Hydraulic control system for a clutch and transmission

Claim 1

A fluid control system for use in the combination which includes an input member, a continuously variable transmission connected to drive the input member, an output member, first and second drive trains, a fluid-actuated clutch engageable for coupling said input member with the selected one of said drive trains, and means for selectively engaging one of said drive trains with said output member to establish a torque delivery path from said input member to said output member, said fluid control system comprising: a first fluid control valve, a second fluid control valve, a pressure modulator valve with a first end and a second end, a first conduit communicating between said first and second control valves, an input conduit communicating between a source of fluid at a line pressure and said modulator valve, a sump for receiving fluid at a second pressure lower than said line pressure, a second conduit communicating between said modulator valve and said first fluid control valve, a third conduit communicating between said sump and said first and second fluid control valves, a fourth conduit communicating between said second fluid control valve and said fluid actuated clutch, a fifth conduit communicating between said fluid actuated clutch and said modulator valve first end, and a sixth conduit communicating between said second conduit and said second end of said modulator valve; a fluid motor including a housing, a slidable piston positioned in said housing to define a first variable volume chamber on one side of said slidable piston and a second variable volume chamber on the other side of said slidable piston, connecting means operatively connecting said piston to said selective engaging means and to said second fluid control valve; a seventh and an eighth conduit communicating between said first fluid control valve and said fluid motor first and second variable volume chambers, respectively, to supply fluid under pressure to move said fluid motor, said second fluid control valve, and said engaging means to effect selective engagement of one of said drive trains, movement of said second fluid control valve initially interrupting fluid flow to said clutch and thereafter completing a fluid flow path for fluid communication from said input conduit through said modulator valve and said first and second fluid control valves to move said fluid-actuated clutch to engagement only after selective engagement of one of said drive trains for completion of said torque delivery path between said input and output members, and fluid pressure from said fluid actuated clutch providing, through said fifth conduit, a biasing force to said modulator valve first end to control flow through said modulator valve.