(1) The structure of the pilot control valve
(2) Working principle of Doosan excavator pilot control valve
working principle 1
1, the middle position of the operating handle → the working device does not move
①The middle position of the handle
②The oil of port A and B is connected to the oil tank through the small hole f in the slide valve (1)
③The main spool is kept in the middle position under the action of the internal spring
④The working device does not operate.
working principle 2
2, operating handle action → working device action:
①Turn the operating handle to the left
②The disc (5) pushes the plunger (4) down
③The positioner (9) also moves down
④The spring (2) pushes the slide valve (1) down
⑤P1 port of PPC valve is connected with f port on spool valve (1)
@Pilot pressure oil flows to port A through the control orifice f
⑦The main control valve spool moves to the right, and the oil at port B returns to the tank
③The oil from the main pump flows to the working device through this spool
@Working device starts to move
working principle 3
3. If the stroke of the handle becomes larger, the speed of the working device increases
①The stroke of the operating handle becomes larger
②The compression of the spring (2) becomes larger
③The force of the spring (2) becomes larger
④The spool valve (1) moves downward more
⑤The flow area of the small hole f port becomes larger
⑥P1 port pressure increases
⑦The movement of the main control valve spool becomes larger
③The flow rate to the working device increases
③The working device works faster
