Splined Driveshaft Inner Surface for Torsional Strength
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Solution Overview
Problem
Conventional driveshafts require a large outer diameter and wall thickness to maintain critical speed and torsional strength, which adversely affects vehicle packaging and vibration attenuation properties.
Innovation Solution
A driveshaft with a hollow shaft and splined inner surface, coupled with universal joints and caps, which increases the area moment of inertia and torsional yield strength, allowing for a reduced outer diameter while maintaining critical speed and vibration damping properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the outer diameter and wall thickness of a conventional driveshaft are increased to maintain critical speed and torsional strength, then the critical speed and torsional strength are improved, but the vehicle packaging is adversely affected
Solution Approach 1:
The patent applies local quality by adding splines only to the inner surface of the driveshaft tube rather than increasing the overall outer diameter. This localized structural modification increases the area moment of inertia and torsional strength where needed (at the inner surface) without affecting the external dimensions, thereby resolving the contradiction between maintaining strength and reducing volume.
2Speed
If the outer diameter and wall thickness of a conventional driveshaft are increased to maintain critical speed, then the critical speed is improved, but the vehicle packaging is adversely affected
Solution Approach 1:
The splined inner surface provides localized structural reinforcement that increases the area moment of inertia, which directly improves critical speed. This allows the driveshaft to achieve the desired critical speed without increasing the outer diameter, thus resolving the contradiction between critical speed and vehicle packaging.
3Object-affected harmful factors
If the wall thickness of a conventional driveshaft is increased to improve vibration attenuation properties, then the vibration damping is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Rather than varying the wall thickness throughout the driveshaft (which would increase manufacturing complexity), the patent applies a uniform splined structure to the inner surface. This localized modification improves vibration attenuation through increased structural rigidity and altered mass distribution without requiring complex variable wall thickness design or multi-step manufacturing processes.
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 enables improved vehicle packaging without compromising critical speed or torsional strength, while enhancing vibration attenuation, by increasing the area moment of inertia through the use of splines on the inner surface of the driveshaft.
Implementation Method 1
The splines extend the length of the hollow shaft. Decreasing the outer diameter and/or wall thickness of a conventionally designed driveshaft decreases the area moment of inertia (critical speed is proportional to the square root of area moment of inertia) and torsional strength
Implementation Method 2
Maintaining a desired critical speed and torsional strength is typically achieved at the expense of vehicle packaging. Decreasing the outer diameter and/or wall thickness of a conventionally designed driveshaft decreases the area moment of inertia (critical speed is proportional to the square root of area moment of inertia) and torsional strength, and thereby adversely affects the critical speed and vibration attenuation properties
Data Source
AI summary
A driveshaft with a hollow shaft, a pair of caps and a universal joint. The hollow shaft is rotatable about an axis and has an annular wall member that defines an outer surface, an inner surface and a pair of opposite ends. At least one of the outer surface and the inner surface includes a plurality of longitudinally extending splines. The caps are fixedly coupled to the opposite ends of the hollow shaft to at least substantially close the opposite ends of the hollow shaft. The universal joint is coupled to one of the caps. The splines extend the length of the hollow shaft.