Internal-Circulation Ball Screw Reducing Thread Crest Impact
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Solution Overview
Problem
Existing internal-circulation-type ball screws face challenges with durability and cyclical stability due to the impact of balls on thin thread crests and the complexity of interrupted-thread designs, which complicates processing and reduces reliability.
Innovation Solution
The design incorporates a nut with an internal-thread groove, a screw shaft with an external-thread groove and receiving recesses, and returning members with redirecting channels, forming a closed path for ball circulation that eliminates the need for interrupted-thread designs, minimizing the nut's outer diameter and preventing ball impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a circulation groove is used that strides across a single pitch, then the structure is simple, but the thread crest becomes thin and balls impact and get damaged
Solution Approach 1:
The circulation path is divided into multiple segments: a first circulation groove in the first pitch, a second circulation groove in the second pitch, and a connection groove linking them. This segmentation allows each groove to be properly formed without compromising thread crest thickness, while maintaining reliable ball circulation paths.
2Ease of operation
If an interrupted-thread design is used, then ball circulation can be achieved, but processing becomes difficult and cyclical stability deteriorates
Solution Approach 1:
The connection groove acts as an intermediary element that links the first and second circulation grooves. It provides a smooth transition path for balls between pitches, eliminating the need for interrupted-thread designs while maintaining ease of ball circulation and improving manufacturability.
3Length of moving object
If the lead is low and close to the ball's diameter, then compact design is achieved, but the thread crest becomes thin and ball impact damage occurs
Solution Approach 1:
The circulation path is extended into the axial dimension by utilizing multiple pitches (first pitch and second pitch) with separate circulation grooves. This allows the circulation function to be distributed across different axial positions, preventing local thinning of the thread crest while maintaining compact lead dimensions.
Data Source
AI summary
An internal-circulation-type ball screw includes a nut, a screw shaft, and two returning members. The nut has an internal-thread groove. The screw shaft passes through the nut and has an external-thread groove. The internally and external-thread grooves are aligned to form a helix channel. The screw shaft has a returning channel and two opposite receiving recesses. Each of the receiving recesses is radially communicated between the external-thread groove and the returning channel. The returning members are received in the receiving recesses of the screw shaft and each have a redirecting channel. The redirecting channel is connected between the helix channel and the returning channel, so that balls are allowed to circulate along the helix channel, the redirecting channel and the returning channel. Thereby, the internal-circulation-type ball screw provides good durability, reliability and smoothness in use.