Two-Speed Countershaft Transmission Layout for High Input Speeds
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Solution Overview
Problem
Existing multi-speed transmissions for electric vehicles face issues such as increased package size, weight, and decreased efficiency due to additional gears, shafts, and bearings, which are not suitable for space-constrained vehicle platforms and demand higher torque ratios.
Innovation Solution
A two-speed countershaft transmission system with two wet friction clutches and an optional layshaft, allowing high input speeds and reduced slip speeds, along with a compact layout that supports various vehicle platforms and electric motor configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If additional gears, shafts, and bearings are added to compensate for high input speeds, then the transmission can handle high input speeds, but the package size and weight increase
Solution Approach 1:
The patent employs dynamic clutch engagement strategies where the second wet friction clutch is selectively engaged based on input speed conditions. At high input speeds, the second clutch engages the input shaft directly, bypassing the need for additional speed-reducing gears and shafts. This dynamic switching allows the transmission to handle high input speeds without permanently incorporating the bulkier mechanical components, thus resolving the contradiction between speed capability and package size.
2Speed
If additional gears, shafts, and bearings are added to compensate for high input speeds, then the transmission can handle high input speeds, but the weight increases
Solution Approach 1:
The transmission system dynamically engages the second wet friction clutch to directly connect the input shaft at high speeds, eliminating the need for heavy additional gears, shafts, and bearings that would be required to mechanically handle high input speeds through the entire transmission. This conditional engagement strategy reduces overall weight while maintaining high-speed capability.
3Adaptability or versatility
If additional gears, shafts, and bearings are added to the transmission, then the gear ratios can be increased, but the complexity and size of the housing increase
Solution Approach 1:
The second wet friction clutch serves multiple functions: it engages the input shaft directly at high speeds, provides an alternative power transmission path, and enables the transmission to achieve high gear ratios without adding complex housing structures. This multi-functional component allows the same housing to accommodate both high-speed direct engagement and traditional gear transmission paths, resolving the contradiction between gear ratio versatility and housing complexity.
4Adaptability or versatility
If additional gears, shafts, and bearings are added to the transmission, then the torque ratio can be increased, but the overall efficiency decreases
Solution Approach 1:
The transmission dynamically selects the optimal power transmission path based on operating conditions. At high input speeds, the second wet friction clutch engages to provide a direct connection, minimizing energy losses that would occur through multiple gear meshes. This dynamic path selection maintains high efficiency while still providing access to high torque ratios when needed, resolving the contradiction between torque ratio capability and overall efficiency.
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
The system achieves high efficiency, flexibility, and compactness by reducing slip speeds and maintaining shift quality across different electric motors, while allowing for adjustable torque ratios and motor compatibility.
Implementation Method 1
a first wet friction clutch positioned to selectively engage the countershaft and a second wet friction clutch positioned to selectively engage the input shaft
Data Source
AI summary
Systems and methods for an electric transmission system are herein provided. The electric transmission system, in one example, comprises an electric motor driving an input shaft, a first wet clutch position on a first end of a countershaft, and a second wet clutch positioned on a second end of the input shaft. The first wet clutch selectively engages the countershaft with a first clutch gear and the second wet clutch selectively engages the input shaft with second clutch gear. The input shaft meshes with the second clutch gear and the countershaft meshes with the first clutch gear. The electric transmission system further comprises an output shaft rotationally coupled to the countershaft.