Variable-Lock Limited-Slip Differential for Natural Torque Control
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Solution Overview
Problem
Existing limited-slip differentials either provide inflexible characteristics, which skilled drivers find unnatural, or require electronic control that interferes with the driver's intended actions, lacking adaptability to varying driving conditions.
Innovation Solution
A differential system with a clutch, actuator, and electronic control unit that dynamically controls clutch torque based on input torque and vehicle conditions, mimicking mechanical LSD behavior while allowing electronic adaptability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electronic control is used to optimize differential motion limitation, then adaptability to different driving conditions is improved, but natural driving feel and driver control are worsened due to unintended electronic intervention
Solution Approach 1:
The system dynamically adjusts the differential characteristics by varying the locking rate in real-time based on driving conditions. The electronic control unit modifies the clutch torque dynamically, allowing the differential to adapt its behavior from locked to unlocked states, providing both adaptability and natural driving feel through controlled dynamic adjustment rather than fixed characteristics.
Solution Approach 2:
The system changes the torque distribution parameters dynamically by adjusting the locking rate between 0% and 100%. The electronic control unit varies the clutch torque parameter based on wheel speed differential, slip rate, and driving conditions, enabling the differential to exhibit different characteristics (mechanical LSD-like or unlocked) without physical replacement, thus maintaining natural driving feel while providing adaptability.
2Ease of operation
If mechanical LSD is used to provide natural driving feel, then driver control and vehicle behavior predictability are improved, but flexibility and adaptability to different conditions are worsened
Solution Approach 1:
The differential system incorporates multiple functions within a single device: it can operate as a mechanical LSD providing natural driver control, or as an electronically controlled differential providing adaptability. The system universally handles both mechanical friction-based torque limitation and electronic torque distribution, allowing one device to serve multiple driving scenarios and control preferences.
Solution Approach 2:
The system replaces the need for multiple mechanical LSD units with different fixed characteristics by using an electronically controlled clutch mechanism. The electronic control unit substitutes for multiple mechanical devices by dynamically adjusting the locking rate, allowing the same physical differential to provide different torque distribution characteristics without mechanical replacement.
3Device complexity
If fixed characteristic LSD is used, then device simplicity is improved, but ability to optimize performance for different situations is worsened
Solution Approach 1:
The differential system performs self-adjustment by automatically modifying the locking rate based on real-time driving conditions such as wheel speed differential and slip rate. The electronic control unit monitors the differential motion and autonomously adjusts the clutch torque without driver intervention, enabling the system to optimize its performance characteristics for each situation while maintaining a relatively simple overall structure.
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
Provides a driving experience similar to mechanical LSDs without the unnatural interventions, offering adaptable characteristics and the ability to change settings without replacing the differential, enhancing driver control and vehicle performance.
Implementation Method 1
a clutch interposed between the casing and the first side gear to frictionally brake the first side gear relative to the casing so as to limit differential motion between the first side gear and the second side gear
Implementation Method 2
an actuator configured to exert a pressure force on the clutch to control the differential motion
Data Source
AI summary
A differential used for distributing input torque, is provided with: a casing to receive the input torque; a differential gear set supported by the casing for differentially distribute the input torque to first and second side gears; a clutch interposed between the casing and the first side gear to limit differential motion between the first side gear and the second side gear; an actuator to exert a pressure force on the clutch to control the differential motion; and an electronic control unit configured to calculate a locking rate from a selected differential torque ratio, calculate a requesting torque from a product as a result of multiplying the input torque by the locking rate, and control an electric power to be input to the actuator on the basis of the requesting torque.