Planetary Gear Train for Automatic Transmission with 10 Speed Stages
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Solution Overview
Problem
Current automatic transmissions with multiple speed stages face challenges in achieving significant fuel efficiency and power delivery performance due to increased internal components, which lead to deteriorated mountability, cost, weight, and transmission efficiency, with 8-speed transmissions showing limited fuel efficiency improvement and non-linear step ratio changes affecting drivability.
Innovation Solution
A planetary gear train design that achieves ten forward speed stages and one reverse speed stage using a minimum number of components, incorporating four simple planetary gear sets and seven friction elements to selectively connect rotation elements and the transmission housing, allowing for almost linear increase or decrease in step ratios between transmission steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of transmission steps is increased to improve fuel efficiency, then fuel efficiency is improved, but the number of internal components increases leading to deteriorated mountability, cost, weight, and transmission efficiency
Solution Approach 1:
The patent merges multiple planetary gear sets (first, second, third, and fourth planetary gear sets) into a single integrated transmission system. The friction elements are designed to simultaneously connect multiple rotation elements across different planetary gear sets, consolidating what would otherwise require separate component sets. This merging approach achieves 10 forward speed stages without proportionally increasing the number of independent internal components, thereby improving fuel efficiency while controlling device complexity.
Solution Approach 2:
The friction elements in the patent are designed with multi-functionality, where each friction element can selectively connect various rotation elements (sun gears, planet carriers, ring gears) across different planetary gear sets. This universal connectivity allows a single friction element to serve multiple functions in achieving different speed stages, reducing the total number of components needed while maintaining 10 forward speed stages for improved fuel efficiency.
2Use of energy by moving object
If the span of shift ratios is enlarged to improve fuel efficiency, then fuel efficiency is improved, but step ratios between transmission steps may not increase or decrease linearly affecting drivability
Solution Approach 1:
The patent employs parameter changes in the gear ratio design of the four planetary gear sets to achieve a span of shift ratios of 9.0 or greater while maintaining almost linear step ratios between transmission steps. By carefully adjusting the gear ratios of individual planetary gear sets and their combinations, the system enlarges the overall span for fuel efficiency while controlling the linearity of intermediate steps for drivability.
Solution Approach 2:
The patent implements dynamic control through seven friction elements that can selectively connect various rotation elements in different combinations. This dynamic reconfiguration allows the transmission to achieve 10 forward speed stages with optimized step ratios, ensuring that the span is enlarged for fuel efficiency while the intermediate steps maintain near-linear progression for smooth drivability and acceleration characteristics.
3Device complexity
If a minimum number of components is used to achieve ten forward speed stages, then device complexity is reduced, but achieving a span of shift ratios greater than or equal to 9.0 and linear step ratios becomes more difficult
Solution Approach 1:
The patent structures four planetary gear sets in a nested configuration where rotation elements of one planetary gear set are connected to rotation elements of adjacent sets through friction elements. This nesting allows compact arrangement that achieves 10 forward speed stages with minimized component count while maintaining the geometric relationships necessary for achieving a span of shift ratios ≥9.0 and linear step ratios.
Solution Approach 2:
The patent utilizes multi-dimensional connectivity through friction elements that can engage with multiple rotation elements (sun gears, planet carriers, ring gears) across different planetary gear sets simultaneously. This dimensional approach to component connectivity enables the system to achieve complex gear ratio patterns (span ≥9.0 with linear steps) using a minimal number of physical components by exploiting the multi-dimensional engagement possibilities.
Data Source
AI summary
A planetary gear train of an automatic transmission for a vehicle may include an input shaft, an output shaft, first to fourth planetary gear sets and seven friction elements disposed to selectively connect the rotation elements with the rotation element and selectively connect the rotation elements with a transmission housing, and wherein the input shaft is continuously connected to the second rotation element, the output shaft is continuously connected to the eleventh rotation element, the first rotation element is continuously connected to the sixth rotation element, the first rotation element is continuously connected to the eighth rotation element, the third rotation element is continuously connected to the seventh rotation element, the ninth rotation element is continuously connected to the tenth rotation element, and the output shaft is selectively connected with the third rotation element, and wherein three friction elements among seven friction elements are operated at each speed stage.