Fuel Injector Characterization via Rail Pressure Sampling
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Solution Overview
Problem
Current fuel injection systems in internal combustion engines face issues with inconsistent fuel quantity injection due to pressure drops caused by rail leaks and pressure wave propagation, leading to deviations from desired injection amounts.
Innovation Solution
A method that involves sampling rail pressure, regulating it to a desired injection pressure, measuring leakage variations, calculating injection effects, and determining the actual injected quantity to accurately characterize fuel injection and correct for deviations, using an electronic control unit to manage fuel injectors and high-pressure pumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuel injection is performed using conventional multi-injection pattern, then torque generation and emission reduction are achieved, but fuel quantity accuracy deteriorates due to pressure drops from rail leaks and pressure wave propagation
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring rail pressure during injection events and using this information to calculate actual fuel quantity injected. The system measures pressure drops, correlates them with injection timing and duration, and uses this feedback to determine precise fuel delivery amounts, compensating for the harmful pressure drops caused by rail leaks and pressure wave propagation.
Solution Approach 2:
The patent replaces direct mechanical measurement of fuel quantity with a pressure-based measurement system. Instead of mechanically measuring the volume or mass of fuel injected, the system uses pressure sensors to monitor rail pressure variations and calculates fuel quantity through mathematical relationships between pressure drops, injection parameters, and fuel properties.
2Manufacturing precision
If rail pressure is regulated to desired injection pressure, then injection consistency is improved, but system complexity increases due to additional sensing and control requirements
Solution Approach 1:
The patent makes the pressure sensor serve multiple functions: it monitors rail pressure for injection timing control, measures pressure drops for fuel quantity calculation, and provides data for diagnosing rail leak conditions. By making the pressure sensing system multi-functional, the patent avoids adding separate sensors and control mechanisms, thereby improving injection consistency without proportionally increasing system complexity.
Solution Approach 2:
The system uses its own operational data (pressure variations during normal injection events) to characterize and compensate for its own deviations. The fuel injection system self-diagnoses its performance by analyzing pressure drops during its own operation, eliminating the need for external calibration equipment or separate diagnostic systems.
3Measurement precision
If leakage measurement is performed between two engine positions, then fuel injection characterization accuracy is improved, but measurement time increases due to additional measurement cycles
Solution Approach 1:
The patent performs preliminary characterization of the fuel injection system during normal engine operation by continuously measuring pressure drops during injection events. This preliminary action builds a database of injection characteristics that can be used for real-time fuel quantity calculation without requiring separate, time-consuming measurement cycles, thus improving accuracy without significant time penalty.
Solution Approach 2:
The system performs leakage and injection characterization measurements periodically during normal engine operation at specific crankshaft positions. By utilizing the periodic nature of engine cycles and performing measurements at predetermined intervals rather than continuously or before each injection, the patent achieves accurate characterization while minimizing interference with normal engine operation and reducing measurement time.
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 method ensures precise fuel injection by accounting for leakage and pressure variations, improving the accuracy of fuel delivery and reducing emissions and noise, thereby enhancing engine performance.
Implementation Method 1
an electro-magnetic actuator (e.g. solenoid), which moves the needle towards an open position in response of an energizing electrical current
Implementation Method 2
a needle, which is normally biased in a closed position by a spring
Data Source
AI summary
A method of operating a fuel injection system for a motor vehicle includes one or more of the following: operating a fuel injector to perform a fuel injection, the fuel injector being in fluid communication with a fuel rail; sampling a rail pressure in the fuel rail during the fuel injection; regulating the rail pressure at a desired injection pressure, Pinj, to the fuel injector; measuring an overall leakage on variations of the rail pressure across an engine cycle for the motor vehicle and between two engine positions of an internal combustion engine for the motor vehicle; and restarting a new measurement cycle for a new pressure measurement target.