Volkswagen Group Components have produced a 1-speed gearbox for all electric vehicles based on the modular electric drive matrix (MEB). The mechanism used has only a small number of cogs making it highly compact catering for all driving situations with just a single gear. The 1-speed gearbox will be used in the Volkswagen ID.3 which enters a new era of e-mobility – quiet but will a lot of power. The typical properties of an electric drive system change the in which power in transmitted. But why is a single gear enough for the drive motor?
How power is transmitted to the wheels
The traction, i.e. the force that allows movement, and speed of a motor vehicle depend on the rotational speed of its drive system. As the speed of the drive system increases, the force transmitted to the wheels – the torque – can vary. With a vehicle with a combustion engine, the torque increases along with the engine speed and then falls again. With an electric drive system, however, the maximum torque is available immediately and remains constant over a wide range of speeds. The use of a multi-speed gearbox to achieve the desired speed or the necessary torque along the speed curve is therefore not absolutely necessary.
One gear for every situation
That is why a 2-stage 1-speed gearbox is used in the Volkswagen ID.3. When reversing the car, the direction of the electric drive system is simply reversed. In addition to various other components, power electronics is responsible for this and for the power characteristics of the drive system. In order to achieve the maximum power of 150 kW, the electric drive unit must rotate at high speeds. In order to provide a high level of torque, a 10x transmission ratio is used. To save space, the gearbox has a two-stage design with two smaller cogs instead of one big one. As a result, the electric drive motor in the ID.3 provides the maximum torque of 310 Nm constantly over a wide range of speeds. The maximum speed of 160 km/h is reached at a maximum of 16,000 rpm. For the ID.3 which is optimized for maximum range, the use of a single gear for all driving situations is perfectly adequate.
Precision manufacturing makes the e-vehicle particularly quiet
Because an electric drive system is very quiet, the level of noise in an e-vehicle is very important. Even the tiniest sources of noise can suddenly be heard. The parts for the 1-speed gearbox must therefore be manufactured with great precision to ensure that they do not cause any additional noise. At the end of the production line, not only the power characteristics of the electric drive system are checked – the relevant noise values are too. All drive systems for European and North American e-vehicles based on the MEB – including the 1-speed gearbox – are manufactured at the component plant in Kassel. Other important parts are produced at the component plants in Salzgitter, Poznań and Hannover.