JPS62121818A - Exhaust muffler for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve a muffling effect as checking an increase in ventilation resistance, by forming a part of an exhaust passage with a pipe body whose sectional area gradually grows larger toward both directions of a throat part, and interconnecting the throat part to a resonance chamber with an opening. CONSTITUTION:A part 10 of an exhaust passage inside an exhaust muffler 3 is formed with a pipe body 10 whose sectional area gradually comes smaller toward a flowing direction of exhaust, turning to the minimum at a throat part 10a, and gradually grows larger at the downstream of the throat part 10a. In addition, an opening 12 is installed in the throat part 10a of the pipe body 10, interconnecting the exhaust passage inside to the inside of a resonance chamber 6. With this constitution, a damping effect in the resonance chamber is improvable as checking an increase in ventilation resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exhaust silencing device for an internal combustion engine that drives a motorcycle or the like.

[Conventional technology]

Some exhaust silencing devices for internal combustion engines of this type include a resonance chamber that attenuates exhaust noise by causing it to resonate.

[Problems to be Solved by the Invention] In recent years, demands for noise reduction in internal combustion engines such as motorcycles have become stricter, and there is a need to improve the noise reduction performance of exhaust silencing devices.

In order to meet this demand, it is conceivable to make the internal structure more complex, but if this is done, the ventilation resistance will increase, resulting in a problem that the output of the internal combustion engine will decrease.

Therefore, the applicant investigated the silencing performance of the exhaust silencing device and conducted experiments based on the results. the result,
When damping noise by resonance, we focused on the point G that the smaller the cross-sectional area of the exhaust passage, the greater the damping effect by resonance.

[Means for solving problems]

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an exhaust muffling device for an internal combustion engine that has improved muffling performance and can suppress a decrease in the output of the internal combustion engine. In the exhaust silencer according to the present invention, a part of the exhaust passage is formed by a pipe body whose cross-sectional area gradually becomes smaller in the direction in which the exhaust gas flows and gradually becomes larger downstream of the throat part, and the throat part of the pipe body An opening is provided to communicate the inside of the resonance chamber and the inside of the exhaust passage.

[Effect]

In the present invention, the damping effect due to resonance is enhanced, and an increase in ventilation resistance is suppressed.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. The figure is a partial sectional view showing an exhaust silencer for an internal combustion engine according to the present invention. In the figure, the reference numeral 1 indicates an exhaust silencer for a motorcycle. The exhaust pipe 2 is connected to an exhaust port of the exhaust pipe 2, and an exhaust muffler 3 is connected to the other end of the exhaust pipe 2. The exhaust pipe 2 is formed so as to descend from the front side of the engine, extend horizontally toward the rear of the vehicle body, and then move upward. The exhaust muffler 3 is formed into a box shape, and the interior thereof is divided into three rooms by partition walls 4.5. That is, 6 is a resonance chamber formed between the partition walls 4.5, 7 is a first expansion chamber formed on the rear side of the resonance chamber 6, and 8 is a second expansion chamber formed on the front side of the resonance chamber 6. be. The exhaust pipe 2 is inserted from the front lower side of the exhaust muffler 3, passes through the lower part of the partition wall 4 and the partition wall 5, and opens into the first expansion chamber 7. For this reason, the exhaust pipe 2 is formed relatively long.

Reference numeral 10 denotes a tube that forms an exhaust passage from the first expansion chamber 7 through the resonance chamber 6 to the second expansion chamber 8.

This tube body 10 is disposed in the upper part of the exhaust muffler 3, and both ends are supported by the partition walls 4 and 5. 11
is a tail pipe for discharging the exhaust gas that has flowed into the second expansion chamber 8 to the outside, and after passing through the center of the partition walls 4 and 5, it heads downward and extends outward from the rear lower side of the exhaust silencer 3. There is.

The tube body 10 is formed so that the cross-sectional area on the upstream side gradually decreases in the direction in which the exhaust gas flows, as indicated by the arrow in the figure, and reaches its minimum at the throat portion 10a. Further, the downstream side of the throat portion 10a is formed so that the cross-sectional area gradually increases in the direction in which the exhaust gas flows. In other words, the tubular body 10 is shaped like a venturi meter or a diverging nozzle. In the embodiment, the cross-sectional area change rate on the upstream side of the throat portion 10a is set larger than on the downstream side. Therefore, the throat portion 10a is provided slightly upstream of the central portion of the tubular body 10, and is located on the partition wall 5 side of the resonance chamber 6.

Reference numeral 12 denotes an opening that communicates the interior of the resonance chamber 6 with the exhaust passage formed by the tubular body 10, and is opened downward in the throat portion 10a of the tubular body 10. Reference numeral 13 denotes a sound absorbing material made of, for example, glass wool, which is adhered to the entire inner surface of the exhaust silencer 3.

In the exhaust silencer for an internal combustion engine configured in this way, exhaust gas flows into the first expansion chamber 7 from the exhaust pipe 2, passes through the pipe body 10, flows into the second expansion chamber 8, and then flows into the tail pipe. It is discharged from 11.

By restricting the exhaust gas at the throat portion 10a, the tube body 10
Compared to a cylindrical tube without a restriction, the acoustic inertance to exhaust noise can be increased and exhaust noise can be reduced. The resonance chamber 6 can block part of the sound waves of the exhaust noise from propagating toward the exit of the pipe body 10 due to the resonance effect, thereby reducing the exhaust noise.

Here, the exhaust gas passing through the tube body 10 is continuously and gradually constricted and then gradually diffused, so the loss caused by the change in cross-sectional area is small, and the throat Since the cross-sectional area is relatively large before and after 10a, the friction loss is also small.

Therefore, the ventilation resistance is suppressed.

Further, since the resonance chamber 6 is communicated with the throat portion 10a, which is a portion of the exhaust passage having a small cross-sectional area, through the opening 12 provided in the tube body 10, the damping effect due to resonance can be enhanced.

〔Effect of the invention〕

As explained above, according to the present invention, a part of the exhaust passage is formed by a pipe body whose cross-sectional area gradually decreases in the direction in which the exhaust gas flows, and gradually becomes thicker downstream of the throat. Even if the cross-sectional area of the passage is made small, ventilation resistance can be suppressed from increasing.Also, since an opening is provided in the throat of the pipe body to communicate the resonance chamber and the exhaust passage, the resonance chamber and the exhaust passage are These can be communicated with each other at a portion where the cross-sectional area of the exhaust passage is small, thereby increasing the damping effect due to resonance.

Therefore, the silencing performance can be improved, and a decrease in the output of the internal combustion engine can be suppressed.

[Brief explanation of drawings]

The figure is a partially sectional view showing an exhaust muffling device for an internal combustion engine according to the present invention. 3... Exhaust silencer, 4.5... Bulkhead, 6...
・Resonance chamber, 10...tube, 10a...throat,
12...Opening.

Claims (1)

[Claims] A part of the exhaust passage is formed by a pipe whose cross-sectional area gradually decreases in the direction of flow of the exhaust, reaching its minimum at the throat, and whose cross-sectional area gradually increases downstream of this throat. An exhaust silencing device for an internal combustion engine, which is provided with an opening that communicates between a resonance chamber and an exhaust passage.