JPH09144526A - Resonator device for exhaust system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resonator device for an exhaust system effectively separated from a high temperature of exhaust gas and an exhaust pipe with a necessary heat insulating structure only simple required. SOLUTION: A metal-made branch pipe part 17 is made to branch from an exhaust pipe 16, a resin molded part 18 is mounted in an end part of the branch pipe part 17. In the resin molded part 18, a space part 28 and a sleeve 20 are integrally molded by resin. Guide shapes 31, 32 are formed in the space part 28, partly a flow of air under a car body 10 according to running is scooped up, the sleeve 20 and the branch pipe part 17 are deheated from the outside, so as to low maintain a temperature thereof, with no necessity for exceeding a heat resistance temperature of resin. Since radiation is improved by providing a radiation structure 19 in a surface of the branch pipe part 17, a heating value conducted to a side of the resin molded part 18 is further reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust system resonator device mounted on an exhaust system of an automobile to reduce exhaust noise.

[0002]

2. Description of the Related Art Proposals have been made to reduce exhaust noise by providing a resin resonator in an exhaust system of an automobile. Conventionally, resin resonators have been exclusively equipped in the air supply system of engines that are not exposed to harsh thermal environments, but they have the characteristics of low pressure loss, excellent sound deadening performance, and freedom of molding to reduce the number of parts. It has been evaluated and research and development for practical use for mounting it in an exhaust system are underway. When a resin resonator is attached to the exhaust system, it is necessary to provide a special heat insulation structure or cooling structure so that the resin-molded portion is not directly exposed to the exhaust system or the high temperature of the exhaust gas.

An example in which a resonator is attached to the exhaust system is disclosed in JP-A-6-280702 and JP-A-5-171931.
JP-A-6-26321.
The resonator shown in JP-A-6-280702 is a so-called Helmholtz type, and includes a branch pipe portion branched from the exhaust system, and a space portion formed in a dead end bag shape and connected to the tip of the branch pipe portion. Work together to produce a sound deadening effect. In the resonator disclosed in Japanese Patent Laid-Open No. 5-171931, a resonance box is arranged so as to surround a pipe line of an exhaust system. Here, in order to avoid softening and deformation of the outer part of the resin-molded resonance box, a thick heat insulating material is provided on the entire inner surface of the resin-molded part, so that heat conduction from the conduit and high-temperature exhaust gas in the resonance box Eliminates contact with. JP-A-6-2632
The resonator shown in Japanese Patent No. 1 has a resonance box formed by resin molding at the outlet of the exhaust system. In order to avoid thermal deformation of the resin-molded resonance box, only the portion of the inner wall surface of the resonance box that is directly exposed to exhaust gas is covered with a heat insulating material.

[0004]

The temperature of the exhaust system of an automobile during operation is close to 200 ° C. even at the main muffler at the rear of the vehicle body and at the exit of the exhaust pipe, and the temperature becomes higher as the exhaust system goes upstream. 700 ° C at the outlet of the catalytic converter
Reach In such a high temperature environment, the resin molded product is also softened and deformed by the radiant heat from the exhaust pipe. Therefore, a resonator of the type surrounding the periphery of the exhaust pipe as disclosed in JP-A-5-171931, 6-263
Resin-molded parts cannot be used in a resonator of the type that is arranged in the vicinity of the exhaust system as shown in Japanese Patent No. 21.

Further, in the exhaust system of an automobile, acoustic nodes and antinodes are formed for each frequency component of exhaust sound. Therefore, in order to enhance the silencing effect, the frequency component to be silenced is specified and its frequency is reduced. It is necessary to place a resonator of a structure and dimensions adapted to the component close to the acoustic antinode of the frequency component. However, since the resonator is usually arranged by utilizing an empty space after the structure of the vehicle body and the arrangement of parts are determined, in the resonator as disclosed in Japanese Patent Laid-Open No. 5-171931, a thick heat insulating material is provided inside. Since the structure is provided to surround the exhaust pipe, the external appearance becomes large for its volume, and the possibility that it cannot be arranged at an acoustically convenient position of the exhaust system increases.

Further, in the resonators disclosed in Japanese Patent Application Laid-Open Nos. 5-171931 and 6-26321, the necessary heat insulating structure complicates the entire structure and increases the number of parts. The structural restrictions of the molded parts are increased, and the moldability of the resin cannot be fully utilized. For example, the resonance box disclosed in JP-A-6-26321 can be integrally molded in appearance, but
It is necessary to make a split structure and attach a heat insulating material inside.

The present invention makes it possible to use a resin molded part that is effectively shielded from exhaust gas and high temperature of an exhaust pipe and fully utilizes the moldability of resin, and a resonator having a great effect of reducing exhaust noise can be provided with a small number of parts. It is an object of the present invention to provide an exhaust system resonator device that can be made compact.

[0008]

According to a first aspect of the present invention, there is provided an exhaust system resonator device which is mounted on an exhaust system of an automobile to reduce exhaust noise, and branches from an exhaust gas passage at an intermediate position of the exhaust system. And a metal branch pipe part extended to a predetermined position spaced from the exhaust system, and a resin molding part formed of a resin in a dead end bag shape and connected to the tip of the branch pipe part. And a guide shape that takes in an air flow under the vehicle body due to traveling and forms an air flow that flows into a connecting portion between the branch pipe section and the resin molding section is given to the resin molding section.

According to a second aspect of the present invention, in an exhaust system resonator device mounted on an exhaust system of an automobile to reduce exhaust noise, the exhaust system is branched from an exhaust gas flow path at an intermediate position of the exhaust system. A branch pipe made of metal that is stretched to a predetermined position apart from, and a resin molding portion that is molded into a dead end bag of resin and connected to the tip of the branch pipe portion, and runs Accordingly, the branch pipe portion is provided with a metal heat radiating member that radiates heat in contact with the airflow generated around the branch pipe portion.

[0010]

In the exhaust system resonator device according to the first aspect, the air flow under the vehicle body generated during traveling is scooped up by the guide shape and guided to the connecting portion between the branch pipe portion and the resin molding portion, and this portion is from the outside. Allow to air cool.

In the exhaust system resonator device according to the second aspect of the present invention, since the heat radiation member attached to the branch pipe section increases the heat radiation area of the heat introduced from the exhaust system side by heat conduction,
As the vehicle travels, the amount of heat carried away by the airflow flowing around it increases, and the amount of heat conducted to the resin molding portion side is reduced. As a result, the surface temperature of the portion of the branch pipe portion located on the resin molding portion side decreases.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An exhaust system resonator device according to an embodiment will be described with reference to FIGS. 1 is an explanatory view of an automobile exhaust system, FIG. 2 is an explanatory view of a structure of a resin molding portion, and FIG.
FIG. 4 is an explanatory diagram of a structure of a heat dissipation member. 2A is a plan view and FIG. 2B is a side view. As shown in FIG. 1, an exhaust system of a vehicle is an engine 1 arranged in a front portion of a vehicle body 10.
1 to flexible tube 12, catalytic converter 1
3 is an exhaust gas path that passes through the sub muffler 14 and reaches the main muffler 15 at the rear of the vehicle body 10. The flexible tube 12 has a function of insulating engine vibration and preventing it from being transmitted to the downstream side, and the catalytic converter 13 has a function of purifying exhaust gas. The sub muffler 14 and the main muffler 15 attenuate the sound waves that propagate in the exhaust gas to reduce the leakage of exhaust noise to the outside.

A branch pipe portion 17 is welded to a bent portion of an exhaust pipe 16 connecting the sub muffler 14 and the main muffler 15 to draw out exhaust gas in a straight direction. Branch pipe section 1
A resin molding portion 18 formed of a resin and formed into a dead end is connected to the tip of 7. The resin molding portion 18 is provided for the vehicle body 10 that does not interfere with other parts such as the differential mechanism 10A.
It is located in the empty space below. The branch pipe portion 17 and the resin molding portion 18 constitute a so-called Helmholtz type resonator, and the dimensions of each portion are such that relatively low specific frequency components that are not sufficiently attenuated by the sub muffler 14 and the main muffler 15 are attenuated. Has been set.

Specifically, the inner radius of the branch pipe portion 17 is r, the length is L, the cross-sectional area is S, the volume of the resin molding portion 18 is V, the circular constant is π, the sound velocity is c, When the central frequency (resonance frequency) of the specific frequency component to be attenuated is f, the relationship of f = (c / 2π) × {S / [(L + πr / 2) × V]} ^1/2 is satisfied. There is. Further, the length and bending position of the exhaust pipe 16 are adjusted so that the connection position of the branch pipe portion 17 in the exhaust system does not overlap the acoustic node with respect to the specific frequency component.

As shown in FIG. 2 (a), the resin molding portion 18 is a single component integrally molded by blow molding by heating thermoplastic nylon resin to 250 ° C. or higher to soften it. Composed of. The resin molding part 18 is 150
It has heat resistance of C to 200 C. Resin molding part 18
Is a structure in which the sleeve 20 into which the branch pipe portion 17 is inserted is connected to the space portion 28 having the above-mentioned volume V. A slit 26 is formed in the sleeve 20 so that the diameter of the sleeve 20 can be reduced, and an opening 2 for holding a protrusion 21 formed in the branch pipe 17 is formed.
2 are formed. The resin molding portion 18 is locked in relative rotation with respect to the branch pipe 17 by inserting the sleeve 20 into the branch pipe 17 and dropping the protrusion 21 into the opening 22. In this state, the clamper 24 and U are attached to the outside of the sleeve 20.
By disposing the V-shaped bolts 23 and tightening the nuts 25 on the U-shaped bolts 23, the resin molded portion 18 is firmly fixed to the branch pipe 17.

As shown in FIG. 2B, the resin molding portion 1
Guidance shapes 31 and 32 are formed on the outer appearance of the space portion 28 of No. 8. Although not shown, the shape of the resin molding portion 18 viewed from the front side is a quadrangle with rounded corners. The guide shape 31 projects in the space below the vehicle body 10 in the traveling direction, and scoops up a part of the airflow passing under the vehicle body 10 as the vehicle travels and guides it upward. The airflow rises so as to wrap the outside of the sleeve 20, and then escapes rearward through the gap between the ceiling portion 33 of the resin molding portion 18 and the vehicle body 10. Left and right guide shape 32
Is a ceiling part 3 with both left and right wings widened toward the upstream side.
The height up to 3 is projected in the traveling direction, and as shown by the arrow in FIG. 2A, the airflow rising on both sides of the sleeve 20 is narrowed inward to enhance the heat removal effect of the sleeve 20. In FIG. 2B, for convenience of illustration, the clamper 2
The front guide shape 32 overlapping with No. 4 is not shown.

In order to suppress the temperature rise of the sleeve 20,
A heat radiating member 19 having a cross-sectional shape as shown in FIG. 3 is brazed to the outer periphery of the branch pipe 17 part. The heat dissipation member 19 is
A thin iron plate is formed into a wavy shape, and each wave bottom portion is brazed to the outer circumference of the branch pipe portion 17. The heat dissipation member 19 is
The surface area of the branch pipe part 17 is kept low by increasing the heat radiation area of the branch pipe part 17 and increasing the amount of heat carried away by the surrounding air. Since the heat radiation of the heat radiating member 19 expands the surface temperature difference of the branch pipe portion 17 before and after the heat radiating member 19, even if the surface temperature of the exhaust pipe 16 side portion greatly exceeds the heat resistant temperature of the sleeve 20, it is inserted into the sleeve 20. The surface temperature of the broken portion does not exceed the heat resistant temperature of the sleeve 20.

A part of the air flow formed by the cooperation of the guide shapes 31, 32 and the ceiling 33 rises on both sides of the heat dissipation member 19 and participates in heat removal of the heat dissipation member 19. Guide shape 31, 3
2 enhances the air flow generated around the branch pipe portion 17 as the vehicle travels, and synergistically enhances the cooling effect of the heat radiation member 19 on the branch pipe portion 17.

According to the exhaust system resonator device of the embodiment, since the Helmholtz type resonator which resonates with the specific frequency component is connected to a position acoustically convenient for the attenuation of the specific frequency component, the inside of the exhaust pipe 16 is connected. The exhaust noise can be reduced by effectively attenuating the specific frequency component of. Also,
Since the branch pipe portion 17 is drawn out from the bent portion of the exhaust pipe 16 in the straight direction of the exhaust gas, the noise component in the exhaust pipe 16 is efficiently input to the Helmholtz type resonator and passes through the exhaust pipe 16 as it is. Is reduced, and exhaust noise emitted to the outside is reduced. Further, even when the length of the branch pipe portion 17 is changed, the volume of the resin molding portion 18 can be adjusted to maintain the resonance frequency of the Helmholtz type resonator constant, so that the branch pipe can be adjusted according to the position of the empty space under the vehicle body 10. A Helmholtz type resonator having good mountability in which the length and shape of the portion 17 are freely determined can be configured. Also,
The interior space of the branch pipe portion 17 and the resin molding portion 18 has a dead end bag-like structure, and high-temperature exhaust gas does not flow in, and at most, the exhaust gas is restricted in and out due to the pressure change. The exhaust gas temperature in 18 is kept low. Therefore, there is no fear of thermal damage even in the thin resin molding portion 18 having no heat insulating material inside.

Further, heat conduction occurs from the exhaust pipe 16 side to the resin molding portion 18 side through the branch pipe portion 17. However, by providing guide shapes 31 and 32 on the outer appearance of the resin molding portion 18, the branch pipe which is running. Since the airflow is formed around the 17 parts and the sleeve 20, the branch pipe part 17 and the sleeve 20 are removed from the outside to keep the surface temperature low. Therefore, the temperature of the sleeve 20 is kept low, the strength and shape are maintained, and there is no fear of thermal deformation. Further, since the heat dissipation member 19 that cooperates with the airflow formed by the guide shapes 31 and 32 to realize efficient heat dissipation is attached to the branch pipe portion 17, even if the branch pipe portion 17 is considerably short, the sleeve 20 is attached to the sleeve 20. The temperature of the branch pipe portion 17 to be inserted is suppressed so that the heat resistance temperature of the sleeve 20 is not exceeded.

Further, even when heat is trapped in the space under the vehicle body 10 and the surface temperature of the resin molding portion 18 is increased while the vehicle is idle, the ventilation path is provided between the ceiling portion 33 and the vehicle body 10. When the traveling is restarted, the entire resin molding portion 18 is quickly cooled by the airflow flowing along the surface of the box body 28. Further, during running, an air flow is formed in the gap between the exhaust pipe 16 and the resin molding portion 18, so that heat transfer due to air or convection does not occur between the exhaust pipe 16 and the resin molding portion 18. Moreover, the rise in the surface temperature of the resin molding portion 18 due to the radiant heat is also suppressed by the heat removal effect of the air flow.

[0022]

According to the invention of claim 1, the air flow formed by the guide shape of the resin molding portion during running removes heat from the outside of the connecting portion between the branch pipe portion and the resin molding portion to keep the temperature low. Therefore, the heat load on the resin molding portion is reduced, and even a resin molding portion having a simple structure that does not have a resin-molded low heat resistance connecting portion or a heat insulating structure can be used without exceeding the heat resistance of the material. Further, since the resin molding portion itself is provided with the guide shape, it is not necessary to provide the peripheral parts with the same guide shape or to attach a dedicated member having the guide shape to the periphery. Therefore, an exhaust system resonator device that has a small number of parts and is easy to assemble and install is constructed, and such an exhaust system resonator device is not limited to the vicinity of the exhaust system outlet, but has a higher temperature than the exhaust system. Can be installed in any position.

According to the second aspect of the present invention, since the heat dissipating member is provided to enhance the heat removal effect of the branch pipe portion, even if the branch pipe portion is short or thick, the high temperature on the exhaust system side is resin-molded. You don't have to tell the department. Therefore, it is possible to use a resin molded connection part with low heat resistance or a resin molded part that does not have a heat insulating structure without exceeding the heat resistance of the material, and an exhaust system resonator device with a small number of parts and easy to assemble and install. Can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an exhaust system of an automobile.

FIG. 2 is an explanatory diagram of a structure of a resin molding unit device.

FIG. 3 is an explanatory diagram of a structure of a heat dissipation member.

[Explanation of symbols]

 10 Car Body 10A Differential Mechanism 11 Engine 12 Flexible Tube 13 Catalytic Converter 14 Sub Muffler 15 Main Muffler 16 Exhaust Pipe 17 Branch Pipe 18 Resin Molding Part 19 Heat Dissipating Member 20 Sleeve 21 Projection 22 Opening 23 U-Shaped Screw 24 Clamper 25 Nut 26 Slit 28 Box 31, 32 Guide shape 33 Ceiling

Claims (2)

[Claims] 1. An exhaust system resonator device mounted on an exhaust system of an automobile to reduce exhaust noise, wherein the exhaust system is branched from an exhaust gas flow path at an intermediate position of the exhaust system and is separated from the exhaust system. A branch pipe part (17) made of metal extended to a predetermined position, and a resin molding part (18) molded into a dead end bag shape with resin and connected to the tip of the branch pipe part (18), The branch pipe section (1
A guide device (31, 32) for forming an airflow flowing into a connection portion between the resin molding portion (18) and the resin molding portion (18) is provided in the resin molding portion (18). . 2. An exhaust system resonator device mounted on an exhaust system of an automobile to reduce exhaust noise, wherein the exhaust system is branched from an exhaust gas flow path at an intermediate position of the exhaust system and is separated from the exhaust system. A branch pipe part (17) made of metal extended to a predetermined position, and a resin molding part (18) molded into a dead end bag shape with resin and connected to the tip of the branch pipe part (18), An exhaust system resonator, characterized in that the branch pipe part (17) is provided with a metal heat radiating member (19) that radiates heat in contact with an airflow generated around the branch pipe part (17) as the vehicle travels. apparatus.