Planetary Gear Train Merging Nested Sets for Fuel Economy

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Solution Overview

Problem

Conventional automatic transmissions with increased speed stages face challenges in mountability, cost, weight, and transmission efficiency due to the number of internal components, particularly planetary gear sets, which hinders fuel economy and drivability improvements.

Innovation Solution

A planetary gear train design that achieves at least ten forward and four reverse speed stages using four simple planetary gear sets and six control elements, including clutches and brakes, to optimize power delivery and fuel economy while minimizing component count.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the number of speed stages is increased to enhance fuel economy and drivability, then fuel economy is improved, but the number of internal components (particularly planetary gear sets) increases, causing the transmission length to increase and deteriorating mountability, cost, weight, and transmission efficiency

Engineering Contradiction:

Improvefuel economyVSAvoidnumber of planetary gear sets

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent merges multiple planetary gear sets into a single integrated structure where the first, second, third, and fourth planetary gear sets share common components. Specifically, the sun gear of the first planetary gear set serves as the sun gear of the second planetary gear set, the ring gear of the second planetary gear set serves as the ring gear of the third planetary gear set, and the planet carrier of the third planetary gear set serves as the planet carrier of the fourth planetary gear set. This merging reduces the total number of components while achieving ten forward speed stages and four reverse speed stages, thereby improving fuel economy without proportionally increasing device complexity.

Inventive Principle:

Principle #5Merging (Combining)

2Adaptability or versatility

If the number of planetary gear sets is increased to achieve more speed stages, then speed stages are increased, but the transmission length increases, deteriorating mountability

Engineering Contradiction:

Improvenumber of speed stagesVSAvoidtransmission length

Core Design Contradiction:

Adaptability or versatilityVSLength of moving object

Solution Approach 1:

The patent applies a nested doll structure by arranging planetary gear sets concentrically around a common input shaft. The first planetary gear set is positioned at the center, with the second planetary gear set nested around it, the third planetary gear set nested around the second, and the fourth planetary gear set nested around the third. This nested arrangement allows multiple gear sets to occupy overlapping radial spaces, significantly reducing the axial length of the transmission while achieving ten forward speed stages and four reverse speed stages, thereby improving mountability.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Adaptability or versatility

If the number of planetary gear sets is increased to achieve more speed stages, then speed stages are increased, but the weight increases

Engineering Contradiction:

Improvenumber of speed stagesVSAvoidtransmission weight

Core Design Contradiction:

Adaptability or versatilityVSWeight of moving object

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

4Adaptability or versatility

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

Engineering Contradiction:

Improvenumber of speed stagesVSAvoidmanufacturing cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS10533642B2Planetary gear train of automatic transmission for vehicles

Publication Date: 2020.01.14 HYUNDAI MOTOR CO LTD

AI summary

A planetary gear train of an automatic transmission for a vehicle may include an input shaft receiving torque of an engine, an output shaft outputting torque, a first planetary gear set including first, second, and third rotation elements, a second planetary gear set including fourth, fifth, and sixth rotation elements, a third planetary gear set including seventh, eighth, and ninth rotation elements, and a fourth planetary gear set having tenth, eleventh, and twelfth rotation elements. The planetary gear train may further include a first plurality of shafts each fixedly connected with at least one of the rotation elements from the first, second, third, or fourth planetary gear sets, a second plurality of shafts, each selectively connected to a transmission housing and fixedly connected to a rotation element of the first and third planetary gear sets that is not fixedly connected with any of the first plurality of shafts.