Cage for deep groove ball bearing and method for manufacturing same

Abstract

This cage for a deep groove ball bearing is made of resin and includes a first pocket for preventing the cage from falling off in a radial direction from the bearing, and a second pocket for preventing the cage from falling off in an axial direction from the bearing. The first pocket has the same cross-sectional shape along the axial direction, and includes, on at least a radially inner edge side or outer edge side, a narrowing portion that narrows an interval between a pair of adjacent pillar portions. The second pocket has the same cross-sectional shape along the radial direction, and includes a claw portion that narrows the interval between a pair of adjacent pillar portions at an edge portion on the opposite side from an annular portion.

Description

Deep groove ball bearing retainer and manufacturing method thereof

[0001] The present invention relates to a cage for a deep groove ball bearing and a method for manufacturing the same.

[0002] Deep groove ball bearings are widely used to support the rotating parts of various rotary machines. In deep groove ball bearings, multiple balls are held by a crown-type cage between an outer ring and an inner ring at equal intervals in the circumferential direction so that they can roll freely.

[0003] A typical crown cage has an annular portion and a plurality of pillars that protrude axially to one side at predetermined intervals around the annular portion. The annular portion and a pair of pillars adjacent to each other in the circumferential direction form a plurality of pockets that hold balls. The inner surfaces of the plurality of pockets that hold the balls have a spherical shape. Furthermore, to prevent the crown cage from falling out of the axial direction from between the outer ring and the inner ring, the pillars are provided with elastic claws.

[0004] Crown cages are generally manufactured by injection molding synthetic resin. To manufacture resin cages at low cost, an injection molding technique called the axial draw method is used. In axial draw injection molding, in the process of removing the product from the mold, i.e., the demolding process, the crown cage is demolded in the axial direction from the mold. At this time, the crown cage is pushed in the axial direction with a pin or the like, which causes the claws on the column parts to elastically deform and the cage is removed from the mold.

[0005] When the number of balls in a bearing is increased to improve the bearing's load capacity, the circumferential thickness of the columns in a crown-type cage becomes smaller, which can cause molding defects when the claws and columns cannot withstand elastic deformation during demolding.

[0006] The cages described in Patent Documents 1 and 2 include both pockets with spherical inner surfaces that have claws that hold the balls in the axial direction, and pockets with cylindrical inner surfaces that extend in the axial direction and that do not have claws that hold the balls in the axial direction. These cages have in common the aim of limiting the number of pockets with claws that cause problems during demolding, thereby allowing the balls to retain the cage in the axial direction while still allowing for axial demolding during molding.

[0007] Japanese Utility Model Registration No. 3122529 International Publication No. 2019 / 198762

[0008] The cages described in Patent Documents 1 and 2 are designed for low-cost axial draw injection molding. That is, when releasing the spherical pockets from the mold, these cages undergo a process in which the claws on the posts are elastically deformed and the cage is pulled axially out of the mold. This process can cause the cage to whiten due to deformation, resulting in molding defects. In the future, as bearings with even higher load capacities are required and the number of balls is increased, it is expected that the shape and size of the claws and posts will be further restricted, resulting in a deterioration in moldability.

[0009] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a retainer for a deep groove ball bearing that has the function of preventing the crown-type retainer from falling off the bearing in the axial direction even when there are a large number of balls, is easy to demold, has excellent formability, and is low-cost, as well as a method for manufacturing the same.

[0010] The above object of the present invention is achieved by the following configuration: (1) A resin cage for a deep groove ball bearing comprising: an annular portion, a plurality of pillar portions protruding in the axial direction from the annular portion, and a plurality of pocket portions formed by the annular portion and a pair of circumferentially adjacent pillar portions and holding a plurality of balls, wherein the plurality of pocket portions include: a first pocket for preventing the deep groove ball bearing cage from falling off in the radial direction from the bearing, and a second pocket for preventing the deep groove ball bearing cage from falling off in the axial direction from the bearing, wherein the first pocket has the same cross-sectional shape along the axial direction and is provided with a narrowed portion at at least one of the radial inner end side or outer end side that narrows the spacing between a pair of adjacent pillar portions, and the second pocket has the same cross-sectional shape along the radial direction and is provided with a claw portion at an end opposite the annular portion that narrows the spacing between a pair of adjacent pillar portions. (2) A method for manufacturing a resin cage for a deep groove ball bearing, the cage comprising: an annular portion; a plurality of pillar portions protruding in the axial direction from the annular portion; and a plurality of pocket portions formed by the annular portion and a pair of the pillar portions adjacent in the circumferential direction and holding a plurality of balls, wherein the plurality of pocket portions include a first pocket for preventing the cage for the deep groove ball bearing from falling off in the radial direction from the bearing, and a second pocket for preventing the cage for the deep groove ball bearing from falling off in the axial direction from the bearing, wherein the first pocket has the same cross-sectional shape along the axial direction and is provided with a narrowed portion on at least one of the radial inner end side or outer end side that narrows the gap between a pair of adjacent pillar portions, and the second pocket has the same cross-sectional shape along the radial direction and is provided with a claw portion on an end opposite the annular portion that narrows the gap between a pair of adjacent pillar portions, wherein the first pocket is injection molded by an axial draw method, and the second pocket is injection molded by a radial draw method. A manufacturing method for a cage for a deep groove ball bearing.

[0011] According to the present invention, it is possible to provide a retainer for a deep groove ball bearing, which has the function of preventing the crown type retainer from falling off the bearing in the axial direction even when there are a large number of balls, is easy to demold, has excellent formability, and is low cost, and a manufacturing method thereof.

[0012] Fig. 1 is a perspective view of a cage for a deep groove ball bearing according to an embodiment of the present invention. Fig. 2 is a partially enlarged view of Fig. 1. Fig. 3 is a perspective view showing the arrangement of first pockets and second pockets of the cage for a deep groove ball bearing according to an embodiment of the present invention.

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a perspective view of a cage for a deep groove ball bearing according to an embodiment of the present invention, Fig. 2 is a partially enlarged view of Fig. 1. Fig. 3 is a perspective view showing the arrangement of first pockets and second pockets of the cage according to the embodiment of the present invention.

[0014] 1 to 3, a deep groove ball bearing cage 10 according to this embodiment includes an annular portion 11, a plurality of pillar portions 12 protruding from the annular portion 11 to one side in the axial direction, and a plurality of pocket portions 50 formed by pairs of pillar portions 12 adjacent to the annular portion 11 in the circumferential direction and holding a plurality of balls (not shown). Hereinafter, the deep groove ball bearing cage 10 may be simply referred to as cage 10. In addition, in this embodiment, the axial direction in which the pillar portions 12 protrude from the annular portion 11 (the upper side in FIGS. 1 to 3) is referred to as the "one axial side," and the opposite side to the one axial side (the lower side in FIGS. 1 to 3) is referred to as the "other axial side."

[0015] The plurality of pocket portions 50 include a first pocket 51 for preventing the retainer 10 from falling off in the radial direction from the bearing, and a second pocket 52 for preventing the retainer 10 from falling off in the axial direction from the bearing. That is, the first pocket 51 restricts radial movement of the retainer 10 by being caught on the balls, and the second pocket 52 restricts axial movement of the retainer 10 by being caught on the balls.

[0016] 1 and 3 , the cage 10 according to this embodiment is provided with 23 pocket portions 50. Of the 23 pocket portions 50, five are second pockets 52 and 18 are first pockets 51. Three or four first pockets 51 are arranged in the circumferential direction between circumferentially adjacent second pockets 52.

[0017] The numbers of the second pockets 52 and the first pockets 51 need to be adjusted depending on the total number of pocket portions 50, but in order to simplify the mold shape, it is preferable that the number of the second pockets 52 be equal to or less than the number of the first pockets 51. As will be described later, the more the number of the second pockets 52 increases, the more complex the mold shape becomes. It is more preferable that the number of the second pockets 52 be equal to or less than half the number of the first pockets 51, and it is even more preferable that the number of the second pockets 52 be equal to or less than one-third the number of the first pockets 51.

[0018] Furthermore, it is desirable that the number of second pockets 52 is at least three, and that the second pockets 52 are arranged at approximately equal intervals in the circumferential direction. Here, "approximately equal intervals" refers to a case where, when the number of first pockets 51 arranged between any pair of adjacent second pockets 52 is M and the number of first pockets 51 arranged between another pair of adjacent second pockets 52 is N, the difference between M and N for any combination is always 2 or less, including a case where the difference between M and N is always 0, i.e., an equal interval. In the illustrated example, the number of first pockets 51 arranged between a pair of second pockets 52 is 3 and 4, and M and N are 3 or 4, respectively. That is, the difference between M and N is at most 1, and in any combination of M and N, the difference between M and N is 2 or less. By arranging the second pockets 52, which prevent the cage from falling off in the axial direction, at approximately equal intervals in the circumferential direction, the cage 10 is supported in a balanced manner in the circumferential direction, and the posture of the cage 10 is stabilized.

[0019] Here, the pillar portions 12 will be described. As shown in FIGS. 1 to 3 , the pillar portions 12 separate a pair of circumferentially adjacent pockets 50. More specifically, the multiple pillar portions 12 include a first pillar portion 12a separating a first pocket 51 and a second pocket 52 that are circumferentially adjacent, and a second pillar portion 12b separating a pair of circumferentially adjacent first pockets 51. The first pillar portion 12a has a claw portion 21 at the tip of its circumferential side surface facing the second pocket 52, but does not have a claw portion 21 on its circumferential side surface facing the first pocket 51. The second pillar portion 12b does not have a claw portion 21. The pair of circumferentially adjacent first pillar portions 12a constitutes the second pocket 52, the circumferentially adjacent first pillar portion 12a and the second pillar portion 12b constitute the first pocket 51, and the pair of circumferentially adjacent second pillar portions 12b constitutes the first pocket 51.

[0020] The first pocket 51 has the same cross-sectional shape along the axial direction. That is, the first pocket 51 is formed on the circumferential side surfaces of a pair of adjacent column portions 12 (a pair of adjacent second column portions 12b, or a pair of adjacent first column portions 12a and second column portions 12b). The first pocket 51 includes a pair of peripheral surfaces 33 that are axially cylindrical surfaces with a central axis O1 extending in the axial direction. Therefore, the cross-sectional shape of the pair of peripheral surfaces 33 that constitute the first pocket 51, perpendicular to the central axis O1, is constant regardless of the axial position. Furthermore, the first pocket 51 includes a narrowed portion 37 on at least one of the radial inner end side and the radial outer end side that narrows the gap between the pair of adjacent column portions 12. In this embodiment, the pair of adjacent column portions 12 that form the pair of peripheral surfaces 33 each have a narrowed portion 37 formed so as to approach each other from both the radial inner end side and the radial outer end side of the column portions 12. At each of the radially inner and outer ends of the column portion 12, the circumferential distance between a pair of opposing narrowed portions 37 is formed to be narrower than the diameter of the balls. That is, the balls arranged in the first pockets 51 catch on the narrowed portions 37, preventing the cage 10 from falling out of the bearing in the radial direction. The first pockets 51 also include a flat bottom surface 31 formed on one axial end surface of the annular portion 11, and further include curved connecting portions 35 that connect the bottom surface 31 and a pair of peripheral surfaces 33.

[0021] The second pocket 52 has a uniform cross-sectional shape along the radial direction. That is, the second pocket 52 includes an inner surface 20, which is a radially cylindrical surface with a central axis O2 extending radially, formed across one axial end face of the annular portion 11 and the circumferential side faces of a pair of adjacent first columnar portions 12a. Therefore, the cross-sectional shape perpendicular to the central axis O2 of the inner surface 20 constituting the second pocket 52 is constant regardless of the radial position. The second pocket 52 also includes claw portions 21 at the end opposite the annular portion 11 that narrow the gap between the pair of adjacent first columnar portions 12a. The claw portions 21 of the pair of adjacent first columnar portions 12a constituting the second pocket 52 protrude from the tips of the first columnar portions 12a so as to approach each other. The inner surface 20 forms a radial cylindrical surface with the central axis O2 extending radially by smoothly connecting the end face on one axial side of the annular portion 11, the opposing circumferential side surfaces of a pair of adjacent first columnar portions 12a, and the claw portions 21. That is, the cross-sectional shape of the inner surface 20 perpendicular to the central axis O2 has an arc shape that extends from the tip of one of the pair of opposing claw portions 21 to the tip of the other claw portion 21, and this shape remains unchanged regardless of the radial position.

[0022] 2, the circumferential width W1 between the tips of the pair of claws 21 is smaller than the diameter of the ball, so that the ball disposed in the second pocket 52 is caught by the claws 21, preventing the cage 10 from falling off the bearing in the axial direction.

[0023] The first pillar portions 12a also have tip surfaces 15 facing one axial direction. Each of a pair of adjacent first pillar portions 12a constituting the second pocket 52 has a chamfered portion 23 between the tip surfaces 15 and the tip ends of the claw portions 21. When the balls are assembled into the cage 10, the chamfered portions 23 come into contact with the balls and guide the balls into the second pocket 52 while elastically deforming the first pillar portions 12a.

[0024] The cage 10 is made of a resin material and is formed by injection molding. Known injection molding methods used for resin cages include the axial draw method and the radial draw method. In axial draw method injection molding, the cage is released from the mold in the axial direction in the process of removing the product from the mold, i.e., the demolding process. On the other hand, in radial draw method injection molding, the cage is released from the mold in the radial direction. Generally, in the manufacture of crown type cages, axial draw method injection molding requires fewer steps and is less expensive than radial draw method injection molding.

[0025] In this embodiment, the second pocket 52 is injection molded by the radial draw method, and the first pocket 51 is injection molded by the axial draw method. The cage 10 according to this embodiment is injection molded by combining an axial draw mold using mold parts that are movable in the axial direction with the same number of mold parts that are movable in the radial direction as the number of second pockets 52. After the cage 10 is integrally molded, when releasing it from the mold, the mold parts that are mainly in contact with the inner surface 20 of the second pocket 52 are removed radially from the cage 10, and then the remaining mold parts that are movable in the axial direction are removed axially from the cage 10.

[0026] Therefore, the greater the number of second pockets 52, the more die parts that can move radially, which complicates the die structure and increases the size of the molding device, leading to increased manufacturing costs. On the other hand, from the perspective of preventing the cage 10 from falling off the bearing in the axial direction, the greater the number of second pockets 52 that can hold the balls in the axial direction, the more advantageous it is. Due to these conflicting circumstances, it is necessary to appropriately adjust the number of second pockets 52 to be optimal depending on the number of pocket portions 50 of the cage 10. Therefore, as described above, it is preferable that the number of second pockets 52 be equal to or less than the number of first pockets 51 and be three or more.

[0027] As described above, this specification discloses the following: (1) A resin cage for a deep groove ball bearing comprising: an annular portion, a plurality of pillar portions protruding in the axial direction from the annular portion, and a plurality of pocket portions formed by the annular portion and a pair of the pillar portions adjacent in the circumferential direction and holding a plurality of balls, wherein the plurality of pocket portions include: a first pocket for preventing the deep groove ball bearing cage from falling off in the radial direction from the bearing, and a second pocket for preventing the deep groove ball bearing cage from falling off in the axial direction from the bearing, wherein the first pocket has the same cross-sectional shape along the axial direction, and is provided with a narrowed portion on at least one of the radial inner end side or outer end side that narrows the spacing between a pair of adjacent pillar portions, and the second pocket has the same cross-sectional shape along the radial direction, and is provided with a claw portion on an end opposite the annular portion that narrows the spacing between a pair of adjacent pillar portions. With this configuration, the claws of the columns that form the second pocket hold the balls, preventing the cage from falling off in the axial direction. Furthermore, because the second pocket is formed in a cylindrical shape with a central axis extending in the radial direction, it can be easily molded using radial draw injection molding, i.e., a molding method in which the mold is released in the radial direction. Because the first pocket is formed in a cylindrical shape with a central axis extending in the axial direction, it can be easily molded using axial draw injection molding, i.e., a molding method in which the mold is released in the axial direction.

[0028] (2) The cage for a deep groove ball bearing according to (1), wherein the number of the second pockets is equal to or less than the number of the first pockets. With this configuration, it is possible to reduce the number of radially movable die parts used in combination with an axially movable die, thereby preventing the die shape from becoming complicated and the accompanying deterioration in formability.

[0029] (3) The cage for a deep groove ball bearing according to (1) or (2), which has at least three second pockets, and the second pockets are arranged at approximately equal intervals in the circumferential direction. With this configuration, the second pockets that hold the balls are arranged at approximately equal intervals in the circumferential direction, so that the cage is supported in a balanced manner in the circumferential direction and its posture is stable.

[0030] (4) A method for manufacturing a resin cage for a deep groove ball bearing, the cage comprising: an annular portion; a plurality of pillar portions protruding in the axial direction from the annular portion; and a plurality of pocket portions formed by the annular portion and a pair of the pillar portions adjacent in the circumferential direction and holding a plurality of balls, wherein the plurality of pocket portions include a first pocket for preventing the cage for the deep groove ball bearing from falling off in the radial direction from the bearing, and a second pocket for preventing the cage for the deep groove ball bearing from falling off in the axial direction from the bearing, wherein the first pocket has the same cross-sectional shape along the axial direction, and is provided with a narrowed portion on at least one of the radial inner end side or outer end side that narrows the gap between a pair of adjacent pillar portions, and the second pocket has the same cross-sectional shape along the radial direction, and is provided with a claw portion on an end opposite the annular portion that narrows the gap between a pair of adjacent pillar portions, wherein the first pocket is injection molded by an axial draw method, and the second pocket is injection molded by a radial draw method. This method of manufacturing a cage for a deep groove ball bearing makes it possible to manufacture, at low cost, a cage that is easy to release from a mold and has excellent formability, while also having the function of preventing the cage from falling off the bearing in the axial direction.

[0031] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0032] This application is based on a Japanese patent application (Patent Application No. 2024-070853) filed on April 24, 2024, the contents of which are incorporated herein by reference.

[0033] REFERENCE SIGNS LIST 10 Cage for deep groove ball bearing (cage) 11 Annular portion 12 Column portion 12a First column portion 12b Second column portion 15 Tip surface 20 Inner surface 21 Claw portion 23 Chamfered portion 31 Bottom surface 33 Circumferential surface 35 Connection portion 37 Narrowed portion 50 Pocket portion 51 First pocket 52 Second pocket O1 Central axis O2 Central axis W1 Circumferential width

Claims

1. A resin cage for a deep groove ball bearing comprising: an annular portion; a plurality of pillar portions protruding in the axial direction from the annular portion; and a plurality of pocket portions formed by the annular portion and pairs of circumferentially adjacent pillar portions and holding a plurality of balls, wherein the plurality of pocket portions include: a first pocket for preventing the deep groove ball bearing cage from falling off in the radial direction from the bearing; and a second pocket for preventing the deep groove ball bearing cage from falling off in the axial direction from the bearing, wherein the first pocket has the same cross-sectional shape along the axial direction, and is provided with a narrowed portion at at least one of the radial inner end side or outer end side that narrows the spacing between adjacent pairs of pillar portions, and the second pocket has the same cross-sectional shape along the radial direction, and is provided with a claw portion at the end opposite the annular portion that narrows the spacing between adjacent pairs of pillar portions.

2. The cage for a deep groove ball bearing according to claim 1, characterized in that the number of said second pockets is equal to or less than the number of said first pockets.

3. A cage for a deep groove ball bearing according to claim 1 or 2, characterized in that it has at least three second pockets, and the second pockets are arranged at approximately equal intervals in the circumferential direction.

4. A method for manufacturing a resin cage for a deep groove ball bearing comprising: an annular portion; a plurality of pillar portions protruding in the axial direction from the annular portion; and a plurality of pocket portions formed by the annular portion and a pair of the pillar portions adjacent in the circumferential direction and holding a plurality of balls, wherein the plurality of pocket portions comprise: a first pocket for preventing the deep groove ball bearing cage from falling off in the radial direction from the bearing; and a second pocket for preventing the deep groove ball bearing cage from falling off in the axial direction from the bearing, wherein the first pocket has the same cross-sectional shape along the axial direction and is provided with a narrowed portion on at least one of the radial inner end side or outer end side that narrows the gap between a pair of adjacent pillar portions, and the second pocket has the same cross-sectional shape along the radial direction and is provided with a claw portion on an end opposite the annular portion that narrows the gap between a pair of adjacent pillar portions, wherein the first pocket is injection molded by an axial draw method, and the second pocket is injection molded by a radial draw method. A method for manufacturing a cage for a deep groove ball bearing, comprising:

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