Ball bearing

Abstract

The invention provides a ball bearing, which can reduce interference force between a cage and a rolling body caused by advance / lag of the rolling body due to offset of an inner ring and an outer ring, and can stabilize the movement of the cage and the like. A deep groove ball bearing (1) is provided with inner and outer rings (2, 3), a plurality of balls (4) interposed between the inner and outer rings (2, 3), and a corrugated steel sheet holder (5) for guiding rolling elements and holding the balls (4). And the circumferential section and the radial section of the deepest part of a pocket (8) penetrating through the corrugated steel plate retainer (5) are arc-shaped curved surfaces respectively. In the radial cross-section of the corrugated steel sheet retainer (5), the contact points of the pockets (8) and the balls (4) are located in the pocket surfaces of the retainer, and the radial curvature radius of the retainer pocket surfaces is smaller than or equal to the circumferential curvature radius of the retainer pocket surfaces.

Description

[0001] Related Applications

[0002] This application claims the priority of Japanese Patent Application No. 2022-195884 filed on December 7, 2022 and Japanese Patent Application No. 2023-038531 filed on March 13, 2023, and the entire disclosures of which are incorporated herein by reference in their entireties. Technical Field

[0003] The present invention relates to a ball bearing that can be used, for example, in industrial machinery such as electric motors or compressors, and particularly to a ball bearing that can prevent problems with a cage when misalignment occurs in the ball bearing. Background Art

[0004] Various ball bearings for industrial machinery have been disclosed.

[0005] In Patent Document 1, a ball bearing with a cage is disclosed. In this ball bearing, by making the relationship between the circumferential maximum displacement amount δc and the radial maximum displacement amount δr of the rolling elements in the cage pockets, the diameter Dw of the rolling elements, and the diameter guiding clearance Cg between the cage and the raceway rings satisfy 0.04Dw < δc and Cg < δr, even when misalignment occurs between the inner and outer rings of the ball bearing, the inner circumferential surface of the outer ring shoulder or the outer circumferential surface of the inner ring shoulder that can prevent problems with the cage can guide.

[0006] In Patent Document 2, a ball bearing with a cage is disclosed. In this ball bearing, by making the cage pocket surface into a cylindrical shape, the concentration of the interference force between the rolling elements and the cage is alleviated when misalignment occurs between the inner and outer rings of the ball bearing, thereby improving durability.

[0007] [Prior Art Documents]

[0008] [Patent Documents]

[0009] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2012-149733

[0010] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2008-281065 Summary of the Invention

[0011] [Problems to be Solved by the Invention]

[0012] The ball bearings disclosed in Patent Documents 1 and 2 are both ball bearings that can alleviate the load acting on the cage from the rolling elements and prevent problems with the cage even when misalignment occurs between the inner and outer rings.

[0013] The ball bearing disclosed in Patent Document 1 has a cage guided by either the inner circumferential surface of the outer ring shoulder or the outer circumferential surface of the inner ring shoulder (hereinafter referred to as "raceway ring-guided cage"). In a ball bearing having a raceway ring-guided cage, since the cage slides together with the raceway ring guiding surface, there is a risk that friction, wear, and increased heat generation may occur between the cage and the guiding surface of the raceway ring under severe conditions such as poor lubrication.

[0014] The ball bearing disclosed in Patent Document 2 prevents deformation of the cage in the radial direction caused by the leading or lagging of the rolling elements due to offset by making the pocket surface of the cage cylindrical, and avoids excessive interference force between the rolling elements and the cage. However, since the pocket surface of the cage is a cylindrical surface, the contact area between the spherical rolling element and the pocket surface is narrower than that of a general ball surface pocket surface, resulting in a higher contact surface pressure and a risk of cage breakage.

[0015] Furthermore, in Patent Document 2, under usage conditions accompanied by offset, since the displacement of the cage becomes larger, the cage sometimes contacts the shoulders of the outer ring or the inner ring, generating contact loads, which may cause problems with the cage.

[0016] An object of the present invention is to provide a ball bearing that can reduce the interference force between the cage and the rolling elements caused by the leading / lagging of the rolling elements due to the offset between the inner ring and the outer ring, and can stabilize the movement of the cage and the like.

[0017] [Solution to the problem]

[0018] The ball bearing of the present invention includes an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and a corrugated cage for guiding and holding the rolling elements, wherein

[0019] The circumferential cross-section and the radial cross-section passing through the deepest part of the pocket of the cage are respectively curved surfaces in a circular arc shape. In the radial cross-section of the cage, the contact point between the pocket and the rolling element is located within the pocket surface of the cage, and the radial curvature radius of the pocket surface of the cage is less than or equal to the circumferential curvature radius of the pocket surface of the cage.

[0020] According to this structure, in the radial cross-section of the corrugated steel retainer for guiding rolling elements, the contact point between the pocket and the rolling element is located within the pocket surface of the retainer. Moreover, the radial curvature radius of the pocket surface of the retainer is less than or equal to the circumferential curvature radius of the pocket surface of the retainer. Therefore, even when an offset occurs between the inner ring and the outer ring, it is possible to ensure that there is sufficient circumferential allowable movement amount of the rolling elements within the pockets of the retainer to allow the leading / lagging of the rolling elements, and it is possible to suppress the radial movement amount of the retainer. Thus, it is possible to reduce the interference force between the retainer and the rolling elements generated due to the leading / lagging of the rolling elements caused by the offset between the inner ring and the outer ring, and it is possible to stabilize the movement of the retainer and the like.

[0021] The retainer and the rolling elements preferably satisfy the following formula:

[0022] [Mathematical formula 1]

[0023]

[0024] where,

[0025] r: radius of the rolling element, R c : circumferential curvature radius of the pocket surface of the retainer,

[0026] R R : radial curvature radius of the pocket surface of the retainer, d: depth of the pocket of the retainer,

[0027] h: unilateral width of the retainer (radial width from the deepest point of the pocket of the retainer to the radial outer or radial inner edge of the pocket of the retainer).

[0028] According to this structure, it is possible to reduce the interference force between the retainer and the rolling elements generated due to the leading / lagging of the rolling elements caused by the offset, and it is possible to suppress the collision energy between the retainer and the rolling elements under the conditions of vibration and shock. Thereby, it is possible to reduce the repeated stress applied to the retainer due to the leading / lagging of the rolling elements, prevent fatigue failure of the retainer, and thus it is possible to provide a ball bearing with a retainer having high reliability. In addition, it is also possible to prevent the generation of vibration and noise caused by unstable operation of the retainer.

[0029] The ball bearing may also be a deep groove ball bearing for industrial machinery. In this case, for example, in industrial machinery such as an electric motor or a compressor, a deep groove ball bearing with high reliability and suppressed generation of vibration and noise can be applied.

[0030] Here, deep groove ball bearings composed of steel plate cages, which have relatively low manufacturing costs, are used in servo motors, generators, etc. with low rotational speed specifications. However, steel plates are more prone to wear than resin and are heavier. As a result, the steel plate cages wear prematurely and have a relatively high temperature rise. Therefore, steel plate cages are not used for bearings in servo motors, generators, etc. with medium and high rotational speed specifications.

[0031] The prior arts of Japanese Patent Laid-Open No. 2017-172749 and Japanese Patent Laid-Open No. 2018-162875 form a coating film, a solid lubricating layer composed of a resin composition such as fluororesin, on the cage pockets that slide together with the rolling elements. Thereby, wear of the cage pockets is reduced, and an increase in torque and temperature rise are suppressed.

[0032] The above prior arts are effective in reducing pocket wear, suppressing torque increase, and temperature rise. However, since an additional step of forming a resin coating film on the pocket surfaces of the original steel plate cage stampings is added, the manufacturing cost is significantly increased. Therefore, the above prior arts have not been applied to servo motors, generators, etc.

[0033] The ball bearing of the second structure of the present invention includes an inner ring, an outer ring, balls as a plurality of rolling elements interposed between these inner and outer rings, and a corrugated cage for guiding the rolling elements and holding these balls. Among them,

[0034] This ball bearing satisfies the following formula:

[0035] [Mathematical formula 2]

[0036]

[0037] H: The depth of the pocket of the corrugated cage,

[0038] S: The radius of curvature of the pocket of the corrugated cage,

[0039] R: The radius of the ball.

[0040] In this specification, the ball bearing as a rolling bearing is sometimes referred to as a bearing, and the corrugated cage is sometimes referred to as a cage.

[0041] The corrugated cage is extruded by the rolling elements and rotates. Among them, the component force of the extrusion load F in the rotation direction of the cage is the guiding load of the cage. If the angle of contact between the rolling element and the cage pocket is set as the contact angle θ, then the magnitude of the cage guiding load is 2Fcosθ. Among the extrusion load F, the component force in the axial direction is the load that attempts to axially expand the cage fixed by rivets, and its magnitude is 2Fsinθ.

[0042] During the rotation of the bearing, the extrusion load F applied by the rolling elements to the corrugated cage depends on the rolling element load and the rolling friction coefficient. As long as the operating conditions remain unchanged, the extrusion load F will not change.

[0043] From the above load analysis, it can be seen that under the same operating conditions and for the same bearing, the extrusion force from the rolling elements to the cage remains constant without change. Therefore, it can be known that the contact angle θ between the rolling elements and the pocket is the only factor that distributes the extrusion load F into the driving force Fcosθ of the cage and the axial load Fsinθ.

[0044] When the corrugated cage is subjected to the guiding load Fcosθ from the rolling elements in the rotation direction, the cage and the rolling elements rotate together. For the axial load Fsinθ from the rolling elements, the cage cannot avoid it axially, and the wear is significant. Therefore, the axial load Fsinθ is the main cause of pocket wear. In order to reduce pocket wear, the pocket shape of the cage should be optimized so that the contact angle θ is less than 45 degrees to reduce the axial load Fsinθ.

[0045] For example, in the case of a ball bearing as a rolling bearing, when a specified rotation test is carried out on a deep groove ball bearing used for industrial machinery and other applications, it is found that when the contact angle θ is less than 45 degrees, no pocket wear occurs, and the temperature rise can be suppressed compared with the comparative example. When the contact angle θ is 45 degrees or more, pocket wear occurs, and during rotation, the vibration is greater than when the contact angle θ is less than 45 degrees.

[0046] According to this structure, since the above-mentioned effects can be achieved only by optimizing the pocket shape of the cage, compared with the prior art of forming a resin coating film on the pocket surface, the manufacturing cost can be reduced, the wear can be reduced, the rotational torque can be reduced, and the temperature rise can be suppressed.

[0047] The corrugated cage can also satisfy the following formula:

[0048] [Mathematical formula 3]

[0049]

[0050] B: Cage width,

[0051] t: Cage thickness,

[0052] Cr: Basic dynamic load rating.

[0053] According to this structure, by making the cross-sectional area of the cage obtained by multiplying the cage width by the cage thickness reach a set value or more, the strength required for the corrugated cage can be ensured.

[0054] The corrugated cage can also satisfy the following formula:

[0055] [Mathematical Formula 4]

[0056]

[0057] D1: Inner diameter of the outer ring,

[0058] D2: Outer diameter of the inner ring,

[0059] B: Width of the cage,

[0060] H: Pocket depth of the wave cage,

[0061] S: Pocket curvature radius of the wave cage,

[0062] R: Radius of the ball.

[0063] According to this structure, on the premise of satisfying the above-mentioned cage cross-sectional area formula and ensuring the guiding clearance reduced due to centrifugal force, the cage width is set within a specified range. In this case, compared with the conventional wave cage, the cage weight can be reduced by narrowing the cage width. Thereby, it helps to reduce the rotational torque and enables a higher-speed rotation.

[0064] The ball bearing of the third structure of the present invention includes an inner ring and an outer ring, balls as a plurality of rolling elements between these inner and outer rings, and a wave cage for guiding the rolling elements and holding these balls, wherein,

[0065] This ball bearing satisfies the following formula:

[0066] [Mathematical Formula 5]

[0067]

[0068] And

[0069]

[0070] B: Width of the cage,

[0071] t: Thickness of the cage,

[0072] Cr: Basic dynamic load rating,

[0073] D1: Inner diameter of the outer ring,

[0074] D2: Outer diameter of the inner ring,

[0075] H: Pocket depth of the wave cage,

[0076] S: Pocket curvature radius of the wave cage,

[0077] R: Radius of the ball.

[0078] According to the rolling element load analysis in cases considering the retainer weight, the weight of the retainer hinders the rolling direction state of the rolling elements. Therefore, by reducing the retainer weight, a reduction in rotational torque can be expected.

[0079] According to this structure, without changing the curvature radius and pocket depth of the pockets of the conventional wave-shaped retainer, only the retainer width is reduced. In this case, the retainer weight can be made lower than that of the conventional wave-shaped retainer without the need to manufacture a new die for the wave-shaped retainer. Furthermore, by setting the cross-sectional area of the retainer to a specified value or more, the strength required for the wave-shaped retainer can be ensured. In this structure, reduction in manufacturing cost and wear can also be achieved, and reduction in rotational torque and suppression of temperature rise can be realized.

[0080] The present invention includes any combination of at least two configurations disclosed in the claims and / or the specification and / or the drawings. In particular, any combination of two or more of each claim in the claims is included in the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] The present invention will be more easily understood from the following description of preferred embodiments with reference to the drawings. However, the embodiments and the drawings are only for illustration and explanation and should not be used to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. In the drawings, the same reference numerals in multiple drawings denote the same or corresponding parts.

[0082] Figure 1 is a longitudinal sectional view of a ball bearing according to a first embodiment of the present invention.

[0083] Figure 2 is a radial sectional view of the retainer of the rolling bearing.

[0084] Figure 3 is a circumferential sectional view of the retainer.

[0085] Figure 4 is a schematic view of a radial section showing a unilateral model of the retainer.

[0086] Figure 5 is a schematic view of a radial section showing the completed state of the retainer.

[0087] Figure 6 is a schematic view of a radial section showing the state when balls are placed in the pocket space of the retainer.

[0088] Figure 7 is a schematic view of the pocket space.

[0089] Figure 8 ​​​​​​​​It is a diagram for explaining the amount of movement of the balls in the retainer pocket.

[0090] Figure 9 It is a cross-sectional view schematically showing an example of the use of this ball bearing in an industrial machine.

[0091] Figure 10 It is a longitudinal cross-sectional view of a rolling bearing according to a second embodiment of the present invention.

[0092] Figure 11 It is a three-dimensional view of the wave-shaped retainer of this rolling bearing.

[0093] Figure 12 It is a view of observing the wave-shaped retainer from the radially outer side.

[0094] Figure 13 It is cut along the XIII plane Figure 11 and is a cross-sectional view obtained by observing the wave-shaped retainer.

[0095] Figure 14 It is an enlarged view of the main parts of the wave-shaped retainer and the rolling elements.

[0096] Figure 15 It is a diagram for explaining the relationship between the extrusion load from the rolling elements, the rolling element load on the inner and outer ring sides, and the rolling friction coefficient.

[0097] Figure 16 It is a diagram for explaining the relationship between the contact angle of the rolling elements, the pocket depth, the pocket curvature radius, and the ball radius.

[0098] Figure 17 It is a diagram for explaining the rolling element load analysis when considering the weight of the retainer for a rolling bearing according to a third embodiment of the present invention.

[0099] Figure 18 It is a diagram for explaining the retainer width range of this rolling bearing.

[0100] Figure 19 It is a diagram showing the results of a rotation test when the contact angle of the rolling elements is different.

[0101] Figure 20 It is a diagram showing the results of a rotation test when the retainer bandwidth is different. Detailed implementation mode

[0102] [First embodiment]

[0103] Combined Figures 1 to 8 The deep groove ball bearing (ball bearing) according to the embodiment of the present invention will be described.

[0104] ​​​​​​​​​​​​<Summary Structure of Deep Groove Ball Bearing>

[0105] Figure 1 It is a longitudinal sectional view observed after cutting the deep groove ball bearing 1 according to the embodiment by an imaginary plane passing through the axis of the bearing and the center O of the ball. The deep groove ball bearing 1 is used, for example, in industrial machinery such as motors or compressors. However, the deep groove ball bearing 1 can be applied not only to motors and compressors but also to other aspects. The deep groove ball bearing 1 includes an inner ring 2, an outer ring 3, balls 4 as rolling elements, and a cage 5 for guiding the rolling elements. A plurality of balls 4 between the raceway surfaces 2a and 3a of the inner ring 2 and the outer ring 3 are held by the cage 5 at regular intervals in the circumferential direction.

[0106] In Figure 2 the bearing space between the inner ring 2 and the outer ring 3, a lubricant such as grease is filled. The inner ring 2, the outer ring 3, and the balls 4 are made of, for example, high-carbon chromium bearing steel such as SUJ2 or martensitic stainless steel. However, it is not limited to these steels. In addition, a sealing member (not shown) for closing the bearing space can be installed on the outer ring 3.

[0107] <Cage>

[0108] As Figure 3 shown, the cage 5 is a wave-shaped cage, which is formed by axially combining two ring-shaped cage plates 5a, 5a provided at a predetermined interval in the circumferential direction and having hemispherical bulging portions. In this specification, the wave-shaped cage is sometimes simply referred to as the "cage". Each ring-shaped cage plate 5a has hemispherical bulging portions 6 provided in the circumferential direction and flat portions 7 connecting the adjacent hemispherical bulging portions 6 in the circumferential direction.

[0109] In the state where the ring-shaped cage plates 5a, 5a are combined, the flat portions 7 overlap each other, and these flat portions 7, 7 are connected together by rivets or engaging claws (not shown). The respective hemispherical bulging portions 6 face each other to form ring-shaped pockets 8. The balls (spheres) 4 are held in the respective pockets 8. As Figure 2 and Figure 3 shown, the pocket surface 8a is formed of a curved surface such as a spherical surface. In other words, the circumferential section ( Figure 3 ) and the radial section ( Figure 2 ) passing through the deepest part 8b of the pocket 8 of the cage 5 are respectively arc-shaped curved surfaces. Figure 3 Each ring-shaped cage plate 5a in

[0110] However, when a deep groove ball bearing is used under operating conditions accompanied by misalignment, a phenomenon of the rolling elements leading / lagging occurs. Also, if the circumferential allowable movement amount of the rolling elements in the pockets of the cage is small, the interference force between the cage pockets and the rolling elements increases. As a result, repeated stress acts on the cage body and the rivets, and there is a risk of problems such as fatigue failure. To avoid such problems, it is necessary to provide a sufficient circumferential allowable movement amount of the rolling elements in the cage pockets to allow the leading / lagging of the rolling elements due to misalignment.

[0111] <Explanation of the cage - ball model>

[0112] Here, for a single cage pocket, if the radial cross - section at the center of the pocket is considered, according to the radial curvature radius R of the cage pocket surface and the cage pocket depth d, the pocket in the radial cross - section of the cage can be expressed by Figure 4 In Figures 4 to 7 ,"x" represents the bearing radial direction, and "y" represents the bearing axial direction. For the Figure 4 single - side model, the cage mating surface M is symmetrically applied to the opposite side, and the completed state of the corrugated steel cage is as shown in Figure 5 . At this time, the part Pa shaded in Figure 5 corresponds to the pocket space of the cage. As shown in Figure 6 , consider the case of placing a ball 4 with a radius of r into this pocket space. In addition, consider the case of moving this ball 4 from the pocket center coordinates OC(0, 0) in the outer diameter direction, that is, the x - axis direction. When the ball 4 contacts the pocket at point P(n, m), the ball center coordinates O'(a, 0) can be obtained.

[0113] By finding the contact point P, when the cage width ≥ the contact point P, the movement amount of the ball can be obtained. The pocket space can be expressed by Figure 7 .

[0114] The ball 4 contacts the pocket at the contact point P1. Since the two share a tangent line, the normal line of the tangent line at the contact point P1 passes through the ball center O' and the pocket center OC'. After organizing the four elements of "origin O", "ball center O'", "pocket center OC'", and "contact point P1", it can be processed within the right - triangle system of Figure 8 .

[0115] The X - coordinate n'( Figure 7 ) of the contact point P1( Figure 7 ) is defined by the following formula.

[0116] [Mathematical formula 6]

[0117] P(x,y) = P(Rcosθ,Rsinθ)

[0118] At this time

[0119]

[0120] According to

[0121]

[0122] When the ball and the pocket hole are in this relationship, the ball movement amount t is

[0123]

[0124] Study the circumferential section passing through the deepest point (deepest part) of the retainer pocket hole and the center point of the retainer pocket hole surface. The circumferential allowable movement amount of the rolling element in the retainer pocket hole is geometrically determined by Equation (1) based on the rolling element radius r, the circumferential curvature radius Rc of the retainer pocket hole surface, and the retainer pocket hole depth d. The "circumferential allowable movement amount of the rolling element in the retainer pocket hole" mentioned here refers to the circumferential movement amount of the rolling element from the following state until the rolling element contacts the retainer pocket hole surface when the rolling element is moved circumferentially. This state is that the center of the rolling element is located on the straight line connecting the deepest point of the retainer pocket hole and the center of the retainer pocket hole surface and is in the middle of the two retainer pocket holes on both sides.

[0125] [Mathematical formula 7]

[0126]

[0127] Among them,

[0128] Δ c : The circumferential allowable movement amount of the rolling element in the retainer pocket hole,

[0129] r: Rolling element radius, R c : The circumferential curvature radius of the retainer pocket hole surface, d: The depth of the retainer pocket hole.

[0130] Next, study the radial section passing through the deepest point (deepest part) of the retainer pocket hole and the center point of the retainer pocket hole surface. When studying the radial section passing through the center of the retainer pocket hole, the radial allowable movement amount of the rolling element in the retainer pocket hole is expressed by Equation (2).

[0131] The "radial allowable movement amount of the rolling element in the retainer pocket hole" mentioned here refers to the radial movement amount of the rolling element from the following state until the rolling element contacts the retainer pocket hole surface on the radially outer side or the retainer pocket hole surface on the radially inner side when the rolling element is moved radially. This state is that the center of the rolling element is located on the straight line connecting the deepest point of the retainer pocket hole and the center of the retainer pocket hole surface and is in the middle of the two retainer pocket holes on both sides.

[0132] [Mathematical Formula 8]

[0133] When the contact point between the pocket hole and the rolling element is located within the pocket surface of the cage, the relationship between the cage and the ball satisfies the following formula:

[0134]

[0135] At this time, the radial allowable movement amount of the rolling element in the cage pocket is represented by Equation (2):

[0136]

[0137] Wherein,

[0138] Δ R : The radial allowable movement amount of the rolling element in the cage pocket, r: The radius of the rolling element,

[0139] R R : The radial curvature radius of the cage pocket surface,

[0140] d: The depth of the cage pocket, h: The unilateral width of the cage (the radial width from the deepest point of the cage pocket to the radial outer or inner edge of the cage pocket).

[0141] In addition, considering that the cage is annular, the radial movement amount of the cage is dominated by the smaller value of the circumferential allowable movement amount and the radial allowable movement amount of the rolling element in the cage pocket. That is to say, when the radial allowable movement amount of the rolling element in the cage pocket is less than the circumferential allowable movement amount, in the side view of the ball bearing, the radial allowable movement amount of the pocket at the circumferential 0-degree position or 180-degree position becomes the radial movement amount of the cage.

[0142] When the circumferential allowable movement amount of the rolling element in the cage pocket is less than the radial allowable movement amount, in the side view of the ball bearing, the circumferential allowable movement amount at the circumferential 90-degree position or 270-degree position becomes the radial movement amount of the whole cage.

[0143] If the radial movement amount of the cage is large, then when the ball bearing is used under service conditions accompanied by vibration or shock (such as vibration, etc.), due to vibration and other reasons, the energy generated by the collision between the cage and the rolling element will increase. In this way, there is a risk of fatigue failure of the cage body and the rivets. In addition, when the ball bearing rotates, the movement of the cage will become unstable, and it may also become the cause of vibration or noise of the ball bearing. Therefore, it is preferable to suppress the radial movement amount of the cage.

[0144] <Regarding the characteristics of the pocket hole>

[0145] In view of the above, when there is an offset between the inner ring and the outer ring of the ball bearing, in order to ensure that the rolling elements in the pockets of the cage have sufficient circumferential allowable movement to allow the leading / lagging of the rolling elements, and to suppress the radial movement of the cage, the following relationship is preferably satisfied. That is, the contact point between the pocket and the rolling element in the radial cross-section of the cage is located within the pocket surface of the cage (satisfying Equation (3)), and the radial curvature radius of the pocket surface of the cage is less than or equal to the circumferential curvature radius of the pocket surface of the cage (satisfying Equation (4)).

[0146] [Mathematical formula 9]

[0147]

[0148] R R ≤R C Equation (4)

[0149] Wherein,

[0150] r: radius of the rolling element, R c : circumferential curvature radius of the pocket surface of the cage,

[0151] R R : radial curvature radius of the pocket surface of the cage, d: depth of the pocket of the cage,

[0152] h: unilateral width of the cage (radial width from the deepest part of the pocket of the cage to the radial outer or inner edge of the pocket of the cage).

[0153] <Comparison between the present application and Patent Document 1>

[0154] The ball bearing disclosed in Patent Document 1 is a ball bearing having a cage with a raceway ring guiding method. When the diameter guiding clearance between the cage and the raceway ring is set as Cg and the maximum radial displacement amount of the rolling elements in the pockets is set as δr, by satisfying Cg < δr which is one of the invention components of Patent Document 1, the cage is guided by either the outer peripheral surface of the inner ring shoulder or the inner peripheral surface of the outer ring shoulder. In contrast, the ball bearing of the present application is different from the ball bearing disclosed in Patent Document 1 in that it has a cage for guiding the rolling elements.

[0155] <Comparison between the present application and Patent Document 2>

[0156] The ball bearing disclosed in Patent Document 2 is characterized in that the portion of the pocket surface of the cage in contact with the rolling element surface is a cylindrical surface.

[0157] In contrast, the ball bearing of the present application has a curved pocket surface of the cage, which is different from the ball bearing disclosed in Patent Document 2.

[0158] <Function and effect>

[0159] According to the deep groove ball bearing 1 described above Figure 1 In the radial cross-section of the cage 5 for guiding the rolling elements, the contact point between the pocket 8 and the rolling element 4 is located within the cage pocket surface. Moreover, the radial curvature radius of the cage pocket surface is less than or equal to the circumferential curvature radius of the cage pocket surface. Therefore, even when an offset occurs between the inner ring 2 and the outer ring 3, it is possible to ensure that there is sufficient circumferential allowable movement amount of the balls 4 within the cage pocket 8 to allow the lead / lag of the balls 4, and it is also possible to suppress the radial movement amount of the cage 5. Therefore, it is possible to reduce the interference force between the cage 5 and the balls 4 generated by the lead / lag of the rolling elements due to the offset between the inner ring 2 and the outer ring 3, and it is possible to stabilize the movement of the cage 5 and the like.

[0160] By satisfying the above-described formula (4) and formula (5), it is possible to reduce the interference force between the cage 5 and the balls 4 generated by the lead / lag of the rolling elements due to the offset, and it is possible to reduce the repeated stress acting on the cage body and the rivets due to the collision between the cage 5 and the balls 4. As a result, it is possible to suppress problems such as those occurring in the cage 5, and it is also possible to prevent vibrations and noises generated due to the unstable movement of the cage 5. Furthermore, it is possible to provide a deep groove ball bearing 1 having a cage 5 that does not have the risk of excessive friction, wear, and heat generation due to sliding between the cage 5 and the raceway ring guiding surface and has high reliability.

[0161] <Usage example of the ball bearing>

[0162] As Figure 9 shown, the deep groove ball bearing 1 is used, for example, in a motor 10. On the housing (not shown) of the motor 10, the outer rings 3, 3 are fixed at a predetermined interval, and the output shaft 11 of the motor 10 is fitted and fixed to the inner rings 2, 2 as rotating wheels. A ring-shaped stator 12 is fixed to the housing, and a rotor 13 facing the stator 12 with a radial gap therebetween is fitted and fixed to the output shaft 11. In such a motor 10, a deep groove ball bearing 1 having high reliability and capable of suppressing the generation of vibrations and noises can be applied.

[0163] <Other embodiments>

[0164] In the following description, parts corresponding to matters previously described in each embodiment are denoted by the same reference numerals, and repeated descriptions are omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those of the previously described embodiment unless otherwise specifically described. The same configuration exhibits the same effects. Not only combinations of parts specifically described in each embodiment, but also parts of the embodiments can be partially combined with each other as long as the combination is not particularly hindered.

[0165] [Second Embodiment]

[0166] Combined with Figures 10 to 16 and Figure 19 The rolling bearing according to the second embodiment of the present invention will be described. The deep groove ball bearing as the rolling bearing (ball bearing) according to this embodiment is applied to industrial machines such as servo motors and generators, for example. However, the deep groove ball bearing can also be applied to other fields other than uses such as servo motors.

[0167] <General Structure of Rolling Bearing>

[0168] As Figure 10 shown, the deep groove ball bearing 1 of the second embodiment has substantially the same structure as the deep groove ball bearing of the above first embodiment. In the second embodiment, the same reference numerals are assigned to the same structures as those in the first embodiment, and the detailed description thereof is omitted.

[0169] <Cage>

[0170] As Figure 11 shown, the structure of the cage 5 is such that in a state where the annular retaining plates 5a, 5a are combined, the flat portions 7 overlap each other, and these flat portions 7, 7 are connected via rivets Rb or engaging claws (not shown) etc.

[0171] <Regarding Pocket Curvature Radius, Pocket Depth and Cage Width>

[0172] In this embodiment, by improving the pocket shape of the cage 5, sliding wear between the rolling elements and the pockets and temperature rise during bearing rotation are suppressed, thereby achieving high-speed rotation at the same level as that of a resin cage. Figure 12 is a view of the wave cage 5 observed from the radially outer side ( Figure 11 view A).

[0173] The feature of this embodiment is that for the pocket curvature radius S, pocket depth H that determine the pocket shape, and Figure 13 the cage width B shown in the figure, the following two points (1) and (2) are improved.

[0174] (1) Pocket curvature radius and pocket depth

[0175] As Figure 12 shown, by setting the pocket curvature radius S and pocket depth H, the contact angle θ ( Figure 10 ) between the pocket 8 and the rolling element 4 ( Figure 14 ) is brought to an optimal state, thereby enabling reduction of sliding wear. The pocket depth H refers to the axial depth from the pocket center to the deepest position of the hemispherical bulging portion 6.

[0176] (2) Cage width

[0177] like Figure 13 As shown, on the basis of ensuring the required strength of the retainer 5, the retainer width B is shortened to be smaller than the conventional structure, thereby helping to reduce the rotational torque and suppress the temperature rise. The retainer width B refers to the width dimension of the hemispherical bulge 6 in the radial direction. The method of shortening the retainer width B is, for example, to increase the retainer inner diameter and reduce the retainer outer diameter relative to the conventional structure.

[0178] <Load Analysis>

[0179] like Figure 14 As shown in FIG. 1 , the retainer 5 is squeezed by the rolling element 4 and rotates in the rotation direction R1. The component of the squeeze load F in the retainer rotation direction is the retainer guide load. If the contact angle between the rolling element 4 and the retainer pocket 8 is set to the contact angle θ, the magnitude of the retainer guide load is 2Fcosθ. In the squeeze load F, the axial component is the load that attempts to open the retainer 5 fixed by rivets in the axial direction C1, and its magnitude is 2Fsinθ.

[0180] like Figure 15 As shown, during the bearing rotation process, the extrusion force F applied from the rolling element 4 to the corrugated retainer is determined by the rolling element load and the rolling friction coefficient, and its calculation formula is: F = 2μ r P i / (1+μ c )(In the numerator of the formula, assuming that P e ≒P i , so μ r P e +μ r P i Simplified to 2μ r P i ). When the use conditions remain unchanged, the extrusion load F remains constant. Figure 15 In, P e is the rolling element load on the outer ring side, P i is the rolling element load on the inner ring side, μ r is the rolling friction coefficient between the rolling element and the raceway ring, μ c is the rolling friction coefficient between the cage and the rolling element. However, the weight of the cage is not taken into account here.

[0181] According to the above load analysis, under the same use conditions and for the same bearing, the pressing force of the rolling element 4 on the retainer remains constant and does not change. Therefore, it can be known that Figure 14 The contact angle θ between the rolling element 4 and the pocket 8 shown is the only factor that distributes the pressing load F into the driving force Fcosθ of the cage 5 and the axial C1 load Fsinθ.

[0182] When the waveform retainer 5 is subjected to the guiding load Fcosθ from the rolling element 4 in the rotational direction R1, the retainer 5 rotates together with the rolling element 4. For the axial C1 load Fsinθ from the rolling element 4, the retainer 5 cannot avoid it axially, and the wear is significant. Therefore, the axial C1 load Fsinθ is the main cause of the wear of the pocket. In order to reduce the pocket wear, the pocket shape of the retainer 5 should be optimized so that the contact angle θ is less than 45 degrees to reduce the axial load Fsinθ.

[0183] In order to make the contact angle θ less than 45 degrees, as Figure 16 shown, the pocket curvature radius S and the pocket depth H of the waveform retainer should satisfy the following formula:

[0184] [Mathematical formula 10]

[0185]

[0186] H: Pocket depth of the waveform retainer,

[0187] S: Pocket curvature radius of the waveform retainer,

[0188] R: Radius of the ball.

[0189] <Rotational test>

[0190] The rotational tests were respectively carried out on the following two deep groove ball bearings:

[0191] Example: A deep groove ball bearing equipped with a steel plate waveform retainer with a contact angle θ between the rolling element and the pocket of the retainer less than 45 degrees (specifically θ = 35°).

[0192] Comparative example: A deep groove ball bearing equipped with a steel plate waveform retainer with a contact angle θ greater than 45 degrees (specifically θ = 65°).

[0193] For this rotational test, a servo motor with a medium-high speed rotation specification and a deep groove ball bearing with a nominal model of 6330 used in actual generator equipment were adopted.

[0194] The usage conditions are as follows:

[0195] The so-called dn value (inner ring inner diameter × rotational speed): 400,000

[0196] Lubrication method: Grease lubrication

[0197] Load conditions:

[0198] Radial load: 16.4 kN

[0199] Axial load: 2.9 kN

[0200] Rotational time: 24 hours

[0201] Rotation mode: The inner ring rotates at a constant speed that satisfies the above dn value of 400,000.

[0202] In the rotation test, temperature detection devices such as temperature sensors are used to measure the temperatures of the inner and outer rings in real time. At the same time, vibration detection devices such as vibration sensors installed on the housing supporting the outer ring, etc., are used to measure the temperatures of the inner and outer rings in real time. After a specified test time, each bearing is disassembled, and the pockets of the cage are visually inspected for wear.

[0203] Figure 19 Pocket wear occurred in the comparative example on the left, and the vibration during rotation was Figure 19 greater than that of the example on the right. No pocket wear occurred in the example, and the temperature rise was about 3°C lower than that of the comparative example. The test results are summarized in Table 1.

[0204] [Table 1]

[0205]

[0206] In Table 1, "○" indicates good, "△" indicates that the effect is worse than "○" but can tolerate use, and "×" indicates bad. In the examples where the contact angle θ is less than 45 degrees, no pocket wear occurred, and the suppression of temperature rise was achieved compared with the comparative example. In the comparative examples where the contact angle θ is 45 degrees or more, not only did pocket wear occur, but also the vibration during rotation was greater than that of the examples.

[0207] [Function and effect]

[0208] According to the deep groove ball bearing 1 described above Figure 10 shown, since the above-mentioned function and effect can be achieved only by optimizing the pocket shape of the cage 5, compared with the prior art in which a resin coating film is formed on the pocket surface, the manufacturing cost can be reduced, wear can be reduced, the rotational torque can be reduced, and the temperature rise can be suppressed. By making the cage cross-sectional area obtained by multiplying the cage width by the cage thickness reach a value equal to or greater than the basic dynamic load rating divided by 9, the strength required for the wave cage 5 can be ensured.

[0209] On the premise of satisfying the above cage cross-sectional area formula and ensuring the guiding clearance reduced by centrifugal force, when reducing the cage width, the cage weight can be reduced compared with the traditional wave cage. Thus, it helps to reduce the rotational torque and enables rotation at a higher speed.

[0210] [Third embodiment: Cage width setting, Figure 17 , Figure 18 , Figure 20

[0211] ​The rolling bearing (ball bearing) according to the third embodiment sets the cage width within a specific range. The general structure of the rolling bearing is the same as that of the rolling bearing shown above Figure 10 shown.

[0212] <Load Analysis>

[0213] As Figure 17 shown, when considering the cage weight, through the analysis of the rolling element load, it can be known that: the weight of the cage will interfere with the attitude of the rolling element 4 in the rolling direction. Therefore, by reducing the cage weight, it is helpful to reduce the rotational torque. Figure 17 Among them, P e is the rolling element load on the outer ring side, P i is the rolling element load on the inner ring side, μ r is the rolling friction coefficient between the rolling element 4 and the raceway ring, μ c is the rolling friction coefficient between the cage and the rolling element 4. N is the load borne by the rolling element 4 due to the cage weight.

[0214] In the rolling bearing 1 according to this embodiment Figure 18 , without changing the curvature radius and depth of the traditional cage pocket, only the cage width B is reduced. In this case, the cage weight can be made lower than that of the traditional corrugated cage without making a new mold. Taking the steel plate corrugated cage as an example, in order to ensure the required strength, calculations are carried out based on the following conditions and formulas are derived:

[0215] · Set the maximum radial load borne by the deep groove ball bearing to 10% of the bearing basic dynamic load rating.

[0216] · When the bearing starts, make the sliding friction coefficient between the rolling element and the inner and outer rings 0.15.

[0217] · Tensile strength of the steel plate corrugated cage: 270 MPa

[0218] · The cross-sectional area of the cage is B×t obtained by multiplying the cage width B by the cage thickness t.

[0219] Equation (2) must be satisfied:

[0220] The extrusion force of the ball as the rolling element on the cage:

[0221] 0.1Cr (basic dynamic load rating) × 0.15 (sliding friction coefficient)

[0222] The stress of the cage generated by extrusion:

[0223] 0.1Cr (basic dynamic load rating) × 0.15 (sliding friction coefficient) / Bt

[0224] The retainer stress caused by extrusion < 0.5 × 270 Mpa (tensile strength of the steel plate corrugated retainer) = 135 MPa

[0225] → Bt ≥ (Cr / 9) … Equation (2).

[0226] Among them, the unit of Cr is kN, and the units of b and t are mm.

[0227] Under the premise of satisfying the said Equation (2) and being able to ensure the guiding clearance reduced due to centrifugal force, the retainer width b is set to the following range values.

[0228] [Mathematical formula 11]

[0229]

[0230] D1: Inner diameter of the outer ring,

[0231] D2: Outer diameter of the inner ring,

[0232] B: Retainer width,

[0233] H: Pocket depth of the corrugated retainer,

[0234] S: Pocket curvature radius of the corrugated retainer,

[0235] R: Radius of the ball,

[0236] Unit (mm).

[0237] <Rotation test>

[0238] Bearings with only different retainer widths were prepared and the same rotation test as above was carried out. Figure 20 The comparative example on the left is a deep groove ball bearing with a conventional steel plate corrugated retainer that does not satisfy Equation (3), Figure 20 The example on the right is a deep groove ball bearing with a steel plate corrugated retainer that satisfies Equation (2) and Equation (3). For this rotation test, a servo motor with a medium and high speed rotation specification and a deep groove ball bearing with a nominal model of 6330 used in actual generator equipment were adopted.

[0239] The usage conditions are as follows:

[0240] The so-called Dn value (inner diameter of the inner ring × rotation speed): 525,000

[0241] Lubrication method: Grease lubrication

[0242] Load conditions:

[0243] Radial load: 16.4 kN

[0244] Axial load: 2.9 kN

[0245] Rotation mode: The inner ring rotates at a constant speed that satisfies the above dn value of 525,000.

[0246] In the rotation test, temperature detection devices such as temperature sensors are used to measure the temperatures of the inner ring and the outer ring in real time. At the same time, vibration detection devices such as vibration sensors provided on the housing supporting the outer ring, etc., are used to measure the temperatures of the inner ring and the outer ring in real time. After a specified test time, each bearing is disassembled, and the pockets of the cage are visually inspected for wear.

[0247] Figure 20 No wear was observed in the pockets of the comparative example on the left side. Figure 20 No wear was observed in the pockets of the example on the right side, and the temperature rise was about 10 °C lower than that of the comparative example. The test results are summarized in Table 2.

[0248] [Table 2]

[0249]

[0250] In Table 2, "○" indicates good, and "×" indicates bad.

[0251] According to this structure, without changing the pocket curvature radius and pocket depth of the conventional wave cage, only the Figure 18 width B of the cage is reduced to a specified range value. Thus, without manufacturing a new mold for the wave cage, the weight of the cage can be made lower than that of the conventional wave cage. In addition, by setting the cross-sectional area Bt of the cage to a value above a specified value, the strength required for the wave cage 5 can be ensured. In this structure, it is also possible to reduce the manufacturing cost and wear, and to reduce the rotational torque and suppress the temperature rise.

[0252] In the deep groove ball bearing, a sealing member (not shown) for enclosing the bearing space may be provided only on one side.

[0253] It is also possible to use a lubricating oil other than grease as a lubricant in the deep groove ball bearing.

[0254] As described above, the preferred embodiments have been described with reference to the drawings, but various additions, changes, and deletions can be made without departing from the gist of the present invention. Therefore, such cases are also included in the scope of the present invention.

[0255] [Symbol description]

[0256] 1... Deep groove ball bearing (ball bearing)

[0257] 2... Inner ring

[0258] 3... Outer ring

[0259] 4…Ball (rolling element)

[0260] 5…Cage

[0261] 8…Pocket.

Claims

1. A ball bearing, which includes an inner ring and an outer ring, a plurality of rolling elements interposed between these inner and outer rings, and a cage for guiding the rolling elements and holding the rolling elements in a wavy shape, wherein, The circumferential cross-section and the radial cross-section passing through the deepest part of the pockets of the cage are respectively arc-shaped curved surfaces. In the radial cross-section of the cage, the contact point between the pocket and the rolling element is located within the cage pocket surface, and the radial curvature radius of the cage pocket surface is less than or equal to the circumferential curvature radius of the cage pocket surface.

2. The ball bearing according to claim 1, wherein, The cage and the rolling element satisfy the following formula: [Mathematical formula 12] Wherein, r: radius of the rolling element, R c : circumferential curvature radius of the cage pocket surface R R : Radial curvature radius of the retainer pocket surface, d: Depth of the retainer pocket h: The unilateral width of the cage (the radial width from the deepest point of the cage pocket to the radial outer or inner edge of the cage pocket).

3. The ball bearing according to claim 1 or claim 2, wherein This ball bearing is a deep groove ball bearing for industrial machinery.

4. A ball bearing, which includes an inner ring and an outer ring, balls as a plurality of rolling elements interposed between these inner and outer rings, and a wavy cage for guiding the rolling elements and holding these balls, wherein, This ball bearing satisfies the following formula: [Mathematical formula 13] H: The pocket depth of the wavy cage, S: The pocket curvature radius of the wavy cage, R: The radius of the ball.

5. The ball bearing according to claim 4, wherein, The wavy cage satisfies the following formula: [Mathematical formula 14] B: The cage width, t: The cage thickness, Cr: The basic dynamic load rating.

6. The ball bearing according to claim 5, wherein The wavy cage satisfies the following formula: [Mathematical formula 15] D1: The inner diameter of the outer ring, D2: The outer diameter of the inner ring, B: The cage width, H: The pocket depth of the wavy cage, S: The pocket curvature radius of the wavy cage, R: The radius of the ball.

7. A ball bearing, which includes an inner ring and an outer ring, balls as a plurality of rolling elements interposed between these inner and outer rings, and a wavy cage for guiding the rolling elements and holding these balls, wherein, This ball bearing satisfies the following formula: [Mathematical formula 16] And B: The cage width, t: The cage thickness, Cr: The basic dynamic load rating, D1: The inner diameter of the outer ring, D2: The outer diameter of the inner ring, H: The pocket depth of the wavy cage, S: The pocket curvature radius of the wavy cage, R: The radius of the ball.

Images