Patent ID: 7884517
Filing Date: 2011-02-08
Classification: H02K,H02P

Abstract:
1. An electric machine comprising: a coil group including a plurality of electrically interconnected coils disposed along a predetermined direction at a predetermined pitch; a magnet group including at least one magnet, wherein N poles and S poles are disposed alternately opposite the coil group and a relative position of the magnet group with the coil group is changeable along the prescribed direction; a magnetic sensor associated with the coil group, the magnetic sensor being configured to detect magnetic flux change due to movement of the magnet group to thereby generate a sinusoidal output signal; and a drive signal generation circuit that executes PWM control based on the sinusoidal output signals of the magnetic sensor to thereby generate an AC drive signal to be supplied to the coil group, wherein the drive signal generation circuit generates the AC drive signal so that polarity of each coil in the coil group are switched when center of each coil is opposite to one of centers of the magnets in the magnet group, and that magnetic flux density in the coil group reaches a maximum value at a timing when midway points between two adjacent coils in the coil group are opposite to the centers of the magnets in the magnet group, wherein the drive signal generation circuit includes: wherein the masking circuit masks the PWM signal in temporal ranges that are symmetrically centered around a timing at which polarities of the AC drive signal are inverted while maintaining the PWM signals in other temporal ranges that are symmetrically centered around peaks of the AC drive signal.