JP2000060166A - Ultrasonic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily extract a plurality of drive outputs in an ultrasonic motor. SOLUTION: Inner peripheral side circular parts 4 and outer peripheral side circular parts 5, which are divided in the radial direction by peripheral grooves 2b and which form a plurality of concentric resonators, are installed in elastic bodies 2 to which piezoelectric bodies 7 are adhered. Tooth comb parts 4a and 5a are formed, and the respective peripheral wall pasts 8b and 9b of rotors 8 and 9 are repulsively brought into contact with each other. An inner peripheral side electrode group and an outer peripheral side electrode group, which are polarized in accordance with the number of setting orders by individual resonance frequencies of the respective circular parts, are installed in the piezoelectric bodies. The high frequency voltage of the number of setting orders is inputted, and the corresponding rotor is driven. Since the resonance frequency in the number of the setting orders of the circular part and the resonance frequency in the number of setting orders in the adjacent circular part are separated for, the number of orders before and after the respective numbers of setting orders are mutually detached, stable and independent resonance is realized without interference, and a plurality of independent driving forces can be extracted with a simple structure in which are elastic body is divided by the peripheral direction groove.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor.

[0002]

2. Description of the Related Art Conventionally, a stator formed by pasting an annular piezoelectric body to an annular elastic body, and a stator provided coaxially with the stator and elastically contacting the elastic body. In the ultrasonic motor having the rotator, a traveling wave is generated in the vibrator by simultaneously applying two phases of high-frequency voltages, which are out of phase with each other, to the piezoelectric body. There is one that obtains a driving force to the motor.

In such an ultrasonic motor, a plurality of driving forces are provided from a rotor which is provided concentrically with annular elastic bodies having different diameters and which are independently rotatable in correspondence with the respective elastic bodies. However, there is a problem that the structure becomes complicated if separate annular elastic bodies having different diameters are arranged concentrically.

Therefore, by forming a plurality of annular portions having different diameters by providing a circumferential groove in the elastic body, each annular portion has a different resonance frequency from each other. A part can be provided. It is conceivable to attach a piezoelectric body to the bottom surface of the elastic body, input a high-frequency voltage corresponding to each resonance frequency to the piezoelectric body, and use each annular portion as a separate drive source.

[0005]

In the case where each of the annular portions provided as described above is vibrated by a common piezoelectric material polarized in the nth order, when the piezoelectric material is set to, for example, the fifth polarization, , The resonating portion that resonates at that order vibrates relatively large even at the fourth and sixth orders before and after it. As described above, when the annular portions having different diameters are provided and resonated by the piezoelectric body having a predetermined set order, the set order (for example, the annular portion to be resonated and the adjacent annular portion) is set. Resonance frequencies (both fifth order) do not match each other due to the wavelength difference due to the difference between the inner and outer circumferences.

However, as shown in FIG. 5, the fifth resonance frequency of the inner resonance part shown by the solid line and the fourth resonance frequency of the outer resonance part shown by the imaginary line substantially coincide with each other. It is conceivable that the sixth-order resonance frequency of the inner-side resonance portion and the fifth-order resonance frequency of the outer-side resonance portion substantially match each other. In this case, vibrations at the time of resonance interfere with each other, and it is difficult to obtain independent resonances, and there is a problem that independent driving forces cannot be taken out.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to easily extract a plurality of drive outputs in an ultrasonic motor, in the present invention, an annular elastic body is used. An ultrasonic motor having a stator to which an annular piezoelectric body is attached, and a rotor coaxially provided with the stator and provided so as to resiliently contact the elastic body in the axial direction, The elastic body has an annular portion forming a plurality of resonators having different diameters that are radially divided by a circumferential groove and are concentrically arranged on the same plane, and the rotor is
A plurality of rotors respectively corresponding to the respective annular portions and rotatably provided independently of each other, and a plurality of electrode groups corresponding to the respective plurality of annular portions are provided on the annular piezoelectric body. The plurality of electrode groups are set to have different polarization orders.

By doing so, the annular portions forming a plurality of corresponding resonators resonate at different set orders, respectively. Therefore, when an arbitrary annular portion resonates at a predetermined set order, the resonance occurs. The set order and the set order of the adjacent annular portion can be largely separated, and the orders before and after affecting the interference of vibration can also be separated. Also, by setting the polarization order on the inner circumference side of the plurality of electrode groups to a higher order than the polarization order on the outer circumference side, the inner circumference side annular part is more likely to be deviated from the inner circumference difference of each annular part. Since the natural frequency is high, the interference of vibration can be prevented more suitably by setting the polarization order of the inner annular portion to a higher order.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to specific examples shown in the accompanying drawings.

FIG. 1 is a side sectional view of an ultrasonic motor to which the present invention is applied. As shown in FIG. 1, a step-like boss 1a is provided at the center of the bottom wall of the case 1 so as to protrude upward, and the lowermost part thereof has a disk shape having an opening at the center. The elastic body 2 is fixed coaxially by screwing the outer peripheral portion of the opening. The first drive shaft 3 is coaxially and rotatably mounted on the uppermost portion of the boss 1a via a bearing.
Is supported.

The elastic body 2 has an outward flange portion 2a extending radially outward from a central annular portion screwed to the boss portion 1a, and a function of a resonator divided radially by a circumferential groove 2b. It comprises an inner annular portion 4 and an outer annular portion 5. The respective annular portions 4 and 5 are arranged concentrically with respect to the boss portion 1a (first drive shaft 3), and mutually connected via a connecting portion 6 serving as a bottom wall of the circumferential groove 2b. Are linked.

The connecting portion 6 is provided such that the center of the connecting portion 6 is located at a position (a position where bending stress does not occur) in the axial direction of the annular portions 4 and 5 in the axial direction. The connecting portion 6 is formed by processing the circumferential groove 2b and also processing the circumferential groove 2c on the side of the connecting portion 6 opposite to the circumferential groove 2b.

A piezoelectric member 7 made of one annular thin plate common to both annular portions 4 and 5 is attached to the bottom surfaces (lower surfaces in the drawings) of both annular portions 4 and 5. As shown in FIG. 2, one of the axial end faces of the annular portions 4 and 5 on the side opposite to the side on which the piezoelectric body 7 is adhered (upper part in the drawing) has a circumferential direction. By providing a plurality of radial slits at an equal pitch, an inner comb-shaped portion 4a and an outer comb-shaped portion 5a in the form of an annular comb are formed. Thus, the stator is configured.

Since the annular portions 4 and 5 forming the resonator are concentrically arranged on the same plane, the axial length of the motor device can be minimized. In addition, since a relatively large torque is obtained as a characteristic of the ultrasonic motor, the size is not increased in the radial direction, so that a compact and thin structure can be achieved.

The inner peripheral rotor 8 has a thin disk portion 8a as a disc spring integrally extending radially outward from the bearing portion of the first drive shaft 3, and a wall provided on the outer peripheral portion thereof. And a peripheral wall 8b having a large thickness.
Is integrated with a cylindrical second drive shaft 10 rotatably and coaxially provided on the first drive shaft 3 via a bearing, and like the inner peripheral rotor 8, the second drive shaft It has a thin disk portion 9a as a disc spring extending integrally in the radial direction outward from the bearing portion 10 and a thick peripheral wall portion 9b provided on the outer peripheral portion thereof.

The inner peripheral side annular portion 4 has an axial lower end surface of the peripheral wall portion 8b of the inner peripheral side rotor 8, and the outer peripheral side annular portion 5 has an axial line of the peripheral wall portion 9b of the outer peripheral side rotor 9. The lower end surfaces in the direction resiliently come into contact with the respective thin disk portions 8a and 9a by the disc spring action.

The piezoelectric body 7 is provided with an electrode to which a high-frequency voltage from the AC power supplies 11 and 12 is input. According to the present invention, as shown in FIG. 4
Small-diameter annular inner-circumference-side electrode group 1 positioned so as to correspond to
3 and a large-diameter outer-electrode group 14 similarly located to correspond to the outer-circumferential annular portion 5 are concentrically provided to form a piezoelectric polarization pattern. Each of the electrode groups 13 and 14 has a substantially symmetrical semi-circular shape in the figure in order to enable each of the rotors 8 and 9 to rotate forward and backward.
A-phase and B-phase surface electrodes (not shown) provided on the back surface of
It is configured corresponding to. The normal rotation and the reverse rotation of each of the rotors 8 and 9 are performed by the A phase supplied from the AC power supply 11 and the AC power supply 12.
Is switched by the phase difference. For example, the B-phase is advanced by 1/4 cycle with respect to the A-phase to perform normal rotation, and the B-phase is delayed by 1/4 cycle to perform reverse rotation.

In this embodiment, the inner electrode group 1
The inner electrode group 13 is constituted by the sixth polarization by the respective electrodes 13a constituting the A phase 3 and the respective electrodes 13b constituting the B phase, and similarly, the A phase of the outer electrode 14 is constituted. By each electrode 14a and each electrode 14b constituting the B phase,
The outer peripheral electrode 14 is configured with fifth-order polarization. Accordingly, when rotating the inner rotor 8, a sixth-order high-frequency voltage having a resonance frequency is input to the inner electrode group 13 to resonate the corresponding inner annular portion 4, and the outer rotor 8 is rotated. When rotating 9, a fifth-order high frequency voltage of the resonance frequency is input to the outer electrode group 14 so that the corresponding outer annular portion 5 resonates.

Next, the operation of the ultrasonic motor will be described below. Each of the annular portions 4 and 5 of the elastic body 2 is connected to the connecting portion 6 provided at an intermediate portion between the two in the radial direction.
Through the circumferential groove 2 between the two.
b is provided, and is divided into an inner peripheral side and an outer peripheral side so as to sandwich the circumferential groove 2b. Therefore, the resonance frequencies of the annular portions 4 and 5 forming a plurality of resonators made of the same material are different from each other so that the inner peripheral side elastic body 4 has a higher frequency in the case of the same order.

Further, by changing the frequency of the input AC voltage to one piezoelectric body 7 in correspondence with each resonance frequency of the annular portions 4 and 5 constituting the resonator, each frequency is changed according to the change of the input frequency. A separate driving force can be obtained for each of the rotors 8 and 9. In the illustrated example, the first drive shaft 3
Can be used as a first drive source and a two-axis motor using the second drive shaft 10 as a second drive source.

In this embodiment, an example of a biaxial output has been described. However, by providing two or more concentric circumferential grooves for dividing the elastic body 3 in the radial direction with different diameters, the annular portion can be formed in three directions. Two or more concentrically arranged motors can be provided, in which case a multiple output motor capable of extracting three or more independent driving forces can be obtained.

According to the present invention, the relationship between the above-described set orders and the respective vibration frequencies in the order before and after the set orders is as shown in FIG. In FIG. 4, the fifth, sixth, and seventh vibration frequencies of the inner annular part 4 are indicated by solid lines, and the fourth, fifth, and sixth vibrations of the outer annular part 5 are indicated by solid lines. The frequency is indicated by imaginary lines.

As shown in FIG. 4, the inner annular portion 4
And the fifth-order vibration frequency, which is the set order of the outer annular portion 5, are largely separated from each other. Therefore, even when considering the set order and the vibration frequencies of the order before and after the set order, there are few things that substantially match each other, there is no interference of one vibration with the other, and each independent stable resonance can be realized, Independent driving force can be taken out.
As shown in FIG. 4, the natural frequency of the inner annular portion 4 is higher than that of the outer annular portion 5. By setting the order higher than the set order of the annular portion 5, even if the order difference is the first order, interference of one vibration with the other can be prevented.

[0024]

As described above, according to the present invention, the annular portions forming the plurality of resonators corresponding to the set orders different from each other resonate, so that the annular portion is adjacent to the resonance frequency at the set order. Since the resonance frequency of the annular portion at the set order is largely separated, the orders before and after each set order affecting vibration interference can be separated from each other, and stable independent resonance without interference can be realized. A plurality of independent driving forces can be taken out with a simple structure in which one elastic body is divided by a circumferential groove.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an ultrasonic motor to which the present invention is applied.

FIG. 2 is an exploded perspective view of a main part of the ultrasonic motor of FIG. 1;

FIG. 3 is a plan view showing a polarization pattern of a piezoelectric body.

FIG. 4 is a diagram illustrating a relationship between a resonance frequency and a set order of inner and outer resonance units.

FIG. 5 is a diagram showing the relationship between the resonance frequency and the same set order of the inner and outer resonance units.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Case, 1a boss part 2 Elastic body, 2a Outward flange part, 2b, 2c Circumferential groove 3 First drive shaft 4 Inner peripheral annular part, 4a Inner peripheral comb tooth part 5 Outer peripheral annular part, 5a outer periphery Side comb 6 Connecting part 7 Piezoelectric body 8 Inner peripheral rotor, 8a thin disk part, 8b peripheral wall part 9 Outer peripheral rotor, 9a thin disk part, 9b peripheral wall part 10 Second drive shaft 11.12 AC power supply 13 Inner circumference electrode group 14 Outer circumference electrode group

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Koji Kobayashi Inventor 1-2682-1 Hirosawa-cho, Kiryu-shi, Gunma F-term in Mitsuba Co., Ltd. 5H680 AA00 AA01 AA08 AA19 BB03 BB16 BB19 BB20 CC07 DD01 DD15 DD23 DD35 DD53 DD66 DD75 DD87 DD92 DD97 DD98 EE03 EE07 EE10 FF03 FF04 FF08 FF26 FF33

Claims (2)

[Claims] 1. A stator in which an annular piezoelectric body is attached to an annular elastic body, and a rotor provided coaxially with the stator and elastically contacting the elastic body in the axial direction. An ultrasonic motor comprising: an elastic body, wherein the elastic body is divided into a plurality of resonators having different diameters radially divided by a circumferential groove and arranged concentrically with each other on the same plane. The rotor includes a plurality of rotors respectively corresponding to the respective annular portions and rotatably provided independently of each other, and the annular piezoelectric body is provided for each of the plurality of annular portions. An ultrasonic motor, comprising a plurality of corresponding electrode groups, wherein the plurality of electrode groups have different polarization orders. 2. The ultrasonic motor according to claim 1, wherein the polarization order on the inner circumference side of the plurality of electrode groups is set to a higher order than the polarization order on the outer circumference side.