Reverse-input blocking clutch

Abstract

The present invention achieves a structure capable of reducing contact surface pressure of a contact portion between an input member and an engagement element, a contact portion between an output member and the engagement element, or both of the contact portions, in addition to reducing an increase in manufacturing cost. The present invention comprises: a pressed member 2 that has a pressed surface 6; and an input member 3, an output member 4, and an engagement element 5 that are disposed radially inward of the pressed surface 6. The engagement element 5 has a pressing surface 34 facing the pressed surface 6, an input-side engaged part 35 capable of engaging with an input-side engaging part 13 of the input member 3, and an output-side engaged part 36 capable of engaging with an output-side engaging part 21 of the output member 4. The engagement element is also disposed to be movable in a first direction that is a far-and-near direction with respect to the pressed surface 6, and has protruding curved surface parts 37, 38 in a portion to be engaged with the input-side engaging part 13 in the input-side engaged part 35 and / or a portion to be engaged with the output-side engaging part 21 in the output-side engaged part 36.

Description

Reverse input cutoff clutch

[0001] The present disclosure relates to a reverse input cutoff clutch that transmits rotational torque input to an input member to an output member, while completely cutting off rotational torque that is reversely input to the output member, so that it is not transmitted to the input member, or that transmits only a portion of the torque to the input member and cuts off the remainder.

[0002] A reverse input cut-off clutch has an input member connected to an input side mechanism such as a drive source, and an output member connected to an output side mechanism such as a reduction mechanism, and has the function of transmitting the rotational torque input to the input member to the output member, while completely cutting off the rotational torque input in reverse to the output member, so that it is not transmitted to the input member, or by transmitting only a portion of it to the input member and cutting off the remainder.

[0003] Reverse input cutoff clutches differ in the mechanism for cutting off the rotational torque reversely input to the output member. There are two types of reverse input cutoff clutches: a locking type reverse input cutoff clutch equipped with a mechanism for preventing the output member from rotating when rotational torque is reversely input to the output member, and a free type reverse input cutoff clutch equipped with a mechanism for causing the output member to spin freely when rotational torque is input to the output member. Whether to use a locking type reverse input cutoff clutch or a free type reverse input cutoff clutch is determined appropriately depending on the application of the device into which the reverse input cutoff clutch is incorporated, etc.

[0004] In the locking reverse input cut-off clutch described in WO 2019 / 026794, when rotational torque is input to an input member, the input-side engaging portion of the input member engages with the input-side engaged portion of an engager, causing the engager to move in a direction away from a pressed surface provided on a pressed member and engaging the output-side engaged portion of the engager with the output-side engaging portion of an output member, thereby transmitting the rotational torque input to the input member to the output member. On the other hand, when rotational torque is reversely input to the output member, the output-side engaging portion engages with the output-side engaged portion, causing the engager to move in a direction approaching the pressed surface, pressing the pressing surface against the pressed surface and frictionally engaging the pressing surface with the pressed surface.

[0005] WO 2023 / 085127 describes a locking reverse input cutoff clutch that can prevent the generation of peak torque when switching from a locked or semi-locked state to an unlocked or semi-unlocked state, and can ensure good torque transmission efficiency.

[0006] In this reverse input cut-off clutch, as the output member rotates in a predetermined direction, the two pressing surfaces provided on the engaging element are pressed against the pressed surface provided on the pressed member, and as the input member rotates in the direction opposite to the predetermined direction, the input side engaging portion provided on the input member and the input side engaged portion provided on the engaging element are engaged, and the distance between the contact portion between the input side engaging portion and the input side engaged portion and the center of rotation of the input member in a second direction perpendicular to both a first direction which is the radial direction of the engaging element and the center of rotation of the input member is smaller than the distance between the contact portion between the output side engaging portion provided on the output member and the output side engaged portion of the engaging element and the center of rotation of the output member in the second direction.

[0007] Furthermore, when a rotational torque is input in reverse to the output member and the two pressing surfaces are in contact with the pressed surface, the contact portion between the output side engaging portion and the output side engaged portion is located closer to the center of rotation of the output member in the first direction than the virtual line connecting the abutment portion between one of the two pressing surfaces and the pressed surface and the center of rotation of the output member.

[0008] Furthermore, International Publication No. 2023 / 085395 describes a locking type reverse input cutoff clutch that can suppress rattle of the input member.

[0009] In this reverse input cut-off clutch, as the output member rotates in a predetermined direction, the two pressing surfaces provided on the engaging element are pressed against the pressed surface provided on the pressed member, and as the input member rotates in the direction opposite to the predetermined direction, the input side engaging portion provided on the input member and the input side engaged portion provided on the engaging element are engaged, and in a second direction perpendicular to both a first direction which is the radial direction of the engaging element and the center of rotation of the input member, the distance between the contact portion between the input side engaging portion and the input side engaged portion and the center of rotation of the input member is greater than the distance between the contact portion between the output side engaging portion provided on the output member and the output side engaged portion of the engaging element and the center of rotation of the output member in the second direction.

[0010] Furthermore, when a rotational torque is input in reverse to the output member and the two pressing surfaces are in contact with the pressed surface, the contact portion between the output side engaging portion and the output side engaged portion is located closer to the center of rotation of the output member in the first direction than the virtual line connecting the abutment portion between one of the two pressing surfaces and the pressed surface and the center of rotation of the output member.

[0011] In the reverse input cutoff clutch described in WO 2023 / 085395, when rotational torque is transmitted from the input member to the output member, the pressing surface on the rear side in the rotation direction of the input member out of the two pressing surfaces tends to be pressed against the pressed surface. Therefore, with this reverse input cutoff clutch, switching from an unlocked state or a half-unlocked state to a locked state or a half-locked state can be performed smoothly, i.e., good locking performance can be ensured.

[0012] International Publication No. 2019 / 026794 Pamphlet International Publication No. 2023 / 085127 Pamphlet International Publication No. 2023 / 085395 Pamphlet

[0013] In the reverse input blocking clutches described in any of WO 2019 / 026794, WO 2023 / 085127, and WO 2023 / 085395, the portion of the input side engaging portion that engages with the input side engaged portion, and the portion of the output side engaging portion that engages with the output side engaged portion are each configured with a convex curved surface portion, thereby preventing the contact surface pressures at the contact portions between the input side engaging portion and the input side engaged portion, and the contact portions between the output side engaging portion and the output side engaged portion from becoming excessive.

[0014] However, to provide convex curved surfaces on the portion of the input-side engaging portion of the input member (which is a shaft-shaped member) that engages with the input-side engaged portion and the portion of the output-side engaging portion of the output member (which is a shaft-shaped member) that engages with the output-side engaged portion, it is necessary to forge a metal material to form the approximate outer shape and then cut the convex curved surfaces, which can increase the manufacturing costs of the input member and the output member.

[0015] The present disclosure aims to realize a reverse input cut-off clutch structure that can reduce the contact surface pressure at the contact portion between the input member and the engaging element, the contact portion between the output member and the engaging element, or both, while suppressing increases in manufacturing costs.

[0016] A reverse input disconnecting clutch according to one aspect of the present disclosure includes a pressed member, an input member, an output member, and an engagement element.

[0017] The pressed member has a pressed surface on its inner circumferential surface.

[0018] The input member has an input-side engaging portion disposed radially inside the pressed surface, and is disposed coaxially with the pressed surface.

[0019] The output member has an output-side engaging portion disposed radially inward of the input-side engaging portion, and is disposed coaxially with the pressed surface.

[0020] The engaging element has a pressing surface facing the pressed surface, an input side engaged portion that can engage with the input side engaging portion, and an output side engaged portion that can engage with the output side engaging portion, and is arranged so as to be able to move in a first direction, which is the direction towards or away from the pressed surface.

[0021] When a rotational torque is input to the input member, the engaging element moves in the first direction away from the pressed surface based on the engagement of the input side engaging portion with the input side engaged portion, and transmits the rotational torque input to the input member to the output member by engaging the output side engaged portion with the output side engaging portion, whereas when a rotational torque is input in the reverse direction to the output member, the output side engaging portion engages with the output side engaged portion, and presses the pressing surface against the pressed surface, causing the pressing surface to frictionally engage with the pressed surface.

[0022] In particular, in one aspect of the reverse input disconnection clutch of the present disclosure, the engaging element has a convex curved surface portion on at least one of the portion of the input side engaged portion that engages with the input side engaging portion and the portion of the output side engaged portion that engages with the output side engaging portion.

[0023] In one aspect of the reverse input cut-off clutch of the present disclosure, the convex curved surface portion can be provided on the portion of the input side engaged portion that engages with the input side engaging portion so as to be convex toward the input side engaging portion, and the input side engaging portion can have a flat surface portion on the portion that engages with the input side engaged portion.

[0024] In the reverse input cutoff clutch according to one aspect of the present disclosure, the outer peripheral surface of the input side engagement portion can be composed of a partial cylindrical surface portion centered on the central axis of the input member, and the flat surface portion.

[0025] In one aspect of the reverse input cut-off clutch of the present disclosure, the convex curved surface portion can be provided on the portion of the output side engaged portion that engages with the output side engaging portion so as to be convex toward the output side engaging portion, and the output side engaging portion can have a flat surface portion on the portion that engages with the output side engaged portion.

[0026] In the reverse input cutoff clutch according to one aspect of the present disclosure, the outer peripheral surface of the output side engaging portion can be composed of a partial cylindrical surface portion centered on the central axis of the output member, and the flat surface portion.

[0027] In one aspect of the reverse input cut-off clutch of the present disclosure, the convex curved surface portion can be provided at two locations on the radially inner surface of the input side engaged portion facing radially outward of the engaging element, which is the first direction, spaced apart in a second direction perpendicular to both the first direction and the axial direction of the pressed surface.

[0028] In one embodiment of the reverse input disconnection clutch of the present disclosure, the input side engaged portion can have a single partially cylindrical convex surface portion on the radially inner surface, and the convex curved surface portion can be provided at two positions on the convex surface portion that are spaced apart in the second direction.

[0029] In one aspect of the reverse input disconnection clutch of the present disclosure, the input side engaged portion can have a connecting surface portion that connects the two convex curved surface portions and is composed of a flat surface that is perpendicular to the first direction.

[0030] In one aspect of the reverse input cut-off clutch of the present disclosure, the convex curved surface portion can be provided at two locations on the output side engaged portion that are spaced apart in a second direction that is perpendicular to both the first direction and the axial direction of the pressed surface.

[0031] In one aspect of the reverse input disconnection clutch of the present disclosure, the output side engaged portion can be constituted by a single partial cylindrical surface, and the convex curved surface portion can be provided at two locations on the output side engaged portion that are spaced apart in the second direction.

[0032] In one aspect of the reverse input disconnection clutch of the present disclosure, the output side engaged portion can have a connecting surface portion that connects the two convex curved surface portions and is composed of a flat surface that is perpendicular to the first direction.

[0033] In the reverse input disconnecting clutch according to one aspect of the present disclosure, the engagement element may be a press-formed product made of a metal plate.

[0034] According to one aspect of the reverse input cut-off clutch of the present disclosure, it is possible to reduce the contact surface pressure at the contact portion between the input member and the engaging element, the contact portion between the output member and the engaging element, or both, while suppressing increases in manufacturing costs.

[0035] FIG. 1 is a cross-sectional view of a reverse input cutoff clutch according to a first embodiment of the present disclosure. FIG. 2 is a cross-sectional view taken along the line X-X of FIG. 1. FIG. 3 is a cross-sectional view taken along the line X-X of FIG. 1, showing a state in which a rotational torque is input to an input member, with a retaining member and a biasing member omitted. FIG. 4 is a cross-sectional view taken along the line X-X of FIG. 1, showing a state in which a rotational torque is input to an output member, with the retaining member and the biasing member omitted. FIG. 5 is a front view showing an engagement element of the reverse input cutoff clutch according to the first embodiment. FIG. 6 is a front view showing an engagement element of the reverse input cutoff clutch according to a second embodiment of the present disclosure. FIG. 7 is a front view showing an engagement element of the reverse input cutoff clutch according to a third embodiment of the present disclosure. FIG. 8 is a front view showing an engagement element of the reverse input cutoff clutch according to a fourth embodiment of the present disclosure. FIG. 9 is a front view showing an engagement element of the reverse input cutoff clutch according to a fifth embodiment of the present disclosure.

[0036] First Example A first example of an embodiment of the present disclosure will be described with reference to FIGS. 1 to 5. FIG.

[0037] In the following description, unless otherwise specified, the axial direction, radial direction, and circumferential direction refer to the axial direction, radial direction, and circumferential direction of the pressed surface 6. The axial direction, radial direction, and circumferential direction of the pressed surface 6 coincide with the axial direction, radial direction, and circumferential direction of the input member 3, and also coincide with the axial direction, radial direction, and circumferential direction of the output member 4. Furthermore, one axial side refers to the input member 3 side (the right side in FIG. 1), and the other axial side refers to the output member 4 side (the left side in FIG. 1).

[0038] The direction toward or away from the engaging element 5 or the pressing surface 34 of the engaging element 5 relative to the pressed surface 6 is defined as the first direction (the up-down direction in FIGS. 2 to 4), and the direction perpendicular to both the axial direction of the pressed surface 6 and the first direction is defined as the second direction (the left-right direction in FIGS. 2 to 4). With respect to the engaging element 5, the direction coinciding with the first direction is defined as its radial direction (the direction indicated by arrow α in FIG. 3), and the direction coinciding with the second direction is defined as its width direction (the direction indicated by arrow β in FIG. 3).

[0039] <Explanation of the Structure of the Reverse Input Cutoff Clutch> The reverse input cutoff clutch 1 includes a pressed member 2, an input member 3, an output member 4, and an engaging element 5. The reverse input cutoff clutch 1 transmits the rotational torque input to the input member 3 to the output member 4, while having a reverse input cutoff function that completely cuts off the rotational torque that is reversely input to the output member 4 and does not transmit it to the input member 3, or that transmits only a portion of the torque to the input member 3 and cuts off the remainder.

[0040] The pressed member 2 has a pressed surface 6 on its inner circumferential surface.

[0041] The pressed member 2 is supported and fixed to a portion that does not rotate even when the reverse input cutoff clutch 1 is in use, or is provided integrally with the fixed portion, so that its rotation is restricted.

[0042] The pressed surface 6 constitutes a surface that comes into contact with the pressing surface 34 of the engaging element 5 when the engaging element 5 moves radially outward, that is, in a direction approaching the pressed surface 6. The shape of the pressed member 2 is not limited as long as it is configured to have the pressed surface 6 on its inner circumferential surface. The pressed surface 6 has an annular shape when viewed in the axial direction, and in this example, has a cylindrical shape whose inner diameter does not change in the axial direction, although this is not limited to this.

[0043] The input-side engaging portion 13 of the input member 3 and the output-side engaging portion 21 of the output member 4 are disposed radially inside the pressed surface 6. The input-side engaging portion 13, the output-side engaging portion 21, and the engaging element 5 are rotatable radially inside the pressed surface 6.

[0044] In this example, the pressed member 2 comprises a housing element 7 .

[0045] The housing element 7 has an inner peripheral surface in the form of a stepped cylindrical surface. Specifically, the inner peripheral surface of the housing element 7 is formed by connecting a large-diameter cylindrical surface portion 8 on one axial side with a small-diameter cylindrical surface portion 9 on the other axial side by a connecting surface portion 10 facing one axial side. In this example, the large-diameter cylindrical surface portion 8 forms the pressed surface 6.

[0046] The housing element 7 has an inward flange portion 11 that protrudes radially inward at the other axial end of the small-diameter cylindrical surface portion 9, and has threaded holes 12 that open at multiple locations in the circumferential direction on the side surface on the other axial side. The pressed member 2 in this example is supported and fixed to the fixed portion by threading bolts that are inserted into through holes provided in the fixed portion into the threaded holes 12.

[0047] The pressed member 2 may also include another housing element that closes the opening on one axial side of the housing element 7. In this case, the pressed member 2 is configured by fitting (spigot fitting) the other housing element to the end on one axial side of the housing element 7 without any rattle, thereby positioning the housing element 7 and the other housing element in the radial direction, and then joining the housing element 7 and the other housing element to each other with joining members such as bolts.

[0048] The input member 3 has an input-side engaging portion 13 arranged radially inside the pressed surface 6 , and is arranged coaxially with the pressed surface 6 .

[0049] The input member 3 is connected to an input mechanism such as an electric motor, and receives rotational torque. Specifically, the input member 3 may be configured as an output shaft of the input mechanism, or may be configured as a separate member from the output shaft and fixed coaxially to the output shaft. Additionally, an input shaft portion 14 provided on the input member 3 may be rotatably supported relative to the fixed portion.

[0050] The input-side engaging portion 13 is provided at a portion radially outwardly displaced from the center of rotation of the input member 3, and has a portion that engages with, or more specifically, comes into contact with, the input-side engaged portion 35 of the engaging element 5. The input-side engaging portion 13 is configured so that, as the input member 3 or the engaging element 5 rotates, its radially inner surface 15 engages with, or comes into contact with, the radially inner surface of the input-side engaged portion.

[0051] Furthermore, the input side engaging portion 13 can have a flat surface portion 16 at a portion that engages with the input side engaged portion 35. The flat surface portion 16 can be provided only on the portion of the radial inner surface 15 of the input side engaging portion 13 that engages with the input side engaged portion 35, or can be provided on the entire radial inner surface 15 of the input side engaging portion 13. In this example, the flat surface portion 16 is provided on the entire radial inner surface 15 of the input side engaging portion 13.

[0052] The outer peripheral surface of the input side engaging portion 13 can have any configuration as long as it has a portion that engages with the input side engaged portion 35, but it is preferable that it is composed only of a flat surface portion 16 and a partial cylindrical surface portion 17 centered on the central axis of the input member 3.

[0053] In this example, the outer peripheral surface of the input-side engaging portion 13 is composed only of a flat surface portion 16 provided on the radially inner surface 15 and a partial cylindrical surface portion 17 provided on the radially outer surface 18. In other words, the input-side engaging portion 13 has an arched end face shape when viewed in the axial direction. The flat surface portion 16 and the partial cylindrical surface portion 17 are connected by a sharp ridge portion 19. However, the flat surface portion 16 and the partial cylindrical surface portion 17 may also be connected by a chamfered portion such as a corner chamfered portion or a rounded chamfered portion.

[0054] Therefore, when manufacturing the input member 3 having the input-side engaging portion 13, there is no need to perform cutting on the connection portion between the radially inner surface 15 and the radially outer surface 18 of the input-side engaging portion 13. For example, the input member 3 can be manufactured by forging a metal material to form its outer shape, and then performing finishing processes such as grinding as necessary. This reduces the manufacturing cost of the input member 3. However, the input member 3 can also be manufactured by performing machining, including cutting, on a metal material.

[0055] In this example, the input member 3 has an input shaft portion 14 and an input flange portion 20 in addition to the input side engaging portion 13 .

[0056] The input shaft portion 14 has a cylindrical shape.

[0057] The input flange portion 20 protrudes radially outward from the outer peripheral surface of the other axial end of the input shaft portion 14 over the entire circumference.

[0058] The input side engaging portion 13 protrudes toward the other axial side from a portion of the side surface of the input flange portion 20 that is radially outwardly spaced from the center of rotation.

[0059] The number of input side engaging portions 13 is determined according to the number of engaging elements 5 , and when the engaging elements 5 are made up of a plurality of engaging elements 5 , the input side engaging portion 13 is also made up of a plurality of input side engaging portions 13 .

[0060] In the reverse input cutoff clutch 1 of this example, the engaging elements 5 are configured by two engaging elements 5. Therefore, the input side engaging portion 13 is configured by two input side engaging portions 13 to match the number of engaging elements 5. The two input side engaging portions 13 are arranged at two radially opposite positions on the side surface on the other axial side of the input flange portion 20, and are spaced apart from each other in the radial direction of the input member 3.

[0061] The input member 3 can be rotatably supported relative to the pressed member 2 or the fixed portion. In this example, the input member 3 is rotatably supported inside the fixed portion by a radial bearing.

[0062] The output member 4 has an output-side engaging portion 21 that is arranged radially inward of the input-side engaging portion 13, and is arranged coaxially with the pressed surface 6. In other words, the output member 4 is also arranged coaxially with the input member 3.

[0063] The output member 4 is connected to an output mechanism such as a reduction gear mechanism, and is configured to output a rotational torque to the output mechanism as the output member 4 rotates. Specifically, the output member 4 may be configured as an input shaft of the output mechanism, or may be configured as a separate member from the input shaft and fixed coaxially to the input shaft.

[0064] The output side engaging portion 21 has a portion that engages with the output side engaged portion 36 of the engaging element 5, and this engaging portion is located radially inward of the input side engaging portion 13 and radially outward from the central axis of the output member 4, and is arranged in a position where it can engage with the output side engaged portion 36 of the engaging element 5. The output side engaging portion 21 is configured so that its outer circumferential surface engages with, i.e., comes into contact with, the output side engaged portion 36 as the output member 4 or the engaging element 5 rotates.

[0065] The output-side engaging portion 21 has a cam function. The distance from the rotational axis of the output member 4 to the outer circumferential surface of the output-side engaging portion 21, which is the portion that engages with the output-side engaged portion 36, is not constant in the circumferential direction.

[0066] The number of portions of the output-side engaging portion 21 that engage with the output-side engaged portions 36 is determined according to the number of engaging elements 5, and when the engaging elements 5 are made up of a plurality of engaging elements 5, the output-side engaging portion 21 is also configured to have a plurality of engaging portions. In this example, the output-side engaging portion 21 is configured to have portions that engage with two of the output-side engaged portions 36, matching the number of engaging elements 5. However, even when there is only one engaging element 5, it is possible to adopt a structure similar to this example.

[0067] The output side engaging portion 21 can have a flat surface portion 22 at a portion that engages with the output side engaged portion 36. In this example, the output side engaging portion 21 has the flat surface portion 22 at a portion of its outer circumferential surface that faces the output side engaged portion 36.

[0068] The outer peripheral surface of the output side engaging portion 21 can have any configuration as long as the output side engaging portion 21 has a cam function, but it is preferable that it is composed of a flat surface portion 22 and a partial cylindrical surface portion 23 centered on the central axis of the output member 4.

[0069] In this example, the outer peripheral surface of the output-side engaging portion 21 is composed of two flat surface portions 22 and two partial cylindrical surface portions 23 arranged parallel to each other. The output-side engaging portion 21 is plane-symmetric with respect to an imaginary plane that passes through the central axis of rotation of the output member 4 and is perpendicular to the two flat surface portions 22. Furthermore, the output-side engaging portion 21 is plane-symmetric with respect to an imaginary plane that passes through the central axis of rotation of the output member 4 and is parallel to the two flat surface portions 22. In other words, the output-side engaging portion 21 has a shape that is two-fold symmetric with respect to the central axis of the output member 4. The flat surface portions 22 and the partial cylindrical surface portions 23 are connected by a sharp ridge portion 24. However, the flat surface portions 22 and the partial cylindrical surface portions 23 may also be connected by a chamfered portion such as a corner chamfered portion or a rounded chamfered portion.

[0070] Therefore, when manufacturing the output member 4 having the output-side engaging portion 21, there is no need to perform cutting on the portion of the output-side engaging portion 21 that engages with the output-side engaged portion 36. For example, the output member 4 can be manufactured by forging a metal material to form its outer shape, and then performing finishing processes such as grinding as necessary. This reduces the manufacturing cost of the output member 4. However, the output member 4 can also be manufactured by performing machining, including cutting, on a metal material.

[0071] The output side engaging portion 21 is disposed radially inward of the two input side engaging portions 13 and between the output side engaged portions 36 of the two engaging elements 5 .

[0072] In this example, the output member 4 has an output shaft portion 25 , an output flange portion 26 , and a small diameter shaft portion 27 in addition to the output side engaging portion 21 .

[0073] The output shaft portion 25 has a stepped cylindrical shape.

[0074] The output flange portion 26 protrudes radially outward from the outer peripheral surface of one axial end of the output shaft portion 25 over the entire circumference.

[0075] The output side engaging portion 21 protrudes from the center of an end face on one axial side of the output shaft portion 25 toward one axial side.

[0076] The small diameter shaft portion 27 has a cylindrical shape and protrudes from the center of an end surface on one axial side of the output side engaging portion 21 toward one axial side.

[0077] The output member 4 can be rotatably supported on the pressed member 2 or the fixed portion. In this example, the output member 4 is rotatably supported radially inside the housing element 7 of the pressed member 2 by a radial rolling bearing 28. An outer ring 29 of the radial rolling bearing 28 is fitted securely into the small-diameter cylindrical surface portion 9 of the housing element 7, and is axially sandwiched between a side surface on one axial side of the inward flange portion 11 and a snap ring 30a engaged with one axial end of the small-diameter cylindrical surface portion 9. An inner ring 31 of the radial rolling bearing 28 is fitted securely onto the outer surface of one axial end of the output shaft portion 25, and is axially sandwiched between a side surface on the other axial side of the output flange portion 26 and a snap ring 30b engaged with the outer peripheral surface of an axially intermediate portion of the output shaft portion 25.

[0078] In the illustrated example, the radial rolling bearing 28 is configured as a ball bearing that uses balls as the rolling elements 32. However, the radial rolling bearing for supporting the output member 4 can also be configured as a tapered roller bearing that uses tapered rollers as the rolling elements or a roller bearing that uses cylindrical rollers.

[0079] Furthermore, the small diameter shaft portion 27 of the output member 4 is supported by a sliding bearing (also called a "sleeve bearing") 33 inside the input member 3 so as to be able to rotate freely relative to the input member 3 .

[0080] The engaging element 5 has a pressing surface 34 facing the pressed surface 6, an input side engaged portion 35 that can engage with the input side engaging portion 13, and an output side engaged portion 36 that can engage with the output side engaging portion 21, and is arranged so that the engaging element 5 can move radially (= first direction).

[0081] When rotational torque is input to the input member 3, the engaging element 5 moves radially away from the pressed surface 6 based on the input side engaging portion 13 engaging with the input side engaged portion 35, and transmits the rotational torque input to the input member 3 to the output member 4 by engaging the output side engaged portion 36 with the output side engaging portion 21, whereas when rotational torque is input in the reverse direction to the output member 4, the output side engaging portion 21 engages with the output side engaged portion 36, and presses the pressing surface 34 against the pressed surface 6, causing frictional engagement of the pressing surface 34 with the pressed surface 6.

[0082] The engaging element 5 has convex curved surface portions 37, 38 on at least one of the portion of the input side engaged portion 35 that engages with the input side engaging portion 13 and the portion of the output side engaged portion 36 that engages with the output side engaging portion 21.

[0083] That is, the engaging element 5 can have the convex curved surface portion 37 at a portion of the input-side engaged portion 35 that engages with the input-side engaging portion 13. Each input-side engaged portion 35 has portions that engage with two input-side engaging portions 13. Therefore, the input-side engaged portion 35 has the convex curved surface portion 37 at two locations.

[0084] Additionally or alternatively, the engaging element 5 may have a convex curved surface portion 38 at a portion of the output-side engaged portion 36 that engages with the output-side engaging portion 21. Each output-side engaged portion 36 has portions that engage with two output-side engaging portions 21. Therefore, the output-side engaged portion 36 has convex curved surface portions 38 at two locations.

[0085] In this example, the engaging element 5 has a convex curved surface 37 at the portion of the input side engaged portion 35 that engages with the input side engaging portion 13, and a convex curved surface 38 at the portion of the output side engaged portion 36 that engages with the output side engaging portion 21. Therefore, with the reverse input cutoff clutch 1 of this example, the contact surface pressure at the contact portions between the engaging element 5 and both the input member 3 and the output member 4 can be kept low.

[0086] The pressing surface 34 is provided on the radially outer surface of the engaging element 5 that faces the pressed surface 6. In this example, the pressing surface 34 is composed of two pressing surfaces 34 provided at two positions spaced apart from each other in the circumferential direction on the radially outer surface of the engaging element 5. Each pressing surface 34 is composed of a partially cylindrical convex curved surface having a radius of curvature smaller than the radius of curvature of the pressed surface 6.

[0087] When viewed from the axial direction, the portion of the radially outer surface of the engaging element 5 that is circumferentially offset from the two pressing surfaces 34 is located radially inward of an imaginary circle that is centered on the central axis of the input member 3 and that is tangent to the two pressing surfaces 34. In other words, when the two pressing surfaces 34 are in contact with the pressed surface 6, the portion that is circumferentially offset from the two pressing surfaces 34 does not come into contact with the pressed surface 6.

[0088] The pressing surface 34 preferably has a surface property that has a higher coefficient of friction with the pressed surface 6 than the other parts of the engaging element 5. The pressing surface 34 may be formed integrally with the other parts of the engaging element 5, or may be formed by the surface of a friction material fixed to the other parts of the engaging element 5 by sticking, bonding, or the like.

[0089] In this example, the input-side engaged portion 35 is provided in a radially (i.e., first direction) intermediate portion of the widthwise center portion of the engaging element 5. More specifically, although not limited thereto, the input-side engaged portion 35 has a substantially arch-shaped opening when viewed in the axial direction, and is configured as a through-hole that axially passes through a radially intermediate portion at the widthwise (i.e., second direction) center position of the engaging element 5.

[0090] The input-side engaged portion 35 has a size that allows the input-side engaging portion 13 to be loosely inserted therein. Therefore, with the input-side engaging portion 13 inserted inside the input-side engaged portion 35, there is a gap between the input-side engaging portion 13 and the inner surface of the input-side engaged portion 35 in both the width direction and the radial direction of the engaging element 5. Therefore, the input-side engaging portion 13 is displaceable relative to the input-side engaged portion 35 in the rotational direction of the input member 3, and the input-side engaged portion 35 is displaceable relative to the input-side engaging portion 13 in the radial direction of the engaging element 5 (= the first direction).

[0091] The convex curved surface portion 37 is provided on a radially inner surface 39 of the inner surface of the input-side engaged portion 35, which faces outward in the radial direction (=first direction), at a portion that engages with the input-side engaging portion 13, so as to be convex toward the input-side engaging portion 13. The convex curved surface portion 37 is provided at two positions: a portion of the radially inner surface 39 that engages with the input-side engaging portion 13 when the input member 3 rotates to one side relative to the engaging element 5, and a portion of the radially inner surface 39 that engages with the input-side engaging portion 13 when the input member 3 rotates to the other side relative to the engaging element 5.

[0092] Specifically, a convex surface portion 40 is provided in the widthwise (= second direction) middle portion of the radial inner surface 39 of the input side engaged portion 35, protruding radially outward more than the adjacent portions on both sides in the widthwise direction, and convex curved surface portions 37 are provided at two widthwise positions of the convex surface portion 40, respectively.

[0093] In this example, the convex curved surface portions 37 are provided at both widthwise end portions of the convex surface portion 40. The convex surface portion 40 also has a connecting surface portion 50 in the widthwise intermediate portion between the two convex curved surface portions 37, which connects the two convex curved surface portions 37 and is formed of a flat surface perpendicular to the radial direction.

[0094] The cross-sectional shape, curvature radius, etc. of the convex curved surface portion 37 are not particularly limited as long as they can prevent excessive contact surface pressure at the contact portion with the input-side engaging portion 13. For example, the cross-sectional shape of the convex curved surface portion 37 may be a substantially arc shape, a substantially ellipse shape, etc. The cross-sectional shape, curvature radius, etc. of the convex curved surface portion 37 can be determined by experiments, simulations, etc.

[0095] In this example, the radially outer surface 41 of the inner surface of the input-side engaged portion 35, which faces radially inward, is configured as a curved surface having a substantially arc-shaped contour when viewed from the axial direction or a compound surface having a substantially V-shaped contour. The circumferential side surface 42 connecting the radially inner surface 39 and the radially outer surface 41 is configured as a concave curved surface having a partially cylindrical shape.

[0096] The output-side engaged portion 36 is provided at the center in the width direction (= second direction) of the radially inner surface (= first direction) of the engaging element 5. The shape of the output-side engaged portion 36 is not limited as long as it is configured to be able to engage with the output-side engaging portion 21. In this example, the output-side engaged portion 36 is provided at the center in the width direction of the radially inner surface of the engaging element 5 so as to protrude radially inward beyond the portions adjacent to it on both sides in the width direction.

[0097] The convex curved surface portion 38 is provided at two positions: a portion of the output side engaged portion 36 that engages with the output side engaging portion 21 when the output member 4 rotates to one side, and a portion of the output side engaged portion 36 that engages with the output side engaging portion 21 when the output member 4 rotates to the other side relative to the engager 5, so as to be convex toward the output side engaging portion 21.

[0098] In this example, the convex curved surface portions 38 are provided at both ends in the width direction (= second direction) of the output-side engaged portion 36. The output-side engaged portion 36 also has a connecting surface portion 51 in the width direction intermediate between the two convex curved surface portions 38, which connects the two convex curved surface portions 38 and is formed of a flat surface perpendicular to the radial direction.

[0099] The cross-sectional shape, curvature radius, etc. of the convex curved surface portion 38 are not particularly limited as long as they can prevent excessive contact surface pressure at the contact portion with the output-side engaging portion 21. For example, the cross-sectional shape of the convex curved surface portion 38 may be a substantially arc shape, a substantially ellipse shape, etc. The cross-sectional shape, curvature radius, etc. of the convex curved surface portion 38 can be determined by experiments, simulations, etc.

[0100] The method for manufacturing the engaging element 5 is not particularly limited, and any method can be used. For example, the engaging element 5 can be made by stamping a metal plate with a press. Alternatively, the engaging element 5 can be made by subjecting a metal material to sintering, forging, casting, cutting, or a combination of these processes.

[0101] In this example, the engaging element 5 is made by stamping a metal plate using a press, i.e., the engaging element 5 is a press-formed product of a metal plate.

[0102] In this example, the engaging element 5 is provided with convex curved surface portions 37, 38 for reducing the contact surface pressure at the contact portions between the input member 3 and the output member 4 and the engaging element 5. Therefore, the manufacturing cost can be reduced compared to when the contact portions between the input member 3 and the output member 4 and the engaging element 5 are provided with convex curved surface portions by cutting.

[0103] In this example, the distance between the two convex curved surface portions 37 of the input-side engaged portion 35 in the width direction (= second direction) of the engaging element 5 is greater than the distance between the two convex curved surface portions 38 of the output-side engaged portion 36 in the width direction (= second direction) of the engaging element 5. Therefore, when the two pressing surfaces 34 are pressed against the pressed surface 6 as the output member 4 rotates in a predetermined direction, and the input-side engaging portion 13 and the input-side engaged portion 35 are engaged as the input member 3 rotates in the direction opposite to the predetermined direction, the distance between the contact portion between the input-side engaging portion 13 and the convex curved surface portion 37 of the input-side engaged portion 35 in the width direction (= second direction) of the engaging element 5 and the center of rotation of the input member 3 is greater than the distance between the contact portion between the output-side engaging portion 21 and the convex curved surface portion 38 of the output-side engaged portion 36 in the width direction (= second direction) of the engaging element 5 and the center of rotation of the output member 4.

[0104] Furthermore, in this example, when a rotational torque is input in reverse to the output member 4 and the two pressing surfaces 34 are in contact with the pressed surface 6, the contact portion between the output side engaging portion 21 and the output side engaged portion 36 (convex curved surface portion 38) is located closer to the center of rotation of the output member 4 in the radial direction (= first direction) of the engaging element 5 than the virtual line connecting the abutment portion between the pressing surface 34 and the pressed surface 6 of one of the two pressing surfaces 34 in the circumferential direction (the side closer to the contact portion between the output side engaging portion 21 and the output side engaged portion 36 than the center of rotation of the output member 4 in the width direction (= second direction) of the engaging element 5).

[0105] Therefore, according to the reverse input cutoff clutch 1 of this example, good locking performance can be ensured for the same reasons as the reverse input cutoff clutch described in WO 2023 / 085395.

[0106] The reverse input disconnecting clutch 1 of this example further includes a biasing member 43 and a holding member 44 as optional components.

[0107] The biasing members 43 elastically bias the engaging elements 5 in a direction that brings them closer to the pressed surface 6. The biasing members 43 can be made of springs such as leaf springs, coil springs, or disc springs, or elastic materials such as rubber, elastomer, or synthetic resin. The number of biasing members 43 is not particularly limited and is determined appropriately depending on the number of engaging elements 5.

[0108] In this example, the biasing member 43 is configured by two biasing members 43 arranged at two positions in the width direction between the radially inner surfaces of the two engaging members 5, and each biasing member 43 is configured by a compression coil spring. Each biasing member 43 is fitted and held in a holding hole 47 of the holding member 44, thereby preventing it from falling out from the portion between the two engaging members 5.

[0109] The two biasing members 43 elastically bias the two engaging elements 5 in a direction that brings them closer to the pressed surface 6 by the force that attempts to elastically restore the original shape. As a result, in a neutral state in which no torque is applied to either the input member 3 or the output member 4, the pressing surfaces 34 of the two engaging elements 5 are in contact with the pressed surface 6.

[0110] The retaining member 44 comprises a first spacer portion 45 and a second spacer portion 46 arranged axially spaced apart, and two connection portions 48 arranged on either side of the first spacer portion 45 and the second spacer portion 46 in the second direction, each connecting the first spacer portion 45 and the second spacer portion 46, and each having a retaining hole 47 extending in the first direction.

[0111] The retaining member 44 is attached to the output member 4 with the engaging element 5 disposed between the first spacer portion 45 and the second spacer portion 46 in the axial direction, thereby restricting axial movement of the engaging element 5 relative to the output member 4. Specifically, a retaining ring 49 engaged with the small diameter shaft portion 27 of the output member 4 restricts movement of the retaining member 44 to one axial side, and the side surface of the other axial side of the second spacer portion 46 abuts or faces closely against the end face of the output shaft portion 25 on one axial side, thereby restricting movement of the retaining member 44 to the other axial side.

[0112] <Explanation of Operation of Reverse Input Cutoff Clutch> The operation of the reverse input cutoff clutch 1 of this example will be described with reference to Figures 3 and 4. Note that Figures 3 and 4 omit the biasing member 43 and the holding member 44, and exaggerate the radial gaps between the input member 3 and the output member 4 and the two engaging elements 5.

[0113] When a rotational torque is input to the input member 3, the two engaging elements 5 move in a direction away from the pressed surface 6, regardless of the rotational direction of the input member 3. More specifically, as shown in Figure 3, the input-side engaging portion 13 rotates inside the input-side engaged portion 35 in the rotational direction of the input member 3 (counterclockwise in the example of Figure 3).

[0114] This reduces the gap between the radial inner surface 15 of the input side engaging portion 13 and the radial inner surface 39 of the input side engaged portion 35, and brings the radial inner surface 15 of the input side engaging portion 13 into contact with the radial inner surface 39 of the input side engaged portion 35.

[0115] In this example, the radially inner surface 15 of the input side engaging portion 13 is brought into contact with one of the two convex curved surface portions 37 provided on the input side engaged portion 35 .

[0116] When the input member 3 rotates further from this state, one of the convex curved surfaces 37 is pressed radially inward by the radially inner surface 15 of the input-side engaging portion 13, and the engaging element 5 moves in a direction away from the pressed surface 6. That is, the two engaging elements 5 move radially inward, that is, toward each other, based on their engagement with the input member 3, and the radially inner surfaces of the two engaging elements 5 approach each other, and the output-side engaging portion 21 of the output member 4 is sandwiched from both radial sides by the output-side engaged portions 36 of the two engaging elements 5.

[0117] In this way, while the output member 4 is rotated so that the flat surface 22 of the output side engaging portion 21 is parallel to the connection surface 51 of the output side engaged portion 36, the output side engaging portion 21 and the output side engaged portion 36 of the engaging element 5 are engaged without rattle. As a result, the rotational torque input to the input member 3 is transmitted to the output member 4 via the two engaging elements 5 and is output from the output member 4.

[0118] When a rotational torque is input in reverse to the output member 4, the two engaging elements 5 move in a direction approaching the pressed surface 6, regardless of the rotational direction of the output member 4. Specifically, as shown in Fig. 4 , the output-side engaging portion 21 rotates in the rotational direction of the output member 4 (clockwise in the example of Fig. 4 ) inside the output-side engaged portions 36 of the two engaging elements 5. The flat surface portion 22 of the outer circumferential surface of the output-side engaging portion 21 presses the output-side engaged portions 36 radially outward, and the two engaging elements 5 move in a direction approaching the pressed surface 6.

[0119] That is, based on engagement with the output member 4, the two engaging elements 5 move radially outward, that is, away from each other, and the pressing surfaces 34 of the two engaging elements 5 come into contact with the pressed surface 6 and frictionally engage with the pressed surface 6.

[0120] As a result, the rotational torque input inversely to the output member 4 is completely blocked and not transmitted to the input member 3, or only a portion of the rotational torque input inversely to the output member 4 is transmitted to the input member 3 and the remainder is blocked.

[0121] In order to completely block the rotational torque input in reverse to the output member 4 and prevent it from being transmitted to the input member 3, the pressing surface 34 of the engaging element 5 slides against the pressed surface 6, and the engaging element 5 is stretched or clamped between the output side engaging portion 21 and the pressed member 2 so that the engaging element 5 and the pressed member 2 do not rotate relative to each other, thereby locking the output member 4.

[0122] In order to transmit only a portion of the rotational torque input inversely to the output member 4 to the input member 3 and block the remainder, the engaging element 5 is stretched or clamped between the output side engaging portion 21 and the pressed member 2 so that the pressing surface 34 of the engaging element 5 slides against the pressed surface 6, thereby semi-locking the output member 4.

[0123] In the reverse input cutoff clutch 1 of this example, the size of the gap between each component is adjusted to enable the above operation. In particular, when the pressing surfaces 34 of the two engaging elements 5 are in contact with the pressed surfaces 6, a gap is set to exist between the radially inner surface 15 of the input-side engaging portion 13 and the convex surface 40 of the input-side engaged portion 35.

[0124] This prevents the input side engaging portion 13 from blocking the radially outward movement of the engaging element 5 when a rotational torque is input in reverse to the output member 4, and even after the pressing surface 34 comes into contact with the pressed surface 6, the surface pressure acting on the contact point between the pressing surface 34 and the pressed surface 6 changes depending on the magnitude of the rotational torque input in reverse to the output member 4, ensuring that the output member 4 is locked or semi-locked appropriately.

[0125] Second Example A second example of the embodiment of the present disclosure will be described with reference to FIG.

[0126] In the engaging element 5a of this example, the widthwise dimension of the convex surface portion 40a provided in the middle portion of the engaging element 5a in the widthwise direction (= second direction) of the radially (= first direction) inner surface of the input side engaged portion 35 is smaller than the widthwise dimension of the convex surface portion 40 of the engaging element 5 of the first example. When such an engaging element 5a is incorporated into the reverse input cut-off clutch 1, as the output member 4 rotates in a predetermined direction, the two pressing surfaces 34 are pressed against the pressed surface 6, and as the input member 3 rotates in the direction opposite to the predetermined direction, the input side engaging portion 13 and the input side engaged portion 35 are engaged, and the distance between the contact point between the input side engaging portion 13 and the convex curved surface portion 37 of the input side engaged portion 35 in the width direction of the engaging element 5a (= second direction) and the center of rotation of the input member 3 becomes smaller than the distance between the contact point between the output side engaging portion 21 and the convex curved surface portion 38 of the output side engaged portion 36 in the width direction of the engaging element 5a (= second direction) and the center of rotation of the output member 4.

[0127] Therefore, according to the reverse input cut-off clutch 1 incorporating the engaging element 5a of this example, it is possible to ensure good torque transmission efficiency for the same reasons as the reverse input cut-off clutch described in International Publication No. 2023 / 085217.

[0128] The other configurations and effects of the second example are the same as those of the first example.

[0129] Third Example A third example of the embodiment of the present disclosure will be described with reference to FIG.

[0130] In this example, the engaging element 5b has a convex curved surface 38 at a portion of the output-side engaged portion 36 that engages with the output-side engaging portion 21, whereas the input-side engaged portion 35 does not have a convex curved surface at a portion that engages with the input-side engaging portion 13. Specifically, the entire radially inner surface 39a of the input-side engaged portion 35, including the portion that engages with the input-side engaging portion 13, is configured as a flat surface that is perpendicular to the radial direction (= first direction) of the engaging element 5b.

[0131] Therefore, when the engaging element 5b is incorporated into the reverse input cut-off clutch 1 and used, it is preferable to provide a convex curved surface portion on the portion of the input side engaging portion 13 of the input member 3 that engages with the input side engaged portion 35.

[0132] In this example, the engaging element 5 b is provided with a convex curved surface 38 for reducing the contact surface pressure at the contact portion between the output member 4 and the engaging element 5 b. Therefore, the manufacturing cost can be reduced compared to when a convex curved surface is provided by cutting the contact portion of the output member 4 with the engaging element 5 b.

[0133] The configuration and effects of other parts of the third example are the same as those of the first example.

[0134] Fourth Example A fourth example of the embodiment of the present disclosure will be described with reference to FIG.

[0135] In this example, the engaging element 5c has a convex curved surface portion 37 at a portion of the input-side engaged portion 35 that engages with the input-side engaging portion 13, whereas the output-side engaged portion 36a does not have a convex curved surface portion at a portion that engages with the output-side engaging portion 21. Specifically, the entire radially inner surface of the engaging element 5c, including the output-side engaged portion 36a, is formed by a flat surface that is perpendicular to the radial direction (= first direction) of the engaging element 5c.

[0136] Therefore, when the engaging element 5c is incorporated into the reverse input cutoff clutch 1, it is preferable to provide a convex curved surface portion on the portion of the output side engaging portion 21 of the output member 4 that engages with the output side engaged portion 36a.

[0137] In this example, the engaging element 5c is provided with a convex curved surface 37 for reducing the contact surface pressure at the contact portion between the input member 3 and the engaging element 5b. Therefore, the manufacturing cost can be reduced compared to when a convex curved surface is provided by performing cutting work on the contact portion of the input member 3 with the engaging element 5c.

[0138] The remaining configurations and effects of the fourth example are the same as those of the first example.

[0139] Fifth Example A fifth example of the embodiment of the present disclosure will be described with reference to FIG.

[0140] In the present example, the engaging element 5d has a partially cylindrical convex surface 40b that protrudes radially outward (i.e., in the first direction) beyond adjacent portions on both sides in the width direction of the engaging element 5d on the radially inner surface 39b of the input-side engaged portion 35 at a widthwise (i.e., second) intermediate portion of the engaging element 5d. The convex surface 40b has a contour shape that is a single arc when viewed from the axial direction. The convex curved surface portions 37a of the input-side engaged portion 35 that engage with the input-side engaging portion 13 are provided at two widthwise positions on the convex surface 40b.

[0141] The output-side engaged portion 36b is formed of a partially cylindrical surface. When viewed from the axial direction, the output-side engaged portion 36b has a contour shape that is a single arc. Convex curved surface portions 38a that engage with the output-side engaging portion 21 are provided at two locations in the width direction of the output-side engaged portion 36b.

[0142] The remaining configurations and effects of the fifth example are the same as those of the first example.

[0143] The first to fifth examples of the embodiment of the present disclosure can be implemented in any suitable combination as long as no contradiction occurs.

[0144] REFERENCE SIGNS LIST 1 reverse input cutoff clutch 2 pressed member 3 input member 4 output member 5, 5a, 5b, 5c, 5d engagement element 6 pressed surface 7 housing element 8 large diameter cylindrical surface portion 9 small diameter cylindrical surface portion 10 connection surface portion 11 inward flange portion 12 threaded hole 13 input side engagement portion 14 input shaft portion 15 radially inner surface 16 flat surface portion 17 partial cylindrical surface portion 18 radially outer surface portion 19 ridge portion 20 input flange portion 21 output side engagement portion 22 flat surface portion 23 partial cylindrical surface portion 24 ridge portion 25 output shaft portion 26 output flange portion 27 small diameter shaft portion 28 radial rolling bearing 29 outer ring 30a, 30b retaining ring 31 inner ring 32 rolling element 33 sliding bearing 34 pressing surface 35 Input side engaged portion 36, 36a, 36b Output side engaged portion 37, 37a, 37b Convex curved surface portion 38, 38a, 38b Convex curved surface portion 39 Radial inner surface 40 Convex surface portion 41 Radial outer surface 42 Circumferential side surface 43 Urging member 44 Retaining member 45 First spacer portion 46 Second spacer portion 47 Retaining hole 48 Connection portion 49 Retaining ring 50 Connection surface portion 51 Connection surface portion

Claims

1. A pressed member having a pressed surface on its inner circumferential surface; an input member having an input side engaging portion arranged radially inward of the pressed surface and arranged coaxially with the pressed surface; an output member having an output side engaging portion arranged radially inward of the input side engaging portion and arranged coaxially with the pressed surface; and an engager having a pressing surface facing the pressed surface, an input side engaged portion engageable with the input side engaging portion, and an output side engaged portion engageable with the output side engaging portion, and arranged to be movable in a first direction which is a direction towards or away from the pressed surface, a reverse input cut-off clutch, wherein when a rotational torque is input to the input member, the input side engaging portion engages with the input side engaged portion, and the engaging element moves in a direction away from the pressed surface in the first direction, thereby engaging the output side engaged portion with the output side engaging portion, thereby transmitting the rotational torque input to the input member to the output member, whereas when a rotational torque is input in reverse to the output member, the output side engaging portion engages with the output side engaged portion, and the pressing surface is pressed against the pressed surface, thereby frictionally engaging the pressing surface with the pressed surface, and the engaging element has a convex curved surface on at least one of a portion of the input side engaged portion that engages with the input side engaging portion and a portion of the output side engaged portion that engages with the output side engaging portion.

2. A reverse input cutoff clutch as set forth in claim 1, wherein the convex curved surface portion is provided on the portion of the input side engaged portion that engages with the input side engaging portion so as to be convex toward the input side engaging portion, and the input side engaging portion has a flat surface portion on the portion that engages with the input side engaged portion.

3. A reverse input cutoff clutch as set forth in claim 2, wherein the outer peripheral surface of the input side engaging portion is composed of a partially cylindrical surface portion centered on the central axis of the input member and the flat surface portion.

4. A reverse input cut-off clutch as set forth in any one of claims 1 to 3, wherein the convex curved surface portion is provided on the portion of the output side engaged portion that engages with the output side engaging portion so as to be convex toward the output side engaging portion, and the output side engaging portion has a flat surface portion on the portion that engages with the output side engaged portion.

5. A reverse input cutoff clutch as set forth in claim 4, wherein the outer peripheral surface of said output side engaging portion is composed of a partially cylindrical surface portion centered on the central axis of said output member and said flat surface portion.

6. A reverse input cutoff clutch as set forth in any one of claims 1 to 5, wherein the convex curved surface portions are provided at two locations on the radially inner surface of the input side engaged portion that faces radially outward of the engaging element, which is the first direction, and that are spaced apart in a second direction that is perpendicular to both the first direction and the axial direction of the pressed surface.

7. A reverse input cutoff clutch as described in claim 6, wherein the input side engaged portion has a single partially cylindrical convex surface portion on the radially inner surface, and the convex curved surface portion is provided at two positions on the convex surface portion that are spaced apart in the second direction.

8. A reverse input cutoff clutch as described in claim 6 or 7, wherein the input side engaged portion has a connecting surface portion that connects the two convex curved surface portions and is composed of a flat surface that is perpendicular to the first direction.

9. A reverse input cutoff clutch as set forth in any one of claims 1 to 5, wherein the convex curved surface portion is provided at two positions on the output side engaged portion that are spaced apart in a second direction that is perpendicular to both the first direction and the axial direction of the pressed surface.

10. A reverse input cutoff clutch as set forth in any one of claims 6 to 8, wherein the convex curved surface portion is provided at two positions on the output side engaged portion that are spaced apart in the second direction.

11. A reverse input cut-off clutch as described in claim 9 or 10, wherein the output side engaged portion is configured by a single partial cylindrical surface, and the convex curved surface portion is provided at two locations on the output side engaged portion that are spaced apart in the second direction.

12. A reverse input cutoff clutch as described in any one of claims 9 to 11, wherein the output side engaged portion has a connecting surface portion that connects the two convex curved surface portions and is composed of a flat surface that is perpendicular to the first direction.

13. A reverse input cutoff clutch according to any one of claims 1 to 12, wherein the engaging element is a press-molded part made of a metal plate.

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