Special Issue; Products for Industrial Machinery - NTN

NTN TECHNICAL REVIEW No.742006
Photo 2 Example of test pieces after evaluation (occurred split and crack)
The result of evaluation for base oils used on
bearings and typically used resin materials is
summarized in Table 7.
Table 7 Results of chemical attack test
Ester oil Fluorine oil Mineral oil PAO
ABS
PC
POM
PA
PBT
PEEK
PPS
The oil does not attack the resin much.
In certain cases, the oil attacks the resin.
The oil attacks the resin.
Color copying machines and color LBPs incorporate
many components made of ABS (acrylonitrilebutadiene-styrene)
and PC (polycarbonate).
Therefore, the grease prefilled in bearings and the rust
preventive oil must be oils that do not have chemical
attack effects on resin materials.
Based on the chemical attack results of the
evaluation described above, NTN is using greases
and rust preventive oils that employ PAO and fluorine
oils as their base oils. Additionally, the conductive
greases previously described in Sec. 4.2 are also
types that do not cause chemical attacks.
4.3 Fuser roller support bearings that prevent
frictional noise
On the fuser roller support bearings, the fit between
the inner ring and the shaft is loose to simplify the
assembly work. Subjected to heat and load, the fuser
roller is affected by both thermal expansion in the axial
direction and bending. Due to the loose fit, the thermal
expansion in the axial direction and the bending, the
attitude of the roller is disturbed, the inner ring hits the
shaft and, as a result, frictional noise occurs at a
frequency of once per revolution. Previously, to control
this problem, grease or a resin sleeve (heat-insulating
sleeve) was placed between the shaft and the inner
ring.
Through a special lubricating surface treatment on
the bore surface of the inner ring, NTN has succeeded
in decreasing the friction coefficient on the bore
surface of the inner ring by 40%. As a result, the
attitude of the inner ring is not disturbed in spite of the
thermal expansion and bending on the fuser roller,
and the inner ring can follow the motion of the roller,
thereby frictional noise that would occur otherwise is
prevented.
The result of the durability evaluation of the special
lubricating surface treatment on the bore surface of
the inner ring is shown graphically in Fig. 8. After the
elapse of 600 operating hours under the test
conditions summarized in Table 8, there was virtually
no change in the inner ring bore diameter, and it is
apparent that wear did not occur on the treated
surface.
Table 8 Test condition of wear test for special lubricant film
Test bearing
Bearing temperature (˚C)
Running speed (min -1 )
Radial load (N)
Shaft material/
surface roughness
Variation in dimension m
3
2
1
0
-1
-2
Test conditions
2TS3-6804ZZ 20mm32mm7mm
200
120
294
A5052Ra0.5
-3
0 100 200 300 400 500 600 700
Test duration h
Fig. 8 Results of wear test for special lubricant film
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