Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-10-27
2002-07-09
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S332000, C310S333000, C310S355000
Reexamination Certificate
active
06417601
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to piezoelectric motors, and more specifically to piezoelectric torsional vibration driven motors.
2. Description of the Background Art
The use of piezoelectric ceramic materials such as lead zirconate titanate (PZT) is well known for applications for sensors, transducers, actuators, and other electromechanical devices.
Many actuators have been developed using electroactive materials, including the torsional actuator disclosed in U.S. Pat. No. 6,020,674. This torsional actuator uses an even number of alternately poled segments of electroactive material which are arranged side by side. The segments are bound together in an integral structure, with conductors positioned between adjacent segments. Under an applied electric field, the torsional actuator produces large angular displacement and a high torque. Similarly, a torsional piezoelectric actuator is described in Glazounov, A. E. Zhang, Q. M., Kim, C. “Piezoelectric Actuator Generating Torsional Displacement from Piezoelectric d
15
Shear Response” Applied Physics Letters 72, pages 2526-2528, 1998.
For some applications, a large rotational motion with a large torque output is demanded. For example, vibration and noise control systems for helicopter rotor blades require an actuator which can provide large amplitude rotational motion with a high torque.
Piezoelectric ultrasonic motors have been developed using traveling wave and standing wave theories which provide higher torque density than electromagnetic motors. An example of the current art in piezoelectric motor technology is provided in “Development of a Two-Sided Piezoelectric Rotary Motor for High Torque”, T. S. Glenn, W. G. Hagwood, SPIE Volume 3041, 1997. These piezoelectric ultrasonic motors are of limited application, however, because they have either lower power density or lower efficiency than conventional electromagnetic motors.
A compact, simple, lightweight motor which uses a torsional actuator as a stator could provide high torque density, high power density, and high efficiency in response to an alternating electric field.
Therefore, it is an object of this invention to provide a piezoelectric motor with high torque density, high power density, and high efficiency.
It is an object of this invention to provide a compact and lightweight piezoelectric motor.
It is an object of this invention to provide a simple piezoelectric motor which converts an alternating electric field to torsional vibration and directly into rotary motion.
It is an object of this invention to provide a full cycle piezoelectric torsional vibration motor.
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Glazounov, et al., “piezoelectric Stepper Motor with Direct Coupling Mechanism to Achieve High Efficiency and Precise Contorl of Motion” IEEE Transaction of Ultrasonic, Ferroelectronics, and Frequency Control, vol. 47, No. 4 Jul. 2000.*
Kim, et al, “Development of Piezoelectric Ceramic Torsional Actuators Based on Shear Piezoelectric Response and Their Potential Applications”, presented at 9thUS-Japan Seminar on Dielectrics and Piezoelectric Ceramics, Nov.3-5, 1999.
Glazounov et al, “Piezoelectric Actuator Generating Torsional Displacement From Piezoelectric d15Shear Response”, Applied Physics Letters, vol. 72, No. 20, May 18, 1998, pp. 2526-2528.
Glazounov et al, “High-efficiency Piezoelectric Motor Combining Continous Rotation With Precise Control Over Angular Positioning”, Applied Physics Letters, vol. 75, No. 6, Aug. 9, 1999, pp. 862-864.
Glazounov et al, “A New Torsional Actuator Based on Shear Piezoelectric Response”, Applied Physics Letters, Proceedings of the SPIE—The International Society for Optical Engineering, 1998, vol. 3324, pp. 82-91.
Kim et al, “Piezoelectric Torsional Actuators”, DARPA Actuator Technology Interchange Meeting #3, Jun. 17-18, 1999, Hampton, VA.
Glenn et al, “Development of a Two-sided Piezoelectric Rotary Ultrasonic Motor for High Torque”, SPIE vol. 3041, pp. 326-338.
Kim et al, “Piezoelectric Ceramic Assembly Tubes for Torsional Actuators”, SPIE vol. 3675, Mar. 1999, pp. 53-62.
Kim et al, “High Authority Piezoelectric Torsional Actuators”, IEEE, 1998, 0-7803-4959-8/98, pp. 277-280.
Kim et al, “Composite Piezoelectric Assemblies for Torsional Actuators”, Sep. 30, 1997, Naval Research Laboratory Report.
Addison Karen
Dougherty Thomas M.
Karasek John J.
Mills III John Gladstone
The United States of America as represented by the Secretary of
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