Multi-Spark Ignition Control via Dynamic PWM and Current Feedback
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Solution Overview
Problem
Existing multi-charge ignition systems for lean air-fuel mixtures face issues with spark plug wear and energy inefficiency due to uncontrolled secondary currents and fixed PWM-signal settings, leading to misfires and increased emissions.
Innovation Solution
A communication protocol is implemented to control primary and secondary current thresholds and voltages through the EST line, allowing for dynamic adjustment of current levels and voltage parameters to optimize spark plug operation, reducing wear and energy wastage by stabilizing current flows and managing secondary current peaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multi-charge ignition systems are used to reduce ignition system size and improve spark duration, then the ignition system size is reduced and spark duration is extended, but the spark is interrupted during recharge periods causing misfires and higher emissions
Solution Approach 1:
The system performs preliminary charging of the capacitor during the recharge period before the spark is needed. This ensures that the capacitor is fully charged and ready to deliver the required energy immediately when the spark event occurs, eliminating the interruption problem while maintaining compact size
2Device complexity
If fixed PWM-signal values are used in the step-down-converter stage, then the control system is simple, but the primary current becomes non-stable under various operating conditions
Solution Approach 1:
The PWM signal duty cycle is dynamically adjusted based on operating conditions such as battery voltage and load requirements. This dynamic adaptation allows the step-down-converter to maintain stable primary current despite varying operating conditions, while the adjustment logic remains relatively simple
3Device complexity
If uncontrolled secondary current is allowed to flow, then the system operation is simple, but spark plug wear increases and energy is wasted
Solution Approach 1:
The system implements current sensing and feedback control to monitor and regulate secondary current flow. This feedback mechanism ensures that current is only drawn when needed for combustion, preventing energy waste and reducing spark plug wear, while the control logic remains relatively straightforward
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 solution effectively reduces spark plug wear and energy wastage, stabilizes current flows, and minimizes secondary current peaks, enhancing the efficiency and reliability of the ignition system.
Implementation Method 1
a step-down converter which has a primary coil and a secondary coil and in which the ratio of the number of windings of the primary coil to the number of windings of the secondary coil is greater than 1
Implementation Method 2
an ignition coil which has a primary coil and a secondary coil and in which the ratio of the number of windings of the primary coil to the number of windings of the secondary coil is greater than 1
Data Source
Figure 1
Figure 2a~2c
Figure 3
AI summary
A method of controlling an ignition system, said ignition system including a spark plug control unit adapted to control at least one coil stage (T1, T2), said coil stage (T1, T2) adapted to successively energise and de-energise said coil stage(s) (T1, T2) to provide a current to a spark plug, each of said coil stage(s) (T1, T2) including a primary winding (L1, L3) inductively coupled to a secondary winding (L2, L4), comprising: measuring the low side voltages at the one or more of each primary and/or secondary windings, and controlling the duty cycle or the pulse width of the PWM-signal of the step-down-converter (M1, D3) dependent on the battery voltage, maximum primary current threshold and said measured voltages.