Patent ID: 7358719
Filing Date: 2008-04-15
Classification: G01D

Abstract:
1. A rotational angle detector for detecting an absolute value of a rotational angle of a rotor, the rotational angle detector comprising: a drive gear integrally rotatable with the rotor; a first driven gear mated with the drive gear and having teeth, a second driven gear mated with the drive gear and having a quantity of teeth differing from that of the first driven gear; a first magnetic sensor for detecting a rotational angle of the first driven gear and outputting a detection signal corresponding to the detected rotational angle; a second magnetic sensor for detecting a rotational angle of the second driven gear and outputting a detection signal corresponding to the detected rotational angle; a control circuit for calculating the rotational angle of the first driven gear based on a first analog signal and a second analog signal corresponding to the detection signal of the first magnetic sensor, the rotational angle of the second driven gear based on a third analog signal and a fourth analog signal corresponding to the detection signal of the second magnetic sensor, and the absolute value of the rotational angle of the rotor based on the calculated rotational angles of the first and second driven gears; and an abnormality detection circuit having an upper threshold value and a lower threshold value, wherein the abnormality detection circuit: