Reverse-input cutoff clutch

Abstract

A reverse-input cutoff clutch 1 comprises a pressed member 2, an input member 3, an output member 4, and a mating element 5. The mating element 5 includes, among the surfaces thereof, a hardened layer 52 in a portion including a pressing surface 34 frictionally mated with a pressed surface 6 of the pressed member 2. The effective hardened layer depth d of the hardened layer 52 is 1 mm or less, and the surface hardness of the pressing surface 34 is HRC 50 or more.

Description

Reverse input blocking clutch

[0001] The present disclosure relates to a reverse input blocking clutch that transmits the rotational torque input to the input member to the output member, while completely blocking the rotational torque reversely input to the output member from being transmitted to the input member or transmitting only a part thereof to the input member and blocking the remainder.

[0002] The reverse input blocking clutch includes 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 speed reduction mechanism, and transmits the rotational torque input to the input member to the output member, while having a function of completely blocking the rotational torque reversely input to the output member from being transmitted to the input member or transmitting only a part thereof to the input member and blocking the remainder.

[0003] 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 input to the output member, depending on the difference in the mechanism for blocking the rotational torque 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 by the application of the device incorporating the reverse input blocking clutch or the like.

[0004] In the lock-type reverse input blocking clutch described in International Publication No. 2019 / 026794, when a rotational torque is input to the input member, the input-side engaging portion of the input member engages with the input-side engaged portion of the engaging element, based on which the engaging element moves in a direction away from the pressed surface provided on the pressed member, and the output-side engaged portion of the engaging element is engaged with the output-side engaging portion of the output member, thereby transmitting the rotational torque input to the input member to the output member. On the other hand, when a rotational torque is reversely input to the output member, based on the output-side engaging portion engaging with the output-side engaged portion, the engaging element moves in a direction approaching the pressed surface, presses the pressing surface against the pressed surface, and frictionally engages the pressing surface with the pressed surface.

[0005] International Publication No. 2019 / 026794

[0006] In the reverse input shutoff clutch described in International Publication No. 2019 / 026794, when the output member is locked or semi-locked, the pressing surface of the engaging element is pressed with strong force against the pressed surface of the pressed member. Therefore, in order to prevent wear on the pressing surface and ensure good durability of the engaging element, it is conceivable to form a hardened layer on the surface of the engaging element, including the pressing surface, by heat treatment.

[0007] However, if the engaging element is hardened to its core by, for example, deep quenching, it may increase the aggressiveness towards at least one of the pressed member, input member, or output member that engages with or contacts the engaging element. As a result, wear may occur more easily in the portion of at least one of the pressed member, input member, or output member that engages with or contacts the engaging element, making it difficult to ensure the durability of the reverse input blocking clutch.

[0008] This disclosure aims to realize a reverse input blocking clutch structure that has excellent durability.

[0009] 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.

[0010] The member to be pressed has a surface to be pressed on its inner circumferential surface.

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

[0012] 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.

[0013] 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 to be movable in the radial direction.

[0014] 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 pressing surface against the pressed surface based on the output-side engaging portion engaging with the output-side engaged portion, causing the pressing surface to frictionally engage with the pressed surface.

[0015] In particular, in a reverse input shutoff clutch according to one aspect of the present disclosure, the engaging element is made of a metal material and has a hardened layer on its surface, including the pressing surface. The effective hardened layer depth is 1 mm or less. The surface hardness of the pressing surface is HRC 50 or higher.

[0016] In a reverse input blocking clutch according to one aspect of the present disclosure, the hardened layer is provided on the entire surface of the engaging element.

[0017] In a reverse input blocking clutch according to one aspect of the present disclosure, the engaging element has a non-hardened portion with a hardness of HV200 or less in its core.

[0018] In a reverse input blocking clutch according to one aspect of the present disclosure, the engaging element is a press-formed product of a metal plate.

[0019] In a reverse input shutoff clutch according to one aspect of the present disclosure, the metal plate is made of hot-rolled steel sheet (SPHC).

[0020] 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 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.

[0021] According to one aspect of the present disclosure, a reverse input interruption clutch can achieve excellent durability.

[0022] Figure 1 is a cross-sectional view of a reverse input shutoff 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 applied 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 applied to the output member, with the holding member and biasing member omitted. Figure 5 is a front view showing the engaging element of the reverse input shutoff clutch removed. Figure 6 is a cross-sectional view taken along line II-II of Figure 5.

[0023] An example of an embodiment of the present disclosure will be described with reference to Figures 1 to 6.

[0024] In the following description, unless otherwise specified, axial, radial, and circumferential directions refer to the axial, radial, and circumferential directions of the pressed surface 6. 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).

[0025] The direction of the pressing surface 34 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 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 (left and right direction in Figures 2 to 4). For the engaging element 5, the direction coinciding with the first direction is defined as its radial direction (direction indicated by arrow α in Figure 3), and the direction coinciding with the second direction is defined as its width direction (direction indicated by arrow β in Figure 3).

[0026] <Explanation of the 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 rotational torque that is reverse input to the output member 4 is either completely blocked and not transmitted to the input member 3, or only a portion of it is transmitted to the input member 3 and the rest is blocked, thus having a reverse input blocking function.

[0027] (Pressed member) The pressed member 2 has a pressed surface 6 on its inner circumferential surface.

[0028] 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.

[0029] The pressed surface 6 constitutes the surface that contacts the pressing surface 34 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, but is not limited to this, although in this example it has a cylindrical shape in which the inner diameter does not change with respect to the axial direction.

[0030] The surface hardness of the pressed surface 6 can be made harder than the surface hardness of the pressing surface 34, softer than the surface hardness of the pressing surface 34, or approximately the same as the surface hardness of the pressing surface 34.

[0031] The input-side engaging portion 13 of the input member 3 and the output-side engaging portion 21 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 21, and the engaging element 5 are rotatable radially inward of the pressed surface 6.

[0032] In this example, the pressed member 2 includes a housing element 7.

[0033] 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. The pressed surface 6 is formed by the large-diameter cylindrical surface portion 8.

[0034] 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 side surface on the other axial side. The pressed member 2 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.

[0035] 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.

[0036] (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.

[0037] 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 14 provided on the input member 3 can be rotatably supported relative to the stationary portion.

[0038] 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, extends in the axial direction, and has a portion that engages, specifically contacts, with the input-side engaged portion 35 of the engaging element 5. The input-side engaging portion 13 is configured to engage or contact its radially inner surface 15 with the radially inner surface of the input-side engaged portion as the input member 3 or engaging element 5 rotates.

[0039] 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 35. For example, it can have an end face shape such as a roughly fan-shaped, roughly 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 15 and a partially cylindrical radially outward surface 17 centered on the central axis of the input member 3.

[0040] In this example, the outer peripheral surface of the input-side engaging portion 13 is composed only of a flat radial inner surface 15 and a partial cylindrical radial outer surface 17. That is, the input-side engaging portion 13 has an arcuate end face shape when viewed from the axial direction. The radial inner surface 15 and the radial outer surface 17 are connected by a sharp ridge portion 19.

[0041] Therefore, when manufacturing the input member 3 having the input-side engaging portion 13, it is not necessary to perform cutting on the connecting portion between the radial inner surface 15 and the radial outer surface 17 of the input-side engaging portion 13. For example, the input member 3 can be manufactured by forging a metal material to form the outer shape and then performing finishing such as grinding as necessary. For this reason, the manufacturing cost of the input member 3 can be suppressed. However, the input member 3 can also be manufactured by subjecting a metal material to machining including cutting. In this case, the radial inner surface 15 and the radial outer surface 17 can also be connected by a chamfered portion such as a corner chamfered portion or an R chamfered portion.

[0042] In addition to the input-side engaging portion 13, the input member 3 can have an input shaft portion 14 and an input flange portion 20 as in this example.

[0043] The input shaft portion 14 has a cylindrical shape.

[0044] The input flange portion 20 projects radially outward over the entire circumference from the outer peripheral surface of the end portion on the other side in the axial direction of the input shaft portion 14.

[0045] In this example, the input-side engaging portion 13 projects toward the other side in the axial direction from a portion that deviates radially outward from the rotation center among the side surfaces on the other side in the axial direction of the input flange portion 20.

[0046] 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.

[0047] 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 engaging elements 5. The two input-side engaging portions 13 are arranged at two positions on the opposite side in the radial direction of the side surface on the other side in the axial direction of the input flange portion 20, and are separated from each other in the radial direction of the input member 3.

[0048] 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 inside the stationary portion by a radial bearing.

[0049] The surface hardness of the input member 3, particularly the input-side engaging portion 13, can be made harder than the surface hardness of the engaging element 5, can be made softer than the surface hardness of the engaging element 5, or can be made substantially the same as the surface hardness of the engaging element 5.

[0050] (Output member) The output member 4 has an output-side engaging portion 21 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.

[0051] 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 composed of 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.

[0052] The output-side engaging portion 21 extends in the axial direction and has a portion that engages with the output-side engaged portion 36 of the engaging element 5. The engaging portion is radially inward of 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 arranged at 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 to engage or contact its outer peripheral surface with the output-side engaged portion 36 as the output member 4 or the engaging element 5 rotates.

[0053] The output-side engaging portion 21 has a cam function. The distance from the rotational center axis of the output member 4 to the outer circumferential surface of the output-side engaging portion 21, which engages with the output-side engaged portion 36, is not constant in the circumferential direction. As a result, when rotational torque is input in reverse to the output member 4, the output-side engaging portion 21 can press the engaging element 5 radially outward as the output member 4 rotates.

[0054] The number of parts of the output-side engaging portion 21 that engage with the output-side engaged portion 36 is determined according to the number of engaging elements 5. When the engaging element 5 is composed of multiple engaging elements 5, the output-side engaging portion 21 is also configured to have multiple engaging parts. In this example, the output-side engaging portion 21 is configured to have two parts that engage with the output-side engaged portion 36, corresponding to 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.

[0055] The outer circumferential surface of the output-side engaging portion 21 can adopt any configuration as long as the output-side engaging portion 21 has a cam function, and its shape is appropriately set according to the number of portions of the output-side engaging portion 21 that engage with the output-side engaged portion 36. When there are portions that engage with two output-side engaged portions 36, the output-side engaging portion 21 can be, for example, roughly rectangular, roughly oval, parallelogram, or trapezoidal in shape. However, from the standpoint of reducing the manufacturing cost of the output member 4, it is preferable that the outer circumferential surface of the output-side engaging portion 21 has a flat surface portion 22 in the portion that engages with the output-side engaged portion 36, and it is even more preferable that it is composed of a flat surface portion 22 and a partially cylindrical surface portion 23 centered on the central axis of the output member 4.

[0056] In this example, the outer circumferential surface of the output-side engaging portion 21 is composed of two parallel flat surfaces 22 and two partially cylindrical surfaces 23. The output-side engaging portion 21 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 22. Furthermore, the output-side engaging portion 21 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 22. In other words, the output-side engaging portion 21 has a shape that is twice symmetrical with respect to the central axis of the output member 4. The flat surfaces 22 and the partially cylindrical surfaces 23 are connected by a pointed edge 24.

[0057] Therefore, when manufacturing the output member 4 having the output-side engaging portion 21, it is not necessary to perform machining 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 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 22 and the partially cylindrical surface portion 23 can be connected by chamfered portions such as corner chamfers and rounded chamfers.

[0058] In this example, the output-side engaging portion 21 is located radially inside the two input-side engaging portions 13, and is positioned between the output-side engaged portions 36 of the two engaging elements 5.

[0059] As in this example, the output member 4 may have, in addition to the output-side engaging portion 21, an output shaft portion 25, an output flange portion 26, and a small-diameter shaft portion 27.

[0060] The output shaft portion 25 has a stepped cylindrical shape.

[0061] The output flange portion 26 protrudes radially outward from the outer circumferential surface of one axial end of the output shaft portion 25 along its entire circumference.

[0062] In this example, the output-side engaging portion 21 protrudes from the center of the end face on one axial side of the output shaft portion 25 toward the axial side.

[0063] The small-diameter shaft portion 27 has a cylindrical shape and protrudes from the center of the end face on one axial side of the output-side engaging portion 21 toward the one axial side.

[0064] The output member 4 can be rotatably supported by the pressed member 2 or the stationary portion. 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 28. The outer ring 29 of the radial rolling bearing 28 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 30a that is locked to one axial end of the small-diameter cylindrical surface portion 9. The inner ring 31 of the radial rolling bearing 28 is fitted snugly onto one axial end of the output shaft portion 25 and is axially clamped between the other axial side surface of the output flange portion 26 and a retaining ring 30b that is locked to the outer circumferential surface of the axial intermediate portion of the output shaft portion 25.

[0065] In this example, the radial rolling bearing 28 is a ball bearing using balls as rolling elements 32. However, the radial rolling bearing for supporting the output member 4 can also be constructed using tapered roller bearings or cylindrical roller bearings using tapered rollers as rolling elements.

[0066] Furthermore, the small-diameter shaft portion 27 of the output member 4 is supported on the inside of the input member 3 via a sliding bearing 33 such as a sleeve bearing, allowing for free relative rotation with respect to the input member 3. However, instead of the sliding bearing 33, a radial rolling bearing can be arranged around the small-diameter shaft portion 27. Alternatively, the small-diameter shaft portion 27 can be fitted to the inner circumferential surface of the input member 3 without radial play and in a manner that allows relative rotation. Alternatively, the small-diameter shaft portion 27 can be omitted.

[0067] The surface hardness of the input member 3, particularly the output-side engaging portion 21, can be made harder than the surface hardness of the engaging element 5, softer than the surface hardness of the engaging element 5, or approximately the same as the surface hardness of the engaging element 5.

[0068] (Engaging element) 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 to allow movement of the engaging element 5 in the radial direction (first direction).

[0069] 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. Conversely, when rotational torque is input in reverse to the output member 4, the engaging element 5 presses the pressing surface 34 against the pressed surface 6 based on the output-side engaging portion 21 engaging with the output-side engaged portion 36, thereby frictionally engaging the pressing surface 34 with the pressed surface 6.

[0070] The engaging element 5 is made of a metal material and has a hardened layer 52 on the portion of its surface that includes the pressing surface 34. The hardened layer 52 is an element that improves the surface hardness of the pressing surface 34 that comes into contact with the pressed surface 6 of the pressed member 2, thereby ensuring wear resistance.

[0071] The effective hardened layer depth d of the hardened layer 52 is 1 mm or less, and the surface hardness of the pressed surface 34 is HRC (Rockwell hardness C scale) 50 or higher. The effective hardened layer depth d is the distance from the surface of the hardened layer 52 to the position of the critical hardness, HV550, and can be measured by the measurement method specified in JIS G 0557:2019. Furthermore, HRC can be determined by the test method specified in JIS Z 2245:2016.

[0072] In the reverse input blocking clutch 1, by defining the effective hardened layer depth d of the hardened layer 52 and the surface hardness of the pressing surface 34 within the above-mentioned range, it is possible to prevent the core portion 53 of the engaging element 5 from becoming excessively hard. This ensures the wear resistance of the pressing surface 34 while preventing the engaging element 5 from becoming excessively aggressive towards at least one of the pressed member 2, input member 3, or output member 4 that engages with or comes into contact with the engaging element 5.

[0073] The lower limit of the effective hardened layer depth d of the hardened layer 52 is not particularly limited as long as it is finite (not zero), but can be, for example, 10 μm or more. By setting the effective hardened layer depth d of the hardened layer 52 to 10 μm or more, even if wear occurs on the pressing surface 34 due to the use of the reverse input blocking clutch 1, the surface hardness of the pressing surface 34 can be maintained at a desired level, specifically HRC 50 or higher, for a long period of time.

[0074] The hardened layer 52 can be formed on any area of ​​the surface of the engaging element 5, as long as it includes the pressing surface 34. Specifically, the hardened layer 52 can be formed only on the pressing surface 34, or it can be formed on the entire radial outer surface of the engaging element 5 including the pressing surface 34. Additionally, the hardened layer 52 can be formed on at least one of the parts of the input-side engaged portion 35 that engage with the input-side engaged portion 13, or the parts of the output-side engaged portion 36 that engage with the output-side engaged portion 21. Furthermore, the hardened layer 52 may be formed on the entire surface of the engaging element 5. From the standpoint of facilitating the heat treatment for forming the hardened layer 52, it is preferable to form the hardened layer 52 on the entire surface of the engaging element 5. In this example, the hardened layer 52 is formed on the entire surface of the engaging element 5.

[0075] The hardened layer 52 can be formed on the entire engaging element 5, that is, on the entire surface and the core portion 53 (the interior excluding the surface), but it can also be formed only on the surface of the engaging element 5. In other words, the engaging element 5 may additionally have an unhardened portion 54 in the core portion 53 with a Vickers hardness (HV) of 200 or less. The unhardened portion 54 is a part that is hardly affected by the heat treatment for forming the hardened layer 52. In other words, the unhardened portion 54 is a part in which the hardness of the base material of the engaging element 5 is maintained almost as is.

[0076] The engaging element 5 may also have a heat-affected layer 55 with an HV of 200 or more and less than 550 in the portion between the hardened layer 52 and the unhardened portion 54. That is, the engaging element 5 may have a hardened layer 52, a heat-affected layer 55, and an unhardened portion 54 in order from its surface toward the core portion 53. In this example, the engaging element 5 has an unhardened portion 54 and a heat-affected layer 55, and the core portion 53 is composed of the unhardened layer 54.

[0077] The method for forming the shape of the engaging element 5 is not particularly limited and can be formed by any method. For example, the engaging element 5 can be formed by pressing and punching a metal sheet. That is, the engaging element 5 can be a press-formed product of a metal sheet. This reduces the cost of forming the shape of the engaging element 5 compared to forming the shape of the engaging element 5 by applying at least one of the following processes to a metal material: sintering, forging, casting, or cutting.

[0078] When forming a metal sheet by press punching, the type of metal sheet is not limited to this, but hot-rolled steel sheet (SPHC), which is produced by heating steel to a temperature above its recrystallization point and rolling it, can be used. By using hot-rolled steel sheet, the hardness of the base material can be lowered, specifically to HV of 200 or less, making it easier to provide a non-hardened portion 54 in the core portion 53 of the engaging element 5.

[0079] However, the engaging element 5 can also be manufactured by subjecting a metal material to at least one of the following processes: sintering, forging, casting, or machining.

[0080] The method for forming the hardened layer 52 is not particularly limited.

[0081] For example, the hardened layer 52 can be formed by heat treatment of the metal material that is the base material of the engaging element 5. The type of heat treatment used to form the hardened layer 52 is not particularly limited, but for example, carburizing, high-frequency induction hardening, and through quenching can be applied. When quenching is applied as the heat treatment to form the hardened layer 52, tempering can be performed after quenching as needed.

[0082] Alternatively, if, at the time the shape of the engaging element 5 is formed, the engaging element 5 has a hardened layer 52 having a desired effective hardened layer depth d, and the surface hardness of the pressing surface 34 is at the desired value, then it is not necessary to perform any further processing to form the hardened layer 52.

[0083] In this example, the engaging element 5 is formed by cold-pressing a hot-rolled steel sheet, followed by carburizing, quenching, and tempering. In other words, the engaging element 5 is a press-formed product of a hot-rolled steel sheet.

[0084] 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.

[0085] 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.

[0086] The shape of the engaging element 5 is arbitrary as long as it has a pressing surface 34, an input-side engaged portion 35, and an output-side engaged portion 36, 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.

[0087] The engaging element 5 may have, as an optional component, convex curved surfaces 37 and 38 on at least one of the parts of the input-side engaged portion 35 that engages with the input-side engaging portion 13, and the output-side engaged portion 36 that engages with the output-side engaging portion 21. This makes it possible to bring the convex curved surface 37 of the input-side engaged portion 35 into contact with the radially inner surface 15 of the input-side engaged portion 13, or to bring the convex curved surface 38 of the output-side engaged portion 36 into contact with the flat surface 22 of the output-side engaging portion 21, when the reverse input blocking clutch 1 is operated.

[0088] In other words, the engaging element 5 may have a convex curved surface portion 37 on the part of the input-side engaged portion 35 that engages with the input-side engaging portion 13. Each input-side engaged portion 35 has a portion that engages with two input-side engaging portions 13. Therefore, the convex curved surface portion 37 is provided at two locations on the input-side engaged portion 35.

[0089] Additionally or alternatively, the engaging element 5 may have a convex curved surface portion 38 on the 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 convex curved surface portion 38 is provided at two locations on the output-side engaged portion 36.

[0090] In this example, the engaging element 5 has a convex curved surface portion 37 in the portion of the input-side engaged portion 35 that engages with the input-side engaging portion 13, and a convex curved surface portion 38 in the portion of the output-side engaged portion 36 that engages with the output-side engaging portion 21. 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.

[0091] In particular, in this example, the shape of the engaging element 5, which is formed by pressing and punching a metal plate, is provided with convex curved surfaces 37 and 38 to reduce the contact pressure at the contact points with the input member 3 and the output member 4. 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.

[0092] The pressing surface 34 is provided on the radially outer surface of the engaging element 5 facing the pressed surface 6. The pressing surface 34 may consist of the entire radially outer surface of the engaging element 5, or it may be provided on a part thereof. The radius of curvature of the pressing surface 34 may be the same as or smaller than the radius of curvature of the pressed surface 6. Also, there may be one or two pressing surfaces 34. In this example, the pressing surface 34 is composed of two pressing surfaces 34 provided at two locations on the radially outer surface of the engaging element 5 that are spaced apart from each other in the circumferential direction. 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.

[0093] Of the radially outer surface of the engaging element 5, the portion that is circumferentially away from the two pressing surfaces 34 is located radially inward from a virtual circle that is centered on the central axis of the input member 3 and tangent to the two pressing surfaces 34, when viewed from the axial direction. In other words, when the two pressing surfaces 34 are in contact with the surface to be pressed 6, the portion that is circumferentially away from the two pressing surfaces 34 does not come into contact with the surface to be pressed 6.

[0094] The input-side engaged portion 35 is provided in the radially intermediate portion of the widthwise center of the engaging element 5 and can be formed in any shape that is large enough to allow the input-side engaged portion 13 to be loosely inserted, for example, by a through hole in the axial direction for the engaging element 5 or by a recess formed radially inward from the radially outer surface of the engaging element. In this example, although not limited thereto, the input-side engaged portion 35 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 35 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 35, there are gaps between the input-side engaged portion 13 and the inner surface of the input-side engaged portion 35 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 35 in the rotational direction of the input member 3, and the input-side engaged portion 35 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 37 is provided on the radially inner surface 39 of the inner surface of the input-side engaged portion 35, which faces radially outward, in the portion that engages with the input-side engaged portion 13, so as to be convex toward the input-side engaged portion 13. The convex curved surface portion 37 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] For example, the engaging element 5 may have a convex portion 40 on the second intermediate portion of the radially inner surface 39 of the input-side engaged portion 35 that protrudes radially outward more than the portions adjacent to it on both sides in the second direction, and convex curved portions 37 may be provided at two locations in the second direction on the convex portion 40.

[0098] In this example, the convex curved surface portion 37 is provided at both ends of the convex surface portion 40 in the second direction. The convex surface portion 40 also has a connecting surface portion 50 in the second direction intermediate portion 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 first direction.

[0099] The cross-sectional shape and radius of curvature of the convex curved surface portion 37 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 cross-sectional shape of the convex curved surface portion 37 can be approximately arc-shaped, approximately elliptical, etc. The cross-sectional shape and radius of curvature of the convex curved surface portion 37 can be determined by experiment, simulation, etc.

[0100] In this example, the radially outer surface 41 of the inner surface of the input-side engaged portion 35, 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 42 connecting the radially inner surface 39 and the radially outer surface 41 is composed of a partially cylindrical concave curved surface.

[0101] The output-side engaged portion 36 is provided at the center of the width direction of the radially inner surface of the engaging element 5. The shape of the output-side engaged portion 36 is not limited as long as it is configured to engage with the output-side engaged portion 21. For example, the output-side engaged portion 36 is provided at the center of the width direction of the radially inner surface of the engaging element 5 and is composed of a flat surface that extends in the width direction of the engaging element 5 and is perpendicular to the radial direction, a recess that is recessed radially outward of the engaging element 5, a convex portion that protrudes radially inward of the engaging element 5, etc. In this example, the output-side engaged portion 36 is provided at the center of the width direction of the radially inner surface of the engaging element 5 so as to protrude radially inward from the adjacent portions on both sides in the width direction.

[0102] The convex curved portion 38 is provided at two locations within the output-side engaging portion 36: the portion that engages with the output-side engaging portion 21 when the output member 4 rotates to one side, and the portion that engages with the output-side engaging portion 21 when the output member 4 rotates to the other side relative to the engaging element 5. The convex curved portion 38 is provided so as to be convex toward the output-side engaging portion 21.

[0103] In this example, the convex curved surface portion 38 is provided at both ends of the output-side engaged portion 36 in the width direction (second direction). 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 by a flat surface perpendicular to the radial direction.

[0104] The cross-sectional shape and radius of curvature of the convex curved surface portion 38 are not particularly limited, as long as they can prevent the contact pressure at the contact point with the output-side engaging portion 21 from becoming excessive. For example, the cross-sectional shape of the convex curved surface portion 38 can be approximately arc-shaped, approximately elliptical, etc. The cross-sectional shape and radius of curvature of the convex curved surface portion 38 can be determined by experiment, simulation, etc.

[0105] (Biasing member and holding member) The reverse input blocking clutch 1 further comprises, as optional components, a biasing member 43 and a holding member 44.

[0106] The biasing member 43 elastically biases the engaging element 5 toward the pressed surface 6. The biasing member 43 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 43 is not particularly limited and is appropriately determined according to the number of engaging elements 5.

[0107] The biasing member 43 elastically biases the engaging element 5 toward the pressed surface 6 by the force that attempts to restore its elasticity. As a result, in the neutral state where no torque is applied to either the input member 3 or the output member 4, the pressing surface 34 of the engaging element 5 comes into contact with the pressed surface 6.

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

[0109] The retaining member 44 comprises a first spacer portion 45 and a second spacer portion 46 arranged spaced apart in the axial direction, and two connecting portions 48 arranged on both sides of the first spacer portion 45 and the second spacer portion 46 with respect to a 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.

[0110] The retaining member 44 is attached to the output member 4 with the engaging element 5 positioned between the first spacer portion 45 and the second spacer portion 46 in the axial direction, thereby restricting the axial movement of the engaging element 5 relative to the output member 4. Specifically, the retaining ring 49, which is locked to the small-diameter shaft portion 27 of the output member 4, restricts the movement of the retaining member 44 to one side in the axial direction, and the other side of the second spacer portion 46 is brought into contact with or close to the end face of the output shaft portion 25 on one side in the axial direction, thereby restricting the movement of the retaining member 44 to the other side in the axial direction.

[0111] <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. In Figures 3 and 4, the biasing member 43 and the holding member 44 are omitted in the reverse input blocking clutch 1 of this example, and the radial gap between the input member 3 and the output member 4 and the two engaging elements 5 is exaggerated.

[0112] 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 35 in the direction of rotation of the input member 3 (counterclockwise in the example of Figure 3).

[0113] This reduces the gap between the radially inner surface 15 of the input-side engaging portion 13 and the radially inner surface 39 of the input-side engaged portion 35, causing the radially inner surface 15 of the input-side engaging portion 13 to come into contact with the radially inner surface 39 of the input-side engaged portion 35.

[0114] 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 surfaces 37 provided on the input-side engaged portion 35.

[0115] From this state, as the input member 3 rotates further, the radially inner surface 15 of the input-side engaging portion 13 presses the radially inner surface 39 or one of the convex curved surfaces 37 of the input-side engaged portion 35 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, causing the radially inner surfaces of the two engaging elements 5 to approach each other, and the output-side engaged portion 21 of the output member 4 is clamped from both radial sides by the output-side engaged portions 36 of the two engaging elements 5.

[0116] In this way, the output member 4 is rotated so that the flat surface portion 22 of the output-side engaging portion 21 is parallel to the connecting surface portion 51 of the output-side engaged portion 36, while the output-side engaging portion 21 and the output-side engaged portion 36 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.

[0117] When rotational torque is applied 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 21 rotates in the direction of rotation of the output member 4 (clockwise in the example of Figure 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, causing the two engaging elements 5 to move toward the pressed surface 6.

[0118] 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 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.

[0119] 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.

[0120] In order to completely block the rotational torque that is input in reverse to the output member 4 and prevent it from being transmitted to the input member 3, the output member 4 is locked by bracing or clamping the engaging element 5 between the output-side engaging part 21 and the pressed member 2, so that the pressing surface 34 of the engaging element 5 does not slide against the pressed surface 6 and rotate relative to it.

[0121] 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 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 can slide and rotate relative to the pressed surface 6, thereby semi-locking the output member 4.

[0122] In the reverse input blocking clutch 1, the size of the gaps between each component is adjusted so that the above operations can be performed. In particular, in this example, when the pressing surfaces 34 of the two engaging elements 5 are in contact with the pressed surface 6, a gap exists between the radially inner surface 15 of the input-side engaging portion 13 and the convex portion 40 of the input-side engaged portion 35.

[0123] This prevents the radially 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 34 contacts the pressed surface 6, the surface pressure acting on the contact area between the pressing surface 34 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.

[0124] 1 Reverse input blocking clutch 2 Pressed member 3 Input member 4 Output member 5, 5a, 5b, 5c, 5d 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 Input shaft 15 Radial inner surface 17 Radial outer surface 19 Ridge 20 Input flange 21 Output side engaging part 22 Flat surface 23 Partial cylindrical surface 24 Ridge 25 Output shaft 26 Output flange 27 Small diameter shaft 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 part 36 Output side engaging portion 37 Convex curved portion 38 Convex curved portion 39 Radial inner surface 40 Convex portion 41 Radial outer surface 42 Circumferential surface 43 Biasing member 44 Holding member 45 First spacer portion 46 Second spacer portion 47 Holding hole 48 Connecting portion 49 Retaining ring 50 Connecting surface portion 51 Connecting surface portion 52 Hardened layer 53 Core portion 54 Unhardened portion 55 Heat-affected layer

Claims

1. A pressed member having a pressed surface on its inner circumferential surface; an input member having an input-side engaging portion located radially inward of the pressed surface and arranged coaxially with the pressed surface; an output member having an output-side engaging portion located radially inward of the input-side engaging portion and arranged coaxially with the pressed surface; and an engaging element having 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 arranged to be movable in the radial direction. The engaging element, when rotational torque is input to the input member, moves radially away from the pressed surface based on the input-side engaging portion engaging 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. Conversely, when rotational torque is input in reverse to the output member, the engaging element presses the pressing surface against the pressed surface based on the output-side engaging portion engaging with the output-side engaged portion, thereby frictionally engaging the pressing surface with the pressed surface. The engaging element is made of a metal material and has a hardened layer on its surface, including the pressing surface, with an effective hardened layer depth of 1 mm or less, and a surface hardness of the pressing surface of HRC 50 or higher. Reverse input blocking clutch.

2. The reverse input blocking clutch according to claim 1, wherein the hardened layer is provided on the entire surface of the engaging element.

3. The reverse input blocking clutch according to claim 1 or 2, wherein the engaging element has a non-hardened portion with a hardness of 200 or less in its core.

4. The reverse input blocking clutch according to any one of claims 1 to 3, wherein the engaging element is a press-formed product of a metal plate.

5. The reverse input shutoff clutch according to claim 4, wherein the metal plate is made of hot-rolled steel sheet.

6. The reverse input shutoff clutch according to any one of claims 1 to 5, 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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