JPH11247862A - Sealed roller bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the service life of grease from being affected by forming a chemical formation treated film on a raceway surface of an outer ring, specifying the film thickness, and specifying the concentration of calcium in the film relative to zinc to keep the rust-proof property and the galling preventive function. SOLUTION: A chemical formation treated film 8 is formed of manganese phosphate, zinc phosphate or calcium zinc phosphate on a surface of raceway surfaces 4, 5 of an inner ring 2 and an outer ring 3 of a bearing 1, and grease 6 is sealed with a seal member 7. The film thickness of the chemical formation treated film is >=1 μm to <=5 μm, and the concentration of calcium in the chemical formation treatment solution to be used in forming the thin film is >=0.4 to <0.8 to the concentration of zinc in the treatment solution. Spherical crystals are especially effective taking into consideration the crystalline shape in forming the thin film, and the time of durability is rapidly reduced when the film thickness exceeds 5 μm, while the time of durability is increased but the rust-proof property becomes inferior if the film thickness is <=1 μm. When the grain becomes coarse, the service life of grease is reduced. Thus, the rust-proof property and the galling preventive function are kept, and the service life of grease is not affected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment of a sealed roller bearing for a railway vehicle axle by grease lubrication.

[0002]

2. Description of the Related Art Among sealed roller bearings, a sealed roller bearing for an axle of a railway vehicle imparts rust-preventive force to an outer diameter surface of an outer ring.
In addition, it is necessary to provide a function of preventing galling when the wheel axle is pressed into the inner surface of the inner ring. Therefore, conventionally, the entire surface of the inner and outer rings is subjected to a phosphate treatment so as to satisfy the above functions required for the bearing. As these treatments, a chemical conversion treatment film having a film thickness of 5 to 8 μm, such as manganese phosphate treatment, is known. Conventionally, even if the above treatment is performed up to the raceway surfaces of the inner and outer rings, the performance of the bearing is not affected at all. There was no problem. Such bearings have been lubricated with a lubrication unit.

[0003]

However, with the recent reduction in the weight of railway vehicles, the method of lubricating bearings is changing from oil lubrication to grease lubrication without a lubrication unit. On the other hand, sealed rolling bearings are often used, which tends to lengthen the maintenance period of the bearings. In this case, the life of the grease greatly affects the durability of the bearing.

[0004] When the inner and outer races are subjected to the chemical conversion treatment as described above, the chemical conversion coating film is removed from the raceway surface by the rolling contact motion between the raceway surface and the rolling element, and is dispersed in the grease. As a result, when the coating has a certain concentration or more, the grease is accelerated in deterioration. Therefore, it is desirable that the amount of wear powder from the chemical conversion treatment such as manganese phosphate on the raceway surface be as small as possible. In other words, for the durability of the bearing, (1) no coating film is formed on the raceway surfaces of the inner and outer races, and (2) when the coating film is formed by the chemical conversion process, the raceway surface is subsequently machined (wrapped). It is preferable to remove the coating film. (1)
Is a method of applying a chemical conversion treatment after applying an acid-resistant masking agent to the raceway surface. However, if this method is adopted, the number of manufacturing steps of the bearing is increased, so that the processing cost is increased, and the yield of using incomplete masking is reduced. Further, the method (2) has a problem that the bus shape of the bearing raceway surface is deteriorated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a chemical conversion coating which does not affect the life of the grease to be sealed, while retaining the function of preventing rusting and galling of the bearing.

[0006]

In order to solve the above problems, the present invention relates to a sealed roller bearing lubricated with grease, wherein a chemical conversion treatment film is formed on the surfaces of the raceways of the inner ring and the outer ring of the bearing. The thickness of the chemical conversion treatment film is 1 μm or more and 5 μm or less, and the strength of calcium in the chemical conversion treatment film is 0.4% of the strength of zinc in the chemical conversion treatment film.
That is all.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A sealed roller bearing according to the present invention is a sealed roller bearing lubricated with grease, wherein a chemical conversion film is formed on the surfaces of raceway surfaces of an inner ring and an outer ring of the bearing. Has a film thickness of 1 μm or more and 5 μm or less,
The concentration of calcium in the chemical conversion treatment liquid used for forming the chemical conversion treatment film is 0.4 or more with respect to the concentration of zinc in the treatment liquid.
It is preferably less than 8.

The sealed roller bearing of the present invention is a sealed roller bearing which is lubricated with grease, wherein a chemical conversion film is formed on the surface of the raceway surface of the inner ring and the outer ring of the bearing, and the chemical conversion film is 2 μm or more. It is composed of spherical crystals of 10 μm or less, and the weight ratio of calcium in the chemical conversion treatment film is 4 wt.
% And the weight ratio of zinc is preferably 40% by weight or less.

The sealed roller bearing of the present invention is a sealed roller bearing lubricated with grease, wherein a chemical conversion film is formed on the surface of the raceway surfaces of the inner ring and the outer ring of the bearing, and the chemical conversion film is 2 μm or more. It is composed of spherical crystals of 10 μm or less, and the concentration of calcium in the chemical conversion treatment solution used for forming the chemical conversion treatment film is 0.1% with respect to the concentration of zinc in the treatment solution.
It is preferably from 4 to less than 0.8.

[0010]

FIG. 1 is a sectional view showing a sealed cylindrical roller bearing for an axle of a railway vehicle according to this embodiment. Bearing 1 of the present embodiment
Manganese phosphate, zinc phosphate, or zinc phosphate.
The conversion coating 8 is formed by calcium. Bearing 1
Are sealed by a seal member 7 using grease 6 as a lubricant.

The bearing according to this embodiment may be a tapered roller bearing or a needle roller bearing. Further, the chemical conversion coating may be applied not only to the raceway surfaces of the inner ring and the outer ring but also to the entire surface of the inner ring and the outer ring.

FIG. 2 is a diagram showing the relationship between the coating thickness of the sealed roller bearing and the endurance time of the bearing. For forming a thin film, spherical crystals are particularly effective in consideration of the crystal shape. The durability test was carried out using a cylindrical roller bearing with an inner ring flange (FIG. 1) having an outer diameter of 52 mm, an inner diameter of 25 mm, and a width of 15 mm as a test piece.
The acceleration test was performed under the following conditions. Table 1 Rotational speed Radial load Lubricant Temperature 10000 rpm 180 kgf Emarove 120 ° C Here, the durability time means that the load current value of the motor for rotating the wheel set pressed into the bearing, which is the specimen, becomes larger than the steady value (2 A). , Refers to the time to exceed 4A, which corresponds to the time to grease deterioration.

As can be seen from FIG. 2, the coating thickness is 5 μm.
Is exceeded, the durability time sharply decreases, and the thickness of the chemical conversion treatment film is desirably 5 μm or less. On the other hand, when the thickness is 1 μm or less, the durability time is prolonged, but the rust prevention is poor. Therefore, preferably 4 μm to 2 μm, more preferably 3 μm to
It is desirable that the thickness be 2 μm or less. As described above, FIG.
The relationship between the thickness of the chemical conversion coating, the galling of the bearing, and the endurance time can be known.

FIG. 3 shows the relationship between the size or particle size of the spherical crystal grains of the chemical conversion coating formed on the raceway surfaces of the inner and outer races of the bearing (FIG. 1) and the durability time of the bearing, that is, the durability life of the grease. is there.

For the formation of the spherical crystals, a chemical conversion treatment solution of phosphoric acid containing zinc and calcium was used, but a nitric acid solution containing zinc and calcium may be used. Depending on the stoichiometric ratio of the spherical crystals, needle-like crystals (zinc phosphate) having a size of 15 μm or more may be formed. In this case, the film thickness increases and the durability time decreases.

Even when spherical crystals are used, the crystal grains may become coarse, in which case the grease life is shortened. In consideration of the above, it is possible to control the film thickness to 5 μm or less, which is about half or less of the particle diameter, by making the spherical crystal 10 μm or less. In addition, the particle diameter of the spherical crystal is 10 μm
When the particle size is larger, the film thickness increases and the grease life is deteriorated. That is, the particle size of the desired spherical crystal is 10 μm to 2 μm, preferably 8 μm to 4 μm, more preferably 6 μm.
It is desirable that the thickness be 4 μm or less.

As described above, FIG.
It is possible to know the relationship between bearing galling and durability time.

The horizontal axis is EDS (Energy dispe
The ZAF correction was performed using a rsive spectroscopy, and the weight ratio was obtained (measured for 100 seconds under the conditions of an acceleration voltage of 15 kV and a fixed area of 0.01 mm ² ).

These rust preventive coatings are composed of four components of oxygen, phosphorus, zinc, calcium and iron, and zinc and calcium are particularly important as the weight ratio of each element in the surface crystal. The weight ratio of zinc capable of forming spherical crystals determined by the above analysis method is desirably 25 to 40 wt%, and the weight ratio of calcium is desirably 4 to 10 wt%. That is, the composition ratio of calcium to zinc is preferably from 0.1 to 0.4, and more preferably from 0.15 to 0.3. If these constituent ratios are larger than 0.3, spherical crystals cannot be formed, and the base metal is only corroded by phosphoric acid, resulting in poor rust prevention. On the other hand, if it is less than 0.15, needle-like crystals are generated instead of dense spherical crystals, the film thickness increases, and the roughness of both the surface and the base deteriorates. The respective weight ratios of oxygen, phosphorus, and iron obtained in the same manner do not directly affect the formation of spherical crystals, but approximately 30 to 50 wt.
%, Phosphorus 10-15 wt%, and iron 5-15 wt%, there is no particular problem.

The composition ratio of calcium and zinc (weight ratio of calcium / weight ratio of zinc) in the crystals precipitated on the bearing surface by the chemical conversion treatment is plotted, and the vertical axis is plotted with the time until the occurrence of rust. .

In the rust prevention test, specimens of the same type having different calcium strength ratios were placed side by side on outdoor concrete,
The observation was performed by visually observing the state of rust generation.

As shown in FIG. 4, when the composition ratio of calcium is less than 0.1, needle-like crystals (hopite) of zinc phosphate grow, the coating thickness increases, and the grease deteriorates. In addition, since coarse needle-like crystals appear, dense spherical crystals cannot be grown, and the rust prevention effect is low. On the other hand, when the composition ratio of calcium was 0.4 or more, uniform spherical crystals were obtained, so that the rust preventing effect was high, and no rust was observed up to 72 hours. That is, the desirable composition ratio of calcium is 0.1 to 0.4, preferably 0.15
０．３0.3. As described above, the relationship between the components of the chemical conversion coating and the rust preventive power can be known from FIG.

FIG. 5 is a graph showing the relationship between the calcium concentration ratio in the chemical conversion treatment solution and the rust prevention performance of the bearing. Here, the concentration ratio of calcium is a value obtained by dividing the concentration of calcium in the chemical conversion treatment solution by the concentration of zinc in the solution.

Whether or not the crystals precipitated by the chemical conversion treatment become spherical depends on the stoichiometric ratio of zinc phosphate and calcium phosphate. Zinc ions and calcium ions dissolved in the treatment solution are converted into inorganic acids such as nitric acid and hydrochloric acid. Since it is also possible to supply, the ion concentration can be adjusted individually.

The chemical conversion treatment solution is used as an index representing the concentration of the entire acid, and the amount required for neutralization with 0.1 N sodium hydroxide is 15 to 35 ml per 10 ml of the treatment solution, and 20 to 30 ml Is desirable. The hydrogen ion concentration is 4
5 is appropriate, and the iron content in the processing solution is 1 g
/ L or less, preferably 0.5 g / l is a suitable condition.

According to this example, when the concentration ratio of zinc ion to calcium ion is smaller than 0.4, the precipitation of needle-like crystals (hopite) of zinc phosphate is conspicuous, and as a result, the rust preventive power is reduced and the coating thickness is reduced. Increases, and the grease tends to deteriorate due to the increase in the amount of the coating. Conversely, if the concentration ratio is larger than 0.8, a dense spherical crystal cannot be grown, so that a film is not formed and the rust-preventive power is poor. That is, a desirable calcium concentration ratio is 0.4 to 0.8.

As described above, the relationship between the components of the chemical conversion coating and the rust preventive power can be seen from FIG.

This is because one factor in the chemical conversion treatment solution that promotes the formation of spherical crystal grains is the concentration ratio of zinc ions to calcium ions, and the presence of zinc ions is essential for crystal formation.

As described above, by setting the coating thickness of the chemical conversion film, the crystal grain size, the strength ratio of calcium in the crystals or the concentration ratio of calcium in the chemical conversion treatment solution to an appropriate value, the desired value can be obtained. It is possible to obtain the durability time or the rust-preventive force, but of course, at the same time as the appropriate value of the chemical conversion coating film thickness, the crystal grain size, the calcium strength ratio in the crystal or the calcium concentration ratio in the chemical conversion treatment solution. By,
Desired durability time and rust prevention can be obtained.

[0030]

As described above, according to the present invention, it is possible to provide a chemical conversion coating which does not affect the life of the sealed grease while maintaining the rust-preventing force and the function of preventing galling. In addition, by setting the coating thickness or crystal grain size of the chemical conversion coating to a predetermined value, the durability of the bearing of the bearing can be extended, and by setting the component ratio of the chemical conversion treatment liquid to a predetermined value, the bearing Rust prevention performance can be improved. Also, by appropriately combining the thickness or crystal grain size of the chemical conversion coating with an appropriate value and the component ratio of the chemical conversion treatment solution with an appropriate value, the durability time and rust prevention performance of the bearing can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a sealed roller bearing according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a film thickness and a durability time of a sealed roller bearing.

FIG. 3 is a view showing the relationship between the particle size of spherical crystal grains of a chemical conversion treatment film and the durability time.

FIG. 4 is a graph showing the relationship between the composition ratio of calcium to zinc in a chemical conversion treatment film and the time until rust occurs.

FIG. 5 is a diagram showing the relationship between the concentration ratio of calcium in the chemical conversion treatment solution and the time until rust generation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Roller bearing 2 Inner ring 3 Outer ring 4 Inner ring raceway surface 5 Outer ring raceway surface 6 Grease 7 Seal member 8 Chemical conversion coating

Claims (1)

[Claims] 1. A sealed roller bearing lubricated with grease, wherein a chemical conversion treatment film is formed on surfaces of raceway surfaces of an inner ring and an outer ring of the bearing, and the film thickness of the chemical conversion treatment film is 1 μm or more and 5 μm or less. Wherein the weight ratio of calcium in the chemical conversion film is 0.15 to 0.3 with respect to the weight ratio of zinc in the chemical conversion film.