Ultrasonic motor and ultrasonic motor-equipped electronic appliance

• US 6,570,294 B1
• Filed: 06/01/1999
• Issued: 05/27/2003
• Est. Priority Date: 06/02/1998
• Status: Expired due to Term

• Current Assignee: Seiko Instruments Incorporated (Seiko Group)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Iino, Akihiro, Kasuga, Masao
• Primary Examiner(s): Dougherty, Thomas M.
• Application Number:
  US09/323,504
• Time in Patent Office: 1,456 Days
• Field of Search: 310/316.01, 310/317
• US Class Current: 310/316.01
• CPC Class Codes: H02N 2/142 Small signal circuits; Means for controlling position or derived quantities, e.g. speed, torque, starting, stopping, reversing
• CPC Class Codes: H02N 2/166 Motors with disc stator

Abstract

The present invention discloses an ultrasonic motor and an electronic appliance equipped with the ultrasonic motor, wherein an input signal to a control circuit which is a command signal for driving a moving body of the ultrasonic motor or a driven body driven in response to the moving body is restricted by a signal processing circuit. The frequency component of the input signal equal to or exceeding a specified frequency is cut by means of a filter circuit or an output from a control circuit is controlled in response to a fluctuation width thereof.

Claims

1. An ultrasonic motor comprising:

a control circuit to which a processed input signal is supplied for controlling at least one of a direction and speed of the motor in accordance with the processed input signal;

a drive circuit for receiving a control signal output by the control circuit and outputting a drive signal in accordance therewith;

a vibrating body having a piezoelectric element to which the drive signal output by the drive circuit is supplied so that vibration of the vibrating body is controlled in accordance with the control signal;

a moving body driven in response to vibration of the vibrating body;

a position detecting circuit for producing an output signal in accordance with a position of the moving body; and

a signal processing circuit for receiving an input signal, processing the input signal by one of eliminating a frequency component thereof above a predetermined frequency level, eliminating fluctuations in level of the input signal below a predetermined value, and sampling the input signal to output a mean value thereof, and outputting the processed input signal to the control circuit so that minor fluctuations in the input signal are eliminated by the signal processing circuit and do not affect operation of the motor;

wherein the control circuit includes means for comparing the processed input signal with the output signal of the position detecting circuit and producing the control signal in accordance with a difference therebetween.

2. An ultrasonic motor according to claim 1;

wherein the signal processing circuit comprises a filter circuit for eliminating a component of the input signal equal to or exceeding the predetermined frequency.

3. An ultrasonic motor according to claim 1;

wherein the signal processing circuit includes means for processing the input signal so that the control signal is output by the control circuit to the drive circuit only when a fluctuation in the input signal exceeds the predetermined value.

4. An ultrasonic motor according to claim 1;

wherein the signal processing circuit includes means for sampling the input signal and outputting to the control circuit a mean value of the samples taken of the input signal.

5. In an electric appliance having an output mechanism for producing an output movement;

an ultrasonic motor according to claim 1 for driving the output mechanism.

6. An ultrasonic motor according to claim 1;

wherein the control signal comprises one of a start signal for starting movement of the moving body, a stop signal for stopping movement of the moving body, a normal movement signal for continuing movement of the moving body, and a reverse signal for reversing movement of the moving body.

7. An ultrasonic motor according to claim 1;

wherein the control signal comprises one of a start signal for starting movement of the moving body, a stop signal for stopping movement of the moving body, a normal movement signal for continuing movement of the moving body, and a reverse signal for reversing movement of the moving body.

8. An ultrasonic motor according to claim 1;

wherein the input signal comprises a linear signal for producing output motion of the moving body proportional to the level of the input signal.

9. An ultrasonic motor according to claim 1;

wherein the input signal has three states for driving the moving body in three states comprising a moving state, a stop state, and a reverse rotation state.

10. An ultrasonic motor comprising:

a control circuit to which an input signal is supplied for controlling at least one of direction and speed of the motor in accordance with the input signal;

a drive circuit for receiving a control signal output by the control circuit and outputting a drive signal in accordance therewith;

a vibrating body having a piezoelectric element to which the drive signal output by the drive circuit is supplied so that vibration of the vibrating body is controlled in accordance with the control signal; and

a moving body driven in response to vibration of the vibrating body;

wherein a drive range of the moving body is defined as a range of motion through which the moving body may be driven in response to the input signal, a possible operating range of the moving body is defined as an extent of motion through which the moving body may be driven in response to the control signal output by the control circuit, and the possible operating range of the moving body is a range which includes the full range of motion of the drive range and which exceeds the drive range; and

wherein the control circuit includes means for selectively driving the moving body through the possible operating range to reduce uneven wear of components of the motor based on repetitive motion of the moving body through the drive range.

11. An ultrasonic motor according to claim 10;

wherein at the time of starting a drive operation of the moving body or stopping a drive operation thereof, the control circuit drives the moving body through the possible operating range and thereafter returns the moving body to a reference position.

12. An ultrasonic motor according to claim 11;

wherein the control circuit includes means for periodically changing a drive width of the possible operating range.

13. In an electric appliance having an output mechanism for producing an output movement;

an ultrasonic motor according to claim 10 for driving the output mechanism.

14. An ultrasonic motor comprising:

a control circuit to which an input signal is supplied for controlling at least one of a direction and a speed of the motor in accordance with the input signal;

a drive circuit for receiving a control signal output by the control circuit and outputting a drive signal in accordance therewith;

a vibrating body having a piezoelectric element to which the drive signal output by the drive circuit is supplied so that vibration of the vibrating body is controlled in accordance with the control signal;

a moving body driven in response to vibration of the vibrating body; and

a plurality of groups of electrode patterns formed on the piezoelectric element each for generating a different standing wave in the vibrating body so that by selecting a respective group of electrode patterns to which the drive signal is to be applied, a moving direction, a rotational speed and a torque of the moving body may be changed;

wherein the control circuit includes means for selecting more than one group of electrode patterns to stop movement of the moving body.

15. An ultrasonic motor according to claim 14;

wherein the control circuit includes means for stopping the drive signal output by the drive circuit from being applied to the respective groups of electrode patterns and for applying the drive signal to a plurality of the groups of the electrode patterns simultaneously.

16. An ultrasonic motor according to claim 14;

the drive circuit and the vibrating body constitute a self-oscillating circuit, and the self-oscillating circuit generates an alternating current signal for producing a standing wave in the vibrating body.

17. An ultrasonic motor according to claim 16;

wherein at the time of starting the moving body to move or stopping the moving body from moving, at least one of a voltage and a frequency of the drive signal applied to the piezoelectric element is varied.

18. In an electric appliance having an output mechanism for producing an output movement;

an ultrasonic motor according to claim 14 for driving the output mechanism.

19. An ultrasonic motor comprising:

a drive circuit for producing a drive signal in accordance with, a processed input signal;

a piezoelectric element for receiving the drive signal;

a vibrating body attached to the piezoelectric element to undergo vibration in accordance with. the drive signal;

a moving body in contact with the vibrating body to undergo movement in response to vibration of the vibrating body; and

a signal processing circuit for receiving an input signal, processing the input signal by one of eliminating a frequency component thereof above a predetermined frequency level, eliminating fluctuations in level of the input signal below a predetermined value, and sampling the input signal to output a mean value thereof, and outputting the processed input signal to the driving circuit so that minor fluctuations in the input signal are eliminated by the signal processing circuit and do not affect operation of the motor;

wherein a first range of motion through which the moving body may be moved in response to the input signal is smaller than a second range of motion through which the moving body may be moved in response to the control signal; and

wherein the control circuit includes means for selectively driving the moving body through the second range of motion to prevent uneven component wear based on repetitive motion of the moving body through the first range of motion; and

wherein the signal processing circuit includes means for sampling the input signal and outputting to the driving circuit a mean value of the samples taken of the input signal.

20. An ultrasonic motor according to claim 19;

wherein the drive circuit comprises a control circuit for outputting a control signal to control at least one of a direction and a speed of the moving body, and a self-oscillation circuit for driving the moving body according to the control signal.

21. An ultrasonic motor according to claim 19;

wherein when starting a drive operation of the moving body or stopping a drive operation thereof, the control circuit drives the moving body through the second range of motion and thereafter returns the moving body to a reference position.

22. An ultrasonic motor according to claim 19;

wherein the control circuit includes means for periodically changing a drive width of the second range of motion.

23. An ultrasonic motor according to claim 19;

wherein the signal processing circuit comprises a filter circuit for eliminating a component of the input signal equal to or exceeding the predetermined frequency.

24. An ultrasonic motor according to claim 19;

wherein the signal processing circuit includes means for processing the input signal so that the drive signal is applied to the piezoelectric element only when a fluctuation in the input signal exceeds the predetermined value.