JPH0280154A - Expendable pattern structure for cylinder block - Google Patents

Abstract

PURPOSE:To improve the hardness and wear resistance only in necessary cylinder liner part by forming coating layer of metal for hardening at the part corresponding to liner surface in the cylinder liner part formed with an expendable pattern. CONSTITUTION:On the inner face of the part 12 corresponding to the cylinder liner formed with the expendable pattern 11 for cylinder block, that is, on the part 12a corresponding to the liner surface, the coating layer 15 of the metal is formed. The metal is an element making pearlite of a cast iron structure, for example, Cu, Sn, Te, etc., and is stuck as metal powder. This expendable pattern 11 is embedded into molding sand, and by pouring molten metal from a sprue 9, the expendable pattern 11 is replaced with the molten metal. By this method, the cylinder block having the prescribed performance, which improves the hardness and wear resistance only to the necessary cylinder liner part, can be cast.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an evanescent mold structure used in evanescent model casting of an engine cylinder block, and in particular, to a structure in which the hardness of a cylinder liner portion is partially improved. , relates to an evanescent structure for a cylinder block.

[Conventional technology] Compared to the conventional sand casting method, the vanishing model casting method (CEPC method) has two advantages: ■ No core is required when manufacturing hollow parts, and ■ Adhesive is not mixed into the sand. It has various advantages such as being easy to collect and reuse, and being applicable to objects with complex shapes.For example, its development is progressing1. It is attracting attention as the Ha method for cylinder blocks, etc.

This vanishing model casting method usually involves placing an extinguishable polystyrene mold (Eps model) made of expanded polystyrene in the same shape as the cast product to be obtained in a casting container, and filling the casting container with casting sand to form the vanishing mold. This is done by burying the mold in casting sand, and then injecting molten metal through a Styrofoam sprue connected to the fugitive mold.

As a result, within the casting sand, the sprue and the fugitive mold are sequentially thermally decomposed, and these parts are replaced with the corresponding molten metal, producing the desired metal casting.

By the way, in order to cast the cylinder block of an engine by such an investment model casting method, there is a case where the cylinder liner is integrally formed with the cylinder block.

It is conceivable that a separate cylinder liner may be cast inside the cylinder block.

For example, the former cylinder block, in which the cylinder liner is integrally formed with the cylinder block, is as shown in FIG. In FIG. 3, 1 is a cylinder block, 2 is a cylinder liner in the upper part of the cylinder block, 3 is a water jacket formed around the cylinder liner, and 4 is a skirt part formed in the lower part of the cylinder block.

[Problems to be Solved by the Invention] Incidentally, cylinder liners are generally required to have high hardness and high wear resistance.

As a countermeasure to this problem, when the cylinder liner is integrally formed with the cylinder block by the investment casting method, it is conceivable to use a molten metal that becomes a hard and highly wear-resistant material after casting.

However, such molten metal, which becomes hard and wear-resistant after casting, is more expensive than manufacturing normal cast iron, and in particular, casting the entire cylinder block with such molten metal results in Even parts other than the liner that do not require high hardness or wear resistance will have high hardness and wear resistance, resulting in the unnecessary use of expensive molten metal.

Therefore, it is desired to develop a means to make only the cylinder liner part of the cylinder block high in hardness and wear resistance while casting the cylinder block by the lost model casting method.The present invention was developed in view of these problems. It was devised,
It is an object of the present invention to provide an evanescent structure for a cylinder block, which can increase the hardness and wear resistance of only the necessary cylinder liner portions.

[Means for Solving the Problems] Therefore, the disappearing structure for cylinder blocks of the present invention has the following features:
In the investment mold that is replaced with molten metal when casting the engine cylinder block as an investment model, a metal that can harden the liner surface is placed on a portion of the investment mold that corresponds to the liner surface of the cylinder liner portion of the cylinder block. It is characterized by a coating layer formed thereon.

[Function] In the above-described fugitive mold structure for cylinder blocks of the present invention, when molten metal is injected into the fugitive mold, the fugitive mold is not destroyed by the heat of the molten metal and is replaced by the molten metal, but the cylinder block A metal coating layer formed on a portion corresponding to the liner surface of the cylinder liner portion of the cylinder liner unit hardens the liner surface formed after the molten metal solidifies while bonding with the molten metal.

[Example 2] An extinguishable structure for a cylinder block as an embodiment of the present invention will be explained with reference to the following drawings. Fig. 1 is a longitudinal sectional view of the main part thereof, and Figs. 2 (a) to (d) show its function. FIG.

As shown in FIG. 1, the vanishing type 11 according to this embodiment is
This is for casting the engine cylinder liner integrally with the cylinder block, and is made of 1-foamed polystyrene (polystyrene), and is formed in almost the same shape as the cylinder block, which is the cast product to be obtained. Therefore, like the cylinder block 1 to be cast (see FIG. 3), this fugitive mold 11 includes a portion 12 corresponding to the cylinder liner 2 at the upper part of the cylinder block 1, and a water mold formed around the cylinder liner 2. It has a portion 13 corresponding to the jacket 3 and a portion 14 corresponding to the skirt portion 4 formed at the lower part of the cylinder block 1.

The inner circumferential surface 12a of the portion 12 corresponding to the cylinder liner of the fugitive type 11 (that is, the portion corresponding to the liner surface of the cylinder liner portion 2) is coated with a metal coating layer 1.
5 is formed. This metal is, for example, copper (Cu
), tin (Sn), tellurium (Te), and other cast iron pearlitizing elements, which are adhered to the inner circumferential surface 12a as metal powder to form the coating N15.

In addition, in FIG.
8 is the disappearing type 1 of runners 7a to 7c.
A gate 9 is provided at the connection portion with 1, and 9 is a sprue connected to the extinguishable mold 11.

Since the evanescent type structure for a cylinder block as an embodiment of the present invention is constructed as described above, this evanescent type 1
1, the cylinder block was cast as an expendable model as follows.

First, a mold coating agent (a solution containing a binder as a main component mixed with fine refractory particles) is applied to the entire surface of the fugitive mold 11.
Furthermore, this is dried.

The solution containing the binder 1 as a main component used at this time is an organic solvent that does not attack the dissipating mold 11, and examples of this solution include an aqueous solution or an alcohol solution. In the case of an aqueous solution, it is an aqueous solution containing a binder, a surfactant, and an antifoaming agent. Among these, starch, vinyl acetate, carboxymethylcellulose (CMC), etc. can be used as the binder, and cationic type as the surfactant. , anionic or amphoteric surfactants can be used, and as the antifoaming agent, commonly used ones such as alcoholic antifoaming agents or silicones can be used. Further, in the case of an alcohol solution, for example, one containing about 1 to 30% of vinyl acetate resin as a binder in alcohol can be mentioned, and in this case, a surfactant and an antifoaming agent are not necessary.

In addition, as the refractory fine particles used at this time, for example,
Examples include fine particles such as silica (Sin2), zirconia (ZrO2), or mica, but in the case of forging iron materials,
Usually, silica or zirconia is used, but in the case of forging aluminum-based materials, mica fine particles with a heat-insulating space are suitable.

After the surface treatment has been applied to the fugitive mold 11 in this way, in the subsequent process, the fugitive mold 11 is removed from the casting sand 16 together with the sprue 9, etc.
bury it inside.

That is, first, as shown in FIG. 2(a), the casting container 1
An appropriate amount of casting sand (casting sand to which a binder has not been added and mixed) 16 is stored in the lower part of the container 7, and the fugitive mold 11 is placed in the container 17 in a desired posture. At this time, for example, by placing the fugitive mold 11 while clamping a portion of the runner 7a near the sprue 9, the fugitive mold 11 can be prevented from being damaged.

Then, the container 17 is further filled with casting sand 16 (casting sand to which no binder has been added or mixed), and the fugitive mold 11 is completely buried.

The purpose of this filling with casting sand 16 is to ensure that the hollow part 12 of the part 12 corresponding to the water jacket of the fugitive mold 11 is filled with casting sand 16, and also to strengthen the bonding force between each particle of casting sand 16. In order to
Perform step 7 while shaking.

In this way, as shown in FIG. 2(b), the vanishing type 11
is buried in the casting sand 16, in the subsequent process, molten metal (in this case, molten iron-based metal) 5 is injected into the fugitive mold 11 through the sprue 9, and the fugitive mold 11 is buried in the molten metal. Replace with 5.

In other words, the metal molten 15 flows into the fugitive mold 11 through the sprue 9.
As the molten metal 5 is injected, the high-temperature molten metal 5 penetrates into the fugitive mold 11 that does not thermally decompose the sprue 9 and the runners 7a to 7c, and gradually thermally decomposes the fugitive mold 11. See Figure 2 (c)].

Then, this thermally decomposed part, that is, the sprue 9 and the extinguishing mold 1
The space where 1 was located is replaced by molten metal 5, and when this molten metal is cooled to a predetermined temperature, a desired metal casting (
In other words, the engine cylinder block 1 is manufactured [see FIG. 2(d)]. The thermally decomposed fugitive mold 11 and the like become gaseous and are discharged to the outside through gaps in the casting sand 16 and the like.

During this molten metal replacement, on the inner circumferential surface 12a of the portion 12 corresponding to the cylinder liner of the fugitive mold 11, the metal of the metal coating layer 15 promotes pearlite formation of the cast iron. That is, the metal of the coating layer 15 (Cu, Sn or Te)
) have lower melting points than cast iron, so they easily melt at the temperature of the molten metal 5 and melt into the molten metal 5, and form a layer of ferrite (pure iron) and cementite (Fe, C). It performs the function of agglomeration (that is, promotion of pearlite formation).

Therefore, the liner surface of the cylinder liner 2 of the cast cylinder block 1 and its vicinity are made of pearlite, which increases hardness and wear resistance.

Thereafter, the casting 10 formed by the runners 78 to 7C and the sprue 9 is removed from the casting 1 at the part where the gate 8 was, and the necessary parts of the casting 1, such as the cylinder liner, are polished and completed.

In this way, by performing the investment model casting method using this investment structure for cylinder blocks, it becomes possible to increase the hardness and wear resistance of only the necessary parts of the cylinder liner, at low cost and easily. Therefore, it is possible to cast a cylinder block with predetermined performance.

[Effects of the Invention] As detailed above, according to the fugitive structure for cylinder blocks of the present invention, in the fugitive mold that is replaced with molten metal when casting an engine cylinder block as a fugitive model, one of the fugitive molds is With a simple configuration in which a metal coating layer that can harden the liner surface is formed at a location corresponding to the liner surface of the cylinder liner portion of the cylinder block, the investment model casting method using the investment mold of this structure is possible. By doing so, it becomes possible to increase the hardness and wear resistance of only the necessary parts of the cylinder liner, and there is an advantage that a cylinder block having a predetermined performance can be easily cast at low cost.

[Brief Description of the Drawings] Figures 1 and 2 show an extinguishable structure for a cylinder block as an embodiment of the present invention. (d) is a longitudinal cross-sectional view of a main part explaining the action, and the third @ is a longitudinal cross-sectional view of a general cylinder block. 1.- cylinder block, 2- cylinder liner, 3-.
・Water jacket, 4-skirt, 5-molten metal (molten iron-based metal), 6-vibration device, 7a-7cm runner, 8-gate, 9-gate, 10-casting made by runner and gate Item, 11... Disappearance type, 12- Portion corresponding to the cylinder liner, 12a...- Inner peripheral surface of the portion corresponding to the cylinder liner (portion corresponding to the liner surface of the cylinder liner part) 13... ~ Water jacket Part corresponding to 14-.- Part corresponding to skirt part, 1
5-metal coating layer, 16...-casting sand, 17-
Casting container.

Claims (1)

[Claims] In the investment mold that is replaced with molten metal when casting the engine cylinder block as an investment model, a metal that can harden the liner surface is placed on a portion of the investment mold that corresponds to the liner surface of the cylinder liner portion of the cylinder block. A fugitive structure for a cylinder block, characterized by a coating layer formed thereon.