Fuel Pump Phasing via Rail Pressure Correlation
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Solution Overview
Problem
Current methods for determining the phase of piston fuel pumps driven by a crankshaft are not accurate enough, leading to significant scatter and precision issues, particularly in high-pressure fuel systems where precise timing is required for digital inlet valve control.
Innovation Solution
A method involving measuring pressures before and after a pumping stroke in a high-pressure piston pump, determining the average pressure, and correlating this with the crankshaft position to identify the mid-stroke point, which is used to calculate the relative phasing between the crankshaft and pump, utilizing existing crankshaft signals and cam geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical indexation by a pin between pump shaft and engine timing pulley is used, then the pump phasing can be established, but the accuracy is insufficient with scatter up to +/- 20°
Solution Approach 1:
The patent replaces the mechanical indexation system (pin between pump shaft and timing pulley) with a measurement-based approach using pressure sensors and crankshaft position signals. This substitution eliminates mechanical tolerances and dispersion sources, achieving the required +/- 3° precision for DIV control.
Solution Approach 2:
The patent introduces fuel pressure as an intermediary measurement parameter to indirectly determine pump phasing. By measuring pressure before and after pumping strokes and correlating with crankshaft position, the system achieves accurate phasing detection without direct mechanical coupling.
2Ease of manufacture
If mechanical indexation with pin and timing pulley is used, then pump phasing can be determined, but mechanical dispersion from timing belt, crank wheel, and sensor location affects precision
Solution Approach 1:
The patent replaces the entire mechanical indexation chain (timing belt, crank wheel, sensor location) with an electrical measurement system using existing sensors. This eliminates cumulative mechanical tolerances while maintaining ease of implementation through software-based phasing determination.
3Adaptability or versatility
If pump TDC scatter of +/- 20° is accepted, then mechanical indexation can be used, but digital inlet valve control requiring +/- 3° precision cannot be achieved
Solution Approach 1:
The patent uses feedback from pressure sensors and crankshaft position signals to accurately determine pump TDC and mid-stroke positions. This feedback mechanism enables precise timing for digital inlet valve control by continuously correlating pressure changes with crankshaft position.
Solution Approach 2:
The patent substitutes mechanical phasing methods with an electrical measurement and calculation system that processes pressure and position signals to determine precise pump timing, achieving the +/- 3° accuracy required for modern DIV control systems.
Data Source
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AI summary
A method of determining the relative phasing between a crankshaft and a crankshaft driven high pressure piston pump via a cam mechanism, said piston pump adapted to provide high pressure fuel to a common rail, comprising: a) measuring the pressure P1 in said common rail at a time before a pumping stroke/event; b) measuring the pressure P2 in said common rail at a time after the pumping stroke/event; c) determining the average pressure of said measured pressure from steps a) and b); d) determining the time point where the measured pressure reaches the average pressure determined form step c) e) correlating said time point with from d) with crankshaft position to determine said relative phasing.