Ball Screw Circulation Path Layout to Avoid Load Path Interference
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Solution Overview
Problem
Conventional ball screw devices face interference issues in automotive applications due to the circulation path design, which affects their ability to achieve a small size, high thrust generation, and large load capacity with a small drive torque.
Innovation Solution
The ball screw device features a circulation path with a return path, scooping paths, and connecting paths, where the scooping paths have an arc-shaped center line curving outward in the radial direction, and the connecting paths have a straight and arc-shaped center line, ensuring the radius of curvature and length configurations prevent interference with the load path, allowing for efficient ball circulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the circulation path is designed with conventional routes (return path, scooping paths, connecting paths), then the ball screw device can circulate balls, but the circulation path interferes with the load path in automotive applications
Solution Approach 1:
The circulation path is designed to extend in the axial direction rather than only radially, utilizing the third dimension to route balls from the end point to the start point of the load path without interfering with the radial load transmission path. The return path includes an axial extension portion that projects in the axial direction, allowing balls to be returned along the axial dimension while keeping the radial load path clear.
Solution Approach 2:
The circulation path is divided into distinct segments: a return path portion for returning balls axially, and a radial extension portion for radial ball movement. This segmentation allows each portion to be optimized independently - the return path handles axial ball transport while the radial extension handles radial positioning, preventing interference with the load path.
2Power
If the ball screw device is designed for small size with high thrust generation, then it can achieve large load capacity with small drive torque, but the circulation path design becomes more complex and prone to interference
Solution Approach 1:
The circulation path is designed to serve multiple functions: it returns balls from the end point to the start point of the load path, maintains proper ball circulation flow, and simultaneously avoids interfering with the load path. The axial extension portion of the return path serves both as a ball return通道 and as a space-efficient routing solution that prevents interference with radial load transmission.
Solution Approach 2:
By utilizing the axial direction for ball return rather than confining circulation to the radial plane, the design achieves compact sizing while maintaining clear separation between the circulation path and load path. This dimensional approach allows high thrust generation with compact dimensions without circulation path interference.
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 design provides a suitable circulation path route for automotive applications, preventing interference and ensuring efficient operation by aligning tangent lines and maintaining sufficient installation heights to avoid load path interference, thus enhancing the device's performance and load capacity.
Implementation Method 1
a ball screw device rolls and moves balls between a screw shaft and a nut
Implementation Method 2
a screw shaft having a spiral shaft-side ball screw groove on the outer-circumferential surface, a nut having a spiral nut-side ball screw groove on the inner-circumferential surface
Implementation Method 3
a circulation component which returns the balls from the end point to the start point of the load path. The circulation component has a circulation path (no-load ball rolling path) which connects the start point and the end point of the load path inside
Data Source
AI summary
In the ball screw device, the circulation path that returns balls from the end point to the start point of the load path includes a return path, scooping paths, and connecting paths. The scooping path has an arc-shaped center line that is curved outward in the radial direction as going toward the reference imaginary flat plane including the center axis of the screw shaft and the center line of the return path in the circumferential direction. The connecting path is arranged on the reference imaginary flat plane and includes a straight path having a linear center line extending in a direction orthogonal to the center axis of the screw shaft. When the radius of curvature of the center line of the scooping path is R1, the scooping angle is θ, and the entire length of the straight path is S, R1 cos(90°−θ)+S is made larger than the diameter of the balls.