Latched-pump applied clutch
A latched-pump applied clutch circuit is provided for a vehicle transmission having a controllable pump, a controllable pump pressure, and a main sump, the latched-pump applied clutch circuit comprising a clutch, a clutch piston disposed within a cylinder, a plurality of fluid passages, an accumulator, and one or more solenoid valves in fluid communication with the accumulator for building of a backside boost pressure within the accumulator. The backside boost pressure is used to increase, boost, or otherwise assist clutch-apply pressure within the latched-pump applied clutch circuit during transient periods requiring increased torque capacity. The circuit may include an alternative electro-mechanical device for directly applying a controllable backside boost pressure independent of the controllable pump pressure.
1. A vehicle transmission comprising:
a controllable hydraulic pump operable for generating a line pressure;
a latched-pump applied clutch (LPAC) circuit including:
a clutch in fluid communication with said hydraulic pump, said clutch including:
a clutch cylinder having a variable clutch-apply pressure; and
a clutch-apply piston disposed within said clutch cylinder;
an accumulator in fluid communication with said hydraulic pump and said clutch-apply piston, said accumulator containing an accumulator piston and being operable for accumulating a boost pressure as a compressive force acting on a first side of said accumulator piston, and for selectively transmitting said boost pressure to said clutch from a second side of said accumulator piston that is opposite said first side to temporarily increase said variable clutch-apply pressure in response to predetermined conditions; and
a plurality of valves including a first valve in fluid communication with each of said hydraulic pump and said accumulator at said first side of said accumulator piston for selectively admitting said boost pressure into said accumulator, and with said clutch at said second side of said accumulator piston, and a second valve in fluid communication with each of said hydraulic pump and said clutch-apply piston and positioned therebetween for admitting said pressurized fluid into said clutch cylinder to thereby provide at least part of said variable clutch-apply pressure;
wherein the selective transmission of said boost pressure to said clutch-apply piston temporarily increases said variable clutch-apply pressure by boosting said line pressure, and wherein said first valve opens when said clutch is in one of a fully engaged state and a disengaging state, and wherein said second valve opens when said clutch is in one of an engaging state and a disengaging state, both of said first and said second valves otherwise remaining closed.
2. The transmission of claim 1 , wherein said first valve is operable for shifting between an open state and a closed state, and is further configured to selectively exhaust said pressurized fluid, and wherein said second valve is configured for selectively latching to thereby capture and seal off said pressurized fluid.
3. The transmission of claim 1 , wherein said boost pressure is transmittable to said clutch-apply piston when said variable clutch-apply pressure falls below a predetermined level.
4. The vehicle transmission of claim 1 , wherein said predetermined conditions are selected from the group consisting essentially of: a step-in throttle condition and a leak-induced pressure loss within said LPAC circuit.
5. A vehicle transmission comprising:
a controllable hydraulic pump;
a latch-applied clutch (LPAC) circuit in fluid communication with said hydraulic pump and having:
a clutch cylinder containing a clutch-apply piston, said clutch-apply piston being selectively moveable using a variable clutch-apply pressure;
an accumulator in fluid communication with said pump and said clutch cylinder, said accumulator having an accumulator piston adapted to transmit a boost pressure to said clutch-apply piston;
an electro-mechanical device operatively connected to said accumulator and operable to directly apply said boost pressure to said accumulator piston; and
a valve in fluid communication with said hydraulic pump and said clutch-apply piston for selectively capturing and sealing off a line pressure provided from said hydraulic pump to the LPAC circuit;
wherein said accumulator is adapted to selectively transmit said boost pressure to said clutch-apply piston using said accumulator piston to thereby temporarily boost said variable clutch-apply pressure in response to at least one predetermined condition, wherein said variable clutch-apply pressure is defined by the sum of said boost pressure and said line pressure.
6. The transmission of claim 5 including a main sump, wherein said accumulator is continuously exhaustible to said main sump.
7. The transmission of claim 5 , wherein said boost pressure is transmittable from said accumulator to said clutch-apply piston when said clutch-apply pressure falls below a predetermined level.
8. The transmission of claim 5 , wherein said at least one predetermined condition is selected from the group consisting essentially of: a step-in throttle condition and a leak-induced pressure loss within the LPAC circuit.