Patent ID: 8324892

Claim:
An electric motor ( 19 ), comprising: a rotor ( 14 ) arranged on a shaft ( 87 ) rotatable about an axis ( 85 ); a stator ( 12 ), associated with said rotor; an absolute-value rotational angle sensing arrangement, said sensing arrangement having a plurality of rotational angle sensors; a sensor magnet ( 82 ), mounted on said rotatable shaft ( 87 ) for rotation about said axis ( 85 ) and having an even number SP of at least two sensor magnetic poles ( 71 , 72 , 73 , 74 ), the sensor magnet ( 82 ) generating a rotation-angle-dependent magnetic flux ( 88 ) having a substantially sinusoidal profile; and an evaluation apparatus ( 32 ) for generating an absolute value representing the instantaneous rotational position (phi) of said rotor ( 14 ) based upon output signals from two analog rotational angle sensors ( 460 , 465 ), arranged at a predetermined spacing (As) with respect to each other, and each having a respective generally planar surface ( 462 , 467 ) sensitive to said rotation-angle-dependent magnetic flux ( 88 ), which sensors are arranged on the stator ( 12 ) such that lines ( 461 ) normal to said magnetically sensitive surfaces ( 462 , 467 ) do not intersect said rotation axis ( 85 ) of said sensor magnet ( 82 ); said analog sensors being configured to sense, at the location of the respective sensor ( 460 , 465 ), a respective vector component of the locally effective magnetic flux, which components extend along said normal lines ( 461 ) in order to generate at each sensor, during operation, a respective rotor position signal (B_S 1 , B_S 2 ) that characterizes the magnitude and sign of the sensed vector component, said analog sensors ( 460 , 465 ) being arranged on a common circuit board ( 468 ) at said predetermined spacing (As) with respect to each other, said common circuit board ( 468 ) extending substantially parallel to said rotation axis ( 85 ) of the sensor magnet ( 82 ), said magnetically sensitive surfaces ( 462 , 467 ) being arranged in a sensor plane ( 469 ) that extends substantially parallel to the rotation axis ( 85 ) of the sensor magnet ( 82 ) said rotor ( 14 ) . comprising a rotor magnet ( 13 ) having a number RP of rotor poles that interact with the stator ( 12 ), and wherein SP<=RP.