Komatsu Galeo PC800-8 Shop Manual page 146

SEN00383-03
3. When load pressure (P3F) is high
• Change in the fan revolution speed increases
load pressure (P3) and, as the result, pump de-
livery is increased.
• Since pressure (P3F) increases, [(φd area × P3F
pressure) > the force of spring (2) + (φd area ×
PR pressure)]. As the result, valve (1) is moved
to the right up to the stroke end.
• Since the opening between ports (P3F) and (P3)
increases, resistance along the passage is re-
duced and the loss horsepower of the engine is
reduced.
• As pressure (PR) reaches a level higher than the
set pressure, poppet (4) opens.
• The pressurized oil flows from port (PR) to inter-
nal orifice (a) of spool (6) and then flows to tank
drain port (T) through the opening of poppet (4).
• The differential pressure is generated through in-
ternal orifice (a) of spool (6), actuating spool (6)
to close the opening from port (P3F) to (PR).
• The self pressure reducing valve reduces pres-
sure (P3F) to a specific level (set pressure) in or-
der to supply the difference as pressure (PR).
4. When abnormally high pressure is
generated
• If pressure (PR) of the self pressure reducing
valve turns to an abnormally high pressure, valve
(1) compresses spring (2).
• Port (A) opens and ports (PR) and (TS) are con-
nected.
• Allows the pressurized oil to (TS) from port (PR)
and lowers pressure (PR).
• Protects PPC valve, solenoid valve and other de-
vices from abnormal pressure.
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10 Structure, function and maintenance standard
PC800, 850-8