Driving, Function - GF08.30-P-2002GRH
ENGINE 276.821 in MODEL 166
Driving mode
Depending on the power requirement, the charge level of the high-voltage battery (A100g1) and the selected operating mode, the vehicle is powered using electricity 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). 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 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 internal combustion engine serves as a main drive source, and the electrical machine (A79/1) is used in regenerative operation to supply the onboard energy consumers such the air conditioning system and the DC/DC converter control unit (N83/1) 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.
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 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
With hybrid vehicles the Premium ESP® system has been modified in such a way that the hydraulic connection between the master brake cylinder and the rear axle brake circuit is locked via a separation valve integrated in the ESP® system with the regenerative braking system 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 that is generated during this 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 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 transmission modes and four operating modes are available to the driver, which can be selected manually.
The following four transmission modes can be selected via the transmission mode control (N72/4s1):
- Comfort transmission mode
- Sport transmission mode
- Slippery conditions transmission mode
- Individual "ECO" transmission mode
Comfort transmission mode
The standard transmission mode "Comfort" is selected via the transmission mode control. Transmission mode "Comfort" 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 if "Sport" transmission mode is selected. The transmission program tends towards low gears and thus ensures a 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" transmission mode has a fixed connection with hybrid operation.
Slippery conditions transmission mode
By selecting "slippery conditions" transmission mode, the driver receives optimized handling characteristics on slippery or snow-covered streets. Only electrical operation is possible.
Individual "ECO" transmission mode
The transmission mode "Individual" is selected via the transmission mode control. The menu for setting the Individual transmission mode appears on the Audio/COMAND display (A40/8). Individual "ECO" transmission mode is selected by the Audio/COMAND control panel (A40/9) via the "Drive" sub-menu. Transmission mode customization "ECO" is then selected in the "Drive" submenu. The "ECO" transmission mode customization further reduces consumption in Cruising mode in combination with the ECO support systems described in the following.
Sailing mode
In individual "ECO" transmission mode, the overrun torque that occurs 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 operating mode can be selected in the respective transmission mode and how the operating energy input is generated.
| Operating modes | Operating energy input | Individual "ECO" transmission mode | Comfort | Sport | Slippery conditions |
|---|---|---|---|---|---|
| (HYBRID) | Internal combustion engine + electrical machine | Selectable | Selectable | Selectable | Selectable |
| E-MODE | Electrical machine | Selectable | Selectable | Not selectable, internal combustion engine running | Selectable |
| E-SAVE | Internal combustion engine | Selectable | Selectable | Not selectable, internal combustion engine running | Selectable |
| CHARGE | Internal combustion engine | Selectable | Selectable | Not selectable, internal combustion engine running | Selectable |
ECO support systems
The following four operating modes can be selected by pressing the operating mode selection button (N72/1s16):
- (HYBRID)
- E-MODE
- E-SAVE
- CHARGE
While the handling characteristics can be essentially set by the transmission modes Comfort, Sport, Slippery and Individual "ECO", the operating modes offer the opportunity to have an immediate influence on the use of the electrical energy and therefore on the charge level of the high-voltage battery.
The status of the operating mode selection button is read in by the transmission mode control panel and is forwarded via the CAN network to the instrument cluster and the powertrain control unit. The powertrain control unit sets the operating mode and the IC shows the set operating mode.
(HYBRID)
Operating mode HYBRID represents the standard mode. In the Comfort and Individual "ECO" transmission modes, it provides hybrid operation with a load condition-dependent proportion of electrical operation and maximum starting comfort by retaining an appropriate reserve power for the electrical machine. If the Individual "ECO" transmission mode and active route guidance have been selected, Route-based energy management is active in this mode.
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 comfort that the driver can be relieved of the decision-taking concerning the route-optimized sequence of the operating mode while taking account of map data.
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
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. Here a noticeable over-center preload is produced shortly over the accelerator pedal before request for an additional start of 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 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 uprating 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:
- Deceleration mode, function
- Hybrid drive system test conditions, function
- Automatic engine stop, function
- Automatic engine start, function
- Torque coordination for a hybrid drive system, function
- Monitoring a hybrid drive system, function
- Recuperative braking, function
| Deceleration mode, function | GF08.30-P-2004GRH | ||
| Hybrid drive system test conditions, function | GF08.30-P-2005GRH | ||
| Automatic engine stop, function | GF08.30-P-3001GRH | ||
| Automatic engine start, function | GF08.30-P-3002GRH | ||
| Torque coordination for a hybrid drive system, function | GF08.30-P-4001GRH | ||
| Monitoring a hybrid drive system, function | GF08.30-P-5001GRH | ||
| Recuperative braking, function | GF42.22-P-1010GRH | ||
| Overview of system components, hybrid drive system | GF08.30-P-9999GRH |