(Driving, Function - GF08.30-P-2002LFH)
Engine 276 in model 222.057/157
Engine 276 in model 222.163
Engine 651.9 in model 222.004/104
Driving mode
Depending on the power requirement, the charge level of the high-voltage battery (A100g1) and the selected operating mode (model 222.163), the vehicle is driven using electric power only. With a high power requirement, the internal combustion engine is started using a procedure developed specifically for hybrid drives with direct-injection gasoline engines and then rapidly and comfortably switched-in by means of driving condition-dependent actuation of the wet clutch (NAK). The Mercedes-Benz starting procedure uses a combination of suitable actuation of the starter (M1) and the so-called direct starting of direct-injection gas engines for which the start is optimized through targeted injections and ignitions.
This and simultaneous automatic addition of the wet clutch with an appropriate additional acceleration effect on the starting internal combustion engine make 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 combustion engine serves as a main drive source and the electric machine (A79/1) is used in alternator mode to supply the onboard energy consumers such as the air conditioning system and DC/DC converter control unit (N83/1) (model 222.163) or to discharge or recharge 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. Depending on the power requirements of the drive and the onboard network consumers and on the charge level of the high-voltage battery, the combustion engine is switched off and the vehicle returned to electric mode.
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 wet clutch is opened and the internal combustion engine is switched off by the ME-SFI [ME] control unit if certain prerequisites are fulfilled.
Regenerative braking
For the hybrid vehicles 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 electrical machine supports the internal combustion engine in order to reach the requested specified torque as quickly as possible or to further amplify the drive torque to amplify the maximum achieved internal combustion engine torque.
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 wet clutch.
Operating mode and drive programs (model 222.163)
In order to use the vehicle in an optimum way in accordance with the driver's requirements and the driving profile, three transmission modes and four operating modes are available to the driver, which can be selected manually.
The following three transmission modes can be selected over the transmission mode button (A40/9s8) by pressing a button:
- Transmission mode "E"
- Transmission mode "S"
- Transmission mode "E+"
The status of the drive program button is read in by the Audio/COMAND control panel (A40/9) and passed on via the CAN network to the instrument cluster (A1) and to the powertrain control unit (N127). The powertrain control unit sets the transmission mode and the IC shows the set transmission mode.
Audio/COMAND control panel (model 222.163)
Transmission mode "E"
Drive program "E" represents the standard program, which brings the responsiveness of the plug-in hybrid vehicle into perfect harmony with the refined comfort of a luxury limousine.
Transmission mode "S"
By selecting the transmission mode "S" sporty characteristics of the drivetrain are the main features. 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 transmission mode "S" has a fixed connection with the hybrid drive.
Transmission mode "E+"
The transmission mode "E+" stands for continued savings on consumption in combination with the ECO support systems described below
The following four operating modes can be selected using the operating mode selection button:
- (HYBRID)
- E-MODE
- E-SAVE
- CHARGE
While the basic handling characteristics can be set by choosing drive programs "E", "S" and "E+", the operating modes allow the driver to directly influence electrical energy usage and hence the charge level of the high-voltage battery.
The status of the operating mode selection button is read in by the Audio/COMAND control panel and passed on via the CAN interface to the instrument cluster and the powertrain control unit. 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 transmission modes "E" and "E+" it offers the hybrid drive with a load condition dependent driving part electrical operation and a maximum additional start comfort through retention of appropriate reserve power for the electrical machine.
In transmission mode "S" the setting is made for the maximum responsiveness and, apart from changes in the gear selector of the transmission and design of the accelerator pedal curve, one dispenses with all electrical operation as well as the boost output.
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 additional start is only executed according to the overpressure of the over-center preload.
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 engine at a standstill or in deceleration mode 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.
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 route-based energy management and the charge level of the high-voltage battery can also be set 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
Actuation of the hybrid drive system
ECO support systems
In transmission mode "E+" the driving torque arising during electrical operation is reduced to a minimum, which allows maximum use of cruising 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 wet 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.
| Mode | Operating energy input | "E+" | "E" | "S" |
|---|---|---|---|---|
| (HYBRID) | Internal combustion engine + electrical machine | Selectable | Selectable | Selectable |
| E-MODE | Electric machine | Selectable | Selectable | Not selectable, internal combustion engine running |
| E-SAVE | Combustion engine | Selectable | Selectable | Not selectable, internal combustion engine running |
| CHARGE | Combustion engine | Selectable | Selectable | Not selectable, internal combustion engine running |
The driving mode of the hybrid 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
| Deceleration mode, function | GF08.30-P-2004LFH | ||
| Hybrid drive system test conditions, function | GF08.30-P-2005LFH | ||
| Automatic engine stop, function | GF08.30-P-3001LFH | ||
| Automatic engine start, function | GF08.30-P-3002LFH | ||
| Torque coordination for a hybrid drive system, function | GF08.30-P-4001LFH | ||
| Monitoring a hybrid drive system, function | GF08.30-P-5001LFH | ||
| Recuperative braking, function | GF42.22-P-1010LFH | ||
| Overview of system components, hybrid drive system | GF08.30-P-9999LFH |