Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2000-09-13
2002-08-13
Hannon, Thomas R. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S475000, C384S504000, C384S520000
Reexamination Certificate
active
06431760
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an angular type ball bearing which is used in a rotation support portion included in various machines and apparatus, especially in the spindle main shaft portion of a machine tool to support loads in radial and thrust directions and, in particular, to a structure for improving the lubricating performance of the spindle main shaft portion of the machine tool.
Further, the present invention also relates to a shaft support structure with the above-mentioned angular type ball bearing.
Referring here to
FIG. 11
, recently, as a shaft support structure
80
which is applied to the spindle main shaft portion of a machine tool, there is known a structure in which, between the outer peripheral surface of a main shaft
81
and the inner peripheral surface of a housing
82
, there are arranged a plurality of angular type ball bearings
90
(which is hereinafter referred to as a bearing
90
simply) side by side along the axial direction of the main shaft
81
.
Between the inner rings
91
of the respective bearings
90
, there are interposed inner-ring-spacers
83
respectively. Also, between the outer rings
92
of the respective bearings
90
as well as between the outer ring
92
of the bearing
90
that is located in the end of the bearings
90
and a cover body fixed to the left end portion (in
FIG. 11
) of the housing
82
, there are interposed outer-ring-spacers
85
respectively.
Each bearing
90
is structured such that a ball row
93
is rollably inserted together with a retainer
94
into a raceway formed between the inner ring
91
and outer ring
92
and, in the anti-load-side portion of the outer ring
92
, there is formed a counter bore
96
for enhancing the oil discharge performance of the bearing
90
(more specifically, in the case of the two bearings
90
that are arranged on the left side in
FIG. 11
, in the portions thereof that are situated on the left-hand side of balls
95
in the ball rows
93
, there are respectively formed counter bores
96
; and, in the case of the two bearings
90
that are arranged on the right side in
FIG. 11
, in the portions thereof that are situated on the right-hand side of the balls
95
, there are respectively formed counter bores
96
). That is, due to provision of the counter bores
96
, the oil discharge performance of the respective bearings
90
in discharging lubricating oil is enhanced to thereby be able to reduce the required rotation torque of the main shaft
81
.
In the above-mentioned conventional shaft support structure
80
, in order to improve the oil discharge performance of the respective bearings
90
as well as reduce the required rotation torque of the main shaft
81
, there are formed the counter bores
96
in the anti-load side portions of the outer rings
92
of the respective bearings
90
.
However, the counter bores
96
of the bearings
90
are respectively very small as the lubricating oil discharge spaces. For this reason, especially, to support the main shaft
81
of a machine tool, the oil discharge performance of the bearings
90
is insufficient, which makes it impossible to secure the proper lubricating performance of the bearings
90
.
This raises a problem that a rise in the temperatures of the bearings and the required rotation torque of the shaft to be supported cannot be reduced. That is, failure to reduce a rise in the bearing temperature and the shaft required rotation torque makes it impossible to secure the high working precision of the machine tool.
Also, the cover body
84
is fixed to the left end portion (in
FIG. 11
) of the housing
82
through a bolt, and the outer rings
92
of the bearings
90
are respectively fixed in the thrust direction by the cover body
84
through their associated outer-ring-spacers
85
.
However, when the tightening amount of the cover
84
to the housing
82
becomes excessively large, there is a fear that the outer rings
92
of the bearings
90
can be deformed. In case where the outer rings
92
of the bearings
90
are deformed, there arises a problem that the raceway surfaces of the outer rings
92
forming the raceways for the balls
95
can be deformed, thereby lowering the running accuracy of the main shaft
81
.
On the other hand, when the tightening amount of the cover
84
to the housing
82
becomes excessively small, although there is reduced the fear that the outer rings
92
of the bearings
90
can be deformed, the creep and contact rigidity of the outer rings
92
are affected.
In view of the above, the tightening amount of the cover body
84
to the housing
82
is set in the range of 10-30 &mgr;m based on previous results. However, in fact, there cannot be avoided the deformation of the outer rings
92
of the bearings
90
. Therefore, there is still left the problem that, due to the deformation of the raceway surfaces of the outer rings
92
, the running accuracy of the main shaft
81
is degraded.
SUMMARY OF THE INVENTION
The present invention aims at eliminating the drawbacks found in the above-mentioned conventional angular type ball bearing.
Accordingly, it is an object of the invention to provide an angular type ball bearing which is simple in structure, can reduce the manufacturing cost thereof, and can secure the proper lubricating performance of a shaft to be supported thereby, whereby the bearing temperature rise reduction and the shaft required rotation torque reduction can be achieved as well as the running accuracy of the shaft to be supported thereby can be improved.
According to the invention, the above object can be attained by the following structures that are respectively set forth in the following first to fifth aspects of the invention.
In the first aspect of the invention, an angular type ball bearing structured such that a ball row is rollably inserted together with a retainer in a raceway formed between an inner ring and an outer ring, wherein the anti-load-side end portion of the outer ring is situated nearer to rolling bodies (balls) existing along the axial direction of a shaft to be supported by the bearing than the load-side end portion of the inner ring.
In a second aspect of the present invention, an angular type ball bearing structured such that a ball row is rollably inserted together with a retainer in a raceway formed between an inner ring and an outer ring, wherein the anti-load-side end portion of the outer ring is situated nearer to rolling bodies (balls) existing along the axial direction of a shaft to be supported by the bearing than the load-side end portion of the inner ring, and the anti-load-side end portion of the inner ring is situated nearer to the rolling bodies existing along the axial direction of the shaft to be supported by the bearing than the load-side end portion of the outer ring.
In a third aspect of the invention, a shaft support structure in which the angular type ball bearings set forth in the above first or second aspect are disposed in two or more rows side by side along the axial direction of a shaft to be supported by the ball bearings between the outer peripheral surface of the shaft to be supported and the inner peripheral surface of a housing, inner-ring-spacers are respectively interposed between the inner rings of the bearings in the respective rows, and outer-ring-spacers are respectively interposed between the outer rings of the bearings in the respective rows as well as between the outer ring of the endmost bearing and a cover body fixed to the end portion of the housing.
By the way, as the material of the inner-ring-spacers and outer-ring-spacers, preferably, material having high thermal conductivity may be used. This can enhance the thermal conductivity of the shaft support structure as a whole as well as can control a rise in the temperature of the angular type ball bearings in the respective rows down to a low level.
In a fourth aspect of the invention, a shaft support structure as set forth in the above third aspect, wherein oil discharge holes for discharging lubricating oil are formed at the given p
Nawamoto Taikou
Yui Hideto
Hannon Thomas R.
NSK Ltd.
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