Patent ID: 7358629

Claim:
An electromagnetic actuator, comprising: a rotor ( 30 , 30 a , 30 b ) which has multiple magnetic poles (Nr, Sr) on a circumferential surface ( 31 ) thereof, and a plurality of stators ( 10 , 10 a , 10 b , 20 , 20 a , 20 b , 60 , 70 ) in an electromagnet form which have at least two magnetic poles ( 13 , 14 , 23 , 24 , 63 , 64 , 73 , 74 ) facing said circumferential surface ( 31 ) of said rotor ( 30 , 30 a , 30 b ), wherein each stator in said plurality of stators ( 10 , 10 a , 10 b , 20 , 20 a , 20 b , 60 , 70 ) individually includes a respectively associated yoke ( 11 , 21 , 61 , 71 ) and coil ( 12 , 22 , 62 , 72 ), wherein each coil is configured to magnetize its respectively associated yoke, an auxiliaiy yoke ( 40 , 40 a , 40 b , 50 , 50 a , 50 b , 80 , 90 ) extending in a circumferential direction (A) of the magnetic poles (Nr, Sr) of said rotor ( 30 , 30 a , 30 b ) over an angular range which is larger than a spread angle (α) of said magnetic poles (Nr, Sr) of said rotor ( 30 , 30 a , 30 b ) in said circumferential direction (A) is provided between said magnetic poles ( 13 , 14 , 23 , 24 , 63 , 64 , 73 , 74 ) of at least one of said stators ( 10 , 10 a , 10 b , 20 , 20 a , 20 b , 60 , 70 ), wherein said auxiliary yoke ( 40 , 40 a , 40 b , 50 , 50 a , 50 b , 80 , 90 ) is not directly magnetized by said coil ( 12 , 22 , 62 , 72 ).