JPS63108936A - Manufacture of piston - Google Patents

Abstract

PURPOSE:To form the piston for engine in light weight and high intensity by blow-forming the disk on the lower side upward and press-forming the disk on the upper side downward after performing the diffused junction of a steel pipe and stainless steel disk with their heating and pressurizing by placing two sets in order. CONSTITUTION:A superplastic stainless steel disk 2 is placed on the upper end face 1a of the steel pipe 1 in about same length as that of a shirt part A. The steel pipe 3 in about same length as that of a head part B is placed on the upper face of the disk 2 and a superplastic stainless steel disk 4 is placed on the upper end face 3a of a pipe 3. The lower end face 1b of the pipe 1 is then placed on a backup die 8, the disks 2, 4 and pipes 1, 3 are pressurized in a furnace by a pressing die 9, and the steel pipe 1, steel pipe 3 and disks 2, 4 are subjected to a diffused junction. The gas in the specified pressure is fed into the steel pipe 1 from the hole 8a of the backup die 8 inside the furnace and the disk 2 at the lower side is faced to the upper part to perform a blow forming. Simultaneously a recessed hollow part forming die 10 is descended along the die 9 and the disk 4 on the upper side is pressure-formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing an engine piston.

2. Description of the Related Art A piston used in a conventional engine consists of a cylindrical skirt portion and a head portion having a concave portion forming a combustion chamber, and is manufactured by a casting method.

The piston, which requires light weight, is cast from aluminum alloy, and the piston, which requires durability and strength, or which absorbs thermal expansion with the cylinder, is cast from cast iron.

Problems that the invention aims to solve Pistons made of aluminum alloy are lightweight, but
On the other hand, it has poor high-temperature strength, so it does not have enough strength and durability to be used as a piston in a high-output engine, such as an engine mounted on a large construction machine. Since there is a large difference in coefficient of thermal expansion, the gap between them must be increased, resulting in a decrease in efficiency.

In addition, since a piston made of cast iron has a complicated hollow shape, it is difficult to reduce the thickness of the piston, and this combined with the high specific gravity of the material increases the weight, making it impossible to reduce the weight.

Therefore, an object of the present invention is to provide a method for manufacturing a lightweight and high-strength piston.

Means and Effects for Solving Problems A steel vibrator, a superplastic stainless steel disk, a steel vibrator, and a superplastic stainless steel disk are sequentially joined, and the whole is pressurized at a predetermined temperature and pressure to perform diffusion bonding, and then The lower disc is pulled upwards and the upper disc is pressure molded downwards to join the discs together, and a concave part is formed, which is then finished by machining to reduce weight. In addition to this, it is also possible to achieve high strength.

Embodiment As shown in FIG. 1(a), a superplastic stainless steel disk 2 is placed on the upper end surface 1aK of a long steel pipe 1 having approximately the same length as the skirt portion, and the upper surface of the disk 2 is A short steel pipe 3 having approximately the same length as the head is placed on the head, and a superplastic stainless steel disk 4 is placed on the upper end surface 3a of the steel pipe 3.

Small-diameter pipes 5 are welded and fixed to the circumferential wall of the steel pipe 1 so as to face each other in the radial direction to form a pin hole 6 for connection to the small end boss portion of the connector/glue. A auxiliary ring 7 is placed on the holder, and this auxiliary ring 7 has a substantially conical shape.

The lower end surface +b of the steel pipe 1 is placed on a back amplifier mold 6, and a cylindrical pressing mold 9 is pressed against the disc 4 under pressure in a furnace at a temperature of 900 to 1050°C. Disk 2
, 4 and the steel pipes 1, 3 by pressurizing the press die 9 so that a surface pressure of 1 to 3 Kg/w' acts on the contact area between the steel pipe 1, the steel pipe 3, and the disc 2.4. do.

As shown in FIG. 1(b), a predetermined pressure (for example, about 5 Kt/
A gas (e.g., inert gas such as Ar or N2) is supplied into the steel pipe 1, and the lower disk 2 is turned upward and formed into a concave shape along the pressing die 9. Molding mold (
0 and press-forms the upper disk 4. At this time, the small diameter pipe 5 is closed with a cap (not shown) to prevent gas from leaking.

As a result, the upper and lower discs 4, 2 and the supplementary ring 7 are joined to form a recess 11 for forming a combustion chamber, and the recess 11 has the shape of the recess mold 10. The supplementary ring 7 creates a shape with a high center.

As shown in FIG. 1(C), after being taken out of the furnace and cooled, the bottle hole 6 is machined to a predetermined shape and dimension, and the outer circumferential surface of the steel pipe 3 constituting the head has a Kffl-shaped groove 1.
form 2.

As a result, the skirt portion having the bottle hole 6 and the recessed portion 11
It becomes a piston consisting of a head B having .

As described above, since the rigid pipes 1 and 3 are joined using the superplastic stainless steel discs 2 and 4, the joint strength of the steel pipes 1 and 3 is equal to that of the rigid pipe, and the strength of the piston is increased. .

In other words, the characteristics of superplastic stainless steel are as shown in Figure 2, and the proof stress (strength) is more than 5 times that of aluminum alloy pistons, and superplastic stainless steel exhibits low stress and high ductility under constant temperature conditions. Among the known ones + 000
It shows a remarkable elongation of ~3000%.

In addition, superplastic stainless steel has excellent diffusion bonding ability and has a bonding strength equivalent to that of the base metal.

Therefore, the steel pipe 1 and the steel pipe 3 can be joined with a joining strength equivalent to that of steel.

Effects of the Invention Since the steel pipes 1 and 3 are used, the piston can be made thin and lightweight, and since it is diffusion-bonded with the superplastic stainless steel disc 2.4, the joint strength can be increased and the entire piston can be made high in strength.

Carbon steel, tool steel, high-speed summer steel, etc. can be used as the material for the steel pipes 1 and 3, and the material for the skirt and head can be selected according to the requirements of the piston, but stainless steel has a lower coefficient of thermal expansion than aluminum. Since it is about 30% smaller and close to cast iron, even if a cast iron cylinder ζ is used, the gap between them can be made smaller and the combustion efficiency will be improved.

Compared to aluminum alloy pistons, they have higher strength and heat resistance even when the weight is almost the same, so they can be made lighter and more compact, and in turn, the engine itself can be made smaller.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and <c> are process order explanatory diagrams showing one embodiment of the present invention, and FIG. 2 is a chart showing an example of the tensile properties of superplastic stainless steel. 1 is a steel pipe, 2 is a disc, 3 is a steel pipe, 4 is a disc, 1
1 is the concave part, A is the skirt part, and B is the head part.

Claims (1)

[Claims] A disk 2 made of superplastic stainless steel is placed on a steel pipe 1 having approximately the same length as the skirt portion A, and a head B is placed on this disk 2.
A steel pipe 3 of approximately the same length is placed, and a disk 4 made of superplastic stainless steel is placed on top of it, and the whole is pressurized at a predetermined temperature and pressure to form a superplastic stainless steel disk 2,
The steel pipes 1 and 3 and the disks 2 and 4 are diffusion bonded using the diffusion bonding ability of step 4, and then the lower disk 2 is blow-molded upward and at the same time the upper disk 4 is pressure-formed downward. A method for manufacturing a piston, characterized in that the disks 1 and 2 are joined together, a concave portion 11 is formed, and the piston is then finished by machining.