Metal working – Method of mechanical manufacture – Prime mover or fluid pump making
Reexamination Certificate
2000-09-20
2002-07-02
Rosenbaum, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Prime mover or fluid pump making
C029S888022, C029S888020
Reexamination Certificate
active
06412171
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a method of producing a body member for a piston for a swash plate type compressor, and more particularly to a method of producing, by die-casting, such a body member having a hollow cylindrical head portion.
2. Discussion of the Related Art
A swash plate type compressor is adapted to compress a gas by a plurality of pistons which are reciprocated by a rotary movement of a swash plate. In general, the piston includes a head portion slidably fitted in a cylinder bore formed in a cylinder block of the compressor, and an engaging portion which slidably engages the swash plate. For reducing the weight of the piston, it has been proposed to form the piston with a hollow cylindrical head section. As one example of the method of producing such a piston, the assignee of the present invention proposed in JP-A-11-152239 a method of producing a blank for the piston, comprising the steps of: preparing a body member including a hollow head section which is closed at one of its opposite ends and is open at the other end, and an engaging section which is formed integrally with the head section; and fixing a closing member prepared separately from the body member, to the body member so as to close the open end of the head section. While the closing member may be produced by any method, the body member is preferably produced by die-casting.
SUMMARY OF THE INVENTION
The present invention was made in the light of the background art described above. It is an object of the present invention to provide an improved method of producing, by die-casting, a body member for a swash plate type compressor piston, which body member includes a hollow cylindrical head section closed at one of its opposite ends, and an engaging section integrally formed with the head section.
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 features and their combinations described below. It is also to be understood that any technical feature described below in combination with other technical features may be a subject matter of the present invention, independently of those other technical features.
(1) A method of producing a body member of a piston for a swash plate type compressor, the body member including a generally hollow cylindrical head section having a closed end and an open end which is closed by a closing member so as to provide a head portion of the piston, and an engaging section which is formed integrally with a bottom portion of the hollow cylindrical head section which is located at the closed end, the engaging section giving an engaging portion of the piston for engagement with a swash plate of the compressor, comprising the steps of preparing a die-casting device including a casting mold consisting of two mold halves which are spaced apart from each other and butted together in a direction perpendicular to a centerline of the hollow cylindrical head section, the two mold halves having respective molding surfaces; and a slide core which is slidably movable in a direction parallel to the centerline such that the slide core is advanced into and retracted from the casting mold, the slide core cooperating with the molding surfaces of the mold halves to define therebetween a mold cavity when the slide core is advanced into the casting mold, the mold cavity having a configuration following that of the body member which includes the hollow cylindrical head section and the engaging section, at least a front end portion of the slide core having a nonaxisymmetric configuration with respect to a centerline of the slide core; and die-casting the body member using the die-casting device, such that the hollow cylindrical head section has an inner bottom surface having a three-dimensional configuration which is nonaxisymmetric with respect to the centerline of the hollow cylindrical head section corresponding to the nonaxisymmetric configuration of the front end portion of the slide core.
In the method according to the above mode (1) of this invention, when the slide core is advanced into the casting mold consisting of the two mold halves, the slide core cooperates with the molding surfaces of the two mold halves to define therebetween a mold cavity having a configuration following that of the body member which includes the hollow head section and the engaging section. The mold cavity is filled with a molten metal, so that the intended body member is formed in the mold cavity. Thereafter, the slide core is retracted out of the formed hollow cylindrical head section so that the front end portion of the slide core is located outside the casting mold. Subsequently, the two mold halves are moved apart from each other to remove the formed body member therefrom. In the present arrangement wherein at least the front end portion of the slide core has a nonaxisymmetric configuration with respect to its centerline, the formed hollow cylindrical head section has an inner bottom surface which has a three-dimensional configuration which is nonaxisymmetric with respect to its centerline, which configuration corresponds to the nonaxisymmetric configuration of the front end portion of the slide core.
For reducing the weight of the piston, the hollow cylindrical head section of the body member may be subjected to a machining operation such as a cutting operation effected on its inner circumferential surface prior to fixing the closing member to the open end of the head section. When the inner bottom surface of the head section is subjected to the cutting operation concurrently with the cutting operation on the inner circumferential surface of the head section, the inner bottom surface preferably has a configuration defined by a plurality of circles concentric with the head section, that is, coaxial with a cutting tool used in the cutting operation.
However, in order to minimize the weight of the body member wherein the engaging section is integral with the bottom portion of the head section, the inner bottom surface of the head section preferably has a configuration other than that described above.
By effecting another cutting operation on the inner bottom surface of the head section using a drill or an end mill, in addition to the above-described cutting operation on the inner circumferential surface of the head section, the inner bottom surface of the head section can be formed into a three-dimensional configuration which is different from the above-described configuration defined by a plurality of circles concentric with the head section. This additional step, however, inevitably pushes up the cost of manufacture of the piston.
According to the method of the present invention, in contrast, the inner bottom surface of the head section of the body member can be formed into a desired three-dimensional configuration. In other words, the inner bottom surface of the head section may have any configuration, provided that the slide core can be easily retracted from the formed body member. In the present method, the inner bottom surface of the head section has the three-dimensional configuration which is effective to reduce the weight of the body member including the head section and the engaging section formed integrally with the bottom portion of the head section.
The above description is based on an assumption that the inner circumferential surface of the head section of the body member is subjected to a machining operation such as a cutting operation for reducing the weight of the piston. However, the inner surface of the head section, which includes the inner circumferential surface and the inner bottom surface, need not be machined. When the body m
Kato Takayuki
Takamatsu Masato
Cuda Rosenbaum I
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Woodcock & Washburn LLP
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