Cam Follower Roller Recesses for High Pressure Fuel Pump Stress
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Solution Overview
Problem
The manufacturing of rollers with a crowning profile for high-pressure fuel pumps is difficult and costly due to the need for precise curvature to avoid mechanical stress concentration at the contact segment.
Innovation Solution
The roller design incorporates symmetrical recesses on its transverse faces, reducing material thickness near the edges to enhance elasticity and distribute contact pressure evenly, with optional filler material and a centering member to maintain the roller's position and low-friction thrust bearing members for reduced friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a crowning profile is applied to the roller to avoid mechanical stress concentration, then the reliability is improved, but the manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent applies local quality by creating recesses only at specific locations (the ends of the contact segment) rather than applying a complex crowning profile across the entire roller surface. This localized material removal provides the necessary stress distribution improvement while maintaining a simpler overall manufacturing process compared to full crowning.
Solution Approach 2:
The patent changes the geometric parameter of the roller by introducing recesses that modify the material thickness distribution. This parameter change achieves the stress equalization effect of crowning but through a simpler geometric modification that is easier to manufacture than a full logarithmic or multi-arc crowning profile.
2Manufacturing precision
If a crowning profile is applied to the roller, then the contact pressure distribution is improved, but the manufacturing precision requirements increase
Solution Approach 1:
Instead of requiring high-precision machining of a complex crowning profile across the entire roller, the invention applies local quality by creating recesses only at the critical end regions. This localized approach reduces the overall manufacturing precision requirements while still achieving the necessary contact pressure distribution.
Solution Approach 2:
The invention segments the roller surface into different zones: the central contact region maintains the standard cylindrical profile, while the end regions feature recesses. This segmentation allows each zone to be manufactured with appropriate precision levels, reducing the overall manufacturing complexity compared to a single complex crowning profile.
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 simplifies the manufacturing process while providing equalized contact pressure and reduced mechanical stress, improving the durability and efficiency of the high-pressure fuel pump's cam follower mechanism.
Implementation Method 1
reducing material thickness near the edges to enhance elasticity and distribute contact pressure evenly
Implementation Method 2
the recess, is filled with a filler material
Implementation Method 3
said centering member maintaining, in use, the roller in a central position relative to the body
Implementation Method 4
The sliding face of the thrust bearing member may have low friction properties as being either coated over a core member with low friction material or as being integrally made from low friction material such as PTFE
Data Source
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AI summary
A high pressure fuel pump (14) having a pumping head (16) from which protrudes a piston (12) at an extremity (22) of which is arranged a cam follower (28) maintained, in use, in contact with a cam (10) which rotates and imparts to the piston (12) a reciprocal movement. The cam follower (28) has a body (30) in which is arranged a roller (32) adapted to be arranged in a cam actuated fuel pump has a cylindrical outer face (34) extending along a roller axis (X2) between a first transverse face and an opposed second transverse face, the cylindrical face intersecting the first transverse face along a first edge and, the second transverse face along a second edge. The roller is further provided with a first recess opening in the first transverse face, the material thickness between the area of the cylindrical face that is in the vicinity of the first edge and said first recess being reduced relative to an area of the cylindrical face distant from the first and from the second edges.