JPH0385320A - Exhaust gas purifying device for internal combustion engine - Google Patents

Abstract

PURPOSE:To oxidize the exhaust gas to be purified efficiently by forming an intermediate film on the inner and outer surfaces of an inner tube provided inside of an exhaust pipe of an internal combustion engine, while impregnating a catalyst solution in a carrier layer formed on the surface of the intermediate film, and burning it. CONSTITUTION:An inner tube 5 having multiple vent holes 4 is provided inside an exhaust pipe 3 of an internal combustion engine with the predetermined space 6. The inner and outer surfaces of the inner tube 5 is coated with metal such as aluminna non-toxic against a catalyst by aluminize method to form an intermediate film 7. Furthermore, the surface of the intermediate film 7 is flame sprayed with metal oxide such as aluminna to form a carrier layer 8 having multiple vacancies. The carrier layer 8 is impregnated with catalyst solution, and it is dried and burned to fix particles of catalyst 10 on the carrier layer 8. The exhaust gas flowing inside the exhaust pipe 3 thereby contacts the catalyst 10, and the combustible component thereof can be oxidized to be purified.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an exhaust gas purification device for an internal combustion engine.

[Conventional technology]

In internal combustion engines installed in automobiles, etc., a catalyst body with a catalyst attached to a ceramic honeycomb-shaped carrier is attached to the exhaust manifold that connects to the exhaust port of the internal combustion engine, and exhaust gas is passed between the catalyst bodies to carry out the oxidation reaction. This is done to purify unburned components in the exhaust gas. In addition, in small internal combustion engines installed in motorcycles, etc., a catalyst body with a catalyst agent attached to a material such as glass wool is stretched on the inner surface of the exhaust pipe that connects to the exhaust port of the internal combustion engine, and the The exhaust gas is brought into contact with the catalyst body to purify unburned components. For example, Japanese Patent Publication No. 59-1324, Japanese Patent Publication No. 6
See Publication No. 1-96120.

[Problem to be solved by the invention]

In the honeycomb-shaped catalyst body, exhaust gas passes through a large number of honeycomb-shaped small holes, so the flow path area decreases and resistance increases, resulting in a decrease in engine output. Particularly in small engines, the impact of a drop in performance due to a drop in output is significant. Another disadvantage is that the exhaust manifold becomes large and heavy. Exhaust pipes covered with cloth-like catalyst bodies are expensive because it is troublesome to hold down the catalyst body, and there are also problems with heat resistance and durability.

In view of this, this invention installs an inner pipe with a large number of ventilation holes on the inside of the exhaust pipe with gaps in between, and attaches a catalyst to the inner pipe to purify the exhaust gas by hitting the catalyst with less resistance. To provide an exhaust gas purifying device for an internal combustion engine which is easy to manufacture, inexpensive and lightweight, has good adhesion and is highly durable.

[Means to solve the problem]

In order to achieve the above object, an exhaust gas purification device for an internal combustion engine according to the present invention is configured such that an inner pipe having a large number of ventilation holes is installed with gaps in the exhaust pipe connected to the exhaust port of the internal combustion engine. An intermediate film made of aluminum or the like, which is non-toxic to the catalyst, is formed on the inner and outer surfaces of the tube, a carrier layer is formed by spraying a metal oxide such as alumina on the surface of the intermediate film, and the carrier layer is impregnated with a catalyst solution. This is done by drying and firing the exhaust gas, which then hits the catalyst to purify the exhaust gas flowing through the exhaust pipe.

[For production]

The inner pipe installed inside the exhaust pipe has many ventilation holes and a gap between it and the inner surface of the exhaust pipe, so exhaust gas can flow in and out of the ventilation holes, and the surface of the inner pipe is Easy to hit the catalyst. The intermediate film that coats the surface of the inner tube is non-toxic to the catalyst, prevents the catalyst from coming into direct contact with the inner tube, prevents the catalyst from causing a chemical reaction, and prevents metal ions from eluting, increasing durability. be able to. Since the carrier layer provided on the intermediate film is formed by thermal spraying a metal oxide, a large number of pores are formed, which improves the adhesion of the catalyst solution.

Furthermore, the carrier layer can be firmly adhered to the carrier layer by mitigating thermal distortion caused by thermal shock and thermal cycles by means of the intermediate film.

Then, the exhaust gas flowing through the exhaust pipe is applied to the catalyst in the inner pipe, causing an oxidation reaction and purifying unburned components in the exhaust gas.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

An exhaust pipe 3 is connected to an exhaust port 2 of an internal combustion engine 1.

Inside the exhaust pipe 3, an inner pipe 5 in which a large number of ventilation holes 4 are formed by bunching is attached with gaps 6 provided. The exhaust pipe 3 and the inner pipe 5 are made of steel plates or stainless steel plates, and are molded separately into left and right parts, which are then welded together.The mating edges of the inner pipe 5 are placed between the mating edges of the exhaust pipe 3. It is designed to be attached by sandwiching it between the two and welding it together. As shown in FIG. 2, the inner and outer surfaces of the inner tube 5 are coated with a metal such as aluminum, which is non-toxic to the catalyst, by an aluminizing method or the like to form an intermediate film 7. Then, as shown in FIG. 3, a metal oxide such as alumina is thermally sprayed onto the surface of the intermediate film 7 to form a carrier layer 8 having many pores. Next, as shown in FIG. 4, the carrier layer 8 is immersed in the catalyst solution 9 to impregnate the carrier layer 8 with the catalyst solution 9. When this is dried and fired, a catalyst 1 is deposited on the carrier layer 8 as shown in FIG.
0 grains stick. The intermediate film 7 can prevent the catalyst 10 from coming into contact with the inner tube 5 and the like, thereby preventing chemical reactions and elution of metal ions, thereby increasing durability. Further, the intermediate film 7 alleviates thermal distortion caused by thermal shock and thermal cycles, maintains a state in which the carrier layer 8 is firmly adhered, and prevents peeling. The intermediate film 7 is
A material having a coefficient of thermal expansion between the inner tube 5 and the carrier layer 8 is selected.

Similarly, an intermediate film 7 and a carrier layer 8 may be formed on the inner surface of the exhaust pipe 3, and particles of the catalyst 10 may be fixed thereto.

Exhaust gas flowing through the exhaust pipe 3 hits the catalyst 10 in the inner pipe 5 and causes an oxidation reaction to purify unburned components in the exhaust gas. A fat expansion chamber 11 is connected to the rear end of the exhaust pipe 3, and a muffler 12 is further connected to the fat expansion chamber 11.
The exhaust gas is muffled and released from the rear end of the muffler 12.

〔Effect of the invention〕

As explained above, since the present invention is configured as described above, exhaust gas can be purified by hitting the catalyst in the inner pipe provided with ventilation holes, and there is little resistance to the flow of exhaust gas, and there is no reduction in output. You can make it smaller.

Moreover, the intermediate film can prevent deterioration of the catalyst, and also prevent peeling of the carrier layer, allowing for strong adhesion and durability. Furthermore, the inner tube can be easily installed, inexpensively, and lightweight.

[Brief explanation of drawings]

The figures show one embodiment of the present invention. Fig. 1 is a cross-sectional view of an exhaust pipe, Fig. 2 is a partial sectional view of an inner pipe coated with an intermediate film, and Fig. 3 is a portion of a carrier layer provided on an inner pipe. 4 is a partially enlarged sectional view of the carrier layer impregnated with the catalyst solution, FIG. 5 is a partially enlarged sectional view of the carrier layer with the catalyst fired, and Fig. 6 is a partially longitudinal sectional view of the exhaust pipe. Figure 7 is an overall side view. 1... Internal combustion engine, 2... Exhaust port, 3... Exhaust pipe,
4...Vent hole, 5...Inner pipe, 6...Gap, 7...
- Intermediate film, 8... Carrier layer, 9... Catalyst solution, 10
···catalyst.

Claims (1)

[Claims] An inner pipe with many ventilation holes is installed in the exhaust pipe connected to the exhaust port of the internal combustion engine with gaps between them, and an intermediate film of aluminum or other non-toxic material is formed on the inner and outer surfaces of the inner pipe. A carrier layer is formed by thermally spraying metal oxide such as alumina on the surface of the intermediate film, and the carrier layer is impregnated with a catalyst solution and dried and fired to purify the exhaust gas flowing in the exhaust pipe by hitting the catalyst. An exhaust gas purification device for an internal combustion engine, characterized by: