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LUBRICATION
(3) Splash Lubrication (5) Jet Lubrication This lubricating method is used in bearings for the high Oil
With this lubricating method, oil is splashed onto the speed spindles of machine tools, high speed pumps, Oil
bearings by gears or a simple rotating disc installed Jet lubrication is often used for ultra high speed roll necks of rolling mills, etc (Fig. 12.9).
near bearings without submerging the bearings in oil. bearings, such as the bearings in jet engines with a For oil mist lubrication of large bearings, it is advisable (a) (b)
It is commonly used in automobile transmissions to consult NSK. Fig. 12.8 Jet Lubrication
and final drive gears. Fig. 12.6 shows this lubricating dmn valve (dm: pitch diameter of rolling element set
method used on a reduction gear. in mm; n: rotational speed in min–1) exceeding one (7) Oil/Air Lubricating Method Fig. 12.9 Oil Mist Lubrication
(4) Circulating Lubrication Oil/air inlets × 5 places
Circulating lubrication is commonly used for high million. Lubricating oil is sprayed under pressure from Using the oil/air lubricating method, a very small
speed operation requiring bearing cooling and for one or more nozzles directly into the bearing. amount of oil is discharged intermittently by a
bearings used at high temperatures. As shown in Fig. Fig. 12.8 shows an example of ordinary jet lubrication. constant-quantity piston into a pipe carrying a constant
12.7 (a), oil is supplied by the pipe on the right side, The lubricating oil is sprayed on the inner ring and flow of compressed air. The oil flows along the wall of
it travels through the bearing, and drains out through cage guide face. In the case of high speed operation, the pipe and approaches a constant flow rate.
the pipe on the left. After being cooled in a reservoir, it the air surrounding the bearing rotates with it causing The major advantages of oil/air lubrication are:
returns to the bearing through a pump and filter. the oil jet to be deflected. The jetting speed of the (a) Since the minimum necessary amount of oil is
The oil discharge pipe should be larger than the supply oil from the nozzle should be more than 20 % of the supplied, this method is suitable for high speeds
pipe so an excessive amount of oil will not back up in circumferential speed of the inner ring outer surface because less heat is generated.
the housing. (which is also the guide face for the cage). (b) Since the minimum amount of oil is fed
More uniform cooling and a better temperature continuously, bearing temperature remains stable.
Fig. 12.6 Splash Lubrication distribution is achieved using more nozzles for a given Also, because of the small amount of oil, there is
amount of oil. It is desirable for the oil to be forcibly almost no atmospheric pollution.
discharged so the agitating resistance of the lubricant (c) Since only fresh oil is fed to the bearings, oil
can be reduced and the oil can effectively carry away deterioration need not be considered.
the heat. (d) Since compressed air is always fed to the bearings,
the internal pressure is high, so dust, cutting fluid, etc.
(6) Oil Mist Lubrication cannot enter.
For these reasons, this method is used in the main
Oil mist lubrication, also called oil fog lubrication, spindles of machine tools and other high speed
utilizes an oil mist sprayed into a bearing. This method applications (Fig. 12.1O).
has the following advantages:
(a) Because of the small quantity of oil required, the
oil agitation resistance is small, and higher speeds are
possible.
(b) Contamination of the vicinity around the bearing is
slight because the oil leakage is small.
(c) It is relatively easy to continuously supply fresh oil;
therefore, the bearing life is extended.
Oil
Oil (c) Oil/air discharge ports × 2 places
Fig. 12.10 Oil/Air Lubrication
Oil
(a) (b)
Fig. 12.7 Circulating Lubrication
A 108 A 109
