Yanmar ViO12-2A, Service Manual

Page: 120 / 409

6 . HYDRAULIC SYSTEM
6- 1- 6
6
-1-1 Control Valve Operation
1) Oil Flow from Hydraulic Pump
(1) Oil flow from piston pump P2
The oil from the piston pump P2 flows to the sections
through the port P2 of the inlet section and the parallel
passage.
The travel (L) section is positioned the most upstream in
the control valve, and then the swing, arm and P.T.O.
sections are arranged in that order.
The P.T.O. section is supplied with the oil from both the
piston pumps P1 and P2.
(2) Oil flow from piston pump P1
The oil from the piston pump P1 flows to the sections
through the port P1 of the inlet section and the parallel
passage.
The track gauge change section is positioned the most
upstream in the control valve, and then the boom swing,
boom, bucket, travel (R) and blade sections are
arranged in that order.
2) Simultaneous Operation of Boom and Bucket
The parallel passage in the bucket section has a throttle
Ø1.4 mm so that the oil can flow to the boom section
more smoothly than to the bucket section even when the
boom is given a heavy load. Therefore, the boom and
the bucket can be operated simultaneously.
3) Simultaneous Operation of Travel and Blade
When the blade is operated while the machine is travel-
ing, the blade cylinder is supplied with the same quantity
of oil from the piston pumps P1 and P2 each through the
throttles in the parallel passage. Therefore, the blade
can be operated while the machine is traveling, with no
travel deviation. However, the travel speed is slowed
down.