Roller and roller bearing

Abstract

To provide a roller and a roller bearing capable of preventing electrolytic corrosion by an inexpensive bearing and coping with higher speed rotation.SOLUTION: The roller 3 is a ceramic roller interposed between an inner ring and an outer ring, and a roller outer peripheral surface 3a part of the roller 3 includes crowning parts 5 and 5 of both axial end parts and a straight part 6 for connecting these crowning parts 5 and 5, and has a chamfering part 8 between the crowning part 5 of the roller 3 and a roller end surface 7. The roller 2 is a roller bearing satisfying all of the following expressions (1) and (2). 0.85 (L-2Lc) ≤ Ls formula (1) 0. 0005Dw ≤ Dx formula (2) Where L is a total length of the roller 3, Lc is an axial length of the chamfered portion 8, Ls is a length of the straight portion 6, Dw is a roller diameter, and Dx is a drop amount that is a difference in generatrix height caused by the crowning portion 5 SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to rollers and roller bearings, and in particular to rollers and roller bearings used in devices such as general-purpose motors, generators, and main motors for railway vehicles, which have a structure in which current may flow inside the bearing during use, but in which excessive loads are not applied to the bearings. [Background technology]

[0002] There is a risk of electrolytic corrosion occurring in bearings used in devices with a structure in which current may flow inside the bearing. Conventionally, techniques have been proposed for forming a ceramic insulating coating on the outer ring, etc., and for forming a resin insulating coating on the surface of the bearing ring.

[0003] Furthermore, a prior art rolling bearing has been proposed that offers better performance than the ceramic-sprayed insulated bearings or resin-insulated bearings conventionally used for electric motors (Patent Document 1). As shown in FIG. 7, this rolling bearing is a cylindrical roller bearing comprising a pair of raceways 50, 51 and a plurality of rolling elements 52 interposed between the pair of raceways 50, 51. The rolling elements 52 are ceramic rollers with no crowning on the rolling surface. The surface of at least one of the raceways 50 facing the other raceway is formed by crowning portions 50a, 50a at both axial ends and a straight portion 50b between the crowning portions 50a, 50a. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-2235 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, as motor performance has improved, there is a greater possibility that high-frequency currents will flow inside bearings, necessitating improved bearing insulation. Furthermore, as the rotational speeds used have also increased, bearings with even better rotational performance are required. Using ceramic rollers improves insulation and allows for higher rotational speeds thanks to their low specific gravity, but ceramics are hard and difficult to process, resulting in higher costs.

[0006] An object of the present invention is to provide a roller and a roller bearing that are inexpensive, prevent electrolytic corrosion, and are capable of handling higher speed rotation. [Means for solving the problem]

[0007] The roller of the present invention is a ceramic roller interposed between an inner ring and an outer ring, the roller outer peripheral surface of the roller including crowned portions at both axial ends and a straight portion connecting these crowned portions, and a chamfered portion between the crowned portion of the roller and the roller end surface, The roller satisfies the following formulas (1) and (2) of pattern A. Pattern A 0.85(L-2Lc)≦Ls…Formula (1) 0.0005Dw≦Dx…Formula (2) where L is the total length of the roller, Lc is the axial length of the chamfered portion, Ls is the length of the straight portion, Dw is the roller diameter, and Dx is the drop amount, which is the difference in generatrix height caused by the crowning portion. The "rollers" are cylindrical rollers, needle rollers, or tapered rollers.

[0008] This configuration uses ceramic rollers, improving insulation performance and reducing their specific gravity compared to steel rollers, enabling high-speed rotation. The length (Ls) of the roller's straight portion is set to at least 85% of the total roller length (L) minus the axial length of the chamfered portion, and the drop (Dx) is set to at least 0.05% of the roller diameter (Dw). This prevents surface pressure that would affect functionality under market conditions, providing superior high-speed rotation performance compared to conventional ceramic-sprayed insulated bearings or resin-coated insulated bearings. While ceramic rollers are hard and expensive to process, they can be manufactured inexpensively because only the minimum required drop (Dx) is required. Regarding the insulation performance of the roller bearing, using ceramic rollers themselves eliminates conductive paths between the inner and outer ring raceways, virtually eliminating the risk of electrolytic corrosion compared to conventional ceramic-sprayed insulated bearings or resin-coated insulated bearings.

[0009] It is more desirable that the rollers satisfy both of the following formulas (3) and (4) of pattern B. Pattern B 0.90(L-2Lc)≦Ls…Equation (3) 0.001Dw≦Dx…Formula (4) In this case, by reviewing the shape of the outer surface of the ceramic roller and minimizing the amount of processing required, it is possible to reduce manufacturing costs compared to conventional technology while still maintaining sufficient performance for use.

[0010] In the roller, the crowning portion and the chamfered portion may be smoothly connected, and the straight portion and the crowning portion may be smoothly connected. This configuration makes it possible to avoid edge contact of the rollers with the raceway surfaces of the inner and outer rings, thereby preventing stress concentration on a portion of the raceway surface.

[0011] The rollers may be made of ceramics containing silicon nitride. Silicon nitride exhibits excellent properties such as high-temperature mechanical strength, thermal shock resistance, wear resistance, corrosion resistance, electrical insulation, and high toughness. Therefore, rollers made of ceramics containing silicon nitride exhibit excellent performance as rollers, and can provide a roller bearing that is stable over the long term.

[0012] The roller bearing of the present invention is a roller bearing comprising an inner ring, an outer ring, and a plurality of rollers interposed between the inner ring and the outer ring, characterized in that the rollers are any of the rollers described above. The roller bearing may be used in an electric motor or generator. As the performance of electric motors or generators improves, electrolytic corrosion can be prevented by applying a roller bearing with improved insulation performance, even under conditions where high-frequency current flows inside the bearing. [Effects of the Invention]

[0013] The roller of the present invention is a ceramic roller interposed between an inner ring and an outer ring, the roller outer peripheral surface of the roller including crowned portions at both axial ends and a straight portion connecting these crowned portions, and a chamfered portion between the crowned portion of the roller and the roller end surface, The roller satisfies the following formulas (1) and (2) of pattern A. Pattern A 0.85(L-2Lc)≦Ls…Formula (1) 0.0005Dw≦Dx…Formula (2) where L is the total length of the roller, Lc is the axial length of the chamfered portion, Ls is the length of the straight portion, Dw is the roller diameter, and Dx is the drop amount, which is the difference in generatrix height caused by the crowning portion. This makes it possible to prevent electrolytic corrosion with an inexpensive bearing and to accommodate higher speed rotation. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a longitudinal sectional view of a roller bearing according to a first embodiment of the present invention. [Figure 2]FIG. [Figure 3] FIG. 3 is a partially enlarged view showing the details of part III in FIG. 2. [Figure 4] 10 is a cross-sectional view of an electric motor showing an example in which the roller bearing is applied to an electric motor. FIG. [Figure 5] FIG. 4 is a vertical cross-sectional view of a roller bearing according to a second embodiment of the present invention. [Figure 6] FIG. 10 is a perspective view of a roller bearing according to a third embodiment of the present invention. [Figure 7] FIG. 1 is a longitudinal sectional view of a conventional cylindrical roller bearing. DETAILED DESCRIPTION OF THE INVENTION

[0015] [First embodiment: NU type] A roller bearing according to an embodiment of the present invention will be described with reference to Figures 1 to 3. The roller bearing according to the embodiment is a single-row cylindrical roller bearing that is applicable to, for example, general-purpose motors, generators, and traction motors for railway vehicles. In this specification, the roller bearing may be simply referred to as a "bearing."

[0016] <Outline of cylindrical roller bearing structure> The NU-type cylindrical roller bearing 10 shown in Figure 1 comprises an inner ring 1, an outer ring 2, a plurality of cylindrical rollers (rollers) 3 interposed between raceway surfaces 1a, 2a of the inner ring 1 and outer ring 2, and a cage 4 that holds these cylindrical rollers 3. The inner ring 1 is ribless, while the outer ring 2 has ribs 2b, 2b on both axial sides of the raceway surface 2a. The cylindrical roller bearing 10 is a so-called radial roller bearing, in which the outer ring 2 is arranged radially outward from the outer circumferential surface of the inner ring 1.

[0017] The inner ring 1 and outer ring 2 are made of a metal material such as bearing steel, mechanical structural alloy, or mechanical structural carbon steel. The cylindrical rollers 3 are made of ceramics, which will be described later. The cylindrical rollers 3 are independently tradeable on the market. The cylindrical roller bearing 10 holds the cylindrical rollers 3 in pockets in the cage 4, but the cage may be omitted as a full complement bearing. The axial direction of the central axes of the inner ring 1 and outer ring 2 or a direction parallel to this axial direction is referred to as the "axial direction" C1. The direction perpendicular to the "axial direction" C1 is referred to as the "radial direction." Furthermore, in a cylindrical roller, the axial direction refers to the axial direction of the axis 3X of the cylindrical roller 3.

[0018] In the NU-type cylindrical roller bearing 10, the assembly of the outer ring 2, multiple cylindrical rollers 3, and cage 4 can be separated in the axial direction C1 from the inner ring 1. The cage 4 holds the multiple cylindrical rollers 3 at regular intervals in the circumferential direction. The cage 4 is a machined or stamped cage made of metal or resin. Examples of metals for the cage include cold- or hot-rolled steel, brass, etc. The cylindrical rollers 3 may also be simply referred to as rollers 3.

[0019] <Detailed roller structure> As shown in Figure 2, the rollers 3 are made of ceramics containing silicon nitride. Specifically, the rollers 3 are made of ceramics whose main component is silicon nitride (Si3N4). Ceramics are not limited to silicon nitride, but also include zirconia (Z r ) or alumina (Al2O3), etc.

[0020] The outer peripheral surface 3a of each roller 3 includes crowned portions 5, 5 at both axial ends and a straight portion 6 connecting these crowned portions 5, 5. In a cross section of the roller 3 cut along a plane including the roller axis center 3X, the straight portion 6 is linear, and the diameter of each crowned portion 5 gradually decreases toward both axial ends. Between the crowned portion 5 of each roller 3 and the roller end surface 7, there is a chamfered portion 8. The end face of the roller 3 has a so-called flat shape. The chamfered portion 8 is rounded. The center of the radius of curvature of this rounded chamfer is located inside the roller 3 in Figure 2. The crowned portion 5 may have, for example, a crowned shape with a single radius, a compound radius, or a logarithmic crowned shape. As shown in Figure 3, the crowned portion 5 and the chamfered portion 8 of the roller 3 are smoothly connected, and the straight portion 6 and the crowned portion 5 are also smoothly connected. A connecting portion A between the crowning portion 5 and the chamfered portion 8, and a connecting portion C between the straight portion 6 and the crowning portion 5 are each shown imaginarily by dashed lines in FIG.

[0021] As shown in Fig. 2, the axial length Lc of the rounded chamfered portion 8 is specified based on, for example, the allowable limit value rsmax of the measured chamfer dimension of a roller in JIS B 1506, which conforms to ISO 3096 of the International Organization for Standardization (ISO). However, the axial length Lc of the chamfered portion 8 may be a rounded chamfer that does not conform to JIS B 1506.

[0022] <parameters> The roller 3 satisfies both of the following formulas (1) and (2). 0.85(L-2Lc)≦Ls…Formula (1) 0.0005Dw≦Dx…Formula (2) where L is the total length of the roller 3, Lc is the axial length of the chamfered portion 8, Ls is the length of the straight portion 6, Dw is the roller diameter, and Dx is the drop amount which is the difference in generatrix height caused by the crowning portion 5. According to equations (1) and (2), this roller is characterized by having a longer length Ls of the straight portion 6 than conventional rollers. By actively machining the portion corresponding to the imaginary line B shown in FIG. 3, the chamfer R can be used to determine the drop amount of the crowning portion 5. By determining the minimum drop amount Dx required for the crowning portion 5 shown in FIG. 2, the bearing function can be satisfied at low cost. The length Ls and drop amount Dx of the straight portion 6 are measured as follows. The cross-sectional profile of the roller is obtained by a shape measuring instrument, and the length of the straight portion 6 is calculated to be Ls. The boundary between the straight portion 6 and the crowning portion 5 is set to a position where the drop amount (reduction in outer diameter) from the straight portion 20A is 1 μm. The drop amount Dx is a measured value of the difference in height between the straight portion 6 and the generatrix of the crowning portion 5. The overall length L of the roller is the distance between both end faces of the roller. It is measured using a block gauge and a dial gauge.

[0023] It is more desirable that roller 3 satisfy both of the following formulas (3) and (4). 0.90(L-2Lc)≦Ls…Equation (3) 0.001Dw≦Dx…Formula (4)

[0024] <Action and effect> 1 explained above, the use of ceramic rollers 3 improves insulation performance and has a lower specific gravity than steel rollers, making it possible to handle high-speed rotation. As shown in Figure 2, the length Ls of the straight portion 6 of roller 3 is set to 85% or more of the value obtained by subtracting the axial length of chamfered portion 8 from the total length L of roller 3, and the drop amount Dx is set to 0.05% or more of roller diameter Dw.

[0025] As a result, no surface pressure that would affect functionality is generated under market usage conditions, and they are superior to conventional ceramic-sprayed insulated bearings or resin-coated insulated bearings in terms of high-speed rotation. Ceramic rollers are also hard and expensive to process, but they can be manufactured inexpensively because they only require the minimum required drop amount Dx. In terms of the insulating performance of roller bearings, by making the rollers themselves out of ceramic, no conductive paths are created on the raceway surfaces of the inner and outer rings, and there is almost no risk of electrolytic corrosion compared to conventional ceramic-sprayed insulated bearings or resin-coated insulated bearings.

[0026] When both of the above formulas (3) and (4) are satisfied, by reviewing the shape of the outer peripheral surface of the ceramic roller and minimizing the amount of processing required, it is possible to reduce manufacturing costs compared to conventional technology while still maintaining sufficient performance for use.

[0027] As shown in Figure 3, the crowning portion 5 and the chamfered portion 8 are smoothly connected, and the straight portion 6 and the crowning portion 5 are also smoothly connected. This prevents the rollers 3 from making edge contact with the raceway surfaces 1a and 2a of the inner and outer rings 1 and 2 in Figure 1, and prevents stress concentration from occurring in parts of the raceway surfaces 1a and 2a.

[0028] The rollers 3 are made of ceramics containing silicon nitride. Silicon nitride exhibits excellent properties such as high-temperature mechanical strength, thermal shock resistance, wear resistance, corrosion resistance, electrical insulation, and high toughness. For this reason, rollers 3 made of ceramics containing silicon nitride exhibit excellent performance as rollers, and can provide a roller bearing 10 that is stable over the long term.

[0029] <Example of application to electric motors> As shown in Fig. 4, the electric motor 30 has a stator 34 fixed to the housing 9, a rotor 35 facing the stator 34 radially inward with a predetermined radial gap therebetween, and a shaft 31 that rotatably supports the rotor 35. Roller bearings 10, 10 are provided on both sides of the housing 9 at a predetermined distance in the axial direction, and the shaft 31 is rotatably supported by these roller bearings 10, 10. The electric motor 30 may be, for example, a surface permanent magnet motor, i.e., an SPM synchronous motor or an IPM (Interior Permanent Magnet) synchronous motor.

[0030] Alternatively, various types of motors, such as a switched reluctance motor (SR motor) or an induction motor (IM), can be used for the motor 30. Instead of the motor 30, roller bearings 10, 10 can be used in a generator 30A that has only the power generation function. In this case, the generator 30A is structurally similar to the motor 30.

[0031] <Other embodiments> In the following description, parts corresponding to matters previously described in each embodiment are given the same reference numerals, and duplicated description will be omitted. When only a 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 partially combine embodiments as long as there is no particular problem with the combination.

[0032] [Second embodiment: N type] In an N-type cylindrical roller bearing 10A shown in Figure 5, the outer ring 2 has no rib, and the raceway surface 1a of the inner ring 1 has ribs 1b, 1b on both axial sides. In N-type cylindrical roller bearing 10A, the assembly of the inner ring 1, a plurality of cylindrical rollers 3, and a cage 4 can be separated in the axial direction C1 from the outer ring 2. The detailed structure of the rollers 3 is the same as in the first embodiment described above. Therefore, N-type cylindrical roller bearing 10A also achieves the same effects as the first embodiment.

[0033] [Third embodiment: tapered roller bearing] As shown in Figure 6, a tapered roller bearing 10B can also be used as the roller bearing according to the embodiment. The detailed structure of the tapered rollers, which are rollers 3, is the same as in the first embodiment described above. In this case, the roller diameter Dw used in the above formulas (2) and (4) is the roller diameter of the tapered rollers 3 at the axially intermediate portion. The tapered roller bearing 10B according to this embodiment also achieves the same effects as the first embodiment.

[0034] As the roller bearing according to the embodiment, a needle roller bearing, a double-row cylindrical roller bearing, a four-row cylindrical roller bearing, and a thrust roller bearing can also be applied. The roller bearing according to the embodiment may be applied to an axial gap type electric motor or generator.

[0035] Although the embodiments of the present invention have been described above, the disclosed embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0036] 1...inner ring, 2...outer ring, 3...cylindrical roller (roller), 3a...roller outer peripheral surface, 5...crowning portion, 6...straight portion, 7...roller end face, 8...chamfered portion, 10, 10A...cylindrical roller bearing, 10B...tapered roller bearing, 30...electric motor, 30A...generator

Claims

1. a ceramic roller interposed between an inner ring and an outer ring, the roller outer peripheral surface of each roller including crowned portions at both axial ends and a straight portion connecting these crowned portions, and a chamfered portion between the crowned portion and the roller end surface of each roller, The roller satisfies the following formulas (1) and (2) of pattern A. Pattern A 0.85(L-2Lc)≦Ls...Formula (1) 0.0005Dw≦Dx...Formula (2) where L is the total length of the roller, Lc is the axial length of the chamfered portion, Ls is the length of the straight portion, Dw is the roller diameter, and Dx is the drop amount which is the difference in generatrix height caused by the crowning portion.

2. 2. The roller according to claim 1, wherein the roller satisfies both of the following formulas (3) and (4) of pattern B: Pattern B 0.90(L-2Lc)≦Ls...Formula (3) 0.001Dw≦Dx...Formula (4)

3. 3. The roller according to claim 1, wherein the crowning portion and the chamfered portion are smoothly connected, and the straight portion and the crowning portion are smoothly connected.

4. 3. The roller according to claim 1, wherein the roller is made of ceramics containing silicon nitride.

5. A roller bearing comprising an inner ring, an outer ring, and a plurality of rollers interposed between said inner ring and said outer ring, wherein said rollers are rollers as defined in claim 1 or 2.

6. 6. A roller bearing according to claim 5, which is used in an electric motor or generator.

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