JPH0625536U - Piston for internal combustion engine - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a piston for an internal combustion engine capable of reliably preventing rusting of an expansion suppressing member. A piston for an internal combustion engine in which an expansion suppressing member 3 made of a metal material having a smaller linear expansion coefficient than an aluminum alloy is integrally provided on a skirt portion 1B of a piston body 1 made of an aluminum alloy. Has an insoluble rust preventive coating 4 formed thereon.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 This invention relates to a piston for an internal combustion engine of an automobile or the like.

[0002]

[Prior art]

 Conventionally, in pistons for internal combustion engines made of aluminum alloy, the piston body has large thermal expansion due to its material surface, and the volume of the pin boss portion is large and the thermal expansion of that portion is large. The cross section is made elliptical with the direction of the minor axis so that the piston body has a perfect circular cross section when the engine is running, and the linear expansion coefficient of aluminum alloy on the inner peripheral surface of the skirt of the pin boss is higher than that of the aluminum alloy. In order to suppress the thermal expansion of the piston body in the thrust direction during engine operation and to reduce the clearance between the piston body and the cylinder bore in the thrust direction, an expansion suppression member (so-called strut) made of steel plate with a small There is.

Further, in the above-mentioned piston for internal combustion engine, an expansion suppressing member is encased integrally with a piston body which is cast by a molten metal forging method or the like, and the expansion suppressing member solidifies the piston body at room temperature. Since there is a compressive residual stress due to contraction and thermal contraction, and this compressive residual stress is released by thermal expansion during engine operation, there is a limit to the effect of suppressing thermal expansion in the thrust direction. What is described in the official gazette is further considered. In this piston for an internal combustion engine, as shown in FIG. 3, an expansion suppressing member 11 is integrally provided on the outer peripheral surfaces of the skirt portion 10 on the thrust side and the anti-thrust side, and the bimetal characteristics of the expansion suppressing member 11 suppress the thermal expansion in the thrust direction. Is trying to grow.

[0004]

[Problems to be solved by the device]

 However, in any of the conventional pistons for internal combustion engines, the expansion suppressing member easily rusts before it goes around the skirt, and after it goes around the skirt, it rusts due to the water present in the cylinder bore. easy. When rusted, not only the strength of the expansion suppressing member is lowered, but also the expansion suppressing member peels off from the skirt portion, so that the expansion suppressing effect of the expansion suppressing member is weakened. Further, the rust peeled off from the expansion suppressing member may mix into the engine oil and adversely affect the engine performance.

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 reliably prevent rusting of the expansion suppressing member.

[0006]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention relates to a piston for an internal combustion engine in which a skirt portion of an aluminum alloy piston body is integrally provided with an expansion suppressing member made of a metal material having a linear expansion coefficient smaller than that of the aluminum alloy. A rust preventive film is formed on the surface of the expansion suppressing member.

[0007]

[Action]

 Since the rust preventive film does not cause rust on the surface of the expansion suppressing member, the expansion suppressing function of the expansion suppressing member is maintained while the piston is in use, and peeling rust is not mixed into the engine oil.

[0008]

【Example】

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

FIG. 1 is a transverse sectional view of a piston for an internal combustion engine, and FIG. 2 is a longitudinal sectional view thereof. In these figures, 1 is a piston body made of an aluminum alloy, which is composed of a crown portion 1A and a skirt portion 1B, and a skirt portion 1B has a pin boss 2a having a piston pin hole 2a for mounting a piston pin (not shown). The section 2 is provided opposite.

On each inner peripheral surface of the skirt portion 1 B on the pin boss portion 2 side, an expansion suppressing member 3 made of a steel plate having a linear expansion coefficient smaller than that of an aluminum alloy is integrally formed from the pin boss portion 2 on the thrust side and the anti-thrust side. The expansion restraint member 3 extends in the pin boss portion 2 so as to bypass the piston pin hole 2a.

A rust preventive film 4 is formed on the surface of the expansion suppressing member 3 by the following method. That is, first, a rust preventive coating 4 such as zinc plating, which is insoluble in an aluminum alloy, is formed on the surface of the expansion suppressing member 3, or the expansion suppressing member 3 is processed from a steel plate material on which the rust preventing coating 4 is formed. Thereafter, the expansion suppressing member 3 is cast around the piston main body 1 which is cast by a molten metal forging method or the like to form a rust preventive film 4 on the surface of the expansion suppressing member 3.

Then, the piston pin (not shown) mounted in the piston pin hole 2a of the pin boss portion 2 is connected to the crankshaft via a connecting rod, and the crown surface 1a of the crown portion 1A receives combustion gas pressure to be illustrated. While swinging in the cylinder bore, it swings around the piston pin.

Although the expansion suppressing member 3 is provided on the inner peripheral surface of the skirt portion 1B on the side of the pin boss 2 in this embodiment, it may be provided on the outer peripheral surface of the skirt portion 1B on the thrust side and the anti-thrust side. Of course.

In the above structure, the surface of the expansion suppressing member 3 is protected by the rust preventive film 4, and the skirt portion 1B does not rust before or after the casting, so that the expansion does not occur. The reduction in strength of the suppressing member 3 and the peeling from the skirt portion 1B do not occur.

[0015]

[Effect of device]

 As described above, the present invention provides a piston for an internal combustion engine in which an expansion suppressing member made of a metal material having a linear expansion coefficient smaller than that of an aluminum alloy is integrally provided on the skirt portion of the aluminum alloy piston body. Since the rust preventive film is formed on the surface, the rust preventive film can surely prevent the expansion suppressing member from rusting. Therefore, the strength of the expansion suppressing member is not reduced and the expansion from the skirt is prevented, so that the expansion suppressing effect of the expansion suppressing member can be maintained for a long period of time, and mixing of peeling rust into the engine oil can be eliminated. The maintenance of performance can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a piston for an internal combustion engine which is an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of the piston of FIG.

FIG. 3 is a cross-sectional view of a conventional piston for an internal combustion engine.

[Explanation of symbols]

 1 Piston body 1B Skirt 3 Expansion restraint member 4 Anticorrosion coating

Claims (1)

[Scope of utility model registration request] 1. A piston for an internal combustion engine in which a skirt portion of an aluminum alloy piston body is integrally provided with an expansion suppressing member made of a metal material having a linear expansion coefficient smaller than that of the aluminum alloy. A piston for an internal combustion engine, characterized in that a rust coating is formed.