Air/Fuel Ratio Sensor Output Correction for Alcohol Fuel Engines
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Solution Overview
Problem
The air/fuel ratio of internal combustion engines using alcohol-containing fuel deviates from the stoichiometric range during engine start-up, leading to a decrease in exhaust gas purification rate due to shifts in the air/fuel ratio sensor output caused by characteristic components in the exhaust gas.
Innovation Solution
An exhaust emission control apparatus that includes an air/fuel ratio sensor, feedback control, and sensor output correcting means to adjust for shifts in the air/fuel ratio sensor output based on aldehyde and hydrogen concentrations in the exhaust gas, using alcohol concentration and engine temperature data to optimize the air/fuel ratio control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air/fuel ratio feedback control is performed using only the air/fuel ratio sensor during the period until the sub-exhaust gas sensor is activated, then the air/fuel ratio can be controlled based on available sensor data, but the air/fuel ratio deviates from the purification window due to sensor output shifts caused by aldehyde and unburned alcohol components
Solution Approach 1:
The system performs preliminary classification of the operating state (warm-up period vs. normal operation) and applies different control strategies accordingly. During warm-up, it uses main feedback control with air/fuel ratio sensor only, while in normal operation it switches to sub-feedback control using sub-exhaust gas sensor to correct sensor drift, thus preventing purification rate decline before it occurs
Solution Approach 2:
The system changes the control parameter from relying solely on air/fuel ratio sensor output to using sub-exhaust gas sensor output for correction. By switching the feedback control mode based on sensor activation status, it adapts the measurement precision to the current operational conditions, ensuring reliable air/fuel ratio control throughout all engine phases
2Measurement precision
If the sub-exhaust gas sensor is installed on the downstream side of the air/fuel ratio sensor, then sub-feedback control can correct sensor output shifts, but the sub-exhaust gas sensor takes longer to warm up and is activated later than the air/fuel ratio sensor
Solution Approach 1:
The system prepares for the delayed activation by having the air/fuel ratio sensor and main feedback control ready in advance. During the warm-up period when only main feedback is available, it maintains acceptable control, and then seamlessly transitions to sub-feedback control once the sub-exhaust gas sensor activates, minimizing the overall time loss
Solution Approach 2:
The air/fuel ratio sensor serves as an intermediary during the warm-up period, providing the necessary feedback control data before the sub-exhaust gas sensor is ready. This intermediate solution bridges the time gap, allowing the system to maintain control functionality throughout the entire warm-up process without interruption
3Power
If alcohol-containing fuel is used, then the fuel provides energy, but aldehyde and unburned alcohol components in the exhaust gas cause shifts in the air/fuel ratio sensor output
Solution Approach 1:
The system converts the harmful effect of aldehyde and unburned alcohol components into useful information. By detecting the characteristic output shifts caused by these components and using them to determine when sub-feedback control should activate, the harmful interference becomes a reliable indicator for switching control modes, ensuring accurate air/fuel ratio measurement throughout operation
Data Source
AI summary
An exhaust emission control apparatus for an internal combustion engine includes: an exhaust gas purification catalyst arranged in an exhaust gas passage of the internal combustion engine; an air/fuel ratio sensor installed on an upstream side of the exhaust gas purification catalyst and detects an air/fuel ratio of an exhaust gas discharged from the internal combustion engine; air/fuel ratio feedback control means that performs feedback control of the air/fuel ratio based on an output of the air/fuel ratio sensor; and sensor output correcting means that corrects a shift in the output of the air/fuel ratio sensor. The sensor output correcting means is configured so as to correct a shift in the output of the air/fuel ratio sensor using a lean shift amount of the air/fuel ratio sensor output in accordance with a quantity and/or a proportion of an aldehyde included in the exhaust gas.