Rotation angle detection device and rotation angle correction method

A rotation angle detection device, comprising:

• a multi-rotatable first rotor holding a first target connected to an input axis and having an outer circumferential surface to which magnetic poles of alternate polarities are magnetized at an identical interval;
• a first detector for detecting a rotation angle of the first rotor, which is disposed facing the magnetic pole of the first target;
• a second rotor coupled to the input axis and having a gear;
• a third rotor coupled to the gear of the second rotor and having a gear provided with a second target in a center portion;
• a second detector for detecting a rotation angle of the third rotor;
• a fourth rotor coupled to the gear of the third rotor and having a gear provided with a third target in a center portion;
• and
• a third detector for detecting a rotation angle of the fourth rotor.

A rotation angle correction method of a rotation angle detection device including a first rotation angle detection unit disposed in a position facing a target connected to an axis to be detected;

• a mechanism for reducing a rotation speed of the axis to be detected;
• and a second rotation angle detection unit for detecting a rotation angle whose rotation speed is reduced, wherein a rotation angle of the axis to be detected is calculated from signals of the first rotation angle detection unit and the second rotation angle detection unit,
• the method comprising:
• by using a motor for rotating the axis to be detected, a motor controller for controlling a rotation angle of the motor, and an encoder for detecting the rotation angle of the motor,
• storing a difference between the rotation angle of the axis to be detected actually rotated by the motor and the calculated rotation angle of the axis to be detected obtained by the first and the second rotation angle detection units as a corrected angle in a nonvolatile memory;
• and
• correcting the calculated rotation angle of the axis to be detected with the corrected angle.