Abstract:
A self-adjusting twin or dual dry clutch assembly for a dual clutch transmission includes a single actuator. The clutch assembly includes one center and two outer clutch drive plates or discs which independently engage a pair of interleaved driven clutch plates or discs which are coupled to and drive a respective pair of transmission countershafts or layshafts. The single actuator translates an internal clutch carrier which acts upon the outer clutch plates through respective pluralities of linear one way clutches. Self-adjustment of the dual clutch assembly is achieved by additional linear one way clutches acting through pairs of spring biased control rods.

Description:
FIELD 
       [0001]    The present disclosure relates to a dry dual clutch for use with a dual clutch transmission and more particularly to a self-adjusting dry dual clutch having a single actuator which is especially suited for use with a dual clutch transmission. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    Dual clutch transmissions (DCT&#39;s) are becoming increasingly popular in passenger cars because of their performance and efficiency. Because a gear to be selected for an upshift or downshift can be pre-selected or “pre-staged” before a currently engaged gear is disengaged, the actual upshift or downshift essentially involves simply the disengagement of the engaged clutch and engagement of the disengaged clutch—an operation that can be accomplished in a small fraction of a second. Such rapid shifts lend a highly desirable and sporty performance to the powertrain and the vehicle. Since the dual clutch transmission is essentially a manual transmission incorporating a plurality of pairs of meshed gears and two driveline clutches, fuel economy is also very good. Not only does the dual clutch transmission have fewer components but it also eliminates the torque converter. The dual clutch transmission is thus also less expensive to manufacture than a comparable automatic transmission 
         [0004]    Because of its increasing popularity, significant research and development have recently been directed to improving the construction and operation of dual clutch transmissions. A target of such work has been the dual clutch arrangement that selectively and mutually exclusively provides drive torque to the two drive assemblies, usually layshaft or countershafts, in the transmission. Current transmission configurations utilize a pair of essentially identical clutches disposed on the axes of the countershafts or a pair of clutches in tandem which drive concentric shafts. 
         [0005]    The current design state of clutch assemblies for dual clutch transmissions suggests that improvements in such clutches are both possible and desirable. 
       SUMMARY 
       [0006]    The present invention provides a self-adjusting twin or dual dry clutch assembly for a dual clutch transmission having a single actuator. The clutch includes one center or intermediate and two outer drive plates or discs which independently engage an interleaved pair of driven clutch plates or discs which are coupled to and drive a respective pair of transmission countershafts or layshafts. The single actuator translates an inner clutch carrier which acts upon the outer clutch plates through pluralities of linear one-way clutches. 
         [0007]    Each of the outer clutch plates is coupled to respective control rods through additional linear one-way clutches. Strong compression springs disposed about the control rods bias the respective linear one-way clutches and the associated outer clutch plates away from the center clutch plate. Weak compression springs bias the control rods, strong springs and outer clutch plates away from the center clutch plate. Translation of the actuator and inner carrier selectively engage one of the two clutches. Cooperation between the inner carrier, the linear one-way clutches, the control rods and the springs provide self adjustment to the dual clutch assembly as the clutch facing material wears. 
         [0008]    Thus it is an aspect of the present invention to provide a clutch assembly for a dual clutch transmission. 
         [0009]    It is a further aspect of the present invention to provide a dual clutch assembly for a dual clutch transmission. 
         [0010]    It is a still further aspect of the present invention to provide a dry clutch assembly for a dual clutch transmission. 
         [0011]    It is a further aspect of the present invention to provide a self-adjusting dual clutch assembly for a dual clutch transmission. 
         [0012]    It is a still further aspect of the present invention to provide a self-adjusting dry clutch assembly for a dual clutch transmission. 
         [0013]    It is a still further aspect of the present invention to provide a self-adjusting dual dry clutch assembly for a dual clutch transmission. 
         [0014]    Further aspects, advantages and areas of applicability 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 diagrammatic view of a portion of a dual clutch transmission incorporating a clutch assembly according to the present invention; 
           [0017]      FIG. 2  is an enlarged diagrammatic view of a portion of a dual clutch assembly according to the present invention in neutral; 
           [0018]      FIG. 3  is an enlarged diagrammatic view of a portion of a dual clutch assembly according to the present invention with one clutch engaged; 
           [0019]      FIG. 4  is an enlarged diagrammatic view of a portion of a dual clutch assembly according to the present invention with another clutch engaged; and 
           [0020]      FIG. 5  is an enlarged diagrammatic view of a portion of a dual clutch assembly according to the present invention illustrating its self-adjusting action. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0022]    With reference now to  FIG. 1 , a portion of a dual clutch transmission is illustrated and generally designated by the reference number  10 . The dual clutch transmission  10  includes a clutch housing  12  having various shoulders, flanges and features which receive, locate and retain components of the dual clutch transmission  10 . An input shaft  14  is coupled to and driven by a prime mover  16  such as a gasoline, Diesel, flex fuel or hybrid or electric power plant. The input shaft  14  is supported on bearings such as ball bearing assemblies  18 . 
         [0023]    A twin or dual dry clutch assembly  20  is disposed within the clutch housing  12  and includes an outer rotating housing or carrier  22  that is coupled to and driven by the input shaft  14 . The outer housing or carrier  22  defines a cylinder having a closed end or radial wall  24 A which is coupled to and driven by the input shaft  14  and an opposite end or partial wall  24 B having an annular seal  26 . Concentrically disposed within the outer housing or carrier  22  is a smaller, inner clutch carrier  30 . The inner clutch carrier  30  is rotationally coupled to the outer housing or carrier  22  by an annular interengaging set of male and female splines  32 A and  32 B. A fluid seal  33  is disposed at the juncture of the input shaft  14  and the inner clutch carrier  30 . The inner clutch carrier  30  may thus translate axially within the outer housing  22  but will remain coupled to and driven by the outer housing  22 . 
         [0024]    Disposed concentrically with the inner clutch carrier  30  of the dual clutch assembly  20  is a first annular friction clutch drive disc or plate  34  which is connected to and driven by the inner clutch carrier  30 . The first clutch drive plate  34  includes clutch facing material  36  on its inner surface. Spaced from the first clutch drive plate  34  is a second, intermediate annular friction clutch drive disc or plate  38  which includes clutch facing material  42  on both surfaces. The second, intermediate clutch drive plate  38  is coupled to and driven by both the inner clutch carrier  30  and the outer clutch housing  22  by a radially extending drive disc  44 . The radial drive disc  44  also fixes the axial position of the second, intermediate clutch drive plate  38  relative to the outer housing or carrier  22 . At the intersection of the inner clutch carrier  30  and the drive disc  44 , one of the components is discontinuous and a plurality of fluid tight seals  46  are incorporated. The second, intermediate clutch drive plate  38  is also piloted on an inner ball bearing assembly  48 . Spaced from the second, intermediate clutch drive plate  38  is a third annular friction clutch drive disc or plate  52  which is also connected to and driven by the inner clutch carrier  30 . The third clutch drive plate  52  includes clutch facing material  54  on its inner surface. 
         [0025]    Between both the first and the second clutch plates  34  and  38  and the second and the third clutch plates  38  and  52  are driven annular clutch discs or plates. A first driven clutch plate  60 , disposed between the first clutch plate  34  and the second clutch plate  38 , may include clutch facing material and is coupled to and drives a first output shaft or member  62 . The first output shaft or member  62  is supported on suitable bearing assemblies  64  and is coupled to and drives a first output gear  66  which, for example, may be associated with the even numbered gears of the transmission  10 . A second driven clutch plate  70 , disposed between the second clutch plate  38  and the third clutch plate  52 , may include clutch facing material and is coupled to and drives a second drive tube, quill or output member  72 . The second drive tube, quill or output member  72  is supported for rotation by suitable ball bearing assemblies  74  and is coupled to and drives a second output gear  76  which, for example, may be associated with the odd numbered gears of the transmission  10 . 
         [0026]    The first output gear  66  is in constant mesh with a first countershaft or layshaft input gear  68  which is secured to and drives a first countershaft or layshaft  82  which may be associated with, as noted, the even numbered gears, reverse, second and fourth, for example. The second output gear  76  is in constant mesh with a second countershaft or layshaft input gear  78  which is secured to and drives a second countershaft or layshaft  84  which may be associated with, as noted, the odd numbered gears, first, third and fifth, for example. Alternatively, the first output shaft or member  62  and the concentric second drive tube, quill or output member  72  may be coupled to and directly drive a countershaft  62  and a concentric quill or tubular countershaft  72  within the transmission  10  which are essentially extensions of these components of the clutch  10  beyond the clutch housing  20 . 
         [0027]    Referring now to  FIGS. 1 and 2 , operably disposed between the inner clutch carrier  30  and the first and third annular friction clutch drive disc or plates  34  and  52  are pluralities of linear one way clutches. A first plurality of linear one way or overrunning clutches  90  are mounted on the left side of the inner clutch carrier  30  behind the first annular clutch plate  34 . Preferably, there are three linear one way clutches  90  disposed at equal 120° intervals around the inner clutch carrier  30  which engage a like number of first drive members, rods or shafts  92  which extend axially from the rear surface  94  of the first friction clutch plate  34 . It will be appreciated that additional one way clutches  90  and shafts  92  disposed in suitable equal circumferential intervals may be utilized but that use of fewer than three of the assemblies is not recommended. The first plurality of one way clutches  90  each include a first housing  96  and a plurality of, for example, pawls, sprags or balls  98  which couple and translate the first rods or shafts  92  and the first friction clutch plate  34  to the right in  FIGS. 1 and 2  when the housings  96  are translated to the right by translation of the inner clutch carrier  30  but release the coupling between the housings  96  and the rods or shafts  92  when the housings  96  and the inner clutch carrier  30  are translated to the left. 
         [0028]    In a similar, symmetrical arrangement, a second plurality of linear one way or overrunning clutches  100  are mounted on the right side of the inner clutch member  30  behind the third annular clutch plate  52 . Again, there are preferably three linear one way clutches  100  disposed in 120° intervals around the inner carrier  30  which engage a like number of second drive members, rods or shafts  102  which extend axially from the rear surface  104  of the third annular clutch plate  52  The second plurality of one way clutches  100  each include a second housing  106  and a plurality of pawls, sprags or balls  108  which couple and translate the second rods or shafts  102  and the third annular clutch plate  52  to the left in  FIGS. 1 and 2  when the housings  106  are translated to the left by translation of the inner clutch carrier  30  but release the coupling between the second housings  106  and the rods or shafts  102  when the housings  106  and the inner clutch carrier  30  are translated to the right. 
         [0029]    The inner clutch carrier  30  includes a tubular or cylindrical extension or member  30 A at its end opposite the input shaft  14  which is coupled to an output of a single acting or bi-directional electric, hydraulic or pneumatic actuator or operator  110 . The actuator or operator  110  is secured to the housing  12 . An annular compression spring  112  which may take the form of a stack of spring washers such as wave washers or Belleville springs or a plurality of circumferentially spaced apart coil compression springs or spring washers provides a biasing or restoring force to the inner clutch carrier  30  relative to the outer housing  22  which opposes the force and travel of the actuator or operator  110 . Activation of the operator  110  thus translates the inner clutch carrier  30 , locks one of the one way clutches  90  or  100  and translates one of the annular clutch plates  34  or  52  while releasing the other one way clutch  90  or  100  and the associated annular clutch plate  34  or  52 . 
         [0030]    It will be appreciated that alternate configurations of the single acting or bi-directional operator  110  and spring  112  include a bi-directional actuator or operator which may eliminate the need for the spring  112  or an arrangement in which, for example, the spring  112  is utilized and the annular volume adjacent the right end  24 A of the outer carrier or housing  22  is pressurized with hydraulic fluid to achieve translation of the inner clutch carrier  30 . Furthermore, it may be desirable to incorporate a linear position sensor which senses the instantaneous position of the inner clutch carrier  30  and provides a signal or data regarding same to an associated transmission control module (TCM) (not illustrated). 
         [0031]    The first annular clutch plate  34  also includes a radially extending first annulus  114  which is secured to a plurality of housings  118  of a plurality of third linear one way or overrunning clutches  120 . The plurality of third linear one-way clutches  120  include pawls, sprags or balls  122  which engage and release a plurality of axially disposed first control rods  124 . The plurality of third one way clutches  120  are configured to lock when the first annulus  114  (and the first annular clutch plate  34 ) translates to the left in  FIGS. 1 and 2  relative to the first control rods  124  and release when the first annulus  114  translates to the right relative to the first control rods  124 . A plurality of first compression springs  126  are received about the first control rods  124  between the housings  118  of the third one way clutches  120  and a plurality of stops  128  such as taper pins or C-washers and bias the first control rods  124  to the right relative to the third one way clutches  120 . 
         [0032]    A similar, symmetrical configuration is associated with the third annular clutch plate  52  which includes a radially extending second annulus  134  which is secured to a plurality of housings  138  of a plurality of fourth linear one-way or overrunning clutches  140 . The plurality of fourth one way clutches  140  include pawls, sprags or balls  142  which engage and release a like plurality of axially disposed second control rods  144  which are preferably axially aligned with the first control rods  124 . The fourth one way clutches  140  are configured to lock when the second annulus  134  (and the third annular clutch plate  52 ) translates to the right in  FIGS. 1 and 2  relative to the second control rods  144  and release when the second annulus  134  translates to the left relative to the second control rods  144 . A plurality of second compression springs  146  are received about the second control rods  144  between the housings  138  of the fourth one way clutches  140  and a plurality of stops  148  such as a taper pins or C-washers and bias the second control rods  144  to the left relative to the fourth one way clutches  140 . The spring constants (rates) of the first and the second compression springs  126  and  146  are the same. 
         [0033]    The second, intermediate clutch drive plate  38  includes, as noted, the radially extending drive disc  44  which extends beyond the axis of the control rods  124  and  144 . Disposed between the adjacent ends of the first control rods  124  and the drive disc  44  are a plurality of third compression springs  152  and between the adjacent ends of the second control rods  144  and the drive disc  44  are a plurality of fourth compression springs  154 . The spring constants (rates) of the third and the fourth compression springs  152  and  154  are the same and are very much smaller than the spring constants of the first and the second compression springs  126  and  146 . The third and the fourth compression springs  152  and  154  provide a biasing or restoring force to the respective first and the second control rods  124  and  144 , driving them away from the drive disc  44 . 
         [0034]    The operation of the twin clutch assembly  20  will now be described with reference to  FIGS. 1 ,  2 ,  3 ,  4  and  5 . In  FIG. 2 , the dual clutch assembly  20  is in neutral, the first, the second and the third clutch drive discs  34 ,  38  and  52  are separated from the first and the second driven clutch plates  60  and  70 . There is, therefore, no drive torque being transmitted from the input shaft  14  to either of the first or the second countershafts  82  or  84 . 
         [0035]    In  FIG. 3 , the actuator  110  has been energized to translate the inner clutch carrier  30  to the left. The plurality of second linear one way clutches  100  lock the rods or shafts  102  to the inner carrier  30  and the third clutch drive plate  52  translates to the left to engage the second driven clutch plate  70  between the second and the third clutch drive plates  38  and  52 , thereby transferring drive torque from the input shaft  14  to the second drive tube, quill or output member  72 , the second output gear  76 , the second countershaft gear  78  and the second countershaft  84 . 
         [0036]    In  FIG. 4 , the actuator  110  has been energized to translate the inner clutch carrier  30  to the right, to disengage the second driven clutch plate  70  and engage the first driven clutch plate  60 . Motion of the output of the actuator  110 , assisted by the compression spring  112 , translates the inner clutch carrier  30  to the right and releases engagement between the plurality of second one way clutches  100  and the second rods or shafts  102 . Thus, the third clutch drive plate  52  translates to the right due to the force of the second compression spring  146  and the fourth compression spring  154 , such that no drive torque is transmitted therethrough. At the same time, the plurality of first linear one way clutches  90  lock the inner carrier  30  to the first rods or shafts  92  and the first clutch drive plate  34  translates to the right to engage the first driven clutch plate  60  between the first clutch drive plate  34  and the second clutch drive plate  38 , thereby transferring drive torque from the input shaft  14  to the first output shaft  62 , the first output gear  66 , the first countershaft gear  68  and the first countershaft  82 . 
         [0037]    In  FIG. 5 , the dual clutch assembly  20  returns to neutral as the actuator  110  centers the inner carrier  30 . The plurality of first linear one way clutches  90  thus release and the first and the third compression springs  126  and  152  translate the first clutch drive plate  34  to the left and disengage the first driven clutch plate  60  from the first and the second clutch drive plates  34  and  38 . At the same time, the plurality of second linear one way clutches  100  has locked and moves the third clutch drive plate  52  to the left to prepare for re-engagement and to compensate for wear. In this regard, note the separation between the clutch plates  34 ,  60 ,  38 ,  70  and  52  in  FIG. 2  which represents a start-up or initial activation state and the separation in  FIG. 5  which represents an operational or self-adjusted state. In both figures, the separation has been exaggerated for purposes of explanation and understanding. 
         [0038]    It should be understood that, as noted, since the pluralities of linear one way or overrunning clutches  90 ,  100 ,  120  and  140  and the associated pluralities of rods or shafts  92  and  102  and the control rods  124  and  144  are discrete components, they will preferably and typically be disposed in threes or fours about the center axis of the clutch assembly  20  at equally spaced circumferential intervals of 120° or 90°, respectively. It should also be understood that for reasons of clarity and explanation, certain of these components have been rotated into the viewing plane in the various drawing figures. The actuator  110  is, however, preferably an annular component that surrounds the shafts or quills of the clutch assembly  20  and includes (if hydraulic or pneumatic) an annular piston slidably disposed within an annular cylinder. 
         [0039]    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 and the following claims.