JPH06568Y2 - Exhaust noise reduction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a vehicle exhaust noise reduction device, and more particularly to a structure of an exhaust noise reduction device that attenuates noise due to air column resonance generated in an exhaust pipe.

[Conventional technology]

As a conventional exhaust noise reduction device, for example, the actual development number 59
No. 167907, Japanese Utility Model Laid-Open No. 61-187914, and Japanese Patent Laid-Open No. 61-138813 are known.

The device disclosed in Japanese Utility Model Laid-Open No. 59-167907 described above bypasses a section of the main exhaust passage of the exhaust system in order to suppress exhaust noise including a resonance frequency component that resonates with the natural vibration frequency of the vehicle in the exhaust pipe. And a device disclosed in Japanese Patent Laid-Open No. 61-138813.
The noise due to air column resonance in the exhaust pipe caused by the exhaust pulsation is reduced, and the main muffler and the prima muffler are arranged at a specific position from the sliding portion of the exhaust manifold of the engine.

The apparatus disclosed in Japanese Utility Model Laid-Open No. 61-187914 reduces the air column resonance in the exhaust pipe, so that
Two tail pipes having different lengths are attached, and switching control is performed so that exhaust gas is discharged from either one of the two tail pipes in accordance with operating conditions of the engine.

[Problems to be solved by the device]

In general, it is often difficult to arrange the muffler at a specific position to attenuate the air column resonance because of the relationship with the underfloor structure of the vehicle. In other words, if the underfloor structure of the vehicle is redesigned to secure a space for installing the muffler, the vehicle interior volume, the fuel tank capacity, the luggage capacity, etc. must be reduced, and other functions are largely sacrificed.

The device disclosed in Japanese Utility Model Laid-Open No. 61-187914 described above eliminates the inevitable arrangement position of the muffler due to restrictions on the shape, size or position of the rear axle and floor panel of the vehicle. However, in this device, a switching valve must be provided in the exhaust passage, which is problematic in terms of cost and reliability.

Further, in the device disclosed in Japanese Patent Laid-Open No. 61-138813, the air column resonances generated individually are superimposed on each other to form a standing wave, and the sound is silenced by a single resonance element, thereby effectively reducing noise. However, since the main muffler and the primary muffler must be arranged at the characteristic position from the exhaust manifold collecting portion, there is a problem that other functions are impaired as described above.

An object of the present invention is to provide a highly reliable exhaust noise reduction device capable of attenuating the noise caused by air column resonance generated in the exhaust pipe without changing the underfloor structure of the vehicle.

[Means for Solving the Problems]

An exhaust noise reduction device according to the present invention which meets this object has an exhaust pipe connected to an engine mounted on a vehicle, and a bypass passage communicating with a pressure abdominal pressure of air column resonance generated in the exhaust pipe and the vicinity of a muscle position. And a reed valve that has a spring force and is opened by the pressure difference of the exhaust gas is provided at the opening of the bypass passage to the exhaust pipe.

[Action]

In the exhaust noise reduction device configured as described above, air column resonance occurs in the exhaust pipe due to exhaust pulsation during engine operation, and a pressure distribution is generated in the exhaust pipe. That is, the high-pressure portion in the exhaust pipe becomes the pressure antinode of the air column resonance, and the low pressure portion becomes the node of the air column resonance. The exhaust pipe is formed with a bypass passage that connects the pressure antinode of air column resonance and the vicinity of the node, so exhaust gas with high pressure at the pressure antinode position is passed through the reed valve to the position of the node with low pressure. By bypassing to, the pressure in the exhaust pipe is made uniform, and the air column resonance is attenuated.

Further, in the present invention, since it is not necessary to arrange the muffler at a specific position, it is not necessary to change the underfloor structure of the vehicle. Further, the reed valve attached to the opening of the bypass passage to the exhaust pipe is opened by the pressure difference of the exhaust gas, and has a switching valve that operates according to the operating conditions of the engine of the conventional structure. The reliability is significantly higher than that of.

〔Example〕

Hereinafter, preferred embodiments of an exhaust noise reduction device according to the present invention will be described with reference to the drawings.

1 to 4 show an embodiment of the present invention.
In the figure, 1 indicates an exhaust manifold of an engine mounted on a vehicle. Exhaust manifold 1
The flange portion 2a of the exhaust pipe 2 extending toward the rear portion of the vehicle is connected to the flange portion 11a at the downstream end of the.
A muffler 3 is attached to the downstream end of the exhaust pipe 2, and a tail pipe 4 is connected to the downstream side of the muffler 3.

The exhaust manifold 2 in the exhaust pipe 2 is connected between the connection part with 1 and the connection part with the muffler 3.
A tubular member 5 extending along is disposed, and both ends and a central portion of the tubular member 5 are connected to the exhaust pipe 2.
In the tubular member 5, a bypass passage 6 that communicates the pressure antinode of the air column resonance generated in the exhaust pipe 2 and the vicinity of the node position is formed. That is, the tubular member 5 has three connecting portions 5a,
5b and 5c are formed, and the respective connection portions 5a and 5 are formed.
b and 5c are connected to be able to communicate with the exhaust gas passage 7 in the exhaust pipe 2.

Openings 6a, 6b, 6c of the bypass passage 6 to the exhaust pipe 2
Each of them is provided with a lead 8 which opens due to a pressure difference of exhaust gas. In other words, the bypass passage 6 can communicate with the exhaust gas passage 7 of the exhaust pipe 2 via each reed valve 8. As shown in FIGS. 2 and 3, the reed valve 8 includes a plate-shaped member 9 having two square holes 9a, and two plate-shaped members having one end fixed to the plate-shaped member 9 and having a spring force. It is composed of the valve body 10. The valve bodies 10 are arranged on the front surface side and the back surface side of the plate-shaped member 9, respectively, and normally, the respective square holes 9 are arranged.
It is designed to block a. Each valve body 10 is curved in a direction away from the plate-shaped member 9 by the pressure of exhaust gas, and the bypass passage 6 and the exhaust gas passage 7 of the exhaust pipe 2 communicate with each other when the valve body 10 is curved. It is like this.

FIG. 4 shows the positional relationship with the opening where the mode reed valve 8 for air column resonance generated in the exhaust pipe 2 is provided. A, B, and C of FIG. 4 show the modes of pressure of air column resonance for a predetermined operating range, where A is the two-node mode, B is the three-node mode, and C is the four-node mode. Each mode occurs based on whether the engine speed is high or low. In the 2-node mode, the engine speed is, for example, about 2000 rpm, the 3-node mode is, for example, about 4000 rpm, and the 4-node mode is, for example, about 6000 r.
It happens at pm. The nodes in the two-node mode A are A ₁ and A ₂ , and the pressure antinodes are A ₃ and A ₄ . The nodes in the three-node mode B are B ₁ , B ₂ , and B ₃ , and the pressure antinodes are B ₄ , B ₅ , and B ₆ . Similarly, the nodes in the four-node mode C are C ₁ , C ₂ , C ₃ , and C ₄ , and the pressure antinode is C ₅ ,
C _6, a _C 7 _{C 8.}

The openings 6a, 6b, 6c in which the reed valves 8 are provided are
The exhaust pipe 2 is arranged as follows. Assuming that the length L from the exhaust port outlet 19 on the upstream side of the exhaust manifold 1 to the downstream end of the exhaust pipe 2 is L, the opening 6c on the most downstream side is located 1 / 5L from the downstream end of the exhaust pipe 2. There is. The opening 6b located between the opening 6a and the opening 6c is arranged so as to be between 2 / 5L and 1 / 3L from the downstream end of the exhaust pipe 2. The opening 6a on the most upstream side is arranged so as to be between 3 / 5L and 2 / 3L from the downstream end of the exhaust pipe 2.

Although the bypass passage 6 is formed by the tubular member 5 extending along the exhaust pipe 2 in this embodiment, the present invention is not limited to this, and the exhaust pipe may have a double pipe structure to form the bypass passage. Alternatively, the inside of the exhaust pipe may be divided into two by a partition wall or the like, and one of them may be a bypass passage.

Next, the operation of the above exhaust noise reduction device will be described.

First, an explanation will be given by taking the 2-section mode A shown in FIG. 4 as an example. As shown in the figure, the node in the 2-node mode A is A ₁ ,
Is A _2, of which one section A ₂ is located at the downstream end of the exhaust pipe 2, the other sections A ₁ will be located in the vicinity of the opening 6a of the bypass passage 6. Further, the pressure antinode A ₄ in the two-node mode A is located near the opening 6 b of the bypass passage 6. Therefore, in a predetermined operation range, as shown in FIG. 2, the valve body 10 of the reed valve 8 provided in the opening 6b is opened by the exhaust gas G in the pressure antinode A ₄ portion where the pressure becomes high, and the bypass is obtained. The valve body 10 of one of the reed valves 8 of the front portion 6a located near the node A _{1 having} a low pressure is opened via the passage 6, and the exhaust gas having a high pressure flows into the node A ₁ side. That is, the high pressure exhaust gas at the pressure return position is bypassed to the pressure node position. Therefore, the pressure in the exhaust pipe 2 can be made almost uniform,
Air column resonance generated in the exhaust pipe is attenuated.

The same effect can be obtained in the three-bar mode B. This 3
The nodes in the node mode B are B ₁ , B ₂ , and B ₃ , and the node B ₂ among them is located near the opening member 6 b of the bypass passage 6. Also, the pressure antinode B _{5 in the} three-bar mode B
Is located in the opening 6 a of the bypass passage 6 and the pressure antinode B ₆ is located in the vicinity of the opening 6 c of the bypass passage 6. Therefore, the high pressure exhaust gas of the pressure antinodes B ₅ and B ₆ is discharged to the opening 6
The exhaust gas flowing out to the bypass passage 6 through the reed valves 8 of a and 6c and flowing out flows into the position of the node B _{2 having} a low pressure through the reed valve 8 of the opening 6b. Therefore, the second
Similar to the node mode, it becomes possible to make the pressure in the exhaust pipe substantially uniform, and the air column resonance generated in the exhaust pipe is attenuated.

Also in the case of the four-node mode C, the pressure in the exhaust pipe is made uniform via the reed valves 8 of the openings 6a, 6b, 6c,
Air column resonance is damped as described above. In this embodiment, 2
Although the arrangement for reducing the air column resonance in the nodal or quadruple mode has been shown, if it is desired to attenuate the air column resonance in other modes, in each mode, the opening of the opening should be made to communicate the pressure antinode and the node position. Just set the position.

[Effect of device]

As described above, according to the exhaust noise reduction device of the present invention, the exhaust pipe is formed with the bypass passage communicating between the pressure antinode of the air column resonance generated in the exhaust pipe and the vicinity of the node,
Since the reed valve having a spring force and opening by the pressure difference of the exhaust gas is provided at the opening of the bypass passage to the exhaust pipe, air column resonance generated in the exhaust pipe can be attenuated. The attenuation of the air column resonance can reduce the muffled sound, and at the same time, can prevent the deterioration of the tone color and the generation of the abnormal sound due to the air column resonance.

Furthermore, since the muffled sound can be reduced, it is possible to reduce the capacity of the muffler that reduces the muffled sound.
Therefore, the mountability of the muffler on the vehicle can be improved, and the cost can be reduced.

Further, since it is not necessary to dispose the muffler at a specific position as in the conventional structure, it is not necessary to change the structure of the underfloor of the vehicle, and other functions are not impaired. Further, by adopting the reed valve having a simple structure, it is possible to improve reliability as compared with the conventional device having the switching valve.

[Brief description of drawings]

1 is a front view of an exhaust noise reduction device, FIG. 2 is a partially enlarged sectional view of FIG. 1, FIG. 3 is an enlarged perspective view of a reed valve in the device of FIG. 1, and FIG. 4 is of FIG. FIG. 6 is a relational diagram showing the relation between the position of the reed valve and the pressure mode of air column resonance in the apparatus. 1 ... Exhaust manifold 2 ... Exhaust pipe 3 ... Muffler 6 ... Bypass passage 8 ... Reed valve A ₁ , A ₂ , B ₁ , B ₂ , B ₃ , C ₁ , C ₂ , C ₃ , C
₄ ...... air column resonance section A _{3 of, A 4, B 5, B} 4, B 6, C 5, C 6, C 7, C
₈ …… Pressure belly of air column resonance

Claims (1)

[Scope of utility model registration request] 1. An exhaust pipe connected to an engine mounted on a vehicle, wherein a bypass passage communicating between a pressure antinode of air column resonance generated in the exhaust pipe and a vicinity of a muscle is formed, and the exhaust pipe of the bypass passage. An exhaust noise reduction device characterized in that a reed valve having a spring force and opened by a pressure difference of exhaust gas is provided in an opening portion of the exhaust noise reduction device.