Exhaust Gas Control Adjusting Air-Fuel Ratio for Catalyst Activity
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Solution Overview
Problem
The challenge is to reduce degradation in exhaust emissions caused by hydrogen's influence on air-fuel ratio sensors in internal combustion engines, particularly when the catalyst activity is low, leading to deviations in sensor output due to varying hydrogen production.
Innovation Solution
An exhaust gas control apparatus and method that includes a catalyst, a downstream air-fuel ratio sensor, an air-fuel ratio control unit, and a catalyst state estimation unit, which adjusts the air-fuel ratio based on catalyst activity to maintain a target air-fuel ratio, setting it richer when catalyst activity is higher and leaner when lower, using temperature and desorption amount calculations to optimize hydrogen management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the air-fuel ratio is controlled based on downstream air-fuel ratio sensor output, then exhaust gas control performance is improved, but sensor output deviation occurs due to hydrogen influence
Solution Approach 1:
The system performs preliminary estimation of catalyst activity based on temperature and cumulative desorption amount before the downstream sensor measurement is affected by hydrogen. This allows the target air-fuel ratio to be adjusted in advance to compensate for expected hydrogen interference, preventing sensor output deviation rather than reacting to it after occurrence.
Solution Approach 2:
The invention introduces catalyst activity estimation as an intermediary parameter between the downstream sensor and the air-fuel ratio control. By using temperature and cumulative desorption amount as intermediate indicators to infer catalyst state and hydrogen production potential, the system can adjust the target air-fuel ratio to compensate for hydrogen's interfering effect on sensor measurements.
2Quantity of substance
If catalyst activity is low (immediately after engine start), then hydrogen production decreases, but sensor output deviation becomes more significant
Solution Approach 1:
The system applies preliminary anti-action by estimating catalyst activity and predicting hydrogen's interfering effect before the sensor measurement is corrupted. Even when hydrogen production is low, the system proactively adjusts the target air-fuel ratio based on estimated catalyst state to prevent sensor output deviation, rather than waiting for deviation to occur and then correcting it.
3Device complexity
If the target air-fuel ratio is fixed, then control simplicity is maintained, but exhaust emissions degradation occurs due to varying catalyst activity
Solution Approach 1:
The system transitions from a static fixed target air-fuel ratio to a dynamic adjustable target air-fuel ratio based on real-time catalyst activity estimation. The target air-fuel ratio is dynamically modified according to temperature and cumulative desorption amount, allowing the control system to adapt to varying catalyst activity while maintaining relatively simple control logic through pre-established adjustment rules.
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 reduces exhaust emissions degradation by accurately controlling the air-fuel ratio according to catalyst activity, minimizing output deviations from the air-fuel ratio sensor and maintaining optimal catalyst performance.
Implementation Method 1
a catalyst 20, a downstream air-fuel ratio sensor 42, an air-fuel ratio control unit 61, and a catalyst state estimation unit 62. The catalyst 20 is disposed in an exhaust passage of the internal combustion engine and is configured to store oxygen
Implementation Method 2
The downstream air-fuel ratio sensor 42 is configured to detect an air-fuel ratio of outgoing exhaust gas flowing out of the catalyst
Implementation Method 3
the reactivities of a water-gas shift reaction and a steam reforming reaction for producing hydrogen decrease
Implementation Method 4
the reactivities of a water-gas shift reaction and a steam reforming reaction for producing hydrogen decrease
Implementation Method 5
The air-fuel ratio control unit 61 is configured to control an air-fuel ratio of incoming exhaust gas flowing into the catalyst
Data Source
AI summary
An exhaust gas control apparatus for an internal combustion engine includes: a catalyst which is capable of storing oxygen; a downstream air-fuel ratio sensor that detects the air-fuel ratio of outgoing exhaust gas flowing out of the catalyst; an air-fuel ratio control unit that controls the air-fuel ratio of incoming exhaust gas flowing into the catalyst; and a catalyst state estimation unit that estimates the activity of the catalyst. The air-fuel ratio control unit controls the air-fuel ratio of the incoming exhaust gas so that the air-fuel ratio of the outgoing exhaust gas detected by the downstream air-fuel ratio sensor is maintained at a target air-fuel ratio. The air-fuel ratio control unit sets the target air-fuel ratio to a richer value when the activity of the catalyst is equal to or higher than a predetermined value than when the activity of the catalyst is lower than the predetermined value.