JP3280516B2 - Piston for internal combustion engine and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As is well known, in recent years, pistons of internal combustion engines for automobiles have been formed of aluminum alloy instead of cast iron in order to reduce weight in response to demands for higher output and higher performance. A plurality of piston ring grooves in which piston rings are mounted are formed on the outer peripheral surface facing the inner wall surface of the cylinder bore. Further, among the piston ring grooves, the top ring groove closest to the combustion chamber is particularly exposed to a high temperature and directly receives the combustion pressure, so that the piston ring (top ring) is heavily worn. For this reason, 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 technique in which an inorganic fiber aggregate is compounded on the surface of a top ring groove to reinforce it (Japanese Unexamined Patent Application Publication No. 201953) or (2) In-
Application of hybrid MMC (metal-based composite material) to the piston by the Situ process (Automotive Technology 198)
9-5. No. 891056), and (3) a method in which a nickel porous body is compounded on the surface of the top ring groove to strengthen it (Japanese Patent Publication No. 3-30708). Also, (4)
An alloy layer is formed by strengthening the surface of the top ring groove with an alumite treatment layer (JP-A-1-190951), or (5) melting and diffusing copper or the like with an electron beam on the surface of the top ring groove. Things (Mitsubishi Motors 19
88, NO1 "Technical Review"), and (6) a ring support member by casting a niresist cast iron in the top ring groove portion and subjecting it to an aluminum alloy, and (7) a low Si aluminum −
Many improved techniques have been proposed, such as casting of a magnesium-based alloy member and alumite treatment (Japanese Patent Application Laid-Open No. 1-190951).

[0004]

However, each of the conventional examples has the following disadvantages. That is, (1),
In the conventional examples (2) and (3), a high-pressure solidification method must be used as a molding method from the viewpoint of materials such as inorganic fiber materials. Therefore, not only is the production cost increased, but also the shape of the piston is restricted.

Further, in the conventional example of (4), although the alumite-treated layer improves the adhesion resistance to the piston ring, the alumite-treated layer only forms the alumite-treated layer, so that the abrasion resistance is poor. Will be enough. Further, in the conventional example of (5), there is a possibility that the adhesion resistance is insufficient.

The prior art (6) is the oldest technique. Although it is possible to secure abrasion resistance and adhesion resistance, it is made of cast iron, so that the weight must be increased. .

Further, in the conventional example of (7), aluminum-
Since the wrought magnesium alloy is used, the wear resistance and the adhesion resistance are also insufficient in this case.

[0008]

SUMMARY OF THE INVENTION The present invention has been devised in view of the circumstances in each of the above-mentioned conventional examples. The invention according to claim 1 is directed to a piston body made of an aluminum alloy.
Internal Combustion with Multiple Piston Ring Grooves Formed Outside
In an engine piston, a wear-resistant ring of an aluminum alloy containing silicon carbide (SiC) particles is cast into a position corresponding to a top ring groove of an aluminum alloy piston, and a surface of the ring groove formed by the wear-resistant ring is formed. To form an anodized layer by anodizing (anodizing)
Dispersing the silicon carbide particles in the alumite treatment layer
It is characterized by being exposed . Claim 2
Akira is the outer periphery of the piston body made of aluminum alloy
Internal combustion engine with multiple piston ring grooves formed in
A method of manufacturing a piston, comprising:
While pre-forming a wear ring containing silicon carbide in the part,
During casting of the piston body, the piston ring groove
At least at the position corresponding to the top ring groove,
And then the ring groove formed by the wear-resistant ring is cast.
Form anodized layer by anodizing the surface
And dispersing the silicon carbide particles in the alumite treatment layer.
It is characterized by being exposed.

[0009]

According to the present invention having the above-described structure, the wear-resistant ring itself can be formed by casting or the like from the viewpoint of the material, and the wear-resistant ring is simply cast when the piston is formed, so that the manufacturing cost can be reduced. Can be achieved.

Further, in the present invention, silicon carbide (SiC) is dispersed in an aluminum alloy as a wear-resistant ring. In particular, at least the upper and lower surfaces of, for example, the top ring groove on which the alumite-treated layer is formed, the SiC deposited from the wear-resistant ring on the surface of the alumite-treated layer.
Particles are dispersed and exposed.

The alumite-treated layer is hard in itself and, because it is a non-metal layer, hardly adheres to the piston ring as a mating material. Therefore, the alumite-treated layer is formed on the upper and lower surfaces of the top ring groove. Although abrasion resistance and scuff resistance are improved to some extent just by forming, it is not always sufficient. That is, if the alumite treatment layer itself is worn and the base material is exposed, scuffing and abrasion will rapidly progress. Therefore, in the present invention, by using the aluminum alloy obtained by dispersing SiC particles alloy as ring carrier, a significantly hard SiC particles of about H _V 3000 deposited from the ring carrier to the anodized layer surface are dispersed exposed, thereof rigid The load from the counterpart material is supported by the SiC particles to prevent the alumite-treated layer from advancing wear. That is, the alumite treatment layer and the SiC
Wear resistance of top ring groove, due to synergistic effect with particles,
It has become possible to significantly improve the adhesion resistance.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 and 2 show a sectional view of a piston according to the present invention. In this piston, a piston body 1 is made of an aluminum alloy (JISAC8A-T6) and is formed in a substantially cylindrical shape.
A crown portion 2 facing the combustion chamber, three piston ring grooves 4, 5, 6 formed on an outer peripheral surface of a ring land portion 3 provided below the crown portion 2, and each of the top, second and oil ring grooves 4 6, and a skirt portion 10 below each of the ring grooves 4-6.

The top ring groove 4 is formed to have a width of 4 mm and a depth of 8 mm around a position 9 mm away from the top surface of the crown portion 2 and only this surface portion is formed by a molding method described later. It is formed by the wear ring 11.

The wear ring 11 is made of an aluminum alloy 11b containing particles 11a of silicon carbide (SiC), as shown in FIG. 3, and forms the surface of the top ring groove 4 in the piston body 1. It is buried in it.

An anodized aluminum layer 20 is formed on the surface of the ring 11 and on the outer peripheral surface of the crown 2 and the ring land 3 near the top ring groove 4 of the piston body 1 by anodizing. This anodized aluminum layer 20
Silicon carbide SiC particles 20a inside, like the wear ring 11
Is contained. That is, as described above, during the anodizing treatment, the SiC particles in the wear-resistant ring 11 are bent out and contained in the alumite treatment layer 20.

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

Thereafter, Si is placed in the lower mold 12 shown in FIG.
The molten aluminum alloy 13 containing the C particles is poured and solidified by applying pressure with the upper mold 14. Next, after cooling,
After taking out the rough material of the wear ring 11 from inside the lower mold 12,
If the hot water is cut and machined as needed, the forming operation of the wear-resistant ring 11 is completed.

It is also possible to use a die casting method or a molten metal casting method in addition to the gravity casting method for the crude material of the wear ring 11. Another method is a powder forging method. In this method, after mixing the SiC particles and the aluminum alloy particles, the mixture is filled in a mold and molded by applying pressure with the upper mold 14. Then, after heating, forging is performed 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 obtained, subsequent machining is not required, and workability is improved.

The anti-wear ring 1 thus formed is
1 is cast-fixed to the piston body 1. As an example of the conditions for this insert, the preheating temperature of the wear ring 11 is 673.
K, the pouring temperature of the piston body 1 is 993 K, the mold temperature is 473 K, and the chemical conversion treatment of the wear ring 11 is performed by heating a solution of Parcol 3756 manufactured by Parkerizing Co., Ltd. to 313 K and immersing for 60 seconds.

Here, the reason why the chemical conversion treatment is applied to the wear ring 11 in advance is that, in the case of aluminum-based materials, a dense oxide film is firmly formed on the surface, so that the contact interface with the molten metal is sufficiently welded. Therefore, the joining between the aluminum layer portion of the piston body 1 formed by the molten metal and the wear-resistant ring 11 of the aluminum alloy becomes insufficient. In addition, the degree of heating of the molten metal can be increased, and
However, when preheating is sufficiently performed, the phenomenon of welding is observed, but the condition range is extremely narrow, and it is difficult to adhere uniformly.

In particular, the preheating of the wear ring 11 may increase the thickness of the oxide film, making the adhesion more difficult.

Therefore, if the chemical conversion treatment is performed in advance as described above, the chemical conversion treatment layer is oxidized by preheating, but is not oxidized up to the aluminum alloy material of the wear-resistant ring 11. Since the aluminum alloy of the piston body 1 is easily removed by the molten aluminum alloy, the aluminum alloy of the piston body 1 and the aluminum alloy 11b of the wear ring 11 can be bonded with high bonding strength.

In addition to the upper and lower surfaces of the top ring groove 4 where wear is severe, only the outer peripheral surface near the top ring groove 4 of the crown portion 2 and the ring land portion 3 is provided. The reason why the coating was not applied to the skirt portion is that if applied to this portion, the oil film would break there and scuffing would easily occur.

The thickness of the anodized aluminum layer 20 was set in the range of 10 to 50 μm based on the experimental results described later. That is, if the thickness is less than 10 μm, sufficient wear resistance cannot be obtained, while if it exceeds 50 μm, the surface roughness increases and the processing cost increases.

Further, the size of the SiC particles 11a and 20a is set in a range of 3 to 40 μm. Because, from the experimental results described below, when the diameter is less than 3 μm, it is difficult to sufficiently support the load of the piston ring 7, and it is difficult to show sufficient wear resistance.
If the thickness exceeds, the surface roughness after the groove processing increases, the roughness after the alumite treatment also increases, and the alumite treatment layer 20 may be easily cracked and peeled off.

In the following, when the alumite-treated layer 20 is applied to the wear ring 11 formed in the above-described process, a change in characteristics of wear resistance and adhesion resistance and the machinability of the material of the wear ring 11 are described. Will be described.

First, the components of the matrix aluminum alloy are shown in the table. In this experiment, a sample manufactured by a casting method was used. The amount of the SiC particles having a particle size of 9.3 ± 4 μm was evaluated for the alumite-treated seven materials at 0, 5, 10, 15, 20, 25, and 30% by volume.

Next, assuming that the volume ratio of the SiC particles is 10.0%, the particle size of the SiC particles to be added is 2, 5, 10, 2
The alumite treatment of six types of materials of 0, 30, and 40 μm was evaluated. At the same time, an aluminum alloy of the matrix alone without addition of SiC particles and alumite-treated aluminum alloy were also evaluated.

[0030]

[Table 1]

The wear resistance was evaluated using the apparatus shown in FIG. That is, the piston ring 7 is fixed on a turntable 15 that is rotated by a motor (not shown), and a test piece 17 fixed to a lower end of the heater 16 is pressed against the piston ring 7 to be worn. The test piece 17 is a wear-resistant ring cut out from a ring groove of the piston body 1. Test conditions such as temperature and lubrication condition in this method were assumed to be correlated with the actual engine piston. The evaluation was performed based on the wear depth after the test.

The adhesion resistance was evaluated using the apparatus shown in FIG.
The acceleration test method was used in which the piston ring 7 was pressed against the lower surface and slid in only one direction of the arrow via the actuators 18 and 19. The evaluation was made on the piston ring 7 in the ring groove 4
The measurement was performed at the ratio of the area where the adhesive wear occurred to the sliding area. The test was performed by the number of sliding operations until the alumite film was not sufficiently removed.

The evaluation of machinability was performed by machining a columnar coarse material having a diameter of 70 mm under the following processing conditions and reducing the amount of wear of the tool to 0.3.
It was evaluated by the number of processings until it became mm. Cutting speed: 200
m / min, depth of cut: 0.3 mm, feed amount: 0.0
3 mm (per rotation), tool: vapor phase synthetic diamond tool (manufactured by Asahi Diamond Co., Ltd.) Tables 2 and 3 show the evaluation results.

[0034]

[Table 2]

[0035]

[Table 3]

Here, the abrasion resistance refers to a ratio where the amount of abrasion without alumite treatment is 100 when no SiC particles are added, that is, O. The smaller the value, the less wear.

The adhesion resistance indicates a ratio of the area where the SiC particles adhered without addition of the alumite treatment to 100, where the area was 100.
The smaller the value, the less adhesion.

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

As is clear from Tables 2 and 3, the abrasion resistance was remarkably improved when the alumite treatment was not performed, even when the amount of added SiC particles was 5% by volume, and the effect was substantially improved at 10% by volume. Is constant.

When alumite treatment is performed, the wear resistance of the alumite film is superior to that of aluminum alloy, so
When the alumite treatment is performed on the aluminum alloy to which the C particles are added, the abrasion resistance is improved as compared with the case where no alumite treatment is performed.

On the other hand, the adhesion resistance has the same tendency, and it can be seen that the adhesion resistance is remarkably improved as the amount of added SiC particles increases without alumite treatment. At 25% by volume or more, no adhesion occurs.

When the alumite treatment was performed, no adhesion occurred even when the amount of SiC added was 5% by volume, indicating that the adhesion resistance was remarkably improved.

In addition, the machinability is poor even when the SiC particles are added in an amount of 5% by volume as compared with the case where no SiC particles are added. Furthermore, the processability deteriorated with the increase of the addition amount,
At volume%, the cutting edge of the tool is chipped and cannot be machined.

The effect of the size of the SiC particles is that the abrasion resistance is remarkably improved if the alumite treatment is not performed and 5 μm or more precisely 3 μm or more. The adhesion resistance also seems to improve as the size of the particles increases, but there is no significant improvement when the volume fraction of the SiC particles is constant.

However, when the alumite treatment is performed, if the size of the SiC particles is 5 μm, more precisely, 3 μm or more, the abrasion resistance is remarkably improved and the generation of adhesion is eliminated.

Further, as the size of the particles increases, the workability deteriorates, and when the particle size is 40 μm, the roughness after processing deteriorates, and the roughness due to the subsequent alumite treatment significantly deteriorates.

From the above experiments, it can be seen that the optimum amount of SiC particles to be added is 5 to 25% by volume, preferably 10 to 20% by volume.

The size of the particles is 3 μm or more and 40 μm or less, preferably 20 μm or less.

The dispersed particles may be those having the same or higher hardness than the above-described SiC particles.
_{i 3 n 4, Al 2 O} 3, WC, TiC, TiB 2, may be used particles equal.

The above-described wear ring 11 made of an aluminum alloy to which SiC particles are added is assembled into an internal combustion engine by mounting an alumite-treated piston in a piston main body 1 made of an aluminum alloy. The test was performed. Here, the addition amount of the SiC particles in the wear ring 11 was set to 10% by volume. For comparison, a test was performed on a piston that was not subjected to an alumite treatment and a piston that did not cast the above-described wear ring into the piston body.

The operating conditions are as follows.
oil temperature 150 ° C, cooling water temperature 1 using diesel engine
The continuous operation was performed at 20 degrees for 200 hours.

As a result, the piston which does not cast the wear ring has a wear of 50 μm, and the piston under the top ring groove has a wear of 85 μm.
%, While the occurrence of adhesion was recognized,
If the alumite treatment is not performed with a piston that is made of cast iron, abrasion of 5 μm occurs and 50% of the bottom surface of the top ring groove
No abrasion or adhesion was observed in the anodized aluminum alloy.

[0053]

As is apparent from the above description, according to the present invention, a ring groove is formed by casting a wear-resistant ring on an aluminum alloy material containing silicon carbide (SiC) particles and casting it into a piston body made of an aluminum alloy. Since it is formed, not only the wear resistance with the piston ring and the like are improved, but also it can be formed by a simple molten metal casting method, so that the manufacturing cost can be reduced.

In particular, since the alumite-treated layer is formed on the surface of the ring groove of the ring, the synergistic effect of the alumite-treated layer and the silicon carbide particles in the alumite-treated layer results in wear resistance and adhesion resistance of the ring groove surface. The properties are significantly improved.

[Brief description of the drawings]

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

FIG. 2 is a longitudinal sectional view of a piston according to the embodiment.

FIG. 3 is an enlarged sectional view of a main part of the piston of the embodiment.

FIG. 4 is an explanatory view showing molding of a wear-resistant ring of the present embodiment.

FIG. 5 is an explanatory view showing a test state of wear resistance.

FIG. 6 is an explanatory view showing a test state of adhesion resistance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Piston main body 2 ... Crown part 3 ... Ring land part 4 ... Top ring groove 7 ... Top ring 11 ... Wear-resistant ring 11a ... SiC particle 20 ... Alumite treatment layer

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02F 3/00 F02F 3/00 301 F02F 3/00 302 F02F 3/10

Claims (2)

(57) [Claims] 1. A piston of an internal combustion engine in which a plurality of piston ring grooves are formed on the outer periphery of a piston body made of an aluminum alloy, wherein silicon carbide particles are provided at least in positions corresponding to the top ring grooves of the piston ring grooves. And an anodized aluminum layer formed by anodic oxidation on the surface of the ring groove formed by the anodized aluminum alloy material .
A piston for an internal combustion engine, wherein particles are dispersed and exposed . 2. A method for manufacturing a piston of an internal combustion engine, comprising a piston body made of an aluminum alloy and having a plurality of piston ring grooves formed on an outer periphery thereof, comprising: a wear-resistant ring containing silicon carbide inside an aluminum alloy material. While being molded in advance, when casting the piston body,
The casting of the ring carrier in a position corresponding to at least the top ring groove of the piston ring groove, then the anodic oxidation treatment of the surface of the ring groove formed in the ring carrier lines Do I
Forming an alumite-treated layer;
A method for manufacturing a piston of an internal combustion engine , wherein particles of the silicon carbide are dispersed and exposed .