Planetary Roller Screw Actuation for Precise Linear-Rotary Output
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Solution Overview
Problem
Current planetary roller screw mechanisms face limitations in achieving high precision linear displacement at low speeds under heavy loads and high linear displacement speeds at low loads, while also being costly and bulky, and they do not allow for a compact output movement combining both linear translation and rotation effectively.
Innovation Solution
The proposed actuating mechanism incorporates a roller screw mechanism with a screw and nut having identical helix angles, along with an annular guide for roller retention, coupled to both a main and secondary rotational drive, allowing for optimized linear displacement precision and speed, and enabling a compact, cost-effective output movement that combines linear and rotational displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a planetary roller screw mechanism is used to achieve high precision linear displacement at low speeds under heavy loads, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces a variable pitch threading configuration where the pitch of the screw threading varies along the axial direction. This allows the mechanism to dynamically adapt its characteristics: smaller pitch sections provide high precision for low-speed heavy-load operations, while larger pitch sections enable high-speed low-load movements. This dynamic variation resolves the contradiction by allowing the same mechanism to optimize for different operating conditions without increasing overall complexity
Solution Approach 2:
The patent changes the geometric parameter of the screw threading (pitch) along its length. By having different pitch values in different axial sections, the mechanism can achieve both high precision (small pitch) and high speed (large pitch) capabilities. This parameter variation allows the system to overcome the limitation of fixed-pitch mechanisms that must compromise between precision and speed
2Productivity
If a planetary roller screw mechanism is designed for high linear displacement speed at low loads, then productivity is improved, but manufacturing precision deteriorates
Solution Approach 1:
The variable pitch configuration allows the mechanism to switch between operational modes: sections with larger pitch enable high-speed movement for productivity, while sections with smaller pitch provide precision when needed. This dynamic adaptability resolves the contradiction between speed and precision by allowing the system to optimize for the current operational requirement
3Adaptability or versatility
If two separate screw mechanisms are used to achieve combined linear translation and rotation output movement, then adaptability is improved, but device complexity and volume increase
Solution Approach 1:
The patent merges the functions of linear motion and rotation into a single planetary roller screw mechanism. The planetary configuration inherently provides both axial (linear) and rotational degrees of freedom, eliminating the need for two separate mechanisms. This consolidation achieves the same versatility while significantly reducing the overall volume and complexity of the system
Solution Approach 2:
The planetary roller screw mechanism is designed to provide multiple output movements (linear translation and rotation) from a single mechanism. This multi-functionality allows the system to replace what would traditionally require two separate mechanisms, thereby reducing volume while maintaining adaptability for different motion requirements
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 solution achieves high precision and speed in linear and rotational displacement by controlling the combined rotational speeds of the drives, allowing for modulated linear displacement speeds and reducing actuation time, while maintaining a compact and cost-effective design.
Implementation Method 1
roller screw mechanism that makes it possible to transform a rotational movement into a linear translational movement and vice versa
Implementation Method 2
A roller screw mechanism has the principal advantage of having higher permissible load capacities, relative to a ball screw mechanism
Implementation Method 3
when the screw rotates relative to the nut, the rollers rotate in place while rotating around the screw
Implementation Method 4
The rollers are guided in rotation parallel to the axis of the screw by teeth that are attached to the nut and engage with teeth furnished on the rollers
Implementation Method 5
an annular guide for circumferential and axial retention of the rollers
Implementation Method 6
The helix angles of the threadings of the rollers, screw, and nut are selected such that, when the screw rotates relative to the nut, the rollers will rotate in place around the screw and move axially in the nut
Data Source
AI summary
An actuating mechanism has a main rotational drive and a roller screw mechanism coupled to the main rotational drive. The roller screw mechanism has a screw, a nut, and a plurality of rollers. One of the screw and the nut is coupled to the main rotational drive, while the other is movable relative to the rollers both translationally and rotationally. The roller screw mechanism also has an annular guide for circumferential and axial retention of the rollers. The annular guide contains a cylindrical sleeve that extends axially outward from one of the annular heels beyond the nut. The screw extends into a bore of the sleeve, and the sleeve is coupled to a secondary rotational drive.