Roller Screw Mechanism Gear Teeth Profile for Wear Reduction
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Solution Overview
Problem
Current roller screw mechanisms experience premature wear of synchronizing gear teeth due to high contact pressure and require large clearance for milling, limiting loading capacity and rigidity, especially with involute gear teeth profiles.
Innovation Solution
The design features rollers with outer gear teeth having planar faces and a connecting radius, outside diameter less than the thread root, and convex synchronizing gear teeth profiles, allowing for reduced wear and increased thread length without axial clearance, enabling higher loading capacity and rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If involute gear teeth profile is used for rollers, then the gear teeth can be conventionally produced by milling, but large axial clearance is required which limits the length of outer thread and reduces loading capacity and rigidity
Solution Approach 1:
The patent changes the gear teeth profile from involute to a new profile with planar faces and convex synchronizing gear teeth, which eliminates the need for large axial clearance during milling while maintaining manufacturability. This parameter change in the gear geometry allows the milling cutter to operate without requiring excessive clearance, thereby enabling longer outer thread length on the rollers and improving loading capacity and rigidity.
2Ease of manufacture
If thread-cutting tool cuts outer gear teeth at each end of the roller, then the outer thread can be formed, but threads are present on the gear teeth causing high contact pressure and premature wear on synchronizing gear teeth
Solution Approach 1:
The patent applies local quality by creating a distinct zone separation: the gear teeth are given planar faces that are free of thread cuts, while the outer thread is formed in the cylindrical portion of the roller. This local differentiation ensures that the gear engagement surfaces do not have threaded features, eliminating the high contact pressure and premature wear on synchronizing gear teeth while still allowing outer thread formation through controlled material removal.
3Ease of manufacture
If large axial clearance is provided for milling cutter, then gear teeth can be milled, but the length of outer thread is limited which reduces loading capacity
Solution Approach 1:
By changing the gear teeth profile to have planar faces with convex synchronizing gear teeth instead of involute profile, the patent eliminates the requirement for large axial clearance during milling. This allows the milling cutter to operate with minimal clearance, thereby maximizing the available length for the outer thread on the roller, which directly increases loading capacity.
Data Source
AI summary
A roller screw mechanism comprises a screw having an outer thread and a nut disposed around and coaxially with the screw. The nut comprises an inner thread. A plurality of rollers are disposed radially between the screw and the nut; each roller being provided with an outer thread engaged with the outer and inner threads of the screw and of the nut and with two outer gear teeth. The mechanism also comprises two synchronizing gear teeth that are each engaged with one of the gear teeth of the rollers. An outside diameter of each gear teeth of each roller is less than a diameter of a root of the thread of the roller. Each tooth of the gear teeth of the rollers comprises planar faces that engage with the synchronizing gear teeth.