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. 26, 1998
Filed:
Sep. 20, 1994
Kimio Sato, Akishima, JP;
Nippon Ferro Fluidics, Tokyo, JP;
Abstract
The invention is intended to facilitate surface processing for generation of dynamic pressure and to prevent degradation of the bearing performance due to temperature changes. To this end, a shaft is composed of an axially magnetized magnet and shafts of magnetic material holding the magnet therebetween. The shaft is press-fitted in an insertion hole in a non-magnetic sleeve. Pole pieces are placed on the upper and lower edges of a hole in a motor hub. Clearances defined by the outer peripheral surface of the sleeve and the inner peripheral surface of the motor hub are filled with a magnetic fluid. In order to generate a dynamic pressure in the magnetic fluid, surface processing is applied not to the magnet but to the outer peripheral surface of the sleeve. Further, the thermal expansion coefficient of the sleeve is greater than that of the motor hub.