Patent ID: 7197945

Claim:
A torque direction detecting device for a brushless motor having a plurality of phase-windings comprising: a resolver for providing two sinusoidal signals having the same cycle and a phase different from each other by a prescribed electric angle according to rotation of the brushless motor; means for calculating an electric angle of the brushless motor from the two sinusoidal signals; a current sensor for detecting current flowing through the phase windings; and means for determining a torque direction of the brushless motor by comparing magnitudes of phase currents flowing through two of the phase-windings in a prescribed section of the electric angle, wherein said means for determining a torque direction comprises first means for comparing magnitudes of the phase currents flowing through two of the phase-windings to provide a signal when a difference in magnitude between the phase currents is in a prescribed magnitude relation and second means for providing a timing signal when the electric angle is in the prescribed section of the electric angle, and a logic circuit that provides a signal determining a torque direction when said second means provides the timing signal, and wherein the second means comprises a comparator circuit that directly compares the two sinusoidal signals and a circuit for examining whether the electric angle is in the prescribed section or not.