Resin cage and ball bearing

Abstract

To provide a resin cage hardly causing deformation due to centrifugal force during high-speed rotation and capable of preventing starvation of lubricating oil.SOLUTION: In the resin-made cage 5 in which the plurality of hemispherical recesses 10 are formed at intervals in the circumferential direction on the axial inner side surface 9 of each of the pair of annular body side 8a and side 8b, the axial outer side surface 11 of each of the pair of annular body side 8a and side 8b is a flat surface continuous in the circumferential direction over the entire circumference, and the lightening portion 12 recessed in the axial direction between the recesses 10 adjacent to each other in the circumferential direction is formed on the axial inner side surface 9 of each of the pair of annular body side 8a and side 8b.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a resin cage and a ball bearing using the resin cage. [Background technology]

[0002] Planetary gear reducers are often used for electric motors, such as those used in electric vehicle traction motors, to reduce size. The output shaft and planetary carrier of these planetary gear reducers have relatively large diameters and require limited space around them, so they are supported by large-diameter, thin-walled bearings.

[0003] Ball bearings are generally used to support the output shaft of planetary gear reducers because they operate at high speeds and have relatively light loads. Furthermore, the cages that hold the balls in these bearings are often made of resin, which is lighter than metal cages, in order to reduce the torque of the bearings.

[0004] Meanwhile, known resin cages for holding balls in ball bearings are those disclosed in Patent Documents 1 to 3. The resin cages disclosed in Patent Documents 1 to 3 are mating-type cages that have a pair of annular bodies configured such that arc-shaped pocket walls for accommodating balls and connecting plate portions connecting circumferentially adjacent pocket wall portions are alternately arranged in the circumferential direction, and the pair of annular bodies are joined together by axially opposing each other and inserting an engaging claw formed on the connecting plate portion of one annular body into an engaging hole formed on the connecting plate portion of the other annular body, and engaging a hook portion formed on the engaging claw with a step portion formed on the inner surface of the engaging hole. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-245762 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-076778 [Patent Document 3] Patent No. 5257771 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, there has been a trend in ball bearings that support the output shaft of planetary gear reducers, etc., to reduce the number of balls (i.e., to increase the distance between the centers of adjacent balls in the circumferential direction) in order to reduce torque, and there has also been a trend toward higher rotation speeds for the bearings.

[0007] Therefore, if the resin retainers (hereinafter simply referred to as "retainers") of Patent Documents 1 to 3 are used in ball bearings that support the output shaft of a planetary gear reducer, etc., the circumferential length of the connecting plate portion that connects adjacent pocket wall portions in the circumferential direction becomes longer, making the retainer more susceptible to deformation due to centrifugal force, which may result in a problem of insufficient strength of the retainer.

[0008] Therefore, the inventors of the present application studied how to make the cages used in ball bearings that support the output shafts of planetary gear reducers, etc., less susceptible to deformation due to centrifugal force. As a result of their study, they came up with the idea of ​​increasing the axial thickness of the pair of annular bodies that make up the cage so that the end faces on both axial sides of the cage have continuous flat surfaces all around, in order to increase the rigidity of the mating type cages such as those in Patent Documents 1 to 3, and at the same time, providing axially recessed portions on both axial end faces of the cage to reduce the weight of the cage.

[0009] However, if the cage has a lightening portion on both axial end faces, there is a risk that starvation (depletion) of the lubricating oil may occur during high-speed rotation.

[0010] Specifically, if the axial thickness of the pair of annular bodies constituting the cage is increased so that both axial end faces of the cage are flat and continuous around the entire circumference, and if a recess is provided on both axial end faces of the cage, the recess will cause the both axial end faces of the cage to have an uneven shape. Therefore, when a ball bearing is used at high speeds, the lubricating oil supplied from outside the bearing is scraped off by the uneven end faces of the rotating cage, making it difficult for the lubricating oil to penetrate into the bearing. This can result in starvation of the lubricating oil inside the bearing, which can lead to seizure inside the bearing. In particular, in recent years, the viscosity and amount of lubricating oil used in the reducers of electric vehicle traction motors have been reduced, making the situation more susceptible to lubricating oil starvation.

[0011] The problem to be solved by this invention is to provide a resin cage that is less likely to deform due to centrifugal force during high-speed rotation and that can prevent starvation of lubricating oil. [Means for solving the problem]

[0012] The inventors of the present application came up with the idea that in order to increase the rigidity of a laminated type resin retainer consisting of a pair of annular bodies joined opposite each other in the axial direction, the axial thickness of the pair of annular bodies can be increased so that the end faces on both axial sides of the retainer are flat surfaces that are continuous in the circumferential direction around the entire circumference, and at the same time, in order to reduce the weight of the retainer, by providing an axially recessed cutout portion on the axial inner surface of each of the pair of annular bodies (i.e., the opposing surfaces of the pair of annular bodies), the end faces on both axial sides of the retainer can be made to have a smooth shape, and starvation of the lubricating oil can be prevented during high-speed rotation.

[0013] Based on this idea, the present invention provides a method for solving the above problems, which has the following configuration: A resin cage is provided. [Configuration 1] a pair of annular resin bodies joined together in an axially opposed relationship; In a resin cage, a plurality of hemispherical recesses are formed at intervals in the circumferential direction on the axially inner surface of each of the pair of annular bodies, Each of the pair of annular bodies has an outer axial surface (i.e., a surface on the opposite side of the inner axial surface) formed as a flat surface that is continuous in the circumferential direction over the entire circumference, A resin cage characterized in that a hollowed-out portion is formed on the axial inner surface of each of the pair of annular bodies between circumferentially adjacent recesses, the hollowed-out portion being recessed in the axial direction.

[0014] By adopting this configuration, the axially outer surface of each of the pair of annular bodies constituting the cage is made flat and continuous around the entire circumference, and each of the pair of annular bodies has a lightening portion formed therein, thereby increasing the rigidity of the cage while reducing its weight and making it possible to suppress deformation of the cage due to centrifugal force during high-speed rotation. Furthermore, because the lightening portion is formed on the axially inner surface of each annular body rather than on the axially outer surface, the axially outer surface of the annular body does not have an uneven shape due to recesses in the lightening portion. Therefore, lubricating oil supplied from outside the bearing is less likely to be scraped away by the axially outer surface of the annular body, making it possible to prevent starvation of the lubricating oil during high-speed rotation.

[0015] [Configuration 2] The resin cage according to configuration 1, wherein the hollowed-out portion is surrounded by a partially cylindrical outer peripheral wall extending in the circumferential direction, a partially cylindrical inner peripheral wall extending in the circumferential direction facing the radially inner side of the outer peripheral wall, a one end wall connecting one circumferential ends of the outer peripheral wall and the inner peripheral wall, an other end wall connecting the other circumferential ends of the outer peripheral wall and the inner peripheral wall, and a bottom wall connecting axial outer ends of the outer peripheral wall and the inner peripheral wall.

[0016] By adopting this configuration, it is possible to ensure the rigidity of each annular body while effectively reducing the weight of each annular body by using the lightening portion.

[0017] [Configuration 3] A resin cage according to configuration 1 or 2, wherein an outer periphery side communicating groove that communicates the hollowed-out portion with the outer periphery of the annular body is formed on the axially inner surface of each annular body.

[0018]

[0004] By adopting this configuration, it is possible to prevent weight imbalance of the cage caused by lubricating oil accumulating in the lightening holes. That is, when lightening holes are formed in the axially inner surfaces of a pair of annular bodies joined opposite each other in the axial direction, the lightening holes are located inside the cage, so lubricating oil supplied from the outside accumulates in the lightening holes, and the lubricating oil accumulated in the lightening holes may cause weight imbalance of the cage during rotation of the bearing. Therefore, by forming outer-periphery-side communicating grooves in the axially inner surfaces of each annular body that communicate between the lightening holes and the outer periphery of the annular bodies, the lubricating oil accumulated in the lightening holes is discharged through the outer-periphery-side communicating grooves by centrifugal force, making it possible to prevent weight imbalance of the cage caused by lubricating oil accumulating in the lightening holes.

[0019] [Configuration 4] 4. The resin cage according to configuration 3, wherein the inner surface of the radially outer side of the hollowed-out portion of each of the annular bodies is inclined radially outward toward the axially inner side.

[0020] With this configuration, during rotation of the bearing, centrifugal force causes lubricating oil present in the recessed portion to flow toward the outer-periphery communicating groove along the inclined inner surface of the radially outer recessed portion, thereby enabling the lubricating oil present in the recessed portion to be efficiently discharged from the outer-periphery communicating groove.

[0021] [Configuration 5] A resin cage according to configuration 3, wherein an inner circumferential communicating groove that communicates the hollowed-out portion with the inner periphery of the annular body is formed on the axially inner surface of each of the annular bodies.

[0022] With this configuration, the hollowed-out portion and the inner periphery of the annular body are in communication with each other via the inner-periphery-side communicating groove, so that when the lubricating oil in the hollowed-out portion is discharged through the outer-periphery-side communicating groove by centrifugal force, negative pressure in the hollowed-out portion can be prevented, and the lubricating oil in the hollowed-out portion can be smoothly discharged.

[0023] [Configuration 6] 6. The resin cage according to configuration 5, wherein the inner circumferential communicating groove is disposed radially opposite the outer circumferential communicating groove.

[0024] With this configuration, the inner periphery-side communicating groove and the outer periphery-side communicating groove face each other in the radial direction, so that when lubricating oil flows into the lightening portion through the inner periphery-side communicating groove during bearing rotation, the lubricating oil can be efficiently discharged from the outer periphery-side communicating groove. Here, the lubricating oil discharged from the outer periphery-side communicating groove is supplied to the outer ring raceway groove formed on the inner periphery of the outer ring, and the balls roll against the inner surface of the outer ring raceway groove. Therefore, when the lubricating oil is discharged from the outer periphery-side communicating groove, the lubricating condition inside the bearing is improved, and it is possible to effectively prevent starvation of the lubricating oil during high-speed rotation.

[0025] [Configuration 7] 7. The resin cage according to configuration 6, wherein the inner periphery of each annular body is inclined radially outward toward the axially inward direction.

[0026] With this configuration, during bearing rotation, centrifugal force causes lubricating oil present on the radially inner side of each annular body to flow along the inclined inner periphery of the annular body toward the inner periphery communicating groove, thereby enabling the lubricating oil present on the radially inner side of each annular body to efficiently flow through the inner periphery communicating groove into the lightening portion and then be discharged from the outer periphery communicating groove.

[0027] [Configuration 8] 8. The resin cage according to any one of configurations 1 to 7, wherein an oil passage groove that connects the hollowed portion and the recessed portion is formed on an axially inner surface of each of the annular bodies.

[0028] This configuration allows the lubricating oil present in the hollowed-out portion to be supplied to the recessed portion through the oil passage groove, and the lubricating oil can be used to lubricate the balls housed in the recessed portion, effectively preventing starvation of the lubricating oil during high-speed rotation.

[0029] [Configuration 9] 9. The resin cage according to any one of configurations 1 to 8, wherein an oil reservoir groove is formed in the recess, extending in the circumferential direction from one circumferential end to the other circumferential end.

[0030] By adopting this configuration, lubricating oil is collected in the oil collection groove and can be used to lubricate the balls housed in the recesses, making it possible to effectively prevent starvation of the lubricating oil during high-speed rotation.

[0031] The present invention also provides a ball bearing using the above-mentioned resin cage, which has the following configuration. [Configuration 10] an outer ring having an outer ring raceway groove formed on its inner periphery; an inner ring having an inner ring raceway groove formed on its outer periphery; a plurality of balls mounted at intervals in the circumferential direction in an annular bearing space formed between the outer ring and the inner ring, the balls being in rolling contact with the inner surface of the outer ring raceway groove and the inner surface of the inner ring raceway groove; A ball bearing having a resin cage according to any one of configurations 1 to 9 that holds the plurality of balls.

[0032] [Configuration 11] A ball bearing as described in configuration 10, wherein a resin protrusion extending in the axial direction formed on one of the pair of annular bodies is inserted into a crimped hole formed axially through the other annular body, and the resin protrusion is prevented from coming out of the crimped hole by a crimped head formed by melting the tip of the resin protrusion.

[0033] This configuration allows the pair of annular bodies to be reliably coupled and also makes it easy to confirm whether the pair of annular bodies is completely coupled. Specifically, when a configuration is adopted in which an engagement claw formed on one of the pair of annular bodies is inserted into an engagement hole formed on the other annular body, and a hook portion formed on the engagement claw is engaged with a step portion formed on the inner surface of the engagement hole, as in the resin cages of Patent Documents 1 to 3, the engagement claw must be forcibly inserted while elastically deforming to enter the engagement hole, and then the hook portion of the engagement claw must be restored to its original shape before being engaged with the step portion on the inner surface of the engagement hole. This makes it difficult to stably engage the hook portion of the engagement claw with the step portion on the inner surface of the engagement hole. Furthermore, when the hook portion of the engagement claw is engaged with the step portion on the inner surface of the engagement hole, the engaging portion is located inside the engagement hole and cannot be seen from the outside, making it impossible to visually confirm the engagement state between the hook portion and the step portion, making it difficult to confirm whether the pair of annular bodies is completely coupled. In contrast, if a configuration is adopted in which a resin protrusion formed on one of a pair of annular bodies is inserted into a crimping hole formed on the other annular body and the tip of the resin protrusion is melted to form a crimping head, thereby preventing the resin protrusion from slipping out of the crimping hole, the resin protrusion is inserted into the crimping hole without a crimping head being formed at the tip of the resin protrusion, and then a crimping head is formed at the tip of the resin protrusion, so that the pair of annular bodies can be reliably joined and it is also easy to check whether the pair of annular bodies have been completely joined.

[0034] [Configuration 12] A ball bearing according to configuration 11, wherein a counterbore portion is provided at the axially outer end of the crimping hole to accommodate the crimping head so that the crimping head does not protrude from the axially outer surface of the annular body.

[0035] With this configuration, the crimp head is housed in the counterbore of the crimp hole so as not to protrude beyond the flat axial outer surface of the annular body, and the axial outer surface of the annular body is not made uneven by the crimp head. As a result, lubricating oil supplied from outside the bearing is less likely to be scraped away by the axial outer surface of the annular body, making it possible to prevent starvation of the lubricating oil during high-speed rotation.

[0036] [Configuration 13] 13. The ball bearing according to any one of configurations 10 to 12, wherein the distance between the centers of the balls adjacent in the circumferential direction is four times or more the diameter of the balls.

[0037] When this configuration is adopted, the distance between the centers of adjacent balls in the circumferential direction is long (i.e., the number of balls is small), so it is possible to reduce the torque of the bearing.

[0038] [Configuration 14] 14. A ball bearing according to any one of configurations 10 to 13, wherein both axial ends of the bearing space are open without providing a sealing member.

[0039] By adopting this configuration, it becomes possible to efficiently introduce lubricating oil supplied from outside the bearing into the annular space, and to effectively lubricate the inside of the bearing with that lubricating oil. [Effects of the Invention]

[0040] In the resin cage of this invention, the axially outer surface of each of the pair of annular bodies constituting the cage is a flat surface that continues circumferentially around the entire circumference, and each of the pair of annular bodies has a lightening portion formed therein, thereby increasing the rigidity of the cage while reducing its weight and making it possible to suppress deformation of the cage due to centrifugal force during high-speed rotation. Furthermore, because the lightening portions are formed on the axially inner surface of each annular body rather than on the axially outer surface, the axially outer surface of the annular body does not have an uneven shape due to recesses in the lightening portions. As a result, lubricating oil supplied from outside the bearing is less likely to be scraped away by the axially outer surfaces of the annular bodies, making it possible to prevent starvation of the lubricating oil during high-speed rotation. [Brief explanation of the drawings]

[0041] [Figure 1] FIG. 1 is a view of a ball bearing according to a first embodiment of the present invention, viewed from the axial direction; [Figure 2] Cross-sectional view along line II-II in Figure 1 [Figure 3] Enlarged view of a ball bearing in Figure 1 [Figure 4] Cross-sectional view along line IV-IV in Figure 3 [Figure 5] FIG. 5 is a cross-sectional view showing a state before the pair of annular bodies shown in FIG. 4 are joined together. [Figure 6] FIG. 6 is a perspective view of a pair of annular bodies shown in FIG. [Figure 7] 6(a) is a diagram showing the state in which the resin protrusion shown in FIG. 5 is inserted into the crimping hole, and FIG. 6(b) is a diagram showing the state in which the tip of the resin protrusion shown in FIG. 6(a) is melted and deformed to form a crimping head. [Figure 8] FIG. 3 is a diagram showing a modified example in which the inner periphery of the cage shown in FIG. 2 is inclined radially outward toward the axial center. [Figure 9] FIG. 10 is a view of a ball bearing according to a second embodiment of the present invention, viewed from the axial direction. [Figure 10] Enlarged view of the ball bearing shown in Figure 9 [Figure 11] Cross-sectional view taken along line XI-XI in Figure 10 [Figure 12] Cross-sectional view taken along line XII-XII in Figure 10 [Figure 13] Cross-sectional view taken along line XIII-XIII in Figure 10 [Figure 14] FIG. 12 is a cross-sectional view showing a state before the pair of annular bodies shown in FIG. 11 are joined together. [Figure 15] 15 is a perspective view of a pair of annular bodies shown in FIG. 14; [Figure 16] FIG. 10 is a view of a ball bearing according to a third embodiment of the present invention, viewed from the axial direction. [Figure 17] Enlarged view of the ball bearing shown in Figure 16 [Figure 18] Cross-sectional view taken along line XVIII-XVIII in Figure 17 [Figure 19] FIG. 19 is a cross-sectional view showing a state before the pair of annular bodies shown in FIG. 18 are joined together. [Figure 20] 20 is a perspective view of a pair of annular bodies shown in FIG. 19; [Figure 21] FIG. 21 is a partially enlarged perspective view of one of the annular bodies shown in FIG. 20; [Figure 22] FIG. 21 is a partially enlarged perspective view of the other annular body shown in FIG. 20; DETAILED DESCRIPTION OF THE INVENTION

[0042] 1 and 2 show a ball bearing using a resin cage (hereinafter simply referred to as "cage") according to a first embodiment of the present invention. This ball bearing has an outer ring 1, an inner ring 2 provided coaxially and radially inward of the outer ring 1, a plurality of balls 4 mounted at regular intervals in the circumferential direction in an annular bearing space 3 (see FIG. 2) formed between the outer ring 1 and the inner ring 2, and a cage 5 that holds the plurality of balls 4.

[0043] The axial direction is the direction parallel to the central axis of the outer ring 1 (the central axis of the bearing), the radial direction is the direction perpendicular to the central axis of the outer ring 1, and the circumferential direction is the direction along the circumference that revolves around the central axis of the outer ring 1. The central axis of the outer ring 1 coincides with the central axis of the cage 5. Furthermore, the axially inner side is the side closer to the center of the balls 4 along the axial direction, and the axially outer side is the side farther from the center of the balls 4 along the axial direction.

[0044] This ball bearing is a large-diameter, thin-walled bearing that supports the output shaft or planetary carrier of a planetary gear reducer (not shown), and the inner diameter of the inner ring 2 is set to 50 mm or more and 90 mm or less, and the radial height dimension from the inner circumference of the inner ring 2 to the outer circumference of the outer ring 1 is set to 13.5% or more and 30% or less of the inner diameter of the inner ring 2.

[0045] Furthermore, in order to reduce the torque of the bearing, this ball bearing has fewer balls 4 than a standard ball bearing, and the circumferential distance between the centers of adjacent balls 4 in the circumferential direction is set to be greater than the center-to-center distance between adjacent balls 4 in the circumferential direction of the standard ball bearing. Specifically, the number of balls 4 is set so that the circumferential distance between the centers of adjacent balls 4 in the circumferential direction (i.e., the value of (pitch circle diameter of balls 4) x π / (number of balls 4)) is four or more times the diameter of the balls 4. The pitch circle diameter of the balls 4 is the diameter of an imaginary circle connecting the centers of multiple balls 4.

[0046] As shown in Figure 2, an outer ring raceway groove 6 in which balls 4 roll is formed on the inner circumference of outer ring 1. Outer ring raceway groove 6 is a groove with an arc-shaped cross section that extends circumferentially around the inner circumference of outer ring 1. Similarly, an inner ring raceway groove 7 in which balls 4 roll is formed on the outer circumference of inner ring 2. Inner ring raceway groove 7 is a groove with an arc-shaped cross section that extends circumferentially around the outer circumference of inner ring 2.

[0047] The balls 4 are in rolling contact with the inner surfaces of the outer ring raceway groove 6 and the inner surfaces of the inner ring raceway groove 7. The outer ring raceway groove 6 is formed symmetrically with respect to the axial center of the outer ring 1, and the inner ring raceway groove 7 is also formed symmetrically with respect to the axial center of the inner ring 2. This ball bearing is a deep groove ball bearing. Steel balls can be used as the balls 4.

[0048] The bearing space 3 between the outer ring 1 and the inner ring 2 is open to the outside of the bearing on either axial side, with no sealing members provided. In other words, the bearing space 3 between the outer ring 1 and the inner ring 2 is in communication with the external space on both axial sides, so that lubricating oil supplied from outside the bearing can be introduced into the bearing space 3 between the outer ring 1 and the inner ring 2 while the bearing is rotating and used to lubricate the interior of the bearing.

[0049] As shown in Figures 3 and 4, the cage 5 is a mating type formed by joining a pair of annular bodies 8a, 8b that are joined and opposed in the axial direction. As shown in Figure 4, a plurality of hemispherical recesses (pockets) 10 for accommodating balls 4 are formed at intervals in the circumferential direction on the axially inner surface 9 of the annular body 8a (i.e., the surface of the annular body 8a facing the annular body 8b). Similarly, a plurality of hemispherical recesses 10 for accommodating balls 4 are formed at intervals in the circumferential direction on the axially inner surface 9 of the annular body 8b (i.e., the surface of the annular body 8b facing the annular body 8a). Note that the axially inner side refers to the side that approaches the axial center of the cage 5 (the position of the mating surfaces of the pair of annular bodies 8a, 8b) along the axial direction, and the axially outer side refers to the side that moves away from the axial center of the cage 5 along the axial direction.

[0050] The pair of annular bodies 8a, 8b are each formed of a resin. Specifically, each annular body 8a, 8b is formed of a resin composition in which a fiber reinforcement material is added to a resin material. As the resin material constituting the resin composition, polyamide resin (PA), polyether ether ketone resin (PEEK), polyphenylene sulfide resin (PPS) can be used. As the polyamide resin (PA), polyamide 46 (PA46), polyamide 66 (PA66), polynonamethylene terephthalamide (PA9T), etc. can be used. As the fiber reinforcement material added to the resin material, glass fiber, carbon fiber, aramid fiber, etc. can be used. The fiber reinforcement material is blended in a proportion of 10 to 50% by weight of the resin composition.

[0051] The axially outer side surfaces 11 of each of the pair of annular bodies 8a, 8b (i.e., the end surfaces on both axial sides of the cage 5) are flat surfaces that are continuous in the circumferential direction over the entire circumference and perpendicular to the axial direction. In addition, the axially inner side surfaces 9 of each of the pair of annular bodies 8a, 8b are formed with lightening portions 12 that are recessed in the axial direction between circumferentially adjacent recesses 10.

[0052] As shown in Figures 2 and 4, the lightening portion 12 is formed in a box shape surrounded by a partially cylindrical outer peripheral wall 13 (see Figure 2) extending in the circumferential direction, a partially cylindrical inner peripheral wall 14 extending in the circumferential direction opposite the radially inner side of the outer peripheral wall 13, a one end wall 15 (see Figure 4) connecting one circumferential end of the outer peripheral wall 13 and the inner peripheral wall 14, an other end wall 16 (see Figure 4) connecting the other circumferential ends of the outer peripheral wall 13 and the inner peripheral wall 14, and a bottom wall 17 connecting the axial outer ends of the outer peripheral wall 13 and the inner peripheral wall 14.

[0053] As shown in Figure 2, the bottom wall 17 is formed as a flat surface perpendicular to the axial direction and extends circumferentially with a constant radial width. The outer peripheral wall 13 of the lightening portion 12 of each annular body 8a, 8b, i.e., the inner surface on the radially outer side of the lightening portion 12, is inclined radially outward toward the axially inner side. The circumferential length of the lightening portion 12 (i.e., the circumferential length from one end wall 15 to the other end wall 16) is set to be 1.0 times or more (preferably 1.2 times or more) the diameter of the ball 4.

[0054] As shown in Figures 5 to 7, the pair of annular bodies 8a, 8b are joined by resin crimping, which melts and deforms the tip of a resin protrusion. That is, as shown in Figures 5 and 6, a resin protrusion 18 extending in the axial direction and formed on the annular body 8a is inserted into a crimping hole 19 formed axially penetrating the annular body 8b. Then, as shown in Figures 7(a) and 7(b), a high-temperature heating jig 20 is pressed against the tip of the resin protrusion 18, and the tip of the resin protrusion 18 is melted and pressurized by the heating jig 20 to form a crimping head 21, which prevents the resin protrusion 18 from slipping out of the crimping hole 19 and joins the pair of annular bodies 8a, 8b. Here, the crimping head 21 refers to the head portion of the resin protrusion 18 that is formed by melting and deforming the tip portion of the resin protrusion 18, and then cooling and solidifying it.

[0055] Here, the heating jig 20 has been described as an example of a method in which a high-temperature heating jig 20 is pressed against resin, and the heat transferred from the heating jig 20 to the resin melts and deforms the resin (the so-called thermal crimping method). However, it is also possible to use a method in which an ultrasonically vibrating heating jig 20 is pressed against resin, and the frictional heat generated by the ultrasonic vibrations melts and deforms the resin (the so-called ultrasonic crimping method).

[0056] 5, the resin protrusions 18 are formed on the axially inner surface 9 of the annular body 8a in a portion between the recess 10 and the lightening portion 12 located on one circumferential side of the recess 10, and a portion between the recess 10 and the lightening portion 12 located on the other circumferential side of the recess 10. Similarly, the crimping holes 19 are formed on the axially inner surface 9 of the annular body 8b in a portion between the recess 10 and the lightening portion 12 located on one circumferential side of the recess 10, and a portion between the recess 10 and the lightening portion 12 located on the other circumferential side of the recess 10.

[0057] As shown in FIG. 7(b), the crimping hole 19 has a straight hole portion 22 that has a constant cross-sectional shape and extends in the axial direction (vertical direction in the figure), and a counterbore portion 23 that is adjacent to the axially outer side of the straight hole portion 22. The counterbore portion 23 has a cross-sectional shape larger than that of the straight hole portion 22, and accommodates the crimping head portion 21, which is formed by melting the tip of the resin protrusion 18, so that it does not protrude from the axially outer surface 11 of the annular body 8b. The crimping head portion 21 is formed in a flange shape that protrudes in a direction perpendicular to the longitudinal direction of the resin protrusion 18. The seating surface of the crimping head portion 21 contacts the bottom surface of the counterbore portion 23.

[0058] As shown in FIGS. 2 and 6 , an outer-periphery communicating groove 24 is formed in the axially inner surface 9 of each of the annular bodies 8 a and 8 b, connecting the cutout portions 12 to the outer peripheries of the annular bodies 8 a and 8 b. As shown in FIG. 6 , the outer-periphery communicating groove 24 has the same width as the circumferential width of the cutout portions 12 and extends radially outward from the position of the outer peripheral wall 13 of the cutout portions 12. The width of the outer-periphery communicating groove 24 can be set smaller than the circumferential width of the cutout portions 12. As shown in FIG. 2 , the depth of the outer-periphery communicating groove 24 is smaller than the axial depth of the cutout portions 12 (i.e., the axial distance from the axially inner surface 9 of each of the annular bodies 8 a and 8 b to the bottom wall 17 of the cutout portions 12). The depth of the outer-periphery communicating groove 24 is set to be less than half (preferably less than 20%) of the axial depth of the cutout portions 12.

[0059] Similarly, as shown in FIGS. 2, 4, and 6, an inner periphery-side communicating groove 25 is formed on the axially inner surface 9 of each of the annular bodies 8a and 8b, connecting the cutout portions 12 with the inner periphery of each of the annular bodies 8a and 8b. As shown in FIG. 6, the inner periphery-side communicating groove 25 has the same width as the circumferential width of the cutout portions 12 and extends radially inward from the position of the inner periphery wall 14 of the cutout portions 12. The width of the inner periphery-side communicating groove 25 can also be set smaller than the circumferential width of the cutout portions 12. As shown in FIG. 4, the depth of the inner periphery-side communicating groove 25 is smaller than the axial depth of the cutout portions 12. The depth of the inner periphery-side communicating groove 25 is set to be less than half (preferably less than 20%) of the axial depth of the cutout portions 12.

[0060] 2, the inner-periphery-side communicating groove 25 is disposed radially opposite to the outer-periphery-side communicating groove 24. That is, the outer-periphery-side communicating groove 24 and the inner-periphery-side communicating groove 25 are formed so that, when viewed radially, the opening at the radially inner end of the outer-periphery-side communicating groove 24 and the opening at the radially outer end of the inner-periphery-side communicating groove 25 overlap with each other.

[0061] As shown in Fig. 4, in this ball bearing, the axially outer surface 11 of each of a pair of annular bodies 8a, 8b constituting the cage 5 is a flat surface that continues in the circumferential direction over the entire circumference, and each of the pair of annular bodies 8a, 8b is formed with a lightening portion 12. This allows the cage 5 to be made lighter while increasing its rigidity, making it possible to suppress deformation of the cage 5 due to centrifugal force during high-speed rotation. Furthermore, because the lightening portions 12 are formed on the axially inner surface 9 rather than on the axially outer surface 11 of each of the annular bodies 8a, 8b, the axially outer surface 11 of the annular bodies 8a, 8b does not have an uneven shape due to the recesses of the lightening portions 12. As a result, lubricating oil supplied from outside the bearing is less likely to be scraped away by the axially outer surface 11 of the annular bodies 8a, 8b, making it possible to prevent starvation of the lubricating oil during high-speed rotation.

[0062] As shown in Figures 2 and 4, this ball bearing employs a box-shaped recessed portion 12 surrounded by an outer peripheral wall 13 (see Figure 2), an inner peripheral wall 14, a one end wall 15 (see Figure 4) connecting one circumferential end of the outer peripheral wall 13 and the inner peripheral wall 14, an other end wall 16 (see Figure 4) connecting the other circumferential ends of the outer peripheral wall 13 and the inner peripheral wall 14, and a bottom wall 17 connecting the axial outer ends of the outer peripheral wall 13 and the inner peripheral wall 14. This makes it possible to effectively reduce the weight of each annular body 8a, 8b while ensuring the rigidity of each annular body 8a, 8b by using the recessed portion 12.

[0063] Furthermore, as shown in Fig. 2, this ball bearing has outer-periphery-side communicating grooves 24 formed in the axially inner surface 9 of each of the annular bodies 8a, 8b, which connect the lightening holes 12 with the outer peripheries of the annular bodies 8a, 8b, thereby preventing imbalance in the weight of the cage 5 due to lubricating oil collecting in the lightening holes 12. That is, when lightening holes 12 are formed in the axially inner surface 9 of a pair of annular bodies 8a, 8b that are joined opposite each other in the axial direction as shown in Fig. 2, the lightening holes 12 are located inside the cage 5, so lubricating oil supplied from the outside will collect in the lightening holes 12, and the lubricating oil collected in the lightening holes 12 may cause an imbalance in the weight of the cage 5 during rotation of the bearing. Therefore, by forming an outer periphery communicating groove 24 on the axial inner surface 9 of each annular body 8a, 8b that connects the lightening portion 12 with the outer periphery of the annular body 8a, 8b, the lubricating oil that has accumulated in the lightening portion 12 is discharged through the outer periphery communicating groove 24 by centrifugal force, thereby making it possible to prevent the weight of the retainer 5 from becoming unbalanced due to the lubricating oil that has accumulated in the lightening portion 12.

[0064] 2, in this ball bearing, the inner surfaces on the radially outer sides of the lightening portions 12 of each of the annular bodies 8a, 8b are inclined radially outward toward the axially inner side, so that during rotation of the bearing, centrifugal force causes the lubricating oil present in the lightening portions 12 to flow along the inclination of the inner surfaces on the radially outer sides of the lightening portions 12 in a direction approaching the outer-periphery-side communicating groove 24. Therefore, the lubricating oil present in the lightening portions 12 can be efficiently discharged from the outer-periphery-side communicating groove 24.

[0065] 2, in this ball bearing, the lightening hole 12 and the inner periphery of the annular bodies 8a, 8b are in communication with each other via the inner periphery communicating groove 25, so that it is possible to prevent negative pressure from building up in the lightening hole 12 when the lubricating oil present in the lightening hole 12 is discharged by centrifugal force through the outer periphery communicating groove 24. This makes it possible to smoothly discharge the lubricating oil present in the lightening hole 12.

[0066] 2, in this ball bearing, the inner circumference-side communicating groove 25 and the outer circumference-side communicating groove 24 are arranged radially opposite each other, so that when lubricating oil flows into the lightening hole 12 through the inner circumference-side communicating groove 25 during rotation of the bearing, the lubricating oil can be efficiently discharged from the outer circumference-side communicating groove 24. The lubricating oil discharged from the outer circumference-side communicating groove 24 is supplied to the outer ring raceway groove 6 formed on the inner circumference of the outer ring 1, and the balls 4 roll against the inner surface of the outer ring raceway groove 6. Therefore, when the lubricating oil is discharged from the outer circumference-side communicating groove 24, the lubricating condition inside the bearing is improved, making it possible to effectively prevent starvation of the lubricating oil during high-speed rotation.

[0067] Furthermore, as shown in Figure 5, this ball bearing has a resin protrusion 18 formed on the annular body 8a and extending in the axial direction, which is inserted into a crimping hole 19 formed by axially penetrating the annular body 8b, and as shown in Figure 4, the tip of the resin protrusion 18 is melted to form a crimping head 21, which prevents the resin protrusion 18 from coming out of the crimping hole 19. This makes it possible to reliably join the pair of annular bodies 8a, 8b, and also makes it easy to check whether the pair of annular bodies 8a, 8b are completely joined.

[0068] That is, in a configuration such as that described in Japanese Patent Application Laid-Open No. 2013-245762 and Japanese Patent Application Laid-Open No. 2004-076778, in which an engagement claw formed on one of a pair of annular bodies is inserted into an engagement hole formed in the other annular body and a hook portion formed on the engagement claw is engaged with a step portion formed on the inner surface of the engagement hole, when the engagement claw is inserted into the engagement hole, the hook portion formed on the engagement claw must be forcibly inserted while deforming so as to enter the engagement hole, and the hook portion of the engagement claw must be restored to its original shape before deformation to engage with the step portion on the inner surface of the engagement hole, making it difficult to stably engage the hook portion of the engagement claw with the step portion on the inner surface of the engagement hole. Moreover, when the hook portion of the engagement claw is engaged with the step portion on the inner surface of the engagement hole, the engaging portion is located inside the engagement hole and cannot be seen from the outside, so the engaged state of the hook portion and the step portion cannot be visually confirmed, making it difficult to confirm whether the pair of annular bodies are completely coupled. In contrast to this, as shown in Figure 5, if a configuration is adopted in which a resin protrusion 18 formed on annular body 8a is inserted into a crimping hole 19 formed in annular body 8b, and the tip of the resin protrusion 18 is melted to form a crimping head 21 as shown in Figure 4, thereby preventing the resin protrusion 18 from slipping out of the crimping hole 19, the resin protrusion 18 is inserted into the crimping hole 19 without the crimping head 21 being formed at the tip of the resin protrusion 18, and then the crimping head 21 is formed at the tip of the resin protrusion 18, so that the pair of annular bodies 8a, 8b can be reliably joined, and it is also easy to check whether the pair of annular bodies 8a, 8b are completely joined.

[0069] 7(b), this ball bearing is housed in a counterbore 23 formed at the axially outer end of the crimping hole 19 so that the crimped head 21 does not protrude from the flat axially outer surface 11 of the annular body 8b, and therefore the axially outer surface 11 of the annular body 8b does not become uneven due to the crimped head 21. As a result, lubricating oil supplied from outside the bearing is less likely to be scraped off by the axially outer surface 11 of the annular body 8b, making it possible to prevent starvation of the lubricating oil during high-speed rotation.

[0070] 8, the inner periphery of each annular body 8a, 8b may be formed so as to be inclined radially outward toward the axially inward direction. In this way, during rotation of the bearing, centrifugal force causes lubricating oil present on the radially inner side of each annular body 8a, 8b to flow along the inclination of the inner periphery of each annular body 8a, 8b toward the inner periphery side communicating groove 25. This allows the lubricating oil present on the radially inner side of each annular body 8a, 8b to efficiently flow through the inner periphery side communicating groove 25 into the lightening hole 12 and then be discharged from the outer periphery side communicating groove 24.

[0071] 9 to 15 show a second embodiment of the present invention. The second embodiment differs from the first embodiment in the circumferential positions of the lightening holes 12, the resin protrusions 18, and the crimping holes 19, but has the same basic configuration. Therefore, parts corresponding to those in the first embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0072] 11, the resin protrusion 18 is formed on the axially inner surface 9 of the annular body 8a at a midpoint between the recesses 10 adjacent to each other in the circumferential direction, and a lightening portion 12 is formed between the resin protrusion 18 and the recesses 10. Similarly, the crimping hole 19 is formed on the axially inner surface 9 of the annular body 8b at a midpoint between the recesses 10 adjacent to each other in the circumferential direction, and a lightening portion 12 is formed between the crimping hole 19 and the recesses 10.

[0073] 11 and 12, an oil reservoir groove 26 is formed on the inner surface of the recess 10, extending circumferentially from one circumferential end to the other circumferential end of the recess 10. As shown in Fig. 12, the oil reservoir groove 26 is formed to have an arc-shaped cross section.

[0074] 11 , an oil passage groove 27 that connects the recessed portion 10 to the lightening portion 12 is formed on the axially inner surface 9 of each of the annular bodies 8a, 8b. The oil passage groove 27 is formed by circumferentially penetrating a wall-like portion that separates the recessed portion 10 from the lightening portion 12 (the portion that forms the circumferential end wall 15 or the other end wall 16 of the lightening portion 12). The oil passage groove 27 is connected to the circumferential end of the oil reservoir groove 26.

[0075] 11, the ball bearing of this embodiment has an oil reservoir groove 26 formed on the inner surface of recess 10, extending circumferentially from one circumferential end to the other circumferential end of recess 10, so that lubricating oil is stored in oil reservoir groove 26 and can lubricate the balls 4 housed in recess 10. This makes it possible to effectively prevent starvation of the lubricating oil during high-speed rotation.

[0076] 11, this ball bearing has oil passage grooves 27 formed on the axially inner surface 9 of each of the annular bodies 8a, 8b that connect the lightening holes 12 with the recesses 10, so that the lubricating oil present in the lightening holes 12 can be supplied to the recesses 10 through the oil passage grooves 27 and used to lubricate the balls 4 accommodated in the recesses 10. This makes it possible to effectively prevent starvation of the lubricating oil during high-speed rotation.

[0077] 16 to 22 show a third embodiment of the present invention. The third embodiment is different from the second embodiment in that the arrangement of the resin protrusions 18 and the crimping holes 19 is different, but the other configurations are the same. Therefore, parts corresponding to those in the second embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0078] On the axially inner surface 9 of the annular body 8a, resin protrusions 18 and crimping holes 19 are formed alternately in the circumferential direction, with recesses 10 interposed between them. That is, on the axially inner surface 9 of the annular body 8a, the resin protrusions 18 and the crimping holes 19 are formed alternately in the circumferential direction, and an even number of recesses 10 are formed at equal intervals in the circumferential direction so that the resin protrusions 18 and the crimping holes 19 are each located at the midpoint between two recesses 10 adjacent to each other in the circumferential direction.

[0079] Similarly, on the axially inner surface 9 of the annular body 8b, resin protrusions 18 and crimping holes 19 are alternately formed in the circumferential direction with recesses 10 interposed therebetween. That is, on the axially inner surface 9 of the annular body 8b, the resin protrusions 18 and the crimping holes 19 are alternately formed in the circumferential direction, and an even number of recesses 10 are formed at equal intervals in the circumferential direction so that the resin protrusions 18 and the crimping holes 19 are located at the midpoints of the recesses 10 adjacent to each other in the circumferential direction.

[0080] In the ball bearing of this embodiment, the pair of annular bodies 8a, 8b constituting the cage 5 have the same shape. Therefore, it is possible to use a common mold for molding the annular bodies 8a, 8b, which reduces costs.

[0081] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0082] 1 outer ring 2. Inner circle 3 Bearing space 4 balls 5 Resin cage 6 Outer ring raceway groove 7 Inner ring raceway groove 8a, 8b cyclic bodies 9 Axial inner surface 10 recess 11 Axial outer surface 12 Cutout 13 Peripheral wall 14 Inner wall 15 One end wall 16 Other end wall 17 Bottom wall 18 Resin projection 19 Crimping hole 21 Crimp head 23 Counterbore 24 Outer periphery communicating groove 25 Inner circumference communication groove 26 Oil reservoir groove 27 Oil passage groove

Claims

1. a pair of annular resin bodies (8a, 8b) joined together in an axially opposed relationship; In the resin cage, a plurality of hemispherical recesses (10) are formed at intervals in the circumferential direction on an axially inner surface (9) of each of the pair of annular bodies (8 a, 8 b), The pair of annular bodies (8a, 8b) each have an axially outer surface (11) that is a flat surface that is continuous in the circumferential direction over the entire circumference, A resin cage characterized in that a lightening portion (12) is formed on the axial inner surface (9) of each of the pair of annular bodies (8a, 8b) between the recesses (10) adjacent in the circumferential direction, the lightening portion (12) being recessed in the axial direction.

2. 2. The resin cage according to claim 1, wherein the hollowed-out portion (12) is surrounded by a partially cylindrical outer peripheral wall (13) extending in the circumferential direction, a partially cylindrical inner peripheral wall (14) extending in the circumferential direction opposite the radially inner side of the outer peripheral wall (13), a one end wall (15) connecting one circumferential end of the outer peripheral wall (13) and the inner peripheral wall (14), an other end wall (16) connecting the other circumferential end of the outer peripheral wall (13) and the inner peripheral wall (14), and a bottom wall (17) connecting the axial outer ends of the outer peripheral wall (13) and the inner peripheral wall (14).

3. 3. A resin cage according to claim 1, wherein an outer periphery communicating groove (24) is formed on an axially inner surface (9) of each of the annular bodies (8a, 8b), the outer periphery communicating with the hollowed-out portion (12) and the outer periphery of the annular body (8a, 8b).

4. 4. The resin cage according to claim 3, wherein the inner surface of the radially outer side of the hollowed-out portion (12) of each of the annular bodies (8a, 8b) is inclined radially outward toward the axially inner side.

5. 4. The resin cage according to claim 3, wherein an inner circumferential communicating groove (25) is formed on an axially inner surface (9) of each of the annular bodies (8a, 8b), the inner circumferential communicating groove (25) communicating the hollowed-out portion (12) with the inner periphery of the annular body (8a, 8b).

6. 6. The resin cage according to claim 5, wherein the inner circumferential communicating groove (25) is disposed radially opposite the outer circumferential communicating groove (24).

7. 7. The resin cage according to claim 6, wherein the inner periphery of each of the annular bodies (8a, 8b) is inclined radially outwardly toward the axially inward direction.

8. 3. The resin cage according to claim 1, wherein an oil passage groove (27) communicating with the recess (10) and the hollowed portion (12) is formed on an axially inner surface (9) of each of the annular bodies (8a, 8b).

9. 3. The resin cage according to claim 1, wherein an oil reservoir groove (26) is formed in the recess (10) so as to extend in the circumferential direction from one circumferential end to the other circumferential end.

10. an outer ring (1) having an outer ring raceway groove (6) formed on its inner periphery; an inner ring (2) having an inner ring raceway groove (7) formed on its outer periphery; a plurality of balls (4) that are installed at intervals in the circumferential direction in an annular bearing space (3) formed between the outer ring (1) and the inner ring (2) and that are in rolling contact with the inner surface of the outer ring raceway groove (6) and the inner surface of the inner ring raceway groove (7); A ball bearing comprising: a resin cage (5) according to claim 1 or 2 that holds the plurality of balls (4).

11. 11. A ball bearing as described in claim 10, wherein a resin protrusion (18) extending in the axial direction formed on one of the pair of annular bodies (8a, 8b) is inserted into a crimping hole (19) formed axially through the other annular body (8b), and the resin protrusion (18) is prevented from coming out of the crimping hole (19) by a crimping head (21) formed by melting the tip of the resin protrusion (18).

12. A ball bearing as described in claim 11, wherein a counterbore portion (23) is provided at the axially outer end of the crimping hole (19) to accommodate the crimping head (21) so that the crimping head (21) does not protrude from the axially outer surface (11) of the annular body (8b).

13. 11. A ball bearing according to claim 10, wherein the distance between the centers of the balls (4) adjacent to each other in the circumferential direction is four times or more the diameter of the balls (4).

14. 11. A ball bearing according to claim 10, wherein both axial ends of the bearing space (3) are open without providing any sealing member.

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