Metal working – Method of mechanical manufacture – Prime mover or fluid pump making
Reexamination Certificate
2001-02-13
2002-05-07
Cuda Rosenbaum, I (Department: 3726)
Metal working
Method of mechanical manufacture
Prime mover or fluid pump making
C029S888040, C029S888042, C029S888022
Reexamination Certificate
active
06381842
ABSTRACT:
This application is based on Japanese Patent Application No. 2000-041659 filed Feb. 18, 2000, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a method of producing a hollow piston for a compressor of reciprocating type.
2. Discussion of the Related Art
In general, a piston for a reciprocating type compressor has a head portion which is slidably fitted in a cylinder bore of the compressor, and an engaging portion which engages a reciprocating drive device of the compressor for reciprocating the piston. Upon actuation of the reciprocating drive device with the engaging portion of the piston being in engagement with the reciprocating drive device, the piston is moved such that the head portion of the piston is reciprocated in the cylinder bore to effect suction and compression of a gas. A swash plate type compressor is one example of the compressor which uses such a piston. In the piston used for the swash plate type compressor, the engaging portion is generally U-shaped, and engages the opposite surfaces of the swash plate of the compressor through a pair of shoes. The piston is reciprocated by a rotary movement of the swash plate.
For reducing the weight of the piston for the compressor, at least the head portion of the piston is made hollow. As disclosed in JP-A-11-303747 and JP-A-11-294320, such a piston is produced by preparing a hollow cylindrical member having an open end at at least one of its opposite ends, and a closure member, and closing the open end of the hollow cylindrical member with the closure member. According to the methods disclosed in those publications, a hollow head portion of the piston is formed by closing, with the closure member, an open end of a body member of a blank for manufacturing the piston, which body member of the blank includes a bottom portion and a hollow cylindrical portion. When the body member of the blank is formed integrally with the engaging portion, the closure member is a circular plate member, or a cylindrical member including a circular bottom plate portion and a cylindrical portion. When the body member of the blank is separate from the engaging portion, the closure member is formed integrally with the engaging portion.
Where the head portion of the piston is formed by closing the open end of the hollow cylindrical member with the closure member, it is generally known that one of the hollow cylindrical member and the closure member is formed to have a female corner portion which is defined by an annular shoulder surface and a circumferential surface adjacent to the shoulder surface, while the other of the hollow cylindrical member and the closure member is formed to have a male corner portion which corresponds to the female corner portion. If the closure member includes an annular abutting surface which is to be held in abutting contact with an end face of the hollow cylindrical member at its open end, and a radially inner fitting portion which protrudes axially from the annular abutting surface and which is to be inserted into the open end of the hollow cylindrical member, for instance, the annular abutting surface of the closure member functioning as the shoulder surface cooperates with an outer circumferential surface of the fitting portion to define the female corner portion, while the open end portion of the hollow cylindrical member defines the male corner portion. If the open end portion of the hollow cylindrical member includes a large-diameter portion and a small-diameter portion, and the closure member is inserted into the large-diameter portion of the hollow cylindrical member, an annular surface which connects the large-diameter and small-diameter portions functions as the shoulder surface, and cooperates with an inner circumferential surface of the large-diameter portion to define the female corner portion. In this case, the male corner portion is defined by an end face of the closure member which is to be held in abutting contact with the shoulder surface of the cylindrical member, and an outer circumferential surface of the closure member adjacent to the end face.
The hollow cylindrical member and the closure member are fixed to each other generally by welding, bonding, friction compression, caulking, etc., with the male corner portion being held in abutting contact with the shoulder surface of the female corner portion. The female corner portion, however, is usually rounded to provide a fillet at a boundary between the shoulder surface and the circumferential surface, for easier manufacture of the hollow cylindrical member or the closure member by casting, forging, or cutting, so that the fillet of the female corner portion interferes with the edge of the male corner portion upon engagement of the hollow cylindrical member and the closure member with each other. In this case, there is formed a gap between the shoulder surface of the female corner portion and the abutting surface of the male corner portion, which must be held in abutting contact with the shoulder surface. Since this gap is negligibly small in general, the fixing of the two members is conventionally effected without taking the gap into account. It has turned out, however, that the gap undesirably gives adverse influences on the performance of the piston.
Described in detail, when the hollow cylindrical member and the closure member are fixed to each other by beam-welding the shoulder surface of the female corner portion and the abutting surface of the male corner portion (i.e., the welding surfaces at which the two members are welded together), materials of welded portions of the two members are excessively fused to fill up the gap. In this case, the welded portions of the two members may be recessed due to the excessive fusion of the materials of the two members. In an extreme case, there may be formed a hole in the welded surfaces of the two members, undesirably lowering the weld strength of the two members at the welding surfaces. When the hollow cylindrical member and the closure member are fixed to each other by bonding with an adhesive agent, the thickness of the layer of the adhesive agent formed between the shoulder surface and the abutting surface tends to be larger than a predetermined nominal or optimum thickness value, resulting in reduction of the bonding strength of the two members at the bonding surfaces. When the hollow cylindrical member and the closure member are fixed to each other by pressure welding, the edge of the male corner portion is forced against the fillet of the female corner portion, and collapses so as to substantially follow the fillet, so that the gap between the shoulder surface and the abutting surface is less likely to give adverse influences on the strength of fixing of the two members. Where the fillet of the female corner portion is relatively large, however, the two members may not be fixed together with a sufficient strength. Where the two members are fixed to each other by caulking, the edge of the male corner portion is repeatedly pressed onto the fillet of the female corner portion during operation of the piston, undesirably causing plastic deformation of the edge and the fillet. In this case, the hollow cylindrical member and the closure member which are caulked together may suffer from a rattling movement relative to each other, rendering the piston inoperable.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of producing a hollow piston used for a compressor, which has a sufficiently high degree of durability.
The object indicated above may be achieved according to any one of the following forms or modes of the present invention, each of which is numbered like the appended claims and depend from the other form or forms, where appropriate, to indicate and clarify possible combinations of technical features of the present invention, for easier understanding of the invention. It is to be understood that the present invention is not limited to the technical f
Enokijima Fuminobu
Hoshida Takahiro
Kato Takayuki
Takamatsu Masato
Cuda Rosenbaum I
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Woodcock & Washburn LLP
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