Recently, a heavy snowfall swept through the northern region, and the Beijing-Tianjin-Hebei region has not had such a heavy snow for many years.
Unlike the friends in the Northeast who change into snow tires early every year, the friends in Beijing, Tianjin and Hebei do not seem to have the tradition of changing snow tires - after all, there will not be so much snow in previous winters, and the winters in North China are indeed not as long as those in the Northeast.
In the same way, in most places except the northeast and northwest, snow tires are useless. It's a bit of a waste to prepare a snow tire specifically for this snow. But,There is a set of four-wheel drive system, which can better ensure the safety of driving in such weather
Except for the situation where cars fly like in Fast and Furious, the main reason for the loss of control of the vehicle is that the wheels lose their adhesion, resulting in the trajectory of the vehicle being out of the driver's control. This adhesion is longitudinal and transverse, and the loss of control of the vehicle is caused by the driving force greater than the friction force, or because the ground is slippery, and there is also due to the inconsistent adhesion of the front and rear axles or the left and right wheels.
All in all, the core element to be solved by vehicle steady-state control is to ensure the consistency of adhesion to the four tires of the vehicle as much as possible. Systems such as ABS, ESP, TCS are designed to control the brakes to achieve steady-state control of the vehicle in special scenarios. The four-wheel drive system allows the wheels of the rear or front axle to have more control and adhesion.
To put it bluntly, running on four legs is certainly less likely to fall than running on two legs – especially with electric vehicles. If you can buy a two-wheel drive fuel car, then you must buy a four-wheel drive as much as possible to buy an electric car.
Electric vehicles are inherently buggy when dealing with such low-adhesion roads:
One is the straightforward constant power and constant torque output of the electric motor, and the starting acceleration is indeed easy to abuse the fuel vehicle into slag, and on the slippery ice and snow road, such output will also be easier to break through the limit of ground friction than the fuel vehicle.
The second is the large battery hanging on the chassis of the electric car, which is often hundreds of kilograms, which virtually allows an unloaded Tesla to achieve the effect of a fully loaded Prado, and the ground gives so much friction, although the increase in the weight of the car can slightly increase the friction, but this increase is absolutely unable to drag a heavier body.
Why are there so many Wuling noodles in the short ** can abuse luxury cars, one is to rely on the light car, and the other is to rely on weak power. Therefore, electric vehicles often need more driving wheels to drive the vehicle forward - fortunately, the configuration of electric vehicles to achieve four-wheel drive, will be much simpler than gasoline vehicles - nothing more than adding a motor on the front or rear axle.
Speaking of which, another question arises, what kind of four-wheel drive is good
Full-time four-wheel drive is better than timely four-wheel drive, and timely four-wheel drive is better than four-wheel drive。Isn't it a bit subverting the traditional perception that time-sharing four-wheel drive off-road performance is better?Yes, but I didn't say that driving on low-adhesion roads must be off-road
Like I mentioned earlier,For a vehicle to achieve a steady-state ride, all four tires are capable of achieving the same grip；But if you think about it, how is it possible to drive on the road?
One of the characteristics of time-sharing four-wheel drive is that the front and rear axles are completely independent, and there is no difference structure between the two.
Wait!Dry motorcycle and skidding, isn't it just to make a four-wheel drive system so that the vehicle does not skid, how can this still come out because of the skidding of the four-wheel drive system?Therefore, the structure of time-sharing four-wheel drive can provide a more stable driving performance than two-wheel drive vehicles on roads with relatively low ground adhesion, relatively continuous low adhesion roads, and no large turns.
However, when encountering the kind of mountain road with snow on the shady side and no snow on the sunny side, or the working conditions of snow suddenly, the time-sharing four-wheel drive cannot cope with it. For example, like the road conditions in the image below.
In complex and changeable road conditions, full-time four-wheel drive and timely four-wheel drive are better choices
In fact, the concept of full-time four-wheel drive and just-in-time four-wheel drive is now somewhat vague. Because most of the timing four-wheel drive rear axle or front axle will have some power, and the frequency of four-wheel drive intervention to drive the vehicle is quite high. So, let's talk about the two together.
Compared with time-sharing four-wheel drive, full-time four-wheel drive and timely four-wheel drive is to increase the difference between the front and rear axles, with this differential, the friction between the front and rear axles no longer needs the ground to solve the problem of different speeds, plus the current electronic equipment control is more diversified, so,Full-time all-wheel drive and just-in-time all-wheel drive can also control the torque distribution between the front and rear axles and even the left and right wheels more precisely- If the front axle is going to slip, then there is less torque, and if you want to push the head, then the rear axle will have more torque.
You see, with one more axle to provide power, the more stability the vehicle can getIt's like carrying 200 yuan and carrying 400 yuan, and the things you can buy are indeed different
Going back to electric vehicles, the most valuable thing about electric drive is the reduction of control difficulty - the differential problem that used to be solved by a large number of gear shaft multi-plate clutch Torsen differentials has only a few wires and an electrical signal left in front of the electric motor.
For example, the Great Wall's Hi4 four-wheel drive system is a set of simple and efficient things. Simple, really simple, no driveshaft, no power take-off, not even a gearbox.
The drive motor of the engine and the front axle completes the power coupling through a set of multi-plate clutches, and then is specifically responsible for driving the front axle, and the rear axle is driven by a motor, and there is no mechanical connection between the two, but it can realize the problem of front and rear axle differential speed and front and rear axle torque control that many four-wheel drive vehicles can not solve.
By the way, it also carries a significant improvement in pure electric drive and fuel economy, and the production cost of the whole system is not expensive. The effect of this is that you can buy a four-wheel drive Thunder Dragon for 150,000 or 60,000 **, and you can also get a Raptor that can play off-road with some points.
Since the relationship between the front and rear axles is completely decoupled, the Hi4 model also has a more diverse drive system. For example,Economy mode and good road conditions, it is a front-wheel drive car;Pure electric mode for urban commuting, it is a rear-wheel drive car;Intensely driven, it's a full-time four-wheel drive car
So you see, an electric four-wheel drive like Hi4 is indeed a good thing, and the expansion ability of scenarios far exceeds any previous four-wheel drive form. Well, speaking of which, I think you should no longer be entangled in fuel consumption or battery life when looking at the car to see the two-wheel drive car, right?!Again, that's itWhen you buy a car, if you can buy a four-wheel drive, of course, you can buy a four-wheel drive。If it's a two-wheel drive like Hi4 to buy a four-wheel drive, there's nothing to worry about!