EGR Gas Flow Estimation Using Temperature Sensors
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Solution Overview
Problem
In internal combustion engines, it is challenging to accurately calculate the flow rate of EGR gas when the pressure sensor cannot be installed at a suitable location, affecting the accuracy of EGR gas flow rate estimation and clogging detection in the EGR passage.
Innovation Solution
An internal combustion engine control system is equipped with temperature sensors upstream and downstream of the throttle valve, an EGR temperature sensor, and an airflow meter, which calculates a correction temperature to accurately estimate the EGR gas amount using thermal relationships, allowing for effective clogging detection without requiring high-heat-resistant pressure sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pressure sensor is installed in the EGR passage to measure EGR gas flow rate, then measurement accuracy is improved, but device complexity and heat resistance requirements increase
Solution Approach 1:
The patent replaces the pressure sensor-based measurement system with a temperature sensor-based measurement system. Instead of using pressure sensors to directly measure EGR gas flow rate, the invention uses temperature sensors to detect temperature differences in the intake passage, which are then converted to EGR gas flow rate information through calculation. This substitution eliminates the need for pressure sensors in the high-temperature EGR passage.
Solution Approach 2:
The patent introduces temperature sensors as intermediary measurement devices. Rather than directly measuring EGR gas parameters in the hot EGR passage, the system uses temperature sensors placed in the cooler intake passage to detect temperature changes caused by EGR gas mixing, which then serve as indirect indicators of EGR flow rate.
2Device complexity
If temperature sensors are used to estimate EGR gas amount, then device complexity is reduced, but measurement precision deteriorates due to temperature variations
Solution Approach 1:
The patent employs feedback mechanisms where the control device continuously monitors temperature differences between upstream and downstream temperature sensors and adjusts the estimation calculations accordingly. The system uses the detected temperature difference as feedback to refine the EGR gas amount estimation, ensuring accurate measurement despite temperature variations in the intake passage.
Solution Approach 2:
The patent changes the measurement parameter from direct pressure measurement to temperature difference measurement. By focusing on the temperature difference between two points in the intake passage rather than absolute temperature or pressure values, the system achieves accurate EGR gas amount estimation while using simpler temperature sensors.
3Productivity
If the EGR valve is positioned on the exhaust passage side of the EGR cooler, then supercharging efficiency is maintained, but EGR gas temperature increases
Solution Approach 1:
The patent positions the EGR valve upstream of the EGR cooler in the exhaust passage, allowing EGR gas to be diverted before entering the cooler. This preliminary positioning enables the system to maintain supercharging efficiency by controlling EGR flow early in the process, while the subsequent cooler still provides necessary temperature reduction for the recirculated gas.
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 configuration ensures high accuracy in estimating the EGR gas amount and detecting clogging, while maintaining supercharging efficiency by positioning the EGR valve on the exhaust passage side of the EGR cooler, and avoids the need for high-heat-resistant sensors.
Implementation Method 1
a downstream temperature sensor that detects a temperature of intake air in the intake passage in a region downstream of the throttle valve
Implementation Method 2
an upstream temperature sensor that detects a temperature of intake air in the intake passage in a region upstream of the downstream temperature sensor
Implementation Method 3
an EGR temperature sensor that detects a temperature of EGR gas as exhaust gas returned to the intake passage through the EGR passage
Implementation Method 4
an airflow meter that detects a flow rate of intake air introduced into the intake passage
Implementation Method 5
a temperature correction unit that calculates a corrected temperature of that one of the mounted temperature sensors by correcting the temperature detected by that one of the mounted temperature sensors by the correction temperature of that one of the mounted temperature sensors during operation of the internal combustion engine
Data Source
AI summary
An internal combustion engine is equipped with a downstream temperature sensor arranged in an intake passage, an upstream temperature sensor arranged in the intake passage upstream of the downstream temperature sensor, an EGR temperature sensor arranged in an EGR passage, and an airflow meter arranged in the intake passage. A control device corrects a temperature detected by each of the temperature sensors based on an amount of deviation of the temperature detected by that one of the temperature sensors upon activation of the control device after the lapse of a prescribed time or more since stoppage of the internal combustion engine from a reference temperature. Then, the control device calculates a flow rate of EGR gas based on the corrected temperature of that one of the temperature sensors and a flow rate of intake air, and detects the clogging of the EGR passage based on the flow rate.