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Hybrid Drive System Test Conditions, Function - GF08.30-P-2005LFH

Engine 276 in model 222.057/157 

Engine 276 in model 222.163 

Engine 276 in model 222.173 

Engine 651.9 in model 222.004/104 

Function requirements for hybrid drive system test conditions, general 

Hybrid drive system test conditions, general 

Differentiation of the driving conditions during operation is made between internal combustion engine, hybrid driving mode (drive with internal combustion engine and electrical machine) and electric driving mode (cruising mode, maneuvering).

For the driving operation with an internal combustion engine the electrical machine (A79/1) is mostly run as an alternator (alternator mode).

According to the request and charge level of the high-voltage battery (A100g1), in hybrid driving mode, the torque from the electrical machine operates together (supportively) with the torque of the internal combustion engine. The support occurs during moving off and acceleration (boost mode).

In electrical driving mode driving of the vehicle is purely electrical powered by the electrical machine.

The CDI control unit (N3/9) (for a diesel engine) or ME-SFI [ME] control unit (N3/10) (for a gasoline engine) reads in the following signals in decel mode:

Function sequence for test conditions 

The function sequence is described in the following steps:

Function sequence for drive with the internal combustion engine 

The drive with the internal combustion engine represents the standard driving mode.

Driving occurs in standard driving mode if

Additional function requirements for driving off 

Function sequence for driving off 

The vehicle moves according to the torque request of the driver which is read in by the ME-SFI [ME] control unit, initially purely electrically. For a respectively high performance request the internal combustion engine is started, rotational speed-synchronized and then coupled to the traction drive. In the case of strong acceleration the electrical machine is supported by the internal combustion engine, in particular for acceleration from low rotational speeds. If the vehicle is started off while in a combustion engine operating status, the wet clutch (except model 222.173) or the engine separator clutch (model 222.173) is used as the starting device.

During driving off the request for torque by the driver is read in by the CDI control unit or the ME-SFI [ME] control unit. The CDI control unit or ME-SFI [ME] control unit calculates and distributes the required starting torque to the internal combustion engine and the electrical machine. To do this the CDI control unit or ME-SFI [ME] control unit requests an additional motorized torque via the power electronics control unit.

The electrical machine is supplied over the power electronics control unit with energy from the high-voltage battery.

Driving off purely electrically can occur, if

IMPORTANT If the internal combustion engine is off (e.g. automatic engine stop), the oil supply for the A/T is secured over the electrical auxiliary oil pump (M42).

Additional information on automatic engine start, automatic engine stop and oil supply for the automatic transmission is available in the descriptions of the associated functions.

Function sequence for 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. When starting off in boost mode, torque synchronization between the combustion engine and the electric machine is realized by means of appropriate actuation of the wet clutch or engine separator clutch. To do this the ME-SFI [ME] control unit requests actuation of the wet clutch or engine separator clutch via the CAN network. In boost mode in higher vehicle speed ranges the wet clutch or engine separator clutch is actuated in such a way that just a regulated zero slip situation is set. In order to match the torque request from the driver, the ME-SFI [ME] control unit requests in the same way from the power electronics control unit, as for electrical operation, a torque from the electrical machine which then operates together with the internal combustion engine on the drive.

Further information concerning actuation of the wet clutch or engine separator clutch is available in the associated documents.

In order to meet the request for torque from the driver the CDI control unit or the ME-SFI [ME] control unit makes a request to the power electronics control unit for the maximum available torque from the electrical machine.

The power electronics control unit actuates the electrical machine appropriately based on the signals tolerable discharge voltage/current reported by the CDI control unit or the ME-SFI [ME] control unit.

To do this the CDI control unit or the ME-SFI [ME] control unit requests from the power electronics control unit the previously calculated motorized torque from the electrical machine. This is provided with energy from the high-voltage battery over the power electronics control unit and works together with the internal combustion engine on the drive.

Function sequence for 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 or engine separator clutch is opened, the combustion engine switched off by the ME-SFI [ME] control unit, and the sound generator activated (H4/16) (model 222.173) provided certain prerequisites are fulfilled.

At least all of the following prerequisites must be fulfilled and releases awarded:

The function sequence is subdivided into the following transmission modes:

Function sequence for electrical driving mode 

In order to meet the request for torque from the driver the ME-SFI [ME] control unit or the CDI control unit makes a request to the power electronics control unit for the required immediate torque from the electrical machine according to the load request.

The power electronics control unit actuates the electrical machine appropriately on the basis of the tolerable discharge voltage/tolerable current signal from the ME-SFI [ME] control unit or the CDI control unit. To do this the ME-SFI [ME] control unit or the CDI control unit requests from the power electronics control unit the previously calculated motorized torque from the electrical machine. This is provided with energy from the high-voltage battery over the power electronics control unit and acts on the drive. To do this the high-voltage battery supplies the power electronics control unit with a direct voltage, which is converted into a 3-phase AC voltage.

The ME-SFI [ME] control unit or the CDI control unit requests actuation of the wet clutch or engine separator clutch via the CAN network to the fully integrated transmission control unit in order to disconnect the combustion engine from the powerplant. After receiving feedback that the wet clutch or engine separator clutch is open, the ME-SFI [ME] control unit shuts off the combustion engine and activates the sound generator (model 222.173). If during the automatic engine stop a release is retracted or a prerequisite is no longer fulfilled, the internal combustion engine will automatically be started without any defined action on the part of the driver.

Function sequence for creeping 

If the brake and accelerator pedals are not applied, the creeping that is typical of automatic transmissions is simulated by the electric machine or by the combustion engine and slipping of the wet clutch or engine separator clutch. For creeping in electrical mode the electrical machine is supplied with a low current and operates directly on the drivetrain with acts with the torque that is generated in this way. If, for example, the high-voltage battery has a low charge level, creeping is realized by the combustion engine and slipping of the wet clutch or engine separator clutch.

Additional function requirements for alternator operation 

Function sequence for cruising mode 

If the brake and accelerator pedals are not applied while the vehicle is in motion in drive program "E" (Economy), the wet clutch or engine separator clutch is opened to disconnect the combustion engine from the powerplant up to a speed < 160 km/h.

For a slightly actuated accelerator pedal, the electrical machine supports the drive for an adequately high charge level of the high-voltage battery in order to counteract the falling vehicle speed.

To do this the CDI control unit or the ME-SFI [ME] control unit requests an engine-generated torque from the power electronics control unit via the CAN network. This actuates according to the request from the electrical machine.

Function sequence for alternator operation 

During alternator operation the electrical machine, driven by the internal combustion engine, is used as an alternator in order to generate electrical energy.

In order to do this, the rotational energy of the crankshaft is taken up by the rotor of the electrical machine. Rotation of the rotor causes an AC voltage to be induced in the three stator windings. The electrical energy in the form of a 3-phase AC voltage that is generated in this way is limited, monitored and converted into high voltage direct voltage by the power electronics control unit.

The power electronics control unit uses the energy generated to supply the high voltage on-board electrical system, the electrical A/C compressor (A9/5) and the 12 V on-board electrical system and its assembly parts.

Additional function requirements for load point shifting 

Function sequence for load point shifting 

The possibility of take up of recuperation energy by the high-voltage battery increases with increasing deviation from the optimal charge level of the high-voltage battery (SOC operating point). This means, if the high-voltage battery is charged or discharged for a low or very high SOC value, increased energy losses are incurred in the form of heat. In order to reduce this and to keep space open for potentially arising regenerative energy, the high-voltage battery is discharged with the support of the internal combustion engine by the electrical machine for exceeding of a defined SOC value.

In this way the load point of the internal combustion engine is shifted. That means that the torque of the internal combustion engine is reduced by the CDI control unit or the ME-SFI [ME] control unit.

The goal is to shift the load points as much as possible within the load point range while maintaining a good efficiency. The load point shifting is also used to more strongly load the internal combustion engine. In this way the CATs are brought up to operating temperature more quickly and the exhaust temperature required for regeneration of the diesel particulate filter is reached (for a diesel engine).

  Electrical function schematic for vehicle statuses of the hybrid drive system   PE08.30-P-2069-97SEH 
  Overview of system components, hybrid drive system   GF08.30-P-9999LFH 
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