Variable Stiffness Spring for Steering Preload and Impact Absorption
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Solution Overview
Problem
Conventional steering systems face challenges in balancing preload and impact absorption, leading to high friction and wear, particularly in rack and pinion and recirculating-ball style systems, where high stiffness springs result in tight engagement and undesirable user experience due to increased force requirements.
Innovation Solution
The steering system incorporates an elastic member with varying stiffness coefficients, allowing for suitable preload application and impact absorption by deforming differently under different load ranges, and is designed to be non-linear or a combination of springs with distinct lengths and stiffness coefficients to manage load effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a high stiffness spring is used to apply preload to the engagement members, then the engagement between gear and rack becomes tighter and more stable, but the friction and wear increase and user experience deteriorates due to increased force requirements
Solution Approach 1:
The patent applies a progressive stiffness spring where the stiffness coefficient varies along the length of the spring. The spring has a first stiffness coefficient in the first portion and a second stiffness coefficient in the second portion, allowing it to provide higher force when needed while maintaining lower force during normal operation. This parameter variation resolves the contradiction by enabling the spring to adapt its stiffness to different operational states.
Solution Approach 2:
The spring transitions from a static, uniform stiffness design to a dynamic, variable stiffness design. The progressive stiffness characteristic allows the spring to automatically adjust its mechanical properties based on the load conditions, providing tight engagement when necessary while minimizing steering effort during normal use.
2Stability of the object's composition
If a high stiffness spring is used to ensure stable engagement, then the preload application becomes more effective, but the impact absorption capability decreases and friction increases
Solution Approach 1:
By varying the stiffness coefficient along the spring length, the patent enables the spring to provide different levels of resistance to different types of loads. The progressive stiffness design allows effective preload application for stable engagement while reducing resistance to impact loads, thereby minimizing friction and wear between engagement members.
Solution Approach 2:
Different portions of the spring have different stiffness properties tailored to specific functions. The first portion with one stiffness coefficient handles normal operational loads, while the second portion with a different stiffness coefficient handles impact absorption, optimizing performance for each local requirement.
3Ease of manufacture
If a linear spring is used, then the design is simpler and manufacturing is easier, but the ability to apply optimal preload and absorb impact loads simultaneously is reduced
Solution Approach 1:
The patent implements a progressive stiffness spring with varying geometric parameters along its length, creating non-linear elastic characteristics. This design achieves optimal preload application and impact absorption performance by tailoring the stiffness profile, while remaining manufacturable through conventional spring forming processes with adjusted geometry.
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
This approach reduces friction and wear by applying optimal preload and absorbing impact loads efficiently, enhancing user experience by minimizing the force needed for steering while maintaining system stability.
Implementation Method 1
The elastic member may have a first deformation under a first load and at least a second deformation under a second load greater than the first load
Implementation Method 2
The relationship of load with deformation of the elastic member may be non-linear
Implementation Method 3
an elastic member at least partially enclosed in the supporting portion to apply preload to the second engagement member and to absorb an impact load
Data Source
AI summary
A steering system comprises a first engagement member; a second engagement member to be engaged with the first engagement member; a supporting portion to support the second engagement member; and an elastic member at least partially enclosed in the supporting portion to apply a preload to the second engagement member and absorb an impact load. The elastic member has a first deformation under a first load and at least a second deformation under a second load greater than the first load, and a ratio of the first load to the first deformation is less than a ratio of the second load to the second deformation.