A3 | Drive control (CPC) control unit |
A5 | Transmission control (TCM) control unit |
CAN 4 | Drive train CAN |
LIN 3 | Right multifunction control lever LIN |
S23 | Right multifunction lever (optional) |
S23 s1 | Transmission position switch (D/N/R) |
S23 s2 | Gearshift paddle (+/-) |
S23 s3 | Transmission mode (M/A) button |
G26.21-3139-76
Normal mode
The shift commands are detected via the following control elements integrated into the right multifunction lever (optional) (S23):
Transmission position (D/N/R) switch (S23 s1)
Gearshift paddle (+/-) (S23 s2)
Transmission mode (M/A) button (S23 s3)
The drive control (CPC) control unit (A3) reads in the shift signals from the right multifunction lever (optional) (S23) via the right multifunction lever LIN (LIN 3). Then the drive control (CPC) control unit (A3) evaluates them and transmits corresponding CAN messages to the transmission control unit (TCM) (A5) via the drive CAN (CAN 4).
12 forwards gears, 4 reverse gears and neutral can be engaged.
Automatic operation (the optimal gear (the target gear specification) is determined by the drive control (CPC) control unit (A3))
Gear selection is dependent on the following influencing variables:
Ground speed (only relevant for the start-off gear)
Accelerator pedal position (specified torque)
Load condition of engine
Operating point of the target gear
Rotational speed of the transmission
Operation of the permanent brake
Load condition of vehicle
Shift program
Lay of the land for the driving lane
Manual mode
Difference to automatic mode:
The shift operations must be initiated by the driver, this means that the driver determines the shift timing point and shift direction.
The kickdown function is not available.
Operation of the driving functions
Driving functions help the driver in daily operating status with fuel-saving driving. They increase the ride comfort and support him in difficult situations.
Selectable driving functions are:
EcoRoll mode in certain driving situations for supporting a fuel-saving driving style through automatic shifting to neutral position "N" when the accelerator pedal is not depressed
Rocking mode for rocking the vehicle out of an off-road recess
Crawler mode for automatic rolling when the service brake is released and sustained crawling without accelerator pedal actuation
EcoRoll mode
Preconditions
EcoRoll mode function activated
Vehicle speed was > 35 km/h and is > 25 km/h (hysteresis)
Accelerator not operated
Service brake or permanent brake not actuated
Driver assistance systems not in control mode
Brake assistant systems not in control mode
Power take-off switched off
Limiter for maximum speed not exceeded
CC speed tolerance not exceeded
Function sequence
If the preconditions are fulfilled, the drive control (CPC) control unit (A3) requests the neutral position from the transmission control unit (TCM) (A5) via the drive CAN (CAN 4). The transmission (TCM) control unit (A5) actuates the transmission positioner (Y900) to open the clutch. After successful opening of the clutch, read in over the clutch position sensor (B503), the transmission positioner (Y900) is actuated to engage neutral. After ending the switching the transmission (TCM) control unit (A5) transmits the engaged neutral to the drive control (CPC) control unit (A3) via the drive train CAN (CAN 4).
Due to the reduced engine speed, there may be somewhat diminished steering support and, as a result of this, larger steering forces in certain driving situations, for example on slightly curving downward slopes. The operation or road safety is not endangered by this.
Crawler mode
Crawler mode is always switched on after an engine start and is activated after first moving off.
Crawler mode is deactivated under the following conditions:
Crawler mode is switched off via the crawler mode switch
Transmission is in neutral position for longer than 2 s
The parking brake is tightened
Rocking mode is activated
Driver assistance systems switch to control mode
Idle speed > 700 rpm
Threat of clutch overloading
An excessively high air drag and rolling resistance
An excessively high tire grip
Crawler mode has, in terms of behavior, similarities with an automatic torque converter. Since the function is realized over the clutch the function is not wear-free and the vehicle in the slip range of the clutch is not capable of permanently crawling.
Function sequence
Crawler mode consists of 2 parts:
In gears 1 to 6, R1 and R2, self-actuated crawling by releasing the service brake (only for active crawler mode)
In gears 1 to 6, R1 and R2 further crawling (=freewheeling) for a non-actuated accelerator pedal
The driving off dosing occurs for first driving off over the accelerator pedal. The system is taught in in the process to the torque prescribed by the driver. After the first "real" drive, the crawling torque is determined depending on the detected vehicle mass and the incline of the roadway.
If trailer recognition determines that there is trailer operation, then the mass and incline dependent creeping torque is reset in the drive control (CPC) control unit (A3) and taught in when first starting off.
Rocking mode
Function sequence
Rocking mode is activated via the rocking mode button.
If rocking mode has been activated, transmission control changes from automatic to manual mode.
Accelerator pedal requests are implemented more directly and the clutch is opened more rapidly for a non-actuated accelerator pedal. The clutch is closed quickly again as soon as the accelerator pedal is actuated again. Through repeated actuation and release of the accelerator pedal can put the vehicle into a rocking mode condition and in this way can rock the vehicle free out if a hollow.