Pressure and Flow Regulation: Notes
A gear driven pump is integrated into the M DCT transmission and is responsible for circulating the oil through the unit.
The transmission oil pump is driven by a gear on the drive input side which connects to the center input shaft of the M DCT. The engine must be running for the oil pressure to build up.
| Index | Explanation |
|---|---|
| 1 | Oil pump gears |
| 2 | Oil pressure pipe to the hydraulic control unit |
| 3 | Oil return pipe |
| 4 | M DCT gear oil pump housing |
| 5 | Drive gear |
| 6 | Oil intake side (oil supply) |
The operating pressure is determined by a regulated control valve depending on the load and the function selected. The system is protected by a pressure relief valve in the pump.
The pressure is regulated according to the following priorities:
- Clutch engagement and disengagement
- Gear changes
- Cooling the clutch
- Lubrication cycle.
The transmission oil pressure should be high enough to:
- Be able to engage the clutches reliably.
- Allow the gear selector rod to reach the required control shift speed.
The normal operating pressure range is between 5 and 20 bar, although it can be increased up to 30 bar if necessary to maintain proper transmission operation.
At maximum shifting force, the pressure required to operate the selector rods can be the same as the operating pressure.
The pressure required for the clutches is limited to 18 bar. The clutch is regulated by an integrated proportioning valve.
Overpressure protection is ensured by a pressure relief valve.
Clutch cooling is map-controlled using a proportional valve.
| Index | Explanation |
|---|---|
| 1 | Inner input shaft 2 |
| 2 | Selector linkage |
| 3 | Intermediate case |
| 4 | Inner input shaft 1 |
| 5 | Constant |
| 6 | Output shaft |
| 7 | Countershaft |
| 8 | Lubricating pipe |
| 9 | Oil pump (sectional view) |
| 10 | Dual clutch housing and oil pump drive gear |