One-way clutch and reverse input prevention clutch

Abstract

To prevent roll-over of a rolling body in a one-way clutch in which the rolling bodies to be engage elements are integrated while being abutted to each other and a cam surface is formed in an inner member which is engaged with the rolling body radially inside of an array of the rolling bodies.SOLUTION: The other end of a C-shaped spring 5 of which one end is locked to an inner ring (inner member) 2 is abutted to a roller 4 arranged in a one row end of an array of mutually abutted rollers (rolling bodies) 4 in such a manner that each roller 4 is engaged with an outer ring (outer member) 1 and the inner ring 2. A radius R1L of a cam surface 2a of the inner ring 2 opposed with the roller 4 which is arranged in the other row end of the array, in an engage side end A1L is made larger than a radius R1 of the cam surface 2a of the inner ring 2 opposed with the other roller 4 of the array in an engage side end A1. The roller 4 is made hard to move over the engage side ends A1 and A1L of the cam surface 2a of the inner ring 2, thereby preventing roll-over of the roller 4.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a one-way clutch and a reverse input prevention clutch in which rolling elements serving as engagers are assembled in a state of contact with each other. [Background technology]

[0002] A one-way clutch has multiple cam surfaces inclined in a predetermined direction on either the inner surface of the outer member or the outer surface of the inner member, and the other is a cylindrical surface. A plurality of wedge-shaped spaces that are narrow on one circumferential side are formed between the outer and inner members, and an elastic member is used to press the rolling elements that serve as engagers contained in each wedge-shaped space into the narrow part of the wedge-shaped space, thereby engaging with the outer and inner members. When one of the outer and inner members rotates in a predetermined direction, the two members are locked and torque is transmitted to the other member, and when one of the members rotates in the opposite direction, the locked state of the two members is released and only one of the members spins freely.

[0003] Furthermore, some one-way clutches as described above have all the rolling elements assembled in a state of abutment with each other in order to increase the number of rolling elements arranged and thereby increase the torque transmission capacity (when the rolling elements are rollers, this is called a full roller type).In addition, in a full roller type one-way clutch, a C-shaped spring as an elastic member is arranged between the outer member and the inner member so as to extend along the arrangement of the rollers, and a hook portion at one end of the spring is engaged with the outer member or the inner member, and a hook portion at the other end is brought into contact with the rollers arranged at one end of the row of the roller arrangement, thereby transmitting the pressing force to all the rollers and forcing each roller into the narrow portion of the wedge-shaped space (see Patent Document 1).

[0004] On the other hand, a reverse input prevention clutch is a clutch that has the function of transmitting rotation to the output member when an input torque is applied to the input member, and preventing the input member from rotating when a reverse input torque is applied to the output member.

[0005] As a specific configuration of this reverse input prevention clutch, for example, a torque transmission means is provided between an input member and an output member which rotate about the same axis, for transmitting the rotation of the input member to the output member with a slight angular delay, a plurality of cam surfaces inclined in one predetermined direction and a plurality of cam surfaces inclined in the other predetermined direction are provided consecutively on the outer circumferential surface of the output member, a fixed member having a cylindrical surface facing each of these cam surfaces is provided, and a plurality of first wedge-shaped spaces narrowed on one side in the circumferential direction and a second wedge-shaped space narrowed on the other side in the circumferential direction are provided consecutively between the output member and the fixed member. In one example, rollers are housed in each wedge-shaped space as rolling elements that act as engagers in a state in which they abut against each other, and hook portions at both ends of a C-shaped spring (elastic member) extending along the arrangement of the rollers are brought into abutment with the rollers arranged at the end of one row of the abutting roller arrangement, thereby forcing each roller into the narrow portion of the first or second wedge-shaped space to engage with the fixed member and the output member, and a pillar portion of a cage connected to rotate integrally with the input member is inserted at a position where the narrow portion of the first wedge-shaped space and the narrow portion of the second wedge-shaped space face each other in the circumferential direction (see Patent Document 2).

[0006] In the reverse input prevention clutch described in Patent Document 2, the rollers are pushed into the narrow portion of the first or second wedge-shaped space by the elastic force of the C-shaped spring and engage with the fixed member and the output member, so that even if a reverse input torque is applied to the output member in either direction, the output member is locked to the fixed member and the input member does not rotate. On the other hand, when an input torque is applied to the input member, regardless of the direction in which the input member rotates, the column portion of the retainer that rotates integrally with the input member pushes the rollers facing in the rotation direction toward the wider side of the first or second wedge-shaped space against the elastic force of the C-shaped spring, and the output member is released from the locked state. After that, the torque is transmitted to the output member by the torque transmission means provided between the input member and the output member, and the output member rotates. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 3989702 [Patent Document 2] Patent No. 6633277 Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, in a clutch having a structure in which rollers are in contact with each other as in Patent Documents 1 and 2, the circumferential length of the cam surface formed in accordance with the circumferential pitch of the rollers becomes short. For this reason, particularly when a cam surface is formed on the outer peripheral surface of a member that engages with the rollers radially inward of the roller arrangement (the inner member of a one-way clutch, the output member of a reverse input prevention clutch), the difference between the dimension from the axis of the inner member to the wide end of the wedge-shaped space (the radius at the disengagement end of the cam surface) and the dimension to the narrow end of the wedge-shaped space (the radius at the engagement end of the cam surface) becomes small. In other words, the step between two consecutive cam surfaces becomes small.

[0009] As a result, when a large torque is applied to the inner and outer members that engage via the rollers in a direction that relatively pushes the rollers into the narrow portion of the wedge-shaped space, the rollers may climb over the engaging end of the cam surface and move into the adjacent wedge-shaped space (this phenomenon is called roller "rollover"). When roller rollover occurs, the inner and outer members are not in a locked state, so in a one-way clutch, the torque transmission operation becomes unstable, and in a reverse input prevention clutch, the input member rotates due to the reverse input torque.

[0010] Therefore, an object of the present invention is to prevent rollover of the rolling elements in a one-way clutch and a reverse input prevention clutch in which the engaging rolling elements are assembled in a state in which they abut against each other and a cam surface is formed on a member that engages with the rolling elements radially inward from the arrangement of the rolling elements. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention provides a one-way clutch in which the inner peripheral surface of an outer member is cylindrical, and the outer peripheral surface of an inner member arranged inside the outer member is provided with a plurality of successive cam surfaces inclined in a predetermined direction, so that a plurality of successive wedge-shaped spaces which become narrower on one circumferential side are formed between the outer member and the inner member, and rolling elements are accommodated in each of the wedge-shaped spaces in a state of abutting against each other, and an elastic member engaged with the outer member or the inner member is brought into abutment against the rolling elements arranged at one row end of the arrangement of the abutting rolling elements, thereby forcing each of the rolling elements into the narrow portion of the wedge-shaped space and engaging with the outer member and the inner member, wherein the inner member has a configuration in which the radius at the engagement end of the cam surface facing the rolling elements arranged at the other row end of the arrangement of the abutting rolling elements is made larger than the radius at the engagement end of the cam surface facing the other rolling elements in that arrangement.

[0012] In a one-way clutch of the above configuration, even if a large input torque is applied to one of the outer member and the inner member in a direction that relatively pushes the rolling elements into the narrow portion of the wedge-shaped space, the rolling elements are unlikely to climb over the engagement side end of the cam surface, so that rollover of the rolling elements can be effectively prevented.

[0013] Here, when the cam surface of the inner member is formed as an arc surface that is convex radially outward, the arc radius of the cam surface that faces the rolling element arranged at the other row end of the array of the rolling elements that abut against each other may be made larger than the arc radius of the cam surface that faces the other rolling elements in the array. In this case, the arc radius of the cam surface that faces the rolling element arranged at the other row end of the array of the rolling elements that abut against each other is desirably 1.5 times or more the arc radius of the cam surface that faces the other rolling elements in the array.

[0014] Alternatively, the cam surface of the inner member that faces the rolling element arranged at the other end of the row of the arrangement of the mutually abutting rolling elements may be formed as a flat surface or an arcuate surface that is concave radially outward.

[0015] The present invention also provides a torque transmission means between an input member and an output member which rotate about the same axis, for transmitting the rotation of the input member to the output member with a slight angular delay, and a plurality of cam surfaces inclined in one predetermined direction and inclined in the other predetermined direction are provided consecutively on the outer circumferential surface of the output member, and a fixed member having a cylindrical surface opposed to each of these cam surfaces is provided, and a plurality of first wedge-shaped spaces narrowed on one circumferential side and a plurality of second wedge-shaped spaces narrowed on the other circumferential side are formed consecutively between the output member and the fixed member, and rolling elements are accommodated in each of the wedge-shaped spaces in a state of contact with each other, and one row of the arrangement of the rolling elements in contact with each other is provided. In this reverse input prevention clutch, an elastic member is provided that abuts against the rolling elements arranged at one end of the row, and the elastic force of this elastic member is used to push each of the rolling elements into the narrow portion of the first or second wedge-shaped space to engage with the fixed member and output member, and a column portion of a retainer connected to the input member so as to rotate integrally is inserted at a position where the narrow portion of the first wedge-shaped space and the narrow portion of the second wedge-shaped space face each other in the circumferential direction, and the output member is configured so that the radius at the engagement end of the cam surface facing the rolling elements arranged at the other row end of the arrangement of the mutually abutting rolling elements is larger than the radius at the engagement end of the cam surface facing the other rolling elements in the arrangement.

[0016] In the reverse input prevention clutch of the above configuration, even if a large reverse input torque is applied to the output member, the rolling elements are less likely to climb over the engagement side end of the cam surface, so that rollover of the rolling elements can be effectively prevented.

[0017] Here, when the cam surface of the output member is formed as an arc surface that is convex toward the radially outward direction, the arc radius of the cam surface that faces the rolling element arranged at the other row end of the array of the rolling elements that abut against each other may be made larger than the arc radius of the cam surface that faces the other rolling elements in the array. In this case, the arc radius of the cam surface that faces the rolling element arranged at the other row end of the array of the rolling elements that abut against each other is desirably 1.5 times or more the arc radius of the cam surface that faces the other rolling elements in the array.

[0018] Alternatively, the cam surface of the output member that faces the rolling element arranged at the other end of the row of the arrangement of the mutually abutting rolling elements may be formed as a flat surface or an arcuate surface that is concave radially outward. Effect of the Invention

[0019] As described above, the present invention makes it possible to prevent rollover of the rolling elements in a one-way clutch and a reverse input prevention clutch. Therefore, in a one-way clutch, stable torque transmission operation can be obtained even when a large input torque is applied, and in a reverse input prevention clutch, rotation of the input member can be reliably prevented even when a large reverse input torque is applied. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a longitudinal sectional front view of a one-way clutch according to a first embodiment; [Diagram 2] Cross-sectional view taken along line II-II in Figure 1. [Diagram 3] FIG. 2 is an enlarged longitudinal sectional front view of the main part of FIG. 1; [Figure 4] 2A and 2B are longitudinal sectional front views showing modified examples of the cam surface of the inner ring in FIG. [Diagram 5] FIG. 11 is a longitudinal sectional front view of a reverse input prevention clutch according to a second embodiment; [Figure 6] Cross-sectional view taken along line VI-VI in Figure 5. [Figure 7] FIG. 6 is an enlarged longitudinal sectional front view of the main part of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figures 1 to 3 show a one-way clutch of the first embodiment. As shown in Figures 1 and 2, this one-way clutch is of a full-roller type in which the inner peripheral surface of an outer ring (outer member) 1 is a cylindrical surface, a plurality of cam surfaces 2a inclined in a predetermined direction are continuously provided on the outer peripheral surface of an inner ring (inner member) 2 that is passed through the outer ring 1, a plurality of wedge-shaped spaces 3 that are narrowed on one side in the circumferential direction are continuously formed between the outer ring 1 and the inner ring 2, rollers (rolling elements that become engaging elements) 4 are housed in each wedge-shaped space 3 in a state of abutting against each other, and each roller 4 is pressed into the narrow part of the wedge-shaped space 3 by a C-shaped spring 5 arranged so as to extend along the arrangement of the rollers 4 between the outer ring 1 and the inner ring 2.

[0022] The outer ring 1 has a plurality of axially extending protrusions 1a integrally formed on its outer circumferential surface as torque transmission means. The inner ring 2 is fixed to the outer periphery of a rotating shaft 7 via a key 6, and is provided with a locking groove 2b for locking one end of a C-shaped spring 5, as described below, at one circumferential location on its outer circumferential surface. The cam surface 2a of the inner ring 2 is formed as an arc surface that protrudes radially outward.

[0023] The C-shaped spring 5 is formed from a round wire and has a hook portion 5a at one end that extends linearly radially inward of the clutch, and a roughly L-shaped hook portion 5b at the other end that extends in the clutch axial direction.

[0024] In addition, this C-shaped spring 5 is assembled so that, in its elastically contracted state, the hook portion 5a at one end is engaged with one side wall of the locking groove 2b of the inner ring 2, and the hook portion 5b at the other end is in contact with a roller 4 arranged at one end of the row of rollers 4 that abut against each other, near the other side wall of the locking groove 2b of the inner ring 2. As a result, the pressing force due to the elastic force of the C-shaped spring 5 is transmitted from the roller 4 in contact with the C-shaped spring 5 to all the other rollers 4, and each roller 4 is pushed into the narrow portion of the wedge-shaped space 3 and engages with the outer ring 1 and the inner ring 2.

[0025] As shown in FIG. 3, the inner ring 2 has a cam surface 2a (hereinafter referred to as the "last cam surface") that faces the roller 4 arranged at the other end of the row of the rollers 4 that abut against each other, and the radius of the arc of the cam surface 2a (hereinafter referred to as the "other cam surfaces") that faces the other rollers 4 in the row is set to 1.5 times or more. L Radius R1 at L is larger than the radius R1 at the engagement side end A1 of the other cam surface 2a.

[0026] This one-way clutch has the above-mentioned configuration, and when input torque is applied to the outer ring 1, as shown in Fig. 1, when the outer ring 1 rotates clockwise, the outer ring 1 and the inner ring 2 are locked via the rollers 4, and the torque of the outer ring 1 is transmitted to the inner ring 2, and when the outer ring 1 rotates counterclockwise, the locked state between the outer ring 1 and the inner ring 2 is released and only the outer ring 1 spins freely. Conversely, when input torque is applied to the inner ring 2 from the rotating shaft 7 via the key 6, the torque is transmitted to the outer ring 1 when the inner ring 2 rotates counterclockwise, and when the inner ring 2 rotates clockwise, the inner ring 2, the rollers 4, and the C-shaped spring 5 spin freely together.

[0027] In this one-way clutch, the engagement end A1 of the last cam surface 2a of the inner ring 2 L Radius R1 at L is formed to be larger than the radius R1 at the engagement side end A1 of the other cam surface 2a, so that the roller 4 is L As a result, even when a large input torque is applied to one of the outer ring 1 and the inner ring 2 in a direction that relatively pushes the rollers 4 into the narrow portion of the wedge-shaped space 3 (the direction in which torque is transmitted between the outer ring 1 and the inner ring 2), it is possible to prevent the rollers 4 from rolling over, and stable torque transmission operation is achieved.

[0028] In addition, the cam surface 2a of the inner ring 2 is formed as an arc surface that is convex toward the outside in the radial direction as in the example of FIG. 1 to FIG. 3 described above, and it is preferable that the arc radius of the last cam surface 2a is 1.5 times or more the arc radius of the other cam surfaces 2a, but it is not limited to this.L Radius R1 at L It is sufficient that the radius R1 at the engagement side end A1 of the other cam surface 2a is larger than the radius R1 at the engagement side end A1 of the other cam surface 2a.

[0029] Therefore, for example, the last cam surface 2a of the inner ring 2 can be formed as a flat surface as shown in FIG. 4(a), or as an arcuate surface that is concave radially outward as shown in FIG. 4(b).

[0030] 5 to 7 show a reverse input prevention clutch of a second embodiment. As shown in Fig. 5 and Fig. 6, this reverse input prevention clutch includes an input shaft (input member) 11, an output member 14 consisting of an output shaft 12 and an inner ring 13, a fixed member 18 consisting of a housing 15, an outer ring 16 and a pressing cover 17, a cage 19 having two pillar portions 19a inserted between the inner ring 13 and the outer ring 16, rollers (rolling elements serving as engagers) 20 incorporated between the two pillar portions 19a of the cage 19, and two C-shaped springs 21 arranged to extend along the arrangement of the rollers 20 between the inner ring 13 and the outer ring 16.

[0031] The input shaft 11 has an engagement portion 11a having a two-face width portion near its tip, and this engagement portion 11a is inserted into an engagement hole 13a provided in the center of the inner ring 13, while the small diameter tip portion 11b is fitted into a shaft hole 12a provided in the center of the end face of the output shaft 12, so that the input shaft 11 rotates around the same axis as the output shaft 12.

[0032] The output member 14 connects the output shaft 12 and the inner ring 13 so that they rotate integrally. An engagement hole 13a of the inner ring 13 is formed with a two-face width portion that faces the two-face width portion of the engagement portion 11a of the input shaft 11 with a small gap therebetween, so that the rotation of the input shaft 11 is transmitted to the inner ring 13 and the output shaft 12 with a small angular delay.

[0033] The fixed member 18 is formed by fitting an outer ring 16 and a cover 17 in that order onto the inner periphery of a housing 15. The outer ring 16 is restrained by the housing 15 so as not to rotate, and is prevented from coming off by the cover 17.

[0034] The retainer 19 has pillar portions 19a provided at opposing positions on the periphery of a disc portion 19b through which the input shaft 11 passes, and the disc portion 19b is fitted and fixed to the outer periphery of the engagement portion 11a of the input shaft 11 so as to rotate integrally with the input shaft 11.

[0035] The outer peripheral surface of the inner ring 13 is provided with a plurality of continuous cam surfaces 13b inclined in one direction and a plurality of continuous cam surfaces 13c inclined in the other direction, so that a plurality of first wedge-shaped spaces 22a narrowed on one side in the circumferential direction and a plurality of second wedge-shaped spaces 22b narrowed on the other side in the circumferential direction are formed between the inner ring 13 and the outer ring 16. The cam surfaces 13b and 13c of the inner ring 13 are each formed as an arc surface that is convex toward the outside in the radial direction. The rollers 20 are accommodated in the continuous wedge-shaped spaces 22a and 22b in a state of abutting against each other, and the pillar portions 19a of the cage 19 are inserted at positions where the narrow portions of the first wedge-shaped spaces 22a and the narrow portions of the second wedge-shaped spaces 22b face each other in the circumferential direction.

[0036] Each of the C-shaped springs 21 is formed of a round wire material, and is provided at both ends with a generally dogleg-shaped hook portion 21a extending in the clutch axial direction. In an elastically contracted state, the hook portion 21a at one end abuts against a roller 20 arranged at one end of an array of rollers 20 accommodated in a continuous first wedge-shaped space 22a and abutting against each other, and the hook portion 21a at the other end abuts against a roller 20 arranged at one end of an array of rollers 20 accommodated in a continuous second wedge-shaped space 22b and abutting against each other. As a result, each of the C-shaped springs 21 uses its elastic force to press each roller 20 into the narrow portion of the first or second wedge-shaped space 22a, 22b.

[0037] As shown in FIG. 7, the inner ring 13 has the cam surfaces (last cam surfaces) 13b, 13c that face the rollers 20 arranged at the other end of the row of the mutually abutting rollers 20, the arc radius of which is 1.5 times or more the arc radius of the cam surfaces (other cam surfaces) 13b, 13c that face the other rollers 20 in the row.L Radius R2 at L is larger than the radius R2 at the engagement side ends A2 of the other cam surfaces 13b, 13c.

[0038] This reverse input prevention clutch has the above-mentioned configuration, and each roller 20 is pressed into the narrow portion of the first or second wedge-shaped space 22a, 22b by the elastic force of the C-shaped spring 21 and engages with the outer ring 16 and the inner ring 13. Therefore, even if reverse input torque is applied to the output shaft 12 in either direction, the output member 14 is locked to the fixed member 18 and the input shaft 11 does not rotate either.

[0039] On the other hand, when an input torque is applied to the input shaft 11, regardless of the direction in which the input shaft 11 rotates, the column portions 19a of the retainer 19, which rotates integrally with the input shaft 11, push the rollers 20 facing in the rotational direction toward the wider side of the first or second wedge-shaped space 22a, 22b against the elastic force of the C-shaped springs 21, thereby releasing the output member 14 from the locked state. Then, when the input shaft 11 further rotates and the two-face width portion of the engagement portion 11a engages with the two-face width portion of the engagement hole 13a of the inner ring 13, the rotation of the input shaft 11 is transmitted to the output shaft 12 via the inner ring 13.

[0040] Here, in this reverse input prevention clutch, the engagement side end A2 of the last cam surface 13b, 13c of the inner ring 13 L Radius R2 at L is formed to be larger than the radius R2 at the engagement side end A2 of the other cam surfaces 13b, 13c, so that the rollers 20 are L As a result, even if a large reverse input torque is applied to the output member 14, the rollers 20 can be prevented from rolling over, and the rotation of the input shaft 11 can be reliably prevented.

[0041] In this reverse input prevention clutch, as in the one-way clutch of the first embodiment, the cam surfaces 13b, 13c of the inner ring 13 are not limited to those in the examples of Figures 5 to 7, and the last cam surfaces 13b, 13c of the inner ring 13 can also be formed as a flat surface or an arcuate surface that is concave toward the radially outward side (not shown).

[0042] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0043] For example, in each of the above-described embodiments, a C-shaped spring is used as the elastic member that presses the roller into the narrow portion of the wedge-shaped space, but the elastic member may also be a coil spring or a leaf spring (S-shaped, Z-shaped, V-shaped, etc.).

[0044] Furthermore, the present invention is not limited to one-way clutches and reverse input prevention clutches that use rollers as rolling elements as in the embodiment, but can of course also be applied to one-way clutches and reverse input prevention clutches that use balls or the like other than rollers as rolling elements. [Explanation of symbols]

[0045] 1 Outer ring (outer component) 2 Inner ring (inner component) 2a Cam surface 3 Wedge-shaped space 4 Rollers (rolling elements) 5 C-shaped spring 5a, 5b Hook part 6 Key 7 Rotation Axis 11 Input shaft (input member) 12 Output shaft 13. Inner Circle 13b, 13c Cam surface 14 Output member 15 Housing 16 Outer ring 17 Presser cover 18 Fixing member 19 Cage 19a Column 20 Rollers (rolling elements) 21 C-shaped spring 21a Hook part 22a First wedge-shaped space 22b Second wedge space A1, A2 (other cam surface) engagement end A1 L , A2 L (The last cam surface) Engagement end

Claims

1. a one-way clutch in which an inner peripheral surface of an outer member is cylindrical, an outer peripheral surface of an inner member disposed inside the outer member is provided with a plurality of successive cam surfaces inclined in a predetermined direction, a plurality of successive wedge-shaped spaces narrowed on one circumferential side between the outer member and the inner member, a step is provided between two successive cam surfaces, rolling elements are accommodated in each wedge-shaped space in a state of abutting against each other, all of the rolling elements arranged in the circumferential direction between the outer member and the inner member are in a state of abutting against each other, an elastic member engaged with the outer member or the inner member is brought into abutment against a rolling element arranged at one end of the arrangement of the rolling elements abutting against each other, thereby forcing each of the rolling elements into the narrow portion of the wedge-shaped space and engaging with the outer member and the inner member, and the elastic member is a C-shaped spring disposed so as to extend along the arrangement of the rolling elements abutting against each other between the outer member and the inner member, a cam surface facing the rolling element at the other row end of the arrangement of the mutually abutting rolling elements has a radius at the engagement side end that is larger than the radius at the engagement side end of the cam surface facing the other rolling element in the arrangement.

2. 2. The one-way clutch according to claim 1, wherein the cam surface of the inner member is formed as an arcuate surface that is convex radially outward, and the arc radius of the cam surface that faces the rolling element arranged at the other row end of the arrangement of the mutually abutting rolling elements is larger than the arc radius of the cam surface that faces the other rolling elements in the arrangement.

3. 3. The one-way clutch according to claim 2, characterized in that the arc radius of the cam surface facing the rolling element arranged at the other row end of the arrangement of the mutually abutting rolling elements is 1.5 times or more the arc radius of the cam surface facing the other rolling element in the arrangement.

4. 2. The one-way clutch according to claim 1, wherein the cam surface of the inner member that faces the rolling element disposed at the other row end of the arrangement of the rolling elements in contact with each other is formed as a flat surface or an arcuate surface that is concave radially outward.

5. A torque transmission means is provided between an input member and an output member which rotate about the same axis, for transmitting the rotation of the input member to the output member with a slight angular delay, a plurality of cam surfaces inclined in one predetermined direction and a plurality of cam surfaces inclined in the other predetermined direction are provided consecutively on the outer peripheral surface of the output member, a step is provided between two consecutive cam surfaces, and a fixed member is provided having a cylindrical surface facing each of these cam surfaces, and a plurality of first wedge-shaped spaces which are narrower on one side in the circumferential direction and a second wedge-shaped space which is narrower on the other side in the circumferential direction are formed consecutively between the output member and the fixed member, and rolling elements are disposed in each of the wedge-shaped spaces. a C-shaped spring disposed between the fixed member and the output member so as to extend along the arrangement of the rolling elements, and a column portion of a retainer connected to the input member so as to rotate integrally with the input member is inserted at a position where the narrow portion of the first wedge-shaped space and the narrow portion of the second wedge-shaped space face each other in the circumferential direction, The output member is opposed to the rolling element arranged at the other row end of the arrangement of the rolling elements abutting against each other. The radius of the engagement end of the facing cam surface is the same as the engagement end of the opposing cam surface of the other rolling elements in the array. A reverse input prevention clutch characterized in that the radius at the side ends is larger than that at the rear ends.

6. 6. A reverse input prevention clutch as described in claim 5, characterized in that the cam surface of the output member is formed as an arcuate surface that is convex radially outward, and the arc radius of the cam surface that faces the rolling element arranged at the other row end of the arrangement of the mutually abutting rolling elements is made larger than the arc radius of the cam surface that faces the other rolling elements in the arrangement.

7. 7. A reverse input prevention clutch as claimed in claim 6, characterized in that the arc radius of the cam surface facing the rolling element arranged at the other row end of the arrangement of the mutually abutting rolling elements is 1.5 times or more the arc radius of the cam surface facing the other rolling element in the arrangement.

8. 6. The reverse input prevention clutch according to claim 5, wherein the cam surface of the output member that faces the rolling element arranged at the other row end of the arrangement of the rolling elements that abut against each other is formed as a flat surface or an arcuate surface that is concave toward the radially outward side.

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