JP2023100728A - rolling bearing - Google Patents

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 The present invention relates to a rolling bearing containing a grease composition, and more particularly to a rolling bearing for rotary electric machines such as servomotors and encoders.

Servo motors are equipped with detectors for position, speed, etc., and are capable of high-precision positioning and fine rotation speed control. Among them, servomotors 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. Detectors and brakes are placed near the rolling bearings in order to reduce the size. is required to have low dust generation.

Dust generation occurs when a part of the grease evaporates or scatters due to the heat generated by the rotation of the rolling bearing and the increase in pressure inside the bearing, and is discharged outside the bearing. In order to suppress dust generation, it is effective to increase the viscosity of the base oil of the grease to increase the surface tension, or to reduce the amount of the base oil in the grease. On the other hand, however, the supply of the base oil to the rolling or sliding surfaces tends to be insufficient, which may lead to damage such as excessive temperature rise of the bearings, surface roughness of the rolling or sliding surfaces, and wear.

Conventionally, various studies have been made on grease compositions for the purpose of reducing dust generation. For example, in Patent Document 1, a base oil having a kinematic viscosity at 40° C. of 30 mm ² /s to 180 mm ² /s and containing at least one selected from synthetic hydrocarbon oils and ether oils, and a urea compound A grease composition has been proposed which contains a thickener consisting of and further contains an additive consisting only of non-metallic elements in an amount of 0.1 to 1% by weight based on the total amount of the grease.

Further, in Patent Document 2, in a rolling bearing unit incorporated in a motor that rotates forward and backward, the rolling bearing disposed near the encoder is made of at least one selected from synthetic hydrocarbon oil and ether oil, and , a grease composition containing a base oil having a kinematic viscosity at 40° C. of 80 mm ² /s to 120 mm ² /s.

JP-A-11-166191 JP 2010-127344 A

In recent years, with the miniaturization and high output of motors, there are more cases where the operating environment of the bearing becomes high temperature, and the use in an environment unfavorable for dust generation is increasing. In addition, durability such as wear resistance and grease life is also required for rolling bearings that require low dust generation. The grease composition described in Patent Document 1 is for a rolling device used in a clean room such as a semiconductor manufacturing facility. There are concerns about In addition, the grease composition described in Patent Document 2 is used in a bearing unit for a motor that rotates forward and backward. may be insufficient in terms of

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rolling bearing capable of achieving low dust generation while suppressing deterioration in wear resistance and service life.

A rolling bearing according to the present invention comprises an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, sealing members provided at openings at both ends of the inner ring and the outer ring in the axial direction, and an inner space of the bearing. and a grease composition, wherein the grease composition comprises a base oil and a thickener, the base oil comprises a synthetic hydrocarbon oil and an ether oil, and at 40°C It is a mixed oil having a kinematic viscosity of 120 mm ² /s or more, the thickener is an aliphatic diurea compound and an alicyclic diurea compound, and the total amount of the base oil and the thickener is 100 parts by mass. 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. Characterized by

The organic acid metal salt is characterized by being sodium salt or calcium salt. Further, the organic acid metal salt is a metal salt of an organic carboxylic acid having 2 to 18 carbon atoms, and the grease composition is characterized by not containing additives containing sulfur and phosphorus in the molecular structure.

The grease composition further comprises an amine antioxidant, which is N-phenyl-N'-isopropyl-p-phenylenediamine (PIPA).

The seal member is formed of nitrile rubber containing a trimellitate ester plasticizer.

The rolling bearing is a rotating electrical machine bearing.

In the rolling bearing of the present invention, the grease composition is enclosed in the space inside the bearing, and in the grease composition, the base oil contains a synthetic hydrocarbon oil and an ether oil, and the kinematic viscosity at 40° C. is 120 mm ² /s or more. It is a mixed oil, and the thickener is an aliphatic diurea compound and an alicyclic diurea compound. Since it has a consistency of 200 to 240 and contains an organic acid metal salt that is solid at 20° C., it is possible to achieve low dust generation while suppressing deterioration in wear resistance and service life. Specifically, by adding a solid organic acid metal salt 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 the base oil It is thought that the organic acid metal salt melts and protects the steel surface as an extreme pressure agent when the supply of is insufficient and wear is a concern.

INDUSTRIAL APPLICABILITY The rolling bearing of the present invention is suitable for, for example, a bearing used in a rotary electric machine such as a servomotor, and can contribute to miniaturization and higher output of the rotary electric machine, leading to higher functionality.

In addition, since the sealing member is made of nitrile rubber containing a trimellitate ester plasticizer, the use of a low volatile trimellitate ester plasticizer as the plasticizer suppresses the evaporation of the plasticizer itself. It is possible to further improve the low dust generation property of the bearing.

1 is a cross-sectional view of a deep groove ball bearing that is an example of the rolling bearing of the present invention; FIG. 1 is a schematic diagram of a servomotor to which the rolling bearing of the present invention is applied; FIG.

The grease composition used for the rolling bearing of the present invention contains a base oil having a predetermined kinematic viscosity, a predetermined thickener, and an additive, and the additive contains an organic acid metal salt that is solid at 20°C. It is characterized by

The base oil used in the grease composition is a mixed oil containing a synthetic hydrocarbon oil and an ether oil and having a kinematic viscosity at 40° C. of 120 mm ² /s or more. This kinematic viscosity is the kinematic viscosity of the mixed oil, and is preferably 120 mm ² /s to 160 mm ² /s, more preferably 125 mm ² /s to 140 mm ² /s at 40°C.

Poly-α-olefin oil (PAO oil) is more preferable as the synthetic hydrocarbon oil. PAO oils are mixtures of alpha-olefins or isomerized alpha-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, 1-tetradocosene and the like, and mixtures thereof are usually used.

Ether oils include, for example, polyphenyl ether oils, alkyldiphenyl ether oils, alkyltriphenyl ether oils, and alkyltetraphenyl ether oils. Among these, from the viewpoint of durability at high temperatures, alkyldiphenyl ether oils are preferable, and it is more preferable that the alkyldiphenyl ether oils be contained in an amount of 50% by mass or more of the entire base oil (mixed oil). The alkyldiphenyl ether oils include monoalkyldiphenylether oils, dialkyldiphenylether oils, polyalkyldiphenylether oils and the like.

The base oil may be a mixed oil of only synthetic hydrocarbon oil and ether oil, or a mixed oil to which other oil is added. Other oils that are usually used for rolling bearings can be used without particular limitation. Examples thereof include mineral oils such as paraffinic mineral oils and naphthenic mineral oils, ester oils, silicone oils, and fluorine oils.

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 and a monoamine component. An aliphatic diurea compound is obtained from an aliphatic monoamine as a monoamine component and a diisocyanate component, and an alicyclic diurea compound is obtained from an alicyclic monoamine as a monoamine component and a diisocyanate component. Diisocyanate components include phenylene diisocyanate, tolylene diisocyanate, diphenyldiisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, hexane diisocyanate, and the like. Aliphatic monoamines include hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine, stearylamine, oleylamine, and the like. Cyclohexylamine etc. are mentioned as an alicyclic monoamine. The content of the aliphatic diurea compound in the thickener is preferably higher than the content of the alicyclic diurea compound.

A base grease is obtained by adding a diurea compound as a thickening agent to a base oil. A base grease containing a diurea compound as a thickener is prepared by reacting a diisocyanate component and a monoamine component in a base oil. The thickener is contained in an amount of 12 to 15 parts by mass based on 100 parts by mass of the total amount of the base oil and the thickener.

Organic acid metal salts used in the grease composition include organic carboxylic acids, organic sulfonic acids such as alkylbenzenesulfonic acids, organic sulfuric acids such as alkylsulfuric acids, organic phosphonic acids such as alkylphosphonic acids, and organic phosphinic acids such as alkylphosphinic acids. is a salt of an aliphatic compound or an aromatic compound having a substituent of and a metal ion. The above organic acid metal salt is solid at 20° C., that is, 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, more preferably 150° C. or higher.

As the metal constituting the organic acid metal salt, any metal can be used as long as it can form a salt with the above organic acid, and lithium, sodium, potassium, magnesium, calcium, barium, zinc, aluminum and the like can be used. The metal salt is preferably sodium salt or calcium salt, more preferably sodium salt.

The organic acid constituting the organic acid metal salt has a substituent such as a halogen group, a hydroxyl group, an amino group, an alkyl group, an alkoxy group, an epoxy group, etc. on the aliphatic group or aromatic group in the molecular structure. good too. In addition, the above organic acid preferably does not contain a sulfur atom and a phosphorus atom in its molecular structure, and the constituent atoms are more preferably atoms selected from carbon, hydrogen, nitrogen, and oxygen atoms. preferable. Examples of such organic acids include acetic acid, propionic acid, butyric acid, hexanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, and the like. Among them, organic carboxylic acids having 10 to 18 carbon atoms are preferred, and linear organic carboxylic acids having no substituent are more preferred.

Specifically, sodium acetate (melting point: 324°C), calcium acetate (melting point: 160°C), sodium stearate (melting point: 220°C), calcium stearate (melting point: 179°C), and the like can be used as the organic acid metal salt.

The amount of the organic acid metal salt compounded in the grease composition is preferably 0.5 parts by mass to 5 parts by mass, more preferably 0.5 parts by mass to 3 parts by mass, with respect to 100 parts by mass of the total amount of the base oil and the thickener. part is more preferable, and 1 part by mass to 3 parts by mass is even more preferable.

The grease composition preferably further contains an antioxidant as an additive. As the antioxidant, amine-based antioxidants, phenol-based antioxidants, sulfur-based antioxidants, and the like can be used. Among these, it is preferable to use amine-based antioxidants. naphthylamine, diphenyl-p-phenylenediamine, dipyridylamine, phenothiazine, N,N'-diisopropyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, dialkyldiphenylamine (DDPA) and the like.

In addition, other additives such as rust inhibitors and oily agents such as esters and alcohols can be added to the grease composition as needed. For example, it is preferable to add an antirust agent in order to ensure the antirust performance of the grease itself. The rust preventive agent is not particularly limited, but an ester rust preventive agent is preferable. Ester-based rust preventives 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. It is more preferable that the amount of the ester-based rust preventive compounded is 0.2 parts by mass to 0.6 parts by mass with respect to 100 parts by mass of the total amount of the base oil and the thickener.

It is preferable that the grease composition does not contain an additive containing a phosphorus atom or a sulfur atom in its molecular structure. As shown in Examples below, the inclusion of these additives results in a reduction in the surface tension of the base oil, and as a result, there is a tendency for the amount of dust generated to increase. Examples of such additives include phosphate esters such as tricresyl phosphate, phosphites such as tricresyl phosphite, thiophosphates, thiophosphites, zinc alkyldithiophosphates (ZnDTP), alkyldithiophosphates, Extreme pressure agents such as molybdenum (MoDTP) and zinc dithiocarbamate (ZnDTC) are included.

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

A rolling bearing containing the above grease composition will be described with reference to FIG. 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 the outer peripheral surface and an outer ring 3 having an outer ring raceway surface 3a on the inner peripheral surface are arranged concentrically. Rolling elements 4 are arranged. This rolling element 4 is held by a retainer 5 . Also, the axial end openings 8a and 8b of the inner and outer rings are sealed by sealing members 6, and the above-described grease composition 7 is enclosed at least around the rolling elements 4. As shown in FIG. The seal member 6 in FIG. 1 is a contact type seal member in which the inner diameter lip contacts inside the seal groove. The inner ring 2, the outer ring 3 and the rolling elements 4 are made of a ferrous metal material, and the grease composition 7 intervenes between the raceway surfaces of the rolling elements 4 to lubricate them.

In the rolling bearing 1, the iron-based metal material that constitutes the bearing members such as the inner ring 2, the outer ring 3, the rolling elements 4, and the cage 5 is any material that is generally used as a bearing material. Bearing steel (SUJ1, SUJ2, SUJ3, SUJ4, SUJ5, etc.; JIS G 4805), carburizing steel (SCr420, SCM420, etc.; JIS G 4053), stainless steel (SUS440C, etc.; JIS G 4303), high speed steel (M50, etc.) , cold rolled steel and the like.

Moreover, the sealing member 6 may be made of a metal or a rubber molding alone, or may be a composite of a rubber molding and a metal plate, a plastic plate, or a ceramic plate. A composite of a rubber molding and a metal plate, as shown in FIG. 1, is preferable from the viewpoint of durability and ease of fixation. Nitrile rubber (NBR), acrylic rubber, silicone rubber, fluororubber, etc. are used as the material of the rubber molding, and the rubber molding contains a plasticizer.

式（１）において、Ｒ^１、Ｒ^２、Ｒ^３は同一であっても異なってもよい。好ましくは同一である。また、Ｒ^１、Ｒ^２、Ｒ^３は炭素数が７～９の脂肪族１価アルコール残基であることが好ましい。この脂肪族１価アルコール残基は、直鎖状アルキル基であっても分岐状アルキル基であってもよい。具体的には、トリメリット酸トリ－ｎ－オクチル、トリメリット酸トリ－２－エチルヘキシルなどが挙げられる。トリメリット酸エステル系可塑剤としては、レオルーブＬＴＭ、レオルーブＴＭ１０（ＦＭＣ製）などを用いることができる。 The plasticizer can be appropriately selected from known plasticizers and used, but it is preferable to use an ester plasticizer. Examples of ester plasticizers include phthalate plasticizers such as di-n-octyl phthalate, di-2-ethylhexyl phthalate, and diisononyl phthalate, adipate plasticizers, and trimellitate ester plasticizers. Ester compounds such as plasticizers and pyromellitic acid ester plasticizers can be mentioned. Among these, the trimellitate ester plasticizer is more preferable from the viewpoint of suppressing the amount of dust generated. The trimellitate ester plasticizer is represented by the following formula (1).

In Formula (1), R ¹ , R ² and R ³ may be the same or different. preferably identical. R ¹ , R ² and R ³ are preferably C 7-9 aliphatic monohydric alcohol residues. 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 the trimellitate ester plasticizer, Rheolube LTM, Rheolube TM10 (manufactured by FMC) and the like can be used.

In addition to the above plasticizers, the rubber molding may optionally contain flame retardants, lubricants, stabilizers, fillers, foaming agents, antioxidants, processing aids, neutralizers, UV absorbers, pigments. , an antistatic agent, a dispersant, a thickener, a metal deterioration inhibitor, an antifungal agent, and a flow control agent.

In FIG. 1, a ball bearing was exemplified as a bearing, but rolling bearings of the present invention include cylindrical roller bearings, tapered roller bearings, self-aligning roller bearings, needle roller bearings, thrust cylindrical roller bearings, thrust tapered roller bearings, and thrust needles. It can also be used as a shaped roller bearing, thrust self-aligning roller bearing, etc.

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

The rolling bearing of the present invention is used not only in servomotors but also in other rotary electric machines that require low dust generation. Examples include a generator, and an electric motor other than a servomotor, such as a spindle motor, a stepping motor, and a fan motor.

Grease compositions having compositions shown in Tables 1 and 2 were prepared. In Tables 1 and 2, the content of the base oil, thickener and additive indicates the percentage content (% by mass) relative to the base grease (base oil + thickener). The grease compositions of Examples 1 to 8 in Table 1 contain only the organic acid metal salt and the amine antioxidant as additives. As DDPA in Tables 1 and 2, dioctyldiphenylamine was used. 1) to 9) below in Table 1 are also the same in Table 2.

<Dust generation test>
Each grease composition was enclosed in a deep groove ball bearing 6900 (inner diameter 10 mm×outer diameter 22 mm×width 6 mm) equipped with a contact-type sealing member to prepare a test bearing. For sealing members other than Example 8, NBR containing a phthalate plasticizer (di-2-ethylhexyl phthalate) as a plasticizer was used, and for the sealing members of Example 8, trimellitic acid was used as a plasticizer. An NBR containing an ester plasticizer (Reolube LTM, manufactured by FMC, kinematic viscosity at 40° C. of 53 mm ² /s) was used. The inner ring of the obtained test bearing was rotated at an ambient temperature of 120° C. and 6000 min ⁻¹ for 200 hours. Glass plates were placed on both ends of the test bearing in the axial direction, and the grease composition scattered from the bearing was adhered thereto. The amount of dust generated was obtained by subtracting the weight of the glass plate before the test from the weight of the glass plate after the test. The evaluation of the amount of dust generated is shown in Tables 1 and 2, with ⊚ for 3 mg or less, ∘ for 3 mg to 4 mg, Δ for 4 mg to 6 mg, and X for 6 mg or more.

<Fretting wear test>
A wear test was performed on each grease composition using a ball-on-disk type reciprocating motion tester. Each grease composition was applied to a steel flat plate (20 mm square and 5 mm thick) type test piece, and one SUJ2 steel ball (7/16 inch) was pressed with a load of 98 N, an amplitude of 0.47 mm, and a frequency of 30 Hz. 8 hours of micro-reciprocating sliding. The wear depth (μm) of the steel flat plate after this test was measured. The evaluation of the wear depth is shown in Tables 1 and 2 with ⊙ for 3 μm or less, ◯ for 3 μm to 5 μm, Δ for 5 μm to 10 μm, and X for 10 μm or more.

<Grease life test>
1.8 g of each grease composition was enclosed in a deep groove ball bearing 6204 (inner diameter: 20 mm, outer diameter: 47 mm, width: 14 mm) to prepare a test bearing. The resulting test bearing was rotated at a rotational speed of 10000 min ⁻¹ under conditions of an outer diameter temperature of the bearing outer ring of 180° C., an axial load of 67 N, and a radial load of 67 N, and the time until seizure was measured. . The evaluation of the grease life time is shown in Tables 1 and 2 with ⊚ for 300 hours or more, ◯ for 230 to less than 300 hours, Δ for 150 to less than 230 hours, and X for less than 150 hours.

Regarding the evaluation of the amount of dust generation in Table 1, the amount of dust generated in Example 8 was 2 mg or less, and the result was superior in terms of dust generation property to the other test examples marked with ⊚.

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

Comparative Examples 1, 4, and 10, in which ZnDTP was added as an additive, had relatively good wear resistance and grease life, but resulted in increased dust generation. Separately, when a surface tension test was performed in accordance with JIS K2241, the surface tension of PAO oil alone with a kinematic viscosity of 47 mm ² / s at 40 ° C. was 29.8 mN / m. On the other hand, the surface tension of the test oil containing 2% by mass of ZnDTP was 26 mN/m. From this result, the reason why the amount of dust generation increased by adding ZnDTP is considered to be the decrease in surface tension. In the case of TCP as well, it is considered that the amount of dust generation increased as a result of the decrease in surface tension (Comparative Example 3).

In addition, when NBR containing a trimellitate ester plasticizer is used as a sealing member (Example 8), the amount of dust generated is lower than when NBR containing a phthalate ester plasticizer is used (Example 3). decreased. Compared to the phthalate ester plasticizer, the trimellitate ester plasticizer has lower volatility (higher boiling point), and as a result, the evaporation of the plasticizer itself is suppressed and the amount of dust generated is reduced. be done. In this way, the heat-resistant NBR sealing member improves the low dust generation property.

As described above, in the rolling bearing of the present invention, the grease composition is a combination of a predetermined base oil and a predetermined thickener. By adding an organic acid metal salt that is solid at 20°C to a combination with low volatility/separation, the surface tension of the base oil is not affected, and the supply of the base oil is insufficient, and there is concern about wear. In the case, the organic acid metal salt melts and can protect the steel surface as an extreme pressure agent.

INDUSTRIAL APPLICABILITY The rolling bearing of the present invention can achieve low dust generation while suppressing deterioration in wear resistance and service life, and is therefore suitable for rolling bearings for rotating electric machines such as servo motors and encoders, which particularly require low dust generation. available for

1 Rolling Bearing 2 Inner Ring 3 Outer Ring 4 Rolling Element 5 Cage 6 Sealing Member 7 Grease 8a, 8b Opening 11 Servo Motor 12 Rotor 13 Stator 14 Shaft 15 Encoder 16 Rolling Bearing

Claims (5)

An inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, sealing members provided at openings at both ends of the inner ring and the outer ring in the axial direction, and a grease composition sealed in the bearing inner space. A rolling bearing having
The grease composition comprises a base oil and a thickener,
The base oil is a mixed oil containing a synthetic hydrocarbon oil and an ether oil and having a kinematic viscosity at 40° C. of 120 mm ² /s or more,
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 based on 100 parts by mass of the total amount of the base oil and the thickener,
A rolling bearing, wherein the grease composition has a worked penetration of 200 to 240 measured in accordance with JIS K 2220 and contains an organic acid metal salt that is solid at 20°C. 2. A rolling bearing according to claim 1, wherein said organic acid metal salt is sodium salt or calcium salt. the organic acid metal salt is a metal salt of an organic carboxylic acid having 2 to 18 carbon atoms,
3. A rolling bearing according to claim 1, wherein said grease composition does not contain additives containing sulfur and phosphorus in its molecular structure. The grease composition of claims 1 to 3, wherein the grease composition further comprises an amine antioxidant, and the amine antioxidant is N-phenyl-N'-isopropyl-p-phenylenediamine. A rolling bearing according to any one of the preceding claims. 5. A rolling bearing according to any one of claims 1 to 4, characterized in that the rolling bearing is a rotating electrical machine bearing.

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