Inclined-Axis Suspension Bushing for Fatigue and Noise Reduction

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Solution Overview

Problem

Conventional suspension bushings with non-orthogonal fixing and support axes suffer from conical stresses, leading to rapid deterioration and reduced fatigue life due to asymmetrical loading, and contribute to noise issues in vehicles.

Innovation Solution

A suspension design featuring a bushing with an inclined fixing axis, where the axis of the fixing element is inclined relative to the support axis, reducing conical stresses and allowing uniform loading, thereby extending the bushing's fatigue life and improving acoustic comfort.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a conventional bushing with non-orthogonal fixing and support axes is used, then the suspension can be installed in available space, but the bushing suffers from conical stresses and asymmetrical loading causing rapid deterioration

Engineering Contradiction:
Improveinstallation flexibilityVSAvoidbushing fatigue life
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The bushing is designed with an asymmetric geometry where the fixing axis is inclined relative to the support axis. This intentional asymmetry allows the bushing to accommodate non-orthogonal mounting conditions while distributing stresses uniformly across the rubber material, eliminating the conical stress concentration that would otherwise occur with symmetric bushings installed at non-perpendicular angles.

Inventive Principle:
Principle #4Asymmetry

2Reliability

If a ball joint is used to connect the shock absorber and suspension arm, then acceptable fatigue life is guaranteed, but acoustic comfort deteriorates due to unwanted noise

Engineering Contradiction:
Improvejoint fatigue lifeVSAvoidacoustic comfort
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention replaces the mechanical ball joint system with a bushing-based connection system. The bushing uses friction-based rubber-metal contact instead of spherical surface contact, eliminating the metallic knocking and clicking noises characteristic of ball joints while maintaining adequate fatigue life through proper stress distribution in the rubber material.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Volume of moving object

If the fixing element axis and support element axis are not perpendicular, then space constraints at the wheel well are satisfied, but the bushing is subjected to asymmetrical stress causing rapid deterioration

Engineering Contradiction:
Improvewheel well space utilizationVSAvoidbushing stress resistance
Core Design Contradiction:
Volume of moving objectVSStrength

Solution Approach 1:

The bushing is designed with specific geometric parameters including an inclined fixing axis at a predetermined angle relative to the support axis. This parameter change allows the bushing to accommodate the non-perpendicular mounting conditions required by wheel well space constraints while the asymmetric geometry ensures uniform stress distribution, preventing the rapid deterioration that would occur with conventional symmetric bushings.

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

The inclined axis design reduces fatigue loads and stress on the bushing, extends its lifespan, enhances acoustic comfort by minimizing noise, and allows for more flexible suspension design and easier implementation in existing systems.

Implementation Method 1

The bushing is made of a viscoelastic material which, as known to those skilled in the art, is capable of reducing fatigue loads

Methodology Applied
Scientific EffectHysteresis: Hysteresis

Implementation Method 2

The bushing is made of a viscoelastic material which, as known to those skilled in the art, is capable of reducing fatigue loads and, as will be explained below, of ensuring uniform loading conditions

Methodology Applied
Scientific EffectViscoelasticity: Viscoelasticity

Data Source

PatentEP4230446A1Suspension with bushing having inclined fixing axis and relative road vehicle
Publication Date: 2023.08.23 FERRARI SPA

AI summary

Suspension (3) for a road vehicle (1) comprising: a swinging arm (7); a shock absorber (10) connected by means of a joint (13) to the swinging arm (7); wherein the joint (13) comprises a central support element (14) and a bifurcated element (15) joined together by a fixing element (16); the joint (13) comprises at least one bushing (20) supported by the support element; the bushing (20) comprising at least a first ring-shaped portion (21) provided with a passing through hole (22) which, in use, is crossed by the fixing element (16); the first ring-shaped portion (21) having an outer surface (23) which develops around a first axis (A1) of symmetry and an inner surface (24) which develops around a second axis (A2) of symmetry different from the first axis (A1) of symmetry.