All-wheel drive with active dry disconnect system

Abstract

A vehicle drive train for transferring torque to first and second sets of wheels includes a first driveline adapted to transfer torque to the first set of wheels and a first power disconnection device. A second driveline is adapted to transfer torque to the second set of wheels and includes a second power disconnection device. A hypoid gearset is positioned within one of the first driveline and the second driveline in a power path between the first and second power disconnection devices. The hypoid gearset is selectively disconnected from being driven by the first driveline and the second driveline when the first and second power disconnection devices are operated in a disconnected, non-torque transferring, mode. At least one of the first and second power disconnection devices includes an active dry friction clutch.

1 . A vehicle drive train for transferring torque to first and second sets of wheels, the drive train comprising:
 a first driveline being adapted to transfer torque to the first set of wheels and including a first power disconnection device;   a second driveline being adapted to transfer torque to the second set of wheels and including a second power disconnection device; and   a hypoid gearset positioned within one of the first driveline and the second driveline in a power path between the first and second power disconnection devices, wherein the hypoid gearset is selectively disconnected from being driven by the first driveline and the second driveline when the first and second power disconnection devices are operated in a disconnected, non-torque transferring, mode, wherein at least one of the first and second power disconnection devices includes an active dry friction clutch.   
     
     
         2 . The vehicle drive train of  claim 1  wherein the first power disconnection device is positioned within a power take-off unit and includes a multi-plate clutch. 
     
     
         3 . The vehicle drive train of  claim 2  wherein the first driveline includes a differential assembly having an output coupled to the multi-plate clutch. 
     
     
         4 . The vehicle drive train of  claim 1  wherein the second driveline includes another hypoid gearset driven by the hypoid gearset and positioned in the power path between the first and second power disconnection devices. 
     
     
         5 . The vehicle drive train of  claim 1  wherein the second power disconnection device includes a clutch for selectively connecting separate portions of an axle shaft adapted to drive one of the wheels of the second set of wheels. 
     
     
         6 . The vehicle drive train of  claim 5  further including a third power disconnection device including a clutch for selectively connecting separate portions of another axle shaft adapted to drive the other of the wheels of the second set of wheels, wherein the second and third power disconnection devices include dry friction clutches. 
     
     
         7 . The vehicle drive train of  claim 5  wherein the second power disconnection device is one of a synchronizer and a roller clutch operable to connect members rotating at different speeds. 
     
     
         8 . The vehicle drive train of  claim 1  wherein the first power disconnection device is positioned within a transfer case and includes an active dry multi-plate clutch. 
     
     
         9 . A vehicle drive train for transferring torque from a power source to first and second sets of wheels, the drive train comprising:
 a first driveline adapted to transfer torque from the power source to the first set of wheels and including a power take-off unit, the power take-off unit including a hypoid gearset and a first power disconnection device selectively ceasing the transfer of torque to the hypoid gearset; and   a second driveline in receipt of torque from the hypoid gearset, the second driveline transferring torque to the second set of wheels and including a second power disconnection device selectively interrupting a transfer of torque from the second set of wheels to the hypoid gearset, wherein one of the first and second power disconnection devices includes an active dry friction clutch.   
     
     
         10 . The vehicle drive train of  claim 9  wherein the power take-off unit includes a drive gear rotatably supported on an input shaft, the first power disconnection device including a clutch having a hub fixed for rotation with the input shaft, a drum fixed for rotation with the drive gear and a plurality of clutch plates alternatively fixed for rotation with the hub and the drum. 
     
     
         11 . The vehicle drive train of  claim 10  wherein the power take-off unit includes a countershaft having a driven gear in meshed engagement with the drive gear, a ring gear of the hypoid gearset being fixed for rotation with the countershaft. 
     
     
         12 . The vehicle drive train of  claim 11  wherein the power take-off unit includes a pump supplying pressurized fluid to a piston applying an actuation force to the clutch. 
     
     
         13 . The vehicle drive train of  claim 9  wherein the first driveline includes a differential assembly having an output coupled to the multi-plate clutch. 
     
     
         14 . The vehicle drive train of  claim 9  wherein the second driveline includes a rear driving axle including a ring and pinion gearset, a differential assembly and the second power disconnection device, the differential assembly including a carrier containing a pair of pinion gears in meshed engagement with a pair of side gears, the carrier being fixed for rotation with a first rotatable member of the second power disconnection device, the ring being fixed for rotation with a second rotatable member of the second power disconnection device. 
     
     
         15 . The vehicle drive train of  claim 14  wherein the carrier includes opposed axially extending first and second journals, wherein the first journal is fixed for rotation with the first rotatable member and the second journal rotatably supports the second rotatable member. 
     
     
         16 . The vehicle drive train of  claim 9  further including an actuator for applying a compressive load to the dry friction clutch and varying the magnitude of torque transferred to the first driveline. 
     
     
         17 . The vehicle drive train of  claim 9  wherein the other of the first and second power disconnection devices includes one of a roller clutch and a synchronizer. 
     
     
         18 . A vehicle drive train for transferring torque to first and second sets of wheels, the drive train comprising:
 a first driveline being adapted to transfer torque to the first set of wheels and including a first power disconnection device;   a second driveline being adapted to transfer torque to the second set of wheels; and   a transfer case adapted to transfer torque from the power source to the first and second drivelines, the transfer case including a second power disconnection device including an actively controlled dry friction clutch operable to selectively connect and disconnect the power source with a hypoid gearset, the hypoid gearset being positioned within the first driveline in a power path between the first and second power disconnection devices, wherein the hypoid gearset is selectively disconnected from being driven by the first driveline and the second driveline when the first and second power disconnection devices are operated in a disconnected, non-torque transferring, mode.   
     
     
         19 . The vehicle drive train of  claim 18  wherein the transfer case includes an input shaft adapted to be driven by the power source, a rear output shaft driving the second driveline and a front output shafting driving the first driveline. 
     
     
         20 . The vehicle drive train of  claim 19  wherein the transfer case includes an actuator for applying a compressive load to the dry friction clutch and varying the magnitude of torque transferred to the first driveline. 
     
     
         21 . The vehicle drive train of  claim 20  wherein the actuator includes an electric motor driving a force multiplier. 
     
     
         22 . The vehicle drive train of  claim 21  wherein the first driveline includes another actuator for placing the first power disconnection device in one of a torque transferring and a non-torque transferring mode. 
     
     
         23 . The vehicle drive train of  claim 22  further including a controller in receipt of a signal indicative of a speed of rotation of the hypoid gearset, the controller controlling actuation of the first and second power disconnection devices.