Two-Speed Transmission Using Nested Planetary Gears
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Solution Overview
Problem
Existing electrified vehicles require efficient transmission systems to optimize power delivery from electric motors to wheels, particularly in semi-tractor vehicles, which demand versatile speed configurations to handle various driving conditions effectively.
Innovation Solution
A two-speed automatic transmission system utilizing two interconnected planetary gear sets with a rotary input and output, along with connecting and holding clutches, to establish two same-sign transmission ratios, enabling efficient power delivery across different driving scenarios while minimizing transmission size, complexity, and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a two-speed automatic transmission system is used to optimize power delivery across different driving conditions, then the adaptability and versatility of the vehicle is improved, but the device complexity increases due to the presence of multiple planetary gear sets and clutch mechanisms
Solution Approach 1:
The patent combines two planetary gear sets into a single integrated transmission system where the first planetary gear set and second planetary gear set share common components (input shaft, output shaft, carrier). This merging approach enables two distinct transmission ratios to be achieved through coordinated clutch engagement while maintaining a compact structure, thus improving adaptability without proportionally increasing complexity.
Solution Approach 2:
The first output planetary carrier serves multiple functions: it acts as the output of the first planetary gear set and simultaneously serves as the input to the second planetary gear set. This multi-functionality reduces the number of separate components needed, allowing the system to achieve two-speed operation while controlling overall device complexity.
2Productivity
If two interconnected planetary gear sets are used to establish two same-sign transmission ratios, then the productivity and efficiency of power delivery is improved, but the manufacturing precision requirements increase due to the need for precise gear meshing and clutch alignment
Solution Approach 1:
The transmission system is segmented into two distinct planetary gear sets, each capable of providing a transmission ratio. By dividing the overall transmission function into two separate but interconnected stages, the system can achieve two same-sign ratios through selective clutch engagement. This segmentation allows for modular manufacturing and assembly, which can help manage precision requirements.
Solution Approach 2:
The first output planetary carrier acts as an intermediary element that connects the first planetary gear set to the second planetary gear set. This intermediary component facilitates the transfer of rotational motion and torque between the two gear sets, enabling the system to achieve two distinct transmission ratios while maintaining smooth power flow and reducing the impact of manufacturing tolerances through the buffering effect of the intermediate carrier.
3Ease of operation
If multiple clutches are used to enable shifting between two speeds, then the ease of operation is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The transmission system employs two clutches (first clutch and second clutch) that can be dynamically engaged or disengaged to shift between two transmission ratios. The first clutch connects the input shaft to the first input gear, while the second clutch connects the first output planetary carrier to the second input gear. This dynamic clutch control enables automatic shifting between speeds, improving ease of operation. The system uses sensors and a control module to automatically manage clutch engagement based on driving conditions, which helps manage the complexity of the control system.
4Volume of moving object
If a compact transmission design is used to reduce size, then the volume and weight are reduced, but the reliability may be compromised due to tighter tolerances and increased stress on components
Solution Approach 1:
The transmission system employs a nested arrangement where the first planetary gear set and second planetary gear set are concentrically positioned around a common input shaft and output shaft. The first output planetary carrier is nested within the second planetary gear set's operational space. This nested doll configuration allows both gear sets to occupy overlapping spatial volumes, significantly reducing the overall transmission size while maintaining adequate clearance and stress distribution for reliable operation.
Data Source
AI summary
A transmission includes a first planetary gear set and a second planetary gear set that are the only planetary gear sets interconnected from an input to an output. The first planetary gear set includes an input-only first input gear and a first non-input/output gear, a first pinion gear meshed therebetween, and a first output planetary carrier carrying the first pinion gear. The first output planetary carrier is alternatively output-only or output-and-input. Moreover, the first non-input/output gear is alternatively held when the first output planetary carrier is output-only or released when the first output planetary carrier is output-and-input. The second planetary gear set includes an input-only second input gear and a grounded second non-input/output gear, a second pinion gear meshed therebetween, and an output-only second output planetary carrier carrying the second pinion gear.