Steering Rack Dummy Tooth Layout for Longer Forging Punch Life
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Solution Overview
Problem
The existing manufacturing methods for steering racks, particularly those using cold forging, face challenges in maintaining the longevity of the tooth-forming punch due to unbalanced moments and stress concentration, leading to potential fractures and reduced tool lifetime.
Innovation Solution
Incorporating dummy teeth with specific inclined angles and tooth heights adjacent to the rack teeth, which do not mesh with the pinion, to balance the moments applied to the tooth-forming punch, thereby reducing stress concentration and extending the punch's lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cold forging is used to form rack teeth, then manufacturing cost is reduced and processing time is shortened, but stress concentration occurs in the tooth-forming punch leading to reduced tool lifetime
Solution Approach 1:
The patent applies preliminary anti-action by designing dummy teeth with specific inclined angles that counterbalance the harmful moments acting on the tooth-forming punch during cold forging. The dummy teeth create opposing forces that prevent stress concentration at the punch roots, thereby extending tool lifetime while maintaining the efficiency benefits of cold forging
2Reliability
If dummy teeth are added to balance moments, then tool lifetime is extended, but device complexity increases
Solution Approach 1:
The patent applies local quality by adding dummy teeth only at specific locations where stress concentration occurs, rather than modifying the entire rack structure. The dummy teeth have specific inclined angles (different from rack teeth) tailored to the local stress conditions, providing targeted stress balancing while minimizing overall 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 balanced moments and reduced stress concentration significantly extend the lifetime of the tooth-forming punch, preventing fractures and improving the manufacturing process efficiency.
Implementation Method 1
forming a plurality of rack teeth on a radial one side surface of a part of a rod part, which is extending in an axial direction and is made of a metal material, in an axial direction by pressing a tooth-forming punch having rack tooth processing concave and convex having a rack shape toward the radial one side surface and plastically deforming the radial one side surface
Data Source
AI summary
A steering rack (11a) meshes with a pinion rotatably driven by the input shaft (6) of a steering gear (5) constituting an automotive steering device. The steering rack (11a) is provided with a an axially extending rod part (15) of round cross section, and a plurality of rack teeth (16) formed on a radial one side surface of an axial portion of the rod part (15), the rack teeth (16) meshing with the pinion. At least one dummy tooth (42) is formed in portions that are axial parts of the rod part (15) and are adjacent to both axial sides of the plurality of rack teeth (16). The dummy tooth (42) has a tooth height less than the rack teeth (16) and does not mesh with the pinion.