Jade Axis

Abstract

To provide a rolling bearing which can inhibit a shortage in the amount of oil on a rolling surface to inhibit occurrence of seizure and wear even when rotating at high speed.SOLUTION: A ball bearing includes: an outer ring 21 in which an outside raceway 21a is formed on an inner peripheral surface; an inner ring 22 in which an inside raceway 22a is formed on an outer peripheral surface; a plurality of rolling elements 23 disposed between the outside raceway 21a and the inside raceway 22a; and an annular retainer 25 formed with a plurality of pockets 24 which retain the rolling elements 23 in a rollable manner at intervals in a circumferential direction. A single or a plurality of grooves 24a recessed toward the circumferential direction are formed on at least one side as seen in the circumferential direction of the pocket 24. In a state that the rolling element 23 is retained in the pocket 24, the groove 24a forms a gap between the retainer 25 and the rolling element 23.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a ball bearing. [Background technology]

[0002] Patent Document 1 discloses a ball bearing in which the shape of a pocket that rotatably holds the rolling elements in an annular cage, as viewed in the radial direction, is composed of both semi-elliptical circumferential ends and a circumferential central part that connects the two circumferential ends with a straight line extending in the circumferential direction. Patent Document 2 discloses a ball bearing in which the inner surface of a pocket that rotatably holds the rolling elements in an annular cage is provided with four radial grooves that divide the inner surface into a pair of arc-shaped inner surfaces that face each other in the circumferential direction and a pair of arc-shaped inner surfaces that face each other in the axial direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-185315 A [Patent Document 2] JP 2009-14205 A Summary of the Invention [Problem to be solved by the invention]

[0004] The ball bearing disclosed in Patent Document 1 has a pocket of the cage with a non-circular shape, but the purpose of making both circumferential ends semi-elliptical is to reduce the contact surface pressure during the rotation of the bearing, so that the cage and the rolling elements are in contact with each other at both circumferential ends of the semi-elliptical shape during the rotation of the bearing, and the oil on the surface of the rolling elements is scraped off by the cage due to the rotation of the rolling elements. In addition, the ball bearing disclosed in Patent Document 2 has a pocket of the cage with a radial groove, but the rolling elements contact the circumferential ends of the pocket, which are arc-shaped, during the rotation of the bearing, so that the oil on the surface of the rolling elements is scraped off by the cage due to the rotation of the rolling elements. Furthermore, if the inflow of oil to the rolling surfaces where the rolling elements roll and contact the raceway surfaces of the outer and inner rings is extremely reduced by rotating the ball bearing at high speed, it may not be possible to suppress the shortage of oil on the rolling surfaces.

[0005] Therefore, a testing machine capable of visualizing the lubrication state inside a ball bearing rotating at high speed was created, and the lubrication state inside a ball bearing of the prior art was observed when the ball bearing was rotated at high speed. The ball bearing 1 used in the evaluation test was a visualized bearing with a shape equivalent to type 6808, with only the outer ring 2 made of quartz. The overall configuration of ball bearing 1 is shown in Figures 9 and 10. As shown in Figures 9 and 10, ball bearing 1 comprises an outer ring 2 made of transparent quartz, an inner ring 3 made of steel, steel balls 4 as rolling elements, and a cage 5 that holds the steel balls 4 so that they can roll at intervals in the circumferential direction.

[0006] The shape of the cage 5 is shown in Figures 11, 12 and 13. In order to clearly show the shape of the cage 5, Figure 12 shows a cross section of only the cage 5 and the steel balls 4. The cage 5 has pockets 6 formed on one axial side for holding the steel balls 4 in a rollable manner, and the pocket 6 has a shape that is open on one side. The side surface 7 on the other axial side of the cage 5 is flat. No oil passage holes that pass through in the axial direction are formed on the side surface 7 of the cage.

[0007] The testing machine used in the evaluation tests is shown in Figure 14. A rotating shaft 8 extending horizontally is rotatably supported by two shaft support bearings 9 and is rotated by a motor 10. The rotating shaft 8 is inserted into and fixed to the inside of the inner ring 3 of a ball bearing 1, and the inner ring 3 rotates integrally with the rotating shaft 8. The outer ring 2 of the ball bearing 1 is fixed inside a housing 11. A camera 12 is disposed above the ball bearing 1, and an observation hole 13 is formed in the housing 11 above the ball bearing 1, so that the camera 12 can photograph the topmost part of the outer ring 2 from above.

[0008] An oil supply nozzle 14 supplies oil between the top of the outer ring 2 and the inner ring 3, and the oil that accumulates in the housing 11 below the ball bearing 1 is collected and circulated by an oil pump 15. The oil used was Toyota Auto Fluid WS, a commercially available ATF (Automatic Transmission Fluid), mixed with Coumarin-6, a fluorescent agent, and the oil volume distribution was observed by the fluorescence method. LED flash lighting with a wavelength of 405 nm was used as the excitation light.

[0009] Figure 15 is a top view of ball bearing 1. Because outer ring 2 is made of transparent quartz, the raceway surface 3a of inner ring 3 and the position of steel balls 4 can be confirmed when ball bearing 1 is viewed from above. The area surrounded by the dashed line in Figure 13 is the observation area of ​​camera 12. The observation area has a field of view of 23.6 mm × 17.7 mm. The LED flash light was set to emit light for 3 μsec, and the light was synchronized with the frame rate of 40 fps of camera 12 to observe the oil distribution inside the rotating ball bearing 1. The amount of oil supplied to ball bearing 1 was kept constant at 100 ml / min, and the radial load applied to ball bearing 1 from above was also kept constant at 300 N, and the shaft rotation speed was changed to approximately 2000 rpm and approximately 20,000 rpm for observation.

[0010] The results of observing the oil amount distribution around the rolling surface are shown in schematic form in Fig. 16 and Fig. 17. Fig. 16 shows the results when the shaft rotation speed is about 2000 rpm (1910 rpm to be exact), and Fig. 17 shows the results when the shaft rotation speed is about 20000 rpm (20200 rpm to be exact). In Fig. 16 and Fig. 17, the position of the steel ball 4 is indicated by a solid line, the center line of the steel ball 4 by a dashed line, and the position of the cage 5 by a dashed line. The steel ball 4 revolves toward the right side of Fig. 16 and Fig. 17. The oil supply nozzle 14 is also shown in Fig. 16 and Fig. 17. In Fig. 16 and Fig. 17, the areas where more oil is present are indicated by a darker gray color, and the white areas indicate that there was almost no oil present.

[0011] As shown in Fig. 16, under the low rotation condition of the shaft rotation speed of about 2000 rpm, the outlet side of the steel ball 4 (Fig. 16 The area was generally filled with oil, except for the area to the left of steel ball 4 in Fig. 1. An area with little oil was observed on the outlet side of steel ball 4, but this is presumably due to the oil being expelled by the revolution of steel ball 4 or the occurrence of cavitation.

[0012] As shown in Fig. 17, under high rotation conditions with a shaft rotation speed of about 20,000 rpm, the revolution orbit of the steel balls 4 and the cage 5 was not filled with oil, and the oil was distributed on the axial outside of the revolution orbit and near the boundary. This is thought to be due to the fact that at high speeds, the speed at which the oil is removed by the revolution of the steel balls 4 and the rotation of the cage 5 increases excessively compared to the inflow speed of the oil, and the cavitation area at the outlet side of the steel balls 4 (to the left of the steel balls 4 in Fig. 17) expands with the increase in the revolution speed of the steel balls 4. In addition, at the inlet side of the steel balls 4 (to the right of the steel balls 4 in Fig. 17), there was a triangular part with a lot of oil. This is thought to be because oil is supplied from the inner ring 3 side at the opening of the U-shaped pocket 6 of the cage 5. However, in any case, compared to the low speed condition, at the high speed condition, there is less oil at the inlet side of the steel balls 4 and at the apex of the steel balls 4, which is the rolling surface with the outer ring 2, and it is judged that there is a shortage of oil. From the viewpoint of reducing friction torque, the less oil there is on the rolling surfaces the better, but from the viewpoint of preventing wear and seizure, it is necessary to prevent excessive deficiency of oil.

[0013] Thus, as a result of observing the oil amount distribution inside the ball bearing 1, it was found that during high-speed rotation, the oil is pushed aside by the steel balls 4 and the cage 5 rotating at high speed, and the amount of oil flowing into their orbital parts is extremely small. In this case, even if the oil retention can be improved by the method disclosed in Patent Document 1 to suppress seizure and wear during short-term use, it is considered that the oil will eventually run out under long-term use conditions, making it impossible to suppress seizure and wear. Therefore, in order to suppress seizure and wear over long periods of use in a high-speed ball bearing, it is necessary to promote the flow of oil into the inlet side of the steel balls 4.

[0014] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a ball bearing that can prevent a shortage of oil on the rolling surfaces and prevent the occurrence of seizure and wear, even when rotating at high speeds. [Means for solving the problem]

[0015] A ball bearing according to the present invention comprises an outer ring having an outer raceway formed on its inner circumferential surface, an inner ring having an inner raceway formed on its outer circumferential surface, rolling elements arranged between the outer raceway and the inner raceway, and an annular cage in which a number of pockets are formed for rotatably holding the rolling elements at intervals in the circumferential direction, wherein the outer ring and the inner ring are relatively rotatable about a central axis, and at least one side of the pockets in the circumferential direction are formed with a number of grooves that are recessed toward the circumferential direction, penetrate the cage in the radial direction, and are connected at both radial ends of the cage, and when the rolling elements are held in the pockets, a gap is provided between the cage and the rolling elements by the grooves. The projections disposed between the grooves adjacent to each other in the direction of the central axis have a shape in which the thickness in the direction of the central axis becomes thinner from the center toward both ends in the radial direction of the cage. It is characterized by:

[0016] The present invention provides a rolling bearing in which a groove that is recessed in the circumferential direction is formed on at least one circumferential side of the pocket, so that in the area in which the groove is formed, the oil on the surface of the rolling body is not scraped off into the retainer due to the rotation of the rolling body, but can pass through the groove to reach the contact point between the outer or inner ring and the rolling ball on the radially opposite side.This makes it possible to provide a rolling bearing in which, even when rotating at high speed, a shortage of oil on the rolling surface is suppressed and the occurrence of seizure and wear is suppressed.

[0017] In one aspect of the ball bearing according to the present invention, the range in which the groove is provided along the direction of the central axis may be greater than or equal to the greater of the width of the outer raceway and the width of the inner raceway along the direction of the central axis.

[0018] According to this aspect, the oil on the surface of the rolling body is not scraped off into the retainer due to the rotation of the rolling body, but can pass through the groove to reach the contact point between the outer or inner ring on the radially opposite side and the rolling ball. Therefore, even when rotating at high speed, a shortage of oil on the rolling surface can be suppressed, and the occurrence of seizure and wear can be suppressed.

[0019] In one aspect of the ball bearing according to the present invention, the pocket may be provided with a rolling element retaining portion having a surface shape corresponding to a surface shape of the rolling elements.

[0020] According to this aspect, by providing the rolling element holding portion, the pocket can reliably hold the rolling balls, while preventing a shortage of oil on the rolling surface and preventing the occurrence of seizure and wear.

[0021] In one embodiment of the ball bearing according to the present invention, the rolling element retaining portion may have a width in the direction of the central axis of 1 mm or more.

[0022] According to this aspect, by setting the axial width of the rolling element holding portion to an appropriate value, the pocket can reliably hold the rolling ball.

[0023] In one embodiment of the ball bearing according to the present invention, a plurality of the grooves are formed, the distance between adjacent grooves in the direction of the central axis is not more than 0.5 times the semi-major axis of a osculating ellipse at which the rolling element contacts the outer raceway or the inner raceway, and the width of the apex of the groove in the direction of the central axis is not more than 0.25 times the semi-major axis.

[0024] According to this aspect, by setting the axial width of the groove and the spacing between the grooves to appropriate values, oil can easily pass between the retainer and the rolling balls, thereby preventing a shortage of oil on the rolling surfaces and suppressing the occurrence of seizure and wear, even when rotating at high speeds.

[0025] In one embodiment of the ball bearing according to the present invention, the circumferential depth of the groove may be at least 5 times the greater of the contact depth indicating the amount of elastic deformation between the rolling element and the pocket or the arithmetic mean roughness of the inner surface of the pocket, and may be no more than 0.25 times the distance between adjacent pockets in the circumferential direction.

[0026] According to this aspect, by setting the depth of the groove to an appropriate value, oil can easily pass between the cage and the rolling balls, so that the pockets can reliably hold the rolling balls. Effect of the Invention

[0027] The present invention can provide a rolling bearing that can prevent a shortage of oil on the rolling surfaces and prevent the occurrence of seizure and wear, even when rotating at high speed. [Brief description of the drawings]

[0028] [Figure 1] 2 is an enlarged view showing a portion of a side surface of the ball bearing according to the first embodiment. FIG. [Diagram 2] FIG. 2 is a cross-sectional view taken along line DD in FIG. [Diagram 3] 2 is a diagram showing the shape of the area of ​​the cage depicted in FIG. 1 as viewed from the radially outside. FIG. [Figure 4] FIG. 4 is a diagram in which rolling elements are added to FIG. 3, and a cross-sectional view taken along line EE in the diagram. [Diagram 5] 5 is a cross-sectional view taken along the line FF in FIG. 4. [Figure 6] 11A and 11B are diagrams showing elastic deformation due to contact between a rolling element and a cage. [Figure 7] 2 is a diagram showing the shape of the area depicted in FIG. 1 of the cage of a ball bearing according to a second embodiment as viewed from the radial outside, and a cross-sectional view taken along line GG in the diagram. [Figure 8] 13 is a diagram showing the shape of a groove when axially adjacent grooves are connected at a radial end of a cage. FIG. [Figure 9] FIG. 2 is a side view of a ball bearing used in an evaluation test for observing an internal lubrication state. [Figure 10] 10 is a cross-sectional view taken along line AA in FIG. 9. [Figure 11] FIG. 2 is an enlarged view of a portion of a side surface of a ball bearing used in an evaluation test. [Figure 12] 12 is a cross-sectional view of the cage taken along line BB in FIG. 11. [Figure 13] 12 is a cross-sectional view taken along line CC in FIG. 11. [Figure 14] FIG. 2 is a diagram showing an outline of a testing machine used in an evaluation test for observing the internal lubrication state of a ball bearing. [Figure 15] FIG. 2 is a diagram showing observation areas in an evaluation test for observing the lubrication state inside a ball bearing. [Figure 16]FIG. 13 is a diagram showing a schematic diagram of the observation result of the oil amount distribution around the rolling surface when the shaft rotation speed is set to about 2000 rpm. [Figure 17] FIG. 13 is a diagram showing a schematic diagram of the observation result of the oil amount distribution around the rolling surface when the shaft rotation speed is set to about 20,000 rpm. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] <First embodiment> Hereinafter, a ball bearing 20 according to a first embodiment will be described with reference to the drawings. FIG. 1 is an enlarged view of a portion of the side surface of the ball bearing 20, and FIG. 2 is a cross-sectional view taken along the line DD in FIG. 1. As shown in FIGS. 1 and 2, the ball bearing 20 includes an outer ring 21, an inner ring 22, rolling elements 23, and a cage 25. The outer ring 21 and the inner ring 22 are annular members. An outer raceway 21a is formed on the inner peripheral surface of the outer ring 21, and the inner raceway 22a is formed on the outer peripheral surface of the inner ring 22, and the inner raceway 22a is formed on the outer peripheral surface of the inner ring 22, and the inner raceway 22a is formed on the outer peripheral surface of the inner ring 22, and the outer raceway 21a of the outer ring 21 and the inner raceway 22a of the inner ring 22 are provided at a predetermined interval along the circumferential direction of the annular ball bearing 20. The rolling elements 23 are held in a rollable state within a space formed by the outer raceway 21a of the outer ring 21 and the inner raceway 22a of the inner ring 22. Additionally, retainer 25 is disposed between outer ring 21 and inner ring 22, and holds multiple rolling elements 23 rotatably at predetermined intervals in the circumferential direction. Ball bearing 20 is configured such that rolling elements 23 roll between outer ring 21 and inner ring 22, allowing outer ring 21 and inner ring 22 to rotate relatively with the central axis of outer ring 21 and inner ring 22 serving as a rotation axis (hereinafter simply referred to as axis).

[0030] Fig. 3 shows the shape of the area of ​​cage 25 depicted in Fig. 1 as viewed from the radial outside. As shown in Fig. 3, cage 25 is formed with pockets 24 that rotatably hold rolling elements 23. On one axial side of pocket 24, rolling element holding portion 24b is provided, the inner surface of which is spherically shaped corresponding to the surface of rolling element 23 and has a fitting structure with rolling element 23. On the other axial side of pocket 24, claw-shaped rolling element holding portion 24c is provided, the inner surface of which is spherically shaped corresponding to the surface of rolling element 23 and has a fitting structure with rolling element 23.

[0031] A groove 24a recessed in the circumferential direction is formed on each of both circumferential sides of the pocket 24. The groove 24a penetrates the cage 25 in the radial direction of the cage 25.

[0032] In Fig. 4, a diagram in which the rolling element 23 is added to Fig. 3 is shown on the left side, and a cross-sectional view of the left diagram taken along line EE is shown on the right side. Fig. 5 is a cross-sectional view of the left diagram in Fig. 4 taken along line FF. As shown in Fig. 4, when the rolling element 23 is held in the pocket 24 of the cage 25, a gap of depth D1 is provided between the rolling element 23 and the cage 25 by the groove 24a. The contact ellipse 23a shown with diagonal lines in Fig. 4 indicates the region where the rolling element 23 contacts the outer raceway 21a and the inner raceway 22a. In the diagram on the right side of Fig. 4, the portion corresponding to the contact ellipse 23a is drawn with a thick solid line.

[0033] As shown in Fig. 5, for example, when the inner ring 22 is rotated in a clockwise direction as indicated by the arrow A1 with the outer ring 21 fixed, the rolling element 23 in sliding contact with the inner ring 22 rotates in a counterclockwise direction as indicated by the arrow A2, while revolving in a clockwise direction as indicated by the arrow A3. Since the groove 24a is formed in the pocket 24, the oil that is rolled up on the surface of the rolling element 23 from the contact point between the outer ring 21 and the rolling element 23 is not scraped off by the edge of the cage 25 or the like, and can reach the contact point between the inner ring 22 and the rolling element 23 on the radially opposite side through the groove 24a as indicated by the arrow A4. Similarly, the oil that is rolled up on the surface of the rolling element 23 from the contact point between the inner ring 22 and the rolling element 23 is not scraped off by the edge of the cage 25 or the like, and can reach the contact point between the outer ring 21 and the rolling element 23 on the radially opposite side through the groove 24a as indicated by the arrow A5. Therefore, even if the ball bearing 20 rotates at high speed, it is possible to prevent a shortage of oil on the rolling surfaces and to prevent the occurrence of seizure and wear.

[0034] In the ball bearing 20 of this embodiment, the grooves 24a are provided on both circumferential sides of the pocket 24 of the retainer 25, but a certain degree of effect can be obtained even if the groove 24a is provided on only one side.

[0035] Here, it is preferable that the range W1 in which the grooves 24a are provided along the axial direction of the ball bearing 20 is equal to or larger than the width W2 of the outer raceway 21a provided on the outer ring 21. Also, it is preferable that the range W1 of the grooves 24a along the axial direction of the ball bearing 20 is equal to or larger than the width W3 of the inner raceway 22a provided on the inner ring 22. In other words, it is preferable that the range W1 of the grooves 24a is equal to or larger than the width W2 of the outer raceway 21a and the width W3 of the inner raceway 22a, whichever is larger. As a result, in the raceway from the outer ring 21 to the inner ring 22 shown by the arrow A4 in FIG. 5 and the raceway from the inner ring 22 to the outer ring 21 shown by the arrow A5, the oil that is stirred up on the surface of the rolling element 23 can effectively pass through the grooves 24a without being scraped off by the edge of the cage 25 or the like. However, in order to increase the mechanical strength of the retainer 25 and the ability of the retainer 25 to hold the rolling elements 23, it is preferable that the range W1 of the groove 24a be approximately equal to the width W2 of the outer raceway 21a and the width W3 of the inner raceway 22a.

[0036] FIG. 6 shows elastic deformation caused by contact between the rolling element 23 and the cage 25. The position of the rolling element 23 before elastic deformation is shown by a dashed line, and the position of the rolling element 23 after elastic deformation is shown by a solid line. As shown in FIG. 6, when the outer ring 21 or the inner ring 22 of the ball bearing 20 is rotated to revolve the rolling element 23 toward the right side of FIG. 6, a contact depth (amount of elastic deformation) d between the rolling element 23 and the pocket 24 occurs in the circumferential direction. Here, as shown in FIG. 6, the distance between the pockets 24 adjacent in the circumferential direction is D2. The depth D1 of the groove 24a shown in FIG. 4 is preferably 0.25 times or less the distance D2 between the pockets 24 adjacent in the circumferential direction. In addition, the depth D1 of the groove 24a is preferably 5 times or more the larger of the arithmetic mean roughness of the inner surface of the pocket 24 or the amount of elastic deformation d.

[0037] Furthermore, it is preferable that the axial width D3 of the rolling element holding portion 24b constituting the pocket 24 for holding the rolling elements 23 in the cage 25 is 1 mm or more. It is preferable that the axial width D4 of the rolling element holding portion 24c constituting the pocket 24 for holding the rolling elements 23 in the cage 25 is 1 mm or more. By making the axial width D3 of the rolling element holding portion 24b and the axial width D4 of the rolling element holding portion 24c 1 mm or more in this way, the rolling elements 23 can be reliably held by the pocket 24 of the cage 25.

[0038] <Second embodiment> Next, a ball bearing 30 of a second embodiment will be described with reference to the drawings. The ball bearing 30 has the same configuration as the ball bearing 20 of the first embodiment, except that a plurality of grooves 34a are formed on both circumferential sides of the pocket 34 of the cage 35. Therefore, the same components as those of the ball bearing 20 of the first embodiment are denoted by the same reference numerals and will not be described.

[0039] 7 shows a diagram on the left side illustrating the shape of the area of ​​the cage 35 of the ball bearing 30 depicted in FIG. 1 as seen from the radial outside, and a cross-sectional view of the left side diagram along line GG on the right side. As shown in FIG. 7, the cage 35 is formed with a pocket 34 for holding the rolling elements 23 so that they can roll. On one axial side of the pocket 34, a rolling element holding portion 24b is provided, the inner surface of which is spherically shaped to correspond to the surface of the rolling elements 23 and has a fitting structure with the rolling elements 23. On the other axial side of the pocket 34, a claw-shaped rolling element holding portion 24c is provided, the inner surface of which is spherically shaped to correspond to the surface of the rolling elements 23 and has a fitting structure with the rolling elements 23.

[0040] A plurality of grooves 34a recessed in the circumferential direction are formed on both circumferential sides of the pocket 34. In the present embodiment, an example is shown in which five grooves 34a are formed on each side. All of the grooves 34a penetrate the cage 35 in the radial direction of the cage 35.

[0041] By providing the groove 34a in the pocket 34, the oil that is rolled up on the surface of the rolling element 23 from the contact point between the outer ring 21 and the rolling element 23 is not scraped off by the cage 35 in the portion where the groove 34a is provided, but can reach the contact point between the inner ring 22 and the rolling element 23 on the radially opposite side through the groove 34a. Similarly, the oil that is rolled up on the surface of the rolling element 23 from the contact point between the inner ring 22 and the rolling element 23 is not scraped off by the cage 35 in the portion where the groove 34a is provided, but can reach the contact point between the outer ring 21 and the rolling element 23 on the radially opposite side through the groove 34a. Therefore, even if the ball bearing 30 rotates at high speed, the shortage of oil on the rolling surface can be suppressed, and the occurrence of seizure and wear can be suppressed.

[0042] In the ball bearing 30 of this embodiment, the grooves 34a are provided on both circumferential sides of the pocket 34 of the retainer 35, but a certain degree of effect can be obtained even if the grooves 34a are provided on only one side.

[0043] It is preferable that the range W4 of the grooves 34a along the axial direction of the ball bearing 30 be equal to or larger than the width W5 of the outer raceway 21a of the outer ring 21. It is also preferable that the range W4 of the grooves 34a along the axial direction of the ball bearing 30 be equal to or larger than the width W6 of the inner raceway 22a of the inner ring 22. Note that the shape of the grooves 34a is not limited to the shape shown in Fig. 7, and the grooves 34a adjacent to each other in the axial direction may be connected at both radial ends of the cage 35 as shown in Fig. 8. 8, by providing grooves 34a in pocket 34, oil that is rolled up on the surface of rolling element 23 from the contact point between outer ring 21 and rolling element 23 can reach the contact point between inner ring 22 and rolling element 23 on the radially opposite side through groove 34a without being scraped off by cage 35. Similarly, oil that is rolled up on the surface of rolling element 23 from the contact point between inner ring 22 and rolling element 23 can reach the contact point between outer ring 21 and rolling element 23 on the radially opposite side through groove 34a without being scraped off by cage 35. Therefore, even if ball bearing 30 rotates at high speed, it is possible to suppress a shortage of oil on the rolling surface and suppress the occurrence of seizure and wear.

[0044] The interval I between adjacent grooves 34a in the axial direction is preferably 0.5 times or less the semimajor axis S of the osculating ellipse 23a shown in Fig. 4. Moreover, the axial width D5 of the apex of the groove 34a is preferably 0.25 times or less the semimajor axis S of the osculating ellipse 23a.

[0045] Also in ball bearing 30, similarly to ball bearing 20 of the first embodiment, it is preferable that depth D6 of groove 34a is at least 5 times the greater of the arithmetic mean roughness or elastic deformation d of the inner surface of pocket 24, and is not more than 0.25 times distance D2 shown in Fig. 6. Furthermore, also in ball bearing 30, axial width D7 of rolling element retaining portion 24b and axial width D8 of rolling element retaining portion 24c are both preferably at least 1 mm. [Explanation of symbols]

[0046] 1 ball bearing, 2 outer ring, 3 inner ring, 3a raceway surface, 4 steel ball, 5 cage, 6 pocket, 7 side surface, 8 rotating shaft, 9 shaft support bearing, 10 motor, 11 housing, 12 camera, 13 observation hole, 14 oil supply nozzle, 15 oil pump, 20, 30 ball bearing, 21 outer ring, 21a outer raceway, 22 inner ring, 22a inner raceway, 23 rolling element, 23a contact ellipse, 24, 34 pocket, 24a, 34a groove, 24b, 24c rolling element retainer, 25, 35 cage.

Claims

1. A ball bearing comprising: an outer ring having an outer raceway formed on an inner peripheral surface thereof; an inner ring having an inner raceway formed on an outer peripheral surface thereof; rolling elements disposed between the outer raceway and the inner raceway; and an annular cage having a plurality of pockets formed therein for rotatably holding the rolling elements at intervals in the circumferential direction, wherein the outer ring and the inner ring are rotatable relative to one another around a central axis, At least one side of the pocket in the circumferential direction is formed with a plurality of grooves that are recessed in the circumferential direction, penetrate the retainer in the radial direction of the retainer, and are connected at both ends of the retainer in the radial direction, a gap is provided between the cage and the rolling elements by the groove when the rolling elements are held in the pocket, A ball bearing characterized in that the protrusions arranged between adjacent grooves in the direction of the central axis have a shape in which the thickness in the direction of the central axis becomes thinner from the radial center of the retainer toward both ends.

2. 2. A ball bearing according to claim 1, A ball bearing characterized in that the range in which the groove is provided along the direction of the central axis is equal to or greater than the greater of the width of the outer raceway and the width of the inner raceway along the direction of the central axis.

3. 3. A ball bearing according to claim 1 or 2, A ball bearing characterized in that the pocket is provided with a rolling element retaining portion having a surface shape corresponding to the surface shape of the rolling element.

4. 4. A ball bearing according to claim 3, A ball bearing characterized in that the width of the rolling element retaining portion in the direction of the central axis is 1 mm or more.

5. A ball bearing according to any one of claims 1 to 4, A ball bearing characterized in that the circumferential depth of the groove is at least 5 times the greater of the contact depth indicating the elastic deformation of the rolling element and the pocket or the arithmetic mean roughness of the inner surface of the pocket, and is not more than 0.25 times the distance between adjacent pockets in the circumferential direction.

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