Planetary Gear Train Nested Doll Configuration
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Solution Overview
Problem
Current automatic transmissions with more than eight speeds face challenges in achieving efficient fuel consumption and drivability due to increased complexity, weight, and power flow inefficiencies, often requiring multiple planetary gear sets and control elements that complicate installation and deteriorate shift feel.
Innovation Solution
A planetary gear train with four single pinion planetary gear sets and six control elements, including clutches and brakes, is designed to achieve nine forward speeds and one reverse speed, minimizing parts while improving power delivery and fuel efficiency by utilizing a low engine rotation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of planetary gear sets is increased to achieve more shift stages, then fuel consumption and drivability are improved, but total length increases and installability deteriorates
Solution Approach 1:
The patent applies nested doll principle by arranging planetary gear sets in a compact configuration where the third planetary gear set is positioned within the space defined by the first and second planetary gear sets. This nesting approach allows multiple gear sets to occupy overlapping spatial volumes, achieving nine shift stages without proportionally increasing the overall transmission length, thereby resolving the contradiction between achieving more shift stages and maintaining compact dimensions for installability.
2Productivity
If the number of planetary gear sets is increased to achieve more shift stages, then fuel consumption and drivability are improved, but the number of parts increases and production cost increases
Solution Approach 1:
The patent applies universality principle by designing control elements that serve multiple functions across different shift stages. The same clutch and brake components are reused in various combinations to achieve nine different forward speeds and reverse gear, rather than requiring dedicated control elements for each shift stage. This multi-functional design reduces the total number of parts needed while still achieving the desired number of shift stages for improved fuel consumption.
Solution Approach 2:
The patent merges the functions of multiple planetary gear sets into a unified transmission system where the first, second, and third planetary gear sets work cooperatively through shared control elements. By combining these gear sets with common clutches and brakes, the patent achieves nine shift stages without requiring three to four separate planetary gear sets with five to seven control elements each, thereby reducing overall part count and production cost while maintaining fuel efficiency benefits.
3Adaptability or versatility
If three to four planetary gear sets and five to seven control elements are used, then more shift stages are achieved, but total length increases which has drawbacks of deteriorating installability
Solution Approach 1:
The patent implements nested doll principle by positioning the third planetary gear set within the spatial envelope of the first and second planetary gear sets. This nested arrangement enables nine shift stages to be achieved while keeping the transmission compact, avoiding the length increase that would normally accompany three to four separate planetary gear sets, thereby resolving the installability issue.
4Adaptability or versatility
If a dog clutch is applied in place of wet control elements, then applicable structure is expanded, but shift feel is deteriorated
Solution Approach 1:
The patent applies the principle of using simpler, less durable components (dog clutches) only where appropriate while reserving premium components (wet control elements) for critical functions. Wet control elements are used for main clutch and brake operations where smooth shift feel is essential, while dog clutches are used for auxiliary locking functions where shift feel is less critical. This selective application expands applicable structure while preserving shift feel in key areas.
Data Source
AI summary
A planetary gear train includes an input shaft and an output shaft. A first planetary gear set has first, second, and third rotational elements. A second planetary gear set has fourth, fifth, and sixth rotational elements. A third planetary gear set has seventh, eighth, and ninth rotational elements. A fourth planetary gear set has tenth, eleventh, and twelfth rotational elements. A first shaft is fixedly connected with the twelfth rotational element and fixedly connected with the input shaft. A second shaft is fixedly connected with the fifth rotational element and the eighth rotational element, and fixedly connected with the output shaft. A third shaft is fixedly connected with the fourth rotational element. A fourth shaft is fixedly connected with the seventh rotational element. A fifth shaft is fixedly connected with the sixth rotational element and the ninth rotational element.