Two-Speed Planetary Gearbox for EV Off-Road Torque and Range
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Solution Overview
Problem
Battery electric vehicles typically have single-speed gearboxes that cannot provide sustained high torque required for off-road driving, which is a limitation for both performance and range in on-road usage.
Innovation Solution
A two-speed gearbox assembly with twin planetary gear sets and independently controlled clutches allows for selective engagement of different gear ratios, enabling both on-road and off-road performance with a single electric motor, eliminating the need for complex and costly dual motors or high-power inverters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If higher ratio gearing is used to provide sustained high torque, then off-road torque capability is improved, but on-road performance and range are worsened
Solution Approach 1:
The patent implements a two-speed gearbox with selectable gear ratios that allows the vehicle to dynamically switch between on-road and off-road modes. The system uses clutches to engage different planetary gear set configurations, enabling the vehicle to adapt its torque multiplication ratio based on driving conditions, thus resolving the contradiction between sustained high torque needs and energy efficiency
2Force
If additional gearing in the transfer case is used for off-road driving, then torque capability is improved, but device complexity is worsened
Solution Approach 1:
The patent combines two planetary gear sets within a single transfer case housing, sharing common components such as the input shaft and differential. This merging approach provides multiple gear ratios and torque capabilities while minimizing the increase in overall system complexity compared to using separate gearing systems
Solution Approach 2:
The transfer case is designed to perform multiple functions: it provides both on-road and off-road gear ratios, incorporates differential locking capabilities, and enables torque distribution to multiple axles. This multi-functionality reduces the need for separate specialized systems, thereby managing complexity while delivering enhanced torque capability
3Ease of operation
If independent control of axle rotation is implemented, then maneuverability is improved, but device complexity is worsened
Solution Approach 1:
The patent divides the clutch control system into separate, independently controllable units for each axle and each clutch position. This segmentation allows each clutch to be controlled independently to achieve different drive modes (e.g., four-wheel drive, two-wheel drive, differential locking), providing enhanced maneuverability while keeping individual control units relatively simple
Data Source
AI summary
A two-speed gearbox assembly for an electric drive vehicle includes a housing, a first planetary gear set configured to operably connect to an output of an electric motor to drive a first axle, the first planetary gear set including a first sun gear, a first carrier, and a first ring gear, a first clutch configured to selectively ground the first ring gear, and a second clutch configured to selectively ground the first carrier. A second planetary gear set is configured to operably connect to the output of the electric motor to drive a second axle, the second planetary gear set including a second sun gear, a second carrier, and a second ring gear. A third clutch is configured to selectively ground the second ring gear, and a fourth clutch is configured to selectively ground the second carrier. The first, second, third, and fourth clutches are independently controlled.