AWD vehicle with active disconnect coupling having multi-stage ball ramp

A disconnectable driveline for a motor vehicle having a power source supplying drive torque to a set of primary wheels, the disconnectable driveline comprising:

• a power take-off unit having a first hypoid gearset and a first disconnect clutch operable for selectively interrupting the supply of drive torque from the power source to the first hypoid gearset;
• a propshaft driven by the first hypoid gearset;
• an axle assembly including an axle housing rotatably supporting first and second axle shafts driving a set of secondary wheels, a second hypoid gearset rotatably supported by the axle housing and driven by the propshaft, a differential assembly driven by the second hypoid gearset, and a second disconnect clutch operable for selectively interrupting the supply of drive torque from the differential assembly to the secondary wheels, wherein the second disconnect clutch includes a first rotary component connected for rotation with a first output gear of the differential assembly, a second rotary component connected for rotation with the second axle shaft, a clutch pack of interleaved clutch plates disposed between the first and second rotary components, an apply plate axially moveable relative to the clutch plates for applying a clutch engagement force to the clutch pack, and a ball ramp actuator operable for controlling axial movement of the apply plate and configured to provide a first rate of apply plate travel to eliminate clearances and minimize spacing between the clutch plates and a second lesser rate of apply plate travel to vary a magnitude of a clutch engagement force to control torque transmitted through the second disconnect clutch;
• a control system for controlling actuation of the ball ramp actuator, wherein the ball ramp actuator includes a first cam member having a first groove, a second cam member having a second groove, and a roller disposed in rolling engagement with the first and second grooves, wherein relative rotation between the first and second cam members causes the second cam member to translate for axially translating the apply plate, wherein the first groove defines a first angled portion and second angled portion, wherein the second groove defines a third angled portion and a fourth angled portion, wherein the first and third angled portions extend along lengths at first angles to establish the first rate of axial apply plate travel and the second and fourth angled portions extend along lengths at second angles to establish the second rate of axial apply plate travel, and wherein the ball ramp clutch actuator reduces frictional losses by maximizing distances between the interleaved clutch plates when disconnected.

A drivetrain for a vehicle having a power source and first and second sets of wheels, comprising:

• a first driveline for transferring power from the power source to the first set of wheels;
• a power take-off unit including a first hypoid gearset and a first disconnect coupling for selectively cutting off the transfer of torque from the power source to said first hypoid gearset;
• a second driveline operably connected with said first hypoid gearset of said power take-off unit for transferring power to the second set of wheels;
• said second driveline including a second hypoid gearset and a propeller shaft extending between said first and second hypoid gearsets and a differential which is driven by said second hypoid gearset and a second disconnect coupling for selectively cutting off the transfer of torque between the second set of wheels and said second hypoid gearset;
• said second disconnect coupling including a multi-plate clutch with a plurality of clutch plates that are interleaved with one another and including a ball ramp clutch actuator for moving said interleaved clutch plates into and out of engagement with one another and for controlling the transfer of torque between the second set of wheels and said second hypoid gearset when said interleaved clutch plates are in engagement with one another, wherein the ball ramp clutch actuator includes a first cam member having a first groove, a second cam member having a second groove, and a roller disposed in rolling engagement with the first and second grooves, wherein relative rotation between the first and second cam members causes the second cam member to translate for axially translating the apply plate, wherein the first groove defines a first angled portion and a second angled portion, wherein the second groove defines a third angled portion and a fourth angled portion, and wherein the first and third angled portions have the same angle and extend along complementary lengths of the first and second grooves, respectively, to establish a first rate of axial apply plate travel in response to the relative rotation between the first and second cam members and, wherein the second and fourth angled portions have the same angle, different from the first and third angled portions, and extend along complementary lengths of the first and second grooves, respectively, to establish the second rate of axial apply plate travel in response to the relative rotation between the first and second cam members, wherein the first rate of axial apply plate travel is larger than the second rate of axial apply plate travel, and wherein the ball ramp clutch actuator reduces frictional losses by maximizing distances between the interleaved clutch plates when disconnected.