Planetary Gear Pin Flexure for Backlash-Free Robot Gearing

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Solution Overview

Problem

Precision robotics require gearings with minimal or no play between tooth flanks to prevent inaccuracies, torque peaks, and noise, which existing planetary gearings fail to achieve effectively.

Innovation Solution

A planetary gearing design with elastically deformable planet pins and recesses on the carrier, biased in specific circumferential directions to ensure consistent meshing engagement between the sun gear, ring gear, and planetary gears, reducing or eliminating backlash.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional planetary gearing is used with rigid planet pins, then the structure is simple and manufacturing is easy, but play between tooth flanks occurs causing inaccuracies and torque peaks

Engineering Contradiction:

Improvemeshing precisionVSAvoidgearing structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The planet pins are designed with elastic deformability, changing the mechanical parameter from rigid to flexible. This allows the pins to deform elastically under load, maintaining consistent meshing engagement between gears and eliminating play between tooth flanks, thereby improving manufacturing precision without excessive complexity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The gearing system transitions from a static rigid structure to a dynamic flexible structure. The planet pins can dynamically adjust their position through elastic deformation to compensate for manufacturing tolerances and maintain optimal meshing conditions, resolving the contradiction between precision and simplicity

Inventive Principle:

Principle #15Dynamics

2Reliability

If planet pins are made elastically deformable to reduce play, then meshing precision improves, but the manufacturing complexity increases

Engineering Contradiction:

Improvemeshing engagement consistencyVSAvoidplanet pin fabrication

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The planet pins are designed as flexible elastic elements that can deform within their elastic limit. This flexibility allows them to adapt to variations in gear positioning and maintain reliable meshing engagement, improving reliability while using a relatively simple elastic component design

Inventive Principle:

Principle #30Flexible shells and thin films

3Manufacturing precision

If the planet carrier is biased in circumferential directions, then backlash is reduced, but the device complexity increases due to additional biasing mechanisms

Engineering Contradiction:

Improvebacklash controlVSAvoidcarrier structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The planet carrier is biased in circumferential directions opposite to each other, creating counteracting forces that pre-load the planetary gears. This counter-biasing approach eliminates backlash by ensuring continuous contact between gear tooth flanks, improving manufacturing precision while using a relatively simple symmetric carrier design

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The biasing forces are applied asymmetrically in different circumferential directions to compensate for the inherent play in the gear meshing. By applying bias in specific directions, the design addresses the asymmetric nature of gear contact and eliminates backlash effectively

Inventive Principle:

Principle #4Asymmetry

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 design effectively reduces or prevents backlash, ensuring precise movement and reducing torque peaks and noise, by ensuring consistent meshing engagement between gears regardless of rotation direction.

Implementation Method 1

The first planet pin of the first planetary gear is at least partially elastically deformable in the second circumferential direction and/or the second planet pin of the second planetary gear is at least partially elastically deformable in the first circumferential direction

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS11298817B2Planetary gearing for a robot gearing arrangement

Publication Date: 2022.04.12 SCHAEFFLER TECHNOLOGIES AG & CO KG

AI summary

A planetary gearing for a robot gearing arrangement includes a sun gear, a ring gear, and a planet carrier with at least three planetary gears rotatably mounted thereon. The planetary gears are arranged on planet pins arranged perpendicular to the planet carrier and are in meshing engagement with the sun gear and the ring gear. At least one first planetary gear is biased in a first circumferential direction and/or at least one second planetary gear is biased in a second circumferential direction. A first planet pin of the first planetary gear is at least partially elastically deformable in the second circumferential direction and/or the second planet pin of the second planetary gear is at least partially elastically deformable in the first circumferential direction.