JPH09291818A - Exhaust pipe of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce generation of high frequency sound by taking the range to be brought in surface-contact with at least either the outer peripheral side of an upstream side inner pipe part or the outer peripheral side of a downstream side inner pipe part in relation to an outer pipe part to be vibrated by exhaust pulsation as a vibration transmission damping part. SOLUTION: An upstream side inner pipe part 10, a downstream side inner pipe part 11, and an outer pipe part 12 are provided in a bent part of an exhaust manifold. The upstream side inner pipe part 10 is taken as the upstream side in an exhaust system of an engine. The downstream side inner pipe part 11 is taken as the downstream side in the exhaust system of the engine. The outer pipe part 12 is so arranged as to be brought in surface-contact with the outer peripheral side of the upstream side inner pipe part 10 and the outer peripheral side of the downstream side inner pipe part 11, and the end surface 12a on the upstream side and the end surface 12b on the downstream side are airtightly connected to the upstream side inner pipe part 10 and the downstream side inner pipe part 11 over the whole circumference by welding. Surface contact parts 13, 14 to be brought in surface-contact with the outer peripheral side of the upstream side inner pipe part 10 and the outer peripheral side of the downstream side inner pipe part 11 in relation to the outer pipe part 12 to be vibrated by exhaust pulsation are taken as vibration transmission damping parts.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Exhaust manifolds for conventional engines include, for example, a first cylinder for a four-cylinder engine.
6k due to exhaust pulsation synchronized with explosion from cylinder 4
High-frequency sound of up to 20 kHz is generated from the entire pipe, which causes high-frequency noise in engine noise.

Therefore, an object of the present invention is to reduce the generation of high frequency sounds.

[0004]

According to the first aspect of the invention, the outer pipe portion vibrates due to exhaust pulsation in a partial region of the exhaust system of the internal combustion engine. The transmission of this vibration is attenuated in a region that comes into surface contact with at least one of the outer peripheral side of the upstream inner pipe section and the outer peripheral side of the downstream inner pipe section. In this way the vibration is dampened,
In at least one of the upstream inner pipe portion and the downstream inner pipe portion, vibration due to exhaust pulsation becomes weak, and generation of high-frequency abnormal noise is suppressed.

According to the second aspect of the invention, the exhaust gas hits the outer pipe portion at the bent portion of the exhaust manifold, and the outer pipe portion vibrates due to exhaust pulsation. The transmission of this vibration is attenuated in a region that comes into surface contact with at least one of the outer peripheral side of the upstream inner pipe section and the outer peripheral side of the downstream inner pipe section.
In this way, the vibration is damped, and the vibration due to the exhaust pulsation becomes weak in at least one of the upstream side inner pipe part and the downstream side inner pipe part, and the generation of high frequency abnormal noise is suppressed.

According to the third aspect of the invention, since the upstream inner pipe portion, the downstream inner pipe portion and the outer pipe portion are made of stainless steel, it is possible to use all-around welding as a method of joining in an airtight state. it can.

According to the fourth aspect of the invention, the exhaust gas hits the pipe at the bent portion of the exhaust pipe of the internal combustion engine, and the pipe vibrates due to exhaust pulsation. The transmission of this vibration is attenuated by the surface contact with the damping plate material on the pipe surface outside the bent portion. In this way, the vibration is attenuated, the vibration due to the exhaust pulsation becomes weak, and the generation of high-frequency abnormal noise is suppressed.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of the exhaust manifold according to this embodiment, and FIG. 2 is a front view of the exhaust manifold. 4-cylinder gasoline engine E
An exhaust manifold 1 is attached to n. The stainless exhaust manifold 1 has four branch pipes 2, 3, 4, 5 and one collecting pipe 6. That is, the first cylinder branch pipe 2 for discharging the exhaust gas of the first cylinder, the second cylinder branch pipe 3 for discharging the exhaust gas of the second cylinder, and the exhaust gas of the third cylinder are discharged. A branch pipe 4 for the third cylinder and a branch pipe 5 for the fourth cylinder for discharging the exhaust gas of the fourth cylinder are provided, and the respective branch pipes are connected to communicate with the collecting pipe 6. A front pipe 7 is connected to the collecting pipe 6. The exhaust manifold 1 is attached to the engine En and the front pipe 7 by attachment flanges 8 and 9.

Exhaust gas from the first to fourth cylinders of the engine En is discharged to the branch pipes 2 to 5 corresponding to each cylinder, and the exhaust gas of all the cylinders is collected in the collecting pipe 6 to the front pipe 7. The gas flows into the atmosphere through a muffler (not shown).

As shown in FIG. 3, the bent portion (A portion in FIG. 2) of the exhaust manifold 1 has a double pipe structure for vibration isolation. That is, it is provided with an upstream inner pipe portion 10 made of stainless steel, a downstream inner pipe portion 11 made of stainless steel, and an elbow type outer pipe portion 12 made of stainless steel. The upstream side inner pipe section 10 becomes the upstream side in the exhaust system of the engine, and the exhaust gas of the engine is supplied to the upstream side inner pipe section 10. The downstream inner pipe portion 11 is on the downstream side in the exhaust system of the engine, and the exhaust gas of the engine is discharged from the downstream inner pipe portion 11. The outer pipe portion 12 is
The outer peripheral side of the upstream inner pipe section 10 and the outer peripheral side of the downstream inner pipe section 11 are arranged so as to make surface contact by a predetermined length. The upstream end surface 12a of the outer pipe portion 12 is joined to the upstream inner pipe portion 10 in an airtight state, and the downstream end surface 12b is joined to the downstream inner pipe portion 11 in an airtight state. More specifically, they are joined in an airtight state by full circumference welding (outer circumference welding). In FIG. 3, welded portions are indicated by reference numerals 20 and 21.

The outer pipe portion 12 becomes a portion that vibrates due to exhaust pulsation. Further, the surface contact portion 13 between the inner peripheral surface of the outer pipe portion 12 and the outer peripheral surface of the upstream side inner pipe portion 10 serves as the first vibration transmission damping portion, and the outer pipe portion 1
The surface contact portion 14 between the inner peripheral surface of 2 and the outer peripheral surface of the downstream inner pipe portion 11 serves as a second vibration transmission damping portion.

The length L1 of the first vibration transmission damping portion (surface contact portion 13) is 20 to 40 mm, and the length L2 of the second vibration transmission damping portion (surface contact portion 14) is 20 to 40 mm. . Here, in the present embodiment, since the surface contact portions 13 and 14 are arranged at the bent portions, the lengths L1 and L2 are
Refers to the length at the center of the pipe.

This structure (vibration-proof surface contact double pipe structure) is adopted in all the bent portions of the exhaust manifold 1. Next, the operation will be described.

When a structure is adopted in which one branch pipe made of stainless steel is bent at several points so that the branch pipes are gathered at the gathering portion, the pressure wave generated by the exhaust at the bent portion of the pipe causes the pressure wave of the pipe to bend at the bent portion. The high-frequency vibrations that collide with the inner wall of the pipe are transmitted to the entire pipe, and high-frequency abnormal noise that is synchronized with the engine exhaust is simultaneously generated from the entire exhaust manifold. On the other hand, in the present embodiment, the high frequency noise is reduced by the following operation.

Exhaust gas from the engine collides with the inner wall of the outer pipe portion 12 at the bent portion, and the collision causes vibration. This vibration is transmitted from the outer pipe portion 12 to the upstream inner pipe portion 10 and the downstream inner pipe portion 11. At this time, in the first and second vibration transmission damping portions (pipe surface contact portions 13 and 14), the transmission of vibration is reduced due to the mutual interference of the pipe walls. As a result, the radiated sound is reduced.

FIG. 4 shows noise measurement results (experimental results) regarding the effect of reducing radiated sound. The sample used for the experiment is shown in FIG. In FIG. 5, the upstream inner pipe portion 10
The downstream inner pipe portion 11 and the outer pipe portion 12 are all made of SUS304 material and have a thickness of 1 mm.
As for the pipe size, the outer diameter of the inner pipe parts 10 and 11 is 36.
mm, the outer diameter of the outer pipe portion 12 is 38 mm, and the outer peripheral surfaces of the inner pipe portions 10 and 11 and the outer pipe portion 12 are
A space of 0.05 mm is provided between the inner peripheral surface and the inner peripheral surface. Furthermore, the outer pipe portion 12 is R70 (bending radius 70 m
m). The length L1 of the first vibration transmission damping portion (surface contact portion 13) is 30 mm, and the length L2 of the second vibration transmission damping portion (surface contact portion 14) is 30 mm. Other dimensions are as shown in FIG.

A 2000 cc in-line 4-cylinder gasoline injection engine was used as the engine, and the engine conditions during the experiment were 1500 rpm and the load torque was 15 kgfm. This is a condition where a high-frequency sound feels abnormal. Furthermore, the microphone was installed at a position 20 cm from the center of the tube.

In FIG. 4, a solid line shows a case where the structure (vibration isolating surface contact double pipe structure) in FIG. 5 is adopted, and an R70 stainless pipe (simple bending pipe) having an outer diameter of 36 mm indicated by a two-dot chain line. ) Is used.

It can be seen from FIG. 4 that the noise reduction effect is better when the anti-vibration surface contact double pipe structure is adopted. More precisely, the O.I. It was found that the A value (overall value) has a reducing effect of 4 dB.

As described above, even if the excitation force is the same at the location of the excitation source, the vibration can be attenuated by the first and second vibration transmission damping portions (pipe surface contact portions),
This has the effect of reducing the radiated sound to the extent that there is a difference in the sense of hearing.

As described above, this embodiment has the following characteristics (a) and (b). (A) In the curved portion of the exhaust manifold 1, since the vibration damping surface contact double pipe structure including the upstream inner pipe portion 10, the downstream inner pipe portion 11 and the elbow type outer pipe portion 12 is adopted, the exhaust manifold 1 Exhaust gas from the outer pipe portion 12 at the bend
The outer pipe portion 12 vibrates due to exhaust pulsation, and this vibration is attenuated at the surface contact portion 13 between the outer pipe portion 12 and the upstream inner pipe portion 10 and the outer pipe portion 12 and the downstream inner pipe portion 11 are attenuated. The transmission is attenuated at the surface contact portion 14 with. In this way, the vibration is attenuated, and the upstream inner pipe portion 1
The vibration due to the exhaust pulsation is weak in the 0 and downstream inner pipe portions 11, and the generation of high-frequency abnormal noise is suppressed. (B) Since the upstream inner pipe portion 10, the downstream inner pipe portion 11 and the outer pipe portion 12 are made of stainless steel, it is possible to use omnidirectional welding as a method of joining in an airtight state.

As an application example of this embodiment, it may be implemented as follows. In the above-described embodiment, the bending portion of the exhaust manifold is applied, but the present invention is not limited to this, and vibration is provided by providing a vibration isolation surface contact double pipe structure in a partial area of the exhaust pipe (exhaust system) other than the exhaust manifold. Suppresses transmission and reduces radiated sound. Further, in addition to the curved portion, a vibration damping surface contact double pipe structure is provided in a straight portion or the like to suppress vibration transmission and reduce radiated sound.

Further, in the above-described embodiment, the outer pipe portion 12 is arranged so as to make surface contact with the outer peripheral side of the upstream inner pipe portion 10 and the outer peripheral side of the downstream inner pipe portion 11, and the upstream end face 12a and the downstream end face are arranged. 12b designates an upstream side inner pipe section 10 and a downstream side inner pipe section 11
The outer pipe portion 12 is arranged so as to be in surface contact with only one of the outer peripheral side of the upstream inner pipe portion 10 and the outer peripheral side of the downstream inner pipe portion 11, and The end surface (upstream side or downstream side) of the outer pipe portion 12 at the contact portion is joined to the outer peripheral surface of the inner pipe portion (the outer peripheral surface of the upstream inner pipe portion 10 or the outer peripheral surface of the downstream inner pipe portion 11) in an airtight state. May be. (Second Embodiment) Next, a second embodiment of the present invention will be described, focusing on differences from the first embodiment.

FIG. 6 shows a plan view of the exhaust manifold in this embodiment, and FIG. 7 shows a front view of the exhaust manifold. In the curved portion (B portion in FIG. 7) of the exhaust manifold 1, as shown in FIG. 8, a vibration damping plate member 31 is arranged on the surface of the stainless pipe 30 outside the curved portion. Damping plate 31
Is made of stainless steel plate and has a rectangular shape. The vertical and horizontal dimensions are 20 mm × 80 mm, and the thickness is 2 mm. The vibration damping plate member 31 is spotted on the pipe 30 by electric welding (spot welding) at a total of three positions, that is, both ends and the central portion in the longitudinal direction, with the longitudinal direction being the extending direction of the stainless steel pipe 30. , Are arranged in surface contact with the pipe 30. In FIG. 8, points to be marked are indicated by 32a, 32b and 32c. The surface contact portion between the pipe 30 and the vibration damping plate material 31 serves as a vibration damping portion for exhaust pulsation. The thickness of the stainless steel pipe 30 is 2m
m.

As shown in FIGS. 6 and 7, the damping plate member 31 is arranged at two locations in the exhaust pipe 2 for the first cylinder of the engine, and the exhaust pipe 3 for the second, third, and fourth cylinders. , 4 and 5 are arranged one each.

Next, the operation will be described. Exhaust gas from the engine becomes a pressure wave and the pipe 30 is bent at the bend.
Collides with the inner wall of the pipe, and the surface of the pipe 30 vibrates due to the collision. This vibration is transmitted from the bent portion of the pipe 30 to the upstream side and the downstream side. At this time, the pipe 30 and the vibration damping plate 3
The transmission of vibration is reduced due to the mutual interference of the wall surfaces at the surface contact portion between the first and second surfaces. As a result, the radiated sound is reduced.

FIG. 9 shows noise measurement results (experimental results) regarding the effect of reducing radiated sound. 2000c for the engine
c In-line 4-cylinder gasoline injection engine was used, the engine condition during the experiment was 1500 rpm, and the load torque was 15 kgf.
m. This is a condition where a high-frequency sound feels abnormal. Furthermore, the microphone was installed 40 cm from the engine.

In FIG. 9, a solid line shows a case where the structure (surface contact plate structure) in FIG. 8 is adopted, and a case where a bent stainless pipe (simple bent pipe) is used is shown by a two-dot chain line.

From FIG. 9, it can be seen that the one employing the surface contact plate structure has a noise reducing effect. To be more precise, 1500 rpm at which high frequency abnormal noise is particularly felt, 15
O.K. It was found that the A value (overall value) had a reducing effect of 3 dB.

FIG. 10 shows 6 when the engine load is changed.
Sound pressure level O.S. at ~ 20 kHz. The measurement result of A value (overall value) is shown. The engine speed is 150
It is measured at 0 rpm. It can be seen from FIG. 10 that when the engine load is greater than 7 kgfm, the noise reduction effect is exhibited by adopting the structure (surface contact plate structure) in FIG.

As described above, this embodiment has the following features. (A) The vibration damping plate member 31 is spotted on the outer surface of the pipe 30 in the bent portion of the exhaust manifold, and the vibration damping plate member 31 is arranged in surface contact with the pipe 3.
The vibration damping against exhaust pulsation is performed by the surface contact between 0 and the vibration damping plate member 31. Therefore, the exhaust gas hits the pipe 30 at the bent portion of the exhaust manifold, and the pipe 30 vibrates due to the exhaust pulsation. This vibration is generated on the pipe surface outside the bent portion by the damping plate member 31.
The transmission is attenuated by the surface contact with. In this way, the vibration is attenuated, the vibration due to the exhaust pulsation becomes weak, and the generation of high-frequency abnormal noise is suppressed.

Further, in comparison with the case where the thickness of the pipe at the bent portion of the exhaust manifold is increased to reduce the high frequency abnormal noise by the mass effect, the high frequency abnormal noise is not caused in the present embodiment without increasing the cost and the weight. Can be reduced.

In the above embodiment, one vibration damping plate member 31 is marked at three points, but the number may be any number other than "3" and the size of the vibration damping plate member 31 may be changed. The number may be set according to the sheath thickness, the material, and the like.

[Brief description of drawings]

FIG. 1 is a plan view of an exhaust manifold according to a first embodiment.

FIG. 2 is a front view of the exhaust manifold according to the first embodiment.

FIG. 3 is a sectional view of a bent portion of the exhaust manifold according to the first embodiment.

FIG. 4 is a frequency characteristic diagram showing a noise measurement result.

FIG. 5 is a sectional view of a sample used in an experiment.

FIG. 6 is a plan view of an exhaust manifold according to a second embodiment.

FIG. 7 is a front view of the exhaust manifold according to the second embodiment.

FIG. 8 is a sectional view of a bent portion of the exhaust manifold according to the second embodiment.

FIG. 9 is a frequency characteristic diagram showing a noise measurement result.

FIG. 10 is a characteristic diagram showing a noise measurement result.

[Explanation of symbols]

En ... Gasoline engine, 1 ... Exhaust manifold, 10 ... Upstream inner pipe part, 11 ... Downstream inner pipe part, 12 ... Outer pipe part, 13, 14 ... Surface contact part, 30 ... Pipe, 31 ... Damping plate material.

Claims (4)

[Claims] 1. An upstream inner pipe portion which is provided in a partial region of an exhaust system of an internal combustion engine and which is an upstream side in the exhaust system of the internal combustion engine, and a downstream which is a downstream side in the exhaust system of the internal combustion engine. A side inner pipe part, and is arranged so as to make surface contact with at least one of the outer peripheral side of the upstream side inner pipe part and the outer peripheral side of the downstream side inner pipe part, and at least one end face of the upstream side and the downstream side. Is equipped with an outer pipe part joined in an airtight state to at least one of the upstream side inner pipe part and the downstream side inner pipe part, with respect to the outer pipe part vibrating due to exhaust pulsation, of the upstream side inner pipe part. A region that comes into surface contact with at least one of the outer peripheral side and the outer peripheral side of the downstream inner pipe section is used as the vibration transmission damping section. Exhaust pipe of an internal combustion engine to be butterflies. 2. An upstream inner pipe portion, which is provided at a bent portion of an exhaust manifold, is an upstream side in an exhaust system of an internal combustion engine, and a downstream inner pipe portion is a downstream side in an exhaust system of the internal combustion engine. And arranged so as to make surface contact with at least one of the outer peripheral side of the upstream side inner pipe section and the outer peripheral side of the downstream side inner pipe section, and the end surface of at least one of the upstream side and the downstream side is the upstream side. An outer pipe portion joined to at least one of the inner pipe portion and the downstream inner pipe portion in an airtight state, wherein the outer pipe portion vibrates due to exhaust pulsation and the outer peripheral side and the downstream side of the upstream inner pipe portion. The area that makes surface contact with at least one of the outer peripheral sides of the side inner pipe section is the vibration transmission damping section. An exhaust pipe of an internal combustion engine, characterized in that. 3. The exhaust pipe for an internal combustion engine according to claim 1, wherein the upstream inner pipe portion, the downstream inner pipe portion, and the outer pipe portion are made of stainless steel. 4. A vibration damping plate material is attached to the outer surface of the pipe in a bent portion of an exhaust pipe of an internal combustion engine, and the vibration damping plate material is arranged in surface contact with the pipe and the vibration damping plate. An exhaust pipe for an internal combustion engine, characterized in that vibration damping against exhaust pulsation is performed by surface contact with a plate material.