Cylindrical roller bearing

Details Cylindrical roller bearing Cylindrical roller bearing

1999-07-12

2001-03-20

Hannon, Thomas R. (Department: 3682)

Bearings

Rotary bearing

Antifriction bearing

C384S470000, C384S523000, C384S572000

Reexamination Certificate

active

06203205

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a cylindrical roller bearing incorporated in a general machine such as a middle-size electric motor, a large-size electric motor, or the like, and particularly to a cylindrical roller bearing in need of low vibration and low noise.
As a vibration
oise reducing technique for a cylindrical roller bearing, for example, as shown in Japanese Utility Model Unexamined Publication No. Hei. 3-67718, there is known a technique in which a roller guide system is used as a system for guiding a cage so that the weight of the cage is loaded on rollers which are existed within unloading-zone (hereinafter refering unloading-zone rollers). The load of the weight of the cage is set against centrifugal force acting on rolling rollers so that the pressure of contact of rollers with an outer race is reduced. As a result, the motion of the unloading-zone rollers is restricted so that reduction of vibration
oise of the bearing is attained.
In a pressed cage for low vibration and low noise, generally, a roller guide surface d of a cage a is formed so as to be opposite to a crowning portion e of a roller rolling surface as shown in FIG.
7
.
In the bearing vibration
oise reducing technique disclosed in Japanese Utility Model Unexamined Publication No. Hei. 3-67718, however, as shown in
FIG. 8
, the pitch circle diameter of pocket holes b of a cage a was set to be smaller than the pitch circle diameter of rollers c. Accordingly, if the bearing was produced with an improper difference between the pitch circle diameters, the restriction in the unloading zone by the cage a became intense. As a result, the rollers c interfered with the cage a superfluously. There was a disadvantage that impact noise (cage noise) was produced due to collision of the rollers c with the cage a.
Further, when the restriction by the cage a was intense, the bearing was apt to be affected by error in production of individual cages. Accordingly, vibration and noise levels of the bearing often scattered. Furthermore, since the guide system was limited to a roller guide system, the specification of the bearing was limited necessarily.
Further, since the roller guide surfaces d of the cage a were formed in portions, respectively, opposite to the crowning portions e on the roller rolling surface as shown in
FIG. 7
, rollers in the unloading zone in which the roller motion was limited by being guided by the cage a were made unstable by the crowning portions so that skew, or the like, occurred easily. As a result, there was a disadvantage that vibration
oise was produced in the bearing inclusive of the cage.
Note that an occurrence of this disadvantage is not limited by a type of guiding system of cage. This disadvantage is generated in a bearing having a cage of a race guiding system, as well.
The present invention is designed to solve the aforementioned disadvantages and an object of the present invention is to provide a cylindrical roller bearing in which not only squeaking noise caused by rubbing of rollers against inner and outer race surfaces in the unloading zone, cage noise caused by collision of rollers with the cage and vibration
oise of the bearing, inclusive of the cage, caused by occurrence of skew, or the like, can be prevented well but also variations in vibration and noise levels of individual bearings can be suppressed.
SUMMARY OF THE INVENTION
In order to achieve above object, according to the present invention, there is provided a cylindrical roller bearing satisfying following relationships
1.5×10
−3
D≦H≦
9.0×10
−3
D
and
A/B=
0.6~1.0
where D is a diameter of a cage circumferential surface which is either one of inner and outer circumferential surfaces of an axial end portion of a cage, H is a size of an annular clearance between the cage circumferential surface and a race circumferential surface which is either one of an outer race rib inner-diameter surface and an inner race rib outer-diameter surface opposite to the cage circumferential surface, A is an axial length of the cage circumferential surface and B is an axial length of the race circumferential surface, wherein a roller guide surface of the cage is provided in a portion opposite to a linear-form portion at least except crowning portions in an axial direction of a roller rolling surface.
In the above-mentioned bearing, it is preferable that the bearing uses as a system for guiding the cage a roller guide system in which a radial displacement of the cage is limited by engagement between each pocket and a corresponding roller, or the bearing uses as a system for guiding the cage a race guide system in which a radial displacement of the cage is limited by the race.
In the present invention, first, the motion of the rollers existing in the unloading zone is suppressed through the cage by the damping force of a lubricant in the annular clearance between the cage circumferential surface and the race circumferential surface so that squeaking noise caused by rubbing of rollers against inner and outer race surfaces is suppressed, the sound pressure level of the cage caused by collision of rollers with the cage is reduced, and variations in vibration and noise levels of individual bearings are suppressed.
That is, the size H of the annular clearance between the cage circumferential surface and the race circumferential surface is restricted to be in the range of 1.5×10
−3
D≦H≦9.0×10
−3
D as the relation to the diameter D of the cage circumferential surface and the ratio of the axial length A of the cage circumferential surface to the axial length B of the race circumferential surface is set to be in a range of from 0.6 to 1.0. Accordingly, the resistance against a flow of the lubricant to pass through the aforementioned clearance becomes sufficiently intense so that the cage can be hardly displaced.
As a result, there is no displacement of the cage in accordance with the motion of rollers even in the case where an irregular motion (revolution of rollers around their common axis without regular rotation of rollers on their own axes and radial displacement of rollers) occurs in rollers existing in the unloading zone.
Further, the cage is controlled by the roller guide system in which the radial displacement of the cage is limited by engagement between pockets and rollers. There is a lubricant such as grease, or the like, between the pockets and the rollers. Since the motion of the cage and the motion of the rollers restrict each other, the motion of the plurality of rollers held by the cage is restricted when the clearance size H is limited to restrict the motion of the cage. As a result, not only the production of the aforementioned squeaking noise can be suppressed but also the sound pressure level of cage noise can be reduced. Furthermore, variations in vibration and noise levels of individual bearings can be suppressed.
Note that, even if the roller guide system of the bearing in which the radial displacement of the cage is limited by engagement between pockets and rollers is changed to a race guide system in which a radial displacement of the cage is limited by the race, the motion of the rollers held by the cage and the motion of the cage can be controlled as well, to thereby enjoy the same effects described above. In this case, a relationship between the peripheral surface of the cage and the peripheral surface of the race meets a geometrical and positional relationship.
If the clearance size H is smaller than 1.5×10
−3
D, a sufficient amount of the lubricant can be hardly interposed in this clearance. This causes abnormal abrasion or abnormal temperature rising. If the clearance size H is larger than 9.0×10
−3
D, the resistance against a flow of the lubricant to pass through the clearance is reduced. As a result, neither the effect of preventing the production of squeaking noise and cage noise nor the effect of suppressing variations in vibration and noise levels of individual bearings can be obtained suff

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