JPS6226576Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an exhaust muffling device for an internal combustion engine that has a structure to prevent clogging of a porous sound absorber.

Generally, in internal combustion engines, an exhaust silencing device is installed at the exit of the exhaust system to reduce exhaust noise, but since this exhaust silencing device has a certain resistance to the exhaust gas flow, it This results in an increase in pressure and a decrease in engine output. Therefore, for internal combustion engines, an exhaust muffling device with low pressure loss and high muffling effect is desired.

Here, in order to reduce pressure loss, the exhaust passage within the device must first be formed linearly.
Furthermore, in order to arrange the exhaust passage in the device in a straight line and obtain the required sound-dampening performance, there is no proper means other than using a sound-absorbing material. In addition, exhaust noise usually consists of spectrum sounds in a wide frequency band, so
As a sound absorbing material, a porous sound absorbing body having a sound absorbing power capable of dealing with a wide frequency band is desirable.

As a conventional exhaust muffling device manufactured in accordance with the above requirements, the one shown in FIG. 1 is known.

In FIG. 1, 1 is a housing of a silencer;
An exhaust inlet pipe 2 is connected to its front end, and an exhaust outlet pipe 3 is connected to its rear end. 4 is housing 1
A cylindrical porous sound absorber is housed inside the porous sound absorber 4, and the inside of the porous sound absorber 4 serves as a sound absorbing exhaust passage 5, which connects the exhaust inlet pipe 2 and the exhaust outlet pipe 3 in a straight line. ing. Note that the internal diameters of the exhaust inlet pipe 2 and the exhaust outlet pipe 3 are approximately the same as the diameter of the sound-absorbing exhaust passage 5.

In the above configuration, exhaust gas discharged from the internal combustion engine passes from the exhaust inlet pipe 2 through the sound-absorbing exhaust passage 5 of the porous sound absorber 4, and enters the atmosphere from the exhaust outlet pipe 3, as shown by the solid arrow in the figure. is discharged.

On the other hand, the exhaust sound emitted from the internal combustion engine along with the exhaust gas is also radiated into the atmosphere through the same route as the exhaust gas, but during that time, the sound waves are absorbed by the porous sound absorber 4, and the sound waves are absorbed at the exhaust outlet. Exhaust noise radiated into the atmosphere from the pipe 3 is reduced.

However, in the above configuration, tar, carbon, etc. contained in the exhaust gas are removed from the porous sound absorber 4.
By adhering to the surface of the porous sound absorber 4, the porous sound absorber 4 becomes clogged, making it difficult for sound waves to penetrate into the porous sound absorber 4, and the sound absorption power is significantly reduced.

Therefore, in order to apply the porous sound absorber 4 to an exhaust silencer for an internal combustion engine, consideration must be given to prevent tar, carbon, etc. from adhering to the surface of the porous sound absorber 4.

This idea was made from the above point of view. A cylindrical porous sound absorber through which exhaust gas passes is provided inside the housing, an air pump is connected to the outer space of the sound absorber inside the housing, and the air pump is used to absorb the porous sound absorber. An exhaust for internal combustion engines that prevents clogging of the porous sound absorber with tar, carbon, etc. by passing airflow from the outer periphery to the inner periphery of the sound absorber, and provides a stable sound damping effect over a long period of time. The purpose is to provide a silencer.

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

FIG. 2 is a longitudinal sectional side view of an exhaust silencer for an internal combustion engine according to an embodiment of the invention. In this figure, reference numeral 1 denotes a housing, to which an exhaust inlet pipe 2 is connected to the front end, and an exhaust outlet pipe 3 is connected to the rear end. Reference numeral 4 denotes a cylindrical porous sound absorber housed in the casing 1, and the inside of the porous sound absorber 4 serves as a sound absorbing exhaust passage 5, which runs between the exhaust inlet pipe 2 and the exhaust outlet pipe 3. connected in a straight line. Further, an air pump 8 is connected to the sound absorber outer circumferential space 6 in the housing 1 via a pipe 7.

In the exhaust silencer configured as described above, exhaust gas (solid arrow) discharged from the internal combustion engine (not shown) passes from the exhaust inlet pipe 2 through the sound-absorbing exhaust passage 5 of the porous sound absorber 4, and is then exhausted to the exhaust gas. It is discharged into the atmosphere from the outlet pipe 3, and the exhaust sound is passed through the porous sound absorber 4.
absorbed into. At this time, compressed air is forcibly supplied from the air pump 8 to the sound absorber outer circumferential space 6 in the housing 1, so that the compressed air passes from the sound absorber outer circumferential space 6 to the porous sound absorber 4 from its outer circumference to its inner circumference. An air flow (dotted line arrow) is formed that reaches the sound absorbing exhaust passage 5. Tar, carbon, etc. contained in the exhaust gas are prevented from adhering to the porous sound absorber 4 by the air flow passing through the porous sound absorber 4, and as a result, stable sound deadening is achieved over a long period of time. Effects can be obtained.

Figure 3 shows the results of adjusting for the deterioration in noise reduction performance when a 1400 c.c. passenger car was equipped with the exhaust noise reduction device of this invention and was driven for approximately 10,000 km. In the figure, curve A shows the noise reduction performance before driving, and curve B shows the noise reduction performance after driving for 10,000 km. After driving, there is a slight deterioration in the silencing performance, but it is of a negligible degree. The disassembly results of the silencer also showed that there was very little tar or carbon adhering to the surface of the porous sound absorbing material.
In the figure, the C curve is the case without the air pump 8, that is, the case corresponding to the conventional example shown in FIG.
Because the air flow was cut off, tar, carbon, and other substances adhered to the sound-absorbing material, causing a rapid deterioration of sound-absorbing performance.

FIG. 4 shows another embodiment of this invention. As shown in this figure, as an exhaust outlet pipe connected to the exhaust outlet portion of the porous sound absorber 4, a trumpet-shaped expansion tube 9 expanding in the exhaust direction can be provided. With this configuration, the exhaust speed at the inlet of the expansion tube 9 becomes higher than that at the outlet, and the pressure inside the porous sound absorber 4 decreases, so that the air volume from the air pump 8 can be increased.

The air pump 8 may be configured exclusively for use as a silencer, or may be configured to be used in common with air pumps used for other purposes. FIG. 5 shows an example in which the silencer 10 of this invention is installed in a passenger car 11, and in this example, the air pump 8 is configured to be used in common with the air pump for fuel injection.

Note that porous sound absorbers that can be used in this invention include porous bodies made of ceramic or glass, or commercially available porous metal bodies such as foamed metal, metal fibers, or inorganic fiber-reinforced metals. The materials of the above metal porous body include Ni, Cu, Al, Ni-Cr, Fe-Cr, Fe-
Ni-Cr, Fe-Cr-Al, Ni-Fe-Cr-Al, etc. are suitable.

As explained above, according to this invention, a cylindrical porous sound absorber through which exhaust gas passes is provided in a housing, an air pump is connected to the outer circumferential space of the sound absorber in the housing, and this air pump For internal combustion engines, it prevents clogging of the porous sound absorber with tar, carbon, etc. by passing airflow from the outer periphery to the inner periphery of the porous sound absorber, and provides a stable noise reduction effect over a long period of time. An exhaust silencer can be provided.

[Brief explanation of drawings]

FIG. 1 is a longitudinal side view of a conventional exhaust silencing device for an internal combustion engine, FIG. 2 is a longitudinal sectional side view of an exhaust silencing device for an internal combustion engine according to an embodiment of this invention, FIG. 3 is a silencing characteristic diagram, and FIG. The figure is a longitudinal side view showing another embodiment of this invention, and FIG. 5 is a schematic diagram showing an example in which this invention is installed in a passenger car. 1... Housing, 4... Porous sound absorber, 8... Air pump, 9... Expansion tube. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A cylindrical porous sound absorber through which exhaust gas passes is provided in a housing, an air pump is connected to the outer circumferential space of the sound absorber in the housing, and this air pump 1. An exhaust muffling device for an internal combustion engine, characterized in that an airflow is passed from an outer circumference to an inner circumference of a sound absorbing body. (2) The exhaust silencing device for an internal combustion engine according to claim 1, which is a registered utility model, wherein the exhaust outlet of the porous sound absorber is provided with an expansion tube that expands in the exhaust direction.