SP001647Travel Control Valve (with Damper)
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Pressure Reducing Valve
1. Neutral Condition
If pedal is in neutral, spool is pushed up by return spring
and spring seat. Port (P) is blocked by bottom part of spool
and four operating ports (left forward and backward, right
forward and backward) are connected to port (T) through
inner hole of spool.
2. Half Operation Condition
If pedal is moved, push rod moves down, and they transmit
this force through spring seat and control spring to spool. If
spool is moved, primary pressure is transmitted through an
inner hole of spool to operating port. If lever is stopped in
middle position, compressed control spring force and
secondary pressure transmitted through hole acts at
bottom part of spool, balance is maintained by hydraulic
force acted upward, and then this pressure is transmitted
to traveling spool of control valve. That is, primary pressure
is transmitted to operating port as secondary pressure
equivalent to control spring force compressed by spool.
3. Full Operating Condition
If pedal is moved to a maximum, bottom part of push rod
presses spool seat to a maximum, and compresses control
spring to a maximum. Primary pressure is transmitted
through inner hole of spool to operation port, secondary
pressure transmitted through spool overcomes control
spring force and pushes spool up, but spool is restricted by
push rod and does not move any more. That is, when
pedal lever is moved to a maximum, control spring does
not function, spool is restricted by push rod, and then
primary pressure equalizes to secondary pressure.
