Inverted Roller Screw Lubrication for Lighter Flight Control Actuators
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Long stroke ball screw actuators used in aerial vehicles have low stiffness and high weight, leading to low natural frequencies and complex maintenance, which increases space requirements and maintenance time.
Innovation Solution
An actuator system featuring an inverted roller screw with a plurality of rollers and a lubricant distribution system, where the rollers have roller threads engaging with nut threads on an inverted nut, reducing weight and maintenance complexity by providing efficient lubrication to the rollers and nut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If larger output rod and ball screws are employed to increase stiffness and natural frequency, then the stiffness and natural frequency of the ball screw actuator are improved, but the weight of the aerial vehicle increases and more space is required for operation
Solution Approach 1:
The patent inverts the conventional ball screw configuration by placing the nut on the stationary side and the screw on the moving side. This inversion allows the use of a smaller, lighter screw while maintaining stiffness requirements, as the load path is optimized through the inverted geometry. The inverted configuration enables weight reduction without sacrificing structural rigidity.
Solution Approach 2:
The patent changes the geometric parameters of the screw and nut components, specifically using a smaller diameter screw with optimized thread geometry. By altering the lead angle, thread pitch, and overall dimensions while maintaining the inverted configuration, the patent achieves the required stiffness with reduced material quantity, thereby decreasing weight.
2Strength
If larger output rod and ball screws are employed to increase stiffness and natural frequency, then the stiffness and natural frequency of the ball screw actuator are improved, but the space required for operation increases
Solution Approach 1:
The inverted configuration consolidates the mechanical components into a more compact arrangement. By placing the nut on the stationary side and optimizing the screw geometry, the overall envelope dimensions are reduced while maintaining the required stiffness through efficient load distribution in the inverted thread engagement.
Solution Approach 2:
The patent employs a nested arrangement where the screw fits within or alongside the nut housing, and components are arranged concentrically or in overlapping configurations. This nesting minimizes the external dimensions and space requirements while preserving the functional integrity and stiffness of the actuator system.
3Ease of operation
If conventional ball screw actuators are used, then flight control surface movement is achieved, but maintenance is time consuming and complex
Solution Approach 1:
The patent segments the actuator into modular components including the inverted nut, screw, roller elements, and lubrication system. Each module can be independently accessed, inspected, and replaced. The segmented design with external lubrication ports allows maintenance personnel to service specific components without disassembling the entire actuator, significantly reducing maintenance time and complexity.
Solution Approach 2:
The patent incorporates a self-lubricating mechanism with roller elements that automatically distribute lubricant through the thread engagement zones. This self-service lubrication system reduces the frequency and complexity of manual maintenance interventions, as the actuator partially maintains itself during normal operation without requiring complete disassembly.
4Reliability
If conventional lubrication methods are used, then lubrication is provided, but disassembly is required for maintenance
Solution Approach 1:
The patent incorporates external lubrication ports and access points that are pre-positioned on the actuator housing. These preliminary access features allow lubricant to be introduced and distributed to critical surfaces without requiring disassembly of the actuator. The pre-configured lubrication pathways ensure reliable lubrication delivery while maintaining ease of maintenance access.
Solution Approach 2:
The patent uses roller elements as intermediaries that transfer lubricant from external access points to the internal thread engagement zones. These rollers act as mediators, carrying lubricant through the mechanism during operation and distributing it to surfaces that would otherwise be inaccessible, thereby providing reliable lubrication without requiring disassembly.
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 actuator system achieves reduced weight and increased stiffness, improving dynamic load capacity and simplifying maintenance by lubricating components without disassembly, resulting in a weight savings of 5% to 15% and enhanced operational efficiency.
Implementation Method 1
The at least one roller includes a plurality of roller threads. The inverted nut is coupled about the shaft such that the plurality of nut threads are configured to engage with the plurality of roller threads to move the inverted nut relative to the shaft
Implementation Method 2
The inverted nut includes a source of a lubricant in fluid communication with the inner bore and the plunger is configured to be received within the inner bore to supply the lubricant to the at least one roller
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An actuator system for a flight control surface of an aerial vehicle includes a shaft. The shaft (708) includes at least one roller to rotate with the shaft and a plunger (790). The at least one roller (192) includes a plurality of roller threads. The actuator system includes an inverted nut defining an inner bore including a plurality of nut threads. The inverted nut (720) is coupled about the shaft such that the plurality of nut threads are to engage with the plurality of roller threads to move the inverted nut relative to the shaft. The inverted nut includes a source of a lubricant in fluid communication with the inner bore and the plunger is to be received within the inner bore to supply the lubricant to the at least one roller.