Split-Carrier Gearwheel Structure for High-Ratio EV Transmissions
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Solution Overview
Problem
Spur gear drives in electric vehicle transmissions face limitations in achieving high gear ratios with low weight and minimal losses, leading to noise issues and increased weight due to the need for multiple gear pairs, which are not suitable for high-speed applications like electric motorsports.
Innovation Solution
A weight-optimized gearwheel design featuring a toothed ring with a gearwheel carrier formed by two partially axially spaced partial carriers, a pinion engagement, and a specific center distance, allowing for a high gear ratio with reduced weight and improved stability, using a single gearwheel pair and a differential housing for efficient power transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single spur gear pair is used to achieve high gear ratio, then the transmission structure is simple, but the coverage (number of teeth in engagement) becomes small and dimensional stability is compromised
Solution Approach 1:
The gearwheel carrier is divided into two partial carriers that are axially spaced apart, creating a segmented support structure. This segmentation allows the toothed ring to be supported at multiple locations along its circumference, improving dimensional stability without requiring a single complex monolithic carrier structure.
2Speed
If multiple gearwheel pairs are used to achieve high gear ratio, then the gear ratio is achieved, but the transmission weight increases and transmission losses increase
Solution Approach 1:
Instead of achieving high gear ratio through multiple gear pairs in sequence (one-dimensional approach), the invention uses a single gear pair with an optimized carrier structure that spans axially (introducing a second dimension). The two partial carriers spaced apart axially create a larger effective support baseline, enabling high gear ratio in a single stage without the weight penalty of multiple gear pairs.
3Ease of manufacture
If the toothed ring is supported by a single monolithic carrier, then the structure is simple, but the weight cannot be optimized and stability at high rotational speeds is compromised
Solution Approach 1:
The monolithic carrier is segmented into two partial carriers that can be manufactured separately and then assembled. This segmentation enables weight optimization by removing unnecessary material from each partial carrier while maintaining structural integrity through the distributed support of the toothed ring at multiple axial locations.
4Object-affected harmful factors
If helical-cut gearwheels are used to reduce noise, then noise development is reduced, but axial load increases which requires additional support structure
Solution Approach 1:
The invention addresses the axial load issue by extending the support structure in the axial dimension. The two partial carriers spaced apart axially create a longer support baseline, distributing the axial loads from helical teeth engagement over a greater distance. This allows the use of helical-cut gearwheels for noise reduction without requiring excessively thick or heavy carrier structures.
Data Source
AI summary
A gearwheel (20) for a gear step in an electric vehicle transmission (18) includes a gearwheel carrier and a toothed ring (30) having an external toothing (42). The toothed ring is rotationally fixable to the gearwheel carrier. The gearwheel carrier is formed by a first partial carrier (38) and a second partial carrier (40) that are at least partially axially spaced apart and extend from the toothed ring radially inward. An axial spacing of the two partial carriers is greater, at least partially, than an axial length of the toothed ring.