Planetary Gearbox Journal Pin Stiffness for Uniform Oil Film
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Solution Overview
Problem
In planetary gearboxes, the oil film thickness and pressure distribution along the journal bearing are uneven due to deformations of the planet gear and journal bearing pin, leading to suboptimal performance.
Innovation Solution
A journal bearing pin with varying bending stiffness along its longitudinal axis is used, matching the radial deformation of the planet gear, ensuring a more uniform oil film thickness and pressure distribution by reducing stiffness in areas of maximum radial deflection and increasing it where necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a journal bearing pin with fixed bending stiffness is used, then the structure is simple and easy to manufacture, but the oil film thickness and pressure distribution become uneven due to planet gear deformation
Solution Approach 1:
The patent applies local quality by varying the bending stiffness of the journal bearing pin along its longitudinal axis. Different axial sections of the pin have different stiffness characteristics, with higher stiffness in regions where the planet gear experiences greater radial deflection and lower stiffness where deflection is minimal. This non-uniform stiffness distribution compensates for the deformation patterns of the planet gear, maintaining more uniform oil film thickness and pressure distribution throughout the journal bearing.
Solution Approach 2:
The patent implements parameter changes by modifying the bending stiffness parameter of the journal bearing pin along its length. The stiffness parameter varies continuously or in discrete steps from one axial position to another, allowing the pin to adapt its mechanical properties to match the deformation characteristics of the planet gear at different locations, thereby optimizing lubrication performance.
2Reliability
If the bending stiffness of the pin is reduced in axial areas with maximum radial deflection, then the oil film thickness becomes more uniform, but the pin becomes more flexible and may deform excessively
Solution Approach 1:
The patent resolves this contradiction by applying local quality through spatially varying stiffness. The pin is designed with higher bending stiffness in axial regions where the planet gear undergoes maximum radial deflection, providing the necessary structural strength to prevent excessive pin deformation. Conversely, in regions where planet gear deflection is minimal, the pin has lower stiffness, which allows it to conform to the gear deformation and maintain uniform oil film thickness and pressure distribution.
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 approach optimizes the oil film thickness and pressure distribution, preventing metal-to-metal clashing and achieving a more robust lubrication system with a single maximum oil film pressure, thereby enhancing the journal bearing's performance.
Implementation Method 1
the bending stiffness of the pin varies along the longitudinal axis of the pin such that the bending stiffness of the pin is reduced in axial areas in which the radial deflection of the planet gear is maximal during operation
Data Source
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AI summary
The invention regards a planetary gearbox (30) which comprises a sun gear (28), a plurality of planet gears (32) which are driven by the sun gear (28), a ring gear (38), and a plurality of journal bearing pins (6). Each of the journal bearing pins (6) is located in an inner bore of one of the planet gears (32), wherein the journal bearing pins (6) each have a longitudinal axis which extends in the axial direction of the planetary gearbox (30). In each case a journal bearing pin (6) and a planet gear (32) form a journal bearing (65). It is provided that the journal bearing pin (6) comprises, along the length of the journal bearing (65), a stiffness which varies along the longitudinal axis of the pin (6).