NTN - Precision Rolling Bearings

Technical Data
4 Bearing jacket cooling system
With a built-in motor drive system, the main spindle is
directly driven by a motor and is therefore suitable for
rapid acceleration or deceleration. However, this
system can be adversely affected by temperature rise.
A cooling jacket with a spiral groove around the housing
allows cooling oil to flow through the unit.
If heat generated by the motor affects the bearing,
overheating of the bearing as well as degradation of the
grease can occur. This situation must be strictly
avoided. When designing a cooling system with jacket
cooling, the following should be considered.
Considerations about cooling of jacket
A typical bearing arrangement is shown in Fig. 5.4
and 5.5, comprising a double-row cylindrical roller
bearing and an angular contact ball bearing set. The
cooling groove on the jacket in Fig. 5.4 starts at around
an area above the angular contact ball bearings and
does not cool the double-row cylindrical roller bearing
effectively.
(Note that the fit of the angular contact ball bearings
with the bore of the housing is a clearance fit-the
bearings are not in direct contact with the housing) In
the configuration in Fig. 5.5, the cooling groove extends
to the region above the double-row cylindrical roller
bearing, and cools both the angular contact ball
bearings and the double-row cylindrical roller bearing
effectively.
IN
OUT
Cooling groove
on jacket
IN
Cooling groove
on jacket
OUT
Fig. 5.4 Inadequate cooling groove on jacket
Fig. 5.5 Adequate cooling groove on jacket
Test conditions
Test bearing
Preload after assembled
Lubrication system
5S-2LA-HSE014DB
100N (Fixed position preloading)
Air-oil lubrication
Test conditions
Test bearing
Mounted radial clearance
Lubrication system
NN3028HST7
-5μm
Grease lubrication
Temperature increase on outer ring ˚C
70
60
50
40
30
20
10
0
6000
w/ jacket cooling
w/o jacket cooling
10000 14000 18000
22000
Speed min -1
Temperature increase on outer ring ˚C
70
60
50
40
30
20
10
0
0
w/ jacket cooling
w/o jacket cooling
1000 2000 3000
4000
5000
Speed min -1
100 150
dmn value 10 4
Fig. 5.6 Variation in bearing temperature depending
on presence/absence of jacket cooling
(angular ball bearing)
0 25 50 75
dmn value 10 4
Fig. 5.7 Variation in bearing temperature depending
on presence/absence of jacket cooling
(cylindrical roller bearing)
26