Deceleration Mode, Function - GF08.30-P-2004LFH

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 

The subfunction "Deceleration mode function" is considered and described from the point of view of the hybrid drive system.

We will not go into more detail here about internal signals and function sequences of the internal combustion engine. These are described in the associated document:

Function requirements for deceleration mode - general points 

• Hybrid drive system "READY"
• Accelerator not operated
• Service brakes not operated
• Vehicle rolling
• Gear range "D"

Deceleration mode - general points 

If the brake and accelerator pedal is not actuated for a rolling vehicle, then:

• kinetic energy is taken up over the electrical machine (A79/1) and converted into electrical energy (regenerative braking) for a low charge level of the high-voltage battery (A100g1).
• A deceleration fuel shutoff of the internal combustion engine can also take place.

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

If the brake pedal is actuated regenerative braking occurs.

Detailed information can be found in the associated function.

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:

• Accelerator pedal sensor (B37), accelerator pedal position
• Fully integrated transmission control unit (Y3/8n4) via the CAN network:
  • Gear range status
  • Wet clutch status
  • Transmission oil temperature, signal
  • Status of the electrical auxiliary oil pump (M42)
• Electronic Stability Program control unit (N30/4), via the CAN network:
  • Wheel speed
  • Service brake, status
• Battery management system control unit (N82/2) via the CAN network:
  • High-voltage battery voltage
  • Temperature of high-voltage battery
• Power electronics control unit (N129/1) via the CAN network:
  • Status of electrical machine
  • Torque of electrical machine
  • Rotational speed of electrical machine
  • Tolerable charging voltage/current signal

Function sequence for deceleration mode 

The CDI or ME-SFI [ME] control unit calculates a nominal overrun torque depending on the charge level of the high-voltage battery and the selected drive program which the CDI control unit or the ME-SFI [ME] control unit implements with overrun mode fuel shutoff and/or recuperation.

Cruising mode without use of the accelerator pedal 

If the brake and accelerator pedal are not applied when the vehicle is in motion and recuperation can take place, the combustion engine will in drive program "E" (Economy) up to a speed < 180 km/h be disconnected from the drive train through the opening of the wet clutch and switched off. If it is not possible for recuperation to take then the deceleration fuel shutoff of the internal combustion engine can also be activated.

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.

Regenerative braking in deceleration mode 

Kinetic energy is taken up over the electrical machine and converted into electrical energy (regenerative braking) for a low charge level of the high-voltage battery. To do this the CDI control unit or the ME-SFI [ME] control unit requests a generative torque from the power electronics control unit via the hybrid CAN (CAN L).

This actuates according to the request from the electrical machine. Regenerative actuation of electrical machines and generates an AC voltage. This is converted by the power electronics control unit into a direct voltage and fed to the high-voltage battery.

In overrun mode > 180 km/h or in drive program "S" (Sport), the wet clutch remains closed and the combustion engine goes into overrun mode fuel shutoff and generates an overrun torque. The electrical machine supports this deceleration torque if necessary by a generative torque.

In deceleration mode and active deceleration fuel shutoff the internal combustion engine generates a boost torque which can be greater together with the recuperative boost torque than the calculated specified boost torque. In this case the deceleration fuel shutoff is not activated and the internal combustion engine generates a minimum actuatable torque. This concept ensures that the drive always remains the same for the driver as much as possible, with and without deceleration fuel shutoff.

The decel mode with deceleration fuel shutoff is more effective from an energy usage point of view. At a low charge level for the high-voltage battery and a low nominal deceleration torque the regenerative braking in deceleration mode without deceleration fuel shutoff is actually more meaningful.

	Deceleration mode electrical function schematic		PE08.30-P-2061-97SEH
	Overview of system components, hybrid drive system		GF08.30-P-9999LFH