Method for controlling a motor-vehicle provided with an internal combustion engine having a system for variable actuation of the intake valves

摘要

A motor vehicle provided with an internal combustion engine having a system for variable actuation of the intake valves has a phase of activation of an operating mode with the engine off and the vehicle moving, in which the fuel supply to the engine is cut-off. After the cut-off of the fuel supply to the engine, the system for variable actuation of the intake valves is controlled to vary the opening time and/or closing time and/or the lift of the intake valves so as to control the losses due to the pumping effect which occur within the engine in cut-off condition.

主权项

1. Method for controlling a motor vehicle provided with an internal combustion engine having a system for variable actuation of intake valves, wherein said method comprises a phase of activation of an operating mode with the engine off and the vehicle moving, in which the fuel supply to the engine is cut-off, and in that after the cut-off of the fuel supply to the engine the system for variable actuation of the intake valves is controlled to vary the opening time and/or closing time and/or the lift of the intake valves so as to control the losses due to a pumping effect which occur within the engine in said cut-off condition, according to one of the following strategies:
if the speed of the engine is above a minimum-run threshold, the intake valves are controlled so as to temporarily minimize the pumping losses, to increase an engine run-down time required to reach a stop of a drive shaft of the engine, so as to allow a possible change-of-mind of the driver, and a restart of the engine by reactivating the fuel supply; if the speed of the engine is below the minimum-run threshold one of the following strategies are actuated: if the motor vehicle is provided with an electric start motor capable of operating with the internal combustion engine moving, the intake valves are controlled so as to temporarily minimize the pumping losses to increase the run-down time so as to be able to restart the internal combustion engine when it is still moving; if the motor vehicle is provided with an electric start motor capable of operating only when the internal combustion engine is stationary, the intake valves are controlled 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; and wherein the control of the intake valves to temporarily maximize the pumping losses of the internal combustion engine is obtained by controlling the system for variable actuation of the intake valves to cause a delayed opening of the intake valves with respect to a conventional intake cycle, or a total absence of opening of the intake valves.