Limiting branch pressure to a solenoid valve in a fluid circuit

A control system for a transmission having a clutch, a pump in fluid communication with the clutch through a branch of a fluid circuit, a pressure control variable force solenoid (PVFS), and a flow control variable force solenoid (QVFS) valve, wherein the PVFS and QVFS valves are positioned in the branch upstream of the clutch, the system comprising:

• a host machine in electrical communication with the clutch, the pump, and the PVFS and QVFS valves;
• a temperature sensor positioned in the fluid circuit in electrical communication with the host machine, wherein the temperature sensor measures a temperature of the oil;
• and
• a tangible, non-transitory computer-readable medium on which is recorded instructions for limiting branch pressure, wherein the host machine executes the instructions from the computer-readable medium to thereby:
• calculate an area of a variable orifice of the QVFS valve at the start of a clutch shift event as a function of a commanded branch pressure and a measured oil temperature;
• record the calculated area as a maximum area;
• calculate, in a calibrated loop during the shift event, a maximum branch pressure in the branch as a function of the calculated maximum area;
• and
• limit actual branch pressure in the branch during the shift event to the calculated maximum branch pressure.

A method comprising:

• calculating an area of a variable orifice of a flow control variable force solenoid (QVFS) valve at the start of a clutch shift event in a vehicle, wherein the vehicle includes a pump that is in fluid communication with a clutch through a pressure control variable force solenoid (PVFS) valve and the QVFS valve in a branch of a fluid circuit;
• recording the calculated area as a maximum area;
• calculating, in a calibrated loop during the shift event, a maximum branch pressure in the branch as a function of the calculated maximum area;
• and
• limiting, via a controller, fluid pressure in the branch during the shift event to the calculated maximum branch pressure.