JP2021063166A - Lubricant composition and rolling bearing - Google Patents

Abstract

To provide a lubricant composition capable of effectively preventing premature peeling due to hydrogen embrittlement, and a rolling bearing having an encapsulated lubricant composition.SOLUTION: A lubricant composition 7 comprises a base oil and an antioxidizing agent, wherein the base oil is a synthetic hydrocarbon oil or an ester oil, the antioxidizing agent is a phenolic antioxidant or an amine antioxidant, the antioxidizing agent is contained in an amount of 10 mass% or more based on a total amount of the lubricant composition 7, and the antioxidizing agent reduces the amount of hydrogen per wear amount in a ball-on-disk sliding test by 10% or more as compared with the amount of hydrogen when the antioxidizing agent is not added.SELECTED DRAWING: Figure 1

Description

The present invention relates to a lubricant composition and a rolling bearing in which the lubricant composition is encapsulated, and more particularly to a lubricant composition used for a rolling bearing for automobile electrical equipment and auxiliary machinery and a rolling bearing thereof.

In recent years, in response to demands for miniaturization, weight reduction, and quietness improvement of automobiles, the electrical components and auxiliary machinery parts have been miniaturized, lightened, and sealed in the engine room. On the other hand, there is an increasing demand for high output and high efficiency in the performance of the device itself, and in the electrical equipment and auxiliary equipment in the engine room, there is a method to compensate for the decrease in output caused by miniaturization by rotating at high speed. It has been taken. As a result, usage conditions such as rapid acceleration / deceleration, high temperature, and high rotation are severe.

Rolling bearings are used in the rotating parts of electrical components and auxiliary machinery parts in automobiles. Under the severe conditions as described above, there is a possibility that premature peeling accompanied by a peculiar structural change on the rolling surface of the rolling bearing may occur. This specific exfoliation is considered to be hydrogen brittleness caused by hydrogen generated by decomposition of the base oil or the like in the grease, unlike the exfoliation due to normal metal fatigue. For example, it is considered that the base oil is decomposed to generate hydrogen, which invades the steel of the rolling bearing, resulting in premature peeling due to hydrogen brittleness.

Conventionally, as a method of suppressing a peculiar peeling phenomenon accompanied by such an early change in white structure, for example, a method of adding a passivation agent to grease (see Patent Document 1), ZnDTC, MoDTC, etc. A method of adding an anti-wear agent has been proposed (see Non-Patent Document 1).

Japanese Patent No. 2878749

Tribology Transition, 2006, 49, p. 53-60

However, the conditions for using rolling bearings in electrical components and auxiliary machinery parts in automobiles in recent years are becoming more and more severe, and the conventional technology is insufficient as a measure to prevent the peeling phenomenon. Therefore, a further method for preventing premature peeling is required.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a lubricant composition capable of effectively preventing premature peeling due to hydrogen brittleness, and a rolling bearing in which the lubricant composition is encapsulated. And.

The lubricant composition of the present invention is a lubricant composition containing a base oil and an antioxidant, wherein the base oil is a synthetic hydrocarbon oil or an ester oil, and the antioxidant is a phenolic antioxidant. It is an agent or an amine-based antioxidant, and is characterized in that it is contained in an amount of 10% by mass or more based on the entire lubricant composition.

The base oil is a poly-α-olefin oil (hereinafter referred to as PAO oil).

The antioxidant is an alkylated diphenylamine.

The lubricant composition is characterized by containing only the base oil and the antioxidant.

The antioxidant is characterized in that the amount of hydrogen per wear amount in the ball-on-disk sliding test is reduced by 10% or more as compared with the case where the antioxidant is not added. Here, the amount of hydrogen per amount of wear is a value obtained by dividing the amount of hydrogen generated in the ball-on-disk sliding test by the amount of wear obtained from the wear marks of the balls generated in the sliding test.

In the ball-on-disc sliding test, a ball made of SUS440C and a disc made of SUJ2 were used, and in the presence of the lubricant composition, the degree of vacuum was 1 × ^10-5 Pa or less, the load was 2.0 GPa, and the sliding speed was 0.1 m. It is characterized in that it is carried out under the condition of / s and a sliding time of 3 minutes.

The rolling bearing of the present invention is a rolling bearing formed by encapsulating a lubricant composition, and the lubricant composition is the lubricant composition of the present invention.

Since the lubricant composition of the present invention contains a predetermined base oil and a phenol-based antioxidant or an amine-based antioxidant, and the antioxidant is contained in an amount of 10% by mass or more based on the entire lubricant composition. The alkyl radicals generated in the reaction process of hydrogen generation react with the antioxidant, so that the reaction process of hydrogen generation is blocked and hydrogen production is suppressed. As a result, premature exfoliation due to hydrogen brittleness can be suppressed.

Since the rolling bearing of the present invention is formed by encapsulating the lubricant composition of the present invention, early peeling due to hydrogen brittleness can be prevented even under harsh usage conditions, and longer use is realized. it can.

It is sectional drawing of the deep groove ball bearing which is an example of the rolling bearing of this invention. It is the schematic which shows the ball-on-disc sliding test. It is a figure which shows the hydrogen amount per wear amount of each test example.

Hydrogen, which causes premature abruption, is considered to be generated by the following process. That is, it is considered that the base oil is decomposed by energy such as heat to generate an alkyl radical, the alkyl radical is adsorbed on the iron surface, and then hydrogen is generated by the progress of the β-hydrogen elimination reaction. As a result of diligent studies on a lubricant composition to be used for lubrication in order to prevent premature peeling, the present inventors have found that hydrogen production can be unexpectedly suppressed by a predetermined antioxidant. The present invention is based on such findings.

The lubricant composition of the present invention contains a base oil and an antioxidant. In the aspect of the lubricant composition of the present invention, (1) a lubricating oil containing a predetermined base oil and an antioxidant as an essential composition, and (2) a predetermined base oil, a thickener and an antioxidant are used. There are two types of grease, which is an essential configuration.

The base oil used in the present invention is a synthetic hydrocarbon oil such as PAO oil or alkylbenzene oil, or an ester oil. These base oils may be used alone or in combination of two or more.

PAO oil is more preferable as the synthetic hydrocarbon oil. PAO oils are α-olefins or mixtures of isomerized α-olefin oligomers or polymers. Specific examples of the α-olefin include 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1 -Nonadecene, 1-eicosene, 1-dodecene, 1-tetradodecene and the like are mentioned, and a mixture thereof is usually used.

Ester oils include diester oils such as dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecylglutarate, and methyl acetylsinolate, trioctyl remeritate, and tridecyl. Aromatic ester oils such as trimellitate and tetraoctylpyromerite, polyol ester oils such as trimethylolpropane caprilate, trimethylolpropane verargonate, pentaerythritol-2-ethylhexanoate and pentaerythritol verargonate, Examples thereof include carbonic acid ester oil and phosphoric acid ester oil.

The kinematic viscosity of the base oil (in the case of a mixed oil, the kinematic viscosity of the mixed oil) ^{is preferably 20 to 150 mm 2} / s at 40 ° C. It is more preferably 20 to 100 mm ² / s, and even more preferably 20 to 50 mm ² / s.

The antioxidant used in the present invention is a phenolic antioxidant or an amine-based antioxidant. These antioxidants are included in the lubricant composition to capture the alkyl radicals generated by the decomposition of synthetic hydrocarbon oils or ester oils. Only one type of antioxidant may be used, or two or more types may be used in combination.

Phenolic antioxidants include, for example, 2,6-di-tert-p-cresol (BHT), n-octadecyl-3- (3', 5'-di-tert-butyl-4-hydroxyphenyl) propionate, Tetrakiss- (methylene-3- (3', 5'-di-tert-butyl-4-hydroxyphenyl) propionate) methane, 2,2'-methylenebis- (4-methyl-6-tert-butylphenol), 4, Examples thereof include 4'-butylidenebis- (3-methyl-6-tert-butylphenol). Of these, BHT is preferable.

As the amine-based antioxidant, for example, diphenylamines, phenyl-α-naphthylamines, phenylenediamines and the like can be used. Examples of diphenylamines include octylated / butylated diphenylamines, p, p'-dioctyldiphenylamines and the like. Examples of phenyl-α-naphthylamines include N-phenyl-α-naphthylamine, N-butylphenyl-α-naphthylamine, N-octylphenyl-α-naphthylamine and the like. Examples of phenylenediamines include p-phenylenediamine and N-phenyl-N'-isopropyl-p-phenylenediamine. Among these, octylated / butylated diphenylamines are preferable, and examples of commercially available products thereof include Irganox L57 manufactured by BASF.

The blending amount of the above-mentioned antioxidant (when two or more kinds are used, the total amount) is 10% by mass or more with respect to the entire lubricant composition. By using 10% by mass or more of the antioxidant, alkyl radicals can be easily captured and hydrogen generation can be suitably suppressed. The blending amount of the antioxidant is preferably 10 to 20% by mass, more preferably 10 to 15% by mass.

In a ball-on-disk sliding test, the antioxidant used in the present invention reduces the amount of hydrogen per amount of wear when the antioxidant is added by 10% or more as compared with the case where the antioxidant is not added. It is preferable to let it. The reduction rate is more preferably 15% or more, and even more preferably 30% or more.

Here, the "amount of hydrogen per amount of wear" is a value obtained by dividing the amount of hydrogen generated in the ball-on-disk sliding test by the amount of wear obtained from the wear marks of the balls generated in the sliding test. As the amount of wear of the ball, for example, the diameter of the wear mark that can be measured with an optical microscope can be used. The wear mark diameter of the ball is an average wear mark diameter (unit: μm) obtained by measuring the diameter of the circular scratches generated on the ball in the sliding direction and the diameter in the direction perpendicular to the sliding direction. The method for measuring hydrogen generated during the test is not particularly limited, but can be measured using, for example, a quadrupole mass spectrometer. In this case, the integral value of the increased ion current value and the sliding time (seconds) is defined as the amount of hydrogen (unit: As).

The ball-on-disc sliding test is carried out using an independently manufactured device 3 ball-on-disc tester. Specific test conditions are a ball made of SUS440C and a disc made of SUJ2, a vacuum degree of 1 × ^10-5 Pa or less, a load of 2.0 GPa, and a sliding speed of 0.1 m / s in the presence of a lubricant composition. It is carried out under the condition that the sliding time is 3 minutes.

The lubricant composition of the present invention may further contain other additives as long as the object of the present invention is not impaired. For example, extreme pressure agents such as organic zinc compounds and organic molybdenum compounds, antioxidants such as sulfur compounds and phosphorus compounds, abrasion inhibitors such as sulfur compounds and phosphorus compounds, sulfonates and polyhydric alcohol esters, etc. Examples thereof include rust preventives, friction reducing agents such as graphite, and oily agents such as esters and alcohols. It is preferable that the lubricant composition of the present invention does not contain an antioxidant other than a phenolic antioxidant and an amine-based antioxidant. For example, it is preferable that the sulfur-based antioxidant such as phenothiazine and dilaurylthiodipropionate and the phosphorus-based antioxidant such as zinc dithiophosphate are not contained.

When the above lubricant composition is used as grease, a thickener is further added. The thickener is not particularly limited, and general ones usually used in the field of grease can be used. For example, soap-based thickeners such as metal soaps and composite metal soaps, and non-soap-based thickeners such as Benton, silica gel, diurea compounds, triurea compounds, tetraurea compounds, and urea-urethane compounds can be used. Examples of the metal soap include sodium soap, calcium soap, lithium soap and the like, and examples of the composite metal soap include composite lithium soap and the like. Among these, it is preferable to use a diurea compound as a thickener.

The diurea compound is obtained by reacting a diisocyanate component with a monoamine component. Examples of the diisocyanate component include phenylenediocyanate and diphenylmethane diisocyanate (MDI). As the diurea compound, an aliphatic diurea compound, an alicyclic diurea compound, and an aromatic diurea compound are used, and these are classified according to the type of substituent of the monoamine component used. In the case of an aliphatic diurea compound, an aliphatic monoamine (octylamine or the like) is used as a monoamine component. In the case of an alicyclic diurea compound, an alicyclic monoamine (cyclohexylamine or the like) is used as a monoamine component. In the case of an aromatic diurea compound, an aromatic monoamine (p-toluidine or the like) is used as a monoamine component.

A base grease containing a diurea compound as a thickener is prepared by reacting a diisocyanate component and a monoamine component in a base oil. The mixing ratio of the thickener in the base grease is, for example, 5% by mass to 30% by mass, preferably 10% by mass to 20% by mass.

In the case of the above grease, the mixing consistency (JIS K 2220) is preferably in the range of 200 to 350. If the consistency is less than 200, oil separation may be small and lubrication may be poor. On the other hand, when the consistency exceeds 350, the grease is soft and easily flows out of the bearing, which is not preferable.

The rolling bearing of the present invention has an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and a lubricant composition sealed around the rolling elements. The rolling bearing of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of a deep groove ball bearing. In the rolling bearing 1, an inner ring 2 having an inner ring rolling surface 2a on the outer peripheral surface and an outer ring 3 having an outer ring rolling surface 3a on the inner peripheral surface are arranged concentrically with the inner ring rolling surface 2a and the outer ring rolling surface 3a. A plurality of balls 4 which are rolling elements are arranged between the two. The ball 4 is held by the cage 5. Further, the openings 8a and 8b at both ends in the axial direction of the inner and outer rings are sealed by the sealing member 6, and the lubricant composition 7 is sealed at least around the ball 4. The lubricant composition 7 is lubricated by interposing the rolling surface with the rolling element 4.

In the rolling bearing 1, the iron-based metal material constituting the bearing member such as the inner ring 2, the outer ring 3, the rolling element 4, and the cage 5 is an arbitrary material generally used as the bearing material, for example, high carbon chromium. Bearing steel (SUJ1, SUJ2, SUJ3, SUJ4, SUJ5, etc .; JIS G 4805), carburized steel (SCr420, SCM420, etc .; JIS G 4053), stainless steel (SUS440C, etc .; JIS G 4303), high-speed steel (M50, etc.) , Cold rolled steel and the like. Further, the sealing member 6 may be made of metal or a rubber molded body alone, or may be a composite of a rubber molded body and a metal plate, a plastic plate, or a ceramic plate. A composite of a rubber molded body and a metal plate is preferable because of its durability and ease of fixing.

In FIG. 1, a ball bearing is illustrated as a rolling bearing, but the rolling bearings of the present invention include cylindrical roller bearings, cone roller bearings, self-aligning roller bearings, needle roller bearings, thrust cylindrical roller bearings, and thrust cone rollers other than the above. It can also be used for bearings, thrust needle roller bearings, thrust self-aligning roller bearings, etc.

The present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these examples.

The lubricant compositions having the compositions shown in Table 1 were prepared respectively. The lubricant composition in Table 1 is in the form of a lubricating oil. The lubricating oils of Examples 1 to 3 contain only a base oil and an antioxidant.

<Ball-on-disc sliding test>
The obtained test oil was subjected to a sliding test using the ball-on-disk sliding tester shown in FIG. As shown in FIG. 2, the testing machine has a disc 11 and three balls 12 fixed to the disc 11. Each ball 12 is fixed at equal angular intervals with respect to the center of rotation. A predetermined amount of test oil 13 is applied to the disc 11, and a load F is applied to the disc 11 via the balls 12 in a vacuum chamber (not shown). Then, the air in the vacuum chamber was exhausted, and after reaching a predetermined degree of vacuum, the ball 12 side was rotated by a motor (not shown) and slid between the ball and the disk. The specific test conditions are as follows.
(Test condition)
Disc: φ24 mm SUJ2 disc ball: φ1 / 4 inch SUS440C ball 3 pieces Oil application amount: 10 μL
Load: 2.0 GPa
Radius of rotation: 20 mm
Sliding speed: 0.1 m / s
Vacuum degree: 1 x ^10-5 Pa or less Sliding time: 3 minutes

The hydrogen generated during the test was measured with a quadrupole mass analyzer, and the integrated value of the increased ion current value and the sliding time was taken as the amount of hydrogen. After the test, the diameters of the wear marks of the three balls were measured with an optical microscope, and the average value was taken as the amount of wear. The value obtained by dividing the obtained amount of hydrogen by the amount of wear, that is, the amount of hydrogen per wear amount was calculated. The same sliding test was performed three times for each test oil, and the average value was calculated.

FIG. 3 shows a plot of the amount of hydrogen per wear amount of Examples 1 and 2 and Comparative Example 1. Hydrogen amount per each wear amount (unit: A · s / μm) is Example 1 7.35 × ^{10 -11} Example 2 5.3 × ^{10 -11,} Comparative Example 1 is 9.03 × It is ^10-11. In Examples 1 and 2, the amount of hydrogen per wear amount under the above test conditions is 7.5 × ^10-11 or less. As shown in FIG. 3, the amount of hydrogen per wear amount was reduced by adding the antioxidant, and it was found that the antioxidant contributed to the suppression of hydrogen production.

Further, in order to see the effect of adding the antioxidant in Examples 1 to 3 and Comparative Examples 1 to 5, the ratio of the amount of hydrogen per amount of wear calculated by the following formula is also shown in Table 1.
Ratio of hydrogen amount per wear amount = (hydrogen amount per wear amount when antioxidant is added) / (hydrogen amount per wear amount when antioxidant is not added)

As shown in Comparative Examples 3 to 5 in Table 1, when ether oil was used as the base oil, the amount of hydrogen per wear amount did not decrease even when the antioxidant was added, and the result was a slight increase. It was. On the other hand, as shown in Examples 1 to 3 and Comparative Examples 1 and 2, when synthetic hydrocarbon oil or ester oil is used as the base oil, the amount of hydrogen per amount of wear can be increased by adding an antioxidant. Diminished. In this case, the reduction rate of the amount of hydrogen per amount of wear ((1-ratio of the amount of hydrogen per amount of wear) x 100) is 19% in Example 1, 41% in Example 2, and 17% in Example 3. Met. That is, the antioxidant reduces the amount of hydrogen per wear amount by 10% or more as compared with the case where no addition is added. In particular, in the case of the combination of PAO oil and an amine-based antioxidant, the amount of hydrogen per amount of wear was significantly reduced.

As described above, in the present invention, hydrogen generation due to decomposition of the base oil is suppressed by adding an antioxidant that reacts with alkyl radicals generated in the reaction process of hydrogen generation. As a result, premature exfoliation due to hydrogen brittleness can be suppressed.

Since the lubricant composition of the present invention can effectively prevent specific premature peeling accompanied by a change in white structure occurring on the rolling surface, it is excellent in bearing life of rolling bearings. The rolling bearings are particularly suitable for alternators, electromagnetic clutches for car air conditioners, intermediate pulleys, automobile electrical components such as electric fan motors, rolling bearings for auxiliary machinery, and bearings for motors.

1 Rolling bearing 2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Sealing member 7 Lubricant composition 8a, 8b Openings

Claims (7)

A lubricant composition containing a base oil and an antioxidant.
The base oil is a synthetic hydrocarbon oil or an ester oil.
A lubricant composition, wherein the antioxidant is a phenolic antioxidant or an amine-based antioxidant, and is contained in an amount of 10% by mass or more based on the total amount of the lubricant composition. The lubricant composition according to claim 1, wherein the base oil is a poly-α-olefin oil. The lubricant composition according to claim 1 or 2, wherein the antioxidant is an alkylated diphenylamine. The lubricant composition according to any one of claims 1 to 3, wherein the lubricant composition comprises only the base oil and the antioxidant. Claims 1 to 4 are characterized in that the antioxidant reduces the amount of hydrogen per wear amount in a ball-on-disk sliding test by 10% or more as compared with the case where the antioxidant is not added. The lubricant composition according to any one of the above. In the ball-on-disc sliding test, a ball made of SUS440C and a disc made of SUJ2 were used, and in the presence of the lubricant composition, the degree of vacuum was 1 × ^10-5 Pa or less, the load was 2.0 GPa, and the sliding speed was 0.1 m. The lubricant composition according to claim 5, wherein the lubricant composition is carried out under the conditions of / s and a sliding time of 3 minutes. A rolling bearing in which a lubricant composition is sealed.
A rolling bearing according to any one of claims 1 to 6, wherein the lubricant composition is the lubricant composition.

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