Ball bearing

Abstract

To suppress deformation of a holder due to a centrifugal force.SOLUTION: A holder for a ball bearing is a crown-type holder having an annular base part 11 and a plurality of holding parts 12 protruding on one axial side of the base part 11, and comprising a plurality of pockets 20 formed along a circumferential direction between the plurality of holding parts 12. In an axial cross section passing through an axial center line of the holder and a bottom p0 of the pocket 20, the base 11 comprises a mass addition part 15 that protrudes from a base part reference line E, which is located a predetermined distance from the bottom p0 of the pocket 20 toward the other axial side, on the axial other side with respect to the base part reference line E and is continuous around the entire circumferential direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a ball bearing that can be used for high-speed rotation. [Background technology]

[0002] For example, in automobiles, industrial machinery, railways, aerospace, and all other industrial fields, numerous bearings are used in devices equipped with electric motors. The bearings used in these devices are generally operated under higher speed conditions than the bearings used to support shafts in general equipment. In addition, in recent years, there has been a trend in electric vehicles to increase the rotational speed and make them smaller and lighter in order to increase the output density of electric motors as a means of improving power consumption and driving performance. In particular, in drive units known as "e-Axles" that integrate a drive motor, transmission, speed increaser / reduction gear, etc., the bearings that support the motor's rotating shaft are often operated at higher rotation speeds than the bearings used in general equipment.

[0003] In ball bearings that use balls as rolling elements, a crown-type cage may be used as the cage for holding the balls. A crown-type cage has an annular base and multiple pockets arranged circumferentially around the base. The pockets are arranged in parallel on one axial side of the cage relative to the base. Each pocket penetrates the cage in the radial direction, opens to one axial side, and has a pair of claws on both circumferential sides of the opening of each pocket to hold the balls.

[0004] In the case of ball bearings that use crown cages, there is a concern that as the bearing rotation speed increases, the claws will deform toward the outer diameter due to centrifugal force, causing the balls to become trapped.When trapping occurs, the strong contact between the balls and the cage increases rotational resistance, causes abnormal heat generation, and can hinder high-speed operation, so preventing cage deformation is an issue that needs to be resolved.

[0005] For this reason, for example, Patent Document 1 discloses that a ceramic coating is applied to the back surface of the annular portion (base) of a crown-type cage for a bearing to increase rigidity and suppress deformation of the cage. Also, Patent Document 2 discloses that contact between the claws of the cage and the outer ring during high-speed rotation can be avoided by providing circumferential grooves on the inner circumference of the outer ring. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2023-30439 [Patent Document 2] Japanese Patent Application Publication No. 2023-89646 Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, in the case of a resin crown-type cage for a ball bearing, suppression of deformation of the claws toward the outer diameter side during high-speed rotation (Problem 1) is an issue that needs to be resolved.

[0008] Furthermore, at high speeds, the number of balls passing per hour increases, which increases oil resistance and reduces oil permeability. For this reason, ensuring lubrication at high speeds (issue 2) has become an issue.

[0009] Furthermore, in motor bearings and other applications where the number of balls is reduced to reduce resistance, the difference in lag / lead between adjacent balls in the circumferential direction tends to increase (the pitch between the balls increases). This increases the circumferential compressive and tensile load on the cage, making it necessary to improve the cage's circumferential ring rigidity and strength (issue 3).

[0010] In response to this, Patent Document 1 states that the rigidity of the cage can be improved by coating the back surface of the annular portion of the cage with ceramic, but this has the following problems. (1) Ceramics coated on resin, which is a viscoelastic material, are prone to chipping and peeling, and are difficult to follow repeated expansion and contraction due to the difference in thermal expansion coefficient from the base material (resin), which raises concerns that they may partially peel off and fall off. (2) If hard ceramic fragments get into and bite into the rolling contact area, they can interfere with smooth rolling and even cause wear and damage to bearings and mechanical devices, potentially causing them to malfunction. (3) Special equipment and processes are required for manufacturing, which inevitably increases costs. (4) Depending on the processing temperature, it may be difficult to guarantee dimensions due to deformation of the base material. (5) Depending on the coating binder and thickness, it may be difficult to ensure sufficient rigidity.

[0011] Furthermore, Patent Document 2 states that contact between the claws and the outer ring during high-speed rotation can be avoided by providing circumferential grooves on the inner periphery of the outer ring, but this has the following problems. (1) The interference between the ball and the cage caused by the claws rising due to centrifugal force cannot be alleviated. (2) The circumferential grooves on the outer ring cannot allow rolling contact of the balls, so the load and clearance conditions are restricted. (3) If the contact ellipse of the ball rides up onto the relief groove of the cage, the ball and outer ring may be damaged, causing a malfunction. (4) Depending on the strain and stress level of the cage, permanent deformation or creep deformation may occur. (5) Special equipment and processes are required for manufacturing, which inevitably increases costs.

[0012] Therefore, the object of this invention is to first suppress deformation of the retainer due to centrifugal force, secondly ensure lubrication during high-speed rotation, and thirdly improve the circumferential ring rigidity and strength of the retainer. [Means for solving the problem]

[0013] In order to solve the first and third problems, the present invention provides a crown-type cage for a ball bearing, which has an annular base and a plurality of retaining portions protruding on one axial side of the base, and is provided with a plurality of pockets formed along the circumferential direction between the plurality of retaining portions, and the base is provided with mass-adding portions that protrude further on the other axial side than a base reference line that is located a predetermined distance from the bottom of the pocket toward the other axial side in an axial cross section passing through the axial center line of the cage and the bottom of the pocket, and that are continuous around the entire circumferential direction (Configuration 1).

[0014] In the configuration 1, the base reference line may be on the base end surface on the side opposite to the pocket side of the base (configuration 2).

[0015] In configuration 1 or 2, a configuration can be adopted in which the center of gravity of the mass adding portion in the axial cross section is located on the inner diameter side of a neutral line that passes through the center of the pocket and is parallel to the center line in the axial direction (configuration 3).

[0016] In addition, in order to solve the second problem, the present invention can adopt a configuration in any one of configurations 1 to 3, in which the outer diameter of the retaining portion is provided with an inclined surface that approaches the inner diameter side of the retaining portion as it moves toward one axial side (configuration 4).

[0017] Similarly, in order to solve the second problem, the present invention can employ, in any one of configurations 1 to 4, a configuration in which the inner diameter of the mass-adding portion is provided with a first guide inclined surface for lubricating oil that approaches the inner diameter surface of the base portion as it moves toward one axial side and is connected to the inner diameter surface of the base portion (configuration 5).

[0018] In any one of configurations 1 to 5, a configuration can be adopted in which the outer diameter of the mass adding portion is provided with a second guide inclined surface that approaches the outer diameter surface of the base portion toward one axial side (configuration 6).

[0019] Furthermore, in a ball bearing comprising an inner member, an outer member, balls arranged between the inner member and the outer member, and a retainer for holding the balls, a ball bearing having a retainer described in any one of configurations 1 to 6 can be adopted (configuration 7).

[0020] In the ball bearing of Configuration 7, a configuration can be adopted in which the predetermined distance is a required thickness defined as 0.2 times the diameter Dw of the ball (Configuration 8).

[0021] In the ball bearing of Configuration 7 or 8, a configuration can be adopted in which the distance between the centers of the circumferentially adjacent pockets is equal to or greater than the diameter Dw of the balls (Configuration 9).

[0022] A bearing device can be employed in which the ball bearing according to any one of configurations 7 to 9 is used to support a rotating shaft of a drive motor, reducer, or speed increaser for an electric transport device (configuration 10). [Effects of the Invention]

[0023] According to this invention, deformation of the cage due to centrifugal force can be suppressed, sufficient lubrication can be ensured during high-speed rotation, and the ring rigidity and strength of the cage in the circumferential direction can be improved. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a front view showing an embodiment of the present invention. [Figure 2] II-II cross section of Figure 1 [Figure 3] Enlarged cross-sectional view of the main part showing the position of the cage and balls [Figure 4] Enlarged perspective view of the main part of the cage [Figure 5] Enlarged plan view of the cage [Figure 6] FIG. 10 is a cross-sectional view showing the center of gravity of a cage in a modified example (first modified example) of the embodiment. [Figure 7] Graph showing cage performance [Figure 8A] Enlarged cross-sectional view of a key part showing the flow of lubricant from outside the bearing into the bearing's internal space [Figure 8B] Enlarged cross-sectional view of a key part showing the outflow of lubricant from the bearing's internal space to the outside of the bearing [Figure 9] FIG. 10 is an enlarged perspective view of a main part showing a second modified example. [Figure 10A] 10 is an enlarged cross-sectional view of a main part showing a third modified example. [Figure 10B] 10 is an enlarged cross-sectional view of a main part showing a fourth modified example. [Figure 10C] 10 is an enlarged cross-sectional view of a main part showing a fifth modified example. [Figure 10D] 10 is an enlarged cross-sectional view of a main part showing a sixth modified example. [Figure 10E] 10 is an enlarged cross-sectional view of a main part showing a seventh modified example. DETAILED DESCRIPTION OF THE INVENTION

[0025] 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 equipped in an electric transport device such as an electric vehicle, or the rotating shaft of a reducer or speed increaser equipped in such an electric transport device.

[0026] As shown in Figures 1 and 2, rolling bearing 1 (hereinafter simply referred to as bearing 1) is a ball bearing comprising an inner member 3 and an outer member 4 that constitute a raceway, an inner raceway groove 3a that has an arc-shaped cross section and is formed in the inner member 3, an outer raceway groove 4a that has an arc-shaped cross section and is formed in the outer member 4, a plurality of rolling elements 5 arranged between the inner raceway groove 3a and the outer raceway groove 4a, and a cage 10 that holds the rolling elements 5.

[0027] Here, balls (steel balls) are used as the rolling elements 5, and will hereinafter be referred to as balls 5. In addition, in this embodiment, the inner raceway groove 3a and the outer raceway groove 4a each have an arc-shaped cross section of a single radius in any vertical cross section including the axis. Hereinafter, the direction along the bearing center line c of the bearing 1 will be referred to as the "axial direction," the direction perpendicular to the axial direction will be referred to as the "radial direction," and the circumferential direction around the bearing center line c will be referred to as the "circumferential direction."

[0028] A rotating shaft (not shown) is fixed to the inner diameter portion 3b of the inner member 3 (referred to as the inner ring 3 in this embodiment) and rotates circumferentially together with the rotating shaft. A fixing member for a housing, gear, or other component (not shown) is attached to the outer diameter portion 4b of the outer ring 4 (referred to as the outer ring 4 in this embodiment). In this way, the bearing 1 supports the rotating shaft rotatably relative to the fixing member. Examples of the rotating shaft include 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 1 can form part of a bearing device (bearing unit) that supports these rotating shafts. The bearing center axis of the bearing 1 and the rotation center axis of the rotating shaft are set coaxially.

[0029] When the bearing 1 is assembled, the bearing internal space is filled with a lubricant such as grease or lubricating oil. A sealing member (not shown) is attached to the opening at the axial end of the bearing internal space. The sealing members may be provided at both axial ends of the bearing internal space, or, depending on the specifications, may be provided only at one of the axial ends, or no sealing member may be provided at all. The bearing internal space may also contain lubricating and rust-preventive oil that has been poured into it, or lubricating and rust-preventive oil that has been applied to the bearing components (outer ring 4, inner ring 3, rolling elements 5, etc.) in advance.

[0030] The cage 10 is a crown-shaped cage molded from engineering plastic. Examples of engineering plastic include materials containing polyether ether ketone resin and polyphenylene sulfide resin. By constructing the cage 10 from a material containing engineering plastic, the amount of deformation of the components when centrifugal force is applied can be reduced. Even if the cage 10 is constructed from a material that does not contain engineering plastic, it is desirable to use a resin material that is resistant to centrifugal deformation, such as a material containing polyamide resin. However, the material and type of the cage 10 can be changed as appropriate depending on the specifications of the bearing 1. If the material of the cage 10 contains carbon fiber, glass fiber, or the like as a reinforcing material, the amount of deformation of the components when centrifugal force is applied can be further reduced.

[0031] As shown in FIGS. 2 to 5 , the cage 10 includes an annular base 11 and a plurality of retaining portions (retaining claws) 12 that protrude axially from the base 11. The outer diameter surface of the cage 10 is a curved surface (cylindrical surface) without any steps. The space between the base 11 and the circumferentially adjacent retaining portions 12, 12 forms pockets 20 that retain the balls 5 in the circumferential direction. That is, a plurality of pockets 20 are arranged side by side in the circumferential direction on one axial side of the base 11. The outer diameter surface and inner diameter surface of the cage 10 are connected at the pockets 20. The tips of the retaining portions 12 form claws 14, and the pair of claws 14 that sandwich the pocket 20 are curved toward each other. The balls 5 revolve between the inner raceway groove 3 a and the outer raceway groove 4 a while being held in the pockets 20.

[0032] The pocket 20 is surrounded by the inner surfaces of the retaining portions 12, 12 on both circumferential sides of the pocket center a0, and the inner surface of one axial side of the base portion 11, and these inner surfaces retain the ball 5. These surfaces that retain the ball 5 are called the pocket surface 21. The pocket surface 21 is spherical over its entire area, facing the spherical outer surface of the ball 5. In addition, as shown in the perspective view of Figure 4, a recess 19 recessed toward the base portion is formed between circumferentially adjacent pockets 20, 20, and the space between adjacent retaining portions 12, 12 is lightened.

[0033] As shown in FIG. 5, in a cross section (called a circumferential cross section) that is perpendicular to a radial line passing through the pocket center a0 and that passes through the pocket center a0, 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 to be larger than the diameter Dw of the balls 5. For ease of understanding, in FIG. 5, the cross section of the cage 10, which is originally cylindrical, is expanded laterally and depicted as a flat surface. The pocket center a0 and the center of the balls 5 (ball center) are coincident by design.

[0034] In the cross sections shown in the upper part of Fig. 2 and Fig. 3, i.e., in cross sections that pass through the pocket center a0 and include the axial center line of the cage, i.e., the bearing center line c (referred to as axial cross sections), the diameter of the arc of the pocket surface 21 is also HP. Furthermore, in the cross section shown in Fig. 1, i.e., in a cross section that passes through the pocket center a0 and is perpendicular to the axial center line of the cage, i.e., the bearing center line c (referred to as orthogonal axial cross section), the diameter of the arc of the pocket surface 21 is also HP. However, if a recess such as an oil reservoir is provided on the pocket surface 21, the location of the recess is excluded. Hereinafter, the diameter HP of the pocket surface 21 will be referred to as the pocket diameter HP.

[0035] In an axial cross section that includes the axial center line of the cage, i.e., the bearing center line c (see FIGS. 1 and 2) and passes through the bottom p0 of the pocket 20 (see FIG. 3), the base 11 is set to an axial thickness that extends from the bottom p0 on the base 11 side of the pocket 20 to a base reference line E that is located at the position of the required thickness L2 toward the other axial side. In this embodiment, the base reference line E coincides with the base end face (back face) 13 on the side of the base 11 opposite the pocket 20 side. Here, the bottom p0 of the pocket 20 is the point that is located furthest to the other axial side in the axial cross section shown in FIG. 3 and the circumferential cross section shown in FIG. 5. In other words, the bottom p0 of the pocket 20 is the portion that is located in the center of the retainer and has the thinnest axial thickness.

[0036] The required wall thickness L2 is set to a predetermined ratio with respect to the diameter Dw of the balls 5. 0.2 is usually used as the predetermined ratio. This is because if the predetermined ratio is less than 0.2, problems will arise with the strength and durability of the base 11 at the bottom p0 of the pocket 20. Even if the predetermined ratio is set to a value equal to or greater than 0.2, it is generally not set to a value much greater than 0.2 in order to prevent the cage 10 from becoming larger and heavier overall.

[0037] A mass adding portion 15 is provided on the other axial side of the base reference line E, i.e., in this embodiment, on the other axial side of the base end face 13, protruding from the base end face 13 toward the other axial side and continuing around the entire circumferential direction (Condition 1). The mass adding portion 15 is an annular convex portion (protrusion) that continues in the circumferential direction.

[0038] (For the first issue) By satisfying condition 1, the present invention is expected to have the effect of suppressing radial expansion of the member when centrifugal force acts on the cage 10, and in particular suppressing rising of the pawls 14 at the tips of the retaining portions 12 toward the outer diameter (Effect 1). That is, by providing the mass-additional portions 15 on the base end face 13 of the cage 10, the ring rigidity in the radial direction of the base 11 can be increased. Increasing the ring rigidity in the direction of the base 11 suppresses radial expansion of the member when centrifugal force acts, and can eliminate or reduce interference between the pockets 20 and the balls 5. This makes it possible to realize a bearing 1 that is compatible with high-speed rotation.

[0039] Furthermore, by satisfying condition 1, the center of gravity (coordinates) of the base portion 11 and the retaining portion 12 in the axial cross section can be shifted to the other axial side (back side). In this respect, the above-mentioned effect 1 can also be expected. That is, according to this invention, compared to conventional crown-type cages with a flat back surface, it is possible to minimize increases in volume and mass while improving ring rigidity and suppressing deformation by adjusting the center of gravity.

[0040] In FIG. 3, reference symbol h1 denotes the distance between the inner diameter surface 17 of the cage 10 and the neutral line e. The neutral line e passes through the center a0 of the pocket 20 and is parallel to the axial centerline of the cage, i.e., the bearing axis c, and is perpendicular to the circumferential PCD line d (see FIG. 1) passing through the center a0 of the pocket 20. Reference symbol h2 denotes the distance between the inner diameter end of the front end face 15a of the mass addition portion 15 (excluding the portion where the first guide inclined surface 16, described below, is located) and the neutral line e. Reference symbol h3 denotes the distance between the outer diameter surface 15b of the mass addition portion 15 and the neutral line e. Reference symbol L1 denotes the axial protrusion length of the mass addition portion 15 from the base end face 13. Reference symbol L2 denotes the required axial thickness of the thinnest portion of the base 11. Reference symbol L3 denotes the axial length from the pocket center a0 to the base end face 13. The symbol L4 indicates the axial length of the portion where the first guide inclined surface 16, which will be described later, is interposed. w indicates the axial length from the pocket center a0 to the front end face 15a of the mass adding portion 15.

[0041] In order to expect the above-mentioned effect 1, it is advantageous to set the axial width (corresponding to L1 in the example of FIG. 3) of the mass adding portion 15 to be large relative to its radial height (corresponding to h2-h3 in the example of FIG. 3). This is because if the axial width is large relative to the radial height, the center of gravity position in the axial direction of the cage 10 can be moved further toward the rear side. In the example of FIG. 3, L1 <h2-h3となっている。

[0042] As in the embodiment of Figure 6, it is desirable that the center of gravity G2 of the mass adding portion 15 in the axial cross section is the geometric center. Furthermore, in order to set the center of gravity G2 as close to the inner diameter as possible, it is desirable that the outer diameter surface 15b of the mass adding portion 15 be located closer to the inner diameter of the cage than the neutral line e. By moving the center of gravity of the base portion 11 and the retaining portion 12 in the axial cross section as close to the inner diameter of the cage as possible, it is possible to further enhance the above-mentioned effect 1. However, it is not excluded that the outer diameter surface 15b be located closer to the outer diameter than the neutral line e.

[0043] In FIG. 6, G0 denotes the center of gravity of the cage 10 without the mass addition portions 15 (a conventional crown-type cage with a flat back surface). G1 denotes the center of gravity of the cage 10 with the mass addition portions 15. As described above, G2 denotes the center of gravity of the mass addition portions 15. The center of gravity G1 is shifted toward the other axial side and toward the inner diameter side with respect to the center of gravity G0. Therefore, X0 > X1 holds between the distance X0 from the base reference line E to the center of gravity G0 and the distance X1 from the base reference line E to the center of gravity G1. Furthermore, Y0 > Y1 holds between the distance Y0 from the inner diameter surface 17 to the center of gravity G0 and the distance Y1 from the inner diameter surface 17 to the center of gravity G1. Note that FIG. 6 illustrates a modified example (first modified example) in which the first guide inclined surface 16, which will be described later, is omitted, and therefore the center of gravity G0 without the mass addition portions 15 is illustrated on the neutral line e. It should be noted that FIG. 6 shows the center of gravity position conceptually, and the center of gravity position shown in the figure is not a position that has been precisely calculated based on the dimensions of the components in the figure.

[0044] The analytical results of Effect 1 obtained by providing Condition 1 are shown in Figure 7. In Figure 7, symbol (1) indicates the analytical results of a conventional crown-type cage with a flat back surface, symbol (2) indicates the analytical results of a cage 10 provided with a mass addition portion 15, and symbol (3) indicates the analytical results of a cantilever-type cage 10 (see Figure 10A) described below. According to these analytical results, the rotational speed at which interference between the balls 5 and the pockets 20 of the cage 10 begins is increased by 15% or more compared to a conventional crown-type cage with a flat back surface.

[0045] (For the second issue) In this embodiment, as shown in FIGS. 3 and 4, the mass adding portion 15 has an inner diameter provided with a first guide inclined surface 16 for lubricating oil that approaches the inner diameter side toward one axial side and is connected to the inner diameter surface 17 of the base portion 11.

[0046] The provision of first guide inclined surface 16 is expected to function as a so-called oil scoop, ensuring good oil permeability into the interior space of the bearing during high-speed rotation and good lubrication at the contact points between balls 5 and inner raceway groove 3a and outer raceway groove 4a (Effect 2). In this case, the provision of mass adding portion 15 ensures a long axial length L4 of the portion where first guide inclined surface 16 is provided.

[0047] As shown in Figure 8A, in an environment where lubricating oil flows into the bearing internal space from outside the bearing, the provision of first guide inclined surface 16 allows the lubricating oil to be smoothly guided so that it is sucked in in the direction in which the cross section of the flow path gradually narrows, as shown by arrows A, B, and C. Furthermore, even in an environment where lubricating oil flows out of the bearing from the bearing internal space to the outside, as shown in Figure 8B, the lubricating oil can be guided in the direction in which the cross section of the flow path gradually widens, as shown by arrows C', B', and A'.

[0048] The first guide inclined surface 16 may be provided only on the inner diameter surface of the convexly protruding mass adding portion 15, or may be provided across the mass adding portion 15 and the base 11 (outside the area of ​​the mass adding portion 15) as in this embodiment. It is desirable that the first guide inclined surface 16 is connected to the inner diameter surface 17 of the base 11 without any steps. The connecting portion may also be formed in a smooth arc shape. Furthermore, the first guide inclined surface 16 may be a linear inclined surface (conical) with a single gradient, or may be an arc-shaped inclined surface with a gradient that changes midway.

[0049] (For the third issue) Furthermore, by satisfying condition 1, the present invention is expected to have the effect of increasing the circumferential ring rigidity and strength of the cage 10. As a result, sufficient strength and rigidity can be ensured against the tensile and compressive stresses between the pockets 20 that act on the cage 10 due to the advance and delay of the balls 5 (Effect 3).

[0050] Generally, depending on the internal clearance of the bearing 1 and the load distribution, the state of contact between each ball 5 and the inner ring 3 and outer ring 4 may not be uniform. In such cases, the angular velocity of the revolution of the balls 5 will not be constant, but may speed up or slow down, which is called "lag / lead (of the rolling elements)." This lag / lead applies a load to the cage 10 that pushes and pulls between the pockets 20 in the revolution direction of the balls 5 (circumferential direction), and is therefore an important factor in determining the strength of the cage 10.

[0051] In this invention, by providing the mass addition portions 15, the thickness at the bottoms p0 of the pockets 20, i.e., the thickness of the thinnest portion of the base portion 11, can be reinforced by the thickness of the mass addition portions 15. This makes it possible to ensure sufficient strength and rigidity even in a bearing 1 having a reduced number of balls 5 to reduce rotational resistance. A reduced number of balls 5 increases the speed difference between circumferentially adjacent balls 5, placing a load on the cage 10, so reinforcing the base portion 11 with the mass addition portions 15 is effective. In other words, by providing the mass addition portions 15, the cage 10 of this invention can be applied to a bearing 1 in which, for example, the distance between circumferentially adjacent balls 5 (length in the arc direction), i.e., the distance between the pocket centers a0 of circumferentially adjacent pockets 20 (length in the arc direction), is set to be equal to or greater than the diameter Dw of the balls 5. It is also effective for various bearings 1 used under conditions of bearing specifications (clearance etc.) or usage conditions where the balls 5 are likely to lag or lead, or where the speed difference between circumferentially adjacent balls 5 is likely to become large.

[0052] Furthermore, in this invention, by reinforcing the bottom p0 of the pocket 20 with the thickness of the mass-adding portion 15, it is possible to increase the strength of the vicinity of the weld portion that occurs in the base portion 11 when manufacturing the cage 10 by injection molding. It is also possible to prevent damage to the bottom p0 of the pocket 20 and whitening of the resin when assembling the cage into the bearing.

[0053] Furthermore, while a highly elastic material was sometimes used to suppress the deformation of the cage 10 in the past, the present invention allows the deformation of the cage 10 to be suppressed by configuring the mass-adding portion 15. Therefore, it is no longer necessary to use a costly highly elastic material as the resin material for the cage 10, and a material with a low elastic modulus can be adopted. Therefore, the present invention expands the range of material options, enabling products to be provided at low cost. For example, it is possible to use PA46 (polyamide 46 / nylon engineering plastic) instead of the conventionally used PA9T (polyamide 9T / nylon engineering plastic) and still achieve the same level of deformation.

[0054] A second modified example is shown in Figure 9. In this second modified example, a lightening portion 22 is provided on the outer diameter side of the base portion 11. The provision of the lightening portion 22 is expected to reduce the mass of the cage 10 and the amount of material used, as well as the resulting reduction in centrifugal force. Furthermore, the provision of the lightening portion 22 makes it possible to move the center of gravity of the cage 10 further in the inner diameter direction.

[0055] In the embodiment, the lightening portion 22 is configured by a bottom 22a having a surface direction perpendicular to the axial center line of the cage, i.e., the bearing center line c, and inclined side surfaces 22b extending from both circumferential sides of the bottom 22a to the other axial side, but the lightening portion 22 may have a shape other than that shown in Figure 9. For example, the pair of side surfaces 22b may be parallel to each other and their surface directions may be perpendicular to the surface direction of the bottom 22a. Alternatively, the lightening portion 22 may have an arc-shaped cross section in the circumferential cross section.

[0056] Various embodiments can be adopted for the position and shape of the mass adding portion 15. Modified examples thereof are shown in Figs. 10A to 10E.

[0057] 10A shows a third modified example. The cage 10 of the third modified example has an inclined surface 23 on the outer diameter of the retaining portion 12 that approaches the inner diameter side as it moves toward one axial side. Therefore, the retaining portion 12 has a shape that gradually becomes thinner (lower in the radial direction) as it moves toward one axial side, and is a so-called cantilever shape. By making the retaining portion 12 cantilever-shaped, it is possible to reduce the centrifugal force of the claws 14 at the tip of the retaining portion 12 and reduce the mass. Therefore, it is easier to move the center of gravity of the cage 10 closer to the back side and closer to the inner diameter side.

[0058] Here, the outer diameter surface 18 of the cage 10 may be guided by contacting the bottom surface of a ground portion provided on the inner diameter of the outer ring 4. The ground portion may be formed, for example, in the outer raceway groove 4a. Alternatively, a large gap may be secured between the inner diameter surface 17 of the cage 10 and the outer diameter of the inner ring 3 to facilitate the introduction of lubricating oil to the inner ring 3. Furthermore, by providing the aforementioned lightening portion 22 on the back surface side of the cage 10, it is possible to make it easier to retain lubricating oil between the inner diameter of the outer ring 4 and the cage 10.

[0059] Fig. 10B shows a fourth modified example. In the cage 10 of the fourth modified example, the outer diameter surface 15b of the mass addition portion 15 is configured as a second inclined guide surface 15c that approaches the outer diameter side as it moves toward one axial side. In Fig. 10B, the second inclined guide surface 15c is located on the inner diameter side of the neutral line e, but it may also be located on the neutral line e or on the outer diameter side of the neutral line e. Note that the first inclined guide surface 16 is provided only on the inner diameter portion of the mass addition portion 15, but it may also be provided across the mass addition portion 15 and the base portion 11 (outside the area of ​​the mass addition portion 15).

[0060] By providing the second guide inclined surface 15c, the lubricating oil can be guided toward the outer ring 4. This ensures good lubrication between the inner diameter of the outer ring 4 and the cage 10, and between the balls 5 and the outer raceway groove 4a.

[0061] As the rotational speed of bearing 1 increases, the number of balls 5 passing per unit time increases, which increases the resistance of the lubricating oil passing between inner ring 3 and outer ring 4, potentially creating a curtain effect that impedes lubrication. Therefore, by providing radial grooves (not shown) on pocket surface 21 of cage 10, it is possible to improve the retention and flow of lubricating oil.

[0062] 10C shows a fifth modified example. In the cage 10 of the fifth modified example, the outer diameter surface 15b of the mass adding portion 15 is disposed on the outer diameter side of the neutral line e.

[0063] Fig. 10D shows a sixth modified example, and Fig. 10E shows a seventh modified example. In both examples, a first guide inclined surface 16 is provided on the inner diameter of the mass adding portion 15, and a second guide inclined surface 15c is provided on the outer diameter. In Fig. 10D and Fig. 10E, the first guide inclined surface 16 and the second guide inclined surface 15c are provided only on the inner and outer diameter surfaces of the convexly protruding mass adding portion 15, but they may also be provided across the mass adding portion 15 and the base portion 11 (outside the area of ​​the mass adding portion 15).

[0064] 10D and 10E, a base end surface 13 having a surface direction perpendicular to the axial center line of the cage, i.e., the bearing center line c, is not set. Here, the position of the base reference line E, which is located at the required thickness L2 from the bottom p0 on the base 11 side of the pocket 20 to the other axial side, is referred to as the base end surface imaginary line 13' corresponding to the base end surface 13. The base 11 is designed with an axial thickness from the bottom p0 of the pocket 20 to the base end surface imaginary line 13', and mass adding portions 15 of various shapes are provided on the other axial side of the base end surface imaginary line 13'.

[0065] In Fig. 10D, the entire front end face 15a of the mass addition portion 15 is located radially inward of the neutral line e. This has the advantage of making it easier to move the center of gravity of the cage 10 closer to the inner diameter. However, as shown in Fig. 10E, the entire front end face 15a of the mass addition portion 15 may be located radially outward of the neutral line e. Furthermore, the front end face 15a of the mass addition portion 15 may be disposed across the neutral line e. Even when the position of the front end face 15a, which is the most protruding part of the mass addition portion 15, is radially outward of the neutral line e, it is preferable that at least a portion of the mass addition portion 15 is radially inward of the neutral line e.

[0066] Although the shaft to which the bearing 1 of the present invention is attached has been given as an example in the form of a rotating shaft of a drive motor equipped in an electric vehicle or other electric transport device, or a rotating shaft of a reducer or speed-up gear equipped in such electric transport device, the bearing 1 of the present invention can also be applied to supporting parts of rotating shafts in various other types of transport device, industrial machinery, etc. For example, the bearing can be applied to shafts in power transmission paths in various types of transport device, rotating parts of constant velocity joints, propeller shafts, turbochargers, transmissions, and wheel bearings, or supporting parts of rotating shafts in various machine tools, generators, etc. Furthermore, as in this embodiment, the inner member 3 may be configured as an inner ring or a shaft. Furthermore, as in this embodiment, the outer member 4 may be configured as an outer ring or a housing.

[0067] Furthermore, the bearing 1 of the present invention can be applied to not only the deep groove ball bearing of this embodiment, but also angular contact ball bearings and other ball bearings in general that use balls 5 as rolling elements.

[0068] 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. [Explanation of symbols]

[0069] 1. Bearings (ball bearings) 3 Inner member (inner ring) 3a Inner raceway groove 4 Outer member (outer ring) 4a Outer raceway groove 5 balls (rolling elements) 10 Cage 11 Base 12 Holding part 14 Claws 13 Base end face 13' Base end surface assumed line 15 Mass addition part 20 pockets E Base reference line

Claims

1. A crown-type cage has an annular base portion (11) and a plurality of retaining portions (12) protruding from the base portion (11) on one axial side, and a plurality of pockets (20) formed between the plurality of retaining portions (12) along a circumferential direction, The base (11) is provided with a mass-adding portion (15) that protrudes toward the other axial direction beyond a base reference line (E) that is located a predetermined distance toward the other axial direction from the bottom (p0) of the pocket (20) in an axial cross section passing through the axial center line of the cage and the bottom (p0) of the pocket (20), and that is continuous around the entire circumference.

2. 2. The cage for a ball bearing according to claim 1, wherein the base reference line (E) is a base end face (13) on the side opposite to the pocket (20) side of the base (11).

3. The center of gravity (G ２ 2. The cage for a ball bearing according to claim 1, wherein the first and second neutral lines (e) are located radially inward of the neutral line (e) which passes through the center (a0) of the pocket (20) and is parallel to the center line in the axial direction.

4. 2. A cage for a ball bearing according to claim 1, wherein the outer diameter of the retaining portion (12) is provided with an inclined surface (23) that approaches the inner diameter side of the retaining portion (12) as it moves toward one axial side.

5. 2. The cage for a ball bearing according to claim 1, further comprising a first guide inclined surface (16) for lubricating oil, the first inclined surface (16) being connected to the inner diameter surface (17) of the base (11) as it approaches the inner diameter of the mass adding portion (15) toward one axial side.

6. 2. The ball bearing cage according to claim 1, further comprising a second guide inclined surface (15c) on the outer diameter of the mass adding portion (15) that approaches the outer diameter surface of the base (11) as it moves toward one axial side.

7. A ball bearing comprising an inner member (3), an outer member (4), balls (5) arranged between the inner member (3) and the outer member (4), and a cage (10) that holds the balls (5), the ball bearing comprising the cage according to any one of claims 1 to 6.

8. The predetermined distance is the necessary wall thickness (L) defined as 0.2 times the diameter Dw of the ball (5). ２ 8. The ball bearing according to claim 7, wherein

9. 8. The ball bearing according to claim 7, wherein the distance between the centers (a0) of the pockets (20) adjacent in the circumferential direction is equal to or greater than the diameter Dw of the balls (5).

10. A bearing device using the ball bearing according to claim 7, in which a rotating shaft of a drive motor, a reducer, or a speed increaser for an electric transport device is supported by the ball bearing.

Images