Angular ball bearing and rotation mechanism

Abstract

Provided are an angular ball bearing and a rotation mechanism with which ball wear can be suppressed even when the balls slide against each other, and cost can be reduced. An angular ball bearing (1) is an angular ball bearing having no retainer and comprising an inner ring (2), an outer ring (3), and a plurality of balls (4) interposed between the inner ring (2) and the outer ring (3). The surface roughness of the balls (4) is 0.06 μmRa or less, and the kinematic viscosity (40°C) of a lubricant is 46-220 cst. When the lubricant is grease, the consistency of the grease ranges from No. 1 to No. 00. The surface roughness of the balls (4) is more preferably 0.04 μmRa or less, and the kinematic viscosity (40°C) of the lubricant is more preferably 68-150.

Description

Angular contact ball bearings and rotating mechanisms Related Applications

[0001] This application claims priority to Japanese Patent Application No. 2023-145527 filed on September 7, 2023, and Japanese Patent Application No. 2023-145621 filed on September 7, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an angular contact ball bearing and a rotation mechanism used in the main bearing portion of a reducer of, for example, a robot or construction machine, and relates to a technology specialized for compactness, high load capacity, and high rigidity.

[0003] The following prior art rolling bearing without a cage (full ball type) is available (Patent Document 1). This rolling bearing has only a large number of rolling elements arranged between an inner and outer ring, and the rolling elements are made of martensitic stainless steel, and the surfaces of the rolling elements have a nitride layer with a hardness of Hv 1200 to 1500.

[0004] Japanese Patent Application Laid-Open No. 2004-92686

[0005] For example, bearings used in the main bearing parts of reducers for robots or construction machinery generally need to be compact in addition to long life and high moment rigidity, which means that an improvement in the load rating within a certain bearing size is required, necessitating an increase in ball size or the number of balls. Increasing ball size poses the issue of reduced bearing rigidity because the raceway becomes thinner. On the other hand, one method for increasing the number of balls is to use a full ball bearing without a cage. However, with a full ball bearing, the relative sliding velocities between adjacent balls in contact are in opposite directions, which causes "reverse sliding" in the contact area between the balls, making it necessary to find ways to suppress ball wear.

[0006] The above-mentioned conventional technology solves this problem by forming a nitride layer on the surface of the ball, making the surface very hard (HV 1200 to 1500), thereby suppressing ball wear. However, the problem is that nitride balls with this surface hardness require high heat treatment costs.

[0007] An object of the present invention is to provide an angular contact ball bearing and a rotation mechanism that can suppress ball wear even when reverse sliding occurs between the balls, and that can also reduce costs.

[0008] The angular contact ball bearing in a first configuration of the present invention is a cageless angular contact ball bearing comprising an inner ring, an outer ring, and a plurality of balls interposed between the inner ring and the outer ring, wherein the surface roughness of the balls is 0.06 μm Ra or less, and the kinematic viscosity (40°C) of the lubricant is 46 cst or more and 220 cst or less.

[0009] By using a so-called full-ball angular contact ball bearing without a cage, the ball packing rate is improved compared to an angular contact ball bearing with a cage, resulting in relatively improved load capacity and moment rigidity.Without a cage, the balls come into contact with each other due to the relative difference in revolution speed, and the relative sliding speed between adjacent contacting balls is in the opposite direction, causing "reverse sliding" in the contact area between the balls.

[0010] With this configuration, it was found that by combining a lubricant with an optimal kinematic viscosity and an optimal ball surface roughness to prevent "reverse sliding," wear on the ball surface can be suppressed. In other words, when the ball surface roughness is 0.06 μm or less in arithmetic mean roughness and the lubricant's kinematic viscosity (40°C) is in the range of 46 cst to 220 cst, an oil film is well formed between the balls, and ball wear is feasibly suppressed. This configuration, which combines a lubricant with an optimal kinematic viscosity and an optimal ball surface roughness, can reduce costs compared to conventional techniques such as applying special heat treatment to the ball surface.

[0011] The lubricant may be a grease, and the consistency of the grease may be from No. 1 to No. 00. The consistency is a value expressed in the JIS (Japanese Industrial Standards) classification. Of the consistency numbers from No. 1 to No. 00, the worked consistency of "No. 1" is "310 to 340," and the worked consistency of "No. 0" is "355 to 385." The worked consistency of "No. 00" is "400 to 430." These JIS consistency numbers 1, 0, and 00 correspond, in order, to the NLGI (National Lubricating Grease Institute) consistency numbers 1, 0, and 00. When the lubricant is a grease, it has been found that a lubricant that allows the grease to easily flow between the balls has a high effect of suppressing ball wear. The ease with which the grease can flow between the balls specifically varies depending on the consistency classification. The higher the consistency (softer), the better the grease will flow between the balls, and the lower the consistency (harder), the worse the grease will flow. Greases with consistency classifications in the range of No. 1 to No. 00 have relatively good flowability between the balls, further enhancing the effect of suppressing ball wear.

[0012] The grade of the balls may be 40 or less. The grade is a value specified in JIS B1501 of the Japanese Industrial Standards. By making the grade of the balls 40 or less, it is possible to select balls having a surface roughness of 0.06 μm Ra or less.

[0013] The surface roughness of the balls may be 0.04 μm Ra or less, and the kinematic viscosity (40° C.) of the lubricant may be 68 cst or more and 150 cst or less, in which case the oil film between the balls is more effectively formed, further enhancing the effect of suppressing ball wear.

[0014] The balls may be made of bearing steel, which can reduce manufacturing costs compared to using balls made of martensitic stainless steel, ceramics, etc.

[0015] When the material of the balls is bearing steel, the balls may be subjected to a surface hardening treatment, such as nitriding.

[0016] A rotation mechanism according to a first aspect of the present invention includes any one of the angular contact ball bearings described above. Therefore, the effects described above for the angular contact ball bearing of the present invention can be obtained. In the case of a rotation mechanism in which the inner ring and shaft are integrated, or a rotation mechanism in which the outer ring and housing are integrated, it is possible to achieve high rigidity and high load capacity without increasing the size.

[0017] The following two conventional techniques exist as means for increasing the moment rigidity of a bearing without increasing the bearing size (Japanese Patent Laid-Open No. 2005-201294 and Japanese Patent No. 4515039). The angular ball bearing of Japanese Patent Laid-Open No. 2005-201294 is a multi-point contact type in which balls contact the raceway surfaces of the inner and outer rings at two points each at a required contact angle. The angular ball bearing of Japanese Patent No. 4515039 is a double-row integral angular ball bearing that has multiple rows of balls with different pitch circle diameters and a single cage that holds the multiple rows of balls, and in which the balls in each row contact the inner and outer ring raceway surfaces at a required contact angle.

[0018] Generally, ball bearings have a contact ellipse, which is the contact point where the load of the raceway and ball acts, and when the ball rolls, it is not possible for it to roll purely at all points on this contact ellipse, and slippage (differential slippage) occurs within the contact ellipse.Multi-point contact angular contact ball bearings contact one ball at two points with a contact angle, so large differential slippage occurs at one of the contact points, posing the problem of accelerating wear on the raceway surface.

[0019] In double-row one-piece angular contact ball bearings, the bearing ring shoulders are thin because the balls are arranged in double rows. As a result, when double-row one-piece angular contact ball bearings are subjected to moment loads, the shoulders are affected by elastic deformation, which reduces moment rigidity. In addition, the bearing rings of double-row one-piece angular contact ball bearings have a complex shape, which makes them difficult to manufacture and increases costs.

[0020] An angular ball bearing according to a second configuration of the present invention is an angular ball bearing comprising an inner ring, an outer ring, and a plurality of balls interposed between the inner ring and the outer ring, wherein the contact angle is 40° or more and 50° or less, the ratio W / Dw of the axial length W of the outer peripheral surface on the back side of the inner ring to the ball diameter Dw which is the diameter of the balls is 0.15 or more and 0.35 or less, and the ratio V / Dw of the axial length V of the inner peripheral surface on the back side of the outer ring to the ball diameter Dw is 0.15 or more and 0.35 or less.

[0021] With this configuration, in a so-called full-contact angular contact ball bearing, when the contact angle is in the range of 40° to 50°, W / Dw is in the range of 0.15≦W / Dw≦0.35, and V / Dw is in the range of 0.15≦V / Dw≦0.35, high moment rigidity and high load capacity can be achieved without increasing the size. This configuration can also solve the problems seen in the multi-point contact angular contact ball bearings mentioned above, such as wear due to differential sliding, reduced moment rigidity due to axial thinning of the shoulder, and high costs due to manufacturing difficulties.

[0022] In the case of an angular contact ball bearing without a cage, the ball filling rate can be improved compared to an angular contact ball bearing with a cage.

[0023] A rotation mechanism according to a second aspect of the present invention is a rotation mechanism equipped with an angular contact ball bearing including an inner ring, an outer ring, and a plurality of balls interposed between the inner ring and the outer ring, and is provided with inner ring shoulder deformation suppression means for suppressing deformation of the inner ring shoulder, and the angular contact ball bearing has a contact angle of 40° or more and 50° or less, and a ratio V / Dw of the axial length V of the inner peripheral surface on the back side of the outer ring to the ball diameter Dw which is the diameter of the balls is 0.15 or more. The "inner ring shoulder" is the outer peripheral portion on the back side of the inner ring.

[0024] In this way, in a rotation mechanism equipped with a so-called full-ball angular contact ball bearing, if an inner ring shoulder deformation suppression means is provided and the contact angle is in the range of 40° to 50° and V / Dw is in the range of 0.15 or more, high rigidity, high load capacity, etc. can be achieved without increasing the size.

[0025] When a rotating mechanism is equipped with an angular contact ball bearing without a cage, the ball filling rate can be improved compared to an angular contact ball bearing with a cage, contributing to higher rigidity and load capacity as a rotating mechanism.

[0026] The inner ring shoulder deformation suppression means may be formed by integrating the inner ring with the rotating shaft of the rotation mechanism. In this case, the inner ring shoulder can be made thicker than that of a typical angular contact ball bearing. In this case, a decrease in moment rigidity does not occur as long as the contact angle is in the range of 40° to 50° and V / Dw is in the range of 0.15 or more.

[0027] The inner ring shoulder deformation suppression means may be such that the shoulder diameter of a member facing the back surface of the inner ring is equal to or greater than the inner ring shoulder diameter. In this case, deformation of the inner ring shoulder and a decrease in moment rigidity can also be suppressed.

[0028] The member facing the back surface of the inner ring may be the rotating shaft of the rotation mechanism or an annular regulating member. If the shaft shoulder of the rotating shaft is equal to or larger than the inner ring shoulder diameter, the number of parts can be reduced and the structure can be simplified compared to using an annular regulating member. If the annular regulating member is equal to or larger than the inner ring shoulder diameter, the diameter of the rotating shaft can be reduced.

[0029] A rotation mechanism according to a third aspect of the present invention is a rotation mechanism equipped with an angular contact ball bearing including an inner ring, an outer ring, and a plurality of balls interposed between the inner ring and the outer ring, wherein the outer ring is integrally formed with a housing of the rotation mechanism, and the angular contact ball bearing has a contact angle of 40° or more and 50° or less, and a ratio W / Dw of the axial length W of the outer peripheral surface on the back side of the inner ring to the ball diameter Dw which is the diameter of the balls is 0.15 or more.

[0030] In this way, in a rotation mechanism equipped with a so-called full-ball angular contact ball bearing, if the outer ring is integrally formed with the housing of the rotation mechanism, and the contact angle is in the range of 40° to 50° and W / Dw is in the range of 0.15 or more, high rigidity, high load capacity, etc. can be achieved without increasing the size.

[0031] When a rotating mechanism is equipped with an angular contact ball bearing without a cage, the ball filling rate can be improved compared to an angular contact ball bearing with a cage, contributing to higher rigidity and load capacity as a rotating mechanism.

[0032] The speed reducer of the present invention includes any one of the above-described rotation mechanisms of the present invention, and therefore can obtain the effects described above for the rotation mechanism of the present invention.

[0033] Any combination of at least two features disclosed in the claims and / or the specification and / or the drawings is included in the present invention. In particular, any combination of two or more of the claims is included in the present invention.

[0034] 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 merely for illustration and explanation, and should not be used to define the scope of the present invention, which is defined by the appended claims. In the accompanying drawings, the same reference numerals in multiple drawings indicate the same or corresponding parts.

[0035] FIG. 1 is a longitudinal sectional view of an angular contact ball bearing according to a first embodiment of the present invention. FIG. 2 is a perspective view of the angular contact ball bearing. FIG. 3 is a conceptual diagram explaining reverse sliding between balls in the angular contact ball bearing. FIG. 4 is a longitudinal sectional view showing an example of back-to-back assembly of the angular contact ball bearing. FIG. 5 is a longitudinal sectional view of a rotation mechanism including an angular contact ball bearing according to a second embodiment of the present invention. FIG. 6 is a longitudinal sectional view of a rotation mechanism including an angular contact ball bearing according to a third embodiment of the present invention. FIG. 7 is a longitudinal sectional view of an angular contact ball bearing according to a fourth embodiment of the present invention. FIG. 8 is a conceptual diagram explaining the relationship between the contact angle and moment stiffness of the angular contact ball bearing. FIG. 9 is a longitudinal sectional view showing an example of back-to-back assembly of the angular contact ball bearing. FIG. 10 is an enlarged sectional view of a main part of a rotation mechanism including an angular contact ball bearing according to a fifth embodiment of the present invention. FIG. 11 is an enlarged sectional view of a main part of a rotation mechanism including an angular contact ball bearing according to a sixth embodiment of the present invention. FIG. 12 is an enlarged sectional view of a main part of a rotation mechanism including an angular contact ball bearing according to a seventh embodiment of the present invention. FIG. 13 is an enlarged sectional view of a main part of a rotation mechanism including an angular contact ball bearing according to an eighth embodiment of the present invention. FIG. 14 is a longitudinal sectional view showing the entire rotation mechanism of each embodiment of the present invention.

[0036] [First embodiment] An angular contact ball bearing according to an embodiment of the present invention will be described with reference to Figures 1 to 3. This angular contact ball bearing is used, for example, as the main bearing portion of a reducer in a robot, construction machine, etc. In this specification, the angular contact ball bearing may also be simply referred to as a "bearing."

[0037] <General Structure of Angular Contact Ball Bearing> As shown in Figure 1, the angular contact ball bearing 1 is a cageless, so-called full-ball angular contact ball bearing, equipped with an inner ring 2, an outer ring 3, and a plurality of balls 4 interposed between the raceway surfaces 2a, 3a of the inner and outer rings 2, 3. The inner and outer rings 2, 3 and balls 4 are made of high-carbon chromium bearing steel such as SUJ2. In this specification, the "axial direction" refers to the direction along the bearing centerline of the angular contact ball bearing 1. The "radial direction" refers to the direction perpendicular to the line that forms the "axial direction."

[0038] The raceway surface 3a is connected to the front surface of the outer ring 3 via a counterbore 3b. An inner peripheral surface 3d on the back surface side of the outer ring 3 is located radially inward of the counterbore 3b of the outer ring 3. The raceway surface 2a is connected to the front surface of the inner ring 2 via a counterbore 2b. An outer peripheral surface 2d on the back surface side of the inner ring 2 is formed between the raceway surface 2a of the inner ring 2 and the back surface 2c of the inner ring 2. The outer peripheral surface 2d of the inner ring 2 is located radially outward of the counterbore 2b of the inner ring 2. The front surfaces of the inner and outer rings 2 and 3 refer to the side surfaces on the side that do not support an axial load, and the back surfaces 2c and 3c of the inner and outer rings 2 and 3 refer to the side surfaces on the side that support an axial load.

[0039] <Regarding parameters, etc.> To improve the load capacity and moment rigidity of an angular contact ball bearing within a certain size, there are two methods: (1) increasing the number of balls, and (2) increasing the ball diameter. As shown in Figure 2, the angular contact ball bearing 1 according to an embodiment of the present invention is designed without a cage (full ball type) in order to increase the number of balls, and by improving the ball packing rate, the load capacity and moment rigidity are relatively improved compared to angular contact ball bearings with cages. The ball packing rate is calculated using the following formula: Packing rate = (ball diameter Dw x number) / (π x pitch circle diameter PCD). This indicates that the packing rate of the full ball type angular contact ball bearing of the present invention is 95% or more.

[0040] Without a cage, the difference in the relative revolution speeds of the balls causes adjacent balls in the circumferential direction to come into contact with each other, as shown in Figure 3, and the relative sliding velocities R1 and R2 between the adjacent contacting balls 4, 4 are in opposite directions. This causes "reverse sliding" in the contact area between the balls. The thick arrow A1 in Figure 3 indicates the direction of ball movement. It has been found that in angular contact ball bearings without a cage, ball surface wear can be suppressed by combining a lubricant with an optimal kinematic viscosity and optimal ball surface roughness to prevent "reverse sliding." Furthermore, when the lubricant is grease, it has been found that ball wear can be further suppressed by combining it with an optimal consistency in addition to the above.

[0041] The consistency is a value determined by the test method of JIS K2220, and is expressed in JIS classification in the present examples. The kinematic viscosity is a value determined at 40°C by the test method of JIS K2283.

[0042] A rotational durability test was conducted on angular contact ball bearings under the following conditions, and evaluation was performed for each combination of the arithmetic mean surface roughness (μmRa) of the balls and the kinematic viscosity of the lubricant. <Conditions> Ball diameter Dw / Pitch circle diameter PCD: 0.07 Ball packing ratio: 98% dmn value: 50,000 dmn = {(D + d) / 2} × n

[0043] D: outer diameter of outer ring (mm), d: inner diameter of inner ring (mm), n: rotation speed (min －１ ) Load: Under a load condition of 10% to 20% of the basic dynamic load rating (Cr) Ball: Bearing steel In Table 1, ball wear was evaluated as follows: ◯ (possible and had a high wear-suppressing effect); △ (possible but had a lower wear-suppressing effect than ◯); and × (poor wear-suppressing effect).

[0044] <Effects> In angular contact ball bearings without a cage, when the ball surface roughness is 0.06 μm or less in arithmetic mean roughness and the kinematic viscosity of the lubricant (40°C) is in the range of 46 cst to 220 cst as in Examples 1 to 5, an oil film is formed well between the balls and ball wear is suppressed to a feasible extent. When the ball surface roughness is 0.04 μm Ra or less and the lubricant kinematic viscosity (40°C) is 68 cst to 150 cst as in Examples 2 to 4, an oil film is formed even better between the balls, and the effect of suppressing ball wear can be further enhanced.

[0045] This combination of a lubricant with an optimal kinematic viscosity and an optimal ball surface roughness reduces costs compared to conventional techniques such as providing a nitride layer on the surface of the ball. When the lubricant's kinematic viscosity (40°C) is 320 cst, regardless of the ball surface roughness, heat generation increases and it becomes difficult to form an oil film, which in turn reduces the wear suppression effect.

[0046] If the ball surface roughness is 0.04 μm Ra or less, balls of grade 24 or less can be selected, and if the ball surface roughness is 0.06 μm Ra or less, balls of grade 40 or less can be selected. When the lubricant is grease, it has been found that grease that easily flows between the balls has a high effect of suppressing ball wear. The ease with which grease flows between the balls varies specifically depending on the consistency classification. The higher the consistency (softer), the better the grease flows between the balls, and the lower the consistency (harder), the worse the grease flows. Greases with consistency classifications ranging from No. 1 to No. 00 have relatively good flowability between the balls, further enhancing the effect of suppressing ball wear. If the consistency classification is lower than No. 2, the grease is hard and the grease flow is poor, which may conversely reduce the effect of suppressing wear.

[0047] By ensuring that the surface roughness of the balls and the kinematic viscosity (40°C) of the lubricant, or in the case of grease, the consistency classification, are within the above ranges, the effect of suppressing ball wear can be enhanced without the need for special heat treatment of the balls.

[0048] <Back-to-back arrangement, etc.> Moment loads are often applied in industrial machinery. Under operating conditions where moment loads are applied by angular contact ball bearings, arranging angular contact ball bearings 1 in a back-to-back arrangement, as shown in Figure 4, increases the distance between the bearing's application points, allowing for a larger allowable radial load and moment load even if the angular contact ball bearing 1 is made smaller or more compact. Furthermore, by arranging angular contact ball bearings 1 in a back-to-back arrangement, it is possible to withstand axial loads in both directions, and in addition, the addition of preload increases the rigidity of the bearing portion. In the example shown in Figure 4, an inner ring spacer 7 and an outer ring spacer 8 are interposed between axially adjacent angular contact ball bearings 1, 1, but it is also possible to omit these spacers 7, 8 and arrange angular contact ball bearings 1, 1 in a back-to-back arrangement.

[0049] <Regarding Other Embodiments> In the following description, parts corresponding to matters previously described in each embodiment are assigned the same reference numerals, and duplicated description will be omitted. When only part of the configuration is described, the other parts of the configuration are the same as those in the previously described embodiment unless otherwise specified. The same configuration produces the same effects. It is possible to combine not only the parts specifically described in each embodiment, but also parts of the embodiments together, provided that there is no particular problem with the combination.

[0050] [Second embodiment: Inner ring and shaft integrated] As shown in Figure 5, a rotation mechanism 9 may be provided with an angular contact ball bearing 1 in which the inner ring 2 and shaft are integrated. The term "integrated" means that the inner ring 2 and the shaft are not formed by combining multiple elements, but are formed as part or the whole of a single object from a single material by, for example, forging or machining.

[0051] <Axle Unit> This rotation mechanism 9 is a vehicle power unit, or so-called axle unit, mounted on a vehicle, and includes a double-row angular contact ball bearing 1 assembled back-to-back and a traction motor M with a power generator function. The outer ring 3 of the angular contact ball bearing 1 is a rotating ring, and the inner ring 2 integrated with the shaft is a fixed ring. A brake rotor BR and a wheel (not shown) are attached to a wheel mounting flange 3F provided on the outboard end of the outer ring 3, overlapping in the axial direction. In the case of a rotation mechanism 9 in which the inner ring 2 and the shaft are integrated, it is possible to achieve high rigidity and a high load capacity without increasing the size.

[0052] 6, a rotation mechanism 9A may be provided with an angular contact ball bearing 1 in which the outer ring 3 and housing 14 are integrated. Even in the case of the rotation mechanism 9A in which the outer ring 3 and housing 14 are integrated, it is possible to achieve high rigidity and high load capacity without increasing the size.

[0053] At least one of the inner and outer rings and the balls may be made of a material other than bearing steel. Examples of materials other than bearing steel include martensitic stainless steel and ceramics. Angular contact ball bearings can also be used in face-to-face or parallel combinations. Angular contact ball bearings can also be used in multi-row combinations of three or more rows. Angular contact ball bearings and rotation mechanisms can also be used for applications other than reducers.

[0054] When the material of the balls is bearing steel, the balls may be subjected to a surface hardening treatment, such as nitriding.

[0055] [Fourth embodiment] An angular contact ball bearing according to an embodiment of the present invention will be described with reference to Figures 7 to 9. As shown in Figure 7, the angular contact ball bearing 1 according to the fourth embodiment has the same general configuration as the angular contact ball bearing according to the first embodiment described above. In the fourth embodiment, components similar to those in the first embodiment are given the same reference numerals, and detailed descriptions thereof will be omitted.

[0056] <Regarding parameters, etc.> To improve the load capacity and moment rigidity of an angular contact ball bearing within a certain size, there are two methods: (1) increasing the number of balls, and (2) increasing the ball diameter. Another method for improving moment rigidity is (3) increasing the contact angle. The angular contact ball bearing 1 according to an embodiment of the present invention is a cage-less (full ball) type in order to increase the number of balls, and by improving the packing rate of the balls 4, the load capacity and moment rigidity are relatively improved compared to angular contact ball bearings with cages. The packing rate of the balls 4 is calculated using the following formula: Packing rate = (ball diameter Dw × number) / (π × pitch circle diameter PCD). This indicates that the packing rate of the full ball type angular contact ball bearing of the present invention is 95% or more.

[0057] When increasing the ball diameter Dw, if deformation of the bearing rings (the inner and outer rings 2 and 3) is not taken into consideration, the larger the ball diameter Dw, the higher the relative load capacity and moment rigidity. However, in reality, if the shoulders 5 and 6 of the bearing rings are thin, deformation of the shoulders 5 and 6 will occur. For this reason, as a trade-off, increasing the ball diameter Dw requires a thinner axial thickness of the shoulders 5 and 6 of the inner and outer rings 2 and 3. When subjected to a moment load, the thin shoulders deform in the load area, widening the clearance inside the bearing and reducing moment rigidity.

[0058] As shown in the right-hand diagram of Figure 8, when the contact angle θ of the angular contact ball bearing is made larger than that shown in the left-hand diagram of Figure 8, the distance between the points of application increases. For this reason, the moment rigidity of the angular contact ball bearing with the larger contact angle θ shown on the right-hand diagram of Figure 8 is usually improved. However, because the contact areas between the balls and the inner and outer ring raceways come into contact with the tips of the shoulders 5 and 6, deformation of the shoulders 5 and 6 is actually promoted, reducing the moment rigidity. Note that the deformation of the shoulders 5 and 6 on the right-hand diagram of Figure 8 is conceptually exaggerated.

[0059] Therefore, in this embodiment, in order to improve the load capacity and moment rigidity while taking into account the deformation of the shoulder, the following functional comparison was made with a full-ball angular contact ball bearing. This comparison was made using simulations, but similar results were obtained in actual machine tests. The external load that the angular contact ball bearing was subjected to was verified using a moment load imposed by a general reducer. The moment load refers to a load that tilts (bends) the rotation axis, that is, a load that imparts an angle to the rotation axis.

[0060] The bearing size was an angular contact ball bearing with a ball diameter / PCD ratio of 0.05 to 0.10. As shown in Figure 7, 20 types of angular contact ball bearings (Comparative Examples 1 to 16 and Examples 1 to 4) were assumed, with a contact angle θ ranging from 20° to 55°, a ratio W / Dw of the axial length W of the outer peripheral surface 2d on the back side of the inner ring 2 to the ball diameter Dw (diameter of the balls 4) ranging from 0.07 to 0.4, and a ratio V / Dw of the axial length V of the inner peripheral surface 3d on the back side of the outer ring 3 to the ball diameter Dw (diameter of the balls 4) ranging from 0.07 to 0.4. Table 2 shows the load capacity, moment stiffness (when the bearing ring is rigid), and deformation of shoulders 5 and 6 for the comparative examples and examples with different parameters.

[0061]

[0062] In Table 2, the load capacity symbol ◎ indicates that it is possible to implement and can be implemented efficiently, ○ indicates that it is possible to implement although its performance is inferior to ◎, △ indicates that it is not recommended to implement it because its performance is inferior to ○, and × indicates that it is not possible to implement. In Table 2, the arrow of V / Dw indicates that it is the same as the value of W / Dw in the same column.

[0063] Moment stiffness represents the stiffness of the angular contact ball bearing and is expressed as the load moment value required to tilt a unit angle (1 arcmin). The moment stiffness in this example is calculated when the raceway ring is considered to be a rigid body, and the ◎, ◯, △, and × for moment stiffness in Table 2 have the same definition as the load capacity. Regarding shoulder deformation in Table 2, ◯ indicates that there is almost no shoulder deformation and no reduction in moment stiffness, and × indicates that moment stiffness is reduced due to shoulder deformation. Table 2 shows that Examples 1, 2, 3, and 4 have load capacities and moment stiffnesses that are feasible or can be efficiently achieved, and that moment stiffness is not reduced due to shoulder deformation.

[0064] <Effects> Therefore, in a cageless, full-ball angular contact ball bearing, high load capacity and high moment rigidity can be achieved when the contact angle θ is in the range of 40° to 50°, W / Dw is in the range of 0.15≦W / Dw≦0.35, and V / Dw is in the range of 0.15≦V / Dw≦0.35. Furthermore, when W / Dw≧0.15 and V / Dw≧0.15, there is no reduction in rigidity due to deformation of the shoulder. The configuration of this embodiment can also solve the problems of the multi-point contact angular contact ball bearing described above, such as wear due to differential sliding, reduced moment rigidity due to thinning of the shoulder, and high costs due to manufacturing difficulties.

[0065] <Back-to-back arrangement, etc.> Moment loads are often applied in industrial machinery. Under operating conditions where moment loads are applied by angular contact ball bearings, arranging angular contact ball bearings 1 in a back-to-back arrangement, as shown in Figure 9, increases the distance between the bearing's application points, allowing for a larger allowable radial load and moment load even if the angular contact ball bearing 1 is made smaller or more compact. Furthermore, by arranging angular contact ball bearings 1 in a back-to-back arrangement, it is possible to withstand axial loads in both directions, and in addition, the addition of preload increases the rigidity of the bearing portion. In the example shown in Figure 9, an inner ring spacer 7 and an outer ring spacer 8 are interposed between axially adjacent angular contact ball bearings 1, 1, but it is also possible to omit these spacers 7, 8 and arrange angular contact ball bearings 1, 1 in a back-to-back arrangement.

[0066] 10 to 13 are partial views of the rotation mechanism of Fig. 14 described later. [Fifth embodiment: inner ring and rotating shaft integrated] Fig. 10 is an enlarged cross-sectional view of a main part of a rotation mechanism 9 equipped with an angular contact ball bearing according to a fifth embodiment.

[0067] The rotation mechanism 9 may be provided with an inner ring shoulder deformation suppression means 11 that suppresses deformation of the inner ring shoulder 5. Specifically, the inner ring shoulder deformation suppression means that the inner ring 2 of the angular contact ball bearing 1 on the left side of Figure 10 is integrated with the rotating shaft 12 of this rotation mechanism 9. "Integrated" means that the inner ring 2 and the rotating shaft 12 are not formed by joining multiple elements but are formed as part or the whole of a single object from a single material by, for example, forging or machining.

[0068] In this way, in a rotation mechanism 9 equipped with a cageless, full-ball angular contact ball bearing 1, if the inner ring shoulder deformation suppression means 11 is provided and the contact angle θ is in the range of 40° to 50° and V / Dw (see FIG. 7) is in the range of 0.15 or more, high rigidity and high load capacity can be achieved without increasing the size. If the inner ring 2 is integrated with the rotating shaft 12 of the rotation mechanism 9, it becomes possible to make the inner ring shoulder 5 thicker than the inner ring shoulder of a typical angular contact ball bearing. In this case, no reduction in moment rigidity occurs as long as the contact angle θ is in the range of 40° to 50° and V / Dw (see FIG. 7) is in the range of 0.15 or more.

[0069] [Sixth embodiment: shaft shoulder≧inner ring shoulder diameter] As shown in Figure 11, in a rotation mechanism 9 equipped with a cage-less, so-called full-ball angular contact ball bearing 1, the inner ring shoulder deformation suppression means may set the shoulder diameter D1 of the member facing the back surface 2c of the inner ring 2 to be equal to or greater than the inner ring shoulder diameter D2. The member facing the back surface 2c of the inner ring 2 is the rotating shaft 12 of the rotation mechanism 9. If the shaft shoulder D1 of this rotating shaft 12 is set to be equal to or greater than the inner ring shoulder diameter D2, the number of parts can be reduced and the structure can be simplified compared to providing an annular restricting member or the like, which will be described later. In addition, the same effects as those of the rotation mechanism described above can be achieved.

[0070] [Seventh embodiment: Shoulder diameter (outer diameter) of regulating member ≧ inner ring shoulder diameter] As shown in Fig. 12 , the member facing the back surface of the inner ring 2 may be an annular regulating member 13. The regulating member 13 may be formed, for example, with a rectangular cross section, and is interposed between the inner surface of the flange portion 12a of the rotating shaft 12 and the back surface 2c of the inner ring 2. In a rotation mechanism 9 equipped with a full-ball angular contact ball bearing 1, the diameter of the rotating shaft 12 can be reduced by setting the shoulder diameter D3, which is the outer diameter of the regulating member 13, to be equal to or greater than the inner ring shoulder diameter D2. In addition, the same effects as those of the rotation mechanism of the fifth embodiment can be achieved.

[0071] 13 , in a rotation mechanism 9 equipped with a full-ball angular contact ball bearing 1, the outer ring 3 may be integrally provided with the housing 14 of the rotation mechanism 9. "Integrated" means that the outer ring 3 and the housing 14 are not formed by joining multiple elements but are formed as part or the whole of a single object from a single material by, for example, forging or machining.

[0072] In this way, in a rotation mechanism 9 equipped with a cageless, full-ball angular contact ball bearing 1, if the outer ring 3 is provided integrally with the housing 14 of the rotation mechanism 9, and the contact angle is in the range of 40° to 50° and W / Dw (see Figure 7) is in the range of 0.15 or more, high rigidity, high load capacity, etc. can be achieved without increasing the size.

[0073] <Axle Unit> The rotation mechanism 9 shown in Figure 14 is a vehicle power unit, or so-called axle unit, provided on a vehicle, and includes a double-row angular contact ball bearing 1 assembled back-to-back and a traction motor M with a power generator function. The outer ring 3 of the angular contact ball bearing 1 is a rotating ring, and the inner ring 2 integrated with the shaft is a fixed ring. A brake rotor BR and a wheel (not shown) are attached to a wheel mounting flange 3F provided on the outboard end of the outer ring 3, overlapping in the axial direction. When this rotation mechanism 9 is configured as shown in the partial views of Figures 10 to 13, the effects described above can be achieved.

[0074] The rotation mechanisms 9 in Figures 10 to 13 may be used in the main bearing portion of a reducer 10 of, for example, a robot or construction machine. In other words, the reducer 10 may be equipped with any of the rotation mechanisms 9 described above. Angular contact ball bearings can also be used in face-to-face combinations, parallel combinations, etc. Angular contact ball bearings can also be used in multi-row combinations of three or more rows. Angular contact ball bearings and rotation mechanisms can also be used for applications other than reducers.

[0075] As described above, the preferred embodiment has been described with reference to the drawings, but various additions, modifications, and deletions can be made without departing from the spirit of the present invention. Therefore, such additions, modifications, and deletions are also included in the scope of the present invention.

[0076] DESCRIPTION OF SYMBOLS 1...Angular contact ball bearing 2...Inner ring 3...Outer ring 4...Balls 9, 9A...Rotation mechanism 10...Reduction gear 11...Inner ring shoulder deformation suppression means 12...Rotating shaft 13...Regulating member 14...Housing

Claims

1. An angular contact ball bearing without a cage, comprising an inner ring, an outer ring, and a number of balls interposed between the inner ring and the outer ring, wherein the surface roughness of the balls is 0.06 μm Ra or less, and the kinetic viscosity of the lubricant (40°C) is 46 cst or more and 220 cst or less.

2. An angular contact ball bearing as defined in claim 1, wherein the lubricant is grease, and the consistency of the grease is from No. 1 to No.

00.

3. An angular contact ball bearing as claimed in claim 1 or 2, wherein the balls have a class of 40 or less.

4. An angular contact ball bearing as set forth in claim 1 or 2, wherein the surface roughness of the balls is 0.04 μm Ra or less, and the kinetic viscosity (40° C.) of the lubricant is 68 cst or more and 150 cst or less.

5. An angular contact ball bearing according to claim 1 or 2, wherein the material of the balls is bearing steel.

6. The angular contact ball bearing according to claim 5, wherein the balls are surface-hardened.

7. The angular contact ball bearing according to claim 6, wherein the surface hardening treatment is nitriding.

8. A rotating mechanism comprising an angular ball bearing according to any one of claims 1 to 7.

9. A rotating mechanism as claimed in claim 8, in which the inner ring and the shaft are integrated.

10. A rotating mechanism according to claim 8, wherein the outer ring and the housing are integrated.

11. A reducer equipped with a rotation mechanism according to any one of claims 8 to 10.

12. An angular contact ball bearing having an inner ring and an outer ring and a number of balls interposed between the inner ring and the outer ring, wherein the contact angle is between 40° and 50°, the ratio W / Dw of the axial length W of the outer peripheral surface on the back side of the inner ring to the ball diameter Dw which is the diameter of the balls is between 0.15 and 0.35, and the ratio V / Dw of the axial length V of the inner peripheral surface on the back side of the outer ring to the ball diameter Dw is between 0.15 and 0.

35.

13. An angular contact ball bearing according to claim 12, which is a cageless angular contact ball bearing.

14. A rotating mechanism equipped with an angular contact ball bearing including an inner ring, an outer ring, and a plurality of balls interposed between the inner ring and the outer ring, wherein an inner ring shoulder deformation suppression means is provided to suppress deformation of the inner ring shoulder, and the angular contact ball bearing has a contact angle of 40° or more and 50° or less, and the ratio V / Dw of the axial length V of the inner peripheral surface on the back side of the outer ring to the ball diameter Dw, which is the diameter of the balls, is 0.15 or more.

15. A rotating mechanism according to claim 14, comprising an angular contact ball bearing without a cage.

16. A rotating mechanism as claimed in claim 14 or 15, wherein the inner ring shoulder deformation suppression means is formed by integrating the inner ring with the rotating shaft of the rotating mechanism.

17. A rotating mechanism as claimed in claim 14 or 15, in which the inner ring shoulder deformation suppression means is a member facing the back surface of the inner ring, the shoulder diameter of which is equal to or larger than the inner ring shoulder diameter.

18. A rotating mechanism as claimed in claim 17, wherein the member facing the back surface of the inner ring is the rotating shaft of the rotating mechanism or an annular regulating member.

19. A rotating mechanism equipped with an angular ball bearing including an inner ring, an outer ring, and a plurality of balls interposed between the inner ring and the outer ring, wherein the outer ring is integrally formed with a housing of the rotating mechanism, the angular ball bearing has a contact angle of 40° or more and 50° or less, and the ratio W / Dw of the axial length W of the outer peripheral surface on the back side of the inner ring to the ball diameter Dw, which is the diameter of the balls, is 0.15 or more.

20. A rotating mechanism according to claim 19, comprising an angular contact ball bearing without a cage.

21. A reducer equipped with the rotation mechanism according to claim 14 or 15.

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