Takeuchi TB175W, Руководство по ремонту

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HYDRAULIC UNITS
PILOT VALVE
IV-87
TB175W
OPERATION
The pilot valve casing contains a vertical shaft hole
with a reducing valve incorporated into it. When the
handle is tilted, the push rod and spring seat are
pushed down changing the secondary pressure spring’s
pressure.
The casing also contains an inlet port for hydraulic oil
port P (primary pressure) and an outlet port, port T
(tank) and secondary pressure is taken from 4 ports,
port 1, port 2, port 3 and port 4, on the bottom of the
vertical shaft hole.
When the Handle is in Neutral
In this case, the force of the secondary pressure setting
spring, which determines the pilot valve’s output
pressure (secondary pressure), is not transmitted to
the spool. Therefore, the spool is pushed up by the
return spring and is in the output port C position
shown above, with oil not flowing between port P and
the output port C but flowing between the T port and
output port C.
When the Handle is Tilted
When the handle (1) is tilted and the push rod is
pushed, the spool moves downward and port P and
port A are joined. The oil in the pilot valve pump flows
out to port A, generating pressure.
a. When the pressure in port A is the same as the set
force of the spring (set pressure), there is a balance
between the hydraulic pressure and the spring
force.
b. When the pressure in port A is greater than the set
pressure, port A and port P close and port A and
port T open.
c. When the pressure at port A is lower than the set
pressure, port A and port P open and port A and port
T close.
In this way, the secondary pressure is kept constant.
IV-86