Direct Injection Fuel Pump Command Clipping for Accuracy
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Solution Overview
Problem
Existing control methods for direct injection fuel pumps, such as those described in U.S. Pat. No. 7,950,371, face inaccuracies and variability in controlling lower pump displacement volumes, leading to unpredictable fuel delivery and potential engine inefficiencies.
Innovation Solution
A control strategy that clips pump commands to specific regions, issuing zero flow lubrication commands when necessary, and threshold commands to maintain accurate and repeatable fuel delivery, thereby operating the pump within more precise control zones, reducing variability and enhancing fuel rail pressure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lower pump displacement volumes (0-40%) are commanded to reduce fuel delivery, then fuel quantity control is achieved, but pump control accuracy and repeatability deteriorate
Solution Approach 1:
The patent changes the control parameter from direct pump displacement control to a binary control approach using a spill valve. By controlling whether the spill valve is open or closed, the system achieves accurate fuel quantity control without relying on imprecise low-displacement pump commands. The spill valve parameter (open/closed state) replaces the problematic continuous displacement parameter.
Solution Approach 2:
The spill valve acts as an intermediary device between the pump and the fuel rail. Instead of directly controlling the pump displacement to achieve low fuel quantities, the spill valve mediates the fuel flow by diverting excess fuel back to the inlet, enabling precise control of the actual fuel delivery even when the pump operates at higher displacements.
2Quantity of substance
If pump commands are reduced to achieve zero or near-zero fuel delivery, then fuel quantity control is improved, but pump lubrication deteriorates
Solution Approach 1:
The patent segments the fuel flow path by introducing a spill valve that creates two separate flow paths: one through the pump discharge to the fuel rail, and another through the spill valve back to the pump inlet. This segmentation allows the pump to maintain its normal lubricating flow through the piston-bore interface while independently controlling the net fuel delivery to the rail via the spill valve.
Solution Approach 2:
The spill valve serves as an intermediary that decouples the pump's internal lubrication flow from the net fuel delivery to the rail. The pump continues to pump fuel at its normal displacement for lubrication purposes, while the spill valve diverts the appropriate amount back to the inlet, achieving zero or near-zero net delivery to the rail without compromising pump lubrication.
3Productivity
If variable displacement control is implemented to optimize fuel delivery, then fuel system efficiency is improved, but control variability and diagnostic reliability deteriorate
Solution Approach 1:
The patent changes the control parameter from continuous variable pump displacement to a binary spill valve state (open/closed). This parameter change eliminates the variability inherent in low-displacement pump control while maintaining fuel system efficiency through the spill valve's ability to precisely control net fuel delivery. The binary parameter improves diagnostic reliability by providing clear, unambiguous control states.
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 improves the accuracy and repeatability of fuel delivery, especially for small pump volumes, leading to more reliable engine operation and enhanced fuel vapor detection, while maintaining efficient fuel rail pressure management.
Implementation Method 1
The high-pressure fuel pump may include a solenoid actuated 'spill valve' (SV) or fuel volume regulator (FVR) that may be actuated to control flow of fuel into the high-pressure fuel pump
Implementation Method 2
a mechanically driven higher pressure pump (i.e., a direct injection pump) arranged respectively in series between the fuel tank and the fuel injectors along a fuel passage
Data Source
AI summary
Methods are provided for controlling a direct injection fuel pump, wherein a solenoid spill valve is energized and de-energized according to certain conditions. A control strategy is needed to operate the direct injection fuel pump outside regions where pump operation may be variable and inaccurate, where the regions may be characterized by smaller pump commands as well as smaller displacement volumes. To maintain a suitable range of pump commands and displacements while operating outside the low accuracy regions, a method is proposed that involves clipping calculated pump commands when the calculated pump commands lie within the low accuracy regions.