Tapered roller bearings

Abstract

To provide a tapered roller bearing capable of suppressing wear due to slippage between tapered rollers and a raceway surface regardless of a mutual difference in roller diameter.SOLUTION: A tapered roller bearing 1 includes an inner ring 2 having a conical inner ring raceway surface 2a at least on an outer periphery, a plurality of tapered rollers 4, and a cage 5 for accommodating the tapered rollers 4. In the (n-1)th tapered roller 4 and the (n+1)th tapered roller 4, which are adjacent to the nth tapered roller 4 among the plurality of tapered rollers 4, the (n-1)th tapered roller 4 and the (n+1)th tapered roller 4 are combined so that a diameter difference ΔDn of adjacent rollers, which is an average of roller diameter differences between the nth tapered roller 4 and the adjacent tapered rollers, is larger than -2 μm.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a tapered roller bearing. [Background technology]

[0002] Conventionally, high runout accuracy is required for roller bearings used in precision machinery such as hydraulic motors. For this reason, it is necessary to minimize the difference in rolling element diameters, which is the difference between the maximum and minimum average rolling element diameters of multiple rolling elements inside the bearing. However, it is impossible to reduce the difference in rolling element diameters to zero, and the smaller the difference in rolling element diameters is, the higher the cost becomes. For this reason, there is known a rolling bearing that improves the accuracy of the entire bearing by controlling the difference in rolling element diameters. For example, it is as described in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-173635 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the rolling bearing described in Patent Document 1, the rolling elements inside the bearing are divided into two groups, large and small, based on the rolling element diameter. The large rolling element group is a collection of rolling elements with a larger average rolling element diameter than the small rolling element group. In the rolling bearing, the rolling elements belonging to the large rolling element group and the rolling elements belonging to the small rolling element group are arranged alternately on the raceway surface. In this way, the runout accuracy of the rolling bearing is improved by adjusting the arrangement of the rolling elements to manage the difference in rolling element diameter (tapered roller diameter). However, in the technology described in Patent Document 1, the rolling elements belonging to the large rolling element group and the rolling elements belonging to the small rolling element group are arranged alternately, so that depending on the difference in the rolling element diameter, the contact surface pressure of the rolling elements belonging to the small rolling element group may decrease, causing wear due to slip between the rolling elements and the raceway surface. For this reason, it is desirable to make the difference in the rolling element diameter of the rolling bearing 2 μm or less, but this is disadvantageous in terms of increased costs.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a tapered roller bearing that can suppress wear due to sliding between the tapered rollers and the raceway surface regardless of the difference in roller diameter. [Means for solving the problem]

[0006] That is, the first invention is a tapered roller bearing comprising an inner ring having a conical raceway surface on its outer circumference, an outer ring having a conical raceway surface on its inner circumference, a plurality of tapered rollers assembled between the two raceway surfaces, and a retainer that houses the tapered rollers, wherein the n-1th tapered roller and the n+1th tapered roller adjacent to the nth tapered roller among the plurality of tapered rollers are combined so that the adjacent roller diameter difference of the nth tapered roller calculated from equation (1) is greater than -2 μm.

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[0007] A second invention is a tapered roller bearing, wherein the difference between the maximum roller diameter and the minimum roller diameter among the roller diameters of the plurality of tapered rollers is greater than 2 μm. Effect of the Invention

[0008] The present invention has the following advantages.

[0009] That is, in the first and second inventions, the tapered rollers are arranged to satisfy a standard that takes into account the roller diameters of the adjacent tapered rollers on both sides, so that the roller diameters of the adjacent tapered rollers are equalized, thereby making it possible to suppress wear due to slippage between the tapered rollers and the raceway surface regardless of the difference in roller diameters. [Brief description of the drawings]

[0010] [Figure 1] 1 is a partial cross-sectional view showing an overall configuration of an embodiment of a tapered roller bearing; [Diagram 2] FIG. 4 is a partial side view showing the contact surface pressure of a tapered roller in one embodiment of a tapered roller bearing. [Diagram 3] FIG. 4 is a schematic diagram showing a manner in which the roller diameter of a tapered roller is measured. [Figure 4] FIG. 4 is a graph showing the roller diameter difference between each tapered roller and the adjacent roller diameter difference; [Diagram 5] FIG. 13 is a graph showing the slip ratio of selected tapered rollers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Referring to FIG. 1, a tapered roller bearing 1 which is one embodiment of a tapered roller bearing according to the present invention will be described.

[0012] As shown in Fig. 1, tapered roller bearing 1 comprises an inner ring 2, an outer ring 3, a plurality of tapered rollers 4 interposed for free roll between the inner ring 2 and the outer ring 3, and a cage 5 that houses these tapered rollers 4. In the following, the axial direction refers to the direction along the rotation axis of tapered roller bearing 1. Also, the roller axial direction refers to the direction along the roller axis, which is the rotation axis of tapered rollers 4.

[0013] The inner ring 2 is a raceway ring on the inside in the radial direction that guides the tapered rollers 4. The outer peripheral surface of the inner ring 2 is formed with an inner ring raceway surface 2a that has a rounded gradient corresponding to the taper of the outer peripheral surface of the tapered rollers 4, or has a rounded gradient partially formed on both axial ends. A small rib portion 2b protruding outward in the radial direction is provided on the periphery of the small diameter end of the inner ring raceway surface 2a. In addition, a large rib portion 2c protruding outward in the radial direction is provided on the periphery of the large diameter end of the inner ring raceway surface 2a. The small rib portion 2b and the large rib portion 2c are each continuous all around along the circumferential direction.

[0014] The outer ring 3 is a radially outer raceway that guides the tapered rollers 4. The outer peripheral surface of the outer ring 3 is formed with an outer ring raceway surface 3a that has a rounded gradient corresponding to the taper of the outer peripheral surface of the tapered rollers 4, or has a rounded gradient partially on both axial ends. The outer ring 3 is arranged coaxially with the inner ring 2.

[0015] The tapered roller 4 is a rolling element having a small end face 4a, a large end face 4b, and a rolling surface 4c formed in a cone shape. The small end face 4a is the side surface on the small diameter side of the tapered roller 4. The large end face 4b is the side surface on the large diameter side of the tapered roller 4. The small end face 4a and the large end face 4b are surface portions that do not roll on the inner ring raceway surface 2a of the inner ring 2 or the outer ring raceway surface 3a of the outer ring 3. The rolling surface 4c is a surface portion that rolls on the inner ring raceway surface 2a of the inner ring 2 and the outer ring raceway surface 3a of the outer ring 3.

[0016] The small end face 4a of the tapered roller 4 may come into contact with the small rib portion 2b of the inner ring 2 when the tapered roller 4 is skewed. The large end face 4b of the tapered roller 4 is always in contact with the large rib portion 2c of the inner ring 2 during rolling. The side surface of the tapered roller 4 rolls on the inner ring raceway surface 2a of the inner ring 2 and the outer ring raceway surface 3a of the outer ring 3. As a result, the tapered roller 4 is guided along the inner ring raceway surface 2a of the inner ring 2 by the small rib portion 2b and the large rib portion 2c. In this embodiment, the tapered roller bearing 1 is equipped with 15 tapered rollers 4.

[0017] The cage 5 holds the tapered rollers 4. The cage 5 is formed in a truncated cone shape. The cage 5 may be a resin molded body or a stamped cage made of a press-formed metal plate material such as steel. The cage 5 is formed with a plurality of trapezoidal window-shaped pockets 5a. The pockets 5a are formed at equal intervals in the circumferential direction.

[0018] Next, referring to FIG. 2, the adjacent roller diameter of the n-th tapered roller among the multiple tapered rollers 4 constituting the tapered roller bearing is difference ΔDn will now be explained.

[0019] As shown in Fig. 2, the adjacent roller diameter of the nth tapered roller difference ΔDn is the average difference between the roller diameter at a given position of an arbitrarily selected n-th tapered roller 4 among the multiple tapered rollers 4 arranged inside the tapered roller bearing 1 and the roller diameter of the tapered roller 4 adjacent to that tapered roller 4. Adjacent roller diameter of n-th tapered roller 4 difference ΔDn is calculated by formula (1) from roller diameter difference Dn (hereinafter simply referred to as "roller diameter difference Dn"), which is the difference between the roller diameter and the nominal diameter at a predetermined position of the nth tapered roller 4, roller diameter difference D(n-1) (hereinafter simply referred to as "roller diameter difference D(n-1)"), which is the difference between the roller diameter and the nominal diameter at a predetermined position of the n-1th tapered roller 4 adjacent to the nth tapered roller 4, and roller diameter difference D(n+1) (hereinafter simply referred to as "roller diameter difference D(n+1)"), which is the difference between the roller diameter and the nominal diameter at a predetermined position of the n+1th tapered roller 4.

[0020]

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[0021] Equation (1) indicates that the adjacent roller diameter difference ΔDn becomes smaller as at least one of the roller diameter difference D(n-1) of the n-1th tapered roller 4 and the roller diameter difference D(n+1) of the n+1th tapered roller 4 becomes larger than the roller diameter difference Dn of the nth tapered roller 4. In other words, as the adjacent roller diameter difference ΔDn of the nth tapered roller 4 becomes smaller, the contact surface pressure (hereinafter simply referred to as "contact surface pressure") (see white arrows) of the nth tapered roller 4 with respect to the inner ring raceway surface 2a and the outer ring raceway surface 3a becomes smaller than the contact surface pressure of the n-1th tapered roller 4 (see black arrows) and the contact surface pressure of the n+1th tapered roller 4 (see black arrows), so slippage is likely to occur between the inner ring raceway surface 2a and the outer ring raceway surface 3a.

[0022] On the other hand, the contact pressure of the nth tapered roller 4 becomes higher than the contact pressure of the n-1th tapered roller 4 and the contact pressure of the n+1th tapered roller 4 as the adjacent roller diameter difference ΔDn becomes larger. Therefore, the nth tapered roller 4 in such an arrangement is unlikely to slip between the inner ring raceway surface 2a and the outer ring raceway surface 3a. In this way, the adjacent roller diameter difference ΔDn of the nth tapered roller 4 shown in formula (1) indirectly represents the influence of the n-1th tapered roller 4 and the n+1th tapered roller 4 on the slip between the nth tapered roller 4 and the inner ring raceway surface 2a and the outer ring raceway surface 3a.

[0023] A method for measuring the roller diameter of tapered roller 4 will be described below with reference to Fig. 3. In this embodiment, the roller diameter of tapered roller 4 is a length perpendicular to the roller axis at a position away from large end face 4b of tapered roller 4 by an arbitrary length in the roller axial direction.

[0024] The tapered roller 4 to be measured has the nominal number 30319DJ3 (JIS B1534). The specific specifications of the tapered roller 4 (nominal number 30319DJ3) are: inner diameter 95mm, outer diameter 200mm, overall width 49.5mm, inner ring width 45mm, outer ring width 32mm, tapered roller nominal diameter 28.234mm (the nominal diameter of a tapered roller is defined as the diameter of an imaginary circle where the outer diameter surface and the large end face intersect, according to Table 2 in Appendix 1 of JIS B1506), number of rollers 15, contact angle α: 28°48′39″ (JIS B1534), outer ring small end diameter 151.584mm (JIS B1534), basic dynamic load rating: 296000N.

[0025] As shown in Figure 3, the rolling surface 4c of the tapered roller 4 is supported by a V-block 100 so that the roller axis is horizontal. Furthermore, the position of the tapered roller 4 in the roller axial direction is fixed by contacting a positioning member 101 having a protrusion with the large end face 4b. The contact position of the positioning member 101 on the tapered roller 4 is preferably approximately the center of the radial range of the large end face 4b with which the large rib portion 2c (see Figure 1) of the inner ring 2 contacts when the tapered roller 4 rolls on the inner ring raceway surface 2a. The rolling surface 4c of the tapered roller 4 at an arbitrary roller axial length L from the large end face 4b is measured with a dial gauge 102 in a direction perpendicular to the roller axis.

[0026] Next, using Figures 4 and 5, the roller diameter and speed of each of the 15 tapered rollers 4 from roller No. 1 to roller No. 15 that are equipped in the tapered roller bearing 1 are measured, and the roller diameter difference D15 is calculated from the roller diameter difference D1 and the adjacent roller diameter difference ΔD15 is calculated from the adjacent roller diameter difference ΔD1.

[0027] As shown in Figure 4, the roller diameter of each tapered roller 4 from roller No. 1 to roller No. 15 of tapered roller bearing 1 is measured using the measurement method shown in Figure 3. Furthermore, based on the measured roller diameter of each tapered roller 4, roller diameter differences D1 to D15 are calculated, and adjacent roller diameter differences ΔD1 to ΔD15 are calculated using formula (1).

[0028] The adjacent roller diameter difference ΔD1 of roller No. 1 is calculated from the roller diameter of adjacent roller No. 15 and the roller diameter of roller No. 2 using formula (1). Similarly, the adjacent roller diameter difference ΔD2 of roller No. 2 is calculated from the roller diameter of adjacent roller No. 1 and the roller diameter of roller No. 3 using formula (1). Similarly, the adjacent roller diameter difference ΔD3 of roller No. 3 is calculated from the roller diameter of adjacent roller No. 2 and the roller diameter of roller No. 4 using formula (1). In this way, the adjacent roller diameter difference ΔD1 to adjacent roller diameter difference ΔD15 of each tapered roller 4 are calculated as roller diameter differences that take into account the combination of tapered rollers 4 that make up tapered roller bearing 1.

[0029] As shown in Fig. 5, the slip ratios Sr3, Sr5, Sr10 and Sr11 are measured and analyzed for the tapered rollers 4 of rollers No. 3, No. 5, No. 10 and No. 11, for which the roller diameter difference Dn and adjacent roller diameter difference ΔDn were calculated. The slip ratio represents the ratio of the speed difference between the large rib portion 2c of the inner ring 2 and the large end face 4b of the tapered roller 4 to the speed of the tapered roller bearing 1. The adjacent roller diameter difference ΔD3 of the tapered roller 4 of roller No. 3 is 0.25μm, the adjacent roller diameter difference ΔD5 of the tapered roller 4 of roller No. 5 is -1.75μm, the adjacent roller diameter difference ΔD10 of the tapered roller 4 of roller No. 10 is 0.00μm and the adjacent roller diameter difference ΔD11 of the tapered roller 4 of roller No. 11 is -5.00μm.

[0030] The slip ratios Sr3, Sr5, Sr10 and Sr11 are calculated from the speed of the large rib portion 2c of the inner ring 2 and the speed of the large end face 4b of the tapered roller 4, which are measured by rotating the tapered roller bearing 1 under a specified load. The slip ratios Sr3, Sr5, Sr10 and Sr11 obtained by analysis are calculated using known simulation software under the same conditions as the speed measurements. Each slip ratio is measured using a test machine in which the inner ring rotates. The test machine measures the speed of the large rib portion 2c of the inner ring 2 and the speed of the large end face 4b of the tapered roller 4 using a high-speed camera. The lubrication method during the test is oil application (mineral oil with an ISO viscosity grade of ISO VG10). The rotation speed of the test machine is 1500 revolutions per minute. The test temperature is room temperature.

[0031] The tapered roller bearing 1 is rotated continuously for a predetermined time under a predetermined load in order to measure the speed of the large rib portion 2c of the inner ring 2 and the speed of the large end face 4b of each tapered roller 4 and to check whether the tapered rollers 4 are worn due to slippage. It was confirmed that the rolling surface 4c of the tapered roller 4 of roller No. 11, which had the largest slip ratio by measurement and analysis among the tapered rollers 4 of rollers No. 3, No. 5, No. 10, and No. 11, was mirror-finished due to wear. On the other hand, the tapered roller 4 of roller No. 5, which has the second largest slip ratio after the tapered roller 4 of roller No. 11, did not show mirror-finishing of the rolling surface 4c. In other words, the tapered roller 4 of roller No. 5 does not have slippage to the extent that it would cause wear. Therefore, at the adjacent roller diameter difference ΔD11 of the tapered roller 4 of roller No. 11, wear due to slippage occurs in the tapered roller 4. On the other hand, when the adjacent roller diameter difference ΔD5 of tapered roller 4 of roller No. 5 is reached, no wear due to slipping occurs. From the above, it is inferred that in tapered roller bearing 1, when the adjacent roller diameter difference ΔDn of the arbitrarily selected nth tapered roller 4 is greater than -2 μm, taking into account measurement error etc., no wear due to slipping occurs.

[0032] In the tapered roller bearing 1 of this embodiment, the roller diameter difference ΔD is 4 μm when the tapered roller 4 of the roller No. 11 where wear is occurring is excluded. In this way, in the tapered roller bearing 1 in which the adjacent roller diameter difference ΔDn is greater than -2 μm, wear due to slip does not occur even if the roller diameter difference ΔD is greater than 2 μm. From the above, even if the roller diameter difference ΔD is greater than 2 μm, the tapered roller bearing 1 does not generate wear due to slip as long as the adjacent roller diameter difference ΔD1 to adjacent roller diameter difference ΔD15 in each tapered roller 4 are all greater than -2 μm. In other words, even if the roller diameter difference ΔD is large, the tapered roller bearing 1 can suppress wear due to slip without increasing costs to reduce the roller diameter difference ΔD by adjusting the arrangement of the tapered rollers 4 to make the adjacent roller diameter difference ΔDn greater than -2 μm.

[0033] Although the embodiment of the present invention has been described above, the present invention is not limited to these embodiments, which are merely examples, and can of course be embodied in various other forms without departing from the spirit of the present invention, and the scope of the present invention is defined by the claims, and further includes the equivalent meanings set forth in the claims, and all modifications within the scope of the claims. Also, in this embodiment, a tapered roller bearing using tapered rollers as rolling elements is described, but the present invention can be applied to all bearings having multiple rolling elements. [Explanation of symbols]

[0034] 1 Tapered roller bearing 2. Inner Circle 2a Inner ring raceway surface 3 Outer ring 3a Outer ring raceway 4 Tapered roller 5 Cage ΔDn Adjacent roller diameter difference

Claims

[Claim 1] an inner ring having at least a conical raceway surface on an outer periphery thereof; A plurality of tapered rollers, A tapered roller bearing comprising: a retainer that accommodates the tapered rollers; a tapered roller bearing in which, among the plurality of tapered rollers, an n-1th tapered roller and an n+1th tapered roller adjacent to an nth tapered roller are combined such that an adjacent roller diameter difference of the nth tapered roller calculated from equation (1) is greater than -2 μm, and a difference between a maximum roller diameter and a minimum roller diameter of each of the plurality of tapered rollers is greater than 2 μm. [0010] ΔDn: average value of difference between the roller diameter at a predetermined position of an arbitrarily selected nth tapered roller among a plurality of tapered rollers arranged inside a tapered roller bearing and the roller diameter of a tapered roller adjacent to that tapered roller; D(n-1): roller diameter difference which is the difference between the roller diameter at a predetermined position of the n-1th tapered roller and the so-called diameter; Dn: roller diameter difference which is the difference between the roller diameter at a predetermined position of the nth tapered roller and the so-called diameter; D(n+1): roller diameter difference which is the difference between the roller diameter at a predetermined position of the n+1th tapered roller and the so-called diameter

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