Steering Rack Coupling Assembly for Precise Dual-Pinion Mesh

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Solution Overview

Problem

Existing vehicle steering systems face challenges in maintaining a tight angular relationship between rack teeth of two-piece rack assemblies, which is difficult to establish and maintain during manufacturing and assembly, particularly in dual pinion electric power steering (DPEPS) and rack assist electric power steering (REPS) systems, where weld integrity and joint reliability are concerns.

Innovation Solution

A multi-piece steering system rack assembly with separate components that utilize a coupling assembly featuring radial protrusions and biasing members to securely join and allow independent rotation of the rack components, ensuring optimal gear mesh and durability, while allowing for different materials and diameters, and facilitating cost-effective mass production.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If friction welding is used to join two rack halves, then a continuous rack structure is obtained, but weld integrity concerns arise

Engineering Contradiction:

Improverack structure continuityVSAvoidweld integrity

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The rack is divided into two separate rack halves that are not welded together. Instead, each rack half operates independently with its own pinion gear, eliminating the welded joint and its associated integrity concerns while maintaining the functional continuity of the steering system through the dual pinion configuration.

Inventive Principle:

Principle #1Segmentation

2Reliability

If threaded connections are used to join rack sections, then joint integrity concerns are reduced, but angular relationship precision between rack teeth deteriorates

Engineering Contradiction:

Improvejoint integrityVSAvoidangular relationship between rack teeth

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The rack is segmented into two independent halves that each engage with their own pinion gear. This segmentation eliminates the need for precise angular alignment between rack teeth from different sections, as each rack half-pinion pair operates independently with its own meshing relationship, thereby maintaining manufacturing precision while ensuring joint integrity through separate connections.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The coupling assembly acts as an intermediary device that connects the two rack halves. It provides a precise mounting interface that maintains the correct angular relationship between each rack half and its corresponding pinion gear, eliminating the need for direct precision alignment between the two rack halves themselves.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If a tight angular relationship is maintained between rack teeth, then gear mesh quality improves, but manufacturing and assembly difficulty increases

Engineering Contradiction:

Improvegear mesh qualityVSAvoidmanufacturing and assembly process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The steering system is segmented into two independent rack-half-and-pinion assemblies. Each assembly can be manufactured and pre-assembled separately with precise gear mesh, then combined through the coupling assembly. This segmentation allows quality control to be applied to each smaller unit independently, improving overall gear mesh quality while simplifying the manufacturing and assembly process.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each rack half and its corresponding pinion gear can be pre-assembled and pre-adjusted to achieve optimal gear mesh quality before final assembly. This preliminary action ensures that the critical angular relationship is established under controlled conditions, reducing the complexity of the final assembly process while maintaining high gear mesh quality.

Inventive Principle:

Principle #10Preliminary action

4Ease of manufacture

If a single rack component is used, then manufacturing simplicity is maintained, but adaptability to different materials and diameters is reduced

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidmaterial and diameter variation

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The rack is segmented into two separate halves that can be manufactured from different materials and with different diameters as needed. Each rack half can be optimized for specific requirements (e.g., different tooth profiles, materials, or strength requirements) while maintaining relatively simple manufacturing processes for each individual half, thereby achieving both manufacturing simplicity and adaptability.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS11400973B2Coupling for multi-piece steering system rack

Publication Date: 2022.08.02 STEERING SOLUTIONS IP HOLDING CORP

AI summary

A rack assembly for a vehicle steering system includes a first rack component extending longitudinally from a first outer end to a first inner end, the first rack component having a first shoulder extending radially outwardly from a neck region to a head region. The rack assembly also includes a second rack component extending longitudinally from a second outer end to a second inner end, the second rack component having a second shoulder extending radially outwardly from a neck region to a head region. The rack assembly further includes a coupling assembly having an inner surface defining a hollow region that the head region of the first rack component and the head region of the second rack component are each disposed within, the inner surface having a first radial protrusion in abutment with the first shoulder and a second radial protrusion in abutment with the second shoulder.