Rack Shaft Axial Length Reduction via Merged Padding
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Solution Overview
Problem
Conventional rack shafts have limitations in reducing axial length due to the formation of ineffective rack teeth and padding portions, which affect the accuracy and meshing capability of rack teeth, leading to increased size and material costs.
Innovation Solution
A rack shaft design incorporating an effective rack tooth row formed by plastic deformation, an ineffective rack tooth, and a padding portion that extends from the non-rack tooth portion to cover the ineffective rack tooth, allowing for reduced axial length and improved accuracy by utilizing the excess material escape region and enhancing the strength of the effective rack tooth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional rack shaft design with ineffective rack teeth and padding portions is used, then the accuracy and meshing capability of rack teeth are maintained, but the axial length of the rack shaft increases
Solution Approach 1:
The patent merges the padding portion with the ineffective rack tooth structure, making them an integrated component rather than separate elements. The padding portion is formed as part of the ineffective rack tooth during the same plastic working process, eliminating the need for additional space and reducing the overall axial length while maintaining both the accuracy of effective rack teeth and the functionality of the padding portion
Solution Approach 2:
The ineffective rack tooth structure serves multiple functions simultaneously: it acts as a sacrificed tooth to prevent underfill in effective rack teeth, provides a padding portion to improve punch release from the die, and maintains structural integrity. This multi-functionality eliminates the need for separate dedicated padding portions, thereby reducing axial length
2Manufacturing precision
If the rack tooth formation portion is designed to prevent underfill in effective rack teeth, then manufacturing precision is improved, but the device complexity increases due to additional ineffective rack teeth and padding portions
Solution Approach 1:
The padding portion and ineffective rack tooth are merged into a single integrated structure formed during the same plastic working process. This integration reduces the number of separate components and simplifies the overall structure while maintaining the dual functionality of preventing underfill and improving punch release
Solution Approach 2:
The ineffective rack tooth structure automatically serves as its own padding portion, eliminating the need for separate dedicated padding structures. The design uses the ineffective rack tooth's own geometry to provide the necessary padding function, thereby reducing structural 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
The design reduces the axial length of the rack shaft by incorporating an ineffective rack tooth covered by the padding portion, ensuring accurate formation of the effective rack tooth row and enhancing the strength of the rack shaft, thus enabling a more compact and efficient steering system.
Implementation Method 1
an effective rack tooth row formed by plastic deformation of a shaft member and having a plurality of rack teeth that mesh with a pinion
Data Source
AI summary
A rack shaft of the present invention includes: an effective rack tooth row formed by plastic deformation of a shaft member and having a plurality of rack teeth that mesh with a pinion; a ball screw portion having no rack tooth; an ineffective rack tooth that is formed between the effective rack tooth row and the ball screw portion and that does not mesh with the pinion; and a padding portion that extends from an end of the ball screw portion toward the ineffective rack tooth and that covers at least a part of the ineffective rack tooth.