Dual-Motor Reduction Architecture for EV Launch Torque and High-Speed Power
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Solution Overview
Problem
Existing electrified vehicles face challenges in achieving high torque at low speeds and high power at high speeds without the performance compromises associated with multispeed transmissions, particularly in performance and off-road vehicles.
Innovation Solution
A dual electric motor system with one low torque and one high torque motor, combined with reduction assemblies, including a one-way clutch, to provide high torque at launch and high power at high speeds without a multispeed gearbox, using a combination of reduction ratios to optimize torque distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a multispeed transmission is used to achieve high torque at launch and high power at high speeds, then vehicle performance is improved, but gear shifting adversely affects performance characteristics and increases device complexity
Solution Approach 1:
The powertrain is segmented into two separate electric motors instead of using a single motor with a multispeed transmission. The first motor (50-100 Nm) handles high-torque launch conditions through a high reduction ratio (8-12), while the second motor (400-500 Nm) handles high-speed cruising through a lower reduction ratio (3-5). This segmentation eliminates the need for gear shifting while maintaining optimal performance across the entire operating range.
Solution Approach 2:
The solution transitions from a single motor with variable transmission ratios (one-dimensional solution) to a two-motor system with fixed reduction ratios (adding the dimension of multiple power sources). This dimensional change allows each motor to operate in its optimal efficiency range simultaneously, eliminating the compromise inherent in single-motor multispeed systems.
2Speed
If a single electric motor with high power is used, then high speed performance is achieved, but torque at launch is insufficient
Solution Approach 1:
Two electric motors with complementary characteristics are merged into a single powertrain system. The first motor is optimized for high torque output at low speeds with a high reduction ratio, while the second motor is optimized for high speed operation with a lower reduction ratio. The merging of these two motors allows the vehicle to achieve both high launch torque and high top speed without the compromises of using a single oversized motor.
3Force
If a single electric motor with high torque is used, then launch performance is improved, but power at high speeds is insufficient
Solution Approach 1:
Each motor is designed with local quality optimized for its specific operating domain. The first motor has characteristics (higher reduction ratio of 8-12) specifically tailored for high-torque launch conditions, while the second motor has characteristics (lower reduction ratio of 3-5) specifically tailored for high-speed power delivery. This localized optimization of each motor's reduction ratio ensures peak performance in its respective operating range without compromising the other.
Data Source
AI summary
An electric drive module for an electrified vehicle includes first and second electric motors, first and second reduction assemblies and a driveline. The first electric motor has a first rotatable output. The second electric motor has a second rotatable output. The first electric motor has a lower output capacity than the second electric motor. The first reduction assembly is driven by the first rotatable output and includes a first reduction output that is coupled to the second electric motor. The second reduction assembly is driven by the second rotatable output of the second electric motor. The first reduction assembly and the second reduction assembly cooperate to provide a combined first effective reduction ratio driven by the first rotatable output and wherein the second reduction assembly provides a second effective reduction ratio driven by the second rotatable output, the first effective reduction ratio being higher than the second first effective reduction ratio.