Controller for a vibration wave motor

• US 5,500,578 A
• Filed: 06/07/1995
• Issued: 03/19/1996
• Est. Priority Date: 02/23/1983
• Status: Expired due to Term

• Current Assignee: Mando Corporation
• Original Assignee: Masaharu Kawamura
• Inventors: Kawamura, Masaharu
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US08/479,821
• Time in Patent Office: 286 Days
• Field of Search: 310/323, 310/328, 310/316, 310/317, 318/116
• US Class Current: 318/116
• CPC Class Codes: H02N 2/14 Drive circuits; Control arrangements or methods
• 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 2/163 Motors with ring stator

Abstract

In a vibration motor for driving a movable member contacted to a vibration member by a travelling vibration wave generated by the vibration member by applying a periodic voltage to an electrostrictive element contacted to the vibration member, a frequency of the periodic voltage is sequentially changed, a drive speed of the movable member is measured at each frequency, the measurements are sequentially compared, a frequency which results in the largest measurement is stored, and the movable member is driven by the periodic voltage of the stored frequency.

Claims

1. A vibration wave motor apparatus comprising:

a vibration member for generating a traveling wave, said member including a first electro-mechanical energy conversion element and a second electro-mechanical energy conversion element phase-differently arranged on said member with respect to said first element;

a member contacted to said vibration member, said member being pushed by said traveling vibration wave generated in said vibration member;

a control circuit for applying periodic voltage phase-differently to said first and second electro-mechanical energy conversion elements, a frequency of said periodic voltage being controlled by said control circuit so that said vibration member reaches a resonance state;

wherein said control circuit comprises oscillation means for applying a periodic voltage to said first and second electro-mechanical conversion elements to generate a traveling vibration wave in said vibration member, said oscillation means sequentially changing a frequency of said periodic voltage;

detection means for detecting speed of said contact member and relative speed between said vibration member and said contact member at the changing frequencies; and

processing means for changing the frequency of said oscillation means, storing, in accordance with the speed detected by said detection means, a frequency which results in a maximum of one of the speeds detected by said detection means and setting the frequency of said oscillation means to the stored frequency.

2. A system according to claim 1, wherein said first and second electro-mechanical conversion elements comprises electro-strictive elements.

3. A vibration motor apparatus comprising:

a vibration member;

electro-mechanical conversion elements coupled to said vibration member;

drive circuit for applying periodic signals to said electro-mechanical conversion elements;

a control circuit for setting a frequency of the periodic signals at a predetermined relatively high level upon start of said motor apparatus, and then gradually shifting the frequency toward a lower level, whereby a speed of said motor apparatus is controlled upon the start so as to change from a low speed to a high speed.

4. An apparatus according to claim 3, wherein said control circuit effects the shifting by sequentially decreasing the frequency by a predetermined value.

5. An apparatus according to claim 4, wherein said drive circuit produces plural kinds of periodic signals which are different in their phases, and the respective kinds of signals are applied to predetermined one of said electro-mechanical conversion elements.

6. An apparatus according to claim 3, wherein said electro-mechanical conversion elements are of electrostrictive material.

7. An apparatus according to claim 3, wherein said vibration member produces traveling vibration wave by application of plural kinds of periodic signals which have different phases to the predetermined electro-mechanical conversion elements, and said apparatus produces the vibration wave as an output drive force.

8. A control apparatus for a vibration motor providing driving force by vibrating a vibration member by application of periodic signals to electro-mechanical conversion elements, comprising:

a control circuit for controlling frequency of the periodic signals; and

a shifting circuit for setting, upon starting of the motor, the frequency at a predetermined first value and for sequentially decreasing the frequency, whereby a speed of said motor is controlled upon the start so as to change from a low speed to a high speed.

9. An apparatus according to claim 8, wherein said electro-mechanical conversion elements are of electrostrictive material.

10. A vibration motor apparatus for causing relative motion between an object and said vibration motor apparatus comprising:

a vibration member adapted to be in contact with the object;

electro-mechanical conversion elements coupled to said vibration member;

drive circuit for applying periodic signals to said electro-mechanical elements to produce vibration of said vibration member so as to cause relative movement between said vibration member and the object;

speed detecting means for detecting relative speed between said vibration member and the object; and

processing circuit for periodically receiving outputs of said detecting means and storing datum relating to the relative speed, and for controlling a frequency of periodic signals in accordance with the stored data.

11. An apparatus according to claim 10, wherein said processing circuit controls the frequency on the basis of at least two stored data.

12. An apparatus according to claim 11, wherein said processing circuit controls the frequency on the basis of change of the stored datum.

13. An apparatus according to claim 10, wherein said detecting means includes pulse generating means for generating pulse signals corresponding to the relative speed.

14. A vibration motor apparatus comprising:

a vibration member;

electro-mechanical conversion elements coupled to said vibration member;

drive circuit for applying periodic signals to said electro-mechanical conversion elements;

wherein

said drive circuit produces plural kinds of periodic signals which are different in their phases, and the respective kinds of signals are applied to at least predetermined one of said electro-mechanical conversion elements; and

a control circuit for setting a frequency of the periodic signals at a predetermined relatively high level upon start of said motor apparatus, and then gradually shifting the frequency toward a lower level.

15. An apparatus according to claim 14, wherein said control circuit effects the shifting by sequentially decreasing the frequency by a predetermined value.

16. An apparatus according to claim 14, wherein said vibration member produces traveling vibration wave by application of plural kinds of periodic signals which have different phases to the predetermined electro-mechanical conversion elements, and said apparatus produces the vibration wave as an output drive force.

17. An apparatus according to claim 14, wherein said electro-mechanical conversion elements are of electrostrictive material.

18. An apparatus according to claim 14, wherein said drive circuit comprises an oscillating circuit for producing the periodic signals and a setting circuit for setting a datum for determining the frequency of the periodic signals, and said control circuit changes the datum from a datum for a high frequency to a low frequency.

19. A vibration motor apparatus comprising:

a vibration member;

electro-mechanical conversion elements coupled to said vibration member;

drive circuit for applying periodic signals to said electro-mechanical conversion elements;

a control circuit for setting a frequency of the periodic signals at a predetermined relatively high level upon start of said motor apparatus, and then gradually shifting the frequency toward a lower level, wherein said drive circuit comprises an oscillating circuit for producing the periodic signals and a setting circuit for setting a datum for determining the frequency of the periodic signals, and wherein said control circuit changes the datum from a datum for a high frequency to a low frequency.

20. A vibration motor apparatus comprising:

a vibration member;

electro-mechanical conversion elements coupled to said vibration member;

a drive circuit for applying periodic signals to said electro-mechanical conversion elements;

wherein said drive circuit produces plural kinds of periodic signals which are different in their phases, and the respective kinds of signals are applied to predetermined ones of said electro-mechanical conversion elements;

detecting means for detecting the state of driving of said motor apparatus and producing an electrical signal in accordance with the state of driving;

a microcomputer for receiving the electric signal from said detecting means to control the driving state of said motor apparatus in accordance with the electrical signal.

21. A motor apparatus according to claim 20, wherein said microcomputer receives the electrical signal from said detecting means, and effects frequency control of the periodic signal in accordance with the electrical signal from said microcomputer.

22. A motor apparatus according to claim 20, wherein said detecting means includes a detecting member for detecting a speed of relative motion between said vibration member and an object imparted by vibrations caused therein by application of the periodic signal to said electro-mechanical conversion elements, said detecting elements including a portion rotatable in accordance with the relative motion and switching element for effecting switching in accordance with the rotation of the rotatable portion to produce an electric signal.

23. A motor apparatus according to claim 20 wherein said vibration member is annular and said detecting member includes an electro-mechanical conversion element, which has a width smaller than that of said vibration member, in a diametrical direction of the surface to which said electro-mechanical conversion member is contacted.

24. A control apparatus for a vibration motor providing driving force by vibrating a vibration member by application of periodic signals to electro-mechanical conversion element parts, comprising:

a control circuit for controlling frequency of the periodic signals;

a shifting circuit for setting, upon starting of the motor, the frequency at a predetermined first value and for sequentially decreasing the frequency,

a signal producing circuit for producing plural kinds of periodic signals which are different in their phases, and wherein the respective kinds of signals are applied to predetermined one of said electro-mechanical conversion element parts by which a traveling vibration wave is produced in the vibration member as a driving force.