JP2001164919A - Exhaust muffler for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of after-burn during a stop of an engine, the occurrence of blowout of flame due to the after-burn, and the generation of noise by a method wherein by preventing over heat of a partition wall and its peripheral member due to collision of exhaust gas from an inlet pipe through extremely simple structure, in an extension chamber type exhaust muffler formed such that the internal part of a muffler body is divided into upper and lower chambers by a partition wall having a small passage for exhaust gas. SOLUTION: In an extension chamber type exhaust muffler for an engine formed such that the internal part of a muffler body is divided into upper and lower chambers by a partition wall having a small passage for exhaust gas, an inlet pipe through which exhaust gas is introduced is obliquely opened to the upper chamber such that the angle of the outlet center of the inlet pipe with the inner surface of the upper chamber is acute, and an exhaust outlet is caused to communicate with the lower chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust muffler for an expansion chamber type engine in which the inside of a muffler body is divided into an upper chamber and a lower chamber by a partition having a small exhaust passage.

[0002]

2. Description of the Related Art FIGS. 5 and 6 show an example of a prior art exhaust muffler (hereinafter referred to as a muffler) used for a small general-purpose gasoline engine. In FIG.
It is configured as follows. 1a is an upper lid, 1b is a lower lid, 2 is an exhaust gas inlet pipe, and 3 and 4 are partition walls. An upper chamber 021 is provided inside the upper lid 1a.
b, lower chambers 022 are respectively formed therein,
21 and the lower chamber 022 are partitioned by the partition walls 3 and 4 to form a box-shaped space.

[0003] The partition walls 3 and 4 are stacked one on another,
The periphery is inserted into the ends of the upper lid 1a and the lower lid 1b and fixed by welding. The partition walls 3 and 4 are in close contact with each other at a part thereof, that is, a part near the entrance, and a large number of small holes 8 serving as an exhaust gas passage are formed in the contact parts 3b and 4b. At the portion near the exit, the portion is bent into a cylindrical shape to form cylindrical portions 3a and 4a,
An exhaust gas passage 9 is formed inside the cylindrical portions 3a, 4a. Reference numeral 7 denotes a passage hole that communicates the passage 9 with the upper chamber 021.

[0004] The exhaust gas inlet pipe 2 is connected to the lower chamber 0.
22 is open. Reference numeral 5 denotes an exhaust gas collision plate which is fixed to the lower surface of the contact portion 4b of the partition wall 4 so as to face the opening of the inlet pipe 2.

During operation of the engine equipped with the muffler, the exhaust gas introduced from the inlet pipe 2 into the lower chamber 022 collides with the collision plate 5 as shown by the arrow in FIG. After being diffused and expanded, it flows into the upper chamber 21 through the small hole 8 of the close contact portion, where it further expands and passes from the passage hole 7 through the cylindrical passage 9 to a tail outlet 9b (exhaust outlet). ) To the atmosphere.

In the muffler for a general-purpose engine provided in Japanese Utility Model Laid-Open No. 2-131017, an upper chamber is formed inside an upper lid, and a lower chamber is formed inside a lower lid, respectively. Is divided by a double partition to form a box-shaped space, and the double partition is fixed by welding by inserting its periphery into the ends of the upper lid and the lower lid. . The partition forms an inlet-side volume at a portion near the inlet, forms an outlet-side volume at a portion near the outlet, and communicates the outlet-side volume with the exhaust outlet.

[0007]

In the muffler shown in FIGS. 5 and 6, the exhaust gas introduced from the inlet pipe 2 into the lower chamber 022 collides with the collision plate 5 and becomes lower.
However, the collision plate 5 and the partition walls 3 and 4 are significantly heated by the collision of the exhaust gas with the collision plate 5. And since the partition walls 3 and 4 are not in contact with the outside air except at the junction with the upper and lower lids 1a and 1b on the outer periphery, the heat thereof cannot move by convection or radiation, and during the operation of the engine, The partitions 3, 4 are always exposed to high temperatures.

When the engine is stopped under such conditions, the general-purpose engine of this type generally supplies fuel by a carburetor. Therefore, even if the ignition in the cylinder is cut off, the engine is inerted for several seconds. Rotate. For this reason, the unburned air-fuel mixture is supplied from the rotating engine into the muffler, and a phenomenon of igniting by contacting a high temperature portion in the muffler, that is, the collision plate 5 and the partition walls 3 and 4, that is, an afterburn is caused. appear. For this reason, in the related art, there is a risk that a flame may be blown out from the tail exit of the muffler due to the afterburn, and a problem that loud noise is generated.

Also, in the technique of Japanese Utility Model Application Laid-Open No. 2-131017, similar to the prior art, the partition wall is overheated due to the collision of the exhaust gas flowing from the inlet pipe into the lower chamber, and the emission of flame and the generation of loud noise are observed. There is a problem that.

The present invention has been made in view of the problems of the prior art,
An expansion chamber exhaust silencer in which the inside of the muffler body is divided into an upper chamber and a lower chamber by a partition having a small exhaust passage, and has an extremely simple structure. An object of the present invention is to prevent overheating of a partition wall and its peripheral members, thereby preventing afterburn when the engine is stopped and the emission of flame and noise caused by the afterburn.

[0011]

According to the present invention, in order to solve the above-mentioned problems, the inside of the muffler main body is divided into an upper chamber and a lower chamber by a partition having a small exhaust passage. In the expansion chamber type exhaust muffler, the inlet pipe into which the exhaust gas is introduced is obliquely opened in the upper chamber so that the outlet center of the inlet pipe is at an acute angle with respect to the inner surface of the upper chamber. An exhaust muffler for an engine, characterized in that an exhaust outlet communicates with the lower chamber.

According to a fourth aspect of the present invention, in the first aspect, the exhaust pipe after flowing into the upper chamber is vertically swirled along the side wall of the upper chamber with respect to the side wall of the upper chamber. The opening is formed so as to form

According to a fifth aspect of the present invention, in the first aspect, the inlet pipe is connected to a side wall of the upper chamber.
The exhaust gas after flowing into the upper chamber is opened so as to form a horizontal swirling flow along the side wall.

According to this invention, the exhaust gas introduced into the upper chamber from the inlet pipe is obliquely opened such that the inlet pipe is at an acute angle with respect to the side wall forming the outer wall of the upper chamber. Therefore, after flowing into the upper chamber, a vertical swirling flow is formed along the inner surface of the side wall as described in claim 4, or a horizontal swirling flow is formed along the side wall as described in claim 5. After flowing and expanding to form a swirling flow,
It enters the lower chamber, where it expands again and is exhausted to the atmosphere through an exhaust outlet.

Therefore, according to the invention, the high-temperature exhaust gas from the engine flows in the upper chamber while swirling along the inner surface of the outer wall of the upper chamber, so that the partition wall and the outer wall are widely and evenly heated. Therefore, there is no local high-temperature portion unlike the prior art. Therefore, even when the ignition is shut off when the engine is stopped and the unburned air-fuel mixture is supplied into the muffler by the inertia rotation, as described above, the air-fuel mixture is not overheated because there is no overheating of the partition wall and the outer wall facing the upper chamber. It prevents ignition and afterburn.

According to the invention, the exhaust gas inlet pipe is attached to the upper chamber so that the center of the outlet of the inlet pipe opens obliquely so as to be at an acute angle with respect to the inner surface of the upper chamber. With an extremely simple and low-cost structure, the above-described effect of preventing afterburn can be obtained. The angle (acute angle) between the center of the outlet of the inlet pipe and the inner surface of the upper chamber is preferably 45 degrees or less.

According to a second aspect of the present invention, in the first aspect, the muffler body has a double structure in which the outside of an outer wall of the upper chamber is covered with a cover member with an air passage through which cooling air flows. Characterized in that it is formed on the outer wall.

According to this invention, the outer wall of the upper chamber through which the high-temperature exhaust gas introduced from the inlet pipe flows is cooled by the cooling air flowing through the air passage formed outside the upper wall. The temperature of the outer wall is lowered, and the occurrence of the afterburn can be more reliably avoided.

According to a third aspect of the present invention, in the first aspect, the outlet of the air passage is disposed outside the exhaust outlet so as to perform an ejector action by exhaust gas flowing out of the exhaust outlet. I do.

According to the invention, the cooling air is sucked from the outlet of the air passage arranged so as to surround the outside of the exhaust outlet by the ejector action of the exhaust gas flowing out from the exhaust outlet at a high speed. , The flow rate of the cooling air is increased, and the cooling effect of the outer wall of the upper chamber is improved.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment shown in the drawings. However, unless otherwise specified, the dimensions, materials, shapes, and other relative arrangements of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. Not just.

FIG. 1 is a sectional view showing a first example of an exhaust silencer (hereinafter referred to as a muffler) for a small general-purpose gasoline engine according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA of FIG.
FIG. 3 is a view corresponding to FIG. 1 showing a second embodiment, and FIG.
It is a B sectional view.

In FIGS. 1 and 2 showing the first embodiment, reference numeral 1 denotes a muffler main body, which is constructed as follows. That is,
1a is an upper lid, 1b is a lower lid, 2 is an exhaust gas inlet pipe,
3 and 4 are partition walls. An upper chamber 21 is formed inside the upper lid 1a, and a lower chamber 22 is formed inside the lower lid 1b. The upper chamber 21 and the lower chamber 22 are partitioned by the partitions 3 and 4, and have a box shape. The space is formed.

The partition walls 3 and 4 are overlapped with each other,
The periphery is inserted into the ends of the upper lid 1a and the lower lid 1b and fixed by welding. The partition walls 3 and 4 are in close contact with each other at a part thereof, that is, at a portion near the entrance, and a large number of small holes 8 serving as exhaust gas passages are drilled at the close contact portions 3b, 4b. At the portion near the exit, the portion is bent into a cylindrical shape to form cylindrical portions 3a and 4a,
An exhaust gas passage 9 is formed inside the cylindrical portions 3a, 4a. Reference numeral 7 denotes a passage hole that communicates the passage 9 with the upper chamber 21. The above configuration is the same as that of the related art shown in FIGS. In the present invention, the exhaust gas inlet pipe 2
And the structure of the upper chamber 21 is improved.

That is, the exhaust gas inlet pipe 2 is open to the upper chamber 21. As shown in FIG. 2, the inlet pipe 2 is formed so that an angle α formed between the center 2a of the inlet pipe 2 and the side wall 1c of the upper lid 1a becomes an acute angle.
Opening from the inlet pipe 2 to the upper chamber 2
The exhaust gas that has flowed into the inside 1 flows along the inner surface of the upper lid 1a.

A cover 10 covers the outside of the upper cover 1a, and an air passage 23 for cooling air flow is formed between the inner surface of the cover 10 and the outer surface of the upper cover 1a.
It constitutes the outer wall of the heavy structure. And the air passage 2
An open end 11 of the outlet 3 is disposed so as to slightly wrap from the tail outlet 9b of the cylindrical passage 9 and ejects air flowing through the air passage 23 by exhaust gas flowing out of the cylindrical passage 9. It sucks out by action.

During operation of the general-purpose engine having the exhaust silencer having the above-described structure, the upper pipe 21 is moved from the inlet pipe 2 to the upper chamber 21.
The exhaust gas introduced into the upper chamber 21
Is opened obliquely to the side wall 1c constituting the outer wall of the upper chamber 2 so that the angle α <45 degrees.
After flowing into the side wall 1, it flows so as to form a vertical swirling flow along the inner surface of the side wall 1 c and expands, and then enters the lower chamber 22 through the small holes 8 of the partitions 3 and 4 and expands. The exhaust gas in the lower chamber 22 enters the cylindrical passage 9 through the passage hole 7 and is discharged to the atmosphere from the tail outlet 9b.

Therefore, according to this structure, the high-temperature exhaust gas from the engine flows inside the upper chamber 21 while swirling along the inner surface of the upper lid 1a. As a result, there is no generation of a high-temperature portion due to local heating unlike the prior art.

As a result, the ignition is cut off when the engine is stopped, and even if unburned air-fuel mixture is introduced into the upper chamber 21 from the inlet pipe 2 by inertial rotation, the partition wall 3 facing the upper chamber 21 as described above. 4 and the upper lid 1a are not overheated, so that the mixture is prevented from igniting and generating afterburn.

On the other hand, the outer wall of the upper chamber, that is, the upper lid 1a through which the high-temperature exhaust gas introduced from the inlet pipe 2 flows.
Is cooled by the cooling air flowing through the air passage 23 formed outside thereof, whereby the temperature of the upper lid 1a is reduced, and the occurrence of the afterburn can be avoided more reliably.

Further, the tail outlet 9b is actuated by the ejector action of the exhaust gas flowing out of the tail outlet 9b at a high speed.
b, the cooling air is sucked from the opening end 11 of the air passage 23 arranged so as to surround the outside of the upper chamber 21, so that the flow rate of the cooling air in the air passage 23 increases, and the upper lid 1 a constituting the outer wall of the upper chamber 21 is cooled. The cooling effect is improved, and the afterburn prevention effect is further improved.

According to this embodiment, the exhaust gas inlet pipe 2 is opened obliquely in the upper chamber 21 such that the center of the outlet of the inlet pipe 2 is at an acute angle with respect to the inner surface of the upper lid 1a. So that a very simple and low-cost structure is obtained. The outlet center 2a of the inlet pipe 2 and the upper lid 1
It is preferable that the angle α (a sharp angle) between the inner surface a and the inner surface is 45 degrees or less.

In the second embodiment shown in FIGS. 3 and 4, the exhaust gas inlet pipe 2 is opened in the upper chamber 21 in the horizontal direction, and as shown in FIG. And the side wall 1c of the upper lid 1a is opened at an acute angle, preferably α <45 degrees.

In this embodiment, the exhaust gas flowing into the upper chamber 21 from the inlet pipe 2 is supplied to the side wall 1 of the upper lid 1a.
It flows while turning horizontally along the inner surface of c.
Thereby, the partition walls 3, 4 and the upper lid 1a are widely and evenly heated. Other configurations are the same as those of the first embodiment, and the same members are denoted by the same reference numerals.

[0035]

As described above, according to the present invention, the high temperature exhaust gas from the engine flows in the upper chamber while swirling along the inner surface of the outer wall of the upper chamber. Heating is performed on average, and there is no local high-temperature portion as in the prior art. For this reason, even if the unburned air-fuel mixture is supplied into the muffler by inertia rotation when the ignition is shut off when the engine is stopped, as described above,
Since there is no overheating of the partition wall and the outer wall facing the upper chamber, the mixture is ignited to prevent the occurrence of afterburn.

According to the present invention, the exhaust gas inlet pipe is attached to the upper chamber so that the center of the outlet of the inlet pipe opens obliquely so as to form an acute angle with the inner surface of the upper chamber. With the extremely simple and low-cost structure, the above-described effect of preventing afterburn can be obtained.

Further, according to the present invention, the outer wall of the upper chamber through which the high-temperature exhaust gas introduced from the inlet pipe flows is cooled by the cooling air flowing through the air passage formed outside the upper chamber. By cooling, the temperature of the outer wall is reduced, and the occurrence of the afterburn can be more reliably avoided.

Further, according to the third aspect of the invention, the cooling air is sucked from the outlet of the air passage arranged so as to surround the outside of the exhaust outlet by the ejector action of the exhaust gas flowing out from the exhaust outlet at a high speed. The flow velocity of the cooling air in the air passage is increased, and the cooling effect of the outer wall of the upper chamber is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first example of an exhaust silencer for a small general-purpose gasoline engine according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a view corresponding to FIG. 1, showing a second embodiment.

FIG. 4 is a sectional view taken along line BB of FIG. 3;

FIG. 5 is a diagram corresponding to FIG. 1 showing a conventional technique.

6 is a sectional view taken along line CC of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Muffler main body 1a Upper lid 1b Lower lid 2 Inlet pipe 3, 4 Partition wall 7 Passage hole 8 Small hole 9 Passage 9b Tail outlet 10 Cover 11 Open end 21 Upper chamber 22 Lower chamber 23 Air passage

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshimitsu Miyawaki 1-Fujimichi, Iwazuka-cho, Nakamura-ku, Nagoya-shi F-term in Nagoya Machinery Works, Mitsubishi Heavy Industries, Ltd. 3G004 CA07 CA11 DA08 DA14 DA22 EA06 3G091 AA05 BA00 BA37

Claims (5)

[Claims] 1. An expansion chamber type exhaust silencer in which the interior of a muffler body is divided into an upper chamber and a lower chamber by a partition having a small exhaust passage, wherein an inlet pipe through which exhaust gas is introduced is connected to the upper part of the muffler body. An exhaust muffler for an engine, wherein an outlet center of the inlet pipe is opened obliquely so as to form an acute angle with respect to an inner surface of the upper chamber, and an exhaust outlet communicates with the lower chamber. 2. The muffler body has a double-structured outer wall in which the outside of the outer wall of the upper chamber is covered with a cover member with an air passage through which cooling air flows. An exhaust muffler for an engine according to claim 1. 3. The air outlet according to claim 1, wherein the outlet of the air passage is disposed outside the exhaust outlet so as to perform an ejector action by exhaust gas flowing out of the exhaust outlet.
Exhaust silencer for the described engine. 4. The inlet pipe is opened to a side wall of the upper chamber so that exhaust gas flowing into the upper chamber forms a vertical swirling flow along the side wall. An exhaust muffler for an engine according to claim 1. 5. The inlet pipe is opened to a side wall of the upper chamber so that the exhaust gas flowing into the upper chamber forms a horizontal swirling flow along the side wall. An exhaust muffler for an engine according to claim 1.