Steering Circuit - Hitachi ZW180 Technical Manual

STEERING CIRCUIT

Normal Steering Circuit
•
Normally, pressure oil from the main pump flows
to the steering valve through the priority valve. As
pilot line (LS2) is connected to the hydraulic oil
tank, pressure is lost.
•
The priority valve spool is moved to rightward
pushed as pressure (LS1) from the own pump
overcomes the spring force of the priority valve.
Therefore, all pressure oil is supplied to the
control valve.
•
When the steering wheel is turned, the steering
pilot valve spool is shifted, and pressure oil from
the pilot pump moves the steering valve spool.
•
When the steering wheel is quickly turned, as a
large amount of pilot pressure oil is supplied in a
short period of time to the end of the steering
valve spool through the steering pilot valve, the
steering valve spool moves quickly and largely.
•
When the steering wheel is slowly turned, as a
small amount of pilot pressure oil is supplied
gradually to the end of the steering valve spool
through the steering pilot valve, the steering valve
spool moves slowly and slightly.
•
In proportion to the movement of the steering
valve spool, pressure in pilot line (LS2) rises.
Therefore, the priority valve spool is pushed
leftward by the spring force of priority valve and
pressure of pilot line (LS2).
•
In this way, pressure oil from the main pump flows
to the steering cylinders through the priority valve
and the steering valve, and the steering cylinders
are actuated. (Refer to the COMPONENT
OPERATION / Pump Device group.)
SYSTEM / Hydraulic System
T2-3-26
NOTE: When pressure oil passes inside the
steering pilot valve, pressure oil flows to
the steering valve through the gerotor part.
As the gerotor is connected to the middle
shaft of the pilot steering valve, powered
steering effect is generated. (Refer to the
COMPONENT OPERATION / Steering
Pilot Valve group.)