Abstract:
The present invention provides a dry, dual clutch module having reduced axial length. The clutch module includes a larger diameter, single plate outer clutch which drives a first transmission input shaft or drive quill and a smaller diameter, double plate inner clutch which drives a second transmission input shaft or drive quill. The smaller diameter clutch is nested within the larger diameter clutch and thus they essentially reside within the same axial space.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/120,633, filed on Dec. 8, 2008, which is hereby incorporated in its entirety herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to driveline clutches and more particularly to a dry, dual clutch module for use with a dual clutch transmission. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0004]    Within the motor vehicle transmission art, the dual clutch transmission (DCT) is a relative newcomer. A typical dual clutch transmission configuration includes a pair of mutually exclusively operating input clutches which drive parallel layshafts or countershafts spaced from a parallel output shaft. One of each of a plurality of pairs of constantly meshing gears, which provide the various forward gear ratios is freely rotatably disposed on one of the countershafts and the other of each pair of gears is coupled to the output shaft. A plurality of synchronizer clutches selectively couple one of the gears to a countershaft to achieve a forward gear ratio. 
         [0005]    Dual clutch transmissions are known for their sporty, performance oriented shift characteristics. Moreover, with appropriate peripheral electronic and hydraulic components, a dual clutch transmission can function as either a manual, semi-automatic or automatic transmission. In every case, they typically exhibit good fuel economy due to their good gear mesh efficiency and ratio selection flexibility. The clutches have low spin losses which also contribute to overall operating efficiency. 
         [0006]    Dual clutch transmissions do, however, have certain unique design considerations which present engineering challenges. For example, because of the input torque throughput during launch and the heat that can be generated with clutch slip. The input clutches must be of relatively large size. This size requirement applies as well to the thermal heat sink which must be able to absorb large quantities of heat. Additionally, because such transmissions typically have many sets of axially aligned gears, their overall length may limit their use to certain vehicle platforms. 
         [0007]    The present invention is directed to a clutch module for a dual clutch transmission having reduced axial length which reduces the overall length of the transmission and thus provides greater flexibility of transmission application. 
       SUMMARY 
       [0008]    The present invention provides a dry, dual clutch module having reduced axial length. The dual clutch module includes a larger diameter, single plate outer clutch which drives a first transmission input shaft or drive quill and a smaller diameter, double plate inner clutch which drives a second transmission input shaft or drive quill. The smaller diameter clutch is nested within the larger diameter clutch and they thus essentially reside within the same axial space. 
         [0009]    Thus it is an object of the present invention to provide a dual clutch module for a transmission having a short axial length. 
         [0010]    It is a further object of the present invention to provide a dual clutch module for a transmission having inner and outer clutches. 
         [0011]    It is a still further object of the present invention to provide a dry, dual clutch module for a dual clutch transmission. 
         [0012]    It is a further object of the present invention to provide a dual clutch module having a single plate outer clutch and a dual plate inner clutch. 
         [0013]    It is a still further object of the present invention to provide a dual clutch module for a dual clutch transmission having a short axial dimension and wherein an inner clutch is essentially nested within an outer clutch. 
         [0014]    Further objects, advantages and areas of applicability of the present invention will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0015]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0016]      FIG. 1  is a full sectional view of a portion of a dual clutch transmission incorporating a dual clutch module according to the present invention; 
           [0017]      FIG. 2  is an enlarged, full sectional view of a dual clutch module according to the present invention, and 
           [0018]      FIG. 3  is a pictorial view in full section of a dual clutch module according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0020]    With reference to  FIG. 1 , a portion of a dual clutch transmission incorporating the present invention is illustrated and generally designated by the reference number  10 . The transmission  10  includes a typically cast metal housing  12  having openings, flanges, bores and other machined surfaces which receive, support, locate and protect the various components of the transmission  10 . A bell housing  14  which is secured to the transmission housing  12  encloses a compact dry dual clutch module  20  according to the present invention. As utilized herein, the term “dry” means that the clutch and more specifically the clutch plates operate dry, without a cooling or lubricating fluid and are thus generally mounted outside the housing  12  of the transmission  10 , such as in the bell housing  14  illustrated. 
         [0021]    With reference now to  FIGS. 1 ,  2  and  3 , a clutch input shaft  16  receives drive torque from a prime mover (not illustrated) such as an internal combustion gasoline, Diesel or flexible fuel engine or hybrid power plant. The clutch input shaft  16  is coupled to a flywheel  22  which includes a starter ring (gear teeth)  24  about its periphery and an isolator  26 . A plurality of fasteners  28  such as machine bolts secure the flywheel  22  to the clutch input shaft  16 . The flywheel  22  functions as the drive member of the dual clutch module  20 . 
         [0022]    The dual clutch module  20  includes a first, outer friction clutch assembly  30  and a second, inner friction clutch assembly  70 . The flywheel  22  and the isolator  26  define a flat, annular surface  32  which abuts, supports and drives a first outer clutch drive plate or disc  34 . Spaced from and coupled to the first outer clutch drive plate or disc  34  by an annular collar  38  and therefore rotating with the first outer clutch drive plate  34  is a second, outer clutch drive plate or disc  40 . Disposed between the first and second outer drive plates  34  and  40  is an outer driven clutch plate or disc  44  which includes suitable friction clutch facing material  46  on both faces. The driven clutch plate  44  includes a deep drawn, “top hat” portion  48  as well as a collar or hub  50  having internal splines  52  which engage external splines  54  on a transmission input shaft  56 . The input shaft  56  is associated with and drives certain gears (not illustrated) within the dual clutch transmission  10  which, when engaged, provide certain gear drive ratios. 
         [0023]    A first, outer apply plate or spring  58  which is retained within the annular collar  38  by a snap ring assembly  60  functions as a lever to actuate the first outer friction clutch assembly  30 . The outer apply plate or spring  58  engages a circular pivot plate  62  radially inwardly of the snap ring assembly  60  and an first, outer thrust or apply bearing assembly  64  adjacent its inner edge. Axial force applied to the outer thrust bearing assembly  64  by a first, outer clutch actuator  66  deflects the apply plate or spring  58  to the left in  FIG. 2 , pivoting the spring  58  about the plate  62 , pulling the first outer clutch drive plate  34  to the right, compressing the outer drive and driven clutch plates  34 ,  40  and  44  and achieving torque transfer from the clutch input shaft  16  to the transmission input shaft  56 . The first, outer clutch actuator  66  may be a hydraulic, pneumatic or electric actuator. 
         [0024]    Turning now to the second, inner friction clutch assembly  70 , the second, outer clutch drive plate or disc  40  is also a “top hat” shape in section and includes a hub  72  having internal or female splines  74  and a radially inwardly extending stop plate  76 . A pair of inner clutch drive plates or discs  80  having external or male splines  82  reside within the hub  72  and engage the female splines  74 . Accordingly, the pair of inner clutch drive plates  80  rotate with the hub  72 , the second, outer clutch drive plate or disc  40  and the flywheel  22 . Disposed between the stop plate  76  and the adjacent inner clutch drive plate  80  and between the pair of inner clutch drive plates  80  are a pair of inner, driven clutch plates or discs  86  having suitable clutch facing material  88  on each face. The inner, driven clutch plates  86  are coupled to an inner driven clutch hub  90  which, in turn, is splined by interengaging splines  92  to a transmission input quill or drive tube  94 . The input quill or drive tube  94  is associated with and drives certain other gears (not illustrated) within the dual clutch transmission  10  which, when engaged, provide other gear drive ratios and, for example, reverse. 
         [0025]    Another lever assembly actuates the second, inner friction clutch assembly  70 . An inner apply plate or spring  102  which is axially restrained at its periphery by an inward extension of the circular pivot point plate  62  or a similar structure engages a circular pivot ridge  104  on the rear face of the inner clutch drive plate  80  adjacent the inner apply plate or spring  102 . An inner thrust or apply bearing assembly  106  engages the inner apply plate or spring  102  adjacent its inner edge. Axial force applied to the inner thrust or apply bearing assembly  106  by a second, inner clutch actuator  108  deflects the apply plate or spring  102  to the left in  FIG. 2 , pivoting the spring  102  about the ridge  104 , translating the adjacent inner clutch drive plate  80  to the left, compressing the inner drive and driven clutch plates  80  and  86  and achieving torque transfer from the clutch input shaft  16  to the transmission input quill or drive tube  94 . 
         [0026]    While the axial space saving achieved by nesting the clutches  30  and  70  associated with the dual drives to the transmission  10  is a significant benefit of the present invention, it should be understood that the configuration generally necessitates an inner clutch assembly  70  having more plates or discs and thus more active clutch surface area than the outer clutch assembly  30  in order to provide comparable torque throughput and service life due to its smaller nominal diameter. Thus while the outer clutch assembly  30  has been described herein as having a single driven clutch plate or disc  44  and the inner clutch assembly  70  as having a pair of driven clutch plates or discs  86 , said configuration is primarily illustrative and exemplary and different numbers of clutch plates in both clutch assemblies  30  and  70  and different ratios of the number of clutch plates (other than 1:2) are all within the purview of the present invention. 
         [0027]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.