Differential Lock Control Reducing Wear via Speed Feedback

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Solution Overview

Problem

Existing differential gear lock control systems in vehicles experience high mechanical wear due to frequent activations and deactivations when driving on slippery surfaces, leading to inefficient traction and drivability.

Innovation Solution

The control and regulation unit detects the time between deactivation and reactivation conditions, and if this time exceeds a predetermined threshold, it activates the lock only if the vehicle's driving speed is below a specified maximum permissible speed and the accelerator pedal is actuated, ensuring the lock remains active within a tolerance range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the differential lock is activated automatically whenever a predetermined rotational speed difference is exceeded, then traction is improved on slippery surfaces, but mechanical wear of the locking mechanism increases significantly

Engineering Contradiction:
ImprovetractionVSAvoidservice life of locking mechanism
Core Design Contradiction:
ReliabilityVSDuration of action of moving object

Solution Approach 1:

The control unit stores the driving speed before lock activation and uses this stored value to determine whether to reactivate the lock after deactivation. By performing this preliminary speed storage action, the system avoids unnecessary reactivation cycles when the vehicle is already moving at acceptable speeds, thereby reducing mechanical wear while maintaining traction when needed.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The control unit continuously monitors the driving speed and uses this feedback to决定是否 reactivate the differential lock after deactivation. The system compares the stored driving speed with a maximum permissible speed threshold and only reactivates the lock if the speed is below the threshold and the accelerator pedal is pressed, creating a feedback loop that prevents unnecessary activation cycles and reduces mechanical wear.

Inventive Principle:
Principle #23Feedback

2Speed

If the differential lock reacts quickly to rotational speed differences, then vehicle handling is improved, but the number of locking cycles increases leading to more wear

Engineering Contradiction:
Improveresponse speedVSAvoidnumber of locking cycles
Core Design Contradiction:
SpeedVSProductivity

Solution Approach 1:

The control unit uses feedback from the driving speed sensor to modulate the lock activation behavior. After initial lock activation, the system checks the stored driving speed and accelerator pedal status before allowing reactivation. This feedback mechanism maintains quick response to actual traction needs while preventing spurious reactivation cycles that would increase wear.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The control unit dynamically adjusts the lock activation behavior based on real-time driving conditions. The system transitions from a static on/off control to a dynamic control that considers driving speed and accelerator pedal status, allowing the lock to remain deactivated when the vehicle is already moving at acceptable speeds, thereby reducing the number of locking cycles while maintaining appropriate response to traction needs.

Inventive Principle:
Principle #15Dynamics

Data Source

PatentEP3243682B1Control and management device for a block of a differential of driven wheels and/or driven axes of a motor vehicle
Publication Date: 2019.08.28 ZF FRIEDRICHSHAFEN AG
  • EP3243682B1 patent drawingFigure 1

AI summary

The invention relates to an automatic control device for locking a differential gear of driven wheels 6, 7, 10, 11 and/or driven axles 3, 4 of a motor vehicle, comprising wheel speed sensors 19, 20, 21, 22 for detecting the rotational speeds and/or rotational speeds of the wheels 6, 7, 10, 11 and/or axle speed sensors 16, 17 for detecting the rotational speeds and/or rotational speeds of the axles 3, 4. The locking mechanism of the differential gear can be activated for a specific holding time and deactivated again after the holding time has elapsed.The actual time between a deactivation and the subsequent occurrence of the activation conditions for an activation can be recorded and compared to a predetermined time. If the predetermined time is exceeded by the measured time, the lock is activated. If the predetermined time is undershot by the measured time and the lock is activated, the vehicle's speed is measured and stored. The lock remains active as long as the stored speed is below a predetermined maximum permissible speed, an accelerator pedal for load control of engine 1 of the vehicle is being actuated, and/or the speed is within a tolerance range of the stored speed.