Abstract:
A dual clutch transmission for a vehicle is provided. The transmission includes a first input shaft driven by a first clutch and a second input shaft driven by a second clutch. An output shaft or shafts are driven by the input shafts having selective mesh torsional force transferring gear contact therewith. A differential input gear is driven by the output shaft or shafts. At least one of the input shafts has at least one input gear that torsionally engages with the output shaft via an idler shaft having an idler input shaft torsionally connected on the idler shaft with an idler shaft output gear through a one-way clutch and wherein the idler shaft output gear is meshed with another gear on the one input shaft.

Description:
FIELD OF THE INVENTION 
     The present invention relates to dual clutch transmissions for automotive vehicles. 
     BACKGROUND OF THE INVENTION 
     Generally speaking, land vehicles require a powertrain consisting of three basic components. These components include a power plant (such as an internal combustion engine), a power transmission, and wheels. The power transmission component is typically referred to simply as the “transmission.” Engine torque and speed are converted in the transmission in accordance with the tractive-power demand of the vehicle. Presently, there are two typical transmissions widely available for use in conventional motor vehicles. The first and oldest type is the manually operated transmission. These transmissions include a foot-operated start-up or launch clutch that engages and disengages the driveline with the power plant and a gearshift lever to selectively change the gear ratios within the transmission. When driving a vehicle having a manual transmission, the driver must coordinate the operation of the clutch pedal, the gearshift lever, and the accelerator pedal to achieve a smooth and efficient shift from one gear to the next. The structure of a manual transmission is simple and robust and provides good fuel economy by having a direct power connection from the engine to the final drive wheels of the vehicle. Additionally, since the operator is given complete control over the timing of the shifts, the operator is able to dynamically adjust the shifting process so that the vehicle can be driven most efficiently. One disadvantage of the manual transmission is that there is an interruption in the drive connection during gear shifting. This results in losses in efficiency. In addition, there is a great deal of physical interaction required on the part of the operator to shift gears in a vehicle that employs a manual transmission. 
     The second and newer choice for the transmission of power in a conventional motor vehicle is an automatic transmission. Automatic transmissions offer ease of operation. The driver of a vehicle having an automatic transmission is not required to use both hands, one for the steering wheel and one for the gearshift, and both feet, one for the clutch and one for the accelerator and brake pedal in order to safely operate the vehicle. In addition, an automatic transmission provides greater convenience in stop and go situations, because the driver is not concerned about continuously shifting gears to adjust to the ever-changing speed of traffic. Although conventional automatic transmissions avoid an interruption in the drive connection during gear shifting, they suffer from the disadvantage of reduced efficiency because of the need for hydrokinetic devices, such as torque converters, interposed between the output of the engine and the input of the transmission for transferring kinetic energy therebetween. In addition, automatic transmissions are typically more mechanically complex and therefore more expensive than manual transmissions. 
     For example, torque converters typically include impeller assemblies that are operatively connected for rotation with the torque input from an internal combustion engine, a turbine assembly that is fluidly connected in driven relationship with the impeller assembly and a stator or reactor assembly. These assemblies together form a substantially toroidal flow passage for kinetic fluid in the torque converter. Each assembly includes a plurality of blades or vanes that act to convert mechanical energy to hydrokinetic energy and back to mechanical energy. The stator assembly of a conventional torque converter is locked against rotation in one direction but is free to spin about an axis in the direction of rotation of the impeller assembly and turbine assembly. When the stator assembly is locked against rotation, the torque is multiplied by the torque converter. During torque multiplication, the output torque is greater than the input torque for the torque converter. However; when there is no torque multiplication, the torque converter becomes a fluid coupling. Fluid couplings have inherent slip. Torque converter slip exists when the speed ratio is less than 1.0 (RPM input&gt;than RPM output of the torque converter). The inherent slip reduces the efficiency of the torque converter. 
     While torque converters provide a smooth coupling between the engine and the transmission, the slippage of the torque converter results in a parasitic loss, thereby decreasing the efficiency of the entire powertrain. Further, the torque converter itself requires pressurized hydraulic fluid in addition to any pressurized fluid requirements for the actuation of the gear shifting operations. This means that an automatic transmission must have a large capacity pump to provide the necessary hydraulic pressure for both converter engagement and shift changes. The power required to drive the pump and pressurize the fluid introduces additional parasitic losses of efficiency in the automatic transmission. 
     In an ongoing attempt to provide a vehicle transmission that has the advantages of both types of transmissions with fewer of the drawbacks, combinations of the traditional “manual” and “automatic” transmissions have evolved. A type of combination type transmission is commonly referred to as a dual clutch transmission. 
     Examples of dual clutch transmissions and control methods can be found by a review of U.S. Patents and Patent Application Publications U.S. Pat. Nos. 5,711,409; 6,966,989; 6,887,184; 6,909,955; 2006/0101933A1; and 2006/0207655A1 commonly assigned. 
     Dual clutch transmissions can be utilized in front wheel drive engines. When utilizing a dual clutch transmission in a transverse mounted engine, it is desirable to make the width of the transmission as short as possible. An example of a dual clutch transmission for a front wheel drive vehicle is shown in Patent Application 2008/004288. It is desirable to provide a dual clutch transmission suitable for a transverse mounted front wheel drive vehicle or other vehicle which is axially shorter than that described in Patent Application 2008/004288. 
     SUMMARY OF THE INVENTION 
     To meet the above noted and other desires, a revelation of the present invention is brought forth. 
     In a preferred embodiment, the present invention brings forth a vehicle dual clutch transmission which includes a dual clutch transmission for a vehicle. The transmission includes a first input shaft driven by a first clutch and a second input shaft driven by a second clutch. An output shaft or shafts are driven by the input shafts having selective meshed torsional force transferring gear contact therewith. A differential input gear is driven by the output shaft or shafts. At least one of the input shafts has at least one input gear that torsionally engages with the output shaft via an idler shaft having an idler shaft input gear torsionally connected on the idler shaft with an idler shaft output gear through a one-way clutch and wherein, the idler shaft output gear is meshed with another gear on the one input shaft. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a schematic view of a six speed version of a dual clutch transmission according to the present invention; 
         FIG. 2  is a sectional view of the transmission shown in  FIG. 1 ; 
         FIG. 3  is a schematic view of an alternative preferred embodiment dual clutch transmission according to the present invention; 
         FIG. 4  is a schematic view of another alternate preferred embodiment dual clutch transmission according to the present invention; and 
         FIG. 5  is still yet another alternate preferred embodiment dual clutch transmission according to the present invention. 
         FIG. 6  is a schematic side view of illustration the relative position of the components of the transmission shown in  FIGS. 1 and 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     Referring to  FIGS. 1 ,  2  and  6 , a transverse mounted engine (not shown) of a front wheel drive vehicle powers a six speed dual clutch transmission  7  of the present invention. The engine typically will have a fly wheel connected with a damper  14 . The damper is torsionally connected with a first clutch input shaft  16 . The first clutch input shaft  16  is connected with a first clutch housing  18 . The first clutch housing  18  is torsionally connected with a sprocket  20 . The sprocket  20  is torsionally connected with a chain  22 . The chain  22  is torsionally engaged with a second clutch housing sprocket  24 . The second clutch housing sprocket  24  is fixably connected with a second clutch housing  26 . The first clutch housing sprocket  20  has a diameter that is smaller than the diameter of the second housing sprocket  24 ; consequently, the first clutch housing  18  spins faster than the second clutch housing  26 . 
     The second clutch housing  26  is selectively connected with a hub  28  via a friction pack  30 . The housing  26  also has a gear that powers an output gear  29  powering an oil pump  37 . A clutch actuator piston  31  is provided to engage the friction pack  30  with the hub  28 . The hub  28  is torsionally connected with a second input shaft  32 . The second input shaft  32  has torsionally affixed thereto, a first gear ratio input gear  34 . The second input shaft  32  also has rotatably mounted thereon third gear ratio input gear  36  and fifth gear ratio input gear  38 . To torsionally selectively connect the fifth input gear  38  or the third input gear  36  with the second input shaft  32 , there is provided a fifth/third synchronizer  40 . 
     The first input gear  34  is continually meshed with an idler gear input gear  42 . The idler gear input gear  42  is rotatably mounted on an idler shaft  44 . The idler shaft input gear  42  is torsionally connected via a one-way clutch  46  with a idler shaft output gear  48 . The idler shaft output gear  48  is in continual mesh with the third input gear  36 . 
     Fifth input gear  38  is in mesh with a fifth output gear  50 . Third input gear  36  is meshed with a third output gear  52 . Output gears  50  and  52  are torsionally affixed to an output shaft  54 . Output shaft  54  also has torsionally affixed thereto a final drive pinion  56 . Final drive pinion  56  is meshed with a differential input gear  58 . Differential input gear  58  is a ring gear which is connected with a differential housing  60  which in turn drives two axial shafts  64  and  66 . In other embodiments, (not shown), the transmission can have dual output shafts similar to that shown in “DCT TRANSMISSION UTILIZING TWO AXIS CHAIN”, U.S. Provisional Application No. 61/269,781, filed Jun. 29, 2009, to Pritchard et al. 
     The first clutch housing  18  via a friction pack  70  is selectively torsionally engaged with a hub  72  which is splined to a first input shaft  74 . The first input shaft  74  rotatably mounts a reverse drive input gear  76 , a second gear ratio input gear  78 , a fourth gear ratio input gear  80  and a sixth gear ratio input gear  82 . The reverse drive or input gear  76  is in a bisecting coaxial plane of the final drive pinion  56 . To torsionally affix the reverse input gear  76  or the second input gear  78  with the first input shaft  74 , there is provided a second/reverse synchronizer actuator  84 . To torsionally connect the sixth input gear  82  or the fourth gear ratio input gear  80  with the first input shaft  74 , there is provided a sixth fourth synchronizer  86 . The reverse input gear  76  is continually meshed with a reverse idler shaft input gear  88  which is in turn torsionally connected via reverse idler shaft  90  with a reverse idler shaft output gear  92  which meshes with a second output gear  94 . Gear  50  also serves as an output gear for sixth input gear  82 . Gear  52  also functions as an output gear for the fourth input gear  80 . 
     In operation transmission  7  is powered by the damper  14  which is connected to the output shaft of an engine (not shown). The damper  14  dampens torsional vibrations provided by the reciprocating piston nature of the engine. The damper  14  rotates the clutch input shaft  16  and thus the clutch housing  18  and sprocket  20 . The sprocket  20  drives chain  22  that drives the larger sprocket  24  associated with the second clutch housing  26 . The second friction pack  30  is engaged by clutch piston  31  therefore, torsionally connecting the second clutch housing  26  with the hub  28  and the second input shaft  32 . The first gear  34  powers the idler shaft input gear  42  which in turn via one-way clutch  46  torsionally turns idler shaft output gear  48 . Rotation of output gear  48  causes rotation of the third input gear  36  and subsequent rotation of the third output gear  52 . Rotation of third output gear  52  causes rotation of the output shaft  54  and the final drive pinion  56  thereby torsionally turning differential input ring gear  58  and thereby rotating the differential shafts  66  and  64 . While the above is happening, according to the parameters of an electronic controller (not shown), the friction pack  70  is disengaged by depressurizing piston  73  and the force of biasing spring  91  and the synchronizer  84  is actuated leftward as shown in  FIG. 1  to torsionally connect the second gear  78  with the first input shaft  74 . When the controller signals for the transmission to engage in second gear, the friction pack  30  is released by depressurizing piston  31  and the force of biasing spring  33  and the friction pack  70  is engaged by piston  73 . The transmission  7  is now in second gear. The above noted sequence of operation is commonly referred to a pre-selecting sequence. In a non-pre-selecting sequence, the synchronizer  84  does not connect the second gear  78  to the first output shaft  74  until friction pack  30  is released. Although the remainder of the operation of transmission  7  as described in a pre-selecting mode, it is apparent to those skilled in the art, that a combination of both pre-selecting and non-pre-selecting modes can be utilized. After the shift to complete to second gear, to prepare for the shift to third gear, synchronizer  84  is brought to a neutral position allowing the second gear  78  to be torsionally disengaged from the first input shaft  74 . Simultaneously, fifth/third synchronizer  40  is moved rightward engaging third gear  36  with the second input shaft  32 . This movement is primarily completed while the friction pack  30  is disengaged. Upon re-engagement of the friction pack  30 , to connect the hub  28  with the clutch housing  26 , the rotation of the second input shaft  32  moves the third gear  36 . Third gear  36  now has torsional force transferring meshed contact with output gear  52  which in turn causes final drive pinion  56  to rotate the differential input gear  58 . While in third gear, idler shaft output gear  48  is spun about faster than the differential input gear  42  is spun by the first input gear  34 . Accordingly, the one-way clutch  46  allows a continual slippage and does not cause the combination of the third gear  36  first, gear  34  idler shaft output gear  48 , and idler  42  shaft input gear  42  and idle shaft input gear  48  to lock up. 
     To shift to fourth gear, the fifth/third synchronizer  40  is moved leftward to disengage the third gear  36 , simultaneously the friction pack  70  is engaged and synchronizer  86  engages the fourth gear  80  with the first input shaft  74 . To switch to the fifth gear  38 , friction pack  70  is disengaged. The fifth gear  38  previously engaged by synchronizer  40  meshes with output gear  50  and accordingly, turns the differential input ring gear  58 . For a switch to the sixth gear, synchronizer  86  is moved leftward engaging gear  82  with the first input shaft  74  while the friction pack  70  is disengaged. Synchronizer  40  is moved rightward disengaging the fifth gear  38  from the second input shaft  32 . After engagement with the shaft  74  and upon engagement of the friction pack  70 , sixth gear  82  has torsional force transferring meshed contact with gear  50 . Gear  50  causes the output shaft  54  to be rotated thereby rotating final drive output pinion  56  and input gear  58  of the differential  50 . 
     Referring to  FIG. 3 , a dual clutch transmission according to the present invention is provided. Transmission  107  in its structure and operation is almost identical to transmission  7  with the exception in that the input shaft  16  of the clutch of transmission has an axis coterminous with the input axis of the second input shaft  32  instead of the first input shaft  74  as shown in the prior transmission  7 . Although the structure and operation are virtually identical, there may be slight changes in some of the gear ratios for packing considerations. 
     Referring to  FIG. 4 , an alternate preferred embodiment transmission according to the present invention with identical or similar items which perform similar functions being given the same reference numeral. In the embodiment of the transmission  207 , the locations of the even numbered forward gears are switched with the sixth gear ratio  282  being most adjacent to the clutch housing  18  and fourth gear  280  being furthest away from clutch housing  218 . Fourth/second synchronizer  295  and sixth/reverse synchronizer  293  are provided on the first input shaft  274 . Additionally, the second gear  278  is moved leftward as compared with the location of the second gear  78  in the embodiment  107  transmission. Another change of transmission  207  is that the reverse idler shaft  290  is extended as compared with the reverse idler shaft  90  in the  107  transmission. Output gear  52  now functions as the output gear for the first gear  34  and, third gear  36 , second gear  278  and reverse idler shaft output gear  292 . 
     Referring to  FIG. 5 , an alternate embodiment transmission  307  of the present invention is shown. Transmission  307  varies from transmission  207  in that its third gear  336  is switched in position with its fifth gear  338 . Additionally, second input gear  378  is switched with its relative position with sixth input gear  382 . First gear  34  is continually meshed with idler input gear  342 . Idler gear  342  has a smaller diameter than idler output gear  348 . Idler output gear  348 , which is connected to idler input gear  342  through a one-way clutch  346 , is continually meshed with gear  396  which is rotatably mounted upon the second input shaft  32 . Output gear  352  serves as a common output gear for the second input gear  378  and the first gear  34  via its idler input  342  and output gears  348 . 
     The description of the invention is merely exemplary in nature and, thus, 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.