JPH06279153A - Sliding member - Google Patents

Abstract

PURPOSE:To provide a sliding member hardly causing seizing or abnormal wear even in an atmosphere of fluorocarbon free from chlorine. CONSTITUTION:This sliding member with a sliding face disposed in an atmosphere of a fluorine-contg. cooling medium contains ceramics and the sliding face has a carbon-based film formed on the surface of the ceramics. The center line average surface roughness Ra of the sliding face is <=1.0mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member, and more particularly to a sliding member used in an atmosphere of a cooling medium.

[0002]

2. Description of the Related Art Conventionally, sliding parts such as sliding bearings have been incorporated in sliding parts of compressors such as refrigerators, refrigerators and car air conditioners. In this case, the sliding part of the bearing body is placed in the cooling medium. As the cooling medium, chlorofluorocarbon (CFC), which is one type of fluorocarbon (hereinafter referred to as CFC), has been used. Among these chlorofluorocarbons, CFC12 is a typical cooling medium. Chlorine (Cl) is contained in the molecule of this CFC12. This chlorine prevents adhesion and reaction of the sliding member on the sliding surface. That is, chlorine, as an extreme pressure additive, prevents seizure between sliding surfaces. Therefore, CFC12 containing this chlorine
It itself acts as a very effective lubricant. Therefore, in a fluorocarbon atmosphere such as CFC12, the sliding portion of the sliding member is unlikely to be seized or abnormally worn. For this reason, conventionally, a metallic member such as cast iron has been used for a sliding portion used in an atmosphere of a cooling medium such as a refrigerator compressor. As described above, in a fluorocarbon atmosphere containing chlorine, seizure or abnormal wear of the sliding portion did not occur even if a metal member such as cast iron was used for the sliding portion.

[0003]

However, in recent years,
Due to the problem of ozone depletion in the stratosphere, the use of chlorofluorocarbons represented by CFC12 has been regulated. This is because chlorine contained in chlorofluorocarbon is one of the causes of destroying the ozone layer. As a substitute for this chlorofluorocarbon, for example, HFC134a, which does not contain chlorine in its molecule, is considered promising. In this way, studies are underway to use chlorofluorocarbon-free fluorocarbon as a cooling medium. However, with CFCs that do not contain chlorine, the lubricating effect of chlorine cannot be expected. Therefore, there is a problem that metals such as cast iron used for sliding parts of compressors are seized with each other or abnormal wear occurs.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a sliding member which is unlikely to cause seizure or abnormal wear even in a fluorocarbon atmosphere containing no chlorine. To aim.

[0005]

A sliding member according to the present invention is a sliding member having a sliding surface placed in an atmosphere of a cooling medium containing fluorine, the sliding member including ceramics. The sliding surface has a film containing carbon as a main component formed on the surface of the ceramic.

According to a preferred embodiment of the present invention, the sliding surface has a center line average roughness Ra of 1.0 μm or less. More preferably, the sliding surface has a center line average roughness R
It has a surface roughness of 0.1 μm or less. Here, the center line average roughness Ra is JIS B0601 (ISO468)
Is defined by

[0007]

As a result of intensive studies, the inventors of the present invention have found that the inclusion of ceramics in the sliding member used in the atmosphere of the cooling medium containing fluorine is effective in preventing seizure and abnormal wear. It was found to be very effective.

The reason why seizure and abnormal wear can be prevented is considered as follows. Ceramics have a higher Young's modulus and less chemical reactivity than metal materials such as cast iron. Since ceramics have poor chemical reactivity, reactions such as chemical adhesion hardly occur on the sliding surface of the sliding member containing ceramics. As a result, it is possible to prevent seizure and abnormal wear due to chemical adhesion or the like in the sliding member containing ceramics.
Therefore, even when used in an atmosphere of a cooling medium containing fluorine such as freon that does not contain chlorine, the sliding member containing ceramics operates normally.

The atmosphere of the cooling medium containing fluorine in the present invention may be at least one of the fluorocarbon gas and the liquid. Furthermore, the cooling medium of the present invention may be at least one of hydrofluorocarbon (HFC) and hydrochlorofluorocarbon (HCFC).

The molecular formulas for representative hydrofluorocarbons are shown in Table 1.

[0011]

[Table 1]

The sliding member of the present invention is also effective under hydrofluorocarbon atmospheres other than those shown in Table 1.

Further, the molecular formula of a typical hydrochlorofluorocarbon is shown in Table 2.

[0014]

[Table 2]

The sliding member of the present invention is also effective under hydrochlorofluorocarbon atmospheres other than those shown in Table 2.

The ceramic constituting the sliding member of the present invention is preferably at least one selected from the group consisting of oxides, carbides, nitrides, borides and silicides. Tables 3 and 4 show typical monolithic ceramics and composite materials using those ceramics.

[0017]

[Table 3]

[0018]

[Table 4]

It should be noted that ceramics other than those shown in Tables 3 and 4 or a composite material using these ceramics can be used as the ceramics constituting the sliding member of the present invention.

The sliding member is composed of a pair of members forming a pair of sliding surfaces that are in contact with each other, and at least one member preferably contains ceramics. In this case, one member that constitutes the sliding member needs to include ceramics, but the other member may be metal, and may be composed of the same or different ceramics, carbon material, resin such as Teflon, or other material. Good.

Further, the inventors of the present invention form a film containing carbon as a main component on the sliding surface of the sliding member,
It was found that the sliding surface exhibits a low friction coefficient and high wear resistance. This is because the solid lubricating action of carbon reduces friction and wear. By forming the film containing carbon as the main component on the sliding surface in this way, it becomes possible to further reduce the mechanical friction phenomenon even in the atmosphere of the cooling medium containing fluorine.

The inventors of the present application have found that there is a relationship between the surface roughness and wear resistance of a sliding member having a film containing carbon as the main component on the sliding surface. According to this, it is preferable that the surface roughness of the sliding member on which the film containing carbon as the main component of the present invention is formed is 1.0 μmRa or less. This is because when the surface roughness of the sliding surface exceeds 1.0 μmRa, one member may damage the carbon-based film formed on the surface of the other member depending on the surface pressure of the sliding surface.
Alternatively, abnormal wear may occur, and as a result, the solid lubricating action of the film containing carbon as a main component may not be sufficiently obtained.

Further, the inventors of the present invention set the surface roughness of the sliding member having the film containing carbon as the main component of the present invention to be 0.
It has been found that by setting the thickness to 1 μmRa or less, a low friction coefficient and excellent wear resistance can be achieved in the atmosphere of the cooling medium containing fluorine. This is because by setting the surface roughness to 0.1 μmRa or less, the unevenness of the sliding surface can be further reduced, and as a result, the mechanical friction phenomenon is further enhanced even in the atmosphere of the cooling medium containing fluorine. It is considered that this can be reduced.

The present inventors adopt a material such as cast iron containing free carbon in one of the sliding members of the present invention to form a film containing carbon as a main component on the sliding surface during sliding. I found a way. According to this, free carbon falls off at the initial stage of sliding, and a carbon film is formed on the sliding surface of the other sliding member. When the surface roughness of the sliding surface exceeds 1.0 μmRa, the abrasion rate becomes higher than the formation rate of the film containing carbon as the main component, and the film is not formed. On the other hand, when the surface roughness of the sliding surface is 1.0 μmRa or less, abrasion is unlikely to occur, so that a film containing carbon as a main component is formed. According to this, the mechanical friction phenomenon can be suppressed without coating the sliding surface with a substance having a solid lubricating property such as carbon or molybdenum disulfide before using the sliding member.

Further, the surface roughness of the sliding surface is 0.5 μmR
By setting it to be a or less, a film containing carbon as a main component can be formed on the sliding surface during sliding in a cooling medium containing fluorine, and further has a low friction coefficient and is particularly excellent in wear resistance. It was found that a smooth sliding surface was obtained. This is because by setting the surface roughness to 0.5 μmRa or less,
It is based on the fact that the unevenness of the sliding surface can be made even smaller and a film containing carbon as the main component can be stably formed on the surface, and as a result, the solid lubricating action of carbon can be obtained appropriately. Is. Thereby, the mechanical friction phenomenon can be further suppressed even in the atmosphere of the cooling medium containing fluorine.

More preferably, the sliding surface has a surface roughness of 0.
By setting it to 1 μmRa or less, the above effect can be more remarkably realized.

As described above, the sliding member of the present invention can prevent seizure and abnormal wear even when used in an atmosphere of a cooling medium containing fluorine.

[0028]

【Example】

Example 1 A spheroidal graphite cast iron ring was produced as one member constituting the sliding surface. The other member that constitutes the sliding surface is made of spheroidal graphite cast iron, bearing steel, alumina, silicon carbide, silicon nitride, boron nitride, carbon fiber reinforced silicon nitride, silicon carbide whisker reinforced alumina, and silicon carbide nanoparticle dispersion reinforced alumina. As a ring was produced. While sliding the one ring and the other ring and changing the load under the condition of the peripheral speed of 2 m / sec in the liquid of HFC134a,
The seizure load was measured using a ring-on-ring tester. The results of this experiment are shown in Table 5. In the table,
No. 1-1 to 1-7 are examples, and No. 1-8,
1-9 is a comparative example.

[0029]

[Table 5]

As is clear from the results shown in Table 5, in the embodiment in which one member constituting the sliding surface is made of ceramics (monolithic ceramics, composite material),
It was found that the seizure load was extremely high as compared with the comparative example. Thus, in this example, it was found that seizure hardly occurred even in the atmosphere of the cooling medium containing fluorine.

Further, when the sliding surface was examined in detail, a film containing carbon as a main component was formed on the surface.
The film containing carbon as the main component contained about 70% by weight of carbon (C) and about 20% by weight of oxygen (O), and the balance consisted of elements constituting the sliding member. Example 2 A disc made of silicon nitride, a disc having a sliding surface formed by vapor-depositing a carbon film having a thickness of 1.0 μm on the surface of a disc made of silicon nitride, and a disc made of bearing steel were produced. Further, a ring in contact with the sliding surface of each of the above disks was made of bearing steel. Each disk and the ring were slid in the atmosphere of HFC134a. At this time, the peripheral speed is 1 m / sec. The seizure load was measured by using a ring-on-disc type friction tester while changing the load under the conditions. The results of this experiment are shown in Table 6. The surface roughness in Table 6 indicates the surface roughness of the base material of the disk.
The surface roughness of the sliding surface of the disk on which the carbon film was formed was maintained below the value in the table.

[0032]

[Table 6]

As is clear from Table 6, it was found that the seizure load was higher in this example in which one member constituting the sliding surface was made of a carbon film than in the comparative example. As a result, in this example, it was found that seizure was less likely to occur on the sliding surface even in the atmosphere of the cooling medium containing fluorine. Example 3 A disk having a diamond-like carbon film with a thickness of 3 μm formed on the sliding surface of each disk made of silicon nitride and high-speed steel by the CVD method was produced. In addition, a disk made of silicon nitride was produced. A ring having a sliding surface in contact with the sliding surface of each disk was made from bearing steel. Each disk and the ring were slid in the liquid of HFC134a. At this time, the peripheral speed is 1 m / sec. Under the conditions, the seizure load was measured using a ring-on-disc type friction tester while changing the load. The results of this experiment are shown in Table 7. The surface roughness in Table 7 indicates the surface roughness of the base material of the disc. The surface roughness of the sliding surface of the disk on which the carbon film was formed was maintained below the value in the table.

[0034]

[Table 7]

As is clear from Table 7, the seizure load was extremely high in this example in which one of the members constituting the sliding surface had a diamond-like carbon film, as compared with the comparative example.

From this, in this example, it was revealed that the sliding surface was even more difficult to seize even in the atmosphere of the cooling medium containing fluorine. Example 4 A disk was prepared from alumina, zirconia, silicon carbide, silicon nitride, aluminum nitride, and high speed steel, and the surface roughness of the sliding surface was 0.05 μmRa, 0.5 μmRa, 3 respectively.
Finished to μmRa. A ring having a sliding surface in contact with the sliding surface of each disk was made from flake graphite cast iron. Each disk and the ring were slid in the gas of HFC134a. At this time, the peripheral speed is 1 m / sec. A ring-on-disc type friction test was conducted under a load of 10 kgf to measure the amount of disc wear. In addition, squeal occurred during the test,
It was considered that seizure had occurred when the test machine vibrated. The results of this experiment are shown in Table 8. In the table, Comparative Example No. For 4-7 to 4-11, rings made of bearing steel were used.

[0037]

[Table 8]

As is clear from Table 8, it was found that the wear resistance of the present embodiment in which the member constituting the sliding surface was ceramics and the mating member was cast iron was excellent.

Next, the sliding surface is replaced with ESCA (Electron Spect
roscopy for Chemical Analysis), it was found that the film formed on the sliding surface during sliding mainly contains carbon. From this, it was found that the sliding surface was excellent in abrasion resistance in this example having the film containing carbon as a main component formed during sliding.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Katayama 1-1-1 Kunyokita, Itami City, Hyogo Prefecture Sumitomo Electric Industries, Ltd. Itami Works (72) Inventor Akira Yamakawa 1-chome, Konyo Kita, Itami City, Hyogo Prefecture No. 1 Itami Works, Sumitomo Electric Industries, Ltd.

Claims (3)

[Claims] 1. A sliding member having a sliding surface placed in an atmosphere of a cooling medium containing fluorine, wherein the sliding member contains ceramics, and the sliding surface is formed on the surface of the ceramics. Member having a film containing the above-mentioned carbon as a main component. 2. The sliding surface has a center line average roughness Ra of 1.
The sliding member according to claim 1, which has a surface roughness of 0 μm or less. 3. The center line average roughness Ra of the sliding surface is 0.
The sliding member according to claim 2, which has a surface roughness of 1 µm or less.