Ballscrew Lubrication via Annular Bath
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Solution Overview
Problem
Existing ballscrew actuators face challenges in ensuring effective lubrication of all contact surfaces, particularly in the return tracks, which can lead to increased frictional losses and reduced efficiency, especially in applications like aircraft and aircraft engines.
Innovation Solution
A re-circulating ballscrew assembly with a return track that extends through an annular lubricant bath, featuring grooves on the annular sleeve and ballnut body, and pressure-balancing ports to maintain lubricant distribution and prevent pressure gradients, ensuring continuous lubrication and reduced friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional lubrication methods are used in ballscrew actuators, then the structure remains simple, but effective lubrication of all contact surfaces cannot be ensured
Solution Approach 1:
An annular lubricant bath is introduced as an intermediary medium between the ballscrew components and the return track. The lubricant bath fills the annular cavity and provides continuous lubrication to the balls as they pass through the return track, ensuring effective lubrication of all contact surfaces without requiring complex lubrication delivery mechanisms
Solution Approach 2:
The patent employs a fluid-based lubrication system where an annular lubricant bath (hydraulic principle) is used to provide continuous lubrication. The lubricant circulates through the annular cavity and contacts the balls in the return track, using fluid dynamics to ensure consistent lubrication coverage without mechanical lubrication components
2Reliability
If the return track is positioned radially outward of the ballnut, then lubrication access is improved, but pressure gradients and uneven lubricant distribution occur
Solution Approach 1:
The annular cavity is specifically designed with a geometry that ensures uniform lubricant distribution. The cavity is positioned and dimensioned to create equal flow paths and pressure distribution across the lubricant bath, ensuring that all balls receive consistent lubrication regardless of their position in the return track
Solution Approach 2:
The annular cavity geometry is designed to create equipotential conditions for the lubricant pressure. By positioning the cavity radially outward from the ballnut and configuring its cross-sectional area appropriately, the system ensures uniform pressure distribution across the lubricant bath, eliminating pressure gradients that would cause uneven lubrication
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 effective lubrication to all contact surfaces within the ballscrew assembly, reducing frictional losses and enhancing the efficiency and reliability of the actuator, particularly in high-demand applications such as aircraft and aircraft engines.
Implementation Method 1
The annular cavity may be at least partially filled with an oil or grease lubricant to form the annular lubricant bath
Implementation Method 2
The plurality of ports may be arranged such that the inner openings are radially outward of the helical ridge, and wherein the outer openings are distributed uniformly around an circumference of the ballnut body
Data Source
AI summary
A re-circulating ballscrew assembly comprises a plurality of balls. A ballnut has a ballnut body with a radially inner surface and a helical ballnut groove formed on the radially inner surface. A ballscrew is disposed within the ballnut, the ballscrew comprising a radially outer surface and a ballscrew groove formed on the outer surface, the ballscrew groove cooperating with the ballnut groove to define a helical raceway for the plurality of balls, the helical raceway having a start point and an end point. The ballscrew assembly comprises a return track for the plurality of balls, the return track disposed radially outward of the radially inner surface of the ballnut and connecting the start point and the end point of the helical raceway. The return track extends at least in part through an annular lubricant bath.