ROLLING BEARING CAGE AND ROLLING BEARING

Abstract

According to a crown retainer (11) of a ball guide type, a pocket (9) of the retainer (11) has a straight surface (9a) and a tapered surface (9b) where a ball (7) comes into surface contact therewith. A connection point (9c) between the straight surface (9a) and the tapered surface (9b) is on an inner diameter side of an intersection position (I) between an extension plane (F) of a rolling element equatorial plane and a wall surface of the pocket (9). In a two-dimensional cross section passing through centers (O) of a plurality of balls (7), a distance (P) between the ball (7) and the wall surface of the pocket (9) in the extension plane (F) in a neutral position is smaller than a shortest distance (T) between the tapered surface (9b) and the ball (7) in a direction perpendicular to a straight line (L).

Claims

1. A retainer for rolling bearings, being of a rolling element guide type, having a plurality of pockets that are disposed at a predetermined interval in a circumferential direction and configured to hold a plurality of rolling elements respectively, wherein the pocket of the retainer has, in a neutral position where a revolution axis of the rolling element coincides with a rotation axis of the retainer, a straight surface that is parallel to a straight line connecting a center of the rolling element and the rotation axis, and a tapered surface that connects the straight surface on an inner diameter side of the straight surface, the tapered surface extending and being inclined toward the straight line as moving radially away from the straight surface, wherein the tapered surface comes into surface contact with the rolling element when the rolling element and the retainer move relative to each other along the straight line, wherein a connection point between the straight surface and the tapered surface is on an inner diameter side of an intersection portion between an extension plane of a rolling element equatorial plane and a wall surface of the pocket, the extension plane passing through the center of the rolling element and being perpendicular to the straight line, wherein, in a two-dimensional cross section passing through centers of the plurality of rolling elements, a distance between the rolling element and the wall surface of the pocket in the extension plane of the rolling element equatorial plane in the neutral position is smaller than a shortest distance between the tapered surface and the rolling element in a direction perpendicular to the straight line, and wherein, in the two-dimensional cross section passing through centers of the plurality of rolling elements, an angle between a first line and the extension plane of the rolling element equatorial plane is smaller than an angle between a second line and the extension plane of the rolling element equatorial plane, the first line connecting a contact point, which is formed when the rolling element and the retainer move relative to each other along the straight line and the tapered surface and the rolling element are in contact with each other, and the center of the rolling element, and the second line connecting an intersection of a shoulder maximum outer diameter of an inner ring and a contour of the rolling element and the center of the rolling element.

2. The retainer for rolling bearings according to claim 1, wherein the retainer has an inner diameter side convex portion protruding radially inward at an axial intermediate portion of the retainer, and a minimum inner diameter of the inner diameter side convex portion is larger than at least one of shoulder maximum outer diameters of the inner ring.

3. The retainer for rolling bearings according to claim 1, wherein the retainer is a crown retainer having an annular portion and a plurality of column portions extending axially from the annular portion.

4. The retainer for rolling bearings according to claim 3, wherein a center position of the rolling element in an axial direction of the rolling bearing is shifted from a center position of the inner ring and an outer ring so as to be separated from the annular portion.

5. The retainer for rolling bearings according to claim 3, wherein an inner diameter of the annular portion is smaller than an inner diameter of a tip portion of the column portions.

6. The retainer for rolling bearings according to claim 1, wherein the retainer is formed of a synthetic resin.

7. The retainer for rolling bearings according to claim 1, wherein the rolling element is a ball.

8. A rolling bearing comprising the retainer for rolling bearings according to claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0027] FIG. 1 is a cross-sectional view of a deep groove ball bearing that includes a retainer for rolling bearings according to a first embodiment of the present invention.

[0028] FIG. 2 is a cross-sectional view that is taken along a line II-II in FIG. 1 and illustrates a state in which a ball and the retainer according to the first embodiment are in a neutral position.

[0029] FIG. 3 is a radial view of the ball and the retainer in FIG. 2.

[0030] FIG. 4 illustrates a state in which the ball moves radially relative to the retainer and comes into contact with a tapered surface of the retainer.

[0031] FIG. 5A illustrates a state in which the radially moving ball and the tapered surface of the retainer according to this embodiment are in surface contact due to an increase in a pocket circumferential length of the retainer, and FIG. 5B illustrates a state in which a radially moving ball and a retainer in the related art are in edge contact due to an increase in a pocket circumferential length of the retainer.

[0032] FIG. 6A illustrates a state in which a ball and a retainer having a small tapered gradient angle according to a comparative example are in a neutral position, and FIG. 6B illustrates a state in which the ball moves radially relative to the retainer according to the comparative example and comes into contact with a tapered surface of the retainer.

[0033] FIG. 7A illustrates a state in which a ball and a retainer having a large tapered gradient angle according to another comparative example are in a neutral position, and FIG. 7B illustrates a state in which the ball moves radially relative to the retainer according to the comparative example and comes into contact with a tapered surface of the retainer.

[0034] FIG. 8A is a cross-sectional view of a deep groove ball bearing that includes a retainer for rolling bearings according to a second embodiment of the present invention, and FIG. 8B is a radial view of a ball and the retainer.

[0035] FIG. 9 is a cross-sectional view of a deep groove ball bearing that includes a retainer for rolling bearings according to a third embodiment of the present invention.

[0036] FIG. 10 is a cross-sectional view of a deep groove ball bearing according to a modification of the third embodiment.

[0037] FIGS. 11A to 11D are cross-sectional views of deep groove ball bearings that each include a modification of a retainer for rolling bearings having a different shape on an inner diameter side convex portion.

[0038] FIGS. 12A to 12C are radial views of modifications of a retainer for rolling bearings in which axial positions of an inner diameter side convex portion are different from each other.

[0039] FIGS. 13A and 13B are radial views illustrating modifications of a retainer for rolling bearings.

DESCRIPTION OF EMBODIMENTS

[0040] Hereinafter, a retainer for rolling bearings and a rolling bearing according to one embodiment of the present invention will be described in detail with reference to the drawings.

First Embodiment

[0041] First, a deep groove ball bearing 1 that includes a crown retainer 11 according to the first embodiment of the present invention will be described. As illustrated in FIG. 1, the deep groove ball bearing 1 includes an outer ring 3 having an outer ring raceway surface 3a on an inner peripheral surface, an inner ring 5 having an inner ring raceway surface 5a on an outer peripheral surface, a plurality of balls 7 rotatably disposed between the outer ring raceway surface 3a and the inner ring raceway surface 5a, and the crown retainer 11 disposed between the outer ring 3 and the inner ring 5. The crown retainer 11 holds the balls 7 rotatably within pockets 9. Grease is enclosed in an internal space of the deep groove ball bearing 1 as a lubricant. The lubricant may also be oil.

[0042] The outer ring 3 has a shoulder portion 3b on both axial sides of the outer ring raceway surface 3a on the inner peripheral surface, and the inner ring 5 has a shoulder portion 5b on both axial sides of the inner ring raceway surface 5a on the outer peripheral surface.

[0043] Referring also to FIGS. 2 and 3, the crown retainer 11 is a retainer of a ball guide type made of a synthetic resin, and includes an annular portion 15, a plurality of column portions 17 axially extending from the annular portion 15 at a predetermined interval in a circumferential direction, and a plurality of pockets 9 that rotatably hold the balls 7 with the annular portion 15 and adjacent column portions 17. Therefore, the pockets 9 are opened on both radial sides and one axial side (right side in FIG. 1).

[0044] Examples of a synthetic resin material of the crown retainer 11 includes polyamide, polyacetal, polyether ether ketone, polyimide, and polyphenylene sulfide, and the like, and a reinforcing material such as a glass fiber, a carbon fiber, and an aramid fiber may be added to the resin as necessary.

[0045] As illustrated in FIG. 2, the pocket 9 of the crown retainer 11 has, in a neutral position where a revolution axis X1 of the ball 7 coincides with a rotation axis X2 of the crown retainer 11, a straight surface 9a that is parallel to a straight line L connecting a center O of the ball 7 and the rotation axis X2, and a tapered surface 9b that connects the straight surface 9a on an inner diameter side of the straight surface 9a. The tapered surface 9b extends and is inclined toward the straight line L as moving radially away from the straight surface 9a. Specifically, in this embodiment, the straight surface 9a has a cylindrical shape having the straight line L as a central axis, and the tapered surface 9b has a conical shape having the straight line L as a central axis.

[0046] The crown retainer 11 has, at an axial intermediate portion, an inner diameter side convex portion 19 protruding radially inward from an inner peripheral surface of the column portion 17, so that a pair of tapered surfaces 9b crosses over adjacent column portions 17 and inner diameter side convex portions 19. The inner diameter side convex portions 19 are line-symmetrical with respect to an axial center, and have an inclined surface 19a on both axial sides such that an axial width of the inclined surface 19a becomes smaller as approaching a radial inner side, as is illustrated in FIG. 1. Further, as illustrated in FIG. 3, when viewed from a radial outer side, the inner diameter side convex portions 19 have another inclined surface 19b on both axial sides such that an axial width of the inclined surface 19b becomes smaller as approaching a center of the pocket 9. A minimum inner diameter d of the inner diameter side convex portion 19 is larger than at least one of maximum outer diameters D of shoulder portions 5b of the inner ring 5.

[0047] The inner diameter side convex portion 19 forming the tapered surface 9b is not provided on another axial side (left side in FIGS. 1 and 3) of the pocket 9. Accordingly, a gap can be defined between the pocket 9 and the ball 7, so that a lubricant can be supplied from the gap.

[0048] As described above, in the crown retainer 11 in this embodiment, an increase in a gap amount between the retainer 11 and the ball 7 due to a centrifugal force of the retainer 11 is prevented, a proper gap amount between the retainer 11 and the ball 7 is maintained in a wide range of a rotational speed, and a retainer noise is prevented. Therefore, it is important to define a gap (hereinafter referred to as pocket gap (2P)) in a rotation direction of the retainer 11 between the pocket 9 of the retainer 11 and the ball 7, and a gap in a radial direction of the retainer 11 between the pocket 9 of the retainer 11 and the ball 7 (hereinafter referred to as pocket gap (2R)).

[0049] Therefore, a pair of tapered surfaces 9b comes into surface contact with the ball 7 when the ball 7 and the retainer 11 move relative to each other along the straight line L (that is, radially), which is a first condition. Further, as illustrated in FIG. 5A, the pair of tapered surfaces 9b also comes into surface contact with the ball 7 when a pocket circumferential length of the retainer 11 increases due to the centrifugal force and the retainer 11 moves radially. In this case, a contact position of the ball 7 with the tapered surfaces 9b does not change before and after deformation of the crown retainer 11. That is, an angle between a line a and an extension plane F of a rolling element equatorial plane does not change. The line a connects a contact point P.sub.1, which is formed when the tapered surface 9b and the ball 7 are in contact with each other, and a center O of the ball 7.

[0050] On the other hand, in a crown retainer in the related art illustrated in FIG. 5B, the tapered surface 9b and the ball 7 abut at an edge. Accordingly, a contact point between the tapered surface 9b and the ball 7 moves (the angle changes) before and after deformation of the crown retainer 11. Therefore, in the crown retainer in the related art, a radial change amount of the retainer is a radial increase amount of the retainer 11.

[0051] In the crown retainer 11, as illustrated in FIG. 2, a connection point 9c between the straight surface 9a and the tapered surface 9b is on an inner diameter side of an intersection portion I between the extension plane F of the rolling element equatorial plane and a wall surface of the pocket 9, which is a second condition. The extension plane F passes through the center O of the ball 7 and is perpendicular to the straight line L. At the same time, in a two-dimensional cross section passing through centers O of the plurality of balls 7, a distance P between the ball 7 and the wall surface of the pocket 9 in the extension plane F of the rolling element equatorial plane, in the neutral position illustrated in FIG. 2, is designed to be smaller than a shortest distance T between the tapered surface 9b and the ball 7 in a direction (a direction F parallel to the extension plane F of the rolling element equatorial plane) perpendicular to the straight line L.

[0052] Accordingly, the pocket gap (2P) can be determined only by the ball 7 and the straight surface 9a without interference of the tapered surface 9b. That is, when the retainer 11 moves parallel to the revolution axis X1 of the ball 7 relative to the ball 7 and comes into contact with the ball 7, a reaction force acts in a direction opposite to a movement direction of the retainer 11, so that wild movement of the retainer 11 can be prevented. That is, the ball 7 first comes into contact with the tapered surface 9b, and a reaction force is generated in the radial direction of the retainer 11, so that the wild movement of the retainer 11 can be prevented. Further, friction between the pocket 9 and the ball 7 is also reduced, and it is possible to prevent heat generation, an increase in torque, and the like.

[0053] In addition, T is given by a relationship between the radial movement amount R of the retainer and the angle (T=Rtan ).

[0054] As a third condition, in the two-dimensional cross section passing through the centers O of the plurality of balls 7 illustrated in FIG. 4, the angle between the line a and the extension plane F of the rolling element equatorial plane is smaller than an angle between a line b and the extension plane F of the rolling element equatorial plane. The line a connects the contact point P.sub.1, which is formed when the ball 7 and the retainer 11 move relative to each other along the straight line L and the tapered surface 9b and the ball 7 are in contact with each other, and the center O of the ball 7, and the line b connects an intersection P2 of the shoulder maximum outer diameter D of the inner ring 5 and a contour of the ball 7 and the center O of the ball 7.

[0055] This is in order to ensure bearing assembly, and the minimum inner diameter d of the retainer 11 has to be larger than at least one of the shoulder maximum outer diameters D of the inner ring 5. Particularly, the angle needs to be smaller than the angle under a condition where the retainer 11 is in contact with the ball 7, so as to maintain a tapered contact during contact between the retainer 11 and the ball 7.

[0056] When the first condition is satisfied (that is, the tapered surface 9b and the ball 7 come into surface contact when the ball 7 and the retainer 11 move relative to each other along the straight line L), an angle (hereinafter, referred to as tapered gradient angle) a between the straight surface 9a and the tapered surface 9b of the retainer 11 is equal to a.

[0057] FIGS. 4, 6, and 7 illustrate a relationship between and when the tapered gradient angle is changed in a state in which P and R are constant and the tapered contact is established. That is, FIG. 4 satisfies all of the first to third conditions in this embodiment including <. On the other hand, as illustrated in FIG. 6, the second condition is not satisfied when is too small, and the ball 7 comes into contact with the tapered surface 9b of the retainer 11. When is too large (=>), as illustrated in FIG. 7, the minimum inner diameter d of the retainer 11 is smaller than the shoulder maximum outer diameter D of the inner ring 5, and the retainer 11 cannot be assembled from a shoulder portion side.

[0058] As described above, according to the crown retainer 11 and the deep groove ball bearing 1 in this embodiment, the pocket 9 of the retainer 11 has the straight face 9a and the tapered surface 9b that comes into surface contact with the ball 7. The connection point 9c between the straight surface 9a and the tapered surface 9b is on the inner diameter side of the intersection position I between the extension plane F of the rolling element equatorial plane and the wall surface of the pocket 9. In the two-dimensional cross section passing through the centers O of the plurality of balls 7, the distance P between the ball 7 and the wall surface of the pocket 9 in the extension plane F of the rolling element equatorial plane in the neutral position is smaller than the shortest distance T between the tapered surface 9b and the ball 7 in the direction perpendicular to the straight line L. In the two-dimensional cross section passing through the centers O of the plurality of balls 7, the angle between the line a and the extension plane F of the rolling element equatorial plane is smaller than the angle between the line b and the extension plane F of the rolling element equatorial plane. The line a connects the contact point P.sub.1, which is formed when the ball 7 and the retainer 11 move relative to each other along the straight line L and the tapered surface 9b and the ball 7 are in contact with each other, and the center O of the ball 7, and the line b connects the intersection P2 of the shoulder maximum outer diameter D of the inner ring 5 and the contour of the ball 7 and the center O of the ball 7. Accordingly, an increase in a gap amount between the retainer 11 and the ball 7 due to the centrifugal force of the retainer 11 is prevented, and a proper gap amount between the retainer 11 and the ball 7 is maintained in a wide range of a rotational speed. As a result, a retainer noise can be prevented. As a result, a retainer noise can be prevented.

Second Embodiment

[0059] FIG. 8A is a cross-sectional view of a deep groove ball bearing that includes a retainer for rolling bearings according to the second embodiment of the present invention, and FIG. 8B is a radial view of a ball and the retainer.

[0060] In this embodiment, an axial thickness of the annular portion 15 is increased, so as to increase rigidity of the annular portion 15. Accordingly, an increase in a pocket circumferential length due to a centrifugal force is prevented, and it is possible to prevent an increase in a pocket gap and a retainer radial movement amount. Therefore, in an axial direction of the deep groove ball bearing 1 in this embodiment, a center position L1 of the ball 7 is shifted to a side opposite to the annular portion 15 from a center position L2 of the outer ring 3 and the inner ring 5, so that the annular portion 15 can be as thick as possible in the axial direction.

[0061] Other configurations and operations are the same as those in the first embodiment.

Third Embodiment

[0062] FIG. 9 is a cross-sectional view of a deep groove ball bearing that includes a retainer for rolling bearings according to the third embodiment of the present invention.

[0063] In this embodiment, a shape of the crown retainer 11 on an inner diameter side is different from that in the first embodiment, and an inner diameter db of the column portion 17 at a tip portion is large so that a thickness thereof is small. Therefore, on the tip portion side of the column portion 17, the inclined surface 19a of the inner diameter side convex portion 19 is longer than the inclined surface 19a on the annular portion side, and is continuous to the column portion 17.

[0064] Accordingly, the crown retainer 11 in this embodiment satisfies both a relationship of at least one of shoulder maximun outer diameters D of the inner ring 5<the minimum inner diameter d of the retainer 11 and a relationship of a retainer inner diameter da on the annular portion side<the inner diameter db of the retainer 11 on the tip portion.

[0065] As described above, D<d is a condition for assembly establishing. Further, da<db is a condition to improve insertion assemblability of the ball 7 into the retainer 11 while maintaining rigidity of the annular portion 15.

[0066] Other configurations and operations are the same as those in the first embodiment.

[0067] In this embodiment, as illustrated in FIG. 10, an axial thickness of the annular portion 15 may be increased as is in the second embodiment.

[0068] The present invention is not limited to the embodiments described above, and can be appropriately modified, improved, and the like.

[0069] For example, a contour shape of a pocket surface of the crown retainer 11 is not limited to that in the embodiments as long as the pocket surface has a straight surface and a tapered surface, and can be arbitrarily formed. Specifically, the crown retainer 11 may have the rectangular inner diameter side convex portion 19 as illustrated in FIG. 11A or the dovetail-shaped inner diameter side convex portion 19 as illustrated in FIG. 11B. The crown retainer 11 may have the curved inner diameter side convex portion 19 as illustrated in FIG. 11C or have no inner diameter side convex portion 19 as illustrated in FIG. 11D.

[0070] As illustrated in FIGS. 12A to 12C, an axial position of the inner diameter side convex portion 19 preferably overlaps the center position L1 of the ball 7 in the axial direction as illustrated in FIG. 12A to 12C, so that the tapered surface 9b can hold the ball 7. Particularly, as illustrated in FIGS. 12A to 12C, the tip portion 19c preferably overlaps the center position L1 of the ball 7 when the inner diameter side convex portion 19 has a flat tip portion 19c along the axial direction of the crown retainer 11.

[0071] The tip portion of the column portion 17 of the crown retainer 11 may have a claw portion 21 as illustrated in FIGS. 13A and 13B, and an axial thickness of the annular portion 15 may also be increased in this case, as is illustrated in FIG. 13B.

[0072] As illustrated in FIGS. 13A and 13B, when the claw portion 21 is provided at the tip portion of the column portion, as in the third embodiment, the inner diameter of the annular portion 15 is smaller than an inner diameter of the claw portion 21, so that rigidity of the annular portion 15 can be ensured, and assemblability of the ball 7 can be improved.

[0073] The rolling bearing of the present invention may be, for example, appropriately used to support a main shaft in a spindle device such as a machine tool, or be applied to supporting a motor shaft of a high speed motor.

[0074] The rolling bearing of the present invention is not limited to the deep groove ball bearing in the embodiments, and may be another type of rolling bearing such as an angular ball bearing or a cylindrical roller bearing. Therefore, a rolling element is not limited to a ball. Further, the retainer for rolling bearings is not limited to the crown retainer in the embodiments as long as the retainer is a retainer of a rolling element guide type, and may have a shape having an annular portion at both axial end portions, for example.

[0075] Still further, the shoulder minimum inner diameter of the inner ring of the present invention refers to an inner diameter of a lower shoulder on both axial sides of the raceway surface in an angular ball bearing or the like.

[0076] This application is based on Japanese Patent Application 2016-223002, filed Nov. 16, 2016, contents of which are incorporated herein by reference.

DESCRIPTION OF REFERENCE NUMERALS

[0077] 1 deep groove ball bearing (rolling bearing) [0078] 3 outer ring [0079] 5 inner ring [0080] 7 ball (rolling element) [0081] 9 pocket [0082] 9a straight surface [0083] 9b tapered surface [0084] 9c connection point [0085] 11 crown retainer (retainer for rolling bearings) [0086] 19 inner diameter side convex portion [0087] F extension surface of rolling element equatorial plane [0088] P distance between rolling element and wall surface of pocket [0089] T shortest distance between tapered surface 9b and ball 7