Method of controlling a vehicle

Abstract

A vehicle and method for controlling a vehicle having a variable displacement engine with an auxiliary machine connected directly to the engine crankshaft and to an energy storage device includes switching from a cylinder disablement (VDE) mode to a normal mode when the torque demand and engine speed lie outside an outer range defined by a first threshold (Tout), and switching from the normal mode to the VDE mode when the torque demand and engine speed lie within an inner range, which lies within the outer range and defined by a second threshold (Tin). When operating in a band between the two thresholds, the auxiliary machine draws energy from the energy storage device and supplements the output torque from the engine if operating in the VDE mode, and derives torque from the engine crankshaft to recharge the energy storage device if operating in the normal mode.

Description

technical field [0001] The invention relates to a method of controlling a vehicle having a drive train comprising a variable displacement engine connected to the drive wheels of the vehicle through a transmission. Background technique [0002] The term "variable displacement engine" is used herein to refer to an engine with cylinder deactivation, that is, an engine in which one or more cylinders may be selectively prevented from firing and from providing output power. Cylinder deactivation can be performed in various ways in spark-ignition and diesel engines by controlling fuel delivery and, in some cases, also by modifying valve timing. The manner in which the displacement of the engine is changed is not critical to the invention and need not be described in detail here. [0003] When the vehicle is equipped with a variable displacement engine, there are only certain regions of the speed / load map where it is more efficient to operate with cylinder deactivation. [0004] i...

AI Technical Summary

Problems solved by technology

[0005] Under dynamic driving conditions, especially when the engine is operating around the threshold of the VDE deactivation mode, i.e. at figure 1 Around the range marked in , frequent switching between VDE and normal (i.e. all cylinders firing) modes may occur

In addition to such frequent mode changes being unsettling to the driver, they wear down engine components and affect engine durability

Countermeasures needed to improve robustness will have an impact on system cost

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