JP3456063B2 - Anti-seizure rolling bearing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing typified by, for example, a gas turbine bearing for an aircraft, which is operated at a high speed, and in particular, the supply of lubricating oil is temporarily cut off during operation. The present invention relates to rolling bearings with excellent seizure resistance and wear resistance that enable the bearing function to be maintained even under severe boundary lubrication conditions.

[0002]

2. Description of the Related Art Conventionally, as a method for preventing galling and seizure on the metal surface of a sliding member, an extreme pressure agent, an oiliness improver, etc. have been added to the lubricating oil to adsorb the lubricating oil to the metal surface. Strengthening efforts are being made. This prevents welding between metal surfaces due to sliding under boundary lubrication conditions where partial metal contact occurs, by promoting the formation of a lubricating oil adsorption film on the metal surface, and prevents galling and seizure. It is intended to prevent the occurrence.

However, the lubricating oil adsorption film formed on the metal surface by the addition of the extreme pressure agent, the oiliness improver and the like is a physical adsorption film mainly composed of van der Waals force acting between molecules, and the adsorption energy. Is only a few kcal / mol. Moreover, since it is a reversible reaction, it is difficult for the adsorption film itself to be stably retained on the metal surface. Therefore, the effect of preventing galling and improving seizure resistance under severe conditions such as the supply of lubricating oil being interrupted for several tens of seconds during operation at high speed is small.

On the other hand, the applicant of the present invention has filed in Japanese Patent Laid-Open No. 2-1.
According to No. 54813, a large number of minute groove-shaped recesses intersecting with each other are formed on the contact surface of a rolling bearing which is a sliding member, and a surface layer of a reaction film such as a phosphorus compound is formed.
We proposed a technology to prevent galling and seizure of bearings under severe conditions where the supply of lubricating oil is interrupted. After that, as a result of further research on the prevention of galling and seizure under the severe condition of blocking the lubricating oil, it was found that the thickness of the compound reaction film on the sliding surface had a great influence.
Based on this finding, the surface of the sliding member is chemically treated to form a compound reaction film such as a metal phosphorus compound in an amount of 0.05 to
A sliding or rolling member previously formed to a thickness of 0.5 μm was proposed in Japanese Patent Application Laid-Open No. 2-256920. This is one in which, for example, a phosphoric acid ester which is an organic phosphorus compound is used as a phosphorus compound, and this is reacted with a metal surface in an organic solvent, and the reaction temperature is from room temperature to 120 ° C. at the maximum, usually 40 to 60 ° C. By chemically treating the surface of the metallic sliding member while controlling the reaction time within the range and the reaction time within the range of 0.5 to 8 hours, a compound of phosphorus and iron with the specific thickness described above on the surface of the member. The reaction layer is formed in advance to prevent galling and seizure of the rolling bearing under boundary lubrication conditions. As the above-mentioned organic phosphorus compound, acidic phosphoric acid ester, orthophosphoric acid ester, phosphorous acid ester and the like can be used alone or in combination of two or more kinds, and by adjusting the amount, reaction temperature and time. The seizure resistance can be improved.

[0005]

However, a large number of fine groove-shaped recesses are provided on the metal surface to control the unstable sliding motion of the rolling elements of the rolling bearing, and at the same time, the oil sump function of the recesses allows the recesses to function under severe conditions. The technique disclosed in Japanese Patent Application Laid-Open No. 2-154813 for preventing galling and seizure of a bearing in
There is still room for improvement in the following points.

Since stress is concentrated on the concave portion of the contact surface formed by machining, surface damage is likely to occur in the boundary lubrication region. In the bearing, since the raceway surface and the surface roughness of the rolling elements influence the conditions for forming the oil film, the groove-shaped recess may adversely affect the seizure resistance. On the other hand, in the case of the technique disclosed in JP-A-2-256920 in which the surface of the sliding member is chemically treated to previously form a compound reaction film of a metal phosphorus compound or the like in a specific thickness, a groove shape is formed on the surface. Since no recess is formed, the problems of stress concentration and surface roughness are not as great as in the former case.

However, in the latter case, when the metal surface and the phosphoric acid ester are chemically reacted in an organic solvent, the reaction rate of the metal phosphorous compound formation is controlled by adjusting the kind and concentration of the phosphoric acid ester. However, nevertheless, the reaction rate is difficult to reach an equilibrium state due to the influence of a trace amount of water contained in the organic solvent, for example, about several tens of ppm. Therefore, even if a slight change in temperature is detected, the reaction rate is accelerated and the reaction speed is accelerated. Even if the film thickness of the reaction product is controlled, the roughness of the metal surface is deteriorated, and the seizure resistance of the high-speed bearing is increased. There is a problem that it deteriorates.

By the way, a rolling bearing in which the surface of the bearing was chemically treated to form a metal phosphorus compound reaction film by the method of JP-A-2-256920 was tested by rotating it at a high speed of 30,000 rpm or more to shut off oil. However, the temperature rise of the inner ring of the bearing was large due to heat generation, and satisfactory results could not be obtained regarding seizure resistance. Therefore, the present invention has been made by focusing on the problem of seizure resistance of a conventional rolling bearing under boundary lubrication conditions. By forming a compound layer that has a large bonding force with a metal and has an oiliness improving property without a thermal decomposition reaction, the seizure resistance is greatly improved without changing the roughness of the metal surface. The purpose is to provide a rolling bearing.

[0009]

The seizure-resistant rolling bearing according to claim 1 of the present invention, which achieves the above object, has a metal surface,
A first layer is formed of a phosphorus compound layer mainly containing the metal component and oxygen and phosphorus, and a second layer is formed of an oxygen compound layer mainly containing the metal component and oxygen to form a reaction layer having seizure resistance. It is characterized by having done.

In a preferred embodiment, the phosphorus compound layer may have a layer thickness of 0.003 to 0.12 μm, and the oxygen compound layer may have a layer thickness of 0.005 to 0.005 μm. The reaction layer having seizure resistance may be a continuous layer, and the total layer thickness may be in the range of 0.008 to 0.32 μm. The reaction layer having the seizure resistance may be formed on at least one of the raceways of the outer ring and the inner ring and the rolling elements, and the hardness of the metallic material is HRC55. There can be more than one.

In the seizure-resistant rolling bearing of the present invention, an oxygen compound layer (second layer) of the metal is formed in advance on the metal surface of the bearing, and then the phosphorus compound of the reaction system is thermally decomposed to form a metal surface on the metal surface. The compound layer (first layer) of the metal, phosphorus and oxygen is formed, and the first layer in the present invention is an outer layer composed of a composition ratio of phosphorus, oxygen and a metal element (for example, iron). Of layers. The second layer refers to an inner layer having a composition ratio of only a metal element (for example, iron) and oxygen.

Firstly formed oxygen compound layer (second layer)
Is an intermediate layer, and when the phosphorus compound is subsequently pyrolyzed and reacted with the metal surface, it prevents deterioration of the metal surface roughness due to the reaction, and forms a phosphorus compound layer of the metal and the metal substrate. It has the function of strengthening the adhesiveness of. That is, the surface roughness of the rolling bearing differs depending on the presence or absence of the oxygen compound layer. Also, depending on the presence or absence of the oxygen compound layer, whether or not the phosphorus compound layer can be maintained and the welding of the metal surfaces can be prevented when partial metal contact occurs on the sliding surface of the bearing under boundary lubrication . The present invention has an oxygen compound layer at the interface between the bearing metal ground surface and the phosphorus compound layer formed on the surface thereof, so that the bond between the phosphorus compound layer and the metal surface is strong without degrading the metal surface roughness. As a result, a surface effective for seizure resistance of the bearing is obtained, and as a result, the friction between the surface of the rolling element, which is the bearing member, and the raceway surface is reduced, and the bearing function can be improved. .

In order to selectively form the oxygen compound layer of the present invention in the vicinity of the surface of the bearing metal material, nitric acid or the like may be used to make the surface layer portion of the bearing metal material a passivation layer or preheat the bearing. It is possible to employ a means such as forming an oxide film layer on the surface of the bearing metal material in advance. The formation of the phosphorus compound layer of the first layer of the present invention can be carried out by diluting the organic phosphorus compound with hydrocarbon oil to various concentrations, immersing the bearing in the solution, and subjecting the bearing to heat treatment. The phosphorus compound that contributes to the formation reaction of the metal phosphorus compound at that time is not particularly limited, but for example, orthophosphoric acid esters, phosphorous acid esters, acidic phosphoric acid esters, etc. may be used alone or in combination of two or more. good. Orthophosphoric acid esters and phosphorous acid esters include aromatic or aliphatic esters having a carbon chain length such as alkyl, phenyl, cresyl, and allyl. Further, among the acidic phosphoric acid esters, there are aromatic or aliphatic esters of mono- or dihydroacid phosphates having monobasic or dibasic hydroxyl groups. Among them, orthophosphoric acid esters and phosphorous acid esters are most suitable for the reaction with the metal surface.

The thickness of the compound layer such as a phosphorus compound and an oxide formed on the bearing surface of the present invention can be measured by using an Auger electron spectroscopy analyzer (AES). This is the qualitative or quantitative information and binding of elements on the sample surface by irradiating the sample surface with an electron beam and conducting energy analysis of Auger electrons emitted from the outermost surface (about several angstroms) of the sample. Although the state can be obtained, it is possible to analyze the distribution state of the elements in the depth direction by further measuring the surface of the sample by sputtering with an argon ion gun.

In FIGS. 1 and 2, tricresyl phosphite was used as the organic phosphorus compound, and the thicknesses of the phosphorus compound layer (first layer) and the oxygen compound layer (second layer) formed on the bearing metal surface were measured. An example is shown, the depth profile of the sample is taken by AES, and the film thickness is obtained from the etching time by sputtering using a SiO ₂ substrate. Photoelectrons of phosphorus (P) and oxygen (O) in the compound layer Each layer thickness is determined from the value of the sputtering time immediately before the strength stops changing and the known sputtering rate.

In the figure, the first layer is the surface side of the bearing metal surface, and the layer composition is a layer composed of a composition ratio of phosphorus, oxygen and iron (alloying element). The second layer refers to a layer inside the first layer, the layer composition of which is a composition ratio of iron (alloying element) and oxygen only. Next, the relationship between the layer thickness (film thickness) of the compound layers such as the phosphorus compound layer and the oxygen compound layer thus obtained and the seizure resistance will be described in the following embodiments.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. [A] Effective thickness of the first layer: (1) Fabrication of specimen: seizure resistant coating on ball bearings with inner diameter 40 mm, outer diameter 82 mm, width 26 mm, number of rolling elements 11 and rolling element diameter 12.54 mm The bearing subjected to the test was used as a test bearing. Bearing material is AMS-M50 material (Aero-M50 material, which was tempered at 540 ℃ after quenching for inner ring, outer ring and rolling elements.
space Material Specification; Its hardness is HRC61.

This test bearing was immersed in petroleum benzine, ultrasonically cleaned for 120 seconds, and then dried at room temperature, taking care not to leave oil. Next, the bearing was heated in the atmosphere for 2 hours to form a second oxygen compound layer on the surface of the bearing in a thickness of 0.05 μm. Thereafter, these test bearings were treated with a synthetic hydrocarbon oil (polyα-olefin) containing 3% by weight of trioctyl ruphosphate and 4% by weight of PAN (phenyl-α-naphthylamine) as an antioxidant. The thickness of the phosphorus compound layer is 0.001 μm, 0.003 μm, 0.0
1 μm, 0.05 μm, 0.1 μm, 0.12 μm,
Seven types were manufactured that differed from 0.2 μm.

(2) Boundary lubrication operation test: The seizure resistance rolling bearing thus obtained was subjected to a boundary lubrication operation test to evaluate seizure resistance. The test device is shown in FIG. The shaft 3 is supported by a pair of bearings consisting of the rolling bearing 1 and the support bearing 2 of the specimen, and the axial load Fa is applied from the support bearing 2 side via the housings 4 and 5. One end of the shaft 3 is connected to a motor via a coupling (not shown) and is driven to rotate at high speed.

A gas turbine oil of 3 liters per minute is supplied to the specimen bearing 1 and the support bearing 2 to lubricate them while rotating at a rotational speed of 30,000 rpm and an axial load Fa of 980.
Rotate at high speed under N condition. Then, the supply of the lubricating oil to the sample bearing 1 was cut off, and the temperature of the inner ring of the sample bearing 1 after the oil supply was cut off was measured. The inner ring temperature rises linearly with an upward slope from the start of refueling cutoff, then reaches equilibrium, is maintained constant for a certain period of time, and then starts to rapidly increase.
The point at which the rapid rise after the equilibrium starts is the point at which seizure occurs. The time required for the acceleration of the inner ring temperature rise after the oil supply was cut off to become positive after the passage of time as described above was measured and defined as the durability time (seconds). It has already been experimentally known that if this durability time exceeds approximately 200 seconds, it can be evaluated as having seizure resistance that enables the bearing function to be maintained even in an actual machine under boundary lubrication conditions in which lubricating oil cutoff occurs. .

In this test, the test was stopped at 520 seconds for the sample which required 520 seconds or more before the rise of the inner ring temperature from the oil supply cutoff reached the equilibrium and the rapid rise was started. In addition, after discontinuing each of the test-piece bearings 1 after the completion of the operation test, each raceway surface of the inner ring and the outer ring and the rolling element surface were visually observed. The seizure occurrence state (seizure resistance) was determined by the occurrence of damage (pits) on the bearing surface due to the temperature rise, and the adhesion between the phosphorus compound layer and the metal surface was determined by the residual state of the phosphorus compound on the bearing surface.

The results are shown in FIG. When the phosphorus compound layer of the present invention had a thickness within the range of 0.003 μm to 0.12 μm, the durability time was a reference value of 200 seconds or more, and it was judged that the seizure resistance was excellent. On the other hand, when the phosphorus compound layer has a thickness of less than 0.003 μm, it is clear that the durability time is much less than the reference value and there is no effect on the seizure resistance. On the other hand, the thickness of the phosphorus compound layer is 0.12
For those having a thickness of more than μm, deterioration of the surface roughness was observed, which is considered to have caused a reduction in the durability time.

[B] Effective thickness of the second layer: (1) Fabrication of specimen: seizure resistance on ball bearings with inner diameter 30 mm, outer diameter 62 mm, width 26 mm, 9 rolling elements, and rolling element diameter 7.64 mm The bearing that was subjected to the functional coating treatment was used as a test bearing.
As the bearing material, for the inner ring, the outer ring and the rolling elements, a bearing steel material SUJ2 (hardness HRC58) based on Japanese Industrial Standards, which was tempered at 840 ° C. and then tempered at 280 ° C., was used.

This test bearing was immersed in petroleum benzine, ultrasonically cleaned for 120 seconds, and then dried at room temperature, taking care not to leave oil. Next, the bearing was heated in the atmosphere for 2 hours to form a second oxygen compound layer on the bearing surface. In this case, by changing the heating temperature,
Thickness of oxygen compound layer is 0.001μm, 0.003μ
m, 0.005 μm, 0.01 μm, 0.05 μm,
Eight types were manufactured, different from 0.1 μm, 0.2 μm, and 0.3 μm.

Then, these test bearings were immersed in a liquid of a synthetic hydrocarbon oil (Hemkel, trade name Emery 2939) containing 3% by weight of tricresyl phosphite, and the temperature was 180 ° C. for 50 hours. By keeping it constant, the phosphorus compound layer of the first layer is 0.05 μm.
Formed with a thickness of. (2) Boundary lubrication operation test: The seizure resistance rolling bearing thus obtained was subjected to a boundary lubrication operation test in the same manner as in [A] First layer effective film thickness to evaluate seizure resistance.

After completion of the operation test, each bearing of the test piece was disassembled, and the raceway surfaces of the inner ring and outer ring and the rolling element surfaces were observed to investigate the seizure occurrence state (seizure resistance) and the surface roughness. . Results are shown in FIG. When the thickness of the oxygen compound layer of the present invention is within the range of 0.005 μm to 0.2 μm,
It has been confirmed that the durability time exceeds the standard value of 200 seconds, and that the adhesion between the 0.05 μm thick phosphorus compound layer, which is the first layer, and the bearing metal surface is also good, and that it has excellent seizure resistance. It was determined that On the other hand, in the case where the thickness of the oxygen compound layer is less than 0.005 μm, the phosphorus compound layer on the bearing surface is removed and the adhesiveness with the metal surface of the bearing is reduced, so the seizure resistance deteriorates. is doing. On the other hand, when the thickness of the oxygen compound layer exceeds 0.2 μm, the surface of the oxygen compound layer becomes uneven due to the thickening of the oxygen compound layer, and as a result, the surface roughness is deteriorated and the durability time is shortened. .

From the above test results, the effective film thickness range for the seizure resistance of the entire compound layer including the phosphorus compound layer which is the first layer and the oxygen compound layer which is the second layer of the present invention is 0.0.
08-0.32 μm, but preferably 0.01-
0.2 μm, more preferably 0.03 to 0.1
μm. In the above description, the case where the phosphorus compound layer and the oxygen compound layer of the present invention are formed in all the components of the rolling bearing has been described, but the present invention is not limited to this, and the outer ring and the inner ring of the rolling bearing can be formed. It also includes the case where the phosphorus compound layer and the oxygen compound layer of the present invention are formed on at least one of the raceways and the rolling elements.

As described above, in the seizure-resistant rolling bearing of the present invention, the metal component, oxygen, and oxygen are formed on the metal surface of the bearing member through the oxygen compound layer mainly containing the metal component and oxygen. the reaction layer having a seizure resistance consisting of phosphorus compound layer and phosphorus mainly was formed by temperatures exceeding the thermal decomposition reaction 100 ° C.. Therefore, it is possible to prevent the deterioration of the surface roughness during the reaction in the formed oxide intermediate layer, and to remove the influence of a small amount of water in the organic solvent used in the reaction solution due to the high temperature conditions, thereby forming a conventional phosphorus compound layer. hypersensitivity is eliminated with respect to a change in temperature <br/> of time, so that the effect of seizure resistance rolling with greatly improved seizure resistance without changing the roughness of the metal surface can be obtained Play.

[Brief description of drawings]

FIG. 1 is a diagram showing a depth profile of a component composition ratio of a compound layer formed on a bearing surface of the present invention measured by using an Auger electron spectroscopy analyzer (AES).

FIG. 2 is a diagram showing a depth profile measured by an Auger electron spectroscopy analyzer (AES) of a component composition ratio of a compound layer formed on a bearing surface of the present invention.

FIG. 3 is a schematic explanatory diagram of a seizure resistance test device for a rolling bearing.

FIG. 4 is a graph showing the relationship between the film thickness of the phosphorus compound layer and the durability time in the embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the film thickness of the oxygen compound layer and the durability time in the embodiment of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuji Nazume 1-5-50 Kumeiuma, Kuninuma, Fujisawa-shi, Kanagawa NSK Ltd. (72) Tetsuo Watanabe 1-5-50, Kumei, Kugenuma, Fujisawa, Kanagawa Within NSK Ltd. (72) Inventor Yukio Oura 1-5-50 Kumei Kugenuma, Fujisawa-shi, Kanagawa Within NSK Ltd. (56) Reference JP-A-2-256920 (JP, A) JP-A-3- 271378 (JP, A) JP 7-190073 (JP, A) JP 7-11456 (JP, A) JP 57-200726 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F16C 33/58-33/64 F16C 19/00-19/56 C23C 30/00

Claims (5)

(57) [Claims] 1. An outer ring, an inner ring, and a plurality of rolling elements between them.
In a rolling bearing having, each raceway surface of the outer ring and the inner ring
And, on at least one metal surface of the rolling surfaces of the rolling elements , the first layer comprises a phosphorus compound layer mainly containing the metal component and oxygen and phosphorus, and the second layer contains the metal component and oxygen. A seizure-resistant rolling bearing having a seizure-resistant reaction layer formed of an oxygen compound layer as a main component. 2. The reaction layer according to claim 1,
Forming the second layer as an inner layer on the metal surface, and then
In addition, the first layer is subjected to phosphatization of the reaction system at a temperature exceeding 100 ° C.
That the compound was formed on the outside of the second layer by a thermal decomposition reaction.
Characteristic rolling bearing. 3. The phosphorus compound according to claim 1,
The layer contains orthophosphoric acid ester or phosphorous acid ester as a component.
A rolling bearing characterized in that 4. The method according to claim 1, wherein
The thickness of the phosphorus compound layer is 0.003 to 0.12 μm,
The thickness of the oxide compound layer is 0.005-0.2 μm.
Then, the film thickness of the reaction layer is set to 0.008 to 0.32 μm.
Rolling bearings characterized by 5. The method according to any one of claims 1 to 4, wherein
Characteristic that the thickness of the reaction layer is 0.03 to 0.1 μm
And rolling bearings.