Simpson Gearbox Layout for High-Speed EV Drag Torque Reduction
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Solution Overview
Problem
Existing vehicle transmissions are not compact and efficient, particularly when combined with high-speed electric machines, leading to drag torques and wobbling issues.
Innovation Solution
A transmission system with a Simpson gearset comprising two planetary gearsets connected via a shifting unit with three shifting elements, allowing for a compact design and efficient gear ratios, including a straight-through gear with minimal tooth losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional transmission design is used, then the structure is simpler, but the transmission is not compact and causes drag torques and wobbling at high rotation speeds
Solution Approach 1:
The patent implements a nested planetary gear configuration where a first planetary gearset is positioned within a second planetary gearset. The first sun shaft and second sun shaft are concentrically arranged, with the first planetary gearwheels meshing with both sun shafts, and the second planetary gearwheels meshing with the sun shafts and ring gear shafts. This nesting arrangement achieves a compact transmission structure that reduces volume while maintaining structural integrity and minimizing drag torques at high rotation speeds.
2Power
If high-speed electric machines are connected to conventional transmissions, then power output is increased, but drag torques and bearing losses increase
Solution Approach 1:
The patent divides the transmission into two separate planetary gearsets with distinct functional roles. The first planetary gearset handles high-speed power transmission from the electric machine through its sun shaft and planetary gearwheels, while the second planetary gearset provides additional gear reduction. This segmentation allows each gearset to operate in its optimal speed range, reducing overall drag torques and bearing losses while maintaining high power output capability.
3Adaptability or versatility
If multiple planetary gearsets are combined, then gear ratios are improved, but the structure becomes more complex
Solution Approach 1:
The patent merges two planetary gearsets into a single integrated transmission unit where the first and second planetary gearsets share common components. The first web shaft and second ring gear shaft are connected, and both gearsets operate from common sun shafts. This merging achieves versatile gear ratio ranges through the combination of the two gearsets while minimizing the number of separate components and simplifying the overall structure.
Data Source
AI summary
A vehicle transmission has a first, second, and third shifting elements. First and second planetary gearsets each have a sun shaft, a ring gear shaft, and a web shaft. The first sun shaft is connected rotationally fixed to the second sun shaft and form the drive input. The first web shaft is connected rotationally fixed to the second ring gear shaft, which is configured as the drive output. The shift elements are combined to form a shifting unit with five shift positions and having a single axially displaceable sliding sleeve. In the closed condition of the first shifting element, the first web shaft and the second ring gear shaft are connected to a stationary component. In the closed condition of the second shifting element, the first ring gear shaft is connected to a stationary component. In the closed condition of the third shifting element, the planetary gearsets are blocked.