Hollow Rack Bar Friction Welding Phase Alignment

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Solution Overview

Problem

The existing methods for fabricating rack bars for electric power steering devices, such as solid, hollow, and frictionally joined types, face challenges including increased weight, potential phase misalignment of toothed parts during machining, and precision issues due to rotational direction deviations, which are not suitable for precise positioning in electric power steering applications.

Innovation Solution

A method involving the precise positioning of two toothed parts on hollow rack bars using a joint member for friction pressure welding, ensuring high precision in phase difference alignment, which includes supporting the rack bars on shafts, aligning the joint member with their axial centerlines, and performing friction pressure welding to secure the joint member between them.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a solid rack bar is used with toothed parts on both axial sides, then the structural strength is improved, but the weight increases and machining operations such as gun drilling cannot be performed

Engineering Contradiction:

Improvestructural strengthVSAvoidrack bar weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The rack bar is divided into a hollow structure with internal cavity, segmenting the solid material into outer shell and inner space, reducing weight while maintaining structural integrity through the hollow configuration

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The hollow interior of the rack bar creates negative weight effect by removing material, counterbalancing the weight of the toothed parts and joint member, achieving overall weight reduction while preserving structural strength

Inventive Principle:

Principle #8Anti-weight (Counterweight)

2Weight of moving object

If flat-crushing machining is used to form toothed parts on hollow rack bar, then the rack bar weight is reduced, but the rotational phases of toothed parts become dislocated during post tooth-formation and annealing processes

Engineering Contradiction:

Improverack bar weightVSAvoidrotational phase precision

Core Design Contradiction:

Weight of moving objectVSManufacturing precision

Solution Approach 1:

The rotational phase positioning is performed in advance during the friction pressure welding process before tooth-formation operations, establishing precise rotational relationships that are maintained through subsequent annealing and tooth-cutting processes

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The joint member integrates multiple functions: structural connection between rack bars, rotational phase positioning reference, and alignment fixture, combining positioning and joining operations into a single integrated component

Inventive Principle:

Principle #5Merging (Combining)

3Ease of manufacture

If frictional press joining is used to join solid or hollow materials with toothed parts, then the rack bar can be assembled, but two-way taking or drilling is required due to positioning in rotational direction and precision degrades

Engineering Contradiction:

Improveassembly capabilityVSAvoidposition precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The joint member acts as an intermediary component between the two rack bars, providing a standardized interface that simplifies assembly while maintaining precision through its integrated positioning features and friction pressure welding mechanism

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The traditional mechanical positioning and drilling system is replaced with friction pressure welding, which achieves both positioning and joining in a single operation, eliminating the need for separate two-way taking or drilling operations

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 method allows for precise positioning of toothed parts at a specified phase difference, enhancing precision and reducing weight by up to 50% compared to solid shafts, while maintaining high precision in coaxiality and straightness, making it suitable for electric power steering devices.

Implementation Method 1

rotating the joint member about the axial center lines of the first and second rack bars relative to the first and second rack bars; and simultaneously bringing an end of the first rack bar and an end of the second rack bar into friction pressure welding with the joint member

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS10612642B2Method for manufacturing rack and hollow rack bar

Publication Date: 2020.04.07 NETUREN CO LTD

AI summary

A method of fabricating a rack, the method includes: supporting a first rack bar having a first toothed part on a shaft of the first rack bar; supporting a second rack bar having a second toothed part on a shaft of the second rack bar such that an axial center line of the second rack bar coincides with an axial center line of the first rack bar; supporting a joint member between the first and second rack bars such that an axial center line of the joint member coincides with the axial center lines of the first and second rack bars; rotating the joint member about the axial center lines of the first and second rack bars relative to the first and second rack bars; and bringing an end of the first rack bar and an end of the second rack bar into friction pressure welding with the joint member.