Engine Air-Fuel Ratio Control During Catalyst Oxygen Occlusion
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Solution Overview
Problem
During engine startup, the combustion state of the air-fuel mixture is not stabilized, leading to increased uncombusted components in the exhaust gas, which causes deviations in the output value of the air-fuel ratio sensor, resulting in ineffective air-fuel ratio control and deteriorated emissions.
Innovation Solution
A control device with upstream and downstream air-fuel ratio sensors and a catalyst with oxygen occlusion capability performs air-fuel ratio control using PID feedback to stabilize the air-fuel mixture, switching control methods based on sensor output deviation and catalyst functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air-fuel ratio control is performed based on the output value of the air-fuel ratio sensor during engine startup, then air-fuel ratio control is attempted, but the output value of the sensor is deviated from the actual air-fuel ratio due to uncombusted components, resulting in ineffective control and deteriorated emissions
Solution Approach 1:
The control device performs preliminary identification of engine startup state and pre-establishes alternative control strategies before the sensor output becomes unreliable. During engine startup, the system detects the transient state and switches to using catalyst oxygen occlusion capability as the primary control reference, avoiding reliance on inaccurate sensor readings during this period.
Solution Approach 2:
The catalyst serves as an intermediary element with oxygen occlusion capability that provides a reliable reference for air-fuel ratio control during engine startup. The control device uses the catalyst's oxygen storage/release characteristics as a mediator to infer the actual air-fuel ratio when sensor output is compromised by uncombusted components.
2Speed
If the upstream-side air-fuel ratio sensor is used for control during engine startup, then control response is fast, but the sensor output is affected by uncombusted components causing deviation from actual air-fuel ratio
Solution Approach 1:
The control device dynamically switches between different control references based on engine operating conditions. During engine startup, it transitions from using the upstream-side sensor (fast response but inaccurate) to using the catalyst's oxygen occlusion capability (slower but more reliable), and eventually returns to the upstream sensor when combustion stabilizes and sensor output becomes accurate.
3Device complexity
If conventional air-fuel ratio control is used during engine startup, then the control system operates simply, but emissions deteriorate due to uncombusted components affecting sensor output
Solution Approach 1:
The control device implements dynamic adaptation by switching control strategies based on engine startup state detection. It monitors engine operating conditions and transitions between different control modes (sensor-based during normal operation, catalyst-based during startup), maintaining simple control during stable operation while ensuring emission control during startup transitions.
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 suppresses emissions after engine startup by accurately controlling the air-fuel ratio, purifying uncombusted components, and ensuring the catalyst's oxygen occlusion capability is effectively utilized.
Implementation Method 1
a catalyst that is provided in an exhaust passage and that possesses an oxygen occlusion capability
Data Source
AI summary
The control device controls the air-fuel ratio of the air-fuel mixture based on the output value of the downstream-side air-fuel ratio sensor until a period from the engine startup start until the oxygen occlusion capability function is obtained in the catalyst elapses. The control device performs air-fuel ratio control of the air-fuel mixture on the basis of the output value of the upstream-side air-fuel ratio sensor after the elapse of the period from the engine startup start until the oxygen occlusion capability function is obtained in the catalyst.