Wind Turbine Gear Transmission With Phase-Selective Tooth Lubrication
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Solution Overview
Problem
Wind turbine gearboxes require high gear ratios, leading to increased size and mass, which complicates their use in tall turbines and reduces efficiency when operated in reverse directions, especially in high torque applications.
Innovation Solution
A transmission system with a fixed gear ring and radially arranged slidable tooth elements, where lubrication fluid is selectively delivered to tooth elements during high loading phases to enhance efficiency and reduce parasitic losses, allowing for a compact and efficient speed increasing gearbox design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a high gear ratio is achieved using conventional parallel or epicyclic gearboxes, then the speed increase from rotor shaft to generator is sufficient, but the gearbox size and mass increase significantly
Solution Approach 1:
The gearbox is divided into multiple independent planetary gear stages, each providing a portion of the total gear ratio. This segmentation allows the overall high gear ratio to be achieved through composition of smaller ratio stages, reducing the size and mass of each individual stage compared to a single-stage design.
Solution Approach 2:
Multiple planetary gear stages are nested within each other, with each stage contained within the housing of the previous stage. This nested arrangement achieves compact packaging of multiple gear reduction functions, minimizing the overall gearbox volume and mass while maintaining the required high gear ratio.
2Weight of stationary object
If the gearbox mass is reduced to minimize the pendulum effect on tall towers, then the structural load on the tower is reduced, but the gear ratio and torque handling capability may be compromised
Solution Approach 1:
The torque transmission function is distributed across multiple planetary gear stages rather than concentrated in a single stage. Each stage handles a portion of the torque multiplication, allowing the use of smaller, lighter components that collectively achieve the required torque handling capability without compromising strength.
Solution Approach 2:
The planetary gears and housing utilize high-strength, low-density materials and optimized geometries that provide maximum strength-to-weight ratio. This allows the gearbox to maintain adequate torque handling capability while minimizing mass to reduce the pendulum effect on tall towers.
3Volume of stationary object
If radial-moving-teeth gearbox design is used to achieve compact layout and high gear ratio, then the gearbox size is reduced, but the efficiency decreases when operated in reverse driven direction
Solution Approach 1:
The radial-moving-teeth mechanism is implemented in multiple discrete planetary stages rather than as a single continuous mechanism. This segmentation allows each stage to be optimized for bidirectional operation, improving reverse drive efficiency while maintaining the compact volume advantage of the radial-moving-teeth design.
Solution Approach 2:
The tooth elements are designed with dynamic characteristics that allow smooth transition between forward and reverse operation modes. The radial movement of teeth is controlled to maintain optimal engagement angles and contact patterns in both directions, minimizing energy losses during reverse driven operation while preserving the compact layout.
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 transmission system reduces the mass and cost of wind turbine gearboxes while maintaining efficiency, even in high torque applications, by selectively lubricating tooth elements and enabling a compact, high-speed reduction ratio, thus addressing the pendulum effect and reverse operation inefficiencies.
Implementation Method 1
a lubrication arrangement comprising a plurality of lubrication passages configured to provide lubricating fluid to at least some of the circumferentially-arranged tooth elements, wherein the lubrication arrangement is further configured to deliver lubricating fluid to a selected group of the slidable tooth elements during a predetermined loading phase for those respective tooth elements
Data Source
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AI summary
A transmission which may find particular utility in wind turbine application, but may also be used in other applications. The transmission comprises a fixed gear ring, a first drive member rotationally supported within the fixed gear ring, the first drive member defining a plurality of radially arranged apertures each of which accommodates a tooth element, each tooth element having a tooth tip and a tooth base that are opposed along a tooth axis, the first drive member further comprising a radially outer face and a radially inner face, wherein the tooth tips of the tooth elements engage a corresponding tooth surface defined by the fixed gear ring. The transmission further comprises a second drive member which is rotationally supported such that it extends within the first drive member, the second drive member defining an eccentric cam profile which engages the tooth base of each of the plurality of tooth elements. The transmission further includes a lubrication arrangement comprising a plurality of lubrication passages configured to provide lubricating fluid to at least some of the circumferentially-arranged tooth elements, wherein the lubrication arrangement is further configured to deliver lubricating fluid to a selected group of the tooth elements during a predetermined loading phase for those respective tooth elements. Beneficially, the invention involves providing lubrication fluid to the tooth elements of the transmission during selected period where loading is relatively high. As the loading point progresses angularly around the transmission, the lubrication fluid is delivered to the tooth elements which most require lubrication which means lubrication fluid is applied selectively and more efficiently. This can present a saving in lubrication fluid and reduce parasitic losses.