Coupling Rod with 45-Degree Transverse Struts for Buckling Stability

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Solution Overview

Problem

Coupling rods for articulated chassis connections face a challenge in achieving maximum buckling and tensile stability while minimizing space and mass, particularly in cramped wheel suspension areas, where existing designs struggle to balance stability and weight requirements.

Innovation Solution

The coupling rod features transverse struts angled at 45°±10° with a central wall connecting outer struts, forming trapezoidal pockets for increased rigidity, and incorporates a ball joint mount with a dome-shaped section and double-walled support structure, optimized for injection molding to enhance strength and flow behavior.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the coupling rod is designed with a strut structure to provide buckling and tensile stability, then the stability requirement is met, but the mass increases

Engineering Contradiction:
Improvebuckling and tensile stabilityVSAvoidmass of coupling rod
Core Design Contradiction:
Stability of the object's compositionVSWeight of moving object

Solution Approach 1:

The coupling rod is segmented into multiple functional components: outer struts, inner struts, transverse struts, and a central wall, each performing specific structural functions. This segmentation allows optimization of each component's contribution to stability while minimizing unnecessary material usage, resolving the contradiction between stability and mass.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention transitions from a two-dimensional cross-sectional profile to a three-dimensional strut structure with transverse struts at 45° angles and a central wall. This dimensional enhancement provides superior buckling and tensile stability without proportionally increasing mass, as the 3D geometry efficiently distributes structural loads.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Stability of the object's composition

If the coupling rod is designed with increased strut wall thickness to improve stability, then buckling and tensile stability increase, but the mass increases

Engineering Contradiction:
Improvebuckling and tensile stabilityVSAvoidmass of coupling rod
Core Design Contradiction:
Stability of the object's compositionVSWeight of moving object

Solution Approach 1:

Different wall thicknesses are applied to different components: the outer struts have a first wall thickness, the inner struts have a second wall thickness, and the central wall has a third wall thickness. This local differentiation allows each component to have the minimum necessary thickness for its specific structural role, optimizing the stability-mass balance.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The coupling rod is produced as an injection-molded plastic part, utilizing composite material properties to achieve high strength-to-weight ratio. The plastic material allows for complex geometries with optimized wall thickness distributions that would be difficult to achieve with traditional materials, providing stability without excessive mass.

Inventive Principle:
Principle #40Composite materials

3Stability of the object's composition

If the coupling rod uses a complex strut structure to maximize stability in cramped space, then stability improves, but the manufacturing complexity increases

Engineering Contradiction:
Improvebuckling and tensile stabilityVSAvoidstructural complexity
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

Multiple structural functions are merged into a single injection-molded component. The outer struts, inner struts, transverse struts, and central wall are all integrated into one monolithic coupling rod structure, eliminating the need for separate parts and complex assembly processes despite the geometric complexity.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The invention replaces traditional mechanical joining methods (welding, bolting, or snap-fitting multiple separate struts) with a single injection molding process. This substitution of manufacturing methodology simplifies production despite the complex geometry, as the mold directly forms the intricate strut structure in one operation.

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

4Ease of manufacture

If the coupling rod uses triangular pockets in injection molding, then material flow is improved, but the cores wear out prematurely or break off

Engineering Contradiction:
Improveplastic flow during injection moldingVSAvoiddurability of injection molding cores
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The invention uses trapezoidal pockets instead of symmetric triangular pockets. The asymmetric trapezoidal geometry with angled sides provides adequate material flow paths while creating larger, more robust core structures in the injection mold that resist wear and breakage under high temperature and pressure conditions.

Inventive Principle:
Principle #4Asymmetry

Data Source

PatentEP3934923B1Coupling rod
Publication Date: 2023.03.15 ZF FRIEDRICHSHAFEN AG
  • EP3934923B1 patent drawingFigure 1a~1b(A-A)
  • EP3934923B1 patent drawingFigure 1b(B-B)~2

AI summary

The present invention relates to a coupling rod for articulated connection of suspension parts, the coupling rod having two joint sockets which are interconnected along a longitudinal axis by a strut structure, wherein the strut structure comprises two outer struts which are aligned in parallel and are interconnected by a plurality of transverse struts. In order to produce a coupling rod which provides a maximum amount of stability against buckling and traction with the smallest possible amount of required installation space, according to the invention, the transverse struts are at an angle of 45° ± 10° with respect to the longitudinal axis and a central wall is provided which is aligned at a right angle to the outer struts and interconnects the outer struts.