Planetary Gear Stage With Plain Bushing for Axial Load Support
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Solution Overview
Problem
Existing planetary gear systems in wind turbine gearboxes face challenges in achieving reduced weight, cost-effectiveness, and compact design, particularly due to the complexity of manufacturing tapered bushings and the need for thrust washers to handle axial and radial loads.
Innovation Solution
A planetary gear stage with a single cylindrical plain bushing coaxially coupled to the planet shaft, which radially and axially supports the planet gear, eliminating the need for thrust washers and allowing for a compact design that can be easily assembled and manufactured, thus reducing weight and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If tapered bushings are used to withstand axial and radial loads, then the bearing capacity is improved, but the manufacturing complexity increases significantly
Solution Approach 1:
The bearing system is segmented into two separate components: a cylindrical plain bushing for radial loads and a thrust washer for axial loads. This segmentation allows each component to be manufactured with simpler geometry (cylindrical rather than tapered), reducing manufacturing complexity while maintaining the combined load-bearing capability through the assembly of multiple simple parts
Solution Approach 2:
The cylindrical plain bushing and thrust washer are combined in an assembly where the thrust washer is mounted on the planet shaft and the plain bushing fits over it. This merging of simple components achieves the functional equivalence of a complex tapered bushing, allowing radial and axial loads to be withstood through the coordinated action of two easily manufactured parts
2Ease of manufacture
If cylindrical bushings with extra thrust washers are used to bear axial loads, then the manufacturing complexity is reduced, but the device complexity increases
Solution Approach 1:
The thrust washer is designed to serve multiple functions: it bears axial loads, provides a mounting surface for the plain bushing, and contributes to the overall structural integrity of the planet gear assembly. This multi-functionality reduces the need for separate specialized components, simplifying the overall device structure while maintaining manufacturing simplicity
Solution Approach 2:
The thrust washer and plain bushing assembly is designed to self-align and self-support within the planet gear system. The components automatically position themselves through their geometric features (shoulders, fits, and contacts), eliminating the need for complex adjustment mechanisms or additional fastening elements, thereby reducing device complexity
3Strength
If traditional roller bearings are used instead of journal bearings, then the load capacity is improved, but the weight and overall dimension increase
Solution Approach 1:
The bearing type is changed from roller bearings to journal bearings (plain bearings), representing a fundamental parameter change in the bearing mechanism. Journal bearings have inherently lower weight and smaller dimensions while the addition of the thrust washer compensates for the reduced axial load capacity, achieving an optimal balance between weight reduction and load-bearing requirements for wind turbine applications
4Length of stationary object
If the plain bushing axial length is reduced for compact design, then the overall dimension is improved, but the axial load bearing capability may be compromised
Solution Approach 1:
The axial load-bearing function is extracted from the plain bushing and assigned to a dedicated thrust washer component. This allows the plain bushing to be shortened for compact design while the thrust washer, positioned at the appropriate location, provides the necessary axial load support. The separation of functions enables independent optimization of each component's dimensions
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 solution achieves weight savings and cost reductions by eliminating the need for thrust washers and simplifying the manufacturing process, while effectively supporting both radial and axial loads, enabling the gearbox to fit within standard transportation dimensions.
Implementation Method 1
the plain bushing radially supports the planet gear, that is, the plain bushing is radially loaded by the planet gear
Implementation Method 2
the planet gear and the plain busing are axially in contact in at least one axial direction, either directly or indirectly, by means of the annular abutment, so that, the plain bushing is also axially loaded by the planet gear in one axial direction
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
The invention refers to a planetary gear stage for a gear box, wherein the gear stage comprises: a planet shaft, at least one plain bushing coaxially coupled with the planet shaft, a planet gear rotatably mounted on the plain bushing, such that the plain bushing radially supports the planet gear. The planet gear has an annular abutment projecting inwardly towards the planet shaft, such that the planet gear and the plain busing are axially in contact in at least one axial direction directly or indirectly by means of the annular abutment, so that the plain bushing is also axially loaded by the planet gear. The invention features a reduced weight and reduced manufacturing cost, and exhibits a compact design. The invention also refers to a gearbox for a wind turbine incorporating the planet gear stage, and to a wind turbine incorporating the gearbox.