What is a hydraulic retarder? How does it work?

The hydraulic retarder is a safe, efficient and economical auxiliary braking system that improves the active safety of the vehicle through wear-free continuous braking. The hydraulic retarder is often used in large and heavy vehicles such as large buses, heavy trucks and special vehicles. During the driving process of the vehicle, up to 90% of the service braking can be completed by the hydraulic retarder, which can maximize the guarantee that the vehicle's brake system is always in a cold state, so that truck drivers can more effectively deal with various emergencies that may occur on the road.

How does a hydraulic retarder work?

When the driver activates the hydraulic retarder through the handle switch, the retarder receives an electronic input signal sent from the control unit. Through the control of the control unit, the proportional valve adjusts the compressed air entering the oil chamber, and presses the retarder oil from the oil chamber into the working chamber composed of the stator and the rotor. The rotor in the working chamber accelerates the oil to rotate on the stator. After the speed direction of the oil changes, it reacts to the rotor, generating a reverse force in this process, reducing the speed of the retarder rotor, and then transmitting the braking force to the vehicle through the meshing of the gears, thereby slowing down the vehicle. In the process of slow braking using the hydraulic retarder, the kinetic energy of the vehicle is converted into heat energy, which is dissipated through the heat exchanger of the hydraulic retarder and the vehicle cooling system, and so on. During the braking process, the electronically controlled engine does not spray oil, which means that basically no combustion heat is generated, and the cooling capacity of the vehicle cooling system is mainly used for heat dissipation of the hydraulic retarder. The system has an overheating protection function, and the electronic control unit ECU monitors the temperature of the entire system in real time through a temperature sensor.