Control strategy for transitions between homogeneous-charge compression-ignition and spark-ignition combustion modes

摘要

A direct-injection internal combustion engine includes an intake camshaft with a low-lift intake cam and a high-lift intake cam, a variable lift control for selectively operating an intake valve in one of a low-lift intake valve profile with the low-lift intake cam and a high-lift intake valve profile with the high-lift intake cam, a variable cam phase control operative on the intake camshaft for simultaneously controlling the phase of the low-lift intake cam and the high-lift intake cam, an ignition spark control, a fuel injection control, an exhaust gas recirculation control, and an intake throttle control. A method of operating the engine includes operating the engine in one of a) a homogeneous-charge compression-ignition (HCCI) combustion mode including the low-lift intake valve profile, and b) a spark ignition (SI) combustion mode including the high-lift intake valve profile, and within a predetermined range of engine loads and camshaft phasings, wherein the low-lift intake valve profile and the high-lift intake valve profile effect a respective intake airflow in the corresponding HCCI combustion mode and SI combustion mode conducive to stable combustion exclusively through fuel and spark control. The method further includes transitioning between the HCCI and SI combustion modes exclusively through adjustments to the variable lift control, the ignition spark control, and the fuel injection control.

主权项

1. A method of operating a direct-injection internal combustion engine including an intake camshaft with a low-lift intake cam and a high-lift intake cam, a variable lift control for selectively operating an intake valve in one of a low-lift intake valve profile with the low-lift intake cam and a high-lift intake valve profile with the high-lift intake cam, a variable cam phase control operative on the intake camshaft for simultaneously controlling the phase of the low-lift intake cam and the high-lift intake cam, an ignition spark control, a fuel injection control, an exhaust gas recirculation control, and an intake throttle control, said method comprising:
initially operating the engine in one of
a) a homogeneous-charge compression-ignition (HCCI) combustion mode including the low-lift intake valve profile, andb) a spark ignition (SI) combustion mode including the high-lift intake valve profile;in response to achieving a predetermined load point and a predetermined camshaft phasing point within a predetermined range of engine loads wherein the camshaft phasing is such that combustion would be stable during a transition between combustion modes without requiring adjustment to the camshaft phasing, during the normal operation of the engine in the initial one of the HCCI combustion mode and the SI combustion mode, commanding a transition to the other one of the HCCI combustion mode and the SI combustion mode, comprising:
adjusting said variable lift control, said ignition spark control and said fuel injection control during a single engine cycle to effect respective control settings conducive to stable combustion in the corresponding commanded combustion mode without adjusting the camshaft phasing from a respective control setting corresponding to the initially operated combustion mode; andafter the transition to the commanded combustion mode is complete, adjusting the camshaft phasing to effect a respective control setting corresponding to the commanded combustion mode;wherein the predetermined engine load point and predetermined camshaft phasing point are conducive to combustion both in the HCCI combustion mode and the SI combustion mode.