Reverse input cutoff clutch

1 . 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.

2 . The reverse input cutoff clutch according to claim 1 , wherein

the first contact part, the second contact part, the third contact part, the fourth contact part, the fifth contact part, the sixth contact part, the seventh contact part, and the eighth contact part respectively have a first distance, a second distance, a third distance, a fourth distance, a fifth distance, a sixth distance, a seventh distance, and an eighth distance as a distance from the first reference line in the second radial direction, and

the first distance and the second distance are respectively smaller than the fifth distance and the sixth distance, and the third distance and the fourth distance are respectively larger than the seventh distance and the eighth distance.

3 . The reverse input cutoff clutch according to claim 1 , wherein

the first engagement element includes a ninth contact part and a tenth contact part being able to come into contact with the inner wall surface of the fixed part when the rotational torque is input to the output member, the ninth contact part and the tenth contact part being disposed apart from each other in the second radial direction,

the second engagement element includes an eleventh contact part and a twelfth contact part being able to come into contact with the inner wall surface of the fixed part when the rotational torque is input to the output member, the eleventh contact part and the twelfth contact part being disposed apart from each other in the second radial direction, and

in at least one of four quadrants divided by the first reference line and the second reference line, when the rotational torque is input to the output member, the fifth contact part or the eighth contact part is disposed in a region between the second reference line and a virtual straight line connecting the ninth contact part or the twelfth contact part, and the central axis.

4 . The reverse input cutoff clutch according to claim 3 , wherein when the rotational torque is input to the output member, the fifth contact part or the eighth contact part is disposed in a region between the second reference line and the virtual straight line in each of two quadrants which are in a positional relationship diagonally opposite to each other among the four quadrants.

5 . The reverse input cutoff clutch according to claim 1 , wherein

the first engagement element includes a ninth contact part and a tenth contact part being able to come into contact with the inner wall surface of the fixed part when the rotational torque is input to the output member, the ninth contact part and the tenth contact part being disposed apart from each other in the second radial direction,

the second engagement element includes an eleventh contact part and a twelfth contact part being able to come into contact with the inner wall surface of the fixed part when the rotational torque is input to the output member, the eleventh contact part and the twelfth contact part being disposed apart from each other in the second radial direction, and

in at least one of four quadrants divided by the first reference line and the second reference line, when the rotational torque is input to the output member, the sixth contact part or the seventh contact part is disposed in a region between the second reference line and a virtual straight line connecting the tenth contact part or the eleventh contact part, and the central axis.

6 . The reverse input cutoff clutch according to claim 5 , wherein when the rotational torque is input to the output member, the sixth contact part or the seventh contact part is disposed in a region between the second reference line and the virtual straight line in each of two quadrants which are in a positional relationship diagonally opposite to each other among the four quadrants.

7 . 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 third contact part, and a second group including the second contact part and the fourth contact part are disposed apart from each other with a first reference line passing through the central axis and parallel to the first radial direction interposed therebetween,

the first contact part and the third contact part of the first group are respectively disposed closer to the first reference line than the fifth contact part and the seventh contact part, and

the second contact part and the fourth contact part of the second group are respectively disposed farther from the first reference line than the sixth contact part and the eighth contact part.

8 . The reverse input cutoff clutch according to claim 7 , wherein

the first contact part, the second contact part, the third contact part, the fourth contact part, the fifth contact part, the sixth contact part, the seventh contact part, and the eighth contact part respectively have a first distance, a second distance, a third distance, a fourth distance, a fifth distance, a sixth distance, a seventh distance, and an eighth distance as a distance from the first reference line in the second radial direction, and

the first distance and the third distance are respectively smaller than the fifth distance and the seventh distance, and the second distance and the fourth distance are respectively larger than the sixth distance and the eighth distance.