Planetary Gear Train for Automatic Transmission with Nine Speeds

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Solution Overview

Problem

Automatic transmissions face challenges in achieving a high number of shift-stages with minimal components, leading to increased weight, production costs, and reduced power transfer efficiency, while maintaining driving silence and fuel consumption improvements.

Innovation Solution

A planetary gear train configuration with four planetary gear sets and eight shafts, utilizing three clutches and three brakes to achieve at least nine forward speeds and one reverse speed, allowing for efficient torque transfer and reduced component count.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the number of shift stages is increased to improve fuel consumption and drivability, then fuel consumption improves, but the number of planetary gear sets increases causing increased weight, length, and production cost

Engineering Contradiction:

Improvefuel consumptionVSAvoidtransmission weight

Core Design Contradiction:

Use of energy by moving objectVSWeight of moving object

Solution Approach 1:

The patent merges multiple planetary gear sets into a unified structure where gear sets share common components. Specifically, the first and second planetary gear sets share a sun gear, and the third and fourth planetary gear sets share a sun gear, allowing multiple gear stages to be achieved with fewer independent planetary gear sets, thereby reducing overall weight while maintaining 9 forward speed stages

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent makes certain components serve multiple functions across different gear stages. The shared sun gears and carrier structures perform multiple roles in different planetary gear sets, enabling a single component to contribute to multiple speed reduction stages, thus reducing the total component count and weight while achieving the required number of shift stages

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Use of energy by moving object

If the number of shift stages is increased to improve fuel consumption and drivability, then fuel consumption improves, but the full length of the transmission increases causing mountability deterioration

Engineering Contradiction:

Improvefuel consumptionVSAvoidtransmission length

Core Design Contradiction:

Use of energy by moving objectVSLength of moving object

Solution Approach 1:

The patent employs a nested arrangement where planetary gear sets are positioned concentrically around a common input shaft. The first and second planetary gear sets are arranged with their sun gears sharing the same axis, and the third and fourth planetary gear sets similarly share another sun gear axis, creating a compact nested structure that minimizes the radial and axial footprint of the transmission while accommodating multiple gear stages

Inventive Principle:

Principle #7Nested doll (Nesting)

3Productivity

If the number of planetary gear sets is increased to achieve more shift stages, then the number of shift stages increases, but production cost increases

Engineering Contradiction:

Improvenumber of shift stagesVSAvoidproduction cost

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent combines multiple planetary gear sets into a integrated assembly where components are shared between adjacent gear sets. The first and second planetary gear sets share a sun gear, and the third and fourth planetary gear sets share a sun gear, reducing the total number of individual planetary gear sets needed while achieving 9 forward speed stages, thereby simplifying manufacturing and reducing production costs

Inventive Principle:

Principle #5Merging (Combining)

4Productivity

If a double row structure is adopted to implement 8-speed or more, then shift stages increase, but the applicable structure is limited and shift sense deteriorates

Engineering Contradiction:

Improvenumber of shift stagesVSAvoidapplicable structure

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent divides the transmission into four distinct planetary gear sets (first, second, third, and fourth) that can be selectively engaged through six control elements. This segmentation allows for flexible configuration of different gear ratios and provides multiple applicable structures for various vehicle applications, unlike the more rigid double row structure, while maintaining smooth shift characteristics through progressive engagement of gear sets

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10047836B2Planetary gear train of automatic transmission for vehicles

Publication Date: 2018.08.14 HYUNDAI MOTOR CO LTD

AI summary

A planetary gear train of an automatic transmission may include input shaft, output, first planetary gear set having first to third rotational elements, second planetary gear set having fourth to sixth rotational elements, third planetary gear set having seventh to ninth rotational elements, fourth planetary gear set having tenth to twelfth rotational elements, first shaft interconnecting the first and fourth rotational elements, and may be selectively connected with the input shaft or transmission housing, second shaft interconnecting the second rotational element, the sixth rotational element, the seventh rotational element, and the tenth rotational element connect, third shaft connected with the third rotational element, fourth shaft connected with the fifth rotational element, fifth shaft connected with the ninth rotational element, sixth shaft connected with the eighth rotational element and connected with the output shaft, a seventh shaft connected with the eleventh rotational element and connected with the input shaft, and eighth shaft connected with the twelfth rotational element and selectively connected with the respective third shaft and sixth shaft.