Air-Fuel Ratio Control Using Upstream Sensor
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Solution Overview
Problem
The richer the air-fuel ratio in an internal combustion engine, the higher the carbon monoxide in exhaust gas, leading to increased hydrogen production in the exhaust purification catalyst, which causes the downstream air-fuel ratio sensor to deviate, resulting in prolonged high hydrogen concentrations and increased oxygen storage, deteriorating exhaust emissions.
Innovation Solution
An internal combustion engine with an air-fuel ratio control system that switches the target air-fuel ratio based on oxygen storage estimates and sensor readings to maintain the air-fuel ratio closer to stoichiometric, using upstream and downstream air-fuel ratio sensors to adjust fuel input and prevent rich-side deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the target air-fuel ratio is switched to a lean set air-fuel ratio to reduce oxygen storage in the exhaust purification catalyst, then oxygen storage is reduced, but the downstream side air-fuel ratio sensor output deviates to the rich side due to high hydrogen concentration, causing the air-fuel ratio control to become inaccurate
Solution Approach 1:
The patent introduces an upstream side air-fuel ratio sensor as an intermediary measurement device located before the exhaust purification catalyst. This sensor provides accurate air-fuel ratio information that is not affected by hydrogen interference, allowing the control system to maintain precise air-fuel ratio control even when the downstream sensor output is deviated by high hydrogen concentration. The upstream sensor acts as a mediator to bypass the measurement error caused by hydrogen.
Solution Approach 2:
The patent divides the air-fuel ratio measurement function into two separate locations: upstream of the exhaust purification catalyst (for accurate measurement) and downstream (for monitoring). By segmenting the measurement system, the patent isolates the hydrogen interference problem to only affect the downstream sensor, while the upstream sensor provides clean measurement data for control purposes.
2Measurement precision
If the target air-fuel ratio is maintained at a rich set air-fuel ratio to improve sensor measurement accuracy, then measurement accuracy is maintained, but oxygen storage in the exhaust purification catalyst increases, deteriorating exhaust emission
Solution Approach 1:
The patent implements a feedback control system that uses the upstream side air-fuel ratio sensor output to continuously adjust the fuel injection amount. The control unit compares the upstream sensor reading with the target air-fuel ratio and dynamically adjusts fuel supply to maintain the desired air-fuel ratio, preventing excessive oxygen storage while ensuring accurate measurement through the upstream sensor that is not affected by hydrogen interference.
3Object-generated harmful factors
If the target air-fuel ratio is frequently switched between rich and lean sets to optimize emission control, then emission control is improved, but the response time is delayed due to hydrogen interference with the downstream sensor
Solution Approach 1:
The upstream side air-fuel ratio sensor serves as an intermediary that provides immediate and accurate feedback for air-fuel ratio switching decisions. Since this sensor is not affected by hydrogen interference, it enables rapid and accurate detection of air-fuel ratio changes, allowing the control system to respond quickly to switching requirements without the delays caused by hydrogen interference in the downstream sensor.
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 effectively suppresses exhaust emission deterioration by maintaining optimal air-fuel ratios and oxygen storage, ensuring efficient exhaust gas purification and reduced NOx and HC emissions.
Implementation Method 1
an exhaust purification catalyst arranged in an exhaust passage and able to store oxygen
Implementation Method 2
a downstream side air-fuel ratio sensor arranged at a downstream side of the exhaust purification catalyst in a direction of exhaust flow and detecting an air-fuel ratio of an outflowing exhaust gas flowing out from the exhaust purification catalyst
Implementation Method 3
hydrogen has a fast speed of passing through a diffusion regulating layer of an air-fuel ratio sensor
Data Source
AI summary
An air-fuel ratio control device switches a target air-fuel ratio from a lean set air-fuel ratio to a rich set air-fuel ratio after judging that an air-fuel ratio of an outflowing exhaust gas has become a stoichiometric air-fuel ratio and an oxygen storage amount of an exhaust purification catalyst has become a switching reference storage amount, and makes an average value of the target air-fuel ratio the stoichiometric air-fuel ratio to less than the lean set air-fuel ratio, from after the estimated value of the oxygen storage amount has become the switching reference storage amount or more until judging that the air-fuel ratio of the outflowing exhaust gas has become the stoichiometric air-fuel ratio if the estimated value of the oxygen storage amount becomes the switching reference storage amount or more before judging that the air-fuel ratio of the outflowing exhaust gas has become the stoichiometric air-fuel ratio.