Hyundai HX130LCR Manual page 71

3) BOOM OPERATION
(1)
BOOM UP OPERATION
During boom up operation, the pilot secondary pressure from RCV is supplied to the port Pa20 of
the spring side and shifts the boom 1 spool in the left direction. The bypass passage is shut off by
the movement of the boom 1 spool and the hydraulic oil fluid from pump A2 is entered P1 parallel
passage and then passes through the load check, bridge passage and boom holding valve then
flows into the port A2. Following this it flows into the head side of the boom cylinder. (In this case,
the boom holding valve is free flow condition)
At the same time, the pilot pressure from RCV is supplied to the port Pa21 of the spring side of
boom 2 and shifts the boom 2 spool. The bypass passage is shut off by the movement of the
boom 2 spool and the hydraulic oil fluid from pump A1 entered boom summation passage via the
P2 parallel passage, the land of the swing priority spool, notch of the boom 2 spool, arm 2 spool
and the check. The flows combine in passage and are directed to port A2 and head side of boom
cylinder.
At the same time, the flow from rod side of the boom cylinder return to the boom 1 spool through
the port B2. Thereafter it is directed to the hydraulic oil tank through the tank passage.
Tank passage
Boom 1 spool
Boom summation
passage
P2 Parallel passage
Swing priority
spool
Arm 2 spool
Boom summation passage
Boom summation passage
P1 Bypass passage
B2 A2
P1 Parallel passage
Arm summation passage
Load check
2-27
Swing spool
Holding valve
From RCV
Pa20
P2 Bypass passage
Boom 2 spool
From RCV
Pa21
125LCR2MC24