Ball bearing and bearing device

Abstract

The present invention makes it possible to realize a bearing that can be applied under high-speed rotation conditions. In this ball bearing, when Da represents the ball diameter, D represents the bearing outer diameter, d represents the bearing inner diameter, and PCD represents the pitch circle diameter of a ball (5), the minimum wall thickness t in the axial direction of an annular part (11) at the bottom of a pocket (12) is 15-30% of the ball diameter Da, the bearing inner diameter d is 25-55 mm, the bearing outer diameter D is 50-90 mm, the bearing width H is 10-20 mm, the ball diameter Da is 7 / 32 inches or less, and the ratio of the value that is specified by 1 / 2 of the difference between the pitch circle diameter PCD and the bearing inner diameter d with respect to the bearing inner diameter d is 10-20%.

Description

Ball bearings and bearing devices

[0001] The present invention relates to a ball bearing and a bearing device.

[0002] For example, in various vehicles such as automobiles and construction machinery, as well as in various industrial machines, many bearings are used for rotating shafts such as transmissions (speed-increasing / reducing gears) equipped with drive motors. The bearings used in these devices are generally used at higher rotation speeds than bearings used to support shafts in general devices. Furthermore, with the recent spread of electric vehicles (EVs) and hybrid cars (HEVs), there is a demand for bearings that can handle even higher rotation speeds.

[0003] For example, Patent Document 1 discloses that in a ball bearing using a crown-type cage with a ring portion and a pocket, making the axial width of the thinnest part of the bottom thickness of the pocket 20% or more of the diameter of the ball is effective in preventing skidding, heat generation, seizure, and damage to the cage during high-speed rotation, and in reducing the agitation resistance of the lubricating oil.

[0004] JP 2012-207699 A

[0005] In Patent Document 1, the shape of the cage is improved to make the ball bearing compatible with higher speeds. However, there are cases where the improvement in the shape of the cage as described in Patent Document 1 alone is not enough to accommodate higher speeds, and there is a demand for ball bearings that can accommodate even higher speeds.

[0006] Therefore, an object of the present invention is to apply the bearing to conditions of higher speed rotation.

[0007] In order to solve the above problems, the present invention provides a ball bearing comprising an inner ring, an outer ring, balls arranged between the inner ring and the outer ring, and a cage that holds the balls in a circumferential direction, the cage having an annular portion and multiple pairs of cantilever-shaped retaining claws extending axially to one side of the annular portion, and a pocket for accommodating the balls formed between each pair of retaining claws, the ball bearing comprising: a ball diameter Da of the balls; a bearing outer diameter D defined by the maximum outer diameter of the outer ring; a bearing inner diameter d defined by the minimum inner diameter of the inner ring; an outer ring groove bottom diameter D; ０ , inner ring groove bottom diameter d ０ , radial internal clearance median value gr１ Pitch circle diameter PCD = {D ０ +d ０ -gr １} / 2, the minimum axial thickness t of the retainer is 15% to 30% of the ball diameter Da, the bearing inner diameter d is 25 mm to 55 mm, the bearing outer diameter D is 50 mm to 90 mm, the bearing width H of the inner ring and the outer ring in the axial direction is 10 mm to 20 mm, and the ratio of the value defined as 1 / 2 of the difference between the pitch circle diameter PCD and the bearing inner diameter d to the bearing inner diameter d is 10% to 20% (Configuration 1).

[0008] In configuration 1, a configuration can be adopted in which the ratio of the difference between the outer ring inner diameter D1 defined by the minimum inner diameter of the outer ring and the inner ring outer diameter d1 defined by the maximum outer diameter of the inner ring to the difference between the bearing outer diameter D and the bearing inner diameter d is 15% or more and 25% or less (configuration 2).

[0009] In the configuration 1 or 2, a configuration can be adopted in which the ratio of the distance C from the bearing end face to the other axial end face of the annular portion to the bearing width H is 20% or more and 30% or less (configuration 3).

[0010] In any one of configurations 1 to 3, a configuration can be adopted in which the pitch circle diameter PCD and the ball diameter Da are in the range of 112 < PCD × Da < 384, and the pitch distance P of the balls in the circumferential direction of the bearing is in the range of 20 < P × Da / 2 < 34 (configuration 4).

[0011] In any one of the configurations 1 to 4, the end face on the other axial side of the annular portion may be a flat surface with no recesses over the entire area (configuration 5).

[0012] Furthermore, in any one of configurations 1 to 5, a configuration can be adopted in which the material of the cage contains nylon resin (configuration 6).

[0013] In any one of the configurations 1 to 6, the dmn value is equal to the pitch circle diameter PCD×n, where n is the rotation speed (min －１ ) is within the motor use condition range and is 650,000 or more, so that the motor can be used at least intermittently (Configuration 7).

[0014] In addition, in any one of configurations 1 to 6, a configuration in which the ball diameter Da is 7 / 32 inches or less can be adopted (configuration 8).

[0015] A bearing device using the ball bearing according to any one of configurations 1 to 8 can be employed to rotatably support the rotary shaft of a drive motor (configuration 9).

[0016] According to the present invention, a bearing that can be used under conditions of higher speed rotation can be realized.

[0017] 2A; FIG. 2A; FIG. 2B; FIG. 2C;

[0018] A rolling bearing 1 according to an embodiment of the present invention will now be described with reference to the drawings. The rolling bearing 1 is a ball bearing, and as shown in FIGS. 1 to 3 , includes an inner ring 3, an outer ring 2, a plurality of rolling elements 5 arranged between the inner ring 3 and the outer ring 2, and a cage 10 that holds the rolling elements 5 in the circumferential direction. In this embodiment, spherical elements (steel balls) are used as the rolling elements 5, and these will be referred to hereinafter as balls 5. This ball-bearing type rolling bearing 1 will be referred to hereinafter simply as bearing 1. The direction along the bearing center axis of bearing 1 will be referred to simply as the "axial direction," the direction perpendicular to the axial direction will be referred to simply as the "radial direction," and the circumferential direction around the bearing center axis will be referred to simply as the "circumferential direction."

[0019] The inner ring 3 is annular, and a rotating shaft (not shown) is fixed to its inner diameter portion 3b, rotating circumferentially together with the rotating shaft. The outer ring 2 is also annular, and is attached to a fixed member (not shown), such as a housing or gear, that bears the load from the rotating shaft. In this way, the bearing 1 rotatably supports the rotating shaft relative to the fixed member. The rotating shaft referred to here may be, for example, the rotating shaft of a drive motor provided in an electric transport device such as an electric vehicle, or the rotating shaft of a reducer or speed increaser provided in such an electric transport device. The bearing center axis of the bearing 1 and the rotation center axis of the rotating shaft are set coaxially.

[0020] When the bearing 1 is assembled, an appropriate lubricant such as grease is sealed in the bearing internal space. During use, a lubricant (lubricating oil) is supplied from the outside into the bearing internal space through an opening at the axial end of the bearing internal space.

[0021] The lubricating oil that lubricates devices such as drive motors and transmissions contains gear wear powder, clutch wear powder, and other foreign matter depending on the device into which bearing 1 is installed. It is desirable for these foreign matter to be captured somewhere rather than floating in the lubricating oil. For this reason, an appropriate seal member (not shown) is often attached to the opening at the axial end of the bearing's internal space.

[0022] The cage 10 is a crown-shaped cage molded from engineering plastic and reinforced fiber. As shown in FIGS. 4 and 5 , the cage 10 includes a continuous annular portion 11 and a plurality of column portions 13 protruding from the annular portion 11 toward one axial direction. Pairs of column portions 13, 13 are arranged in parallel along the circumferential direction and are spaced at regular intervals along the circumferential direction. Recessed pockets 12 for holding balls 5 are formed between the column portions 13, 13, which are arranged in parallel along the circumferential direction at regular intervals on one axial side of the annular portion 11. The outer and inner diameter surfaces of the cage 10 are curved (cylindrical) surfaces without any steps. The outer and inner diameter surfaces of the cage 10 are connected at the pockets 12.

[0023] The tip of the column portion 13 is a retaining claw 14. The retaining claws 14, 14 on both sides of the pocket 12 are curved in a direction approaching each other. Note that in the embodiment, a recess 15 recessed toward the annular portion 11 is formed between circumferentially adjacent pockets 12, but adjacent column portions 13, 13 may be connected to each other without providing a recess 15 to remove weight. The balls 5 held by the pockets 12 revolve between the raceway grooves 3 a of the inner ring 3 and the raceway grooves 2 a of the outer ring 2 while being held by the pockets 12.

[0024] The pocket 12 is surrounded by the inner surfaces of the columnar portions 13, 13 on both circumferential sides of the pocket center a, and the surface on one axial side of the annular portion 11, and these surfaces hold the ball 5. The surface of the pocket 12 facing the ball 5 is a concave spherical surface 16.

[0025] As shown in the upper part of FIG. 2A and FIG. 3 , the diameter of the spherical surface 16 is HP in a cross section (called an axial cross section; see FIG. 3 ) that passes through the pocket center a and includes the bearing center line o. The diameter of the spherical surface 16 is also HP in a cross section (called an orthogonal-axial cross section; see FIG. 1 ) that passes through the pocket center a and is perpendicular to the bearing center line o. The diameter of the spherical surface 16 is also HP in a cross section (called a circumferential cross section; see FIG. 5 ) that passes through the pocket center a and is perpendicular to the radial line of the bearing that passes through the pocket center a. Note that in FIG. 5 , for ease of understanding, the cross section of the cage 10, which is originally cylindrical, is expanded laterally and depicted as a flat surface. If a recess such as an oil reservoir is provided in part of the pocket 12, the portion excluding the recess will be the spherical surface 16. Hereinafter, the diameter HP of the spherical surface 16 of the pocket 12 will be referred to as the pocket diameter HP.

[0026] The ball diameter Da, which is defined by the diameter of the ball 5, and the pocket diameter HP are usually set so that Da<HP. Here, the pocket center a and the center of the ball 5 (ball center) are coincident by design.

[0027] As shown in Figure 2, the maximum outer diameter of the outer ring 2 (outer diameter of the maximum diameter part) is defined as the bearing outer diameter D, the minimum inner diameter of the inner ring 3 (inner diameter of the minimum diameter part) is defined as the bearing inner diameter d, and the pitch circle diameter is defined as PCD. The pitch circle diameter PCD can be calculated using the following formula: Pitch circle diameter PCD = {D ０ +d ０ -gr １} / 2 D ０ : Outer ring groove bottom diameter d ０ : Inner ring groove bottom diameter gr １ : Median radial internal clearance

[0028] Radial internal clearance median value gr １is determined by placing a measuring probe in the radial direction at the center of the width of the free bearing ring in the ball-top state, and subtracting the amount of elastic deformation of the rolling elements and bearing ring due to the measurement load from the amount of movement of the free bearing ring. Here, the ball-top state refers to the state in which the ball is positioned at 12 o'clock on a clock. The measurement load is changed for each bearing bore size, as shown in Table 1. The amount of elastic deformation of the rolling elements and bearing ring can also be calculated, for example, using Hertz's formula.

[0029] The inner diameter of the outer ring 2 (the inner diameter of the smallest diameter portion excluding the raceway grooves 2a) is defined as outer ring inner diameter D1, and the outer diameter of the inner ring 3 (the outer diameter of the largest diameter portion excluding the raceway grooves 3a) is defined as inner ring outer diameter d1. Furthermore, the radial distance between the outer diameter surface 2b of the outer ring 2 and the inner diameter surface 3b of the inner ring, i.e., half the distance between the bearing outer diameter D and the bearing inner diameter d, is defined as the bearing cross-sectional height b (= (D - d) / 2). The axial width of the cage 10, i.e., the axial distance from the back surface (end face) 11a on the other axial side of the annular portion 11 of the cage 10 to the tips of the retention claws 14, is defined as the axial width HB.

[0030] As shown in FIG. 3, the axial width of the outer ring 2 and the inner ring 3 is defined as the bearing width H, the axial distance from the end faces 2c and 3c on the other axial side of the outer ring 2 and the inner ring 3 to the back surface 11a on the other axial side of the annular portion 11 of the cage 10 is defined as the other-side clearance length c, and the radial thickness of the outer ring 2 is defined as t ２ , the thickness of the inner ring 3 in the radial direction is t ３ The radial distance between the inner diameter of the outer ring 2 (the inner diameter of the smallest diameter portion excluding the raceway groove 2a) and the outer diameter of the inner ring 3 (the outer diameter of the largest diameter portion excluding the raceway groove 3a) is defined as e (= (D1 - d1) / 2).

[0031] 5, the minimum axial thickness of the annular portion 11 at the bottom of the pocket 12 of the cage 10 is defined as t. This minimum thickness t is the distance to the back surface 11a of the annular portion 11 at point f, where the spherical surface 16 of the pocket 12 is closest to the back surface 11a, in the circumferential cross section of the pocket 12 shown in Fig. 5. This point f is also the point where the spherical surface 16 of the pocket 12 is closest to the back surface 11a of the annular portion 11 in the axial cross section shown in Fig. 3.

[0032] Here, the bearing 1 adopts the specifications of requirements 1 to 6 shown in configuration 1 below.

[0033] (Configuration 1) Requirement 1: The minimum axial thickness t of the annular portion 11 at the bottom of the pocket 12 is 15% or more and 30% or less of the ball diameter Da. Requirement 2: The bearing inner diameter d is 25 mm or more and 55 mm or less. Requirement 3: The bearing outer diameter D is 50 mm or more and 90 mm or less. Requirement 4: The bearing width H of the inner ring 3 and outer ring 2 in the axial direction is 10 mm or more and 20 mm or less. Requirement 5: The ball diameter Da is 7 / 32 inch or less. Requirement 6: The ratio of the value defined as 1 / 2 the difference between the pitch circle diameter PCD and the bearing inner diameter d to the bearing inner diameter d is 10% or more and 20% or less. By setting the bearing specifications, including the shape of the cage, according to requirements 1 to 6, torque reduction and cage deformation suppression during high-speed rotation are achieved compared to conventional methods, enabling operation at even higher speeds.

[0034] Regarding the relationship between pitch circle diameter PCD and ball diameter Da, it can be said that a smaller ball diameter Da is generally better for reducing centrifugal force. When comparing bearings under similar load conditions, a smaller ball diameter Da and a larger number of balls 5 results in lower agitation resistance and lower torque than a larger ball diameter Da and a smaller number of balls 5. For this reason, the ratio of the value defined as half the difference between pitch circle diameter PCD and bearing bore diameter d to bearing bore diameter d is set to 10% to 20% (Requirement 6). A ratio of 13% to 17% is preferable for this requirement. In particular, when oil flows within a bearing device (bearing unit) equipped with a bearing, the distance between the back surface 11a of the cage 10 and the balls 5 from the end faces 2c and 3c of the bearing 1 reduces obstructions and facilitates oil inflow. Furthermore, a smaller ball diameter Da reduces agitation resistance when oil enters the bearing's internal space, reducing rolling torque and contributing to a low-torque effect. Furthermore, since the pitch circle diameter PCD is close to the bearing inner diameter d, the torque is reduced.

[0035] Requirement 6 allows the axial width HB of the cage 10 to be small. However, if the axial width HB of the cage 10 is small, there is a high possibility that the cage 10 cannot be molded during manufacturing (for example, due to insufficient strength of the annular portion 11 or the column portion 13) or that the rigidity of the entire cage 10 will be insufficient. To avoid such concerns, the minimum wall thickness t at the bottom of the pocket 12 of the cage 10 is set to 15% to 30% of the ball diameter Da (Requirement 1).

[0036] The above effect is most pronounced when the ball diameter Da is 7 / 32 inch or less (Requirement 5); for example, the ball diameter Da may be 3 / 16 inch. In the embodiment, the addition of Requirement 5 as Configuration 1 produces a significant effect, but the desired effect has also been confirmed in a configuration that does not include Requirement 5, i.e., a configuration in which the ball diameter Da exceeds 7 / 32 inch. Furthermore, the minimum wall thickness t is set to 15% to 30% of the ball diameter Da (Requirement 1), but is more preferably set to 18% to 25%. Furthermore, the bearing size can be set to any value within the following ranges: bearing inner diameter d is 25 mm to 55 mm (Requirement 2), bearing outer diameter D is 50 mm to 90 mm (Requirement 3), and bearing width H is 10 mm to 20 mm (Requirement 4).

[0037] Furthermore, if the following configuration 2 is adopted in addition to configuration 1, further effects can be expected.

[0038] (Configuration 2) Requirement 7: The ratio of the difference between the outer ring inner diameter D1 and the inner ring outer diameter d1 to the difference between the bearing outer diameter D and the bearing inner diameter d is 15% or more and 25% or less. The ratio specified in Requirement 7 is 15% or more and 25% or less, and more preferably 17% or more and 21% or less.

[0039] Furthermore, in an embodiment that includes configuration 1 or an embodiment that adds configuration 2 to configuration 1, employing the following configuration 3 will provide even better results.

[0040] (Configuration 3) Requirement 8: The ratio of the distance C from the bearing end face to the other axial end face 11 a of the annular portion 11 to the bearing width H is 20% or more and 30% or less. The ratio specified in Requirement 8 is 20% or more and 30% or less, and more preferably 24% or more and 28% or less.

[0041] Furthermore, in an embodiment that includes configuration 1, or an embodiment that adds configuration 2 or 3, or both, to configuration 1, employing the following configuration 4 will provide even better results.

[0042] (Configuration 4) Requirement 9: The pitch circle diameter PCD and the ball diameter Da satisfy the following relationship: 112 < PCD × Da < 384 (Equation 1), and Requirement 10: When the pitch distance between the balls 5 in the circumferential direction of the bearing is P, the relationship is 20 < P × Da / 2 < 34 (Equation 2).

[0043] By satisfying 112 < PCD × Da < 384 as in (Equation 1), the rolling torque of the bearing caused by the bearing specifications (bearing size) can be set to a low torque range. Also, by satisfying 20 < P × Da / 2 < 34 as in (Equation 2), the oil agitation torque caused by oil flowing into the bearing can be set to a low torque range. By satisfying both the ranges of (Equation 1) and (Equation 2), the bearing torque can be significantly reduced.

[0044] Furthermore, in an embodiment that includes configuration 1 or an embodiment that adds one or more configurations selected from configurations 2 to 4 to configuration 1, even better results can be obtained by adopting the following configuration 5.

[0045] (Configuration 5) Requirement 11: The back surface 11a on the other axial side of the annular portion 11 of the cage 10 is made flat across the entire area. By not removing any lightening from the back surface 11a of the annular portion 11 of the cage 10, a decrease in the rigidity of the cage 10 is suppressed, and deformation due to centrifugal force during high-speed rotation is suppressed, allowing the cage 10 to accommodate higher speeds.

[0046] Furthermore, in each of the above aspects, even better results can be obtained by adopting the following configuration 6.

[0047] (Configuration 6) Requirement 12: The material of the cage 10 contains nylon resin (polyamide). Examples of polyamides that can be used include 66, 46, 9T, and 10T. Engineering plastics may also be used as the material of the cage 10. Polyphenylene sulfide is particularly suitable as an engineering plastic. Furthermore, if the material of the cage 10 is a composite of these materials and reinforcing fibers, it will be possible to accommodate higher speed rotation.

[0048] Furthermore, in the ball bearings of the above-described embodiments, better effects can be achieved under the conditions of configuration 7 below.

[0049] (Configuration 7) Requirement 13: dmn value = pitch circle diameter PCD × n (Equation 3) where n: rotation speed (min －１ ) The dmn value specified in the above must be within the range of motor use conditions and be 650,000 or more, and the motor must be usable continuously or at least intermittently.

[0050] Generally, the design load of bearings for supporting motor shafts is not particularly large, and the bearing size is often limited to the range of configuration 1. For this reason, if a ball bearing according to any of the above aspects is used to form a bearing device that rotatably supports the rotating shaft of a drive motor, it will be possible to meet the demand for higher speeds.

[0051] Although steel is generally used as the material for the balls 5, ceramics may also be used. Examples of ceramics include nitride ceramics (Si ３ N ４ By using ceramics for the balls 5, the centrifugal force acting on the balls 5 can be reduced, and the contact pressure acting on the raceway grooves 2a of the outer ring 2 can be reduced. Also, by suppressing the centrifugal deformation of the cage 10, it is possible to accommodate operation in a higher speed range.

[0052] 6 to 8 show another embodiment.

[0053] 6 and 7 each have a groove 2d formed around the entire circumferential direction on the outer diameter portion of the outer ring 2, with an O-ring 20 attached to the groove 2d. The O-ring 20 abuts against the housing (not shown), suppressing vibration and noise generation between the housing and the outer ring 2 and also preventing creep between the housing and the outer ring 2. The number of grooves 2d and O-rings 20 can be one as shown in FIG. 6, or two as shown in FIG. 7, and the number can be determined as needed.

[0054] Figure 8 shows a case where the thickness of the outer ring 2 is set thinner than in the above-described embodiments. In Figure 8, the position of the pitch circle diameter PCD within the range of the bearing cross-sectional height b is closer to the center of the width of the bearing cross-sectional height b (the center in the radial direction). Even in such an embodiment, the effects of the present invention can be expected as long as the embodiment including the above-described configuration 1, or the embodiment including configuration 1 plus any configuration selected from configurations 2 to 7, is also included.

[0055] Table 2 shows a comparison between the examples of the bearing 1 of the present invention and the conventional examples. In Table 2, the torque reduction effect is verified for the bearings 1 of Examples 1 to 3 and the bearings 1 of Conventional Examples 1 to 3.

[0056]

[0057] Examples 1 to 3 all satisfy Configuration 1 (Requirements 1 to 6), Configuration 2 (Requirement 7), Configuration 3 (Requirement 8), and Configuration 4 (Requirements 9 and 10), and a predetermined torque reduction effect can be confirmed in comparison with Conventional Examples 1 to 3. This effect is useful for a bearing 1 that supports a shaft that rotates at high speed, such as the rotating shaft of a drive motor. In Conventional Examples 1 to 3, such a torque reduction effect could not be confirmed.

[0058] In the above embodiment, the rotating shaft supported by the bearing 1 is, for example, the rotating shaft of a drive motor equipped in an electric transport device such as an electric vehicle, or the rotating shaft of a reducer or speed increaser equipped in such electric transport device, but the bearing 1 of the present invention and a bearing device using the bearing 1 can also be applied to supporting parts of rotating shafts in various other types of transport devices, industrial machinery, etc. For example, the bearing can be applied to rotating parts of shafts in power transmission paths in various types of transport devices, constant velocity joints, propeller shafts, turbochargers, transmissions, and wheel bearings, or supporting parts of rotating shafts in various machine tools, generators, etc.

[0059] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0060] REFERENCE SIGNS LIST 1 bearing 2 outer ring 3 inner ring 5 ball (rolling element) 10 cage 11 annular portion 11a end face 12 pocket 16 spherical surface

Claims

1. A ball bearing comprising an inner ring (3) and an outer ring (2), balls (5) arranged between the inner ring (3) and the outer ring (2), and a cage (10) for holding the balls (5) in the circumferential direction, wherein the cage (10) has an annular portion (11) and multiple pairs of cantilever-shaped retaining claws (14) extending from one axial side of the annular portion (11), and a pocket (12) for accommodating the balls (5) is formed between each pair of the retaining claws (14), wherein the ball diameter Da of the balls (5), the bearing outer diameter D defined by the maximum outer diameter of the outer ring (2), the bearing inner diameter d defined by the minimum inner diameter of the inner ring (3), and the outer ring groove bottom diameter D ０ , inner ring groove bottom diameter d ０ , radial internal clearance median value gr １ Pitch circle diameter PCD = {D ０ +d ０ -gr １ } / 2, wherein the minimum axial wall thickness t of the retainer (10) is 15% to 30% of the ball diameter Da, the bearing inner diameter d is 25 mm to 55 mm, the bearing outer diameter D is 50 mm to 90 mm, the bearing width H of the inner ring (3) and the outer ring (2) in the axial direction is 10 mm to 20 mm, and the ratio of a value defined as 1 / 2 of the difference between the pitch circle diameter PCD and the bearing inner diameter d to the bearing inner diameter d is 10% to 20%.

2. A ball bearing as described in claim 1, wherein the ratio of the difference between the outer ring inner diameter D1, defined by the minimum inner diameter of the outer ring (2), and the inner ring outer diameter d1, defined by the maximum outer diameter of the inner ring (3), to the difference between the bearing outer diameter D and the bearing inner diameter d is 15% or more and 25% or less.

3. A ball bearing according to claim 1, wherein the ratio of the distance C from the bearing end face to the other axial end face (11a) of the annular portion (11) to the bearing width H is 20% or more and 30% or less.

4. A ball bearing according to claim 1, wherein the pitch circle diameter PCD and the ball diameter Da satisfy the relationship 112<PCD×Da<384, and the pitch distance P of the balls (5) in the circumferential direction of the bearing satisfies the relationship 20<P×Da / 2<34.

5. A ball bearing according to claim 1, wherein the end face (11a) on the other axial side of the annular portion (11) is a flat surface with no recesses over the entire area.

6. A ball bearing according to claim 1, wherein the material of said cage (10) includes nylon resin.

7. dmn value = pitch circle diameter PCD x n, where n: rotation speed (min －１ 2. The ball bearing according to claim 1, wherein the dmn value defined by the following formula is within the range of motor use conditions and is 650,000 or more, and the ball bearing can be used at least intermittently.

8. A ball bearing according to claim 1, wherein the ball diameter Da is 7 / 32 inches or less.

9. A bearing device using a ball bearing according to any one of claims 1 to 8, for rotatably supporting the rotating shaft of a drive motor.

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