JP2019172760A - Grease composition and grease-sealed rolling bearing - Google Patents

Abstract

To provide a grease composition suitable for a rolling bearing used in a high load condition and excellent in lifetime, and a rolling bearing sealed with the same.SOLUTION: A grease composition of this invention includes base oil, a thickener, and an additive. The base oil consists of PAO oil as a major component; the thickener is at least one diurea compound selected from a group composed of an alicyclic diurea compound, an aromatic diurea compound, and an aliphatic diurea compound; and the additive includes neutral Ca sulfonate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a grease composition and a grease-filled rolling bearing, and particularly to a grease composition and a grease-filled rolling bearing used under high temperature and high load conditions.

  Rolling bearings are widely used as bearings for automobiles and industrial power transmission systems. Such a rolling bearing is filled with grease in order to impart lubricity. In recent years, along with the downsizing and higher performance of equipment that uses grease-enclosed rolling bearings, the usage environment of these rolling bearings has become increasingly severe, and greases that exhibit excellent lubrication characteristics even under severer conditions. Considerations are being made. In particular, under high load conditions, fretting occurs on the rolling element surface and the rolling surface, and there is a concern about deterioration of the bearing life, such as an increase in bearing torque and separation starting from a damaged portion.

  Conventionally, for the purpose of suppressing the fretting and prolonging the life of the bearing, for example, a lubricating oil containing at least one selected from a stearic acid metal salt, a phosphate ester, a sulfonate metal salt and a salicylate metal salt, A lubricating composition (Patent Document 1) in which a predetermined amount is added has been proposed. Moreover, a grease composition (Patent Document 2) including a base oil containing two components each having a kinematic viscosity at 40 ° C. belonging to a predetermined range has been proposed.

JP 2014-237739 A Japanese Patent No. 570683

  By the way, a fretting test generally performed is performed by periodically applying a predetermined thrust load to the thrust ball bearing and observing the damage. However, there may be a difference between the test result and the life time obtained by actually operating the bearing for a long time. The lubricating composition of Patent Document 1 is only subjected to a fretting test at a high surface pressure, and is not actually tested using a bearing in which the lubricating composition is enclosed. Similarly, the grease composition of Patent Document 2 only assumes the life of the bearing from the amount of wear in the fretting test. Therefore, when the bearing is actually operated, a long life effect may not be obtained.

  The present invention has been made in view of the above circumstances, and is suitable for a rolling bearing used under high load conditions, and an object thereof is to provide a grease composition excellent in life time and a rolling bearing in which the grease composition is enclosed. And

  The grease composition of the present invention is a grease composition containing a base oil, a thickener, and an additive, wherein the base oil contains poly-α-olefin oil (PAO oil) as a main component and the thickener. The agent is one or more diurea compounds selected from the group consisting of alicyclic diurea compounds, aromatic diurea compounds, and aliphatic diurea compounds, and the additive contains neutral Ca sulfonate.

  The neutral Ca sulfonate is contained in an amount of 0.5 to 3% by mass with respect to the entire grease composition.

  The thickener is a mixture of an alicyclic diurea compound and an aromatic diurea compound.

  The grease-filled rolling bearing of the present invention is used under a high temperature and high load condition, and is enclosed around the inner ring and outer ring which are raceway rings, a plurality of rollers rolling between the inner ring and the outer ring, and the periphery of the rollers. A grease-filled rolling bearing comprising the grease composition according to the present invention, wherein the grease composition is the grease composition of the present invention.

  The high load condition is characterized in that the maximum contact surface pressure of the raceway is 2.0 GPa or more.

  The grease composition of the present invention includes a base oil mainly composed of PAO oil, a thickener composed of a diurea compound, and an additive. Since the additive includes neutral Ca sulfonate, the lifetime is excellent. In addition, since the grease-filled rolling bearing of the present invention contains the grease composition, fretting can be suppressed even under high temperature and high load conditions, and the life of the rolling bearing can be extended.

It is sectional drawing which shows an example of the grease enclosure rolling bearing of this invention.

  The present inventors have studied a grease composition sealed in a bearing so as to suppress fretting and extend the life of the bearing even when the rolling bearing is actually used under a high temperature and high load condition. As a result, by adding a specific metal sulfonate (neutral Ca sulfonate) to the grease composition containing mainly PAO oil as the base oil and diurea compound as the thickener, the fretting is suppressed and the bearing life is extended. I found out that I can do it. The present invention is based on such knowledge.

  The grease composition of the present invention includes a base oil, a thickener, and an additive. PAO oil is used as the base oil. PAO oil is a mixture of α-olefins or oligomers or polymers of isomerized α-olefins. 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-docosene, 1-tetradocosene, etc. are mentioned, Usually, these mixtures are used.

  As a base oil, you may mix | blend the general base oil normally used in the field | area of grease, making PAO oil the main component. For example, as other base oils, highly refined oils, mineral oils, ester synthetic oils, ether synthetic oils, silicone oils, fluorine oils, and mixed oils thereof can be used.

The kinematic viscosity of the base oil (in the case of a mixed oil, the kinematic viscosity of the mixed oil) is preferably 10 to 100 mm ² / s at 40 ° C. More preferably, it is 30-80 mm < ² > / s, More preferably, it is 40-70 mm < ² > / s.

A preferred form of the base oil is an oil having a kinematic viscosity of 40 to 70 mm ² / s at 40 ° C. using only PAO oil (not including other base oils). In this case, a plurality of commercially available PAO oils may be mixed and used. For example, a PAO oil having a kinematic viscosity at 40 ° C. of 60 to 70 mm ² / s and a PAO oil having a kinematic viscosity at 40 ° C. of 40 to 50 mm ² / s are mixed, and the base oil has a kinematic viscosity at 40 ° C. of 40. It is good also as -70mm < ² > / s.

  As the thickener, a diurea compound selected from the group consisting of an alicyclic diurea compound, an aromatic diurea compound, and an aliphatic diurea compound is used. The diurea compound is obtained by reacting a diisocyanate component and a monoamine component. The alicyclic diurea compound is obtained from an alicyclic monoamine and a diisocyanate component as a monoamine component, the aromatic diurea compound is obtained from an aromatic monoamine and a diisocyanate component as a monoamine component, and the aliphatic diurea compound is It is obtained from an aliphatic monoamine as a monoamine component and a diisocyanate component. Examples of the diisocyanate component include phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, and hexane diisocyanate. Examples of the alicyclic monoamine include cyclohexylamine. Aromatic monoamines include aniline, p-toluidine and the like. Examples of the aliphatic monoamine include hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine, stearylamine, oleylamine and the like.

  Among the above diurea compounds, it is particularly preferable to use a combination of an alicyclic diurea compound and an aromatic diurea compound as a thickener. In this case, the mass ratio of the alicyclic diurea compound and the aromatic diurea compound is preferably 1: 2 to 2: 1, and more preferably 1: 2 to 1: 1.

  A base grease can be obtained by blending a base oil with a diurea compound as a thickener. A base grease using a diurea compound as a thickener is prepared by reacting a diisocyanate component and a monoamine component in a base oil. The blending ratio of the thickener in the base grease is 10% by mass or more and less than 20% by mass.

  The present invention is characterized in that the additive contains neutral Ca sulfonate. Examples of the neutral Ca sulfonate include a calcium salt of petroleum sulfonic acid and a calcium salt of alkyl aromatic sulfonic acid such as dinonylnaphthalene sulfonic acid and alkylbenzene sulfonic acid. These can be used alone or in combination.

  The total base number (TBN) of the Ca sulfonate used in the present invention is less than 10 mgKOH / g, preferably less than 5 mgKOH / g, more preferably less than 3 mgKOH / g, and still more preferably less than 1 mgKOH / g. TBN is measured according to JIS K 2501. TBN is defined as the number of milligrams (mg) of potassium hydroxide equivalent to hydrochloric acid or perchloric acid required to neutralize all basic components contained in 1 g of sample. The measurement of TBN is performed by the perchloric acid method, for example.

  In the present invention, neutral Ca sulfonate is targeted, and overbased Ca sulfonate obtained by uniformly dispersing fine particles such as calcium hydroxide in neutral Ca sulfonate is not targeted. Further, examples of the metal of the metal sulfonate include Ca, Na, Ba, Li, Zn, Pb, Mg, and the like. In the grease composition of the present invention, neutral Ca sulfonate is an essential component. In addition, although the other metal sulfonate may be contained in the grease composition of this invention, it is more preferable that only neutral Ca sulfonate is contained as a metal sulfonate.

  The content of neutral Ca sulfonate in the entire grease composition of the present invention is preferably 0.5 to 3% by mass, more preferably 0.5 to 2% by mass.

  As additives, other known additives can be contained as required. Examples of the additives include amine-based, phenol-based, and sulfur-based antioxidants, chlorine-based, sulfur-based, phosphorus-based compounds, extreme pressure agents such as organic molybdenum, and rust inhibitors such as sorbitan esters. Since the grease composition of the present invention is used under high temperature and high load conditions, it is preferable to contain an antioxidant or an extreme pressure agent. For example, it is preferable to use a combination of a neutral Ca sulfonate, a phosphorus extreme pressure agent, and a sulfur antioxidant as additives. In this case, the content of the additive as a whole is more preferably 5% by mass or less with respect to the entire grease composition.

  The grease penetration (JIS K 2220) is preferably in the range of 200 to 350. When the consistency is less than 200, oil separation is small and there is a risk of poor lubrication. On the other hand, if the consistency exceeds 350, the grease is soft and easily flows out of the bearing, which is not preferable.

  An example of the grease-filled rolling bearing of the present invention is shown in FIG. FIG. 1 is a sectional view of a grease-enclosed rolling bearing (deep groove ball bearing) in which a grease composition is encapsulated. 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, and the inner ring rolling surface 2a and the outer ring rolling surface 3a A plurality of rolling elements 4 are arranged between the two. A cage 5 holds the plurality of rolling elements 4. Further, the axially opposite end openings 8 a and 8 b of the inner and outer rings are sealed by the seal member 6, and the grease composition 7 is sealed at least around the rolling element 4.

  Although FIG. 1 illustrates a deep groove ball bearing as a bearing, the rolling bearing of the present invention is a cylindrical roller bearing, a tapered roller bearing, a self-aligning roller bearing, a needle roller bearing, a thrust cylindrical roller bearing, or a thrust tapered roller other than those described above. It can also be used as a bearing, a thrust needle roller bearing, a thrust spherical roller bearing and the like.

  The grease-enclosed rolling bearing of the present invention is suitable for use under high temperature and high load conditions because the grease composition is encapsulated. Specifically, the high load condition is a condition where the maximum contact surface pressure in the race is 1.5 GPa or more, and preferably 2.0 GPa or more. Specifically, as the high temperature condition, the outer diameter temperature of the bearing outer ring is 80 ° C. or higher, preferably 100 ° C. or higher.

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

<High temperature high load life test>
Each grease composition having the composition shown in Table 1 was sealed in a deep groove ball bearing 6204 (bearing dimensions: inner diameter 20 mm, outer diameter 47 mm, width 14 mm) to produce a test bearing. The obtained test bearing was rotated at a rotational speed of 10000 min ⁻¹ under the conditions of a radial load of 1960 N and a radial load of 3920 N under the outer diameter temperature of the bearing outer ring of 150 ° C. Time was measured. In this test, the maximum contact surface pressure of the race was 2.5 GPa when the radial load was 1960 N and 3.2 GPa when the radial load was 3920 N. In addition, the radial load 1960N passed 200h or more, and the 3920N passed 45h or more. The results are shown in Table 1.

In addition, tests under light load conditions were also conducted as reference data. In this test, the test bearing obtained above was rotated at a rotational speed of 10000 min ⁻¹ under the conditions of the outer diameter temperature of the bearing outer ring of 150 ° C. and the radial load of 67 N, and the time until seizure was reached. It was measured. The maximum contact surface pressure of the raceway was 0.9 GPa. The results are shown in Table 1.

  The result passed only when the grease of Example 1 was used. From Table 1, under high load conditions, when neutral Ca sulfonate was used as an additive as a thickener (Example 1), when neutral Ba sulfonate was used as a metal sulfonate (Comparative Example 1) or metal Compared to the case where sulfonate was not used (Comparative Example 2), the bearing life could be greatly extended. On the other hand, under light load conditions as reference data, the bearing life of neutral Ca sulfonate and neutral Ba sulfonate was reversed. That is, in this light load condition test, the grease composition containing neutral Ba sulfonate as an additive has a longer bearing life than the grease composition containing neutral Ca sulfonate.

  Since the grease composition of the present invention is suitable for rolling bearings used under high temperature and high load conditions and has excellent life time, it is widely used as grease for grease-filled roller bearings used under such conditions.

DESCRIPTION OF SYMBOLS 1 Rolling bearing 2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Seal member 7 Grease composition 8a, 8b Opening part

Claims (5)

A grease composition comprising a base oil, a thickener and an additive,
The base oil is based on poly-α-olefin oil,
The thickener is one or more diurea compounds selected from the group consisting of alicyclic diurea compounds, aromatic diurea compounds, and aliphatic diurea compounds;
The grease composition, wherein the additive contains neutral Ca sulfonate.   2. The grease composition according to claim 1, wherein the neutral Ca sulfonate is contained in an amount of 0.5 to 3 mass% with respect to the entire grease composition.   The grease composition according to claim 1 or 2, wherein the thickener is a mixture of an alicyclic diurea compound and an aromatic diurea compound. Grease used under high temperature and high load conditions, comprising inner and outer rings that are raceways, a plurality of rollers that roll between the inner and outer rings, and a grease composition sealed around the rollers Encapsulated rolling bearing,
A grease-filled rolling bearing, wherein the grease composition is the grease composition according to any one of claims 1 to 3.   5. The grease-filled rolling bearing according to claim 4, wherein the high load condition is that the maximum contact surface pressure of the raceway is 2.0 GPa or more.

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