Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2000-12-18
2002-11-12
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S544000, C384S913000
Reexamination Certificate
active
06478471
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a wheel-support rolling bearing unit, which is used for rotatably supporting vehicle wheels on suspension devices, and also a method for manufacturing the same.
The vehicle wheels are supported on the suspension devices by the wheel-support rolling bearing unit. A wheel-support rolling bearing unit is known which structured not using nuts for firmly coupling the hub and the inner ring for the purposes of cost reduction by reducing the number of the number of components parts, and the size and weight reduction, as disclosed in Japanese Patent Unexamined Publication No. Hei.11-129703.
FIGS. 4 through 6
show the wheel-support rolling bearing unit
1
disclosed in the publication.
The conventional wheel-support rolling bearing unit
1
includes a hub
2
, an inner ring
3
, an outer ring
4
, and a plurality of rolling elements
5
. A first flange
6
for supporting the wheel is formed at a portion of the hub
2
which is located closer to the outer end of its outer peripheral surface (the word “outer side or outside” means the outer side of the vehicle body as viewed in the widthwise direction in a state that the unit is assembled into the motor vehicle, and the left side in those figures except
FIGS. 3 and 7
. The word “inner side or inside” means locations closer to the center of the vehicle body as viewed in the widthwise direction, and the right side in those figures except
FIGS. 3 and 7
.). A first inner raceway
7
is formed in the outer surface of a middle portion of the hub
2
, and a stepped part
8
whose outside diameter is small is formed at the inner end thereof. The inner ring
3
is fit to the stepped part
8
and fastened by a caulking portion
9
. The first inner raceway
7
is formed directly in the outer surface of the middle portion of the hub
2
, and sometimes is formed in the outer surface of a separate inner ring fit to the middle portion of the hub. In the later case, a portion of the end of the hub
2
, which is protruded to the inner side as viewed in the axial direction beyond the separate inner ring, serves as the stepped part which receives the inner ring
3
.
To this end, a cylindrical portion
10
, which is used for forming the caulking portion
9
, is formed in the inner end of the hub
2
. A thickness of the cylindrical portion
10
becomes small toward its top end before the cylindrical portion
10
shown in
FIG. 6
is expanded, for caulking, outward in the diameter directions. Accordingly, a tapered hole
11
is formed in the inner end face of the hub
2
. The inside diameter of the tapered hole becomes small toward a recess.
To expand, for caulking, the top end of the cylindrical portion
10
in order to fasten the inner ring
3
to the inner end of the hub
2
, a force piston
12
is forcibly pressed against the top end of the cylindrical portion
10
in a state that the hub
2
is fixed so as not to shift in the axial direction, as shown in FIG.
5
. An outward curved portion
13
, shaped like a truncated cone, which may be thrust into the cylindrical portion
10
, is formed in the central portion of the end surface (left end surface in
FIG. 5
) of the force piston
12
. An inward curved portion or recess
14
is formed surrounding the outward curved portion
13
. A cross section of the recess
14
is configured to have a complex curved surface whose radius of curvature becomes small toward the outside so that a cross section of the caulking portion
9
, which is formed by plastically forming the top end of the cylindrical portion
10
by the recess
14
, gradually reduces in size from the base end to the top end, and abruptly reduces at the top end.
By pressing the force piston
12
having the outward curved portion
13
and the recess
14
, which are shaped and have dimensions as mentioned above, against the top end of the cylindrical portion
10
, the top end of the cylindrical portion
10
is forcibly expanded outward in the diameter directions for caulking, to thereby form the caulking portion
9
. The inner ring
3
is firmly held between the caulking portion
9
and a step surface
23
of the stepped part
8
formed at the inner end of the hub
2
, whereby the inner ring
3
is fastened to the hub
2
.
A first outer raceway
15
and a second outer raceway
17
are formed in the inner surface of the outer ring
4
. The first outer raceway
15
is formed in the outer peripheral surface of the middle portion of the hub
2
, while being confronted with the first inner raceway
7
. The second outer raceway
17
is formed while being confronted with a second inner raceway
16
formed in the outer peripheral surface of the inner ring
3
. A plurality of rolling elements
5
, while being rollably held within an element holder
18
, are located between the first inner raceway
7
and the first outer raceway
15
. A plurality of rolling elements
5
, while being rollably held within an element holder
18
, are located between the second inner raceway
16
and the element holder
18
. In the illustrated instance, the rolling elements
5
are balls; however, in the case of the wheel-support rolling bearing unit for motor vehicles which is heavy, those may be tapered rollers.
To assemble the wheel-support rolling bearing unit
1
into the motor vehicle, the outer ring
4
is fixed to a suspension device with a second flange
19
formed on the outer peripheral surface of the outer ring
4
, and the wheel is fixed to the first flange
6
. As a result, the wheel is rotatably supported on the suspension device.
For a work to form the caulking portion
9
by plastically deforming (expanding for caulking) the cylindrical portion
10
in order to form the wheel-support rolling bearing unit
1
thus constructed and operated, it is preferable to use a swing press
20
as shown in FIG.
7
. The swing press
20
is made up of a force piston
12
, a holding tool
21
and a holder
22
. In forming the caulking portion
9
by expanding for caulking the cylindrical portion
10
, the force piston
12
is displaced in a swing manner while pushing upward the hub
2
with the aid of the holder
22
. In a state that the center axes of the force piston
12
and the hub
2
are inclined at an angle &thgr; with respect to each other, the force piston
12
is turned about the center axis of the hub
2
, while being in contact with each other. In forming the caulking portion
9
by the swing press as just-mentioned, a part of the circumference of the force piston
12
is pressed against the cylindrical portion
10
, so that the caulking expanding work of the caulking portion
9
continuously progresses in part in the circumferential direction. For this reason, in forming the caulking portion
9
by ordinary forging process, a load acting on the cylindrical portion
10
may be reduced during the forging process. The holding tool
21
prevents the inner ring
3
and the hub
2
from moving in the radial direction during the caulking expanding work of the caulking portion
9
by the force piston
12
.
A technique that in the above structure, a portion of the outer peripheral surface of the hub
2
, cross hatched in
FIG. 4
, is quenched to be hardened to improve the durability thereof, is also disclosed in the Japanese Patent Unexamined Publication No. Hei. 11-129703. Specifically, the first inner raceway
7
portion, the base end portion of the first flange
6
, and the half of the base end portion of the stepped part
8
are quenched to increase hardness of those portions to about Hv550 to 900. On the other hand, the hardness of the cylindrical portion
10
which will form the caulking portion
9
is decreased to about Hv200 to 300 so that the cylindrical portion is easy to be plastically deformed.
Of those cross hatched portions to be quenched, the first inner raceway
7
portion receives a great surface pressure upon contact of it with the rolling surfaces of the rolling elements
5
. Accordingly, it is hardened order to secure a rolling fatigue lifetime. The base end portion of the first flange
6
is h
Ishida Hirohide
Miyazaki Hiroya
Footland Lenard A.
NSK Ltd.
Sughrue & Mion, PLLC
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