JPH06117242A - Connection structure of exhaust system in internal combustion engine - Google Patents

Abstract

PURPOSE:To strengthen the connection part of the exhaust system and prevent the stress concentration at the weld part by increasing the thickness of the connection part as the exhaust tube, using a butted tube where the wall thickness of other parts is reduced, and coiling the thick connection part to the connected part. CONSTITUTION:In a connection part to hold the connecting part with the engine side and the middle part of the exhaust tube to a vehicle body, the wall thickness of the main part of an exhaust tube 10 is made small, and the wall thickness of the connection part to a flange joint 11 is made large when the flange joint 11 is fixed to the exhaust tube 10, and the part from this small wall thickness part 10a to the large wall thickness part 10b is made a wall thickness changing part 10c where the wall thickness is gradually changed. That means, in this exhaust tube 10, the small wall thickness part 10a and the large wall thickness part 10b are integrated without any joint part, and composed of a butted tube which is formed by the normal working method such as drawing. After the large wall thickness part 10b is inserted into a connecting hole 11a formed in the flange joint 11, the periphery is welded at the part X, and both parts 10, 11 are fixed to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust system connection structure for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 7, an exhaust system of an automobile has an engine 1, a flexible pipe 2, a sub muffler 3 and a main muffler 4 connected by exhaust pipes 5a to 5d, and a tail pipe 6 to the main muffler 4. It is configured by connecting.

In such an exhaust system, the exhaust pipe 5a
.About.5d and the tail pipe 6 need to be connected to the above-mentioned respective parts and the exhaust pipe holding flange joint 7 at the connection portions A to H. Conventionally, as a connecting structure of such a connecting portion, as shown in FIG. 8, a method of inserting the end portion of the exhaust pipe 5 into the flange joint 8 to weld and fix the entire circumference of the X portion, or as shown in FIG. ,
There is a method of connecting the exhaust pipe 5 and the flange joint 8 via another member 9 (for example, Japanese Utility Model Laid-Open No. 62-184127).

[0004]

In the conventional method shown in FIG. 8, since the cross-sectional area (wall thickness) changes abruptly at the entire circumference welded portion of the X portion, bending stress concentrates here, and the welded portion There is a problem leading to damage.

Further, in the conventional method shown in FIG. 9, it is possible to gradually reduce the cross-sectional change of the connection portion to alleviate the stress concentration as described above, but the structure becomes complicated and the processing cost and weight increase. In addition, the number of welded points increases, the reliability of strength decreases, and further, since the cross-sectional change is gradual, stress concentration may still occur, resulting in the problem of damage to the connection part.

Therefore, an object of the present invention is to propose a connection structure for solving the above-mentioned problems in an exhaust system of an internal combustion engine having large vibration.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an exhaust pipe, wherein the connecting portion has a thick plate and the other portions are thin butted. The present invention is characterized in that a pipe is used and the thick connecting portion is fitted to the connected component.

According to a second aspect of the present invention, the connected component is a flange joint, and the flange joint is fitted to a thick connecting portion of the exhaust pipe. According to a third aspect of the present invention, the connected component is a muffler, the exhaust pipe is a tail pipe attached to the muffler, and a thick connecting portion of the tail pipe is fitted to the muffler.

[0009]

By using a butted pipe whose connecting portion has a large plate thickness for the exhaust pipe, the connecting portion becomes strong. Further, by using the butted pipe, it is possible to moderate the change in the plate thickness from the thin part of the plate thickness to the thick part,
When the component to be connected is welded and fixed to the connecting portion of the changed portion, stress concentration at the welded portion is not caused.

Further, since the connecting portion requiring high strength is made thick, the other pipe portions can be made thin so that the weight can be greatly reduced. Furthermore, since the outer surface of the connecting portion can be bulged outward without changing the inner diameter of the connecting portion to a large thickness to form a thick wall, the flow area of exhaust gas is not narrowed and back pressure is not increased. Furthermore, if the tube of the butted pipe of the present invention is used for the tail pipe of the muffler, the natural frequency can be increased by the thick portion, and the length of the thick portion can be changed to suit the vehicle type. The frequency can be easily tuned.

[0011]

FIG. 1 shows a first embodiment of the present invention, which is an embodiment in which a flange joint 11 is fixedly mounted on an exhaust pipe 10. For example, a connecting portion A with the engine 1 side in FIG. At the connecting portion F for holding the middle of the pipe to the vehicle body,
This is a case where the flange joint 11 is fixedly installed in the exhaust pipe.

The exhaust pipe 10 has a thin main body, a thick connecting portion with the flange joint 11, and a gradual change in thickness between the thin portion 10a and the thick portion 10b. The wall thickness changing portion 10c is used, and the thin wall portion 10
A butted tube in which a and the thick portion 10b are integrally formed without a joint is used.

The butted pipe shown in FIG. 1 is formed by a conventional method such as drawing. The thick portion 10b which is the connecting portion of the exhaust pipe 10 is fitted into the connecting hole 11a formed in the flange joint 11, and the entire circumference is welded at the X portion to fix the two.

FIG. 2 shows another embodiment of the exhaust pipe,
A butted tube formed by a method of thickening the tube end is used. An example of this construction method will be described with reference to FIG. First, the end 12a of the exhaust pipe 12 made of a thin steel pipe is fitted into the clamp die 13 (the upper half of FIG. 3A), and then expanded by the first punch 14 (the lower half of the FIG. 3A). ) Do. Next, the second punch 15 having a diameter slightly larger than the inner diameter of the expanded tube portion 12b expanded as described above is press-fitted into the expanded tube portion 12b,
From the opening end side of the expanded pipe portion 12b, a part of the meat is pushed and moved to the inner part to collect and increase the thickness. The chain line in the upper half of FIG. 3B shows the first increase in thickness, and 12c shows the increase in thickness. Next, a third punch 16 having a diameter slightly larger than that of the second punch 15 is press-fitted into the expanded tube portion 12b in the same manner as described above, and the thickness is increased in the same manner as described above. Further, the punch diameter is gradually increased and the thickness increasing operation is performed several times to form a thick portion 12d having a required length L as shown in the lower half of FIG. 3B.

In this method, the inclined surface 13a of the clamp die 13 and the inclined end surfaces 14a to 16 of the punches 14 to 16 are used.
By grading the inclination angle of a, the change portion (inclined surface) 12f of the wall thickness between the thin wall portion 12e and the thick wall portion 12d of the exhaust pipe 12 formed as shown in FIG.
12h can be changed gently.

In FIG. 4, the thick portion 12d has an inner surface having the same diameter as the thin portion 12e, and the outer surface is swollen and enlarged. FIG. 5 shows the present invention applied to the tail tube of a muffler. In the present embodiment, 6 is a tail pipe, its main body portion 6a is formed in a thin wall portion 12e, and the connection portion 6b is formed in a thick wall portion 12d whose outer surface is bulged. 4 is a muffler, 4
a is an outer shell, 4b is an outer plate, and 4c is an outlet pipe. The connecting portion 6b of the tail pipe 6 is fitted to the outlet pipe 4c and fixed at the welded portion X. The thick portion 12d of the tail pipe 6 has the function of increasing the natural frequency of the tail pipe 6, and the thick portion 12d
The frequency can be tuned by changing the length L of the vehicle according to the vehicle type.

FIG. 6 shows a modification of the above-mentioned FIG.
The inner surface side is bulged to form the thick portion 12d.

[0018]

As described above, according to the present invention, the connection portion of the exhaust system becomes strong, and the stress concentration at the welded portion can be prevented to prevent the damage.

Further, the thickness of the portion other than the connecting portion can be reduced to achieve a great reduction in weight of the exhaust system, and since no member for thickening the connecting portion is used, further reduction in weight and cost can be achieved.

Furthermore, since the connecting portion can be made thick without reducing the inner diameter, a large flow passage area of the exhaust gas can be obtained, and a reduction in engine output due to an increase in back pressure can be prevented. Furthermore, in order to warm up the catalytic converter early, it is essential to reduce the heat mass of the upstream parts, but this also contributes greatly because the parts other than the exhaust pipe connecting part can be made thinner.

Further, by applying the present invention to the tail pipe of the muffler, there is an effect that the natural frequency of the tail pipe can be easily tuned according to the vehicle type, in addition to the above effects.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is an explanatory view for molding the butted pipe of the second embodiment.

FIG. 4 is a sectional view showing a third embodiment of the present invention.

FIG. 5 is a sectional view in which the present invention is applied to a tail tube of a muffler.

FIG. 6 is a cross-sectional view showing another embodiment in which the present invention is applied to a tail tube of a muffler.

FIG. 7 is a diagram showing an exhaust system to which the present invention is applied.

FIG. 8 is a cross-sectional view showing a conventional connection structure.

FIG. 9 is a sectional view showing another example of a conventional connection structure.

[Explanation of symbols]

 4 Muffler 6 Tail pipe 10, 12 Exhaust pipe consisting of butted pipe 11 Flange joint 12d Thick part 12e Thin part

Claims (3)

[Claims] 1. An exhaust pipe is a butted pipe in which a connecting portion has a thick plate thickness and other portions have a thin wall thickness, and the thick connecting portion is fitted to a component to be connected. Connection structure of exhaust system in internal combustion engine. 2. A connection structure for an exhaust system in an internal combustion engine, wherein the connected component in claim 1 is a flange joint, and a flange joint is fitted in a thick connecting portion of the exhaust pipe. 3. The internal combustion engine according to claim 1, wherein the connected component is a muffler, the exhaust pipe is a tail pipe attached to the muffler, and a thick connecting portion of the tail pipe is fitted to the muffler. Exhaust system connection structure.