Cellulose Nanofiber Resin Gear for Void-Resistant Durable Sliding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing gear systems, particularly those used in electric power steering (EPS), face challenges with high-torque durability, slidability, and continuous moldability, as well as issues with voids and stress concentration due to the use of glass fibers, which affect the mechanical properties and dimensional stability of resin compositions.
Innovation Solution
A gear system comprising a resin composition with a thermoplastic resin and cellulose nanofibers, where the thermoplastic resin has a specific molecular weight and a thixotropic index of 2 to 10 at 25°C higher than its melting point, with a gear surface roughness of 3.0 µm or lower, and an average fiber diameter of 1000 nm or smaller, enhancing the gear's roundness and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If glass fibers are used as reinforcing material in resin compositions, then mechanical strength is improved, but specific gravity increases and weight increases
Solution Approach 1:
The patent changes the key parameter from glass fiber diameter to cellulose fiber diameter, specifically using cellulose fibers with a diameter of 1 µm or less. This parameter change allows achieving comparable mechanical strength while reducing specific gravity from 2.5 (glass) to approximately 1.5 (cellulose), thereby reducing the weight of the molded article.
Solution Approach 2:
The patent uses cellulose fibers as a natural fiber reinforcement in thermoplastic resin matrices, creating a composite material that combines the advantages of natural fibers (low density, high strength-to-weight ratio) with thermoplastic processing capabilities. This composite approach replaces traditional glass fiber composites with a lighter alternative.
2Strength
If glass fibers are used in resin compositions for injection molding, then mechanical properties are improved, but orientation of glass fibers produces stress concentration and reduces durability
Solution Approach 1:
The patent changes the fiber diameter parameter to 1 µm or less, which is significantly finer than conventional glass fibers. This ultra-fine diameter reduces fiber orientation effects and stress concentration, improving durability while maintaining mechanical properties. The fine diameter allows for more uniform distribution and reduced anisotropy in the molded article.
3Productivity
If glass fibers are continuously used in injection molding, then production continues, but significant deviation of molded article dimensions occurs between articles
Solution Approach 1:
The patent uses cellulose fibers with a diameter of 1 µm or less, which provides more consistent flow and packing characteristics during injection molding. This fine fiber diameter reduces variability in molded article dimensions between articles, improving manufacturing precision while maintaining continuous production capability.
4Ease of manufacture
If resin compositions containing glass fibers are used for shaping, then production is achieved, but interior voids form due to cooling rate differences, leading to stress concentration and inferior durability
Solution Approach 1:
The patent uses ultra-fine cellulose fibers with a diameter of 1 µm or less, which significantly reduces the formation of interior voids during cooling. The fine fiber diameter allows for more uniform heat transfer and reduced thermal gradients, eliminating vacuum cavities and improving durability while maintaining ease of manufacture.
5Ease of manufacture
If cellulose nanofibers are dried into powder form for distribution in resin, then processing is enabled, but they change from microdispersed state to strong aggregates, making redispersion difficult
Solution Approach 1:
The patent uses cellulose fibers with a diameter of 1 µm or less, which maintains better dispersion stability compared to finer nanofibers. This optimized fiber diameter reduces hydrogen bonding aggregation while remaining processable, achieving a balance between ease of manufacture and dispersion stability in the resin composition.
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 provides a gear system with improved continuous moldability, high slidability, and durability, reducing voids and stress concentrations, resulting in enhanced performance and silent operation under high-torque conditions.
Implementation Method 1
hydrolyzing the hemicellulose portion to weaken the pulp, and then defibrating it using a pulverizing method with a high-pressure homogenizer, microfluidizer, ball mill or disk mill, and in water they form a very finely dispersed state known as a 'nanodispersion'
Implementation Method 2
hydrolyzing the hemicellulose portion to weaken the pulp
Implementation Method 3
The aggregating force is exhibited due to hydrogen bonding by the hydroxyl groups of the cellulose, and is considered to be extremely strong
Implementation Method 4
the resin composition has a thixotropic index of 2 to 10 at a temperature of 25°C higher than the melting point of the thermoplastic resin (A)
Data Source
Figure 1(A)~1(B)
Figure 2(A)~2(B)
AI summary
A gear is provided that has excellent continuous moldability for practical use, and both high slidability and high durability. The provided gear is a molded resin constructed of a resin composition comprising a thermoplastic resin (A) and cellulose nanofibers (B) with an average fiber diameter of 1000 nm or smaller, and having a number average molecular weight of the thermoplastic resin (A) in the range of 10,000 to 150,000, wherein a sliding surface of the gear with another gear teeth has an arithmetic mean surface roughness Sa of 3.0 µm or lower.