Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2001-11-21
2003-06-24
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S516000
Reexamination Certificate
active
06582128
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a deep groove ball bearing as a small size ball bearing, extra small ball bearing or a miniature ball bearing, which is incorporated into a bearing device of the business machine, AV home use device, HDD device and the like, and a bearing device using the deep groove ball bearing.
In related art, when a raceway groove
1
formed in a raceway of a deep groove ball bearing is worked, the absolute values of the upper and lower limit values of the groove radius of the raceway groove are selected for each bearing number of the deep groove ball bearing, and the raceway groove is worked to be within the tolerance of those values as shown in FIG.
1
. Such working of raceway groove makes possible to prevent the ball from climbing over the shoulder of the raceway and suppress the influence of the groove radius on the wear and life of the ball bearing.
However, not only the groove radius of the raceway groove
1
but also a deformation of an arc profile of the raceway groove
1
affect the bearing functions, such as sound life and wear. In a case where the cross section of the raceway groove
1
is an arc profile having the groove radius as designed in average value, it the arc profile is undulated, the bearing functions are adversely affected by the undulation.
Particularly, the undulation problem of the arc profile of the raceway groove
1
is more serious in the case of the small bearing, such as the small size ball bearing, extra small ball bearing or the miniature ball bearing.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a deep groove ball bearing and a bearing device in which the bearing functions are improved by limiting the profile deformation quantity of the raceway groove within specific ranges of values.
To achieve the above object, there is provided a deep groove ball bearing according to a first aspect of the present invention, having an inner ring, an outer ring and a plurality of balls located between the inner ring and the outer ring. In the deep groove ball bearing, a profile deformation quantity &Dgr;i (mm) of a raceway groove of the inner ring and a profile deformation quantity &Dgr;o (mm) of a raceway groove of the outer ring are defined by the following equations (1) and (2).
Here, as shown in
FIG. 2
, the profile deformation quantity means the maximum value of the amplitude of surface waviness (represented by broken line in
FIG. 2
) along an arc direction of the raceway groove
1
with respect to the arc profile of the raceway groove
1
. For example, the profile deformation quantity is the maximum value of the amplitude of the sinusoidal wave shaped waviness.
Δ
i
≦
36
(
1
Ei
′
)
2
(
1.0003
+
0.5968
Rxi
Ryi
)
{
1.5227
+
0.6023
ln
(
Ryi
Rxi
)
}
Rxi
·
Ryi
Rxi
+
Ryi
wherein
1
Ei
′
=
1
2
(
1
-
vi
2
Ei
+
1
-
va
2
Ea
)
Rxi
=
Da
2
×
dm
-
Da
cos
α
dm
Ryi
=
ri
·
Da
2
ri
-
Da
cos
α
=
ri
+
ro
-
(
Da
+
c
/
2
)
ri
+
ro
-
Da
(
1
)
Δ
o
≦
89
(
1
Eo
′
)
2
(
1.0003
+
0.5968
Rxo
Ryo
)
{
1.5227
+
0.6023
ln
(
Ryo
Rxo
)
}
Rxo
·
Ryo
Rxo
+
Ryo
wherein
1
Eo
′
=
1
2
(
1
-
vo
2
Eo
+
1
-
va
2
Ea
)
Rxo
=
Da
2
×
dm
+
Da
cos
α
dm
Ryo
=
ro
·
Da
2
ro
-
Da
cos
α
=
ri
+
ro
-
(
Da
+
c
/
2
)
ri
+
ro
-
Da
(
2
)
where
dm: pitch circle diameter (mm)
Da: ball diameter (mm)
c: diameter clearance (mm)
ri: radius (mm) of the raceway groove of the inner ring
ro: radius (mm) of the raceway groove of the outer ring
Ei: Young's modulus of the inner ring
&ngr;i: Poisson's ratio of the inner ring
Eo: Young's modulus of the outer ring
&ngr;o: Poisson's ratio of the outer ring
Ea: Young's modulus of the ball
&ngr;a: Poisson's ratio of the ball
The diameter clearance “c” is two times as large as a radial internal clearance.
The validity of the equations (1) and (2) will be described hereunder. Empirically, if a waviness of the raceway groove profile takes a sinusoidal wave in shape, a waviness length is approximately ⅓ as long as an arc length of the raceway groove.
Where a waviness length of a raceway groove profile of a ball bearing of the bearing number 696 (inner diameter=6 mm; outer diameter=15 mm; width=5 mm, bearing pitch circle diameter (dm)=10.5 mm; ball diameter=2.8 mm; curvature radius ratio of the inner ring groove=54%, and curvature radius ratio of the outer ring groove=56%) is assumed to be ⅓ as long as the groove arc length, a maximum surface pressure increases in accordance with the profile deformation quantity as shown in FIG.
3
. That is, the maximum surface pressure increases in accordance with the presence of the waviness. In this case, an axial load is 6.3N, which is the pre-load usually used.
In
FIG. 3
, the horizontal axis represents a distance from the groove shoulder (see FIG.
1
). Where the length of the waviness is ⅓ as long as the groove arc length, a contact position with the ball is located at the groove bottom and near the peak of the wave of the waviness.
As seen from
FIG. 3
, as the profile deformation quantity increases, the contact area of the raceway groove with the ball becomes narrow, and a maximum value Pmax of the contact surface pressure increases.
In the case of the small size ball bearing, extra small ball bearing or the miniature bearing, it is known and confirmed that when the maximum value Pmax of the contact surface pressure exceeds 1.6 GPa, abnormal phenomenon, such as an early minute wear or sound occur (see FIG.
10
).
The surface pressure of a small ball bearing of the bearing number 696 was analyzed. Calculation was made about a variation of the maximum value of the contact surface pressure when the profile deformation quantity &Dgr; is varied. The calculation results are shown in
FIGS. 4 and 5
.
In
FIGS. 4 and 5
, the horizontal axis represents &Dgr;/&dgr;o, which has not the dimension for clarifying a magnitude of the profile deformation quantity &Dgr;. &dgr;o is an elastic approaching quantity (Hertzian elastic approaching quantity) when the raceway groove is not deformed in its profile or when no profile deformation is present.
From
FIGS. 4 and 5
, it was found that when the ratio &Dgr;/&dgr;o of the inner ring is 2.55 or above, and that of the outer ring is 8.30 or above, the maximum value Pmax of the contact surface pressure exceeds 1.6 GPa. Accordingly, if the profile deformation quantity is selected so as to satisfy
&Dgr;
i
≦2.55·&dgr;
o
&Dgr;
o
≦8.30·&dgr;
o,
then the early wear and the like are not affected by the profile deformation even if the profile deformation occurs in the raceway groove.
The Hertzian elastic approaching quantity between the rolling element and the surface of the raceway when no profile deformation is present may approximately be expressed by the following equations (3) and (4).
δ
i
=
8
(
1
Ei
′
)
2
(
1.0003
+
0.5968
Rxi
Ryi
)
{
1.5227
+
0.6023
ln
(
Ryi
Rxi
)
}
Rxi
·
Ryi
Rxi
+
Ryi
(
P
max
i
)
2
(
3
)
δ
o
=
8
(
1
Eo
′
)
2
(
1.0003
+
0.5968
Rxo
Ryo
)
{
1.5227
+
0.6023
ln
(
Ryo
Rxo
)
}
Rxo
·
Ryo
Rxo
+
Ryo
(
P
max
o
)
2
(
4
)
where Pmaxi and Pmaxo are the maximum surface pressure values of the inner and outer raceways.
The maximum surface pressure values Pmaxi and Pmaxo when the deep groove ball bearing as axially pre-loaded is not deformed
Nakano Yuji
Natsumeda Shinichi
Tsuruga Yoshiyuki
Footland Lenard A.
NSK Ltd.
Sughrue & Mion, PLLC
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