JP2006249271A - Grease composition and anti-friction bearing sealed with grease - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To definitely inhibit noises caused by a cold weather. <P>SOLUTION: The grease composition contains a base oil and a thickening agent. The above thickening agent contains a urea compound represented by formula (1), where R<SB>1</SB>and R<SB>3</SB>are 1-7C monovalent aliphatic hydrocarbon groups and can be either same or different and R<SB>2</SB>is a 6-12C divalent aromatic hydrocarbon group. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a grease composition enclosed in a rolling bearing incorporated in various industrial machines and vehicles, and is particularly suitable for a bearing used at a high speed rotation in a wide temperature range from a very low temperature to a high temperature where abnormal noise is generated during cold. The present invention relates to a grease composition.

  A rolling bearing incorporated in various industrial machines, vehicles and the like is filled with a grease composition in order to impart lubricity. This grease composition is obtained by kneading a base oil and a thickener. Examples of the base oil include mineral oils, ester oils, silicone oils, ether oils, fluorine oils and other synthetic lubricating oils. Metal soaps such as lithium soap, urea compounds, and fluororesins are generally used. In recent years, rolling bearings tend to be used at high speed rotation, and accordingly, grease compositions are required to have high temperature resistance. However, when metal soap is used as a thickener, the oxidation of the base oil is promoted at a high temperature to lower the lubricating action. Regarding the base oil, a grease composition using a mineral oil as a base oil is more likely to be oxidized than a grease composition using a synthetic lubricating oil as a base oil, and the lubricating life at a high temperature tends to be shortened. In recent years, therefore, grease compositions using synthetic lubricants as base oils and urea compounds or fluororesins as thickeners are becoming mainstream in rolling bearings used at high temperatures and high speeds.

With the miniaturization and high performance of various industrial machine members, the usage conditions tend to become stricter. Accordingly, further lubrication performance and lubrication life are required for the grease composition. To meet the demand for long life at high temperatures, formulations using high viscosity base oils and urea compounds as thickeners are being investigated. Sound is likely to occur.
On the other hand, when a pulley or the like of a device driven by an automobile engine is operated in cold weather, a singular sound (whispering noise) in cold weather, that is, a so-called cold noise may be generated depending on the pulley specifications and operating conditions. The cause of the generation of this cold abnormal noise has not yet been clearly clarified, but it is presumed to be due to the self-excited vibration of the rolling elements due to the oil film unevenness of the grease. In other words, when the oil is cold, unevenness of the oil film on the raceway surface is likely to occur due to an increase in the base oil viscosity of the grease, but if there is oil film unevenness, the friction coefficient between the rolling elements and the raceway surface will cause minute periodic changes. Causes self-excited vibration in the rolling element. It is considered that the pulley system resonates due to this self-excited vibration, and the outer ring vibrates in the axial direction (translational movement), resulting in generation of cold noise.

As a grease that has excellent high-temperature durability and suppresses abnormal noise during cold, 8 or more ester groups are arranged in a comb-teeth shape on one side of 8 or more carbon atoms that constitute the chain molecule of synthetic hydrocarbon oil and oil. A grease is known in which a urea compound is blended as a thickener and a dithiophosphate is added as an extreme pressure agent to a base oil composed of a mixed oil with an ester synthetic oil (see Patent Document 1).
In addition, an alicyclic diurea compound was added as a thickener to a base oil composed of a mixed oil of poly-α-olefin (hereinafter abbreviated as PAO) oil and ester oil, and zinc dithiocarbamate was added as an additive. A bearing in which a grease composition is enclosed, and a plurality of balls interposed between an inner ring constituting the bearing and an outer ring are brought into contact with the ball and at least the outer ring of the inner ring or the outer ring at two points. An automotive pulley bearing having a contact angle is known (see Patent Document 2).

These attempts aimed at improving the stability of the oil film at low temperatures and prolonging the service life at high temperatures as a countermeasure against abnormal noise during cold, but it is sufficient to simply mix synthetic hydrocarbon oil and ester oil. There is a problem that the result of preventing abnormal cold noise is not obtained.
In addition, the usage conditions tend to become more severe with the miniaturization and higher performance of the various mechanical members listed above, and accordingly, further lubrication performance and lubrication life are required for the grease composition. . Formulas that add antioxidants, rust inhibitors, etc. to grease compositions based on heat-resistant, high-viscosity synthetic hydrocarbon oils and urea compounds as thickeners in response to demands for longer life at high temperatures However, there is a problem that cold noise is likely to occur during cold weather.
Japanese Patent Laid-Open No. 9-208982 JP-A-11-270566

  An object of the present invention is to provide a grease composition and a grease-filled rolling bearing capable of reliably preventing the occurrence of cold abnormal noise during cold weather.

式（１）中において、Ｒ₁ 、Ｒ₃ は、炭素数 1〜炭素数 7 の１価の脂肪族系炭化水素基を表わし、Ｒ₁ 、Ｒ₃は同一であっても異なっていてもよい。Ｒ₂ は、炭素数 6〜炭素数 12 の２価の芳香族系炭化水素基を表わす。 The grease composition of the present invention is a grease composition containing a base oil and a thickener, wherein the thickener contains a urea compound represented by the following formula (1).

In the formula (1), R ₁ and R ₃ represent a monovalent aliphatic hydrocarbon group having 1 to 7 carbon atoms, and R ₁ and R ₃ may be the same or different. . R ₂ represents a divalent aromatic hydrocarbon group having 6 to 12 carbon atoms.

  The base oil contains an aliphatic hydrocarbon oil. The grease composition includes at least one compound selected from polymethacrylate and polyacrylate (hereinafter abbreviated as poly (meth) acrylate) as an additive. The grease composition includes a dithiophosphate as an additive.

The grease-filled rolling bearing of the present invention is a rolling bearing comprising an inner ring and an outer ring, and a rolling element interposed between the inner ring and the outer ring, and a grease composition sealed around the rolling element, and the grease The composition is a grease composition as described above.
The grease-filled rolling bearing of the present invention is used in an automotive electrical accessory that rotatably supports a rotating shaft, which is driven to rotate by engine output, on a stationary member, and is a heat and cold resistant noise bearing. To do.
The automotive electrical accessory is a fan coupling device, an alternator, an idler pulley, a tension pulley, an electromagnetic clutch, or a compressor.

  The grease composition of the present invention is a grease composition containing a base oil and a thickener, and since the thickener contains the urea compound represented by the above formula (1), the viscosity at low temperature is Reduction is suppressed. As a result, it exhibits good lubricity in a wide temperature range from low temperature to high temperature, can prevent the occurrence of cold noise immediately after starting at low temperature, and can maintain high temperature durability for a long time It becomes a grease composition, and it becomes a grease composition for enclosing a bearing capable of extending the life of the bearing as much as possible.

The grease-enclosed rolling bearing of the present invention is a bearing comprising an inner ring and an outer ring, and rolling elements interposed between the inner ring and the outer ring, and the grease composition is sealed around the rolling elements. Rolling bearings that exhibit good lubricity in a wide temperature range up to high temperatures, can prevent the occurrence of cold noise immediately after starting at low temperatures, and can maintain high temperature durability properties for a long time. The bearing life can be extended as much as possible.
Since the grease-enclosed rolling bearing is a rolling bearing used in an automotive electrical accessory, it is possible to reliably prevent the generation of cold noise during cold weather while maintaining lubrication performance at high temperature.

  As a result of intensive studies aimed at providing grease compositions and grease-filled rolling bearings that can reliably prevent the occurrence of cold noise during cold weather, It has been found that a rolling bearing in which a grease composition containing a urea compound represented by the formula (1) is sealed can prevent cold noise. It is considered that the blending of the urea compound prevents an increase in the viscosity of the grease composition during cold weather, and suppresses the occurrence of oil film unevenness on the bearing raceway surface, thereby increasing the cold noise prevention effect. The present invention is based on such knowledge.

（Ｒ₁ 、Ｒ₃ は、炭素数 1〜炭素数 7 の１価の脂肪族系炭化水素基を表わし、Ｒ₁ 、Ｒ₃ は同一であっても異なっていてもよい。Ｒ₂ は、炭素数 6〜炭素数 12 の２価の芳香族系炭化水素基を表わす。） The thickener used in the grease composition of the present invention is a urea compound, preferably diurea having two urea bonds in the molecule, and is represented by the following formula (1).

(R ₁ and R ₃ represent a monovalent aliphatic hydrocarbon group having 1 to 7 carbon atoms, and R ₁ and R ₃ may be the same or different. R ₂ represents carbon. It represents a divalent aromatic hydrocarbon group having 6 to 12 carbon atoms.)

In addition, as an example of the manufacturing method of a urea compound, obtaining by making the isocyanate compound equivalent amine compound react with a diisocyanate compound is mentioned.
For component represented by the formula (1), R ₁ and R ₃ is a linear or branched aliphatic hydrocarbon group having a carbon number of 1 to 7 carbon atoms, the number 3 carbon carbon number 5 Gayori preferable. Particularly preferably, it has 4 carbon atoms. Moreover, it is preferable that it is linear. Preferable specific examples of R ₁ and R ₃ include n-butyl group.
When R ₁ and R _{3 have} a carbon number of less than 1, that is, when aniline is used in the production of a urea compound, the fiber of the thickening agent becomes large, and noise during cold tends to occur. In addition, when the number of carbon atoms is 8 or more, the heat resistance is inferior and the high-temperature life is reduced.

  The penetration of the grease composition that can be used in the present invention is measured by JIS K 2220 and is preferably in the range of 150 to 400. If it is less than 150, the lubrication performance at low temperatures deteriorates, and if it exceeds 400, the grease composition tends to leak, which is not preferable.

As the base oil that can be used in the present invention, a mineral oil, a synthetic oil, or a mixed oil usually used for grease can be used.
Specifically, the mineral oil can include paraffinic mineral oil and naphthenic mineral oil, and the synthetic oil includes ester oil, ether oil, or synthetic hydrocarbon oil. These can be used alone or in any mixture.
Specifically, as the ether oil, dialkyl phenyl ether oil, alkyl triphenyl ether oil, alkyl tetraphenyl ether oil, etc.
Examples of ester oils include diester oils, polyol ester oils, complex ester oils thereof, and aromatic ester oils.
Among these, it is preferable that synthetic hydrocarbon oil, alkyl diphenyl ether oil, ester oil and the like are contained in consideration of lubrication performance and lubrication life at high temperature and high speed. Synthetic hydrocarbon oil is a hydrocarbon compound composed of a compound of carbon and hydrogen. PAO oil, copolymer of α-olefin and olefin, aliphatic hydrocarbon oil such as polybutene, alkylbenzene, alkylnaphthalene, polyphenyl There are aromatic hydrocarbon oils such as synthetic naphthenes.
Further, high temperatures, for lubrication performance and lubrication life at a high speed is not lowered, it is preferable that the kinematic viscosity of the base oil at 40 ° C. is ^{15 mm 2 / s~200 mm 2 /} s. The kinematic viscosity of the base oil is a kinematic viscosity measured according to JIS K 2283. In the present invention, it is preferable to mix any two oils.

  The PAO oil is usually an α-olefin or an isomerized α-olefin oligomer or polymer mixture. Specific examples of the α-olefin include 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1 -Nonadecene, 1-eicocene, 1-docosene, 1-tetracocene and the like can be mentioned, and usually a mixture thereof is used.

（Ｒ₄ 、Ｒ₅ は、炭素数 1〜炭素数 20 の脂肪族系炭化水素基を表わし、Ｒ₄ 、Ｒ₅ は、同一であっても異なっていてもよい。）
Ｒ₄ の炭素数は 8、Ｒ₅ の炭素数は 10 であることが好ましい。 The synthetic hydrocarbon oil suitable for the present invention can achieve both the stability of the oil film at a low temperature and the durability at a high temperature when a urea thickener and an extreme pressure agent described later are blended. It is an aliphatic hydrocarbon oil.
Among the aliphatic hydrocarbon oils, PAO oil, a copolymer of α-olefin and olefin, and polybutene are preferable. For example, a structure in which hydrogen is added to a terminal double bond of an oligomer which is a low polymer of α-olefin, and one represented by the following formula (2) can be exemplified. n is an integer, and it may be an integer in a range in which the synthetic hydrocarbon oil retains the kinematic viscosity described later in consideration of lubrication performance and lubrication life at high temperature and high speed. Polybutene, which is a kind of PAO, can also be used, and this polybutene can be produced by polymerization from a starting material mainly composed of isobutylene using a catalyst such as aluminum chloride. Polybutene may be used as it is or after hydrogenation.

(R ₄ and R ₅ represent an aliphatic hydrocarbon group having 1 to 20 carbon atoms, and R ₄ and R ₅ may be the same or different.)
Preferably, R ₄ has 8 carbon atoms and R ₅ has 10 carbon atoms.

The grease composition of the present invention contains the above base oil and thickener as essential components, and further includes conventional pressure agents such as extreme pressure agents, antioxidants, rust inhibitors, metal deactivators, and oil agents. A grease additive can be further blended.
Extreme pressure agent:
By blending an extreme pressure agent, load resistance and extreme pressure properties can be improved. For example, the following compounds can be used. As organometallic compounds, organic molybdenum compounds such as molybdenum dithiocarbamate and molybdenum dithiophosphate, organic zinc compounds such as zinc dithiocarbamate, zinc dithiophosphate and zinc phenate, organic antimony compounds such as antimony dithiocarbamate and antimony dithiophosphate, Organic selenium compounds such as selenium dithiocarbamate, organic bismuth compounds such as bismuth naphthenate and bismuth dithiocarbamate, organic iron compounds such as iron dithiocarbamate and iron octylate, organic copper compounds such as copper dithiocarbamate and copper naphthenate, naphthenic acid Organic lead compounds such as lead and lead dithiocarbamate, organic tin compounds such as tin maleate and dibutyltin sulfide, or organic sulfonates, phenates and phosphates of alkali metals and alkaline earth metals Sulfonates, gold, silver, titanium, an organometallic compound such as cadmium can also be used if necessary. As the sulfur compounds, sulfides such as dibenzyl disulfide or polysulfide compounds, sulfurized fats and oils, ashless carbamic acid compounds, thiourea compounds, thiocarbonates, and the like can be used. As the phosphoric acid extreme pressure agent, it is possible to use phosphate compounds such as trioctyl phosphate, tricresyl phosphate, etc., phosphate esters, acidic phosphate esters, phosphite esters, acidic phosphite esters, etc. it can. In addition, halogen-based extreme pressure agents such as chlorinated paraffin, or solid lubricants such as boron compounds such as molybdenum disulfide, tungsten disulfide, graphite, polytetrafluoroethylene, antimony sulfide, and boron nitride are used. be able to.
Among these extreme pressure agents, dithiocarbamic acid compounds and dithiophosphoric acid compounds can be suitably used.

Antioxidant:
As the antioxidant, an antioxidant, an ozone deterioration inhibitor, and an antioxidant that are added to rubber, plastic, lubricating oil, and the like can be appropriately selected and used. For example, the following compounds can be used. That is, phenyl-1-naphthylamine, phenyl-2-naphthylamine, diphenyl-p-phenylenediamine, dipyridylamine, phenothiazine, N-methylphenothiazine, N-ethylphenothiazine, 3,7-dioctylphenothiazine, p, p'-dioctyldiphenylamine An amine compound such as N, N′-diisopropyl-p-phenylenediamine, N, N′-di-sec-butyl-p-phenylenediamine, or the like can be used.

  A phenolic antioxidant can also be used. Examples of the phenolic antioxidant include 2,6-di-t-dibutylphenol, n-octadecyl-3- (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate, tetrakis- ( Methylene-3- (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate) methane, 2,2′-methylenebis- (4-methyl-6-tert-butylphenol), 4,4′- Butylidenebis- (3-methyl-6-tert-butylphenol) and the like.

anti-rust:
As a rust inhibitor, for example, the following compounds can be used. That is, ammonium salts of organic sulfonic acids, alkali metals such as barium, zinc, calcium and magnesium, organic sulfonates of alkaline earth metals, organic carboxylates, phenates, phosphonates, alkyls such as alkyl or alkenyl succinates, alkenyls Succinic acid derivatives, partial esters of polyhydric alcohols such as sorbitan monooleate, hydroxy fatty acids such as oleoylsarcosine, mercapto fatty acids such as 1-mercaptostearic acid or metal salts thereof, higher fatty acids such as stearic acid, Higher alcohols such as isostearyl alcohol, esters of higher alcohols and higher fatty acids, thiazoles such as 2,5-dimercapto-1,3,4-thiadiazole, 2-mercaptothiadiazole, 2- (decyldithio) -be Imidazole compounds such as diimidazole and benzimidazole, disulfide compounds such as 2,5-bis (dodecyldithio) -benzimidazole, phosphate esters such as trisnonylphenyl phosphite, dilaurylthiopropio Thiocarboxylic acid ester compounds such as nates can be used. Corrosion inhibitors such as nitrites, nitrates, chromates, phosphates, molybdates, tungstates that passivate the metal surface can also be used.

Metal deactivator:
As the metal deactivator, for example, a triazole compound such as benztriazole or tolyltriazole can be used.

Oiliness agent:
As the oily agent, for example, the following compounds can be used. That is, fatty acids such as oleic acid and stearic acid, fatty acid alcohols such as oleyl alcohol, fatty acid esters such as polyoxyethylene stearic acid ester and polyglyceryl oleic acid ester, phosphoric acid, tricresyl phosphate, lauric acid ester or polyoxyethylene oleyl Phosphoric esters such as ether phosphoric acid can be used.

Viscosity index improver:
Examples of the viscosity index improver include poly (meth) acrylate. The poly (meth) acrylate is a polymer or copolymer of an acrylate monomer represented by an alkyl (meth) acrylate. Here, the alkyl (meth) acrylate refers to at least one monomer selected from alkyl methacrylate and alkyl acrylate. Specific examples of the alkyl group include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, Examples include icosyl group, docosyl group, tetracosyl group, octacosyl group and triacontyl group. These compounds may be used alone or as a mixture of any two or more of them. Among these, poly (meth) acrylates having a weight average molecular weight of 20,000 to 1,500,000 are preferable.

In the grease composition of the present invention, the blending ratio of the additive is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the total amount of the base oil and the thickener. If the blending ratio of the additive is less than 0.1 parts by weight, the effect of adding the additive is poor, and if it exceeds 20 parts by weight, the grease is softened and leaks easily.
The blending ratio of the base oil is preferably 50 to 95 parts by weight with respect to 100 parts by weight of the total amount of the base oil and the thickener. If the blending ratio of the base oil is less than 50 parts by weight, the grease is hard and the lubricity at low temperatures is poor. If it exceeds 95 parts by weight, it will be soft and leaky.
The blending ratio of the thickener is preferably 5 to 50 parts by weight with respect to 100 parts by weight of the total amount of the base oil and the thickener. If it is less than 5 parts by weight, it becomes a liquid with a low viscosity and easily leaks, making it difficult to seal the bearing. Also, if it exceeds 50 parts by weight, it will solidify to a consistency of 100 or less, making it impractical as a grease for enclosing a bearing.

An example of a grease-filled rolling bearing according to the present invention is shown in FIG. FIG. 1 is a cross-sectional view of a deep groove ball bearing.
In the grease-filled rolling bearing 1, an inner ring 2 having an inner ring rolling surface 2a on the outer peripheral surface and an outer ring 3 having an outer ring rolling surface 3a on the inner peripheral surface are arranged concentrically, and the inner ring rolling surface 2a and the outer ring rolling surface are arranged. Several rolling elements 4 are arrange | positioned between 3a. Sealers 6 that are fixed to the cage 5, the outer ring 3, and the like that hold the plurality of rolling elements 4 are provided in the axially opposite end openings 8a, 8b of the inner ring 2 and the outer ring 3, respectively. A grease composition 7 is enclosed at least around the rolling element 4.

An example of an automotive electrical accessory is shown in FIG. FIG. 2 is a cross-sectional view of the fan coupling device. The fan coupling device includes an oil chamber 11 in which a viscous fluid such as silicone oil is filled in a case 10 that supports a cooling fan 9 and a stirring chamber 12 in which a drive disk 18 is incorporated. A port 14 is formed in the partition plate 13 provided therebetween, and an end of a spring 15 that opens and closes the port 14 is fixed to the partition plate 13.
A bimetal 16 is attached to the front surface of the case 10, and a piston 17 of a spring 15 is provided on the bimetal 16. The bimetal 16 becomes flat when the temperature of the air that has passed through the radiator is below a set temperature, for example, 60 ° C., the piston 17 presses the spring 15, and the spring 15 closes the port 14. When the temperature of the air exceeds the set temperature, the bimetal 16 bends outward as shown in FIG. 3B, the piston 17 releases the pressure of the spring 15, and the spring 15 is elastically deformed. Port 14 is opened.
When the temperature of the air that has passed through the radiator is lower than the set temperature of the bimetal 16 in the operating state of the fan coupling device having the above configuration, the port 14 is closed by the spring 15, so that the viscous fluid in the oil chamber 3 is Does not flow into the stirring chamber 12, and the viscous fluid in the stirring chamber 12 is sent into the oil chamber 11 from the circulation hole 19 provided in the partition plate 5 by the rotation of the drive disk 18.
For this reason, the amount of viscous fluid in the stirring chamber 12 becomes small, and the shear resistance due to the rotation of the drive disk 18 becomes small. Therefore, the transmission torque to the case 10 decreases, and the fan 9 rotates at a low speed.
When the temperature of the air that has passed through the radiator exceeds the set temperature of the bimetal 16, the bimetal 16 is bent outward as shown in FIG. 3B, and the piston 17 releases the pressure of the spring 15. At this time, since the spring 15 is elastically deformed in a direction away from the partition plate 13, the port 14 is opened, and the viscous fluid in the oil chamber 11 flows from the port 14 into the stirring chamber 12.
For this reason, the shear resistance of the viscous fluid due to the rotation of the drive disk 18 increases, the rotational torque to the case 10 increases, and the fan 9 supported by the rolling bearing rotates at high speed.
In the fan coupling device, the rotation speed of the fan 9 changes according to the temperature change, so that the warm-up can be accelerated and the cooling water can be prevented from being overcooled, thereby effectively cooling the engine. When the engine temperature is low, the fan 9 is equivalent to being disconnected from the drive shaft 20, and when the engine temperature is high, it is equivalent to being connected. Thus, the rolling bearing 1 is used in a wide temperature range and a wide rotation range from a low temperature to a high temperature.

An example of an alternator for an automotive electrical accessory is shown in FIG. FIG. 3 is a sectional view of the alternator. The alternator includes a pair of frames 21 a and 21 b that form a stationary member housing, and a rotor rotating shaft 23 having a rotor 22 mounted thereon is rotatably supported by a pair of ball bearings 1. A rotor coil 24 is attached to the rotor 22, and a three-turn stator coil 26 is attached to a stator 25 disposed on the outer periphery of the rotor 22 with a phase of 120 °.
The rotor rotating shaft 23 is rotationally driven with a rotational torque transmitted by a belt (not shown) to a pulley 27 attached to the tip thereof. Since the pulley 27 is attached to the rotor rotating shaft 23 in a cantilever state and vibration is also generated as the rotor rotating shaft 23 rotates at high speed, the ball bearing 1 that supports the pulley 27 side in particular receives a severe load. .

An example of an idler pulley used as a belt tensioner for an automobile accessory drive belt is shown in FIG. FIG. 4 is a sectional view of the idler pulley.
The pulley includes a pulley body 28 made of a steel plate press and a single row deep groove ball bearing 1 fitted to the inner diameter of the pulley body 28. The pulley main body 28 includes an inner diameter cylindrical portion 28a, a flange portion 28b extending from one end of the inner diameter cylindrical portion 28a to the outer diameter side, an outer diameter cylindrical portion 28c extending in the axial direction from the flange portion 28b, and the other end of the inner diameter cylindrical portion 28a. This is an annulus composed of a flange portion 28d extending to the inner diameter side. The outer ring 3 of the ball bearing 1 is fitted to the inner diameter of the inner cylindrical portion 28a, and a pulley peripheral surface 28e that contacts the belt driven by the engine is provided on the outer diameter of the outer cylindrical portion 28c. By bringing the pulley peripheral surface 28e into contact with the belt, the pulley functions as an idler.
The ball bearing 1 includes an outer ring 3 fitted to the inner diameter of the inner cylindrical portion 28a of the pulley body 28, an inner ring 2 fitted to a fixed shaft (not shown), and the transfer surfaces 2a, 3a of the inner / outer rings 2, 3. A plurality of incorporated rolling elements 4, a cage 5 that holds the rolling elements 4 at equal intervals around the circumference, and a pair of seal members 6 that seal grease are formed. The inner ring 2 and the outer ring 3 are integrally formed. .

An electromagnetic clutch and a compressor using the rolling bearing for an automotive electrical accessory according to the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view of the electromagnetic clutch and the scroll compressor.
The operation of the electromagnetic clutch 29 is shown below. The rolling bearing 1 incorporated in the pulley 31 is attached to the nose portion 37 of the compressor 30 and its outer ring is always rotated by belt driving. When the coil 34 a of the stator 34 is energized, the clutch plate 36 fixed to the compressor rotating shaft 35 is attracted to the pulley 31 by the magnetic flux generated by the coil current and connected to drive the compressor rotating shaft 35.
The electromagnetic clutch has functions such as transmission and interruption of torque between the engine and the compressor by the above operation, adjustment of the compressor rotation speed by selection of the pulley diameter, shock reduction during compressor operation, and absorption of torque fluctuation during steady rotation.
The scroll-type compressor 30 includes a movable scroll 32 and a fixed scroll 33 that are a pair of spiral parts, and a structure in which a space formed between both scrolls is reduced in volume while moving from the outside to the center to compress the refrigerant. It has become.
The rotation speed of the compressor rotating shaft 35 is 10000 rpm or more, the maximum is about 12000 rpm, and the ambient temperature may rise to about 180 ° C. Therefore, the rolling bearing 1 of the electromagnetic clutch 29 and other rolling bearings (not shown) in the compressor shown in FIG. 5 need to have sufficient durability even under the use conditions.

Examples 1 to 3
Base oils, thickeners and additives were blended in the proportions shown in Table 1 for each example to obtain grease compositions. For the additive, the blending amount with respect to 100 parts by weight of the total of the thickener and the base oil was expressed in parts by weight. The obtained grease composition was subjected to cold noise measurement and high temperature grease life test, and the results are also shown in Table 1. Test methods and test conditions are as follows.

Comparative Examples 1 to 3
For each comparative example, a base oil and a thickener were blended in the proportions shown in Table 1 to obtain a grease composition. The obtained grease composition was subjected to cold abnormal noise measurement and high temperature grease life test in the same manner as in the Examples, and the results are also shown in Table 1. Test methods and test conditions are as follows.

Cold noise measurement:
0.9 g of the grease composition obtained in each of the examples and comparative examples is sealed in a rolling bearing (6203) having a radial clearance of 0 to 8 μm when incorporated in a test pulley, and is kept in a low temperature bath at −60 ° C. for a certain period of time. After being put in, it is taken out and attached to a bearing rotating device installed at room temperature. When the bearing temperature reaches −20 ° C., it is rotated at a rotational speed of 2700 rpm under a radial load of 127 N. The presence or absence of occurrence was confirmed by hearing. The ratio (%) of the number of cold abnormal noise occurrences to the total number of tests (n = 10) was measured.

High temperature grease life test:
The grease composition obtained in each example and each comparative example (1.8 g) was sealed in a rolling bearing (6204), under an axial load of 670 N and a radial load of 67 N, at a bearing temperature of 150 ° C. and a rotational speed of 10,000 rpm. The time (h) until rotating and baking was measured.

Comprehensive evaluation:
When the ratio of the number of cold noise generation is 20% or less in the above cold noise measurement, it is evaluated that the cold noise resistance is excellent, and the time until baking in the high temperature grease life test Was evaluated as being excellent in heat resistance when it was 500 hours or longer. Table 1 shows “○” for a grease composition with a ratio of the number of abnormal noise generated during cold of 20% or less and a time to baking of 500 hours or longer, and “×” for other cases. It was written together.

  As shown in Table 1, the grease using the thickener represented by the formula (1) is unlikely to generate abnormal noise during cold and has a high temperature and long life. This is because the increase in viscosity of the grease composition during cold weather was prevented by the addition of the above thickener, and the occurrence of oil film unevenness on the bearing raceway surface was suppressed, thereby increasing the cold noise prevention effect. It is done. Therefore, it can be suitably used for a rolling bearing used in cold weather, especially a rolling bearing for electrical equipment.

  The grease composition of the present invention exhibits good lubricity in a wide temperature range from low temperature to high temperature, and can prevent the occurrence of cold abnormal noise immediately after starting at low temperature, so the grease composition of the present invention is enclosed. Such a bearing can be suitably used for a bearing for a vehicle such as an automobile during cold weather.

It is sectional drawing of a rolling bearing. It is sectional drawing of a fan coupling apparatus. It is sectional drawing of an alternator. It is sectional drawing of an idler pulley. It is sectional drawing of an electromagnetic clutch and a compressor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Deep groove ball bearing 2 Inner ring 3 Outer ring 4 Rolling body 5 Cage 6 Seal member 7 Grease composition 8a Opening 8b Opening 9 Cooling fan 10 Case 11 Oil chamber 12 Stirring chamber 13 Partition plate 14 Port 15 Spring 16 Bimetal 17 Piston 18 Drive disk 19 Distribution hole 20 Drive shaft 21a Frame
21b frame
DESCRIPTION OF SYMBOLS 22 Rotor 23 Rotor rotating shaft 24 Rotor coil 25 Stator 26 Stator coil 27 Pulley 28 Pulley main body 29 Electromagnetic clutch 30 Compressor 31 Pulley 32 Movable scroll 33 Fixed scroll 34 Stator 35 Compressor rotating shaft 36 Clutch plate 37 Nose part

Claims (7)

A grease composition comprising a base oil and a thickener, wherein the thickener contains a urea compound represented by formula (1).

(R ₁ and R ₃ represent a monovalent aliphatic hydrocarbon group having 1 to 7 carbon atoms, and R ₁ and R ₃ may be the same or different. R ₂ represents carbon. It represents a divalent aromatic hydrocarbon group having 6 to 12 carbon atoms.)   The grease composition according to claim 1, wherein the base oil contains an aliphatic hydrocarbon oil.   The grease composition according to claim 1 or 2, wherein the grease composition contains at least one compound selected from polymethacrylate and polyacrylate as an additive.   The grease composition according to claim 1, wherein the grease composition contains a dithiophosphate as an additive.   A rolling bearing comprising an inner ring and an outer ring, and a rolling element interposed between the inner ring and the outer ring, wherein a grease composition is enclosed around the rolling element, wherein the grease composition is claimed in claims 1 to 5. 5. A grease-filled rolling bearing comprising the grease composition according to claim 4.   The grease-filled rolling bearing is used in an automotive electrical accessory that rotatably supports a rotating shaft that is driven to rotate by engine output on a stationary member, and is a heat-resistant and cold-resistant abnormal noise bearing. The grease-filled rolling bearing according to claim 5.   The grease-filled rolling bearing according to claim 6, wherein the automobile electrical accessory is a fan coupling device, an alternator, an idler pulley, a tension pulley, an electromagnetic clutch, or a compressor.

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