The present invention relates to tapered roller bearings for use in speed reducers of robots and construction machines, and in particular relates to a tapered roller bearing having a small-diameter end and a large-diameter end of an outer ring track surface of an outer ring, and a small-diameter end and a large-diameter end of an inner ring track surface of an inner ring in which, of these four ends, a flange portion that radially inwardly protrudes is formed only at the large-diameter end of the outer ring track surface of the outer ring.
Patent Literature 1 and Patent Literature 2 individually disclose a tapered roller bearing in which a flange portion is not formed at the large-diameter end of the inner ring track surface of the inner ring, and the flange portion that radially inwardly protrudes is formed only at the large-diameter end of the outer ring track surface of the outer ring. However, this type of tapered roller bearing has rarely been made into products.
Patent Literature 1: JP-U H01-85521 Gazette
Patent Literature 2: JP-A 2016-196944 Gazette
The reason is that the tapered roller bearing in which the flange portion is formed at the large-diameter end of the outer ring track surface of the outer ring has an extremely decreased pure axial load capacity when compared with a tapered roller bearing in which the flange portion is formed at the large-diameter end of the inner ring track surface of the inner ring.
Therefore, it is an object of the present invention to provide a tapered roller bearing in which a flange portion is formed at the large-diameter end of the outer ring track surface of the outer ring, capable of providing high moment stiffness and long life without extremely decreasing its pure axial load capacity.
In order to solve the above-described problem, the present invention provides a tapered roller bearing including: an outer ring having an outer ring track surface on its inner circumferential surface; an inner ring having an inner ring track surface on its outer circumferential surface; a plurality of tapered rollers rotatably disposed between the outer ring track surface and the inner ring track surface; and a retainer having a plurality of pockets for retaining the plurality of tapered rollers at a predetermined interval. The outer ring track surface of the outer ring has a small-diameter end and a large-diameter end, the inner ring track surface of the inner ring has a small-diameter end and a large-diameter end, and, of these four ends, a flange portion which radially inwardly protrudes is formed at the large-diameter end of the outer ring track surface of the outer ring. In this arrangement, the tapered roller bearing has a contact angle (angle made by a center axis of the bearing and the outer ring track surface) of 40 through 50° and a roller angle not greater than 3.5°. With the arrangement disclosed above, the bearing becomes capable of providing high moment stiffness and long life without extremely decreasing its pure axial load capacity.
In tapered roller bearings, in a case where two bearings have a same roller size, quantity, contact angle, roller angle, and angle x made by a location at point of tangency of the roller relative to the flange portion and the flange-side track surface, when comparing the bearing as shown in
Calculation formulas for the rolling element loads when the pure axial load is applied to the outer-ring-flange bearing as shown in
Fio: Outer ring side rolling element load (Inner-ring-flange bearing),
Foo: Outer ring side rolling element load (Outer-ring-flange bearing),
Fii: Inner ring side rolling element load (Inner-ring-flange bearing),
Foi: Inner ring side rolling element load (Outer-ring-flange bearing),
Fir: Flange side rolling element load (Inner-ring-flange bearing),
For: Flange side rolling element load (Outer-ring-flange bearing),
α: Outer ring half angle,
θ: Inner ring half angle,
β: Roller angle,
x: Angle made by a location at point of tangency of the roller relative to the flange portion and the flange-side track surface.
Y: Angle at point of tangency between a roller large end surface and an inner ring flange portion (θ+x), and
δ: Angle at point of tangency between a roller large end surface and an outer ring flange portion (α−x).
With the above, here are the formulas:
Fio=Fa/sin α
Foo=Foi(sin θ·sin δ+cos θ·cos δ)/(cos α·cos δ+sin α·sin δ)
Fii=Fio(sin α·sin Y+cos α·cos Y)/(cos θ·cos Y+sin θ·sin Y)
Foi=Fa/sin θ
Fir=(Fii cos θ−Fio cos α)/sin Y
For=(Foi cos θ−Foo cos α)/sin δ
Using the above-described calculating formulas, maximum rolling element load and maximum contact surface pressure when the pure axial load Fa is applied are obtained for each example in which the contact angle is set to 40 through 500, and the roller angle is set to a value not greater than 3.5°, and for each example in which the contact angle is set to a value not greater than 40°, and the roller angle is set to a value not smaller than 3.5°. Results are shown in Table 1 through Table 6.
From the results shown in Table 1 through Table 6, when comparing the outer ring flange bearing with the inner ring flange bearing, both of which have a same bearing dimension, with the maximum rolling element load and maximum contact surface pressure of the inner ring flange bearing being 100 percent, it was confirmed that the outer ring flange bearings within the specifications set by the present invention are capable of holding both of the maximum rolling element load and the maximum contact surface pressure within 10 percent increase over their counterpart inner ring flange bearings, while in the outer ring flange bearings which are out of the specifications set by the present invention, at least one of the maximum rolling element load or the maximum contact surface pressure increased at a rate greater than 10 percent over their counterpart inner ring flange bearings.
Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.
A tapered roller bearing 11 according to the present invention has a steep contact angle α of 40° through 50°, and a gentle roller angle not greater than 3.5°. The tapered roller bearing 11 according to an embodiment as shown in
As shown in
The tapered roller bearing 11 according to the present invention is intended for high moment stiffness with a steep contact angle α of 40 through 50°. The tapered roller bearing 11 according to the embodiment in
In the tapered roller bearing 11 according to the embodiment of the present invention, the outer ring track surface 12a of the outer ring 12 has a small-diameter end and a large-diameter end, the inner ring track surface 13a of the inner ring 13 has a small-diameter end and a large-diameter end, and, of these four ends, a flange portion 12b that radially inwardly protrudes is formed only at the large-diameter end of the outer ring track surface 12a of the outer ring 12.
The small-diameter end of the inner ring 13 does not have a small flange, and the rollers have an increased length as much as the length of eliminated small flange, for increased load capacity. At the same time, the flange portion 12b that radially inwardly protrudes is formed only at the large-diameter end of the outer ring track surface 12a of the outer ring 12. The large-diameter end of the inner ring track surface 13a of the inner ring 13 does not have a flange portion.
The tapered roller bearing 11 with the steep contact angle of 40 through 50° has a large space in its axial direction between the large-diameter end of the outer ring track surface 12a of the outer ring 12 and the large-diameter-side end surface of the inner ring 13. In the present invention, the flange portion 12b that radially inwardly protrudes is formed by using the space.
By forming the flange portion 12b that radially inwardly protrudes only at the large-diameter end of the outer ring track surface 12a of the outer ring 12 and by eliminating the flange portion at the large-diameter end of the inner ring track surface 13a of the inner ring 13, it becomes possible to compactify its axial dimension.
Namely, as indicated in alternate long and two short dashes lines in
By forming the flange portion 12b that radially inwardly protrudes at the large-diameter end of the outer ring track surface 12a of the outer ring 12 as disclosed in the present invention, it becomes possible to increase stiffness of the flange portion compared with a conventional tapered roller bearing 1 as shown in
Namely, when comparing a case where the flange portion 12b that radially inwardly protrudes is formed at the large-diameter end of the outer ring track surface 12a of the outer ring 12 as shown in
Also, in the conventional arrangement as shown in
In the present invention, the retainer 15 may be made of a resin.
As shown in
As shown in
From the results in Table 7 through Table 11, it was confirmed that those bearings which have their contact angles set to 40 through 50° exhibit better insertability of the roller-retainer assay when |P−P′|≥C and the flange's large-diameter-side angle γ is 35° through 50°.
The tapered roller bearing 11 according to the present invention, having the contact angle of 40 through 50°, has moment stiffness expressed in a graph in
The present invention is not limited to any of the embodiments described thus far, and it is obvious that the invention may be modified in many other ways within the scope of the present invention. The scope of the present invention is defined by the CLAIMS and includes all equivalents thereto and any variations therein.
Number | Date | Country | Kind |
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2018-229909 | Dec 2018 | JP | national |
2019-197666 | Oct 2019 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2019/047323 | 12/4/2019 | WO | 00 |