JPH03273874A - Torus-type supersonic motor - Google Patents

Abstract

PURPOSE:To obtain a machining accuracy by enabling machining of a vibrating body to be in a plane shape for simplification by providing a recessed part on a surface which is partially in contact with a traveling body for a width of the vibrating body. CONSTITUTION:A first elastic body 1 constitutes a torus-shaped vibrating body 3 along with a piezoelectric body 2 and a recessed part 4 is provided at the inside which does not reach an outer diameter in a width of a plane of the tours-shaped vibrating body 3. A vibrating body 5 is in contact with this vibrating body 3 through a friction material 8 by pressing. The amount of displacement of a vibration displacement in the radial direction of the torus- shaped plate vibrating body 3 becomes larger toward the outside since a primary vibration mode is in use. However, since mechanical rigidity changes in proportion to a power of three of the plate thickness by providing the recessed part 4 at the inside, the amount of displacement can be flattened in the radial direction so that a stable contact can be achieved even when the center is shifted due to poor accuracy of shaft. Also, since the traveling body is driven at the inside where the amplitude of the vibration body 3 is small, stable property against fluctuation of load can be achieved.

Description

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

2. Description of the Related Art In recent years, ultrasonic motors have attracted attention in which elastic vibrations are excited in a vibrating body using a piezoelectric material such as a piezoelectric ceramic, and the vibrations are used as a driving force.

Hereinafter, the conventional technology of an ultrasonic motor will be explained in detail with reference to the drawings.

FIG. 6 is a cutaway perspective view of an annular ultrasonic motor excited in a vibration mode of first order in the radial direction, third order in the circumferential direction or higher;
A vibrating body 3 is constructed by bonding an annular expanding piezoelectric body 2 to a first annular elastic body l. Projections 9 are provided on the vibrating body 3 in an annular shape at equal intervals. 8 is a friction material made of a wear-resistant material, and 10 is a second elastic body, which are pasted together to form the movable body 5. The movable body 5 is in pressure contact with the vibrating body 3 via the friction material 8 . When an electric field is applied to the piezoelectric body 2, a traveling wave of bending vibration is excited in the circumferential direction of the vibrating body 3, thereby driving the movable body 5. Note that arrow A in the figure indicates the rotation direction of the moving body 50.

FIG. 7 shows an example of the electrode structure of the piezoelectric body 2 used in the annular ultrasonic motor shown in FIG. In the figure, nine elastic waves are excited in the circumferential direction. A and B
are electrode groups each consisting of a small region corresponding to a half wavelength, C is an electrode corresponding to a three-quarter wavelength, and D is an electrode corresponding to a quarter wavelength. Electrodes C and D are provided to create a positional phase difference of 1/4 wavelength (=90 degrees) between electrode groups A and B.

Adjacent small electrode portions in electrodes A and B are polarized oppositely to each other in the thickness direction. The adhesive surface of the piezoelectric body 2 with the first elastic body 1 is the surface opposite to the surface shown in FIG. 7, and the electrode is a peta electrode. During driving, electrode groups A and B are used while being short-circuited, as indicated by diagonal lines in the figure.

Piezoelectric body 2 of the annular ultrasonic motor configured as above
V+=VsXsin(ωt) ---(
1) V2 = Ve X cos(ωt)
--- (2) However, if VII: voltage instantaneous value ω: angular frequency t: voltage V expressed in time, and ■2 are applied, respectively,
In the vibrating body 3, ξ=ξe X (cos(ωt) X cos(kx)
+5in(ωt) x 5in(kx)): ξ5Xcos
(ωt-kx) ---(3) However, ξ:
Bending vibration amplitude value ξ [l: instantaneous value of bending vibration: wave number (2π/λ) λ: wavelength

Fig. 8 shows that point A on the surface of the vibrating body 3 moves in an ellipse with a long axis 2W and a short axis 2u due to the excitation of the traveling wave, and the moving body 5 placed under pressure on the vibrating body 3 moves in an ellipse. This figure shows how the waves move at a speed of V:ω×u in the direction opposite to the direction of wave propagation due to frictional force due to contact near the apex.

In such a configuration, in order to increase the speed of the motor,
Projections 9 for the purpose of increasing the lateral displacement U are provided at regular intervals and in a circumferential manner over the entire width of the vibrating body 3 on the contact surface with the movable body 5.

Problems to be Solved by the Invention However, providing the protrusions 9 on the vibrating body 3 poses problems in processing. For example, when processing with a milling cutter, the mechanical strength of the root of the protrusion 9 and the vibrating body 3 is weak and care must be taken during processing, resulting in a longer processing time. In this case, the contact surface of the tip of the protrusion with the movable body 5 is difficult to achieve precision, so it was necessary to polish the contact surface. Furthermore, the accuracy with respect to the thickness of the vibrating body 3 and the height of the protrusion 9 is determined by the resonance characteristics in vibration, that is, the direct characteristics such as deviations in the amplitude ratio and resonance frequency of each standing wave component during excitation of an elastic traveling wave. There is a problem in that there are very strict requirements for processing accuracy with respect to both the thickness and the height of the protrusion 9.

Furthermore, although the provision of the protrusions 9 increases the speed of the motor, cogging corresponding to the number of protrusions appears in the characteristics, which adversely affects the control characteristics. Therefore, increasing the number of protrusions 9 improves control characteristics, but problems arise in mechanical strength and workability, and there are limits in that respect as well.

In addition, in the case of a flat vibrating body without protrusions 9 on the contact surface with the movable body 5, the amplitude of the vibrating body is 10 μm or less, making pressure contact with the movable body 5 uniform and stable. Since this cannot be done well, there is a problem that the contact positions between the movable body 5 and the vibrating body 3 are different, making it impossible to obtain stable motor characteristics. Furthermore, there was the problem that audible sounds were generated due to unstable contact.

Therefore, an object of the present invention is to provide an annular ultrasonic motor that solves the above-mentioned conventional problems.

Means for Solving the Problems The present invention provides a vibrating body in which a first annular elastic body and a toroidal piezoelectric body are bonded together, and a movable body in which a toroidal friction material and a second toroidal elastic body are bonded together. In an annular ultrasonic motor that is brought into pressure contact with a body and drives the moving body by applying an electric field to the piezoelectric body to excite a traveling wave of vibration in the circumferential direction of the vibrating body, the vibration A recessed portion that does not reach the outer peripheral edge and/or the inner peripheral edge of the vibrating body is formed on the contact surface of the body with the moving body.

Function: The annular ultrasonic motor of the present invention includes a vibrating body in which a first annular elastic body and a toroidal piezoelectric body are bonded together, and a vibrating body in which a toroidal friction material and a second toroidal elastic body are bonded together. The piezoelectric body is brought into pressure contact with the piezoelectric body, and by applying an electric field to the piezoelectric body, a traveling wave of vibration is excited in the circumferential direction of the vibrating body to drive the movable body, and furthermore, the vibration of the vibrating body is By forming a recess that does not reach the outer circumferential edge and/or inner circumferential edge of the vibrating body on the contact surface with the movable body, excellent output characteristics can be achieved.

EXAMPLE Hereinafter, an example of the annular ultrasonic motor according to the present invention will be described in detail with reference to the drawings.

FIGS. 1(a) and 1(b) are a plan view and an end view of a vibrating body of an annular ultrasonic motor according to the present invention. In the figure, the first elastic body 1 constitutes an annular vibrating body 3 together with a piezoelectric body 2, and a recess 4 is provided inside the annular vibrating body 3, which does not reach the outer diameter in the width of the plane of the annular vibrating body 3. The recess 4 is the first
Although it is preferable to provide them at equal intervals in the circumferential direction as shown in the figure, this is not a limitation.

As shown in FIG. 6, a movable body 5 is brought into pressurized contact with the vibrating body 3, which has a concave portion 4 that does not reach the outer diameter, as described above, via a friction material 8. .

The shape of the recess 4 may be partially hollowed out into a spherical shape as shown in FIG. 2(a), hollowed out into a rectangular parallelepiped shape as shown in FIG. ) As shown in the figure, various types of V-shape hollowed out like a saw can be considered, but this is not the only option.

As shown in FIG. 3, the distribution of vibration displacement in the radial direction in the annular plate vibrating body shows that the amount of displacement increases toward the outside because the first-order vibration mode is used. but,
By providing the recess 4 on the inside, the mechanical rigidity changes in proportion to the cube of the plate thickness, so the amount of displacement can be flattened in the radial direction, so stable contact can be achieved even against eccentricity due to shaft accuracy. It becomes possible. On the other hand, since the moving body is driven inside the vibrating body 3 where the amplitude is small, it is stable against load fluctuations.

Next, the operation of an embodiment of the annular ultrasonic motor according to the present invention will be described.

By constructing the vibrating body 3 with a simple annular vibrating body 3 which is basically a flat plate as described above, processing problems (accuracy, cost, etc.) can be solved as in the past. Furthermore, since the dimensions and shape of the recessed portion 4 do not require precision, integral molding using powder metallurgy, which can reduce costs, is also possible.

The depth of the four parts 4 is basically not particularly required if the moving body 5 is on a mold that deforms toward the vibrating body 3 side by applying pressure.

Furthermore, since the number of recesses 4 can be set freely, by increasing the number, a motor with stable characteristics with less cogging can be obtained.

Furthermore, since there is an increase in frictional resistance due to catching in the recess 4, etc., it is desirable to obtain an excellent annular ultrasonic motor with stable characteristics and without sudden fluctuations in output due to slipping on the high torque side. I can do it.

Unlike conventional methods, the influence of local mechanical rigidity changes and thickness changes on the vibrating body due to protrusions on the resonance characteristics has become extremely small, and this has made it possible to eliminate the causes of audible noise and uneven rotation during elastic traveling wave drive. There is no generation of unnecessary standing wave components.

FIG. 4 shows another embodiment in which the recess 6 is provided outside the annular vibrating body 3 so as not to reach the inner diameter thereof. By bringing the movable body 5 into pressure contact with the outer recess 6, it can be driven with the maximum amplitude as shown in FIG. high output can be achieved.

Further, in FIG. 5, a recess 7 is provided in the center of the annular vibrating body 3 so that the outer peripheral edge and the inner peripheral edge do not reach the above-mentioned recess 4 and recess 6. This is another embodiment in which the two are brought into pressure contact. With this configuration, the effects obtained by the recesses 4 and 6 can be obtained at the same time.

It goes without saying that the recesses 4.6.7 may be provided on the contact surface of the movable body 5 with the vibrating body 3. At this time, the recess 4.6.7 of the vibrating body 3 is not necessarily required.

Effects of the Invention In the present invention, by providing a concave portion in the contact surface with the movable body in a portion of the width of the vibrating body, the vibrating body can be easily machined into a flat plate shape, and machining accuracy can be easily obtained.

In addition, mechanical output can be transmitted efficiently by catching in recesses, etc., resulting in an annular ultrasonic motor that is stable and reliable, and has excellent output characteristics without cogging or audible noise. It is possible.

[Brief explanation of drawings]

FIG. 1(a) is a plan view of a vibrating body of an embodiment of an annular ultrasonic motor according to the present invention, FIG. 1(b) is an AA' end view thereof, FIG. 2(a), (b) and (c) are cross-sectional views showing an example of the shape of the concave portion of the same example, Fig. 3 is a view showing the radial vibration displacement distribution in the thin plate of the annular ultrasonic motor, and Fig. 4 (a) is a plan view of a vibrating body according to another embodiment of the present invention, FIG. 4(b) is an AA' end view thereof, and FIG. 5(a) is a plan view of a vibrating body according to another embodiment of the present invention. , FIG. 5(b) is an A-A' end view thereof, FIG. 6 is a cutaway perspective view of a conventional annular ultrasonic motor, and FIG. 7 is a piezoelectric body used in the ultrasonic motor of FIG. 6. FIG. 8 is a plan view showing the shape and electrode structure of the ultrasonic motor, and FIG. 8 is an explanatory diagram of the operating principle of the ultrasonic motor. 2... Piezoelectric body, 3... Vibrating body, 4.6.7... Concave portion, 5... Moving body, 8... Friction material. Fig. 1 (a) Fig. 2 Circumferential direction A-A' jr*] (3) Fig. 3 Cow lining. Figure 5 (a) A-A' Standing bdb interval d Figure (a) Figure 7 Figure △ Figure

Claims (4)

[Claims] (1) A vibrating body in which a first annular elastic body and a piezoelectric body in an annular shape are bonded together, and a movable body in which a friction material in a toroidal shape and a second elastic body in a toric shape are bonded together are pressed into contact with each other, In an annular ultrasonic motor that drives the movable body by applying an electric field to the piezoelectric body to excite a traveling wave of vibration in the circumferential direction of the vibrating body, the vibrating body contacts the movable body. An annular ultrasonic motor, characterized in that a concave portion that does not reach the outer circumferential edge and/or the inner circumferential edge of the vibrating body is formed in the surface. (2) The annular ultrasonic motor according to claim 1, wherein the recess is located on the inner diameter side in the radial direction of the contact surface of the vibrating body with the movable body, and does not reach the outer peripheral edge. (3) The annular ultrasonic motor according to claim 1, wherein the recess is located on the outer diameter side in the radial direction of the contact surface of the vibrating body with the movable body, and does not reach the inner peripheral edge. (4) The annular ultrasonic motor according to claim 1, wherein the recess is located on a contact surface of the vibrating body with the movable body and does not reach an outer circumferential edge and an inner circumferential edge of the vibrating body.