Cylindrical roller bearing

Details Cylindrical roller bearing Cylindrical roller bearing

1999-03-31

2001-03-06

Estremsky, Sherry (Department: 3681)

Bearings

Rotary bearing

Antifriction bearing

C384S565000

Reexamination Certificate

active

06196724

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cylindrical roller bearing for use in a general machine such as a middle-size electric motor, a large-size electric motor, or the like. Particularly, the present invention relates to an improvement of a cylindrical roller bearing for use in an apparatus requiring both low vibration and low noise.
2. Description of the Related Art
As a technique for reducing both vibration and noise of a cylindrical roller bearing, heretofore, there is a technique in which the contact position between each rolling element and a cage varies in accordance with difference in the guiding method (race guiding or rolling element guiding) of the cage as described, for example, in Japanese Utility Model Publication No. Hei. 3-67718, or a technique in which the contact form is changed as described, for example, in Japanese Patent Publication No. Hei. 7-127645.
Further, in the cage described in Japanese Utility Model Publication No. Hei. 3-67718, particularly the motion of each rolling element in an unloading range is limited to thereby attain the reduction of both vibration and noise of the bearing. That is, since the guiding method of this cage is of the rolling element guiding type, the weight of the cage is loaded on each rolling element in the unloading range. The load becomes a counter force to a centrifugal force acting on the rolling element when the bearing is rotating. Accordingly, the contact pressure between the rolling element in the unloading range and an outer race is reduced. As a result, the vibration of the bearing is suppressed.
Here, in a press cage, it is general that a roller guide surface of the cage is provided from a neighbor of an annular portion and formed in a crowning portion of a rolling surface of each roller as described, for example, in Japanese Utility Model Publication No. Hei. 6-87723, or the like.
In the bearing described in Japanese Utility Model Publication No. Hei. 3-67718, however, as shown in
FIG. 10
, the pitch circle diameter of each pocket
50
a
of the cage
50
is set to be smaller than the pitch circle diameter of each roller
51
. Accordingly, if the bearing is produced so that the difference between the two pitch circle diameters is not made proper, the limitation given by the cage
50
to the roller
51
becomes severe. When the limitation was too severe, the roller
51
and the cage
50
interfered with each other more intensively than necessary so that noise of collision was often produced between the cage
50
and the roller
51
(cage noise).
Further, when the limitation of the cage
50
was severe, the vibration and noise levels of the bearing often varied because the bearing was easily affected by error in individual production of the cage
50
.
Further, since the guiding method was limited to the rolling element guiding type, the specifications of the bearing were often limited inevitably.
Incidentally, in the conventional cylindrical roller bearing, the whole contour of a rolling surface of each roller
51
along the direction of an axis of the roller was generally shaped like a composite circular arc crown (partial crowning shape) having a linear portion and a curved portion or like a curved full crown in order to relax edge loading. Accordingly, each roller
51
moving in the unloading range was pressed against a surface (pillar-side surface) of the pocket
50
a
of the cage
50
facing the roller
51
in the circumferential direction by point contact. The axis of the roller
51
varied easily regardless of presence/absence of inclinations of the pillar-side surface of the pocket
50
a
with respect to the circumferential and radial directions, so that there was no function to allow the roller
50
to take a stable posture.
SUMMARY OF THE INVENTION
The present invention is designed upon the aforementioned problem and an object of the present invention is to provide a cylindrical roller bearing in which each roller moving in an unloading range is aggressively promoted to move in a geometrically ideal posture and both the inclination (skew) of the roller with respect to the circumferential direction and the inclination (tilt) of the roller with respect to the radial direction are suppressed so that the vibration and noise levels of the bearing can be reduced securely.
In order to achieve the above object, according to a first aspect of the invention, there is provided a cylindrical roller bearing comprising a cage having pockets and rollers received in the pockets, each of the rollers having a rolling surface, a contour of the rolling surface along a direction of an axis of the roller having at least a center portion linearly shaped in parallel with the axis. Each of the pockets is formed so that an inclination of a portion of the pocket opposite to the rolling surface of the roller with respect to a line parallel with a center axis of rotation of the bearing is set to be equal to or less than {fraction (1.5/1000)} as large as a length of the roller.
Further, according to a second aspect of the invention, there is provided a cylindrical roller bearing comprising a cage having pockets and rollers received in the pockets, each of the rollers having a rolling surface, a contour of the rolling surface along a direction of an axis of the roller having at least a center portion linearly shaped in parallel with the axis. Each of the pockets is formed so that an inclination of a portion of the pocket opposite to the roller in a circumferential direction is set to be equal to or less than {fraction (1.5/1000)} as large as a length of the roller.
Still further, according to a third aspect of the invention, there is provided a cylindrical roller bearing comprising a cage having pockets and rollers received in the pockets, each of the rollers having a rolling surface, a contour of the rolling surface along a direction of an axis of the roller having at least a center portion linearly shaped in parallel with the axis. A portion of the pocket faces the roller in a circumferential direction, and each of the pockets is formed so that inclinations of the portion of the pocket in the circumferential direction and in a radial direction is set to be equal to or less than {fraction (1.5/1000)} as large as a length of the roller.
Assume now that a portion of each pocket facing the aforementioned roller in the circumferential direction is referred to as pocket surface. Then, “the pocket surface inclined in the circumferential direction” means a state in which the aforementioned pocket surface is inclined in the circumferential direction relative to a line parallel with the center axis of rotation of the bearing when viewed from the radial direction (see FIG.
6
). Further, “the pocket surface inclined in the radial direction” means a state in which the aforementioned pocket surface is inclined in the radial direction relative to a line parallel with the center axis of rotation of the bearing when viewed from the circumferential direction (see FIG.
5
).
Further, when an unloaded roller comes into linear contact with a pocket surface over the axial direction so that the posture of the roller is limited by the pocket surface in the case where the aforementioned pocket surface is inclined in the circumferential or radial direction, as shown in
FIG. 11
, a line S
1
formed by the axis of rotation of the roller when its posture is limited as described above and a line S
2
(parallel with the center axis of rotation of the bearing) formed by the axis of rotation of the roller when the bearing makes a geometrically ideal motion (in a state in which the axis of rotation of each roller becomes parallel with the center axis of revolution of rollers (the center axis of rotation of the bearing)) intersect each other, that is, the roller is fallen down from its ideal posture. With respect to points P
2
and P
3
which are taken along the lines S
1
and S
2
respectively so as to be far from a point P
1
of the aforementioned intersection by the roller length (L), the offset quantity &Dgr;&th

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