Reverse input shutoff clutch, electric valve timing adjustment device, variable compression ratio device, and electric power steering device

A reverse input shutoff clutch, comprising:

• an input member;
• an output member coaxially arranged with the input member;
• a pressed member having a pressed surface;
• and
• an engaging element that, when a rotational torque is inputted to the input member, moves in a direction away from the pressed surface due to engagement with the input member, and by engaging with the output member, transmits the rotational torque that is inputted to the input member to the output member;
• and when a rotational torque is reversely inputted to the output member, moves in a direction toward the pressed surface due to engagement with the output member, and by coming in contact with the pressed surface, completely shuts off not to transmit the rotational torque that is reversely inputted to the output member, or transmits part of the rotational torque that is reversely inputted to the output member to the input member, and shuts off a remaining part of the rotational torque that is reversely inputted to the output member,
• wherein
• the pressed surface is an arc-shaped concave surface with regard to a circumferential direction,
• the engaging element has a pair of pressing surfaces that is provided at two locations spaced apart in the circumferential direction on an outer side surface in a radial direction thereof and that is pressed against the pressed surface, and
• each of the pair of pressing surfaces is an arc-shaped convex surface in the circumferential direction having a radius of curvature smaller than a radius of curvature of the pressed surface
• wherein
• the engaging element is arranged between the pressed surface and an output member side engaging portion provided on the output member, and causes an input member side engaging portion provided at a portion of an end surface of the input member and separated in a radial direction from a center of rotation of the input member to engage with an engaging element side input engaging portion provided in the engaging element to enable movement of the engaging element toward or away from the pressed surface.