Shift From 1 To 2, Function

Fig 1: Shift From 1 To 2, Function (1st Gear Engaged)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Fig 2: Shift From 1 To 2, Function (Shift Phase)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Fig 3: Shift From 1 To 2, Function (Second Gear Engaged)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Aim 

Engage front multiple-disc clutch (K1), disengage front multiple-disc brake (B1).

Operation 

1st gear engaged

The end face of the 1-2/4-5 command valve (31a) is kept depressurized via the 1-2 and 4-5 shift solenoid valve (Y3/6y3). Via the 1-2/4-5 holding pressure shift valve (28a), working pressure (p-A) is applied to the front mutiple-disc clutch (K1) is depressurized.

Shift Phase 

Via the 1-2 and 4-5 shift solenoid valve (Y3/6y3), the shift valve pressure (p-SV) is directed onto the end face of the command valve 1-2/4-5 (31a). The 1-2/4-5 command valve (31a) is displaced and the shift pressure (p-S) coming from the 1-2/4-5 shift pressure shift valve (29a) via the 1-2/4-5 command valve (31a) is directed to the front multiple-disc clutch (K1). At the same time the front multiple-disc brake (B1) is subjected to overlap pressure from the 1-2/4-5 overlap regulating valve (30a).

The B1 pressure acting on the end face of the 1-2/4-5 shift pressure shift valve (29a) is superseded by the working pressure (p-A). The increasing shift pressure (p-S) at the front multiple-disc clutch (K1) acts on the annular area of the 1-2/4-5 overlap regulating valve (30a). With an appropriate pressure level at the 1-2/4-5 holding pressure shift valve (28a) this valve switches over.

2nd Gear Engaged 

After the gear change is complete, the pressure on the end face of the 12-/4-5 command valve (31a) is reduced via the 1-2 and 4-5 shift solenoid valve (Y3/6y3) and the command value is pushed back into its original position. Via the 1-2/4-5 holding pressure shift valve (28a) working pressure (p-A) now reaches the front multiple-disc clutch (K1) via the 1-2/4-5 command valve (31a).

The front multiple-disc brake (B1) is disengaged (depressurized). The spring in the 1-2/4-5 shift pressure shift valve (29a) pushes this into its original position.

1. Operating Pressure, Function
   
   See OPERATING PRESSURE, FUNCTION  .
2. Shift Pressure, Function
   
   See SHIFT PRESSURE, FUNCTION  .
3. Modulating Pressure, Function
   
   See MODULATING PRESSURE, FUNCTION  .
4. Shift Valve Pressure, Function
   
   See SHIFT VALVE PRESSURE, FUNCTION  .
5. Lubricating Pressure, Function
   
   See LUBRICATING PRESSURE, FUNCTION  .
6. Regulating Valve Pressure, Function
   
   See REGULATING VALVE PRESSURE, FUNCTION  .