JP2012202245A - Muffler and engine working machine including the same - Google Patents

Abstract

A muffler capable of preventing the overheating of a muffler wall with a high degree of freedom in changing the shape of the muffler and an engine working machine including the muffler.
A muffler is partitioned by a partition wall into a first expansion chamber and a second expansion chamber having an exhaust inlet. The partition wall 12 is provided with a cylindrical first catalyst 23 and a second catalyst 24 separated from each other. The partition wall 12 has a first catalyst cover 25 having a first through hole 28 and covering the first catalyst 23, and a second catalyst having a second through hole 30 and covering the second catalyst 24. The catalyst cover 26 is provided. The first through hole 28 is formed on the first cylindrical curved surface 27 of the first catalyst cover 25 toward the side wall of the second expansion chamber 14. The second through hole 30 is on the second cylindrical curved surface 29 of the second catalyst cover 26 and is directed to a portion different from the portion of the side wall of the second expansion chamber 14 facing the first through hole 28. It is formed.
[Selection] Figure 2

Description

  The present invention relates to a muffler to be attached to an engine, in particular, a muffler suitable for a portable engine working machine such as an engine cutter and a chain saw, and an engine working machine including the muffler.

  In portable engine working machines, a catalyst is often provided in the muffler to reduce the HC (hydrocarbon) concentration in the exhaust gas. In such a muffler with a catalyst, HC in the exhaust gas burns in the catalyst, the temperature of the exhaust gas rises, and the wall surface of the muffler that comes into contact with the high-temperature exhaust gas directly under the catalyst is overheated. In order to prevent overheating of the muffler wall surface, for example, as shown in Patent Document 1, the inside of the muffler is partitioned into an inner guide chamber close to the engine and an outer guide chamber away from the engine by a partition plate provided with a catalyst. Some exhaust gases are guided to the outer guide chamber and then passed through the catalyst to be guided to the inner guide chamber and then released to the outside.

JP 2000-170518 A

  By the way, in the case of the muffler shown in the above-mentioned patent document 1, since exhaust gas is introduced into the inner guide chamber after being led to the outer guide chamber, there is a problem that the internal structure becomes complicated and it is difficult to change the shape of the muffler.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a muffler capable of preventing the overheating of a muffler wall with a high degree of freedom in changing the shape of the muffler and an engine work machine including the muffler. And

In order to achieve the above object, the muffler according to the first aspect of the present invention is:
A substantially rectangular parallelepiped muffler whose interior is partitioned into a first expansion chamber and a second expansion chamber by a substantially rectangular partition wall,
An exhaust inlet into which exhaust gas flows provided on a first side wall facing the partition wall of the first expansion chamber;
An exhaust outlet for exhaust gas exhaust;
A cylindrical first catalyst provided on the partition wall, which extends in a normal direction of the partition wall and guides exhaust gas from the first expansion chamber to the second expansion chamber;
A tube that extends in the normal direction of the partition wall and guides exhaust gas from the first expansion chamber to the second expansion chamber, and is provided in the partition wall so as to be separated from the first catalyst in the longitudinal direction of the partition wall. A second catalyst in the form of
A first catalyst cover having a first through hole and provided on the partition wall so as to cover the first catalyst in the second expansion chamber;
A second catalyst cover that has a second through hole and is provided on the partition wall so as to cover the second catalyst in the second expansion chamber,
The first through hole is formed on a surface substantially perpendicular to the partition wall of the first catalyst cover toward the side wall of the second expansion chamber,
The second through hole is on a surface substantially perpendicular to the partition wall of the second catalyst cover and is different from a portion of the side wall of the second expansion chamber facing the first through hole. Formed towards,
It is characterized by that.

Further, the volume of the first catalyst is larger than the volume of the second catalyst,
In the normal direction view of the partition wall, the first catalyst may be arranged farther from the exhaust inlet than the second catalyst.

Further, the second catalyst cover has a shorter distance from the partition wall than the first catalyst cover with respect to the normal direction of the partition wall,
The first through hole may be formed at a position where a distance from the partition wall is longer than an end of the second catalyst cover with respect to a normal direction of the partition wall.

  The second through hole may be formed toward a side wall adjacent to the second side wall extending substantially parallel to the longitudinal direction of the partition wall of the second expansion chamber.

Further, the exhaust inflow port is arranged so as to be biased toward one end side in the longitudinal direction of the partition wall,
The exhaust outlet provided in the second expansion chamber is arranged to be biased toward the other end side in the longitudinal direction of the partition wall,
The first through hole is a side close to the exhaust inlet adjacent to the second side wall of the second expansion chamber and a side wall extending in the longitudinal direction of the partition wall in the normal direction of the partition wall. It may be formed toward the side wall.

In addition, the second side wall has an inclined surface that becomes longer as the distance from the partition wall becomes longer from one end in the longitudinal direction of the partition wall toward the other end.
The first through hole may be formed toward the inclined surface.

  Furthermore, the first through hole may be formed toward the second catalyst cover in a normal direction view of the partition wall.

  The first through hole may be formed toward a side wall adjacent to the second side wall extending substantially parallel to the longitudinal direction of the partition wall of the second expansion chamber.

  An engine work machine according to a second aspect of the present invention is characterized in that it is driven by an engine having the above-described muffler.

  According to the muffler of the present invention and the engine working machine including the muffler, the degree of freedom in changing the shape of the muffler is increased, and overheating of the muffler wall surface can be prevented.

The side view of the engine cutter carrying the muffler which concerns on this invention. Sectional drawing of the muffler part of the engine cutter of FIG. III-III sectional view taken on the line of FIG. The figure which shows the calorie | heat amount of exhaust gas with respect to the movement distance of exhaust gas in a muffler. The figure corresponding to FIG. 3 which shows the modification of a muffler.

  Embodiments of the present invention will be described below with reference to FIGS. As shown in FIG. 1, an engine cutter (engine working machine) 1 includes a blade 3 partially covered by a blade cover 2, a two-cycle engine (engine) 4 that drives the blade 3, and a substantially rectangular parallelepiped muffler 5. And a casing 6 accommodating a carburetor (not shown), a front handle 7 held by an operator, and a rear handle 9 provided with a trigger 8 for adjusting the output of the engine.

  As shown in FIG. 2, the muffler 5 provided inside the casing 6 has an open surface of each of the first muffler half 10 and the second muffler half 11 made of a substantially rectangular parallelepiped iron plate. It is configured in a hollow box shape with caulking the periphery. The inside of the muffler 5 is separated by a partition wall 12 from a first expansion chamber 13 formed from the first muffler half 10 and the partition wall 12, a second expansion formed from the second muffler half 11 and the partition wall 12. It is partitioned into a chamber 14. In addition, the partition wall 12 is fixed by being sandwiched between the respective open surfaces of the first muffler half 10 and the second muffler half 11.

  The first side wall 15 of the first expansion chamber 13 that faces the partition wall 12 is provided with an exhaust inlet 16 through which exhaust gas flows. The exhaust inflow port 16 is arranged so as to be biased toward the upper end 17 side in the drawing with respect to the longitudinal direction of the muffler 5. Further, the second side wall 18 of the second expansion chamber 14 facing the partition wall 12 is a parallel surface extending substantially parallel to the partition wall 12 from a lower end 19 in the drawing to a predetermined upper position in the longitudinal direction of the muffler 5. 20 and an inclined surface 21 whose distance from the partition wall 12 becomes shorter from the parallel surface 20 toward the upper end 17 of the muffler 5. The parallel surface 20 is provided with an exhaust outlet 22 for discharging exhaust gas. That is, the exhaust outlet 22 is arranged on the second side wall 18 so as to be biased toward the end 19 side below the muffler 5.

  A cylindrical first catalyst 23 and a second catalyst 24 that extend in the normal direction of the partition wall 12 and communicate with the first expansion chamber 13 and the second expansion chamber 14 are separated from the partition wall 12. Provided. The first catalyst 23 and the second catalyst 24 are oxidation catalysts that oxidize HC, CO, etc., which are fixed by inserting and fixing a honeycomb-like stainless steel foil in which palladium, rhodium, etc. are vapor-deposited, respectively, inside a stainless steel outer cylinder. It is. The diameter and length of the first catalyst 23 are both larger than the diameter and length of the second catalyst 24. The first catalyst 23 is arranged so as to be biased toward the lower end 19 side facing the parallel surface 20 with respect to the longitudinal direction of the muffler 5. Further, the second catalyst 24 is disposed at a position facing the inclined surface 21 below the exhaust inflow port 16 above the first catalyst 23 with respect to the longitudinal direction of the muffler 5.

  The partition wall 12 is provided with a cylindrical first catalyst cover 25 with one end closed so as to cover the first catalyst 23 protruding into the second expansion chamber 14 on the second expansion chamber 14 side. Similarly, the partition wall 12 is provided with a cylindrical second catalyst cover 26 with one end closed so as to cover the second catalyst 24 protruding into the second expansion chamber 14 on the second expansion chamber 14 side. . A first through hole 28 penetrating the first catalyst cover 25 is formed in the first cylindrical curved surface 27 perpendicular to the partition wall 12 of the first catalyst cover 25. Further, a second through hole 30 penetrating the second catalyst cover 22 is formed in the second cylindrical curved surface 29 perpendicular to the partition wall 12 of the second catalyst cover 26. The distance from the partition wall 12 of the first closed end portion 31 substantially parallel to the partition wall 12 of the first catalyst cover 25 is the second closed end portion substantially parallel to the partition wall 12 of the second catalyst cover 26. It is larger than the distance from 32 partition walls 12. That is, with respect to the normal direction of the partition wall 12, the first closed end portion 31 is located on the parallel plane 20 side (the side away from the partition wall 12, the left side in the drawing) from the second closed end portion 32. The first through hole 28 is arranged on the parallel surface 20 side (the side away from the partition wall 12, the left side in the drawing) from the second closed end portion 32 with respect to the normal direction of the partition wall 12.

  As shown in FIG. 3, when viewed from the normal direction of the partition wall 12, the exhaust inlet 16, the first catalyst 23, and the second catalyst 24 are approximately centered in a direction substantially perpendicular to the longitudinal direction of the partition wall 12. It is arranged to line up. Further, the exhaust outlet 22 is arranged to be biased toward one side wall 33 side of the second expansion chamber 14 adjacent to the second side wall 18 extending substantially parallel to the longitudinal direction of the partition wall 12 (right side in the figure). The first through-hole 28 opens beyond the second catalyst cover 26 toward the upper side wall 17 or the inclined surface 21 of the second expansion chamber 14 located at the upper end 17 of the muffler 5 (see FIG. 2). ). Two second through holes 30 are provided in the second catalyst cover 26. One of the second through holes 30 opens toward the upper portion (upper end 17 side) of one side wall 33 of the second expansion chamber 14 extending obliquely upward in the longitudinal direction of the muffler 5, The other 302 of the hole 30 opens toward the lower part (downward end 19 side) of the other side wall 34 (the left side in the figure) of the second expansion chamber 14 extending obliquely downward in the longitudinal direction of the muffler 5.

  In the muffler 5 configured as described above, the exhaust gas discharged from the engine flows into the first expansion chamber 13 from the exhaust inlet 16 as indicated by an arrow A in FIG. A part of the exhaust gas flowing into the first expansion chamber flows into the second catalyst 24 as shown by an arrow B, and the other part flows into the first catalyst 23 as shown by an arrow C. Exhaust gas that has passed through the first catalyst 23 passes through the second closed end portion 32 of the second catalyst cover 26 from the first through hole 28 of the first catalyst cover 25 as indicated by the arrow D. It flows into the second expansion chamber 14 toward the inclined surface 21 on the side wall 17 side above the second expansion chamber 14. Further, the exhaust gas that has passed through the second catalyst 24 passes through the upper part of one side wall 33 of the second expansion chamber 14 as indicated by an arrow E from one of the second through holes 30 of the second catalyst cover 26. And flows into the second expansion chamber 14 toward the lower side of the other side wall 34 of the second expansion chamber 14 as indicated by an arrow F from the other 302 of the second through hole 30 of the second catalyst cover 26. Toward the second expansion chamber 14. The exhaust gas flowing out from the first through hole 28, one of the second through holes 30, and the other 302 of the second through hole 30 toward a different part in the second expansion chamber 14 is second The gas is discharged from the exhaust outlet 22 of the expansion chamber 14 to the outside.

  As shown in FIG. 4, the amount of heat of the exhaust gas in the muffler 5 decreases as it moves in the first expansion chamber from a high state at the exhaust inlet 16 of the first expansion chamber 13. When the exhaust gas flows into the second catalyst 24, HC and CO in the exhaust gas react to increase the amount of heat of the exhaust gas in the second catalyst 24. Further, when the exhaust gas flows into the first catalyst 23, HC and CO in the exhaust gas react to increase the amount of heat of the exhaust gas in the first catalyst 23. Here, since the volume of the first catalyst 23 is larger than the volume of the second catalyst 24, the amount of heat of the exhaust gas rising when the exhaust gas passes through the first catalyst 23 is the same as that of the second catalyst. Greater than the amount of heat that rises when passing through 24. However, since the first catalyst 23 is arranged farther from the exhaust inlet 16 than the second catalyst 24, the amount of movement of the exhaust gas is increased by the amount of movement of the first catalyst 23 from the exhaust inlet 16. Compared with the heat quantity of the exhaust gas just before the flow into 24, it can be further lowered just before the flow into the first catalyst 23. For this reason, in the example shown in FIG. 4, the amount of heat of the exhaust gas immediately after flowing out from the first catalyst 23 and the second catalyst 24 can be made substantially equal. In FIG. 4, a dotted line indicates that the partition wall 12 of the muffler 5 has a volume equal to the sum of the volume of the first catalyst 23 and the volume of the second catalyst 24, that is, a catalyst whose exhaust gas purification performance does not change. This is a state of the amount of heat of the exhaust gas passing through the catalyst when one catalyst having a volume is arranged at an intermediate position between the first catalyst 23 and the second catalyst 24. The increase in the amount of heat of the exhaust gas after passing through the catalyst when there is one catalyst is substantially equal to the sum of the amounts of heat of the exhaust gas rising in each of the first catalyst 23 and the second catalyst 24, but the exhaust gas having a high heat capacity Will flow out of the catalyst, and the amount of heat will be locally concentrated and overheated. However, since the catalyst is dispersed in the first catalyst 23 and the second catalyst 24, the exhaust gas after flowing out from the first catalyst 23 and the second catalyst 24 is compared with the case where there is only one catalyst. An increase in the amount of heat can be suppressed.

  As described above, since the first catalyst 23, the second catalyst 24, and the catalyst are disposed in the muffler 5 in a dispersed manner, the calorific value of the exhaust gas after flowing out from the first catalyst 23 and the second catalyst 24, respectively. Can be prevented from rising excessively. The first through hole 28, one of the second through holes 30, and the other 302 of the second through hole 30 are formed toward different portions in the second expansion chamber 14, respectively. For this reason, the exhaust gas flowing into the second expansion chamber 14 from the first through hole 28, one 301 of the second through hole 30, and the other 302 of the second through hole 30, respectively, does not interfere with each other, To different parts in the second expansion chamber 14. Therefore, a local excessive temperature rise due to the concentration of exhaust gas can be more effectively suppressed in the side wall portion of the second expansion chamber 14. Then, the exhaust gas purified by the first catalyst 23 and the second catalyst 24 is discharged to the outside from the exhaust outlet 22 without generating red heat on the side wall of the muffler 5 (second expansion chamber 14). be able to. Further, by dispersing the catalyst in the first catalyst 23 and the second catalyst 24, the volume and size of each catalyst can be suppressed, so that the restrictions on the internal shape and size of the muffler 5 are relaxed, The degree of freedom in designing such as changing the shape of the muffler 5 can also be improved. In addition, since the catalyst used for the engine with a small displacement and a large amount of circulation can be used as the first catalyst 23 or the second catalyst 24, the cost of each catalyst can be suppressed, so that the cost of the muffler 5 is also suppressed. Can do.

  In addition, since the first catalyst 23 having a larger volume is farther away from the exhaust inlet 16 than the second catalyst 24 having a smaller volume, the amount of heat of the exhaust gas is effectively reduced before flowing into the first catalyst 23. Therefore, the maximum value of the amount of heat of the exhaust gas after flowing out from the first catalyst 23 can be suppressed. For this reason, the excessive temperature rise of the muffler 5 can be suppressed and the overheating of the wall surface of the muffler 5 can be effectively prevented.

  Further, the first through hole 28 of the first catalyst cover 25 is arranged on the parallel surface 20 side from the second closed end portion 32 of the second catalyst cover 26 with respect to the normal direction of the partition wall 12. Therefore, since the positions of the first through hole 28 and the second through hole 30 in the normal direction of the partition wall 12 are different, the exhaust gas discharged from the first through hole 28 and the second through hole 30 are different. It is possible to effectively suppress a rise in temperature locally in the second expansion chamber 14 by combining with the exhaust gas discharged from the second expansion chamber 14. Even when the first through hole 28 faces the second catalyst cover 26, the exhaust gas discharged from one through hole 28 collides with the second catalyst cover 26 and the second catalyst cover 26. The catalyst cover 26 can be prevented from overheating, and the back pressure can be prevented from increasing due to interference of the second catalyst cover 26 and the like downstream of the first through hole 28. Further, the first through hole 28 extends beyond the second catalyst cover 26 toward the upper side wall 17 or the inclined surface 21 of the second expansion chamber 14 located at the upper end 17 of the muffler 5. For this reason, the exhaust gas having an increased amount of heat that has passed through the first catalyst 23 having a large volume reaches the exhaust outlet 22 through a long path. Therefore, it is possible to efficiently reduce the amount of heat of the exhaust gas flowing out from the first through hole 28 until it reaches the exhaust outlet 22, and also from this point, the muffler 5 can be overheated efficiently. Can be suppressed.

  The second through hole 30 is formed toward one side wall 33 of the second expansion chamber 14 and the other side wall 34 of the second expansion chamber 14, which are different from the direction in which the first through hole 28 faces. Yes. Then, one of the second through holes 30 located on the exhaust outlet 22 side is opened obliquely upward in a direction away from the exhaust outlet 22, and the other 302 of the second through hole 30 is inclined downward. Open toward. For this reason, the exhaust gas flowing out from the second through hole 30 into the second expansion chamber 14 does not interfere with the exhaust gas flowing out from the first through hole 28 immediately after the outflow, so that the inside of the second expansion chamber 14 Head toward different side wall parts. Therefore, local excessive temperature rise due to concentration of exhaust gas can be more effectively suppressed in the side wall portion of the second expansion chamber 14. In addition, one of the second through holes 30 faces obliquely upward, and the other 302 of the second through holes 30 faces obliquely downward. For this reason, it is possible to effectively reduce the temperature of the exhaust gas discharged from the exhaust outlet 22 by securing the moving distance of the exhaust gas moving to the exhaust outlet 22, and the second By separating the distance between one side 301 of the through hole 30 and one side wall 33 of the second expansion chamber 14 and the distance between the other side 302 of the second through hole 30 and the other side wall 34 of the second expansion chamber 14. An increase in pressure can also be effectively suppressed.

  The positions and the numbers of the first through holes 28 provided in the first catalyst cover 25 and the second through holes 30 provided in the second catalyst cover 26 are not limited to the above-described configuration. A configuration as shown in FIG. 5 may be used. In this case, the first through hole 28 includes two through holes, one 281 of the first through hole 28 and the other 281 of the first through hole 28. Then, one side 281 of the first through-hole 28 is located approximately at the center of one side wall 33 of the second expansion chamber 14 extending in the longitudinal direction of the muffler 5 obliquely upward to the right (the upper end 17 and the lower end 19 The other side 282 of the first through-hole 28 opens substantially in the middle (upper side) of the side wall 34 on the other side (left side of the drawing) of the second expansion chamber 14 extending in the longitudinal direction of the muffler 5 obliquely to the left. Of the end 17 and the lower end 19). In addition, one of the second through holes 30 opens to the upper part (upper end 17 side) of one side wall 33 of the second expansion chamber 14 extending in the longitudinal direction of the muffler 5 obliquely upward to the right. The other 302 of the two through-holes 30 opens toward the upper part (upper end 17 side) of the other side wall 34 (the left side in the figure) of the second expansion chamber 14 extending in the longitudinal direction of the muffler 5 obliquely to the left. To do. The positions of the first through holes 30 (301, 302) and the second through holes 28 (281, 282) in the normal direction of the partition plate 12 are the same as the positions in FIG.

  Even in this case, the first through-hole 30 and the second through-hole 28 are configured to face different portions as in the above-described case. That is, the positions of the first through hole 30 and the second through hole 28 in the normal direction of the partition plate 12 are different, and one 281 of the first through hole 28 is formed on one side wall 33 of the second expansion chamber 14. While facing the center, one 301 of the second through hole 30 faces the upper side of one side wall 33 of the second expansion chamber 14. The other side 282 of the first through hole 28 faces the center of the other side wall 34 of the second expansion chamber 14, and faces the upper side of the other side wall 34 of the other 302 of the second through hole 30. Therefore, the exhaust gas flowing out from the first through hole 28 into the second expansion chamber 14 and the exhaust gas flowing out from the second through hole 30 into the second expansion chamber 14 may interfere with each other immediately after the outflow. Instead, it goes to a different side wall portion in the second expansion chamber 14. Therefore, local excessive temperature rise due to concentration of exhaust gas can be more effectively suppressed in the side wall portion of the second expansion chamber 14. Further, the distance between one side 281 of the first through hole 28 and one side 301 of the second through hole 30 and one side wall 33 of the second expansion chamber 14, the other side 281 of the first through hole 28 and the second through hole. By increasing the distance between the other 302 of the hole 30 and the other side wall 34 of the second expansion chamber 14, it is possible to effectively suppress an increase in back pressure at the through hole.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention is not limited to the above-mentioned embodiment, In the range of this invention, it can change suitably. For example, the muffler 5 is not limited to being mounted on the engine cutter 1 and may be mounted on other engine working machines such as a chain saw, a hedge trimmer, and a blower. The engine 4 to which the muffler 5 is attached is not limited to a two-cycle engine, and may be a four-cycle engine. Further, the volume of each catalyst, the position, size, shape, and volume, shape of the muffler of each through-hole can be appropriately changed according to the type and displacement of the engine or the use and shape of the engine working machine.

1 Engine cutter (engine work machine)
3 blade 4 2-cycle engine (engine)
5 Muffler 7 Front handle 9 Rear handle 10 First muffler half 11 Second muffler half 12 Partition wall 13 First expansion chamber 14 Second expansion chamber 15 First side wall 16 Exhaust inlet 17 End 18 Second side wall 19 Lower end 20 with respect to the longitudinal direction of the muffler Parallel surface 21 Inclined surface 22 Exhaust outlet 23 First catalyst 24 Second catalyst 25 First catalyst cover 26 Second catalyst cover 27 First cylindrical curved surface 28 First through hole 29 Second cylindrical curved surface 30 Second through hole 31 First closed end portion 32 Second closed end portion 33 One side wall 34 of the second expansion chamber Second expansion The other side wall 301 of the chamber 302 One of the second through holes 302 The other of the second through holes

Claims (9)

A substantially rectangular parallelepiped muffler whose interior is partitioned into a first expansion chamber and a second expansion chamber by a substantially rectangular partition wall,
An exhaust inlet into which exhaust gas flows provided on a first side wall facing the partition wall of the first expansion chamber;
An exhaust outlet for exhaust gas exhaust;
A cylindrical first catalyst provided on the partition wall, which extends in a normal direction of the partition wall and guides exhaust gas from the first expansion chamber to the second expansion chamber;
A tube that extends in the normal direction of the partition wall and guides exhaust gas from the first expansion chamber to the second expansion chamber, and is provided in the partition wall so as to be separated from the first catalyst in the longitudinal direction of the partition wall. A second catalyst in the form of
A first catalyst cover having a first through hole and provided on the partition wall so as to cover the first catalyst in the second expansion chamber;
A second catalyst cover that has a second through hole and is provided on the partition wall so as to cover the second catalyst in the second expansion chamber,
The first through hole is formed on a surface substantially perpendicular to the partition wall of the first catalyst cover toward the side wall of the second expansion chamber,
The second through hole is on a surface substantially perpendicular to the partition wall of the second catalyst cover and is different from a portion of the side wall of the second expansion chamber facing the first through hole. Formed towards,
A muffler characterized by that. The volume of the first catalyst is greater than the volume of the second catalyst;
In the normal direction view of the partition wall, the first catalyst is arranged farther from the exhaust inlet than the second catalyst.
The muffler according to claim 1. The second catalyst cover has a shorter distance from the partition wall than the first catalyst cover with respect to the normal direction of the partition wall,
The first through hole is formed at a position where a distance from the partition wall is longer than an end of the second catalyst cover with respect to a normal direction of the partition wall.
The muffler according to claim 2. The second through hole is formed toward a side wall adjacent to the second side wall extending substantially parallel to the longitudinal direction of the partition wall of the second expansion chamber.
The muffler according to any one of claims 1 to 3. The exhaust inlet is arranged to be biased to one end side in the longitudinal direction of the partition wall,
The exhaust outlet provided in the second expansion chamber is arranged to be biased toward the other end side in the longitudinal direction of the partition wall,
The first through hole is a side close to the exhaust inlet adjacent to the second side wall of the second expansion chamber and a side wall extending in the longitudinal direction of the partition wall in the normal direction of the partition wall. Formed toward the side wall of the
The muffler according to any one of claims 1 to 4, wherein the muffler is provided. The second side wall has an inclined surface that becomes longer as the distance from the partition wall increases from one end in the longitudinal direction of the partition wall toward the other end.
The first through hole is formed toward the inclined surface.
The muffler according to claim 5. The first through hole is formed toward the second catalyst cover in a normal direction view of the partition wall.
The muffler according to any one of claims 1 to 6, wherein the muffler is characterized by that. The first through hole is formed toward a side wall adjacent to the second side wall extending substantially parallel to the longitudinal direction of the partition wall of the second expansion chamber.
The muffler according to any one of claims 1 to 4, wherein the muffler is provided. It is driven by an engine provided with the muffler according to any one of claims 1 to 8.
An engine working machine characterized by that.

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