Patent ID: 7378841

Claim:
A rotation angle detecting apparatus comprising: a first permanent magnet rotating together with a rotator; a second permanent magnet disposed so as to face said first permanent magnet, said second permanent magnet also rotating together with said rotator; an arc-shaped first magnetic member having two end surfaces fixed to South-seeking (S) pole sides of said first permanent magnet and said second permanent magnet, respectively; an arc-shaped second magnetic member having two end surfaces fixed to North-seeking (N) pole sides of said first permanent magnet and said second permanent magnet, respectively, said arc-shaped second magnetic member facing said first magnetic member; and a magnetic resistor disposed in an air gap formed between said first magnetic member and said second magnetic member so as to be axially aligned with said rotator and fixed to a non-rotator, said first magnetic member and said second magnetic member each comprising: a first wall portion having a tip end projected toward said magnetic resistor; and second and third wall portions surrounding said magnetic resistor so as to prevent influence from external magnetic fields, wherein said second and third wall portions are disposed between said first permanent magnet and said first wall portion, and said second permanent magnet and said first wall portion, respectively, wherein heights of said first, second and third wall portions in an axial direction are substantially same, and said magnetic resistor detecting a rotation angle of said rotator by detecting a change in orientation of magnetic flux arising in said first permanent magnet and said second permanent magnet in said air gap.