EV Axle Assembly With Common Shaft and Dual Motor Spur Gear
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Solution Overview
Problem
Existing axle assemblies for electric vehicles face inefficiencies due to multiple bearing units causing friction and mechanical losses, and they often require complex gear configurations that complicate packaging and electromagnetic optimization.
Innovation Solution
The axle assembly incorporates a common shaft shared by two electric machines and a non-shiftable spur gear unit coupled with a differential gear unit, reducing the number of bearing units and allowing for compact, efficient power transfer with minimal electromagnetic losses by optimizing the electric machines for different operational points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple bearing units are used to support the shafts and gear units, then the mechanical support and stability are improved, but the friction and mechanical losses increase
Solution Approach 1:
The patent combines multiple shaft functions into a common shaft that serves as the output shaft for both the first and second electric machines simultaneously. This merging eliminates the need for separate bearing units for each shaft, reducing the total number of bearing units from four to two, thereby reducing friction and mechanical losses while maintaining adequate mechanical support
Solution Approach 2:
The common shaft performs multiple functions: it serves as the output shaft for the first electric machine, the output shaft for the second electric machine, and the input shaft for the spur gear unit all at once. This multi-functionality reduces the number of components and bearing units required, addressing the contradiction between reliability and energy loss
2Device complexity
If a single electric machine is used, then the device complexity is reduced, but the packaging efficiency and electromagnetic optimization across different operational points are compromised
Solution Approach 1:
The patent segments the electric machine function into two separate electric machines (first and second electric machines) that can be independently optimized for different operational points. This segmentation allows each machine to be tailored for specific performance characteristics, improving overall packaging efficiency and electromagnetic efficiency across a broader range of driving conditions
Solution Approach 2:
Each electric machine is optimized for different operational points or ranges, creating local quality optimization. The first electric machine can be optimized for one operational range while the second is optimized for another, ensuring high electromagnetic efficiency across the entire operational spectrum rather than compromising a single machine to cover all ranges
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 configuration enhances mechanical and electromagnetic efficiency by reducing friction, improving packaging, and enabling operation over a broad range of driving conditions with fewer bearings and optimized electric machine performance.
Implementation Method 1
a drive power being generated by the first electric machine and/or the second electric machine
Implementation Method 2
a spur gear stage and a differential gear unit. The at least one spur gear stage is drivingly coupled to the differential gear unit
Implementation Method 3
The differential gear unit comprises a ring gear and a bevel gear unit having four bevel years being rotatorily supported on a bevel gear cage
Data Source
Figure 1~2
Figure 3
AI summary
The disclosure relates to an axle assembly (16) for an electric vehicle. The axle assembly (16) comprises a first electric machine (18), a second electric machine (20), and a spur gear unit (22) comprising at least one spur gear stage (24) and a differential gear unit (26). The at least one spur gear stage (24) is drivingly coupled to the differential gear unit (26). Moreover, an output shaft of the first electric machine (18), an output shaft of the second electric machine (20), and an input shaft of the spur gear stage (24) are formed by a common shaft (36). Additionally, the differential gear unit (26) comprises a first output flange (66) for drivingly coupling a first wheel (14) to the axle assembly (16) and a second output flange (68) for drivingly coupling a second wheel (14) to the axle assembly (16). Furthermore, a vehicle comprising such an axle assembly (16) is presented. The differential gear unit (26) is arranged centrally with respect to a vehicle width direction (W). Also a method for operating such an axle assembly (16) is described.