The function of constant vehicle speed. It is widely used in commercial vehicles (such as trucks, buses), special vehicles (such as construction machinery, fire trucks) and some high-performance passenger cars, especially in long downhill and heavy-load transportation. The following are its core functions and characteristics:
1. Core function: efficient auxiliary braking to ensure driving safety
1. Control the vehicle speed in long downhill scenarios to avoid brake overheating
Limitations of traditional braking: When the vehicle is on a long downhill, if the service brakes (such as drum brakes/disc brakes) are frequently used, friction heat will cause the brake pad temperature to rise sharply (up to 600°C or more), causing the braking performance to decay or even fail (i.e. "thermal decay" phenomenon).
Working principle of hydraulic retarder:
Hydraulic oil is injected into the retarder cavity through the oil pump, and the rotor (connected to the drive shaft) drives the hydraulic oil to rotate. The oil collides with the stator (fixed housing) to generate resistance torque, converting the vehicle's kinetic energy into oil heat energy.
The braking torque can be controlled in real time by adjusting the oil pressure (without mechanical friction), continuously providing stable braking force, and avoiding the risk of overheating of traditional brakes.
Data comparison: When a 30-ton truck is driving downhill for a long time, it needs to stop every 2 kilometers to cool the brakes when using only the service brakes, while the hydraulic retarder can drive downhill continuously without stopping, and the braking distance is shortened by more than 30%.
2. Reduce the wear of the service brakes and extend the service life
The hydraulic retarder bears most of the braking load (can contribute 70%-90% of the braking force), greatly reducing the frequency of use of the service brakes and the number of replacements of brake pads, brake drums and other components.
Economic efficiency: Taking heavy trucks as an example, after installing a hydraulic retarder, the brake pad replacement cycle can be extended from every 100,000 kilometers to more than 300,000 kilometers, saving about 20,000-30,000 yuan in maintenance costs each year.
3. Improve braking stability on slippery roads
On slippery roads such as rain, snow, and ice, traditional brakes are prone to side slipping or loss of control due to wheel locking.
The hydraulic retarder has a soft and uniform braking torque (non-mechanical locking), and can accurately adjust the braking force through the electronic control system, reduce the risk of wheel slippage, and improve driving stability (especially suitable for buses and dangerous goods transport vehicles).
2. Applicable scenarios and vehicle types
1. Commercial vehicle field
Long-distance heavy trucks: In mountain roads and plateau transportation scenarios, hydraulic retarders are standard safety devices (such as European regulations requiring dangerous goods transport vehicles to install them).
Coaches/tourist buses: Ensure passenger comfort (no frustration of traditional braking) and reduce driver fatigue (reduce frequent braking operations).
Garbage trucks/engineering vehicles: In scenarios with large load changes and frequent start-stop, auxiliary braking improves operational safety.
2. Special vehicles and high-performance vehicles
Fire trucks/ambulances: In emergency missions, the speed needs to be quickly stabilized to avoid brake failure and delay rescue.
Racing cars/high-performance sedans: Some high-end models (such as the Porsche 911 GT series) use hydraulic retarders to enhance track braking performance and reduce brake thermal decay.