China's EV crisis: Multi-gear transmissions are coming

China's EV crisis: Multi-gear transmissions are coming

At present, a company called 'Drive System Design' (hereinafter referred to as DSD) is seeking investors all over the world, and its purpose is to commercialize the company's latest multi-gear gearbox..

Seeing this now, some might disagree - it's not just the gearbox!As for the fanfare?

In fact, well-known companies such as AVL, Delta Racing, GKN, Jaguar Land Rover, Indian Tata Steel, Williams, Zytek, etc. have established a joint venture consortium for this project.The university provides ongoing technical support for the commercial development of the project.

It has to be popularized here first.The internal code of this multi-speed gearbox developed by DSD is MSYS, and it has five independent global patented technologies.Target models are electric vehicles and hybrid vehicles.

Because the torque output of the electric motor is independent of the speed of the electric motor, most new energy vehicles that rely on the electric motor for end drive are equipped with a single-stage gearbox or reducer - often called a fixed ratio gearbox.

Limitations of Fixed Ratio Transmissions

Compared with ordinary gearboxes, fixed gear ratio gearboxes have higher transmission efficiency, simple and reliable structure, small size, easy installation, and no calibration difficulties, so they become the first choice for terminal motor drive models.

Recently, however, there has been a lot of technical clamor for multi-ratio gearboxes.The reason is the problem of the driving structure.

The Tesla Model S accelerates well from 100km, but is limited by the lack of a multi-ratio gearbox, poor mid-to-rear acceleration, and poor battery life per unit

Take, for example, a DC battery car that travels across the street.At the speed limit, the torque output remains the same as at start, but no further speed increase is possible.

On the high end, asynchronous motors (also known as induction motors) are better than DC motors for battery cars.Its maximum speed is twice that of a DC motor, and its power density is also much higher than that of a DC motor.

Under the premise of the same rated power, the electric vehicle with asynchronous motor has a faster speed, but after matching with a transmission with a fixed transmission ratio, there is still the problem of low-speed economy.

For example, the Tesla Model S driven by an asynchronous motor has a strong starting ability, but the acceleration performance in the middle and late stages is also very poor, and the endurance per kilowatt-hour is even lower than that of a domestic Tengshi-due to the limitation of the box, this is actually fixed gear ratio gear.

To remedy this, BMW matched the i8's drive motor to a GKN-supplied 2-speed automatic transmission.Although in the industry, this 2AT can only be called 1.5AT at most, but it is enough for the BMW i8 to enter the pure electric mode and accelerate to 250km/h much shorter than the Tesla Model S.The main reason why BMW is confident in firing Tesla.

2AT alone is enough to reduce speed.So, why can't electric vehicles be equipped with ordinary gearboxes?The main reason is that compared with electric vehicles, the size and weight of ordinary gearboxes are too large, their transmission efficiency is low, and installation design and matching are difficult.

Taking the current dual-clutch gearbox with the highest transmission efficiency as an example, the actual transmission efficiency is about 87%, which means that the original 100km endurance is only 87km. Considering the weight of the gearbox, the actual endurance is still reduced-as we all know, endurance It is the greatest destiny of electric vehicles!

Durability may be reduced at 100km/h if a fixed ratio gearbox is used