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:
Dec. 01, 1992
Filed:
Sep. 10, 1991
Hirokazu Yashiro, Gifu, JP;
Ibiden Co., Ltd., , JP;
Abstract
A spindle motor for high speed hand tools includes a rotor and a sleeve that is journaled about the rotor. A pressure generating mechanism creates sufficient air pressure in a clearance between the rotor and the sleeve to form a pressurized air film in the clearance when the spindle motor is in normal operation. A plurality of armature coils and a plurality of magnetic sensors for detecting magnetism of magnetic poles in the rotor are provided on the outer surface of the sleeve. The rotor has a field magnet with multiple magnetic poles. The sleeve is formed of a ceramic material whose dielectric constant is 10 or lower. The pressurized air film created by the pressure generating mechanism is sufficient to radially support the rotor so that the rotor does not significantly contact the sleeve during normal operation of the spindle motor. The armature coils cooperate with the field magnet to rotate the rotor by the magnetic interaction between magnetic fields formed by the armature coils and the poles of the field magnet. The excitation of the armature coils is controlled at least in part by signals provided by the magnetic sensors.