Compound Planetary Gear Train for 9-Speed Automatic Transmission

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Solution Overview

Problem

Existing planetary gear trains in automatic transmissions face challenges in achieving a high number of shift speeds, which increases the number of components, affecting mountability, cost, weight, and power delivery efficiency, particularly in front-wheel drive vehicles.

Innovation Solution

A planetary gear train design that includes a compound planetary gear set connected to a first shaft through externally-meshed gears, with a second shaft in parallel, and frictional elements like clutches and brakes to achieve nine forward speeds and one reverse speed, optimizing gear ratios and reducing component count.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the number of shift speeds is increased to improve fuel economy, then fuel economy is improved, but the number of components increases leading to deteriorated mountability and power delivery efficiency

Engineering Contradiction:

Improvefuel economyVSAvoidnumber of components

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent combines multiple planetary gear sets into a compound planetary gear set where rotation elements of one planetary gear set are connected to rotation elements of another planetary gear set. This merging approach allows achieving nine forward speeds and one reverse speed with a reduced number of components compared to traditional multi-planetary gear arrangements, thereby improving mountability and power delivery efficiency while maintaining fuel economy benefits

Inventive Principle:

Principle #5Merging (Combining)

2Use of energy by moving object

If the number of shift speeds is increased to improve fuel economy, then fuel economy is improved, but mountability is deteriorated due to increased component count

Engineering Contradiction:

Improvefuel economyVSAvoidmountability

Core Design Contradiction:

Use of energy by moving objectVSEase of operation

Solution Approach 1:

The compound planetary gear set merges multiple planetary gear sets by connecting rotation elements directly, reducing the overall component count and simplifying the transmission layout. This enables better mountability in front-wheel drive vehicles while achieving nine forward speeds and one reverse speed for improved fuel economy

Inventive Principle:

Principle #5Merging (Combining)

3Use of energy by moving object

If the number of shift speeds is increased to improve fuel economy, then fuel economy is improved, but power delivery efficiency is deteriorated

Engineering Contradiction:

Improvefuel economyVSAvoidpower delivery efficiency

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The compound planetary gear set reduces the number of friction elements and connection points compared to traditional multi-planetary gear arrangements. By merging gear sets and using externally-meshed gears for selective connection, the patent minimizes energy losses at connection interfaces while achieving nine forward speeds and one reverse speed, thereby improving power delivery efficiency

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent uses externally-meshed gears as intermediary elements to selectively connect rotation elements of different planetary gear sets. This intermediary connection method provides more efficient power transmission compared to direct friction-based connections, reducing energy losses and improving power delivery efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design improves mountability, power delivery performance, and fuel economy by simplifying the component layout and allowing for easier gear ratio changes, reducing the need for a torque converter and enhancing shift control.

Implementation Method 1

frictional elements including clutches selectively connecting the first, third, and fourth rotation elements to the first shaft and brakes selectively connecting the third and fourth rotation elements to a transmission housing

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS9097320B2Planetary gear train of automatic transmission for vehicles

Publication Date: 2015.08.04 HYUNDAI MOTOR CO LTD

AI summary

A planetary gear train of an automatic transmission may include: a first input shaft; a second parallel shaft; a compound planetary gear set on the second shaft, and including a first rotation element engageable with the first shaft through two paths respectively having an external gear, a second rotation element connected to an output gear so as to be operated as an output element, a third rotation element engageable with the first shaft through one path having an external gear and selectively fixed, and a fourth rotation element engageable with the first shaft through one path having an external gear and selectively fixed; four transfer gears forming the external gears; frictional elements including clutches selectively connecting the first, third, and fourth rotation elements to the first shaft and brakes selectively connecting the third and fourth rotation elements to a transmission housing.