Engine Start

Engine Start

When the vehicle is operating with the internal combustion engine OFF and auxiliary fluid pump ON, and the HPCM determines that vehicle operating conditions (low state of charge) are appropriate for starting the internal combustion engine (ICE), it commands the following changes to the transmission's hydraulic and electrical systems.

Torque Dampener Clutch Applies

Pressure Control (PC) Solenoid 5

The PC solenoid 5 is energized (ON) allowing actuator feed limit fluid to enter the PCS 5 signal circuit. PCS 5 signal fluid is then routed through orifice #13 to the dampener bypass clutch valve.

Dampener Bypass Clutch Valve

PCS 5 signal fluid, at the dampener bypass clutch valve, opposes dampener bypass clutch valve spring force and orificed dampener clutch fluid pressure to regulate line or auxiliary line pressure into the dampener clutch circuit. Dampener clutch fluid is routed to the torque dampener clutch.

Torque Dampener Clutch Assembly

A feed hole in the input shaft allows fluid to enter the torque dampener assembly behind the torque dampener clutch piston. Dampener clutch fluid pressure moves the dampener clutch piston against spring force to apply the dampener clutch plates. When fully applied, the dampener clutch apply plate, the dampener clutch plates, and the dampener clutch plate assemblies are locked together, forming a direct mechanical connection between the engine flywheel and the transmission input shaft. With the engine flywheel and transmission input shaft locked together, the HPCM is able to use the generator/drive motor - unit A (107, 108) to start the ICE. The torque dampener clutch may be applied in any range when the vehicle is operating with the internal combustion engine OFF.

Engine Start