Patent ID: 8393452

Claim:
A one way clutch comprising: an inner ring; an outer ring disposed coaxially with said inner ring; a plurality of concave cams provided on one of an outer circumferential surface of said inner ring and an inner circumferential surface of said outer ring, each cam including a recessed portion and a slope; a plurality of torque transmission members interposed between the other of the outer circumferential surface of said inner ring and the inner circumferential surface of said outer ring and the concave cams; a plurality of biasing members that are respectively paired with said torque transmission members and bias said torque transmission members toward the slopes in said concave cams, a block bearing that maintains a space between said inner ring and said outer ring with respect to a radial direction; and a retainer disposed between said inner ring and said outer ring to retain said torque transmission members and said biasing members, wherein said torque transmission members roll in said concave cams against the biasing force of said biasing members only when said inner ring and said outer ring turn in one direction, to transmit torque between said inner ring and said outer ring, a groove that holds said block bearing is provided on said one of the outer circumferential surface of said inner ring and the inner circumferential surface of said outer ring, and an engagement projection that engages with said groove is provided on said block bearing, said biasing members are springs having a spring force that allows reduction of drag, said retainer has pocket portions that radially pass through it and are arranged at predetermined circumferential intervals and column portions that extend in an axial direction and are provided circumferentially between adjacent pocket portions, the lengths of said column portions along a circumferential direction are designed in such a way as to cause said biasing members to exert a biasing force that is so strong that said torque transmission members are prevented by biasing by said biasing members from being dislocated in a sub-assembly state in which the one-way clutch lacks one of the inner ring and the outer ring, and the width of said engagement projection along the circumferential direction is smaller than the width of said groove along the circumferential direction, and when a torque greater than a predetermined level is input, said retainer can shift by a distance equal to a gap between said engagement projection and a circumferential end of said groove.