Bosch Rexroth R900917774

The pressure valve type 3DR is a pilot-operated 3-way pressure reducing valve with pressure limitation of the secondary circuit. It is used to reduce the system pressure. The pressure reducing valve basically consists of the main valve (1) with control spool (2) and pilot control valve (3) with pressure adjustment element (10). The valve is open in initial position. Hydraulic fluid can flow from channel P to channel A without restrictions. The pressure in channel A is simultaneously applied via the bore (4) at the piston area opposite the compression spring (9). Simultaneously, pressure is applied via the nozzle (6) to the spring-loaded side of the control spool (2) and via channel (5) to ball (7) in the pilot control valve (3). Depending on the setting of the compression spring (11), pressure builds up upstream of the ball (7) and in channel (5) holding the control spool (2) in open position. Hydraulic fluid flows from channel P via the control spool (2) to channel A until a pressure builds up in channel A exceeding the pressure value set at the compression spring (11) and opening the ball (7). The control spool (2) moves to closed position. The desired reduced pressure is reached if there is a balance between the pressure in channel A and the pressure value set at the compression spring (11). If the pressure in channel A increases further due to an external force effect at the actuator, the control spool (2) is pushed further against the compression spring (9). In this way, channel A is connected to channel T via the control edge (8) at the control spool (2). So much hydraulic fluid is discharged into the tank that the pressure can no longer increase. The pilot oil return from the spring chamber (12) is always realized externally via the control line (13) at port Y. A depressurized connection to the tank must always be ensured. The pressure gauge connection (14) enables control of the reduced pressure in channel A. Type 3DR 10 P4–6X/…