10-Speed Transmission Using Nested Planetary Gear Sets
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Solution Overview
Problem
Current power transmissions for passenger vehicles are limited by complexity, size, and cost, which restrict the development of higher gear ratios such as seven-, eight-, nine-, and ten-speed transmissions, despite their potential for improved acceleration and fuel economy.
Innovation Solution
A power transmission system utilizing three planetary gear sets with six torque-transmitting devices, including brakes and clutches, to achieve ten forward speed ratios and one reverse speed ratio, allowing for efficient gear shifting and reduced complexity through strategically interconnected gear members and torque-transmitting devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of forward speed ratios is increased to improve acceleration and fuel economy, then vehicle performance is improved, but transmission complexity and size increase
Solution Approach 1:
The transmission is divided into three separate planetary gear sets (first, second, and third planetary gear sets), each capable of providing gear reduction. By segmenting the overall gear reduction task across multiple independent planetary sets, the system achieves high speed ratios without requiring a single overly complex gear train, thereby improving acceleration and fuel economy while managing transmission complexity through modular architecture.
Solution Approach 2:
The planetary gear sets are interconnected in a nested configuration where the output of one planetary set feeds into the input of the next, with shared components such as the ring gear of the first planetary set being connected to the sun gear of the second planetary set. This nesting allows multiple gear reduction stages to be compactly arranged, achieving high speed ratios in a space-efficient manner while managing overall transmission size.
2Adaptability or versatility
If more torque-transmitting devices are added to achieve more speed ratios, then gear shifting capability is improved, but device complexity and cost increase
Solution Approach 1:
Each planetary gear set is designed with multi-functionality where the same basic components (sun gear, ring gear, planet carrier) serve multiple purposes across different gear ratios. The torque-transmitting devices are strategically positioned to control multiple gear sets simultaneously, allowing a limited number of torque-transmitting devices to achieve ten forward speed ratios and one reverse speed ratio through various engagement combinations, thereby improving gear shifting capability while managing device complexity.
Solution Approach 2:
The patent merges the functionality of multiple planetary gear sets by interconnecting them through shared components and common torque-transmitting devices. For example, the ring gear of the first planetary set is continuously connected to the sun gear of the second planetary set, and the same torque-transmitting devices control multiple gear sets in different operating modes. This merging allows ten forward speed ratios and one reverse speed ratio to be achieved with only six torque-transmitting devices, improving adaptability while reducing the number of individual components needed.
3Adaptability or versatility
If the number of planetary gear sets is increased to provide more speed ratios, then the speed ratio range is improved, but transmission size increases
Solution Approach 1:
The three planetary gear sets are arranged in a nested configuration where components of one set are mechanically integrated with components of adjacent sets. The ring gear of the first planetary set is continuously connected to the sun gear of the second planetary set, and the planet carrier of the second planetary set is continuously connected to the ring gear of the third planetary set. This nesting allows the transmission to achieve a wide speed ratio range (ten forward ratios and one reverse ratio) while maintaining a compact overall size, as the gear sets share space and structural support rather than being separately mounted.
Solution Approach 2:
The transmission merges multiple planetary gear sets into a single integrated unit with shared housing, mounting structures, and torque-transmitting device actuation systems. The interconnecting members continuously link the gear sets, allowing them to function as a unified system. This merging reduces the total transmission size compared to having three separate planetary gear assemblies, while still providing the required speed ratio range through the combined action of all three sets.
Data Source
AI summary
The transmission has a plurality of members that can be utilized in powertrains to provide ten forward speed ratios and one reverse speed ratio. The transmission includes three planetary gear sets, six torque-transmitting devices, and two fixed interconnections. The powertrain includes an engine and torque converter that is continuously connected to one of the planetary gear members and an output member that is continuously connected with another one of the planetary gear members. The six torque-transmitting devices provide interconnections between various gear members, and the transmission housing, and are operated in combinations of three to establish ten forward speed ratios and one reverse speed ratio.