JPS636407Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a muffler (silencer) used to reduce noise radiated to the outside from an exhaust port of an internal combustion engine.

Exhaust noise from internal combustion engines consists of fundamental frequency or low-order infrasound (below 500Hz) caused by fuel explosion in each cylinder, and high-frequency noise caused by abnormal combustion such as spark knock and surface ignition in each cylinder. The following high-frequency sounds (over 2000Hz), high-order medium-frequency sounds caused by the fuel explosion (500 to 2000Hz), high-frequency airflow noise caused by the flow of exhaust gas (over 2000Hz), and intermittent opening of exhaust valves. The main noise component is medium-frequency pulsating noise generated by the instantaneous pressure difference between the cylinder and the exhaust pipe, and mufflers for internal combustion engines respond to changes in engine speed and load without producing abnormal noise. It has been required to be able to attenuate exhaust noise whose frequency fluctuates at a substantially constant attenuation rate.

In general, expansion type mufflers,
There are various types of silencers such as expansion tube type, branch tube type, interference type, resonance type, and sound absorption type. Silencers or branch pipe type silencers have good attenuation performance against noise at a specific frequency corresponding to the length of the insertion pipe or branch pipe, while interference and resonance type silencers have good attenuation performance against noise at a specific frequency. Although its performance is particularly excellent, its attenuation performance deteriorates against high-speed airflow, and noise at a specific frequency may be amplified. It had excellent noise damping performance.

Therefore, in conventional mufflers for internal combustion engines,
There are few interference type and resonance type silencers, and there are two types: expansion type, insertion tube expansion type, branch pipe type, and sound absorption type.
There were many silencers that were either combinations of both.

As an example of a conventional muffler for an internal combustion engine, the first
In the muffler shown in FIGS. 2 and 2, a porous inner tube 02 is fitted to the end of an exhaust pipe 01, and glass wool 03 having a function as a sound absorbing material is wrapped around the outer periphery of the porous inner tube 02. A glass wool mounting case 04 is wrapped around the glass wool mounting case 04, and a muffler outer plate 05 is fitted onto the exhaust pipe 01 so as to seal the glass wool mounting case 04 at a required interval. The compartments 07 and 08 separated by the partition plate 06 communicate with each other by a communication pipe 09.
A glass wool 03 and a glass wool presser perforated plate 010 were sequentially attached to the inner peripheral surface of the front compartment 07, and an exhaust pipe 011 was inserted through the rear end of the rear compartment 08.

In the mufflers shown in FIGS. 1 and 2, the porous inner cylinder 02 has a branch pipe type noise reduction function, the glass wool 03 has a sound absorption type noise reduction function, and the compartments 07 and 08 are separated by a partition plate 06. The communication pipe 09 had an insertion tube expansion type silencing function, and this total silencing function uniformly attenuated noise in a wide band ranging from low frequencies to high frequencies, but the front compartment 07
Because the muffler outer plate 05 is long from front to back, the rigidity of the muffler outer plate 05 is insufficient, and the muffler outer plate 05 tends to vibrate due to the fundamental frequency or low-order low-frequency sound caused by fuel explosion. There are three fitting parts: the fitting part with the tube 02, the fitting part between the porous inner cylinder 02 and the case 04, and the fitting part between the pipe 01 and the muffler outer plate 05, which requires a lot of assembly man-hours. This was a factor in increasing costs.

As an improvement on this, instead of deeply inserting the exhaust pipe 01 into the front compartment 07, a glass wool mounting case 04 is fitted onto the muffler outer plate 05, as shown in Figs. A muffler equipped with glass wool 03 and a glass wool holding perforated plate 012 was attached to the partition plate 06 at the part facing the extending direction of the pipe 01.
Partition plate 0 with glass wool 03 attached to partition plate 06
Although the vibrations occurring in the muffler 6 can be absorbed to some extent, the rigidity of the muffler outer plate 05 does not change much, and the above-mentioned drawbacks cannot be sufficiently eliminated.

Further, as shown in FIG. 5, the glass wool mounting case 04 is fitted to the muffler outer plate 05 so that the exhaust pipe 01 is biased to one side with respect to the muffler outer plate 05, and the glass wool mounting case 04 is fitted inside the front compartment 07. In a conventional muffler in which both left and right ends of an outer vibration damping plate 013 located in the vertical center and oriented in the left and right horizontal directions are fixed to the muffler outer plate 05, the rigidity of the muffler outer plate 05 is improved by the outer vibration damping plate 013. Although the low frequency attenuation performance was improved, the structure was complicated and the manufacturing cost was high.

The present invention relates to an improvement of a muffler for an internal combustion engine that eliminates these drawbacks, and its purpose is to:
An object of the present invention is to provide a muffler for an internal combustion engine that can attenuate exhaust noise over a wide frequency band and is inexpensive to manufacture.

An embodiment of the present invention shown in FIGS. 6 and 7 will be described below.

Reference numeral 1 denotes an exhaust pipe whose tip end is connected to an exhaust port of an internal combustion engine (not shown), and a lower front end of a muffler outer plate 2 is integrally fitted to the rear end of the exhaust pipe 1. As shown in FIG. 7, the muffler outer plate 2 is formed into a left-right split type, and its outer peripheral ribs 3 are integrally joined to each other by welding or the like.

Further, the muffler outer plate 2 defines the muffling chamber, which is located directly above the discharge port of the exhaust pipe 1, and includes a horizontal wall 4a that extends sufficiently long in the front-rear direction across the interior of the muffler, and a horizontal wall 4a that extends sufficiently long in the front-rear direction. It is partitioned by a partition plate 4 formed by an upstanding wall 4b extending vertically from the rear end, and the partitions 5 and 6 separated by the partition plate 4 are communicated with each other by a communication pipe 7. is communicated with the outside air through a tail pipe 14 that is fitted through the partition plate 4 and the muffler outer plate 2.

Further, on the inner surface of the muffler outer plate 2 that defines the compartment 5, glass wool 8, 12 and glass wool retaining perforated plates 9, 13 are sequentially attached. ,
And a glass wool holding porous plate 11 is attached.

Since the embodiment shown in FIGS. 6 and 7 is constructed as described above, the exhaust pipe 1
The exhaust gas discharged from the rear end flows through a space A defined by the glass wool holding perforated plates 11 and 9, then reaches a wide space B defined by the perforated plates 9 and 13, and then passes through the communication pipe 7. It flows into the compartment 6 through the tail pipe 14 and is discharged to the outside air.

By the way, in order to effectively absorb the relatively high-frequency exhaust noise that accompanies the discharge of exhaust gas, it is preferable to narrow the space communicating with the exhaust pipe and mount a sound-absorbing material on its inner wall.

The reason for this is that the gas pressure (sound pressure) of exhaust gas changes in inverse proportion to the cross-sectional area of the gas flow path, so sound-absorbing materials should be installed in areas where the cross-sectional area is small and the gas pressure (sound pressure) is high. For example, even if a sound absorbing material is installed in a place with a high sound absorption coefficient, a large cross-sectional area, and a low gas pressure (sound pressure), the sound absorption coefficient will be low.

Therefore, in the muffler of the present invention, among the sounds emitted from the exhaust gas discharged from the exhaust pipe 1, relatively high frequency component noise is produced by the glass wool holding porous plate 11 attached to the horizontal wall 4a of the partition plate 4. In the narrow space A defined by the perforated glass wool presser plate 9 and the perforated glass wool presser plate 9, the glass wool is absorbed at a high rate by the glass wools 10 and 8 held by the perforated glass wool presser plates 11 and 9, and also in the space B. 8, 12, and medium and relatively low frequency noises are attenuated by an inflatable structure or an inflatable silencer consisting of compartments 5, 6 and a communicating tube 7. Furthermore, the vibration noise of the muffler outer plate 2 and the partition plate 4 is absorbed by the glass wools 8 and 12 and the glass wool 10.

Thus, from low to high frequencies,
Noise is reduced at an approximately average attenuation rate.

In addition, the porous inner cylinder 02, glass wool 03, and glass wool mounting case 04 are not attached to the rear end of the exhaust pipe 1, and the glass wool 8, 10, and 13 are used to absorb exhaust sound, and the muffler outer plate 2 and the partition. Since it is also used to absorb the vibration sound of the plate 4, the structure is simple and the number of assembly steps is reduced.
Cost reduction is possible.

As is clear from the above explanation, there is a horizontal wall extending in the front and back direction across the silencing chamber from near the exhaust inlet of the silencing chamber defined by the outer panel, and a horizontal wall extending from the rear end of the horizontal wall to the silencing chamber. The silencing chamber is divided into a large first compartment and a small second compartment by a partition plate consisting of an upright wall extending in the vertical direction, and the two compartments are communicated through a communication portion provided in the upright wall. A tail pipe for discharging the exhaust gas in the second compartment to the outside air is provided through the partition plate and the outer plate, and a sound absorbing material is installed on the inner surface of the first compartment along the exhaust gas flow path through a perforated plate. A muffler for internal combustion engines was proposed, which consisted of an attached muffler.

In such a configuration, the exhaust gas that enters the first compartment from the exhaust inlet flows through a narrow space surrounded by sound-absorbing material, during which relatively high-frequency noise is absorbed by the sound-absorbing material at a high rate. The high frequency noise that is absorbed and not absorbed in the narrow space is absorbed by the sound absorbing material in the wide space of the same first compartment.

In addition, moderate and relatively low frequency noises are effectively attenuated by the expansion type muffling structure which goes from the exhaust inlet to the first compartment and from the first compartment to the second compartment.

In this way, in the present invention, the exhaust gas flows evenly inside the sound-absorbing chamber defined by the outer panel (particularly in the first compartment provided with the sound-absorbing material), making it difficult for stagnation to occur. During the flow, noise over a wide frequency range can be evenly and effectively muffled.

Moreover, in the present invention, the sound absorbing material placed in the narrow space near the exhaust inlet is used for absorbing exhaust sound.
Since the muffler outer plate and the partition plate are also used to absorb vibration noise, the structure is simplified compared to conventional mufflers for internal combustion engines, and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a known muffler for an internal combustion engine, FIG. 2 is a sectional view taken along the - line in FIG. 1, and FIG. 3 is a sectional view of another known muffler for an internal combustion engine. , FIG. 4 is a sectional view taken along the - line in FIG. 3, FIG. 5 is a sectional view of another known muffler for an internal combustion engine, and FIG. A sectional view of the engine muffler, FIG. 7 is a sectional view taken along the - line in FIG. 6. 1...Exhaust pipe, 2...Muffler outer plate, 3...Outer circumferential rib, 4...Partition plate, 5, 6...Compartment, 7...Insertion pipe, 8...Glass wool, 9...
Glass wool presser perforated plate, 10...Glass wool, 11...Glass wool presser perforated plate, 12...
Glass wool, 13...Glass wool presser perforated plate, 14...Tail pipe.

Claims (1)

[Scope of utility model registration request] A horizontal wall that extends in the front and back direction across the silencing room from near the exhaust inlet of the silencing room defined by the outer panel, and an upstanding wall that extends in the vertical direction of the silencing room from the rear end of the horizontal wall. The silencing chamber is divided into a large first compartment and a small second compartment by a partition plate,
The two compartments are communicated through a communication part provided in the upright wall,
The tail pipe that releases the exhaust gas in the second compartment to the outside air is
A muffler for an internal combustion engine, which is provided through a partition plate and an outer plate, and has a sound absorbing material attached to the inner surface of a first compartment along an exhaust gas flow path via a perforated plate.