GF27.60-P-3009ACK Engage Gear Range, Function
GF27.60-P-3009ACK Engage Gear Range, Function
- TRANSMISSION 722.695 in MODEL 171.4 as of Model Year 09 /modification year 08 model refinement package
Function requirements for gear range engagement, general
^ Circuit 87 ON
^ Circuit 61 OFF
^ Electronic selector lever module control unit (N15/5) in position N or P
^ No pressure in hydraulic system
^ All valves in the shift plate in neutral position
^ Shifting 1st gear for transmission mode "S"
^ Shifting 2nd gear for transmission mode "C"
Gear range engagement, general
Each gear change is triggered by the electronic transmission control. Each shift sequence is assigned a control block.
For this purpose an overlap regulating valve, a holding pressure shift valve, a shift pressure shift valve, a command valve as well as an electromagnetically operated switchover valve (shift solenoid valve).
Actuation of the solenoid valve switches over from stationary mode to the shift phase.
When the gear change is complete the solenoid valves are no longer actuated as the different gears are subject to a self-hold function in stationary mode.
Gear range engagement, function sequence
The function sequence is subdivided into the following steps:
^ Start engine (circuit 61 ON)
^ Shift N to D (engagement process active)
^ Shift N to R
Start engine (circuit 61 ON)
The working pressure reaches the multidisk clutch K3 via the ball valve and the end face of the 3-4 shift pressure shift valve via the 3 - 4 command valve. The 3-4 shift pressure shift valve is switched against the force of the spring towards the right. At the same time the 3-4 shift solenoid valve is energized.
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.
Shown: shift position with circuit 61 ON
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 or 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 62 Shift valve B2 control solenoid valve
Y3/6y4 3-4 shift solenoid valve
Shift N to D (engagement process active)
The selector valve opens the connection of the supply of shift pressure from the ball valve 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 at the same time reaches the opposed surface of the multidisk brake piston B2. The multidisk brake B2 starts to close.
The compression on the opposite surface of the piston of the multidisk brake B2 causes multidisk brake to be connected gently B2.
The ETC control unit (N15/3) monitors the engagement process via the reduced speed of the input shaft as the frictional connection of the B2 multi-disk brake increases. With a corresponding rpm drop the ETC 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 activation sequence is complete; 1st gear is engaged.
Shown: shift position for shift N to D
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 or 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 62 Shift valve B2 control solenoid valve
Y3/6y4 3-4 shift solenoid valve
Shift N to R
The selector valve opens the connection of the supply of shift pressure with the multidisk brake B3. There is no opposed surface on the piston of the multidisk brake B3. The further procedure of the engagement process corresponds to the procedure when the multidisk brake engages B2.
Residual pressure
The line system remains filled with oil in the stationary operation of the transmission. As a result no air can enter the hydraulic system and reduce the shift quality.
Shown: shift position for shift N to R
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 or 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 62 Shift valve B2 control solenoid valve
Y3/6y4 3-4 shift solenoid valve
