Engine Stop Fuel Control to Reduce Hydrocarbon Emissions
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Solution Overview
Problem
During engine stopping and restarting, fuel puddles in engine cylinder ports can lead to raw hydrocarbon emissions as these unburned hydrocarbons are ejected into the exhaust system, contributing to vehicle emissions, and existing methods fail to effectively reduce these emissions during the cranking process.
Innovation Solution
A method involving a controller that ceases fuel supply to the engine based on an anticipated stop request, followed by reintroducing fuel after a predetermined time to minimize fuel puddles and ensure seamless engine operation, using a combination of direct and port fuel injection strategies and electric machine assistance to rotate the engine unfueled, thereby reducing hydrocarbon emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuel is injected into the engine before stopping, then the engine has sufficient fuel for operation, but fuel puddles form in cylinder ports leading to increased hydrocarbon emissions during restart
Solution Approach 1:
The controller anticipates an engine stop request and ceases fuel injection before the actual stop occurs. This preliminary action removes fuel from the cylinder ports before the engine stops, preventing fuel puddles from forming and thereby reducing hydrocarbon emissions during subsequent restart, while still maintaining reliable operation by timing the fuel cessation appropriately
2Object-generated harmful factors
If fuel injection is ceased before engine stop, then fuel puddles are reduced, but engine stopping duration is extended
Solution Approach 1:
Fuel injection is ceased in advance of the actual engine stop request, allowing fuel puddles to be reduced before the stop occurs. The controller is configured to resume fuel injection if the stop request is not received within a threshold time, ensuring that the engine can restart seamlessly without significant stopping duration extension while still achieving emission reduction
3Object-generated harmful factors
If the engine is rotated without fuel during cranking, then fuel puddles are minimized, but the catalyst cannot process the fuel effectively
Solution Approach 1:
The engine is rotated without fuel injection during the cranking phase before restart, which minimizes fuel puddles in the cylinder ports. After the engine starts running normally, fuel injection is resumed so that the catalyst can process the fuel effectively. This sequential approach ensures both emission reduction during cranking and proper emission control during normal operation
Data Source
AI summary
Systems and methods for stopping an engine of a vehicle are described. In one example, the method anticipates when an engine is expected to stop and modifies engine operation so that less fuel is in the engine's intake ports when the engine is stopped so that the fuel may not escape the engine when the engine is restarted.