The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 20, 1997
Filed:
May. 08, 1995
Kazuo Kato, Toukai-mura, JP;
Takashi Sase, Hitachi, JP;
Kikuo Tomita, Hitachioota, JP;
Shuzo Oshima, Mizusawa, JP;
Muneo Chiba, Chigasaki, JP;
Tomohiko Douken, Hitachi, JP;
Kazuyoshi Takizawa, Hiratsuka, JP;
Hitachi, Ltd., Tokyo, JP;
Hitachi Media Electronics Co. Ltd., Misusawa, JP;
Abstract
An electrostrictive revolution type ultrasonic motor includes a piezoelectric ceramic disk shaped stator and a rotor. The piezoelectric ceramic disk shaped stator has an eccentric movement via excitation by two phase pulse like voltage. The rotor is fitted around the circumference of the stator and is transmitted by a rotating torque due to the eccentric movement via frictional contact therebetween. The rotor is formed of a plastic material by injection molding to achieve a reduction of a size variation of the rotor and a stable contact with the stator. A high and stable rotating torque is thereby obtained with a reduced production cost. Further, a driving device for the ultrasonic motor which varies the frequency of a voltage applied to the ultrasonic motor in a stepped manner discriminates the magnitude of the corresponding motor currents and drives the ultrasonic motor with the frequency which causes the maximum motor current. In this manner, a simple structured and low cost driving device which operates at a high speed and at a high resolution with a high efficiency is achieved.