Pump Control Circuit - Kubota KX080-3 Workshop Manual

WSM KX080-3 Mechanism
f. Pump control circuit
(1) (18)
P P
LS
(2)
(3)
P
P
(4)
(5)
(6)
P
S
(7)
P
C
(8)
( ump structure)
P1, P2 : Variable displacement pump + PC horsepower control + LS flow control (Q1 = Q2) (Travel, arm,
bucket, SP1, boom, swing, AUX)
: Split flow
: Spherical valve plate
: Cradle bearing
: No small-diameter piston provided (self-pressing moment used)
P3 : Gear pump (swivel, dozer, SP2) (Used for LS system in using the travel and LS control)
P4 : Gear pump ((Pilot pump) and to use also for LS engine rpm proportional control)
( ump control)
1. Horsepower: Orifice-controlled P1 + P2 average pressure to make the power double, instead of gener-
ating the P1 + P2 horsepower with a stepped piston. P3 also controlled together.
2. Engine rpm gain control: P4 pilot pump s discharge throttled, resulting in differential pressure. LS differ-
ential pressure modified accordingly. (Same mechanism as on KX121-3S/ and KX161-3S/ )
3. Introduction of response improvement check valve (LS flow control valve bypassed) at P3 under pres-
sure. In this way, swivel horsepower control response quicker and engine drop reduced.
4. Tilting swash plate s moment for larger flow rate controlled by repositioning the turning center of the
swash plate and generating the self-tilting moment. (The small-diameter piston on KX121-3S/
KX161-3S/ is abolished out.) Tilt moment assist spring also adopted to boost the tilting moment at low
pressure.
PS
(17)
(16)
(15)
P P
3 1
b
d
c
a
b
e
P P
3
(9) (10)
(1) PLS control pressure from CV
(2) LS differential pressure setting spring
(3) Engine rpm proportional gain control piston
(4) Response improvement check valve at P3
under pressure
(5) Engine rpm proportional gain control aperture
(6) P3 pump horsepower shift piston
(7) P4 pilot pump
(8) P3 pump
P
(14)
2
(9) Large-diameter tilt control piston
(10) Tilting moment assist spring
(11) P1, P2 pump
(13)
(12) Horsepower control spring
(13) PC horsepower control spool
(14) High-pressure selector check valve
(12)
(15) Aperture for P1 + P2 average pressure
(16) LS control regulator
Basically common with L3
(17) LS flow control spool
(18) PPS control pressure from CV
Eng.
a : Pmax
b : Tank
c : P
3
P
d : P =
e : PC
(11)
IV-M-17
IV Hydraulic System
+P
1 2
2
and