JP2005321064A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of peeling in a four-point contact or three-point contact rolling bearing incorporated in an electric equipment of an automobile or an engine auxiliary machine and to extend the life.
A four-point contact or three-point contact rolling bearing incorporated in an electrical equipment of an automobile or an engine accessory, and a plurality of rolling elements are rolled by a cage between a fixed wheel and a rotating wheel. A rolling bearing characterized by being held freely and encapsulating a grease composition containing a conductive substance in a proportion of 0.1 to 10% by mass.
[Selection] Figure 1

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-point contact or four-point contact rolling bearing encapsulated with grease. It is related with the said rolling bearing used for the components used by.

  In recent years, low fuel consumption and high efficiency of vehicles have been demanded from the viewpoint of energy saving and environmental problems. As a result, FF vehicles for miniaturization and weight reduction have become widespread, and the engine room space has been reduced due to the demand for expansion of the cabin space. The weight reduction is further advanced, and each component incorporated in it is required to have higher performance and higher output. However, a reduction in output is unavoidable due to miniaturization, and for example, an alternator or a pulley for a car air conditioner compressor compensates for the reduction in output by increasing the speed, and accordingly, the idler 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, the load applied to the bearing is increased due to the increased tension of the drive belt.

  On the other hand, replacement from a reverse row bearing to a single row bearing is progressing in response to demands for weight reduction, downsizing, cost reduction, and the like. However, simply replacing the conventional reverse row bearing with a single row bearing reduces the rigidity and increases the inclination of the bearing, so that the four row contact (see FIG. 1) or the three point contact ( (See FIG. 2). However, a four-point or three-point contact bearing is apt to generate more heat because slippage is more likely to occur on the contact surface between the rolling element and the raceway than an ordinary single groove R bearing. As the bearing temperature rises, peeling with the above white structure change is likely to occur.

  In general, the durability of rolling bearings is greatly reduced when moisture is mixed in the lubricant. For example, Furumura et al. Reported that when 6% of water was mixed in lubricating oil (# 180 turbine oil), the rolling fatigue strength was reduced by a factor of 1 to 20 times compared to the case without mixing. (Furumura Shinzaburo, Shirota Shinichi, Hirakawa Kiyoshi: NSK Bearing Journal, No.636, pp.1-10, 1977). Schatzberg et al. Also reported that the rolling strength of steel decreased by 32 to 48% when only 100 ppm of water was mixed in the lubricating oil (P. Schatzberg. IMFelsen; Effects of water). and oxygen during rolling contact Iubrication, wear, 12, pp.331-342, 1968).

  Since the above-described bearings for each part are often used under high temperature, high speed, and high load, hydrogen may be generated by the decomposition of grease. In addition, these bearings are belt-driven auxiliary machine bearings outside the engine, so that muddy water and rainwater splashed from the road surface are likely to enter. These bearings are usually configured to prevent water from entering from the outside by a contact rubber seal, but at present, they cannot be completely prevented. Furthermore, since the engine of an automobile is a machine that repeatedly operates and pauses, when the engine is paused, the temperature in the bearing housing decreases, reaches the dew point, and moisture in the air around the bearing condenses and drops of water. And may adhere to the bearing or be mixed in the lubricant. As a result, hydrogen generated by the intrusion moisture penetrates into the bearing steel and causes separation with white structure change due to hydrogen embrittlement.

  Furthermore, since each of the above-described component bearings is rotated by a pulley driven by a belt, static electricity is generated between the belt and the pulley. Normally, while the bearing is rotating, the inner and outer rings are insulative due to the oil film of the lubricant. However, when a metal contact is caused by strong vibration or the like, the inner and outer rings are connected at once and a large potential difference is generated between the inner and outer rings. Then, the generated direct current voltage causes water to be electrolyzed to promote the generation of hydrogen ions, and the peeling with the white texture change as described above is more likely to occur.

  Thus, four-point or three-point contact rolling bearings incorporated in electrical equipment for automobiles or engine accessories are used under high temperature, high speed, and high load conditions, and further involve sliding between the rolling elements and the raceway. Therefore, peeling is likely to occur. In addition, there is a problem that peeling due to a change in white structure is likely to occur due to moisture entering from the outside, and further peeling due to static electricity is promoted. Conventionally, urea-synthetic oil-based grease is generally enclosed in this type of rolling bearing (see, for example, Patent Document 1), but a sufficient effect is not obtained.

JP-A-6-17079

  The present invention has been made in view of such a situation, and suppresses the occurrence of separation in a rolling bearing with a four-point contact or a three-point contact incorporated in an electrical equipment of an automobile or an engine accessory, thereby extending the life. For the purpose.

In order to achieve the above object, the present invention provides the following rolling bearing.
(1) Rolling bearings with 4-point contact or 3-point contact built into automobile electrical equipment or engine accessories, and a plurality of rolling elements can be freely rolled between a fixed ring and a rotating ring by a cage. And a grease bearing containing a conductive material at a ratio of 0.1 to 10% by mass.
(2) The rolling bearing according to (1), wherein the conductive material is carbon black.
(3) The rolling bearing according to (2), wherein the carbon black has an average particle size of 10 to 300 nm.
(4) The rolling bearing according to (1), wherein the conductive substance is a carbon nanotube.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the peeling in the rolling bearing of 4 point contact or 3 point contact incorporated in the electrical equipment of a motor vehicle or an engine accessory can be suppressed effectively, and lifetime can be achieved.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  The rolling bearing according to the present invention is incorporated in an electric equipment for an automobile or an engine accessory, and the rolling element and the race are in contact at four or three points. That is, as shown in a cross-sectional view in FIG. 1, a plurality of rolling elements 17 are held by a retainer 25 between an outer ring 15 and an inner ring 16 so as to be able to roll, and will be described later in a bearing space 21. The grease composition is filled and sealed with a seal 20, and the rolling element 17 is in contact with the outer ring raceway 18 at two points and the inner ring raceway 19 is in contact at two points, as indicated by a dashed line, A total of 4 points are in contact. Further, as shown in FIG. 2, the rolling element 17 and the outer ring raceway 18 may be in contact with each other at two points, and the rolling element 17 and the inner ring raceway 19a may be in contact at one point. In the figure, 16a is an inner ring. In any bearing, the amount of the grease composition enclosed is not particularly limited.

In the encapsulated grease composition, the base oil is not particularly limited, and any lubricating oil that is normally used as a base oil for lubricating oil can be used. Preferably, the kinematic viscosity at 40 ° C. is 10 to 400 mm ² / s, more preferably 20 to 250 mm ² / s, in order to avoid generation of abnormal noise at low temperature startup and seizure that occurs because an oil film is hardly formed at high temperature. The base oil is preferably s, more preferably 40 to 150 mm ² / s.

  Examples of the base oil include mineral oil, synthetic oil and natural oil. As the mineral oil-based lubricating oil, one obtained by refining mineral oil by appropriately combining vacuum distillation, solvent removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay purification, hydrogenation purification, and the like is preferable. Examples of synthetic oils include hydrocarbon oils, aromatic oils, ester oils, ether oils, and the like. Examples of the hydrocarbon oil include normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, poly-α-olefin such as 1-decene and ethylene co-oligomer, and hydrides thereof. Examples of the aromatic oil include alkylbenzenes such as monoalkylbenzene and dialkylbenzene, and alkylnaphthalenes such as monoalkylnaphthalene, dialkylnaphthalene and polyalkylnaphthalene. Examples of ester oils include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, methyl acetyl cinnolate and other diester oils, trioctyl trimellitate, trioctyl trimellate Aromatic ester oils such as decyl trimellitate, tetraoctyl pyromellitate, polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol verargonate, Examples thereof include complex ester oils that are oligoesters of polyhydric alcohols and mixed fatty acids of dibasic acids and monobasic acids. Examples of ether oils include polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, and polypropylene glycol monoether, monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether, tetraphenyl ether, and monoalkyl tetraphenyl. Examples thereof include phenyl ether oils such as ether and dialkyl tetraphenyl ether. Other synthetic lubricating oils include tricresyl phosphate, silicone oil, perfluoroalkyl ether and the like. Examples of natural oil-based lubricating oils include beef tallow, lard, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, palm kernel oil, and other oils and hydrides thereof. These lubricating oils can be used alone or as a mixture, and are adjusted to the above-mentioned preferable kinematic viscosity.

  The thickener is not particularly limited as long as it has the ability to form a gel structure and retain the base oil in the gel structure. For example, non-soaps such as metal soaps made of Li, Na, etc., metal soaps such as composite metal soaps selected from Li, Na, Ba, Ca, etc., benton, silica gel, urea compounds, urea / urethane compounds, urethane compounds, etc. However, considering the heat resistance of the grease composition, a urea compound, a urea / urethane compound, a urethane compound, or a mixture thereof is preferable. Specific examples of the urea compound, urea / urethane compound, and urethane compound include diurea compounds, triurea compounds, tetraurea compounds, polyurea compounds, urea / urethane compounds, diurethane compounds, and mixtures thereof. Among these, diurea compounds , Urea / urethane compounds, diurethane compounds or mixtures thereof are more preferred. In view of heat resistance and acoustic properties, it is more preferable to blend a diurea compound.

  In addition, a conductive material is blended in the grease composition. The conductive material is not limited as long as it has excellent conductivity, and may be liquid or solid. Among them, it is preferable to use carbon black for reasons such as handling and availability, and not reducing the lubricity. This carbon black preferably has an average particle size of 10 to 300 nm in consideration of dispersibility in the grease composition, acoustic characteristics, and the like.

  Moreover, a carbon nanotube is also preferable as the conductive substance. As schematically shown in FIG. 3, the carbon nanotube is a carbon polyhedron having a tubular shape in which a network structure of a carbon six-membered ring is mainly rounded and both ends are closed. In addition, in the tube junction part and terminal closing part of a different diameter, it may become a carbon 5-membered ring or a carbon 7-membered ring. Some carbon nanotubes have a spherical structure. For example, C60 and C70 are known as fullerenes, but in the present invention, these fullerenes can also be used. These carbon nanotubes are particularly preferably those having a diameter of 0.5 nm to 15 nm and a length of 0.5 μm to 50 μm.

  The addition amount of these conductive substances is 0.1 to 10% by mass of the total amount of the grease composition. If the addition amount is less than 0.1% by mass, sufficient conductivity cannot be imparted, and the effect of suppressing peeling accompanied by a change in white structure will not be exhibited. On the other hand, when the addition amount exceeds 10% by mass, the grease is hardened and the seizure life may be reduced, which is not preferable.

  The above grease composition is No. in terms of the blending consistency after the addition of the conductive material. It is more preferable that it is 1-3, and the compounding quantity of a thickener and an electroconductive substance is adjusted.

  In addition, various additives such as antioxidants, extreme pressure agents, oiliness agents, rust inhibitors, metal deactivators, viscosity index improvers and the like are added to the grease composition as necessary in order to further improve its performance. Can be added alone or in combination of two or more. Any of these may be known ones, and the addition amount is not particularly limited, but it is preferably 20% by mass or less based on the total amount of the grease composition.

  The method for producing the grease composition is not particularly limited, but it is generally obtained by reacting a thickener in a base oil. It is preferable that a predetermined amount of the conductive substance is blended in the obtained grease composition. However, after adding the conductive substance with a kneader or a roll mill, it is necessary to sufficiently stir and uniformly disperse. At that time, heating is also effective. In addition, it is preferable on the process that other additives are added simultaneously with an electroconductive substance.

  The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

(Example 1)
First, a base oil mixed with a diisocyanate (polyalphaolefin oil; PAO, kinematic viscosity 50 mm ² / s, 40 ° C.) is reacted with a base oil mixed with an amine, heated to a semi-solid product obtained by stirring and heating. Then, an amine-based antioxidant previously dissolved in the base oil was added and sufficiently stirred. After slow cooling, carbon black (average particle size 30 nm) was added in an amount of 0.05 to 12% by weight, and a test grease with a different amount of carbon black added was obtained by passing through a roll mill. The consistency of the test grease is NLGI No. It adjusted to 1-3.

The test life was evaluated by rapidly accelerating and decelerating the four-point contact bearing incorporated in the compressor pulley using the test grease. That is, a four-point contact bearing (inner diameter φ35 mm, outer diameter φ52 mm, width 12 mm, with contact rubber seal) in which 1.0 g of test grease is sealed is incorporated in a compressor pulley (repeated bearing rotation speed 2400 to 13300 min ⁻¹ , at room temperature) The bearing was continuously rotated under the condition of a pulley load of 2000 N, and the test was conducted with a target of 500 hours, and when the vibration was generated on the rolling surface of the bearing outer ring, or when the separation did not occur, 500 At the end of the test, the test was completed, and after the test was completed, visual observations were also made for the presence or absence of structural changes inside the bearing. Each was calculated.
Peeling occurrence probability = (number of peeling occurrence / number of tests) × 100
Probability of tissue change = (Number of tissue changes / number of tests) x 100

In addition, a four-point contact bearing (with an inner diameter of 35 mm, an outer diameter of 52 mm, and a width of 12 mm with a contact rubber seal) filled with 1.0 g of test grease was tested under the conditions of an inner ring rotational speed of 20000 min ⁻¹ , a bearing temperature of 140 ° C., and a radial load of 98 N. Rotated continuously. And the time until seizure occurred and the bearing outer ring temperature rose to 150 ° C. or higher was measured.

  The results are shown in a graph in FIG. 4, and in the test grease to which 0.1 to 10% by mass of carbon black is added according to the present invention, the occurrence of peeling and white color change is suppressed, and the seizure life is also improved.

(Example 2)
A test grease was prepared and evaluated in the same manner as in Example 1 except that carbon nanotubes (diameter 0.7-2 nm, total length 10-30 μm) were used instead of carbon black.

  The results are shown in a graph in FIG. 5. As in the case of carbon black, the test grease to which 0.1 to 10% by mass of carbon nanotubes were added according to the present invention was able to suppress peeling and white color change and seize. The service life is also improved.

It is sectional drawing which shows one Embodiment (4-point contact) of the rolling bearing of this invention. It is sectional drawing which shows other embodiment (3 point contact) of the rolling bearing of this invention. It is a schematic diagram which shows the whole structure of a carbon nanotube. It is a graph which shows the relationship between the addition amount of carbon black and the structure change generation | occurrence | production probability, exfoliation generation | occurrence | production probability, or a seizure lifetime obtained in the Example. It is a graph which shows the relationship between the addition amount of the carbon nanotube obtained in the Example, the structure change occurrence probability, the separation occurrence probability, or the seizure life.

Explanation of symbols

15 outer ring 16 inner ring 16a inner ring 17 rolling element 18 outer ring raceway 19 inner ring raceway 19a inner ring raceway 20 seal 21 bearing space 25 cage

Claims (4)

  A four-point contact or three-point contact rolling bearing incorporated in an electrical equipment of an automobile or an engine accessory, and a plurality of rolling elements are rotatably held by a cage between a fixed wheel and a rotating wheel. A rolling bearing characterized by enclosing a grease composition containing a conductive substance in a proportion of 0.1 to 10% by mass.   The rolling bearing according to claim 1, wherein the conductive material is carbon black.   The rolling bearing according to claim 2, wherein an average particle diameter of the carbon black is 10 to 300 nm. The rolling bearing according to claim 1, wherein the conductive substance is a carbon nanotube.

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