Pump-Synchronous Rail Pressure Control for Combustion Stability
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Solution Overview
Problem
Classic time-synchronous rail pressure control methods for internal combustion engine fuel supply systems lead to under-sampling or over-sampling of engine-synchronous pump events, resulting in pressure oscillations and aliasing issues, especially in dynamic conditions, and are inefficient with modern high-pressure pumps that provide volume flow for each work cycle.
Innovation Solution
Implementing a volume-based, pump-synchronous rail pressure control method that discretizes control deviations per crankshaft revolution, calculating cylinder-selective discrete volume control differences and using these to adjust the high-pressure pump and pressure control valve actuators synchronously, while accounting for permanent fuel leakage and non-linear fuel properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If classic time-synchronous rail pressure control is used, then control simplicity is maintained, but pressure oscillations and aliasing occur due to under-sampling or over-sampling of pump events
Solution Approach 1:
The patent transitions from a fixed time-synchronous control grid to a dynamic pump-synchronous control grid that adapts to the actual pump delivery events. The control system now synchronizes with the mechanical pump cycle based on crank angle or cam angle, allowing the sampling instants to move dynamically with the pump piston position. This resolves the contradiction by making the control system flexible enough to avoid under-sampling/over-sampling while maintaining reliability.
Solution Approach 2:
The patent changes the fundamental parameter of the control grid from fixed time intervals to variable intervals synchronized with pump events. By using crank angle or cam angle as the basis for control timing instead of fixed time steps, the system adapts to varying engine speeds and pump delivery characteristics, eliminating pressure oscillations and aliasing effects.
2Measurement precision
If pump-synchronous control with per-cycle discretization is implemented, then pressure control precision is improved, but computational complexity increases
Solution Approach 1:
The patent segments the control calculation into discrete intervals based on pump delivery events within each crankshaft revolution. By dividing the control task into smaller, manageable segments synchronized with pump cycles, the system achieves precise pressure control at each delivery event while keeping computational requirements manageable through structured segmentation of the control algorithm.
Solution Approach 2:
The patent implements periodic control calculations synchronized with the pump delivery cycle, performing discrete volume control difference calculations at regular pump events. This periodic approach maintains precision by consistently measuring and correcting pressure deviations at each pump delivery, while the regular periodic nature of the calculations optimizes computational efficiency through predictable processing intervals.
3Stability of the object's composition
If cylinder-selective volume control is applied, then combustion stability is enhanced, but control system complexity increases
Solution Approach 1:
The patent applies local quality by implementing cylinder-selective volume control, where each cylinder's fuel injection volume is individually adjusted based on its specific combustion characteristics and pressure conditions. This allows precise, localized control of fuel delivery to each cylinder, enhancing combustion stability and efficiency while addressing individual cylinder variations through targeted volume adjustments.
Data Source
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AI summary
The invention relates to a method for controlling a rail pressure (p7Set) for a fuel supply system (100) of an internal combustion engine, which is caused by a high-pressure pump (1) in a fuel storage tank (4), wherein a fixed angle difference of the internal combustion engine, related to the crank angle or cam angle, between a top dead center position of a cylinder piston of a cylinder of the internal combustion engine and a top dead center position of the pump piston of the high-pressure pump (1) of the fuel supply system (100) is taken into account when metering the delivery volume of the high-pressure pump (1).It is provided that, recurringly and synchronously with the pump operation, for each segment corresponding to one revolution of a crankshaft and thus to the movement of the pump piston of the high-pressure pump (1) from the top dead center position of the pump piston to the next top dead center position, a discretization of a control deviation (Δp7) of the rail pressure (p7) in the fuel storage tank (4) is carried out and, starting from the discrete control deviation (Δp7), a volume-related discrete volume control deviation (ΔVRail), in particular a volume-related discrete cylinder-selective volume control deviation (ΔVRail), is calculated.