Metal working – Method of mechanical manufacture – Prime mover or fluid pump making
Reexamination Certificate
2002-05-09
2004-01-13
Cuda-Rosenbaum, I (Department: 3726)
Metal working
Method of mechanical manufacture
Prime mover or fluid pump making
C029S888020, C148S693000
Reexamination Certificate
active
06675475
ABSTRACT:
This application is based on Japanese Patent Application No. 2001-139540 filed May 10, 2001, 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 shoe which is formed of an aluminum alloy and which is disposed between a swash plate and a piston of a swash plate type compressor.
2. Discussion of the Related Art
A swash plate type compressor is adapted to compress a gas by converting a rotary movement of the swash plate into a reciprocating movement of a plurality of pistons. Between the swash plate which is rotated at a relatively high speed and each piston which is reciprocated at a relatively high speed, a shoe as a sliding member is disposed for permitting a smooth relative movement therebetween. In the swash plate type compressor which is required to have a reduced weight for use in an air conditioning system of an automotive vehicle, for instance, it has been proposed to use a shoe formed of an aluminum alloy.
The shoe formed of the aluminum alloy is produced, for instance, by a method comprising: a forging step of forging a blank into a shoe; a thermal refining step of thermally refining the shoe according to a T6 or a T7 treatment specified in the Japanese Industry Standard (JIS) H0001; and a grinding step of grinding the shoe to adjust its size, so that the shoe has desired dimensions. The shoe has sliding surfaces which are to be held in sliding contact with the swash plate and the piston, respectively. In operation, the shoe slides on both of the swash plate and the piston with lubricant oil films being formed between the sliding surfaces of the shoe and the sliding surfaces of the swash plate and the piston. Accordingly, suitable clearances need to be formed between the sliding surfaces of the shoe and the sliding surfaces of the swash plate and the piston. Therefore, the shoe is required to have a high degree of dimensional accuracy.
In the thermal refining treatment such as the T6 or T7 treatment, the shoe is subjected to heating, rapid cooling, etc., so that the shoe inevitably suffers from deformation due to the thermal refining treatment. Since some variation in the amount of deformation of the shoe due to the thermal refining treatment is inevitable, however, the forging operation in the forging step is arranged such that the shoe obtained after the forging step has a size which is larger than a nominal or desired value. In the grinding step following the thermal refining step, the grinding operation is effected on the shoe for adjusting its size to the nominal value. In the size-adjustment grinding operation, however, the required amount of stock removal is inevitably large, resulting in an increase of the time required for adjusting the size of the shoe after the thermal refining step and an increase of the cost of its manufacture.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of quickly and economically producing a shoe formed of an aluminum alloy and having a high degree of dimensional accuracy. This object may be achieved according to any one of the following modes of the present invention, each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate and clarify possible combinations of elements or 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 or any combinations thereof which will be described for illustrative purpose only. It is to be further understood that a plurality of elements or features included in any one of the following modes of the invention are not necessarily provided all together, and that the invention may be embodied without some of the elements or features described with respect to the same mode.
(1) A method of producing a shoe for a swash plate type compressor, the shoe being disposed between a swash plate and a piston of the swash plate type compressor and formed of an aluminum alloy, the method comprising: a main forging step of forging a blank for producing the shoe into a roughly-shaped precursor shoe; a thermal refining step of thermally refining the roughly-shaped precursor shoe; and a size-adjustment forging step of forging the roughly-shaped precursor shoe which has been thermally refined, into a size-adjusted shoe.
The method of producing a shoe according to the above mode (1) is characterized by conducting an additional or a supplemental forging operation to adjust the size of the roughly-shaped precursor shoe obtained after the main forging step and the thermal refining step. The shoe is inevitably deformed due to the thermal refining treatment in the thermal refining step, and the amount of deformation of the shoe due to the thermal refining treatment varies depending upon individual shoes. In the present method according to the above mode (1), the roughly-shaped precursor shoe which has been thermally refined is subjected to the additional forging operation for size-adjustment, for thereby permitting the obtained shoe to have a high degree of dimensional accuracy. Since the forging operation can be generally effected in a relatively short period of time, the size-adjustment forging step according to the above mode (1) of the present invention can be quickly effected without considerably increasing the time required for producing the shoe. Accordingly, the present method according to the above mode (1) permits an economical manufacture of the shoe.
The aluminum alloy used for producing the shoe is not particularly limited, but may be selected from among aluminum alloys conventionally used for producing the shoe and various known aluminum alloys. For example, it is possible to use an Al—Si alloy having a ratio of content of Al to Si which is nearly equal to that at which an eutectic mixture is formed. The Al—Si alloy is, for instance, A4032 specified in JIS H4100. The Al—Si alloy has a small coefficient of thermal expansion and exhibits a good wear resistance, so that the shoe formed of the Al—Si alloy exhibits good sliding characteristics. It is possible to use an Al—Cu—Mg alloy such as A2017, A2024 specified in JIS H4100, which alloy has a high degree of strength. The shoe formed of the Al—Cu—Mg alloy exhibits high degrees of strength and durability.
The shape of the blank used in the main forging step is not particularly limited, but may be suitably determined depending upon the shape of the shoe to be obtained. For instance, the blank may have a spherical shape, a hemi-spherical shape, a cylindrical shape, a disc-like shape, a truncated conic shape, or a truncated pyramid shape. Where the shoe has a part-spherical crown shape which will be described, it is desirable to use a cylindrical blank having a diameter which is smaller than an outer diameter of the shoe as the end product (hereinafter referred to as “end product shoe”) and a height which is larger than that of the end product shoe, for permitting a forging operation at a relatively low forging ratio. The blank may be prepared according to any methods. For example, the blank is prepared by casting, punching of a plate member by a press, or cutting of a long cylindrical member. Where the blank has the cylindrical shape described above, the cylindrical blank is prepared first by extruding a billet having a predetermined shape and formed of an aluminum alloy which is obtained by casting and which has a predetermined composition, drawing the billet to provide a bar-shaped member having a predetermined diameter, and then cutting, by a shearing machine or a sawing machine, the bar-shaped member into pieces each having a predetermined length. The blank to be used in the main forging step is desirably subjected to an annealing treatment for facilitating the forging operation performed on the blank in the main forging step and obtaining a roughly-shaped precursor shoe which has good characteristics, e.
Murakami Tomohiro
Ohkubo Shino
Onoda Akira
Sugioka Takahiro
Sugiura Manabu
Cuda-Rosenbaum I
Kabushiki Kaisha Toyota Jidoshokki
Morgan & Finnegan , LLP
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