Hitachi NEXT Series Service Manual page 37

Oil-free screw compressor
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4.15.3 Cleaning and Checking
① Clean the oil pump body, inner rotor, outer rotor,
and bearing housing. Then check the sliding
sur faces of the components. If any damage is
detected, hand finish the component using an
oilstone of #400 to #1000.
② Clean the shaft. Then, check the ball bearing, bush
bearing, oil seal insertion section, and key groove. If
any damage is detected, hand finish the component
using an oilstone of #400 to #1000.
③ Clean the O-ring, shaft key, inner key, and bolts.
After that, check the components for damage.
4.15.4 Assembling
If the shaft does not rotate smoothly, make an
adjustment by lightly tapping the pump-side end of
the shaft.
① Press-fit the ball bearing from the driving side of the
shaft.
② Attach the shaft assembly in [1] to the oil pump
body using the tool shown in Fig.4. Then, confirm
that the shaft rotates smoothly.
Driving Tool
Oil Pump body
Before pushing the bearing in, fit the driving-side
end of the shaft to a wooden block or a similar
material to prevent any damage. During the press-
fit of the bearing, ensure that the upper end of the
bearing and the shaft end are parallel to each
other. If the end surfaces are not parallel, the shaft
is displaced to the driving side. In such a case,
push the bearing in again using the same tool and
when the bearing is fitted in a manner that the
bearing and the shaft end are parallel, check
whether the shaft rotates smoothly. If the shaft
does not rotate smoothly, lightly tap both the ends
of the shaft to adjust it.
③ Attach the inner key to the pump side of the shaft.
Then fit the inner rotor and the outer rotor in this
order.
④ Attach a bush bearing to the baring housing.
⑤ Attach an O-ring to the bearing housing. Then fit the
bearing housing to the oil pump body in accordance
with the matching mark. After that, tighten the bolts.
⑥ Fit the oil seal to the driving side of the shaft and
attach the snap ring.
Pay attention to the direction of the oil seal when
attaching it. Also note that the tool must be lightly
tapped when fitting the oil seal. If the tool is hit
hard, the shaft may dislocate, and will not rotate
smoothly. Manually rotate the shaft to check the
rotating condition. If the shaft does not rotate
smoothly, lightly tap the pump-side end of the
shaft to adjust it.
Driving Tool
⑦ Fix the gear support to the oil pump gear using bolts
Driving-side
(M5, at four places). Then, heat it to approximately
210℉(100℃).
⑧ Attach the shaft key, and shrink-fit the oil pump gear
assembly in ⑦. Before attaching the assembly, push
the oil pump gear assembly until the gear support
Rotor-side
comes in contact with the end of the oil pump gear
shaft.
⑨ Insert a bolt (M8) in the center hole of the gear
support and securely tighten it at the end of the oil
pump gear shaft.
M6 Bolt
(4 places)
M8 Bolt
After the components are assembled completely,
manually rotate the shaft again to check the
rotating condition.
35
Confidential to Customer
Oil Seal
Housing
Gear Support
Oil Pump Gear
Oil Pump Gear Assembly
Driving-side
Rotor-side
Oil Pump body

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