High-Pressure Fuel Pump Sealing to Prevent Plunger Sticking
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Solution Overview
Problem
The sealability of the surface pressing portion in high-pressure fuel supply pumps is unstable, leading to issues with fuel leakage and sticking between the plunger and cylinder, affecting the discharge amount and volumetric efficiency of the fuel pump.
Innovation Solution
A fuel pump design with a plunger that reciprocates within a cylinder with a guide hole, a pump body with a cylinder insertion hole, and a pressurizing chamber that adjusts its volume, ensuring the pressure of the fixed gap between the cylinder and pump body is equal to or higher than the sliding gap pressure, thereby stabilizing the seal and preventing sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional fuel pump with a fuel inlet passage and fuel outlet passage is used, then the pump can deliver fuel, but foreign substances or impurities in the fuel can clog the fuel inlet passage or fuel outlet passage, causing fuel delivery failure
Solution Approach 1:
A screen is introduced as an intermediary component between the fuel inlet passage and the pump chamber to filter foreign substances before they can clog the fuel inlet passage or fuel outlet passage. The screen acts as a mediator that allows fuel to pass through while blocking impurities, thus preventing clogging while maintaining fuel delivery reliability.
Solution Approach 2:
The screen converts the harmful effect of foreign substances (which would cause clogging) into a beneficial filtering function. By allowing the screen to trap impurities, the design transforms the potential harm of contaminated fuel into a protective mechanism that prevents clogging and ensures reliable fuel delivery.
2Ease of manufacture
If the fuel pump structure is simplified, then manufacturing cost decreases, but the pump chamber may not be sufficiently sealed from the atmosphere, allowing air to be drawn in
Solution Approach 1:
The pump chamber is formed by merging the cylindrical body and the lid into a single integrated component, eliminating the need for separate sealing elements between them. This merging simplifies manufacturing while maintaining sealing performance by creating a unified structure that inherently prevents atmospheric air from entering the pump chamber.
3Reliability
If the pump chamber is completely sealed, then air intake is prevented, but the diaphragm cannot be sufficiently pressed by the drive shaft to pump fuel efficiently
Solution Approach 1:
The pump chamber is segmented into an atmospheric side and a fuel side by the diaphragm, allowing the drive shaft to press the diaphragm for efficient fuel pumping while the check valve maintains sealing to prevent atmospheric air from entering the fuel side. This segmentation enables both effective sealing and efficient fuel pumping by separating the functions of air exclusion and fuel delivery.
4Reliability
If a check valve is added to prevent atmospheric air from entering the pump chamber, then sealing is improved, but the device complexity increases
Solution Approach 1:
The check valve function is extracted and integrated directly into the lid structure, where it selectively prevents atmospheric air from entering the pump chamber through the fuel outlet passage while allowing fuel to be pumped out. This extraction of the sealing function into a dedicated valve component provides reliable sealing without significantly increasing overall device complexity.
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 configuration allows for high-pressure fuel discharge while preventing sticking between the plunger and cylinder, ensuring efficient fuel delivery and maintaining pump performance.
Implementation Method 1
a diaphragm (33) which is disposed in the pump chamber (32) and is pressed by the drive shaft (31) to move back and fourth
Data Source
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AI summary
The present invention provides a fuel pump capable of discharging fuel at high pressure and suppressing sticking between a plunger and a cylinder. A high-pressure fuel supply pump includes a plunger that reciprocates, a cylinder in which a guide hole for guiding a reciprocating motion of the plunger extends in an axial direction, and a pump body including a third room (cylinder insertion hole) into which the cylinder is press-fitted, and a pressurizing chamber that communicates with the third room and has a volume increased or decreased by the reciprocating motion of the plunger. The pressure of a fixed gap generated between the cylinder and the pump body is set to be equal to or higher than pressure of a sliding gap generated between the plunger and the cylinder.