JP2003214133A - Automobile exhaust muffler having dual tube structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automobile exhaust muffler having dual tube structure suitable for a driver preferring, for example, a sport type vehicle by emphasizing low exhaust noise during acceleration. <P>SOLUTION: A ratio of a section area S1 of an outer tail tube to a tube length L1 thereof is set such that a resonance frequency of Helmholtz resonance generated at an outer tail tube 36 approximately coincides with a frequency in the idle vibration region of an engine, and a ratio of a cross area S2 to a tube length 2 of the inner tail tube is set such that a resonance frequency of Hlemholtz resonance occurring to an inner tail tube 38 approximately coincides with a frequency in a middle rotation area where an engine is rotated at 1000-2000 rpm. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an exhaust muffler for a vehicle having a dual tube structure having two tail tubes.

[0002]

2. Description of the Related Art As a conventional exhaust muffler for a vehicle having a dual tube structure, for example, a technique described in Japanese Patent Laid-Open No. 09-242525 is known. The exhaust muffler described in this publication has a muffler shell 1 as shown in FIG.
By partitioning the inside of the chamber with the end plates 5 and 6, three sound deadening chambers, that is, the dead space chamber 2 and the volume chamber 4, and the expansion chamber 3 located between the dead space chamber 2 and the volume chamber 4, are formed. There is.

Exhaust gas is introduced into the expansion chamber 3 through an inlet tube 7. This expansion room 3
Communicates with the volume chamber 4 via the neck pipe 10 and
The tail tube 8 also communicates with the atmosphere. The dead space chamber 2 communicates with the atmosphere via the second tail tube 13, while the dead space chamber 2 is different from the volume chamber 4 in the expansion chamber 3
They are communicated with each other via a pass tube 11 penetrating through. The end plate 5 has a pressure relief valve 12 for opening and closing the opening of the pass tube 11 to the dead space chamber 2.
Is provided, and exhaust gas is selectively introduced into the dead space chamber 2 when the exhaust pressure sensitive valve 12 is opened and closed.

The exhaust pressure sensitive valve 12 is closed by the spring force of a spring (not shown) when the exhaust pressure is low, such as in a region where the engine speed is low. In this state,
The volume chamber 4 that communicates only with the expansion chamber 3 and the neck 10 functions as a resonance element, and effectively reduces low-frequency exhaust noise. On the other hand, when the exhaust pressure exceeds a predetermined value as the engine speed increases, the exhaust pressure sensitive valve 1
2 opens, and part of the exhaust gas introduced into the expansion chamber 3
The remaining exhaust gas is discharged from the volumetric chamber 4 to the pass tube 1 while being discharged to the atmosphere through the first tail tube 8.
1 is introduced into the dead space chamber 2 and further discharged to the atmosphere via the second tail tube 13. As a result, the volume chamber 4 changes from a resonance element to an expansion element, which reduces high-frequency exhaust noise, suppresses an increase in exhaust pressure loss, and contributes to an improvement in engine output.

[0005]

By the way, the vehicle equipped with the dual tube structure exhaust silencer of FIG. 5 has a low-pitched sound at the time of acceleration in which the engine speed is increased from the idle vibration range to the middle rotation range of about 1000 to 2000 rpm. (Low-frequency)
It is difficult to give a sporty feeling to a driver who likes to generate a low-pitched exhaust sound, such as a sports type vehicle.

That is, the device of FIG. 5 increases the total cross-sectional area of the first and second tail tubes 8 and 13 forming the dual tube, so that the exhaust gas which increases due to the increase of the engine speed can be efficiently supplied. Although it can be discharged, each of the first and second tail tubes 8 and 13 can be discharged due to layout restrictions with other tubes (inlet tube 7, neck tube 10, pass tube 11) arranged in the muffler shell 1. The cross-sectional area of is set small. As described above, the first and second tail tubes 8 and 13 having a small cross-sectional area generate high-frequency exhaust noise like the tubes shown in FIG. 6A, and a driver who prefers low-pitched exhaust noise. It was an unsatisfactory dual-tube structure exhaust silencer. To make low-pitched (low-frequency) exhaust noise,
As shown in FIG. 6B, the large-diameter tail tube 14
Is suitable, but at the present stage where the constraints of the layout inside the muffler shell cannot be cleared, a dual-tube structure vehicle exhaust silencer capable of emphasizing low-pitched exhaust noise has not been developed.

The present invention has been made in view of the above circumstances, and by emphasizing a low-pitched exhaust sound at the time of acceleration, for example, a dual-tube structure automotive exhaust silencer suitable for a driver who likes a sports type vehicle. Is intended to provide.

[0008]

According to a first aspect of the present invention, there is provided an exhaust noise device for a vehicle having a dual tube structure, wherein an outer tail tube and an inner tube having a double tube structure are provided in a specific muffler chamber formed in a muffler shell. Both end openings of the tail tubes are open, and the other end openings of the tubes are open to the atmosphere, and the ratio of the cross-sectional area and the pipe length of the outer tail tube to the cross-sectional area and the pipe length of the inner tail tube. By determining the shapes of the outer tail tube and the inner tail tube so that the ratio of the two becomes different, a Helmholtz resonance that resonates with sounds of two types of frequencies is generated.

According to a second aspect of the present invention, in the vehicle exhaust noise device having the dual tube structure according to the first aspect, when the resonance frequency of the Helmholtz resonance generated in the outer tail tube is in the engine idle vibration region. The cross-sectional area of the outer tail tube and the ratio of the tube length are set to substantially match the frequency of, and the resonance frequency of the Helmholtz resonance generated in the inner tail tube is in the middle rotation range where the engine is rotating at 1000 to 2000 rpm. The ratio of the cross-sectional area and the tube length of the inner tail tube was set so as to substantially match the frequency at the time.

According to a third aspect of the present invention, in the exhaust noise device for a vehicle having a dual tube structure according to the first or second aspect, the outer tail tube is a member having a longer pipe length than the inner tail tube. did.
Further, the invention according to claim 4 is the exhaust noise device for a vehicle having a dual tube structure according to any one of claims 1 to 3, wherein the inner tail tubes are circumferentially spaced at predetermined intervals on the outer circumferences of both ends thereof. It is fixed to the inner peripheral surface of the outer tail tube through a plurality of support legs connected to the open position.

[0011]

According to the first aspect of the present invention, by adopting the outer tail tube and the inner tail tube having the double pipe structure, the layout constraint with other pipes in the muffler shell is improved, and 2 A specific exhaust sound can be emphasized by generating Helmholtz resonance that resonates with sounds of different frequencies.

According to the second aspect of the present invention, in the idle vibration region, the outer tail tube generates Helmholtz resonance that resonates with the frequency of the idle vibration region, so that the low-pitched exhaust sound is emphasized and the acceleration is in progress. In the rotation range, the inner tail tube generates Helmholtz resonance which resonates at a frequency in the middle rotation range, so that a low-pitched exhaust sound is maintained. Therefore, the low-pitched exhaust sound is emphasized even when the engine is accelerated from the idle vibration area to the middle rotation area, so that the driver who likes the low-pitched exhaust sound is satisfied with the exhaust sound and has a sufficiently sporty feeling. Can be given.

According to the third aspect of the present invention, the length of the outer tail tube is long, so that Helmholtz resonance that resonates at a low frequency in the idle vibration region is generated.
As a result, a driver who likes a low-pitched exhaust sound can be given a comfortable low-pitched sound. Further, according to the invention of claim 4, since the inner tail tube is securely fixed to the outer tail tube by a plurality of support legs arranged in the circumferential direction at the outer circumferences of both end portions, the inner tail tube is connected to the inner flow path of the inner tail tube. The exhaust gas flowing in the flow path between the outer circumference of the inner tail tube and the inner circumference of the outer tail tube can be moved at a constant flow velocity without causing turbulence such as turbulence. Therefore, the resonance frequencies of the inner tail tube and the outer tail tube can always be set stably, and the Helmholtz resonance of a predetermined level can be reliably generated.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of an automobile exhaust muffler having a dual tube structure of the present invention will be described with reference to the drawings. In the exhaust muffler for an automobile shown in FIG. 1, the inside of the cylindrical muffler shell 20 is partitioned by the end plates 22 and 24, so that the first muffler chamber 2
6, the second muffler chamber 28 and the third muffler chamber 30 are formed with three muffling chambers, and the inlet tube 32, the pass tube 34, the outer tail tube 36 and the inner tail tube 38 having a double tube structure are formed.
Are arranged.

The inlet tube 32 is arranged so as to pass from the outside of the muffler shell 20 through the first muffler chamber 26 and the second muffler chamber 28, and an opening 32a at one end thereof opens in the third muffler chamber 30 to form a muffler shell. An exhaust gas supply tube (not shown) is connected to the other end opening 32b that is open outside 20. A plurality of small holes 32c are formed in the portion of the inlet tube 32 that passes through the first muffler chamber 26.

The pass tube 34 is provided in the second muffler chamber 28.
The first muffler chamber 26 and the third muffler chamber 30 are open at one end opening 34a and the other end opening 34b. Also, the second muffler chamber 28
A plurality of small holes 34c are formed in the portion passing through. The outer tail tube 36 is a large-diameter tube, is arranged to extend to the outside through the second muffler chamber 28 and the third muffler chamber 30, and the one end opening 3
6a opens in the first muffler chamber 26, and the other end opening 36b
Is open in the atmosphere.

The inner tail tube 38 is a tube having a shorter diameter and a smaller diameter than the outer tail tube 36, and is coaxially arranged inside the outer tail tube 36. One end opening 38a opens in the first muffler chamber 26, The other end opening 38 b opens inside the outer tail tube 36. The inner tail tube 38 includes the outer peripheries of both ends 38a and 38b and the outer tail tube 36.
It is fixed in the outer tail tube 36 by a support leg 40 arranged between the inner periphery of the outer tail tube 36 and the inner periphery of the outer leg tube. Specifically, as shown in FIG. 2, the inner tail tube 38 is fixed to the outer tail tube 36 by three support legs 40 arranged at predetermined intervals in the circumferential direction on the outer peripheries of both ends 38a, 38b. Has been done.

The exhaust gas supplied from the exhaust gas supply tube into the inlet tube 32 partially flows from the one end opening 32a into the third muffler chamber 30, and the rest passes through the small hole 32c. First muffler room 2
Pour into 6. Further, the exhaust gas flowing from the third muffler chamber 30 into the pass-tube 34 partially flows into the first muffler chamber 26 from the other end opening 34b, and the rest passes through the small holes 34c and then into the second muffler chamber. Flows into 28.
Then, the exhaust gas in the first muffler chamber 26 passes through the inside of the inner tail tube 38 and flows into the atmosphere, and also passes through the flow path defined between the outer periphery of the inner tail tube 38 and the outer tail tube 36. Then it flows into the atmosphere.

Here, both the outer tail tube 36 and the inner tail tube 38 have one end opening 36.
Since a and 38a communicate with the volume chamber (first muffler chamber 26), Helmholtz resonance that resonates with a sound of a predetermined frequency is generated. In this embodiment, the Helmholtz resonance is generated at the resonance frequency f of each of the outer tail tube 36 and the inner tail tube 38.

That is, the resonance frequency f is, as shown in the model diagram of FIG. 3, the sound velocity C (331 m / sec), the volume of the volume chamber V, the tube length of the tail tube L, and the cross-sectional area of the tail tube S. Then,

[0021]

[Equation 1]

It is represented by In the present embodiment, two types can be set by appropriately setting the ratio of the cross-sectional area to the tube length of each of the outer tail tube 36 and the inner tail tube 38 communicating with the common volume chamber (first muffler chamber 26). The two resonance frequencies f1 and f2 are set so that the Helmholtz resonance that resonates with the sound of the frequency is generated.

That is, the resonance frequency f1 of the inner tail tube 38 is constant because the volume of the first muffler chamber 26, which is the volume V of the volume chamber that determines the resonance frequency, is constant. Although it is determined by the cross-sectional area S2 of the tube 38,
The resonance frequency f1 is 1000 to 2000rp for the engine speed.
The ratio of the cross-sectional area S2 and the pipe length L2 is set so as to substantially match the frequency in the middle rotation range near m.

The resonance frequency f2 of the outer tail tube 36 is equal to the pipe length L1 of the outer tail tube 36 and the cross-sectional area S1 of the outer tail tube 36 because the volume V of the volume chamber is constant with the volume of the first muffler chamber 26. However, the ratio of the cross-sectional area S1 and the pipe length L1 is set so that the resonance frequency f2 thereof substantially matches the frequency when the engine speed is in the idle vibration region.

The resonance frequency f of the inner tail tube 38 is determined by the volume V of the first muffler chamber 26, the tube length L1 and cross section S1 of the outer tail tube 36, and the tube length L2 and cross section S2 of the inner tail tube 38.
1 and Table 2 show examples of specific numerical values of the resonance frequency f2 of the outer tail tube 36.

[0026]

[Table 1]

[0027]

[Table 2]

Further, in the structure shown in FIG. 4, the resonance frequency f1 of the inner tail tube 38 is set to 1000 rpm.
Measurement of the sound pressure level of the apparatus according to the present embodiment, in which the frequency that substantially coincides with the frequency in the middle rotation range around 2,000 rpm and the resonance frequency f2 of the outer tail tube 36 that substantially coincides with the frequency in the idle vibration region It is a characteristic view showing a value (solid line). For comparison with the present embodiment, the first embodiment in which the resonance frequency is set only in the idle vibration region
Comparative example (dashed line) and resonance frequency in the middle rotation range (1000 ~
The second comparative example (broken line) set only to 2000 rpm) is shown.

As shown in this figure, in the first comparative example, the low-pitched exhaust noise can be emphasized in the idle vibration region, but as the vehicle accelerates, the low-pitched exhaust noise is not generated, The exhaust noise is not satisfactory for drivers who prefer sports type vehicles. In addition, the second comparative example can emphasize low-pitched exhaust noise in the middle revolution range, but does not generate low-pitched exhaust noise in the idle vibration region, which is also satisfactory for a driver who prefers a sports type vehicle. The exhaust sound will be unnecessary.

On the other hand, in the present embodiment, in the idle vibration region, the outer tail tube 36 generates Helmholtz resonance that resonates with the frequency of the idle vibration region, so that the low-pitched exhaust sound is emphasized and accelerates. In the rotation range, the inner tail tube 38 generates Helmholtz resonance that resonates at a frequency in the middle rotation range, so that a low exhaust sound is maintained. Therefore, the low-pitched exhaust sound is emphasized even when the engine is accelerated from the idle vibration area to the middle rotation area, so that the driver who likes the low-pitched exhaust sound is satisfied with the exhaust sound and has a sufficiently sporty feeling. Can be given.

Further, by using the outer tail tube 36 and the inner tail tube 38 having the double pipe structure, the layout constraint with other pipes (inlet tube 32, pass tube 34) in the muffler shell 20 is cleared. At the same time, the low-pitched exhaust sound can be emphasized. Further, as is clear from the above-described formula (1) indicating the resonance frequency f, when the pipe length L of the tail tube is set to a large value, a low resonance frequency is determined. From this, by increasing the tube length L1 of the outer tail tube 36, Helmholtz resonance that resonates at a low frequency in the idle vibration region occurs, so that a comfortable low-tone sound can be given to the driver.

Further, the inner tail tube 38 is
Since it is securely fixed to the outer tail tube 36 by the three support legs 40 arranged at predetermined intervals in the circumferential direction on the outer peripheries of the both end portions 38a and 38b, the inner flow path of the inner tail tube 38 and the inner tail tube 38 are The exhaust gas flowing through the flow path between the outer circumference of the tube 38 and the inner circumference of the outer tail tube 36 can be moved at a constant flow velocity without causing turbulence such as turbulence. Thereby, the resonance frequency f of the inner tail tube 38
1 and the resonance frequency f2 of the outer tail tube 36 can always be set stably, and the Helmholtz resonance in the idle vibration region and the Helmholtz resonance in the middle rotation region can be reliably generated.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an internal structure of an automobile exhaust muffler according to the present invention.

FIG. 2 is a diagram showing a structure of an outer tail tube and an inner tail tube of a double pipe structure of an exhaust muffler for an automobile.

FIG. 3 is a model diagram for explaining Helmholtz resonance.

FIG. 4 is a characteristic diagram showing the sound pressure level of the exhaust sound of the automobile exhaust muffler of the present invention.

FIG. 5 is a cross-sectional view showing the internal structure of a conventional vehicle exhaust silencer.

FIG. 6 is a model diagram showing characteristics of exhaust noise of a tube having a small cross section and characteristics of exhaust sound of a tube having a large cross section.

[Explanation of symbols]

20 muffler shell 26 1st muffler room (silence room) 28 Second muffler room 30 3rd muffler room 36 Outer tail tube 36a One end opening 36b Opening on the other end 38 Inner tail tube 38a One end opening 38b Opening on the other end 40 support legs f1 Inner tail tube resonance frequency f2 Resonant frequency of outer tail tube L1 outer tail tube length L2 inner tail tube pipe length Cross section of S1 outer tail tube S2 Inner tail tube cross-sectional area V Volume of the first muffler chamber

Claims (4)

[Claims] 1. A specific muffler chamber formed in a muffler shell has one end opening of both the outer tail tube and the inner tail tube having a double pipe structure, and the other end opening of the tubes opens to the atmosphere. In addition, the shapes of the outer tail tube and the inner tail tube are determined such that the ratio of the cross-sectional area and the tube length of the outer tail tube and the ratio of the cross-sectional area and the tube length of the inner tail tube have different values. By that,
An exhaust noise device for a vehicle having a dual tube structure, which is configured to generate Helmholtz resonance that resonates with sounds of two kinds of frequencies. 2. The ratio of the cross-sectional area and the pipe length of the outer tail tube is set so that the resonance frequency of the Helmholtz resonance generated in the outer tail tube substantially matches the frequency in the idle vibration region of the engine. The resonance frequency of the Helmholtz resonance generated in the inner tail tube is set so that the cross-sectional area and the length of the inner tail tube are set so that the resonance frequency of the Helmholtz resonance is substantially equal to the frequency when the engine is rotating at 1000 to 2000 rpm. The exhaust noise device for a vehicle having a dual-tube structure according to claim 1, wherein 3. The exhaust noise device for a vehicle having a dual tube structure according to claim 1, wherein the outer tail tube is a member having a longer tube length than the inner tail tube. 4. The inner tail tube is fixed to the inner peripheral surface of the outer tail tube via a plurality of support legs connected to the outer circumferences of both ends of the inner tail tube at positions at predetermined intervals in the circumferential direction. An exhaust noise device for an automobile having a dual tube structure according to any one of claims 1 to 3, wherein