Ion Current Detection in Engine Ignition Coils
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Solution Overview
Problem
Conventional combustion state detection apparatuses for internal combustion engines struggle to accurately detect abnormal combustion due to the inability to detect ion current during the period immediately before and after ignition, as the spark discharge and negative voltage applied to the ignition plug prevent accurate ion current measurement.
Innovation Solution
The apparatus includes an ignition coil with a primary and secondary winding, an ignition plug, a switching element, and control means to manage the spark discharge, allowing for the detection of ion currents generated during combustion and determining abnormal combustion by comparing crank angles where the ion current exceeds a predetermined value, with the spark discharge being ended at a predetermined timing to minimize the period of negative voltage application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spark discharge is maintained for normal combustion, then the air-fuel mixture is properly ignited, but the ion current cannot be detected during the spark discharge period
Solution Approach 1:
The control unit ends the spark discharge at a predetermined timing while the spark discharge is in progress, before the ion current detection period begins. This preliminary action of terminating the spark discharge ensures that the negative voltage application is minimized, allowing the ion current to be detected with high accuracy during the subsequent detection period without interference from the spark discharge.
2Duration of action of moving object
If the ion current detection period includes the spark discharge period, then continuous monitoring is achieved, but the ion current detection accuracy decreases
Solution Approach 1:
The detection period is segmented into distinct phases: a spark discharge period where the ignition plug generates spark, and an ion current detection period where the control unit measures ion current. By dividing the monitoring timeline into these separate segments with the spark discharge ended at predetermined timing, the system achieves both continuous monitoring coverage and high detection accuracy in the ion current period.
3Power
If the negative voltage application duration is extended, then the spark discharge effectiveness is maintained, but the ion current detection period is reduced
Solution Approach 1:
The system employs periodic action by ending the spark discharge at a predetermined timing while the spark discharge is in progress, creating a cyclic pattern of spark generation followed by ion current detection. This periodic alternation between spark discharge phase and detection phase ensures that the negative voltage application is minimized, maximizing the ion current detection time while maintaining effective spark discharge during its active period.
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
This approach enables high-accuracy detection of abnormal combustion, reducing the duration of undetectable ion current periods and improving engine efficiency, thereby addressing issues related to engine durability and environmental impact.
Implementation Method 1
an ignition coil that has a primary winding and a secondary winding, and generates a high voltage in the secondary winding when a primary current flowing through the primary winding is shut off
Implementation Method 2
an ignition plug that is connected to the secondary winding, and generates a spark discharge for firing an air-fuel mixture in a combustion chamber
Implementation Method 3
ion current detection means for detecting, as an ion current, ions generated in combustion of the air-fuel mixture by the spark discharge
Data Source
AI summary
Disclosed is a combustion state detection apparatus for an internal combustion engine, which is capable of detecting abnormal combustion with high accuracy. The combustion state detection apparatus for an internal combustion engine includes: a variety of sensors; an ignition coil; an ignition plug; a transistor; a switching control unit; an ion current detection unit; and abnormal combustion detection units for determining that abnormal combustion has occurred in a case where a crank angle at a point of time when the ion current exceeds a predetermined current value or when the ion current that exceeds the predetermined current value reaches a peak value thereof is on a spark-advance side compared with a crank angle for determining abnormal combustion. The switching control unit ends the spark discharge at a predetermined timing while the spark discharge is in progress after the primary current is shut off and the spark discharge is generated.