Injected Carrier Ring Worm Gear for Steering Connection Rigidity

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Solution Overview

Problem

Existing worm gear designs for motor vehicle steering systems face challenges in achieving an optimal connection between the carrier ring and the ring gear, leading to restricted design freedom and increased production costs due to radial elevation arrangements that create unfavorable flow conditions and inhomogeneous plastic structures during injection molding.

Innovation Solution

A worm gear design featuring a ring gear with radial teeth and reinforcing ribs, where injection holes between the longitudinal axis and reinforcing ribs allow for the injection of plastic to form a carrier ring that connects the hub and ring gear in a form-fitting manner, using a one-component plastic part and injection molding process to ensure economic production and even plastic distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If radial elevation arrangements are used for the carrier ring connection, then the connection between carrier ring and ring gear is improved, but the plastic flow conditions during injection molding deteriorate and inhomogeneous plastic structure is created

Engineering Contradiction:
Improveconnection strengthVSAvoidplastic structure homogeneity
Core Design Contradiction:
StrengthVSManufacturing precision

Solution Approach 1:

The injection molding process is segmented into multiple injection holes distributed around the ring gear, allowing plastic to flow from multiple directions simultaneously. This segmentation of the injection process enables the carrier ring to be formed without radial elevations, achieving both strong connection and homogeneous plastic structure.

Inventive Principle:
Principle #1Segmentation

2Strength

If radial clearance is increased to achieve optimal connection between carrier ring and gear ring, then connection quality is improved, but design freedom is restricted and manufacturing effort increases

Engineering Contradiction:
Improveconnection qualityVSAvoiddesign freedom
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The hub and ring gear are merged into a single integrated component through injection molding, eliminating the need for separate carrier ring and gear ring assemblies. This merging achieves optimal connection through material interlocking via injection holes while simplifying the overall design and reducing manufacturing complexity.

Inventive Principle:
Principle #5Merging (Combining)

3Adaptability or versatility

If multiple components are used for hub and gear ring assembly, then design flexibility is improved, but manufacturing complexity and production costs increase

Engineering Contradiction:
Improvedesign flexibilityVSAvoidproduction complexity
Core Design Contradiction:
Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The hub and ring gear are combined into a single injection-molded component with integrated teeth and connection features. This merging maintains design flexibility through the modular tooth design while dramatically simplifying manufacturing by eliminating separate assembly steps and reducing production costs.

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 solution enables a robust, economically produced worm gear with a high level of rigidity and optimal connection between the carrier ring and ring gear, reducing production costs and design constraints while ensuring even plastic distribution and material fit.

Implementation Method 1

the support body is a support ring injected between the toothed ring and the hub by means of an injection molding process

Methodology Applied
Scientific EffectInjection molding:

Data Source

PatentEP3728899B1Worm gear for a worm gear mechanism of a vehicle steering system with a carrier ring injected between a hub and a toothed wheel
Publication Date: 2022.02.02 THYSSENKRUPP PRESTA AG
  • EP3728899B1 patent drawingFigure 1~3
  • EP3728899B1 patent drawingFigure 4~6
  • EP3728899B1 patent drawingFigure 7~8

AI summary

The invention relates to a worm gear (12) for a worm gear mechanism (11) of a vehicle steering system with a hub (15), a carrier body (16) and a toothed wheel (17), wherein the toothed wheel (17) has a plurality of teeth (171) which project radially outwards from a central circumferential annular web (172), and wherein the carrier body (16) is a carrier ring injected between the toothed wheel (17) and the hub (15) by means of an injection moulding process, the carrier ring interlockingly connecting the hub (15) and the toothed wheel (17).