Such a control valve is, for example, known from DE 10 2005 043 458 B4. The high pressure port is connected to a proportional valve. The proportional valve is connected to a changeover valve having two outputs, each output being connected to one of the pressure chambers. The proportional valve allows to adjust the pressure coming from the high pressure port. The changeover valve is meant to direct said pressure coming from the proportional valve to one of the pressure chambers. Depending on which pressure chamber is supplied with the higher pressure from the proportional valve the valve element will be moved in one of the two directions until an equilibrium between the pressure force and a force of a spring is reached. Each pressure chamber is also connected to one of two two-way magnetic valves, wherein both two-way magnetic valves lead to a low pressure supply and, when opened, allow hydraulic fluid to escape from the pressure chamber to the low pressure port.
For a hydraulic valve arrangement it is often required that a control valve cannot just be adjusted manually but also remotely. To this end the valve element is charged with a pressure depending upon the desired direction in which the valve element shall be moved. A pressure may then be maintained until the valve element has reached the desired position.
This functionality can be achieved in several ways. First of all one may connect both pressure chambers to two magnetic valves each. For each pressure chamber one magnetic valve may be connected to the high pressure port and one other magnetic valve will be connected to the low pressure port. In order to move the valve element one of the two pressure chambers will then be charged with a higher pressure by opening the corresponding magnetic valve leading to the high pressure port. At the same time the other pressure chamber will be charged with a lower pressure by opening the corresponding magnetic valve leading to the low pressure port. The two magnetic valves stay open until the valve element has reached the desired position.
Such a valve arrangement is reliable but requires four magnetic valves and the corresponding control parts. Consequently, the production costs are relatively high.
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