Nested Differential Housing and Hollow Shaft Oil Feed
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Solution Overview
Problem
Oil supply to differentials in motor vehicle gearboxes is challenging, especially at low speeds and high torques, when no oil pump is present, leading to difficulties in lubrication.
Innovation Solution
A drive assembly for motor vehicle drivetrains featuring a differential with a hollow drive shaft partially nested within the differential housing, directing oil from the drive shaft into the differential housing to lubricate the spider gears, ensuring effective lubrication by creating axial and annular gaps for fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a differential is supplied with oil via oil sump lubrication without an oil pump, then the structure is simpler, but oil supply is difficult especially at low speeds and high torques
Solution Approach 1:
The hollow drive shaft is nested within the differential housing, creating internal oil passages that directly channel oil from the sump to the differential gears. This nested configuration allows oil supply without requiring an external pump, maintaining structural simplicity while ensuring reliable lubrication under all operating conditions.
2Reliability
If the hollow drive shaft is nested within the differential housing, then oil supply is improved, but the device complexity increases
Solution Approach 1:
The hollow drive shaft serves multiple functions: it transmits rotational power from the engine to the differential gears while simultaneously acting as an oil conduit to deliver lubrication to the differential components. This multi-functionality eliminates the need for separate oil supply mechanisms, reducing overall device complexity while ensuring reliable oil supply.
Solution Approach 2:
The differential system uses its own rotating mass (the drive shaft) to generate and distribute oil through centrifugal force and pressure gradients created during rotation. The system serves itself by utilizing the natural dynamics of operation to pump and distribute lubrication without external assistance.
3Reliability
If the hollow drive shaft directs oil into the differential housing, then lubrication is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The differential housing includes localized features such as oil guide surfaces and passage configurations that direct oil flow precisely to the gear contact points. These local structural qualities ensure proper oil distribution without requiring extremely tight tolerances across the entire assembly, making manufacturing more feasible while maintaining effective lubrication.
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
Enhances oil supply and lubrication to the differential, improving power transmission efficiency by allowing the first and second output shafts to rotate at different speeds, even under low-speed and high-torque conditions.
Implementation Method 1
The hollow drive shaft is partially nested radially within the differential housing to direct oil from inside of the hollow drive shaft into the differential housing. A radially extending end surface of the hollow drive shaft that axially faces toward the first side gear is axially closer to the first side gear than a radially extending end surface of the differential housing. The hollow drive shaft, the guide portion of the differential housing and the tubular hub of the first side gear are arranged to direct fluid flowing axially within the hollow drive shaft toward the first side gear radially outward through the axial gap, and axially through the annular gap into the spider gears.
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. The differential includes a first side gear on a first side of the differential configured for being drivingly connected to the first output shaft; a second side gear on a second side of the differential configured for being drivingly connected to the second output shaft; a differential housing enclosing the first and second side gears; support pins non-rotatably fixed to the differential housing; and spider gears rotatably mounted on the support pins and positioned between the first side gear and the second side gear. Each of the spider gears intermeshes with both the first side gear and the second side gear to transmit power from the support pins to the first side gear and the second side gear. The drive assembly further includes a hollow drive shaft for driving the differential. The differential housing is configured for transmitting power from hollow drive shaft to the support pins. The hollow drive shaft is partially nested radially within the differential housing to direct oil from inside of the hollow drive shaft into the differential housing.