2-35
MAIN AND PORT RELIEF VALVE OPERATION
(13)
Main relief valve operation
Main relief valves (MRV) are different in the uses for P1/P2 and P3; however, their structures and
operation are the same.
Pressure oil flows through the inside of the piston built in the pressure regulating valve (poppet-
main V') and the orifice B and then into the internal chamber A until it is filled up. The filled up
pressure causes both of the pressure regulating valve and the socket and body seat to be seated
securely.
Η
Tank passage
P
Body seat
Pressure regulating
(Poppet-main V')
Regulating valve spring
(Spring-pilot)
Socket
Orifice B
Piston
Chamber A
Regulating valve
(poppet-pilot)
MRV operation (1)
R35Z72MCV29
When the oil pressure at port P increases up to the setting pressure of regulating valve spring, the
pressure oil is applied to the regulating valve via the piston to open the regulating valve. Then, the
pressure oil flows through a passage in the direction of piston inside
Ą
orifice B
Ą
chamber A
Ą
circular orifice C
Ą
Drill hole D and the external of socket and then into the tank passage.
Θ
MRV operation (2)
Circular orifice C
Drill hole D
R35Z72MCV30
Since the pressure inside the chamber A decreases when the regulating valve is opened, which
causes the pressure regulating valve to open to let the pressure oil port P flows into the tank
passage through drill hole E.
Ι
MRV operation (3)
Drill hole E
R35Z72MCV31
Also, since the regulating valve is pressed to the seat by regulating valve spring when the
pressure at port P decreases below the setting pressure of regulating valve spring, the pressure
inside chamber A becomes the same as the pressure at port P to cause the pressure regulating
valve to be pressed to the seat, resulting in the original condition (
Η
).
Κ