JPS60234763A - Production of piston - Google Patents

Abstract

PURPOSE:To produce easily a piston consisting of a composite material having high quality by using a mat obtd. by molding ceramic fibers and metallic base metal to form a rough material consisting of the composite material having a simple shape and casting a molten metal into a casting mold thereby forming the molded composite material having the prescribed shape by which an anchor effect is induced. CONSTITUTION:The ceramic fibers (including whiskers) of alumina, silicon carbide, etc. are molded to manufacture the cylindrical mat 10 having the simple shape. Said mat is installed in the casting mold and the molten metallic base material such as aluminum alloy is poured into the mold to form the part 12 consisting of the metallic base material alone. The cylindrical rough material 14 is thus obtd. A part 20 forming part of the inside circumferential surface of a combination chamber 18 and a wedge-shaped anchor part 22 are suitably worked to such material 14 to form a mold composite material 24. Such material 24 is subjected to a cleaning treatment and is installed in the casting mold for the piston. The molten metal of the metallic base material is cast therein and the casting piston 16 is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing pistons, particularly pistons for internal combustion engines.

In the piston of an internal combustion engine that operates in contact with high-temperature, high-pressure combustion gas, the desired part, especially the piston crown,
Inorganic fibers such as alumina and silicon carbide (including whiskers)
Or powdered aluminum alloy, magnesium alloy,
It is well known that thermal shock resistance, abrasion resistance, etc. can be improved by constructing a composite material impregnated with a metal base material such as an iron-based alloy. Conventional methods for manufacturing composite pistons involve placing the above-mentioned inorganic fiber molded body, which has been pre-formed into a desired shape, directly into a desired position within a piston mold, and then using an autoclave method or a cold sintering method. A composite piston was obtained by compounding the piston with a metal base material by a method such as a hot pressing method, a hot pressing method, or a molten metal forging method.

However, with the above manufacturing method, it is difficult to uniformly distribute the inorganic fibers in a complicated shape in a desired region of the piston, and to obtain a piston that is homogeneous and therefore has stable characteristics.

The present invention was devised to improve the drawbacks of the conventional manufacturing methods described above. A method of impregnating a metal base material such as an alloy by molten metal forging, a method of high-pressure injection of ceramic fibers (or powder) and a metal base material, a method of mixing and sintering a metal powder with a laminate, a 7-grip fiber, or a powder, etc. a step of producing a composite rough material with a simple shape; a step of producing a molded composite material by processing the composite material rough material into a shape that produces an anchoring effect and fits a mold after casting; The gist of the present invention is a method for manufacturing a piston, which includes the steps of placing the piston in a piston mold, pouring a metal base material, performing molten metal forging, and casting the piston.

Embodiments of the method of the present invention will be described in detail below with reference to the accompanying drawings. In carrying out the method of the present invention, first, as shown in FIG.
100 simple + aspect ratio 10-500 or more 2 volume content V, several to 30%), silicon carbide (diameter 005-1 μm,
length 10-500 μm, aspect ratio 10-5002, volume content V, several to 30%) or ceramics such as zirconia fibers and silicon nitride whiskers. The fibers (including whiskers) are molded to form a cylindrical matrix (...) 10 which is simple in shape and easy to obtain homogeneity, and placed in a mold with a corresponding shape. A cylindrical composite rough material 14 is produced by pouring a molten metal base material and using a well-known molten metal forging method. The cylindrical rough material 14 shown in FIG.
(g) 10 and a portion 12 made of a single metal base material. As another example, as shown in Fig. 3, there is a disk-shaped ma, which is simple in shape and has a slightly thicker outer circumferential portion than the central portion.
) 10 is molded with the same inorganic fiber as above, and is impregnated with the same metal base material by the molten metal forging method, and is made from a hole and a throat impregnated with the metal base material, and a portion 12 made of a single metal base material. A disk-shaped composite material 14 was obtained. Alternatively, the composite material 14 may be manufactured by a molten metal forging method using a metal base material such as ceramic, tsuku powder, and aluminum alloy. Since the composite material 14 of the present invention has an extremely simple shape such as a cylinder or a disk, it is easy to form it, and it also does not lose its shape during molten metal forging. As a result, both the finished product and the raw material are extremely homogeneous and of stable quality. (As is well known, the molded body itself is most commonly made of felt-like layers of inorganic fibers, but one or more layers of woven inorganic fibers are layered.) (or may have felt-like inorganic fibers interposed between woven fabrics), but is not limited to composites made by ceramic fibers, whiskers, ceramic rough powder, metal base material, and molten metal forging method. ,
The composite material 14 manufactured in the above manner is then subjected to a method such as combining ceramic fibers or powder and a metal base material by a high-pressure injection method or sintering ceramic fibers or powder and metal powder. ,
For example, in the case of the piston 16 shown in FIG.
A portion 20 forming a part of the inner circumferential surface of and a wedge-shaped anchor portion 22
The molded composite material 24 is processed into a molded composite material 24 by a suitable molding method such as machining. After performing cleaning treatments such as degreasing as necessary, it is placed in a separately prepared piston mold, and the molten metal base material is again cast using the molten metal forging method to produce the cast piston as a product. be done. In the process of casting the piston 16 by the molten metal forging method, it is important to preheat the molded composite material 24 (below its melting point), which has the advantage of making casting easier and more reliable.

In the above final casting process, by adopting the molten metal forging method, the oxide film of the metal base material that tends to occur on the surface of the molded composite material is effectively destroyed. It is clear that the bonding strength at the interface or boundary area with the material is high -19, and by further providing the wedge-shaped anchoring portion 22, the bonding strength between the two is further strengthened. The piston 16 manufactured in this way has a high homogeneity of the composite material part in its crown, has excellent properties such as desired heat resistance, mechanical strength, and wear resistance, and is of excellent quality with little variation. be. (Note that part No. 2, which forms part of the inner circumferential surface of the upper self-combustion chamber 18, may be cut by machining after the entire piston is cast.) The wedge-shaped anchoring portion shown by the chain line inside. 22a is cut into the plain metal base portion 12 shown in FIG. 3, and then the piston 16 is cast in the same manner as in the case shown in FIG. It is clear that a high quality product similar to that described above can be obtained with this piston.

Furthermore, the embodiment of the method of the present invention shown in FIG.
This piston differs from the pistons shown in FIGS. 1 and 4 in that the anchoring portion 22b is formed in a step-like manner.
Otherwise, it is substantially the same as the piston described above, and a similar high quality product can be obtained.

Next, the results of a thermal shock test and a wear resistance comparison test between a piston according to the method of the present invention and a piston having a conventional structure are shown in FIGS. 6 and 7. Figure 6 shows the results of the thermal shock test, and compares the number of cracks caused by the heating and cooling cycle test shown in Figure 8 according to the number of cycles. It is clear that compared to piston A, piston B, which uses a silicon carbide and aluminum alloy composite material by the method of the present invention, has a significantly reduced number of cracks. Also, Fig. 7 shows a sliding distance of 570 m,
Sliding speed 0.12 m/sec, pressing force 18.9 kg
, the amount of wear was measured using boron cast iron as a mating material, and it is clear that the amount of wear of piston B manufactured by the method of the present invention is extremely smaller than that of piston A having a conventional structure.

Note that the piston openings shown in FIGS. 1, 4, and 5 relate to cases in which a composite material is provided in the crown of the piston, but other parts of the piston, such as the piston skirt, are provided with a composite material. It is obvious that the same effect as above can be achieved by forming a part.

As mentioned above, the piston manufacturing method according to the present invention uses ceramics such as alumina and silicon carbide. Ceramic 1. A method of impregnating a metal base material such as an aluminum alloy into a matt beta or ceramic powder formed by molding fibers (including whiskers) with a metal base material such as an aluminum alloy by molten metal forging. 5. A method of high-pressure injection of fibers (or powder) and metal substrates or metal powders and ceramics. A process of making a simple-shaped composite material by mixing and sintering the composite material with fibers or powder, and shaping the composite material into a shape that produces an anchoring effect and fits the mold after casting. It is characterized by including the steps of processing to produce a molded composite material, and placing the molded composite material in a piston mold, pouring a metal base material, performing molten metal forging, and casting the piston. This method is extremely advantageous because it can easily manufacture high-quality composite pistons with no variation in quality compared to other manufacturing methods.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a piston showing a first embodiment of the method of the present invention, FIGS. 2 and 3 are sectional views of a composite raw material used in carrying out the method of the present invention, and FIGS. 4 and 5 are , a sectional view of a piston showing the second and third embodiments of the method of the present invention, FIG. 6 is a diagram showing the results of a thermal shock test of a piston according to the method of the present invention, and FIG. 7 shows the amount of wear of a piston according to the method of the present invention. FIG. 8 is a diagram showing the test results of the measurement of . 10...Fiber molded body 16...Pist/14...-
Composite raw material 24... Molded composite Figure 1 Figure 2 Figure 4 Figure 5

Claims (1)

[Claims] A method of impregnating a mat or ceramic powder made of ceramic fibers (including whiskers) such as alumina or silicon carbide with a metal base material such as aluminum alloy by molten metal forging, ceramic, Tsuku fiber (or powder), and metal base material A process of making a simple-shaped composite raw material by high-pressure injection or a method of mixing and sintering metal powder with ceramic, fiber, or powder, and creating an anchoring effect after casting the composite raw material. and a step of producing a molded composite material by processing it into a shape that fits the mold, and a step of placing the molded composite material in a piston mold, pouring a metal base material, and performing molten metal forging to cast a piston. A method for manufacturing a piston, comprising: