Multi-plate dry clutch having hub movement limiting means

Abstract: In one embodiment, in a multi-plate clutch (100), drive plates (7) and driven plates (8) and (8') are interposed between a flywheel (2) and a clutch pressure assembly (10). The driven plates (8') having contact portions (51) each extending further from projections (27) and further extending radially inwardly therefrom, and contactable at both end in the axial direction of the second cylindrical portion (13). In an alternate embodiment, only one driven plate (8') is provided and a plate member (55) is fixed to a hub flange (6) to limit axial movement between the driven plate (8') and the hub flange (6). In another embodiment a multi-plate clutch (200) includes a cushion ring (60) is disposed between the pressure plate (29) and a diaphragm spring (30). Further, the diaphragm spring (30) has inner circumferential slits (66) and outer circumferential slits (67) to improve air flow therethrough for cooling. The diaphragm spring in another embodiment includes a first diaphragm spring (30A) and a second diaphragm spring (30B) both coated with solid lubricant films.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-plate clutch, and more particularly to a multi-plate clutch having a hub member which engages an input shaft of a transmission, where the hub member is axially displaceable and axial displacement of the hub member is limited by the configuration of the multi-plate clutch. 2. Description of the Related Art In general, a multi-plate clutch used in a racing car or the like is provided with a first cylindrical portion that is configured to be attached to a flywheel. Within the first cylindrical portion, a hub flange is disposed, the hub flange being connected to an input shaft of a transmission. At an outer radial portion of the hub flange, the hub flange is formed with a second cylindrical portion disposed radially inwardly of the first cylindrical portion. Drive plates and driven plates are disposed between the first and second cylindrical portions and directly engage each, respectively. A pressure plate mechanism is attached to the first cylindrical portion for selectively engaging and disengaging the drive plates and driven plates from rotation with the flywheel. The pressure plate mechanism includes a pressure plate and a diaphragm spring for biasing the pressure plate. The hub flange has gear teeth formed on an outer circumferential surface of the second cylindrical portion and spline grooves formed on an inner circumferential portion. The outer circumferential gear teeth engage corresponding teeth formed on the driven plates, and the inner circumferential spline grooves engage spline teeth formed on the input shaft of the transmission. The hub and the driven plates both may undergo movement in the axial direction when the clutch is in a clutch dis-engaged state in order to prevent drag between relatively rotating parts in clutch mechanism, such as the driven plates and the drive plates. However, in the absense of some kind of movement restriction, the hub would come loose from the splines on the input shaft if it moves too far in the axial direction. It is therefore necessary to provide some structure which limits the axial movement of the hub. One such known structure includes roll pins that are mounted on the outer circumferential spline of the hub flange and which extend in a tangential or radial direction. A portion, exposed in the gearteeth, of each roll pin estends between adjacent two teeth of the driven plates in the axial direction. The axial movement of the driven plates and the drive plates are limited by the flywheel and the pressure plate. The hub flange is engaged in the axial direction through the above-mentioned roll pin with the driven plates whose movement range is thus limited so that the axial position of the hub flange is limited within a predetermined range. In the above-described configuration, since the roll pins are provided only at a couple of predetermined locations, the pressure against the driven plates in the area of contact therebetween is significant enough so that a frictional wear due to contact is likely to occur in the driven plates. As well, when the torque is transmitted through the drive plates and the driven plates, slippage between the plates generates heat. The service life of the plates and other engagin parts is reduced by the heat. In order to cool the plates, in a conventional manner, slits or holes are formed in the first and second cylindrical portions. Air is caused to flow from the inner circumferential side to the outer circumferential side of both plates to thereby cool both plates. However, the entrainment of the air from the outside of the clutch is limited. Air usually can only enter via the slit portions of the diaphragm spring. These slits are insufficient to permit the flow of air from the outside. It is well known in the prior art to use two diaphragm springs in an overlap manner. In this case, when the two diaphragm springs are flexed, a friction is generated therebetween. This means that the flex-load characteristics have an increased hysteresis load due to the friction. As a result, an efficiency is degraded. Therefore, in order to enhance the lubricant effect between the diaphragm springs, a solid lubricant film is formed one of the contacting surfaces. However, since only one surface of each of the two diaphragm springs is subjected to a lubricant treatment, it is necessary to confirm which surface has the film prior to assembly. This requires an additional step in the assembly process, specifically the step of inspecting the surfaces of the two diaphragm spring to see which face has the film thereon. GB-A-2 260 169 discloses a motor vehicle friction clutch conforming to the preamble of claim 1 comprising a flywheel and an annular plate being co-axial and rotatably fixed with the flywheel. The annular plate is biased away from the flywheel by a first spring. A clutch cover assembly is secured to the flywheel and comprises a cover, a pressure plate and a diaphragm spring. A clutch driven plate is sandwiched between the pressure plate and the annular plate. SUMMARY OF THE INVENTION An object of the present invention is to enhance the operatability of a clutch in the engaging and dis-engaging process. According to the invention, this object is achieved by the features of the main claim. The dependent claims contain advantages embodiments of the invention. In accordance with one aspect of the present invention, a multi-plate clutch mechanism includes a first cylindrical portion configured for connection to a flywheel and a hub flange having a second cylindrical portion disposed concentrically within the first cylindrical portion, the hub flange configured to non-rotatably engage an input shaft of a transmission. A plurality of first friction plates are disposed between the first cylindrical portion and the second cylindrical portion, the first friction plates being circumferentially engaged for rotation with the first cylindrical portion but relatively slidable in the axial direction with respect to the first cylindrical portion. A plurality of second friction plates are disposed alternatingly adjacent to the first friction plates in the axial direction, the second friction plates being configured to engage the second cylindrical portion for rotation therewith but configured for limited relative axial movement with respect to the second cylindrical portion. A pressure plate mechanism is fixed to the first cylindrical portion such that the friction plates are disposed between the pressure plate mechanism and the flywheel, the pressure plate mechanism including a clutch cover supported on the first cylindrical portion, a pressure plate disposed between the clutch cover and the first and second friction plates and a diapragm spring disposed between the clutch cover and the pressure plate. A resilient member is disposed between the flywheel and the pressure plate mechanism, the resilient member operably configured to flex and be elastically deformed in the axial direction in response to movement of the diaphragm spring. Thereby the resilient member is disposed between the pressure plate and the diaphragm spring, the resilient member is a cushion ring, wherein the cushion ring has an annular raised portion having a semi-circular cross-section. Preferably, the pressure plate has a taper surface which decreases in height going toward an inner circumferential end of the pressure plate. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing an automotive dry type multi-plate clutch in accordance with a first general example; Fig. 2 is a part corss section, part elevation, part cutaway of the dry type multi-plate clutch depicted in Fig. 1, showing various features including a plate member; Fig. 3 is a side elevational view showing the dry type multi-plate clutch; Fig. 4 is a fragmentary, part cross sectional, perspective view showing a support mechanism of the dry type multi-plate clutch; Fig. 5 is a fragmentary, elevational view similar to Fig. 2, showing a hub flange and a driven plate with the plate member removed; and Fig. 6 is a perspective view showing the plate member; and Fig. 7 is a cross-sectional view showing an automotive dry type multi-plate clutch in accordance with a second general example ' Fig. 8 is a part cross section, part elevation, part cutaway of the dry type multi-plate clutch depicted in Fig. 7, showing various features; Fig. 9 is a cross-sectional view showing an automotive dry type multi-plate clutch in accordance with an embodiment of the present invention, having a pressure plate and diaphragm spring which interact with each other via support members on the pressure plate, the support members including a fulcrum ring; Fig. 10 is a part cross section, part elevation, part cutaway of the dry type multi-plate clutch depicted in Fig. 9, showing various features of the embodiment of the present invention; Fig. 11 is a cross-sectional view showing one of the support members and the fulcrum ring removed from the pressure plate and the dry type multi-plate clutch depicted in Fig. 9; and Fig. 12 is a part cross section, part elevational view of a hub flange shown removed from the dry multi-plate clutch depicted in Figs. 9 and 10. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIRST GENERAL EXAMPLE Fig. 1 is a cross-sectional view showing an automotive dry type multi-plate clutch 1 in accordance with a general example. The line O-O is a rotary axis of the dry type multi-plate clutch 1. For reference, the left hand side of Fig. 1 is hereinafter referred to as the engine side or flywheel side and the right hand side of Fig. 1 is referred to as the transmission side. The dry type multi-plate clutch 1 is used for transmitting/interrupting a torque to an input shaft (not shown) of a transmission from a flywheel 2 of an engine (not shown). The inner circumferential portion of the flywheel 2 is fixed to a crankshaft (not shown) by bolts 2a. The dry type multi-plate clutch 1 is mainly composed of a flywheel ring 5 (first cylindrical portion), a hub flange 6 as an output member, a frictional plate group 9 composed of a plurality of drive plates 7 and a plurality of driven plate 8 interposed between the flywheel ring 5 and the hub flange 6, and a clutch cover assembly 10 for selectively engaging and dis-engaging plates 7 and 8 from engaging and rotation with one another. The hub flange 6 has a centrally located boss 11, a flange 12 extending radially outwardly, integrally from the boss 11 and a second cylindrical portion 13 integrally formed on an outer circumference of the flange 12. A spline hole 11 a is formed in the center of the boss 11. The spline hole 11 a is engaged with spline teeth of the input shaft (not shown) of the transmission (not shown). Thus, the hub flange 6 is not rotatable relative to the input shaft of the transmission but is movable in the axial direction relative to the transmission input shaft. The flange 12 is provided with a plurality of circular air ventilation openings 14 at an interval in the circumferential direction. The second cylindrical portion 13 extends in an axial direction from the flange 12. A number of outer teeth 18a (first tooth portion) extending in the axial direction are formed on the outer circumference of the second cylindrical portion 13. As shown in Fig. 2, a hole 18c is formed to pass through each outer tooth 18a in the axial direction. An air passage hole 19 is formed radially outwardly from each air passage hole 14. A plurality of air passage holes 20 are formed in the second cylindrical portion 13. The air passage holes 19 and 20 extend through the second cylindrical portion 13 substantially radially outwardly, with the radially outward ends thereof open to the bottom portion of an adjacent pair of outer teeth 18a. Slot grooves 13a (Figs. 2 and 5) are formed in a plurality of locations in an end face of the second cylindrical portion 13 on the transmission side. At a radially outer end, each slot 13a has a width generally corresponding to the single outertooth 18, the width gradually decreasing inwardly. The frictional plate group 9 is arranged between the inside of the flywheel ring 5 and the second cylindrical portion 13 of the hub flange 6. The frictional plate group 9 is axially interposed between the frictional surface of the flywheel 2 and an annular pressure plate 29 (described below). The frictional plate group 9 is composed of four drive plates 7 and a driven plate 8' and two driven plates 8 arranged alternatively in the axially direction. The drive plates 7 and the driven plates 8 and 8' are dry type carbon-made annular frictional plates and all arranged coaxially with the input shaft of the transmission. The drive plates 7 are provided with radial projections 26 in their outer circumferential portion. The radial projections 26 are engaged non-rotatably with the internal teeth 23a of the flywheel ring 5 but are slidable in the axial direction. The driven plates 8 are provided with radial projections 27 (second tooth portion) in their inner circumferential direction. The projections 27 are engaged non-rotatably with the outer teeth 18a of the second cylindrical portion 13 but are slidable in the axial direction. The driven plate 8' at the transmission side is formed with contact portions 51 which are engaged relatively unrotatable with the slots 13a formed in the second cylindrical portion 13. The contact portions 51 have the same shape as that of the slots 13a, are longer in width than the protrusion 27 and extend in radially inwardly. A plurality of plate members 55 are fixed to the outer circumferential portion of the hub flange 6 on the transmission side for limiting the axial movement of the driven plate 8' at the transmission side relative to the hub flange 6. Figs. 1 and 2 show a state where the plate members 55 are fixed to the flange 12.. Fig. 5 shows the hub flange 6 and the driven plate 8 prior to installation of the plate members 55 to the flange 12. Fig. 6 shows one of the plate members 55 before installation. As is apparent from Fig. 6, each of the plate members 55 has a retainer portion 56, a joint portion 57 extending from one end of the retainer portion 56 in the axial direction, and a fastening portion 58 extending from the joint portion 57. Rivets extend through holes 59 and holes 12a formed in the flange 12 for fastening the plate members 55 to the hub flange 6. The retainer portion 56 of each plate member 55 in the fastened condition is arranged on the transmission side of the contact portion 51 of the driven plate 8'. Thus, the driven plate 8' on the transmission side is clamped in the axial direction between the surface (slot 13a) of the second cylindrical portion 13 on the transmission side and the retainer portion 56. When the clutch assembly 1 is in a clutch dis-engaged state, the driven plate 8' is movable through a predetermined distance in the axial direction between the flange 12 and the plate member 55. As described above, the hub flange 6 limits the axial relative movement of the single driven plate 8. The clutch cover assembly 10 is mainly provided with a clutch cover 28, an annular pressure plate 29 arranged within the clutch cover 28, a diaphragm spring 30 for urging the pressure plate 29 toward the flywheel 2, and a support mechanism for supporting the diaphragm spring 30 to the clutch cover 28. The clutch cover 28 is fixed to an end face of the flywheel ring 5 by the above-described bolts 22. The clutch cover 28 maybe made of metal, for instance, aluminum or an aluminum alloy to reduce its weight. The pressure plate 29 is provided on its outer circumferential portion with radial projections 32. The projections 32 are engaged non-rotatably with the internal teeth 23a but slidable in the axial direction. An annular raised portion 33 having a semicircular shape in cross section is formed integrally with a portion, on the inner circumferential side, of a back surface of the pressure plate29 (ie., a surface opposite the driven plates 8). The diaphragm spring 30 is composed of an annular portion 30a and a plurality of lever portions 30b extending radially inwardly from the inner circumference of the annular portion 30a. The lever portions 30b are provided at an equal interval in the circumferential direction. A slit is formed between the adjacent lever portions 30b. A cutaway 30c having a relatively large width in the circumferential direction is formed in a radially outward portion of each slit. The support mechanism 31, Fig. 4, includes a pair of first and second support members 35 and 36 for supporting the inner circumferential portion of the annular portion 30a of the diaphragm spring 30, and a plurality of bolts 37 for fastening the two annular support members 35 and 36 to the clutch cover 28. The pair of annular support members 35 and 36 are made of steel. The annular support members 35 and 36 extend in the circumferential direction along the diaphragm spring 30, and each have support portions at their outer circumferential portions. Each of the support portions 38 and 39 has a convex shape such as a semicircular shape or the like in cross section in a portion in contact with the diaphragm spring 30. The support portion 38 of the first annular support member 35 is in contact with the diaphragm spring 30 from the clutch cover 28 side (right side in Fig. 1), and the support portion 39 of the second annular support member 36 is in contact with the diaphragm spring 30 from the hub flange 6 side (left side in Fig. 1). A thin seat portion 40 having an annular shape and extending radially is formed integrally on the inner circumferential side of the support portion 38, as shown in the right side in Fig. 1. A plurality of leg portions 41 extending in the axial direction are formed integrally with the seat portion 40 at an interval in the circumferential direction. Also, a thin annular portion 42 having an annular shape and radially extending, is formed integrally on the inner circumferential side of the support portion 39, as shown on the left side in Fig. 1. A plurality of projections 43 extending in the axial direction are formed integrally at an interval in the circumferential direction. The projections 43 are continuous with the innercircumference of the support portion 39. The leg portions 41 and the projection 43 are projected in a direction close to each other. When assembled, as shown in Fig. 1, the leg portions 41 are engaged with the projections 43 at their front face through the cutaways 30c of the diaphragm spring 30. An annular groove 28a is formed in the clutch cover 28. A back surface, an inner circumferential surface and an outer circumferential surface of the first annular support member 35 are seated in the annular groove 28a. The annular support member 35 is seated in the annular groove 28a and retained in place by the bolts 37. Bolt insertion holes (provided with no screw threads) through which the bolts 37 extend through each leg portion 41 and a portion of the seat portion 40 continuous with the leg portion 41 in the first annular support member 35. Bolt insertion holes coaxial with these holes are formed also in the clutch cover 28. Threaded screw holes are formed in the projections 43 of the second annular support member 36 and a portion of the annular portion 42 continuous with the projections 43. The screw portions of the bolts 37 are fastened to those screw holes. As described above, the annular support members 35 and 36 are fixed to the clutch cover 28 by the plurality of bolts 37. The outer circumferential portion of the annular portion 30a of the diaphragm spring 30 supported to these annular support members 35 and 36 are in contact with the raised portion 33 of the pressure plate 29 to thereby urge the pressure plate 29 toward the flywheel 2 (on the left side in Fig. 1). As described above, the drive plates 7 and the driven plates 8 are clamped in the axial direction between the flywheel 2 and the clutch cover assembly 10 and are limited in the axial movement. With such an arrangement, the hub flange 6 is engaged relatively unmovable in the axial direction with the single driven plate. Accordingly, the axial movement of the hub flange 6 is also limited. Namely, the axial position of the hub flange 6 is determined. The operation will now be described. In a clutch engagement state, the release unit (not shown) is not urged against the diaphragm spring 30 and toward the flywheel 2, thereby allowing the elastic or biasing force of the diaphragm spring 30 to push the pressure plate 29 toward the frictional plate group 9. Thus, the drive plates 7 and the driven plates 8 are pressed into contact with each other. It is therefore possible for torque inputted from the flywheel 2 to the flywheel ring 5 to be transmitted through the drive plates 7 and the driven plates 8 and 8' to the hub flange 6 and further outputted from the hub flange 6 to the input shaft of the transmission (not shown). In order to put the clutch in a clutch dis-engaged state, the release unit (not shown) is forced against the ends of the lever portions 30b of the diaphragm spring 30 toward the flywheel 2, and thus urge the outer circumferential portion of the annular portion 30a of the diaphragm spring 30 in a direction away from the pressure plate 29. The pressure between the drive plates 7 and the driven plates 8 and 8' is released to interrupt torque transmission. The axial position of the hub flange 6 is generally determined by the engagement between the single driven plate 8' and the plate members 55. For this reason, drag associated with contact between relatively rotating members such as plates 7 and 8 and 8' upon torque transmission interruption is prevented due to the limited axial movement of the hub flange 6 and the driven plate 8'. Further, because of the movement limiting effects of the plate members 55 and the plate 8', the hub flange 6 may only undergo limited movement and disengagement with the input shaft of the transmission is prevented. Also, since the hub flange 6 and the driven plate 8' are in contact with each other at contact portions 51 which have a relatively large area, the contact therebetween is distributed across a larger area. As a result, overall wear is not localized. In the multi-plate clutch described above, the first annular frictional plates and the second annular frictional plates are interposed in the axial direction between the rotational flywheel and the pressure mechanism so that they are limited in the axial movement. Furthermore, the plate members are arranged on the opposite side of the single second cylindrical portion, at the end side in the axial direction, of the second frictional plates so that the output member prevents the output member from moving in the axial direction relative to the second annular frictional plates. Thus, the axial movement of the output member is limited. It should be noted that the contact area is increased by the contact of the retainer portion of the plate member with the contact portion of the second annular frictional plate. As a result, the wear of the second annular frictional plates may be suppressed. SECOND GENERAL EXAMPLE A second general example will now be described with reference to Figs. 7 and 8. Fig. 8 is a cross-sectional view showing an automotive dry type multi-plate clutch 100 in accordance with a second embodiment of the present invention. Many of the features of the dry type multi-plate clutch 100 are similar or the same as those features described above with respect to the first general example. Therefore, some of the description of the common elements and features has been omitted. In the second general example, a hub flange 106 has a centrally located boss 11, a flange 12 expanding radially outwardly, integrally from the boss 11 and a second cylindrical portion 13 integrally formed on an outer circumference of the flange 12. Holes 18c are formed in each outer tooth 18a, each hole 18c extending in the axial direction through each tooth 18a. A flywheel ring 5 is coaxially arranged radially outwardly of the second cylindrical portion 13. The flywheel ring 5 is fixed to the flywheel 2 of the engine at one end on the left side in Fig. 7 by a plurality of bolts 22 (whose center axis only is shown in Figs. 7 and 8). The flywheel ring 5 is provided with internal teeth 23a. A plurality of air passage slots 24 are provided at a plurality (for example, three) of locations at an interval in the axial direction on the outer circumference of the flywheel ring 5. As shown in Fig. 7, the air passage slots 24 are provided radially outwardly of the driven plates 8 and 8'. Each air passage slot 24 extends arcuately along the circumferential direction of the flywheel ring 5 with its bottom opening to the bottom surface of the plurality of internal teeth 23a. Due to the fact that the air passage slots 24 extend in the circumferential directions, the weight of the flywheel ring 5 is reduced. The frictional plate group 9 is arranged between the inside of the flywheel ring 5 and the second cylindrical portion 13 of the hub flange 6. The frictional plate group 9 is composed of four drive plates 7 and one driven plate 8 and two driven plates 8' arranged alternatively in the axially direction. The drive plates 7 and the driven plates 8 and 8' are dry type carbon-made annular frictional plates and all arranged coaxially with the input shaft of the transmission. The drive plates 7 are provided with radial projections 26 in their outer circumferential portion. In the second general example, there are two driven plates 8' each provided with contact portions 51 engaged non-rotatably with grooves 13a formed in the second cylindrical portion 13 but may slide in the axial direction. Since there are grooves 13a formed on each axial end of the second cylindrical portion 13 and two driven plates 8', one driven plate 8' being disposed on each opposing axial end thereof, the second cylindrical portion 13 is restrained against axial movement by the plurality of contact portions 51 of the two driven plates 8'. A gap G is maintained between each end face of the second cylindrical portion 13 and each contact portion 51, as shown in Fig. 7, when the dry type multi-plate clutch 101 is newly manufactured. The clutch cover 28 is fixed to an end face of the flywheel ring 5 by the above-described bolts 22. The clutch cover 28 is preferably made of aluminum or an aluminum alloy to reduce its weight. The operation of the second general example is similar to that of the first general example, described above. However, in the second general example depicted in Figs. 7 and 8, the general position of the hub flange 6 in the axial direction is maintained by the contact portions 51 of the two driven plates 8'. Thus, since the positioning of the hub flange 6 is performed without the addition of extra elements or structure, the number of the parts is reduced. Also, since the hub housing 6 and the driven plates 8' are in contact with each other through the contact portions 51 having a large contact area, the contact area is increased and the frictional wear is less localized. In the multi-plate clutch the first annular frictional plates and the second annularfrictional plates are interposed in the axial direction between the rotational flywheel and the pressure mechanism and their axial motion is limited. Furthermore, since the contact portions of both annular frictional plates are contacted against both ends of the second cylindrical portion in the axial direction, the movement of the output member in the axial direction is limited. Since the planar contact portions are brought into contact with the second annular frictional plates, the contact area is increased to thereby suppress wear. FIRST EMBODIMENT OF THE PRESENT INVENTION Fig. 9 is a cross-sectional view showing an automotive dry type multi-plate clutch 200 in accordance with a first embodiment of the present invention. The line O-O is a rotary axis of the dry type multi-plate clutch 200. The dry type multi-plate clutch 200 shown in Figs. 9,10,11 and 12 has many features similarto those described above with respect to the first and second general examples. Like components have like reference numerals. Description of some similar or identical parts has therefore been omitted. In the first embodiment of the present invention, the dry type multi-plate clutch 200 does not include the grooves 13a described above with respect to the first and second general examples. In the first embodiment of the present invention, the axial movement of the hub flange 6 is effected differently. The frictional plate group 9 is composed of four drive plates 7 and three driven plates 8 arranged alternatively in the axially direction. The drive plates 7 and the driven plates 8 are dry type carbon-made annular frictional plates and all arranged coaxially with the input shaft of the transmission. The clutch cover assembly 10 includes a clutch cover 28, an annular pressure plate 129 arranged within the clutch cover 28, a diaphragm spring 30 for urging the pressure plate 129 toward the flywheel 2, and a support mechanism 31 for supporting the diaphragm spring 30 to the clutch cover 28 side. The clutch cover 28 is fixed to an end face of the flywheel ring 5 by the previously described bolts 22. The pressure plate 129 is disposed on the right side of Fig. 9 of the drive plate 7 disposed proximate to the clutch cover 28. The pressure plate 129 is provided at its outer circumferential portion with radial projections 32. The projections 32 are non-rotatable relative to internal teeth 5a but slidable in the axial direction. The pressure plate 129 is formed with a taper surface 129a which decreases in height going toward an inner circumferential end thereof. As shown in more detail in Fig. 11, a cushion ring 60 is disposed on the back surface side of the pressure plate 129. The outer circumferential portion of the cushion ring 60 is in contact with the taper surface 129a. With the clutch in a dis-engaged state, the inner circumferential portion of the cushion ring 60 has a gap S 1 between it and the taper surface 129a. The gap S 1 serves as a warpage allowance. An annular raised portion 60a having a semi-circular cross-section is formed on the cushion ring 60 on the inner circumferential clutch cover 28 side. The diaphragm spring 30 is formed of two overlapping disc-like members. The diaphragm spring 30 is further formed of an annular elastic or resilient portion 30a and a plurality lever portions 30b extending radially inwardly from the inner circumference of the annular resilient portion 30a. The support mechanism 31 is generally the same as described above with respect to the first embodiment. As described above, the annular support members 35 and 36 are fixed to the clutch cover 28 by the plurality of bolts 37. The outer circumferential portion of the annular portion 30a of the diaphragm spring 30 supported by the annular support members 35 and 36 are in contact with the raised portion 60a of the cusion ring 60 to thereby urge the pressure plate 129 toward the flywheel 2. When a clutch engagement/dis-engagement mechanism, or release unit (not shown) engages the ends of the lever portions 30b of the diaphragm spring 30 and pushes them toward the flywheel 2, the outer circumference of the annular portion 30 of the diaphragm spring 30 is separated away from the pressure plate 129. As a result, the clutch is dis-engaged. In the above-described structure, the hub flange 6 is movable in the axial direction relative to the input of the transmission. Accordingly, it is necessary to limit the axial movement of the hub flange 6. For this reason, as shown in Fig. 12, three arcuate plates 52 are connected to the second cylindrical portion 13 of the hub flange 6. The structure of the arcuate plates and the method for mounting them will now be described. A circumferencial groove 56 is formed on the flywheel 2 side of the outer teeth 18a of the second cylindrical portion 13. The circumferencial groove 56 has a depth close to the bottom portions of the outer teeth 18a. Three receiving portions 56a which extend radially inwardly and pass through the second cylindrical portion 13 are formed at an equal interval in the circumferencial direction in the circumferencial groove 56. The circumferential width of the receiving portions 56a decreases going from the radially outward side to the radially inward side, as is shown in Fig. 12. Each arcuate plate 52 has an arcuate portion 52a and fastening portions 52b its both ends. Each fastening portion 52b extends radially inwardly and has a bolt insertion hole. Each arcuate plate 52 is fitted in the circumferential groove 56. Each fastening portion 52b is inserted into the receiving portion 56a together with the adjacent fastening portion 52b. Each fastening portion 52a is fixed to the second cylindrical portion 13 by bolts 53. Thus, the arcuate portions 52a of the arcuate plates 52 are disposed between the projections 27 of two of the second driven plates 8. The above-described flywheel 2 and the pressure plate 129 are used to limit the axial movement of the drive plates 7 and the driven plates 8. Thus, the plurality of arcuate plates 52 located between the projections 27 of the two driven plates 8 limited the axial movement of the hub flange 6. The operation will now be described. When the pressure applied to the diaphragm 30 toward the flywheel 2 is released by the release unit (not shown), the annular resilient portion 30a of the diaphragm spring 30 urges the cushion ring 60 toward the flywheel 2. The cushion ring 60 is flexed and deformed so that the inner circumferential portion thereof finally comes into contact with the taper surface 129a of the pressure plate 129. Then, the pressure plate 129 is pushed against the frictional plate group 9 so that the drive plates 7 and the driven plates 8 are pressed against each other. As a result, the torque that has been inputted from the flywheel 2 to the flywheel ring 5 is transmitted to the hub flange 6 through the drive plates 7 and the driven plates 8 and further outputted to the input shaft of the transmission. As described above, the cushion ring 60 is flexed and deformed to thereby obtain a cushion effect. As a result, a shock generated upon the clutch engagement is reduced. When the clutch is dis-engaged, the ends of the lever portions 30b are pushed toward the flywheel 2 by the release unit (not shown) so that the outer circumferetial portion of the annular resilient portion 30a is moved in a direction away from the pressure plate 129. Thus, the pressure against the drive plates 7 and the driven plates 8 is released and the clutch is disengaged. In the release operation described above, the cushion ring 60 tends to take the original position to thereby urges the diaphragm spring 30 in the direction away from the pressure plate 129. Therefore, the force necessary to dis-engage the clutch is maintained at a low level so that the semi-clutch operation becomes less difficult for an operator. The hub flange 6 is engaged with the drive plates 7 and the driven plates 8 by the three arcuate plates 52 and positioned in the axial direction. In other words, the arcuate plates 52 are contacted with the projections 27 of the two driven plates 8 in the axial direction. In the above-described structure, the annular portion composed of the three arcuate plates 52 are brought into contact with the projections 27 of the driven plates 8 over the entire circumference. Namely, the area to be contacted with the projections 27 are larger than that of the prior art. For this reason, the contact surface pressure on the projections 27 is reduced, in comparison to prior art configurations and the projections 27 of the driven plates 8 are less likely to become worn. Each arcuate plate 52 may readily be attached to detached from the circumferential groove 56 of the second cylindrical portion 13. Also, as is apparent from Fig. 12, fastened portions 52b of the respective arcuate plate 52 are not overlapped in the axial direction but are individually fixed to the second cylindrical portion. For this reason, it is not necessary to thin a thickness of the fasten portions 52b. The thickness of the arcuate portions 52a is the same as that of the fastened portions 52b. As a result, the mechanical strength of the fastened portions 52 is enhanced. Means for fastening the arcuate plates 52 may be any other means in addition to the bolts. The number of the arcuate plate 52 is not limited to three. Various details of the invention may be changed without departing from its scope. Furthermore, the foregoing description of the embodiments according to the present invention is provided for the purpose of illustration only, and not for the purpose of limiting the invention as defined by the appended claims.

Claims: A multi-plate clutch mechanism, comprising a first cylindrical portion (5) configured for connection to a flywheel (2); a hub flange (6) having a second cylindrical portion (13) disposed concentrically within said first cylindrical portion, said hub flange (6) configured to non-rotatably engage an input shaft of a transmission; a plurality of first friction plates (7) disposed between said first cylindrical portion (5) and said second cylindrical portion (13), said first friction plates being circumferentially engaged for rotation with said first cylinderical portion (5) but relatively slidable in the axial direction with respect to said first cylindrical portion (5); a plurality of second friction plates (8) disposed alternatingly adjacent to said first friction plates (7) in the axial direction, said second friction plates (8) being configured to engage said second cylindrical portion (13) for rotation therewith but configured for limited relative axial movement with respect to said second cylindrical portion (13); and a pressure plate mechanism (10) fixed to said first cylindrical portion (5) such that said friction plates (7, 8) are disposed between said pressure plate mechanism (10) and the flywheel (2), said pressure plate mechanism including a clutch cover (28) supported on said first cylindrical portion (5), a pressure plate (129) disposed between said clutch cover (28) and said first and second friction plates (7, 8) and a diaphragm spring (30) disposed between said clutch cover (28) and said pressure plate (129); characterized in that a resilient member (60) disposed between the pressure plate (129) and said diaphragm spring (30), said resilient member operably configured to flex and be elastically deformed in the axial direction in response to movement of said diaphragm spring (30), wherein the resilient member (60) is a cushion ring and the cushion ring has an annular raised portion (60a) having a semi-circular cross-section. The multi-plate clutch mechanism according to claim 1, characterized in that the pressure plate (129) has a taper surface (129a) which decreases in height going toward an inner circumferential end of the pressure plate.

Inventors: FUKUDA YOSHINOBU, KOSUMI TOSHIYA, FUKUDA, YOSHINOBU, KOSUMI, TOSHIYA
Applicants: EXEDY CORP, EXEDY CORPORATION
Application year: 1997
Main classification: F16D13
IPC codes: F16D13