Cam Ring High-Pressure Fuel Pump Durability
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Solution Overview
Problem
Existing high pressure fuel pumps for diesel engines face durability issues due to high cycle fatigue of plunger return springs and leakage concerns, particularly with the design of multiple circumferentially positioned pumping units that occupy space and create an unfavorable footprint.
Innovation Solution
A high pressure fuel pump design featuring a cam ring that surrounds the pumping unit, using a spacer element with a fixed length to maintain contact between the plunger and the cam surface, eliminating the need for coil springs and containing any failure within the cam ring, thus preventing leakage and reducing fatigue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plunger return spring is used to maintain contact between plunger end and shaft eccentric segment, then plunger can be driven reciprocally, but spring undergoes high cycle fatigue leading to durability issues
Solution Approach 1:
The invention extracts and eliminates the plunger return spring from the system by using a cam ring with cam surfaces that directly drive the plunger reciprocally. The cam ring's cam surfaces provide the necessary driving force without requiring a separate return spring mechanism, thereby removing the source of high cycle fatigue and improving durability.
Solution Approach 2:
The invention replaces the mechanical spring-based return system with a cam-based mechanical system. The cam ring with its specially shaped cam surfaces provides a more reliable and durable mechanism for achieving plunger reciprocation, substituting the fragile spring system with a robust cam-driven system that has no moving parts subject to fatigue.
2Productivity
If multiple circumferentially positioned pumping units are used, then sufficient fuel can be supplied under high pressure, but package space is taken up and unfavorable footprint is created
Solution Approach 1:
The invention merges multiple pumping functions into a single integrated cam ring structure. Instead of having separate pumping units arranged circumferentially, the cam ring with its multiple cam surfaces combines the driving function for all plungers into one compact component, reducing the overall footprint while maintaining the ability to supply sufficient fuel under high pressure.
Solution Approach 2:
The cam ring serves multiple functions simultaneously: it drives multiple plungers reciprocally, maintains proper timing between them, and provides structural support for the entire pumping assembly. This multi-functional design eliminates the need for separate drive mechanisms for each pumping unit, optimizing space utilization.
3Strength
If pumping unit is bolted, then assembly is secure, but leakage occurs especially at bolted joints
Solution Approach 1:
The invention employs elastomeric seals and flexible sealing elements at the bolted joints and interfaces of the pumping unit. These flexible seals compensate for minor misalignments and vibrations, maintaining secure sealing without requiring overly tight bolted connections, thereby preventing leakage while keeping the assembly secure.
Solution Approach 2:
The pumping unit utilizes composite construction with different materials optimized for specific functions: metallic components for structural strength and elastomeric materials for sealing. This combination allows the bolted joints to maintain both mechanical strength and leak-free sealing performance.
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 design enhances durability by eliminating spring fatigue and leakage, while optimizing the pump's footprint through the use of a cam ring and spacer element, ensuring reliable high-pressure fuel delivery to the common rail.
Implementation Method 1
the cam ring having an inner peripheral surface defining an inner cam surface. The pumping unit is positioned so as to be surrounded by the cam ring with the plunger foot portion being arranged to follow the inner cam surface of the cam ring in such a way that the rotation of the cam ring causes the plunger to reciprocate in its respective bore.
Data Source
Figure 1
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AI summary
A high pressure fuel pump for an internal combustion engine comprises a pumping unit (18) comprising a body (20) with a bore (22) therein and a plunger (26) reciprocally movable in the bore, the plunger having a front portion defining, with said bore, a pressure chamber (30) in said bore and an opposite foot portion (32). Drive means are provided for driving the plunger by its foot portion, the drive means comprise a cam ring (40) arranged to be rotatable about an axis (A), the cam ring having an inner cam surface (42). The pumping unit (18) is positioned so as to be surrounded by the cam ring (40) with the plunger foot portion (32) arranged to follow said inner cam surface (42) of said cam ring (40) in such a way that the rotation of the cam ring causes the plunger to reciprocate in the bore (22).