Torque Distribution Control for Four-Wheel Drive Coupler Protection
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Solution Overview
Problem
Existing four-wheel-drive vehicle torque distribution systems fail to effectively protect the coupler from overheating due to permanent slip, which can be caused by incorrect wheel mounting, differences in tire diameter, or other issues, and do not seamlessly integrate torque distribution control with the vehicle's management system, leading to potential damage and unnecessary interruption of the four-wheel-drive mode.
Innovation Solution
A torque distribution control method that determines and discriminates between normal and permanent slip by using a configurable duration to assess slip values and conditions, suppressing torque transfer to the affected axle when permanent slip is detected, and incorporating a counter mechanism to validate sustained slip conditions, while also considering temperature and torque values to maintain the four-wheel-drive mode availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If torque distribution control is implemented to reduce slip, then coupler wear is reduced, but the system cannot effectively protect the coupler from overheating due to permanent slip
Solution Approach 1:
The control system performs preliminary detection of permanent slip conditions using speed sensors and counter mechanisms before significant overheating damage occurs. By identifying slip patterns that indicate permanent slip (through counter incrementing when slip exceeds thresholds during configurable durations), the system can preemptively adjust torque distribution to protect the coupler from thermal damage.
Solution Approach 2:
The system continuously monitors wheel speeds and calculates slip values, feeding this information back to the torque distribution control. When the counter reaches thresholds indicating permanent slip, the feedback loop triggers torque suppression to the affected axle, creating a closed-loop protection mechanism that responds to actual coupler stress conditions in real-time.
2Reliability
If torque transfer is suppressed to protect the coupler, then overheating is prevented, but four-wheel-drive mode availability is reduced
Solution Approach 1:
The torque distribution is dynamically adjusted based on real-time slip detection rather than being statically suppressed. The system maintains four-wheel-drive operation under normal conditions and only suppresses torque to the affected axle when the counter mechanism detects permanent slip patterns, allowing the system to adapt between full four-wheel-drive functionality and protective torque suppression as conditions require.
Solution Approach 2:
The system changes operational parameters (torque distribution ratios) based on detected slip conditions. When the counter reaches thresholds indicating permanent slip, the torque distribution parameter is modified to suppress torque to the problematic axle. This parameter change is reversible - when slip conditions resolve and the counter decreases, normal torque distribution is restored, maintaining four-wheel-drive availability.
3Measurement precision
If slip detection is made sensitive to detect permanent slip, then coupler protection is improved, but normal slip during driving conditions is falsely detected
Solution Approach 1:
The system uses periodic evaluation over configurable durations rather than instantaneous slip measurement. By accumulating slip events in a counter over defined time periods and only triggering protection when the counter reaches thresholds, the system filters out transient normal slip during driving maneuvers while detecting sustained permanent slip patterns that indicate actual coupler damage risk.
Solution Approach 2:
The counter mechanism performs preliminary accumulation and evaluation of slip events before triggering torque suppression. This preliminary action over a configurable duration allows the system to distinguish between temporary normal slip (which won't sustain the counter threshold) and permanent slip conditions (which will progressively increment the counter), reducing false detections while maintaining detection sensitivity.
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
Effectively protects the coupler from overheating and damage by preventing torque transfer during permanent slip without unnecessarily interrupting the four-wheel-drive mode, ensuring a balance between coupler protection and mode availability through precise slip detection and counter mechanisms.
Implementation Method 1
In the case where the coupler is based on a controlled clutch, the dry friction linked to the contact between the discs can lead to deterioration by wear of the discs by heating.
Implementation Method 2
when there is a speed difference between the transfer shaft and the shaft connected to the second axle, the discs shear the oil, the temperature of which increases and then expands and thickens
Data Source
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AI summary
The invention relates to a motor vehicle (Ve) with four drive wheels (1a, 1b, 1c, 1d) mounted on two axles (2AV, 2AR), comprising: a transfer shaft (8) connected to the first axle and a controlled coupling (9) which can transfer part of the torque from the transfer shaft (8) to the second axle, means for determining the respective speeds of the two axles, and a torque distribution control system (11) capable of determining a slip value representative of the speed difference between the two axles and of controlling the coupling. The torque distribution control system is configured to control the coupling (9) such as to suppress any torque transfer via the coupling when the average slip value over a pre-determined period (MinTime) exceeds a threshold.