Bosch Rexroth R900915963

The valves of type ZDRE are electrically pilot-operated 3-way pressure reducing valves with pressure limitation of the actuator. They are used for reducing a system pressure. Technical set-up: The valve consists of three main assemblies:

• Pilot control valve (1)

• Proportional solenoid (2)

• Main valve (3) with main control spool (4)

Function: General function:

• Command value-dependent setting of the pressure to be reduced in channel P1 via the proportional solenoid (2).

• In the depressurized port P, the spring (17) holds the main control spool (4) in the initial position.

• Thus, opening the connection from P1 to T and blocking of the connection from P to P1.

• Pressure connection from port P to the ring channel (5).

• Pilot oil flows from the bore (6) to port T, via the flow controller (7), the nozzle (8) to the pilot control valve (1), the throttle gap (9) to the longitudinal groove (10) and the bores (11, 12).

Pressure reduction:

• Build-up of the pilot pressure in the control chamber (16) as function of the command value.

• Movement of the main control spool (4) to the right, hydraulic fluid flows from P to P1.

• Actuator pressure present in port P1 to the spring chamber (15) via channel (13) and nozzle (14).

• Increase in the pressure in port P1 to the set pressure of the pilot control valve (1) leads to the movement of the main control spool (4) to the left. Pressure in port P1 is almost identical with the set pressure at the pilot control valve (1).

Pressure limitation:

• If the pressure in port P1 exceeds the set pressure of the pilot control valve (1), the main control spool (4) is moved further to the left.

• This opens the connection from P1 to T and limits the pressure present in port P1 to the set command value.

The valves of type ZDREE are electrically pilot-operated 3-way pressure reducing valves with pressure limitation of the actuator. They are used for reducing a system pressure. Technical set-up: The valve consists of three main assemblies:

• Pilot control valve (1)

• Proportional solenoid (2) with control electronics (18)

• Main valve (3) with main control spool (4)

Function: General function:

• Command value-dependent setting of the pressure to be reduced in channel P1 via the proportional solenoid (2).

• In the depressurized port P, the spring (17) holds the main control spool (4) in the initial position.

• Thus, opening the connection from P1 to T and blocking of the connection from P to P1.

• Pressure connection from port P to the ring channel (5).

• Pilot oil flows from the bore (6) to port T, via the flow controller (7), the nozzle (8) to the pilot control valve (1), the throttle gap (9) to the longitudinal groove (10) and the bores (11, 12).

• Supply and command value voltage or command value current are applied to the connector (19).

• At the factory, the command value pressure characteristic curve is adjusted with little manufacturing tolerance.

Pressure reduction:

• Build-up of the pilot pressure in the control chamber (16) as function of the command value.

• Movement of the main control spool (4) to the right, hydraulic fluid flows from P to P1.

• Actuator pressure present in port P1 to the spring chamber (15) via channel (13) and nozzle (14).

• Increase in the pressure in port P1 to the set pressure of the pilot control valve (1) leads to the movement of the main control spool (4) to the left. Pressure in port P1 is almost identical with the set pressure at the pilot control valve (1).

Pressure limitation:

• If the pressure in port P1 exceeds the set pressure of the pilot control valve (1), the main control spool (4) is moved further to the left.

• This opens the connection from P1 to T and limits the pressure present in port P1 to the set command value.