Komatsu ecot3 PC300LC-8 Shop Manual page 108

SEN01993-00
1. LS valve
PA: Pump port
PDP: Drain port
PLP: LS control pressure output port
PLS: LS pressure input port
PP: Pump port
PPL: Control pressure input port
PSIG: LS mode selector pilot port
Function
q The LS (load sensing) valve detects the load
and controls the discharge amount.
This valve controls main pump delivery (Q)
q
according to differential pressure (
– LS], called the LS differential pressure (the
difference between main pump pressure PP
and control valve outlet port pressure PLS).
Main pump pressure (PP), pressure (PLS)
q
(called the LS pressure) coming from the con-
trol valve output, and pressure (PSIG) (called
the LS selector pressure) from the proportional
solenoid valve enter this valve.
q The relationship between the LS differential
pressure between the main pump pressure
(PP) and LS pressure (PLS) (EPLS) [= (PP) –
(PLS)] and the pump delivery (Q) changes as
shown in the diagram according to LS selector
current (ISIG) of the LS-EPC valve.
q If (ISIG) changes from 0 to 1A, setting force
the spring changes, too. As the result, the
specified median of the pump delivery volume
switching point changes as shown in the dia-
gram. As for the front pump side, it will change
in the range of 0.98 to 2.45 MPa {in the range
of 10 to 25 kg/cm
side, it will change in the range of 1.08 to 2.55
MPa {in the range of 11 to 26 kg/cm
12
E
PLS)[= PP
2
] and as for the rear pump
2
}.
10 Structure, function and maintenance standard
1. Sleeve
2. Piston
3. Spool
4. Spring
5. Seat
6. Sleeve
7. Plug
8. Locknut
Front pump
Rear pump
PC300, 350-8