Komatsu Galeo PC800-8 Shop Manual page 144

SEN00383-03
2. When signal current is very small
(coil is energized)
• When a very small signal current flows to coil (5),
coil (5) is energized, and a propulsion force is
generated on the left side of plunger (6).
• Rod (4) pushes spool (2) to the left, and the pres-
surized oil flows from port (P) to port (C).
• Pressure on port (C) increases and the force to
act on surface (a) of spool (2) + the spring load
on spring (3) become larger than the propulsion
force of plunger (6).
• Spool (2) is pushed to the right, and port (P) is
shut off from port (C).
• Port (C) and port (T) are connected.
• Spool (2) moves up and down so that the propul-
sion force of plunger (6) may be balanced with
pressure of port (C) + the spring load of spring
(3).
• The circuit pressure between the EPC valve and
the VC valve is controlled in proportion to the
size of the signal current.
3. When signal current is maximum
(coil is energized)
• As the signal current flows to coil (5), coil (5) is
energized.
• When this happens, the signal current is at its
maximum, so the propulsion force of plunger (6)
is also at its maximum.
• Spool (2) is pushed to the left by rod (4).
• The maximum volume of pressurized oil is con-
ducted from port (P) to port (C), increasing the
circuit pressure across EPC valve and VC valve
to the maximum level.
• Since port (T) is closed, pressurized oil does not
flow to the tank.
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10 Structure, function and maintenance standard
PC800, 850-8