Dual-Clutch Transmission Control, Basic Function - GF27.19-P-9900A
Model All with Transmission 700.4, 724.0/1
Overview
This document contains information on:
- General
- Function
- Dual clutch control
- Clutch power-flow change
General
In the dual-clutch transmission, shift operation are automatically realized through a dual clutch. The clutch control depends on the driver's request and is controlled by the dual-clutch Transmission control unit or the fully integrated Transmission control electrohydraulic controller unit.
Function
Dual clutch control
The dual clutch consists of two combined wet clutches. The wet clutches shift one of two respective sub-transmissions alternately.
Sub- Transmission 1 contains the odd gears, depending on the number of gears involved. Sub- Transmission 2 contains the even gears and the reverse gear.
In drive mode, one sub- Transmission gear is always engaged, while the next gear expected to be shifted to is prepared for engaging by the Transmission control. The relevant clutch of the previously engaged gear is not yet opened and therefore the torque is not transferred.
In first gear, the drive torque to be transmitted is the largest compared with the remaining gears. Therefore, the clutch of the first sub- Transmission is larger in size and located on the outside of the dual clutch.
The combustion engine drives both Transmission input shafts. One clutch is on the hollow drilled Transmission input shaft, the other is on the Transmission input shaft running in the first shaft.
The next gear can always be pre-selected on the non-engaging Transmission input shaft. One clutch opens at the shift point, while the other closes.
Clutch power-flow change
The power flow is changed with an overlap gearshift system operation. During overlap gearshift system operation, torque transfer is reduced through a clutch proportionate to the increase at the clutch.
During torque transfer, the drive torque is also reduced, within a defined time window, by the combustion engine control unit.
| Function schematics | |||
| Function schematic for gearshift system | Model 118, 177, 247 with Transmission 700.4, 724.0/1 | PE27.60-P-2500-97A | |
| Additional basic functions | |||
| Dual clutch control, basic function | Transmission 700.420/421/422/423 Transmission 724.033/044/045/103/114/115/120 | GF25.30-P-1000A | |
| Start off and stop, basic function | Transmission 724.033/044/045/103/114/115/120 | GF27.10-P-1004A | |
| Limp-home mode, basic function | Model all with Transmission 700.4, 724.0/1 | GF27.60-P-9900A | |
| Fully integrated Transmission control electrohydraulic controller unit, basic function | Model all with Transmission 724.0/1 | GF27.19-P-2003A | |
| Detailed information | |||
| Dual-clutch Transmission control unit, detailed information | Transmission 700.420/421/422/423 | GF27.60-P-0002A |