Kubota M108S, Workshop Manual

Page: 383 / 523

8-M6
M108S, WSM HYDRAULIC SYSTEM
■
Lifting to Neutral (Acting the shockless
mechanism)
In returning from Lifting to Neutral, the spool (3) is
pushed back to the arrow-mark direction. When the
Neutral position comes near, the groove part D of the
spool (3) makes the pressure difference at the P port and
C port. Therefore, the poppet 1 (1) gradually closes, and
absorbs any shock at lifting stop. In that case, since oil
is remained in the chamber A of the unload poppet (4)
and closes. However, the unload poppet 2 (5) opens
because of low pressure in chamber B, and then the oil
from the pump returns to the transmission case through
T2 port until unload poppet 1 (4) opens.
W1020929
■
Lowering
When the control lever is moved to “DOWN” position,
spool (3) moves to arrow-mark direction, and pushes the
poppet 2 (2). If forms a circuit with the C port and T3 port.
The oil in the hydraulic cylinder is forced out by the
weight of the implement, and returns to the tank through
the C port and T3 port, lowering the implement. The
pressurized oil pushes open unload poppet (4) and
returns to the tank from T1 port.
■
Floating
When the control lever is kept at lowest position,
spool (3) and poppet 2 (2) keeps same as lowering
position. The hydraulic cylinder is unloading condition.
Therefore pressurized oil pushes open unload poppet (4)
and returns to tank.
W1021318
(1) Poppet 1
(2) Poppet 2
(3) Spool
(4) Unload Poppet 1
(5) Unload Poppet 2 P : Pump Port
C : Cylinder Port
A : Chamber A
B : Chamber B
D : Groove
T1 : Tank Port 1
T2 : Tank Port 2
T3 : Tank Port 3
(1) Poppet 1
(2) Poppet 2
(3) Spool
(4) Unload Poppet 1
(5) Unload Poppet 2 P : Pump Port
C : Cylinder Port
T1 : Tank Port 1
T2 : Tank Port 2
T3 : Tank Port 3
KiSC issued 06, 2007 A