Sealed Rolling Bearing

Abstract

To provide a lubricant composition that is used for lubrication of rolling bearings and the like and capable of achieving both low-torque performance and rust prevention property, and a sealed rolling bearing using the lubricant composition.SOLUTION: A grease 16 contains a base oil and rust prevention agents. A steady-state viscosity after applying a shear for 30 min. at a shear rate of 10 s-1 by a time-dependent measurement method using a rheometer is less than 30 Pa s. The rust prevention agents include a polyhydric alcohol ester type rust-prevention agent and one or more other rust-prevention agents. The grease 16 contains 0.5 to 3 mass% of the rust-prevention agents relative to the whole lubricant composition.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a lubricant composition and a sealed rolling bearing using the lubricant composition, and more particularly to a sealed rolling bearing such as a hub bearing that supports an axle. [Background technology]

[0002] Generally, a lubricant composition such as lubricating oil or grease is enclosed inside a rolling bearing. Bearings containing a lubricant composition have a long life, do not require an external lubrication unit, and are inexpensive, so they are often used for general-purpose applications such as automobiles and industrial equipment. In particular, when high sealing performance is required, a contact-type sealed rolling bearing is used, in which the seal lip of a seal member contacts the sliding surface of a mating member such as a raceway ring to seal the bearing space.

[0003] For example, Patent Document 1 describes a hub unit bearing that is a sealed rolling bearing and is filled with grease of a specific composition. This grease contains a base oil, a thickener, three types of rust inhibitors, and an anti-wear agent, and is said to have excellent water resistance and other properties.

[0004] Here, grease leakage from the bearings can contaminate external mechanical components. Furthermore, the intrusion of water or other foreign matter from the outside can significantly reduce the durability (wear resistance and bearing life) of the bearing. In the unlikely event that water or other foreign matter gets into the seal due to seal wear, the grease will also need to be rust-resistant. Some rust-resistant greases are hydrophilic, and others affect the grease's viscosity. As such, ensuring sealing performance is important in sealed rolling bearings. At the same time, from the perspective of energy and resource conservation, low torque is also required for the sliding of the seal lip.

[0005] Conventionally, a technique for applying grease to the seal lip or its mating member has been known to reduce the sliding resistance of the seal lip and ensure the sealing performance of the seal lip. For example, Patent Document 2 describes a rolling bearing in which grease is pre-applied to one side of the tip of the seal lip, which is in sliding contact with the surface of the hub wheel during use. Also, Patent Document 3 describes a rolling bearing in which grease is pre-applied to the surface of the mating member with which the seal lip slides. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5110843 [Patent Document 2] Patent No. 4475055 [Patent Document 3] Patent No. 4997532 Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Document 2, the shape of the sealing member (e.g., the dimensions of the seal lip) is considered to prevent the grease applied to the seal lip from peeling off in advance. This increases frictional resistance and reduces sealing defects. However, the frictional resistance and other characteristics of the grease itself that is pre-applied to the seal lip are not taken into consideration. Furthermore, Patent Document 3 attempts to reduce rotational torque by specifying the kinematic viscosity of the grease's base oil. However, it is considered difficult to achieve both sufficient sealing performance and reduced rotational torque simply by specifying the kinematic viscosity of the base oil. Furthermore, because rainwater and water from the road easily penetrate into rolling bearings and hub bearings used in automotive electrical accessories, it is important to prevent water intrusion and rust. However, the greases in Patent Documents 2 and 3 do not consider these characteristics at all.

[0008] Furthermore, although Patent Document 1 aims to improve the water resistance of the grease sealed in the hub bearings and the like, it does not consider reducing the rotational torque.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lubricant composition that can be used to lubricate rolling bearings and the like, and that can achieve both low torque and rust prevention, and a sealed rolling bearing that uses the lubricant composition. [Means for solving the problem]

[0010] The lubricant composition of the present invention is a lubricant composition containing a base oil and a rust inhibitor, and the lubricant composition has a viscosity of 10 s when measured by a time-dependent measurement method using a rheometer. -1 The viscosity at a steady state after 30 minutes of shear at a shear rate of 100 Pa·s or less is less than 30 Pa·s, and the rust inhibitor contains a polyhydric alcohol ester rust inhibitor and other rust inhibitors.

[0011] The lubricant composition is characterized in that it contains the rust inhibitor in an amount of 0.5% by mass to 3% by mass based on the total amount of the lubricant composition.

[0012] The other rust inhibitor is characterized in that it is a sulfonate-based rust inhibitor or a carboxylate-based rust inhibitor.

[0013] The base oil is at least one selected from synthetic hydrocarbon oils, ester oils, and ether oils.

[0014] The lubricant composition is a grease, and the base oil has a kinematic viscosity of 15 mm at 40°C. 2 / s or less, and the grease is characterized in that the worked penetration measured in accordance with JIS K2220 is 260 to 300.

[0015] The thickener of the grease is characterized in that it is a urea compound obtained by reacting a polyisocyanate component with at least one monoamine component selected from an aliphatic monoamine and an alicyclic monoamine, or a lithium complex soap.

[0016] The sealed rolling bearing of the present invention is a sealed rolling bearing comprising a seal member that seals a bearing space, is fixed to a fixed-side member, and is in sliding contact with a rotating-side member, and is characterized in that the lubricant composition of the present invention is used for lubrication in the sealed rolling bearing.

[0017] The seal member has a seal lip that is in sliding contact with the rotating-side member, and in the sealed rolling bearing, the lubricant composition is applied to at least one of the sliding contact surface of the seal lip and the sliding contact surface of the rotating-side member with which the seal lip is in sliding contact.

[0018] The seal member is formed of nitrile rubber, has a plurality of seal lips as the seal lips, and is characterized in that the lubricant composition is applied to the sliding contact surfaces of these seal lips. [Effects of the Invention]

[0019] The lubricant composition of the present invention has a viscosity of 10 s when measured by a time-dependent measurement method using a rheometer. -1 The lubricant composition has a steady viscosity of less than 30 Pa·s after 30 minutes of shear at a shear rate of 100°C, and the rust inhibitor contains a polyhydric alcohol ester-based rust inhibitor and other rust inhibitors. Because the rust inhibitor is a combination of these, the viscosity of the lubricant composition under specified rotation conditions (particularly low-speed rotation) can be suitably reduced. Furthermore, by using a combination of rust inhibitors, rust prevention can be improved compared to using a single rust inhibitor. This results in a lubricant composition that combines low torque and rust prevention.

[0020] The lubricant composition contains 0.5% by mass to 3% by mass of the rust inhibitor relative to the total amount of the lubricant composition, which makes it easy to achieve a low viscosity of the lubricant composition while favorably exhibiting rust prevention properties.

[0021] Furthermore, since the other rust inhibitor is a sulfonate-based rust inhibitor or a carboxylate-based rust inhibitor, it is easy to achieve a low viscosity of the lubricant composition while favorably exhibiting rust prevention properties.

[0022] The lubricant composition is a grease, and the base oil has a kinematic viscosity of 15 mm at 40°C. 2 / s or less, and the grease has a worked penetration of 260 to 300 as measured in accordance with JIS K2220. Therefore, for example, when the lubricant composition is applied to the sliding surface of a seal lip in a sealed rolling bearing, channeling properties are ensured, oil film breakdown at low speeds is prevented, low torque is achieved, and high sealing properties can be obtained.

[0023] The thickener of the above grease is a urea compound obtained by reacting a polyisocyanate component with at least one monoamine component selected from aliphatic monoamines and alicyclic monoamines, or a lithium complex soap, which further contributes to lower torque.

[0024] The sealed rolling bearing of the present invention can achieve both low torque and rust prevention because the lubricant composition of the present invention is sealed in the bearing space and used for lubrication. In particular, in the sealed rolling bearing, the lubricant composition is applied to at least one of the sliding contact surface of the seal lip and the sliding contact surface of the rotating member with which the seal lip slides, and used for lubrication, thereby achieving low torque, high sealing performance, and rust prevention.

[0025] The sealing member is formed of nitrile rubber and has a plurality of seal lips as seal lips, and the sliding surfaces of these seal lips are coated with a lubricant composition, so that low torque properties can be ensured while further improving sealing properties.

[0026] Furthermore, when the sealed rolling bearing is a bearing that rotatably supports an axle, it can contribute to improving the performance (fuel economy) of axle bearings such as hub bearings. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic diagram showing an example of a rotational rheometer. [Figure 2] 1 is a longitudinal sectional view showing an example of a sealed rolling bearing of the present invention. [Figure 3] FIG. 4 is a partial vertical cross-sectional view showing another example of a sealed rolling bearing according to the present invention. [Figure 4] FIG. 4 is a vertical cross-sectional view showing another example of a sealed rolling bearing according to the present invention. [Figure 5] FIG. 5 is an enlarged cross-sectional view showing the inboard-side bearing sealing device of FIG. 4. [Figure 6] FIG. 5 is an enlarged cross-sectional view showing the outboard side bearing sealing device of FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0028] The lubricant composition of the present invention is used for lubricating rolling parts such as rolling bearings. For example, in a rolling bearing, the lubricant composition may be filled into the bearing space to lubricate the raceway surface, or may be applied to the seal lip of a sealing member to lubricate the space between the seal lip and a rotating member (such as a bearing ring).

[0029] The lubricant composition of the present invention can be embodied in two forms: (A) a lubricating oil essentially containing a base oil and a rust inhibitor, and (B) a grease essentially containing a base oil, a thickener, and a rust inhibitor.

[0030] In the lubricant composition of the present invention, a polyhydric alcohol ester-based rust inhibitor and another rust inhibitor (hereinafter referred to as "other rust inhibitor") are used in combination as the rust inhibitor. By using two or more rust inhibitors including at least a polyhydric alcohol ester-based rust inhibitor as the rust inhibitor, the viscosity of the lubricant composition can be suitably reduced and the rust prevention properties can be further improved.

[0031] The lubricant composition preferably contains 0.5 to 3 mass % of the rust inhibitor (total amount of the polyhydric alcohol ester-based rust inhibitor and other rust inhibitors) relative to the total amount of the lubricant composition, and more preferably 0.5 to 2 mass %. By containing the amount within the above range, the lubricant composition exhibits low viscosity and rust prevention properties, while also easily retaining its shape even when in contact with water, resulting in excellent water resistance.

[0032] Regarding the amount of rust inhibitor blended, when the lubricant composition is used as a lubricating oil, it is preferable to blend 0.5 to 3 parts by mass (preferably 0.5 to 2 parts by mass) of rust inhibitor with respect to the total amount of base oil (100 parts by mass).When the lubricant composition is used as a grease, it is preferable to blend 0.5 to 3 parts by mass (preferably 0.5 to 2 parts by mass) of rust inhibitor with respect to the total amount of base oil and thickener (100 parts by mass).

[0033] The polyhydric alcohol ester-based rust inhibitor used in the present invention is a partial ester of a polyhydric alcohol, which is an ester in which at least one of the hydroxyl groups in the polyhydric alcohol is not esterified but remains as a hydroxyl group.

[0034] Examples of the polyhydric alcohol include polyhydric alcohols having 2 to 10 hydroxyl groups in the molecule and 2 to 20 carbon atoms. Specific examples include sorbitan, sorbitol, pentaerythritol, sucrose, and glycerin. Examples of the carboxylic acid include carboxylic acids having 6 to 24 carbon atoms. The carbon chain in the molecule of this carboxylic acid may be linear or branched. The carboxylic acid may be either saturated or unsaturated. Specific examples include saturated fatty acids such as hexanoic acid, octanoic acid, decanoic acid, dodecanoic acid (lauric acid), tetradecanoic acid, octadecanoic acid, and eicosanoic acid; and unsaturated fatty acids such as oleic acid and linoleic acid.

[0035] In the present invention, it is preferable to use a sorbitan fatty acid ester as the polyhydric alcohol ester-based rust inhibitor. Examples of the sorbitan fatty acid ester include sorbitan fatty acid monoesters such as sorbitan monolaurate, sorbitan monostearate, and sorbitan monooleate, and sorbitan trioleate.

[0036] Examples of other rust inhibitors that can be used in combination with the polyhydric alcohol ester-based rust inhibitor include sulfonate-based rust inhibitors, carboxylic acid-based rust inhibitors such as straight-chain fatty acids such as lauric acid and stearic acid, succinic acid and alkylsuccinic acid, carboxylate-based rust inhibitors that are metal salts of fatty acids, naphthenic acid, alkylsalicylic acid, etc., and amine-based rust inhibitors such as alkoxyphenylamine. As the other rust inhibitor, one of these may be used alone, or two or more may be used in combination.

[0037] In the present invention, it is preferable to use at least one selected from sulfonate-based rust inhibitors and carboxylate-based rust inhibitors as the other rust inhibitor, and it is more preferable to use a sulfonate-based rust inhibitor.

[0038] Examples of sulfonate-based rust inhibitors include salts of benzenesulfonic acid (which may be substituted with an alkyl group), salts of naphthalenesulfonic acid (which may be substituted with an alkyl group), and salts of petroleum-based sulfonic acids obtained by sulfonating aromatic components of petroleum distillate components. Among these, salts of benzenesulfonic acid (which may be substituted with an alkyl group) and salts of petroleum-based sulfonic acids are preferred. In addition, salts of petroleum-based sulfonic acids (petroleum-based sulfonates) are also referred to as synthetic salts. Examples of the salts include alkaline earth metal salts such as barium, calcium, and magnesium; alkali metal salts such as sodium, potassium, and lithium; zinc salts; ammonium salts; and amine salts such as ethylenediamine. Among these, alkaline earth metal salts are preferred. The sulfonate-based rust inhibitor may be a neutral sulfonate or a basic sulfonate.

[0039] The carboxylate-based rust inhibitor is preferably a metal salt of alkylsalicylic acid. Examples of the metal salt include alkaline earth metal salts such as barium, calcium, and magnesium, and alkali metal salts such as sodium, potassium, and lithium. The carboxylate-based rust inhibitor may be a neutral carboxylate or a basic carboxylate.

[0040] As for other rust inhibitors, it is preferable not to use rust inhibitors containing a naphthalene ring in the molecule (e.g., salts of naphthalenesulfonic acid) in order to reduce the viscosity of the lubricant composition, as will be shown in the examples described later.

[0041] The lubricant composition more preferably contains 0.5 to 1.5 mass % of the polyvalent ester rust inhibitor and 0.5 to 1.5 mass % of the other rust inhibitor, based on the total amount of the lubricant composition. Furthermore, the content (mass %) of the polyvalent ester rust inhibitor in the lubricant composition may be the same as or less than the content (mass %) of the other rust inhibitor.

[0042] Here, the lubricant composition of the present invention has a viscosity of 10 s when measured by a time-dependent measurement method using a rheometer. -1 The lubricant composition is characterized in that the viscosity at steady state after 30 minutes of shear at a shear rate of 1000 kJ / min is less than 30 Pa·s. The viscosity of the lubricant composition is preferably 20 Pa·s or less, more preferably 15 Pa·s or less, and even more preferably 10 Pa·s or less. The lower limit of the viscosity is, for example, 5 Pa·s.

[0043] The viscosity of the lubricant composition can be calculated using a rheometer. It is preferable to use a rheometer with a cone-plate cell. An overview of such a rheometer is shown in FIG. 1. As shown in FIG. 1, the rotational rheometer 1 is composed of a cone-plate cell 2 and a horizontal disk plate 3. The cell 2 and the plate 3 are arranged so that they contact at a single point (with a small gap), and a sample lubricant composition 4 is placed between them. In this rheometer, the shear rate applied to the lubricant composition 4 is constant at any position, regardless of the distance from the center of the cell. In the present invention, the rheometer is rotated at a constant temperature and in a constant direction for 30 minutes, and the shear stress is measured when the shear stress becomes constant (steady state). The viscosity of the lubricant composition is calculated using this shear stress. The time-dependent measurement is preferably performed at a frequency of 1 Hz and at a temperature of 25°C.

[0044] To calculate the viscosity, for example, the Herschel-Bulkley equation, a general flow equation for non-Newtonian fluids, is used. The Herschel-Bulkley equation is expressed as follows:

[0045]

number

[0046] The yield stress and each constant in the above formula can be determined based on an evaluation of the rheological properties of the lubricant composition using a rheometer.

[0047] The base oil used in the lubricant composition of the present invention can be a commonly used one in the field of greases. Examples include mineral oils such as paraffinic mineral oil and naphthenic mineral oil, synthetic hydrocarbon oils (non-polar oils) such as poly-α-olefin (PAO) oil, alkylbenzene oil, alkylnaphthalene oil, polyphenyl oil, synthetic naphthenic oil, and polybutene oil, ester oil, ether oil, silicone oil, and fluorine oil. These oils may be used alone or in combination of two or more.

[0048] Among the above, the base oil is preferably at least one selected from synthetic hydrocarbon oils, ester oils, and ether oils, and more preferably contains at least a synthetic hydrocarbon oil. For example, when a mixed oil of a synthetic hydrocarbon oil with an ester oil or an ether oil is used as the base oil, the synthetic hydrocarbon oil preferably accounts for 60 mass % or more of the total base oil (mixed oil), and more preferably 65 mass % to 90 mass %.

[0049] PAO oil, a synthetic hydrocarbon oil, is a mixture of α-olefins or isomerized α-olefin oligomers or polymers. Specific examples of α-olefins include 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 1-docosene, and 1-tetradocosene, and mixtures of these are usually used.

[0050] Examples of ester oils include diester oils such as dibutyl sebacate, di-2-ethylhexyl sebacate, and dioctyl adipate, aromatic ester oils such as trioctyl trimellitate, tridecyl trimellitate, and tetraoctyl pyromellitate, polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane bellargonate, and pentaerythritol ester oil, carbonate ester oils, and phosphate ester oils. Among these, pentaerythritol ester oil is preferred.

[0051] The kinematic viscosity of the base oil of the lubricant composition of the present invention at 40°C (in the case of a mixed oil, the kinematic viscosity of the mixed oil, the same applies hereinafter) is 40mm 2 / s or less is preferable, and 30 mm 2 / s or less is more preferable, and 15 mm 2 The lower limit of the kinematic viscosity of the base oil at 40°C is, for example, 7 mm / s or less. 2 / s.

[0052] When the lubricant composition of the present invention is used as a grease, it further contains a thickener. There are no particular limitations on the thickener, and any of the commonly used thickeners in the field of greases can be used. For example, soap-based thickeners such as metal soaps and complex metal soaps, and non-soap-based thickeners such as bentone, silica gel, diurea compounds, triurea compounds, tetraurea compounds, and urea-urethane compounds can be used. Examples of metal soaps include sodium soaps, calcium soaps, and lithium soaps, and examples of complex metal soaps include lithium complex soaps. Among these, it is preferable to use diurea compounds or lithium complex soaps.

[0053] Diurea compounds are obtained by reacting a polyisocyanate component with a monoamine component. Examples of polyisocyanate components include phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, and hexane diisocyanate. Furthermore, the monoamine component may be an aliphatic monoamine, an alicyclic monoamine, or an aromatic monoamine. Examples of aliphatic monoamines include hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine, stearylamine, and oleylamine. Examples of alicyclic monoamines include cyclohexylamine. Examples of aromatic monoamines include aniline and p-toluidine.

[0054] Among these diurea compounds, it is preferable to use an aromatic diisocyanate as the polyisocyanate component and at least one of an aliphatic monoamine and an alicyclic monoamine as the monoamine component, because this provides superior low torque. In particular, it is more preferable to use an aliphatic / alicyclic diurea compound prepared using an aromatic diisocyanate as the polyisocyanate component and an aliphatic monoamine and an alicyclic monoamine having 6 to 12 carbon atoms as the monoamine components, as the thickener. The ratio of the aliphatic monoamine to the alicyclic monoamine used in preparing this aliphatic / alicyclic diurea compound is not particularly limited, and may be, for example, a molar ratio of aliphatic monoamine:alicyclic monoamine = (3:1) to (1:3), with a molar ratio of (2:1) to (1:2) being preferred. Furthermore, the number of moles of the aliphatic monoamine may be greater than the number of moles of the alicyclic monoamine.

[0055] The base grease containing a diurea compound as a thickener is prepared by reacting the polyisocyanate component and the monoamine component in a base oil.

[0056] Lithium complex soaps are synthesized from lithium hydroxide, aliphatic monocarboxylic acids, and dibasic acids such as aliphatic dicarboxylic acids. Examples of aliphatic monocarboxylic acids include stearic acid, 12-hydroxystearic acid, 12-hydroxylauric acid, and 16-hydroxypalmitic acid. Examples of aliphatic dicarboxylic acids include azelaic acid, sebacic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, undecanedioic acid, and dodecanedioic acid.

[0057] Among the lithium complex soaps, it is preferable to use a combination of a fatty acid monocarboxylic acid having 10 or more carbon atoms and a fatty acid dicarboxylic acid having less than 10 carbon atoms. In particular, 12-hydroxystearic acid is more preferable as the fatty acid monocarboxylic acid having 10 or more carbon atoms, and azelaic acid is more preferable as the fatty acid dicarboxylic acid having less than 10 carbon atoms.

[0058] In the above grease, the thickener is preferably contained in an amount of 10% by mass to 30% by mass, more preferably 10% by mass to 20% by mass, and even more preferably 12% by mass to 18% by mass, based on the total amount (100% by mass) of the base oil and thickener. By using a relatively small amount of thickener, the proportion of the base oil can be increased accordingly, which tends to lead to lower torque.

[0059] In the case of the above grease, its worked penetration (JIS K2220) is, for example, in the range of 220-300, preferably in the range of 240-300, and more preferably in the range of 260-300.

[0060] The lubricant composition may contain known additives as needed, provided that the object of the present invention is not impaired. Examples of such additives include antioxidants such as amine-based, phenol-based, and sulfur-based compounds, and extreme pressure agents such as organic zinc compounds and organic molybdenum compounds.

[0061] A particularly preferred embodiment of the lubricant composition of the present invention is a grease containing a base oil, a thickener, and a rust inhibitor, and the lubricant composition has a viscosity of 10 s or less as measured by a time-dependent measurement method using a rheometer. -1 The lubricant composition has a steady viscosity of less than 30 Pa·s after 30 minutes of shear at a shear rate of 100°C, the rust inhibitor contains a polyhydric alcohol ester-based rust inhibitor and a sulfonate-based rust inhibitor, and the lubricant composition contains these rust inhibitors in an amount of 0.5% by mass to 3% by mass based on the total amount of the lubricant composition, and the base oil has a kinematic viscosity of 15 mm at 40°C. 2 / s or less, and the worked penetration measured in accordance with JIS K2220 is 260 to 300.

[0062] The sealed rolling bearing lubricated with the lubricant composition of the present invention will now be described.

[0063] FIG. 2 shows an example of a sealed rolling bearing in which the lubricant composition of the present invention is sealed within the bearing space. FIG. 2 is a cross-sectional view of a deep groove ball bearing. Rolling bearing 11 comprises an inner ring 12 having an inner ring raceway on its outer circumferential surface and an outer ring 13 having an outer ring raceway on its inner circumferential surface, which are concentrically arranged. A plurality of rolling elements 14 are disposed between the inner ring raceway and the outer ring raceway. These rolling elements 14 are held in place by a cage 15. Furthermore, the axial end openings of the inner and outer rings are sealed by bearing sealing devices 17, and grease 16, serving as the lubricant composition described above, is sealed around at least the rolling elements 14. The inner ring 12, outer ring 13, and rolling elements 14 are made of bearing steel, an iron-based metal, and grease 16 is interposed between the raceway surfaces of the rolling elements 14 to provide lubrication. This reduces running torque and improves rust prevention within the bearing.

[0064] Figure 3 shows an example of a sealed rolling bearing in which the lubricant composition of the present invention is applied to the seal lip of a sealing member. The basic bearing configuration of the sealed rolling bearing of Figure 3 is the same as that of Figure 2. As shown in Figure 2, a bearing sealing device 27 is composed of a disk-shaped core 28 formed by pressing a cold-rolled steel plate or the like, and a sealing member 29 that is integrally vulcanized and bonded to this core 28. The material of the sealing member 29 may be nitrile rubber (NBR), acrylic rubber, silicone rubber, fluororubber, or the like.

[0065] The seal member 29 has a main lip 29a formed at its end on the inner ring 22 side with a bifurcated tip, and a dust lip 29b located outward of the main lip 29a in the bearing space. A portion of the seal member 29 is fixed to a seal groove on the inner periphery of the end of the outer ring 23, which is the stationary member, and each seal lip slides into a seal groove with a generally U-shaped cross section formed on the outer periphery of the end of the inner ring 22, which is the rotating member. In the configuration shown in FIG. 3 , the surface of each seal lip 29a, 29b that slides against the inner ring 22—specifically, one side of the tip of each seal lip—is coated with grease 30, serving as the lubricant composition described above. In this case, it is sufficient that the grease 30 is coated on at least the sliding surface of the seal lip, and it may also be coated on the entire seal lip. As a result, reduced seal torque and excellent waterproof and rust-resistant properties can be achieved.

[0066] In FIG. 3, the grease 26 (or lubricating oil) sealed in the bearing space may be the lubricant composition of the present invention or a known lubricant composition.

[0067] In the sealed rolling bearing shown in FIG. 3, the lubricant composition of the present invention is applied in advance to the sliding contact surface of the seal lip of the sealing member. Alternatively or additionally, the grease may be applied in advance to the surface of the rotating member with which the seal lip slides.

[0068] In Figures 2 and 3 above, a deep groove ball bearing is shown as an example of a sealed rolling bearing, but the sealed rolling bearing of the present invention can also be used as a cylindrical roller bearing, tapered roller bearing, self-aligning roller bearing, needle roller bearing, thrust cylindrical roller bearing, thrust tapered roller bearing, thrust needle roller bearing, thrust self-aligning roller bearing, etc.

[0069] 4 to 6 show longitudinal cross-sectional views of a hub bearing as another example of the sealed rolling bearing of the present invention. In this hub bearing, the lubricant composition of the present invention is applied to the seal lip of the seal member. Hub bearing 31 shown in Fig. 4 is an axle bearing on the drive wheel side that rotatably supports the axle.

[0070] As shown in FIG. 4, the hub bearing 31 includes an outer member 32 which has, integrally with it on its outer periphery, a vehicle body mounting flange 32b which is attached to a vehicle body (not shown) and has double-row outer raceways 32a, 32a formed on its inner periphery, and an end portion which is integrally formed with a wheel mounting flange 34b to which a wheel (not shown) is attached, and which has, on its outer periphery, one inner raceway 34a which faces the double-row outer raceways 32a, 32a, and a cylindrical small-diameter step 34c which extends axially from the inner raceway 34a, and which has serrations 36 for transmitting torque formed on its inner periphery, and an inner ring 35 which is press-fitted into the small-diameter step 34c and has the other inner raceway 35a formed on its outer periphery.

[0071] Double-row rolling elements (balls) 37 are rollably accommodated by a cage 38 between the double-row outer raceways 32a, 32a and the opposing inner raceways 34a, 35a. Bearing sealing devices 41, 46 are mounted in the annular spaces formed between the inner member 33, which is the rotating member and comprises the hub ring 34 and the inner ring 35, and the outer member 32, which is the fixed member. These bearing sealing devices prevent leakage of grease sealed in the bearing space 39 and prevent intrusion of rainwater, dust, and the like into the bearing space 39 from the outside. The grease (or lubricating oil) sealed in the bearing space 39 may be the lubricant composition of the present invention or a known lubricant composition. Of the bearing sealing devices 41, 46, the inboard-side bearing sealing device 41 mounted between the outer member 32 and the inner ring 35 will be described using FIG. 5.

[0072] 5, bearing sealing device 41 includes a seal ring 44 made up of a core metal 42 formed with an L-shaped cross section and fitted inside an outer member, and a seal member 43 integrally vulcanized and bonded to core metal 42, and a slinger 45 fitted onto the inner ring and also formed with an L-shaped cross section. Slinger 45 and core metal 42 of seal ring 44 are formed by pressing an austenitic stainless steel plate (JIS standard SUS304 series, etc.) or a rust-proofed cold-rolled steel plate (JIS standard SPCC series, etc.).

[0073] The material of seal member 43 may be nitrile rubber (NBR), acrylic rubber, silicone rubber, fluororubber, or the like. In Fig. 5, seal member 43 has three seal lips 43a, 43b, and 43c, in that order from the inside of the bearing space, namely, inner, middle, and outer seal lips, with the leading edge of outer seal lip 43c in sliding contact with the inner surface of upright portion 45b of slinger 45, and the leading edges of the remaining middle seal lip 43b and inner seal lip 43a in sliding contact with cylindrical portion 45a of slinger 45. In this configuration, core 42 corresponds to the fixed-side member, and slinger 45 corresponds to the rotating-side member.

[0074] In the configuration of Fig. 5, grease is applied to the sliding contact surfaces of the seal lips of the seal member. Specifically, as shown in Fig. 5, grease G is applied to the sliding contact surfaces of seal lips 43a, 43b, and 43c that come into sliding contact with slinger 45. In this case, it is sufficient that grease G is applied to at least the sliding contact surfaces of the seal lips, and it may also be applied to the entire seal lips.

[0075] Next, the bearing sealing device attached to the outboard side of the hub bearing will be described with reference to Figure 6. Bearing sealing device 46 is fitted into outer member 32 and consists of an annular core 47, and a seal member 48 that is integrally vulcanized and bonded to core 47. Core 47 is formed in the same manner as the slinger described above. Seal member 48 is made of an elastic material such as nitrile rubber and has two side lips (dust seals) 48b, 48c and a single radial lip (grease seal) 48a, the leading edge of each of which is in direct sliding contact with the surface of hub ring 34; specifically, sliding surface 49 formed in an arc at the inboard base of the wheel mounting flange.

[0076] 6, in the bearing sealing device 46, grease G is also applied to the surface of each seal lip 48a, 48b, 48c that comes into sliding contact with the hub wheel 34, specifically, to one side of the tip of each seal lip. As a result, it is possible to reduce the seal torque and achieve excellent waterproof and rust-resistant properties.

[0077] The lubricant composition of the present invention may be used as a lubricant to be filled in the bearing space of a hub bearing, and a hub bearing filled with the lubricant composition of the present invention may be used as the sealed rolling bearing of the present invention.

[0078] The sealed rolling bearing of the present invention is not particularly limited in its applications, but as will be shown in the examples below, it is particularly suitable for low-speed rotation applications because it can prevent oil film breakdown during low-speed rotation and results in low torque. -1 This applies to bearings used in the following rotational speed ranges: 2000 min -1 The term "used in the following rotational speed range" means that the main rotational speed (steady-state rotational speed) of the bearing in use is 2000 min-1 -1 The rotation speed is 1500 min -1 It may be less than 1000min -1 It may be the following: [Example]

[0079] First, greases were prepared with the compositions shown in Tables 1 and 2. In Tables 1 and 2, the mass % of the base oil and thickener indicates the content relative to the base grease (base oil + thickener). The mass parts of the rust inhibitor indicate the blended amount relative to 100 mass parts of the base grease.

[0080] Note that 1) to 12) below in Table 1 are the same in Table 2. Note that 6) in Table 1 is a barium salt of a petroleum-based sulfonic acid, 7) in the table is a barium salt of an alkylbenzenesulfonic acid, 8) in Table 1 is a calcium salt of a petroleum-based sulfonic acid, and 10) to 12) in Table 1 are various metal salts (calcium salt, barium salt, magnesium salt) of alkylnaphthalenesulfonic acid.

[0081] The grease used in the examples was prepared as follows. An isocyanate (4,4'-diphenylmethane diisocyanate, MDI) was dissolved in half of the base oils shown in Tables 1 and 2 in the proportions shown in the tables, and a monoamine was dissolved in the remaining half of the base oil. The monoamine solution was added to the MDI solution while stirring, and the mixture was then stirred at 100°C to 120°C for 30 minutes to react, producing a diurea compound in the base oil and obtaining a base grease. Each rust inhibitor was added to the mixture in the proportions shown in Tables 1 and 2, and the mixture was further stirred thoroughly. The mixture was then homogenized using a triple-roll mill to obtain the test greases.

[0082] The resulting grease was subjected to the following physical property measurements and tests.

[0083] <Worked penetration> The 60-stroke worked penetration of the grease was measured in accordance with JIS K2220.

[0084] <Viscosity> A cone-plate type rheometer (diameter 20 mm, gap distance 53 μm) was used to measure each grease at a temperature of 25°C, a frequency of 1 Hz, and a shear rate of 10 s -1 The mixture was rotated at 400°C for 30 minutes, and the shear stress at which it reached a steady flow was determined. Furthermore, the viscosity was calculated using the Herschel-Barkley equation, where n = 1. The viscosity evaluation is shown in Tables 1 and 2, with a ◎ for less than 10 Pa·s, a ○ for 10 Pa·s or more but less than 30 Pa·s, and an × for 30 Pa·s or more.

[0085] <Seal torque test> A total of 0.6 g of grease was applied to one side of the tip of the three seal lips of a nitrile rubber seal member (φ60 to 70 mm). The seal member was attached to a member simulating the outer ring of a hub, and a SUS430 slinger was attached to a member simulating the inner ring of a hub, and the seal lips and slinger were assembled so that they came into contact with each other. Rotation speed: 600 min -1The torque (N m) caused by the sliding contact of the seal lip was measured for 1 minute 30 minutes after the start of the test at room temperature with the inner ring rotating. The results of this test are shown in Tables 1 and 2 with a ◎ for less than 0.1 N m, a ○ for 0.1 N m or more but less than 0.15 N m, and an × for 0.15 N m or more.

[0086] <Bearing torque test> A total of 0.4 g of grease was applied to one side of the tip of the two seal lips of a nitrile rubber seal member (φ25-40 mm). The seal member was attached to a deep groove ball bearing (6204LLU) and assembled so that the seal lip and inner ring were in contact. Mineral oil grease (kinematic viscosity 100 mm at 40°C) was also applied to the bearing space. 2 / s) was enclosed at 0.05%. Rotation speed: 1800 min -1 The bearing torque (N·mm) was measured for 1 minute 30 minutes after the start of the test at room temperature with the inner ring rotating. The results of this test are shown in Tables 1 and 2 with a ◎ for less than 25 N·mm, a ○ for 25 N·mm to 30 N·mm, and an × for 30 N·mm or more.

[0087] <Water resistance test> 0.1 g and 0.3 g of the above grease were applied to the seal grooves formed on the outer circumference of the inner ring and the inner circumference of the outer ring of a 6204 stainless steel LLH bearing, and a nitrile rubber seal was attached so that the seal lip contacted the seal groove of the inner ring. 0.05 g of a known grease composition (with a different composition from the greases prepared in Tables 1 and 2) was sealed into the bearing space. Using this test bearing, the following test, which was a modified version of the water washout resistance test specified in JIS K2220, was conducted.

[0088] After the test bearing was installed in the housing of a water wash resistance tester, the test bearing was submerged in warm water at 79°C. Then, while the test bearing was submerged, it was rotated at a speed of 600 min -1 While rotating at 40°C, 79°C hot water was sprayed onto the test bearing from a spray nozzle at a rate of 6 ml / s for 120 minutes. After the test, the amount of water that had penetrated into the test bearing was calculated using the following formula. Water intrusion amount (g) = (bearing weight after operation - bearing weight before operation) The evaluation of the amount of water penetration is shown in Tables 1 and 2, with less than 0.5 g marked with a ◎, 0.5 g or more but less than 1.0 g marked with a ○, and 1.0 g or more marked with an ×.

[0089] <Rust test> The tapered roller bearings coated with the grease were immersed in 1% by mass salt water for 10 seconds and left to stand in a high-humidity environment. After the test, the bearings were removed and the outer ring rolling surface was visually inspected. The outer ring rolling surface was divided into 32 sections, and the rust occurrence rate was calculated based on how many of those sections had rust (modified ASTM D1743). Bearing: 4T-30204 Grease content: 2.0g Test temperature: 40℃ Test humidity: 100%RH Test duration: 48 hours The rust occurrence rate is evaluated in Tables 1 and 2, with less than 30% marked with a ◎, 30% or more but less than 60% marked with a ○, and 60% or more marked with an ×.

[0090] [Table 1]

[0091] [Table 2]

[0092] As shown in Tables 1 and 2, Examples 1 to 7, which had a grease viscosity of less than 30 Pa·s and used a combination of a polyhydric alcohol ester-based rust inhibitor and another rust inhibitor, showed good results in all tests.

[0093] Furthermore, a strong correlation was observed between the evaluation of grease viscosity and the evaluation of the seal torque test and bearing torque test. Examples 1 to 7, which had a grease viscosity of less than 30 Pa·s, showed low torque in the seal torque test and bearing torque test, while Comparative Examples 2 to 4, which had a grease viscosity of 30 Pa·s or more, showed increased torque in the seal torque test and bearing torque test. It was suggested that the viscosity could be affected by other rust inhibitors combined with the polyhydric alcohol ester-based rust inhibitor. Furthermore, a tendency was observed for the viscosity to increase as the amount of rust inhibitor added to the mixture increased, resulting in increased torque (Examples 1, 2, 5, and 6).

[0094] It was found that the results of water penetration (water resistance) were particularly affected by the worked penetration of the grease and the amount of rust inhibitor blended. Comparative Example 9 (worked penetration 200), which had a lower worked penetration compared to the others, and Comparative Example 10 (worked penetration 320), which had a higher worked penetration compared to the others, both showed increased water penetration. It is believed that Comparative Example 10, because of its high consistency and softness, caused the grease to leak from near the lip, resulting in a decrease in sealing performance. On the other hand, Comparative Example 9, because of its hardness and poor fluidity, is more likely to cause gaps to form, which is thought to have reduced sealing performance. Furthermore, an increase in the amount of rust inhibitor tended to increase the amount of water penetration (Examples 3 and 5, Comparative Examples 5 and 7). Rust inhibitors are effective in terms of rust prevention, but this suggests that they may be detrimental to the grease's sealing ability against water penetration. It is presumed that as the amount of rust inhibitor increases, the grease becomes more compatible with water, making it more difficult for the grease near the lip to maintain its shape.

[0095] Regarding the rust occurrence rate, the results showed that the rust prevention properties were improved when the polyhydric alcohol ester-based rust inhibitor was used in combination with other types of rust inhibitors rather than when it was used alone (Examples 1 to 7, Comparative Examples 1 and 6).

[0096] The results in Tables 1 and 2 show that in this example, by appropriately combining the grease viscosity, type and amount of rust inhibitor, consistency, etc., the grease ensures channeling properties, prevents oil film breakdown at low speeds, and achieves low torque, leakage resistance, high water resistance, and rust prevention. Furthermore, by using an appropriate rust inhibitor, it is possible to maintain rust prevention within the seal and prevent rust formation, even in the unlikely event that muddy water or the like enters due to seal wear. Furthermore, because it is easy to achieve an appropriate consistency range while using a low-viscosity base oil, in this example, a specified base oil (a mixture of synthetic hydrocarbon oil and ester oil) is combined with a specified thickener (an aliphatic or alicyclic diurea compound). [Industrial Applicability]

[0097] The lubricant composition of the present invention can achieve both low torque and rust prevention, and in particular, a sealed rolling bearing having the lubricant composition applied to the seal lip or the like exhibits low torque and excellent leakage resistance, which leads to high performance (low fuel consumption) of the rolling bearing, and can therefore be widely used as a sealed rolling bearing. In particular, because of its excellent rust prevention properties, it can be suitably used for hub bearings that are prone to intrusion of muddy water, etc. [Explanation of symbols]

[0098] 1 Rheometer 2. Cone-plate type cell 3 Horizontal disc plate 4. Lubricant composition 11 Rolling bearings (sealed rolling bearings) 12 Inner Circle 13 Outer ring 14 Rolling elements 15 Cage 16 Grease (lubricant composition) 17 Bearing sealing device 18 Core 19 Sealing material 21 Rolling bearings (sealed rolling bearings) 22 Inner Circle 23 Outer ring 24 rolling elements 25 Retainer 26 Grease 27 Bearing sealing device 28 Core 29 Sealing material 30 Grease (lubricant composition) 31 Hub bearing (sealed rolling bearing) 32 Outer member 33 Inner member 34 Hub wheel 35 Inner Circle 36 serrations 37 Rolling elements 38 Retainer 39 Bearing space 41 Bearing sealing device 42 Core 43 Sealing material 44 Seal ring 45 Slinger 46 Bearing sealing device 47 Core 48 Sealing material 49 Sliding surface Grease (lubricant composition)

Claims

1. A sealed rolling bearing comprising a seal member that seals a bearing space, is fixed to a fixed member, and is in sliding contact with a rotating member, and in which a lubricating grease composition is sealed in the bearing space, the seal member has a seal lip that is in sliding contact with the rotating member, and in the sealed rolling bearing, a grease having a composition different from that of the lubricating grease composition is applied as a lubricant composition to at least one of a sliding contact surface of the seal lip and a sliding contact surface of the rotating member with which the seal lip is in sliding contact, The applied grease contains a base oil, a thickener, and a rust inhibitor, and the base oil has a kinematic viscosity at 40°C of 15 mm 2 / s or less; The grease was measured by a time-dependent measurement method using a rheometer. －１ The viscosity at a steady state after 30 minutes of shear at a shear rate of less than 30 Pa s, 1. A sealed rolling bearing, wherein the rust inhibitor comprises a polyhydric alcohol ester-based rust inhibitor and other rust inhibitors.

2. 2. The sealed rolling bearing according to claim 1, wherein the lubricant composition contains the rust inhibitor in an amount of 0.5 to 3 mass % based on the total amount of the lubricant composition.

3. 3. A sealed rolling bearing according to claim 1, wherein the other rust inhibitor is a sulfonate-based rust inhibitor or a carboxylate-based rust inhibitor.

4. 4. The sealed rolling bearing according to claim 1, wherein the base oil is at least one oil selected from the group consisting of synthetic hydrocarbon oils, ester oils, and ether oils.

5. 5. The sealed rolling bearing according to claim 1, wherein the grease has a worked penetration of 260 to 300 as measured in accordance with JIS K2220.

6. A sealed rolling bearing as described in any one of claims 1 to 5, characterized in that the thickener is a urea compound obtained by reacting a polyisocyanate component with at least one monoamine component selected from aliphatic monoamines and alicyclic monoamines, or a complex lithium soap.

7. 7. A sealed rolling bearing according to claim 1, wherein the seal member is formed from nitrile rubber, has a plurality of seal lips as the seal lips, and the grease is applied to the sliding surfaces of these seal lips.

Images