JPH08151954A - Piston for internal combustion engine and manufacture thereof - Google Patents

Abstract

PURPOSE: To satisfy wear resistance and adhesion resistance, while ensuring reducing a cost of manufacture and lightening weight of a piston, also to attain improving connecting strength of a connection boundary surface between a piston main unit and a wear resisting ring. CONSTITUTION: Three piston ring grooves are formed in a ring land part 3 of a piston main unit 1 made of an aluminum alloy. A wear resisting ring 11 of aluminum alloy material, containing a grain of silicon carbide SiC, is internally chilled in a top ring groove 4 of a piston ring groove 4. A connection boundary surface 20 between upper/lower surfaces of the wear resisting ring 11 and an internal surface of the top ring groove 4 is remelting connected by applying irradiation of an electron beam of high energy density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a piston of an internal combustion engine such as an automobile.

[0002]

2. Description of the Related Art As is well known, in recent years, pistons for internal combustion engines for automobiles are formed of aluminum alloy instead of cast iron in order to reduce weight in response to demand for higher output and higher performance. Further, a plurality of piston ring grooves into which the piston rings are mounted are formed on the outer peripheral surface facing the inner wall surface of the cylinder bore. Furthermore, of these piston ring grooves, the top ring groove closest to the combustion chamber is
In particular, the piston ring (top ring) is exposed to high temperatures and is directly subjected to combustion pressure, so that the piston ring (top ring) is severely worn. Therefore, aluminum adhesion easily occurs between the top ring groove and the top ring.

Therefore, various techniques for preventing such aluminum adhesion have been developed. For example, (1) a method in which an inorganic fiber aggregate is compounded on the surface portion of the top ring groove to strengthen it (JP-A-59-59). (201953), and (2) In-
Application of hybrid MMC (metal matrix composite material) by Situ process to piston (Automotive Technology 198)
9-5. No. 891056), and (3) a porous nickel body is compounded on the surface portion of the top ring groove to strengthen it (Japanese Patent Publication No. 3-30708). Also, (4)
The surface portion of the top ring groove is strengthened by an alumite treatment layer (JP-A-1-190951), or (5) an alloy layer is formed on the surface portion of the top ring groove by melting and diffusing copper or the like with an electron beam. Things (Mitsubishi Motors 19
88, NO1 "Technical Review", Japanese Patent Laid-Open No. 2-12
No. 5952), and further, (6) many improved techniques have been proposed, such as a method in which Niresist cast iron is subjected to Alfin treatment in the top ring groove portion and cast around an aluminum alloy to form a ring support member.

[0004]

However, each of the conventional examples described above has the following drawbacks. That is, (1),
In the conventional examples of (2) and (3), the high pressure solidification method must be used as the forming method in view of the material such as the inorganic fiber material. Therefore, not only is the manufacturing cost increased, but the shape of the piston is restricted.

Further, in the conventional example of (4), the alumite treatment layer improves the adhesion resistance to the piston ring, but the abrasion resistance becomes insufficient. Further, in the conventional example of (5), on the contrary, the adhesion resistance may be insufficient.

Further, the conventional example of (6) is the technology that has been used for the longest time, and although it is possible to secure wear resistance and adhesion resistance, since it is made of cast iron, the weight must be increased. . Further, as another conventional example, Japanese Patent Laid-Open No. 2-1011
No. 41, the aluminum alloy contains Si, Cu, Mg, Fe, and Mn in predetermined weight percentages, respectively.
Is also provided to form a high-strength aluminum alloy by dispersing one kind of particles such as Al ₂ O ₃ in this matrix, but this material is remelted by a heat source with high energy density. Then, a blowhole may be generated in the remelted portion when the remelted portion is joined. This is because there is a possibility that unavoidable air exists between the powder particles and remains until the final processing.

[0007]

The present invention has been devised in view of the actual situation in each of the above-mentioned conventional examples, and the invention of claim 1 is such that a plurality of pistons are provided on the outer periphery of a piston body made of an aluminum alloy. In a piston of an internal combustion engine in which a ring groove is formed, at least a top ring groove of the piston ring groove is surrounded by a wear ring of an aluminum alloy material containing particles of silicon carbide, and at least on the wear ring. It is characterized in that the joining boundary surface between the lower surface and the inner surface of the top ring groove is remelted and joined by a heat source having a high energy density.

According to a second aspect of the present invention, there is provided a method of manufacturing a piston for an internal combustion engine, wherein the wear ring is fixed to a plurality of piston ring grooves formed on the outer circumference of a piston body made of an aluminum alloy. While preforming with an aluminum alloy material containing particles, at the time of forming the piston body, the wear ring is cast into at least the top ring groove of the piston ring groove, and then at least the upper and lower surfaces of the wear ring and the top ring groove. It is characterized in that the joint surface with the inner surface of is re-melted by a heat source of high energy density and cooled and joined.

According to a third aspect of the present invention, in a piston of an internal combustion engine in which a plurality of piston ring grooves are formed on the outer circumference of a piston body made of an aluminum alloy, silicon carbide is provided in at least the top ring groove of the piston ring groove. The wear-resistant ring of the aluminum alloy material containing the above-mentioned particles and containing a higher concentration of alloying elements than the base material of the piston body, and the joining boundary surface between the upper and lower surfaces of the wear-resistant ring and the inner surface of the top ring groove. And the entire wear ring are remelted by a high energy density heat source, and the aluminum alloy in the remelted portion is 7.0 wt% ≤ Si ≤ 28.0 wt%, 10.0 wt% ≤ Cu ≤ 23.0. % By weight, 0.3% by weight ≦ Mg ≦ 3.
5% by weight, 0.5% by weight ≦ Mn ≦ 2.9% by weight, and an aluminum alloy matrix containing inevitable impurities, A
l ₂ O ₃ particles, 0 to Sic particles, Si ₃ N ₄ particles, ZrO ₂ particles, SiO ₂ particles, at least one of the hard particles are selected from TiO ₂ particles and metallic Si particles, relative to the aluminum alloy matrix. 5% by weight or more, 15.0
It is characterized in that it is dispersed by less than or equal to wt%.

[0010]

According to the inventions of claims 1 and 2 having the above-mentioned structure, the wear resistant ring itself can be formed by casting or the like from the point of view of the material, and the wear resistant ring is simply encircled at the time of piston molding. The manufacturing cost can be reduced. Also,
The SiC particles in the wear ring improve wear resistance to the piston ring and also improve adhesion resistance.

Moreover, since the joining boundary surface between the inner surface of the piston ring groove and at least the upper and lower surfaces of the wear ring is re-melted by, for example, irradiating with an electron beam and then cooled and joined, a homogeneous alloy layer by re-melting is formed. Is formed, and the bonding strength at the interface between the two can be significantly increased.

According to the third aspect of the present invention, the alloy component of the remelted portion after melting is optimally adjusted to prevent a decrease in alloy concentration and to improve wear resistance and adhesion resistance. be able to.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

1 and 2 are sectional views of a piston according to the present invention, in which the piston body 1 is made of aluminum alloy (JIS AC8A-T6) and is formed into a substantially cylindrical shape.
The crown portion 2 facing the combustion chamber, the three piston ring grooves 4, 5, 6 formed on the outer peripheral surface of the ring land portion 3 provided at the lower portion of the crown portion 2, the respective top, second and oil ring grooves 4 1 to 6, piston rings 7, 8 and 9 are fitted, and a skirt portion 10 below each of the ring grooves 4 to 6 is provided.

The top ring groove 4 is formed on the top surface 2 of the crown portion 2.
A width of 4 mm and a depth of 8 mm are formed centering on a position 9 mm away from a, and only this surface portion is formed by a wear resistant ring 11 formed by a molding method described later.

The wear resistant ring 11 is made of an aluminum alloy containing particles of silicon carbide (SiC), and is cast to form a surface portion of the top ring groove 4 in the piston body 1.

Hereinafter, a specific method for manufacturing the wear resistant ring 11 will be described. That is, first, an aluminum alloy cast ingot containing 10 to 20% of SiC particles having a maximum diameter of several μm to several tens of μm was melted in an inert atmosphere such as argon gas and held at 993K, followed by mechanical stirring. The SiC particles are uniformly dispersed in the aluminum alloy material.

Then, in the lower mold 12 shown in FIG.
The molten aluminum alloy 13 containing C particles is injected and pressure is applied by the upper mold 14 to solidify. Then, after cooling,
After taking out the rough shaped material of the wear ring 11 from the lower mold 12,
If the riser is cut and machined if necessary, the work of forming the wear-resistant ring 11 is completed (molten forging method).

Further, as shown in FIGS. 13A and 13B, the molten metal is injected from an injection port 25 into an annular cavity 24 formed inside the left and right mating dies 22 and 23, and the molten metal is cut after the completion of solidification. Then, the wear resistant ring 11 having a predetermined shape can be obtained without the need for machining (gravity casting method). still,
In FIG. 13, reference numeral 26 is a feeder.

As the rough shape material of the wear resistant ring 11, a die casting method may be used in addition to the molten metal forging method and the gravity casting method. Furthermore, there is a powder forging method as another method. This is done by mixing SiC particles and aluminum alloy particles, filling them in a mold, and applying pressure with an upper mold 14 for molding. Then, after heating, forging is added to increase the density. When the density does not increase, the density increases when the casting is repeated after heating again. According to this method, since the final product shape is finished, the subsequent machining is unnecessary and the workability is improved.

The wear-resistant ring 1 molded in this way
1 is fixed to the piston body 1 by casting. The preheating temperature of the wear-resistant ring 11 is 673 if one example of the conditions of this cast-molding is shown.
K, the pouring temperature of the piston body 1 is 993 K, the mold temperature is 473 K, and the surface of the wear resistant ring 11 is washed and degreased with an alkaline solution or an organic solvent.

Further, when the heating temperature of the molten metal is raised, or when the wear-resistant ring 11 is sufficiently preheated, a phenomenon in which the interface 20 between the two is sufficiently welded is recognized, but the temperature condition range is extremely high. Narrow and difficult to bond uniformly. Therefore, in this embodiment, the wear resistant ring 11 and the piston body 1 are
The boundary surface of 1 is remelted and joined by a heat source having a high energy density such as an electron beam or a TiG laser.

Hereinafter, the wear-resistant ring 11 will be attached to the piston body 1 as follows.
The process of remelting and joining will be described with reference to FIGS. That is, first, as shown in FIG. 4A, the outer periphery of the ring land portion 3 of the piston body 1 in which the wear resistant ring 11 is cast is cut to expose the outer circumferential surface 11a of the wear resistant ring 11 as shown in FIG. 4B. Let After that, as shown in FIGS. 5A and 5B, the boundary surface 20 between the upper and lower surfaces of the wear resistant ring 11 and the ring land portion 3 is irradiated with a high energy beam of an electron beam and remelted by a high heat source. That is, the aluminum alloy of the piston body 1 and the aluminum alloy of the wear resistant ring 11 are re-melted and then rapidly cooled to solidify. Therefore, a uniform alloy layer is formed on the boundary surface 20 by the remelting portion 21 and high joint strength is obtained. After remelting and firmly joining, a ring groove 4a is annularly cut on the outer peripheral portion of the wear resistant ring 11 as shown in FIG. 5C.

FIGS. 6A and 6B show a second embodiment in which the entire boundary surface between the wear resistant ring 11 and the ring land portion 3 is remelted and joined. That is, the ringland part 3
After cutting the outer peripheral portion of the wear resistant ring 11, the ring groove 4a is formed in the outer peripheral portion of the wear resistant ring 11 as shown in the figure, which is the same as the previous embodiment. A strong joint between the piston body 1 and the piston body 1 can be obtained. Particularly, in this embodiment, the SiC particles in the remelting portion 21 are very uniformly dispersed. This is due to the stirring effect and the quenching effect of the high energy beam of the electron beam.

FIG. 7A is a drawing showing a cross-sectional structure photograph before remelting with the high energy beam, and FIG. 7B is a drawing showing a cross-sectional structure photograph after remelting. As is apparent, SiC particles (black dots) in the aluminum alloy near the upper and lower surfaces of the wear resistant ring 11 before remelting.
Are locally aggregated, but after re-melting, SiC particles are uniformly dispersed throughout as shown in FIG. 7B, and the wear-resistant ring 11 and each aluminum alloy of the piston body 1 are It becomes a homogeneous alloy phase and is strongly metallurgically bonded.

The wear-resistant ring 11 and the piston body 1 are such that the aluminum alloys themselves are remelted and metal-bonded to each other, so that the volume percentage of the SiC particles in the remelted portion 21 is slightly lowered. . Therefore, when the ring groove 4a does not reach the remelting portion 21 as in the first embodiment, no problem occurs, but in the case where the ring groove 4a reaches the remelting portion 21 or in the case of the second embodiment, the volume percentage of the SiC particles is In order not to significantly reduce the amount of aluminum alloy, it is necessary to reduce the melting amount of the aluminum alloy on the piston body 1 side. Therefore, it is desirable that the melting amount of the aluminum alloy on the piston body 1 side is at least about 1 mm from the outer peripheral surface of the wear resistant ring 11.

8 to 9 show a third embodiment of the present invention,
This shows a manufacturing method in which the wear-resistant ring 11 is exposed to the crown portion 2 of the piston body 1 to minimize the top land height H.

That is, as shown in FIG. 4A, after the wear-resistant ring 11 has been cast into the crown portion 2 of the piston body 1 in advance, as shown in FIG.
And, as shown in FIG. 9A, the top of the crown portion 2 is first cut by the height of the upper surface of the wear resistant ring 11. Next, as shown in FIG. 9B, a high energy beam of an electron beam is applied to the wear ring 11 and the boundary surface from above the crown portion 2 to remelt it, and then the remelting portion 21 is cooled and solidified to bond them. . Subsequently, as shown in FIG. 9C, the outer peripheral portion of the ring land portion 3 is cut to expose the outer peripheral surface of the wear resistant ring 11, and then the ring groove 4 a is formed on the outer peripheral surface of the wear resistant ring 11.

Therefore, according to this embodiment, the top land height H can be made as small as possible, and since the corner portion C of the crown portion 2 is the wear resistant ring 11, the strength is high. It will be remarkably improved, and it will be possible to sufficiently cope with the high output of the engine.

Further, in this case, the boundary surface 20 between the wear resistant ring 11 and the piston body 1 is exposed on the upper surface of the crown portion 2 exposed to high heat, but this portion is a remelted portion having a large bonding strength. Therefore, the peeling phenomenon between the two is reliably prevented. That is, when the resist ring and the piston body are joined to each other by the Alfin treatment of Ni-resist cast iron as in the above-mentioned (6) of the conventional example, there is a fear that the thermal stress generated in the crown portion cannot be endured and the boundary surface is peeled off. However, in the case of the present embodiment, such peeling phenomenon can be surely avoided.

Below, the results of experiments on changes in the characteristics of the joint boundary surface 20 of the wear ring 11 formed by the above-mentioned process will be described, with respect to the strength, wear resistance, adhesion resistance and machinability.

First, the components of the matrix aluminum alloy are shown in the table. In this experiment, a sample manufactured by the casting method was used. The amount of SiC particles added is 0, 5,
Seven types of materials were evaluated as 10, 15, 20, 25, and 30% by weight.

[0033]

[Table 1]

Then, the abrasion resistance was evaluated by using the apparatus shown in FIG. That is, the piston ring 7 is fixed on the rotary table 15 which is rotated by a motor (not shown), and the test piece 17 fixed to the lower end of the heater 16 is pressed against the piston ring 7 to wear it. The test piece 17 is an anti-wear ring cut out from the ring groove of the piston body 1. The test conditions such as temperature and lubrication condition in this method are assumed to be correlated with the actual piston of the engine. Evaluation,
The wear depth was measured after the test.

The method for evaluating the anti-adhesion property is carried out by using the apparatus shown in FIG. 11, and the piston ring 7 is pressed against the lower surface of the top ring groove 4 of the piston body 1, and the arrow marks are given via the actuators 18 and 19. It was based on the accelerated test method of sliding only in one direction. The evaluation was performed by the ratio of the area where the ring groove 4 was adhered and worn to the sliding area of the piston ring 7.

The machinability was evaluated by machining a cylindrical rough material having a diameter of 70 mm under the following processing conditions, and the wear amount of the tool was 0.3 mm.
It was evaluated by the number of processing until it became. Cutting speed: 200m / mi
n, Depth of cut: 0.3 mm, Feed: 0.03 mm (per rotation), Tool: Vapor phase synthetic diamond tool (manufactured by Asahi Diamond Co., Ltd.) Table 2 shows the evaluation results.

Here, the abrasion resistance refers to a ratio with the abrasion amount of SiC particles not added (O) as 100. The smaller the value, the less wear.

The anti-adhesion property is the ratio of the adhered area of SiC particles to 100. The smaller the value, the less the adhesion.

As for machinability, the tool life was set to 100 when a rough material without addition of SiC particles was machined using CPX as a tool. However, the coarse material to which the SiC particles are added is processed by the vapor phase synthetic diamond tool.

[0040]

[Table 2]

As is clear from Table 2, even if the amount of SiC particles added is 5% by weight, the wear resistance is remarkably improved as compared with the case where no addition is made, and at 10% by weight, the effect becomes almost constant.

On the other hand, the adhesion resistance tends to be the same as that of Si.
It can be seen that even when the addition amount of C particles is 5% by weight, it is significantly improved as compared with the case where no addition is made. However, at 10% by weight or more, no adhesion occurs.

As for the machinability, the machinability becomes worse even if the amount of SiC particles added is 5% by weight, as compared with the case where no SiC particles are added. Further, as the addition amount increases, the workability deteriorates, and
When the content is% by weight, the cutting edge of the tool is chipped and machining is impossible.

From the above experiment, it is understood that the optimum addition amount of SiC particles is 5% by weight to 25% by weight, preferably 10% by weight to 20% by weight.

Further, a test was carried out by incorporating the piston, in which the wear-resistant ring 11 was cast into the aluminum alloy piston body 1 described above, into an internal combustion engine. Here, the amount of SiC particles added to the wear resistant ring 11 was set to 10% by weight. For comparison, a test was also conducted on a piston in which the wear ring as described above was not cast around the piston body.

The operating conditions are four cylinders and a displacement of 1,600.
Oil temperature 150 degrees, cooling water temperature 1 using a cc gasoline engine
Continuous operation was performed at 20 degrees for 100 hours.

As a result, the piston, which does not encircle the wear ring, is worn by 50 μm, and the wear of 85 on the lower surface of the top ring groove occurs.
%, While the occurrence of adhesion was observed, the wear-resistant ring 11
No wear or adhesion was observed on the piston that had been cast.

Further, the shear strength of the joint between the wear ring 11 containing 10% by weight of SiC particles and the piston body 1 in the example of the present invention was determined by the conventional method. Experiments were performed comparing strength. As a result, it was revealed that the shear strength according to the present invention is four times or more that of the conventional example, as shown in FIG.

In the embodiment of the invention described in claim 3, the components contained in the aluminum alloy base material of the wear resistant ring 11 cast in the piston body 1 in each of the above-mentioned embodiments are changed, and remelting described later is carried out. This is an optimal adjustment of the alloy composition of the part.

That is, the wear resistant ring 11 melts the aluminum alloy ingot containing 20% by volume of Sic particles and holds the temperature of the molten metal at about 740 ° C. The aluminum alloy ingot is a product name DURALCAN (F3K / 20
Cu, Ni, Mn, and Si in the form of a mother alloy or pure metal, respectively, as shown in the following table, based on the main component (see S catalog) as a target component. here,
Cu is copper wire, Ni is powder or wire, Mn is Al-
60Mn and Si were added in the form of an Al-40Si mother alloy.

[0051]

[Table 3]

When the addition amount of the hard particles is specified as described above, the dispersion state of the hard particles in the aluminum alloy matrix is optimum for improving the wear resistance of the aluminum alloy. Further, hard particles fix crystal dislocations in the aluminum alloy matrix to improve creep properties and stress corrosion cracking resistance properties, lower thermal expansion coefficient, Young's modulus and fatigue strength, wear resistance, adhesion resistance, etc. Have various effects.

However, if the content of the hard particles in the aluminum alloy matrix is less than 0.5% by weight, the wear resistance is not improved, and the Young's modulus is improved and the coefficient of thermal expansion is also decreased. , 15.0% by weight, the wear of the mating material increases.

The reasons for containing the other components and the reasons for limiting the contents are as follows.

(A) About Si Si has the effects of improving wear resistance, Young's modulus and thermal conductivity, and lowering the coefficient of thermal expansion. However, 7.0
If it is less than wt%, the above effect cannot be obtained, while
If it exceeds 28.0% by weight, castability and workability deteriorate,
It tends to crack.

(B) Regarding Cu Cu has an effect of forming an intermetallic compound and strengthening an aluminum alloy matrix to improve wear resistance and adhesion resistance. However, if it is less than 10% by weight, the above effect cannot be obtained, while if it exceeds 23% by weight, it becomes very hard and brittle and wear resistance deteriorates. Then, the amount of Cu in the fusion zone was changed and a wear test was conducted,
The result of 4 is obtained. In addition, the evaluation method of wear resistance is
It carried out using the apparatus shown in FIG. That is, a piston ring is fixed on a rotary table that is rotated by a motor (not shown), and a test piece fixed to the lower end of the heater is pressed against the piston ring to wear it. This test piece is an anti-wear ring cut out from the ring groove of the piston body. The test conditions such as temperature and lubrication state in this method are assumed to be correlated with the actual piston of the engine. The evaluation was performed by the wear depth after the test.

(C) About Mg Like Mg, Mg has the effect of strengthening the aluminum alloy matrix during heat treatment. However, 0.3
If it is less than wt%, the above effect cannot be obtained, while
If it exceeds 3.5% by weight, stress corrosion cracking resistance is deteriorated and hot forgeability is deteriorated.

(D) Mn Mn forms an intermetallic compound with Fe and improves wear resistance and adhesion resistance. However, if less than 0.5% by weight,
The above effect cannot be obtained, and on the other hand, when it exceeds 2.9% by weight, adverse effects such as deterioration of castability and workability appear. The components of the wear resistant ring are adjusted in advance so as to have such a composition.

After adjusting to the target component, the molten metal is stirred so that the SiC particles are sufficiently uniform in the molten metal. After that, the wear resistant ring 11 is cast with a mold.

Since the alloy base material of the wear resistant ring 11 after casting has a high hardness, it becomes difficult to perform the cutting process.
It is desirable to cast in a near net (near net) shape.

After casting the wear resistant ring 11,
As in the above-described first embodiment, the cast body is fixed to the piston body 1 at a position corresponding to the top ring groove. The conditions of the cast gurney are the same as in the first embodiment.

After casting the wear resistant ring 11, the outer periphery of the ring resistant portion 3 is exposed to expose the outer peripheral surface of the wear resistant ring 11, and then the upper and lower surfaces of the wear resistant ring 11 and the inner surface of the top ring groove 4 are exposed. The interface 20 between them is remelted and joined by a heat source having a high energy density of the electron beam.

Here, when the aluminum alloy base material of the piston body 1 is, for example, AC8A, the alloy concentration of the remelting portion 21 becomes lower than the target component described above, Si is about 12 wt% and Cu is about 20. 0% by weight, Mn is about 1% by weight, Ni
Is about 2% by weight, Mg is about 1% by weight, and SiC is about 10% by volume. These are typical values of the alloy components to be finally obtained.

That is, the aluminum alloy of the remelting portion 21 contains 7.0% by weight ≦ Si ≦ 28.0% by weight, 10.0% by weight ≦ Cu ≦ 23.0% by weight, 0.3% by weight ≦ Mg ≦ 3.5
% By weight, 0.5% by weight ≦ Mn ≦ 2.9% by weight.

By setting the alloy concentration in the remelting portion 21 in this manner, it is possible to prevent the generation of blowholes in the remelting portion 21 and prevent the alloy concentration from decreasing.

That is, if the alloy concentration of the remelting portion 21 is set as in the present embodiment, it is possible to prevent air from remaining between the powder particles and prevent the alloy concentration from decreasing, resulting in wear resistance, It is possible to improve adhesion resistance and the like.

[0067]

As is apparent from the above description, claim 1
According to the inventions described in (1) and (2), since the wear ring made of the aluminum alloy containing SiC particles is cast around the piston body made of the aluminum alloy, it is possible to simply perform gravity casting without using the conventional high pressure solidification method. Since it can be molded, the manufacturing cost can be reduced.

Moreover, since the boundary surface between the piston body and the wear ring is remelted by the high energy heat source and cooled and bonded, the bonding strength at the boundary surface portion becomes extremely high. Further, not only the unique internal structure of the wear-resistant ring makes it possible to reduce the weight, but also the SiC particles are uniformly dispersed, so that the wear resistance and the adhesion resistance can be improved.

Furthermore, according to the third aspect of the present invention, a decrease in alloy concentration is prevented, and wear resistance, adhesion resistance and the like are further improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a piston showing an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of a piston of this embodiment.

FIG. 3 is an explanatory view showing die molding of the wear resistant ring of the present embodiment.

FIG. 4A is a longitudinal sectional view showing a first embodiment of the present invention, showing a state in which a wear ring is cast in a piston body, FIG.
[FIG. 4] is a vertical cross-sectional view showing a state in which a ring land portion of a crown portion of a piston body is cut.

5A is an enlarged view of an essential part of FIG. 4B, B is an enlarged view of an essential part showing a remelted portion at the interface between the piston body and the wear resistant ring, and C is a view showing a state in which a ring groove is cut on the wear resistant ring. Enlarged view of part.

FIG. 6A is an enlarged sectional view showing a remelted portion according to the second embodiment of the present invention, and FIG. 6B is an enlarged sectional view showing a state in which a ring groove is cut on a wear ring.

FIG. 7A is a structural diagram showing a photomicrograph of a wear-resistant ring before remelting, and B is a structural diagram showing a micrograph of an interface portion after remelting.

FIG. 8 is a vertical cross-sectional view showing a third embodiment of the present invention and showing a state in which the top land upper portion of the crown portion is cut.

FIG. 9A is an enlarged view of a main part before remelting of the present embodiment,
B is an enlarged view of an essential part showing a state in which the entire wear ring and the interface of the piston body are remelted, and C is the outer peripheral side of the top land is cut after remelting and the ring ring is cut on the outer periphery of the wear ring. The principal part enlarged view which shows the processed state.

FIG. 10 is an explanatory diagram showing a wear resistance test device.

FIG. 11 is an explanatory view showing an adhesion resistance test device.

FIG. 12 is a bar graph showing the shear strengths of the present invention and a conventional example in comparison.

13A is a front view showing a mold used in the gravity casting method of the present embodiment, and B is a sectional view taken along line AA of A. FIG.

FIG. 14 is a graph showing the results of a wear test.

[Explanation of Codes] 1 ... Piston body 2 ... Crown part 3 ... Ring land part 4 ... Top ring groove 7 ... Top ring 11 ... Wear ring 20 ... Boundary surface 21 ... Remelting part.

Claims (3)

[Claims] 1. A piston of an internal combustion engine having a plurality of piston ring grooves formed on the outer circumference of a piston body made of aluminum alloy, wherein silicon carbide particles are contained in at least the top ring groove of the piston ring groove. Along with casting a wear resistant ring of an aluminum alloy material, at least the bonding interface between the upper and lower surfaces of the wear resistant ring and the inner surface of the top ring groove is remelt-bonded by a high energy density heat source. piston. 2. A method for manufacturing a piston of an internal combustion engine, wherein a wear ring is fixed to a plurality of piston ring grooves formed on the outer circumference of a piston body made of an aluminum alloy, wherein the wear ring is made of aluminum containing silicon carbide particles. While preforming with an alloy material, at the time of forming the piston body, the wear ring is cast into at least the top ring groove of the piston ring groove, and thereafter at least the upper and lower surfaces of the wear ring are joined to the inner surface of the top ring groove. A method for manufacturing a piston of an internal combustion engine, characterized in that the surfaces are remelted by a heat source having a high energy density and then cooled and bonded. 3. A piston for an internal combustion engine, comprising a piston body made of an aluminum alloy and having a plurality of piston ring grooves formed on the outer circumference thereof, wherein at least the top ring groove of the piston ring groove contains silicon carbide particles. And, the wear-resistant ring of the aluminum alloy material containing a higher concentration of alloying elements than the base material of the piston body is cast, and the joint boundary surface between the upper and lower surfaces of the wear-resistant ring and the inner surface of the top ring groove and the entire wear-resistant ring are formed. The aluminum alloy in the remelted portion is re-melted by a high energy density heat source, and is 7.0 wt% ≤ Si ≤ 28.0 wt%, 10.0 wt% ≤ Cu ≤ 23.0 wt%, 0.0 3 wt% ≦ Mg ≦ 3.5% by weight, the aluminum alloy matrix containing 0.5 wt% ≦ Mn ≦ 2.9 wt% and unavoidable impurities, Al ₂ O ₃ particles, SiC particles, Si ₃ N ₄ particles ZrO
_At least one kind of hard particles selected from ₂ particles, SiO ₂ particles, TiO ₂ particles and metal Si particles is 0.5% by weight or more with respect to the aluminum alloy matrix, 1
A piston for an internal combustion engine, characterized by being dispersed in an amount of 5.0% by weight or less.