"In 2022, is the traditional mechanical four-wheel drive really still useful?"
Since the rise of new energy vehicles, the automotive industry has faced unprecedented reforms, such as the transformation of the core three major parts from "engine, chassis and gearbox" to "battery, electronic control, motor", and the transformation of mechanical instrument panels to digital instrument clusters. Behind all these changes, almost all of them have been affected by the rapid development of pure electric vehicles. However, just when most predicted that mechanical four-wheel drive would become the next "elimination", the results were unexpected.
Mechanical four-wheel drive "status is not guaranteed"!
As we all know, in the process of automobile development, a number of four-wheel drive technologies with strong strength have emerged, including BMW X-Drive, Audi Quattro, Volkswagen 4Motion, Mitsubishi S-AWC, Subaru Synmetrical AWD and so on. To some extent, almost every mature car company has its own exclusive four-wheel drive system solution, and formed its own "moat", which makes it difficult for latecomers to overcome. However, with the gradual maturity of electrification, more and more electric vehicle products have begun to carry electric four-wheel drive, which is why many people will think that mechanical four-wheel drive will be replaced by electric four-wheel drive.
So will mechanical four-wheel drive really be replaced? This point should first be analyzed from the structure of the traditional mechanical four-wheel drive system. The traditional mechanical four-wheel drive is mainly based on the engine as the power source, after the engine output, the power through the gearbox, the transfer box, and finally to the front and rear axles of the differential, and finally to the wheel. Specifically, the types of traditional mechanical four-wheel drive mainly include full-time four-wheel drive, time-sharing four-wheel drive, time-time four-wheel drive, time-based four-wheel drive, which are suitable for different use scenarios, and have different impacts on maneuverability, ability to get rid of difficulties, fuel economy, etc. As for the difference between the three, it mainly depends on the difference in the form of the central differential lock.
Different from the traditional mechanical four-wheel drive system, the electric four-wheel drive is arranged in the front and rear axles separately, and then the control of the electronic control system is used to achieve full-time four-wheel drive, time-sharing four-wheel drive, time-time four-wheel drive, and theoretically even achieve front drive, rear drive and four-wheel drive. For electric four-wheel drive, the most obvious advantage of this four-wheel drive system is that it does not need to be equipped with gearboxes, transfer cases and other components like traditional four-wheel drive systems, saving a lot of space. In addition, from the perspective of transmission efficiency alone, electric four-wheel drive has more advantages than mechanical four-wheel drive. At the same time, because the electric four-wheel drive requires fewer spare parts, the failure rate of the electric four-wheel drive will be lower and the stability will be higher.
In addition to having a low failure rate and high stability, electric four-wheel drive as a product of the development of intelligent electric vehicles, it can rely on software as the dominant, can rely on software to define different modes, or according to the scene needs, working conditions and other self-adjustment, greatly reducing the difficulty of operation. In contrast, the traditional four-wheel drive system, when the vehicle slips in the front/rear axle wheels, it is necessary to rely on the central differential lock to distribute the front and rear power, and then distribute the power to the left and right wheels through the electronic auxiliary system, this mechanical + electronic structure design, not only depends on the performance of the differential itself, but also tests the electronic system tuning.
In other words, the biggest advantage of electric four-wheel drive is that it gives the vehicle a faster reaction speed. Audi has previously said that the biggest advantage of electric energy four-wheel drive is that it does not require the connection of mechanical components, which can achieve faster reaction speed. Compared with the traditional four-wheel drive system, the power four-wheel drive only needs 0.03 seconds of torque distribution from the perceptron calculation to the start of the motor, which is equivalent to about 1/4 of the time of the traditional four-wheel drive system. It can be seen from this that the electric four-wheel drive has the reaction ability to lead the traditional four-wheel drive system. However, if the electric four-wheel drive is to successfully replace the traditional mechanical four-wheel drive, the cylinder brother believes that it will take a long time to develop.
"Electric four-wheel drive" can not cross the "hurdle"!
"Why is it still difficult to replace the traditional mechanical four-wheel drive" ? On this issue, the cylinder brother believes that this is mainly related to the design of pure electric vehicles. Taking the Wrangler as an example, assuming that the road conditions of the limit are encountered on the non-paved road, such as the vehicle has only one wheel with adhesion, then after locking three differential locks, without considering the transmission loss, the power of the whole vehicle will be transmitted to the adhesion wheel, thus helping the vehicle to get out of trouble in time.
However, if the same situation occurs in an electric all-wheel drive SUV model equipped with dual motors in front and rear, the results will be very different. When the trapped vehicle also has only a single wheel with adhesion, then the front axle motor will not play any role in the process of getting out of the trap, which means that the total power of the vehicle is cut by half, and the power is obviously less than the same power of the mechanical four-wheel drive. It should be noted that assuming that the vehicle uses a wheel hub motor, in the context of only one wheel with adhesion, the output power is only a quarter, and the ability to get out of trouble will be greatly reduced.
At the same time, the application scenario of pure electric vehicles is relatively small, most of the precision components are concentrated in the battery, motor, if in the process of off-road and bumping with the bumpy road surface, the safety of the battery pack will have a certain threat, and may even directly affect the mechanical performance of the vehicle. In addition to the non-paved road surface will have a certain impact on the off-road performance of the vehicle, the mileage of pure electric vehicles is also a key factor affecting the user's off-road experience. For example, if the front and rear motors of pure electric vehicles are working at high power, the battery will consume more power, and there will be insufficient power supply.
In the battery energy density and other aspects have not yet appeared in the context of qualitative breakthroughs, the electric four-wheel drive system is not suitable for long-term high-current discharge, can only cope with the non-paved pavement in a short period of time, which is why the cylinder brother has always emphasized that the electric four-wheel drive is difficult to compete with the mechanical four-wheel drive. At the same time, when the electric four-wheel drive encounters a harsh environment, its performance has never been comparable to the safety and stability of the mechanical four-wheel drive.
summary
It has to be said that the electric four-wheel drive does have the strength of the leading mechanical four-wheel drive in some fields, can easily cope with most road conditions, and is simpler than the mechanical four-wheel drive in terms of operation difficulty. However, it is a relative pity that due to the structural design at this stage and the power and endurance of pure electric vehicles, it is difficult for electric four-wheel drive to have better performance in a short period of time, and in the face of non-paved roads or harsh environments, the unstable performance of electric four-wheel drive is difficult to meet the needs of users. However, the cylinder brother believes that at the time of the full electrification acceleration, the electric four-wheel drive may be able to be further optimized in the near future, which may be able to change the current dilemma.