Angular ball bearing

Abstract

Provided is an angular ball bearing configured to have an increased number of balls and capable of preventing a decrease in the strength of the entire retainer including a column part. An angular ball bearing (1) is provided with an inner race (2), an outer race (3), a plurality of balls (4) interposed between the inner race (2) and the outer race (3), and an annular retainer (5) having pockets (Pt) for retaining the balls (4). In the retainer (5), each of the pockets (Pt) includes annular parts (7, 8) and a column part (6). The retainer (5) is configured so that the inside diameter or the outside diameter of the column part is in the range of 8% to 50% inclusive of the ball diameter (φDa) from the pitch circle center (P4) of the balls (4). Further, T / dp × 100 is in the range of 0.40 to 1.50 inclusive, where dp denotes the pitch circle diameter of the balls (4), and T denotes the dimension of a part having the narrowest column width in the circumferential direction of the column part (6).

Description

Angular contact ball bearings Related Applications

[0001] This application claims priority from Japanese Patent Application No. 2024-111681, filed July 11, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an angular contact ball bearing, and more particularly to an angular contact ball bearing with a separable outer ring, used for example as a main bearing portion of a reduction gear device for an industrial robot or the like.

[0003] Eccentric oscillating reducers are commonly used in the joints of industrial robots. The bearings used in reducers may be, for example, angular contact ball bearings with a separable outer ring. When incorporating angular contact ball bearings into reducers, the outer ring may be separated and first incorporated into the case, and the inner ring may be incorporated into the shaft or flange, which may then be combined with the outer ring incorporated into the case.

[0004] Previously, an angular contact ball bearing was proposed in which the outer diameter of the counterbore of the inner ring and the diameter of the ball inscribed circle when the balls are assembled in a synthetic resin cage were controlled (Patent Document 1). By controlling the diameters in this way, the inner ring, balls, and cage are kept integral, improving the ease of assembly using the above assembly method.

[0005] In the case of retainers used in full-ball angular contact ball bearings, openings are provided between each pocket on the pitch circle of the balls, making it possible to use the retainer with full-ball angular contact ball bearings (Patent Document 2).

[0006] Patent No. 4824457 Publication JP-A-8-296650

[0007] In recent years, one of the measures to meet the demand for greater moment rigidity and longer life for bearings used in reducers has been to increase the number of balls. When the number of balls is increased, the total weight of the balls increases. As a result, when the weight of the balls acts on the cage, the cage deforms, causing the balls to overcome the inner ring counterbore diameter, resulting in separation of the inner ring, balls, and cage. Furthermore, with conventional synthetic resin cages, increasing the number of pockets to accommodate a larger number of balls results in thinner cage columns, which reduces the strength of the cage columns.

[0008] An object of the present invention is to provide an angular contact ball bearing that allows an increase in the number of balls while preventing a decrease in the strength of the entire cage including the posts.

[0009] The angular contact ball bearing of the present invention comprises an inner ring, an outer ring, a plurality of balls interposed between the inner ring and the outer ring, and an annular resin cage that holds the balls, the cage having a pair of annular portions and a plurality of column portions connecting the annular portions, and having pockets formed by the annular portions and the column portions that hold the balls, the cage being characterized in that, in a radial cross section, the column portions do not overlap with the pitch circle centers of the balls, and the shortest distance from the pitch circle center of the balls to the column portions is between 8% and 50% of the ball diameter. The "radial cross section" is a cross section of the cage seen by cutting it along an imaginary plane that includes the axial direction of the cage, a so-called longitudinal cross section.

[0010] In the cage, the bar portions do not overlap the pitch circle center of the ball in a radial cross section, and the shortest distance from the pitch circle center of the ball to the bar portions is 8% to 50% of the ball diameter. In other words, the inner or outer diameter of the bar portions of the cage is in the range of 8% to 50% of the ball diameter from the pitch circle center of the ball. With this configuration, the inner or outer diameter of the bar portions is 8% to 50% of the ball diameter from the pitch circle center of the ball. This allows for an increase in the number of balls while preventing a decrease in the strength of the entire cage, including the bar portions. If the inner or outer diameter of the bar portions is less than 8% of the ball diameter from the center of the ball, the thinnest part of the circumferential bar width of the bar portions becomes too thin, resulting in a decrease in the strength of the bar portions compared to conventional structures. If the inner or outer diameter of the bar portions is more than 50% of the ball diameter from the center of the ball, the radial thickness of the cage becomes thin, resulting in a decrease in the strength of the entire cage compared to conventional structures.

[0011] If the pitch circle diameter of the balls is dp and the dimension T is the thinnest part of the circumferential column width of the column portion, T / dp x 100 may be 0.40 or more and 1.50 or less. In this case, the rigidity of the thinnest part of the column portion can be ensured and a decrease in the strength of the entire cage can be more reliably prevented. If the ratio of T to dp is less than 0.40%, the thinnest part may be too thin, and the strength of the column portion may be lower than that of a conventional structure. If the ratio of T to dp is greater than 1.50, the radial thickness of the cage may be thin, and the strength of the entire cage may be lower than that of a conventional structure.

[0012] The ball packing rate may be 88% or more and 96% or less. The ball packing rate is calculated using the following formula: Packing rate = (ball diameter x number of balls) / (pitch circle diameter x π) By setting the ball packing rate to 88% or more and 96% or less, it is possible to satisfy the required rated load and prevent interference between the balls during operation. If the ball packing rate is less than 88%, the number of balls is too small to satisfy the required rated load. If the ball packing rate is more than 96%, the distance between the balls becomes small, causing interference between the balls during operation.

[0013] The inner peripheral surface of the cage may be provided with claws that protrude radially inward, and an inner ring counterbore portion on the outer peripheral surface of the inner ring may be provided with an annular recess and a filling groove that allows the claws to pass into the bearing. The raceway surface of the inner ring is connected to the front surface of the inner ring via the inner ring counterbore portion. The front surface of the inner ring refers to the side surface that does not support axial loads. The inside of the bearing is synonymous with the bearing space between the inner and outer rings.

[0014] With this configuration, even if the cage is deformed by the weight of the balls and the balls unexpectedly go over the inner race counterbore, the claws of the cage will catch on the recesses in the inner race counterbore, preventing the cage and balls from separating from the inner race.

[0015] The outer peripheral surface of the cage may be provided with claws that protrude radially outward, and an outer ring counterbore portion on the inner peripheral surface of the outer ring may be provided with an annular recess and a filling groove that allows the claws to pass into the bearing. The raceway surface of the outer ring is connected to the front surface of the outer ring via the outer ring counterbore portion. The front surface of the outer ring refers to the side surface that does not support the axial load.

[0016] When the outer ring, balls, and cage are integrated, even if the cage is deformed by the weight of the balls and the balls unexpectedly climb over the outer ring counterbore, the claws on the cage will catch on the recesses in the outer ring counterbore, preventing the cage and balls from separating from the outer ring.

[0017] A plurality of the filling grooves may be provided, and the plurality of filling grooves may be arranged at equal intervals in the circumferential direction.

[0018] A plurality of the claws may be provided, and these claws may be evenly spaced in the circumferential direction. In this case, the load acting on the contact points between the claws of the cage and the recesses of the inner ring can be evenly distributed in the circumferential direction, thereby enabling the cage and balls to be stably held.

[0019] The claws may be provided in two or more rows at different axial positions, and the claws in different rows may be arranged at different phases in the circumferential direction. When the inner ring, balls, and cage are integrated, it may be possible for the circumferential phase of the claws in the first row to match the circumferential phase of the filling groove in the inner ring counterbore, causing the claws in the first row to pass through the filling groove. Even in this case, the claws in the second row will catch on the recesses in the inner ring, preventing separation of the inner ring, balls, and cage.

[0020] Any combination of at least two features disclosed in the claims and / or the specification and / or the drawings is included in the present invention. In particular, any combination of two or more of the claims is included in the present invention.

[0021] The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are merely for illustration and explanation, and should not be used to define the scope of the present invention, which is defined by the appended claims. In the accompanying drawings, the same reference numerals in multiple drawings indicate the same or corresponding parts.

[0022] 9A is a longitudinal sectional view of an angular contact ball bearing according to a first embodiment of the present invention; FIG. 9B is a longitudinal sectional view showing a post relief portion of a cage in the angular contact ball bearing; FIG. 9C is a partial sectional view of a conventional cage taken along a plane perpendicular to the axial direction; FIG. 9D is a partial sectional view of the cage of the angular contact ball bearing according to the first embodiment taken along a plane perpendicular to the axial direction; FIG. 9E is a perspective view of a part of the cage taken from the inner diameter side; FIG. 9F is a perspective view of a part of the cage taken from the inner diameter side when a pocket is cut; FIG. 9G is a perspective view of a part of the cage taken from the outer diameter side when a pocket is cut; FIG. 9H is a partial sectional view of a main part illustrating the post width of the cage; FIG. 9H is a partial sectional view of a main part showing that a part of the post portion of the cage is on the pitch circle diameter; FIG. 9I is a partial sectional view of a main part showing that a part of the post portion of the cage is on the pitch circle diameter; FIG. 9I is a partial sectional view of a main part of the cage taken along a pitch circle diameter; FIG. 10B is a longitudinal sectional view of an angular contact ball bearing according to a fifth embodiment of the present invention. FIG. 10C is a longitudinal sectional view of the angular contact ball bearing at a different phase from FIG. 10A. FIG. 10D is a plan view of the cage of the angular contact ball bearing as seen from the axial direction. FIG. 10E is a partially enlarged view showing the claw portions of the cage. FIG. 10F is a perspective view of a main part of the cage showing the positional relationship of the claw portions. FIG. 10G is a longitudinal sectional view illustrating a method of assembling an inner ring assembly including an inner ring, balls and a cage of the angular contact ball bearing. FIG. 10H is a longitudinal sectional view of a stage during assembly of the inner ring assembly. FIG. 10I is a longitudinal sectional view illustrating the function of the first row of claw portions when assembling the inner ring assembly. FIG. 10I is a longitudinal sectional view of an outer ring assembly of an angular contact ball bearing according to a sixth embodiment of the present invention.

[0023] [First embodiment] An angular contact ball bearing according to an embodiment of the present invention will be described with reference to Figures 1 to 5B. This angular contact ball bearing is used, for example, as a main bearing portion of a reducer for an industrial robot or the like. Examples of the reducer include an eccentric differential reducer, a strain wave gear reducer, and a planetary gear reducer. In this specification, the angular contact ball bearing may be simply referred to as a "bearing."

[0024] <Overall configuration of angular contact ball bearing> As shown in Figure 1, an angular contact ball bearing 1 comprises an inner ring 2, an outer ring 3, a plurality of balls 4 interposed between the inner ring 2 and the outer ring 3, and an annular resin cage 5 in which pockets Pt for holding the balls 4 are formed. The cage 5 has a pair of annular portions 7, 8 and a plurality of column portions 6 connecting the annular portions 7, 8, and the pockets Pt are made up of the pair of annular portions 7, 8 and the column portions 6. Note that the resin cage 5 may also be simply referred to as the cage 5. The angular contact ball bearing 1 in this example is a type in which the outer ring 3 is separated in the axial direction.

[0025] For example, when incorporating the angular contact ball bearing 1 into a reducer or the like, the outer ring 3 is separated and first incorporated into a case (not shown), and the inner ring 2 is then incorporated into a shaft or flange (not shown). The inner ring assembly, which integrates the inner ring 2, balls 4, and cage 5, is then combined with the outer ring 3 incorporated into the case, thereby assembling the angular contact ball bearing 1. The inner and outer rings 2 and 3 are made of, for example, high-carbon chromium bearing steel such as SUJ2 specified in JIS G 4805, which conforms to ISO 100Cr6, or martensitic stainless steel. The balls 4 are made of, for example, steel balls or ceramics.

[0026] The direction along the bearing center line C1 of the angular contact ball bearing 1 or the direction parallel to the bearing center line C1 is referred to as the "axial direction." The direction perpendicular to the "axial direction" is referred to as the "radial direction." The circumferential direction around the center axis is referred to as the "circumferential direction."

[0027] The raceway surface 3a is connected to the front surface of the outer ring 3 via the inner peripheral surface. The inner peripheral surface 3d on the back surface side of the outer ring 3 is located radially inward of the inner peripheral surface on the front surface side of the outer ring 3. The raceway surface 2a is connected to the front surface of the inner ring 2 via an inner ring counterbore portion 2b. The outer peripheral surface 2d on the back surface side of the inner ring 2 is formed between the raceway surface 2a of the inner ring 2 and the back surface 2c of the inner ring 2. This outer peripheral surface 2d on the back surface side is located radially outward of the counterbore 2b, which is the outer peripheral surface on the front surface side of the inner ring 2. The front surface of the inner and outer rings 2, 3 refers to the side surface on the side that does not support an axial load, and the back surfaces 2c, 3c of the inner and outer rings 2, 3 refer to the side surface on the side that supports an axial load.

[0028] 2 and 3C , the cage 5 is made of synthetic resin and formed in a tapered cylindrical annular shape, with pockets Pt, which are window-shaped holes that hold the balls 4, provided in the axially middle portion of the cage 5. The cage 5 holds the balls 4 in the pockets Pt. The cage 5 includes a column portion 6, a small-diameter annular portion 7, and a large-diameter annular portion 8, which are integrally formed. The phrase "integrally formed" means that the column portion 6, the small-diameter annular portion 7, and the large-diameter annular portion 8 are not formed by combining multiple elements but are molded as part or the whole of a single object from a single material by, for example, injection molding or machining.

[0029] As shown in Fig. 3B, the column portions 6 of the cage 5 are between the pockets Pt, and as shown in Figs. 2 and 3D, they are partition walls that slope radially outward toward one side in the axial direction (the right side in Fig. 2). The inner surfaces of the column portions 6 that face the balls 4 (the shape of the pockets Pt) are formed in a partially spherical shape corresponding to the outer diameter of the balls 4. The small-diameter side annular portion 7 is an annular portion on the smaller diameter side than the pockets Pt, and its inner circumferential surface 7a is formed in a cylindrical shape. As shown in Fig. 3E, the large-diameter side annular portion 8 is an annular portion on the larger diameter side than the pockets Pt, and its outer circumferential surface 8a is formed in a cylindrical shape.

[0030] <Regarding the relationship between the bar portions and the pitch circle diameter of the balls> As shown in Figure 2, the cage 5 has a bar portion relief portion Es, which is a range in the radial cross section of Figure 2 where no bar portions 6 are provided on the pitch circle diameter dp of the balls 4. In other words, the inner diameter surface 6a of the bar portions of the cage is configured to be in a range from 8% to 50% of the ball diameter φDa from the pitch circle center P4 of the balls 4. In other words, as with the conventional cage 50 shown in Figure 3A, the circumferential bar width of the bar portions 51 is thinnest on the pitch circle diameter dp. For this reason, if the number of balls 52 (number of pockets) is increased, the bar width on the pitch circle diameter dp becomes thinner, and the strength of the thinnest part T1 of the cage bar portions decreases.

[0031] 3B, when no column portion 6 is provided on the pitch circle diameter dp, the dimension T, which is the thinnest part of the column width in the circumferential direction of the column portion 6 (hereinafter, sometimes referred to as "column width T"), can be made thicker than in the conventional example (FIG. 3A). This increases the strength of the cage 5 compared to the conventional example, and prevents contact between adjacent balls 4, 4 in the circumferential direction.

[0032] <Definition of cage post width> Assuming that the balls 4 move on the pitch circle diameter dp as shown in Figure 4, the shortest distance between the points of contact between the post portions 6 of the cage 5 and the circumferentially adjacent balls 4, 4 is defined as the post width T. Therefore, as shown in Figures 5A and 5B, if there are no post width T portions within a certain range near the pitch circle diameter dp, there may be post portions that are not in contact with the balls 4.

[0033] <T / dp> As shown in Figure 3B, the dimension T, which is the thinnest part of the circumferential column width of the column portion 6, is 0.40% to 1.50% of the pitch circle diameter dp of the balls 4. In other words, T / dp x 100 is 0.40 or more and 1.50 or less. If the ratio of the column width T to the pitch circle diameter dp is less than 0.40%, the thinnest part will be too thin, and the strength of the column portion 6 may be reduced compared to conventional structures. If the ratio of the column width T to the pitch circle diameter dp is greater than 1.50, the radial thickness of the cage 5 will be thinner, and the strength of the entire cage may be reduced compared to conventional structures.

[0034] <Ball packing rate> The packing rate of the balls 4 is 88% or more and 96% or less. Packing rate = (ball diameter x number of balls) / (pitch circle diameter x π) By setting the packing rate of the balls 4 to 88% or more and 96% or less, it is possible to satisfy the required rated load and prevent interference between the balls 4, 4 during operation. If the packing rate of the balls 4 is less than 88%, the number of balls is too small to satisfy the required rated load. If the packing rate of the balls 4 is more than 96%, the distance between the balls becomes small and interference between the balls 4, 4 occurs during operation.

[0035] <Effects> Table 1 shows the relationship between the inner diameter of the bar portion and the strength of the cage. In Table 1, an "x" in the "Strength of the bar width portion of the cage" column means that there is a problem of reduced strength of the bar width portion, and the bearing usage conditions, cage material, etc. are limited. An "o" in the "Strength of the bar width portion of the cage" column means that the desired strength of the bar width portion is met, and the bearing usage conditions, cage material, etc. are not limited. An "x" in the "Strength of the entire cage" column means that there is a problem of reduced strength of the entire cage, and it is not feasible. An "o" in the "Strength of the entire cage" column means that the desired strength of the entire cage is met, and it is feasible.

[0036]

[0037] In the angular contact ball bearing 1 of Figure 2 described above, the inner diameter surface 6a of the cage bar portion is in the range of 8% to 50% of the ball diameter φDa from the pitch circle center P4 of the balls 4. This allows for an increase in the number of balls while preventing a decrease in the strength of the entire cage, including the bar portion 6. If the inner diameter surface 6a of the cage bar portion is in the range of less than 8% of the ball diameter φDa from the pitch circle center P4 of the balls 4, the thinnest part of the circumferential column width of the bar portion 6 becomes too thin, resulting in a decrease in the strength of the bar portion 6 compared to a conventional structure. If the inner diameter surface 6a of the cage bar portion is in the range of more than 50% of the ball diameter φDa from the center P4 of the balls 4, the radial thickness of the cage 5 becomes thin, resulting in a decrease in the strength of the entire cage compared to a conventional structure.

[0038] If the pitch circle diameter of the balls 4 is dp and the dimension T of the thinnest part of the circumferential column width of the column portion 6 is 0.40 or more and 1.50 or less, T / dp x 100 is 0.40 or more and 1.50 or less. In this case, the rigidity of the thinnest part of the column portion 6 is ensured and a decrease in the strength of the entire cage can be more reliably prevented. By setting the filling rate of the balls 4 to 88% or more and 96% or less, it is possible to satisfy the required rated load and prevent interference between the balls 4, 4 during operation.

[0039] <Regarding Other Embodiments> In the following description, parts corresponding to matters previously described in each embodiment are assigned the same reference numerals, and duplicated description will be omitted. When only part of the configuration is described, the other parts of the configuration are the same as those in the previously described embodiment unless otherwise specified. The same configuration produces the same effects. It is possible to combine not only the parts specifically described in each embodiment, but also parts of the embodiments together, provided that there is no particular problem with the combination.

[0040] [Second embodiment] As shown in Fig. 6, the shape of the pocket Pt of the cage 5A may be a shape other than a partial spherical shape. In the example of Fig. 6, the shape of the pocket Pt is cylindrical. In the second embodiment, the inner diameter surface 6a of the column portion is in a range of 8% to 50% of the ball diameter φDa from the center of the ball 4, T / dp x 100 is 0.40 to 1.50, and the filling rate of the balls 4 is 88% to 96%. In this case, the same effects as those of the first embodiment described above are achieved.

[0041] 7 , a claw portion 9 protruding radially inward is provided on the inner circumferential surface 7 a of the small diameter side annular portion 7 of the cage 5. This claw portion 9 is provided at one location on the axial tip of the inner circumferential surface 7 a of the small diameter side annular portion 7, but the position and number of the claw portion 9 are not limited to this example.

[0042] An annular recess 10 is provided in the inner race counterbore 2b on the outer peripheral surface of the inner race 2. At the same time, the inner race counterbore 2b is provided with a filling groove 11 that allows the claws 9 to pass into the bearing. The filling groove 11 is, for example, a recess with an arc-shaped cross section that extends axially in a portion of the circumferential direction of the inner race counterbore 2b (see FIG. 9B), and is formed to facilitate the axial insertion of the claws 9 of the cage 5. The groove bottom of the filling groove 11 is formed, for example, to have the same diameter as the annular recess 10.

[0043] With this configuration, even if the cage 5 is deformed by the weight of the balls and the balls 4 undesirably climb over the inner race counterbore 2b, the claws 9 of the cage 5 and the recesses 10 of the inner race counterbore 2b will catch on each other. This prevents the cage 5 and balls 4 from separating from the inner race 2.

[0044] [Fourth embodiment] As shown in Figures 8 and 9A, a plurality of (two in this example) filling grooves 11 are provided, and these plurality of filling grooves 11 are arranged at equal intervals in the circumferential direction. A plurality of claw portions 9 are provided so that the number is the same as the number of filling grooves 11 shown in Figure 9A. As shown in Figure 8, these plurality of claw portions 9 are arranged at equal intervals in the circumferential direction. In this case, the load acting on the contact points between the claw portions 9 of the cage 5 and the recesses 10 of the inner ring 2 can be distributed evenly in the circumferential direction. This allows the cage 5 and balls 4 to be stably held.

[0045] 10A and 10B, two or more rows of claw portions 9 may be provided at different positions in the axial direction. Specifically, as shown in Fig. 10A, a first row of claw portions 9 is provided at the axial tip portion of the inner circumferential surface 7a of the small-diameter side annular portion 7. Furthermore, as shown in Fig. 10B, a second row of claw portions 9 is provided near the axial middle portion of the inner circumferential surface 7a of the small-diameter side annular portion 7.

[0046] As shown in Fig. 11 , each row has a plurality of claws 9 (two in this example), and these plurality of claws 9 are arranged at equal intervals in the circumferential direction. As shown in Figs. 12 and 13 , the claws 9 in different rows are arranged at different phases in the circumferential direction. As shown in Figs. 10A and 10B , the claws 9 in the same row are arranged so that their axial positions are aligned. As shown in Fig. 11 , because the claws 9 in the same row are arranged at two equal intervals in the circumferential direction, the axial positions of the claws 9, 9 at diagonal corners are the same.

[0047] <Assembly method> When assembling the inner ring assembly, the balls 4, cage 5, and inner ring 2 are assembled into a single unit, as shown in Figure 14. First, the inner ring 2 is installed so that the claws 9 in the axially inner row of the cage 5 mesh with the filling grooves 11 in the inner ring counterbore portion 2b. After the first row of claws 9 (Figure 14) have passed through the filling grooves 11, as shown in Figure 15, the inner ring 2 or cage 5 is rotated circumferentially, and the claws 9 in the next row mesh with the filling grooves 11. This completes the assembly of the inner ring assembly.

[0048] 16 and 17 , even in the fifth embodiment, if the cage 5 is deformed by the weight of the balls and the balls 4 undesirably go over the inner race counterbore 2b, the claws 9 of the cage 5 will catch on the recesses 10 in the inner race counterbore 2b. This prevents the cage 5 and balls 4 from separating from the inner race 2. When the inner race 2, balls 4, and cage 5 are integrated, there may be a case where the circumferential phase of the first row of claws 9 ( FIG. 16 ) matches the circumferential phase of the filling grooves 11 ( FIG. 15 ) in the inner race counterbore 2b, causing the first row of claws 9 to pass through the filling grooves 11 ( FIG. 15 ). Even in this case, the second row of claws 9 ( FIG. 17 ) will catch on the recesses 10 in the inner race 2, preventing the inner race 2, balls 4, and cage 5 from separating.

[0049] [Sixth Embodiment] In the case of an outer ring assembly in which the outer ring 3, balls 4, and cage 5 are integrated as shown in Figure 18, an annular recess 10A is provided in the outer ring counterbore 3b on the inner peripheral surface of the outer ring 3. Additionally, the outer peripheral surface 8a of the large-diameter annular portion 8 of the cage 5 is provided with claws 9A that protrude radially outward. Furthermore, the outer ring counterbore 3b is provided with filling grooves 11A that allow the claws 9A to pass into the bearing. In this case, even if the cage 5 is deformed by the weight of the balls and the balls 4 undesirably go over the outer ring counterbore 3b, the claws 9A of the cage 5 and the recess 10A of the outer ring counterbore 3b are caught. This prevents the cage 5 and balls 4 from separating from the outer ring 3. In Figure 18, the outer diameter surface 6b of the cage column portion is within a range of 8% to 50% of the ball diameter from the pitch circle center of the balls 4. This allows for an increase in the number of balls while preventing a decrease in the strength of the entire cage, including the bar portions 6. If the outer diameter surfaces 6b of the bar portions of the cage are in a range from the pitch circle center P4 of the balls 4 that is less than 8% of the ball diameter φDa, the thinnest part of the circumferential column width of the bar portions 6 becomes too thin, and the strength of the bar portions 6 becomes lower than in the conventional structure. If the inner diameter surfaces 6b of the bar portions of the cage are in a range from the pitch circle center P4 of the balls 4 that is more than 50% of the ball diameter φDa, the radial thickness of the cage 5 becomes thinner, and the strength of the entire cage becomes lower than in the conventional structure.

[0050] Generally, angular contact ball bearings are mounted on a shaft and a housing for use, but the features of the cage and inner ring described in each embodiment can also be applied to configurations in which the inner ring and shaft, and the outer ring and housing are integrated.

[0051] In order to meet the required moment rigidity, it is possible to increase the ball size and contact angle. Increasing the ball size and contact angle changes the load bearing location on the raceway. Therefore, when applying preload in applications such as reducers, bearing support is required at the shaft shoulder. Therefore, it is preferable that the outer diameter of the shaft or flange that houses the inner ring be larger than the outer diameter of the inner ring, and the inner diameter of the case that houses the outer ring be smaller than the inner diameter of the outer ring. Even when applying preload using an inner shim, it is preferable to use an inner shim with an outer diameter larger than the outer diameter of the inner ring, and to apply a fixed-position preload. Furthermore, when increasing the ball size, it becomes difficult to attach a seal to the bearing due to its dimensions. When using main bearings with grease or oil lubrication, a shaft seal must be installed on the axial outside of the bearing.

[0052] Moment loads are often applied to industrial machinery. Under operating conditions where moment loads are applied by angular contact ball bearings, arranging angular contact ball bearings in a back-to-back configuration increases the distance between the bearing's application points, allowing for larger allowable radial and moment loads even when the angular contact ball bearings are made smaller or more compact. Furthermore, by arranging angular contact ball bearings in a back-to-back configuration, they can withstand axial loads in both directions, and the addition of preload increases the rigidity of the bearing section.

[0053] Between axially adjacent angular contact ball bearings, angular contact ball bearings may be assembled back-to-back via inner ring spacers and outer ring spacers, or these inner ring spacers and outer ring spacers may be omitted and angular contact ball bearings may be assembled back-to-back.

[0054] Angular contact ball bearings can also be used in face-to-face combinations, parallel combinations, etc. Angular contact ball bearings can also be used for applications other than industrial robots.

[0055] As described above, the preferred embodiment has been described with reference to the drawings, but various additions, modifications, and deletions can be made without departing from the spirit of the present invention. Therefore, such additions, modifications, and deletions are also included in the scope of the present invention.

[0056] DESCRIPTION OF SYMBOLS 1...Angular contact ball bearing 2...Inner ring 2b...Inner ring counterbore portion 3...Outer ring 3b...Outer ring counterbore portion 4...Balls 5, 5A...Cage 6...Column portion 6a...Inner diameter surface of column portion 6b...Outer diameter surface of column portion 9, 9A...Pawl portion 10, 10A...Recess portion 11, 11A...Filling groove Es...Column portion relief portion

Claims

1. An angular contact ball bearing comprising an inner ring, an outer ring, a plurality of balls interposed between the inner ring and the outer ring, and an annular resin cage that holds the balls, the cage having a pair of annular portions and a plurality of column portions connecting the annular portions, and having pockets formed by the annular portions and column portions, and the balls are held in the pockets, characterized in that in a radial cross section of the cage, the column portions do not overlap with the pitch circle centers of the balls, and the shortest distance from the pitch circle center of the balls to the column portions is between 8% and 50% of the ball diameter.

2. An angular contact ball bearing as described in claim 1, wherein T / dp x 100 is 0.40 or more and 1.50 or less, where dp is the pitch circle diameter of the ball and T is the dimension of the thinnest part of the circumferential width of the column portion.

3. An angular contact ball bearing according to claim 2, wherein the ball filling rate is 88% or more and 96% or less.

4. An angular contact ball bearing as set forth in claim 3, wherein the inner peripheral surface of the retainer is provided with claws that protrude radially inward, and the inner ring counterbore portion on the outer peripheral surface of the inner ring is provided with an annular recess and a filling groove that allows the claws to pass into the bearing.

5. An angular contact ball bearing as set forth in claim 3, wherein the outer peripheral surface of the retainer is provided with claws that protrude radially outward, and the outer ring counterbore portion on the inner peripheral surface of the outer ring is provided with an annular recess and a filling groove that allows the claws to pass into the bearing.

6. An angular contact ball bearing according to claim 4, wherein a plurality of said filling grooves are provided, and these filling grooves are arranged at equal intervals in the circumferential direction.

7. An angular contact ball bearing according to claim 6, wherein a plurality of said claw portions are provided, and these claw portions are provided at equal intervals in the circumferential direction.

8. An angular contact ball bearing as set forth in claim 7, wherein the claw portions are provided in two or more rows at different positions in the axial direction, and the claw portions in different rows are arranged at different phases in the circumferential direction.

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