Screw Thread Grease Groove Structure for Electric Actuators
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Solution Overview
Problem
Existing electric actuators face challenges in forming helical oil grooves, circular arc-shaped grooves, and grid-shaped recessed portions on thread flanks, which are time-consuming and costly, and the single linear oil groove provides limited lubrication with potential strength issues.
Innovation Solution
The electric actuator features threads with groove portions cut from the crest to the root, arranged in a straight line or circumferentially, with taper surfaces for efficient grease distribution, and a grease holding portion with a cover member to ensure even lubrication and prevent grease scatter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex groove patterns (helical, circular arc, grid) are formed on thread flanks to improve lubrication, then lubrication effect is enhanced, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The thread structure is segmented by dividing each thread into multiple groove portions (first, second, third groove portions) at different positions (crest, middle, root). This segmentation allows grease to be distributed to different areas of the thread engagement, improving lubrication coverage without requiring complex continuous groove patterns.
Solution Approach 2:
Different groove portions are positioned at specific locations with different characteristics - first groove portions at crests for grease retention, second groove portions at middle sections for distribution, and third groove portions at roots for capillary action. This local differentiation optimizes lubrication at each critical area without requiring complex overall groove patterns.
2Ease of manufacture
If a single deep linear oil groove is formed on the feed screw to simplify processing, then manufacturing is easier, but lubrication effectiveness decreases and local strength is compromised
Solution Approach 1:
Instead of a single continuous deep groove, the lubrication system is segmented into multiple shallow groove portions distributed at different positions on each thread. This segmentation maintains structural strength while providing multiple grease distribution points for improved lubrication effectiveness.
Solution Approach 2:
The groove portions are arranged in multiple dimensions - circumferentially around the thread and axially along the thread length. This multi-dimensional arrangement ensures comprehensive grease distribution to all thread engagement areas without requiring excessive groove depth that would compromise strength.
3Reliability
If multiple groove portions are formed on each thread to improve grease distribution, then lubrication is enhanced, but processing time increases
Solution Approach 1:
The groove portions are designed to be formed during the initial thread machining process itself, rather than requiring subsequent separate operations. The groove formation is integrated into the thread cutting or rolling process, allowing preliminary creation of all groove portions in one manufacturing step.
Solution Approach 2:
The same machining tool and process that creates the thread profile also creates all the groove portions. This multi-functional approach allows a single machining operation to accomplish both thread formation and groove creation, eliminating the need for specialized separate groove machining operations.
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 reduces processing time and cost, enhances motion conversion efficiency, minimizes wear, and maintains strength by effectively lubricating the threadedly engaged portions with a sufficient grease supply, ensuring durability.
Implementation Method 1
A taper surface, which flares as becoming circumferentially farther away from the groove portion, is formed on at least a part of each of peripheral edges of the groove portion on flank sides
Implementation Method 2
A groove portion, which is cut out from the crest portion toward a root portion side, is formed on each of the threads of at least one of the first screw member or the second screw member. The threadedly engaged portion between the first screw member and the second screw member is lubricated with grease
Implementation Method 3
since the second screw member threadedly inserted through the rotating first screw member linearly moves relative to the first screw member, sliding friction occurs on a threadedly engaged portion between this second screw member and the first screw member
Data Source
AI summary
An electric actuator includes an electric motor, a nut, and a screw shaft threadedly inserted through the nut so as to be able to advance and retreat. The threads of the screw shaft include two flanks and a crest portion connecting the two flanks to each other. Grease is used as a lubricant. A groove portion, which is cut out from the crest portion toward a root portion side of the threads and holds grease, is formed on the threads of the screw shaft. Further, a tapered surface is formed at a groove portion side end of at least one of the two flanks, and the tapered surface inclines in a direction away from the groove portion and drags the grease held in the groove portion onto a threadedly engaged portion with the aid of the wedge effect. As a result, the electric actuator can promote lubrication.