Five-Set Planetary Gear Train for Ten-Speed Transmission
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Solution Overview
Problem
Current automatic transmissions face challenges in achieving high fuel efficiency and drivability due to increased parts and complexity, particularly with eight-speed transmissions where gear ratio spans are limited, leading to compromised power flow efficiency and step ratio linearity.
Innovation Solution
A planetary gear train with five planetary gear sets and six friction elements is designed to achieve at least tenth forward speeds and one reverse speed, incorporating a torque parallel structure to reduce torque sharing and friction drag loss, thereby enhancing power transmission efficiency and fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of planetary gear sets and friction elements is increased to achieve more shift stages, then fuel efficiency and drivability are improved, but device complexity and installation difficulty increase
Solution Approach 1:
The patent combines multiple planetary gear sets (first through fifth planetary gear sets) into a single integrated transmission system where gear sets share common components such as the sun gear, planet gears, and ring gear. This merging approach enables achievement of tenth forward speeds and reverse speeds without proportionally increasing the total number of discrete parts, thereby improving fuel efficiency while controlling device complexity.
Solution Approach 2:
The planetary gear sets are designed with multi-functional capability where the same basic structure (sun gear, planet carrier, ring gear) serves multiple gear ratio purposes. By configuring different friction elements (clutches and brakes) to engage different components of the universal planetary gear structure, the system achieves multiple shift stages including tenth forward speeds and reverse speeds without requiring entirely separate gear sets for each function.
2Adaptability or versatility
If friction elements are increased to control more gear ratios, then shift stage flexibility is improved, but power transmission efficiency deteriorates due to increased friction drag loss
Solution Approach 1:
The patent extracts and optimizes the friction element configuration by selecting only six specific friction elements (first through sixth clutches and brakes) to control the planetary gear sets, rather than using a larger number of friction elements. This extraction approach maintains gear ratio flexibility for achieving tenth forward speeds and reverse speeds while minimizing the total friction drag loss by removing unnecessary friction control points from the system.
Solution Approach 2:
The patent changes the operational parameters of the friction elements by designing them to operate in coordinated sequences where not all friction elements are engaged simultaneously. The control strategy adjusts the engagement and disengagement timing of each friction element to maintain gear ratio flexibility while reducing cumulative friction drag loss during power transmission through the transmission system.
3Productivity
If gear ratio span is increased above 9.0 to improve fuel consumption, then fuel efficiency is enhanced, but step ratio linearity deteriorates undermining drivability
Solution Approach 1:
The patent implements dynamic gear ratio adjustment capability through the coordinated engagement of six friction elements controlling five planetary gear sets. The system can dynamically select from multiple gear ratios including tenth forward speeds and reverse speeds, allowing the gear ratio span to reach above 9.0 for improved fuel consumption while maintaining step ratio linearity through optimized gear ratio distribution across the available shift stages.
Data Source
AI summary
A planetary gear train of an automatic transmission for a vehicle provides at least ten forward speeds and one reverse speed by operating rotational elements of five planetary gear sets by controlling three clutches and three brakes. The planetary gear train further includes input and output shafts, and nine shafts. In particular, two shafts selected from the nine shafts are selectively connected to a transmission housing via the corresponding brakes, and also respectively connected to a corresponding rotation element of third and fourth planetary gear sets that is unconnected to another rotational element selected from the rotational elements of the five planetary gear sets.