JP4643547B2 - Piston of internal combustion engine - Google Patents

Description

  The present invention relates to a piston for an internal combustion engine, and more particularly to a piston for an internal combustion engine in which a U-shaped piston ring is fitted in a top land portion.

  Conventionally, a piston ring having a U-shaped cross section (hereinafter, also simply referred to as a U-shaped ring) is known as a piston ring fitted into a piston of an internal combustion engine (for example, Patent Documents 1 to 3). The U-shaped ring can secure a larger area of the sliding part with the bore (cylinder wall surface) than a general piston ring with a flat cross-section, so for example, cooling of the piston via the piston ring and the piston ring This is advantageous in that the promotion effect can be enhanced. For this reason, in the said patent documents 1 to 3, the technique for solving the problem which the piston in which a U-shaped ring and a U-shaped ring are fitted is proposed so that it may become more useful. On the other hand, with respect to cooling of the piston, a technique for cooling the piston by forming a cooling channel is known (for example, Patent Documents 4 to 6). The cooling channel disclosed in Patent Document 5 or 6 (referred to as a cooling cavity in Patent Document 6) mainly serves to cool a portion near the top surface of the piston that is exposed to a high temperature. On the other hand, a cooling channel (referred to as a cooling cavity in Patent Document 4) disclosed in Patent Document 4 cools a ring groove for a piston ring formed in a wear-resistant ring.

JP 2005-226522 A Japanese Utility Model Publication No. 5-47615 Japanese Utility Model Publication No. 5-42661 Japanese Patent Laid-Open No. 11-823838 No. 8-487 JP 2000-220520 A

  An aluminum alloy is often applied to the piston material to reduce weight. However, the mechanical strength of an aluminum alloy generally decreases as the temperature rises at a temperature that is below the temperature range of the piston during operation of the internal combustion engine. For this reason, it can be said that it is effective to apply a wear-resistant ring in which a ring groove is formed as in the technique proposed in Patent Document 4, for example, to the portion of the piston into which the piston ring is fitted. However, the wear-resistant ring causes an increase in weight, and the coefficient of thermal expansion differs from that of the piston. Therefore, a gap is formed at the interface between the piston and the wear-resistant ring, and a heat insulating layer is formed. In this case, heat is hardly transferred from the piston to the bore via the wear-resistant ring and the piston ring, so that the temperature of the piston rises, and on the contrary, there is a possibility that the piston is likely to be cracked. . In addition, since a general piston ring is applied in the technique proposed in Patent Document 4, the sliding suppression portion of the piston ring that comes into contact with the bore has a lower wear-inhibiting effect than the U-shaped ring. There is concern over the increase in blow-by gas and oil consumption due to wear of the parts.

  On the other hand, since the U-shaped ring can secure a large area of the sliding portion with the bore, wear of the sliding portion can be suppressed to a small extent, and as described above, the piston ring and the piston cooling effect through the piston ring is enhanced. Also have. Moreover, there is no possibility that the above-mentioned inconvenience will occur if a wear ring is not used. However, even when a U-shaped ring with a high cooling acceleration effect is applied to the piston ring, the temperature of the top land cannot always be suppressed sufficiently low due to heat transfer from the top land to the U-shaped ring. It has been found that the mechanical strength of the land portion may be lowered more than expected.

  For this reason, when a U-shaped ring is applied to the piston ring, for example, as the mechanical strength of the top land portion decreases, wear of the portion of the top land portion where the U-shaped ring abuts is promoted. As a result, it has been found that the sealing performance is greatly deteriorated, and as a result, the blow-by gas and oil consumption may be increased. In addition, when a U-shaped ring is applied to the piston ring, forces having different operating directions are repeatedly applied from the U-shaped ring to the top land portion according to the reciprocating motion of the piston during operation of the internal combustion engine. . For this reason, when a U-shaped ring is applied to the piston ring, cracks occur at the base of the top land where stress concentrates as the mechanical strength of the top land decreases. It was found that the U-shaped ring might fall off.

  Therefore, the present invention has been made in view of the above-described problems, and suppresses the mechanical strength of the top land portion into which the piston ring having a U-shaped cross section is fitted from being reduced due to heat, thereby the top land portion. It is another object of the present invention to provide a piston for an internal combustion engine capable of improving the mechanical strength of the entire piston.

In order to solve the above-mentioned problem, the present invention is a piston of an internal combustion engine in which a top land portion into which a U-shaped piston ring is fitted is formed, and is sandwiched between opposing portions of the piston ring, A cooling channel is formed between the facing surfaces of the top land portion facing the facing portion. That is, the present invention pays attention to the fact that the mechanical strength of the top land portion may be reduced by heat even when a U-shaped ring having a high cooling acceleration effect is applied to the piston ring. Is formed. According to the present invention, since the top land portion can be more reliably cooled by the cooling channel, it is possible to suppress the mechanical strength of the top land portion from being reduced by heat.

  Depending on the shape, the mechanical strength of the top land portion may be greatly reduced by the formed cooling channel itself. On the other hand, if the cooling channel is formed in consideration of the improvement effect of the mechanical strength due to cooling and the decrease of the mechanical strength due to the formation of the cooling channel, the overall mechanical strength of the top land can be improved. You can also. For this reason, in view of the above-mentioned problems, the present invention dares to be sandwiched between and opposed to the top land portion, specifically, the opposed portion of the U-shaped ring, in order to cool the top land portion more reliably. It is characterized in that a cooling channel is formed between the two opposing surfaces of the top land part, and in this respect, the patent does not form a cooling channel between the ring grooves where the mechanical strength tends to decrease. This is different from the technique proposed in Document 4. In addition, the present invention differs from the technique proposed in Patent Document 4 in that it is intended to achieve high wear resistance of the top land portion without providing a wear-resistant ring. According to this, since there is no wear-resistant ring, it is possible to obtain a configuration that is advantageous in terms of cost.

  The cooling channel is preferably formed from the top land part to the piston center side part from the top land part in order to cool the base part more reliably. The cooling channel is preferably formed in an annular shape along the top land portion. As a result, the portion near the top surface of the piston exposed to a high temperature can be cooled widely and uniformly, so that the mechanical strength of the entire piston can be improved. Further, the present invention is particularly suitable when an aluminum alloy is applied to the material of the piston, but is not limited to this, as long as it is a material whose mechanical strength decreases as the temperature rises under the operating temperature range of the internal combustion engine, An effect can be produced also to the piston to which other materials are applied.

  Further, according to the present invention, the cooling channel further extends to a portion closer to the piston center than the top land portion, and extends from the portion to a portion closer to the piston center than the second ring groove to have an L-shaped cross section. You may have the formed part. According to the present invention, since the second ring groove can be cooled at the same time, the progress of wear of the second ring groove can also be suppressed. Moreover, according to the present invention, since the heat radiation from the piston to the bore through the sliding portion of the piston ring can be promoted by cooling the entire land, the mechanical strength of the entire piston can be improved. .

  According to the present invention, the mechanical strength of the top land portion into which the piston ring having a U-shaped cross section is fitted is prevented from being reduced by heat, thereby improving the mechanical strength of the top land portion and further the entire piston. It is possible to provide a piston for an internal combustion engine capable of achieving the above.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram schematically showing, in cross section, the main part of a piston (hereinafter simply referred to as a piston) 1A of an internal combustion engine according to the present embodiment. Specifically, in FIG. 1A, the main part of the piston 1A is schematically shown in cross section together with the U-shaped ring 2, the second ring 3, the oil ring 4 and the cylinder block 5, and in FIG. A portion around the top land portion T of the piston 1A shown in FIG. 1A is further enlarged. A piston 1 </ b> A is incorporated in each cylinder of the cylinder block 5. The piston 1A has a top land portion T for fitting the U-shaped ring 2, a second ring groove M2ND for fitting the second ring 3, and an oil ring groove OL for fitting the oil ring 4. It is formed in an annular shape, and three piston rings, a U-shaped ring 2, a second ring 3 and an oil ring 4, are fitted into these. The U-shaped ring 2 mainly performs gas sealing, the second ring 3 performs gas sealing and oil control, and the oil ring 4 mainly performs oil control. That is, these piston rings can satisfy the required qualities related to gas sealing performance and oil control performance as a set.

  As shown in FIG. 1B, the cooling channel C1 is formed in the top land portion T. Specifically, the cooling channel C1 is formed between the opposing surfaces S1 and S2 of the top land portion T. The opposed surfaces S1 and S2 are opposed to and slide against the opposed portions R1 and R2 of the U-shaped ring 2. Note that the facing surface S1 and the facing portion R1 (or the facing surface S2 and the facing portion R2) may be formed so as not to contact each other as disclosed in, for example, the above-described JP-A-2005-226522. More specifically, the cooling channel C1 is further formed from the top land portion T to the portion closer to the piston center than the roots N1 and N2 of the top land portion T. The cooling channel C1 is specifically formed in an annular shape along the top land portion T. The cooling channel C1 has one inlet port and one outlet port (not shown), and oil injected from an oil injection nozzle (not shown) flows into the cooling channel C1 from the inlet port, and from the outlet port. It is supposed to be discharged.

  In the present embodiment, since the cooling channel C1 is formed as described above, the top land portion T can be more reliably cooled by the oil flowing through the cooling channel C1, and as a result, the machine of the top land portion T It is possible to suppress a decrease in the mechanical strength due to heat. In particular, since the cooling channel C1 is formed in the top land portion T, the opposing surfaces S1 and S2 can be more reliably cooled, and as a result, the progress of wear of the opposing surfaces S1 and S2 is suitably suppressed. be able to. In particular, since the cooling channel C1 is formed from the top land portion T to the portion closer to the piston center than the roots N1 and N2 of the top land portion T, the roots N1 and N2 can be cooled more reliably. As a result, it is possible to suitably suppress the occurrence of cracks at the bases N1 and N2 and the drop of the U-shaped ring 2 as the cracks progress. In the present embodiment, since the cooling channel C1 is formed in an annular shape along the top land portion T, the top land portion T can be cooled over the entire circumference by the oil flowing through the cooling channel C1.

  FIG. 2 is a graph showing a relationship between the temperature of the land portion of the piston 1A or the temperature of the piston ring and the position of the piston ring. FIG. 2 shows that, in the piston 1A, the higher the position of the land or piston ring (the closer to the top surface side of the piston 1A), the lower these temperatures. That is, it is shown that the U-shaped ring 2 and the top land portion T are particularly effectively cooled by the cooling channel C1 formed as described above. FIG. 3 is a graph showing the relationship between the strength of the piston 1A and the temperature. FIG. 3 shows the strength characteristics of the piston 1A corresponding to the temperature range of the piston 1A during operation of the internal combustion engine. From FIG. 3, the strength of the piston 1A decreases greatly as the temperature rises, particularly in the temperature range of 200 ° C. or higher. I understand. Therefore, the strength of the top land portion T can be significantly increased by cooling the top land portion T by the cooling channel C1 formed as described above and slightly lowering the temperature.

  In this embodiment, since the cooling channel C1 is formed in an annular shape in the top land portion T, the cooling channel is compared with a case where the cooling channel is formed only in a portion closer to the piston center than the top land portion T. A long total length of C1 can be secured. As a result, the high-temperature portion near the top surface of the piston 1A can be cooled widely and uniformly, so that the mechanical strength of the entire piston 1A can be improved. In addition, since it is possible to give the top land portion T appropriate elasticity by the cooling channel C1, cracks are generated in the bases N1 and N2 while suppressing the progress of wear of the opposing surfaces S1 and S2. The effect of suppressing this can be expected. As described above, the mechanical strength of the top land portion T in which the U-shaped ring 2 is fitted is suppressed from being reduced by heat, thereby improving the mechanical strength of the top land portion T and the piston 1A as a whole. A piston 1A that can be realized can be realized.

  FIG. 4 is a diagram schematically showing a cross section of the periphery of the top land portion T of the piston 1B according to this embodiment. FIG. 4 also shows a U-shaped ring 2, a second ring 3, and a cylinder block 5 together with the piston 1B. ing. The piston 1B extends the cooling channel C1 from the portion closer to the piston center than the top land portion T to the portion closer to the piston center than the second ring groove M2nd to cool the cooling channel C2 formed in an L-shaped cross section. The piston 1A is the same as the piston 1A according to the first embodiment except that it is provided instead of the channel C1. The cooling channel C2 is also formed in an annular shape along the top land portion T.

  In the present embodiment, since the cooling channel C2 is formed as described above, the second ring groove M2nd can be simultaneously cooled. Accordingly, it is possible to simultaneously suppress the progress of wear of the second ring groove M2nd. Further, since the land portion can be cooled as a whole, heat radiation from the piston 1B to the bore via the U-shaped ring 2 and the sliding portions L1 and L2 of the second ring 3 can be promoted. Thereby, the mechanical strength of the whole piston 1B can also be improved. Note that the cooling channel C2 may further extend to another portion. That is, the above-described effect can be obtained even with a cooling channel that includes the cooling channel C2 as a part. As described above, the mechanical strength of the top land portion T in which the U-shaped ring 2 is fitted is suppressed from being reduced by heat, thereby improving the mechanical strength of the top land portion T and the piston 1B as a whole. The piston 1B that can be achieved can be realized.

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

It is a figure which shows typically the principal part of 1 A of pistons in a cross section. It is a figure which shows the relationship between the temperature of the land part of 1 A of pistons, or the temperature of a piston ring, and the position of a piston ring with a graph. It is a figure which shows the relationship between the intensity | strength of piston 1A, and temperature with a graph. It is a figure which shows typically the cross section of the top land part T periphery part of piston 1B which concerns on a present Example.

Explanation of symbols

1 Piston 2 U-shaped ring 3 Second ring 4 Oil ring 5 Cylinder block

Claims (2)

A piston of an internal combustion engine in which a top land portion into which a U-shaped piston ring is fitted is formed,
A piston for an internal combustion engine, characterized in that a cooling channel is formed between opposing surfaces of the top land portion that are sandwiched between opposing portions of the piston ring and that oppose the opposing portion . The cooling channel further extends to a portion closer to the piston center than the top land portion, and a portion formed from the portion to a portion closer to the piston center than the second ring groove is formed in an L-shaped cross section. The internal combustion engine piston according to claim 1, further comprising:

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