Ignition Coil Energization Control for Pre-Ignition Protection
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Solution Overview
Problem
In internal combustion engines, pre-ignition can lead to a no-discharge state during high in-cylinder gas density conditions, potentially damaging the spark plug due to excessive coil-generated voltage, especially in low-speed high-load regions, and existing solutions either risk spark plug damage or fail to ensure ignition in flammable regions like those with high exhaust gas recirculation.
Innovation Solution
The energization time for the primary coil is set shorter in low-speed high-load regions to prevent excessive voltage during no-discharge states, while maintaining sufficient discharge energy in other regions, ensuring spark plug safety and reliable ignition across various operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the primary coil energization time is lengthened in a high-load region to increase discharge energy, then ignition reliability is improved, but the risk of spark plug damage from no-discharge voltage increases
Solution Approach 1:
The patent applies dynamics by making the energization time variable rather than fixed. The control device dynamically adjusts the energization time based on real-time detection of pre-ignition conditions and no-discharge states. When pre-ignition is detected, the system switches to a shorter second energization time to prevent spark plug damage, while using a longer first energization time under normal conditions to ensure reliable ignition.
Solution Approach 2:
The patent changes the parameter of energization time based on operating conditions. Two distinct energization time values are defined: a first energization time for normal operation and a second energization time (shorter than the first) for pre-ignition conditions. The control device selects the appropriate energization time parameter based on detected engine state, thereby optimizing both ignition reliability and spark plug protection.
2Object-affected harmful factors
If the energization time is shortened to prevent spark plug damage during no-discharge, then spark plug safety is improved, but ignition reliability in hardly-flammable regions deteriorates
Solution Approach 1:
The system dynamically selects energization time based on detected conditions. When pre-ignition is detected and no-discharge occurs, the shorter second energization time protects the spark plug. When no pre-ignition is detected, the longer first energization time ensures reliable ignition even in hardly-flammable regions such as high EGR or lean-burn conditions.
Solution Approach 2:
The control device changes the energization time parameter based on engine operating state. The first energization time is sufficient for reliable ignition in challenging conditions, while the second energization time is specifically used when pre-ignition is detected to limit voltage exposure. This conditional parameter switching resolves the contradiction between protection and reliability.
3Device complexity
If a fixed energization time is used for all operating conditions, then control simplicity is maintained, but optimal performance across different regions cannot be achieved
Solution Approach 1:
The patent implements dynamic control where the energization time automatically adjusts based on detected operating conditions. The control device monitors engine parameters and selectively applies the first or second energization time, providing optimized performance for different operating regions while maintaining automated control that does not require complex manual intervention.
Data Source
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AI summary
When an operating condition including load and speed of an internal combustion engine (1) is in a prescribed low-speed high-load region (an energy suppression region A) having a possibility causing pre-ignition, energization time TDWLMIN for the energy suppression region is selected as an energization time for a primary coil (22a). In other normal regions, normal energization time TDWL is selected. Normal energization time TDWL has a characteristic such that the normal energization time shortens, as the engine speed increases. In a low speed region, a given energization time that can fulfil a discharge energy required in a high exhaust gas recirculation region is provided. Energization time TDWLMIN for the energy suppression region A is constant regardless of engine speeds and relatively short, and is set to a level such that a coil generated maximum voltage does not exceed a withstand voltage of a spark plug (9) even when no-discharge occurs due to pre-ignition.