Engine Purge Gas Concentration Estimation Control
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Solution Overview
Problem
Existing engine control systems face challenges in accurately estimating the concentration of purge gas, leading to degraded estimation accuracy and controllability, especially at low purge gas flow rates, due to increased calculation errors and individual sensor discrepancies.
Innovation Solution
A control apparatus that includes an air-fuel ratio calculation unit, a purge rate calculation unit, and a concentration calculation unit, with a decision unit that inhibits concentration calculation at low purge rates and during certain engine conditions, such as sudden acceleration or low load states, to maintain accurate estimation and prevent errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If concentration calculation is performed based on air-fuel ratio and purge rate, then purge gas concentration estimation is achieved, but calculation error increases as purge gas flow rate decreases
Solution Approach 1:
The system dynamically adjusts the calculation strategy based on purge rate conditions. When purge rate is high, concentration calculation is performed using air-fuel ratio and purge rate. When purge rate is low, the system switches to maintaining a fixed concentration value or using alternative calculation methods, thereby adapting to changing flow conditions and preventing error propagation
Solution Approach 2:
The system changes the calculation parameters based on operating conditions. At low purge rates, instead of using the standard concentration calculation formula that becomes unreliable, the system switches to using a predetermined concentration value or modifies the calculation approach to account for the low flow rate condition, thus maintaining estimation accuracy across different operating ranges
2Productivity
If concentration calculation is continuously performed, then real-time purge gas concentration data is available, but calculation errors propagate under certain engine conditions
Solution Approach 1:
The system performs concentration calculation selectively rather than continuously. Calculation is performed only when conditions are favorable (adequate purge rate, stable engine operation). Under unfavorable conditions, the system skips calculation or uses alternative methods, avoiding the propagation of erroneous data while maintaining real-time data availability through interpolation or fixed values
3Loss of energy
If purge controlling valve opening is reduced to control purge gas flow rate, then fuel economy improves, but purge gas concentration estimation accuracy degrades
Solution Approach 1:
The system dynamically switches between different concentration estimation strategies based on purge rate. When purge rate is low (energy-saving mode), the system uses predetermined concentration values or alternative calculation methods that are not dependent on air-fuel ratio measurements, thereby maintaining estimation accuracy while allowing aggressive fuel economy measures
Data Source
AI summary
A control apparatus for an engine introduces purge gas containing fuel gas evaporated from a fuel tank into an intake system includes an air-fuel ratio calculation unit that calculates an air-fuel ratio (AF) of the engine, and a purge rate calculation unit that calculates a purge rate (RPRG) corresponding to an introduction rate of the purge gas. The control apparatus further includes a concentration calculation unit that calculates a concentration (KAF_PRG) of the purge gas based on the air-fuel ratio (AF) calculated by the air-fuel ratio calculation unit and the purge rate (RPRG) calculated by the purge rate calculation unit. A decision unit permits or inhibits the concentration calculation unit to calculate the concentration (KAF_PRG) based on the purge rate (RPRG) calculated by the purge rate calculation unit. The estimation accuracy of the concentration (KAF_PRG) of purge gas is improved.