Komatsu PC500LC-10R, Руководство по ремонту, Страница: 301 / 758

5: Joint
6: Plate
7: Retainer 8: Body
9: Filter
OPERATION OF WORK EQUIPMENT AND SWING PPC VALVE
When it is in neutral
The port (A) and port (B) of the control valve, and the port (P1)
and port (P2) of PPC valve are respectively connected to the
drain chamber (D) through the fine control hole (f) of spool (1).
When operating the fine control (from neutral to the fine control)
1.
When the piston (4) is pushed by the disc (5), the retainer
(9) is pushed. The spool (1) is also pushed through meter-
ing spring (2), and it moves down.
2.
The fine control hole (f) is disconnected from the drain
chamber (D), and it is connected to the pump pressure
chamber (PP) almost simultaneously.
3.
The pilot pressure oil of the main pump flows to port (A)
through fine control hole (f) and port (P1).
4.
The spool (1) is pushed back when the pressure in the port
(P1) increases. The fine control hole (f) is disconnected
from the pump pressure chamber (PP), and it is connected
to the drain chamber (D) almost simultaneously. Then the
pressure in the port (P1) is decreased.
5.
The spool (1) moves up and down so that the thrust of the
metering spring (2) is balanced with the pressure of the
port (P1).
6.
The positional relationship between spool (1) and body
(10) “fine control hole (f) is in an intermediate position be-
tween drain chamber (D) and pump pressure chamber
(PP)” does not change until retainer (9) touches spool (1).
7.
The metering spring (2) is compressed in proportion to the travel of control levers.
8.
The pressure in the port (P1) increases in proportion to the travel of control levers.
9.
The control valve spool moves to a position where the pressure in the port (A) which is “equal to the pres-
sure in the port (P1)” is balanced with the reaction force of the return spring of the control valve spool.
10 STRUCTURE AND FUNCTION COMPONENT PARTS OF WORK EQUIPMENT SYSTEM
PC500LC-10R 10-207