Nested Planetary Gear Train for Compact Automatic Transmission

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current automatic transmissions with increased shift stages face challenges in installability, power flow efficiency, and production cost due to the complexity and weight of multiple planetary gear sets and control elements, while also requiring improvement in gear ratio span for better fuel consumption.

Innovation Solution

A planetary gear train configuration using four planetary gear sets, two external gears, and five control elements, with strategically arranged shafts and transfer gears to achieve at least eight forward speeds and one reverse speed, reducing the length of the transmission and allowing for a wide range of gear teeth variations to optimize gear ratios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If three to four planetary gear sets and five to six control elements are used to achieve eight or more shift stages, then the number of shift stages is increased, but the transmission becomes lengthy and installability deteriorates

Engineering Contradiction:

Improvenumber of shift stagesVSAvoidtransmission length

Core Design Contradiction:

ProductivityVSLength of moving object

Solution Approach 1:

The patent employs nested planetary gear sets where smaller planetary gears are positioned within the space of larger planetary gear sets. Specifically, the second planetary gear set is arranged within the first planetary gear set, and the fourth planetary gear set is arranged within the third planetary gear set, allowing multiple gear stages to be compacted into a shorter transmission length while maintaining 8 forward speeds and 1 reverse speed

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent transitions from a linear arrangement of planetary gear sets to a multi-dimensional compact layout by positioning planetary gear sets in overlapping spatial configurations. The nested arrangement creates a three-dimensional structure that reduces the axial length of the transmission while preserving all necessary gear ratio stages

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Productivity

If three to four planetary gear sets are used to achieve eight or more shift stages, then the number of shift stages is increased, but the device complexity and production cost increase

Engineering Contradiction:

Improvenumber of shift stagesVSAvoidcomplexity of planetary gear sets and control elements

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent merges the functions of multiple planetary gear sets by arranging them in a nested configuration where the second planetary gear set shares space with the first, and the fourth shares with the third. This merging approach reduces the overall number of independent control elements needed while achieving 8 forward speeds and 1 reverse speed through coordinated operation of the nested gear sets

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The nested planetary gear sets are designed to perform multiple functions simultaneously. Each planetary gear set can operate independently or in combination with others, allowing the same hardware configuration to achieve different gear ratios and speed stages, thereby reducing the need for dedicated control elements for each shift stage

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Productivity

If three to four planetary gear sets and five to six control elements are used, then eight or more shift stages are achieved, but the weight increases

Engineering Contradiction:

Improvenumber of shift stagesVSAvoidtransmission weight

Core Design Contradiction:

ProductivityVSWeight of moving object

Solution Approach 1:

By nesting the second planetary gear set within the first and the fourth within the third, the patent eliminates redundant structural components and support elements that would otherwise be required for separate linear arrangements. This nested configuration reduces the overall material usage and transmission weight while maintaining 8 forward speeds and 1 reverse speed

Inventive Principle:

Principle #7Nested doll (Nesting)

4Device complexity

If dog clutches are used instead of wet-type control elements, then the number of parts is reduced, but shift-feel deteriorates

Engineering Contradiction:

Improvenumber of control elementsVSAvoidshift-feel

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

The patent employs dry-type clutches that function as simple, reliable switching elements without the complexity of wet-type control elements. These clutches are designed for precise engagement and disengagement to achieve clean shifts, maintaining good shift-feel while reducing the number of control elements needed in the nested planetary gear set configuration

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS10047835B2Planetary gear train of automatic transmission for vehicle

Publication Date: 2018.08.14 HYUNDAI MOTOR CO LTD

AI summary

A planetary gear train of an automatic transmission for a vehicle may include a first planetary gear set including, a second planetary gear set, a third planetary gear set, a fourth planetary gear set, an input shaft, an output shaft disposed in parallel with the input shaft and mounted with the fourth planetary gear set on external circumference of the output shaft, a first shaft selectively acting as a fixed element, a second shaft directly connected with the input shaft, a third shaft, a fourth shaft selectively connectable with the second shaft, a fifth shaft, a sixth shaft engaged with the output shaft selectively, a seventh shaft selectively acting as a fixed element, an eighth shaft directly connected with the output shaft, a ninth shaft engaged with the fifth shaft, and two transfer gears, each of which is gear-meshed with one of the shafts.