Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2000-08-25
2002-09-17
Hannon, Thomas R. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S462000
Reexamination Certificate
active
06450691
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rolling bearing with a sealing plate having a grease enclosed therein, which is used to form the rotary supporting portion of automobile auxiliary machineries to be installed in engine room such as alternator and compressor. In other words, the present invention is intended to improve the reliability and durability of a rolling bearing with a sealing plate having a grease enclosed therein which is used at high temperatures (e.g., 170° C. or higher).
2. Description of the Related Art
In order to form the rotary supporting portion of various mechanical devices, rolling bearings with a sealing plate
1
and
1
a
as shown in
FIGS. 1 and 2
, respectively, are used. The rolling bearings with a sealing plate
1
and
1
a
each composed of an outer race
3
having an outer raceway
2
formed in the middle portion of the inner surface thereof, an inner race
5
having an inner raceway
4
formed in the middle portion of the outer surface thereof, and a plurality of rolling elements rotatably provided between the outer raceway
2
and the inner raceway
4
. Provided extending between the both ends of the inner surface of the outer race
3
and the both ends of the inner race
5
is a sealing plate
7
a
or
7
b.
The sealing plate
7
a
or
7
b
blocks the both axial opening ends of a space
8
defined by the inner surface of the outer race
3
and the outer surface of the inner race
5
having the rolling elements
6
provided therein. A grease is enclosed in the space
8
between the pair of sealing plates
7
a
or
7
b
to lubricate the area at which the outer raceway
2
and the inner raceway
4
come in rolling contact with the rolling surface of the rolling elements
6
.
The sealing plates
7
a
and
7
b
each comprise a circular core metal
9
formed by a metal plate such as steel plate, and an elastic material
10
a
or
10
b
provided covering the core metal
9
and reinforced by the core metal
9
. The inner and outer edges of the elastic materials
10
a
and
10
b
radially protrude beyond the inner and outer edges of the core metal
9
. The sealing plates
7
a
and
7
b
engage the elastic materials
10
a
and
10
b,
respectively, with a stop groove
11
formed on the both ends of the inner surface of the outer race
3
so that they are supported at the both axial ends of the space
8
. The inner edge of the elastic material
10
a
shown in
FIG. 1
comes in sliding contact with a part of the surface of the inner race
5
while the inner edge of the elastic material
10
b
shown in
FIG. 2
is closely opposed to a part of the surface of the inner race
5
. In other words, the sealing plate
7
a
shown in
FIG. 1
is a contact type seal while the sealing plate
7
b
is a non-contact type seal.
As the grease to be enclosed in the space
8
, which constitutes the rolling bearing
1
or
1
a
having a grease enclosed therein, and the elastic material
10
a
or
10
b,
which constitutes the sealing plate
7
a
or
7
b,
respectively, there have been heretofore used usually the following materials (
1
) to (
5
).
[Grease]
(
1
) Urea-based grease comprising as a thickening agent a urea compound comprising isocyanate and amine and as a base oil comprising PAO and ether singly or in admixture;
(
2
) Fluorine-based grease having excellent high temperature characteristics;
[Elastic Materials
10
a,
10
b]
(
3
) Acrylic rubber obtained by the polymerization of ethyl acryate;
(
4
) Fluororubber obtained by the copolymerization of vinylidene fluoride with hexafluoropropylene; and
(
5
) Fluororubber obtained by the copolymerization of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene
Heretofore, a grease selected from the group consisting of the foregoing materials (
1
) and (
2
) and a sealing plate
7
a
or
7
b
comprising the elastic material 10
a
or
10
b,
respectively, made of a rubber selected from the foregoing materials (
3
) to (
5
) have been properly combined to form a rolling bearing
1
or
1
a
with a sealing plate having a grease enclosed therein.
The foregoing combination of the grease and elastic material
10
a
or
10
b
made of the material which has been heretofore known cannot necessarily assure sufficient reliability and durability at high temperatures.
The combination of the fluorine-based grease (
2
) and the fluororubber (
4
) or (
5
) exhibits a sufficient heat resistance but exhibits an insufficient grease durability under high rate and high load working conditions. Accordingly, this combination is not suitable for the construction of the rotary supporting portion of alternator, compressor, etc.
Further, the combination of the fluorine-based grease (
2
) and the acrylic rubber (
3
) not only exhibits an insufficient grease durability under high rate and high load working conditions but also exhibits a deteriorated elasticity of acrylic rubber after prolonged use at high temperatures, causing the sealing plate
7
a
or
7
b
to show a deterioration of sealing properties. Accordingly, this combination, too, is not suitable for the construction of the rotary supporting portion of alternator, compressor, etc.
Moreover, the combination of the urea-based grease (
1
) and the acrylic rubber (
3
) exhibits a deteriorated elasticity (hardening) of acrylic rubber after prolonged use at high temperatures, causing the sealing plate
7
a
or
7
b
to show a deterioration of sealing properties. Accordingly, this combination, too, is not suitable for the construction of the rotary supporting portion of alternator, compressor, etc.
Further, the combination of the urea-based grease (
1
) and the fluororubber (
4
) or (
5
) exhibits a deteriorated elasticity of fluororubber due to the effect of urea compound at high temperatures, causing the sealing plate
7
a
or
7
b
to show a deterioration of sealing properties. Accordingly, this combination, too, is not suitable for the construction of the rotary supporting portion of alternator, compressor, etc.
As mentioned above, a urea-based grease, if used as a grease, exhibits an insufficient durability under high rate and high load working conditions in any case. The resulting rolling bearing with a sealing plate having a grease enclosed therein cannot be secured with a sufficient durability. The results of experiment made by the inventors in this respect will be described in connection with FIG.
3
. The experiment was made with a deep groove ball bearing having an inner diameter of 17 mm, an outer diameter of 52 mm and a width of 17 mm. In some detail, this ball bearing was operated at a rotary speed of 18,000 r.p.m. at an ambient temperature of 180° C. and a radial load of 150 kgf. Under these conditions, the time required until seizing due to mallubrication occurs was measured. As samples there were prepared two each for rolling bearing having a urea-based grease enclosed therein and rolling bearing having a fluorine-based grease enclosed therein, totaling four. As can be seen in
FIG. 3
, which shows the results of the foregoing experiment, the rolling bearing having a fluorine-based grease showed seizing in about 10 to 20 hours. On the contrary, any samples comprising a urea-based grease didn't show seizing even after 500 hours. The experiment was terminated after 500 hours.
As can be seen in the results of the foregoing experiment, the grease to be enclosed in a rolling bearing with a sealing plate which constitutes the rotary supporting portion of automobile auxiliaries to be installed in engine room such as alternator and compressor is preferably urea-based. As previously mentioned, on the other hand, the combination of a urea-based grease and the conventional fluororubber (
4
) or (
5
) is liable to hardening of fluororubber at high temperatures that makes it difficult to secure sufficient sealing properties as previously mentioned. The results of experiment made by the inventors in this respect are shown in Table 1.
TABLE 1
Grease
Urea-based
Fluorine-based
Elastic
Fluororubber
x
∘
mat
Goto Koichi
Nakai Katsuyuki
Okuma Kenji
Saigusa Shigeharu
Uchiyama Takahiko
Hannon Thomas R.
NSK Ltd.
Sughrue & Mion, PLLC
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