Ball Screw Turning Unit With Simplified Ball Circulation Path
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Solution Overview
Problem
Existing turning units with increased reduction ratios face challenges in maintaining a lightweight driven pulley design due to increased outer diameter requirements, leading to weight gain and complex circulation member shapes.
Innovation Solution
A turning unit design featuring a ball screw mechanism with a simplified circulation path configuration using through holes and passages in the ball screw nut, combined with a thin portion on the driven pulley to maintain radial clearance and a pressing lid to prevent component displacement, which reduces the weight and complexity of the driven pulley.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the outer diameter of the driven pulley is increased to increase the reduction ratio, then the reduction ratio is improved, but the weight of the driven pulley is increased
Solution Approach 1:
The driven pulley is divided into a hub portion and a rim portion that are integrated together. The rim portion has a reduced cross-sectional area compared to the hub portion, creating a lightweight structure. This segmentation allows the pulley to achieve a larger outer diameter for higher reduction ratio while minimizing weight increase through the optimized rim design.
2Reliability
If the circulation path is configured by a passage formed inside the circulation member, then the circulation function is achieved, but the shape of the circulation member becomes complicated
Solution Approach 1:
The circulation member integrates multiple functions into a single component: it includes a pressing portion that presses the circulation ball against the ball screw nut, a guiding portion that guides the circulation ball, and a through-hole that serves as part of the circulation path. This merging of functions simplifies the overall structure compared to having separate components for each function.
Solution Approach 2:
The circulation path is configured to extend in the axial direction of the ball screw mechanism rather than being contained within a single radial plane. The through-hole passes through the circulation member axially, and the circulation ball moves through this path in three dimensions, simplifying the member's shape while maintaining effective circulation.
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 configuration effectively suppresses weight increases in the driven pulley while maintaining smooth rotation and reducing the number of parts, thereby enhancing the overall efficiency and reliability of the turning unit.
Implementation Method 1
a belt mechanism having a driving pulley coupled to a motor, a driven pulley disposed on an outer periphery of the turning shaft so that the driven pulley is rotatable, and a belt that is wound around between the driving pulley and the driven pulley
Implementation Method 2
a ball screw mechanism that has a ball screw nut coupled to the driven pulley so that the ball screw nut is integrally rotatable, and a plurality of balls disposed in a ball raceway that has a helical shape and that is provided such that a screw groove provided on an outer periphery of the turning shaft face a screw groove provided on an inner periphery of the ball screw nut
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A ball screw nut (71) has a pair of through holes (101, 102) and a first passage (103) that allows the through holes (101, 102) to communicate with each other and that opens radially outward. In each of the through holes (101, 102), a ball screw mechanism (33) has a circulation member (105) having a second passage (104) in which a ball (72) can move between a ball raceway (R1) and the first passage (103). The ball screw mechanism (33) has a circulation path (R2) for communicating the two connection points (P1, P2) set on the ball raceway (R1) by the first passage (103) and each of the second passages (104). A driven pulley (63) has a thin portion (68) that defines a radial clearance between an inner periphery of the driven pulley (63) and an outer periphery of the ball screw nut (71). The ball screw mechanism (33) has a pressing lid that presses down each of the circulation members (105) from the outer periphery of the ball screw nut (71) and that covers the first passage (103).