What is the working principle of a hydraulic retarder?
2 Answers
The working principle of a hydraulic retarder is: after activating the hydraulic retarder, by altering the operation of the engine exhaust valves, the engine is transformed into an air compressor that absorbs power, providing a decelerating force to the vehicle's drive wheels. The hydraulic retarder can perform continuous hydraulic braking. The principle involves directing the high-temperature working oil to the cooler for cooling, and then continuously replenishing the cooled working oil through the oil pump, creating a continuous cycle. The hydraulic retarder is also known as a hydraulic buffer, hydraulic deceleration device, or engine retarder, and serves as an auxiliary device for vehicle deceleration and control. With a hydraulic retarder, even without using the service brake, the vehicle can achieve excellent braking performance, allowing it to maintain a constant speed when descending long slopes with a full load.
I've been driving trucks for a long time, and the hydraulic retarder is my essential tool. Its working principle is actually quite straightforward: when you press the button to activate it, the engine drives a rotor to stir oil inside a chamber. The rapidly rotating oil forms vortices, creating significant resistance that converts the vehicle's kinetic energy into heat, which is then dissipated through the cooling system, allowing the vehicle to slow down smoothly. The advantage is reduced brake pad wear, especially on continuous downhill sections, eliminating the need to slam on the brakes and avoid overheating risks. I often use it to control speed on mountain roads, where the vehicle slows down steadily, reducing driving fatigue. It's simple to operate—just a control lever on the steering wheel, pull it and you're good to go. Just be careful not to use it for too long to prevent excessive oil temperature, but new truck designs include automatic protection features, making it overall safe, reliable, and practical.
