Reverse input blocking clutch

Abstract

Provided is a reverse input blocking clutch capable of properly maintaining pressing forces exerted by two pressing surfaces of an engagement element against a pressed surface of a pressed member. In a cross section orthogonal to the center axis O of the pressed surface 6, with the two pressing surfaces 32 being in contact with the pressed surface 6, an inclination angle α of each imaginary straight line L is from 10° to 40°. The inclination angle α is an angle formed between the imaginary straight line L and the width direction of the engagement element 5 orthogonal to both the center axis O of the pressed surface 6 and the radial direction of the engagement element 5. The imaginary straight lines L connect the center axis O of the pressed surface 6 and respective contact portions X between the corresponding pressing surfaces 32 and the pressed surface 6.

Description

Reverse Input Blocking Clutch

[0001] The present disclosure relates to a reverse input blocking clutch that transmits the rotational torque input to an input member to an output member, while blocking the rotational torque reversely input to the output member.

[0002] The reverse input blocking clutch transmits the rotational torque input to an input member connected to an input side mechanism such as a drive source to an output member connected to an output side mechanism such as a reduction mechanism, while completely blocking the rotational torque reversely input to the output member from being transmitted to the input member, or having a function of transmitting only a part of it to the input member and blocking the remainder.

[0003] Depending on the difference in the mechanism for blocking the rotational torque reversely input to the output member, the reverse input blocking clutch includes a lock-type reverse input blocking clutch provided with a mechanism for preventing the rotation of the output member when a rotational torque is reversely input to the output member, and a free-type reverse input blocking clutch provided with a mechanism for idling the output member when a rotational torque is reversely input to the output member. Which of the lock-type reverse input blocking clutch and the free-type reverse input blocking clutch to use is appropriately determined according to the application of the device incorporating the reverse input blocking clutch and the like.

[0004] In the lock-type reverse input blocking clutch described in International Publication No. 2019 / 026794 pamphlet, when a rotational torque is input to the input member, based on the engagement of the input-side engaging portion of the input member with the input-side engaged portion of the engaging element, the engaging element moves in a direction away from the pressed surface of the pressed member, and the output-side rotational torque input to the input member is transmitted to the output member by engaging the output-side engaged portion of the engaging element with the output-side engaging portion of the output member. On the other hand, when a rotational torque is reversely input to the output member, based on the engagement of the output-side engaging portion with the output-side engaged portion, the engaging element moves in a direction approaching the pressed surface, and the two pressing surfaces of the engaging element are pressed against the pressed surface to frictionally engage the two pressing surfaces with the pressed surface.

[0005] International Publication No. 2019 / 026794 pamphlet

[0006] In the conventional reverse input blocking clutch described in International Publication No. 2019 / 026794, the pressing force between the two pressing surfaces of the engaging element against the pressed surface of the pressed member becomes excessively large, making it impossible to smoothly switch the reverse input blocking clutch from the locked or semi-locked state to the unlocked or semi-unlocked state. Alternatively, when rotational torque is being input in reverse to the output member, if a rotational torque in the same direction as the rotational torque being input in reverse to the output member is input to the input member, a phenomenon called "chasing lock phenomenon" occurs in which the input member and the output member rotate intermittently, repeatedly switching between the locked or semi-locked state and the unlocked or semi-unlocked state in a short period of time. Alternatively, the pressing force becomes excessively small, and it may not be possible to sufficiently block the rotational torque being input in reverse to the output member when the reverse input blocking clutch is in the locked or semi-locked state.

[0007] The present disclosure aims to provide a reverse input blocking clutch that can appropriately ensure the pressing force of the two pressing surfaces of the engaging element against the pressed surface of the pressed member.

[0008] A reverse input blocking clutch according to one aspect of the present disclosure comprises a pressed member, an input member, an output member, and an engaging element.

[0009] The member to be pressed has a surface to be pressed on its inner circumferential surface.

[0010] The input member has an input-side engaging portion located radially inward of the pressed surface and is arranged coaxially with the pressed surface.

[0011] The output member has an output-side engaging portion that is located radially inward from the input-side engaging portion and is arranged coaxially with the pressed surface.

[0012] The engaging element has two pressing surfaces facing the pressed surface and spaced apart from each other in the circumferential direction, 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 to be movable in the radial direction.

[0013] When rotational torque is input to the input member, the engaging element moves radially away from the pressed surface based on the input-side engaging portion engaging with the input-side engaged portion, thereby engaging the output-side engaged portion with the output-side engaging portion and transmitting the rotational torque input to the input member to the output member. Conversely, when rotational torque is input in reverse to the output member, the engaging element presses the two pressing surfaces against the pressed surface based on the output-side engaging portion engaging with the output-side engaged portion, causing the two pressing surfaces to frictionally engage with the pressed surface.

[0014] In a cross-section perpendicular to the central axis of the pressed surface, with the two pressing surfaces in contact with the pressed surface, the inclination angle α of the imaginary straight line connecting the contact portion between each of the two pressing surfaces and the pressed surface and the central axis of the pressed surface, with respect to the width direction of the engaging element which is perpendicular to both the central axis of the pressed surface and the radial direction of the engaging element, is 10° or more and 40° or less.

[0015] In a reverse input blocking clutch according to one aspect of the present disclosure, the inclination angle α is 15° or more and less than 25°.

[0016] In a reverse input blocking clutch according to one aspect of the present disclosure, both end faces of the engaging element in the width direction are configured with planar portions perpendicular to the width direction.

[0017] In a reverse input shutoff clutch according to one aspect of the present disclosure, the engaging element has a convex curved surface portion on at least one of the portions 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.

[0018] According to one embodiment of the reverse input blocking clutch of the present disclosure, the pressing force of the two pressing surfaces of the engaging element against the pressed surface of the pressed member can be appropriately ensured.

[0019] Figure 1 is a cross-sectional view showing a reverse input blocking clutch according to one embodiment of the present disclosure. Figure 2 is a cross-sectional view taken along line I-I of Figure 1. Figure 3 is a cross-sectional view taken along line I-I of Figure 1, showing the state in which rotational torque is input to the input member, with the holding member and biasing member omitted. Figure 4 is a cross-sectional view taken along line I-I of Figure 1, showing the state in which rotational torque is reverse input to the output member, with the holding member and biasing member omitted. Figure 5 is a front view showing the engaging element removed. Figure 6 is a schematic diagram for explaining the restricting range of the circumferential position of the contact portion of the two pressing surfaces with respect to the pressed surface. Figure 7 is a diagram of curve C1 representing the amplification factor 1 / (2・sinα) of the pressing force f, and curve C2 representing the rate of change of the amplification factor. Figure 8 is a diagram showing the relationship between the error of the inclination angle α from the design value and the rate of change of the amplification factor 1 / (2・sinα) of the pressing force f, for each design value of the inclination angle α.

[0020] A reverse input interruption clutch according to one embodiment of the present disclosure will be described with reference to Figures 1 to 8.

[0021] <Structure of the reverse input blocking clutch> The reverse input blocking clutch 1 comprises a pressed member 2, an input member 3, an output member 4, and an engaging element 5. The reverse input blocking clutch 1 transmits the rotational torque input to the input member 3 to the output member 4, while the reverse input blocking function either completely blocks the rotational torque that is reverse input to the output member 4 and does not transmit it to the input member 3, or transmits only a portion of it to the input member 3 and blocks the rest.

[0022] In the following description, unless otherwise specified, the axial, radial, and circumferential directions refer to the axial, radial, and circumferential directions of the pressed surface 6 of the pressed member 2. The axial, radial, and circumferential directions of the pressed surface 6 coincide with the axial, radial, and circumferential directions of the input member 3, and also coincide with the axial, radial, and circumferential directions of the output member 4. Furthermore, one axial side refers to the input member 3 side (right side in Figure 1), and the other axial side refers to the output member 4 side (left side in Figure 1).

[0023] The direction of the engaging element 5 relative to the pressed surface 6 is defined as the first direction (up and down direction in Figures 2 to 6), and the direction perpendicular to both the axial direction of the pressed surface 6 and the first direction is defined as the second direction (left and right direction in Figures 2 to 6). With respect to the engaging element 5, the direction coinciding with the first direction is defined as its radial direction (direction indicated by arrow A in Figure 3), and the direction coinciding with the second direction is defined as its width direction (direction indicated by arrow B in Figure 3). Furthermore, with respect to the width direction of the engaging element 5, the inside refers to the center side of the engaging element 5 in the width direction, and the outside refers to both sides of the engaging element 5 in the width direction.

[0024] (Pressed member) The pressed member 2 has a pressed surface 6 on its inner circumferential surface.

[0025] The pressed member 2 is supported and fixed to a stationary part that does not rotate even when the reverse input blocking clutch 1 is in use, or it is integrally provided with the stationary part so that its rotation is restrained.

[0026] The pressed surface 6 constitutes the surface that contacts the two pressing surfaces 32 of the engaging element 5 when the engaging element 5 moves radially outward, which is the direction towards 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 is annular when viewed from the axial direction. Furthermore, although not limited to this, in this example the pressed surface 6 has a cylindrical shape in which the inner diameter does not change with respect to the axial direction.

[0027] The input-side engaging portion 13 of the input member 3 and the output-side engaging portion 19 of the output member 4 are positioned radially inward of the pressed surface 6. The input-side engaging portion 13, the output-side engaging portion 19, and the engaging element 5 are rotatable radially inward of the pressed surface 6.

[0028] When the pressed member 2 is supported and fixed to the stationary portion, known means can be used. In this example, the pressed member 2 includes a housing element 7 as an optional element supported and fixed to the stationary portion.

[0029] The housing element 7 has a stepped cylindrical inner surface. Specifically, the inner surface of the housing element 7 is formed by connecting a large-diameter cylindrical surface portion 8 on one axial side and a small-diameter cylindrical surface portion 9 on the other axial side with a connecting surface portion 10 facing one axial side. In this example, the large-diameter cylindrical surface portion 8 constitutes the pressed surface 6.

[0030] Furthermore, the housing element 7 has an inwardly projecting flange portion 11 at the other axial end of the small-diameter cylindrical surface portion 9, and has screw holes 12 opening at multiple locations in the circumferential direction on the other axial side surface. The pressed member 2 in this example is supported and fixed to the stationary portion by screwing a bolt, which is inserted through a through hole provided in the stationary portion, into the screw holes 12.

[0031] 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 constructed by fitting the other housing element to the axial end of the housing element 7 without any play (spigot fitting), thereby positioning the housing element 7 and the other housing element radially, and then connecting the housing element 7 and the other housing element with a connecting member such as a bolt.

[0032] (Input Member) The input member 3 has an input-side engaging portion 13 located radially inward of the pressed surface 6 and is arranged coaxially with the pressed surface 6.

[0033] The input member 3 is connected to an input-side mechanism such as an electric motor, and rotational torque is input to it. Specifically, the input member 3 is composed of the output shaft of the input-side mechanism, or it is composed as a separate component from the output shaft and can be fixed coaxially to the output shaft. Additionally, the input shaft portion 17 provided on the input member 3 can be rotatably supported relative to the stationary portion.

[0034] The input-side engaging portion 13 is provided on a part of the input member 3 that is radially outward from the center of rotation, and has a portion that engages, specifically contacts, with the input-side engaged portion 33 of the engaging element 5. The input-side engaging portion 13 is configured to engage (contact) its radially inner surface 14 with the radially inner surface 39 of the input-side engaged portion 33 as the input member 3 or the engaging element 5 rotates.

[0035] The outer circumferential 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 33. For example, it can have an end face shape such as a substantially fan-shaped, substantially trapezoidal, or arched shape, where the circumferential width increases towards the radially outward direction when viewed from the axial direction. From the standpoint of reducing the manufacturing cost of the input member 3, it is preferable that the outer circumferential surface of the input-side engaging portion 13 consists only of a flat radially inward surface 14 and a partially cylindrical radially outward surface 15 centered on the central axis of the input member 3.

[0036] In this example, the outer circumferential surface of the input-side engaging portion 13 consists only of a flat radial inner surface 14 and a partially cylindrical radial outer surface 15. That is, the input-side engaging portion 13 has an arc-shaped end face when viewed from the axial direction. The radial inner surface 14 and the radial outer surface 15 are connected by a pointed edge 16.

[0037] Therefore, in the reverse input blocking clutch 1 of this example, when manufacturing the input member 3 having the input side engaging portion 13, it is not necessary to perform machining on the connection between the radially inner surface 14 and the radially outer surface 15 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 needed. This reduces the manufacturing cost of the input member 3. However, the input member 3 can also be manufactured by machining a metal material, including cutting. In this case, the radially inner surface 14 and the radially outer surface 15 can be connected by chamfered portions such as C-chamfers and R-chamfers.

[0038] In this example, the input member 3 has, in addition to the input-side engaging portion 13, an input shaft portion 17 and an input flange portion 18.

[0039] The input shaft portion 17 has a cylindrical shape.

[0040] The input flange portion 18 is an element for disposing the input-side engaging portion 13 at a portion radially outward from the rotation center of the input member 3. The input flange portion 18 can be fixed or integrally formed with an output shaft of the input-side mechanism or the input shaft portion 17. In this example, the input flange portion 18 projects radially outward over the entire circumference from the outer peripheral surface of the end portion on the other axial side of the input shaft portion 17.

[0041] The input-side engaging portion 13 projects axially toward the other axial side from a portion radially outward from the rotation center among the side surfaces on the other axial side of the input flange portion 18.

[0042] The number of the input-side engaging portions 13 is determined according to the number of the engaging elements 5. When the engaging element 5 is composed of a plurality of engaging elements 5, the input-side engaging portion 13 is also composed of a plurality of input-side engaging portions 13.

[0043] In the reverse input blocking clutch 1 of this example, the engaging element 5 is composed of two engaging elements 5. Therefore, the input-side engaging portion 13 is composed of two input-side engaging portions 13 according to the number of the engaging elements 5. The two input-side engaging portions 13 are arranged at two positions on the radially opposite sides of the side surface on the other axial side of the input flange portion 18 and are separated from each other in the radial direction of the input member 3.

[0044] The input member 3 can be rotatably supported by the pressed member 2 or the stationary portion. In this example, the input member 3 is rotatably supported by the stationary portion by a radial bearing (not shown) and is arranged coaxially with the pressed surface 6.

[0045] (Output member) The output member 4 has an output-side engaging portion 19 arranged radially inward of the input-side engaging portion 13 and is arranged coaxially with the pressed surface 6. That is, the output member 4 is also arranged coaxially with the input member 3.

[0046] The output member 4 is connected to an output-side mechanism such as a speed reduction mechanism, and is configured to output rotational torque to the output-side mechanism as it rotates. Specifically, the output member 4 is constituted by an input shaft of the output-side mechanism or the like, or is configured as a separate member from the input shaft or the like, and can be fixed coaxially to the input shaft or the like.

[0047] The output-side engaging portion 19 has a portion that engages with the output-side engaged portion 34 of the engaging element 5, and the engaging portion is radially inside the input-side engaging portion 13 and is a portion that deviates radially outward from the central axis of the output member 4, and is disposed at a position where it can engage with the output-side engaged portion 34 of the engaging element 5. The output-side engaging portion 19 is configured such that its outer peripheral surface engages (contacts) with the output-side engaged portion 34 as the output member 4 or the engaging element 5 rotates.

[0048] The output-side engaging portion 19 has a cam function. The distance from the rotation center axis of the output member 4 to the outer peripheral surface of the output-side engaging portion 19, which is the portion that engages with the output-side engaged portion 34, is not constant in the circumferential direction. Thereby, when rotational torque is reversely input to the output member 4, as the output member 4 rotates, the output-side engaging portion 19 can press the engaging element 5 in the radial direction of the engaging element 5, which is the first direction.

[0049] The number of portions of the output-side engaging portion 19 that engage with the output-side engaged portion 34 is determined according to the number of engaging elements 5. When the engaging element 5 is constituted by a plurality of engaging elements 5, the output-side engaging portion 19 is also configured to have a plurality of the engaging portions. In this example, the output-side engaging portion 19 is configured to have two portions that engage with the output-side engaged portions 34 in accordance with the number of engaging elements 5. However, even when the number of engaging elements 5 is one, it is possible to adopt the same structure as in this example.

[0050] The outer circumferential surface of the output-side engaging portion 19 can adopt any configuration as long as the output-side engaging portion 19 has a cam function, and its shape is appropriately set according to the number of portions of the output-side engaging portion 19 that engage with the output-side engaged portion 34. When there are portions that engage with two output-side engaged portions 34, the output-side engaging portion 19 can be, for example, roughly rectangular, roughly oval, parallelogram, or trapezoidal in shape. However, from the viewpoint of reducing the manufacturing cost of the output member 4, it is preferable that the outer circumferential surface of the output member 4 has a flat surface portion 20 in the portion that engages with the output-side engaged portion 34, and it is even more preferable that it is composed of a flat surface portion 20 and a partially cylindrical surface portion 21 centered on the central axis of the output member 4. In this example, the portion of the flat surface portion 20 located in the axial middle and widthwise middle constitutes the portion that engages with the output-side engaged portion 34.

[0051] In this example, the outer circumferential surface of the output-side engaging portion 19 is composed of two parallel flat surfaces 20 and two partially cylindrical surfaces 21. The output-side engaging portion 19 is symmetrical with respect to a virtual plane that passes through the rotational axis of the output member 4 and is perpendicular to the two flat surfaces 20. Furthermore, the output-side engaging portion 19 is symmetrical with respect to a virtual plane that passes through the rotational axis of the output member 4 and is parallel to the two flat surfaces 20. In other words, the output-side engaging portion 19 has a shape that is twice symmetrical with respect to the central axis of the output member 4. The flat surfaces 20 and the partially cylindrical surfaces 21 are connected by pointed edges 22.

[0052] Therefore, when manufacturing the output member 4 having the output-side engaging portion 19, it is not necessary to perform machining on the portion of the output-side engaging portion 19 that engages with the output-side engaged portion 34. 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 needed. This reduces the manufacturing cost of the output member 4. However, the output member 4 can also be manufactured by machining a metal material, including cutting. In this case, the flat surface portion 20 and the partially cylindrical surface portion 21 can be connected by chamfered portions such as C-chamfered portions and R-chamfered portions.

[0053] The output-side engaging portion 19 is located radially inward of the two input-side engaging portions 13, and is positioned between the output-side engaged portions 34 of the two engaging elements 5.

[0054] The output member 4 can be rotatably supported by the pressed member 2 or the stationary part via a rolling bearing or the like.

[0055] In this example, the output member 4 has, in addition to the output-side engaging portion 19, an output shaft portion 23, an output flange portion 24, and a small-diameter shaft portion 25.

[0056] The output shaft portion 23 is formed by the input shaft of the output mechanism, or, as in this example, if the output member 4 is configured as a separate component from the input shaft, it can be fixed coaxially to the input shaft, etc. In this example, the output shaft portion 23 has a stepped cylindrical shape.

[0057] The output flange portion 24 protrudes radially outward from the outer circumferential surface of one axial end of the output shaft portion 23 over its entire circumference. The output flange portion 24 is an element for attaching the output member 4 to the pressed member 2 or the stationary portion so that it can rotate and cannot be displaced in the axial direction.

[0058] The output-side engaging portion 19 protrudes from the center of the end face on one axial side of the output shaft portion 23 toward the axial side.

[0059] The small-diameter shaft portion 25 has a cylindrical shape and protrudes from the center of the axial end face of the output-side engaging portion 19 toward the axial direction toward the axial direction. The small-diameter shaft portion 25 is an element that ensures the coaxiality of the output member 4 with respect to the input member 3.

[0060] In this example, the output member 4 is rotatably supported radially inward of the housing element 7 of the pressed member 2 by a radial rolling bearing 26. The outer ring 27 of the radial rolling bearing 26 is fitted snugly into the small-diameter cylindrical surface portion 9 of the housing element 7 and is axially clamped between one axial side surface of the inward flange portion 11 and a retaining ring 28a that is locked to one axial end of the small-diameter cylindrical surface portion 9. The inner ring 29 of the radial rolling bearing 26 is fitted snugly onto one axial end of the output shaft portion 23 and is axially clamped between the other axial side surface of the output flange portion 24 and a retaining ring 28b that is locked to the outer circumferential surface of the axial intermediate portion of the output shaft portion 23.

[0061] In the illustrated example, the radial rolling bearing 26 is constructed using a ball bearing with balls as the rolling elements 30. However, the radial rolling bearing for supporting the output member 4 can also be constructed using a tapered roller bearing with tapered rollers as the rolling elements or a roller bearing with cylindrical rollers.

[0062] Furthermore, the small-diameter shaft portion 25 of the output member 4 is supported by a sliding bearing (sleeve) 31 inside the input member 3, allowing for free relative rotation with respect to the input member 3.

[0063] (Engaging element) The engaging element 5 has two pressing surfaces 32 facing the pressed surface 6 and spaced apart from each other in the circumferential direction, an input-side engaged portion 33 that can engage with the input-side engaging portion 13, and an output-side engaged portion 34 that can engage with the output-side engaging portion 19, and is arranged to allow movement in the radial direction (first direction).

[0064] 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 33, and transmits the rotational torque input to the input member 3 to the output member 4 by engaging the output-side engaged portion 34 with the output-side engaging portion 19. Conversely, when rotational torque is input in reverse to the output member 4, the engaging element 5 is configured to press the two pressing surfaces 32 against the pressed surface 6 based on the output-side engaged portion 34 engaging with the output-side engaging portion 19, thereby frictionally engaging the two pressing surfaces 32 with the pressed surface 6.

[0065] In this example, with the two pressing surfaces 32 in contact with the pressed surface 6 within a cross-section perpendicular to the central axis O of the pressed surface 6, the inclination angle α of the imaginary straight line L connecting the contact portion X between each of the two pressing surfaces 32 and the central axis O of the pressed surface 6, with respect to the central axis O of the pressed surface 6, is 10° or more and 40° or less with respect to the width direction (second direction) of the engaging element 5. This ensures that the pressing force f of the two pressing surfaces 32 against the pressed surface 6 is appropriately secured. The reason for this will be explained with reference to Figures 6 to 8. Note that the inclination angle α includes an error from the design value of the inclination angle α; that is, the error from the design value is permissible.

[0066] As shown in Figure 6, when rotational torque is input in reverse to the output member 4, if F is the radial (first direction) force acting from the output-side engaging portion 19 to the engaging element 5, then the pressing force f (normal force) of the pressing surface 32 against the pressed surface 6 at each contact portion X is expressed as a function of the inclination angle α, f = F / (2 sinα). That is, the pressing force f changes with respect to the radial force F acting from the output-side engaging portion 19 to the engaging element 5 with an amplification factor of 1 / (2 sinα).

[0067] Curve C1 in Figure 7 represents the amplification factor 1 / (2・sinα) of such a pressing force f. The amplification factor 1 / (2・sinα) increases as the inclination angle α decreases. For example, when the inclination angle α is 30°, the amplification factor 1 / (2・sinα) is 1, and f = F. Also, when the inclination angle α is 15°, the amplification factor 1 / (2・sinα) is 2, and f = 2F.

[0068] If the coefficient of friction between the pressed surface 6 and each of the pressing surfaces 32 is μ, then the frictional force Fx of each contact point X is expressed as Fx = μ・f. In other words, the frictional force Fx of each contact point X also increases as the inclination angle α decreases.

[0069] In a reverse input blocking clutch 1 having such characteristics, if the inclination angle α is greater than 40°, the pressing force f of the two pressing surfaces 32 against the pressed surface 6, and consequently the frictional force Fx of each contact part X, may become insufficient, potentially preventing sufficient blocking of the rotational torque reversed into the output member 4. Therefore, in this example, the inclination angle α is restricted to 40° or less. This prevents insufficient pressing force f of the two pressing surfaces 32 against the pressed surface 6, and consequently the frictional force Fx of each contact part X, when rotational torque is reversed into the output member 4, thereby ensuring reliable blocking of the rotational torque reversed into the output member 4.

[0070] On the other hand, if the inclination angle α is made smaller than 10°, the pressing force f of the two pressing surfaces 32 against the pressed surface 6, and consequently the frictional force Fx of each contact part X, may become excessively large, potentially making it impossible to smoothly switch the reverse input blocking clutch 1 from the locked or semi-locked state to the unlocked or semi-unlocked state. Alternatively, if a rotational torque is being input in reverse to the output member 4, and a rotational torque in the same direction as the rotational torque being input in reverse to the output member 4 is input to the input member 3, a phenomenon may occur in which the input member 3 and the output member 4 rotate intermittently, repeatedly switching between the locked or semi-locked state and the unlocked or semi-unlocked state in a short period of time (chasing lock phenomenon).

[0071] Furthermore, if the inclination angle α is to be made smaller than 10°, it becomes necessary to position the portions of the engaging element 5 that do not overlap with the output-side engaging portion 19 in the radial direction to protrude radially inward from the radially inward side surface of the intermediate portion in the radial direction that overlaps with the output-side engaging portion 19 in the radial direction, which may complicate the shape of the engaging element 5.

[0072] Therefore, in this example, the inclination angle α is restricted to 10° or more. This prevents the pressing force f of the two pressing surfaces 32 against the pressed surface 6, and consequently the frictional force Fx of each contact part X, from becoming excessive, thereby enabling smooth switching of the reverse input blocking clutch 1 from the locked or semi-locked state to the unlocked or semi-unlocked state, or preventing the occurrence of the chase lock phenomenon. Furthermore, it prevents the shape of the engaging element 5 from becoming complex.

[0073] The inclination angle α is preferably 15° or greater and less than 25°. The reason for this will be explained below.

[0074] Curve C2 in Figure 7 represents the derivative of the amplification factor 1 / (2・sinα) of the pressing force f represented by curve C1, that is, the rate of change of the amplification factor 1 / (2・sinα) of the pressing force f with respect to the change in the slope angle α. The rate of change of the amplification factor 1 / (2・sinα) of the pressing force f increases as the slope angle α decreases.

[0075] Figure 8 is a diagram that more specifically illustrates the relationship of curve C2 in Figure 7. When manufacturing the reverse input blocking clutch 1, an unavoidable error occurs with respect to the design value of the inclination angle α. Figure 8 is a diagram that shows the relationship between the error with respect to the design value of the inclination angle α and the rate of change of the amplification factor 1 / (2・sinα) of the pressing force f for each design value of the inclination angle α (8°, 10°, 15°, 25°, 30°).

[0076] As shown in Figure 8, the absolute value of the rate of change of the amplification factor 1 / (2・sinα) of the pressing force f increases as the design value decreases, provided that the error from the design value of the inclination angle α is the same magnitude. For example, when the error from the design value of the inclination angle α is +2°, the rate of change of the amplification factor 1 / (2・sinα) is approximately -0.05 (-5%) when the design value is 30°, whereas it is approximately -0.17 (-17%) when the design value is 10°. Also, when the error from the design value of the inclination angle α is -2°, the rate of change of the amplification factor 1 / (2・sinα) is approximately +0.07 (+7%) when the design value is 30°, compared to approximately +0.25 (+25%) when the design value is 10°.

[0077] Since the frictional force Fx at each contact point X is expressed as Fx = μ・f = μ・F / (2・sinα), this frictional force Fx also changes in the same way as the rate of change of the amplification factor 1 / (2・sinα) of the pressing force f with respect to the error from the design value of the inclination angle α.

[0078] If the rate of change of the frictional force Fx with respect to the error from the design value of the inclination angle α becomes large, the variation in the frictional force Fx in the completed reverse input blocking clutch 1 will increase. As a result, problems may arise, such as being unable to properly set whether to lock or partially lock the output member 4 when rotational torque is input in reverse to the output member 4, or difficulty in ensuring the reliability of the control when the reverse input blocking clutch 1 is used to control the blocking force of the rotational torque input in reverse to the output member 4.

[0079] Therefore, from the perspective of suppressing the rate of change of frictional force Fx with respect to the error in the inclination angle α, it is preferable that the inclination angle α (including the error) is 15° or more. On the other hand, from the perspective of making it easier to secure the frictional force Fx of the contact portion X of each pressing surface 32 with respect to the pressed surface 6 when rotational torque is input in reverse to the output member 4, it is preferable that the inclination angle α (including the error) is less than 25°. It is more preferable that the inclination angle α (including the error) is 20° or less.

[0080] The engaging element 5 may consist of one engaging element 5 or two or more engaging elements 5, as long as it has the above configuration.

[0081] In this example, the engaging element 5 is composed of two engaging elements 5. Each engaging element 5 has the function of an engaging element 5.

[0082] The engaging element 5 can be manufactured by any method. For example, the engaging element 5 can be manufactured by pressing, sintering, forging, casting, or machining. From the standpoint of reducing the manufacturing cost of the engaging element 5, it is preferable that the engaging element 5 be manufactured by pressing. In this example, the engaging element 5 is a press-formed product of a metal plate manufactured by pressing.

[0083] The shape of the engaging element 5 is arbitrary as long as it has two pressing surfaces 32, an input-side engaged portion 33, and an output-side engaged portion 34, and can perform the functions described above. In this example, since the engaging element 5 is composed of two engaging elements 5, each engaging element 5 has a substantially semicircular end face shape when viewed from the axial direction and has a shape that is symmetrical with respect to the width direction.

[0084] The engaging element 5 can be configured such that both end faces in the width direction (second direction) are made of planar portions 35 perpendicular to the width direction. This allows for easy and accurate dimensional measurement during the manufacturing of the reverse input blocking clutch 1, by using the two parallel planar portions 35 provided on both end faces of the engaging element 5 in the width direction as a reference to confirm the dimensional accuracy of each part of the engaging element 5. Furthermore, for example, when performing an assembly process in which two engaging elements 5 are simultaneously inserted radially inward into the pressed surface 6, the planar portions 35 provided on each engaging element 5 can be used to maintain the position of the two engaging elements 5 so that their widthwise positions coincide, thus making the assembly process easy and accurate.

[0085] The radial width dimension of each planar portion 35 can be set arbitrarily, as long as it does not interfere with other elements provided on the engaging element 5. The radial width dimension of each planar portion 35 is not limited to this, but from the viewpoint of enabling the dimensional measurement process and assembly process described above to be carried out appropriately, it is preferable to have a width of 1 mm or more.

[0086] The engaging element 5 may have, as an optional component, convex curved surfaces 36 and 37 on at least one of the parts of the input-side engaged portion 33 that engages with the input-side engaging portion 13, and the output-side engaged portion 34 that engages with the output-side engaging portion 19. This makes it possible to bring the convex curved surface 36 of the input-side engaged portion 33 into contact with the radially inner surface 14 of the input-side engaged portion 13, or to bring the convex curved surface 37 of the output-side engaged portion 34 into contact with the flat surface 20 of the output-side engaging portion 19 when the reverse input blocking clutch 1 is operated.

[0087] In other words, the engaging element 5 may have a convex curved surface portion 36 on the part of the input-side engaged portion 33 that engages with the input-side engaging portion 13. Each input-side engaged portion 33 has a portion that engages with two input-side engaging portions 13. Therefore, the convex curved surface portion 36 is provided at two locations on the input-side engaged portion 33.

[0088] Additionally or alternatively, the engaging element 5 may have a convex curved surface portion 37 on the portion of the output-side engaged portion 34 that engages with the output-side engaging portion 19. Each output-side engaged portion 34 has portions that engage with two output-side engaging portions 19. Therefore, the convex curved surface portion 37 is provided at two locations on the output-side engaged portion 34.

[0089] In this example, the engaging element 5 has a convex curved surface portion 36 in the portion of the input-side engaged portion 33 that engages with the input-side engaging portion 13, and a convex curved surface portion 37 in the portion of the output-side engaged portion 34 that engages with the output-side engaging portion 19. Therefore, with the reverse input shutoff clutch 1 of this example, the contact pressure at the contact points between the input member 3 and the output member 4 and the engaging element 5 can be kept low.

[0090] The pressing surfaces 32 are provided at two positions on the radially outer surface of the engaging element 5 facing the pressed surface 6, spaced apart from each other in the circumferential direction. Each pressing surface 32 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.

[0091] Of the radially outer surface of the engaging element 5, the portion that is circumferentially away from the two pressing surfaces 32 is located radially inward from a virtual circle that is centered on the central axis of the pressed surface 6 and tangent to the two pressing surfaces 32, when viewed from the axial direction. In other words, when the two pressing surfaces 32 are in contact with the pressed surface 6, the portion that is circumferentially away from the two pressing surfaces 32 does not come into contact with the pressed surface 6.

[0092] The pressing surface 32 preferably has a surface property that results in a higher coefficient of friction with respect to the pressed surface 6 than the other parts of the engaging element 5. Furthermore, the pressing surface 32 can be integrally formed with the other parts of the engaging element 5, or it can be formed from the surface of a friction material fixed to the other parts of the engaging element 5 by means of adhesion or bonding.

[0093] In this example, the radially outer end of the flat portion 35 is directly connected to the radially inner end of the pressing surface 32, and the radially inner end of the flat portion 35 is connected to the widthwise outer end of the radially inner surface of the engaging element 5 via a chamfered portion 38. However, when implementing this disclosure, the radially outer end of the flat portion 35 can also be connected to the radially inner end of the pressing surface 32 via a connecting portion having any shape that does not contact the pressed surface 6. Alternatively, the radially inner end of the flat portion 35 can be directly connected to the widthwise outer end of the radially inner surface of the engaging element 5 without using a connecting portion such as a chamfered portion 38.

[0094] In this example, the input-side engaged portion 33 is provided in the radially intermediate portion of the widthwise center of the engaging element 5. More specifically, although not limited to this, the input-side engaged portion 33 has a substantially arc-shaped opening when viewed from the axial direction and is composed of a through hole that penetrates the radially intermediate portion of the widthwise center of the engaging element 5 in the axial direction.

[0095] The input-side engaged portion 33 is sized to allow the input-side engaged portion 13 to be loosely inserted. Therefore, when the input-side engaged portion 13 is inserted inside the input-side engaged portion 33, there are gaps between the input-side engaged portion 13 and the inner surface of the input-side engaged portion 33 in the width direction and the radial direction of the engaging element 5. As a result, the input-side engaged portion 13 can be displaced relative to the input-side engaged portion 33 in the rotational direction of the input member 3, and the input-side engaged portion 33 can be displaced relative to the input-side engaged portion 13 in the radial direction of the engaging element 5.

[0096] The convex curved surface portion 36 is provided on the radially inner surface 39 of the inner surface of the input-side engaged portion 33, which faces radially outward, specifically on the portion that engages with the input-side engaged portion 13, and more precisely, on the portion that engages with the radially inner surface 14, so as to be convex toward the input-side engaged portion 13. The convex curved surface portion 36 is provided at two locations on the radially inner surface 39: the portion that engages with the input-side engaged portion 13 when the input member 3 rotates to one side relative to the engager 5, and the portion that engages with the input-side engaged portion 13 when the input member 3 rotates to the other side relative to the engager 5.

[0097] Specifically, the radial inner surface 39 of the input-side engaged portion 33 is provided with a convex portion 40 that protrudes radially outward from the adjacent portions on both sides in the second direction, and convex curved portions 36 are provided at two locations in the second direction of the convex portion 40.

[0098] In this example, the convex curved surface portion 36 is provided at both ends of the convex portion 40 in the second direction. The convex portion 40 also has a connecting surface portion 41 in the second direction intermediate portion between the two convex curved surface portions 36, which connects the two convex curved surface portions 36 and is formed by a flat surface perpendicular to the first direction.

[0099] The shape and radius of curvature of the convex curved surface portion 36, as viewed from the axial direction, are not particularly limited, as long as they can prevent the contact pressure at the contact point with the input-side engaging portion 13 from becoming excessive. For example, the shape of the convex curved surface portion 36, as viewed from the axial direction, can be a roughly circular arc, a roughly elliptical arc, etc. The shape and radius of curvature of the convex curved surface portion 36, as viewed from the axial direction, can be determined by experiment, simulation, etc.

[0100] In this example, the radially outer surface 42 of the inner surface of the input-side engaged portion 33, which faces radially inward, is composed of a curved surface having a substantially arc-shaped contour or a composite surface having a substantially V-shaped contour when viewed from the axial direction. The circumferential surface 43 connecting the radially inner surface 39 and the radially outer surface 42 is composed of a partially cylindrical concave curved surface.

[0101] The output-side engaged portion 34 is provided at the center of the width direction on the radially inner surface of the engaging element 5. The shape of the output-side engaged portion 34 is not limited as long as it is configured to engage with the output-side engaged portion 19. In this example, the output-side engaged portion 34 is provided at the center of the width direction on the radially inner surface of the engaging element 5, so as to protrude radially inward from the portions adjacent to it on both sides in the width direction.

[0102] The convex curved portion 37 is provided at two locations within the output-side engaged portion 34, specifically the portion that engages with the output-side engaged portion 19 when the output member 4 rotates to one side relative to the engager 5, and the portion that engages with the output-side engaged portion 19 when the output member 4 rotates to the other side relative to the engager 5, so as to be convex toward the output-side engaged portion 19.

[0103] In this example, the convex curved surface portion 37 is provided at both ends of the output-side engaged portion 34 in the width direction (second direction). The output-side engaged portion 34 also has a connecting surface portion 44 in the width direction intermediate between the two convex curved surface portions 37, which connects the two convex curved surface portions 37 and is formed by a flat surface perpendicular to the radial direction.

[0104] The shape and radius of curvature of the convex curved surface portion 37, as viewed from the axial direction, are not particularly limited, as long as it is possible to prevent the contact pressure at the contact point with the output-side engaging portion 19 from becoming excessive. For example, the shape of the convex curved surface portion 37, as viewed from the axial direction, can be a roughly circular arc, a roughly elliptical arc, etc. The shape and radius of curvature of the convex curved surface portion 37, as viewed from the axial direction, can be determined by experiment, simulation, etc.

[0105] In this example, the engaging element 5 is provided with convex curved surfaces 36 and 37 to reduce the contact pressure at the contact points between the input member 3 and the output member 4 and the engaging element 5. Therefore, compared to the case where the convex curved surfaces are provided by machining the contact points of the input member 3 and the output member 4 with the engaging element 5, manufacturing costs can be reduced.

[0106] Furthermore, in this example, the engaging element 5, which has convex curved surfaces 36 and 37 at the contact points with the input member 3 and the output member to reduce contact pressure, is manufactured by press stamping. This also helps to reduce manufacturing costs.

[0107] (Biasing member and holding member) In this example, the reverse input blocking clutch 1 further comprises, as optional components, a biasing member 45 and a holding member 46.

[0108] The biasing member 45 elastically biases the engaging element 5 toward the pressed surface 6. The biasing member 45 can be made of a spring such as a leaf spring, coil spring, or disc spring, or an elastic material such as rubber, elastomer, or synthetic resin. The number of biasing members 45 is not particularly limited and is appropriately determined according to the number of engaging elements 5.

[0109] In this example, the biasing member 45 is composed of two biasing members 45 positioned at two locations in the width direction between the radially inner surfaces of the two engaging elements 5, and each biasing member 45 is composed of a compression coil spring. Each biasing member 45 is fitted and held in the holding hole 49 of the holding member 46, thereby preventing it from falling out from the portion between the two engaging elements 5.

[0110] The two biasing members 45 elastically bias the two engaging elements 5 toward the pressed surface 6 by the force that attempts to restore them elastically. As a result, in the neutral state where no torque is applied to either the input member 3 or the output member 4, the two pressing surfaces 32 of the two engaging elements 5 come into contact with the pressed surface 6.

[0111] The retaining member 46 comprises a first spacer portion 47 and a second spacer portion 48 arranged spaced apart in the axial direction, and two connecting portions 50 arranged on both sides of the first spacer portion 47 and the second spacer portion 48 with respect to a second direction, each connecting the first spacer portion 47 and the second spacer portion 48, and each having a retaining hole 49 extending in the first direction.

[0112] The retaining member 46 is attached to the output member 4 with the engaging element 5 positioned between the first spacer portion 47 and the second spacer portion 48 in the axial direction, thereby restricting the axial movement of the engaging element 5 relative to the output member 4. Specifically, the retaining ring 51, which is locked to the small-diameter shaft portion 25 of the output member 4, restricts the movement of the retaining member 46 to one side in the axial direction, and the other side of the second spacer portion 48 is brought into contact with or close to the end face of the output shaft portion 23 on one side in the axial direction, thereby restricting the movement of the retaining member 46 to the other side in the axial direction.

[0113] <Explanation of the operation of the reverse input blocking clutch> The operation of the reverse input blocking clutch 1 will be explained using Figures 3 and 4. Note that Figures 3 and 4 omit the biasing member 45 and the holding member 46, and exaggerate the radial gap between the input member 3 and the output member 4 and the two engaging elements 5.

[0114] When rotational torque is applied to the input member 3, the two engaging elements 5 move away from the pressed surface 6, regardless of the rotation 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 33 in the direction of rotation of the input member 3 (counterclockwise in the example of Figure 3).

[0115] This reduces the gap between the radially inner surface 14 of the input-side engaging portion 13 and the radially inner surface 39 of the input-side engaged portion 33, causing the radially inner surface 14 of the input-side engaging portion 13 to come into contact with the radially inner surface 39 of the input-side engaged portion 33.

[0116] In this example, the radially inner surface 14 of the input-side engaging portion 13 is brought into contact with one of the two convex curved surfaces 36 provided on the input-side engaged portion 33.

[0117] From this state, as the input member 3 rotates further, the radially inner surface 14 of the input-side engaging portion 13 presses one of the convex curved portions 36 radially inward, causing the engaging element 5 to move away from the pressed surface 6. That is, the two engaging elements 5 move radially inward, moving closer to each other based on their engagement with the input member 3, so that the radially inner surfaces of the two engaging elements 5 come closer to each other, and the output-side engaged portions 34 of the two engaging elements 5 clamp the output-side engaging portion 19 of the output member 4 from both radial sides.

[0118] In this way, the output member 4 is rotated so that the flat surface portion 20 of the output-side engaging portion 19 is parallel to the connecting surface portion 44 of the output-side engaged portion 34, while the output-side engaging portion 19 and the output-side engaged portion 34 of the engaging element 5 are engaged without any 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 output from the output member 4.

[0119] When rotational torque is input in reverse to the output member 4, the two engaging elements 5 move toward the pressed surface 6, regardless of the rotation direction of the output member 4. Specifically, as shown in Figure 4, the output-side engaging portion 19 rotates in the direction of rotation of the output member 4 (clockwise in the example of Figure 4) inside the output-side engaged portions 34 of the two engaging elements 5. The output-side engaging portion 19 then presses the output-side engaged portions 34 radially outward. In this example, the flat surface portion 20 of the outer circumferential surface of the output-side engaging portion 19 presses one of the two convex curved surfaces 37 provided on the output-side engaged portions 34 radially outward. As a result, the two engaging elements 5 move toward the pressed surface 6.

[0120] In other words, the two engaging elements 5 move radially outward, away from each other, based on their engagement with the output member 4, so that the two pressing surfaces 32 of the two engaging elements 5 come into contact with the pressed surface 6 and frictionally engage with the pressed surface 6.

[0121] As a result, the rotational torque reversed into the output member 4 is either completely blocked and not transmitted to the input member 3, or only a portion of the rotational torque reversed into the output member 4 is transmitted to the input member 3 and the rest is blocked.

[0122] In order to completely block the rotational torque that is reverse-input to the output member 4 and prevent it from being transmitted to the input member 3, the engaging element 5 is braced (clamped) between the output-side engaging part 19 and the pressed member 2 so that the pressing surface 32 of the engaging element 5 does not slide (rotate relative to) the pressed surface 6, thereby locking the output member 4.

[0123] To ensure that only a portion of the rotational torque inverted to the output member 4 is transmitted to the input member 3 and the remainder is blocked, the engaging element 5 is braced (clamped) between the output-side engaging portion 19 and the pressed member 2 so that the pressing surface 32 of the engaging element 5 slides against the pressed surface 6, thereby partially locking the output member 4.

[0124] When rotational torque is input in reverse to the output member 4, the setting for whether to lock or partially lock the output member 4 is performed by appropriately adjusting the magnitude of the frictional force Fx of the contact portion X of each pressing surface 32 with respect to the pressed surface 6.

[0125] In particular, when implementing the reverse input blocking clutch 1 in this example, if the inclination angle α (including error) is 15° or more, the rate of change of the frictional force Fx with respect to the error in the inclination angle α can be effectively suppressed. Therefore, it becomes easy to appropriately adjust the magnitude of the frictional force Fx.

[0126] In the reverse input blocking clutch 1 of this example, the size of the gaps between each component is adjusted so that the above operation is possible. In particular, when the two pressing surfaces 32 of the two engaging elements 5 are in contact with the pressed surface 6, a gap exists between the radially inner surface 14 of the input-side engaging portion 13 and the protrusion 40 of the input-side engaged portion 33.

[0127] This prevents the radial outward movement of the engaging element 5 from being blocked by the input-side engaging part 13 when rotational torque is input in reverse to the output member 4, and also ensures that even after the pressing surface 32 contacts the pressed surface 6, the surface pressure acting on the contact portion between the pressing surface 32 and the pressed surface 6 changes according to the magnitude of the rotational torque input in reverse to the output member 4, thereby ensuring that the output member 4 is properly locked or partially locked.

[0128] 1 Reverse input blocking clutch 2 Pressed member 3 Input member 4 Output member 5 Engaging element 6 Pressed surface 7 Housing element 8 Large diameter cylindrical surface 9 Small diameter cylindrical surface 10 Connecting surface 11 Inward flange 12 Screw hole 13 Input side engaging part 14 Radial inner surface 15 Radial outer surface 16 Ridge 17 Input shaft 18 Input flange 19 Output side engaging part 20 Flat surface 21 Partial cylindrical surface 22 Ridge 23 Output shaft 24 Output flange 25 Small diameter shaft 26 Radial rolling bearing 27 Outer ring 28a, 28b Retaining ring 29 Inner ring 30 Rolling element 31 Sliding bearing 32 Pressing surface 33 Input side engaged part 34 Output side engaged part 35 Flat surface 36 Convex curved surface portion 37 Convex curved surface portion 38 Chamfered portion 39 Radial inner surface portion 40 Convex portion 41 Connecting surface portion 42 Radial outer surface portion 43 Circumferential surface portion 44 Connecting surface portion 45 Biasing member 46 Holding member 47 First spacer portion 48 Second spacer portion 49 Holding hole 50 Connecting portion 51 Retaining ring

Claims

A member to be pressed having a surface to be pressed on its inner circumferential surface, An input member having an input-side engaging portion arranged radially inward from the surface to be pressed, and arranged coaxially with the surface to be pressed, An output member having an output-side engaging portion located radially inward from the input-side engaging portion, and arranged coaxially with the pressed surface, An engaging element having two pressing surfaces facing the pressed surface and spaced apart from each other in the circumferential direction, 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 arranged to be movable in the radial direction, Equipped with, When rotational torque is input to the input member, the engaging element moves radially away from the pressed surface based on the input-side engaging portion engaging with the input-side engaged portion, thereby engaging the output-side engaged portion with the output-side engaging portion and transmitting the rotational torque input to the input member to the output member. Conversely, when rotational torque is input in reverse to the output member, the engaging element presses the two pressing surfaces against the pressed surface based on the output-side engaging portion engaging with the output-side engaged portion, thereby frictionally engaging the two pressing surfaces with the pressed surface. In a cross-section perpendicular to the central axis of the pressed surface, with the two pressing surfaces in contact with the pressed surface, the inclination angle α of the imaginary straight line connecting the contact portion between each of the two pressing surfaces and the pressed surface and the central axis of the pressed surface, with respect to the width direction of the engaging element which is perpendicular to both the central axis of the pressed surface and the radial direction of the engaging element, is 10° or more and 40° or less. Reverse input blocking clutch. 　 The reverse input cutoff clutch according to claim 1, wherein the inclination angle α is 15° or more and less than 25°. 　 The reverse input blocking clutch according to claim 1 or 2, wherein both end faces of the engaging element in the width direction are formed by planar portions perpendicular to the width direction. 　 The reverse input shutoff clutch according to any one of claims 1 to 3, wherein the engaging element has a convex curved surface portion on at least one of the portions 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.

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