Ball Screw Fitting Shaft Crimp Structure for Axial Retention
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Solution Overview
Problem
The fitting shaft portion of a ball screw device is prone to coming out in the axial direction due to moments acting perpendicular to the center axis, which can cause misalignment and failure.
Innovation Solution
A ball screw device with a fitting shaft portion featuring an inner-diameter engaging portion with external teeth and an outer-diameter engaging portion with internal teeth, where the fitting member is fixed to prevent relative rotation, and a crimped portion is formed at the end of the shaft to enhance axial stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a crimped portion is formed at the tip-end of the fitting shaft portion, then axial retention is improved, but the fitting shaft portion may still come out when a moment acts perpendicular to the center axis
Solution Approach 1:
The fitting shaft portion is divided into multiple functional segments: a crimped portion at the tip-end for axial retention, and multiple engagement portions with teeth along the shaft for resisting moments and preventing misalignment. This segmentation allows each segment to address specific stability requirements independently.
Solution Approach 2:
The solution transitions from a single-dimensional axial retention approach (crimped portion) to a multi-dimensional stabilization system by adding circumferential teeth that engage with the fitting member, providing resistance in both axial and radial directions simultaneously.
2Ease of manufacture
If the fitting shaft portion is designed with simple crimping, then manufacturing is easier, but the structure cannot prevent axial displacement under perpendicular moments
Solution Approach 1:
The crimped portion is formed in advance during manufacturing to provide preliminary axial retention. Additionally, engagement portions with teeth are pre-formed along the shaft to prepare for resisting moments before assembly, ensuring both ease of manufacture and high reliability.
Solution Approach 2:
The fitting shaft design incorporates multiple geometric parameters including tooth pitch, tooth depth, crimped portion diameter, and engagement length, which can be optimized to balance manufacturing complexity with anti-displacement reliability for different application requirements.
Data Source
AI summary
A fitting shaft portion has an inner-diameter side engaging portion on an outer peripheral surface with external teeth arranged in a circumferential direction; a fitting member has an outer-diameter side engaging portion on an inner peripheral surface with internal teeth arranged in the circumferential direction and engaging with the inner-diameter side engaging portion; an engaging portion between the inner-diameter side engaging portion and the outer-diameter side engaging portion includes a portion having interference in the radial direction in a portion in the axial direction; and the fitting shaft portion has a crimped portion at an end portion on one side in the axial direction that engages in the axial direction with the fitting member.