Leaf Spring Curvature Profile for Stable Suspension

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Solution Overview

Problem

Conventional leaf springs for motor vehicle suspension systems experience length variations due to load changes, leading to stiffening, potential blade elongation, parasitic lateral wheel displacements, and steering issues, especially when positioned transversely, affecting vehicle trajectory and balance.

Innovation Solution

A leaf spring design with a central part that can deform while maintaining distance between fixed assembly zones, featuring a curvature profile with adjacent lateral zones of opposite curvature, and using pivot or ball joint connections to the chassis for stable suspension and stabilization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a conventional leaf spring with parabolic curve is used, then the suspension provides basic load support, but the length between ends varies with load causing stiffening and parasitic lateral displacements

Engineering Contradiction:
Improvesuspension stabilityVSAvoidleaf spring length variation
Core Design Contradiction:
Stability of the object's compositionVSLength of moving object

Solution Approach 1:

The leaf spring is divided into three distinct zones: a central part with first curvature, two lateral zones with second curvature opposite to the central part, and two end zones with third curvature opposite to the lateral zones. This segmentation allows each zone to contribute differently to the overall deformation behavior, enabling the central part to deform while maintaining end distance.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention uses a complex multi-curvature profile instead of a simple parabolic curve. The central part has a first curvature, the lateral zones have a second curvature opposite to the central part, and the end zones have a third curvature opposite to the lateral zones. This alternating curvature design enables controlled deformation that maintains constant end distance.

Inventive Principle:
Principle #14Spheroidality (Curvature)

2Device complexity

If the leaf spring ends are directly attached to the chassis, then the connection is simplified, but the suspension becomes overly stiff and may cause violent blistering under load

Engineering Contradiction:
Improveconnection complexityVSAvoidsuspension flexibility
Core Design Contradiction:
Device complexityVSStrength

Solution Approach 1:

The leaf spring structure is segmented into functional zones with different curvatures, allowing the central part to absorb deformation while the end zones maintain attachment points. This eliminates the need for complex twin-type joints or elastic wedges while preserving suspension flexibility.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The leaf spring's own geometry serves the dual function of providing suspension compliance and maintaining constant end distance. The alternating curvature profile inherently compensates for load-induced length variations, eliminating the need for separate compensation mechanisms.

Inventive Principle:
Principle #25Self-service

3Stability of the object's composition

If the leaf spring is positioned transversely to improve suspension, then the suspension performance is enhanced, but parasitic lateral displacements occur affecting vehicle trajectory and steering

Engineering Contradiction:
Improvesuspension performanceVSAvoidparasitic lateral displacements
Core Design Contradiction:
Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The alternating curvature profile (central part with first curvature, lateral zones with opposite second curvature, end zones with opposite third curvature) creates a deformation mode where the central part absorbs vertical loads while the end zones maintain fixed positions, preventing lateral displacements even when the spring is positioned transversely.

Inventive Principle:
Principle #14Spheroidality (Curvature)

Solution Approach 2:

The invention changes the geometric parameters of the leaf spring by introducing alternating curvatures with different radii and directions. This parameter modification transforms the deformation characteristics, allowing the spring to accommodate vertical deflection without generating lateral displacements that would affect vehicle trajectory.

Inventive Principle:
Principle #35Parameter changes

4Stability of the object's composition

If complex assemblies with fixed points and articulations are used, then length variation is compensated, but the device complexity and manufacturing cost increase

Engineering Contradiction:
Improvelength variation compensationVSAvoidassembly complexity
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The invention extracts the length compensation function from separate external assemblies (twin-type joints, elastic wedges) and integrates it directly into the leaf spring's geometry. The alternating curvature profile inherently compensates for load-induced length variations, eliminating the need for additional compensation components.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The invention merges multiple functions into a single integrated leaf spring structure: load support, length variation compensation, and constant end distance maintenance are all achieved through the alternating curvature profile, eliminating the need for separate assemblies and reducing overall system complexity.

Inventive Principle:
Principle #5Merging (Combining)

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 design ensures stable vehicle suspension and improved trajectory following by eliminating parasitic lateral movements and simplifying attachment, reducing costs by eliminating complex assemblies and enhancing road behavior and wheel control.

Implementation Method 1

the central part being arranged so as to be able to deform while maintaining a distance between the fixed assembly zones

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Implementation Method 2

the assembly means form a pivot connection with an axis perpendicular to the leaf spring between the assembly zones of the leaf spring and the chassis of the vehicle

Methodology Applied
Scientific EffectPivot connection: Hinge

Implementation Method 3

the assembly means form a ball joint between the assembly zones of the leaf spring and the chassis of the vehicle

Methodology Applied
Scientific EffectBall joint: Ball

Data Source

PatentEP2814676B8Spring leaf suspension system for vehicle and suspension system including the same
Publication Date: 2016.09.07 HUTCHINSON SA

AI summary

The invention relates to a spring leaf (10) for a motor vehicle suspension system, comprising a central portion (11, 12, 13), two end zones (14, 15) located on each side of the central portion, and assembly zones located between the central portion and the end zones. The central portion is arranged such that it can deform while retaining a distance between the stationary assembly zones.