Expansible chamber devices – Relatively movable working members – Interconnected with common rotatable shaft
Reexamination Certificate
1999-05-21
2001-02-27
Lopez, F. Daniel (Department: 3745)
Expansible chamber devices
Relatively movable working members
Interconnected with common rotatable shaft
C092S155000
Reexamination Certificate
active
06192784
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a swash plate compressor, and more specifically, to a soft surface coating substrate treatment applied to sliding surfaces between a swash plate and shoes.
BACKGROUND OF THE INVENTION
Conventionally, swash plate compressors are used in automotive air conditioners and the like as a device for compressing a refrigerant gas. The swash plate compressor is composed of a cylinder block having a plurality of cylinder bores disposed in a direction parallel to an axial center, a swash plate held on a drive shaft in the cylinder block so as to rotate integrally with the drive shaft, pistons sidably inserted in the cylinder bores, and shoes for reciprocatively moving the pistons by the rotation of the swash plate.
Generally, a large load and a large slipping speed act on the sliding surfaces of the swash plate and the shoes of the swash plate compressor. In particular, the effect of the load is large when aluminum or an aluminum alloy is used as the base metal of the swash plate to reduce the weight thereof. Accordingly, consideration must be given to the lubricating ability under severe sliding conditions such as when there is no lubrication at start up or when there is a high sliding load.
A soft surface coating having a low frictional resistance which is applied to one of the opposed surfaces of the swash plate and the shoes to reduce the frictional resistance of the sliding surfaces between the swash plate and the shoes is disclosed in, for example, Japanese Patent Application Laid-open No. 2-130272 and Japanese Patent Application Laid-open No. 60-22080. That is, a soft surface coating composed of only tin or tin and a metal selected from copper, nickel, zinc, lead, indium, etc. is proposed in the former publication, and a coating containing a solid lubricant such as molybdenum disulfide, tungsten disulfide, graphite, boron nitride, lead oxide, fluoro-resin, etc. is proposed in the latter publication
When a surface coating is applied, a common practice in the conventional way of thinking is to coarsen the surface of the base or substrate for the surface coating by shot blasting or the like. Specifically, a average coarseness of the substrate is made to be about 10 &mgr;mRz at ten point mean roughness to increase the adhesive properties of the surface coating with the substrate so that the surface coating does not exfoliate easily.
Note that when the surface coating is directly formed on the surface of the base metal of the swash plate or the shoes, the surface of the base metal serves as the substrate referred to here. However, when a coating having a high wear resistance is applied to the surface of the base metal, as a countermeasure to the surface coating being worn, and then the soft surface coating is applied thereon, the surface of the high wear resistance coating serves as the substrate. When the base metal is composed of, for example, aluminum, it is known to apply an aluminum anode coating to the surface of the base metal as the high wear resistance coating.
However, the conventional arrangement as described above has a problem in that although excellent lubricating properties can be achieved when the soft surface coating is not worn, the life of the soft surface coating cannot be prolonged because it has low resistance to wear. Further, although a soft surface coating such as one containing molybdenum disulfide and the like is characterized in that it fluidizes as its temperature increases, it has not yet been conceived of to make use of this feature because the surface of the substrate of the soft surface coating is coarsened to increase mechanical adhesive properties between the soft surface coating and the substrate.
Accordingly an object of the present invention made in view of the problems of the prior art is to enhance the lubricating ability and wear resistance of the sliding surfaces of a swash plate and shoes and maintain them for a long period of time.
SUMMARY OF THE INVENTION
To achieve the above object, in the invention, a swash plate compressor includes a cylinder block having a plurality of cylinder bores, a drive shaft rotatably supported in the cylinder block, a swash plate rotating with the drive shaft, pistons sidably disposed in the cylinder bores, and shoes sidably interposed between the pistons and the swash plate to reciprocatively move the pistons by the rotation of the swash plate, in which a soft surface coating is formed on the sliding surfaces of any one of the swash plate and the shoes which come into contact with each other, wherein the coarseness of the surface of the substrate for the soft surface coating is made to be a coarseness of 8 &mgr;mRz or less at ten points.
In this case, the soft surface coating is one having a high lubricating ability and when the surface coating is partially worn or exfoliated by the sliding contact of the swash plate with the shoes during operation of the compressor, the surface coating at the periphery of the portions that are worn or exfoliated are softened and fluidized by the temperature increase due to sliding friction.
Since the above arrangement permits the soft surface coating having a high lubricating ability to be formed on the sliding surfaces of the swash plate which comes into contact with the shoes, the lubricating ability is improved.
Note here that the soft surface coating has a drawback in that it has low wear resistance.
However, observed at particular points, a load acting on the swash plate through the shoes is large when the pistons are at their top dead centers and small when they are at their bottom dead centers. Thus, when the pistons are at their top dead centers a large sliding contact force acts on the swash plate through the shoes and the portions where the sliding contact force acts are worn or exfoliated when the compressor is used for a long period of time. When the soft surface coating is partially worn or exfoliated as described above, the soft surface coating at the peripheries of the worn or exfoliated portions are softened and fluidized by the temperature increase due to frictional heat. On the other hand, the mechanical adhesive properties between the soft surface coating and the substrate thereof are weakened when the coarseness of the surface of the substrate is processed to an average coarseness of 8 &mgr;mRz or less at ten point mean roughness. As a result, when the sliding load is intermittently reduced, the softened soft surface coating material at the peripheries of the worn or exfoliated portions flows to the portions where the soft surface coating is worn or exfoliated and the soft surface coating is thereby repaired.
Although the sliding load acting on the sliding surface of the swash plate and the shoes periodically increases and decreases as described above, the soft surface coating is always repaired when the load decreases. Accordingly, high wear resistance and high lubricating ability can be maintained for a long period of time.
In the invention, it is preferable that the coarseness be 5 &mgr;mRz or less at ten point mean roughness , and it is more preferable that it is 3 &mgr;mRz or less at ten point mean roughness.
With this arrangement, since the mechanical adhesive properties between the soft surface coating and the substrate are further weakened, the fluidity of the soft surface coating is further increased and the portions where the soft surface coating are worn or exfoliated are more promptly repaired, and the high wear resistance and high lubricating ability can thereby be maintained for a longer period of time.
In the invention, the soft surface coating is, for example, a coating layer containing molybdenum disulfide.
With this arrangement, the fluidity of the soft surface coating is further increased, and the high wear resistance and high lubricating ability are further exhibited and maintained.
In the invention, a plating layer mainly composed of soft metal, more specifically, tin, is formed on the sliding surfaces of any one of the swash plate and the shoes, and a coating layer containing molyb
Deto Norikazu
Gouhara Chiaki
Ikeda Hayato
Kanayama Hiroshi
Katayama Seiji
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Lopez F. Daniel
Morgan & Finnegan L.L.P.
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