Gear Selector Switch And Twin-Clutch Gearbox
Gear Selector Switch And Twin-Clutch Gearbox
Gear selector switch (GWS) and twin-clutch gearbox (DKG)
The gear selector switch (GWS) is used for selecting a drive position of the twin-clutch gearbox. The gear selector switch is positioned in the front of the centre console of the vehicle. The gear selector switch is configured as a control unit in its own right. With the gear selector switch, instead of being actuated mechanically, the transmission is now actuated electronically. In BMW vehicles with powerful motorization, an M Double-clutch Transmission with Drivelogic is utilized. The twin-clutch gearbox has seven gears and it enables gearshifts without tractive power interruptions. On the twin-clutch gearbox, the clutch control and gear changes are automated. An electrohydraulic control system handles clutch operation and gearshifts. The clutch pedal is no longer required. The M Double-clutch Transmission Drivelogic includes the launch control function for maximum acceleration from a standstill. The twin-clutch gearbox also has a function for low speeds which supports the comfort in stop-and-go traffic. This allows the vehicle to move with minimum speed in stop-and-go traffic by lightly pressing on the accelerator pedal.
Brief component description
The following components are described:
- Gear selector switch (GWS) with selector lever
- Centre console operating facility
- Shift paddle and programming buttons
- Twin-clutch gearbox (DKG)
- Holding magnet, parking lock
Gear selector switch (GWS) with selector lever
The gear selector switch is configured as a control unit in its own right. The twin-clutch gearbox is electronically activated via the gear selector switch. The gear selector switch is supplied with voltage via terminal 30B. The gear selector switch consists of the control electronics and the gearshift lever. 13 hall effect sensors for non-contacting detection of the gear lever position are integrated in the control electronics circuit. The gear lever position is transferred to the twin-clutch gearbox (DKG) via PT-CAN2 and, redundantly, via PT-CAN. This means that data are sent to the DKG control unit even if one of the two transmission lines fails.
The following positions can be selected with the selector lever:
- R: for reverse gear
- N: for Neutral
- D/S: for automatic mode or sequential (manual) mode
The gear shift lever is monostable: The gearshift lever always returns to its initial position. The shift to the gear lever position R is bistable: The gearshift lever remains in the selected gear lever position. A shift from the gear lever position "R" into the automatic mode "D" or the manual mode "S" can only be carried out manually.
The Drivelogic button is electrically connected to the gear selector switch (GWS).
Centre console operating facility
The vehicle can be configured depending on the driving situation and the driver's choice. Here, the following functions can be influenced:
- Dynamic Stability Control setting
- Engine response characteristics
- Characteristic curves of the shock absorbers
- Characteristic curves of the steering (Servotronic)
- Shift program of the twin-clutch gearbox via Drivelogic
The settings can be further influenced individually via the standard control centre.
The M Drive configuration also includes the Head-Up Display which belongs to the standard equipment of the new BMW M5.
The M-specific version of the Head-Up Display shows the selected gear as well is a multicolored engine speed display, including the display for the optimum shift point, in addition to the digital road speed information.
Shift paddle and programmable buttons
Alternatively, a manual shifting is possible using the standard shift paddles on the steering wheel. The right shift paddle is pulled for shifting up and the left shift paddle is pulled for shifting down.
For the first time, two programmable M Drive buttons on the steering wheel are available for storing and individually configured setting. Advantage for the driver: By pressing just one button, the driver can switch from the setting for a comfortable driving style to the tuning for markedly sporty driving style.
In each case, the selected program remains activated until the switch-off by pressing the button again, respectively, until the change to a different M Drive tuning. After switching off and likewise after the engine start, the vehicle setting oriented for efficiency and driving comfort is again available.
Twin-clutch gearbox (DKG)
The twin-clutch gearbox combines two sub-gearboxes with two clutches (designed as oil-bath clutches). One sub-gearbox with clutch is responsible for the even-numbered transmission stages (2, 4, 6). The other sub-gearbox with clutch is responsible for the odd-numbered transmission stages (1, 3, 5, 7) as well as for reverse gear.
While driving, one of the two clutches is closed. With each gear change, one clutch opens parallel to the other clutch closing. This achieves jolt-free and rapid gear changes without tractive power interruptions.
The use of two clutches enables a very rapid gear change without tractive power interruptions. Reason: Because the electronic transmission control preselects and prepares the next gear with the ideal ratio for the current engine speed and vehicle speed. Example: The vehicle is accelerating in 3rd gear. In the sub-gearbox with the even-numbered transmission stages, the gear required to continue the acceleration, in this case 4th gear, is already engaged. If the clutch responsible for 4th gear now closes, the clutch for the 3rd gear opens simultaneously. This gear shift operation takes only a few milliseconds.
The twin-clutch gearbox can be used manually in the S sequential mode and in the D automated drive mode. The gear selector switch is a bus user. The shift pulses are transferred electrically to the DKG control unit. With this gearshift method ("shift-by-wire") there is no mechanical connection between the gearshift lever or shift paddles and the transmission.
Holding magnet, parking lock
A locking magnet parking lock is connected to the twin-clutch gearbox control unit (DKG). The parking lock is engaged when the locking magnet is supplied with current.
When the ignition is off, the locking magnet is no longer supplied with current by the twin-clutch gearbox control unit. The retaining tab moved back. The release lever becomes free. The parking lock is engaged on the twin-clutch gearbox through spring force via the cable.
The automatic parking lock is engaged automatically for the following conditions:
- After stopping the engine with ignition off, if Position R or D is engaged.
- For ignition off, if D is engaged.
- At a standstill with engaged transmission position R or D if the seat belt of the driver's seat is put off, the driver's door is opened and the brake is not applied.
System functions
The following system functions are described:
- Functional networking
- M Drive settings
Functional networking
The system overview shows the following functional network:
M Drive settings
- Dynamic Stability Control with M dynamic mode
The Dynamic Stability Control (DSC) also includes the M dynamic mode. The setting can be called up by button press and facilitates the M-typical self-steering response for particularly dynamic cornering by increasing the DSC control thresholds.
- Engine characteristics
The power characteristics of the V8 engine can be influenced by a button on the centre console. There are three settings for selection. The response characteristics are varied accordingly: from markedly comfortable and consumption-optimised, to dynamically sporty to extremely spontaneous.
- Electronic Damper Control
Jounce and rebound stage of the electronically controlled shock absorbers are regulated independently of each other. The characteristic curve of the shock absorbers can be varied appropriate to the situation. In the {Comfort} mode, they react adaptively to road unevenness. The {Sport} setting ensures a stiffer, {Sport Plus} for especially dynamically oriented damping characteristics.
- Speed-dependent steering servo Servotronic
The hydraulic rack-and-pinion steering of the new BMW M5 is combined with a speed-dependent steering servo. It makes 3 characteristic curves available in the settings {Comfort}, {Sport} and {Sport Plus}. Depending on what is needed, it can thus increase the comfort when parking or the precision at higher speeds. The Servotronic button is read in by the engine control. The engine control sends the signal via the bus to the Servotronic (SVT) control unit. The Servotronic control unit activates the Servotronic valve on the hydraulic steering.
- M Double-clutch Transmission Drivelogic
The M DKG Drivelogic offers three shift programs in both automatic and manual mode. The selection is made via a rocker switch. After the engine start, the program D1 is automatically made available, in which the gear selection is set up for a driving style which is as efficient as possible. The setting D2 supports a comfort-oriented driving style with speed-dependent and load-dependent gear change. For the benefit of a sporty driving style with dynamic acceleration, the shift points in the setting D3 are set so that the gear change first occurs with higher engine speeds.
In manual mode as well, the driver can adapt the shifting characteristics to his/her respective desires accordingly. The setting S1 creates especially comfortable and smooth gear changes. In the setting S2, the gear shifts are noticeably faster and accompanied by significant gearshift jolts at higher engine speeds. For the highest driving dynamics, the program S3 is available, which offers even more sporty gear changes and also includes the launch control function. When DSC is deactivated, the driver can achieve the highest acceleration (taking the road condition and consideration) from a stop by pressing the accelerator pedal to its maximum. The required gear change is carried out automatically at the optimum linking speed.
Notes for Service department
General notes
Parking lock emergency release
If the parking lock can no longer be released hydraulically, mechanical emergency release is possible. This allows the vehicle to be pushed or pulled in case of emergency. For the emergency release, the cup holder insert in the centre console must be removed. Then unlock the parking lock using the release tool from the tool kit.
After stopping the vehicle, lock the parking lot again.
WARNING: Do not tow away vehicle.
Only transport the vehicle with hoisting frame with raised rear axle as damages will otherwise occur. Follow the instructions in the operating instructions.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.