Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2001-05-22
2002-10-15
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S564000, C384S565000
Reexamination Certificate
active
06464398
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a roller bearing which forms a drive device or an axle used in a railroad vehicle, a differential gear used in a car, or a rotary support part used in machinery. A roller bearing according to a first aspect of the invention can be applied to all of small- and medium-sized roller bearings having an inside diameter of the order of 20-200 mm. And, a roller bearing according to a second aspect of the invention can be applied to tapered roller bearings of all sizes. Especially, in a roller bearing according to the invention, when the quantity of lubricating oil existing in the rotary support part incorporating the present roller bearing therein is small, or when the lubricating oil has dried up in a short time, the present roller bearing can be prevented against seizure or scuffing; and, further, in case where a lubricating device is out of order, the present roller bearing can be prevented against quick seizure.
Conventionally, a roller bearing is assembled in a rotary support part disposed in various machines and, as a roller bearing for forming a rotary support part to which a large load is applied, there is used a roller bearing which employs a roller (for example, a cylindrical roller, a tapered roller, or a spherical roller) as a rolling body.
FIGS. 1
to
3
show, as an example of such roller bearing, a tapered roller bearing
1
to be assembled into a rotary support part to which large radial load and axial load can be applied. This tapered roller bearing
1
is composed of an outer ring
3
having a conical-concave-surface-shaped outer ring raceway
2
formed on the inner peripheral surface thereof, an inner ring
5
having a conical-convex-surface-shaped inner ring raceway
4
formed on the outer peripheral surface thereof, and a plurality of tapered rollers
6
,
6
slidably interposed between the outer ring raceway
2
and inner ring raceway
4
. Also, each of the tapered rollers
6
,
6
has an outer peripheral surface formed as a conical-convex-surface-shaped rolling surface
7
which can be contacted with the outer ring raceway
2
and inner ring raceway
4
. Further, of the outer peripheral surface two end portions of the inner ring
5
, in the large-diameter-side end portion, there is formed a large-diameter-side flange portion
8
and, in the small-diameter-side end portion, there is formed a small-diameter-side flange by portion
9
.
When the above-structured tapered roller bearing
1
is in operation, the tapered rollers
6
,
6
, as shown in
FIG. 2
, each rotate about their own axes as well as rotate along the outer ring raceway
2
and inner ring raceway
4
in such a manner that they are present nearer to the large-diameter sides of the outer ring raceway
2
and inner ring raceway
4
, thereby allowing the outer ring
3
and inner ring
5
to rotate with respect to each other. When the above-structured tapered roller bearing
1
is in operation, the head portions
10
of the tapered rollers
6
, that is, the large-diameter-side end faces of the tapered rollers
6
and the inner surface
11
of the large-diameter-side flange portion
8
, as can be seen clearly from the Hertz' elastic contact theory, are contacted with each other in such a contact ellipse
12
portion as shown by oblique lattices in FIG.
3
. Since the contact state between the head portion
10
and inner surface
11
is a rolling contact with slippage, this is a severe condition from the viewpoint of friction control. Therefore, in case where the quantity of lubricating oil supplied to the tapered roller bearing
1
is excessively small or dries up, in a terrible case, there is a possibility that there can occur damage such as seizure in the tapered roller bearing
1
. By the way, damage such as seizure can occur in various portions of various roller bearings including the tapered roller bearing
1
and, of these portions, the portion where the condition is the severest and damage is easy to occur is the contact portion between the head portion
10
of the tapered roller
6
and the inner surface
11
of the large-diameter-side flange portion
8
. The present invention aims at preventing the contact portion from being damaged. Accordingly, the term “seizure” used in the present specification means seizure in the contact portion between the head portion
10
and inner surface
11
.
In order to prevent the above seizure from occurring, there are conventionally known the following techniques (1)-(7).
That is:
(1) As, disclosed in JP-A-7-91452, JP-A-7-103243 and JP-A-10-110733 as well as in the Japanese Patent No. 2508178, the head portion of the tapered roller and the inner surface of the large-diameter-side flange portion are enhanced in roughness or are plateau worked into shapes in which the lubricating oil can be retained easily.
(2) Extreme-pressure additive for enhancing seizure resistance and wear resistance is added to the lubricating oil.
(3) As disclosed in JP-A-9-177774, JP-A-9-287616, JP-A-11-132242 and JP-A-7-8628U, on the head portion of the tapered roller and the inner surface of the large-diameter-side flange portion, there are formed chemically reformed films or ceramic films.
(4) As disclosed in JPA-7-259864, JP-A-8-135664, JP-A-8-135666, JP-A-9-32859, JP-A-10-47360, and JPA-11-141557, in the interior portion of the roller bearing or in the peripheral portion of the roller bearing, there is disposed an oil basin for storing lubricating oil temporarily or a reservoir for storing grease; and, when the lubricating condition is worsened, the lubricating oil or grease is supplied from the oil basin or reservoir to thereby prevent the roller bearing from seizing.
(5) As disclosed in JP-A-4-331813, JP-A-7-12133 and JP-A-10-196660 as well as in the registered utility model No. 2584623, the edge of the connecting portion between the end face and chamfered portion of the roller is rounded, whereby, even in case where the roller is skewed and the contact ellipse is in part pressed out into the chamfered portion, an edge load occurring in the contact portion can be relieved.
(6) As disclosed in JP-A-6-63932U and in the registered utility model No. 2538263, the roller bearing is formed as a sealed structure, whereby a lubricant charged once into the interior portion of the roller bearing can be prevented from flowing out therefrom.
(7) As disclosed in JP-A-9-196068 and JP-A-9-236131, by modifying the shape of the end portion of the roller, the contact point height between the end face of the roller and inner surface of the flange portion (the diameter-direction distance from the rolling surface of the roller) is made zero, thereby preventing slippage at the contact point thereof.
Of the conventional seizure preventive techniques respectively described in the above-mentioned articles (1) to (7), the five techniques (1), (3), (4), (6) and (7) respectively relate to a specially specified roller bearing but cannot be applied to an ordinary roller bearing, or, even in case where they can be applied to the ordinary roller bearing, most of them increase the cost of production. Some of the techniques shown in the article (3) can produce the roller bearing at a relatively low cost but the durability and recycling capacity of a film obtained by these techniques are not satisfactory; that is, the film can provide moderate initial performance but, due to its change with the passage of time (such as deterioration or wear), the film fails to provide its expected performance.
Also, of the remaining techniques set forth in the articles (2) and (5), the technique in the article (2) is a measure obtained by changing the property of the lubricant; that is, it has a certain degree of effect but is not an improvement in the roller bearing itself. Therefore, in order to attain seizure prevention of a higher order, it is desired that the present technique should be used in combination with an improvement in the roller bearing itself.
Further, the technique set forth in the article (5) can provide a high seizure preventive effec
Matsubayashi Kiyohito
Mihara Hirohisa
Nakano Yuji
Takehara Tetsu
Footland Lenard A.
NSK Ltd.
Sughrue & Mion, PLLC
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