JPS6316820Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field]

The present invention relates to a sub-muffler that is installed in the exhaust pipe of a vehicle and has a resonance chamber formed by an inner cylinder in which a resonance hole is formed and an outer cylinder arranged concentrically with the inner cylinder. In particular, the present invention relates to a structure for forming a resonance hole formed in an inner cylinder.

[Conventional technology]

When exhaust gas from the combustion chamber of the engine flows into the exhaust pipe that connects the engine and the muffler (main muffler), air column resonance corresponding to the length of the exhaust pipe occurs. This phenomenon causes the resonant frequency to change depending on the engine speed, resulting in various exhaust sounds (so-called muffled sounds) ranging from low to high frequencies. As described above, when exhaust noise (muffled sound) is generated, depending on its frequency, it may cause discomfort to the driver and the like. Therefore, in order to reduce this exhaust noise (muffled sound), the engine and muffler (main muffler)
A structure in which a so-called resonance type sub-muffler is interposed between the two is known. 1 and 2 are vertical cross-sectional views showing the structure of a conventional resonant sub-muffler. FIG. 1 is a vertical cross-sectional view cut along the flow direction of exhaust gas, and FIG. FIG. 3 is a vertical cross-sectional view taken along a line. As shown in Figs. 1 and 2, the conventional sub-muffler for automobiles has an inner cylinder 2 through which exhaust gas flows.
and an outer cylinder 4 disposed approximately concentrically with the inner cylinder 2, and a resonance chamber 1 is formed between the inner and outer cylinders. The inner tube 2 is provided with a plurality of resonance holes 3 that communicate the resonance chamber 1 with the inside of the inner tube. In such a resonance type sub-muffler, by appropriately setting the dimensions (length, volume) of the resonance chamber 1 and the diameter and position of the resonance hole 3, air column resonance at a predetermined frequency is suppressed, and the exhaust pipe (muffled) is suppressed. noise) can be reduced. 5 and 6 are heat shield plates, which respectively suppress heat transfer to a floor panel (not shown) and the ground.

[Problem that the invention attempts to solve]

However, in the above-mentioned conventional sub-muffler for automobiles, since a plurality of resonance holes 3 that communicate the inside of the inner cylinder 2 and the resonance chamber 1 are bored in the upper and lower and left and right walls of the inner cylinder 2, water flows out from the resonance holes 3. The heat of the exhaust gas causes a local temperature rise on the wall surface of the outer cylinder 4. In particular, when the resonance holes 3 are formed in the upper and lower walls of the inner tube 2, the degree of temperature rise in the upper and lower walls of the outer tube 4 increases, and heat is transferred to the floor panel and objects on the ground.
Therefore, for example, heat damage such as deterioration of rubber parts such as parking brakes and heating of objects on the ground occurs. In order to avoid heat damage caused by heat transfer from the sub-muffler, it becomes necessary to cover the entire sub-muffler with heat shield plates 5 and 6, or an integrated heat shield plate, which increases the cost of the vehicle and reduces installation costs. This resulted in deterioration of assembly workability at times. Therefore, as a result of various experiments, the applicant found that although the silencing performance of a resonant sub-muffler varies depending on the dimensions (length, volume) of the resonant chamber 1, the diameter and position of the resonant hole 3, as mentioned above, It was found that even if the number of holes 3 was changed, the silencing performance did not change much. That is, although the frequency characteristics of the exhaust sound (muffled sound) differ from engine to engine, for a particular engine, even if the number of resonance holes 3 is reduced, the sound at the target frequency can be sufficiently reduced. Furthermore, it has been found that by changing the drilling position of the resonance hole 3, the temperature distribution in the outer cylinder 4 changes, and it is possible to suppress a local temperature rise. That is, by appropriately setting the drilling position of the resonance hole 3, its diameter, and the dimensions of the resonance chamber 1, it is possible to improve the exhaust noise reduction effect and suppress the temperature rise of the outer cylinder 4. This also makes it possible to downsize and reduce the number of plates. Therefore, the present invention prevents various heat damage by suppressing the local temperature rise of the sub-muffler outer cylinder due to the heat of the exhaust gas flowing out from the resonance hole, and is installed to prevent heat damage. The purpose of reducing the number of component parts was to avoid increasing vehicle costs and deteriorating assembly workability.

[Means to solve the problem]

Therefore, in order to solve the above-mentioned problems, the present invention is characterized in that the drilling position of the resonance hole that communicates the inside of the inner cylinder and the resonance chamber is changed. Specifically, FIGS. 3, 4, and 5 of the present invention
To explain using the figure as an example, the sub-muffler 7 for an automobile includes an inner cylinder 2 in which a resonance hole 3 is formed, and an inner cylinder 2 in which a resonance hole 3 is formed.
and an outer cylinder 4 arranged substantially concentrically. The upper and lower ends of the outer cylinder 4 are welded to the inner cylinder 2 upstream and downstream of the resonance hole 3, and the resonance chamber 1 is constituted by the space formed between these inner and outer cylinders. The resonance hole 3 is located at the top T of the inner cylinder on the side facing the floor panel 18 of the vehicle when mounted on the vehicle.
Perforated only in the wall.

[Effect]

Since the resonance chamber 1 formed between the inner tube 2 and the outer tube 4 communicates with the inside of the inner tube 2 through the resonance hole 3, the muffled noise generated from the exhaust pipe is muffled by the resonance effect. Since the resonance hole 3 drilled in the inner cylinder 2 is drilled only on the top T wall surface of the inner cylinder, the rise in temperature of the lower wall of the outer cylinder 4 due to the heat of the exhaust gas flowing out from the resonance hole 3 is suppressed. be done.

【Example】

Hereinafter, embodiments of the present invention will be described based on the drawings. 3, 4, and 5 are diagrams showing the structure of an automobile sub-muffler according to an embodiment of the present invention, and FIG. 3 is a side view of a vehicle equipped with the sub-muffler of the present embodiment, and FIG. Figure 4 is a vertical cross-sectional view taken along the flow direction of exhaust gas, and Figure 5 is a vertical cross-sectional view taken along the flow direction of exhaust gas.
FIG. 3 is a vertical cross-sectional view taken along a line. In this embodiment, parts corresponding to the symbols shown in FIGS. 1 and 2 will be described using the same symbols as in FIGS. 1 and 2. As shown in FIG. 3, the sub-muffler 7 is interposed in the coating of the exhaust pipe 10 that connects the catalytic converter 8 and the main muffler 9. There is a sub-muffler 7 between this sub-muffler 7 and the floor panel 18 of the vehicle.
A heat shield plate 5 is provided to suppress heat from being transmitted to the floor panel 18. The specific structure of the sub-muffler 7 will be explained based on FIGS. 4 and 5. The sub-muffler 7 includes a hollow cylindrical inner cylinder 2 connected to an exhaust pipe 10 and an outer cylinder 4 disposed approximately concentrically with the inner cylinder 2. The inner cylinder 2 includes an inlet inner cylinder 14 connected to an upstream exhaust pipe and an outlet inner cylinder 15 connected to a downstream exhaust pipe.
In this embodiment, a resonance hole 3 is bored in the inner cylinder 14 on the inlet side. The outer cylinder 4 is composed of a main body part 11, an inlet flange part 12 and an outlet flange part 13 formed at the upper and lower ends of the main body part 11, and these flange parts are connected to the inner cylinder 2.
The upstream and downstream parts 16 and 17 of the resonance hole 3 bored in the resonance hole 3 are welded to the inlet-side inner cylinder 14 and the outlet-side inner cylinder 15 over the entire circumference, respectively, and are integrally constructed. In this way, by forming the inner cylinder 2 and the outer cylinder 4 into an integral structure, a space is formed between the inner cylinder 2 and the outer cylinder 4, and this space is communicated with the inside of the inner cylinder 2 through the resonance hole 3. By doing so, a so-called resonance chamber 1 is formed. As shown in FIG. 5, the resonance hole 3 is bored in the wall surface of the longest portion T of the inner cylinder 2 and has an appropriate diameter capable of reducing exhaust noise at a predetermined frequency. The operation of this embodiment based on the above configuration will be explained. After passing through the catalytic converter 8, the high-temperature exhaust gas discharged from the combustion chamber of the engine flows into the sub-muffler 7 through the inlet-side inner cylinder 14, the outlet-side inner cylinder 15, the exhaust pipe 10, and the main muffler 9. and is emitted into the atmosphere. Since the exhaust gas flowing in the exhaust pipe 10 pulsates due to so-called air column resonance, an exhaust pipe (muffled sound) corresponding to the engine speed is generated. However, as shown in this embodiment, since the resonance type sub-muffler 7 is disposed in the coating of the exhaust pipe 10, the resonance hole 3 is connected to the abdomen of the pulsating waveform of the exhaust gas flowing inside the exhaust pipe 10. By matching the node portions of the pulsating waveform of the exhaust gas that has entered the resonance chamber 1 through the filter, the exhaust sound (muffled sound) at a predetermined frequency is reduced. Furthermore, since the resonance hole 3 in this embodiment is drilled only on the top T wall surface of the inner cylinder 2 on the side facing the floor panel 18 when mounted on the vehicle, it is particularly important to drill the resonance hole 3 in the lower wall of the outer cylinder 4. It becomes possible to suppress heat transfer to. That is, the top T of the inner cylinder 2 on the side where the heat shield plate 5 necessary for suppressing heat transfer to the rubber parts of the parking brake cable conventionally attached to the lower wall of the floor panel 18 is disposed. That is, since the resonance hole 3 is drilled only in the part farthest from the lower wall of the outer cylinder 4, the local temperature increase in the outer cylinder 4 caused by the heat of the exhaust gas is suppressed in the part facing the heat shield plate 5. By using only the upper wall of the outer cylinder 4, heat transfer to the lower wall can be suppressed. In this way, by suppressing the temperature rise on the lower wall of the outer cylinder 4, it is possible to eliminate the heat shield plate that was installed between the sub-muffler 7 and the ground in conventional equipment, reducing costs by reducing the number of parts. This makes it possible to improve assembly workability during installation. Although a specific embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and includes various embodiments within the scope of the claims for utility model registration. For example, the resonance hole may be formed at the top wall of the inner cylinder on the side facing the floor panel when mounted on the vehicle, or at the entrance side inner cylinder depending on the frequency characteristics of each vehicle. Alternatively, it is sufficient if it is bored at an appropriate location in the inner cylinder on the outlet side. Further, the inner cylinder does not necessarily have to be of a so-called split type composed of an inlet-side inner cylinder and an outlet-side inner cylinder, and may be composed of a single cylindrical body.

[Effect of the idea]

As described above, according to the present invention, by appropriately setting the dimensions of the resonance chamber, the diameter and position of the resonance holes, etc., it is possible to reduce the number of resonance holes without deteriorating the silencing performance. By placing the hole only in the topmost wall of the inner cylinder facing the vehicle floor panel when mounted on the vehicle, it is possible to reduce the number of places where the temperature of the outer cylinder locally increases due to the heat of the exhaust gas. At the same time, heat transfer to the lower wall of the outer cylinder can be suppressed, making it possible to eliminate the heat shield plate disposed between the sub-muffler and the ground. Therefore, it is possible to reduce costs by reducing the number of parts and improve assembly workability without degrading the noise reduction performance of the sub-muffler.

[Brief explanation of drawings]

1 and 2 are vertical cross-sectional views showing the structure of a conventional resonant sub-muffler. FIG. 1 is a vertical cross-sectional view cut along the flow direction of exhaust gas, and FIG. Longitudinal cross-sectional view cut along the line, 3rd
4 and 5 are diagrams showing the structure of a sub-muffler for an automobile according to an embodiment of the present invention, and FIG. 3 is a side view of a vehicle equipped with the sub-muffler of this embodiment, and FIG. is a vertical sectional view taken along the flow direction of exhaust gas, and FIG. 5 is a vertical sectional view taken along the - line in FIG. 4. 1...Resonance chamber, 2...Inner cylinder, 3...Resonance hole, 4
...Outer cylinder, 5...Heat shield plate, 7...Sub muffler, 1
8...Floor panel.

Claims (1)

[Claims for Utility Model Registration] An inner cylinder in which a resonance hole is bored, and an outer cylinder arranged substantially concentrically with the inner cylinder, the upper and lower ends of which are welded to the inner cylinder at the upstream and downstream sides of the resonance hole. In an automobile sub-muffler that is installed in the exhaust pipe of a vehicle, the space formed between the inner tube and the outer tube constitutes a resonance chamber, and the resonance hole is inserted into the floor panel when mounted on the vehicle. A sub-muffler for an automobile, characterized in that the sub-muffler is bored only in the topmost wall surface of the inner cylinder on the side facing the .