What is the working principle of a hydraulic retarder?
2 Answers
The working principle of a hydraulic retarder is: 1. Working principle: The hydraulic retarder utilizes liquid damping to generate a retarding effect. The stator of the hydraulic retarder also serves as the retarder housing, which is connected to the rear of the transmission or the vehicle frame. The rotor is connected to the driveshaft via a hollow shaft, and both the rotor and stator are cast with blades. During operation, pressure is applied to the oil reservoir through the control valve, allowing the working fluid to fill the working chamber between the rotor and stator. When the rotor rotates, it exerts a torque on the stator through the working fluid. The counter-torque of the stator then becomes the braking torque of the rotor, the value of which depends on the amount and pressure of the working fluid in the chamber (determined by the braking intensity set by the control valve) and the rotational speed of the rotor. 2. Practical function: The kinetic energy of the vehicle is consumed by the friction of the working fluid and the impact on the stator, converting into heat energy and raising the temperature of the working fluid. The working fluid is circulated through a heat exchanger, transferring the heat to the cooling water, which is then dissipated through the engine cooling system. In vehicles equipped with hydraulic transmission, the oil reservoir, oil pump, heat exchanger (which needs to be enlarged in size), and the working fluid used in hydraulic transmission can be omitted. Therefore, hydraulic retarders are commonly used in vehicles with hydraulic transmission.
How does a hydraulic retarder work? Let me explain from my experience driving heavy trucks. When the driver presses the switch to activate it, the device connects to the vehicle's drivetrain, like a small gadget installed near the transmission. Inside, a rotor spins rapidly, agitating special hydraulic fluid to create resistance. This resistance absorbs the vehicle's kinetic energy, slowing it down, and converts that energy into heat, which is then dissipated through the radiator. So, on steep or long downhill roads, it helps me slow down safely, avoiding the risk of overheating or even fire caused by hard braking. The key benefit is that it extends brake pad life and reduces maintenance costs—I save a lot on repairs every month. Overall, it's very user-friendly and makes driving more worry-free, especially on mountainous highways where it’s a real lifesaver.
