Active Differential Coupling Device for Torque Distribution

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Solution Overview

Problem

Active differentials in motor vehicles experience excessive stress due to small rotational speed differences between drive axles, leading to continuous strain on both electrical and mechanical components, especially when tires are unevenly worn or during weight shifts in the vehicle.

Innovation Solution

An active differential with a coupling device that only transmits torque from the planetary gear train to the distributor shaft when the rotational speed difference exceeds a predetermined limit value and is activated based on the operating state of the distributor motor, using a centrifugal or viscous clutch to decouple at low speeds, thereby reducing unnecessary torque transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the distributor shaft is continuously coupled to the planetary gear train to enable torque distribution control, then the active differential can respond to steering and driving conditions, but small rotational speed differences cause continuous strain on electrical and mechanical components

Engineering Contradiction:

Improvetorque distribution controlVSAvoidcomponent strain

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The coupling between the distributor shaft and planetary gear train is made dynamic rather than continuous. The coupling device engages and disengages based on operational conditions, allowing the system to adapt between coupled and decoupled states. This resolves the contradiction by enabling torque distribution control when needed while preventing continuous strain during normal operation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

A coupling device acts as an intermediary between the distributor shaft and planetary gear train. This mediator selectively transmits torque based on rotational speed differences and operational requirements, preventing direct continuous coupling that causes strain while maintaining the capability for controlled torque distribution when conditions warrant engagement.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a centrifugal or viscous clutch is used to decouple at low speeds, then component stress is reduced, but the device complexity increases

Engineering Contradiction:

Improvecomponent stress reductionVSAvoidcoupling device structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The centrifugal or viscous clutch is a self-regulating device that automatically engages and disengages based on rotational speed conditions without requiring external control systems. The clutch inherently senses speed differences and adjusts coupling accordingly, reducing component stress during low-speed operation while avoiding complex electronic control architectures.

Inventive Principle:

Principle #25Self-service

3Reliability

If torque transmission is prevented at low rotational speed differences, then unnecessary stress on components is reduced, but the ability to respond to steering inputs and driving conditions is limited

Engineering Contradiction:

Improvecomponent stressVSAvoidresponse to driving conditions

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The system changes the operational parameter of coupling engagement based on rotational speed difference thresholds. When speed differences exceed predetermined limits, the coupling device engages to enable torque distribution response. When differences remain below thresholds, the system decouples to reduce stress. This parameter-based control resolves the contradiction by dynamically adjusting system responsiveness.

Inventive Principle:

Principle #35Parameter changes

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 reduces the stress on electrical and mechanical components by preventing speed-dependent torque transmission at low rotational speed differences, allowing controlled torque distribution during specific driving conditions like starting or navigating obstacles, while maintaining efficient torque management.

Implementation Method 1

using a centrifugal or viscous clutch to decouple at low speeds

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

using a centrifugal or viscous clutch to decouple at low speeds

Methodology Applied

Scientific EffectViscous damping: Viscous Damping

Data Source

PatentUS10060523B2Active differential and motor vehicle

Publication Date: 2018.08.28 AUDI AG

AI summary

An active differential for the controlled distribution of a drive torque generated by a drive motor to two drive shafts includes a planetary gear train configured to couple the two drive shafts to a drive shaft of the drive motor, and a distributor motor including a distributor shaft. The distributor motor produces a torque, with a distribution of a drive torque to the two drive shafts being dependant on the torque produced by the distributor motor. The distributor shaft and the planetary gear train are coupled by a coupling device which only transmits a torque from the planetary gear train to the distributor shaft when a rotational speed difference between rotational speeds of the two output shafts exceeds a predetermined limit value and when a connection condition depending on an operating condition of the distributor motor is satisfied.