Rolling bearing

Abstract

The purpose of the present invention is to provide a rolling bearing in which a grease composition containing molybdenum dithiocarbamate and triphenyl thiophosphate is sealed, the rolling bearing being capable of improving frictional characteristics and suppressing deterioration of acoustic characteristics, and to provide a motor incorporating the bearing. A rolling bearing includes: an inner ring; an outer ring disposed on the outer peripheral side of the inner ring so as to be coaxial with the inner ring; a plurality of rolling bodies disposed between the inner ring and the outer ring; the retainer is used for retaining the rolling bodies; and a grease composition held between the inner ring and the outer ring, the grease composition containing a base oil, a thickener, molybdenum dithiocarbamate having an alkyl group having 8 or more carbon atoms, and triphenyl thiophosphate, the rolling bearing having an outer diameter of 22 mm or less, the Andru value of the M band after the inner ring is rotated for 30 seconds at a rotation speed of 1800 rpm under room temperature and air atmosphere in a state that the outer ring is pre-pressed from the axial direction so that the average surface pressure of the inner ring becomes 800 MPa is 1.2 or less; and a motor provided with the rolling bearing.

Description

Technical Field

[0001] The present invention relates to a rolling bearing encapsulated with a grease composition comprising molybdenum dithiocarbamate and triphenyl thiophosphate, and a motor having the rolling bearing. Background Technology

[0002] In the field of grease and lubricating oil technology, thiophosphates such as triphenyl thiophosphate (TPPT (CAS RN 597-82-0: also known as triphenyl thiophosphate, triphenyloxyphosphine sulfide)) are traditionally used as anti-friction agents (wear-resistant agents), and organomolybdenum compounds are used as extreme pressure agents. In order to improve the friction reduction effect of sliding components, a grease composition in which these components are used together has been proposed (Patent Document 1).

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 6-330072 Summary of the Invention

[0004] The problem that the invention aims to solve For motors used in automobiles, home appliances, and other similar devices, such as fan motors and cleaner motors, and the bearings used in them, in addition to durability, lower noise levels have become increasingly desirable in recent years. Lubricant compositions suitable for bearings in such motors are also expected to possess properties that improve frictional characteristics, contributing to increased durability, without deteriorating acoustic properties.

[0005] Although the grease composition described in Patent Document 1 has been studied for its coefficient of friction, wear resistance, temperature suppression, compatibility with sealing materials, and heat resistance, the document makes no attention to the acoustic properties of the grease composition when applied to bearings.

[0006] The object of the present invention is to provide a rolling bearing that improves frictional characteristics and suppresses acoustic deterioration in a rolling bearing encapsulated with a grease composition containing molybdenum dithiocarbamate and triphenyl thiophosphate, and to provide a motor incorporating the bearing.

[0007] Solution for solving the problem One aspect of the present invention relates to a rolling bearing comprising: an inner ring; an outer ring coaxially disposed on the outer periphery of the inner ring; a plurality of rolling elements disposed between the inner ring and the outer ring; a retainer for retaining the rolling elements; and a grease composition retained between the inner ring and the outer ring, the grease composition comprising a base oil, a thickener, molybdenum dithiocarbamate having an alkyl group having 8 or more carbon atoms, and triphenyl thiophosphate, wherein the rolling bearing is a rolling bearing with an outer diameter of 22 mm or less, wherein, under a preload applied axially to the outer ring with an average surface pressure of 800 MPa on the inner ring, the Andron value in the M-band after rotating the inner ring at a speed of 1800 rpm for 30 seconds at room temperature and atmospheric atmosphere is 1.2 or less.

[0008] Furthermore, the present invention relates to a motor equipped with the aforementioned rolling bearing. Attached Figure Description

[0009] Figure 1 This is a schematic diagram illustrating an example of the rolling bearing structure of the present invention.

[0010] Figure 2 This is a schematic diagram illustrating an example of the structure of the motor of the present invention.

[0011] Figure 3 This is a graph showing the results of friction coefficient measurements for Examples 1, 2, and Comparative Examples 1 and 2 in the friction characteristic evaluation (metal-metal).

[0012] Figure 4 The graph shows the measurement results of the Andrew values ​​(M band) of Examples 1, 2, and Comparative Examples 1 and 2 in the acoustic evaluation.

[0013] Figure 5 The graph shows the measurement results of the Andrew value (M band) of Examples 3-4 and Comparative Example 3, and Examples 5-6 and Comparative Example 4 in the acoustic evaluation. Detailed Implementation

[0014] The inventors, focusing on the acoustic properties of rolling bearings, confirmed during their research on greases suitable for such bearings that the grease composition used in the embodiments of the previous Patent Document 1—a urea-based grease composition incorporating a 4-carbon dialkyl dithiocarbamate with molybdenum and triphenyl thiophosphate—while exhibited superior frictional properties compared to a urea-based grease composition containing only triphenyl thiophosphate, actually had worse acoustic properties than a composition using only triphenyl thiophosphate.

[0015] In response to the problem of deterioration in acoustic properties, the inventors have focused on the alkyl chain length contained in the above-mentioned molybdenum compound and discovered for the first time that the acoustic properties can be changed without affecting the frictional properties by means of this alkyl chain length.

[0016] That is, it was discovered that by using molybdenum dithiocarbamate with an alkyl group having 8 or more carbon atoms and triphenyl thiophosphate, the frictional properties can be improved without deteriorating the acoustic properties, thus completing the present invention.

[0017] As demonstrated by the results of the embodiments described later, the inventors have confirmed that the combination of molybdenum dithiocarbamate with a specific number of carbon atoms and triphenyl thiophosphate can suppress the deterioration of acoustic properties without being affected by other components of the grease, such as the base oil. This is an unprecedented new insight.

[0018] The present invention will now be described in detail.

[0019] [Rolling bearings] First, the preferred embodiments of the rolling bearing of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to the following embodiments.

[0020] Figure 1 This is a radial cross-sectional view of a rolling bearing 10 according to a preferred embodiment of the present invention. The rolling bearing 10 has the same basic structure as prior art rolling bearings, including an annular inner ring 11, an outer ring 12, a plurality of rolling elements 13, a retainer 14, and a sealing member 15.

[0021] The inner ring 11 is a cylindrical structure coaxially disposed on the outer periphery of the shaft (not shown in the figure) with the central shaft. The outer ring 12 is a cylindrical structure coaxially disposed on the outer periphery of the inner ring 11. Each of the plurality of rolling elements 13 is a ball disposed in a track within an annular bearing space 16 formed between the inner ring 11 and the outer ring 12. That is, the rolling bearing 10 in this embodiment is a ball bearing.

[0022] A retainer 14 is disposed within the track and holds a plurality of rolling elements 13. The retainer 14 is an annular body coaxially arranged with the central axis of the shaft, and has the following structure: on one side in the direction of the central axis, it has a plurality of pockets for holding the rolling elements 13, and the rolling elements 13 are accommodated in each pocket. The rolling elements 13 are held by the retainer 14 at predetermined intervals in the circumferential direction of the inner ring 11 and the outer ring 12, thereby preventing the rolling elements 13 from falling off and preventing contact between adjacent rolling elements 13. It should be noted that the shape (crown-shaped, wave-shaped, etc.) and material (steel plate or resin, etc.) of the retainer 14 are arbitrary and not limited to a specific shape or material.

[0023] The sealing member 15 is fixed to the inner circumferential surface of the outer ring 12 and extends towards the inner ring 11 to seal the bearing space 16. A grease composition G is sealed within the bearing space 16 sealed by the sealing member 15. That is, the grease composition G is held between the inner ring 11 and the outer ring 12. The grease composition G used is one described later. It should be noted that the amount of grease G sealed into the bearing space 16 can, for example, be 5% to 50% of its volume.

[0024] The sealing member 15 is formed, for example, of steel plate or rubber, and examples include a steel plate shield that does not contact the outer periphery of the inner ring 11, and a non-contact rubber seal that does not contact the outer periphery of the inner ring 11. In this invention, any sealing member from the steel plate shield or the non-contact rubber seal can be used. It should be noted that... Figure 1 The present invention includes a rolling bearing having a sealing member 15, and also includes a rolling bearing without a sealing member.

[0025] In the rolling bearing 10 with the above structure, the grease composition G functions to reduce friction between the rolling elements 13 and the cage 14, and between the rolling elements 13 and the inner ring 11 and even the outer ring 12. By reducing friction, frictional torque is reduced, and the generation of frictional heat is suppressed, promoting smooth rotation of the inner ring 11 and the outer ring 12. Figure 1 As can be seen from the structure shown, the grease composition G sealed in the rolling bearing 10 lubricates the rolling element 13 and the inner ring 11 and even the outer ring 12 when the rolling bearing 10 rotates.

[0026] This invention is particularly effective in rolling bearings with an outer diameter of, for example, less than 22 mm.

[0027] The rolling bearing of the present invention can be used as a rolling bearing for motors (e.g., fan motors, cleaner motors) used in automobiles, home appliances, information equipment, etc.

[0028] <On Acoustic Properties> The rolling bearing of the present invention is characterized in that, by combining molybdenum dithiocarbamate containing an alkyl group having 8 or more carbon atoms and triphenyl thiophosphate in the grease composition described below, not only can a bearing with improved frictional properties be obtained, but it also becomes a bearing that suppresses the deterioration of acoustic properties.

[0029] In the rolling bearing of the present invention, for example, it is characterized in that, under a state in which the outer ring is preloaded axially with an average surface pressure of 800 MPa on the inner ring, the Andrew value in the M-band after rotating the inner ring at a speed of 1800 rpm for 30 seconds at room temperature and in atmospheric atmosphere is 1.2 or less. In the present invention, the Andrew value of 1.2 or less is preferably 1.1 or less from the viewpoint of acoustic characteristics, and particularly preferably 1.0 or less.

[0030] [motor] As an example, in Figure 2 The present invention will be described in detail with respect to the embodiments of the motor having the rolling bearing of the present embodiment, but the present invention is not limited to the following embodiments.

[0031] Figure 2 This is a cross-sectional view of a motor in the axial direction according to one embodiment of the present invention. The motor 20 has the same basic structure as motors in the prior art, consisting of a housing 21, a stator 22, a coil 23, a rotor magnet 24, a shaft 25, and a rolling bearing 26 supporting the shaft 25.

[0032] As for motor 20, the current supplied by the power source (not shown above) through the drive circuit flows through the coil 23 wound on the stator 22 to generate magnetic force, thereby causing the rotor magnet 24 to rotate and transmitting the rotation to the external rotating body through the shaft 25.

[0033] [Lubricating Grease Composition] The grease composition used in the rolling bearings of the present invention comprises a base oil, a thickener, molybdenum dithiocarbamate having an alkyl group having 8 or more carbon atoms, and triphenyl thiophosphate.

[0034] The grease composition encapsulated in the rolling bearing of the present invention will be described below.

[0035] <Base Oils> In the grease composition sealed in the rolling bearing of this embodiment, synthetic oils such as synthetic hydrocarbon oils, ether-based synthetic oils, and ester-based synthetic oils, which are commonly used as grease base oils, can be used alone or in combination.

[0036] Examples of synthetic hydrocarbon oils include, for example, n-alkanes, isoalkanes, polybutene, polyisobutene, 1-decene oligomers, 1-decene and ethylene co-oligomers, and other polyalphaolefins (PAOs).

[0037] Examples of ester-based synthetic oils include: dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl sebacate, dioctyl adipate, diisodecyl adipate, di(tridecyl) adipate, di(tridecyl) phthalate, methyl acetyl ricinoleate, and other diester oils; trioctyl trimellitate, tri-2-ethylhexyl trimellitate, tridecyl trimellitate, tetraoctyl pyromellitic acid, tetra-2-ethylhexyl pyromellitic acid, and other aromatic ester oils; trimethylolpropane octanoate, trimethylolpropane nonanoate, pentaerythritol-2-ethylhexanoate, pentaerythritol nonanoate, and other polyol ester oils; and carbonate oils.

[0038] In addition, examples of ether-based synthetic oils include monoalkyl diphenyl ethers, dialkyl diphenyl ethers, polyalkyl diphenyl ethers, and other alkyl ether oils and alkyl diphenyl ether oils.

[0039] Furthermore, the viscosity of the base oil used in this invention is not particularly limited, but considering the dispersion stability of molybdenum dithiocarbamate and triphenyl thiophosphate (described later), a dynamic viscosity of 20–150 mm at 40°C can be used, for example. 2 Base oils within the range of / s.

[0040] The base oil described above may be contained in a proportion of 70% by mass or more based on the total mass of the grease composition used in this invention, for example, it may be set to contain the base oil in a proportion of 70% to 90% by mass based on the total mass of the grease composition.

[0041] <Thickener> In the grease composition used in this invention, the type of thickener is not particularly limited, but for example, urea-based thickeners may be preferred.

[0042] Urea compounds exhibit excellent heat and water resistance, especially good stability at high temperatures, making them a preferred choice for use as thickeners in high-temperature environments.

[0043] Urea compounds such as diurea compounds, triurea compounds, and polyurea compounds can be used as urea thickeners. From the perspective of acoustic properties (quietness), diurea compounds are preferred. Furthermore, as for the types of urea compounds, at least one of aliphatic-aromatic urea, alicyclic-aliphatic urea, and aliphatic urea is preferred.

[0044] As these urea-based thickeners, conventionally known urea compounds can be used.

[0045] As an example of a diurea compound used as a urea-based thickener, a diurea compound represented by the following formula (2) can be listed.

[0046] Equation (2): R5-NHCONH-R6-NHCONH-R7.

[0047] In equation (2) above, R5 and R7 each independently represent a monovalent aliphatic hydrocarbon group, a monovalent alicyclic hydrocarbon group, or a monovalent aromatic hydrocarbon group, and at least one of R5 and R7 represents a monovalent aliphatic hydrocarbon group or a monovalent alicyclic hydrocarbon group. For example, one of R5 and R7 can be set to represent an aliphatic hydrocarbon group, and the other to represent a monovalent alicyclic hydrocarbon group or a monovalent aromatic hydrocarbon group, or one of R5 and R7 can be set to represent an aliphatic hydrocarbon group, and the other to represent a monovalent aromatic hydrocarbon group.

[0048] In addition, R6 represents a divalent aromatic hydrocarbon group.

[0049] It should be noted that the scheme shown in formula (2) can also be a mixture of multiple substances. As an example, it can be a mixture of compounds in which R5 and R7 represent monovalent aliphatic hydrocarbon groups, compounds in which R5 and R7 represent monovalent aromatic hydrocarbon groups, and compounds in which one of R5 and R7 represents an aliphatic hydrocarbon group and the other represents a monovalent aromatic hydrocarbon group.

[0050] Examples of monovalent aliphatic hydrocarbon groups include, for example, straight-chain or branched saturated or unsaturated alkyl groups with 6 to 26 carbon atoms.

[0051] Examples of monovalent alicyclic hydrocarbon groups include cycloalkyl groups with 5 to 12 carbon atoms.

[0052] In addition, examples of the aforementioned aromatic hydrocarbon groups include monovalent or divalent aromatic hydrocarbon groups with 6 to 20 carbon atoms.

[0053] Urea compounds used as urea-based thickeners can be synthesized using amine compounds and isocyanate compounds.

[0054] Examples of amine compounds include aliphatic amines such as hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine (stearylamine), behenamine, and oleylamine, as well as alicyclic amines such as cyclohexylamine, and aromatic amines such as aniline, p-toluidine, and ethoxyphenylamine. Two or more of these amine compounds can also be used in combination during the synthesis of urea compounds.

[0055] In addition, as isocyanate compounds, aromatic diisocyanates such as phenylene diisocyanate, toluene diisocyanate (TDI), diphenyl diisocyanate, diphenylmethane diisocyanate (MDI), and dimethylbiphenyl diisocyanate (TODI) can be used; aliphatic diisocyanates such as octadecane diisocyanate, decane diisocyanate, and hexane diisocyanate can also be used.

[0056] It should be noted that when aromatic diurea compounds obtained by using aromatic monoamines and aromatic diisocyanates as amine raw materials are used as urea-based thickeners, abnormal noises may occur, so further research is needed on their use.

[0057] The aforementioned urea-based thickener (urea compound) can be formulated relative to the total amount of the grease composition used in this invention, for example, in a manner that is 10 to 20% by mass.

[0058] <Molybdenum dithiocarbamate (MoDTC)> The grease composition used in this invention is characterized in that, together with the triphenyl thiophosphate described later, it must contain molybdenum dithiocarbamate (MoDTC).

[0059] The molybdenum dithiocarbamate used in this invention contains an alkyl group having 8 or more carbon atoms. For example, a substance containing molybdenum dithiocarbamate having 13 or more carbon atoms can be used.

[0060] Examples of molybdenum dithiocarbamate include compounds represented by formula (1) below. In the above formula (1), R1 to R4 each independently represent hydrocarbon groups with 8 to 14 carbon atoms, and X1 to X4 each independently represent oxygen atoms or sulfur atoms.

[0061] As the hydrocarbon group with 8 to 14 carbon atoms in R1 to R4, examples include alkyl groups or aromatic hydrocarbon groups with 8 to 14 carbon atoms, such as octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, etc., which are alkyl groups with 8 to 14 carbon atoms. The alkyl group can be straight-chain, branched, cyclic, or any combination thereof. Furthermore, at least one of R1 to R4 can be an alkyl group with 13 to 14 carbon atoms.

[0062] X1 to X4 represent oxygen or sulfur atoms. For example, it can be set that 2 to 3 of X1 to X4 are sulfur atoms and the rest are oxygen atoms. Alternatively, it can be set that there are 2 sulfur atoms and 2 oxygen atoms in X1 to X4. For example, X1 and X2 are sulfur atoms and X3 and X4 are oxygen atoms.

[0063] The molybdenum dithiocarbamate represented by formula (1) can be molybdenum dithiocarbamate with a symmetrical hydrocarbon group or molybdenum dithiocarbamate with an asymmetrical hydrocarbon group.

[0064] As molybdenum dithiocarbamates with symmetrical hydrocarbon groups, examples include molybdenum dithiocarbamates where all R1 to R4 are the same hydrocarbon group, or molybdenum dithiocarbamates where R1 and R2 are the same hydrocarbon group, and R3 and R4 are the same hydrocarbon group that is different from R1 and R2.

[0065] Examples of molybdenum dithiocarbamates with asymmetric hydrocarbon groups include molybdenum dithiocarbamates where all R1 to R4 are different hydrocarbon groups, molybdenum dithiocarbamates where R1 to R3 are the same hydrocarbon group but R4 is a different hydrocarbon group, and molybdenum dithiocarbamates where at least R1 and R2 are different hydrocarbon groups or R3 and R4 are different hydrocarbon groups (e.g., molybdenum dithiocarbamates where R1 and R3 are the same hydrocarbon group, R2 and R4 are the same hydrocarbon group, and R1 and R2 are different hydrocarbon groups).

[0066] Examples of molybdenum dithiocarbamate used in this invention include: compounds in which all R1 to R4 are alkyl groups having 8 carbon atoms, or compounds in which each of R1 to R4 is independently a group selected from alkyl groups having 8 carbon atoms and alkyl groups having 13 carbon atoms (a mixture of compounds in which all R1 to R4 are alkyl groups having 8 carbon atoms and compounds in which all R1 to R4 are alkyl groups having 13 carbon atoms; a compound in which at least one of R1 to R4 is an alkyl group having 8 carbon atoms and the remainder is an alkyl group having 13 carbon atoms; and a mixture thereof).

[0067] The molybdenum dithiocarbamate described above can be formulated in an amount of, for example, 0.01 to 0.5% by mass relative to the total amount of the grease composition used in this invention, based on the content of molybdenum atoms contained in the molybdenum dithiocarbamate.

[0068] <Triphenyl Thiophosphate (TPPT)> The grease composition used in this invention is characterized in that, together with the molybdenum dithiocarbamate described above, it must contain triphenyl thiophosphate (TPPT).

[0069] Triphenyl thiophosphate can be formulated in amounts of, for example, 0.1 to 10% by mass relative to the total amount of the grease composition used in this invention.

[0070] <Other Additives> In the grease compositions used in this invention, additives commonly used in grease compositions may be included, as needed, to a extent that does not impair the effects of this invention.

[0071] Examples of such additives include: antioxidants, extreme pressure agents (extreme pressure additives), metal passivators, anti-friction agents (wear-resistant agents), rust inhibitors, oiliness improvers, viscosity index improvers, and thickeners.

[0072] When these other additives are included, their addition amount (total amount) is typically 0.1 to 10% by mass relative to the total amount of the grease composition.

[0073] For example, examples of the aforementioned antioxidants include: octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylaniline)-1,3,5-triazine, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], and 1,6-hexanediol-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. Hindered phenolic antioxidants include phenylpropionate, 2,2-thio-diethylidene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxy-hydrogenated cinnamicamide), octyl-3,5-di-tert-butyl-4-hydroxy-hydrogenated cinnamic acid ester, etc.; other phenolic antioxidants include 2,6-di-tert-butyl-4-methylphenol and 4,4-methylenebis(2,6-di-tert-butylphenol); and amine antioxidants include diphenylamine, alkylated diphenylamine, triphenylamine, hindered amines, phenyl-α-naphthylamine, alkylated phenyl-α-naphthylamine, phenothiazine, alkylated phenothiazine, etc.

[0074] In addition, extreme pressure agents include, for example, phosphorus compounds such as phosphate esters, phosphites, and phosphate ester amine salts; sulfur compounds such as thioethers and dithioethers; chlorine compounds such as chlorinated paraffins and chlorinated biphenyls; and metal salts of sulfur compounds such as zinc dialkyl dithiophosphate.

[0075] Examples of metal passivating agents include: benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]-4-methylbenzotriazole and other benzotriazole compounds; thiadiazole, 2-mercaptothiadiazole, 2,5-bis(alkyldithio)-1,3,4-thiadiazole and other thiadiazole compounds; benzimidazole, 2-mercaptobenzimidazole, 2-(decyldithio)-benzimidazole and other benzimidazole compounds; sodium nitrite, etc.

[0076] In addition, anti-friction agents (wear-resistant agents) include tricresyl phosphate and polymeric esters.

[0077] Examples of the aforementioned polymeric esters include, for example, esters of aliphatic monocarboxylic acids and dicarboxylic acids with polyols. Specific examples of the aforementioned polymeric esters include, but are not limited to, the PRIOLUBE (registered trademark) series manufactured by Croda Japan.

[0078] The grease composition used in this invention can be obtained by combining the above-mentioned base oil, thickener, molybdenum dithiocarbamate having an alkyl group having 8 or more carbon atoms, triphenyl thiophosphate, and other additives as needed.

[0079] In addition, for example, a grease composition can be obtained by combining molybdenum dithiocarbamate containing alkyl groups having 8 or more carbon atoms, triphenyl thiophosphate, and other additives as needed, into a grease (base grease) containing the base oil and the thickener.

[0080] Typically, the content of thickener relative to the base grease is about 10 to 30% by mass. For example, the content of diurea compound (urea-based thickener) relative to the above-mentioned urea-based grease can be set to about 10 to 25% by mass, or even about 10 to 20% by mass.

[0081] This invention is not limited to the embodiments or specific examples described in this specification, and various changes and modifications can be made within the scope of the technical concept described in the claims.

[0082] [Example] The present invention will be described in more detail below through embodiments. However, the present invention is not limited thereto.

[0083] The grease compositions of Examples 1-6 and Comparative Examples 1-4 were prepared according to the compositions shown in Table 1 below, and various evaluations were performed in the order described below. In the following description, the example numbers of the grease compositions are also treated as the example numbers of the ball bearings into which these compositions were sealed, as well as the example numbers of the evaluations of each test.

[0084] It should be noted that the detailed information and abbreviations of the components used in the preparation of the lubricating grease composition are as follows.

[0085] <Base Oils> • PAO: Polyalphaolefin [Dynamic viscosity at 40°C: 48 mm] 2 / s].

[0086] • Ether + PAO: A mixture of alkyl diphenyl ether oil and polyalphaolefin [Dynamic viscosity at 40°C: 80 mm] 2 / s].

[0087] • Ether + Ester: A mixture of alkyl diphenyl ether oil and aromatic ester oil [Dynamic viscosity at 40°C: 80 mm] 2 / s].

[0088] It should be noted that the amount of base oil used is the remainder of the following thickeners and additives (TPPT, MoDTC1-3, and other additives).

[0089] <Thickener> • Diurea compounds: Aliphatic-aromatic diurea compounds (diurea compounds obtained by reacting a mixture of aliphatic and aromatic amines with diisocyanate compounds) It should be noted that the thickener is added in a manner that is 12% by mass relative to the total amount of each grease composition.

[0090] <Additives> •TPPT: Triphenyl thiophosphate (BASF Japan Co., Ltd. IRGALUBE TPPT).

[0091] It should be noted that TPPT is added at a rate of 2% by mass relative to the total amount of each grease composition.

[0092] •MoDTC1: Molybdenum dithiocarbamate containing alkyl groups with 8 and 13 carbon atoms (manufactured by ADEKA Corporation, Sakura Lube (registered trademark) 525).

[0093] •MoDTC2: Molybdenum dithiocarbamate containing an alkyl group with 8 carbon atoms (manufactured by ADEKA Corporation, SakuraLube (registered trademark) 200).

[0094] •MoDTC3: Molybdenum dithiocarbamate containing an alkyl group with 4 carbon atoms (manufactured by ADEKA Corporation, SakuraLube (registered trademark) 600).

[0095] It should be noted that MoDTC1 to MoDTC3 are added in such a way that the molybdenum (Mo) content is 0.1% by mass relative to the total content of each grease composition.

[0096] Other additives: Antioxidants and rust inhibitors are added in such a manner that they total 3% by mass in each grease composition (total mass: 100% by mass).

[0097] <Various Reviews> (1) Evaluation of frictional characteristics (metal-metal: friction test) Metal-to-metal friction and wear tests were conducted using a vibration friction testing machine (trade name: SRV) manufactured by Optimol. The tests were performed using a ball-disc configuration, employing steel balls (material: SUJ2, φ10mm) and discs (material: SUJ2, φ24mm). Test conditions were: load 100N, test temperature 50℃, sliding distance 1mm, frequency 50Hz, and test time 20 minutes (1200 seconds). At the start of the test, 5mg of each grease composition was supplied, and the coefficient of friction was continuously measured during the test.

[0098] Figure 3 The results of the test time (seconds) and friction coefficient measurements for Examples 1, 2, and Comparative Examples 1 and 2 are shown.

[0099] (2) Acoustic evaluation The acoustic performance of ball bearings was evaluated by measuring the Andrew value in the M-band (300–1800 Hz) of each test grease composition using an Andrew meter.

[0100] In a ball bearing (inner diameter 3 mm, outer diameter 8 mm, width 4 mm) with a steel seal, the grease compositions of Examples 1-6 and Comparative Examples 1-4 were sealed in at 25% to 35% of the bearing volume. After applying a 10 N preload to the outer ring of the ball bearing axially, the shaft was connected to the rotating shaft of a test motor, causing the inner ring of the ball bearing to rotate. Under this preload condition, the average surface pressure of the inner ring of the ball bearing was approximately 800 MPa.

[0101] Next, the bearing is rotated at 1800 rpm under ambient temperature and atmospheric conditions. In this state, the velocity-type vibration probe is brought into radial contact with the outer circumference of the outer ring of the ball bearing to detect the mechanical vibration transmitted to the outer ring, and the Andre value (the maximum value of the Andre value in the measurement is 50) is calculated 30 seconds after the start of rotation.

[0102] Three tests were conducted on each of the ball bearings from Examples 1-6 and Comparative Examples 1-4, and the average Andrew values ​​were calculated. The results are shown in Table 1. Furthermore, Figure 4 The Andrew values ​​(M band) of the grease compositions with PAO base oil (Examples 1-2, Comparative Example 1 and Comparative Example 2) are shown 30 seconds after the start of rotation. Figure 5 The Andrew values ​​(M band) of grease compositions with a base oil mixture of ether and PAO (Examples 3-4 and Comparative Example 3) and grease compositions with a base oil mixture of ether and ester (Examples 5-6 and Comparative Example 4) are shown after 30 seconds of rotation.

[0103] It should be noted that the M-band frequency range of 300–1800 Hz is considered to be the frequency range that the human ear perceives as harsh. Regarding the evaluation of frictional characteristics, such as Figure 3 As shown, compared with the grease composition of Comparative Example 1 which only contains triphenyl thiophosphate (TPPT), the grease compositions of Examples 1, 2 and 2, which further contain molybdenum dithiocarbamate, showed that the coefficient of friction was suppressed to a low level regardless of the number of carbon atoms in the alkyl group of molybdenum dithiocarbamate, confirming that the friction characteristics could be improved.

[0104] On the other hand, regarding acoustic characteristics, as shown in Table 1 and... Figure 4As shown, Comparative Example 2, which used a grease composition containing molybdenum dithiocarbamate with an alkyl group having 4 carbon atoms, showed a significant increase in its Andrew value after 30 seconds.

[0105] In contrast, in Examples 1 and 2, which incorporated molybdenum dithiocarbamate containing alkyl groups having 8 or more carbon atoms, Andrew values ​​were observed to be equivalent to those of Comparative Example 1, which did not incorporate molybdenum dithiocarbamate.

[0106] Furthermore, in the cases where the base oil was changed from a single PAO oil to a mixture of ether and PAO (Examples 3, 4, and Comparative Example 3), and in the cases where it was changed to a mixture of ether and ester (Examples 5, 6, and Comparative Example 4), the acoustic properties also changed significantly due to the alkyl groups contained in molybdenum dithiocarbamate. Specifically, in Examples 3 and 4, and Examples 5 and 6, which contained molybdenum dithiocarbamate with alkyl groups containing 8 or more carbon atoms, the Andrew values ​​after 30 seconds were lower than those in Comparative Examples 3 and 4, which contained molybdenum dithiocarbamate with alkyl groups containing 4 carbon atoms.

[0107] The above results demonstrate that, in the rolling bearing of the present invention, by using a grease composition comprising molybdenum dithiocarbamate containing alkyl groups having 8 or more carbon atoms and triphenyl thiophosphate, excellent frictional characteristics can be achieved and the deterioration of acoustic properties can be suppressed.

[0108] The preferred embodiments have been described in detail above, but the present invention is not limited to the above embodiments. Modifications and improvements made within the scope of achieving the purpose of the present invention are also included in the present invention.

[0109] Explanation of reference numerals in the attached figures 10: Rolling bearing; 11: Inner ring; 12: Outer ring; 13: Rolling element; 14: Retainer; 15: Sealing component; 16: Bearing space; 20: Motor; 21: Housing; 22: Stator; 23: Coil; 24: Rotor magnet; 25: Shaft; 26: Bearing.

Claims

1. A rolling bearing, wherein, Include: Inner circle; The outer ring is coaxially disposed on the outer periphery of the inner ring; Multiple rolling elements are disposed between the inner ring and the outer ring; A retainer, which holds the rolling element; and A grease composition is retained between the inner and outer rings. The grease composition comprises a base oil, a thickener, molybdenum dithiocarbamate having an alkyl group having eight or more carbon atoms, and triphenyl thiophosphate. The rolling bearing is a rolling bearing with an outer diameter of 22mm or less. Under the condition that the outer ring is preloaded axially with an average surface pressure of 800MPa on the inner ring, the Andrew value of the M-band after rotating the inner ring at 1800rpm for 30 seconds at room temperature and atmospheric atmosphere is 1.2 or less.

2. The rolling bearing according to claim 1, wherein, The molybdenum dithiocarbamate comprises molybdenum dithiocarbamate having an alkyl group having 13 or more carbon atoms.

3. The rolling bearing according to claim 1, wherein, The molybdenum dithiocarbamate is a compound represented by the following formula (1). In the formula, R1 to R4 each independently represent a hydrocarbon group with 8 to 14 carbon atoms. X1 to X4 each independently represent an oxygen atom or a sulfur atom.

4. The rolling bearing according to claim 3, wherein, The molybdenum dithiocarbamate is a compound in formula (1) in which at least one of R1 to R4 is an alkyl group having 13 to 14 carbon atoms.

5. The rolling bearing according to claim 3, wherein, The molybdenum dithiocarbamate is a compound in formula (1) in which R1 to R4 are alkyl groups with 8 carbon atoms.

6. The rolling bearing according to claim 3, wherein, The molybdenum dithiocarbamate is a compound in which R1 to R4 are each independently selected from alkyl groups having 8 carbon atoms and alkyl groups having 13 carbon atoms.

7. A motor, wherein, It has a rolling bearing as described in any one of claims 1 to 6.

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