Electric Linear Actuator Helical Roller Design
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Solution Overview
Problem
Existing electric linear motion actuators require additional speed reduction mechanisms to achieve sufficient power, increasing complexity and size, and feature numerous thrust bearings that raise costs and torque loss due to uneven contact radii between planetary rollers and components.
Innovation Solution
An electric linear motion actuator design with a central shaft and outer ring member, where the central shaft has annular ribs engaging with annular grooves on planetary rollers, and the outer ring member has a helical rib engaging with helical grooves, eliminating the need for thrust bearings and ensuring equal contact radii to prevent slippage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a speed reduction mechanism such as a planetary gear mechanism is mounted to increase power to a sufficient level, then the power output is improved, but the complexity and size of the electric linear motion actuator increase
Solution Approach 1:
The patent merges the motion conversion function and power amplification function into a single integrated mechanism. The planetary rollers simultaneously convert rotary motion to linear motion and amplify power through their dual engagement with the rotary shaft and outer ring member, eliminating the need for a separate speed reduction mechanism while achieving sufficient power output
2Reliability
If thrust bearings are mounted between planetary rollers and carrier member, and between support member and shaft support member to support axial loads, then the reliability is improved, but the cost increases
Solution Approach 1:
The patent extracts and eliminates the thrust bearings from the system by redesigning the load support mechanism. The axial loads are supported directly through the engagement between the planetary rollers and the outer ring member via helical grooves and helical rib, removing the need for separate thrust bearing components and reducing manufacturing cost
3Reliability
If the rigidities of the carrier member, support member and shaft support member are increased by increasing their sizes to prevent uneven loads from being applied to thrust bearings, then the reliability is improved, but the size of the entire electric linear motion actuator increases
Solution Approach 1:
By removing the thrust bearings entirely, the patent eliminates the need to increase the sizes of carrier member, support member and shaft support member for rigidity purposes. The load distribution is improved through the helical groove engagement geometry, allowing compact component design while maintaining reliability
4Productivity
If planetary rollers are brought into contact with rotary shaft and outer ring member at different contact radii to enable motion conversion, then the motion conversion function is achieved, but slippage occurs at contact portions increasing torque loss
Solution Approach 1:
The patent changes the geometric parameters of the engagement surfaces by introducing helical grooves on planetary rollers and a helical rib on the outer ring member. This helical geometry ensures that the contact radius remains constant during engagement, preventing slippage and reducing torque loss while maintaining effective motion conversion
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 the number of thrust bearings, lowers costs and size, and minimizes torque loss by supporting axial loads at specific contact points, enhancing the actuator's efficiency and reliability.
Implementation Method 1
the planetary rollers revolve around the rotary shaft while rotating about their respective axes due to frictional contact between the planetary rollers and the rotary shaft
Data Source
AI summary
An electric linear motion actuator includes an outer ring member provided around a central shaft, and planetary rollers disposed between the central shaft and the outer ring member. One of the central shaft and the outer ring member serves as an input member which is rotatable and immovable in the axial direction and rotated by an electric motor, while the other serves as an output member which is rotationally stationary and movable in the axial direction. The input member has a peripheral surface formed with a plurality of annular ribs which are equal in pitch. Each planetary roller has a radially outer surface formed with annular grooves which are equal in pitch to the annular ribs and in which the annular ribs are engaged. The output member has a peripheral surface formed with a helical rib which is equal in pitch to the annular grooves of the planetary rollers.