
2-36
Travel straight operation
(7)
Simultaneous operating of both travel spools and other spool.
A case where both travel spools and swing spool are changed over will be considered.
(The pilot ports PAL, PAr and PAs are pressurized.)
[Pilot Circuit]
Since the side bypass sections of both travel spools close and the side bypass section of the
downstream-side swing closes, the pilot pressure from the port Pa enters through the port PTa
to transfer the travel straight spool.
[Main Circuit]
After changeover of the travel straight spool, the port P2 and both travel spools are connected
preferentially and the port P1 and the parallel paths of swing, boom 2, option and arm 1 / boom
1, bucket and arm 2 are connected preferentially. Therefore, the pressurized oil entering through
port P2 passes through mainly ports AL and Ar, and flows to both travel motors separately.
On the other hand, the pressurized oil entering through port P1 flows to port As and is supplied
to the swing motor.
When the pressure of port P2 is lower than the pressure of port P1, part of oil entering through
port P1 flows into port P2 side. Therefore, it prevents the rapid slowdown of travel.
to boom 1
side
P2g
P2
P1g
P1
to travel
left
to travel
right
to swing
side
(PTb)
PAL
PBL
PTa
3607A2MC23