EV Drivetrain Multi-Motor Transmission for Shift-Continuous Traction
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Solution Overview
Problem
Existing drive devices for electric vehicles, particularly off-road commercial vehicles, face challenges in achieving high driving comfort due to limitations in power transmission and gear ratio switching, which can result in interruptions in tractive power and reduced driving range.
Innovation Solution
A drive device comprising multiple electric machines and a transmission system with switchable gear ratios, where a first electric machine is connected to the input shaft and a second electric machine is permanently connected to the output side, allowing for continuous tractive power and flexible gear ratio adjustments via an intermediate clutch and countershaft, enabling efficient power distribution and maintaining drive power during gear changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electric machine is connected to the input shaft of the transmission, then the structure is simple, but interruptions in tractive power occur during gear ratio switching
Solution Approach 1:
The drive device is segmented into two independent electric machines: a first electric machine connected to the input shaft for gear ratio changes, and a second electric machine permanently connected to the output side for continuous power delivery. This segmentation allows each machine to perform its specific function without interfering with the other, eliminating power interruptions during transmission shifts.
Solution Approach 2:
The transmission acts as an intermediary between the first electric machine and the output side. During gear ratio changes, the transmission can temporarily disconnect from the first electric machine while the second electric machine maintains the power connection, serving as a mediator that allows smooth transition without power interruption.
2Reliability
If multiple electric machines are added to provide continuous power during gear changes, then driving comfort improves, but device complexity increases
Solution Approach 1:
The second electric machine serves multiple functions: it provides continuous tractive power during gear changes, acts as a backup power source, and can independently drive the vehicle. This multi-functionality justifies the addition of the second machine by maximizing its utility across different operating conditions.
Solution Approach 2:
The system dynamically switches between different power delivery modes: during normal operation, the first electric machine provides power through the transmission; during gear changes, the system transitions to rely on the second electric machine for continuous power while the transmission ratio changes. This dynamic adaptation optimizes performance while managing complexity.
3Adaptability or versatility
If gear ratio switching is implemented in the transmission, then adaptability to different driving conditions improves, but interruptions in power transmission occur
Solution Approach 1:
The second electric machine is permanently connected to the output side of the transmission, ensuring that power delivery to the drive axles is continuous at all times. While the first electric machine and transmission undergo gear ratio changes, the second electric machine maintains uninterrupted power flow, ensuring continuous useful action is delivered to the wheels.
Data Source
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AI summary
The invention relates to a drive unit (7) for a motor vehicle powertrain of an electric vehicle, comprising several electric motors (12, 13, 14) and a transmission in which different gear ratios can be selected between an input shaft and an output side. A first electric motor (13) is connected to, or can be connected to, the input shaft of the transmission, the output side of the transmission being coupled to at least one output (9, 10) which, in the motor vehicle powertrain, serves to connect each of the drive axles of the electric vehicle. To achieve the highest possible driving comfort via this drive unit (7), a second electric motor (14) is also permanently connected to the output side.