Reverse input cutoff clutch

A reverse input cutoff clutch comprising:

• a fixed part having an inner wall surface;
• an input member including an input shaft, and first and second input side engaging parts disposed apart from each other in a first radial direction with a central axis of the input shaft interposed therebetween;
• an output member including an output shaft disposed coaxially with the input shaft, and an output side engaging part disposed between the first input side engaging part and the second input side engaging part in the first radial direction;
• and
• first and second engagement elements disposed to be able to change a position and/or a posture thereof, and configured such that if a rotational torque is input to the input member, the rotational torque is transmitted to the output member via at least one of the first and second engagement elements, and if a rotational torque is input to the output member, at least a part of the rotational torque is transmitted to at least one of the first and second engagement elements to be cut off by a contact between at least one of the first and second engagement elements and the inner wall surface of the fixed part, wherein
• the first input side engaging part includes a first contact part and a second contact part being able to come into contact with the first engagement element when the rotational torque is input to the input member, the first contact part and the second contact part being disposed apart from each other in a second radial direction orthogonal to the first radial direction,
• the second input side engaging part includes a third contact part and a fourth contact part being able to come into contact with the second engagement element when the rotational torque is input to the input member, the third contact part and the fourth contact part being disposed apart from each other in the second radial direction,
• the output side engaging part includes a fifth contact part and a sixth contact part being able to come into contact with the first engagement element when the rotational torque is input to the output member, the fifth contact part and the sixth contact part being disposed apart from each other in the second radial direction,
• the output side engaging part includes a seventh contact part and an eighth contact part being able to come into contact with the second engagement element when the rotational torque is input to the output member, the seventh contact part and the eighth contact part being disposed apart from each other in the second radial direction,
• a first group including the first contact part and the second contact part, and a second group including the third contact part and the fourth contact part are disposed apart from each other with a second reference line passing through the central axis and parallel to the second radial direction interposed therebetween,
• the first contact part and the second contact part of the first group are respectively disposed closer to a first reference line passing through the central axis and parallel to the first radial direction than the fifth contact part and the sixth contact part, and
• the third contact part and the fourth contact part of the second group are respectively disposed farther from the first reference line than the seventh contact part and the eighth contact part.