JPH0544486Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to a muffler used in internal combustion engines such as automobiles, and in particular to a muffler that uses a resonance chamber to reduce sound waves in the low frequency range. It concerns the improvement of utensils.

[Conventional technology]

Conventionally, as shown in FIG. 6, this type of silencer has a cylinder body 1 whose front and rear sides are closed with end plates 2 and 3 and two partition plates 4 and 5 provided inside, and this cylinder body 1. The tube end 6a is opened into the first expansion chamber 10 formed between the two partition plates 4 and 5 by penetrating the end plate 2 and the partition plate 4 from the upstream side of the engine (not shown). ), an exhaust inlet pipe 6 connected to the
A resonance pipe 7 is attached to the partition plate 5 so as to be located coaxially with the exhaust introduction pipe 6, and has an upstream pipe end 7a opening into the expansion chamber 10 and a downstream pipe end 7b opening into the resonance chamber 11. , a past tube 8 that passes through the partition plate 4 and communicates the first expansion chamber 10 and the second expansion chamber 12, and a past tube 8 that penetrates the partition plates 4, 5 and the end plate 3 and connects the upstream tube end 9a to the second expansion chamber. While opening into the chamber 12,
It is composed of an exhaust outlet pipe 9 whose downstream side is open to the atmosphere.

According to the muffler configured in this manner, exhaust gas discharged from the engine is first taken into the first expansion chamber 10 from the exhaust introduction pipe 6. Here, the exhaust gas and exhaust noise are subjected to a predetermined expansion action and flow down to the second expansion chamber 12 via the past tube 8. Then, after being subjected to the same action in the second expansion chamber 12, it is discharged into the atmosphere via the exhaust outlet pipe 9. Furthermore, in the resonance chamber 1 facing the first expansion chamber 10, sound waves in a predetermined low frequency range are taken in from the resonance tube 7 and are attenuated by resonance.

[The problem that the idea aims to solve]

However, in this muffler, the resonance tube 7 and the resonance chamber 11
Since this is fixed, the width of the sound waves in the low frequency range that can be reduced is narrow, making it difficult to cover the range that requires reduction.

Therefore, as disclosed in, for example, Japanese Utility Model Application No. 61-142113, there is a known system in which two resonance tubes are provided and one of the resonance tubes is closed when the internal combustion engine rotates at extremely low speeds.

As is well known, the resonant frequency ₀ is However, C is the speed of sound, V is the volume of the resonant chamber, and C ₀ is the conductivity. The resonant frequency when there are two resonant tubes is expressed by the combination of this C ₀ (conductivity), As a result, the resonant frequency moves toward the higher side.

However, with this variable resonance tube, the range of sound waves in the low frequency range that needs to be reduced is expanded compared to the fixed resonance tube, but since it does not correspond to the operating conditions of the internal combustion engine, its contribution rate is It was low.

Therefore, as a result of intensive research in order to vary the resonance frequency, the inventor of the present invention did not use the complicated means of providing a second resonance tube as in the above-mentioned known example.
The present invention was developed based on the realization that the resonant frequency changes when the cross-sectional area of the resonant tube is changed by changing its length and radius using the resonant tube itself.

The present invention was developed based on this observation, and its purpose is to provide a muffler that can reduce sound waves in a low frequency range over a wide range depending on the operating conditions of an internal combustion engine. be.

[Means to solve the problem]

In the silencer according to the present invention, a small hole smaller than the diameter of the resonance pipe is bored in the silencer in which a resonance chamber is provided with an expansion chamber interposed on the downstream side of the pipe end of the exhaust introduction pipe. A valve that adjusts the opening ratio of the resonance tube according to the situation,
It is installed in the resonance tube inside the resonance chamber.

Further, the silencer according to the present invention is a silencer in which a resonance chamber is provided on the downstream side of the pipe end of the exhaust gas introduction pipe with an expansion chamber interposed therebetween, and a small hole is bored in the resonance pipe in the resonance chamber. A movable valve is provided in this part, and the opening ratio of this resonance pipe is adjusted by moving the valve in the area where the small hole is provided depending on the operating conditions. .

[Operation] In the present invention, for example, when the engine speed is low, the valve narrows down the opening ratio of the resonance tube to bring the resonance chamber into a resonance damped state with a single resonance tube, thereby damping the resonance in the extremely low frequency region. Reduce sound waves. Then, as the engine speed increases, the valve gradually increases the opening ratio of the resonance pipe, changing the sound range to be reduced from a low frequency range to a medium to high frequency range.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on the drawings.

FIGS. 1 and 2 show an embodiment of the present invention. Reference numeral 20 is a cylinder whose front and back are closed with end plates 21 and 22, and which has two partition plates 23 and 24 inside.

From the upstream side of this cylindrical body 20, an end plate 21, a partition plate 2
3 and the pipe end 25a is connected to the two partition plates 2.
An exhaust gas introduction pipe 25 opens into a first expansion chamber 29 formed between 3 and 24, and the upstream side thereof communicates with an engine (not shown). A resonance tube 26 is attached to the partition plate 24 and has an upstream tube end 26a opening into the first expansion chamber 29 and a downstream tube end 26b into the resonance chamber 30. room 2
9 and the second expansion chamber 31.
7, penetrates the partition plates 23, 24 and the end plate 22,
Exhaust outlet pipe 2 that opens the upstream pipe end 28a to the second expansion chamber 31 and opens the downstream end to the atmosphere.
8, a valve 32 attached to the tube end 26a inserted into the resonance chamber 30 of the resonance tube 26, and a drive device 33 for operating the valve 32.

The valve 32 has a small hole 32 smaller than the diameter of the resonance tube 26.
It is composed of a valve 32a having a U-shaped cross section with opening b, and by moving the valve 32a, the resonance tube 26 is opened.
It is configured to change the aperture ratio of. An actuating rod support plate 32c, which is larger in diameter than the resonance tube 26, is attached to the valve 32a, and an actuating rod 32d connected to an external drive device 33 is attached to the actuating rod support plate 32c.

The drive device 33 is for moving the valve 32a by pushing and pulling the actuating rod 32d. This drive device 33 includes a drive body 33a such as an air cylinder or solenoid that operates according to the engine speed, and a wire cable 33 connected to the drive body 33a.
b, and a fixture 33c for this wire cable 33b.
, a support fitting 33d for attaching the fitting 33c to the end plate 22, and an adjustment spring 33e.

Next, the operation of this embodiment configured in this manner will be explained.

First, when the engine starts and the engine speed is below a predetermined value, the driver 3 of the drive device 33
3a does not operate. Therefore, the valve 32a is located within the tube end 26a of the resonance tube 26, and the tube end 26a of the resonance tube 26 in the resonance chamber 30 and the first expansion chamber 29 communicate with each other via the small hole 32b. When the exhaust gas and exhaust noise discharged from the engine flow into the first expansion chamber 29 through the exhaust introduction pipe 25, they are expanded, and then passed through the past tube 27 into the first expansion chamber 29, similar to the conventional muffler. After flowing into the second expansion chamber 31 and receiving expansion action again, the exhaust outlet pipe 2
8 to the atmosphere.

Further, in the resonance chamber 30, sound waves in a resonance frequency range due to the cross-sectional area corresponding to the small hole 32b are taken in and resonance attenuated.

Then, as the engine speed gradually increases, the driving body 33a pulls the wire cable 33b and pulls the operating rod 32d toward the downstream side. As a result, the aperture ratio of the resonance tube 26 gradually increases, and the resonance frequency in the resonance chamber 30 moves from the low frequency region to the middle and high frequency regions.

During this time, noise is also muted in the first expansion chamber 29 and the second expansion chamber 31 by the expansion action in the same manner as described above.

As described above, according to the present embodiment, by moving the valve 32a according to the level of the engine speed and changing the aperture ratio in the resonance chamber 30 of the resonance tube 26, the operation can be performed over a wide range. By changing the resonant frequency region, it is possible to reduce the noise.

However, according to this embodiment, the existing resonance tube 26 is used to perform the function of a double resonance tube, and a second resonance tube is not specially provided. There are no adverse effects such as increasing the volume of the container, complicating the interior of the main body, or increasing exhaust pressure.

FIG. 3 shows a modification of the valve 32, in which the portion that fits into the tube end 26b of the resonance tube 26 is shortened. In this example, when the rotation speed reaches the set value,
Sound waves in the resonance frequency range can be reduced according to the total cross-sectional area of the resonance tube 26.

FIG. 4 shows another embodiment of the present invention, in which a small hole is not provided in the valve 32a, but a small hole 26d is provided in a portion 26c of the resonance tube 26 in the resonance chamber 30. .

In this embodiment as well, since the aperture ratio of the resonance tube 26 can be changed by moving the valve 32a, the same effects as in the above embodiment can be achieved.

FIG. 5 shows an example in which the small hole 26d in FIG. 4 is made into a long hole.

[Effect of idea]

As described above, according to the present invention, a double resonance tube is constructed using the tube end of the resonance tube inserted into the resonance chamber, and the aperture ratio of the resonance tube is configured to be changed according to the operating conditions. Therefore, it is possible to change the resonant frequency over a wide range.
With this, the car interior noise can be reduced. In particular, since it is configured by using one resonance tube, it is possible to efficiently improve the muffling performance without increasing the volume of the muffler, complicating the internal structure, or increasing the exhaust pressure. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a silencer according to claim 1 of the present invention. FIG. 2 is a detailed diagram thereof. FIG. 3 is a detailed diagram showing a modification of FIG. 2. FIG. 4 is an enlarged view of essential parts showing an embodiment of the silencer according to claim 5 of the present invention. FIG. 5 is a detailed diagram showing a modification of FIG. 4. FIG. 6 is a configuration diagram showing a conventional example. Explanation of symbols of main parts, 20...Cylinder, 2
1, 22... End plate, 23, 24... Partition plate, 25
...Exhaust introduction pipe, 26...Resonance pipe, 28...Exhaust outlet pipe, 29...First expansion chamber, 30...Resonance chamber,
32... Valve, 32a... Valve, 33... Drive device.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a silencer in which a resonance chamber is provided with an expansion chamber on the downstream side of the end of the exhaust introduction pipe, a small hole smaller than the diameter of the resonance pipe is bored. A silencer characterized in that a valve for adjusting the opening ratio of the resonance tube by a drive device according to the operating conditions is provided in the resonance tube in the resonance chamber. (2) In a silencer in which a resonance chamber is provided on the downstream side of the end of the exhaust introduction pipe with an expansion chamber interposed therebetween, a small hole is bored in the resonance tube in the resonance chamber, and a movable By providing a valve and moving the valve in the area where the small hole is provided depending on the operating situation,
A silencer characterized by being configured to adjust the aperture ratio of the resonance tube.