Driving, Function - GF08.30-P-2002LFI
Engine 276 in model 222.173
Driving mode
Depending on the power requirement the vehicle, the charge level of the high-voltage battery (A100g1) and the selected operating mode, the operating mode selected is electricity only. If the power requirement is appropriately high, the internal combustion engine is started using a procedure developed specifically for hybrid drives with direct-injection gasoline engines and then quickly and comfortably switched-in by means of driving condition-dependent actuation of the clutch. When doing this, the Mercedes-Benz starting procedure uses a combination of suitable starter actuation and so-called direct starting of direct-injection gasoline engines for which the start is optimized by means of targeted injections and ignitions.
This and simultaneous automatic addition of the clutch with an appropriate additional acceleration effect on the starting internal combustion engine makes it possible for the hybrid vehicle to start extremely quickly compared to a conventional starting process. This optimizes starting process ensures rapid connection of the drive from the electrical drive.
The various driving conditions during driving can be differentiated between as:
- Hybrid mode
- Electrical operation
- Regenerative braking
- BOOST MODE
Hybrid mode
In hybrid mode, the internal combustion engine acts as the main drive source. The electrical machine (A79/1) is used in alternator mode to supply on-board energy consumers such as the air conditioning system or to charge or top up the high-voltage battery. It is only in cases of strong acceleration that the internal combustion engine supports the electrical machine in so-called boost mode and therefore ensures maximum output and torque at the level on an 8 cylinder engine.
The internal combustion engine is switched off however dependent on the power requirement of the drive and the onboard network consumers as well as from the charge level of the high-voltage battery, in order in turn to go back to electrical operation.
Electrical operation
If the transmission mode or the operating mode of electrical drive allows it, the charge level of the high-voltage battery is high enough, the torque request of the driver can be fulfilled purely electrically and no diagnosis or no system error will prevent electrical operation, then this operating condition is adopted. The clutch is opened and the internal combustion engine is switched off by the ME-SFI [ME] control unit if certain prerequisites are fulfilled. As soon as the combustion engine is shut off, the sound generator (H4/16) is activated and generates audible driving noises. When the vehicle is in electric mode, the sound generator serves to make the vehicle acoustically perceptible to other road users.
Regenerative braking
For the HVs the Premium ESP® system was modified in such a way that the hydraulic connection between the master brake cylinder and rear axle brake circuit is locked out over a separation valve in the ESP® system for RBS in fault-free operation. This means that the rear axle cab either be braked over the electrical machine or over the hydraulic unit.
For regenerative braking, only a part, or at low braking the entire braking torque is generated by the electrical machine. The high-voltage battery is charged with the electrical energy produced in the process.
BOOST MODE
In boost mode the electric machine supports the combustion engine in order to reach the requested specified torque as quickly as possible or to further amplify the drive torque if the maximum engine torque has been reached.
The period and intensity of the boost mode are hereby dependent on the charge level of the high-voltage battery and the position of the accelerator pedal. Torque synchronization between the internal combustion engine and the electrical machine is realized in boost mode during driving off via appropriate actuation of the clutch.
Operating modes and transmission modes
In order to use the vehicle in an optimum way in accordance with the driver's requirements and the driving profile, four drive programs and four operating modes are available to the driver for manual selection.
The following four drive programs can be selected using the DYNAMIC SELECT switch (N72s19) (with code 446 (Touchpad only) or the DYNAMIC SELECT switch (A40/9s19) (except code 446 (Touchpad only):
- "Comfort" transmission mode
- "Sport" transmission mode
- Drive program "E"
- "Individual" transmission mode
The driver can use the DYNAMIC SELECT switch to select the required transmission mode and the driver receives operation feedback in the instrument cluster (A1) as well as in the audio/COMAND display (A40/8). The head unit (A26/17) generates the signal for the display in the Audio/COMAND screen and sends it over a high-speed video link (HSVL).
Engine 276 in model 222.173
with code 446 (Touchpad only)
The signal of the DYNAMIC SELECT switch is read in by the lower control panel (N72). The lower control panel sends the signal via the LCP-LIN (LIN A3), the touchpad (A105), the telematics CAN (CAN A), the head unit, the user interface CAN (CAN HMI), the electronic ignition lock control unit (N73) and the suspension FlexRay (Flex E) to the Electronic Stability Program control unit (N30/4).
Engine 276 in model 222.173
except code 446 (Touchpad only)
The signal of the DYNAMIC SELECT switch is read in by the Audio/COMAND control panel (A40/9). The Audio/COMAND control panel sends the signal via the telematics CAN, the head unit, the user interface CAN, the electronic ignition lock control unit and the suspension FlexRay to the Electronic Stability Program control unit.
The Electronic Stability Program control unit puts the information for the chosen transmission mode on the chassis FlexRay. The control units relevant for the new transmission mode receive the information and switch to the stored parameters for the particular transmission mode.
"Comfort" transmission mode
The standard program "Comfort" is selected using the DYNAMIC SELECT switch. The "Comfort" drive program represents the standard program which brings the responsiveness of the plug-in hybrid vehicle into perfect harmony with the refined comfort of a luxury sedan. Only electrical operation is possible.
"Sport" transmission mode
The sporty characteristics of the drivetrain come to the fore when the "Sport" drive program is selected. The transmission mode has a tendency to select low gears, therefore providing a more free-revving drive characteristic. Furthermore the electrical drive is not used and the electrical energy made available in this way can be used to a maximum for the electrically supporting boost mode. The "Sport" drive program is firmly linked with hybrid mode.
Drive program "E"
The "E+" drive program stands for even more fuel economy with glide mode used in combination with the ECO support systems described below.
"Individual" transmission mode
The "Individual" drive program is selected using the DYNAMIC SELECT switch. The menu for individually setting the drive programs appears in the Audio/COMAND display.
ECO
Driving in hybrid mode with a route-based operating strategy and extended decel mode in combination with radar thrust
Sailing mode
In drive program "E+" the overrun torque during electric mode is reduced to a minimum, thus allowing for maximum glide mode. In this way the vehicle can cover a further travel distance rolling when releasing the accelerator pedal.
Strong braking after a longer stretch in cruising mode or cruising mode occurring too early with subsequent renewed support by the internal combustion engine is disadvantageous. This why a haptic accelerator pedal was installed for the ECO support system.
When using the radar sensor system installed in the vehicle, the clearance and the speed to the vehicle driving immediately ahead are recognized. In the very moment in which release of the accelerator pedal leads to consumption-optimized matching of the speed to a vehicle driving immediately ahead, the ECO support engages. Based on the noticeable double impulse in the haptic accelerator pedal, the driver receives a recommendation to release the accelerator pedal. As soon as the accelerator pedal is released, the internal combustion engine is switched off for available electrical operation, decoupled over the clutch from the drivetrain and the vehicle switches into cruising mode.
If the vehicle driving immediately ahead reduces its speed or if the clearance to it reduces due to other factors, the radar-based thrust control engages. Through adaptation of the thrust torque of the electrical machine the clearance to the vehicle driving immediately ahead is compensated for according to the driving situation.
The following table gives an overview of which transmission mode is selectable in the respective operating mode and how the operating energy input is generated.
| Operating modes | Operating energy input | Comfort | Sport | E | Individual |
|---|---|---|---|---|---|
| (HYBRID) | Internal combustion engine + electrical machine | Selectable | Selectable | Selectable | Selectable |
| E-MODE | Electric machine | Selectable | Not selectable, internal combustion engine running | Selectable | Selectable |
| E-SAVE | Combustion engine | Selectable | Not selectable, internal combustion engine running | Selectable | Selectable |
| CHARGE | Combustion engine | Selectable | Not selectable, internal combustion engine running | Selectable | Selectable |
ECO support system
The operating mode selection button (N72s16) with code 446 (Touchpad only) or the operating mode selection button (A40/9s16) except code 446 (Touchpad only) can be used to select the following four operating modes:
- (HYBRID)
- E-MODE
- E-SAVE
- CHARGE
While the basic handling characteristics can be set by choosing the drive programs of "Comfort", "Sport", "E" and "Individual", the operating modes allow the driver to directly influence electrical energy usage and hence the charge level of the high-voltage battery.
The operating mode selection button is located in the lower control panel (with code 446 (Touchpad only)) or in the Audio/COMAND control panel (except code 446 (Touchpad only)) and its status is forwarded via the CAN network to the instrument cluster and to the powertrain control unit (N127). The powertrain control unit sets the operating mode and the instrument cluster shows the set operating mode.
(HYBRID)
The operating mode HYBRID is the default operating mode. In the "Comfort", "E" and "Individual" drive programs, it provides hybrid operation with charge-dependent proportioning of electric mode driving and maximum starting comfort by retaining sufficient reserve power for the electric machine. If the "E" drive program is selected and route guidance is activated, route-based energy management will be activated in this mode.
The "Sports" transmission mode goes for maximum responsiveness and, besides changes in the gear selector of the transmission and the design of the accelerator pedal curve, electrical operation is dispensed with altogether and the boost output is increased.
Route-based energy management
The various manually selectable operating modes are used by the driver since he knows his route and knows where he wishes to drive electrically and when the high-voltage battery should be discharged.
Route-based energy management accommodates these two desires and combines them with the convenience of optimally sequencing operating modes for the route based on map data instead of the driver having to make a decision.
The selection of the operating mode does not take place purely event-oriented but rather also while taking account of the following:
- The use of electrical energy has differing consumption-reducing effects depending on the route that is being driven.
- The use of electrical energy for electrical operation in a city represents a high emotional additional benefit for the driver.
For highway driving one can, for example, use less electrical energy dependent on need with a route-based operating strategy, and the charge level of the high-voltage battery can also be adjusted in a targeted manner to the remaining stretches, through load-point shifting.
The following fundamentals are necessary for the energy assessment of the router and therefore for the charging control and performance enabling:
- COMAND Online
- Current vehicle weight
- Handling characteristics (vehicle speed, braking behavior)
- Other user load
- Turn-off probability
The "Sports" transmission mode goes for maximum responsiveness and, besides changes in the gear selector of the transmission and the design of the accelerator pedal curve, electrical operation is dispensed with altogether and the boost output is increased.
Actuation of the hybrid drive system
E-MODE
The operating mode E-MODE stands for maximum electrical operation. In order to allow the driver comfortable continuation of driving in electrical operation, the haptic accelerator pedal is activated with an over-center preload. When this occurs, a noticeable actuation point is output via the accelerator pedal just before the request to start the internal combustion engine. The start is not carried out until the actuation point has been passed.
E-SAVE
In operating mode E-SAVE the charge level of the high-voltage battery which was stored upon activation of the operating mode is maintained. Part of the electrical drive continues to be permitted. It is therefore still possible to switch off the internal combustion engine at a standstill or during deceleration phases to prevent consumption while idling. Just as enough energy is taken from the high-voltage battery that the charge level does not fall below the set value.
CHARGE
In the operating mode CHARGE, the high-voltage battery is moderately supercharged in driving mode by load capacity increase of the internal combustion engine. In order to secure continuous charging operation one dispenses with all electrical operation and the boost mode. Just as soon as the high-voltage battery has been completely supercharged, there is automatic changeover into the operating mode E-SAVE.
The driving operation of the hybrid drive system and the active subfunctions are described in the following documents:
- Hybrid drive system test conditions, function
- Monitoring a hybrid drive system, function
- Torque coordination for a hybrid drive system, function
- Automatic engine stop, function
- Automatic engine start, function
- Deceleration mode, function
- Recuperative braking, function
| Hybrid drive system test conditions, function | GF08.30-P-2005LFH | ||
| Monitoring a hybrid drive system, function | GF08.30-P-5001LFH | ||
| Torque coordination for a hybrid drive system, function | GF08.30-P-4001LFH | ||
| Automatic engine stop, function | GF08.30-P-3001LFH | ||
| Automatic engine start, function | GF08.30-P-3002LFH | ||
| Deceleration mode, function | GF08.30-P-2004LFH | ||
| Recuperative braking, function | GF42.22-P-1010LFH | ||
| Overview of system components, hybrid drive system | GF08.30-P-9999LFH |