Suspension Spring Frustoconical End for Coating-Safe Compression

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Solution Overview

Problem

Existing suspension springs for vehicles with varying load capacities face challenges in maintaining optimal stiffness and preventing damage to the wire coating due to differences in wire diameter, leading to inefficiencies and potential damage when compressed.

Innovation Solution

A suspension spring design featuring a stiff portion and a flexible portion with distinct diameters, where the flexible portion ends in a frustoconical tail with a decreasing diameter, allowing the same support model to be used across different vehicle models by adjusting the tail's shape to match the step height, thus preventing wire damage and maintaining optimal stiffness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the flexible portion uses a thin wire section to provide low stiffness for empty vehicle suspension, then the stiffness is adapted for empty state, but the wire diameter becomes smaller increasing risk of coating damage during compression

Engineering Contradiction:
Improvestiffness adaptationVSAvoidcoating integrity
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies parameter changes by varying the wire diameter along the length of the flexible portion. The wire transitions from a thinner section (providing lower stiffness for empty vehicle suspension) to a thicker section (with larger diameter that prevents coating damage during compression). This gradual parameter change allows the same component to satisfy both requirements: low stiffness when needed and structural integrity when compressed.

Inventive Principle:
Principle #35Parameter changes

2Adaptability or versatility

If different wire diameters are used for different vehicle models to optimize stiffness, then optimal suspension performance is achieved, but manufacturing complexity and support model variety increases

Engineering Contradiction:
Improvevehicle model adaptabilityVSAvoidsupport model variety
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing the flexible portion into distinct wire diameter sections (thin section and thick section) within a single spring component. This internal segmentation allows the spring to provide different stiffness characteristics for different vehicle models without requiring different support models. The transition section gradually changes the wire diameter, enabling one universal support model to work across multiple vehicle applications.

Inventive Principle:
Principle #1Segmentation

3Force

If the flexible portion is completely compressed under heavy load, then the stiff portion engages to provide higher stiffness, but the thin wire section may suffer coating damage from angular contact

Engineering Contradiction:
Improveload bearing capacityVSAvoidwire coating damage
Core Design Contradiction:
ForceVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by pre-shaping the wire diameter distribution before the spring is assembled. The wire is manufactured with a gradual diameter increase from the thin section to the thick section, and this gradient is established before the spring is mounted on the support. This preliminary preparation ensures that when the spring is compressed under heavy load, the thicker wire section engages first, preventing angular contact and coating damage on the thinner sections.

Inventive Principle:
Principle #10Preliminary action

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 consistent performance and durability across different vehicle loads by adapting the suspension spring's shape to match varying wire diameters, preventing damage and maintaining optimal stiffness without requiring multiple support models, thereby reducing manufacturing complexity and costs.

Implementation Method 1

a second end portion, called the flexible portion, which has a second determined stiffness less than the first stiffness, and which comprises several active turns made with a second section, called the thin section, of the wire having a second determined diameter less than the first determined diameter

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

the two spring portions act as two springs of different stiffnesses arranged in series between the two supports

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP3914834B1Suspension spring comprising a stiff portion and a flexible frustoconical end portion
Publication Date: 2024.07.03 RENAULT SA
  • EP3914834B1 patent drawingFigure 1~3
  • EP3914834B1 patent drawingFigure 4~6
  • EP3914834B1 patent drawingFigure 7~9

AI summary

The invention relates to a suspension spring (10) for a motor vehicle that is produced by helically winding a wire (12) around a helical axis (A), the suspension spring (10) comprising: - a first end portion, termed stiff portion (17); and - a second end portion, termed flexible portion (18), which has a second predetermined stiffness (K2) which is less than the first stiffness (K1), and which comprises a plurality of active coils formed with a thin section (16) of the wire (12) having a second predetermined diameter (D2) which is less than the first predetermined diameter (D1), the flexible portion (18) terminating in a bearing coil (22) intended to bear on a support (24); characterized in that the bearing coil (22) of the flexible portion (18) is formed in part by a free end tail (46) of the wire (12) having a frustoconical shape of which the diameter in cross section decreases progressively.