Abstract:
A damper assembly for a friction clutch includes a first and second series of springs arranged by a first and second series of spring pockets disposed around the outer circumference of the clutch. Vertical flange sections are configured to influence the springs against perpendicular walls of the damper minimizing frictional input. An arm ring of a turbine assembly rotatably communicates with the first series of springs to displace them a predetermined distance. Subsequent rotation of the arm ring displaces the second series of springs along with continuous displacement of the first series of springs creating a multi-rate damper.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to friction clutches, and more particularly to a friction clutch having a multi-rate damper.  
         BACKGROUND  
         [0002]    Friction clutches are disposed in a torque transmitting relationship between an internal combustion engine and a transmission as is well known. A spring damper assembly is used to limit the transmission of torsional disturbances between the engine and the transmission. Spring damper assemblies generally have a plurality of spring members which are disposed between the input and output members of the damper. Generally, the spring members are limited in their travel which controls the angular excursion permitted within the damper assembly.  
           [0003]    Various types of damper assemblies are configured with caged spring members. During relative rotation of the input and output members of the damper assembly, the spring members compress and are influenced against the contoured walls of their respective cage. Such a relationship can introduce friction around the circumferential surface of the spring. It would be advantageous to provide a method of containment for the spring members while minimizing the amount of contact therebetween.  
           [0004]    Conventional damper assemblies provide a series of spring members having equal length located around the damper. Such a configuration provides a linear rate damping characteristic. It would be desirable to provide a system of spring members arranged to provide multi-rate damping.  
         SUMMARY OF THE INVENTION  
         [0005]    It is a general object of the present invention to provide a friction clutch and damper assembly having a first and second series of dampers located around a circumferential edge of a piston assembly adapted for rotational engagement with a turbine assembly. The turbine assembly includes an arm ring having a series of arms configured to mechanically compress the first series of dampers a predetermined distance prior to engagement of the second series of dampers.  
           [0006]    It is another object of the present invention to provide a friction clutch and damper assembly including a first and second series of pockets adapted to locate the first and second series of dampers alternately around the circumferential edge of the piston assembly. The pockets ends are configured to influence the springs away from the pocket walls and against the perpendicular walls of the piston plate and circumferential flange minimizing frictional contact.  
           [0007]    It is a further object of the present invention to provide a friction clutch and damper assembly having a piston plate rotatably communicating with a friction wafer, the piston plate carbonitrited or nitrited to improve durability and consistent operation.  
           [0008]    It is yet another object of the present invention to provide a friction clutch and damper assembly including a first series of pockets having an integrated stop section adapted to cooperate with the series of arms of the turbine assembly to limit compression of the first series of dampers to a predetermined distance.  
           [0009]    It is still another object of the present invention to provide a friction clutch and damper assembly including a third series of dampers located around the circumference of the piston assembly located within a first series of pockets and adapted to be influenced by the arms of the turbine assembly after the first series of dampers have been partially displaced a predetermined distance.  
           [0010]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0012]    [0012]FIG. 1 is a cross-sectional view of the friction clutch and damper according to the teachings of this invention;  
         [0013]    [0013]FIG. 2 is a partial perspective view of the piston plate, damper assembly and arm ring according to the preferred embodiment;  
         [0014]    [0014]FIG. 3 is a perspective view of the spring pocket plate removed from the damper assembly;  
         [0015]    [0015]FIG. 4 is a perspective view of the rear side of the turbine assembly to illustrate the circumferential arm ring;  
         [0016]    [0016]FIG. 5 is a perspective view of the piston plate and damper assembly according to a second embodiment;  
         [0017]    [0017]FIG. 6 is a cutaway perspective view of the piston plate and damper assembly according to a third embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    With general reference to FIGS.  1 - 5  a torque converter and damper assembly constructed in accordance with the teachings of the present invention will be described. With particular reference to FIG. 1, there is shown a torque converter and damper assembly  10  in accordance with the preferred embodiment of the present invention. As is well known, torque converters utilize the rotating elements in a fluid filled housing to multiply engine torque. All use the engine to drive the impeller  12  which, in turn, impels the fluid against the veins of the turbine  14 . The turbine  14  includes an output hub  16  which is splined to a transmission input shaft  20  at  18 . The transmission input shaft  20  provides an input for a multi-speed transmission. The torque converter  10  operates in a well known manner to provide drive from an engine, not shown, to a transmission of a vehicle, not shown. The torque converter  10  is a fluid drive and therefore accommodates the torsional disturbances which are produced at the engine due to the firing frequency of the pistons. The stator  22  communicates with the reaction shaft  52 , and serves to redirect oil flow from the turbine  14  against the impeller veins  12  to boost impeller action and multiply engine torque.  
         [0019]    To improve the operating efficiency of the torque converter  10 , a torque converter clutch  24  is provided to establish a direct drive connection between the cover assembly  26  and the transmission input shaft  20 . The torque converter clutch  24  can be fluid operated to provide a frictional engagement for transmitting torque from the engine to the transmission. Additionally, it is also well known in these types of torque transmitting connections; i.e., clutches, will transmit torsional disturbances which are found in the drive line at the engine interface.  
         [0020]    A damper assembly  28  is provided to reduce the amount of torsional vibration transmitted to the input shaft  20 . The damper assembly  28  is interconnected to the piston plate  30  which is interconnected to the turbine output hub  16 . When the clutch  24  is engaged, a drive connection is provided through the piston plate  30  and the damper assembly  28  to the output hub  16 .  
         [0021]    Fluid chambers  32 ,  34  are formed on both sides of the piston plate  30 . A thrust bearing  36  is axially located between the output hub  16  and the torque converter front cover  38 . The support ring thrust bearing  36  allows oil flow between front cover  38  and turbine output hub  16 .  
         [0022]    In operation, the turbine wheel  40  is driven by the impeller wheel  42  from the circulation of fluid in the casting  44 . To avoid slip between the impeller wheel  42  and turbine wheel  40  after startup, the torque converter clutch  24  connects front cover  38  with the output hub  16 . This is achieved from the hydraulic pressure in fluid chamber  32  influencing the piston plate  30  against the friction material  46  radially disposed on the inner surface  48  of the cover assembly  26 .  
         [0023]    The outer surface, or friction face  50  of the piston plate  30  is carbonitrited or nitrited to improve wear characteristics thereof. This treatment allows for durable surface texture and microstructure, heat resistance and dimensional stability which are desirable qualities of a surface exposed to such frictional inputs. It is apparent, however, that the friction material  46  may be disposed radially around the outer surface of the piston plate  50 . Likewise, the inner surface of the cover assembly  48  may be carbonitrided or nitrided according to such a configuration providing like results.  
         [0024]    Turning now to FIG. 2, the damper assembly  28  will now be described in greater detail. The damper assembly  28  is interconnected to the piston plate  30 . The damper assembly  28  includes a first and second series of spring pockets  70 , 72  circumferentially located around a spring retainer, or pocket plate  54  of the piston plate  30 . The first series of spring pockets  70  are configured to retain a first series of springs  60  of a first length. The second series of spring pockets  72  are configured to retain a second series of springs  62  of a second length. The first series of springs  60  and spring pockets  70  are adapted to be a length greater than the second series of springs  62  and spring pockets  72 .  
         [0025]    The first and second series of springs  60 , 62  and spring pockets  70 , 72  are alternately disposed around the circumference of the piston plate  30 . The piston plate  30  includes an outer circumferential wall  74  which extends substantially perpendicular therefrom. The placement of the springs  60 , 62  at the most outboard location allows for larger tolerances and eliminates the need of length-sorting the springs which is typical for designs placing springs close to the main axis of the damper assembly  28 .  
         [0026]    The first and second series of spring pockets  70 , 72  are configured such that the springs  60 , 62  realize a three point contact during rotation of the arm ring  76 . To provide a smooth actuation of the piston assembly  78  and to protect spring ends from premature wear, the springs are fitted with end buttons  80 . During compression, a given spring will be influenced at the end buttons  80  from the arms  90  of the arm ring  76  on one end and from the outer flange  92  of the pockets  70 , 72  on the other. A first and second side of a given spring will slidably communicate with the inner surface  94  of the piston plate  30  and the inner surface  96  of the circumferential wall  74 . The curvature of the spring pockets  70 , 72  influence the springs  60 , 62  into the piston plate walls  94 , 96  and away from contact with the contoured radial wall of the spring pocket. Because the springs  60 , 62  are engaged only at the spring ends and by the first and second substantially perpendicular walls  94 , 96  of the piston plate  30 , the frictional inputs of the springs  60 , 62  are minimized. The contoured wall of the spring pockets  70 , 72  are configured such that in case of spring failure due to unforeseen wire problems, the pocket will prevent migration of a loose spring wire.  
         [0027]    As is best shown in FIG. 4, the turbine assembly  98  includes an arm ring  76  disposed therearound. The arm ring  76  includes a series of arms  90  outwardly extending therefrom. The arms are operatively located a predetermined distance apart such that first and second consecutive arms mechanically communicate with springs  60  of the first series in an uncompressed static state. The predetermined distance the arms  90  are separated allows a first series of arms  100  to compress a first series of springs  60  a predetermined distance prior to the second series of arms  102  contacting the second series of springs  62 . Explained further, the first series of arms  100  compress the first series of springs  60  as the turbine assembly  98  rotates in a counterclockwise direction  106 . Once springs  60  have compressed a predetermined distance, arms  102  contact springs  62  of the second series. Subsequent counterclockwise rotation compresses the second series of springs  62  and continues further compression of springs  60  of the first series. This configuration provides a dual rate damping system.  
         [0028]    Referencing FIG. 3 and  5 , a second embodiment of the present invention includes a pocket plate  54 ′. Pocket plate  54 ′ like pocket plate  54  is configured with flanges  92 ′ of pocket walls  70 ′ and  72 ′. Pocket plate  54 ′ includes strap sections  110  integrated on the first series of spring pockets  70 ′. The strap sections  110  are configured to resist spring compression to a predetermined distance. During operation, the arms  90  of the arm ring  76  rotate a predetermined distance until contacting the strap sections  110  of the spring pockets  70 ′. The strap sections  110  can limit the angle of relative rotation between the piston assembly  78 , engaged at the friction face  50  with friction material  46  of the cover assembly  26 , and the turbine assembly  98 . The strap sections  110  are used to either limit the amount of damper travel and/or protect springs  60 , 62  from undesired loads. Straps  110 , however, are not used to support the springs  60 , 62  or to provide a reaction surface for the springs  60 , 62 .  
         [0029]    Turning now to FIG. 6, a damper assembly  28 ′ according to a third embodiment is shown. The first and second series of springs  60 , 62  and spring pockets  70 , 72  are alternately disposed around the circumference of the piston plate as in the first embodiment. The first spring pocket  70  retains the first series of springs  60  as well as an additional third series of springs  114 . The third series of springs  114  are a predetermined distance shorter than the first series of springs  60 . During operation, the first series of springs  60  are displaced a predetermined distance prior to the second set of springs  114  displacing a predetermined distance. Once the first and third set of springs displaces a predetermined distance the second series of springs  62  are compressed. This system allows for a three rate damping system. The third embodiment is shown without the straps  110  of the second embodiment, however the spring configuration of the third embodiment may include the stop sections described in the second embodiment.  
         [0030]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.