JPH04321876A - Piston for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve further the heat-proof strength of a piston by adding at least 5 kinds of elements such as Fe, Mo and others having melting points higher than that of Al to a blank of the piston of Al respectively in specified rates and total amounts. CONSTITUTION:A piston 1 is integrally case of an Al alloy to have a cylindrical part 2 sliding in a cylinder not shown and a top part 3 forming a portion of a combustion chamber not shown. While the cylindrical part 2 is formed on the inside integrally with a pair of bosses 4, 4 opposed radially to each other, the cylindrical part 2 is formed on the upper outer peripheral surface with a plurality of piston ring grooves 5, 6 extending around the whole periphery. Then, the Al alloy of the piston blank is composed by adding at least 5 kinds of elements of Fe, Mg, Ti, Cr, Zr, V, Co, Nb and Mo having the melting point higher than that of Al respectively within 0.1wt.%-1wt.% and in at least 1.6wt.% of total amount.

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 made of an Al alloy.

0002

2. Description of the Related Art Pistons for internal combustion engines are subjected to explosive force in a high-temperature atmosphere (usually 250 to 350° C.) and are subjected to inertial force due to their high-speed reciprocating motion within the cylinder. For this purpose, the material properties required for pistons include being lightweight, having excellent high-temperature strength and heat resistance, having high thermal conductivity, having a small coefficient of thermal expansion, and having excellent wear resistance. Examples include: Al alloys have traditionally been used as materials that almost satisfy these requirements, and AC8A, an Al-Si eutectic alloy commonly known as Roex alloy, is particularly commonly used in 4-stroke engines; Al-Si hypereutectic alloys (high Si alloys), AC9A, and AC9B are generally used in engines.

0003

[Problem to be Solved by the Invention] However, as the performance of internal combustion engines has improved in recent years, the piston has become even hotter (approximately 4
It is required to be able to withstand use at temperatures as high as 00°C. A.C.
Since 8A and AC9B are age-hardening alloys, their strength at temperatures below 200°C is high, but when heated to temperatures above 250°C, they soften and their tensile strength decreases.

The present invention has been made in view of the above circumstances, and its object is to provide a piston for an internal combustion engine that has high heat resistance and strength.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides Fe, Mn, Ti, Cr, Zr, V, Co, N
0.1w each of 5 or more elements of b, Mo
The range is t% or more and 1wt% or less, and the total amount is 1
．． A feature of this invention is that the piston for an internal combustion engine is made of an Al alloy added in an amount of 6 wt% or more.

[0006]

[Operation] The present inventors have discovered that Fe, M, which has a higher melting point than Al,
5 or more elements such as n, Ti, Cr, etc. each with 0.
If it is added in a range of 1 wt% or more and 1 wt% or less, and the total amount is 1.6 wt% or more, the high melting point intermetallic compound is finely (10 μm or less) and dispersed in a large amount in the base material, It has been experimentally found that the strength of the piston is significantly increased at around 400°C, which is the maximum operating temperature of the piston. As a result, the heat resistance strength of the piston according to the present invention is increased, and the piston can be used at high temperatures of about 400° C., contributing to improvement in engine performance.

[0007]

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

FIG. 1 is a longitudinal cross-sectional view of a piston 1 for a two-stroke engine according to the present invention. The piston 1 is integrally cast from an Al alloy, and includes a cylindrical portion 2 that slides inside a cylinder (not shown), It has a top portion 3 that constitutes a part of a combustion chamber (not shown). A pair of boss portions 4, 4 are integrally formed inside the cylindrical portion 2 so as to face each other in the radial direction, and a piston ring (not shown) fits into the upper outer peripheral surface of the cylindrical portion 2. Piston ring grooves 5 and 6 are formed over the entire circumference.

By the way, the material of the piston 1, Al
The alloy is Fe, Mn, Ti, Cr, which has a higher melting point than Al.
, Zr, V, Co, Nb, and Mo, each of which is in the range of 0.1 wt% or more and 1 wt% or less, and the total amount is 1.6 wt% or more. It will be done.

[0010] Here, five elements of Fe, Mn, Cu, Ti, and Zr were selected as impurities, and these impurities were
Figure 2 shows the results of hardness tests at 400°C when various proportions (total amount added) of C was added. As is clear from Figure 2, if the total amount of impurities (Fe, Mn, Cu, Ti, Zr) added is set to 1.6 wt% or more, the Vickers hardness Hv can be dramatically increased and the high temperature strength can also be increased. . That is, at this time, the high melting point intermetallic compound is dispersed in fine particles (10 μm or less) and in large quantities in the base material (AC9B), and due to so-called dispersion strengthening, the Al alloy is heated at around 400°C (the maximum operating temperature of the piston 1). Strength is significantly increased. As a result, the heat resistance strength of the piston 1 according to the present invention is increased, and the piston 1 can be used at high temperatures of about 400° C., contributing to improvement in engine performance.

[0011] In addition, when the piston 1 is obtained by a casting process with a high solidification rate such as a powder metallurgy method or a continuous casting method, even if the total amount of impurities added is increased, fine and uniform dispersion of intermetallic compounds cannot be achieved. can get. In this case, the piston 1 is cast as a billet and then formed by hot forging.

Incidentally, although the above embodiments particularly refer to a piston for a two-stroke engine, it goes without saying that the present invention is also applicable to pistons for other four-stroke engines.

[0013]

Effects of the Invention As is clear from the above explanation, according to the present invention, Fe, Mn, Ti, Cr, Zr, V, Co, Nb
, 0.1wt each of 5 or more elements among Mo.
% or more and 1wt% or less, and the total amount is 1.
Since the piston for an internal combustion engine is made of the Al alloy added in an amount of 6 wt% or more, the effect of increasing the heat resistance strength of the piston can be obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a piston for a two-stroke engine according to the present invention.

FIG. 2 is a diagram showing changes in hardness (Vickers hardness Hv) with respect to the total amount of impurities added when impurities are added to AC9B.

[Explanation of symbols]

1 Piston 2 Cylindrical part 3 Top

Claims (1)

[Claims] [Claim 1] Fe, Mn, Ti, Cr, Zr, V,
For internal combustion engines made of an Al alloy to which five or more elements among Co, Nb, and Mo are added in a range of 0.1 wt% or more and 1 wt% or less, and the total amount is 1.6 wt% or more. piston.