Rolling bearing

Abstract

The present invention provides a rolling bearing which exhibits an elastic behavior, is enclosed with a specific grease composition exhibiting excellent lubricating properties with respect to resins and metals, and has a specific cage, and provides a rolling bearing and a motor incorporating the same, the rolling bearing having excellent life characteristics even at high temperatures exceeding 100 DEG C. A rolling bearing and a motor including the same. The 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 including a base oil, a thickener, an ionic liquid, and a sebacic acid disodium salt, the grease composition having a viscosity in a dynamic viscoelasticity measurement using a rotary rheometer, the viscosity in the grease composition being greater than the viscosity in the dynamic viscoelasticity measurement using the rotary rheometer, and the viscosity in the grease composition being greater than the viscosity in the dynamic viscoelasticity measurement using the rotary rheometer. A crown-shaped retainer made of a resin, the crown-shaped retainer comprising a resin selected from the group consisting of polyparaphthaloyl azelamine (PA9T), polyamide 46 (PA46), and polyetheretherketone (PEEK) resins, the crown-shaped retainer having a storage modulus of 2400 Pa or more at 25 DEG C as measured under the conditions of a film thickness of 0.5 mm, a shear strain of 1%, and a frequency of 1 Hz, the crown-shaped retainer comprising a resin selected from the group consisting of polyparaphthaloyl azelamine (PA9T), polyamide 46 (PA46), and polyetheretherketone (PEEK) resins.

Description

Technical Field

[0001] The present invention relates to a rolling bearing enclosing a grease composition and a motor including the rolling bearing. Background Art

[0002] In recent years, small motors used in server fans and other applications have been required to withstand long-term stable operation even in environments where temperatures around the built-in bearings exceed 100°C. The grease within these motor bearings, which lubricates and ensures smooth operation of these components and device drive, is also required to exhibit long-term durability and reliability in these high-temperature environments.

[0003] For example, a grease composition and a rolling bearing encapsulated with the grease composition have been proposed, wherein the grease composition aims to achieve, for example, low friction, low viscosity, and improved high-temperature durability, and comprises a base oil containing an ionic liquid, a fluorine-based thickener, and a corrosion inhibitor (Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-249585 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] As the industry develops, rolling bearings and greases built into motors and used at temperatures exceeding 100°C are expected to not only prevent rotational failure but also achieve low power consumption through low torque. Furthermore, in fan motors and other applications, motor speeds are being further increased to improve performance, resulting in not only the expectation of use in high-temperature, high-speed rotation environments but also extremely long lifespans.

[0009] An object of the present invention is to provide a rolling bearing exhibiting elastic behavior and enclosing a specific grease composition that exhibits excellent lubricating properties for resins and metals, and having a specific retainer, and to provide a rolling bearing and a motor incorporating the bearing, wherein the rolling bearing has excellent life characteristics even at high temperatures exceeding 100°C.

[0010] Solutions for solving problems

[0011] One embodiment of the present invention relates to a rolling bearing comprising: an inner ring; an outer ring coaxially arranged on the outer peripheral side of the inner ring; a plurality of rolling elements arranged between the inner ring and the outer ring; a retainer 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, an ionic liquid, and disodium sebacate, the grease composition having a storage modulus of 2400 Pa or greater at 25°C, as measured under conditions of a film thickness of 0.5 mm, a shear strain of 1%, and a frequency of 1 Hz, in a dynamic viscoelasticity measurement using a rotational rheometer, the retainer being a crown-shaped retainer made of a resin selected from the group consisting of polynonane terephthalamide (PA9T), polyamide 46 (PA46), and polyetheretherketone (PEEK) resins.

[0012] Furthermore, the present invention relates to a motor including the rolling bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram illustrating an example of the structure of the rolling bearing of the present invention.

[0014] Figure 2 This is a schematic diagram illustrating an example of the structure of the motor of the present invention.

[0015] Figure 3 These are photographs of the wear marks (ball and disc) of Example 1 and Comparative Example 3 in the lubrication property evaluation (metal-metal).

[0016] Figure 4 It is a graph showing the white light interferometer measurement data of the disk side wear marks of Example 1 and Comparative Example 3 in the lubrication property evaluation (metal-metal).

[0017] Figure 5 It is a graph showing the measurement results of the storage modulus (G') and loss modulus (G") of Example 1 and Comparative Example 3 in the viscoelasticity evaluation.

[0018] Figure 6 This is a graph showing the measurement results of the friction coefficient and the test temperature of Examples A to C and Comparative Example A in the lubrication property evaluation (metal-resin).

[0019] Figure 7 These are photographs of wear marks (test pieces) of Example A and Comparative Example A in the lubrication property evaluation (metal-resin). DETAILED DESCRIPTION

[0020] As mentioned above, fan motors used in server fans and other applications are increasingly operating at higher temperatures and higher speeds, requiring high reliability from the bearings incorporated into these motors in these harsh environments. Furthermore, these bearings are also required to have low torque performance. To reduce the grease stirring resistance that increases torque, the amount of grease used is minimized, and lubrication is achieved by forming an oil film with a small amount of oil separation. However, if significant oil separation occurs due to high-temperature operation and frictional heat generation, lubrication problems will quickly occur.

[0021] Furthermore, adding extreme pressure agents to conventional greases forms a lubricating adsorption film (tribological coating) on ​​the metal surface, helping to reduce frictional heat and inhibit wear. However, the lifespan of these server fan motors is currently required to exceed 10,000 hours. The repeated process of adsorption film formation, friction reduction and wear inhibition (film disappearance), and adsorption film reformation by the extreme pressure agent causes the agent to disappear, resulting in deterioration of friction and wear characteristics and, in turn, poor lubrication.

[0022] To address this problem of poor lubrication, the present inventors focused on the shape of the grease enclosed in the rolling bearing. Furthermore, as a structure for maintaining the shape of the grease even in the harsh environment described above, an ionic liquid and disodium sebacate, described below, were employed. This structure was found to produce a grease exhibiting elastic behavior, thereby suppressing the stirring resistance of the grease and the shear heat generated by stirring under high-speed rotation. Furthermore, the oil content in a small amount of grease was retained for a long period of time, leading to the expectation of a longer lubrication life. Furthermore, it was found that the use of these components improved lubrication properties and also helped to extend the lubrication life by reducing frictional heat.

[0023] Furthermore, the inventors of the present invention have also focused on the structure of rolling bearings and have discovered that excellent friction and wear resistance can be achieved by using a retainer made of a resin having excellent adsorption properties for the above-mentioned ionic liquid, particularly a crown-shaped retainer made of a resin component composed of polynonane terephthalamide (PA9T), polyamide 46 (PA46), or polyetheretherketone (PEEK) resin.

[0024] The following is a detailed description.

[0025] [Rolling bearings]

[0026] First, 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.

[0027] Figure 1The figure 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 a conventional rolling bearing, and includes an annular inner ring 11 , an outer ring 12 , a plurality of rolling elements 13 , a cage 14 , and a sealing member 15 .

[0028] The inner ring 11 is a cylindrical structure coaxially arranged on the outer circumference of a shaft (not shown) with its central axis. The outer ring 12 is a cylindrical structure coaxially arranged on the outer circumference of the inner ring 11. The multiple rolling elements 13 are each balls arranged on a track within an annular bearing space 16 formed between the inner ring 11 and the outer ring 12. In other words, the rolling bearing 10 in this embodiment is a ball bearing.

[0029] The retainer 14 is arranged within the raceway and holds the multiple rolling elements 13. The retainer 14 is an annular body coaxial with the central axis of the shaft. It has a structure with multiple pockets on one side of the central axis for holding the rolling elements 13, with each pocket housing a rolling element 13. The retainer 14 holds the rolling elements 13 at predetermined intervals in the circumferential direction of the inner ring 11 and outer ring 12, thereby preventing the rolling elements 13 from falling out and preventing contact between adjacent rolling elements 13.

[0030] Sealing member 15 is fixed to the inner circumferential surface of outer ring 12 and extends toward inner ring 11, sealing bearing space 16. Grease composition G is enclosed in bearing space 16 sealed by sealing member 15. Specifically, grease composition G is retained between inner ring 11 and outer ring 12. This grease composition G is the grease composition described below. The amount of grease G enclosed within bearing space 16 can be set to, for example, 5 to 50% of its volume.

[0031] Sealing member 15 is formed, for example, from a steel plate or rubber. Examples include a steel plate shield that does not contact the outer periphery of inner ring 11 and a non-contact rubber seal that does not contact the outer periphery of inner ring 11. In the present invention, either a steel plate shield or a non-contact rubber seal can be used as a sealing member. From the perspective of suppressing outgassing, a steel plate shield is preferred. It should be noted that while this figure shows a configuration with sealing member 15, the rolling bearing of the present invention also encompasses configurations without a sealing member.

[0032] In the rolling bearing 10 having the above structure, the grease composition G acts to reduce the friction between the rolling elements 13 and the retainer 14, and the friction between the rolling elements 13 and the inner ring 11 and the outer ring 12. By reducing friction, the friction torque is reduced, and the generation of frictional heat is suppressed, which promotes smooth rotation of the inner ring 11 and the outer ring 12. Figure 1As can be seen from the structure shown, the grease composition G enclosed in the rolling bearing 10 lubricates the rolling elements 13 and the inner ring 11 and even the outer ring 12 when the rolling bearing 10 rotates.

[0033] In the rolling bearing of the present invention, a retainer is a crown-shaped resin retainer made of a resin selected from the group consisting of polynonane terephthalamide (PA9T), polyamide 46 (PA46), and polyetheretherketone (PEEK). The retainer can be formed of any material that necessarily contains the aforementioned resin, and may also be formed of a composite material containing a reinforcing agent such as glass fiber or carbon fiber.

[0034] The rolling bearings in the present invention are not particularly limited in size, usage conditions, etc., but rolling bearings with an outer diameter of less than 10 mm are suitable for use under high temperature and / or high speed conditions of temperatures above 100°C, for example, temperatures of 130°C, or rotation speeds above 50,000 rpm, for example, above 100,000 rpm or above 130,000 rpm.

[0035] The rolling bearing of the present invention can be used as a rolling bearing for small motors (for example, fan motors and cleaner motors) used in automobiles, home appliances, information equipment, and the like.

[0036] [motor]

[0037] As an example, in Figure 2 Detailed description will be given of an embodiment of a motor including a rolling bearing according to this embodiment. However, the present invention is not limited to the following embodiment.

[0038] Figure 2 The motor 20 has the same basic structure as a conventional motor and is composed 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 .

[0039] Motor 20 generates magnetic force by passing current supplied from a power source (not shown) via a drive circuit through coil 23 wound around stator 22 , thereby rotating rotor magnet 24 and transmitting the rotation to an external rotating body via shaft 25 .

[0040] In the present invention, the rolling bearing of the present invention can be preferably used as a bearing of a motor used in a blower. In this case, the external rotating body corresponds to the impeller (not shown) of the blower.

[0041] [Grease composition]

[0042] As described above, the present inventors focused on the shape of the grease enclosed in the bearing and employed ionic liquid and disodium sebacate as a structure for maintaining elasticity and making the grease shape less likely to deform, thereby anticipating suppression of stirring resistance, suppression of shear heating, and achievement of high-temperature / high-speed durability, thereby also achieving low torque and reduced power consumption. As a result, the storage modulus of the grease composition was optimized.

[0043] The grease composition enclosed in the rolling bearing of the present invention will be described below.

[0044] <Base oil>

[0045] In the grease composition enclosed in the rolling bearing of this embodiment, synthetic oils such as synthetic hydrocarbon oils, ether-based synthetic oils, and ester-based synthetic oils that are generally used as grease base oils can be used as base oils alone or in combination.

[0046] Examples of the synthetic hydrocarbon oil include normal paraffins, isoparaffins, polybutene, polyisobutene, 1-decene oligomers, and poly-α-olefins (PAO) such as 1-decene and ethylene copolymers.

[0047] Examples of the ester synthetic oil include diester oils such as dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl phthalate, and methyl acetyl ricinoleate; aromatic ester oils such as trioctyl trimellitate, tri-2-ethylhexyl trimellitate, tridecyl trimellitate, tetraoctyl pyromellitate, and tetra-2-ethylhexyl pyromellitate; polyol ester oils such as trimethylolpropane octanoate, trimethylolpropane nonanoate, pentaerythritol-2-ethylhexanoate, and pentaerythritol nonanoate; and carbonate oils.

[0048] Examples of the ether-based synthetic oil include alkyl ether oils such as monoalkyl diphenyl ether, dialkyl diphenyl ether, and polyalkyl diphenyl ether, and alkyl diphenyl ether oil.

[0049] The base oil may be contained in the grease composition used in the present invention at a ratio of, for example, 70% by mass or more, for example, 70% by mass to 90% by mass, based on the total mass of the grease composition.

[0050] Thickener

[0051] The grease composition used in the present invention can preferably use a urea-based thickener as a thickener.

[0052] Urea compounds are excellent in both heat resistance and water resistance, and are particularly stable at high temperatures. Therefore, they are preferably used as thickeners in applications under high-temperature environments.

[0053] Urea thickeners include urea compounds such as diurea compounds, triurea compounds, and polyurea compounds. Diurea compounds are preferred for their heat resistance and acoustic properties (quietness). Urea compounds preferably include at least one of aliphatic-aromatic ureas, alicyclic-aliphatic ureas, and aliphatic ureas.

[0054] As these urea-based thickeners, conventionally known urea compounds can be used.

[0055] As an example of the diurea compound used for the urea thickener, a diurea compound represented by the following formula (1) can be mentioned.

[0056] R1-NHCONH-R2-NHCONH-R3 formula (1)

[0057] In the above formula (1), R1 and R3 each independently represent a monovalent aliphatic hydrocarbon group, a monovalent alicyclic hydrocarbon group, or a monovalent aromatic hydrocarbon group, and at least one of R1 and R3 represents a monovalent aliphatic hydrocarbon group or a monovalent alicyclic hydrocarbon group.

[0058] Furthermore, R2 represents a divalent aromatic hydrocarbon group.

[0059] Examples of the monovalent aliphatic hydrocarbon group include linear or branched saturated or unsaturated alkyl groups having 6 to 26 carbon atoms.

[0060] Examples of the monovalent alicyclic hydrocarbon group include a cycloalkyl group having 5 to 12 carbon atoms.

[0061] Examples of the aromatic hydrocarbon group include monovalent or divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms.

[0062] The urea compound used as the urea thickener can be synthesized using an amine compound and an isocyanate compound.

[0063] Examples of the amine compound include aliphatic amines such as hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine (stearylamine), behenylamine, and oleylamine; alicyclic amines such as cyclohexylamine; and aromatic amines such as aniline, p-toluidine, and ethoxyaniline.

[0064] In addition, as the isocyanate compound, aromatic diisocyanates such as phenylene diisocyanate, tolylene diisocyanate (TDI), diphenyl diisocyanate, diphenylmethane diisocyanate (MDI), and dimethyldiphenyl diisocyanate (TODI); and aliphatic diisocyanates such as octadecane diisocyanate, decane diisocyanate, and hexamethylene diisocyanate can be used.

[0065] When an aromatic diurea compound is obtained using aromatic monoamine and aromatic diisocyanate as amine raw materials and used as a urea thickener, there is a possibility of generating abnormal noise, and therefore, the use thereof needs to be examined.

[0066] The urea thickener (urea compound) may be blended in an amount of, for example, 10 to 20% by mass relative to the total amount of the grease composition used in the present invention.

[0067] Ionic Liquids

[0068] The grease composition used for the rolling bearing of this embodiment must contain an ionic liquid.

[0069] Conventionally, in order to release static electricity generated between parts due to rotational friction, conductivity has been imparted to lubricants as needed, and the addition of ionic liquids has been studied as one of the methods.

[0070] In the present invention, it is believed that by using an ionic liquid in combination with disodium sebacate (described later), the storage modulus of the grease composition is adjusted to an appropriate range, thereby achieving an elastic and non-deformable grease. This suppresses shear heat generated by stirring under high-speed rotation, and further reduces frictional heat by forming a strong tribological film, thereby contributing to the effect of extending the life of lubrication performance.

[0071] As the ionic liquid, a fluorine-based ionic liquid is used, and there are no particular limitations as long as the desired storage elastic modulus can be achieved by combined use with disodium sebacate described later.

[0072] For example, trihexyltetradecylphosphonium-bis(trifluoromethylsulfonyl)imide ([THTDP][TFSI]) shown below can be used.

[0073]

[0074] The ionic liquid may be blended in an amount of, for example, 0.1 to 10% by mass relative to the total amount of the grease composition used in the present invention.

[0075] <Dispersant: Disodium Sebacate>

[0076] The grease composition used for the rolling bearing of this embodiment contains disodium sebacate as a dispersant.

[0077] Disodium sebacate can be blended in an amount of, for example, 0.1 to 10% by mass relative to the total amount of the grease composition used in the present invention.

[0078] <Other additives>

[0079] The grease composition used in the present invention may contain additives commonly used in grease compositions as needed within a range that does not impair the effects of the present invention.

[0080] Examples of such additives include antioxidants, extreme pressure agents, metal deactivators, anti-wear agents (wear-resistant agents), rust inhibitors, oiliness improvers, viscosity index improvers, and thickeners.

[0081] When these other additives are contained, the amount added (total amount) is usually 0.1 to 10% by mass relative to the total amount of the grease.

[0082] For example, examples of the antioxidant include octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-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], 1,6-hexanediol-bis[ Hindered phenol antioxidants such as 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,2-thio-diethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamic acid); phenol antioxidants such as 2,6-di-tert-butyl-4-methylphenol and 4,4-methylenebis(2,6-di-tert-butylphenol); amine antioxidants such as diphenylamine, diarylamine, triphenylamine, phenyl-α-naphthylamine, alkylated phenyl-α-naphthylamine, phenothiazine, alkylated phenothiazine, etc.

[0083] Examples of extreme pressure agents include phosphorus compounds such as phosphates, phosphites, and amine phosphates; sulfur compounds such as sulfides and disulfides; chlorine compounds such as chlorinated paraffins and chlorinated biphenyls; and metal salts of sulfur compounds such as zinc dialkyldithiophosphates and molybdenum dialkyldithiocarbamates.

[0084] Examples of metal deactivators include benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]-4-methylbenzotriazole and the like; thiadiazole, 2-mercaptothiadiazole, 2,5-bis(alkyldisulfide)-1,3,4-thiadiazole and the like; benzimidazole, 2-mercaptobenzimidazole, 2-(dodecyldisulfide)-benzimidazole and the like; sodium nitrite and the like.

[0085] In addition, examples of anti-wear agents include tricresyl phosphate and high molecular weight esters.

[0086] Examples of the polymer esters include esters of aliphatic monocarboxylic acids and dicarboxylic acids with polyols. Specific examples of the polymer esters include, but are not limited to, PRIOLUBE (registered trademark) series manufactured by Croda Japan.

[0087] The grease composition used in the present invention can be obtained by blending the above-mentioned base oil, a urea-based thickener, an ionic liquid, disodium sebacate, and other additives as needed.

[0088] Furthermore, for example, a grease composition may be obtained by blending an ionic liquid, disodium sebacate, and other additives as needed with a urea-based grease (base grease) containing the base oil and the urea-based thickener.

[0089] Typically, the content of the thickener relative to the base grease is about 10 to 30 mass %. For example, the content of the diurea compound (urea thickener) relative to the above-mentioned urea grease can be set to about 10 to 25 mass %, or can be set to about 10 to 20 mass %.

[0090] Storage modulus

[0091] The grease composition used in the present invention can exhibit elastic and non-deformable grease behavior by having a storage modulus within an appropriate range.

[0092] The storage modulus is a value indicating the shape stability of grease, and is an effective parameter for understanding the shape stability of grease immediately after it is enclosed in a rolling bearing and while the rolling bearing is rotating.

[0093] In particular, in rolling bearings used at high temperatures and high speeds, if the shape of the grease changes from its initial shape, the grease can become entangled with the balls (rolling elements), etc. This not only increases the torque of the rolling bearing and causes torque instability, but also disrupts the fiber structure of the thickener due to shearing, causing grease degradation and potentially leading to poor lubrication. Therefore, the ability of grease to maintain its shape (shape stability) is an important factor in ensuring initial and long-term torque stability and preventing poor lubrication.

[0094] From the perspective of the dimensional stability of such greases, it is important for the grease composition used in the present invention to have a storage modulus of 2400 Pa or higher at 25°C under the aforementioned measurement conditions (dynamic viscoelasticity measurement using a rotational rheometer: film thickness 0.5 mm, shear strain 1%, frequency 1 Hz). However, if the storage modulus is too high, the grease will be located on the orbital path of the rolling elements, increasing the resistance when the balls run over the grease and potentially increasing torque. Therefore, the storage modulus is preferably 4500 Pa or lower, and more preferably no more than 3500 Pa.

[0095] The present invention is not limited to the embodiments and 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.

[0096] [Example]

[0097] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0098] The grease compositions used in Example 1 and Comparative Examples 1 to 6 were prepared according to the blending amounts shown in Table 1 below.

[0099] The details of the components used in the preparation of the grease composition and their abbreviations are as follows.

[0100] <Base oil>

[0101] Ester oil: a mixture of trioctyl trimellitate (TOTM) and tetraoctyl pyromellitate (TOPM) [kinematic viscosity at 40°C: 100 mm 2 / s].

[0102] Thickener

[0103] ·Bisurea compounds: aliphatic-aromatic diurea compounds.

[0104] <Additives>

[0105] Ionic liquid: (See the structure shown in the chemical formula below).

[0106] (1)[TFSI][THTDP]

[0107] Trihexyltetradecylphosphonium-bis(trifluoromethylsulfonyl)imide

[0108] (2) [TFSI] [EMI]

[0109] 1-Ethyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide

[0110] (3)[TFSI][BMP]

[0111] 1-Butyl-1-methylpyrrolidinium-bis(trifluoromethylsulfonyl)imide

[0112] (4)[ES][EMI]

[0113] 1-Ethyl-3-methylimidazolium-ethyl sulfate

[0114]

[0115] Dispersant: Disodium sebacate.

[0116] Other additives:

[0117] Extreme pressure additive: a phosphate ester-based extreme pressure additive (triphenyl thiophosphate, product name “Irgalube TPPT”, BASF Japan Co., Ltd.).

[0118] Metal deactivator: Benzotriazole compound (1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, product name "BT-LX", Johoku Chemical Industry Co., Ltd.).

[0119] Antioxidant: diarylamine antioxidant (octylated / butylated diphenylamine, product name "Irganox L57", BASF Japan Co., Ltd.).

[0120] Other Additives The extreme pressure additive, metal deactivator, and antioxidant were added in an amount of 3% by mass in total relative to the total mass of each grease composition of Examples and Comparative Examples.

[0121] The rolling bearings used in the following test evaluations are as follows.

[0122] Rolling bearing: ball bearing with steel shield (inner diameter 3mm, outer diameter 8mm, width 3mm).

[0123] Retainer: Resin crown-shaped retainer.

[0124] Retainer Material

[0125] Cage A: PEEK [carbon fiber (CF) 20% blend].

[0126] Cage B: PA9T [carbon fiber (CF) 20% blend].

[0127] Cage C: PA46 [glass fiber (GF) 30% blend].

[0128] Cage D: PA66 [glass fiber (GF) 30% blend].

[0129] The lubrication property evaluation, viscoelasticity evaluation, and heat resistance evaluation were performed according to the following procedures. The obtained results are shown in Tables 1 and 2.

[0130] <(1) Lubrication property evaluation (metal-metal friction and wear test)>

[0131] Metal-metal friction and wear tests were conducted using an Optimol vibration tribometer (trade name: SRV). The tests were conducted using a ball-on-disc system, using balls (material: SUJ2, φ10 mm) and discs (material: SUJ2, φ24 mm). The test conditions were a load of 100 N, a measurement temperature of 80°C, a sliding distance of 1 mm, a vibration frequency of 50 Hz, and a test time of 20 minutes. At the start of the test, 5 mg of each grease composition was supplied.

[0132] After the test, the wear scar diameter on the ball side was measured (average value for N = 3). Furthermore, for Example 1 and Comparative Example 3, the maximum height difference (PV) of the wear scar on the disk side, in a direction intersecting the sliding direction, was measured using a white light interferometer (trade name: NewView200) manufactured by ZYGO Corporation (N = 1 for each). The wear scar diameter and maximum height difference were evaluated according to the following criteria.

[0133] It should be noted that Figure 3 ] Figures 2 and 3 show photographs of wear marks on the balls and disks of Example 1 and Comparative Example 3 after the friction wear mark test. Figure 3 (A) represents the ball wear mark [(a) Example 1, (b) Comparative Example 3], Figure 3 (B) shows the wear marks of the disc [(a) Example 1, (b) Comparative Example 3].

[0134] also, Figure 4 2 shows the white light interferometer measurement data performed on the disks of Example 1 and Comparative Example 3 after the friction and wear scar test [(a) Example 1, (b) Comparative Example 3].

[0135] <Criteria for Determining Wear Scar Diameter>

[0136] A: The wear scar diameter of the ball is 330 μm or less.

[0137] N: The wear scar diameter of the ball exceeds 330 μm.

[0138] <Judgment criteria for maximum height difference>

[0139] A: The maximum height difference PV value of the wear mark of the disk is less than 0.5μm.

[0140] N: The maximum height difference PV value of the wear mark of the disk exceeds 0.5μm.

[0141] <(2) Oil separation (unit: mm 2 / mg) determination and evaluation>

[0142] 9 mg of each grease composition prepared on the medicine-side of the medicine wrapping paper was placed in a φ3 mm cylindrical shape and left at 80°C for 24 hours. After 24 hours, the area of ​​the oil seepage in the medicine wrapping paper was measured. The area of ​​the oil seepage per unit mass of the grease composition was calculated as the oil separation (mm 2 / mg), and the oil separation amount was evaluated according to the following criteria (average value of N=3).

[0143] It should be noted that in this test, the medicine wrapping paper used was "Pure White Molded (Medium)" (size: 105 mm × 105 mm, thickness: 42 μm, unit area weight: 30 g / m 2 ), as described above, a grease composition is placed on the side where the medicine is placed (glossy side).

[0144] <Judgment Criteria>

[0145] N: Oil distance less than 180mm 2 / mg.

[0146] A: Oil separation distance is 180mm 2 / mg or above and 270mm 2 / mg or less.

[0147] N: Oil clearance exceeds 270mm 2 / mg.

[0148] <(3) Viscoelasticity evaluation (measurement of elastic modulus (unit: Pa) using a rheometer)>

[0149] The storage modulus G' and loss modulus G" of each grease composition were measured using a rotational viscometer (rheometer, trade name MCR302) manufactured by Anton Paar. The measurement mode adopted the strain dispersion method (strain variable from 100% to 0.01%). The measurements were performed at a temperature of 25°C using a parallel plate φ25 mm (PP25) fixture, a plate gap of 0.5 mm, a frequency of 1 Hz, and a temperature of 25°C. The measured value at a strain of 1% was designated as the storage modulus G' (Pa), and the storage modulus was evaluated according to the following criteria (average value of N = 3).

[0150] It should be noted that Figure 5 1 and 2 show the measurement results of the storage modulus (G') and loss modulus (G") with respect to shear strain in Example 1 and Comparative Example 3 [(a) Example 1, (b) Comparative Example 3].

[0151] <Judgment Criteria>

[0152] A: The storage modulus is 2400 Pa or more and 4500 Pa or less.

[0153] N: Storage modulus is less than 2400Pa or exceeds 4500Pa.

[0154] <(4) Heat resistance evaluation (durability test) (1)>

[0155] Each grease composition was filled into a steel ball bearing (3mm inner diameter, 8mm outer diameter, 3mm width, using a PA9T retainer (20% carbon fiber (CF) blend)) at a rate of 25% to 35% of the bearing volume. The ball bearing was mounted in a housing, and a 2N preload was applied to the outer ring in the axial direction. A shaft was then inserted into the bearing's inner diameter and connected to the rotating shaft of a test motor, causing the inner ring of the ball bearing to rotate.

[0156] Next, the housing was heated to 130° C. and rotated at a test temperature of 130° C. and a rotation speed of 120,000 rpm, and the time until the ball bearing stopped was measured.

[0157] Stop condition: The moment when the torque increases and the speed decreases by 10% from the specified value is considered a stop, and the test time until the stop is defined as the elapsed time (hr). For each grease composition, three tests were conducted, and the average value was calculated and evaluated according to the following criteria.

[0158] <Judgment Criteria>

[0159] A: The elapsed time is 10,000 hours or more.

[0160] N: Elapsed time is less than 10,000 hr.

[0161] [Table 1]

[0162]

[0163] <(5) Lubrication Property Evaluation (Metal-Resin: Friction and Wear Test)>

[0164] Metal-resin friction and wear tests were conducted using a BRUKER multifunctional friction and wear tester (trade name: UMT TriboLab). The test was conducted using a ball-on-disk format, using balls (material: SUJ2, φ10 mm) and discs (length: 30 mm, width: 10 mm, thickness: 4 mm) of the materials listed in Table 2. The test conditions were a load of 49 N, room temperature, a sliding distance of 12.5 mm, a vibration frequency of 20 Hz, and a test time of 2 minutes. At the start of the test, 5 mg of the grease composition of Example 1 was applied to the ball.

[0165] In the test, the friction coefficient and the temperature of the upper ball were measured over time, and evaluation was performed based on the friction coefficient value (average value of N=3) after 2 minutes (120 seconds) according to the following criteria.

[0166] It should be noted that Figure 6 The measurement results of the friction coefficient and temperature (° C.) (upper ball) with respect to the test time (seconds) in Examples A to C and Comparative Example A are shown [(A) Friction coefficient, (B) Temperature (upper ball)].

[0167] also, Figure 7 Photos of the wear marks of the disks of Example A and Comparative Example C after the friction wear mark test are shown [(a) Example A, (b) Comparative Example A].

[0168] <Judgment Criteria>

[0169] A: Friction coefficient 0.1 or less.

[0170] N: The friction coefficient exceeds 0.1.

[0171] <(6) Heat resistance evaluation (durability test) (2)>

[0172] Heat resistance evaluation was carried out in the same manner as in <(4) Heat resistance evaluation (durability test) (1)> except that the retainer of the ball bearing for strip steel was changed to the retainer shown in Table 2 and the grease composition of Example 1 was used as the grease composition.

[0173] [Table 2]

[0174]

[0175] Note: *7A (suitable): Friction coefficient (after 120 seconds) less than 0.1 N (unsuitable): Friction coefficient (after 120 seconds) exceeds 0.1

[0176] *8A (suitable): Elapsed time exceeds 10,000 hours N (unsuitable): Elapsed time is less than 10,000 hours

[0177] As shown in Table 1, the storage modulus of the grease composition of Example 1 exceeds 2400 Pa, and the actual grease composition has a tough shape like agar. Figures 3 to 5 As shown, compared with Comparative Example 3 ( Figure 3 (b) in (A) Figure 3 (b) in (B) Figure 4 (b) Figure 5 (b)), in Example 1, it can be confirmed that the wear marks of the ball and the disc are small (thin) ( Figure 3 (a) in (A) Figure 3 (a) in (B)), the surface roughness is small ( Figure 4 (a)), and it can be confirmed that the elastic modulus G' is large when the strain is 1% ( Figure 5 (a)). Thus, in friction and wear tests (metal-to-metal) using this grease composition, the friction wear scar of the ball was less than 330 μm, and the maximum height difference (PV) value of the friction wear scar of the disk was approximately 0.4 μm, confirming that friction and wear are less likely to occur and that lubricity is excellent. Furthermore, in Example 1, in a high-temperature / high-speed rotation test of a rolling bearing using a crown-shaped resin retainer composed of PA9T as a retainer, no abnormal noise or the like was produced even after 10,000 hours, confirming that the bearing exhibits excellent durability under high-temperature and high-speed conditions.

[0178] On the other hand, in Comparative Examples 1 to 3 using ionic liquids (2) to (4) instead of ionic liquid (1) used in the examples, Comparative Example 4 not using disodium sebacate, Comparative Example 5 not using ionic liquid, and Comparative Example 6 not using disodium sebacate and ionic liquid, the storage modulus was less than 2400 Pa, and these grease compositions were soft and difficult to maintain their shape compared to Example 1. In the friction and wear test (metal-metal) using these grease compositions, the friction wear marks of the ball became friction wear marks of less than 330 μm only in Comparative Example 1, but exceeded 330 μm in Comparative Examples 2 to 6, resulting in poor lubricity. Regarding Comparative Example 3, the maximum height difference P-V value of the friction wear marks of the disk was about 0.9 μm, which is more than twice the maximum height difference of Example 1. Figure 3 (b) and (B) Figure 4As shown in (b), deep friction damage was observed along the sliding direction in the disc test piece of the friction and wear test (metal-to-metal) of Comparative Example 3. Furthermore, in a high-temperature, high-speed rotation test of a rolling bearing using a crown-shaped resin retainer made of PA9T as a retainer, in these comparative examples, torque increased between the start of the test and 10,000 hours, resulting in a speed drop of 10% below the specified value, necessitating the termination of the test.

[0179] Furthermore, as shown in Table 2, in the rolling bearings using the resin crown-shaped retainers made of PEEK (Example A), PA9T (Example B), and PA46 (Example C) as retainers, the friction coefficient was as low as 0.1 or less [Refer to Figure 6 (A)], even after the friction and wear test, the temperature rise of the upper ball is suppressed to a lower level compared with the comparative example described later [Refer to Figure 6 In addition, if Figure 7 As shown in (A), the wear marks of the disc after the test (Example A) are also thin. Moreover, in the high temperature / high speed rotation test, no abnormal noise or the like was generated even after 10,000 hours, indicating excellent durability.

[0180] On the other hand, even when the grease composition of Example 1 was used, the friction coefficient of the rolling bearing of Comparative Example A, which used a crown-shaped resin cage composed of PA66 as a cage, increased significantly to 0.224 [refer to Figure 6 (A)], as the friction and wear test time passes, the temperature of the upper ball rises significantly [Refer to Figure 6 In addition, if Figure 7 As shown in (B), the wear marks of the disc after the test are Figure 7 The wear marks of Example A shown in (A) were more obvious than those of Example A. In the high temperature / high speed rotation test, abnormal noise was generated 3500 hours from the start of the test, resulting in rotation failure.

[0181] While the best embodiment has been described in detail above, the present invention is not limited to the above embodiment, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention.

[0182] Description of reference numerals:

[0183] 10: Rolling bearing; 11: Inner ring; 12: Outer ring; 13: Rolling element; 14: Retainer; 15: Sealing member; 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; an outer ring, coaxially arranged on the outer circumference of the inner ring; A plurality of rolling elements are arranged between the inner ring and the outer ring; a retainer that retains the rolling element; and a grease composition held between the inner ring and the outer ring, The grease composition comprises base oil, thickener, ionic liquid and disodium sebacate, The grease composition has a storage modulus of 2400 Pa or more at 25° C. when measured under conditions of a film thickness of 0.5 mm, a shear strain of 1%, and a frequency of 1 Hz in a dynamic viscoelasticity measurement using a rotational rheometer. The cage is a crown-shaped cage made of a resin selected from the group consisting of polynonane terephthalamide (PA9T), polyamide 46 (PA46), and polyetheretherketone (PEEK).

2. The rolling bearing according to claim 1, wherein: The ionic liquid is trihexyltetradecylphosphonium-bis(trifluoromethylsulfonyl)imide THTDP-TFSI.

3. The rolling bearing according to claim 1, wherein: The thickener is a urea thickener, which comprises a diurea compound represented by the following general formula (1): R1-NHCONH-R2-NHCONH-R3(1) In formula (1), R1 and R3 each independently represent a monovalent aliphatic hydrocarbon group, a monovalent alicyclic hydrocarbon group, or a monovalent aromatic hydrocarbon group, and at least one of R1 and R3 represents a monovalent aliphatic hydrocarbon group or a monovalent alicyclic hydrocarbon group, and R2 represents a divalent aromatic hydrocarbon group. 4 . A motor comprising the rolling bearing according to claim 1 .

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