Planetary Carrier Flex Bolts for Gear Misalignment Compensation

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Solution Overview

Problem

Existing planetary gear systems face misalignment issues due to load-related deformations, particularly in wind turbines with constantly changing loads, which are not adequately addressed by existing solutions like flex pins that lack resilience and load capacity.

Innovation Solution

A planetary carrier design featuring a first and second cheek with a pin and socket structure, where the socket is fixed in the second cheek and the pin is free-floating, allowing for axial position variation and deformation compensation, and optionally reinforced with radial ribs to enhance rigidity and counteract torsional deformations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the number of planet gears is increased to increase transmissible power, then the power transmission capability is improved, but the distance between adjacent planet gears is reduced making web connection difficult

Engineering Contradiction:
Improvetransmissible powerVSAvoiddistance between planet gears
Core Design Contradiction:
PowerVSLength of moving object

Solution Approach 1:

The invention extracts the force transmission function from the webs and transfers it to the planetary bolts. By making the planetary bolts load-bearing components that directly connect the two cheeks, the design eliminates the need for additional webs between planet gears, thus resolving the space constraint when increasing the number of planet gears.

Inventive Principle:
Principle #2Taking out (Extraction)

2Area of stationary object

If webs are removed to increase space for more planet gears, then the installation space is improved, but all forces must be transmitted via planetary bolts causing deformation and misalignment

Engineering Contradiction:
Improveavailable space in planet carrierVSAvoidload-bearing capacity of planetary bolts
Core Design Contradiction:
Area of stationary objectVSStrength

Solution Approach 1:

The invention changes the design parameters of the planetary bolts, specifically making them load-bearing components with optimized geometry and material properties. The bolts are designed with appropriate diameter, length, and thread specifications to withstand the full load transmission requirements, transforming them from simple fasteners to structural load-carrying elements.

Inventive Principle:
Principle #35Parameter changes

3Manufacturing precision

If gear correction is applied to compensate for misalignment under specific load, then the tooth engagement accuracy is improved under that load, but errors reoccur under different loads particularly in wind turbines with constantly changing loads

Engineering Contradiction:
Improvetooth engagement accuracyVSAvoidadaptability to varying loads
Core Design Contradiction:
Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The invention introduces dynamic adaptability through the flexible pin-bushing assembly. The bushing can tilt and deform elastically in response to varying loads, allowing the planetary gear to automatically adjust its position and maintain proper tooth engagement under different operating conditions, replacing the static gear correction approach.

Inventive Principle:
Principle #15Dynamics

4Reliability

If flex pins are used to compensate for load-induced deformations, then the misalignment prevention is improved, but the load-bearing capacity is reduced due to the single-cheek design limitation

Engineering Contradiction:
Improvemisalignment compensationVSAvoidload-bearing capacity of planet carrier
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The invention segments the load-bearing function across multiple components: the pin provides structural support, the bushing provides flexible accommodation and misalignment compensation, and together they form a planetary bolt that connects both cheeks. This segmentation allows each component to be optimized for its specific function while working together to achieve both high load capacity and misalignment compensation.

Inventive Principle:
Principle #1Segmentation

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 increases the resilience of the planetary gear system, allows for larger gear dimensions or more gears, and compensates for deformations, improving load handling and reducing misalignment issues.

Implementation Method 1

The bushing serves to accommodate at least one planet gear (107). The planet gear (107) is designed to be rotatably mounted in the bushing (123).

Methodology Applied
Scientific EffectFriction: Friction

Implementation Method 2

A flex pin is a flexible planetary pin that compensates for load-induced deformations and thus prevents misalignment of a planetary gear. A flex pin consists of a flexible pin on which a bushing is mounted. If the pin deforms, this is compensated for by a tilting of the bushing.

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP3707413B1Planetary carrier having flexible bolts
Publication Date: 2021.08.25 ZF FRIEDRICHSHAFEN AG
  • EP3707413B1 patent drawingFigure 1
  • EP3707413B1 patent drawingFigure 2

AI summary

The invention relates to a planetary carrier (103) having a first cheek and a second cheek. The planetary carrier has at least one journal (121) and at least one bushing (123); wherein a first end of the journal (121) is fixed in the first cheek; wherein the bushing (123) is fixed in the second cheek; wherein at least one part of the journal (121) protrudes into the bushing (123); and wherein a second end of the journal (121) is fixed in the bushing (123).