Center Differential Torque Split Without Constant Clutch Slip
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Solution Overview
Problem
Existing all-wheel drive systems face issues of thermal damage, strength, and durability due to constant slipping of the transfer clutch, particularly when changing the front-rear torque distribution ratio, and incur losses in the oil pump due to high clutch engaging pressures.
Innovation Solution
An all-wheel drive system with a center differential, limited-slip differential clutch, and separate front-wheel and rear-wheel torque transmission systems, where the front-rear torque distribution ratio is initially unequal and adjustable, using a controller to manage engaging pressure based on vehicle dynamics to prevent thermal damage and reduce oil pump losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a transfer clutch is used to control the front-rear torque distribution ratio, then the torque distribution can be adjusted, but thermal damage and durability issues occur due to constant slipping of the clutch
Solution Approach 1:
The patent extracts the torque distribution control function from the transfer clutch and relocates it to the center differential mechanism. By doing so, the center differential inherently provides torque distribution control through its mechanical structure, eliminating the need for the transfer clutch to constantly slip during normal operation. This resolves the contradiction by maintaining adaptability through the center differential while improving reliability by removing the thermal damage issue from the clutch.
Solution Approach 2:
The patent introduces a limited-slip differential clutch as an intermediary component within the center differential mechanism. This limited-slip clutch acts as a mediator that provides torque distribution control only when necessary (during low-speed cornering or slippery conditions), rather than requiring constant clutch engagement. This resolves the contradiction by maintaining adaptability when needed while minimizing thermal damage by limiting clutch operation to specific conditions.
2Adaptability or versatility
If high clutch engaging pressure is applied to change the torque distribution ratio, then the torque distribution control is effective, but losses in the oil pump increase
Solution Approach 1:
The patent implements periodic or conditional action by making the limited-slip differential clutch engage only during specific driving conditions (low-speed cornering or slippery road conditions) rather than continuously. This resolves the contradiction by providing effective torque distribution control only when necessary, thereby reducing oil pump losses during normal driving conditions while maintaining adaptability when needed.
Solution Approach 2:
The patent changes the operational parameters of the clutch system by using a limited-slip mechanism that operates based on speed and load conditions rather than maintaining constant high engagement pressure. This resolves the contradiction by providing effective torque distribution when needed while minimizing energy losses during normal operation through parameter-based control.
3Adaptability or versatility
If the reduction ratios of front and rear wheel torque transmission systems are made different, then the front-rear torque distribution ratio becomes initially unequal and changeable, but the system complexity increases
Solution Approach 1:
The patent merges the torque distribution control function with the center differential mechanism by integrating a limited-slip differential clutch into the center differential. This combination allows the system to achieve variable torque distribution ratios through a unified mechanism rather than separate control systems, thereby reducing overall system complexity while maintaining adaptability.
Solution Approach 2:
The center differential mechanism with limited-slip clutch serves multiple functions: it provides inherent torque distribution control through its mechanical structure, offers variable torque distribution ratios through the limited-slip mechanism, and operates automatically based on driving conditions. This multi-functionality resolves the contradiction by achieving adaptability through a single integrated mechanism rather than multiple separate systems.
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
The system effectively changes the front-rear torque distribution ratio while minimizing thermal damage to the clutch and reducing oil pump losses by setting different reduction ratios for front and rear wheels and adjusting engaging pressure dynamically.
Implementation Method 1
The limited-slip differential clutch (407) is configured to limit a differential operation of the center differential in accordance with an engaging pressure
Data Source
AI summary
An all-wheel drive system includes a center differential, a limited-slip differential clutch, a front-wheel torque transmission system, a rear-wheel torque transmission system, and a controller. The center differential distributes torque between front and rear wheels of a vehicle. The limited-slip differential clutch limits a differential operation of the center differential in accordance with an engaging pressure, and changes a front-rear torque distribution ratio between the front and rear wheels. The front-wheel torque transmission system transmits torque between the center differential and the front wheels. The rear-wheel torque transmission system transmits torque between the center differential and the rear wheels. The controller adjusts the engaging pressure based on a driving state of the vehicle. Reduction ratios of the front-wheel and rear-wheel torque transmission systems are set different from each other. The center differential is configured such that the front-rear torque distribution ratio is initially unequal and is changeable.