Double Planet Gear Transmission Assembly Avoiding Self-Locking

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Solution Overview

Problem

Existing planetary transmissions require multiple gears or double planets for force transmission, leading to self-locking issues, especially at high transmission ratios, which limits their reversibility and stability.

Innovation Solution

A transmission assembly with a sun gear, planet carrier, and ring gear, where a single or multiple double planets with different gear teeth sets directly couple the sun gear to the planet carrier and ring gear, implementing a negative transmission to avoid self-locking and reduce component count, and utilizing preloaded double planets to maintain contact and distribute forces effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If multiple gears or double planets are used for force transmission in planetary transmission, then the transmission ratio can be increased, but self-locking occurs and reversibility is limited

Engineering Contradiction:

Improvetransmission ratioVSAvoidreversibility

Core Design Contradiction:

PowerVSAdaptability or versatility

Solution Approach 1:

The patent inverts the traditional positive transmission configuration by using a negative transmission arrangement where the double planet gear directly couples the sun gear and ring gear. This inversion changes the rotation direction relationship from identical (positive transmission) to opposite (negative transmission), eliminating the self-locking effect and enabling reversibility while maintaining high transmission ratios.

Inventive Principle:

Principle #13The other way round (Inversion)

2Power

If multiple gears or double planets are provided for force transmission, then the transmission ratio can be increased, but the number of components increases

Engineering Contradiction:

Improvetransmission ratioVSAvoidnumber of components

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The patent merges the functions of multiple gears or double planets into a single double planet component. The double planet gear integrates both the planet gear and carrier functions, allowing direct force transmission from sun gear to ring gear without requiring intermediate components. This merging reduces the total component count while achieving the desired high transmission ratio.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The double planet gear serves multiple functions simultaneously: it acts as both a planet gear for force transmission and a carrier for the sun gear and ring gear connection. This multi-functionality eliminates the need for separate intermediate gears, reducing component complexity while maintaining the required transmission capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Stability of the object's composition

If the planet carrier is made stationary to provide structural support, then stability is improved, but force transmission efficiency decreases

Engineering Contradiction:

Improvestructural stabilityVSAvoidforce transmission efficiency

Core Design Contradiction:

Stability of the object's compositionVSPower

Solution Approach 1:

The patent inverts the traditional approach by making the ring gear (housing) stationary instead of the planet carrier. This inversion allows the planet carrier to remain mobile for efficient force transmission while the stationary ring gear provides structural support. The negative transmission arrangement enables this configuration to achieve both stability and transmission efficiency simultaneously.

Inventive Principle:

Principle #13The other way round (Inversion)

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 configuration reduces the number of required components, enhances stability by using the ring gear as a housing, prevents self-locking, and ensures adequate lubrication and monitoring of bearing assemblies, enabling high-precision and reversible operation in applications like robots and vehicles.

Implementation Method 1

the first set of gear teeth of the double planet meshes with the outer set of gear teeth of the sun gear

Methodology Applied

Scientific EffectGear meshing: Gear

Implementation Method 2

the second set of gear teeth of the double planet meshes with the inner set of gear teeth of the ring gear

Methodology Applied

Scientific EffectGear meshing: Gear

Implementation Method 3

utilizing preloaded double planets to maintain contact and distribute forces effectively

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS11078988B2Transmission assembly

Publication Date: 2021.08.03 AB SKF SKF PATENT DEPARTMENT

AI summary

A transmission assembly includes a sun gear including an outer set of gear teeth, a planet carrier disposed around the sun gear, and a ring gear surrounding the planet carrier and the sun gear and including an inner set of gear teeth. At least one double planet is attached to the planet carrier. The double planet includes a first set of gear teeth and a second set of gear teeth, the outer set of gear teeth of the sun gear meshes with the first set of gear teeth, and the second set of gear teeth meshes with the inner set of gear teeth of the ring gear.