Hitachi ZW180 Technical Manual page 365

When Brake is Applied
1. When the brake pedal is depressed, spool input
(3) is pushed via roller (2).
Spool input (3) moves spools (7, 8) forward via
spring (5).
2. When spools (7, 8) are moved forward, ports (BR1,
BR2) and port (T) are disconnected. When spools
(7, 8) are further moved forward, ports (BR1, BR2)
and ports (M1, M2) are connected, and pressure
oil in the accumulator flows from ports (BR1, BR2)
and the brake is applied.
COMPONENT OPERATION / Brake Valve
3
5
M2
7
M1
8
3. Pressure oil at the ports (BR1, BR2) side passes
the orifices in spools (7, 8) and acts on plungers
(10, 11) built in spools (7, 8) as the returning force
(hydraulic reaction force) against spools (7, 8).
Summation of this hydraulic reaction force and the
load of spring (9) balances with the load of spring
(5), and controls the brake oil pressure at the
brake ports (BR1, BR2) side.
4. Deflection and the load of spring (5) are fed back
as the stroke and operating force of the brake
pedal, and provides the operator with virtual
operation feeling.
2
T
BR1
BR2
T3-11-5
11
10
9
T4GB-03-11-005