Grease composition for constant velocity joint

Abstract

To provide a grease composition for a constant velocity joint excellent in abrasion resistance and low friction property.SOLUTION: R1NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR10 (1) wherein R1 and R10 are each independently octyls, decyls, dodecyls, tetradecyls, hexadecyls, octadecyls, oleyls or cyclohexyls; ) The grease composition for constant velocity joints comprises (c) a molybdenum dialkyldithiocarbamate, (d) a zinc dialkyldithiophosphate and (e) a zinc sulfonate.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In the automobile industry, front-wheel drive (FF) vehicles have become widespread due to their lightweight design and increased interior space, which are key environmental measures (CO2 reduction). Constant velocity joints (CVJs) are essential for power transmission in FF vehicles. A CVJ is a device that transmits rotation between two shafts that rotate at an angle. There are two types of CVJs: one is an outboard constant velocity joint (also called a fixed constant velocity joint) that is used on the wheel side and allows for a large steering angle, and the other is an inboard constant velocity joint (also called a sliding constant velocity joint) that can absorb axial movement caused by uneven road surfaces, etc. In either type, the parts inside the joint perform a complex rolling and sliding motion, so the performance of the CVJ is directly affected by the performance of the grease sealed in as a lubricant. In recent years, there has been an increased emphasis on preserving the global environment, such as going carbon neutral, and there is an even greater demand for more fuel-efficient automobiles. Therefore, improving transmission efficiency (reducing torque loss) in CVJs is an important issue. Improving transmission efficiency requires reducing the friction between the components inside the joint. For example, in a Birrfield ball joint, a type of fixed constant velocity joint, in addition to the friction between the ball and track, which has a high contact pressure, the friction between the cage and the outer and inner rings, which has a relatively low contact pressure, is also said to be large. Therefore, it is necessary to reduce friction under 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 high height of SUVs (Sport Utility Vehicles), which have become popular recently, means that CVJs are installed at a larger angle (common use angle) in the vertical plane. This increases the slippage of internal components and increases the maximum surface pressure, making lubrication conditions more severe in, for example, a Birrfield-type ball joint, a type of fixed constant velocity joint. This accelerates wear of the internal components, leading to flaking caused by indentations from the resulting wear debris. Therefore, measures to ensure 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 exhibits 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, proposed greases for ball-type constant velocity joints contain 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 surface pressure conditions (see Patent Document 2), and a grease with excellent wear resistance that is obtained by blending benzotriazole and / or a derivative thereof with urea grease, and phosphate esters and / or amine salts thereof (see Patent Document 3). Thus, previous CVJ grease compositions have been studied for their wear resistance and low friction under high contact pressure conditions, which simulate contact between the balls and tracks of a fixed constant velocity joint. However, it cannot be said that sufficient research has been conducted to consider low friction under relatively low contact pressure conditions, which simulate contact between the cage and the outer and inner rings, making it difficult to simultaneously achieve improved transmission efficiency and durability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5641487 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-236354 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-108067 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[0005] According to the present invention, there is provided the following grease composition. 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) (In the formula, R 1 and R 10 are independently octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, oleyl, or cyclohexyl. (c) molybdenum dialkyldithiocarbamates; (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% by mass, and (e) Zinc sulfonate: 0.3 to 2 mass %. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 shows a Birfield type constant velocity universal joint. [Figure 2] Fig. 2(A) shows a fixed type constant velocity universal joint having a different configuration from that shown in Fig. 1. Fig. 2(B) is a view taken along the line AA in Fig. 2(A). [Figure 3] FIG. 3 shows a double offset constant velocity universal joint. DETAILED DESCRIPTION OF THE INVENTION

[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. Paraffinic mineral oil is preferred from the viewpoint of excellent fluidity at low temperatures. 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. The synthetic oil may be so-called biomass oil, which is produced using biological resources derived from animals and plants as raw materials. For example, biomass ester oils synthesized from various fatty acids and alcohols using vegetable oils as raw materials, or biomass hydrocarbon oils using vegetable oils such as palm oil, corn oil, and soybean oil, can also be used. In the present invention, it is preferable to use mineral oil as the base oil from the viewpoint of cost reduction. The base oil preferably contains a large proportion of mineral oil, for example, preferably 50 mass% or more, more preferably 55 mass% or more, and even more preferably 60 mass% or more based on the total mass of the base oil. It is also preferable that the base oil contains 100 mass% of mineral oil based on the total mass of the base oil. The kinematic viscosity of the base oil of the present invention at 100°C is 6 to 25 mm from the viewpoint of oil film forming properties. 2 / s is preferable, and 8 to 20 mm 2 / s is more preferable, and 10 to 17 mm 2 This allows an oil film of appropriate thickness to be formed, resulting in a grease composition that has excellent durability (peeling resistance) required for 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 inflowability 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). R 1 NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR 10 (1) (In the formula, R 1 and 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) is R 1 and R 10 aliphatic diureas, where both R and R are octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, or oleyl groups; 1 and R 10Alicyclic 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) (In the formula, 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). 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) R10 NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR 10 (1-3) (In the formula, 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 within the CVJ, the grease can be easily supplied to the sliding parts, leading to improved durability and low friction. Therefore, the thickener of the present invention is preferably an aliphatic diurea thickener or an alicyclic aliphatic diurea thickener, which 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 represented by the formula (1-1), the formula (1-2), and the formula (1-3), in which 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), wherein R 1 is a cyclohexyl group, and R 10 In 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. The thickener of the present invention is represented by the formula (1-1), the formula (1-2), and the formula (1-3), in which R1 is an octyl group, and R 10 From the viewpoint of consistency yield, the most preferred aliphatic diurea thickener is one in which the molar ratio of octyl groups to octadecyl groups is 50:50.

[0014] The content of the thickener is preferably an amount capable of adjusting 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 preferred because it provides excellent fluidity and facilitates the supply of grease to the sliding parts in the 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 base is molybdenum, and is generally used as a friction modifier. (MoDTC is sometimes classified as an extreme pressure agent, but in recent years it is often 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. Either oil-insoluble or oil-soluble MoDTC may be used in the present invention, but 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 surface pressures, from low to high. 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 or a mixture of the two.

[0016] A preferred example of MoDTC is a compound represented by formula (2). [R 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 represents 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) (In the formula, R 4 is 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 mS n (4) (In the formula, 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 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 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) (In the formula, 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. Particularly preferred is a primary or secondary alkyl group having 3 to 8 carbon atoms. 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. By including component (d) in such a range, sufficient initial compatibility can be obtained, which is preferable.

[0020] (e) Zinc sulfonate can be a zinc salt of sulfonic acid having an organic group as a lipophilic group. 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 dinonylnaphthalene sulfonic acid and heavy alkylbenzene sulfonic acid. Among these, zinc dinonylnaphthalene sulfonate 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) in such a range, sufficient initial compatibility can be obtained, which is preferable.

[0021] In addition to the above components, the grease composition of the present invention may contain other additives that are commonly used in grease compositions, such as other extreme pressure additives, antioxidants, rust inhibitors, solid lubricants, oiliness agents, etc. 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 fats and oils obtained from animals and plants; dialkyldithiocarbamates; mono- and diglycerides; polyhydric alcohols such as glycerin; alkyd resins; hardened oils; chlorinated fats and oils; thiophosphoric acids; and phosphate esters. Examples of antioxidants include amine-based, phenol-based, quinoline-based, and sulfur-based antioxidants. Examples of the rust inhibitor include sulfonate-based, zinc-based, carboxylic acid-based, carboxylic acid salts (for example, dibasic acid salts such as sodium sebacate), and amine-based agents.

[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 ester, pentaerythritol stearate ester, 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, which are obtained by refining and oxidizing brown coal. The content of such optional additives is, for example, 0.1 to 2.0 mass %, preferably 0.3 to 1.0 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, the present invention can be applied to a Birfield constant velocity universal joint (BJ), which is a fixed type 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 a plurality of balls (rolling elements) (for example, six or eight) 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. Note that, in the present invention, the undercut-free type constant velocity universal joint is interpreted as being included in the same category as the Birfield type constant velocity universal joint. FIG. 1 shows a Birfield-type constant velocity universal joint (BJ), one type of fixed-type constant velocity universal joint to which the present invention is applicable. This constant velocity universal joint is primarily composed of an outer ring 1, which is the outer joint member, an inner ring 3, which is the inner joint member, balls 4, and a cage 5. 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 form pairs with the track grooves 1a of the outer ring 1, with the arc centers of the outer ring track grooves and the inner ring track grooves being offset by equal amounts on opposite sides of the joint center in the axial direction. 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 the cage 5, which is 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 is fastened and fixed with boot bands 8 and 9. The inside of the outer ring 1 is completely sealed by this boot 7. The grease of the present invention is sealed inside this boot 7. 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 position where the pair of track grooves abuts against the ball, and when the operating angle of the fixed type constant velocity universal joint is 0°, pairs of track grooves whose wedge angles open toward the opening side of the outer joint member and pairs of track grooves whose wedge angles open toward the back side are formed alternately 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 track grooves of the inner and outer rings intersect with each other, with balls positioned at the intersections. Figure 2(B) is a view seen from the 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 is fastened and fixed with boot bands 28 and 29. The inside of the outer ring 21 is completely sealed by this boot 27. The grease of the present invention is sealed inside this boot 27. The present invention is also applicable 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 balls (rolling elements) (e.g., six or eight) are interposed between the track grooves of the outer joint member and the track grooves of the inner joint member.

[0025] FIG. 3 shows a double offset constant velocity universal joint (DOJ), which is one of the sliding type constant velocity universal joints to which the grease composition of the present invention is applied. The main components of this constant velocity universal joint are an outer ring 41 which is an outer joint member, an inner ring 43 which is an inner joint member, balls 44, and a cage 45. A plurality of linear track grooves 41a extending in the axial direction are 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. Cage 45 has a spherical outer peripheral surface and a spherical inner peripheral surface which are guided in contact with the cylindrical inner peripheral surface of the outer ring 41 and the spherical outer peripheral surface of the inner ring 43, and is configured so that the centers of curvature of the spherical outer peripheral surface and the spherical inner peripheral surface are offset in the axially opposite direction from the joint center. In this constant velocity universal joint, when rotational torque is generated and outer shaft 41 rotates, shaft 46 rotates in response via balls 44. A bellows-shaped boot 47 is attached to the open end of outer ring 41 and shaft 46, and this attachment portion is fastened and fixed with boot bands 48 and 49. Boot 47 completely seals the inside of outer ring 41. The grease composition of the present invention is enclosed in this interior 50. [Example]

[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 in the proportions shown in the table below (the numbers in the table are mass % based on the total mass of the composition), and base oil was further added to obtain the thickener amount 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 according to 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 amines. 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 amines. Alicyclic aromatic diureas were obtained using cyclohexylamine and aniline (cyclohexylamine:aniline = 7:3, molar ratio) as amines. <Additives> Ingredient (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. Ingredient (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 dinonylnaphthalene sulfonate (NA-SUL ZS, manufactured by KING INDUSTRIES) · P-based antiwear agent: Phosphate ester (IRGALUBE TPPT, manufactured by BASF) · SP-based antiwear agent (LUBRIZOL 810, manufactured by Lubrizol) · Ca sulfonate: Calcium dinonylnaphthalene sulfonate salt (NA-SUL 729, manufactured by KING INDUSTRIES) ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ <SRV Test 2 - Evaluation of Low Friction under High Surface Pressure Conditions> The low friction property was evaluated by the arithmetic mean of the friction coefficient during the last 300 seconds of the test. · Test conditions: Surface pressure: 2.8 GPa Sliding speed: 40 mm / s (1.0 mm × 20 Hz) Plate temperature: 40 °C Test time: 3000 seconds Ball diameter: φ10 mm · Evaluation criteria Arithmetic mean of the friction coefficient during the last 300 seconds of the test 〇: Less than 0.065 ×: 0.065 or more

[0029] <High-Speed Four-Ball Wear Test - Evaluation of Wear Resistance> (ASTM D2266 Mod.) The 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 the balls 〇: Less than 0.8 mm ×: 0.8 mm or more[[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ [Explanation of symbols]

[0034] 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 balls 5 cages 5a cage pocket 6-axis 7. Boots 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 balls 25 cages 25a cage pocket 26 axes 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 balls 45 Cage 45a cage pocket 46 axes 47 Boots 48, 49 Boot Band 50 Joint internal space 51 outer ring shaft

Claims

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 1 NH-CO-NH-C 6 H 4 -p-CH 2 -C 6 H 4 -p-NH-CO-NHR 10 (1) (In the formula, R 1 and R 10 are independently octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, oleyl, or cyclohexyl. (c) molybdenum dialkyldithiocarbamates; (d) zinc dialkyldithiophosphate, and (e) Zinc sulfonate.

2. 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% by weight, and (e) Zinc sulfonate: 0.3 to 2% by mass.

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