Off road vehicles are special vehicles designed specifically for complex road environments. They not only hold a high share in the civilian high-end automotive consumer market, but also have important military applications. They are the main equipment used by the army to carry out reconnaissance, patrol, combat and other tasks. In the face of harsh outdoor road conditions, the limited slip differential with anti slip and anti trap functions is the core driving component to ensure the high trafficability and maneuverability of off-road vehicles. Developing high-performance limited slip differentials is of great significance for improving the performance of off-road vehicles in China and even enhancing national defense capabilities.
At present, the mainstream anti slip mechanism of differentials is to connect the half axle of the differential to the housing or the half axle to the half axle through geometric locking or friction when the vehicle is trapped due to wheel slip on one side, thereby improving the overall traction of the vehicle and achieving disengagement. The locking differential connects one side of the drive shaft and the differential housing rigidly through the internal locking mechanism, belonging to geometric locking. Its slip limiting process is very reliable, but ineffective locking on complex road conditions usually reduces the overall handling of the vehicle, and is commonly used in heavy-duty off-road vehicles. Compared to other types of off-road vehicles, friction limited slip differentials are more commonly used, often in the form of mechanical friction discs, electrically controlled friction discs, viscous couplings, and worm gears. However, friction limited slip differentials all have lifespan issues due to wear. In addition, mechanical friction discs and viscous couplings have limited anti slip capabilities, and electrically controlled friction discs rely too much on sensing and control, resulting in complex configurations of worm gear and worm gears, The cost is expensive.
Compared with a limited slip differential, a variable transmission ratio differential composed of non circular gears has the same structure as a regular differential. It redistributes the torque between two wheels through a time-varying transmission ratio to improve the overall traction of the vehicle and assist the vehicle in getting out of trouble. The anti slip mechanism is completely different from other limited slip differentials. Wang Xiaochun et al. studied a design method for non bevel gear tooth profile modification and proposed a single cycle pitch variable transmission ratio differential; Jiang Hong et al. proposed a three cycle variable transmission ratio differential by increasing the transmission ratio variation period of non bevel gears. Through experimental research, it was found that this type of differential can simultaneously improve traction and shorten braking distance; Jia Jumin and others put forward a simplified design method of non bevel gear by combining differential geometry method and equivalent design theory, and put forward a special variable transmission ratio differential for off-road vehicles. In addition, Jia Jumin and others also designed a dual planetary gear differential based on the transmission principle of non-circular planetary gear. At present, there are two main problems with variable transmission ratio differentials. Firstly, the core transmission components of differentials mostly use non bevel gears, which are difficult to design and process and have poor interchangeability; The second is that the locking coefficient of the variable transmission ratio differential is low, and the anti slip ability is weak, which limits the application of the variable transmission ratio differential.