JP2004150473A - Lubricating method for rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricating method for a rolling bearing used under a boundary lubricating condition of a low speed/high load and high temperature. <P>SOLUTION: In this lubricating method for the rolling bearing for supplying a lubricant to the rolling bearing, very fine silica particles of an average particle size of 40 nm or less having a hydroxyl group on their surfaces are directly supplied to the rolling bearing and/or supplied to a pipe for supplying the lubricant to the rolling bearing, to form a silica coating film on a rolling surface of the rolling bearing. Whereby the metal contact can be stably prevented, the sufficient lubricating state can be kept, the abrasion and fatigue deterioration of the rolling surface can be prevented, and the long life of the rolling bearing can be inexpensively achieved. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of lubricating a rolling bearing, and more particularly to a method of lubricating a rolling bearing used under boundary lubrication conditions in an environment of low speed, high load, or even high temperature.
[0002]
[Prior art]
2. Description of the Related Art Generally, a large number of rolling bearings are used as mechanical element parts in a rotary motion part of industrial machine equipment. Above all, the operating environment of steelmaking-related equipment such as rolling mills and continuous casting equipment is harsh, and the rolling bearings used there are in environments that are disadvantageous for bearing lubrication, such as low speed, high load, and high temperature. Generally, the life is short due to the influence of extraneous foreign substances such as dust and water.
[0003]
Generally, a lubricating oil film is formed on the lubricating interface of a rolling bearing to avoid metal-metal contact (metal contact) and reduce friction and wear of the bearing. However, under conditions such as low speed, high load, and even high temperature, a so-called boundary lubrication region is likely to occur. With a normal lubricant (mineral oil, grease), the thickness of the lubricating oil film formed on the lubricating interface becomes extremely thin, and metal contact occurs. Tends to occur. For this reason, heat generation, abrasion, indentation due to abrasion powder, local fatigue delamination damage, and the like occur, and the bearing life is reduced to 1/2 to 1/100 of the normal.
[0004]
To cope with such a problem, a method of improving the lubricity of a bearing by adding an oiliness improver, an extreme pressure additive, or a solid lubricant to a lubricant has been conventionally considered. The oiliness improver is mainly composed of polar molecules, adsorbs on the metal surface to form an adsorbed film on the metal surface, and the extreme pressure additive reacts with the metal surface to form a reactive film or adhere to the metal surface. All are intended to create films and prevent metal contact. In addition, the solid lubricant adheres to the metal surface, such as molybdenum disulfide, graphite, or the like, and forms a slippery layer to reduce slip resistance under boundary lubrication conditions.
[0005]
However, by adding an oiliness improver, extreme pressure additive or solid lubricant to the lubricant, a certain effect on the lubricity improvement of the rolling bearing is recognized, but it is limited to a certain range of lubrication conditions. No remarkable effect was found under more severe lubricating conditions. Therefore, under severe lubrication conditions, strong metal contact still occurred, and the bearing life was short.
[0006]
To cope with such a problem, for example, Patent Document 1 discloses a grease composition containing a base oil, a thickener selected from a metal soap compound or a urea compound, and an inorganic compound filler having a particle size of 2 μm or less. Things have been suggested. By incorporating an inorganic compound filler into the grease composition, the gel structure formed by the thickener is strengthened, the ability to form a grease film is increased, the damping effect against impact load is increased, and the peeling prevention effect is increased. I have to.
[0007]
Further, Patent Document 2 discloses that ultrafine silica particles and / or ultrafine silica particles having an action of lowering the surface pressure of a metal contact portion by interposing in an interface concave portion, acting as a micro roller, and polishing an adhered portion of a metal contact. A lubricant for a rolling bearing has been proposed in which fine silica particles are contained in a base oil or a base grease to maintain high lubricity in a rolling bearing.
[0008]
[Patent Document 1]
Japanese Patent Application Laid-Open No. Hei 9-16989 [Patent Document 2]
JP 2000-105473 A
[Problems to be solved by the invention]
However, even with the technology described in Patent Literature 1, there is a problem that a sufficient lubricating state cannot be maintained under severe environments such as low speed, high load, and high temperature.
Further, the technique described in Patent Document 2 has a problem that the above-described effect of the silica particles may not be sufficiently exerted depending on the viscosity of the base oil or the apparent viscosity of the base grease. In addition, there is also a problem that the cost of the lubricant containing silica is higher than that of a normal lubricant.
[0010]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and provides a lubrication system that can maintain an excellent lubrication state of a rolling bearing used under boundary lubrication conditions, which is a severe environment of low speed, high load, high temperature, and even oscillating. The aim is to propose a method. The lubricant in the present invention includes lubricating oil and grease.
[0011]
[Means for Solving the Problems]
The present inventors have conducted intensive studies on various factors affecting the lubrication of rolling bearings in order to achieve the above-mentioned object. As a result, by forming a silica coating on the rolling surface of the bearing during use of the rolling bearing, metal contact can be achieved even in harsh environments under boundary lubrication conditions such as low speed, high load, high temperature, or oscillating motion. It has been found that sufficient lubrication can be maintained and that rolling surface wear and fatigue damage can be prevented, thereby extending the life of rolling bearings.
[0012]
The present invention has been completed by further study based on the above findings.
That is, the gist of the present invention is as follows.
(1) Supplying a lubricant to a rolling bearing In a lubrication method for a rolling bearing, ultrafine silica particles having a hydroxyl group on the surface and having an average particle size of 40 nm or less are directly supplied to the rolling bearing and / or a lubricant is supplied to the rolling bearing. A lubricating method for a rolling bearing, wherein a silica coating is formed on a rolling surface of the rolling bearing by supplying the lubricating oil to a rolling pipe.
(2) The rolling bearing according to (1), wherein ultrafine silica particles having a hydroxyl group on the surface and having an average particle diameter of 40 nm or less are supplied so as to contain 1 to 20% by mass based on the total amount of the lubricant. Lubrication method.
(3) (1) or (2), wherein the rolling bearing, the following equation (1) _{λ = h / √ (σ 1} 2 + σ 2 2) ......... (1)
(Where, λ: oil film parameter, h: oil film thickness (μm), σ ₁ , σ ₂ : surface roughness (μm) of two rolling bearings (roller or ball and inner or outer ring))
A lubricating method for a rolling bearing, wherein the oil film parameter λ defined in (1) is less than 1.
[0013]
In the present invention, the average particle size is an average value obtained by measuring the primary particle size of several hundred particles by observation with an optical microscope or an electron microscope.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
In a rolling bearing, usually, lubrication is performed by supplying lubricant continuously or intermittently by automatic lubrication or manual lubrication. In the present invention, in addition to such lubrication of the rolling bearing, a silica coating is further formed on the rolling surface to lubricate the rolling bearing. By forming a silica coating on the rolling surface, a strong and thick lubricating film can be formed, metal contact can be prevented stably and sufficient lubrication can be maintained, and wear and fatigue damage on the rolling surface can be prevented. The service life of the rolling bearing can be extended. The silica coating is formed during operation (use) of the bearing, but may be formed in advance on the rolling surface of the bearing.
[0015]
In the present invention, a method of forming a silica coating on a rolling surface of a bearing during operation (use) is as follows. In the present invention, the lubricant supplied to the bearing and / or the supplied lubricant has an average particle size having a hydroxyl group on the surface. Ultrafine silica particles having a diameter of 40 nm or less (hereinafter, also referred to as ultrafine silica particles) are supplied continuously or intermittently. That is, the ultrafine silica particles having a hydroxyl group on the surface are supplied directly to the bearing 1b and / or to a pipe 3a for supplying a lubricant to the bearing 1a, as shown in FIG. It is contained in the agent. Ultrafine silica particles having a hydroxyl group on the surface have heat resistance, and have an advantageous property that a hard and wear-resistant adsorption film is easily formed on the rolling surface of the bearing. By containing ultra-fine silica particles having a hydroxyl group on the surface in the lubricant of the bearing, a silica film is formed on the rolling surface of the bearing, and the wear resistance and fatigue resistance of the bearing are remarkably improved.
[0016]
In addition, by supplying ultra-fine silica particles having a hydroxyl group on the surface to a pipe for directly supplying a lubricant to the bearing and / or for supplying a lubricant to the bearing, a silica coating is formed on a rolling surface to thereby provide wear resistance and fatigue resistance. Ultra-fine silica particles are intensively supplied only to bearings that are required to improve the performance. As a result, the silica particles can be added only when necessary, and the lubricant cost can be reduced as compared with the case where the silica particles are previously added to the lubricant. There is an effect that clogging of the distribution valve and the like can be prevented.
[0017]
On the other hand, if the average particle size of the silica particles contained in the lubricant exceeds 40 nm, the adsorptive power is weak and a silica film is not formed on the rolling surface. The average particle diameter of the silica particles used is preferably 30 nm or less, more preferably 20 nm or less, and further preferably less than 10 nm. If the particle size of the ultrafine silica particles is less than 4 nm, it is difficult to obtain uniform particles, so that it is difficult to obtain a suitable lubricating effect.
[0018]
Further, the amount of the ultrafine silica particles contained in the lubricant is preferably 1 to 20% by mass based on the total amount of the lubricant. When the content of the ultrafine silica particles is less than 1% by mass, formation of a silica coating is not recognized. On the other hand, if it exceeds 20% by mass, there is a problem that the thickening effect becomes large and the lubricant cannot be supplied uniformly. In addition, it is more preferably 2 to 15% by mass, and still more preferably 3 to 10% by mass. In addition, it is preferable to adjust the content of the silica particles in the lubricant in the bearing so that the supply amount of the lubricant and the supply amount of silica are balanced to keep the content as constant as possible in this range.
[0019]
In the present invention, the type of the lubricant supplied to the bearing is not particularly limited. It is preferable to use a lubricant to which a base oil or a base grease suitable for a lubricant property such as a kinematic viscosity and a viscosity index required for the lubricant is applied according to a use environment of the bearing.
As the base oil, lubricating oils such as mineral oils, synthetic oils, natural oils, and silicone oils are preferred. The base grease is preferably one obtained by adding a thickener such as lithium soap, calcium soap, aluminum composite soap, or urea to the above base oil.
[0020]
As the mineral oil-based base oil, a mineral oil obtained by distilling a mineral oil under reduced pressure and removing an unstable component and a wax component by appropriately combining solvent purification, hydrogen purification, sulfuric acid washing, clay treatment, solvent dewaxing and the like can be used.
Synthetic base oils include aliphatic α-olefins, aliphatic hydrocarbon oils such as polybutene, aromatic hydrocarbon oils such as alkylbenzene, ester oils such as polyol esters and phosphate esters, polyphenyl ethers, polyglycols And other ether-based oils.
[0021]
Lubricants that can be suitably used in the present invention include, in the above-described base oil or base grease, conventionally known oiliness improvers, extreme pressure additives, solid lubricants, rust preventives, thickeners, and surfactants. It goes without saying that various additives such as agents may be added as necessary.
For example, in addition to oleic acid, stearic acid, higher alcohols, esters, amines, etc., as oiliness improvers, sulfur-based compounds, such as sulfurized oils and fats, and phosphorus-based compounds, such as tricresyl phosphate, as extreme pressure additives However, examples of the solid lubricant include molybdenum disulfide, graphite, organic molybdenum, and boron nitride.
[0022]
Lubrication method of the present invention described above, the rolling bearing, the following equation (1) _{λ = h / √ (σ 1} 2 + σ 2 2) ......... (1)
(Where, λ: oil film parameter, h: oil film thickness (μm), σ ₁ , σ ₂ : surface roughness (μm) of two rolling bearings (roller or ball and inner or outer ring))
It is preferable to apply the present invention to a rolling bearing in which the oil film parameter λ defined by In a rolling bearing in which the oil film parameter λ is in the range of 1 or more, even when a conventional lubrication method is used, an oil film is sufficiently formed and metal contact hardly occurs. Applying the lubrication method of the present invention only increases costs. Rolling bearings in which the oil film parameter λ is less than 1 include rolling bearings for guide rolls of continuous casting machines, rolling bearings for universal joints, rolling bearings that swing, and rolling bearings that support rolls whose rotation direction is reversed. Etc. can be exemplified. Further, the lubrication method of the present invention can be applied to a bearing in which slippage is likely to occur, for example, a ball bearing, a self-aligning bearing, and the like.
[0023]
【Example】
(Example 1)
A radial load of 1/4 of the static rated load was applied to the self-aligning roller bearing, and the bearing was operated at a rotation speed of 10 rpm for a predetermined time in a high temperature atmosphere of 80 ° C. During operation, a grease composition (lubricant) containing mineral oil (kinematic viscosity 400 mm ² / sec, at 40 ° C.) as a base oil, which is a main component of the base grease, is used in an automatic greasing system as shown in FIG. Ultrafine silica particles were supplied directly to the bearings as well as to the bearings. The ultrafine silica particles were appropriately supplied so as to be always 5% by mass in the lubricant in the bearing.
[0024]
After the operation, the bearing was disassembled, the wear profile was measured on the outer raceway surface, and the presence or absence of a coating was investigated by Auger electron spectroscopy. In this use condition, the oil film thickness h calculated from the base oil viscosity is 0.05 μm, the surface roughness of the rollers and the inner and outer rings is 0.2 μm, and the oil film parameter λ of the formula (1) is less than 1. Of 0.18.
As a result, when the ultrafine silica particles are directly supplied to the bearing and the ultrafine silica particles are contained in the lubricant (Example of the present invention), a silica film is formed on the surface of the rolling surface by about 30 nm, and the ultrafine silica particles are formed. The amount of wear on the raceway surface of the outer ring is reduced to 1/5 or less as compared with the case where the bearing is not supplied (Comparative Example), and a longer life of the rolling bearing can be achieved.
[0025]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, even under severe use environments, such as low speed, high load, high temperature, or oscillating motion, the life of a rolling bearing can be expected to be extended, the frequency of maintenance of mechanical parts is reduced, and productivity is further reduced. It has a remarkable industrial effect, such as improvement.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example of a lubricant supply system suitable for the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rolling bearing 2 Lubricant supply control means 3 Lubricant supply piping 3a, 3b, 3c: Lubricant supply piping branch 4 Ultrafine silica storage tank 5 Lubricant storage tank

Claims (3)

A lubrication method for a rolling bearing for supplying a lubricant to a rolling bearing, wherein a pipe for supplying a lubricant to the rolling bearing directly with ultra-fine silica particles having an average particle diameter of 40 nm or less having a hydroxyl group on a surface thereof, and / or And forming a silica coating on the rolling surface of the rolling bearing. The lubrication of a rolling bearing according to claim 1, wherein ultrafine silica particles having a hydroxyl group on the surface and having an average particle diameter of 40 nm or less are supplied so as to contain 1 to 20% by mass based on the total amount of the lubricant. Method. The lubrication method for a rolling bearing according to claim 1, wherein the rolling bearing is a rolling bearing in which an oil film parameter λ defined by the following equation (1) is less than 1. 4.
Note λ = h / √ (σ ₁ ² + σ ₂ ² ) (1)
Here, λ: oil film parameter h: oil film thickness (μm)
σ ₁ , σ ₂ : Surface roughness (μm) of two rolling bearings (roller or ball and inner or outer ring)

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