Engine Control Device Oxygen Storage Management
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Solution Overview
Problem
The downstream side exhaust purification catalyst in internal combustion engines struggles to maintain oxygen storage, leading to insufficient removal of unburned gases when the oxygen storage amount reaches zero, as it cannot effectively store oxygen even when the air-fuel ratio is made lean.
Innovation Solution
A control device that estimates the oxygen storage amount of the downstream side exhaust purification catalyst and adjusts the fuel cut conditions, including lowering the lowest reference speed for fuel cut execution, and uses feedback control to alternate the air-fuel ratio between rich and lean settings based on sensor data to maintain optimal oxygen storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the air-fuel ratio is made lean to increase oxygen storage in the downstream catalyst, then oxygen storage capacity improves, but unburned gas removal capability deteriorates when oxygen storage reaches zero
Solution Approach 1:
The system periodically alternates between lean air-fuel ratio operation (to charge oxygen storage) and rich air-fuel ratio operation (to utilize stored oxygen for unburned gas removal). This periodic switching ensures the downstream catalyst maintains oxygen storage capacity while reliably removing unburned gases during both lean and rich operation phases.
Solution Approach 2:
The control device dynamically changes the air-fuel ratio parameter based on the oxygen storage state of the downstream catalyst. When oxygen storage is sufficient, the system operates lean to maximize oxygen charging. When oxygen storage depletes, the system switches to rich operation to prevent unburned gas emissions, thus adapting the air-fuel ratio parameter to maintain both oxygen storage and emission control.
2Quantity of substance
If fuel cut control is executed frequently to maintain oxygen storage, then oxygen storage capacity improves, but engine responsiveness and productivity deteriorate
Solution Approach 1:
The system dynamically adjusts the lowest reference speed threshold for fuel cut execution based on the downstream catalyst's oxygen storage state. When oxygen storage is high, the threshold remains high to limit frequent fuel cuts. When oxygen storage decreases, the threshold is lowered to allow fuel cut execution at lower speeds, enabling oxygen recharging while minimizing impact on engine responsiveness during high-load operations.
3Stability of the object's composition
If the lowest reference speed for fuel cut execution is lowered to enable more frequent oxygen storage replenishment, then oxygen storage stability improves, but fuel consumption increases
Solution Approach 1:
The system dynamically adjusts the lowest reference speed threshold based on real-time oxygen storage state. When oxygen storage is sufficient, the threshold is maintained high to prevent unnecessary fuel cuts and conserve fuel. When oxygen storage approaches critical levels, the threshold is lowered to enable fuel cut execution at lower speeds, allowing oxygen replenishment only when necessary. This dynamic adaptation optimizes the balance between oxygen storage stability and fuel consumption.
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 prevents the oxygen storage amount from decreasing to zero, ensuring continuous removal of unburned gases and NOx by maintaining a stable oxygen storage capacity in the downstream catalyst.
Implementation Method 1
the oxygen storage amount of the downstream side exhaust purification catalyst becomes a given limit storage amount or less... the oxygen in the exhaust gas cannot necessarily be stored in the downstream side exhaust purification catalyst
Implementation Method 2
an upstream side exhaust purification catalyst in an exhaust passage of an internal combustion engine and is provided with a downstream side exhaust purification catalyst in the exhaust passage... the unburned gas (unburned HC, CO, etc.) or NOx, etc., which is not removed by the upstream side exhaust purification catalyst is removed by the downstream side exhaust purification catalyst
Data Source
AI summary
An internal combustion engine includes an upstream side exhaust purification catalyst and a downstream side exhaust purification catalyst. The control device includes a storage amount estimating device which estimates the oxygen storage amount of the downstream side exhaust purification catalyst, and can execute fuel cut control which cuts the feed of fuel to the combustion chamber during operation of the internal combustion engine when the engine speed is the lowest reference speed or more. The control device lowers the lowest reference speed when the storage amount estimated by the storage amount estimating device has become a given limit storage amount or less, compared with when it is larger than the limit storage amount. As a result, a control device can effectively keep the oxygen storage amount of the downstream side exhaust purification catalyst from decreasing to zero.