Hyundai HX140L, Manual

Page: 80 / 819

2-27-1
BOOM DOWN OPERATION (TYPE 2)
During the boom lowing operation, the pilot pressure from RCV is supplied to the port Pb2 of the
spring opposite side and shifts the boom 1 spool in the right direction.
The bypass passage is shut off by the movement of the boom 1 spool and the hydraulic fluid from
the pump A2 enters the parallel passage and is directed to the port B2 through the load check.
Following this, it flows into the rod side of the boom cylinder.
At the same time, the return flow from the head side of the boom cylinder returns to the port A2
and boom holding valve. And it is directed to the hydraulic oil tank through opened tank passage
by movement of the boom 1 spool.
Meanwhile some of return flow is directed to P1 parallel passage through the internal passage of
the boom 1 spool. (boom regeneration)
In this case, the holding valve is open condition, for details of the boom holding valve, see page
following page.
During the boom lowering operation, the fluid from A1 pump is not summation.
From RCV
P1 Bypass passage
Tank passage
Boom holding valve
P1 Parallel passage
A2 B2
Boom 1 spool
Load check
Pb2
140L2MC26