Komatsu PC200-8M0, Shop Manual

Page: 139 / 1254

SEN06119-00
PC200, 200LC, 220, 220LC-8M0 10-401
27
401 Hydraulic system, Part 1
Hydraulic pump
2) When signal current is very small
(coil is energized)
q
When a very small signal current flows to coil
(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).
q
Port (C) and port (T) are connected.
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.
3) When signal current is maximum
(coil is energized)
q
As the signal current flows to coil (2), coil (2) is
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).
q
The maximum volume of pressurized oil is
conducted from port (P) to port (C), increasing
the circuit pressure across EPC valve and LS
(PC) valve to the maximum level.
q
Since port (T) is closed, pressurized oil does
not flow to the tank.