Metal working – Method of mechanical manufacture – Process for making bearing or component thereof
Reexamination Certificate
1999-05-13
2001-03-20
Hughes, S. Thomas (Department: 3726)
Metal working
Method of mechanical manufacture
Process for making bearing or component thereof
C029S898062, C384S512000, C384S513000
Reexamination Certificate
active
06202306
ABSTRACT:
FIELD OF THE INVENTION
This invention is related to a method of manufacturing a rolling-bearing device that is assembled in rotating parts of all kinds of precision equipment, for example, spindle motor rotary actuator, or rotary encoder, a video tape recorder (VTR), hard disk drive (HDD), for a laser-beam printer (LBP), and is used for supporting those rotating parts.
DESCRIPTION OF THE PRIOR ART
Ball bearings are used in order to support rotatably and prevent the spindle of a VTR or HDD from wobbling (movement in the direction orthogonal to the axis) and vibrating in the axial direction. However, until now, a pair of ball bearings independently functioning (deep-groove type or angular type) have generally been used. Moreover, it is also thought that using a double row ball bearing could improve the efficiency of assembling the ball bearing in the rotation-support section.
A double row ball bearing comprises a shaft
2
having a pair of deep-groove inner ring raceways
1
formed around its outer peripheral surface as shown in FIG.
5
(A), and an outer race
4
having a pair of deep-groove outer ring raceways
3
formed around its inner peripheral surface as shown in FIG.
5
(B), so that they are assembled to be concentric with each other as shown in FIG.
5
(C), and multiple balls
5
that rotate freely are located between the inner ring raceways
1
and outer ring raceways
3
. Also installed as shown in FIG.
5
(C) are cages
6
for holding the balls
5
which are evenly spaced around in the circumferential direction, and seals
7
a
which prevent dirt or the like from getting into the portion where the balls
5
are located.
These double-row, deep-groove ball bearings as shown in FIG.
5
(C), are of a formerly known construction, however, it is difficult to construct such bearings that are capable of supporting the spindle of the VTR or HDD. The reason for this is described below.
Specifically, the ball bearing for supporting the spindle of a VTR or HDD must have extremely high precision in order to prevent the previously mentioned wobbling motion orthogonal to the axial direction and vibrating motion in the axial direction. Therefore, the ball bearing for supporting this spindle is used with a pre-load applied in the axial direction. On the other hand, if balls
5
are installed between the inner ring raceway
1
and the outer ring raceway
3
in order to assemble the deep-groove ball bearing, the inner ring raceway
1
and outer ring raceway
3
are made to be eccentric with each other, as shown in
FIG. 6
, and the space
8
that runs between the inner ring raceway
1
and outer ring raceway
3
in circumferential direction is partly increased, so that a specified number of balls
5
can be inserted through this large space part in the space
8
between the inner ring raceway
1
and outer ring raceway
3
. Then, the inner ring raceway
1
and outer ring raceway
3
are made to be concentric with each other, and the specified number of balls
5
are evenly spaced around in the circumferential direction.
When rearranging the balls
5
, that are inserted together at one place of the circumferential space, in order that they are evenly located in the space in the circumferential direction, each of the balls
5
must slide with respect to the inner ring raceway
1
and outer ring raceway
3
. When doing this, if the inner ring raceway
1
and outer ring raceway
3
strongly press against the respective balls
5
(pre-load state), it is easy for the rolling surfaces of the inner ring raceway
1
, outer ring raceway
3
and each of balls
5
to become damaged, and if they become damaged, problems such as vibration motion during rotation or decrease in durability may occur.
As a means for solving this kind of problem, for example, in Japanese Patent Publication No. Tokukai Hei 6-344233, assembling steps of the doubling-row rolling bearing unit as shown in FIGS.
7
(A) to
7
(D) and FIGS.
8
(A) to
8
(E) have been disclosed. First, in the case of the assembling steps for the bearing unit in the first example shown in FIGS.
7
(A) to
7
(D), a first member is formed by a shaft
9
as shown in FIG.
7
(A) such that it has a small-diameter section
9
a
and a large-diameter section
9
b
that are continuous through a step section
9
c
, and a first deep-groove inner ring raceway
10
, that is a first raceway, is formed around the first peripheral surface that is the outer peripheral surface of the large-diameter section
9
b
. The inner race
11
, that is a third member, has an inner diameter that is slightly smaller in its free state than the outer diameter of the small-diameter section
9
a
. A second deep-groove inner ring raceway
12
, that is a fourth raceway, is formed around the outer peripheral surface of this inner race
11
, that is a third peripheral surface.
To form a rolling bearing unit which comprises this kind of shaft
9
and inner race
11
, first, in a first step as shown in FIG.
7
(B), the inner race
11
is fitted under sufficient fitting strength (such that it does not slidingly move by the reaction force of the applied pre-load) around the small-diameter section
9
a
of the shaft
9
. Also, the pitch P
1
of the first inner ring raceway
10
formed around the outer peripheral surface of the large-diameter section
9
b
and the second inner ring raceway
12
formed around the outer peripheral surface of the inner race
11
is such that it is a little longer than the pitch p
1
(FIG.
7
(D)) required for applying the prescribed pre-load to the completed rolling bearing unit (P
1
>p
1
).
Next, in a second step omitted from illustration, the shaft
9
and inner race
11
that were assembled together in the first step are inserted inside a second member or cylindrical outer race
13
. A pair of deep-groove outer ring raceways
14
, which are second and third raceways, are formed around the inner peripheral surface of this outer race
13
, that is a second peripheral surface. In this second step, this pair of outer ring raceways
14
are made to face the first and second inner ring raceways
10
,
12
.
Next, in a third step, the shaft
9
and inner race
11
are made to be eccentric with the outer race
13
in order to increase the size in part of the space
8
that runs around in the circumferential direction between the pair of outer ring raceways
14
and the first and second inner ring raceways
10
,
12
, as shown in
FIG. 6. A
specified number of balls
5
are then inserted in this space
8
through the large space part.
Next, in a fourth process as shown in FIG.
7
(C), the shaft
9
and inner race
11
are made to be concentric again with the outer race
13
while moving in the circumferential direction the specified number of balls
5
inserted into the space
8
between the pair of outer ring raceways
14
and the first inner ring raceways
10
and second inner ring raceway
12
in order that the balls
5
are evenly spaced around in the circumferential direction respectively. Together with this process, as shown in FIG.
7
(C), a cage
6
is installed for an area of each row of balls in order to hold each of the balls
5
in their evenly spaced positions around in the circumferential direction. Moreover, as needed, seals
7
a
are attached to the inner peripheral surfaces of the both ends of the outer race
13
, respectively. In this state of FIG.
7
(C), a pre-load has not yet been applied to each of the balls
5
.
Finally, in a fifth process as shown in FIG.
7
(D), by displacing the inner race
11
at the state of FIG.
7
(C) toward the step section
9
c
in the axial direction (left direction in FIG.
7
(C)) on the outer peripheral surface of the small-diameter section
9
a
of the shaft
9
, the pitch of the first and second inner ring raceways
10
,
12
is shortened and let it to become the pitch p
1
(shown in FIG.
7
(D)) required for applying the specified pre-load.
In this state of FIG.
7
(D), the pre-loaded double-row rolling bearing unit is completed with the specified pre-load applied to the balls
5
. Even when completed in this
Butler Marc W.
Helfgott & Karas P.C.
Hughes S. Thomas
NSK Ltd.
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