Patent ID: 8054017

Claim:
An apparatus for estimating rotor position for brushless motors which includes a brushless motor having a stator with coils wound thereon and a rotor rotatably supported relative to the stator and estimates the stop position of the rotor, the estimating apparatus comprising: a current detecting means for directly or indirectly detecting wiring current which is current passed through the coils; a voltage supplying means capable of supplying voltage to the coils so that magnetic flux is produced in each of a plurality of directions perpendicular to the direction of rotation of the rotor; a voltage supply controlling means which controls the voltage supplying means so that magnetic flux is produced in sequence in predetermined directions among the directions and, when the wiring current detected at the current detecting means exceeds a predetermined threshold value, terminates the supply of voltage by the voltage supplying means; a supply period acquiring means which acquires a period equivalent value equivalent to a voltage supply period in each direction in which magnetic flux is produced under control of the voltage supply controlling means; and a rotor position estimating means which compares period equivalent values to identify a direction in which the voltage supply period is minimized and estimates the stop position of the rotor based on the identified direction.