Drive circuit for surface-wave driven motor utilizing ultrasonic vibration

Abstract

A surface-wave driven motor comprises a moving member for being displaced, a resilient member having a surface urged against the moving member, a piezo-electric member provided in contact with the resilient member to impart vibration to the resilient member and create an elastic wave in the surface, means having electrode means provided on the piezo-electric member and applying an AC voltage to the piezo-electric member through the electrode means, means for detecting an electrical output produced in the piezo-electric member from an area on the piezo-electric member which is electrically insulated from the electrode means, and means for determining the frequency of the AC voltage on the basis of the detected electrical output.

We claim: .[.1. A surface-wave driven motor comprising: 
     
        direction in which said moving member is displaced..]. 4. A surface-wave driven motor .[.according to claim 1,.]. .Iadd.comprising: a moving member for being displaced;   a resilient member having a surface urged against said moving member;   a piezo-electric member provided in contact with said resilient member to impart vibration to said resilient member and create an elastic wave in said surface;   means having electrode means provided on said piezo-electric member and applying an AC voltage to said piezo-electric member through said electrode means;   means for detecting an electrical output produced in said piezo-electric member from an area on said piezo-electric member which is electrically insulated from said electrode means; and   means for determining the frequency of said AC voltage on the basis of the detected electrical output, .Iaddend.wherein said detecting means includes means for selecting an AC output which is within a predetermined frequency range created in said piezo-electric member. .[.5. A surface-wave driven motor according to claim 1, wherein said detecting means detects an AC voltage produced in said piezo-electric member, and said determining means includes means for controlling the frequency of the AC voltage of said applying means at a frequency whereat the detected AC voltage becomes maximum..]. .[.6. A motor provided with a rotor rotated by a surface wave, comprising:   an annular resilient member disposed with its surface being in contact with said rotor;   an annular piezo-electric member provided in contact with said resilient member to impart bending vibration to said resilient member;   means having electrode means provided on said piezo-electric member and applying an AC voltage to said piezo-electric member through said electrode means;   means for detecting an electrical output produced in said piezo-electric member from an area on said piezo-electric member which electrically insulated from said electrode means; and   means for detecting the frequency of said AC voltage on the basis of the detected electrical output..]. .[.7. A motor according to claim 6, wherein said piezo-electric member is subjected to polarization treatment so that the polarity thereof is inverted at predetermined intervals in the circumferential direction..]. .[.8. A motor according to claim 6, wherein said detecting means includes another electrode means electrically insulated from said electrode means of said applying means and provided on said piezo-electric member..]. .[.9. A motor according to claim 8, wherein said another electrode means is disposed at a position adjacent to the outer peripheral surface of the annulus of said piezo-electric member..]. .[.10. A motor according to claim 6, wherein said rotor, said resilient member and said piezo-electric member are coaxial with one another with respect to the axis of rotation of said rotor and axially contact one   
     
     
        another..]. .Iadd.11.  A surface-wave driven motor comprising: a moving member for being displaced;   a resilient member having a surface urged against said moving member;   a piezo-electric member provided in contact with said resilient member to impart vibration to said resilient member and create an elastic wave in said surface;   means having electrode means provided on said piezo-electric member and applying an AC voltage to said piezo-electric member through said electrode means;   means for detecting an electrical output produced in said piezo-electric member from an area on said piezo-electric member which is electrically insulated from said electrode means, said detecting means including an electrode on said area; and   means for determining the frequency of said AC voltage on the basis of the detected electrical output, said determining means including means for controlling the frequency of said AC voltage in response to said detected electrical output each time said electrical output varies throughout said applying of said AC voltage. .Iaddend. .Iadd.12. A surface-wave driven motor according to claim 11, wherein said piezo-electric member is subjected to polarization treatment so that the polarity thereof is inverted at predetermined intervals in a direction in which said moving   
     
     
        member is displaced. .Iaddend. .Iadd.13.  A surface-wave driven motor according to claim 11, wherein said piezo-electric member is subjected to polarization treatment so that the polarity thereof is inverted at each length of about 1/2 of a bending vibration wavelength created in said resilient member in a direction in which said moving member is displaced. .Iaddend. .Iadd.14. A surface-wave driven motor according to claim 11, wherein said detecting means detects an AC voltage produced in said piezo-electric member, and said controlling means adjusts the frequency of the AC voltage of said applying means to a frequency whereat the detected AC voltage becomes maximum. .Iaddend. .Iadd.15. A surface-wave driven motor comprising: a moving member for being displaced;   a resilient member having a surface urged against said moving member;   a piezo-electric member provided in contact with said resilient member to impart vibration to said resilient member and create an elastic wave in said surface;   means having electrode means provided on said piezo-electric member and applying an AC voltage to said piezo-electric member through said electrode means to drive said motor;   the efficiency of said motor being dependent upon the frequency of said AC voltage, and optimum frequency of said AC voltage for enhancement of said motor efficiency being variable with change in an extraneous condition such as the pressure between said moving member and said resilient member and the temperature of said motor;   means for detecting, during driving of said motor, an electrical output produced in said piezo-electric member from an area on said piezo-electric member which is electrically insulated from said electrode means; and   means for determining the frequency of said AC voltage on the basis of the detected electrical output, said determining means including means for controlling the frequency of said AC voltage in response to said electrical output each time said electrical output varies throughout the driving of said motor, and for adjusting the frequency of said AC voltage to provide an optimum frequency. .Iaddend. .Iadd.16. A surface-wave driven motor comprising;   a moving member for being displaced;   a resilient member having a surface urged against said moving member;   a piezo-electric member provided in contact with said resilient member to impart vibration to said resilient member and create an elastic wave in said surface;   means having electrode means provided on said piezo-electric member and applying an AC voltage to said piezo-electric member through said electrode means;   means for detecting an electrical output produced in said piezo-electric member from an area on said piezo-electric member which is electrically insulated from said electrode means;   means for determining the frequency of said AC voltage on the basis of the detected electrical output; and   filtering means provided between said detecting means and said determining means to pass therethrough a predetermined frequency band and to impede a frequency band other than said predetermined frequency band. .Iaddend.   
     
     
        .Iadd.17.  A surface-wave driven motor according to claim 16, wherein said electrical output includes two peak voltage values at two frequencies, respectively, of said AC voltage, only one of said peak values being a maximum peak value, and wherein said predetermined frequency band includes said maximum peak value and excludes the other of said two peak values. .Iaddend. .Iadd.18. A surface-wave driven motor according to claim 16, wherein said determining means includes means for adjusting the frequency of the AC voltage of said applying means to a frequency whereat the detected electrical output passed through said filtering means becomes maximum. .Iaddend. .Iadd.19. A surface-wave driven motor according to claim 16, wherein said piezo-electric member is subjected to polarization treatment so that the polarity thereof is inverted at predetermined intervals in a direction in which said moving member is displaced. .Iaddend. .Iadd.20. A surface-wave driven motor according to claim 16, wherein said piezo-electric member is subjected to polarization treatment so that the polarity thereof is inverted at each length of about 1/2 of a bending vibration wavelength created in said resilient member in a direction in which said moving member is displaced. .Iaddend. .Iadd.21. A surface-wave driven motor comprising; a moving member for being displaced;   a resilient member having a surface urged against said moving member;   a piezo-electric member provided in contact with said resilient member to impart vibration to said resilient member and create an elastic wave in said surface;   means having electrode means provided on said piezo-electric member and applying an AC voltage to said piezo-electric member through said electrode means;   means for detecting an electrical output produced in said piezo-electric member from an area on said piezo-electric member which is electrically insulated from said electrode means, said electrical output assuming a maximum peak value for a predetermined frequency of said AC voltage and assuming a small peak value for a frequency considerably distant from said predetermined frequency;   means for determining the frequency of said AC voltage on the basis of the detected electrical output; and   filtering means provided between said detecting means and said determining means to pass therethrough a predetermined frequency band including said predetermined frequency and to impede a frequency band including said distant frequency. .Iaddend. .Iadd.22. A surface-wave driven motor comprising;   a moving member for being displaced;   a resilient member having a surface urged against said moving member;   a piezo-electric member provided in contact with said resilient member to impart vibration to said resilient member and create an elastic wave in said surface;   means having electrode means provided on said piezo-electric member and applying an AC voltage to said piezo-electric member through said electrode means;   means for detecting an electrical output produced in said piezo-electric member from an area on said piezo-electric member which is electrically insulated from said electrode means, said detecting means including an electrode on said area;   means for determining the frequency of said AC voltage on the basis of the detected electrical output, said determining means including means for controlling the frequency of said AC voltage in response to said electrical output each time said electrical output varies throughout said applying of said AC voltage; and   filtering means provided between said detecting means and said determining means to pass therethrough a predetermined frequency band and to impede a frequency band other than said predetermined frequency band. .Iaddend.   
     
     
        .Iadd.23.  A surface-wave driven motor comprising; a moving member for being displaced;   a resilient member having a surface urged against said moving member;   a piezo-electric member provided in contact with said resilient member to impart vibration to said resilient member and create an elastic wave in said surface;   means having electrode means provided on said piezo-electric member and applying an AC voltage to said piezo-electric member through said electrode means to drive said motor;   the efficiency of said motor being dependent upon the frequency of said AC voltage, an optimum frequency of said AC voltage for enhancement of said motor efficiency being variable with change in an extraneous condition such as the pressure between said moving member and said resilient member and the temperature of said motor;   means for detecting, during driving of said motor, an electrical output produced in said piezo-electric member from an area on said piezo-electric member which is electrically insulated from said electrode means, said electrical output assuming a maximum peak value for an optimum frequency of said AC voltage and assuming a small peak value for a frequency considerably distant from an optimum frequency;   means for determining the frequency of said AC voltage on the basis of the detected electrical output, said determining means including means for controlling the frequency of said AC voltage in response to said electrical output each time said optimum said electrical output varies throughout said driving of said motor, and for adjusting the frequency of said AC voltage to provide an optimum frequency; and   filtering means provided between said detecting means and said determining means to pass therethrough a predetermined frequency band including an optimum frequency and to impede a frequency band including said distant frequency. .Iaddend. .Iadd.24. A motor provided with a rotor rotated by a surface wave, comprising;   an annular resilient member disposed with its surface being in contact with said rotor;   an annular piezo-electric member in contact with said resilient member to impart bending vibration to said resilient member, said annular piezo-electric member comprising a ring having at one side thereof an inner peripheral area and an outer peripheral area that is positioned farther from the center of the ring than said inner peripheral area;   means having electrode means provided on said piezo-electric member and applying an AC voltage to said piezo-electric member through said electrode means;   means for detecting an electrical output produced in said piezo-electric member from an area on said piezo-electric member which is electrically insulated from said electrode means, said detecting means having an electrode provided at said outer peripheral area but not at said inner peripheral area; and   means for determining the frequency of said AC voltage on the basis of the   
     
     
        detected electrical output. .Iaddend. .Iadd.25.  A surface-wave driven motor according to claim 24, wherein said electrode means includes a portion at said inner peripheral area at a sector of said annular piezo-electric member that is common to said electrode of said detecting means. .Iaddend. .Iadd.26. A motor provided with a rotor rotated by a surface wave, comprising: an annular resilient member disposed with its surface being in contact with said rotor;   an annular piezo-electric member provided in contact with said resilient member to impart bending vibration to said resilient member, said piezo-electric member comprising a ring having a plurality of sections which are arranged in a circumferential direction of said ring and which include first and second sections spaced from each other and a third section positioned between said first and second sections, said third section having a length of about 1/4 of a wavelength of said bending vibration in the circumferential direction;   means having electrode means provided on said first and second sections of said piezo-electric member and applying an AC voltage to said piezo-electric member through said electrode means;   means for detecting an electrical output produced in said piezo-electric member from an area on said piezo-electric member which is electrically insulated from said electrode means, said area including said third section of said piezo-electric member and having an electrode on said third section for detecting an electrical output produced in said third section; and   means for determining the frequency of said AC voltage on the basis of the detected electrical output. .Iaddend. .Iadd.27. A motor according to claim 26, wherein said third section lies between first ends of said first and second sections, and wherein said plurality of sections of said piezo-electric member further includes a fourth section lying between second ends of said first and second sections and having a length of about 3/4 of a wavelength of said bending vibration in the circumferential direction. .Iaddend. .Iadd.28. A motor according to claim 26, wherein said determining means includes means for controlling the frequency of said AC voltage in response to said electrical output detected by said detecting means each time said electrical output varies throughout said applying of   
     
     
        said AC voltage. .Iaddend. .Iadd.29.  A surface-wave driven motor comprising; a moving member for being displaced;   a resilient member having a surface urged against said moving member;   a piezo-electric member provided in contact with said resilient member to impart vibration to said resilient member and create an elastic vibration wave in said surface that is propagated along said surface;   means having electrode means provided on said piezo-electric member and applying an AC voltage to said piezo-electric member through said electrode means;   means for detecting an electrical output produced in said piezo-electric member from an area on said piezo-electric member which is electrically insulated from said electrode means; and   means for determining the frequency of said AC voltage on the basis of the detected electrical output;   wherein said means having electrode means includes first, second, and third electrodes electrically insulated from each other and provided on one side of said piezo-electric member, and a fourth electrode provided on the opposite side of said piezo-electric member between said piezo-electric member and said resilient member, electrically conductive paste means extending from said third electrode to said fourth electrode over a periphery of said piezo-electric member in order to electrically connect said fourth electrode to said third electrode, and means for applying first and second AC voltages which are out of phase with each other between said first and third electrodes, and between said second and third   
     
     
        electrodes, respectively. .Iaddend. .Iadd.30.  A surface-wave driven motor according to claim 29, wherein said means having electrode means further comprises first, second, and third terminals on said first, second, and third electrodes, respectively, and wherein said first and second AC voltages are applied between said first terminal and said third terminal, and between said second terminal and said third terminal, respectively. .Iaddend. .Iadd.31. A surface-wave driven motor according to claim 29, wherein said resilient member and said piezo-electric member are annular and said third electrode has a length of 3/4 wavelength of said vibration wave in a circumferential direction of said piezo-electric member. .Iaddend. .Iadd.32. A surface-wave driven motor according to claim 2, wherein said piezo-electric member is ring-shaped and said electrically conductive paste means is coated on an outer periphery of said 
     
     
        piezo-electric member. .Iaddend. .Iadd.33.  A surface-wave driven motor comprising: a moving member for being displaced;   a resilient member having a surface urged against said moving member;   a piezo-electric member provided in contact with said resilient member to impart vibration to said resilient member and create an elastic vibration wave in said surface that is propagated along said surface;   means having electrode means provided on said piezo-electric member and applying an AC voltage to said piezo-electric member through said electrode means;   means for detecting an electrical output produced in said piezo-electric member from an area on said piezo-electric member which is electrically insulated from said electrode means; and   means for determining the frequency of said AC voltage on the basis of the detected electrical output;   wherein said means having electrode means includes first and second groups of electrodes provided on one side of said piezo-electric member, and an electrode member provided on the opposite side of said piezo-electric member between said piezo-electric member and said resilient member, each of said electrodes has a length of 1/2 wavelength of said vibration wave and said electrode member as a length longer than said each electrode, and means for applying first and second AC voltages which are out of phase with each other between said first group of electrodes and said electrode member and between said second group of electrodes and said electrode member, respectively. .Iaddend. .Iadd.34. A surface-wave driven motor according to claim 33, wherein said resilient member, said piezo-electric   
     
     
        member, and said electrode member are annular. .Iaddend. .Iadd.35.  A surface-wave driven motor comprising: a moving member for being displaced;   a resilient member having a surface urged against said moving member;   a piezo-electric member provided in contact with said resilient member to impart vibration to said resilient member and create an elastic vibration wave in said surface that is propagated along said surface;   means having electrode means provided on said piezo-electric member and applying an AC voltage to said piezo-electric member through said electrode means;   means for detecting an electrical output produced in said piezo-electric member from an area on said piezo-electric member which is electrically insulated from said electrode means; and   means for determining the frequency of said AC voltage on the basis of the detected electrical output;   wherein said means having electrode means includes first and second electrode members each of which has a plurality of electrodes provided on one side of said piezo-electric member, a third electrode member provided on the opposite side of said piezo-electric member between said piezo-electric member and said resilient member, electrically conductive paste means for electrically connecting said plurality of electrodes of said first electrode member with one another and electrically connecting said plurality of electrodes of said second electrode member with one another, and means for applying first and second AC voltages which are out of phase with each other between said first electrode member and said third electrode member and between said second electrode member and said third electrode member, respectively. .Iaddend. .Iadd.36. A surface-wave driven motor according to claim 35, wherein said detecting means includes a fourth electrode member provided on said one side of said piezo-electric member between said first and second electrode members. .Iaddend.