JP2997883B2 - Method of manufacturing piston for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a piston for an internal combustion engine made of an aluminum alloy for an automobile or the like.

[0002]

2. Description of the Related Art A piston for an internal combustion engine manufactured by a conventional manufacturing method will be described below.

In a conventional aluminum alloy piston for an internal combustion engine, as shown in FIG. 4, an outer peripheral surface of a ring land portion 1 of a piston body 10, an inner surface of a piston ring groove 2,
An oxide film 8 formed by hard alumite treatment is formed on the inner peripheral surface of the piston pin insertion hole 5 to prevent occurrence of scuffing, abrasion, and the like. In order to reduce the number of masking steps, an oxide film 8 is also formed on the crown 3 of the piston body 10 by hard alumite treatment.

[0004] These hard alumite treatments are performed after the shape of each part of the piston main body 10 is finished to a predetermined size by a machine or the like. The symbol is engraved.

[0005] A piston having a similar structure is disclosed in, for example, JP-A-63-289370.

[0006]

However, in the structure of the piston for the internal combustion engine according to the above-mentioned conventional manufacturing method, the engraving of the identification symbol for selecting the outer diameter of the piston is performed by hard anodizing the crown surface portion 3. Since the coating is performed on the oxide film 8, a high load is required for the engraving, the abrasion of the engraving jig is fast, and the engraving is apt to be unclear.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a method for manufacturing a piston for an internal combustion engine, which can easily and clearly apply a mark on a crown surface.

[0008]

In order to achieve this object, a method of manufacturing a piston for an internal combustion engine according to the present invention is directed to a piston for an internal combustion engine in which an oxide film is formed on a crown surface of an aluminum alloy body by hard alumite treatment. A manufacturing method, wherein a ring land outer peripheral surface, a piston ring groove, a crown surface portion, a piston pin insertion hole, and a skirt portion are finished to predetermined dimensions using a center processing boss, and a piston ring groove, a center processing boss. A step of forming an oxide film by hard alumite treatment on the ring land part, and a step of removing the center processing boss to form a hard alumite untreated part on the crown part of the removed part,
Engraving a piston outer diameter dimension identification number on the hard alumite unprocessed portion.

According to such a manufacturing method, a center processing boss is provided in advance on the crown surface portion, and after finishing each portion of the piston body, an oxide film is formed on the crown surface portion by hard anodizing while leaving the center processing boss. Then, by removing the center processing boss, a hard anodized untreated portion is obtained on the crown surface.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a front view showing a piston for an internal combustion engine manufactured according to an embodiment of the present invention, and FIG. 2 is a top view of the same. The same components as those shown in the conventional example are denoted by the same reference numerals.

In the drawing, 10 is a piston body, 1 is a ring land portion, 3 is a crown surface portion, and 9 is a hard alumite untreated portion.

The ring land 1, the pin boss 4, and the skirt 6 constitute an aluminum alloy piston body 10, and the top of the ring land 1 forms a crown 3. An oxide film 8 is formed on the ring land portion 1 including the crown surface portion 3 by hard alumite treatment.
A hard alumite unprocessed portion 9 is formed at the center of the crown surface portion 3.

The pin boss 4 is connected to the crown 3 of the ring land 1, and a piston pin insertion hole 5 is formed in the center of the pin boss 4.

Next, the processing steps of the piston body 10 will be described.

The outer peripheral surface of the ring land 1, the piston ring groove 2, the crown 3, the piston pin insertion hole 5, the skirt 6, and the like are maintained in a predetermined state with the center processing boss 7 of the crown 3 shown in FIG. Finish to dimensions.

Next, an oxide film 8 is formed on the ring land 1 such as the piston ring groove 2 and the crown 3 having the center processing boss 7 by hard alumite treatment.

Finally, by removing the center processing boss 7, a hard anodized untreated portion 9 can be obtained on the crown surface portion 3 of the removed portion.

Thus, since the hard anodizing treatment is not applied to the place where the piston outer diameter dimension identification code for selective fitting is engraved, it can be imprinted in the same manner as the piston to which the hard anodizing processing is not applied. . Accordingly, it is not necessary to engrave a high load, and it is possible to prevent the abrasion of the engraving jig, and to obtain a clear engraving, thereby improving workability in assembling the engine.

[0020]

As described above, the present invention relates to a piston for an internal combustion engine in which an oxide film is formed on the crown surface of a piston body made of aluminum alloy by hard alumite treatment.
By removing the center processing boss provided on the crown surface portion, it is possible to easily form a hard anodized unprocessed portion on the crown surface portion. It can be performed in the same way as a piston that does not apply. Therefore, it is not necessary to apply the high load required when engraving the hard anodized surface, and it is possible to prevent the abrasion of the engraving jig and to obtain a clear engraving, thereby improving the workability when assembling to the engine. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a front view of a piston for an internal combustion engine showing an embodiment of the present invention.

FIG. 2 is a top view of the internal combustion engine piston.

FIG. 3 is a front view of the internal combustion engine piston before hard anodizing.

FIG. 4 is a front view of a conventional piston for an internal combustion engine.

[Description of Signs] 1 Ring land part 3 Crown part 7 Center processing boss 8 Oxide film 9 Hard anodized untreated part 10 Piston body

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B23P 15/10 B25H 7/00 F02F 3/00 F02F 3/10 F16J 1/01

Claims (1)

(57) [Claims] 1. A method of manufacturing a piston for an internal combustion engine in which an oxide film is formed on a crown surface of an aluminum alloy body by hard alumite treatment, comprising: a ring land outer peripheral surface;
A processing step of finishing the piston ring groove, crown surface, piston pin insertion hole, and skirt to predetermined dimensions using the center processing boss, and hard anodizing the crown surface and ring land with the piston ring groove, center processing boss. A step of forming an oxide film, a step of removing the center processing boss, and a step of forming a hard alumite untreated portion on the crown surface of the removed portion, and engraving a piston outer diameter dimension identification number on the hard alumite untreated portion. And a method for manufacturing a piston for an internal combustion engine.