Patent ID: 7649300

Claim:
An electromagnetic actuator comprising: a rotor that has a cylindrical outer peripheral surface and that is capable of rotating within a predetermined angular range; a magnetizing coil; and a U-shaped yoke that has a first magnetic-pole part defining a first circular arc surface and a first end surface, and a second magnetic-pole part defining a second circular arc surface and a second end surface, the first and second circular arc surfaces facing the outer peripheral surface of the rotor in a radial direction of the rotor, and the first and second end surfaces facing in a circumferential direction of the rotor so as not to face the outer peripheral surface of the rotor, the first and second magnetic-pole parts generating mutually different magnetic poles by energizing the coil; wherein the rotor includes: a magnetized rotor part that defines the outer peripheral surface of the rotor and faces the first and second circular arc surfaces in the radial direction of the rotor so as to generate a magnetic action, and that is magnetized to have different magnetic pole portions at different locations along the circumferential direction, said different magnetic pole portions including a first magnetic pole portion having a first magnetic pole and a second magnetic pole portion having a second magnetic pole different than said first magnetic pole; a driving pin that is not magnetized and is configured so as to rotate together with the magnetized rotor part; and a protrusion part that is protruded in a radial direction from said outer peripheral surface of the magnetized rotor part, said protrusion part being magnetized to have the same magnetic pole as a portion of the outer peripheral surface from which said protrusion part radially protrudes, wherein said protrusion part is formed so as to rotate together with said magnetized rotor part and is formed so as to be able to face the first end surface of the first magnetic-pole part or the second end surface of the second magnetic-pole part in the circumferential direction so as to generate a magnetic action.