Komatsu PC200-8M0 Shop Manual page 139

401 Hydraulic system, Part 1
Hydraulic pump
2) When signal current is very small
(coil is energized)
When a very small signal current flows to coil
q
(2), coil (2) is energized, and a propulsion force
is generated on the right side of plunger (7).
q Rod (6) pushes spool (5) to the right, and pres-
surized oil flows from port (P) to port (C).
q Pressure on port (C) increases and the force to
act on spool (5) surface and the spring load on
spring (4) become larger than the propulsion
force of plunger (7).
q Spool (5) is pushed to the left, and port (P) is
shut off from port (C).
Port (C) and port (T) are connected.
q
q Spool (5) moves up and down so that the pro-
pulsion force of plunger (7) may be balanced
with pressure of port (C) + spring load of spring
(4).
q The circuit pressure between the EPC valve
and the LS (PC) valve is controlled in propor-
tion to the size of the signal current.
PC200, 200LC, 220, 220LC-8M0
3) When signal current is maximum
(coil is energized)
As the signal current flows to coil (2), coil (2) is
q
energized.
q When this happens, the signal current is at its
maximum, so the propulsion force of plunger
(7) is also at its maximum.
q Spool (5) is pushed toward right side by rod
(6).
The maximum volume of pressurized oil is
q
conducted from port (P) to port (C), increasing
the circuit pressure across EPC valve and LS
(PC) valve to the maximum level.
Since port (T) is closed, pressurized oil does
q
not flow to the tank.
SEN06119-00
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10-401