JPH05214930A - Exhaust device for automobile - Google Patents

Abstract

PURPOSE:To make an exhaust pipe firm against vibration by changing its resonance frequency. CONSTITUTION:An exhaust pipe 10 which has a pair of cavity pipe sections 12 formed along the axial direction on the outer periphery of a main pipe 11 having a round cross section is installed on a car body frame 5 while the cavity pipe sections 12 are located in the direction where external force is applied to the exhaust pipe 10. Even when a resonance mode is generated on the car body frame 5, the main pipe 11 and the cavity pipe sections 12 are connected in the direction where the external force is applied to the exhaust pipe 10, the rigidity is large, and the deformation of the exhaust pipe 10 is prevented. No vibration noise is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle exhaust system using exhaust pipes connected to each other.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, an exhaust pipe 4 is connected to an engine 2 mounted on an automobile 1 via a flange 3 and a shock absorbing member 6 arranged on a body frame 5. Are suspended. The exhaust pipe 4 has a cylindrical shape and connects the converter 7 and the muffler 8 to each other. Further, since the exhaust pipe 4 is long in the front-rear direction of the vehicle body, it resonates with the vibration of the vehicle body to generate a resonance mode shown by a broken line as shown in FIG. Therefore, when the external force due to resonance is strong, the exhaust pipe 4 may be deformed. Therefore, the exhaust pipe 4 is reinforced by having a double pipe structure or a thickness t of 2t (see a and b in FIG. 7). In addition, a double pipe structure is formed in the muffler 8 (see Japanese Utility Model Publication No. 59-5143), and a partition is provided inside the outlet pipe of the muffler (see Japanese Utility Model Publication No. 61-197211). ).

Further, as shown in FIGS. 8 and 9, the lean reinforcement 9 is provided along the bent portion of the exhaust pipe 4.
Is attached, and the reinforcement 9 is attached to the connection portion with the muffler 8 to strengthen the attachment.

[0004]

However, if the exhaust pipe 4 has a double pipe structure or the like and the thickness t is 2t, the weight increases, and if the lean reinforcement 9 is used, the number of parts increases. The processing steps will be increased. In this way, the resonance frequency cannot be sufficiently increased due to manufacturing restrictions.

It is an object of the present invention to provide an exhaust system for an automobile using an exhaust pipe which is rigid in the diameter direction.

[0006]

In order to achieve the above object, the present invention provides an exhaust pipe in which a hollow pipe portion is formed at one or a pair along the axial direction on the outer peripheral surface of a main pipe having a round cross section, It is characterized in that the hollow pipe portion is positioned in a direction in which an external force is applied to the exhaust pipe and is installed on the vehicle body frame.

[0007]

Since the present invention is configured as described above, even if a resonance mode is generated in the vehicle body frame, the main pipe and the hollow pipe portion are connected in the direction in which the force is applied to the exhaust pipe, so that the rigidity is improved. It is large and deformation of the exhaust pipe is prevented.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, an exhaust pipe 10 is suspended from a vehicle body frame 5 via a cushioning member 6, and a hollow pipe portion 12 is continuously provided above and below a main pipe 11 as shown in FIG. In the embodiment, the radius r of the hollow tube portion 12 is d / 4, the outer shape is semicircular, and the thickness t is uniform.
In addition, the hollow tube portion 12 may be provided on only one of the outer circumferences, or the cavity tube portion 12 may have the radius r equal to that of the main tube 11 (see FIGS. 2B and 2C).

As shown in FIG. 1, the automobile 1 having the exhaust pipe 10 having the above-described structure is deformed due to the bending resonance frequency exerting an external force in the direction of the arrow, but the hollow pipe portion 12 is continuously provided and has a large rigidity. Hard to do. Further, as shown in FIGS. 3 and 4, the resonance frequency shifts to the higher side,
The muffled sound in the room can also be suppressed. In this way, by providing the hollow tube portions 12 in series, the bending rigidity in the deformation direction can be improved, and the vibration noise due to the exhaust system bending resonance can be reduced.

Here, the increasing weight ratio V of the exhaust pipe 10 of the embodiment and the conventional double pipe structure with increased rigidity will be described. However, the hollow tube portion 12 has an inner diameter r = d / 4, and is made a complete circle by two. Further, the thickness t is sufficiently smaller than the diameter d. A: Cross-sectional area of exhaust pipe of Example x L (overall length) B: Cross-sectional area of exhaust pipe of double pipe structure x L V = A / B = 2πr / 2π (d / 2) = (d / 4) / (D / 2) = 1/2 Therefore, the weight increase is half that of the conventional method.

Since it is not necessary to add the lean reinforcement 9, the working process is reduced and the number of parts is also reduced, so that workability is good. Further, since the exhaust gas passage has a round cross section as in the conventional case, it does not affect exhaust noise and engine output characteristics. Further, in the case of a long pipe on the intake pipe side of an engine or the like, the hollow pipe portion 12 is continuously provided as in the embodiment so that the pipe can be made lightweight and have high rigidity.

[0012]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, the rigidity can be increased by installing the hollow pipe portion according to the direction of the external force without increasing the thickness of the pipe over the entire circumference. Therefore, the deformation of the exhaust pipe is prevented. Therefore, the resonance frequency can be increased without significantly increasing the weight. Further, since the thickness can be reduced to be integrated, workability and workability are improved.

[Brief description of drawings]

FIG. 1 is a side view of an exhaust system for an automobile according to an embodiment of the present invention.

[Fig. 2] Various a, b, c of the exhaust pipe of the embodiment
FIG.

FIG. 3 is a graph showing changes in bending resonance frequency of the exhaust pipe of the example.

FIG. 4 is a graph showing the relationship between the indoor muffled sound of an automobile using the exhaust pipe of the embodiment and the engine speed.

FIG. 5 is a side view of a conventional automobile exhaust system.

FIG. 6 is a side view of a conventional automobile exhaust pipe.

FIG. 7 is a cross-sectional view of various types a and b of a conventional exhaust pipe.

FIG. 8 is a perspective view of a bent portion of a conventional exhaust pipe.

FIG. 9 is a perspective view of a conventional exhaust pipe and a connecting portion with a muffler.

[Explanation of symbols]

 5 Body frame 10 Exhaust pipe 11 Main pipe 12 Hollow pipe

Claims (1)

[Claims] 1. An exhaust pipe having a hollow pipe portion formed at one or a pair along an axial direction on an outer peripheral surface of a main pipe having a round cross section, and the hollow pipe portion is positioned in a direction in which an external force is applied to the exhaust pipe. The exhaust system for automobiles is characterized by being installed on the vehicle body frame.