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:
Nov. 21, 1995
Filed:
Jun. 03, 1994
Naoto Iwao, Nagoya, JP;
Shoji Yamada, Konan, JP;
Brother Kogyo Kabushiki Kaisha, Aichi, JP;
Abstract
The rotational shaft 22 is provided with a pair of permanent magnets 31a and 31b, at its opposite ends. The bearing device 30 for the light scanning apparatus includes: a pair of electromagnets 32a and 32b; and a pair of voltage control circuits 33a and 33b. The electromagnet 32a is constructed from an iron core 321a provided with a coil 322a. Similarly, the electromagnet 32b is constructed from an iron core 321b provided with a coil 322b. When the rotational number increases to exceed a predetermined rotational number, the control signal generating circuit 53 switches the electric voltage applied through each of the coils 322a and 322b so as to switch the bearing stiffness of the bearing device. As a result, the resonant frequencies of the conical and cylindrical modes become much lower than the present actual rotational number .omega.0 of the rotational shaft. Accordingly, it is possible to prevent the rotational shaft from exhibiting any of the conical and cylindrical mode resonant actions.