The present invention relates to a tapered roller bearing, and in particular to a tapered roller bearing allowing contact between a cage and a raceway surface.
In the field of rolling bearings, a method of increasing the number of rolling elements is generally known as a technique of improving load carrying capacity. When the number of rolling elements is increased, a circumferential interval between the rolling elements is reduced. In this regard, by increasing a diameter of a cage, the cage has a relatively wide circumferential width, and rigidity of the cage can be ensured. Therefore, from the viewpoint of improving the rigidity of the cage, it is desirable to minimize a clearance between the cage and a raceway surface (an outer ring/an inner ring).
A bearing allowing contact between a cage and a raceway surface of an outer ring during operation is disclosed, for example, in Japanese Patent Laying-Open No. 2005-188738 (Patent Document 1).
In a tapered roller bearing in which a cage comes into contact with a bearing ring during operation, interference between the cage and the bearing ring causes a change in a behavior of the cage, thereby causing a change in a pattern of interference between a roller and the cage. Accordingly, an interference force between the roller and the cage may be drastically increased, when compared to a tapered roller bearing in which a cage cannot come into contact with a bearing ring. This phenomenon is unfavorable from the viewpoint of ensuring the strength of the cage.
In this regard, Patent Document 1 does not disclose a lower limit of a clearance between a cage and a bearing ring.
The present invention has been made in view of the problems as described above, and one object of the present invention is to provide a tapered roller bearing suppressing an increase in an interference force between a roller and a cage.
A tapered roller bearing in accordance with the present invention includes, in one aspect, bearing rings including an inner ring and an outer ring, a rolling element rolling between the inner ring and the outer ring, and a cage having a pocket holding the rolling element and located adjacent to the outer ring. A radial clearance 6 between the cage and the outer ring when the cage is in a neutral position, a radial clearance δpr between the rolling element held in the pocket and the cage, and a circumferential clearance δpc between the rolling element held in the pocket and the cage satisfy relations δpr>δpc and −2≦(δ−δpr)/(δpr−δpc)≦0.
The tapered roller bearing in accordance with the present invention includes, in another aspect, bearing rings including an inner ring and an outer ring, a rolling element rolling between the inner ring and the outer ring, and a cage having a pocket holding the rolling element and located adjacent to the inner ring. A radial clearance δ between the cage and the inner ring when the cage is in a neutral position, a radial clearance δpr between the rolling element held in the pocket and the cage, and a circumferential clearance δpc between the rolling element held in the pocket and the cage satisfy relations δpr>δpc and −2≦(δ−δpr)/(δpr−δpc)≦0.
In the tapered roller bearing, an increase in an interference force between a roller and the cage is suppressed and reduction in life of the cage is prevented by satisfying the relations described above.
In the specification of the present application, “clearance δ between the cage and the outer ring/inner ring” refers to a minimum clearance between the cage and the outer ring/inner ring. The “neutral position” refers to a position at which the center of the cage coincides with a bearing axis under conditions (A) a rolling contact surface of the roller is in contact with a raceway surface of the inner ring, and (B) the rolling contact surface of the roller is in contact with a raceway surface of the outer ring, and (C) a large end face of the roller is in contact with a cone back face rib of the inner ring, and (D) the large end face of the roller is in contact with the pocket of the cage. Further, “radial clearance δpr and circumferential clearance δpc between the rolling element and the cage” refer to distances for which the cage can be moved in a radial direction and in a circumferential direction, respectively, when the outer ring, the inner ring, and one rolling element are fixed at positions satisfying the above conditions (A) to (D) and only the cage is moved in the radial direction, that is, in a direction toward the rolling element, and in the circumferential direction orthogonal to the radial direction.
In the tapered roller bearing described above, the cage is made of a metal as an example.
When the cage is made of a metal, the interference force between the roller and the cage is increased, when compared to a case where the cage is made of a resin. In this regard, in the tapered roller bearing described above, even when the cage is made of a metal, an increase in the interference force between the roller and the cage can be suppressed by satisfying the relations described above.
According to the present invention, in a tapered roller bearing, an increase in an interference force between a roller and a cage is suppressed and reduction in life of the cage is prevented.
1 roller, 2 cage, 3 outer ring, 4 inner ring.
Hereinafter, embodiments of a tapered roller bearing based on the present invention will be described. It is to be noted that identical or corresponding parts will be designated by the same reference numerals, and the description thereof may not be repeated.
In
(A) a rolling contact surface of roller 1 is in contact with a raceway surface of inner ring 4, and
(B) the rolling contact surface of roller 1 is in contact with a raceway surface of outer ring 3, and
(C) a large end face of roller 1 is in contact with a cone back face rib of the inner ring (a portion a in
(D) the large end face of roller 1 is in contact with the pocket of cage 2 on a larger diameter side (a portion P in
When the center of the cage coincides with a bearing axis under a condition satisfying the above conditions (A) to (D), a radial clearance 6 is left between cage 2 and outer ring 3.
In the tapered roller bearing shown in
The inventors of the present application have defined a clearance ratio φ specified by φ=(δ−δpr)/(δpr−δpc), and determined the interference force between roller 1 and cage 2 by analysis, with the clearance ratio changed.
The following conditions are assumed for the analysis:
A friction coefficient μbd under boundary lubrication is given by a formula (1) obtained by modifying a model of Kragelskii (Kragelskii, I. V., Friction and Wear, Butterworths (1965)).
μbd=(−0.1+22.28s)exp(−181.46s)+0.1 (1)
μr=μbd (A<0.01) (2-1)
μr={(μbd−μhd)/0.01−1.5)6}×(A−1.5)6+μhd (0.01≦A<1.5) (2-2)
μr=μhd (1.5≦A) (2-3),
where μr is a tangential force coefficient, and A is an oil film parameter.
Table 1 shows a bearing subjected to the analysis and operating conditions.
As described above, in the tapered roller bearing described above, when δ≦δpr, cage 2 may come into contact with the raceway surface of outer ring 3 while the bearing is in operation. Therefore, under the condition of δpr>δpc, when φ≦0, cage 2 may come into contact with the raceway surface of outer ring 3 while the bearing is in operation. Further, as φ decreases, the degree of interference between cage 2 and the raceway surface of outer ring 3 increases.
The above description can be summarized as follows. Specifically, the tapered roller bearing in accordance with the present embodiment includes bearing rings including inner ring 4 and outer ring 3, roller 1 rolling between inner ring 4 and outer ring 3, and cage 2 having a pocket holding roller 1 and located adjacent to outer ring 3. Radial clearance 6 between cage 2 and outer ring 3 when cage 2 is in a neutral position, radial clearance δpr between roller 1 held in the pocket and cage 2, and circumferential clearance δpc between the roller 1 held in the pocket and cage 2 satisfy relations δpr>δpc and −2≦(δ−δpr)/(δpr−δpc)≦0.
In the present embodiment, the description has been given on a tapered roller bearing in which a portion of cage 2 facing roller 1 is formed in a planar shape. The portion may be formed in a curved surface shape. Even when there is a change in the cross sectional shape of cage 2, an effect similar to that described above can be obtained by specifying the range of clearance ratio φ.
In the above analysis, it is assumed that cage 2 is made of a metal (iron). When cage 2 is made of a resin, a critical value at which the interference force between roller 1 and cage 2 is drastically changed is considered to be slightly smaller than φ=−2.
Also in the present embodiment, even when cage 2 may come into contact with inner ring 4 while the bearing is in operation, an increase in the interference force between roller 1 and cage 2 can be suppressed by specifying the range of clearance ratio 4, as in the first embodiment. Specifically, the tapered roller bearing in accordance with the present embodiment includes bearing rings including inner ring 4 and outer ring 3, roller 1 rolling between inner ring 4 and outer ring 3, and cage 2 having a pocket holding roller 1 and located adjacent to inner ring 4. Radial clearance 6 between cage 2 and inner ring 4 when cage 2 is in a neutral position, radial clearance δpr between roller 1 held in the pocket and cage 2, and circumferential clearance δpc between roller 1 held in the pocket and cage 2 satisfy relations δpr>δpc and −2≦(δ−δpr)/(δpr−δpc)≦0.
While the embodiments of the present invention have been described, it should be understood that the embodiments herein disclosed are by way of illustration in all respects and not to be taken by way of limitation. The scope of the present invention is defined by the appended claims, and is intended to include all the modifications within the meaning and the scope equivalent to those of the claims.
Number | Date | Country | Kind |
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2005-310190 | Oct 2005 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2006/315603 | 8/7/2006 | WO | 00 | 4/21/2008 |