AC Generator with low noise claw tooth rotor

DETAILED DESCRIPTION According to the present invention, in order to decrease the magnetic sound which is generated due to the torque variation, at least two pole pieces of at least one of a pair of finger magnetic poles are arranged so as to be deviated relative to the opposed tooth portions of the armature iron core which are arranged at an equal pitch, so that the pole pieces may be passed through the tooth portions of the armature iron core irregularly, when the rotor is rotated.
As a result, the torque variation having a fundamental frequency T.
multidot.
N and the integral order harmonics thereof, can be sharply decreased and the magnetic sound generated due to the torque variation can be greatly reduced.
According to the present invention, the deviated angle .
DELTA.
.
theta.
of each of the deviated pole pieces relative to the opposed tooth portions in the state where at least one claw-shaped pole piece and at least one tooth portion are positioned at the same angular position with each other is expressed by an equation: ##EQU1## where the constant n is all of the integral number from 0 to (P-1) The deviated pole pieces having the deviated angles .
DELTA.
.
theta.
are freely arranged.
However, it is desirable to arrange them so that the interval between adjacent pole pieces may be as long as possible in order not to lower the output of the ACG.
The first embodiment of the pole piece arrangement in the ACG of the present invention is shown in FIG.
3 as compared with that of the conventional ACG.
In this case, the number of pole pieces of each of an N pole and an S pole is 6 and the total number of the tooth portions of the armature iron core is 36.
Therefore, one of the pole pieces of the N pole and the S pole is arranged every three tooth portions of the armature iron core.
In FIG.
3, the pole pieces of the finger magnetic pole 4N of the conventional ACG are arranged at an equal pitch, as shown by broken lines.
The arrangement of the pole pieces of the finger magnetic pole 4N' of the present invention is shown by solid lines