JPH11294158A - Muffler of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a muffler of an internal combustion engine which can effectively lower temperature of exhaust gas discharged from a final discharge port or surface temperature of the muffler. SOLUTION: This muffler of an internal combustion engine has expansion chambers to which exhaust gas injected from an exhaust port of the internal combustion engine is introduced, and a discharge port 71 for discharging the exhaust gas inside the expansion chambers to the outside. A venturi pipe 65 in which an external air introduction port 66 is formed on a throat part 65a is attached to a portion in the vicinity of the discharge port 71, so as to form an external air introduction gap 85 in between the discharge port 71 for mixing the external air with the exhaust gas discharged from the discharge port 71, by the use of injection flow of the exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffler for an internal combustion engine suitable for a portable small working machine such as a bush cutter or a chain saw, for example, a muffler for a small air-cooled two-stroke gasoline engine. Regarding what can be handled.

[0002]

2. Description of the Related Art Recently, due to increasing interest in environmental issues, even in internal combustion engines such as small air-cooled two-stroke gasoline engines used for portable work machines such as brush cutters and chainsaws, HC in exhaust gas discharged therefrom has been considered. , C
There is a strong demand for reducing and purifying O, NOx and the like. For example, an exhaust gas regulation bill in California, the United States, so-called CARB TIER
It is assumed that emission regulations will become more and more strict in the future, such as 2).

In order to cope with such exhaust gas regulations, the applicant of the present invention has been vigorously researching and developing an internal combustion engine, particularly a muffler, to have an exhaust gas purifying function. A muffler having such a configuration has been proposed (see Japanese Patent Application Laid-Open No. 9-273416). This muffler is
An expansion chamber into which exhaust gas ejected from an exhaust port of the engine is introduced; the expansion chamber is divided into a first expansion chamber and a second expansion chamber by a partition member; An exhaust gas purifying member such as an oxidation catalyst made of a metal foam having the following structure is disposed, and the exhaust gas is guided from the first expansion chamber through the exhaust gas purifying member to the second expansion chamber.

Further, in Japanese Patent Application Laid-Open No. 9-273416, in addition to the above configuration, the outer peripheral portion of the expansion chamber is
It is also disclosed to be formed by a double wall portion composed of an inner wall panel and an outer wall panel appropriately separated so that a gap space is formed therebetween. Further, in Japanese Patent Application No. 10-14246, the expansion chamber is vertically divided into a first expansion chamber and a second expansion chamber by a partition member along the cylinder axis of the internal combustion engine.
An exhaust gas purifying member such as an oxidation catalyst is disposed on the partition member, and exhaust gas from the exhaust port is guided from the first expansion chamber to the second expansion chamber through the inside of the exhaust gas purifying member. I have proposed a muffler.

[0005]

The proposed muffler has been proved effective for an exhaust gas purifying function of reducing and purifying HC, CO, NOx and the like in exhaust gas. However, in the muffler of the internal combustion engine used in the above-mentioned portable working machine, the temperature of the exhaust gas discharged from the discharge port (final discharge port), the surface temperature of the muffler, and the like are considered from the viewpoint of safety and operability. It is desired that the temperature be as low as possible, and various standards related thereto are defined. For example, in the so-called SAE (spark arrester muffler) standard in the United States, the temperature of exhaust gas discharged from the muffler and the surface temperature of the exposed part are set to predetermined values or less. However, in the conventional muffler, there is a possibility that the exhaust gas temperature, the muffler surface temperature, and the like cannot satisfy the requirements. The present invention has been made in view of such circumstances, and an object of the present invention is to provide an internal combustion engine capable of effectively lowering the temperature of exhaust gas discharged from a final discharge port and the surface temperature of an exposed portion. To provide a muffler.

[0006]

In order to achieve the above object,
The muffler of the internal combustion engine according to the present invention is basically
An expansion chamber into which exhaust gas ejected from an exhaust port of the internal combustion engine is introduced, and an exhaust port for discharging the exhaust gas in the expansion chamber to the outside are provided. And, in the vicinity of the outlet,
An outside air introduction hole is formed in the throat portion so that an outside air introduction gap is formed between the exhaust port and the outside air by using the jet of the exhaust gas in the exhaust gas discharged from the discharge port. A venturi tube is attached. In a preferred aspect, an outside air introduction tube is connected to the outside air introduction hole of the Venturi tube. In another preferred aspect, an outer wall panel defining the expansion chamber includes:
An exhaust gas guide member into which the exhaust gas from the expansion chamber is introduced is attached, and the Venturi tube is attached near the outlet provided in the exhaust gas guide member.

In the muffler of the present invention, preferably, the expansion chamber is divided into a first expansion chamber and a second expansion chamber by a partition member, and an exhaust gas purifying member such as an oxidation catalyst is disposed in the partition member. The exhaust gas from the exhaust port is guided from the first expansion chamber to the second expansion chamber through the inside of the exhaust gas purifying member. More preferably, the entirety of the expansion chamber is an internal combustion engine. It is vertically long along the cylinder axis of the engine. In a preferred aspect, the exhaust gas purifying member can be arranged at an arbitrary distance from the exhaust port in a direction intersecting a direction in which the exhaust gas is ejected. In a further preferred embodiment,
A discharge opening for exhaust gas is provided in an outer wall panel defining the second expansion chamber, and a container-like inner space forming member is attached so as to cover the discharge opening from the inside, and the exhaust gas is introduced into the second expansion chamber. The exhaust gas is discharged to the outside through the outlet opening and the discharge opening formed in the inner space forming member.

[0008] In a preferred embodiment of the muffler for an internal combustion engine according to the present invention having such a configuration, the exhaust gas ejected from the exhaust port of the internal combustion engine is, for example, one of the expansion chambers divided vertically by a partition member. Is radially introduced into the first expansion chamber at a speed close to the speed of sound, where it is expanded and diffused, whereby the exhaust sound is attenuated. In this case, substantially all of the exhaust gas ejected into the first expansion chamber hits a panel portion (outer wall panel) defining the first expansion chamber facing the exhaust port, and the exhaust gas reflected there is exhaust gas. It will be guided to the inlet side of the purification member in a substantially uniform state. For this reason, the exhaust gas from the exhaust port of the internal combustion engine can be prevented from directly hitting the exhaust gas purification member, and can be uniformly guided to the entire inlet side of the exhaust gas purification member. In a preferred embodiment, the expansion chamber including the first expansion chamber and the second expansion chamber is vertically elongated as a whole, so that the degree of freedom of arrangement of the exhaust gas purification member is increased. Since it can be arranged at an arbitrary distance in the direction crossing the exhaust gas ejection direction from the exhaust port,
The arrangement position of the exhaust gas purifying member can be selected as an optimal position. As a result, the temperature distribution on the inlet side of the exhaust gas purifying member can be made more uniform, and the temperature can be set to an optimal temperature for activation thereof. By arranging the exhaust gas purifying member at the optimum position, it is possible to suppress the rise of the exhaust gas outlet temperature and the surface temperature of the exposed portion such as the muffler due to the heat generated by the exhaust gas purifying member, and to reduce the deterioration rate of the exhaust gas purifying member. Can be minimized to improve durability.

The exhaust gas introduced into the first expansion chamber is caused to pass through the partition member by a pressure difference between the exhaust gas and the second expansion chamber adjacent to the partition member. It is guided to the second expansion chamber through the purifying member. At this time, the exhaust gas reacts efficiently with the oxygen in the expansion chamber (oxidative combustion) by the action of the exhaust gas purifying member (oxidation catalyst or the like).
O and HC components are greatly reduced. And the second
Exhaust gas introduced into the expansion chamber of the above is again expanded and diffused to further attenuate the exhaust noise, and then, in a preferred embodiment, is covered with an outlet opening formed in the inner space forming member and a spark arrestor screen. Through the discharge opening, for example, it is led to an exhaust gas guide member attached to the outer wall panel, and while being guided by the exhaust gas guide member in an appropriate direction, squirts from a discharge port provided therein into a Venturi tube attached near it. I'm sullen.

Here, since the venturi tube is attached so as to form a gap for introducing outside air between the venturi tube and the discharge port, the outside air is jetted by the exhaust gas ejected into the venturi tube. Along with being sucked into the reduced-diameter passage portion forming the first half of the Venturi tube through the outside air introduction gap, and sucked into the throat portion through an outside air introduction hole provided in the throat portion of the Venturi tube, The exhaust gas flowing therethrough is mixed, whereby the exhaust gas flowing through the Venturi pipe is further diluted and cooled, and the exhaust gas diluted and cooled by the outside air passes through a large-diameter passage forming the rear half of the Venturi pipe. And diffused out from the outlet end.

As described above, the venturi pipe is attached near the discharge port, and the outside air is mixed into the exhaust gas by using the jet flow of the exhaust gas, so that the exit side of the venturi pipe which is the final exhaust gas outlet in the muffler is provided. It has been confirmed by the inventors of the present invention that the temperature of the exhaust gas discharged from the end to the outside (final exhaust temperature) is effectively reduced and the surface temperature of the muffler is also significantly reduced. Further, since the final exhaust temperature of the exhaust gas and the surface temperature of the muffler can be kept low, it is not necessary to use an expensive and difficult-to-process heat-resistant special material such as a high-temperature muffler stainless steel material for an outer wall panel or the like constituting the muffler. This is advantageous from the viewpoints of cost and manufacturing.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of a muffler according to the present invention together with an internal combustion engine. In the figure, an internal combustion engine 1 is a small air-cooled two-stroke gasoline engine (hereinafter simply referred to as an internal combustion engine) of a Schnüle scavenging type incorporated as a power source of a hand-held working machine such as a brush cutter or a chain saw. For example, it is about 23 to 26 cc. The engine 1 includes a cylinder 2 having a hemispherical combustion chamber 5 to which a spark plug 15 is mounted, and a crankcase 3 connected to a lower side of the cylinder 2. A piston 4 is inserted into the cylinder 2. At the same time, an intake port 7 to which a mixture supply passage portion 8 of a carburetor is connected to the left and right thereof in FIG. 1 and an exhaust port 10 to which a muffler 20 described later are connected are provided in a known manner, respectively. A pair of scavenging ports 9 (only one of them is shown) are provided in a predetermined manner before and after that in FIG.

As in the case of a normal internal combustion engine, the reciprocating motion of the piston 4 in the vertical direction is converted into the rotational motion of a crankshaft 12 having a balance weight 14 via a connecting rod 11, and the shaft output is converted. The portable work machine is used as power. A muffler 20 which is vertically elongated along the cylinder axis XX of the engine 1 as a whole also serves as a gasket on the outer side of the cylinder 2 of the internal combustion engine 1 having the above configuration on the exhaust port 10 side. It is attached via a heat insulating plate 22. The muffler 20 has a first expansion chamber 31 and a second expansion chamber 32 partitioned vertically by a partition member 40 arranged substantially horizontally in the lateral direction (the width direction of the internal combustion engine 1). ing.

The first expansion chamber 31 and the second expansion chamber 32 are provided with left and right outer wall panels 36 and 37 having one side opened.
Is defined by the combination of That is, the outer peripheral edge portions 36a, 37a of the outer wall panel 37 on the side opposite to the inner wall panel 36 on the side of the internal combustion engine 1 are hermetically joined to each other by welding or the like.
The partition member 40 is hermetically joined to the inner peripheral surfaces of the outer wall panels 36 and 37 by welding or the like so as to partition the space between the first and second expansion chambers 31 and 36 vertically. A chamber 32 is defined. The outer peripheral edge portion 36a of the inner outer wall panel 36 on the side of the internal combustion engine 1 has an L-shaped cross section, and as can be clearly understood by referring to FIG. Is provided with a wide portion 36c in which a bolt insertion hole 36d is formed, and a female screw member 35 for attaching and fixing a muffler cover (not shown) is fixed to the back side of the wide portion 36c by welding or the like.

The partition member 40 has an exhaust gas contact made of a metal carrier so as to penetrate the partition member 40 in a vertical direction, in other words, protrude into both the first expansion chamber 31 and the second expansion chamber 32. In order to increase the area as much as possible, a prismatic oxidation catalyst 50 is arranged as an exhaust gas purifying member. That is, the partition member 40 includes:
A rectangular catalyst mounting opening 40a is formed, and a rectangular tubular shell 52 is inserted through the catalyst mounting opening 40a.
A prismatic oxidation catalyst 50 made of the metal carrier is fixed on the shell 52 by welding or the like to the partitioning member 40 by welding or the like. (Outlet side) 50b
Is inserted and fixed in a state of being exposed to the expansion chamber 32.
Thus, the oxidation catalyst 50 integral with the shell 52
Is held by the partition member 40, so that the shape of the oxidation catalyst can be simplified, and the size of the oxidation catalyst and the mounting position can be easily changed, exchanged, expanded, and the like. Further, the partition member 40
The oxidation catalyst 50 can be disposed at an arbitrary distance from the exhaust port 10 in a direction orthogonal to a direction in which exhaust gas is ejected. Here, the catalyst separation distance L from the center line O of the exhaust port 10 to the upper surface (inlet surface) 50a of the oxidation catalyst 50 is about 10 mm (see FIG. 4 in addition to FIG. 1).

As the oxidation catalyst, any catalyst other than the metal catalyst having the prismatic shell may be used. On the other hand, at the same height position as the exhaust port 10 and the exhaust inlet port 27 in the first expansion chamber 31, as can be seen from FIGS. 3 and 4 in addition to FIGS. The bolt insertion fastening sleeves 55, 55 are laterally provided so as to bridge the reinforcing plate member 24 and the outer outer wall panel 37. Therefore, when attaching the muffler 20 to the outside of the cylinder 2,
Bolts 56, 56 are inserted into the bolt insertion fastening sleeves 55, 55 from the right side of the muffler 20, respectively, and the ends of the male screw portions are inserted into the female screw portions 10 a, 10 a provided on the outer portion of the cylinder 2. It is screwed in and firmly tightened.

On the other hand, in addition to FIGS. 1 and 2, FIGS.
As can be understood by referring to FIG.
7, a substantially rectangular discharge opening 37 for discharging the exhaust gas from the second expansion chamber 32 to the outside is formed in the tapered lower slope portion 37a located on the side opposite to the engine 1 in FIG.
A is formed, and a spark arrestor screen 72 made of a stainless steel mesh is disposed so as to cover the discharge opening 37A from the inside. Further, the exhaust gas introduced into the second expansion chamber 32 is linearly discharged to the outside. In order not to be directly discharged to the second expansion chamber, a container-shaped inner space forming member 81 having a triangular cross section is arranged so as to cover both the discharge opening 37A and the spark arrestor screen 72 from the inside. The exhaust gas introduced into the inner space forming member 81 is formed on the front and rear side surfaces of the inner space forming member 81.
2 and 82, after being introduced into its internal space 80, the spark arrestor screen 72 and the discharge opening 3
7A, the slope portion 37a of the outer wall panel 37
It is designed to be discharged to the outside.

The inner space forming member 81 is formed by bending a sheet metal in a state of a developed view like a folding box, and joining important points to the inner surface of the outer outer wall panel 37 by welding or the like. The slope portion 37a of the outer wall panel 37
As shown in FIGS. 2, 5 and 6, an exhaust gas guide member 75 having a discharge port 71 is provided on the outer surface of the cover member so as to cover the discharge opening 37A and the spark arrestor screen 72. Have been. Nuts 76, 76, 76 are welded and fixed to three places around the inner space forming member 81 arranged on the inner surface side (rear surface side) of the outer wall panel 37 near the periphery of the discharge opening 37 </ b> A. The exhaust gas guide member 75 and the spark arrestor screen 72 are fixed together by screws 77, 77, 77 screwed into the nuts 76, 76, 76 from outside of the outer wall panel 37 (FIG. 6).

The exhaust gas guide member 75 has a box-shaped main body 75a having a rectangular cross-sectional shape slightly larger than the discharge opening 37A and having an open bottom surface and one side surface, and a discharge portion connected to one side surface of the box-shaped main body portion 75a. The bottom surface and one side surface are formed in a convex shape, and the outer end opening portion of the discharge passage portion 75b is formed in the muffler 2.
0 is an exhaust gas outlet 71 (see FIG. 6). Further, in the vicinity of the outer side of the exhaust port 71 of the exhaust gas guide member 75 along the exhaust gas ejection direction, as can be understood by referring to FIG. 7 in addition to FIG. Both ends are larger than the opening area of the discharge port 71 so that an outside air introduction gap 85 is formed between the discharge port 75 and the discharge port 75 in order to mix outside air into the discharged exhaust gas by using the jet flow of the discharge gas. A large diameter venturi tube 65 is attached. More specifically, the venturi tube 65 has an elongated plate-like bracket 67 inserted into a tapered conical passage portion 65A forming a front half thereof.
Through the discharge passage portion 7 of the exhaust gas guide member 75
5b, is fixed to the exhaust gas guide member 75 by spot welding, and is connected to the exhaust port 71 of the venturi tube 65 at the exhaust port 71 side.
b and the discharge port 71, a gap 8 for introducing outside air in an annular shape.
5 are formed (see FIGS. 5 and 6).

The venturi tube 65 has a total length K of about 30 mm, and an outside air introduction hole 66 having a diameter of about 6 to 8 mm is formed in the throat portion 65a. As shown in FIG. 8, the outside air introduction pipe 9 is inserted into (the outside air introduction hole 66) of the throat portion 65a of the venturi tube 65.
0 may be connected and joined by welding or the like, and a low-temperature outside air may be introduced from a portion slightly away from the Venturi tube 65 from a portion close to the Venturi tube 65. Further, a flexible pipe or the like may be connected to the outside air introduction pipe 90 so that low-temperature outside air may be introduced from an arbitrary place. In the muffler 20 of the present embodiment having such a configuration, the exhaust gas from the exhaust port 10 of the internal combustion engine 1 is first radially introduced into the first expansion chamber 31 at a speed close to the speed of sound, where it is expanded and diffused. The exhaust noise is thereby attenuated. In this case, substantially all of the exhaust gas ejected into the first expansion chamber 31 hits a panel portion (outer wall panel 37) defining the first expansion chamber 31, which faces the exhaust port 10, and is reflected there. The discharged exhaust gas is led to the oxidation catalyst 50 as an exhaust gas purifying member.

Therefore, the exhaust gas from the exhaust port 10 of the internal combustion engine 1 can be prevented from directly hitting the oxidation catalyst 50, and can be uniformly guided to the entire inlet side of the oxidation catalyst 50. Further, the first expansion chamber 31
Since the entire expansion chamber including the second expansion chamber 32 is vertically elongated along the cylinder axis XX, the degree of freedom in the position of the oxidation catalyst 50 increases, and
Can be arranged, for example, at a required distance in a direction orthogonal to the direction in which the exhaust gas is ejected from the exhaust port 10. Therefore, by setting the arrangement position, the inlet side of the oxidation catalyst 50 can be set. The temperature distribution of is more uniform, and the temperature can be optimized for its activation.
The rise of the exhaust gas outlet temperature and the muffler surface temperature caused by the heat generated by the oxidation catalyst 50 can be kept low, and the deterioration rate of the oxidation catalyst 50 can be minimized to improve the durability. The exhaust gas introduced into the first expansion chamber 31 passes through the partition member 40 due to a pressure difference between the exhaust gas and the second expansion chamber 32 which is disposed adjacently below the partition member 40 with the partition member 40 interposed therebetween. Is guided to the second expansion chamber 32 through the inside of the oxidation catalyst 50 disposed in the second direction. At this time, the exhaust gas is supplied to the expansion chambers 31 and 3 by the action of the oxidation catalyst 50.
Since it reacts efficiently with oxygen (oxidative combustion) in the chamber 2, CO and HC components contained in the exhaust gas are greatly reduced.

The exhaust gas introduced into the second expansion chamber 32 is again expanded and diffused to further attenuate the exhaust sound, and then the outlet opening 82 formed in the inner space forming member 81 and the spark arrester. The discharge opening 37A covered with the screen 72 and the exhaust gas guide member 75 lead out. In this case, due to the presence of the inner space forming member 81 and the spark arrestor screen 72, even if sparks that could not be extinguished in the second expansion chamber 32 remain,
It can be reliably prevented from being directly discharged to the outside, the temperature of the exhaust gas discharged to the outside is further reduced, and the durability of the spark arrestor screen 72 is improved, and the clogging of the screen is reduced. be able to. The exhaust gas guided to the exhaust gas guide member 75 is ejected from a discharge port 71 provided therein into a venturi pipe 65 attached near the exhaust gas while being guided in an appropriate direction by the exhaust gas guide member 75. Can be

Here, since the venturi pipe 65 is attached so that a gap 85 for introducing outside air is formed between the venturi pipe 65 and the discharge port 71, the venturi pipe 65 is formed.
The outside air is sucked into the tapered reduced-diameter passage portion 65A forming the front half of the Venturi tube 65 through the outside air introduction gap 85 by the jet of the exhaust gas ejected into the inside, and the throat of the Venturi tube 65 Part 65
a is sucked into the throat portion 65a through an outside air introduction hole 66 provided in the exhaust gas, and is mixed into the exhaust gas flowing therethrough.
The exhaust gas flowing through the inside is diluted and cooled, and the exhaust gas diluted and cooled by the outside air is diffused and discharged to the outside from the outlet side end portion 65c through the tapered enlarged passage portion 65B forming the rear half of the venturi tube 65. Is done. As described above, by attaching the venturi pipe 65 having the outside air introduction hole 66 provided in the throat portion 65a in the vicinity of the discharge port 71, the outside air is effectively mixed into the exhaust gas by using the jet flow of the exhaust gas. The temperature (final discharge temperature) of the exhaust gas discharged to the outside from the outlet end 65c of the venturi tube 65, which is the final exhaust gas outlet in the muffler, is effectively reduced, and the surface temperature of the muffler 20 is also significantly reduced. This was confirmed by the inventors of the present invention (see the evaluation test results described later).

In addition, since the final exhaust temperature of the exhaust gas and the surface temperature of the muffler are kept low, the muffler 2
Since an expensive and difficult-to-process heat-resistant special material such as a stainless steel material for a high-temperature muffler does not have to be used for the outer wall panel or the like constituting the outer wall panel 0, it is advantageous from the viewpoint of cost and manufacturing. 9 and 10 show a second example of the muffler according to the present invention.
1 shows an embodiment. The muffler 20 of the illustrated embodiment
Although the basic configuration and appearance including the Venturi tube 65 are the same as those of the first embodiment, the positions of the partition member 40 and the oxidation catalyst 50 are lowered. That is, in the present embodiment, the catalyst separation distance L from the center line O of the exhaust port 10 to the upper surface (inlet surface) 50a of the oxidation catalyst 50 is equal to the catalyst separation distance L (about 10
mm), which is about 33 mm longer. As described above, by increasing the catalyst separation distance L, the gas temperature on the inlet side of the oxidation catalyst 50 becomes lower than that in the first embodiment, and does not exceed the temperature required for the oxidation reaction. Can be. Accordingly, the gas temperature at the outlet side of the oxidation catalyst 50 also decreases, and as a result, the temperature of exhaust gas discharged from the muffler 20 to the outside also decreases. Further, by increasing the catalyst separation distance L, the volume of the first expansion chamber 31 can be increased, whereby the back pressure is reduced, and in particular, the stability in the operating rotation range is improved. Can be.

In addition to the above, in the muffler 20 of the present embodiment, the inner space forming member 81 having a triangular cross section used in the first embodiment is replaced by a rectangular parallelepiped having a larger inner space volume. By using the space forming member 83, the inner space forming member 83 can also perform the function of the third expansion chamber, thereby improving the noise reduction effect and further improving the stability of the engine rotation. I have. The inner space forming member 83 used in the present embodiment is also formed by bending a sheet metal in a state of an exploded view and joining key points by welding or the like like a folding box. 84, 84 are formed. 11 and 12 show a third embodiment of the muffler according to the present invention. The muffler 20 of the illustrated embodiment has the same basic configuration and external appearance including the venturi tube 65 as the above-described embodiment, but an inner wall panel 41 is disposed on the inner surface side of the outer wall panels 36 and 37, and these panels are arranged. 36-37,4
A gap space S for heat insulation is formed between the first expansion chamber 3 and the outside air in the first expansion chamber 31 near the introduction portion of the exhaust gas using the jet of the introduced exhaust gas.
A venturi tube 25 is disposed as outside air suction means for sucking the exhaust gas through the inside thereof, and an outside air introduction tube 26 for communicating the throat portion 25a of the venturi tube 25 with the outside is provided. . Also in this muffler 20, in addition to obtaining substantially the same operation and effect as the above-described embodiment, since the heat insulating gap space S is formed, the outer surface temperature of the muffler 20 is further reduced. And external air is introduced into the first expansion chamber 31 through the outside air suction pipe 26 and the venturi pipe 25, so that the amount of O ₂ in the first expansion chamber 31 increases. Is enhanced, and the CO component is greatly reduced.

[Evaluation Test] In order to confirm the exhaust gas temperature reduction effect and the muffler surface temperature reduction effect of the muffler according to the present invention as described above, in particular, by attaching the venturi tube 65, the following was carried out. An evaluation test was conducted under the conditions, and the test results as shown in Table 1 were obtained for the exhaust gas temperature reduction effect, and the test results were shown in Table 2 for the muffler surface temperature reduction effect. (1) To evaluate the exhaust gas temperature reduction effect of the present invention,
The muffler 20 having the catalyst separation distance L of 10 mm and the venturi tube 65 of the first embodiment shown in FIG.
As shown in FIGS. 8 and 13, an outside air introduction pipe 90 is connected to the outside air introduction hole 66 of the venturi tube 65, and the outside air introduction pipe 90 is kept open. A product which is closed by attaching a blind lid or the like to the outside air introduction tube 90 is referred to as a product I ′ of the present invention, and a product obtained by removing the venturi tube 65 (shown by a solid line in FIG. 13) is referred to as a comparison product I. Also, a muffler 20 having a catalyst separation distance L of 33 mm and a venturi tube 65 according to the second embodiment shown in FIG. 9 is prepared, and as shown in FIGS. The outside air introduction pipe 90 is connected to the outside air introduction hole 66, and the outside air introduction pipe 90 kept open is referred to as a product II of the present invention. The outside air introduction pipe 90 is closed with a blind lid or the like attached thereto. Inventive product II ′, taking out the venturi tube 65 Which had been used (shown in solid lines in FIG. 13) as a comparative product II, the present invention product I,
With respect to I ′, II, and II ′, the exhaust gas temperature was measured at points 5 mm away from the outlet end 65 c of the venturi tube 65 (this is the final discharge port in the present invention), and the comparative product I was measured. , II, the exhaust gas temperature was measured at a position separated by 5 mm from the outlet 71 (this is the final outlet in the comparative product).

[0027]

[Table 1]

As can be seen from Table 1, the product I of the present invention,
For I ', II, II', its final outlet (65c)
At a point about 10 to 15 mm away from the exhaust gas temperature,
For example, while the temperature has dropped to 246 ° C. or less, which is the exhaust gas temperature regulation value according to the SAE standard, the comparative product I,
In II, 35-45 from its final outlet (71)
mm, the exhaust gas temperature regulation value of 24
It does not drop below 6 ° C. From this, it can be understood that according to the present invention, a remarkable exhaust gas temperature reduction effect can be obtained. (2) In order to evaluate the muffler surface temperature reduction effect according to the present invention, the muffler 20 having the catalyst separation distance L of 10 mm and the venturi tube 65 of the first embodiment shown in FIG. As shown in FIG. 13, the outside air introduction pipe 90 is inserted into the outside air introduction hole 66 of the venturi tube 65.
Are connected to each other and the outside air introduction pipe 90 is kept open as the product I of the present invention, and the product from which the venturi tube 65 is removed (shown by a solid line in FIG. 13) is a comparison product I.
Also, a muffler 20 having a catalyst separation distance L of 33 mm and a venturi tube 65 according to the second embodiment shown in FIG. 9 is prepared, and as shown in FIGS. The outside air introduction pipe 90 is inserted into the outside air introduction hole 66.
And the outside air introduction pipe 90 kept open is referred to as a product II of the present invention, and the one obtained by removing the venturi tube 65 (shown by a solid line in FIG. 13) is used as a comparison product II. For the products I and II of the present invention and the comparative products I and II, the upper surface (UP), the front surface (FR), the lateral surface (RI), and the rear surface (B) of the muffler 20 as shown in FIGS.
A) The temperature at each point on the lower surface (UN) was measured.

[0029]

[Table 2]

As can be seen from Table 2, the products I and II of the present invention
In the muffler surface temperature, the comparison product I at each measurement point,
It is about 15-50 ° C lower than II,
It will be understood that the present invention provides a significant muffler surface temperature reduction effect. As described above, one embodiment of the present invention has been described in detail. However, the present invention is not limited to the above-described embodiment, and various designs may be made without departing from the spirit of the invention described in the claims. Can be changed. For example, the muffler of the present invention can be similarly applied to a four-cycle engine other than the air-cooled two-cycle gasoline engine used in the embodiment. Further, as the exhaust gas purifying member 50, a foam molded body, a ceramic carrier, or the like other than those described above can be used, and various methods such as a method of attaching the partition member 40 to the adhesive member can be adopted. .

[0031]

As can be understood from the above description, the muffler for an internal combustion engine according to the present invention has a venturi tube attached near the discharge port, and allows the outside air to be mixed into the exhaust gas by using the jet flow of the exhaust gas. Therefore, the temperature (final discharge temperature) of the exhaust gas discharged to the outside from the outlet end of the venturi tube, which is the final outlet of the exhaust gas in the muffler, can be effectively reduced, and the surface temperature of the muffler also decreases. Since it is possible to greatly reduce the final exhaust temperature of exhaust gas and the surface temperature of the muffler, the outer wall panel and the like constituting the muffler are expensive and difficult to process such as stainless steel material for a high-temperature muffler. It is not necessary to use a heat-resistant special material, which is advantageous in terms of cost and manufacturing.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of a muffler according to the present invention, together with an internal combustion engine to which the muffler is attached.

FIG. 2 is a perspective view of the muffler shown in FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG. 1;

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1;

FIG. 5 is a partially enlarged cross-sectional view showing the vicinity of an exhaust gas outlet of the muffler shown in FIG. 1 in an enlarged manner.

FIG. 6 is a sectional view taken along the line VI-VI in FIG. 5;

FIG. 7 is a sectional view taken along the line VII-VII in FIG. 6;

FIG. 8 is a sectional view showing a modified example in which an outside air introduction pipe is connected to the venturi pipe shown in FIG. 6;

FIG. 9 is a longitudinal sectional view showing a second embodiment of the muffler according to the present invention, together with an internal combustion engine to which the muffler is attached.

10 is a partially enlarged cross-sectional view showing, in an enlarged manner, the vicinity of an exhaust gas outlet of the muffler shown in FIG.

FIG. 11 is a longitudinal sectional view showing a third embodiment of the muffler according to the present invention, together with an internal combustion engine to which the muffler is attached.

FIG. 12 is a partially cutaway perspective view of the muffler shown in FIG. 11;

FIG. 13 is a diagram provided for explaining an evaluation test performed to confirm the operation and effect of the muffler according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Air-cooled two-cycle gasoline engine (internal combustion engine) 10 ... Exhaust port 20 ... Muffler 31 ... First expansion chamber 32 ... Second expansion chamber 36, 37 ... Outer wall panel 37A ... Discharge opening 40 ... Partition member 50 ... Oxidation Catalyst (exhaust gas purifying member) 65 ... Venturi tube 65a ... Throat portion 66 ... Outside air introduction hole 71 ... Exhaust port 75 ... Exhaust gas guide member 81 ... Inner space forming member 82 ... Derivation opening 85 ... Outside air introduction gap 90 ... Outside air introduction tube L … Catalyst separation distance XX… Cylinder axis

Claims (8)

[Claims] An expansion chamber (31, 32) into which exhaust gas ejected from an exhaust port (10) of an internal combustion engine (1) is introduced.
And an exhaust port (71) for exhausting exhaust gas in the expansion chambers (31, 32) to the outside. In order to mix the outside air into the exhaust gas discharged from the discharge port (71) using the jet of the exhaust gas, the throat is formed so as to form a gap (85) for introducing outside air between the discharge port and the discharge port (71). A muffler for an internal combustion engine, wherein a venturi pipe (65) having an outside air introduction hole (66) formed therein is attached to the portion (65a). 2. The muffler for an internal combustion engine according to claim 1, wherein an outside air introduction pipe (90) is connected to the outside air introduction hole (66) of the venturi pipe (65). 3. An exhaust gas guide member (75) through which exhaust gas from the expansion chambers (31, 32) is introduced is attached to an outer wall panel (37) defining the expansion chambers (31, 32). The muffler for an internal combustion engine according to claim 1 or 2, wherein the venturi pipe (65) is attached near the discharge port (71) provided in the exhaust gas guide member (75). 4. The expansion chamber is divided into a first expansion chamber (31) and a second expansion chamber (32) by a partition member (40), and the partition member (40) includes an exhaust gas purification member (40). 50) is disposed, and the exhaust gas from the exhaust port (10) is guided from the first expansion chamber (31) to the second expansion chamber (32) through the exhaust gas purification member (50). 4. The method according to claim 1, wherein:
The muffler for an internal combustion engine according to any one of the preceding claims. 5. The expansion chamber (31, 32) is entirely vertically elongated along a cylinder axis XX of the internal combustion engine (1). A muffler for an internal combustion engine according to claim 1. 6. The exhaust gas purifying member (50) can be arranged at an arbitrary distance (L) from the exhaust port (10) in a direction intersecting the exhaust gas ejection direction. The muffler for an internal combustion engine according to claim 4 or 5, wherein: 7. The exhaust gas purifying member comprises an oxidation catalyst (5).
The muffler for an internal combustion engine according to any one of claims 1 to 6, wherein 0). 8. An outer wall panel (37) defining the second expansion chamber (32) is provided with a discharge opening (37A) for exhaust gas, and has a container shape so as to cover the discharge opening (37A) from the inside. The inner space forming member (81) is attached, and the exhaust gas introduced into the second expansion chamber (32) is discharged from the outlet opening (8) formed in the inner space forming member (81).
The muffler for an internal combustion engine according to any one of claims 4 to 7, wherein the exhaust is discharged to the outside through the discharge opening (2) and the discharge opening (37A).