Gearbox Speed Ratio Layout for Cross-Shaft Vibration Reduction
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Solution Overview
Problem
Rotating machinery, such as gearboxes in gas turbine engines, experiences significant vibrations due to imbalances and external forces, leading to resonance issues that conventional damping systems often fail to fully mitigate, especially at critical speeds, and these vibrations can lead to increased wear and reduced lifespan.
Innovation Solution
A method for manufacturing gearboxes that avoids integer speed ratios by designing a transmission ratio within a predefined interval around an integer, using irrational numbers to minimize vibrations, and incorporating gear tooth numbers that are coprime to reduce resonant frequencies and enhance structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional damping systems are used to reduce vibrations, then vibration levels are reduced within nominal design conditions, but the system weight increases and vibration may increase outside nominal conditions
Solution Approach 1:
The invention changes the fundamental parameter of speed ratio from integer to irrational number, transforming the vibration problem from one requiring passive damping to one prevented through operational parameter optimization. This allows reduction of damping system weight while maintaining vibration control across the full operational envelope.
Solution Approach 2:
The invention introduces dynamic adjustment of speed ratios during operation, allowing the system to avoid critical vibration conditions as they arise. This dynamic approach replaces static heavy damping systems with active parameter control, reducing weight while improving performance across varying operating conditions.
2Object-affected harmful factors
If damping systems are added to reduce vibrations, then resonance effects are mitigated, but the overall system complexity and component count increase
Solution Approach 1:
By changing the speed ratio parameter to an irrational number, the invention prevents resonance conditions from occurring in the first place, eliminating the need for complex damping systems. The vibration control is achieved through parameter selection rather than additional components.
Solution Approach 2:
The invention extracts the vibration control function from the mechanical damping system and relocates it to the control system through speed ratio management. This separates the vibration prevention function from physical damping components, reducing mechanical complexity.
3Ease of manufacture
If integer speed ratios are used in gearbox design, then manufacturing and operation are simplified, but cross-shaft vibrations and resonances occur at critical speeds
Solution Approach 1:
The invention changes the speed ratio parameter from integer to irrational number, preventing cross-shaft vibrations while maintaining manufacturing feasibility through standardized gear components. The irrational ratio is achieved through gear tooth number selection rather than complex manufacturing processes.
Solution Approach 2:
By using irrational speed ratios instead of symmetric integer ratios, the invention breaks the periodicity that causes cross-shaft vibrations. This asymmetric approach prevents synchronized vibration patterns between different shafts while maintaining practical gear design.
4Productivity
If gearbox operates at critical speeds, then power transmission efficiency is maintained, but resonant vibrations increase and reduce system lifespan
Solution Approach 1:
The invention introduces dynamic speed ratio adjustment to avoid critical speeds during operation. The control system continuously monitors operating conditions and modifies speed ratios to prevent resonant conditions, maintaining efficiency while protecting against vibration-induced damage over the system lifecycle.
Solution Approach 2:
The invention performs preliminary identification of critical speed ranges and pre-plans speed ratio adjustments to avoid these conditions before they are reached during operation. This preventive approach protects the system from vibration damage before it occurs, extending lifespan without compromising productivity.
Data Source
AI summary
Embodiments of the invention are shown in the figures, where a method for manufacturing a gearbox, the method comprising: providing a predefined interval around an integer; providing a gearbox setup; determining a speed ratio of at least two components of the gearbox setup; comparing the speed ratio with the predefined interval around the integer; and manufacturing a gearbox in accordance with the gearbox setup in dependence on the comparison.