Ultrasonic motor

• US 5,416,375 A
• Filed: 09/09/1994
• Issued: 05/16/1995
• Est. Priority Date: 06/15/1992
• Status: Expired due to Term

• Current Assignee: Olympus Optical Company Ltd. (Olympus Corporation)
• Original Assignee: Olympus Optical Company Ltd. (Olympus Corporation)
• Inventors: Fujimura, Takanao, Taniguchi, Yoshihisa, Tsubata, Toshiharu, Ouchi, Takashi, Funakubo, Tomoki, Imabayashi, Hiroyuki
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US08/304,083
• Time in Patent Office: 249 Days
• Field of Search: 310/321, 310/323, 310/328, 310/316, 310/317, 310/319, 318/116
• US Class Current: 310/323.16
• CPC Class Codes: H02N 2/004 Rectangular vibrators
• CPC Class Codes: H02N 2/026 by pressing one or more vibrators against the driven body

Abstract

An ultrasonic motor comprising an elastic body, at least two laminated piezoelectric bodies clamped by a portion of the elastic body, an ultrasonic oscillator for exciting simultaneously a plurality of shrunk and retreated oscillation modes on the elastic body, to generate ultrasonic elliptic oscillation, and an element to be driven urged against a portion of the ultrasonic oscillator and movable with respect to the ultrasonic oscillator.

Claims

1. An ultrasonic motor comprising:

an elastic body having at least one driving element;

at least two laminated piezoelectric bodies each arranged in a recess provided in said elastic body and clamped by portions of said elastic body at ends of its associated recess said elastic body and said laminated piezoelectric bodies forming an ultrasonic oscillator;

said driving element being displaced from a central point of said elastic body;

voltage applying means for applying to said two laminated piezoelectric bodies first phase and second phase alternating voltages having phases which differ from one another by 90 degrees causing the elastic body to simultaneously experience two degenerate oscillation modes to generate elliptical oscillation in a portion of said driving element; and

a driven element engaging said driving element and being driven thereby.

2. An ultrasonic motor according to claim 1, wherein said elastic body has a substantially rectangular parallelepiped shape except for the clamped portion, wherein the two degenerate oscillation modes are respectively longitudinal oscillation and bending oscillation modes, wherein each of said laminated piezoelectric bodies has a center thereof which is arranged at a position where strain of the bending oscillation mode is substantially maximized and at a position where the laminated piezoelectric body has an end thereof which does not exceed a position of a node of the bending oscillation mode, and wherein the two laminated piezoelectric bodies are arranged at a position where strain of the longitudinal oscillation mode is generated uniformly in the same direction and at the same phase.

3. An ultrasonic motor according to claim 1 wherein the portion of said elastic body clamping said piezoelectric bodies is comprised of a pair of separate grooves provided along one surface of said elastic body and each having a pair of ends, each piezoelectric body being placed in an associated one of said grooves and being pre-loaded therein by the ends of said groove.

4. An ultrasonic motor according to claim 1 wherein said laminated piezoelectric bodies are of similar size.

5. An ultrasonic motor according to claim 1 wherein each of said laminated piezoelectric bodies is comprised of a plurality of piezoelectric layers laminated to one another.

6. An ultrasonic motor according to claim 1 wherein said driving portion is removably mounted to said elastic body.

7. An ultrasonic motor according to claim 1 wherein said driving portion is comprised of a removably mounted frictional member.

8. An ultrasonic motor according to claim 1 wherein a portion of the elastic body extending between said driving element and a recess for a laminated piezoelectric body closer to said driving portion is provided with a plurality of lateral grooves in at least one major surface of said elastic body for reducing Young'"'"'s modulus of said elastic body.

9. An ultrasonic motor according to claim 1 wherein a portion of the elastic body extending between said driving element and a recess for a laminated piezoelectric body closer to said driving portion is provided with a plurality of lateral grooves in both major surfaces of said elastic body for reducing Young'"'"'s modulus of said elastic body.

10. An ultrasonic motor according to claim 1 wherein said driving element comprises means for mounting any one of a plurality of driving members any one of which may be releasably mounted to said elastic body, each of said driving members having one of a shape and a mass which differs from the other driving members whereby the driving member mounted to said elastic body is selected according to an application most suitable to a shape and a mass of the selected driving member.

11. An ultrasonic motor according to claim 1 wherein said movable member and said ultrasonic oscillator are fixed to a stationary member whereby relative movement between said movable member and said ultrasonic oscillator results in movement of said ultrasonic motor relative to said stationary member.

12. An ultrasonic motor according to claim 1 wherein said ultrasonic oscillator is fixed to a stationary member whereby relative movement between said movable member and said ultrasonic oscillator results in movement of said movable member relative to said stationary member.

13. An ultrasonic motor according to claim 1 further comprising first and second piezoelectric detection bodies mounted upon said elastic body for respectively detecting only longitudinal vibration and only bending vibration;

and

means for comparing detected signals from said detecting bodies with at least one of the signals employed to drive one of said first and second piezoelectric bodies and means for adjusting an AC voltage of said applying means to compensate for temperature changes during operation thereof.

14. An ultrasonic motor according to claim 1 wherein said laminated piezoelectric bodies comprise a plurality of thin piezoelectric elements stacked one upon another to form an elongated stack of a plurality of said piezoelectric elements having a top and a bottom;

the ends of each recess respectively engaging a top and a bottom of said stack.

15. An ultrasonic motor according to claim 1 wherein said driving element projects from a surface of said elastic body.

16. An ultrasonic motor according to claim 1 wherein the alternating voltages are of the order of 10 volts peak-to-peak.

18. An ultrasonic motor according to claim 1 or 17, wherein said elastic body has a substantially rectangular parallelepiped shape,

said two degenerate oscillation modes are respectively longitudinal oscillation and bending oscillation, and

at least one of the laminated piezoelectric bodies experiencing bending oscillation being clamped by a portion of said elastic body.

21. An ultrasonic motor according to claim 1, 18 or 20 further comprising a first oscillation detecting piezoelectric element provided on said elastic body for detecting only longitudinal oscillation, and a second oscillation detecting piezoelectric element provided on said elastic body for detecting only bending oscillation.

22. An ultrasonic motor according to claim 21 wherein said piezoelectric oscillation detecting elements have a thickness of the order of 0.1 mm.

23. An ultrasonic motor according to claim 21, wherein said first oscillation detecting element is arranged such that piezoelectric elements having polarization in the same orientation are bonded to each other and are electrically connected in series to each other at two locations of said elastic body, that is, at two locations where oscillation strain of the first oscillation mode is brought to the same level and to the same phase and where the oscillation strain of the second oscillation mode is brought to the same level and a reversed phase, and wherein said second oscillation detecting element is arranged such that piezoelectric elements having polarization in the reversed orientation are bonded to each other and are electrically connected in series to each other at two locations of said elastic body different from the two locations of the fist oscillation detecting element, that is, at two locations where oscillation strain of the first oscillation mode is brought to the same level and to the same phase and where the oscillation strain of the second oscillation mode is brought to the same level and to a reversed phase.

24. An ultrasonic motor according to claim 1 or 17 or 19, wherein said applying means provides a DC voltage superimposed on said alternating voltage in an elongated direction of the laminated piezoelectric body at least during movement of the ultrasonic motor.

17. An ultrasonic motor comprising:

an elastic body having at least one driving element;

four laminated piezoelectric bodies each arranged in a recess in said elastic body and being clamped by portions of said elastic body at ends of its associated recess;

said elastic body and said piezoelectric bodies forming an ultrasonic oscillator;

said elastic body having first and second major faces each containing recesses for receiving two of said piezoelectric bodies, the recesses on each major surface being on opposite sides of a central portion of said elastic body;

voltage applying means for applying first phase and second phase alternating voltages, having phases different from one another by 90 degrees, to said four laminated piezoelectric bodies to cause said ultrasonic oscillator to simultaneously experience two degenerate oscillation modes to generate elliptical oscillation at a portion of said driving element, a first and a second one of said piezoelectric bodies being arranged side by side in the first major face, a third and a fourth one of said piezoelectric bodied being arranged in the second major face, said first and third bodies being opposite one another, said second and fourth bodies being opposite one another, said four laminated piezoelectric bodies being divided into first and second groups each respectively including said first and fourth and said second and third piezoelectric bodies, said first and second groups being respectively driven by said first phase and second phase alternating voltages; and

a driven element engaging said driving element and being driven thereby.

19. An ultrasonic motor comprising:

an elastic body having at least one driving element;

first, second and third laminated piezoelectric bodies arranged in first, second and third recesses in said elastic body and being respectively clamped by portions of said elastic body at ends of said first, second and third recesses;

said elastic body and said first, second and third laminated piezoelectric bodies forming an ultrasonic oscillator;

said recesses being arranged at spaced intervals along said elastic body;

said first and second recesses being on opposite sides of a central portion of said elastic body and on opposite sides of said third recess;

said drive element being displaced from said central portion;

voltage applying means for applying first and second alternating voltages to said first and second piezoelectric bodies whereby said first and second alternating voltages different phase from one another by 180 degrees and simultaneously therewith applying a third alternating voltage to said third piezoelectric body whereby said third alternating voltage differs in phase from said first and second alternating voltages by 90 degrees, to generate two degenerate oscillation oscillated modes in said ultrasonic oscillator to cause elliptical oscillation of a portion of said driving element; and

a driven element engaging said driving element and being driven thereby.

20. An ultrasonic motor according to claim 19 wherein said elastic body has a substantially rectangular parallelepiped shape;

said two degenerate oscillation modes respectively being a longitudinal oscillation and a bending oscillation of said elastic body; and

said first and second laminated piezoelectric bodies being arranged in a bending oscillation portion of said elastic body and said third laminated piezoelectric body being clamped by a joint portion experiencing longitudinal oscillation.

25. A method for operating an ultrasonic motor comprised of an elongated elastic body, a pair of laminated piezoelectric bodies arranged within recesses provided at spaced intervals along one surface of said elastic body and a driving portion arranged along said elastic body, said method comprising the steps of:

applying electrical energy in the form of alternating voltage signals to said piezoelectric bodies of substantially equal frequency and amplitude; and

providing a phase difference of approximately 90 degrees between said alternating voltages chosen to cause said driving portion to experience elliptical oscillation;

applying a DC voltage to each piezoelectric body to maintain said piezoelectric bodies under compression;

placing a movable member against said driving portion; and

urging said movable member toward engagement with said driving portion whereby the electrical energy applied to said laminated piezoelectric bodies causes movement of said movable body relative to said ultrasonic motor.

26. An ultrasonic motor comprising:

an elastic body having a substantially rectangular parallelepiped shape;

first and second laminated piezoelectric bodies;

first, second and third retaining bodies fixedly secured at spaced intervals to one surface of said elastic body;

said first laminated piezoelectric body being arranged in a gap space between said first and second retaining bodies;

said second laminated piezoelectric body being clamped in a gap space between said second and third retaining bodies;

said first and second piezoelectric bodies being on opposite sides of a central portion of said elastic body;

said elastic body having at least one driving portion arranged on a surface opposite and parallel to said one surface;

means for applying alternating voltage signals which differ in phase by 90°

to said piezoelectric bodies to cause said driving portion to experience elliptical oscillation; and

means for urging a movable member against said driving portion whereby said movable member experiences movement relative to said elastic body due to said elliptical oscillations.