Clutch release mechanism and clutch assembly including same

A clutch release mechanism includes a fixed cam plate having a cylindrical boss portion, and a movable cam plate supported on the cylindrical boss portion through a cylindrical projecting portion thereof. A ball unit is retained on the cylindrical boss portion by a retainer, and a release member disengages a clutch by transmitting a thrust force, generated by relative turning between the fixed and movable cam plates which hold the ball unit therebetween, to a pressure-applying plate. A pressing member is pressed by the movable cam plate to transmit the thrust force to the release member. The cylindrical projecting portion of the movable cam plate projects toward the pressing member, and is fitted a the hollow portion thereof with a gap therebetween. The movable cam plate presses the pressing member so as to be relatively shiftable on a flat surface perpendicular to a pressing direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority under 35 USC 119 based on Japanese patent application No. 2010-028662, filed on Feb. 12, 2010. The entire subject matter of this priority document, including specification claims and drawings thereof, is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a clutch release mechanism used to release the engagement of a multiple disk clutch device installed in a power unit, which may be freestanding, or alternatively, which may be incorporated into a vehicle such as a motorcycle, an all-terrain vehicle or the like.

2. Background Art

There is known a clutch release mechanism of a multiple disk clutch device configured as below, as disclosed in e.g. Patent Document 1 mentioned below. A plurality of balls are interposed between a fixed cam plate and a movable cam plate which are opposed to each other. A release member is pressed by use of a thrust force generated by the relative turning of both the cam plates to release the engagement of the clutch.

When the clutch release mechanism configured as disclosed in Patent Document 1 is assembled, the following is necessary. The movable cam plate is engaged with a pressure-applying plate and the balls are arranged on the movable cam plate. A fixed cam plate mounted to a case member covering a multiple disk clutch device is mounted along with the movable cam plate so as to hold the balls therebetween at accurate positions.

However, when the case member is assembled, it is necessary to perform the assembly while maintaining the state where the balls are received in the recessed portions of the movable cam plate. Therefore, there is a problem of poor workability.

In addition, to solve such a problem, for example, Patent Document 2 mentioned below discloses a clutch release mechanism as below. A retainer for balls is attached to a fixed cam plate. A plurality of balls are attached as a ball unit. The ball unit is prevented from coming off by a retaining member. A movable cam plate is fitted to a release member.

However, in the case of the clutch release mechanism configured as in Patent Document 2, a cylindrical boss portion of the fixed cam plate is inserted into the fixed cam plate. In addition, the relative positions of the respective axes of the movable cam plate and the release member are fixed. Therefore, to prevent the misalignment between the fixed cam plate and the movable cam plate, it is necessary to significantly reduce the cumulative tolerances from the clutch member to clutch inner member of a multiple disk clutch device.Patent Document 1—Japanese Patent Laid-Open No. 2005-249083 (FIGS. 1 and 2)Patent Document 2—Japanese Patent Laid-Open No. 2007-177873 (FIGS. 1 to 8)

SUMMARY OF THE INVENTION

The present invention aims to solve the problem associated with the conventional clutch release mechanism of a multiple disk clutch device as described above.

In addition, it is an object of the present invention to provide a clutch release mechanism that can avoid erroneous assembly due to misalignment of balls and facilitate assembly to improve workability during assembly of a case member of a multiple disk clutch device, that can increase a permissible range of misalignment between a fixed cam plate and a pressing member on a movable cam plate side and alleviate a requested tolerance for clutch constituent members, and that further restricts the axial length thereof to be configured compactly.

In order to achieve the above object, a first aspect of the invention is characterized in that in a clutch release mechanism includes a fixed cam plate held by a case member covering a multiple disk clutch device, and provided with a cylindrical boss portion projecting in a direction coaxial with, and away from a main shaft of a transmission, the cylindrical boss portion turnably supporting a movable cam plate so as to be turnable coaxially with the main shaft; the movable cam plate formed with a cylindrical projecting portion, supported turnably and axially slidably by the fixed cam plate by inserting the cylindrical boss portion through the cylindrical projecting portion, and turned through engagement with a clutch arm of the transmission; a ball unit housed between the fixed cam plate and the movable cam plate and held by the fixed cam plate by means of a retainer member provided on the fixed cam plate; a release member for releasing engagement of a clutch by transmitting, to a pressure-applying plate, a thrust force generated by relative turning of the fixed cam plate and the movable cam plate which hold the ball unit therebetween; and a pressing member fitted to the release member via a bearing, and pressed by the movable cam plate to receive the thrust force and transmit the thrust force to the release member via the bearing; the pressing member has a hollow portion passing therethrough in the main shaft direction, and the movable cam plate is formed to allow the cylindrical projecting portion to project toward the pressing member, and the cylindrical projecting portion is configured to be fitted into the hollow portion with a gap defined therebetween and to press the pressing member so as to be relatively shiftable on a flat surface perpendicular to a pressing direction.

A second aspect of the invention is characterized in that in the clutch release mechanism according to the first aspect, the hollow portion of the pressing member is formed with a step such that an inner diameter on a side adapted to receive the cylindrical projecting portion of the movable cam plate fitted therein is greater than an inner diameter on a side fitted to the bearing.

A third aspect of the invention is characterized in that in the clutch release mechanism according to the first aspect, the pressing member and the movable cam plate are pivotally supported to be turnable with each other with a positioning member holding a relative alignment position serving as a fulcrum and the hollow portion of the pressing member is formed to have an expanded hollow portion extending to a turning area of the cylindrical projecting portion of the movable cam plate with the positioning member serving as a fulcrum.

A fourth aspect of the invention is characterized in that in the clutch release mechanism according to the first aspect, the positioning member holding a relative alignment position between the pressing member and the movable cam plate is not provided.

According to the clutch release mechanism of the first aspect hereof, the pressing member is formed to have the hollow portion, and the cylindrical projecting portion of the movable cam plate is formed to project toward the pressing member and is fitted into the hollow portion with the gap defined therebetween. Therefore, the hollow portion and the cylindrical projecting portion of the movable cam plate overlap each other and extend in the main shaft direction. Thus, even in the configuration where the ball unit is held by the fixed cam plate side and the pressure-applying plate is pressed via the pressing member, the clutch release mechanism is restricted in axial length so that it can be configured compactly.

The movable cam plate is positioned by the engaging portion with the clutch arm turned along with the change spindle of the transmission and the fitting of the pressing member fitted to the release member into the hollow portion. Therefore, the position of the movable cam plate attached to the transmission side can be set easily and accurately. The ball unit is held at the predetermined position on the fixed cam plate side. Therefore, during the assembly of the clutch release mechanism, the position of the movable cam plate can easily be aligned with the position of the fixed cam plate including the ball unit attached to the case member side. Thus, the possibility of the erroneous assembly due to the misalignment of the ball position can be eliminated, which enhances assembly workability.

The cylindrical boss portion of the fixed cam plate is inserted through the cylindrical projecting portion of the movable cam plate. The pressing position of the movable cam plate is restricted by the cylindrical boss portion on the case member side. On the other side, the pressing member is fitted to the release member via the bearing. Therefore, the pressed position is restricted by the release member on the transmission side.

However, the movable cam plate of the present invention is configured such that the cylindrical projecting portion is fitted into the hollow portion of the pressing member with the gap defined therebetween and presses the pressing member so as to be relatively shiftable on the flat surface perpendicular to the pressing direction.

Misalignment may be present between the case member side and the transmission side. Specifically, there may be misalignment between the movable cam plate defined in position by the cylindrical boss portion of the fixed cam plate and the pressing member defined in position by the release member. Even in such a case, with the configuration as above, since the movable cam plate presses the pressing member so as to be relatively shiftable on the flat surface perpendicular to the pressing direction, the pressing direction is not deflected.

Thus, clutch release can be done without trouble and with comfort, which improves a shift feeling. In addition, since the permissible range of misalignment is large, the requested tolerance for the clutch constituent members can be alleviated, which contributes to a cost reduction.

According to the clutch release mechanism of the invention of the second aspect hereof, in addition to the effects of the invention of the first aspect, the cylindrical projecting portion of the movable cam plate can be fitted into the hollow portion of the pressing member with the gap defined therebetween without increasing the diameter of the bearing. Therefore, the space for the clutch release mechanism can be restricted.

According to the clutch release mechanism of the third aspect hereof, in addition to the effects of the invention of the first aspect, the hollow portion of the pressing member pivotally supported by the movable cam plate and the positioning member has the extended hollow portion. The extended hollow portion extends to the turning area of the cylinder projecting portion along the turning direction of the movable cam plate with the positioning member serving as a fulcrum. Therefore, a range can be enlarged where the deflection of the pressing due to the misalignment between the pressing member and the movable cam plate defined in position by the cylindrical boss portion of the fixed cam plate can be prevented substantially. Thus, the shift feeling can be more stabilized. In addition, the permissible range of the misalignment between the fixed cam plate and the pressing member on the movable cam plate side can be more enlarged.

According to the clutch release mechanism of the fourth aspect, in addition to the effects of the first aspect, the cylindrical projecting portion of the movable cam plate is fitted into the hollow portion of the pressing member fitted to the release member via the bearing. Therefore, during the assembly of the clutch release mechanism, the movable cam plate can be positioned by the engaging portion with the crank arm and the cylindrical projecting portion. Thus, it is possible to omit the positioning member holding the relative alignment position between the pressing member and the movable cam plate, whereby the number of component parts can be reduced.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

It should be understood that only structures considered necessary for clarifying the present invention are described herein. Other conventional structures, and those of ancillary and auxiliary components of the system, will be known and understood by those skilled in the art.

A clutch release mechanism according to a number of selected illustrative embodiments of the present invention, and a modification resulting from modifying part of the clutch release mechanism, will now be described with reference toFIGS. 1 through 5.

A clutch release mechanism20, according to a first illustrative embodiment of the present invention described herein, is used to release the engagement of a multiple disk clutch device installed in a power unit of a motorcycle, an all-terrain vehicle or the like. However, the present invention shall not be limited to the use of a power unit in a vehicle. A clutch mechanism according to an embodiment of the present invention may also be applied to a stationary power unit. In addition, the engine type, the number of cylinders and the like of an internal combustion engine constituting part of the power unit are not restricted.

In the embodiment illustrated inFIG. 1, a multiple disk clutch device1is disposed on a rotary power transmission path extending from a crankshaft2of a power unit whose whole picture is not illustrated, to a main shaft4of a transmission3. During operation, the clutch device does not transmit the rotary power of the crankshaft2to the main shaft4of the transmission3during the gear shifting of the transmission3, but instead, transmits the rotary power to the main shaft4of the transmission3upon completion of the gear shifting.

FIG. 1is a cross-sectional view of the multiple disk clutch device1of the power unit where the crankshaft2and the main shaft4are arranged generally horizontally when mounted on the vehicle, additionally illustrating a portion of the transmission3and the like adjacent to the multiple disk clutch device. However, the on-board arrangement direction of the main shaft4is not restrictive. The main shaft4arranged in the normal vehicle-traveling direction or in the vehicle-widthwise direction as well as in various directions is applicable.

Referring toFIG. 1, the main shaft4of the transmission3is configured to receive the rotary power of the crankshaft2, transmitted either directly or via a centrifugal start clutch (not illustrated) from a primary drive gear5carried on the crankshaft2via the multiple disk clutch device1.

The multiple disk clutch device1is provided with a bottomed cylindrical clutch outer cover6rotatably supported by the main shaft4of the transmission3. A primary driven gear7meshing with the primary drive gear5is mounted to the bottom outer side of the clutch outer cover6. The primary drive gear5, having a relatively small diameter, and the primary driven gear7having a larger diameter than that of the primary drive gear5cooperate to form a primary reduction gear.

A bottomed cylindrical clutch inner member9is disposed inside the clutch outer cover6so as to be spline-fitted and secured to the main shaft4by means of a nut8. A plurality of driven friction plates10slidably spline-engaged with a circumferential wall portion of the clutch inner member9alternately overlap a plurality of drive friction plates11slidably spline-engaged with a circumferential wall portion of the clutch outer cover6.

A pressure-receiving plate12formed integrally with the clutch inner member9is located opposite a frictional drive plate11located on the outermost side. A pressure-applying plate13, slidably supported by the outer circumferential surface of a boss9aof the clutch inner member9, is located opposite a frictional drive plate11located on the innermost side.

A plurality of support bosses14(only one is shown inFIG. 1) passing through the bottom of the clutch inner member9are integrally provided on the pressure-applying plate13so as to project therefrom. A connection plate15is secured by use of bolts16so as to connect the leading ends of the support bosses14together. A clutch spring17is compressively provided between the connection plate15and the bottom of the clutch inner member9.

In this way, in the multiple disk clutch device1, the clutch spring17normally biases the connection plate15and the bottom of the clutch inner member9to widen the interval therebetween. The pressure-applying plate13is biased to come close to the pressure-receiving plate12of the clutch inner member9, so that the drive friction plates11and the driven friction plates10are brought into press-contact with each other. Thus, the multiple disk clutch device1is engaged (brought into a connection state).

That is to say, the rotary power is transmitted from the clutch outer cover6to the clutch inner member9; therefore, the rotary power of the crankshaft2is transmitted from the crankshaft2side to the main shaft4side.

The clutch release mechanism20for releasing the engagement of the multiple disk clutch device1includes, primarily, a collar member21(“the release member” of the present invention), a release bearing22(“the bearing” of the present invention), a fixed cam plate32, a movable cam plate40, a pressing member42, and a ball unit50.

The collar member21is capable of pressing the pressure-applying plate13via the connection plate15and the support bosses14. The release bearing22is installed inside the collar member21. The fixed cam plate32is held by a case member30, and includes a cylindrical boss portion31projecting in a direction away from the main shaft4of the transmission3. The boss portion31of the fixed cam plate32is disposed coaxial with a central axis X of the main shaft4. The case member30constitutes part of the power unit case29and covers the multiple disk clutch device1. The movable cam plate40is rotatably supported by the cylindrical boss portion31, and is slidably movable along an axis coaxial with the central axis X of the main shaft4. The pressing member42is pivotally supported by the movable cam plate40by means of a rivet43(“the positioning member” of the present invention) and is fitted to the collar member21via the release bearing22. The ball unit50is disposed between the fixed cam plate32and the movable cam plate40.

The collar member21is cylindrically formed to internally house the release bearing22by use of a bearing abutment portion21aformed to bend inwardly at one end, and is retained in a central opening portion of the connection plate15by use of a connection plate abutment portion21bformed to bend outwardly at the other end.

If the release bearing22is attached to the inside of the collar member21, the bearing abutment portion21acomes into abutment against a lateral surface, of an outer race22aof the release bearing22, opposed to the multiple disk clutch device1. In addition, the inner lateral surface of the collar member21comes into abutment against the outer circumferential surface of the outer race22a.

In addition, an adjustment bolt33is provided on the case member30, arranged to be coaxial with the main shaft4in the assembled state. The adjustment bolt33extends through a hollow bore formed in the case member, and is secured to the case member30by a medial flange33aformed integrally thereon, and by a nut34threadably engaged therewith.

The cylindrical boss portion31of the fixed cam plate is formed with an internal female thread along its axis. In addition, the cylindrical boss portion31is threadably engaged with the leading end of the adjustment bolt33, and extends from the adjustment bolt33to the inside of the pressing member42which, in turn, is disposed in the inner race22bof the release bearing22.

A structure of the fixed cam plate32and of the ball unit50is described below, with reference also toFIG. 2.

The cylindrical boss portion31is formed at a leading end portion with a movable cam support portion31a, which rotatably and axially slidably supports a cylindrical projecting portion41of the movable cam plate40thereon, coaxially with the main shaft4. The movable cam support portion31ais formed on a leading end side with a tapered outer tip portion31dto make it easy to receive the movable cam plate40attached thereto.

The cylindrical boss portion31is formed at an intermediate portion with a retainer fitting portion31bhaving a diameter slightly greater than that of the cam support portion31a. The retainer fitting portion31bis configured such that the retainer51of the ball unit50is fitted thereto.

The cylindrical boss portion31is formed at a proximal end with a fixed cam joint portion31chaving a diameter slightly greater than that of the retainer fitting portion31b. A plate portion35of the fixed cam plate32is joined to the outer circumferential portion of the fixed joint portion31cso as to be substantially parallel to the movable cam plate40. The cylindrical boss portion31and the plate portion35form the integral fixed cam plate32.

The plate portion35of the fixed cam plate32is formed with cam-like recessed portions36respectively engaged with balls52of the ball unit50at three positions at circumferentially regular intervals.

The plate portion35has a pin-engaging portion38formed in a circumferential edge portion thereof, which receives a rotation-prevention pin37therein. The rotation-prevention pin37is fixedly provided in the case member30, and prevents the turning of the fixed cam plate32by its engagement with the pin-engaging portion38.

The ball unit50is positioned between the fixed cam plate32and the movable cam plate40. The ball unit50includes a retainer51, fitted to the cylindrical boss portion31of the fixed cam plate32, and three steel balls52held by the retainer51.

The retainer51is formed at a central portion with a fitting hole51acapable of being fitted to the retainer fitting portion31bof the cylindrical boss portion31. The retainer51is formed with three ball-holding holes51bat regular intervals in a rotary, i.e., circumferential direction of the movable cam plate40. The balls52are rotatably held by the respective ball-holding holes51b.

A biasing spring (a compressive coil spring)53is attached to the outer circumferential portion of the retainer fitting portion31bso as to bias the ball unit50in a direction of slidably shifting it toward the movable cam plate40. The biasing spring53is designed to have one end coming into contact with the retainer51and the other end coming into contact with a stepped portion54of the cylindrical boss portion31, between the retainer fitting portion31band the fixed cam joint portion31b. The biasing force of the biasing spring53is set at a level sufficiently smaller than that of the clutch spring17. A C-clip56(the locking member of the present invention) is attached to a ring groove55formed on the outer circumferential portion of the retainer fitting portion31b. This prevents the ball unit51from coming off from the cylindrical boss portion31.

In addition, the movable cam plate40is formed with a cylindrical projecting portion41thereon, which extends coaxially with the main shaft4toward a main shaft end4a. The cylindrical projecting portion41of the movable cam plate40has a hollow central bore41bformed therethrough, as shown inFIG. 4. In addition, the cylindrical projecting portion41is rotatably and axially slidably supported on the outer circumference of the movable cam support portion31bof the cylinder boss portion31coaxially with the main shaft4.

The movable cam plate40is formed with cam-like recessed portions44at three positions at circumferentially regular intervals at respective portions opposed to and fitted to the corresponding balls52of the ball unit50held by the fixed cam plate32side.

In this way, each of the balls52held at both ends by the corresponding ball holding hole51bof the retainer51is put between the respective cam-like recessed portions36,44of the fixed cam plate32and the movable cam plate. Thus, the rotation of the ball unit50is restricted.

The outer circumferential portion of the movable cam plate40partially extends outwardly to form a control lever40a. The control lever40ais formed at a leading end with an engaging groove46with which a leading end of a clutch arm61is engaged. The clutch arm61is secured to one end of a change spindle60of the transmission3.

A roller62is pivotally connected to the leading end of the clutch arm61and is engaged with the engaging groove46. Thus, the clutch arm61is turned to make the control lever40asmoothly turn. The change spindle60is supported by the power unit case29in an orientation substantially parallel to the main shaft4, and is operatively turned by a change pedal, a motor or the like (not illustrated).

The pressing member42is pivotally supported on the movable cam plate40by means of a rivet43extending therebetween and arranged so as to be in contact with a main shaft-side surface of the movable cam plate40.

The relationship between the pressing member42and associated components including the movable cam plate40, the release bearing22, the collar member21and the like is hereinafter described, with reference also toFIG. 3.

The rivet43is a positioning member adapted to hold a relative alignment position between the movable cam plate40and the pressing member42. The movable cam plate40and the pressing member42are pivotally supported so as to be relatively turnable with the rivet43serving as a fulcrum. For convenience of assembly, the movable cam plate40and the pressing member42do not come into close contact with each other in the axial direction of the rivet43in the vicinity of the rivet43. A coil spring47is interposed between the movable cam plate40and the pressing member42, so that the movable cam plate40and the pressing member42are swingable with respect to each other, in a limited range, in the axial direction of the rivet43. InFIG. 3, reference numeral49denotes a rivet hole formed through the pressing member42for receiving a shaft portion of the rivet43.

The pressing member42has a hollow portion45passing therethrough in a main shaft direction, and this hollow portion45includes a cylindrical portion42aextending toward the main shaft end4a, and a flange portion42bhaving a flat surface vertical to the main shaft direction and in contact with the movable cam plate40. The pressing member42is pivotally supported on the movable cam plate40by the rivet43, with the spring47interposed therebetween as described above. In addition, the cylindrical portion42aof the pressing member42is fitted into the inner race22bof the release bearing22, as shown.

In this way, the pressing member42is turnably connected to the collar member21via the release bearing22, and is disposed coaxially with the main shaft4.

The cylindrical projecting portion41of the movable cam plate40, formed to protrude toward the pressing member42, is fitted into the hollow portion45of the pressing member42with a gap48defined therebetween along with the end (indicated with a two-dot chain line inFIG. 3), of the cylindrical boss portion31, extending through the cylindrical projecting portion41.

Because of this, in the present embodiment, the hollow portion45is formed with a bearing-side hollow portion45aadapted to receive at least the cylindrical boss portion31therein with a gap therebetween, and also with a movable cam-side hollow portion45badapted to receive the cylindrical projecting portion41therein with another gap48defined therebetween. A stepped portion45c(“the step” of the present invention) is formed between the bearing-side hollow portion45aand the movable cam-side hollow portion45b.

In other words, the hollow portion45of the pressing portion42is formed to have the stepped portion45cin such a manner that the inner diameter of the movable cam-side hollow portion45binto which the cylindrical projecting portion41of the movable cam plate40is fitted is greater than that of the bearing-side hollow portion45afitted to the release bearing22.

Thus, the cylindrical projecting portion41of the movable cam plate40can be fitted into the hollow portion45of the pressing member42with the gap48defined therebetween without increasing the diameter of the release bearing22.

The flange portion42bis formed to contact the movable cam plate40at a flat surface perpendicular to a direction where the movable cam plate40presses the pressing member42. Thus, the movable cam plate40is formed to press the pressing member42so as to be relatively shiftable on the flat surface of the flange portion42b.

In the clutch release mechanism20described above, if the control lever40ais pressed, the movable cam plate40and the pressing member42connected to the movable cam plate40with the rivet43is turned around the cylindrical boss portion31of the fixed cam plate32. Then, while rolling, the ball52of the ball unit50smoothly mounts the slope of the cam-like recessed portion44of the movable cam plate40. In this way, the movable cam plate40and the pressing member42are pressed and shifted rightward (the main shaft4side) inFIG. 1by a reaction force (a thrust force) received via the ball52from the plate portion35of the fixed cam plate32secured.

The pressing member42transmits the thrust force to the collar member21via the release bearing22and the collar member21transmits it to the connection plate15. The connection plate15compresses the compressive spring17against its biasing force and transmits the thrust force to the pressure-applying plate13via the support bosses14to shift the pressure-applying plate13rightward in the figure. In this way, the frictional engagement between the drive friction plate11and the driven friction plate10is released, which releases the engagement state of the multiple disk clutch device1.

A description is given of the characteristics and the like of the clutch release mechanism20in the present embodiment encountered during assembly.

During assembly of the clutch release mechanism20in the present embodiment, as illustrated inFIG. 4, while the main shaft end4aon the transmission3side is made to face the substantial upside, the collar member21is attached to the connection plate15and the release bearing22is fitted to the collar member21.

To attach the movable cam plate40there, the engaging groove46of the control lever40ais engaged with the roller62of the clutch arm61. In addition, the cylindrical portion42aof the pressing member42pivotally supported by the movable cam plate40with the rivet43is fitted into the inner race22bof the release bearing22, the cylindrical portion42aextending toward the main shaft4.

The cylindrical projecting portion41of the movable cam plate40is fitted into the movable cam-side hollow portion45bof the hollow portion45of the pressing member42with the gap48defined therebetween.

With this, during the assembly, the movable cam plate40is permitted to swing in a given range with respect to the pressing member42with the rivet43severing as a fulcrum as well as to be turned according to the gap48. However, the movable cam plate40is positionally determined in a given range by the roller62of the clutch arm61and the pressing member42.

In addition, the fixed cam plate32and the like are additionally mounted to the case member30side. With its inner surface side faced generally downward, the members are assembled to cover the transmission3side already assembled as indicated with a blank arrow inFIG. 4.

With the assembly, the cylindrical boss portion31of the fixed cam plate32turnably and axially slidably supporting the movable cam plate40goes into the hollow bore41bin the cylindrical projecting portion41of the movable cam plate40, while being guided by the tapered outer tip portion31dat the leading end thereof.

The axis Y of the cylindrical boss portion31is positionally determined by the cylindrical boss portion31being attached to the case member30side. However, the axis Y of the cylindrical boss portion31may probably misalign with the axis X of the main shaft4because of the cumulated tolerances resulting from the assembly of the members on the case member30side and on the transmission3side (the main shaft4side).

In addition, since the pressing member42is fitted to the release bearing22, the axis A of the pressing member42is generally aligned with the central axis X of the main shaft4. Therefore, there is a possibility that the axis A of the pressing member42is misaligned with the axis Y of the cylindrical boss portion31.

However, the pressing member42attached to the transmission3side and the movable cam plate40are permitted to swing in a given range with the rivet43serving as a fulcrum as well as to be turned according to the gap48. Therefore, the axis B of the cylindrical projecting portion41of the movable cam plate40has room for swing and turning in a given range during assembly, and does not always follow the axis A.

Therefore, when the cylindrical boss portion31is placed into the cylindrical projecting portion41, the axis B follows and aligns with the axis Y, thereby avoiding the difficulty of the assembly due to the misalignment. The leading end of the cylindrical boss portion31passing through the cylindrical concave portion41is fitted into the bearing-side hollow portion45ainside the cylindrical portion42aof the pressing member42with the gap defined therebetween (seeFIGS. 1 and 3). Thus, the assembly can be done successfully.

In this case, the ball unit50is supported on the fixed cam plate32on the case member30side. Therefore, if the position of the ball unit50is accurately set, the balls52of the ball unit50are accurately positioned and held between the cam-like recessed portions36and44as the plate portion35of the fixed cam plate32are allowed to come close to the movable cam plate40.

Thus, the present embodiment eliminates an excessive request of accuracy for the members and the assembly to reduce the cumulated tolerances as in the conventional example. This reduces the manufacturing costs and the assembly workability is more enhanced.

A further detailed description is given of the characteristics of the clutch release mechanism of the present embodiment. In the characteristic structure, the pressing member42is formed to have the hollow portion45. In addition, the cylindrical projecting portion41of the movable cam plate40is formed to project toward the pressing member42and is fitted to the hollow portion45with the gap48defined therebetween.

In this way, the hollow portion45and the cylindrical projecting portion41of the movable cam plate40overlap each other and extend in the direction of the main shaft4. Therefore, even in the configuration in which the ball unit50is held by the fixed cam plate32side and the release bearing22, the collar member21and the connection plate15are sequentially pressed via the pressing member42to press the pressure-applying plate13, the clutch release mechanism20is restricted in axial length and formed compactly.

The movable cam plate40is positioned by the engaging portion with the clutch arm61turned along with the change spindle60of the transmission3and the fitting of the pressing member42fitted to the collar member21(the release member) via the release bearing22into the hollow portion45of the pressing member42. Therefore, the position of the movable cam plate40attached to the transmission3side can be set easily and accurately.

The ball unit50is held at a predetermined position on the fixed cam plate32side. Therefore, during the assembly of the clutch release mechanism20, the position of the movable cam plate40can easily be aligned with that of the fixed cam plate32, including the ball unit50, attached to the case member side. Therefore, the possibility of erroneous assembly due to the positional misalignment of the balls52is eliminated to enhance assembly workability.

The cylindrical boss portion31of the fixed cam plate32is inserted through the cylindrical projecting portion41of the movable cam plate40. In addition, the pressing position of the movable cam plate40is defined by the cylindrical boss portion31on the case member30side. In addition, the pressing member42is fitted to the collar member21via the release bearing22; therefore, the pressed position is defined by the collar member21on the transmission3side.

However, the movable cam plate40of the present embodiment is configured such that the cylindrical projecting portion41is fitted to the hollow portion45of the pressing member42with the gap48defined therebetween. In addition, the movable cam plate40presses the pressing member42so as to be relatively shiftable on the flat surface perpendicular to the pressing direction.

The case member30side may be misaligned with the transmission3side. Specifically, the movable cam plate40defined in position by the cylindrical boss portion31of the fixed cam plate32may be misaligned with the pressing member42defined in position by the collar member21. With the configuration as above, even if there is such misalignment, the movable cam plate40presses the pressing member42so as to be relatively shiftable on the flat surface perpendicular to the pressing direction. Therefore, the pressing direction will not be deflected.

Accordingly, the clutch release can be done without any problem and with comfort, so that a shift feeling during shifting is improved. In addition, since the permissible range of misalignment is large because of the gap48, a requested tolerance for the clutch constituent member can be alleviated, which can contribute to a cost reduction.

The hollow portion45of the pressing member42is formed with the stepped portion45csuch that the inner diameter of the movable cam-side hollow portion45bto which the cylindrical projecting portion41of the movable cam plate40is fitted is greater than that of the bearing-side hollow portion45ato which the release bearing22is fitted. Therefore, the cylindrical projecting portion41of the movable cam plate40can be fitted to the hollow portion45of the pressing member42with the gap48defined therebetween without increasing the diameter of the release bearing22. Thus, the space for the clutch release mechanism20can be restricted.

A modification of the present embodiment is next described with reference toFIG. 5.

The present modification is the same as the embodiment except the shape of a pressing member142in the modified embodiment is partially different from the pressing member42of the first embodiment. The same portions as in the present embodiment are described with only the terms and reference numerals in the explanation with their illustrations omitted.

There is shown a pressing member of the modified embodiment inFIG. 5, in which portions are denoted with reference numerals in the 100 s whose last two digits are the same as the reference numerals of the corresponding portions of the present embodiment and new portions are denoted with additional reference numerals in the 100 s.

A pressing member142of the present modification is formed with a bearing-side hollow portion145aand a movable cam-side hollow portion145bin a hollow portion145. The bearing-side hollow portion145ais adapted to receive the leading end of the cylindrical boss portion31fitted thereinto with a gap defined therebetween, the cylindrical boss portion31going into the cylindrical projecting portion41of the movable cam plate40. The movable cam-side hollow portion145bis adapted to receive the cylindrical projecting portion41fitted thereinto with a gap48defined therebetween, similar to the gap48shown inFIG. 4. A stepped portion145cis formed between the bearing-side hollow portion145aand the movable cam-side hollow portion145b.

The pressing member142and the movable cam plate40are pivotally supported so as to be turnable with each other with the rivet43serving as a fulcrum. The rivet43acts as a positioning member which holds the relative alignment position between the pressing member142and the movable cam plate40.

The movable cam-side hollow portion145bis formed to have expanded hollow portions171therein. The expanded hollow portions171extend to corresponding turning areas141aof the cylindrical projecting portion41of the movable cam plate40. Each of the turning areas141afollows a corresponding turning direction Z of the cylindrical projecting portion41of the movable cam plate40with the rivet serving as a fulcrum. In the figure, reference numeral149denotes a rivet hole.

In the present modified embodiment, the hollow portion145of the pressing member142pivotally supported by the movable cam plate40and the rivet43has the expanded hollow portions171formed therein, which extend to the corresponding turning areas141aof the cylindrical projecting portion41along the corresponding turning directions of the movable cam plate40, with the rivet43serving as a fulcrum. This enlarges a range where a possible deflection of the pressing due to the misalignment between the pressing member142and the movable cam plate40defined in position by the cylindrical boss portion31of the fixed cam plate32is minimized or substantially prevented. Thus, the shift feeling during shifting can be more stable. In addition, the permissible range of acceptable alignment between the fixed cam plate32and pressing member142is increased by the provision of the expanded hollow portions171.

The clutch release mechanism according to the embodiment and its modification of the present invention has been described thus far. However, the clutch release mechanism of the invention includes various modes within the scope of the gist of the invention and is not limited to the embodiment and the like as described above.

For example, in the present embodiment, the clutch release mechanism may not require the rivet43to function as a positioning member holding the relative alignment position between pressing member42and the movable cam plate40.

During the assembly process, the pressing member42is defined in position in the collar member21via the release bearing22interposed therebetween. The cylindrical projecting portion41of the movable cam plate40is fitted into the hollow portion45of the pressing member42, so that it does not almost move even without the rivet43. Since the other end of the movable cam plate40is engaged with the clutch arm61, the position of the movable cam plate40is sufficiently determined for starting of the assembly.

Specifically, the axis Y of the cylindrical boss portion31of the fixed cam plate32may be slightly misaligned with the axis B of the movable cam plate40. Even in such a case, if the cylindrical boss portion31is once started to go into the hollow bore41bin the cylindrical projecting portion41of the movable cam plate40, the axis B of the movable cam plate40is shifted along the axis Y to achieve relative alignment. Thus, accurate assembly is done by the coaxial alignment of the cylindrical boss portion31in of the cylindrical projecting portion41which, in turn, is coaxially received in the hollow portion45of the pressing member42.

After the insertion of the cylindrical boss portion31into the cylindrical projecting portion41, the movable cam plate40is turned in the state where the cylindrical projecting portion41is then fitted into the pressing member42, while pivotally supported on the cylindrical boss portion31. Therefore, the rivet43is unnecessary.

In this way, it is possible to eliminate the rivet43serving as the positioning member holding the relative alignment position between the pressing portion42and the movable cam plate40. Thus, the number of component parts can be reduced.

Although the present invention has been described herein with respect to a number of specific illustrative embodiments, the foregoing description is intended to illustrate, rather than to limit the invention. Those skilled in the art will realize that many modifications of the illustrative embodiment could be made which would be operable. All such modifications, which are within the scope of the claims, are intended to be within the scope and spirit of the present invention.