Patent ID: 7775129

Claim:
A rotation angle sensor comprising: a shaft portion having a torsion bar; a rotation angle sensing portion for detecting rotation angle of the shaft portion; and a torque sensing portion for detecting angle of torsion of the torsion bar; wherein: the rotation angle sensing portion improves its own detecting accuracy by using results of detection by the torque sensing portion; the rotation angle sensing portion detects the rotation angle of the shaft portion based on rotation angle of an input side or an output side of the torsion bar which is used by the torque sensing portion when detecting the angle of torsion of the torsion bar; the rotation angle sensing portion includes: a first rotatable body which is joined to the shaft portion and which rotates in synchronism with rotation of the shaft portion; a second rotatable body which is not joined to the shaft portion and which rotates in synchronism with rotation of the first rotatable body; and a first sensing part for detecting rotation angle of the second rotatable body; and the second rotatable body rotates at a lower speed than the first rotatable body.