Patent ID: 7772836

Claim:
A multiple rotation absolute angle detecting device which comprises: a reduction gear mechanism including an eccentric ring fitted to a rotatable member, an internally threaded member arranged in a stationary member and having inwardly oriented teeth, an externally threaded member having outwardly oriented teeth and capable of undergoing a speed-reduced rotation at a reduction gear ratio of 1/L, where L represents an arbitrarily chosen number exceeding 1, about an axis of eccentric rotation of the eccentric ring when meshed with the internally threaded member, and a speed reducing member driven by the externally threaded member to undergo a speed-reduced rotation at the reduction gear ratio of 1/L around the rotatable member at a velocity equal to that of rotation of the externally threaded member on the axis of eccentric rotation; a multiple rotation detecting unit, capable of outputting a sinusoidal or sawtooth wave having one period during each complete rotation, including a to-be-detected member of provided in the speed reducing member, and a detecting member arranged in the stationary member so as to confront the to-be-detected member; and a single rotation detecting mechanism having a single rotation detecting unit, which is a rotation detector to output a sinusoidal or sawtooth wave having n periods, where n is a natural number, during each complete rotation, including a to-be-detected member provided in the rotatable member, and a detecting member disposed in the stationary member so as to confront the to-be-detected member, wherein the single rotation detecting unit is operable to output a sinusoidal or sawtooth wave having n periods, where n is a natural number, during each complete rotation of the rotatable member to detect the absolute angle of the rotatable member and the multiple rotation detecting unit is operable to output a sinusoidal or sawtooth wave having one period during each complete rotation of the speed reducing member to detect the absolute angle of the reduction gear mechanism output unit, and wherein the value of L in the gear reduction ratio of 1/L of the reduction gear mechanism is chosen to be a non-integer.