Non-Circular Wrist Pin Design for Engine Wear Reduction
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Solution Overview
Problem
Internal combustion engines face challenges with friction, wear, and noise due to lubrication film breakdown between wrist pin and piston pin bores, and connecting rod small end bore, exacerbated by high pressures and temperatures, which are difficult to manage with precise machining and high manufacturing costs.
Innovation Solution
A two-piece wrist pin design with non-circular, elongate portions that minimize sliding motion and prevent relative rotation, combined with a lubrication interface to maintain oil supply and reduce contact pressure, allowing for improved lubrication and damping characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If more clearance is incorporated between bearing surfaces to enhance lubrication, then lubrication is improved, but noise generation increases due to excessive clearance
Solution Approach 1:
The patent changes the geometric parameters of the wrist pin from circular to non-circular cross-section (oval, elliptical, or rectangular). This parameter change allows the pin to maintain optimal clearance for lubrication while minimizing relative rotation and sliding motion, thereby reducing noise without sacrificing lubrication effectiveness
Solution Approach 2:
The non-circular cross-section creates a dynamic fit between the wrist pin and pin bores that allows controlled movement. The varying clearance around the perimeter of the non-circular pin optimizes lubrication flow while limiting excessive motion that causes noise
2Object-generated harmful factors
If clearance between bearing surfaces is minimized to reduce noise, then noise is reduced, but lubrication breakdown occurs due to insufficient clearance
Solution Approach 1:
By changing from a circular to a non-circular cross-section, the patent creates varying clearance zones around the pin perimeter. This allows sufficient clearance in critical areas for lubrication maintenance while minimizing clearance in other areas to reduce noise, achieving both objectives simultaneously
3Reliability
If precise machining operations are performed to attain tight tolerances for bearing surfaces, then lubrication and noise control are improved, but manufacturing cost increases
Solution Approach 1:
The non-circular cross-section can be manufactured using standard forming or casting processes without requiring expensive precision grinding or machining operations. The geometric change itself provides the functional benefits that would otherwise require tight tolerances and complex machining to achieve
Solution Approach 2:
The patent may incorporate bearing materials or coatings on the non-circular wrist pin, combining the geometric advantage with material properties to achieve reliable lubrication and noise control through simpler, more cost-effective 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 solution significantly reduces wear and noise by maintaining a lubrication film and minimizing contact pressure between wrist pin components, enhancing durability and performance under high engine loads while reducing manufacturing complexity and costs.
Implementation Method 1
providing a lubrication interface between the first and second wrist pin members to maintain supplied oil with limited contact pressure between the first and second wrist pin members
Implementation Method 2
The second portion is configured for relative movement with the first portion... minimize sliding motion between the first and second portions
Implementation Method 3
insufficient damping occurs between mating bearing surfaces... providing a lubrication interface... to maintain supplied oil with limited contact pressure... and providing a reduced sliding speed
Data Source
AI summary
A wrist pin and method of reducing wear between members thereof, a piston, a connecting rod, and methods of construction thereof are provided. The wrist pin has a first portion extending between opposite ends configured for receipt in piston pin bores and a second portion extending between opposite ends configured for receipt in the pin bores. The second portion is configured for relative movement with the first portion. The piston includes a piston body having axially aligned pin bores, wherein at least one of the pin bores has a feature to prevent relative rotation of a wrist pin member. The connecting rod includes a connecting rod body having small end bore. The small end bore has a contour to allow relative rotation of a first wrist pin member therein and a feature to prevent relative rotation of a second wrist pin member therein.