Step Pinion Two-Speed Transmission With Nested Reduction Gearing
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Solution Overview
Problem
Existing multi-speed transmissions for electric commercial vehicles require compact designs with large torque multiplication ratios, which traditional step pinion planetary gear sets struggle to achieve, especially in maintaining small size and achieving necessary high and low range gear ratios.
Innovation Solution
The transmission design incorporates a step pinion planetary gear set with two sun gears and a primary reduction gear set, where one sun gear and the second ring gear are rigidly fixed, allowing for selective shifting between high and low gear ratios through a synchronizing clutch assembly, enabling larger gear ratios within a compact axial and radial footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single step pinion planetary gear set is used, then the structure is simple, but the gear ratio is insufficient
Solution Approach 1:
The patent combines a step pinion planetary gear set with a primary reduction gear set into a single integrated transmission system. The step pinion gear set provides two different gear ratios through its design, while the primary reduction gear set provides additional torque multiplication, achieving a maximum overall gear ratio of 24:1 without requiring multiple separate gear sets.
2Productivity
If additional sun gears are added to increase gear ratios, then the ratio capability improves, but the axial and radial size increases
Solution Approach 1:
The primary reduction gear set is positioned within the same radial space as the step pinion planetary gear set, with both gear sets sharing a common central axis. The pinion gears of the step pinion set mesh with both sun gears, and the entire assembly is contained within a single radial envelope, minimizing the overall transmission size while achieving high gear ratios.
3Volume of moving object
If a compact transmission design is implemented, then the vehicle integration is improved, but the torque multiplication ratio is reduced
Solution Approach 1:
The patent merges the functions of multiple gear sets into a single integrated assembly where the step pinion planetary gear set and primary reduction gear set work together. This combination achieves a maximum gear ratio of 24:1 within a compact single-radial-envelope design, providing sufficient torque multiplication for heavy-duty electric vehicles without requiring a large transmission housing.
Data Source
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AI summary
A family of two speed transmissions has a plurality of members that can be utilized in drive trains to provide varying gear ratios. The transmission family members include step pinion planetary gear sets. In one embodiment, there is a single step pinion planetary gear set with two sun gears configured selectively as the transmission input, two ring gears, one of which is rigidly attached to ground and the other is configured to act as the transmission output. In another embodiment, there is removed one of the ring gears and there is added a planetary reduction gear set comprised of a sun gear, a ring gear rigidly attached to ground and a planetary carrier configured to act as the transmission output. In another embodiment, there is provided a transmission comprising a plurality of helical gear sets and a planetary gear set for speed reduction.