Hitachi ZW180 Technical Manual page 340

Clutch Connection from Neutral (Clutch Pressure
Increase)
•
During Clutch Connection
(Refer to Oil Pressure Waveform A on T3-9-32.)
When the transmission is shifted by the lever, the
electric signal is transmitted from the controller to
proportional solenoid valve (1).
During oil pressure waveform A, pressure oil to oil
passage (a) of proportional solenoid valve (1) is
regulated to the pressure corresponding to the
electric signal of the controller, and is supplied to
oil passage (c).
1. Pressure oil to oil passage (c) is supplied to
pressure chamber (e) of modulation spool (2),
overcomes the force of modulation spring (3), and
moves modulation spool (2) leftward.
Therefore, pressure oil is supplied from oil
passage (b) to oil passage (d) of the clutch piston,
and the clutch pressure increases.
1
1 - Proportional Solenoid
Valve
2 - Modulation Spool
3 - Modulation Spring
COMPONENT OPERATION / Drive Unit
a 3
2. In addition, pressure oil to oil passage (d) passes
back chamber (f) of modulation spool (2), and is
supplied to back chamber (g) of modulation spool
(2).
As modulation spring (3) is installed in back
chamber (g) of modulation spool (2), it overcomes
the oil pressure in oil passage (d), moves
modulation spool (2) rightward and closes oil
passage (d) temporarily.
Electric current from the controller is enlarged
gradually, and steps 1 and 2are repeated. Therefore,
the clutch oil pressure gradually increases.
To Clutch
g f b
Piston
T3-9-34
c 2 e
d
T4GD-03-09-014