Grease composition for constant-velocity joint

Abstract

The present invention provides a grease composition for a constant-velocity joint, the composition containing (a) a base oil, (b) a diurea thickener represented by formula (1), R1NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR10 (1) (in the formula, R1 and r10 independently are octyl, decyl dodecyl, tetradecyl, hexadecyl, octadecyl, oleyl, or cyclohexyl.), (c) a molybdenum dialkyldithiocarbamate, (d) a zinc dialkyldithiophosphate, and (e) a zinc sulfonate.

Description

Grease composition for constant velocity joints

[0001] The present invention relates to a grease composition for a constant velocity joint.

[0002] Front-wheel-drive (FF) vehicles have become widespread due to their environmentally friendly (CO2 reduction) objectives of reducing vehicle weight and ensuring interior space. Constant-velocity joints (CVJs), essential for FF vehicle power transmission, are used. CVJs transmit rotation between two shafts that rotate at an angle. There are two types of CVJs: outboard constant-velocity joints (also known as fixed constant-velocity joints) that are used on the wheel side and allow for large steering angles; and inboard constant-velocity joints (also known as sliding constant-velocity joints) that can absorb axial movement caused by road surface irregularities. In both types, the components inside the joint undergo complex rolling and sliding motion, and the performance of the grease used as a lubricant is directly related to the performance of the CVJ. In recent years, environmental conservation, such as carbon neutrality, has become increasingly important, leading to increased demand for improved fuel efficiency in automobiles. Therefore, improving the transmission efficiency of CVJs (reducing torque loss) is a key challenge. Improving transmission efficiency requires reducing friction between components within the joint. For example, in a Birrfield ball joint, a type of fixed constant velocity joint, not only is there high friction between the ball and track, but there is also a high friction between the cage and the outer and inner rings, which have relatively low contact pressures. This requires reducing friction across a wide range of contact pressure conditions. Ensuring the durability of CVJs to ensure long-term vehicle operation has long been a fundamental performance requirement. In particular, the height of SUVs (Sport Utility Vehicles), which have become popular recently, means that CVJs are mounted at a larger angle (common use angle) in the vertical plane. This increases slippage of internal components, increases maximum contact pressure, and severers lubrication conditions in a Birrfield ball joint, a type of fixed constant velocity joint. This accelerates wear on the internal components, leading to flaking caused by the indentations of wear debris. Therefore, measures to improve durability at large common use angles are essential.To date, a grease composition that has been proposed as a grease composition for constant velocity joints that has excellent low friction properties under high surface pressure conditions is, for example, a grease composition containing a base oil, a urea-based thickener, molybdenum dithiocarbamate, zinc sulfonate, and a sulfur-phosphorus-based extreme pressure agent that is a mixture of at least one selected from the group consisting of sulfurized fats and oils, sulfurized olefins, and polysulfides, and at least one selected from the group consisting of phosphate-based and phosphide-based compounds (see Patent Document 1). As grease compositions for constant velocity joints that address durability, for example, greases for ball-type constant velocity joints containing a diurea-based thickener, a base oil, zinc dialkyldithiophosphate, molybdenum dialkyldithiocarbamate, melamine cyanurate, calcium carbonate, zinc dialkyldithiocarbamate, and a sulfur-nitrogen-based extreme pressure additive for the purpose of improving wear resistance and flaking resistance under high contact pressure conditions (see Patent Document 2), and a grease with excellent wear resistance in which benzotriazole and / or a derivative thereof, and phosphate esters and / or amine salts thereof are blended with urea grease (see Patent Document 3) have been proposed. As such, while previous grease compositions for CVJs have been studied for wear resistance and low friction under high contact pressure conditions that simulate contact between the balls and tracks of fixed constant velocity joints, it cannot be said that sufficient studies have been conducted that take into account low friction under relatively low contact pressure conditions that simulate contact between the cage and the outer and inner rings, making it difficult to simultaneously achieve improved transmission efficiency and durability.

[0003] Japanese Patent No. 5641487 Japanese Patent Application Laid-Open No. 2011-236354 Japanese Patent Application Laid-Open No. 2015-108067

[0004] Therefore, an object of the present invention is to provide a grease composition that is excellent in wear resistance and low friction under a wide range of surface pressure conditions.

[0005] The present invention provides the following grease composition: 1. A grease composition for constant velocity joints, comprising the following components (a) to (e): (a) a base oil; (b) a diurea thickener represented by the following formula (1); R 1NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR 10 (1) (wherein, R 1 and R 10 are independently octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, oleyl, or cyclohexyl.) (c) molybdenum dialkyldithiocarbamate, (d) zinc dialkyldithiophosphate, and (e) zinc sulfonate. 2. The grease composition for constant velocity joints according to 1 above, containing components (c) to (e) in the following proportions relative to the total mass of the composition: (c) molybdenum dialkyldithiocarbamate: 0.3 to 2 mass%, (d) zinc dialkyldithiophosphate: 0.3 to 2 mass%, and (e) zinc sulfonate: 0.3 to 2 mass%.

[0006] According to the present invention, it is possible to provide a grease composition for constant velocity joints that can achieve wear resistance and low friction characteristics over a wide range of contact pressure conditions, and that has excellent durability and transmission efficiency.

[0007] Figure 1 shows a Birfield type constant velocity universal joint. Figure 2(A) shows a fixed type constant velocity universal joint which is different from that shown in Figure 1. Figure 2(B) is a view taken along the line AA in Figure 2(A). Figure 3 shows a double offset type constant velocity universal joint.

[0008] (a) Base Oil The type of base oil that can be used in the present invention is not particularly limited, and mineral oil, synthetic oil, or a mixture thereof can be used. Examples of mineral oils include paraffinic mineral oil and naphthenic mineral oil. From the viewpoint of excellent fluidity at low temperatures, paraffinic mineral oil is preferred. Examples of synthetic oils include hydrocarbon synthetic oils such as poly-α-olefins, ether synthetic oils typified by alkyl diphenyl ether, ester synthetic oils, silicone oil, and fluorinated oil. Synthetic oils may also be so-called biomass oils produced from biological resources derived from animals and plants. For example, biomass ester oils synthesized from various fatty acids and alcohols using vegetable oil as a raw material, or biomass hydrocarbon oils using vegetable oils such as palm oil, corn oil, and soybean oil, can also be used. From the viewpoint of cost reduction, mineral oil is preferably used as the base oil in the present invention. It is preferable that the base oil contains a large proportion of mineral oil, for example, preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more, based on the total mass of the base oil. It is also preferred that the base oil contains 100% by mass of mineral oil based on the total mass of the base oil. From the viewpoint of oil film forming properties, the kinematic viscosity at 100°C of the base oil of the present invention is 6 to 25 mm 2 / s, and 8 to 20 mm 2 / s is more preferable, and 10 to 17 mm 2 / s. This allows an oil film of appropriate thickness to be formed, resulting in a grease composition with excellent durability (peeling resistance) required of CVJ greases. The content of the base oil in the composition of the present invention is preferably 60 to 93 mass%, more preferably 70 to 90 mass%, and even more preferably 80 to 90 mass%, based on the total mass of the composition. By including the base oil in such a range, the flowability of the grease composition of the present invention is improved, and as a result, excellent low friction can be exhibited in the lubricated parts.

[0009] (b) Thickener The thickener of the present invention is a diurea thickener represented by the following formula (1): 1 NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR 10 (1) (wherein, R 1and R 10 are independently an octyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, an octadecyl group, an oleyl group, or a cyclohexyl group.) The diurea thickener of formula (1) includes a compound represented by the formula (1): 1 and R 10 aliphatic diureas in which both of R are octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, or oleyl groups; 1 and R 10 Alicyclic aliphatic diureas including diurea compounds in which one of R is an octyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, an octadecyl group, or an oleyl group, and the other is a cyclohexyl group, and 1 and R 10 and alicyclic diureas in which both are cyclohexyl groups.

[0010] The aliphatic diurea used in the present invention is a reaction product of an alkylamine and 4',4-diphenylmethane diisocyanate (MDI). When two or more alkylamines are reacted with MDI, the reaction product becomes a mixture of three compounds represented by the following formulas (1-1), (1-2), and (1-3). R 1 NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR 1 (1-1) R 1 NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR 10 (1-2) R 10 NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR 10 (1-3) (wherein, R 1 and R 10 are different and are an octyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, an octadecyl group, or an oleyl group.

[0011] The alicyclic aliphatic diurea used in the present invention is a reaction product of a mixture of alkylamine and cyclohexylamine with MDI, and therefore the reaction product is a mixture of three compounds represented by the following formulas (1-1), (1-2), and (1-3).1 NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR 1 (1-1) R 1 NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR 10 (1-2) R 10 NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR 10 (1-3) (wherein, R 1 and R 10 one of which is an octyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, an octadecyl group, or an oleyl group, and the other is a cyclohexyl group.

[0012] Since the grease easily flows in the CVJ, the grease can be easily supplied to the sliding parts, leading to improved durability and low friction, the thickener of the present invention is preferably an aliphatic diurea thickener or an alicyclic aliphatic diurea thickener that is easily softened by shear. From the viewpoint of flowability into the sliding parts, an aliphatic diurea thickener is preferred. From the viewpoint of adhesion to the sliding parts after flowing, an alicyclic aliphatic diurea thickener is preferred. The aliphatic diurea thickener used in the present invention is a thickener represented by the formula (1-1), formula (1-2), and formula (1-3), where R 1 is an octyl group, and R 10 From the viewpoint of consistency yield, the molar ratio of octyl groups to octadecyl groups in the aliphatic diurea thickener is preferably 80:20 to 20:80, more preferably 60:40 to 40:60.

[0013] The alicyclic aliphatic diurea thickener used in the present invention is a diurea thickener represented by the formula (1-1), the formula (1-2), and the formula (1-3), 1 is a cyclohexyl group, and R 10In order to ensure the fluidity of the grease, the molar ratio of cyclohexyl groups to octadecyl groups in the alicyclic aliphatic diurea thickener is preferably 90:10 to 70:30, more preferably 90:10 to 80:20, and more preferably 90:10 to 80:20. 1 is an octyl group, and R 10 From the viewpoint of consistency yield, an aliphatic diurea thickener having an octyl group to octadecyl group molar ratio of octyl group:octadecyl group=50:50 is most preferred.

[0014] The content of the thickener is preferably an amount that can adjust the consistency of the grease composition of the present invention to 280 to 370, more preferably 295 to 355, and even more preferably 310 to 340. Specifically, the content is preferably 4 to 13 mass%, more preferably 5 to 12 mass%, even more preferably 5 to 10 mass%, and even more preferably 5 to 7 mass%, based on the total mass of the composition. A consistency of 310 to 340 for the grease composition of the present invention is preferable because it provides excellent fluidity and facilitates the supply of grease to the sliding parts in a CVJ. In this specification, "consistency" refers to the 60-stroke worked consistency measured in accordance with JIS K 2220 7.

[0015] (c) Molybdenum dialkyldithiocarbamate (MoDTC) is a general term for organometallic load-bearing additives whose metal group is molybdenum, and is widely used as a friction modifier. (Note that MoDTC is sometimes classified as an extreme pressure additive, but in recent years it has often been classified as a friction modifier.) MoDTC exists in oil-insoluble (i.e., solid at 25°C) and oil-soluble (i.e., liquid at 25°C) forms. While either oil-insoluble or oil-soluble MoDTC may be used in the present invention, using both in combination is preferred because a stable low-friction coating is formed and excellent low-friction properties are obtained over a wide range of contact pressures, from low to high. Note that, in this specification, when simply referring to "molybdenum dialkyldithiocarbamate" or "MoDTC," no distinction is made between oil-soluble and oil-insoluble. That is, it may refer to either one alone or a mixture of the two.

[0016] A preferred example of MoDTC is a compound represented by formula (2): 2 R 3 N-CS-S]2-Mo2O m S n (2) In formula (2), R 2 and R 3 may be the same or different and each independently represent a linear or branched alkyl group having 1 to 24 carbon atoms, preferably 3 to 18 carbon atoms, m is 0 to 3, n is 1 to 4, and m + n = 4. From the viewpoint of low friction, the content of MoDTC is preferably 0.1 to 3.0 mass%, more preferably 0.4 to 2.0 mass%, even more preferably 0.5 to 1.5 mass%, and still more preferably 0.5 to 1.0 mass%, based on the total mass of the composition. By including component (e) in such a range, sufficient low friction can be obtained, which is preferable.

[0017] The oil-insoluble molybdenum dialkyldithiocarbamate (oil-insoluble MoDTC) is preferably one represented by the following formula (3): [R 4 2N-CS-S]2-Mo2O m S n (3) (wherein, R 4is a primary or secondary alkyl group having 1 to 4 carbon atoms, preferably a primary or secondary alkyl group having 2 to 4 carbon atoms, m is 0 to 3, n is 1 to 4, and m+n=4.) From the viewpoint of low friction, the content of the oil-insoluble MoDTC is preferably 0.1 to 3.0 mass%, more preferably 0.1 to 1.5 mass%, and even more preferably 0.1 to 1.0 mass%, based on the total mass of the composition. By including the oil-insoluble MoDTC in such a range, sufficient low friction can be obtained, which is preferable.

[0018] The oil-soluble molybdenum dialkyldithiocarbamate (oil-soluble MoDTC) is preferably one represented by the following formula (4): [R 5 2N-CS-S]2-Mo2O m S n (4) (wherein, R 5 is a primary or secondary alkyl group having 5 to 24 carbon atoms, preferably a primary or secondary alkyl group having 5 to 18 carbon atoms, m is 0 to 3, n is 1 to 4, and m+n=4.) From the viewpoint of low friction, the content of the oil-soluble MoDTC is preferably 0.05 to 1.5 mass%, more preferably 0.1 to 0.5 mass%, and even more preferably 0.1 to 0.3 mass%, based on the total mass of the composition. By including the oil-soluble MoDTC in such a range, sufficient low friction can be obtained, which is preferable.

[0019] (d) Zinc dialkyldithiophosphate (ZnDTP) is preferably one represented by the following formula (5): [(R 6 O)2SP-S]2-Zn (5) (wherein, R 6 is a primary or secondary alkyl group having 1 to 24 carbon atoms or an aryl group having 6 to 30 carbon atoms. A primary or secondary alkyl group having 3 to 8 carbon atoms is particularly preferred.) The content of component (d) is preferably 0.1 to 3.0 mass%, more preferably 0.2 to 2.0 mass%, and even more preferably 0.5 to 1.0 mass%, based on the total mass of the composition. Inclusion of component (d) in such a range is preferred because sufficient initial compatibility can be obtained.

[0020] As the (e) zinc sulfonate, a zinc salt of a sulfonic acid having an organic group as a lipophilic group can be used. Examples of such organic sulfonic acids include petroleum sulfonic acids obtained by sulfonating aromatic hydrocarbon components in lubricating oil fractions, and synthetic sulfonic acids such as dinonylnaphthalenesulfonic acid and heavy alkylbenzenesulfonic acid. Among these, zinc dinonylnaphthalenesulfonate is preferred. The base number of component (e) is preferably 10 mgKOH / g or less. The content of component (e) is preferably 0.1 to 3.0 mass%, more preferably 0.2 to 2.0 mass%, and even more preferably 0.5 to 1.0 mass%, based on the total mass of the composition. By including component (d) within this range, sufficient initial compatibility can be obtained, which is preferred.

[0021] In addition to the above components, the grease composition of the present invention may contain other additives commonly used in grease compositions, such as other extreme-pressure additives, antioxidants, rust inhibitors, solid lubricants, and oiliness agents. Examples of other extreme-pressure additives include phosphate esters such as triphenyl phosphate, triaryl phosphate, and tricresyl phosphate; azole compounds such as benzotriazole and dialkylmercaptothiadiazole; fatty acids obtained by decomposing and modifying oils and fats derived from animals and plants; dialkyldithiocarbamates; mono- and diglycerides; polyhydric alcohols such as glycerin; alkyd resins; hardened oils; chlorinated oils and fats; thiophosphoric acids; and phosphate esters. Examples of antioxidants include amine-based, phenol-based, quinoline-based, and sulfur-based. Examples of rust inhibitors include sulfonate-based, zinc-based, carboxylic acid-based, carboxylic acid salts (e.g., dibasic acid salts such as sodium sebacate), and amine-based.

[0022] Examples of solid lubricants include inorganic substances such as molybdenum disulfide, soil graphite, flaky graphite, carbon black, boron nitride, potassium borate, and calcium carbonate, and organic substances such as melamine cyanurate, polytetrafluoroethylene, copper salts and iron salts of dithiocarbamic acid, and calcium, aluminum, sodium, or lithium salts of stearic acid or sebacic acid. Examples of oily agents include fats and oils obtained from animals and plants, such as beef tallow, lard, fish oil, castor oil, palm oil, soybean oil, and rapeseed oil; esters such as trimethylolpropane oleate, pentaerythritol stearate, dioctyl sebacate, dioctyl adipate, dioctyl phthalate, and dibutyl phthalate; higher alcohols such as cetyl alcohol, stearyl alcohol, and oleyl alcohol; and ester waxes based on montanic acid obtained by purifying and oxidizing brown coal. The content of such optional additives is, for example, 0.1 to 2.0% by mass, preferably 0.3 to 1.0% by mass, based on the total mass of the composition.

[0023] The grease composition for constant velocity joints of the present invention can be applied to various constant velocity universal joints. For example, it can be applied to a Birrfield constant velocity universal joint (BJ), a type of fixed constant velocity universal joint in which the inner peripheral surface of the outer joint member and the outer peripheral surface of the inner joint member are spherical, and multiple (e.g., six or eight) balls (rolling elements) are interposed between track grooves formed on the inner peripheral surface of the outer joint member and the outer peripheral surface of the inner joint member. In this invention, undercut-free constant velocity universal joints are considered to be in the same category as Birrfield constant velocity universal joints. A Birrfield constant velocity universal joint (BJ), one of the fixed constant velocity universal joints to which the present invention can be applied, is shown in Figure 1. This constant velocity universal joint is primarily composed of an outer ring 1, which is the outer joint member, an inner ring 3, balls 4, and a cage 5, which are the inner joint member. The outer ring 1 has a plurality of arc-shaped track grooves 1a formed on its spherical inner peripheral surface, and the inner ring 3 has a plurality of track grooves 3a formed on its spherical outer peripheral surface that pair with the track grooves 1a of the outer ring 1. The arc centers of the outer ring track grooves and the inner ring track grooves are offset by equal amounts on opposite axial sides of the joint center. A plurality of balls 4 are interposed between the track grooves 1a of the outer ring 1 and the track grooves 3a of the inner ring 3, and these balls 4 are held in pockets 5a of a cage 5 disposed between the outer ring 1 and the inner ring 3. A bellows-shaped boot 7 made of a heat-, oil-, and abrasion-resistant elastomer such as rubber or resin is attached from the open end of the outer ring 1 to the shaft 6, and this attachment portion is fastened and fixed with boot bands 8 and 9. The boot 7 completely seals the interior of the outer ring 1. The grease of the present invention is sealed within the interior 10. The present invention can also be applied to a constant velocity universal joint of the cross track groove type, which is another form of fixed type constant velocity universal joint.

[0024] 2(A) is mainly composed of an outer ring 21, which is an outer joint member having an open side and a rear side separated in the axial direction, an inner ring 23, which is an inner joint member having a plurality of track grooves extending in the axial direction formed on its spherical outer peripheral surface, balls 24, and a cage 25. The outer ring 21 has a plurality of track grooves 21a formed on its spherical inner peripheral surface. The inner ring 23 has a plurality of track grooves 23a formed on its spherical outer peripheral surface, which pair with the track grooves 21a of the outer ring 21, and a plurality of balls 24 are interposed between the track grooves 21a of the outer ring 21 and the track grooves 23a of the inner ring 23, and the balls 24 are held in pockets 25a of the cage 25, which are arranged between the outer ring 21 and the inner ring 23. A wedge angle is formed between the track grooves at the contact position between the pair of track grooves and the ball. When the operating angle of the fixed constant velocity universal joint is 0°, pairs of track grooves with the wedge angle opening toward the opening side of the outer joint member and pairs of track grooves opening toward the rear side are alternately formed in the circumferential direction. The track grooves of the inner and outer rings are inclined in the axial direction, adjacent track grooves are arranged in mirror symmetry, and the inclinations of the inner and outer ring track grooves intersect with each other, with balls positioned at their intersections. Figure 2(B) is a view taken along arrow AA in Figure 2(A). A bellows-shaped boot 27 made of a heat-, oil-, and abrasion-resistant elastomer such as rubber or resin is attached from the open end of the outer ring 21 to the shaft 26, and this attachment portion is tightened and fixed with boot bands 28 and 29. The boot 27 completely seals the interior of the outer ring 21. The grease of the present invention is sealed within the interior 30. The present invention can also be applied to a double offset constant velocity universal joint (DOJ), which is a type of sliding type constant velocity universal joint in which a plurality of linear track grooves extending in the axial direction are formed on the cylindrical inner peripheral surface of the outer joint member, a plurality of linear track grooves pairing with the track grooves of the outer joint member are formed on the spherical outer peripheral surface of the inner joint member, and a plurality of (e.g., six or eight) balls (rolling elements) are interposed between the track grooves of the outer joint member and the track grooves of the inner joint member.

[0025] A double offset constant velocity universal joint (DOJ), one of the sliding type constant velocity universal joints to which the grease composition of the present invention can be applied, is shown in Figure 3. This constant velocity universal joint is mainly composed of an outer ring 41, which is the outer joint member, an inner ring 43, which is the inner joint member, balls 44, and a cage 45. A plurality of linear track grooves 41a extending in the axial direction is formed on the cylindrical inner peripheral surface of the outer ring 41, and a plurality of linear track grooves 43a, which form pairs with the track grooves 41a of the outer ring 41, are formed on the spherical outer peripheral surface of the inner ring 43. A plurality of balls 44 are interposed between the track grooves 41a of the outer ring 41 and the track grooves 43a of the inner ring 43, and these balls 44 are held in pockets 45a of the cage 45. The cage 45 has a spherical outer peripheral surface and a spherical inner peripheral surface that contact and guide the cylindrical inner peripheral surface of the outer ring 41 and the spherical outer peripheral surface of the inner ring 43, and the center of curvature of the spherical outer peripheral surface and the center of curvature of the spherical inner peripheral surface are offset axially opposite the joint center. In this constant velocity joint, when rotational torque is generated and the outer shaft 41 rotates, the shaft 46 rotates in response via the balls 44. A bellows-shaped boot 47 is attached to the open end of the outer ring 41 and the shaft 46, and this attachment portion is tightened and fixed with boot bands 48, 49. The inside of the outer ring 41 is completely sealed by the boot 47. The grease composition of the present invention is enclosed within the interior 50.

[0026] The grease compositions of the Examples and Comparative Examples were prepared using the following components. Specifically, 1 mole of 4',4-diphenylmethane diisocyanate and 2 moles of a specific amine were reacted in a base oil, heated, cooled, and then kneaded on a three-roll mill to obtain a base grease. The additives were blended thereto in the proportions shown in the table below (the numbers in the table are mass % based on the total mass of the composition), and further base oil was added so that the amount of thickener was the proportion shown in the table below. The mixture was then dispersed on a three-roll mill to obtain the grease compositions of the Examples and Comparative Examples. The consistency was measured in accordance with JIS K2220 7. and standardized to 325. <(a) Base Oil> Mineral oil (kinematic viscosity at 100°C = 13.5 mm 2 / s) <(b) Thickener> Aliphatic diurea A was obtained using octylamine and octadecylamine (octylamine:octadecylamine=5:5, molar ratio) as the amine. Aliphatic diurea B was obtained using octylamine as the amine. Aliphatic diurea C was obtained using octadecylamine as the amine. Alicyclic aliphatic diurea was obtained using cyclohexylamine and octadecylamine (cyclohexylamine:octadecylamine=9:1, molar ratio) as the amine. Alicyclic aromatic diurea was obtained using cyclohexylamine and aniline (cyclohexylamine:aniline=7:3, molar ratio) as the amine. <Additives> Component (c): MoDTC (oil-insoluble): molybdenum dialkyldithiocarbamate (ADEKA Sakuralube 600, manufactured by ADEKA) In formula (2), R 3 and R 4 is a linear alkyl group having 4 carbon atoms, m is 2, and n is 2. Component (c): MoDTC (oil-soluble): molybdenum dialkyldithiocarbamate (ADEKA Sakuralube 525, manufactured by ADEKA) A mixture of a compound in which R3 and R4 in formula (2) are 2-ethylhexyl, m is 2, and n is 2, and a compound in which R3 and R4 in formula (2) are isotridecane, m is 2, and n is 2. Component (d): ZnDTP: zinc dialkyldithiophosphate (LUBRIZOL 1395, manufactured by Lubrizol) Component (e): zinc sulfonate: zinc dinonylnaphthalenesulfonate (NA-SUL ZS, manufactured by KING INDUSTRIES) P-based anti-wear agent: phosphate ester (IRGALUBE TPPT, manufactured by BASF) SP-based anti-wear agent (LUBRIZOL 810, manufactured by Lubrizol) Ca sulfonate: calcium dinonylnaphthalenesulfonate (NA-SUL 729, manufactured by KING INDUSTRIES)

[0027] Test method Each grease composition of the examples and comparative examples was tested by the following method. The results are shown in the table below. <SRV test 1 - Evaluation of low friction under low surface pressure conditions> Low friction was evaluated by the arithmetic mean of the friction coefficient for the last 300 seconds of the test. Test conditions: Surface pressure: 89 MPa Sliding speed: 108 mm / s (4.5 mm x 12 Hz) Plate temperature: 80°C Test time: 3000 seconds Roller diameter and length: φ17.5 mm x 22 mm Evaluation criteria Arithmetic mean of friction coefficient for the last 300 seconds of the test ◯: Less than 0.135 ×: 0.135 or more

[0028] Test method Each grease composition of the examples and comparative examples was tested by the following method. The results are shown in the table below. <SRV test 2 - evaluation of low friction under high surface pressure conditions> Low friction was evaluated by the arithmetic mean of the friction coefficient for the last 300 seconds of the test. Test conditions: Surface pressure: 2.8 GPa Sliding speed: 40 mm / s (1.0 mm x 20 Hz) Plate temperature: 40°C Test time: 3000 seconds Ball diameter: φ10 mm Evaluation criteria Arithmetic mean of the friction coefficient for the last 300 seconds of the test ◯: Less than 0.065 ×: 0.065 or more

[0029] <High-Speed ​​Four-Ball Wear Resistance Test - Evaluation of Wear Resistance> (ASTM D2266 Mod.) Wear resistance was evaluated by measuring the average wear scar diameter of the balls after the test. Test conditions: Load: 862 N Rotation speed: 1200 rpm Temperature: 25°C Test time: 300 seconds Evaluation criteria Average wear scar diameter of balls ◯: Less than 0.8 mm ×: 0.8 mm or more

[0030]

[0031]

[0032]

[0033]

[0034] REFERENCE SIGNS LIST 1 Outer ring (outer joint member) 1a Outer ring (outer joint member) track groove 3 Inner ring (inner joint member) 3a Inner ring (inner joint member) track groove 4 Ball 5 Cage 5a Cage pocket 6 Shaft 7 Boot 8, 9 Boot band 10 Joint internal space 21 Outer ring (outer joint member) 21a Outer ring (outer joint member) track groove 23 Inner ring (inner joint member) 23a Inner ring (inner joint member) track groove 24 Ball 25 Cage 25a Cage pocket 26 Shaft 27 Boots 28, 29 Boot band 30 Joint internal space 41 Outer ring (outer joint member) 41a Outer ring (outer joint member) track groove 43 Inner ring (inner joint member) 43a Inner ring (inner joint member) track groove 44 Ball 45 Cage 45a Cage pocket 46 Shaft 47 Boot 48, 49 Boot band 50 Joint internal space 51 Outer ring shaft

Claims

1. A grease composition for constant velocity joints containing the following components (a) to (e): (a) a base oil; (b) a diurea thickener represented by the following formula (1); R 1 NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR 10 (1) (wherein, R 1 and R 10 are independently octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, oleyl, or cyclohexyl. (c) molybdenum dialkyldithiocarbamates; (d) zinc dialkyldithiophosphates; and (e) zinc sulfonates.

2. The grease composition for constant velocity joints according to claim 1, comprising components (c) to (e) in the following proportions relative to the total mass of the composition: (c) molybdenum dialkyldithiocarbamate: 0.3 to 2 mass%, (d) zinc dialkyldithiophosphate: 0.3 to 2 mass%, and (e) zinc sulfonate: 0.3 to 2 mass%.

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