With the technological development and promotion of pure electric vehicles, quite a few consumers are willing to buy pure electric vehicles when choosing their first car. What's more, it is already a "veteran player" of pure electric vehicles, and it has been or is about to undergo consumption upgrades and replaced with new EV models with updated technology and longer battery life.
Most of the friends who have experienced pure electric vehicles will never forget the smooth dynamics. There is no longer the sound of the engine and the mellow and frustrated shifting experience, and will naturally be attracted by pure electric vehicles. In addition to the wide output characteristics of the motor, it is also possible to provide such a hearty experience thanks to the single-stage reduction mechanism that does not need to change the transmission ratio. However, the Porsche Taycan, which was unveiled and announced the pre-sale price not long ago, uses a 2AT gearbox. Why does a pure electric vehicle need a gearbox? And what kind of power performance can a gearbox with only two gears achieve?
Motor characteristics
As we all know, the reaction speed of electric motors is faster and faster than that of fuel engines. According to the type, the motors used in pure electric vehicles are divided into AC and DC motors. At present, the permanent magnet synchronous motors are widely used. Among them, permanent magnet synchronous motors benefit from high efficiency, wide speed range, small size, light weight, and power. Low cost and other characteristics have become the main driving motor in the pure electric passenger car market.
According to the engine power calculation formula P=(nVp)/30t(n: speed rpm, V: displacement L, p: average pressure in the cylinder (MPa, t: engine stroke), power and speed show a positive correlation, so the engine (motor) must output high power first and the speed must be high. Generally speaking, the speed range of the permanent magnet synchronous motor can work between 4000-15000 rpm, and the speed range of its power output is far more advantageous than the traditional gasoline engine.
Why does our car need a multi-stage deceleration mechanism to achieve acceleration, power output and Balance between economics. The deep-seated reason is that fuel engines are restricted by universal characteristics. Generally speaking, the universal characteristic range of ordinary engines is about 1-6000rpm. In the relatively narrow universal characteristic area, the range of high efficiency interval is smaller, so A multi-stage reduction mechanism, or gear, is needed to assist the engine speed to fall into the high efficiency range.
As mentioned earlier, the range of universal characteristics of the electric motor is wider, and the driver only needs to control the switch under his feet. The opening and the amplitude can maintain the operating range of the motor; thus, it can get rid of the gearbox and use a fixed gear ratio reduction mechanism to transmit power. In addition, fixed gear ratio gearboxes are much less difficult for automakers to calibrate power matching.
The birth of 2AT
It is true that the motor's wide output range can indeed provide efficient output in the low and medium speed range, and It can reduce the mechanical loss caused by the multi-stage reduction structure to a certain extent. However, under high-speed driving conditions, the motor speed is maintained in a relatively high range, and the power output is not in the high-efficiency range. At the same time, the motor itself needs to consume more power to maintain output. Furthermore, even if a vehicle traveling at high speed needs to overcome the friction and air resistance of the ground, it needsThe power is not large, which means that part of the energy of the motor is wasted at this time.
Traditional automobile gearbox, after years of development and technical optimization, its stability, economy and The experience of use has been affirmed by the market. However, the volume and weight of the box and the gear ratio design for the distribution of power are more cumbersome for pure electric vehicles, so most solutions do not choose traditional automotive gearboxes.
In fact, 2AT gearboxes are not unfamiliar to us. In some models such as imported BMW i8 and domestic WEY Both P8 and 2018 MG 6 new energy have used similar structures.
What car is suitable for?
On the Porsche Taycan, we have seen that pure electric vehicles use 2AT gearboxes. There is no doubt that this is to take care of it. Performance output and endurance. But with the continuous deepening of electrification, some models that we pay less attention to, such as buses, trucks and tractors, have already begun their electrification road.
The pure electric gearbox introduced by the manufacturer that is specially matched for commercial vehicles in China can be used in the light truck logistics with a full load of 4.5 tons. The energy consumption is about 3.6 kilometers per kilowatt-hour. In this way, on the basis of retaining the high torque and zero emission of pure electric commercial vehicles, the endurance of pure electric commercial vehicles is improved, the life cycle of a single charge is increased, and the transportation efficiency is improved.
Whether or not a gearbox is required for pure electric vehicles, in my opinion, it is not only necessary but also necessary. You know, the deep-seated goal of the birth of pure electric vehicles is to change the energy structure and reduce emissions. Looking at the current domestic production of electricity, it is still not clean energy, so it becomes necessary to increase the usage and efficiency of electricity in automobiles.
Furthermore, in the key areas of battery technology, including battery energy density, cost and volume, etc., when all aspects have not been achieved, the battery life can be improved by adding a gearbox. Ability can be said to be a "slow strategy" for the development of pure electric vehicles to buy time for the development of battery technology.
(The source network of the article with pictures, intrusion and deletion)
