Bosch Rexroth AG, RE 64602/2019-08-05
4 MHDBN | Pressure limitation and feed valve
Functional description
Functional description
General
The pressure valve type MHDBN is a pilot-operated pres-
sure relief valve for installation in block designs. It is used
to limit a system pressure. The system pressure can be set
steplessly via the adjustment spindle (4).
Pressure relief function
The valve is closed in initial position. The pressure in port P
acts on the spool (1). Simultaneously, pressure is applied
to the spring-loaded side of the spool (1) and to the pilot
poppet (6) via the nozzle (2).
If the pressure in port P exceeds the value set at the spring
(5), the pilot poppet (6) opens. Hydraulic fluid flows from
the spring-loaded side of the spool (1) via the nozzle (3)
and the channel (7) directly into port T.
The resulting pressure drop causes the spool (1) to move
and thus opens the connection from port P to T while
maintaining the pressure adjustment on the spring (5).
The pilot oil return is implemented internally via the chan-
nel (7) into port T.
Feed function
The feed function makes up for lacking hydraulic fluid
volumes caused, for example, by leakage when pressure
valves respond or in the case of leading loads.
If the pressure at port P is lower than the one at port T, the
spool (1) will be lifted out of its seat. Hydraulic fluid flows
from port T to port P.
Notice
▶ The maximum operating pressure is the sum of the set
pressure and the return flow pressure at port T.
▶ The pilot-operated pressure valves are virtually leak-
age-free thanks to their design.
▼ Section and symbol MHDBN
P
T
2 1 3 6 7 5 4
T
P
P = Pump port
T = Tank port
1 Spool
2 Nozzle
3 Nozzle
4 Adjustment spindle
5 Spring
6 Pilot poppet
7 Channel to port T