Step-Pinion Multi-Speed Transmission for High Torque Ratios
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Solution Overview
Problem
Existing multi-speed transmissions for electric commercial vehicles face challenges in achieving large torque multiplication ratios while maintaining a compact axial and radial design, as typical step pinion planetary gear sets often fail to provide sufficient gear ratios, especially when integrated with other components within gearbox assemblies.
Innovation Solution
The transmission design incorporates a single step pinion planetary gear set with two sun gears and ring gears, where one ring gear is grounded, and a synchronizing clutch assembly to selectively shift between high and low gear ratios, allowing power transfer through interconnected pinion gears, enabling larger gear ratios within a compact footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single step pinion planetary gear set is used, then the transmission maintains a compact design, but the gear ratio is insufficient
Solution Approach 1:
The patent segments the single planetary gear set into two independent sun gear systems (first sun gear with first pinions, second sun gear with second pinions) that share a common ring gear. This segmentation allows each sun gear to be independently controlled by separate clutches, enabling multiple gear ratios while maintaining a compact single-gear-set structure.
Solution Approach 2:
The ring gear serves multiple functions: it acts as the common output for both sun gear systems and provides the fixed reference structure for both planetary systems. This multi-functionality allows the single gear set to deliver multiple gear ratios without requiring additional gear sets, maintaining compactness while improving productivity.
2Productivity
If additional sun gears are added to increase gear ratio, then the torque multiplication increases, but the axial dimension increases
Solution Approach 1:
The patent nests the second sun gear and its pinions within the same radial space as the first sun gear system, with both systems sharing the common ring gear. The second plurality of pinions is positioned axially between the first sun gear and the ring gear, creating a nested configuration that increases torque multiplication without proportionally increasing axial dimension.
Solution Approach 2:
Instead of arranging gear elements sequentially along the axial dimension, the patent utilizes the radial and circumferential dimensions by implementing two independent sun gear systems that share the common ring gear. This dimensional reorganization allows multiple gear ratios to be achieved within a compact axial footprint.
3Productivity
If two independent planetary gear sets are used to achieve multiple ratios, then the gear ratio range increases, but the device complexity increases
Solution Approach 1:
The patent merges two planetary gear systems into a single integrated structure by sharing the ring gear between both sun gear systems. This consolidation reduces the total number of independent gear sets while maintaining the capability to achieve multiple gear ratios through independent clutch control of each sun gear.
Solution Approach 2:
The common ring gear performs multiple functions: it serves as the output for both planetary systems, provides the fixed reference for both systems, and enables both sun gears to independently generate different gear ratios. This multi-functionality reduces device complexity while expanding the gear ratio range.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration achieves the required gear ratios of 24:1 in low range and 14:1 in high range, or 17.9:1 and 8.8:1, while maintaining a compact size, allowing for efficient torque transmission and flexible gear shifting, thus addressing the need for compact and high-ratio transmissions.
Implementation Method 1
a first plurality of interconnected pinion gears meshing with the first sun gear and first ring gear with a second plurality of interconnected pinions meshing with the second sun gear and the second ring gear
Implementation Method 2
first and second input clutches driveably connected to the transmission input so that the first and second input clutches may be actuator so that either the first input clutch or the second input clutch operates as the transmission input
Data Source
Figure 1
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Figure 4
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.