Electronically-controlled rear module for all-wheel drive system
A drive axle assembly for an all-wheel drive vehicle includes an adaptively controlled first hydraulic coupling for providing front-to-rear torque transfer control to a first wheel and an adaptively controlled second hydraulic coupling for providing front-to-rear torque control to a second wheel. The drive axle assembly is contained with a common housing and communicates with a traction control system to actively control actuation of the first and second hydraulic couplings based on the operating characteristics of the vehicle as detected by suitable sensors.
1. A drive axle assembly for use in a motor vehicle to transfer drive torque from a powertrain to a pair of wheels, comprising:
a housing defining a pump chamber, a gear chamber, and first and second clutch chambers;
a pinion shaft adapted to receive drive torque from the powertrain and having a shaft segment extending through said pump chamber and a pinion gear disposed in said gear chamber;
a drive assembly supported for rotation in said gear chamber and having a ring gear meshed with said pinion gear;
a first output shaft supported for rotation relative to said housing and said drive assembly and adapted for connection to one of the wheels;
a second output shaft supported for rotation relative to said housing and said drive assembly and adapted for connection to the other of the wheels;
a first hydraulic coupling located within said first clutch chamber and including a first transfer clutch operably disposed between said drive assembly and said first output shaft, a first piston for engaging said transfer friction clutch in response to fluid pressure exerted thereon, and a first control valve for controlling the fluid pressure exerted on said first piston;
a first seal mechanism for providing a fluid-tight seal between said first clutch chamber and said gear chamber;
a second hydraulic coupling located within said second clutch chamber and including a second transfer clutch operably disposed between said drive assembly and said second output shaft, a second piston for engaging said second transfer clutch in response to fluid pressure exerted thereon, and a second control valve for controlling the fluid pressure exerted on said second piston;
a second seal mechanism for providing a fluid-tight seal between said second clutch chamber and said gear chamber;
a pump disposed in said pump chamber and driven by said pinion shaft for supplying pressurized fluid to said first and second control valves; and
a traction control system including speed sensors for detecting the rotary speed of at least two of said pinion shaft and said first and second output shafts, a first temperature sensor for detecting the fluid temperature in said first clutch chamber, a second temperature sensor for detecting the fluid temperature in said second clutch chamber, and a control unit receiving signals from said speed sensors and said temperature sensors and generating control signals in response thereto, said control signals delivered to said first and second control valves to independently vary the fluid pressure exerted on said first and second pistons.
2. The drive axle assembly of claim 1 wherein said control unit includes logic for controlling actuation of said first control valve in response to predetermined relationships related to speed differences between said pinion shaft and said first output shaft.
3. The drive axle assembly of claim 2 wherein said logic is further operable to control actuation of said second control valve in response to predetermined relationships related to speed differences between said pinion shaft and said second output shaft.
4. The drive axle assembly of claim 1 wherein said logic is further operable to control actuation of said first and second control valves in response to speed differences between said first and second output shafts.
5. The drive axle assembly of claim 1 wherein said logic is further operable to compensate for changes in fluid viscosity based on the fluid temperature detected by a third temperature sensor.
6. The drive axle assembly of claim 1 wherein said control unit is adapted to open said first control valve and vent fluid for releasing engagement of said first transfer clutch when the fluid temperature detected by said first temperature sensor exceeds a predetermined value.
7. The drive axle assembly of claim 1 further comprising an accumulator in fluid communication with an outlet of said pump and an inlet to each of said first and second control valves.
8. The drive axle assembly of claim 1 wherein a first fluid is entrained in said gear chamber and a second fluid is entrained in said first and second clutch chambers and is in fluid communication with said pump.
9. The drive axle assembly of claim 1 wherein said housing includes a gear housing, first and second support plates fixed to said gear housing to define said gear chamber therebetween, a first clutch housing fixed to said first support plate to define said first clutch chamber therebetween, and a second clutch housing fixed to said second support plate to define said second clutch chamber therebetween.
10. The drive axle assembly of claim 1 wherein said housing further includes a pump housing fixed to said gear housing to define said pump chamber therebetween.