Control method and apparatus for a transmission clutch system

A method for controlling the hydraulic actuation of a selectively engageable torque transmitting device in a hybrid electric vehicle comprising:

• generating a predetermined pressure level of a hydraulic fluid;
• transferring the pressurized hydraulic fluid through an open valve and to the selectively engageable torque transmitting device such that the selectively engageable torque transmitting device is engaged;
• closing the valve so that the predetermined pressure level of hydraulic fluid at the selectively engageable torque transmitting device remains relatively constant, wherein the selectively engageable torque transmitting device remains engaged without requiring the continuous generation of pressure such that the fuel economy of the hybrid electric vehicle is improved;
• monitoring the pressure of the hydraulic fluid at a point between the valve and the selectively engageable torque transmitting device;
• and
• generating additional pressure if the monitored pressure of the hydraulic fluid drops below a predefined minimum pressure.

An apparatus for controlling the hydraulic actuation of a selectively engageable torque transmitting device in a hybrid electric vehicle comprising:

• a hydraulic fluid distribution device configured to transfer hydraulic fluid at a predetermined pressure level;
• a selectively engageable torque transmitting device in fluid communication with the distribution device, the selectively engageable torque transmitting device configured to engage when pressurized hydraulic fluid at the predetermined pressure level is transferred thereto;
• and
• said selectively engageable torque transmitting device, a latching valve configured to selectively open and thereby allow the transfer of pressurized hydraulic fluid from the distribution device to the selectively engageable torque transmitting device such that the selectively engageable torque transmitting device is engaged, said latching valve thereafter controllable to close so that the predetermined pressure level of hydraulic fluid at the selectively engageable torque transmitting device remains relatively constant, wherein the selectively engageable torque transmitting device remains engaged without requiring continuous generation of pressure such that the fuel economy of the hybrid electric vehicle is improved.