Ball Screw Raceway Offset for Smooth Ball Recirculation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ball chipping occurs due to contact between balls and sharp edges at the mouths of the recirculation channel in existing ball screw mechanisms, significantly reducing their service life.
Innovation Solution
A ball screw mechanism component with a helical raceway featuring axial offsets at recirculation sections to reduce forces on balls and create clearance, allowing smooth recirculation without contact with channel edges, using offsets that vary progressively and are aligned with the reference axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If recirculators are arranged at the mouths of the recirculation channel to guide ball movement, then ball guidance is improved, but ball chipping occurs due to contact with sharp edges at the mouths
Solution Approach 1:
The patent applies preliminary action by creating axial offsets at the recirculation sections before the balls reach the recirculation channel mouths. The first flank is turned axially towards the middle section at the first recirculation section and away from the middle section at the second recirculation section, which reduces the forces on the balls before they enter the recirculation channel, preventing contact with the sharp edges and eliminating the need for recirculators
Solution Approach 2:
The patent changes the geometric parameters of the helical raceway by introducing axial offsets D11 and D21 at the recirculation sections. These offsets modify the position of the first flank relative to the imaginary theoretical flank, creating clearance that allows balls to recirculate without contacting the sharp edges at the channel mouths, thereby preventing ball chipping while maintaining smooth ball guidance
2Reliability
If axial offsets are introduced at recirculation sections to create clearance, then ball chipping is prevented, but manufacturing complexity increases
Solution Approach 1:
The patent modifies the geometric parameters of the helical raceway by introducing axial offsets D11 and D21 at the recirculation sections. These offsets are small (greater than 1 μm and less than 25 μm) and can be implemented through standard machining processes, making the manufacturing complexity acceptable while effectively preventing ball chipping
Solution Approach 2:
The axial offsets are applied locally only at the recirculation sections where the balls transition between the helical raceway and the recirculation channel, rather than throughout the entire raceway. This localized modification minimizes the impact on manufacturing complexity while effectively preventing ball chipping at the critical locations
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A ball screw mechanism (10) includes a component (14) having a helical raceway (28) with a first flank (32). The raceway (28) has a median section (36) of several successive turns forming a helix with a constant pitch equal to P, and a first recirculation section (38) at a first axial end (40) of the median section (36). A first imaginary theoretical flank (56) is defined by an imaginary geometric extension of the first flank (32) of the helical raceway (28) of the component (14), with constant pitch P, from the median section (36) beyond the first axial end (40).At the level of the first recirculation section (38), the first flank (32) of the helical raceway (28) of the component (14) is axially turned towards the median section (36), and has an axial offset D 11 with respect to the first theoretical imaginary flank (56), the first flank (32) of the helical raceway (28) of the component (14) being further from the median section (36) than the first theoretical imaginary flank (56).