GF27.51-P-1002AHV Wet Clutch, Function

GF27.51-P-1002AHV Wet Clutch, Function
- TRANSMISSION 722.930 in MODEL 204.0 /2 /3

Function requirements for wet clutch, general

^ Circuit 87 (connected circuit 15) ON
^ Circuit 61 (engine running)

Wet clutch, general

The pressure from the wet clutch control solenoid valve (Y3/8y9) is boosted by the wet clutch regulating valve.

A lubricating oil volume flows through the housing of the wet clutch.

In the process a lubrication oil pressure adjusts which has an opening action on the clutch piston. The lubrication oil pressure is fed back hydraulically to the regulating valve and is taken into account when adjusting the piston pressure. The lubrication oil volume flow and a special geometry of the clutch linings ensure optimum cooling of the wet clutch.

A specified valve pressure is calculated from the specified clutch torque by means of an inverted distance model of the wet clutch

The pressure regulator adjusts the valve pressure, the regulator output quantity being a specified valve current. A low-mounted flow regulator sets the required valve flow at the wet clutch control solenoid valve.

Wet clutch function sequence

The function sequence is subdivided into the following steps:
^ "Engagement process", function sequence
^ "Creeping", function sequence
^ "Start-off", function sequence
^ "Slip control", function sequence
^ "Clutch change", function sequence
^ "Stopping", function sequence

The shift strategy of condition transitions depends on engine load and vehicle speed or vehicle acceleration. The transitions between the individual conditions is controlled by a function coordinator.

"Engagement process", function sequence

The engagement process controls the filling of the clutch piston and the application of the clutch.

"Creeping", function sequence

In this condition the specified clutch torque is calculated so that the vehicle starts to roll automatically when the driver deactivates the brake.

"Start-off", function sequence

The wet clutch enables a strategy-capable startup to be executed.

If the "Race start" is activated, the wheel slip is regulated by the wet clutch during the startup process.

A suitable startup strategy is selected depending on engine load and vehicle speed or vehicle acceleration.

"Slip control", function sequence

If the startup process is complete, then slip control of the wet clutch is activated. The specified clutch torque is calculated so that a microslip is adjusted at the wet clutch. This suppresses driveline vibrations.

"Clutch change", function sequence

During a clutch change the specified clutch torque at the wet clutch is calculated so that with upshifts no slip expansion occurs but with downshifts a slip expansion at the wet clutch occurs.

"Stopping", function sequence

The specified clutch torque is calculated depending on the type of deceleration.

Wet clutch temperature model

A temperature model of the wet clutch and the measured state variables are used to calculate the temperature on the wet clutch's steel lamellas. If the calculated temperature exceeds a limit value, then protective functions are activated to match the driving condition that then minimize the friction power on the wet clutch. Substitute values are calculated in the event of mechanical and hydraulic sensor faults. If a hydraulics fault is detected, then the wet clutch control solenoid valve is flushed out in a controlled manner