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STRUCTURE, FUNCTION AND MAINTENANCE STANDARD
ARM THROTTLE VALVE
Function
When arm and boom are operated at same time
•
When the arm and boom are operated at the
same time, a large amount of the pressure oil
flows to the arm circuit where the load is small, so
little pressure oil flows to the boom circuit.
•
This makes the arm speed too fast for the boom
speed, and causes poor combination in simulta-
neous operation. This is a particular problem
when the arm OUT and boom RAISE are operat-
ed at the same time.
•
To overcome this, the arm throttle valve is actu-
ated to throttle the pressure oil flowing to the arm
Hi control valve in order to restrict the arm speed
and improve the simultaneous operation per-
formance.
1) When arm is operated independently
Operation
•
No pilot pressure oil flows from the travel shuttle
valve, so the arm throttle valve is not actuated.
PC600, 600LC-7
When arm and bucket are operated at same time
•
The arm is actuated by the merged flow from two
pumps and the bucket is actuated by the oil from
one pump.
•
In this condition, if the arm and bucket are oper-
ated at the same time, a large amount of the
pressure oil flows to the arm circuit, so little pres-
sure oil flows to the bucket circuit. This makes
the arm speed too fast for the bucket speed, and
causes poor combination in simultaneous opera-
tion. This is a particular problem when the arm
OUT and bucket CURL are operated at the same
time.
•
To overcome this, the arm throttle valve is actu-
ated to throttle the pressure oil flowing to the arm
Hi control valve in order to restrict the arm speed
and improve the simultaneous operation per-
formance.
•
For this reason, all the pressure oil from the rear
main pump passes through port PL and flows to
the arm Hi control valve.
CONTROL VALVE
10-81
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