Planetary Gear Train for 10-Speed Automatic Transmission
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Solution Overview
Problem
Current automatic transmissions face challenges in achieving a large number of shift stages while maintaining efficiency, as increasing the number of planetary gear sets and control elements leads to increased length, weight, and production costs, and existing solutions like double row structures and dog clutches limit applicability and deteriorate shift sense.
Innovation Solution
A planetary gear train configuration with four planetary gear sets and seven control elements, arranged in a specific order, which allows for ten forward speeds and one reverse speed by selectively connecting shafts and using clutches and brakes to achieve a gear ratio span of over 10.0, ensuring linearity of step ratios and improved drivability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of planetary gear sets and control elements is increased to achieve more shift stages, then the number of forward speeds increases, but the length of the transmission increases causing deteriorated mountability and production cost
Solution Approach 1:
The patent merges multiple planetary gear sets into a single integrated structure where multiple planetary gears share common elements (sun gear, ring gear, planet carriers). This consolidation achieves multiple forward speeds (10 speeds) without proportionally increasing the number of discrete planetary gear set assemblies, thereby controlling transmission length while maintaining high productivity
Solution Approach 2:
The planetary gear sets are designed with multi-functionality where the same basic structure (sun gear, ring gear, planet carriers) serves multiple gear ratio functions. By selectively engaging different planetary gears and control elements, the system achieves 10 forward speeds and reverse gear using a unified structure rather than separate dedicated gear sets for each function
2Productivity
If the number of planetary gear sets and control elements is increased to achieve more shift stages, then the number of forward speeds increases, but the weight increases
Solution Approach 1:
The patent combines multiple planetary gear mechanisms into a single integrated transmission assembly where components are shared across different gear ratios. This merging approach achieves 10 forward speeds without requiring separate heavy planetary gear sets for each speed, thereby controlling weight while maintaining high productivity
Solution Approach 2:
The planetary gear components are designed to serve multiple functions simultaneously. The same sun gear, ring gear, and planet carrier structure provides multiple gear ratios through selective engagement, eliminating the need for additional dedicated components for each speed, thus controlling weight while achieving high speed multiplication capability
3Productivity
If the number of planetary gear sets and control elements is increased to achieve more shift stages, then the number of forward speeds increases, but the production cost increases
Solution Approach 1:
The patent merges multiple planetary gear sets into a single integrated structure with shared components. This consolidation reduces the total number of parts that need to be manufactured, assembled, and quality-checked, thereby controlling production cost while achieving 10 forward speeds
Solution Approach 2:
The planetary gear components are designed as universal multi-functional elements that provide multiple gear ratios. This approach reduces component variety and standardization requirements, simplifying manufacturing processes and reducing production cost while maintaining the capability to deliver 10 forward speeds
4Productivity
If a double row structure or dog clutch is applied to achieve more shift stages, then the number of forward speeds increases, but the applicable structure is limited and shift sense deteriorates
Solution Approach 1:
The patent merges multiple planetary gear sets into a single integrated structure that is adaptable to various transmission layouts and vehicle applications. This unified approach provides broader applicability compared to specialized double-row structures or dog clutch mechanisms, achieving 10 forward speeds with enhanced versatility
Solution Approach 2:
The planetary gear mechanism serves multiple functions including providing forward speeds, reverse gear, and potential future extensions for additional ratios. This multi-functionality enhances the applicable structure's versatility, allowing the same basic design to be adapted to different vehicle types and transmission configurations unlike more specialized mechanisms
Data Source
AI summary
A planetary gear train disclosed herein includes an input shaft for receiving engine torque; an output shaft for outputting shifted torque; a first planetary gear set having first, second, and third rotational elements; a second planetary gear set having fourth, fifth, and sixth rotational elements; a third planetary gear set having seventh, eighth, and ninth rotational elements; a fourth planetary gear set having tenth, eleventh, and twelfth rotational elements; a first shaft interconnecting the first, fifth, ninth, and tenth rotational elements; a second shaft connected with the second rotational element and the input shaft; a third shaft connected with the third rotational element; a fourth shaft interconnecting the sixth and eighth rotational elements, and selectively connected with the second shaft; a fifth shaft connected with the seventh rotational element and selectively connected with the second shaft; and a sixth shaft connected with the eleventh rotational element and the output shaft.