Time-sharing four-wheel drive systems have been a hotly debated topic in the automotive industry. For strong off-road enthusiasts, time-sharing 4WD is considered one of the most powerful systems for off-road ability, but for non-off-road enthusiasts, it can almost be seen as a decoration in everyday use. With the continuous advancement of technology, the status of time-sharing four-wheel drive systems is being re-evaluated, and this change is gradually subverting people's traditional perception of four-wheel drive systems.
Part-time four-wheel drive, as the name suggests, is a system that allows you to manually select the two-wheel drive or four-wheel drive mode. It is mainly for hard-core off-road enthusiasts or some special field work occasions, because its off-road ability and ability to get out of trouble have been fully exerted in these scenarios. For general daily driving, a full-time all-wheel drive system is more suitable because it provides better handling stability.
The drive modes of the time-sharing four-wheel drive system include 2H high-speed two-wheel drive, 4H high-speed four-wheel drive and 4L low-speed four-wheel drive. If an Auto gear is found on a hardcore off-road model, then the car will be classified as a timely four-wheel drive. This system automatically switches between 2WD and 4WD when needed, similar to the automatic mode of full-time 4WD, for improved handling stability.
The time-sharing four-wheel drive system is not without its drawbacks. Its mechanical structure results in a relatively large weight and high fuel consumption. In addition, the driver needs to manually select the drive mode, which has high requirements for adapting to various road conditions, so there are certain requirements for the driver's technical level.
The transfer case of the time-sharing four-wheel drive system is one of its most striking features. The transfer unit has two functions: one is to distribute power to the front and rear axles, so that the vehicle can switch between two-wheel drive and four-wheel drive;Second, it has two gear options, namely 4H gear and 4L gear, which correspond to high-speed four-wheel drive and low-speed four-wheel drive respectively. The reduction ratio of the transfer case in low gear is 2-2 in most cases5, that is, the torque can be amplified by 2-25 times. This design gives the time-sharing all-wheel drive system an advantage in off-road performance, especially in extreme off-road conditions, as demonstrated by the Jeep Wrangler of the Robin Hood model.
There are also some limitations to the use of time-sharing four-wheel drive systems. In the early days, in order to switch to 4WD mode, the driver needed to stop and hang in N gear, but with the development of technology, most modern time-sharing 4WD systems have added synchronizers, which can switch 4WD gears while driving, although there is a certain speed limit.
Why can't the time-sharing four-wheel drive system be used at will when driving on normal roads?The crux of the problem was the lack of a differential in the transfer case to eliminate the speed difference between the front and rear wheels. As a result, once the 4WD mode is enabled, the front and rear wheels will rev exactly the same. When the vehicle is turning, there is a wheel speed difference between the left and right wheels, and there is also a wheel speed difference between the front and rear wheels.
At this time, the speed difference between the front and rear wheels can only be released by the slippage of the front or rear wheels and the ground, and once the wheels slip, they will lose directionality, increasing the driving risk. As a result, activating the time-sharing all-wheel drive system can be potentially dangerous under normal road conditions, but it can be very comfortable in off-road situations, especially on soft, unpaved roads.
With the continuous advancement of electronic control technology, some models have begun to use BorgWarner's TOD (Torque On Demand) transfer case. This system retains the advantages of the time-sharing four-wheel drive system while overcoming its shortcomings in handling stability. BorgWarner's TOD transfer cases are designed to be all-wheel drive at the right time and can be used off-road in a variety of applications. In the international market, the application of this electronic control technology has become dominant, and has gradually been introduced into some models in the Chinese market, such as the Tank 400 and 500, the Ford Raptor, the Great Wall Cannon and the Road Shaker.
Headquartered in Auburn Hills, Michigan, BorgWarner's TOD transfer cases are the market leader in advanced technology and reliable performance. BorgWarner has cooperated with almost every car factory in China that produces 4WD models, and its products are widely recognized internationally.
Although models with TOD transfer cases are classified as timing four-wheel drive by international standards, in fact, many people prefer to call them electronically controlled time-sharing four-wheel drive. The rise of this system marks the continuous evolution and innovation of four-wheel drive system technology.
The time-sharing four-wheel drive system excels in off-road ability, but it may have some deficiencies in handling stability in daily driving. With the development of electronic control technology, the emergence of timely four-wheel drive systems fills this gap, so that the off-road ability and handling stability have been better balanced.
When choosing the right four-wheel drive system for themselves, consumers should make reasonable trade-offs according to their actual car needs and driving scenarios to find the most suitable car configuration. This process also reflects the continuous innovation and advancement of automotive technology in meeting the needs of different consumers.