Electronically-tuned hydromechanical coupling

A drive axle assembly for use in a motor vehicle to transfer drive torque from a powertrain to a pair of wheels, comprising:

• a hydromechanical coupling having an input shaft driven by the powertrain, a pinion shaft, a transfer clutch disposed in a clutch chamber between said input shaft and said pinion shaft, a piston disposed in a piston chamber and actuatable to engage said transfer clutch for transferring drive torque from said input shaft to said pinion shaft a fluid pump for pumping hydraulic fluid from a sump to said piston chamber in response to relative rotation between said input shaft and said pinion shaft;
• first and second output shafts adapted for connection to the pair of wheels;
• a differential assembly including a casing driven by said pinion shaft and a gearset interconnecting said casing to said first and second output shafts;
• a primary fluid control system including a first flow path communicating with said piston chamber, a second flow path communicating with said clutch chamber, and a control valve operable in a first mode to prevent fluid flow from said first flow path to said second flow path and in a second mode to permit fluid flow from said first flow path to said second flow path;
• a secondary fluid control system including a second pump operable for pumping fluid from said sump into said first flow path and an electric motor for controlling the fluid pressure generated by said second pump;
• and
• a traction control system including sensors for detecting operating characteristics of the motor vehicle and a control module for receiving signals from said sensors and controlling actuation of said control valve and said electric motor in response thereto.

A hydraulic coupling for transferring drive torque from a power source to an output member, comprising:

• an input shaft driven by the power source and having a first flow passage;
• an output shaft driving the output member;
• an intermediate shaft disposed between said input shaft and said output shaft, said intermediate shaft having a second flow passage in communication with said first flow passage;
• a piston housing driven by said input shaft and defining a pump chamber and a piston chamber, said piston housing having a third flow passage in communication with said second flow passage;
• a fluid pump disposed in said pump chamber and having a first component driven by said intermediate shaft and a second component driven by said piston housing such that relative rotation therebetween causes said fluid pump to pump hydraulic fluid from a sump to said piston chamber;
• a transfer clutch including a drum fixed for rotation with said input shaft, a hub coupling said intermediate shaft to said output shaft, and a clutch pack operably disposed between said drum and said hub;
• a piston disposed in said piston chamber and moveable to engage said clutch pack in response to the fluid pressure in said piston chamber;
• a control valve having an inlet in fluid communication with said first flow passage and an outlet in fluid communication with a fourth flow passage supplying fluid to lubricate and cool said clutch pack;
• a pressure relief valve operable to vent fluid from said first flow passage to said fourth flow passage when the fluid pressure in said piston chamber exceeds a predefined pressure value;
• and
• a traction control system for determining a speed difference between said input shaft and said output shaft and controlling actuation of said control valve in response thereto.

A drive axle for use in a motor vehicle to transfer drive torque from a powertrain to a pair of wheels, comprising:

• a housing;
• an input shaft rotatably supported within said housing and adapted to be driven by the powertrain;
• a torque transmission mechanism supported by said housing and driven by said input shaft, said torque transmission mechanism comprising a first transfer clutch operably interconnecting said input shaft and a pinion shaft, a first piston selectively moveable in a first piston chamber to engage said first transfer clutch, and a pump for selectively pumping hydraulic fluid to said first piston chamber for actuating said first piston;
• a differential assembly supported within said housing, and including a drive case rotatably driven by said pinion shaft, first and second output shafts driven by said drive case and adapted for connection to the wheels, a second transfer clutch operably disposed between said drive case and said first output shaft, and a second piston moveable in a second piston chamber to engage said second transfer clutch for limiting relative rotation between said drive case and said first output shaft;
• and
• a fluid control system having a control flow path in communication with said first piston chamber, a return flow path in communication with said first transfer clutch, a supply flow path in communication with said second piston chamber, a first electric control valve for selectively venting fluid from said control flow path to said return flow path, a second electric control valve for selectively venting fluid from said control flow path to said supply flow path, a third control valve for selectively venting fluid from said first piston chamber to a sump, and a traction control module to control actuation of said first and second control valves.