JP2002327758A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing having a longer life and capable of preventing flaking accompanying a white structure change caused by hydrogen brittleness under conditions such as high temperature, high speed, high load, and an environment apt to suffer water invasion from the outside. SOLUTION: In the rolling bearing 1 which is used for an electric accessory of an automobile and auxiliary units of an engine lubricated by grease, comprising an inner ring 10, an outer ring 11, a plurality of rolling bodies 13, and a retainer 12 retaining the rolling bodies 13, grease in which carbon black as a thickener is arranged in base oil is filled up in the rolling bearing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing used for an electric component of an automobile, an alternator or an intermediate pulley as an engine accessory, an electromagnetic clutch for a car air conditioner, and the like.

[0002]

2. Description of the Related Art Rolling bearings are generally used for electric parts of automobiles, alternators and intermediate pulleys as engine accessories, electromagnetic clutches for car air conditioners, and the like, and grease is mainly used for lubrication thereof.

[0003] For these electrical components and engine accessories, miniaturization and high performance and high output are required. However, a reduction in output due to miniaturization is inevitable. For example, in an alternator or an electromagnetic clutch for a car air conditioner, a high speed is required. This compensates for the decrease in output. However, with the increase in speed, the intermediate pulley is also increased in speed and generates heat. Therefore, the rolling bearings used for these components are required to have high-temperature durability.

[0004] Against this background, these parts are:
Rolling bearings in which a synthetic lubricating oil is used as a base oil, and a urea-synthetic oil-based grease in which a urea compound is blended as a thickener, are predominantly used. However, recently, demands for improved quietness have reduced the size of the engine room in order to make the engine room more sealed and further increase the space in the vehicle compartment. There is a tendency. The urea-synthetic oil-based grease has a long bearing lubrication life up to an ambient temperature of about 170 to 180 ° C., and can be used sufficiently.
Even in the case of urea-synthetic oil grease, the base oil evaporates, the grease hardens, and the grease softens due to the thermal decomposition of the thickener.

[0005] Further, since the bearings for the above-mentioned parts are often used under high temperature, high speed, and high load, see Japanese Patent No. 28,028.
As described in Japanese Patent No. 78749, hydrogen may be generated by decomposition of grease, and this hydrogen enters the bearing steel forming the inner ring, the outer ring, and the rolling elements, and is accompanied by a change in white structure due to hydrogen embrittlement. Causes peeling. Furthermore,
Since these bearings are belt-driven auxiliary machine bearings outside the engine, muddy water and rainwater that jump up from the road surface easily enter. These bearings are usually configured to prevent water from entering from outside by a contact rubber seal, but at present, it cannot be completely prevented. In addition, since the engine of an automobile is a machine that repeatedly starts and stops operation, the temperature inside the bearing housing decreases when the engine is stopped, and reaches the dew point, condensing moisture in the air around the bearing and causing water droplets. And may adhere to bearings or mix into grease. As a result, as described in Japanese Patent Application Laid-Open No. H11-72120, hydrogen generated by infiltration water causes peeling with similar white structure change.

Further, since each of the component bearings is rotated by pulley drive by a belt, static electricity is generated between the belt and the pulley. Normally, the inner and outer rings are insulated from each other by the oil film of the lubricant during the rotation of the bearing. However, when 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, water is electrolyzed by the generated direct-current voltage, and the generation of hydrogen ions is promoted, and the peeling accompanied by the white structure change as described above is more likely to occur.

[0007]

As described above, in each of the above-mentioned bearings for components, exfoliation accompanied by a change in white structure due to hydrogen embrittlement due to external infiltration water easily occurs.
Furthermore, there is a problem that it is accelerated by static electricity, and prevention thereof has become a new important issue. To cope with such a problem, Japanese Patent No. 2878749 proposes that a passivating oxidizing agent be mixed into grease to form an oxide film on the surfaces of the inner ring, the outer ring and the rolling elements to prevent hydrogen from entering. Japanese Patent Application Laid-Open No. 11-72120 proposes that the pH of grease be adjusted to be in the range of 5 to 13 to suppress the progress of the cathode reaction which causes hydrogen embrittlement.

However, in the former method, it is impossible to prevent hydrogen from entering until an oxide film is formed, and a sufficient effect cannot be obtained unless the oxide film is formed without gaps. On the other hand, in the latter case, the initially adjusted pH may fluctuate due to a change over time, and it is difficult to obtain a stable effect.

Therefore, the present invention does not cause exfoliation accompanied by white structure change due to hydrogen embrittlement even when used in an environment of high temperature, high speed, high load, and susceptible to ingress of water from the outside. An object of the present invention is to provide a long-life rolling bearing.

[0010]

In order to achieve the above object, the present invention comprises an inner ring, an outer ring, a plurality of rolling elements, and a retainer for holding the rolling elements, and is grease-lubricated. Provided is a rolling bearing for an electric component of an automobile or an engine auxiliary machine, wherein a grease obtained by blending carbon black as a thickener in a base oil is sealed.

As described above, the static electricity generated between the belt and the pulley promotes the generation of hydrogen ions.
By using carbon black, which is a conductive substance, as a thickener, the grease is always maintained in a conductive state, so there is almost no potential difference between the inner and outer rings, so that water electrolysis does not occur, and peeling accompanied by white structure change Generation and progress can be suppressed. Moreover, this effect appears immediately after the grease is sealed, and there is little change over time.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The rolling bearing of the present invention will be described below in more detail.

The configuration of the rolling bearing of the present invention is not limited. For example, a ball bearing 1 shown in a sectional view in FIG. 1 can be exemplified. In the ball bearing 1, a plurality of balls 13 as rolling elements are rotatably held at substantially equal intervals between an inner ring 10 and an outer ring 11 via a retainer 12, and furthermore, the inner ring 10, the outer ring 11, and A bearing space S formed by the balls 13 is filled with a grease composition (not shown) described later in a predetermined amount, and is sealed with a seal 14.

[Base oil] The base oil used in the grease composition is not particularly limited, and any oil that is usually used as a base oil for lubricating oils can be used. However, no noise at low temperature startup due to lack of low temperature fluidity, especially at 200 ° C
In consideration of the durability to high temperatures such that the kinematic viscosity at 40 ° C. is preferably 30 to 250 mm ² / s
ec, and more preferably a synthetic lubricating oil having a viscosity of 50 to ²⁰⁰ mm ² / sec. Kinematic viscosity at 40 ° C is 30
If it is less than mm ² / sec, it is difficult to form a sufficient oil film at a high temperature exceeding 200 ° C., causing metal contact and early seizure. On the other hand, when the kinematic viscosity at 40 ° C. exceeds 250 mm ² / sec,
Since the agitation resistance of the grease increases and the amount of heat generated increases, each element (the inner ring, the outer ring, and the rolling element) of the rolling bearing expands to reduce the internal clearance, thereby easily causing abnormal wear and seizure. In addition, the fluidity at low temperatures is also poor, and it is difficult to sufficiently satisfy the low-temperature startability as a rolling bearing for automotive electrical components and engine accessories.

Examples of the synthetic lubricating oil include hydrocarbon oils, aromatic oils, ester oils, ether oils and the like.
Examples of the hydrocarbon-based 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 the ester oil include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate,
Ditridecyl adipate, ditridecyl glutarate,
Diester oils such as methyl acetylsinolate, or aromatic ester oils such as trioctyl trimellitate, tridecyl trimellitate, and tetraoctyl pyromellitate; trimethylolpropane caprylate, trimethylolpropaneperargonate, and pentane Polyol ester oils such as erythritol-2-ethylhexanoate and pentaerythritol belargonate; and complex ester oils which are oligoesters of polyhydric alcohols and mixed fatty acids of dibasic acids and monobasic acids. Can be As the ether-based oil, polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, polyglycol such as polypropylene glycol monoether,
Or monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether,
Examples include phenyl ether oils such as pentaphenyl ether, tetraphenyl ether, monoalkyl tetraphenyl ether, and dialkyl tetraphenyl ether. Other synthetic lubricating base oils include tricresyl phosphate, silicone oil, perfluoroalkyl ether and the like. These synthetic lubricating oils can be used alone or as a mixture, and are adjusted to the preferable kinematic viscosity described above.

Mineral oils and natural oil-based lubricating oils can be used in combination as long as durability at high temperatures is not impaired. As the mineral oil-based lubricating oil, one obtained by appropriately combining mineral oil under reduced pressure distillation, oil removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay refining, hydrorefining, etc., is used. Can be. Natural oil-based lubricating oils include tallow, lard, soybean oil, rapeseed oil, rice bran oil, coconut oil,
Fats and oils such as palm oil and palm kernel oil and hydrides thereof are exemplified.

[Thickener] Any type of carbon black can be used. That is, it can be used irrespective of the raw material and the production method. Although the particle size is not particularly limited, it is preferable to select an average particle size of about 10 to 300 nm in consideration of dispersibility in grease and the like. Further, a plurality of types of carbon black may be used in combination.

However, in consideration of the fluidity of the grease, the penetration is set to the grade specified in the NLGI.
o. 1 to No. The amount is adjusted so as to be 3. As a specific compounding amount, 4 to 30 of the total amount of grease
It is preferable to set it as mass%. 4 carbon blacks
When the amount is less than mass%, the kinetic viscosity is insufficient, so that it is difficult to obtain grease of the above preferable grade. On the other hand, if it exceeds 30% by mass, the base oil amount is relatively reduced, so that lubrication tends to be insufficient.

[Additives] In order to further enhance the lubricating performance, if necessary, an antioxidant, a rust inhibitor, an extreme pressure agent, an oil agent, a metal deactivator, a viscosity index improver, and a detergent / dispersant are used alone. Or an appropriate combination of them can be added to the grease. Any of these may be known ones, and the amount of addition is not particularly limited. However, if the amount is too large, the amount of the base oil or carbon black is relatively too small. % Is preferred.

[Preparation Method] The method for preparing the above grease composition is not particularly limited. However, since carbon black is a solid, it is necessary to add carbon black, sufficiently stir using a kneader or a roll mill, etc., and uniformly disperse. There is. When performing this treatment, heating is also effective. still,
Additives such as antioxidants and rust inhibitors are preferably added simultaneously with carbon black in the process.

[0021]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Preparation of Test Grease) Test greases A to C having the compositions shown in Table 1 were prepared. The carbon black used had an average particle size of 30 nm, and was sufficiently stirred using a roll mill to be uniformly dispersed in the base oil.
In addition, in grease A, the kinematic viscosity at 40 ° C. is 20 to
Different ones are used within the range of 410 mm ² / sec, and the grease B has a carbon black content of 3 to 50% by mass.
It was prepared by changing within the range. Each grease was adjusted to have a mixing consistency shown in Table 1.

[0023]

[Table 1]

(High Temperature Seizure Life Test) A deep groove ball bearing with a contact rubber seal having an inner diameter of 17 mm, an outer diameter of 47 mm, and a width of 14 mm having the structure shown in FIG.
Grease A was sealed so as to occupy 0% by volume to obtain test bearing A. In addition, grease C was sealed in the same ball bearing so as to occupy 30% by volume of the bearing space (S) to obtain a test bearing C.

The test was performed using a test device shown in FIG. The illustrated test apparatus supports a rotating shaft 20 with a pair of support bearings 22, 22, mounts a test bearing 21 at an intermediate portion thereof, and further maintains a constant temperature vessel (not shown) so that the whole can be maintained at a predetermined temperature. ).
The test was performed by rotating the shaft 20 to rotate the test bearing 21 at the inner ring rotation speed of 20,000 min ^-1 , at the bearing outer ring temperature of 200 ° C.,
The test was continuously performed under the condition of a radial load of 686 N, when seizure occurred and the temperature of the bearing outer ring rose to 220 ° C. or higher, and when the rotational torque sharply increased, the test was terminated, and the time until that time was measured. The test was performed on four cases each, and the test bearing C
The results are shown in FIG. 3 as relative values with the image sticking time taken as 1.

As shown in FIG. 3, the use of a synthetic lubricating oil having a kinematic viscosity at 40 ° C. of 30 to 250 mm ² / sec as a base oil can improve the seizure life to about twice or more, especially at 40 ° C. Kinematic viscosity 50-200mm ² / s
It can be seen that the synthetic lubricating oil of ec can achieve a high service life improvement effect of about three times or more.

(Sudden acceleration / deceleration test) Having a structure shown in FIG.
Grease B was sealed in a deep groove ball bearing with a contact rubber seal having an inner diameter of 17 mm, an outer diameter of 47 mm, and a width of 14 mm to occupy 30% by volume of the bearing space (S) to obtain a test bearing B. Then, the peeling life of the test bearing B was evaluated using the test device shown in FIG. In the illustrated test apparatus, an inner ring of a test bearing 35 is fitted to an end of a shaft 30 supported by a pair of support bearings 31, 31, an outer ring is fixed to a holder 32, and an engine is connected via a pulley 33. The rotation from (not shown) is transmitted to the test bearing 35. Reference numeral 34 denotes a thermometer for measuring the temperature of the outer ring, and reference numeral 36 denotes a heater for heating the outer ring. Then, the test bearing 35 was continuously rotated under the conditions of an engine rotation speed of 1200 to 9600 min ⁻¹ , a bearing outer ring temperature of 120 ° C., and a pulley load of 980 N, and a test was performed for a target of 300 hours. The test was performed for each of 10 cases, and the peeling occurrence probability was calculated by the following equation. Probability of peeling = (number of peelings / number of tests) × 100

FIG. 5 shows the results. It can be seen that peeling can be prevented by enclosing grease using carbon black as a thickener.

The results of the high-temperature seizure life test are shown in FIG. 5 in which the seizure time of a test bearing in which grease having a carbon black content of 50% by mass is sealed is set to 1 and the relative value is set to 1. Black content of 4% by mass or more 3
It can be seen that when the grease of 0% by mass or less is sealed, a particularly excellent life improving effect is obtained. This is due to the presence of a certain amount of carbon black in the grease,
This is considered to be due to the fact that the outer ring, the inner ring, and the rolling elements were kept in a good conduction state to suppress hydrogen embrittlement, and that appropriate grease fluidity was obtained.

[0030]

As described above, according to the present invention,
It is possible to obtain a long-life rolling bearing that is extremely excellent in high-temperature seizability and peeling prevention effect, and is particularly suitable as a rolling bearing for automotive electrical components such as alternators, intermediate pulleys, electromagnetic clutches for car air conditioners, and engine auxiliary equipment. Can be used.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a rolling bearing of the present invention.

FIG. 2 is a schematic sectional view showing a test apparatus used in a high-temperature seizure life test in Examples.

FIG. 3 is a graph showing the results of a high-temperature seizure life test.

FIG. 4 is a schematic cross-sectional view showing a test apparatus used for a rapid acceleration / deceleration test in Examples.

FIG. 5 is a graph showing the results of a rapid acceleration / deceleration test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ball bearing 10 Inner ring 11 Outer ring 12 Cage 13 Ball 14 Seal

Claims (4)

[Claims] 1. A rolling bearing for an electronic component and an engine auxiliary machine of a grease-lubricated automobile, comprising an inner ring, an outer ring, a plurality of rolling elements, and a retainer for holding the rolling elements. A rolling bearing characterized by sealing grease containing carbon black as a thickener. 2. The grease contains 4 to 3 carbon blacks.
0% by mass and NLGI grade No. 1
-No. 3. The rolling bearing according to claim 1, wherein the mixing consistency is 3. 3. The base oil has a kinematic viscosity at 40.degree.
The rolling bearing according to claim 1, wherein the rolling bearing is a synthetic lubricating oil of 250 mm ² / sec. 4. The rolling bearing according to claim 1, wherein the rolling bearing is used for belt-driven electrical components and engine accessories.