CAGE, ROLLING BEARING AND METHOD FOR FORMING A CAGE

Abstract

A resin cage 14 comprising an annular body 17, a plurality of prongs 19, a plurality of gate marks 28 formed spaced apart from each other in a circumferential direction, a weld line 24 formed between the gate marks 28 adjacent to each other in the circumferential direction, and a plurality of pocket forming portions 21 each disposed between the gate marks 28 and in which pockets 15 are formed. Each of the pocket forming portions 21 has a through hole 23 formed through a bottom of the pocket 15 in an axial direction. The weld line 24 is formed between the gate marks 28 only in a region R1 on one circumferential side of the through hole 23 or only in a region R2 on the other circumferential side of the through hole 23.

Description

Technical FieldThe present invention relates to a cage, a rolling bearing, and a method of forming the cage.Prior ArtThere is a need for rolling bearings to be used in power units such as automotive transmissions to have reduced axial width dimensions in conjunction with downsizing of the power units. When a cage that holds rolling elements protrudes beyond the surfaces of an outer ring and an inner ring in the axial direction by reducing the width dimension of the rolling bearing, the cage may interfere with elements other than the rolling bearing and may be damaged during a manufacturing process, packaging, transportation, etc. of the rolling bearing. For this reason, in reducing the width dimension of the rolling bearing, it is necessary that the cage does not protrude beyond the surfaces of the outer ring and the inner ring in the axial direction. Therefore, a snap cage made of synthetic resin (see, for example, Patent Document 1) can be used to reduce the width dimension of the rolling bearing.FIG. 10 is a perspective view showing a part of a conventional snap cage 90 made of synthetic resin. FIG. 11 is a sectional view of a rolling bearing 80 including the snap cage 90. As shown in FIGS. 10 and 11, the snap cage 90 includes an annular body 91 and a plurality of prongs 92. The annular body 91 has a circular ring shape. The annular body 91 is disposed on an axial side between an outer ring 81 and an inner ring 82. The plurality of prongs 92 project from the annular body 91 to the other axial side. A pocket 93 is a space surrounded by two adjacent prongs 92 and the annular body 91 between the prongs 92. A rolling element 83 is accommodated in the pocket 93. In the snap cage 90, an axial thickness t 11 of a bottom 91 aof the pocket 93 of the annular body 91 is reduced. Since the thickness t 11 is small, an axial width dimension W 11 of the rolling bearing 80 is smaller than that of a rolling bearing according to the standard dimension system.Prior Art DocumentsPatent DocumentsPatent Document 1: JP 2019-127 974 ASUMMARY OF THE INVENTIONObject to be Achieved by the InventionAs described above, the axial width dimension W 11 of the rolling bearing can be reduced by reducing the thickness t 11 of the bottom 91 aof the annular body 91 of the snap cage 90. Since the thickness t 11 is small, the strength of the snap cage 90 is lower than that of a rolling bearing according to the standard dimension system. For this reason, there is a limit to the reduction in the thickness of the bottom 91 aof the annular body 91.The present invention is intended to minimize the axial width dimension of a rolling bearing while securing the strength of a cage.means for achieving the objectA cage of the present invention is made of synthetic resin and includes an annular body and a plurality of prongs spaced apart from each other in a circumferential direction of the annular body and protruding from the annular body toward an axial side. The cage has a plurality of pockets for holding a plurality of rolling elements of a rolling bearing in a freely rollable manner. Each of the pockets is formed between the prongs that are adjacent to each other in the circumferential direction. The cage includes a plurality of sprue marks formed spaced apart from each other in the circumferential direction, a weld formed between the sprue marks adjacent to each other in the circumferential direction, and a plurality of pocket forming portions each disposed between the sprue marks and in which the pockets are formed. Each of the pocket forming portions has a through hole formed through a bottom of the pocket in an axial direction. The weld is formed between the sprue marks only in a region on one circumferential side of the through hole or only in a region on another circumferential side of the through hole.A rolling bearing of the present invention includes an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and the above cage.A method of forming a cage according to the present invention is a method of forming the above cage using a mold having a plurality of channels, a plurality of gates connected to the channels, and an annular cavity to which the plurality of gates are connected away from each other in the circumferential direction. In the cavity, a plurality of pocket molding spaces in which the pocket molding portions are molded and a plurality of tine molding spaces in which the tine molding portions are molded are alternately formed in the circumferential direction. One of the gates is connected to each of all of the tine forming spaces. When molten resin is poured from the channels into the cavity through the gates, a volume of the molten resin poured from one of the two gates adjacent to each other in the circumferential direction is made larger than a volume of the molten resin poured from the other of the two gates.Effects of the InventionAccording to the present invention, it is possible to minimize the axial width dimension of the rolling bearing while securing the strength of the cage.Brief Description of the DrawingsFIG. 1 is a sectional view of a rolling bearing according to an embodiment of the present invention. FIG. 2 is a perspective view showing a cage of the rolling bearing. FIG. 3 is a perspective view showing an annular component of the cage. FIG. 4 is a sectional view taken along line I-I in FIG. 2. FIG. 5 is a front view of the annular component as viewed from an axially inner side. FIG. 6 is a perspective view showing a part of the annular components. FIG. 7 is a diagram of a part of a pair of disassembled annular components as viewed from a radially inner side. FIG. 8 is a perspective view showing a mold for forming the annular component by injection molding. FIG. 9 is a plan view of the mold. FIG. 10 is a perspective view showing a part of a conventional snap cage made of synthetic resin. FIG. 11 is a sectional view of a rolling bearing including the conventional snap cage.EMBODIMENTS FOR CARRYING OUT THE INVENTIONFirst, the contents of an embodiment will be listed and described.< On Embodiment>1. A cage of the embodiment is formed of synthetic resin and includes an annular body and a plurality of prongs spaced apart from each other in a circumferential direction of the annular body and protruding from the annular body toward an axial side. The cage has a plurality of pockets for holding a plurality of rolling elements of a rolling bearing in a freely rollable manner. Each of the pockets is formed between the prongs that are adjacent to each other in the circumferential direction. The cage includes a plurality of sprue marks formed spaced apart from each other in the circumferential direction, a weld formed between the sprue marks adjacent to each other in the circumferential direction, and a plurality of pocket forming portions each disposed between the sprue marks and in which the pockets are formed. Each of the pocket forming portions has a through hole formed through a bottom of the pocket in an axial direction. The weld is formed between the sprue marks only in a region on one circumferential side of the through hole or only in a region on the other circumferential side of the through hole.In the above cage, the through hole is formed in the bottom of the pocket in the pocket forming portion. Thus, the axial thickness at the bottom of the pocket forming portion can be minimized. Thus, the axial width dimension of the rolling bearing can be reduced. The weld is formed between the sprue marks formed adjacent to each other in the circumferential direction only in the region on the one circumferential side or the other circumferential side of the through hole. Thus, it is possible to suppress the formation of the weld line having the lowest strength in a region (stress concentration portion) of the pocket formation portion on a radially outer side or a radially inner side of the through hole when the rolling bearing is in use. Thus, the strength of the cage can be secured even when the through hole is formed in the pocket forming portion.(2) In the cage according to (1), the weld may preferably include a first weld portion that extends entirely in a radial direction in an axial view and a second weld portion that extends from a radial center of the first weld portion to the through hole in the circumferential direction in the axial view.In this case, the strength of the cage can be further increased compared to a case where only the second weld portion is formed to extend fully in the circumferential direction in the region on the one circumferential side or the other circumferential side of the through hole.(3) Preferably, the cage according to (2) further includes a plurality of tine forming portions in which the tines are formed, and one of the sprue marks may be formed in each of all the tine forming portions.In this case, when the cage is molded using a mold, molten resin flows into the mold from the gate points associated with all the tine forming portions. Therefore, the first weld portion and the second weld portion can be easily formed in the area on the one circumferential side or the other circumferential side of the through hole by controlling the volumes of the molten resin poured from the gates.(4) In the cage according to any one of (1) to (3), a pair of annular components each having the annular body and the plurality of prongs may be connected in the axial direction.In this case, the cage is formed by the pair of annular components. Therefore, the strength of the cage can be further increased compared to a case where the cage is formed by only a single annular component and has cage bars structured by connecting the prongs of the pair of annular components.(5) A rolling bearing of the embodiment includes an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and the cage according to any one of (1) to (3).The above rolling bearing provides the same functions and effects as those of the above cage.(6) A rolling bearing of the embodiment includes an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and the cage according to (4).The above rolling bearing provides the same functions and effects as those of the above cage.(7) A method of forming a cage according to the embodiment is a method of forming the cage according to (3) using a mold having a plurality of channels, a plurality of gates connected to the channels, and an annular cavity to which the plurality of gates are connected away from each other in the circumferential direction. In the cavity, a plurality of pocket molding spaces in which the pocket molding portions are molded and a plurality of tine molding spaces in which the tine molding portions are molded are alternately formed in the circumferential direction. One of the gates is connected to each of all of the tine forming spaces. When molten resin is poured from the channels into the cavity through the gates, a volume of the molten resin poured from one of the two gates adjacent to each other in the circumferential direction is made larger than a volume of the molten resin poured from the other of the two gates.In the above method of forming the cage, in the pocket molding space formed between one tine molding space to which one gate is connected and the other tine molding space to which the other gate is connected, the volume of the molten resin poured from the one tine molding space is larger than the volume of the molten resin poured from the other tine molding space. Therefore, the molten resin flowing from the one tine forming space and the molten resin flowing from the other tine forming space more easily join on the one circumferential side or the other circumferential side of the through hole of the pocket forming portion. Thus, the first weld portion and the second weld portion can be more easily formed in the region on the one circumferential side or the other circumferential side of the through hole.<Details of Embodiment>A preferred embodiment will be described below with reference to the drawings.[Rolling Bearings]FIG. 1 is a sectional view of a rolling bearing 10 according to the embodiment of the present invention. The rolling bearing 10 includes an inner ring 11, an outer ring 12, a plurality of rolling elements 13, and a cage 14. In the following description, a side closer to an axial center C 1 of the rolling bearing 10 may be referred to as an axially inner side, and a side farther from the axial center C 1 may be referred to as an axially outer side.The inner ring 11 has a circular ring shape. The outer ring 12 has a circular ring shape. The outer ring 12 is disposed on a radially outer side of the inner ring 11. The plurality of rolling elements 13 are disposed between the inner ring 11 and the outer ring 12. The rolling elements 13 of the present embodiment are balls. The rolling bearing 10 of the present embodiment is a deep groove ball bearing. The outer circumferential surface of the inner ring 11 has a raceway 11 aalong which the balls 13 roll. The raceway 11 ahas a substantially concave arc shape in cross section. The inner circumferential surface of the outer ring 12 has a raceway 12 aalong which the balls 13 roll. The raceway 12 ahas a substantially concave arc shape in cross section.FIG. 2 is a perspective view showing the cage 14 of the rolling bearing 10. As shown in FIGS. 1 and 2, the cage 14 includes a plurality of pockets 15. The plurality of pockets 15 hold the plurality of balls 13 in a freely rollable manner. The plurality of pockets 15 are spaced apart from each other in a circumferential direction in the cage 14. In a radial view, each pocket 15 has a circular shape. The inner surface of the pocket 15 has a concave shape which is part of a spherical surface. The radius of the concave shape is slightly larger than the radius of the outer circumferential surface of the ball 13 (see also FIG. 4 ).The cage 14 of the present embodiment is a two-piece cage that holds the balls 13 from both axial sides. The cage 14 is formed by a pair of annular components 16 connected to each other in the axial direction. The pair of annular components 16 have the same shape. The pair of annular components 16 are connected in an inverted state. Each annular component 16 is formed of synthetic resin. Each annular component 16 is integrally molded by injection molding.FIG. 3 is a perspective view showing the annular component 16. As shown in FIGS. 2 and 3, each annular component 16 includes an annular body 17 and a plurality of prongs 19. The annular body 17 has a circular ring shape. The annular body 17 is defined as an axially outer portion of a cylindrical or conical plane connecting a first imaginary circle K 1 connecting axially outermost positions of radially outer openings of the pockets 15 and a second imaginary circle K 2 connecting axially outermost positions of radially inner openings of the pockets 15. A plurality of rear hollow portions 17 aare provided spaced apart from each other in the circumferential direction. The plurality of rear hollow portions 17 aare open at the end surface of the annular body 17 on the axially outer side and are inserted axially inward into the prongs 19 (see also FIG. 1 ). The plurality of prongs 19 are integrally formed with the annular body 17 and spaced apart from each other in the circumferential direction of the annular body 17. The plurality of prongs 19 project from the annular body 17 toward the one axial side toward the mating annular component 16. Each tine 19 is a portion (except for the annular body 17) between adjacent pocket forming portions 21 (described later) in the annular component 16.The annular component 16 is structured by alternately forming a plurality of pocket forming portions 21 and a plurality of tine forming portions 22 in the circumferential direction. The pocket forming portion 21 is a portion of the annular component 16 in which each pocket 15 is formed. The tine forming portion 22 is a portion of the annular component 16 in which each tine 19 is formed. The tine forming portion 22 is each tine 19 and a portion of the annular body 17 in which the tine 19 is connected.The tine 19 has a tine body 20 and a tine protrusion 18. The tine protrusion 18 extends axially inward from a tip end surface 22 aof the tine body 20.FIG. 4 is a perspective view showing a part of the annular component 16. FIG. 5 is a diagram of a part of a pair of disassembled annular components 16 as viewed from the radially inner side. As shown in FIGS. 4 and 5, the tip end surface 22 aof each tine body 20 has a flat shape on the axially inner side in the radial view. The tip end surface 22 aof each tine body 20 comes into contact with the tip end surface 22 aof each tine body 20 of the mating annular component 16 (see FIG. 2 ).The tine protrusion 18 is connected to the tip end surface 22 aof each tine body 20. The tine protrusion 18 extends in the axial direction toward the mating annular component 16. the tine protrusion 18 is connected to a radially inner portion of the tip end surface 22 aof the tine body 20 and is connected to a position offset to a circumferential side from a circumferential center C 2 of the tip end surface 22 aof the tine body 20. The tine protrusion 18 has a substantially quadrangular prism shape. A radially inner surface 18 aof each tine protrusion 18 forms the inner circumferential surface of the annular component 16 (see FIG. 2 ). The tine protrusion 18 includes a tine protrusion body 18 cextending in the axial direction and a latch protrusion 18 bprotruding radially outward at the tip of the tine protrusion body 18 c.The inner circumferential surface of each tine 19 has a latching groove 22 bextending in the axial direction. The latching groove 22 bis open at the position of the tip end surface 22 aof the tine body 20. The latching groove 22 bis provided at a position offset from the tine protrusion 18 from the circumferential center C 2 of the tip end surface 22 aof the tine body 20. The tine protrusion 18 of the mating annular component 16 is inserted into the latching groove 22 bfrom the tip end surface 22 aside of the tine body 20. The tine protrusion 18 of the mating annular component 16 is inserted into the latching groove 22 bof the latching protrusion 18 b.As shown in FIG. 1, the locking groove 22 bcommunicates with the rear hollow portion 17 athat is recessed axially inward from the end surface of the annular body 17 on the axially outer side. A radial step surface 22 cis formed at the center of the detent groove 22 bin the axial direction. The locking protrusion 18 bis locked to the step surface 22 cof the locking groove 22 bin the axial direction. The tine protrusion body 18 cis accommodated in the latching groove 22 b. Since the locking protrusion 18 bis locked to the step surface 22 c, the pair of annular components 16 are not separated in the axial direction. The pair of annular components 16 are connected to each other.As shown in FIG. 3, each tine forming portion 22 of each annular component 16 has a sprue mark 28 (see also FIG. 5 ). The sprue mark 28 is a shear mark formed when a sprue 46 (described later) of a mold 40 is separated after the annular component 16 is molded using the mold 40 (described later). In the present embodiment, the sprue mark 28 is located at a position offset to a circumferential side (tine protrusion 18 side) of an inner surface 22 dof each tine forming portion 22 on the radially inner side. The sprue mark 28 has a circular shape.As described above, a plurality of sprue marks 28 are provided on the inner circumferential surface of the annular component 16 spaced apart from each other in the circumferential direction. The pocket forming portion 21 is provided between the sprue marks 28 adjacent to each other in the circumferential direction. The illustration of the sprue marks 28 is omitted in FIG. 2.As shown in FIGS. 2 and 3, an end surface 21 aof each pocket formation portion 21 on the axially inner side in the radial view has a semi-circular shape. The end surface 21 aof each pocket forming portion 21 on the axially inner side is part of a spherical surface having a radius slightly larger than the radius of the ball 13. A pocket 15 is formed by disposing the pocket forming portions 21 of the pair of annular components 16 so as to face each other in the axial direction. The one pocket 15 is part of a spherical surface defined by two end surfaces 21a. The cage 14 has a plurality of cage bars 25 in the circumferential direction. A cage bar 25 is formed by connecting the prongs 19 of the pair of annular components 16 in the axial direction. Each pocket 15 is formed between the cage bars 25 adjacent to each other in the circumferential direction of the cage 14.FIG. 6 is a sectional view taken along line I-I in FIG. 2 ; as shown in FIGS. 3 and 6, a circular through hole 23 is open at the bottom of each pocket forming portion 21 located at the axially outermost side of the pocket 15. The through hole 23 passes through the annular body 17 in the axial direction. The through hole 23 is open to the end surface of the annular body 17 on the axially outer side. By providing the through hole 23, an axial thickness t 1 of the bottom of the pocket forming portion 21 can be reduced as compared to the thickness t 11 (see FIG. 11 ) of the pocket bottom of the conventional annular body. Consequently, an axial width dimension W 1 of the rolling bearing 10 (see FIG. 1 ) is smaller than the width dimension W 11 of the conventional rolling bearing (see FIG. 11 ).FIG. 7 is a front view of the annular component 16 as viewed from the axially inner side. As illustrated in FIG. 7, the annular component 16 has a weld (weld line) 24 between the sprue marks 28 adjacent to each other in the circumferential direction. The weld 24 is generated when the annular component 16 is formed using the mold 40 (described later). The weld 24 is a thin line generated at a portion where molten resin flows join and merge with each other within the mold 40 described later.The weld 24 is formed between the adjacent sprue marks 28 only in a region R 1 on one circumferential side of the through hole 23 or only in a region R 2 on the other circumferential side. The regions R 1 and R 2 are regions including the tine forming portions 22 and the pocket forming portion 21 except for a region R 3. The region R 3 is a region located on the radially outer side and the radially inner side of the through hole 23 in a region where the through hole 23 exists in the circumferential direction of the tine forming portion 22. The weld 24 is not formed in the region R 3 which is a stress concentration portion of each pocket formation portion 21. In the present embodiment, the weld 24 is formed in the pocket forming portion 21 and / or the tine forming portion 22 in the region R 1 or the region R 2. The weld bead 24 is formed over the total thickness of the pocket forming portion 21 in the axial direction (direction perpendicular to the drawing sheet of FIG. 7 ).The weld 24 includes a first weld portion 24 aand a second weld portion 24 b. The first weld portion 24 aextends fully in the radial direction and the axial direction in the region R 1 or the region R 2 in the axial view (front view in FIG. 7 ). In the axial view, the second weld portion 24 bextends in the circumferential direction and entirely in the axial direction from a radial center (in this case, a center position) of the first weld portion 24 ato the through hole 23.[FORM]FIG. 8 is a perspective view showing the mold 40 for molding the annular component 16 by injection molding. FIG. 9 is a plan view of the mold 40. As illustrated in FIGS. 8 and 9, the mold 40 includes a first mold portion 41 and a second mold portion 42 divided into two parts in the axial direction of the annular component 16. The first mold portion 41 is a fixed mold. The second mold portion 42 is a movable mold movable in the axial direction relative to the first mold portion 41. In FIG. 8, for convenience, the first mold portion 41 and the second mold portion 42 are drawn by imaginary lines (long dashed double short dashed lines).The mold 40 further includes a cavity 43, a gate 44, a plurality of channels 45, and a plurality of gate holes 46. The cavity 43 is a space to be filled with molten resin. The cavity 43 has an annular shape corresponding to the shape of the annular component 16. Therefore, in the cavity 43, a plurality of pocket molding spaces 43 ain which the pocket molding portions 21 are molded and a plurality of tine molding spaces 43 bin which the tine molding portions 22 are molded are alternately formed in the circumferential direction. Although illustration is omitted, cylindrical molding columns for molding the through holes 23 are provided in the first molding portion 41 or the second molding portion 42 at positions corresponding to the through holes 23 in the pocket molding spaces 43 a.The sprue 44, the plurality of channels 45, and the plurality of sprue holes 46 are passages for supplying molten resin to the cavity 43. The sprue 44 extends in the axial direction at the center of the annular cavity 43.The channel 45 is a passage formed between the first mold portion 41 and the second mold portion 42. A channel 45 is provided for (each) a tine forming portion 22. The plurality of channels 45 extend radially outward from the tip of the sprue 44. Each channel 45 of the present embodiment has a quadrangular shape in cross section.The plurality of gates 46 are connected to the radially outer ends of the channels 45. Each gate 46 extends from the radially outer end of each passage 45 to the radially outer side and the one axial side (upper side in FIG. 8 ). Each gate 46 of the present embodiment has a circular shape in cross section and is formed so that the diameter gradually decreases toward the tip.The tips of the plurality of gates 46 are connected away from each other in the circumferential direction of the cavity 43. Specifically, the tip of each gate 46 in each tine forming space 43 bis connected at a position offset to a circumferential side (tine protrusion 18 side) of the location corresponding to the inner surface 22 dof the tine forming portion 22. Thus, the gates 46 are connected to all the tine forming spaces 43b.The method of forming the annular component 16 is as follows. Molten resin supplied to the sprue 44 of the mold 40 passes through each channel 45 and each sprue opening 46 in sequence and flows into each tine forming space 43 bof the cavity 43. The molten resin then fills the entire cavity 43, and the molten resin is cured and the cured resin is taken out of the mold 40 as the ring-shaped component 16.As illustrated in FIG. 9, the plurality of gates 46 of the present embodiment includes a plurality of first gates 46A, a plurality of second gates 46B, and a third gate 46C. The diameter at the position where the tip of the first gate 46A is open to the cavity 43, the diameter at the position where the tip of the second gate 46B is open to the cavity 43, and the diameter at the position where the tip of the third gate 46C is open to the cavity 43 are different from each other. Four first gates 46A and four second gates 46B are provided. A third gate 46C is provided. The tip diameter of the first gate 46A is larger than the tip diameter of the second gate 46B. The tip diameter of the second gate 46B is larger than the tip diameter of the third gate 46C.The first gate 46A and the second gate 46B are arranged so as to be adjacent to each other in the circumferential direction. The third gate 46C is disposed between the first gate 46A and the second gate 46B at a predetermined position in the circumferential direction (substantially a 10 o'clock position in FIG. 9 ). Therefore, the diameters of the tips of two gates 46 adjacent to each other in the circumferential direction are different from each other. Thus, the flow rate of the molten resin flowing into the tine forming space 43 bfrom one of the adjacent gates 46 having a larger tip diameter is higher than the flow rate of the molten resin flowing into the tine forming space 43 bfrom the other gate 46 having a smaller tip diameter.The flow rate of the molten resin flowing through the first gate 46A is higher than the flow rate of the molten resin flowing through the second gate 46B. The flow rate of the molten resin flowing through the first gate 46A is higher than the flow rate of the molten resin flowing through the third gate 46C. The flow rate of the molten resin flowing through the second gate 46B is higher than the flow rate of the molten resin flowing through the third gate 46C.The molten resin flowing through the first gate 46A flows from the first gate 46A to one side in the circumferential direction of the cavity 43 and to the other side in the circumferential direction of the cavity 43. The molten resin flowing through the second gate 46B flows from the second gate 46B to one side in the circumferential direction of the cavity 43 and to the other side in the circumferential direction of the cavity 43. The molten resin flowing through the third gate 46C flows from the third gate 46C to one side in the circumferential direction of the cavity 43 and to the other side in the circumferential direction of the cavity 43, That are adjacent to each other, the volume of the molten resin flowing from the first gate 46A to the one side in the circumferential direction of the cavity 43 can be made different from the volume of the molten resin flowing from the second gate 46B to the other side in the circumferential direction of the cavity 43. With respect to the first gate 46A and the second gate 46B that are adjacent to each other, the volume of the molten resin flowing from the first gate 46A to the other side in the circumferential direction of the cavity 43 can be made different from the volume of the molten resin flowing from the second gate 46B to the one side in the circumferential direction of the cavity 43. With respect to the first gate 46A and the third gate 46C that are adjacent to each other, the volume of the molten resin flowing from the first gate 46A to the one side in the circumferential direction of the cavity 43 can be made different from the volume of the molten resin flowing from the third gate 46C to the other side in the circumferential direction of the cavity 43. With respect to the second gate 46B and the third gate 46C that are adjacent to each other, the volume of the molten resin flowing from the second gate 46B to the other side in the circumferential direction of the cavity 43 can be made different from the volume of the molten resin flowing from the third gate 46C to the one side in the circumferential direction of the cavity 43. By combining the tip diameter and the arrangement of the first gate 46A, the tip diameter and the arrangement of the second gate 46B, and the tip diameter and the arrangement of the third gate 46C, the streams of molten resin can join at a position different from the circumferential center between adjacent gates 46.As described above, as shown in FIG. 7, in the molded annular component 16, the weld 24 is formed in the pocket forming portion 21 in the region R 1 on the one circumferential side of each through hole 23 or in the region R 2 on the other circumferential side of each through hole 23. The second weld portion 24 bof the weld 24 is a thin line generated at a portion where the streams of molten resin that have passed from one of the tine forming spaces 43 bthrough the radially outer side and the radially inner side of the through hole 23 join and merge with each other. The first weld portion 24 aof the weld 24 is a thin line generated at a portion where the flows of molten resin that have passed through the radially outer side and the radially inner side of the through hole 23 and the flow of molten resin from the other one of the tine forming spaces 43 bconnect and merge with each other.[Functions and Effects of Embodiment]As described above, in the cage 14 of the present embodiment, the through holes are formed in the bottoms of the pockets 15 in the pocket forming portions 21. Thus, the axial thickness t 1 at the bottoms of the pocket forming portions 21 can be reduced. Thus, in the rolling bearing 10 using the cage 14 of the present embodiment, the axial width dimension W 1 of the rolling bearing 10 can be reduced. The weld bead 24 is formed between the sprue marks 28 formed adjacent to each other in the circumferential direction only in the area R 1 on the one circumferential side of the through hole 23 or only in the area R 2 on the other circumferential side. Thus, in the cage 14 of the present embodiment, it is possible to suppress the formation of the weld with the lowest strength in the region R 3 that is a stress concentration portion of the pocket formation portion 21 when the rolling bearing 10 is in use. Thus, the cage 14 of the present embodiment has strength even when having the through hole 23 in the pocket forming portion 21.The weld 24 includes the first weld portion 24 aextending entirely in the radial direction in the axial view and the second weld portion 24 bextending from the radial center of the first weld portion 24 ato the through hole 23 in the circumferential direction in the axial view. Therefore, in the cage 14 of the present embodiment, it is possible to further increase the strength of the cage 14 as compared with a case where only the second weld portion 24 bis formed to extend fully in the circumferential direction of the region R 1.All the tine forming portions 22 of the cage 14 of the present embodiment have the sprue marks 28. That is, when the cage 14 of the present embodiment is molded using the mold 40, molten resin flows into the mold 40 from the gates 46 associated with all the tine forming portions 22.The cage 14 of the present embodiment is structured by connecting the pair of annular components 16 in the axial direction. Therefore, in the cage 14 of the present embodiment, it is possible to further increase the strength of the cage 14 as compared with a snap cage structured by only a single annular component.Two gates 46 of the mold 40 adjacent to each other in the circumferential direction have different diameters at their tips. Therefore, the volume of the molten resin flowing from one of the two gates 46 adjacent to each other in the circumferential direction into the cavity 43 on the one side in the circumferential direction is larger than the volume of the molten resin flowing from the other gate 46 into the cavity 43 on the other side in the circumferential direction. Consequently, the first weld portion 24 aand the second weld portion 24 bcan be formed more easily in the region R 1 or the region R 2 instead of the region R 3 by controlling the volumes of the molten resin poured from the gates 46.[Other]The embodiment disclosed above is illustrative in all respects and is not restrictive. For example, the rolling bearing 10 may be a tapered ball bearing instead of the deep groove ball bearing. The cage 14 may be a snap cage or a tine-like cage in addition to the two-part cage. The weld 24 may be formed in the pocket forming portion 21 or the tine forming portion 22 in the region R 1 or the region R 2.The gate 46 of the mold 40 is connected in each tine forming space 43 bat the location corresponding to the inner surface 22 dof the tine forming portion 22, but is not limited thereto. For example, the gate 46 may be connected in each tine forming space 43 bat a location corresponding to the tine protrusion 18. In this case, it is understood that the sprue mark 28 is formed on the tine protrusion 18 of the molded cage 14.The number of the gates 46 is not limited to that in the present embodiment. When there are an even number of gates 46, these gates 46 may be composed of two kinds of gates having different tip diameters. Two gates 46 of the mold 40 adjacent to each other in the circumferential direction have different diameters at their tips to vary the volumetric flows of the molten resin, but this is not limiting. For example, two gates 46 adjacent to each other in the circumferential direction may be connected to independent flow paths, and the inflow pressures of the molten resin to the gates 46 may be made different from each other.Description of the Reference Numerals10 Rolling bearing 11 Inner ring 12 Outer ring 13 Ball (rolling element) 14 Cage 15 Pocket 16 Annular component 17 Annular body 18 Tine protrusion 19 Tine 20 Tine body 21 Pocket molding portion 22 Tine molding portion 23 Through hole 24 Weld 24 aFirst weld portion 24 bSecond weld portion 25 Cage bar 28 Gate mark 40 Mold 43 Cavity 43 a Pocket molding space 43 b Zinken molding space 45 Gate 46 Gate R 1 Region R 2 Region R 3 RegionReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedJP 2019-127 974 A

[0004]

Claims

A cage made of synthetic resin, comprising an annular body and a plurality of prongs spaced apart from each other in a circumferential direction of the annular body and protruding from the annular body toward an axial side, the cage having a plurality of pockets for holding a plurality of rolling elements of a rolling bearing in a freely rollable manner, each of the pockets being formed between the prongs adjacent to each other in the circumferential direction, the cage comprising: a plurality of sprue marks formed spaced apart from each other in the circumferential direction; a weld formed between the sprue marks adjacent to each other in the circumferential direction; and a plurality of pocket forming portions each disposed between the sprue marks and in which the pockets are formed, each of the pocket forming portions having a through hole formed through a bottom of the pocket in an axial direction, and the weld between the sprue marks being formed only in a region on one circumferential side of the through hole or only in a region on another circumferential side of the through hole.The cage of claim 1, wherein the weld includes: a first weld portion that extends entirely in a radial direction in an axial view; and a second weld portion that extends from a radial center of the first weld portion to the through hole in the circumferential direction in the axial view.The cage according to claim 2, further comprising a plurality of tine forming portions in which the tines are formed, wherein one of the sprue marks is formed in each of all the tine forming portions.The cage according to any one of claims 1 to 3, wherein: a pair of annular components each having the annular body and the plurality of prongs are connected in the axial direction; and the cage has cage bars structured by connecting the prongs of the pair of annular components.A rolling bearing including an inner ring, an outer ring, a plurality of rolling elements disposed between the inner ring and the outer ring, and the cage according to any one of claims 1 to 3.A rolling bearing comprising an inner ring, an outer ring, a plurality of rolling elements disposed between the inner ring and the outer ring, and the cage according to claim 4.A method of forming the cage according to claim 3 using a mold having a plurality of channels, a plurality of gates connected to the channels, and an annular cavity to which the plurality of gates are connected away from each other in the circumferential direction, wherein in the cavity, a plurality of pocket mold spaces in which the pocket mold portions are formed and a plurality of tine mold spaces in which the tine mold portions are formed are alternately formed in the circumferential direction, one of the gates is connected to each of all the tine mold spaces, and when molten resin is poured from the channels into the cavity through the gates, a volume of the molten resin poured from one of the two gates adjacent to each other in the circumferential direction is measured, larger than a volume of the molten resin poured from the other of the two gates.

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