JP2007084779A - Grease composition and rolling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition exhibiting excellent lubricity over a low temperature of about -40°C and a high temperature near to 200°C; and to provide a rolling device obtained by sealing the grease composition, acting well in the above temperature range, and exhibiting a long life even at the high temperature near to 200°C. <P>SOLUTION: The grease composition contains a base oil containing ≥50 mass% diphenyl ether oil having two branched alkyl side chains based on the whole base oil. The rolling device is obtained by sealing the grease composition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is, for example, an automotive electrical component such as an alternator, an electromagnetic clutch, an automobile engine accessory such as an idler pulley, an idle speed control device, an exhaust gas recirculation device, a fuel injection control device such as an electronic throttle control device, etc. The present invention relates to a rolling device suitable for a rotating part or auxiliary part of equipment used at high speed, and a grease composition enclosed in the rolling device.

  Automobiles are forced to reduce the engine room space due to demands for smaller size and lighter living space, and further miniaturization of electrical components and engine accessories has been promoted. In addition, since the sealing of the engine room is progressed due to a demand for improvement in quietness and the high temperature in the engine room is promoted, it is also important that each of the above components can withstand high temperatures. Conventionally, it has been used at a bearing temperature of 130 to 150 ° C. However, in recent years, a bearing that can withstand a high temperature of 160 to 180 ° C. has been required.

  Conventionally, bearings of 160 ° C. or lower have been dealt with by encapsulating grease containing, for example, linear alkyl side chain diphenyl ether-based lubricating oil in which α-olefin is added to diphenyl ether (see, for example, Patent Documents 1 and 2). . However, since these greases also seize early at a high temperature of 160 ° C. or higher, a grease with higher heat resistance is required. In terms of low temperature characteristics, fluidity is insufficient in an extremely low temperature environment of about −40 ° C., and abnormal noise may occur in the bearing.

  In order to improve heat resistance and low-temperature properties, for example, polytetrafluoroethylene (PTFE) is blended in a thickener, and a fluorine-based grease based on perfluoropolyether oil is enclosed, so that the temperature is 160 ° C. or higher. It is known that the bearing can be used even in an environment. However, it is difficult to add an additive blended with a general grease, and the fluorine-based grease tends to be inferior in lubricity, rust prevention, and metal corrosion performance. Further, there is a problem that the fluorine-based grease is about 5 to 20 times more expensive than the synthetic grease.

  In addition, a grease composition in which a fluorine-based grease is mixed with urea grease to improve heat resistance is also known (see, for example, Patent Document 3). However, since mineral oil or synthetic oil, which is a base oil of urea grease, has poor affinity with fluorine oil, the grease composition has a large oil separation and is not suitable for bearings for parts rotating at high speed. There was a problem.

  Furthermore, there is a high demand for high temperature durability even in rolling bearings used in automobile fuel injection control devices such as idle speed control devices, exhaust gas recirculation devices, and electronic throttle control devices. Further, the rolling bearing for the fuel injection control device is also required to have low temperature torque performance. Therefore, conventionally, lithium soap-ester oil grease, urea-synthetic hydrocarbon oil grease, etc. are enclosed as lubricants, and synthetic oil is used as a base oil to satisfy high temperature durability and low temperature torque performance. I came. When the demand for low-temperature torque performance is particularly strong, lubricating oil such as ester oil or fluorine oil has been used to cover the performance.

  However, in recent years, performance requirements for rolling bearings used in the fuel injection control device have become stricter. For example, in an exhaust gas recirculation device, in order to further reduce NOx contained in engine exhaust gas, The exhaust gas is recirculated, and the rolling bearing used therein is placed at a high temperature close to 200 ° C. Accordingly, it has become impossible to maintain high-temperature durability with lithium soap-ester oil grease, urea-synthetic hydrocarbon oil grease, or lubricating oil such as ester oil or fluorine oil, which has been encapsulated in the past. From this point of view, the present applicant has previously proposed a rolling bearing in which grease containing fluorine resin particles as a thickener is encapsulated in a base oil having a specific viscosity composed of a perfluoropolyether oil having a linear structure. (See Patent Document 4).

Japanese Patent No. 2764724 Japanese Patent No. 2965794 Japanese Patent Laid-Open No. 11-181465 JP 2000-119673 A

  The present invention has been made in view of the above situation, and includes a grease composition exhibiting excellent lubricity from a low temperature of about −40 ° C. to a high temperature close to 200 ° C., and the grease composition, An object of the present invention is to provide a rolling device that operates well in a region and has a long life even at a high temperature close to 200 ° C.

In order to achieve the above object, the present invention provides the following grease composition and rolling device.
(1) A grease composition comprising a base oil containing a branched alkyl side chain diphenyl ether oil represented by the general formula (I) in a proportion of 50% by mass or more of the total amount of the base oil, and a thickener.

[In the formula (I), one of R1, R2 and R3 is a hydrogen atom, and the remaining two are the same or different branched alkyl groups. ]
(2) The grease composition as described in (1) above, which comprises a linear alkyl side chain diphenyl ether represented by the general formula (II).

[In the formula (II), one of R4, R5 and R6 is a hydrogen atom, and the other two are the same or different linear alkyl groups. ]
(3) The grease composition as described in (1) or (2) above, wherein the base oil has a kinematic viscosity at 40 ° C. of ²⁰ to 500 mm ² / s.
(4) The grease composition as described in any one of (1) to (3) above, wherein the penetration is 220 to 385.
(5) In a rolling device comprising an inner member, an outer member, and a plurality of rolling elements that are arranged to roll between the inner member and the outer member, The grease composition according to any one of the above (1) to (4) is filled in a gap formed between a member and the outer member and in which the rolling element is provided. Rolling device to do.
(6) The rolling device according to (5), which is incorporated in a fuel injection control device of a vehicle.

  The grease composition of the present invention uses a base oil containing 50% by mass or more of the branched alkyl side chain diphenyl ether oil based on the total amount of the base oil, so that the low temperature characteristics and the high temperature characteristics are greatly improved. The apparatus operates well from a low temperature of about −40 ° C. to a high temperature close to 200 ° C. and has a long life.

  Hereinafter, the present invention will be described in detail.

  In the grease composition of the present invention, the base oil contains a branched alkyl side chain diphenyl ether oil represented by the general formula (I) in a proportion of 50% by mass or more of the total amount of the base oil.

  In the formula (I), one of R1, R2, and R3 is a hydrogen atom, and the remaining two are the same or different branched alkyl groups. In the branched alkyl group, the carbon number is preferably 10 to 26, more preferably 12 to 24. In the branched alkyl group having more than 26 carbon atoms, the pour point is increased and the fluidity at low temperature becomes poor, which causes a problem in use. Moreover, in the case of a branched alkyl group having less than 10 carbon atoms, the amount of evaporation becomes large, causing a problem in use.

  Of the branched alkyl groups, a branched decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group and the like are preferable.

  The base oil may be used in combination with a linear alkyl side chain diphenyl ether represented by the general formula (II).

  In the formula (II), one of R4, R5 and R6 is a hydrogen atom, and the other two are preferably straight chain alkyl groups having 8 to 20 carbon atoms, more preferably 12 to 14 carbon atoms. In the case of a linear alkyl group having more than 20 carbon atoms, the pour point is increased and the fluidity at low temperature is poor, which causes a problem in use. Moreover, in the case of a linear alkyl group having less than 8 carbon atoms, the amount of evaporation increases, which causes a problem in use.

The base oil may be mixed with a lubricating oil other than the linear alkyl side chain diphenyl ether. As the other lubricating oil, it is preferable to use at least one of an ester synthetic oil and a polyalphaolefin oil. Examples of ester synthetic oils include diesters such as di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, polyol esters such as trimethylolpropane caprylate, pentaerythritol-2-ethylhexanoate, and trioctyl. Examples include trimellitic acid esters such as trimellitate and tridecyl trimellitate, and aromatic ester oils of pyromellitic acid esters such as tetraoctyl pyromellitate. The poly α-olefin oil is preferably one represented by the following general formula (III) or (IV).
_{CH 3 - (CH 2) n} -CH = CH 2 (III)
_{H- (CH 2 -CHR7) m-} H (IV)

  (III) n in a formula is an integer of 5-9, Preferably it is n = 8. R7 in the formula (IV) is an alkyl group, and two or more different alkyl groups may be mixed in the molecule, but all are preferably n-octyl groups. Moreover, m is an integer of 3-8.

The base oil preferably has a kinematic viscosity at 40 ° C. of ²⁰ to 500 mm ² / s. If the kinematic viscosity at 40 ° C. exceeds 500 mm ² / s, the torque of the rolling device will increase too much, and the fluidity at low temperature will be insufficient, and noise will be generated when the rolling device is started at low temperature. May occur. Further, if the kinematic viscosity at 40 ° C. is less than 20 mm ² / s, there is a concern about evaporation loss and lubricity problems. For example, sufficient lubrication to avoid metal contact between the raceway surface and the rolling element during rotation of the bearing at high temperature. Oil film formation may be difficult. From such a point, the kinematic viscosity at 40 ° C. of the base oil is more preferably 30 to 400 mm ² / s.

  The thickener can be used without limitation as long as it is a substance that is colloidally dispersed in the above base oil to make the base oil semi-solid or solid. Examples of such a thickener include lithium soap, calcium soap, sodium soap, aluminum soap, lithium complex soap, calcium complex soap, sodium complex soap, barium complex soap, and aluminum complex soap. And metal based soaps, bentonite, clay based inorganic compounds, monourea based, diurea based, triurea based, tetraurea based, urethane based, sodium terephthalate based organic compounds, and the like. Among these, a urea system can be preferably used. These thickeners may be used alone or in combination of two or more.

  The content of the thickener is 3 to 40% by mass of the total amount of grease, and preferably 5 to 25% by mass is dispersed in the base oil. If the amount is less than 3% by mass, it is difficult to maintain the grease state, and if it exceeds 40% by mass, the grease composition becomes too hard to exhibit a sufficient lubrication state.

  The penetration is preferably in the range of 220 to 395, more preferably in the range of 265 to 350 in terms of penetration. If the penetration is less than 220, the grease composition becomes too hard and a sufficient lubricating effect cannot be expected. If it is greater than 395, the grease composition is too soft and may leak from the bearing.

  In order to further improve the various performances, the grease composition may be mixed with various additives as desired. For example, antioxidants such as amines such as phenyl-1-naphthylamine, phenols such as 2,6-di-tert-dibutylphenol, sulfurs and zinc dithiophosphate; organic sulfones such as alkali metals and alkaline earth metals Rust preventive agents such as acid, alkyl, alkenyl succinic acid esters such as alkyls, alkenyl succinic acid derivatives, partial esters of polyhydric alcohols such as sorbitan monooleate; extreme pressure agents such as phosphorus, zinc dithiophosphate and organic molybdenum Oiliness improvers such as fatty acids and animal and vegetable oils; metal deactivators such as benzotriazole and the like can be added alone or in admixture of two or more. In addition, the addition amount of these additives will not be specifically limited if it is a grade which does not impair the objective of this invention.

  In addition, the manufacturing method of a grease composition is not specifically limited.

  The grease composition exhibits excellent lubricating performance from a low temperature of about −40 ° C. to a high temperature close to 200 ° C. at the application site, as shown in the examples described later. Therefore, for example, automotive electrical components such as alternators, electromagnetic clutches, automotive engine accessories such as idler pulleys, idle speed control devices, exhaust gas recirculation devices, fuel injection control devices such as electronic throttle control devices, etc. It can be suitably used for rotating parts and sliding parts of equipment used at high temperatures and high speeds.

  The present invention also relates to a rolling device in which the above grease composition is enclosed. Examples of the rolling device include a rolling bearing, a ball screw, a linear guide device, and a linear motion bearing.

  FIG. 1 is a longitudinal sectional view showing a structure of a ball bearing which is an embodiment of a rolling device. The ball bearing 1 includes an inner ring 10 that is an inner member, an outer ring 11 that is an outer member, a plurality of balls 13 that are rotatably disposed between the inner ring 10 and the outer ring 11, and a plurality of balls. 13, and a contact type seal 14, 14 attached to the outer ring 11. The bearing space surrounded by the inner ring 10, the outer ring 11, and the seals 14 and 14 is filled with the above grease composition G, and is sealed in the ball bearing 1 by the seal 14. The contact surface between the raceway surfaces of the wheels 10 and 11 and the balls 13 is lubricated by the grease composition G.

  As the rolling bearing, in addition to the ball bearing, for example, a radial rolling bearing such as an angular ball bearing, a self-aligning ball bearing, a cylindrical roller bearing, a tapered roller bearing, a needle roller bearing, or a self-aligning roller bearing. Thrust-type rolling bearings such as bearings, thrust ball bearings, thrust roller bearings and the like can be mentioned, and the above grease composition is similarly encapsulated.

  In other rolling devices, the inner member means a screw shaft in the case of a ball screw, a guide rail in the case of a linear guide device, and a shaft in the case of a linear motion bearing. The outer member means a nut in the case of a ball screw, a slider in the case of a linear guide, and an outer cylinder in the case of a linear motion bearing. The above grease composition is similarly encapsulated in these rolling devices.

  EXAMPLES The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

(Examples 1-5, Comparative Examples 1-2)
As shown in Tables 1 and 2, urea greases having different base oil compositions were prepared and used as test greases. Each test grease has 2 mass% amine-based antioxidant, 1 mass% calcium sulfonate anticorrosive and 0.05 mass% benzotriazole as additives. A system metal deactivator is added.

  In each test grease, the contents of the base oil and the thickener are values when the total amount of the base oil and the thickener is 100, and the above additives are not considered. Moreover, the numerical value described in the column of the kind of base oil has shown the quantity ratio (mass%) of each component in the whole base oil.

Using the above test greases, the following seizure tests were performed. The results are shown in Tables 1 and 2.
• Seizure test A deep groove ball bearing with an inner diameter of 8 mm, an outer diameter of 22 mm, and a width of 7 mm (same structure as in Fig. 1) is filled with each test grease to occupy 50% of the bearing space volume. 2 was installed in a testing machine similar to the ASTM D1741 bearing life testing machine as shown in FIG. Then, the inner ring is rotated at a rotational speed of 3000 min ⁻¹ under conditions of a bearing temperature of 180 ° C. and an axial load of 98 N (other conditions conform to ASTM D1741), and seizure occurs and the temperature of the outer ring rises to 190 ° C. or higher. The time until (burn-in time) was measured. The results are shown as relative values with the seizure time of Comparative Example 2 as 1.

  As shown, good seizure life can be obtained by encapsulating each test grease of Examples 1 to 5 according to the present invention.

(Examples 6 to 10, Comparative Examples 3 to 5)
As shown in Tables 3 and 4, urea greases having different base oil compositions were prepared and used as test greases. Each test grease has 2 mass% amine-based antioxidant, 1 mass% calcium sulfonate anticorrosive and 0.05 mass% benzotriazole as additives. A system metal deactivator is added.

  In each test grease, the contents of the base oil and the thickener are values when the total amount of the base oil and the thickener is 100, and the above additives are not considered. Moreover, the numerical value described in the column of the kind of thickener and the kind of base oil has shown the quantity ratio (mass%) of each component in a thickener and the whole base oil.

The following tests were conducted using the above test greases. The results are shown in Tables 3 and 4.
(1) Seizure test Each test grease occupies 50% of the bearing space volume on an iron shielded deep groove ball bearing with an inner diameter of 8 mm, an outer diameter of 22 mm, and a width of 7 mm (having the same structure as FIG. 1). Filled and mounted in a tester similar to ASTM D1741 bearing life tester as shown in FIG. Then, the inner ring is rotated at a rotational speed of 3000 min ⁻¹ under conditions of a bearing temperature of 180 ° C. and an axial load of 98 N (other conditions conform to ASTM D1741), and seizure occurs and the temperature of the outer ring rises to 190 ° C. or higher. The time until (burn-in time) was measured. The results are shown as relative values with the seizure time of Comparative Example 4 as 1.
(2) Low temperature torque test A deep groove ball bearing with an inner diameter of 8 mm, an outer diameter of 22 mm, and a width of 7 mm with a steel seal (substantially the same structure as in FIG. 1, but the cage is a press cage). It filled so that 30% of space volume might be occupied. After this ball bearing was placed in a high temperature bath at −40 ° C. for 4 hours, the inner ring was rotated at a rotation speed of 100 min ⁻¹ for 10 minutes, and the dynamic torque of the ball bearing during rotation was measured. The results are indicated by ◎ when the dynamic torque value is 20 N · cm or less, ◯ when it is more than 20 N · cm and 25 N · cm or less, and × when it is more than 25 N · cm.

  As shown, good seizure life and low temperature characteristics can be obtained by encapsulating each of the test greases of Examples 6 to 10 according to the present invention.

It is a longitudinal section showing the structure of the ball bearing which is one embodiment of the rolling device concerning the present invention. It is sectional drawing which shows the structure of the bearing life tester used for the seizure test in the Example.

Explanation of symbols

1 Ball Bearing 10 Inner Ring 11 Outer Ring 13 Ball G Grease Composition

Claims (6)

A grease composition comprising a base oil containing a branched alkyl side chain diphenyl ether oil represented by the general formula (I) in a proportion of 50% by mass or more of the total amount of the base oil, and a thickener.

[In the formula (I), one of R1, R2 and R3 is a hydrogen atom, and the remaining two are the same or different branched alkyl groups. ] The grease composition according to claim 1, comprising a linear alkyl side chain diphenyl ether represented by the general formula (II).

[In the formula (II), one of R4, R5 and R6 is a hydrogen atom, and the other two are the same or different linear alkyl groups. ] The grease composition according to claim 1, wherein the base oil has a kinematic viscosity at 40 ° C. of ²⁰ to 500 mm ² / s.   The grease composition according to any one of claims 1 to 3, wherein the penetration is 220 to 385.   A rolling device comprising: an inner member; an outer member; and a plurality of rolling elements that are freely rollable between the inner member and the outer member. A rolling device, wherein the grease composition according to any one of claims 1 to 4 is filled in a gap formed between the outer member and the rolling element.   The rolling device according to claim 5, wherein the rolling device is incorporated in a fuel injection control device of a vehicle.

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