Method for controlling a motor-vehicle provided with a propulsion system of the “mild-hybrid” type

A method for controlling a motor vehicle of the type comprising:

• an internal combustion engine having a drive shaft with an output end connected through a transmission to at least one pair of wheels of the motor vehicle and an upstream end connected to one or more auxiliary devices through a belt transmission,
• a BAS unit comprising an electric machine connected to said upstream end of the drive shaft through said belt transmission and controlled to operate as an electrical power generator, as an electric motor for starting the internal combustion engine and as an auxiliary engine for the propulsion of the motor vehicle, additionally to the internal combustion engine,
• the method comprising:
• maintaining the internal combustion engine in a cut-off condition and using the drive shaft as a simple transmission shaft in an e-motoring operating condition of the vehicle, said BAS unit being used as the only propulsion engine of the motor vehicle in the e-motoring operating condition,
• providing said internal combustion engine with a system for variable actuation of the intake valves, and
• in the e-motoring operating condition wherein the BAS unit is used as the only propulsion engine, controlling the system for variable actuation of the intake valves of the internal combustion engine to vary the opening time and/or the closing time and/or the lift of the intake valves, so as to reduce the losses due to a pumping effect which occur within the internal combustion engine when it is driven in rotation by said BAS unit in a cut-off condition;
• switching to a freewheel operating mode, such that the internal combustion engine is off and the wheels of the vehicle are not connected to the propulsion system.
• wherein when the freewheel operating mode is activated, with the internal combustion engine in a run-down mode, the following strategies are activated:
• if the speed of the internal combustion engine is above a minimum-run threshold, the intake valves are controlled so as to temporarily minimize the pumping losses to increase the engine run-down time, to allow a possible freewheel output with fuel re-injection thus avoiding a BAS or starter engine start when a starter is also provided for besides the BAS;
• if the speed of the engine is below the minimum-run threshold one of the following strategies are actuated:
• the intake valves are controlled so as to temporarily minimize the pumping losses to increase the engine run-down time, to prepare to restart the engine with the engine moving;
• the intake valves are controlled so as to temporarily maximize the pumping losses to reduce the engine run-down time, with the aim of allowing a possible engine restart with the engine stationary as soon as possible.

A method for controlling a motor vehicle of the type comprising:

• an internal combustion engine having a drive shaft with an output end connected through a transmission to at least one pair of wheels of the motor vehicle and an upstream end connected to one or more auxiliary devices through a belt transmission,
• a BAS unit comprising an electric machine connected to said upstream end of the drive shaft through said belt transmission and controlled to operate as an electrical power generator, as an electric motor for starting the internal combustion engine and as an auxiliary engine for the propulsion of the motor vehicle, additionally to the internal combustion engine,
• the method comprising:
• maintaining the internal combustion engine in a cut-off condition and using the drive shaft as a simple transmission shaft in an e-motoring operating condition of the vehicle, said BAS unit being used as the only propulsion engine of the motor vehicle in the e-motoring operating condition;
• providing said internal combustion engine with a system for variable actuation of the intake valves;
• in the e-motoring operating condition wherein the BAS unit is used as the only propulsion engine, controlling the system for variable actuation of the intake valves of the internal combustion engine to vary the opening time and/or the closing time and/or the lift of the intake valves, so as to reduce the losses due to a pumping effect which occur within the internal combustion engine when it is driven in rotation by said BAS unit in a cut-off condition;
• accelerating a switching off of the engine when the e-motoring operating condition is activated to allow a driver to promptly restart the engine in case of a change-of-mind of the driver;
• and
• switching to a freewheel operating mode, such that the internal combustion engine is off and the wheels of the vehicle are not connected to the propulsion system.