JP2678640B2 - Casting mold. - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a piston of an internal combustion engine, and more particularly to a casting mold in which main parts made of a plurality of materials are integrally cast as a whole.

<< Prior Art >> Conventionally, as a piston for an internal combustion engine, a piston made of an aluminum alloy, which is easy to reduce in weight, is often used in order to cope with a higher speed.

By the way, the piston receives high-temperature and high-pressure gas generated in the combustion chamber as a pressing force on the crown surface and transmits the resultant force to the crankshaft side through the connecting rod, and reciprocally slides in the cylinder.

For this reason, the piston as a whole is required to have sufficient mechanical strength, in particular, its crown surface is required to have sufficient heat resistance due to being exposed to high temperature and high pressure, and moreover, the outer peripheral surface of the piston is in sliding contact with the inner wall surface of the cylinder. Therefore, sufficient abrasion resistance is required.

Particularly, in the piston, a ring groove is formed on the side of the outer peripheral surface of the piston facing the crown surface to prevent gas leakage between the inner wall of the cylinder and the outer peripheral surface of the piston, and the piston ring is fitted therein. However, when an aluminum alloy is used as the main base material of the piston, when the piston ring is directly fitted in the ring groove and used, wear and fatigue occur early, and this crown face facing part of the piston The durability will be greatly affected.

Therefore, usually, the piston ring is attached to the piston through the wear ring (ring carrier) of iron type or aluminum type which is harder than the main base material and has good wear resistance on the opposite side of the crown surface, and the resistance of the ring groove is Abrasion resistance is secured.

However, when the ring carrier is cast and wrapped in the aluminum alloy piston body, if the two metals do not fit well, peeling occurs between the interfaces of the two metals due to the difference in the coefficient of thermal expansion, resulting in a decrease in mechanical strength. Sometimes. Therefore, the conventional ring carrier is formed by surface treatment (aluminizing treatment) with a metal film that is easily diffusion-bonded to the base material before casting, thereby ensuring the bonding strength.

Further, as the ring carrier, in particular, a foam metal with high wear resistance is used, which is cast around the main base material, thereby ensuring wear resistance of the ring groove and the joint strength between the ring carrier and the main base material. The proposal to secure the above is disclosed in JP-A-60-175748 and JP-A-60-168959.

Furthermore, by forming the crown facing portion by melt forging FRM and improving the mechanical strength of that portion, or by remelting the aluminum alloy layer with good wear resistance on the crown facing portion (remelt It is also known that a ring groove having a high durability is formed on the same portion by the treatment).

<< Problems to be Solved by the Invention >> However, in order to carry out the cast turning of the ring carrier as in the prior art, prior to the cast turning, casting of the ring carrier itself, machining, pretreatment, aluminizing treatment are required, There are problems that the number of pre-processes is large, the cost is high, and the yield is low.

Further, in the case of the molten metal forging method and the method of strengthening the wear resistance of the piston while maintaining the mechanical strength of the crown surface facing portion by the remelting treatment, there is a problem that a special treatment device is required. .

An object of the present invention is to provide a casting die that can integrally cast a piston that can obtain different characteristics required for each main part of the piston by using a plurality of raw materials.

<< Means for Solving the Problem >> A casting mold according to the present invention is provided with a fixed mold and a top surface of the fixed mold slidably opposed to each other. A pair of open / close movable molds that form a space to be injected, an upper mold that covers the upper surface of the open / close movable mold, and a movable wall provided in the fixed mold, and an annular wall on the lower outer periphery of the space when moved upward. And a first hot water supply port which is formed in the opening and closing movement type and is always open to the space, and the opening and closing movement type, the switching movement type moves upward and the annular wall forms the space. When it is inside, it is characterized by being provided with a second hot water supply port whose opening is closed by the annular wall.

<< Operation >> A pair of opening / closing movable dies are brought into contact with each other on the fixed die, the upper die is placed on the opening / closing movable die, and the switching movable die is moved upward to close the second hot water supply port, resulting in a space. Is formed as a first shape space, and a first product portion having the shape of the first shape space is formed. Next, when the switching movable die is moved downward, a second shape space is formed on the outer periphery of the lower end of the first product portion, and the second hot water supply port opens in the second shape space. When the second molten metal is poured from the second hot water supply port, the second product portion is integrally formed on the outer periphery of the lower end of the first product portion.

<< Example >> The piston shown in FIG. 1 is cast using the casting die of the present invention. In this piston, the body 1 is composed of a body portion 3 having a crown surface 2 and a skirt portion 4 thereunder, and in the whole, the main portion is made of an aluminum alloy, and the crown surface facing portion C is a main base material. It is cast from a different material than the alloy.

Here, the main part of the piston is AC-8A or AC according to JIS standard.
An aluminum alloy for casting of -8C is adopted, and an aluminum alloy having a high wear resistance as a different material is used for the crown surface facing portion C (for example, the ratio of silicon and magnesium is relatively high, and the hardness of its own and heat treatment Those that are easy to strengthen) are used.

The main body 1 has a flat crown surface 2, and a top ring groove 13, a second ring groove 14, and an oil ring groove 15 having a well-known configuration are formed on the outer peripheral surface 12 thereof in this order from above. Here, the crown surface facing portion C, which is the annular outer peripheral wall on the crown surface 2 side of the piston, can only accommodate the width t sufficiently larger than the depth S of each ring groove and all three ring grooves 13, 14, 15. It is configured to have a vertical width h. In addition, each ring groove has a shape such that a top ring (not shown), a second ring, and an oil ring can be fitted to them,
Is formed.

Here, a casting mold for casting the piston of FIG. 1 is shown in FIG. This casting mold includes a fixed mold 5, left and right open / close movable molds 6 and 7, an upper movable mold (upper mold) 8, a switching switching movable mold 9 supported by the fixed mold 5, and a switching movable mold 9. It is composed of an air cylinder 10 as a switching means and a well-known melt supply means (not shown).

The fixed die 5 is supported by a base (not shown), an air cylinder 10 is held vertically in the center thereof, and a switching movable die 9 is attached to the upper end of its piston rod. Switching movement type 9
Is a base 90 having a pair of through holes 16 formed in the center thereof.
1 and an annular protrusion 902 protruding from the upper surface thereof, and is supported in the accommodation hole 17 of the fixed mold 5 so as to be vertically movable. Moreover, a pair of brackets 18 are loosely fitted into the through holes 16, and the brackets 18 integrally couple the piece-shaped fixed die 19 above the switching movable die 9 to the fixed die 5. Here, the switching movable die 9 is supported so as to be switchable between a projecting position P1 shown by a solid line and a retracted position P0 shown by a two-dot chain line in FIGS. 4 (a) and 4 (b).

The left and right open / close movable dies 6, 7 are attached to each other, and a casting surface F of the cast piston is formed between the opposing surfaces of the two. Moreover, the left open / close movable die 7 is formed with the main molten metal passage 20 following the upper movable die 8, and the left openable movable die 6 is formed with the different molten metal passage 21 following the upper movable die 8. The upper moving path 8 is formed with the main molten metal passage 20 and the respective pouring ports 22, 23 of the different molten metal passage 21.

The left and right moving paths 6 and 7 and the upper moving die 8 are respectively closed by the air cylinders (not shown) at the mold clamping position (the position shown by the solid line in FIG. 3) and the mold opening position (shown by the two-dot chain line in FIG. 3). It is supported so that it can be moved.

In this case, the open / close movable molds 6 and 7 are at the mold clamping position,
When the switching movable die 9 is at the retreat position P0, the first casting space A1 and the second casting space A1 in which the piston body 1 can be completely cast in the casting die.
A synthetic space with the casting space A2 is secured. Further, when the switching movable die 9 is switched to the projecting position P1, only the first casting space A1 is secured in the casting die (see FIGS. 4 (a) and 4 (b)). reference).

 Here, the operation of the casting mold of the present invention will be described.

Here, the piston body 1 made of an aluminum alloy is cast using a casting die as shown in FIG.

First, the opening and closing movable molds 6 and 7 in the casting mold are clamped,
At the same time, the switching movable die 9 is driven by the air cylinder 10,
It is held at the protruding position P1. As a result, in the casting mold,
Only the first casting space (see Fig. 4 (b)) A1 is secured,
The first mold clamping step is performed.

Next, the first pouring step of pouring the main molten metal through the gate 22 is started. In this case, the main molten metal is supplied to all the spaces except the second casting space A2 closed by the switching movement die 9 and the dissimilar molten metal passage 21, and enters the solidification.

Next, after the solidification of the main melt, at least a predetermined time for solidifying only the outer shell of the first casting space A1 of the piston,
Drive the air cylinder 23 to move the switching movable die 9 to the retracted position P0.
Then, the second mold clamping step is achieved (see FIG. 4 (a)). As a result, an annular second casting space A2 surrounded by the outer shell generated by solidification of the main molten metal, the left and right opening / closing moving dies 6, 7 and the switching moving die 9 is secured in the casting die.

After this, a second pouring step of pouring a different molten metal having excellent wear resistance into the second casting space A2 from the gate 23 is performed. By this, for the outer shell of the main molten metal that has not entered into complete solidification,
The different kinds of molten metal completely infiltrate without any gap, and both alloys are diffusion-bonded to achieve integral casting.

Furthermore, after performing the second pouring step and immediately after the molten metal near the sprue 23 solidifies, the air cylinder 23
Is driven to be pushed from the retracted position P0 side toward the protruding position P1 side. As a result, the pressurizing step of switching the switching movable die 9 to the pressurizing position P2 is performed. By this pressurizing step, the different molten metal is pressed into the gap of the outer shell of the main molten metal of the first casting space A1 more completely without pressure, and the diffusion bonding of both alloys is surely performed, and Casting of an integrated piston is achieved.

After that, the cast piston is subjected to a mold opening process and a grinding process to have its outer shape adjusted, and in particular, a plurality of ring grooves 13, 14 and 15 are formed in the crown surface facing portion C, and the production of the piston is completed. To do.

The thus manufactured piston has a sufficiently high mechanical strength and can suppress wear and fatigue of each ring groove of the crown-face facing portion C, thereby improving the durability of the piston.

In the above-mentioned process, the pressurizing step was performed after the second pouring step, but instead of this, if the dynamic casting characteristics are sufficiently utilized in the second pouring step, for example, the length of the different molten metal passage 21 in the height direction is increased. If it is made sufficiently large, it is possible to achieve sufficient integration of both alloys by itself, and it is not necessary to perform the pressurizing step.

<< Effects of the Invention >> As described above, according to the casting mold of the present invention, the fixed mold,
A pair of open / close movable molds which are slidably opposed to the upper surface of the fixed mold and form a space into which molten metal is injected in the central portion when the mutually opposed surfaces contact each other, and the upper surface of the open / close movable mold. An upper mold for covering the upper mold, a switching movable mold that is movably provided in the fixed mold and forms an annular wall on the lower outer periphery of the space when moved upward, and an open-close movable mold that is always open in the space. A first hot water supply port and a second hot water supply port which is formed in the opening and closing movable type and whose opening is closed by the annular wall when the switching movable type moves upward and the annular wall is in the space. Since it is constituted by including, the piston having high mechanical strength and durability can be cast at a low cost at a high yield.
In particular, when a different kind of molten metal having high wear resistance is used as the different type of molten metal, there is an effect that the weight of the piston can be reduced and the ring groove can be easily anti-weared to further improve the durability of the piston.

[Brief description of the drawings]

FIG. 1 is a sectional view of a piston obtained by the method of the present invention,
FIG. 2 is a process explanatory view showing an example of the method of the present invention, FIG. 3 is a schematic sectional view of a casting apparatus for casting the piston of FIG. 1, and FIGS. 4 (a) and 4 (b) are FIG. FIG. 3 is an operation explanatory view of the casting apparatus of FIG. 1 ... Piston body, 5,6,7,8 ... Casting mold, 9 ... Switching movable type, A1 ... 1st casting space, A2 ... 2nd casting space, C ... Crown facing portion.

Claims (1)

(57) [Claims] 1. A utility model registration claim. A fixed die and a space provided slidably opposite to the upper surface of the fixed die. A space into which molten metal is poured is provided in the center when the opposite surfaces abut each other. A pair of opening and closing movable dies to be formed, an upper die for covering the upper surface of the opening and closing movable die, and a switching movement that is movably provided in the fixed die and forms an annular wall on the lower outer periphery of the space when moving upward. A mold and a first opening / closing movable mold that is always open to the space
A hot water supply port and a second hot water supply port which is formed in the open / close movable type and whose opening is closed by the annular wall when the switching movable type moves upward and the annular wall is in the space. A casting mold characterized by having it.