Kubota KX080-4 Workshop Manual page 146

KX080-4, WSM
(2) Function and Structure
[A] Function
The pilot valve is the valve that controls the direction and volume of the stroke of the control valve, and lowers the
primary pressure from the unload valve to a secondary pressure only as much as is necessary to move the control
valve spool.
[B] Operation
1. When the control lever is in neutral
The force of the secondary pressure spring (1) does
not press on the spool (2). Consequently, spool (2) is
pushed up by the return spring (3), and port 1 (a)and port
T (T) are connected.
(1) Secondary Pressure Spring
(2) Spool
(3) Return Spring
2.When the control lever has been actuated
When the control lever is tilted and pushrod (1) goes
through its stroke, spool (2) moves downwards, port
P(P)and port 1 (a) are connected, and oil from the pilot
pump flows via port 1 to the control valve.
The pressure at the port rises until it is equivalent to
the force of the secondary pressure spring (3), thus
balancing the hydraulic pressure on the spool with the
tension of the secondary
maintaining a fixed port pressure.
(1) Pushrod
(2) Spool
(3) Secondary Pressure Spring
3-M50
HYDRAULIC SYSTEM
RY9212001HYM0001US0
(a) Port 1
(b) Port 2
(P) Port P
(T) Port T
RY9212158HYM0005US0
pressure spring and
(a) Port 1
(b) Port 2
(P) Port P
(T) Port T
RY9212158HYM0006US0
KiSC issued 08, 2015 A