Matsushita Electric Industrial Co., Ltd.

Shinya Yukino

Yasuhiro Goto

Hiromi Nakase

Kuniichi Ozawa

Shouichi Yoshikawa

Masahiro Naba

A magneto-optic disk-driving spindle motor has a rotary shaft for driving a spindle hub. Bearings support the rotary shaft for free rotation. A stator core is fixed relative to the bearings, and a driving magnet is fixed relative to the spindle hub. The spindle hub is provided with an upper side having a magneto-optic disk loading face for receiving and supporting a magneto-optic disk, and an axial part that is to be fitted into the center hole of the magneto-optic disk. A lower side of the spindle hub has a connection for connecting the axial upper end of the rotary shaft to the lower shaft of the spindle hub so as to fix the spindle hub to the rotary shaft. By having the axial part on the spindle hub as opposed to the end of the rotary shaft, the rotary shaft can have a diameter other than the diameter required for engagement with the center hole of the magneto-optic disk.

Spindle motor for driving disk

An optical rotation detecting apparatus for a bushless dc motor detects rotation information of the shaft by the slits arranged at equal pitches along the circumference of a rotary disk and a photoelectric conversion element arranged circumferentially at a pitch which is an integral multiple of the slit pitch and including a first set of photoelectric conversion element pieces arranged alternately with the former thereby generating a first rotation information signal having a frequency proportional to the rotational speed of the shaft and a second rotation information signal having a 90-degree phase difference with the first rotation information signal. The phases of the first and second rotation information signals are compared to detect the direction of rotation of the shaft. The accuracy of rotation information can be further improved by increasing the number of photoelectric conversion element pieces per slit pitch. The photoelectric conversion element includes an amorphous silicon photoelectric conversion element.

Growing community of inventors

Yonago, Japan

Shinya Yukino