Stock material or miscellaneous articles – Metal continuous phase interengaged with nonmetal continuous...
Reexamination Certificate
2000-06-09
2002-05-07
Copenheaver, Blaine (Department: 1775)
Stock material or miscellaneous articles
Metal continuous phase interengaged with nonmetal continuous...
C428S632000, C428S633000, C428S212000, C428S220000, C428S293100, C501S095100, C501S095200
Reexamination Certificate
active
06383656
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a preform for metal matrix composite and a cylinder block made by pouring molten matrix metal into a preform. More specifically, the present invention relates to a preform including a porous structure made of inorganic materials such as inorganic particles and inorganic fibers.
2. Description of the Related Art
A cylinder block of an engine for automobile is well known in which metal matrix such as aluminum alloy is cast round a cylinder liner made of cast iron. This type cylinder block is manufactured by the following conventional manufacturing method. First, a cylinder liner made of cast iron, which is manufactured in a different manufacturing process, is arranged in a casting mold of a cylinder block, and then molten metal of aluminum alloy is poured into the casting mold, so that the cylinder block can be obtained. An inner circumferential face of the cylinder liners in the cylinder block is polished so as to form a sliding face on which a piston slides. This cylinder block includes the cylinder liner made of cast iron as described above. Therefore, the cylinder block is heavy. Further, since this cylinder block is made of different metals of cast iron and aluminum alloy, the coefficients of thermal expansion of which are different from each other. Therefore, there are problems of lower characteristics in that the different metals can be tightly joined to each other and that heat can be efficiently radiated or not. In order to solve the above problems, a large number of cylinder blocks are proposed in which the cylinder liners are made of aluminum alloy. These cylinder blocks are disclosed in Japanese Examined Patent Publication Nos. Hei. 4-11612, Hei. 5-33295 and Hei. 8-9093.
This type cylinder block, the cylinder liner of which is made of aluminum alloy, is manufactured as follows. First, a porous structure made of inorganic fibers such as aluminum fibers or carbon fibers is formed into a predetermined shape. That is, the porous structure made of inorganic fibers is formed into a shape of a cylinder liner. This porous structure, which is formed into a predetermined shape, is referred to as a preform in this specification, hereinafter. The thus obtained preform is arranged in the casting mold for casting the cylinder block, and aluminum alloy is poured into the casting mold, so that molten aluminum alloy is impregnated into voids formed in the preform. In this way, the cylinder block is obtained. The cylinder block taken out from the casting mold after cooling is composed in such a manner that the cylinder liner is made of fiber reinforced composite material, the frame of which is the preform, and the entire body of the cylinder is made of aluminum alloy by means of integral casting.
Japanese Unexamined Patent Publication Nos. Sho. 63-149342, Hei. 2-194132, Hei. 3-44432 and Hei. 9-14045 disclose a preform, which is a porous structure, made of not only inorganic fibers but also ceramic particles. In Japanese Unexamined Patent Publication No. Hei. 9-14045, there is a description that a preform made of ceramic particles and short fibers of alumina is suitable for fiber reinforced metallic material because no deformation, crack, deflection and defective impregnation into metallic matrix are caused in the process of manufacturing the preform of a cylinder liner.
In Japanese Unexamined Patent Publication No. Hei. 3-44432, there is a description that a porous body, which is obtained when short fibers, inorganic particles and binder are mixed with each other and subjected to sucking dehydrating formation, can lead to a good fiber reinforced metallic material. In this example, the average fiber diameter of short fibers is not more than 1 &mgr;m, and the average particle diameter of inorganic particles is 10 to 50 &mgr;m.
The preform of the above conventional example is advantageous as follows. When the preform is made, heat-resistant fiber material such as inorganic fibers are used. Therefore, appropriate voids are formed in the preform, and the metal matrix can be easily impregnated into the voids, and further the inorganic fibers are entangled with each other at random, so that the mechanical strength of the preform can be enhanced. However, fiber material is a secondary processed product. Therefore, fiber material is generally expensive. For example, when inorganic fiber material is compared with inorganic particle material, the price of the inorganic fiber material is 10 times as high as that of the inorganic particle material. Accordingly, when the preform is made of only fiber material, the price of a final product such as the price of a cylinder block is raised.
Therefore, a conventional example in which a portion of the fiber materials are replaced with ceramics, metals, intermetallic compounds and carbon particles is very advantageous in that the high performance of fiber materials as a preform can be compatible with the price of the preform. However, when inspection is made into the above conventional example, the above method is disadvantageous in that dehydration can not be sufficiently conducted in the process of sucking dehydrating formation in the process of manufacturing the perform, so that the productivity is lowered. To be specific, the preform is made in such a manner that slurry containing fiber materials and ceramic particles is put into a mold of a predetermined shape and subjected to sucking dehydrating formation through a filter, and then dried and baked. In this process of sucking dehydrating formation, clogging of the filter is caused, and the dehydrating property is remarkably deteriorated, and the productivity is lowered.
Further, according to the inspection of the conventional example, the following problems are found. Voids among the fiber materials tend to be densely filled with inorganic particles such as ceramic particles, and the thus obtained preform is difficult to impregnate with molten metal of metallic matrix. In this case, if the impregnation of molten metal is forcibly conducted, the preform is given an excessively high pressure, and cracks and deformation are caused in the preform. When the metal group composite material obtained from this preform is applied to the cylinder liner of a cylinder block, the cylinder liner is damaged and deformed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a preform and a cylinder block having cylinder liners made of fiber reinforced metallic composite material, the abrasion resistance property of which is high.
In order to solve the above problems, the present inventors made investigation in earnest and found the followings. A porous structure is made to be a preform of a cylinder liner, and the preform is impregnated with metallic matrix so as to make the cylinder liner, and this cylinder liner is incorporated into a cylinder block. In this case, it is possible to provide a cylinder block of high heat-resistance, high mechanical strength and high abrasion resistance when the porous structure is made as follows. Heat-resistance fiber materials are divided into small-diameter inorganic fibers, the average fiber diameter of which is 2 to 5 &mgr;m and the average fiber length of which is 10 to 200 &mgr;m, and large-diameter inorganic fibers, the average fiber diameter of which is 4 to 20 &mgr;m and the average fiber length of which is 10 to 200 &mgr;m. These small-and large-diameter inorganic fibers and inorganic particles, the average particle diameter of which is 1 to 50 &mgr;m, are dispersed in water together with binder and put into a mold of an objective shape such as a cylinder liner and then subjected to sucking dehydrating formation through a filter. Then, the small-diameter inorganic fibers mainly catch the inorganic particles, so that the inorganic particles are dispersed in the preform and prevented from being densely filled into voids among the large-diameter inorganic fibers so as to enhance the sucking dehydrating forming property. Further, this action of the small-diameter ino
Iida Takahiro
Iwata Koji
Kaneda Kazumi
Kawamoto Susumu
Kimura Koichi
Copenheaver Blaine
Nichias Corporation
Nixon & Vanderhye
Savage Jason
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