrations due to variations in the amplitude of each standing wave that excites the traveling wave can be absorbed by the recess 4 formed in the elastic body 1 of the moving body 3, noise and flat surfaces due to the beat component of the unnecessary vibration frequency and the drive frequency can be absorbed. Vibrating body 6 due to poor accuracy
It is possible to prevent the deterioration of the surface contact state between the motor and the moving body 3, thereby improving the output torque of the motor and obtaining stable characteristics.

On the other hand, the number of recesses 7 provided in the vibrating body 6 can be made very shallow compared to the protrusion structure of the first embodiment or the conventional example, and can be freely set. The resonance characteristics of the protrusion are determined by the relationship that it is inversely proportional to the thickness.In order to obtain the mechanical strength of the protrusion, it is stable to set the resonance of the protrusion to more than twice the driving frequency of the vibrating body 6. Furthermore, by increasing the number of recesses 7, it is possible to obtain stable motor characteristics such as low-speed rotation with less cogging.

The radial width of the grinding protrusion does not need to be smaller than the radial width of the recess 4 provided in the movable body 3, and there are no restrictions on the shape, but it is preferably larger than the width of the protrusion to improve the absorption effect of unnecessary vibrations. The effect along the surface can be increased.

Furthermore, no problem will arise even if the friction material 2 having the convex portions 5 of the second embodiment is applied to other embodiments.

Mana Recess 4 (In each of the above embodiments, the force receiver is hollow. For example, it is filled with a material such as a rubber material or a sponge-like material such as felt, which has a lower sound velocity and elastic modulus or a material with a larger internal loss than a friction material. In that case, a greater effect of absorbing unnecessary vibrations can be obtained. In this case (ζ) the recess 4 is not limited to a cavity as in the first and second embodiments.

Effects of the Invention In the present invention, a concave portion is provided in an elastic body constituting a moving body,
By forming the friction material so as to cover at least the concave portion, even if the surface accuracy of the vibrating body is poor, the contact state between the vibrating body and the movable body can be significantly improved due to the surface correction effect due to the deformation of the friction material.

In addition, by absorbing unnecessary vibrations due to amplitude variations in each standing wave that generates a traveling wave, it is possible to suppress noise in the audible range due to beat components of conventional unnecessary vibration frequencies and drive frequencies.

Furthermore, by forming a recess in the vibrating body, the cost for machining and constraints on machine accuracy can be significantly reduced compared to when forming a protrusion.

Furthermore, by increasing the number of recesses, a disk-type ultrasonic motor with reduced cogging and other motor characteristics and excellent stability can be realized.

[Brief explanation of drawings]

Figure 1 is a cross-section of a moving body in a first embodiment of the disc type ultrasonic motor of the present invention. Figure 2 is a cross-section of a moving body in a second embodiment of the present invention. A plan view and a cross section of the vibrating body used in the embodiment are shown in FIG. 4, and a combined cross section of the vibrating body and moving body in the second embodiment are shown in FIG. 5. Figure 6 is a cutaway perspective view of a conventional disk-type ultrasonic motor. Figure 7 is a plan view showing the shape and electrode structure of the piezoelectric body used in the disk-type ultrasonic motor of Figure 6. Figure 8 is an ultrasonic Doctor explaining the operating principle of the motor. FIG. 9 is a radial vibration displacement distribution diagram of the disc-type ultrasonic motor. 2, 11... Friction eraser 3... Moving object 4, 6...
Concave plate 5...Ham 7...Vibrating body 9...Piezoelectric body
10... Protrusion. Figure 1 Figure 2 Figure 3 (L) Figure 4 Figure 5 (Figure 6 Figure 7

Claims (3)

[Claims] (1) A piezoelectric body is driven with an alternating current voltage, and a vibrating body composed of the piezoelectric body and an elastic body having protrusions is moved in the radial direction.
Next, in a disc-type ultrasonic motor that excites third-order or higher-order elastic waves in the circumferential direction and drives a moving body composed of a friction material and an elastic body by pressurizing and contacting the protrusion of the vibrating body, . A disc type ultrasonic motor, wherein the elastic body of the movable body is provided with a recess on the friction material side. (2) The piezoelectric body is driven with an alternating current voltage to excite elastic waves of second order in the radial direction, third order in the circumferential direction or higher in the vibrating body composed of the piezoelectric body and the elastic body, and the friction material and the elastic body are A disc-type ultrasonic motor that drives a movable body made of A disc type ultrasonic motor, characterized in that a concave portion is provided on the material pasting side, and the friction material is provided with a convex portion facing the concave portion of the vibrating body. (3) The disk type ultrasonic motor according to claim 1 or 2, wherein the recess provided in the moving body is filled with a material having a larger internal loss than a friction material.