Kubota KX080-4 Workshop Manual page 112

KX080-4, WSM
During fine operation of LS section
(1) Independent travel valve
section
(2) LS drain plug
• When the spool section is switched, the oil in the pump pressure passage passes through the main spool and is
discharged to the cylinder port. The operating load pressure of the cylinder port is guided from inside the spool
section to the PLS pressure passage (4) and becomes the PLS pressure. (Refer to the explanation of how the
spool section operates.)
• As long as the amount switched from the spool section is small (fine operation), the open area of the spool section
becomes also small, so it increases the pressure differential (PPS-PLS) between the pump pressure PPS and
PLS.
• Once the pressure differential (PPS-PLS) between the pump pressure PPS and PLS reaches the unload valve
setting pressure, the unload spool moves to the right side, automatically adjusting the open area in the notch
between the pump pressure passage and the tank passage, thus maintaining a steady pressure differential
(PPS-PLS) between the pump pressures PPS and PLS.
• The mechanism described above maintains a constant pressure differential (PPS-PLS) between the pump
pressures PPS and PLS, even when there is a change in the spool section operating load pressure.
• The unload valve is set at a pressure somewhat higher than the LS control differential pressure value set for the
pump, so the pump maintains it at standby flow rate discharge status (fixed flow rate).
(3) Micro-orifice
(4) PLS pressure passage
(5) Notch
3-M16
HYDRAULIC SYSTEM
(a) To each spool section
RY9212158HYM0015US0
KiSC issued 08, 2015 A