Hydraulic actuator for clutch assemblies

A vehicle drive system comprising:

• a first shaft having a first shaft clutch disc which is rotatable with said first shaft;
• a second shaft having a second shaft clutch disc which is rotatable with said second shaft;
• and
• an actuator for forcing said first and second shaft clutch discs towards each other to control the relative torque between said first and second shafts, said actuator comprising at least a first piston in contact with said first shaft clutch disc, a second piston received in a fluid chamber, a motor for reciprocating said second piston within said fluid chamber, and a fluid line connecting a face of said second piston with a face of said first piston, such that reciprocation of said second piston in said fluid chamber causes movement of said first piston towards and away from said first shaft clutch disc to control the relative torque between said first and second shafts.

A clutch control system comprising:

• a first piston for selective engagement with a clutch disc;
• a second piston received in a fluid chamber, a motor for reciprocating said second piston within said fluid chamber, said motor comprising a ball screw arrangement such that the reciprocation of said second piston in said chamber may be quickly and accurately controlled;
• and
• a fluid path connecting said fluid chamber and said first piston, said fluid chamber and said fluid path adapted to receive a fluid such that reciprocation of said second piston in said second chamber causes corresponding reciprocation of said first piston.