Hollow Rack Bar Drawing With Variable Wall Thickness
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Solution Overview
Problem
Existing methods for manufacturing hollow rack bars for rack-and-pinion steering systems do not effectively reduce weight and material usage, as they lack a specific drawing process to achieve the desired thickness distribution between toothed and shaft sections.
Innovation Solution
A manufacturing method involving a mandrel press-fitted into the hollow shaft material, with a tooth die forming the rack section and a plug with varying diameters to draw the material, allowing for a 10-35% reduction in sectional area, resulting in a thinner shaft section and a thicker toothed section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a hollow shaft material with constant cross-section is used, then the manufacturing process is simple, but the weight and material usage are excessive due to uniform thickness
Solution Approach 1:
The patent applies local quality by creating a hollow shaft material with non-uniform wall thickness, where the toothed section has greater thickness than the shaft section. This is achieved through a two-stage forming process: first forming the basic hollow shaft shape, then selectively thickening the toothed section area. This resolves the contradiction by maintaining manufacturing feasibility while optimizing material distribution to reduce overall weight.
2Weight of moving object
If the shaft section is formed thinner to reduce weight, then material usage decreases, but the structural integrity may be compromised
Solution Approach 1:
The patent ensures structural integrity by concentrating material where it is most needed - the toothed section - while reducing material in the shaft section where less strength is required. The controlled thickness distribution maintains adequate structural performance in critical areas while achieving weight reduction overall.
Solution Approach 2:
The patent employs preliminary action by pre-forming the hollow shaft material with the desired non-uniform thickness profile before final tooth formation. This pre-shaping ensures that the material is optimally positioned and distributed prior to subsequent manufacturing steps, preventing structural weaknesses.
3Weight of moving object
If a drawing process is implemented to achieve variable thickness, then weight reduction is achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges the thickness variation creation and tooth formation processes into an integrated manufacturing sequence. The hollow shaft is formed with variable thickness through drawing, and the toothed section is subsequently formed in the same workpiece without requiring separate complex operations, thereby achieving weight reduction while controlling manufacturing complexity.
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 enables the production of hollow rack bars that reduce weight and material usage while maintaining structural integrity, allowing for efficient material distribution and enhanced pitch flexibility in tooth formation.
Implementation Method 1
a material of the toothed section forming region is caused to plastically flow towards the tooth die to form the rack
Implementation Method 2
a plug with varying diameters to draw the material, allowing for a 10-35% reduction in sectional area
Data Source
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AI summary
A manufacturing method for a hollow rack bar made of a hollow shaft material and including a toothed section which has a rack on an outer surface and a shaft section which is formed thinner than the toothed section, the manufacturing method includes drawing the hollow shaft material by using a die and a plug, and preforming regions of the hollow shaft material including a toothed section forming region configured to form the toothed section and a shaft section forming region configured to form the shaft section to have thicknesses according to the regions respectively, and forming the rack at the toothed section forming region of the hollow shaft material which is preformed.