Fuel Injection Control via Closed EGR Circuit Oxygen Measurement
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Solution Overview
Problem
Existing methods for determining the actual fuel quantity injected into internal combustion engine cylinders are inaccurate due to difficulties in measuring air mass flow, particularly in diesel engines, leading to deviations from setpoint fuel quantities, which can result in unfavorable exhaust gas composition, unequal torque distribution, and increased fuel consumption.
Innovation Solution
A method involving a closed exhaust gas recirculation circuit is formed during deceleration phases, where the air mass enclosed is determined, and oxygen content is measured before and after a test injection to calculate the actual fuel mass injected, allowing for precise adjustment of fuel injection amounts without relying on air mass flow sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If air mass flow sensors are used to measure air quantity during test injection, then fuel quantity can be determined, but measurement accuracy deteriorates due to humidity and other environmental factors
Solution Approach 1:
The patent introduces a closed exhaust gas recirculation circuit as an intermediary system. Instead of directly measuring air mass flow during test injection (which is affected by humidity), the system recirculates exhaust gas through a controlled closed loop and measures oxygen content changes in this closed circuit. This intermediary approach isolates the measurement from environmental humidity effects while still allowing accurate determination of fuel quantity injected during test injection events.
Solution Approach 2:
The patent replaces the mechanical air mass flow sensing system with a chemical/computational approach. Instead of using physical sensors to measure air flow (which are sensitive to humidity), the system uses oxygen content measurements combined with known exhaust gas recirculation rates and stoichiometric calculations to determine fuel quantity. This substitution eliminates the problematic mechanical sensing element while achieving the same measurement objective with higher reliability.
2Manufacturing precision
If test injection is performed to determine actual fuel quantity, then fuel injection accuracy can be improved, but engine operation stability deteriorates due to additional fuel injections
Solution Approach 1:
The patent implements test injections as periodic, intermittent events rather than continuous operations. Test injections are performed only at specific intervals when the engine is in a deceleration phase or idle condition, allowing the system to gather calibration data without continuously disrupting normal engine operation. This periodic approach maintains engine stability while still enabling regular updates to fuel injection accuracy.
Solution Approach 2:
The patent performs test injections and measurements during deceleration phases or idle conditions before returning to normal operation. By conducting the measurement action in advance during a suitable window, the system can determine fuel quantity characteristics without interfering with the main propulsion function, thereby maintaining operational stability while achieving precision calibration.
3Measurement precision
If closed exhaust gas recirculation circuit is formed during deceleration phase, then measurement accuracy is improved, but device complexity increases due to additional control requirements
Solution Approach 1:
The patent makes the exhaust gas recirculation system multi-functional. The same EGR valves and recirculation pathways that serve the primary function of reducing NOx emissions during normal operation are also used to create the closed circuit for test injection measurements during deceleration phases. This universality allows the system to achieve precise fuel mass measurement without adding dedicated measurement hardware, thereby limiting the increase in device complexity.
Solution Approach 2:
The system uses its own exhaust gas recirculation infrastructure to serve the measurement function. Rather than requiring external measurement equipment or separate dedicated circuits, the engine's existing EGR system is leveraged to create the closed loop necessary for accurate fuel mass determination. This self-service approach minimizes additional complexity while achieving high measurement precision.
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 enables more accurate determination of the fuel quantity injected, improving engine control, reducing pollutant emissions, and preventing torsional vibrations by ensuring consistent fuel delivery to all cylinders.
Implementation Method 1
detecting a first oxygen content of the air quantity, carrying out a test injection with an injection valve, detecting a second oxygen content of the air quantity
Implementation Method 2
a test injection is carried out with an injection valve. Afterwards, a second oxygen content of the enclosed air quantity is detected. From this, the fuel quantity which has been injected in the test injection can be determined
Data Source
AI summary
Embodiments are provided herein for controlling a motor-vehicle internal combustion engine fitted with a fuel injection system and an exhaust gas recirculation system. In one example, in a deceleration phase a closed exhaust gas recirculation circuit is formed, a mass (mcirc) of an air quantity enclosed therein is determined, a first oxygen content (O2,exh1, O2,man1) of the air quantity is detected, a test injection is carried out with an injection valve, a second oxygen content (O2,exh2, O2,man2) of the air quantity is detected, and the fuel mass (mfuel) injected in the test injection is determined from the mass (mcirc) of the air quantity and the first and the second oxygen content (O2,exh1, O2,man1, O2,exh2, O2,man2). The disclosure also relates to a corresponding device for controlling a motor-vehicle internal combustion engine fitted with a fuel injection system and an exhaust gas recirculation system.