Planetary Gear Train for Linear Shift Ratios
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Solution Overview
Problem
Current automatic transmissions with multiple speed stages face challenges in maintaining efficiency due to increased complexity, weight, and manufacturing costs, with eight-speed transmissions showing limited fuel consumption enhancement and deteriorated drivability from non-linear gear ratio spans.
Innovation Solution
A planetary gear train design for automatic transmissions that includes multiple interconnected planetary gear sets and control elements, allowing for at least nine forward speeds and one reverse speed, with a gear ratio span exceeding 9.0, to enhance power delivery and fuel efficiency while maintaining linear step ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of internal components is increased to achieve more gear shift stages, then the number of shift stages is increased, but the device complexity, weight, and manufacturing cost increase
Solution Approach 1:
The patent merges multiple planetary gear sets (first, second, third, and fourth planetary gear sets) into a single integrated transmission system where rotational elements from different gear sets are selectively connectable. This allows achieving 9+ forward speeds and reverse speeds without proportionally increasing the number of independent planetary gear sets, thereby reducing overall device complexity while maintaining high shift stage count
Solution Approach 2:
The control elements (clutches and brakes) are designed to perform multiple functions by selectively connecting different rotational elements across multiple planetary gear sets. For example, a single clutch can connect rotational elements from both the first and second planetary gear sets, enabling one component to control multiple gear ratios and shift stages, thus reducing the total number of control elements needed
2Use of energy by moving object
If the gear ratio span is increased to improve fuel consumption, then fuel efficiency is enhanced, but the linearity of step ratios between adjacent shift stages deteriorates
Solution Approach 1:
The patent employs a dynamic control system where clutches and brakes are selectively engaged and disengaged to achieve different gear ratios. This dynamic switching mechanism allows the transmission to adaptively select optimal gear combinations that maintain linear step ratios across a wide gear ratio span, improving both fuel efficiency and drivability
Solution Approach 2:
The patent changes the operational parameters of the planetary gear sets by selectively connecting different rotational elements (sun gears, planet carriers, ring gears) through control elements. By varying which elements are connected and which are held stationary, the system achieves multiple gear ratios with linear step relationships while maintaining a gear ratio span exceeding 9.0
3Use of energy by moving object
If the number of planetary gear sets is increased to achieve more shift stages, then the fuel consumption enhancement is improved, but the manufacturing cost and weight increase
Solution Approach 1:
The patent arranges multiple planetary gear sets in a nested or coaxial configuration where rotational elements from different gear sets share common axes or are positioned in close proximity. This nesting approach allows achieving 9+ forward speeds without proportionally increasing the overall transmission size, weight, and manufacturing cost, while still providing the fuel consumption benefits of multiple shift stages
Data Source
AI summary
A planetary gear set of an automatic transmission for a vehicle may include input and output shafts for receiving and outputting torques, first to fourth planetary gear sets respectively forming first to third, fourth to sixth, seventh to ninth, and tenth to twelfth rotational elements, and six control elements each of which selectively interconnects a corresponding pair among the input and output shafts, the rotational elements, and a transmission housing, where the input and output shafts are fixedly connected to the first and eleventh rotational elements respectively, respective pairs of the first and sixth rotational elements, the second and ninth rotational elements, the third and tenth rotational elements, the fifth and eleventh rotational elements are fixedly interconnected, and the seventh rotational element is selectively connected to the transmission housing.