Abstract:
An arrangement of a vehicle is provided having normal transverse engine/transmission normal two-wheel drive operation which can be selectively placed into four-wheel drive operation wherein a pump which powers the coupling or uncoupling can be positioned downstream of a power takeoff unit without utilization of an electrically powered pump or transmission powered pump.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 61/987,608, filed May 2, 2014. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to arrangement of front wheel drive vehicles transverse mounted engines with four wheel drive capabilities upon demand. 
     BACKGROUND OF THE INVENTION 
     To increase fuel economy, many vehicles have been switched over to front wheel drive so that the vehicle engine&#39;s weight can be over the main traction axle of a vehicle. To further increase fuel economy, many front wheel drive vehicles utilize a transverse mounted engine and transmission. To provide improved performance in inclement weather, many vehicles have selective four wheel drive capabilities. Typically in most front wheel drive vehicles with four wheel drive capability, the transmission powers a front differential. Torsionally downstream of the front differential is a power takeoff unit (PTU). The PTU couples the front differential with a prop shaft extending longitudinally to a rear axle and differential. To maximize fuel efficiency in selective four wheel drive vehicles, it is desirable to torsionally not only cut off the rear axle from the vehicle engine, but additionally cause the propeller (prop) shaft and most of the PTU to stop rotating. For quickest actuation/shift time for the demand of four wheel drive, the PTU requires some type of hydraulic actuation from a pressure source. Typically, it is not desirable to use the transmission pump as a source of pressurized fluid since it is expensive to increase the capacity of the transmission pump and because of the hydraulic line routing required between the transmission and PTU. It has been customary that the PTU hydraulic actuation be supplied by an auxiliary electric pump so that the coupling and uncoupling of the prop shaft from the vehicle engine can occur when the vehicle has previously been in an uncoupled condition. It is desirable to provide an arrangement of a vehicle wherein a pump for the PTU can be placed torsionally downstream of the coupling/uncoupling mechanism while still not requiring an auxiliary electric pump. It is also desirable to provide the pressurized hydraulic fluid necessary for the coupling function without utilizing the hydraulic pump typically associated with the transmission. 
     SUMMARY OF THE INVENTION 
     To meet the above noted desires and to provide other advantages, a revelation of the present invention is brought forth. The present invention brings forth an arrangement of a vehicle having normal transverse engine/transmission normal two wheel drive operation which can be selectively placed into four wheel drive operation wherein the pump which powers the coupling or uncoupling can be downstream of the PTU that without utilization of an electrically powered pump or transmission pump. 
    
    
     
       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 the transmission in the arrangement of an automotive passenger vehicle having normal front-wheel drive and selective four-wheel drive 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 the remainder of a power train of the invention shown in  FIGS. 1 and 2 ; 
         FIG. 4  is a sectional with partial schematics of an actuator utilized for selectively coupling a rear axle input gear with a rear axle input shaft of the arrangement shown in  FIGS. 1-3 ; and 
         FIG. 5  is a partial sectional view of alternative embodiment actuator utilized in the arrangement of a normal front-wheel drive selective four-wheel drive vehicle illustrating an actuator for selectively coupling or uncoupling a rear axle input gear with a driving member. 
     
    
    
     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 3 , a transverse mounted engine  8  of a normally front wheel drive selectively four wheel drive vehicle arrangement powers a six speed dual clutch transmission  7  of the present invention. The engine  8  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 an 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 front differential casing  60  (sometimes referred to as a housing) 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 . 
     The front differential  60  casing  100  is torsionally connected with a rear input shaft  110 . The front differential also has a side gear connected with a wheel shaft  64 . The wheel shaft  64  is connected via a half shaft (not shown) with a wheel  113 . The wheel shaft  64  extends through a rear axle input shaft  110 . On the opposite side of the front differential  60  is a wheel shaft  66  which via a half shaft (not shown) is connected with a wheel  103 . 
     Referring additionally to  FIG. 4 , the casing  100  of the front differential in a manner similar to transmission  7  extends transversely to a main axis of the vehicle. The rear axle input shaft  110  is spline connected to the differential casing  100 . Rotatably mounted on the rear axle input shaft is a rear axle input gear  120 . The rear axle input gear  120  either directly or through a series of intermediate gears is torsionally connected with a prop shaft input gear  130 . Prop shaft input gear  130  is connected with a longitudinally rearward extending prop shaft  140 . The prop shaft  140  may be a single elongated member or a plurality of members joined by universal joints. The end of the prop shaft  140  has connected thereto an output gear  144 . The output gear  144  is torsionally connected with a ring gear  146  of a rear axle differential  150 . Rear differential  150  has a casing  152  with drive gears  154 . Drive gears  154  mesh with side gears  156 . Side gears  156  are connected with rear wheel shafts  158  which are in turn connected with rear wheels  160 . In a first state of operation the rear axle differential  150  differentially powers the rear wheels  160 . The rear axle differential  150  has a clutch  162  which can selectively couple the side gears  156  of the rear differential with the rear wheels  160 . When the clutch  162  is open, the ring gear  146  and the casing  152  and prop shaft output gear  144  and prop shaft  140  do not have rotational movement. However, the rear wheels  160  will rotate upon any movement of the vehicle even though the rear wheels  160  are unpowered. Rear axle differential  150  in a second state of operation wherein the clutch  162  is open, the wheels  160  are non-driven and can freewheel with respect to one another. 
     The rear axle input gear  120  is typically a helical gear that is mounted by bearings in the power take off unit  170 . The rear axle input gear has a shaft extension  172  having a flat  174  which is splined along its outer surface. The rear axle input shaft along its inner diameter also has a splined flat  176 . 
     To selectively couple the rear axle input gear  120  with the rear axle input shaft  110 , there is provided a shift collar  180 . The shift collar  180  is connected with and is translated by a shaft of a hydraulic actuator  190 . The hydraulic actuator  190  includes a cylinder  192 . A piston  194  is connected with the shaft  182 . The piston  194  sealably bifurcates the cylinder into two pressure chambers  196 ,  198  each side of the piston. The pressure in chamber  196  can be determined from a pressure sensor  204  and the pressure in chamber  198  can be determined from a pressure sensor  206 . Pressure chamber  196  is controlled by a solenoid  208  to either be fluidly connected with a pump  210  or a sump  212 . Pressure chamber  198  is controlled by a solenoid valve  212  to be alternatively connected with the pump  210  or with the sump  212 . A pressure sensor  216  monitors the pressure in the hydraulic line delivered by pump  210  after it passes through check valve  218 . Fluidly connected with the chambers  196  and  198  via the solenoid valves  208  and  214  respectively is an accumulator  230 . The pump  210  is torsionally connected with the rear axle output gear  120  and may be directly meshed therewith or with a gear downstream thereof or with a gear torsionally connected with the prop shaft  140 . However, when the gear  120  is not rotational, there is no power input into the pump  210 . 
     To provide for fluid pressure to power the actuator  190  (when the rear axle output gear  120  is not rotating), there is provided the accumulator  230 . The pressure in the actuator is monitored by the pressure sensor  216 . The accumulator  230  is fluidly connected with both the actuator  190  and the pump  210  and typically will be charged to an amount to have at least four engagements of the actuator to couple the rear axle input gear  120  with the rear axle input shaft  110  without being recharged. Therefore if the vehicle is in a two wheel drive mode of operation which is typically its normal mode of operation there is sufficient pressurized fluid within the accumulator  230  to actuate to translate the shift collar from its non-actuated position to its actuated position. Upon being actuated, hydraulic pressure will be developed by pump  210  and the accumulator  230  will be recharged. An advantage of the vehicle arrangement of the present invention is that an auxiliary electric pump is not required and it allows for advantages of placement of the hydraulic pump in a position wherein the pump is powered torsionally downstream of the rear axle input gear  120  to allow for better location of the pump. Additionally, hydraulic pressure is not required from the transmission  7  which would require a larger transmission pump and possibly cumbersome fluid line routing between the actuator and the transmission  7 . 
     Referring to  FIG. 5  an embodiment  307  of the present invention has a driving member or rear axle input shaft  310 . Shaft  310  is rotatably mounted within a PTU frame  312  by a bearing  314  and is sealed by a seal  396 . The frame  312  has a rectangular cross-sectional angular groove  316  with a first outer radius  318 . The frame  312  also has a second outer radius  320  and a third outer radius  322 . Second outer radius  320  is intersected with an applied pressure bore  326  and a release pressure bore  328 . 
     An aluminum piston  330  is provided. The piston  330  has a leg  332  aligned by the frame groove  316 . The piston leg  332  has an outer radial surface seal  334  to seal an apply chamber  336  that is fluidly connected with the apply pressure bore  326 . The seal  334  seals at the second radius  318 . The piston  330  also has a seal  338  sealing at radius  320  to separate the apply chamber  336  from a release chamber  342 . The release chamber  342  fluidly connects with the release pressure bore  328 . A stopper  344  has a seal  348  which seals chamber  342 . Stopper  344  has a point  352  that limits axial travel of a radial arm  354  of the piston  330 . The stopper  344  abuts a shoulder  358  of the frame  312 . The stopper  344  is held in position by a snap ring  360 . The stopper  344  inner radial surface is sealed by a piston seal  362  in a head  364  of the piston. Seal  362  is at the same radius as seal  334 . The seal  362  seals the apply pressure chamber  342 . Along its inner radius, the piston  332  has an annular groove to hold in a snap ring  370 . The snap ring  370  retains an aluminum blocker ring  372  against a shoulder  374  of the piston. The piston has a blocker portion  376 . A steel shift collar  380  is shown in  FIG. 5  spline connected along its inner radius with a driving member produced by the rear axle input shaft  310  and with an extension of a rear axle input gear  390 . The shift collar  380  has a head  392  covered with a polymeric plastic bumper  394  for contact with the blocker portion  376  of the piston and the blocker ring  374 . To actuate the shift collar  380  to connect the driven rear axle input shaft  310  with the rear axle input gear  390 , pressure chamber  336  is pressurized and pressure chamber  342  is relieved to sump. To disengage the rear axle of the vehicle to go back to two-wheel drive, pressure chamber  342  is pressurized and pressure chamber  336  is relieved to sump. A seal  392 , bearing  314 , piston  332 , shift collar  380 , and the remainder of the actuator components can all be assembled from the left side of the snap ring  360  as shown in  FIG. 5 . 
     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.