3-13
3
FUNCTION
PROPORTIONAL CONTROL SOLENOID VALVE
PROPORTIONAL CONTROL SOLENOID VALVE
3KAD01Z
1
2
4
S=A1-B1
S
Paxs
Paxs Fk Fs Fks
B1 A1
AP T
Fs Fks
Fk
This valve controls the secondary pressure by using the
built-in proportional pressure reducing valve.
The secondary pressure generated corresponds to the
changes in current, because the force used to generate the
secondary pressure is applied to the solenoid according to
the current passing through the coil.
When a current flows in the solenoid, a thrust force propor-
tional
to the current is generated and it pushes the spool
(1) so that the oil supplied from the port P is directed to the
secondary pressure side port A to increase the pressure
Pa in the port A.
This
pressure Pa works on the differential area S between
the cross sections A1 and B1 of the spool (1), and the spool
(1) is pushed to the solenoid side by the oil pressure Pa x S.
The spool (1) stops at the position where the sum of the oil
pressure Pa x S and the force Fk exerted by the springs (2)
is balanced with the thrust force Fs generated by the sole-
noid.
The weight Fks of the spring (4) for fine adjustment of
the secondary pressure works in the direction (left) to assist
the thrust force from the solenoid.
When the thrust force becomes larger than the set value,
the spool (1) is moved to the left, connecting the port P
(supply side) and the port A (secondary side) through the
notch (5).
When
the thrust force becomes smaller than the set value,
the spool (1) is moved to the right, connecting the port A
(secondary side) and the port T (tank side) through the
notch (6).
Ther
efore, the opening areas of the supply side notch (5)
and discharge side notch (6) are controlled by the move-
ment
of the spool (1), and secondary (pilot) pressure cor-
r
esponding to the thrust force generated by the solenoid
can be provided.
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