Dual Ignition Coil System for Lean Burn Combustion
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Solution Overview
Problem
The existing ignition apparatus for internal combustion engines faces a contradiction in requiring a rapid rise in secondary voltage for favorable ignition performance and a long discharge time for lean burn combustion, which is challenging to achieve simultaneously due to the increased size of ignition coils needed for high withstand voltages.
Innovation Solution
The apparatus employs a configuration with two ignition coils, where a voltage applying unit and a voltage boosting unit, along with switching elements, control the primary and secondary coils to maintain electric discharge after initiation, allowing for optimal discharge current control and reducing the required voltage for maintaining discharge, thus lowering the design withstand voltage of the second ignition coil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the number of secondary windings of an ignition coil is reduced to rapidly raise the secondary voltage, then the ignition performance is improved, but the discharge time is shortened
Solution Approach 1:
The ignition system is divided into multiple ignition coils, each responsible for a portion of the total discharge energy. This segmentation allows each coil to have fewer secondary windings (enabling rapid voltage rise) while the combined output of multiple coils maintains sufficient total discharge time and energy for lean burn combustion.
2Reliability
If a high withstand voltage is applied to both ignition coils to enable electric discharge, then the ignition performance is improved, but the insulation distance and size of the ignition coils are increased
Solution Approach 1:
The voltage requirement for the second ignition coil is dynamically reduced after discharge initiation. The control unit switches from requiring high withstand voltage (for discharge initiation) to lower voltage (for discharge maintenance), allowing the second ignition coil to be designed with smaller insulation distance and reduced size.
Solution Approach 2:
The voltage parameter for the second ignition coil is changed from high voltage (during discharge initiation) to low voltage (during discharge maintenance). This parameter change enables the second ignition coil to be designed with reduced insulation requirements and smaller physical dimensions while maintaining effective ignition performance.
3Reliability
If multiple ignition coils are used to achieve both rapid voltage rise and long discharge time, then the ignition performance is improved, but the device complexity is increased
Solution Approach 1:
The second ignition coil serves multiple functions: it assists the first ignition coil during discharge initiation and then takes over for discharge maintenance. This multi-functionality allows the system to achieve both rapid voltage rise and long discharge time with a moderate number of coils rather than requiring many coils for each function separately.
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 configuration enables continuous electric discharge with reduced voltage requirements, allowing for a compact design by shortening the insulation distance and reducing the physical size of the second ignition coil while maintaining efficient ignition performance.
Implementation Method 1
a voltage boosting unit that boosts the voltage supplied by the voltage applying unit
Implementation Method 2
a first ignition coil and a second ignition coil that include a primary coil and a secondary coil and apply a voltage to the spark plug by the secondary coil
Data Source
AI summary
An ignition apparatus for an internal combustion engine includes: a spark plug; a first ignition coil and a second ignition coil; a battery; a booster circuit that boosts a voltage supplied from the battery; a power transistor that conducts and interrupts a primary current flowing to a primary coil included in the first ignition coil; a MOSFET that applies and interrupts the voltage boosted by the booster circuit to a primary coil included in the second ignition coil; and an ECU that starts electric discharge by the spark plug by controlling the power transistor, and repeatedly applies and interrupts the voltage boosted by the booster circuit by the MOSFET so that the electric discharge that is started is maintained.