CN107313833B

CN107313833B - Silencer for engine

Info

Publication number: CN107313833B
Application number: CN201710134022.0A
Authority: CN
Inventors: 奥见正义
Original assignee: Makita Corp
Current assignee: Makita Corp
Priority date: 2016-04-26
Filing date: 2017-03-08
Publication date: 2020-06-05
Anticipated expiration: 2037-03-08
Also published as: DE102017001983A1; US20170306817A1; CN107313833A; JP2017198112A

Abstract

The invention provides a muffler for an engine. The muffler for an engine improves the noise reduction effect of the muffler. The muffler (50) includes: a box-shaped casing (51) having an inlet (52a) into which exhaust gas flows and an outlet (53a) from which exhaust gas is discharged; and a partition plate (56) that divides the interior of the housing into a1 st chamber (61) that includes the inlet port and a 2 nd chamber (62) that includes the outlet port. The partition plate includes a flat plate-like body portion (56a) and a recessed portion (56b) protruding toward the 2 nd chamber side. The main body has a through hole (57) on one side for communicating the 1 st chamber with the 2 nd chamber. A region (56bt3) of the bottom (56bt) of the recessed portion abuts against the inner surface of the 2 nd chamber of the housing. The exhaust gas flowing from the inlet into the 1 st chamber and reaching one side of the 2 nd chamber through the through hole flows in the 2 nd chamber so as to bypass the 2 nd concave portion (56b2) of the concave portion and reaches the outlet through the other side of the 2 nd chamber.

Description

Silencer for engine

Technical Field

The present invention relates to a muffler for an engine.

Background

A muffler for an engine mounted on a portable working machine such as a brush cutter includes, for example, a box-shaped case having an inlet port connected to an exhaust port of the engine and through which exhaust gas flows and an outlet port through which the inflowing exhaust gas is discharged. The case is divided by a partition plate into a1 st chamber including the inlet port and a 2 nd chamber including the outlet port. The partition plate has a plurality of through holes that communicate the 1 st chamber and the 2 nd chamber.

Patent document 1 discloses such a muffler for an engine.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2014-181580

Disclosure of Invention

Problems to be solved by the invention

However, in the muffler disclosed in patent document 1, the actual flow distance (moving distance) of the exhaust gas from the through hole of the partition plate to the discharge port of the housing is relatively short. This makes it difficult to efficiently reduce the pressure of the exhaust gas in the 2 nd chamber, and to sufficiently obtain the noise reduction effect of the muffler.

In view of such circumstances, an object of the present invention is to improve the noise reduction effect of a muffler.

Means for solving the problems

Therefore, according to the 1 st aspect of the present invention, there is provided an engine muffler comprising: a box-shaped casing having an inlet connected to an exhaust port of the engine and through which exhaust gas flows, and an outlet through which the inflowing exhaust gas is discharged; and a partition plate that divides the interior of the case into a1 st chamber including the inlet port and a 2 nd chamber including the outlet port. The partition plate includes a flat plate-shaped main body and a recessed portion protruding toward the 2 nd chamber side from the main body. At least one through hole for communicating the 1 st chamber with the 2 nd chamber is provided on one side of the body. At least a part of the bottom of the concave portion abuts against the inner surface of the 2 nd chamber of the housing. The exhaust gas flowing into the 1 st chamber from the inlet and reaching one side of the 2 nd chamber through the through hole flows in the 2 nd chamber so as to bypass the concave portion and reaches the outlet via the other side of the 2 nd chamber.

In accordance with claim 2 of the present invention, a muffler for an engine includes: a box-shaped casing having an inlet connected to an exhaust port of the engine and through which exhaust gas flows, and an outlet through which the inflowing exhaust gas is discharged; a partition plate that divides the interior of the housing into a1 st chamber including the inlet port and a 2 nd chamber including the outlet port; and a flow restricting portion that locally restricts a flow of the exhaust gas in the 2 nd chamber. At least one through hole for communicating the 1 st chamber with the 2 nd chamber is formed on one side of the partition plate. The exhaust gas flowing from the inlet into the 1 st chamber and passing through the through hole to reach the one side in the 2 nd chamber flows in the 2 nd chamber so as to bypass the flow restricting portion and reaches the outlet via the other side in the 2 nd chamber.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the 1 st aspect of the present invention, at least a part of the bottom of the concave portion of the partition plate abuts against the inner surface of the 2 nd chamber of the housing. The exhaust gas that flows into the 1 st chamber from the inlet port of the casing and reaches one side of the 2 nd chamber through the through hole of the partition plate flows so as to bypass the concave portion of the partition plate in the 2 nd chamber and reaches the outlet port of the casing through the other side of the 2 nd chamber. This makes it possible to increase the substantial flow distance (travel distance) from the through hole of the partition plate to the discharge port of the housing, and therefore, the pressure of the exhaust gas can be efficiently reduced in the 2 nd chamber, and the noise reduction effect of the muffler can be improved.

According to the 2 nd aspect of the present invention, the flow restricting portion locally restricts the flow of the exhaust gas in the 2 nd chamber. The exhaust gas that flows into the 1 st chamber from the inlet port of the casing and reaches the 2 nd chamber through the through hole of the partition plate flows in the 2 nd chamber so as to bypass the flow restricting portion and reaches the discharge port of the casing through the other side in the 2 nd chamber. This makes it possible to increase the substantial flow distance (travel distance) from the through hole of the partition plate to the discharge port of the housing, and therefore, the pressure of the exhaust gas can be efficiently reduced in the 2 nd chamber, and the noise reduction effect of the muffler can be improved.

Drawings

Fig. 1 is a perspective view of a brush cutter according to an embodiment of the present invention.

Fig. 2 is an explanatory view of a state of use of the brush cutter of the embodiment.

Fig. 3 is a sectional view showing a schematic configuration of the engine and the muffler of the embodiment.

Fig. 4 is a front view of the muffler of this embodiment.

Fig. 5 is a sectional view taken along line I-I of fig. 4.

Fig. 6 is a sectional view II-II of fig. 4.

Fig. 7 is a front view of the partition plate of this embodiment.

Fig. 8 is a diagram showing the flow of exhaust gas in the muffler of the embodiment.

Fig. 9 is a diagram showing the flow of exhaust gas in the muffler of the embodiment.

Description of the reference numerals

1. A brush cutter; 3. an engine assembly; 11. a cover; 21. an engine; 36. an exhaust port; 50. a muffler; 51. a housing; 52. 1, a first container; 52a, an inflow port; 53. a 2 nd container; 53a, an outlet; 53a1, opening portion; 53p, convex portion; 53q, an opening; 54. 55, an outer flange portion; 56. a partition plate; 56a, a main body portion; 56b, a concave portion; 56b1, concave part 1; 56b2, 2 nd concave portion; 56bt, bottom; 56bt1, exhaust passage forming portion; 56bt2, exhaust guide; 56bt3, region; 57. a through hole; 58. a guide member; 61. a1 st chamber; 62. a 2 nd chamber; 65. a cylindrical portion; 65a, a through hole; 67. an exhaust passage; 70. a flow restricting section; S1-S5, and the flow of exhaust gas.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 is a perspective view of a brush cutter according to an embodiment of the present invention. Fig. 2 is an explanatory diagram of a use state of the brush cutter. In the present embodiment, a brush cutter will be described below as an example of a portable working machine on which the muffler for an engine according to the present invention is mounted, but the portable working machine on which the muffler for an engine according to the present invention is mounted is not limited to this.

The brush cutter 1 has an operating rod 2 formed of a long pipe. An engine assembly 3 as a power source is provided at the rear end of the operating rod 2. A tool attachment portion 4 serving as a working portion is provided at the tip of the operating lever 2. The tool can be mounted in an exchangeable manner on the mounting portion 4 of the tool. The tool attachment portion 4 is connected to the motor unit 3 by a drive shaft incorporated in the operating lever 2. The tool mounting portion 4 is rotationally driven by the engine unit 3 (specifically, the engine 21).

A handle 5 is attached to a central portion of the operating lever 2 in the longitudinal direction. A vibration-proof housing 6 is provided between the handle 5 and the engine block 3. A hanger 7 is attached to the outer periphery of the vibration-proof housing 6.

The brush cutter 1 is suspended by a hanger 8 from the shoulder of the worker M. The spreader 8 has a harness 9 and a metal fitting 10. The worker M wears the harness 9 on the upper body. In fig. 2, the metal fitting 10 hangs down on the right side of the worker M. The worker M attaches the hanger 7 to the metal fitting 10 and uses the brush cutter 1 in the suspended state. The operator M can perform the brush cutting work by holding the handle 5 of the brush cutter 1 with both hands and operating the brush cutter 1.

The engine unit 3 mainly includes a cover 11 constituting an outer shell thereof, an engine 21 (see fig. 3 described later) covered with the cover 11, and a muffler 50. Here, the muffler 50 corresponds to the "muffler for an engine" of the present invention. The cover 11 is made of, for example, resin.

Fig. 3 is a sectional view showing a schematic configuration of the engine 21 and the muffler 50. Here, fig. 3 shows the engine 21 in a state where the piston 25 is positioned near the top dead center. In the present embodiment, the upper side substantially coincides with the vertical upper side of the engine 21 in the most common state (upright state).

The engine 21 is a four-stroke engine of the ohv (over Head valve) type, and is air-cooled. The engine 21 includes a cylinder block 22, a crankcase 23 attached to a lower portion of the cylinder block 22, and an oil tank 24 provided below the crankcase 23.

The cylinder portion 22 has a cylindrical space for sliding the piston 25 in the vertical direction in fig. 3. A piston 25 is inserted into the space with a gap, and the piston 25 is slidable in the vertical direction in fig. 3.

A crank chamber 27 is formed by the cylinder block 22, the crankcase 23, and the piston 25. That is, a crank chamber 27 is formed by a cylindrical space on the crankcase 23 side formed by the side surface of the cylinder block 22 and the piston 25, and a space in the crankcase 23. The volume of the internal space of the crank chamber 27 changes as the piston 25 slides.

A combustion chamber 29 is formed by the cylinder head 28, the cylinder portion 22, and the piston 25.

The oil tank 24 is defined by an oil tank case, and is provided separately from the crankcase 23, for storing oil for lubrication.

A check valve 30 is provided between the oil tank 24 and the crankcase 23, and the check valve 30 allows only the oil to flow from the crankcase 23 (crank chamber 27) to the oil tank 24.

Here, the pressure in crank chamber 27 becomes negative as piston 25 moves from the bottom dead center to the top dead center. Conversely, the pressure in crank chamber 27 becomes positive as piston 25 moves from top dead center to bottom dead center. Accordingly, when the pressure in the crank chamber 27 is positive, the check valve 30 opens, and oil flows from the crank chamber 27 to the oil tank 24. When the pressure in the crank chamber 27 becomes negative, the check valve 30 closes.

A crank 33 is rotatably supported in the crankcase 23. The crank 33 includes a crankshaft 33a as a rotation center, a counterweight, and the like. The piston 25 and the crank 33 are connected by a connecting rod 34. The connecting rod 34 and the piston 25 are connected in a swingable manner. The connecting rod 34 and the crank 33 are rotatably connected. With such a configuration, the piston 25 reciprocates in the cylinder portion 22.

A cylinder head 28 is provided on the upper wall of the cylinder block 22. The cylinder head 28 is provided with an intake port 35 and an exhaust port 36.

The intake port 35 communicates with a carburetor (not shown) via an insulator (not shown). An air cleaner (not shown) is provided upstream of the carburetor. The engine unit 3 further includes the above-described insulator, carburetor, air filter, and fuel tank (not shown) for storing fuel. The insulator, carburetor, and air filter are covered by a cover 11. The carburetor is a device that mixes fuel with air that has passed through the air filter to generate a mixed gas.

The muffler 50 is formed as a thin muffler elongated in the vertical direction. In the present embodiment, the muffler 50 is directly connected to the exhaust port 36 of the engine 21 and communicates with each other. The details of the muffler 50 will be described later with reference to fig. 4 to 7.

The cylinder head 28 is provided with an intake valve 37 for opening and closing the intake port 35. The cylinder head 28 is provided with an exhaust valve 38 for opening and closing the exhaust port 36. Here, the intake valve 37 and the exhaust valve 38 open and close the combustion chamber 29.

Next, the muffler 50 will be described in detail with reference to fig. 4 to 7 in addition to fig. 3.

Fig. 4 is a front view of the muffler 50. Fig. 5 is a sectional view taken along line I-I of fig. 4. Fig. 6 is a sectional view II-II of fig. 4. Fig. 7 is a front view of the partition plate 56. For convenience of explanation, the upper, lower, left, and right sides are defined as shown in fig. 4 to 7. The side closer to the engine 21 is an inflow side, and the side opposite to the side closer to the engine 21 (in other words, the side farther from the engine 21) is a discharge side. Here, as described above, the "upper side" in fig. 4 to 7 substantially coincides with the vertical upper side in the most common state (upright state) of the engine 21. In fig. 4 to 7, "left side" corresponds to "one side" and "one lateral side" of the present invention, and "right side" corresponds to "other side" and "one lateral side" of the present invention.

The muffler 50 includes a housing 51, a partition plate 56, and a guide member 58.

The housing 51 has a substantially rectangular box shape and includes a1 st container 52 and a 2 nd container 53. In the present embodiment, the 1 st container 52 and the 2 nd container 53 are made of metal, and may be made of resin such as frp (fiber reinforced plastics) which can withstand high temperature.

The 1 st receptacle 52 constitutes the inflow side of the housing 51. The 1 st container 52 has a substantially rectangular box shape with a discharge side open. The 1 st container 52 has an outer flange portion 54 protruding outward at the peripheral edge portion on the discharge side thereof.

An inlet 52a is provided at the upper part of the 1 st container 52. The inlet 52a is connected to the exhaust port 36. Here, since the inlet 52a is provided at the upper portion of the 1 st container 52, the amount of projection of the muffler 50 from the engine 21 to the upper side can be suppressed to be small.

The 2 nd tank 53 constitutes a discharge side of the housing 51. The 2 nd tank 53 has a substantially rectangular box shape with an inlet side opened. The 2 nd tank 53 has an outer flange portion 55 protruding outward at the peripheral edge portion on the inflow side thereof.

A convex portion 53p is formed to protrude outward (on the side opposite to the 2 nd chamber 62) at a position slightly below the vertical center portion of the 2 nd container 53. As shown in fig. 4, the convex portion 53p has a horizontally long rectangular shape when viewed from the front. The convex portion 53p has a substantially U-shaped cross-sectional shape and extends in the lateral direction (left-right direction). An opening 53q is formed at the left end of the convex portion 53 p. Here, a substantially rectangular opening portion of the inflow-side end portion of the convex portion 53p (in other words, a substantially rectangular opening portion of the base-end portion of the convex portion 53 p) corresponds to the discharge port 53 a. Thus, the convex portion 53p protrudes outward so as to cover the discharge port 53a, and has an opening portion 53 q.

The metal or resin partition plate 56 includes a substantially rectangular flat plate-like body portion 56a and a recessed portion 56b formed in the lateral (left-right) center thereof.

The main body portion 56a of the partition plate 56 is caulked and fixed to the 1 st vessel 52 and the 2 nd vessel 53 with the peripheral edge portion thereof sandwiched between the outer flange portion 54 of the 1 st vessel 52 and the outer flange portion 55 of the 2 nd vessel 53. Therefore, in the case 51, the 1 st chamber 61 is defined by the 1 st container 52 and the partition plate 56, and the 2 nd chamber 62 is defined by the 2 nd container 53 and the partition plate 56. Here, the 1 st chamber 61 includes an inflow port 52 a. On the other hand, the 2 nd chamber 62 includes the discharge port 53 a. The 1 st chamber 61 communicates with the exhaust port 36 through the inlet 52 a.

The concave portion 56b of the partition plate 56 includes a1 st concave portion 56b1 constituting an upper portion thereof and a 2 nd concave portion 56b2 constituting an upper and lower central portion thereof.

The 1 st concave portion 56b1 faces the inlet 52a of the 1 st container 52 with the guide member 58 interposed therebetween. In other words, in a state where the guide member 58 is positioned between the 1 st concave portion 56b1 and the inflow port 52a of the 1 st container 52, the 1 st concave portion 56b1 and the inflow port 52a of the 1 st container 52 are opposed to each other.

The 1 st concave portion 56b1 curves in an arc shape so as to extend downward from the inlet 52a side toward the discharge side (i.e., from the inlet side toward the discharge side). Here, the 1 st concave portion 56b1 has a function of receiving the exhaust gas flowing into the 1 st chamber 61 from the inlet 52a and guiding it downward (for example, the 2 nd concave portion 56b 2).

The lower end portion of the 1 st concave portion 56b1 is continuous with the upper end portion of the 2 nd concave portion 56b 2. The 2 nd concave portion 56b2 protrudes toward the discharge side than the 1 st concave portion 56b 1.

As shown in fig. 7, the 2 nd concave portion 56b2 has a substantially rectangular shape when viewed from the front, and at least a part of the bottom portion 56bt thereof (see, for example, a portion P shown in fig. 6) abuts against the inner surface of the 2 nd container 53. That is, at least a part of the bottom 56bt of the concave portion 56b abuts against the inner surface of the 2 nd chamber 62 of the housing 51. Here, the bottom portion 56bt refers to a portion forming an end wall on the discharge side in the 2 nd concave portion 56b2 of the concave portion 56 b.

The bottom 56bt of the 2 nd concave portion 56b2 has an exhaust passage forming portion 56bt1 that protrudes slightly toward the discharge side. The exhaust passage forming portion 56bt1 closes a part (at least the left half in the present embodiment) of the discharge port 53 a. Here, a portion of the discharge port 53a that is not closed by the exhaust passage forming portion 56bt1 becomes a substantial opening portion 53a1 of the discharge port 53 a. The exhaust passage forming portion 56bt1 corresponds to "a portion of the bottom surface of the concave portion that closes a part of the discharge port" in the present invention.

The exhaust guide portion 56bt2 is formed adjacent to the right side of the exhaust passage forming portion 56bt1 in the 2 nd concave portion 56b 2. As shown in fig. 7, the exhaust guide portion 56bt2 is formed in a groove shape recessed toward the 1 st chamber 61 side when viewed from the front. The exhaust guide portion 56bt2 has a function of introducing the exhaust gas in the 2 nd chamber 62 into the substantial opening portion 53a1 of the discharge port 53 a.

As shown in fig. 7, a plurality of (ten in fig. 7) through holes 57 are formed in the left side portion of the body portion 56a of the partition plate 56. Here, the through hole 57 is located at a position lower than the inlet 52a of the 1 st container 52. In fig. 7, ten through holes 57 are shown, but the number of through holes 57 is not limited to this.

In the present embodiment, as shown in fig. 6, the concave portion 56b (particularly, the 2 nd concave portion 56b2) is located between the discharge port 53a (particularly, the substantial opening portion 53a1 of the discharge port 53a) and the plurality of through holes 57 in the lateral direction (left-right direction). Here, in the present embodiment, as shown in fig. 7, the C-shaped region 56bt3 of the bottom portion 56bt of the 2 nd concave portion 56b2 of the concave portion 56b, which region extends so as to surround the upper side, the lower side, and the left side of the exhaust passage forming portion 56bt1, abuts against the inner surface of the 2 nd chamber 62 in the housing 51.

The tubular exhaust passage 67 having a substantially rectangular cross-sectional shape is formed by the convex portion 53p of the 2 nd container 53 and the exhaust passage forming portion 56bt1 of the 2 nd concave portion 56b2 of the partition plate 56. The exhaust passage 67 extends in the lateral direction (left-right direction) and communicates with the 2 nd chamber 62 at its right side portion via the discharge port 53a (in particular, the substantial opening portion 53a 1). The left end of the exhaust passage 67 corresponds to the opening 53 q. The exhaust passage 67 guides exhaust gas from the exhaust port 53a (particularly, the substantial opening portion 53a1) to the opening portion 53 q.

At least one (two in fig. 4 and 6) cylindrical portion 65 is formed to penetrate the housing 51. The cylindrical portion 65 is formed to penetrate the 1 st container 52, the 2 nd container 53, and the partition plate 56, respectively, and bolts (not shown) for fixing the housing 51 to the engine 21 can be inserted into the cylindrical portion 65. In fig. 4 and 6, two cylindrical portions 65 are shown, but the number of cylindrical portions 65 is not limited to this. In fig. 7, a through hole 65a into which the cylindrical portion 65 is inserted is shown.

The guide member 58 is made of metal or resin and is attached to the inlet 52a of the 1 st container 52. The guide member 58 has a U-shaped cross-sectional shape with an open lower surface, and extends from the inlet 52a of the first container 52 toward the discharge side. The guide member 58 has a function of smoothly guiding the exhaust gas flowing from the exhaust port 36 into the 1 st chamber 61 through the inlet 52a to the concave portion 56b of the partition plate 56.

In the present embodiment, the concave portion 56b (particularly, the 2 nd concave portion 56b2) of the partition plate 56 functions as the flow restricting portion 70, and locally restricts the flow of the exhaust gas in the 2 nd chamber 62. Here, the flow restricting portion 70 restricts a straight flow of the exhaust gas in the lateral direction from the through hole 57 toward the discharge port 53a (particularly, the substantial opening portion 53a1) particularly in the 2 nd chamber 62. In the present embodiment, the flow restricting portion 70 is a part of the partition plate 56 (the concave portion 56b (particularly, the 2 nd concave portion 56b 2)). The flow restricting portion 70 is interposed between the housing 51 (particularly, the 2 nd container 53) and the partition plate 56 (particularly, the main body portion 56a) in the 2 nd chamber 62.

In the present embodiment, as shown in fig. 5, the partition plate 56 is provided in the case 51 so that the flow direction F1 of the exhaust gas at the inlet 52a of the 1 st container 52 and the extending direction F2 of the main body portion 56a of the partition plate 56 from the lower end to the upper end form an obtuse angle θ 1. The obtuse angle θ 1 is preferably in the range of 95 ° to 125 °, and more preferably in the range of 100 ° to 120 °.

In the present embodiment, a distance L1 between a portion of the inner wall of the lower end portion of the 1 st chamber 61 opposed to the lower end portion of the main body portion 56a of the partition plate 56 and the lower end portion of the main body portion 56a of the partition plate 56 is longer than a distance L2 between a portion of the inner wall of the lower end portion of the 2 nd chamber 62 opposed to the lower end portion of the main body portion 56a of the partition plate 56 and the lower end portion of the main body portion 56a of the partition plate 56. Further, the partition plate 56 has a concave portion 56 b. This can sufficiently secure the volume of the 1 st chamber 61 into which the high-temperature and high-pressure exhaust gas can flow.

Next, the flow of the exhaust gas discharged from the exhaust port 36 to the outside via the muffler 50 will be described.

Fig. 8 and 9 are diagrams showing the flow of the exhaust gas in the muffler 50 according to the present embodiment. Here, fig. 8 (a) corresponds to fig. 5, fig. 9 (a) corresponds to fig. 6, and fig. 8 (B) and 9 (B) correspond to fig. 7.

The direction of the flow of the exhaust gas flowing from the exhaust port 36 into the 1 st chamber 61 through the inlet 52a of the muffler 50 is changed to the downward direction by the concave portion 56B (particularly, the 1 st concave portion 56B1) of the partition plate 56 (see the flow S1 of the exhaust gas indicated by the arrow in fig. 8 a and 8B). Here, the concave portion 56b (particularly, the 1 st concave portion 56b1) of the partition plate 56 fulfills the function of receiving the exhaust gas flowing into the 1 st chamber 61 from the inflow port 52a and guiding it downward.

The exhaust gas is diffused and cooled in the 1 st chamber 61, and then flows into the left portion of the 2 nd chamber 62 through the through holes 57 of the partition plate 56 (see the flow S2 of the exhaust gas indicated by the arrow in fig. 8 a, 8B, and 9 a).

The exhaust gas flowing into the left portion of the 2 nd chamber 62 flows in the 2 nd chamber 62 so as to go above and below the concave portion 56B (particularly, the 2 nd concave portion 56B2) of the partition plate 56 and reaches the right portion of the 2 nd chamber 62 (refer to flows S3 and S4 of the exhaust gas indicated by arrows in fig. 9 a and 9B). In addition, the exhaust gas can be diffused and cooled in the 2 nd chamber 62.

Then, the exhaust gas passes through the exhaust passage 67 via the exhaust guide portion 56bt2 and the discharge port 53a (particularly, the substantial opening portion 53a1) of the partition plate 56, and is released from the opening portion 53q of the exhaust passage 67 to the outside (see the flow S5 of the exhaust gas indicated by the arrow in fig. 9 (a) and 9 (B)).

The 1 st vessel 52, the 2 nd vessel 53, and the partition plate 56 receive heat from the exhaust gas passing through the muffler 50, and release the heat to the outside from the outer surface of the 1 st vessel 52 and the outer surface of the 2 nd vessel 53.

According to the present embodiment, the muffler 50 includes: a box-shaped casing 51 having an inlet 52a connected to the exhaust port 36 of the engine 21 and into which exhaust gas flows, and an outlet 53a through which the inflowing exhaust gas is discharged; and a partition plate 56 that partitions the inside of the case 51 into a1 st chamber 61 including the inlet 52a and a 2 nd chamber 62 including the outlet 53 a. The partition plate 56 includes a flat plate-shaped body portion 56a and a recessed portion 56b protruding toward the 2 nd chamber 62 side from the body portion 56 a. The body portion 56a has at least one through hole 57 on one side (left side) thereof, which communicates the 1 st chamber 61 with the 2 nd chamber 62. At least a part of the bottom 56bt of the concave portion 56b (for example, the region 56bt3) abuts against the inner surface of the 2 nd chamber 62 of the housing 51. The exhaust gas flowing from the inlet port 52a into the 1 st chamber 61 and reaching one side (left side) of the 2 nd chamber 62 through the through hole 57 flows in the 2 nd chamber 62 so as to bypass the concave portion 56b (particularly, the 2 nd concave portion 56b2) and reaches the discharge port 53a (particularly, the substantial opening portion 53a1) through the other side (right side) of the 2 nd chamber 62 (refer to flows S1 to S5 of the exhaust gas shown in fig. 8 and 9). This makes it possible to increase the substantial flow distance (travel distance) of the exhaust gas from the through hole 57 of the partition plate 56 to the discharge port 53a of the housing 51, and therefore, the pressure of the exhaust gas can be efficiently reduced in the 2 nd chamber 62, and the noise reduction effect of the muffler can be improved.

In addition, according to the present embodiment, the concave portion 56b (particularly, the 2 nd concave portion 56b2) is located between the discharge port 53a (particularly, the substantial opening portion 53a1) and the through hole 57. This makes it possible to increase the substantial flow distance (travel distance) of the exhaust gas from the through hole 57 of the partition plate 56 to the discharge port 53a of the housing 51 with a simple configuration.

In addition, according to the present embodiment, the concave portion 56b (particularly, the 1 st concave portion 56b1) faces the inlet 52 a. Thus, the exhaust gas flowing into the 1 st chamber 61 from the inlet 52a can be smoothly received by the concave portion 56b (particularly, the 1 st concave portion 56b 1).

In addition, according to the present embodiment, the inlet 52a is positioned above the 1 st chamber 61. The concave portion 56b receives the exhaust gas flowing into the 1 st chamber 61 from the inlet 52a and guides the exhaust gas downward. This allows the exhaust gas to be satisfactorily diffused and cooled in the 1 st chamber 61.

In addition, according to the present embodiment, the body portion 56a has a through hole 57 at one lateral side (left side) thereof. The exhaust gas flowing from the inlet port 52a into the 1 st chamber 61 and reaching one lateral side (left side) in the 2 nd chamber 62 through the through hole 57 flows in the 2 nd chamber 62 so as to go above and below the concave portion 56b (particularly, the 2 nd concave portion 56b2) and reaches the outlet port 53a (particularly, the substantial opening portion 53a1) via the other lateral side (right side) in the 2 nd chamber 62 (see flows S1 to S5 of the exhaust gas shown in fig. 8 and 9). This makes it possible to increase the substantial flow distance (travel distance) of the exhaust gas from the through hole 57 of the partition plate 56 to the discharge port 53a of the housing 51, and therefore, the pressure of the exhaust gas can be efficiently reduced in the 2 nd chamber 62, and the noise reduction effect of the muffler can be improved.

In addition, according to the present embodiment, the case 51 (particularly, the 2 nd container 53) includes the convex portion 53p, and the convex portion 53p protrudes outward so as to cover the discharge port 53a, and has the opening portion 53 q. The portion (the exhaust passage forming portion 56bt1) of the bottom portion 56bt of the concave portion 56b that closes part of the discharge port 53a and the convex portion 53p form a tubular exhaust passage 67 that guides the exhaust gas from the discharge port 53a (particularly, the substantial opening portion 53a1) to the opening portion 53 q. This makes it possible to omit a duct for air exhaust, which is a separate member conventionally attached to the outer surface of the casing 51 (particularly, the 2 nd container 53), and to realize the function of the duct by the air exhaust passage 67, thereby reducing the number of components of the duct. Further, since the portion that can function as the duct can be formed only by combining the convex portion 53p of the case 51 and the exhaust passage forming portion 56bt1 of the partition plate 56, the work required for forming the duct can be significantly reduced as compared with the conventional one.

In addition, according to the present embodiment, the muffler 50 includes: a box-shaped casing 51 having an inlet 52a connected to the exhaust port 36 of the engine 21 and into which exhaust gas flows, and an outlet 53a through which the inflowing exhaust gas is discharged; a partition plate 56 that divides the interior of the housing 51 into a1 st chamber 61 including the inlet 52a and a 2 nd chamber 62 including the outlet 53 a; and a flow restricting portion 70 that locally restricts the flow of the exhaust gas in the 2 nd chamber 62. The partition plate 56 has at least one through hole 57 on one side (left side) thereof, which communicates the 1 st chamber 61 with the 2 nd chamber 62. The exhaust gas flowing from the inlet port 52a into the 1 st chamber 61 and reaching one side (left side) of the 2 nd chamber 62 through the through hole 57 flows in the 2 nd chamber 62 so as to bypass the flow restricting portion 70 and reaches the discharge port 53a (particularly, the substantial opening portion 53a1) via the other side (right side) of the 2 nd chamber 62 (see flows S1 to S5 of the exhaust gas shown in fig. 8 and 9). This makes it possible to increase the substantial flow distance (travel distance) of the exhaust gas from the through hole 57 of the partition plate 56 to the discharge port 53a of the housing 51, and therefore, the pressure of the exhaust gas can be efficiently reduced in the 2 nd chamber 62, and the noise reduction effect of the muffler can be improved.

In addition, according to the present embodiment, the flow restricting portion 70 is located between the discharge port 53a (particularly, the substantial opening portion 53a1) and the through hole 57. This makes it possible to increase the substantial flow distance (travel distance) of the exhaust gas from the through hole 57 of the partition plate 56 to the discharge port 53a of the housing 51 with a simple configuration.

In addition, according to the present embodiment, the body portion 56a has a through hole 57 at one lateral side (left side) thereof. The exhaust gas flowing from the inlet port 52a into the 1 st chamber 61 and reaching one lateral side (left side) in the 2 nd chamber 62 through the through hole 57 flows in the 2 nd chamber 62 so as to go above and below the flow restricting portion 70 and reaches the discharge port 53a (particularly, the substantial opening portion 53a1) via the other lateral side (right side) in the 2 nd chamber 62 (see flows S1 to S5 of the exhaust gas shown in fig. 8 and 9). This makes it possible to increase the substantial flow distance (travel distance) of the exhaust gas from the through hole 57 of the partition plate 56 to the discharge port 53a of the housing 51, and therefore, the pressure of the exhaust gas can be efficiently reduced in the 2 nd chamber 62, and the noise reduction effect of the muffler can be improved.

In addition, according to the present embodiment, the flow restricting portion 70 is a part of the partition plate 56 (the concave portion 56b (particularly, the 2 nd concave portion 56b 2)). This eliminates the need to use an additional member for forming the flow restricting portion 70, and further, can suppress an increase in the number of components.

In addition, according to the present embodiment, the flow restricting portion 70 is interposed between the housing 51 (particularly, the 2 nd tank 53) and the partition plate 56 (particularly, the main body portion 56a) in the 2 nd chamber 62. Thus, the exhaust gas flowing from the left portion to the right portion in the 2 nd chamber 62 can flow while bypassing above and below the flow restricting portion 70.

In the present embodiment, the example in which the exhaust gas flowing from the left portion to the right portion in the 2 nd chamber 62 flows while bypassing the flow restriction portion 70 (the concave portion 56b of the partition plate 56 (particularly, the 2 nd concave portion 56b2)) above and below is illustrated, but the bypass path of the exhaust gas may be at least one of above and below the flow restriction portion 70 (the concave portion 56b of the partition plate 56 (particularly, the 2 nd concave portion 56b 2)). That is, the exhaust gas flowing from the left portion to the right portion in the 2 nd chamber 62 may flow while bypassing the flow restriction portion 70 (the concave portion 56b of the partition plate 56 (particularly, the 2 nd concave portion 56b2)) above or below.

In the present embodiment, the concave portion 56b of the partition plate 56 (particularly, the 2 nd concave portion 56b2) is described as an example of the flow restriction portion 70, but the configuration of the flow restriction portion 70 is not limited to this.

As another example of the flow restriction portion 70, instead of forming the 2 nd concave portion 56b2 on the partition plate 56, a case may be mentioned in which the 2 nd container 53 is integrally formed so as to include a portion corresponding to the flow restriction portion 70. In this case, the flow restricting portion 70 is a part of the housing 51 (particularly, the 2 nd tank 53).

As still another example of the flow restriction portion 70, it is also possible to provide the partition plate 56 as a flat plate-shaped main body portion 56a, and to mount an additional member in place of the 2 nd concave portion 56b2 between the main body portion 56a of the partition plate 56 and the inner surface of the 2 nd container 53. In this case, the additional member is interposed between the housing 51 (particularly, the 2 nd tank 53) and the partition plate 56 in the 2 nd chamber 62, corresponding to the flow restriction portion 70.

In the present embodiment, the brush cutter has been described as an example of the portable working machine on which the muffler 50 is mounted, but the portable working machine on which the muffler 50 is mounted is not limited to this. For example, the muffler 50 can be mounted on a portable working machine such as a drilling machine or a concrete cutter. The muffler 50 may be mounted on a backpack-type working machine such as a backpack blower, a sprayer (atomizing machine), a duster, or a backpack brush cutter.

In the present embodiment, the example in which the engine 21 is an OHV type four-stroke engine is illustrated, but the configuration of the engine 21 is not limited to this, and for example, the engine 21 may be an OHC type engine.

In the present embodiment, the engine 21 is exemplified in which the cylinder head 28 and the block portion 22 are independent, but instead of this, the cylinder head and the block portion may be integrated.

As described above, the embodiments described above are merely illustrative of the present invention, and it is obvious that the present invention includes various modifications and changes that can be made by those skilled in the art within the scope of the claims, in addition to the contents directly shown by the embodiments described above.

Claims

1. A muffler for an engine, wherein,

this silencer for engine includes:

a box-shaped casing having an inlet connected to an exhaust port of the engine and through which exhaust gas flows, and an outlet through which the inflowing exhaust gas is discharged; and

a partition plate that divides the case into a1 st chamber including the inlet port and a 2 nd chamber including the outlet port,

the partition plate includes a flat plate-like body portion and a recessed portion projecting toward the 2 nd chamber side from the body portion,

the body portion has at least one through hole communicating the 1 st chamber and the 2 nd chamber on one side thereof,

at least a portion of a bottom of the concave portion abuts against an inner surface of the 2 nd chamber of the housing,

the exhaust gas flowing from the inlet into the 1 st chamber and reaching the one side of the 2 nd chamber through the through hole flows in the 2 nd chamber so as to bypass the concave portion and reaches the outlet through the other side of the 2 nd chamber,

the housing includes a convex portion that protrudes outward so as to cover the discharge port and has an opening,

a tubular exhaust passage for guiding exhaust gas from the exhaust port to the opening is formed by the convex portion and a portion of the bottom of the concave portion that closes a part of the exhaust port.

2. The muffler for an engine according to claim 1,

the concave portion is located between the discharge port and the through hole.

3. The muffler for an engine according to claim 1,

the concave portion is opposed to the inflow port.

4. The muffler for an engine according to claim 2,

the concave portion is opposed to the inflow port.

5. The muffler for an engine according to claim 3,

the inflow port is located at the upper part of the 1 st chamber,

the concave portion receives the exhaust gas flowing into the 1 st chamber from the inlet and guides the exhaust gas downward.

6. The muffler for an engine according to claim 4,

the inflow port is located at the upper part of the 1 st chamber,

7. The muffler for an engine according to any one of claims 1 to 6,

the body portion has the through hole at one side in the lateral direction,

the exhaust gas flowing from the inlet into the 1 st chamber and reaching the one side in the lateral direction in the 2 nd chamber through the through hole flows in the 2 nd chamber so as to go around above and/or below the concave portion and reaches the outlet via the other side in the lateral direction in the 2 nd chamber.

8. A muffler for an engine, wherein,

this silencer for engine includes:

a box-shaped casing having an inlet connected to an exhaust port of the engine and through which exhaust gas flows, and an outlet through which the inflowing exhaust gas is discharged;

a partition plate that divides the case into a1 st chamber including the inlet port and a 2 nd chamber including the outlet port; and

a flow restricting portion that locally restricts a flow of the exhaust gas in the 2 nd chamber,

at least one through hole communicating the 1 st chamber and the 2 nd chamber is formed on one side of the partition plate,

the exhaust gas flowing into the 1 st chamber from the inlet port and reaching the one side in the 2 nd chamber through the through hole flows so as to bypass the flow restricting portion in the 2 nd chamber and reaches the outlet port through the other side in the 2 nd chamber,

a tubular exhaust passage for guiding exhaust gas from the discharge port to the opening is formed by the convex portion and a portion of the bottom of the flow restricting portion that closes a part of the discharge port.

9. The muffler for an engine according to claim 8,

the flow restricting portion is located between the discharge port and the through hole.

10. The muffler for an engine according to claim 8,

the partition plate has the through hole on one side in the lateral direction,

the exhaust gas flowing from the inlet into the 1 st chamber and passing through the through hole to the one side in the 2 nd chamber flows in the 2 nd chamber so as to go above and/or below the flow restricting portion and reaches the outlet via the other side in the 2 nd chamber.

11. The muffler for an engine according to claim 9,

the partition plate has the through hole on one side in the lateral direction,

12. The muffler for an engine according to any one of claims 8 to 11,

the flow restriction portion is a part of the partition plate or a part of the housing.

13. The muffler for an engine according to any one of claims 8 to 11,

the flow restriction portion is interposed between the housing and the partition plate in the 2 nd chamber.