JP2008002320A - Muffler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a muffler capable of efficiently mixing exhaust gas and ambient air so as to certainly lower the temperature of the exhaust gas and being miniaturized as a whole. <P>SOLUTION: The muffler for a small-sized two-cycle engine comprises a muffler body 10 having an expansion chamber 2, an exhaust gas guidance member 21 for covering an exhaust gas outlet port 12A formed in the muffler body 10, and a cover hood 22 for covering the side of an exhaust gas discharge opening 23A of the exhaust gas guidance member 21. A guidance section 23 for guiding the exhaust gas in the exhaust gas guidance member 21 is formed such that the closer it is to the discharge opening 23A, the more it expands toward the top surface 24H of the cover hood 22. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a muffler, and more particularly to a muffler for a small engine mounted on a portable work machine such as a blower, a chain saw, a cut-off saw, or a brush cutter.

  Conventionally, engine blowers, chainsaws, and the like are known as portable working machines driven by an engine. The engine of such a portable work machine is driven at a position relatively close to the worker, and the exhaust gas temperature from the muffler may be regulated because it is necessary to consider the surrounding environment. Emissions are desired. Specifically, the exhaust gas temperature from the engine cover that covers the engine and the muffler is regulated.

  As a method for lowering the temperature of the exhaust gas coming out of the muffler, for example, it has been proposed to reduce the temperature by taking in outside air by a jet of exhaust gas and mixing the exhaust gas and outside air (for example, Patent Document 1). Specifically, an exhaust gas guide member for discharging exhaust gas from the muffler body in a predetermined direction is provided on the surface of the muffler body, and the exhaust gas guide member is covered with a cover hood. Due to the ejector effect of the exhaust gas discharged from the exhaust gas guide member, the outside air is taken into the cover hood, and the outside air and the exhaust gas are mixed to reduce the exhaust gas temperature.

Japanese Patent Laid-Open No. 53-44998

  However, in patent document 1, there exists a problem that the cover hood required in order to take in external air will enlarge, and the size reduction as a muffler will be inhibited. Therefore, it is desired to adopt a member shape that can efficiently mix exhaust gas and outside air, and thus to promote downsizing of the muffler.

  An object of the present invention is to provide a muffler that can efficiently reduce exhaust gas temperature by efficiently mixing exhaust gas and outside air, and that can be downsized as a whole.

  A muffler according to claim 1 of the present invention covers a muffler main body having an expansion chamber, an exhaust gas guide member covering an exhaust gas outlet provided in the muffler main body, and an exhaust gas exhaust port side provided in the exhaust gas guide member. A guide portion that includes a cover hood, and that guides the exhaust gas in the exhaust gas guide member, is widened toward the top surface of the cover hood toward the discharge port.

  A muffler according to claim 2 of the present invention covers a muffler body having an expansion chamber, an exhaust gas guide member that covers an exhaust gas outlet provided in the muffler body, and an exhaust gas exhaust port provided in the exhaust gas guide member. And a cover hood, wherein a distance from the center of the delivery port to the discharge port is equal to or less than a height of an opening portion at the discharge port.

  A muffler according to a third aspect of the present invention covers a muffler main body having an expansion chamber, an exhaust gas guide member covering an exhaust gas outlet provided in the muffler main body, and an exhaust gas exhaust port provided in the exhaust gas guide member. A cover hood and a tail pipe attached to the delivery port in the expansion chamber are provided, and the height of the opening at the discharge port is equal to or less than the inner diameter of the tail pipe.

  A muffler according to a fourth aspect of the present invention is the muffler according to any one of the first to third aspects, wherein the cover hood is mixed with exhaust gas ejected from the exhaust port and outside air taken in from the outside. In a portion corresponding to the narrowest portion of the reduced diameter portion provided in the outside air mixing portion, the opening area in the cross section intersecting with the flow direction of the exhaust gas is the opening of the discharge port. It is more than 4 times the area.

  A muffler according to a fifth aspect of the present invention is the muffler according to any one of the first to fourth aspects, in the vicinity of the exhaust port of the cover hood toward the center in the in-plane direction of the exhaust port. A protruding protrusion is provided.

  In the above, according to the first to third aspects of the invention, the guide part of the exhaust gas guide member is expanded toward the top surface of the cover hood, or the dimension setting of the main part is optimized. The discharged exhaust gas can be reliably ejected toward the top surface, and the mixed state can be improved by crossing the air taken into the cover hood and the exhaust gas. For this reason, it is possible to efficiently mix the air and the exhaust gas without enlarging the cover hood and taking in a large amount of air, and it is possible to reduce the temperature of the exhaust gas satisfactorily while downsizing the entire muffler.

  According to the fourth aspect of the present invention, a sufficient amount of air can be taken in by the cover hood with respect to the amount of exhaust gas discharged from the exhaust gas guide member, and the temperature of the exhaust gas can be more reliably reduced. .

  According to the invention of claim 5, the exhaust gas from the exhaust port of the cover hood passes through the projecting piece, so that the exhaust gas discharged can be brought into contact with the outside air in a larger area, and the temperature of the exhaust gas is more efficiently Can be reduced.

[First Embodiment]
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings.
FIG. 1 is an overall perspective view showing a muffler 1 according to the present embodiment. 2 is a cross-sectional view of the muffler 1 shown in FIG. 1 taken along the line II-II. 3 is a cross-sectional view of the muffler 1 shown in FIG. 1 taken along line III-III. FIG. 4 is an enlarged plan view showing the attachment 20 of the muffler 1. 5 is a view of the attachment 20 shown in FIG. 4 as viewed from the front side, and FIG. 6 is a view of the attachment 20 as viewed from the rear side. In the present specification, the front side refers to the front side in the exhaust gas flow direction, and the rear side refers to the rear side in the exhaust gas flow direction.

  The muffler 1 of the present embodiment is for a small two-cycle engine mounted on an engine blower (not shown), and is attached to a box-like muffler body 10 having an expansion chamber 2 formed therein, and an outer surface of the muffler body 10. Attachment 20.

  The muffler body 10 includes a base cover 11 having an introduction port 11A into which exhaust gas from the engine side is introduced, and a cover member 12 is attached to the base cover 11 by caulking of a peripheral portion. A baffle 13 having a plurality of round holes 13A is provided inside the introduction port 11A. After the exhaust gas entering from the introduction port 11A hits the facing surface 13B of the baffle 13, the baffle 13 passes through each round hole 13A. It spreads in the expansion chamber 2 while being dispersed. The back side of the cover member 12 has a double structure, and a sound deadening material 14 having heat resistance is disposed inside the cover member 12.

  Further, the cover member 12 is provided with an outlet 12A for sending exhaust gas. The delivery port 12A and the introduction port 11A described above are provided at positions that do not overlap in the thickness direction of the muffler main body 10, respectively. One end of the tail pipe 15 is fixed to the delivery port 12A via a bracket 15A.

  Further, the cover member 12 is provided with a pair of bolt insertion holes 12B, and the base cover 11 is provided with communication holes (not shown) corresponding to the respective insertion holes 12B. The insertion hole 12 </ b> B and the communication hole communicate with each other through a guide pipe 17 in the muffler body 10, and the muffler 1 is bolted to the engine by a bolt inserted into the guide pipe 17.

  The attachment 20 has a configuration in which an exhaust gas guide member 21 that covers the delivery port 12A and a cover hood 22 that covers the exhaust gas guide member 21 are integrally provided. The exhaust gas guide member 21 is provided with a guide part 23 bulging upward, and a discharge port 23 </ b> A is provided on one end side of the guide part 23.

  At the periphery of the guide portion 23, a flange-like insertion portion 23B is provided. A mounting piece 23C continuous with the insertion portion 23B is provided on the front side of the discharge port 23A. In the same plane of the mounting piece 23C, a portion immediately before the discharge port 23A is an opening 23D.

  The cover hood 22 includes an outlet 23A and an outside air mixing unit 24 that covers the front side thereof. On the rear side of the outside air mixing unit 24, a fixed piece 24 </ b> A whose tip is fixed to the upper surface of the guide unit 23 is extended. A gap between the outside air mixing unit 24 and the guide unit 23 serves as an outside air introduction gap 24 </ b> B for introducing outside air into the outside air mixing unit 24.

  Attachment pieces 24C having the same shape as the attachment pieces 23C of the guide portion 23 are provided on both sides of the outside air mixing portion 24, and the attachment pieces 23C and 24C are fixed to each other by spot welding or the like. Such attachment pieces 23C, 24C are provided with a semi-elliptical engagement portion 25 that is open to the rear side.

  On the front end side of the outside air mixing unit 24, an exhaust port 24D for exhausting the exhaust gas after the outside air mixing is provided. On the upper edge of the exhaust port 24D, there is provided a projecting piece 24E bent toward the center in the in-plane direction of the opening. The projecting piece 24E only needs to be provided in the vicinity of the exhaust port 24D so as to close the exhaust port 24D, and the position is not limited to the upper edge. Further, in the middle of the outside air mixing portion 24, a reduced diameter portion 24F having a cross-sectional area that decreases toward the front side is provided, and a recess 24G that is recessed inward is provided on the upper surface of the reduced diameter portion 24F. ing.

  In such an attachment 20, the exhaust gas guide member 21 and the cover hood 22 are integrated in advance, and the insertion portion 23 </ b> B is provided on the surface of the cover member 12 by sliding from the front side to the rear side. The engaging portions 25 are engaged with the screws 19 temporarily fixed to the cover member 12, and the screws 19 are fastened to be fixed to the muffler body 10. At this time, the spark arrester 16 is disposed inside the exhaust gas guide member 21 in a state of partially protruding from the discharge port 23A.

Below, based on FIG. 7, the detailed structure in the attachment 20 is demonstrated.
In FIG. 7, the attachment surface 12 </ b> C on the cover member 12 to which the attachment 20 is attached is slightly inclined from the direction orthogonal to the axis of the tail pipe 15 in this embodiment.

  The inclination direction is a direction in which the thickness of the muffler main body 10 becomes smaller toward the front side in the exhaust gas flow direction. The magnitude of such an inclination is for determining the direction of the exhaust gas exhausted from the exhaust port 24D, and is arbitrarily determined in the implementation. Accordingly, there may be a case where there is no such inclination. That is, the mounting surface 12 </ b> C may be a surface that is orthogonal to the axis of the tail pipe 15.

  In the exhaust gas guide member 21, the guide portion 23 is expanded upward slightly toward the top surface 24H of the cover hood 22 toward the discharge port 23A. However, the width dimension of the guide part 23 is constant over the whole area (FIG. 4). As a result, the exhaust gas is surely ejected from the discharge port 23A toward the top surface 24H of the cover hood 22.

  Further, the discharge port 23A is provided slightly on the front side of the delivery port 12A, and the distance L1 from the center of the delivery port 12A to the discharge port 23A in the plane parallel to the mounting surface 12C is an attachment. The height from the surface 12C to the inner upper edge of the discharge port 23A is set to be equal to or lower than H1 (L1 / H1 ≦ 1). By such setting, the exhaust gas from the discharge port 23A can be more easily directed to the top surface 24H.

  FIG. 8 shows a case where two levels of L1 / H1 = 1.14 and L1 / H1 = 0.75 are used, and the area ratio S1 / S2 between the opening area S1 and the opening area S2 is varied. The simulation result of the exhaust gas outlet temperature is shown. Here, the opening area S1 is a portion where the inner space is the narrowest at the front end of the reduced diameter portion 24F (for example, a portion VII-VII line in FIG. 7 and a portion orthogonal to the flow direction of the exhaust gas, but the depression 24G The opening area S2 is the area of the discharge port 23A of the guide portion 23.

  The simulated outlet temperature is assumed to be measured at a position away from the exhaust outlet 24D by a predetermined distance. As a result of the simulation, it can be seen that the outlet temperature of L1 / H1 = 1.14 is higher and the outlet temperature of L1 / H1 = 0.75 is lower at any area ratio.

  Returning to FIG. 7, the tip of the cover hood 22 protrudes from the side surface of the muffler main body 10, and the exhaust gas exhausted from the exhaust port 24 </ b> D is caught on the side surface, thereby suppressing the generation of vortex and It is designed to flow linearly toward. At this time, the projecting piece 24E has a function of exhausting the exhaust gas from the exhaust port 24D in a concave shape when viewed from the front, thereby increasing the area of the exhaust gas in contact with the outside air and further reducing the exhaust gas temperature. is there.

Hereinafter, the flow of exhaust gas will be described with reference to FIG.
The exhaust gas that has entered the expansion chamber 2 from the introduction port 11 </ b> A (FIG. 2) is sent into the exhaust gas guide member 21 through the tail pipe 15, and is discharged into the cover hood 22 from the discharge port 23 </ b> A of the exhaust gas guide member 21. At this time, the exhaust gas from the discharge port 23A gradually expands toward the top surface 24H side of the cover hood 22 as the cross-sectional shape of the guide portion 23 moves toward the front end side in the flow direction of the exhaust gas. It spouts so as to expand while facing the surface 24H.

  Then, due to the ejector effect when the exhaust gas is ejected from the discharge port 23 </ b> A, the outside air enters the outside air mixing unit 24 of the cover hood 22 through the outside air introduction gap 24 </ b> B formed between the exhaust gas guide member 21 and the cover hood 22. be introduced. In the outside air mixing unit 24, the discharged exhaust gas and the introduced outside air are mixed, and the mixed exhaust gas is exhausted from the exhaust port 24D.

  In the muffler 1 described above, since the cross-sectional shape of the guide portion 23 provided on the exhaust gas guide member 21 is gradually expanded toward the top surface 24H of the cover hood 22, the flow of exhaust gas discharged from the discharge port 23A. Can be reliably directed to the upper side in the cover hood 22, the exhaust gas and the outside air that has entered the cover hood 22 can cross each other efficiently, and the exhaust gas temperature can be effectively reduced. In addition, by setting L1 / H1 ≦ 1, the exhaust gas can be more reliably ejected toward the top surface 24H, and the exhaust gas and the outside air can be more efficiently mixed to further reduce the temperature of the exhaust gas. .

  Further, the depression 24G provided in the cover hood 22 can direct the flow of outside air flowing in the upper side in the cover hood 22 downward, and the degree of mixing between the outside air flowing downward and the exhaust gas flowing upward is changed. Can be better. The reduced diameter portion 24F provided in the cover hood 22 not only simply increases the flow rate of the exhaust gas but also has a function of promoting the mixing of the exhaust gas and the outside air, so that the mixing can be performed well in this respect.

  In addition, in the attachment 20, the exhaust gas guide member 21 and the cover hood 22 are integrally provided, and can be easily attached to the muffler main body 10 in a sliding manner, and can be easily removed. In addition, at this time, it is not necessary to completely remove the screw 19, and the operation is simple also in this respect. Therefore, since the attachment 20 can be easily engaged and disengaged, cleaning of the spark arrester 16 and the tail pipe 15 can be facilitated, and workability can be improved.

[Second Embodiment]
In the attachment 20 of the second embodiment shown in FIGS. 9 and 10, the height H1 of the discharge port 23A of the exhaust gas guide member 21 is set to be equal to or smaller than the inner diameter D1 of the tail pipe 15 (H1 ≦ D1). Other configurations are the same as those of the first embodiment. By setting such dimensions, the ejection speed of the exhaust gas from the discharge port 23A is increased, the ejector effect is improved, the outside air can be drawn efficiently, and the exhaust gas temperature can be satisfactorily reduced.

  Further, in the present embodiment, in the cover hood 22, at the front end of the reduced diameter portion 24F, a portion where the internal space is the narrowest (for example, a portion IX-IX line portion in FIG. 9 and a portion orthogonal to the exhaust gas flow direction. However, the opening area S1 of the recess 24G is not less than four times the opening area S2 of the discharge port 23A of the guide portion 23 (S1 / S2 ≧ 4). By doing so, the exhaust gas and the outside air are mixed well in the outside air mixing section 24, and the exhaust gas temperature is effectively reduced.

  In FIG. 11, three levels of H1 = 0.67 × D1, H1 = D1, and H1 = 1.3 × D1 are used. By changing the distance L1, the dimensional ratio L1 / H1 with respect to the height H1 is obtained. The simulation result of the exhaust gas outlet temperature when different is shown. As a result, it can be seen that the exhaust gas temperature of H1 = 0.67 × D1 is low at any dimensional ratio. The dimensional relationship shown in FIG. 9 is H1 = 0.88 × D1.

  Then, as shown in FIG. 8, if the ratio of the opening areas S1 and S2, that is, S1 / S2 is 4 or more, particularly at L1 / H1 = 0.75 (when L1 / H1 ≦ 1). It can be seen that the outlet temperature of the exhaust gas is 300 ° C. or lower and is sufficiently low. Moreover, even when L1 / H1 = 1.25, when S1 / S2 is 4 or more, it can be seen that the outlet temperature can be kept lower than when 4 or less.

[Third Embodiment]
12 to 14 show a muffler 1 according to a third embodiment of the present invention and its main part. The present embodiment is characterized in that all of L1 / H1 ≦ 1, H1 ≦ D1, and S1 / S2 ≧ 4 described in the first and second embodiments are satisfied.

  Further, as a detailed shape of the attachment 20, the attachment piece 23C of the exhaust gas guide member 21 extends laterally from the muffler body 10, whereas the attachment piece 24C of the cover hood 22 does not extend, and the cover hood The overall length of 22 is shortened. For this reason, the position of the exhaust port 24D is also provided closer to the delivery port 12A than in the first and second embodiments. However, even in such a case, the attachment piece 23C extends to the side, so that the exhaust gas exhausted from the exhaust port 24D is prevented from being entrained, and smooth exhaust can be realized as described above.

  The cover hood 22 is fixed to the exhaust gas guide member 21 by crimping with a pair of folded portions 24I provided on the attachment piece 23C of the exhaust gas guide member 21 and is screwed by a screw 19 inserted through the through hole 24J. The muffler body 10 is fastened together with the exhaust gas guide member 21. The structure in which the entire attachment 20 is fixed to the muffler body 10 by fitting the insertion portion 23B of the exhaust gas guide member 21 to the fitting portion 18 and screwing the screw 19 is the same as in the first and second embodiments. is there.

  Further, the outside air mixing portion 24 of the cover hood 22 has the same width dimension along the flow direction of the exhaust gas, and does not have a reduced diameter portion as in the first and second embodiments. This is an effective shape for satisfying S1 / S2 ≧ 4 while suppressing the height dimension of the cover hood 22, and can prevent the attachment 20 from becoming large.

  And in this embodiment, even when the cover hood 22 which does not have such a reduced diameter part is used, it has been confirmed that the suction of the external air by the ejector effect in the attachment 20 can be performed satisfactorily. Rather, in the present embodiment, the settings of the dimensions H1, L1, and D1 and the settings of the opening areas S1 and S2 are all optimized, so that a superior ejector effect can be exhibited. The exhaust gas temperature can be further reduced as compared with the second embodiment.

Although the best configuration, method and the like for carrying out the present invention have been disclosed in the above description, the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of quantity, other details, and the like.
Therefore, the description limited to the shape, quantity and the like disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

  For example, in the first and second embodiments, the shape of the guide portion 23 of the exhaust gas guide member 21 is a shape that expands toward the discharge port 23A, but in the first embodiment, L1 / H1 ≦ 1. In the second embodiment, it is sufficient if H1 ≦ D1 is satisfied, and the shape of the guide portion 23 is uniform along the flow direction of the exhaust gas (when the shape is not expanded toward the discharge port 23A). However, it is included in the inventions of claim 2 and claim 3. On the contrary, if the shape of the guide part 23 is expanded toward the discharge port 23A, even if L1 / H1 ≦ 1 or H1 ≦ D1 is not satisfied, the invention of claim 1 is included.

  The present invention can be suitably used as a muffler for a small engine mounted on a portable work machine such as a blower, a chain saw, a cut-off saw, or a brush cutter.

1 is an overall perspective view showing a muffler according to a first embodiment of the present invention. II-II sectional view taken on the line of the muffler shown in FIG. The III-III sectional view taken on the line of the muffler shown in FIG. The figure which expands and shows the attachment of a muffler. The figure which looked at the attachment shown in FIG. 4 from the front side. The figure which looked at the attachment shown in FIG. 4 from the back side. Sectional drawing which shows the principal part of a muffler. The figure which shows the simulation result of the exit temperature in 1st Embodiment. Sectional drawing which shows the principal part of the muffler which concerns on 2nd Embodiment of this invention. The figure which looked at the attachment shown in FIG. 9 from the front side. The figure which shows the simulation result of the exit temperature in 2nd Embodiment. The front view which shows the muffler of 3rd Embodiment. The figure which shows the attachment of 3rd Embodiment. Sectional drawing which shows the principal part of 3rd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Muffler, 2 ... Expansion chamber, 10 ... Muffler main body, 12A ... Outlet, 15 ... Tail pipe, 21 ... Exhaust gas guide member, 22 ... Cover hood, 23 ... Guide part, 23A ... Exhaust port, 24 ... Outside air mixing part 24E ... projecting piece, 24F ... reduced diameter part, 24H ... top surface, D1 ... inner diameter, H1 ... height, L1 ... distance, S1, S2 ... opening area.

Claims (5)

A muffler body having an expansion chamber;
An exhaust gas guide member covering the exhaust gas outlet provided in the muffler body;
A cover hood that covers the exhaust gas outlet side of the exhaust gas guide member;
A muffler characterized in that a guide portion for guiding exhaust gas in the exhaust gas guide member is expanded to the top surface side of the cover hood toward the discharge port. A muffler body having an expansion chamber;
An exhaust gas guide member covering the exhaust gas outlet provided in the muffler body;
A cover hood that covers the exhaust gas outlet side of the exhaust gas guide member;
The distance from the center of the said delivery port to the said discharge port is below the height of the opening part in the said discharge port. The muffler characterized by the above-mentioned. A muffler body having an expansion chamber;
An exhaust gas guide member covering the exhaust gas outlet provided in the muffler body;
A cover hood that covers the exhaust gas outlet provided on the exhaust gas guide member;
A tail pipe attached to the delivery port in the expansion chamber,
The height of the opening part in the said discharge port is below the internal diameter of the said tail pipe. The muffler characterized by the above-mentioned. The muffler according to any one of claims 1 to 3,
The cover hood is provided with an outside air mixing unit in which the exhaust gas ejected from the discharge port and outside air taken in from the outside are mixed,
In the portion corresponding to the narrowest portion of the reduced diameter portion provided in the outside air mixing portion, the opening area in a cross section intersecting with the flow direction of the exhaust gas is at least four times the opening area of the exhaust port. A muffler characterized by. The muffler according to any one of claims 1 to 4,
In the vicinity of the exhaust port of the cover hood, a projecting piece protruding toward the center in the in-plane direction of the exhaust port is provided.

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