Electric Vehicle Transmission Using Compound Planetary Gears

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Solution Overview

Problem

Electric vehicle transmissions face challenges in achieving maximum hill-climbing ability, maximum speed performance, and energy efficiency while minimizing motor size and capacity, heat generation, and preventing shift shock.

Innovation Solution

A transmission system for electric vehicles incorporating multiple motors, planetary gear sets, and clutches, with a control method that synchronizes motor torques and shifts between low and high gear states to optimize power distribution and reduce heat generation, incorporating torque vectoring for improved high-speed curve driving.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a transmission is mounted in the electric vehicle to provide multiple gear ratios, then hill-climbing ability and speed performance are improved, but device complexity increases

Engineering Contradiction:

Improvehill-climbing ability and speed performanceVSAvoidtransmission configuration complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The transmission system is divided into multiple independent planetary gear sets (first, second, and third planetary gear sets), each capable of providing different gear ratios. This segmentation allows the system to achieve multiple gear ratios while maintaining modular simplicity, resolving the contradiction between adaptability and device complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs a nested structure where multiple planetary gear sets are integrated within a single transmission housing, with gear sets arranged concentrically or in series. This nesting approach enables multiple gear ratios to be achieved within a compact configuration, reducing overall system complexity while maintaining versatility.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Use of energy by moving object

If motor capacity is reduced to improve energy efficiency, then driving distance per charge increases, but maximum hill-climbing ability and speed performance deteriorate

Engineering Contradiction:

Improveenergy efficiency (driving distance per charge)VSAvoidmaximum hill-climbing ability and speed performance

Core Design Contradiction:

Use of energy by moving objectVSAdaptability or versatility

Solution Approach 1:

The transmission system dynamically switches between different gear ratios based on driving conditions. During hill-climbing or high-speed operations, lower gear ratios provide increased torque multiplication, allowing a smaller motor to deliver equivalent performance to a larger motor. This dynamic adaptation resolves the contradiction between energy efficiency and performance capability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the effective gear ratio parameter according to driving demands. By using a transmission with multiple gear ratios, a smaller motor can operate at optimal efficiency points while the transmission compensates for reduced motor capacity by providing appropriate torque multiplication, thus maintaining hill-climbing ability and speed performance.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If clutch engagement is used for gear shifting, then gear ratio change is achieved, but shift shock and heat generation occur

Engineering Contradiction:

Improvegear shifting capabilityVSAvoidshift shock and heat generation

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces a second motor as an intermediary device during gear shifting operations. This second motor provides compensating torque to counterbalance the torque difference caused by clutch engagement, thereby preventing shift shock. The intermediary motor acts as a buffer that smooths the transition between gear ratios, resolving the contradiction between shifting capability and harmful effects.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system prepares for gear shifting by pre-engaging the second motor to provide counter-torque before the actual clutch engagement occurs. This beforehand cushioning prevents the sudden torque changes that cause shift shock and reduces heat generation in the clutch, allowing smooth gear transitions while maintaining productivity.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS11305630B2Transmission for electric vehicle and control method thereof

Publication Date: 2022.04.19 HYUNDAI MOTOR CO LTD

AI summary

A transmission for an electric vehicle may include a first planetary gear set; a first motor configured to input power to a first rotation element of the first planetary gear set; a differential configured to receive power output from a second rotation element of the first planetary gear set; a second motor configured to selectively provide power to a third rotation element of the first planetary gear set; a second planetary gear set including a first rotation element which is directly connected to the differential, and a second rotation element which is configured to selectively receive power from the second motor; and a third planetary gear set including a third rotation element which is directly connected to a third rotation element of the second planetary gear set, a second rotation element which is fixed, and a first rotation element which is directly connected to a selected output shaft of the differential.