EV Power Transmission Layout With Split Axle Cases for Compact Casting
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Solution Overview
Problem
Existing electric-vehicle power transmission units that drive right and left wheels with a single electric motor face challenges in size reduction due to difficulties in casting a mold that maintains the strength of the connection between the axle case and gear cover portion, making it hard to achieve a compact design.
Innovation Solution
The power transmission unit incorporates a motor case positioned on the same side as the second axle, with a separable second axle case fixed to the first axle case housing the reduction and differential gear mechanisms, allowing for easier casting and reducing the overall size by eliminating the need for a single cast connection and optimizing the placement of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the electric motor is placed closer to one of the axles to reduce the size of the power transmission unit, then the size is reduced, but it becomes difficult to form a fixing surface of the motor case while maintaining the strength of the connection between the axle case portion and gear cover portion in a cast structure
Solution Approach 1:
The power transmission unit is divided into separate components: the gear cover portion housing the gear mechanism and the axle case portion supporting the axles. This segmentation allows each component to be optimized independently - the gear cover can be positioned closer to the electric motor to reduce overall size, while the axle case maintains its structural integrity for strong connections, resolving the casting difficulty issue.
2Volume of moving object
If the electric motor is placed closer to one of the axles to reduce the size of the power transmission unit, then the size is reduced, but the strength of the connection between the axle case portion and gear cover portion is compromised
Solution Approach 1:
By separating the gear cover portion from the axle case portion, the design allows the gear cover to be repositioned closer to the electric motor for compactness, while the axle case maintains its original robust structure and connection points, preserving the strength of the connection between components.
3Ease of manufacture
If a single cast structure is used to house both the axle and gear mechanism, then manufacturing is simplified, but the ability to optimize component placement for size reduction is limited
Solution Approach 1:
The power transmission unit is divided into separate cast components - the gear cover portion and the axle case portion. This allows each component to be cast independently with optimized geometries, enabling the gear cover to be positioned closer to the electric motor for size reduction while maintaining manufacturing simplicity through separate, well-defined casting operations.
Solution Approach 2:
While the unit is segmented into separate cast components, the gear cover portion and axle case portion are combined through fixed connection to form an integrated power transmission unit. This merging allows the benefits of separate casting (optimized placement and size reduction) while maintaining the structural integrity and simplicity of a unified assembly.
Data Source
AI summary
Disclosed is a power transmission unit including a motor case that is provided on the same side as a second axle with respect to a center between a first axle and the second axle, separated to right and left, in a right-left direction and that houses the electric motor, a first axle case housing a reduction gear mechanism, a differential gear mechanism, and the first axle, and a second axle case that is fixed to the first axle case in a separable manner and houses the second axle.