Ball Nut End-Stop Notch Layout for Reliable Axial Positioning
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Solution Overview
Problem
Existing ball nut drive assemblies lack a cost-effective and reliable spring end-stop interface, relying on return springs and end-stop components that are not always efficient in maintaining the axial position of the ball screw assembly.
Innovation Solution
A ball screw assembly with a nut featuring an outer raceway, inner raceway, and a ball-spring assembly supported by reset springs, where an end-stop component with greater stiffness is positioned within notches on the nut, providing a reliable and cost-effective interface by engaging with the spindle and notches to maintain axial position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If return springs are used to bias balls back to original position, then the ball nut drive can operate without a ball return assembly, but the axial positioning reliability and stiffness are insufficient
Solution Approach 1:
The ball nut is segmented into multiple notches (first notch and second notch) that are circumferentially offset from each other. Each notch receives an end-stop component, creating distributed positioning points around the nut circumference. This segmentation provides redundant axial positioning capability, ensuring reliable operation even if one notch-end-stop interface experiences wear or misalignment.
Solution Approach 2:
The end-stop components are positioned at specific locations within the notches, creating localized high-stiffness regions. The notches themselves are strategically positioned circumferentially offset to provide localized support zones. This local quality enhancement at critical positions (where end-stops contact the nut) provides superior axial positioning stiffness exactly where needed, rather than uniformly throughout the structure.
2Device complexity
If a single end-stop component is used, then the structure is simple, but the axial positioning reliability is insufficient
Solution Approach 1:
The single end-stop component is segmented into multiple identical components (first end-stop component and second end-stop component), each positioned in separate notches. This segmentation provides redundant axial positioning capability, ensuring reliable operation even if one notch-end-stop interface experiences wear or misalignment.
Solution Approach 2:
The notches are positioned circumferentially offset from each other, creating an asymmetric distribution of end-stop components around the nut. This asymmetric arrangement ensures that the end-stop components engage at different angular positions, providing more uniform radial support and improving overall axial positioning stability compared to symmetric placement.
3Ease of manufacture
If notches are formed by cold-forming process, then manufacturing cost is reduced, but the precision of notch geometry may be affected
Solution Approach 1:
The cold-forming process changes the physical state and properties of the notches during formation, creating a plastic deformation that locks the notch geometry into the nut structure. This parameter change (from elastic to plastic state) allows the notches to be formed with adequate precision for functional operation while using a cost-effective manufacturing process, balancing manufacturing ease with sufficient geometric precision.
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
The solution provides a reliable and cost-effective spring end-stop interface that effectively biases the ball-spring assembly, ensuring precise axial positioning and efficient operation of the ball screw assembly by utilizing a stiffer end-stop component and notches formed by a cold-forming process.
Implementation Method 1
A ball-spring assembly includes a plurality of balls supported between the outer raceway and the inner raceway, and at least one reset spring engaged against at least one ball of the plurality of balls
Implementation Method 2
at least one reset spring engaged against at least one ball of the plurality of balls
Implementation Method 3
At least one end-stop component is engaged against a terminal end of the ball-spring assembly and positioned within the at least one notch. A radially inner side of the at least one end-stop component abuts the spindle
Implementation Method 4
The notch can be formed by a cold-forming process
Data Source
AI summary
A ball screw assembly is disclosed herein. The assembly includes a nut having an outer raceway, and at least one notch. A spindle extends inside of the nut, and the spindle defines an inner raceway. A ball-spring assembly includes a plurality of balls supported between the outer raceway and the inner raceway, and at least one reset spring engaged against at least one ball of the plurality of balls. At least one end-stop component is engaged against a terminal end of the ball-spring assembly and positioned within the at least one notch. A radially inner side of the at least one end-stop component abuts the spindle. A method of forming the nut for a ball screw assembly is also disclosed herein.