The invention is based on a precontrolled 3-way pressure control valve.
A 3-way pressure control valve of kind is known from the book "Hydraulik Trainer Band 1" [Hydraulics Trainer Volume 1], published in 1991 by Mannesmann Rexroth GmbH, pages 236 to 239. In this pressure control valve, the main piston has a piston bead by which the middle control chamber can be sealed off from the first and second control chambers and which is abutted on either side by a piston neck from which control grooves distributed around the circumference extend into the piston bead. The control grooves that begin at a piston neck are located at an axial distance from the control grooves departing from the other piston neck, said distance being approximately equal to the axial extent of the middle control chamber.
The pilot valve of the known precontrolled pressure-regulating valve is a direct-controlled pressure-regulating valve with a pressure connection, a tank connection, and a control connection. The control connection is connected with a pressure chamber in front of one end of the main piston by fluid. Control oil from the pressure connection of the main valve flows to the pressure connection of the pilot valve. Depending on the adjustment of a spring, a certain pressure is set in the control connection of the pilot valve and hence in front of one end of the main piston. The middle control chamber of the valve bore of the main valve is connected by a housing channel with a pressure chamber in front of the other end of the main piston. In each case, a pressure becomes established in the middle control chamber and hence in the control connection such that an equilibrium exists at the main piston between the various pressure and spring forces. A precontrolled 3-way pressure control valve in which the pilot valve is supplied with the control oil from the pressure connection of the main valve is referred to as being high-pressure-controlled. The special advantage of this type of precontrol consists in the main piston not tightening even with a large volume flow and a large pressure differential between the pressure connection and the control connection of the main valve, i.e. the connection between the pressure connection and the control connection is interrupted by the main piston and hence the applicability of the valve is limited. It is disadvantageous that the known precontrolled pressure control valve has a tendency toward instability under certain operating conditions, in other words pressure fluctuations occur at the control connection.