Travel Pilot Valve (With Damper) Function; Reducing Valve Section When The Pilot Valve Operating Section Is At The Neutral Position; Reducing Valve Section When The Pilot Valve Operating Section Is Tilted From The Neutral Position - Kubota KX080-3 Workshop Manual

WSM KX080-3 Mechanism
d. Function
The damper-embedded pilot valve includes in its main body a damping function to prevent hunting (lever
hunting) in the man-machine system.
The following explains the operation of the damper-embedded pilot valve, separating it into 2 sections: a.
reducing valve and b. operation section damping mechanism based on the hydraulic circuit diagram
below, the assembly cross-section drawing in 31(RCVD8C), 32(RCVD8CC), and the damping operation
explanation drawing in 9. The following figure shows a typical usage of the pilot valve.
(1)
(2)
1. Reducing valve section
1.1 When the pilot valve operating section is at the neutral position
The spool (301), pushed upward by the return spring (335), washer 1(215) through the spring seat (311), is
at its neutral position as shown in the assembly cross-section drawing. Since the outlet port is joined only
with the tank port T as a result of the spool switching function, the pressure at the outlet ports 1 and 2 is the
same as the pressure at the tank port T.
1.2 When the pilot valve operating section is tilted from the neutral position
As shown in the assembly cross-section drawing, when the cam (420) is rotated clockwise, the push rod
(214) at the port 1 is pressed downward, which pushed the spool downward with the help of the washer 1,
the spring seat, the secondary-pressure-setting spring (324), the washer 2 (217), and the washer 3 (313).
As a result, the port P and the port 1 are joined each other and the oil supplied from the pilot pump starts to
flow into the port 1, generating a flow pressure.
When the pressure at the port 1 increases to a pressure equivalent to the force of the secondary-pressure-
setting spring, having been set by the tilted operating section, the oil pressure applied to the spool and the
spring force are kept in balance, which keeps the port 1 outlet pressure constant.
Since the spool at the port 2 remains neutral, the return oil from the control valve flows out through the tank
port T.
Depending on the specifications, the push rod touches the top of the spool directly when the operating sec-
tion is tilted fully, which forcefully pushes down the spool, joining the port P and the outlet port, resulting in an
equal pressure at both ports.
(3)
Hydraulic circuit diagram
IV-M-69
(5)
(4)
(1) Pilot valve
(2) Pilot pump
(3) Main pump
(4) Control valve
(5) Hydraulic motor
(6) Hydraulic cylinder
(7) Shuttle valve(RCVD8CC only)
IV Hydraulic System
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