Planetary Gear Train for 11-Speed Automatic Transmission
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Solution Overview
Problem
The development of automatic transmissions with multiple shift-stages faces challenges in reducing the number of parts, weight, and production cost while maintaining fuel efficiency and power flow efficiency, particularly with the introduction of eight-speed transmissions which often require three to four planetary gear sets and five to seven control elements, affecting vehicle stability and shift feel.
Innovation Solution
A planetary gear train configuration with three planetary gear sets and six control elements, including clutches and brakes, is designed to achieve eleven forward speeds and one reverse speed, reducing the number of parts and improving power delivery and fuel efficiency by optimizing the arrangement of rotational elements and control connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If three to four planetary gear sets and five to seven control elements are used to achieve eight or more shift-stages, then the number of shift-stages is increased, but the weight and device complexity increase significantly
Solution Approach 1:
The patent combines multiple planetary gear sets (first, second, third, and fourth planetary gear sets) into a single integrated transmission device, where rotational elements from different planetary gear sets are selectively connectable to each other. This merging approach enables achieving eleven forward speeds and one reverse speed with only four planetary gear sets and six control elements, reducing device complexity compared to conventional designs that require three to four planetary gear sets and five to seven control elements for eight-speed transmissions.
Solution Approach 2:
The patent implements multi-functionality through selective connectability of rotational elements. The first rotational element can be selectively connected to multiple other rotational elements (second, fourth, fifth, seventh, eighth rotational elements) through control elements, allowing a single element to serve multiple functions across different speed stages. This universal connectability enables the transmission to achieve eleven forward speeds and one reverse speed with fewer control elements (six) than conventional designs.
2Adaptability or versatility
If the number of planetary gear sets and control elements is increased to achieve more shift-stages, then fuel efficiency and drivability are enhanced, but the weight of the vehicle increases
Solution Approach 1:
The patent merges multiple planetary gear sets into a compact integrated structure where rotational elements are selectively connectable. By combining the functions of multiple gear sets into a unified device with shared components and selective connectivity, the overall weight of the transmission device is reduced while maintaining the capability to achieve eleven forward speeds and one reverse speed for enhanced fuel efficiency and drivability.
Solution Approach 2:
The selective connectability mechanism enables control elements to serve multiple functions across different speed stages. This multi-functionality reduces the total number of control elements required (six instead of five to seven in conventional designs), thereby reducing the weight of the transmission device while maintaining the ability to provide enhanced fuel efficiency and drivability through multiple shift stages.
3Adaptability or versatility
If more control elements are used to achieve more shift-stages, then the transmission ratio range is expanded, but the power flow efficiency decreases
Solution Approach 1:
The patent merges the power flow paths of multiple planetary gear sets into a unified selective connection system. By consolidating power flow through shared rotational elements and control elements with selective connectability, the number of separate power flow paths is reduced, minimizing energy losses and improving overall power flow efficiency while maintaining an expanded transmission ratio range through eleven forward speeds and one reverse speed.
Solution Approach 2:
The selective connectability of rotational elements creates universal power flow paths that can be dynamically configured. This multi-functional connectivity allows power to flow efficiently through the most direct path for each speed stage, reducing energy losses compared to conventional designs with multiple separate control elements. The six control elements can selectively engage different rotational elements to optimize power flow across the expanded transmission ratio range.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances driving stability and fuel efficiency by minimizing the number of parts, improving power delivery performance, and optimizing engine rotation speed compatibility, while maintaining the complexity of shift-stages in automatic transmissions.
Implementation Method 1
a first planetary gear set having a first, a second, and a third rotational elements; a second planetary gear set having a fourth, a fifth, and a sixth rotational elements; a third planetary gear set having a seventh, an eighth, and a ninth rotational elements; a fourth planetary gear set having a tenth, an eleventh, and a twelfth rotational elements
Data Source
AI summary
The present disclosure provides a planetary gear train of an automatic transmission for a vehicle including an input shaft, an output shaft, four planetary gear sets respectively having three rotational elements, and six control elements for selectively interconnecting the rotational elements and a transmission housing, thereby being capable of performing eleven forward speeds and one reverse speed.