Hitachi ZW180 Technical Manual page 198

Increasing Flow
1. When the control lever stroke is larger, pressure
difference (difference between pressure Pi1 and
Pi2) arising at the flow control valve in the control
valve is reduced.
2. Force due to spring (1) and pump control
pressure Pi2 pushes spool 1 (3) and spool 1 (3)
moves toward the arrow.
3. Therefore, the circuit of servo piston 1 (10) is led
to the hydraulic oil tank.
4. As pilot primary pressure Pg is always applied to
servo piston 2 (12), swash plate (11) tilts toward
the flow increasing direction.
5. Movement of swash plate (11) is transmitted to
sleeve 1 (2) through the feedback lever link (13).
Sleeve 1 (2) moves toward the movement of
spool 1 (3).
6. When sleeve 1 (2) has moved the same distance
as spool 1 (3) servo piston 1 (10) is not connected
to the hydraulic oil tank. Therefore, servo piston 1
(10) stops and the flow increase is completed.
COMPONENT OPERATION / Pump Device
Flow (Q)
0
3
Pi1
ST
Pd1
1 - Spring
2 - Sleeve 1
3 - Spool 1
4 - Piston
Pd1 - Own Pump Pressure
ST - Pump Torque Control
Pressure
T - Returning to Hydraulic Oil
Tank
T3-1-10
Pump Control Pressure (Pi1-Pi2)
2
Air
T
Bleeding
T
10
Increase
Decrease
Displacement Angle
10 - Servo Piston 1
11 - Swash Plate
12 - Servo Piston 2
13 - Feedback Lever Link
Pi1 - Pump Control
Pressure 1
Pi2 - Pump Control
Pressure 2
Pg - Primary Pilot Pressure
(From Pilot Pump)
1
4
Pi2
Pg
T
13
12
T4GB-03-01-006