Light Metal Sliding Screw Actuator with DLC Coating
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Solution Overview
Problem
Electric actuators using ball screw shafts have large nut sizes and generate significant operation noises, while those using sliding screw shafts suffer from abrasion issues, and both face challenges in reducing weight and size, especially in noise-sensitive applications like hospitals.
Innovation Solution
The electric actuator employs a sliding screw shaft made of light metal or alloy with a diamond-like carbon film applied to the threaded parts of both the screw shaft and nut, particularly within the range from the starting end to the third thread, to reduce abrasion and noise, and incorporates a clearance space for lubricant storage to enhance durability and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ball screw shaft is used, then abrasion resistance is improved, but the nut size becomes large and operation noises increase
Solution Approach 1:
The patent replaces the ball screw shaft mechanism with a sliding screw shaft mechanism, substituting the rolling contact system with a sliding contact system. This eliminates the steel ball circulation that generates noise while maintaining acceptable abrasion resistance through the DLC coating and lubrication system.
Solution Approach 2:
The patent introduces a diamond-like carbon (DLC) film as an intermediary layer on the sliding screw shaft and nut contact surfaces. This DLC coating acts as a mediator that reduces friction and abrasion between the sliding surfaces, compensating for the inherent disadvantages of sliding contact compared to rolling contact.
2Object-generated harmful factors
If a sliding screw shaft is used, then nut size and operation noises are reduced, but abrasion occurs easily
Solution Approach 1:
The patent applies a diamond-like carbon (DLC) film coating to the sliding screw shaft and nut contact surfaces, transforming the surface properties to provide low friction and high wear resistance. This allows the sliding mechanism to achieve abrasion resistance comparable to ball screw systems while maintaining the noise and size advantages.
Solution Approach 2:
The patent uses composite material structure by combining the base metal material of the sliding screw shaft with a diamond-like carbon coating layer. This composite structure provides both the mechanical strength of the metal substrate and the low friction, high wear resistance properties of the DLC coating.
3Weight of moving object
If light metal such as aluminum is used for the sliding screw shaft and nut, then weight and size are reduced, but abrasion occurs more easily
Solution Approach 1:
The patent creates a composite material system by applying a diamond-like carbon coating to the light metal (aluminum) sliding screw shaft and nut. This composite structure combines the low weight and good corrosion resistance of aluminum with the high wear resistance and low friction properties of the DLC coating, achieving both weight reduction and improved abrasion resistance.
Solution Approach 2:
The patent changes the surface parameters of the light metal components by applying a DLC coating, which fundamentally alters the surface friction and wear characteristics. This allows the base material to remain lightweight aluminum while the surface properties become comparable to hardened steel through the coating layer.
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 configuration improves abrasion resistance and durability, reduces the size and weight of the actuator, and significantly decreases operational noise, allowing for increased maximum working load without motor size increase, while maintaining efficient screw performance.
Implementation Method 1
A diamond-like carbon film is formed on at least one of a region of a threaded part of the nut, which is located within a range from a starting end of the threaded part of the nut in an axial direction thereof to at least a third thread of the threaded part of the nut, and a threaded part of the sliding screw shaft
Implementation Method 2
incorporates a clearance space for lubricant storage to enhance durability and noise reduction
Data Source
AI summary
An electric actuator such that a nut threadedly engaged with a sliding screw shaft is displaced along an axial direction under the operation of a motor, the sliding screw shaft being made of a light metal or light metal alloy. A diamond-like carbon film is formed on at least either a portion of screw threads of the nut that is located at least within three threads from a starting end in the axial direction, or screw threads of the sliding screw shaft.