Air-Fuel Ratio Control Device Feedback Precision Management
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Solution Overview
Problem
Air-fuel ratio feedback control in internal combustion engines is limited by the deterioration of detection precision in air-fuel ratio sensors due to oxygen deficiencies, leading to poorer control precision and performance indices such as engine output, fuel efficiency, and exhaust emissions during open loop control.
Innovation Solution
Implementing a control routine that continues air-fuel ratio feedback control for a predetermined period after the detection precision of the air-fuel ratio sensor deteriorates, switching to open loop control only when necessary, allowing for extended feedback control and improved precision by setting a threshold air-fuel ratio and measurement possible period based on sensor limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air-fuel ratio feedback control is terminated when detection precision deteriorates, then sensor reliability is protected, but control precision and performance indices deteriorate
Solution Approach 1:
The patent applies dynamics by making the control mode switchable between feedback control and open-loop control based on real-time detection precision assessment. The system dynamically adjusts the control strategy rather than using a fixed termination threshold, allowing optimization of both reliability and precision under varying operating conditions.
Solution Approach 2:
The patent changes the parameter of control mode (feedback vs. open-loop) based on the detection precision status. By monitoring whether the detected air-fuel ratio remains within a predetermined range and switching control strategies accordingly, the system maintains optimal performance while protecting against sensor limitations.
2Measurement precision
If air-fuel ratio feedback control is continued beyond sensor detection limits, then control precision is maintained, but detection reliability deteriorates
Solution Approach 1:
The patent uses feedback control by continuously monitoring the detected air-fuel ratio and comparing it against predetermined ranges. When the detection value remains within the acceptable range for a specified duration, feedback control is maintained. This closed-loop approach ensures precision is preserved while reliability is protected through continuous verification.
Solution Approach 2:
The patent implements preliminary action by establishing predetermined ranges and timing thresholds before control decisions are made. The system pre-defines the conditions under which feedback control should be maintained or terminated, allowing proactive management of the precision-reliability trade-off rather than reactive switching.
3Reliability
If open loop control is used when feedback control terminates, then sensor limitations are avoided, but fuel injection precision deteriorates
Solution Approach 1:
The patent uses the predetermined time range and detection value verification as an intermediary mechanism between the sensor and the control decision. This intermediary layer filters out premature termination signals, ensuring that feedback control is only terminated when genuinely necessary, thereby maintaining fuel injection precision while still protecting against sensor limitations.
4Measurement precision
If feedback control switching threshold is lowered, then control precision is improved, but oxygen supply deficiency occurs more frequently
Solution Approach 1:
The patent applies periodic action through the predetermined time duration requirement. Instead of switching control modes immediately upon detecting a boundary condition, the system requires the condition to persist for a specified time period. This periodic verification reduces false switching caused by transient oxygen supply variations while maintaining precision control when conditions are genuinely sustained.
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 enables continuous air-fuel ratio feedback control, enhancing engine output, fuel efficiency, and reducing exhaust emissions by maintaining precision during sensor limitations, compared to immediate switching to open loop control.
Implementation Method 1
When the air-fuel ratio of the exhaust gas is richer than the stoichiometric air-fuel ratio, oxygen in an atmosphere duct of the air-fuel ratio sensor is ionized by an atmosphere side electrode
Implementation Method 2
when resulting oxygen ions move to an exhaust side electrode through a solid electrolyte layer, a current flows through the air-fuel ratio sensor
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An air-fuel ratio control device includes an air-fuel ratio sensor configured such that an output current value thereof varies linearly in accordance with an oxygen concentration, and air-fuel ratio feedback control means capable of executing air-fuel ratio feedback control for feedback-controlling a fuel injection amount on the basis of a detection value from the air-fuel ratio sensor so that exhaust gas of an internal combustion engine reaches a predetermined air-fuel ratio. The air-fuel ratio control device further includes prohibiting means for prohibiting the feedback control when the air-fuel ratio reaches or exceeds a predetermined rich air-fuel ratio. The air-fuel ratio control device permits the feedback control for a predetermined period after the air-fuel ratio reaches or exceeds the predetermined rich air-fuel ratio.