External Planetary Gear Set for Axle Assembly Adaptation
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Solution Overview
Problem
Existing axle assemblies for commercial vehicles, designed for internal combustion engines, are inadequate for hybrid electric vehicles as they require higher gear ratios, necessitating significant design changes or internal access to accommodate smaller, higher-speed electric motors.
Innovation Solution
A planetary gear set or bevel gear set is mounted externally to the axle assembly housing, using existing bolt patterns, to increase gear ratios from 2:1 to 40:1, allowing adaptation of existing axle assemblies for use with high-speed electric motors without internal modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing axle assemblies are used for internal combustion engines, then the gear ratio is suitable for ICE (2.69:1 to 7.17:1), but the axle assembly cannot accommodate smaller high-speed electric motors requiring higher gear ratios (20:1 to 80:1)
Solution Approach 1:
The transmission system is divided into two separate parts: the existing axle assembly housing containing the differential, and an externally mounted planetary gear set. This segmentation allows the planetary gear set to provide the necessary gear ratio multiplication (20:1 to 80:1) without modifying the internal components of the original axle assembly, thereby accommodating electric motors while preserving the existing differential design.
Solution Approach 2:
Instead of increasing gear ratio through internal modifications within the axle housing, the solution moves the gear multiplication function to an external dimension by mounting the planetary gear set outside the housing. This external mounting on the head assembly portion allows the axle assembly to achieve high gear ratios (20:1 to 80:1) suitable for electric motors without altering the internal differential structure.
2Adaptability or versatility
If the axle assembly is redesigned internally to accommodate electric motors, then the gear ratio can be increased, but the design complexity and manufacturing cost increase significantly
Solution Approach 1:
The externally mounted planetary gear set serves as a universal adapter that can be attached to existing axle assembly head assembly portions to enable compatibility with electric motors. This multi-functional approach allows the same planetary gear set design to work with various existing axle assemblies without requiring internal redesign, thereby maintaining ease of manufacture while achieving hybrid electric system compatibility.
Solution Approach 2:
The planetary gear set acts as an intermediary component between the electric motor and the existing axle assembly differential. By mounting externally on the head assembly portion, it mediates the connection between the high-speed electric motor output and the differential input, providing the necessary gear ratio multiplication without requiring direct internal modifications to the axle assembly.
3Ease of operation
If existing bolt hole patterns are used for attachment, then the installation is simplified, but the mounting location is constrained to the head assembly portion
Solution Approach 1:
The planetary gear set is designed to utilize existing bolt hole patterns on the head assembly portion for attachment, making it compatible with various existing axle assemblies. This universal mounting approach simplifies installation by reusing existing fastening locations while the external mounting configuration accommodates the constraint of being limited to the head assembly portion area.
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
Enables the use of smaller, cost-effective electric motors in commercial vehicles by converting gear ratios externally, allowing existing axle assemblies to support hybrid electric power systems without redesigning internal components.
Implementation Method 1
The planetary gear set can have a central sun gear engaged to planet gears positioned around the sun gear. A ring gear can surround and be engaged to the planet gears. A carrier gear can connect to all the planet gears for rotation with the revolution of the planet gears about the sun gear.
Data Source
AI summary
A gear box having a gear set therein for mounting to the outside of a housing of an axle assembly and connected to the input shaft of the differential of the axle assembly can allow high speed electric motor(s) to connect to the differential via the gear box for driving the axle assembly. The gear box can be mounted using existing bolt hole pattern on the axle assembly housing such as the input cover of the axle head assembly housing the differential. The gear set can be a planetary gear set where the rotor of the electric motor can be rotationally connected to the sun gear and the carrier gear can be connected to the input pinion shaft. In another embodiment an axle assembly having a differential can also have a gear box mounted to the outside of the axle housing and connected to the input pinion shaft to allow use of a high speed electric motor by providing an appropriate gear ratio conversion.