To hold down ventilation loss to the minimum and keep the braking action constant so as to enable reproduction by providing a switching valve in the midway of a pipe for connecting between a working medium container and the hydrodynamic center of a retarder.
A retarder 1 is so constructed that a working chamber having the hydrodynamic center 1.3 are formed by an outer ring 1.1 of a rotor and an outer ring 1.2 of a stator, and connected to a coolant circulating system container 3 opened below the level 3.1 of a working medium through the connecting pipes 4, 5. A valve 2 disposed between the pipes 4, 5 is closed except the period of braking operation. At this time, the working fluid in the connecting pipe 4 is sucked in the hydrodynamic center 1.3 having low pressure so that the residual quantity of working fluid in the whole of the retarder working chamber becomes minimum. Accordingly, the absorbed power becomes minimum. During the braking operation, the valve 2 is opened to communicate the container 3 with the hydrodynamic center 1.3, so that the retarder 1 is quickly filled with a required quantity of working medium to immediately cause the braking action.
HEILINGER PETER
FRIEDRICH JUERGEN
MONDORF KARL
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