Multi-plate clutch mechanism

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 with inner portions (166) and wider outer portions (167) to improve air flow therethrough for cooling. The diaphragm spring in another embodiment includes a first diaphragm spring and a second diaphragm spring 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 gear teeth, 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. DE 195 17 968 A1 describes a dry multi-disk clutch comprising clutch friction disks, a diaphragm spring, a clutch cover and a support structure. The periphery portion of the diaphragm spring loads the clutch friction disks. The support structure comprises certain elements which are fixed to the diaphragm spring. Further, there is provided a hub flange having a positioning pin or a fixing plate for maintaining the position of the hub flange in axial direction relative to the clutch friction disks. SUMMARY OF THE INVENTION One object of the present invention is to reduce friction wear of various contacting members of a clutch mechanism. Another object of the present invention is to enhance the operatability of a clutch in the engaging and dis-engaging process. According to the invention, the object is solved by the features of the main claim. The sub-claims contain further preferred 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 and to axially slide with respect to the input shaft. 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, one of the second friction plates being engaged with 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. A plate member is fixed to the hub flange, the plate member confining the one of the second friction plates between the plate member and the hub flange limiting axial movement of the hub flange between the pressure plate and the flywheel. The one of the second friction plates has a radially inwardly protruding portion extending between the plate member and the second cylindrical portion. Preferably, one outer circumferential surface of the second cylindrical portion is formed with a plurality of first tooth portions extending in the axial direction, the second friction plates have, on their inner circumferential portion, a plurality of second tooth portions engaged relatively unrotatable with the first tooth portions of the second cylindrical portion but relatively movable in the axial direction thereto, and the radially inwardly protruding portion extends radially inwardly of the second tooth portions. Preferably, a slot is formed in the second cylindrical portion which engages the radially inwardly protruding portion. Preferably, a plurality of the radially inwardly protruding portions are formed in the circumferential direction on the one of the second friction plates and the second cylindrical portion is formed with a plurality of corresponding slots. 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 embodiment of the present invention; 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 of the present invention, 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 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Fig. 1 is a cross-sectional view showing an automotive dry type multi-plate clutch 1 in accordance with one embodiment of the invention. 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 11a is formed in the center of the boss 11. The spline hole 11a 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 outer tooth 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 60 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 plate 29 (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 inner circumference 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 according to the present invention, 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.

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 (5), said hub flange (6) configured to non-rotatably engage an input shaft of a transmission and to axially slide with respect to the input shaft; a plurality of first friction plates (7) disposed between said first cylindrical portion (5) and said second cylindrical portion (13), said first friction plates (7) being circumferentially engaged for rotation with said first cylindrical 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, one (8') of said second friction plates being engaged with said second cylindrical portion (13) for rotation therewith but configured for limited relative axial movement with respect to said second cylindrical portion (13); 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); and a plate member (55) fixed to said hub flange (6), said plate member (55) confining said one (8') of said second friction plates (8) between that plate member (55) and said hub flange (6) limiting axial movement of said hub flange (6) between said pressure plate (29) and the flywheel (2) characterized in that said one (8') of said second friction plates has a radially inwardly protruding portion (51) extending between said plate member (55) and said second cylindrical portion (13). The multi-plate clutch mechanism according to claim 1, wherein one outer circumferential surface of said second cylindrical portion (13) is formed with a plurality of first tooth portions (18a) extending in the axial direction, said second friction plates (8) have, on their inner circumferential portion, a plurality of second tooth portions (27) engaged relatively unrotatable with said first tooth portions (18a) of said second cylindrical portion (13) but relatively movable in the axial direction thereto, and said radially inwardly protruding portion extends radially inwardly of said second tooth portions (27). The multi-plate clutch mechanism according to claim 2, wherein a slot (13a) is formed in said second cylindrical portion (13) which engages said radially inwardly protruding portion (51). The multiple-plate clutch mechanism according to claim 3, wherein a plurality of said radially inwardly protruding portions (51) are formed in the circumferential direction on that one (8') of said second friction plates and said second cylindrical portion (13) is formed with a plurality of corresponding slots (13a).

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