US Patent 11173882 Hydrodynamic retarder system

A hydrodynamic retarder system for a vehicle is provided. In a first operational state with the vehicle powered on and a retarder deactivated, a pump directs fluid flow from a fluid sump to a retarder inlet valve in the closed position and directs fluid flow to a second sump. In a second operational state with the vehicle on and the retarder activated, the retarder inlet valve moves to the open position directing fluid flow into a retarder chamber and flowing out of the retarder chamber after filling a second volume and discharging to the second sump.