Rolling bearing and method of making the same

Details Rolling bearing and method of making the same Rolling bearing and method of making the same

2001-05-25

2003-03-11

Hannon, Thomas R. (Department: 3682)

Bearings

Rotary bearing

Antifriction bearing

C384S625000, C384S907100

Reexamination Certificate

active

06530695

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention is to improve abrasion resistance of rolling bearings to be incorporated in rotation supporters of jet engines for aircraft or gear boxes and to be served under circumstance at high temperatures, thereby to heighten endurance of rolling bearings.
In rotation supporters of jet engines for aircraft or gear boxes, rolling bearings
1
a
to
1
c
as shown in
FIGS. 1A
to
1
C are incorporated as bearings for aircraft. Three kinds of rolling bearings
1
a
to
1
c
are shown in
FIGS. 1A
to
1
C. The rolling bearing
1
a
of
FIG. 1A
is a ball bearing of single row deep groove type with four point-contact points in which two-piece housing inner ring
2
a
is provided. The rolling bearing
1
b
of
FIG. 1B
is an angular ball bearing having an inner ring
2
b
of counter bored type. The bearing of
FIG. 1C
is a single row cylindrical roller bearing.
In each of these cases, the rolling bearings
1
a
to
1
c
have inner rings
2
a
to
2
c
, outer rings
5
a
to
5
c
, a plurality rolling elements
6
a
to
6
c
rotatably disposed therebetween, and retainers
7
a
to
7
c
, respectively. The inner rings
2
a
to
2
c
are made of iron based alloy and respectively have inner ring raceways
3
a
to
3
c
in outer circumferential surfaces thereof. The outer rings
5
a
to
5
c
are made of iron-alloy and respectively have outer ring raceways
4
a
to
4
c
in inner circumferential surfaces thereof. The plurality rolling elements
6
a
to
6
c
are rotatably disposed between the inner ring raceways
3
a
to
3
c
and the outer ring raceways
4
a
to
4
c
, respectively. The retainers
7
a
to
7
c
rotatably hold the rolling elements
6
a
to
6
c
, respectively. The outer circumferential surface of each of the retainers
7
a
to
7
c
is prevented from displacement in an radial direction thereof by guiding the outer circumferential surface of respective retainer
7
a
to
7
c
by means of one part of the inner circumferential surface of the outer ring
5
a
to
5
c
which (one part) is disposed outside of the outer ring raceway
4
a
to
4
c.
For using the rolling bearings
1
a
to
1
c
of the structures as shown in
FIGS. 1A
to
1
C in applications particularly requiring large corrosion resistance in bearings for aircraft, there are many cases manufacturing the inner rings
2
a
to
2
c
and the outer rings
5
a
to
5
c
with SUS440C (the iron-alloy containing C 1.05 wt %, P 0.040 wt % or lower, S 0.030 wt % or lower, Mn 1.00 wt %, Si 1.00 wt %, Cr 17.00 wt %, Mo 0.75 wt %, the balance being Fe and unavoidable impurities).
Using SUS440C under circumstances at high temperatures as jet engine for aircraft or gear boxes, it did not always have enough corrosion resistance and so was disadvantageous in view of securing endurance. That is, since the inner rings
2
a
to
2
c
and outer rings
5
a
to
5
c
constituting the rolling bearings
1
a
to
1
c
to be applied to usage as above mentioned are tempered at high temperatures in the course of the production, the hardness in the surfaces including the inner ring raceways
3
a
to
3
c
and the outer ring raceways
4
a
to
4
c
is around Hv650 at the most. This value is poor in the corrosion resistance comparing with the hardness Hv being about 700 of heat resistant bearing steels such as M50 (the iron-alloy containing C: 0.80 wt %, P: 0.030 wt % or lower, S: 0.030 wt % or lower, Mn: 0.30 wt %, Si: 0.25 wt %, Cr: 4.00 wt %, V: 1.00 wt %, Mo: 4.25 wt %, the balance being Fe and unavoidable impurities). On the other hand, the heat resistant bearing steels as M50 are difficult to secure a sufficient endurance in term of corrosion resistance.
In view of such circumstances, there are cases of using heat resistant and corrosion resistant steels such as Pyrowear 675 (trade name=iron-alloy containing C: 0.07 wt %, P: 0.005 wt % or lower, S: 0.003 wt % or lower, Mn: 0.65 wt %, Si: 0.40 wt %, Cr: 13.00 wt %, V: 0.60 wt %, Mo: 1.80 wt %, Ni: 2.60 wt %, Co: 5.40 wt %, the balance being Fe and unavoidable impurities). However, if fabricating the inner rings
2
a
to
2
c
and the outer rings
5
a
to
5
c
of the rolling bearings
1
a
to
1
c
with such heat resistant and corrosion resistant steels, being accompanied with carburizing treatments for hardening surfaces, Cr carbides are precipitated in the surfaces of the inner rings
2
a
to
2
c
and the outer rings
5
a
to
5
c
, so that the corrosion resistance in the surface is lowered and it is still difficult to secure the enough endurance.
Further, in case of using the rolling bearings
1
a
to
1
c
as shown in
FIGS. 1A
to
1
C for supporting such as turbines of jet engines for aircraft, parts guiding the outer circumferential surfaces of the retainers
7
a
to
7
c
often causes abrasion or damage in parts of the inner circumferential surfaces of the outer rings
5
a
to
5
c
. For avoiding such accidents, the conventional technique carries out a treatment for forming a hard film such as TiN in the guiding part of the outer circumferential surfaces. But since this hard film treatment is very expensive, and not only it invites cost-up of the rolling bearings
1
a
to
1
c
, but also the hard film often comes off, it does not always bring about an effect of improving a secure abrasion resistibility.
Besides, with respect to the rolling bearings
1
a
to
1
c
to be used to jet engines for aircraft or gear boxes, in a case of a so-called hybrid bearing where the inner rings
2
a
to
2
c
as well as the outer rings
5
a
to
5
c
are made of bearing steels, but the rolling elements are made of ceramic in order to heighten a seizure resistance, the improvement of the abrasion resistibility in the inner rings
2
a
to
2
c
and the outer rings
5
a
to
5
c
become a furthermore problem. That is, in the hybrid bearing, since the contacting condition between the inner rings
2
a
to
2
c
and the rolling elements
6
a
to
6
c
and/or the contacting condition between the outer rings
5
a
to
5
c
and the rolling elements
6
a
to
6
c
takes place between materials of heterogeneous kinds, the seizure resistance of the rolling elements
6
a
to
6
c
can be improved in comparison with the bearing having the rolling elements made of bearing steels (as well as the inner and outer rings). However, the hardness of the bearing steel comprising the inner rings
2
a
to
2
c
and the outer rings
5
a
to
5
c
is far lower than that of the ceramic composing the rolling elements
6
a
to
6
c
, so that when foreign matters as dust or dirt go into the bearings
1
a
to
1
c
, the inner raceways
3
a
to
3
c
and the outer raceways
4
a
to
4
c
are considerably worn.
SUMMARY OF THE INVENTION
In view of these situations, the invention has been made to realize such rolling bearings at low cost, having excellent abrasion resistance, and good corrosion resistance, if needed.
In addition, the invention has also been made to realize a method of making such rolling bearings.
The above-mentioned object can be achieved by a rolling bearing according to a first aspect of the invention comprising an inner ring, an outer ring, a plurality of rolling elements rotatably disposed therebetween, and a retainer. The inner ring is made of iron-alloy and has an inner ring raceway in an outer circumferential surface thereof. The outer ring is made of iron-alloy and has an outer ring raceway in an inner circumferential surface thereof. The plurality of rolling elements are rotatably disposed between the inner ring raceway and the outer ring raceway. The retainer has the inner circumferential surface and the outer circumferential surface and rotatably holds each of the rolling elements. Either of the inner and outer circumferential surfaces of the retainer is guided by a part of either of the outer circumferential surface of the inner ring and the inner circumferential surface of the outer ring for preventing the displacement in the radial direction of the retainer.
In the rolling bearing of the invention, a fine nitride layer comprising a compound layer and a d

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