Two-Part Planet Pin Assembly for Rigid Planetary Gearboxes
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Solution Overview
Problem
The design of planet pins in planetary gear boxes for gas turbine engines faces a challenge where increasing the diameter to enhance load-bearing capacity compromises the rigidity of the carrier plates, limiting dimensioning options and affecting assembly efficiency.
Innovation Solution
A two-part planet pin design is implemented, with a radially outer pin part having a larger diameter and a radially inner pin part with a smaller diameter, allowing for a larger pin diameter without increasing the fixing opening size in the carrier plates, thereby maintaining rigidity and enabling weight reduction and easier assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the planet pin diameter is increased to improve load-bearing capacity, then the load-bearing capacity is improved, but the carrier plate rigidity deteriorates due to larger fixing openings
Solution Approach 1:
The planet pin is divided into two separate parts: an inner pin part and an outer pin part. The inner pin part has a smaller diameter that fits through the carrier plate fixing openings, while the outer pin part has a larger diameter that provides the required load-bearing capacity. This segmentation allows each part to be optimized for its specific function without compromising the other.
Solution Approach 2:
The inner pin part is nested within the outer pin part, with the inner pin part passing through the carrier plate and the outer pin part surrounding it. The two parts are connected to form a complete planet pin assembly, where the inner part serves as a core structural element and the outer part provides additional bearing surface area.
2Strength
If the planet pin diameter is increased to improve load-bearing capacity, then the load-bearing capacity is improved, but the assembly difficulty increases due to larger fixing openings required
Solution Approach 1:
By segmenting the planet pin into inner and outer parts with different diameters, the fixing openings in the carrier plate can be kept small (matching the inner pin part diameter), which simplifies manufacturing and assembly. The outer pin part is then assembled around the inner pin part, allowing the bearing assembly to be completed without requiring large openings in the carrier plate.
3Strength
If the planet pin diameter is increased to improve load-bearing capacity, then the load-bearing capacity is improved, but the carrier plate thickness must be increased to maintain rigidity, which increases weight
Solution Approach 1:
The segmentation of the planet pin allows the carrier plate to maintain its original thickness and rigidity characteristics. Since the fixing openings remain small (sized for the inner pin part), the carrier plate does not need to be thickened, thereby avoiding additional weight while still accommodating the larger-diameter outer pin part that provides enhanced load-bearing capacity.
Data Source
AI summary
A planetary gear box (and method of assembly), where the gear box includes a sun gear, a plurality of planet gears, a ring gear, a plurality of planet pins, an axially forward carrier plate and an axially rearward carrier plate. Each planet pin is fixed respectively at its axially forward end on the axially forward carrier plate and at its axially rearward end on the axially rearward carrier plate of the planetary gear box. The planet pin is of two-part design and forms a radially outer pin part and a radially inner pin part, which are connected to one another in a manner precluding relative rotation therebetween, wherein the radially outer pin part forms a bearing with the planet gear, and only the radially inner pin part is fixed at its axial ends to the forward and rearward carrier plates.