JPS6268668A - Manufacture of exhaust manifold - Google Patents

Abstract

PURPOSE:To remove entirely the sand of a core and to form an air insulating layer having a high insulating degree by providing as a core a heat resistance insulating material in advance, on a part where the sand of the air insulating layer is apt to remain, which is formed between an inner shell and an outer shell. CONSTITUTION:The first core is formed by providing a heat resistance insulating material 7 on the outside of the inlet part 6b and outlet part 6a of an inner shell 6. Subsequently, the inner shell 6 is integrated into the outside case together with the insulating member 7 for forming the first core, sand is pressed into the outside part of the inner shell 6, and by removing the outside case, the second core consisting of the insulating member 7 for forming the first core, and the sand is formed. The second core is integrated into the upper and the lower casting molds, an outer shell 11 is formed in the outside part of the inner shell 6 by pouring a molten metal from a pouring gate, and subsequently, the casting molds are released, and the second core and the outer shell 11 are formed integrally. The sand of the second core is removed through the hole which is formed in the outer shell 11, and closing up the hole, an exhaust manifold is completed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an exhaust manifold, and particularly to a method for manufacturing an exhaust manifold, and in particular, a method for manufacturing an exhaust manifold. When forming a heat insulating layer on an exhaust manifold, an air heat insulating layer and a solid heat insulating layer can be integrally formed, and sand in the core forming the air heat insulating layer can be completely removed. Regarding manufacturing methods.

[Prior Art 1] As a measure against exhaust gas between internal combustion lines in automobiles, etc., it is necessary to maintain the exhaust gas at a high temperature in order to promote the temperature rise of the catalyst. Therefore, it is effective to provide the exhaust manifold that forms the exhaust system with a heat insulating structure so that the exhaust gas passing through the exhaust manifold does not radiate heat.

Therefore, conventionally, a solid heat insulating material layer is formed on the outer side of the exhaust manifold to cover it, or an inner shell is molded to form an exhaust passage through which exhaust gas passes, and the outer side of this inner shell is It is known that the outer shell is integrally cast in order to form a predetermined air insulation layer in the outer shell. To form an air insulating layer covering the outer part of the inner shell through which exhaust gas passes, the outer shell is cast with a sand core interposed between the inner shell and the outer shell. , which is molded by removing the core after the outer shell is molded.

[Problem to be Solved by the Invention 1] By the way, when considering the degree of insulation of the exhaust manifold, air has the lowest thermal conductivity as shown below.

Therefore, covering the entire outer part of the exhaust manifold with a solid heat insulating material has the problem that a sufficient heat insulating effect cannot be obtained. In addition, when forming an air insulation layer between the inner shell and the outer shell, the sand in the core interposed between the inner shell and the outer shell may be baked into the outer shell or the inner shell after casting. There was a problem in that sand remained in the space between the shell and the shell, making it impossible to completely remove it. There is a problem in that the degree of insulation cannot be improved due to the sand remaining between the inner shell and the outer shell.

Furthermore, Japanese Patent Laid-Open No. 54-46130 proposes a method for manufacturing a warm-up exhaust manifold.

This proposal is based on the inner core 1 as shown in FIGS. 8 and 9.
is molded from a heat-resistant metal plate, this inner core 1 is set inside the core a, the outer case 2 is cast on the outside of the core a, and finally the sand in the core a is removed to create a warm-up exhaust. The manifold 3 is manufactured. By this manufacturing method, a heat insulating air layer is formed between the inner core 1 and the outer case 2.

In this proposal, as shown in Fig. 10, when forming the heat insulating air layer, a gap between the inner core 1 and the outer case 2 is created so that sand in the core a interposed between the inner core 1 and the outer case 2 can be easily discharged. A sufficient gap e is formed on the inlet section C side and the outlet section d side. Therefore, in this conventional example, exhaust gas enters into the heat insulating air layer through these gaps e, and there is a problem in that it is difficult to obtain a sufficient heat insulating effect. Further, inserting the boat 4 into the inlet portion C as shown in the illustrated example results in an increase in cost due to an increase in the number of parts.

Furthermore, as shown in FIG. 9, the flange protrusion 5 provided on the inner core 1 makes it possible to center the inner core 1 on the outer case 2; There was a problem in that the sand of the core a was burned and remained in the bent portion or the gap, which caused a reduction in the degree of insulation.

[Objective of the Invention 1] The present invention has been devised to effectively solve problems in conventional exhaust manifold manufacturing methods.

An object of the present invention is to provide air insulation between the inner shell and the outer shell when integrally casting the inner shell of the exhaust manifold through which exhaust gas passes and the outer shell to form a heat insulating layer covering the inner shell. This makes it possible to integrally form the air insulation layer with the solid insulation layer, completely removes the sand core that forms the air insulation layer, and eliminates any sand remaining in the core, creating an exhaust with high insulation effects. A method for manufacturing a manifold is provided.

[Summary of the Invention] In order to achieve the above object, the present invention includes molding an inner shell with a metal tube and interposing a core made of sand and a heat-resistant heat insulating material on the outer side of the inner shell. After the outer shell is cast, sand from the core is removed to form an air insulation layer and a heat insulation layer between the inner shell and the outer shell. In order to prevent the sand from the core that forms this layer from remaining in the air insulation layer formed between the inner shell and the outer shell, heat-resistant insulation material is provided as a core in advance in areas where sand tends to remain. This makes it possible to completely remove sand from the core, forming a highly insulating air insulation layer.

[Example] An example of the method for manufacturing an exhaust manifold according to the present invention will be described in detail below with reference to the accompanying drawings.

First, as shown in FIG. 2, the inner shell 6, which essentially forms an exhaust gas passage through which exhaust gas passes, is molded from a metal tube with excellent heat resistance, such as stainless steel. In the illustrated example, the inner shell 6 is formed by a tube branched from an outlet portion 6a into four inlet portions 6b.

The inner shell 6 molded in this manner is provided with a heat-resistant heat insulating member γ. As the heat-resistant heat insulating member 7, for example, fibrous alumina or the like is used. As shown in the illustrated example, this heat-resistant heat insulating member 7 is provided on the outer side of the inlet portion 6b and outlet portion 6a of the inner shell 6, and forms a first core.

Next, the inner shell 6 and the heat-resistant heat insulating member 7 forming the first core are assembled into the outer case 8, as shown in FIG. At this time, the inner shell 6 is centered at a predetermined position with respect to the outer case 8 so that a uniform gap is formed between the inner shell 6 and the outer case 8.

After the inner shell 6 is centered and positioned at a predetermined position within the outer case 8, sand 9 is press-fitted into the outer side of the inner shell 6 and filled. That is, as shown in FIG. 4, sand 9 is filled along the outer side of the inner shell 6, and the outer case 8 is
By removing the sand 9, a second core made of the heat-resistant heat insulating member 7 forming the first core and sand 9 is molded.

The second core is molded so that the heat-resistant heat insulating member 7 forming the first core is connected and continuously covers the outer circumference of the inner shell 6 along the outer circumference thereof.

The outer case 8 is provided with a plurality of holes 8a for forming a second core of uniform sand 9 on the outer side of the inner shell 6.

After the second core containing the first core and covering the inner shell 6 is molded in this way, the outer shell 11 covering the second core is cast as described later.

First, the second core is assembled into the upper and lower molds 10 as shown in FIG. The second core is centered within the mold 10 so that a void is formed on its outer side.

Thereafter, by pouring metal from the sprue 10a of the mold 10, an outer shell 11 is formed on the outer side of the inner shell 6.

At this time, the mold 10 is provided with a plurality of protrusions 10b radially inward so that holes 11a for removing the sand 9 of the second core are provided in the molded outer shell 11.

By releasing the mold 10 after the outer shell 11 is cast,
The second core and the outer shell 11 that covers it are integrally molded.

Next, as shown in FIG. 6, only the sand 9 of the second core is removed through the plurality of holes 11a formed in the outer shell 11. For example, the cast surface is finished by shot blasting.

After only the sand 9 of the second core is removed, the outer shell 11
The hole 11a formed in the hole 11a is closed. As shown in FIG. 7, these holes 11a are filled with thermosetting plastic. In other words, it will be sealed.

By closing the hole 11a formed in the outer shell 11, the exhaust manifold according to the present invention is completed.

That is, as shown in FIG. 1, an exhaust manifold 12 is completed in which the inner shell 6 and the outer shell 11 that covers the outer side of the inner shell 6 are integrated.

By removing the sand 9 of the second core, an air insulation layer A is formed between the inner shell 6 and the outer shell 11, which covers the outer side of the inner shell 6 to insulate them.

In addition, a heat insulating material layer B made of a heat-resistant heat insulating member 7 formed as a first core is formed between the inner shell 6 and the outer shell 11, thereby providing heat insulation.

In particular, as shown in FIG. 1, the insulation layer B is formed in areas where the sand 9 of the second core is likely to seize during casting of the outer shell 11, in areas between the air insulation layers A, or where sand 9 is poured from the outside. By providing the first core in advance in a portion that is difficult to remove, the sand 9 of the second core when forming the air insulation layer A can be completely removed.

Therefore, the insulation layer B serves as a core for molding the outer shell 11 before it is cast, and after casting, it serves as a core for forming the outer shell 11, and together with the air insulation layer A, it acts as a bond between the inner shell 6 and the outer shell 11. In between, a heat insulating layer with low thermal conductivity, that is, a high heat insulating layer is formed.

In this way, the present invention makes it possible to form the air insulation layer A for insulating them between the inner shell 6 and the outer shell 1 by a simple method, and to heat-proof the areas where sand 9 tends to remain. By forming the heat insulating material layer B made of the heat insulating member 7, the degree of heat insulation can be improved. Therefore, the temperature of the exhaust gas passing through the exhaust gas 1 manifold go 2 can be maintained at a high temperature, and the temperature increase of the catalyst can be promoted.

[Effects of the Invention 1 Below-L In short, the present invention exhibits the following excellent effects.

(1) After casting the outer shell with sand and heat-resistant heat insulating material interposed on the outer side of the inner shell, an air heat insulating layer is formed between the inner shell and the outer shell by removing the sand. This simplifies the production of air insulation layers.

(2) Since a heat insulating layer is formed between the inner shell and the outer shell in areas where sand tends to remain, sand can be completely removed and the degree of heat insulation can be improved.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the Exis 1 to manifold completed by the manufacturing method of the present invention, Fig. 2 is a schematic diagram showing the inner shell, and Fig. 3 is a schematic diagram showing the inner shell assembled in the outer case. , Figure 4 is a schematic diagram showing the core with the inner shell filled with sand, Figure 5 is a schematic diagram showing the core assembled in the mold, and Figure 6 is the inner shell and outer shell integrated. A schematic diagram showing the state, Figure 7 is an enlarged view showing the main part of Figure 6, Figures 8 and 9.
1 and 10 are schematic diagrams showing a conventional example. In the figure, 6 is an inner shell, 7 is a heat-resistant heat insulating material, 9 is sand, 11 is an outer shell, 12 is an exhaust manifold, A is an air heat insulating layer, and B is a heat insulating layer.

Claims (2)

[Claims] (1) After molding the inner shell with a metal tube and inserting a core made of sand and heat-resistant heat insulating material on the outside of the inner shell, casting the outer shell, A method for manufacturing an exhaust manifold, characterized in that an air heat insulating layer and a heat insulating material layer are formed between the inner shell and the outer shell by removing the above. (2) Manufacture of the exhaust manifold according to claim 1, wherein the heat-resistant heat insulating material of the core is formed in areas where sand is baked during casting of the outer shell or in areas where it is difficult to extract sand to the outside. Law.