JP2002317763A - Sliding member for compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sliding property of a sliding member to be used under a cooling medium atmosphere. SOLUTION: A solid lubricating material in addition to a fluoride based formation coating formed of an Al-OH-F compound or a NH4 MgAlF6 compound or both compounds are formed on the surface of an aluminum based substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an HFC (Hydro Fluoro Carbon) such as a swash plate type compressor and a CO ₂ refrigerant (R744).
The present invention relates to a surface treatment for improving the sliding characteristics of a sliding member of a compressor used under various refrigerant atmospheres.

[0002]

2. Description of the Related Art A swash plate compressor includes a swash plate fixed to a rotating shaft at a fixed angle or a variable angle, a piston ring fitted in a cylinder provided parallel to the rotating shaft, and a swash plate and a piston. Including a shoe which is a sliding member disposed therebetween, the piston is reciprocated by the rotation of the swash plate, and gas is introduced into the cylinder and compressed. The structure of the swash plate type compressor itself is, for example,
No. 636, FIG. 1 and publication, column 3, line 42 to column 4, line 16,
See the description from column line 14, to column 6, line 2. As such a swash plate, quenched cast iron has been used for a long time.
Aluminum alloy forgings are used, and at present, cast iron swash plates are used particularly from the viewpoint of rotational performance of variable capacity compressors. Is used. On the other hand, chromium steel, especially bearing steel (SUJ2) is used as the shoe (Japanese Patent Publication No. 1-35190). In a swash plate compressor, the lubricating oil circulates inside the machine in a mist state or dissolved in the refrigerant together with the refrigerant.
Part of the lubrication surface remains on the sliding surface. In addition, the tendency to reduce the amount of lubricating oil is still continuing, and the sliding conditions are becoming increasingly severe. In particular, there is a problem of insufficient performance of the sliding surface between the swash plate and the shoe.

Further, the shoe is composed of a spherical portion fitted into the piston and a flat portion in contact with the swash plate. The convex portion has a vertex at the center of the flat portion and has a very large radius of curvature of 15 μm or less. By using a curved surface and a chamfered outer peripheral edge of the flat portion, variations in seizure resistance are reduced (Japanese Patent Publication Nos. 61-1636, 63-27554, and 1-35190). A shoe having such a convex portion and a chamfered portion is employed in an actual machine and greatly contributes to improving the performance of a swash plate of a swash plate compressor. Increasing the height of the convex surface makes it easier to form an oil film, but on the other hand, the variation in seizure resistance increases, so
A height range of 55 μm is employed.

As a refrigerant, a conventional CFC (Chloro Fluoro Ca
rbon), HCFC (Hydro Chloro FuloroCarbon) and the like have been used, but these are being replaced by HFC (Hydro Fluoro Carbon) and the like. These refrigerants have a function of cleaning the lubricating oil on the sliding surface of the swash plate type compressor, and the refrigerant that reaches the sliding surface in the initial operation has a low lubricating oil concentration, so that the cleaning effect is more remarkable than the lubricating effect. It causes seizure. In order to cope with such a situation, countermeasures such as spraying a Cu-Pb alloy on a swash plate have conventionally been taken. The main point of this measure is to prevent the effect of the lubricating oil in the early stage of compressor operation, so that Pb is dispersed as finely as possible in a copper alloy with excellent conformability and seizure is prevented by its excellent conforming action. is there. In fact, when observing the surface of the swash plate of a swash plate compressor that has been operated for a certain period of time, there is no significant change in the measurement with a roughness meter, but the Pb phase and its surroundings are shaved off in a shallow dish, confirming the familiar effect. Was done.

[0005] By the way, even if a means for mechanically roughening the sliding surface to form an oil reservoir is employed in a swash plate type compressor, the refrigerant is present in a recess formed mechanically because of the washing and hardening. As a result, the lubricating oil also flows out of the recess
Almost no lubricating oil remains in the recess.

[0006] Further, surface treatment measures such as PTFE coating have been taken on the aluminum housing or the sliding portion composed of a cylinder and a piston of a reciprocating compressor operated in a refrigerant environment.

[0007] As for the sliding material in a refrigerant environment,
Examples of using flaky graphite cast iron for cylinders, rollers, pistons, etc. and spheroidal graphite cast iron for shafts, and examples of using high-speed steel and alloy steel for vanes ("Tribologist" Vol. 43 / No. .3.1998, pp. 22-23). The magazine also introduces a method to moderately soften the surface to optimize lubrication and adapt it at the beginning of sliding;
Surface treatments such as oxynitriding, chromium plating, titanium nitride film formation, and chromium nitride film formation are also mentioned (p2
Four).

[0008]

[Problems to be Solved by the Invention] Spraying of a Cu-Pb-based alloy, which has the feature of forming a conformable surface at the beginning of sliding, is excellent in terms of stable seizure resistance, but leads to environmental pollution, such as lead. Containment may be harmful in the future. In addition, Cu-Pb-based alloys have excellent conformability, but have a property of easily adhering to a mating material. Therefore, in a situation where lubricating oil cannot be expected for several to several tens of seconds at the beginning of operation, the risk of seizure increases. Accordingly, the present invention solves such problems, and in a compressor in which lubricating oil cannot be expected for several to several tens of seconds in the initial operation, a sliding portion having excellent performance under a refrigerant atmosphere and at high speed or high load conditions. The purpose is to provide.

[0009]

The present applicant has conducted various experiments on conventional copper or aluminum alloy spraying, Sn plating, hardening treatment such as nitriding, mechanical surface roughening treatment, formation of solid lubricant film, etc. Fluoride-based chemical treatment, which treats the surface of an aluminum alloy piston, is effective in preventing seizure of sliding members in compressors where lubricating oil cannot be expected for several to several tens of seconds at the beginning of operation. It has been found that the solid lubricating material can improve the conformability of the film due to this treatment. Therefore, the present invention is formed on the aluminum-based substrate surface,
A sliding member of a compressor which is slid in a refrigerant atmosphere, which is coated with a fluoride-based chemical conversion film composed of an Al-OH-F compound or an NH ₄ MgAlF ₆ compound or both compounds, and further coated with a solid lubricant. Is provided. Hereinafter, the present invention will be described in detail.

The above-mentioned chemical conversion coating composed of the Al-OH-F compound or the NH ₄ MgAlF ₆ compound or both of them is an invention described in Japanese Patent Application Laid-Open No. 11-193748, and includes a piston made of an Al-Si alloy. Examples of application to surface treatment are described in detail. It has been known that lubricating oil may not be supplied sufficiently to the sliding part between the piston and the piston ring.However, it is crucial that this sliding part is not under the refrigerant atmosphere as the compressor sliding part. Is different. Since there is no difference between the piston and the compressor in the other points, particularly in the structure and the production method of the chemical conversion film, the descriptions of paragraphs 0004 to 0022 in JP-A-11-193478 are cited in the present specification. However, "piston" is read as "compressor sliding member". Paragraph number 0019, column 7 of the publication is not quoted. Paragraph No. 0111 states, "The object of the surface treatment of the present invention is an abrasion-resistant aluminum alloy. As the pretreatment, it is sufficient to remove deposits such as oil, but caustic soda is used. Surface treatment may be performed after alkali etching or pickling. " Under a refrigerant atmosphere, the fluoride chemical conversion film
When a Cu-Pb sprayed layer or MoS ₂ coating is used, the effect of forming a conformable surface is small. However, the complicated uneven surface shape formed on the film surface is excellent in the holding power of the lubricating oil, and the lubricating oil is hardly washed by the refrigerant.

The aluminum alloy used for the substrate in the present invention is preferably an Al-Si alloy having a Si content of 7 to 50% by mass. If the Si content is less than 7% by mass, the abrasion resistance will be insufficient, while if it exceeds 50% by mass, the seizure resistance will be poor. The preferred Si content is 10 to 40% by mass, and more preferably 10.5 to 25% by mass. Furthermore, if necessary, a small amount of alloying elements such as Cu and Mg can be contained.

Al-Si alloys of the above composition are mostly made of S
iDispersed in the matrix as a eutectic or primary crystal. Furthermore, since the aluminum in the matrix is preferentially dissolved when the substrate is etched during the fluorination treatment, these Si eutectics or primary crystals protrude from the surface of the aluminum-based substrate above the chemical conversion film. ing. The protruding Si particles come into contact with the surface of the mating material and exhibit wear resistance. On the other hand, since the fluoride-based chemical conversion film is worn as described above, the sliding surface is in a state where oil sumps and convex portions of Si particles are mixed, and the seizure resistance is further improved. In order to protrude the Si particles as described above, it is preferable to first perform normal etching, and then perform a chemical conversion treatment.

As described above, the fluoride-based chemical conversion film itself used in the present invention lacks initial compatibility. To compensate for this, at least one of graphite, molybdenum disulfide and PTFE must be used.
A coating containing a seed as a solid lubricant is formed using a resin binder, and coating is performed. As a result, the coefficient of friction is reduced, and the effect of preventing heat generation due to friction and a conforming effect is obtained. It is preferable that the solid lubricant film is thinned, for example, to 3 to 20 μm, and a part of the irregular surface of the fluoride conversion film is exposed by abrasion to some extent at the beginning of sliding. If the solid lubricant film is formed as a film, there is no problem even if it is thinner than 3 μm. In addition, it is preferable that the protruding Si particles be coated with the solid lubricant to such an extent that the protruding Si particles come into contact with the counterpart material and exhibit a wear resistance effect after the solid lubricant film is worn to some extent. The solid lubricant can be formed together with the resin binder or alone. In the case of a single film formation, the solid lubricant may be rubbed against the fluoride chemical conversion film. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0014]

EXAMPLE 1 An aluminum alloy sheet containing 17% Si was prepared as disclosed in
Under the condition (0023) of JP-A-193478 and Example 1, a fluoride-based chemical conversion film was formed to a thickness of 5 μm. A film of a mixture of polyamide imide (resin binder: 20 wt%) and molybdenum disulfide (80 wt%)
The following test was performed using the disk subjected to m) as a test material and the mating shoe as bearing steel (SUJ2).

Seizure test form: 3 shoes / fluoride conversion coating disk Rotation speed: 7200 rpm Surface pressure: 4 MPa + 2 MPa gradually increasing Time: Each step 15 minutes Refrigerant atmosphere: R134a Test section pressure: 3 kgf / cm ² Lubricating oil: Refrigeration oil (10 wt. %) Lubrication method: atomization test result : no seizure occurs even at 15 MPa. Coefficient of friction =
0.008

The up-down test mode: 3 shoes / fluoride conversion coating disk rotational speed: 600 increasing and decreasing speed the surface pressure between 6000 rpm: 10 MPa Time: 10 min / cycle, × 6 cycles refrigerant Atmosphere: R134a test unit pressure: 3 kgf / cm ² lubricating oil: refrigerating machine oil (10 wt%) Lubricating method: atomization test result Seizure does not occur even in 6 cycles. Coefficient of friction = 0.014 (6000 rpm)-0.007
(600 rpm)

Dry test form: 3 shoes / fluoride conversion coating disk Rotation speed: 1000 rpm Surface pressure: 4 MPa Time: 120 minutes Refrigerant atmosphere: R134a Test section pressure: 3 kgf / cm2 Lubrication: Dry environment test result : Seizure immediately after start Outbreak

Comparative Example 1 A baking test was carried out without applying a fluoride chemical conversion film, and baking occurred at 6 to 8 MPa.

Comparative Example 2 A baking test was performed by spraying a Cu-Pb alloy, and baking occurred at 15 MPa. When the test was performed under dry conditions, seizure occurred immediately after the start.

As described above, according to the examples of the present invention, both the seizure test and the up-down test show good results. From these results, it can be seen that the fluoride-based chemical conversion film has excellent seizure resistance even in the initial stage of operation and under high pressure conditions in sliding in a refrigerant atmosphere. The coefficient of friction in the seizure test is as low as 0.008, which is almost the same as that of the resin coating. Further, the examples of the present invention are not suitable for use conditions in which no lubricating oil is supplied since the results of the dry test are poor.

[0021]

As described above, many studies and developments have been made on surface treatments and materials applied to members conventionally used in a refrigerant atmosphere, but the present invention focuses on the oil accumulation effect. Surface treatment that can be adapted to severe operating conditions.

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Claims (7)

[Claims] 1. An aluminum-based base material formed on an aluminum base material surface.
A sliding member of a compressor that slides under a refrigerant atmosphere, in which a fluoride chemical conversion coating composed of an Al-OH-F compound or an NH ₄ MgAlF ₆ compound or both of these compounds is further coated with a solid lubricant. . 2. The sliding member for a compressor according to claim 1, which is applied to a swash plate surface of a swash plate compressor. 3. The sliding member for a compressor according to claim 1, wherein the aluminum-based substrate is made of an Al—Si-based alloy. 4. The Al—Si alloy has a Si content of 7 to 50.
The sliding member of the compressor according to claim 2, wherein the amount is mass%. 5. The aluminum-based alloy according to claim 4, wherein the Si eutectic or primary crystal of the Al-Si alloy projects from the surface of the aluminum-based substrate to a position above the surface of the fluoride-based chemical conversion film. Sliding member of compressor. 6. A sliding member for a compressor according to claim 1, wherein said solid lubricant is at least one selected from the group consisting of graphite, molybdenum disulfide and PTFE. 7. The sliding member for a compressor according to claim 4, wherein said solid lubricant film covers said protruding Si eutectic or primary crystal.