Patent ID: 8339125

Claim:
A magnetic pole position detecting device that calculates and detects, based on a phase difference between sensor outputs of two magnetic sensors among two or more magnetic sensors arranged at predetermined intervals along a magnetic pole arraying direction of a motor, a magnetic pole position where a movable unit is located, the magnetic pole position detecting device comprising: a first operation system that detects, when an advanced phase side sensor output of the two sensor outputs is represented as “a”, a delay phase side sensor output is represented as “b”, and the phase difference is represented as φ, a magnetic pole position θin the case of a sine value of the phase difference larger than a determination threshold by performing a following arithmetic operation: θ=tan −1 { a ·sinφ/( b−a ·cosφ)}; and a second operation system that detects the magnetic pole position θ in the case of a sine value of the phase difference smaller than the determination threshold by performing a following arithmetic operation: θ={sin −1 ( a )+sin −1 ( b )−φ}/2.