Ball-Roller Differential on Elliptical Tracks With Reduced Diameter
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Solution Overview
Problem
Existing gear differentials face challenges with high production costs and jamming issues due to excessive bulk, particularly in the double overlap configuration of eccentric tracks on coplanar discs separated by a central cross, which limits their effectiveness and adoption by major car manufacturers.
Innovation Solution
The solution involves replacing the bulky central tube with a simpler system using translators and semi-elliptical tracks with inclined sections, allowing for a more compact and efficient differential mechanism that reduces the external diameter by over 50% while maintaining torque transmission, utilizing steel components and numerically controlled machining to lower production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a central tube with double overlap eccentric tracks is used, then torque transmission is achieved, but the external diameter becomes excessively large and production cost increases
Solution Approach 1:
The patent transitions from a planar double overlap configuration to a three-dimensional spatial arrangement with inclined tracks. The tracks are positioned at angles (e.g., 45 degrees) relative to each other in space, allowing the mechanism to achieve the same torque transmission function with reduced external diameter by utilizing the third dimension rather than expanding in the planar direction.
Solution Approach 2:
The invention nests the eccentric tracks within a compact cylindrical housing where the inclined tracks are arranged concentrically. The inner track and outer track are positioned such that they occupy overlapping radial spaces but at different angular orientations, effectively nesting the functional elements to minimize the overall external diameter while maintaining torque transmission capability.
2Power
If a central tube with double overlap eccentric tracks is used, then torque transmission is achieved, but production cost increases
Solution Approach 1:
The differential mechanism is divided into separate modular components: the housing with inclined tracks, the eccentric elements, and the connecting links. This segmentation allows each component to be manufactured independently using standard machining processes, simplifying production and reducing costs compared to manufacturing a complex integrated central tube assembly.
Solution Approach 2:
Instead of starting with a central tube and adding tracks, the invention inverts the approach by first creating the housing with inclined tracks and then inserting the eccentric elements. This reverse assembly sequence simplifies manufacturing by allowing the housing to be a simple cast or machined component rather than a complex assembled structure, thereby reducing production cost.
3Strength
If inclined sections are added to semi-elliptical tracks, then mechanical resistance to torsion improves, but device complexity increases
Solution Approach 1:
The patent merges the semi-elliptical track shape with inclined sections into a single integrated track geometry. Rather than adding separate inclined components to the elliptical tracks, the incline is built into the track profile itself, creating a unified structure that provides both the elliptical motion path and the inclined force transmission, thereby reducing device complexity while maintaining torsional resistance.
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 results in a more cost-effective, compact, and efficient differential system that can be used in electric traction technologies and automotive applications, offering improved mechanical resistance to torsion and reduced friction, with the potential for miniaturization without sacrificing power transmission.
Implementation Method 1
The spheres are constrained in the slots of the translators and constrained simultaneously in the guide tracks, made in the shafts, by friction contact
Data Source
AI summary
A differential made without gears in the satellites and planetaries, in the planetary shafts elliptical tracks are obtained on the fronts and on the circumferences of the shafts, the shape of the tracks is semi-spherical or semi-cylindrical and requires the profile of half spheres or half rollers to roll tangentially within the tracks for a part of their circumference, the balls or rollers being constrained partly in the tracks, partly in the translators and, sometimes, partly in the cylinder and otherwise in the cross that divides the two shafts. The whole is contained by the cylinder in which the longitudinal seats are dedicated to the translators and the spheres that drag the balls or rollers. This cylinder can also be composed of two parts joined at the center to block the cross. In some cases, inside the shafts a bilateral locking and unlocking solenoid (SBL) is installed.