Metal working – Method of mechanical manufacture – Prime mover or fluid pump making
Reexamination Certificate
1999-07-30
2001-03-20
Rosenbaum, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Prime mover or fluid pump making
Reexamination Certificate
active
06202301
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a piston of a variable-capacity type compressor.
2. Description of the Related Art
There has heretofore been known a variable-capacity type compressor which is so constituted as to vary the discharge capacity by adjusting the pressure in the crank chamber in which a swash plate (inclusive of a wobble plate) is contained, and by varying the angle of inclination of the swash plate as taught in Japanese Unexamined Patent Publication (Kokai) No. 62-191673.
The compressor of the above prior art comprises an arm member that moves with a drive shaft, a swash plate mounted to the drive shaft so as to be able to change an inclined angle and rotate with the arm member, a piston accommodated in the cylinder bore so as to reciprocatingly move therein, and a piston rod of which an end forming a ball joint is engaged with a slide surface of the wobble plate via a shoe and of which the other end is coupled to the piston. Here, in coupling the piston and the piston rod together, a hole is perforated in the central boss portion of the piston to fit the piston rod in the piston, piston rod is press-fitted, and the piston rod is prevented from escaping by using a knock pin.
However, if the piston and the piston rod after they are machined are simply press-fittedly coupled together, the overall length of the coupled unit, i.e., the length from the top surface of the piston to the outer end (or the center of the sphere) of the ball joint of the piston rod, is the sum of the length from the bottom surface of the fitting hole of the piston to the top surface of the piston and the overall length of the piston rod. Therefore, the overall length of the coupled unit is determined including production tolerance of the piston and the piston rod. Besides, the overall length of the coupled unit is not only affected by the degree of tolerance (that is simply accumulated) but is also affected by very small bucklings (brought to the contacting surfaces of the two members) caused by the pressure of press-in coupling. Consequently, therefore, there arises a problem of deviation in the top clearance in the cylinder bores.
Moreover, in a piston having an outer cylindrical shell portion of a relatively small thickness, reinforcing ribs are formed between the outer cylindrical shell portion and the central boss portion to suppress the deformation of the outer cylindrical shell portion. Therefore, if there exist the reinforcing ribs, the central boss portion expands due to the interference fitted by the piston rod that is press-fit, and the effect spreads through the reinforcing ribs to the outer cylindrical shell portion, causing the outer peripheral surface of the piston to lose precision.
SUMMARY OF THE INVENTION
The object of the present invention is to improve the fitting precision of the piston with respect to the cylinder bore, and to decrease deviation in the top clearance.
In order to solve the above-mentioned problem, the present invention provides a method for manufacturing a piston of a variable-capacity type compressor, the compressor comprising a casing and at least one cylinder bore, said piston reciprocatingly arranged in said cylinder bore, a drive shaft, a rotatable member movable with the drive shaft, a swash plate mounted to said drive shaft at a variable inclined angle and rotatable with said rotatable member, and a connecting rod comprising a cylindrical body having a first end associated with a slide surface of said swash plate via a shoe and a second end coupling the connecting rod to said piston, the method comprising the steps of connecting said connecting rod to said piston, and subsequently, finishing the outer peripheral surface and top surface of the piton.
The accumulated tolerance and deformation of the piston and the connecting rod that are coupled together, can all be corrected by the finishing work of the piston that is effected after the coupling. Therefore, the precision of fitting to the cylinder bore as well as dispersion in the top clearance can be confined to lie within predetermined ranges. Preferably, the piston and the connecting rod are press-fitted coupled together, which is the simplest coupling, and reinforcing ribs are extending between the outer cylindrical shell portion of the piston and the central boss portion. Accordingly, the precision of the outer peripheral surface of the piston and the precision of the overall length of the coupled unit can be favorably maintained owing to the finishing work being done after the coupling by using the spherical portion of the connecting rod and the cylindrical portion exposed from the piston as a reference.
REFERENCES:
patent: 4379425 (1983-04-01), Ishizuka
patent: 4505016 (1985-03-01), Roberts
patent: 4620475 (1986-11-01), Watts
patent: 5101555 (1992-04-01), Hauser
patent: 5537743 (1996-07-01), Hibino et al.
patent: 5842580 (1998-12-01), Lee et al.
patent: 6038767 (2000-03-01), Ito
patent: 62-191673 (1987-08-01), None
patent: 9-209930 (1997-08-01), None
patent: 9-329080 (1997-12-01), None
Cuda Rosenbaum I
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
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