Planet Carrier Pivot Geometry for Load-Balanced Reduction Gears
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Solution Overview
Problem
Current satellite carrier connections in turbomachine speed reducers experience misalignment issues due to significant forces transmitted via cylindrical pivots, leading to concentrated contact pressure and stress concentrations at one end of the pivot, which can cause misalignment and poor pressure distribution.
Innovation Solution
The satellite carrier design incorporates pivots with an external surface having a convex shape, preferably rounded, or an internal orifice with a matching convex shape, redistributing the contact pressure area from the pivot ends to the apex or crest, thereby reducing misalignment and stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If cylindrical pivots with small clearance are used to connect cage and cage holder, then the connection allows radial sliding movement, but significant forces cause misalignment and concentrated contact pressure at one end of the pivot
Solution Approach 1:
The patent applies curvature by replacing the cylindrical pivot surface with a convex (rounded) external surface on the pivot or a convex internal surface in the orifice. This curved surface geometry redistributes the contact pressure from being concentrated at one end to being distributed across the apex or crest of the convex surface, eliminating stress concentrations while maintaining the sliding connection functionality
2Device complexity
If cylindrical pivots are used to connect cage and cage holder, then the structure is simple, but misalignment occurs under load causing increased contact pressure
Solution Approach 1:
The convex surface geometry inherently compensates for misalignment by providing a self-centering effect. When misalignment occurs under load, the convex shape allows the pivot to naturally settle into the correct position, with the apex or crest of the convex surface making contact, thereby maintaining alignment stability without increasing structural complexity
Solution Approach 2:
The patent changes the geometric parameter of the pivot surface from cylindrical (straight) to convex (curved). This parameter change in surface geometry fundamentally alters the contact mechanics, allowing the connection to accommodate misalignment while distributing contact pressure evenly across the convex apex or crest
3Stress or pressure
If pivots with convex surfaces are used, then contact pressure is redistributed to the apex or crest, but manufacturing precision requirements increase
Solution Approach 1:
The convex surface geometry provides a self-compensating mechanism where the apex or crest of the curved surface naturally becomes the contact point. This parameter change in surface shape makes the connection less sensitive to manufacturing tolerances, as the rounded geometry accommodates variations while maintaining proper contact pressure distribution
Data Source
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AI summary
The planet carrier (213) for a reduction gear (10) of a turbomachine (1), particularly an aircraft turbomachine, comprises: - a carrier frame (220) having at its periphery axial housings (280) distributed about said axis (X), - a carrier frame holder (222) comprising axial fingers (282) distributed about the axis (X) and engaged in said axial housings (280), and - connecting elements connecting said fingers (282) to walls of said housings (280), each of these connecting elements comprising a pivot (289) extending in a radial direction (A) relative to said axis (X), this pivot (289) being borne by one of the members and having an external surface (292) which in axial section has a convex shape and which collaborates with a cylindrical internal surface (285a) of an orifice (285) of the other of these members.