Torque/power transmission reduction, function

W25.40-1042-01

Retarder on

Engine control/permanent brake operating lever actuated. Braking with the retarder is indicated by the broken line.

As the engine brake and constant throttle are connected automatically there is also a braking effect due to the engine.

L Stator

P Impeller

T Turbine wheel

Arrow Power transmission

The retarder decelerates the vehicle when braking from high speed and during prolonged periods of driving downhill. The retarder is a permanent brake which if used spares the service brake. It is particularly effective to use the retarder when driving in a low gear with high engine speeds.

The retarder is controlled by the retarder control valve. The retarder control valve controls all functions of the oil circuit and is in turn controlled by compressed air. The compressed-air for the control of the retarder control valve is continuously adjustable in the range of 3.8 to 6.8 bar, via the retarder proportioning valve .

The retarder proportioning valve is actuated in 4 stages by the engine control/permanent brake operating lever on the steering column.

The existing pressure in the oil circuit is surpassed when a control pressure of approx. 3 bar is applied. As a result the retarder has only a small braking effect. The retarder begins to operate at a pressure of 3 bar up to its maximum braking effect at a control pressure of 6.8 bar.

If the drive clutch is operated during retarder operation, the retarder proportioning valve shuts off the compressed air supply to the retarder control valve. The retarder is then switched off, thus sparing the drive clutch.

The time required to build up the braking effect depends on how quickly the empty vaned chambers of the retarder can be filled with oil. This is achieved by the oil reservoir which is installed separately.