Motor core and motor using the same

DETAILED DESCRIPTION The present invention reduces the cycle of the cogging torque produced due to a basic configuration of a core to one-quarter or less of the cycle of basic cogging torque determined by a least common multiple of the number of core salient poles and the number of field poles, and to minimize the absolute value of the cogging torque as well.
The motor core of the present invention has the following structure.
A core used in a motor having magnetic field generating means having N and S magnetic poles for generating a magnetic field and the core made of magnetic material and opposed to the magnetic field generating means, where one of the magnetic field generating means and the core rotates with respect to the other: in which the number of magnetic poles is 2m and the number of core slots is 6n (m and n are integers), and in which a basic configuration of the core is determined by setting its slot opening angles (where "slot opening angle" is an angle a slot opening forms with respect to the center of the core) to a value ranging from 80.
degree.
to 95.
degree.
in electrical angle .
alpha.
(each corresponding to (.
alpha.
/m).
degree.
in mechanical angle) and from 20.
degree.
to 35.
degree.
in electrical angle .
beta.
(each corresponding to (.
beta.
/m).
degree.
in mechanical angle).
This configuration allows the cycle of produced cogging torque to be reduced to one-half the cycle of basic cogging torque.
Electrical angle is defined in relationship to that portion of the core occupied by a pair of N and S magnets.
One N and S magnet pair are assumed to occupy an electrical angle of 360 degrees.
Thus, for example, if a slot occupies one half of the circumference occupied by an N and S magnet pair, then the slot is said to have an electrical angle of 180 degrees.
In addition, two core shapes are combined so that the slots in each core are displaced by an angle equal to one-quarter the cycle of the basic cogging torque ((90/k).
degree.
in mechanical angle [k is a least multiple of 2m and 6n])