Patent ID: 7419039

Claim:
A rotation transmission device comprising: an outer ring; an inner ring mounted inside said outer ring, said outer and inner rings being rotatable relative to each other; a two-way clutch including engaging elements mounted between said outer ring and said inner ring for selectively engaging opposed surfaces of said outer and inner rings, and a retainer retaining said engaging elements; and an electromagnetic clutch mounted adjacent to said two-way clutch for selectively engaging and disengaging said two-way clutch; said electromagnetic clutch including an armature rotationally fixed and axially movable relative to said retainer, a cylindrical rotor guide connected to said outer ring at its open end and covering said armature, a rotor made of a magnetic material and pressed into an open end of said rotor guide to axially face said armature, and an electromagnet axially facing said rotor to attract said armature to said rotor when energized; wherein said rotor guide is made of a magnetic material having the same or substantially the same coefficient of linear expansion as the magnetic material of said rotor, said rotor guide being formed with a plurality of circumferentially elongated and circumferentially spaced apart slits, said slits being axially offset from a portion of said rotor guide into which said rotor is pressed.