Electronic Differential: Notes

Courtesy of JAGUAR CARS, INC.

The electronic differential has the same functionality as the open differential, but it also incorporates a locking and torque biasing function to give improved traction performance and vehicle dynamic stability.

The basic construction of the electronic differential is similar to the open differential. However, the electronic differential also has the following:

• Two additional planet gears in the differential case, to cater for the higher torque of the supercharger (SC) engine.
• A multi-plate clutch and actuator assembly installed on the left-hand (LH) sun gear.
• A motor and reduction gearbox, attached to the cover.
• A temperature sensor installed in the cover.

The DLM (differential locking module) operates the motor of the electronic differential under the control of the ADCM (adaptive damping control module).

Exploded View of Electronic Differential

Courtesy of JAGUAR CARS, INC.

The multi-plate clutch is contained in a clutch basket attached to the differential case with the drive gear securing bolts. Alternate plates of the clutch pack are keyed to the clutch basket and the left-hand (LH) sun gear. A pressure disc is installed on the outer end of the clutch pack and keyed to the clutch basket. A thrust plate on the end of the clutch basket incorporates lugs which extend through the clutch basket onto the pressure disc.

The actuator assembly is mounted on bearings on the outboard end of the clutch basket, against the thrust race. The actuator assembly consists of input and output actuators separated by five ball bearings. A locking pin in the cover engages with a slot in the output actuator to prevent it turning, but allow it to move axially. The input actuator engages with the reduction gearbox and is free to rotate relative to the cover. Ball bearings locate in curved grooves in the mating faces of the input and output actuators. The bottom surface of each groove incorporates a ramp. Rotation of the input actuator forces the ball bearings up the ramps in the grooves and induces an axial movement in the output actuator. The thrust race and pressure disc transfer the axial movement from the output actuator to the clutch pack.

Section Through Multi-plate Clutch

Courtesy of JAGUAR CARS, INC.

The motor is a 12 Vdc motor that adjusts the frictional loading of the multi-plate clutch, via the reduction gearbox and the actuator assembly, under the control of the DLM. Adjusting the frictional loading of the multi-plate clutch adjusts the locking torque between the crown wheel drive gear and the sun gear.

Four bolts attach the motor to the reduction gearbox, which is located in position on the cover with two dowels, and secured with four bolts. An O-ring seals the joint between the motor and the reduction gearbox.

The motor is driven by a 12 V PWM (pulse width modulated) feed from the DLM. The motor also incorporates the following connections with the DLM:

• A motor temperature sensor, to prevent excessive use from damaging the motor.
• Two Hall effect motor position sensors, to enable closed loop control of the motor.

The temperature sensor provides a differential oil temperature signal to the DLM, to prevent excessive use from damaging the multi-plate clutch.