JP2604521Y2 - Piston for internal combustion engine - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for an internal combustion engine of an automobile or the like.

[0002]

2. Description of the Related Art Conventionally, in a piston for an internal combustion engine made of an aluminum alloy, the thermal expansion of the piston main body is large due to its material, and the volume of the pin boss is large and the thermal expansion of the portion is large. The piston pin hole direction is made into an elliptical cross section with a short diameter, so that the piston body becomes a perfect cross section during engine operation, and the inner peripheral surface of the skirt portion on the pin boss portion side is made of aluminum alloy. An expansion suppressing member (a so-called strut) made of a steel plate having a small linear expansion coefficient is integrally provided to suppress 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. Like that.

[0003] In the piston for internal combustion engines of the above, are insert cast is pin <br/> piston body and integral to the expansion suppressing member,
This expansion suppressing member has a compressive residual stress due to solidification contraction and thermal contraction of the piston body at normal temperature, and since this compressive residual stress is released by thermal expansion during engine operation, thermal expansion in the thrust direction is suppressed. As the effect is limited,
For example, the one described in Japanese Utility Model Laid-Open No. 2-61164 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 on the thrust side and the anti-thrust side of the skirt portion 10, and thermal expansion is suppressed in the thrust direction by its bimetal characteristic. Trying to increase the effect.

[0004]

However, in the above-mentioned conventional pistons for internal combustion engines, the expansion suppressing member is easily rusted before being cast into the skirt portion, and the cylinder bore is formed after being cast into the skirt portion. It is easily rusted due to moisture present in the interior. If it rusts, not only will the strength of the expansion suppressing member decrease, but it will peel off from the skirt,
The expansion suppressing function of the expansion suppressing member is weakened. Further, rust peeled from the expansion suppressing member may be mixed into the engine oil to adversely affect engine performance.

The present invention has been made to solve the above-mentioned problem, and has as its object to provide a piston for an internal combustion engine which can reliably prevent rust of an expansion suppressing member.

[0006]

In order to achieve the above object, the present invention provides a skirt portion and a pin boss portion of an aluminum alloy piston body such that the skirt portion and the pin boss portion of the aluminum alloy piston body are connected. The inner peripheral surfaces of the skirt portion and the pin boss portion are made of a metal material having a smaller linear expansion coefficient than an aluminum alloy, and a galvanized rust-preventive coating is formed on the entire surface in advance to suppress expansion. The member is provided integrally by casting, between the inner peripheral surfaces of the skirt portion and the pin boss portion and the expansion suppressing member, and a table of the expansion suppressing member.
The surface has a galvanized rust preventive film interposed.

[0007]

Since no rust is generated on the surface of the expansion suppressing member by the rust preventive film, the expansion suppressing function of the expansion suppressing member is maintained while the piston is in use, and no exfoliated rust is mixed into the engine oil. .

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

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

A skirt portion 1B is provided on each inner peripheral surface of the skirt portion 1B on the pin boss portion 2 side and on the inner peripheral surface of the pin boss portion.
The expansion restraining member 3 made of a steel plate having a linear expansion coefficient smaller than that of the aluminum alloy is integrally extended from the pin boss portion 2 to the thrust side and the anti-thrust side so as to be connected to the pin boss portion 2B and the skirt portion 1B. Connect pin boss 2
Thus, the intermediate portion of each expansion suppressing member 3 extends into the pin boss portion 2 so as to bypass the piston pin hole 2a.

A rust preventive coating 4 is formed on the entire surface of the expansion suppressing member 3 by the following method. That is,
First, either the shape formed the antirust coating 4 of zinc plating insoluble on the surface of the expansion suppressing member 3, or, after processing the expansion suppressing member 3 from the steel plate antirust coating 4 is formed material, the piston body The rust-preventive coating 4 is formed on the surface of the expansion suppressing member 3 by casting the expansion suppressing member 3 integrally with 1.

The piston pin hole 2 of the pin boss 2
The piston pin is connected to a crankshaft via a connecting rod and a piston pin (not shown) mounted on the piston pin a. As a swing motion.

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

In the above configuration, the surface of the expansion suppressing member 3 is protected by the rust-preventive coating 4, and the skirt portion 1B
Since it does not rust before and after the casting, the strength of the expansion suppressing member 3 is not reduced, and peeling from the skirt portion 1B does not occur.

[0015]

As described above, according to the present invention, the metal having a smaller linear expansion coefficient than the aluminum alloy is provided on the inner peripheral surfaces of the skirt portion and the pin boss portion so as to connect the skirt portion and the pin boss portion of the aluminum alloy piston body. An anti-expansion member made of a material and formed by forming a galvanized rust-preventive coating on the entire surface in advance is provided integrally by casting, and the inner peripheral surface of the skirt portion and the pin boss portion and the anti-expansion member are formed. Between the member and the surface of the expansion suppressing member.
Since the rust-preventive coating of lead plating is interposed, rust of the expansion suppressing member can be reliably prevented by the rust-preventive coating. Therefore, the strength of the expansion suppressing member is not reduced and peeling from the skirt portion is eliminated, and the expansion suppressing action of the expansion suppressing member can be maintained for a long time, and the mixing of peeling rust into the engine oil can be eliminated.
Maintain and improve engine performance.

[Brief description of the drawings]

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

FIG. 2 is a longitudinal sectional view of the piston of FIG. 1;

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

[Description of Signs] 1 Piston main body 1B Skirt part 3 Expansion suppression member 4 Rust prevention coating

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-41875 (JP, A) JP-A-57-47571 (JP, A) JP-A-1-210662 (JP, A) 61164 (JP, U) Fully open sho 61-14785 (JP, U) Fully open sho 62-103603 (JP, U) Really open sho 56-1554547 (JP, U)

Claims (1)

(57) [Scope of request for utility model registration] An inner peripheral surface of the skirt portion and the pin boss portion is made of a metal material having a smaller linear expansion coefficient than that of the aluminum alloy so as to connect the skirt portion and the pin boss portion of the piston body made of aluminum alloy. pre-sub to
An expansion suppressing member formed by forming a rust-preventive coating of lead plating is integrally provided by casting, and is provided between the inner peripheral surfaces of the skirt portion and the pin boss portion and the expansion suppressing member .
A piston for an internal combustion engine, wherein a rust-preventive coating of zinc plating is interposed on the surface of the expansion suppressing member .