Internal-Deflector Ball Screw Piece Member for High-Speed Durability
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Solution Overview
Problem
The engaging portions in ball screws are prone to breakage due to repeated impact forces, limiting the permissible rotation speed.
Innovation Solution
The design incorporates a piece type ball screw with a piece member featuring a fillet-shaped joint portion, relief portions, and protruding portions to distribute stress and enhance the strength of the engaging portions, reducing stress concentration and improving durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the piece member is used to circulate rolling elements at high speed rotation, then the ball screw can operate at higher rotation speeds, but the engaging portions are subjected to repeated impact forces that may cause breakage
Solution Approach 1:
The patent applies curvature by forming the engaging portion with a fillet shape at the joint between the piece body and engaging portion. This curved transition eliminates sharp corners that would cause stress concentration, allowing the engaging portion to withstand repeated impact forces during high-speed rotation without breaking.
Solution Approach 2:
The patent provides relief portions at specific locations where stress concentration is likely to occur, such as at the joint between the piece body and engaging portion. These relief portions locally modify the structure to reduce stress concentration, while maintaining the overall functionality of the engaging portion for circulating rolling elements.
2Strength
If the engaging portions are made stronger to withstand impact forces, then breakage is prevented, but stress concentration at the joint between piece body and engaging portion may still occur
Solution Approach 1:
The fillet shape at the joint between the piece body and engaging portion creates a smooth curved transition that distributes stress evenly, preventing stress concentration at sharp corners while maintaining the strength of the engaging portion.
Solution Approach 2:
Relief portions are strategically positioned at the joint area between the piece body and engaging portion to locally reduce stress concentration. These relief portions create a gradual transition in cross-sectional area, preventing stress buildup at the joint while preserving the overall strength of the engaging portion.
Data Source
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AI summary
A piece type ball screw includes a screw shaft with a spiral external thread groove on an outer peripheral surface, a nut which is fitted onto the screw shaft and has a spiral internal thread groove on an inner peripheral surface, a plurality of balls rotatably arranged in a track path formed between the external thread groove and the internal thread groove, and a piece member which is attached to the nut and connects the internal thread grooves to each other. The piece member includes a piece body in which a return groove connecting the internal thread grooves is formed and a pair of engaging portions which are provided on the piece body, extend in opposite directions in a circumferential direction of the nut, and engage with the internal thread groove of the nut. A joint portion between the piece body and the engaging portion has a fillet shape.