Ball bearing

Abstract

The present invention relates to a ball bearing, which suppresses deformation of a retainer caused by centrifugal force and shape damage of the retainer when the retainer is molded and when balls are inserted into pockets. The ball bearing is used in an environment in which the dmn value defined by dmn = {(D + d) / 2} * n is 900,000 or more, D: the outer diameter (mm) of the outer member (4), d: the inner diameter (mm) of the inner member (3), and n: the rotational speed (min-1), where a cage (10) that holds the balls (5) is a crown cage provided with an annular base (11) and a plurality of pockets (20) formed on one side of the base (11) in the axial direction in the circumferential direction, and each pocket (20) is formed on the other side of the base (11) in the axial direction in the circumferential direction. The minimum wall thickness t in the axial direction of the base section (11) at the bottom section (22) on the other side in the axial direction of the pocket (20) is 0.06 Da < = t < = 0.22 Da with respect to the diameter Da of the ball (5).

Description

Technical Field

[0001] The present invention relates to a ball bearing suitable for high-speed rotation. Background Art

[0002] For example, in various vehicles such as automobiles and construction machinery, as well as various other industrial machines, devices equipped with electric motors use a large number of bearings. Compared to bearings used for shaft support in general equipment, bearings used in these types of equipment are generally used under high-speed conditions. In addition, in recent years, especially in electric vehicles, there has been a trend to increase the rotational speed and reduce the size and weight of the motors in order to improve the output density of the motors. If the maximum rotational speed of the bearings increases with the speed of the motors, the centrifugal force acting on the internal components of the bearings will increase.

[0003] In recent years, drive units called "e-axles," which integrate drive motors, transmissions, and speed reducers, have become increasingly popular. As output increases, motor speeds are also increasing. The bearings supporting the motor's rotating shaft in e-axles typically have an inner ring diameter (d) of 20 mm ≤ d ≤ 40 mm and operate at higher rotational speeds than bearings in other equipment.

[0004] However, in ball bearings using balls as rolling elements, a crown-type retainer is sometimes used as a retainer to hold the balls. A crown-type retainer comprises an annular base and multiple pockets circumferentially extending from the base. The pockets are arranged axially to one side of the retainer relative to the base. Each pocket extends radially through the retainer and opens axially to one side. Each pocket has a pair of claws on either side of the opening circumferentially to retain the balls.

[0005] In ball bearings using crown-type retainers, as the bearing rotates at higher speeds, the centrifugal force of the retainer pockets causes the claws to deform outwardly due to the centrifugal force, potentially trapping the balls. Therefore, for example, Patent Document 1 discloses a method of attaching metal deformation prevention members to the openings of the pockets to prevent deformation of the claws on both sides of the pockets.

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-285506

[0007] Installing a deformation prevention member such as that described in Patent Document 1 presents the following problems: it increases the number of components and complicates the retainer structure, leading to higher costs. Alternatively, for example, a method is being considered: increasing the bottom wall thickness of the retainer pocket, i.e., the axial thickness of the base portion at the bottom of the pocket, compared to conventional methods to increase retainer rigidity and suppress deformation caused by centrifugal force.

[0008] However, if the rigidity of the pocket is excessively increased, the shape of the claw tip is likely to be broken when the ball is inserted into the pocket or when the component is removed from the mold during cage molding. Summary of the Invention

[0009] Therefore, an object of the present invention is to suppress deformation of the cage due to centrifugal force and to suppress shape destruction of the cage during cage molding and when balls are inserted into pockets.

[0010] In order to solve the above-mentioned problems, the present invention adopts a ball bearing comprising: an inner member and an outer member; balls arranged between the inner member and the outer member; and a retainer for retaining the balls.

[0011] Use in an environment where the dmn value specified by dmn = {(D + d) / 2} × n is 900,000 or more.

[0012] D: outer diameter of the above outer part (mm)

[0013] d: Inner diameter of the above inner part (mm)

[0014] n: Speed ​​(min -1 )

[0015] In which, the above-mentioned retainer is a crown-shaped retainer, which has an annular base and a plurality of pockets, the plurality of pockets are formed along the circumferential direction on one axial side of the above-mentioned base and retain the above-mentioned balls, and the minimum axial wall thickness t of the above-mentioned base at the bottom of the other axial side of the above-mentioned pockets is 0.06Da≤t≤0.22Da relative to the diameter Da of the above-mentioned balls (Structure 1).

[0016] On the basis of structure 1, the following structure can be adopted, namely: the axial distance H between the edge of the axial one end side of the connecting portion connecting the circumferentially adjacent pockets and the edge of the axial other end side of the base portion relative to the pocket diameter HP specified by the diameter of the pocket is H≤t+HP / 2 (structure 2).

[0017] On the basis of Structure 1 or Structure 2, the following structure can be adopted, namely: the relationship between the cross-sectional area S of the above-mentioned base in the axial cross-section passing through the above-mentioned bottom and including the axis of the above-mentioned base and the cross-sectional area S' of the above-mentioned base in the axial cross-section passing through the circumferential center of the connecting portion connecting the circumferentially adjacent pockets and including the axis of the above-mentioned base is S<S' (Structure 3).

[0018] In addition to the configuration 1 or the configuration 1 with one or both of the configurations 2 and 3 added thereto, a configuration (configuration 4) in which the material of the retainer includes engineering plastic can be adopted.

[0019] In addition to the structure 4, a structure (structure 5) can be adopted in which the raw material of the retainer contains carbon fiber or glass fiber as a reinforcing material.

[0020] A bearing device can be used that uses structure 1, or a ball bearing in a form in which one or more elements selected from structures 2 to 5 are added to structure 1, and uses the above-mentioned ball bearing to support the rotating shaft of the drive motor, reducer or speed increaser used in electric conveying equipment.

[0021] According to the present invention, deformation of the cage due to centrifugal force can be suppressed, and the shape of the cage can be suppressed from being damaged during the molding of the cage and when the balls are inserted into the pockets. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a front view showing one embodiment of the present invention.

[0023] Figure 2 yes Figure 1 II-II sectional view.

[0024] Figure 3 It is a cross-sectional view showing a state where the balls are held in the cage.

[0025] Figure 4 yes Figure 3 IV-IV sectional view of FIG.

[0026] Figure 5 yes Figure 3 VV cross-sectional view.

[0027] Figure 6 This is a graph showing the relationship between the cage pocket bottom thickness / ball diameter and the clearance between the cage and the raceway ring.

[0028] Figure 7 This is a graph showing the relationship between the cage pocket bottom thickness / ball diameter and the cage shape-breaking safety factor.

[0029] Description of Reference Numerals

[0030] 1…bearing (ball bearing); 3…inner member (inner ring); 3a…inner raceway groove; 4…outer member (outer ring); 4a…outer raceway groove; 5…ball (rolling element); 10…retainer; 11…base; 12…retaining portion; 13…recess; 14…claw; 15…connecting portion; 16…circumferential center; 20…pocket; 22…bottom. DETAILED DESCRIPTION

[0031] An embodiment of the present invention will be described with reference to the drawings. A rolling bearing 1 of this embodiment is used to support the rotating shaft of a drive motor included in electric conveying equipment such as an electric vehicle, or the rotating shaft of a speed reducer or speed increaser included in such electric conveying equipment.

[0032] like Figure 1 and Figure 2 As shown, the rolling bearing 1 (hereinafter referred to as bearing 1) is a ball bearing, which comprises: an inner part 3 and an outer part 4 constituting a raceway ring; an inner raceway groove 3a with an arc-shaped cross section formed in the inner part 3; an outer raceway groove 4a with an arc-shaped cross section formed in the outer part 4; a plurality of rolling elements 5 arranged between the inner raceway groove 3a and the outer raceway groove 4a; and a retainer 10 for retaining the rolling elements 5, wherein the inner diameter d of the inner ring satisfies 20mm≤d≤40mm.

[0033] Here, balls (steel balls) are used as rolling elements 5, and therefore are hereinafter referred to as balls 5. Furthermore, in the embodiment, the inner raceway groove 3a and the outer raceway groove 4a each have an arc-shaped cross-section with a single radius in any longitudinal section including the axis. Hereinafter, the direction along the bearing centerline c of the bearing 1 will be referred to as the "bearing axial direction" or simply the "axial direction," the direction orthogonal to the axial direction will be referred to as the "bearing radial direction" or simply the "radial direction," and the circumferential direction around the bearing centerline c will be referred to as the "bearing circumferential direction" or simply the "circumferential direction."

[0034] The inner member 3 (referred to as the inner ring 3 in this embodiment) has a rotating shaft (not shown) fixed to its inner diameter portion 3b and rotates integrally with the rotating shaft in the circumferential direction. The outer member 4 (referred to as the outer ring 4 in this embodiment) is similarly mounted on a fixed member (not shown) such as a housing or a gear, at its outer diameter portion 4b. Thus, the bearing 1 supports the rotating shaft so that it can rotate freely relative to the fixed member. Examples of the rotating shaft mentioned here include the rotating shaft of a drive motor included in electric conveying equipment such as electric vehicles, or the rotating shaft of a speed reducer or speed increaser included in these electric conveying equipment. Furthermore, the bearing center axis of the bearing 1 and the rotation center axis of the rotating shaft are set coaxially.

[0035] When the bearing 1 is assembled, a lubricant such as grease is enclosed within the bearing's internal space. Furthermore, sealing members (not shown) are attached to the openings at the axial ends of the bearing's internal space. Seal members may be provided at both axial ends of the bearing's internal space, while other configurations may include sealing members only at one axial end, or no sealing members at all, depending on the specifications.

[0036] The retainer 10 is a crown-shaped retainer molded from engineering plastics. Examples of engineering plastics include raw materials containing polyetheretherketone resin and polyphenylene sulfide resin. By forming the retainer 10 from a raw material containing engineering plastics, the amount of deformation of the component under the action of centrifugal force can be suppressed. Even if the retainer 10 is formed from a raw material that does not contain engineering plastics, it is desirable to use a resin material that is resistant to deformation due to centrifugal force, such as a raw material containing polyamide resin. However, the raw material and type of the retainer 10 can be appropriately changed according to the specifications of the bearing 1. If the raw material of the retainer 10 contains carbon fiber or glass fiber as a reinforcing material, the amount of deformation of the component under the action of centrifugal force can be further suppressed.

[0037] like Figures 2 to 5 As shown, the retainer 10 comprises an annular base 11 and a plurality of retaining portions (retaining claws) 12 projecting axially from the base 11. The side from which the retaining portion 12 projects is referred to as the axially one side, and the opposite side is referred to as the axially other side. The outer diameter surface of the retainer 10 is a curved surface (cylindrical surface) without steps. The space between the circumferentially adjacent retaining portions 12, 12 and the base 11 forms pockets 20 that circumferentially retain the balls 5. Specifically, a plurality of pockets 20 are arranged circumferentially on the axial side of the base 11. The outer diameter surface and the inner diameter surface of the retainer 10 communicate at the pockets 20. The tips of the retaining portions 12 serve as claws 14, and the pair of claws 14, 14 are curved toward each other across the pockets 20. The balls 5 are retained by the pockets 20 and revolve between the inner raceway groove 3a and the outer raceway groove 4a.

[0038] Pocket 20 is formed by being surrounded by the inner surfaces of retaining portions 12, 12 on both circumferential sides of the bearing and the inner surface of base portion 11 on one axial side, with pocket center a0 sandwiched therebetween. These inner surfaces retain the ball 5. These surfaces that retain the ball 5 are referred to as pocket surfaces 21. Pocket surface 21 is spherical throughout the entire area facing the outer surface of the spherical ball 5.

[0039] exist Figure 3 In the cross section shown, i.e., the cross section perpendicular to the straight line in the bearing radius passing through the pocket center a0 (referred to as the circumferential cross section), the pocket surface 21 is formed by an arc around the pocket center a0. The diameter of this arc is HP. The diameter HP of the pocket surface in the circumferential cross section is usually set larger than the diameter Da of the ball 5. In addition, Figure 3 In the figure, for ease of understanding, a cross section of the originally cylindrical retainer 10 in a plan view is laterally developed and described as a flat surface.

[0040] exist Figure 4In the cross section shown, that is, the cross section passing through the pocket center a0 and including the bearing center line c (called the axial cross section), the diameter of the arc of the pocket surface 21 is also HP. Figure 1 In the cross section shown, i.e., the cross section passing through the pocket center a0 and perpendicular to the bearing centerline c (referred to as the axially perpendicular cross section), the diameter of the arc of the pocket surface 21 is also HP. However, if a recessed portion such as an oil reservoir is provided in the pocket surface 21, the location of the recessed portion is excluded. Hereinafter, the diameter HP of the pocket surface 21 is referred to as the pocket diameter HP.

[0041] Where D is the outer diameter of the bearing (outer diameter of the outer ring 4) (mm), d is the inner diameter of the bearing (inner diameter of the inner ring 3) (mm), and n is the speed (min -1 ),

[0042] The bearing 1 is designed for use in a high-speed rotation environment with a dmn value of 900,000 or more, as defined by dmn={(D+d) / 2}×n. The dmn value is defined by the bearing inner ring rotational speed×the pitch diameter.

[0043] Here, the minimum wall thickness t of the base portion 11 in the axial direction at the bottom portion 22 on the other axial side of the pocket 20 (hereinafter referred to as the bottom wall thickness t) is set to be 1 / 2 of the diameter Da of the ball 5.

[0044] 0.06Da≤t≤0.22Da…(Condition 1).

[0045] This improves the ring rigidity of the retainer 10, suppressing deformation of the tip of the retaining portion 12 due to centrifugal force, thereby preventing entrapment of the balls 5. Consequently, the bearing 1 can be used under high-speed conditions, where the dmn value reaches 900,000 or more at the highest rotational speed in its operating environment.

[0046] Here, as Figure 3 and Figure 4 As shown, the bottom wall thickness t refers to the wall thickness of the thinnest part of the bottom 22 on the other side of the pocket 20 in the axial direction, that is, the thickness of the axial part of the part with the smallest axial thickness of the base 11. Figure 3 The circumferential cross section is located at the position closest to the other axial side (see reference numeral 22) and is Figure 4 In the illustrated axial cross section, it is located at the position closest to the other axial side (see reference numeral 22 ).

[0047] Furthermore, if the ring rigidity of the retainer 10 is too high, when the ball 5 is inserted into the pocket 20, excessive stress is generated at the front end of the retaining portion 12, and there is a concern that the shape of the claw 14 may be destroyed. Therefore, it is desirable that the rigidity of the front end of the retaining portion 12 be low. Therefore, in order to reduce the rigidity of the front end of the retaining portion 12, it is also desirable to reduce the axial distance H (see FIG. 1 ) between the edge of the connecting portion 15 on one axial end side, which connects the circumferentially adjacent pockets 20, 20, and the edge of the base portion 11 on the other axial end side. Figure 3 and Figure 4 ) is set relative to the pocket diameter HP

[0048] H≤t+HP / 2…(Condition 2).

[0049] Furthermore, in the embodiment, the base portion 11 is reduced in weight by forming the recess 13 opened on the other axial side surface of the coupling portion 15. This can suppress an increase in the weight of the cage 10 associated with an increase in the ring rigidity of the cage 10.

[0050] The relationship between the ratio of the bottom wall thickness t of the pocket 20 of the retainer 10 to the diameter Da of the ball 5 and the presence or absence of the ball 5 being clamped is verified as follows: Figure 6 shown.

[0051] Figure 6 The experimental example is the verification result when the size of the single row deep groove ball bearing 6005 is used as the size of the retainer 10 and the dmn value is set to 900,000. Figure 6 As shown, when the ratio of the bottom wall thickness t of the pocket 20 of the cage 10 to the ball diameter Da is 6% or greater, even with a dmn of 900,000, it is possible to prevent the ball 5 from being trapped. Similar results can be expected in other types of single-row deep groove ball bearings.

[0052] Furthermore, the centrifugal force associated with the high-speed rotation of the bearing 1 causes the retainer 10 to deform, generating maximum stress near the bottom 22 of the pocket 20. Generally, welded portions of resin products have more dislocated reinforcement fiber orientation than non-welded portions, resulting in a tendency for strength to decrease. Therefore, if the location of maximum stress due to component deformation caused by centrifugal force overlaps with a welded portion, there is a concern that the reliability of the retainer may be reduced. Therefore, it is preferable that the welds of the retainer 10 be located at the connection 15 between circumferentially adjacent pockets 20, avoiding the bottom 22 of the pocket 20.

[0053] In addition, Figure 4 The cross section shown is an axial cross section ( FIG. 1 ) passing through the bottom 22 of the pocket 20 and including the axis of the base 11 (the axis of the bearing 1 ). Figure 3 The cross-sectional area S of the base 11 in the IV-IV section) is Figure 5The cross section shown is the circumferential center 16 (refer to FIG. 1 ) of the connecting portion 15 connecting the circumferentially adjacent pockets 20 and 20. Figure 3 ) and includes the axial cross section of the axis of the base 11 (the axis of the bearing 1) ( Figure 3 In the relationship between the cross-sectional area S' of the base 11 in the VV cross section, it is preferably set to

[0054] S<S'...(Condition 3).

[0055] This is because, by satisfying S<S', it is easy to position the welding position at the connection portion 15. The cross-sectional area S and the cross-sectional area S' can be measured by cutting the cage cross section and using an image measuring device.

[0056] It is desirable that the condition 3 is not only applied to the axial section ( Figure 3 The VV section) is established, and the circumferential ends 17, 17 (refer to Figure 3 ) also holds true for any point in the cross section.

[0057] Furthermore, as described above, if the bottom wall thickness t of the pocket 11 is increased in order to increase the ring rigidity of the retainer 10, the stress applied to the claw 14 when the ball 5 is assembled into the pocket 20 increases, and there is a problem in that the risk of the claw 14 being deformed increases. The results of verifying whether the retainer 10 is deformed when the ball 5 is assembled into the pocket 20 are as follows: Figure 7 shown.

[0058] Figure 7 The experimental example also uses the size of the single row deep groove ball bearing 6005 as the size of the retainer 10. Figure 7 As shown, if the bottom wall thickness t of pocket 20 is 22% or less relative to the diameter Da of ball 5, a shape failure safety factor of retainer 10 of 1 or greater can be ensured. A safety factor of 1 or greater reliably prevents shape failure of retainer 10 during molding and bearing assembly. Similar results can be expected for other types of single-row deep groove ball bearings.

[0059] As described above, by adopting condition 1 in a crown-type resin retainer for a ball bearing, it is possible to simultaneously prevent the balls 5 from being trapped due to centrifugal deformation in operating environments with a dmn value of 900,000 or greater, and to prevent the claw tip shape from being damaged during the molding of retainer 10 and the insertion of the balls 5 into pockets 20. Furthermore, by adding condition 2, condition 3, or both, further enhanced effects can be expected.

[0060] Examples of shafts to which the bearing 1 of the present invention may be mounted include the rotating shafts of drive motors in electric conveying equipment such as electric vehicles, or the rotating shafts of speed reducers or speed increasers in such equipment. However, the bearing 1 of the present invention can also be used in supporting portions of rotating shafts in various conveying equipment, industrial machinery, and the like. For example, the bearing 1 of the present invention can also be used in shafts in power transmission paths for various conveying equipment, rotating portions of constant velocity joints, drive shafts, superchargers, transformers, and wheel bearings, or in supporting portions of rotating shafts in various machine tools, generators, and the like. Furthermore, as in this embodiment, the inner member 3 can be comprised of either an inner ring or a shaft. Furthermore, as in this embodiment, the outer member 4 can be comprised of either an outer ring or a housing.

[0061] Furthermore, the bearing 1 of the present invention can be applied not only to the deep groove ball bearing of this embodiment but also to angular contact ball bearings and any other ball bearings that use balls 5 as rolling elements.

[0062] The embodiments disclosed herein are illustrative in all respects and should not be construed as restrictive. The scope of the present invention is not defined by the above description but by the scope of the claims for protection of this application, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims for protection of this application.

Claims

1. A ball bearing comprising: An inner member (3) and an outer member (4); a ball (5) disposed between the inner member (3) and the outer member (4); and a retainer (10) for retaining the ball (5). Use in an environment where the dmn value specified by dmn = {(D + d) / 2} × n is 900,000 or more. D: outer diameter of the outer member (4) (mm) d: Inner diameter of the inner part (3) (mm) n: Speed ​​(min -1 ) The ball bearing is characterized in that The retainer (10) is a crown-shaped retainer having an annular base (11) and a plurality of pockets (20), wherein the plurality of pockets (20) are formed circumferentially on one axial side of the base (11) and retain the ball (5), and the minimum axial wall thickness t of the base (11) at the bottom (22) on the other axial side of the pocket (20) is 0.06Da≤t≤0.22Da relative to the diameter Da of the ball (5).

2. The ball bearing according to claim 1, characterized in that The axial distance H between the edge of the connecting portion (15) connecting the circumferentially adjacent pockets (20) on one axial end side and the edge of the base portion (11) on the other axial end side is H≤t+HP / 2 relative to the pocket diameter HP specified by the diameter of the pocket (20).

3. The ball bearing according to claim 1 or 2, characterized in that: The relationship between the cross-sectional area S of the base (11) in the axial cross-section passing through the bottom (22) and including the axis of the base (11) and the cross-sectional area S' of the base (11) in the axial cross-section passing through the circumferential center (16) of the connecting portion (15) connecting the circumferentially adjacent pockets (20, 20) and including the axis of the base (11) is S<S'.

4. The ball bearing according to any one of claims 1 to 3, characterized in that The raw material of the retainer (10) contains engineering plastics.

5. The ball bearing according to claim 4, characterized in that The raw material of the retainer (10) contains carbon fiber or glass fiber as a reinforcing material.

6. A bearing device, characterized in that: The ball bearing according to any one of claims 1 to 5 is used to support a rotating shaft of a drive motor, a speed reducer, or a speed increaser for electric conveying equipment.

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