GF27.60-D-4014H Shifting N to D (1st Gear), Function
GF27.60-D-4014H Shifting N to D (1st Gear), Function
- TRANSMISSION 722.6
Circuit 61 ON
Activation sequence active
1st gear engaged
0 Oil sump drain
21 Multidisk brake B1
22a Multidisk brake piston B2
22b opposite surface of multidisk brake piston B2
23 Multidisk brake B3
24 Multidisk clutch K1
26 Multidisk clutch K3
28c 3-4 holding pressure shift valve
29c 3-4 shift pressure shift valve
30c 3-4 overlap regulating valve
31a 1-2/4-5 command valve
31c 3-4 command valve
32 Pressure holding valve
33a Ball valve
33b Ball valve
42 Shift pressure regulating valve
52 Selector valve
62 Shift valve B2
m Annular surface
p-A Working pressure
p-Mod Modulating pressure
p-RV Control valve pressure
p-S Shift pressure
p-S/RMV Shift pressure control solenoid valve
p-SV Shift valve pressure
Y3/6y2 Shift pressure control solenoid valve
Y3/6y4 3-4 shift solenoid valve
Starting situation:
^ ESM [EWM] control unit (N15/5) in position "N" or "P"
^ Circuit 61 OFF
^ No pressure in hydraulic system
^ All valves in the shift plate in neutral position
Aim
Shifting of 1st gear
Function
Start engine
The working pressure is formed and reaches the multidisk clutch via the 2-3 2-3 holding pressure shift valve, 2-3 command valve and ball valve (33a) K3 and via the 3-4 command valve to the end face of the 3-4 shift pressure shift valve. The 3-4 3-4 shift pressure shift valve is pressed to the right against the force of the spring. The 3-4 shift solenoid valve is energized simultaneously. As a result shift valve pressure reaches into the spring chamber of the shift valve B2 and onto the end face of the 3-4 command valve.
The shift valve B2 is held in the upper position and the 3-4 command valve shifts to the right.
The working pressure is replaced by the shift valve pressure on the end face of the 3-4 shift pressure shift valve. (See picture "circuit 61 ON".)
Shift ESM [EWM] control unit from "N" to "D"
The selector valve opens the connection of the shift pressure supply from the ball valve (33b) with the shift valve B2. In the upper position of the shift valve B2 shift pressure reaches behind the piston of the multidisk brake B2 and simultaneously reaches the opposite surface of the piston of the multidisk brake B2. The multidisk brake B2 starts to close (see picture "Switch-on process active").
The compression on the opposite surface of the piston of the multidisk brake B2 causes multidisk brake to be connected gentlyB2. The EGS control unit (N15/3) monitors the switch-on process via the rpm of the input shaft decelerated by the increasing frictional connection of the multidisk brake. B2.
With a corresponding drop in rpm the EGS control unit switches off the current to the 3-4 shift solenoid valve. The spring chamber of the shift valve B2 is unpressurized and switches downwards. As a result the line to the opposite surface of the piston of the multidisk brake B2 is connected to the pressure holding valve. The pressure on the opposite surface of the multidisk brake B2 drops to a residual pressure.
The 3-4 command valve switches to the left. Working pressure reaches the piston of the multidisk brake via the 3-4 holding pressure shift valve and 3-4 command valve B2.
The switch-on process is finished, 1st gear engaged (see picture "1st gear engaged").
Shift ESM [EWM] control unit from "N" to "R"
The selector valve opens the connection of the shift pressure supply with the multidisk brake B3. The further sequence of the switch-on process corresponds to the sequence when connecting the multidisk brake B2.
No opposite surface on the piston of the multidisk brake B3.
Residual pressure
The shift quality is reduced if air gets into the hydraulic system. The line system in the steady-state operation of the automatic transmission remains filled with oil.
