Differential Lock Engagement Timing for Accurate Wheel Slip Detection

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Solution Overview

Problem

Existing methods for controlling differential locks in vehicles fail to effectively and efficiently engage or disengage the lock based on accurate wheel slip detection and vehicle conditions, leading to potential unnecessary engagement or disengagement, which can affect traction and tire wear.

Innovation Solution

A method that actuates the differential lock when wheel slip exceeds a pre-activation buffer, with delays adjusted by vehicle speed and acceleration, and disengages it based on predetermined speed and time conditions, using existing speed sensors to monitor wheel speeds and determine appropriate engagement and disengagement buffers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the differential lock is actuated immediately when wheel slip is detected, then traction control response is improved, but unnecessary engagement occurs leading to increased tire wear and reduced drivability

Engineering Contradiction:

Improveresponse speed of differential lock engagementVSAvoidaccuracy of wheel slip detection

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The system performs preliminary monitoring and evaluation of wheel slip conditions before actuating the differential lock. It calculates a pre-activation buffer based on acceleration and vehicle speed, and only engages the lock when wheel slip duration exceeds this buffer, ensuring the slip is genuine and not a false signal.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The pre-activation buffer is dynamically adjusted based on vehicle acceleration and speed conditions. At higher accelerations and speeds, the buffer is reduced for faster response; at lower conditions, the buffer is increased to prevent false engagement, making the system adaptive to different driving scenarios.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the differential lock engagement buffer is increased to prevent premature engagement, then false activation is reduced, but response time to actual wheel slip increases

Engineering Contradiction:

Improveaccuracy of lock engagement timingVSAvoiddelay in differential lock engagement

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The differential lock engagement buffer is dynamically adjusted based on vehicle speed and acceleration conditions. At higher speeds and accelerations where wheel slip is more critical, the buffer is reduced to enable faster engagement. At lower conditions, the buffer is increased to prevent false engagement, optimizing the trade-off between responsiveness and accuracy.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the buffer parameter based on operating conditions (speed and acceleration). By modifying the buffer duration according to these parameters, the system achieves reliable detection without excessive delay, adapting the time threshold to match the severity and likelihood of actual wheel slip conditions.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If wheel slip detection threshold is lowered to detect mild slip conditions, then traction control coverage is improved, but false detection increases leading to unnecessary lock engagement

Engineering Contradiction:

Improvesensitivity of wheel slip detectionVSAvoidfalse wheel slip detection

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

Before actuating the differential lock, the system performs preliminary verification by monitoring wheel slip duration against a calculated pre-activation buffer. This preliminary action filters out brief speed differences that are not genuine wheel slip, reducing false detection while maintaining sensitivity to actual traction loss conditions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors wheel speed differences and provides feedback to the control logic. By comparing real-time wheel slip duration against the dynamically calculated buffer and repeatedly verifying conditions, the system distinguishes between genuine wheel slip requiring intervention and normal speed variations, reducing false engagement while maintaining adaptability.

Inventive Principle:

Principle #23Feedback

4Productivity

If the differential lock is disengaged immediately when vehicle speed exceeds threshold, then readiness for acceleration is improved, but disengagement occurs during critical low-speed traction situations

Engineering Contradiction:

Improvevehicle acceleration readinessVSAvoidtraction maintenance during disengagement

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system uses periodic monitoring of vehicle speed over defined time periods (first and second predetermined periods) before disengaging the differential lock. This periodic verification ensures the vehicle is truly ready for acceleration and prevents premature disengagement during critical low-speed traction situations, balancing readiness with reliability.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS11746870B1Method of controlling a differential lock

Publication Date: 2023.09.05 ARVINMERITOR TECHNOLOGY LLC

AI summary

A method of controlling a differential lock. The differential lock is actuated to lock a differential assembly when wheel slip of a first wheel assembly is detected and a duration of the wheel slip exceeds a pre-activation buffer. The pre-activation buffer is based on acceleration of the first wheel assembly and vehicle speed.