Multi-Stage Planetary Transmission for Electric Vehicles
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Solution Overview
Problem
Existing drive devices for electric vehicles lack a compact and efficient multi-speed transmission system that allows for high efficiency at both high and low speeds, while also simplifying lightweight construction and enabling reverse gears without additional motor components.
Innovation Solution
A drive device with a multi-stage transmission featuring three planetary gear stages, where the planetary gear carriers of the second and third stages are permanently connected, and a third switching unit connects the planet carrier of the second stage torque-proof to the third stage, allowing for compact design, efficient torque delivery, and adaptive gear ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multi-stage transmission with three planetary gear stages is implemented, then different forward gears can be achieved for efficient torque delivery at various speeds, but the device complexity increases
Solution Approach 1:
The patent merges multiple planetary gear stages (first, second, and third planetary gear sets) into a single integrated transmission system. The planetary gear carriers are permanently connected to each other, combining the functions of multiple gear stages into one compact structure, thereby achieving multiple gear ratios without proportionally increasing overall system complexity
Solution Approach 2:
The transmission system employs nested planetary gear sets where the first, second, and third planetary gear sets are arranged concentrically around a common rotation axis. This nesting allows multiple gear stages to occupy overlapping spatial volumes, reducing the overall footprint while maintaining the complexity of multi-stage gearing
2Strength
If permanently non-rotatable connections are used between planetary gear carriers, then structural stability and torque-proof connection are improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent combines multiple torque-proof connections into a unified structural arrangement where planetary gear carriers are permanently connected through integrated mounting structures. This merging of connection functions reduces the number of separate fastening operations and simplifies the manufacturing process while maintaining strong torque transmission capability
Solution Approach 2:
The transmission system is segmented into modular planetary gear sets that can be manufactured and tested independently before final assembly. Each planetary gear set with its permanent connections can be produced as a standardized module, reducing overall manufacturing complexity despite the strength requirements
3Volume of moving object
If the planetary gear carrier of the second stage is permanently connected to the third stage, then the drive device becomes more compact, but the adaptability for different operating conditions decreases
Solution Approach 1:
The permanent connection of planetary gear carriers enables nested arrangement of planetary gear sets, allowing them to occupy overlapping radial and axial spaces. This nesting dramatically reduces the transmission volume while the switching units provide operational flexibility by selectively engaging or disengaging specific gear stages based on driving conditions
4Productivity
If switching units are used to connect planetary gear carriers torque-proof, then the multi-speed transmission can be implemented, but the device complexity increases
Solution Approach 1:
The patent combines the switching function with the permanent connection structure of the planetary gear carriers. The switching units are integrated into the carrier mounting arrangement, merging the gear selection function with the structural connection function, thereby reducing overall device complexity while maintaining multi-speed capability
Data Source
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AI summary
The invention relates to a drive device, in particular for an electric vehicle, comprising an electric motor (10a-e), an axle drive (11a-e), and a multistage transmission (12a-e) which is arranged between the electric motor (10a-e) and the axle drive (11a-e), which is structurally designed to shift at least two forward transmission gears (V1a-e, V2a-e, V3a-e), and which has precisely three operatively interconnected planetary gear stages (P1a-e, P2a-e, P3a-e) with sun gears (P11a-e, P21a-e, P31a-e), ring gears (P13a-e, P23a-e, P33a-e), and planetary gear carriers (P12a-e, P22a-e, P32a-e); a transmission input element (13a-e) for attaching the electric motor (10a-e) in a rotationally fixed manner; and a transmission output element (14a-e) for attaching the axle drive (11a-e) in a rotationally fixed manner. The transmission input element (13a-e) is connected to the sun gear (P11a-e) of the first planetary gear stage (P1a-e) in a permanently rotationally fixed manner; the transmission output element (14a-e) is connected at least to the planetary gear carrier (P32a-e) of the third planetary gear stage (P3a-e) in a permanently rotationally fixed manner; and at least the planetary gear carrier (P12a-e) of the first planetary gear stage (P1a-e) and the sun gear (P31a-e) of the third planetary gear stage (P3a-e) are connected together in a permanently rotationally fixed manner.