Push Rod Polygonal Guide Finishing for Low-Friction Torque Support

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Solution Overview

Problem

Existing motor vehicle steering systems face challenges in stabilizing torque support for push rods over their service life while minimizing friction, as conventional solutions are expensive and inefficient.

Innovation Solution

The method involves producing a push rod with a spindle section and a guide section featuring a polygonal profile, where the final shape of the polygonal profile is achieved through burnishing, reducing friction and ensuring stability by creating a work-hardened surface with low surface roughness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If roller-guided torque supports are used, then torque support stability is improved, but manufacturing cost increases significantly

Engineering Contradiction:
Improvetorque support stabilityVSAvoidmanufacturing cost
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces expensive roller-guided torque supports with a cost-effective sliding guide made of polygonal-profiled push rod sections. The sliding guide uses simple sliding contact instead of complex roller mechanisms, significantly reducing manufacturing costs while maintaining adequate torque support functionality throughout the service life

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes the mechanical roller guidance system with a simplified sliding guidance mechanism. By using a polygonal profile on the push rod that slides within a corresponding guide, the complex roller-based torque support is replaced with a simpler sliding contact system that achieves the same functional goal at lower cost

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

2Ease of manufacture

If sliding guide is used instead of roller guide, then manufacturing cost is reduced, but friction increases

Engineering Contradiction:
Improvemanufacturing costVSAvoidfriction losses
Core Design Contradiction:
Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent changes the surface parameters of the sliding guide by applying specific surface treatments (such as coating or heat treatment) to reduce the coefficient of friction. By modifying surface properties like roughness and material composition, the sliding guide achieves low friction characteristics comparable to roller guidance while maintaining the cost advantages of sliding contact

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent introduces an intermediary layer or coating on the sliding surfaces of the polygonal profile. This intermediate layer (such as a lubricating coating or low-friction material layer) mediates the contact between sliding surfaces, reducing direct metal-to-metal friction and energy losses while allowing the simple sliding guide structure to function efficiently

Inventive Principle:
Principle #24Intermediary (Mediator)

3Loss of energy

If smooth rolling is used to produce final polygonal profile, then surface roughness is reduced and friction is minimized, but manufacturing complexity increases

Engineering Contradiction:
Improvefriction lossesVSAvoidmanufacturing process complexity
Core Design Contradiction:
Loss of energyVSDevice complexity

Solution Approach 1:

The patent applies smooth rolling as a final finishing operation after the polygonal profile has been established by less complex forming processes. By performing the smooth rolling operation last, the process achieves low surface roughness and minimal friction without requiring complex equipment for the entire manufacturing sequence, as the bulk shaping is completed by simpler methods first

Inventive Principle:
Principle #10Preliminary action

4Measurement precision

If minimal twist angles are maintained, then steering precision is improved, but torque support requirements increase

Engineering Contradiction:
Improvesteering precisionVSAvoidtorque support requirement
Core Design Contradiction:
Measurement precisionVSForce

Solution Approach 1:

The patent employs composite construction or material combinations in the push rod and guide sections to achieve high structural stiffness and strength. By using materials or structures that combine different properties (such as high-strength alloys, composite materials, or optimized cross-sections), the system can resist torque-induced twisting with minimal angular deviation while distributing the torque support requirements across the composite structure

Inventive Principle:
Principle #40Composite materials

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 approach allows for minimal rotation angles and reduced friction losses, enhancing the durability and stability of the torque support, thereby improving the steering system's performance.

Implementation Method 1

a cold-worked surface can be produced on the guide section by smooth rolling, resulting in a high durability of the push rod

Methodology Applied
Scientific EffectCold working: Cold-forming

Implementation Method 2

creating a work-hardened surface with low surface roughness

Methodology Applied
Scientific EffectWork hardening: Shock Hardening

Implementation Method 3

The push rod (10) is smoothed in the region of this preform by rolling to obtain the final shape of the polygonal profile (12a)

Methodology Applied
Scientific EffectAbrasion: Abrasion

Data Source

PatentEP4306263A1Method for producing a push rod for a motor vehicle steering system
Publication Date: 2024.01.17 VOLKSWAGEN AG
  • EP4306263A1 patent drawingFigure 1
  • EP4306263A1 patent drawingFigure 2~3
  • EP4306263A1 patent drawingFigure 2

AI summary

In a method for manufacturing a push rod (10) for a motor vehicle steering system (1), wherein the push rod (10) has at least one spindle section (11) with a threaded spindle (11a) and a guide section (12) with a polygonal profile (12a) for sliding guidance and anti-rotation on a stationary guide device of the motor vehicle steering system (1), it is provided that the final shape of the polygonal profile (12a) is produced on the guide section (12) by smooth rolling.