Planetary Gear Train for 9-Speed Automatic Transmission
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Solution Overview
Problem
Current automatic transmissions with multiple speed stages face challenges in improving fuel efficiency and power flow efficiency due to increased internal components, leading to higher production costs and potential degradation in engine running efficiency and drivability, especially with 8-speed transmissions that struggle to maintain a sufficient gear shift ratio span and interstage ratio linearity.
Innovation Solution
A planetary gear train configuration for a vehicle automatic transmission that implements nine forward speeds and one reverse speed using a minimum number of components, comprising four planetary gear sets and six control elements, which allows for direct connections and selective connections between rotating elements and the transmission housing, optimizing gear shift ratios and maintaining linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of gear shift stages is increased to improve fuel efficiency, then fuel efficiency is improved, but the number of internal components increases which deteriorates installability, production cost, weight and power flow efficiency
Solution Approach 1:
The patent combines multiple planetary gear sets (first, second, third, and fourth planetary gear sets) into a single integrated transmission system where rotating elements from different gear sets are selectively connectable to each other. This merging approach achieves 9-speed functionality without requiring separate, independent gear sets for each speed range, thereby reducing overall component count while maintaining fuel efficiency benefits
Solution Approach 2:
The rotating elements (sun gears, planet carriers, ring gears) are designed with multi-functionality where each element can serve multiple purposes across different speed stages. For example, the first sun gear can be selectively connected to different planet carriers depending on the desired speed stage, allowing a single component to fulfill multiple functional roles throughout the 9-speed range
2Use of energy by moving object
If the span of gear shift ratio is increased to improve fuel efficiency, then fuel efficiency is improved, but linearity of interstage ratio deteriorates which degrades engine running efficiency and drivability
Solution Approach 1:
The transmission system employs dynamic control through selective connection mechanisms that can adaptively engage different planetary gear sets based on operating conditions. The control elements dynamically reconfigure the gear train topology to maintain optimal interstage ratio linearity across the 9-speed range, ensuring smooth transitions that preserve both fuel efficiency and drivability
Solution Approach 2:
The patent achieves a gear shift ratio span of 9.0 or more by strategically designing the gear ratios of individual planetary gear sets and their interconnections. The parameter optimization ensures that while the overall span is large (improving fuel efficiency), the interstage ratios between consecutive speeds maintain linearity (preserving drivability) through carefully calculated gear tooth counts and connection configurations
3Ease of manufacture
If 8-speed automatic transmission is implemented with span of shift ratio at 6.5 to 7.5, then installability is maintained, but fuel efficiency improvement effect is not great
Solution Approach 1:
The patent transitions from traditional 8-speed configurations to a 9-speed arrangement by adding an additional speed stage through the selective connection of rotating elements. This dimensional expansion in the gear ratio spectrum allows achieving a span of 9.0 or more without proportionally increasing component count, as the new speed stage is integrated into the existing planetary gear set architecture rather than adding entirely separate mechanisms
Data Source
AI summary
A planetary gear train of an automatic transmission for a vehicle, the planetary gear train may include an input shaft receiving power from an engine, an output shaft outputting shifted power of the engine, a first planetary gear set including first, second, and third rotating elements, a second planetary gear set including fourth, fifth, and sixth rotating elements, a third planetary gear set including seventh, eighth, and ninth rotating elements, a fourth planetary gear set including tenth, eleventh, and twelfth rotating elements, and six control elements which are disposed at positions where at least one of the rotating elements is selectively connectable with another of the rotating elements or disposed at positions where rotating elements are selectively connectable to a transmission housing.