Four-Speed EV Transmission Using Nested Planetary Gearsets
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Solution Overview
Problem
Traditional transmissions configured for internal combustion engines are overly complex and inefficient in electric drive trains, necessitating simpler and more reliable transmission designs for electric vehicles.
Innovation Solution
A drive system for fully electric or hybrid vehicles incorporating a first and second planetary gearset with synchronizers and clutches/brakes, allowing for selective coupling of gear components to achieve various gear ratios and simplify the transmission design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional transmissions configured for internal combustion engines are used in electric drive trains, then the transmission can provide multiple gear ratios, but the device complexity increases and reliability decreases due to more components
Solution Approach 1:
The transmission is divided into two separate planetary gearsets (first and second planetary gearsets), each capable of independently providing gear ratios. This segmentation allows the system to achieve multiple gear ratios through different combinations of the two gearsets, reducing the complexity of any single gearset while maintaining overall versatility.
Solution Approach 2:
The second planetary gearset is nested within the first planetary gearset, with the carrier of the first planetary gearset coupled to the sun gear of the second planetary gearset. This nested configuration allows both gearsets to occupy the same space and work together to provide multiple gear ratios without requiring separate housings or additional external components.
2Adaptability or versatility
If traditional transmissions configured for internal combustion engines are used in electric drive trains, then the transmission can provide multiple gear ratios, but the reliability worsens due to more wear parts
Solution Approach 1:
By dividing the transmission into two planetary gearsets, each with its own synchronizer (first synchronizer for the first planetary gearset, second synchronizer for the second planetary gearset), the wear is distributed across multiple simpler components rather than concentrated in a single complex mechanism, improving overall reliability.
Solution Approach 2:
The transmission uses dynamic engagement of synchronizers to selectively couple or decouple the planetary gearsets and their components (ring gears, carriers, sun gears) based on the desired gear ratio. This dynamic reconfiguration allows the system to adapt to different operating conditions while maintaining reliability through controlled engagement of wear parts.
3Adaptability or versatility
If traditional transmissions configured for internal combustion engines are used in electric drive trains, then the transmission can provide multiple gear ratios, but the efficiency decreases
Solution Approach 1:
The transmission dynamically engages or disengages the first and second synchronizers based on the required gear ratio and operating conditions. This allows the system to selectively use only the necessary planetary gearset for each operating mode, minimizing energy losses associated with unnecessary component engagement and mechanical friction.
Solution Approach 2:
The transmission changes the effective gear ratio by altering the engagement state of the synchronizers, which couple or decouple the ring gears, carriers, and sun gears of the planetary gearsets. This parameter change approach allows smooth transitions between different gear ratios with minimal energy loss compared to traditional mechanical shifting mechanisms.
Data Source
AI summary
A drive system for a hybrid or electric vehicle that includes a transmission with four forward and four reverse gears. The transmission optionally includes a first and a second planetary gearset, and optionally a first and second range selector assembly. The range selector assemblies may include a clutch and a brake, and/or a synchronizer. The drive system may include a single electric motor with any example of a transmission of the present disclosure, or multiple electric motors individually driving separate transmissions. The motors may be arranged upstream or downstream of portions of a transmission, and they may be aligned parallel with or perpendicular to a drive axle, input shaft, output shaft, and any suitable combination thereof. An internal combustion engine may be included as well.