Locking Differential Curve Control to Prevent Torque Overload

Solution Overview

Problem

Existing locking differentials in motor vehicle drivetrains are over-dimensioned to handle large torques during curve driving, leading to increased costs and space requirements due to the inability to effectively manage torques from both the drive aggregate and the road.

Innovation Solution

A method and control unit that disengage the locking differential when the vehicle is driving around a curve by applying brakes to the outside wheel, reducing axle load, and adjusting air suspension pressure to shift load to axles without locking differentials, ensuring the differential is only engaged at maximum drive input torque.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the locking differential is designed to withstand large torques from the road during curve driving, then the locking differential can handle torques during curve driving, but the locking differential requires over-dimensioning leading to higher costs and more fitting space

Engineering Contradiction:

Improvelocking differential torque handling capabilityVSAvoidlocking differential fitting space

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The control device disengages the locking differential before large road torques can act on it during curve driving. By detecting curve driving conditions and proactively disengaging the locking differential, the system prevents torque overload without requiring the differential to be over-dimensioned, thus reducing fitting space while maintaining reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the mechanical solution of over-dimensioning the locking differential with a control-based solution. Instead of designing a larger mechanical component to handle torques, the system uses a control device to manage torque transmission by disengaging the locking differential when appropriate, substituting mechanical oversizing with intelligent control

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If the locking differential is designed to withstand large torques from the road during curve driving, then the locking differential can handle torques during curve driving, but the locking differential requires over-dimensioning leading to higher costs

Engineering Contradiction:

Improvelocking differential torque handling capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The control device disengages the locking differential before large road torques can act on it during curve driving. By detecting curve driving conditions and proactively disengaging the locking differential, the system prevents torque overload without requiring the differential to be over-dimensioned, thus reducing manufacturing costs while maintaining reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the mechanical solution of over-dimensioning the locking differential with a control-based solution. Instead of designing a larger mechanical component to handle torques, the system uses a control device to manage torque transmission by disengaging the locking differential when appropriate, substituting mechanical oversizing with intelligent control to reduce manufacturing costs

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Prevents overloading of locking differentials, reducing the need for over-dimensioning and minimizing space and cost by managing torques effectively during curve driving.

Implementation Method 1

a brake is applied to the wheel of the axle concerned on the outside of the curve

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

at the driven axle with the engaged locking differential an air pressure of an air suspension is reduced whereas at the driven axle with the disengaged locking differential an air pressure of the air suspension is increased

Methodology Applied

Scientific EffectAir pressure: Pressure Gradient

Data Source

PatentUS12409839B2Method and control device for operating a motor vehicle

Publication Date: 2025.09.09 ZF FRIEDRICHSHAFEN AG

AI summary

A method for operating a motor vehicle (1) having at least one driven axle (3) with a locking differential (10a), where when the motor vehicle (1) is driving and the locking differential (10a) concerned is engaged on at least one driven axle (3), it is checked whether the motor vehicle is driving round a curve. If it is found that the motor vehicle is driving round a curve, the engaged locking differential (10a) is actuated to disengage it and it is checked whether the locking differential (10a) concerned has in fact been disengaged. If it is found that the locking differential (10a) concerned has not been disengaged, the wheel of the driven axle (3) concerned on the outside of the curve is braked.