Multi-speed Transmission Using Nested Planetary Gear Sets

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Solution Overview

Problem

Current power transmissions for passenger vehicles are limited by complexity, size, and cost, which restrict the development of higher gear ratios, such as seven-, eight-, nine-, and ten-speed transmissions, despite their potential for improved acceleration and fuel economy.

Innovation Solution

A power transmission system utilizing four planetary gear sets and six torque-transmitting devices, including brakes and clutches, to achieve at least ten forward speed ratios and one reverse speed ratio, allowing for varied tooth ratios and efficient gear progression.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the number of speed ratios in automatic transmission is increased to seven, eight, nine or ten, then vehicle acceleration and fuel economy are improved, but transmission complexity, size and cost increase

Engineering Contradiction:

Improvevehicle acceleration and fuel economyVSAvoidtransmission complexity, size and cost

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent employs nested planetary gear sets where smaller planetary gear assemblies are positioned within or around larger planetary gear assemblies. This nesting arrangement allows multiple gear reduction stages to be compacted into a single transmission housing, enabling 7-10 forward speed ratios without proportionally increasing the overall transmission size or complexity

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The planetary gear sets are designed with members that can serve multiple functions across different gear ratios. The same planetary carriers, sun gears, and ring gears are engaged in different combinations to produce various forward and reverse ratios, reducing the need for dedicated components for each ratio and thereby lowering overall device complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If the number of planetary gear sets is increased to provide more speed ratios, then the number of available ratios increases, but the transmission size and complexity increase

Engineering Contradiction:

Improvenumber of available speed ratiosVSAvoidtransmission size

Core Design Contradiction:

Adaptability or versatilityVSVolume of stationary object

Solution Approach 1:

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

Multiple planetary gear sets share common components such as planetary carriers, sun gears, and ring gears. By merging these components across different gear sets, the patent achieves multiple speed ratios while minimizing the total number of discrete parts and reducing the overall transmission volume

Inventive Principle:

Principle #5Merging (Combining)

3Adaptability or versatility

If the number of torque-transmitting devices is increased to control more planetary gear sets, then more speed ratios are achievable, but device complexity and cost increase

Engineering Contradiction:

Improvenumber of achievable speed ratiosVSAvoidnumber of torque-transmitting devices

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Each torque-transmitting device is designed to control multiple planetary gear sets simultaneously or to perform multiple functions across different gear ratios. For example, a single clutch or brake may engage different planetary carriers or gear members to achieve various forward and reverse ratios, reducing the total number of torque-transmitting devices needed

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent combines the control functions of multiple torque-transmitting devices into fewer devices by designing them to act on multiple planetary gear sets at once. This merging of control functions reduces the number of clutches and brakes required while still achieving 7-10 forward speed ratios and reverse capability

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS8052566B2Multi-speed transmissions

Publication Date: 2011.11.08 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

The transmission has a plurality of members that can be utilized in powertrains to provide at least ten forward speed ratios and one reverse speed ratio. The transmission includes four planetary gear sets, six torque-transmitting devices, and four fixed interconnections. The powertrain includes an engine and torque converter that is continuously connected to one of the planetary gear members and an output member that is continuously connected with another one of the planetary gear members. The six torque-transmitting devices provide interconnections between various gear members and the transmission housing, and are operated in combinations of three to establish at least ten forward speed ratios and one reverse speed ratio.