Engine Ignition Timing Control via Ion Current Fuel Estimation
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Solution Overview
Problem
Existing combustion control systems in engines struggle to effectively suppress preignition and abnormal combustion while maintaining thermal efficiency, as they determine preignition after the ignition event, leading to inefficient engine operation.
Innovation Solution
A combustion control system that estimates fuel properties, such as the isooctane ratio, based on ion current detection before ignition, and adjusts the ignition timing accordingly to prevent knocking and improve thermal efficiency by correcting the ignition timing in the same cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If preignition is determined based on accumulated ion current during the electricity-conducting period, then preignition detection is achieved, but combustion has already advanced considerably and substantial suppressing control cannot be executed until the next cycle
Solution Approach 1:
The system performs preliminary detection of preignition conditions by monitoring ion current during the electricity-conducting period, and executes suppressing control actions (adjusting ignition timing, fuel injection) in the same combustion cycle rather than waiting for the next cycle. This preliminary detection and immediate response approach reduces the time loss while maintaining detection accuracy.
2Reliability
If the engine is designed on the safer side to avoid abnormal combustion like preignition, then preignition suppression is improved, but thermal efficiency of the engine is lowered
Solution Approach 1:
The system dynamically adjusts ignition timing based on real-time detection of preignition conditions and fuel properties. Instead of using a fixed conservative ignition timing that reduces thermal efficiency, the system advances ignition timing when preignition risk is low and retards it when risk is detected, optimizing the balance between abnormal combustion avoidance and thermal efficiency.
Solution Approach 2:
The system uses feedback from ion current detection to continuously monitor combustion conditions and adjust ignition timing accordingly. The detected ion current provides real-time information about preignition risk, allowing the control system to optimize ignition timing dynamically rather than relying on conservative fixed settings, thereby maintaining both safety and efficiency.
3Reliability
If ignition timing is corrected based on fuel property estimation, then knocking prevention is improved, but the system complexity increases
Solution Approach 1:
The system uses ion current as an intermediary parameter to estimate fuel properties (such as octane number) without requiring direct fuel analysis. The ion current characteristics during combustion provide indirect information about fuel composition, which is then used to adjust ignition timing. This intermediary approach enables knocking prevention based on actual fuel properties while avoiding the complexity of direct fuel sensing or analysis systems.
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
The system prevents knocking and improves thermal efficiency by adjusting the ignition timing based on real-time fuel properties, allowing for optimal ignition timing considering the risk of knocking and ensuring efficient engine operation.
Implementation Method 1
an igniter which induces high voltage in the secondary coil through ON/OFF of supply of electric current to the primary coil, and causes electric discharge between plug electrodes of the spark plug by the induced high voltage
Implementation Method 2
a bias voltage generator which applies bias voltage for detecting ion current to the plug electrodes, the ion current occurring between the plug electrodes and originating in ions inside the cylinder
Data Source
AI summary
An engine combustion control system includes an ignition coil, an igniter which induces high voltage in the ignition coil to cause electric discharge between plug electrodes of an engine spark plug, a bias voltage generator which applies bias voltage to the plug electrodes, an ion current detector, an ignition controller which controls the bias voltage to be applied simultaneously to a start of a low-temperature oxidation reaction, and the electric discharge occurs at an ignition timing later than the reaction start, and an estimator which estimates a fuel property based on an ion current detected during a period from the bias voltage application start to a given timing earlier than the ignition timing. The ignition controller corrects the ignition timing according to the fuel property in the same cycle as that of the fuel property estimation, and controls so that the electric discharge occurs at the corrected ignition timing.