Fuel Pump Roller Profile Reduces Edge Stress
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Solution Overview
Problem
Mechanical fuel pump rollers experience premature failure due to high contact pressures and subsurface stresses at the edge portions during operation, which is exacerbated by the need for adequate hydrodynamic wedging and lift, leading to conflicting design challenges.
Innovation Solution
A roller profile with specific areas of reduced cross section, featuring radii of curvature to alleviate contact pressure at the axial ends, and a uniform circular cross section over a defined length, optimizing hydrodynamic wedging and lift while reducing stress on the roller-cam contact areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the roller length is increased to achieve adequate hydrodynamic wedging and lift, then hydrodynamic performance is improved, but contact pressure at the edge portions increases causing premature failure
Solution Approach 1:
The roller transitions from a uniform cylindrical shape to a non-uniform profile where different sections have different cross-sectional areas. The intermediate portion maintains a larger cross-section for hydrodynamic performance, while the end portions have reduced cross-sections to lower contact pressure and prevent premature failure.
Solution Approach 2:
The roller profile incorporates curved transitions between sections with different cross-sectional areas. These curved portions smooth the stress distribution and eliminate sharp edges that would concentrate stress, while maintaining the beneficial reduced contact pressure at the ends.
2Reliability
If the roller length is increased to achieve adequate hydrodynamic wedging and lift, then hydrodynamic performance is improved, but the roller complexity increases
Solution Approach 1:
The roller is divided into distinct sections along its length: end portions with reduced cross-sections and an intermediate portion with a larger cross-section. This segmentation allows each section to be optimized for its specific function while maintaining manufacturing feasibility through standard processes.
3Ease of manufacture
If the roller length is decreased to reduce manufacturing complexity, then ease of manufacture is improved, but hydrodynamic wedging and lift are insufficient
Solution Approach 1:
The roller cross-sectional area parameter is varied along its length rather than remaining constant. This parameter change creates a profile that optimizes both hydrodynamic performance and stress distribution, achieving better overall performance without requiring complex manufacturing processes.
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 optimized roller profile significantly reduces contact pressures at the axial ends, preventing premature failure and maintaining adequate hydrodynamic performance, as demonstrated by contact pressure analysis and testing.
Implementation Method 1
The exterior surface 24 rotates hydro-dynamically on a hydraulic wedge of lubricant 40 in the seating surface 34 of the shoe 30
Implementation Method 2
a hydraulic wedge of lubricant 40 in the seating surface 34 of the shoe 30, as shown in FIG. 3. The wedge 40 lifts the roller 20 away from the shoe 30
Implementation Method 3
The exterior surface 24 of the roller 20 rolls on the cam surface 22B as the cam 22 rotates around an axis A2
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A roller (120) for a mechanical fuel pump assembly includes an elongate body. The elongate body defines an effective length (L1) that is less than its overall length (L). The elongate body defines a uniform circular cross section over a second length (L2) of the elongate body. The second length (L2) is 75 to 90 percent of the effective length (L1) and the second length (L2) extends between a first plane (A) and a second plane (A'). A first area of reduced cross section extends axially outward from the first plane (A) to a third plane (B) located axially inward of the first axial end; and a second area of reduced cross section extends axially outward from the second plane (A') to a fourth plane (B') located axially inward of the second axial end.