JPS59183964A - Squeeze casting of piston - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to squeezing of aluminum or aluminum alloy pistons of the type having inserts spaced axially from the crown of the piston, such as reinforcing piston ring groove inserts.
Squeeze casting of metals (ast, ing) is a process that has been known for many years. This is a method in which molten metal is fed into a die, the die is then closed, and pressure is applied to the molten metal as it solidifies. The applied force may be on the order of several hundred tons. Such solidification can produce castings that are stronger and particularly homogeneous in structure than similar castings produced by conventional gravity die casting.

Because of these advantages, skeeze casting has long been considered for the manufacture of aluminum or aluminum alloy pistons for internal combustion engines or compressors, because it produces pistons of superior strength than gravity die-cast pistons. This strength was previously only achievable through the use of more expensive and complex forging methods, and therefore offers the potential for the production of special purpose pistons, such as car pistons. It was just applied.

Although the objective of squeezing such pistons has existed for many years, widespread commercial use has not been achieved due to various manufacturing difficulties encountered.

Among these difficulties is the incorporation into squeezing cast pistons of inners that are axially spaced from the crown of the piston, such as piston ring groove reinforcing inserts. Such inserts are generally annular in shape and are made of a more wear-resistant metal than the aluminum or aluminum alloy of the piston. The inner is
It extends around the piston at a location between the bottom of the skirt and the crown and, in the completed piston, has one or more piston ring grooves formed in the inner.

British Patent Nos. 2090779A and 209078
No. 0A both relate to the incorporation of such inserts. In these specifications, the piston is squeeze cast crown-up (i.e., with the crown toward the top of the lower die member), and the inner has a tab that injects the molten metal into the lower die part, 1. before engaging the protrusion in the lower die member. This die part (the lower part of O is
It is sculpted to form the skirt of the piston.

After injecting the molten metal into the lower die member, the upper die member closes the die and applies pressure to the molten metal while it solidifies.

GB 2072065A also relates to the incorporation of such inserts. Again, the piston is squeez-cast using a crown amp with the inner placed on the protrusion of the young T that is integrally formed with the lower die member. Molten metal is injected into the lower die member, and the upper die member closes the die and applies pressure to the molten metal while it solidifies.

The squeegee casting methods described in these publications have a number of drawbacks.

First, the molten metal generally solidifies upward from the bottom of the die, and variations in the rate of solidification across the cross-section of the piston can occur. This is because the inner is facing the top of the casting where the change is greatest, so part of the insert is in the solidified metal and the other part is in the molten metal. This means that the insert can cause stresses that can cause it to warp, warp, and crack. This is because, in crown/tsuno casting, the molten metal at the depth of the pin below the insert shrinks during solidification and separates from the insert length, which is firmly supported by the protrusion of the lower lS die member. It gets even worse.

When the lower die member projection only provides support over a small portion of its circumferential length (typically about 4 degrees) and is no longer provided with downward support by the solidifying and shrinking metal;
The insert would likely become distorted, cracked or damaged by the squeezing force. This cannot be prevented by increasing the number or size of the support projections. This is because this at the same time prevents the downward movement of the insert by the solidifying and shrinking metal, which is important to obtain the necessary bond between the insert and the metal.

British Patent Nos. 2090779A and 209078
In 0A, it is attempted to overcome this shrinkage problem by arranging the tabs to break during solidification, thus allowing the insert to move. This arrangement does not resolve the condyle during coagulation differences (in fact, some protrusions may fail before others, increasing the risk of dislocation and cracking). Additionally, protrusions that do not break properly may damage the lower die member, which is clearly undesirable.

No provision is made in GB 2,072,065A to adjust for differential clotting or shrinkage.

The second disadvantage is that the part of the die that forms the skirt of the piston is at the lower end of the die, so that the first molten metal entering the die passes all the way through the die and reaches the part of the die that forms the skirt, filling the remaining part of the die and leaving the second part. The die member should not be under pressure until it is lowered and closes the die. Because of this, and because of the thinness of the piston skirt, the molten metal forming the piston skirt generally solidifies at least partially before pressure is applied. This results in the piston having a skirt portion that is not squeezy cast but merely gravity die cast, thus lacking the strength and homogeneous structure of the remaining portion of the piston. This can result in piston failure under severe conditions.

It is also disadvantageous that the inner faces the top of the die. This is because impurities such as scum and oxides tend to float to the top of the die, which can interfere with the bond between the cast metal and the insert and reduce the quality of the metal at the piston crown. The crown of the piston is the part of the piston that is subject to unfavorable conditions during use.

According to the present invention, there is provided a method for manufacturing a piston for an internal combustion engine or a compressor having a reinforcing inner spaced axially from the crown of the piston, the method comprising forming a piston with a υ crown by squeezing casting. Casting with down, the inner or reinforcement is positioned facing the bottom of the lower die member before it is filled by gravity with molten metal, and then the lower die member is placed in the upper die. It consists of closing with a member and solidifying the molten metal under pressure.

Furthermore, pistons for internal combustion engines made by the method of the invention are also within the scope of the invention.

The invention will now be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, the skies casting apparatus includes a lower die member 10.
and a movable upper die member 11 attached to the lower die member part.

The lower die member 10 has an inner shape that is the outer shape of the required internal combustion engine piston, and the upper die member 11 has a protrusion '12 that forms the required inner shape of the piston.

The lower die member 10 has a number of spaced apart lugs 13 adjacent the lower end of the lower die member 10, on which an annular reinforcing strip 14 is placed before casting. The reinforcing material 14 is
It may be of ferrous material and may be an annular piston ring groove reinforcing insert or an expansion control insert.

The molten metal 15 is then fed into the lower die member 10.

The amount of molten metal 15 is determined to ensure that there is sufficient, but not a large excess, to form a piston of the required dimensions.Then, in the first stage of movement, the upper die member 11 is from the retracted position shown in Figure 1 to the second
The upper die member 11 is moved to the position shown in the figure.
is adjacent to the surface of the molten metal. The speed of movement may typically be 200 mm per second, so there is minimal delay in the application of pressure to the molten metal. In the position shown in FIG. 2, the upper die member 11 slowly descends into the melt 15 in a second stage of movement until it reaches the position shown in FIG. The speed of this movement may typically be from 1 to 10 mm per second, depending on the geometry of the casting being made. The movement speed of the upper die member 11 in the second stage of movement is:
It matches as highly as possible with a satisfied foundry.

Upper die member 11 then applies a squeezing force, typically 200 to 600 tons, to the molten metal while it solidifies. This creates a strong, homogeneous structure. The contraction of the metal as it solidifies is absorbed by the movement of the upper die member.

The pressure is maintained until solidification is complete. The upper die member 11 is then raised and the casting piston is removed from the lower die member 10 for finish machining.

Since the insert 14 is located at the lower end of the lower gouging member 10, the first portion of the piston solidifies. This means that there is substantially no differential solidification around the insert, reducing insert distortion and cracking. Furthermore, since the depth of the metal below the insert is very small, the momentum induced by contraction is very small;
It is much smaller than if the insert were at the upper end of the lower gouer member 10. Incies 1 and 14 are the upper die member 11
The upper die member 11 and the insert 14 are far away from each other, so there is no possibility of interference between the upper die member 11 and the insert 14. There is also much less chance that impurities such as floats and oxides in the melt will interfere with the bond between the melt and the insert. The reason is that all these impurities float to the surface. Furthermore, the supply of molten metal into the lower die member 10 with minimal turbulence is provided by the unrestricted space provided by the inlet 14.

Additionally, there is a careful flow of the melt between the melt feeds and before the squeeze to ensure filling of the die. In crown upskize casting, where the insert is on top of the lower gouge, it is necessary to inject the molten metal into the center of the lower gouge so that the inner does not interfere with the flow of the molten metal. Also, this injection must be above the final level of the molten metal in the lower die member 10. This complicates injection and may cause undesirable turbulence in the molten metal within the lower die member 10.

In the crown down skies casting method described,
The molten metal can be fed into the lower goo member 10 at or near the wall of the die member 10 and the final metal liquid level.

For this reason, filling is much less complicated in crown upskies casting 9 and the piston skirt 17 (see FIG. 3), which also helps to minimize turbulence, is located at the upper end of the lower gouer member 10. . This means that the skirt is formed from the final portion of the molten metal that is injected into the lower die member 10. Because of this, and because the upper die member 11 enters the metal spool in the lower gouer member 10 before the metal has solidified, there is no possibility that the skirt metal will solidify before pressure is applied. This ensures that the p1 skirt is always fully squeezed. The skirt can be made as thin as necessary without the possibility of forming a heavy duty skirt.

It is clear that the upper and lower goo members 10.11 can be heated before squeezing to ensure that the early solidification of the molten metal 15 is free from spinal pressure. moreover,
Once pressure has been applied by the upper gouers 11, these gouers can be cooled during casting in order to ensure solidification of the molten metal as quickly as possible.

To facilitate the manufacture of pistons of various geometries, it is clear that the upper and lower gouging members can have any desired structure.Also, the piston ring groove reinforcing inserts can be of any desired shape. It is also clear that a similar and similar method can be used to incorporate expansion control inners (although in this case it is not necessary to support the insert on the upper gouging member).

[Brief explanation of the drawing]

The drawings show some preferred embodiments of the present invention, and FIG. 1 is a schematic cross-sectional view of a crown and down skies casting apparatus at the beginning of the skies casting process for molding pistons for internal combustion engines. and FIG. 2 is a cross-sectional view similar to FIG. 1 showing the apparatus at the end of the first stage, and FIG.
1 is a cross-sectional view similar to FIGS. 1 and 2, showing the apparatus at about the end of the 1-skies casting process; FIG. 10...Lower goo member, 11...Upper goo member, 12
. . . Projection, 13 . . Lug with spacer, 141.
Inner, 15...molten metal

Claims (1)

[Claims] 1. Incorporate into the piston a reinforcing insert (14) spaced axially from the crown of the piston, fill the piston with (15) by squeezing casting, and then insert the lower die member into the upper die. In a method for manufacturing a piston for an internal combustion engine or compressor, the piston is closed by a member (11) to solidify the molten metal under pressure, the lower die member (10)
forms the entire crown of the piston at its bottom and the skirt of the piston at its top, and inserts the insert into the bottom of the lower die member (10) before the lower die member (10) is filled with molten metal (15). A method for manufacturing a piston for an internal combustion engine or compressor, characterized in that the piston is positioned facing the piston. 2.-The movement of the upper die member (11) is in two stages, the first stage is a small one from the withdrawn position to the position adjacent to the surface of the molten metal (15), and the remaining movement is in the second stage. , the speed of the upper die member (15) in the first stage is faster than the movement speed of the upper die member (11) in the second stage,
The movement speed of the upper die member (11) in the second stage is:
2. The method of claim 1, wherein the upper die member is slow enough to prevent brushing of the melt as it enters the melt (15). 6. The method of claim 1, wherein the speed of the upper die member (11) in the first stage is approximately 200 +nrn per second. 4. A method according to claim 2 or 6, wherein the speed of the upper die member (11) in the second stage is between 1 and 10 mm per second. 5. Attach the upper die member (11) to the lower die part (O (10)
6. Method 6 according to any one of claims 1 to 4, in which the upper and lower die members (10, 11) are cooled during solidification of the molten metal. Method 7 according to any one of the ranges 1 to 5
The lower die member (10) has a projection (13) for supporting and positioning the piston ring groove reinforcing insert (14)' therein.
The method according to any one of paragraph 6. 8. The method according to any one of claims 1 to 6, wherein the inner length is formed integrally with a support for positioning the inner in the lower die member (10). .