Yanmar ViO12-2A, Service Manual

Page: 192 / 409

6.
HYDRAULIC SYSTEM
6-
6
-1
6-
6
Control Valve
1. Outline
This control valve is a mono-block valve comprising ten-series connected three-position directional control valves
which control the operation of the actuators by switching the circuit, system relief valves which control the circuit
pressure, circuit relief valves, an anti-cavitation valve, load check valves, throttles and others.
1) Circuit Configuration
There are two pump ports at both right and left ends of the circuit. Oil from the port P2 flows to the left travel, swing,
arm and P.T.O. spool sections, which are connected via parallel passages.
The parallel passage allows simultaneous operation of more than one spool, however, they cannot always operate in
the same motion. Specifically, due to the differences in load and capacity between the actuators, pressures to be
generated vary and the spool with a smaller load pressure operates earlier.
To allow the simultaneous operation of the spools in the same motion as a single operation, the spool stroke of the
spool section with a heavier load needs to be adjusted to the full stroke while that of the spool section with a lighter
load needs to be adjusted to half a stroke or smaller.
Oil from the port P1 flows to the track gauge change, boom swing, boom, bucket, right travel and blade spool sec-
tions, which are also connected via parallel passages.