Engine Control System for Stable HCCI-SI Mode Transition
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Solution Overview
Problem
Conventional engine control systems face challenges in stabilizing combustion when switching between Homogeneous-Charge Compression Ignition (HCCI) and Spark-Ignition (SI) combustion modes, leading to unstable combustion and increased nitrogen oxide generation, which degrades emission performance and fuel consumption.
Innovation Solution
A control system that includes an exhaust variable valve mechanism, a fuel injection controlling module, and in-cylinder state quantity estimating modules to adjust fuel injection timing based on the operating state of the engine, ensuring suitable fuel injection for combustion stability and minimizing stratified spark-ignition combustion duration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the exhaust valve operation mode is switched from HCCI mode to SI mode during combustion mode transition, then the engine can operate in the SI combustion range, but the internal EGR amount becomes insufficient for HCCI combustion and excessive for SI combustion, causing unstable combustion and knocking
Solution Approach 1:
The patent applies dynamics by making the fuel injection timing adjustable based on the combustion mode. The control device dynamically changes the fuel injection timing to a timing suitable for stratified spark-ignition combustion during the transition period, allowing the system to adapt to changing combustion modes while maintaining stability. This resolves the contradiction by enabling the engine to handle transient states where the exhaust valve operation mode does not yet match the desired combustion mode.
Solution Approach 2:
The patent changes the fuel injection timing parameter during combustion mode transition. When the control device detects that the combustion mode is transitioning and the current fuel injection timing is not suitable for the target combustion mode, it adjusts the fuel injection timing to an appropriate value for stratified spark-ignition combustion. This parameter change enables stable combustion during transition periods, resolving the instability caused by mismatched exhaust valve operation modes.
2Reliability
If stratified spark-ignition combustion is performed to assist self-ignition during combustion mode switching, then unstable combustion can be prevented, but nitrogen oxide generation increases and fuel consumption degrades
Solution Approach 1:
The patent uses feedback by continuously monitoring the combustion mode and detecting transitions between HCCI and SI combustion modes. The control device detects when the operating state shifts ranges and when the exhaust valve operation mode does not match the combustion mode, then responds by adjusting the fuel injection timing. This feedback mechanism ensures stratified spark-ignition combustion is performed only when necessary during transitions, minimizing nitrogen oxide emissions while maintaining combustion stability.
Solution Approach 2:
The patent applies periodic action by limiting stratified spark-ignition combustion to specific transition periods rather than performing it continuously. The control device performs stratified spark-ignition combustion only during the transient period when combustion mode switching is detected and the exhaust valve operation mode has not yet matched the combustion mode. Once the transition is complete and combustion mode matches the operating state, the system returns to standard combustion mode, thereby reducing overall nitrogen oxide emissions while maintaining stability during critical transition periods.
3Speed
If the exhaust valve operation mode is switched during combustion mode transition, then the engine can respond to operating state changes, but the transition period causes insufficient EGR for HCCI and excessive EGR for SI, leading to unstable combustion
Solution Approach 1:
The patent applies preliminary action by proactively adjusting the fuel injection timing before the exhaust valve operation mode completes its transition. When the control device detects a combustion mode transition and identifies that the current fuel injection timing is unsuitable for the target combustion mode, it提前 (in advance) changes the fuel injection timing to the appropriate value for stratified spark-ignition combustion. This preliminary adjustment ensures combustion stability is maintained during the transition period, preventing instability that would occur if the system waited for the exhaust valve mode to naturally transition.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents unstable combustion and reduces emission performance degradation and fuel consumption by optimizing fuel injection timing during mode switches between HCCI and SI combustion, while maintaining stable combustion performance.
Implementation Method 1
use a so-called internal exhaust gas recirculation (EGR) system for opening an exhaust valve in a predetermined valve-open period during an intake operation to reverse burned gas back into a combustion chamber from an exhaust port, so as to increase a temperature of a mixture gas inside the combustion chamber
Implementation Method 2
fuel is injected by a fuel injector on a compression stroke to form a stratified mixture gas concentrating around an ignition plug
Implementation Method 3
the stratified mixture gas is ignited to combust (stratified spark-ignition combustion), so as to induce self-ignition of the pre-mixture gas
Data Source
AI summary
A control system of an engine is provided. The control system includes an exhaust variable valve mechanism for changing an operation mode of an exhaust valve, a fuel injection controlling module for controlling a fuel injector to inject fuel at a fuel injection timing associated with an operating state of the engine, a variable valve mechanism controlling module for operating the exhaust valve via the exhaust variable valve mechanism in a first operation mode when the operating state of the engine is within a compression self-ignition range, and in a second operation mode when the operating state of the engine is within a spark-ignition range, and a first in-cylinder state quantity estimating module for estimating a first state quantity inside the cylinder relating to a burned gas amount within the cylinder.