JP2003097571A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing having superior conductivity and not adversely impacting the natural environment. SOLUTION: In a deep groove ball bearing 10 provided with an inner ring 11, on outer ring 12, and plural balls 13 rollably provided between both rings 11, 12, conductive and biodegradable grease G containing base oil composed of at least one of biodegradable vegetable oil and ester oil and thickener of metallic soap and carbon black is filled in a space part 16 formed between the inner ring 11 and the outer ring 12 and having the balls provided therein.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has excellent conductivity (low electric resistance between inner and outer rings), water quality,
The present invention relates to a rolling bearing that does not easily adversely affect the natural environment such as soil.

[0002]

2. Description of the Related Art Greasing is generally used in machines and appliances having rotating parts, sliding parts, friction parts, etc. in order to lubricate and prevent rust. Among such machines and appliances, rolling bearings may have a large potential difference between the inner and outer rings due to the influence of static electricity, electric arc, etc.Therefore, conductive grease may be added to such rolling bearings from the viewpoint of antistatic. It is enclosed inside. And as the conductive grease, the one in which carbon black is added as a thickening agent and a conductivity imparting additive is the mainstream (for example,
Japanese Patent Publication No. 63-24038).

On the other hand, rolling bearings are often used in applications where the enclosed grease or lubricating oil is easily released into the natural environment. Since the grease and lubricating oil released to the natural environment may cause pollution of water quality and soil, it has become a big problem these days when environmental issues are being highlighted. As a grease that does not easily cause such an environmental problem, a grease composition containing a polyol ester as a main component (JP-A-6-1989) or a grease composition containing pentaerythritol as a main component (JP-A-8-20789). It has been known. The grease composition has biodegradability, and even if it is released into the natural environment, it is decomposed by microorganisms and the like, so it is unlikely to adversely affect the natural environment.

[0004]

However, since the above-mentioned biodegradable grease composition has no conductivity,
The antistatic effect as described above cannot be expected at all. Therefore, an object of the present invention is to provide a rolling bearing which solves the above-mentioned problems of the prior art and has excellent conductivity and is less likely to adversely affect the natural environment.

[0005]

In order to solve the above-mentioned problems, the present invention has the following constitution. That is, the rolling bearing of the present invention is a rolling bearing including an inner ring, an outer ring, and a plurality of rolling elements rotatably arranged between the inner ring and the outer ring, and a vegetable oil having biodegradability. And a base oil consisting of at least one of an ester oil, and a thickening agent consisting of metallic soap and carbon black, and a conductive and biodegradable grease formed between the inner ring and the outer ring. It is characterized in that the rolling element is filled in the void portion provided therein.

[0006] Such a rolling bearing has excellent conductivity, and even if grease is leaked from the rolling bearing and released to the natural environment, it is decomposed naturally, so that it can be used in natural environments such as water and soil. Less likely to have an adverse effect.
The components contained in the grease will be described below. [Base oil] At least one of vegetable oil and ester oil is used as the base oil of the grease. Since vegetable oils and ester oils are biodegradable, grease is given biodegradability.

Examples of the vegetable oil include rapeseed oil, sunflower oil, soybean oil, cottonseed oil, corn oil and castor oil, which can be used alone or in combination of two or more kinds. However, rapeseed oil having an excellent balance between fluidity at low temperature and oxidation stability is most preferable. Also, as the ester oil,
Examples thereof include natural ester oils and synthetic ester oils, which may be used alone or in admixture of two or more.

The base oil is most preferably a vegetable oil as a main component, but if the main component is a vegetable oil, a mixture of ester oil or other oil may be used as the base oil. Further, in order to adjust the kinematic viscosity depending on the application, a synthetic ester oil containing a polyol ester compound (for example, pentaerythritol ester compound) as a main component may be appropriately blended.

[Thickener] As the thickener for grease, it is preferable to use both conductive carbon black and metallic soap which is a metal salt of a fatty acid. In addition,
Carbon black acts as a thickening agent in grease and also as a conductivity imparting additive.

Examples of the fatty acid which is one of the constituents of the metallic soap include 12-hydroxystearic acid which is a castor oil fatty acid and stearic acid which is a beef tallow fatty acid. Examples of the metal that is the other component of the metallic soap include alkaline earth metals such as calcium and barium, alkaline metals such as lithium and sodium, and aluminum.

Among these metal soaps, lithium soaps such as lithium 12-hydroxystearate soap and lithium complex soap are preferable, and particularly,
Lithium 12-hydroxystearate soap is preferable because it has excellent adhesion to steel materials and has the effect of improving the fretting resistance and wear resistance of the rolling bearing. The content of the thickening agent in the whole grease is preferably 2.2 to 12% by mass in order to impart appropriate flexibility to the grease without impairing the biodegradability of the base oil.
If it is less than 2.2% by mass, the fluidity of the grease is too high, and the grease tends to leak. Then,
It is not preferable because the lubricant is lost early and is easily exhausted. On the other hand, if it exceeds 12% by mass, the fluidity of the grease is lowered and the bearing life is adversely affected.

The compounding ratio of the base oil and the thickening agent in the grease may be within the above range, and may be a consistency suitable for the application of the rolling bearing and its operating temperature, and is not particularly limited. It is not something, but usually JIS
A ratio is selected such that the K2220 consistency number is in the range of 1 to 3 (NLGI blending consistency is No. 1 to No. 3).

The content of carbon black in the entire grease is preferably 0.2 to 10% by mass. If it is less than 0.2% by mass, sufficient conductivity cannot be obtained,
If it exceeds 10% by mass, the consistency of the grease becomes too large (grease becomes too hard). Further, the type of carbon black used in the present invention is not particularly limited, but a carbon black rich in oil absorption (DBP oil absorption is 150 ml / 100 g or more) is desirable from the viewpoint of dispersibility. It also has lipophilicity and a specific surface area of 200
It is preferable to use carbon black as large as m ² / g or more.

If the specific surface area of the carbon black or the DBP oil absorption amount is out of the above range, the oil separation of the base oil becomes too large because of poor affinity with the base oil. If the oil separation is large, the base oil is unevenly distributed in the grease, which not only increases the electric resistance value of the bearing, but also accelerates the leakage of the base oil and grease from the rolling bearing to shorten the bearing life. [Additive] If desired, various additives such as an oiliness agent, an extreme pressure agent, an antioxidant, and a rust inhibitor may be added to the grease.

First, the oiliness agent will be described. The oiliness agent has an effect of preventing the conductivity of the rolling bearing from decreasing with time, and the content of the oiliness agent in the whole grease is 0.5 to 1
When it is 0% by mass, the conductivity is stable for a long period of time.
If it is less than 0.5% by mass, the effect of stabilizing conductivity is insufficient, and if it exceeds 10% by mass, the effect of stabilizing conductivity is improved but the biodegradability of grease may be insufficient.

Surfactants, organic fatty acids, and organic fatty acid derivatives can be used as the oily agent. As the surfactant, a nonionic surfactant such as sorbitan fatty acid ester such as sorbitan monooleate, glycerin fatty acid ester, polyglycerin fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine / fatty acid amide, N-acyl Amino acid or salt thereof, polyoxyethylene alkyl ether acetate, polyoxyethylene alkyl ether phosphate, alkylsulfocarboxylate, alkyl phosphoric acid or salt thereof, polyoxyalkylene alkyl ether phosphoric acid or salt thereof, aromatic phosphoric acid Examples include anionic surfactants such as esters, cationic surfactants such as alkyl ammonium salts and alkylbenzyl ammonium salts, and amphoteric surfactants such as betaine acetate and imidazolinium betaine. That.

The organic fatty acids include oleic acid,
Examples thereof include adipic acid, naphthenic acid and succinic acid, and alkenylsuccinic acid is particularly preferable. Furthermore, examples of the organic fatty acid derivative include alkyl succinic acid ester and alkenyl succinic acid ester. Among the oiliness agents, succinic acid derivatives and the like exhibit the action as extreme pressure agents.

Next, the extreme pressure agent will be described. Since the extreme pressure agent adsorbs well on the rolling surface and sliding surface of the rolling bearing to form a film, it has the effect of improving the wear resistance and fretting resistance of the rolling bearing. The content of the agent is preferably 0.5 to 5% by mass. If it is less than 0.5% by mass, the effect of improving the fretting resistance is insufficient, and if it exceeds 5% by mass, the fretting resistance is improved but the biodegradability of the grease may be insufficient.

As the extreme pressure agent, organic phosphorus compounds and sulfur-phosphorus extreme pressure agents (compounds containing sulfur and phosphorus in the molecule) can be used. Examples of the organic phosphorus compound include phosphoric acid esters, phosphorous acid esters,
Examples thereof include orthophosphoric acid esters and acidic phosphoric acid esters, and specific examples thereof include tricresyl phosphate. Further, as the sulfur-phosphorus extreme pressure agent, for example,
Examples include Anglemol 99 manufactured by Lubrizol Japan.

If a compound containing a heavy metal is used as the extreme pressure agent, the biodegradability of the grease may be significantly reduced. Therefore, it is preferable to use an extreme pressure agent containing no heavy metal. Next, the antioxidant will be described. Examples of the antioxidant include amine compounds such as aliphatic amine and aromatic amine, and specific examples thereof include dioctylphenylamine. The content of the antioxidant with respect to the entire grease is preferably about 0.5 to 3 mass%. If it is less than 0.5% by mass, oxidation may not be sufficiently prevented, and if it is more than 3% by mass, many antioxidants have poor biodegradability, so that the biodegradability as a grease decreases. .

Next, the rust preventive agent will be described. Examples of the rust preventive agent include sulfonate compounds, and specific examples thereof include dinonylnaphthalenesulfonic acid calcium salt. The content of the rust preventive agent in the entire grease is 0.
It is preferably set to 2 to 5 mass%. If it is less than 0.2% by mass, the rust preventive effect will be insufficient, and if it exceeds 5% by mass, the rust preventive effect will be improved but the biodegradability of the grease may be insufficient. However, some oil-based agents also have a rust preventive effect, so the rust preventive agent may not be added in some cases.

A rust preventive agent is usually applied to the inner and outer surfaces of the rolling bearing in order to maintain its rust preventive property. As this rust preventive agent, rust preventive agent in which 0.5 to 2% by mass of dinonylnaphthalenesulfonic acid calcium salt is added as an additive for imparting rust preventive property to oil having excellent biodegradability similar to the base oil of grease It is desirable to use oil. The contents of these various additives are as described above, but the total content of all the additives is preferably 0.5 to 10% by mass with respect to the entire grease. If it is less than 0.5% by mass, the effect of each additive is insufficient, and if it exceeds 10% by mass, the effect of each additive is improved but the biodegradability of the grease may be insufficient.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a rolling bearing according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial vertical sectional view showing the structure of a deep groove ball bearing 10 which is an embodiment of a rolling bearing according to the present invention. This deep groove ball bearing 10 (Nominal number: 6305, inner diameter 25 mm, outer diameter 62
mm, width 17 mm) are the inner ring 11, the outer ring 12, a plurality of balls 13 rotatably arranged between the inner ring 11 and the outer ring 12, and a plurality of balls between the inner ring 11 and the outer ring 12. Cage 14 for holding 13 and shield groove 12b of outer ring 12,
And shields 15 and 15 attached to 12b. Also, the inner ring 11, the outer ring 12, and the shield 1
A gap G surrounded by 5 and 15 is filled with grease G for lubrication, and is sealed inside the ball bearing 10 by a shield 15. The amount of grease G enclosed is 1
It is 35% of the volume of 6.

This grease G uses a vegetable oil such as rapeseed oil as a base oil and a metallic soap such as lithium soap as a thickener. Further, carbon black is added as a thickening agent and an additive for imparting conductivity (addition amount is 0.2 to 10% by mass of the entire grease G), and as various additives, an extreme pressure agent, an antioxidant, Oiliness agent and rust inhibitor are added.

Since such a grease G contains carbon black, it has excellent conductivity. Therefore, the raceways 11a and 12a of both wheels 11 and 12 and the ball 1
The contact surface with 3 is lubricated, and the inner ring 11 and the outer ring 1 are
2 and the ball 13 are in a conductive state. Since the inner ring 11 or the outer ring 12 is grounded (not shown), the ball bearing 10
The static electricity generated by the rotation of the is removed.

Since the base oil is composed of biodegradable vegetable oil, the grease G has excellent biodegradability. Therefore, even if the grease G leaks into the natural environment when the deep groove ball bearing 10 is used outdoors, the grease G is naturally decomposed by microorganisms and the like, which adversely affects the natural environment. Hard to exert. Further, since the grease G also has excellent lubricity, the deep groove ball bearing 10 has a long life. Further, metal contact between the raceways 11a and 12a of the ball bearing 10 and the balls 13 is unlikely to occur,
Since an oxide film is less likely to be formed on the raceway surfaces 11a and 12a, the conductivity is less likely to decrease with time.

The shield 15 may be a contact type seal made of elastic rubber having conductivity. Then, since the seal has conductivity, and the lip portion of the seal is in sliding contact with the outer peripheral surface of the inner ring 11, the inner ring 11
Between the outer ring 12 and the outer ring 12 is electrically conductive via a seal, which is preferable. The present embodiment shows an example of the present invention, and the present invention is not limited to this embodiment.

For example, in this embodiment, a deep groove ball bearing has been described as an example of the rolling bearing, but the rolling bearing of the present invention can be applied to various other types of rolling bearings. For example, radial type ball bearings, self-aligning ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, self-aligning roller bearings and other radial type rolling bearings, and thrust ball bearings, thrust roller bearings and other thrust type bearings. It is a rolling bearing.

The grease G is not limited to rolling bearings, and can be applied to rolling devices equipped with members that move relative to each other, such as ball screws, linear guides, and linear motion bearings. Furthermore, the use of the grease G is not limited to the rolling device, and can be applied to various members that require lubricity and conductivity. If this grease is used when it is easily released to the natural environment, the adverse effect on the natural environment can be reduced.

Next, the biodegradability of several kinds of greases (Examples 1 to 5 and Comparative Examples 1 to 3) having different compositions such as base oil, thickener and various additives were evaluated. Table 1 shows the composition and physical properties (NLGI miscibility and biodegradability) of these greases. In Table 1, the extreme pressure agent is an organic phosphorus compound, the antioxidant is an amine compound, and the oily agent is an organic fatty acid derivative.

The values of biodegradability in Table 1 are CEC.
Standard (European Standards Advisory Committee Standard) L-33-A-93
The degree of biodegradation specified in. The grease used for rolling bearings can be decomposed when released into the natural environment.
The degree of biodegradation is preferably 80% or more, particularly preferably 90% or more.

[0032]

[Table 1]

Since the rapeseed oil was used as the base oil in the greases of Examples 1 to 5, the degree of biodegradation was 90% or more, and the grease was excellent in biodegradability. On the other hand, the greases of Comparative Examples 2 and 3 were inferior in biodegradability because they used mineral oil or poly-α-olefin oil (PAO) that did not have biodegradability as the base oil. Next, Examples 1 to 5
The grease of Comparative Examples 1 to 3 was applied to the deep groove ball bearing 10 described above.
Enclosed in a ball bearing with almost the same configuration as the
The bearing life was evaluated.

The deep groove ball bearing was attached to a bearing rotation tester manufactured by NSK Ltd., and an axial load of 1470N and a radial load of 98N were applied, and at high temperature (outer ring temperature 1
The rotation test was performed at 20 ° C.) at a rotation speed of 10,000 min ⁻¹ . Then, the rotation time until the temperature or the rotation torque of the outer ring reaches a predetermined value is defined as the life of the deep groove ball bearing. The results are also shown in Table 1. The bearing life in Table 1 is the life of the bearing in Example 1 filled with grease.
Is shown as a relative value.

As can be seen from Table 1, the grease-filled bearings of Examples 1 to 5 were all excellent in life. On the other hand, in the grease of Comparative Example 1, the additives such as the oiliness agent and the extreme pressure agent were not added, and therefore the bearing life was inferior. Next, the bearing resistance value (conductivity) of the rolling bearing will be described. The rotation test of the test bearing was performed, and the initial rotation and 5
The electric resistance value (maximum value) between the inner and outer rings after the rotation for 00 hours was measured by the circuit shown in FIG. 2 to evaluate the degree of change in conductivity with time. Since the circuit includes a data collection system that converts the voltage measurement results of the inner ring and the outer ring into resistance values, it is possible to obtain electric resistance values during rotation.

The bearing used in this test is a ball bearing having an inner diameter of 8 mm, an outer diameter of 22 mm and a width of 7 mm.
155 to 165 mg of the grease of Examples 1 to 5 and Comparative Examples 1 to 3 is enclosed therein. The measurement conditions are shown below.・ Rotation speed: 150min ^-1・ Radial load applied to the bearing (Fr): 19.6N ・ Applied voltage: 6.2V ・ Maximum current: 100μA ・ Series resistance: 62kΩ ・ Ambient temperature: 25 ℃ ・ Ambient humidity: 50% RH -Sampling cycle: 50 kHz, 0.326 seconds Table 1 also shows the measurement results. The bearing resistance value in Table 1 is the bearing resistance value after rotation for 500 hours, and
The bearing resistance value in the initial stage of rotation of the bearing with grease
Is shown as a relative value.

Comparing the grease-filled bearings of Examples 1 to 5 with the grease-filled bearings of Comparative Examples 1 to 3, the former has a smaller change in bearing resistance over time (increase in bearing resistance). I understand. Next, the grease of Example 1 was prepared in which the specific surface area (value by the nitrogen adsorption method) of carbon black was changed variously, and the bearing resistance value was measured in the same manner as above. The results are shown in the graph of FIG. In addition, the numerical value of each plot of this graph is a bearing resistance value after 500 hours of rotation, and the bearing resistance value at the initial stage of rotation of the grease-filled bearing of Example 1 (□ in the graph of FIG. 3).
It is shown as a relative value when () is 1.

From the graph of FIG. 3, it can be seen that the larger the specific surface area of carbon black, the smaller the temporal change in bearing resistance value (increase in bearing resistance value) tends to be, and that 200 m ² / g or more is particularly preferable. Next, the grease of Example 1 was prepared by variously changing the DBP oil absorption of carbon black (value by dibutyl phthalate upsorpometer), and the bearing resistance value was measured in the same manner as above.
The result is shown in the graph of FIG. The numerical value of each plot in this graph is the bearing resistance value after 500 hours of rotation, and the bearing resistance value (marked with □ in the graph of FIG. 4) in the initial rotation of the grease-filled bearing of Example 1 is 1. It is shown as a relative value in the case of doing.

From the graph of FIG. 4, the carbon black D
The larger the BP oil absorption, the smaller the change in bearing resistance over time (increase in bearing resistance) tends to be small.
It turns out that 100 g or more is preferable. Next, Example 1
Various greases having different kinematic viscosities of the base oil at 40 ° C. were prepared, and the bearing resistance value was measured in the same manner as above. The biodegradability of grease was also evaluated. The result is shown in the graph of FIG. The numerical value of each plot in this graph is the bearing resistance value after 500 hours of rotation, and the bearing resistance value (marked with Δ in the graph of FIG. 5) at the beginning of rotation of the grease-filled bearing of Example 1 is 1. It is shown as a relative value in the case of doing.

First, it can be seen that the degree of biodegradation of grease is almost constant regardless of the kinematic viscosity of the base oil, and the influence of the kinematic viscosity of the base oil on the biodegradability is small. On the other hand, regarding conductivity, the lower the kinematic viscosity of the base oil, the smaller the change in bearing resistance with time (increase in bearing resistance) tends to be small, and it is particularly preferable that 30 to 90 mm ² / s is preferable. . If it is less than 30 mm ² / s, the lubricity becomes insufficient, which is not suitable.

[0041]

As described above, the rolling bearing of the present invention is
Since it has a grease having excellent conductivity and biodegradability, it has excellent conductivity and is unlikely to adversely affect the natural environment.

[Brief description of drawings]

FIG. 1 is a partial vertical sectional view showing the structure of a deep groove ball bearing which is an embodiment of a rolling bearing according to the present invention.

FIG. 2 is a schematic configuration diagram of an apparatus for measuring an electric resistance value of a bearing.

FIG. 3 is a graph showing the correlation between the specific surface area of carbon black and the bearing resistance value after rotation for 500 hours.

FIG. 4 is a graph showing a correlation between a DBP oil absorption amount of carbon black and a bearing resistance value after rotation for 500 hours.

FIG. 5 is a graph showing the correlation between the kinematic viscosity of the base oil and the bearing resistance value and biodegradability after rotation for 500 hours.

[Explanation of symbols]

10 deep groove ball bearings 11 inner ring 12 outer ring 13 balls 16 void G grease

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C10M 117/04 C10M 117/04 125/02 125/02 169/00 169/00 // C10N 10:02 C10N 10:02 10:04 10:04 10:06 10:06 20:00 20:00 Z 30:00 30:00 Z 30:02 30:02 30:06 30:06 30:10 30:10 30:12 30:12 40:02 40:02 50:10 50:10 F-term (reference) 3J101 AA02 AA32 AA42 AA52 AA62 EA52 EA54 EA64 EA72 FA11 FA60 4H104 AA04B AA04C BB17B BB19B BB31A DA06A EA14C EB05 EB08 LA01 FA03 FA10 EB09 FA03 EB09 FA10 FB09 FA03 LA20 PA01 QA18

Claims (6)

[Claims] 1. A rolling bearing comprising an inner ring, an outer ring, and a plurality of rolling elements rotatably arranged between the inner ring and the outer ring, wherein a biodegradable vegetable oil and ester oil are used. A conductive oil and biodegradable grease containing at least one base oil and a thickening agent made of metal soap and carbon black is formed between the inner ring and the outer ring, and the rolling element is A rolling bearing characterized by being filled in an established void. 2. The rolling bearing according to claim 1, wherein the content of the thickener with respect to the entire grease is 2.2 to 12 mass%. 3. The rolling bearing according to claim 1, wherein the content of the carbon black with respect to the entire grease is 0.2 to 10% by mass. 4. The specific surface area of the carbon black is 20.
It is 0 m < ² > / g or more, The rolling bearing in any one of Claims 1-3 characterized by the above-mentioned. 5. The rolling bearing according to claim 1, wherein the carbon black has a DBP oil absorption of 150 ml / 100 g or more. 6. The grease contains an additive comprising at least one of an oiliness agent, an extreme pressure agent, an antioxidant, and a rust inhibitor, and the content of the additive with respect to the entire grease is It is 0.5-10 mass%, The rolling bearing in any one of Claims 1-5 characterized by the above-mentioned.