JPH0424123Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a piston for an internal combustion engine in which an oil ring groove is subjected to anti-wear treatment.

[Conventional technology]

A piston of a reciprocating internal combustion engine has a plurality of piston ring grooves extending around the entire circumference formed on the upper outer periphery of the piston, and the lowermost piston ring groove is used as an oil ring groove. A piston ring is fitted into the top ring groove and second ring groove to suppress gas blow-through, and an oil ring is fitted into the oil ring groove to scrape off oil adhering to the cylinder bore wall and reduce oil consumption. Ru.

A three-piece combination oil ring consisting of an expander and a pair of side rails disposed above and below the expander is often used as the oil ring because it has good followability to the cylinder bore. The three-piece oil ring is disclosed in Japanese Utility Model Application Publication No. 60-102446, and as shown in FIG. It has a panda 2 and a pair of plate-shaped and annular side rails 4 and 6 that extend in the circumferential direction and have one cut on the circumference. A pair of side rails 4, 6
is engaged with the claws 8 and 10 formed above and below the inner circumference of the expander 2, so that
It receives an expansion force F from the expander 2 and is slidably pressed against the inner surface of the cylinder bore 12. As a result, when the piston 14 reciprocates, the outer periphery of the side rails 4, 6 is exposed to the cylinder bore 12.
Scrape off the oil adhering to the inside surface. The claws 8, 10 of the expander 2 extend diagonally in the vertical direction toward the inner circumference and are inclined, and the pushing force F of the side rails 4, 6 is applied in the diagonal vertical direction, thereby causing the side rails 4, 6 to move in the diagonal vertical direction. A force F ₁ pushing in the vertical direction is generated to press the side rails 4 and 6 against the upper and lower surfaces 18 and 20 of the oil ring groove 16, blocking the bypass passage of oil through the oil ring groove 16 and reducing oil consumption. The effect is increasing.

Side rails 4 and 6 are oil ring groove upper and lower surfaces 1
8 and 20, and as a result of repeated use for a long time, dents 22 and 24 as shown in FIG. The side rails 4 and 6 make this recess 2 on the upper and lower surfaces of the inner circumference.
2, 24 and the oil ring groove upper and lower surfaces 1
When held between the side rails 4 and 20 and the expander 2, even if the component F ₂ of the expansion force F of the expander 2 directed toward the outer circumference acts on the side rails 4 and 6,
The expansion of the side rails 4, 6 may be inhibited, and the side rails 4, 6 may no longer follow the cylinder bore 12 sufficiently, resulting in increased oil consumption.

Such problems arise from wear of the oil ring groove. As a structure for reducing wear of piston ring grooves, a method is known in which the surface of piston ring grooves is formed of a composite material, as disclosed in Japanese Patent Application Laid-Open No. 101249/1983. However, the conventional proposal is not an oil ring groove,
This relates to anti-wear measures for the top ring groove and the second ring groove, and uses a composite material as the means.

[Problem that the invention attempts to solve]

The conventionally proposed wear suppression was achieved by reducing the temperature by efficiently dissipating the heat in the piston ring groove, which is particularly high, through the piston ring and into the cylinder bore using a composite material.

On the other hand, the temperature near the oil ring groove does not become as high as that near the top ring, and in order to prevent wear, it is desirable to achieve hardening of the oil ring groove surface rather than lowering the temperature. However, conventionally, the oil ring grooves are made of piston aluminum alloys such as AC8A and AC8B, and are not subjected to any hardening treatment. Therefore, wear has become a particular problem when nitrided side rails, which are highly aggressive to opponents, are used.

Moreover, even if hardening treatment was applied, conventionally a hard layer was laminated on the piston base material using plating, as in Japanese Patent Publication No. 58-9160 and Japanese Patent Publication No. 52-23018. Since the aluminum alloy of the piston base material is a relatively soft metal, there was a problem in that when the hard layer was formed and the hard layer was subjected to a thermal cycle, it would peel or crack.
Furthermore, no conventional proposals have been found that take such peeling and cracking into consideration.

The present invention is designed to harden the surface of the oil ring groove of a piston made of aluminum alloy to prevent dents due to wear even when a three-piece oil ring is inserted. The purpose is to prevent peeling and cracking.

[Means for solving problems]

To achieve the above object, the piston of the internal combustion engine of the present invention has an oil ring groove extending around the entire circumference of the piston, an expander in the oil ring groove, and a pair of oil ring grooves disposed above and below the expander. A piston for an internal combustion engine made of an aluminum alloy into which a combination oil ring consisting of a side rail is inserted has silicon carbide particles directly embedded in the piston base material on at least the upper and lower surfaces of the oil ring groove.

[Effect]

In the internal combustion engine piston of the present invention constructed as described above, the hardness of the hardened layer in which silicon carbide particles are embedded is equivalent to Witzkers hardness.
With Hv=700 or more, it is sufficiently hard and has a small wear coefficient. Side rails are usually treated with nitriding to create a hardened surface for wear resistance, but nitrided side rails are aggressive and may eat away at other parts, but the hardened layer with embedded SiC particles is Since it is extremely hard, it does not wear out easily and is less prone to dents due to wear during use, unlike conventional products. Furthermore, the friction coefficient is small, allowing the side rails to slide smoothly. These actions can improve the followability of the side rail to the cylinder bore, promote scraping off of oil by the side rail, and promote reduction in oil consumption.

In the above, the SiC particle-embedded hardened layer was formed by directly embedding particles into the base material, rather than being laminated on the surface of the soft piston aluminum alloy base material by plating, etc., so it is less likely to peel off from the base material. Cracks are less likely to occur even when force is applied from the side rails and thermal cycles are applied. Also, if the thickness of the SiC particle embedded layer is about 1 to 5 μm, the hardened part will expand due to the expansion of the aluminum alloy.
Since it is easy to follow the contraction, no cracks occur.

〔Example〕

Hereinafter, preferred embodiments of a piston for an internal combustion engine according to the present invention will be described with reference to the drawings.

Figure 1A shows the oil ring groove of the piston of the internal combustion engine of the present invention and the structure around it.
Figure B is shown enlarged. In the drawings, the same reference numerals as those in FIGS. 2 and 3 are given to the parts having a structure similar to the conventional structure to the members in FIG. 1, thereby omitting redundant explanation, and only the parts different from the conventional structure will be explained.

On the surface of the oil ring groove 16 of the piston 14 made of Al alloy, at least the upper and lower surfaces 18,
A SiC particle-embedded hardened layer 26 is formed by embedding SiC (silicon carbide) particles 30 having a size of 1 to 5 μm in the substrate 20 by rolling or the like. The hardened layer 26 may be formed on the bottom surface 28 of the oil ring groove 16. The hardness of SiC particles 30 is
Hv=1800 or more, the average hardness of the SiC particle embedded hardened layer 26 is about Hv=700 or more, and the buried depth is about 20μ. The hardened layer 26 can be easily formed by embedding the SiC particles 32 with a roll.

The reason why the depth of the hardened layer 26 embedded with SiC particles is set to about 20μ is that if it is made too thin, there is a possibility that a large amount of the piston aluminum alloy base material will come out to the surface when slight wear occurs during long-term use. This is because the purpose of forming the hardened layer 26 is lost. Furthermore, if the thickness is significantly greater than 20μ, the ability of the hardened layer 26 to spread integrally with the piston aluminum alloy base material becomes poor, and the piston 14
This is because there is a risk that cracks will occur in the hardened layer 26 when the hardened layer 26 is subjected to thermal cycles, and an excessive load will be applied when embedding with a roll or the like, making it impossible to ensure the accuracy of the groove surface. Also,
The reason why the size of the SiC particles 30 is set to 1 to 5μ is that it is a suitable size for embedding the particles to a thickness of about 20μ by roll processing.If it is too small, the wear resistance will decrease due to increased hardness. Cannot be secured.
Also, if it is too large, the side rails will wear out due to the hard SiC.

The average hardness of the hardened layer 26, Hv=700, is comparable to the surface hardness of the nitrided side rail, and
The SiC particle-embedded hardened layer 26 has excellent wear resistance and erosion resistance, and has a small wear coefficient.
Excellent sliding properties.

In the internal combustion engine piston configured as described above, the SiC particle-embedded hardened layer 26 has a high hardness, so even if the side rails 4 and 6 are nitrided, the oil ring groove 16 will have a dent 22 due to wear. , 24 (as seen in FIG. 3) does not occur, and the sliding properties are good, so that deterioration in the followability of the side rails 4 and 6 to the cylinder bore 12 is prevented. This prevents oil consumption from worsening during engine operation.

[Effect of idea]

According to the internal combustion engine piston of the present invention, SiC particles are directly embedded in the piston base material to form a hardened layer in the oil ring groove of the piston made of aluminum alloy, so nitrided side rails are used for the oil ring side rails. Also, wear is less likely to occur in the oil ring groove, and deterioration in the followability of the side rail to the cylinder bore, which may occur when the oil ring groove is worn, can be prevented, and oil consumption can be reduced. Moreover, since it is directly embedded into the piston base material, it is possible to suppress the occurrence of peeling and cracking unlike plating.

[Brief explanation of the drawing]

Figures 1A and 1B are cross-sectional views of the oil ring groove and its vicinity in a piston of an internal combustion engine according to the present invention; Figure 2 is a cross-sectional view of the oil ring groove and its vicinity in a conventional piston; FIG. 3 is a cross-sectional view of the oil ring groove of the piston after wear. 2...Expander, 4,6...Side rail, 12...Cylinder bore, 14...Piston,
16... Oil ring groove, 18, 20... Upper and lower surfaces of oil ring groove, 22, 24... Dent, 2
6...SiC particle embedded hardened layer, 30...SiC particle.

Claims (1)

[Scope of utility model registration request] An aluminum alloy having an oil ring groove extending around the entire circumference of the piston, into which a combination oil ring consisting of an expander and a pair of side rails disposed above and below the expander is fitted. A piston for an internal combustion engine comprising: a piston for an internal combustion engine, characterized in that silicon carbide particles are directly embedded in the piston base material on at least the upper and lower surfaces of the oil ring groove.