Mercedes-Benz 7G-DCT
7G-DCT is the marketing name of the seven-speed dual clutch transmission ( D UAL C Lutch T ransmission) series 724 of Daimler AG for various Mercedes-Benz passenger cars with transverse front engine and front-wheel or all-wheel drive . The transmission was introduced in the new B-Class (W 246) at the end of 2011 and replaces the Autotronic CVT transmission installed in the predecessor . The transmission is produced at the Daimler plant in Stuttgart-Hedelfingen and, since 2014, at Star Transmission in Sebeș , Romania . The development took place in Stuttgart-Untertürkheim . In June 2016, the one millionth 7G-DCT transmission was produced.
technology
The development goals of the 7G-DCT transmission included, in particular, the presentation of an efficient overall concept with a high degree of efficiency, the use of a modular gear set, a compact design and low overall weight, high shifting comfort and the integration of additional functions such as stop-start capability and a electrically operated parking lock.
The transmission is designed for a maximum torque of 350 Nm as standard, there is a reinforced variant for the Mercedes-AMG vehicles (A 45, CLA 45, GLA 45). The gear unit weighs 81.2 kg dry (plus approx. 6 liters of oil).
Couplings & wheelset
The outer of the two oil-cooled multi - plate clutches are connected to gears 1, 3, 5 and 7, while the inner clutch operates gears 2, 4, 6 and reverse. The use of multi-plate clutches enables the torque capacity to be expanded by increasing the number of plates.
The basic transmission consists of the interlocking input shafts (hollow and inner shaft) with a total of five fixed gears, with gears 4/6 and 5/7 each accessing a fixed gear, two gear shafts with the idler gears, the synchronization and the shift sleeves as well as a differential. In order to achieve the most compact transmission possible, a separate reverse gear shaft was dispensed with in addition to the double assignment of two fixed gears. The direction of rotation is reversed by interconnecting both gear shafts. In order to better serve the requirements of different engines, there are two variants of the transmission: For small gasoline engines the total spread is 7.142, for larger gasoline engines and diesel engines 7.990.
Total translation:
| Small gasoline engines | Larger gasoline and diesel engines | |
|---|---|---|
| 1st gear | 15.943 | 15.943 |
| 2nd gear | 10.038 | 10.038 |
| 3rd gear | 6,927 | 6.359 |
| 4th gear | 4,915 | 4,335 |
| 5th gear | 3.606 | 3.205 |
| 6th gear | 2.771 | 2.501 |
| 7th gear | 2.232 | 1.995 |
| R gear | 12.807 | 13,950 |
Oil supply
The gearbox is equipped with two oil pumps for an energy-efficient oil supply: a vane pump arranged next to the input shafts , which is driven by a gear drive, and a separate electrically driven auxiliary oil pump (also based on the vane principle). The mechanically driven pump is responsible for the basic supply of the transmission, whereby the delivery volume flow depends on the speed of the combustion engine. The additional oil pump is switched on by the electronic transmission control as required, for example at low engine speeds or when the clutch needs more cooling. When the combustion engine is at a standstill ( start-stop function ), the transmission is supplied solely by the electrical auxiliary oil pump and remains ready to start.
A cooling module consisting of a gear oil heat exchanger (stacked plate cooler) and a pressure oil filter is flanged to the gearbox housing . The coolant flow absorbs the waste heat from the heated transmission oil and transfers it to the coolant circuit. A suction oil filter is also integrated below the transmission control. The transmission has a metal oil pan, which is installed on the side in front of the electrical transmission control.
control
The 7G-DCT has a fully integrated hydraulic control unit which is equipped with a 32-bit microcontroller with integrated flash memory and RAM . It also includes the evaluation electronics of the twelve sensors (five position, three speed and two pressure and temperature sensors each), the output stages for controlling the solenoid valves and controlling the electric oil pump. The sensors themselves are also fully integrated into the control unit.
A total of eight control solenoid valves and one shift valve are used to control gear selection and the parking lock.
use
The 7G-DCT is used in all current compact class series ( New Generation Compact Cars , NGCC ) from Mercedes-Benz. These are the A-Class (W 176) , the B-Class (W 246) , the CLA (117 series) and the GLA (X 156) . The vehicles of the NGCC vehicle architecture have a transversely installed front engine with front-wheel or all-wheel drive .
literature
- Ralf Wörner, Ansgar Damm, Ralph Eberspächer, Carsten Gitt: Efficient front-transverse transmissions from Mercedes-Benz , in: ATZ 113 (2011), No. 12, pp. 914–921, Springer Vieweg, Wiesbaden
- Gerhard Henning, Tobias Gödecke, Ansgar Damm: New transmissions for the new compacts , in: ATZ extra - The new A-Class from Mercedes-Benz , pp. 70–73, Springer Vieweg, Wiesbaden, September 2012
Individual evidence
- ↑ Star Transmission, the Romanian Daimler subsidiary, develops the Sebes production site. April 4, 2014, accessed March 14, 2017 .
- ↑ One million double clutch transmissions produced from Untertürkheim. MBPassion.de, June 21, 2016, accessed July 8, 2016 .
- ↑ a b c d Ralf Wörner, Ansgar Damm, Ralph Eberspächer, Carsten Gitt: Efficient front-transverse transmissions from Mercedes-Benz , in: ATZ 113 (2011), No. 12, pp. 914–921, Springer Vieweg, Wiesbaden