JP2007077244A - Grease composition and rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition and a rolling bearing which have a good enough heat resistance to be serviceable in a severe high temperature environment of over 180°C, exhibit excellent lubrication and load bearing performances and are suitable for use particularly in automobile electric equipment and engine auxiliaries exposed to the environment described above. <P>SOLUTION: The base oil of the grease composition is a mixture of a polyphenyl ether and a hindered ester. The thickener is a lithium soap, a lithium complex soap or a diurea compound. The grease composition contains 0.1-10 mass% of a phosphate and 0.5-10 mass% of a hindered amine to the base oil. The rolling bearing is filled with the grease composition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is, for example, an electrical component for automobiles, an alternator that is an engine auxiliary machine, an intermediate pulley, an electromagnetic clutch for a car air conditioner, and the like, and a grease composition that is suitable for parts used at high temperatures and high speeds. It is related with the rolling bearing suitable for.

  Due to the spread of FF vehicles aimed at reducing the size and weight of automobiles, and due to the demand for expanding the living space, the engine room space has been reduced, and the above-mentioned electrical components and engine accessories have been reduced in size and weight. Further progress is being made, and higher performance and higher output are increasingly required for the components incorporated in the system. However, a reduction in output is unavoidable due to miniaturization, and for example, an alternator and an electromagnetic clutch for a car air conditioner compensate for the reduction in output by increasing the speed, and accordingly, the intermediate pulley is also increased in speed. Furthermore, since the engine room is being sealed due to a demand for improvement in quietness and the high temperature in the engine room is promoted, these parts are also required to withstand high temperatures.

  In addition, electric parts and engine auxiliary machines are required to be smaller and lighter and to be rotated at higher speeds. On the other hand, demands for resource saving and energy saving are high, and maintenance-free is also demanded. For this reason, rolling bearings to be incorporated are also required to have reliability and durability in addition to heat resistance. Specifically, it may be used in an environment where the bearing temperature exceeds 180 ° C., and in order to withstand such a high temperature environment, the present applicant also encloses a grease composition previously blended with a clay mineral. (For example, refer patent documents 1-3). In addition, as a grease composition considering heat resistance, a mixed oil of a polyol ester oil and an alkylphenyl ether oil is used as a base oil, and a dialkyldithiocarbamate compound and a hindered phenol compound are added as an antioxidant. Some are also known (see, for example, Patent Document 4).

JP 2002-250353 A JP 2003-42166 A JP 2004-2696 A JP-A-8-188790

  Although the clay mineral greases and synthetic oil greases listed above are excellent in heat resistance, there is room for improvement in lubricity and load resistance. Therefore, the present invention has heat resistance that can withstand use even in a severe high temperature environment exceeding 180 ° C., and is excellent in lubrication performance and load resistance, particularly in the above-described automobile electrical parts and engine accessories. It is an object of the present invention to provide a suitable grease composition and a rolling bearing.

In order to achieve the above object, the present invention provides the following grease composition and rolling bearing.
(1) A mixed oil of polyphenyl ether and a hindered ester is used as a base oil, a lithium soap, a lithium complex soap or a diurea compound is used as a thickener, and phosphites are used in an amount of 0. A grease composition comprising 1 to 10% by mass and hindered amines in a proportion of 0.5 to 10% by mass.
(2) The above characterized in that the base oil contains a hindered ester in a proportion of 5 to 20% by mass of the total amount of the base oil, and the kinematic viscosity of the base oil at 40 ° C. is 15 to 100 mm ² / s. (1) The grease composition as described.
(3) A rolling bearing comprising the grease composition as described in (1) or (2) above.

  In the grease composition of the present invention, both polyphenyl ether and hindered ester constituting the base oil have excellent heat resistance, and excellent oxidation is achieved by adding phosphite esters and hindered amines in combination. Prevention performance is added, and the heat resistance of the entire grease composition is further improved. Furthermore, since the hindered ester has an effect of suppressing the precipitation of the additive, the solubility of the phosphites and hindered amines in the base oil is increased, and the antioxidant performance is further enhanced. Moreover, lubricity and abrasion resistance are also improved by using polyphenyl ether and a hindered ester in combination. Thus, the grease composition of the present invention has both excellent heat resistance and lubricity and load resistance.

  In addition, the rolling bearing of the present invention is sealed with the above grease composition, so that it has excellent heat resistance, lubrication performance and load resistance, and can be used at high temperatures and high speeds such as automotive electrical parts and engine accessories. Can be suitably used for applications used in

  Hereinafter, the present invention will be described in detail.

  In the grease composition of the present invention, a mixed oil of polyphenyl ether and hindered ester is used as the base oil. Polyphenyl ether is a lubricating oil with extremely excellent heat resistance, as used in automotive ceramic turbines, turbo engines, cogeneration engines, jet engines, and the like. In the present invention, known polyphenyl ethers can be used including those for the above applications.

  Hindered esters also have excellent heat resistance, although not as much as polyphenyl ethers. Moreover, since this hindered ester has the effect of suppressing the precipitation of additives, the solubility of various additives, including phosphites and hindered amines, in base oils is improved, and the effects of the additives are stable. Then it will be expressed. The hindered ester is an ester of a polyhydric alcohol and a fatty acid (including a polyvalent carboxylic acid), and a wide variety is known depending on the combination of both. In the present invention, although not particularly limited, esters having a neopentyl skeleton such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, complex esters, and the like can be preferably used. However, since the complex ester has a high viscosity, a polyol ester other than the complex ester is more preferable in consideration of the high-speed application intended by the present invention.

  The blending ratio of the polyphenyl ether and the hindered ester is preferably such that the hindered ester is 5 to 20% by mass of the total amount of the base oil. When the hindered ester exceeds 20% by mass of the total amount of the base oil, the content of polyphenyl ether is relatively reduced and the intended heat resistance cannot be obtained. On the other hand, when the hindered ester is less than 5% by mass of the total amount of the base oil, the effect of preventing precipitation of the additive is not sufficient, and the effect of the additive including the antioxidant effect cannot be stably obtained.

The base oil composed of the mixed oil of the polyphenyl ether and the hindered ester desirably has a low viscosity in consideration of high-speed use, and preferably has a kinematic viscosity at 40 ° C. of 15 to 100 mm ² / s. Selection of polyphenyl ether and hindered ester and adjustment of the blending ratio within the above range are performed so as to achieve such kinematic viscosity.

  In order to improve the antioxidant performance, phosphites and hindered amines are added to the base oil. For antioxidants, it is known that it is effective to use a primary antioxidant that traps the generated radicals and a secondary antioxidant that decomposes the generated peroxides and converts them into inert substances. Yes. In the present invention, hindered amines function as primary antioxidants, and phosphites function as secondary antioxidants. By using these in combination, an excellent antioxidant effect can be obtained. In addition, since hindered amines have light resistance (light resistance), the grease composition of the present invention can also be prevented from being deteriorated by ultraviolet rays or the like.

  Phosphites include tris (nonyl phenyl) phosphite, tris (mixed mono- and di-nonylphenyl) phosphite, diphenyl mono (2-ethylhexyl) phosphite, triisodecyl phosphite, diphenyl iso Decyl phosphite, tetraphenyltetra (tridecyl) pentaerythritol tetraphosphite and the like can be suitably used.

  Further, as hindered amines, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate represented by the following formula (1), bis (1,2,2, represented by the following formula (2) 6,6-pentamethyl-4-piperidyl) sebacate, tetraxy (2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate represented by the following formula (3), Decandioic acid bis (2,2,6,6-tetramethyl-1 (octyloxy) -4-piperidinyl ester, 1,1-dimethylhydroxyperoxide, and the like represented by the following formula (4) can be preferably used.

  The addition amount of phosphites and hindered amines is 0.1 to 10% by mass, more preferably 0.3 to 2% by mass, based on the total amount of the base oil. If the addition amount is less than 0.1% by mass, a sufficient antioxidant effect cannot be obtained, and adding more than 10% by mass not only saturates the effect but also deteriorates the thermal stability, which is not practical. .

  As the thickener, any of lithium soap, lithium complex soap and diurea compound may be used, but diurea compound having excellent heat resistance is preferable in view of durability at high temperature.

  The blending amount of the thickener is not limited as long as it can form a gel structure with the base oil, but is preferably 5 to 30% by mass of the total amount of the grease composition. Further, the blending degree of the grease composition is preferably 200 to 350.

  The grease composition of the present invention may contain various additives in addition to the above-mentioned blend depending on the purpose. For example, a rust inhibitor and an antiwear agent can be added so that it may become 1-10 mass% of the grease composition whole quantity.

  There is no limitation on the method of preparing the grease composition. For example, the grease composition is increased in a base oil in which polyphenyl ether and hindered ester are mixed at a predetermined ratio and a predetermined amount of phosphites and hindered amines are added. What is necessary is just to synthesize | combine a funnel and add another additive as needed and to stir with a kneader or a roll mill. At this time, heating is also effective.

  The present invention also provides a rolling bearing in which the above grease composition is enclosed. There are no restrictions on the structure and type of rolling bearings, but the above grease composition has excellent heat resistance in addition to lubricity and wear resistance, so rolling bearings used in high temperature and high speed environments are suitable. It is. For example, rolling bearings incorporated in electrical components of automobiles, alternators and intermediate pulleys that are engine auxiliary machines, electromagnetic clutches for car air conditioners, and the like can be exemplified.

(Examples 1-6, Comparative Examples 1-4)
As shown in Table 1, a test grease was prepared by blending a base oil, a thickener and an additive. The blending amount is a value relative to the total amount of grease. Moreover, “S-3103” (tetraphenyl ether, 120 mm ² / s @ 40 ° C.) manufactured by Matsumura Oil Research Co., Ltd. is used as polyphenyl ether, and “Unistar H-” manufactured by Nippon Oil & Fats Co., Ltd. is used as a hindered ester. 334R "(20 mm ² / s @ 40 ° C) was used. PAO is a polyalphaolefin oil and PFPE is a perfluoropolyether oil. Moreover, tris (nonyl phenyl) phosphite (manufactured by Asahi Denka Co., Ltd.) was used as the phosphite, and bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate (Sankyo ( "Sanol LS-770" manufactured by the same company) was used.

Each test grease was subjected to the following (1) heat resistance test, (2) wear resistance test, and (3) seizure life test.
(1) Heat resistance test About 10 g of test grease was placed in a petri dish, and placed in a constant temperature bath at 180 ° C. for 100 hours. After standing, the evaporation amount and total acid value of the test grease were measured. The results are shown in Table 1.
(2) Abrasion resistance test A test grease is applied on a mirror-finished flat plate, and a bearing steel ball having a diameter of 10 mm is placed thereon. At an ambient temperature of 80 ° C., an amplitude of 0.7 mm and a vibration frequency of 10 Hz are applied while applying a load of 59 N. After rocking for 10 minutes, the trace diameter of the flat plate due to wear was measured. The test was performed 3 times, and the average value was obtained. The results are shown in Table 1.
(3) Seizure life test Test grease is sealed in a ball bearing with heat-resistant rubber seal “6305 (outer diameter 62 mm, inner diameter 25 mm, width 17 mm)” manufactured by NSK Ltd. so as to be 30% of the space volume. A test bearing was prepared. When the test bearing is continuously rotated under the conditions of an outer ring temperature of 180 ° C., a radial load of 98 N, an axial load of 98 N, and an inner ring rotational speed of 10000 min ⁻¹ , a seizure life occurs when a temperature rise and a torque rise (motor current value) occur. And time until that time was measured. The test was performed 3 times, and the average value was obtained. The results are shown in Table 1 as relative values with the result of Comparative Example 1 being 1.

  As shown in Table 1, according to the present invention, a mixed oil of polyphenyl ether and hindered ester is used as a base oil, and by adding both phosphites and hindered amines, heat resistance, wear resistance and Excellent seizure resistance. On the other hand, as in Comparative Examples 1 and 2, even if a mixed oil of polyphenyl ether and hindered ester is used as the base oil, it does not contain both phosphite esters and hindered amines. Inferior and the seizure life is shortened. In addition, as in Comparative Examples 3 and 4, even when both phosphites and hindered amines are added, if the base oil is not a mixed oil of polyphenyl ether and hindered ester, heat resistance and wear resistance And inferior to all of seizure resistance.

Claims (3)

  A mixed oil of polyphenyl ether and hindered ester is used as a base oil, lithium soap, lithium complex soap or diurea compound is used as a thickener, and phosphites are added in an amount of 0.1 to 10 with respect to the total amount of the base oil. A grease composition containing 0.5% by mass and 0.5% by mass of hindered amines. The base oil contains a hindered ester in a proportion of 5 to 20% by mass of the total amount of the base oil, and the kinematic viscosity at 40 ° C of the base oil is 15 to 100 mm ² / s. Grease composition.   A rolling bearing comprising the grease composition according to claim 1 or 2 enclosed therein.