Komatsu PC58UU-3 User Manual

STRUCTURE, FUNCTION AND MAINTENANCE STANDARD HYDRAULIC PUMP
10-28
PC58UU-3
2. EPC Valve
• When the pump discharge pressure
PP
rises, the control valve spool stroke will
increase and the opening area will
enlarge. So, the PC valve controls the
pump delivery
Q
so that the delivery
Q
does not increase above a certain level
depending on the discharge pressure
PP
.
The valve also controls the pump absorb-
ing hydraulic horsepower to approxi-
mately equal horsepower so that the
pump absorbing horsepower does not
exceed the engine horsepower.
• This means that, when a load to the actu-
ator increases during operation and the
pump discharge pressure
PP
rises, this
valve will reduce the pump delivery
Q
, or
when the pump discharge pressure
PP
drops, this valve will increase the delivery
Q
.
• The relationship between the
PAVE
pump
average pressure (When the double pump
is employed, the average of
P1
and
P2
is
sensed) and
Q
pump discharge is shown
in the figure at right.
• Usually, the swing pump is installed
behind the main pump. When it operates,
the absorption torque on the main pump
side is lowered by the quantity absorbed
by the swing pump so that the total of the
main pump absorption torque and swing
pump absorption torque will be the all
absorption torque (about 100%).
•If the
X
command current sent to the EPC
valve is increased, the relationship
between the
PAVE
pump average pres-
sure and
Q
pump discharge is translated
in proportion to the pressing force of the
EPC valve solenoid.
• Since the pressing force of the EPC valve
solenoid is added to the pressing force on
the left side caused by the pump pressure
applied to spool (10), the relationship
between the PAVE pump average pres-
sure and Q is translated from (1) to (2) as
X is increased.

Komatsu PC58UU-3 Specifications

General

Brand	Komatsu
Model	PC58UU-3
Category	Construction Equipment
Language	English