GF27.60-P-3009AHS Engage Gear Range, Function

GF27.60-P-3009AHS Engage gear range, function
- Transmission 722.9


Function requirements for gear range engagement, general
^ Circuit 87 ON
^ Circuit 61 ON

Gear range engagement, general
Each gear change is triggered by the fully integrated transmission control (VGS). In the process one component group is assigned to each shift operation.

One component group consists of the respective control solenoid valve, regulating valve involved, shift valve responsible and the required multidisk brake or multidisk clutch.

The pressure in the multidisk brake or multidisk clutch to be engaged is increased constantly while at the same time the pressure in the multidisk brake or multidisk clutch to be disengaged is reduced. The process is a smooth transition and the components affected are actuated directly. This makes it possible to downshift, even through several gears.

Gear range engagement, function sequence

Shift operation N to D (1st gear)
In position "N" of the DIRECT SELECT gear selector switch (S16/13), multidisk brake B3 and multidisk clutch K3 are engaged. Shifting from position "N" to position "D" of the intelligent servo module for DIRECT SELECT (A80) means that the feed to the multidisk brake B2 is enabled by the selector valve. The fully integrated transmission control unit (VGS) (Y3/8n4) actuates brake control solenoid valve B2 (VGS) (Y3/8y6) and multidisk brake B2 is filled with oil.

By the rpm difference (actual slip) of engine speed to turbine speed the fully integrated transmission control unit (VGS) detects whether the multidisk brake B2 is filled.

The brake control solenoid valve B2 (VGS) actuates the regulating valve B2 and BR which converts the adjacent working pressure into shift pressure and passes it on to the multidisk brake B2

In the fully integrated transmission control unit (VGS), the required slip (specified slip) is stored for the respective gear. Depending on the specified slip, the control pressure on regulating valves B2 and BR is changed via brake control solenoid valve B2 (VGS).

The pressure in multidisk brake B2 is changed until the specified slip stored in the fully integrated transmission control unit (VGS) is reached.

The shift pressure produced by the regulating valve B2 and BR depends on the geometry of the regulating valve B2 and BR.

"No power" in gear range "D" on model 221 in combination with engine 642 as of 1.12.2008

Function requirements
^ The vehicle speed v = approx. 15 km/h must be exceeded once after engaging gear selector switch position "D".
^ The function sequence of "no power" in gear range "D" is activated in gear selector switch position "D" if the following conditions are met:
- The driver has braked the vehicle to a standstill
- Transmission oil temperature in range of 10 degrees C to 110 degrees C
- Coolant temperature in range of 0 degrees C to 120 degrees C
- Accelerator pedal not actuated
- Engine speed in range of 570 rpm 1000 rpm
- Braking torque is at least 250 Nm and brake light switch (S9/1) is actuated
- Transmission-internal uphill slope calculation value less than 18 %
- Transmission mode "C" or "S" selected
- 1st gear engaged by VGS [fully integrated transmission control]
- VGS operating without faults

Vehicle standstill can be reached via one of the following conditions:
- The driver has braked the vehicle to a standstill
- "HOLD function" (Hill Start Assist) is active

Function sequence
The VGS reduces the flow at the brake control solenoid valve B2 (VGS) in such a way that the shift pressure is reduced to the back pressure spring level via the regulating valve B2 and BR and therefore the multidisk brake B2 is converted to a regulated slip. This leads to a reduction in transmission output torque when the vehicle is stationary and to a reduction in fuel consumption.

The function sequence of "no power" in gear range "D" is deactivated when at least one of the following conditions is met:
- Vehicle speed v greater than 0 km/h
- Transmission oil temperature t greater than 110 degrees C
- Coolant temperature t greater than 120 degrees C
- Accelerator pedal actuated
- Engine speed n less than 570 rpm or n greater than 1000 rpm
- Braking torque less than 250 Nm or brake light switch not actuated
- Transmission-internal uphill slope calculation value greater than 25 %
- A touch shift was detected or the gear selector switch was shifted out of gear selector switch position "D" to "N", "R" or "P"
- A VGS system fault was detected