EGR Valve Control Using Manifold Humidity Detection
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Solution Overview
Problem
Existing methods for estimating the EGR rate in internal combustion engines face errors due to individual differences and changes over time in engines and humidity variations, particularly during transient operations, leading to inaccuracies in controlling the recirculation exhaust gas amount.
Innovation Solution
A controller and control method that detect manifold pressure, temperature, humidity, intake-air pressure, temperature, and humidity, and intake-air flow rate to calculate a humidity detecting EGR rate, which is used to determine the opening area of the EGR valve and control the recirculation exhaust gas flow rate, accounting for changes and variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the EGR rate is indirectly estimated using intake air amount and EGR valve opening degree, then the cost is reduced by not adding dedicated sensors, but the measurement precision deteriorates due to individual differences and changes over time in engine characteristics and sensor characteristics
Solution Approach 1:
The patent introduces a humidity sensor as an intermediary measurement device in the intake manifold to directly detect the humidity of the mixed gas (intake air + recirculated exhaust gas). This mediator provides a direct physical quantity measurement that reflects the EGR rate, avoiding the need for complex indirect calculations based on valve opening degrees and air flow rates, thereby improving measurement accuracy without significantly increasing system cost.
Solution Approach 2:
The patent replaces the mechanical/indirect estimation method (based on EGR valve opening degree and air flow rate measurements) with a sensor-based direct detection method (humidity sensor measuring the humidity of the mixed gas in the intake manifold). This substitution transitions from a mechanical system relying on multiple sensors and calculations to a more accurate sensor-based direct measurement system.
2Measurement precision
If the EGR rate is controlled based on humidity detected by a humidity sensor in the intake manifold, then the measurement precision improves, but the device complexity increases due to adding a dedicated sensor
Solution Approach 1:
The patent makes the humidity sensor serve multiple functions: it not only detects the humidity of the mixed gas to determine the EGR rate, but also provides information about the humidity of intake air when the EGR valve is closed. This multi-functionality reduces the need for separate sensors and makes the added sensor more justifiable by its multiple uses in the system.
Solution Approach 2:
The humidity sensor in the intake manifold serves the system by providing direct measurement data that the control unit can use to accurately determine the EGR rate. The sensor essentially serves itself by providing raw humidity data that automatically translates into EGR rate information through the control unit's calculations, reducing the need for additional measurement devices.
3Ease of operation
If feedback control is performed using only manifold humidity without considering intake air humidity, then the control is simplified, but the measurement precision deteriorates due to errors from atmospheric humidity variations
Solution Approach 1:
The patent implements a feedback control mechanism where the control unit continuously monitors both the manifold humidity and intake air humidity, calculates the EGR rate based on these measurements, and adjusts the EGR valve opening degree accordingly. This feedback loop ensures that the system automatically compensates for atmospheric humidity variations and maintains accurate EGR rate control.
Solution Approach 2:
The patent changes the control parameters from a single humidity measurement to a differential measurement approach, where the control unit calculates the difference between manifold humidity and intake air humidity. This parameter change allows the system to isolate the effect of recirculated exhaust gas humidity from atmospheric humidity variations, improving control accuracy while maintaining relatively simple control logic.
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 allows for accurate detection of the EGR rate and control of the EGR valve, reducing calculation errors and improving responsiveness, even under conditions of deposit buildup or aging degradation, thus enhancing the control accuracy of the internal combustion engine.
Implementation Method 1
a humidity sensor that detects humidity of the mixed gas
Implementation Method 2
the recirculation exhaust gas amount is feedback-controlled based on the humidity in the intake manifold; however, because the effect of the humidity of intake air that is newly taken into the intake manifold from the atmosphere
Data Source
AI summary
To provide a controller and a control method for an internal combustion engine capable of reducing the calculation error of recirculation exhaust gas amount due to changes with time of the internal combustion engines, and humidity change of intake air, and also capable of reducing the calculation error of recirculation exhaust gas amount at transient operation. The controller and the control method for the internal combustion engine calculates humidity detecting EGR rate based on intake-air humidity and manifold humidity, calculates humidity detecting opening area which realizes humidity detecting recirculation flow rate calculated based on humidity detecting EGR rate, calculates learned opening area corresponding to present opening degree of EGR valve using learning value of opening area calculated based on humidity detecting opening area, and calculates flow rate of recirculation exhaust gas for control based on learned opening area.