Fuel Pump Gap Pressure Balancing 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 such as reduced discharge amount or sticking between the plunger and cylinder, depending on operation conditions or environment.
Innovation Solution
A fuel pump design with a plunger that reciprocates in a cylinder with a guide hole, press-fitted into a pump body, where the pressure of the fixed gap between the cylinder and pump body is equal to or higher than the sliding gap pressure, stabilizing the seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the sliding gap between the plunger and cylinder is reduced to prevent fuel leakage, then the discharge amount and volumetric efficiency improve, but the plunger and cylinder stick to each other due to insufficient lubrication
Solution Approach 1:
Fuel is introduced as an intermediary substance into the sliding gap between the plunger and cylinder. This fuel layer acts as a mediator that prevents direct metal-to-metal contact, eliminating sticking while maintaining a sufficiently small sliding gap for high discharge amount and volumetric efficiency.
Solution Approach 2:
The invention utilizes hydraulic pressure by introducing fuel under pressure into the sliding gap. The pressurized fuel creates a hydrodynamic lubrication effect that maintains separation between the plunger and cylinder surfaces, preventing sticking while allowing for optimized gap dimensions that maximize discharge performance.
2Ease of manufacture
If the surface pressing portion between the cylinder and body is designed for simple assembly, then the manufacturing ease improves, but the sealability becomes unstable leading to fuel leakage or sticking
Solution Approach 1:
Fuel serves as an intermediary that stabilizes the seal at the surface pressing portion. By introducing fuel into the gap between the cylinder and body, it creates a hydrodynamic effect that maintains consistent sealing pressure, preventing both leakage and sticking regardless of assembly variations.
Solution Approach 2:
The invention changes the physical state and pressure parameters of the fuel to stabilize sealing. By controlling fuel pressure and introducing it at specific locations, the system compensates for variations in surface pressing portion geometry, maintaining stable sealability across different assembly conditions.
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
Enables high-pressure fuel discharge while preventing sticking between the plunger and cylinder, improving stability and efficiency.
Implementation Method 1
a plunger (2) that reciprocates, a cylinder (6) in which a guide hole (6a) for guiding a reciprocating motion of the plunger (2) extends in an axial direction
Implementation Method 2
a pressurizing chamber (11) that communicates with the third room (1c) and has a volume that increases or decreases by the reciprocating motion of the plunger (2)
Implementation Method 3
The pressure of a fixed gap generated between the cylinder (6) and the pump body (1) is set to be equal to or higher than pressure of a sliding gap generated between the plunger (2) and the cylinder (6)
Data Source
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.