Pumps – Three or more cylinders arranged in parallel – radial – or...
Reexamination Certificate
1999-06-09
2001-04-17
Freay, Charles G. (Department: 3746)
Pumps
Three or more cylinders arranged in parallel, radial, or...
C417S222200, C092S155000
Reexamination Certificate
active
06217295
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a swash plate type compressor and, more particularly, to a swash plate type compressor provided with a swash plate and pistons which are finished by improved surface treatment to exercise enhanced performance, and capable of functioning with improved reliability.
BACKGROUND ART
A double-headed swash plate type compressor applied to an automobile air conditioning system, for example, has a drive shaft, a pair of cylinder blocks supporting the drive shaft for rotation, and a swash plate fixedly supported on the drive shaft for rotation together with the drive shaft in a swash plate chamber formed in a region including the boundary between the pair of cylinder blocks. A plurality of cylinder bores are formed so as to extend in both the cylinder blocks and are arranged around the drive shaft. Double-headed pistons are fitted for axial movement in the cylinder bores, respectively. Each piston is operatively engaged with the swash plate by shoes. The rotary motion of the swash plate is converted into the linear motion of the pistons for the suction, compression and discharge of a refrigerant gas.
A single-headed swash plate type compressor has a cylinder block and a housing closing the inner end of the cylinder block and having a swash plate chamber or a crank chamber. A swash plate is mounted on a drive shaft in the swash plate chamber and is linked to pistons by shoes. In a variable-displacement swash plate compressor, a swash plate is linked to single-headed pistons fitted in a plurality of cylinder bores by shoes, and is mounted on a drive shaft so as to wobble on a supporting point. The inclination of the swash plate is changed according to pressure in the crank chamber so that gas pressures acting on the opposite ends of the single-headed piston balance each other. Consequently, the stroke of the single-headed piston is adjusted to control the displacement of the compressor.
A significant demand for weight reduction in those swash plate type compressors has progressively increased in order to apply the swash plate type compressors to automobile air conditioning systems, and most of the swash plates and the pistons, as well as the cylinder blocks, of those swash plate type compressors are made of aluminum alloys in lightweight constructions. Therefore, abrasion-resistant and seizing-preventive measures have been examined for protecting surfaces exposed to severe, high-speed abrasive action for a long time, such as the surfaces of the swash plate in sliding contact with the shoes, and the sliding contact surface of the piston in sliding contact with the surface of the bore. Such measures include the formation of a fluorocarbon resin film on the sliding contact surface of the piston and the formation of a film of a solid lubricant on the sliding contact surface of the swash plate.
However, the double-headed piston is provided with a recess extending across the periphery of the swash plate, and interfering surfaces formed in the recess to restrain the piston from rotation come into impulsive contact with the outer circumference of the swash plate to restrain the piston from rotation by a rotation moment acting on the piston. The single-headed piston is provided with a rotation-preventive interfering surface in its base end part, and the interfering surface comes into impulsive contact with the inner surface of the housing to restrain the piston from rotation. Accordingly, it is possible, under a substantially nonlubricated state which occurs at the start of the compressor, that seizing occurs at the interfering surface of the piston and the outer circumference of the swash plate, and attempts have been made to form a lubricating film over the interfering surface of the piston and the outer circumference of the swash plate. Nevertheless, the yield of a coating material used in, for example, a spray coating process for coating the pistons and the swash plate with a lubricating film is extremely low. Furthermore, the spherical surfaces of the pistons must be masked in the spray coating process and the spray coating process is hardly satisfactory in working efficiency.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide an improved swash plate type compressor capable of providing improved functional reliability attained by employing, in combination, an improved swash plate and improved pistons provided with an excellent lubricating film capable of being manufactured with a high productivity.
Another object of the present invention is to provide a long-life swash plate type compressor capable of properly functioning for an extended period of use when applied to an automobile air conditioning system and driven by the engine of a vehicle to compress a refrigerant.
In accordance with the present invention, there is provided a swash plate type compressor which comprises: a cylinder block provided with a plurality of cylinder bores; pistons fitted in the cylinder bores; a drive shaft supported for rotation about its axis of rotation; and a swash plate supported for rotation together with the drive shaft, having at least sliding contact surfaces to be in sliding contact with shoes and linked to the pistons by the shoes;
wherein the pistons are made of an aluminum alloy as a base material, each piston has an interfering surface which is interfered with by another member to restrain the piston from rotation, and the interference surfaces of the pistons are coated with a film of at least one solid lubricant selected from molybdenum disulfide, tungsten disulfide and graphite.
In the described swash plate type compressor, the excellent lubricating performance of the film of the solid lubricant formed on the interfering surface for retraining the piston from rotation effectively prevents the seizing of the interfering surface, and the outer circumference of the swash plate, i.e., another member, or the inner surface of a crank chamber with which the interfering surface comes into nonlubricated contact, enhances the functional reliability of the swash plate compressor, and extends the life of the swash plate compressor.
The seizing preventing effect of a film of a solid lubricant containing molybdenum disulfide as an essential component is particularly remarkable.
If the sliding contact surface of the piston in sliding contact with a surface defining the cylinder bore is coated with a film of a material containing a fluorocarbon resin as a principal component or a film of a solid lubricant, the abrasion resistance and the seizing preventing capability of the piston sliding in the bore can be improved.
When a transfer method is employed in forming the lubricating films on the sliding contact surfaces of the pistons in sliding contact with surfaces defining the cylinder bores, and the rotation-preventive interfering surfaces of the pistons, the coating material is not wasted, masking work is unnecessary when forming the film, and it is very advantageous in quality assurance, such as film thickness control.
In a swash plate type compressor in which the rotation-preventive interfering surfaces of pistons come into impulsive contact with the outer circumference of a swash plate to prevent the pistons from rotation, it is preferable to plate the outer circumference of the swash plate with a metal containing tin as a principal component or to form a lubricating film of a solid lubricant on the outer circumference of the swash plate. In the swash plate compressor, the cooperative effect of the outer circumference of the swash plate and the interfering surfaces of the pistons further effectively prevents the seizing of the pistons and the swash plate.
A metal layer of a material containing tin as a principal component formed by plating so as to underlie the film of the solid lubricant formed on the outer circumference of the swash plate will further enhance the durability of the film.
Obviously, the film of the solid lubricant can quite simply be formed on the outer circumference of the swash plate by a transfer method.
REFERENC
Ikeda Hayato
Katayama Seiji
Kato Takayuki
Taga Masaaki
Burgess, Ryan & Wayne
Freay Charles G.
Gray Michael K.
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Moran William R.
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