Variable Discharge Fuel Pump Pressure Fluctuation Control
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Solution Overview
Problem
Existing variable discharge fuel pumps in common rail fuel systems experience pressure fluctuations due to the check valve remaining open during the intake stroke, leading to undesirable fuel pressure variations.
Innovation Solution
A fuel pump design where the high-pressure outlet terminates pressurized fluid discharge before the plunger completes its movement from the first to the second end position, utilizing a spill passageway and outlet check valves to control pressure build-up and discharge, ensuring the outlet check valve closes before the end of the pumping stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump continues to discharge fuel into the fuel rail until the end of the pumping stroke, then the fuel displacement is maximized, but the fuel pressure fluctuates undesirably
Solution Approach 1:
The outlet check valve is designed to close before the end of the pumping stroke, performing the action of sealing the high-pressure outlet in advance. This preliminary closure prevents fuel from flowing back into the pumping chamber during the intake stroke, thereby eliminating pressure fluctuations while maintaining effective fuel displacement into the rail.
2Stability of the object's composition
If the outlet check valve closes before the end of the pumping stroke, then pressure fluctuations are reduced, but the pumping stroke is not fully utilized
Solution Approach 1:
The outlet check valve closes at a point before the pumping stroke is completely finished, representing a partial utilization of the stroke. This partial closure is sufficient to prevent pressure fluctuations and fuel backflow, while the excessive portion of the stroke (after valve closure) is used for plunger repositioning and intake preparation, optimizing the overall cycle efficiency.
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 design reduces pressure fluctuations in the common rail by ensuring the outlet check valve closes before the end of the pumping stroke, maintaining consistent pressure and improving fuel injection system efficiency and hot-starting capabilities.
Implementation Method 1
a plunger slidably disposed within the at least one pumping chamber. The plunger is movable between a first and second spaced apart end positions to pressurize a fluid
Implementation Method 2
The pump also has an outlet check valve in selective fluid communication with the pumping chamber and the high-pressure outlet. The passing of pressurized fluid through the high-pressure outlet terminates before the plunger completes movement from the first end position to the second end position
Implementation Method 3
When the pump piston is undergoing its pumping stroke, the fuel displaced is initially pumped into a low-pressure reservoir past a spill control valve. When the spill control valve is energized, it closes the spill passageway causing fuel in the pumping chamber to quickly rise in pressure
Data Source
AI summary
A pump has a housing defining at least one pumping chamber, and a plunger slidably disposed within the at least one pumping chamber. The plunger is movable between a first and second spaced apart end positions to pressurize a fluid. The pump also has a driver operatively engaged with the plunger to move the plunger between the first end position and the second end position. The pump further has a high-pressure outlet in fluid communication with the at least one pumping chamber. The high pressure outlet passes pressurized fluid during movement of the plunger between the first end position and the second end position. The passing of pressurized fluid through the high-pressure outlet terminates before the plunger completes movement from the first end position to the second end position.