Rolling bearing, rotary device, and manufacturing method of rolling bearing

Abstract

Provided are a rolling bearing capable of suppressing an adverse condition caused by creep and the like, a rotary device, and a manufacturing method of a rolling bearing. A rolling bearing (1) includes: an inner ring (10) and an outer ring (20) disposed coaxially with each other; and a rolling element (30) disposed between the inner ring (10) and the outer ring (20). A covering film (81, 82) containing a mixture of calcium sulfonate and calcium carbonate or a compound obtained from calcium sulfonate and calcium carbonate is formed on at least one of an inner peripheral surface (10a) of the inner ring (10) and an outer peripheral surface (20b) of the outer ring (20).

Description

Technical Field

[0001] This invention relates to rolling bearings, rotating equipment, and methods for manufacturing rolling bearings. Background Technology

[0002] Rolling bearings typically include: an outer ring and an inner ring arranged coaxially; a plurality of rolling elements disposed between the inner and outer rings; and a retainer that holds the rolling elements in a rolling manner. Such rolling bearings are used in rotating equipment such as fan motors. Ball bearings, which use balls as rolling elements, are suitable for rotating equipment with shafts where the rotating body rotates at high speeds.

[0003] In recent years, high-speed rotation has become a common requirement for rotating equipment. If the rotation of such equipment becomes high-speed, there is a possibility of creep caused by the rotation of the fixed rings in the inner and outer rings of the rolling bearings. Additionally, there is a possibility of fretting wear caused by the vibrating movement of the fixed rings. Creep and fretting wear can sometimes lead to damage, abnormal heating, rust, and other adverse conditions in rolling bearings caused by abrasive powder. As a countermeasure against adverse conditions caused by creep, it is proposed to apply urea grease to the surface of the rolling bearing where friction increases, thereby reducing the friction on that surface (for example, see Patent Document 1). Prior art literature Patent documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 2013-60990. Summary of the Invention The problem that the invention aims to solve

[0005] However, in rolling bearings coated with lubricants such as urea grease, the suppression of adverse conditions such as creep can sometimes become insufficient due to lubricant depletion caused by prolonged use.

[0006] One objective of this invention is to provide a rolling bearing, a rotating device, and a method for manufacturing a rolling bearing capable of suppressing adverse conditions caused by creep and the like. Solution for solving the problem

[0007] One aspect of the present invention relates to a rolling bearing comprising: an inner ring and an outer ring arranged coaxially to each other; and a rolling element disposed between the inner ring and the outer ring, wherein at least one of the inner circumferential surface of the inner ring and the outer circumferential surface of the outer ring is formed with a coating film comprising a mixture of calcium sulfonate and calcium carbonate or a compound obtained from calcium sulfonate and calcium carbonate.

[0008] Based on this structure, the coating film is a hard film with excellent frictional properties. Therefore, it can suppress adhesive wear caused by metal-to-metal contact during creep or fretting wear, and suppress the generation of heat or wear powder. In particular, when the contact object is made of a material containing iron (steel, stainless steel, etc.), if friction occurs between the contact object and the contact object, a film can form on the sliding surface, further improving wear resistance and rust prevention. The coating film has a high rust prevention effect, thus inhibiting rusting even in high temperature / high humidity environments.

[0009] Preferably, the aforementioned covering film is formed only on the inner circumferential surface of the inner ring and the outer circumferential surface of the inner ring.

[0010] Based on this configuration, the torque smoothness during the operation of the rolling bearing can be improved and noise can be suppressed.

[0011] Preferably, the aforementioned covering film is formed only on the aforementioned outer peripheral surface of the aforementioned outer ring and the aforementioned outer peripheral surface of the aforementioned outer ring.

[0012] Based on this configuration, the torque smoothness during the operation of the rolling bearing can be improved and noise can be suppressed.

[0013] Alternatively, the aforementioned covering film may be formed on at least one of the axial end face of the aforementioned inner ring and the axial end face of the aforementioned outer ring.

[0014] Based on this configuration, even when the end face is in contact with other components, it can suppress wear and heat generation.

[0015] Preferably, the aforementioned covering film contains at least one of calcium soap, calcium complex soap, and calcium salt.

[0016] Based on this composition, the rust prevention and wear resistance are further improved.

[0017] Preferably, the aforementioned covering film contains a base oil.

[0018] Based on this composition, the lubricity of the coating film is improved by using base oil.

[0019] Alternatively, a rust-preventive layer may be formed on the entire surface of the aforementioned inner ring and the entire surface of the aforementioned outer ring, with the aforementioned masking film formed on the aforementioned rust-preventive layer.

[0020] Based on this structure, rust prevention can be achieved even in areas where no protective film is formed.

[0021] Preferably, the aforementioned covering film contains a solid lubricant.

[0022] Based on this configuration, wear at the contact points between rolling bearings and shafts can be suppressed.

[0023] One aspect of the present invention relates to a rotating device comprising: the aforementioned rolling bearing; a rotating body having a shaft portion; and a base supporting the aforementioned rotating body, wherein the aforementioned rolling bearing is assembled to the aforementioned base to rotatably support the aforementioned shaft portion.

[0024] Based on this structure, the coating film is a hard film with excellent frictional properties. Therefore, it can suppress adhesive wear caused by metal-to-metal contact during creep or fretting wear, and suppress the generation of heat or wear powder. In particular, when the contact object is made of a material containing iron (steel, stainless steel, etc.), if friction occurs between the contact object and the contact object, a film can form on the sliding surface, further improving wear resistance and rust prevention. The coating film has a high rust prevention effect, thus inhibiting rusting even in high temperature / high humidity environments.

[0025] One aspect of the present invention relates to a rotating device comprising a rotating body having a shaft, a base supporting the rotating body, and a rolling bearing mounted on the base and supporting the shaft in a rotatable manner. The rolling bearing has an inner ring and an outer ring arranged coaxially with each other, and a rolling element disposed between the inner ring and the outer ring. At least one of the areas of the rolling bearing contact in the outer peripheral surface of the shaft and the areas of the rolling bearing contact in the inner peripheral surface of the base is formed with a coating film comprising a mixture of calcium sulfonate and calcium carbonate or a compound obtained from calcium sulfonate and calcium carbonate.

[0026] Based on this design, it can suppress adhesive wear caused by metal-to-metal contact during creep or fretting wear, and inhibit the generation of heat or wear powder. It can also inhibit rusting even in high temperature / high humidity environments.

[0027] One aspect of the present invention relates to a method for manufacturing a rolling bearing in which rolling elements are disposed between an inner ring and an outer ring arranged coaxially. The method includes a step of forming a masking film on at least one of the inner circumferential surface of the inner ring and the outer circumferential surface of the outer ring by applying a grease composition comprising a mixture of calcium sulfonate and calcium carbonate or a compound obtained from calcium sulfonate and calcium carbonate. In this step, the masking film is formed on at least one of the inner circumferential surface of the inner ring and the outer circumferential surface of the outer ring by applying the grease composition using a coating component.

[0028] According to this method, the bonding strength of the aforementioned covering film with respect to at least one of the inner peripheral surface of the aforementioned inner ring and the outer peripheral surface of the aforementioned outer ring can be improved. The effects of the invention

[0029] According to one aspect of the present invention, it is possible to provide rolling bearings and rotating devices that can suppress adverse conditions caused by creep and the like. Attached Figure Description

[0030] Figure 1 This is a longitudinal cross-sectional view illustrating an embodiment of the fan motor. Figure 2 This is a longitudinal cross-sectional view of the first rolling bearing according to the first embodiment. Figure 3 This is a longitudinal cross-sectional view of the first rolling bearing in the second embodiment. Figure 4 This is a longitudinal cross-sectional view of the first rolling bearing in the third embodiment. Figure 5 This is an exploded view of a longitudinal section showing a portion of a fan motor according to another embodiment. Detailed Implementation

[0031] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. Furthermore, in the following description, components having the same or similar functions will be labeled with the same reference numerals. Also, repeated descriptions of these components will sometimes be omitted.

[0032] Figure 1 This is a longitudinal cross-sectional view illustrating an embodiment of the fan motor. Figure 1 The fan motor 100 shown is an example of a rotating device. The fan motor 100 includes a rotating body 110, a base 120, a drive unit 130, and a first rolling bearing 1 and a second rolling bearing 2. The rotating body 110 has a shaft portion 111. The base 120 supports the rotating body 110. The drive unit 130 rotates the rotating body 110 relative to the base 120. The drive unit 130, the first rolling bearing 1, and the second rolling bearing 2 are assembled to the base 120. The first rolling bearing 1 and the second rolling bearing 2 support the shaft portion 111 in a rotatable manner. The first rolling bearing 1 and the second rolling bearing 2 are examples of "rolling bearings".

[0033] In the following description, the rolling bearing may sometimes be referred to simply as a bearing. In this embodiment, the direction in which the central axis O of the shaft portion 111 of the rotating body 110 extends is called the axial direction. The direction orthogonal to the central axis O and extending radially from the central axis O is called the radial direction. The direction of rotation around the central axis O is called the circumferential direction. One of the directions parallel to the axial direction and pointing in opposite directions is defined as upward (first direction). The other of the directions parallel to the axial direction and pointing in opposite directions is defined as downward (second direction).

[0034] The base 120 has a cylindrical portion 121 extending in the axial direction. A shaft portion 111 of a rotating body 110 is inserted into the cylindrical portion 121. The cylindrical portion 121 is made of metal, for example. Preferably, the cylindrical portion 121 is formed of a metal containing iron (steel, stainless steel, etc.). The material of the cylindrical portion 121 is not particularly limited. The cylindrical portion 121 may also be formed, for example, of a metal not containing iron (brass, etc.), resin, etc.

[0035] The rotating body 110 is positioned above the base 120. The rotating body 110 includes a shaft portion 111 and a fan 112. The shaft portion 111 is made of metal, for example. Preferably, the shaft portion 111 is formed of a metal containing iron (steel, stainless steel, etc.). The material of the shaft portion 111 is not particularly limited. The shaft portion 111 may also be formed of, for example, a metal not containing iron (brass, etc.), resin, etc. The fan 112 is connected to the shaft 111 outside the cylinder 121. The fan 112 is fixed to the upper end of the shaft 111.

[0036] The fan 112 includes a flange 113, a peripheral wall portion 114, and a plurality of blades 115. The flange 113 extends radially outward from the upper end of the shaft portion 111. The flange 113 is integrally formed throughout the circumferential direction of the shaft portion 111. The peripheral wall portion 114 extends downward from the outer periphery of the flange 113. The peripheral wall portion 114 is radially spaced relative to the cylinder portion 121 and covers the entire circumference of the cylinder portion 121. The plurality of blades 115 are arranged circumferentially spaced on the radially outward side of the peripheral wall portion 114.

[0037] The drive unit 130 is a motor. The drive unit 130 includes a stator 131 with coils and a rotor 132 with magnets. The stator 131 is fixed to the base 120 on the outside of the shaft portion 111. The rotor 132 is fixed to the peripheral wall portion 114 of the fan 112 on the radially outer side of the stator 131.

[0038] The first bearing 1 and the second bearing 2 are located between the inner circumferential surface of the cylindrical portion 121 and the outer circumferential surface of the shaft portion 111. The first bearing 1 and the second bearing 2 are ball bearings. The first bearing 1 and the second bearing 2 are coaxially arranged. The first bearing 1 and the second bearing 2 are spaced apart and arranged side by side in the axial direction. The first bearing 1 is located closer to the center of gravity of the rotating body 110 than the second bearing 2. The first bearing 1 is located higher than the second bearing 2.

[0039] The first bearing 1 is inserted into the cylinder 121 from above. The lower end of the first bearing 1 is restricted from downward displacement by a step on the inner circumferential surface of the cylinder 121. The first bearing 1 is in contact with the force-applying member 102. The force-applying member 102 is a coil spring. The force-applying member 102 is externally inserted into the shaft 111 of the rotating body 110 and is arranged coaxially with the central axis O.

[0040] The force-applying component 102 is positioned in a compressed state between the first bearing 1 and the flange 113 of the fan 112. The upper end of the force-applying component 102 contacts the flange 113 from below. The lower end of the force-applying component 102 contacts the inner ring of the first bearing 1 from above. Thus, the force-applying component 102 applies a force downward to the first bearing 1 relative to the rotating body 110.

[0041] The second bearing 2 is inserted into the cylinder 121 from below. The outer ring of the second bearing 2 is restricted from upward displacement by the step on the inner circumferential surface of the cylinder 121. The inner ring of the second bearing 2 contacts the C-ring 103 mounted on the lower end of the shaft 111 from above. Thus, the downward displacement of the second bearing 2 relative to the shaft 111 is restricted.

[0042] [First Implementation] Figure 2 This is a longitudinal cross-sectional view of the first rolling bearing according to the first embodiment. like Figure 2 As shown, the first bearing 1 includes an inner ring 10 and an outer ring 20 as raceways, a plurality of rolling elements 30, a retainer 40, and a pair of sealing components 50. The inner ring 10 and the outer ring 20 share a common axis about the central axis O. The second bearing 2 (see reference) Figure 1 It has the same configuration as the first bearing 1.

[0043] The inner ring 10 is provided as a rotating ring. The inner ring 10 is inserted into the shaft portion 111. The outer ring 20 is provided as a fixed ring. The outer ring 20 surrounds the inner ring 10 from the outer side in the radial direction, with an annular space between the outer ring 20 and the inner ring 10. A plurality of rolling elements 30 are disposed between the inner ring 10 and the outer ring 20, and are held in a rolling manner by a retainer 40. The retainer 40 holds each rolling element 30 in a rotatable manner with the plurality of rolling elements 30 evenly arranged in the circumferential direction. The sealing member 50 covers the annular space between the inner ring 10 and the outer ring 20 from the outer side in the axial direction.

[0044] The outer ring 20 is formed in a circular shape from a metal material such as stainless steel or bearing steel. The outer ring 20 is not limited to metal and can also be formed from other materials. The outer ring 20 includes an outer ring body 21 and a protrusion 22. The width (axial dimension) of the outer ring body 21 is the same as the width (axial dimension) of the inner ring 10. The protrusion 22 protrudes from the inner circumferential surface of the outer ring body 21 toward the radial direction. The protrusion 22 is integrally formed throughout the circumferential direction of the outer ring body 21. The protrusion 22 is formed in the portion of the outer ring body 21 including the central part in the axial direction. The width (axial dimension) of the protrusion 22 is smaller than the width (axial dimension) of the outer ring body 21. The width (axial dimension) of the protrusion 22 is larger than the outer diameter of the rolling element 30.

[0045] On the inner circumferential surface of the protrusion 22, an outer ring track surface 23 is formed that is recessed outward in the radial direction. The outer ring track surface 23 is arc-shaped in cross-sectional view, extending along the outer surface of the rolling element 30. The outer ring track surface 23 is formed in a ring shape extending circumferentially over the entire circumference of the inner circumferential surface of the protrusion 22. The outer ring track surface 23 is formed in the central portion of the inner circumferential surface of the protrusion 22, including the axial direction. The inner diameter of the portion of the inner circumferential surface of the protrusion 22 other than the outer ring track surface 23 is constant. The protrusion 22 has a pair of end faces 22a facing the axial direction. The end faces 22a are formed by the difference in inner diameter between the protrusion 22 and the outer ring body 21. The end faces 22a are parallel to both the radial and circumferential directions.

[0046] The outer ring body 21 has a pair of inner peripheral surfaces 21a extending from the outer periphery of each end face 22a of the protrusion 22 to the opening edge of the outer ring 20.

[0047] The inner ring 10 is formed in a circular shape from a metal material such as stainless steel or bearing steel. The inner ring 10 is not limited to metal and can also be formed from other materials. An inner ring track surface 11, recessed radially inward, is formed on the outer circumferential surface of the inner ring 10. The inner ring track surface 11 is arc-shaped in cross-sectional view, extending along the outer surface of the rolling element 30. The inner ring track surface 11 is formed in a ring shape extending circumferentially across the entire circumference of the outer circumferential surface of the inner ring 10. The inner ring track surface 11 is formed in the central portion of the outer circumferential surface of the inner ring 10, including the axial direction. The inner ring track surface 11 faces the outer ring track surface 23 radially. The outer diameter of the portion of the outer circumferential surface of the inner ring 10 other than the inner ring track surface 11 is constant.

[0048] Multiple rolling elements 30 are formed in a spherical shape. Examples of materials used to construct the rolling elements 30 include metals (stainless steel, bearing steel, etc.) and ceramics (zirconia, etc.). The rolling elements 30 are disposed between the outer ring track surface 23 and the inner ring track surface 11. The rolling elements 30 are supported by the outer ring track surface 23 and the inner ring track surface 11 in a rolling manner. The multiple rolling elements 30 are spaced apart in the circumferential direction by a retainer 40.

[0049] The retainer 40 is integrally formed in a ring shape from synthetic resin or metal. The retainer 40 is coaxially arranged with respect to the central axis O. The retainer 40 includes an annular portion 41 and a plurality of column portions 42. The annular portion 41 is formed in a ring shape and is positioned below the plurality of rolling elements 30. The column portions 42 protrude upward from the annular portion 41. The plurality of column portions 42 are spaced apart in the circumferential direction. The plurality of column portions 42 are evenly arranged in the circumferential direction. A pair of adjacent column portions 42 in the circumferential direction forms a ball cavity between them. The ball cavity penetrates the retainer 40 in the radial direction. The ball cavity opens upward at the upper end face of the retainer 40. The number of ball cavities corresponds to the number of rolling elements 30, holding each rolling element 30 in a rolling manner. Thus, the retainer 40 evenly arranges the rolling elements 30 in a circumferentially spaced manner.

[0050] The sealing member 50 is formed in the shape of an annular plate. The sealing member 50 is coaxially arranged with the central axis O. The sealing member 50 is fitted onto the outer ring 20. One sealing member 50 is arranged on each side of the plurality of rolling elements 30 in the axial direction. The sealing member 50 includes a base portion 51, a step portion 52, a cover portion 53, and a locking portion 54. The base portion 51 overlaps with the end face 22a of the protrusion 22 of the outer ring 20 from the outer side in the axial direction. The step portion 52 extends from the inner periphery of the base portion 51 to the outer side in the axial direction. The cover portion 53 extends from the outer end edge of the step portion 52 in the axial direction to the inner side in the radial direction. The locking portion 54 extends from the outer periphery of the base portion 51 to the outer side in both the radial and axial directions.

[0051] The sealing member 50 extends radially such that it at least crosses the center of the rolling element 30 when viewed from above. In this embodiment, the cover portion 53 overlaps with the center of the rolling element 30 when viewed from above. However, the stepped portion 52 may also extend axially outward and radially inward from the inner periphery of the base portion 51, overlapping the center of the rolling element 30 when viewed from above. The inner periphery of the cover portion 53 is configured with a gap between it and the outer peripheral surface of the inner ring 10. The outer periphery of the locking portion 54 engages with the inner peripheral surface 21a of the outer ring body 21 from the inner side in the axial direction. Thus, the sealing member 50 is fixed to the outer ring 20.

[0052] The first bearing 1 includes a grease 60. The grease 60 contains a base oil and a thickener. For its excellent heat resistance, the thickener is preferably a urea compound. The grease 60 is disposed in the annular space between the inner ring 10 and the outer ring 20. The amount of grease 60 applied and the application location are not particularly limited. The grease 60 may, for example, cover the entire circumference and contact the inner circumferential surface 20a of the outer ring 20. The grease 60 may also contact the outer circumferential surface 10b of the inner ring 10. The grease 60 may be disposed only on one side relative to the axial direction of the rolling element 30, or it may be disposed on both sides in the axial direction. The grease 60 may also be applied to the rolling element 30. The grease 60 may also cover the entire area of ​​the inner circumferential surface of the outer ring 20, the outer circumferential surface of the inner ring 10, and the surface of the rolling element 30.

[0053] A masking film 81 is formed on the inner circumferential surface 10a of the inner ring 10 of the first bearing 1. The masking film 81 may be formed on at least a portion of the inner circumferential surface 10a of the inner ring 10, but ideally, it may be formed over the entire area of ​​the inner circumferential surface 10a. The masking film 81 is not formed on the outer circumferential surface 10b of the inner ring 10. That is, the masking film 81 is formed only on the inner circumferential surface 10a, which is the inner circumferential surface 10a of the inner circumferential surface 10b.

[0054] In this embodiment, the masking film 81 is not formed on the end faces 10c of both inner rings 10 in the axial direction. That is, it can be said that the masking film 81 is only formed on the inner peripheral surface 10a, the outer peripheral surface 10b, and the end face 10c.

[0055] A masking film 82 is formed on the outer peripheral surface 20b of the outer ring 20. The masking film 82 may be formed on at least a portion of the outer peripheral surface 20b of the outer ring 20, but ideally, it may be formed over the entire area of ​​the outer peripheral surface 20b of the outer ring 20. The masking film 82 is not formed on the inner peripheral surface 20a of the outer ring 20. That is, the masking film 82 is formed only on the outer peripheral surface 20b of the inner peripheral surface 20a and the outer peripheral surface 20b.

[0056] In this embodiment, the masking film 82 is not formed on the end faces 20c of both outer rings 20 in the axial direction. That is, it can be said that the masking film 82 is only formed on the outer peripheral surface 20b of the inner peripheral surface 20a, outer peripheral surface 20b, and end face 20c.

[0057] The masking film 81 is formed only on the inner peripheral surface 10a of the inner peripheral surface 10a and the outer peripheral surface 10b. The masking film 82 is formed only on the outer peripheral surface 20b of the inner peripheral surface 20a and the outer peripheral surface 20b. By forming the masking films 81 and 82 in this way, the rotating body 110 (see reference) Figure 1 The torque smoothness (the property of the torque being the same during rotation) becomes good when the first bearing 110 is rotating (i.e., when the first bearing 1 is operating). In addition, the noise when the rotating body 110 is rotating can be suppressed.

[0058] The following reasoning can be made regarding the improvement of torque smoothness and noise characteristics by forming the shielding films 81 and 82 as described above. The calcium compounds contained in the shielding films 81 and 82 have the potential to form hard particles. Therefore, the shielding films 81 and 82 sometimes have a rough, uneven surface due to the hard particles. It is assumed that if the rough surface unevenness comes into contact with the rolling element 30, then in the rotating body 110 (refer to...) Figure 1 When rotating, it causes a decrease in torque smoothness and an increase in noise.

[0059] In contrast, the masking film 81 is formed only on the inner peripheral surface 10a of the inner peripheral surface 10a and the outer peripheral surface 10b. The masking film 82 is formed only on the outer peripheral surface 20b of the inner peripheral surface 20a and the outer peripheral surface 20b. Therefore, even if the masking films 81 and 82 have large surface irregularities, these surface irregularities will not contact the rolling element 30. Thus, the rotating body 110 (refer to...) Figure 1 The torque smoothness during rotation becomes better. In addition, the noise during the rotation of the rotating body 110 can be suppressed. There is no masking film on the outer peripheral surface 10b of the inner ring 10 and the inner peripheral surface 20a of the outer ring 20, but grease 60 is filled between the inner ring 10 and the outer ring 20, so the outer peripheral surface 10b and the inner peripheral surface 20a have good rust prevention.

[0060] The covering films 81 and 82 contain a mixture of calcium sulfonate and calcium carbonate, or a compound obtained from calcium sulfonate and calcium carbonate. The term "mixture of calcium sulfonate and calcium carbonate, or a compound obtained from calcium sulfonate and calcium carbonate" is simply referred to as "calcium sulfonate composition". Calcium sulfonate composition is also called calcium sulfonate complex.

[0061] Calcium sulfonate is represented, for example, by the following general formula (1).

[0062] [R1-SO3]2Ca…(1) R1 is preferably an alkyl, alkenyl, alkylnaphthyl, dialkylnaphthyl, alkylphenyl, or high-boiling-point petroleum fraction residue. R1 preferably has 6 to 28 carbon atoms. For example, R1 is an alkyl group with 6 to 28 carbon atoms or an alkylphenyl group with 7 to 28 carbon atoms.

[0063] Examples of calcium sulfonates include calcium salts of alkyl aromatic sulfonic acids such as dodecylbenzenesulfonic acid, octadecylbenzenesulfonic acid, dilauryl cetylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, paraffin-substituted benzenesulfonic acid, polyolefin-substituted benzenesulfonic acid, and polyisobutylene-substituted benzenesulfonic acid; calcium salts of aromatic sulfonic acids; calcium salts of alkyl sulfonic acids; and calcium salts of petroleum sulfonic acids.

[0064] As a calcium sulfonate composition, a compound represented by the following general formula (2) is preferred.

[0065] [R2-SO3]2Ca·nCaCO3…(2) (R2 is an alkyl group having 6 to 28 carbon atoms or an alkylphenyl group having 7 to 28 carbon atoms. n is an integer from 6 to 50.)

[0066] "R2" can be, for example, a straight-chain or branched alkyl group having 6 to 28 carbon atoms. "R2" can also be, for example, a straight-chain alkyl group bonded to a phenyl group having 7 to 28 carbon atoms. "R2" can also be, for example, a branched alkyl group bonded to a phenyl group having 7 to 28 carbon atoms. In particular, alkylphenyl groups are preferred, especially straight-chain alkyl groups bonded to phenyl groups. The alkylphenyl group preferably has 12 to 24 carbon atoms, particularly preferably 12, 14, 18, or 20. The alkyl group is preferably at the para-position of the alkylphenyl group.

[0067] It is believed that the calcium sulfonate composition adopts a structure in which calcium carbonate is configured within a polymer (micelle) formed by the calcium sulfonate molecules.

[0068] Alternatively, in addition to the calcium sulfonate composition, the covering films 81 and 82 may also contain at least one of calcium soap, calcium complex soap, and calcium salt. One of the calcium soap, calcium complex soap, and calcium salt may be used, or two or more may be used in combination.

[0069] Calcium soaps are calcium salts of carboxylic acids (e.g., fatty acids). The number of carbon atoms in a carboxylic acid can range from 10 to 36. Examples of carboxylic acids include long-chain fatty acids such as stearic acid, lauric acid, myristic acid, palmitic acid, oleic acid, and behenic acid. Specific examples of calcium soaps include calcium bis(behenic acid), calcium bis(stearic acid), and calcium bis(12-hydroxystearic acid). They can be used alone or in combination of two or more.

[0070] Calcium complex soaps are calcium salts of carboxylic acids. "Complex" means using multiple carboxylic acids. Both long-chain and short-chain fatty acids can be used as carboxylic acids. For example, long-chain fatty acids with 12 or more carbon atoms (e.g., 12 to 24) and short-chain fatty acids with 10 or fewer carbon atoms (e.g., 2 to 6) can be used in calcium complex soaps. Examples of long-chain fatty acids include stearic acid, lauric acid, myristic acid, palmitic acid, oleic acid, and behenic acid. Examples of short-chain fatty acids include acetic acid, propionic acid, and butyric acid. A specific example of a calcium complex soap is a complex soap of calcium stearate and calcium acetate.

[0071] Calcium salts are compounds in which the hydrogen atoms of an acid are replaced by calcium ions. Specific examples of calcium salts include calcium acetate, calcium borate, and calcium phosphate. They can be used alone or in combination of two or more.

[0072] Calcium sulfonate compositions, by comprising at least one of calcium soap, calcium complex soap, and calcium salt, can adjust thickening ability, dropping point, abrasion resistance, extreme pressure properties, etc. Therefore, they can enhance the function of calcium sulfonate compositions as thickeners.

[0073] The calcium sulfonate composition is preferably mixed with a base oil. Thus, the base oil is contained in the covering films 81 and 82. Base oils can include mineral oils, synthetic oils, and blends thereof. As long as lubrication is not impaired, base oils can also include fatty oils and other greases.

[0074] Examples of synthetic oils include hydrocarbon synthetic oils, ester synthetic oils, phenyl ether synthetic oils, glycol synthetic oils, silicone synthetic oils, and fluorinated synthetic oils. One type or a mixture of two or more types can be used as a synthetic oil. Hydrocarbon synthetic oils are particularly preferred.

[0075] Examples of hydrocarbon synthetic oils include polyalphaolefins (PAO), ethylene-alphaolefin copolymers, polybutene, alkylbenzenes, and alkylnaphthalenes. Polyalphaolefins are particularly preferred.

[0076] Examples of monomers forming polyalphaolefins include alphaolefins having 3 to 22 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tetracene, 1-tetradecene, 1-pentadene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadene, 1-eicosene, 1-cuicosodeene, and 1-cuicosodeene. In particular, alphaolefins having 6 to 18 carbon atoms, such as 1-decene, are especially preferred.

[0077] Examples of polyα-olefins include dimers to heptamers of α-olefins. For example, dimers, trimers, or tetramers of α-olefins are preferred. Hydrocarbon synthetic oils can be mixed with ester synthetic oils, phenyl ether synthetic oils, etc., as long as the lubricity is not impaired.

[0078] Examples of mineral oils include cycloalkanes, paraffins, and mixtures thereof.

[0079] The kinematic viscosity and pour point of the base oil are not particularly defined. For example, the kinematic viscosity of the base oil at 40°C could be 15 mm. 2 / s or higher, 80mm 2 / s or less. The kinematic viscosity at 40°C can be determined by the method specified in "5. Test method for kinematic viscosity" of "JIS K2283:2000". The pour point of the base oil is preferably below -30°C, more preferably below -40°C.

[0080] The base oil ratio of the masking films 81 and 82 can be 40% by mass or more and 90% by mass or less. The calcium sulfonate composition ratio of the masking films 81 and 82 can be 10% by mass or more and 60% by mass or less.

[0081] Additives such as antioxidants, corrosion inhibitors, rust inhibitors, extreme pressure agents, solid lubricants, wear-resistant agents, thickeners, oiliness agents, anti-wear agents, structure stabilizers, colorants, detergent dispersants, color stabilizers, metal inerting agents, viscosity index improvers, pour point depressants, and surfactants can also be added to the calcium sulfonate composition. These additives can be added, for example, to grease compositions comprising the calcium sulfonate composition and base oil. Thus, the additives are included in the coating films 81 and 82.

[0082] As solid lubricants, one or more of molybdenum disulfide, graphite, and polytetrafluoroethylene (PTFE) can be listed. If a solid lubricant is used, even when the inner ring 10 is relative to the shaft portion 111 (see reference...) Figure 1 Even under heavy loads and simultaneous rotation, wear at the contact points between the shaft 111 and the inner ring 10 can be further suppressed. If a solid lubricant is used, even when the outer ring 20 is subjected to heavy loads and rotates simultaneously, wear can be further suppressed at the contact points between the shaft 111 and the inner ring 10. Figure 1 Even when subjected to heavy loads and rotating simultaneously, it can further suppress wear at the contact points between the cylinder 121 and the outer ring 20.

[0083] In the first bearing 1 and the second bearing 2, covering films 81 and 82 are respectively formed on the inner peripheral surface 10a of the inner ring 10 and the outer peripheral surface 20b of the outer ring 20. However, the covering film only needs to be formed on at least one of the inner peripheral surface 10a of the inner ring 10 and the outer peripheral surface 20b of the outer ring 20. For example, the covering film may also be formed on only one of the inner peripheral surface 10a and the outer peripheral surface 20b.

[0084] like Figure 1 As shown, the first bearing 1 and the second bearing 2 are located between the inner circumferential surface of the cylindrical portion 121 and the outer circumferential surface of the shaft portion 111. The inner circumferential surface of the cylindrical portion 121 and the outer circumferential surface of the shaft portion 111 become the contact objects of the covering film.

[0085] When both the inner circumferential surface of the cylinder 121 and the outer circumferential surface of the shaft 111 are made of a metal containing iron (steel, stainless steel, etc.), the covering film only needs to be formed on both the inner circumferential surface 10a of the inner ring 10 and the outer circumferential surface 20b of the outer ring 20. However, if one of the inner circumferential surface of the cylinder 121 and the outer circumferential surface of the shaft 111 is not made of a metal containing iron, the covering film may not need to be formed on the circumferential surface (inner circumferential surface 10a or outer circumferential surface 20b) facing the contacting object.

[0086] According to this configuration, wear of the contact object (the inner circumferential surface of the cylindrical portion 121 or the outer circumferential surface of the shaft portion 111) made of materials other than ferrous metals can be suppressed due to the covering film. Wear of the contact object can be suppressed because, since there is no facing covering film, even if the covering film has surface irregularities, these irregularities will not contact the contact object. Furthermore, when the contact object is made of materials other than ferrous metals, adhesive wear is less likely to occur.

[0087] The covering films 81 and 82 can be formed, for example, by applying a grease composition comprising a calcium sulfonate composition and a base oil to the inner peripheral surface 10a of the inner ring 10 and the outer peripheral surface 20b of the outer ring 20. In the grease composition, the calcium sulfonate composition acts as a thickener.

[0088] When applying the grease composition to the inner peripheral surface 10a and the outer peripheral surface 20b, it is ideal to use a soft application tool such as cloth or paper to apply the grease composition to the inner peripheral surface 10a and the outer peripheral surface 20b. By applying the grease composition to the inner peripheral surface 10a and the outer peripheral surface 20b, the bonding strength of the masking films 81 and 82 with respect to the inner peripheral surface 10a and the outer peripheral surface 20b can be improved. By applying the grease composition to the inner peripheral surface 10a and the outer peripheral surface 20b, a hard masking film 81 and 82 can be reliably formed.

[0089] Alternatively, the grease composition may contain not only the calcium sulfonate composition but also other thickener components. Commonly used thickeners can be used as these thickener components. Examples of thickener components include, for example, metallic soaps and non-soap types. Examples of metallic soaps include, for example, one or more of lithium soaps, lithium complex soaps, aluminum soaps, and aluminum complex soaps. Examples of non-soap types include, for example, one or more of urea compounds, polytetrafluoroethylene (PTFE), organo-modified bentonite, and silica gel.

[0090] The total amount of thickener components (thickeners other than calcium sulfonate compositions) and additives can be, for example, less than 30% by mass in the grease composition (excluding diluent oil). The total amount of thickener components and additives can be more than 0.1% by mass in the grease composition (excluding diluent oil).

[0091] The amount of additive added can be 0.1% by mass or more in the grease composition (excluding diluent oil). The amount of additive added can be less than 10% by mass in the grease composition (excluding diluent oil).

[0092] Regarding calcium sulfonate compositions, separately synthesized calcium sulfonate compositions can also be dispersed in base oils. Calcium sulfonate compositions can also be dispersed in base oils by synthesis within the base oil.

[0093] Diluent oil can also be added to the grease composition. The viscosity of the diluent oil is lower than that of the base oil. Examples of diluent oils include hexane. Using diluent oil reduces the viscosity of the grease composition, thus facilitating the formation of a coating film 81, 82 through the application of the grease composition. The diluent oil can also be mineral oil, synthetic oil, or a mixture thereof. The calcium sulfonate composition of the grease composition can also be dispersed in the diluent oil.

[0094] When a diluent oil is added to the grease composition, after the grease composition is applied, the diluent oil evaporates, but other components (base oil, etc.) remain at the applied area, forming a film 81, 82. High-viscosity base oils are difficult to evaporate and have high heat resistance. Therefore, when using a high-viscosity base oil, good lubrication characteristics are easily obtained even when the inner ring 10 and outer ring 20 rotate relative to the shaft portion 111 and the barrel portion 121. To obtain good characteristics, the kinematic viscosity of the base oil at 40°C can be 80 mm. 2 / s or higher. Considering the ease of application of the grease composition, the kinematic viscosity of the base oil at 40°C is preferably 40 mm. 2 / s or higher, 150mm 2 / s or less.

[0095] An example illustrating the method of manufacturing the first bearing 1. (Step 1: Bearing Assembly) Assemble the first bearing 1 having an inner ring 10, an outer ring 20, rolling elements 30, a retainer 40, and a sealing component 50 (see reference). Figure 2 ).

[0096] (Step 2: Formation of the covering film) The grease composition is applied to the inner circumferential surface 10a of the inner ring 10 and the outer circumferential surface 20b of the outer ring 20. Ideally, a soft application tool, such as cloth or paper, is used to apply the grease composition to the inner circumferential surface 10a and the outer circumferential surface 20b. The application tool can be any part that is softer than the surfaces being coated (inner circumferential surface 10a and outer circumferential surface 20b). By allowing the diluent oil in the grease composition coating to dry, a masking film 81, 82 can be formed.

[0097] By applying and coating the grease composition to the inner peripheral surface 10a and the outer peripheral surface 20b, the bonding strength of the masking films 81 and 82 with respect to the inner peripheral surface 10a and the outer peripheral surface 20b can be improved. By applying and coating the grease composition to the inner peripheral surface 10a and the outer peripheral surface 20b, a hard masking film 81 and 82 can be reliably formed. The second bearing 2 can be manufactured in the same way as the first bearing 1.

[0098] Figure 1The fan motor 100 shown can be assembled by assembling bearings 1 and 2 with pre-formed covering films 81 and 82 onto the shaft portion 111 and the cylinder portion 121.

[0099] In this embodiment, the first bearing 1 and the second bearing 2 are provided with shielding films 81 and 82. These shielding films 81 and 82 are hard films with excellent frictional properties, thus reducing friction and suppressing phenomena caused by creep or fretting wear. For example, they can suppress adhesive wear caused by metal-to-metal contact and suppress the generation of heat or wear powder. In particular, when the contact surfaces of the first bearing 1 and the second bearing 2 (the inner circumferential surface of the cylinder 121, the outer circumferential surface of the shaft 111, the force-applying component 102, etc.) are made of a material containing iron (steel, stainless steel, etc.), if friction occurs between them, a film can be formed on the sliding surface, further improving wear resistance and rust prevention. The covering films 81 and 82 have high rust prevention effect, and therefore can inhibit rust formation even in high temperature / high humidity environments. (Refer to...) Figure 1 Rusting of items such as )

[0100] When the covering films 81 and 82 contain at least one of calcium soap, calcium complex soap and calcium salt, the rust prevention and wear resistance are further improved.

[0101] When the masking films 81 and 82 contain base oil, the grease composition tends to remain on the coated area and easily forms the masking film when the masking films 81 and 82 are formed by applying the grease composition. When the masking films 81 and 82 contain base oil, the lubricity of the masking films 81 and 82 is improved by the base oil.

[0102] In the fan motor 100 of this embodiment, shielding films 81 and 82 are formed on the first bearing 1 and the second bearing 2, thereby reducing friction between the first bearing 1 and the second bearing 2 and suppressing phenomena caused by creep or fretting wear. For example, it can suppress adhesive wear caused by metal contact and suppress the generation of heat or wear powder. In addition, it can suppress rusting even in high temperature / high humidity environments.

[0103] [Second Implementation] Figure 3 This is a longitudinal cross-sectional view of the first rolling bearing in the second embodiment. like Figure 3As shown, a masking film 281 is formed on the inner circumferential surface 10a and the end face 10c of the inner ring 10 of the first bearing 201. The masking film 281 is not formed on the outer circumferential surface 10b of the inner ring 10. That is, the masking film 281 is formed only on the inner circumferential surface 10a, the outer circumferential surface 10b, and the end face 10c. The masking film 281 is formed continuously from the inner circumferential surface 10a to the end face 10c.

[0104] The masking film 281 may be formed on at least a portion of the end face 10c of the inner ring 10, but ideally, the masking film 281 may be formed over the entire area of ​​the end face 10c.

[0105] A covering film 282 is formed on the outer peripheral surface 20b and end face 20c of the outer ring 20 of the first bearing 201. The covering film 282 is not formed on the inner peripheral surface 20a of the outer ring 20. That is, the covering film 282 is formed only on the outer peripheral surface 20b and end face 20c of the inner peripheral surface 20a, the outer peripheral surface 20b, and the end face 20c. The covering film 282 is continuously formed from the outer peripheral surface 20b to the end face 20c.

[0106] The masking film 282 may be formed on at least a portion of the end face 20c of the outer ring 20, but ideally, the masking film 282 may be formed over the entire area of ​​the end face 20c.

[0107] In addition to being formed on end faces 10c and 20c, the masking films 281 and 282 are the same as those in the first embodiment (see reference 81 and 82). Figure 2 They have the same composition. The second bearing has the same configuration as the first bearing 201.

[0108] The first bearing 201 of this embodiment, like the first bearing 1 of the first embodiment, can reduce friction and suppress phenomena caused by creep or fretting wear through the covering films 281 and 282. For example, it can suppress adhesive wear caused by metal-to-metal contact and suppress the generation of heat or wear powder. When the contact objects (the inner circumferential surface of the cylinder 121, the outer circumferential surface of the shaft 111, the force-applying component 102, etc.) are formed of a material containing iron (steel, stainless steel, etc.), the wear resistance or rust prevention effect is further improved. The covering films 281 and 282 have a high rust prevention effect, so even in high temperature / high humidity environments, the first bearing 201, the second bearing, the cylinder 121, and the shaft 111 (see reference) can be suppressed. Figure 1 Rusting of items such as )

[0109] In this embodiment, the first bearing 201 also has a covering film 281, 282 formed on the end face 10c of the inner ring 10 and the end face 20c of the outer ring 20. Therefore, even when the end faces 10c, 20c are in contact with other components (e.g., the cylinder 121, the force-applying component 102, etc.), it can suppress wear and heat generation.

[0110] exist Figure 3 The first bearing 201 shown has shielding films 281 and 282 formed on both the end face 10c of the inner ring 10 and the end face 20c of the outer ring 20, but the shielding film only needs to be formed on at least one of the end face 10c of the inner ring 10 and the end face 20c of the outer ring 20. In the first bearing 201, a masking film 281 is formed on both end faces 10c of the inner ring 10, but the masking film 281 may be formed on at least one of the two end faces 10c. A masking film 282 is formed on both end faces 20c of the outer ring 20, but the masking film 282 may be formed on at least one of the two end faces 20c.

[0111] [Third Implementation] Figure 4 This is a longitudinal cross-sectional view of the first rolling bearing in the third embodiment. like Figure 4 As shown, in the first bearing 301, a rust-preventive layer 91 is formed on the entire surface of the inner ring 10 (inner circumferential surface 10a, outer circumferential surface 10b, and end face 10c) by applying rust-preventive oil. A rust-preventive layer 92 is formed on the entire surface of the outer ring 20 (inner circumferential surface 20a, outer circumferential surface 20b, and end face 20c) by applying rust-preventive oil. The rust-preventive oil can be obtained, for example, by blending well-known rust inhibitors with base oils such as mineral oils and synthetic oils.

[0112] In addition to having anti-rust layers 91 and 92, the first bearing 301 is the same as the first bearing 1 in the first embodiment (see reference). Figure 2 The second bearing has the same configuration as the first bearing 301. Ideally, the rust inhibitor should not contain components that degrade the bearing characteristics (noise characteristics, torque smoothness, etc.) of the grease composition, such as hard particulate components.

[0113] A masking film 381 is formed on the anti-rust layer 91 formed on the inner peripheral surface 10a of the inner ring 10. A masking film 382 is formed on the anti-rust layer 92 formed on the outer peripheral surface 20b of the outer ring 20. Masking films 381 and 382 are the same as the masking films 81 and 82 of the first embodiment (see reference). Figure 2 They have the same composition.

[0114] The first bearing 301 has anti-rust layers 91 and 92, so that even in areas where the covering film 381 and 382 is not formed (such as the outer peripheral surface 10b of the inner ring 10 and the inner peripheral surface 20a of the outer ring 20), the anti-rust effect can be obtained.

[0115] [Another implementation method] Figure 1The fan motor 100 shown has covering films 81 and 82 formed on the first bearing 1 and the second bearing 2, but the fan motor (rotating device) of the embodiment may also have a covering film formed on the contact object of the rolling bearing. For example, a covering film may be formed on both the rolling bearing and the contact object, or a covering film may be formed only on the contact object of the rolling bearing and the contact object. That is, the covering film only needs to be formed on at least one of the rolling bearing and the contact object.

[0116] Figure 5 This is an exploded view of a longitudinal section of a portion of a fan motor 200 according to another embodiment. like Figure 5 As shown, in the fan motor 200, the first bearing 1 abuts against the outer peripheral surface of the shaft portion 111, the inner peripheral surface of the cylinder portion 121, and the force-applying component 102 (see reference). Figure 1 The lower end of ). The covering film can be formed in one or more of (i) to (iii) shown below. (i) The area where bearings 1 and 2 contact on the outer peripheral surface of shaft portion 111. (ii) The area where bearings 1 and 2 contact on the inner peripheral surface of cylindrical portion 121. (iii) Force-applying member 102 (see reference) Figure 1 The area in contact with the first bearing 1 in the lower end face of the bearing.

[0117] The fan motor 200 is located at the points where the first bearing 1 and the second bearing 2 do not have a protective film, and at the points where the shaft portion 111 and the cylinder portion 121 have protective films 481 and 482 respectively, which are related to the fan motor 100 (see reference). Figure 1 )different.

[0118] A masking film 481 is formed in the area of ​​the outer peripheral surface 111b of the shaft portion 111 that contacts the inner rings 10 of the first bearing 1 and the second bearing 2. A masking film 482 is formed in the area of ​​the inner peripheral surface 121a of the cylindrical portion 121 that contacts the outer rings 20 of the first bearing 1 and the second bearing 2. Masking films 481 and 482 are related to masking films 81 and 82 (see reference). Figure 2 They have the same composition.

[0119] In the fan motor 200 of this embodiment, shielding films 481 and 482 are formed on the shaft portion 111 and the cylinder portion 121, thereby reducing friction and suppressing phenomena caused by creep or micro-vibration wear. For example, it can suppress adhesive wear caused by metal contact and suppress the generation of heat or wear powder. In addition, it can suppress rusting even in high temperature / high humidity environments.

[0120] Furthermore, the present invention is not limited to the embodiments described above with reference to the accompanying drawings, and various modifications can be considered within its technical scope. In the above embodiments, a fan motor is exemplified as a rotating device, but the rotating device is not limited to this. For example, the present invention can also be applied as a rotating device to dental handheld devices or spindle motors of hard disk drives.

[0121] exist Figure 5 The fan motor 200 shown does not have a shielding film formed on the first bearing 1, but a shielding film may also be formed on the first bearing 1 (see reference). Figure 2 ).exist Figure 5 The fan motor 200 shown has a covering film formed on both the outer peripheral surface 111b of the shaft portion 111 and the inner peripheral surface 121a of the cylinder portion 121, but the covering film only needs to be formed on at least one of the outer peripheral surface 111b and the inner peripheral surface 121a. Symbol Explanation

[0122] 1, 201, 301……First rolling bearing (rolling bearing) 2……Second rolling bearing (rolling bearing) 10……Inner ring 10a……Inner circumferential surface 10b……Outer circumferential surface 10c……End face 20……Outer ring 20a……Inner circumferential surface 20b……Outer circumferential surface 20c……End face 30……Rolling element 81, 82, 281, 282, 381, 382, ​​481, 482……Covering film 91, 92……Rust-proof layer 100, 200……Fan motor (rotating equipment) 110……Rotating element 111……Shaft 120……Base.

Claims

1. A rolling bearing comprising: The inner and outer rings are arranged coaxially with each other; and Rolling elements and lubricating grease are disposed between the inner ring and the outer ring. A coating film comprising a mixture of calcium sulfonate and calcium carbonate, or a compound obtained from calcium sulfonate and calcium carbonate, is formed on the inner circumferential surface of the inner ring and the outer circumferential surface of the outer ring. The covering film is not formed on the outer peripheral surface of the inner ring and the inner peripheral surface of the outer ring.

2. The rolling bearing according to claim 1, wherein, The covering film is formed on at least one of the axial end face of the inner ring and the axial end face of the outer ring.

3. The rolling bearing according to claim 1, wherein, The covering film contains at least one of calcium soap, calcium complex soap, and calcium salt.

4. The rolling bearing according to claim 1, wherein, The covering film contains base oil.

5. The rolling bearing according to claim 1, wherein, A rust-preventive layer is formed on the entire surface of both the inner and outer rings. The covering film is formed on the anti-rust layer.

6. The rolling bearing according to claim 1, wherein, The covering film contains a solid lubricant.

7. A rotating device comprising: The rolling bearing according to any one of claims 1 to 6; A rotating body having a shaft; and The base, which supports the rotating body, The rolling bearing is assembled on the base to support the shaft in a rotatable manner.

8. A rotating device, wherein, It comprises a rotating body having a shaft, a base supporting the rotating body, and a rolling bearing mounted on the base and supporting the shaft in a rotatable manner. The rolling bearing has an inner ring and an outer ring arranged coaxially with each other, and rolling elements and grease disposed between the inner ring and the outer ring. At least one of the rolling bearing contact area on the outer peripheral surface of the shaft and the rolling bearing contact area on the inner peripheral surface of the base is formed with a coating film comprising a mixture of calcium sulfonate and calcium carbonate or a compound obtained from calcium sulfonate and calcium carbonate. The covering film was not formed on the rolling bearing.

9. A method for manufacturing a rolling bearing, comprising a rolling bearing having rolling elements and lubricating grease disposed between an inner ring and an outer ring arranged coaxially, wherein... The process involves forming a coating film on the inner circumferential surface of the inner ring and the outer circumferential surface of the outer ring by applying a grease composition comprising a mixture of calcium sulfonate and calcium carbonate or a compound derived from calcium sulfonate and calcium carbonate. In this process, the masking film is formed by applying the grease composition to the inner circumferential surface of the inner ring and the outer circumferential surface of the outer ring using a coating component. The grease composition is not applied to the outer circumferential surface of the inner ring and the inner circumferential surface of the outer ring.

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