1t-3.5t R Series Internal Combustion Counterbalanced Forklift Truck. Manual - part 14

3. Main pump

3.1 W21 main pump

1-1.8t W21 main pump is a gear type consisting of a pump body, pump cover, a pair of
gear, bearing and seal ring. This pump uses pressure-balance type bearing and a
special lubrication method so as to get the minimum clearance of the gear flank.
Since the pump body and cover are made of aluminum alloy, they are light and rigid.
The drive gear and driven gear are integrated with their respective shafts, which are
held against the pump body with bearing. The bearing, made of special material,
serves both as bearing for each shaft and as side plates for the gear flank.
At the drive shaft side, an oil seal is press-fitted into the pump body to provide oil
tightness performance. Oil tightness between pump body and pump cover is secured
with a packing of a special shape.
Main pump maintenance remove (refer to Fig.7-1)
f． Hold the pump in a vice lightly and remove blot 12.
g． Remove pumps cover 1 and remove seals 8, 9, 10 and 11.
h． Remove forward end-cover 7, 8, 9, 10 and 11.
i． Remove bearing 3, 4 and gear 5, 6 from pump body 2. If remove bearing difficult,
you can press gear.
j． For the convenience of correct reassemble, it is to put the disassembled parts as
shown in Figs.7-1.

Fig. 7-1

clockwise gear pump

1.End cover

2. Gear plate

3. Bearing

4. Bearing

5. Driving gear

6. Driven gear

7. Front end cover

8. Seal ring

9. Seal ring

10. Seal ring

11. Seal ring

12. Bolt

13. Lock washer

14. Oil seal

15. Snap ring

The main pump of 1t-1.8t G26 is the same as the above mentioned pump, just the
direction of turning is not the same.

Clockwise

3.2 2t-3.5t main pump

2t-3.5t hydraulic system adopts CBHZG model gear pump. Gear pump CBHZG is

an  external  gear  pump  with  axial  interval  self-compensation  and  radial  hydraulic
balance.  By  using  special  structure,  low  noise  comparing  with  those  in  symmetry.
backing boarderials used in the parts effectively improve the performance and make it
reliable, i.g, DU sleeve in bearing, double metal backing boarderial of side plate, AL.
alloy die casting of front and rear cover, extruding AL. alloy of middle section, etc.
CHBZG  left  rotation  see  fig.7-2,  right  rotation  see  fig.7-3.  The  difference  of
counter-clockwise  and  clockwise  pump  is  3  shape  backing  plate.  The  direction  of
them is different.

Fig. 7-2 CBHZG counterclockWise rotation gear pump (left)

1. Snap ring

2. Oil seal

3. Mounting flange

4.Seal plate

5. 3 shape backing plate

6. Pressure plate

7. Bush

8. Driven gear

9. Drive gear

10. Gear plate

11. End cover

12. Washer

13. Mounting bolt

Fig. 7-3CBHZG clockwise (Right) rotation gear pump

1. Snap ring

2. Oil seal

3. Mounting flange

4.Seal plate

5. 3 shape backing plate

6. Pressure plate

7. Bush

8. Driven gear

9. Drive gear

10. Gear plate

11. End cover

12. Washer

13. Mounting bolt

4. Control valve

Two pieces type control valve consists of four pieces of valve body, two plungers,
a relief valve and a divided valve. Four pieces of valve body are assembled with three
blots and nuts. Tilting plunger is fitted by tilting lock-self valve. According to
requirement of work device, it is capable to add combined lock vale and rotating valve.

Fig.7-4 Control valve for 1t～3.5t forklift truck

4.1 Main relief valve and flow dividing valve

Main relief valve is a pilot valve; it is used for limiting the maximum pressure of

system. Main relief valve disk is not opened in normal condition. When the truck works
at overload condition, or hydraulic system faults come, the system pressure is up to
the set value of main relief valve ,the pilot valve disk firstly opens, and then control
valve disk opens to make system pressure not increase continuously, so, it ensure
system safe.

Steering relief valve is a directly operated type valve. Its set value is lower than

main relief valve, when steering system occurs faults or load is too big, pressure is up
to set value by spring, and pressure overcome spring and friction force to open relief
valve. So it ensures steering system safe.

One end of pilot valve disk connects with oil inlet of steering valve, and the other

end connects with steering valve outlet(signal port), so it make the pressure difference
keep invariableness, pilot valve supply proper oil flow according to the rotated speed
of steering wheel by driver.

Extra oil flows to supply other working devices via control valve. This device can

improve system efficiency, reduce oil temperature, improve experimental environment
of system

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