Patent ID: 7648014

Claim:
A one-way clutch for transmitting rotation from an input rotational member side toward an output rotational member side but for preventing rotation from being transmitted from the output rotational member side toward the input rotational member side, the one-way clutch comprising: a stationary member having a cylindrical surface; the input rotational member and the output rotational member each provided rotatably relative to the stationary member; an output cam provided bodily with the output rotational member and having a cutout of sector shape coaxial with the axis of the output rotational member; an input cam provided bodily with the input rotational member and inserted into the cutout with clearances secured in the circumferential direction between circumferentially outer end surfaces thereof and circumferentially inner end surfaces of the cutout; a coil spring placed in an annular space between the circumferential surface of the stationary member and respective circumferential surfaces of the input and output cams and frictionally engageable with the circumferential surface of the stationary member when pressured resiliently on the circumferential surface of the stationary member, the coil spring having at least at one end thereof a curved portion which is placed in one of the clearances; a cam surface formed on one of a part of the cutout and a part of the curved portion which are brought into contact with each other when the rotation of the output rotational member is about to be transmitted toward the input rotational member, the cam surface being inclined to generate a force which expands the outer diameter of the coil spring to increase the friction force of the coil spring with the cylindrical surface of the stationary member and to generate a force which pressures the neighborhood of the curved portion of the coil spring on the circumferential surface of the stationary member, upon contact with the other of the parts of the cutout and the curved portion; and a protruding portion formed on, and protruded from, one of a circumferentially outer end surface of the input cam and a circumferentially inner end surface, facing the circumferentially outer end surface, of the cutout toward the other of the circumferentially outer and inner end surfaces, the protruding portion being contactable with the other of the circumferentially outer and inner end surfaces when the rotation of the input rotational member is about to be transmitted toward the output rotational member, for separating the cam surface from the other of the parts of the cutout and the curved portion and for performing the rotation transmission.