Fuel Pump Deflector Surface for Hot Leakage Management
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Solution Overview
Problem
High pressure fuel pumps using a rider/tappet arrangement experience significant leakage of hot fuel between the plunger and plunger bore, leading to excessive heat transfer and wear at interfaces due to the alignment of plunger-tappet and cam rider interfaces with the longitudinal axis of motion, particularly during the pumping stroke.
Innovation Solution
A spring seat with a deflector surface is introduced in the fuel pump assembly, positioned approximately 3.0mm to 4.0mm from the interface between the plunger and tappet, directing high temperature fuel through vents from the upper cam box to the lower cam box, increasing the flow path and mixing time, thereby cooling and shielding sensitive components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the plunger-tappet and cam rider interfaces are aligned with the longitudinal axis of motion, then the drive mechanism is simplified and compact, but hot fuel leakage directly impacts these interfaces causing excessive heat transfer and wear
Solution Approach 1:
A fuel deflector is introduced as an intermediary component between the plunger and tappet interface. This deflector intercepts the hot leaking fuel and redirects it away from the cam rider-tappet interface, preventing direct contact between the harmful hot fuel and the sensitive interface surfaces, thereby reducing heat transfer and wear while maintaining the aligned interface configuration
Solution Approach 2:
The invention converts the harmful hot fuel leakage into a beneficial cooling mechanism by directing the hot fuel through a longer flow path that passes over the fuel deflector surface. The hot fuel cools down as it travels along this extended path, and the deflector surface itself becomes a heat dissipation surface that protects the underlying interfaces from thermal damage
2Ease of operation
If vents are provided in the tappet to allow lubricating fluid flow, then hydraulic forces do not inhibit sliding movement, but hot fuel can escape through these vents and exacerbate wear at interfaces
Solution Approach 1:
The fuel deflector is positioned specifically at the location where hot fuel emerges from the pumping chamber, creating a localized protection zone around the cam rider-tappet interface. The deflector has a specific geometry with a leading edge that intercepts fuel and a surface area designed for heat dissipation, providing targeted protection exactly where it is needed without affecting the overall tappet venting function
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
The solution effectively reduces the impact of high pressure fuel on sensitive parts by increasing the cooling and mixing time of leaked fuel, minimizing wear and heat transfer at interfaces, thus enhancing the longevity and efficiency of the fuel pump components.
Implementation Method 1
The fuel deflector surface is configured to cause the leaked fuel to take a longer flow path from the upper cam box to the lower cam box and thereby increase mixing and cooling of the leaked fuel
Implementation Method 2
a spring seat including a fuel deflector surface for a fuel pump assembly configured to shield sensitive parts from high pressure, high temperature leakage fuel
Data Source
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AI summary
During the operation of a high pressure fuel pump, it is normal to expect internal fuel leakage between a pumping plunger (30') and plunger bore (28'). Current pump designs position critical interfaces (55', 59') directly in-line with the leaking fuel. A fuel deflector surface (58') may be used to re-direct the flow of hot, leaking fuel away from the critical interfaces (55', 59') and toward a lower cam box (51') where the fuel may be cooled with other resident fuel. The deflector surface (58') may be shaped and vents (52') positioned to channel (B) the hot fuel to flow toward a lower cam box (51').