JP5499830B2 - Combination ball bearings and double row ball bearings - Google Patents

Description

  The present invention includes, for example, combination ball bearings used in industrial machines, robot joints and turning mechanisms, rotary tables and spindle turning mechanisms in machine tools, medical equipment, semiconductor / liquid crystal manufacturing devices, optical and optoelectronic devices, etc. The present invention relates to a double row ball bearing, and more particularly to a ball bearing used for an application in which a radial load and an axial load in both directions, particularly a large moment load acts as a load.

  Normally, in a ball bearing, for example, a deep groove ball bearing, as shown in FIG. 9, the ball 3 is rotatably held between the raceway surfaces of the inner ring 2 and the outer ring 1 to hold sealed grease and prevent leakage to the outside. Or the seal | sticker 5 is mounted | worn on the axial direction end surface between the inner ring | wheel 2 and the outer ring | wheel 1 in order to prevent the foreign material penetration | invasion from the exterior to the inside of a bearing. Further, as a ball guide holder 4 for holding the balls 3, as shown in FIG. 10, a crown-shaped (cantilever ring structure) ball guide synthetic resin holder in which a required number of pocket portions 6b are formed in a ring portion 6a. Is adopted as standard.

As shown in FIG. 10, the ball guide holder 4 normally has a pocket inner surface 6 c that holds the ball 3 formed in a spherical shape having a curvature slightly larger than the curvature of the ball 3. As shown in FIG. 11, the movement amount in the radial direction is determined by the smaller one of the clearance ΔR ₁ between the ball 3 and the pocket inner diameter side end surface or the clearance ΔR ₂ between the ball 3 and the pocket outer diameter side end surface. The
Further, as shown in FIG. 12, the amount of movement of the cage 4 in the axial direction is determined by the clearance ΔS ₁ between the ring-side pocket inner surface 6c and the ball 3 in one direction, and the other direction is that of the pocket column portion 6d. The ball is positioned by a clearance ΔS ₂ between the ball locking portion 6 e formed at the tip and the ball 3.

  The cage 4 is usually manufactured by injection molding. However, when the cage is separated from the mold, the cage 4 is separated in the axial direction (so-called axial draw type). At this time, since the relationship between the inner diameter φdP of the pocket surface and the distance between the pair of ball locking portions 6e, that is, the diameter H of the mouth diameter is φdP> H, the ball locking portion 6e forms a pocket at the time of release. When the mold member (spherical member) passes, it is deformed. You have to take the so-called unreasonable form.

Therefore, it is necessary for the ball engaging portion 6e to maintain flexibility so as not to leave a breakage, a crack, or a large plastic deformation that causes a functional problem when releasing.
Further, the ball locking portion 6e has a relationship that the ball diameter φDa with respect to the mouth diameter H between the opposing ball locking portions 6e is φDa> H. When the cage 4 is assembled into the bearing, that is, the ball 3 is inserted into the pocket portion. When inserting into the ball 6b, it is necessary that the ball locking portion 6e is not damaged or chipped even when passing between the ball locking portions 6e. The structure is such that it cannot be removed from 3.

  On the other hand, in the case of an angular ball bearing, as shown in FIGS. 13 and 14, a so-called rice bran cage 7 having a double-sided ring structure is generally used. In the case of a narrow ball bearing, a ball guide cage having a crown-shaped cantilever ring structure has been proposed as a measure for further reducing the axial width of the ball bearing.

In Patent Document 1, as shown in FIG. 15 (b), the adjacent pocket portions 113 are cut in advance at least at one place in the circumferential direction of the ring portion 111, and a predetermined gap ΔR is set between the cut surfaces. A cage having a held structure is disclosed.
By adopting such a structure, due to the difference in thermal expansion coefficient between the cage 110 and the inner and outer rings and the variation in the dimensional accuracy and roundness of the cage, the rolling element pitch circle diameter and the pitch circle diameter of the cage pocket are reduced. Even in the case of misalignment, it has both radial flexibility due to the cantilever shape and circumferential elastic deformation (circumferential flexibility) due to the gap ΔR between each cut surface. The cushioning force between the ball 103 and the pocket 113 can be buffered to prevent the cage 110 from being damaged and worn, and the torque unevenness and heat generation due to the sliding contact resistance between the ball 103 and the pocket 113 can be further reduced. .

  Further, in the cage structure shown in FIG. 15 (b), as shown in FIG. 15 (c), the circumference between the opposing cages is formed at the corners of the cut surface and the side surface of the cage ring portion. A C chamfered portion 115 is provided as a guide mechanism for preventing directional interference.

  For example, when an external load such as a moment load is applied to the bearing, the revolving speeds of the balls and the cage between the combined bearing rows differ depending on the relative inclination of the inner and outer rings and the deformation of the inner and outer rings. As shown in FIG. 15D, the cages 110 may be deformed relative to each other in the axial direction and interfere with each other in the circumferential direction so as to stick to each other and apply a load to the cage 110. Therefore, by forming the chamfered portion as described above, as shown in FIG. 15 (e), it is possible to avoid the interference in the circumferential direction between the cages 110 in each row, increasing the rotational torque, Problems such as wear and damage can be eliminated.

  However, in the cage of the narrow ball bearing disclosed in Patent Document 1, detailed examination has not been made on the optimum shape of the C chamfered portion 115.

JP 2008-169998 A

  Therefore, the present invention has been made paying attention to the above-mentioned unsolved problems of the conventional example, and when a crown-shaped cage is adopted for the purpose of space saving in the axial direction, the wear and damage of the ball and the cage An object of the present invention is to provide a ball bearing capable of exhibiting stable rotational performance without damaging the shaft.

In order to achieve the above object, a combination ball bearing according to claim 1 is configured by combining two rows of narrow ball bearings, and each narrow ball bearing has a ring portion on one side, and the other of the ring portions. A combined ball bearing in which a ring-shaped ball guide retainer having a required number of pocket portions for holding balls on its side is arranged on the combined surface side, and the pocket portion is the ring portion. A ball locking portion that prevents the ball from being pulled out formed on the tip portion opposite to the tip portion of the pocket portion with respect to the axial distance between the center of curvature of the pocket portion and the tip of the ball locking portion. The value obtained by adding the axial clearance between the pocket surface of the pocket portion and the ball to the axial clearance between the end portions of the two opposing cages in a state where the center of curvature coincides with the center of curvature of the ball is small. The ring part is at least The pocket portions adjacent to each other in one circumferential direction are cut in advance so that a predetermined gap is provided between the cut surfaces, and C is provided at the corner between the cut surface and the side surface of the ring portion. When a chamfered portion is provided, the angle between the C chamfered portion and the side surface of the ring portion is α, and the coefficient of static friction between the cages is μ, the value of α is larger than the value of tan ⁻¹ μ. The dimension of the C chamfered portion is set as C, the axial clearance between the ball engaging portion and the ball is set as M, and the curvature center of the pocket portion and the curvature center of the ball are made to coincide with each other. When the axial clearance between the ends of the ring portions of the two opposing cages in the state is ΔG, the value of C is set to be larger than the value of (2 × M−ΔG) / 2. It is characterized by that.

Furthermore, the double-row ball bearing according to claim 2 has a configuration of a narrow double-row ball bearing, and each row has a ring portion on one side and holds the ball on the other side of the ring portion. A double row ball bearing in which a crown-shaped ball guide retainer in which a required number of pocket portions are formed is arranged with the ring portion side facing the inner side in the axial direction of the bearing, the pocket portion being the ring A ball engaging portion that prevents the ball formed at the tip opposite to the portion from slipping out, and the pocket portion with respect to the axial distance between the center of curvature of the pocket portion and the tip of the ball engaging portion The value obtained by adding the axial clearance between the pocket surface of the pocket portion and the ball to the axial clearance between the ring portion end portions of the two opposing cages in a state where the center of curvature of the ball and the center of curvature of the ball coincide with each other. The ring portion is set to be at least one circumferential direction. The pocket portions adjacent to each other in advance are cut in advance so that a predetermined gap is provided between the cut surfaces, and a chamfered portion is provided at the corner between the cut surface and the side surface of the ring portion. When the angle between the C chamfered portion and the side surface of the ring portion is α and the coefficient of static friction between the cages is μ, the value of α is set to be larger than the value of tan ⁻¹ μ. And the dimension of the C chamfered portion is C, the axial clearance between the ball locking portion and the ball is M, and the pocket center and the center of curvature of the ball are opposed to each other. When the axial clearance between the ends of the ring portions of the two cages is ΔG, the value of C is set to be larger than the value of (2 × M−ΔG) / 2. It is said.

According to the present invention, in the combination bearing in which two rows of narrow ball bearings are combined, or in the double row ball bearing with narrow width, the ring portion is arranged in advance between the pocket portions adjacent to each other at least at one place in the circumferential direction. The cut surface is structured to have a predetermined gap between the cut surfaces, and a C chamfered portion is provided at a corner between the cut surface and the side surface of the ring portion, and the C chamfered portion and the side surface of the ring portion are provided. Is set so that the value of α is larger than the value of tan ⁻¹ μ, where α is the angle between and the static friction coefficient between the cages. Even when the cage moves in the axial direction, it is possible to avoid circumferential interference between the cages, and to reliably prevent problems such as an increase in rotational torque and wear and damage of the cage. The effect is obtained.

It is principal part sectional drawing for demonstrating the combination ball bearing made into the back combination which is an example of the 1st Embodiment of this invention. It is sectional drawing in alignment with the radial direction of a holder | retainer. It is the fragmentary perspective view which looked at the cage | basket from the radial inside. It is the arrow line view seen from the arrow Y direction of FIG. It is sectional drawing on the ZZ line of FIG. It is explanatory drawing explaining an effect | action when a holder | retainer moves to an axial direction. (A) is an arrow view seen from the arrow X direction of FIG. 2, (b) is an enlarged view which shows the holder | retainer shown to (a). It is principal part sectional drawing for demonstrating the double row angular contact ball bearing which is an example of the 2nd Embodiment of this invention. It is sectional drawing which shows the conventional deep groove ball bearing. It is a perspective view which shows the holder | retainer of FIG. It is sectional drawing on the BB line of FIG. It is sectional drawing on the AA line of FIG. It is sectional drawing which shows the conventional angular contact ball bearing. It is a side view which shows the holder | retainer of FIG. (A) is the arrow view which looked at the conventional cage from the axial direction, (b) is an arrow view which shows the modification of (a), (c) shows the modification of the cage shown in (b). (D) is a figure which shows the interference state of a holder | retainer, (e) is a figure which shows the interference avoidance state of a holder | retainer.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an essential part showing a state in which two rows of single-row ball bearings according to the first embodiment of the present invention are combined, FIG. 2 is a cross-sectional view showing a ball guide cage, and FIG. 4 is a partial perspective view as seen from the inside of the direction, FIG. 4 is an arrow view as seen from the direction of the arrow Y in FIG. 2, FIG. 5 is a sectional view taken along the line ZZ in FIG. FIG. 7 is a view showing the cage of the present invention.

As shown in FIG. 1, the combination bearing 100 of the present invention has a configuration in which two single-row angular ball bearings 100A and 100B are combined in two rows on the back so that the contact angle represents a square shape.
Here, in each of the single row angular ball bearings 100A and 100B, as shown in FIG. 1, a large number of balls 103 are rotatably arranged between the raceway groove 101a of the outer ring 101 and the raceway groove 102a of the inner ring 102. It has the structure of a narrow bearing.

In addition, the material of the inner ring 102, the outer ring 101, and the ball 103 is a bearing steel (for example, SUJ2, SUJ3, etc.) under standard use conditions, but depending on the use environment, a stainless steel material (for example, a corrosion resistant material) Martensitic stainless steel materials such as SUS440C, austenitic stainless steel materials such as SUS304, precipitation hardened stainless steel materials such as SUS630), titanium alloys and ceramic materials (for example, Si ₃ N ₄ , SiC, Al ₂ O ₃ , ZrO) ₂ etc.) may be adopted.

The lubrication method is not particularly limited, and mineral oil-based grease or synthetic oil-based grease (for example, lithium-based or urea-based grease) or oil can be used in a general use environment, and fluorine-based grease or fluorine in high-temperature environment applications. Series lubricants or solid lubricants such as fluororesin and MoS ₂ can be used.
Narrow bearings are sizes not applicable to standard angular contact ball bearings (78XX, 79XX, 70XX, 72XX, 73XX series, etc.) defined by the International Organization for Standardization (ISO). The sectional dimension ratio (B / H) between the axial sectional width B and the radial sectional height H (= (outer ring outer diameter D−inner ring inner diameter d) / 2) is (B / H) < The bearing is 0.63.

A narrow double-row ball bearing has a cross-sectional dimension ratio (B2 / H2) of an axial cross-sectional width B2 and a radial cross-sectional height H2 (= (outer ring outer diameter D2-inner ring inner diameter d2) / 2). B2 / H2) A narrow double row angular contact ball bearing with <1.2.
For example, in the case of 7208A (angular ball bearing with a contact angle of 30 degrees) as a conventional ball bearing, the inner ring inner diameter φ40 mm, the outer ring outer diameter φ80 mm, and the axial sectional width (bearing unit width) B is 18 mm. (B / H) = 0.9.

  Therefore, in the angular ball bearings 100A and 100B of the present embodiment, the sectional dimension ratio (B / H) = 0.45 (the inner ring inner diameter and the outer ring outer diameter remain the same, and the axial sectional width (bearing single body width) is 9 mm. ). As a result, radial load, axial load in both directions, and moment load can be received, space saving of 1/2 in the axial dimension can be achieved, and the single row 7208A can be replaced, and torque can be reduced. High rigidity can be achieved.

  Single-row ball bearings are difficult to apply preload or moment load in one row, but by combining multiple rows of two or more rows, radial load, axial load and moment load can be applied. It becomes possible to do.

  Further, since each ball always contacts the inner and outer raceway grooves at two points, an increase in torque due to a large spin of the ball can be suppressed as in a four-point contact ball bearing. Since the rolling resistance is lower than that of the bearing, a reduction in torque can be realized.

Note that the contact angle θ is approximately 60 ° or less, preferably 50 ° or less, more preferably, in order to suppress the ball and the inner / outer ring groove contact portion from climbing onto the shoulder portions of the inner and outer rings when a large moment load is applied. 40 ° or less is preferable, but if it is less than 20 °, the allowable axial load and the allowable moment load are reduced, which is not preferable.
In this embodiment, a ball guide retainer 110 for positioning a large number of balls 103 in the circumferential direction is disposed on the combination surface side of the single row angular ball bearings 100A and 100B, and an annular seal is provided on the opposite side to the combination surface. A body 120 is provided.

  As shown in FIGS. 2 to 4, the ball guide retainer 110 includes a ring portion 111, and column portions 112 protruding in the axial direction at a plurality of locations at substantially equal intervals in the circumferential direction on one end portion of the ring portion 111. , A plurality of pockets 113 formed between the pillars 112 to hold the balls 103 so as to be able to roll in the circumferential direction, and the balls 103 formed at the front ends of the pockets 113 opposite to the ring parts 111. And a pair of ball locking portions 114 for preventing the slipping out of the flexible crown-shaped cage. The material of the cage 110 is, for example, a synthetic resin material such as polyamide, polyacetal, or polyphenylene sulfide, and a material in which a reinforcing material such as glass fiber or carbon fiber is mixed into the synthetic resin material is used as necessary.

As shown in FIG. 1, the ball guide cage 110 is arranged on the single row angular ball bearings 100 </ b> A and 100 </ b> B so that the ring portion 111 is on the combination surface side.
Here, as shown in FIG. 5, the center of curvature 113 of the pocket portion 113 and the center of curvature of the ball 103 coincide with the axial distance L between the center of curvature O of the pocket portion 113 and the tip of the ball locking portion 114. The value ΔG + ΔP obtained by adding the axial clearance ΔP between the pocket surface 113a of the pocket portion 113 and the ball 103 to the axial clearance ΔG between the ends of the ring portions 111 in the two opposing cages 110 in the state where they are set to be (1 ) Is set so as to be small as represented by the formula.

L> ΔG + ΔP (1)
By adopting such a dimensional configuration, the cage 110 is changed from the state shown in the chain line to the state shown in the solid line by one single-row angular ball bearing, for example, 100A, as shown in FIG. When the ring portion 111 moves in the axial direction, the large diameter portion of the ball 103 is brought into contact with the ring engaging portion 114 by contacting the ring portion 111 of the cage 110 of the other single-row angular ball bearing 100B combined with the ring portion 111. The tip is not exceeded (that is, Δ in FIG. 6 becomes a positive value), and it is possible to reliably prevent the retainer 110 from dropping, that is, the ball 103 from being detached from the pocket portion 113 (that is, FIG. 6). A margin is left for Δ in the middle).

By disposing the retainer 110 so as to have the relationship of the above formula (1) in the combined bearing 100, it is possible to reliably prevent the retainer 110 from coming off from the ball 103, and the ball engagement of the retainer 110. The selection range of the shape design of the stopper 114 can be expanded, and the design is facilitated.
Further, in this embodiment, in order to increase the load capacity and rigidity of the bearing, the circumferential pitch between the adjacent balls 103 is shifted as much as possible to the opposite side of the combination side end face (FIG. 1: X1> X2), and the cage 110. The ring part 111 is arranged on the bearing combination end face side so that the distance between the operating points for increasing moment rigidity can be increased.

  In addition, as shown in FIG. 7A, the retainer 110 cuts in advance between the pocket portions 113 adjacent to each other at least at one place in the circumferential direction of the ring portion 111, and a predetermined gap between the cut surfaces. The structure has ΔR.

Further, as shown in FIG. 7B, C as a guide mechanism for preventing circumferential interference between opposing cages at the corners of the cut surface and the side surface of the cage ring portion 111. A chamfered portion 115 is provided.
For example, when an external load such as a moment load is applied to the bearing, the revolution speeds of the balls 103 and the cage 110 between the combined bearing rows differ depending on the relative inclination of the inner and outer rings, the deformation of the inner and outer rings, and the cage. 110 may be deformed relative to each other in the axial direction, and the cages 110 may interfere with each other in the circumferential direction and stick together to apply a load to the cage 110. Therefore, by forming the chamfered portion as described above, circumferential interference between the cages 110 in each row can be avoided, and problems such as an increase in rotational torque and wear and damage of the cage 110 can be eliminated. It becomes possible.

Furthermore, the angle α formed between the C chamfered portion 115 and the side surface of the ring portion 111 is set so that the value of α is larger than the value of tan ⁻¹ μ when the coefficient of static friction between the cages is μ. It is desirable. With the above setting, when the circumferential phase of the slit clearance ΔR of each cage 110 matches, even if the cages 110 in each row interfere with each other in the circumferential direction, the inclination of the C chamfer 115 Since the contact is smoothly performed between the parts, the cages 110 can surely escape in the axial direction. For example, when a polyamide resin is used as the material of the cage 110, μ = 0.15 to 0.30. Therefore, when μ is calculated as the maximum value 0.30, α> tan ⁻¹ μ = 16.699 °. It becomes. The value of α may be equal to or greater than this value. However, in order to avoid interference between the chamfered portion 115 and the minimum thickness portion between the pocket portion 113 and the ring portion 111 facing each other with a slit clearance ΔR, α is 70 to 80 °. It is preferable to set the following.

The dimension C of the C chamfered portion 115 is preferably set as follows.
In the two cages 110 facing each other in a state in which the axial clearance between the ball locking portions 114 and 103 is M (see FIG. 5), and the center of curvature of the pocket portion 113 and the center of curvature of the ball 103 are matched. When the axial clearance between the ends of the ring portion 111 is ΔG, the value of C is set to be larger than the value of (2 × M−ΔG) / 2. With the setting as described above, contact between the C chamfered portions 115 is surely generated in the circumferential direction, and the state of contact with the cut surface having the clearance ΔR can be reliably prevented.

  Next, a double-row angular contact ball bearing which is an example of the second embodiment of the present invention will be described with reference to FIG. In this double row angular contact ball bearing 200, a plurality of balls 203 are rolled by a cage 210 between the double row raceway groove 201a of the outer ring 201 and the raceway grooves 202a of two inner rings 202A and 202B formed separately from each other. The sectional dimension ratio (B2 / H2) between the axial sectional width B2 and the radial sectional height H2 (= (outer ring outer diameter D2—inner ring inner diameter d2) / 2) is (B2 / H2) < 1.2.

  Here, the retainer 210 is a crown-shaped retainer having the same configuration as that of the first embodiment described above, and the same reference numerals are given to the corresponding parts to the first embodiment, and the detailed description thereof will be given here. Although omitted, as shown in FIG. 5 in the first embodiment described above, the pocket portion 113 curvature center O with respect to the axial distance L between the curvature center O of the pocket portion 113 and the tip of the ball locking portion 114. And the axial clearance ΔP between the pocket surface 113a of the pocket portion 113 and the axial direction of the ball 203 in the axial clearance ΔG between the ends of the ring portion 111 in the two cages 210 facing each other in a state where the center of curvature of the ball 203 and the ball 203 are matched. Is set to be small (L> ΔG + ΔP).

  As a result, the same effects as those of the first embodiment can be obtained, and the radial load, the axial load in both directions, and the moment load can be received. Torque and higher rigidity can be achieved.

As in the first embodiment described above, the ring portion 111 of the retainer 210 is preliminarily cut between the pocket portions 113 adjacent to each other at least at one place in the circumferential direction, and a predetermined interval is formed between the cut surfaces. A structure having a clearance ΔR is provided, and a C chamfered portion 115 is provided at a corner between the cut surface and the side surface of the ring portion 111, and an angle formed between the C chamfered portion 115 and the side surface of the ring portion 111 is defined as α. When the static friction coefficient between 210 is μ, the value of α is set to be larger than the value of tan ⁻¹ μ. Interference can be avoided, and problems such as an increase in rotational torque and wear and damage of the cage 210 can be reliably prevented.

  The combination ball bearing and double-row ball bearing of the present invention are, for example, industrial machines, robot joints and turning mechanisms, machine tool rotary tables and spindle turning mechanisms, medical equipment, semiconductor / liquid crystal manufacturing apparatuses, optics, and optical components. It can be suitably used for an electronic device or the like, especially for a combination ball bearing and a double row ball bearing in which a radial load and an axial load in both directions, particularly a large moment load are applied as a load.

100 Combination ball bearings 100A, 100B Single row angular contact ball bearing 101 Outer ring 101a Outer ring raceway groove 102 Inner ring 102a Inner ring raceway groove 103 Ball 110 Ball guide retainer 111 Ring part 112 Column part 113 Pocket part 114 Ball locking part 115 C chamfering part 120 Annular seal bodies 121 and 122 Seal receiving groove 200 Double row angular contact ball bearing 201 Outer ring 201a Outer ring raceway grooves 202A and 202B Inner ring 202a Inner ring raceway groove 230 Ball 220 Annular seal bodies 221 and 222 Seal receiving groove

Claims (2)

Each of the narrow ball bearings is composed of two rows of narrow ball bearings. Each narrow ball bearing has a ring portion on one side and a required number of pocket portions for holding balls on the other side of the ring portion. A combined ball bearing in which the guide retainer is arranged on the combination surface side on the ring side,
The pocket portion has a ball locking portion that prevents a ball formed at a tip portion on the opposite side to the ring portion, and an axial distance between the center of curvature of the pocket portion and the tip of the ball locking portion. In contrast, the axial clearance between the pocket surface of the pocket portion and the ball in the axial clearance between the ring portion end portions of the two opposing cages in a state in which the center of curvature of the pocket portion and the center of curvature of the ball coincide with each other. The ring portion is set to have a small value, and the ring portion is preliminarily cut between the pocket portions adjacent to each other at least at one place in the circumferential direction, and has a predetermined gap between the cut surfaces. A chamfered portion is provided at a corner between the cut surface and the side surface of the ring portion, an angle formed between the C chamfered portion and the side surface of the ring portion is α, and static friction between the cages If the coefficient was μ, tan The value of α to the value of ¹ mu is set to increase,
The dimension of the C chamfered portion is C, the axial clearance between the ball engaging portion and the ball is M, and the two opposing surfaces in the state where the center of curvature of the pocket portion and the center of curvature of the ball are matched. When the axial clearance between the ends of the ring portion in the cage is ΔG, the value of C is set to be larger than the value of (2 × M−ΔG) / 2. Combination ball bearing. A crown-shaped ball having a configuration of a narrow double-row ball bearing, each row having a ring portion on one side and a required number of pocket portions holding the ball on the other side of the ring portion. A double row ball bearing in which the guide cage is arranged with the ring side facing the inner side in the axial direction of the bearing,
The pocket portion has a ball locking portion that prevents a ball formed at a tip portion on the opposite side to the ring portion, and an axial distance between the center of curvature of the pocket portion and the tip of the ball locking portion. In contrast, the axial clearance between the pocket surface of the pocket portion and the ball in the axial clearance between the ring portion end portions of the two opposing cages in a state in which the center of curvature of the pocket portion and the center of curvature of the ball coincide with each other. The ring portion is set to have a small value, and the ring portion is preliminarily cut between the pocket portions adjacent to each other at least at one place in the circumferential direction, and has a predetermined gap between the cut surfaces. A chamfered portion is provided at a corner between the cut surface and the side surface of the ring portion, an angle formed between the C chamfered portion and the side surface of the ring portion is α, and static friction between the cages If the coefficient was μ, tan The value of α to the value of ¹ mu is set to increase,
The dimension of the C chamfered portion is C, the axial clearance between the ball engaging portion and the ball is M, and the two opposing surfaces in the state where the center of curvature of the pocket portion and the center of curvature of the ball are matched. When the axial clearance between the ends of the ring portion in the cage is ΔG, the value of C is set to be larger than the value of (2 × M−ΔG) / 2. Double row ball bearing.