Abstract:
A clutch apparatus includes a clutch pack having a plurality of friction disks. The clutch pack will selectively transfer torque from a torque supplying member to a first torque receiving member. The apparatus also includes a first piston chamber positioned radially outward of the clutch pack. The first piston chamber is operably connected to the clutch pack for exerting a compressive force on at least a portion of the clutch pack as a first fluid is pressurized into the first piston chamber.

Description:
TECHNICAL FIELD 
       [0001]    The disclosure relates to clutches for torque transmission. 
       BACKGROUND 
       [0002]    Twin-clutch, twin-shaft, dual shaft, or dual clutch transmissions of the alternating shifting type are well known in the prior art. Various types of twin clutch transmissions have been proposed and put into practical use, particularly in the field of wheeled motor vehicles. Traditional twin clutch transmissions are of a type in which gears are parted into two groups, each group having an individual main clutch, so that the operative condition of each group of gears is carried out by selectively engaging a corresponding main clutch. Twin clutch transmissions are used in vehicles to improve the transition from one gear ratio to another and, in doing so, improve the efficiency of the transmission. The gears of each group are typically individually engaged so as to rotatably connect a transmission input shaft to a transmission output shaft for transmitting torque at differing ratios. The differing ratios may be engaged by multiple shift clutches. 
         [0003]    A typical dual clutch is illustrated in commonly owned U.S. Pat. No. 7,082,850, to Hughes, the disclosure of which is hereby incorporated by reference in its entirety. Many main clutches for dual clutch transmissions include clutch packs, having a plurality of clutch disks, for engaging and disengaging each gear group with the engine. In some applications, the clutches are actuated by hydraulic pistons for engaging and disengaging each clutch pack. Typically, the clutch packs are located radially outside of the hydraulic pistons to prevent fluids that are heated by the clutch packs from contacting the outer surfaces and seals of the piston assemblies. 
       SUMMARY 
       [0004]    A clutch apparatus includes a clutch pack having a plurality of friction disks. The clutch pack will selectively transfer torque from a torque supplying member to a first torque receiving member. The apparatus also includes a first piston chamber positioned radially outward of the clutch pack. The first piston chamber is operably connected to the clutch pack for exerting a compressive force on at least a portion of the clutch pack as a first fluid is pressurized into the first piston chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Referring now to the drawings, illustrative embodiments are shown in detail. Although the drawings represent some embodiments, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present invention. Further, the embodiments set forth herein are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description. 
           [0006]      FIG. 1  is a schematic illustration of a vehicle according to an embodiment. 
           [0007]      FIG. 2  is a schematic illustration of a transmission and twin clutch arrangement according to an embodiment. 
           [0008]      FIG. 3  is a partial sectional view of a twin clutch arrangement according to an embodiment. 
           [0009]      FIG. 4  is an enlarged view of portion  4  of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0010]      FIG. 1  illustrates a powertrain system  20  is shown in accordance with an embodiment. In the illustrated embodiment, the powertrain system  20  includes a prime mover  22 , such as a spark-ignited or compression-ignited internal combustion engine, and a transmission  24 . A shift control system  26  operates to engage and disengage gear ratios within the transmission  24 , as discussed in greater detail below. A main clutch assembly  28  is positioned between the prime mover  22  and transmission  24  to selectively engage/disengage the prime mover  22  from transmission  24 . 
         [0011]    In an embodiment, powertrain system  20  also includes an electronic control unit (ECU)  30  for controlling operation of the prime mover  22 , main clutch assembly  28  generally defining an axis A-A, and transmission  24 . The ECU  30  may include a programmable digital computer that is configured to receive various input signals, including without limitation, the operating speed of the prime mover  22 , transmission input speed, selected transmission ratio, transmission output speed and vehicle speed, and processes these signals accordingly to logic rules to control operation of powertrain system  20 . For example, ECU  30  may be programmed to deliver fuel to the prime mover  22  when the prime mover  22  functions as an internal combustion engine. To support this control, each of the prime mover  22 , and main clutch assembly  28  may include its own control system (not shown) contained within ECU  30 . However, it will be appreciated that the present invention is not limited to any particular type or configuration of ECU  30 , or to any specific control logic for governing operation of powertrain system  20 . A transmission output torque from an output shaft, or output member,  32  is distributed to wheels  34  through a drive shaft  36  and a differential  38 . 
         [0012]      FIG. 2 , illustrates an embodiment of the transmission  24  to include a first input shaft  40 , a second input shaft  42 , a countershaft  44  that extends substantially parallel with first and second input shafts  40  and  42 , and a plurality of gears which are arranged on and/or around shafts  40 ,  42  and  44 . Although shafts  40 ,  42  and  44  are illustrated as being mounted in a common plane in  FIG. 2 , these shafts may be arranged in different planes. 
         [0013]    In the embodiment shown in  FIG. 2 , first input shaft  40  is connectable to an output member  46  of the prime mover  22 , such as a flywheel, through a first main clutch C  1  that is used to establish even speed gearing (viz., second speed gearing, fourth speed gearing and reverse gearing), while second input shaft  42  is connectable to flywheel  46  through a second main clutch C 2  that is used for establishing odd speed gearing (viz., first speed gearing, third speed gearing and fifth speed gearing). In an embodiment, first and second main clutches C 1  and C 2  are of a normally ON type, which assumes the ON (viz., engaged) state due to a biasing force of a spring and the like under a normal condition and establishes the OFF (viz., disengaged) state due to work of a hydraulic or electric actuator upon receiving a given instruction. Engagement and disengagement of first and second main clutches C 1 , C 2  may function automatically under the control of ECU  30 , and without intervention of a vehicle driver, when powertrain systems operates like an “automatic” transmission. 
         [0014]    To first input shaft  40  there are connected a 2nd speed input gear  48 , a 4th speed input gear  50  and a reverse input gear  52 , such that gears  48 ,  50  and  52  rotate together with first input shaft  40 . Similarly, to second input shaft  42  there are connected a 5th speed input gear  54 , a 3rd speed input gear  56  and a 1st speed input gear  58 , such that gears  54 ,  56  and  58  rotate together with second input shaft  42 . The number of input gears provided on first and second input shafts is not limited to the number shown in  FIG. 2 , and may include more or less input gears depending on the number of ratios desired in the transmission. The term “gear,” as stated herein, is used to define the toothed wheels schematically illustrated in  FIG. 2 , as well as manufacturing the toothed features of the wheels directly into first and second input shafts  40 ,  42  and countershaft  44 . 
         [0015]    To countershaft  44  there are rotatably connected a 1st speed output gear  62 , a 3rd speed output gear  64 , a 5th speed output gear  66 , a reverse output gear  68 , a 2nd speed output gear  70  and a 4th speed output gear  72 . Thus, output gears  62 - 72  rotate around countershaft  44 . Like input gears  48 - 58 , the number of output gears provided on countershaft  44  is not limited to the number schematically illustrated in  FIG. 2 . 
         [0016]    Referring still to  FIG. 2 , 1st speed output gear  62 , 3rd speed output gear  64  and 5th speed output gear  66  are meshed with 1st speed input gear  58 , 3rd speed input gear  56  and 5th speed input gear  54 , respectively. Similarly, reverse output gear  68 , 2nd speed output gear  70 , and 4th speed output gear  72  are meshed with reverse input gear  52  (through idler  94 ), 2nd speed input gear  48 , and 4th speed input gear  50 , respectively. In another embodiment, transmission  24  may include a second countershaft (not shown) that includes one or more of the output gears rotatably disposed on first countershaft  44 . 
         [0017]    To countershaft  44  there is also integrally connected a final drive pinion gear  73  that rotates together with countershaft  44 . Final drive pinion  73  is arranged perpendicular to an axis of a rotational output member  74 , such as a final drive ring gear, and is meshed with output member  74 . In the embodiment shown in  FIGS. 1 and 2 , a transmission output rotation from drive pinion  73  to output member  74  is distributed to wheels  34  through a drive shaft  36  and a differential  38 . 
         [0018]    Referring again to  FIG. 2 , transmission  24  also includes axially moveable clutches  82 ,  84 ,  86  and  88 , such as synchronized single or double acting dog-type clutches, which are splined to countershaft  44  for rotation therewith. Clutch  82  is moveable by a conventional shift fork (not shown) in an axial direction toward main clutch assembly  28  to fix countershaft  44  for rotation with 1st speed output gear  62 . Similarly, clutch  84  may be moved in opposite axial directions to rotationally fix output gear  64  or output gear  66  to countershaft  44 . Clutch  86  may be selectively moved in opposite axial directions to rotationally fix output gear  68  or output gear  70  to countershaft  44 . Clutch  88  may be moved in an axial direction toward main clutch assembly  28  to fix countershaft  44  for rotation with output gear  72 . In another embodiment, clutches  82 ,  84 ,  86  and  88  may also be provided on first and second input shafts  40 ,  42  to engage and disengage gears rotatably supported on input shafts  40 ,  42  in a manner substantially similar to the manner in which the gears are engaged on countershaft  44 . 
         [0019]    In an embodiment, the transmission  24  also includes axially moveable input shaft clutches  90  and  92 , such as synchronized single acting dog-type clutches, which are splined to first input shaft  40  for rotation therewith. In the illustrated embodiment, clutch  90  may be moved in an axial direction toward main clutch assembly  28  to fix first input shaft  40  for rotation with second input shaft  42 . Similarly, clutch  92  may be moved in an axial direction away from main clutch assembly  28  to fix first input shaft  40  for rotation with output member  74 . 
         [0020]    As described above, ECU  30  delivers commands to the components of powertrain system  20  based on the receipt and evaluation of various input signals. These commands may include gear ratio interchange commands to a shift control device that indirectly moves clutches  82 ,  84 ,  86 ,  88 ,  90  and  92  to establish the gear ratios between first and second input shafts  40 ,  42  and countershaft  44 . The shift control system  26  may be a conventional device, or any other suitable device that controls the axial position of each of clutches  82 ,  84 ,  86 ,  88 ,  90  and  92 . 
         [0021]    Operation of hybrid powertrain system  20  will now be described with reference to  FIG. 2 . In a first mode of operation employed during vehicle launch and acceleration, first and second main clutches C 1  and C 2  are initially disengaged and clutch  82  is moved leftward from the neutral position shown in  FIG. 2 , so that 1st speed output gear  62  is fixed to countershaft  44  by clutch  82 . Upon this movement, power from prime mover  22  may be transmitted to countershaft  44  by engaging second main clutch C 2 . The power applied to second input shaft  42  is transmitted through 1st speed input gear  58  to countershaft  44  through 1st speed output gear  62 , and then to final drive pinion  73  so that a first speed ratio is established in transmission  24 . 
         [0022]    As the vehicle accelerates and the second speed ratio is desired, clutch  86  is moved rightward from the neutral position shown in  FIG. 2 , so that 2nd speed output gear  70  is fixed to countershaft  44  by clutch  86 . The engagement of clutch  86  occurs while first main clutch C 1  is disengaged and no power is being transmitted from prime mover  22  to first input shaft  40 . Once clutch  86  is engaged, the currently engaged second main clutch C 2  is disengaged while simultaneously or nearly simultaneously engaging first main clutch C 1 . The resulting power applied to first input shaft  40  is transmitted through 2nd speed input gear  48  to countershaft  44  through 2nd speed output gear  70 , and then to final drive pinion  73  so that a second speed ratio is established in transmission  24 . This process is repeated, including the selective activation of the appropriate clutch, in the same manner for up-shifting through the remaining gear ratios, and in a reverse manner for down-shifting from one gear ratio to another. 
         [0023]    To achieve the reverse gear in transmission  24 , first and second main clutches C 1  and C 2  are disengaged and clutch  86  is moved leftward from the neutral position shown in  FIG. 2 , so that reverse output gear  68  is fixed to countershaft  44  by clutch  86 . The power applied to first input shaft  40  is transmitted from reverse input gear  52  to countershaft  44  through an idler gear  94  and reverse output gear  68 , and then to final drive pinion  73 . 
         [0024]    Under a normal operating state, wherein transmission  24  assumes a certain speed gearing, both first and second main clutches C  1  and C 2  may be kept in their engaged conditions while one of clutches  82 ,  84 ,  86 , and  88  is kept at a given power transmitting position. For example, when transmission  24  assumes the 5th speed ratio, both first and second main clutches C 1  and C 2  may be engaged while clutch  84  is engaged with 5th speed output gear  66  and clutches  82 ,  86  and  88  are in their neutral position shown in  FIG. 2 . Although first and second main clutches are engaged, no power is transmitted through the unselected output gears  62 ,  64 ,  68 ,  70  and  72  because the output gears are free to rotate on countershaft  44  when not engaged by a corresponding clutch  82 ,  86  or  88 . 
         [0025]    In the embodiment shown in  FIG. 2 , gears  58  and  62  establish a “low” gear ratio between second input shaft  42  and countershaft  44  when clutch  82  fixes gear  62  for rotation with countershaft  44 . Gears  54  and  66  establish a “high” gear ratio between second input shaft  42  and countershaft  44  when clutch  84  fixes gear  66  for rotation with countershaft  44 . 
         [0026]    As best seen in  FIG. 3 , the main clutch assembly  28  includes a housing  100 , a damper  102 , a clutch collar  104 , a clutch drum  106 , a first clutch hub  108 , a second clutch hub  110 , a first piston assembly  114 , and a second piston assembly  116 . 
         [0027]    The housing  100  is connected to a portion of the transmission  24  and the prime mover  22 . In the embodiment illustrated, the damper  102  is a lubricated noise, vibration and harshness (NVH) damper for reducing at least undesired drivetrain torque oscillations and other vibrations. The clutch drum  106  is coupled to an outer portion of the damper  102  for rotation therewith. 
         [0028]    In the embodiment illustrated, the clutch drum  106  includes a plurality of annular first drum disks  122  and a plurality of annular second drum disks  124  extending radially therefrom. The first clutch hub  108  includes a plurality of annular first hub disks  128  extending radially therefrom. The second clutch hub  110  includes a plurality of annular second hub disks  130  extending radially therefrom. The first drum disks  122  are interleaved with the first hub disks  128 , and the second drum disks  124  are interleaved with the second hub disks  130 , as described in greater detail below. 
         [0029]      FIG. 4  illustrates an enlarged portion of the main clutch assembly  28  of  FIG. 3 . As best seen in  FIG. 4 , the first drum disks  122  include a first pressure plate  140 , a first drum first disk  142 , a first drum second disk  144 , a first drum third disk  146 , and a first reaction plate  148 . The second drum disks  124  include a second pressure plate  150 , a second drum first disk  152 , a second drum second disk  154 , a second drum third disk  156 , and a second reaction plate  158 . The first hub disks  128  include a first hub first disk  162 , a first hub second disk  164 , a first hub third disk  166 , and a first hub fourth disk  168 . The second hub disks  130  include a second hub first disk  172 , a second hub second disk  174 , a second hub third disk  176 , and a second hub fourth disk  178 . 
         [0030]    The first pressure plate  140  includes a first pressure plate forward surface  180  and a first pressure plate rearward surface  182 . The first drum first disk  142  includes a first drum first disk forward surface  184  and a first drum first disk rearward surface  186 . The first drum second disk  144  includes a first drum second disk forward surface  188  and a first drum second disk rearward surface  190 . The first drum third disk  146  includes a first drum third disk forward surface  192  and a first drum third disk rearward surface  194 . The first reaction plate  148  includes a first reaction plate forward surface  196  and a first reaction plate rearward surface  198 . 
         [0031]    The second pressure plate  150  includes a second pressure plate forward surface  200  and a second pressure plate rearward surface  202 . The second drum first disk  152  includes a second drum first disk forward surface  204  and a second drum first disk rearward surface  206 . The second drum second disk  154  includes a second drum second disk forward surface  208  and a second drum second disk rearward surface  210 . The second drum third disk  156  includes a second drum third disk forward surface  212  and a second drum third disk rearward surface  214 . The second reaction plate  158  includes a second reaction plate forward surface  216  and a second reaction plate rearward surface  218 . 
         [0032]    The first hub first disk  162  includes a first hub first disk forward surface  220  and a first hub first disk rearward surface  222 . The first hub second disk  164  includes a first hub second disk forward surface  224  and a first hub second disk rearward surface  226 . The first hub third disk  166  includes a first hub third disk forward surface  228  and a first hub third disk rearward surface  230 . The first hub fourth disk  168  includes a first hub fourth disk forward surface  232  and a first hub fourth disk rearward surface  234 . 
         [0033]    The second hub first disk  172  includes a second hub first disk forward surface  240  and a second hub first disk rearward surface  242 . The second hub second disk  174  includes a second hub second disk forward surface  244  and a second hub second disk rearward surface  246 . The second hub third disk  176  includes a second hub third disk forward surface  248  and a second hub third disk rearward surface  250 . The second hub fourth disk  178  includes a second hub fourth disk forward surface  252  and a second hub fourth disk rearward surface  254 . 
         [0034]    The first piston assembly  114  includes an annular first apply plate  260 , an annular first piston  262 , an annular first return spring  264 . The first piston  262  includes a first piston reaction surface  266  and a first piston apply surface  268 . The second piston assembly  116  includes an annular second apply plate  270 , an annular second piston  272 , an annular second return spring  274 . The second piston  272  includes a second piston reaction surface  276  and a second piston apply surface  278 . The clutch drum  106 , the first apply plate  260  and the first piston  262  define an annular first piston chamber  280 . The clutch drum  106 , the second apply plate  270  and the second piston  272  define an annular second piston chamber  282 . The first piston assembly  114  and the second piston assembly  116  include annular piston seals  290  for sealing the piston chambers  280 ,  282 . In the embodiment illustrated, the first return spring  264  is axially restrained by a first piston retaining ring  292  and a first drum retaining ring  294 . The second return spring  274  is axially restrained by a second piston retaining ring  296  and a second drum retaining ring  298 . 
         [0035]    In the embodiment illustrated, the piston seals  290  are constructed of a material that will withstand heated fluid from the clutch disks  122 ,  124 ,  128 ,  130 , such as DuPont™ Vamac®, or other suitable material. 
         [0036]    The clutch collar  104  supplies fluid to the clutch drum  106 , which supplies fluid to the first piston assembly  114 , the second piston assembly  116 , and the clutch disks as discussed in greater detail below. The clutch drum  106  includes a first piston chamber port  300 , and a second piston chamber port  302 . The shafts  40 ,  42  define a first clutch cooling port  304  and a second clutch cooling port  306 . The clutch collar  104  is adapted to supply a cooling fluid (not shown) to the ports  300 ,  302  and control the pressure thereof, as is conventionally known. 
         [0037]    The clutch drum  106  is further defined by a central web  310 , an annular first balance chamber wall  312 , a cylindrical first balance chamber connecting wall  314 , a second balance chamber wall  316 , and a cylindrical second balance chamber connecting wall  318 . The first piston  262 , the first balance chamber wall  312 , and the first balance chamber connecting wall  314  define a first balance chamber  320 . The clutch drum  106  is also defined by a first coolant passage  322 , a first reservoir  324 , a first cooling first inlet  326 , a first cooling second inlet  328 , a first cooling third inlet  330 , and a first cooling fourth inlet  332 . The second piston  272 , the second balance chamber wall  316 , and the second balance chamber connecting wall  318  define a second balance chamber  340 . 
         [0038]    As the main clutch assembly  28  rotates about the axis A-A ( FIG. 3 ), fluid supplied through the ports  300 ,  302 ,  304 ,  306  will tend to rotate with the main clutch assembly  28  and will be accelerated away from the axis A-A. As fluid present within the first piston chamber  280  and the second piston chamber  282  is accelerated away from the axis A-A, the fluid will bias the respective piston  262 ,  272  away from the respective apply plate  260 ,  270  and act against the biasing force of springs  264 ,  274 . Additionally, the fluid supplied through the ports  304 ,  306  will cool the clutch disks  122 ,  124  then fill the balance chambers  320 ,  340 . 
         [0039]    When fluid pressure is supplied through the first piston chamber port  300 , the first piston  262  will move in the rearward direction (illustrated as the arrow R in  FIGS. 3 and 4 ) as the first apply plate  260  remains generally stationary relative to the clutch hub  106 . The first return spring  264  is axially deflected due to interference between the first piston retaining ring  292  and the first hub retaining ring  294  as the first piston  262  moves in the direction R, biasing the first piston in the direction of arrow F. As the first piston  262  moves in the direction R, the first piston will move toward the first balance chamber wall  312  and reduce the volume of fluid within the first balance chamber  320 . Generally, the volume of fluid that is forced into the first piston chamber  280  is equal to the volume of fluid that is displaced from the first balance chamber  320 , thereby maintaining the rotational weight and the rotational inertia of the main clutch assembly  28 . 
         [0040]    As the first piston  262  moves in the direction of the arrow, the first piston reaction surface  266  urges the first pressure plate  140  toward the first reaction plate  148 , thereby actuating the first clutch C 1 . While the first clutch C 1  and the second clutch C 2  are illustrated as a clutch pack having interleaved disks, the clutches used in the main clutch assembly may be any clutch configuration, having any number of engaging frictional surfaces. 
         [0041]    By providing components of the main clutch assembly  28 , such as the clutch disks  122 ,  124 ,  128 ,  130  interposed radially within the piston assemblies  114 ,  116 , the resulting clutch assembly may have a desirably shorter axial length when compared to clutch assemblies that have components orientated solely in an axial orientation. Generally, the weight of the clutch disks  122 ,  124 ,  128 ,  130  is greater than the weight of the piston assemblies  114 ,  116 . Accordingly, positioning the clutch disks  122 ,  124  radially inward of the piston assemblies  114 ,  116  will result in a main clutch assembly  28  with a lower rotational inertia when compared to a clutch assembly having clutch packs positioned radially outward of piston assemblies. In the embodiment illustrated, the clutch disks  122 ,  124 ,  128 ,  130  are axially adjacent with a minimum number of clutch components positioned between the clutch disks  122 ,  124 ,  128 ,  130  and the shafts  40 ,  42  to further decrease the rotational inertia of the main clutch assembly  28 . 
         [0042]    The preceding description has been presented only to illustrate and describe exemplary embodiments of the methods and systems of the present invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. The invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. The scope of the invention is limited solely by the following claims.