One-way clutch and electric parking brake device using the same

Abstract

In a one-way clutch as used preferably in an electric parking brake device, a sector-shape input cam provided bodily with an input rotational member is inserted into a sector-shape cutout of an output cam provided bodily with an output rotational member, with clearances secured in the circumferential direction between circumferentially end surfaces of the input and output cams. A coil spring is placed in an annular space between an internal surface of a stationary cylinder member and external surfaces of the input and output cams and is provided at both ends thereof with curved portions which are placed respectively in the clearances. A cam surface is formed on a part of each circumferentially inner end surface of the cutout. The cam surface is contactable with a part of the curved portion facing therewith for generating, in addition to a force expanding the outer diameter of the coil spring, another force which pressures the neighborhood of the curved portion of the coil spring on the internal surface of the cylinder member thereby to additionally prevent the rotation transmission from the output rotational member toward the input rotational member.