Clutch disc

A clutch disc includes a hub having a flange portion extended in a radial direction and a boss portion connected to a driven shaft, a side plate arranged coaxially with and relatively rotatable with the hub, a friction member connected to an external periphery of the side plate and frictionally engaged with a drive shaft, an accommodation window formed on an external periphery portion of the hub and on the side plate, the accommodation window on the hub and the accommodation window on the side plate being positioned facing each other, springs elastically connecting the hub to the side plate in the accommodation window, and a thrust member provided in a space between the hub and the side plate. The thrust member includes a ring shape member biased towards the flange portion of the hub by a biasing device. An opposing surface configured to face the hub is tapered.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. §119 with respect to Japanese Patent Application No. 2004-333753 filed on Nov. 17, 2004, the entire content of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a clutch disc which absorbs fluctuation of torque by means of a coil spring as it is transmitting torque. More particularly, the present invention pertains to a clutch disc which is provided with the properties of hysteresis by the provision of a thrust member between a hub and side plates.

BACKGROUND

Known mechanisms have been proposed for providing properties of hysteresis to a clutch disc for transmitting torque from an engine to a transmission on the basis of an elastic deformation of coil springs.

For example, JPH07-054291A describes a construction in which properties of hysteresis are generated by supporting and sandwiching a drive ring40, which is engaged with a spring90within a closed ring36, between friction rings38,39at one side of a hub13.

JPH09-112569A describes a hysteresis mechanism which securely causes sliding friction with a fiction plate122, a mechanism in which projecting portions of a first friction member120and a second friction member121are engaged at both ends of a flange105, and the first friction member120and the second friction member121are rotated unitarily with the flange105.

JPH10-103407A describes a construction in which properties of hysteresis are generated in two steps by dividing a bush at one side into a first bush16and a second bush18and by causing friction between, on the one hand, the first bush16and a hub2and, on the other hand, the second bush and a separate flange5.

Hysteresis mechanisms of clutch discs described in JPH09-112569A and JPH10-103407A are constructed on the presumption that opposing surfaces of a thrust member (e.g., a friction member, or a bush) and a friction surface of a hub (e.g., a friction plate, or a separate flange) make contact uniformly at plane surfaces, generate frictional force, and generate properties of hysteresis.

The thrust member is most often formed by injection molding with resin in order to reduce manufacturing costs and weight, and an opposing surface of the thrust member may also in these circumstances be formed by injection molding. In these circumstances, the opposing surface is not necessarily formed uniformly, either because of cooling contracture during injection molding, which becomes the cause of dispersion during manufacturing, or because of uneven dents caused by the configuration of the thrust member. Surface waviness and warping may thus on occasions be generated at the opposing surface.

In other words, when the thrust member having surface waviness and warping on the opposing surface is applied to a hysteresis mechanism of a clutch disc described in JPH07-54921, JPH09-112569, or JPH10-103407, the opposing surface of the thrust member does not make contact uniformly with the frictional surface of the hub (e.g., the friction plate or separate flange). Properties of hysteresis are accordingly dispersed when the clutch disc is initially assembled and thus there has been a danger of the properties of hysteresis not being able to perform an adequate level of torsion cushioning performance of the clutch disc.

SUMMARY OF THE INVENTION

In light of the foregoing, the present invention provides a clutch disc, which includes a hub having a flange portion extended in a radial direction and a boss portion connected to a driven shaft, a side plate arranged coaxially with and relatively rotatable with the hub, a friction member connected to an external periphery of the side plate and frictionally engaged with a drive shaft, an accommodation window formed on an external periphery portion of the hub and on the side plate, the accommodation window on the hub and the accommodation window on the side plate being positioned facing each other in a rotational axial direction, a plurality of springs elastically connecting the hub to the side plate in a rotational direction in the accommodation window, and a thrust member provided in a space in an axial direction between the hub and the side plate. The thrust member includes a ring shape member which is biased towards the flange portion of the hub by a biasing means. An opposing surface configured to face the hub is tapered.

DETAILED DESCRIPTION

Embodiments of the present invention will be explained with reference to illustrations of drawing figures as follows.

A clutch disc1includes an inner hub11which is engaged by means of splines with an input shaft of a transmission of a driven shaft of an outer hub110, the outer hub110which is configured in a ring shape and coaxially positioned at an outer periphery of the inner hub11, four sub-coil springs30for elastically connecting the inner hub11to the outer hub110in a peripheral direction, a pair of sub-spring sheets140A,140B for supporting each of the sub-coil springs30relative to the inner hub11and the outer hub110, a first side plate12A which is co-axially arranged at a first side of the inner hub11and a first side of the outer hub110, and a second side plate12B which is co-axially arranged at a second side of the inner hub11and a second side of the outer hub110in such a way that the first side plate12A and the second side plate12bare both relatively rotatable with the inner hub11and the outer hub110, four coil springs13(i.e., serving as a spring) for elastically connecting the outer hub110to the first and second side plates12A,12B in a peripheral direction, a pair of springs14A,14B for supporting each of the coil springs13relative to the outer hub110and to the first and second side plates12A,12B, a first inner thrust member31A and a first outer thrust member32A (i.e., serving as a thrust member) which are both positioned between, on the one hand, the first side plate12A, and, on the other hand, the inner hub11and the outer hub110, a second inner thrust member31B and a second outer thrust member32B (i.e., serving as a thrust member) which are both positioned between, on the one hand, the second side plate12B, and, on the other hand, the inner hub11and the outer hub110, an inner coned disc spring33for biasing the second inner thrust member31B towards the inner hub11, and an outer coned disc spring34for biasing the second outer thrust member32B towards the outer hub110.

The first side plate12A and the second side plate12B are fixed by means of rivets22at an external periphery in a radial direction of the outer hub110keeping a predetermined distance from each other, and thus the first side plate12A and the second side plate12B integrally rotate. A cushioning plate19which is configured to have a ring shape having waviness on surface thereof in a thickness direction is fixed on an external periphery portion of the first side plate12A. Friction members21A,21B are fixed on first and second surfaces of the cushioning plate19respectively by means of the rivets20. The friction members21A,21B are positioned between a flywheel fixed on a crankshaft of an engine and a pressure plate of a clutch cover fixed to the flywheel by means of bolts. Because the friction members21A,21B are pushed onto the pressure plate so as to frictionally engage with the flywheel with the pressure plate, rotational torque of the engine is inputted into the first side plate12A.

The coil springs13are arranged in accommodation windows16provided on the first side plate12A and the second side plate12B. The accommodation window16is a recess formed on the outer hub110by recessing an external periphery portion of the outer hub110in a radial outward direction. External periphery surface side of the sheet portion of the spring sheets14A,14B is positioned at outside in a radial direction compared to the external periphery surface of the outer hub110. Accordingly, the coil springs13can be positioned at as external periphery side as possible, a size of the coil springs13applied to the clutch disc can be increased, and the clutch disc can cope with larger degree of torque fluctuation. Accommodation windows17formed on the first side plate12A and the second side plate12B are window bores formed by punching at an external periphery side relative to the coil springs13, and are provided at positions opposing each of the accommodation windows16of the outer hub110relative to a rotational axis. Each coil spring13, while being supported by a pair of the spring sheets14A,14B, is accommodated in the accommodation windows16,17formed with the first side plate12A, the second side plate12B, and the outer hub110. The accommodation window17formed on the side plates12A,12B is formed in semi-chambered configuration by punching, and pinches and supports the spring sheets14A,14B by covering both ends of the sheet portion of the spring sheets14A,14B. A concave portion is formed at a central portion of the sheet portion of the spring sheets14A,14B and a convex portion formed on the outer hub110is fitted into the concave portion, and thus the spring sheets14A,14B are pinched and supported by the outer hub110. In other words, the coil springs13are supported by the side plates12A,12B and the outer hub110through the spring sheets14A,14B. Upon a rotation of the side plates12A,12B the coil springs13are deformed, and restoring force of the coil springs13rotates the side plates12A,12B.

A projecting portion14C, projecting towards opposing spring sheet14A or14B in the accommodation windows16,17, is integrally formed on each of the spring sheet14A,14B. The projecting portions14C formed on the spring sheets14A,14B are configured not to allow further relative rotation upon a timing when ends of the projecting portions14C contact each other by the relative rotation between, on the one hand, the first side plate12A and the second side plate12B, and, on the other hand, the outer hub110(i.e., a timing when a relative rotation angle reaches a predetermined angle θ1from zero). In other words, by contacting projecting portions14C,14C each other when the relative rotation angle reaches the predetermined angle θ1, relative rotation between, on the one hand, the outer hub110and, on the other hand, the first side plate12A and the second side plate12B is allowed only within a predetermined angle θ1, and relative rotation equal to or greater than the predetermined angle θ1is not allowed.

Configuration of the projecting portion14C will be further explained as follows. The end of the projecting portion14C includes a plane shape, and tapered to be smaller as closer to the end of the projecting portion14C. When the relative rotation angle reaches a predetermined angle θ1, the planes of the ends of the projecting portions14C,14C come to be arranged in parallel to each other, and an axial center of the projecting portions14C,14C come to be arranged on an identical line. The projecting portions14C,14C which are arranged opposing each other have the identical configurations, and the spring sheets14A,14B arranged opposing each other have the identical configuration.

The sub-coil springs30are arranged in space formed by recess portions28,29provided on the outer hub110and the inner hub11. The recess portion28, formed on the inner hub11including a flange portion and a boss portion engaged by means of splines with an input shaft of a transmission of a driven shaft, is formed by recessing an external periphery of the flange portion of the inner hub11. The recess portion29is formed on the outer hub110by recessing an internal periphery portion of the outer hub110which is shaped in a ring, and the recess portion29is formed at a position which opposes to the recess portion28in a radial direction. Each of the sub-coil springs30is supported by a pair of the sub-spring sheets140A,140B, and a half of the sheet portion of the sub-spring sheet140A is engaged with the recess portion28in a circumferential direction and a half of the sheet portion of the sub-spring sheet140B is engaged with the recess portion29in a circumferential direction. When the outer hub110rotates relative to the inner hub11, the sub-coil springs30are compressed, and the inner hub11is rotated by the restoring force of the sub-coil springs30. Accordingly, torque transmitted to the side plates12A,12B is transmitted to the inner hub11through the outer hub110.

Projections11A projecting to an external peripheral side are formed on the inner hub11, and projections110A projecting to an internal peripheral side are formed on the outer hub110. Upon a timing that the outer hub110rotates relative to the inner hub11by a predetermined angle θ2(i.e., a timing when the relative rotation between the outer hub110and the inner hub reaches a predetermined angle θ2from zero), the projections11A and the projections110A contact to restrict the relative rotation of the inner hub11and the outer hub110.

As explained above, the inner hub11and the outer hub110are elastically connected in a rotational direction through the sub-coil springs30, and the outer hub110and the side plates12A,12B are elastically connected in a rotational direction through the coil springs13, and thus the inner hub11and the outer hub110can rotate relative to each other and the outer hub110and the side plates12A,12B can rotate relative to each other. Spring constant of the coil springs13is set several times greater than spring constant of the sub-coil springs30. When torque from an engine is inputted to the first side plate12A by means of the frictional engagement between the friction members21A,21B, the coil springs13is not elastically deformed immediately after the input of the torque because the spring constant of the coil springs13is adequately greater than the spring constant of the sub-coil springs130, and thus the outer hub110and the side plates12A,12B rotate integrally. By this integral rotation, the outer hub110rotates relative to the inner hub11, the sub-coil springs30is elastically deformed, and the torque is transmitted to the input shaft of the transmission through the inner hub11. When the relative rotation between the outer hub110and the inner hub11reaches the predetermined angle θ2, the projections110A and the projections11A contact one another so that the outer hub110and the inner hub11rotate integrally, the coil springs13starts elastically deforming, and the side plates12A,12B starts rotating relative to the outer hub110. Upon further greater torque being inputted, the relative rotation between the outer hub110and the first and second side plates12A,12B reaches the predetermine angle θ1, and the side plates12A,12B, the outer hub110, and the inner hub11rotate integrally, and thus torque of the engine is directly transmitted to the input shaft of the transmission.

With the construction of a relative rotational mechanism with two steps explained above, the clutch disc1according to the embodiment of the present invention absorbs smaller degree of torque fluctuation caused, for example, by combustion of the engine with the sub-coil springs30having smaller spring constant, and absorbs greater degree of torque fluctuation caused, for example, by ON-OFF of an acceleration or at a shift change of the vehicle with the coil springs13having greater spring constant, thus the torque fluctuation can be effectively absorbed.

Detailed construction of the hysteresis mechanism according to the present invention is explained with reference toFIGS. 3-5. As shown inFIG. 3, the hysteresis mechanism includes the outer hub110, the inner hub11, the outer thrust members32A,32B positioned at either side of the outer hub110and the inner hub11, the inner thrust members31A,31B positioned at either side of the outer hub110and the inner hub11, the outer coned disc spring34which biases the second outer thrust member32B from the second side plate12B to the outer hub110and the inner hub11side, and the inner coned disc spring33which biases the second inner thrust member31B from the second side plate12B to the outer hub110and the inner hub11side.

As shown inFIG. 4A, plural detent portions131cwhich project towards external peripheral direction in a radial direction are formed on a boss portion of an internal periphery of the first inner thrust member31A. The detent portions131c, as shown inFIG. 1, are fitted into plural detent grooves12C respectively to be engaged therewith formed by recessing an internal periphery portion of the first side plate12A. By the engagement between the detent portions131cand the detent grooves12C, the first side plate12A and the first thrust member31A rotate integrally. A boss portion of the inner hub11is inserted through an inner diameter portion131dat an internal periphery of the first inner thrust member31A, and the first inner thrust member31A and the inner hub11coaxially positioned. An opposing surface131eat an end surface of the first inner thrust member31A contacts the flange portion of the inner hub11. A contact surface131hat backside of the opposing surface131econtacts the first side plate12A, and a guide portion131fat an external peripheral side defines approximate position of the first outer thrust member32A. The second inner thrust member31B is provided at backside of the inner hub11relative to the side provided with the first inner thrust member31A, and the inner hub11is sandwiched by the first inner thrust member31A and the second inner thrust member31B. The inner-coned disc spring33is provided between the second inner thrust member31B and the second side plate12B to biases the second inner thrust member31B towards the inner hub11. Because the first side plate12A and the second side plate12B are connected by means of the rivets22, by the biasing force of the inner coned disc spring33, a predetermined thrust force is generated between the inner hub11and the first and second inner thrust members31A,31B. Maximum static friction torque value TMIN and dynamic friction torque value TDIN in a rotational direction when the inner hub11and side plates12A,12B rotate relative to one another are determined on the basis of a relationship between thrust force by the inner coned disc spring33and a friction coefficient determined by relationship among the flange portion of the inner hub11, the first and second thrust members31A,31B, and the opposing surface131e.

When the absolute value of smaller degree of the torque fluctuation is less than the maximum static friction torque value TMIN when the smaller level of the torque fluctuation deriving from, for example, the combustion of the engine is inputted into the side plates12A,12B through the friction members21A,21B to be transmitted to the inner hub11, the smaller level of torque fluctuation is directly transmitted to the input shaft of the transmission without causing slips in a rotational direction between the first and second inner thrust members31A,31B and the inner hub11. In these circumstances, because the degree of the torque fluctuation is adequately small, oscillation and noise are unlikely generated in a vehicle.

When a torque fluctuation having greater level of absolute value than the maximum static friction torque TMAX is inputted, slips in a rotational direction is generated between the first and second inner thrust members31A,31B and the inner hub11, a torque fluctuation between the first and second thrust members31A,31B and the inner hub11is absorbed by the clutch disc1by the elastic deformation of the sub-coil springs30, and torque fluctuation transmitted into the input shaft of the transmission can be restrained.

As shown inFIG. 5A, plural detent portions231cprojecting to external peripheral side in a radial direction are formed on a boss portion at an internal periphery of the first outer thrust member32A. As shown inFIG. 1, the detent portions231care configured to fit in plural detent bores12D formed at an internal periphery of the first side plate1, and the first outer thrust member32A rotates integrally with the first side plate12A. The first inner thrust member31A is positioned at an inner diameter portion231dof an internal periphery of the first outer thrust member32A, the first outer thrust member32A and the first inner thrust member31A are coaxially arranged, and an opposing surface231eof end surface of the first outer thrust member32A contacts the outer hub110. A contact surface231hat backside of the opposing surface231econtacts the first side plate12A. The second outer thrust member32B is arranged at the backside of the outer hub110relative to the first outer thrust member32A, and the outer hub110is sandwiched by the first outer thrust member32A and the second outer thrust member32B. The outer-coned disc spring34is arranged between the second outer thrust member32B and the second side plate12B to biases the second outer thrust member32B towards the outer hub110. Because the first side plates12A and the second side plate12B are fastened by means of the rivets22, a predetermined thrust force is generated between the outer hub110and the first and second outer thrust members32A,32B by the biasing force of the outer coned disc spring34. A maximum static friction torque value TMOUT and dynamic friction torque value TDOUT in a rotational direction when the outer hub110and the side plates12A,12B rotate relative to one another is determined on the basis of the relationship between the thrust force by means of the outer coned disc spring34and the frictional coefficient determined on the basis of the mutual relationship among the flange portion of the outer hub110, the first and second outer thrust members32A,32B, and the opposing surface231e.

Greater level of torque fluctuation deriving, for example, from ON-OFF of a throttle pedal and at shift change of the vehicle is inputted into the sidle plates12A,12B through the friction members21A,21B. The torque is transmitted into the inner hub11, the inner hub11and the outer hub110rotate relatively, the projections11A and the projections110A contact, and the inner hub11and the outer hub110starts integral rotation. When the absolute value of the greater level of the torque fluctuation is smaller than the maximum static friction torque value TMOUT, slips in a rotational direction is not generated between the first and second outer thrust members32A,32B and the outer hub110, and the greater level of the torque fluctuation is transmitted into the input shaft to the transmission directly.

When the torque fluctuation with the greater absolute value than the maximum static friction torque TMOUT is inputted, slips in a rotational direction is generated between the first and second outer thrust members32A,32B and the outer hub110, the torque fluctuation between the first and second outer thrust members32A,32B is absorbed by the clutch disc1by the elastic deformation of the coil springs13, and the torque fluctuation transmitted to the input shaft of the transmission is restrained.

Tapers C1, C2are formed on the opposing surfaces131e,231eof the thrust members31A,31B,32A,32B facing the inner hub11and the outer hub110of the hysteresis mechanism, as shown inFIGS. 4C,5C.

Degree of tapering of the taper C1is defined by a difference between a thickness of an external periphery portion and a thickness of an internal periphery portion in an axial direction establishing an external periphery portion of the opposing surface131eas a reference, and the taper C1is formed in a direction so as not to contact the outer hub110. With the foregoing construction, the external periphery portion of the opposing surface131econtacts the flange portion of the inner hub11. Because the external periphery portion contacts the flange portion of the inner hub11with a predetermined width in accordance with a thrust load of the inner coned disc spring33, the pressure is increased, and the external periphery portion constantly contacts the flange portion of the inner hub11by deforming to reduce the influence of the surface waviness and the projections even when the surface waviness and the projections are appeared on the opposing surface131ecaused by the dispersion at manufacturing.

Degree of tapering of the taper C2formed on the opposing surface231eis defined by a difference between a thickness of the external periphery portion and a thickness of an internal periphery portion in an axial direction establishing the external periphery portion as a reference, and the taper2is formed in a direction so as not to contact the outer hub110. With the foregoing construction, the external periphery portion of the opposing surface231econtacts the outer hub110. Because the external periphery portion of the opposing surface231econtacts the outer hub110with a predetermined width corresponding to a thrust load of the outer coned disc spring34, the pressure is increased, and thus the external periphery portion constantly contacts the outer hub110by deforming in order to reduce the influence even when projections and surface waviness are appeared on the opposing surface231ebecause of dispersion during manufacturing.

With the foregoing configuration of tapers C1, C2, the thrust members31A,32A and the inner hub11and the outer hub110uniformly contact when initially assembled, and achieves stable hysterisis properties for generating the friction force. The degrees of tapering of the tapers C1and C2may be identical or not identical, and may be set in accordance with the hysteresis properties. Degree of tapering of tapers provided at the thrust members31B,32B positioned at symmetrical position of the thrust members31A,32A relative to the inner hub11and the outer hub110may be set arbitrarily for gaining desired hysteresis properties.

A second embodiment of the present invention will be explained with reference toFIGS. 6-8as follows. According to the second embodiment of the present invention, the inner hub11and the outer hub110of the clutch disc1of the first embodiment are integrated, the inner thrust member31A and the outer thrust member32A of the first embodiment are integrated, the inner thrust member31B and the outer thrust member32B of the first embodiment are integrated, and the inner coned disc spring33and the outer coned disc spring34of the first embodiment are integrated. Explanations for constructions of the second embodiment of the present invention identical to the first embodiment of the present invention are not repeated.

A clutch disc100according to the second embodiment of the present invention includes a hub311engaged with an input shaft of a transmission of a driven shaft by means of splines, a first side plate312A provided at a first side of the hub311coaxially and to be relatively rotatable, a second side plate312B provided at a second side of the hub311coaxially and to be relatively rotatable, four coil springs313(i.e., serving as a spring) elastically connecting the hub311and the first side plate312A and the second side plate312B in a circumferential direction, a pair of spring sheets14A,14B supporting each of the coil springs13relative to the hub11, and the first and second slide plates12A,12B, a first thrust member331A provided between the hub311and the first side plate312A, a second thrust member331B provided between the hub311and the second side late312B, and a coned disc spring333which biases the second thrust member331B towards the hub311.

The first side plate312A and the second side plate312B are fixed onto each other keeping a predetermined distance from each other by means of rivets322, and are configured to integrally rotate. Further, a ring shape cushioning plate319which has waviness on surface in a thickness direction is fixed on the external periphery portion of the first side plate312A by means of the rivets322. Friction members312A,312B are fixed on either side of the cushioning plate319by means of the rivets320. The friction members312A,312B are positioned between a flywheel fixed on a crankshaft of an engine and a pressure plate of a clutch cover fixed on the flywheel by means of bolts. By thrusting the friction members321A,321B to the pressure plate to frictionally engage the flywheel with the pressure plate, the rotational torque of the engine is inputted into the first side plate312A.

The coil springs313are positioned in accommodation windows316provided at the first side plate312A and the second side plate312B. The accommodation windows316are formed at the hub311by recessing an external periphery portion of the hub311in a radial outward direction, and an external periphery surface side of a sheet portion of the spring sheet14A,14B is positioned at outward in a radial direction compared to the external periphery surface of the hub311. Accordingly, the coil springs313can be positioned at as far external peripheral side as possible, the size of the coil springs which can be applied to the clutch disc can be increased, and thus the clutch disc can cope with the greater level of the torque fluctuation. Accommodation windows17formed on the side plates312A,312B are window bores punched at the external periphery side of the coil springs313, and are provided at positions which oppose the accommodation windows16of the hub311relative to the rotational axis. Each of the coil springs13, while being supported by a pair of the spring sheets14A,14B, is accommodated in the accommodation windows16and17formed by the first side plate312A, the second side plate312B, and the hub311. The accommodation window17formed on the side plates312A,312B are formed as a semi-chambered condition by punching, and pinches and supports both ends of the sheet portions of the spring sheets14A,14B. A concave portion is formed at an central position of the sheet portion of the spring sheets14A,14B, and a convex portion formed on the hub311is fitted into the concave portion, and thus the spring sheets14A,14B are supported by the hub311. In other words, the coil springs313are supported by the side plates312A,312B and the hub311through the spring sheets14A,14B, and the coil springs13are deformed upon the rotation of the side plates312A,312B, and the restoring force of the coil springs313rotates the hub311. In reverse, upon the rotation of the hub311, the coil springs313are deformed, and the restoring force of the coil spring313rotates the side plates312A,312B.

Operations of the hub311and the first and second side plates312A,312B of the clutch disc100according to the second embodiment of the present invention is identical to the operation of the outer hub110, and the first and second side plate12A,12B of the first embodiment of the present invention, and thus the explanation is not repeated.

According to the embodiment of the present invention, the opposing surface of the thrust member is tapered, and the external periphery portion or the internal periphery portion of the opposing surface contacts the hub to generate the hysteresis. With this construction, compared to a case where the opposing surface has a plane surface to contact the hub, substantial dimension of the opposing surface which contacts the hub is reduced, the influence of the waviness surface and warping can be reduced, the pressure applied to the opposing surface which contacts the hub is substantially increased, and thus the thrust member stably contacts the hub.

According to the embodiment of the present invention, because either the external periphery portion or the internal periphery portion of the opposing surface uniformly contacts the hub, the clutch disc can have stable hysteresis properties without being dispersed when the clutch disc is initially assembled.

According to the embodiment of the present invention, because the external periphery of the opposing surface contacts the hub, radius that contacts the hub can be set longer, and thus relatively large degree of hysteresis properties can be generated even when the thrust member is reduced in size. Further, because radius that contacts the hub can be set longer, the biasing means (i.e., coned disc spring) for biasing the thrust member can be reduced in size, and thickness of the side plate which supports the coned disc spring can be reduced.