Double row spherical roller bearing

Abstract

To provide a double-row self-aligning roller bearing which can properly share a load by double-row rollers to not only a fatigue load but also an extremal value load within a constriction range of a dimension specification.SOLUTION: A double-row self-aligning roller bearing (1) comprises an inner ring (2), an outer ring (3) having a spherical raceway surface, and a plurality of double-row rollers (4, 5) interposed between the inner ring (2) and the outer ring (3), and aligned in a bearing width (B) direction. The double-row rollers have external peripheral faces having cross sections along a raceway surface of the outer ring. A ratio of a one-row roller contact angle θ1 and the other-row roller contact angle θ2 is set within a range of 0.25≤θ1 / θ2≤0.5, and a ratio of a distance B1 in a bearing width direction from a bearing end face (E1) of one row side up to a cross point (P) of two action lines forming a double-row contact angle, and a distance B2 from a bearing end face (E2) of the other-row side up to the cross point (P) is set within a range of 0.5≤B1 / B2≤0.6.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a double-row spherical roller bearing used in applications in which unequal loads are applied to two rows of rollers aligned in the bearing width direction, such as for supporting the main shafts of wind power generators and industrial machinery. [Background technology]

[0002] In addition to the radial load due to the weight of the blades and rotor head, the bearing supporting the main shaft of the wind power generator is also subjected to an axial load due to wind force. When the bearing supporting the main shaft is a double row self-aligning roller bearing 41 having an axially symmetrical structure as shown in FIG. 20, of the two rows of rollers 44, 45 interposed between the inner ring 42 and the outer ring 43, only the rollers 45 in one row, which are on the rear side with respect to the axial load Fa, mainly bear the axial load Fa. In other words, the rollers 45 in one row bear both the radial load and the axial load, while the rollers 44 in the other row bear almost only the radial load. For this reason, the contact surface pressure of the rollers 45 in the row that bears the radial load and the axial load is larger than that of the rollers 44 in the row that bears only the radial load, and the surface damage and wear of the rolling surfaces of the rollers 45 and the raceway surface 43a of the outer ring 43 are likely to occur. In this case, the rolling life of rollers 45 in one row will be shorter than the rolling life of rollers 44 in the other row, and the actual life of the entire bearing will be determined by the short rolling life of the row of rollers 45 receiving the axial load.

[0003] In order to address the above-mentioned issues, it has been proposed to make the lengths of the two rows of rollers different from each other (see Patent Document 1) or to make the contact angles of the two rows of rollers different from each other (see Patent Document 2) in order to improve the actual life of the entire bearing. However, due to the restrictions of the bearing dimensional standard (ISO standard; JIS B1512), it is difficult to increase the load capacity of the row of rollers that receives the axial load to an appropriate value by using only one of the above two methods. In other words, since the inner diameter, outer diameter, and bearing width are each determined for the design number by the dimensional standard, if the length of the row of rollers that receives the axial load is made too long, the bearing width will exceed the standard value. Also, if the contact angle of the row of rollers that receives the axial load is made too large, the inner diameter will exceed the standard value.

[0004] Therefore, in order to equalize the contact surface pressure between the row receiving axial loads and the row receiving only radial loads without the dimensions of each part deviating from the bearing dimensional standards, it has been proposed to combine a method of making the lengths of the rollers in the two rows different from each other with a method of making the contact angles of the rollers in the two rows different from each other (see Patent Document 3).In this technology, it is important to increase the contact angle of the rollers in the row receiving axial loads to sufficiently increase the load capacity of those rollers, and therefore an appropriate ratio of the contact angles of the rollers in both rows for this purpose has also been proposed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2005 / 050038 [Patent Document 2] US Patent No. 2014 / 0112607 [Patent Document 3] JP 2017-180831 A Summary of the Invention [Problem to be solved by the invention]

[0006] The bearing disclosed in Patent Document 3 equalizes the contact pressure on both rows against fatigue loads that are routinely applied, improving the actual life of the entire bearing. However, for extreme loads, which are the maximum loads expected to occur over a 50-year period, simply setting the above parameters may result in insufficient load capacity for the row with the shorter roller length.

[0007] The object of the present invention is to provide a double-row self-aligning roller bearing that is suitable for applications in which axial and radial loads are received and loads of different magnitudes act on two rows of axially aligned rollers, and that is capable of appropriately sharing the load between both rows of rollers, not only under fatigue loads but also under extreme loads, within the constraints of dimensional standards. [Means for solving the problem]

[0008] The double-row spherical roller bearing according to the present invention comprises: With the inner circle, an outer ring having a spherical raceway; a plurality of rollers arranged in two rows in a bearing width direction and interposed between the inner ring and the outer ring, a double-row self-aligning roller bearing, wherein each of the two rows of rollers has an outer peripheral surface having a cross-sectional shape that conforms to the raceway surface of the outer ring, the ratio of the contact angle θ1 of the rollers in one row to the contact angle θ2 of the rollers in the other row is in the range of 0.25≦θ1 / θ2≦0.5; The ratio of a distance B1 in the bearing width direction from the bearing end face on one row side to the intersection of the two action lines that form the contact angle between both rows to a distance B2 in the bearing width direction from the bearing end face on the other row side to the intersection is in the range of 0.5≦B1 / B2≦0.6.

[0009] With this configuration, by making the contact angle of the rollers in the other row larger than the contact angle of the one row, the rollers in the other row can bear a large axial load. When this double-row self-aligning roller bearing is used under conditions where an axial load and a radial load act, the rollers with the larger contact angle bear almost all of the axial load and part of the radial load, and the rollers with the smaller contact angle bear the remainder of the radial load. By sharing the axial load and radial load among the two rows of rollers in this manner, the contact surface pressure of the rollers in both rows can be made equal. This ensures a large load capacity for the entire bearing and improves the actual life of the entire bearing.

[0010] Furthermore, multiple double-row spherical roller bearings with different contact angle ratios for both rows of rollers were prepared, and the contact surface pressure of both rows of rollers was analyzed for each double-row spherical roller bearing under load conditions assumed when used as a bearing for supporting the main shaft of a wind power generator. As a result, it was found that the contact surface pressure of both rows of rollers is most equalized when the contact angle ratio is 1:3. The aforementioned assumed load conditions refer to the axial load and radial load, which are fatigue loads, under which an average wind power generator operates most normally, taking into account various conditions such as power generation capacity and installation location. Therefore, in a double-row spherical roller bearing used in a wind power generator with the aforementioned conditions different from those of an average wind power generator, the optimal contact angle ratio may not be 1:3, but even in that case, the optimal contact angle ratio falls within the range of 1:2 to 1:4. In other words, by setting the contact angle ratio of both rows in the range of 0.25≦θ1 / θ2≦0.5, the fatigue load can be appropriately shared between the rollers of both rows.

[0011] Furthermore, by setting the ratio of the distance B1 in the bearing width direction from the bearing end face of the one row with the smaller contact angle to the intersection of the two lines of action that form the contact angle of both rows to the distance B2 in the bearing width direction from the bearing end face of the other row with the larger contact angle to said intersection in the range of 0.5≦B1 / B2≦0.6, the length of the rollers of the one row, which bears almost only radial loads, is not excessively short within the range of the standard dimensions. Therefore, it is possible to avoid the insufficient load capacity of the rollers of the one row even for extreme loads that need to be assumed to be loaded from various directions. Therefore, it is possible for the rollers of both rows to appropriately share the load for both fatigue loads and extreme loads within the constraints of the dimensional standards.

[0012] In the present invention, the ratio of the roller length L1 of the one row to the roller length L2 of the other row is However, L1 / L2 may be in the range of 0.9≦L1 / L2≦1.0. With this configuration, the length of the rollers in the row with the larger contact angle is equal to or greater than the length of the rollers in the row with the smaller contact angle, reliably improving the load capacity of the rollers in the row with the larger contact angle against the axial load. At the same time, by making the length of the rollers in the row with the smaller contact angle 90% or more of the length of the rollers in the other row, as described above, it is possible to prevent the length of the rollers in one row, which bears almost exclusively the radial load, from becoming excessively short within the range of the standard dimensions.

[0013] In the present invention, the inclination angle β2 of the cage that holds the rollers in the other row is expressed by the following formula with respect to the roller maximum diameter angle α2, which is the inclination angle at the position where the rollers in the other row have a maximum diameter: 0≦β2≦α2 The relationship may be as shown in the following equation: The "inclination angle β2 of the cage" is, for example, an angle between the center line of the cylindrical surface and the cage center line (the central axis of the bearing) when the pocket surface of the column portion of the cage is a cylindrical surface. The "inclination angle β2 of the cage" may be the inclination angle of the outer diameter surface of the cage or the inclination angle of the inner diameter surface of the cage.

[0014] Since the maximum diameter angle α2 of the rollers in the other row, i.e., the rear row of rollers relative to the input direction of the axial load, is large, the cage inclination angle β2 may be set appropriately so that the pocket surface of the cage embraces the maximum diameter position of the rollers. In this case, 0≦β2≦α2 By so doing, the stability of the roller position is not impaired. Furthermore, by using such a cage shape, it is possible to prevent the deterioration of installation properties that is unique to the left-right asymmetric design, and to stably hold the rollers.

[0015] In the present invention, each of the rollers has a multi-layered DLC coating on its outer circumferential surface, The DLC coating has a thickness of 2.0 μm or more. The surface roughness of the outer surface of the base material of the roller is Ra≦0.3 and RΔq≦0.05 and The hardness of each layer in the multi-layered DLC coating may be gradually increased from the outer layer to the outer layer. The DLC is an abbreviation for Diamond-like Carbon.

[0016] Wear resistance is improved by applying a DLC coating to the outer peripheral surface of the roller. The DLC coating adopts a multi-layer structure that has excellent adhesion to the base material, and the film thickness is preferably 2.0 μm or more. In addition, aggressiveness to the mating material can be mitigated by setting the roughness value of the outer peripheral surface to which the DLC coating is applied to 0.3 Ra or less in arithmetic mean roughness Ra and 0.05 or less in root-mean-square slope RΔq. Furthermore, the hardness of the DLC coating can be increased stepwise in a multi-layer structure, resulting in high adhesion.

[0017] This double-row self-aligning roller bearing is suitable for supporting the main shaft of a wind turbine generator. A double-row self-aligning roller bearing that supports the main shaft of a wind turbine generator is subjected to radial loads due to the weight of the blades and rotor head, and axial loads due to wind force. Of the two rows of rollers aligned in the bearing width direction, the rollers in the other row receive both radial and axial loads, while the rollers in the one row receive almost only radial loads. In this case, by making the rollers in the row that receives the axial load the rollers in the other row with a larger contact angle, and making the rollers in the row that receives almost only radial loads the rollers in the one row with a smaller contact angle, the load is appropriately shared between both rows of rollers for both fatigue loads and extreme loads. Effect of the Invention

[0018] As described above, with the double-row self-aligning roller bearing according to the present invention, it is possible, within the constraints of dimensional standards, for both rows of rollers to appropriately share loads not only against fatigue loads but also against extreme loads. [Brief description of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view of a double-row self-aligning roller bearing according to a first embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] 13 is a graph showing the results of an analysis of the distribution of contact surface pressure on the front rollers when a combined axial load and radial load are applied to the double-row self-aligning roller bearing and a conventional double-row self-aligning roller bearing, respectively. [Figure 4] 13 is a graph showing the results of an analysis of the distribution of contact surface pressure on the rear rollers when a combined axial load and radial load are applied to the double-row self-aligning roller bearing and a conventional double-row self-aligning roller bearing, respectively. [Diagram 5] 13 is a graph showing the results of an analysis of the distribution of contact surface pressure on the front rollers when a combined axial load and radial load are applied to multiple types of double-row self-aligning roller bearings each having a different ratio of contact angles between the rollers in both rows. [Figure 6]13 is a graph showing the results of an analysis of the distribution of contact surface pressure on the rear rollers when a combined axial load and radial load are applied to multiple types of double-row self-aligning roller bearings each having a different ratio of contact angles between the rollers in both rows. [Figure 7] FIG. 1 is a diagram showing the ratio of roller length to bearing width for a plurality of conventional double-row self-aligning roller bearings on the same drawing. [Figure 8] FIG. 2 is a partially cutaway perspective view of an example of a main shaft support device for a wind turbine generator. [Figure 9] FIG. [Figure 10] FIG. 4 is a cross-sectional view of a double-row self-aligning roller bearing according to another embodiment of the present invention. [Figure 11] 3 is an explanatory diagram showing the configuration of a DLC coating on the surface of a roller in the double-row self-aligning roller bearing according to the embodiment of the present invention. FIG. [Figure 12] FIG. 2 is a perspective view showing an example of a cage used in the double-row self-aligning roller bearing according to each of the embodiments. [Figure 13] 1 is a partially enlarged broken plane view of the cage. [Figure 14] FIG. 4 is a cross-sectional view showing the relationship between pockets and rollers of the cage. [Figure 15] FIG. [Figure 16] FIG. [Figure 17] FIG. 4 is a cross-sectional view of a pillar portion of the cage. [Figure 18] FIG. [Figure 19] FIG. 11 is a partial perspective view of a modified example of the cage. [Figure 20] FIG. 1 is a cross-sectional view of a conventional general double-row self-aligning roller bearing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] A double-row self-aligning roller bearing (hereinafter, sometimes simply referred to as "bearing") 1 according to a first embodiment of the present invention will be described with reference to FIG. 1. This double-row self-aligning roller bearing 1 has two left and right rows of rollers 4, 5 arranged in the bearing width direction (axial direction) interposed between an inner ring 2 and an outer ring 3. A raceway surface 3a of the outer ring 3 is spherical, and the outer peripheral surfaces of the left and right rows of rollers 4, 5 have a cross-sectional shape that follows the raceway surface 3a of the outer ring 3. In other words, the outer peripheral surfaces of the rollers 4, 5 are revolution curved surfaces formed by rotating an arc that follows the raceway surface 3a of the outer ring 3 around center lines C1, C2. The inner ring 2 is formed with double-row raceway surfaces 2a, 2b with a cross-sectional shape that follows the outer peripheral surfaces of the left and right rows of rollers 4, 5. Flanges (small flanges) 6, 7 are provided on both ends of the outer peripheral surface of the inner ring 2, respectively. A center rib 8 is provided at the center of the outer circumferential surface of the inner ring 2, i.e., between the left row of rollers 4 and the right row of rollers 5. Note that the terms "left" and "right" in this specification are merely terms used for convenience to indicate the relative positional relationship in the axial direction of the bearing. In this specification, "left" and "right" are used for ease of understanding. To make it easier to understand, the left and right sides are aligned in each figure.

[0021] The left and right rows of rollers 4, 5 are retained by cages 10L, 10R, respectively. The cage 10L for the left row has multiple bar portions 12 extending leftward from the annular portion 11, and the left row of rollers 4 are retained in pockets between these bar portions 12. The cage 10R for the right row has multiple bar portions 12 extending rightward from the annular portion 11, and the right row of rollers 5 are retained in pockets between these bar portions 12.

[0022] As shown in an exaggerated manner in Figure 2, the rollers 4, 5 in each row on the left and right are asymmetric rollers in that the positions of their maximum diameters D1max, D2max are both off-center A1, A2 of the roller length. The position of the maximum diameter D1max of the left row roller 4 is to the right of the center A1 of the roller length, and the position of the maximum diameter D2max of the right row roller 5 is to the left of the center A2 of the roller length. An induced thrust load is generated in the rollers 4, 5 in each row on the left and right, which are made up of such asymmetric rollers. The center rib 8 of the inner ring 2 is provided to receive this induced thrust load. The combination of the asymmetric rollers 4, 5 and the center rib 8 provides good guiding precision, as the rollers 4, 5 are guided at three points, the inner ring 2, the outer ring 3, and the center rib 8.

[0023] As shown in FIG. 1, the contact angles of the rollers 4, 5 in both rows are greater than 0° and are different from each other. In this example, the contact angle θ2 of the rollers 5 in the right row is greater than the contact angle θ1 of the rollers 4 in the left row. The ratio of the contact angle θ1 of the rollers 4 in the left row to the contact angle θ2 of the rollers 5 in the right row is set to 1:2 to 1:4, that is, within the range of 0.25≦θ1 / θ2≦0.5. The most preferable ratio of the contact angles θ1, θ2 is 1:3 (θ1 / θ2=0.333). The reason for this will be described later. Specifically, the range of the contact angle θ1 is, for example, 3° to 6°, and preferably θ1=5°. The range of the contact angle θ2 is, for example, 12° to 18°, and preferably θ2=15°.

[0024] Furthermore, the left row rollers 4 and the right row rollers 5 have the same maximum diameters D1max, D2max, but different lengths L1, L2 along the center lines C1, C2. It is preferable that the length L2 of the longer roller 5 is 39% or more of the bearing width (the distance in the bearing width direction from the bearing end face E1 on the left row side to the bearing end face E2 on the right row side) B. It is also acceptable for the length L1 of the left row rollers 4 and the length L2 of the right row rollers 5 to be equal. However, as in the illustrated example, by making the length L2 of the rollers in the row with a larger contact angle longer than the length L1 of the rollers in the row with a smaller contact angle, the load capacity of the rollers in the row with a larger contact angle against axial loads is further improved.

[0025] The position in the bearing width direction of the intersection P of the two lines of action S1, S2 that form the contact angles θ1, θ2 of both rows is shifted by a distance K toward the roller 4 with the smaller contact angle from the center position Q of the center rib 8 in the bearing width direction. This makes it possible to increase the contact angle θ2 of the long roller 5 without making the long roller 5 longer than necessary. The lines of action S1, S2 are lines on which the resultant force acts on the contact points between the rollers 4, 5 and the inner ring 2 and the outer ring 3. The point P where the lines of action S1, S2 intersect is located on the bearing central axis O.

[0026] More specifically, the bearing widthwise position of intersection P is set so that the ratio of the bearing widthwise distance B1 from the bearing end face E1 on the left row side, which has the smaller contact angle, to the intersection point P, to the bearing widthwise distance B2 from the bearing end face E2 on the right row side, which has the larger contact angle, to intersection point P, is within the range of 0.5≦B1 / B2≦0.6.

[0027] Bearing 1 of this configuration receives axial and radial loads and is used in applications where loads of different magnitudes act on the left and right roller rows, such as a main shaft support bearing for a wind turbine generator. In such cases, bearing 1 is installed so that the left row of rollers 4 are located on the side closer to the swivel blade (front side: left side in Fig. 1) and the right row of rollers 5 are located on the far side (rear side: right side in Fig. 1). In this case, the axial load Fa from the main shaft is applied in the direction from the front side to the rear side. As a result, the right row of rollers 5, which have the larger contact angle θ2, bear almost all of the axial load and a portion of the radial load, and the left row of rollers 4, which have the smaller contact angle θ1, bear the remainder of the radial load.

[0028] By setting the ratio of the bearing width direction distances B1 and B2 in the range of 0.5≦B1 / B2≦0.6, the length L1 of the left row of rollers, which bears almost only radial loads, is not excessively short within the range of the standard dimensions. If the length of one row of rollers is excessively short, the load capacity of the rollers becomes insufficient, and when an extremely large load such as an extreme load is applied from the radial direction, edge stress occurs at both ends of the rollers, causing a decrease in life. However, in the bearing 1 according to this embodiment, even for extreme loads that must be assumed to be loaded from various directions, it is possible to avoid the insufficient load capacity of the rollers in one row. Therefore, according to this bearing 1, it is possible to appropriately share the load between the rollers in both rows for both fatigue loads and extreme loads within the constraints of the dimensional standards.

[0029] Furthermore, as described above, it is preferable that the roller length L2 of one row (the right row in this example) is longer than the roller length L1 of the other row (the left row in this example), but it is more preferable that the ratio of L1 to L2 is in the range 0.9≦L1 / L2<1.0 so that the roller length L1 of the left row is not excessively short.

[0030] The reason for setting the ratio of the contact angles of the rollers in the range of 0.25 to 0.5 is explained below. For a conventional double-row self-aligning roller bearing 41 shown in Fig. 10 and a double-row self-aligning roller bearing 1 of the present invention shown in Fig. 1, the contact pressure of the rollers in both the left and right rows under a combined axial and radial load assumed when used as a bearing for supporting the main shaft of a wind turbine generator was analyzed. Fig. 3 shows the contact pressure distribution of the front side, i.e., the left row of rollers 44,4, and Fig. 4 shows the analytical distribution of the contact pressure of the rear side, i.e., the right row of rollers 45,5.

[0031] The results shown in Figures 3 and 4 reveal the following. With the conventional product in Figure 10, the contact pressure is low on the front side and high on the rear side, resulting in uneven load distribution between the front and rear sides. In contrast, with the product with the changed contact angle in Figure 1, contact pressure is generated across the entire lever on the front side, lowering the maximum contact pressure on the rear side and reducing the difference in contact pressure between the two rows, making it more equal.

[0032] Additionally, in the same manner as above, the contact pressure of the left and right rows of rollers was analyzed for three types of double-row spherical roller bearings each having a different ratio of contact angle θ1 of left row rollers 4 to contact angle θ2 of right row rollers 5. Figure 5 shows the distribution of contact pressure analysis results for the front side, i.e., left row rollers 4, and Figure 6 shows the distribution of contact pressure analysis results for the rear side, i.e., right row rollers 5. The product with a contact angle ratio of 1:1 is a conventional product, while the products with contact angle ratios of 1:2 and 1:3 are products with modified contact angles according to the present invention.

[0033] The results shown in Figures 5 and 6 reveal the following. Comparing the contact pressure distribution for each contact angle ratio, the contact angle ratio of 1:3 has the most equalized contact pressure between the front and rear sides. The contact angle ratio of 1:2 is not as equalized as the contact angle ratio of 1:3, but is sufficiently equalized compared to the contact angle ratio of 1:1. As can be seen from Figure 1, when the contact angle θ2 of roller 5 becomes large, the thickness of inner ring 2 becomes too thin due to dimensional constraints, making it difficult to arrange rollers 5 that are long in length. For these reasons, it is desirable for the contact angle ratio to be between 1:2 and 1:4.

[0034] The assumed axial and radial loads refer to the axial and radial loads that are fatigue loads when an average wind turbine generator is operating most normally, taking into account various conditions such as power generation capacity and installation location. In double-row spherical roller bearings used in wind power generation equipment with different conditions, the optimum contact angle ratio may not be 1:3, but even in such cases, the optimum contact angle ratio falls within the range of 1:2 to 1:4.

[0035] Furthermore, although it is not essential, by adding the condition that the length L2 of the longer roller 5 be 39% or more of the bearing width B, a double-row spherical roller bearing can be obtained in which the ratio of the contact angles of the rollers in both rows is set as above within the range of the dimensional standard. The ratio of the length L2 of roller 5 to the bearing width B was investigated for conventional double-row spherical roller bearings. As a result, it was found that the ratio was 39% or more, as shown in Figure 7. The above dimensional standard specifies the inner diameter, outer diameter, and bearing width.

[0036] 8 and 9 show an example of a main shaft support device for a wind power generator. A casing 23a of a nacelle 23 is installed on a support base 21 via a swivel bearing 22 (FIG. 9) so as to be horizontally rotatable. A main shaft 26 is installed in the casing 23a of the nacelle 23 so as to be rotatable via a main shaft support bearing 25 installed in a bearing housing 24, and a blade 27 serving as a swivel blade is attached to a part of the main shaft 26 protruding outside the casing 23a. The other end of the main shaft 26 is connected to a speed increaser 28, and an output shaft of the speed increaser 28 is coupled to a rotor shaft of a generator 29. The nacelle 23 is rotated at an arbitrary angle by a swivel motor 30 via a reducer 31. In the illustrated example, two main shaft support bearings 25 are installed side by side, but one may be used.

[0037] 10 and 11 show another embodiment of the present invention. This embodiment is similar to the first embodiment except for the matters specifically described. In double row self-aligning roller bearing 1 of this embodiment, inclination angle β2 of cage 10R which holds rollers 5 of the other row is expressed by the following formula with respect to roller maximum diameter angle α2 which is the inclination angle at the position where rollers 5 of the other row form a maximum diameter: 0≦β2≦α2 The relationship is as shown below. In addition, when the pocket surface 12a of the column portion 12 of the retainer 10R is a cylindrical surface, the "inclination angle β2 of the retainer 10R" is, for example, an angle that the center line C2 of the cylindrical surface forms with the center of the retainer (the central axis O of the bearing). The "inclination angle β2 of the retainer" may be the inclination angle of the outer diameter surface of the retainer 10R or the inclination angle of the inner diameter surface of the retainer 10R.

[0038] Since the maximum diameter angle α2 of the rollers 5 in the other row, i.e., the rollers 5 in the rear row relative to the input direction of the axial load, is large, a retainer inclination angle β2 may be set so that the pocket surface 12a of the retainer 10R embraces the maximum diameter position of the rollers 5. In this case, 0≦β2≦α2 By so doing, the posture stability of the rollers 5 is not impaired. Moreover, by using such a shape for the cage 10R, it is possible to prevent a decrease in ease of assembly that is specific to the left-right asymmetric design, and to stably hold the rollers 5.

[0039] Each row of rollers 4, 5 has a DLC coating 9 with a multi-layer structure (three or more layers) on its outer circumferential surface. The raceway surfaces 2a, 2b, 3a of the inner ring 2 and the outer ring 3 may also be provided with a DLC coating 9 in the same manner as the rollers 4, 5, but here we will explain the DLC coating 9 on the rollers 4, 5. The film thickness of this DLC coating 9 is 2.0 μm or more. In this embodiment, the DLC coating 9 is made up of three layers, consisting of a base layer 9a, a mixed layer 9b, and a surface layer 9c, in that order from the base material side of the rollers 4, 5, as shown diagrammatically in Figure 11, which illustrates the cross section of the DLC coating 9 on the rear roller 5. The surface roughness of the outer surface of the base material of the rollers 4, 5 is, in terms of arithmetic roughness Ra and root mean square slope RΔq, Ra≦0.3 and RΔq≦0.05. It is. The layers 9a, 9b, and 9c in the multi-layered DLC coating 9 have a film hardness that increases stepwise from the outer layer side to the outer layer side.

[0040] Wear resistance is improved by applying a DLC coating to the outer peripheral surfaces of the rollers 4 and 5. Applying the DLC coating 9 improves wear resistance, but it is necessary to ensure peeling resistance. This is improved by adopting the following configuration. The DLC coating 9 adopts a multi-layer structure that has excellent adhesion to the base material. The film thickness is preferably 2.0 μm or more. In addition, aggressiveness to the mating material can be mitigated by setting the roughness value of the outer peripheral surface to which the DLC coating 9 is applied to 0.3 Ra or less in arithmetic mean roughness Ra and 0.05 or less in root-mean-square slope RΔq. Furthermore, the film hardness of the DLC coating 9 can be increased stepwise in a multi-layer structure, thereby obtaining high adhesion.

[0041] The materials of the rollers 4, 5, etc., and the DLC coating 9 will be specifically described. The rollers 4, 5, inner ring 2, and outer ring 3 are made of an iron-based material. As the iron-based material, any steel material generally used as a bearing member can be used, and examples thereof include high carbon chromium bearing steel, carbon steel, tool steel, martensitic stainless steel, etc. In these bearing members, the surface on which the DLC coating 9 is formed preferably has a Vickers hardness of Hv650 or more. By making the hardness Hv650 or more, the difference in hardness with the DLC coating 9 (undercoat layer) can be reduced, and adhesion can be improved.

[0042] It is preferable that a nitride layer is formed by nitriding treatment on the surfaces of the rollers 4, 5 on which the DLC coating 9 is formed, before the coating is formed. As the nitriding treatment, it is preferable to carry out plasma nitriding treatment, which is unlikely to produce an oxide layer that hinders adhesion on the base material surface. In addition, it is preferable that the surface hardness after the nitriding treatment is Hv1000 or more in Vickers hardness in order to further improve adhesion with the DLC coating 9 (undercoat layer).

[0043] The surface of the base material on which the DLC coating 9 of the rollers 4 and 5 is formed, that is, the surface on which the undercoat layer 9a is formed, has an arithmetic mean roughness Ra of 0.1 to 0.3 μm and a root-mean-square slope RΔq of 0.05 or less. RΔq is preferably 0.03 or less, more preferably 0.02 or less. The arithmetic mean roughness Ra and the root-mean-square slope RΔq are values ​​calculated in accordance with JIS B0601 and are measured using a contact or non-contact surface roughness meter or the like. Specific measurement conditions are a measurement length of 4 mm and a cutoff of 0.8 mm. By making the root-mean-square slope RΔq of the base material surface 0.05 or less, the peaks in the roughness curve become gentler, the radius of curvature of the protrusions becomes larger, and the local surface pressure can be reduced. Furthermore, during film formation, electric field concentration at the micro level due to roughness can be suppressed, localized changes in film thickness and hardness can be prevented, and the peeling resistance of the hard film can be improved.

[0044] The maximum peak height Rp obtained from the roughness curve of the base material surface is preferably 0.4 μm or less. The maximum peak height Rp is calculated in accordance with JIS B 0601. The relationship between the maximum peak height Rp obtained from the roughness curve and the arithmetic mean roughness Ra is preferably 1≦Rp / Ra≦2, and more preferably 1.2≦Rp / Ra≦2.

[0045] In addition, the skewness Rsk obtained from the roughness curve of the base material surface is preferably negative. Rsk is an index of the degree of distortion, and is more preferably -0.2 or less. Skewness Rsk is a quantitative expression of the up-down symmetry of the amplitude distribution curve centered on the average line, that is, an index showing the bias of the surface roughness with respect to the average line. Skewness Rsk is calculated in accordance with JIS B0601. A negative skewness Rsk means that the roughness shape is downwardly convex (valley), and there are many flat parts on the surface. As a result, it can be said that the surface has few convex parts and is less likely to cause stress concentration due to protrusions. In addition, one method for reducing roughness is to remove surface protrusions by collision with polishing media, such as barrel polishing, but depending on the processing conditions, new protrusions may be formed, and Rsk may turn positive, so caution is required. be.

[0046] FIG. 11 is a schematic cross-sectional view showing the structure of the DLC coating 9. As shown in the figure, the DLC coating 9 has a three-layer structure consisting of (1) a base layer 9a mainly made of Cr and WC formed directly on the surfaces of the rollers 4 and 5, (2) a mixed layer 9b mainly made of WC and DLC formed on the base layer 9a, and (3) a surface layer 9c mainly made of DLC formed on the mixed layer 9b. Here, the mixed layer 9b is a layer in which the WC content in the mixed layer decreases continuously or stepwise from the base layer 9a side to the surface layer 9c side, and the DLC content in the mixed layer increases. In this embodiment, the DLC coating 9 has a three-layer structure as described above, thereby avoiding a sudden change in physical properties (hardness, elastic modulus, etc.).

[0047] Since the underlayer 9a contains Cr, it is compatible with the base material made of cemented carbide material or iron-based material, and has excellent adhesion to the base material compared to cases where W, Ti, Si, Al, etc. are used. In addition, the WC used in the underlayer 9a has intermediate hardness and elastic modulus between Cr and DLC, and is less likely to cause concentration of residual stress after film formation. In addition, it is preferable that the underlayer 9a has a gradient composition in which the Cr content is smaller and the WC content is higher from the roller surface side to the mixed layer 9b side. This results in excellent adhesion on both sides between the roller surface and the mixed layer 9b.

[0048] The mixed layer 9b is an intermediate layer interposed between the underlayer and the surface layer. As described above, the WC used in the mixed layer 9b has intermediate hardness and elastic modulus between Cr and DLC, and is less likely to cause concentration of residual stress after film formation. The mixed layer 9b has a gradient composition in which the WC content is small and the DLC content is high from the underlayer 9a side to the surface layer 9c side, so that the adhesion between the underlayer 9a and the surface layer 9c is excellent. In addition, the mixed layer has a structure in which WC and DLC are physically bonded, so that damage in the mixed layer can be prevented. Furthermore, the DLC content is increased on the surface layer 9c side, so that the adhesion between the surface layer 9c and the mixed layer 9b is excellent. The mixed layer 9b is a layer in which the highly non-adhesive DLC is bonded to the underlayer 9a side by the anchor effect of WC.

[0049] The surface layer 9c is a film mainly made of DLC. It is preferable that the surface layer 9c has a gradient layer portion 9d on the side adjacent to the mixed layer 9b, in which the hardness increases continuously or stepwise from the mixed layer 9b side. This is a portion obtained by changing (raising) the bias voltage continuously or stepwise in order to avoid a sudden change in the bias voltage when the bias voltage is different between the mixed layer 9b and the surface layer 9c. By changing the bias voltage in this way, the gradient layer portion 9d has a gradient in hardness as described above. The reason why the hardness increases continuously or stepwise is that the composition ratio of the graphite structure (sp2) and the diamond structure (sp3) in the DLC structure becomes biased toward the latter as the bias voltage increases. This eliminates a sudden difference in hardness between the mixed layer and the surface layer, and the adhesion between the mixed layer 9b and the surface layer 9c is further improved.

[0050] The thickness of the DLC coating 9 (total of the three layers) is preferably 0.5 to 3.0 μm. If the thickness is less than 0.5 μm, the abrasion resistance and mechanical strength may be poor, and if it exceeds 5.0 μm, it becomes easy to peel off. Furthermore, it is preferable that the ratio of the thickness of the surface layer 9c to the thickness of the DLC coating 9 is 0.8 or less. If this ratio exceeds 0.8, the gradient structure for physically bonding WC and DLC in the mixed layer 9b is likely to become discontinuous, and there is a risk of degraded adhesion.

[0051] The DLC coating 9 has a three-layer structure of the underlayer 9a, the mixed layer 9b, and the surface layer 9c having the above-mentioned composition, and thus has excellent peeling resistance.

[0052] 12 to 19 show examples of the rear retainer 10R. 12 to 19 are similar to the rear retainer 10R, and the description thereof will be omitted. The configuration example of the retainer 10R is also applicable to both the first embodiment and the embodiment of FIG.

[0053] In FIG. 12, the column portion 12 of the cage 10R has a basic cross-sectional shape ( The cylindrical pocket surface 12a is removed from a rod-shaped portion (shown by imaginary lines in FIG. 14). and has a tapered portion 13 at its tip. The basic cross-sectional shape is a shape consisting of an outer peripheral surface 12b and an inner peripheral surface 12c, each of which forms a part of a cylindrical surface, and flat side surfaces 12d on both sides extending in the radial direction. The diameter of the cylindrical surface forming the pocket surface 12a is slightly larger than the maximum diameter of the roller 5. The pocket surface 12a is a cylindrical surface centered on the center line C2 (Figs. 1 and 10). As shown in Fig. 17, the center line C2 is inclined with respect to the extension direction of the column portion 12 so that the tip side of the column portion approaches the inner diameter side.

[0054] The outer diameter Do, inner diameter Di, and column length L of the cage 10R shown in FIG. 13 are optimized as follows. The outer diameter Do of the annular portion 11 of the cage 10R is larger than the pitch circle diameter PCD of the arrangement of the rollers 5, and the inner diameter Di of the annular portion 11 is smaller than the pitch circle diameter PCD (FIG. 10). The outer diameter Do of the annular portion 11 is, for example, PCD×102 to 105%. The inner diameter Di of the annular portion 11 is, for example, PCD×95 to 98%. The length L of the pillar portion 12, more specifically, the length L of the portion of the pillar portion 12 that constitutes the pocket 7, is set to 65% or less of the roller length L2 (FIGS. 1 and 10).

[0055] The tapered portion 13 (Figs. 12-13, 15-17) is formed on the outer diameter surface of the tip of the bar portion 12 so as to taper down towards the cage inner diameter side as it approaches the very tip. The tapered portion 13 is on a straight line a (shown by a dashed line in Fig. 15) that forms the maximum diameter angle of the roller 5, or starts further towards the bar portion tip side than this straight line a. In other words, the tapered portion 13 starts on a position M (Fig. 10) that forms the maximum diameter on the center line C2 of the roller 5, or starts further towards the bar portion tip side than this position M.

[0056] The tapered portion 13 is formed in the column portion 12, and the cylindrical pocket surface 12a is inclined with respect to the axial direction in which the column portion 12 extends, so that, as shown in Fig. 16, the column width of the column portion 12 when viewed from the outside in the radial direction of the cage toward the center of the cage is narrowest at W1 at the tip of the column portion 12, which is narrower than the width W2 just before the start of the tapered portion 13. In addition, the radial thickness d (Fig. 17) of the tip surface 12e of the column portion 12 is small.

[0057] The retainers 10L and 10R are made of a material such as bearing steel, other iron-based material, or brass-based material.

[0058] According to the cage 10R having this configuration, the pocket surface 12a of the column portion 12 is a cylindrical surface, so that the rollers 5 can be securely held. In addition, since the tapered portion 13 is formed, the rollers 5 can be easily installed.

[0059] The relationship between the tapered portion 13 and the ease of installation of the rollers 5 will now be described. The center line C2 of the cylindrical surface that forms the pocket surface 12a of the pillar portion 12 is inclined toward the inner diameter side at the tip side with respect to the extension direction of the pillar portion 12. Therefore, as in the example of Figure 19, without the tapered portion 13 (see Figure 18), the pillar portion width when the pillar portion 12 is viewed from the outside in the cage radial direction toward the cage center would be widest at the tip end of the pillar portion. Therefore, the rollers 5 are difficult to install in the pockets 15 because they are hindered by the outer diameter part of the tip of the pillar portion 12, and the wide outer diameter part of the tip of the pillar portion 12 becomes a wasted portion that does not have a good effect on strength or functionality.

[0060] In this embodiment, by forming the tapered portion 13, both the circumferential width W1 (FIG. 16) and the radial thickness d (FIG. 17) of the bar end are small. This improves the ease of installation of the rollers 5 and also reduces the weight of the cage 10R. Because the ease of installation of the rollers 5 is improved, there is no need to significantly deform the cage 10R during installation, and deformation of the cage 10R is prevented.

[0061] Tapered portion 13 is formed so as to eliminate unnecessary portions, so that it does not affect the retention of roller 5, and also from the standpoint of weight reduction, it is preferable to form tapered portion 13. However, if the tapered portion 13 is formed too long, the retention of the roller 5 decreases. Therefore, the tapered portion 13 is designed to start at the position M (FIG. 16) where the roller 5 has the maximum diameter or further toward the tip side of the column portion than this position M, thereby ensuring the retention of the roller 5. From the viewpoint of ease of installation of the rollers 5, the thinner the radial thickness d (Figure 17) of the tip of the tapered portion 13, the better. However, since the pocket surface 12a consisting of a cylindrical surface is formed by drilling from the tip side of the column portion 12, it is necessary to leave a flat surface at the tip, and therefore it is preferable to make it as thin as possible without interfering with processing.

[0062] Although the rear retainer 10R has been described, the structure and effects of the above retainer shape are the same for the front retainer 10L as for the rear retainer 10R. These retainers 10L, 10R may have a shape that does not have a tapered portion 13 at the tip of the column portion 12, as in the example of Figure 19, and further may have a shape in which the center line C2 of the cylindrical surface forming the pocket surface 12a is not inclined with respect to the extension direction of the column portion 12.

[0063] Although the embodiment of the present invention has been described above, the disclosed embodiment is illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0064] 1, 1A, 1B...Double row self-aligning roller bearings 2. Inner circle 3…Outer ring 3a…orbital surface Around 4,5 6,7…Small brim 8...Medium brim 9…DLC coating 11...Ring 12...Column part 13...Tapered section 15…Pocket 26...Spindle A1, A2: Center of roller length B…Bearing width B1, B2: Distance in the bearing width direction from the end face of the bearing to the intersection point of the lines of action D1max, D2max: Maximum diameter E1, E2: Bearing end faces L1, L2...Roller length P: Intersection of lines of action θ1, θ2…Contact angle

Claims

1. With the inner circle, an outer ring having a spherical raceway; a plurality of rollers arranged in two rows in a bearing width direction and interposed between the inner ring and the outer ring, a double-row self-aligning roller bearing, wherein each of the two rows of rollers has an outer peripheral surface having a cross-sectional shape that conforms to a raceway surface of the outer ring, the ratio of the contact angle θ1 of the rollers in one row to the contact angle θ2 of the rollers in the other row is in the range of 0.25≦θ1 / θ2≦0.5; a ratio of a distance B1 in the bearing width direction from the bearing end surface on the one row side to an intersection of two action lines forming a contact angle between both rows to a distance B2 in the bearing width direction from the bearing end surface on the other row side to the intersection is in a range of 0.5≦B1 / B2≦0.6; Double row self-aligning roller bearing.

2. A double-row self-aligning roller bearing as described in claim 1, wherein the ratio of the roller length L1 of one row to the roller length L2 of the other row is in the range 0.9≦L1 / L2≦1.

0.

3. In the double row self-aligning roller bearing according to claim 1 or 2, the inclination angle β2 of the cage which holds the rollers of the other row is expressed by the following formula with respect to the roller maximum diameter angle α2 which is the inclination angle at the position where the rollers of the other row have a maximum diameter: ０≦β２≦α２ A double-row self-aligning roller bearing having the relationship shown in

4. A double-row self-aligning roller bearing according to any one of claims 1 to 3, wherein each of the rollers has a multi-layer DLC coating on its outer circumferential surface, The DLC coating has a thickness of 2.0 μm or more, The surface roughness of the outer surface of the base material of the roller is Ra≦0.3 and RΔq≦0.05 and The multi-layered DLC coating has a hardness of each layer that is gradually increased from the outer layer toward the outer layer.

5. A double-row self-aligning roller bearing as described in any one of claims 1 to 4, which is used to support the main shaft of a wind turbine generator.

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