CNG Engine Fuel Switching Control System
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Solution Overview
Problem
Internal combustion engines that use compressed natural gas (CNG) face deterioration in driveability and exhaust emission properties when switching between CNG and other fuels due to changes in CNG properties, particularly after refueling, leading to improper air-fuel ratios.
Innovation Solution
A control system that determines whether CNG properties need to be learned and prohibits fuel switching until the learning process is complete, ensuring the air-fuel ratio is optimized for CNG properties, using determination and prohibition means to manage fuel changes based on feedback control and learning processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fuel switching is permitted during CNG learning period, then fuel flexibility is improved, but air-fuel ratio control deteriorates
Solution Approach 1:
The system performs preliminary learning of CNG properties before permitting fuel switching. The ECU executes learning processing to acquire CNG characteristics (such as Wobbe index and air-fuel ratio properties) during an initial period after refueling, and only after this learning is complete does the system allow fuel type changes. This ensures that when switching occurs, the control parameters are already optimized for the current CNG properties, preventing air-fuel ratio deterioration.
2Reliability
If CNG properties are learned continuously, then air-fuel ratio control is improved, but processing time is increased
Solution Approach 1:
The system implements periodic learning processing rather than continuous learning. The ECU performs learning of CNG properties at specific intervals or under specific conditions (such as after refueling operations or when property changes are detected), rather than continuously monitoring and adjusting. This periodic approach maintains reliable air-fuel ratio control while minimizing the time lost to learning processing.
3Reliability
If fuel switching is restricted during learning period, then air-fuel ratio control is improved, but fuel flexibility deteriorates
Solution Approach 1:
The system dynamically adjusts the fuel switching permission based on the learning status. The ECU monitors whether CNG learning is complete and dynamically changes the state of fuel switching permission accordingly. During the learning period, switching is restricted; after learning completion, switching is permitted. This dynamic control ensures that restrictions are applied only when necessary (during learning) while maintaining fuel flexibility when learning is complete.
Data Source
AI summary
In a control system for an internal combustion engine that can use a plurality of kinds of fuel including compressed natural gas, the invention prohibits a changeover from CNG to another fuel from being made in a period from a time when CNG is used for the first time after the start of the internal combustion engine to a time when it is determined that properties of CNG do not need to be learned, or a period from the time when CNG is used for the first time after the start of the internal combustion engine to a time when a processing of learning the properties of CNG ends.