Angular contact ball bearing

Abstract

Provided is an angular contact ball bearing with which grease tends not to be entrained during initial rotation, and durability during high-speed rotation can be improved. This angular contact ball bearing (1) comprises an inner race (2), an outer race (3), balls (4) that are a plurality of rolling elements interposed between the inner race (2) and the outer race (3), and an annular retainer (5) that retains the plurality of balls (4) and guides the rolling elements. The angular contact ball bearing (1) is lubricated with grease. (a) / (b) = 0.68‒0.73, where (a) denotes the radial dimension between the inner peripheral surface (6b) of the retainer (5) and the outer peripheral surface (2c) of the inner ring (2) on the bearing front surface side, and (b) denotes the radial dimension between the inner peripheral surface (3b) of the outer race (3) and the outer peripheral surface (6a) of the retainer (5) on the front surface side of the bearing. The retainer (5) has an axially asymmetrical structure, including a large-diameter-side annular part (6) provided on the front surface side of the bearing, a small-diameter-side annular part (7) provided on the back surface side of the bearing, and a plurality of column parts (8) connecting the large-diameter-side annular part (6) and the small-diameter-side annular part (7).

Description

Angular ball bearing Related application

[0001] This application claims the priority of Japanese Patent Application No. 2024-189739 filed on October 29, 2024, and is incorporated herein by reference in its entirety as part of this application.

[0002] The present invention relates to a grease-lubricated angular ball bearing, and is applied to, for example, machine tools such as machining centers and composite machining machines, and relates to an angular ball bearing that improves the initial conditioning performance and high-speed durability performance of grease.

[0003] A cage for ball bearings that can be operated at high speeds while guiding rolling elements 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 reduce the heat generation due to the sliding between the cage and the rolling elements.

[0004] 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.

[0005] Japanese Patent Application Laid-Open No. 2016-70485, Japanese Patent Application Laid-Open No. 2003-113846

[0006] 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 during actual use, it may affect the surrounding components due to the metal expansion and vibration of each component. Therefore, it is common to make the grease conform during conditioning operation so that abnormal temperature rise is less likely to occur.

[0007] The entrainment of grease often occurs when the grease moves from the initial grease filling state to the place where the grease conforms. Therefore, it is often dealt with by optimizing the grease filling location or reducing the grease filling amount. However, a lot of man-hours are required to optimally fill the grease, and reducing the grease filling amount may highly affect the durability of the bearing. In addition, when the entrainment of grease occurs in a high-speed rotation state, a high temperature rise occurs, and a partial thin lubrication region occurs due to the decrease in the grease viscosity due to the temperature rise, which may also be a cause of bearing abnormality.

[0008] 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.

[0009] 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, wherein when the radial dimension between the inner circumferential surface of the cage and the outer circumferential surface of the inner ring on the bearing front side is a, and the radial dimension between the inner circumferential surface of the outer ring and the outer circumferential surface of the cage on the bearing front side is b, a / b is 0.68 or more and 0.73 or less. The phrase "guided by 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 and outer ring), but only with the rolling elements (balls), and the cage receives a rotational driving force from the rolling elements (balls). The phrase "bearing front" refers to the bearing end face on the outer ring end face side that does not support an axial load.

[0010] 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.

[0011] 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 resistance of grease agitation. If a / b is greater than 0.73, insufficient grease can be accumulated in space b, reducing durability at high speeds. In addition, the grease accumulated in space b comes into contact with the retainer, causing grease entrapment and a rise in temperature.

[0012] When c is the radial dimension between the inner circumferential surface of the cage and the outer circumferential surface of the inner ring on the bearing back side, and d is the radial dimension between the inner circumferential surface of the outer ring and the outer circumferential surface of the cage on the bearing back side, c / d may be 0.60 or more and 1.00 or less. The "bearing back side" refers to the bearing end face on the outer ring end face side that supports the axial load.

[0013] 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.

[0014] If c / d is less than 0.60, air is drawn in towards the rolling element side, affecting the grease accumulated in space d. This causes grease entrapment during initial rotation, generating heat due to the resistance to grease agitation. If c / d is greater than 1.00, insufficient grease can be accumulated in space d, reducing durability at high speeds. In addition, the grease accumulated in space d comes into contact with the retainer, causing grease entrapment and a rise in temperature.

[0015] 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.

[0016] The width of the cage may be 0.80 to 0.90 of the bearing width. By making the cage width 0.80 or more of the bearing width, grease accumulates on the inner surface of the cage. This grease accumulated on the inner 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 of 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.

[0017] 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.

[0018] The inner circumferential surface of the cage is provided with claws that contact the balls, and it is more preferable that the tips of the claws and the balls make line contact. Line contact between the tips of the claws and the balls allows the tips of the claws to scrape off grease during bearing operation, causing grease to accumulate on the inner circumferential surface of the cage. This prevents excess grease from moving into the cage, thus preventing the balls from becoming entangled in grease and suppressing the temperature rise of the bearing. Therefore, durability at high rotational speeds can be more reliably improved than with conventional structures.

[0019] Any combination of at least two configurations disclosed in the claims and / or the specification and / or drawings is included in the present invention. In particular, any combination of two or more of each claim in the claims is included in the present invention.

[0020] The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are for illustrative and explanatory purposes only and should not be used to define the scope of the invention. The scope of the invention is defined by the accompanying claims. In the accompanying drawings, the same reference numerals in multiple drawings indicate the same or corresponding parts.

[0021] This is a longitudinal cross-sectional view of an angular contact ball bearing according to the first embodiment of the present invention. This is a perspective view of the main part of the cage of the angular contact ball bearing as seen from the outer circumferential surface. This is a cross-sectional view taken along line III-III in Figure 1. This is a diagram illustrating the parameters of the angular contact ball bearing. This is a partially enlarged cross-sectional view of the front side of the bearing of the angular contact ball bearing. This is a partially enlarged cross-sectional view of the rear side of the bearing of the angular contact ball bearing. This is a diagram illustrating the shape of the cage end face of the angular contact ball bearing.

[0022] [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".

[0023] <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, multiple 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 as specified in JIS G 4805 conforming to ISO 100Cr6, 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.

[0024] 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."

[0025] 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 at 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 bearing rear side, the raceway surface 2a is connected to the front of the inner ring 2 via the outer circumferential surface 2b, which is an inner ring counterbore. On the bearing front side, the outer circumferential surface 2c of the inner ring 2 is located radially outward from the inner ring counterbore 2b.

[0026] <Retainer> The retainer 5 is made of synthetic resin and is formed in an annular shape, for example, from 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.

[0027] As shown in Figures 2 and 3, the cage 5 has window-shaped pockets Pt for holding the balls 4, which are provided in the axial middle portion 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.

[0028] 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.

[0029] 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.

[0030] The inner surface 8ab of the claw portion 8a on the pocket Pt side is tapered, inclined 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 predetermined to be 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.

[0031] 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.

[0032] <Parameters, etc.> <a / b = 0.68 to 0.73> At a position where the center line of the cage 5, the center line of the inner ring 2, and the center line of the outer ring 3 coincide with the bearing center line C1 of the angular contact ball bearing 1, 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 bearing front side, 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 bearing front side. In this case, a / b is 0.68 or more and 0.73 or less. In other words, the percentage obtained by multiplying the value of a divided by b (a / b) by "100" is 68% or more and 73% or less. Here, 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 defined as b.

[0033] <c / d = 0.60 to 1.00> Also, 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 of c divided by d (c / d) by "100" is between 60% and 100%.

[0034] <e / W = 0.80 to 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.

[0035] <Retainer End Face Shape> As shown in Figure 7, one 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.

[0036] Either one or both of the cage end faces on the front and rear sides of the bearing may be given the tapered shape. 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. The cage end face on the front side of the bearing may be given the rounded chamfer Rg, and the cage end face on the rear side of the bearing may be given the tapered shape.

[0037] <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.

[0038] <Test Conditions> ・Test apparatus: Horizontal single-row test apparatus ・Axial load: 800N ・Inner ring rotation, rotation speed: Step up by 1000 rotations every 10 minutes to a maximum of 10000 rotations ・During rotation, visually check whether grease is drawn into the rolling elements and whether there is contact between the accumulated grease and the cage.

[0039]

[0040] 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 toward 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.

[0041] When the ratio a / b (percentage) is less than 68%, for the grease deposited in the space Sb of b, a suction flow of air toward the rolling element side occurs. As a result, entrainment of the grease occurs during initial rotation, generating heat due to the stirring resistance of the grease. When the ratio a / b (percentage) is greater than 73%, sufficient grease cannot be deposited in the space Sb of b, and the durability during high-speed rotation decreases. At the same time, the grease deposited in the space Sb of b contacts the cage 5, causing entrainment of the grease and a temperature rise.

[0042]

[0043] In Table 2, for angular ball bearings with a / b (percentage) of 68% or more and 73% or less, various settings of c / d were verified. According to Table 2, since c / d (percentage) is 60% or more and 100% or less, no suction flow toward the rolling element side occurs for the grease deposited in the space Sd of d. As a result, entrainment of the grease during initial rotation is less likely to occur. At the same time, the necessary grease can be deposited in the space Sd of d, and the durability during high-speed rotation can be enhanced compared to the conventional structure.

[0044] When the ratio c / d (percentage) is less than 60%, for the grease deposited in the space Sd of d, a suction flow of air toward the rolling element side occurs. As a result, entrainment of the grease occurs during initial rotation, generating heat due to the stirring resistance of the grease. When the ratio c / d (percentage) is greater than 100%, sufficient grease cannot be deposited in the space Sd of d, and the durability during high-speed rotation decreases. At the same time, the grease deposited in the space Sd of d contacts the cage 5, causing entrainment of the grease and a temperature rise.

[0045]

[0046] According to Table 3, when the width e of the cage 5 is 80% or more of the bearing width W, grease accumulates on the inner peripheral surfaces 6b and 7b of the cage 5. The grease deposited on the inner peripheral surfaces 6b and 7b of the cage 5 contributes to the lubrication of the sliding surface between the cage 5 and the ball 4, so it has the effect of enhancing the durability during high-speed rotation compared to the conventional structure. When the width e of the cage 5 is greater than 90% of the bearing width W, there is a possibility that 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.

[0047] As shown in FIG. 7, by making the cage end face shape a tapered shape or a rounded chamfer Rg, the grease moving from the cage end face to the inner peripheral surfaces 3b and 3c of the outer ring accumulates closer to the raceway surface 3a side, and the durability during high-speed rotation can be further enhanced.

[0048] As shown in FIGS. 2 and 3, the inner peripheral surface of the cage 5 is provided with claw portions 8a that contact the balls 4, and the tip portions 8aa of these claw portions 8a are in line contact with the balls 4. Due to the line contact between the tip portions 8aa of the claw portions 8a and the balls 4, the grease is scraped off by the tip portions 8aa of the claw portions 8a during bearing operation, and the grease accumulates on the inner peripheral surface of the cage 5. Thereby, by avoiding excessive grease from moving inside the cage 5, that is, into the pockets Pt, the balls 4 can be prevented from entraining the grease, and the temperature rise of the bearing can be suppressed. Therefore, the durability during high-speed rotation can be more reliably enhanced compared to the conventional structure.

[0049] <Regarding Other Embodiments> In an angular ball bearing where a / b (percentage) is 68% or more and 73% or less, it may be an angular ball bearing where c / d (percentage) does not satisfy 60% or more and 100% or less. The cage 5 may have a structure that is symmetrical in the axial direction. It is also possible to use the angular ball bearing in a back-to-back combination, face-to-face combination, parallel combination, etc. In these cases, the angular ball bearings may be combined with an inner ring spacer and an outer ring spacer between the angular ball bearings adjacent in the axial direction. It is also possible to use the angular ball bearing for applications other than machine tools.

[0050] As described above, preferred embodiments have been explained with reference to the drawings, but various additions, modifications, and deletions are possible without departing from the spirit of the present invention. Therefore, such additions and deletions are also included within the scope of the present invention.

[0051] 1…Angular contact ball bearing 2…Inner ring 3…Outer ring 4…Balls (rolling elements) 5…Cage 5a…Axial end face 5b…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, wherein when the radial dimension between the inner circumferential surface of the cage and the outer circumferential surface of the inner ring on the bearing front side is a, and the radial dimension between the inner circumferential surface of the outer ring and the outer circumferential surface of the cage on the bearing front side is b, a / b is 0.68 or more and 0.73 or less.

2. An angular contact ball bearing according to claim 1, wherein when c is the radial dimension between the inner circumferential surface of the cage and the outer circumferential surface of the inner ring on the back side of the bearing, and 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 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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