Roller bearing

Abstract

Roller bearings, including: an inner ring and an outer ring extending circumferentially around a central axis; a plurality of rollers arranged between the inner ring and the outer ring; and a cage in which a plurality of column sections extending in an axial direction of the central axis are provided circumferentially, and each of the plurality of rollers is held in a pocket between two circumferentially adjacent column sections of the plurality of column sections, wherein, if a circle passing through an axial center of each of the plurality of rollers around the central axis is defined as a pitch circle, where seen from the axial direction of the central axis, when the two circumferentially adjacent column sections are defined as a first column section and a second column section, and a roller arranged in a pocket between the first column section and the second column section is defined as a first roller, and a distance obtained by subtracting a maximum diameter of the first roller from a distance along the pitch circle between the first column section and the second column section is defined as a pocket gap, a pocket gap ratio, which is calculated by dividing the pocket gap by the maximum diameter of the first roll, is 0.005 or more and less than 0.01.

Description

Technical field

[0001] The present invention relates to a roller bearing. Technical background

[0002] A roller bearing is a type of rolling bearing. The roller bearing includes an inner ring and an outer ring extending circumferentially around a central axis; a roller disposed between the inner ring and the outer ring; and a cage having a pocket for accommodating the roller (see, for example, Patent Literature 1). Patent Literature 1 describes measures for reducing rotational noise of a roller bearing by setting a maximum diameter Dw of the roller and a minimum gap C between an inner surface of a pocket and the roller to values ​​within a predetermined range. Specifically, the relationship between the maximum diameter Dw and the minimum gap C of the roller is expressed as 0.01 × Dw ≤ C ≤ 0.02 × Dw. Citation listPatent literature

[0003] Patent Literature 1: JP 2018-169044 A SummaryTechnical problem

[0004] In recent years, there has been an increasing demand from the industry to extend the service life of a mechanical device that uses a roller bearing, so that the service life of the roller bearing is also desired.

[0005] The aim of the present invention is to provide a roller bearing capable of extending a service life. Solution to the problem

[0006] A roller bearing according to an embodiment of the present disclosure comprises: an inner ring and an outer ring extending circumferentially around a central axis; a plurality of rollers arranged between the inner ring and the outer ring; and a cage in which a plurality of column portions extending in an axial direction of the central axis are provided circumferentially, and each of the plurality of rollers is held in a pocket between two circumferentially adjacent column portions of the plurality of column portions, wherein, if a circle passing through an axial center of each of the plurality of rollers around the central axis is defined as a pitch circle, viewed from the axial direction of the central axis,when the two circumferentially adjacent column portions are defined as a first column portion and a second column portion, and a roller arranged in a pocket between the first column portion and the second column portion is defined as a first roller, and a distance obtained by subtracting a maximum diameter of the first roller from a distance along the pitch circle between the first column portion and the second column portion is defined as a pocket gap, a pocket gap ratio obtained by dividing the pocket gap by the maximum diameter of the first roller is 0.005 or more and less than 0.01.

[0007] In a roller bearing, a roller rotates within a cage pocket as an inner ring and outer ring rotate relative to each other. This results in friction and slippage between the inner ring, outer ring, or cage and the roller. Due to friction and slippage, the inner ring or outer ring may be damaged, such as by wear, or experience high temperatures, which can reduce the service life of the roller bearing.

[0008] When a pocket gap ratio is less than 0.005 and, for example, the inner ring is rotated relative to the outer ring, the roller in a cage pocket and the cage generate abnormally large heat due to partial metal-to-metal contact. As a result, the inner ring and outer ring have excessively high temperatures, rendering the rolling bearing unusable. In contrast, when the pocket gap ratio is 0.01 or more and, for example, the inner ring is rotated relative to the outer ring, the roller in the pocket easily causes large skew and the like, so that slippage increases at a contact portion between the roller and the inner ring and a contact portion between the roller and the outer ring. As a result, especially the inner ring, which has a geometrically high contact pressure, is easily worn, and the service life of the roller bearing decreases.From the above, it can be seen that the service life of the roller bearing can be extended if the pocket gap ratio is set to 0.005 or more and less than 0.01.

[0009] The reason why the service life of the roller bearing can be extended by reducing the pocket gap ratio, as described in NSK TECHNICAL JOURNAL (NO. 682 (2007)), is briefly described here. Reducing the pocket gap ratio causes the roller and an inner surface of the pocket to approach each other and accordingly come into greater contact with each other, preventing rolling behavior (e.g., skew) as described above, which temporarily increases the friction force between the rotating roller and the inner surface of the pocket and reduces the rotational speed of the roller. As a result, the difference between the rotational speed (peripheral speed) of the roller and that of the inner ring decreases, and the slip of the roller relative to the inner ring decreases. Therefore, reducing the pocket gap ratio is considered to extend the actual service life, that is, the time before the inner ring wears out.

[0010] In a desirable embodiment, the pocket gap ratio is 0.00573 or more and 0.0099 or less. This allows for a further extension of the service life of the roller bearing. Advantageous effects of the invention

[0011] According to the present invention, a service life of a roller bearing can be extended. Brief description of the drawings Fig. Figure 1 is a schematic view of a cross-section through a spherical roller bearing. Fig. 2 is a schematic view of a cross section of the spherical roller bearing according to an embodiment. Fig. 3 is a schematic view of a part of a cage according to the embodiment, viewed from an outer peripheral side. Fig. 4 is a plan view of a spherical roller according to this embodiment. Fig. 5 is a schematic view showing cross sections of the cage and the spherical roller as seen in the axial direction. Fig. 6 is a schematic cross-sectional view illustrating the relationship of a gap between the cage and the spherical roller. Fig. Figure 7 is a graph showing the pocket gap ratios and bearing life ratios for the respective cage types in the example. Fig. Figure 8 is a schematic view showing cross sections of the cage and the spherical roller from the axial direction of the cage installed for a bearing rotation test. Fig. Figure 9 is a graph illustrating the relationship between the rotational speed and the outer ring temperature of a bearing. Fig. Figure 10 is a graph illustrating the relationship between a pocket gap ratio and a life ratio of a bearing. Description of embodiments

[0012] An embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited by the content described in the following embodiment. Moreover, the components described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the components described below can be appropriately combined with each other. Furthermore, parts having the same structure are designated by the same reference numerals, and their descriptions are omitted. [Embodiment](Configuration of a spherical roller bearing)

[0013] First, a configuration of a spherical roller bearing, a type of roller bearing, is described. Fig. 1 is a perspective view of a partial cross section showing the spherical roller bearing. Fig. 2 is a schematic view of a cross section of the spherical roller bearing according to the embodiment. Fig. 3 is a schematic view of a part of a cage according to the embodiment, viewed from an outer peripheral side. An X1 side is one side in the axial direction of an inner ring 1 and an outer ring 2. An X2 side is the other side in the axial direction. Fig. 4 is a plan view of a spherical roller according to this embodiment.

[0014] As in the Fig. 1 and Fig. 2, a spherical roller bearing 100 includes the inner ring 1, the outer ring 2, spherical rollers (first rollers) 32, and a cage 4. The inner ring 1 and the outer ring 2 have an annular shape circumferentially extending around a center axis AX10. In the spherical roller bearing 100, a plurality of spherical rollers 32 are arranged in two rows with a center line CL in the axial direction of the inner ring 1 and the outer ring 2 interposed therebetween. That is, rows of the circumferentially arranged spherical rollers 32 are formed on the X1 side (one side in the axial direction) and the X2 side (other side) of the inner ring 1 and the outer ring 2 with the center line CL interposed therebetween.

[0015] As in Fig. 2, in a cross section including the central axis AX10, the axial centers AX20 of the two rows of spherical rollers 32 are inclined with respect to the central axis AX10. Specifically, the axial centers AX20 of the spherical rollers 32 on the X1 side are inclined to approach the central axis AX10 toward the X1 side. In other words, the axial centers AX20 of the spherical rollers 32 on the X1 side are inclined radially inward toward the X1 side.

[0016] As in Fig. 2, the axial centers AX20 of the spherical rollers 32 on the X2 side are inclined to approach the center axis AX10 toward the X2 side. In other words, the axial centers AX20 of the spherical rollers 32 on the X2 side are inclined radially inward toward the X2 side.

[0017] As in Fig. As shown in Figure 2, the inner ring 1 has an outer peripheral surface 11 and an inner peripheral surface 12. The outer peripheral surface 11 has raceway surfaces 13 and 14 for the spherical rollers 32. The raceway surface 13 is provided for the spherical rollers 32 on the X1 side. The raceway surface 13 is inclined radially inward toward the X1 side. The raceway surface 14 is provided for the spherical rollers 32 on the X2 side. The raceway surface 14 is inclined radially inward toward the X2 side.

[0018] The outer ring 2 has an outer peripheral surface 22 and an inner peripheral surface 21. The inner peripheral surface 21 serves as a raceway surface 23 for the rollers 3. Here, if an intersection point of the center axis AX10 and the center line CL is defined as the center O2, the inner peripheral surface 21 is an arc around the center O2. As described above, the spherical roller bearing 100 has an alignment property because the center O2, which is the center of curvature of the raceway surface 23 of the outer ring 2, coincides with the center axis AX10 of the spherical roller bearing 100.

[0019] As in Fig. 3, the cage 4 includes a rim portion (central annular region, hereinafter referred to as a rim portion) 43 and pillar portions 40. The rim portion 43 extends annularly along the center line CL of the cage 4. That is, the rim portion 43 is located at the center in the axial direction of the inner ring 1 and the outer ring 2. The pillar portions 40 extend from the rim portion 43 toward the X1 side or the X2 side. The pillar portions 40 are substantially perpendicular to the rim portion 43. The pillar portions 40 are arranged at equal intervals in the circumferential direction. Here, a pocket 46 is provided between a pair of circumferentially adjacent pillar portions 40 and the rim portion 43, and between the pair of circumferentially adjacent pillar portions 40 and the rim portion 43.Furthermore, as viewed from the axial direction of the center axis AX10, a column portion 40 on the X2 side is arranged between two circumferentially adjacent column portions 40 on the X1 side. Furthermore, a roller 3 that is inserted into the spherical roller bearing 100, for example, the spherical roller 32 in FIG. Fig. 4. An outer peripheral surface 32a of the spherical roller 32 has a spherical shape and a larger diameter in the axial direction center than at the axial ends. The spherical roller 32 has a maximum diameter D100 in the axial direction centered on the axial center AX20. The spherical roller 32 is disposed in the pocket 46. (Representation of the cage and the spherical roller)

[0020] Fig. Figure 5 is a schematic view showing cross sections of the cage and a spherical roller in the axial direction. Fig. 5 is a circle that revolves around the central axis AX10 (see Fig. 1) passes through the axial center AX20 of the spherical roller 32, is defined as the pitch circle C1. In Fig. 5, the circumference of the pitch circle C1 is represented by a straight dashed line.

[0021] As in Fig. 5 shown, illustrated Fig. 1, in which a cage 4A and a cage 4B can be applied, an example in which 4B is used as the cage 4. The cage 4A includes a first column portion 41A and a second column portion 42A, which are two column portions 40. The cage 4B includes a first column portion 41B and a second column portion 42B, which are two column portions 40. Viewed in the axial direction of the central axis AX10, the spherical roller 32 is arranged between two circumferentially adjacent column portions 40.

[0022] Viewed in the axial direction, the first column portion 41A and the second column portion 42A of the cage 4A are arranged on the circumference of the pitch circle C1. The first column portion 41B and the second column portion 42B of the cage 4B are arranged on the radially inner side of the spherical roller bearing 100 as the first column portion 41A and the second column portion 42A. That is, the distance between a radially intermediate portion of the first column portion 41A and the second column portion 42A of the cage 4A and the center axis AX10 of the spherical roller bearing 100 corresponds to a rolling diameter (PCD) (roller pitch circle diameter). The distance between a radially intermediate portion of the first column portion 41B and the second column portion 42B of the cage 4B and the center axis AX10 of the spherical roller bearing 100 is smaller than the PCD.

[0023] The center point of the distance along the circumferential direction of the pitch circle C1 between the radial center point of a side surface 41Aa of the first column portion 41A and the radial center point of a side surface 42Aa of the second column portion 42A of the cage 4A is defined here as the center point O1. A virtual circle C2 passing through the side surface 41Aa and the side surface 42Aa around the center point O1 is represented by a dashed line. The side surface 41Aa and the side surface 42Aa of the cage 4A, and a side surface 41Ba and the side surface 42Ba of the cage 4B have an arc shape along the circumference of the virtual circle C2. (Pocket gap of the cage)

[0024] Fig. 6 is a schematic view showing a gap between the cage and a spherical roller (for clarity, the gap is exaggerated and larger than in Fig. 5). The gaps in the pockets 46 of the cages 4A and 4B are calculated for the case where the axial center AX20 of the spherical roller 32 coincides with the center point O1. The case where the axial center AX20 of the spherical roller 32 coincides with the center point O1 corresponds to the case where a first gap is equal to a second gap. The first gap is formed along the circumference of the pitch circle C1 between the side surface 41Aa of the first column portion 41A in the cage 4A and the outer peripheral surface 32a of the spherical roller 32. The second gap is formed along the circumference of the pitch circle C1 between the side surface 42Aa of the second column portion 42A and the outer peripheral surface 32a of the spherical roller 32. A gap resulting from the combination of the first gap and the second gap is called a pocket gap.Note that in cage 4B, the first gap is the same as the second gap, and a gap formed by the combination of the first gap and the second gap is called a pocket gap. In . Fig. 6, the second gap of the pocket gap is calculated, where the pocket gap is twice the second gap. In other words, the distance obtained by subtracting the maximum diameter D100 of the spherical roller (first roller) 32 from the distance along the pitch circle C1 between the first column portion 41A and the second column portion 42A is the pocket gap. Details are described below.

[0025] First, the second gap between the cage 4A and the spherical roller 32 is calculated. As in Fig. 6, a point in the radial direction at the center of the side surface 42Aa of the second column portion 42A is defined as point P1. An intersection point of a straight line connecting the axial center AX20 of the spherical roller 32 to point P1 with the outer peripheral surface 32a of the spherical roller 32 is defined as point P2. The distance between point P1 and point P2 is defined as distance L10. That is, the second gap between the cage 4A and the spherical roller 32 is defined as distance L10. Therefore, the pocket gap of the cage 4A is calculated as 2 × L10.

[0026] Next, the second gap between the cage 4B and the spherical roller 32 is calculated. Since the cage 4B is located on a radially inner side than the pitch circle C1, the second gap is calculated by applying the following approximate formula.

[0027] As in Fig. 6, a radially inner end on the side surface 42Ba of the second column portion 42B of the cage 4B is defined as point P3. An intersection point of a straight line connecting the axial center AX20 to point P3 with the outer peripheral surface 32a of the spherical roller 32 is defined as point P4. An intersection angle between the straight line connecting the axial center AX20 to point P3 and the straight line connecting the axial center AX20 to point P1 is defined as angle θ.

[0028] A straight line passing through point P4 and parallel to the straight line joining the axial center AX20 to point P1 intersects here at point P5 a straight line passing through point P3 and perpendicular to the straight line joining point P4 to point P3. A right-angled triangle is then formed by point P3, point P4, and point P5. That is, a right-angled triangle is formed by a side p, a side q, and a side r. Side p connects point P3 to point P4. Side q connects point P4 to point P5. Side r connects point P3 to point P5. Side q is a hypotenuse, and side p and side r are two sides that enclose the right angle. Note that the straight line joining point P3 to point P5 is also a tangent to point P3 of the virtual circle C2.Therefore, the second gap between the cage 4B and the spherical roller 32 is equal to a distance L20 (length of side q), which corresponds to the distance between point P4 and point P5. Thus, the pocket gap of the cage 4B can be approximately 2 × L20.

[0029] Next, the size relationship between the pocket gap between the cage 4A and the spherical roller 32 and the pocket gap between the cage 4B and the spherical roller 32 will be described.

[0030] As described for cage 4B, the distance L10 described for cage 4A is equal to the distance between point P3 and point P4 (side length p). Here, (length of side q) = (length of side p) / cosθ. Since 0 degrees < θ < 90 degrees and 0 < cosθ < 1, 1 < 1 / cosθ . Thus, (length of side p) < (length of side q) = (length of side p) / cosθ. This means that distance L10 < distance L20, so the pocket gap of cage 4B is larger than the pocket gap of cage 4A. [Examples]

[0031] In the following, the present invention is described in more detail using examples. [Example 1]

[0032] In Example 1, the life ratios of spherical roller bearings A, B, and C (hereinafter referred to simply as bearings A, B, and C) were examined. The life ratios are the ratio between the actual life and the nominal life, which is based on the dynamic load rating of each bearing. The actual life is the time before an inner ring, outer ring, or the rollers of a bearing wear out. Note that in all examples shown here, the inner ring wore out.

[0033] Bearing A, bearing B, and bearing C had the same surface finish, except that only the pocket gap ratios, obtained by dividing a pocket gap by the maximum diameter of a roller, differed. Specifically, a bearing with model number 22211 (outer diameter of 100 mm, inner diameter of 55 mm, and width of 25 mm) was used as the base bearing for bearing A, bearing B, and bearing C. All outer rings, inner rings, and rollers of the respective bearings A, B, and C had the same surface finish and were subjected to the same heat treatment. The surface finish conditions are described below.In addition, all bearings A, B, and C were adjusted to have an equivalent retention ratio between a roller and an inner ring (radius of curvature of the rolling surface of the roller / radius of curvature of the raceway surface of the inner ring) and an equivalent retention ratio between a roller and an outer ring (radius of curvature of the rolling surface of the roller / radius of curvature of the raceway surface of the outer ring). Fig. 5 and Fig. Cage 4A described in Figure 6 was used for the cages of bearings A and C. The cage shown in the Fig. 5 and Fig. Cage 4B described in Figure 6 was applied to the cage of bearing B. A specific description follows below. (roughness condition) - Roughness of the outer ring: 0.3 µm Ra - Roughness of the inner ring: 0.07 µm Ra - Roughness of the pendulum roller: 0.05 µm Ra

[0034] The test conditions are as follows. - Radial test load: 45200 N - Axial test load: 0 N - Rotational speed of the inner ring: 1500 min -1 (Outer ring fixed) - Lubrication method: JX Nippon Oil & Energy Corporation, FBK oil RO68, forced circulation

[0035] The dynamic load ratings (Cr), the nominal life (H), and the pocket gap ratios of the respective bearings are as follows. Since the 4A cage was used for bearings A and C, the pocket gap ratios of bearings A and C were calculated as 2 × L10 (see Fig. 6). Since the cage 4B was used for bearing B, the pocket gap of bearing B was calculated as 2 × L20 (see Fig. 6). (Warehouse A) Dynamic rated load (Cr): 10400 kgf Nominal lifetime (H): 176 hours Pocket gap ratio: 0.0135 (1.35%) (Camp B) Dynamic rated load (Cr): 12150 kgf Nominal lifetime (H): 278 hours Pocket gap ratio: 0.00866 (0.87%) (Camp C) Rated dynamic load (Cr): 11680 kgf Nominal lifetime (H): 245 hours Pocket gap ratio: 0.00805 (0.805%) (Test results)

[0036] Fig. Figure 7 shows a result obtained by rotating the inner rings of bearings A, B and C to the end of their service life and examining the service life ratio and pocket gap ratio of each bearing. Fig. Figure 7 is a diagram showing the pocket gap ratios and bearing life ratios for the respective cage types in the example. Fig. 8 is a schematic view showing cross sections of a cage and a spherical roller from the axial direction of the cage installed for a bearing rotation test.

[0037] As in Fig. As shown in Figure 7, bearing A (pocket gap ratio: 1.35%) had a life ratio of 0.23. Bearing B (pocket gap ratio: 0.87%) had a life ratio of 1.58. Bearing C (pocket gap ratio: 0.805%) had a life ratio of 2.3.

[0038] It was found that a large pocket gap ratio significantly reduced the service life of bearing A, while a small pocket gap ratio significantly increased the service life of bearing C. In addition, the pocket gap ratio of bearing B, which was between the pocket gap ratios of bearing A and bearing C, indicated an intermediate service life between bearing A and bearing C. From the above findings, it was found that decreasing a pocket gap ratio increased a service life.

[0039] It is believed that one factor contributing to the long life effect is that reducing the pocket gap ratio causes a roller to contact the pocket inner surface (roller guide surface) of a cage, generating frictional force and reducing the rotational speed of the roller, thereby reducing the slip between the roller and the inner ring and inhibiting the surface fatigue of the inner ring. A brief description is given below.

[0040] The rotation of a roller causes contact between the roller and the outer ring and contact between the roller and the inner ring, thereby generating frictional force. In addition, the frictional force is generated by the contact between the roller and the pocket inner surface (roller guide surface) of the cage. In particular, the frictional force is greater in a loaded region (including the transition of the load region) than in a non-load region. Here, a decrease in the pocket gap ratio causes the roller and the pocket inner surface to approach each other and accordingly come into contact with each other more strongly, which temporarily increases the frictional force between the rotating roller and the pocket inner surface and reduces the rotational speed of the roller. As a result, the difference between the rotational speed (peripheral speed) of the roller and that of the inner ring decreases, and the slip of the roller relative to the inner ring decreases.From the above, it can be seen that reducing the pocket gap ratio extends the actual life, i.e. the time before the inner ring wears out, and increases the service life. [Example 2]

[0041] In Example 1, it was successfully demonstrated that reducing the pocket gap ratio increases service life. In Example 2, the minimum value of the pocket gap ratio was verified. Specifically, spherical roller bearings a, b, and c (hereinafter referred to simply as bearings a, b, and c) were provided, and bearing c was compared with bearings a and b. The appropriateness of the pocket gap ratio of bearing a was verified. Details are described below.

[0042] Bearing a has a structure similar to that of bearing A in Example 1. In particular, bearing a is designed by applying the method described in Fig. 5 and Fig. 6 to a bearing with the model number 24128. The bearing c has a structure corresponding to the bearing C in Example 1. In particular, the bearing c is obtained by applying the method described in the Fig. 5 and Fig. 6 to a bearing with the model number 24128. Bearing b has a structure corresponding to that of bearing B and is a bearing (commercial product) obtained by assembling a cage 4B' (two-body raceway surface ring guide press cage) in Fig. 8 with a bearing of model number 24128. (Detailed specifications of each bearing) (Camp a) Dynamic nominal load (Cr): 835 kN Static radial nominal load (C0r): 1160 kN Pocket gap ratio: 0.0163 (1.63%) (Camp b) Dynamic rated load (Cr): 796 kN Static radial nominal load (C0r): 1160 kN (Camp c) Dynamic rated load (Cr): 945 kN Static radial nominal load (C0r): 1330 kN Pocket gap ratio: 0.00573 (0.5733%)

[0043] The test conditions are as follows. - Radial test load: 75700 N - Axial test load: 0 N - Inner ring speed: 1300, 1950, 2600 min -1 , and 3250 min -1 (bearing c only) - Lubrication method: JX Nippon Oil & Energy Corporation, FBK oil VG68, forced circulation (Test results)

[0044] The inner rings of bearings a, b, and c were rotated at the respective speeds, and the temperatures of the outer rings were measured at the respective speeds. As described above, bearing c has a pocket gap ratio of 0.00573 (0.5733%). Therefore, whether there is a problem with the temperature of bearing c or not will be discussed below mainly with reference to Fig. 9 described. Fig. Figure 9 is a graph showing the relationship between the rotational speed and the outer ring temperature of a bearing. Fig. Figure 10 is a graph showing the relationship between the pocket gap ratio and the life ratio of a bearing.

[0045] As in Fig. 9, it was found that the bearing c at the speeds of 1300, 1950 and 2600 min -1 has a temperature rise corresponding to that of bearing a, and that the temperature rise of bearing c is less inhibited than that of bearing b. In addition, at the speed of 3250 min -1 a temperature of 115.1 degrees. 115.1 degrees corresponds to a temperature of 110.3 degrees of bearing b at a speed of 2600 min -1 . More precisely, a speed at which the bearing c has a temperature of 110 degrees is 3100 min -1 Since 3100 - 2600 = 500, the bearing c has a limiting speed of 500 min -1compared to camp b.

[0046] From the above-described results of the temperature rise of the bearing c, it was confirmed that a lower limit of the pocket gap ratio of a bearing is 0.005 (0.5%), preferably 0.00573 (0.5733%).

[0047] These results are shown in the diagram in Fig. 10 is summarized. In Fig. 10, point A indicates a pocket gap ratio of bearing A and a life ratio of the bearing. Point B indicates a pocket gap ratio of bearing B and a life ratio of the bearing. Point C indicates a pocket gap ratio of bearing C and a life ratio of the bearing. The pocket gap ratios of 0.5 and 0.573 are based on the above-described verification of a temperature rise of bearing C.

[0048] If point A, point B, and point C are connected by an approximate curve (dashed line), it can be seen that the life ratio decreases with increasing pocket gap ratio. According to the approximate curve, the pocket gap ratio at which the life ratio becomes 1 is 0.99.

[0049] In summary, the lower limit of the pocket gap ratio of a bearing is 0.005 (0.5%), preferably 0.00573 (0.5733%). The upper limit of the pocket gap ratio is less than 0.01 (less than 1%), preferably 0.0099 (0.99%).

[0050] As described above, the spherical roller bearing (roller bearing) 100 according to the embodiment includes: the inner ring 1 and the outer ring 2; a plurality of spherical rollers 32 (roller 3); and the cage 4 in which a spherical roller (first roller) 32 is held between two circumferentially adjacent column portions 40 of a plurality of column portions 40. When a distance obtained by subtracting the maximum diameter D100 of the spherical roller (first roller) 32 from the distance along the pitch circle C1 between the first column portion 41A and the second column portion 42A is defined as a pocket gap, a pocket gap ratio obtained by dividing the pocket gap by the maximum diameter D100 of the spherical roller 32 is 0.005 or more and less than 0.01.

[0051] In the spherical roller bearing 100, the spherical roller 32 rotates in the cage 4 when the inner ring 1 and the outer ring 2 rotate relative to each other. Therefore, friction and slippage occur between the inner ring 1, the outer ring 2, or the cage 4 and the spherical roller 32. Due to this friction and slippage, for example, the life of the rollers may be reduced due to wear of the inner ring 1 or the outer ring 2, and the like, or the inner ring 1 or the outer ring 2 may have a high temperature. The life of the spherical roller bearing 100 may be reduced due to damage such as burns.

[0052] In contrast, when the pocket gap ratio is less than 0.005, the friction between the roller and the pocket inner surface increases (partial metal-to-metal contact also occurs). For example, when the inner ring 1 is rotated relative to the outer ring 2, the roller is expected to generate abnormal heat and the spherical roller bearing 100 will become unusable due to the resulting excessive increase in the temperatures of the inner ring 1 and the outer ring 2. In this case, it is assumed that the temperature rise gradients of the bearing c and the bearing a in Fig. 9 increase, a larger temperature gradient than that of bearing b occurs and the temperature even at 1950 min -1exceeds 110°C. In addition, if the gap ratio is small, in the worst case, burning will occur shortly after rotation starts. In contrast, if the pocket gap ratio is 0.01 or more, the inner ring 1 is easily worn when the inner ring 1 is rotated relative to the outer ring 2, for example, and the service life of the spherical roller bearing 100 is reduced. From the above, it can be seen that the service life of the spherical roller bearing 100 can be extended by setting the pocket gap ratio to 0.005 or more and less than 0.01. In addition, the service life of the spherical roller bearing 100 can be further extended by setting the pocket gap ratio to 0.00573 or more and 0.0099 or less.

[0053] The reason why the service life of the spherical roller bearing 100 is extended by reducing the pocket gap ratio will be briefly described here. Reducing the pocket gap ratio causes the spherical roller 32 and the pocket inner surface to approach each other and thus come into closer contact with each other, which temporarily increases the frictional force between the rotating spherical roller 32 and the pocket inner surface and reduces the rotational speed of the spherical roller 32. As a result, the difference between the rotational speed (peripheral speed) of the spherical roller 32 and that of the inner ring 1 decreases, and the slip of the roller relative to the inner ring 1 decreases. Therefore, reducing the pocket gap ratio is considered to extend the actual service life, that is, the time before the inner ring 1 wears out. List of reference symbols 1 inner ring 2 outer ring 3 rolls 4, 4A, 4B, 4B' cage 11 Outer peripheral surface 12 inner peripheral surface 13, 14 Running track surface 21 Inner peripheral surface 22 Outer peripheral surface 23 Running track area 32 Pendulum roller (first roller) 32a Outer peripheral surface 40 column section 41A, 41B first column section 41Aa, 41Ba side surface 42A, 42B second column section 42Aa, 42Ba side surface 43 Ring section (central ring-shaped section) 46 bag 100 spherical roller bearings (roller bearings) AX10 center axis AX20 axial center C1 pitch circle C2 virtual circle CL center line D100 maximum diameter L10 distance L20 distance O1, O2 Center QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] NSK TECHNICAL JOURNAL (NO. 682 (2007

[0009]

Claims

[1] Roller bearings, comprising: an inner ring and an outer ring extending circumferentially around a central axis; a plurality of rollers arranged between the inner ring and the outer ring; and a cage in which a plurality of column sections extending in an axial direction of the central axis are provided circumferentially, and each of the plurality of rollers is held in a pocket between two circumferentially adjacent column sections of the plurality of column sections, wherein, if a circle passing through an axial center of each of the plurality of rollers around the central axis is defined as a pitch circle, where seen from the axial direction of the central axis, if the two circumferentially adjacent column sections are defined as a first column section and a second column section and a roller arranged in a pocket between the first column section and the second column section is defined as a first roller, and a distance obtained by subtracting a maximum diameter of the first roller from a distance along the pitch circle between the first column section and the second column section is defined as the pocket gap, a pocket gap ratio, which is calculated by dividing the pocket gap by the maximum diameter of the first roll, is 0.005 or more and less than 0.

01. [2] A roller bearing according to claim 1, wherein the pocket gap ratio is 0.00573 or more and 0.0099 or less.

Images