CFRP Propeller Shaft Layer Structure for Lower Material Cost
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Solution Overview
Problem
The high cost of Carbon Fiber Reinforced Plastic (CFRP) propeller shafts due to the use of high-strength and high-elasticity carbon fibers in all layers, even where lower strength and elasticity is sufficient, limits their adoption.
Innovation Solution
A power transmission shaft with a CFRP tube structure comprising a helical layer part made of high-tensile strength carbon fibers and hoop layer parts made of lower-tensile strength carbon fibers, impregnated with respective resin materials, where the hoop layers are coiled around the shaft to reduce material costs without compromising performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power transmission shaft is used in an in-vehicle power transmission device, then power transmission is enabled, but the shaft requires high manufacturing precision which increases production cost and difficulty
Solution Approach 1:
The power transmission shaft is divided into multiple modular sections that can be manufactured separately and then assembled together. This segmentation allows each section to be produced with standard precision using conventional manufacturing processes, avoiding the need for high-precision machining of the entire shaft as a single piece.
Solution Approach 2:
The shaft design incorporates nested structural elements where inner components are positioned within outer components. This nesting approach enables the shaft to achieve its functional requirements through coordinated assembly of multiple parts rather than requiring a single high-precision component.
2Ease of manufacture
If the shaft structure is simplified for easier manufacture, then manufacturing precision requirements are reduced, but resonance may occur during power transmission
Solution Approach 1:
The shaft design incorporates specific geometric parameters such as optimized diameter transitions, strategically placed ribs, and controlled wall thickness variations. These parameter changes modify the shaft's natural frequencies and mode shapes to avoid resonance conditions during power transmission, while still allowing the shaft to be manufactured with standard precision.
Solution Approach 2:
The shaft employs composite structural design combining different materials or material densities in specific regions. This allows the shaft to achieve desired vibrational characteristics and structural integrity without requiring uniformly high manufacturing precision throughout the entire component.
3Weight of moving object
If the shaft wall thickness is reduced to decrease weight, then weight is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The shaft design implements varying wall thicknesses at different locations along the shaft length. Critical sections have optimized thickness to minimize weight while maintaining structural integrity, and the design incorporates local reinforcement features such as ribs and flanges where needed. This local quality approach allows weight reduction without requiring uniformly high manufacturing precision across the entire shaft.
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 cost-effective CFRP tube structure that maintains required torsion and bending strengths while reducing material costs by using lower-priced carbon fibers for hoop layers, enhancing collision energy control and protecting against chipping.
Implementation Method 1
the first carbon fiber material is impregnated with the first resin material, and is coiled helically around the rotational axis of the first shaft
Implementation Method 2
the second carbon fiber material is impregnated with the second resin material, and is coiled circumferentially around the rotational axis of the first shaft
Data Source
Figure 1
Figure 2~3
AI summary
A propeller shaft (1) as a power transmission shaft of the present invention comprises a CFRP tube (6) formed in a cylindrical shape as a shaft member, wherein a helical layer portion (8) mainly bearing torsional strength and tensile strength is configured from carbon fibers of a first carbon fiber material having a relatively high tensile strength (or tensile modulus of elasticity), and wherein a first hoop layer portion (7) or a second hoop layer portion (9) that is disposed on at least one of the inside and outside in a radial direction with respect to a rotating axis Z of the helical layer portion (8) and that does not bear torsional strength or bending strength is configured from carbon fibers of a second carbon fiber material having a tensile strength (or tensile modulus of elasticity) lower than that of the first carbon fiber material. Thus, it becomes possible to select a relatively inexpensive material for the carbon fibers from which the hoop layer part portion is configured, and to reduce the cost of the CFRP tube (6) for a propeller shaft.