Internal Deflector Ball Screw Return Path for Stable Ball Circulation
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Solution Overview
Problem
Internal deflector type ball screws experience entering-exiting fluctuation due to the complex three-dimensional curve shape of the circulation path, leading to uneven ball circulation, reduced load capacity, and compromised service life, as well as complex assembly and high-speed operation challenges.
Innovation Solution
The ball screw design includes a screw shaft with a spiral groove, a nut with a matching spiral groove, and a ball return path that circulates balls in no more than one turn, with the length of the ball return path between scoop-up points set to between -0.1 to +0.3 times the diameter of the balls, minimizing entering-exiting fluctuation and improving low-speed operation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If circulation internal deflectors are provided with ball return grooves arranged in a row in the axial direction with phases substantially upward, then clogging of balls is prevented and fluctuation in operating torque is reduced, but the complex three-dimensional curve shape of the circulation path causes entering-exiting fluctuation and reduces service life
Solution Approach 1:
The invention optimizes the length parameter of the ball return path, setting it to a specific value that minimizes entering-exiting fluctuation. By carefully controlling the geometric parameter (length) of the ball return path, the invention achieves smooth ball circulation while reducing harmful fluctuations that affect service life.
2Reliability
If elastic bodies are interposed between balls to absorb fluctuation of entering and exiting, then operating torque fluctuation is reduced, but the number of balls must be reduced which lowers load capacity
Solution Approach 1:
Instead of adding elastic bodies that would reduce the number of balls, the invention changes the geometric parameter (length) of the ball return path. This parameter optimization allows full ball circulation without elastic bodies, maintaining both load capacity and torque stability.
3Ease of operation
If the ball return path length is not optimized, then entering-exiting fluctuation occurs causing uneven ball circulation, but optimizing the length reduces fluctuation and improves low-speed operation characteristics
Solution Approach 1:
The invention identifies and optimizes the critical parameter of ball return path length. By setting this parameter to a specific value, the invention simultaneously improves low-speed operation characteristics and ensures uniform ball circulation, resolving the contradiction between operational ease and reliability.
Data Source
Figure 1~2
Figure 3~4B
Figure 5A~6
AI summary
A ball screw is equipped with: a threaded shaft (10) on the outer circumference surface of which a helical first thread groove (11) is formed; a nut (20) arranged around the threaded shaft (10) and on the inner circumferential surface of which a helical second thread groove (21) is formed; multiple balls (30) accommodated within a rolling path (23) formed by the opposing thread grooves (11, 21); and a ball return passage (42) for circulating the multiple balls (30) through a rolling path (23) that coils around one time or less. The length (L) of the ball return passage (42) between pickup points (43a, 43b) for the balls (30) picked up from the first thread groove (11) in the threaded shaft (10) is set to a value between -0.1 to + 0.3 times the diameter of the balls (30), with respect to the integer value of the number of balls filling the interval between the pickup points (43a, 43b).