JP2024062019A - Grease composition for constant velocity joints - Google Patents

Abstract

To provide a grease composition for constant velocity joints having initial conformability and low friction characteristics that can be used for outboard side constant velocity joints and inboard side constant velocity joints.SOLUTION: A grease composition for constant velocity joints contains the following components: (a) a diurea-based thickener, (b) a base oil, (c) molybdenum disulfide, (d-1) an oil-insoluble molybdenum dialkyldithiocarbamate (MoDTC), (d-2) an oil-soluble molybdenum dialkyldithiocarbamate (MoDTC), (e) an over-based Ca sulfonate, (f) a neutral Zn sulfonate, (g) a metal-free sulfur-phosphorus-based extreme pressure agent, and (h) a sulfurized olefin, wherein the ratio of (d-1):(d-2) is 25:75 to 75:25 (mass ratio), and the ratio of (e):(f) is 20:80 to 40:60 (mass ratio).SELECTED DRAWING: None

Description

The present invention relates to a grease composition for constant velocity joints that can be used for both outboard side common constant velocity joints and inboard side constant velocity joints.

In recent years, with the increasing demand for higher performance in automobiles, there has been an increasing demand for lower vibration and longer life in constant velocity joints.
In the automobile industry, the number of front-wheel drive (FF) vehicles has increased dramatically due to the need to reduce vehicle weight and ensure space for passengers in order to protect the environment ( _CO2 emissions). Constant velocity joints (CVJs), which are essential for these vehicles, are now widely used.
There are two types of CVJs: one is an outboard constant velocity joint (also called a fixed type 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 type constant velocity joint) that can absorb axial movement caused by unevenness in the road surface, etc.
For the outboard constant velocity joint, a Birrfield type ball joint or the like is used. When the steering angle is large, the sliding and rolling distance inside the outboard constant velocity joint increases, and in recent years, the outboard constant velocity joint has become smaller and has a higher capacity, increasing the surface pressure per ball. Under such lubrication conditions, it becomes difficult to balance the initial running-in and wear resistance.
The ball grooves of commercially available outboard constant velocity joints are made of metal, and their surfaces are processed by grinding, polishing, etc. Although the processing creates minute protrusions such as surface roughness and waviness, they are larger than the oil film thickness, and the metal contact between the protrusions and the metal balls leads to stress concentration. As a result, cracks are generated, and as the cracks propagate, flaking (surface peeling) occurs on the surface, shortening the life of the constant velocity joint. The countermeasures that have been taken with grease to avoid metal contact between the protrusions generated by processing and the balls have been to increase the oil film strength by increasing the viscosity of the base oil or using a large amount of solid lubricants and extreme pressure additives. However, this leads to an increase in costs and makes it difficult to form a reactive film by additives that reduces the friction coefficient, making it impossible to share the grease with the inboard constant velocity joint. On the other hand, if the wear resistance is poor and wear increases, it can cause problems such as abnormal noise and vibration due to abnormal wear, and even seizure and welding.
For inboard constant velocity joints, tripod constant velocity joints, double offset constant velocity joints, etc. Inboard constant velocity joints perform complex rolling and sliding motions when rotating at a certain angle, which generates sliding resistance in the axial direction, and this becomes the source of vibration during idling, lateral sway of the vehicle body when starting and accelerating, abnormal vibration, and beat noises or muffled noises inside the vehicle at certain speeds.
In order to reduce the axial sliding resistance, it is necessary to form a low-friction coating using additives that can reduce the frictional force of the sliding motion. The solution for grease is to form a low-friction coating by combining friction modifiers, but if the oil film strength increases, the tribological reaction due to metal contact does not occur sufficiently, making it difficult to form a low-friction coefficient coating, and it is not possible to use it with the outboard constant velocity joint.
In order to solve the different problems of the two constant velocity joints mentioned above, up until now, the outboard constant velocity joint and the inboard constant velocity joint have been filled with different types of grease.
An example of a CVJ grease intended for use in an outboard constant velocity joint and an inboard constant velocity joint is a grease composition for constant velocity joints (Patent Document 1), which contains a lubricating oil base oil, at least one thickener selected from a urea-based thickener, a urethane-based thickener, and a urea-urethane-based thickener, organic molybdenum, zinc dithiophosphate, polysulfide, and triglyceride, and has an organic molybdenum content of 1,000 to 5,000 ppm by mass, calculated as elemental molybdenum, based on the total amount of the grease composition.

JP 2014-43526 A

However, as the number of types of grease used increases, the cost of managing inventory also increases, which is a problem.
Therefore, an object of the present invention is to provide a grease composition for constant velocity joints that has good initial running-in properties and low friction characteristics and can be used in outboard constant velocity joints and inboard constant velocity joints.

The present inventors have found that by selecting additives and specifying the ratio of specific additives among them, a chemical reaction film excellent in both conformability and low friction characteristics can be formed. The present invention has been made based on this finding. That is, the present invention provides the following grease composition.
1. The following ingredients:
(a) a diurea-based thickener,
(b) a base oil;
(c) molybdenum disulfide;
(d-1) oil-insoluble molybdenum dialkyldithiocarbamate (MoDTC);
(d-2) oil-soluble molybdenum dialkyldithiocarbamate (MoDTC);
(e) overbased Ca sulfonates;
(f) neutral Zn sulfonate;
(g) metal-free sulfur-phosphorus based extreme pressure agents; and (h) sulfurized olefins.
Contains
a mass ratio of the (d-1) oil-insoluble MoDTC to the (d-2) oil-soluble MoDTC is (d-1):(d-2)=25:75 to 75:25;
The mass ratio of the (e) overbased Ca sulfonate to the (f) neutral Zn sulfonate is (e):(f)=20:80 to 40:60;
A grease composition for constant velocity joints.
2. The grease composition according to 1 above, wherein the base number of component (e) is 200 to 500 mgKOH/g. 3. The grease composition according to 1 above, wherein the base number of component (f) is 100 mgKOH/g or less.
4. The grease composition according to 1 above, wherein component (a) is a mixture of a urea compound represented by the following formula (1-1), a urea compound represented by the following formula (1-2), and a urea compound represented by the following formula (1-3).
R1 ^- NHCONH- ^R2 -NHCONH- ^R1 (1-1)
R ¹ -NHCONH-R ² -NHCONH-R ³ (1-2)
R3 ^- NHCONH- ^R2 -NHCONH- ^R3 (1-3)
(In the formula, R ¹ represents a cyclohexyl group, R ² represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and R ³ represents an alkyl group having 8 to 22 carbon atoms.
5. The grease composition according to 1 above, wherein the component (b) has a kinematic viscosity at 100° C. of 8 to 16 mm ² /s.
6. A constant velocity joint filled with the grease composition according to any one of 1 to 5 above.

According to the present invention, it is possible to provide a grease composition that has good initial break-in properties and low friction characteristics and can be used in outboard constant velocity joints and inboard constant velocity joints. The grease composition of the present invention shows a worn state in which the initial break-in stage has progressed and the roughness on the surface protrusions has been worn away.

The appearance of Rate 1 is shown below. This shows the appearance of Rate 2. The appearance of Rate 3 is shown below.

(a) Diurea-based thickener The thickener of the present invention is a diurea-based thickener. As the diurea-based thickener, a diurea compound selected from the group consisting of an aliphatic diurea compound, an aromatic diurea compound, an alicyclic diurea compound, and an alicyclic aliphatic diurea compound is used. The diurea compound is obtained by reacting a diisocyanate component with a monoamine component. Examples of the diisocyanate include diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, and hexane diisocyanate, and examples of the monoamine include octylamine, dodecylamine, hexadecylamine, stearylamine, oleylamine, aniline, p-toluidine, cyclohexylamine, and mixtures thereof.
The thickener of the present invention is preferably a urea compound represented by the following formula (1-1), a urea compound represented by the following formula (1-2), or a urea compound represented by the following formula (1-3).
R1 ^- NHCONH- ^R2 -NHCONH- ^R1 (1-1)
R ¹ -NHCONH-R ² -NHCONH-R ³ (1-2)
R ³ -NHCONH-R ² -NHCONH-R ³ (1-3)
(In the formula, R ¹ represents a cyclohexyl group, R ² represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and R ³ represents an alkyl group having 8 to 22 carbon atoms. R ³ is preferably an octyl group, a dodecyl group, a hexadecyl group, or an octadecyl group.
As the thickener of the present invention, an alicyclic aliphatic diurea compound which is a mixture of a compound of formula ( ^1-1 ), a compound of formula (1-2), and a compound of formula (1-3) is particularly preferred. In particular, from the viewpoint of ensuring the film thickness of the grease, an alicyclic aliphatic diurea compound in which (molar number of R1)×100/(molar number of ^R1 +molar number of ^R3 ) is 70 to 90% is preferred, and an alicyclic aliphatic diurea compound in which it is 80% is more preferred.
From the viewpoint of ease of filling the grease into joints, the content of the thickener is preferably 4 to 14 mass %, more preferably 6 to 12 mass %, and even more preferably 7 to 10 mass %, based on the total mass of the composition. By including the thickener in such a range, the consistency becomes 300 to 360, which is a hardness that allows easy filling of the grease into joints.

(b) Base oil The type of base oil used in the present invention is not particularly limited. For example, various synthetic oils such as naphthenic and paraffinic mineral oils, polyalphaolefins and synthetic hydrocarbon oils such as polybutene, ether-based synthetic oils such as alkyl diphenyl ether, silicone oils, and fluorinated oils can be mentioned. The base oil may be used alone or in a mixture of two or more kinds. Among them, mineral oil is preferred, and paraffinic mineral oil and naphthenic mineral oil may be used alone or in a mixture.
The kinetic viscosity of the base oil of the present invention at 100°C is preferably ^{8 mm2} /s or more, and more preferably ¹⁰ mm2/s or more, from the viewpoint of ensuring the oil film thickness of the base oil in the lubricated parts and improving durability by preventing metal contact. Since the oil film thickness of the base oil can be ensured in the lubricated parts of the CVJ and durability can be improved by preventing metal contact, the higher the kinetic viscosity at 100°C, the better, but since the viscosity at low temperatures increases, the kinetic viscosity at 100°C is preferably ²⁰ mm2/s or less, and more preferably ¹⁶ mm2/s or less.
From the viewpoint of ease of filling the grease into joints, the content of the base oil is preferably 70 to 95 mass%, more preferably 75 to 92 mass%, and even more preferably 80 to 88 mass%, based on the total mass of the composition. By including the base oil in such a range and including the thickener in such a range, the consistency becomes 300 to 360, which is a hardness that allows easy filling of the grease into joints.

(c) Molybdenum disulfide Molybdenum disulfide is widely used as a solid lubricant. This compound has a layered lattice structure and is easily sheared into thin layers by sliding motion, preventing metal contact and preventing seizure. However, if added in large amounts, it can increase the friction coefficient and increase wear.
From the viewpoint of seizure resistance, the content of molybdenum disulfide is preferably 0.05 to 2.5 mass%, more preferably 0.1 to 2.0 mass%, and even more preferably 0.3 to 1.5 mass%, based on the total mass of the composition. By including molybdenum disulfide in such a range, sufficient seizure resistance can be obtained.

(d-1) Oil-insoluble molybdenum dialkyldithiocarbamate (MoDTC) and (d-2) Oil-soluble molybdenum dialkyldithiocarbamate (MoDTC)
The oil-insoluble MoDTC is preferably one represented by the following formula (2).
[ ^R132N - _CS -S] _{2 - Mo2Om1Sn1} ( ₂ )
(In the formula, R ¹³ 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, m1 is 0 to 3, n1 is 1 to 4, and m1+n1=4.)
The oil-soluble MoDTC is preferably one represented by the following formula (3).
[ ^R142N - _CS -S] _{2 - Mo2Om2Sn2} ( ₃ )
(In the formula, R ¹⁴ is a primary or secondary alkyl group having 5 to 24 carbon atoms, m2 is 0 to 3, n2 is 1 to 4, and m2+n2=4.)
From the viewpoint of low friction, the content of the oil-insoluble MoDTC is preferably 0.01 to 10 mass %, more preferably 0.1 to 5 mass %, and even more preferably 0.3 to 3 mass %, based on the total mass of the composition.
From the viewpoint of low friction, the content of the oil-soluble MoDTC is preferably 0.01 to 10 mass %, more preferably 0.1 to 5 mass %, and even more preferably 0.5 to 3 mass %, based on the total mass of the composition.
The content of oil-insoluble MoDTC and oil-soluble MoDTC is, in mass ratio, oil-insoluble MoDTC:oil-soluble MoDTC=25:75 to 75:25. By including oil-insoluble MoDTC and oil-soluble MoDTC in such a range, sufficiently low friction can be obtained. The ratio is preferably 25:75 to 70:30, more preferably 25:75 to 65:35, and even more preferably 25:75 to 55:45.

(e) Overbased Ca Sulfonate Examples of the overbased Ca sulfonate used in the present invention include overbased calcium salts of alkyl aromatic sulfonic acids, overbased calcium salts of petroleum sulfonic acids, overbased calcium salts of oxidized waxes, and combinations thereof. Among these, overbased calcium salts of alkyl aromatic sulfonic acids are preferred.
The overbased Ca sulfonate is not particularly limited in terms of base number so long as it is overbased, and the base number measured in accordance with JIS K 2501 is, for example, 200 to 500 mgKOH/g, preferably 230 to 470 mgKOH/g, and more preferably 250 to 450 mgKOH/g. As long as the base number is within the above range, the overbased Ca sulfonate may be used in combination with a Ca sulfonate other than the overbased Ca sulfonate (for example, a neutral Ca sulfonate).
The content of the overbased Ca sulfonate is preferably 0.05 to 10 mass %, more preferably 0.1 to 5 mass %, and even more preferably 0.5 to 2 mass %, based on the total mass of the composition. By including the overbased Ca sulfonate in such a range, sufficiently low friction can be obtained.

(f) Neutral Zn Sulfonate Examples of the neutral Zn sulfonate used in the present invention include neutral Zn salts of alkyl aromatic sulfonic acids, neutral Zn salts of petroleum sulfonic acids, neutral Zn salts of oxidized waxes, and combinations thereof. Among these, neutral Zn salts of alkyl aromatic sulfonic acids are preferred.
The neutral Zn sulfonate is not particularly limited in terms of base number so long as it is neutral. The base number measured in accordance with JIS K 2501 is, for example, 100 mgKOH/g or less, preferably 70 mgKOH/g, and more preferably 50 mgKOH/g.
The content of the neutral Zn sulfonate is preferably 0.1 to 10 mass %, more preferably 0.5 to 5 mass %, and even more preferably 1 to 3 mass %, based on the total mass of the composition.
The blending ratio of the overbased Ca sulfonate to the neutral Zn sulfonate is preferably 20:80 to 40:60 by mass ratio. By including the overbased Ca sulfonate and the neutral Zn sulfonate in such a range, sufficient initial running-in performance and low friction characteristics can be obtained. The ratio is preferably 23:77 to 35:65, and more preferably 25:75 to 30:70.

(g) Metal-free sulfur-phosphorus-based extreme pressure agent The metal-free sulfur-phosphorus-based extreme pressure agent ("SP agent") that can be used in the present invention preferably has a sulfur content of 15 to 35% by weight and a phosphorus content of 0.5 to 3% by mass. By adjusting the ratio of the sulfur component and the phosphorus component, it is possible to exhibit excellent anti-wear performance and anti-seizure performance. If the sulfur component is more than the above range, the joint is easily corroded, and if the phosphorus component is more than the above range, it is difficult to obtain the anti-wear effect of the joint. In addition, if both are less than the above range, it is difficult to fully exhibit the desired anti-wear performance and anti-seizure performance.
The content of the SP extreme pressure agent is preferably 0.01 to 2 mass%, more preferably 0.05 to 1.5 mass%, and even more preferably 0.1 to 1 mass%, based on the total mass of the composition. By including the SP extreme pressure agent in such a range, sufficient extreme pressure properties can be obtained.

(h) Sulfurized Olefins The sulfurized olefins may be used alone or in combination of two or more kinds.
The sulfurized olefin that can be used in the present invention can be represented by the following general formula (4).
^R5S- ( _Sx - ^R6 - _Sy ) _z - ^R5 (4)
(In the formula, x is an integer of 0, 1, or 2, y is an integer of 1 to 3, z is an integer of 1 to 10, and ^R5 and ^R6 each independently represent a saturated or unsaturated hydrocarbon group having 4 to 10 carbon atoms.)
The sulfurized olefin may be synthesized by a known method, or a commercially available product may be used.
The content of the sulfurized olefin is preferably 0.3 to 3 mass %, more preferably 0.5 to 2.5 mass %, and even more preferably 0.7 to 2 mass %, based on the total mass of the composition. By including the sulfurized olefin in such a range, sufficient extreme pressure properties can be obtained.

In addition to the above components, the grease composition of the present invention may further contain additives that are commonly used in grease compositions, such as other solid lubricants, extreme pressure additives, antioxidants, rust inhibitors, oiliness agents, etc. Examples of other solid lubricants include inorganic substances such as soil graphite, scaly graphite, carbon black, boron nitride, potassium borate, calcium carbonate, etc., and organic substances such as melamine cyanurate, polytetrafluoroethylene, copper salts and iron salts of dithiocarbamic acid, stearic acid, calcium salts, aluminum salts, sodium salts, and lithium salts of sebacic acid. Other extreme pressure additives include phosphate esters such as triphenyl phosphate, triphenyl thiophosphate, triaryl phosphate, tricresyl phosphate, zinc dialkyl dithiophosphate, etc., organic acid salts such as zinc salt or copper salt of naphthenic acid, zinc salt of dithiocarbamic acid, azole compounds such as benzotriazole and dialkyl mercaptothiadiazole, fatty acids obtained by decomposing and modifying oils and fats obtained from animals and plants, mono- and diglycerides, polyhydric alcohols such as glycerin, alkyd resins, hardened oils, chlorinated oils and fats, sulfurized oils and fats, sulfurized esters, etc. Antioxidants include amines and phenols. Rust inhibitors include sulfonates, carboxylic acids, and amines. 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, and higher alcohols such as cetyl alcohol, stearyl alcohol, and oleyl alcohol. The content of such optional additives is, for example, 0.01 to 10% by mass, preferably 0.1 to 5% by mass, based on the total mass of the composition.

The content of the thickener in the grease composition of the present invention varies depending on the type of thickener. The consistency of the grease composition of the present invention is preferably 280 to 380, more preferably 300 to 360, and even more preferably 310 to 340. The content of the thickener is the amount required to obtain this consistency. The content of the thickener in the grease composition of the present invention is usually 4 to 14 mass%, preferably 6 to 12 mass%, and more preferably 8 to 10 mass%. In this specification, the term "consistency" means 60-fold worked consistency, measured in accordance with JIS K 2220.

The grease composition of the present invention can be used on both the outboard side and the inboard side. Needless to say, an embodiment in which the grease composition of the present invention is used on both the outboard side and the inboard side is within the scope of the present invention. An embodiment in which the grease composition of the present invention is used on either the outboard side or the inboard side and a grease composition other than the grease composition of the present invention is used on the other side is also within the scope of the present invention.

In the base oil, 1 mole of 4,4'-diphenylmethane diisocyanate was reacted with 2 moles of raw amine (cyclohexylamine:stearylamine = 8:2 (molar ratio)), and the mixture was heated and cooled, then milled in a three-stage roll mill to obtain a base grease. The base grease was mixed with the specified amounts of the additives listed below, milled in a roll mill, and degassed to obtain grease compositions of the examples and comparative examples with a consistency of 325 ± 15 (measured according to JIS K 2220). The numbers for (a), (c) to (h) in Table 1 are mass % based on the total mass of the composition.

The following components were used to prepare the grease compositions of the Examples and Comparative Examples.
<Base oil>
(b) Mineral oil (600 neutral oil, 100°C base oil kinematic viscosity 12 mm ² /s, API classification: Group II, manufactured by Chevron)
<Additives>
(c) MoS2: Molybdenum disulfide (Nichimori SF-O, manufactured by Daiso Nichimori)
(d-1) MoDTC (non-oil soluble): molybdenum dithiocarbamate (ADEKA Sakuralube 600, manufactured by ADEKA)
(d-2) MoDTC (oil-soluble): molybdenum dithiocarbamate (ADEKA Sakuralube 525, manufactured by ADEKA)
(e) Ca sulfonate (overbased): calcium salt of alkyl aromatic sulfonic acid (LUBRIZOL 5283C, manufactured by The Lubrizol Corporation, base number 350-400 mg KOH/g)
(e) Ca sulfonate (overbased): calcium salt of alkyl aromatic sulfonic acid (Bryton C-400, manufactured by LANXESS, base number 375-425 mg KOH/g)
(f) Zn sulfonate (neutral): zinc salt of alkyl aromatic sulfonic acid (Na-sul Zs, KING, base number 0-10 mg KOH/g)
(g) Metal-free sulfur-phosphorus extreme pressure agents; sulfur-phosphorus package additives (Lubrizol 810, manufactured by The Lubrizol Corporation)
(h) S-based additive: sulfurized olefin (Anglamol 33, manufactured by The Lubrizol Corporation)

・Evaluation of initial running-in of outboard constant velocity joint (SRV test)
<Test Method>
The test was conducted in accordance with ASTM D5706 under the conditions of a frequency of 50 Hz, an amplitude of 1 mm, a test temperature of 80°C, a load of 200 N, a test time of 30 minutes, and a plate on ball. The plate was machined to have the same roughness and hardness as the outer ring contact surface of a commercially available outboard constant velocity joint, and the initial running-in of an actual joint was simulated.
After the SRV test, the initial conformity characteristics of the ball sliding surface were evaluated and judged according to the following criteria. The evaluation results are shown in Table 1.
<Evaluation criteria>

<Judgment>
○: Rate 2
×: Rate 1 and Rate 3

・Low friction coefficient evaluation test (SRV test)
The friction coefficient was measured under the conditions of a frequency of 50 Hz, an amplitude of 1 mm, a test temperature of 80° C., a load of 200 N, a test time of 30 minutes, and a plate on ball in accordance with ASTM D 5706. The plate used was a standard product described in ASTM D 5706.
The evaluation results are shown in Table 1.
<Evaluation criteria>
According to ASTM D 5706, the average coefficient of friction over the test period is determined.
<Judgment>
○: Friction coefficient is 0.070 or less ×: Friction coefficient is 0.071 or more

Claims (6)

The following ingredients:
(a) a diurea-based thickener,
(b) a base oil;
(c) molybdenum disulfide;
(d-1) oil-insoluble molybdenum dialkyldithiocarbamate (MoDTC);
(d-2) oil-soluble molybdenum dialkyldithiocarbamate (MoDTC);
(e) overbased Ca sulfonates;
(f) neutral Zn sulfonate;
(g) metal-free sulfur-phosphorus based extreme pressure agents; and (h) sulfurized olefins.
Contains
a mass ratio of the (d-1) oil-insoluble MoDTC to the (d-2) oil-soluble MoDTC is (d-1):(d-2)=25:75 to 75:25;
The mass ratio of the (e) overbased Ca sulfonate to the (f) neutral Zn sulfonate is (e):(f)=20:80 to 40:60;
A grease composition for constant velocity joints. The grease composition according to claim 1, in which the base number of component (e) is 200 to 500 mg KOH/g. The grease composition according to claim 1, wherein the base number of component (f) is 100 mg KOH/g or less. The grease composition according to claim 1, wherein the component (a) is a mixture of a urea compound represented by the following formula (1-1), a urea compound represented by the following formula (1-2), and a urea compound represented by the following formula (1-3).
R1 ^- NHCONH- ^R2 -NHCONH- ^R1 (1-1)
R ¹ -NHCONH-R ² -NHCONH-R ³ (1-2)
R ³ -NHCONH-R ² -NHCONH-R ³ (1-3)
(In the formula, R ¹ represents a cyclohexyl group, R ² represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and R ³ represents an alkyl group having 8 to 22 carbon atoms. 2. The grease composition according to claim 1, wherein the component (b) has a kinematic viscosity at 100° C. of 8 to 16 mm ² /s. A constant velocity joint filled with the grease composition according to any one of claims 1 to 5.