Vehicle exhaust system

Abstract

To solve a problem that in conventional vehicular exhaust devices, it is difficult to sufficiently obtain sound absorption effects in a medium-frequency band and a low-frequency band.SOLUTION: A vehicular exhaust device 10 includes a chamber 22 accommodating a part of an exhaust pipe 13, and a first space 24 having a first sound absorption material 26 disposed therein and a second space 25 having a second sound absorption material 27 disposed therein are formed in the chamber 22. The first sound absorption material 26 and the second sound absorption material 27 are disposed in the chamber 22 so as to separate from each other. Due to this structure, in a process in which exhaust gas flows in the chamber 22, various sounds from a low-frequency band to a high-frequency band are substantially dampened from the exhaust gas.SELECTED DRAWING: Figure 2B

Description

[Technical Field]

[0001] The present invention relates to an exhaust system for a vehicle. [Background technology]

[0002] Patent Document 1 discloses a conventional exhaust system for an internal combustion engine, in which an exhaust pipe has a double structure consisting of an inner pipe and an outer pipe. The inner pipe is covered with ceramic wool, and glass wool or rock wool is disposed to cover the ceramic wool. With this structure, the space between the inner pipe and the outer pipe is filled with ceramic wool and glass wool or rock wool. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 7-8524 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described exhaust pipe structure, the ceramic wool and the glass wool or rock wool are continuously laminated, which causes a problem that the sound absorption effect is insufficient. Specifically, since there is no air layer between the ceramic wool and the glass wool or rock wool, the sound absorption effect in the mid- and low-frequency bands is insufficient.

[0005] In particular, in a structure in which multiple inner pipes are arranged inside an outer pipe, the outer pipe resonates due to vibrations caused when exhaust gas is emitted from the inner pipes, generating resonance noise from the exhaust pipe itself, which poses a problem in that the sound absorption effect of the entire exhaust system is not fully achieved.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a vehicle exhaust system that improves heat resistance and sound absorption by arranging two types of sound-absorbing material in the chamber of the silencer of the exhaust system with an air layer between them. [Means for solving the problem]

[0007] The vehicle exhaust system of the present invention is an exhaust system for a vehicle including a chamber that houses a part of an exhaust pipe that guides exhaust gas to the outside of the vehicle, the chamber being connected to a first space in which the exhaust pipe is disposed, and The exhaust pipe is not disposed in the first space. a second space, wherein a first sound-absorbing material is disposed in the first space to cover the exhaust pipe, and a second space is disposed in the second space to cover the first sound-absorbing material. There is an air gap between A second sound-absorbing material is disposed next to the first sound-absorbing material, and the first sound-absorbing material is made of a material that is more heat-resistant than the second sound-absorbing material. [Effects of the Invention]

[0008] The vehicle exhaust system of the present invention has a chamber that houses a portion of the exhaust pipe, and the chamber is formed with a first space in which a first sound-absorbing material is disposed and a second space in which a second sound-absorbing material is disposed. The first sound-absorbing material and the second sound-absorbing material are disposed apart from each other within the chamber. This structure significantly reduces a variety of sounds, from exhaust gas sounds to low- to high-frequency sounds, as the exhaust gas flows through the chamber. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram illustrating a vehicle exhaust system according to an embodiment of the present invention; [Figure 2A] 1 is a plan view illustrating a vehicle exhaust system according to an embodiment of the present invention; [Figure 2B] 1 is a cross-sectional view illustrating a vehicle exhaust system according to an embodiment of the present invention. [Figure 3] 3 is a characteristic diagram illustrating sound absorption characteristics of the vehicle exhaust system according to the embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] A vehicle exhaust system 10 according to one embodiment of the present invention will be described in detail below with reference to the drawings. In the following description of this embodiment, the same components will be designated by the same reference numerals, and repeated description will be omitted. In the following description, the up-down direction refers to the vehicle's height, the left-right direction refers to the vehicle's width, and the front-rear direction refers to the vehicle's length.

[0011] Fig. 1 is a block diagram illustrating a vehicle exhaust system 10 according to this embodiment. Fig. 2A is a plan view illustrating a silencer 15 of the vehicle exhaust system 10 according to this embodiment. Fig. 2B is a cross-sectional view illustrating the silencer 15 of the vehicle exhaust system 10 according to this embodiment, taken along line AA in Fig. 2A. Fig. 3 is a characteristic diagram illustrating the sound absorption characteristics of the silencer 15 of the vehicle exhaust system 10 according to this embodiment.

[0012] 1, a vehicle exhaust system 10 is a system that discharges exhaust gas from a combustion chamber of an engine 11 through an exhaust port to the outside of the vehicle. The vehicle exhaust system 10 mainly includes an exhaust manifold 12, an exhaust pipe 13, a catalytic converter 14, a silencer 15, an air-fuel ratio sensor 16, and a rear oxygen sensor 17.

[0013] The engine 11 is, for example, a four-stroke, horizontally opposed, four-cylinder, direct-injection gasoline engine mounted on an automobile such as a passenger car as a power source for driving the vehicle. The engine 11 is electronically controlled by an ECU 18, and the output from the engine 11 is transmitted to the drive wheels of the vehicle via a driving force transmission mechanism, such as a transmission and a propeller shaft 21 (see FIG. 2A), not shown.

[0014] The exhaust manifold 12 is an exhaust manifold that collects exhaust gases discharged from the exhaust ports of each of the cylinders 11A, 11B, 11C, and 11D of the engine 11. The exhaust pipe 13 is an exhaust pipe that directs the exhaust gases collected through the exhaust manifold 12 to the outside of the vehicle.

[0015] The catalytic converter 14 is an exhaust gas treatment device provided in the middle of the exhaust pipe 13. The catalytic converter 14 uses a three-way catalyst in which a precious metal such as platinum, rhodium, or palladium is supported on a carrier such as alumina to detoxify harmful exhaust components in the exhaust gas.

[0016] Silencer 15 is disposed in the middle of exhaust pipe 13, downstream of catalytic converter 14. As will be described in detail later, silencer 15 has a chamber structure that houses part of exhaust pipe 13 inside, and is a muffler that reduces the sound generated by exhaust gas.

[0017] The air-fuel ratio sensor 16 is provided near the inlet of the catalytic converter 14 and generates an output voltage that varies depending on the air-fuel ratio in the engine 11. The ECU 18 controls the fuel injection amount according to the output value of the air-fuel ratio sensor 16 so that the air-fuel ratio in the engine 11 falls within the activation range of the three-way catalyst.

[0018] The rear oxygen sensor 17 is provided near the outlet of the catalytic converter 14 and generates an output voltage that varies depending on the oxygen concentration in the exhaust gas. The output value from the rear oxygen sensor 17 is fed back to the ECU 18.

[0019] 2A, the propeller shaft 21 and the exhaust pipe 13 extend in the front-rear direction of the vehicle, for example, in the center of the vehicle width direction. The silencer 15 is formed in the middle of the exhaust pipe 13 and has a chamber 22 that houses a part of the exhaust pipe 13 therein.

[0020] Chamber 22 is formed by welding together ends of upper frame 22A (see FIG. 2B) and lower frame 22B (see FIG. 2B). Chamber 22 extends in the front-to-rear direction of the vehicle, below propeller shaft 21, and extends across the vehicle width relative to propeller shaft 21.

[0021] Three reinforcements 23 are disposed at equal intervals in the longitudinal direction of the vehicle in the chamber 22 below the propeller shaft 21. The reinforcements 23 are formed, for example, from cylindrical pipes, and the upper end side of the reinforcements 23 is welded to the upper frame 22A, and the lower end side of the reinforcements 23 is welded to the lower frame 22B. The reinforcements 23 correspond to the reinforcing member of the present invention.

[0022] The chamber 22 has a first space 24 on the left side of the vehicle relative to the reinforcement 23, and a second space 25 on the right side of the vehicle relative to the reinforcement 23. The first space 24 and the second space 25 are in communication with each other through the spaces between the three reinforcements 23. An exhaust pipe 13 is disposed on the outside of the side surface of the chamber 22 on the rear side of the vehicle, in communication with the first space 24 of the chamber 22.

[0023] As will be described in detail later, exhaust gases discharged from the exhaust pipe 13 into the first space 24 of the chamber 22 flow from the first space 24 to the nearby second space 25. The exhaust gases then return from the second space 25 to the first space 24, and are discharged from the chamber 22 through the exhaust pipe 13 to the outside of the vehicle.

[0024] 2B, the chamber 22 is disposed below the propeller shaft 21 in the center of the vehicle in the vehicle width direction, and therefore is formed to be wide and flat in the vehicle width direction due to the vehicle structure. As described above, a plurality of reinforcements 23 are disposed at regular intervals in the approximate center of the chamber 22 in the vehicle width direction. With this structure, the approximate center of the chamber 22 is reinforced along the length of the vehicle, thereby increasing the rigidity of the chamber 22.

[0025] A portion of the tip side of the exhaust pipe 13 is inserted into the first space 24 of the chamber 22. The tip of the exhaust pipe 13 disposed inside the chamber 22 is closed, and a plurality of small holes (not shown) are formed around the circumference of the exhaust pipe 13 for discharging exhaust gas into the first space 24. The exhaust gas flowing through the exhaust pipe 13 is then discharged radially into the first space 24 of the chamber 22 through the small holes.

[0026] The exhaust pipe 13 inserted into the chamber 22 is disposed at the center of the first space 24, spaced apart from its side. At least the area where the small holes of the exhaust pipe 13 are formed is covered all around with a first sound-absorbing material 26. With this structure, exhaust gases released from the small holes of the exhaust pipe 13 pass through the gaps in the wire of the first sound-absorbing material 26 and flow into the first space 24.

[0027] As shown in the figure, a second sound-absorbing material 27, for example, in a compressed and rolled state, is disposed in the second space 25 of the chamber 22. As shown in the figure, the second sound-absorbing material 27 is packed into the second space 25. As described above, three reinforcements 23 are disposed between the first space 24 and the second space 25. The first sound-absorbing material 26 disposed in the first space 24 and the second sound-absorbing material 27 disposed in the second space 25 are disposed at a distance from each other inside the chamber 22. In other words, an air layer is interposed inside the chamber 22 between the first sound-absorbing material 26 and the second sound-absorbing material 27.

[0028] In this embodiment, for example, wire glass wool is used as the first sound-absorbing material 26 and the second sound-absorbing material 27. The first sound-absorbing material 26 is made of a material that is more heat-resistant than the second sound-absorbing material 27.

[0029] Furthermore, the first sound-absorbing material 26 is thinner than the second sound-absorbing material 27 and is disposed around the exhaust pipe 13 in a state of lower density than the second sound-absorbing material 27. Conversely, the second sound-absorbing material 27 is thicker than the first sound-absorbing material 26 and is disposed inside the second space 25 in a state of higher density than the first sound-absorbing material 26.

[0030] FIG. 3 is a characteristic diagram showing the relationship between the packing density of glass wool and sound absorption characteristics. In this test, a first sound-absorbing material 26 was used. FIG. 3 shows the sound absorption coefficient of the test sound when it passed through glass wool arranged in a closed space. It was found that for sounds in the low frequency band of 200 Hz or less, the higher the packing density of the glass wool, the better the sound absorption characteristics. On the other hand, for sounds in the high frequency band of 600 Hz or more, the lower the packing density of the glass wool, the better the sound absorption characteristics.

[0031] Based on the above test results, in this embodiment, the first sound-absorbing material 26 is arranged around the exhaust pipe 13 so that its packing density is lower than that of the second sound-absorbing material 27. When the exhaust gas is released from the small holes in the exhaust pipe 13 into the first space 24, it generates emission sound and flow sound. At this time, the exhaust gas passes through the gaps in the wire material of the first sound-absorbing material 26 and flows into the air space around the first sound-absorbing material 26. As the exhaust gas flows through the first sound-absorbing material 26, high-frequency sounds from the exhaust gas sounds are significantly absorbed.

[0032] The exhaust gas then flows into the second space 25 of the chamber 22, and passes mainly through the gaps in the wire of the second sound-absorbing material 27. The second space 25 does not communicate with the outside of the chamber 22, and the exhaust gas flows again into the first space 24, and then flows into the exhaust pipe 13 outside the chamber 22. At this time, the exhaust gas passes through the gaps in the wire of the second sound-absorbing material 27. As the exhaust gas flows through the gaps in the wire of the second sound-absorbing material 27, low-frequency sounds from the exhaust gas are significantly absorbed.

[0033] Furthermore, in this embodiment, an air layer is interposed between the first sound-absorbing material 26 and the second sound-absorbing material 27 inside the chamber 22, such as between the reinforcements 23. With this structure, the exhaust gases flowing through the air layer significantly absorb sounds in the mid- and low-frequency bands, from the exhaust gases. As described above, the exhaust gases flow through the air layer twice: once when they flow from the first space 24 to the second space 25 and once when they flow from the second space 25 to the first space 24.

[0034] That is, exhaust gases released into the first space 24 of the chamber 22 pass through the first sound-absorbing material 26, the air layer, the second sound-absorbing material 27, and another air layer in that order before flowing out of the chamber 22, thereby significantly absorbing a variety of sounds, from the exhaust gas sounds mentioned above to sounds in the low to high frequency bands, within the chamber 22. As a result, the exhaust gases discharged from the exhaust pipe 13 to the outside of the vehicle are released in a muffled state within a desired range.

[0035] In this embodiment, a first sound-absorbing material 26 having high heat resistance is used in the first space 24 through which high-temperature exhaust gas flows, and a second sound-absorbing material 27 is used in the second space 25 which has a lower temperature than the first space 24. Although the first sound-absorbing material 26 is more expensive than the second sound-absorbing material 27, reducing the amount of first sound-absorbing material 26 used reduces manufacturing costs.

[0036] Finally, as described above, the exhaust gas is radially discharged from the exhaust pipe 13 through a plurality of small holes in the first space 24. The radially discharged exhaust gas is compressed and discharged, increasing its flow velocity. Furthermore, the flat shape of the chamber 22 causes the exhaust gas to collide with the chamber 22, which may cause vibrations in the chamber 22.

[0037] However, three reinforcements 23 are formed in the approximate center of the chamber 22, thereby increasing the rigidity of the chamber 22. With this structure, although the chamber 22 has the above-mentioned flat shape, it is less likely to vibrate due to the released exhaust gas, and the chamber 22 itself is less likely to generate resonance noise.

[0038] In this embodiment, the chamber 22 of the silencer 15 has a flat shape because the driving force transmission mechanism, such as the propeller shaft 21 of the vehicle, is disposed in the center of the vehicle. However, this is not limited to this. Regardless of the shape of the chamber 22, the same effect as the above can be obtained by disposing two types of sound-absorbing material in the chamber with an air layer between them, as in this embodiment. In addition, various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0039] 10 Vehicle exhaust system 11 Engine 12 Exhaust manifold 13 Exhaust pipe 15 silencer 22 Chamber 23 Reinforce 24 First Space 25 Second Space 26 First sound-absorbing material 27 Second sound-absorbing material

Claims

1. a chamber that houses a portion of an exhaust pipe that guides exhaust gas to the outside of the vehicle, The chamber comprises: a first space in which the exhaust pipe is disposed; a second space that is in communication with the first space, is positioned alongside the first space in the vehicle width direction, and does not include the exhaust pipe; a first sound-absorbing material covering the exhaust pipe is disposed in the first space; a second sound-absorbing material is disposed in the second space with an air layer interposed between the second sound-absorbing material and the first sound-absorbing material; The first sound-absorbing material is a material having higher heat resistance than the second sound-absorbing material.

2. a wire diameter of the wire material forming the first sound-absorbing material is smaller than a wire diameter of the wire material forming the second sound-absorbing material; 2. The vehicle exhaust system according to claim 1, wherein the density of the wire material of the first sound-absorbing material is lower than the density of the wire material of the second sound-absorbing material.

3. 3. The vehicle exhaust system according to claim 2, wherein the wires of the first sound-absorbing material and the wires of the second sound-absorbing material are glass wool.

4. An exhaust device for a vehicle as described in any one of claims 1 to 3, characterized in that a reinforcing member extending in the height direction of the chamber is arranged in the air layer, and the reinforcing member is joined to the upper and lower parts of the chamber.

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