JPH0657284A - Grease composition for constant-velocity joint - Google Patents

Abstract

PURPOSE:To obtain the grease compsn. which efficiently lubricates, effectively reduces abrasion, and prevents vibration by compounding a grease with a sulfurized molybdenum dialkyldithiocarbamate, a zinc dithiophosphate compd., and an epoxidized fatty acid ester or glyceride each in a specified proportion. CONSTITUTION:The grease compsn. comprises a grease consisting of a lubricant and a urea-based thickener, 0.5-5wt.% sulfurized molybdenum dialkyldithiocarbamate (A), 0.5-5wt.% extreme-pressure additive (B) consisting of a zinc dithiophosphate compd. of the formula (wherein R is an alkyl or aryl), and an epoxidized fatty acid ester or glyceride (C) in an amt. of 0.04-1 pt.wt. based on 1 pt.wt. the sum of components A and B.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a grease for a constant velocity joint (CVJ) of an automobile. Lubrication conditions for constant velocity joints are extremely high surface pressure, and as a result, abnormal wear and abnormal vibration often occur. The present invention relates to a grease composition for a constant velocity joint which can be applied to such a lubricated portion to efficiently lubricate, effectively reduce friction and further prevent vibration.

[0002]

2. Description of the Related Art Conventionally, lubricating greases used in such constant velocity joints include lithium-based extreme pressure greases containing sulfur-phosphorus extreme pressure additives and lithium-based extreme pressure greases containing molybdenum disulfide. Grease is used. Further, in JP-A-62-207397, one or two selected from the group consisting of molybdenum dialkyldithiocarbamate and sulfurized fats and oils, sulfurized olefins, tricresyl phosphate, and zinc dialkyldithiophosphate.
It is disclosed that an extreme pressure grease composition containing, as an essential component, a sulfur-phosphorus extreme pressure additive composed of a combination of one or more kinds is suitable. However, these greases for constant velocity joints are not always satisfied for more comfortable running which is required of automobiles in recent years.

Japanese Patent Publication No. 51-5409 discloses a lubricant or lubricant concentrate based on mineral oil or synthetic oil, wherein the lubricant or lubricant concentrate is an epoxidized fatty acid ester and additional sulfur. Lubricants or lubricant concentrates are known which are characterized in that they contain a / phosphorus compound and optionally known lubricant additives may be present.

[0004]

In order to reduce the weight and secure a living space, the number of FF vehicles is rapidly increasing, and indispensable constant velocity joints (CVJ) are widely used. Among these CVJs, double offset joint (DOJ) and tripod joint (T
J), etc., causes resistance in the axial direction due to complicated rolling and sliding motion during rotation, so vibration at idling, rolling of the vehicle body at start and acceleration, and source of beat and muffled sound at a specific speed. Has become. To solve this problem, the structure of the constant velocity joint (CVJ) itself has been improved, but it is difficult in terms of space, weight, and cost. The above-mentioned JP
The grease described in JP-A-62-207397 can reduce the generated vibration, but it is insufficient.

[0005]

Means for Solving the Problems In the process of conducting various studies to reduce wear of constant velocity joints and prevent vibration, the present inventors have high surface pressure as described above and are likely to wear,
In addition, for the performance evaluation of grease used under lubrication conditions where vibration is likely to occur, rolling and sliding test method under vibration conditions
(JP-A-2-213748) is newly used. That is,
It was found that there is a relationship between the vibration generated by a constant velocity joint as the vibration source and the friction coefficient under rolling / sliding lubrication conditions, and the friction coefficient of various extreme pressure additives, oiliness agents, solid lubricants alone or in combination of each additive Was examined. As a result,
(A) Molybdenum sulfide dialkyldithiocarbamate
Depending on the combination of (B) zinc dithiophosphate compound and (C) epoxidized fatty acid ester or epoxidized fatty acid glyceride, either alone or in any of the two
A larger effect of reducing the coefficient of friction, which was not observed in the combination of species, was recognized. Furthermore, even in a test using an actual constant velocity joint, it was recognized that vibration was remarkably prevented, and the present invention was achieved. That is, the present invention is
For grease consisting of lubricating oil and urea thickener, (A)
Molybdenum sulfide dialkyldithiocarbamate, (B)
The following formula

[Chemical 2] An extreme pressure additive comprising a zinc dithiophosphate compound represented by the formula (wherein R represents an alkyl group or an aryl group);
(C) Epoxidized fatty acid ester or epoxidized fatty acid glyceride is contained as an essential component, and the content of (A) component is 0.5 to 5% by weight, and the content of (B) component is 0.5 to
5% by weight, and the component (C) is characterized by a mixing ratio of more than 0.04 and less than 1 when the content of {(A) + (B)} is 1. The present invention relates to a grease composition for joints.

[0006]

The urea grease used in the present invention uses, as a base oil, a lubricating oil such as a mineral oil, an ester synthetic oil, an ether synthetic oil, a hydrocarbon synthetic oil or a mixed oil thereof,
It is a grease using a urea compound obtained as a thickener by a reaction of an aliphatic amine, an alicyclic amine, an aromatic amine and the like with various isocyanate compounds, and is not particularly limited.

The molybdenum dialkyldithiodicarbamate, which is the component (A) used in the present invention, has the following formula:

[Chemical 3] (In the formula, R ₁ and R ₂ represent an alkyl group having 1 to 24 carbon atoms, m + n = 4, m is 0 to 3 and n is 4 to 1). It is a solid lubricant.
The compound represented by [Chemical Formula 3] is disclosed in, for example, JP-B-45-24562, wherein m is 2.35 to 3 and n is 1.65 to 1, which is disclosed in JP-B-51-964. There are 0 and n are 4, and in Japanese Patent Publication No. 53-31646, m is
It is disclosed that 0.5 to 2.3 and n is 3.5 to 1.7.
The compound of [Chemical Formula 3] used in the present invention includes all of the above-disclosed compounds.

Further, the component (B) used in the present invention is an extreme pressure additive composed of the zinc dithiophosphate compound represented by the above [Chemical formula 2]. The zinc dithiophosphate compound is represented by [Chemical formula 2]
R group of, depending on the type of alcohol used, primary (primary) alkyl, secondary (secondary-) alkyl,
It can be classified into three types of aryl, but any of them can be applied.
In particular, the combination with a primary (primary) alkyl type is most effective. Next, the epoxidized fatty acid ester that is the component (C) used in the present invention is generally produced by epoxidizing an oleic acid ester, such as epoxy stearate methyl, epoxy butyl stearate, and epoxy stearate octyl. Is applied. Further, epoxidized fatty acid glyceride is similarly produced by epoxidizing soybean oil, linseed oil, castor oil, etc.,
Epoxidized soybean oil, epoxidized linseed oil, epoxidized castor oil, etc. are applied. All are known as plasticizers and stabilizers for rubber and plastics.

In the present invention, a grease is prepared by combining (A) component molybdenum sulfurized dialkyldithiocarbamate, (B) component zinc dithiophosphate compound and (C) epoxidized fatty acid ester or epoxidized fatty acid glyceride in a specific ratio. It is characterized in that it is contained in the composition, which is significantly superior to the case where the component (A), the component (B), and the component (C) are contained alone, and the combination of any two of the three. It is effective and achieves the purpose.

This effect can be considered as follows.
The urea compound, which is the thickener component of urea grease, and the epoxidized fatty acid ester or epoxidized fatty acid glyceride, which is the component (C), are adsorbed on the metal surface to form a uniform protective film and smooth the lubricated part. A reaction film is formed on the smoothed surface by the zinc dialkyldithiophosphate as the component (B). On the reaction film, molybdenum dialkyldithiodithiocarbamate as the component (A) acts. That is, it is presumed that, in these three-layer states, a layer or interface having a low shear stress is formed, and the function of lowering the friction coefficient occurs.

If the mixing ratio of the component (A) is less than 0.5% by weight, the component (B) is less than 0.5% by weight, and the component (C) is {(A) + (B)} is less than 0.04 by weight, all Ineffective, while (A)
More than 5% by weight of component, more than 5% by weight of component (B), and (C) component of {(A) + (B)} in a mixing ratio of 1 by weight.
Even if added above, there is no further increase in effect, and (A) component 0.5
~ 5% by weight, component (B) 0.5 to 5% by weight, component (C) is
Assuming that the content of {(A) + (B)} is 1, the mixing ratio by weight is in the range of more than 0.04 and less than 1. In addition to the components (A), (B) and (C), an antioxidant, an anticorrosive agent and the like can be added if necessary.

[0012]

EXAMPLES Next, the present invention will be described with reference to Examples and Comparative Examples. Examples 1 to 8 and Comparative Examples 1 to 10 Additives were added to the grease in the formulations shown in Tables 4 and 5 and the consistency was adjusted to No. 2 grade with a three-stage roll mill. The greases of Examples 1-10 were obtained. The following base oil was used for grease.

[Table 1]

The physical properties of these greases were evaluated by the following test methods, and the obtained results are shown in Tables 4 and 5. <Consistency> According to JIS K 2220 5.3. <Drop point> According to JIS K 2220 5.4. <SRV needle test>

A test method for evaluating a friction characteristic of the grease for a constant velocity joint by reproducing a complicated rolling / sliding motion by using a vibration friction wear testing machine known as an SRV testing machine will be described. The outline of the test apparatus is shown in FIG. A holder 4 having a rectangular window is inserted between two cylindrical plates 1 and 2 at an arbitrary angle, and a plurality of (three) needles 3 are inserted adjacent to each other in the holder, and under arbitrary load conditions. One of the cylindrical plates 1 was reciprocally moved, and the friction coefficient due to the friction between the plurality of needles and the friction between the needles and the upper and lower two cylindrical plates was measured and evaluated. The above is called the SRV needle test.

The size of each test piece is as follows: cylindrical plate 1 (diameter 20 mm × thickness 13 mm), cylindrical plate 2 (diameter 24 mm
× thickness 7.85 mm), holder (diameter 20 mm × thickness 2.5 mm, hole size 14 mm × 10 mm), needle (diameter 3 mm × thickness 13.8)
mm), and the material is SUJ-2 (bearing steel).

[0016]

[Table 2] Evaluation conditions Load 1000 N Frequency 40 Hz Amplitude 3000 μm Time 10 min Test temperature Room temperature Holder angle 30 ° (0 ° perpendicular to the amplitude direction) Friction coefficient after 10 minutes of measurement item

<Axial Force Measurement Test> For the vibration measurement in the actual joint, the slide resistance in the axial direction during rotation of the tripod type joint was measured as the axial force. The results are shown by the axial force reduction rate based on the base grease of Comparative Example 1.

[Table 3] Measurement conditions Rotational speed 150 rpm Torque 300 Nm Joint angle 7 ° Measurement time 10 minutes after operation

[0018]

[Table 4]

[0019]

[Table 5]

[0020]

As described above, the grease composition for constant velocity joints of the present invention comprises a grease comprising a lubricating oil and a urea thickener, and (A) sulfurized dialkyldithiocarbamate molybdenum and (B) As a result of mixing the zinc dithiophosphate compound of (C) and the epoxidized fatty acid ester of (C) or the epoxidized fatty acid glyceride in the specified amounts, as shown in the test results of Examples and Comparative Examples shown in Tables 4 and 5, significant friction The coefficient reduction effect and the vibration prevention effect can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an SRV needle test device.

[Explanation of symbols]

 1 Cylindrical plate 2 Cylindrical plate 3 Needle 4 Holder

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Claims (1)

[Claims] 1. A grease comprising a lubricating oil and a urea-based thickener, (A) molybdenum sulfurized dialkyldithiocarbamate, and (B) the following formula: (Wherein R represents an alkyl group or an aryl group), an extreme pressure additive comprising a zinc diotilate compound,
(C) Epoxidized fatty acid ester or epoxidized fatty acid glyceride is contained as an essential component, and the content of (A) component is 0.5 to 5% by weight, and the content of (B) component is 0.5 to
5% by weight, component (C) is a grease for constant velocity joints, characterized in that the mixing ratio is a weight ratio of more than 0.04 and less than 1 when the content of {(A) + (B)} is 1. Composition.