Rolling bearings

Abstract

To provide a rolling bearing capable of achieving low dust generation while suppressing deterioration in wear resistance and life.SOLUTION: A rolling bearing 1 comprises an inner ring 2, an outer ring 3, a rolling element 4, a sealing member 6 and a grease composition 7 sealed in a bearing inner space. The grease composition 7 contains a base oil and a thickener. The base oil contains a synthetic hydrocarbon oil and an ether oil, and is a mixed oil having a kinematic viscosity of 120 mm2 / s or more at 40°C, and the thickener is an aliphatic di-urea compound and an alicyclic di-urea compound, is contained in the amount of 12 pts.mass to 15 pts.mass based on 100 pts.mass of a total amount of the base oil and the thickener, has a worked penetration of 200 to 240 as measured in accordance with JIS K 2220, and contains an organic acid metal salt that is solid at 20°C.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a rolling bearing filled with a grease composition, and more particularly to a rolling bearing for use in rotating electrical machines such as servo motors and encoders. [Background technology]

[0002] Demand for servo motors is increasing, mainly for machine tools and robots, as they are equipped with detectors for position and speed, and are capable of high-precision positioning and fine-grained control of rotational speed. Among these, servo motors for robots are often used to drive joints, and are required to be small and high-output in order to increase the shaft speed and acceleration / deceleration of the joints. To achieve miniaturization, detectors and brakes are placed near rolling bearings, but if some of the grease inside the bearings splashes onto the detectors or brakes, it will cause a decrease in detection accuracy and braking performance, so the grease must be low-dust generating.

[0003] Dust generation occurs when heat generated by the rotation of a rolling bearing and an increase in pressure inside the bearing cause some of the grease to evaporate or scatter, and then be released outside the bearing. Effective ways to prevent dust generation include increasing the viscosity of the grease's base oil to increase the surface tension, or reducing the amount of base oil in the grease. However, this can also lead to insufficient supply (flow) of base oil to the rolling and sliding surfaces, which can cause excessive heating of the bearing, and damage such as surface roughness and wear on the rolling and sliding surfaces.

[0004] Conventionally, various grease compositions aimed at low dust generation have been studied. For example, Patent Document 1 discloses a grease composition having a kinetic viscosity of 30 mm at 40°C. 2 / s~180mm 2 The proposed grease composition comprises a base oil having a viscosity of 100 / s and containing at least one oil selected from synthetic hydrocarbon oils and ether oils, a thickener made of a urea compound, and further containing an additive made of only non-metallic elements in an amount of 0.1 to 1% by weight of the total amount of the grease.

[0005] In addition, Patent Document 2 discloses a rolling bearing unit that is incorporated in a motor that rotates forward and backward, in which a rolling bearing disposed near an encoder is made of at least one oil selected from synthetic hydrocarbon oils and ether oils, and has a kinetic viscosity of 80 mm at 40°C. 2 / s~120mm 2 It is described that the grease composition contains a base oil having a molecular weight of 100 to 2000 g / s. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 11-166191 [Patent Document 2] JP 2010-127344 A Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, as motors become smaller and more powerful, the environments in which bearings are used are becoming hotter, and they are increasingly being used in environments that are unfavorable to dust generation. In addition, even for rolling bearings that require low dust generation, durability such as wear resistance and grease life is also required. The grease composition described in Patent Document 1 is for rolling devices used in clean rooms such as semiconductor manufacturing facilities, and dust generation and durability at high temperatures have not been considered, which raises concerns. In addition, the grease composition described in Patent Document 2 is for use in bearing units for motors that rotate forward and backward, and it is considered that simply specifying the base oil and its kinetic viscosity may be insufficient in terms of wear resistance and grease life.

[0008] The present invention has been made in view of the above circumstances, and has an object to provide a rolling bearing that can realize low dust generation while suppressing deterioration in wear resistance and life. [Means for solving the problem]

[0009] The rolling bearing of the present invention has an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, seal members provided at openings at both axial ends of the inner ring and the outer ring, and a grease composition sealed in a space within the bearing, the grease composition containing a base oil and a thickener, the base oil containing a synthetic hydrocarbon oil and an ether oil, and having a kinetic viscosity of 120 mm at 40°C. 2 The thickener is an aliphatic diurea compound and an alicyclic diurea compound, and is contained in an amount of 12 to 15 parts by mass per 100 parts by mass of the total amount of the base oil and the thickener. The grease composition has a worked penetration of 200 to 240 as measured in accordance with JIS K 2220 and contains an organic acid metal salt that is solid at 20°C.

[0010] The organic acid metal salt is a sodium salt or a calcium salt. The organic acid metal salt is a metal salt of an organic carboxylic acid having 2 to 18 carbon atoms, and the grease composition does not contain an additive containing sulfur and phosphorus in its molecular structure.

[0011] The grease composition further contains an amine-based antioxidant, and the amine-based antioxidant is N-phenyl-N'-isopropyl-p-phenylenediamine (PIPA).

[0012] The sealing member is characterized in that it is made of nitrile rubber containing a trimellitic acid ester-based plasticizer.

[0013] The rolling bearing is characterized in that it is a bearing for a rotating electrical machine. Effect of the Invention

[0014] The rolling bearing of the present invention is characterized in that a grease composition is filled in the space inside the bearing, and in that grease composition, the base oil contains a synthetic hydrocarbon oil and an ether oil, and the kinetic viscosity at 40°C is 120 mm 2The thickener is an aliphatic diurea compound and an alicyclic diurea compound, and is contained in an amount of 12 to 15 parts by mass per 100 parts by mass of the total amount of the base oil and the thickener, has a worked penetration of 200 to 240, and contains an organic acid metal salt that is solid at 20° C., so that it is possible to realize low dust generation while suppressing deterioration in wear resistance and life. Specifically, it is considered that by adding an organic acid metal salt that is solid at 20° C. to a combination of a predetermined base oil and a predetermined thickener, the surface tension of the base oil is not affected, and when the supply of the base oil is insufficient and wear is a concern, the organic acid metal salt melts and can protect the steel surface as an extreme pressure agent.

[0015] The rolling bearing of the present invention is suitable for use in rotating electrical machines such as servo motors, for example, and can contribute to the miniaturization and increased output of such rotating electrical machines, leading to higher functionality.

[0016] Furthermore, since the sealing member is formed from nitrile rubber containing a trimellitate ester-based plasticizer, by using a low-volatility trimellitate ester-based plasticizer as the plasticizer, evaporation of the plasticizer itself is suppressed, further improving the low dust generation properties of the bearing. [Brief description of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of a deep groove ball bearing which is an example of a rolling bearing according to the present invention. [Diagram 2] 1 is a schematic diagram of a servomotor to which a rolling bearing according to the present invention is applied; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The grease composition for use in the rolling bearing of the present invention comprises a base oil having a specified kinetic viscosity, a specified thickener, and an additive, wherein the additive contains an organic acid metal salt that is solid at 20°C.

[0019] The base oil used in the above grease composition contains a synthetic hydrocarbon oil and an ether oil, and has a kinetic viscosity of 120 mm at 40°C. 2This kinematic viscosity is the kinematic viscosity of the mixed oil, and is 120 mm / s or more at 40°C. 2 / s~160mm 2 / s is preferred, 125mm 2 / s~140mm 2 / s is more preferred.

[0020] As the synthetic hydrocarbon oil, poly-α-olefin oil (PAO oil) is more preferable. PAO oil is a mixture of α-olefins or isomerized α-olefin oligomers or polymers. Specific examples of α-olefins include 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 1-docosene, and 1-tetradocosene, and mixtures thereof are usually used.

[0021] Examples of the ether oil include polyphenyl ether oil, alkyl diphenyl ether oil, alkyl triphenyl ether oil, and alkyl tetraphenyl ether oil. Among these, alkyl diphenyl ether oil is preferred from the viewpoint of durability at high temperatures, and it is more preferred that alkyl diphenyl ether oil is contained in an amount of 50 mass% or more of the entire base oil (mixed oil). Examples of the alkyl diphenyl ether oil include monoalkyl diphenyl ether oil, dialkyl diphenyl ether oil, and polyalkyl diphenyl ether oil.

[0022] The base oil may be a mixture of synthetic hydrocarbon oil and ether oil, or may further contain other oils. As the other oil, any oil that is normally used for rolling bearings may be used without any particular limitation. For example, mineral oils such as paraffinic mineral oil and naphthenic mineral oil, ester oil, silicone oil, fluorine oil, etc. may be used.

[0023] The thickener used in the grease composition is a mixture of an aliphatic diurea compound and an alicyclic diurea compound. These diurea compounds are obtained by reacting a diisocyanate component with a monoamine component. The aliphatic diurea compound is obtained from an aliphatic monoamine as a monoamine component and a diisocyanate component, and the alicyclic diurea compound is obtained from an alicyclic monoamine as a monoamine component and a diisocyanate component. Examples of the diisocyanate component include phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, and hexane diisocyanate. Examples of the aliphatic monoamine include hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine, stearylamine, and oleylamine. Examples of the alicyclic monoamine include cyclohexylamine. The content of the aliphatic diurea compound in the thickener is preferably greater than the content of the alicyclic diurea compound.

[0024] A base grease is obtained by blending a diurea compound as a thickener with a base oil. The base grease using a diurea compound as a thickener is produced by reacting a diisocyanate component with a monoamine component in the base oil. The thickener is contained in an amount of 12 to 15 parts by mass per 100 parts by mass of the total amount of the base oil and the thickener.

[0025] The organic acid metal salt used in the grease composition is a salt of an aliphatic compound or aromatic compound having a substituent, such as an organic carboxylic acid, an organic sulfonic acid such as an alkylbenzenesulfonic acid, an organic sulfuric acid such as an alkylsulfuric acid, an organic phosphonic acid such as an alkylphosphonic acid, or an organic phosphinic acid such as an alkylphosphinic acid, with a metal ion. The organic acid metal salt is solid at 20°C, that is, it is sufficient that the melting point is above 20°C, and the organic acid and metal ion constituting the organic acid metal salt can be appropriately selected. The melting point of the organic acid metal salt is preferably 100°C or higher, and more preferably 150°C or higher.

[0026] The metal constituting the organic acid metal salt may be any metal capable of forming a salt with the organic acid, and may be lithium, sodium, potassium, magnesium, calcium, barium, zinc, aluminum, etc. The metal salt is preferably a sodium salt or a calcium salt, and more preferably a sodium salt.

[0027] The organic acid constituting the organic acid metal salt may have a halogen group, a hydroxyl group, an amino group, an alkyl group, an alkoxy group, an epoxy group, or other substituent on the aliphatic group or aromatic group in the molecular structure. The organic acid preferably does not contain a sulfur atom or a phosphorus atom in the molecular structure, and more preferably has a constituent atom selected from carbon atoms, hydrogen atoms, nitrogen atoms, and oxygen atoms. Examples of such organic acids include organic carboxylic acids having 2 to 18 carbon atoms, such as acetic acid, propionic acid, butyric acid, hexanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, 12-hydroxystearic acid, oleic acid, and linoleic acid, among which organic carboxylic acids having 10 to 18 carbon atoms are preferred, and linear organic carboxylic acids having no substituent are more preferred.

[0028] Specific examples of organic acid metal salts that can be used include sodium acetate (melting point 324° C.), calcium acetate (melting point 160° C.), sodium stearate (melting point 220° C.), and calcium stearate (melting point 179° C.).

[0029] The amount of the organic acid metal salt in the grease composition is preferably 0.5 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, and even more preferably 1 to 3 parts by mass, per 100 parts by mass of the total amount of the base oil and thickener.

[0030] The grease composition preferably further contains an antioxidant as an additive. As the antioxidant, an amine-based antioxidant, a phenol-based antioxidant, a sulfur-based antioxidant, etc. can be used, and among these, an amine-based antioxidant is preferably used, and examples thereof include phenyl-1-naphthylamine, diphenyl-p-phenylenediamine, dipyridylamine, phenothiazine, N,N'-diisopropyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, and dialkyldiphenylamine (DDPA).

[0031] In addition, other additives such as rust inhibitors and oily agents such as esters and alcohols can be added to the grease composition as necessary. For example, it is preferable to add a rust inhibitor to ensure the rust-preventive performance of the grease itself. The rust inhibitor is not particularly limited, but an ester-based rust inhibitor is preferable. Examples of the ester-based rust inhibitor include partial esters of polyhydric alcohols such as sorbitan, sorbitol, pentaerythritol, sucrose, and glycerin with carboxylic acids such as oleic acid and lauric acid, and succinic acid half esters. The amount of the ester-based rust inhibitor is more preferably 0.2 to 0.6 parts by mass per 100 parts by mass of the total amount of the base oil and the thickener.

[0032] The grease composition preferably does not contain additives containing phosphorus or sulfur atoms in the molecular structure. As shown in the examples below, the inclusion of these additives results in a decrease in the surface tension of the base oil, which tends to increase the amount of dust generated. Examples of such additives include extreme pressure agents such as phosphate esters such as tricresyl phosphate, phosphite esters such as tricresyl phosphite, thiophosphates, thiophosphites, zinc alkyldithiophosphates (ZnDTP), molybdenum alkyldithiophosphates (MoDTP), and zinc dithiocarbamate (ZnDTC).

[0033] The worked penetration (JIS K 2220) of the above grease composition is in the range of 200 to 240. From the viewpoint of suppressing the amount of dust generation, the worked penetration is preferably in the range of 200 to 220.

[0034] The rolling bearing filled with the grease composition will be described with reference to FIG. 1. FIG. 1 is a cross-sectional view of a deep groove ball bearing. In the rolling bearing 1, an inner ring 2 having an inner ring raceway surface 2a on its outer circumferential surface and an outer ring 3 having an outer ring raceway surface 3a on its inner circumferential surface are concentrically arranged, and a plurality of rolling elements 4 are arranged between the inner ring raceway surface 2a and the outer ring raceway surface 3a. The rolling elements 4 are held by a cage 5. In addition, openings 8a, 8b at both axial ends of the inner and outer rings are sealed by a seal member 6, and the above-mentioned grease composition 7 is filled at least around the rolling elements 4. The seal member 6 in FIG. 1 is a contact type seal member in which the inner diameter lip comes into contact inside the seal groove. The inner ring 2, the outer ring 3, and the rolling elements 4 are made of an iron-based metal material, and the grease composition 7 is interposed between the raceway surface and the rolling elements 4 to lubricate them.

[0035] In the rolling bearing 1, the iron-based metallic material constituting the bearing components such as the inner ring 2, the outer ring 3, the rolling elements 4, and the cage 5 is any material commonly used as a bearing material, such as high carbon chromium bearing steel (SUJ1, SUJ2, SUJ3, SUJ4, SUJ5, etc.; JIS G 4805), carburized steel (SCr420, SCM420, etc.; JIS G 4053), stainless steel (SUS440C, etc.; JIS G 4303), high speed steel (M50, etc.), cold rolled steel, etc.

[0036] Furthermore, the sealing member 6 may be made of metal or rubber alone, or may be a composite of a rubber molded body and a metal plate, a plastic plate, or a ceramic plate. In view of durability and ease of attachment, a composite of a rubber molded body and a metal plate, as shown in Fig. 1, is preferred. As the material for the rubber molded body, nitrile rubber (NBR), acrylic rubber, silicone rubber, fluororubber, etc. are used, and the rubber molded body contains a plasticizer.

[0037] The plasticizer can be appropriately selected from known plasticizers, but it is preferable to use an ester-based plasticizer. Examples of the ester-based plasticizer include phthalate ester-based plasticizers such as di-n-octyl phthalate, di-2-ethylhexyl phthalate, and diisononyl phthalate, and ester compounds such as adipate ester-based plasticizers, trimellitate ester-based plasticizers, and pyromellitate ester-based plasticizers. Among these, trimellitate ester-based plasticizers are more preferable from the viewpoint of suppressing the amount of dust generation. The trimellitate ester-based plasticizer is represented by the following formula (1). [ka] In formula (1), R 1 , R 2 , R 3 may be the same or different. Preferably, they are the same. In addition, R 1 , R 2 , R 3 is preferably an aliphatic monohydric alcohol residue having 7 to 9 carbon atoms. This aliphatic monohydric alcohol residue may be a linear alkyl group or a branched alkyl group. Specific examples include tri-n-octyl trimellitate and tri-2-ethylhexyl trimellitate. As trimellitic acid ester plasticizers, Rheolub LTM, Rheolub TM10 (manufactured by FMC), etc. can be used.

[0038] In addition to the above-mentioned plasticizer, the rubber molded product may also contain various known additives, such as flame retardants, lubricants, stabilizers, fillers, foaming agents, antioxidants, processing aids, neutralizing agents, UV absorbers, pigments, antistatic agents, dispersants, thickeners, metal deterioration inhibitors, anti-fungal agents, and flow adjusters, as necessary.

[0039] In FIG. 1, a ball bearing is shown as an example of the bearing, but the rolling bearing of the present invention can also be used as a cylindrical roller bearing, tapered roller bearing, spherical roller bearing, needle roller bearing, thrust cylindrical roller bearing, thrust tapered roller bearing, thrust needle roller bearing, thrust spherical roller bearing, etc.

[0040] A configuration in which the rolling bearing of the present invention is applied to a servo motor will be described with reference to Fig. 2. As shown in Fig. 2, servo motor 11 has rotor 12, stator 13, shaft 14, and encoder 15 on the anti-load side of shaft 14 for reading the angle of rotor 12. Shaft 14 is supported by rolling bearing 16 arranged on the load side, and rolling bearing 1 of the present invention arranged on the anti-load side. Although rolling bearing 1 of the present invention is arranged in the vicinity of encoder 15, the amount of dust generated from the bearing is suppressed, so a decrease in the detection accuracy by encoder 15 can be prevented.

[0041] The rolling bearing of the present invention can be used not only in servomotors but also in other rotating electrical machines that require low dust generation, such as generators and electric motors other than servomotors, such as spindle motors, stepping motors, and fan motors. EXAMPLES

[0042] Grease compositions were prepared according to the compositions shown in Tables 1 and 2. In Tables 1 and 2, the contents of base oil, thickener, and additives are shown as the content (mass%) relative to the base grease (base oil + thickener). The grease compositions of Examples 1 to 8 in Table 1 contain only organic acid metal salts and amine-based antioxidants as additives. Dioctyldiphenylamine was used as the DDPA in Tables 1 and 2. 1) to 9) below in Table 1 are also the same in Table 2.

[0043] <Dust generation test> Each grease composition was filled into a deep groove ball bearing 6900 (inner diameter 10 mm × outer diameter 22 mm × width 6 mm) equipped with a contact type seal member to prepare a test bearing. For the seal members other than Example 8, NBR containing a phthalate ester plasticizer (di-2-ethylhexyl phthalate) was used as a plasticizer, and for the seal member of Example 8, a trimellitate ester plasticizer (Reolube LTM, manufactured by FMC, kinetic viscosity at 40°C 53 mm) was used as a plasticizer. 2 The obtained test bearings were subjected to an ambient temperature of 120°C for 6000 min-1 The inner ring was rotated for 200 hours. Glass plates were placed on both axial ends of the test bearing, and the grease composition that had scattered from the bearing was attached to them. The amount of dust generated was determined by subtracting the weight of the glass plate before the test from the weight of the glass plate after the test. The amount of dust generated is evaluated in Tables 1 and 2 with a ◎ mark for 3 mg or less, a ○ mark for between 3 mg and 4 mg, a △ mark for between 4 mg and 6 mg, and an × mark for more than 6 mg.

[0044] <Fretting wear test> A wear test was carried out for each grease composition using a ball-on-disk type reciprocating tester. Each grease composition was applied to a steel plate (20 mm square, 5 mm thick) test piece, and a single SUJ2 steel ball (7 / 16 inch) was pressed against it with a load of 98 N, and a small reciprocating movement was performed for 8 hours at an amplitude of 0.47 mm and a vibration frequency of 30 Hz. The wear depth (μm) of the steel plate after this test was measured. The evaluation of the wear depth is shown in Tables 1 and 2, with 3 μm or less marked with ◎, 3 μm to 5 μm marked with ○, 5 μm to 10 μm marked with △, and more than 10 μm marked with ×.

[0045] <Grease life test> A test bearing was prepared by filling 1.8 g of each grease composition into a deep groove ball bearing 6204 (inner diameter 20 mm, outer diameter 47 mm, width 14 mm). The obtained test bearing was subjected to a test for 10,000 min under the conditions of an outer diameter part temperature of the outer ring of the bearing of 180°C, an axial load of 67 N, and a radial load of 67 N. -1 The time until seizure occurred was measured while rotating at a rotation speed of 1000 x 1000 x 1000 rpm. The grease life evaluation is shown in Tables 1 and 2 with the following markings: 300 hours or more: ◎, 230 hours or more but less than 300 hours: ○, 150 hours or more but less than 230 hours: △, and less than 150 hours: ×.

[0046] [Table 1]

[0047] [Table 2]

[0048] Regarding the evaluation of the amount of dust generated in Table 1, Example 8 generated an amount of dust of 2 mg or less, which was superior in terms of dust generation to the other test examples marked with ◎.

[0049] As shown in Tables 1 and 2, Examples 1 to 8, which combine a base oil containing PAO oil and ether oil and having a predetermined kinetic viscosity, a thickener containing an aliphatic diurea compound and an alicyclic diurea compound, and an organic acid metal salt, showed good results in all tests. Compared with Comparative Example 2 and Comparative Example 6, it can be seen that the organic acid metal salt contributes particularly to improving wear resistance and grease life. It is considered that by adding an organic acid metal salt that is solid at 20°C, the surface tension of the base oil is not affected, and when the supply of base oil is insufficient and wear is a concern, the organic acid metal salt melts and protects the steel surface as an extreme pressure agent. As the organic acid metal salt, the stearic acid metal salt showed better results in terms of dust generation (Examples 1, 4, 6, and 7), and the sodium salt showed better results in terms of wear resistance (Examples 4 and 5).

[0050] In Comparative Examples 1, 4, and 10, in which ZnDTP was added as an additive, the wear resistance and grease life were relatively good, but the amount of dust generated increased. Separately, a surface tension test was conducted in accordance with JIS K2241, and the kinetic viscosity at 40°C was 47 mm 2 The surface tension of the PAO oil alone at 100 / s was 29.8 mN / m, while the surface tension of the test oil to which 2% by mass of ZnDTP had been added to the PAO oil was 26 mN / m. From this result, the increase in dust generation due to the addition of ZnDTP is thought to be due to a decrease in surface tension. In the case of TCP, the increase in dust generation is also thought to be due to a decrease in surface tension (Comparative Example 3).

[0051] Furthermore, when NBR containing a trimellitate ester plasticizer was used as the sealing member (Example 8), the amount of dust generation was reduced compared to when NBR containing a phthalate ester plasticizer was used (Example 3). It is believed that trimellitate ester plasticizers have lower volatility (higher boiling point) than phthalate ester plasticizers, and as a result, evaporation of the plasticizer itself is suppressed, reducing the amount of dust generation. In this way, the heat-resistant NBR sealing member improves low dust generation.

[0052] As described above, in the rolling bearing of the present invention, the grease composition is a combination of a specified base oil and a specified thickener, specifically a combination of a base oil with excellent heat resistance and high surface tension, a specified thickener, and low volatility / oil separation, to which is added an organic acid metal salt that is solid at 20°C. This does not affect the surface tension of the base oil, and when the supply of base oil is insufficient and wear is a concern, the organic acid metal salt melts and can protect the steel surface as an extreme pressure agent. [Industrial Applicability]

[0053] The rolling bearing of the present invention can achieve low dust generation while suppressing deterioration in wear resistance and life, and can therefore be suitably used as a rolling bearing for rotating electrical machines such as servo motors and encoders, which are particularly required to have low dust generation. [Explanation of symbols]

[0054] 1. Rolling bearings 2. Inner Circle 3 Outer ring 4 Rolling elements 5 Cage 6 Sealing material 7 Grease 8a, 8b opening 11 Servo motor 12 Rotor 13 Stator 14 Shaft 15 Encoders 16 Rolling bearings

Claims

1. A rolling bearing comprising an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, seal members provided at openings at both axial ends of the inner ring and the outer ring, and a grease composition sealed in a space within the bearing, The grease composition includes a base oil and a thickener, The base oil contains a synthetic hydrocarbon oil and an ether oil, and has a kinetic viscosity of 120 mm at 40°C. ２ / s or more mixed oil, the thickener is a diurea compound obtained by reacting a diisocyanate component with a monoamine component, the monoamine component being an aliphatic monoamine and an alicyclic monoamine, and is contained in an amount of 12 parts by mass to 15 parts by mass per 100 parts by mass of the total amount of the base oil and the thickener; The grease composition has a worked penetration of 200 to 240 as measured in accordance with JIS K 2220 and contains an organic acid metal salt that is solid at 20°C, the organic acid metal salt is a sodium salt or a calcium salt of an organic carboxylic acid having 2 to 18 carbon atoms; The rolling bearing is characterized in that the grease composition does not contain any additives containing sulfur and phosphorus in the molecular structure.

2. 2. The rolling bearing according to claim 1, wherein the grease composition further contains an amine-based antioxidant, the amine-based antioxidant being N-phenyl-N'-isopropyl-p-phenylenediamine.

3. 3. The rolling bearing according to claim 1, wherein the rolling bearing is a bearing for a rotating electrical machine.

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