JPH0422052Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a piston for an internal combustion engine, and more particularly, to a piston for an internal combustion engine that can prevent occurrence of scuffing wear on the shoulder of a skirt.

[Conventional technology]

FIG. 5 is a side view of a conventional piston for an internal combustion engine.

In FIG. 5, 1 is the entire piston, 2 is the head, 3 is the skirt, and 4 is the skirt shoulder.

In the piston 1 as shown in FIG. 5, when the piston is at high temperature, scuffing wear occurs on the skirt shoulder 4, and seizing may occur.

This is because the temperature of the skirt shoulder portion 4 of the skirt portion 3 rises the most, so this portion undergoes the largest amount of thermal expansion.In particular, the piston 1
When the skirt is made of aluminum having a large coefficient of thermal expansion, scuffing wear tends to occur on the skirt shoulder portion 4. Incidentally, when the engine is running, the skirt shoulder 4
temperature is 150 to 160°C, whereas the temperature at the tip of the skirt portion 3 marked with 5 is only about 80°C. Further, although the head 2 has a high temperature, scuffing wear does not occur in the head 2 because the diameter is small.

In order to prevent the occurrence of scuffing wear in the skirt shoulder portion 4 as described above, it is conceivable to increase the clearance with the cylinder bore by taking into account the amount of thermal expansion in advance. However, this method is not very preferable because it causes a problem of slapping noise when it is cold.

It does not make a slap sound, and the skirt shoulders 4
In order to prevent scuffing wear from occurring in the skirt, it has been proposed in the past to cast an annular ring 11 into the skirt shoulder 4, as shown in FIG. 8, 1988
Utility Application No. 58-121195 filed on May 2nd).

In FIG. 6, an annular ring 11 is made of fiber-reinforced metal.

[Problem to be solved by the invention] In the case shown in FIG. 6, the skirt shoulder 4 hardly undergoes thermal expansion due to the fastening action of the annular ring 11, and scuffing wear occurs on the skirt shoulder 4. It will never occur.

However, since fiber-reinforced metal is very expensive, there has been a problem in that the cost is extremely high. Furthermore, at the joint surface between the piston 1 and the fiber-reinforced metal (annular ring 11), shearing force is generated in the direction of the joint surface due to the difference in thermal expansion coefficient between the material of the piston 1 (for example, aluminum) and the fiber-reinforced metal. Therefore, there was a problem that the annular ring 11 was easily separated from the piston 1.

The present invention solves these problems of the conventional technology.

An object of the present invention is to prevent the occurrence of scuffing wear on the shoulders of the skirt by using a structure that is low in cost and does not cause peeling.

[Means for solving the problem] In order to achieve this objective, the following measures are taken in the present invention.

In other words, the piston for internal combustion engines according to the present invention is an aluminum piston that is composed of a head portion provided with a ring groove and a skirt portion below the head portion, in which only the skirt shoulder portion of the skirt portion is is formed from an alloyed layer made of a material with a low coefficient of thermal expansion, and the thickness of the alloyed layer is 2 to 5 mm.

[Effect]

In the present invention, the thermal expansion of the skirt shoulder can be suppressed by the fastening effect of the alloyed layer with a low coefficient of thermal expansion formed on the skirt shoulder, and scuffing wear can be prevented from occurring in the skirt shoulder.

Furthermore, since fiber-reinforced metal as shown in FIG. 6 is not used, the cost is very low. Furthermore, since the alloyed layer is formed only on the skirt shoulders where scuffing wear occurs, costs can be further reduced. Incidentally, the manufacturing cost of the present invention is about one-tenth that of the one shown in FIG.

The alloyed layer formed on the skirt shoulder is made by melting and alloying the base material aluminum and a material with a low coefficient of thermal expansion. There is no bonding surface, and the alloyed layer will not peel off.

Further, since the thickness of the alloyed layer is 2 to 5 mm, thermal expansion of the skirt shoulder portion can be reliably suppressed, and peeling of the alloyed layer can be reliably prevented.
That is, if the thickness of the alloyed layer is too shallow, the effect of suppressing the thermal expansion of the skirt shoulder portion will be small, and if it is too thick, it will not be reliably alloyed with the base material, resulting in peeling of the alloyed layer. Therefore, in the present invention, by setting the thickness of the alloyed layer to 2 to 5 mm, it is possible to ensure that the thickness of the alloyed layer is sufficient to suppress the thermal expansion of the skirt shoulder, and also to ensure that the alloyed layer is 2 to 5 mm thick. A protective layer is formed to prevent peeling.

Although it is difficult to form an alloyed layer using a normal method, it is possible using a laser beam, an electron beam, TIG, or the like.

〔Example〕

FIG. 1 is a longitudinal sectional view of a piston for an internal combustion engine according to an embodiment of the present invention.

In FIG. 1, a piston 1 is composed of a head 2 and a skirt portion 3 located below the head 2.

The head 2 is provided with a circumferentially extending ring groove 15 in its side wall 14. The entire piston 1 is made of aluminum.

Skirt shoulder portion 4 of piston 1 according to this embodiment
is alloyed with a material that has a low coefficient of thermal expansion and is easily alloyed with aluminum to form the alloyed layer 9.

Materials that have a low coefficient of thermal expansion and are easily alloyed with aluminum include silicon, molybdenum, tungsten,
Metal materials such as titanium, nickel, or chromium, or ceramic materials such as titanium carbide, tungsten carbide, aluminum oxide, and silicon carbide.

A method of manufacturing the piston 1 according to this embodiment will be explained.

First of all, the raw material of the piston is cast. The raw material of the piston is aluminum alloy, for example,
JIS alloy number AC8A etc. Moreover, as for the casting method, any method such as die casting, molten metal forging, high pressure casting, etc. may be used as in the conventional method.

Next, as shown in FIG. 2, the cast material 22 is roughly machined to form grooves 21 in the portion corresponding to the skirt shoulder 4 (see FIG. 1) (the portion where the coefficient of thermal expansion is desired to be lowered). The groove 21 is coated with powder of a material that has a low coefficient of thermal expansion and is easily alloyed with aluminum. The width a of the groove 21 is about 10 mm, and the depth d is 2 to 5.
It is about mm.

Next, as shown in FIG. 3, while rotating the piston rough material 22 coated with the powder in the direction of arrow A, a high energy density laser beam 29 is irradiated onto the powdered portion. Then, the applied material and the aluminum base material are melted to form an alloyed layer. In FIG. 3, 28 is the laser beam 2
It is a mirror to reflect 9.

When the piston rough material 22 produced in this manner is finished, a piston 1 according to this embodiment as shown in FIG. 1 is completed.

The applicant conducted a comparative experiment using the following test pieces A to E.

Test piece A is a piston that is not subjected to alloying treatment and is made from JIS alloy number AC8C.

Test piece B is also a piston that is not subjected to alloying treatment and is made from JIS alloy number AC8A.

Test piece C used silicon as an alloying material for the aluminum base material. The resulting alloyed layer consists of an alloy of 60% aluminum and 40% silicon.

Test piece D used silicon and titanium as alloying materials for the aluminum base material. The resulting alloyed layer consists of an alloy of 50% aluminum, 40% silicon, and 10% titanium.

Test piece E used silicon, titanium, and titanium carbide as alloying materials for the aluminum base material. The resulting alloyed layer consists of an alloy of 45% aluminum, 40% silicon, and 15% titanium carbide.

For test pieces C to E, the laser irradiation conditions were: output 2.2KW, energy density 500W/
mm ² and irradiation time was 0.05 seconds.

FIG. 4 shows the results of measuring the thermal expansion coefficients of the skirt shoulders 4 for test pieces A to E as described above.

As can be seen from FIG. 4, it can be seen that the coefficient of thermal expansion of the skirt shoulder portion 4 of test pieces C to E according to this example is about half that of test pieces A and B according to the prior art.

As can be seen from the above description, according to this embodiment, the thermal expansion of the skirt shoulder 4 can be suppressed by the fastening action of the alloyed layer 9 with a low coefficient of thermal expansion formed on the skirt shoulder 4. Occurrence of scuffing wear on the portion 4 can be prevented.

Furthermore, this embodiment does not use fiber-reinforced metal as shown in FIG. 6, so the cost is very low. Furthermore, since the alloyed layer 9 is formed only on the skirt shoulder portion 4 where scuffing wear occurs, costs can be further reduced. Incidentally, the manufacturing cost of this example is
It costs about 1/10 compared to the one shown in the figure.

The alloyed layer 9 formed on the skirt shoulder 4 is made by melting and alloying the base material aluminum and a material with a low coefficient of thermal expansion, so it is alloyed with the piston 1 and has a low coefficient of thermal expansion. Since there is no bonding surface with layer 9, alloyed layer 9 does not peel off.

The thickness of the alloyed layer 9 in this embodiment is preferably 2 to 5 mm because if it is too shallow, the effect of suppressing the thermal expansion of the skirt shoulder 4 will be small, and if it is too thick, the laser beam will not penetrate. Desirably, by setting the thickness of the alloyed layer 9 to 2 to 5 mm, the thickness of the alloyed layer 9 can be ensured to be sufficient to suppress the thermal expansion of the skirt shoulder 4, and the thickness of the alloyed layer 9 can be ensured. can be formed to prevent peeling. For the above test pieces C to E, the thickness was set to 2.5 mm.

The reason why a laser beam was used to form the alloyed layer 9 in this example is that the above-mentioned materials do not form alloys with aluminum in normal methods;
This is because using a laser beam creates an alloy with aluminum. This is because rapid heating and cooling are performed. Note that in addition to laser beams, electron beams, TIG, etc. may also be used.

In addition, in this embodiment, since the clearance between the piston and the cylinder bore can be reduced, there is also an advantage that the hitting sound of the piston can be reduced.

[Effect of idea]

According to the present invention, in an aluminum piston for an internal combustion engine, only the skirt shoulder portion is formed from an alloyed layer made of a material with a low coefficient of thermal expansion, and the thickness of the alloyed layer is reduced to 2. ~5mm
Therefore, the thermal expansion of the skirt shoulder can be suppressed by the fastening effect of the alloyed layer with a low coefficient of thermal expansion.
It is possible to prevent scuffing wear from occurring at the shoulders of the skirt. Furthermore, since the alloyed layer is formed only on the skirt shoulders where scuffing wear occurs, costs can be reduced.

Since the alloyed layer is made by melting and alloying the base material aluminum and a material with a low coefficient of thermal expansion, there is no joint surface between the piston and the alloyed layer with a low coefficient of thermal expansion. The alloyed layer will not peel off.

Furthermore, since the thickness of the alloyed layer is 2 to 5 mm, it is possible to ensure the thickness of the alloyed layer sufficient to suppress thermal expansion of the skirt shoulder, and to form the alloyed layer reliably to prevent peeling. .

[Brief explanation of the drawing]

FIG. 1 is a side view of a piston for an internal combustion engine according to an embodiment of the present invention, FIG. 2 is an explanatory diagram illustrating a step of producing the piston shown in FIG. 1, and FIG.
FIG. 4 is a graph showing the experimental results for test pieces A to E. FIG. 5 is a side view of a conventional piston for an internal combustion engine. FIG. 6 is a longitudinal sectional view of a portion of another conventional piston for an internal combustion engine. DESCRIPTION OF SYMBOLS 1...Piston, 2...Head, 3...Skirt part, 4...Skirt shoulder part, 9...Alloyed layer, 15
...Ring groove.

Claims (1)

[Claims for Utility Model Registration] In an aluminum piston consisting of a head provided with a ring groove and a skirt below the head, only the skirt shoulder of the skirt has a coefficient of thermal expansion. A piston for an internal combustion engine, characterized in that the piston is formed from an alloyed layer alloyed with a material having a low carbon content, and the thickness of the alloyed layer is 2 to 5 mm.