JPH0663823U - Engine exhaust gas conduit - Google Patents

Abstract

(57) [Summary] [Object] To provide an exhaust gas conduit of an engine capable of preventing a decrease in temperature of exhaust gas, a decrease in activity of a catalyst, and also emission of exhaust noise. An exhaust gas conduit comprising a pipe part and flanges attached to both ends thereof and connecting an exhaust port of a cylinder head of an engine and a catalyst holder via the flanges, the pipe part being an outer pipe and an inner pipe. And a double tube consisting of
While filling the heat insulating material between the outer pipe and the inner pipe, a flange that is fastened to the flange of the catalyst holder of the exhaust gas conduit,
The inner surface of the exhaust gas pipe is fixed to the outer pipe end with a gap from the inner pipe surface.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an engine exhaust gas conduit.

[0002]

[Prior art]

 FIG. 3 is a sectional view in the vicinity of a conventional exhaust gas conduit in an engine. The exhaust gas 3 discharged from the exhaust port 2 of the cylinder head 1 is guided to the catalyst holder 5 via the exhaust gas conduit 4, and NOx in the exhaust gas 3 due to the catalyst 6 contained in the catalyst holder 5 is introduced. After reduction and oxidation of CO and HC, they are released into the atmosphere through the muffler. The exhaust gas conduit 4 is formed by welding flanges 4b and 4c to both ends of a pipe 4a having a wall thickness of 2 mm. One end is the cylinder head 1 and the other end is the flange 5a of the catalyst holder 5 at the other end through the flanges 4b and 4c. Is fastened to.

[0003]

[Problems to be Solved by the Invention]

 By the way, in the exhaust gas conduit 4, the exhaust gas 3 discharged from the exhaust port 2 of the cylinder head 1 reaches the catalyst 6 in the catalyst holder 5 via the exhaust gas conduit 4 before reaching the exhaust gas conduit 4 The heat is dissipated and the temperature drops when it reaches the catalyst 6. In order for the catalyst 6 to function effectively, it needs to be maintained at a predetermined temperature or higher, and the activity decreases when the temperature becomes lower than the predetermined temperature. Therefore, immediately after the engine starts, the temperature of the exhaust gas will drop and the activity of the catalyst will drop, making it impossible to comply with exhaust gas regulations.

The causes of the heat radiation of the exhaust gas are: (1) Since the thickness of the exhaust gas conduit 4 is as thick as 2 mm, the heat capacity of the conduit 4 increases and the heat is taken away by the gas conduit 4. (2) Since the exhaust gas conduit 4 is not kept warm, the heat radiation from the outer periphery of the conduit 4 is large. (3) The flanges 4b and 4c are welded to both ends of the exhaust gas conduit 4, and in particular, the flange 4c of the catalyst holder 5 that is fastened to the flange 5a is integrated with the flange 5a and has a large surface area. The heat radiation from the flanges 4c and 5a is large. And so on.

In order to prevent such heat radiation, for example, as in the hollow double exhaust pipe 7 disclosed in Japanese Utility Model Publication No. 63-98426 shown in FIG. A double pipe composed of a pipe 8 and an outer pipe 9 may be used, or a hollow double pipe such as an inner pipe 13 and an outer pipe 14 may be used as in the exhaust pipe 12 of Japanese Utility Model Publication No. 56-612323 shown in FIG. There is a means such as enclosing a heat insulating material 15 between them, but in each of the above double pipes, since the flange 11 or 16 is fixed to the end of the double pipe, the heat of the gas inside the pipe is 8 and 13 and the flanges 11 and 16 are diffused, and the temperature drop of the gas in the pipe is inevitable. Further, in the exhaust gas conduit 4, exhaust noise is radiated through the pipe portion of the exhaust gas conduit 4, and countermeasures against the noise are urgently needed.

The present invention has been made to solve the above-mentioned problems in the conventional exhaust gas conduit. It is possible to prevent the temperature of the exhaust gas from decreasing and the activity of the catalyst to decrease, and also to prevent the emission of exhaust noise. The aim is to provide a possible exhaust gas conduit.

[0007]

[Means for Solving the Problems]

 To achieve the above object, the present invention comprises a pipe portion and flanges attached to both ends of the pipe portion, and connects an exhaust port of an engine cylinder head and a catalyst holder through the flange. In the exhaust gas conduit, the pipe part shall be a double pipe consisting of an outer pipe and an inner pipe, and a heat insulating material shall be filled between the outer pipe and the inner pipe, and shall be fastened to the catalyst holder flange of the exhaust gas pipe. The flange to be attached is characterized in that it is fixed to the end of the outer pipe with a gap between its inner surface and the inner pipe surface of the exhaust gas conduit.

[0008]

[Action]

 Since the exhaust gas conduit according to the present invention has a double tube and a heat insulating material is filled between the outer pipe and the inner pipe, heat dissipation from the surface of the exhaust gas conduit is prevented. Furthermore, since the flange that is fastened to the flange of the catalyst holder of the exhaust gas conduit is fixed to the end of the outer pipe with a gap from the inner pipe of the exhaust gas conduit, the heat of the exhaust gas is It does not dissipate into the atmosphere from the part through the flange. Furthermore, by making the pipe part a double pipe and filling a heat insulating material between the outer pipe and the inner pipe, it is possible to prevent exhaust noise from being radiated to the outside and to suppress the occurrence of vibration.

[0009]

【Example】

 FIG. 1 is a cross-sectional view of an exhaust gas conduit according to an embodiment of the present invention, in which 1, 2, 3 and 6 indicate the same reference numerals as those of the conventional apparatus or the corresponding parts. The exhaust gas conduit 20 is a double tube having an inner tube 21 having a thickness of 0.3 to 0.4 mm and an outer tube 22 having a thickness of 0.7 mm, and the exhaust gas conduit 20 is provided at the end on the cylinder head 1 side. The flange 23 is welded to the inner and outer tubes, the end 21a of the inner tube 21 on the side of the catalyst holder 25 is a free end, and the flange 24 is fixed to the outer tube 22. The flange 24 is welded to the end portion of the outer pipe 22 with a gap t between the inner surface 24 a and the surface of the inner pipe 21. The flange 26 of the catalyst holder 25 is also fixed to the holder 25 with a gap t between the inner surface 26a and the surface of the inner pipe 21. A ceramic heat insulating material 27 is filled between the inner pipe 21 and the outer pipe 22 of the exhaust gas conduit, and the end portion is plugged with a heat-expandable ceramic mat 28.

Since the pipe portion of the exhaust gas conduit 20 is a double pipe consisting of an inner pipe 21 and an outer pipe 22, and a heat insulating material 27 is filled between the inner pipe and the outer pipe 21, 22 of the exhaust gas pipe 20, Heat dissipation from the surface is prevented. Further, since the inner surfaces 24a and 26a of the flange 24 of the exhaust gas conduit 20 and the flange 26 of the catalyst holder 25 are arranged with a gap t from the surface of the inner tube 21, the heat of the inner tube 21 is conducted to the flanges 24 and 26. As a result, the heat radiation by the flanges 24 and 26 is greatly reduced. Since one end 21a of the inner pipe 21 is a free end, there is no problem even if the inner pipe 21 expands due to heat. Furthermore, since the pipe portion is a double pipe, and the ceramic-based heat insulating material 27 is filled between them, it has the effect of sound insulation and damping.

Further, as is clear from the situation of the temperature rise of the catalyst immediately after the start shown in FIG. 2, the exhaust gas conduit according to the present invention is used for the line P showing the temperature rise of the catalyst inlet in the conventional device. In the line Q indicating the temperature rise when the temperature rises, the temperature rises immediately after the start.

[0012]

【The invention's effect】

 According to the present invention, in the exhaust gas conduit of an engine, the pipe portion is a double pipe of an outer pipe and an inner pipe, a heat insulating material is filled between the outer pipe and the inner pipe, and the flange of the catalyst holder is fastened. Since the inner surface of the flange is fixed to the outer pipe end with a gap from the inner pipe surface of the exhaust gas conduit, the following excellent effects were obtained.

(1) Since the heat dissipation of the exhaust gas in the exhaust gas conduit is prevented and the temperature of the exhaust gas does not decrease, the catalyst temperature immediately rises to its activation temperature even immediately after the start. Therefore, it is possible to immediately deal with exhaust gas cleaning. (2) Compared with a catalyst with a heater, cost, development man-hours, outfitting and weight can all be reduced. (3) Radiated sound from the exhaust system can be reduced. (4) Noise can be reduced, which significantly improves the commercialability of the engine. (5) Since the exhaust gas temperature does not easily drop, the branch section can be extended to improve the output.

[Brief description of drawings]

FIG. 1 is a sectional view of the vicinity of an exhaust gas conduit according to an embodiment of the present invention.

FIG. 2 is a diagram showing the effect of the present invention.

FIG. 3 is a cross-sectional view in the vicinity of a conventional exhaust gas conduit.

FIG. 4 is a cross-sectional view of a conventional exhaust pipe.

FIG. 5 is a cross-sectional view of a conventional exhaust pipe.

[Explanation of symbols]

 20 Exhaust Gas Conduit 21 Inner Tube 22 Outer Tube 23 Flange 24 Flange 25 Catalyst Holder 26 Flange 27 Ceramic Insulating Material 28 Heat-Expandable Ceramic Mat

Claims (1)

[Scope of utility model registration request] 1. An exhaust gas conduit comprising a pipe part and flanges attached to both ends of the pipe part, and connecting the exhaust port of a cylinder head of an engine and a catalyst holder through the flanges, wherein the pipe part is provided. A double pipe consisting of an outer pipe and an inner pipe is filled with a heat insulating material between the outer pipe and the inner pipe, and the flange of the exhaust gas conduit, which is fastened to the flange of the catalyst holder, has an inner surface and an exhaust gas. An exhaust gas conduit for an engine, wherein the gas conduit is fixed to an outer pipe end with a gap between the gas conduit and an inner pipe surface.