Planetary Gear Slide Bearing Positioning for Thermal Expansion
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Solution Overview
Problem
In planetary gear units used in wind turbine generators, the heat generated by contact sliding between the slide bearing and planetary pin leads to thermal expansion differences, causing clearance issues and potential damage such as seizing and abrasion, especially when the slide bearing is made of resin material.
Innovation Solution
The slide bearing is positioned on the outer periphery of the planetary pin, allowing heat generated at the sliding interface to be primarily transmitted to the planetary gear, reducing the temperature increase of the planetary pin and maintaining clearance, while also being strategically placed at contact regions to ensure stable slidability. Additionally, a metal sleeve with a smoother surface than the oil film is used to enhance slidability, and the slide bearing can be partially or fully circumferential on the pin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the slide bearing is made of resin material with high heat resistance and thermal insulation, then the heat generated on the bearing surface is transmitted to the planetary pin side, but the thermal insulation effect causes heat to be trapped on the planetary pin side, leading to significant temperature difference and thermal expansion clearance loss
Solution Approach 1:
Instead of attaching the slide bearing to the planetary gear side where heat would be trapped by thermal insulation, the bearing is inverted to be attached to the planetary pin side. This allows heat to dissipate to the surrounding environment rather than being trapped, preventing thermal expansion clearance loss while maintaining the benefits of resin material heat resistance.
Solution Approach 2:
The slide bearing is extracted from the planetary gear side and repositioned to the planetary pin side, separating the heat generation source from the thermally insulating component. This extraction prevents the formation of a heat trap between the bearing and planetary gear, resolving the contradiction between heat resistance and clearance maintenance.
2Device complexity
If the slide bearing is positioned on the planetary gear side, then the structure is simple, but heat generated by contact sliding is transmitted to the planetary pin side causing thermal expansion differences and clearance disappearance
Solution Approach 1:
The slide bearing position is inverted from the conventional planetary gear side to the planetary pin side. This simple repositioning changes the heat flow path, allowing heat to dissipate externally rather than being transmitted to the planetary pin, thereby reducing thermal expansion differences without significantly increasing structural complexity.
3Temperature
If the slide bearing is made of resin material, then high heat resistance is achieved, but the thermal insulation effect causes heat to be trapped leading to seizing and abrasion damage
Solution Approach 1:
The slide bearing is repositioned from the planetary gear side to the planetary pin side, inverting the heat flow direction. This allows heat generated by friction to escape to the surrounding environment rather than being trapped by the thermally insulating resin material, preventing seizing and abrasion while preserving the heat resistance advantage of resin bearings.
Solution Approach 2:
The thermal insulation property of the resin material, which originally caused heat trapping and damage, is converted into a beneficial heat shield that protects the planetary pin from excessive heat while allowing controlled heat dissipation to the environment, transforming a harmful effect into a protective function.
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 reduces heat expansion differences between the planetary pin and gear, preventing damage like seizing and abrasion, while maintaining stable slidability and reducing material costs by using less resin for the slide bearing.
Implementation Method 1
heat generated by contact sliding between the inner periphery of the slide bearing 53 and the outer periphery of the planetary pin 51 is transmitted to surrounding components
Implementation Method 2
lubricating oil is supplied to a space between the inner periphery of the slide bearing 53 and the outer periphery of the planetary pin 51 to form an oil film on the bearing surface
Implementation Method 3
the slide bearing 53 is made of resin material such as PEEK resin and Teflon (registered trademark) having high heat resistance
Implementation Method 4
the temperature of the planetary pin 51 becomes higher than that of the planetary gear 52. This causes a significant difference of heat expansion rate between the planetary pin 51 and the planetary gear 52
Data Source
AI summary
A planetary gear unit including a ring gear, a sun gear provided on an inner circumferential side of the ring gear, at least one planetary gear arranged between the ring gear and the sun gear to mesh with the ring gear and the sun gear, a planetary pin fixed to a carrier and inserted in a shaft hole of the planetary gear, and a slide bearing arranged between the planetary gear and the planetary pin, wherein the slide bearing is formed of a resin material and is provided on an outer periphery of the planetary pin at least in a region where the planetary pin slides relative to the planetary gear.