Epicyclic Gear Misalignment Compensation
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Solution Overview
Problem
Existing epicyclic gear devices in turbine engines suffer from low power density and noise due to misalignment issues, leading to premature wear and mechanical impacts, which are exacerbated by the need for increased material thickness and weight constraints.
Innovation Solution
The integration of constant velocity ball transmission joints, such as Rzeppa, Weiss, plunging, or double-offset plunging joints, between the sunwheel and rotor, and the ring and blade sets, provides mechanical flexibility to absorb deformation and misalignment, allowing for continuous tooth contact and reduced stress concentrations, thereby enhancing power density and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If straight teeth are used in epicyclic gearing, then manufacturing is simpler, but misalignment causes premature wear and requires increased material thickness leading to weight increase
Solution Approach 1:
The patent changes the tooth profile from straight to curved (helical or epicycloidal), fundamentally altering the contact mechanics. This parameter change enables continuous contact between teeth, eliminating impact loads and distributing stress evenly, thereby extending gear lifetime without requiring increased material thickness
Solution Approach 2:
The curved tooth design creates dynamic, continuous contact between gear teeth during rotation. Instead of abrupt point-to-point contact in straight teeth, the curved profiles ensure that contact transitions smoothly along the tooth surface, maintaining constant engagement and eliminating the metallic clicking and impact phenomena
2Device complexity
If straight teeth are used in epicyclic gearing, then the structure is simpler, but force transmission is interrupted by jolts generating noise and reducing power density
Solution Approach 1:
Changing from straight to curved teeth fundamentally alters the force transmission mechanism. The curved profiles ensure continuous contact ratios greater than one, meaning at least two tooth pairs are always engaged, which smooths power transmission and eliminates the jolts and metallic clicking that reduce effective power density
Solution Approach 2:
The curved tooth design ensures continuous, uninterrupted force transmission between gears. The overlapping contact zones maintain constant engagement throughout the rotation cycle, eliminating the intermittent contact and force transmission interruptions characteristic of straight teeth, thereby eliminating noise-generating jolts
3Reliability
If shaft flexibility is increased to compensate for misalignment, then misalignment tolerance improves, but the shafts occupy more space and add weight
Solution Approach 1:
The patent changes the fundamental approach to misalignment compensation by modifying the tooth geometry itself rather than increasing shaft flexibility. The curved tooth profiles with increased contact ratios inherently tolerate misalignment through distributed contact, eliminating the need for oversized flexible shafts and their associated volume and weight penalties
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 significantly increases the tolerance to misalignment, reduces stress on the gear teeth, and extends the lifespan by eliminating jolts and impact phenomena, while maintaining essential operational degrees of freedom, resulting in improved power density and reduced noise.
Implementation Method 1
The integration of constant velocity ball transmission joints, such as Rzeppa, Weiss, plunging, or double-offset plunging joints, between the sunwheel and rotor, and the ring and blade sets, provides mechanical flexibility to absorb deformation and misalignment
Data Source
AI summary
An epicyclic gear device for driving rotation of a first blade set of a turbine engine, the device: including a sunwheel centered on a longitudinal axis of the turbine engine and connected to a rotor of the engine in order to be driven in rotation; at least one planet meshing with the sunwheel; a planet carrier rotatably carrying the planet and connected to a first blade set in order to drive it in rotation; and a ring meshing with the planet; the sunwheel being connected to the rotor via a first constant velocity ball transmission joint.