Worm Wheel Polyamide Blend for Wear Resistance and Moldability
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Solution Overview
Problem
Conventional worm wheel materials used in motor-driven power steering systems face limitations in durability, wear resistance, and injection moldability, particularly under long-term repeated loading conditions, leading to premature wear and breakage due to internal stress and chemical corrosion.
Innovation Solution
A composition for a worm wheel comprising a polyamide resin blend with relative viscosities of polyamide 66 and polyamide 12, combined with modified nano-clay, which enhances wear resistance, dimensional stability, and injection moldability, while minimizing moisture absorption and chemical resistance issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-molecular-weight polyamide 66 is used to improve wear resistance, then adhesive wear properties improve, but fluidity decreases leading to lower injection moldability and productivity
Solution Approach 1:
The patent uses a composite material system consisting of polyamide 66 resin blended with polyamide 12 resin. This composite approach allows the material to exhibit both high wear resistance (from PA66) and good fluidity (from PA12), resolving the contradiction between durability and manufacturability.
Solution Approach 2:
The patent optimizes the molecular weight parameters of the polyamide resins used. By selecting specific molecular weight ranges that balance chain length for wear resistance with sufficient chain flexibility for fluidity, the material achieves both durability and injection moldability without compromising either property.
2Reliability
If high-molecular-weight polymer is used to improve adhesive wear properties, then wear resistance improves, but internal stress increases causing deterioration of fatigue wear properties
Solution Approach 1:
The blend of polyamide 66 and polyamide 12 creates a composite structure where the two polymers interact to reduce internal stress while maintaining wear resistance. The PA12 component helps alleviate the internal stress generated by high-molecular-weight PA66, preventing crack formation and improving fatigue wear properties.
Solution Approach 2:
The patent creates different local properties within the material structure through the resin blend. The PA66 provides wear resistance at the surface, while the PA12 contributes to stress distribution and crack prevention in the bulk material, achieving both adhesive wear resistance and fatigue wear resistance through spatial differentiation of material properties.
3Reliability
If lubricant component is added to reduce coefficient of friction, then adhesive wear reduces, but lubricant undergoes adhesive wear itself and promotes dry sliding wear
Solution Approach 1:
The patent makes the worm wheel material itself self-lubricating through the inherent properties of the polyamide resin blend. The material generates its own lubrication effect through surface characteristics and molecular structure, eliminating the need for separate lubricant additives that would otherwise wear away and cause dry sliding wear.
Solution Approach 2:
Instead of using low-molecular-weight lubricant additives that wear away quickly and cause harm, the patent uses the durable polyamide resin structure itself as the long-lasting lubricating component. The resin provides sustained lubrication without degrading into harmful particles, effectively replacing short-lived lubricants with a permanent solution.
Data Source
AI summary
The present disclosure relates to a composition for a worm wheel having excellent durability and wear resistance and a worm wheel manufactured using the same. In one embodiment, the composition for a worm wheel includes a polyamide resin, wherein the polyamide resin includes a polyamide 66 resin having a relative viscosity (RV) of about 2.5 or higher and a polyamide 12 resin having a relative viscosity (RV) of about 1.0 or higher.