JPH0640337U - Piston for internal combustion engine - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a piston for an internal combustion engine that can be manufactured by smoothing the surface of a plating layer without impairing manufacturability. A plating layer 10 is formed on at least the lower surface 4a of the top ring groove 4 of the ring grooves 4, 5, 6 formed in the land portion of the piston body base material 1, and unevenness on the surface of the plating layer 10 is formed. The removed smooth surface 11 was formed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a piston for an internal combustion engine made of a light alloy such as an aluminum alloy, and more particularly to a piston for an internal combustion engine in which a ring groove into which a compression ring is inserted has enhanced heat resistance and wear resistance.

[0002]

[Prior art]

 Conventionally, aluminum alloy pistons for internal combustion engines tend to wear in the top ring groove between the top ring inserted into the groove and the scuffing due to the adhesion of aluminum to the top ring. In order to improve the heat resistance and wear resistance of the top ring groove, an anodized film layer is formed on the inner surface of the top ring groove by a hard alumite treatment (for example, JP-A-63-289370). reference).

[0003]

[Problems to be solved by the device]

 However, in the above-mentioned piston for internal combustion engine, in the aluminum alloy material as the piston base material, a large amount of Si (silicon) is contained in its chemical composition, and a large amount of Si crystallizes in the metal structure. Due to the property of alumite that it is difficult to form an anodized film on the Si particles existing on the surface of the material, the surface of the anodized film layer formed on the surface of the base material often has many irregularities. If the uneven surface formed on the surface of the anodized film layer is present especially on the lower surface of the top ring groove, the sealing property between the lower surface of the top ring groove and the lower surface of the top ring will be insufficient during engine operation. However, there is a risk that oil leakage and combustion gas blow-through from this part may occur, increasing the initial oil consumption and blow-by gas.

Therefore, in order to eliminate such inconvenience, the applicant of the present invention forms an anodized film layer on the lower surface of the top ring groove portion, and grinds it with a grinding wheel or cuts it with a cutting tool. We have already filed an application for a piston for an internal combustion engine that has a smooth surface formed by removing the irregularities on the surface of the oxide film.

Further, the applicant considered that, for example, a nickel plating layer 10 was formed on the inner surface of the top ring groove to replace the anodic oxide coating layer, but in this case, as shown in FIG. The surface roughness of No. 10 becomes non-uniform, and like the above-mentioned anodized film layer, the sealing property between the lower surface of the top ring groove and the lower surface of the top ring is insufficient during engine operation, so that the There is a risk that the initial oil consumption and blow-by gas may increase due to oil leaks and blowout of combustion gas.

The present invention has been made to solve the above problems, and an object thereof is to provide a piston for an internal combustion engine that can be manufactured by smoothing the surface of the plating layer without impairing the manufacturability.

[0007]

[Means for Solving the Problems]

 To achieve the above object, a piston for an internal combustion engine according to the present invention has a plating layer formed on at least a lower surface of a top ring groove portion of a ring groove formed in a land portion of a piston body base material. A smooth surface was formed by removing the irregularities on the surface.

[0008]

[Action]

 According to the above structure, since the surface of the plating layer formed on the lower surface of the top ring groove is a smooth surface, the sealing property between the lower surface of the top ring groove and the upper surface of the top ring is improved.

[0009]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1A is a vertical sectional view showing a part of a piston for an internal combustion engine, and FIG. 1B is an enlarged sectional view of FIG. 1A showing a lower surface of a top ring groove.

In the figure, reference numeral 1 denotes a light alloy piston body preform, and the piston body preform 1 is composed of a crown portion 2 and a skirt portion 3. A ring-shaped top ring groove 4, a second ring groove 5 and an oil ring groove 6 are formed side by side at intervals on the land portion formed on the outer peripheral portion of the crown portion 2, and the top land portion 7 and the second land portion are formed. 8 and the third land portion 9 are formed, a top ring (not shown) is inserted in the top ring groove 4, a second ring (not shown) is inserted in the second ring groove 5, and an oil ring (not shown) is inserted in the oil ring groove 6. Has been done.

A nickel plating layer 10 is formed on the surfaces of the crown surface portion 2 a of the crown portion 2 and the top land portion 7 and the inner surface of the top ring groove 4, and the nickel plating layer 10 is formed on the lower surface 4 a and the upper surface 4 b of the top ring groove 4. A smooth surface 11 is formed on the surface of the nickel-plated layer 10 by removing the irregularities on the surface of the nickel-plated layer 10 shown by an imaginary line in FIG. 1 (2).

The smooth surface 11 is formed by grinding the surface of the nickel plating layer 10 with a grinding wheel or cutting with a bite.

In the above structure, the nickel plating layer 10 has heat resistance, abrasion resistance, scuffing resistance, and excellent low thermal conductivity. Therefore, by forming the nickel plating layer 10 on the crown surface portion 2a of the crown portion 2, heat resistance is improved, and heat from the combustion gas chamber is hard to be transferred to the piston body base material 1 to cause heat loss. Is reduced. Further, since the nickel plating layer 10 is formed on the surface of the top land portion 7 that is in sliding contact with the inner wall of the cylinder bore (not shown), wear resistance and scuffing resistance with respect to the inner wall of the cylinder bore are improved. By forming an oil film of oil on the unevenness of the nickel plating layer 10, the wear resistance and scuffing resistance are further improved. Further, by forming the nickel plating layer 10 on the lower surface 4a and the upper surface 4b of the top ring groove 4, abrasion resistance with the top ring and scuffing resistance are improved, and the surface of the nickel plating layer 10 is smooth. By forming the surface 11, the sealing property with the top ring is improved, and oil leakage and combustion gas blow-through are reduced. In this respect, a further effect can be obtained by forming a plating layer on the lower surface 5a of the second ring groove 5 and forming a smooth surface similar to the smooth surface 11 on the surface of the plating layer. it can.

Although the nickel plating layer 10 is formed on the lower surface 4a and the upper surface 4b of the top ring groove 4 and the smooth surface 11 is formed on the surface of the nickel plating layer 10 in the above embodiment, the smooth surface 11 is formed. The plating layer to be applied is not limited to the nickel plating layer, and the same effect can be obtained even if it is a chromium plating layer, a nickel-phosphorus plating layer, an iron-phosphorus plating layer, or the like. The plating layer may be formed on.

[0016]

[Effect of device]

 As described above, according to the present invention, the plating layer is formed on at least the lower surface of the top ring groove portion of the ring groove formed on the land portion of the piston body base material, and the smooth surface is formed by removing the irregularities on the surface of the plating layer. Therefore, the sealability between the lower surface of the top ring groove and the lower surface of the top ring is improved without impairing the manufacturability of the piston to increase the initial oil consumption due to oil leakage during engine operation. It is possible to reliably reduce the increase in the blow-by gas flow rate due to the blow-off of combustion gas from the combustion chamber.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a part of a piston for an internal combustion engine according to an embodiment of the present invention. (2) It is an enlarged sectional view of (1) showing the lower surface of the top ring groove.

FIG. 2 is a cross-sectional view corresponding to FIG. 1 (1) showing the lower surface of the top ring groove only formed with a nickel plating layer.

[Explanation of symbols]

 1 Piston body base material 4 Top ring groove (ring groove) 4a Lower surface 5 Second ring groove (ring groove) 6 Oil ring groove (ring groove) 10 Plating layer 11 Smooth surface

Claims (1)

[Scope of utility model registration request] 1. A plating layer is formed on at least a lower surface of a top ring groove portion of a ring groove formed on a land portion of a base material of a piston body, and a smooth surface is formed by removing irregularities on the surface of the plating layer. An internal combustion engine piston.