Steering Spindle Tube Structure for Higher Stiffness and Frequency
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Solution Overview
Problem
Traditional methods for increasing the natural frequency and stiffness of steering column spindles, such as using non-traditional materials or increasing cross-section thickness, are either expensive or lead to weight and cost increases, posing challenges for modern steering column assemblies with longer spindles.
Innovation Solution
A steering spindle design featuring a hollow outer tube and inner tube, where the inner tube is press-fit into the outer tube, with specific diameter and length configurations, and transition and connection portions are formed to achieve enhanced natural frequencies and stiffness without increasing weight or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If non-traditional materials are used to increase natural frequency and stiffness, then stiffness is improved, but cost increases
Solution Approach 1:
The patent employs a composite structure consisting of an outer tube and an inner tube made from different materials with complementary properties. The outer tube provides structural support while the inner tube enhances stiffness and natural frequency. This composite approach achieves the desired mechanical performance without requiring expensive non-traditional materials throughout the entire assembly, thereby resolving the contradiction between stiffness improvement and cost increase.
Solution Approach 2:
The spindle is divided into two separate tubular components (outer tube and inner tube) that can be manufactured independently using conventional processes, then assembled together. This segmentation allows each component to be optimized for its specific function and manufactured cost-effectively, avoiding the need to use expensive materials for the entire spindle assembly while still achieving the required overall stiffness.
2Strength
If cross-section thickness is increased to increase natural frequency and stiffness, then stiffness is improved, but weight increases
Solution Approach 1:
The patent uses a composite tubular structure where the inner tube is positioned concentrically within the outer tube. This configuration provides enhanced stiffness and natural frequency comparable to or greater than solid sections of equivalent outer dimensions, while maintaining the weight advantages of hollow structures. The composite action of the two tubes together provides the required stiffness without the weight penalty of increasing the thickness of a single tube.
Solution Approach 2:
Instead of increasing stiffness by adding material in the radial dimension (thickening the tube wall), the patent introduces a new dimension by adding a concentric inner tube. This dimensional approach—placing structural elements in the longitudinal and radial space efficiently—achieves enhanced stiffness without proportionally increasing weight, as the inner tube utilizes the existing hollow space rather than adding external bulk.
3Adaptability or versatility
If longer spindles are used in modern steering column assemblies, then adaptability is improved, but natural frequency decreases
Solution Approach 1:
The patent employs a composite tubular structure where the inner tube acts as a stiffening element within the outer tube. This composite construction significantly increases the overall flexural rigidity and natural frequency of the spindle assembly. The effect is particularly beneficial for longer spindle applications, as the composite structure provides enhanced stiffness that counteracts the frequency-reducing effect of increased length, thereby maintaining reliable natural frequencies even in extended configurations.
Solution Approach 2:
The patent applies the inner tube specifically in regions where stiffness enhancement is most needed, rather than uniformly thickening the entire spindle. The inner tube is positioned to provide local reinforcement that maximizes the natural frequency while minimizing additional weight. This localized quality enhancement allows longer spindles to maintain adequate natural frequencies without requiring uniform increases in cross-sectional dimensions throughout the entire length.
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 design achieves higher natural frequencies and stiffness, minimizing vibration transmission and improving driver satisfaction, while maintaining cost-effectiveness and reducing weight.
Implementation Method 1
The hollow inner tube is press-fit into the outer tube
Data Source
AI summary
One steering column assembly includes a jacket, a bearing, and a steering spindle rotatably supported by the bearing and at least partially extending inside the jacket. The spindle includes a hollow outer tube and a hollow inner tube. The outer tube has lengthening and attachment sections, and the attachment section has transition and connection portions. The lengthening section adjoins the attachment section at an end of the transition portion, and the transition portion is between the lengthening section and the connection portion. The lengthening section has first and second portions, with the second portion being between the first and transition portions, and the outer tube terminates at an end of the connection portion. The inner tube is press-fit into the outer tube, and an end of the inner tube is adjacent the transition portion end. The inner tube does not extend into either the attachment section or the first portion.