Patent Publication Number: US-2010130289-A1

Title: Damper mechanism

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a damper mechanism, and more particularly relates to a damper mechanism for damping torsional vibration in a power transmission system. 
     2. Description of the Related Art 
     A clutch disk assembly used in an automotive vehicle has a clutch function of transmitting and cuffing off torque from the flywheel of an engine to a transmission, and a damper function of absorbing and damping torsional vibration from the flywheel. Vibrations in a vehicle generally include idling noises (rattle), driving noises (acceleration and deceleration rattle and muffled noises), and tip-in and tip-out (low frequency vibrations). The damper function eliminates these noises and vibrations. 
     Idling noises are noises that sound like rattling and are generated from the transmission when a shifter is in neutral and the clutch pedal is out, such as when waiting at a stop light. What causes this raffling is that engine torque is low near idling speed, and torque fluctuates greatly during engine combustion. At such times, gear clash occurs between an input gear and a counter gear of a transmission. 
     Tip-in and tip-out (low frequency vibrations) are large longitudinal vibrations of a vehicle body, which occur when a driver rapidly depresses or releases the accelerator pedal. If a drive transmission system is low in stiffness, torque transmitted to the tires will be transmitted back from the tires to the drive transmission system, and this reaction causes excessive torque to be generated at the tires, the result being longitudinal vibrations that longitudinally cause large, transient vibrations in the vehicle body. 
     With idling noise, problems are encountered in the torsional characteristics of the clutch disk assembly near zero torque, and lower torsional stiffness is better. On the other hand, to reduce tip-in and tip-out longitudinal vibration, the torsional characteristics of the clutch disk assembly must be as solid as possible. 
     To solve the above problems, a clutch disk assembly has been provided that uses two kinds of spring members to achieve two-stage characteristics. With this configuration, torsional stiffness and hysteresis torque are kept low in the first stage (low torsion angle region) of the torsion characteristics, which is effective at preventing noise during idling. The torsional stiffness and the hysteresis torque are set high in the second stage (high torsion angle range) of the torsion characteristics, so tip-in and tip-out longitudinal vibrations can be sufficiently damped. 
     With another known damper mechanism, minute torsional vibrations are effectively absorbed by suppressing the generation of high hysteresis torque in the second stage region when minute torsional vibrations, which are attributable to combustion variations in the engine, are inputted. 
     With this kind of damper mechanism, in a state in which a spring member with high torsional stiffness has been compressed, a gap in the rotational direction with a specific angle is ensured between the spring member with high torsional stiffness and high friction mechanism that generates high hysteresis torque (see Japanese Laid-Open Patent Application 2002-266943, for example). 
     SUMMARY OF THE INVENTION 
     However, depending on the characteristics of the vehicle body, there may be instances when this gap in the rotational direction impedes the effect that the high hysteresis torque is supposed to have, so ensuring a gap in the rotational direction cannot necessarily be considered an effective approach. Therefore, there is a need for a damper mechanism with which a gap in the rotational direction is ensured, and for a damper mechanism in which the gap in the rotational direction is intentionally eliminated in order to generate reliably the desired hysteresis torque. 
     A first object of the present invention is to provide a damper mechanism with which the desired hysteresis torque is reliably generated. 
     When the torsion angle reaches the high torsion angle region while idling noise is absorbed in the low torsion angle region, there is a stopper action between the low torsion angle region and the high torsion angle region. As a result, even with a damper mechanism having a low torsion angle region, there are cases when noise may be generated during idling. 
     A second object of the present invention is to improve reliably the torsional vibration damping performance of a damper mechanism. 
     With this type of damper mechanism, a pair of plate members to which the clutch disk is fixed are disposed in proximity to the flywheel. Therefore, the outside diameter of the damper mechanism cannot be increased so that the plate members will not interfere with the flywheel. Specifically, there is less design latitude with a conventional damper mechanism. 
     A third object of the present invention is to afford greater latitude in the design of a damper mechanism. 
     A damper mechanism according to a first aspect of the invention has a first rotary body, a second rotary body, a third rotary body, a first member, a second member, a third member, and at least one small coil spring. The second rotary body is disposed rotatably within a range of a first angle with respect to the first rotary body. The third rotary body is disposed rotatably within a range of a second angle with respect to the second rotary body. The first member has a friction member that comes into contact with the first rotary body in the axial direction, and is mounted on the second rotary body so as to be incapable of rotation with respect to the second rotary body. The second member is disposed between the second rotary body and the first member in the axial direction, and is mounted on the second rotary body and/or the first member so as to be incapable of rotation with respect to the first member. The third member is disposed between the first member and the second member in the axial direction, and is supported by the third rotary body so as to be capable of rotating integrally with the third rotary body. The small coil spring is supported by the first and second members so as to be capable of elastic deformation in the rotational direction, and elastically links the third member with the first and/or second member in the rotational direction. 
     With this damper mechanism, when the first rotary body rotates with respect to the second rotary body, the friction member of the first member slides with the first rotary body. At this point, since the first and second members are incapable of rotation with respect to the second rotary body, even if the relative rotational angle between the first rotary body and the second rotary body is small, hysteresis torque will still be generated between the first and second rotary bodies. This means that the desired hysteresis torque can be reliably generated with this damper mechanism. 
     A damper mechanism according to a second aspect of the invention is the damper mechanism according to the first aspect, wherein the first member further has a first member main body and a plurality of first protruding components. The first member main body is provided with the friction member and supports the small coil spring. The first protruding components extend in the axial direction from the first member main body and mate with the second rotary body. 
     A damper mechanism according to a third aspect of the invention is the damper mechanism according to the second aspect, further including at least one large coil spring that elastically links the first and second rotary bodies in the rotational direction. The second rotary body has at least one opening in which the large coil spring is housed, and a first recess that is formed in the edge of the opening and in which the first protruding components are fitted. 
     A damper mechanism according to a fourth aspect of the invention is the damper mechanism according to the third aspect, wherein the second member has a second member main body that supports the small coil spring, and a plurality of second recesses that are formed in the outer peripheral part of the second member main body and in which the first protruding components are fitted. 
     A damper mechanism according to a fifth aspect of the invention is the damper mechanism according to the fourth aspect, wherein the second member further has a second protruding component that extends from the second member main body in the axial direction and in which the second rotary body is fitted. 
     A damper mechanism according to a sixth aspect of the invention is the damper mechanism according to the fifth aspect, wherein the second rotary body further has a third recess that is formed in the edge of the opening and in which the second protruding component is fitted. 
     A damper mechanism according to a seventh aspect of the invention is the damper mechanism according to the sixth aspect, wherein the first member has a third protruding component that extends from the first member main body in the axial direction and is shorter than the first protruding components. The third protruding component is fitted into the second member. 
     A damper mechanism according to an eighth aspect of the invention is the damper mechanism according to the seventh aspect, wherein the cross-sectional shape of the first protruding components in a plane perpendicular to the rotational axis is substantially semicircular. The cross-sectional shape of the first recesses in a plane perpendicular to the rotational axis is substantially semicircular and complementary to the first protruding components. 
     A damper mechanism according to a ninth aspect of the invention is the damper mechanism according to the eighth aspect, wherein the third member is capable of pushing the part around the center axis of the end of the small coil spring in the rotational direction. 
     A damper mechanism according to a tenth aspect of the invention is the damper mechanism according to the ninth aspect, wherein the first and second members are made of plastic. 
     A damper mechanism according to an eleventh aspect of the invention includes a first rotary body, a second rotary body, a third rotary body, a first elastic member, a second elastic member, a third elastic member, a fourth elastic member, a support member, a first friction member, and a second friction member. The second rotary body is disposed rotatably within a range of a first angle with respect to the first rotary body. The third rotary body is disposed rotatably within a range of a second angle with respect to the second rotary body. The first elastic member elastically links the second and third rotary bodies in the rotational direction and is compressed in first and second stage regions included in the range of the second angle. The second elastic member elastically links the second and third rotary bodies and is compressed in parallel with the first elastic member in the second stage region. The third elastic member elastically links the first and second rotary bodies and is compressed in third and fourth stage regions included in the range of the first angle. The fourth elastic member elastically links the first and second rotary bodies in the rotational direction and is compressed in parallel with the third elastic member in the fourth stage region. The support member rotates integrally with the second rotary body and supports the first and second elastic members with respect to the second rotary body so as to be capable of elastic deformation in the rotational direction. The first friction member is fixed to the support member and slides in the rotational direction with the first rotary body. The second friction member is disposed between the support member and the second rotary body in the axial direction, and slides with the support member and/or the second rotary body. The second friction member is capable of rotation with respect to the third rotary body within a range of a third angle that is smaller than the second angle. 
     With this damper mechanism, when torque is inputted to the first rotary body, the first elastic member is compressed between the second and third rotary bodies in the rotational direction. When the second rotary body rotates further with respect to the third rotary body, the first and second elastic members are compressed in parallel. Thus, torsional characteristics are obtained in the first and second stage regions. 
     Also, when the rotational angle of the second rotary body with respect to the third rotary body reaches the second angle, the second and third rotary bodies rotate integrally, and the first rotary body rotates with respect to the second rotary body. At this point the third elastic member is compressed in the rotational direction between the first and second rotary bodies. When the first rotary body rotates further with respect to the second rotary body, the third and fourth elastic members are compressed in parallel. Thus, torsional characteristics are obtained in the third and fourth stage regions. 
     Here, since the first rotary body rotates with respect to the second rotary body in the third and fourth stage regions, the first friction member fixed to the support member slides with the first rotary body. Meanwhile, within the range of the third angle, even if the second rotary body rotates with respect to the third rotary body, the second friction member does not slide with the second rotary body and the support member, but once the rotational angle of the second rotary body exceeds the third angle, the second friction member rotates integrally with the third rotary body. As a result, frictional resistance is generated by the second friction member between the second rotary body and the support member. 
     Thus, with this damper mechanism, hysteresis torque can be generated in the second stage region by suitably setting the relationship between the second angle and third angle. The result is that the resistance increases in the rotational direction from the second stage to the third stage, and the torsion angle of the damper mechanism more easily fits within the range of the second stage region, without reaching all the way to the third stage region. That is, it is possible to prevent the generation of the noise of the stopper acting at the boundary between the second and third stages, and to raise torsional vibration damping performance. 
     A damper mechanism according to a twelfth aspect of the invention is the damper mechanism according to the eleventh aspect, wherein the second friction member is a wave spring that is compressed in the axial direction between the second rotary body and the support member. 
     A damper mechanism according to a thirteenth aspect of the invention is the damper mechanism according to the eleventh or twelfth aspect, wherein the second friction member rotates integrally with the second elastic member by coming into contact with the end of the second elastic member in the rotational direction. 
     A damper mechanism according to a fourteenth aspect of the invention is the damper mechanism according to the thirteenth aspect, wherein the second friction member has an annular main body component that slides with the support member and/or the second rotary body, and a pair of tabs that extend from the outer peripheral part of the main body component and come into contact with the ends of the second elastic member in the rotational direction. 
     A damper mechanism according to a fifteenth aspect of the invention is the damper mechanism according to the fourteenth aspect, wherein the support member has a pair of openings that extend in an arc shape in the rotational direction and through which the tabs pass. 
     A damper mechanism according to a sixteenth aspect of the invention is a mechanism used in a clutch disk assembly that transmits and cuts off torque from the flywheel of an engine to the transmission. This damper mechanism has a first rotary body, a second rotary body, and an elastic member. The first rotary body has a first plate member and a second plate member that are linked together. The second rotary body is disposed between the first and second plate members in the axial direction so as to be capable of rotation within the range of a first angle with respect to the first rotary body. The elastic member elastically links the first and second rotary bodies in the rotational direction. The outside diameter of the first plate member disposed on the flywheel side is smaller than the outside diameter of the second plate member. 
     The result of this is that the outside diameter of the damper mechanism is maintained while preventing the first plate member from interfering with the flywheel. That is, there is greater latitude in the design of the damper mechanism. 
     A damper mechanism according to a seventeenth aspect of the invention is the damper mechanism according to the sixteenth aspect, wherein the second plate member has a second plate member main body, a contact component that extends in the axial direction from the outer peripheral edge of the second plate member main body to the outer peripheral edge of the first plate member, and a fixed component that is formed at the end of the contact component and is fixed to the first plate member. 
     A damper mechanism according to an eighteenth aspect of the invention is the damper mechanism according to the seventeenth aspect, wherein the outside diameter of the first plate member is smaller than the outside diameter of the second rotary body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified vertical cross section of a clutch disk assembly; 
         FIG. 2  is a simplified elevational view of the clutch disk assembly; 
         FIG. 3  is a simplified elevational view of a damper mechanism of the clutch disk assembly; 
         FIG. 4  is a simplified elevational view of the damper mechanism; 
         FIG. 5  is a simplified elevational view of the damper mechanism; 
         FIG. 6  is a partial cross section of the damper mechanism; 
         FIG. 7  is a partial cross section of the damper mechanism; 
         FIG. 8  is a partial cross-sectional view of the damper mechanism; 
         FIG. 9  is a simplified oblique view of some of the constituent members that make up the damper mechanism; 
         FIG. 10  is an exploded oblique view of some of the constituent members that make up the damper mechanism; 
         FIG. 11  is an elevational view of a third friction washer of the damper mechanism viewed from the transmission side; 
         FIG. 12  is an elevational view of a bushing of the damper mechanism viewed from the engine side; 
         FIG. 13  is an elevational view of the bushing viewed from the transmission side; 
         FIG. 14  is an elevational view of an output plate of the damper mechanism viewed from the engine side; 
         FIG. 15  is an elevational view of a wave spring of the damper mechanism viewed from the transmission side; 
         FIG. 16  is a mechanical circuit diagram of the damper mechanism (in neutral); 
         FIG. 17  is a graph of the torsional characteristics of the damper mechanism; 
         FIG. 18  is a simplified vertical cross section of a clutch disk assembly according to a second embodiment; 
         FIG. 19  is a simplified elevational view of a clutch disk assembly of  FIG. 18 ; 
         FIG. 20  is a simplified elevational view of a damper mechanism of the clutch disk assembly of  FIG. 18 ; 
         FIG. 21  is a simplified elevational view of the damper mechanism of  FIG. 20 ; 
         FIG. 22  is a simplified elevational view of the damper mechanism of  FIG. 20 ; 
         FIG. 23  is a partial cross section of the damper mechanism of  FIG. 20 ; 
         FIG. 24  is a partial cross section of the damper mechanism of  FIG. 20 ; 
         FIG. 25  is a partial cross-sectional view of the damper mechanism of  FIG. 20 ; 
         FIG. 26  is a simplified oblique view of some of the constituent members of the damper mechanism of  FIG. 20 ; 
         FIG. 27  is an exploded oblique view of some of the constituent members that make up the damper mechanism of  FIG. 20 ; 
         FIG. 28  is an elevational view of a third friction washer of the damper mechanism of  FIG. 20  viewed from the transmission side; 
         FIG. 29  is an elevational view of a bushing of the damper mechanism of  FIG. 20  viewed from the engine side; 
         FIG. 30  is an elevational view of an output plate the damper mechanism of  FIG. 20  viewed from the engine side; 
         FIG. 31  is a mechanical circuit diagram of the damper mechanism of  FIG. 20  (in neutral); and 
         FIG. 32  is a graph of the torsional characteristics of the damper mechanism of  FIG. 20 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments according to the present invention will now be described with reference to the drawings. A clutch disk assembly will be used as an example here. 
     (A) First Embodiment 
     1. Overall Configuration of Clutch Disk Assembly 
     A clutch disk assembly  1  in which the damper mechanism  4  according to the present invention is installed will be described with reference to  FIGS. 1 and 2 .  FIG. 1  is a simplified vertical cross section of the clutch disk assembly  1 , and  FIG. 2  is a simplified elevational view of the clutch disk assembly  1 . The O-O line in  FIG. 1  is the rotational axis of the clutch disk assembly  1 . An engine and a flywheel  7  are disposed on the left side in  FIG. 1 , while a transmission (not shown) is disposed on the right side. The R 1  side in  FIG. 2  is the rotational direction drive side (positive side) of the clutch disk assembly  1 , while the R 2  side is the opposite side (negative side). 
     The clutch disk assembly  1  is a mechanism used in a clutch device that makes up part of a power transmission system of an automotive vehicle, and has a clutch function and a damper function. The “clutch function” is a function of transmitting and cutting off torque by engaging and disengaging the clutch disk assembly  1  with and from the flywheel  7  by means of a pressure plate (not shown). The “damper function” is a function of absorbing and damping torsional vibration inputted from the flywheel  7  side by means of coil springs or the like. 
     As shown in  FIGS. 1 and 2 , the clutch disk assembly  1  mainly has a clutch disk  23  to which torque is inputted from the flywheel  7  by frictional engagement, and the damper mechanism  4  that damps and absorbs torsional vibration inputted from the clutch disk  23 . 
     The clutch disk  23  is a portion that is pressed against the flywheel  7 , and mainly has a pair of annular friction facings  25  and a cushioning plate  24  to which the friction facings  25  are fixed. The cushioning plate  24  is constituted by an annular component  24   a , eight cushioning components  24   b  provided on the outer peripheral side of the annular portion  24   a  and aligned in the rotational direction, and four fixed components  24   c  that extend inward in the radial direction from the annular component  24   a . The friction facings  25  are fixed with rivets  26  to both sides of each of the cushioning components  24   b . The fixed components  24   c  are fixed to the outer peripheral part of the damper mechanism  4 . 
     2. Damper Mechanism 
     2.1: Overview of Damper Mechanism 
     The damper mechanism  4  has the torsional characteristics shown in  FIG. 17  in order to damp and to absorb effectively torsional vibration transmitted from the engine. More specifically, the torsional characteristics of the damper mechanism  4  are four-stage characteristics on the positive and negative sides. On the positive and negative sides of the torsional characteristics, the first and second stage regions (where the torsion angle is 0 to θ 1   p  and 0 to θ 1   n ) are regions of low torsional stiffness and low hysteresis torque, while the third and fourth stage regions (where the torsion angle is θ 1   p  to θ 1   p +θ 3   p , and θ 1   n  to θ 1   n +θ 3   n ) are regions of high torsional stiffness and high hysteresis torque. Because of these torsional characteristics, the damper mechanism  4  can effectively damp and absorb idling noise, tip-in and tip-out (low-frequency vibrations), and other such torsional vibrations. 
     2.2: Configuration of Damper Mechanism 
     To achieve the above-mentioned torsional characteristics, the damper mechanism  4  is configured as follows. The various members that make up the damper mechanism  4  will be described here with reference to  FIGS. 1 to 16 .  FIGS. 3 to 5  are simplified elevational views of the damper mechanism  4 .  FIG. 3  is a simplified elevational view as seen from the transmission side (the right side in  FIG. 1 ), while  FIG. 4  is a simplified elevational view as seen from the engine side (the left side in  FIG. 1 ).  FIG. 5  is a partial elevational view of  FIG. 4 .  FIGS. 6 to 8  are partial cross sections of the damper mechanism  4 .  FIGS. 6 and 7  correspond to the upper and lower halves of  FIG. 1  (an A-A cross section of  FIG. 2 ).  FIG. 9  is a simplified oblique view of some of the constituent members that make up the damper mechanism  4 .  FIG. 10  is an exploded oblique view of some of the constituent members that make up the damper mechanism  4 . For the sake of convenience, a wave spring  95  (discussed below) is omitted in  FIG. 10 .  FIG. 11  is an elevational view of a third friction washer  60  viewed from the transmission side.  FIG. 12  is an elevational view of a bushing  70  viewed from the engine side.  FIG. 13  is an elevational view of the bushing  70  viewed from the transmission side.  FIG. 14  is an elevational view of an output plate  90  viewed from the engine side.  FIG. 15  is an elevational view of the wave spring  95  viewed from the transmission side.  FIG. 16  is a mechanical circuit diagram of the damper mechanism  4 . The mechanical circuit diagram shown in  FIG. 16  is the result of schematically drawing the relationship of the various members in the rotational direction in the damper mechanism  4 . Therefore, in  FIG. 16 , members that rotate integrally are treated as the same member. The left and right directions in  FIG. 16  correspond to the rotational direction around the rotational axis O-O. 
     As shown in  FIGS. 1 and 16 , the damper mechanism  4  mainly includes a first damper  4   a , a second damper  4   b  that is disposed is series with the first damper  4   a , and a friction generating mechanism  5  that generates hysteresis torque. The clutch disk  23  is fixed to the input-side member (namely, the input rotary body  2 ) of the first damper  4   a.    
     2.2.1: First Damper 
     The first damper  4   a  provides high torsional stiffness in the third and fourth stage regions (see  FIG. 17 ), and has the input rotary body  2  (as the first rotary body), a hub flange  6  (as the second rotary body), and four coil spring sets  8  (a large coil spring, a third elastic member, and a fourth elastic member). 
     As shown in  FIG. 1  and  FIGS. 6 to 8 , the input rotary body  2  has a clutch plate  21  and a retaining plate  22  that are fixed to each other. The clutch plate  21  has an annular first main body component  28   a , and four first support components  35   a  disposed and aligned in the rotational direction. The retaining plate  22  has an annular second main body component  28   b , and four second support components  35   b  disposed and aligned in the rotational direction. The first main body component  28   a  and the second main body component  28   b  are linked by four linking components  31 . As shown in  FIG. 1 , the outside diameter L 1  of the first main body component  28   a  is smaller than the outside diameter L 2  of the second main body component  28   b . The outside diameter L 2  of the second main body component  28   b  is substantially the same as the outside diameter of the hub flange  6 . The length of the first support components  35   a  and the second support components  35   b  in the rotational direction substantially coincides with the free length of the coil spring sets  8  (large coil spring  8   a  and small coil spring  8   b ). Therefore, the input rotary body  2  and the coil spring sets  8  rotate integrally. 
     The linking components  31  each have a contact component  32  that extends from the outer peripheral edge of the second main body component  28   b  in the axial direction to the outer peripheral edge of the first main body component  28   a , and a fixed component  33  that extends from the end of the contact component  32  to the inside in the radial direction (see  FIG. 7 ). The fixed component  33  is fixed to the first main body component  28   a  by a rivet  27  along with the fixed components  24   c  of the clutch disk  23 . 
     As shown in  FIGS. 1 to 7 , the hub flange  6  is disposed between the clutch plate  21  and the retaining plate  22  in the axial direction, and is elastically linked by the coil spring sets  8  to the clutch plate  21  and the retaining plate  22  in the rotational direction. The hub flange  6  has an annular main body component  29 , a pair of first window apertures  41  and a pair of second window apertures  42  formed as openings in the outer peripheral part of the main body component  29 , and four cut-outs  43  formed in the outer peripheral part of the main body component  29 . The pair of first window apertures  41  and the pair of second window apertures  42  are disposed at positions corresponding to the first support components  35   a  and the second support components  35   b . The pair of first window apertures  41  are disposed opposite each other in the radial direction, and the pair of second window apertures  42  are disposed opposite each other in the radial direction. 
     As shown in  FIGS. 3 and 17 , the coil spring sets  8  are housed in the first window apertures  41  and the second window apertures  42 . The length of the first window apertures  41  in the rotational direction is set to be greater than the free length of the coil spring sets  8  (the length of the support components  35  in the rotational direction), and the length of the second window apertures  42  in the rotational direction is set to be substantially the same as the free length of the coil spring sets  8  (the length of the support components  35  in the rotational direction). First contact faces  44  that are able to come into contact with the ends of the coil spring sets  8  are formed at both ends of the first window apertures  41  in the circumferential direction. Second contact faces  47  that are able to come into contact with the ends of the coil spring sets  8  are formed at both ends of the second window apertures  42  in the circumferential direction. In the neutral position, the ends of the coil spring sets  8  hit the second contact faces  47 . Meanwhile, in the neutral position, a gap angle θ 2   p  is ensured between the first contact faces  44  and the ends of the coil spring sets  8  on the R 1  side, and a gap angle θ 2   n  is ensured between the first contact faces  44  and the ends of the coil spring sets  8  on the R 2  side. The configuration of these components creates a region in which two of the coil spring sets  8  are compressed in parallel (the third stage region on the positive and negative sides) and a region in which four of the coil spring sets  8  are compressed in parallel (the fourth stage region on the positive and negative sides) ( FIG. 12 ). Also, in the neutral position when no torque is inputted, the relative positions of the input rotary body  2  and the hub flange  6  in the rotational direction are determined by the two coil spring sets  8  housed in the second window apertures  42 . 
     As shown in  FIG. 3 , the damper mechanism  4  has a second stopper  10  that restricts the relative rotation of the input rotary body  2  and the hub flange  6  to within a specific range. More specifically, the second stopper  10  is constituted by the linking components  31  of the input rotary body  2 , and first protruding components  49  and second protruding components  57  of the hub flange  6 . A pair of the first protruding components  49  and a pair of the second protruding components  57  that extend outward in the radial direction are formed at the outer peripheral edge of the main body component  29  of the hub flange  6 . The first protruding components  49  and the second protruding components  57  are disposed on the outer peripheral side of the first window apertures  41  and the second window apertures  42 , and stopper faces  50  and  51  are formed at both ends in the rotational direction. The stopper faces  50  and  51  are able to come into contact with the linking components  31 . 
     In the neutral position shown in  FIG. 3 , a gap is ensured between the linking components  31  and the first protruding components  49  and second protruding components  57  in the rotational direction. The torsion angle corresponding to the gap formed on the R 1  side of the linking components  31  is a gap angle θ 3   p . The torsion angle corresponding to the gap formed on the R 2  side of the linking components  31  is a gap angle θ 3   n . The result is a second stopper  10  that permits relative rotation between the input rotary body  2  and the splined hub  3  within a gap angle range of θ 3   p  and θ 3   n . As shown in  FIG. 17 , the gap angles θ 3   p  and θ 3   n  determine the range of high torsional stiffness. 
     2.2.2: Second Damper 
     The second damper  4   b  creates torsional characteristics of low torsional stiffness at the first and second stages (see  FIG. 17 ), and mainly has the third friction washer  60  (as the first member), the bushing  70  (as the second member), the output plate  90  (as the third member), two first small coil springs  7   a  (as the first elastic member), two second small coil springs  7   b  (as the second elastic member), and the splined hub  3  (as the third rotary body). The first small coil springs  7   a  and the second small coil springs  7   b  are supported by the third friction washer  60  and the bushing  70  so as to be capable of elastic deformation. The first small coil springs  7   a  and the second small coil springs  7   b  are examples of the small coil springs. 
     The third friction washer  60  and the bushing  70  are mounted on the hub flange  6  so as to rotate integrally with the hub flange  6 . More specifically, the third friction washer  60  has a third friction washer main body  61  (as the first member main body), two first housing components  64 , two second housing components  65 , and a second friction plate  69 . When viewed in the axial direction, the third friction washer  60  and the bushing  70  are roughly square members surrounded by the first window apertures  41  and the second window apertures  42 , with the four corners of the square cut off. 
     The first housing components  64  are openings for supporting the first small coil springs  7   a . The second housing components  65  are openings for supporting the second small coil springs  7   b . The third friction washer main body  61  is a roughly annular member made of plastic, and the second friction plate  69  is fixed on the engine side. The second friction plate  69  comes into contact with the clutch plate  21  in the axial direction. 
     Four first protrusions  62  are formed at the four corners of the third friction washer main body  61  as third protruding components that protrude from the third friction washer main body  61  to the transmission side. Second protrusions  63  are formed as first protruding components, two on the R 1  side and two on the R 2  side of the first protrusions  62 . The second protrusions  63  protrude from the third friction washer main body  61  on the transmission side, and are longer than the first protrusions  62 . The first protrusions  62  and the second protrusions  63  are formed integrally with the third friction washer main body  61 . The first protrusions  62  and the second protrusions  63  have a semicircular cross-sectional shape. 
     The distal ends of the second protrusions  63  are fitted into the hub flange  6 . More specifically, a first cut-out  44   a  (as the third recess) and two second cut-outs  44   b  (as the first recesses) are formed in each of the first window apertures  41  of the hub flange  6 . A third cut-out  47   a  and two fourth cut-outs  47   b  are formed in each of the second window apertures  42 . The first cut-outs  44   a , the second cut-outs  44   b , the third cut-outs  47   a , and the fourth cut-outs  47   b  are all semicircular in shape. The distal ends of the second protrusions  63  are fitted into the second cut-outs  44   b  and the fourth cut-outs  47   b . This makes it possible to restrict effectively the relative rotation of the third friction washer  60  and the hub flange  6 . 
     The bushing  70  is a roughly annular member made of plastic, and is sandwiched between the third friction washer  60  and the hub flange  6  in the axial direction. The bushing  70  has a bushing main body  71  (as the second member main body), two first housing components  72 , and two second housing components  73 . The first housing components  72  are openings for supporting the first small coil springs  7   a . The second housing components  73  are openings for supporting the second small coil springs  7   b.    
     Four first cut-outs  76   a  are formed at the four corners of the bushing main body  71  (the outside portions of the second housing components  73  in the radial direction). Second cut-outs  76   b  (as the second recesses) are formed, two on the R 1  side and two on the R 2  of the first cut-outs  76   a . The first cut-outs  76   a  have a semicircular shape that is complementary with the first protrusions  62  of the third friction washer  60 . The second cut-outs  76   b  have a semicircular shape that is complementary with the second protrusions  63 . The first protrusions  62  are fitted into the first cut-outs  76   a , and the second protrusions  63  are fitted into the second cut-outs  76   b . More specifically, the second protrusions  63  pass through the second cut-outs  76   b  in the axial direction, and the distal ends of the second protrusions  63  are fitted into the hub flange  6 . This makes it possible to restrict effectively the relative rotation of the bushing  70  and the third friction washer  60 . 
     Two pairs of protrusions  74  that protrude from the bushing main body  71  to the transmission side are formed as second protruding components in two corners of the bushing main body  71  (the portions to the outside of the first housing components  72  in the radial direction). One pair of protrusions  74  are disposed on the R 1  and R 2  sides with the first cut-outs  76   a  sandwiched in between. The protrusions  74  are fitted into the first cut-outs  44   a  and third cut-outs  47   a  formed in the hub flange  6 . This makes it possible to restrict effectively the relative rotation of the bushing  70  and the third friction washer  60 . 
     As shown in  FIGS. 6 to 8  and  FIG. 13 , the bushing  70  has an annular recess  77  that is recessed toward the engine side. The wave spring  95  (discussed below) is housed in the recess  77 . 
     Also, openings  78   a  and  78   b  that extend in an arc shape in the rotational direction are formed at both ends of the first housing components  72  in the rotational direction. The openings  78   a  and  78   b  are windows for moving tabs  98   a  and  98   b  of the wave spring  95  (discussed below) in the rotational direction with respect to the bushing  70 . The opening  78   a , which corresponds to the tab  98   a , is disposed on the R 1  side of the first housing components  72 , and the opening  78   b , which corresponds to the tab  98   b , is disposed on the R 2  side of the first housing components  72 . The tabs  98   a  and  98   b  of the wave spring  95  (discussed below) are respectively inserted in the openings  78   a  and  78   b.    
     The portion of the third friction washer  60  to the outside in the radial direction has first contact components  67   a ,  67   b ,  67   c , and  67   d  that protrude from the third friction washer main body  61  to the transmission side. The portion of the bushing  70  to the outside in the radial direction has second contact components  77   a ,  77   b ,  77   c , and  77   d  that protrude from the bushing main body  71  to the engine side. When viewed from the same side in the axial direction, the first contact components  67   a ,  67   b ,  67   c , and  67   d  and the second contact components  77   a ,  77   b ,  77   c , and  77   d  have substantially the same shape, and come into contact with each other in the axial direction. The first contact components  67   a ,  67   b ,  67   c , and  67   d  and the second contact components  77   a ,  77   b ,  77   c , and  77   d  form a space capable of housing the output plate  90  in between the third friction washer main body  61  and the bushing main body  71  in the axial direction. 
     The output plate  90  has a plurality of inner peripheral teeth  91 , two first openings  92 , and two second openings  93 . The inner peripheral teeth  91  mesh with second outer peripheral teeth  54   b  of the splined hub  3  with substantially no gap in between. Therefore, the output plate  90  rotates integrally with the splined hub  3  within the space formed by the third friction washer main body  61  and the bushing main body  71 . 
     The first openings  92  are disposed corresponding to the first housing components  64  and  72 . The first small coil springs  7   a  are housed in the first openings  92 . The second openings  93  are disposed corresponding to the second housing components  65  and  73 . The second small coil springs  7   b  are housed in the second openings  93 . The length of the first openings  92  in the rotational direction is set to be substantially the same as the free length of the first small coil springs  7   a . Meanwhile, the length of the second openings  93  in the rotational direction is set to be greater than the free length of the second small coil springs  7   b . As shown in  FIG. 5 , in the neutral position, the torsion angle corresponding to the gap formed on the R 1  side of the second small coil springs  7   b  is a gap angle of θ 4   p . The torsion angle corresponding to the gap formed on the R 2  side of the second small coil springs  7   b  is a gap angle of θ 4   n . The configuration of these components creates a region in which two first small coil springs  7   a  are compressed in parallel (the first stage region on the positive and negative sides) and a region in which two second small coil springs  7   b  are compressed in parallel (the second stage region on the positive and negative sides) ( FIG. 17 ). 
     In the neutral position, the relative positions of the third friction washer  60  (bushing  70 ) and the output plate  90  in the rotational direction are determined by the two first small coil springs  7   a  housed in the first openings  92 . That is, the relative positions of the hub flange  6  and the splined hub  3  in the rotational direction in the neutral position are determined by the first small coil springs  7   a.    
     The spring constant of the first small coil springs  7   a  and the second small coil springs  7   b  is set much lower than the spring constant of the coil spring sets  8 . That is, the coil spring sets  8  are much stiffer than the first small coil springs  7   a  and the second small coil springs  7   b . Therefore, in the first and second stage regions, the coil spring sets  8  are not compressed, but the first small coil springs  7   a  and the second small coil springs  7   b  are compressed. 
     The splined hub  3  is disposed on the inner peripheral side of the clutch plate  21  and the retaining plate  22 . The splined hub  3  has a cylindrical boss  52  that extends in the axial direction, and a flange  54  that extends from the boss  52  to the outside in the radial direction. A splined hole  53  that engages with an input shaft (not shown) of the transmission is formed on the inner peripheral part of the boss  52 . 
     As shown in  FIGS. 1 to 7 , a plurality of first outer peripheral teeth  54   a  and second outer peripheral teeth  54   b  are formed on the outer peripheral part of the flange  54 . The first outer peripheral teeth  54   a  protrude outward in the radial direction farther than the second outer peripheral teeth  54   b . A plurality of inner peripheral teeth  59  are formed on the inner peripheral part of the hub flange  6 . The first outer peripheral teeth  54   a  mesh with the inner peripheral teeth  59  of the hub flange  6  via a specific gap. More specifically, as shown in  FIG. 5 , in neutral a position in which no torque is inputted, the torsion angle corresponding to the gap formed on the R 1  side of the inner peripheral teeth  59  is the gap angle θ 1   p . The torsion angle corresponding to the gap formed on the R 2  side of the inner peripheral teeth  59  is the gap angle θ 1   n . The configuration of these components creates a first stopper  9  that allows relative rotation between the hub flange  6  and the splined hub  3  within the range of the gap angles θ 1   p  and θ 1   n . As shown in  FIG. 17 , the range of low torsional stiffness is determined by the gap angles θ 1   p  and θ 1   n.    
     2.2.3: Friction Generating Mechanism 
     The damper mechanism  4  further has a friction generating mechanism  5  that uses frictional resistance to generate hysteresis torque, in order to damp and to absorb torsional vibration more effectively. More specifically, as shown in  FIGS. 6 and 7 , the friction generating mechanism  5  has a first friction washer  79 , a second friction washer  82 , the above-mentioned third friction washer  60 , a fourth friction washer  89 , and the wave spring  95  (as the second friction member). Low hysteresis torque is achieved by the first friction washer  79  and the fourth friction washer  89 , and high hysteresis torque is achieved by the second friction washer  82  and the third friction washer  60 . Low hysteresis torque in the second stage region is achieved by the wave spring  95 . 
     As shown in  FIGS. 6 and 7 , the first friction washer  79  is disposed between the flange  54  and the retaining plate  22  in the axial direction. A first cone spring  80  is disposed between the first friction washer  79  and the retaining plate  22 . The first friction washer  79  is pressed against the flange  54  by the first cone spring  80 . This generates low hysteresis torque between the input rotary body  2  and the splined hub  3 . 
     The fourth friction washer  89  is disposed between the flange  54  and the clutch plate  21  in the axial direction. The fourth friction washer  89  has a plurality of outer peripheral teeth  89   a , and the outer peripheral teeth  89   a  are fitted into a plurality of slits  21   a  formed in the inner peripheral part of the clutch plate  21 . Therefore, the fourth friction washer  89  rotates integrally with the clutch plate  21 . The flange  54  is pressed against the fourth friction washer  89  by the first cone spring  80 . This generates low hysteresis torque between the input rotary body  2  and the splined hub  3 . 
     The second friction washer  82  is disposed so as to rotate integrally to the outside of the first friction washer  79  in the radial direction. The second friction washer  82  and the first friction washer  79  rotate integrally with the retaining plate  22 . The second friction washer  82  has a first friction plate  83  that comes into contact with the main body component  29 . A second cone spring  81  is disposed between the second friction washer  82  and the clutch plate  21 . The first friction plate  83  of the second friction washer  82  is pressed against the hub flange  6  by the second cone spring  81 . This generates high hysteresis torque between the input rotary body  2  and the hub flange  6 . 
     The hub flange  6  is pushed to the clutch plate  21  side via the second friction washer  82  by the second cone spring  81 . Therefore, the above-mentioned third friction washer  60  and bushing  70  are sandwiched between the hub flange  6  and the clutch plate  21  in the axial direction, and the second friction plate  69  of the third friction washer  60  is pressed against the clutch plate  21 . This generates high hysteresis torque between the input rotary body  2  and the hub flange  6 . 
     The above configuration achieves low hysteresis torque in the entire region of torsional characteristics, and high hysteresis torque generated in the third and fourth stage regions. 
     As shown in  FIGS. 6 to 8 , the wave spring  95  is a member for generating hysteresis torque in the second stage region. More specifically, the wave spring  95  is an annular elastic member capable of elastic deformation in the axial direction, and is disposed between the hub flange  6  and the bushing  70  in a compressed state in the axial direction. Therefore, the wave spring  95  comes into contact with the hub flange  6  and the bushing  70 , and generates frictional resistance upon rotating with respect to the hub flange  6  and the bushing  70 . 
     As shown in  FIG. 15 , the wave spring  95  has an annular main body component  96  and two pairs of tabs  98   a  and  98   b  that extend from the main body component  96  outward in the radial direction. The distal ends of the tabs  98   a  and  98   b  are bent in the axial direction and come into contact with the ends of the second small coil springs  7   b  in the rotational direction. In other words, the second small coil springs  7   b  are disposed between the tabs  98   a  and  98   b  in the rotational direction. The distance between the tabs  98   a  and  98   b  in the rotational direction substantially coincides with the free length of the second small coil springs  7   b . As a result, the wave spring  95  is positioned in the rotational direction by the second small coil springs  7   b , and the second small coil springs  7   b  and the wave spring  95  are able to rotate integrally. 
     Also, two pairs of protruding components  99   a  and  99   b  are formed on the outer peripheral part of the main body component  96 . The pair of protruding components  99   a  and the pair of protruding components  99   b  are disposed opposite each other on either side of the rotational axis. The protruding components  99   a  and  99   b  ensure an adequate sliding surface area for the wave spring  95 . 
     Furthermore, a plurality of inner peripheral teeth  97  are formed on the inner peripheral part of the main body component  96 . The inner peripheral teeth  97  are disposed between the first outer peripheral teeth  54   a  of the splined hub  3  in the rotational direction, and are able to come into contact with the first outer peripheral teeth  54   a  in the rotational direction. In the position of the damper mechanism  4 , a gap is ensured on the R 1  and R 2  sides of the inner peripheral teeth  97 . The torsion angle corresponding to the gap on the R 1  side of the inner peripheral teeth  97  is the gap angle θ 5   p , and the torsion angle corresponding to the gap formed on the R 2  side of the second outer peripheral teeth  54   b  is the gap angle θ 5   n . The gap angles θ 5   p  and θ 5   n  here are set to substantially the same angles as the gap angles θ 4   p  and θ 4   n . The result of ensuring the gap angles θ 5   p  and θ 5   n  is that hysteresis torque is not generated by the wave spring  95  in the first stage region, but hysteresis torque is obtained from the wave spring  95  in the second stage region. 
     3. Operation 
     The operation and torsional characteristics of the damper mechanism  4  of the clutch disk assembly  1  will be described with reference to  FIGS. 1 to 12 . The positive side of the torsional characteristics will be described as an example here, and the operation on the negative side will not be described. 
     3.1: First and Second Stage Regions 
     On the positive side of the torsional characteristics, the input rotary member  2  in the neutral position shown in  FIG. 16  twists toward the R 1  side (the drive side) with respect to the splined hub  3 . Here, since the first small coil springs  7   a  and the second small coil springs  7   b  are not nearly as stiff as the coil spring sets  8 , the coil spring sets  8  are hardly compressed at all, and the input rotary body  2  and the hub flange  6  rotate integrally. Also, since the third friction washer  60  and the bushing  70  rotate integrally with the hub flange  6 , the third friction washer  60  and the bushing  70  rotate with respect to the splined hub  3 . As a result, the first small coil springs  7   a  are compressed between the third friction washer  60  (bushing  70 ) and the output plate  90 . When the input rotary body  2  and the hub flange  6  rotate further with respect to the splined hub  3 , the first friction washer  79  slides with the flange  54  of the splined hub  3 . The above yields torsional characteristics such that the stiffness is low and the hysteresis torque is low in the first stage region. 
     When the input rotary body  2  rotates relative to the splined hub  3  by a torsion angle θ 4   p  to the R 1  side, the second small coil springs  7   b  begin to be compressed between the third friction washer  60  (bushing  70 ) and the output plate  90 . This creates torsional characteristics such that the stiffness is low and the hysteresis torque is low in the second stage region. Since the second small coil springs  7   b  act in parallel with the first small coil springs  7   a , in the second stage region the torsional stiffness is somewhat higher than in the first stage region. 
     Also, since the gap angle θ 5   p  is substantially the same as the gap angle θ 4   p , when the input rotary body  2  rotates relative to the splined hub  3  by a torsion angle θ 4   p  to the R 1  side, the inner peripheral teeth  97  of the wave spring  95  comes into contact with the first outer peripheral teeth  54   a  of the splined hub  3 . When the input rotary body  2  rotates further with respect to the splined hub  3 , the inner peripheral teeth  97  are pushed to the R 1  side by the first outer peripheral teeth  54   a , and the wave spring  95  rotates with respect to the hub flange  6  and the bushing  70 . As a result, the wave spring  95  slides with the hub flange  6  and the bushing  70 , and hysteresis torque is generated in the second stage region. 
     When the torsion angle of the input rotary body  2  with respect to the splined hub  3  reaches an angle of θ 1   p , the first outer peripheral teeth  54   a  come into contact with the inner peripheral teeth  59 , and the first stopper  9  operates. As a result, the relative rotation of the hub flange  6  and the splined hub  3  comes to a halt. Accordingly, the compression of the first small coil springs  7   a  and the second small coil springs  7   b  stops. The generation of hysteresis torque by the wave spring  95  also stops. 
     3.2.3: Third and Fourth Stage Regions 
     When the input rotary body  2  rotates further to the R 1  side with respect to the splined hub  3 , the input rotary body  2  rotates relative to the hub flange  6 , and the two coil spring sets  8  housed in the second window apertures  42  begin to be compressed between the input rotary body  2  and the hub flange  6 . Up until the torsion angle is θ 1   p +θ 2   p , the two coil spring sets  8  are compressed in parallel. At this point, the first friction plate  83  of the second friction washer  82  slides with the hub flange  6 , and the second friction plate  69  of the third friction washer  60  slides with the clutch plate  21 . Since the third friction washer  60  is effectively restricted in its rotation relative to the hub flange  6  by the second protrusions  63 , when the input rotary body  2  rotates with respect to the hub flange  6 , the second friction plate  69  will always slide with the clutch plate  21 , and regardless of the inputted torsion angle, a high hysteresis torque is generated between the input rotary body  2  and the hub flange  6 . This yields torsional characteristics such that the torsional stiffness is high and the hysteresis torque is high in the third stage region. 
     When the torsion angle of the input rotary body  2  with respect to the splined hub  3  reaches θ 1   p +θ 2   p , the four coil spring sets  8  begin to be compressed. Once the torsion angle of the input rotary body  2  reaches θ 1   p +θ 3   p , the second stopper  10  operates, and the relative rotation of the input rotary body  2  and the splined hub  3  comes to a halt. This yields torsional characteristics such that the torsional stiffness is high and the hysteresis torque is high in the fourth stage region. 
     While the damper mechanism  4  is in the process of returning to the neutral position, the ends of the second small coil springs  7   b  push the tabs  98   a  of the wave spring  95  to the R 2  side, and the tabs  98   a  are guided to their initial positions. Therefore, the position of the wave spring  95  in the rotational direction is returned by the tabs  98   a  and  98   b  to the initial setting position. Thus, even if the torsional operation of the damper mechanism  4  is repeated, hysteresis torque will still be reliably generated by the wave spring  95  in the second stage region. 
     4. Effects 
     The effects obtained with the damper mechanism  4  are as follows. 
     (1) 
     With this damper mechanism  4 , when the input rotary body  2  rotates with respect to the hub flange  6 , the second friction plate  69  fixed to the third friction washer  60  slides with the clutch plate  21 . Since the third friction washer  60  and the bushing  70  at this point are effectively restricted from rotating with respect to the hub flange  6 , even if the relative rotation angle of the input rotary body  2  and the hub flange  6  should be small, high hysteresis torque will always be generated between the input rotary body  2  and the hub flange  6 . Therefore, the desired hysteresis torque can be reliably generated with this damper mechanism  4 . 
     (2) 
     With this damper mechanism  4 , the second protrusions  63  of the third friction washer  60  are fitted into the second cut-outs  44   b  and the fourth cut-outs  47   b . Also, the second protrusions  63  are fitted into the second cut-outs  76   b  of the bushing  70 . Further, the first protrusions  62  are fitted into the first cut-outs  76   a  of the bushing  70 . The configuration of these components makes it possible to restrict effectively the relative rotation of the third friction washer  60  and the hub flange  6 , and the relative rotation of the third friction washer  60  and the bushing  70 . 
     Also, in addition to the second protrusions  63  of the third friction washer  60 , the protrusions  74  of the bushing  70  are fitted into the first cut-outs  44   a  and the third cut-outs  47   a.    
     This effectively restricts the relative rotation of the bushing  70  and the hub flange  6 . 
     (3) 
     With this damper mechanism  4 , the second protrusions  63  are fitted into the second cut-outs  44   b  formed in the edge of the first window apertures  41 , and the fourth cut-outs  47   b  formed in the edge of the second window apertures  42 . Therefore, compared to when the holes into which the second protrusions  63  are fitted are formed on the inside of the first window apertures  41  and the second window apertures  42  in the radial direction, the second cut-outs  44   b  and the fourth cut-outs  47   b  can be disposed more to the outside in the radial direction. This allows the effective radius from the rotational axis O-O to the second protrusions  63  to be increased, and allows the load in the rotational direction acting on the second protrusions  63  to be reduced. 
     (4) 
     With this damper mechanism  4 , the first cut-outs  44   a , the second cut-outs  44   b , the third cut-outs  47   a , the fourth cut-outs  47   b , the first cut-outs  76   a , and the second cut-outs  76   b  all have a cross-sectional shape that is roughly semicircular. Therefore, less stress accumulates in these cut-outs, and damage to the hub flange  6  and the bushing  70  can be prevented. 
     (5) 
     With this damper mechanism  4 , the third friction washer  60  and the bushing  70  are made of plastic. Therefore, there is less hysteresis torque generated by sliding the first small coil springs  7   a  and the second small coil springs  7   b  with the third friction washer  60  and the bushing  70 , and this prevents an increase in the hysteresis torque in the first and second stage regions. 
     (6) 
     In the past, with this type of damper mechanism, a pair of plate members to which the clutch disk was fixed were disposed near the flywheel. Accordingly, the outside diameter of the damper mechanism could not be increased so that the plate members would not interfere with the flywheel. That is, there was less latitude in design with a conventional damper mechanism. 
     With this damper mechanism  4 , however, the outside diameter L 1  of the clutch plate  21  disposed near the flywheel  7  may be smaller than the outside diameter L 2  of the retaining plate  22 . Therefore, the clutch plate  21  can be prevented from interfering with the flywheel  7 . This affords greater latitude in the design of the damper mechanism  4 . Also, since the damper mechanism  4  can be applied to a small flywheel  7 , the damper mechanism  4  can be applied over a broader range. 
     (7) 
     With this damper mechanism  4 , hysteresis torque is generated by the wave spring  95  in the second stage region, which has low torsional stiffness. Therefore, there is higher resistance in the rotational direction from the second to third stages, and the torsion angle of the damper mechanism  4  tends to be kept within the range of the second stage region, without reaching the third stage region. For example, even if torsional vibration originating in combustion fluctuation of the engine were inputted to the damper mechanism  4  in a state in which the shifter is put in neutral and the clutch pedal is released, and even if the torsion angle were to exceed the first stage region and reaches the second stage region, torsional vibration will be damped before the first stopper  9  operates (before the first outer peripheral teeth  54   a  of the splined hub  3  come into contact with the inner peripheral teeth  59  of the hub flange  6 ). 
     Thus, by generating hysteresis torque in the second stage region with the wave spring  95 , noise made by the operation of the first stopper  9  at the boundary between the second and third stage regions can be prevented, and torsional vibration damping performance can be enhanced. 
     (8) 
     With this damper mechanism  4 , the wave spring  95  is employed as the member for generating hysteresis torque in the second stage region. Therefore, there is no need to provide an elastic member in addition to a friction member, and hysteresis torque in the second stage region can be achieved with a simple structure. 
     (9) 
     With this damper mechanism  4 , the wave spring  95  is able to rotate integrally with the second small coil springs  7   b  by coming into contact with the ends of the second small coil springs  7   b . More specifically, the wave spring  95  has the tabs  98   a  and  98   b  that extend from the outer peripheral part of the main body component  96  and are able to come into contact with the ends of the second small coil springs  7   b  in the rotational direction. The second small coil springs  7   b  are disposed between the tabs  98   a  and  98   b  in the rotational direction. Therefore, when the damper mechanism  4  is in its neutral position, the position of the wave spring  95  in the rotational direction can be returned to the initial setting position, even if the torsional operation of the damper mechanism  4  is repeated, hysteresis torque will still be reliably generated by the wave spring  95  in the second stage region. 
     (10) 
     With this damper mechanism  4 , the bushing  70  has arc-shaped openings  78   b  through which the distal ends of the tabs  98   a  and  98   b  pass, so the structure can be simplified. 
     (11) 
     With this damper mechanism  4 , since the wave spring  95  is housed in the recess  77  of the bushing  70 , the length in the axial direction can be shortened. 
     5. Modifications of First Embodiment 
     The specific constitution of the present invention is not limited to the embodiment given above, and various changes and modifications are possible without departing from the essence of the invention. 
     (1) 
     In the above embodiment, the clutch disk assembly  1  in which the damper mechanism  4  was installed was described as an example, but the present invention is not limited to this. For example, this damper mechanism can also be applied to lockup devices for fluid torque transmission devices, two-mass flywheels, or other such power transmission devices. 
     (2) 
     Also, the layout of the first protrusions  62 , the second protrusions  63 , and the protrusions  74  is not limited to the above embodiment. 
     (B) Second Embodiment 
     1. Overall Configuration of Clutch Disk Assembly 
     A clutch disk assembly  101  in which a damper mechanism  104  according to the present invention is installed will be described with reference to  FIGS. 18 and 19 .  FIG. 18  is a simplified vertical cross section of the clutch disk assembly  101 , and  FIG. 19  is a simplified elevational view of the clutch disk assembly  101 . The O-O line in  FIG. 18  is the rotational axis of the clutch disk assembly  101 . An engine and a flywheel  107  are disposed on the left side in  FIG. 18 , while a transmission (not shown) is disposed on the right side. The R 1  side in  FIG. 19  is the rotational direction drive side (positive side) of the clutch disk assembly  101 , while the R 2  side is the opposite side (negative side). 
     The clutch disk assembly  101  is a mechanism used in a clutch device that makes up part of a power transmission system of an automotive vehicle, and has a clutch function and a damper function. The “clutch function” is a function of transmitting and cutting off torque by engaging and disengaging the clutch disk assembly  101  with and from the flywheel  107  by means of a pressure plate (not shown). The “damper function” is a function of absorbing and damping torsional vibration inputted from the flywheel  107  side by means of coil springs or the like. 
     As shown in  FIGS. 18 and 19 , the clutch disk assembly  101  mainly includes a clutch disk  123  to which torque is inputted from the flywheel  107  by frictional engagement, and the damper mechanism  104  that damps and absorbs torsional vibration inputted from the clutch disk  123 . 
     The clutch disk  123  is a portion that is pressed against the flywheel  107 , and mainly includes a pair of annular friction facings  125  and a cushioning plate  124  to which the friction facings  125  are fixed. The cushioning plate  124  is constituted by an annular component  124   a , eight cushioning components  124   b  provided on the outer peripheral side of the annular portion  124   a  and aligned in the rotational direction, and four fixed components  124   c  that extend inward in the radial direction from the annular component  124   a . The friction facings  125  are fixed with rivets  126  to both sides of each of the cushioning components  124   b . The fixed components  124   c  are fixed to the outer peripheral part of the damper mechanism  104 . 
     2. Damper Mechanism 
     2.1: Overview of Damper Mechanism 
     The damper mechanism  104  has the torsional characteristics shown in  FIG. 32  in order to damp and to absorb effectively torsional vibration transmitted from the engine. More specifically, the torsional characteristics of the damper mechanism  104  are four-stage characteristics on the positive and negative sides. On the positive and negative sides of the torsional characteristics, the first and second stage regions (where the torsion angle is 0 to θ 1   p  and 0 to θ 1   n ) are regions of low torsional stiffness and low hysteresis torque, while the third and fourth stage regions (where the torsion angle is θ 1   p  to θ 1   p +θ 3   p , and θ 1   n  to θ 1   n +θ 3   n ) are regions of high torsional stiffness and high hysteresis torque. Because of these torsional characteristics, the damper mechanism  104  can effectively damp and absorb idling noise, tip-in and tip-out (low-frequency vibrations), and other such torsional vibrations. 
     2.2: Configuration of Damper Mechanism 
     To achieve the above-mentioned torsional characteristics, the damper mechanism  104  is configured as follows. The various members that make up the damper mechanism  104  will be described here with reference to  FIGS. 18 to 31 .  FIGS. 20 to 22  are simplified elevational views of the damper mechanism  104 .  FIG. 20  is a simplified elevational view as seen from the transmission side (the right side in  FIG. 18 ), while  FIG. 21  is a simplified elevational view as seen from the engine side (the left side in  FIG. 18 ).  FIG. 22  is a partial elevational view of  FIG. 21 .  FIGS. 23 to 25  are partial cross sections of the damper mechanism  104 .  FIGS. 23 and 24  correspond to the upper and lower halves of  FIG. 18  (an A-A cross section of  FIG. 19 ).  FIG. 26  is a simplified oblique view of some of the constituent members that make up the damper mechanism  104 .  FIG. 27  is an exploded oblique view of some of the constituent members that make up the damper mechanism  104 .  FIG. 28  is an elevational view of a third friction washer  160  viewed from the transmission side.  FIG. 29  is an elevational view of a bushing  170  viewed from the engine side.  FIG. 30  is an elevational view of an output plate  190  viewed from the engine side.  FIG. 31  is a mechanical circuit diagram of the damper mechanism  104 . The mechanical circuit diagram shown in  FIG. 31  is the result of schematically drawing the relationship of the various members in the rotational direction in the damper mechanism  104 . Therefore, in  FIG. 31 , members that rotate integrally are treated as the same member. The left and right directions in  FIG. 31  corresponding to the rotational direction around the rotational axis O-O. 
     As shown in  FIGS. 18 and 31 , the damper mechanism  104  mainly includes a first damper  104   a , a second damper  104   b  that is disposed is series with the first damper  104   a , and a friction generating mechanism  105  that generates hysteresis torque. The clutch disk  123  is fixed to the input-side member (namely, the input rotary body  102 ) of the first damper  104   a.    
     2.2.1: First Damper 
     The first damper  104   a  provides high torsional stiffness in the third and fourth stage regions (see  FIG. 32 ), and has the input rotary body  102  (as the first rotary body), a hub flange  106  (as the second rotary body), and four coil spring sets  108  (as the second elastic member). 
     As shown in  FIG. 18  and  FIGS. 23 to 25 , the input rotary body  102  has a clutch plate  121  and a retaining plate  122  that are fixed to each other. The clutch plate  121  has an annular first main body component  128   a , and four first support components  135   a  disposed aligned in the rotational direction. The retaining plate  122  has an annular second main body component  128   b , and four second support components  135   b  disposed aligned in the rotational direction. The first main body component  128   a  and the second main body component  128   b  are linked by four linking components  131 . As shown in  FIG. 18 , the outside diameter L 11  of the first main body component  128   a  is smaller than the outside diameter L 12  of the second main body component  128   b . The outside diameter L 12  of the second main body component  128   b  is substantially the same as the outside diameter of the hub flange  106 . The length of the first support components  135   a  and the second support components  135   b  in the rotational direction substantially coincides with the free length of the coil spring sets  108  (large coil spring  108   a  and small coil spring  108   b ). Therefore, the input rotary body  102  and the coil spring sets  108  rotate integrally. 
     The linking components  131  each have a contact component  132  that extends from the outer peripheral edge of the second main body component  128   b  in the axial direction to the outer peripheral edge of the first main body component  128   a , and a fixed component  133  that extends from the end of the contact component  132  to the inside in the radial direction (see  FIG. 24 ). The fixed component  133  is fixed to the first main body component  128   a  by a rivet  127  along with the fixed components  124   c  of the clutch disk  23 . 
     As shown in  FIGS. 18 to 24 , the hub flange  106  is disposed between the clutch plate  121  and the retaining plate  122  in the axial direction, and is elastically linked by the coil spring sets  108  to the clutch plate  121  and the retaining plate  122  in the rotational direction. The hub flange  106  has an annular main body component  129 , a pair of first window apertures  141  and a pair of second window apertures  142  formed as openings in the outer peripheral part of the main body component  129 , and four cut-outs  143  formed in the outer peripheral part of the main body component  129 . The pair of first window apertures  141  and the pair of second window apertures  142  are disposed at positions corresponding to the first support components  135   a  and the second support components  135   b . The pair of first window apertures  141  are disposed opposite each other in the radial direction, and the pair of second window apertures  142  are disposed opposite each other in the radial direction. 
     As shown in  FIGS. 20 and 32 , the coil spring sets  108  are housed in the first window apertures  141  and the second window apertures  142 . The length of the first window apertures  141  in the rotational direction is set to be greater than the free length of the coil spring sets  108  (the length of the support components  135  in the rotational direction), and the length of the second window apertures  142  in the rotational direction is set to be substantially the same as the free length of the coil spring sets  108  (the length of the support components  135  in the rotational direction). First contact faces  144  that are able to come into contact with the ends of the coil spring sets  108  are formed at both ends of the first window apertures  141  in the circumferential direction. Second contact faces  147  that are able to come into contact with the ends of the coil spring sets  108  are formed at both ends of the second window apertures  142  in the circumferential direction. In the neutral position, the ends of the coil spring sets  108  hit the second contact faces  147 . Meanwhile, in the neutral position, a gap angle θ 2   p  is ensured between the first contact faces  144  and the ends of the coil spring sets  108  on the R 1  side, and a gap angle θ 2   n  is ensured between the first contact faces  144  and the ends of the coil spring sets  108  on the R 2  side. The configuration of these components creates a region in which two of the coil spring sets  108  are compressed in parallel (the third stage region on the positive and negative sides) and a region in which four of the coil spring sets  108  are compressed in parallel (the fourth stage region on the positive and negative sides) ( FIG. 29 ). Also, in the neutral position when no torque is inputted, the relative positions of the input rotary body  102  and the hub flange  106  in the rotational direction are determined by the two coil spring sets  108  housed in the second window apertures  142 . 
     As shown in  FIG. 20 , the damper mechanism  104  has a second stopper  110  that restricts the relative rotation of the input rotary body  102  and the hub flange  106  to within a specific range. More specifically, the second stopper  110  is constituted by the linking components  131  of the input rotary body  102 , and first protruding components  149  and second protruding components  157  of the hub flange  106 . A pair of the first protruding components  149  and a pair of the second protruding components  157  that extend outward in the radial direction are formed at the outer peripheral edge of the main body component  129  of the hub flange  106 . The first protruding components  149  and the second protruding components  157  are disposed on the outer peripheral side of the first window apertures  141  and the second window apertures  142 , and stopper faces  150  and  151  are formed at both ends in the rotational direction. The stopper faces  150  and  151  are able to come into contact with the linking components  131 . 
     In the neutral position shown in  FIG. 20 , a gap is ensured between the linking components  131  and the first protruding components  149  and second protruding components  157  in the rotational direction. The torsion angle corresponding to the gap formed on the R 1  side of the linking components  131  is a gap angle θ 3   p . The torsion angle corresponding to the gap formed on the R 2  side of the linking components  131  is a gap angle θ 3   n . The result is a second stopper  110  that permits relative rotation between the input rotary body  102  and the splined hub  103  within a gap angle range of θ 3   p  and θ 3   n . As shown in  FIG. 32 , the gap angles θ 3   p  and θ 3   n  determine the range of high torsional stiffness. 
     2.2.2: Second Damper 
     The second damper  104   b  creates torsional characteristics of low torsional stiffness at the first and second stages (see  FIG. 32 ), and mainly has the third friction washer  160  (as the first member), the bushing  170  (as the second member), the output plate  190  (as the third member), two first small coil springs  107   a  (as the first elastic member), two second small coil springs  107   b  (as the second elastic member), and the splined hub  103  (as the third rotary body). The first small coil springs  107   a  and the second small coil springs  107   b  are supported by the third friction washer  160  and the bushing  170  so as to be capable of elastic deformation. The first small coil springs  107   a  and the second small coil springs  107   b  are examples of the small coil springs. 
     The third friction washer  160  and the bushing  170  are mounted on the hub flange  106  so as to rotate integrally with the hub flange  106 . More specifically, the third friction washer  160  has a third friction washer main body  161  (as the first member main body), two first housing components  164 , two second housing components  165 , and a second friction plate  169 . When viewed in the axial direction, the third friction washer  160  and the bushing  170  are roughly square members surrounded by the first window apertures  141  and the second window apertures  142 , with the four corners of the square cut off. 
     The first housing components  164  are openings for supporting the first small coil springs  107   a . The second housing components  165  are openings for supporting the second small coil springs  107   b . The third friction washer main body  161  is a roughly annular member made of plastic, and the second friction plate  169  is fixed on the engine side. The second friction plate  169  comes into contact with the clutch plate  121  in the axial direction. 
     Four first protrusions  162  are formed at the four corners of the third friction washer main body  161  as third protruding components that protrude from the third friction washer main body  161  to the transmission side. Second protrusions  163  are formed as first protruding components, two on the R 1  side and two on the R 2  side of the first protrusions  162 . The second protrusions  163  protrude from the third friction washer main body  161  on the transmission side, and are longer than the first protrusions  162 . The first protrusions  162  and the second protrusions  163  are formed integrally with the third friction washer main body  161 . The first protrusions  162  and the second protrusions  163  have a semicircular cross-sectional shape. 
     The distal ends of the second protrusions  163  are fitted into the hub flange  106 . More specifically, a first cut-out  144   a  (as the third recess) and two second cut-outs  144   b  (as the first recesses) are formed in each of the first window apertures  141  of the hub flange  106 . A third cut-out  147   a  and two fourth cut-outs  147   b  are formed in each of the second window apertures  142 . The first cut-outs  144   a , the second cut-outs  144   b , the third cut-outs  147   a , and the fourth cut-outs  147   b  are all semicircular in shape. The distal ends of the second protrusions  163  are fitted into the second cut-outs  144   b  and the fourth cut-outs  147   b . This makes it possible to restrict effectively the relative rotation of the third friction washer  160  and the hub flange  106 . 
     The bushing  170  is a roughly annular member made of plastic, and is sandwiched between the third friction washer  160  and the hub flange  106  in the axial direction. The bushing  170  has a bushing main body  171  (as the second member main body), two first housing components  172 , and two second housing components  173 . The first housing components  172  are openings for supporting the first small coil springs  107   a . The second housing components  173  are openings for supporting the second small coil springs  107   b.    
     Four first cut-outs  176   a  are formed at the four corners of the bushing main body  171  (the outside portions of the second housing components  173  in the radial direction). Second cut-outs  176   b  (as the second recesses) are formed, two on the R 1  side and two on the R 2  of the first cut-outs  176   a . The first cut-outs  176   a  have a semicircular shape that is complementary with the first protrusions  162  of the third friction washer  160 . The second cut-outs  176   b  have a semicircular shape that is complementary with the second protrusions  163 . The first protrusions  162  are fitted into the first cut-outs  176   a , and the second protrusions  163  are fitted into the second cut-outs  176   b . More specifically, the second protrusions  163  pass through the second cut-outs  176   b  in the axial direction, and the distal ends of the second protrusions  163  are fitted into the hub flange  106 . This makes it possible to restrict effectively the relative rotation of the bushing  170  and the third friction washer  160 . 
     Two pairs of protrusions  174  that protrude from the bushing main body  171  to the transmission side are formed as second protruding components in two corners of the bushing main body  171  (the portions to the outside of the first housing components  172  in the radial direction). One pair of protrusions  174  are disposed on the R 1  and R 2  sides with the first cut-outs  176   a  sandwiched in between. The protrusions  174  are fitted into the first cut-outs  144   a  and third cut-outs  147   a  formed in the hub flange  106 . This makes it possible to restrict effectively the relative rotation of the bushing  170  and the third friction washer  160 . 
     The portion of the third friction washer  60  to the outside in the radial direction has first contact components  167   a ,  167   b , and  167   c  that protrude from the third friction washer main body  161  to the transmission side. The portion of the bushing  170  to the outside in the radial direction has second contact components  177   a ,  177   b , and  177   c  that protrude from the bushing main body  171  to the engine side. When viewed from the same side in the axial direction, the first contact components  167   a ,  167   b , and  167   c  and the second contact components  177   a ,  177   b , and  177   c  have substantially the same shape, and come into contact with each other in the axial direction. The first contact components  167   a ,  167   b , and  167   c  and the second contact components  177   a ,  177   b , and  177   c  form a space capable of housing the output plate  190  in between the third friction washer main body  161  and the bushing main body  171  in the axial direction. 
     The output plate  190  has a plurality of inner peripheral teeth  191 , two first openings  192 , and two second openings  193 . The inner peripheral teeth  191  mesh with second outer peripheral teeth  154   b  of the splined hub  103  with substantially no gap in between. Therefore, the output plate  190  rotates integrally with the splined hub  103  within the space formed by the third friction washer main body  161  and the bushing main body  171 . 
     The first openings  192  are disposed corresponding to the first housing components  164  and  172 . The first small coil springs  107   a  are housed in the first openings  192 . The second openings  193  are disposed corresponding to the second housing components  165  and  173 . The second small coil springs  107   b  are housed in the second openings  193 . The length of the first openings  192  in the rotational direction is set to be substantially the same as the free length of the first small coil springs  107   a . Meanwhile, the length of the second openings  193  in the rotational direction is set to be greater than the free length of the second small coil springs  107   b . As shown in  FIG. 22 , in the neutral position, the torsion angle corresponding to the gap formed on the R 1  side of the second small coil springs  107   b  is a gap angle of θ 4   p . The torsion angle corresponding to the gap formed on the R 2  side of the second small coil springs  107   b  is a gap angle of θ 4   n . The configuration of these components creates a region in which two first small coil springs  107   a  are compressed in parallel (the first stage region on the positive and negative sides) and a region in which two second small coil springs  107   b  are compressed in parallel (the second stage region on the positive and negative sides) ( FIG. 32 ). 
     In the neutral position, the relative positions of the third friction washer  160  (bushing  170 ) and the output plate  190  in the rotational direction are determined by the two first small coil springs  107   a  housed in the first openings  192 . That is, the relative positions of the hub flange  106  and the splined hub  103  in the rotational direction in the neutral position are determined by the first small coil springs  107   a.    
     The spring constant of the first small coil springs  107   a  and the second small coil springs  107   b  is set much lower than the spring constant of the coil spring sets  108 . That is, the coil spring sets  108  are much stiffer than the first small coil springs  107   a  and the second small coil springs  107   b . Therefore, in the first and second stage regions, the coil spring sets  108  are not compressed, but the first small coil springs  107   a  and the second small coil springs  107   b  are compressed. 
     The splined hub  103  is disposed on the inner peripheral side of the clutch plate  121  and the retaining plate  122 . The splined hub  103  has a cylindrical boss  152  that extends in the axial direction, and a flange  154  that extends from the boss  152  to the outside in the radial direction. A splined hole  153  that engages with an input shaft (not shown) of the transmission is formed on the inner peripheral part of the boss  152 . 
     As shown in  FIGS. 18 to 24 , a plurality of first outer peripheral teeth  154   a  and second outer peripheral teeth  154   b  are formed on the outer peripheral part of the flange  154 . The first outer peripheral teeth  154   a  protrude outward in the radial direction farther than the second outer peripheral teeth  154   b . A plurality of inner peripheral teeth  159  are formed on the inner peripheral part of the hub flange  106 . The first outer peripheral teeth  154   a  mesh with the inner peripheral teeth  159  of the hub flange  106  via a specific gap. More specifically, as shown in  FIG. 22 , in a neutral position in which no torque is inputted, the torsion angle corresponding to the gap formed on the R 1  side of the inner peripheral teeth  159  is the gap angle θ 1   p . The torsion angle corresponding to the gap formed on the R 2  side of the inner peripheral teeth  159  is the gap angle θ 1   n . The configuration of these components creates a first stopper  109  that allows relative rotation between the hub flange  106  and the splined hub  103  within the range of the gap angles θ 1   p  and θ 1   n . As shown in  FIG. 32 , the range of low torsional stiffness is determined by the gap angles θ 1   p  and θ 1   n.    
     2.2.3: Friction Generating Mechanism 
     The damper mechanism  104  further has a friction generating mechanism  105  that uses frictional resistance to generate hysteresis torque, in order to damp and to absorb torsional vibration more effectively. More specifically, as shown in  FIGS. 23 and 24 , the friction generating mechanism  105  has a first friction washer  179 , a second friction washer  182 , the above-mentioned third friction washer  160 , and a fourth friction washer  189 . Low hysteresis torque is achieved by the first friction washer  179  and the fourth friction washer  189 , and high hysteresis torque is achieved by the second friction washer  182  and the third friction washer  160 . 
     As shown in  FIGS. 23 and 24 , the first friction washer  179  is disposed between the flange  154  and the retaining plate  122  in the axial direction. A first cone spring  180  is disposed between the first friction washer  179  and the retaining plate  122 . The first friction washer  179  is pressed against the flange  154  by the first cone spring  180 . This generates low hysteresis torque between the input rotary body  102  and the splined hub  103 . 
     The fourth friction washer  189  is disposed between the flange  154  and the clutch plate  121  in the axial direction. The fourth friction washer  189  has a plurality of outer peripheral teeth  189   a , and the outer peripheral teeth  189   a  are fitted into a plurality of slits  121   a  formed in the inner peripheral part of the clutch plate  121 . Therefore, the fourth friction washer  189  rotates integrally with the clutch plate  121 . The flange  154  is pressed against the fourth friction washer  189  by the first cone spring  180 . This generates low hysteresis torque between the input rotary body  102  and the splined hub  103 . 
     The second friction washer  182  is disposed so as to rotate integrally to the outside of the first friction washer  179  in the radial direction. The second friction washer  182  and the first friction washer  179  rotate integrally with the retaining plate  122 . The second friction washer  182  has a first friction plate  183  that comes into contact with the main body component  129 . A second cone spring  181  is disposed between the second friction washer  182  and the clutch plate  121 . The first friction plate  183  of the second friction washer  182  is pressed against the hub flange  106  by the second cone spring  181 . This generates high hysteresis torque between the input rotary body  102  and the hub flange  106 . 
     The hub flange  106  is pushed to the clutch plate  121  side via the second friction washer  182  by the second cone spring  181 . Therefore, the above-mentioned third friction washer  160  and bushing  170  are sandwiched between the hub flange  106  and the clutch plate  121  in the axial direction, and the second friction plate  169  of the third friction washer  160  is pressed against the clutch plate  121 . This generates high hysteresis torque between the input rotary body  102  and the hub flange  106 . 
     The above configuration achieves low hysteresis torque in the entire region of torsional characteristics, and high hysteresis torque generated in the third and fourth stage regions. 
     3. Operation 
     The operation and torsional characteristics of the damper mechanism  104  of the clutch disk assembly  101  will be described with reference to  FIGS. 18 to 29 . The positive side of the torsional characteristics will be described as an example here, and the operation on the negative side will not be described. 
     3.1: First and Second Stage Regions 
     On the positive side of the torsional characteristics, the input rotary member  102  in the neutral position shown in  FIG. 31  twists toward the R 1  side (the drive side) with respect to the splined hub  103 . Here, since the first small coil springs  107   a  and the second small coil springs  107   b  are not nearly as stiff as the coil spring sets  108 , the coil spring sets  108  are hardly compressed at all, and the input rotary body  102  and the hub flange  106  rotate integrally. Since the third friction washer  160  and the bushing  170  rotate integrally with the hub flange  106  here, the third friction washer  160  and the bushing  70  rotate with respect to the splined hub  103 . As a result, the first small coil springs  107   a  are compressed between the third friction washer  160  (bushing  170 ) and the output plate  190 . When the input rotary body  102  and the hub flange  106  rotate further with respect to the splined hub  103 , the first friction washer  179  slides with the flange  154  of the splined hub  103 . The above yields torsional characteristics such that the stiffness is low and the hysteresis torque is low in the first stage region. 
     When the input rotary body  102  rotates relative to the splined hub  103  by a torsion angle θ 4   p  to the R 1  side, the second small coil springs  107   b  begin to be compressed between the third friction washer  160  (bushing  170 ) and the output plate  90 . This creates torsional characteristics such that the stiffness is low and the hysteresis torque is low in the second stage region. Since the second small coil springs  107   b  act in parallel with the first small coil springs  107   a , in the second stage region the torsional stiffness is somewhat higher than in the first stage region. 
     When the torsion angle of the input rotary body  102  with respect to the splined hub  103  reaches an angle of θ 1   p , the first outer peripheral teeth  154   a  come into contact with the inner peripheral teeth  159 , and the first stopper  109  operates. As a result, the relative rotation of the hub flange  106  and the splined hub  103  comes to a halt. Accordingly, the compression of the first small coil springs  107   a  and the second small coil springs  107   b  stops. 
     3.2.3: Third and Fourth Stage Regions 
     When the input rotary body  102  rotates further to the R 1  side with respect to the splined hub  103 , the input rotary body  102  rotates relative to the hub flange  106 , and the two coil spring sets  108  housed in the second window apertures  142  begin to be compressed between the input rotary body  102  and the hub flange  106 . Up until the torsion angle is θ 1   p +θ 2   p , the two coil spring sets  108  are compressed in parallel. At this point, the first friction plate  183  of the second friction washer  182  slides with the hub flange  106 , and the second friction plate  169  of the third friction washer  160  slides with the clutch plate  121 . Since the third friction washer  160  is effectively restricted in its rotation relative to the hub flange  106  by the second protrusions  163 , when the input rotary body  102  rotates with respect to the hub flange  106 , the second friction plate  169  will always slide with the clutch plate  121 , and regardless of the inputted torsion angle, a high hysteresis torque is generated between the input rotary body  102  and the hub flange  106 . This yields torsional characteristics such that the torsional stiffness is high and the hysteresis torque is high in the third stage region. 
     When the torsion angle of the input rotary body  102  with respect to the splined hub  103  reaches θ 1   p +θ 2   p , the four coil spring sets  108  begin to be compressed. Once the torsion angle of the input rotary body  102  reaches θ 1   p +θ 3   p , the second stopper  110  operates, and the relative rotation of the input rotary body  102  and the splined hub  103  comes to a halt. This yields torsional characteristics such that the torsional stiffness is high and the hysteresis torque is high in the fourth stage region. 
     4. Effects 
     The effects obtained with the damper mechanism  104  are as follows. 
     (1) 
     With this damper mechanism  104 , when the input rotary body  102  rotates with respect to the hub flange  106 , the second friction plate  169  fixed to the third friction washer  160  slides with the clutch plate  121 . Since the third friction washer  160  and the bushing  170  at this point are effectively restricted from rotating with respect to the hub flange  106 , even if the relative rotation angle of the input rotary body  102  and the hub flange  106  should be small, high hysteresis torque will always be generated between the input rotary body  102  and the hub flange  106 . Therefore, the desired hysteresis torque can be reliably generated with this damper mechanism  104 . 
     (2) 
     With this damper mechanism  104 , the second protrusions  163  of the third friction washer  160  are fitted into the second cut-outs  144   b  and the fourth cut-outs  147   b . Also, the second protrusions  163  are fitted into the second cut-outs  176   b  of the bushing  170 . Further, the first protrusions  162  are fitted into the first cut-outs  176   a  of the bushing  170 . The configuration of these components makes it possible to restrict effectively the relative rotation of the third friction washer  160  and the hub flange  106 , and the relative rotation of the third friction washer  160  and the bushing  170 . 
     Also, in addition to the second protrusions  163  of the third friction washer  160 , the protrusions  174  of the bushing  170  are fitted into the first cut-outs  144   a  and the third cut-outs  147   a . This effectively restricts the relative rotation of the bushing  170  and the hub flange  106 . 
     (3) 
     With this damper mechanism  104 , the second protrusions  163  are fitted into the second cut-outs  144   b  formed in the edge of the first window apertures  141 , and the fourth cut-outs  147   b  formed in the edge of the second window apertures  142 . Therefore, compared to when the holes into which the second protrusions  163  are fitted are formed on the inside of the first window apertures  141  and the second window apertures  142  in the radial direction, the second cut-outs  144   b  and the fourth cut-outs  147   b  can be disposed more to the outside in the radial direction. This allows the effective radius from the rotational axis O-O to the second protrusions  163  to be increased, and allows the load in the rotational direction acting on the second protrusions  163  to be reduced. 
     (4) 
     With this damper mechanism  104 , the first cut-outs  144   a , the second cut-outs  144   b , the third cut-outs  147   a , the fourth cut-outs  147   b , the first cut-outs  176   a , and the second cut-outs  176   b  all have a cross-sectional shape that is roughly semicircular. Therefore, less stress accumulates in these cut-outs, and damage to the hub flange  106  and the bushing  170  can be prevented. 
     (5) 
     With this damper mechanism  104 , the third friction washer  160  and the bushing  170  are made of plastic. Therefore, there is less hysteresis torque generated by sliding the first small coil springs  107   a  and the second small coil springs  107   b  with the third friction washer  160  and the bushing  170 , and this prevents an increase in the hysteresis torque in the first and second stage regions. 
     (6) 
     With this damper mechanism  4 , the outside diameter L 11  of the clutch plate  121  disposed near the flywheel  107  may be smaller than the outside diameter L 12  of the retaining plate  122 . Therefore, the clutch plate  121  can be prevented from interfering with the flywheel  107 . This affords greater latitude in the design of the damper mechanism  104 . Also, since the damper mechanism  104  can be applied to a small flywheel  107 , the damper mechanism  104  can be applied over a broader range. 
     5. Modifications of Second Embodiment 
     The specific constitution of the present invention is not limited to the embodiment given above, and various changes and modifications are possible without departing from the essence of the invention. 
     (1) 
     In the above embodiment, the clutch disk assembly  1  in which the damper mechanism  4  was installed was described as an example, but the present invention is not limited to this. For example, this damper mechanism can also be applied to lockup devices for fluid torque transmission devices, two-mass flywheels, or other such power transmission devices. 
     (2) 
     Also, the layout of the first protrusions  162 , the second protrusions  163 , and the protrusions  174  is not limited to the above embodiment. 
     FIELD OF INDUSTRIAL UTILIZATION 
     With the damper mechanism according to the present invention, the desired hysteresis torque can be reliably generated, so the present invention is useful in power transmission systems for automotive vehicles. 
     With the damper mechanism according to the present invention, torsional vibration damping performance can be effectively improved, so the present invention is useful in power transmission systems for automotive vehicles. 
     With the damper mechanism according to the present invention, design latitude can be increased, so the present invention is useful in power transmission systems for automotive vehicles.