The purpose of the brake or brake system is to safely and reliably decelerate the vehicle, regardless of its speed. The brake also needs to keep the vehicle stationary when the driver is not there and when the vehicle is located on a slope. Active vehicle safety systems such as anti-lock brake systems (ABS) or traction control systems (TCS) supplement the brake system and are designed to keep the vehicle stable in critical situations.
Conventional friction brake
When the driver brakes the vehicle, conventional brake systems use friction to convert kinetic energy into thermal energy. When this happens, the wheel brakes are connected directly to the brake pedal via the hydraulics and brake unit in a process chain. Control devices trigger and regulate the braking action. The force of the driver’s foot pressing down on the brake pedal acts on the brake booster. The master brake cylinder converts the amplified actuation force into hydraulic pressure. Hydraulic transmission systems transmit the brake pressure via brake lines and brake hoses.
The wheel brakes are responsible for actually braking the vehicle by pressing the brake pads or linings against the brake disc or drum. This generates a frictional force, which brakes the brake disc or drum as well as the wheel bolted to it.
Regenerative brake systems
Electric vehicles may also use regenerative brake systems, which operate according to the principle of energy recuperation. When a vehicle with this type of system is braked, kinetic energy is converted into electric energy and stored temporarily in the battery. This energy can then be used again later to power the vehicle.
The recuperation process also generates a braking torque that decelerates the vehicle. The braking power provided by the generator is often sufficient to adequately brake the vehicle. However, the generators used in passenger cars do not produce enough braking power for all the vehicle’s braking needs. For this reason, the conventional friction brake remains an essential component on hybrid and electric vehicles as well.
With regenerative braking, the friction brake is used much less often overall. This means that the wear on brake discs and pads/linings is much lower than on conventional vehicles without such a recuperation function.
As a result of the recuperation process, regenerative brake systems in electric vehicles can also reduce brake particle emissions, in some cases significantly.
The first manufacturers are now working on developing wheel hub drives that do away with mechanical brakes entirely. These systems brake the vehicle using the recuperation effect alone.
Drum brakes may date back almost as far as cars themselves, but they are still installed in some electric and hybrid vehicles today. Together with the disc brake, they are a type of friction brake and supplement the regenerative brake system with recuperation function in many brake systems.
In electric vehicles, regenerative brake systems use the principle of energy recuperation. When the vehicle is braked, kinetic energy is converted into electric energy which is stored temporarily in the battery and can be used later on to power the vehicle.