Segmented Screw Shaft Rolling for Accurate Male Threads
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Solution Overview
Problem
The existing rolling processing methods for forming male threaded portions on screw shafts often result in shape accuracy issues, such as tooth profile errors, screw pitch errors, and the formation of radial burrs and bulges, due to excessive elongation or twisting, which can lead to reduced operational performance of feed screw mechanisms in devices like electric steering wheel position adjusting devices.
Innovation Solution
A screw shaft design incorporating a large-diameter shaft portion with a male threaded portion along its entire axial length, accompanied by medium-diameter and small-diameter shaft portions strategically arranged to manage rolling traces and chamfered portions, ensuring precise formation of the male threaded portion through controlled rolling processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rolling processing is performed using conventional methods, then the male threaded portion can be formed efficiently, but shape accuracy deteriorates due to excessive elongation or twisting causing tooth profile errors, screw pitch errors, and radial burrs
Solution Approach 1:
The screw shaft is divided into multiple shaft portions (first shaft portion with larger outer diameter, second shaft portion with smaller outer diameter) along the axial direction. This segmentation allows different regions to serve different functions: the first shaft portion forms the male threaded portion with high shape accuracy, while the second shaft portion acts as a buffer zone that prevents excessive elongation and twisting during rolling processing, thereby eliminating radial burrs and maintaining manufacturing precision without sacrificing productivity
Solution Approach 2:
Different shaft portions are given different local qualities through varying outer diameters. The first shaft portion has a larger outer diameter optimized for forming the male threaded portion with precise tooth profile and screw pitch, while the second shaft portion has a smaller outer diameter that provides resistance against excessive deformation during rolling. This local differentiation enables the rolling process to maintain high manufacturing precision while continuing to operate efficiently
2Manufacturing precision
If the outer diameter of the shaft portion is reduced to prevent elongation, then shape accuracy improves, but the operational performance and operating stroke of the feed screw mechanism deteriorate
Solution Approach 1:
The screw shaft is segmented into a first shaft portion with larger outer diameter that forms the male threaded portion and a second shaft portion with smaller outer diameter. The first shaft portion maintains sufficient outer diameter to ensure adequate operating stroke and engagement length for the feed screw mechanism, while the second shaft portion with reduced diameter specifically prevents excessive elongation and twisting during rolling processing, thus achieving both high shape accuracy and maintained operational performance
Solution Approach 2:
Different local qualities are assigned to different shaft portions: the first shaft portion has larger outer diameter optimized for operational performance and engagement, while the second shaft portion has smaller outer diameter optimized for preventing deformation during rolling. This local differentiation allows the critical threaded portion to maintain both manufacturing precision and operational functionality
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 design significantly enhances the shape accuracy of the male threaded portion, preventing radial burrs and bulges, and maintains the operational performance of feed screw mechanisms by ensuring precise engagement with female threaded portions, thereby extending the operating stroke of the mechanism.
Implementation Method 1
plastically deforming an outer peripheral surface of the workpiece using these rolling dies
Data Source
AI summary
Provided is a screw shaft in which shape accuracy of a male threaded portion is sufficiently secured. A screw shaft includes a large-diameter shaft portion, medium-diameter shaft portions and small-diameter shaft portions. The large-diameter shaft portion has a male threaded portion along its entire axial length on its outer peripheral surface. The medium-diameter shaft portions are arranged axially adjacent to the large-diameter shaft portion and have an outer diameter smaller than an outer diameter of the large-diameter shaft portion. The small-diameter shaft portions are axially arranged adjacent to the medium-diameter shaft portions on sides opposite to the large-diameter shaft portion, have an outer diameter smaller than the outer diameter of each of the medium-diameter shaft portions, and do not have rolling traces having a helical shape on their outer peripheral surfaces.