Takeuchi TB175W, Руководство по ремонту

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HYDRAULIC UNITS
PROPORTIONAL CONTROL SOLENOID VALVE
IV-76
TB175W
T9H201
S
1
2 4
A1
A P T
B1
S=A1-B1
Fk
Paxs
Paxs Fk Fs Fks
Fs Fks
T9H202
1 5
P A T
T9H203
1 6
P A T
OPERATION PRINCIPLE
This valve controls the secondary pressure by using
the built-in proportional pressure reducing valve. The
secondary pressure of this valve is proportional to the
magnitude of electric current flowing in the valve,
because the force to generate the secondary pressure
is applied by the solenoid based on the current passing
through the coil.
When a current flows in the solenoid, a thrust force
proportional to the current is generated and moves the
spool (1) so that the oil supplied from Port P is led to
the secondary pressure side Port A, thus increasing
pressure Pa of Port A.
Pressure Pa is a function of 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
×
S. The spool (1) stops at a position
where the sum of the oil pressure Pa
×
S and the force
Fk exerted by the springs (2) is balanced with the
thrust force Fs generated by the solenoid. The weight
Fks of the spring (4) for fine adjustment of the
secondary pressure acts in the direction (left) to help
the thrust force from the solenoid.
When the thrust force is larger than the set value, the
spool (1) is moved to the left, connecting Port P
(primary, supply side) and Port A (secondary, dis-
charge side) through the notch (5).
When the thrust force is smaller than the set value, the
spool (1) is moved to the right, connecting Port A
(secondary, discharge side) and Port T (outlet to tank)
through the notch (6).
Therefore, the opening areas of the supply side notch
(5) and discharge side notch (6) are controlled by the
movement of the spool (1), and secondary (pilot)
pressure created by the thrust force generated by the
solenoid can be provided.