Electric Axle Planetary Gear Assembly With Compact Spline-Ring Shifting
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Solution Overview
Problem
Conventional electric axle drives face challenges in achieving a compact design with minimal axial length while maintaining efficiency and mechanical integrity, particularly due to the need for axial shifting of gear wheels in planetary gear sets.
Innovation Solution
The electric axle drive incorporates an innovative arrangement of planetary gears and pinions, utilizing a spline ring with interlock profiles to facilitate axial movement and prevent coupling or decoupling of gear components, thereby reducing the overall length of the gear assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional planetary gear sets with axial shifting are used, then gear ratio changing capability is improved, but axial length of the gear assembly increases
Solution Approach 1:
The patent transitions from axial shifting (one-dimensional movement along the axle) to radial shifting (two-dimensional movement perpendicular to the axle). The planetary gear sets are designed to shift radially outward or inward relative to the wheel axle, allowing gear ratio changes without increasing axial length. This dimensional change resolves the contradiction by providing adaptability through multiple gear ratios while maintaining a compact axial footprint.
Solution Approach 2:
The patent employs a nested arrangement where the first and second planetary gear sets are positioned concentrically around the wheel axle. The gear components are arranged in nested configurations, with planetary wheels, carriers, and ring wheels nested within each other radially. This nesting allows multiple gear sets to occupy minimal axial space while maintaining the capability for gear ratio changes through radial shifting mechanisms.
2Adaptability or versatility
If axial shifting of planetary gears is implemented, then shiftable gear ratios are achieved, but mechanical complexity and bearing challenges increase
Solution Approach 1:
The patent eliminates the need for complex axial shifting mechanisms and their associated bearing requirements by implementing radial shifting instead. The planetary gear sets shift in the radial direction, which simplifies the mechanical design by avoiding the need for complex axial displacement mechanisms, reducing bearing complexity, and lowering the overall mechanical complexity of the system.
3Length of moving object
If compact gear assembly design is pursued, then axial space is reduced, but power transmission efficiency may be compromised
Solution Approach 1:
The nested concentric arrangement of multiple planetary gear sets allows for efficient power transmission pathways. The direct connection between the first and second planetary gear sets through shared components creates optimized torque transmission routes. This nesting enables compact axial design while maintaining efficient power flow from the input shaft through the differential mechanism to the output shaft, minimizing energy losses despite the reduced axial space.
Solution Approach 2:
The patent merges the functions of multiple planetary gear sets into a unified differential mechanism. The first and second planetary gear sets are integrated through shared carriers and ring wheels, creating a combined system that achieves both compactness and efficient power distribution. This merging eliminates redundant components and optimizes the power transmission path, ensuring high efficiency while maintaining a compact axial footprint.
Data Source
AI summary
An electric axle drive comprises a gear assembly having a first planetary gear set and a second planetary gear set. The gear assembly further comprises a spline ring that is provided with internal splines along an axial direction of the spline ring and that is slidably provided over ring wheel of the first planetary gear set having mating splines on its outer surface. The spline ring comprises an external groove along its circumference, for receiving a first shift actuator element to shift the spline ring in axial directions over the ring wheel. The spline ring further comprises a first interlock profile on one axial side, that locks the spline ring to a corresponding profile provided onto the stationary housing. The spline ring comprises a second interlock profile on an another axial side, that locks the spline ring, when slid by the actuator element to a corresponding profile provided on the carrier.