Fuel Supply Control for Exhaust Catalyst Temperature Stability
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Solution Overview
Problem
Existing fuel supply control methods for NOx storage reduction catalysts in internal combustion engines face challenges in maintaining a consistent catalyst temperature, leading to overheating or insufficient temperature increases due to varying cycle lengths, which deviate from the target temperature.
Innovation Solution
A fuel supply control method that adjusts the fuel supply period and stopped period in each cycle to ensure the catalyst temperature remains at the target temperature at both the starting and ending points, using a temperature-based required fuel supply amount calculation and estimated fuel supply amount calculation to set the cycle length and fuel supply stopped period, with optional corrections for engine load changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the average temperature in each cycle is controlled to be equal to the target catalyst temperature, then overheating and insufficient temperature increase are suppressed, but the catalyst temperature fluctuates widely when cycle length increases
Solution Approach 1:
The patent segments the temperature control process into two distinct phases within each cycle: a fuel supply period for temperature increase and a fuel supply stopped period for temperature decrease. By controlling the duration of each phase separately, the patent achieves precise temperature management at cycle boundaries while maintaining stability even when total cycle length varies.
Solution Approach 2:
The patent implements periodic fuel supply and stoppage to achieve cyclic temperature control. By alternating between fuel supply periods (heating phase) and fuel supply stopped periods (cooling phase), the system maintains catalyst temperature within desired ranges through repeated cycles, ensuring temperature stability at the start and end of each cycle regardless of overall cycle duration.
2Adaptability or versatility
If different length cycles are alternately performed to adapt to varying conditions, then flexibility is improved, but catalyst temperature deviates from target temperature due to cumulative effects
Solution Approach 1:
The patent employs feedback control by monitoring the catalyst temperature at the boundary points of each cycle and adjusting the fuel supply period and stopped period durations accordingly. This feedback mechanism ensures that regardless of cycle length variations or alternating cycle patterns, the catalyst temperature returns to the target temperature at each cycle boundary, preventing cumulative temperature deviations.
Solution Approach 2:
The patent makes the fuel supply period and stopped period durations dynamic rather than fixed. By adjusting the length of each phase based on actual catalyst temperature conditions and cycle requirements, the system adapts to varying operating conditions while maintaining temperature consistency, allowing different length cycles to be alternated without compromising temperature reliability.
3Temperature
If fuel is continuously supplied to maintain catalyst temperature, then temperature control is improved, but reductive reactions occur continuously causing excessive temperature increase
Solution Approach 1:
The patent applies periodic fuel supply instead of continuous supply, alternating between fuel supply periods that increase catalyst temperature and fuel supply stopped periods that allow temperature to decrease. This periodic approach prevents continuous reductive reactions, avoiding excessive temperature increases while still maintaining adequate catalyst temperature for NOx storage reduction functionality.
Solution Approach 2:
The patent introduces fuel supply stopped periods as a preliminary counter-action to prevent excessive temperature increase from continuous reductive reactions. By periodically stopping fuel supply, the system preemptively counteracts the harmful effect of continuous reductive reactions before they can cause excessive temperature rise, while still achieving the necessary temperature maintenance through the alternating fuel supply phases.
Data Source
AI summary
In an exhaust gas control apparatus for an internal combustion engine (1) of the invention, including an exhaust gas control catalyst (8) which purifies exhaust gas released from the internal combustion engine (1), and a fuel supply valve (10) which supplies fuel to a portion upstream of the exhaust gas control catalyst (8), the fuel supply valve (10) is operated such that a cycle formed by combining a fuel supply period in which fuel is supplied from the fuel supply valve (10) and a fuel supply stopped period in which fuel is not supplied is repeatedly performed in order to control the temperature of the exhaust gas control catalyst (8) to the target temperature. The arrangement of the fuel supply period and the fuel supply stopped period is controlled such that the temperature of the exhaust gas control catalyst (8) at each of a starting point (P1) and an ending poring (P3) of each cycle is equal to the target temperature.