Reverse input cut-off clutch

A reverse input cut-off clutch comprising:

• a pressed member that includes a pressed surface provided on an inner peripheral surface;
• an input member having at least one input-side engaging part disposed radially inside the pressed surface and disposed coaxially with the pressed surface;
• an output member having an output-side engaging part disposed further inward in a radial direction than the input-side engaging part radially inside each of the pressed surface and disposed coaxially with the pressed surface;
• and
• an engaging element having a pair of pressing surfaces facing the pressed surface and away from each other in a circumferential direction, an input-side engaged part which is engageable with the input-side engaging part, and an output-side engaged part which is engageable with the output-side engaging part, and disposed to be movable in a first direction that is a far-near direction with respect to the pressed surface,
• wherein, the engagement element is configured to be displaced in a direction moving away from the pressed surface in the first direction based on that the input-side engaging part engages with the input-side engaged part when a rotational torque is input to the input member and is configured to transmit the rotational torque input to the input member to the output member based on that the output-side engaged part engages with the output-side engaging part,
• the engagement element is configured to press the pressing surface against the pressed surface so that the pressing surface frictionally engages with the pressed surface based on that the output-side engaging part engages with the output-side engaged part when a rotational torque is reversely input to the output member,
• a state in which, as the output member rotates in a predetermined direction, the pair of pressing surfaces are pressed against the pressed surface, and as the input member rotates in a direction opposite to the predetermined direction, the input-side engaging part is engaged with the input-side engaged part is set to be a first state, and
• a state in which a rotational torque is reversely input to the output member and the pair of pressing surfaces are in contact with the pressed surface is set to be a second state,
• when a direction perpendicular to both the first direction and a central axis of the input member is set to be a second direction,
• wherein in the first state, a distance in the second direction between a contact portion between the input-side engaging part and the input-side engaged part and a rotation center of the input member is larger than a distance in the second direction between a contact portion between the output-side engaging part and the output-side engaged part and a rotation center of the output member, and
• in the second state, the contact portion between the output-side engaging part and the output-side engaged part is located closer to the rotation center of the output member in the first direction than an imaginary straight line connecting a contact portion between one pressing surface of the pair of pressing surfaces and the pressed surface to the rotation center of the output member.