Engine Combustion Control Cylinder Air-Fuel Ratio
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Solution Overview
Problem
Existing engine combustion control systems face challenges in maintaining a consistent air-fuel ratio across multiple cylinders, particularly during low-load operations and when internal EGR is performed, due to variations in re-intake amounts of intake air and return amounts of burned gas, leading to instability in engine output and fuel efficiency.
Innovation Solution
A combustion control device that adjusts the fuel injection amount in each cylinder based on specific re-intake correction amounts, calculated using a polynomial model incorporating valve overlap, intake/exhaust differential pressure, and engine speed, to match air-fuel ratios across cylinders, while also considering structural differences in intake and exhaust passages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If internal EGR is performed by setting valve overlap, then in-cylinder temperature is increased to enable self-ignition, but variation in air-fuel ratio between cylinders occurs due to differences in re-intake amount of intake air
Solution Approach 1:
The control device changes the fuel injection amount as a parameter to compensate for variations in air-fuel ratio. By calculating the re-intake amount of intake air for each cylinder and comparing it with the target value, the system adjusts the fuel injection amount to maintain consistent air-fuel ratio across all cylinders during internal EGR operation
Solution Approach 2:
The system implements feedback control by continuously monitoring the re-intake amount of intake air for each cylinder, comparing it with target values, and adjusting the fuel injection amount accordingly. This closed-loop control ensures that air-fuel ratio variations between cylinders are corrected in real-time
2Volume of moving object
If independent intake passages are made short for compact engine design, then mountability is improved, but intake air is blown out to surge tank during valve overlap and re-intaken into other cylinders causing air-fuel ratio variation
Solution Approach 1:
The control device adjusts the fuel injection amount based on the re-intake amount of intake air calculated for each cylinder. By compensating for the air-fuel ratio variation caused by short independent intake passages through parameter changes in fuel injection, the system maintains consistent combustion across all cylinders while preserving compact engine design
Solution Approach 2:
Instead of modifying the mechanical structure of the intake passages to prevent air blow-out to the surge tank, the system substitutes a control-based solution by adjusting fuel injection amounts to compensate for the resulting air-fuel ratio variations, thereby maintaining performance without increasing mechanical complexity
3Stability of the object's composition
If fuel injection amount is adjusted based on re-intake correction amounts, then air-fuel ratio variation between cylinders is reduced, but calculation complexity increases due to polynomial model requirements
Solution Approach 1:
The control device performs self-service by automatically calculating the re-intake amount of intake air for each cylinder using the polynomial model and adjusting the fuel injection amount accordingly. The system independently determines the necessary corrections without external intervention, maintaining air-fuel ratio consistency through autonomous control calculations
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 reduces variations in air-fuel ratios between cylinders, enhancing engine stability and fuel efficiency by accurately correcting fuel injection amounts based on real-time operating conditions and structural characteristics.
Implementation Method 1
calculated using a polynomial model incorporating valve overlap, intake/exhaust differential pressure, and engine speed
Implementation Method 2
the intake air once blown out of the intake port of one cylinder reaches the surge tank through the independent intake passage due to an intake/exhaust differential pressure
Data Source
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AI summary
A combustion control device for an engine includes a plurality of cylinders, a surge tank disposed in an intake path to the cylinders, an independent intake passage connecting the surge tank and an intake port of each of the cylinders, a fuel injection valve that is disposed for each of the cylinders and that supplies fuel into each of the cylinders, and a control unit that controls a fuel injection amount of each of the fuel injection valves according to an engine operating state. The control unit corrects a target fuel injection amount of each of the cylinders, the target fuel injection amount being determined according to the engine operating state, based on a re-intake correction amount set in each of the cylinders according to a re-intake amount of intake air from the intake port in internal EGR in each of the cylinders.