JPH09217752A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing, the baking life of which is prolonged by inserting a grease composite containing a base oil, an ura group thickening agent, and fine particles consisting of inorganic compounds, the average particle size of which is specified. SOLUTION: The base oil for a grease to be inserted into a bearing is not specially specified. The oil which are usually used as base oils for lubricating oil can be all adopted. An urea-compound group thickening agent forms a gel- structure, and the thickening agent which has the ability to hold a base oil in its gel-structure, can be adopted without special limitations. The composition of the fine particles consisting of inorganic compounds can be merely one material for reinforcing the gel-structure formed by the thickening agent, and there is no limitation to the composition. The particle size which is smaller, is preferable, since it is necessary for the particles to enter between fibers of the thickening agent. When the average particle size is 1μm or less, most good baking effect is confirmed, and when the average particle size is 2μm or more, the number of grains which act as foreign matters, is increased. This promotes the wear on the bearing races or the surface of rolling elements to cause early damage to the bearing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hermetically sealed rolling bearing filled with grease, and more particularly to alternators, electromagnetic clutches for car air conditioners, intermediate pulleys, electric fan motors, electric motor parts such as water pumps, high temperature parts for engine accessories, etc. The present invention relates to a sealed rolling bearing used at high speed rotation.

[0002]

2. Description of the Related Art Rotational motion parts of automobiles and various power plants,
For example, sealed rolling bearings filled with grease are generally used for alternators, electromagnetic clutches for car air conditioners, intermediate pulleys, electric fan motors, water pumps, and other automotive electrical components and engine accessories. FIG. 1 is a sectional view of a main part of a sealed deep groove ball bearing with a contact rubber seal, which is a kind of hermetically sealed rolling bearing. As shown, an inner ring 2 having an inner ring raceway 1 on the outer peripheral surface and an outer ring on the inner peripheral surface. An outer ring 4 having a raceway 3 is arranged concentrically, and a plurality of rolling elements (balls) 5 are rotatably provided between an inner raceway 1 and an outer raceway 3 via a cage 7. . In addition, the outer peripheral edges of circular ring-shaped seals 6 are respectively locked to the inner peripheral surfaces of both ends of the outer ring 4, and grease (not shown) is contained by the both seals 6, and dust from the outside enters or inside the bearing. The generated dust is prevented from leaking to the outside.

In addition, an automobile has an F
With the widespread use of F cars, and the desire to expand living space,
The reduction of the engine room space is unavoidable, and the electrical components and engine accessories mentioned above are being made smaller and lighter. In addition, high performance and high output are increasingly demanded for each of the above components. However, downsizing is inevitable due to downsizing.For example, in electromagnetic clutches for alternators and car air conditioners, increasing the speed compensates for the decrease in the output. Become. Further, due to the demand for quietness improvement, the engine room is hermetically sealed, and the temperature rise in the engine room is promoted. Therefore, it is also necessary for each of the above parts to be able to withstand high temperatures. In addition, the load applied to the bearing is also increasing due to the higher tension of the drive belt.

Accordingly, the grease filled in the rolling bearings used for the above-mentioned parts has a long peeling life and a long grease life, and is excellent in torque performance and rust prevention performance.
In addition, it is required that the bearing acoustic performance be excellent, and as the grease that meets these requirements, a grease that uses synthetic oil with excellent heat resistance as a base oil and mixes it with a urea compound as a thickener is currently the mainstream. Has become.

[0005]

As described above, there is an ever-increasing demand for high-temperature and high-speed rotation durability of rolling bearings used for electrical components and accessories, and the seizure life of bearings is further increased. There is a particular need for improvement. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rolling bearing having a longer seizure life than ever before.

[0006]

[Means for Solving the Problems] In a rolling bearing in which grease is sealed, the grease is splashed off by the seal or the shield, so that a small amount of grease existing near the raceway or the cage contributes to lubrication of the bearing, and It almost determines the seizure life. Then, as a result, the very small amount of grease that adheres to this track or cage or that is present in the vicinity of them becomes oxidatively deteriorated or hardens, resulting in reduced fluidity, resulting in insufficient lubrication and easy wear, leading to a seizure life. . As a result of repeated studies on the seizure phenomenon of rolling bearings, the present inventors have found that it is effective to disperse fine particles of an inorganic compound in grease in order to suppress the above phenomenon. The present invention is based on the above findings. That is, the above object is characterized in that a grease composition containing the base oil of the present invention, a urea thickener, and fine particles of an inorganic compound having an average particle diameter of 2 μm or less is enclosed. Achieved by bearings.

In the rolling bearing according to the present invention, the fine particles are dispersed in the grease to be encapsulated, and even if a large shear stress due to high speed rotation is applied, the grease film between the contact surfaces of the rolling elements and the raceways is formed. It is considered that the retention of the film is ensured by the intervening fine particles, and the seizure is extended in order to prevent metal contact. Further, by using a urea compound as the thickener, the heat resistance is improved and the anti-seizure effect is further improved.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The rolling bearing of the present invention will be described in more detail below. The grease filled in the rolling bearing of the present invention is configured as follows. [Base oil] The base oil is not particularly limited, and any oil that is usually used as a base oil for lubricating oil can be used. Preferably, the kinematic viscosity at 40 ° C. is preferably 10 to 400 in order to avoid an increase in starting torque due to lack of low-temperature fluidity and seizure that occurs when an oil film is difficult to form at high temperatures.
mm ² / s, particularly preferably 20-250 mm ² / s,
More preferably, a base oil of 40 to 150 mm ² / s is desirable. This kinematic viscosity can be based on the value measured usually by a glass capillary viscometer. Also,
In order to extend the bearing lubricating life, it is desirable to contain ester oil, particularly polyol ester oil, in an amount of 10 wt% or more of the base oil.

Specific examples include mineral oil-based, synthetic oil-based or natural oil-based lubricating base oils. As the mineral oil-based lubricating base oil, use one obtained by appropriately combining mineral oil under reduced pressure distillation, solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay refining, hydrorefining and the like. You can Examples of the synthetic oil-based lubricating base oil include hydrocarbon-based oils, aromatic-based oils, ester-based oils and ether-based oils. Examples of the hydrocarbon-based oil include normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, poly-α-olefins such as 1-decene / ethylene cooligomers, and hydrides thereof. Examples of the aromatic oil include alkylbenzene such as monoalkylbenzene, dialkylbenzene and polyalkylbenzene, and alkylnaphthalene such as monoalkylnaphthalene, dialkylnaphthalene and polyalkylnaphthalene. Examples of the ester oil include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, diester such as methyl acetylricinoleate, or trioctyl trimellitate, Aromatic ester oils such as tridecyl trimellitate and tetraoctyl pyromellitate, as well as trimethylolpropane caprylate, trimethylolpropane pelargonate and pentaerythritol-2.
Examples thereof include polyol esters such as ethylhexanoate and pentaerythritol belargonate, and complex esters which are oligoesters of polyhydric alcohols and mixed fatty acids of dibasic acids / monobasic acids. Examples of the ether oil include polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, polyglycol such as polypropylene glycol monoether, or monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether,
Examples thereof include phenyl ethers such as tetraphenyl ether, monoalkyl tetraphenyl ether and dialkyl tetraphenyl ether. Other synthetic lubricating base oils include tricresyl phosphate, silicone oils, perfluoroalkyl ether oils and the like. These base oils can be used alone or as a mixture, and are adjusted to have the above-mentioned preferable kinematic viscosity.

[Urea Compound Thickener] There is no particular limitation as long as it has the ability to form a gel structure and retain the base oil in the gel structure, and for example, diurea or polyurea can be appropriately selected and used. Since these urea compounds have heat resistance themselves, they contribute to the improvement of heat resistance of the grease.
In addition, the thickener has its molecules or crystals connected in a chain to form a fibrous form, which is uniformly dispersed in the grease to form a gel structure. It is considered that the gel structure is strengthened by entering between the thickener fibers.

[Fine Particles Made of Inorganic Compound] (Composition) As described above, there is no particular limitation as long as it is a material that reinforces the gel structure formed by the thickener. Specifically, SiO ₂ , Al ₂ O ₃ , MgO, TiO ₂ , PZ
T, ZnO and other metal oxides, Si ₃ N ₄ , ZrN, Cr
N, metal nitride such as TiAlN, SiC, TiC, WC
Examples thereof include metal carbides such as Bentonite, smectite, (synthetic) clay minerals such as mica, and diamond. Further, solid lubricants such as MoS ₂ , graphite, BN and WS ₂ can be mentioned. Further, in order to improve the affinity with base oils and urea thickeners, those whose surface is modified to be lipophilic may be used. Among the above-mentioned inorganic compounds, metal oxides and clay minerals, which have a thickening effect by themselves, are preferable.

(Particle size) The particle size is such that it does not hinder the grease for rolling bearings, but it is preferable that the particle size is smaller because it must enter between the thickener fibers as described above. In the present invention, it was confirmed that when the average particle diameter is 1 μm or less, a substantially good seizure prevention effect is exhibited. Here, the average particle size is 2 μm
If it is larger than the above, more particles act as foreign matter (dust), which accelerates wear of the bearing raceway and the surface of the rolling elements and causes early damage of the bearing. In addition, the bearing acoustic characteristics may be deteriorated. Further, considering the bearing lubrication life, it is desirable that the particle size used is smaller than the oil film of the base oil, and the oil film thickness under actual bearing usage conditions is about 0.2.
Since it is μm, the average particle size is more preferably less than this. Further, the shape is preferably closer to a sphere, but may be a polyhedron (a cube, a rectangular parallelepiped, etc.) or an extremely needle shape as long as it is within the above average particle diameter.

[Grease composition] Considering that it is used for a hermetically sealed rolling bearing, it is desirable to adjust the grease penetration consistency from No. 3 to No. 1 by NLGI, and the amount of urea-based thickener is based on the total amount of grease. About 10 to 35 wt% is compounded. On the other hand, the fine particles of the inorganic compound are 0.5 to 10 wt% with respect to the total amount of grease.
Is desirable. If the concentration of the inorganic compound fine particles is lower than this, the reinforcing effect cannot be sufficiently obtained, and if it is higher than this, the number of particles is too large, which may adversely affect the bearing acoustic characteristics and wear and adversely affect the bearing lubricating life. It Further, if the seizure life is further extended and the above adverse effects are taken into consideration, 1 to 8 wt% is desirable.

[Other Additives] The grease is formed by mixing fine particles of an inorganic compound and a thickener with a base oil. If necessary, the grease may contain the following additives alone or in combination. Is also good. The compounding amount is 20 wt% or less of the total amount of grease as a whole. Antioxidants: amine-based, phenol-based, sulfur-based, zinc dithiophosphate, etc. Anti-corrosion agent: Petroleum sulfonate, dinonylnaphthalene sulfonate, sorbitan ester, etc. Oiliness agent: fatty acid, vegetable oil, etc. Metal deactivator: benzotriazole, sodium nitrite, etc. Extreme pressure additives: Chlorine type, sulfur type, phosphorus type, zinc dithiophosphate, organic molybdenum, etc. Clay index improver: polymethacrylate, polyisobutylene, polystyrene, etc.

[Production Method] To prepare the grease, it is obtained by reacting a thickening agent in a base oil, but it is preferable to add the inorganic compound fine particles during the reaction. It is also possible to obtain the grease in advance by using a thickener and then mix it with the inorganic compound fine particles. However, it is necessary to add the inorganic compound fine particles with a kneader or a roll and then sufficiently stir them to uniformly disperse them. When doing this process,
It is also effective to heat. In the above production method, it is preferable in view of the process that additives other than the inorganic compound fine particles are added at the same time as the inorganic compound fine particles.

Then, for example, the grease is sealed in the sealed deep groove ball bearing with a contact rubber seal shown in FIG. 1 to complete the rolling bearing of the present invention. The amount of grease filled may be the same as the amount applied to this type of rolling bearing.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. (Grease adjustment) A base oil prepared by reacting a base oil prepared by mixing an amine with a base oil prepared by mixing diisocyanate is added to the semi-solid product obtained by stirring and heating, and an amine antioxidant previously dissolved in the base oil is added thereto. It was stirred. After gradual cooling, a rust preventive agent and inorganic compound fine particles were added, and the mixture was passed through a roll mill to obtain grease. According to the above-mentioned production method, various greases were prepared by changing the types and average particle sizes of the thickener, base oil, and inorganic compound fine particles and the addition amounts thereof as shown in Tables 1 to 3.

(High temperature / high speed seizure test) For a sealed deep groove ball bearing (outer diameter φ52 mm, inner diameter φ17 mm, width 16 mm) with a contact rubber seal incorporating a plastic cage,
2.4 g of each type of grease shown in Tables 1 to 3 was filled and continuously rotated under the conditions of an inner ring rotation speed of 22000 rpm, a bearing outer ring temperature of 140 ° C., and a radial load of 98 N. Then, when the bearing outer ring temperature increased to 155 ° C. or the bearing torque increased and the motor eddy current was reached, it was determined as the seizure life, and the time until then was measured. The measurement results are also shown in Tables 1 to 3.
As for the judgment, those having a seizure life of 700 hours or more were regarded as acceptable. In addition, what passed 1000 hours was considered good, and the test was stopped.

(Acoustic test) Sealed deep groove ball bearing with contact rubber seal (outer diameter φ52 mm, inner diameter φ17 mm, width 16 m)
In m), 2.4 g of each type of grease shown in Tables 1 to 3 was enclosed, and the sound was measured after rotating at 1800 rpm for 30 seconds. Tables 1 to 3 show the measurement results in Anderon values (numerical values).
In addition to the above, the standard judgment value of 6 anderon value or less was regarded as acceptable. The reason why 6 anderon or less was passed is that it was judged to be equal to or higher than the acoustic level of the urea-based commercially available grease.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

From the above test results, it can be seen that the rolling bearing of the present invention in which the grease containing the urea compound and the fine particles of the inorganic compound is sealed has excellent seizure life and acoustic characteristics. From the comparison between Example 4 and Comparative Example 3, it was confirmed that the acoustic characteristics were deteriorated when the blending amount of the inorganic compound fine particles increased, and in order to satisfy 6 Anderon required for practical use, the inorganic compound fine particles were required. It has been found that the upper limit of the compounding amount of is approximately 10 wt%. Further, Comparative Examples 5 and 6 are rolling bearings in which a commercially available grease containing lithium soap as a thickening agent is enclosed. However, when the thickening agent is not the urea compound of the present invention, even if inorganic compound fine particles are blended. However, it was confirmed that the seizure life was not extended.

[0024]

As described above, according to the present invention,
The grease structure of the grease film, which is responsible for lubrication, is reinforced to significantly extend the seizure life of the bearing. Especially, automotive electrical components such as alternators, electromagnetic clutches for car air conditioners, intermediate pulleys, electric fan motors and water pumps, It can be suitably used as a bearing used under high temperature and high speed rotation such as engine accessories.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing a sealed deep groove ball bearing with a contact rubber seal, which is a type of rolling bearing.

[Explanation of symbols]

 1 Inner ring raceway 2 Inner ring 3 Outer ring raceway 4 Outer ring 5 Rolling element (ball) 6 Seal 7 Cage

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michiharu Naka, 1-5-50, Shinmei Kugenuma, Fujisawa-shi, Kanagawa NSK Ltd.

Claims (1)

[Claims] 1. A rolling bearing comprising a grease composition containing a base oil, a urea thickener, and fine particles of an inorganic compound having an average particle size of 2 μm or less.