Electrically Variable Transmission with Three Planetary Gear Sets

Solution Overview

Problem

Conventional vehicle transmission systems, particularly in hybrid electric vehicles, face inefficiencies in fuel consumption and emissions due to the wide variation in engine demands, and existing electrically variable transmissions are heavy and costly due to the need for extensive electric machinery and energy losses in conversions.

Innovation Solution

The development of an electrically variable transmission system with three planetary gear sets, two motor/generators, and five or six torque transmitting devices, allowing for selective operation in power-split variable speed ratios and fixed speed ratios, which reduces the reliance on electric machinery and enhances energy efficiency through regenerative braking and electric-only idling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If a series hybrid electric drive system is used to allow engine independence from vehicle torque and speed requirements, then emissions and efficiency are improved, but weight and cost increase due to extensive electric machinery and energy losses in conversions

Engineering Contradiction:

ImproveemissionsVSAvoidweight

Core Design Contradiction:

Object-generated harmful factorsVSWeight of moving object

Solution Approach 1:

The transmission system divides power flow into two separate paths: an electric path through motor/generators for torque conversion and a mechanical path through planetary gear sets for direct torque transmission. This segmentation allows the system to operate in hybrid mode, reducing reliance on large electric machinery while maintaining emissions benefits.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The planetary gear sets act as mechanical intermediaries between the engine and drive system, enabling direct mechanical torque transmission that bypasses the need for complete electromechanical conversion. This reduces energy losses and the size of required electric machinery while maintaining engine independence benefits.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-generated harmful factors

If a series hybrid electric drive system is used to allow engine independence from vehicle torque and speed requirements, then emissions and efficiency are improved, but cost increases due to extensive electric machinery

Engineering Contradiction:

ImproveemissionsVSAvoidcost

Core Design Contradiction:

Object-generated harmful factorsVSEase of manufacture

Solution Approach 1:

The transmission system divides power flow into two separate paths: an electric path through motor/generators for torque conversion and a mechanical path through planetary gear sets for direct torque transmission. This segmentation allows the system to operate in hybrid mode, reducing reliance on large electric machinery while maintaining emissions benefits.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The planetary gear sets act as mechanical intermediaries between the engine and drive system, enabling direct mechanical torque transmission that bypasses the need for complete electromechanical conversion. This reduces energy losses and the size of required electric machinery while maintaining engine independence benefits.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If conventional electrically variable transmissions are used, then continuous variation in torque and speed ratio is achieved, but weight and cost increase due to extensive electric machinery

Engineering Contradiction:

Improvecontinuous variation in torque and speed ratioVSAvoidweight

Core Design Contradiction:

Adaptability or versatilityVSWeight of moving object

Solution Approach 1:

The transmission system divides power flow into two separate paths: an electric path through motor/generators for torque conversion and a mechanical path through planetary gear sets for direct torque transmission. This segmentation allows the system to operate in hybrid mode, reducing reliance on large electric machinery while maintaining emissions benefits.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The planetary gear sets serve multiple functions: they provide mechanical torque transmission, enable continuous variable ratio operation when combined with electric motors, and allow for fixed ratio modes. This multi-functionality reduces the need for dedicated electric machinery while maintaining adaptability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Adaptability or versatility

If conventional electrically variable transmissions are used, then continuous variation in torque and speed ratio is achieved, but energy losses increase due to repeated conversions between mechanical and electrical energy

Engineering Contradiction:

Improvecontinuous variation in torque and speed ratioVSAvoidenergy losses in conversions

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The planetary gear sets act as mechanical intermediaries between the engine and drive system, enabling direct mechanical torque transmission that bypasses the need for complete electromechanical conversion. This reduces energy losses and the size of required electric machinery while maintaining engine independence benefits.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The transmission system dynamically switches between electric and mechanical power transmission paths based on operating conditions. The planetary gear sets can operate in different modes (fixed ratio, continuous variable ratio) and the system can transition between series hybrid and parallel hybrid operation, optimizing energy efficiency across different driving scenarios.

Inventive Principle:

Principle #15Dynamics

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 solution improves vehicle acceleration, fuel economy, and reduces emissions by optimizing energy efficiency, package size, and ratio coverage, while being lighter and less costly than conventional systems.

Implementation Method 1

An electric generator can transform mechanical power from the engine into electrical power, and an electric motor can transform that electric power back into mechanical power at different torques and speeds

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

A power-split transmission can use what is commonly understood to be 'differential gearing' to achieve a continuously variable torque and speed ratio between input and output

Methodology Applied

Scientific EffectMechanical advantage: Mechanical Advantage

Implementation Method 3

This system also allows the electric machine attached to the remainder of the drive train to act as a generator, recovering energy from slowing the vehicle into the battery by regenerative braking

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS7473201B2Multi-mode electrically variable transmissions with three fixed interconnections and two input clutches

Publication Date: 2009.01.06 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

An electrically variable transmission family having low-content, low-cost electrically variable transmission mechanisms including three differential gear sets, a battery, three interconnecting members, two electric machines serving interchangeably as motors or generators and five or six selectable torque-transfer devices. The selectable torque transmitting devices are engaged to yield an EVT with a continuously variable range of speeds and five fixed speed ratios, including four mechanically fixed forward speed ratios and one reverse speed ratio. The torque transmitting devices and the first and second motor/generators are operable to provide five operating modes in the electrically variable transmission, including battery reverse mode, EVT reverse mode, reverse and forward launch modes, continuously variable transmission range mode, and fixed ratio mode.