Grease composition for outer constant velocity joint

Abstract

A grease composition for an outer constant velocity joint, which contains (a) a diurea-based thickener and (b) a base oil, and (b) a base oil having a kinematic viscosity of 3,000-20,000 mm2 / s at a temperature of-20 DEG C as measured by JIS K 2283, and containing a synthetic oil.

Description

Technical Field

[0001] The present invention relates to a grease composition for an outboard constant velocity universal joint. Background Art

[0002] Among automobiles, FF vehicles are widely used from the viewpoint of reducing weight and ensuring living space for the purpose of environmental measures (CO2 reduction) for vehicles, and constant velocity joints (CVJs) are used, which are indispensable for power transmission in FF vehicles.

[0003] CVJ rotates at an angle, so the parts inside the universal joint perform complex rolling and sliding motions with each other. Inside the CVJ, the outer side moves the wheel to turn, so the working angle sometimes becomes large. At a high working angle, the rolling and sliding speed and load between the ball and the transmission surface of the inner and outer rings become extremely large, making it difficult to form a lubricating film, and sometimes causing abnormal noise caused by stick-slip.

[0004] In particular, if a car is left outdoors for a long time during severe cold weather, the grease fluidity will further deteriorate when the CVJ is completely cooled. If the working angle is increased to start the vehicle, the sound pressure of the abnormal sound generated will be high and the duration will also be longer, which will impair the quietness and become a problem.

[0005] As CVJ greases for the purpose of reducing low-temperature starting rotational torque at low temperatures, it can be said that sufficient research has not been conducted on the effect of suppressing abnormal noise caused by the fluidity of the grease at low temperatures, for a grease comprising a base oil containing synthetic oil, a thickener, zinc dithiophosphate, molybdenum dialkyldithiocarbamate sulfurization and zinc dialkyldithiocarbamate (see Patent Document 1), and a grease comprising a base oil containing 10 to 95% of an ester-based synthetic oil produced from an aliphatic alcohol and an aromatic carboxylic acid and 90 to 5% of a synthetic hydrocarbon oil, a thickener, molybdenum disulfide, molybdenum dialkyldithiocarbamate sulfurization and zinc dithiophosphate (see Patent Document 2).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2009-270058

[0009] Patent Document 2: Japanese Patent Application Publication No. 2008-163201 Summary of the invention

[0010] Problems to be solved by the invention

[0011] An object of the present invention is to provide a grease composition for an outboard type constant velocity joint which is excellent in the effect of suppressing abnormal noise at low temperatures.

[0012] Methods for solving problems

[0013] The present inventors have found that a grease composition comprising a base oil having a specific kinematic viscosity and a urea thickener has excellent noise suppression performance at low temperatures.

[0014] That is, according to the present invention, there are provided the following grease composition for an outboard type constant velocity joint and a constant velocity joint in which the grease composition is sealed.

[0015] 1. A grease composition for an outboard constant velocity joint, comprising the following components:

[0016] (a) diurea thickener,

[0017] (b) a base oil having a kinematic viscosity at a temperature of -20°C of 3,000 to 20,000 mm 2 / s, and contains synthetic oils.

[0018] 2. The grease composition as described in 1 above, wherein the kinematic viscosity of the base oil (b) at 100°C is 8 to 20 mm 2 / s.

[0019] 3. An outboard constant velocity universal joint, wherein the grease composition described in 1 or 2 above is enclosed.

[0020] Effects of the Invention

[0021] The grease composition of the present invention has excellent noise suppression performance in a low-temperature environment. DETAILED DESCRIPTION

[0022] (a) Diurea thickener

[0023] The thickener of the present invention is a diurea thickener. As a diurea thickener, a diurea compound selected from the group consisting of aliphatic diurea compounds, aromatic diurea compounds and alicyclic diurea compounds can be used. The diurea compound is obtained by reacting a diisocyanate component with a monoamine component. As diisocyanates, phenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, hexane diisocyanate, etc. can be listed, and as monoamines, octylamine, dodecylamine, hexadecylamine, stearylamine, oleylamine, aniline, p-toluidine, cyclohexylamine, etc. can be listed.

[0024] The diurea compound preferably used in the present application is preferably a diurea thickener represented by the following formula (1).

[0025] R1NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR1' (1)

[0026] In the formula, R1 and R1' are independently octyl, dodecyl, hexadecyl, octadecyl, cyclohexyl or phenyl.

[0027] Examples of the diurea thickener of formula (1) include aliphatic diureas in which both R1 and R1' are octyl, dodecyl, hexadecyl or octadecyl groups, alicyclic aliphatic diureas containing diurea compounds in which either R1 or R1' is octyl, dodecyl, hexadecyl or octadecyl group and the other is cyclohexyl group, alicyclic diureas in which both R1 and R1' are cyclohexyl groups, aliphatic aromatic diureas containing diurea compounds in which either R1 or R1' is octyl, dodecyl, hexadecyl or octadecyl group and the other is phenyl group, aromatic diureas in which both R1 and R1' are phenyl groups, and alicyclic aromatic diureas containing diurea compounds in which either R1 or R1' is cyclohexyl group and the other is phenyl group.

[0028] Since the grease in the lubricated part is easy to form a thick film, which leads to improved durability, the thickener is more preferably an alicyclic aromatic diurea thickener. As the alicyclic aromatic diurea thickener, a diurea compound in which one of R1 and R1' is a phenyl group and the other is a cyclohexyl group in formula (1) is preferred. It should be noted that the alicyclic aromatic diurea thickener is a reaction mixture of a diisocyanate, an alicyclic amine and an aromatic amine, and therefore also includes a reactant of a diisocyanate and an alicyclic amine (i.e., in formula (1), R1 and R1' are both diurea compounds of cyclohexyl groups) and a reactant of a diisocyanate and an aromatic amine (i.e., in formula (1), R1 and R1' are both diurea compounds of phenyl groups). From the viewpoint of ensuring the film thickness of the grease composed of the thickener and the base oil, the molar ratio of cyclohexyl to phenyl in the alicyclic aromatic diurea thickener is preferably 2:8 to 4:6, and more preferably 7:3.

[0029] The content of the thickener may be an amount that can adjust the consistency of the grease to 310-375. Specifically, based on the total mass of the composition, it is preferably 8-18% by mass, more preferably 10-16% by mass, and even more preferably 11-15% by mass. It should be noted that in this specification, "consistency" refers to the 60-times work cone penetration measured by JIS K 2220.7.

[0030] (b) Base oil

[0031] The kinematic viscosity of the base oil of the present invention at -20°C is 3,000 to 20,000 mm 2 / s. By making the kinematic viscosity at -20°C 3,000~20,000mm 2 / s, which can ensure the fluidity of the grease in the CVJ at low temperatures and suppress the abnormal noise caused by the sticking of the lubricated part. The kinematic viscosity at -20°C is preferably 3300~17000mm2 / s, more preferably 3500~15000mm 2 / s.

[0032] If the kinematic viscosity at -20°C is within such a range, the type of base oil used in the present invention is not particularly limited. For example, various synthetic oils such as mineral oils represented by cycloalkane series and paraffin series, synthetic hydrocarbon oils represented by polyα-olefins and polybutene, ether-based synthetic oils represented by alkyl diphenyl ethers, silicone oils, and fluorinated oils can be cited. Synthetic oil can be so-called biomass oils made from biological resources produced by animals and plants, etc. For example, biomass ester oils synthesized from various fatty acids and alcohols using vegetable oils as raw materials, and biomass hydrocarbon oils using vegetable oils such as palm oil, corn oil, and soybean oil can also be used. Among them, synthetic hydrocarbon oils are preferred, and polyα-olefins are more preferred. The base oil can be used alone or in a mixture of two or more. From the viewpoint of ensuring low temperature properties, it is preferred to contain synthetic hydrocarbon oil. From the viewpoint of ensuring a balance between low temperature properties and costs, a mixture of synthetic hydrocarbon oil and mineral oil is particularly preferred. A mixture of polyα-olefin and mineral oil is further particularly preferred. When the base oil is a mixture of synthetic oil (such as poly-α-olefin) and mineral oil, the kinematic viscosity of the base oil at -20°C may be within the above range. Specifically, the proportion of the synthetic oil in the entire base oil is about 30% by mass or less.

[0033] The base oil of the present invention preferably has a kinematic viscosity of 8 mm at 100° C. from the viewpoint of ensuring the thickness of the base oil film in the lubricated portion of the CVJ at high temperatures and improving durability by preventing metal contact. 2 / s or more, more preferably 10 mm 2 / s or more. Since the base oil film thickness can be ensured in the lubricating part of the CVJ, the durability can be improved by preventing metal contact, so the kinematic viscosity at 100°C is as high as possible, but the viscosity at the low temperature side will increase, so the kinematic viscosity at 100°C is preferably 20 mm 2 / s or less, more preferably 17mm 2 / s or less.

[0034] In addition, the kinematic viscosity of the base oil can be measured according to JIS K 2283.

[0035] The viscosity index of the base oil is preferably 120 to 150, and more preferably 130 to 140. If it is within this range, the change in the kinematic viscosity of the base oil accompanying the temperature change is small, so the increase in the kinematic viscosity at low temperature accompanying the increase in the kinematic viscosity at high temperature can be suppressed. In addition, the viscosity will not become too high at low temperatures. In addition, since the base oil with a kinematic viscosity in the above range contains almost or completely no aromatic or cycloalkane components that will be adsorbed on the metal surface in the universal joint and hinder the operation of various components at low temperatures, it can help to suppress the generation of abnormal noise at low temperatures. It should be noted that the viscosity index of the base oil can be calculated according to JIS K 2283.

[0036] From the viewpoint of grease fluidity, the content of the base oil is preferably 70 to 90% by mass, more preferably 73 to 88% by mass, and even more preferably 75 to 85% by mass based on the total mass of the composition.

[0037] The grease composition of the present invention may contain, in addition to the above-mentioned components, additives generally used in grease compositions, such as extreme pressure additives, antioxidants, and rust inhibitors.

[0038] Examples of the additive used in the present invention include molybdenum dialkyldithiocarbamate (MoDTC), molybdenum disulfide, overbased calcium sulfonate, and sulfur-based extreme pressure agents.

[0039] As the above-mentioned molybdenum dialkyldithiocarbamate, a molybdenum dialkyldithiocarbamate represented by the following formula is particularly preferred. As MoDTC, MoDTC represented by the following formula (2) is preferred.

[0040] [R 30 2N-CS-S]2-Mo2OmSn (2)

[0041] In the formula, R 30 It 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.

[0042] From the viewpoint of low friction, the content of molybdenum dialkyldithiocarbamate is preferably 1.0 to 4.0 mass %, more preferably 1.5 to 3.5 mass %, and even more preferably 2.0 to 3.0 mass %, based on the total mass of the composition. By containing molybdenum dialkyldithiocarbamate within such a range, sufficient low friction can be obtained.

[0043] The above-mentioned molybdenum disulfide is generally widely used as a solid lubricant. This compound has a layered lattice structure and can be easily sheared into a thin layer by sliding motion, thereby hindering metal contact and having an anti-seizure effect.

[0044] From the viewpoint of galling resistance, the content of molybdenum disulfide is preferably 0.3 to 2.5 mass %, more preferably 0.5 to 2.0 mass %, and even more preferably 0.7 to 1.5 mass %, based on the total mass of the composition. By containing molybdenum disulfide within such a range, sufficiently low friction can be obtained.

[0045] Examples of the overbased calcium sulfonate 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 them, overbased calcium salts of alkyl aromatic sulfonic acids are preferred.

[0046] The base value of the overbased calcium sulfonate is not particularly limited as long as it is highly basic, and the base value measured in accordance with JIS K 2501 is, for example, 200 to 500 mgKOH / g, preferably 250 to 450 mgKOH / g, and more preferably 300 to 400 mgKOH / g. It should be noted that as long as the base value is within the above range, it may be used in combination with a calcium sulfonate other than the overbased calcium sulfonate (for example, neutral calcium sulfonate).

[0047] The content of the overbased calcium sulfonate is preferably 0.3 to 2.5 mass %, more preferably 0.5 to 2.0 mass %, and even more preferably 0.7 to 1.5 mass %, based on the total mass of the composition. When the overbased calcium sulfonate is contained within such a range, sufficient low friction can be obtained.

[0048] Examples of the sulfur-based load-bearing additive include sulfided olefins, polysulfides, and sulfurized oils and fats, etc. These may be used alone or in combination of two or more.

[0049] The sulfided olefin that can be used in the present invention can be represented by the following general formula (3).

[0050] R 10 S-(Sx-R 20 -Sy)z 10 (3)

[0051] In the formula, x represents an integer of 0, 1 or 2, y represents an integer of 1 to 3, z represents an integer of 1 to 10, and R 10 and R 20 Each independently represents a saturated or unsaturated hydrocarbon group having 4 to 10 carbon atoms.

[0052] The sulfided olefin can be synthesized by a known method, or a commercially available product can be used.

[0053] The content of the sulfur-based extreme pressure agent is preferably 0.3 to 2.5 mass %, more preferably 0.5 to 2.0 mass %, and even more preferably 0.7 to 1.5 mass %, based on the total mass of the composition. By containing the sulfur-based extreme pressure agent within such a range, sufficient low friction can be obtained.

[0054] The grease composition of the present invention preferably contains MoDTC, molybdenum disulfide, high-based calcium sulfonate and sulfur-based extreme pressure agent. In addition to the above-mentioned components, the grease composition of the present invention may further contain other extreme pressure additives, antioxidants, rust inhibitors and other additives commonly used in grease compositions. As other extreme pressure additives, phosphate esters and the like can be listed. As antioxidants, amines and phenols can be listed. As rust inhibitors, sulfonates, carboxylic acids and amines can be listed. The content of such arbitrary additives is based on the total mass of the composition, for example, 0.1 to 3.0% by mass, preferably 0.3 to 2.0% by mass.

[0055] Example

[0056] The following components were used to prepare the grease compositions of the examples and comparative examples. Specifically, 1 mol of 4',4-diphenylmethane diisocyanate was reacted with 2 mol of amine (cyclohexylamine:aniline=7:3, molar ratio) in a base oil, heated, cooled, and then kneaded with a 3-roll mill to obtain a base grease. The additives shown in Table 1 were blended therein, and the base oil was further added in such a manner that the thickener amount was in the ratio shown in Table 1, and the mixture was dispersed with a 3-roll mill to obtain the working cone penetration shown in Table 1, thereby obtaining the grease compositions of the examples and comparative examples. It should be noted that in Table 1, the "ratio %" of mineral oil and synthetic hydrocarbon oil represents the mass % relative to the total amount of the base oil. The numerical values ​​of components (a), components (b) and additives other than these represent the mass % of each component relative to the total amount of the composition.

[0057] <Thickener>

[0058] Alicyclic aromatic diurea: a product of the reaction of 1 mol of 4',4-diphenylmethane diisocyanate and 2 mol of amine (cyclohexylamine:aniline = 7:3, molar ratio)

[0059] <Base oil>

[0060] Mineral oil (kinematic viscosity: 188.4mm 2 / s@40℃、17.41mm 2 / s@100℃)

[0061] Synthetic hydrocarbon oil: poly α-olefin (kinematic viscosity: 14.21 mm 2 / s@40℃、99.56mm 2 / s@100℃) or polybutene (kinematic viscosity: 160000mm2 / s@40℃、3700mm 2 / s@100℃)

[0062] In Table 1, the base oil “solidified” at -20°C means that the kinematic viscosity at -20°C could not be measured.

[0063] <Additives>

[0064] ·MoDTC: Molybdenum dithiocarbamate

[0065] Molybdenum disulfide

[0066] ·Overbased calcium sulfonate: calcium salt of alkyl aromatic sulfonic acid (base value 300~400mgKOH / g)

[0067] Sulfur additives: sulfided olefins

[0068] <Test method>

[0069] · Working cone penetration of grease: Measured in accordance with JIS K 2220.

[0070] · Kinematic viscosity of base oil: measured at 100°C, 40°C and -20°C in accordance with JIS K 2283.

[0071] · Actual machine low temperature noise measurement: Install a commercially available outside constant velocity universal joint in a rotation test machine and cool it to -40°C. Operate the universal joint under the following conditions and start collecting noise when the temperature reaches the specified value. The test conditions are as follows.

[0072] Universal joint working angle: 35°

[0073] Speed: 200rpm

[0074] Load torque: 600 Nm

[0075] Temperature: -35℃~-33℃

[0076] The actual low-temperature abnormal sound pressure is evaluated by measuring the noise level including the background noise of the rotating test machine using a digital noise meter with a built-in sound collection microphone. The result is expressed as a percentage of the difference between the noise level including the abnormal sound and the background noise measured in advance before the test.

[0077] In addition, the results directly heard by the ears during the measurement of the low-temperature noise of the actual machine are shown according to the following evaluation criteria.

[0078] ○: No abnormal sound was heard

[0079] ×: I heard a strange noise.

[0080] [Table 1]

[0081]

Claims

1. A grease composition for an outboard constant velocity joint, comprising the following components: (a) diurea thickener, (b) a base oil having a kinematic viscosity at a temperature of -20°C of 3,000 to 20,000 mm 2 / s, and contains synthetic oils.

2. The grease composition according to claim 1, wherein (b) The kinematic viscosity of the base oil at 100°C is 8~20 mm 2 / s.

3. An outboard constant velocity universal joint, wherein the grease composition according to claim 1 or 2 is sealed.

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