HCCI Engine Torque Stability During Combustion Mode Switching
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Solution Overview
Problem
HCCI engines face challenges in stabilizing engine torque when switching from HCCI combustion to spark ignition combustion, leading to abrupt torque fluctuations due to insufficient intake air and reduced torque.
Innovation Solution
The implementation of an HCCI engine with a controller that adjusts intake and exhaust valve lift amounts and timing, ensuring internal EGR levels and delaying exhaust valve closure to gradually change intake air amounts, thereby smoothing the transition to spark ignition combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the combustion mode is switched from HCCI combustion to spark ignition combustion by closing the throttle and increasing exhaust valve lift, then the air-fuel ratio returns to stoichiometric and combustion mode transitions, but insufficient intake air occurs and torque fluctuates abruptly
Solution Approach 1:
The patent applies preliminary action by switching the exhaust valve lift amount to the second lift amount before switching the intake valve lift amount when transitioning from HCCI to spark ignition combustion. This preliminary adjustment of the exhaust valve prepares the combustion chamber for the mode transition by controlling internal EGR levels in advance, preventing abrupt torque changes that would occur if both valves were adjusted simultaneously or in the wrong sequence.
Solution Approach 2:
The patent implements dynamics by using variable valve lift mechanisms for both intake and exhaust valves, allowing the lift amounts to be dynamically adjusted based on the combustion mode. The system transitions from fixed valve lift to dynamic, multi-level lift control, enabling smooth transitions between HCCI and spark ignition modes while maintaining torque stability through progressive adjustment of valve characteristics.
2Adaptability or versatility
If the throttle opening degree is reduced to switch from stratified spark ignition combustion to normal spark ignition combustion, then the air-fuel ratio reaches predetermined value, but abrupt changes occur in torque
Solution Approach 1:
The patent applies preliminary action by adjusting the exhaust valve lift amount before reducing the throttle opening degree when transitioning from stratified to normal spark ignition combustion. This preliminary exhaust valve adjustment controls internal EGR levels in advance, preparing the combustion chamber for the subsequent throttle reduction and preventing abrupt torque changes that would result from immediate throttle closure.
Solution Approach 2:
The patent implements dynamics by coordinating dynamic adjustments of both exhaust valve lift and throttle opening degree during the combustion mode transition. The system uses variable valve lift mechanisms to progressively adjust exhaust valve characteristics while simultaneously reducing throttle opening, creating a smooth, controlled transition that maintains torque stability throughout the mode change process.
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 effectively suppresses abrupt torque changes and maintains stable engine operation by gradually adjusting intake air, preventing early ignition and excessive combustion noise.
Implementation Method 1
the exhaust valve 12v is closed at a timing before the exhaust top dead center TDC so as to ensure internal EGR gas in the combustion chamber 10
Implementation Method 2
The temperature increases and the pressure rises in the air-fuel mixture contained inside the combustion chamber as a piston rises at the time of the compression stroke of the engine, so that the mixture spontaneously ignites
Implementation Method 3
An intake variable valve mechanism changes an intake lift amount, which is a lift amount of the intake valve 11v
Data Source
AI summary
An ECU switches a combustion mode of an HCCI engine from HCCI combustion to spark ignition combustion. The ECU executes the following operations a) and b) before switching an intake lift amount from a first intake lift amount to a second intake lift amount:a): switching an exhaust lift amount from a first exhaust lift amount to a second exhaust lift amount while ensuring an internal EGR amount, andb): delaying a closing timing of an exhaust valve so as to reduce the internal EGR amount after switching the exhaust lift amount from the first exhaust lift amount to the second exhaust lift amount.