Ultrasonic motor and drive method

Claim 1

An ultrasonic motor comprising: an annular piezoelectric element having a circumference and a plurality of sub-elements alternately polarized in opposing directions; a stator having a surface with a plurality of protuberances driven by said piezoelectric element to vibrate; a rotor in frictional contact with said stator for rotation; said piezoelectric element having a circumference and a first piezoelectric sub-element row and a second piezoelectric sub-element row of differing phase and separated by a period defined by an integral portion of said circumference; and drive means for applying AC voltages to said first and second piezoelectric sub-element rows; said rotor defining a plurality of gaps at intervals that are one-half said period upon a surface facing said stator for cooperation with said protuberances in a direction of rotation.

Claim 8

A method for driving an ultrasonic motor comprising the steps of: providing an annular piezoelectric element having a circumference and a plurality of sub-elements alternately polarized in opposing directions; providing a stator having a surface with a plurality of protuberances driven by said piezoelectric element to vibrate; providing a rotor in frictional contact with said stator for rotation; providing said piezoelectric element with a circumference and a first piezoelectric sub-element row and a second piezoelectric sub-element row of differing phase and separated by a period defined by an integral portion of said circumference; providing drive means for applying AC voltages to said first and second piezoelectric sub-element rows; providing said rotor with a plurality of gaps at intervals that are one-half said period upon a surface facing said stator for cooperation with said protuberances in a direction of rotation; providing said piezoelectric element with a first electrode having conductive contact on one side of said first piezoelectric sub-element row, a second electrode having conductive contact on one side of said second piezoelectric sub-element row and a common electrode with conductive contact on opposite sides of said first and second piezoelectric sub-element rows; providing said drive means with a first output circuit for outputting drive signals to said first electrode, a second output circuit for outputting drive signals to said second electrode and a third output circuit for outputting drive signals to said common electrode, said output circuits being adjustable to a high impedance output condition in addition to a drive signal output condition; and intermittently rotating said rotor by repeating a first drive condition in which AC voltages with a prescribed mutual phase difference are applied between said first electrode and said common electrode and between said second electrode and said common electrode to induce a progressive wave on said piezoelectric element and a second drive condition in which an AC voltage is applied between said first electrode and said common electrode to induce a standing wave on said piezoelectric element.

Claim 9

A method for driving an ultrasonic motor comprising the steps of: providing an annular piezoelectric element having a circumference and a plurality of sub-elements alternately polarized in opposing directions; providing a stator having a surface with a plurality of protuberances driven by said piezoelectric element to vibrate; providing a rotor in frictional contact with said stator for rotation; providing said piezoelectric element with a circumference and a first piezoelectric sub-element row and a second piezoelectric sub-element row of differing phase and separated by a period defined by an integral portion of said circumference; providing drive means for applying AC voltages to said first and second piezoelectric sub-element rows; providing said rotor with a plurality of gaps at intervals that are one-half said period upon a surface facing said stator for cooperation with said protuberances in a direction of rotation; providing said piezoelectric element with a first electrode having conductive contact on one side of said first piezoelectric sub-element row, a second electrode having conductive contact on one side of said second piezoelectric sub-element row and a common electrode with conductive contact on opposite sides of said first and second piezoelectric sub-element rows; providing said drive means with a first output circuit for outputting drive signals to said first electrode, a second output circuit for outputting drive signals to said second electrode and a third output circuit for outputting drive signals to said common electrode, said output circuits being adjustable to a high impedance output condition in addition to a drive signal output condition; and intermittently rotating said rotor by repeating a first drive condition in which AC voltages with a prescribed mutual phase difference are applied between said first electrode and said common electrode and between said second electrode and said common electrode to induce a progressive wave on said piezoelectric element and a second drive condition in which an AC voltage is applied between said first electrode and said common electrode to induce a standing wave on said piezoelectric element.

Claim 12

A method for driving an ultrasonic motor comprising the steps of: providing an annular piezoelectric element having a circumference and a plurality of sub-elements alternately polarized in opposing directions; providing a stator having a surface with a plurality of protuberances driven by said piezoelectric element to vibrate; providing a rotor in frictional contact with said stator for rotation; providing said piezoelectric element with a circumference and a first piezoelectric sub-element row and a second piezoelectric sub-element row of differing phase and separated by a period defined by an integral portion of said circumference; providing drive means for applying AC voltages to said first and second piezoelectric sub-element rows; providing said rotor with a plurality of gaps at intervals that are one-half said period upon a surface facing said stator for cooperation with said protuberances in a direction of rotation; providing said piezoelectric element with a first electrode having conductive contact on one side of said first piezoelectric sub-element row, a second electrode having conductive contact on one side of said second piezoelectric sub-element row and a common electrode with conductive contact on opposite sides of said first and second piezoelectric sub-element rows; providing said drive means with a first output circuit for outputting drive signals to said first electrode, a second output circuit for outputting drive signals to said second electrode and a third output circuit for outputting drive signals to said common electrode, said output circuits being adjustable to a high impedance output condition in addition to a drive signal output condition; and intermittently rotating said rotor by repeating a first drive condition in which AC voltages with a prescribed mutual phase difference are applied between said first electrode and said common electrode and between said second electtode and said common electrode to induce a progressive wave on said piezoelectric element and a second drive condition in which an AC voltage is applied between said second electrode and said common electrode to induce a standing wave on said piezoelectric element.

Claim 13

A method for driving an ultrasonic motor comprising the steps of: providing an annular piezoelectric element having a circumference and a plurality of sub-elements alternately polarized in opposing directions; providing a stator having a surface with a plurality of protuberances driven by said piezoelectric element to vibrate; providing a rotor in frictional contact with said stator for rotation; providing said piezoelectric element with a circumference and a first piezoelectric sub-element row and a second piezoelectric sub-element row of differing phase and separated by a period defined by an integral portion of said circumference; providing drive means for applying AC voltages to said first and second piezoelectric sub-element rows; providing said rotor with a plurality of gaps at intervals that are one-half said period upon a surface facing said stator for cooperation with said protuberances in a direction of rotation; providing said piezoelectric element with a first electrode having conductive contact on one side of said first piezoelectric sub-element row, a second electrode having conductive contact on one side of said second piezoelectric sub-element row and a common electrode with conductive contact on opposite sides of said first and second piezoelectric sub-element rows; providing said drive means with a first output circuit for outputting drive signals to said first electrode, a second output circuit for outputting drive signals to said second electrode and a third output circuit for outputting drive signals to said common electrode, said output circuits being adjustable to a high impedance output condition in addition to a drive signal output condition; and intermittently rotating said rotor by repeating a first drive condition in which AC voltages with a prescribed mutual phase difference are applied between said first electrode and said common electrode and between said second electtode and said common electrode to induce a progressive wave on said piezoelectric element and a second drive condition in which an AC voltage is applied between said second electrode and said common electrode to induce a standing wave on said piezoelectric element.

Claim 16

A method for driving an ultrasonic motor comprising the steps of: providing an annular piezoelectric element having a circumference and a plurality of sub-elements alternately polarized in opposing directions; providing a stator having a surface with a plurality of protuberances driven by said piezoelectric element to vibrate; providing a rotor in frictional contact with said stator for rotation; providing said piezoelectric element with a circumference and a first piezoelectric sub-element row and a second piezoelectric sub-element row of differing phase and separated by a period defined by an integral portion of said circumference; providing drive means for applying AC voltages to said first and second piezoelectric sub-element rows; providing said rotor with a plurality of gaps at intervals that are one-half said period upon a surface facing said stator for cooperation with said protuberances in a direction of rotation; providing said piezoelectric element with a first electrode having conductive contact on one side of said first piezoelectric sub-element row, a second electrode having conductive contact on one side of said second piezoelectric sub-element row and a common electrode with conductive contact on opposite sides of said first and second piezoelectric sub-element rows; providing said drive means with a first output circuit for outputting drive signals to said first electrode, a second output circuit for outputting drive signals to said second electrode and a third output circuit for outputting drive signals to said common electrode, said output circuits being adjustable to a high impedance output condition in addition to a drive signal output condition; and repeating in any sequence a first drive condition in which an AC voltage is applied between said first electrode and said common electrode to induce a first standing wave on said piezoelectric element, a second drive condition in which an AC voltage is applied between said second electrode and said common electrode to induce a second standing wave on said piezoelectric element, and a third drive condition in which an AC voltage is applied between said first electrode and said common electrode and between said second electrode and said common electrode to induce a third standing wave on said piezoelectric element.

Claim 17

A method for driving an ultrasonic motor comprising the steps of: providing an annular piezoelectric element having a circumference and a plurality of sub-elements alternately polarized in opposing directions; providing a stator having a surface with a plurality of protuberances driven by said piezoelectric element to vibrate; providing a rotor in frictional contact with said stator for rotation; providing said piezoelectric element with a circumference and a first piezoelectric sub-element row and a second piezoelectric sub-element row of differing phase and separated by a period defined by an integral portion of said circumference; providing drive means for applying AC voltages to said first and second piezoelectric sub-element rows; providing said rotor with a plurality of gaps at intervals that are one-half said period upon a surface facing said stator for cooperation with said protuberances in a direction of rotation; providing said piezoelectric element with a first electrode having conductive contact on one side of said first piezoelectric sub-element row, a second electrode having conductive contact on one side of said second piezoelectric sub-element row and a common electrode with conductive contact on opposite sides of said first and second piezoelectric sub-element rows; providing said drive means with a first output circuit for outputting drive signals to said first electrode, a second output circuit for outputting drive signals to said second electrode and a third output circuit for outputting drive signals to said common electrode, said output circuits being adjustable to a high impedance output condition in addition to a drive signal output condition; and repeating in any sequence a first drive condition in which an AC voltage is applied between said first electrode and said common electrode to induce a first standing wave on said piezoelectric element, a second drive condition in which an AC voltage is applied between said second electrode and said common electrode to induce a second standing wave on said piezoelectric element, and a third drive condition in which an AC voltage is applied between said first electrode and said common electrode and between said second electrode and said common electrode to induce a third standing wave on said piezoelectric element.

Claim 18

A method for driving an ultrasonic motor comprising the steps of: providing an annular piezoelectric element having a circumference and a plurality of sub-elements alternately polarized in opposing directions; providing a stator having a surface with a plurality of protuberances driven by said piezoelectric element to vibrate; providing a rotor in frictional contact with said stator for rotation; providing said piezoelectric element with a circumference and a first piezoelectric sub-element row and a second piezoelectric sub-element row of differing phase and separated by a period defined by an integral portion of said circumference; providing drive means for applying AC voltages to said first and second piezoelectric sub-element rows; providing said rotor with a plurality of gaps at intervals that are one-half said period upon a surface facing said stator for cooperation with said protuberances in a direction of rotation; providing said piezoelectric element with a first electrode having conductive contact on one side of said first piezoelectric sub-element row, a second electrode having conductive contact on one side of said second piezoelectric sub-element row and a common electrode with conductive contact on opposite sides of said first and second piezoelectric sub-element rows; providing said drive means with a first output circuit for outputting drive signals to said first electrode, a second output circuit for outputting drive signals to said second electrode and a third output circuit for outputting drive signals to said common electrode, said output circuits being adjustable to a high impedance output condition in addition to a drive signal output condition; and repeating in any sequence a first drive condition in which an AC voltage is applied between said first electrode and said common electrode to induce a first standing wave on said piezoelectric element, a second drive condition in which an AC voltage is applied between said second electrode and said common electrode to induce a second standing wave on said piezoelectric element, a third drive condition in which an AC voltage is applied between said first electrode and said common electrode and between said second electrode and said common electrode to induce a third standing wave on said piezoelectric element, and a fourth drive condition in which an AC voltage is applied between said first electrode and said second electrode with said output switch connected to said common electrode in a cutoff condition to induce a fourth standing wave on said piezoelectric element.

Claim 19

A method for driving an ultrasonic motor comprising the steps of: providing an annular piezoelectric element having a circumference and a plurality of sub-elements alternately polarized in opposing directions; providing a stator having a surface with a plurality of protuberances driven by said piezoelectric element to vibrate; providing a rotor in frictional contact with said stator for rotation; providing said piezoelectric element with a circumference and a first piezoelectric sub-element row and a second piezoelectric sub-element row of differing phase and separated by a period defined by an integral portion of said circumference; providing drive means for applying AC voltages to said first and second piezoelectric sub-element rows; providing said rotor with a plurality of gaps at intervals that are one-half said period upon a surface facing said stator for cooperation with said protuberances in a direction of rotation; providing said piezoelectric element with a first electrode having conductive contact on one side of said first piezoelectric sub-element row, a second electrode having conductive contact on one side of said second piezoelectric sub-element row and a common electrode with conductive contact on opposite sides of said first and second piezoelectric sub-element rows; providing said drive means with a first output circuit for outputting drive signals to said first electrode, a second output circuit for outputting drive signals to said second electrode and a third output circuit for outputting drive signals to said common electrode, said output circuits being adjustable to a high impedance output condition in addition to a drive signal output condition; and repeating in any sequence a first drive condition in which an AC voltage is applied between said first electrode and said common electrode to induce a first standing wave on said piezoelectric element, a second drive condition in which an AC voltage is applied between said second electrode and said common electrode to induce a second standing wave on said piezoelectric element, a third drive condition in which an AC voltage is applied between said first electrode and said common electrode and between said second electrode and said common electrode to induce a third standing wave on said piezoelectric element, and a fourth drive condition in which an AC voltage is applied between said first electrode and said second electrode with said output switch connected to said common electrode in a cutoff condition to induce a fourth standing wave on said piezoelectric element.

Claim 20

A method for driving an ultrasonic motor comprising the steps of: providing an annular piezoelectric element having a circumference and a plurality of sub-elements alternately polarized in opposing directions; providing a stator having a surface with a plurality of protuberances driven by said piezoelectric element to vibrate; providing a rotor in frictional contact with said stator for rotation; providing said piezoelectric element with a circumference and a first piezoelectric sub-element row and a second piezoelectric sub-element row of differing phase and separated by a period defined by an integral portion of said circumference; providing drive means for applying AC voltages to said first and second piezoelectric sub-element rows; providing said rotor with a plurality of gaps at intervals that are one-half said period upon a surface facing said stator for cooperation with said protuberances in a direction of rotation; providing said piezoelectric element with a first electrode having conductive contact on one side of said first piezoelectric sub-element row, a second electrode having conductive contact on one side of said second piezoelectric sub-element row and a common electrode with conductive contact on opposite sides of said first and second piezoelectric sub-element rows; providing said drive means with a first output circuit for outputting drive signals to said first electrode, a second output circuit for outputting drive signals to said second electrode and a third output circuit for outputting drive signals to said common electrode, said output circuits being adjustable to a high impedance output condition in addition to a drive signal output condition; and repeating in any sequence a first drive condition in which an AC voltage is applied between said first electrode and said common electrode to induce a first standing wave on said piezoelectric element, a second drive condition in which an AC voltage is applied between said second electrode and said common electrode to induce a second standing wave on said piezoelectric element, and a third drive condition in which an AC voltage is applied between said first electrode and said second electrode with said common electrode in a cut off condition to induce a third standing wave on said piezoelectric element.

Claim 21

A method for driving an ultrasonic motor comprising the steps of: providing an annular piezoelectric element having a circumference and a plurality of sub-elements alternately polarized in opposing directions; providing a stator having a surface with a plurality of protuberances driven by said piezoelectric element to vibrate; providing a rotor in frictional contact with said stator for rotation; providing said piezoelectric element with a circumference and a first piezoelectric sub-element row and a second piezoelectric sub-element row of differing phase and separated by a period defined by an integral portion of said circumference; providing drive means for applying AC voltages to said first and second piezoelectric sub-element rows; providing said rotor with a plurality of gaps at intervals that are one-half said period upon a surface facing said stator for cooperation with said protuberances in a direction of rotation; providing said piezoelectric element with a first electrode having conductive contact on one side of said first piezoelectric sub-element row, a second electrode having conductive contact on one side of said second piezoelectric sub-element row and a common electrode with conductive contact on opposite sides of said first and second piezoelectric sub-element rows; providing said drive means with a first output circuit for outputting drive signals to said first electrode, a second output circuit for outputting drive signals to said second electrode and a third output circuit for outputting drive signals to said common electrode, said output circuits being adjustable to a high impedance output condition in addition to a drive signal output condition; and repeating in any sequence a first drive condition in which an AC voltage is applied between said first electrode and said common electrode to induce a first standing wave on said piezoelectric element, a second drive condition in which an AC voltage is applied between said second electrode and said common electrode to induce a second standing wave on said piezoelectric element, and a third drive condition in which an AC voltage is applied between said first electrode and said second electrode with said common electrode in a cut off condition to induce a third standing wave on said piezoelectric element.

Claim 22

A method for driving an ultrasonic motor comprising the steps of: providing a rotor; providing a stator having protuberances in contact with said rotor; providing a piezoelectric element, having a plurality of piezoelectric sub-elements, secured to said stator; and switching excitation of a progressive wave, excitation of a standing wave and stoppage of excitation of said stator in time series.

Claim 23

A method for driving an ultrasonic motor comprising the steps of: providing a rotor; providing a stator having protuberances in contact with said rotor; providing a piezoelectric element, having a plurality of piezoelectric sub-elements, secured to said stator; and switching excitation of a progressive wave, excitation of a standing wave and stoppage of excitation of said stator in time series.