Angular contact ball bearing

Abstract

This invention provides an angular contact ball bearing that is less prone to grease entrapment during initial rotation and has improved durability during high-speed rotation. [Solution] The angular contact ball bearing 1 comprises an inner ring 2, an outer ring 3, a plurality of rolling elements, which are balls 4, interposed between the inner ring 2 and the outer ring 3, and an annular cage 5 that holds these balls 4 and guides the rolling elements, and is lubricated with grease. When the radial dimension between the inner circumferential surface 6b of the cage 5 and the outer circumferential surface 2c of the inner ring 2 on the bearing front side is a, and the radial dimension between the inner circumferential surface 3b of the outer ring 3 and the outer circumferential surface 6a of the cage 5 on the bearing front side is b, a / b is 0.68 or more and 0.73 or less. The cage 5 has a structure that is asymmetrical in the axial direction, having a large-diameter annular portion 6 provided on the bearing front side, a small-diameter annular portion 7 provided on the bearing rear side, and a plurality of columnar portions 8 connecting the large-diameter annular portion 6 and the small-diameter annular portion 7.

Description

Technical Field

[0001] The present invention relates to an angular ball bearing lubricated with grease, and is applied to, for example, machine tools such as a machining center or a compound machining machine, and relates to an angular ball bearing that improves the initial conforming performance and high-speed durability performance of grease.

Background Art

[0002] A cage for a ball bearing that can be operated at high speed while being a rolling guide has been proposed (Patent Document 1). In this Patent Document 1, the pocket shape of the cage is optimized so as to reduce the contact area between the cage and the rolling elements and to reduce the heat generation due to the sliding between the cage and the rolling elements.

[0003] In Patent Document 2, in order to reduce the agitation resistance by grease, the initial filling amount of grease in the rolling bearing is decreased.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In bearings used with grease lubrication, temperature rise sometimes occurs due to the entrainment of grease during initial rotation. When the temperature of the bearing rises in actual use, it may affect surrounding components due to the metal expansion and vibration of each component. Therefore, it is common to perform a running-in operation to make the grease conform and prevent abnormal temperature rise.

[0006] Grease entrapment often occurs when the grease moves from its initial sealed state to the area where it settles. Therefore, this is often addressed by optimizing the grease sealing location or reducing the amount of grease sealed inside. However, optimally sealing the bearing with grease requires a significant amount of work, and reducing the amount of grease sealed in is highly likely to affect the durability of the bearing. In addition, if grease entrapment occurs at high rotational speeds, a high temperature rise will occur, and the resulting decrease in grease viscosity will create areas of localized lean lubrication, which could lead to bearing failure.

[0007] The objective of the present invention is to provide an angular contact ball bearing that is less prone to grease entrapment during initial rotation and has improved durability during high-speed rotation. [Means for solving the problem]

[0008] The angular contact ball bearing of the present invention comprises an inner ring, an outer ring, a plurality of rolling elements (balls) interposed between the inner and outer rings, and an annular cage that holds these balls and guides the rolling elements, and is lubricated with grease. The radial dimension between the inner surface of the cage and the outer surface of the inner ring on the bearing front side is a, When b is the radial dimension between the inner surface of the outer ring and the outer surface of the cage on the bearing front side, a / b is 0.68 or more and 0.73 or less. The phrase "guided by the rolling elements" means that the cage does not come into contact with any bearing components other than the rolling elements (balls) (i.e., the inner ring or outer ring), but only with the rolling elements (balls), and that the cage receives the rotational driving force from the rolling elements (balls). The aforementioned "bearing face" refers to the bearing end face on the outer ring end face side that does not support the axial load.

[0009] With this configuration, since a / b is between 0.68 and 0.73, no suction flow occurs toward the rolling elements from the grease accumulated in space b. This makes it less likely for grease to be entangled during initial rotation. At the same time, a sufficient amount of grease can be accumulated in space b, improving durability at high rotational speeds compared to conventional structures. The space b refers to the annular space between the inner surface of the outer ring and the outer surface of the cage on the bearing front side.

[0010] If a / b is less than 0.68, an air suction flow occurs towards the rolling element side, affecting the grease accumulated in space b. This causes grease entrapment during initial rotation, generating heat due to the grease's stirring resistance. If a / b is greater than 0.73, insufficient grease can be deposited in space b, reducing durability during high-speed rotation. Additionally, the grease deposited in space b comes into contact with the retainer, causing it to become trapped and resulting in a temperature increase.

[0011] The radial dimension between the inner surface of the cage and the outer surface of the inner ring on the back side of the bearing is c. When d is the radial dimension between the inner circumferential surface of the outer ring and the outer circumferential surface of the cage on the back side of the bearing, c / d may be 0.60 or more and 1.00 or less. The aforementioned "bearing back surface" refers to the bearing end surface on the outer ring end surface side that supports the axial load.

[0012] With this configuration, since c / d is between 0.60 and 1.00, no suction flow occurs toward the rolling elements from the grease accumulated in space d. This makes it less likely for grease to be entangled during initial rotation. At the same time, the necessary amount of grease can be accumulated in space d, improving durability at high rotational speeds compared to conventional structures. The space d refers to the annular space between the inner surface of the outer ring and the outer surface of the cage on the back side of the bearing.

[0013] If c / d is less than 0.60, an air suction flow occurs towards the rolling element side, affecting the grease accumulated in the space d. This causes grease entrapment during initial rotation, generating heat due to the grease agitation resistance. If c / d is greater than 1.00, insufficient grease can be deposited in the space d, reducing durability during high-speed rotation. Additionally, the grease deposited in space d comes into contact with the retainer, causing it to become trapped and resulting in a temperature increase.

[0014] The cage may have an axially asymmetrical structure, comprising a large-diameter annular portion provided on the front side of the bearing, a small-diameter annular portion provided on the rear side of the bearing, and a plurality of columnar portions connecting the large-diameter annular portion and the small-diameter annular portion. By optimizing the shape of such an axially asymmetrical cage, it is possible to control the movement of grease so that grease entrapment is less likely to occur during initial rotation and so that grease accumulates in the areas where it is needed during high-speed rotation.

[0015] The width of the cage may be 0.80 to 0.90 relative to the bearing width. By making the cage width 0.80 or more relative to the bearing width, grease accumulates on the inner circumferential surface of the cage. This grease accumulated on the inner circumferential surface of the cage contributes to the lubrication of the sliding surfaces between the cage and the balls, thus improving durability at high rotational speeds compared to conventional structures. If the cage width is greater than 0.90 relative to the bearing width, the cage may protrude axially from the end faces of the inner and outer rings due to the clearance inside the bearing.

[0016] The axial end face of the retainer may have a tapered shape that slopes inward in the axial direction as it extends radially outward, or the corner between the axial end face of the retainer and the outer circumferential surface connected to this axial end face may have a rounded chamfer of 60% or more of the retainer's wall thickness. In this case, the grease that moves from the retainer end face to the inner circumferential surface of the outer ring will accumulate closer to the raceway surface of the outer ring, which can further improve durability during high-speed rotation.

[0017] The inner peripheral surface of the retainer is provided with claw portions that contact the balls, and it is more preferable that the tip portions of the claw portions are in line contact with the balls. When the tip portions of the claw portions are in line contact with the balls, the grease is scraped off by the tip portions of the claw portions during bearing operation, and the grease accumulates on the inner peripheral surface of the retainer. By avoiding excessive grease from moving into the retainer, it is possible to avoid the balls from being involved in the grease and suppress the temperature rise of the bearing. Therefore, the durability during high-speed rotation can be more reliably enhanced compared to the conventional structure.

Advantages of the Invention

[0018] The angular ball bearing of the present invention includes an inner ring, an outer ring, balls which are a plurality of rolling elements interposed between the inner ring and the outer ring, and an annular retainer that holds the plurality of balls and is guided for rolling. It is a grease-lubricated angular ball bearing. When the radial dimension between the inner peripheral surface of the retainer and the outer peripheral surface of the inner ring on the front side of the bearing is a, and the radial dimension between the inner peripheral surface of the outer ring and the outer peripheral surface of the retainer on the front side of the bearing is b, a / b is 0.68 or more and 0.73 or less. For this reason, grease entrainment is less likely to occur during initial rotation, and the durability during high-speed rotation can be enhanced.

Brief Description of the Drawings

[0019] [Figure 1] It is a longitudinal sectional view of an angular ball bearing according to a first embodiment of the present invention. [Figure 2] It is a perspective view of a main part of the retainer of the angular ball bearing as viewed from the outer peripheral surface side. [Figure 3] It is a sectional view taken along line III-III of FIG. 1. [Figure 4] It is a diagram for explaining the parameters of the angular ball bearing. [Figure 5] It is a partially enlarged sectional view of the front side of the bearing of the angular ball bearing. [Figure 6] It is a partially enlarged sectional view of the back side of the bearing of the angular ball bearing. [Figure 7] It is a diagram for explaining the shape of the end face of the retainer of the angular ball bearing. [Modes for carrying out the invention]

[0020] [First Embodiment] An angular contact ball bearing according to an embodiment of the present invention will be described with reference to Figures 1 to 7. This angular contact ball bearing is applied to machine tools such as multi-tasking machines and machining centers. In this specification, the angular contact ball bearing may sometimes be simply referred to as a "bearing".

[0021] <Overall configuration of angular contact ball bearing> As shown in Figure 1, the angular contact ball bearing 1 comprises an inner ring 2, an outer ring 3, a plurality of rolling elements (balls 4) interposed between the inner ring 2 and the outer ring 3, and an annular cage 5 that holds these balls 4 and guides the rolling elements, and is lubricated with grease. Grease is sealed in the annular bearing space between the inner and outer rings 2 and 3. The inner and outer rings 2 and 3 are made of, for example, high-carbon chromium bearing steel such as SUJ2 or martensitic stainless steel. The balls 4 are made of, for example, steel balls or ceramics. The cage 5 is a resin cage, which will be described later.

[0022] The direction along the bearing centerline C1 of the angular contact ball bearing 1, or the direction parallel to the bearing centerline C1, is defined as the "axial direction." The direction perpendicular to the "axial direction" is defined as the "radial direction." The direction around the bearing centerline C1 is called the "circumferential direction."

[0023] On the bearing front side (left side of Figure 1), the raceway surface 3a is connected to the front of the outer ring 3 via the inner circumferential surface 3b, which is a counterbore. The inner circumferential surface 3b has an inclination angle α (Figure 5) which is inclined radially outward by a predetermined angle from the axial center to the axial outward side (left side of Figure 1). The inner circumferential surface 3b may also be parallel to the axial direction. On the bearing rear side (right side of Figure 1), the inner circumferential surface 3c of the outer ring 3 is located radially inward from the counterbore 3b. On the rear side of the bearing, the raceway surface 2a is connected to the front surface of the inner ring 2 via the outer circumferential surface 2b, which is the inner ring counterbore. On the front side of the bearing, the outer circumferential surface 2c of the inner ring 2 is located radially outward from the inner ring counterbore 2b.

[0024] <Cage> The retainer 5 is made of a synthetic resin formed in an annular shape, and is made of, for example, a polyamide resin material. Specifically, the retainer 5 is formed by adding additive materials such as glass fibers or carbon fibers to a polyamide resin. The retainer 5 may also be formed by adding glass fibers or carbon fibers to a polyphenylene sulfide resin. In these cases, the rigidity of the retainer can be increased, improving durability during high-speed rotation, even though it is a resin retainer. The retainer 5 may also be formed by adding additive materials to other synthetic resins.

[0025] As shown in Figures 2 and 3, the cage 5 has window-shaped pockets Pt for holding the balls 4, which are located in the axial middle section of the cage 5. The pockets Pt are formed in the shape of cylindrical holes. The cage 5 holds the balls 4 in the pockets Pt. As shown in Figure 1, the cage 5 has an axially asymmetrical structure, having a large-diameter annular portion 6 provided on the front side of the bearing, a small-diameter annular portion 7 provided on the rear side of the bearing, and a plurality of columnar portions 8 connecting the large-diameter annular portion 6 and the small-diameter annular portion 7.

[0026] These large-diameter annular portion 6, small-diameter annular portion 7, and multiple columnar portions 8 are integrally formed. The phrase "integrally formed" means that the large-diameter annular portion 6, small-diameter annular portion 7, and columnar portions 8 are not formed by combining multiple elements, but are formed from a single material, for example, by injection molding, machining, etc., as part of or as a whole of a single object.

[0027] As shown in Figures 2 and 3, the columnar portion 8 of the retainer 5 is the portion between each pocket Pt. The inner circumferential surface of the retainer 5 is provided with claw portions 8a that contact the ball 4. The tip portion 8aa of this claw portion 8a and the ball 4 make line contact. The inner circumferential surface of each columnar portion 8 is provided with tapered claw portions 8a that protrude toward the center PO of the cylindrical hole of the pocket Pt.

[0028] The inner surface 8ab of the claw portion 8a on the pocket Pt side is tapered, inclining radially inward as it approaches the center PO of the cylindrical hole. A pair of claw portions 8a are provided in each pocket Pt, facing each other in the circumferential direction. The pair of claw portions 8a, 8a in each pocket Pt are arc-shaped, extending a predetermined length along the inner diameter periphery of the cylindrical hole. In each pocket Pt, the inclination angle β formed by the inner surfaces 8ab of the pair of claw portions 8a, 8a is preset to an angle such that the tip portion 8aa of the claw portion 8a and the ball 4 make line contact (for example, β = 120°). The outer circumferential surface of the column portion 8 is provided with an outer diameter projection 8b that protrudes radially outward from the axial middle portion.

[0029] As shown in Figure 4, the large-diameter annular portion 6 is located radially outward from the small-diameter annular portion 7. The outer circumferential surface 6a of the large-diameter annular portion 6 is formed in a cylindrical shape, and this cylindrical outer circumferential surface 6a is located radially outward from the outer circumferential surface 7a of the small-diameter annular portion 7. The outer circumferential surface 6a of the large-diameter annular portion 6 and the outer circumferential surface 7a of the small-diameter annular portion 7 are located radially outward from the pitch circle diameter PCD of the ball arrangement. The inner circumferential surface 6b of the large-diameter annular portion 6 is formed in a cylindrical shape, and this cylindrical inner circumferential surface 6b is located radially inward from the outer circumferential surface 7a of the small-diameter annular portion 7, and radially outward from the inner circumferential surface 7b of the small-diameter annular portion 7. The inner circumferential surface 6b of the large-diameter annular portion 6 and the inner circumferential surface 7b of the small-diameter annular portion 7 are located radially inward from the pitch circle diameter PCD. The outer circumferential surface 7a and inner circumferential surface 7b of the small-diameter annular portion 7 are also formed in a cylindrical shape.

[0030] <Parameters, etc.> At a position where the center line C1 of the angular contact ball bearing 1 coincides with the center line of the cage 5, the center line of the inner ring 2, and the center line of the outer ring 3, Let a be the radial dimension between the inner circumferential surface 6b of the cage 5 and the outer circumferential surface 2c of the inner ring 2 on the front side of the bearing, and let b be the radial dimension between the inner circumferential surface 3b of the outer ring 3 and the outer circumferential surface 6a of the cage 5 on the front side of the bearing. In this case, a / b is between 0.68 and 0.73. In other words, the percentage obtained by multiplying the value of a divided by b (a / b) by "100" is between 68% and 73%. ​As mentioned above, the inner circumferential surface 3b, which is the outer ring counterbore, is an inclined surface having a predetermined inclination angle α with respect to the axial direction, as shown in Figure 5. Therefore, the radial dimension between the maximum diameter 3ba of the inner circumferential surface 3b, which is the outer ring counterbore, excluding the chamfer 3d, and the outer circumferential surface 6a of the retainer 5 is denoted as b.

[0031] <c / d=0.60~1.00> As shown in Figure 6, let c be the radial dimension between the inner circumferential surface 7b of the cage 5 and the outer circumferential surface 2b of the inner ring 2 on the back side of the bearing, and let d be the radial dimension between the inner circumferential surface 3c of the outer ring 3 and the outer circumferential surface 7a of the cage 5 on the back side of the bearing. In this case, c / d is between 0.60 and 1.00. In other words, the percentage obtained by multiplying the value obtained by dividing c by d (c / d) by "100" is between 60% and 100%.

[0032] <e / W=0.80~0.90> As shown in Figure 4, the width e of the cage 5 is between 0.80 and 0.90 relative to the bearing width W. In other words, the percentage obtained by multiplying the value obtained by dividing the width e of the cage 5 by the bearing width W (e / W) by "100" is between 80% and 90%. As will be described later, since the cage end face is formed in a tapered shape, for example, the width e of the cage 5 refers to the maximum width of the axial width dimension of the cage 5.

[0033] <Cage end shape> As shown in Figure 7, the axial end face 5a of the retainer 5 is formed in a tapered shape that slopes inward in the axial direction as it extends radially outward. The angle of inclination f with respect to the radial direction of this axial end face 5a of the retainer 5 is set appropriately by testing or simulation. The corner of the retainer 5 between the other axial end face 5b and the outer circumferential surface 7a has a rounded chamfer Rg of 60% or more of the retainer thickness t1. In this example, the retainer thickness t1 is the radial thickness of the small-diameter annular portion 7.

[0034] Either one or both of the cage end faces on the front and rear sides of the bearing may be given the tapered shape described above. Either one or both of the cage end faces on the front and rear sides of the bearing may be given the rounded chamfer Rg described above. The cage end face on the front side of the bearing may be given the rounded chamfer Rg described above, and the cage end face on the rear side of the bearing may be given the tapered shape described above.

[0035] <Evaluation tests, etc.> For an angular contact ball bearing with an inner ring diameter of φ70 mm, an outer ring diameter of φ110 mm, and a width of 20 mm, the parameters were set as follows, and the presence or absence of grease suction flow onto the rolling elements and the presence or absence of contact between the accumulated grease and the cage 5 were verified. The verification results in Tables 1 to 3 described later were also obtained in simulations.

[0036] <Test Conditions> • Testing equipment: Horizontal single-row testing apparatus Axial load: 800N • Inner wheel rotation, rotation speed: increases by 1000 rotations every 10 minutes, up to a maximum of 10000 rotations. • During rotation, visually check whether grease is being drawn into the rolling elements and whether there is contact between the accumulated grease and the retainer.

[0037] [Table 1]

[0038] According to Table 1, as shown in Figure 4, the percentage of the space ratio a / b on the bearing front side is between 68% and 73%, so no suction flow occurs towards the rolling element side from the grease deposited in space Sb of b. This makes it less likely for grease to be entangled during initial rotation. At the same time, a sufficient amount of grease can be deposited in space Sb of b, improving durability at high rotational speeds compared to conventional structures.

[0039] If a / b (percentage) is less than 68%, an air suction flow occurs towards the rolling element side, affecting the grease deposited in space Sb of b. This causes grease entrapment during initial rotation, generating heat due to the grease agitation resistance. If a / b (percentage) is greater than 73%, sufficient grease cannot be deposited in space Sb of b, reducing durability during high-speed rotation. At the same time, the grease deposited in space Sb of b comes into contact with the retainer 5, causing the grease to be drawn in and resulting in a temperature rise.

[0040] [Table 2]

[0041] Table 2 shows that for angular contact ball bearings with a / b (percentage) between 68% and 73%, various c / d values ​​were set and tested. According to Table 2, since c / d (percentage) is between 60% and 100%, no suction flow occurs toward the rolling element side for the grease deposited in space Sd of d. This makes it less likely for grease to be entangled during initial rotation. At the same time, the necessary amount of grease can be deposited in space Sd of d, improving durability at high rotational speeds compared to conventional structures.

[0042] When c / d (percentage) is less than 60%, an air suction flow occurs towards the rolling element side, affecting the grease deposited in space Sd (d). This causes grease entrapment during initial rotation, generating heat due to the grease's stirring resistance. If c / d (percentage) is greater than 100%, sufficient grease cannot be deposited in space Sd of d, reducing durability during high-speed rotation. At the same time, the grease deposited in space Sd of d comes into contact with the retainer 5, causing the grease to be drawn in and resulting in a temperature rise.

[0043] [Table 3]

[0044] According to Table 3, by making the width e of the cage 5 80% or more of the bearing width W, grease accumulates on the inner circumferential surfaces 6b and 7b of the cage 5. This grease accumulated on the inner circumferential surfaces 6b and 7b of the cage 5 contributes to the lubrication of the sliding surfaces between the cage 5 and the balls 4, thus improving durability at high rotational speeds compared to conventional structures. If the width e of the cage 5 is greater than 90% of the bearing width W, the cage 5 may protrude axially from the end faces of the inner and outer rings 2 and 3 due to the clearance inside the bearing.

[0045] As shown in Figure 7, by making the cage end face shape tapered or rounded Rg, the grease that moves from the cage end face to the inner circumferential surfaces 3b and 3c of the outer ring accumulates closer to the raceway surface 3a, which can further improve durability during high-speed rotation.

[0046] As shown in Figures 2 and 3, the inner circumferential surface of the cage 5 is provided with claws 8a that contact the balls 4, and the tip 8aa of these claws 8a and the balls 4 make line contact. Because the tip 8aa of the claws 8a and the balls 4 make line contact, the tip 8aa of the claws 8a scrapes off the grease during bearing operation, and the grease accumulates on the inner circumferential surface of the cage 5. This prevents excess grease from moving into the inside of the cage 5, i.e., into the pocket Pt, thereby preventing the balls 4 from becoming entangled in grease and suppressing the temperature rise of the bearing. Therefore, the durability at high rotational speeds can be more reliably improved than in conventional structures.

[0047] <Regarding other embodiments> An angular contact ball bearing in which a / b (percentage) is 68% or more and 73% or less may also be an angular contact ball bearing in which c / d (percentage) does not satisfy the condition of being 60% or more and 100% or less. The retainer 5 may have a structure that is symmetrical in the axial direction. Angular contact ball bearings can also be used in back-to-back, front-to-front, or parallel configurations. In these cases, angular contact ball bearings can be combined between axially adjacent bearings via inner and outer ring spacers. Angular contact ball bearings can also be used in applications other than machine tools.

[0048] While embodiments for carrying out the present invention have been described above based on the embodiments, the embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0049] 1…Angular contact ball bearing, 2…Inner ring, 3…Outer ring, 4…Balls (rolling elements), 5…Cage, 5a…Axial end face (axial end face), 5b…Axial end face (axial end face), 6…Large diameter annular section, 7…Small diameter annular section, 8…Column section, 8a…Claw section, 8aa…Tip section

Claims

1. An angular contact ball bearing comprising an inner ring, an outer ring, a plurality of rolling elements (balls) interposed between the inner and outer rings, and an annular cage that holds these balls and guides the rolling elements, and which is lubricated with grease, The radial dimension between the inner surface of the cage and the outer surface of the inner ring on the bearing front side is a, An angular contact ball bearing in which, when b is the radial dimension between the inner surface of the outer ring and the outer surface of the cage on the bearing front side, a / b is 0.68 or more and 0.73 or less.

2. In the angular contact ball bearing according to claim 1, the radial dimension between the inner surface of the cage and the outer surface of the inner ring on the back side of the bearing is c, An angular contact ball bearing in which, when d is the radial dimension between the inner surface of the outer ring and the outer surface of the cage on the back side of the bearing, c / d is 0.60 or more and 1.00 or less.

3. An angular contact ball bearing according to claim 1 or claim 2, wherein the cage has a structure that is asymmetrical in the axial direction, comprising a large-diameter annular portion provided on the front side of the bearing, a small-diameter annular portion provided on the rear side of the bearing, and a plurality of columnar portions connecting the large-diameter annular portion and the small-diameter annular portion.

4. An angular contact ball bearing according to claim 1 or claim 2, wherein the width of the cage is 0.80 or more and 0.90 or less relative to the bearing width.

5. An angular contact ball bearing according to claim 1 or claim 2, wherein the axial end face of the cage is tapered inward as it extends radially outward, or the corner between the axial end face of the cage and the outer circumferential surface connected to this axial end face is chamfered to a diameter of 60% or more of the cage wall thickness.

6. An angular contact ball bearing according to claim 1 or claim 2, wherein the inner circumferential surface of the cage is provided with a claw portion that contacts the ball, and the tip of the claw portion and the ball are in line contact.

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