Synchronous Belt Planetary Gearbox for Low-Cost Robot Joints

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Solution Overview

Problem

Conventional planetary gearboxes, particularly cycloidal type, are costly and difficult to manufacture due to complex metal components and high contact stress, and require high-strength, wear-resistant materials, which limits their use in lightweight and cost-effective applications such as robots.

Innovation Solution

The use of a synchronous belt as a coupling member in the planetary gearbox reduces manufacturing and assembly costs and complexity by eliminating the need for complex tooth shapes and pins, allowing for easier replacement and integration with non-metallic materials, thereby enhancing the gearbox's lightweight and cost-effective design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If conventional cycloidal speed reducers are used, then high transmission ratios and compact design are achieved, but manufacturing cost and complexity increase due to complex cycloidal profiles and high contact stress requiring high-strength materials

Engineering Contradiction:

Improvecompact designVSAvoidmanufacturing cost

Core Design Contradiction:

Volume of moving objectVSEase of manufacture

Solution Approach 1:

The patent replaces the traditional mechanical cycloidal tooth engagement with a friction-based contact system. The cycloidal disc with simplified pins contacts the follower gear through friction, eliminating the need for complex tooth profiles and high-precision mechanical engagement. This substitution dramatically simplifies manufacturing while maintaining the compact cycloidal reduction mechanism.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of manufacture

If friction-based cycloid gearbox is used, then manufacturing cost is reduced by eliminating complex cycloidal profile, but elastic and wear-resisting materials are required for contact surfaces

Engineering Contradiction:

Improvemanufacturing costVSAvoidmaterial strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent employs composite material construction, combining a metal cycloidal disc with rubber or elastomeric material attached to its pins. This composite approach allows the metal structure to provide mechanical strength while the rubber material provides the necessary friction, wear resistance, and elastic properties for the friction-based contact mechanism.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the material parameters of the contact surfaces by using rubber or elastomeric materials with specific friction coefficients and elastic properties. This parameter change enables the friction-based transmission to function effectively while reducing the need for high-strength metal-to-metal contact.

Inventive Principle:

Principle #35Parameter changes

3Strength

If conventional planetary gearbox with metal components is used, then high strength and durability are achieved, but weight increases limiting use in lightweight applications

Engineering Contradiction:

ImprovestrengthVSAvoidweight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The patent uses composite materials combining metal structural components with rubber or polymer elements. The metal parts provide necessary strength and rigidity, while the rubber components reduce overall weight and provide friction-based contact. This composite approach enables lightweight design while maintaining sufficient strength for robotic applications.

Inventive Principle:

Principle #40Composite materials

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 synchronous belt-based design significantly reduces manufacturing and maintenance costs, simplifies assembly, and results in a more lightweight and efficient planetary gearbox suitable for use in robots, addressing the limitations of traditional cycloidal gearboxes.

Implementation Method 1

at least one of the first coupling member and the second coupling member comprises a synchronous belt

Methodology Applied

Scientific EffectMechanical transmission: Gear

Implementation Method 2

The synchronous belt is a widely used transmission with low-cost and high-strength features

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS11873891B2Planetary gearbox, assembly method thereof, associated robot joint and robot

Publication Date: 2024.01.16 ABB (SCHWEIZ) AG

AI summary

Embodiments of the present disclosure provide a planetary gearbox. The planetary gearbox includes a housing extending along a first axis; a first coupling member arranged on an inner circumference of the housing; an input component operable to rotate about the first axis; at least one intermediate component, each intermediate component comprising a second coupling member and adapted to be driven by the input component to rotate about a second axis offset from the first axis with the second coupling member engaging with the first coupling member; and an output component coupled to the at least one intermediate component and operable to rotate about the first axis with rotation of the at least one intermediate component, wherein at least one of the first coupling member and the second coupling member comprises a synchronous belt.