9-11
SECTION 4. MAJOR COMPONENTS OF THE HYDRAULIC SYSTEM
1. MAIN CONTROL VALVE
1.1 GENERAL DESCRIPTION (Reference)
This valve controls the lifting and lowering operation of the hydraulic cylinder. It has especially been
developed to control the working height of the implement. It consists of a feed back valve; direction
control valve, flow-control unloading valve,and holding check valve.
1.2 SPECIFICATIONS (Reference)
Maximum operating pressure 175 Kgf./㎠
Maximum flow 45 liters/min
C-port leaks 5 cc/min below
(Fluid temp : 50℃:pressure :100Kgf.cm(1422 psi)
1.3.CONSTRUCTION (Reference)
1) Main spool
it consists of a spool,spool head,and snap ring E and has three functions.
a. It opens and closes passages P to C and C to T and controls the passage wall area successively.
b. It converts unloading pilot pressure to C-port pressure or tank pressure
c. It turns the pilot pressure of the pilot spool on or off.
Fig.9-31
Neutral Position
Lowering Position
Raising Position
Fig.9-30
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