Control valve assembly for electro-hydraulic steering system

摘要

A steering system includes a fluid pump and an electro-hydraulic steering circuit in selective fluid communication with the fluid pump. The electro-hydraulic steering circuit defines a first flow path having a first proportional valve and a first load-sense passage in selective communication with the first proportional valve. The first proportional valve includes a closed position. A hydrostatic steering circuit is in selective fluid communication with the fluid pump and defines a second flow path having a second proportional valve and a second load-sense passage in selective fluid communication with the second proportional valve. The second flow path is in a parallel flow configuration with the first flow path. An isolation valve is disposed in the first flow path in series with the first proportional valve. The isolation valve includes a closed position and is piloted to the closed position by fluid communicated through the second load-sense passage.