Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2002-07-31
2004-03-23
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S513000
Reexamination Certificate
active
06709161
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an angular contact ball bearing with a non-contact seal member having a counterbore formed on an outer ring which is used in a spindle or the like for motors or machine tools which are required to operate at higher speed or exhibit a prolonged life, and a grease-lubricated angular contact ball bearing with a seal member, which is used for rotatably supporting the spindle. Further, the invention relates to a spindle device for machine tool with the angular contact ball bearing.
2. Description of the Related Art
Bearings for the spindle of machine tools are mostly lubricated with grease from the standpoint of cost or because such a lubrication system is free from maintenance. The spindle of machine tools have been required to operate at higher rotating speed from the necessity of meeting the requirements for higher productivity. To this end, bearings have been required to operate at higher rotating speed.
In particular, when an angular contact ball bearing having a counterbore formed on the outer ring operates at a high rotating speed while being lubricated with a grease, the base oil (lubricant) of the grease can be easily discharged due to the presence of the counterbore on the outer ring, deteriorating the retention of the lubricant in the races and hence causing mallubrication. This is disadvantageous in the durability of bearing.
When an angular contact ball bearing comprising a non-contact seal member merely mounted in the vicinity of both the axial ends of the outer ring operates at a high rotating speed, the grease in the bearing moves toward the axial ends and then is attached to the sealed portion. Although the grease itself cannot be scatted from the interior of the bearing, the base oil can be little supplied from the grease attached to the sealed portion back into the races. Thus, this type of angular contact ball bearing is insufficient in the elimination of defective grease lubrication.
In order to solve these problems, the angular contact ball bearing disclosed in Japanese Patent Laid-Open No. 1999-108068 has a grease storing groove machined on the inner surface of the outer ring so that a contact area (contact ellipse) of the outer ring race with the balls can be provided even if no non-contact seal members are mounted. In this arrangement, the base oil (lubricant) can be supplied from the grease accumulated in the storing groove back into the races, making it possible to prolong the life of the bearing as compared with the conventional bearings.
However, the angular contact ball bearing disclosed in the above cited Japanese Patent Laid-Open No. 1999-108068 is disadvantageous in that when dmN (permissible rotating speed) is as high as not lower than 1,000,000, the grease storing groove formed on the inner surface of the outer ring is not enough to inhibit the scattering of the grease accumulated in the bearing, making it difficult to make sufficient use of the grease accumulated in the bearing and hence allow the grease to contribute to lubrication.
Further, it is necessary that a grease storing groove be machined on the inner surface of the outer ring every individual bearing, preventing the reduction of production cost.
In addition,
FIG. 16
is a sectional view of essential part of a conventional sealed angular contact ball bearing. The angular contact ball bearing
100
comprises an outer ring
101
having an outer ring race
101
a
formed on the inner surface thereof, an inner ring
103
having an inner ring race
103
a
formed on the outer surface thereof and a plurality of steel balls
105
disposed as rolling elements between the outer ring race
101
a
of the outer ring
101
and the inner ring race
103
a
of the inner ring
103
. The plurality of balls
105
are peripherally retained at intervals by an annular cage
106
disposed between the inner surface of the outer ring
101
and the outer surface of the inner ring
103
. Further, non-contact type seals
109
,
110
are mounted on the opening of both the ends of the outer ring
101
and the inner ring
103
.
A shoulder portion
102
is formed at one side of the outer ring race
101
a
on the inner surface of the outer ring
101
. On the outer surface of the inner ring
103
is formed a shoulder portion
104
symmetrically with the shoulder portion
102
of the outer ring
101
about the ball
105
. By thus providing the outer ring
101
and the inner ring
103
with the shoulder portions
102
and
104
, respectively, the angular contact ball bearing
100
can receive the radial load as well as the axial load.
The cage
106
is formed annually by a phenolic resin and has a plurality of cylindrical pockets
107
disposed peripherally for receiving and retaining the balls
105
. The outer diameter of the cage
106
is formed slightly smaller than the inner diameter of the shoulder portion
102
of the outer ring
101
. The inner diameter of the cage
106
is formed greater than the outer diameter of the shoulder portion
104
of the inner ring
103
.
There is formed a small guide gap
108
between the outer surface of the cage
106
and the inner surface of the shoulder portion
102
of the outer ring
101
. The grease is injected into the guide gap
108
to lubricate the cage
106
with respect to the outer ring
101
.
However, the conventional sealed angular contact ball bearing
100
as shown in
FIG. 16
is disadvantageous in that since the cage
106
is supported guided by the outer ring
101
, the cage
106
undergoes self-excited vibration that causes the generation of abnormal noise when the guide gap
108
runs out of grease upon high speed rotation of the bearing
100
.
Further, since the inner surface of the outer ring
101
and the outer surface of the cage
106
in the guide gap
108
come in contact with each other, the rise in the rotating speed of the bearing
100
is accompanied by the rise in the heat generation due to friction, causing a temperature rise.
In order to solve this problem, it can be proposed that a snap cage guided by rolling elements for use in deep groove ball bearing be used. This approach causes no generation of friction between the cage and the inner and outer rings but is not suitable for angular contact ball bearings, which have many balls incorporated therein, because such a snap cage has an insufficient strength.
In general, an angular contact ball bearing is used to support the spindle for machine tools which is required to rotate at a high precision. When the aforementioned conventional sealed angular contact ball bearing
100
is mounted on the spindle for machine tools, the temperature of the bearing rises due to self-excited vibration or friction of the cage
106
during the high speed rotation of the spindle, lowering the machining precision of machine tools.
Further, when the machine tools operate, the generation of noise increases due to the generation of abnormal noise by the cage
106
.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to solve these problems and provide an angular contact ball bearing which is little subject to scattering of the grease accumulated in the bearing during high speed rotation and thus can attain the prolongation of life during grease-lubricated high speed rotation at a reduced cost.
Further, an object of the invention is to provide a sealed angular contact ball bearing which can lubricate the cage more fairly to lower the self-excited vibration thereof, making it possible to prevent the generation of abnormal noise and reduce the heat generation due to friction.
In addition, another object of the invention is to inhibit the temperature rise of a sealed angular contact ball bearing for use in supporting of the spindle for machine tools due to self-excited vibration or friction, making it possible to enhance the machining precision of machine tools.
To solve the above object, according to a first aspect of the invention, there is provided an angular contact ball bearing, including:
an outer ring having an outer ring race and
Anzai Takaaki
Matsuyama Naoki
Morita Yasushi
Yakura Kenji
Footland Lenard A.
NSK Ltd.
LandOfFree
Angular contact ball bearing and spindle device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Angular contact ball bearing and spindle device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Angular contact ball bearing and spindle device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3234974