Nested Planetary Transmission Layout for Compact EV Gear Shifting
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Solution Overview
Problem
Existing transmissions for electric vehicles, particularly heavy-duty vehicles like trucks and construction equipment, require shiftable transmissions that are not always necessary and can be improved for compactness and efficiency.
Innovation Solution
A transmission arrangement comprising a first planetary gearset and a second planetary gearset, with additional reduction gearsets and a differential gearset, allowing for multiple gear states and compact configuration, including the use of smaller gearwheels and power units to achieve favorable speed ratios and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a shiftable transmission is used for electric heavy-duty vehicles, then favorable speed ratios can be achieved for different driving situations, but the transmission arrangement becomes larger and more complex
Solution Approach 1:
The patent employs nested planetary gearsets where the second planetary gearset is positioned inside the first planetary gearset, and the third planetary gearset is positioned inside the second planetary gearset. This nested configuration allows multiple gear reduction stages to be compacted into a single transmission arrangement, achieving favorable speed ratios while minimizing transmission volume and avoiding the need for multiple separate transmissions.
2Volume of moving object
If larger speed ratios are placed further downstream in the transmission arrangement, then compactness is improved, but torque values increase upstream components
Solution Approach 1:
The patent segments the total speed reduction into multiple independent planetary gearsets (first, second, and third planetary gearsets), each providing a portion of the overall reduction ratio. This segmentation allows the torque to be distributed across multiple stages rather than concentrated in one large reduction stage, enabling compact design while managing torque values at each stage.
Solution Approach 2:
The nested configuration of planetary gearsets allows each subsequent gearset to be positioned inside the previous one, creating a compact arrangement where larger speed ratios are achieved downstream without proportionally increasing the overall transmission volume. The nested structure optimizes space utilization while distributing torque loads.
Data Source
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AI summary
The disclosure relates to a transmission arrangement (1) for a vehicle (200), comprising a first planetary gearset (2), a first secondary reduction gearset (3), a second planetary gearset (4), and at least one drive shaft (51, 52). The disclosure also relates to a powertrain (100) and a vehicle (200).