CAM-MOUNTED CLUTCH

Abstract

A cam clutch is provided that prevents the occurrence of cam locking, enables smooth switching of the operating mode with an extremely small force, and whose size can be reduced. The cam clutch includes a first contact surface member (130) and a second contact surface member (140), each having cam contact surfaces that come into contact with a first cam (170a) and a second cam (170b) that are engaged with an outer ring (110) and an inner ring (160) in mutually different directions. The first contact surface member (130) and the second contact surface member (140) are provided at different positions in a direction of the rotation axis and are configured to be independently movable in the circumferential direction relative to an outer ring main body (120).The outer ring main body (120) has a first movement restricting part (122) and a second movement restricting part (123) which restrict the movement of the first contact surface element (130) and the second contact surface element (140) in the respective locking directions.

Description

Technical FieldThe present invention relates to a cam clutch configured to be switchable between different modes of operation.Prior ArtAs a clutch that controls transmission and interruption of a rotational force, a 2-way clutch that is switchable between driving and idling in both forward and reverse rotational directions is known.For example, Patent Literature 1 describes a clutch configured to control a retainer that retains a first clamping piece and a second clamping piece, respectively, biased in opposite rotational directions by biasing means so as to be switchable between three operation modes, namely, a two-way free mode that permits two-way rotation in forward and reverse rotational directions, a one-way lock mode that permits rotation only in forward rotational direction while preventing rotation in reverse rotational direction, and a one-way lock mode that permits rotation only in reverse rotational direction while preventing rotation in forward rotational direction.List of References[Patent Literature][Patent Literature 1] Japanese Patent Application Publication No. 2011-231828Overview of the InventionTechnical ProblemHowever, in the above-described two-way clutch, when the operation mode is to be changed, the retainer is controlled to forcibly tilt both the first clamping piece and the second clamping piece, and therefore a two-way lock mode that prevents relative two-way rotation of an outer ring and an inner ring with respect to each other in the forward and reverse rotation directions cannot be implemented.Moreover, in the two-way clutch described above, the first clamping piece and the second clamping piece are biased to come into contact with the outer ring and the inner ring, so that when a torque acts on the outer ring or the inner ring, one of the clamping pieces tilts to promptly engage with the outer ring and the inner ring, while another clamping piece continues to be in slidable contact with the outer ring and the inner ring and maintains an engagement standby state.When the torque is removed, one of the clamping pieces tilts in a disengaging direction to change to an idle state, but at this time, during a period before the one of the clamping pieces is disengaged, the other of the clamping pieces tilts in an engaging direction to start the engagement with the outer ring and the inner ring, which may possibly result in "locking" in which all the cams are simultaneously engaged.In such a state, all the clamping pieces are engaged with each other in a state of high surface pressures, and therefore, when the operation mode of the clutch is to be switched from a lock mode that inhibits relative rotations of the outer ring and the inner ring in either or both of the forward and rearward directions to a free mode, the relative rotations of the outer ring and the inner ring in both directions allows a large force to be required to change the orientations of the clamping pieces, which may possibly damage the engagement surfaces of the clamping pieces engaged with the outer ring and the inner ring as well as the respective raceway surfaces of the outer ring and the inner ring, thereby reducing the durability of the clutch. Another problem is also that high rigidity of an orientation changing member is required for changing the orientation of the clamping pieces.The present invention has been made on the basis of the above circumstances, and an object thereof is to provide a cam shift clutch that prevents the occurrence of cam lock-up, enables smooth switching of the operation mode with an extremely low force, and can be reduced in size.Solution of the ProblemThe present invention solves the above-described problems by providing a cam clutch including: an outer ring and an inner ring that are coaxially provided to be rotatable relative to each other; and a plurality of cams arranged in a circumferential direction between the outer ring and the inner ring, the plurality of cams including a first cam and a second cam that engage with the outer ring and the inner ring in mutually different directions, the cam clutch further including: an operation mode switching mechanism that acts on the first cam and / or the second cam to switch an operation mode, the outer ring or the inner ring including an outer ring main body or an inner ring main body, and a first contact surface member and a second contact surface member each having cam contact surfaces, which come into contact with the first cam and the second cam, the first contact surface member and the second contact surface member are provided at different positions in a direction of the rotational axis and are formed to be independently movable in the circumferential direction relative to the outer ring main body or the inner ring main body, the outer ring main body or the inner ring main body having a first movement restricting part and a second movement restricting part which restrict the movement of the first contact surface member and the second contact surface member in the respective locking directions.Advantageous Effects of the InventionAccording to claim 1 of the present invention, the first contact surface member and the second contact surface member each having the cam contact surfaces that come into contact with the first cam and the second cam are included, wherein the first contact surface member and the second contact surface member are provided at the different positions in the direction of the rotation axis and are formed to be independently movable in the circumferential direction relative to the outer ring main body or the inner ring main body, and wherein the outer ring main body or the inner ring main body includes the first movement restricting part and the second movement restricting part that restrict the movement of the first contact surface member and the second contact surface member in the respective locking directions. As a result, in the case of a two-way lock mode in which both the first cam and the second cam are operable, the first contact surface member or the second contact surface member moves depending on a direction of the rotational load to cause play, and when a rotational load state is changed, the non-rotational load cam, which is either the first cam or the second cam, can be brought into a state in which the cam is not engaged with the first contact surface member or the second contact surface member due to the play movement. Therefore, in a state where no torque is generated between the outer ring and the inner ring, occurrence of locking in which the first cam and the second cam are simultaneously engaged with the outer ring and the inner ring is prevented.Consequently, when the two-way lock mode is changed to another mode, it is possible to smoothly tilt the cam with an extremely small force, and high rigidity and a large driving force are no longer required for the operation mode switching mechanism, and therefore, size reduction can be achieved.According to claim 2 of the present invention, it is possible to use the biasing member that performs the biasing in the unlocking direction to reliably move the first contact surface member or the second contact surface member and cause play, and the locking in which the first cam and the second cam are simultaneously engaged with the outer ring and the inner ring is more reliably prevented.According to claim 3 of the present invention, with the one spring, the first contact surface member or the second contact surface member can be reliably moved, resulting in a simpler structure.According to claim 4 of the present invention, the movement of the first contact surface member or the second contact surface member becomes only a movement resulting from a slight relative rotation of the outer ring and the inner ring for engagement with the cam in the two-way lock mode, and therefore, no movement limiting member needs to be provided, and a configuration of the outer ring or the inner ring can be further simplified.Brief Description of the Drawings[FIG. 1 ] FIG. 1 is a perspective view of a cam shift clutch in an embodiment of the present invention, in which an operation mode switching mechanism is omitted.[FIG. 2 ] FIG. 2 is a perspective cross-sectional view of the cam shift clutch illustrated in FIG. 1, resulting from a section along a plane including a rotational axis thereof.[FIG. 3] FIG. 3 is a perspective view of the cam shift clutch illustrated in FIG. 1 with an outer ring omitted.[FIG. 4] FIG. 4 is a schematic view of a cam shift clutch in a second embodiment of the present invention.[FIG. 5 ] FIG. 5 is a schematic view of a cam shift clutch in a third embodiment of the present invention.[FIG. 6 ] FIG. 6 is a schematic view of a cam shift clutch in a fourth embodiment of the present invention.[FIG. 7 ] FIG. 7 is a schematic view of a cam shift clutch in a fifth embodiment of the present invention.[FIG. 8] FIG. 8 is an explanatory view of an operation of the cam clutch of the present invention.[FIG. 9 ] FIG. 9 is an explanatory view of the operation of the cam clutch of the present invention.[FIG. 10 ] FIG. 10 is an explanatory view of the operation of the cam clutch of the present invention.[FIG. 11 ] FIG. 11 is a schematic view of a cam shift clutch in still another embodiment of the present invention.DESCRIPTION OF EMBODIMENTSAs illustrated in FIGS. 1 to 3, a cam switching clutch 100 in an embodiment of the present invention includes an outer ring 110 and an inner ring 160 that are coaxially provided to be rotatable relative to each other, and a plurality of first cams 170 aand second cams 170 bserving as engaging elements that are disposed in an annular space between the outer ring 110 and the inner ring 160 to be spaced apart from each other in a circumferential direction and perform torque transmission and interruption between the outer ring 110 and the inner ring 160.The outer ring 110 includes an outer ring main body 120, a first contact surface member 130 having a cam contact surface that comes into contact with the first cams 170 aand a second contact surface member 140 having a cam contact surface that comes into contact with the second cams 170 b, and the first contact surface member 130 and the second contact surface member 140 are provided at different positions in a direction of the rotational axis and are formed to be independently movable in the circumferential direction with respect to the outer ring main body 120.The outer ring main body 120 has movement restricting grooves 121 each having a first movement restricting part 122 and a second movement restricting part 123 that restrict the movement of the first contact surface member 130 and the second contact surface member 140 in the respective locking directions, and a first movement restricting protrusion part 131 of the first contact surface member 130 and a second movement restricting protrusion part 141 of the second contact surface member 140 protrude into the movement restricting grooves 121 to restrict their respective ranges of movement in the circumferential direction.In the present embodiment, the movement restricting grooves 121 are provided at three locations in the circumferential direction, but may be provided at not more than two locations or at four or more locations.The first contact surface member 130 and the second contact surface member 140 each have a first biasing protrusion part 132 and a second biasing protrusion part 142, and in the present embodiment, the first contact surface member 130 and the second contact surface member 140 are biased in an unlocking direction by using a spring 150 serving as a biasing member provided to contract the first biasing protrusion part 132 and the second biasing protrusion part 142.The first biasing protrusion part 132, the second biasing protrusion part 142, and the spring 150 are provided in a biasing member-containing groove 124 provided in the outer ring main body 120.In the present embodiment, the biasing member containing groove 124 is provided at one location in the circumferential direction, but may be provided at any of two or more locations.Note that, in the same manner as in a known cam switching clutch, biasing means that biases the plurality of respective cams in an engagement direction to bring the cams into contact with the outer ring 110 and the inner ring 160, cage rings that are provided coaxially between the outer ring 110 and the inner ring 160 to be rotatable together with the outer ring 110 or the inner ring 160 and retain the plurality of individual cams, and the like are included, although not illustrated.Moreover, an operation mode switching mechanism is provided which acts on the first cam 170 aand the second cam 170 bto change their orientations and thereby switch an operation mode, but is not illustrated.The first cams 170 aand the second cams 170 bare engaged with the outer ring 110 and the inner ring 160 in different directions, and have identical outer shapes, for example, in the present embodiment, and what is obtained by reversing each of the first cams 170 afrom front to rear is used as each of the second cams 170 b.The first cams 170 aand the second cams 170 bare arranged so as to be alternately equidistantly arranged in the circumferential direction.The arrangement of the first cams 170 aand the second cams 170 bis not particularly limited, and the first cams 170 aand the second cams 170 bmay not necessarily be arranged to be alternately arranged in the circumferential direction. Further, the number of the first cams 170 amay also be different from the number of the second cams 170 b.The first cams 170 aand the second cams 170 bare formed to have radially narrowed portions at their central portions and to be substantially hourglass-shaped.The engagement direction of each of the first cams 170 ais a counterclockwise direction in FIG. 1 (hereinafter referred to as "reverse rotation direction"), and the first cam 170 ais configured to engage with the outer ring 110 and the inner ring 160 as a result of rotation of the outer ring 110 in the reverse rotation direction or rotation of the inner ring 160 in a clockwise direction (hereinafter referred to as "forward rotation direction") in FIG. 1.The engagement direction of each of the second cams 170 bis the forward rotation direction, and the second cam 170 bis formed to engage with the outer ring 110 or the inner ring 160 as a result of the rotation of the outer ring 110 in the forward rotation direction or the rotation of the inner ring 160 in the reverse rotation direction.Using the not-illustrated operation mode switching mechanism, the cam switching clutch in the present embodiment is switchable between four operation modes, namely, a forward rotation direction locking mode that prevents relative rotation of the outer ring 110 and the inner ring 160 with respect to each other in the forward rotation direction, a reverse rotation direction locking mode that prevents relative rotation of the outer ring 110 and the inner ring 160 with respect to each other in the reverse rotation direction, a two-way locking mode that prevents relative rotation of the outer ring 110 and the inner ring 160 with respect to each other in both the forward rotation direction and the reverse rotation direction, and a two-way free mode, allowing relative rotation of the outer ring 110 and the inner ring 160 with respect to each other in both the forward rotational direction and the reverse rotational direction.In the present embodiment described above, as the biasing member that biases the first contact surface member 130 and the second contact surface member 140 in the unlocking direction, the spring 150 that contracts the first biasing protrusion 132 and the second biasing protrusion 142 is provided, but the biasing member is not limited thereto.As schematically illustrated in FIG. 4, it is also possible, for example, to provide the spring 150 which presses the first contact surface element 130 and the second contact surface element 140 in a direction away from one another. Alternatively, as illustrated in FIG. 5, it may also be possible to provide the respective independent springs 150 between the first biasing protrusion part 132 and the outer ring main body 120 and between the second biasing protrusion part 142 and the outer ring main body 120.In the above-described embodiment, the outer ring 110 also includes the outer ring main body 120, the first contact surface member 130, and the second contact surface member 140 while the first cams 170 aand the second cams 170 bare formed to come into contact with the inner ring 160, the first contact surface member 130, and the second contact surface member 140, but it may be possible as shown in FIG. 6 that the inner ring 160 includes an inner ring main body 161, the first contact surface member 130, and the second contact surface member 140 while the first cams 170 aand the second cams 170 bare formed to come into contact with the outer ring 110, the first contact surface member 130, and the second contact surface member 140.As described later, since the biasing in the unlocking direction serves to cause movement of both the first contact surface member 130 and the second contact surface member 140 to an extent corresponding to the extent of movement of the inner ring 160 in a movement direction of the inner ring 160 as illustrated in FIG. 7, instead of the spring 150 that performs the direct biasing in the unlocking direction, a configuration that presses friction parts 151 of the inner ring 160 against the first contact surface member 130 and the second contact surface member 140 via compression springs 152 may also be used.Next, an operation of the cam clutch 100 according to the present invention will be described in comparison with a conventional cam clutch 500.First, as illustrated in FIG. 8, in the two-way lock mode (a state in which both the first cams 170 aand 570 aand the second cams 170 band 570 bare operable), when a driving force in the reverse rotation direction is applied to the inner rings 160 and 560 in a state in (a) in which the outer rings 110 and 510 are fixed and the outer rings 110 and 510 and the inner rings 160 and 560 are under no load (the relative rotational driving force is zero) as illustrated in (b), the inner rings 160 and 560 slightly move in the reverse rotation direction, and the second cams 170 band 570 bchange slightly to engage, thereby generating a torque, that counteracts the driving force and prevents rotation of the inner rings 160 and 560 in the reverse rotation direction.At this time, each of the first cams 170 aand 570 ais biased by unillustrated biasing means to come into contact with the inner rings 160 and 560, the first contact surface member 130, and the outer ring 510, and thus, in the conventional cam switching clutch 500, the first cam 570 a slips.In contrast, in the cam clutch 100 according to the present invention, the first contact surface member 130 slightly moves in the reverse rotation direction without slipping with the first cam 170 aby the biasing force of the spring 150.Then, as illustrated in FIG. 9, when the driving force in the reverse rotation direction is removed in a state in (b) and the outer rings 110 and 510 and the inner rings 160 and 560 are released again, the slopes of the second cams 170 band 570 bare restored to their initial positions so as to act to return the inner rings 160 and 560 to the forward rotation direction.At this time, in the conventional cam shift clutch 500, each of the first cams 570 a tilts immediately and starts to engage, the inclination of each of the second cams 570 bis not fully restored, the inner ring 560 does not return to a home position, and the first cam 570 aand, as illustrated in (c), the second cam 570 bcomes to rest at positions where the first cam 570 aand the second cam 570 bare in the same engagement state.In contrast, in the cam clutch 100 according to the present invention, in the state in (b), the first contact surface member 130 has moved in the reverse rotation direction by the same distance that the inner ring 160 has moved, and therefore the first cam 170 ais not tilted to engage, and the first contact surface member 130 moves in the forward rotation direction while compressing the spring 150. As illustrated in (c), at a time when the inclination of the second cam 170 bis fully restored, both the first cam 170 aand the second cam 170 breturn to an initial state ((a) of FIG. 8 ) in which no blockage has occurred, as illustrated in (c).Next, as illustrated in FIG. 10, when a driving force in the forward rotation direction is applied to each of the inner rings 160 and 560 in a state in (c) as illustrated in (d), the inner rings 160 and 560 slightly move in the forward rotation direction, and the first cams 170 aand 570 auntilt slightly to engage, thereby generating a torque that counteracts the driving force and prevents the rotation of the inner rings 160 and 560 in the forward rotation direction.At this time, in the conventional cam clutch 500, the inclination is recovered to facilitate the engagement of the second cam 570 a.In contrast, in the cam clutch 100 according to the present invention, the second contact surface member 140 slightly moves in the forward rotational direction without slipping with the second cam 170 b, by the biasing force of the spring 150.In addition, when the driving force in the forward rotation direction is removed and the outer rings 110 and 510 and the inner rings 160 and 560 are released again, in the same manner as in the above-described method of (b) to (c) of FIG. 9, the inclination of each of the first cams 170 aand 570 areturns to the initial state to act to return the inner rings 160 and 560 to the reverse rotation direction.At this time, in the conventional cam shift clutch 500, the second cam 570 bsumpts and starts to engage, the inclination of the second cam 570 ais not fully restored, and the first cam 570 aand the second cam 570 bcomes to rest at positions where the first cam 570 aand the second cam 570 bare in the same engagement state.In contrast, in the cam clutch 100 according to the present invention, in a state in (d) of FIG. 10, the second contact surface member 140 has moved in the forward rotational direction over the same distance over which the inner ring 160 has moved, and therefore the second cam 170 bis not tilted to engage, and the second contact surface member 140 moves in the reverse rotational direction while compressing the spring 150. At a time when the inclination of the first cam 170 ais fully restored, both the first cam 170 aand the second cam 170 breturn to an initial state ((a) of FIG. 8 ) in which no blockage has occurred.Therefore, in the conventional cam switching clutch 500, when the prevention of the driving force occurs at least once in the two-way lock mode although an unloaded state (in which a relative rotational driving force is zero) is achieved, both the first cam 570 aand the second cam 570 bare brought into a locked state, and accordingly, a large operating force is required by the operation mode switching mechanism that acts on the first cam 570 aand the second cam 570 bto change their respective orientations and thereby switch the operation mode.In contrast, in the cam clutch 100 according to the present invention, it is possible to establish, in an unloaded state (in which the relative rotational driving force is zero), a state in which neither the first cam 170a nor the second cam 170b are engaged, so that the switching of the operation mode can be smoothly performed with an extremely small force.Although the embodiment of the present invention has been described above in detail, the present invention is not limited to the above-described embodiment, and various design changes can be made without departing from the present invention as defined in the claims.For example, in the above-described embodiment, the spring 150, the friction members 151, and the like are each used as the biasing member, but as illustrated in FIG. 9, it may also be possible to move the first contact surface member 130 and the second contact surface member 140 only with a contact force between the first cam 170 aand the second cam 170 bwithout using the biasing member.Moreover, a shape of the first cam 170 aand the second cam 170 bmay also be a so-called clamping piece shape as used in the first embodiment, or may also be a cylinder-based shape as illustrated in other schematic views.While the one first contact surface element 130 and the one second contact surface element 140 are arranged in parallel in the axial direction, a plurality of the first contact surface elements 130 and a plurality of the second contact surface elements 140 may also be arranged. It is also possible to form the first contact surface member 130 and the second contact surface member 140 in an interlocked configuration such that the respective parts thereof in contact with the cams are aligned on the same circumference and the first cams 170 aand the second cams 170 bare arranged on the same circumference.List of reference characters100, 500 Cam clutch 110, 510 Outer ring 120 Outer ring main body 121 Movement restricting groove 122 First movement restricting part 123 Second movement restricting part 124 Biasing member containing groove 130 First contact surface member 131 First movement restricting protruding part 132 First biasing protruding part 140 Second contact surface member 141 Second movement restricting protruding part 142 Second biasing protruding part 150 Spring (biasing member) 151 Friction part (biasing member) 152 Compression spring (biasing member) 160, 560 Inner ring 161 Inner ring main body 170 a, 570 aFirst cam 170 b, 570 bSecond camReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedJP 2011-231828

[0004]

Claims

A cam shift clutch, comprising: an inner ring and an outer ring that are coaxially provided to be rotatable relative to each other; and a plurality of cams arranged in a circumferential direction between the outer ring and the inner ring; wherein the plurality of cams include a first cam and a second cam that engage with the outer ring and the inner ring in mutually different directions, wherein the cam shift clutch further comprises: an operation mode switching mechanism that acts on the first cam and / or the second cam to switch an operation mode, wherein the outer ring or the inner ring ring includes an outer ring main body or an inner ring main body and a first contact surface member and a second contact surface member that respectively include cam contact surfaces that contact the first cam and the second cam, wherein the first contact surface member and the second contact surface member are provided at different positions in the direction of the rotational axis and are formed to be independently movable in the circumferential direction relative to the outer ring main body or the inner ring main body, the outer ring main body or the inner ring main body having a first movement restricting part and a second movement restricting part that restrict the movement of the first contact surface member and the second contact surface member in the respective locking directions.The cam clutch according to claim 1, wherein the outer ring or the inner ring includes a biasing member that biases the first contact surface member and the second contact surface member in an unlocking direction.The cam clutch according to claim 2, wherein the biasing member is a spring member having one end contacting the first contact surface member and the other end contacting the second contact surface member.The cam clutch according to claim 1, wherein the first contact surface member and the second contact surface member are formed to obtain moving forces in an unlocking direction from a frictional force between the first contact surface member and the second contact surface member and the inner ring or the outer ring opposing thereto via the first cam and the second cam.

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