Steering Wheel Spoke Tapering for Fatigue and Stiffness Balance
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Solution Overview
Problem
Existing steering wheel skeletons face a trade-off between flexural rigidity and long-term load capacity, where improving one criterion often negatively impacts the other, due to traditional design approaches that either reinforce or reduce these properties.
Innovation Solution
A steering wheel skeleton design featuring a spoke with a support section and a connecting section where the connecting section tapers disproportionately from the support section to the steering wheel rim, allowing for enhanced flexural rigidity and long-term load capacity without compromising resilience, achieved through a design that includes a radially outermost end with a radius matching the inner edge of the rim and a width that decreases abruptly as it approaches the rim.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the connecting section is made wider to increase load-bearing capacity, then the fatigue strength improves, but the bending stiffness increases excessively
Solution Approach 1:
The connecting section features a locally optimized cross-section with a cutout portion that creates an asymmetric shape. This local modification allows the section to have high strength where needed while reducing overall stiffness to achieve the desired balance between fatigue resistance and bending flexibility.
Solution Approach 2:
The connecting section is designed with an asymmetric cross-section due to the cutout portion. This asymmetric geometry allows different structural properties in different directions, enabling the spoke to achieve both high fatigue strength and controlled bending stiffness simultaneously, which would be difficult with symmetric sections.
2Stability of the object's composition
If recesses are incorporated into the steering wheel rim to reduce bending stiffness, then the bending stiffness improves, but the fatigue strength decreases
Solution Approach 1:
Instead of using recesses in the rim, the invention segments the connecting section itself by incorporating a cutout portion. This segmentation allows the reducing of bending stiffness through the cutout while maintaining fatigue strength through the optimized remaining material distribution and asymmetric shape.
3Strength
If the spoke connection to the steering wheel rim is made more robust to increase load-bearing capacity, then the fatigue strength improves, but the bending stiffness increases excessively
Solution Approach 1:
The connecting section is designed with a localized cutout portion that creates an asymmetric cross-section. This local modification allows the spoke-rim connection to achieve high load-bearing capacity and fatigue strength while simultaneously reducing the overall bending stiffness to the desired level, resolving the contradiction between robust connection and excessive stiffness.
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
The invention relates to a steering wheel skeleton (10) with a hub (15), a steering wheel rim (13) and at least one spoke (20a, 20b) connecting the hub (15) and the steering wheel rim (13), wherein the spoke (20a, 20b) has, starting from the hub (15), a supporting portion (25) and a connecting portion (30) following the supporting portion (25), wherein the spoke (20a, 20b) is connected at the outermost end (33) of the connecting portion (30) to the steering wheel rim (13). According to the invention, the width (BV) of the connecting portion (30) decreases at least in sections starting from the supporting portion (25) in the direction of the outermost end (33) of the connecting portion (30) and converges in a superproportionally tapered manner in proximity to the inner edge (14) of the steering wheel rim (13).