ROTATION DETECTING APPARATUS

PROBLEM TO BE SOLVED: To provide a rotation detecting apparatus which can prevent a magnetic piece from being stuck, as far as possible, to the opposite face facing a rotor of a detection case, which can remove the magnetic piece easily even when the magnetic piece is stuck to the opposite face and which can prevent the degradation of a detecting accuracy when the magnetic piece is stuck in the rotation detecting apparatus in which a pair of Hall elements are provided at the inside of the detection case arranged and installed so as to face the rotor and which detects the rotation of the rotor on the basis of detection signals to be output from a pair of Hall elements by means of a change in a magnetic flux due to the rotation of the rotor. SOLUTION: In this rotation detecting apparatus, a Hall element 7 and a Hall element 8 are provided at the inside of a detection case 1 which is arranged and installed so as to face a rotor 3, and the rotation of the rotor 3 is detected on the basis of detection signals to be output from the Hall elements 7, 8 by means of a change in a magnetic flux Φ due to the rotation of the rotor 3. A protrusion 10 and a protrusion 11 which prevent arrangement and installation places of the Hall elements 7, 8 from being simultaneously shielded magnetically when a magnetic piece 13 is stuck to the opposite face 1a facing the rotor 3 of the detection case 1 are formed at the detection case 1.