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 electric 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 electric machine (A79/1) is used in alternator mode to supply on-board energy consumers such as the air conditioning system or to discharge 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 engine separator clutch is opened and the internal combustion engine is switched off by the CDI control unit (N3/9) (for diesel engines) or the ME-SFI [ME] control unit (N3/10) (for gasoline engines) if certain prerequisites are fulfilled.
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 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 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 five transmission modes can be selected via the DYNAMIC SELECT switch (N72/4s1):
Comfort transmission mode
Transmission modes Sport and Sport Plus
Individual "ECO" 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 via the highspeed video link (HSVL).
The signal of the DYNAMIC SELECT switch is read in by the left lower control panel (N72/4). The left lower control panel sends the signal via the LCP-LIN (LIN A3), the Audio/COMAND control panel (A40/9), 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).
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 transmission mode "Comfort" is selected over the DYNAMIC SELECT switch. The Comfort transmission mode 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.
Transmission modes Sport and Sport Plus
The sporty characteristics of the drivetrain come to the fore if "Sport" or "Sport Plus" transmission mode 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“ transmission mode has a fixed connection with hybrid operation.
Individual "ECO" transmission mode
The transmission mode "Individual" is selected over the transmission mode control. The menu for setting the Individual transmission mode appears in the Audio/COMAND display. Individual "ECO" transmission mode is selected using the Audio/COMAND control panel over 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.
ECO
Driving in hybrid mode with a route-based operating strategy and extended decel mode in combination with radar thrust
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 driver assistance 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 assistant 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 | SPORT PLUS | Individual "ECO" |
(HYBRID) | Internal combustion engine + electric machine | Selectable | Selectable | Selectable | Selectable |
E-MODE | Electric machine | Selectable | Not selectable, internal combustion engine running | Not selectable, internal combustion engine running | Selectable |
E-SAVE | Combustion engine | Selectable | Not selectable, internal combustion engine running | Not selectable, internal combustion engine running | Selectable |
CHARGE | Combustion engine | Selectable | Not selectable, internal combustion engine running | Not selectable, internal combustion engine running | Selectable |
ECO driver assistance system
The following four operating modes can be selected via the select operating mode button (N72/4s6) by pressing a button:
(HYBRID)
E-MODE
E-SAVE
CHARGE
While the handling characteristics can essentially be set by the transmission modes Comfort, Sport, Sport Plus, and Individual "ECO", the operating modes offer the opportunity to have an immediate influence on the use of electrical energy and therefore on the charge level of the high-voltage battery.
The button for selecting the operating mode is in the left lower control panel. Its status is read in by the Audio/COMAND control panel and passed on 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 HYBRID operating mode is the standard operating 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 in this operating mode have been selected, Route-based energy management is active in this mode .
The "Sports" and "Sport Plus" transmission mode is set 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 |
1 | Raising the charge level of the high-voltage battery compared to manual energy management |
2 | Pure electrical operation in the city |
3 | Automatic change of the energy management |
A | Driving overland (rural) |
B | Driving in the city |
C | Driving overland (rural) |
D | Arrival at the destination |
SOC | Charge level of high-voltage battery |
P08.30-2100-74
EMODE
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.
ESAVE
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 | |||
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 | |||
Overview of system components, hybrid drive system |
Referenced documents
- gf0830p2004fgh Deceleration mode, function
- gf0830p2005fgh Hybrid drive system test conditions, function
- gf0830p3001fgh Automatic engine stop, function
- gf0830p3002fgh Automatic engine start, function
- gf0830p4001fgh Torque coordination for a hybrid drive system, function
- gf0830p5001fgh Monitoring a hybrid drive system, function
- gf0830p9999fgh Overview of system components, hybrid drive system
- gf4222p1010fgh Recuperative braking, function