Laser-Roughened Steering Shaft Assembly for Direct Plastic Bonding
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Solution Overview
Problem
Existing methods for adhering plastic to metal shafts in steering shaft assemblies require additional materials like primers or phosphate coatings, increasing processing steps and costs, and lack a direct, efficient bonding method.
Innovation Solution
A laser ablation process is used to roughen the surface of the inner shaft, allowing direct application of plastic without intermediate materials, reducing complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a primer bonding agent is applied to the inner shaft before plastic application, then the plastic adhesion to metal shaft is improved, but the number of processing steps and materials increases
Solution Approach 1:
The patent removes the primer bonding agent from the process entirely, extracting this intermediate material step. Instead, a mechanical interlocking mechanism is created through surface roughening of the metal shaft, allowing plastic to adhere directly without requiring chemical primers or bonding agents.
Solution Approach 2:
The patent introduces a surface roughness feature as an intermediary between the metal shaft and plastic. This roughened surface acts as a mechanical mediator that provides anchoring points for the plastic material, replacing the chemical mediation previously provided by primer bonding agents.
2Reliability
If a phosphate coating is applied to the inner shaft before plastic application, then the plastic adhesion to metal shaft is improved, but the number of materials and assembly cost increases
Solution Approach 1:
The patent eliminates the phosphate coating material from the process. Instead of applying a chemical conversion coating, the invention uses direct mechanical surface roughening of the metal shaft to create adhesion points for the plastic, thereby removing this intermediate material layer.
Solution Approach 2:
The roughened surface topology serves as a physical intermediary between the metal shaft and plastic material. This mechanical interface provides sufficient bonding without requiring chemical coatings or conversion layers, reducing the total quantity of materials needed.
3Reliability
If multiple intermediate materials are used to bond plastic to metal shaft, then the adhesion strength is improved, but the manufacturing cost increases
Solution Approach 1:
The patent removes intermediate bonding materials (primers, phosphate coatings) from the manufacturing process. The adhesion strength is achieved through a mechanical interlocking mechanism created by surface roughening, which eliminates the need for costly intermediate chemical materials while maintaining reliable bonding.
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 laser ablation process enables a direct plastic-to-metal bond, enhancing the torsional rigidity and reducing manufacturing costs by eliminating the need for additional bonding agents.
Implementation Method 1
the interface portion is roughened with a laser ablation process
Data Source
AI summary
A steering shaft assembly for a vehicle steering system includes an inner shaft having an interface portion of an outer surface of the inner shaft, wherein the interface portion is roughened with a laser ablation process. The steering shaft assembly also includes an outer shaft defining a bore which receives a portion of the inner shaft therein. The steering shaft assembly further includes a plastic material disposed directly on a portion of the outer surface of the inner shaft without an intermediate material or agent between the plastic material and the outer surface.