Integrated Steering Shaft Structure for Impact Absorption
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Solution Overview
Problem
The existing steering column shafts for electric power steering devices have a high number of components, leading to increased production costs and potentially unreliable torque communication.
Innovation Solution
A shaft for a steering device is designed with integrated portions, including a first, second, and third portion, where the third portion has a smaller outer diameter and higher hardness than the second portion, allowing for reduced component count, lower production costs, and improved torque communication reliability through plastic deformation of the third portion under reference torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the steering column shaft includes many members connected via spline-coupling or press-fitting, then the impact energy absorption characteristic is achieved through plastic deformation of the smaller diameter portion, but the production cost increases and the torque communication reliability decreases
Solution Approach 1:
The patent merges multiple members (upper shaft, middle shaft, input shaft, output shaft) into a single integrated shaft structure. The shaft includes a first portion, second portion, and third portion that are integrally formed, eliminating the need for spline-coupling or press-fitting connections between separate components. This integration maintains the impact energy absorption capability through the third portion's plastic deformation while reducing the number of parts and improving torque communication reliability.
Solution Approach 2:
The patent applies local quality by creating a third portion with specific properties (smaller outer diameter, constant outer diameter along the axial direction, higher hardness) at a specific location of the shaft. This localized structure with constant outer diameter and higher hardness enables controlled plastic deformation for impact energy absorption, while the rest of the shaft maintains its structural integrity and torque transmission function.
2Strength
If multiple members are connected via spline-coupling or press-fitting, then the impact energy absorption characteristic is achieved, but the production cost increases due to increased joining steps
Solution Approach 1:
The patent integrates multiple shaft members into a single piece, eliminating the need for multiple joining operations (spline-coupling, press-fitting). The first portion, second portion, and third portion are formed as one integral structure, which significantly reduces manufacturing steps and production cost while maintaining the impact energy absorption function through the specially designed third portion.
Solution Approach 2:
The patent changes the outer diameter parameter of the third portion to be smaller and constant along the axial direction, and increases the hardness parameter of the third portion relative to other portions. These parameter changes enable the third portion to undergo controlled plastic deformation for impact energy absorption, achieving the strength requirement while simplifying the manufacturing process.
3Strength
If multiple members are connected via spline-coupling or press-fitting, then the impact energy absorption characteristic is achieved, but the torque communication reliability decreases
Solution Approach 1:
The patent merges multiple shaft members into a single integral structure, eliminating connection interfaces between separate components. This integration removes potential failure points at connection locations, ensuring reliable torque communication from the steering wheel through the shaft to the steering mechanism, while the third portion's plastic deformation capability maintains impact energy absorption function.
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 enhances torque communication reliability by absorbing impact energy through the third portion's plastic deformation, while minimizing 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
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.