KR970002552B1 - Grease-sealed rolling contact bearing - Google Patents

Abstract

None.

Description

Grease Sealed Rotating Contact Bearings

1 is a partial cutaway vertical cross-sectional view of an alternator and its bearings.

2 is a diagram showing the mechanism by which hydrogen freezing on the bearing substrate surface is prevented.

3 is a schematic diagram of a measuring device for measuring friction coefficient.

BACKGROUND OF THE INVENTION The present invention relates to a grease-sealed rolling contact bearing for use in supporting components of a car such as rotating shafts and alternators of electronic components, electromagnetic clutches and idler pulleys.

Recently, there is an increasing demand for compact, lightweight and low noise cars. To meet these demands, the car's electrical components and other accessories must be small in size and lightweight. In addition, the engine compartment must be sufficiently sealed. On the other hand, such devices are required to have high power and high efficiency. For example, in the case of an alternator, it is common to use a small size and operate at high speed to compensate for the reduction in output due to the small size.

1 shows a pulley 1 of an alternator of a vehicle designed for high speed operation. The rotational contact bearing 2 supporting the pulley 1 is a grease enclosed type, and a grease is enclosed in the bearing in order to ensure sliding during high speed operation.

In this arrangement, in order to compensate for the reduction in the transmission efficiency caused by the use of the small pulley 1, a plurality of grooves 3 interlocked with the power transmission belt are formed on the pulley 1, and the belt tension is kept higher. . The bearing 2 used near the engine is thus rotated at high speed at high temperature and subjected to a large load.

The service life of such alternator bearings using conventional greases tends to be shortened by the development of flaking on their rotating surfaces by high speed, high load operation. Such flaking, which shortens the life of the bearing, is a particularly detrimental phenomenon which develops abruptly deep inside the bearing material, unlike the conventional flaking which occurs on the rotating surface or surface layer by metal fatigue.

When a bearing is subjected to such flakes, the service life tends to be shorter than the output life of conventional grease-bearing bearings.

The inventors have found that such flaking occurs with the following mechanism. That is, the bearing vibrates by high-speed operation, and the vibration causes the wear of the rotating surface to move into the glass surface to create a new surface, which acts as a catalyst to decompose grease to generate hydrogen, and the hydrogen Penetrating the metal by penetrating into the metal of the bearing (hereinafter referred to as hydrogen rolling). This causes flaking. In order to prevent such flaking, the present inventors have proposed that an inert treatment such as blackening treatment is applied to the steel surface (Japanese Patent Laid-Open No. 2-190615).

As another solution to this problem, the present inventors also disclosed a grease containing phenyl ether as base oil (published patent publication 3-250094). It has a high bond strength for hydrogen.

However, grease containing phenyl ether oil as base oil has poor viscosity temperature characteristics such that a sufficient amount is supplied on the rotating surface of the bearing. Thus, a bearing with such a grease enclosed in it stops, depending on the distance between the bearing cage cross section and the encasement, especially if it is operated at high speed at high loads.

In addition, the hydrogen grease phenomenon is difficult to be prevented with the aforementioned grease containing phenyl ether as a base oil. Moreover, since rolling bearings for electric parts and accessories of cars are used under a variety of different conditions, they are required to have a high resistance to dust, so that they are kept free from dust even when exposed to muddy water.

It is an object of the present invention to provide a rotary contact bearing which is durable and has high resistance to dust because hydrogen rolling does not occur even under high speed and high load operating conditions.

According to the invention, 5-40 weights of at least one of base oil, aromatic diuretic compound and aromatic urea-urethane compound which are a mixture of alkyldiphenylether oil having a weight ratio of 20:80 to 80:20 and poly-α-olipine oil. A grease enclosed rotary contact bearing is enclosed therein with a grease composition comprising% thickener, passivation oxidant and organic sulfonate.

The alkyldiphenyl ether oil used in the present invention is obtained by reacting 1 M diphenyl ether with 1-3 M α-olefin having 10-22 carbon atoms. Typical alkyldiphenyl ether oils are represented by the formula:

Wherein R is a straight chain alkyl group bonded to the aromatic group shown below.

M + n of an alkyl group shows the integer of 9-15 here)

The poly-α-olefin oil used in the present invention is obtained by adding a hydrogen atom to the terminal double bond of the α-olefin in the lower polymer form and is represented by the following formulas (I), (II), (III) and (IV). Things are some examples.

Where R ₁ , R ₂ , R ₃ are C _n H _{2n + 1} and n represents an integer from 6 to 14

Wherein m is one of the integers 1 to 6 and R represents C _n H _{2n + 1} , where n represents an integer from 6 to 14

(Where n represents one of the integers 1 to 6)

(Where X and Y represent one of the integers 1 to 3, Z is C _n H _{2n + 1} and n is one of the integers 1 to 8)

The base oil of the present invention contains alkyldiphenyl ether oil and poly-α-olefin oil in a weight ratio of 20:80 to 80:20. If the ratio of poly-α-olefin oil in the base oil is lower than the lower limit, the performance at low-temperature will be insufficient.

In addition, the ratio of alkyldiphenyl ether oil to poly-α-olefin oil should preferably be 50:50 or higher in order to minimize the amount of hydrogen that can result from decomposition of the grease.

An aromatic diuretic compound used as a thickening agent in the present invention is a compound represented by the following formula having two urea bonds (-NHCONH-) for each molecule. In the method for producing grease, this is obtained by mixing an aromatic diisocyanate and a monoamine in a base oil used as a solvent, which can be separated off purely from the base oil.

(Wherein R ₁ represents an aromatic hydrocarbon group having 7-13 carbon atoms, R ₂ and R ₃ represent an aromatic hydrocarbon group or alkyl group having 8-20 carbon atoms and at least one of R ₂ and R ₃ represents an aromatic hydrocarbon group)

The aromatic urea-urethane compound used in the present invention as another aging agent is a compound having urea bond (-NHCONH-) and urethane bond (-NHCOO-) quantum in the molecule, and is represented by the following formula. This is obtained by reacting an alcohol miamine with isocyanate in a base oil or toluene solvent, which can be decomposed purely in toluene or base oil.

(Wherein R ₁ represents an aromatic hydrocarbon group having 7-13 carbon atoms, R ₂ and R ₃ represent an alkyl group or aromatic hydrocarbon group having 8-20 carbon atoms and at least one of R ₂ and R ₃ is an aromatic hydrocarbon group)

The aromatic diuretic compound and / or the aromatic urea-urethane compound should be added in an amount of 5-40% by weight based on the base oil. This is because the grease obtained by the addition of an aromatic diuretic compound or an aromatic urea-urethane compound of less than 5% by weight becomes a liquid state having insufficient viscosity. If it is 40 weight% or more, grease will become a solid state and will become unpreferable.

The passivation oxidant used in the present invention is an oxidant that provides protection of metal surfaces such as steel forming rotational contact bearings. Cathode-polarized inorganic corrosion inhibitors such as nitrite, nitrate, chromate, phosphate, molybdate or tungstate can be used.

The organic sulfonate used in the present invention is an organic sulfonic acid (RSO ₃ ) having a polar atom group (SO ₃ ^2- ) and a general formula RSO ₃ M having a lipophilic group (R) and an oil hazardous surfactant type compound. And M is an alkaline earth metal such as Ba, Zn or Ca or a metal or amine such as Pb, Na or Li. The organic sulfonic acid may be petroleum sulfuric acid, alkylbenzene sulfuric acid, dinonylnaphthalene sulfuric acid.

In order to increase the wear resistance of the grease composition according to the present invention, 0.1-5% by weight of extreme pressure additives such as zinc dithiophosphate should be added.

The rotating surface of a bearing used under high speed and high load conditions is always subjected to mirror wear by the vibrations during rotation and while the rotating element rotates at high speed in frictional contact with the rotating surface.

The new surface formed by the catalyzed weir causes the chemical decomposition of the grease. Grease decomposes, generating a large amount of hydrogen in areas where new surfaces are formed.

Such hydrogen can penetrate into the steel and diffuse into areas where tension is concentrated. High pressure is generated by the formation of hydrogen molecules deep inside the metal surface where tension is concentrated, causing cracks that can lead to bearing failure.

With reference to FIG. 2, a description will be given of how the bearing according to the present invention prevents hydrogen rolling.

The surface of the substrate 4 of the rotary contact bearing is covered with a passivated film 5 which is a metal oxide formed of a passivation oxidant.

The sulfone group 6a of the organic sulfonate 6 strongly adsorbs to this membrane in a single molecular layer. This is because the passivated film 5 has a polar structure and interacts with the polar sulfone group 6a. The organic sulfonate 6 redirects its lipophilic group 6b outward. Therefore, the oil film 7 of base oil is stably formed outside the lipophilic group 6b.

In this arrangement, even if the oil film 7 is removed when the rotating element (not shown in FIG. 2) is in frictional contact with the surface of the substrate 4, the surface 8 is covered by the passivated film 5 as it is. have. Moreover, even when the passivated film 5 is peeled off and the new surface 8 is exposed, the alkyldiphenylether oil contained in the base oil minimizes the generation of hydrogen because of its physical properties. More specifically, alkyldiphenylether oils have a higher binding halogen energy of C-H, C-C and C-O than esters and are therefore difficult to decompose.

Moreover, the organic sulfonate 6 provided on the passivated film 5 quickly repairs any broken portion of the oil film 7. This further inhibits hydrogen swelling.

The grease-bearing rotary bearings according to the present invention are durable because there is no flaking on the rotating surface due to hydrogen rolling phenomenon even under high speed and high load working conditions. Moreover, it has high corrosion resistance and extends its life. The bearings according to the invention are particularly suitable for use with alternators.

Other features and objects of the present invention will become more apparent in the following description taken in conjunction with the accompanying drawings.

[Examples 1 and 2]

Alkyldiphenyl ether oil and poly-α-olefin oil were mixed in the ratio shown in Table 1 to form a base oil. 1M of 4,4'-diphenylmethanediisocyanate was dissolved in the first half of the base oil and 2M monoamine (paratoluidine) was dissolved in the second half of the base oil. Next, while stirring the mixture, a second half portion was added to the first half portion. The mixture was stirred at 100-120 ° C. for 30 minutes to complete the reaction. Next, 0.5% by weight of phenothiazine was added to the mixture as an oxidant, which was stirred at 100-120 ° C. for 10 minutes. After cooling, 1% by weight of zinc sulfonate, 1% by weight of polyhydric alcohol ester and 0.5% by weight of sodium nitrite were added to the mixture and further stirred. This mixture was then homogenized using a three-roll mill to obtain the appropriate consistency. The consistency, dropping point and coefficient of friction were measured for each of the thus obtained greases. In addition, the durability of each grease was measured by actually operating a bearing enclosed with grease in an alternating current. We also did a rusting test. The measurement results are shown in Table 1.

Consistency: Measured according to JIS K2220 5.3.

Dropping point: According to the grease dropping point test method of JIS K2220 5.4, the temperature (° C) at which the grease was melted and began to drop by gravity was measured.

Coefficient of friction: As shown in FIG. 3, the felt 11 coated with each sample grease is installed in friction contact with the lower part of the ring 10 (40 mm in diameter, SUJ2) fixed to the motor shaft 9 and plated. The ring 10 was rotated at a speed of 1000 rpm while keeping the ball 13 (diameter 6.35 mm, SUJ2) fixed to (12) pressed against the upper end of the ring 10. The coefficient of friction was calculated from this force (F) by measuring the force (F) generated due to friction under the following conditions.

Measurement time: Measurements were taken 5 minutes after the start of rotation: Load: 1.2 kgf; Temperature: Room temperature

Rust Testing: This test was conducted under more stringent conditions than the Rust testing according to ASTM D 1743. In this test, 1.6-1.9 g of each sample grease was enclosed in a bearing 6302 and a rubber seal was mounted on the bearing. First, an applied shaft load of 39.2 N was applied to the bearings and operated for 1 minute at a speed of 1800 rpm. Next, 0.5 ml of 3% brine was injected into the bearing, and then rotated for 3 minutes at a speed of 1800 rpm with a working shaft load of 39.2N. The bearings were placed in a dryer and left at 40 ° C. for 100 hours. Next, the bearing inner ring was divided into 22 identical pieces along the circumferential surface, and the bearing outer ring was divided into 30 identical pieces. The number of fragments in which Rust is observed was counted. This test was carried out four times and the average number in four tests was made into the table | surface as a Rust value.

The durability test was carried out on an actual alternator: each grease sample was enclosed in a rotating bearing 2 mounted near the pulley 1 of the alternator shown in FIG. 1 and the life test was performed n times. The bearing was spun at a speed of 18,000 rpm with a load of 330 kg on one set of pulleys. The elapsed time (called the flaking time) was measured in the period until the vibration of the bearing measured by the vibration detector exceeded a predetermined value due to flaking and the generator eventually stopped. The average of the flaking times of test n is shown in the table as the lifetime determined by flaking.

In addition, the elapsed time (called the seizure time) is the time until the rotational torque of the bearing is excessively increased due to the deterioration of grease in the bearing and the current flowing into the motor driving the alternator exceeds the limit. Measured. The average of the scissor times for the n-times test is shown in the table as the bearing life determined by the scissor.

In addition, the following experiment was conducted to examine the relationship between the base oil content and the friction coefficient. That is, the alkyldiphenyl ether and poly-α-olefin oil were mixed at the ratio shown in Table 2, and the friction coefficient of this mixture was measured using the apparatus shown in FIG. 3 under the same conditions as the aforementioned measuring method. This result is shown in Table 2.

Example 3

The grease composition was prepared by the same method as Example 1 except adding 1 weight% of zinc dithiophosphate as an extreme pressure additive.

Example 4

Alkyl diphenyl ether oil and poly-α-olefin oil were mixed together in the ratio shown in Table 1 to form a base oil. 1M of 4,4'-diphenylmethanediisocyanate was dissolved in the first half portion of the base oil, and 2M monoamine (pyratuluidine) was dissolved in the second half portion of the base oil, respectively. The mixture was stirred at 100-120 ° C. for 30 minutes to react the components to add aromatic diurea to the base oil. 0.5% by weight of phenothiazine was added to this mixture as an oxidant and it was stirred at 100-120 ° C. for 10 minutes. After cooling, 3% by weight of barium sulfonate was added to the mixture and further stirred. This mixture was then homogenized using a three-roll mill to obtain a grease composition. The grease thus obtained and the rotating bearing sealed with grease were tested in the same manner as in Example 1. The results are shown in Table 1.

[Example 5 and Example 6]

One mole of hydroquinone was dispersed in toluene and 2M of 2,4-tolylenediisocyanate was added dropwise. The resulting mixture was stirred for 50 minutes while maintaining the temperature at about 50 ° C. Triethylamine was used as the reaction catalyst. 1 M of aniline was added thereto and the mixture was stirred for 60 minutes while maintaining the temperature at about 80 ° C. Then 1M of toluene solution saturated with laurylamine was added and the mixture was stirred for 180 minutes. As a result a thickening agent in the form of a urea-urethane compound was prepared. The base oil shown in Table 1 which is a mixture of alkyldiphenyl ether oil, poly-α-olefin oil, and phenothiazine as an oxidizing agent was added to the resultant thickening agent. The mixture was stirred for 30 minutes. The resulting liquid was poured into an enamel butt and left overnight at room temperature. Next, this was placed in a muffle furnace kept at 150 ° C. for 30 minutes and dissolved. The resulting mixture was homogenized using a 3-roll mill to obtain a grease composition. The obtained grease composition and the rotating bearing in which grease was enclosed inside were tested similarly to Example 1. The results are shown in Table 1.

Comparative Example 1

As base oil, only alkyl diphenyl ether oil was used. 1M of 4,4'-diphenylmethanediisocyanate was dissolved in the first half of the base oil (in weight percent), and 2M monoamine (pyratoluidine) was dissolved in the second half of the base oil. . Next, while stirring the mixture, a second half portion was added to the first half portion. The mixture was stirred at 100-120 ° C. for 30 minutes to react these components to add aromatic diuretic compound to the base oil. 0.5% by weight of phenothiazine was added to this compound as an oxidant and stirred at 100-120 ° C. for 10 minutes. After cooling, 0.5% by weight sodium nitrite was added to the mixture and homogenized using a 3-roll mill to obtain a grease composition. The resulting grease and the rotating bearing enclosed with grease therein were tested in the same manner as in Example 1. The results are shown in Table 3.

Comparative Example 2

As the base oil, only poly-α-olefin oil was used. 1M of 4,4'-diphenylmethanediisocyanate was dissolved in the first half of the base oil (in weight percent), and 2M monoamine (cyclohexylamine) was dissolved in the second half of the base oil. did. Next, while stirring the mixture, a second half portion was added to the first half portion.

The mixture was stirred at 100-120 ° C. for 30 minutes to react the components to add aliphatic cyclic diuretic compounds to the base oil. 0.5% by weight of phenothiazine was added to the mixture as an oxidant and it was stirred at 100-120 ° C. for 10 minutes.

After cooling, the mixture was homogenized using a 3-roll mill to obtain a grease composition. The resultant grease and the rotating bearing sealed with grease were tested in the same manner as in Example 1. The results are shown in Table 3.

Comparative Examples 3 and 4

Base oils comprising alkyldiphenyl ether oils and mineral oils or polyol ester oils and thickeners were mixed together in the same proportions as shown in Comparative Example 1. The mixture thus obtained was homogenized to obtain a grease composition.

These grease compositions were enclosed in rotating bearings for the rusting and practical alternator tests described above. This result is shown in Table 3.

As is apparent from the test results shown in Tables 1 and 3, passivation with Comparative Examples 1 and 2 in which alkyldiphenylether oil and poly-α-olefin oil were not mixed with each other as base oil in the amounts specified in accordance with the present invention. Comparative Examples 2-4 without oxidizing agent showed poor values in at least one of the coefficient of friction, the evaluation of the rust and the durability in the actual alternator test. In other words, Examples 1 to 6, including a predetermined base oil and a thickening agent, a passivation oxidizing agent and an organic sulfonate added to the base oil in a predetermined ratio, showed satisfactory results for all test items. Overall, Example 3 shows particularly good results.

Claims (1)

5-40% by weight thickener, which is at least one of a base oil, an aromatic diuretic compound and an aromatic urea-urethane compound in which an alkyldiphenyl ether oil and a poly-α-olefin oil are mixed in a weight ratio of 20:80 to 80:20, A grease-packed rotary contact bearing having a grease composition composed of a passivation oxidant and an organic sulfonate.