Hitachi ZW180 Technical Manual page 130

Charging Block Circuit
•
Charging block is installed in order to supply
pressure oil from the pilot pump preferentially to
the service brake circuit and distribute to other
pilot circuits as well.
•
When the engine is started, oil from the pilot
pump is delivered to the charging block.
•
At this time, when the amount of accumulated
pressure of the service brake accumulators is low,
the relief valve is closed.
•
In this case, only pilot pressure is applied to port
B of the priority valve. As both pilot pressure and
the spring force are applied to port A, the priority
valve moves rightward and controls pressure oil
to flow further.
•
Pressure oil from the pilot pump flows to the
service brake circuit through the check valve, and
accumulates the service brake accumulators.
NOTE: The spring of the priority valve is adjusted
so that the priority valve is not completely
closed. Although the priority valve is closed
completely, a certain amount of pressure oil
is being
downstream.
SYSTEM / Hydraulic System
(To be continued to T2-3-16)
supplied to the circuits
T2-3-14