Victor Company of Japan, Limited

Nobuaki Nakamura

Makoto Itonaga

Masakatsu Kai

Kanji Kayanuma

Juichi Shikunami

Yukimi Hirose

A brushless motor of the present invention generally has a stator and a rotor in a clean chamber of contaminant free atmosphere. The stator has a motor base, a shaft provided on the motor base and a plurality of coils on the motor base. The rotor has a bearing holder having a center hole for supporting bearings, a hub connected to the bearing holder for mounting information storage discs such as hard discs and a magnet having magnetic poles provided on the hub facing to the coils. The brushless motor of the present invention further has a top cover provided on the bearing holder for covering the center hole thereof, a cylindrical chamber defined by an outer wall of the bearing holder and an inner wall of the hub in the rotor, the magnet is provided on the inner wall of the bearing holder, and a coreless coil assembly having the plurality of coils without cores made of magnet materials being provided on the motor base in such a manner that the coreless coil assembly protrudes into the cylindrical chamber so as to form narrow clearances between the walls of the cylindrical chamber and the coreless coil assembly for a labyrinth path in the clean chamber.

Brushless motor having coreless coil assembly

A reflective optical rotary encoder device detects an angular speed or position of a rotatable member with a light beam applied to and reflected from a reflective optical encoder disc. The reflective optical rotary encoder disc has an annular encoder track for reflecting the light beam, the encoder track being composed of an annular pattern of angularly spaced pit units each including a plurality of radially spaced arcuate pits, and a pit-free annular focus servo track for focusing the light beam onto the encoder track, the focus servo track extending along and being disposed radially substantially centrally in the annular encoder track. The reflective optical rotary encoder disc further includes at least one arcuate reference pit for reflecting the light beam to produce a reference signal, the reference bit being positioned in the focus servo track and radially aligned with one of the pit units, and an annular tracking servo pit for keeping the light beam applied thereto, the annular tracking servo pit extending along and being disposed radially substantially centrally in the annular focus servo track.

Reflective optical rotary encoder disc

A reflective rotary optical encoder device for detecting an angular speed or position of a movable member includes an optical encoder disc rotatable with the movable member, the optical encoder having an encoder track composed of a series of equally spaced pits alternating with inter-pit lands therebetween, the pits and the inter-pit lands having equal lengths l. A laser beam pickup applies three laser beams as respective laser beam spots to the optical encoder and detects laser beams reflected from the laser beam spots on the optical encoder to produce electric signals representative of the encoder track. Adjacent light beam spots on the optical encoder are spaced at a pitch P expressed by: ##EQU1## where n is an integer of 1 or more. The length l may be substantially the same as or larger than the diameter of each of the laser beam spots. The electric signals produced by the laser beam pickup include a focus servo signal, a tracking servo signal, and two signals each representative of encoder track which are out of phase with each other by a phase angle of 90.degree..

Reflective optical encoder device with light beams applied as spats

An optical detection system for detecting a displacement amount of a movement device with an optical encoder movable in accordance with a movement of the movable device has on a light-reflecting layer a plurality of pits successively strung in a predetermined direction. An optical pickup optically picks up the pit information by irradiating the optical encoder with light beams and receiving reflected light beams from the optical encoder. The optical pickup comprises a light-division device for dividing the light beam from a light-emitting device into three light beams so that the divided three light beams are directed to the pit string to apply three light spots to the pit string. The light-division device is adapted to be rotatable with respect to the optical encoder so that a light passing through the three light spots intersects the pit string at a predetermined angle. The reflected light beams due to the outside light spots are respectively incident on two photosensitive elements each generating an electrical signal. The electrical signals from the photosensitive elements, which are out-of-phase by an amount corresponding to the rotation of the light-division device, are fed to a detection circuit to detect information of the movement of the movable device and produce a pit detection signal indicative of the information.

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Fujieda, Japan

Nobuaki Nakamura