Cylinder Air Charge Estimation via Transient Injector Actuation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for determining cylinder-to-cylinder air-fuel ratio imbalance in engines face challenges such as limited resolution at low engine loads, interference from exhaust gas recirculation, and difficulty in differentiating air and fuel components of errors, leading to inefficient engine operation and increased emissions.
Innovation Solution
A method involving a high pressure pump disabled to reduce direct injection fuel rail pressure, followed by selective opening of the direct injector before a spark event without fuel injection, allowing estimation of air charge through compression pressure measurement, and subsequent estimation of fuel component by correlating fuel rail pressure drops with injection pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fuel line pressure is used to estimate air charge, then air charge estimation is possible, but measurement precision deteriorates at low engine loads due to limited sensor resolution
Solution Approach 1:
The patent segments the air charge estimation process into two distinct measurement phases: a first measurement taken at high engine load where fuel pressure sensor resolution is sufficient, and a second measurement taken at low engine load. The air charge at low load is then derived by scaling the high-load measurement using the ratio of manifold absolute pressures. This segmentation allows the system to use the high-load measurement (where sensor resolution is adequate) to inform the low-load estimation, thereby overcoming the limited resolution issue at low loads.
Solution Approach 2:
Instead of directly measuring air charge at low engine load where the fuel pressure sensor lacks resolution, the patent inverts the approach by measuring at high engine load where the sensor performs adequately, and then mathematically transforming that measurement to represent low-load conditions. The inversion involves using the ratio of manifold absolute pressures between high and low load conditions to scale the high-load air charge measurement to estimate low-load air charge, effectively working backwards from a reliable measurement to an unreliable condition.
2Measurement precision
If direct injector is used to measure compression pressure, then air component learning is enabled, but fuel injection interference makes differentiation difficult
Solution Approach 1:
The patent segments the measurement process into two separate phases: an air component learning phase where the direct injector is actuated to measure compression pressure, and a fuel component learning phase where port fuel injection is used. During the air component phase, the system intentionally prevents fuel injection by maintaining high pressure in the direct injection fuel rail, ensuring that only air charge effects are measured. This temporal and functional segmentation allows clean separation of air and fuel component effects.
Solution Approach 2:
The patent extracts the air component measurement from the combined air-fuel measurement by temporarily removing the fuel injection variable. During air component learning, the system disables fuel injection by keeping the direct injection fuel rail pressure high, thereby extracting only the air charge effect on compression pressure. This extraction allows the system to isolate and learn air component characteristics without contamination from fuel injection effects.
3Productivity
If EGR flow is present during measurement, then normal engine operation is maintained, but measurement accuracy deteriorates due to corrupted sensor output
Solution Approach 1:
The patent applies preliminary action by temporarily pausing the air component learning process when EGR flow is detected during the measurement phase. The system monitors EGR valve position or EGR flow conditions and suspends the direct injector actuation for air charge measurement when EGR is active, preventing corruption of the measurement. After EGR flow ceases, the learning process resumes, ensuring that only clean measurements are taken while maintaining overall operational continuity.
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 accurate learning and differentiation of air and fuel components of air-fuel ratio variations, improving engine efficiency and reducing emissions across a wider range of engine loads and conditions.
Implementation Method 1
commanding the direct injector to selectively open a threshold duration before a spark event in the cylinder... estimating cylinder air-charge based on a rise in fuel rail pressure
Data Source
AI summary
Methods and systems are provided for learning a cylinder-to-cylinder air variation. During conditions when a PFDI engine is operated in a port-injection only mode, prior to port fuel injection, a direct-injection fuel rail pressure may be lowered via direct-injection. Then, prior to a spark event in a port-injected cylinder, the direct-injector may be transiently opened to use the rail pressure sensor for estimating a cylinder compression pressure, and inferring cylinder air charge therefrom.