This section describes the following operations.
(3) Arm in, heavy load operating pilot circuit
(recirculation cut)
(4) Arm in, heavy load operating sequence confluxed
main circuit
22.9.3
ARM IN, HEAVY LOAD
OPERATING PILOT CIRCUIT
(1) Operation:
1.
Left pilot valve actuation due to arm-in operation
is equivalent to that at light load operation.
2.
In arm-in operation, when the heavy loading is
applied to arm and the P2 pump pressure
increases to the set pressure, the voltage output
by P2 pump pressure sensor (SE-23) is converted
to signal (signal processing) by mechatro
controller, consequently the current of arm 2
solenoid proportional valve is controlled according
to the load pressure and the arm variable
recirculation is cut.
When the recirculation is cut, internal confluence
is held similarly to that in light load operation.
22.9.4
ARM IN, HEAVY LOAD
OPERATING RECIRCULATION CUT
MAIN CIRCUIT
(1) Purpose:
Power up for arm in operation
(2) Principle:
Cut the recirculation and reduce rod pressure.
(3) Operation:
1.
P2 pump delivery oil flows in the travel left
section through P2 port of C/V (2) and branched
off in by-pass circuit and parallel circuit.
Consequently the arm spool is switched and
pushes and opens load check valve LCa through
parallel circuit, and flows in the arm spool.
2.
On the other hand, P1 pump delivery oil flows in
P1 port of C/V (2), and flow in travel right
tandem passage through travel straight section.
Then because arm 2 spool was switched, the
delivery oil opens load check valve LCAT2, and
confluences with P2 pump delivery oil in the valve
section, and is flowed into arm cylinder head (H)
side through Aa port of C/V(2).
3.
The return oil from arm cylinder (R) side flows in
Ba port of C/V(2) and is flowed to arm lock valve
CRar, but because the arm lock valve CRar is
open, the return oil goes through arm lock valve
CRar and flows in arm 2 spool.
4.
The return oil returns directly into tank circuit
because arm 2 spool is switched to recirculation
cut position.
Position of arm 2 spool
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22. HYDRAULIC SYSTEM
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