Electric Drive Transmission with Nested Planetary Gears
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Solution Overview
Problem
Existing transmission devices for electric vehicle drives face challenges in achieving a compact design and low-loss operation while minimizing weight, cost, and space requirements.
Innovation Solution
The transmission device incorporates a third planetary gear set with a switching element that allows the third ring gear or planet carrier to be fixed to the housing, along with a non-rotatable coupling between the first ring gear and second sun gear, and an inverse Ravigneaux configuration of the second and third planetary gear sets, enabling efficient torque transmission and reducing the need for additional final drives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a transmission device with multiple planetary gear sets is used to achieve compact design and low-loss operation, then transmission efficiency and compactness are improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the final drive function into the third planetary gear set, eliminating the need for a separate final drive unit. The third ring gear is permanently coupled to the output shaft, integrating multiple functions into a single compact transmission device that reduces overall complexity while maintaining low transmission losses.
Solution Approach 2:
The patent employs a nested arrangement where the second planetary gear set is positioned within or adjacent to the third planetary gear set, and the first planetary gear set is coupled to the second. This nesting approach achieves compact design with reduced installation space while maintaining efficient torque transmission through multiple gear stages.
2Volume of moving object
If additional planetary gear sets are added to reduce installation space and eliminate final drives, then volume and space requirements are reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The final drive function is merged into the third planetary gear set by permanently coupling the third ring gear to the output shaft. This integration eliminates the need for a separate final drive unit, reducing overall transmission volume while the modular planetary gear design maintains manufacturing feasibility through standardized components.
Solution Approach 2:
The transmission is segmented into three distinct planetary gear sets, each with specific functions. The first planetary gear set handles initial torque multiplication, the second provides intermediate gear ratios, and the third serves as the final drive. This segmentation allows for modular manufacturing and assembly, reducing overall manufacturing difficulty despite the complex functionality.
3Area of stationary object
If the third planetary gear set is used with permanent coupling to achieve compact design, then installation space is reduced, but adaptability and versatility are limited
Solution Approach 1:
The patent incorporates switching elements that can dynamically engage or disengage specific planetary gear sets, allowing the transmission to adapt between different operating modes. Despite the permanent coupling of the third ring gear to the output shaft for compactness, the switching mechanism provides versatility by enabling different gear ratio selections and operational configurations.
Solution Approach 2:
The third planetary gear set serves multiple functions: it acts as both a speed reduction stage and the final drive unit through the permanent coupling of the third ring gear to the output shaft. This multi-functionality reduces the need for separate components, minimizing installation space while maintaining transmission adaptability through the switching element system.
Data Source
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AI summary
The invention relates to a transmission device (22) for an electric drive of a motor vehicle, with a housing (24), with a first planetary gear set (26) which is arranged in the housing (24) and has a first sun gear (28), a first planetary carrier (30) and a first internal gear (32), with a second planetary gear set (36) which is arranged in the housing (24) and has a second sun gear (38), a second planetary carrier (40) and a second internal gear (42) which is permanently coupled fixedly to the first planetary carrier (30) so as to rotate with it, with an input shaft (48) which can be driven by a rotor (16) of an electric machine (12), and with an output shaft (52), by means of which at least one wheel (54) of the motor vehicle can be driven, wherein: - the input shaft (48) is permanently connected fixedly to the first sun gear (28) so as to rotate with it; and - the first internal gear (32) is coupled or can be coupled fixedly to the second sun gear (38) so as to rotate with it.