A MUFFLER FOR AUTOMOBILE Technical Field The present invention relates to an exhaust system used in an internal combustion engine of a motor vehicle to accelerate discharge of exhaust gas, and more particularly, the present invention relates to an exhaust system for a motor vehicle, adapted to be applied to or operatively associated with a muffler arranged in an exhaust gas discharge path, and comprising a discharge acceleration pipe which is flared at one end thereof and thereby induces inflow of outside air into a tail pipe of the muffler, with an air inflow rate varying depending upon a speed of the motor vehicle, to accelerate discharge of exhaust gas and thereby improve fuel economy.

Background Art As is well known in the art, a motor vehicle having an internal combustion engine obtains power through 4 strokes, that is, intake, compression, expansion and exhaust strokes.

Considering air flow through the intake and exhaust strokes, in the intake stroke, intake air flows into a cylinder through an air cleaner, a throttle valve, etc., without undergoing significant resistance. On the contrary, in the exhaust stroke, as exhaust gas flows through an exhaust manifold, an exhaust cleaner utilizing catalysts, a muffler, etc. into a tail pipe and is then discharged to the outside, the exhaust gas undergoes significant resistance.

When a next cycle proceeds while exhaust gas is discharged from the cylinder toward the tail pipe, a valve overlap occurs, in which intake and exhaust valves of the cylinder are simultaneously opened. At this time, since exhaust gas, which has been discharged toward the tail pipe, momentarily reflows into the cylinder, a vacuum is formed in the exhaust manifold, and due to this, discharge of exhaust gas is primarily hindered.

Also, in a three dimensional catalytic unit serving as the exhaust cleaner, as exhaust gas passes through fine holes defined in the three dimensional catalytic unit and each having a honeycomb-shaped configuration, a flow velocity of exhaust gas is

considerably decreased, and thereby, discharge of exhaust gas is secondarily hindered.

Thereafter, as exhaust gas flows into the muffler and is routed through several partitioning walls of the muffler to achieve operating noise reduction, discharge of exhaust gas is thirdly hindered.

In the above-described discharge process, since exhaust gas has a pressure of 3-5 kg/cm2 and a temperature of about 600°C, the muffler must be necessarily provided to deaden noise of exhaust gas. The muffler is generally designed to have a volumetric capacity which is 15-20 times as large as a displacement of the motor vehicle. In the muffler, smooth discharge of exhaust gas is hindered due to air resistance, and thereby output of the engine is decreased by 5-10%.

Accordingly, it is to be readily understood that, by accelerating discharge of exhaust gas, output and fuel economy of the engine can be enhanced.

Various suggestions for ensuring smooth discharge of exhaust gas have been disclosed in the art.

Korean Patent Laid-open Publication No. 2000-56951 discloses a vehicle exhaust canister. The vehicle exhaust canister has streamlined outer surfaces for promoting smooth airflow during travel of a motor vehicle. The vehicle exhaust canister is coupled to a tail pipe in a manner such that low-pressure regions can be created as air flows along the streamlined outer surfaces of the exhaust canister. By this fact, as exhaust gas is compulsively drawn out of the exhaust canister, discharge of exhaust gas is promoted.

However, the attachment of the streamlined exhaust canister to the motor vehicle increases structural complexity and requires an additional space. Also, while the motor vehicle is stopped or travels at a low speed, since it is impossible to induce a substantial amount of airflow on the streamlined outer surfaces of the exhaust canister, discharge of exhaust gas is hindered due to narrow discharge openings defined through the streamlined exhaust canister.

Korean Patent Laid-open Publication No. 1998-75223 discloses a tail pipe for a main silencer, having a vortex flow generating device. In this document, a vortex flow generating impeller is disposed in the middle of the tail pipe in a manner such that the impeller can be rotated by exhaust gas to generate vortex flow and thereby facilitate

discharge of exhaust gas. Nevertheless, because the vortex flow generating impeller produces resistance acting against flow of exhaust gas, practicality of the vortex flow generating impeller is deteriorated.

Korean Utility Model Publication No, 1996-4888 discloses an exhaust gas discharging device for a motor vehicle. In this exhaust gas discharging device, a separate pipe is connected to a rear end of a tail pipe by means of bolts, and a plurality of vortex flow generating elements are secured to a circumferential inner surface of the separate pipe, so that vortex flow is generated in exhaust gas to improve discharge efficiency. Notwithstanding, the simple generation of the vortex flow in exhaust gas is insufficient to ensure rapid and smooth discharge of exhaust gas. Therefore, apart from natural discharge of exhaust gas by its pressure, since the generated vortex flow only partially aids discharge of exhaust gas, a significant increase in discharge efficiency cannot be accomplished.

Further, in an exhaust gas discharging device which is described in Korean Patent No. 257874, as shown in FIG. 1, a muffler 4 is arranged in an exhaust gas discharge path. A sub duct 8 is connected to an exhaust pipe 2 forward of the muffler 4. The sub duct 8 has installed therein a valve 9 for adjusting an air flow rate in conformity with a degree to which a throttle valve is opened. A vortex flow generating duct 5 having a vane 7 for generating vortex flow is connected to the sub duct 8. Outside air can flow into the exhaust pipe 2 through the vortex flow generating duct 5 and the sub duct 8.

Nonetheless, this conventional device suffers from defects in that, since the vortex flow generating duct 5 into which outside air flows is connected via the sub duct 8 to the exhaust pipe 2 forward of the muffler 4, noise of exhaust gas leaks to the outside through the ducts 5 and 8, and severe noise pollution is generated. In this regard, upon accelerating a speed of a motor vehicle, as the valve 9 is further opened, noise is generated to an increased degree. Also, because exhaust gas can be discharged to the outside through the ducts 5 and 8 which have less air resistance than the inside of the muffler 4, outside air cannot properly flow into the ducts 5 and 8, by which practicality of the conventional device is deteriorated.

Moreover, in the conventional device, because outside air flows through an

entrance into the inside of the muffler 4, air resistance governing the inside of the muffler 4 acts against the airflow, and thereby, discharge of exhaust gas cannot be rapidly implemented. Also, due to the fact that the valve 9 for adjusting an air flow rate is installed in the sub duct 8 to be operated in an interlocked manner with the throttle valve of an engine, an entire construction of the conventional device is made complicated. Besides, since outside air flows through the entire muffler, foreign matters contained in outside air, such as dust, sand, and the like, are accumulated in the muffler 4, by which functionality of the muffler 4 is degraded.

Disclosure of the Invention Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide an exhaust system for a motor vehicle, which induces inflow of outside air into a tail pipe of a muffler to allow the outside air to be discharged along with exhaust gas to thereby accelerate discharge of exhaust gas.

Another object of the present invention is to provide an exhaust system for a motor vehicle, which ensures rapid discharge of exhaust gas and avoids a valve overlap, thereby preventing backflow of exhaust gas into a cylinder and enhancing output of an engine.

Still another object of the present invention is to provide an exhaust system for a motor vehicle, which is rigidly structured to improve durability and can be applied to existing mufflers without requiring modification of the existing mufflers, thereby achieving compatibility with a diversity of mufflers.

Yet still another object of the present invention is to provide an exhaust system for a motor vehicle, which is configured to allow inflow of outside air to be directed at a high flow velocity to a point adjacent to an exit of an exhaust gas discharge path, thereby preventing noise from leaking to the outside and foreign matters contained in the outside air from accumulating in a muffler.

In order to achieve the above object, according to the present invention, there is provided an exhaust system for a motor vehicle, adapted to be applied to or operatively associated with a muffler arranged in an exhaust gas discharge path to accelerate

discharge of exhaust gas, comprising a funnel-shaped pipe portion flared toward a front end of the motor vehicle and communicated with a rear portion of the exhaust gas discharge path in a manner such that outside air collected in the funnel-shaped pipe portion is mixed with exhaust gas passing through the muffler and flowing through the exhaust gas discharge path to rapidly discharge exhaust gas.

Brief Description of the Drawings The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description when taken in conjunction with the drawings, in which: FIG. 1 is a perspective view illustrating a conventional exhaust device for inducing inflow of outside air into a muffler ; FIG. 2 is a cross-sectional view illustrating an exhaust system for a motor vehicle in accordance with a first embodiment of the present invention, which is applied to a muffler ; FIG. 3 is a cross-sectional view illustrating an exhaust system for a motor vehicle in accordance with a second embodiment of the present invention, which is applied to a muffler ; FIG. 4 is a cross-sectional view illustrating an exhaust system for a motor vehicle in accordance with a third embodiment of the present invention, which is operatively associated with a muffler; FIG. 5 is a cross-sectional view illustrating an exhaust system for a motor vehicle in accordance with a fourth embodiment of the present invention, which is operatively associated with a muffler ; FIG. 6 is a cross-sectional view illustrating an exhaust system for a motor vehicle in accordance with a fifth embodiment of the present invention, which is operatively associated with a muffler; FIG. 7 is a cross-sectional view illustrating an exhaust system for a motor vehicle in accordance with a sixth embodiment of the present invention, which is operatively associated with a muffler ; FIG. 8 is a cross-sectional view illustrating an exhaust system for a motor

vehicle in accordance with a seventh embodiment of the present invention ; and FIG. 9 is a front view illustrating the exhaust system of FIG. 8.

Best Mode for Carrying Out the Invention Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings.

Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts.

FIG. 2 is a cross-sectional view illustrating an exhaust system for a motor vehicle in accordance with a first embodiment of the present invention, which is applied to a muffler.

The muffler 10 is arranged in a path through which exhaust gas is discharged from an engine of the motor vehicle. The exhaust system comprises a funnel-shaped pipe portion 30 and an extended pipe portion 32. The funnel-shaped pipe portion 30 is flared toward a front end of the motor vehicle and communicated with a rear end of an exhaust gas discharge path. The extended pipe portion 32 is integrally connected to the funnel-shaped pipe portion 30 and passes through the muffler 10 to communicate the funnel-shaped pipe portion 30 with a tail pipe 20 connected to an exit of the muffler 10. Outside air collected in the funnel-shaped pipe portion 30 is mixed with exhaust gas which has passed through the muffler 10 and flows through the exhaust gas discharge path, to rapidly discharge exhaust gas. A plurality of fastening brackets 34 are attached to a circumferential inner surface of the tail pipe 20 to fixedly maintain the extended pipe portion 32.

The funnel-shaped pipe portion 30 is welded to a side wall of the muffler 10 in a manner such that the extended pipe portion 32 extends through the side wall of the muffler 10. Since the extended pipe portion 32 is welded to the fastening brackets 34 which are spaced apart one from another in a lengthwise direction of the tail pipe 20, operation noise is not generated while the motor vehicle travels and vibrates on a road.

In this way, the exhaust system has a rigid structure and improved durability.

As can be readily seen from the above description, in the present invention, if exhaust gas discharged through a conventional procedure flows into the muffler 10,

noise is primarily removed in a first expansion room which is defined at a rear end of the muffler 10. Before exhaust gas flows into the first expansion room, a certain amount of exhaust gas passes into a second expansion room through a plurality of first air holes 12 defined in an inlet pipe, by which noise of exhaust gas is secondarily removed. Then, as exhaust gas flows into a third expansion room through a first communication pipe 15, noise of exhaust gas is thirdly removed. Also, while exhaust gas passes into a fourth expansion room through-a second communication pipe 16, noise of exhaust gas is fourthly removed. The second communication pipe 16 is defined with a plurality of second air holes 14 through which exhaust gas can flow into the second expansion room. Exhaust gas which is deprived of noise is discharged to the outside through the tail pipe 20, a front end of which is connected to the fourth expansion room. Since the funnel-shaped pipe portion 30 is flared toward the front end of the motor vehicle, even while the motor vehicle is stopped or travels at a low speed, a substantial amount of airflow is induced therein, and a back pressure is decreased. If the motor vehicle travels at a high speed, as a pressure of outside air, which is collected in the funnel-shaped pipe portion 30 and flows through the extended pipe portion 32, is increased, exhaust gas is rapidly discharged to the outside at a rear end of the tail pipe 20, and thereby discharge of exhaust gas is accelerated.

In the case that the motor vehicle travels at a high speed, as an increased amount of outside air is collected in the funnel-shaped pipe portion 30 and flows through the extended pipe portion 32, an internal pressure developed in the muffler 10, which is increased due to high speed travel of the motor vehicle, can be quickly relieved. Therefore, since the exhaust system according to the present invention operates in step with a speed of the motor vehicle, the exhaust system can reliably satisfy both high speed and low speed travel situations.

Referring to FIG. 3, there is shown a cross-sectional view illustrating an exhaust system for a motor vehicle in accordance with a second embodiment of the present invention, which is applied to a muffler. A person skilled in the art will readily recognize that the present exhaust system can be effectively applied to various muffler constructions.

In this second embodiment of the present invention, the exhaust system is

applied to a muffler 10 which is divided into a plurality of expansion rooms by partitioning walls. Communication holes are defined through the partitioning walls to be arranged in a zigzag pattern. The exhaust system comprises the funnel-shaped pipe portion 30 and the extended pipe portion 32. The extended pipe portion 32 is formed integrally with the funnel-shaped pipe portion 30 and extends through communication pipes and the partitioning walls of the muffler 10 to be communicated with the tail pipe 20. As for functions of the funnel-shaped pipe portion 30 and the extended pipe portion 32, since they are the same as in the first embodiment, detailed explanation thereof shall be omitted herein.

Also, while not shown in the drawings, in the case that a muffler is positioned perpendicularly to a direction where the motor vehicle travels, the exhaust system according to the present invention can be applied to the muffler by bending the funnel- shaped pipe portion 30 to face the front end of the motor vehicle and by bending the extended pipe portion 32 to be communicated with the tail pipe 20. In this way, the exhaust system can be easily modified in its configuration while not departing from the scope and spirit of the present invention.

An air hole 22 which is defined adjacent to the rear end of the tail pipe 20 serves as an outside air inlet hole through which outside air can flow into the tail pipe 20 owing to a high pressure which governs a discharge end of the exhaust gas discharge path.

FIG. 4 is a cross-sectional view illustrating an exhaust system for a motor vehicle in accordance with a third embodiment of the present invention, which is operatively associated with a muffler.

In FIG. 4, the muffler 10 is arranged in a path through which exhaust gas is discharged from an engine of the motor vehicle. The exhaust system comprises a funnel-shaped pipe portion 41 and an extended pipe portion. The funnel-shaped pipe portion 41 is flared toward a front end of the motor vehicle. The extended pipe portion is fitted around and spot-welded to the tail pipe 20 which is formed at the rear end of the muffler 10. A portion of the tail pipe 20, which is substantially surrounded by the funnel-shaped pipe portion 41, is defined at different axial positions with a plurality of outside air inlet openings 43 in a manner such that the outside air inlet openings 43 are

spaced apart one from another in a circumferential direction. Steel pieces 45, which are formed by cutting the tail pipe 20 to define the outside air inlet openings 43 and held connected at one ends thereof to the tail pipe 20, are bent into the tail pipe 20 to generate vortex flow in exhaust gas flowing through the tail pipe 20.

By this construction, if the motor vehicle travels on a road, outside air is collected in the funnel-shaped pipe portion 41. Then, as the collected outside air flows through a neck portion of the funnel-shaped pipe portion 41, the outside air is pressurized to have a high pressure. In this state, the outside air flows into the tail pipe 20 through the outside air inlet openings 43 and is mixed with exhaust gas to increase a pressure of exhaust gas and thereby accelerate discharge of exhaust gas.

At this time, due to the fact that the outside air inlet openings 43 are defined at different axial positions of the tail pipe 20 and spaced apart one from another in the circumferential direction and that the steel pieces 45 are bent into the tail pipe 20, vortex flow is naturally generated due to inflow of outside air into the tail pipe 20. By the vortex flow, a flow velocity of exhaust gas is further increased.

FIG. 5 is a cross-sectional view illustrating an exhaust system for a motor vehicle in accordance with a fourth embodiment of the present invention, which is operatively associated with a muffler.

In this embodiment, an extended pipe portion 42 integrally connected to a rear end of the funnel-shaped pipe portion 41 has a larger diameter than the tail pipe 20 and is fastened to the tail pipe 20 by means of bolts 46, in a manner such that an annular inlet port 44, through which outside air flows into the extended pipe portion 42, is defined between the tail pipe 20 and the extended pipe portion 42.

Consequently, as outside air flowing at a high velocity is mixed with exhaust gas at a discharge end of the exhaust gas discharge path, a pressure of exhaust gas is increased. In this embodiment, it is to be readily understood that the exhaust system can be easily mounted to tail pipes of existing motor vehicles.

FIGs. 6 and 7 are cross-sectional views illustrating exhaust systems for a motor vehicle in accordance with fifth and sixth embodiments of the present invention, which are operatively associated with mufflers.

In these embodiments, the exhaust systems further comprise a spiral plate

segment 47 formed by twisting a metallic plate and placed in the extended pipe portion 42 or the tail pipe 20 through which exhaust gas is discharged, to generate vortex flow.

The spiral plate segment 47 functions to generate vortex flow in exhaust gas.

Therefore, as vortex flow is generated in exhaust gas flowing through a narrow path, discharge of exhaust gas can be accelerated.

FIGs. 8 and 9 illustrate an exhaust system for a motor vehicle in accordance with a seventh embodiment of the present invention.

A separate pipe 48, which has an inner diameter corresponding to an outer diameter of the tail pipe 20 to allow the tail pipe 20 to be fitted therein, is positioned at a center of the funnel-shaped pipe portion 41 which is flared toward the front end of the motor vehicle. The separate pipe 48 is rigidly connected to the funnel-shaped pipe portion 41 by way of a plurality of support vanes 49 which are spaced apart one from another in a circumferential direction.

The support vanes 49 function to generate vortex flow in outside air which passes through the funnel-shaped pipe portion 41. Thus, by the fact that the separate pipe 48, which is positioned at the center of the funnel-shaped pipe portion 41 and fitted around the tail pipe 20, is connected to the funnel-shaped pipe portion 41 by way of the support vanes 49, it is possible to fixedly and stably support the funnel-shaped pipe portion 41.

Industrial Applicability As apparent from the above description, the exhaust system for a motor vehicle according to the present invention provides advantages in that, since a funnel-shaped pipe portion is mounted to a muffler to allow outside air to be mixed with exhaust gas flowing through a tail pipe to thereby rapidly discharge exhaust gas, with an air inflow rate varying depending upon a speed of the motor vehicle, a back pressure is decreased, and output and fuel economy of an engine are improved. Also, due to the fact that the exhaust system has a simple construction while ensuring inflow of outside air and generation of vortex flow, the exhaust system can be applied to existing mufflers without requiring modification of the existing mufflers.

Further, because the exhaust system extending through the muffler is rigidly

structured to improve durability while preventing noise of exhaust gas from leaking to the outside, functionality of the muffler is maintained as it is. Also, by the fact that foreign matters which may be contained in outside air, such as dust, sand, and the like, are discharged to the outside through an extended pipe portion extending adjacent to a rear end of the tail pipe, it is possible to avoid malfunctioning of the muffler due to accumulation of the foreign matters in the muffler, including closure of air holes, functional deterioration of sound absorbing material, and reduction in volumetric capacity of the muffler. In addition, as exhaust gas is rapidly discharged to the outside, an amount of carbon, moisture, etc., which are left in an exhaust cleaner and the muffler, is decreased, whereby an available service time of the exhaust system can be lengthened.