JPH0440105B2 - - Google Patents

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, desired parts, especially the piston crown, are coated with inorganic fibers (including whiskers) such as alumina and silicon carbide, or powder, aluminum alloy, magnesium alloy, and iron base. 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 alloy. The conventional method for manufacturing a composite piston involves directly placing the above-mentioned inorganic fiber molded body, or mat, into a desired shape at a desired position within a piston mold.
Composite with metal base material using autoclave method, cold sintering method, hot press method, molten metal forging method, etc.
The objective was to obtain a composite piston. However, in the above manufacturing method, the inorganic fibers are evenly distributed in a complicated shape at a desired part of the piston,
It is difficult to obtain pistons with homogeneous and therefore stable properties.

The present invention was devised to improve the drawbacks of the conventional manufacturing methods described above, and is made by molding ceramic fibers (including whiskers) of alumina, silicon carbide, etc. into pine or ceramic powder, and then using a metal base such as aluminum alloy. Simple-shaped composite materials can be produced by impregnating materials by molten metal forging, by high-pressure injection of ceramic fibers (or powder) and metal base materials, or by mixing metal powder and ceramic fibers or powder and sintering them. and a step of producing a molded composite material by processing the rough composite material into a shape that produces an anchoring effect and fits the mold after casting;
The method is characterized by including a step of placing the preheated molded composite material in a piston mold, pouring the same type of metal base material as the metal base material or the metal powder, and performing molten metal forging to cast the piston. The gist of this article is a method of manufacturing a 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 Figure 2, for example, alumina (diameter ~30μ, length ~100mm, aspect ratio 10~500)
above, volume content V _f number ~ 30%), silicon carbide (diameter
0.05~1μm, length 10~500μm, aspect ratio 10~
500, volume content V _f ~ 30%) or ceramic fibers (including whiskers) such as zirconia fibers and silicon nitride whiskers to make a cylindrical mat 10 that is simple in shape and easy to obtain homogeneity. This is placed in a mold having a corresponding shape, and a molten metal of a metal base material such as an aluminum alloy is poured into the mold to produce a cylindrical composite rough material 14 by a well-known molten metal forging method. Cylindrical rough material 14 shown in FIG.
It consists of a mat 10 impregnated with a metal base material by a molten metal forging method and a portion 12 made of a single metal base material. As another example, as shown in FIG. 3, a disk-shaped mat 10 with a simple shape and a slightly thicker outer circumferential portion than the central portion is molded from the same inorganic fiber as described above, and a similar metal base material is molded with molten metal. A disk-shaped composite raw material 14 is obtained from a pine impregnated with a metal base material by forging and a portion 12 made of a single metal base material. Alternatively, the composite material 14 may be manufactured by a molten metal forging method using ceramic powder and a metal base material such as an aluminum alloy. These composite rough materials 14 are easy to mold because the mats 10 have an extremely simple shape such as a cylinder or a disk, and they are less likely to lose their shape during molten metal forging, so they can be easily finished. Both the ivy product and the material have extremely uniform and stable quality.
(As is well known, the mat or molded body itself is most commonly made by laminating inorganic fibers in the form of felt, but it is also made by laminating one or more layers of woven inorganic fibers. (Also, felt-like inorganic fibers may be interposed between woven fabrics.)
Note that it is not limited to composites of ceramic fibers or whiskers, ceramic powders, metal base materials, and molten metal forging, but also composites of ceramic fibers or powders and metal base materials using a high-pressure injection method, or ceramic fibers or powders and metal powders. The composite raw material may be manufactured by a method such as sintering.

Next, in the case of the piston 16 shown in FIG.
0 and the wedge-shaped anchoring portion 22 are cut into a molded composite 24 by a suitable molding method, such as machining. After performing cleaning treatments such as degreasing as necessary, the piston 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. is manufactured. In addition, the piston 16 is made by the molten metal forging method.
In the process of casting, 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 final casting process mentioned above, 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, and the molded composite material and the subsequently cast It is clear that the bonding strength at the interface or boundary area with the metal base material is increased, and by providing the wedge-shaped anchoring portion 22, the bonding strength between the two is further strengthened. The piston 16 manufactured in this manner has a high homogeneity of the composite material portion in the crown portion, and has the desired heat resistance and
It has excellent properties such as mechanical strength and abrasion resistance, and is of excellent quality with little variation. (Note that the portion 20 forming part of the inner peripheral surface of the combustion chamber 18 may be cut by machining after the entire piston is cast.) Next, the method of the present invention shown in FIG. In another embodiment, the composite rough material 14 shown in FIG.
After cutting the metal base material plain part 12 in the figure, the first
The piston 16 is cast in the same manner as in the case shown in the figure. 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.
1 and 4 in that a ring-shaped molded composite material 24 is disposed only on the outer peripheral portion of the crown portion of the piston 16, and the anchoring portion 22b is formed in a stepped shape.
Although different from the piston shown in the figure, it is otherwise 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 that occurred during the heating and cooling cycle test shown in Figure 8, depending on the cycle. In comparison, it is clear that the number of cracks is significantly reduced in piston B using the silicon carbide/aluminum alloy composite material produced by the method of the present invention. Figure 7 also shows the sliding distance.
The amount of wear was measured at a distance of 570 m, a sliding speed of 0.12 m/sec, a pressurizing force of 18.9 kg, and a mating material of boron cast iron. Piston B manufactured by the method of the present invention has significantly more wear than piston A of conventional structure. It is clear that there are few.

Note that, in common to the pistons 16 shown in FIGS. 1, 4, and 5, 26 is a piston ring groove;
8 is a piston pin hole. Furthermore, although the above embodiments all relate to the case where a composite material portion is provided in the crown portion of the piston, it is also possible to form the composite material portion in that portion of the piston, for example, the piston skirt portion,
It is clear that the same effects as above can be achieved.

As described above, the method for manufacturing a piston according to the present invention involves impregnating a metal base material such as an aluminum alloy into pine or ceramic powder formed from ceramic fibers (including whiskers) such as alumina or silicon carbide by molten metal forging. a step of producing a simple-shaped composite raw material by a method of high-pressure injection of ceramic fibers (or powder) and a metal base material, or a method of mixing and sintering a metal powder and ceramic fibers or powder; A process of producing a molded composite material by producing an anchoring effect after casting the rough material and processing it into a shape that fits the mold, and placing the preheated molded composite material in a piston mold to produce the metal base material or the metal powder. It is characterized by a process of pouring the same type of metal base material, performing molten metal forging, and casting the piston, and producing a high-quality composite piston with no variation in quality compared to conventional manufacturing methods. It is extremely useful because it can be easily produced.

[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 . DESCRIPTION OF SYMBOLS 10... Fiber molded object, 16... Piston, 14... Composite raw material, 24... Molded composite.

Claims (1)

[Claims] 1 A method of impregnating a metal base material such as an aluminum alloy into pine molded ceramic fibers (including whiskers) such as alumina or silicon carbide (including whiskers) or ceramic powder by molten metal forging, and high-pressure injection of ceramic fibers (or powder) and metal base materials. A process of making a simple-shaped composite raw material by a method of mixing and sintering metal powder and ceramic fiber or powder, and a process of producing an anchoring effect and conforming to the mold after casting the composite raw material. The preheated molded composite is placed in a piston mold, and the metal base material or the metal base material of the same type as the metal powder is poured into the mold for molten metal forging. A method for manufacturing a piston, comprising the step of casting a piston.