Abstract:
An apparatus for transferring torque from a crankshaft to a dual input transmission includes: a flywheel connected at one end to the crankshaft and at the opposite end to a torque transmitting device or dual clutch. The flywheel has a first coupling member that is configured to engage a second coupling member attached to a center plate of the dual clutch. The first coupling member is fixedly secured to the second coupling member by a fastening means. A dual clutch actuation device generates the axial compression force required to compress a first and second set of frictional elements of a dual clutch.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/248,617, filed on Oct. 5, 2009, which is hereby incorporated in its entirety herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to transmissions and more particularly to a system and method for attaching a dual clutch to a flywheel to achieve a compact, dual clutch multiple speed transmission. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
     A typical dual input multiple speed transmission has a first input shaft and a second input shaft that is a hollow sleeve shaft that is concentric with the first input shaft. The first and second input shafts are selectively coupled to the engine crankshaft through a dual clutch. The dual or twin clutch has two independent clutch units that are each separately rotationally fixed to one of the input shafts. The clutch units include friction elements that are axially compressed against friction elements that are ultimately rotationally fixed to the crankshaft. A dual clutch actuation device generates the apply force necessary to axially compress the friction elements and rotationally couple the input shafts with the crankshaft. 
     While current dual clutches achieve their intended purpose, the need for new and improved configurations which exhibit improved performance, is essentially constant. For example, one problem not addressed by the prior art is the relative movement between the flywheel and the dual clutch module. Accordingly, there is a need in the art for a dual clutch having improved torque transfer capability, packaging and ease of assembly while providing a mechanism to reduce or eliminate noise or vibration. 
     SUMMARY 
     The present invention provides a dual clutch and flywheel assembly for a dual clutch transmission. The transmission has two input shafts a first shaft and a second shaft that is a hollow sleeve shaft. The second shaft is concentric with the first shaft. The dual clutch has two clutch units that selectively couple a crankshaft of an engine to one of the two input shafts. More specifically, the dual clutch includes members such as a clutch housing having a first set of frictional elements that are rotationally fixed to the crankshaft through a flywheel and other members such hubs having a second set of frictional elements that are rotationally fixed to the input shafts. The first and second frictional elements are axially compressed against each other to couple one of the hubs to the dual clutch housing, thereby transmitting torque from the crankshaft to one of the input shafts. 
     A dual clutch actuation device is provided to generate the axial compression force required to compress the first and second set of frictional elements. Dual clutch actuation device includes a first and second annular piston. The annular pistons include a first end that is in contact with annular bearing assemblies. The annular bearing assemblies are in contact with actuation levers that are in contact with the first set of frictional elements. The annular pistons are arranged in concentric annular piston slots. Together the piston and annular slots form annular piston chambers. The piston chambers are filled with hydraulic fluid. When the hydraulic fluid is pressurized the pistons slide out of the annular slots and apply a force on the actuation levers which in turn apply an axial compression force on the frictional elements. 
     In one aspect of the present invention, the dual clutch includes a first coupling member formed in a center plate of the dual clutch. 
     In another aspect of the present invention, the first coupling member of the dual clutch includes a radial bore that is threaded and has an open end that opposes a flange or tab fixed to the flywheel. 
     In another aspect of the present invention, the flywheel includes a second coupling member fixedly attached to a periphery of the flywheel wherein the second coupling member opposes the first coupling member of the dual clutch. 
     In yet another aspect of the present invention, a pin or bolt is provided that is configured to engage the first and second coupling members. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIGS. 1A and 1B  is a partial cross-sectional view of a torque transmitting device, actuation device and flywheel for a dual input transmission, in accordance with an embodiment of the present invention; and 
         FIG. 2  is a perspective view of the torque transmitting device attached to the flywheel, in accordance with an embodiment of the present invention. 
     
    
    
     DESCRIPTION 
     Referring to  FIG. 1 , a partial cross-sectional view of a torque transmitting device for a dual input transmission (not shown) is generally indicated by reference number  10 . The torque transmitting device  10  is for example a dual clutch disposed in a vehicle powertrain. Typically the vehicle powertrain includes an engine (not shown) and a transmission (not shown). In the instant embodiment the transmission is a dual input transmission where torque is transferred through selective operation of torque transmitting device  10  from the engine via a crankshaft  12  to two input shafts in the transmission: a first input shaft  14  and a second input shaft  16 . The second input shaft  16  is a sleeve (or hollow) shaft that is concentric with and overlies the first input shaft  14 . Torque transmitting device  10  is disposed in a transmission housing or bell housing  18 . 
     Torque transmitting device  10  has two separate and independent friction clutches  20  and  22  disposed in a clutch housing  24 . Friction clutch  20  includes a friction member  28  and friction clutch  22  includes a friction member  30 . Friction member  28  is fixed to a hub member  34 . Friction member  30  is fixed to a hub member  32 . Hub members  32  and  34  are each separately rotationally fixed to first and second input shafts  14  and  16 , respectively. Clutch housing  24  also includes friction elements  36 ,  38  and a clutch center plate  40  that are each attached and rotationally fixed to housing  24 . Friction members  28 ,  30 , clutch center plate  40  and friction elements  36  and  38  are configured to form a friction clutch, as is known in the art as a dual clutch. Thus, selective engagement through axial compression of friction member  28  with friction element  36  and clutch center plate  40  connects the crankshaft  12  for common rotation with the second input shaft  16 . Selective engagement of friction member  30  with friction element  38  and clutch center plate  40  connects the crankshaft  12  for common rotation with the first input shaft  14 . Friction clutches  20  and  22  may include multiple friction members  28  and  30  that interact with a respective multiple of friction elements  36  and  38  connected to housing  24 . The number and size of the friction members will vary based on appropriate torque transmission requirements. Of course, the torque transmission capability of device  10  may be varied by varying the number of friction elements and amount of surface area of each friction element. 
     Clutch housing  24  is rotationally fixed to a flywheel  26 , as will be described in further detail below. Flywheel  26  is connected to crankshaft  12  by bolts or screws  27  or similar fastening means. Preferably, flywheel  26  is a dual mass flywheel that is configured to dampen and reduce vibration in the crankshaft  12 . 
     The coupling of the crankshaft  12  to the input shafts  14  and  16  is achieved through axial compression of the friction elements and clutch center plate  40  by actuation levers or disks  42  and  44 . Actuation levers or disks  42 ,  44  have first ends  46  and  48  that are in contact with and configured to pivot on housing  24 . The second ends  49  and  51  of actuation levers  42 ,  44  are in contact with and configured to receive an apply force generated by an actuation device  50 . 
     Actuation device  50  includes an annular housing  52 , a pair of annular pistons  54  and  56  and a pair of bearing assemblies  58  and  60 . Housing  52  is mounted and thus rotationally fixed to bell housing  18  and defines a central bore  61 . The central bore  61  is sized to allow the first input shaft  14  and the second input shaft  16  to pass there through. Bearing assemblies  58  and  60  are actuation bearings that torsionally decouple the rotating elements of clutch  10  (i.e. housing  24  and actuation levers or disks  42  and  44 ) from the non-rotating members of the actuation device  50  (i.e. pistons  54  and  56 ). 
     Annular piston  56  is translated axially and presses bearing assembly  60  toward second end  51  of the actuation lever or disk  44 . Actuation lever  44  pivots on housing  24  and compresses friction element  38  axially against friction member  30  and center plate  40  causing hub  32  to rotate at substantially the same speed as friction member  38 . Thus, selectively rotationally coupling crankshaft  12  with first input shaft  14 . Annular piston  54  is translated axially and presses bearing assembly  58  toward second end  49  of the actuation lever or disk  42 . Actuation lever  42  pivots on housing  24  and compresses friction element  36  axially against friction member  28  and center plate  40  causing hub  34  to rotate at substantially the same speed as friction member  36 . Thus, selectively rotationally coupling crankshaft  12  with second input shaft  16 . 
     With continuing reference to  FIG. 1  and referring also to  FIG. 2 , a perspective view the flywheel  26  and torque transmitting device  10  is illustrated, in accordance with an embodiment of the present invention. As illustrated the center clutch plate  40  includes a tab or first coupling member  80  formed in or fixed to a perimeter of plate  40 . In the example provided, the first coupling member  80  is a flywheel for plate  40 . Tab  80  includes a threaded bore  82  that has an open end  84 . Open end  84  opposes or is open to connector disc or a second coupling member or tab/flange  86  attached to flywheel  26 . Second coupling member or tab/flange  86  includes a through bore or aperture  88  that is aligned with threaded bore  82 . Second coupling member or tab/flange  86  has a radially extending portion  87  and an axially extending portion  89 . The axially extending portion  89  includes first and second sides  89 A and  89 B disposed opposite each other. The bore  88  extends through the axially extending portion  89  and therefore has openings on each of the first and second sides  89 A and  89 B. In the instant embodiment, at least three first coupling members  80  (only two shown) are disposed at equal distances around a periphery of plate  40 . However, the present invention contemplates that in alternate embodiments additional first coupling members are disposed at equal distances around a periphery of plate  40 . 
     As shown in  FIGS. 1 and 2 , torque transmitting device  10  is coupled for common rotation with flywheel  26  through mating engagement of first coupling member  80  with second coupling member  86 . More specifically, in an embodiment of the present invention first coupling member  80  is mechanically secured to second coupling member  86  by an engagement member  90 , such as a threaded bolt or pin. Threaded bolt or pin  90  is positioned through bore or aperture  88  and threaded into threaded bore  82  to rigidly and securely rotationally couple flywheel  26  to torque transmitting device or dual clutch  10 . 
     The present invention has many advantages and benefits over the prior art. For example, the novel embodiments of the present invention utilize the required thickness of the center plate  40  to form radial threads that is required for heat sinking. Moreover the present embodiments provide a lower relative mass, a reduced radial and circumferential size as compared to comparable designs. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.