Appeal No. 1997-3279 Page 3
Application No. 08/240,702
motor's efficiency. The disposition of the stator's magnetic
poles simplifies assembly.
Claim 21, which is representative for our purposes,
follows:
21. A brushless DC motor comprising:
a rotor having a rotor yoke and a rotor magnet
forming a plurality of magnetic poles in a
circumferential direction disposed on the rotor
yoke,
a stator having a stator yoke with a plurality
of magnetic poles alternately disposed at regular
intervals in the circumferential direction on the
stator yoke having a constant air gap next to the
rotor magnet,
a coil unit disposed on the stator yoke and
having a magnetic field coil for exciting the
magnetic poles of the stator,
a magnetic pole sensing element set at a
position shifted in the circumferential direction
from an intermediate position of one magnetic pole
of the rotor magnet for detecting a pole of the
rotor magnet,
wherein an open angle of the magnetic poles of
the stator is set at no less than 75% but less than
100% of an open angle per magnetic pole of the rotor
so that a static stable point position where the
rotor stops by a cogging torque in a magnetic
circuit consisting of the rotor and stator is in
vicinity of a maximum point of torque generated by
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