JPH08151953A - Piston for internal combustion engine and manufacture thereof - Google Patents

Abstract

PURPOSE: To strengthen the wear resistance of a groove part while a surface can be smoothed of the ring groove part, where a compression ring is inserted, without worsening manufacturability. CONSTITUTION: In a land part 2 of an aluminum alloy-made piston main unit base material 1 manufactured by casting, a remelting quench hardening layer S is formed, to form a ring groove part 4 by cutting in the remelting quench hardening layer, also to coat by treatment with an anodization coating layer 13 a surface of this top ring groove part 4 or the surface of the top ring groove part 4 and a crown surface 1a of the piston main unit base material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine piston made of an aluminum alloy.

[0002]

2. Description of the Related Art Conventionally, as an internal combustion engine piston made of an aluminum alloy, for example, there is one described in Japanese Patent Application Laid-Open No. 63-289370. In this piston, an anodized film layer is formed by hard alumite treatment on the crown surface of the piston body, the outer peripheral surface of the land portion, the inner surface of the ring groove portion, the surface of the skirt portion, and the inner peripheral surface of the piston pin hole of the pin boss portion.

Generally, in an aluminum alloy material used for pistons for internal combustion engines, a large amount of Si (silicon) is contained in its chemical composition, and a large amount of Si is precipitated in the metal structure as shown in FIG. Therefore, the Si particles are nonuniformly present on the surface 16 of the base material, and moreover, they are present in a large grain state. As a result, like the piston for internal combustion engine described in the above publication, the anodic oxide coating layer 17 is simply formed on the base material surface 16.
If it is difficult to form the anodic oxide coating layer 17 densely and uniformly by simply forming the above, the surface of the formed anodic oxide coating layer 17 becomes uneven and has many irregularities. There will be many. It can be said that this is a phenomenon that occurs because it is difficult to form an anodized film on the surface 16 of the base material due to the non-uniform presence of Si particles due to the properties of alumite.

If the uneven surface 18 formed on the surface of the anodic oxide coating layer 17 exists especially on the inner surface of the top ring groove portion, the top ring and the bottom surface of the top ring groove portion and the top ring inserted in the groove portion during engine operation. There is a risk that the sealing performance between the upper and lower surfaces will deteriorate, and oil leakage and combustion gas blow-through will occur, leading to deterioration of engine performance such as an initial increase in oil consumption and an increase in blow-by gas.

Therefore, in the piston for an internal combustion engine described in Japanese Patent Laid-Open No. 3-3947, a low Si content of 0.4 wt% or less in Si (silicon) content in the top ring groove which is a problem.
Of the Al-Mg (aluminum-magnesium) -based aluminum alloy wrought material, and an anodized film layer is formed by hard alumite treatment on at least the upper and lower surfaces of the inner surface of the top ring groove formed by the stuffed material. The surface is smoothed.

[0006]

However, in the piston for internal combustion engine described in Japanese Patent Laid-Open No. 3-3947, since the Al-Mg type aluminum alloy wrought material, which is a separate member, is cast in the top ring groove, the piston is In addition to being inferior in manufacturability and increasing the cost, there was a problem in the adhesion between the cast-in-gurg material and the piston body such as peeling-off of the cast-in-gum material.

The present invention has been made to solve the above-mentioned problems, and the surface of the ring groove portion into which the compression ring is inserted can be made smooth without impairing the manufacturability, and the wear resistance of the groove portion can be enhanced. An object of the present invention is to provide a piston for an internal combustion engine that can be used.

[0008]

In order to achieve the above object, the internal combustion engine piston according to the present invention is firstly remelted and rapidly quenched and hardened on the land portion of the aluminum alloy piston main body made by casting. A layer is formed, and a ring groove portion is formed by cutting in the remelted quenching hardened layer portion, and at least the ring groove portion or the surface of the ring groove portion and the crown surface of the piston body base material is anodized by anodizing. It is configured by coating.

Secondly, in the piston for an internal combustion engine of the present invention, the land portion of the aluminum alloy piston body base material produced by casting is remelted and then rapidly cooled to be hardened, and then the land portion is formed. Manufactured by cutting the remelted quench-hardened layer part to form a ring groove part, and then performing an alumite treatment to cover at least the ring groove part or the ring groove part and the surface of the crown surface of the piston base material with an anodized film layer. To be done.

[0010]

According to the above construction, after casting the piston body base material,
In the re-melting quench-hardened layer obtained by re-melting and hardening the land portion, Si particles become fine and evenly distributed, and when the ring groove portion formed in the re-melting quench-hardened layer is subjected to alumite treatment, it is homogeneous. In addition, a smooth anodic oxide coating layer is formed. Further, by providing the anodized film layer on the crown surface, sufficient durability can be obtained without causing abnormal wear of the crown surface even at high temperature and high load during operation of the internal combustion engine.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a front view showing a piston for an internal combustion engine, FIG.
3 is a vertical cross-sectional view showing a main part of FIG. 1, and FIG. 3 (1) is a cross-sectional view showing a main part of a piston body base material manufactured by casting.
(2) is a cross-sectional view of an essential part in the case where a remelted and hardened layer formed by remelting and hardening is formed on the land portion of the piston base material shown in FIG. 3 (1), and FIG. 3 (3) is shown in FIG. 3 (2). It is a principal part sectional view at the time of forming a ring groove in the re-melting quenching hardening layer shown by cutting.

In these figures, 1 is a piston body base material made of aluminum alloy, and this piston body base material 1 is composed of a crown portion 2 and a skirt portion 3. On the land portion formed on the outer peripheral portion of the crown portion 2, three ring grooves 4, 5, 6 having a bottomed ring are formed with a gap, and the top ring groove portion 4, the second ring groove portion 5, the oil Each of the ring groove portions 6 constitutes a top land portion 7, a second land portion 8 and a third land portion 9, and each of the ring groove portions 4,
A compression ring (not shown) is inserted in the ring grooves 4 and 5 among the rings 5, 6 and an oil ring (not shown) is inserted in the ring groove 6. Also, the skirt 3
A pin boss portion (not shown) is formed on the.

Such a piston is slidably accommodated in a cylinder of a cylinder block (not shown), and one end of the piston is connected to a piston pin in a pin hole portion 11 formed in the pin boss portion 10. The ring 10, 11 and 12 is constantly pressed against the inner peripheral wall of the cylinder by an appropriate elastic force, and the inside of the cylinder is divided into a combustion chamber and a crank chamber (not shown). Has been done.

The top ring groove 4 is formed by cutting a later-described remelted quench hardening layer formed on the top land portion 7 of the piston body base material 1 manufactured by casting. Then, a hard anodized surface is formed on the crown surface 1a of the piston main body material 1 facing the combustion chamber, the inner surface of the top ring groove portion 4, the outer peripheral surface of the top land portion 7 and a part of the second land portion 8 which are continuous with this. Anodized layer 1 by treatment
3 are formed. However, this anodic oxide coating layer 13
Is the crown surface 1a, the top ring groove portion 4, the top land portion 7
In addition to a part of the second land portion, it is formed on the entire surface of the second land portion 8, the third land portion 9, the inner surfaces of the ring grooves 5 and 6, the surface of the skirt portion 3 and the inner peripheral surface of the piston pin hole of the pin boss portion. You may.

A method of manufacturing the piston for an internal combustion engine having the above structure will be described below with reference to FIG.

That is, when manufacturing the piston for an internal combustion engine, first, as shown in FIG. 3 (1), at least the top ring groove portion 4 is formed by casting in advance by gravity casting or a molten metal forging method. The piston base material 1 which has not been formed is manufactured. Next, as shown in FIG. 3 (2), the portion of the top land portion 7 where the top ring groove portion 4 is to be formed is remelted, and then rapidly cooled and cured to form a remelted and rapidly hardened layer portion. Form S. This remelting process is performed using a high energy density heat source such as an electron beam or a TiG laser. Then, the re-melting quench-hardened layer S formed by the re-melting and the hardening is formed by the quenching-hardening after the re-melting, as shown in FIG. 4, the Si particles in the piston base material 1 become fine and uniform. Will be distributed.

Next, the remelted quench-hardened layer S is formed as shown in FIG.
As shown in, the top ring groove portion 4 is engraved by machining. The piston base material 1 after engraving the top ring groove portion 4 is covered with the inner peripheral surface of the top ring groove portion 4, the outer peripheral surface of the top land portion 7 and a part of the second land portion 8 in a continuous manner with the inner peripheral surface. Alumite treatment is applied to the surface 1a to form the anodized film layer 13 (see FIG. 2).

The anodic oxide coating layer 13 thus formed
Is formed on the remelting and quenching hardened layer S particularly in the top ring groove portion 4. In this remelting and quenching hardening layer S, Si particles are fine and evenly distributed. Thus, the coarse Si particles do not hinder the growth of the film, and a uniform and smooth film layer is formed.

In the above construction, the piston body base material 1
Since the anodic oxide coating layer 13 having excellent heat resistance and small thermal conductivity is formed on the crown surface 1a and the top ring groove portion 4, the heat from the combustion chamber is transferred to the piston body base material 1 during engine operation. It is difficult to transfer and heat loss is reduced.

Further, the top ring groove portion 4 has a uniform and smooth anodic oxide coating layer 13 formed on the surface thereof, so that the surface roughness is small and the sealing property of combustion gas is improved in combination with the top ring. As a result, oil leakage and combustion gas blow-through are reduced during engine operation.

[0021]

As described above, according to the present invention, at least the ring groove portion or the ring groove portion and the surface of the crown surface of the piston base material are formed with the anodic oxide coating layer having excellent heat resistance and small thermal conductivity. Therefore, during engine operation, heat from the combustion chamber is difficult to transfer to the piston body base material, and heat loss is reduced.

Moreover, since the ring groove portion is formed by cutting the remelting and quenching hardened layer which is formed by quenching and hardening after remelting of the piston base material, if the surface thereof is coated with the anodic oxide coating layer, it becomes homogeneous. Since a smooth anodic oxide coating layer is formed, the surface roughness is small and the sealing property of combustion gas is improved in combination with the ring, so that oil leakage and blow-by of combustion gas are reduced during engine operation.

Further, as a result of forming the anodic oxide coating layer in the ring groove portion by coating the remelted and quench-hardened layer, the surface of the anodic oxide coating layer can be easily and surely formed with a fine smooth surface having no unevenness. It can be said that it does not impair the manufacturability of the piston.

Further, by providing the anodized film layer on the crown surface, sufficient durability can be obtained without causing abnormal wear of the crown surface even at high temperature and high load during operation of the internal combustion engine.

[Brief description of drawings]

FIG. 1 is a front view showing a piston for an internal combustion engine.

FIG. 2 is a vertical cross-sectional view showing a main part of FIG.

FIG. 3 (1) is a cross-sectional view showing a main part of a piston body base material produced by casting, and (2) is a remelting quench that is remelted and hardened in the land portion of the piston base material shown in (1). FIG. 3C is a cross-sectional view of a main part when a hardened layer is formed, and FIG. 3C is a cross-sectional view of a main part when a ring groove portion is formed by cutting in the remelted and quenched hardened layer shown in (2).

FIG. 4 is a cross-sectional view showing a state of formation of an anodic oxide coating layer on the ring groove portion shown in FIG. 3 (3).

FIG. 5 is a cross-sectional view showing a state of formation of an anodized film layer in a ring groove portion of a piston for an internal combustion engine of a conventional example.

[Explanation of symbols]

 1 Piston body base material 2 Land part 4 Top ring groove part (ring groove part) 7 Top land part (land part) 8 Second land part (land part) 13 Anodized film layer S Remelting rapid hardening layer

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area F16J 9/00 A

Claims (2)

[Claims] 1. A remelted quench-hardened layer portion is formed on a land portion of an aluminum alloy piston body base material manufactured by casting, and a ring groove portion is formed on the remelted quench-hardened layer portion by cutting, and at least the ring. A piston for an internal combustion engine, characterized in that the groove portion or the ring groove portion and the surface of the crown surface of the piston body base material are covered with an anodic oxide coating layer formed by alumite treatment. 2. A land portion of an aluminum alloy piston body base material produced by casting is remelted and then rapidly cooled to be hardened to form a remelted quench hardened layer, and then the remelted quench hardened layer portion. To form a ring groove portion, and then subjecting at least the ring groove portion or the surface of the ring groove portion and the crown surface of the piston base material to the anodized film layer for an internal combustion engine Piston manufacturing method.