Canon Denshi Kabushiki Kaisha

Canon Kabushiki Kaisha

Yasuaki Imai

Yasuo Ogino

Toru Okada

Shigeki Koizumi

An electric rotary machine which prevents problems involved in leakage flux, and reduces the number of components so that it becomes thin and small in size, and inexpensive. The machine includes a first pulse generating device generating a first frequency generating signal consisting of P1 uniformly spaced pulses per one revolution of the rotor by detecting a counterelectromotive voltage induced in a rotary magnetic field generating device while a driving magnet is rotating, a magnetic body producing magnetic flux during rotation of the rotor, a second pulse generating device generating a second frequency generating signal consisting of P2 uniformly spaced pulses per one revolution of the rotor by detecting changes in the magnetic flux of the magnetic body, and an index position detecting circuit generating an index signal on the basis of a periodic phase difference between the first and second frequency generating signals. The numbers of poles of the driving magnet and the magnetic body are set so that the greatest common divisor of the pulse numbers P1 and P2 become an integer m.

Index position detecting apparatus for an electromagnetic rotary machine

A disk drive system in accordance with the present invention comprises a surface opposing type spindle motor which in turn comprises a spindle which is rotatably supported through a bearing by a chassis and to which is to be mounted a disk, a rotor yoke securely attached to the spindle, a driving magnet assembly, a printed-circuit board upon which are mounted a plurality of driving coils and a stator yoke disposed in opposing relationship with the driving magnet through the driving coils. A chassis has an opening in which is housed a head and the stator yoke is formed with a first recess in a region corresponding to a space in which the head is displaced. The bearing is a radial bearing having a diameter greater than that of the spindle. In order to avoid the interference between the driving coils and the first recess, the driving coils are disposed in an opening formed through the printed-circuit board or the space defined at the position corresponding to the recess. Furthermore, in order to balance the attractive forces of the driving magnet assembly or to cancel the cogging torque, the stator has a second recess at a position in opposing relationship with the first recess across the bearing.

Disk drive device having reduced thickness

A record confirmation apparatus comprises a recording device for recording information on a disc-like record bearing member rotated at a predetermined angular speed, in accordance with a writing signal, a reproducing device disposed at a predetermined distance from the recording device in the tangential direction of the record bearing member for reproducing the recorded information as a read-out signal, and a comparing device for delaying the writing signal and comparing it with the read-out signal, the comparing device having a variable delay circuit for varying the delay time in conformity with the relative position of the recording device and the reproducing device relative to the record bearing member in the radial direction of the record bearing member.

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Saitama, Japan

Yasuaki Imai