Tapered roller bearing

Details Tapered roller bearing Tapered roller bearing

2001-10-16

2003-04-15

Hannon, Thomas R. (Department: 3682)

Bearings

Rotary bearing

Antifriction bearing

C384S450000

Reexamination Certificate

active

06547443

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a tapered roller bearing which can be used with e.g. a driving device for a railroad wheel.
For supporting gears of a driving device for a railroad car, generally, tapered roller bearings are used which can bear relatively large radial and axial loads.
As shown in
FIGS. 8 and 9
, in a driving device
1
for a railroad car, power is transmitted from an output shaft
3
of a main electric motor
2
to an axle
7
supporting wheels
6
through a pinion
4
and a gear wheel
5
. A gear shaft
8
carrying the pinion
4
is rotatably supported by a pair of tapered roller bearings
9
. Compared with the gear wheel
5
, the pinion
4
undergoes a high number of revolutions and a large load. The tapered roller bearings
9
are used in a harsh environment. Even in such an environment, superior rolling fatigue life and reliability are required.
Hereinbelow, description is made of a conventional tapered roller bearing.
FIG. 14
is an enlarged sectional view of a conventional tapered roller bearing
100
which comprises an outer ring
110
, an inner ring
120
, tapered rollers
130
and a retainer
140
. The outer ring
110
has a conical raceway
111
on the inner peripheral surface. The inner ring
120
has a conical raceway
121
on the outer peripheral surface, and a large flange surface
122
on the large-diameter side of the raceway
121
and a small flange surface
123
on the small-diameter side. The tapered rollers
130
are mounted between the raceway
111
of the outer ring
110
and the raceway
121
of the inner ring
120
, and each has a conical rolling surface
131
on its outer peripheral surface and a large end face
132
and a small end face
133
. The retainer
140
rollably houses a large number of the tapered rollers
130
in pockets
141
formed at regular spacings.
As shown in
FIG. 15
, the apexes of the raceway
111
of the outer ring
110
, of the raceway
121
of the inner ring
120
, and of the rolling surfaces
131
of the tapered rollers
130
converge to one point O on the central axis x of the tapered roller bearing
100
. While the bearing is rotating, the tapered rollers
130
are pressed against the large flange surface
122
of the inner ring
120
by the combined force applied from the raceway
111
and the raceway
121
and undergo a rolling motion on the raceways with their large end faces
132
guided by the large flange surface
122
. During rotation of the bearing, the small end faces
133
of the tapered rollers
130
do not contact the small flange surface
123
of the inner ring
120
, such that there is a slight gap present therebetween.
With tapered roller bearings used in a driving device for a railroad car, especially in winter or in a cold district, low-temperature starting performance is important. That is to say, when a car, which has been stopped during a nighttime, begins to travel early in the morning, since the driving device and the bearings in the driving device are accelerated (operate) from a sufficiently cooled state, in the bearing
100
, only the temperature of the inner ring
120
rapidly rises with the temperature of the outer ring
110
not following. Thus, the difference in temperature between the inner and outer rings of the bearing can be large and the initial bearing gaps disappear, so that if oil film formation at the contact portions between the large flange surface
122
of the inner ring
120
and the tapered rollers
130
is bad, the lubricating condition worsens and the bearing
100
can seize.
In particular, with a tapered roller bearing used in a driving device for a railroad car, the lubricating arrangement is such that gear oil lubricating the pinion
4
and the gear wheel
5
is splashed on the bearing making use of the rotation of the pinion
4
and the gear wheel
5
. Thus, in winter or in a cold district, since the viscosity of the gear oil increases due to coldness during a nighttime, oil formation at the contact portions between the large flange surface
122
of the inner ring
120
and the large end faces
132
of the rollers
130
worsens, so that the lubricating condition tends to worsen and the bearing
100
seizes.
Also, if the contact state between the raceways
111
and
121
of the outer ring
110
and the inner ring
120
and the rolling surfaces
131
of the tapered rollers
130
is bad, skew of the tapered rollers
130
tends to grow, and the contact surface pressure at the inner ring large flange surface
122
becomes excessive, so that seizure occurs.
In order to solve these problems, in view of the fact that the oil film forming properties at the contact portions between the inner ring large flange surface and the rollers of the tapered roller bearing depend on their surface roughness, a tapered roller bearing is proposed in which the average roughness (R)[=(Rr
2
+Rb
2
)
½
] of the roughness (Rr) of the roller large end faces and the roughness (Rb) of the large flange surface of the inner ring is set at 0.14 &mgr;m Ra or less (JP patent publication 11-210765).
Also, in view of the fact that the surface pressure at the contact portions between the large flange surface of the inner ring and the tapered rollers depends on the positions of the contact portions therebetween, a tapered roller bearing is also proposed in which the radius of curvature R of the roller large end faces is set at 75-85% of the roller reference radius R
0
, and the central angle of the contact positions between the tapered rollers and the inner ring large flange surface will be {fraction (1/15)} to {fraction (1/10)} of the roller angle (JP utility model publication 5-87330).
But even if both of these solutions are used, it is impossible to completely prevent seizure of the bearing. Thus, confusion occurred in controlling the diagram of the railroad cars. Therefore, tapered roller bearings that are free of seizure in the bearings are strongly desired.
Thus, a first object of the present invention is to provide a tapered roller bearing which does not seize even in a severe winter or in an extremely cold region.
Another conventional tapered roller bearing used in power transmitting devices for vehicles such as ring gear support portions of differentials or shaft support portions of transmissions is shown in FIG.
16
A. It includes an outer ring
222
having a conical raceway
221
, an inner ring
226
having a conical raceway
223
and provided with a large flange surface
224
on the large-diameter side of the raceway
223
and a small flange surface
225
on the small-diameter side, a plurality of tapered rollers
227
rollably arranged between the raceways
221
and
223
of the outer ring
222
and inner ring
226
, and a retainer
228
for retaining the tapered rollers
227
at predetermined equal circumferential distances. The distance between the large flange surface
224
and the small flange surface
225
on the inner ring
226
is designed slightly longer than the length of the tapered rollers
227
.
The tapered rollers
227
are designed such that they are in line contact with the raceways
221
and
223
of the outer ring
222
and the inner ring
226
, and the cone angle apexes of the tapered rollers
227
and the raceways
221
and
223
coincide on a point O on the central axis of the tapered roller bearing. With this arrangement, the tapered rollers
227
can undergo a rolling motion along the respective raceways
221
and
223
.
With this tapered roller bearing, since the cone angles of the raceways
221
and
223
are different, the combined force of the loads applied from the respective raceways
221
,
223
to the tapered rollers
227
acts in such a direction as to push the tapered rollers
227
toward the large flange surface
224
of the inner ring
226
. Thus, during use of the bearing, the tapered rollers
227
are guided with their large end faces
229
pressed against the large flange surface
224
, so that the large end faces
229
and the large flange surface
224
make sliding contact with each other.
O

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