Instruksjonsbok Volvo A25D - A30D

Retardation Systems

Retarder

2 4 1 3

Function principle A25D and A30D have a variable hydraulic retarder, built into the transmission. The retarder consists of a pump impeller, called the rotor (1) , a turbine impeller, called the stator (2) and the back-up bearing (3) . The rotor is driven by the vehicle’s motion whereas the stator is bolted to the transmission housing and is sta- tionary. When the retarder is activated using the retarder pedal, the piston (4) seals off the oil space between the rotor and the stator. The trapped oil is set in motion by the rotor and is pressed against the stator. Since the stator is stationary, the oil flow is retarded and consequently brakes the rotor, and the vehicle. The heat that is gener- ated in the oil by the braking force is effectively absorbed by the hauler’s cooling system, which means that the retarder is constantly usable.

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