Planet Gear Blades for Differential Lubrication at Low Speeds
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Solution Overview
Problem
Existing motor vehicle drivetrains face challenges in supplying oil to differentials, especially at low speeds and high torques, due to the absence of a pump, leading to difficulty in lubrication.
Innovation Solution
A differential configuration with planet gears featuring blades that axially protrude from a radially extending surface to direct fluid flow towards the differential, combined with axially extending holes in the differential housing to supply lubricating oil to spider gears, ensuring effective lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If no pump is present to provide oil to the differential, then the device complexity is reduced, but the oil supply to the differential becomes difficult especially at low speeds and high torques
Solution Approach 1:
The planet gears serve a dual function: transmitting power and pumping oil. The blades on the planet gears automatically draw oil from the sump and deliver it to the differential during normal operation, eliminating the need for a separate pump while ensuring reliable lubrication under all operating conditions
Solution Approach 2:
The planet gears are designed with blades that enable them to perform both their traditional power transmission function and an additional oil pumping function. This multi-functionality resolves the contradiction by providing reliable oil supply without adding the complexity of a separate pump system
2Reliability
If blades are added to planet gears to direct fluid flow, then the oil supply to differential is improved, but the manufacturing complexity of planet gears increases
Solution Approach 1:
The planet gear is segmented into functional zones: the disc-shaped base portion for power transmission, the radially extending surface for structural support, and the axially protruding blades for fluid direction. This segmentation allows each part to be optimized for its specific function while maintaining manufacturability through modular design
3Reliability
If axially extending holes are created in differential housing to supply oil to spider gears, then the lubrication of spider gears is improved, but the manufacturing complexity of differential housing increases
Solution Approach 1:
The axially extending holes are pre-formed in the differential housing during manufacturing, establishing oil flow paths in advance. This preliminary action ensures that oil delivered by the planet gears can automatically reach the spider gears without requiring additional complex lubrication components or assembly steps
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 solution ensures efficient lubrication of differentials even at low speeds and high torques, enhancing the operational efficiency and durability of the drivetrain.
Implementation Method 1
The blades axially protrude from the radially extending surface for directing a fluid flow axially toward the differential during operation of the drive assembly
Data Source
AI summary
A drive assembly for a motor vehicle drivetrain includes a differential configured for driving a first output shaft and a second output shaft about a center axis and for allowing the first output shaft and the second output shaft to rotate about the center axis at different speeds, and planet gears each rotatably mounted on a respective planet carrier. The planet gears each include a radially extending surface and blades circumferentially spaced part from each other. The blades axially protrude from the radially extending surface for directing a fluid flow axially toward the differential during operation of the drive assembly.