Hyster W20-30ZR, Руководство пользователя

Страница: 5 / 48

2000 SRM 1025 Description of Operation
General
This section covers the troubleshooting and repair
procedures for the hydraulic components on the W30/
40ZA, W25/30/40ZC, and W20/30ZR lift trucks.
It also includes the remove and install procedures
for the solenoid coils used to activate the hydraulic
valves.
For troubleshooting and repairs of the electrical com-
ponents, see Electrical System 2200 SRM 1026 and
ZAPI
TM
Controllers 2200 SRM 1064.
Description of Operation
The hydraulic system of the W30/40ZA, W25/30/
40ZC, and W20/30ZR lift trucks includes:
• Reservoir
• Pump
• Check valve
• Relief valve
• Proportional lowering valve
• Lift cylinder(s)
• Connecting hoses and tubes
Based on the model and configuration of the hy-
draulic system, it can also include:
• Lift valve
• Directional valve(s)
• Selector valve(s)
• Counterbalance valve
• Pilot operated check valve
• Sideshift cylinder
• Tilt cylinders
• Reach cylinders
• Auxiliary cylinder(s)
The reservoir contains the hydraulic fluid necessary
for the operation of the system. It acts as a heat sink
to provide cooling. As the hydraulic oil leaves the
reservoir, it is filtered through an internal strainer
in the reservoir.
The hydraulic pump provides the flow of the hy-
draulic oil. It moves the oil to activate the cylinders.
A check valve provides flow of the hydraulic oil in one
direction only. In this hydraulic system, it prevents
the oil from flowing backwards through the pump.
A relief valve limits maximum pressure to protect the
hydraulic system components.
The proportional lowering valve is a normally closed
valve. When it opens, hydraulic oil from the lift cylin-
ders is allowed to return to the reservoir and the
forks lower. Rate of flow is regulated by how far the
valve opens.
The lift cylinder(s) rod extends to raise the forks
through a series of mast channels and chains.
The connecting hoses and tubing connect the various
hydraulic components in the lift truck to complete
the hydraulic circuit.
The lift valve is used on systems that have more than
a lift/lower function. It is a normally closed valve
which opens during the lift function. During other
functions, such as sideshift, it remains closed to pre-
vent flow to the lift cylinders.
The directional valve(s) is a three position normally
closed valve located on the pump. In its normal posi-
tion, it blocks the flow of oil to a double acting cylin-
der, such as a sideshift cylinder. Activated in one po-
sition, it provides flow to extend a cylinder rod. Acti-
vated in the opposite position, it reverses flow to the
cylinder to retract the cylinder rod.
The selector valve(s) is a normally closed valve lo-
cated on the mast. Selector valves are used to direct
the flow from a single pair of hydraulic lines to mul-
tiple double acting hydraulic cylinders.
The counterbalance valve provides free flow in one
direction and resistance to flow in the opposite direc-
tion. It is located in the tilt circuit to control forward
tilt.
The pilot operated check valve is located in the re-
tract circuit and is activated by an auxiliary pres-
sure. Its function is to maintain pressure on the rod
side of the piston to hold the reach mechanism in the
retract position.
The tilt cylinders rods extend to tilt the forks forward
away from the lift truck. The rods retract to tilt the
forks back toward the lift truck.
The reach cylinders rods extend to move the forks
away from the lift truck. The rods retract to move
the forks back toward the lift truck.
1