Hollow Spring Element With Notch Geometry For Uniform Stiffness

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Solution Overview

Problem

Existing suspension spring elements in automobiles face challenges in maintaining a uniform stiffness profile and resisting cyclic loads without buckling, denting, or swelling, leading to inconsistencies in vehicle suspension performance and comfort.

Innovation Solution

The design incorporates narrow, coaxially arranged notches with specific geometry and a flexible lip structure that ensures uniform stiffness and reduces material swelling, featuring notches with a radius of curvature less than 1 mm and a flexible lip with an outwardly directed edge, which enhances manufacturing ease and load distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If cross-sectional changes are introduced on the spring element to modify stiffness characteristics, then the stiffness profile can be adjusted, but jumps in stiffness occur in the spring characteristic leading to non-uniform stiffness

Engineering Contradiction:
Improvestiffness profileVSAvoiduniformity of stiffness
Core Design Contradiction:
StrengthVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by introducing notches at specific locations on the spring element to locally modify stiffness characteristics. The notches are positioned to achieve desired stiffness progression while maintaining overall uniformity through careful geometric design with specific radius of curvature parameters.

Inventive Principle:
Principle #3Local quality

2Strength

If the spring element contour is designed to withstand high cyclic loads, then load resistance is improved, but the material may swell beyond the available space

Engineering Contradiction:
Improvecyclic load resistanceVSAvoidmaterial swelling
Core Design Contradiction:
StrengthVSVolume of moving object

Solution Approach 1:

The patent applies parameter changes by carefully controlling the geometric parameters of the notches, specifically the radius of curvature at the base (less than 1 mm) and the notch angle (less than 90°). These parameter optimizations allow the spring element to resist cyclic loads while minimizing material swelling within the available space.

Inventive Principle:
Principle #35Parameter changes

3Ease of manufacture

If sharp-edged design features are used in notches, then manufacturing is simplified, but the spring elements tend to tear under load and severe deformation creating weak points

Engineering Contradiction:
Improvenotch fabricationVSAvoidresistance to tearing
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent applies spheroidality by designing notches with a controlled radius of curvature at the base (less than 1 mm) and rounded transition edges (radius greater than 3 mm). This curvature eliminates sharp edges that would create stress concentration points, preventing tearing under load while remaining manufacturable.

Inventive Principle:
Principle #14Spheroidality (Curvature)

4Stability of the object's composition

If narrow notches are designed on the spring element, then uniform stiffness profile is achieved, but manufacturing precision requirements increase

Engineering Contradiction:
Improveuniformity of stiffness profileVSAvoidnotch geometry control
Core Design Contradiction:
Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by establishing specific geometric parameters for the notches: base radius of curvature less than 1 mm, notch angle less than 90°, and transition edge radius greater than 3 mm. These defined parameters enable narrow notches that achieve uniform stiffness profiles while providing clear manufacturing targets that control precision requirements.

Inventive Principle:
Principle #35Parameter changes

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 configuration achieves a uniform stiffness profile, prevents sudden rigidity drops, and reduces material swelling under load, enhancing driving comfort and safety by ensuring consistent performance over the spring element's lifespan.

Implementation Method 1

The notches represent constrictions that reduce the outer diameter of the spring element (i) over the entire circumference of the spring element. The notch angle (xvi) of the notch (xii) is less than 90° and the radius of curvature of the notch edge geometry (xv) is greater than 3 mm.

Methodology Applied
Scientific EffectStress concentration:

Implementation Method 2

Spring elements made from polyurethane elastomers are used in automobiles, for example within the chassis. The spring elements assume an end stop function and influence the wheel's force-displacement characteristic by forming or reinforcing a progressive characteristic of the vehicle suspension.

Methodology Applied
Scientific EffectViscoelasticity: Viscoelasticity

Implementation Method 3

The spring elements (i) according to the invention are characterized by very narrow notches. The notches are preferably arranged coaxially. The notches represent constrictions that reduce the outer diameter of the spring element (i) over the entire circumference of the spring element.

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP2326855B1Supplemental spring
Publication Date: 2013.03.06 BASF SE
  • EP2326855B1 patent drawingFigure 1
  • EP2326855B1 patent drawingFigure 2
  • EP2326855B1 patent drawingFigure 3

AI summary

The invention relates to a hollow spring element, the outer surface of which comprises at least one peripheral notch having a notch geometry at the base thereof with a radius of curvature of less than 1 mm.