Step Pinion Planetary Transmission for Compact High Gear Ratios
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Solution Overview
Problem
Existing multi-speed transmissions for electric commercial vehicles face challenges in achieving the necessary gear ratios while maintaining a compact axial and radial design, as standard planetary or step pinion gear sets often fail to provide sufficient ratios, especially when integrated with other components in gearbox assemblies.
Innovation Solution
The proposed multi-speed transmission design incorporates a primary reduction gear set and a step pinion planetary gear set with multiple sun and ring gears, where the first sun gear acts as the transmission input and the second planetary carrier as the output, spaced along the same longitudinal axis, along with a synchronizing clutch assembly to selectively shift between high and low gear ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If standard planetary or step pinion gear sets are used, then the transmission can be kept compact, but the gear ratios achieved are insufficient for vehicle requirements
Solution Approach 1:
The patent applies nesting by placing the step pinion planetary gear set inside the planetary gear set, with the step pinion carrier positioned within the planetary carrier. This nested configuration allows both gear sets to occupy the same radial space while providing compounded gear ratios, achieving sufficient ratio multiplication without increasing the transmission's radial footprint.
Solution Approach 2:
The patent extends the transmission design into the axial dimension by arranging the planetary gear set and step pinion planetary gear set along the same longitudinal axis with their respective inputs and outputs spaced axially. This dimensional arrangement allows the transmission to achieve high gear ratios through axial stacking of gear sets rather than radial expansion, maintaining radial compactness while increasing the axial length to accommodate the necessary ratio multiplication.
2Productivity
If additional sun gears are added to increase gear ratios, then the ratio requirement may be met, but the radial diameter of the transmission increases
Solution Approach 1:
The patent applies nesting by placing the step pinion planetary gear set inside the planetary gear set, with the step pinion carrier positioned within the planetary carrier. This nested configuration allows both gear sets to occupy the same radial space while providing compounded gear ratios, achieving sufficient ratio multiplication without increasing the transmission's radial footprint.
3Productivity
If multiple gear assemblies are combined to achieve necessary ratios, then the gear ratio requirement is met, but the axial cross section of the transmission increases
Solution Approach 1:
The patent merges the planetary gear set and step pinion planetary gear set into a single integrated transmission assembly. Both gear sets share common components including the ring gear, planet gears, and carrier structure. This merging reduces the total axial length compared to using separate gear assemblies, as the components are consolidated into one compact unit rather than stacked as independent assemblies.
Data Source
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.