JPH037532Y2 - - Google Patents

Description

[Detailed explanation of the idea] (Industrial application field) The present invention relates to an improvement in a vehicle exhaust pipe structure.

(Prior art) As shown in FIG. 4, the exhaust pipe 2 of the automobile engine 1 is provided with a flexible tube 3 as a vibration-proof connecting member. The tube 3 has a plurality of bendable ring-shaped bellows parts 4, .
The outer periphery of the tube 3 is covered with a scale net 5.

However, as shown in FIG. 6, the flexible tube 3 is removed from the open end 2c of the upstream exhaust pipe 2a.
When the exhaust gas flow enters the opening end 2 at high speed,
A low-frequency vortex is generated in the exhaust gas flow by the ring-shaped bellows portion 4 near c.

Due to this vortex generation phenomenon and the resonance of the flexible tube (chamber) 3, abnormal noise may be generated from the surface of the flexible tube (chamber) 3 (sounding phenomenon).

For this reason, if the bellows part of the flexible tube is made of a spirally wound multilayer structure (see Japanese Utility Model Application Publication No. 56-70111), no vortex generation phenomenon will occur and no sound generation will occur. It is difficult to manufacture, and there is a risk of exhaust gas leaking from the seams, and there is a further problem that the weight increases.

Therefore, as shown in Fig. 7, a structure has been proposed in which liners 6, 6 are placed inside the flexible tube 3 to cover the bellows part 4 (as shown in
55-110723), since it is necessary to assemble the liners 6, 6 into the flexible tube 3, there are problems in that assembly is difficult and the weight increases.

(Purpose of the invention) The present invention was made to solve the above-mentioned conventional problems, and aims to suppress the sound generation phenomenon by adding a modification to the open end of the exhaust pipe.

(Structure of the invention) For this reason, the present invention provides a turbulence that causes disturbance to the exhaust gas flowing through this part at the open end of the pipe body of the upstream connection part of the connection part between the pipe body of the exhaust pipe and the flexible tube. It is constructed by forming a flow section.

(Effect of the invention) According to the invention, since a turbulent flow part is formed at the open end of the tube body, the exhaust gas flowing through this part has a frequency sufficiently higher than the resonant frequency range of the flexible tube (chamber). This is converted into a disturbance, so the pronunciation phenomenon is suppressed. Further, since the turbulent flow portion can be formed by a notch or the like, manufacturing is extremely easy and the weight does not increase.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, a plurality of square notches (turbulent flow portions) 2d, . . . , 2d are formed at equal intervals on the circumference in the open end 2c of the upstream exhaust pipe 2a.

In this way, when the notch 2d is formed in the open end 2c, the exhaust gas flow is stopped immediately before the exhaust gas flows into the flexible tube (chamber) 3 from the open end 2c of the exhaust pipe 2a at high speed. A part of the outer peripheral portion is diffused by the notch 2d, and the disturbance is converted into a disturbance of a frequency sufficiently higher than the resonant frequency range of the flexible tube 3 (chamber).

Therefore, since the flexible tube 3 is less likely to resonate, the phenomenon of sound generation is suppressed.

In Fig. 1, a rectangular notch 2d is formed as a turbulent flow part, but as shown in Fig. 2a, a plurality of small holes 2e are formed, and as shown in Fig. 2c, , a plurality of triangular notches 2f are formed, and a second
As shown in FIG. c, a plurality of cut and raised portions 2g may be formed.

Figure 3 shows a constant engine speed (2500~
3000 rpm), a microphone was placed on the side of the flexible tube 3, and abnormal noise generated from the flexible tube 3 was measured.

Compared to the conventional type (solid line a) in which no turbulence is formed at the open end 2c of the exhaust pipe 2a, the proposed type in which the notch 2d (Fig. 1) is formed (dashed line b) and the small It can be seen that the sound pressure level is reduced in the type formed with holes 2e (FIG. 2a) (dotted chain line c).

[Brief explanation of drawings]

Fig. 1 is a side view of the exhaust pipe structure according to the present invention, Figs. 2a to 2c are side views showing modifications of Fig. 1, Fig. 3 is an abnormal noise measurement graph, and Fig. 4 is an engine Fig. 5 is a side view showing the relationship between the exhaust pipe and the flexible tube, Fig. 5 is a cross-sectional side view of the main part of the conventional flexible tube, Fig. 6 is a cross-sectional view showing the vortex generation phenomenon, and Fig. 7 is a side view of the conventional flexible tube. FIG. 2, 2a, 2b...Exhaust pipe, 2c...Open end, 2d, 2f...Notch, 2e...Small hole, 2g
...Cut up, 3...Flexible tube, 3
a, 3b... end, 4... bellows part.

Claims (1)

[Claims for Utility Model Registration] A vehicle exhaust pipe in which a flexible tube having a bendable bellows part is disposed in the middle part of a pipe body, and an end of the flexible tube is connected to the outer periphery of the pipe body, A vehicle characterized in that a turbulent flow portion that causes turbulence in exhaust gas flowing through this portion is formed at the open end of the tube at the upstream connection portion of the connection portion between the tube and the flexible tube. Exhaust pipe structure.