JPH06226400A - Manufacture of draft tube - Google Patents

Abstract

PURPOSE:To manufacture a draft tube without faulty parts in the passages by dividing the draft tube, which is an assembly with plural gas passages, into plural gas passages, forming a film molding, which is constituted of hollow parts in the shape of divided plural gas passages and is made of a lost foam material, and thereby forming a lost foam pattern. CONSTITUTION:A draft tube which is an assembly of plural gas passages is divided into plural gas passages, and film moldings 23, 25 are formed which are constituted of hollow parts in the shape of each gas passage and made of a lost foam material. Foaming bodies 27, 29 are integrated around the film moldings 23, 25 to form lost foam pattern elements 31, 33; each lost foam pattern element is bonded to form a lost foam pattern 1, which is arranged in sands, and by pouring molten metal into it, a draft tube is made. That is, the lost foam pattern elements corresponding to a first and a second branch tubes 7, 9 are bonded and integrated, and the lost foam pattern 1 is formed. The flange 35 of the first branch tube 7 side and the flange 39 of the second branch tube 9 side are superposed, and the joining part 43 is bonded with an adhesive. Likewise, the joining part 45 of the flange 37 and the flange 41 is bonded with the adhesive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ventilation pipe having a plurality of gas passages, and more particularly to a method for manufacturing a ventilation pipe having no obstruction in the gas passages.

[0002]

2. Description of the Related Art Vent pipes having a plurality of gas passages include exhaust pipes and intake pipes used in internal combustion engines.
These are branch pipes in which a plurality of gas passages are assembled or a collection of branch pipes. For example, a dual type exhaust manifold is a collection of two branch pipes that are bifurcated. This is manufactured, for example, by the disappearing model casting method. FIG. 8 shows a vanishing model 101 for manufacturing a dual type exhaust manifold, and the vanishing model 101 is formed of a vanishable foam. First, it has a first flange 103 connected to the cylinder head of the engine and a second flange 105 connected to the exhaust pipe.
Two holes are formed in the flange 105. The first flange 103 and the second flange 105 are the first
The branch pipe 107 and the second branch pipe 109 are connected by two branch pipes. Each of the branch pipes 107 and 109 has a base portion 111 and 113 and two bifurcated portions 115,
117, 119, 121, and the base 11 of each branch pipe
1, 113 are connected to the holes of the second flange 105, and
The branches 115, 117, 119 and 121 are the first flange 1.
It is connected to the 03 hole and is integrated.

Next, a conventional vanishing model 101 for a dual type exhaust manifold and a vanishing model casting method using the vanishing model 101 will be described. First, as shown in FIG. 9, the ventilation pipe is divided into a first branch pipe 107, a second branch pipe 109, a first flange 103 and a second flange 105. The first and second branch pipes 107 and 109 are divided into halves along the gas flow direction without separating the base portion and the branch portions, and the first vanishing model element 123, the second vanishing model element 125, and the third vanishing model element. The element 127 and the fourth disappearance model element 129 are divided. Then, the first to fourth vanishing model elements 123, 125, 127, 1
Each of 29 is formed into a predetermined shape by foam molding or the like.
The first flange 103 and the second flange 105 are also formed by foam molding or the like. Then, the first vanishing model element 123 and the second vanishing model element 125 are superposed and adhered with an adhesive, and the third vanishing model element 127 and the fourth vanishing model element 129 are superposed and adhered with an adhesive. Thus, the vanishing model element of the first branch pipe 107 and the second branch pipe 109 is obtained.

Next, these vanishing model elements are inserted into the holes of the first flange 103 and the second flange 105 and bonded with an adhesive. The vanishing model 101 as shown in FIG. 8 is completed as described above, and then the vanishing model 101 is used to perform vanishing model casting to cast a product having the same shape as the vanishing model. still,
A method for casting such a dual type exhaust manifold is disclosed in Japanese Patent Laid-Open No. 3-99747.

[0005]

The above-mentioned conventional structure has the following problems. That is, the disappearance model 101 is formed by dividing it into six members as described above and adhering them with an adhesive. However, when such an adhesive is used, the amount of the adhesive becomes a problem, and for example, as shown in FIG. Among them, those protruding outside the vanishing model can be scraped off, but those protruding inside 131 cannot be easily scraped off. In particular, in the case of the dual type exhaust manifold, burrs project to the gas passage 133, which is the most important functional part of the ventilation pipe, and an obstacle is created. On the contrary, when the amount of adhesive is small,
As shown in 1, a dent 135 is generated on the adhesive surface,
A depression is formed in the gas passage 133, and an obstacle is created.

The present invention has been made on the basis of such a point, and an object of the present invention is to provide a method for manufacturing a ventilation pipe having no obstruction in the gas passage in manufacturing a ventilation pipe in which a plurality of gas passages are assembled. To provide.

[0007]

In order to achieve the above object, a method of manufacturing a ventilation pipe according to the present invention is such that a ventilation pipe in which a plurality of gas passages are assembled is divided into a plurality of gas passages and the shape of each gas passage is changed. A film-shaped molded body made of a vanishable material having a hollow portion is formed, a foam is integrated around the film-shaped molded body to form a vanishing model element, and the vanishing model elements are bonded to form a vanishing model. It is characterized in that it is formed, placed in sand, and the molten metal is poured to cast the ventilation pipe.

[0008]

First, a ventilation pipe having a plurality of gas passages is divided into a plurality of gas passages to form a film-shaped molded body made of a fusible material having a hollow portion in the shape of each gas passage. This molding is performed using a blow molding method or the like. Next, the foam is integrated around the film-shaped molded body to form a vanishing model element. This is performed by an insert molding method or by dividing a foam into halves and forming them by foam molding and bonding them. Next, each vanishing model element is bonded to form the vanishing model. As a result, it is not necessary to bond the gas passages, which are the functional portions of the ventilation pipe, to each other, so that it is possible to manufacture a ventilation pipe having no obstacle in the gas passage.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention will be described below with reference to FIGS.
An example will be described. 1 and 2 show a vanishing model 1 for dual type exhaust manifold casting, and FIGS. 3 to 6 show cross sections of the branch pipes. First, the vanishing model 1 shown in FIG. 2 has a first flange 3 connected to an engine cylinder and a second flange 3 connected to an exhaust pipe.
The flange 5 and the first flange 3 at four locations, the second
The flange 5 is formed with two holes. The first flange 3 and the second flange 5 are connected by two branch pipes, a first branch pipe 7 and a second branch pipe 9. Each branch pipe 7, 9 has a base portion 11, 13 and two bifurcated branch portions 15, 17, 19, 21, respectively, and the base portions 11, 13 of each branch pipe are in the holes of the second flange 5. Connected,
Further, each branch portion 15, 17, 19, 21 is connected to the hole of the first flange 3.

Next, the vanishing model 1 for the dual type exhaust manifold and the vanishing model casting method using the vanishing model 1 will be described. First, the ventilation pipe is divided into a first branch pipe 7 and a second branch pipe 9, and as shown in FIG. 3, a film-shaped molded body 2 having a hollow portion in the shape of a gas passage of each branch pipe 7, 9.
3 and 25 are formed. The film-shaped molded bodies 23 and 25 are molded by the blow molding method. First, a hollow portion having the same shape as the shape of the gas passages of the branch pipes 7 and 9 is formed inside the blow mold. A hollow extinguishing material is placed in the hollow portion, and air or the like is blown into the hollow portion, so that the extinguishing material is formed into a thin film along the shape of the hollow portion. As a result, the film-shaped molded bodies 23, 25 having smooth inner surfaces and having the predetermined shapes of the gas passages of the branch pipes 7, 9 are obtained.

Next, as shown in FIG.
Foams 27, 29 are integrated around 3, 25 to form vanishing model elements 31, 33. This is done by the insert molding method. First, a hollow portion having the same shape as the predetermined outer shape of the branch pipe is formed inside the foaming mold. Both ends of the hollow portion are formed in the same shape as part of the first flange 3 and the second flange 5 formed at both ends of the branch pipes 7 and 9. Next, the film-shaped moldings 23 and 25 are arranged in the hollow portion, the space between the hollow portion and the film-shaped moldings 23 and 25 is filled with foam beads, and steam is blown to foam and mold. is there. Thereby, vanishing model elements 31 and 33 in which the film-shaped molded bodies 23 and 25 and the foamed bodies 27 and 29 are integrated are formed. Further, both ends of the disappearance model elements 31, 33 are flange portions 35, 37, 39, 4 having the same shape as a part of the first flange 3 and the second flange 5 formed at both ends of the branch pipe.
1 is integrally formed.

Next, as shown in FIG. 2, the disappearance model elements 31 and 33 corresponding to the first and second branch pipes 7 and 9 are bonded and integrated to form the disappearance model 1. That is, the flange portion 35 on the side of the first branch pipe 7 and the flange portion 39 on the side of the second branch pipe 9 are overlapped with each other and the joint portion 43 is bonded with an adhesive, and the flange portion 37 on the side of the first branch pipe 7 is also provided. , 37 and the flange portion 41 on the side of the second branch pipe 9 are superposed on each other, and the joint portion 45 is bonded by an adhesive. There are three bonded portions, and there is no bonded portion in the gas passage 49 which is the functional portion of the ventilation pipe.

Next, as shown in FIG. 5, the vanishing model 1 is placed in the sand 47 and the molten metal is poured. This method is the same method as the conventional disappearance model casting method manufacturing method.First, attach the sprue part to the disappearance model and apply a coating agent,
This is placed in a flask and filled with sand 47. Next, the molten model 1 disappears by pouring the molten metal through the sprue part,
The part is filled with molten metal. As a result, the branch pipe 51 having a predetermined shape is cast as shown in FIG.

According to this embodiment, the following effects can be obtained. First, when a ventilation pipe such as a dual type exhaust manifold is manufactured by the disappearance model casting method, it is divided into a first branch pipe 7 and a second branch pipe 9 and has a hollow portion in the shape of a gas passage of each branch pipe. The film-shaped molded bodies 23 and 25 made of a vanishable material are formed, and the foamed bodies 27 and 29 are integrated around the film-shaped molded bodies 23 and 25 to form vanishing model elements 31 and 33. 31,
Since 33 is adhered to form the disappearance model, it is not necessary to adhere the gas passage 49, which is a functional portion, and it is possible to obtain a product having no obstacle in the gas passage 49.
Also, the bonding work is omitted for the gas passage,
Since there are few bonding points, the labor required for bonding can be greatly reduced.

Next, a second embodiment will be described with reference to FIG. In the case of the first embodiment, the film-shaped moldings 23, 25
Although the insert molding method is used to integrate the foams 27 and 29 in this example, in the case of this embodiment, a method is used in which the foams are divided and the foam-molded ones are bonded together. That is, the foams 27 and 29 are divided into halves along the gas flow direction without separating the base portions and the branch portions of the branch pipes 7 and 9 to form the foam elements 53 and 55 each having a predetermined shape. To do. The molding is performed by an ordinary foam molding method. Then, the foam element 5 is formed around the film-shaped moldings 23 and 25.
3, 55 are overlapped and the joint part 57 is adhered by the adhesive 59. In the case of the present embodiment, since the foam is integrated with the periphery of the film-shaped molded bodies 23 and 25 by adhesion, the adhesive 59 may protrude to the outside of the disappearing model, but the adhesive does not protrude to the inside. It is possible to obtain a product having no obstacle in the gas passage 61.

The present invention is not limited to the above embodiments. For example, in the present embodiment, an example of manufacturing a 4-cylinder dual-type exhaust manifold in which two branch pipes are assembled has been shown, but the present invention can be applied to the case where the number of cylinders is different or other types of ventilation pipes are used. Can be applied. For example, a branch pipe having a large number of branch portions or a collection of a branch pipe and a single pipe may be used.

As the method for molding the film-shaped molded article, a molding method such as a vacuum molding method or an injection molding method may be used in addition to the blow molding method. Also, as a method for integrating the film-shaped molded product and the foamed product, various methods can be adopted without being limited to the insert molding method and the bonding method.

[0018]

As described above in detail, according to the method for manufacturing a ventilation pipe of the present invention, a ventilation pipe in which a plurality of gas passages are assembled is divided into a plurality of gas passages to form a hollow portion having a shape of each gas passage. The exfoliated material is formed into a film-shaped molded body, the foam is integrated around the film-shaped molded body to form a vanishing model element, and the vanishing model element is adhered to form the vanishing model. Therefore, it is possible to manufacture a ventilation pipe having no obstruction in the gas passage.

[Brief description of drawings]

FIG. 1 is a perspective view showing a vanishing model element formed in the shape of a branch pipe according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a vanishing model formed in the shape of a ventilation pipe in the first embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a film-shaped molded body in the first embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a first embodiment of the present invention in which a film-shaped molded product and a foamed product are integrated.

FIG. 5 is a cross-sectional view showing a state of casting in the drawing showing the first embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a product cast by the drawing showing the first embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a second embodiment of the present invention in which a film-shaped molded product and a foamed product are integrated.

FIG. 8 is a perspective view of a vanishing model showing a conventional example.

FIG. 9 is an exploded perspective view showing a vanishing model element in a conventional example.

FIG. 10 is a cross-sectional view of a vanishing model in the case where a large amount of adhesive is used in a conventional example.

FIG. 11 is a cross-sectional view of a vanishing model in a case where the amount of adhesive is small, showing a conventional example.

[Explanation of symbols]

 1 Disappearance Model 23 Membrane Formed Body 25 Membrane Formed Body 27 Foamed Body 29 Foamed Body 31 Disappearance Model Element 33 Disappearance Model Element 43 Sand 45 Vent Pipe 49 Gas Passage

Claims (1)

[Claims] 1. A ventilation pipe having a plurality of gas passages is divided into a plurality of gas passages to form a film-shaped molded body made of a fusible material having a hollow portion in the shape of each gas passage. A foam pipe is formed by integrating foam around the molded body to form a vanishing model element, adhering each vanishing model element to form a vanishing model, and arranging this in sand and pouring molten metal. A method for producing a ventilation pipe, wherein the method is a method of casting.