Composite Core Wire Twist Structure for Fatigue-Resistant Drive Belts
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Solution Overview
Problem
Existing power-transmission belts face challenges in achieving both high tensile strength and small elongation, particularly for applications like integrated starter generators, where bending fatigue resistance is insufficient, and composite cords optimized for molding processes are not suitable for grinding methods.
Innovation Solution
A core wire for power-transmission belts is formed by secondary twisting a plurality of hard primary twisted yarns containing aramid fibers with a fineness of 1500 dtex or less and one soft primary twisted yarn containing a low elastic modulus fiber, with a specific ratio of primary twist coefficients to achieve high tensile strength and small elongation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high elastic modulus aramid fibers are used to reduce elongation, then tensile strength is improved, but bending fatigue resistance deteriorates
Solution Approach 1:
The patent applies composite materials by combining high elastic modulus aramid fibers (for tensile strength) with low elastic modulus fibers (for bending fatigue resistance) in a specific ratio (65:35 to 95:5). This composite cord structure allows the high-modulus fibers to provide tensile strength while the low-modulus fibers absorb bending stresses, resolving the contradiction between tensile strength and bending fatigue resistance
2Reliability
If composite cords with low elastic modulus fibers are used to improve bending fatigue resistance, then elongation control during molding is improved, but tensile strength deteriorates
Solution Approach 1:
The patent uses composite materials with a specific fiber ratio (65:35 to 95:5 of high-to-low elastic modulus fibers) to balance bending fatigue resistance and tensile strength. The high proportion of high-modulus fibers ensures sufficient tensile strength while the low-modulus fibers provide bending fatigue resistance and molding elongation control
3Stability of the object's composition
If auto-tensioner is used to absorb elongation, then tension constancy is improved, but power transmission efficiency deteriorates when elongation is too large
Solution Approach 1:
The patent changes the material parameters of the core wire by using composite cords with optimized fiber ratios and specific twist coefficients. This reduces belt elongation to within acceptable limits, eliminating the need for auto-tensioners and maintaining high power transmission efficiency while ensuring tension constancy
Data Source
AI summary
A core wire for a power-transmission belt includes a plied twisted cord formed by putting together and secondary twisting a plurality of primary twisted yarns. The primary twisted yarns include a plurality of hard primary twisted yarns (A) and one soft primary twisted yarn (B). The hard primary twisted yarns (A) include an aramid fiber, and a fineness of each hard primary twisted yarn (A) is 1500 dtex or less. The soft primary twisted yarn (B) includes a low elastic modulus fiber. A ratio (B/A) of a primary twist coefficient of the soft primary twisted yarn (B) to an average value of primary twist coefficients of the hard primary twisted yarns (A) is 0.5 to 1.2.