Roller Screw Circulation Member Reduces Return Path Twist
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Solution Overview
Problem
Conventional roller screws face difficulties in smooth roller circulation due to excessive twisting of the unloaded return path, which increases the likelihood of roller tilting and reduces movement efficiency, especially when the number of turns of the loaded roller-rolling path is set to be larger than 2 or 3.
Innovation Solution
A roller screw design with a circulation member having an unloaded return path with a cross-sectional shape that encloses rollers and is twisted to rotate their attitudes, featuring scooping-up portions at both ends and split members along the diagonal line, allowing for a reduced number of turns in the loaded roller-rolling path, less than one turn, to minimize twisting and prevent roller tilting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of turns of the loaded roller-rolling path is increased to 2.5-3.5 turns (return pipe type) or 3.8-4.8 turns (end-cap type), then the circulation path is extended allowing complete roller return, but the twisted amount of the unloaded return path becomes excessive causing difficulty in smooth roller movement and increasing roller tilting probability
Solution Approach 1:
The patent fundamentally changes the parameter of the loaded roller-rolling path from conventional 2.5-4.8 turns to less than one turn (specifically 0.2-0.8 turns). This parameter change dramatically reduces the required twisted amount of the unloaded return path, enabling smooth roller movement while maintaining complete circulation. The circulation member is designed with a twisted amount of 10-30 degrees, which is sufficient for roller attitude adjustment without causing movement difficulty.
Solution Approach 2:
Instead of extending the loaded roller-rolling path to multiple turns as in conventional designs, the patent inverts the approach by using a very short loaded path (less than one turn) and compensating with an optimized unloaded return path. This inversion allows the circulation system to function effectively with minimal twisting, solving the contradiction between circulation completeness and movement smoothness.
2Reliability
If the number of turns of the loaded roller-rolling path is increased, then the circulation path length increases allowing full roller return, but the probability that rollers tilt becomes higher
Solution Approach 1:
The patent changes the turned parameter from multiple turns to less than one turn, which directly reduces the probability of roller tilting during circulation. The shortened path length means fewer opportunities for attitude deviation while the circulation member's controlled twisting (10-30 degrees) ensures proper roller orientation is maintained throughout the circulation process.
Data Source
AI summary
There is provided a roller screw in which a twisted amount of an unloaded return path is reduced.The roller screw has a screw shaft 1 having a spiral roller-rolling surface 1a on an outer peripheral surface thereof; a nut 2 having a spiral loaded roller-rolling surface 2a on an inner peripheral surface thereof, the spiral loaded roller-rolling surface being opposed to the roller-rolling surface 1a of the screw shaft 1; a circulation member 7 arranged in the nut 2 and formed to have an unloaded return path 8 connecting one end and the other end of the loaded roller-rolling surface 2a, whose turn number is less than one, of the nut 2; and a plurality of rollers 4 arranged in a one-turn roller circulation path composed by a loaded roller-rolling path 6 and the unloaded return path 8. The circulation member 7 guides the rollers which have moved and arrived at the one end of the loaded roller-rolling path 6 having less than one turn, to the unloaded return path 8, and then returns the rollers to the other end of the loaded roller-rolling path 6 having less than one turn. The number of turns of the loaded roller-rolling path 6 is set to be less than one turn, whereby the rollers 4 which have arrived at one end of the loaded roller-rolling path 6 can be transferred to the other end of the loaded roller-rolling path 6 without changing their attitudes.