Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2002-02-22
2004-03-30
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S517000
Reexamination Certificate
active
06712518
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for preloading preload-adjustable rolling bearings adapted to be assembled in various precision rotary components, for example, spindle motors, rotary actuators, rotary encoders and the like for video tape recorders (VTR), hard disk drives (HDD) and laser beam printers (LBP) in order to rotatably support their rotating elements. This invention is also concerned with a method for manufacturing such preload-adjustable rolling bearings.
DESCRIPTION OF THE RELATED ART
A ball bearing is used to rotatably support a spindle of VTR or HDD while preventing whirling (i.e., motions in a direction perpendicular to the spindle) and/or axial deviations. A pair of mutually independent ball bearings (of either the deep groove type or the angular type) have heretofore been employed. With a view toward making efficient the assembly of ball bearings in a rotatably supporting part, use of a double-row ball bearing has also been proposed.
A double-row ball bearing is constructed by concentrically combining a spindle
2
, which has a pair of deep inner race grooves in an outer peripheral wall thereof as shown in FIG.
12
(A), with an outer race
4
, which has a pair of deep outer race grooves
3
,
3
in an inner peripheral wall thereof as depicted in FIG.
12
(B), and then rotatably inserting plural balls
5
,
5
between the inner race grooves
1
,
1
and the corresponding outer race grooves
3
,
3
as illustrated in FIG.
12
(C). FIG.
12
(C) also shows retainers
6
,
6
for holding the balls
5
,
5
at equal angular intervals and seals
7
,
7
for preventing dust and the like from penetrating into the ball-inserted parts.
Although the construction of such a double-row ball bearing as shown in FIG.
12
(C) has been known, it has heretofore been difficult to manufacture a double-row ball bearing suitable for use in supporting a spindle in VTR or HDD. This can be attributed to the reasons to be described next.
A ball bearing for use in supporting a spindle in VTR or HDD is required to have extremely high accuracy in order to avoid whirling motions and axial displacements. Therefore, a ball bearing for use in supporting such a spindle is used in a state preloaded in an axial direction.
Upon insertion of the balls
5
between each inner race groove
1
and its corresponding outer race groove
3
to assemble the deep-groove ball bearing, on the other hand, the inner race groove
1
and the outer race groove
3
are brought into an eccentric relationship to widen a radial spacing
8
, which extends in a circumferential direction between both the grooves
1
and.
3
, at a part thereof as illustrated in FIG.
13
. From the widened part of the spacing
8
, the balls
5
,
5
are inserted between the inner race groove
1
and the outer race groove
3
as many as desired. Thereafter, the inner race groove
1
and the outer race groove
3
are rendered concentric with each other and the desired number of the balls
5
,
5
are disposed at equal angular intervals.
To rearrange the plural balls
5
,
5
, which have been inserted together in the widened part of the spacing
8
, at equal angular intervals as described above, it is necessary to make the individual balls
5
,
5
slide on and relative to the inner race groove
1
and the outer race groove
3
. If the individual balls
5
,
5
are strongly pressed by the inner race groove
1
and the outer race groove
3
, in other words, are in a preloaded state at this time, rolling surfaces of the inner race groove
1
, outer race groove
3
and balls
5
,
5
are prone to damage. Their damage leads to such a problem such that vibrations may occur during rotation or the durability may be impaired.
In the case of the construction that a pair of single-row deep ball bearings are arranged at an interval as disclosed, for example, in Japanese Patent Application Laid-Open (Kokai) No. SHO 57-200722, on the other hand, each ball bearing is assembled in a state not applied with a preload so that this construction is free of such inconvenience as referred to above. However, the assembly work of the ball bearings is cumbersome.
Further, double-row, deep-groove ball bearings useful in tension pulleys or water pumps are disclosed, for example, in Japanese Patent Application Laid-Open (Kokai) Nos. SHO 61-65913 and SHO 61-79899 and Japanese Utility Model Application Laid-Open (Kokai) Nos. SHO 50-101753 and SHO 56-127456. These bearings are however not require to have very high rotational accuracy and are used in a state not applied with preload. They cannot therefore be used to support spindles in VTR, HDD or the like.
Japanese Patent Application Laid-Open (Kokai) No. SHO 61-145761 discloses a double-row angular ball bearing while Japanese Utility Model Application Laid-Open (Kokai) No. SHO 62-22323 discloses a double-row ball bearing constructed in combination of a deep-groove ball bearing and an angular ball bearing. To assemble an angular ball bearing, it is necessary to heat an outer race as disclosed, for example, in Japanese Utility Model Publication (Kokoku) No. SHO 39-3916 so that the outer race is caused to expand to protect shoulder portions of each groove and/or rolling surfaces of balls when the balls pass along the shoulder portions. The assembly work is therefore irksome.
Japanese Patent Publication (Kokoku) No. SHO 57-140912 discloses the invention in which after a double-row, deep-groove ball bearing equipped with an outer race formed in combination of a main outer race and a subordinate outer race axially displaceable relative to the main outer race has been assembled in a state not applied with preload, the subordinate outer race is caused to displace axially to apply a predetermined preload and is then fixed by a presser member. It also discloses the invention in which a predetermined preload is applied by axially pressing the subordinate outer race with a spring. The inventions disclosed in this patent publication, however, requires such a presser member or spring. This results in more cumbersome management or control of parts and also in more irksome assembly work. Moreover, the ball bearing may require an unduly large axial length.
U.S. Pat. No. 4,900,958 discloses such constructions as shown in
FIGS. 14 and 15
, respectively. In the case of the construction depicted in
FIG. 14
, ball bearings
9
,
9
of the deep groove type (or of the angular type) are disposed in a pair between an outer peripheral wall of a spindle
2
and an inner peripheral wall of a housing
10
, and inner races
11
,
11
of both the ball bearings
9
,
9
are pushed in a direction approaching toward each other to apply a preload to balls
5
,
5
of both the ball bearings
9
.
9
.
Described specifically, an end face of one of the inner races, i.e., of the inner race
11
located on the right-hand side as viewed in
FIG. 14
is brought into abutment against a stop ring
12
and the other inner race, i.e., the inner race
11
on the left-hand side as viewed in
FIG. 14
is pushed toward the stop ring
12
, whereby a preload is applied. The left-hand inner race
11
is fixed on the spindle
2
by an adhesive fitting. It is therefore necessary to continuously push the left-hand inner race
11
toward the stop ring
12
under a load equivalent to the preload until the adhesive solidifies or the left-hand inner race so heated shrinks.
In the case of the construction illustrated in
FIG. 15
, on the other hand, inner race grooves
1
,
1
are formed in double rows in an outer peripheral wall of a spindle
2
. A spacer
13
is arranged between outer rings
4
,
4
which are internally fitted in a pair in a housing
10
. By the spacer
13
, both the outer races
4
,
4
are pushed in a direction moving away from each other so that a preload is applied to balls
5
,
5
.
Further, Japanese Utility Model Application Laid-Open (Kokai) No. HEI 3-36517 discloses such a construction as shown in FIG.
16
. By a leaf spring
14
held between outer races
4
,
4
arranged in a pair, the outer races
4
,
4
are both pushed in a direction moving aw
Kitahara Daijiro
Miyazaki Seizo
Takamizawa Toru
Crowell & Moring LLP
Footland Lenard A.
NSK Ltd.
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