Integrated Steering Shaft Structure for Impact Energy Absorption
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Solution Overview
Problem
The existing steering device shafts for automobiles have a high number of components, leading to increased production costs and unreliable torque communication due to the complexity of connections.
Innovation Solution
A simplified shaft design integrating multiple components, such as a first portion, second portion, and third portion, with specific diameter and hardness profiles to absorb impact energy through plastic deformation, reducing the number of members and steps required for assembly, and enhancing torque communication reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple component members are used in the steering column shaft, then the structural complexity increases, but the production cost increases and torque communication reliability decreases
Solution Approach 1:
The patent merges multiple separate component members (upper shaft, middle shaft, input shaft, output shaft) into a single integrated steering column shaft. This consolidation eliminates the need for multiple joining steps and connection interfaces, thereby reducing production cost while improving torque communication reliability by removing potential failure points at connection interfaces.
2Ease of manufacture
If multiple component members are connected via spline-coupling or press-fitting, then the structural flexibility increases, but the number of joining steps increases leading to higher production cost
Solution Approach 1:
The patent integrates multiple shaft components into a single monolithic structure, eliminating all spline-coupling and press-fitting joining steps. This single-piece construction dramatically reduces manufacturing complexity and production cost by removing multiple assembly operations and quality control steps required for joining separate components.
3Reliability
If the middle shaft has a tapered smaller-diameter portion for impact energy absorption, then the impact energy absorption capability is achieved, but the stress concentration at the tapered portion increases
Solution Approach 1:
The patent applies local quality by creating a smaller-diameter portion with different material properties (through plastic deformation) at a specific location along the shaft. This localized region is designed to plastically deform and absorb impact energy, while the rest of the shaft maintains its original strength characteristics. The gradual transition of the smaller-diameter portion minimizes stress concentration compared to abrupt changes.
Solution Approach 2:
The patent changes the physical parameters of a specific portion of the shaft by plastically deforming it to create a smaller-diameter section. This parameter change (reducing diameter) enables the region to yield at lower stresses during impact events, absorbing energy through plastic deformation. The constant outer diameter portion provides a transition zone that manages stress distribution.
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 integrated shaft design reduces production costs and improves torque communication reliability by absorbing impact energy through controlled plastic deformation, suppressing stress concentration and fractures.
Implementation Method 1
even when a torque equal to or greater than the reference torque is applied, the third portion becomes twisted and goes through a plastic deformation, and absorbs the impact energy
Data Source
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AI summary
A shaft for a steering device has a first portion, a second portion, and a third portion that is a shaft integrated with the first portion and the second portion and couples the first portion and the second portion in a first direction. The outer diameter of the third portion is smaller than the length of the second portion in a second direction intersecting with the first direction, and is constant across a direction extending along the first direction. The hardness of the third portion is greater than the hardness of the second portion, and is constant across the direction extending along the first direction.