Rolling bearings

Abstract

To provide a ball bearing which is filled with a specified grease composition and has a specified holder, the ball bearing having excellent life property even under a high temperature environment, and a motor installed with the ball bearing.SOLUTION: The ball bearing includes: an inner ring 11; an outer ring 12 arranged on an outer peripheral side of the inner ring and coaxially with the inner ring; a plurality of rolling elements 13 arranged between the inner ring and the outer ring; a holder 14 holding the rolling element; and a grease composition held between the inner ring and the outer ring, wherein the grease composition includes a base oil, a thickener, an ionic liquid, and sebacic acid disodium salt, the grease composition has a storage modulus of 2,400 Pa or over at 25°C measured under conditions of a film thickness of 0.5 mm, a shearing strain of 1%, and frequency of 1 Hz, and the holder is a resin-made crown type holder constituted of a specified resin, and a motor including the ball bearing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a rolling bearing in which a grease composition is enclosed and a motor including the rolling bearing.

Background Art

[0002] In recent years, small motors used for fans for servers and the like are required to have characteristics that can withstand long-term stable use in a situation where the temperature around the built-in bearing exceeds 100°C. For the bearings built into these motors and the grease that is responsible for lubrication to smooth the operation of these components and the driving of the device, long-term durability and reliability in such a high-temperature environment are required. For example, as a grease composition that measures low friction and low viscosity and aims to improve high-temperature durability, a grease composition containing a base oil containing an ionic liquid, a fluorine-based thickener, and a corrosion additive, and a rolling bearing enclosing the same have been proposed (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] With the development of the industry, for rolling bearings and grease built into motors and used at high temperatures exceeding 100°C, there is a desire not only to suppress rotation failure but also to achieve low torque and low power consumption. In addition, in fan motors and the like, the rotational speed of the motor further increases for performance improvement, and use in a high-temperature and high-speed rotation environment is not only assumed, but the required life is also extremely long.

[0005] The present invention aims to provide a rolling bearing that contains a specific grease composition exhibiting elastic behavior and excellent lubrication properties for resins and metals, and has a specific cage; and to provide a rolling bearing that exhibits excellent lifespan characteristics even at high temperatures exceeding 100°C, as well as a motor incorporating the bearing. [Means for solving the problem]

[0006] One aspect of the present invention is a rolling bearing comprising an inner ring and An outer ring is arranged coaxially with the inner ring on the outer circumference side of the inner ring, A plurality of rolling elements arranged between the inner ring and the outer ring, A retainer for holding the rolling element, The grease composition is held between the inner ring and the outer ring, The grease composition comprises a base oil, a thickener, an ionic liquid, and disodium sebacate salt. The grease composition, in dynamic viscoelasticity measurements using a rotary rheometer, has a storage modulus of 2,400 Pa or more at 25°C, measured under conditions of a film thickness of 0.5 mm, shear strain of 1%, and frequency of 1 Hz. The aforementioned retainer is a resin crown-shaped retainer made of a resin selected from the group consisting of polynonameethylene terephthalamide (PA9T), polyamide 46 (PA46), and polyetheretherketone (PEEK) resin. Regarding rolling bearings. The present invention also relates to a motor equipped with the aforementioned rolling bearing. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram illustrating an example of the structure of a rolling bearing according to the present invention. [Figure 2] This is a schematic diagram illustrating an example of the structure of the motor of the present invention. [Figure 3] These are photographs of the wear marks (ball and disc) from Example 1 and Comparative Example 3 in the lubrication characteristics evaluation (metal-metal). [Figure 4]This figure shows the white light interferometer measurement data for the wear marks on the disk side in Example 1 and Comparative Example 3 of the lubrication characteristics evaluation (metal-metal). [Figure 5] This figure shows the measurement results of the storage modulus (G') and loss modulus (G") for Example 1 and Comparative Example 3 in the viscoelastic evaluation. [Figure 6] This figure shows the measurement results of the friction coefficient and test temperature for Examples A to C and Comparative Example A in the lubrication characteristics evaluation (metal-resin). [Figure 7] These are photographs of the wear marks (test pieces) of Example A and Comparative Example A in the lubrication characteristics evaluation (metal-resin). [Modes for carrying out the invention]

[0008] As mentioned earlier, fan motors used in server fans and the like are increasingly operating at high temperatures and speeds, and the bearings incorporated into these motors require high reliability under such harsh conditions. Furthermore, these bearings also need low torque performance, and in order to reduce the stirring resistance of the grease that leads to increased torque, the amount of grease applied is kept to a minimum, and efforts are made to achieve oil film formation and lubrication with only a small amount of oil separation. However, if significant oil separation occurs due to use in high-temperature environments or frictional heat generation, lubrication failure will quickly occur. Furthermore, general greases contain extreme pressure additives that form a lubricating adsorbent film (tribological film) on metal surfaces, contributing to the reduction of frictional heat generation and the suppression of wear. However, the required lifespan of the server fan motors mentioned above now exceeds 10,000 hours, and as the extreme pressure additive repeatedly forms an adsorbent film, reduces friction and suppresses wear (film disappears), and reforms the adsorbent film, the extreme pressure additive is eventually lost, leading to deterioration of friction and wear characteristics and ultimately, lubrication failure.

[0009] In view of the problem of such lubrication failure, the inventors focused on the shape of the grease encapsulated in the rolling bearing. As a configuration for maintaining the grease shape even under the above severe environment, the adoption of an ionic liquid and disodium sebacate, which will be described later, was achieved. With this configuration, a grease showing elastic behavior is realized, thereby suppressing the stirring resistance of the grease, suppressing the shear heat generation associated with stirring at high speed rotation, and retaining the oil content in a small amount of grease for a long time, and it was found that a long lubrication life can be expected. In addition, it was found that the adoption of these components can contribute to the improvement of lubrication characteristics and the extension of lubrication life by reducing frictional heat generation. Furthermore, the inventors also focused on the configuration of the rolling bearing, and came to adopt a resin cage having excellent adsorptivity to the above ionic liquid. In particular, a resin crowned cage composed of polynonamethylene terephthalamide (PA9T), polyamide 46 (PA46), or polyetheretherketone (PEEK) resin as a resin component was found to realize excellent antifriction and wear characteristics. This will be specifically described below.

[0010] [Rolling Bearing] First, with reference to the accompanying drawings below, a preferred embodiment of the rolling bearing according to the present invention will be described in detail. Note that the present invention is not limited by the following embodiments.

[0011] FIG. 1 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 seal member 15. The inner ring 11 is a cylindrical structure installed coaxially with its central axis on the outer peripheral side of a shaft (not shown). The outer ring 12 is a cylindrical structure arranged coaxially with the inner ring 11 on the outer peripheral side of the inner ring 11. Each of the plurality of rolling elements 13 is a ball arranged on a track in an annular bearing space 16 formed between the inner ring 11 and the outer ring 12. That is, the rolling bearing 10 in the present embodiment is a ball bearing. The retainer 14 is disposed within the raceway and holds a plurality of rolling elements 13. The retainer 14 is an annular body installed coaxially with the central axis of the shaft, and has a plurality of pocket portions for holding the rolling elements 13 on one side in the direction of the central axis, and has a structure in which the rolling elements 13 are accommodated in each pocket portion. The rolling elements 13 are held by the retainer 14 at a predetermined interval in the circumferential direction of the inner ring 11 and the outer ring 12, and the dropping of the rolling elements 13 and the contact between adjacent rolling elements 13 are suppressed. The seal member 15 is fixed to the inner circumferential surface of the outer ring 12 and extends toward the inner ring 11 side to seal the bearing space 16. The bearing space 16 sealed by the seal member 15 is filled with a grease composition G. That is, the grease composition G is held between the inner ring 11 and the outer ring 12. The grease composition G described later is used for the grease composition. The amount of the grease G filled into the bearing space 16 can be, for example, 5 to 50% of its volume. The seal member 15 is formed of, for example, a steel plate or rubber, and examples thereof include a steel plate shield that is non-contact with the outer periphery of the inner ring 11 and a non-contact rubber seal that is non-contact with the outer periphery of the inner ring 11. In the present invention, any of the steel plate shield or the non-contact rubber seal can be used as the seal member. From the viewpoint of suppressing outgassing, it is preferable to use a steel plate shield. Although this figure shows an embodiment including the seal member 15, the rolling bearing of the present invention also targets an embodiment of a rolling bearing that does not include a seal member. In the rolling bearing 10 having the above configuration, the grease composition G acts to reduce the friction between the rolling elements 13 and the retainer 14, and between the rolling elements 13 and the inner ring 11 or the outer ring 12. By reducing the friction, the frictional torque is reduced and the generation of frictional heat is also suppressed, and the smooth rotation of the inner ring 11 and the outer ring 12 is promoted. As can be understood from the configuration shown in FIG. 1, the grease composition G enclosed in the rolling bearing 10 lubricates between the rolling elements 13 and the inner ring 11 or the outer ring 12 when the rolling bearing 10 rotates.

[0012] In the rolling bearing of the present invention, the cage is a resin crown-shaped cage made of a resin selected from the group consisting of polynonameethylene terephthalamide (PA9T), polyamide 46 (PA46), and polyetheretherketone (PEEK) resin. The cage may be formed from a material that contains the above resin as an essential component, and may be made of a composite material that includes a reinforcing agent such as glass fiber or carbon fiber.

[0013] The rolling bearings in the present invention are not particularly limited in size or operating conditions, but are especially suitable for use under high temperature and / or high speed conditions, such as an outer diameter of 10 mm or less, at temperatures of 100°C or higher, for example, 130°C, or at rotational speeds of 50,000 rpm or higher, for example, 100,000 rpm or higher or 130,000 rpm or higher. The rolling bearing of the present invention can be used as a rolling bearing for small motors (for example, fan motors, cleaner motors) used in automobiles, home appliances, information equipment, etc.

[0014] [motor] As an example, Figure 2 will describe in detail an embodiment of a motor equipped with a rolling bearing according to this embodiment, but the present invention is not limited to the following embodiments.

[0015] Figure 2 is a cross-sectional view in the shaft direction of a motor according to one embodiment of the present invention. The motor 20 has a basic structure similar to that of a conventional motor and consists of a housing 21, a stator 22, a coil 23, a rotor magnet 24, a shaft 25, and a rolling bearing 26 that supports the shaft 25. The motor 20 generates a magnetic field by passing current supplied from a power source (not shown) via a drive circuit through a coil 23 wound around the stator 22, thereby generating a magnetic field for the rotor magnet 2 4 rotates, and the rotation is transmitted to the external rotating body through shaft 25. In this invention, the rolling bearing of the present invention can be suitably used as the bearing of a motor used in a blower, in which case the external rotating body is the impeller (not shown) of the blower.

[0016] [Grease composition] As described above, the inventors focused on the shape of the grease sealed in the bearing and adopted an ionic liquid and disodium sebacate as a configuration that is expected to suppress stirring resistance, suppress shear heat generation, achieve high temperature and high speed durability, and further lead to lower torque and reduced power consumption, by maintaining elasticity and preventing deformation of the grease shape. This resulted in an optimization of the storage modulus of the grease composition. The grease composition to be sealed in the rolling bearing of the present invention will be described below.

[0017] <Base oil> In the grease composition sealed in the rolling bearing according to this embodiment, synthetic oils such as synthetic hydrocarbon oil, ether-based synthetic oil, and ester-based synthetic oil, which are commonly used as grease base oils, can be used alone or in combination as the base oil.

[0018] Examples of the synthetic hydrocarbon oils include normal paraffins, isoparaffins, polybutenes, polyisobutylenes, 1-decene oligomers, and polyalphaolefins (PAOs) such as 1-decene and ethylene co-oligomers. Examples of the aforementioned ester-based synthetic oils include diester oils such as dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl phthalate, and methyl acetyl cinolate; aromatic ester oils such as trioctyl trimellitate, tri-2-ethylhexyl trimellitate, tridecyl trimellitate, tetraoctyl pyromelitate, and tetra-2-ethylhexyl pyromelitate; polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, and pentaerythritol pelargonate; and carbonate ester oils. Examples of the aforementioned ether-based synthetic oils include alkyl ether oils such as monoalkyldiphenyl ethers, dialkyldiphenyl ethers, and polyalkyldiphenyl ethers, as well as alkyldiphenyl ether oils.

[0019] The above-mentioned base oil can be included in a proportion of, for example, 70% by mass or more based on the total mass of the grease composition used in the present invention, or, for example, in a proportion of 70% to 90% by mass based on the total mass of the grease composition.

[0020] <Thickener> The grease composition used in the present invention may preferably use a urea-based thickener. Urea compounds exhibit excellent heat and water resistance, and are particularly stable at high temperatures, making them suitable as thickeners in applications involving high-temperature environments. As urea-based thickeners, urea compounds such as diurea compounds, triurea compounds, and polyurea compounds can be used. From the viewpoint of heat resistance and acoustic properties (noise reduction), it is preferable to use diurea compounds. Furthermore, it is preferable that the urea compound includes at least one of fatty-aromatic ureas, alicyclic-aliphatic ureas, and aliphatic ureas. Conventionally known urea compounds can be used as these urea-based thickeners.

[0021] An example of a diurea compound used as a urea thickener is represented by the following formula (1): Diurea compounds can be cited as examples. R1-NHCONH-R2-NHCONH-R3...Formula (1) In formula (1) above, 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. Furthermore, R2 represents a divalent aromatic hydrocarbon group.

[0022] Examples of the monovalent aliphatic hydrocarbon group mentioned above include linear or branched saturated or unsaturated alkyl groups having 6 to 26 carbon atoms. Examples of the monovalent alicyclic hydrocarbon group mentioned above include cycloalkyl groups having 5 to 12 carbon atoms. Examples of the above-mentioned aromatic hydrocarbon groups include monovalent or divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms.

[0023] Urea compounds used as urea thickeners can be synthesized using amine compounds and isocyanate compounds. Examples of the amine compounds include aliphatic amines such as hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine (stearylamine), behenylamine, and oleylamine, as well as alicyclic amines such as cyclohexylamine, and aromatic amines such as aniline, p-toluidine, and ethoxyphenylamine. In addition, aromatic diisocyanates such as phenylenediisocyanate, tolylenediisocyanate (TDI), diphenyldiisocyanate, diphenylmethanediisocyanate (MDI), and dimethylbiphenyldiisocyanate (TODI), as well as aliphatic diisocyanates such as octadecanediisocyanate, decanediisocyanate, and hexanediisocyanate are used as isocyanate compounds. Furthermore, when aromatic diurea compounds obtained using aromatic monoamines and aromatic diisocyanates as amine raw materials are used as urea-based thickeners, there is a risk of abnormal noise generation, so their use should be carefully considered.

[0024] The above-mentioned urea-based thickener (urea compound) can be blended in such an amount as, for example, 10 to 20% by mass relative to the total amount of the grease composition used in the present invention.

[0025] <Ionic Liquid> The grease composition applied to the rolling bearing according to this embodiment includes an ionic liquid as an essential component. Conventionally, lubricants have been made conductive as needed to dissipate static electricity generated between parts due to rotational friction, and one method being considered for this purpose is the addition of ionic liquids. In this invention, by using an ionic liquid in combination with a disodium sebacate salt described later, the storage modulus of the grease composition is set to an appropriate range, resulting in an elastic and deformation-resistant grease. This suppresses shear heat generation associated with stirring at high speeds, and further reduces frictional heat generation by forming a strong tribological film, thereby contributing to the extended lifespan of the lubrication performance.

[0026] The above-mentioned ionic liquid is not particularly limited as long as it is a fluorine-based ionic liquid that can achieve the desired storage modulus when used in combination with disodium sebacate, as described later. For example, the trihexyltetradecylphosphonium bis(trifluoromethanesulfonyl)imide ([THTDP][TFSI]) shown below can be used. [ka]

[0027] The above-mentioned ionic liquid can be blended in such an amount as, for example, 0.1 to 10% by mass relative to the total amount of the grease composition used in the present invention.

[0028] <Dispersant: Disodium sebacate> The grease composition applied to the rolling bearing according to this embodiment contains disodium sebacate as a dispersant. Disodium sebacate can be added to the grease composition used in this invention in an amount of, for example, 0.1 to 10% by mass relative to the total amount.

[0029] <Other additives> The grease composition used in the present invention may, if necessary, contain additives commonly used in grease compositions, to the extent that they do not impair the effects of the present invention. Examples of such additives include antioxidants, extreme pressure agents, metal deactivators, friction inhibitors (wear inhibitors), rust inhibitors, oiliness improvers, viscosity index improvers, and thickeners. If these other additives are included, their total amount is typically 0.1 to 10% by mass of the total amount of grease.

[0030] For example, the above antioxidants include octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-t-butyl- Examples include hindered phenol antioxidants such as 4-hydroxyphenyl)propionate, 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxyhydrocinnamide); phenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and 4,4-methylenebis(2,6-di-t-butylphenol); and amine antioxidants such as diphenylamine, diarylamine, triphenylamine, phenyl-α-naphthylamine, alkylated phenyl-α-naphthylamine, phenothiazine, and alkylated phenothiazine.

[0031] Examples of extreme pressure agents include phosphorus compounds such as phosphate esters, phosphite esters, and phosphate ester amine salts; sulfur compounds such as sulfides and disulfides; chlorine compounds such as chlorinated paraffins and chlorinated diphenyls; and metal salts of sulfur compounds such as zinc dialkyldithiophosphate and molybdenum dialkyldithiocarbamate.

[0032] Examples of metal deactivators include benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]-benzotriazole, and 1-[N,N-bis(2-ethylhexyl Examples include benzotriazole compounds such as [syl)aminomethyl]-4-methylbenzotriazole, thiadiazole compounds such as thiadiazole, 2-mercaptothiadiazole, and 2,5-bis(alkyldithio)-1,3,4-thiadiazole, benzimidazole compounds such as benzimidazole, 2-mercaptobenzimidazole, and 2-(decyldithio)-benzimidazole, and sodium nitrite.

[0033] Other examples of friction-preventing agents (wear-resistant agents) include tricresyl phosphates and polymer esters. Examples of the polymer esters mentioned above include esters of aliphatic monocarboxylic acids and dicarboxylic acids with polyhydric alcohols. Specific examples of the polymer esters mentioned above include, but are not limited to, the PRIOLUBE® series manufactured by Croda Japan.

[0034] The grease composition used in the present invention can be obtained by blending the aforementioned base oil with a urea-based thickener, an ionic liquid, disodium sebacate, and optionally other additives. Furthermore, a grease composition can also be obtained by blending an ionic liquid, disodium sebacate, and optionally other additives with a urea-based grease (base grease) consisting of the base oil and the urea-based thickener. Typically, the thickener content in the base grease is about 10-30% by mass. For example, the content of diurea compounds (urea-based thickeners) in the above-mentioned urea-based grease can be about 10-25% by mass or 10-20% by mass.

[0035] <About the storage modulus> The grease composition used in this invention exhibits elastic and deformation-resistant grease behavior by having a storage modulus within an appropriate range. The storage modulus is a value that indicates the dimensional stability of grease, and it is an effective parameter for understanding the dimensional stability of grease immediately after filling a rolling bearing with grease and during the rotation of the rolling bearing. In rolling bearings, especially those used under high temperature and high speed conditions, if the shape of the grease changes from its shape at the time of sealing, the grease can become entangled with the balls (rolling elements), leading not only to increased torque and torque instability in the rolling bearing, but also to grease deterioration due to the destruction of the thickener's fibrous structure as it is sheared, potentially causing lubrication failure. Therefore, the ability of the grease to maintain its shape (shape stability) is a crucial factor in maintaining initial and long-term torque stability and suppressing lubrication failure. From the viewpoint of the dimensional stability of such greases, it is important that the grease composition used in the present invention has a storage modulus of 2400 Pa or higher at 25°C under the above measurement conditions (dynamic viscoelasticity measurement using a rotary rheometer: film thickness 0.5 mm, shear strain 1%, frequency 1 Hz). However, if the storage modulus becomes too high, the grease will be located on the orbital path of the rolling element, increasing the resistance when the balls pass over the grease and raising concerns about increased torque. Therefore, it is desirable that the storage modulus be 4,500 Pa or less, and more preferably not exceed 3,500 Pa.

[0036] The present invention is not limited to the embodiments or specific examples described herein, and various modifications and variations are possible within the scope of the technical idea described in the claims. [Examples]

[0037] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited thereto.

[0038] Grease compositions for Example 1 and Comparative Examples 1 to 6 were prepared using the formulations shown in Table 1 below. The details and abbreviations of each component used in the preparation of the grease composition are as follows. <Base oil> • Ester oil: Mixture of trioctyl trimellitate (TOTM) and tetraoctyl pyromelitate (TOPM) [Kinematic viscosity at 40°C: 100 mm] 2 / s] <Thickener> • Diurea compounds: Fatty-aromatic diurea compounds <Additives> • Ionic liquid: (See the structure shown in the chemical formula below) (1) [TFSI] [THTDP] Trihexyltetradecylphosphonium bis(trifluoromethanesulfonyl)imide (2) [TFSI][EMI] 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide(3) [TFSI][BMP] 1-Butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide(4) [ES][EMI] 1-Ethyl-3-methylimidazolium ethyl sulfate [ka] • Dispersant: Disodium sebacate Other additives: Extreme pressure additives: Phosphate ester-based extreme pressure additives Triphenylphosphorothionate, product name "Irgalube TPPT", BASF Japan Ltd. Metal deactivator: Benzotriazole compound (1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, product name "BT-LX", Johoku Chemical Industry Co., Ltd.) Antioxidant: Diarylamine antioxidant (octyl / butylated diphenylamine, product name "Irganox L57", BASF Japan Ltd.) Other additives were added to each grease composition (total mass) of the examples and comparative examples in such a way that the total amount of the extreme pressure additive, metal deactivator, and antioxidant was 3% by mass.

[0039] The rolling bearings used in the following tests and evaluations are as follows: • Rolling bearings: Steel shielded ball bearings (inner diameter 3mm, outer diameter 8mm, width 3mm) • Retainer: Resin crown-shaped retainer <Cage material> Retainer A: PEEK [Contains 20% carbon fiber (CF)] Retainer B: PA9T [Contains 20% carbon fiber (CF)] Retainer C: PA46 [Contains 30% glass fiber (GF)] Retainer D: PA66 [Contains 30% glass fiber (GF)]

[0040] Lubrication characteristics, viscoelasticity, and heat resistance were evaluated using the following procedure. The results are shown in Tables 1 and 2.

[0041] <(1) Evaluation of lubrication properties (metal-metal: friction and wear test)> Metal-to-metal friction and wear tests were conducted using an Optimol vibration friction tester (product name: SRV). The tests were performed using a ball-on-disk method, with a ball (material: SUJ2, φ10 mm) and a disc (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. 5 mg of each grease composition was supplied at the start of the test. After the test was completed, the diameter of the wear marks on the ball side was measured (average value for N=3). In addition, for Example 1 and Comparative Example 3, the maximum height difference PV value in the direction intersecting the sliding direction of the wear marks on the disk side was measured using a white light interferometer (product name: NewView200) manufactured by ZYGO Corporation (N=1 for each). The wear mark diameter and maximum height difference were evaluated according to the following criteria. Figure 3 shows photographs of the wear marks on the balls and discs of Example 1 and Comparative Example 3 after the friction wear mark test. Figure 3(A) shows the wear marks on the balls [(a) Example 1, (b) Comparative Example 3], and Figure 3(B) shows the wear marks on the discs [(a) Example 1, (b) Comparative Example 3]. Figure 4 also shows the white light interferometer measurement data obtained for the disks of Example 1 and Comparative Example 3 after the friction wear mark test [(a) Example 1, (b) Comparative Example 3]. <Criteria for determining wear mark diameter> A: Ball wear mark diameter is 330 μm or less N: Ball wear mark diameter exceeds 330 μm <Criteria for determining maximum elevation difference> A: The maximum height difference (PV) of the wear marks on the disk is 0.5 μm or less. N: The maximum height difference (PV value) of the wear marks on the disk exceeds 0.5 μm.

[0042] <(2) Oil separation volume (unit: mm) 2 Measurement and evaluation (mg / mg) 9 mg of each prepared grease composition was placed in a φ3 mm cylindrical shape on the side of a weighing paper where the medicine is placed, and left for 24 hours at 80°C. After 24 hours, the area of ​​the oil seepage on the weighing paper was measured. The area of ​​the oil seepage per unit mass of the grease composition was expressed as the amount of oil released (mm²). 2 The amount of oil released (average value for N=3) was calculated as ( / mg) and evaluated according to the following criteria. For this test, the weighing paper used was "Pure White Imitation (Medium)" from Hakuaisha Co., Ltd. (Size: 105mm x 105mm, Thickness: 42μm, Basis Weight: 30g / m²). 2 Using the above method, the grease composition was placed on the surface (glossy surface) where the medicine would be applied. <Judgment criteria> N: Oil separation volume is 180 mm 2 Less than / mg A: Oil separation volume is 180 mm 2 / mg or more 270mm 2 / mg or less N: Oil separation volume is 270 mm 2 / mg super

[0043] <(3) Viscoelasticity evaluation (measurement of elastic modulus (unit: Pa) using a rheometer)> The storage modulus G' and loss modulus G'' of each grease composition were measured using an Anton Paar rotational viscometer (rheometer, trade name MCR302). The measurement mode was the strain dispersion method (strain varied from 100% to 0.01%), and the fixture was a parallel plate φ25m. Measurements were performed using m(PP25), 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 defined as the storage modulus G'(Pa), and the storage modulus (average value for N=3) was evaluated according to the following criteria. Figure 5 shows the measurement results of the storage modulus (G') and loss modulus (G") with respect to shear strain for Example 1 and Comparative Example 3 [(a) Example 1, (b) Comparative Example 3]. <Judgment criteria> A: Storage modulus is between 2,400 Pa and 4,500 Pa. N: Storage modulus less than 2,400 Pa or greater than 4,500 Pa

[0044] <(4) Heat resistance evaluation (durability test) (1)> Each grease composition was sealed in a steel-reinforced ball bearing (inner diameter 3 mm, outer diameter 8 mm, width 3 mm, cage B (PA9T [containing 20% ​​carbon fiber (CF)])) at a concentration of 25% to 35% of the bearing volume. This ball bearing was set in a housing, and a preload of 2N was applied to the outer ring from the axial direction. Then, a shaft was inserted into the inner diameter of the bearing and connected to the rotating shaft of a test motor so that the ball bearing could rotate at the inner ring. 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. The time until the ball bearing stopped was measured. The stopping condition was defined as the point at which the torque increased and the rotational speed decreased by 10% below the specified value. The test time until stopping was defined as the elapsed time (hr). Each grease composition was tested three times, the average value was calculated, and it was evaluated according to the following criteria. <Judgment criteria> A: Elapsed time is 10,000 hours or more N: Elapsed time is less than 10,000 hours

[0045] [Table 1]

[0046] <(5) Evaluation of lubrication properties (metal-resin: friction and wear test)> Metal-resin friction and wear tests were conducted using a BRUKER UMT TriboLab multi-function friction and wear testing machine. The tests were performed using a ball-on-disk method, with a ball (material: SUJ2, φ10 mm) and a disc (length 30 mm, width 10 mm, thickness 4 mm) made of the material shown in Table 2. The test conditions were a load of 49 N, room temperature, sliding distance of 12.5 mm, vibration frequency of 20 Hz, and test time of 2 minutes. At the start of the test, 5 mg of the grease composition from Example 1 was applied to the ball. During the test, the coefficient of friction and the temperature of the upper sphere were measured over time, and the coefficient of friction value at the end of 2 minutes (120 seconds) (average value for N=3) was evaluated according to the following criteria. Figure 6 shows the measurement results for the coefficient of friction and temperature (°C) (upper sphere) against test time (seconds) in Examples A to C and Comparative Example A [(A) Coefficient of friction, (B) Temperature (upper sphere)]. Figure 7 also shows photographs of the wear marks on the discs of Example A and Comparative Example C after the friction wear mark test [(a) Example A, (b) Comparative Example A]. <Judgment criteria> A: Coefficient of friction 0.1 or less N: Friction coefficient greater than 0.1

[0047] <(6) Heat resistance evaluation (durability test) (2)> The heat resistance evaluation was carried out in the same procedure as in <(4) Heat Resistance Evaluation (Durability Test) (1)> above, except that the cage used in the steel-plated ball bearing was changed to the cage shown in Table 2, and the grease composition of Example 1 was used as the grease composition.

[0048] [Table 2]

[0049] As shown in Table 1, the grease composition of Example 1 had a storage modulus of elasticity exceeding 2,400 Pa, and the actual grease composition had a firm, agar-like consistency. Furthermore, as shown in Figures 3 to 5, compared to Comparative Example 3 (Figures 3(A)(b), 3(B)(b), 4(b), and 5(b)), it was confirmed that both the ball and disc in Example 1 showed smaller (thinner) wear marks (Figures 3(A)(a) and 3(B)(a)), lower surface roughness (Figure 4(a)), and a larger modulus of elasticity G' at 1% strain (Figure 5(a)). Thus, in friction and wear tests (metal-metal) using this grease composition, the friction and wear marks on the ball were 330 μm or less, and the maximum height difference PV value of the friction and wear marks on the disc was approximately 0.4 μm, confirming that friction and wear are less likely to occur and that the grease composition has excellent lubricity. Furthermore, in Example 1, a rolling bearing using a resin crown-shaped cage with PA9T as the resin component was subjected to high-temperature and high-speed rotation tests. Even after 10,000 hours, no abnormal noises occurred, confirming that the rolling bearing exhibits excellent durability under high temperature and high speed conditions. On the other hand, in Comparative Examples 1-3, which used ionic liquids (2)-(4) instead of ionic liquid (1) used in the example, Comparative Example 4, which did not use disodium sebacate, Comparative Example 5, which did not use ionic liquid, and Comparative Example 6, which did not use disodium sebacate or ionic liquid, the storage modulus of elasticity was less than 2,400 Pa in all cases. These grease compositions felt softer and less able to maintain their shape compared to Example 1. In friction and wear tests (metal-metal) using these grease compositions, the friction and wear marks on the balls were 330 μm or less. While Comparative Example 1 showed friction and wear marks of 330 μm or less, Comparative Examples 2-6 exceeded 330 μm, indicating poor lubricity. For Comparative Example 3, the maximum height difference PV value of the friction and wear marks on the disc was approximately 0.9 μm, which was more than twice the maximum height difference of Example 1. As shown in Figures 3(B)(b) and 4(b), deep friction scratches were observed along the sliding direction on the disc test piece in the friction and wear test (metal-metal) of Comparative Example 3. Furthermore, a test was conducted in which a rolling bearing using a resin crown-shaped cage with PA9T as the resin component was rotated at high temperature and high speed. In these comparative examples, however, the torque increased before 10,000 hours had passed since the start of the test, resulting in a rotational speed 10% lower than the specified value, and thus the test had to be stopped.

[0050] As shown in Table 2, in rolling bearings using resin crown-type cages with PEEK (Example A), PA9T (Example B), and PA46 (Example C) as the resin component, the coefficient of friction was low at 0.1 or less [see Figure 6(A)], and even after the passage of time in the friction and wear test, the temperature rise of the upper ball was kept low compared to the comparative examples described later [see Figure 6(B)]. Also, as shown in Figure 7(A), the wear marks on the disc after the test (Example A) were also faint. Furthermore, even after 10,000 hours in a test involving high temperature and high-speed rotation, no abnormal noises occurred, resulting in excellent durability. On the other hand, even when using the grease composition of Example 1, the rolling bearing of Comparative Example A, which used a resin crown-shaped cage with PA66 as the resin component, showed a significant increase in the coefficient of friction to 0.224 [see Figure 6(A)], and the temperature of the upper sphere increased significantly with the passage of time during the friction and wear test [see Figure 6(B)]. Furthermore, as shown in Figure 7(B), the wear marks on the disc after the test were more pronounced compared to the wear marks of Example A shown in Figure 7(A), and in the high-temperature, high-speed rotation test, abnormal noise occurred after 3,500 hours from the start of the test, resulting in rotational failure.

[0051] Although the best embodiment has been described in detail above, the present invention is not limited to the above embodiment, and any modifications, improvements, etc. that can achieve the objectives of the present invention are included in the present invention. [Explanation of Symbols]

[0052] 10...Rolling bearing, 11...Inner ring, 12...Outer ring, 13...Rolling element, 14...Cage, 15...Sealing member, 16...Bearing space 20...Motor, 21...Housing, 22...Stator, 23...Coil, 24...Rotor Magnet, 25...Shaft, 26...Bearing

Claims

1. Insider, An outer ring is arranged coaxially with the inner ring on the outer circumference side of the inner ring, A plurality of rolling elements arranged between the inner ring and the outer ring, A retainer for holding the rolling element, The grease composition is held between the inner ring and the outer ring, The grease composition comprises a base oil, a thickener, an ionic liquid, and disodium sebacate salt. The ionic liquid is trihexyltetradecylphosphonium bis(trifluoromethanesulfonyl)imide ([THDP][TFSI]), The grease composition, in dynamic viscoelasticity measurements using a rotary rheometer, has a storage modulus of 2,400 Pa or more at 25°C, measured under conditions of a film thickness of 0.5 mm, shear strain of 1%, and frequency of 1 Hz. The oil separation rate at 80°C is 180 mm² / mg or more and 270 mm² / mg or less. The aforementioned retainer is a resin crown-shaped retainer made of a resin selected from the group consisting of polynonameethylene terephthalamide (PA9T), polyamide 46 (PA46), and polyetheretherketone (PEEK) resin. Rolling bearings.

2. The aforementioned thickener is a urea-based thickener, and the urea-based thickener contains a diurea compound represented by the following general formula (1): The rolling bearing according to claim 1. R １ -NHGNH-R ２ -NHGNH-R ３ ・・・(1) (In the formula, R １ and R ３ Each independently represents a monovalent aliphatic hydrocarbon group, a monovalent alicyclic hydrocarbon group, or a monovalent aromatic hydrocarbon group, and R １ and R ３ At least one of them represents a monovalent aliphatic hydrocarbon group or a monovalent alicyclic hydrocarbon group, R ２ (This represents a divalent aromatic hydrocarbon group.)

3. A motor comprising a rolling bearing as described in claim 1 or claim 2.

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