Electronically-controlled coupling for all-wheel drive system

A drive axle assembly for transferring drive torque from a vehicular powertrain to a pair of wheels, comprising:

• an input shaft adapted to receive drive torque from the powertrain;
• a pinion shaft;
• a first coupling operable for transferring drive torque from said input shaft to said pinion shaft, said first coupling including a clutch pack interconnected between said input shaft and said pinion shaft, a piston supported in a piston chamber for movement in response to fluid pressure exerted therein to apply a clutch engagement force to said clutch pack for transferring drive torque to said pinion shaft, a fluid sump, a pump having an inlet in communication with said sump and an outlet, an electric flow control valve having an inlet in communication with said pump outlet, a first outlet in communication with said piston chamber, a second outlet in communication with said sump, and a moveable valve element for regulating the control pressure of hydraulic fluid supplied through said first outlet to said piston chamber;
• speed sensors for detecting the rotary speeds of said input shaft and said pinion shaft;
• a first temperature sensor for detecting the fluid temperature at said sump;
• a second temperature sensor for detecting the fluid temperature at said second outlet of said control valve;
• a controller for receiving sensor signals from said speed sensors and said first and second temperature sensors and generating an electric control signal in response thereto that is sent to said electric control valve to control movement of said valve element;
• and
• a drive module for transferring drive torque from said pinion shaft to said axle shafts, said drive module including a drive case having a ring gear driven by a pinion gear fixed to said pinion shaft, a differential unit interconnecting said drive case to said axleshafts, and a second coupling operable disposed between said drive case and one of said axleshafts.

An all-wheel drive vehicle comprising:

• a powertrain including an engine and a transmission;
• a primary driveline driven by said powertrain for transferring drive torque to a pair of primary wheels;
• a power take-off unit driven by said primary driveline;
• and
• a secondary driveline including a drive axle assembly and a pair of secondary wheels, said drive axle assembly having an input shaft driven by said power take-off unit, a pinion shaft, a drive case driven by said pinion shaft, a pair of axleshafts connected to said secondary wheels, a differential interconnecting said drive case to said axleshafts so as to facilitate speed differentiation between said axleshafts, and a hydraulic coupling for transferring drive torque from said input shaft to said pinion shaft, said hydraulic coupling including a clutch pack operably connected between said input shaft and said pinion shaft, an actuator for applying a clutch engagement force on said clutch pack in response to fluid pressure exerted thereon, and a fluid control system capable of varying the fluid pressure exerted on said actuator, said fluid control system includes a source of hydraulic fluid, a pump having an inlet in communication with said fluid source and an outlet in communication with said actuator, and an electric control valve disposed between said pump outlet and said actuator for controllably regulating the control pressure exerted on said actuator;
• speed sensors for determining a speed difference between said input shaft and said pinion shaft;
• a first temperature sensor for detecting the fluid temperature at said fluid source;
• a second temperature sensor for detecting the fluid temperature at said clutch pack;
• and
• a traction control unit receiving speed signals from said speed sensors and temperature signals from said first and second temperature sensors and generating an electric control signal in response thereto, said electric control signal is supplied to said electric control valve for varying the control pressure as a function of said electric control signal.

An all-wheel drive vehicle comprising:

• a powertrain including an engine and a transmission;
• a primary driveline driven by said powertrain for transferring drive torque to a pair of primary wheels;
• a power take-off unit driven by said primary driveline;
• a secondary driveline including a drive axle assembly and a pair of secondary wheels, said drive axle assembly having an input shaft driven by said power take-off unit, a pinion shaft, a first torque coupling operable for transferring drive torque from said input shaft to said pinion shaft, said first torque coupling including a clutch pack interconnected between said input shaft and said pinion shaft, a piston supported in a piston chamber for movement in response to fluid pressure exerted thereon to apply a clutch engagement force to said clutch pack for transferring drive torque to said pinion shaft, a pump having an inlet in communication with a sump and an outlet, and an electric flow control valve, said control valve having an inlet in communication with said pump outlet, a first outlet in communication with said piston chamber, a second outlet in communication with said sump, and a valve element that is moveable for regulating the control pressure of hydraulic fluid supplied through said first outlet to said piston chamber;
• speed sensors for detecting the rotary speeds of said input shaft and said pinion shaft;
• a first temperature sensor for detecting the temperature of fluid in said sump,
• a second temperature sensor for detecting the fluid temperature at said second outlet of said control valve;
• a controller for receiving sensor signals from said speed sensors and said first and second temperature sensors and generating an electric control signal in response thereto that is sent to said electric control valve to control movement of said valve element, and
• a drive module for transferring drive torque from said pinion shaft to said secondary wheels, said drive module including a drive case having a ring gear driven by a pinion gear fixed to said pinion shaft, a differential interconnecting said drive case to said secondary wheels, and a second torque coupling operable disposed between said drive case and one of said secondary wheels.