Cold-Sprayed Bore Coating for Lightweight Connecting Rod Bearings
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Solution Overview
Problem
Current connecting rod designs face high tightening tensions due to shrinking, leading to increased bulk and weight, and the bearing is subjected to excessive stress and heat, necessitating a solution to reduce dimensions and improve heat dissipation while maintaining tribological and thermal properties.
Innovation Solution
A composite coating is deposited using the dynamic cold spraying process, comprising metal or polymer powders, hard ceramic particles, and solid lubricants, which replaces traditional bearings, reducing mass and bulk, and enhancing fatigue, corrosion, and thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional bearings are used in connecting rod design, then the bearing can withstand the repeated pressure and combustion forces, but the bulk and weight of the engine increase
Solution Approach 1:
The patent merges the bearing function directly into the connecting rod big end bore by depositing a functional coating on the bore surface. This eliminates the separate bearing component (steel sheet substrate) and integrates the bearing function into the existing structure, thereby reducing overall weight while maintaining load-bearing capability.
Solution Approach 2:
The patent uses composite coating materials comprising a metal matrix (aluminum, copper, or steel base metal), ceramic hard particles (alumina, silica, zirconia), and solid lubricant particles (graphite, PTFE, MoS2). This composite structure provides the necessary mechanical strength, hardness, and lubrication properties to replace traditional bearings while reducing weight.
2Strength
If the connecting rod bulk is increased to withstand bearing stresses, then the bearing can handle combustion forces, but the thermal resistance between the bearing and big end bore increases
Solution Approach 1:
The patent changes the material parameters of the bearing surface by depositing a coating with superior thermal conductivity properties. The coating materials (particularly aluminum-based matrices and copper) have higher thermal conductivity than traditional bearing materials, enabling more efficient heat dissipation from the contact zone while maintaining the necessary mechanical strength through the composite structure.
3Force
If the diameter of connecting rod screws is increased to support bearing loads, then the bearing can withstand tightening tensions, but the travel zone of the connecting rod increases
Solution Approach 1:
The patent uses composite coating materials with enhanced mechanical properties, including a metal matrix providing base strength, ceramic hard particles (alumina, silica, zirconia) enhancing hardness and load-bearing capacity, and solid lubricants reducing friction. This composite structure allows the bearing to withstand high tightening tensions and combustion forces while maintaining a compact design with reduced screw diameter and shorter connecting rod travel zone.
4Weight of moving object
If a coating is deposited on the big end bore to reduce dimensions, then the mass and bulk are reduced, but the coating must maintain tribological properties under repeated stop/start cycles
Solution Approach 1:
The patent employs a multi-component composite coating system where the metal matrix (aluminum, copper, or steel) provides structural integrity and adhesion to the substrate, ceramic hard particles (alumina, silica, zirconia) provide wear resistance and hardness, and solid lubricant particles (graphite, PTFE, MoS2) provide low-friction surfaces. This synergistic composite structure maintains tribological properties under repeated stop/start cycles while enabling weight and dimension reduction.
Solution Approach 2:
The cold spray deposition process creates a coating with a controlled porous structure that can accommodate thermal expansion and contraction during engine operation. The porous structure also allows for oil retention and distribution, enhancing lubrication and reducing wear during repeated stop/start cycles, thereby improving coating durability despite reduced dimensions.
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 process reduces the dimensions and weight of engine components, improves heat dissipation, and increases seizing resistance, leading to fuel efficiency, reduced CO2 emissions, and enhanced engine reliability by eliminating thermal resistance and misalignment issues.
Implementation Method 1
These speeds lead to plastic deformation on impact of this material on a substrate to be treated, which is large enough to form an adherent coating
Implementation Method 2
The technique of dynamic cold spraying or 'cold spray' consists of accelerating a filler material (300 to 1500 m/s) in powder form beyond a critical speed
Implementation Method 3
good thermal conductivity to dissipate generated heat more quickly by friction
Data Source
Figure 1
AI summary
The invention relates to a method for depositing a coating (11) in a bore of a mechanical part by the Cold Spray process (1). According to the invention, the process comprises the following steps: - a step of mixing a powder comprising metallic or polymeric particles to create a metallic or polymer matrix, hard ceramic particles and solid lubricant particles, - a step of dynamically cold spraying the powder prepared in the previous step onto the bore of the mechanical part (1), and deposition of a coating (11) onto said bore from the sprayed powder.