Hoist System Operation Modes; Float Position Of Pilot Valve And Body On Frame (Figure 7-6) - Komatsu 830E-AC Shop Manual

HOIST SYSTEM OPERATION MODES

The following pages describe hoist circuit operation
in the float, power up, hold, and power down posi-
tions. (Refer to Figures 7-6 through 7-10.)
Float Position Of Pilot Valve And Body On Frame
(Figure 7-6)
This is the condition while the truck is hauling. The
Pilot Valve spool position is as shown in Figure 7-6;
however all Hoist Valve components are in position
shown in Figure 7-10.
Oil from the hoist pumps enters each inlet section of
the Hoist Valve in Port 11, passes through check
valve 18, and stops at the closed High Pressure Pas-
sage 19 at the two main spools. Pressure builds to
approximately 414 kPa (60 psi) on the pilot of the
Flow Control Valve 2 causing the valve to compress
the spring and open, allowing the oil to return to the
tank through Hoist Valve Port 10. Oil also flows out
Hoist Valve Port 12 to Port 12 on the Pilot Valve,
through the Hoist Pilot Valve spool, and out Pilot
Valve Port 10 to the tank. This oil flow is limited by
orifices in the inlet sections of the Hoist Valve and
therefore has no pressure buildup.
L7-8
FIGURE 7-6. HOIST CIRCUIT: FLOAT POSITION
1. Hoist Relief Valve 17237 kPa (2500 psi)
2. Flow Control Valve
3. Low Pressure Relief Valve 517 kPa (75 psi)
4. Counterbalance Valve
5. Rod End Work Port
6. Hoist Cylinders
7. Rod End Spool
8. Head End Spool
9. Head End Work Port
10. Return Port
11. Supply Port
12. Pilot Supply Port
13. Power Up Pilot Line Solenoid Valve
14. Raise Pilot Port
15. Down Pilot Port
16. Power Down Relief Valve,
10342 kPa (1500 psi)
17. Anti-void Check Valve
18. Load Check Valve
19. High Pressure Passage
20. Low Pressure Passage
21. Pilot Operated Check Valve
22. Manifold Power Up Port
23. Manifold Power Down Port
24. Solenoid Valve Return Port
25. Overcenter Manifold Check Valve (CV)
Hoist Circuit L07034