Ultrasonic motor

An ultrasonic motor 1 comprises a stator-side elastic member 30 having a rotationally symmetrical shape, a rotor-side elastic member 40 having a rotationally symmetrical shape, a stator-side piezoelectric element 31 for imparting vibrations to the elastic member 30, a rotor-side piezoelectric element 41 for imparting vibrations to the elastic member 40, an output shaft 10 rotating integrally with the elastic member 40, a rotary transformer 60 for supplying power to the piezoelectric element 41 in non-contacting fashion, and housings 21 and 22 for accommodating therein the above-enumerated elements, wherein of three transformer circuits in the rotary transformer 60, a middle transformer circuit C2 and an outermost transformer circuit C3 are used as a two-phase drive power transformer circuit. This construction achieves stable power supply to the rotor side.

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What is claimed is:

1. An ultrasonic motor comprising:

a stator-side elastic member having a rotationally symmetrical press-contact face;

a rotor-side elastic member having a rotationally symmetrical press-contact face facing the press-contact face of the stator-side elastic member, the rotor-side elastic member being supported so as to be angularly displaceable about a rotationsymmetry axis;

a stator-side vibrating element for generating a rotational displacement wave of frequency Fs on the press-contact face of the stator-side elastic member;

a rotor-side vibrating element for generating a rotational displacement wave of frequency Fr on the press-contact face of the rotor-side elastic member, the rotor-side elastic member being angularly displaced at a rotational speed proportional toa frequency difference .DELTA.F between the frequency Fs and the frequency Fr; and

a rotary transformer for supplying drive power having a phase difference equivalent to N phases (N is an integer equal to or more than 2) to the rotor-side vibrating element which is angularly displaced together with the rotor-side elasticmember, the rotary transformer including more than N transformer circuits concentrically arranged, N transformer circuits which are sequentially arranged inwardly from an outermost one being used as drive power transformer circuits.

2. The ultrasonic motor of claim 1, wherein an innermost one of the transformer circuits is used as a detection signal transformer circuit for transmitting a detection signal resulting from the detection of the rotational displacement wavegenerated on the press-contact face of the rotor-side elastic member.

3. The ultrasonic motor of claim 2, wherein the stator-side vibrating element and the rotor-side vibrating element, respectively, are rotationally symmetrical piezoelectric elements attached to surfaces of the stator-side and rotor-side elasticmembers, which surfaces are opposite to the press-contact faces thereof,

first and second drive electrodes for two-phase driving and a monitor electrode for detecting a vibrating wave are formed on a surface of each of the piezoelectric elements,

the first and second drive electrodes are respectively connected to the drive power transformer circuits, and the monitor electrode is connected to the detection signal transformer circuit.

4. The ultrasonic motor of claim 3, wherein a non-magnetic material for suppressing magnetic coupling is interposed between a detection core forming the detection signal transformer circuit and a drive core forming the drive power transformercircuits.

5. An ultrasonic motor comprising:

a stator-side elastic member having a rotationally symmetrical press-contact face;

a rotor-side elastic member having a rotationally symmetrical press-contact face facing the press-contact face of the stator-side elastic member, the rotor-side elastic member being supported so as to be angularly displaceable about a rotationsymmetry axis;

a rotor-side vibrating element for generating a rotational displacement wave on the press-contact face of the rotor-side elastic member, the rotor-side elastic member being angularly displaced by the rotational displacement wave; and

a rotary transformer for supplying drive power having a phase difference equivalent to N phases (N is an integer equal to or more than 2) to the rotor-side vibrating element which is angularly displaced together with the rotor-side elasticmember,

the rotary transformer including more than N transformer circuits concentrically arranged, N transformer circuits which are sequentially arranged inwardly from an outermost one being used as drive power transformer circuits.

6. An ultrasonic motor comprising:

a stator-side elastic member having a rotationally symmetrical press-contact face;

a rotor-side elastic member having a rotationally symmetrical press-contact face facing the press-contact face of the stator-side elastic member, the rotor-side elastic member being supported so as to be angularly displaceable about a rotationsymmetry axis;

a stator-side vibrating element for generating a rotational displacement wave of frequency Fs on the press-contact face of the stator-side elastic member;

a rotor-side vibrating element for generating a rotational displacement wave of frequency Fr on the press-contact face of the rotor-side elastic member, the rotor-side elastic member being angularly displaced at a rotational speed proportional toa frequency difference .DELTA.F between the frequency Fs and the frequency Fr; and

a rotary transformer, disposed on the rotation symmetry axis side with respect to the press-contact faces of the stator- and rotor-side elastic members, for supplying power to the rotor-side vibrating element which is angularly displaced togetherwith the rotor-side elastic member,

a step-up ratio Nr of the rotary transformer being larger than 1.

7. The ultrasonic motor of claim 6, further comprising:

a fixed transformer for supplying power to the stator-side vibrating element,

wherein a ratio Nr/Ns between the step-up ratio Nr of the rotary transformer and the step-up ratio Ns of the fixed transformer satisfies a relation of 0.5.ltoreq.Nr/Ns.ltoreq.2.

8. An ultrasonic motor comprising:

a stator-side elastic member having a rotationally symmetrical press-contact face;

a rotor-side elastic member having a rotationally symmetrical press-contact face facing the press-contact face of the stator-side elastic member, the rotor-side elastic member being supported so as to be angularly displaceable about a rotationsymmetry axis;

a rotor-side vibrating element for generating a rotational displacement wave on the press-contact face of the rotor-side elastic member, the rotor-side elastic member being angularly displaced by the rotational displacement wave; and

a rotary transformer for supplying power to the rotor-side vibrating element which is angularly displaced together with the rotor-side elastic member,

a step-up ratio Nr of the rotary transformer being larger than 1.

9. An ultrasonic motor comprising:

a stator having a stator-side elastic member and a stator-side vibrator attached to the stator-side elastic member; and

a rotor having a rotor-side elastic member facing and pressed against the stator-side elastic member and a rotor-side vibrator attached to the rotor-side elastic member,

the vibrators being caused to vibrate by supplying signals of prescribed frequency to the respective vibrators,

the rotor being driven by means of traveling waves generated on the press-contact faces of the respective elastic members by the vibrations,

wherein the stator-side elastic member and the rotor-side elastic members are respectively provided with recessed portions opposing each other and are formed into substantially the same shape, and a power feed unit for supplying the signal of theprescribed frequency to the rotor-side vibrator is disposed within a space formed between the opposing recessed portions.

10. The ultrasonic motor of claim 9, wherein the power feed unit is a rotary transformer.

11. The ultrasonic motor of claim 9, wherein the power feed unit is a brush contact power feed unit comprising a conductive brush attached to either the stator or rotor side and a conductor provided at the other side, for contacting theconductive brushes in rubbing fashion.