Engine Start-up Control for Reverse Rotation Air-Fuel Ratio
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In start-stop engine systems, the air-fuel ratio shifts to a lean side when restarting the engine, leading to decreased startability and emission deterioration due to unaccounted air inflow from the exhaust port during the reverse rotation of the crankshaft.
Innovation Solution
A start-up control device with an electronic control unit that adjusts fuel injection in the expansion stroke based on the change in air amount due to gas exchange with the exhaust path, determining whether the exhaust valve is open during reverse rotation to maintain a target air-fuel ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fuel injection amount is determined without considering air inflow from exhaust port during reverse rotation, then control complexity is reduced, but air-fuel ratio shifts to lean side causing decreased startability and emission deterioration
Solution Approach 1:
The ECU determines in advance whether the exhaust valve is open at the timing when the crankshaft reversely rotates before stoppage. Based on this preliminary determination, the ECU calculates the air amount that has flowed into the cylinder from the exhaust port and adjusts the fuel injection amount accordingly. This preliminary action prevents the air-fuel ratio from shifting to lean side, maintaining reliable startability without excessive control complexity.
2Device complexity
If fuel injection amount is determined without considering air inflow from exhaust port during reverse rotation, then calculation process is simplified, but emission control performance deteriorates
Solution Approach 1:
The ECU performs preliminary determination of exhaust valve opening status before calculating fuel injection amount. This allows the system to account for air inflow from the exhaust port during reverse rotation, ensuring accurate air-fuel ratio control and preventing emission deterioration while keeping the calculation process manageable.
3Device complexity
If exhaust valve timing is not considered during reverse rotation, then control logic is simplified, but air-fuel ratio control precision decreases
Solution Approach 1:
The ECU determines in advance whether the exhaust valve is open at the specific timing when the crankshaft reversely rotates. This preliminary determination of exhaust valve timing allows the system to precisely calculate the air amount that has entered the cylinder and adjust fuel injection accordingly, maintaining high air-fuel ratio control precision without excessive control logic complexity.
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 reduces the shift in air-fuel ratio, enhancing engine startability and reducing emission deterioration by accurately controlling fuel injection in response to air changes during the restart process.
Implementation Method 1
Such reverse rotation of the crankshaft is mainly due to a significant cylinder internal pressure (compression reaction force) that the piston in the cylinder in the compression stroke receives
Implementation Method 2
when the exhaust valve is opened, air flows from the exhaust port into the cylinder in which the pressure is negative at the end of the expansion stroke
Implementation Method 3
the electronic control unit is configured to cause a fuel injection valve to inject fuel into the cylinder in the expansion stroke, and is configured to control an amount of fuel injection in accordance with an amount of air in the cylinder in the expansion stroke such that an air-fuel ratio of a mixture of the fuel and the air reaches a target air-fuel ratio
Implementation Method 4
an air-fuel mixture is ignited when the piston reaches a predetermined position near the top dead center. Accordingly, rotating force (combustion torque) is imparted to the crankshaft
Data Source
AI summary
When a crankshaft reversely rotates immediately before a stoppage of an engine, the amount of fuel injection in a cylinder in an expansion stroke is controlled to acquire a target air-fuel ratio in accordance with the amount of air in the cylinder. When the electronic control unit determines that the exhaust valve is opened at the time of reverse rotation, the amount of fuel injection is determined by considering a change in the amount of air due to exchange of gas with an exhaust path.