Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2000-07-13
2002-08-06
Hannon, Thomas R. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S486000
Reexamination Certificate
active
06428212
ABSTRACT:
This application claims the benefits of Japanese Application No. 11-203558 which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, for example, to a lubricating structure of a roll neck bearing which is used in a rolling mill of steel manufacturing facility, and more specifically, to a lubricating structure of a bearing which can prevent wear or scoring in a fit portion between the internal diameter surface of an inner race and a roll neck portion (shaft portion) of the bearing by supplying oil air with certainty.
2. Related Background Art
For example, a roll neck bearing for a rolling mill is used for a work roll or an intermediate roll of a hot rolling mill or a cold rolling mill of steel manufacturing facility. In such a roll neck bearing, clearance fit (loose fit) is often employed between the bearing and the roll in order to facilitate rearrangement of the bearing and the roll.
In such a case, when the roller is rotated in a fit portion between the internal diameter of the inner race of the bearing and the roll neck portion (shaft portion), a creep is created with a slight sliding due to a diametrical difference, thereby bringing about wear or scoring. Consequently, it is required to supply lubricating oil for preventing damages. Thus, oil air lubrication for feeding oil with pressure using compressed air is conducted in the fit portion between the internal diameter of the inner race of this bearing and the roll neck portion (shaft portion).
In a sealed four row tapered roller bearing in this roll neck bearing assembly, double row inner races
4
are provided on the internal diameter side of outer races
1
and a double row outer race
2
through tapered rollers as rolling elements
3
, as shown in FIG.
9
and FIG.
10
. The rolling elements
3
are properly retained by retainers
3
a
. On the internal diameter side of this double row inner race
4
, the roll neck portion (shaft portion)
5
of the roll is clearance fitted (loose fitted).
A chock
6
is provided on the outer diameter side of the outer races
1
and on the double row outer race
2
. This chock
6
is provided with an oil air distributor
9
which is comprised of a plurality of distribution passages
8
for distributing the oil air supplied from an oil air supply apparatus
7
.
Between each outer race
1
and the double row outer race
2
, an outer race spacer ring
11
having an oil bore
10
communicating with the distribution passage
8
is interposed. Oil seals
12
are provided on both of the outer sides of the double row inner races
4
, respectively. An intermediate seal
13
is provided on the inner sides of the double row inner races
4
. Further, there are provided a dust seal
14
, a chock seal
15
on the barrel side, a chock seal
16
on the shaft end side, and a shaft seal
17
. An oil bore
18
is formed on the end surface of each double row inner race
4
, while an oil groove
19
is formed on the internal diameter surface of each double row inner race end surface
4
.
In such a sealed four row tapered rolling bearing, when oil air is supplied from the oil air supply apparatus
7
to the oil air distributor
9
by using compressed air, the oil air flows in a bearing void portion V
0
on the internal diameter side of the oil bore
10
of the outer race spacer ring
11
through this oil bore
10
.
Since the bearing void portion V
0
has a comparatively large capacity, the air oil reaching this bearing void portion V
0
reduces its pressure to be expanded and the air flowing speed thereof is decreased at the same time, the oil and the air are separated from a convey state of a gas-liquid two phase flow, and only the oil advances into the inner portions of the bearing, for example, in the environs of the rolling elements
3
.
The oil thus advancing in the inner portion of the bearing reaches a lower portion of the bearing by gravity, remains at the height level of the oil seals
12
(SLb), and is exhausted from the portion of the oil seals
12
little by little. However, an amount of the supplied oil and an amount of the exhausted oil is balanced in the portion of this oil seal
12
, so that the height level of the oil of the oil seal
12
(SLb) is maintained at the same level all the time.
On the other hand, the air separated from the state of gas-liquid two phase flow in the bearing void portion V
0
is sealed within the bearing at the pressure of 0.1 to 0.3 bars or around by the oil seals
12
provided at the both ends of the bearing and the intermediate seal
13
provided in the middle of the bearing, and flows into the fit portion between the internal diameter surface of the inner race
4
and the roll neck portion (shaft portion)
5
from the oil seals
12
and the intermediate seal
13
through the inner race end surface oil bore
18
.
However, it becomes difficult to supply the oil to this fit portion since the air flow speed (pressure) of this air decelerates in the bearing void portion V
0
and the air has not sufficient flow speed or pressure to send the oil in this fit portion. When the bearing is used for a long time, it is feared that creep is created in this fit portion to cause wear or scoring.
A four row tapered rolling bearing in the roll neck bearing is substantially the same as the sealed four row tapered rolling bearing described above, as shown in FIG.
11
. However, the former is different from the latter chiefly in that oil seals are not provided at the both ends of the bearing.
As described above, since there are no oil seals, the oil invading in the inner portion of the bearing reaches a lower portion of the bearing by gravity, and remains at the height level of the internal diameter surface of the outer races
1
and
2
(Ax) or the height level of the chock seals
15
and
16
(SLc). After that, the oil is exhausted little by little while keeping the balance with the supplied amount thereof.
Also, the air separated in the bearing void portion V
0
has a low pressure in the bearing since no oil seal is provided and hardly flows into the fit portion between the internal diameter surface of the inner race
4
and the roll neck portion (shaft portion)
5
. Thus, it becomes difficult to supply the oil to this fit portion, and when the bearing is used for a long time, a creep may be created in this fit portion to cause wear or scoring.
Incidentally, assuming that there is a chamber (space) when the oil air is conveyed at the flow speed of 6 m/s (the flow speed capable of conveying the oil) or higher, as shown in
FIG. 12
, the oil air advancing into this chamber reduces its flow speed (pressure) to be expanded, whereupon the flow speed decelerates to 6 m/s or lower so that the oil air is separated into air and oil. The separated oil remains as it is inside the chamber, and only the air flows out from the chamber through an outlet. However, if this state continues, the oil remains up to the level of the outlet inside the chamber, and a more pressure loss is generated in the air due to the viscous resistance of the oil, so that the air hardly flows out.
Consequently, in order to convey the oil air to the predetermined destination (the fit portion between the internal diameter surface of the inner race
4
and the roll neck portion
5
), it is preferable to provide in a convey path (supply path) thereof no such a chamber (space) which may bring about a great change in the capacity. Even if it is inevitably required to provide a chamber, it is preferable to reduce the capacity of the chamber to the minimum so that reduction of the pressure or the flow speed of the oil air is suppressed within an appropriate range.
In addition, though the oil air lubrication is conducted in the above-described roll neck bearing shown in
FIG. 9
to
FIG. 11
, grease lubrication is conducted in some cases, as shown in FIG.
13
.
In this grease lubrication, grease is supplied to the fit portion between the internal diameter surface of the inner race
4
and the roll neck portion
5
, so that it is arranged to send the grease
Hannon Thomas R.
Miles & Stockbridge P.C.
NSK Ltd.
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