Planet Gear Oil-Guiding Protrusions to Prevent Imbalance
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Solution Overview
Problem
In planetary gearboxes, oil accumulation in recesses of planet gears leads to imbalance forces and increased power losses due to uneven oil distribution, which existing designs fail to adequately mitigate.
Innovation Solution
The introduction of protrusions on the axially forward and rearward face sides of planet gears, which guide oil emerging from journal bearings in an axial direction, reducing the likelihood of oil accumulation in recesses and enhancing oil flow control, thereby minimizing imbalance forces and power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If recesses are implemented in the planet gear at its face sides to reduce stiffness and allow elastic deformation, then the contact surface of the journal bearing can be elastically deformed under high forces, but oil may flow into such recess and accumulate, leading to imbalance forces
Solution Approach 1:
The harmful effect of oil accumulation in recesses is extracted and redirected by introducing protrusions that guide oil away from the recesses. The protrusions act as flow guides that extract the radial oil flow component and redirect it axially, preventing oil from entering the recesses where it would cause imbalance forces.
Solution Approach 2:
Protrusions are introduced as intermediary elements between the journal bearing and the recesses. These protrusions mediate the oil flow by providing a controlled path that directs oil axially away from the recesses, preventing direct radial flow into the recesses while maintaining the beneficial elastic deformation capability.
2Strength
If recesses are implemented in the planet gear to reduce stiffness, then the planet gear can elastically deform under high forces, but oil accumulation in recesses leads to power losses
Solution Approach 1:
The harmful oil accumulation that causes power losses is extracted and redirected by the protrusions. The protrusions extract the radial oil flow and redirect it axially, preventing oil from pooling in the recesses where it would create drag and energy losses.
3Device complexity
If no protrusions are provided, then the structure is simpler, but oil flow control is poor and oil accumulates in recesses
Solution Approach 1:
The planet gear structure is segmented by adding protrusions that divide the flow path. These protrusions segment the radial oil flow into controlled axial flow paths, improving oil flow control while maintaining relative structural simplicity through geometric features rather than additional components.
Solution Approach 2:
The oil flow direction is changed from purely radial to having an axial component by introducing protrusions. This dimensional change in flow path (from radial to axial) provides better oil flow control and prevents accumulation in recesses without significantly complicating the overall structure.
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 protrusions effectively direct oil away from recesses, reducing oil film thickness and accumulation, leading to improved gearbox reliability and efficiency by preventing imbalance forces and minimizing power losses.
Implementation Method 1
the protrusion is configured to provide for a flow path for oil emerging from the journal bearing that guides the oil away from the journal bearing in a direction having an axial component
Data Source
AI summary
A planetary gearbox having a sun gear, a plurality of planet gears, a ring gear, and a plurality of journal bearing pins. At its axially forward face side and/or at its axially rearward face side, each planet gear forms a recess that extends inside the planet gear starting from the face side. The planet gear forms a protrusion at its axially forward face side and/or at its axially rearward face side. The protrusion has an axial extent and a radial extent, wherein the radial extent is limited at the respective face side to the area between the planet gear inner bore and the radial inner limit of the respective recess in the planet gear, and wherein the protrusion is configured to provide for a flow path for oil emerging from the journal bearing that guides the oil away from the journal bearing.