Engine Control System Switching Fuel Calculation to Intake Pressure
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Solution Overview
Problem
When the closing timing of the intake valve in an internal combustion engine is retarded, blown-back gas in the combustion chamber becomes predominantly air upon fuel injection restart, leading to an insufficient fuel amount for the air-fuel mixture, resulting in a lean air-fuel ratio and poor combustion.
Innovation Solution
A control system that includes a variable valve timing mechanism, a fuel injector, an intake air amount detector, a throttle valve, a pressure sensor, and an electronic control unit, which temporarily stops fuel injection during engine deceleration and switches the fuel injection calculation basis from intake air to pressure in the intake passage upon restart, ensuring an optimal air-fuel mixture by calculating the total air amount in the combustion chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the closing timing of the intake valve is retarded to improve thermal efficiency, then the air-fuel ratio becomes lean upon fuel injection restart, but combustion quality deteriorates
Solution Approach 1:
The system detects engine deceleration conditions in advance and temporarily stops fuel injection before the intake valve closes. This preliminary action prevents fuel from being injected into the combustion chamber when the retarded intake valve would cause blown-back air to mix with the fuel-air mixture, thereby preventing lean combustion upon restart while maintaining the beneficial retarded valve timing for thermal efficiency
Solution Approach 2:
The control unit continuously monitors engine operating conditions including intake air amount, engine speed, and throttle opening degree. Based on this feedback, the system determines when engine deceleration is occurring and adjusts fuel injection timing accordingly. The feedback mechanism enables real-time adaptation of fuel injection strategy to maintain optimal air-fuel ratio despite variable valve timing conditions
2Loss of substance
If fuel injection is temporarily stopped during engine deceleration to replace combustion gas with fresh gas, then the air-fuel ratio becomes excessively lean upon restart, but proper fuel amount cannot be supplied
Solution Approach 1:
Fuel injection is stopped in advance during engine deceleration to allow combustion gases to be replaced with fresh intake air. The system calculates the duration of fuel injection stop based on detected engine conditions, ensuring sufficient fresh gas replacement while preparing for accurate fuel amount calculation upon restart
Solution Approach 2:
The control unit changes the calculation parameter for fuel injection amount from intake air amount to intake passage pressure upon fuel injection restart. This parameter change accounts for the volume of blown-back air that mixed with fresh gas, enabling accurate calculation of the total air volume and appropriate fuel injection quantity to achieve the correct air-fuel ratio
Data Source
AI summary
A control system comprising a variable valve timing mechanism (B) able to set a closing timing of an intake valve (7), a fuel injector (13) for feeding fuel to a combustion chamber (5), an intake air amount detector (17) for detecting an amount of intake air fed to an intake passage from the outside air, and a pressure sensor (16) for detecting the pressure in the intake passage downstream of a throttle valve (16). When air in the combustion chamber (5) is blown back to the intake passage when injection of fuel is restarted after the fuel injection is stopped at the time of deceleration operation, the basis for calculation of the fuel injection amount in the initial cycle when fuel injection is restarted is switched from the amount of intake air detected by the intake air amount detector (17) to the pressure in the intake passage detected by the pressure sensor (18).