Fuel Adjustment Control Using Post-Catalyst O2 Feedback
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Solution Overview
Problem
Existing engine overspeed control systems cause repeated temperature fluctuations in the catalyst due to frequent stop and restart of fuel supply, leading to catalyst deterioration.
Innovation Solution
A fuel adjustment device that uses an oxygen sensor downstream of the catalyst to monitor oxygen concentration and adjust fuel supply based on a monitoring range, maintaining a lean air-fuel ratio to prevent excessive temperature changes in the catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If over-Rev limit control is repeatedly executed to prevent engine overspeeding, then engine rotation speed is controlled, but catalyst temperature increases excessively causing deterioration
Solution Approach 1:
The control device executes preliminary fuel cut control before the engine rotation speed reaches the first threshold value, preventing the conditions that lead to catalyst temperature increase. By anticipating the overspeed condition and acting in advance, the system avoids the harmful thermal effects on the catalyst while still controlling engine speed.
Solution Approach 2:
The system performs preliminary detection of engine rotation speed and executes fuel cut control at appropriate timing before the engine reaches dangerous overspeed conditions. This preliminary action prevents the need for repeated aggressive Rev limit control that would cause catalyst temperature spikes.
2Speed
If fuel supply is stopped during over-Rev limit control to reduce engine speed, then engine rotation speed decreases, but air-fuel ratio becomes irregular causing strong oxidation and reduction reactions in catalyst
Solution Approach 1:
The control device executes preliminary fuel cut control at timing that prevents irregular air-fuel ratio changes. By controlling fuel supply in advance and maintaining it for a predetermined period after engine speed decreases, the system prevents the strong oxidation and reduction reactions that would otherwise occur in the catalyst due to air-fuel ratio fluctuations.
Solution Approach 2:
The system maintains fuel supply for a predetermined period after engine rotation speed decreases to ensure continuous and stable air-fuel ratio. This continuous fuel supply prevents irregular changes in air-fuel ratio that would cause harmful reactions in the catalyst, while still achieving the goal of reducing engine speed during over-Rev limit control.
3Temperature
If fuel supply is adjusted to maintain lean air-fuel ratio during over-Rev limit control, then catalyst temperature increase is suppressed, but engine may experience misfiring
Solution Approach 1:
The control device executes fuel cut control for a predetermined period after engine rotation speed decreases, which is longer than the minimum time needed to reduce engine speed. This excessive duration of fuel cut control ensures that the air-fuel ratio remains stable and lean for a sufficient period, suppressing catalyst temperature increase while maintaining reliable combustion when fuel supply is restored.
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
Prevents catalyst deterioration by stabilizing the air-fuel ratio and reducing temperature fluctuations, thus extending the catalyst's service life without requiring complex additional maps or sensors.
Implementation Method 1
an oxygen sensor that is provided downstream of a catalyst that cleans an exhaust gas in an exhaust system attached to the engine, and detects an oxygen concentration of the exhaust gas
Implementation Method 2
a catalyst that cleans an exhaust gas in an exhaust system attached to the engine
Data Source
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AI summary
There is disclosed a fuel adjustment device, including an ECU (10) and a catalyst (53) downstream oxygen sensor (SE4); ECU (10) controlling a fuel injection device (61) that causes an engine (5) to work; the catalyst downstream oxygen sensor (SE4) being provided downstream of a three-way catalyst (53) in an exhaust system attached to engine (5) and detects an oxygen concentration of an exhaust gas; ECU (10) adjusting a fuel supply amount such that an engine rotation speed decreases when the engine rotation speed reaches a first rotation speed (rs1); the first rotation speed (ra1) being the rotation speed corresponding to overspeeding; when the engine rotation speed decreases and reaches a second rotation speed (rs2), an amount of fuel being supplied to engine (5) is changed back to a normal amount; thereafter, when the engine rotation speed is continuously maintained in a monitoring range, the fuel supply amount being adjusted based on a detection result of the catalyst downstream oxygen sensor (SE4); the monitoring range is a range that includes the second rotation speed (rs2) and is lower than the first rotation speed (rs1).