JP6795104B2 - Muffler and engine work machine equipped with it - Google Patents

Description

The present invention mainly lowers the temperature of exhaust gas discharged from a small engine used as a power source for a portable engine working machine such as a brush cutter, a blower, and a chainsaw, and improves the harmful substance removal and muffling effect. Regarding the muffler structure.

A small engine is used as a power source for portable work machines such as brush cutters, blowers, chainsaws, and power cutters that workers carry and use, and generators. Inside the cylinder of the engine, the piston reciprocates and explodes due to the combustion of the air-fuel mixture, and the high-temperature exhaust gas after combustion is discharged. Therefore, the area around the muffler is prevented from the operator directly touching the heated muffler. Is covered by a muffler cover or placed away from the operator's touch. The muffler connected to the engine is provided with a catalyst unit as in the technique of Patent Document 1 in order to remove harmful substances in the exhaust gas passing through the muffler. When the exhaust gas passes through the inside of the catalyst unit and the exhaust gas comes into contact with the catalyst, harmful substances are removed by a chemical reaction. Since this chemical reaction generates high-temperature heat, the exhaust gas that has passed through the catalyst unit becomes extremely high in temperature and may generate a flame (afterfire). Since it is not preferable that this flame is discharged from the exhaust port of the muffler, the exhaust gas flow path from the catalyst unit to the exhaust port of the muffler is configured to have a labyrinth structure.

Japanese Unexamined Patent Publication No. 2012-97623

In the configuration of Patent Document 1, particularly in the configuration of FIG. 5, the flow rate of the exhaust gas passing through the upper side in the catalyst unit increases, the amount of the exhaust gas passing through the lower side decreases, and the catalyst locally deteriorates to be a catalyst. There was a risk that the life of the unit would be shortened. In addition, it was necessary to provide a large catalyst unit to completely remove harmful substances.

The present invention has been made in view of the above background, and an object of the present invention is to appropriately labyrinth the exhaust gas flow path from the catalyst unit to the discharge port so that the exhaust gas can pass uniformly through the catalyst unit. An object of the present invention is to provide a muffler having further improved catalyst efficiency and an engine working machine equipped with the muffler.
Another object of the present invention is to provide an afterfire from the exhaust port by providing a partition plate having a plurality of small-diameter through holes in the exhaust gas flow path from the catalyst unit included in the muffler to the exhaust port. It is an object of the present invention to provide a muffler and an engine working machine equipped with the muffler. Another object of the present invention is to provide a muffler having a small muffler body and capable of reducing noise by making the exhaust gas flow path labyrinth, and an engine working machine including the muffler.

The typical features of the invention disclosed in the present application will be described as follows.
According to one feature of the present invention, a box-shaped outer shell composed of a front housing and a rear housing is formed, an exhaust gas outlet is provided in the front housing, and exhaust gas passes through the rear housing in the first direction. It is a muffler that is provided with an inflow port so that the rear housing is fixed to the cylinder of the engine, and the inside of the outer shell is interposed between the front housing and the rear housing to form the first expansion chamber and the second expansion chamber. The first partition plate to be divided, the catalyst unit through which the exhaust gas passes through the first partition plate in the second direction orthogonal to the first direction, and the path from the catalyst unit to the discharge port are arranged. A second partition plate provided so as to overlap the catalyst unit in the second direction is provided. Here, the total aperture ratio of the plurality of openings of the second partition plate at positions that do not overlap with the catalyst unit in the second direction is set to be larger than the total aperture ratio of the positions that overlap with the catalyst unit. Further, the first partition plate has a first recess, and the second partition plate has a second recess that is recessed in the opposite direction to the first recess, and the first recess and the second recess are combined. This forms an inner shell that defines the third expansion chamber inside the outer shell.

According to another feature of the present invention, the first partition plate has through holes for penetrating and fixing the catalyst unit on the bottom surface of the first recess, and the second partition plate has a plurality of holes on the upper surface of the second recess. An opening was formed so that the second partition plate was fixed to the first partition plate. Further, the joint surface between the front housing and the rear housing is arranged diagonally so as to pass through the corners of the box-shaped outer shell, and the front housing has two side surfaces, an upper surface and a front surface, and a substantially triangular shape in contact with them. The rear housing has two sides, a bottom surface and a rear surface, and a substantially triangular shape in contact with them. The first partition plate arranged on the joint surface is the bottom surface of the third expansion chamber, and the bottom plate arranged in parallel with the bottom surface of the rear housing is formed, and the second partition plate is the upper surface facing the upper surface of the front housing. Was configured to form. Further, a discharge port is formed on the upper surface of the front housing on the side close to the cylinder, and a plurality of openings formed in the second partition plate are formed by a large number of small-diameter through holes, which are closer to the central axis of the catalyst unit. Many are placed on the non-cylinder side.

According to still another feature of the present invention, the second partition plate is fixed to the first partition plate in a non-contact state between the front housing and the rear housing. Further, the distance d ₂ between the inlet side opening surface of the catalyst unit and the bottom surface of the rear housing is configured to be smaller than the distance d ₁ between the inflow port and the third expansion chamber. On the other hand, the distance d ₂ between the inlet side opening surface of the catalyst unit and the bottom surface of the rear housing is configured to be smaller than the opening height H ₁ of the exhaust port of the cylinder. Further, the distance d ₃ between the outlet side opening surface of the catalyst unit and the upper surface of the second partition plate is configured to be smaller than the axial length L ₁ of the catalyst unit.

According to still another feature of the present invention, the catalyst unit has a cylindrical portion and a honeycomb structure portion that is arranged inside the cylindrical portion and on which a catalyst coat layer containing a catalyst component is formed. A metal cap portion having a large number of holes is fixed to the outlet side opening of the cylindrical portion. The cap portion is a curved plate-shaped member arranged so as to be separated from the opening on the third expansion chamber side by a predetermined distance, and a large number of through holes are formed in the plate-shaped member. The cap portion is formed so that the axial direction of a large number of through holes expands in the direction of increasing diameter. The above muffler was directly attached to the cylinder of a small engine to form a small and portable engine work machine.

In the present invention, in a small muffler provided with the first to third expansion chambers, the effective passage area of the exhaust gas flowing through the catalyst is increased by devising the position of the catalyst and the flow direction of the exhaust gas to the catalyst. By securing a sufficient space after passing through the catalyst, it is possible to promote the reburning of the exhaust gas and achieve purification of the exhaust gas. Further, the exhaust gas flow path from the catalyst unit to the discharge port is labyrinthed by the second partition plate that functions as a shielding plate, and the flow is adjusted, so that the entire catalyst can be reacted evenly. Furthermore, the outlet opening of the second partition plate, which functions as a shielding plate, was optimized by arranging a plurality of small through holes and considering the relationship between the arrangement position of the through holes and the position of the catalyst. It is possible to suppress the ejection of flames from the outlet, suppress the flow velocity of exhaust gas, and reduce noise.

It is a perspective view which shows the whole of the chainsaw 1 which concerns on 1st Example of this invention. It is a front view of the chain saw 1 which concerns on 1st Example of this invention. It is sectional drawing of the part AA of FIG. It is sectional drawing of the BB part of FIG. It is a perspective view which shows the shape of the muffler 30 of FIG. It is a developed perspective view of the muffler 30 of FIG. It is an enlarged view of the 1st partition plate 40 and the 2nd partition plate 45 of FIG. It is a partially enlarged view around the muffler 30 of the cross-sectional view of FIG. It is sectional drawing which shows the shape of the catalyst unit 57 of FIG. It is a top view of the second partition plate 45 of FIG. It is a top view of the muffler 30 of FIG. It is a top view of the muffler 30 of FIG. 5, and is the figure which shows the state before attaching the exhaust gas regulation member 50.

Hereinafter, examples of the present invention will be described with reference to the drawings. In the following figures, the same parts are designated by the same reference numerals, and the repeated description will be omitted. Further, in the present specification, the front-back, left-right, and up-down directions are described as the directions shown in the drawings.

FIG. 1 is a perspective view showing the entire chain saw 1 which is an example of an engine working machine. The chain saw 1 contains a small engine (not visible in the figure) as a drive source inside a main housing 2 made of synthetic resin or light metal, and is a portable device that drives a saw chain (not shown) as a tip tool. It is a type engine work machine. In the chainsaw 1 of the present embodiment, the heat-generating engine body, the power transmission mechanism portion, and the auxiliary machinery portions such as the muffler and the vaporizer are entirely covered with a synthetic resin cover. A flat plate-shaped guide bar 17 projecting toward the front (left side in the drawing) of the chainsaw 1 is attached to the main housing 2. The guide bar 17 guides a saw chain (not shown) to the outer peripheral edge. The main housing 2 is provided with a front handle 5 gripped by an operator with one hand and a rear handle 4 gripped by the other hand. The rear handle 4 is provided with a throttle lever 7a (described later in FIG. 3) that adjusts the output of the engine and a lock lever 7b that enables the operator to operate the throttle lever 7a by grasping the throttle lever 7a. A handle guard 6 is attached to the front side of the front handle 5 so as to extend upward. By tilting the handle guard 6 forward, the saw chain (not shown) being driven can be braked. The upper part of the engine is covered with the engine cover 3 made of synthetic resin. An air cleaner cover 28 that covers an air cleaner (not shown) for filtering intake air is provided above the engine cover 3. A spike 23 is attached to the right front portion of the main housing 2 and to the left side of the guide bar 17.

A fan cover 8 is provided on the left side surface of the engine cover 3 to cover a cooling fan (not shown) fixed to the crankshaft (not shown) of the engine. The fan cover 8 is provided with a large number of wind windows 8a on the upper surface, the rear side surface, the lower surface surface, and the front surface. A recoil type starter (not shown) is provided inside the fan cover 8, and a starter handle 27 is arranged above the recoil type starter (not shown). An oil cap 29a for closing an oil supply port for an oil tank, which will be described later, is provided on the front side of the engine cover 3 to store chain oil supplied to a saw chain (not shown). A fuel tank 25 (described later in FIG. 3) for containing a mixed fuel of gasoline and lubricating oil is provided on the rear side of the engine cover 3, and a fuel cap 25a for closing the fuel filler port is provided.

The muffler 30 is arranged on the front side of the engine. The muffler 30 has a substantially box-shaped housing (muffler body), and is directly fixed to a cylinder 11 described later by a bolt (not shown). A plurality of exhaust gas outlets of the muffler 30 are provided on the upper surface (first surface) of the muffler 30 as shown by an arrow 16, and the exhaust gas is discharged toward the front side. In the upper portion of the muffler 30, the wall surface of the engine cover 3 extends to the front side with a predetermined interval.

FIG. 2 is a front view of the chainsaw 1 according to the first embodiment of the present invention. The outside of the engine is covered with various covers such as an engine cover 3, a fan cover 8, and a side cover 9. Whether to provide all or only a part of the covers for the engine can be selected and designed according to the characteristics of the work equipment to be used, but in recent portable engine work machines, the vicinity of the exhaust port of the muffler 30 is provided. Except for this, almost the entire area is often covered with a synthetic resin cover. One end of the front handle 5 is fixed on the lower side of the main housing 2, extends from the left side to the upper side of the engine so as to separate a predetermined distance, and is fixed on the right side of the main housing 2. A guide bar 17 extending forward is provided on the right side of the main housing 2, and a muffler 30 is provided near the center when viewed from the front. The muffler 30 is arranged adjacent to the left side of the guide bar 17 and is located directly below the handle guard 6. That is, since the muffler 30 opens toward the work space where the saw chain (not shown) rotates, the front surface of the muffler 30 is exposed to the outside in this embodiment.

A centrifugal clutch, a sprocket, etc. (not shown) are provided on one end side (right side) of a crankshaft (not shown), and a side cover 9 for covering these is provided. A cooling fan (not shown) that generates cooling air for cooling the cylinder 11 is provided on the other end side (left side) of the crankshaft. Since the cooling fan rotates at a high speed, outside air is sucked through a large number of air windows 8a of the fan cover 8 and the cooling air is blown toward the cylinder 11 inside the engine cover 3. The cooling fan is integrally configured with the magneto rotor, is manufactured of, for example, an aluminum alloy, and a recoil starter is connected to the inside.

Four exhaust gas outlets (52 to 55) are formed on the upper surface (first surface) of the muffler 30. Since the muffler 30 becomes hot due to the passing exhaust gas, it is important to arrange the muffler 30 at a position where it is easily exposed to the outside air. Further, the upper surface, the right wall surface, and the left side surface of the engine cover 3 are arranged so as to be separated from each other by a sufficient distance so that the radiant heat from the muffler 30 is not easily transmitted to the engine cover 3. In this embodiment, the front side of the muffler 30 is not covered with covers, but this is a configuration applicable when the engine working machine is a chainsaw 1. In other engine working machines, it is preferable that the muffler 30 is substantially entirely covered with a synthetic resin muffler cover except for the opening of the exhaust gas outlet portion.

On the upper portion of the muffler 30, a surface (first surface) that is not horizontal and slightly lowers to the front side is formed, and four raised portions 52 to 55 are formed near the rear end of the surface. The exhaust gas regulation member 50 is attached. The raised portions 52 to 55 are arranged in the left-right direction, and the exhaust gas flow from the respective openings is arranged so as to spread in a fan shape, so that the exhaust gas from the raised portions 52 to 55 is sufficient in the left-right direction. It is discharged to the front side while diffusing. This exhaust gas flow not only diffuses in the left-right direction in a planar shape along the upper surface of the muffler 30, but also flows while being sufficiently diffused so as to be separated from the front end portion of the first surface of the muffler 30 in the vertical direction. .. The positions of the raised portions 52 to 55 are arranged so as to be sufficiently above the upper end position of the guide bar 17 so that the exhaust gas discharge direction does not easily hit the log or the like to be cut.

FIG. 3 is a cross-sectional view of a portion AA of FIG. The engine 10 is a two-cycle air-cooled engine, in which a crankshaft (not shown) is arranged so as to extend in the left-right direction, and the reciprocating movement direction of the piston 12 (the axis of the cylindrical surface of the cylinder) is the up-down direction. A plurality of heat radiation fins are formed on the outer peripheral portion of the cylindrical cylinder 11, and the cylinder 11 is cooled by exposing the heat radiation fins to cooling air generated by a cooling fan (not shown). Here, the cylinder 11 is manufactured by integrally molding a light metal. An exhaust port 11a for exhausting exhaust gas from the combustion chamber is provided on the side surface (here, the upper side) of the cylindrical portion of the cylinder 11, and the muffler 30 is attached to the cylinder 11 so as to be adjacent to the exhaust port 11a. Here, the engine body and the muffler 30 are not connected by a tubular connecting pipe having a certain length, but the opening of the exhaust port 11a of the cylinder 11 and the opening on the inflow side of the muffler 30 are joined. In this way, it is directly fixed with a screw (not shown). Further, a muffler gasket 24 is interposed between the cylinder 11 and the muffler 30 to improve the adhesion. Here, "direct fixing" means that the muffler 30 is connected to the cylinder 11 without passing through a "pipeline" using another member such as an exhaust pipe, and the muffler 30 is connected to the cylinder 11 by using bolts. It is a fixing method that is directly screwed. At this time, the case where a plate-shaped member having an opening such as the muffler gasket 24 is sandwiched is not excluded, and the intervention of the muffler gasket 24 is included in the definition of "direct fixing".

The reciprocating motion of the piston 12 in the cylinder axial direction (vertical direction) is converted into a rotary motion of the crankshaft (not visible in the figure) via the connecting rod 13. Further, the vaporizer 21 and the muffler 30 are arranged so as to be separated from the cylinder 11 by about 180 ° around the axis of the engine. A fuel tank 25 is provided on the rear side of the crankcase 14, and an oil tank 29 is provided on the front side. Fuel is supplied from the fuel tank 25, the air sucked through the filter element 26 is mixed with the fuel by the carburetor 21, and the air-fuel mixture is supplied from the intake port 11b to the inside of the cylinder 11 (combustion chamber). The supplied air-fuel mixture is ignited at a predetermined time by the spark plug 20. When the piston 12 moves to the bottom dead center side after combustion and the exhaust port 11a is opened, the exhaust gas EX1 is discharged from the exhaust port 11a and flows into the internal space of the muffler 30 as shown by the dotted line of EX2.

The exhaust gas EX1 that has flowed into the muffler 30 flows from the first expansion chamber 61 in the muffler 30 into the third expansion chamber 63 through the catalyst unit 57. The exhaust gas then flows from the third expansion chamber 63 into the second expansion chamber 62 in which the exhaust gas discharge port is formed, and flows into the exhaust gas discharge port 38 (described later in FIG. 6) like the exhaust gas EX6. It is guided by the raised portions 52 to 55 of the exhaust gas regulating member 50 (only 54 and 55 can be seen in the figure), and is discharged as the exhaust gas EX7 toward the front side. As shown in the figure, the exhaust gas EX7 is discharged in the horizontal direction and forward when viewed from the side. The upper wall surface of the muffler 30 is formed obliquely so that the front side is slightly inclined downward. This is because the exhaust gas EX7 discharged forward in the horizontal direction flows along the upper wall surface and is also diffused in the vertical direction. The engine cover 3 is arranged so as to be substantially horizontal above the space through which the exhaust gas EX7 flows, but a large distance between the muffler 30 and the engine cover 3 is secured, and a sufficient space through which the exhaust gas EX7 flows is secured. .. Further, the raised portions 52 to 55 are arranged on the side closer to the rear end of the upper surface 36a of the muffler 30. This is because the exhaust gas EX7 emitted from the muffler 30 secures the distance flowing from the rear to the front along the upper surface 36a of the muffler 30, that is, the flow path length in the engine cover 3, so that the muffler 30 and the engine cover 3 This is to lower the exhaust gas temperature before coming out of the opening.

FIG. 4 is a cross-sectional view of a portion BB of FIG. A muffler 30 is arranged on the front surface of the cylinder 11 with the muffler gasket 24 interposed therebetween. The four raised portions 52 to 55 formed on the exhaust gas regulating member 50 together with the outer wall portion of the muffler 30 form a tubular exhaust passage, and determine the outflow direction of the exhaust gas flow. Here, the exhaust direction is determined so as to spread in the arrangement direction (here, the left-right direction) of the raised portions 52 to 55. It spreads like the exhaust gas EX7A of the raised portions 53 and 54 located on the inner side, and its spreading angle is set smaller than the spreading angle of the exhaust gas EX7B of the raised portions 52 and 55 located on the outer side. Since a plurality of small raised portions 52 to 55 are provided and arranged in a fan shape in this way, the exhaust gases EX7A and EX7B can be effectively diffused. In particular, it is possible to realize a sufficient diffusion condition of the exhaust gases EX7A and EX7B while arranging the exhaust openings at narrow intervals. Therefore, the exhaust gas regulation member 50 can be made small.

FIG. 5 is a perspective view showing the shape of the muffler 30. The muffler 30 forms a box-shaped outer shell by aligning the front housing 35 having an opening and the rear housing 31 having an opening so that the recessing directions of the openings are opposite to each other and crimping the peripheral edge portion. That is, the front housing 35 has an upper surface 36a and a front surface, and two side surfaces having a substantially triangular shape in contact with them, and the rear housing 31 has a bottom surface and a rear surface, and two side surfaces having a substantially triangular shape in contact with them. The exhaust gas regulation member 50 is fixed at a position where the exhaust port 38 (see FIG. 6) on the upper surface of the muffler 30 is closed. Notches 52a to 55a obtained by pressing and punching the metal plate 51 are formed on the front side of the raised portions 52 to 55, and the connecting portions of the raised portions 52 to 55 with the notches 52a to 55a are openings. Flat plate-shaped mounting surfaces 51a and 51b are formed on the left and right sides of the exhaust gas regulation member 50, and the mounting surfaces 51a and 51b are welded to the upper surface 36a of the front housing 35.

FIG. 6 is a developed perspective view of the muffler 30. In the housing of the muffler 30, that is, the muffler body, the concave rear housing 31 manufactured by pressing a metal plate and the outer edges of the concave front housing 35 are aligned so that the respective concave openings face each other. A substantially box-shaped outer shell portion is formed by folding back and crimping the outer edge portion of the housing 31. The divided surfaces of the front housing 35 and the rear housing 31 are arranged obliquely so as to pass through the front lower corner portion and the rear upper corner portion of the box-shaped outer shell. The concave portion inside the rear housing 31 is formed in a substantially triangular prism shape, the two bottom surface portions of the triangle are left and right sides (right side surface 32c, left side surface 32d), and the two side surfaces of the quadrangle in contact with these two bottom surface surfaces are the bottom surface 32a. And the rear side surface 32b, and the large quadrangular side surface of the triangular prism is the opening. Here, the shape of the concave portion of the rear housing 31 may be optimized so as to form a large housing of the muffler 30 in the limited space adjacent to the cylinder, and the concave shape does not have to be a strict triangular columnar shape. .. The front housing 35 is formed so as to correspond to the rear housing 31, and the shape of the concave portion thereof is also formed in a substantially triangular columnar shape. Here, the two bottom surface portions having a substantially triangular columnar shape form both left and right sides (right side surface 36c, left side surface 36d), and a substantially rectangular upper surface 36a and front surface 36b are formed so as to connect one side thereof. The recessed shape of the front housing 35 is substantially triangular and columnar, but the shape is broken, and the corner portions of the upper surface 36a and the front surface 36b are formed into smooth cylindrical surfaces that draw a large arc. This is because the exhaust gas discharged from the exhaust gas discharge ports (four raised portions 52 to 55 shown in FIG. 5) formed on the upper surface 36a is optimized to effectively diffuse in the vertical direction. ..

In the muffler 30, in addition to the outer shell portion formed by the front housing 35 and the rear housing 31, an inner shell portion arranged inside is formed. The method of forming the inner shell portion is the same as the method of forming the outer shell portion, and the openings of the two sets of members (first partition plate 40 and second partition plate 45) recessed in a concave shape are joined to each other. It defines a rectangular parallelepiped space. The first partition plate 40 and the second partition plate 45 are manufactured by stamping metal, and like the outer shell portions (31, 35) of the muffler 30, have substantially triangular prismatic recesses that are oriented sideways. The portion of the side surface of the triangular prism that is the largest surface is used as the opening surface, and the inner shell portion of the muffler 30 is formed by matching the opening surfaces. A flat outer edge portion 42 is formed on the outer peripheral portion of the opening of the first partition plate 40, and the outer edge portion 42 is formed to have the same size as the outer edge portion of the front housing 35. At the time of joining the front housing 35 and the rear housing 31, the outer edge portion 42 of the first partition plate 40 is arranged so as to be sandwiched between the outer edge portions of the front housing 35 and the rear housing 31, and the outer edge portion of the rear housing 31. Is bent forward to form a crimped portion 31b (see FIG. 5) by being crimped to the outer edge portion of the front housing 35. This joining method is not limited to the caulking method, and other methods such as welding and adhesion may be used or used in combination. As described above, the method of interposing the first partition plate 40 between the outer edges of the front housing 35 and the rear housing 31 is a conventionally widely used joining method. By this joining, two of the first expansion chamber and the second expansion chamber separated by the first partition plate 40 are partitioned inside the muffler 30.

In this embodiment, the third expansion chamber 63 (see FIG. 3) is partitioned by adding a partition plate, that is, a second partition plate 45, which is interposed inside the outer shell of the muffler 30. The second partition plate 45 has a recess facing the recess of the first partition plate 40, and a laterally oriented substantially triangular columnar recess is formed. The two bottom surfaces of the triangular prism are both left and right sides (right side surface 46c, left side surface 46d), and the two side surface portions are the upper surface 46a and the front surface 46b. Two flat surfaces (47a, 47e) are formed on two side portions of the outer edge portion of the second partition plate 45 in order to join with the first partition plate 40. The outer edge positions of the two flat surfaces (47a, 47e) in the front-rear direction are formed to be slightly smaller than the outer edge positions of the outer edge portion 42 of the first partition plate 40 in the front-rear direction, and the first partition is formed in the front housing 35 and the rear housing 31. The size is set so as not to interfere with the portion sandwiching the plate 40. By forming the inner shell portion by the first partition plate 40 and the second partition plate 45 as described above, three expansion chambers (61 to 63) are partitioned inside the muffler.

The muffler 30 is provided with two cylindrical sleeves 64 and 65 so as to penetrate the two expansion chambers, and two hexagonal screws 68 are attached so as to penetrate the sleeves 64 and 65. The muffler 30 is directly screwed to the exhaust port 11a of the cylinder 11. The closing surfaces 64c and 65c on the rear end side of the sleeves 64 and 65 are provided with through holes for fixing screws (not shown) in the center. Further, the front end side opening surfaces 64a and 65a have a diameter larger than that of the head of the hexagon screw 68. Flange portions 64b and 65b having a large outer diameter are formed in the vicinity of the front end side opening surfaces 64a and 65a of the sleeves 64 and 65. After the front end portions of the sleeves 64 and 65 are passed through the through holes 37a and 37b so that the flange portions 64b and 65b abut on the inner wall surface of the front housing 35, the flange portions 64b and 65b are placed on the inner wall surface of the front housing 35. Fix by caulking or the like. After that, the sleeves 64 and 65 are passed through the through holes 49a and 49b of the second partition plate 45, and are passed through the through holes 44a and 44b of the first partition plate 40. Through holes 33b and 33c (however, 33c cannot be seen in FIG. 6) are formed in the rear housing 31 for penetrating a part of the hexagonal screw 68. A mounting member 76 having through holes 76a and 76b for further screwing the muffler 30 to the cylinder 11 or the main housing 2 is mounted on the lower surface of the rear housing 31 by welding.

An exhaust gas discharge port 38, which is an outlet of the exhaust gas EX7 (see FIG. 3) from the muffler space, is formed on the upper surface 36a portion on the upper side of the front housing 35. The exhaust port 38 is one opening having a sufficient size so as to connect a part of the rear end side of the four exhaust ports (52 to 54) of the plate-shaped exhaust gas regulation member 50 in the left-right direction. Bent portions 39a to 39c are formed on the front side of the discharge port 38 so that the surface thereof is bent diagonally inward. The recessed portions of the bent portions 39a to 39c and the pipelines defined by the raised portions 52 to 55 serve as exhaust passages, and these pipelines are independent and have openings on the front end side, respectively. The exhaust gas regulation member 50 has stepped portions on both sides of the metal plate 51, and the left and right side portions that are lower than the stepped portion are the mounting surfaces 51a and 51b. Then, by welding the mounting surfaces 51a and 51b to the upper surface 36a of the front housing 35, a predetermined gap is formed between the metal plate 51 and the upper surface 36a of the front housing 35 so that the spark arrester 56 can be inserted.

The spark arrester 56 is a metal mesh member having a size substantially equal to that of the metal plate 51, has a through hole 56a formed therein, and is nutted through a nut fixing hole 36e of the front housing 35 by a screw 59a (see FIG. 5). It is screwed into 59b. The nut 59b is previously fixed to the inner wall surface of the front housing 35 by welding or the like. A cutout portion 51c is formed in the portion of the metal plate 51 for fixing the screw 59a (see FIG. 5) to avoid contact with the screw 59a.

A cover 70 is attached to the front side of the front housing 35 of the muffler 30. The cover 70 is a dustproof member provided to prevent wood chips and the like from accumulating in the recessed portions (front end side opening surfaces 64a and 65a) of the two sleeves 64 and 65 exposed on the front side of the front housing 35. It is manufactured of the same metal material as the housing 31 and the front housing 35. A screw seat 72 having a screw hole for fixing with a screw 74 is provided in the central portion of the cover 70. The screw 74 is screwed into the nut 75 through the through hole 72a of the cover 70 and the nut fixing hole 36f of the front housing 35. The nut 75 is previously fixed to the inner wall surface of the front housing 35 by welding or the like. The front wall 71a of the cover 70 is formed flat, and the front wall 71a and the front portion of the front housing 35 are attached so as to have a predetermined gap, but the cover 70 is attached to both the left and right sides so that wood chips and the like do not enter the gap portion. Covering portions 71c and 71d are formed on both the left and right sides so as to be in close contact with the outer wall of the front housing 35. Further, the upper portion 71b of the cover 70 is also brought into close contact with the upper surface 36a of the front housing 35 of the muffler 30 so as to extend rearward along the outer wall of the front housing 35.

An exhaust gas inflow port 33a is formed in the rear housing 31. A mounting plate 34 is provided around the exhaust gas inflow port 33a for reinforcement. The mounting plate 34 has an opening 34a having the same shape as the exhaust gas inflow port 33a, and has through holes 34b and 34c through which the threaded portion of the hexagonal screw 68 is penetrated, and through holes 33b and 33c of the rear housing 31 (in FIG. 6). It is large enough to cover the part (33c is invisible). The mounting plate 34 is fixed to the rear housing 31 by caulking, welding, or brazing. The flow of exhaust gas flows into the first expansion chamber 61 (see FIG. 3) inside the muffler 30 from the inflow port 33a and the opening 34a, and is arranged in the through hole 43 formed in the bottom surface 41a of the first partition plate 40. The gas flows into the third expansion chamber 63 (see FIG. 3) through the catalyst unit 57 and the catalyst cover 58. The through hole 43 is a large circular hole in which the opening surface is arranged in a direction orthogonal to the opening surface of the inflow port 33a communicating with the exhaust port 11a (see FIG. 3) of the cylinder 11. The diameter of the through hole 43 is formed to be larger than the height of the inflow port 33a, and the catalyst unit 57 is attached thereto.

The catalyst unit 57 has a cylindrical shape, and the inlet side opening 57a is arranged on the lower side and the outlet side opening 57b is arranged on the upper side so that the central axis of the catalyst unit 57 is in the vertical direction. It is fixed to the partition plate 40. A punching metal catalyst cover 58 having a large number of through holes 58a is fixed to the outlet side opening 57b of the catalyst unit 57. By providing the catalyst cover 58, uniform use of the entire catalyst becomes possible. The catalyst unit 57 is fixed to the first partition plate 40 by welding or press fitting, and the catalyst cover 58 is fixed to the catalyst unit 57 by welding. The exhaust gas that has passed through the catalyst unit 57 and the catalyst cover 58 and has flowed into the third expansion chamber 63 (see FIG. 3) is distributed through holes 48a and 48b on the left and right sides of the upper surface 46a of the second partition plate 45. It flows into the second expansion chamber 62 (see FIG. 3) inside the front housing 35 through. From the second expansion chamber 62, the muffler 30 is discharged to the outside through the discharge port 38 and the raised portions 52 to 55.

FIG. 7 is an enlarged view of the first partition plate 40 and the second partition plate 45 of FIG. FIG. 7 (1) shows a perspective view of the second partition plate 45, and the second partition plate 45 forms about half of the inner shell by making a hole in one flat plate by press working and then bending it. The upper surface 46a and the front surface 46b are bent at a right angle at the bent portion 47c, the upper surface 46a and the outer edge flat portion 47a are bent at an obtuse angle at the bent portion 47b, and the front surface 46b and the outer edge flat portion 47e are bent at an obtuse angle at the bent portion 47d. Be done. The triangular left side surface 46d connected to the left side of the upper surface 46a is bent at a right angle at the bent portion 47f, and a slightly protruding portion is formed on the front side of the left side surface 46d, and the protruding portion (front surface 46b) is formed. The portion to be connected to the above) is bent inward at a right angle to form a bent portion of 47 g. The bent portion 47g is fixed to the left side portion of the front surface 46b. A triangular right side surface 46c (not directly visible in FIG. 7 (1)) connected to the right side of the upper surface 46a is also formed in the same manner. Through holes 49a and 49b for passing the sleeves 64 and 65 are formed in the front surface 46b of the second partition plate 45. A small-diameter through hole 49c is formed between the through holes 49a and 49b. The through hole 49c is a hole for accommodating the tip portion of the screw 74 for fixing the cover 70 mounted on the front housing 35, and the through hole 49c may not be provided as long as it does not interfere with the screw 74. Here, the substantially triangular columnar concave space formed by the second partition plate 45 is smaller than the substantially triangular columnar concave space formed by the first partition plate 40. Therefore, the third expansion chamber 63 defined by the first partition plate 40 and the second partition plate 45 does not have a perfect square columnar shape, but the exhaust gas flowing in from the first expansion chamber 61 through the catalyst unit 57. By expanding the exhaust gas and bending the direction of exhaust gas flow by a large number of through holes 48a and 48b, the exhaust gas passage opening is also narrowed and restricted, that is, the labyrinth passage. It is composed.

The positions where the through holes 48a and 48b are provided are optimized so that the labyrinth effect can be sufficiently obtained. For example, the plurality of openings formed in the second partition plate 45 are formed by a large number of small-diameter through holes 48a and 48b, and are on the side opposite to the cylinder side (the side away from the cylinder 11; here, the front side) from the central axis of the catalyst unit 57. Many are placed on the side). Further, since the outer edge position of the recess defined by the second partition plate 45 is set inside the outer edge position of the recess defined by the first partition plate 40 to reduce the size of the recess, the outer edge of the second partition plate 45 is reduced. The flat surface portions 47a and 47e can be formed larger by that amount. The area of the outer edge flat portions 47a and 47e is widened because the opening area of the recess of the second partition plate 45 is smaller than the opening area of the recess of the first partition plate 40, so that the opening difference portion is closed. is there. Further, the outer edge positions of the outer edge flat portions 47a and 47e are positioned at the inner portion that does not interfere with the joint surface between the rear housing 31 and the front housing 35, and the second partition plate 45 is sandwiched between the rear housing 31 and the front housing 35. It was prevented from interfering with each other during the manufacturing process of joining. In this way, since the second partition plate 45 has an opening portion in which the number of holes increases along the traveling direction of the exhaust gas EX4, the sound deadening effect due to the labyrinth structure is exhibited, and the catalyst is locally used and early due to the increase in the flow path resistance. Deterioration can be prevented.

FIG. 7 (2) shows a perspective view of the first partition plate 40, and the first partition plate 40 is manufactured by integral molding of metal by press working. The bottom surface 41a and the rear surface 41b are formed on the first partition plate 40, and a recess (first recess) recessed in the direction opposite to the recess (second recess) of the second partition plate 45 is formed. By combining the concave portion of the first partition plate 40 and the concave portion of the second partition plate 45, an inner shell defining the third expansion chamber 63 is formed inside the outer shell of the muffler 30. A through hole 43 for fixing the catalyst unit 57 (see FIG. 6) is formed in the center of the bottom surface 41a, and through holes 44a and 44b for penetrating the sleeves 64 and 65 are formed in the rear surface 41b. The through hole 43 may be formed not only by punching but also by forming a cylindrical flange portion in order to stably hold the cylindrical catalyst unit 57. The bottom surface 41a and the rear surface 41b are arranged so as to be substantially orthogonal to each other, and a substantially triangular right side surface 41c and left side surface 41d are formed on the left and right sides of the bottom surface 41a and the rear surface 41b. Here, stepped step portions 41e and 41f are formed on the right side surface 41c and the left side surface 41d in order to secure the muffler volume so that the width of the region close to the rear surface 41b in the left-right direction is expanded.

The outer edge portions 42 (42a to 42d) are plate-shaped flange surfaces extending outward at all outer edge portions, and the upper outer edge portion 42a and the lower outer edge portion 42c are configured to have a relatively large area. This is to join the second partition plate 45 shown in FIG. 7 (1). The outer edge portions 42b and 42d in the left-right direction are not so large as compared with the upper outer edge portion 42a and the lower outer edge portion 42c. This is because the outer edge portions 42b and 42d and the right side surface 46c and the left side surface 46d of the second partition plate 45 are in contact with each other. At the time of assembly manufacturing, the catalyst unit 57 with the catalyst cover 58 is fixed to the first partition plate 40, and then the first partition plate 40 and the second partition plate 45 are joined. For this joining, for example, the outer edge portion 42a and the outer edge flat portion 47a may be welded or brazed, and the outer edge portion 42c and the outer edge flat portion 47e may be welded or brazed. After the third expansion chamber 63 is formed in this way, the sleeps 64 and 65 are penetrated through these assemblies and sandwiched so as to be interposed at the joint surface between the rear housing 31 and the front housing 35. The outer edge shape of the outer edge portions 42 (42a to 42d) of the first partition plate 40 is the same as the flange-shaped outer edge shape of the front housing 35. Therefore, it is only necessary to position them at the outer edge bent portion of the rear housing 31 and bend and crimp the outer edge portion of the rear housing 31 so as to cover the outer edge portion of the front housing 35 to form the crimped portion 31b.

FIG. 8 is a partially enlarged view of the vicinity of the muffler 30 of FIG. 2, which is a cross-sectional view showing a state in which the muffler 30 is fixed to the cylinder 11. The body of the muffler 30 is formed by joining the rear housing 31 and the front housing 35, and is first formed by interposing a first partition plate 40 and a second partition plate 45 holding the catalyst unit 57 between them. Three expansion chambers, an expansion chamber 61, a second expansion chamber 62, and a third expansion chamber 63, are partitioned. The joint between the rear housing 31 and the front housing 35 is a caulking joint in which the extended outer edge portion of the front housing 35 is bent so as to wrap the outer edge portion of the rear housing 31. At this time, the joint surface between the front housing 35 and the rear housing 31 is diagonally arranged so as to pass through the opposite corners of the box-shaped outer shell of the box-shaped muffler 30. The method of joining the outer edge portion is not limited to caulking, and other known joining methods that can maintain the confidentiality of the rear housing 31 and the front housing 35 may be used.

The exhaust gas EX1 passing from the exhaust port 11a to the inflow port 33a flows in the first direction (the axial direction of the exhaust port 11a), and the exhaust gas EX2 flowing into the first expansion chamber 61 is the rear surface of the first partition plate 40. It collides with 41b and is bent downward, and flows forward in the vicinity of the bottom surface in the first expansion chamber 61. After that, as shown by the arrow EX3, the inside of the catalyst unit 57 is reached from the vicinity of the bottom surface of the first expansion chamber 61. The catalyst unit 57 is fixed to the through hole 43 of the first partition plate 40, the bottom surface 32a of the housing 31 rear and the inlet-side opening 57a of the catalyst unit 57 is disposed so as to face, their spacing d ₂ is narrower ing. This is so as to lower the catalyst unit 57 as much as possible in the lower, is to earn as much as possible the distance d ₃ of the outlet opening 57b of the catalyst unit 57 (see FIG. 9 to be described later) and the upper surface 46a of the second partition plate 45 .. The third volume of the expansion chamber 63 after passing through the catalyst unit 57 by taking the distance d ₃ larger can relatively be increased by the. In this embodiment, the catalyst unit 57 is arranged in the muffler 30 in a downward offset so as to be below the exhaust port 11a. Further, the distance d ₂ is configured to be smaller than the opening height H ₁ of the exhaust port 11a of the cylinder 11, and is smaller than the distance d ₁ between the inflow port 33a and the wall surface (rear surface 41b) of the third expansion chamber 63. It is configured to be. Further, the distance d ₄ of the second partition plate 45 from the upper surface 46 a is configured to be sufficiently larger than the distance d ₂ .

A cap-shaped catalyst cover 58 having a large number of through holes 58a is formed on the outlet side opening side of the catalyst unit 57, and the axis line near the outer periphery of the large number of through holes 58a (see FIG. 6) extends radially, so that the exhaust gas is exhausted. The gas EX4 is also diffused and discharged to the third expansion chamber 63. The exhaust gas EX4 diffused in the third expansion chamber 63 flows as shown by the arrow EX5 through a large number of through holes 48a and 48b (see FIG. 7) formed on the upper surface 46a of the second partition plate 45, and the second It flows into the expansion chamber 62. Here, the flow direction of the exhaust gas EX5 from the third expansion chamber 63 to the second expansion chamber 62 looks linear when viewed from the side as shown in FIG. 8, but as will be described later in FIG. 10, the catalyst unit Since the outlet extension surface of 57 and the through holes 48a and 48b are arranged so as to be offset in the left-right direction, the exhaust gas flow path from the catalyst unit 57 to the discharge port 38 is labyrinthed to be appropriately bent. Since the flow path is appropriately labyrinthized in this way, the exhaust gas can be uniformly dispersed and flowed through a large number of honeycomb-shaped passages of the catalyst unit 57, so that the efficiency of the purification action by the catalyst can be improved. ..

The inside of the second expansion chamber 62 is a flat space along the upper surface 36a and the front surface 36b (see FIG. 6) of the front housing 35, but a predetermined volume can be secured so that the exhaust pressure wave can be effectively used. It is configured in. A discharge port 38 is provided above the second expansion chamber 62 and above the upper surface 36a of the front housing 35. An exhaust gas regulation member 50 having raised portions 52 to 55 (only 54 and 55 can be seen here) is provided on the upper side of the discharge port 38. A spark arrester 56 (see FIG. 6) is mounted between the exhaust gas regulation member 50 and the upper surface 36a so as to cover the entire exhaust port 38. The sleeves 64 and 65 (65 cannot be seen in the drawing) are members for securing a space for passing a hexagonal screw 68 (see FIG. 6) for fixing the muffler 30 to the cylinder 11 (see FIG. 6), and the muffler 30 It is provided so as to penetrate from the front housing 35 to the rear housing 31 side.

The surface shape of the front wall of the front housing 35 is parallel to the mounting surface of the cylinder 11 for fixing the sleeves 64 and 65 (see FIG. 6), but the front wall 71a of the cover 70 is a screw 74. It is formed in an oblique flat shape except for the mounting portion. Further, in order to reduce the radiant heat transmitted from the inside of the muffler 30 to the front side by the cover 70, the wall surface of the front housing 35 and the cover 70 are separated from each other by a predetermined distance. On the other hand, the cover 70 has a shape that closes the openings on the front side of the sleeves 64 and 65.

FIG. 9 is a cross-sectional perspective view showing the shape of the catalyst unit 57. The catalyst unit 57 converts hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas into nitrogen, water, and carbon dioxide by an oxidation / reduction reaction with the catalyst material to make them harmless. Inside the metal outer cylinder of the catalyst unit 57, a ceramic or metal honeycomb structure 57c communicating in the axial direction is arranged. A slurry containing a catalyst component (precious metal or the like) is applied to the wall surface of the honeycomb structure 57c to form a catalyst coat layer (not shown). The exhaust gas EX3 flows in from the inlet side opening 57a of the catalyst unit 57, undergoes an oxidation / reduction reaction while passing upward inside the honeycomb structure 57c, and is discharged from the outlet side opening 57b. The exhaust gas chemically reacted by this catalyst becomes extremely hot, and a part of the exhaust gas continues to be reburned, and afterfire may be generated on the rear side of the catalyst unit 57. Therefore, the catalyst cover 58 having a large number of through holes 58a is provided in the outlet side opening 57b. The catalyst cover 58 promotes the purification reaction in the catalyst unit 57 by limiting the flow path area of the exhaust gas EX3 while providing a predetermined space at a slight distance from the outlet side opening 57b, and the afterfire exhausts the exhaust gas. Suppresses transmission to the downstream side of the gas flow. Further, the catalyst unit 57 guides the exhaust gas flow EX3 directed in the axial direction so as to spread like the flow EX4. The catalyst cover 58 is preferably formed of punching metal, which is a metal member having high heat resistance, and is fixed to the outer cylinder portion of the catalyst unit 57 by welding.

FIG. 10 is a top view of the second partition plate 45. On the upper surface 46a of the second partition plate 45, a large number of through holes 48a and 48b that serve as a flow path for exhaust gas from the third expansion chamber 63 to the second expansion chamber 62 are arranged. The through hole 48a is a group of small diameter holes arranged on the right side of the left and right center lines D2, and the through hole 48b is a group of small diameter holes arranged on the left side of the left and right center lines D2. The through holes 48a and 48b are arranged radially outside the projected position 57d of the catalyst unit 57 shown by the dotted line, and the exhaust gas passing through the catalyst unit 57 is linearly arranged from the second expansion chamber 62 in the axial direction. Exhaust gas that has flowed out in the axial direction through the catalyst unit 57 instead of being discharged once collides with the upper surface 46a and flows into the third expansion chamber 63 from the through holes 48a and 48b while bending the flow path. I did. That is, the aperture ratio (the ratio of the total area of the holes per area) at the position where it does not overlap with the catalyst unit 57 in the second direction is secured, and the aperture ratio at the position where it overlaps with the catalyst unit 57 (the region indicated by the dotted line 57d). Was set to zero. By disturbing the flow path of the exhaust gas flow passing through the catalyst unit 57 in the second expansion chamber 62 in this way, the labyrinth effect can be obtained, and the afterfire generated in the third expansion chamber 63 is the first. (Ii) It was possible to make it difficult to transmit to the expansion chamber 62 side.

A large number of through holes 48a and 48b are arranged on the front side of the projected position 57d of the catalyst unit 57 shown by the dotted line, that is, in front of the virtual line D1 in the left-right direction passing through the central axis of the catalyst to increase the aperture ratio on the front side. Then, the number of through holes 48a and 48b arranged on the rear side of the virtual line D1 was reduced to reduce the aperture ratio on the rear side. This is because the flow of the exhaust gas in the first expansion chamber 61 immediately before flowing into the catalyst unit 57 is from the rear to the front, so after passing through the catalyst unit 57, the front side as much as possible (the front side of the virtual line D1). This is because if a large amount of exhaust gas is allowed to flow through the catalyst unit 57, the bias of the passage portion of the exhaust gas EX3 in the catalyst unit 57 can be reduced. It should be noted that the through holes 48a and 48b may be arranged only on the front side of the virtual line D1, but where and how the through holes 48a and 48b are arranged and what the hole diameters of the through holes 48a and 48b are. The number of holes and the total number of through holes 48a and 48b may be optimized in consideration of the output characteristics of the engine and the like. In addition, the aperture ratio at the position where it overlaps with the catalyst unit 57 in the second direction is slightly secured, and the aperture ratio at the position where it does not overlap (the ratio of the total area of the through holes 48a and 48b per area) is the catalyst. It may be set to be larger than the aperture ratio at the position where it overlaps with the unit 57.

The positions of the through holes 48a and 48b in the left-right direction were arranged symmetrically with respect to the virtual line D2 in the front-rear direction. This is because the center position of the inflow port 33a (see FIG. 6) to the muffler 30 in the left-right direction is on the virtual line D2, and the positions of the catalyst unit 57 and the inflow port 33a in the left-right direction coincide with each other. When the position of the catalyst unit 57 is offset to the right or left side with respect to the position of the inflow port 33a in the left-right direction, the arrangement of the through holes 48a and 48b is asymmetrical in the left-right direction, and the virtual line D2 The total number of holes on the right side or the opening ratio may be different from the total number of holes on the left side or the opening ratio.

The arrangement of the through holes 48a and 48b also affects the position of the exhaust gas discharge port 38 (see FIG. 6) of the second expansion chamber 62. When viewed from above as shown in FIG. 10, the position of the discharge port 38 is arranged on the rear side of the virtual line D1. Therefore, the reason for providing the second partition plate 45 is to make the through holes 48a and 48b in the front-rear direction in order to obtain an effect of increasing the distance from the catalyst unit 57 to the discharge port 38, that is, a large labyrinth effect. Therefore, it is preferable to increase the number on the front side of the virtual line D1. In this way, the opening ratio per unit area of the second partition plate 45 at the position where it does not overlap with the catalyst unit in the second direction is larger than the opening ratio per unit area at the position where it overlaps with the catalyst unit 57. If this is done, the output characteristics of the engine can be improved. In this embodiment, the hole diameters of the plurality of through holes 48a and 48b are made uniform, but the aperture ratio is changed by changing the hole diameter according to the distance from the position where the catalyst unit 57 overlaps in the second direction. The uneven distribution of the flow of the exhaust gas EX5 may be adjusted.

As described above, the muffler 30 of the present embodiment is provided with the second partition plate 45, so that the catalytic action of the exhaust gas EX4 that has passed through the catalyst unit 57 can be promoted to prevent afterfire, and the catalyst unit 57 can be prevented. Since the uneven distribution of the passing exhaust gas EX3 is reduced so that the exhaust gas EX3 passes uniformly through the honeycomb structure 57c portion in the catalyst unit 57, the chemical reaction by the catalyst coat layer can be efficiently performed. Furthermore, since the exhaust gas EX3 can be configured to pass through each part of the honeycomb-shaped flow path in the catalyst unit 57 as evenly as possible, it is possible to prevent partial deterioration of the catalyst unit 57 and extend the life of the catalyst unit 57. I was able to plan.

FIG. 11 is a top view of the muffler 30. Of the plurality of raised portions provided on the exhaust gas regulation member 50, two small raised portions 53 and 54 are provided on the inner side closer to the center side when viewed in the arrangement direction (left-right direction). Two large ridges 52, 55 are provided on the outside in the alignment direction. The width W1 and height of the inner raised portions 53 and 54 are sufficiently smaller than the width W2 and height of the outer raised portions 52 and 55. Therefore, the opening area of the exhaust passage by the inner raised portions 53 and 54 is smaller than the opening area of the exhaust passage by the outer raised portions 52 and 55. In addition to providing a difference in size between the inner raised portions 53 and 54 and the outer raised portions 52 and 55 in this way, the exhaust directions are also made different.

The exhaust directions of the inner raised portions 53 and 54 are arranged so as to slightly expand in the left-right direction, and the angle formed by the center line in each exhaust direction is an angle α ₁ in the top view as shown in FIG. On the other hand, the angle formed by the center lines of the outer raised portions 52 and 55 in the exhaust direction is an angle α _{2 when} viewed from above as shown in FIG. Here, α ₂ has a sufficiently larger angle than α ₁ , and in this embodiment, α ₂ is 40 ° and α ₁ is 10 °. By arranging as described above, the raised portions 52 to 55 are arranged in a fan shape, and the exhaust gas discharged from the openings of the exhaust passage groups is diffused in the left-right direction. Since the angle α ₂ formed by the second exhaust passage having a large opening area of the exhaust passage is set to be larger than the angle α ₁ formed by the first exhaust passage, it becomes more difficult for the exhaust gas flows to mix with each other, and each exhaust gas. Since the gas flow is mixed with the outside air, the exhaust gas temperature can be quickly reduced. Further, the flow rate of the exhaust gas discharged is reduced due to the large pressure loss of the exhaust flow from the inner raised portions 53 and 54 (the flow path resistance is large) due to the difference in the opening area, and the outer raised portion 52, Since the pressure loss of the exhaust flow from 55 is small (the flow path resistance is small), the flow rate increases. Such an exhaust gas diffusion state is an effective configuration for an engine work machine in which the size of the muffler 30 is restricted due to the installation space and it is difficult to increase the size of the exhaust gas regulation member 50. That is, even a small exhaust gas regulation member 50 can discharge the exhaust gas while effectively diffusing it in a plurality of directions. Further, since the plurality of raised portions 52 to 55 can be easily formed by pressing one metal plate 51, the increase in manufacturing cost is small. Furthermore, by simply preparing a plurality of exhaust gas regulation members 50 having different shapes, it is possible to realize a muffler compatible with engine work machines having various engine covers and muffler covers, so that the body part of the muffler should be made into a common part. Can be done.

FIG. 12 is a top view of the muffler 30 and shows a state before the exhaust gas regulation member 50 is attached. As described with reference to FIG. 6, the upper surface 36a on the upper side of the front housing 35 to which the exhaust gas regulation member 50 is attached has an opening hole for discharging exhaust gas from the second expansion chamber 62 (see FIG. 7), that is, An exhaust port 38 is provided. The rear edge of the discharge port 38 is formed in a straight line in the left-right direction, and the front edge has a shape close to a fan-shaped outer edge shape corresponding to the raised portions 52 to 55 arranged in a fan shape. The front edge of the discharge port 38 is formed so that the central portion 38b is linearly formed in the left-right direction, and the side portions 38a and 38c thereof are outer edges that recede rearward as they go outward from the left-right center. Further, the front edge of the discharge port 38 is defined by the trailing edge portions of the bent portions 39a to 39c recessed inward from the upper surface 36a.

The bent portion 39b arranged at the center of the left and right is a flat portion having a substantially rectangular flat surface in which the front edge 39e and the trailing edge (the front edge 38b of the discharge port 38) extend in the left-right direction, and is below the front edge 39e. It is bent toward (inside the muffler 30). The bent portions 39a and 39c are surfaces connected to both sides of the bent portion 39b, and are formed on a substantially rectangular slope in a top view. The bent portions 39a to 39b are arranged so that their long side directions are substantially orthogonal to the exhaust direction. The front edges 39d and 39f of the bent portions 39a and 39c are positioned so as to recede rearward as they go outward. The receding angles of the left and right bent portions 39a and 39c with respect to the central bent portion 39b are planes along the exhaust direction from the raised portions 52 and 55. The bent portion 39a, the vertical line of the left-right center line of 39c is arranged to open at an angle alpha ₃ as shown in FIG. Here, the angle α ₃ is formed in an inclined direction so as to correspond to the angle α ₂ (40 °) formed by the exhaust direction of the outer exhaust passage, and is set to 35 °, which is slightly smaller than the angle α ₂ here. ..

As described above, according to the present embodiment, the second partition plate 45 acting as a shielding plate is provided inside the muffler 30, and the exhaust gas flow path from the catalyst unit 57 to the discharge port 38 is labyrinthed. By adjusting the flow path through the through holes 48a and 48b, the entire catalyst can be reacted evenly. Further, by providing a large number of small-diameter through holes 48a and 48b instead of notches in the second partition plate 45, flames are suppressed from being ejected from the exhaust port, and the flow velocity of the exhaust gas is suppressed to reduce noise. It can be reduced.

Although the present invention has been described above based on the examples, the present invention is not limited to the above-mentioned examples, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the muffler mounted on the 2-cycle engine has been described, but the type of the engine is not limited to the 2-cycle engine and may be a 4-cycle engine. Further, the type of working machine is arbitrary, and it can be widely applied not only to chainsaws but also to engines for operating working equipment such as cutters, blowers, lawnmowers, blowers, lighting equipment, audio equipment, and power generation equipment.

1 ... Chain saw, 2 ... Main housing, 3 ... Engine cover, 4 ... Rear handle, 5 ... Front handle, 6 ... Handle guard, 7a ... Throttle lever, 7b ... Lock lever, 8 ... Fan cover, 8a ... Wind window, 9 ... Side cover, 10 ... engine, 11 ... cylinder, 11a ... exhaust port, 11b ... intake port, 12 ... piston, 13 ... conrod, 14 ... crank case, 17 ... guide bar, 20 ... spark plug, 21 ... vaporizer, 23 ... Spike, 24 ... Muffler Gasket, 25 ... Fuel Tank, 25a ... Fuel Cap, 26 ... Filter Element, 27 ... Starter Handle, 28 ... Air Cleaner Cover, 29 ... Oil Tank, 29a ... Oil Cap, 30 ... Muffler, 31 ... Rear Housing, 31b ... caulking part, 32a ... bottom surface, 32b ... rear side surface, 32c ... right side surface, 32d ... left side surface, 33a ... inflow port, 33b, 33c ... through hole, 34 ... mounting plate, 34a ... opening, 34b, 34c ... through hole, 35 ... front housing, 36a ... top surface, 36b ... front surface, 36c ... right side surface, 36d ... left side surface, 36e, 36f ... nut fixing hole, 37a, 37b ... through hole, 38 ... discharge port, 38a, 38c ... Both sides (front edge), 38b ... Central part (front edge), 39a-39c ... Bent part (recessed part), 39d, 39e, 39f ... Front edge, 40 ... First partition plate, 41a ... Bottom surface , 41b ... rear surface, 41c ... right side surface, 41d ... left side surface, 41e, 41f ... stepped portion, 42, 42a to 42d ... outer edge portion, 43 ... through holes 44a, 44b ... through holes, 45 ... second partition plate, 46a. ... upper surface, 46b ... front surface, 46c ... right side surface, 46d ... left side surface, 47a, 47e ... outer edge flat portion, 47b to 47d, 47f, 47g ... bent portion, 48a, 48b ... through hole, 49a to 49c ... through hole, 50 ... Exhaust gas regulating member, 51 ... Metal plate, 51a, 51b ... Mounting surface, 51c ... Cutout part, 52-55 ... Raised part, ... 52a-55a ... Notch, 56 ... Spark arrester 56a ... Through hole, 57 ... Catalyst unit, 57a ... inlet side opening, 57b ... outlet side opening, 57c ... honeycomb structure, 57d ... (catalyst) projection position, 58 ... catalyst cover, 58a ... through hole, 59a ... screw, 59b ... nut, 61 ... First expansion chamber, 62 ... Second expansion chamber, 63 ... Third expansion chamber, 64, 65 ... Sleeve, 64a, 65a ... Front end side opening surface, 64b, 65b ... Flange portion, 64c, 65c ... Rear end side closing surface , 68 ... Hexagonal screw, 70 ... Cover, 71a ... Front wall, 71b ... Upper part 71c, 71d ... Covering part, 72 ... Screw seat, 72a ... Through hole, 74 ... Screw, 75 ... Nut, 76 ... Mounting member, 76a, 76b ... Through hole, EX1 to EX7, EX7A, EX7B ... Exhaust gas Flow, a1, a2, a3 ... Exhaust passage angle

Claims (15)

Before constitute a housing and a rear housing and a box-shaped outer shell made of, the front housing is provided an outlet of the exhaust gas, an inlet for the exhaust gas to the rear housing going out through provided, the rear housing of the engine A muffler that is fixed to the cylinder
A first partition plate that is interposed between the front housing and the rear housing and divides the inside of the outer shell into a first expansion chamber and a second expansion chamber.
A cylindrical catalyst unit passing so as to penetrate the front Symbol first partition plate of the exhaust gas,
A second partition arranged in the path from the catalyst unit to the discharge port , including a first surface extending in a direction intersecting the axial direction of the catalyst unit and partially overlapping the catalyst unit in the axial direction. With a board,
The second partition plate is formed with a plurality of openings on the one surface so that the opening ratio at a position not overlapping with the catalyst unit in the axial direction is larger than the opening ratio at a position overlapping with the catalyst unit. A muffler characterized by that. The first partition plate has a first recess, and the second partition plate is formed with a second recess that is recessed in the opposite direction to the first recess, and the first recess and the second recess are formed. The muffler according to claim 1, wherein an inner shell that defines a third expansion chamber is formed inside the outer shell by combining the two. The first partition plate has a through hole in the bottom surface of the first recess for allowing and fixing the catalyst unit.
The second partition plate has the plurality of openings formed on the upper surface of the second recess.
The muffler according to claim 2, wherein the second partition plate is fixed to the first partition plate. The joint surface between the front housing and the rear housing is diagonally arranged so as to pass through the corners of the box-shaped outer shell.
The front housing has two sides, an upper surface and a front surface, and a substantially triangular shape in contact with them.
The rear housing has two sides, a bottom surface, a rear surface, and a substantially triangular shape in contact with them.
The first partition plate arranged on the joint surface is a bottom surface of the third expansion chamber, and a bottom plate arranged in parallel with the bottom surface of the rear housing is formed.
The muffler according to claim 3, wherein the second partition plate is formed with an upper surface facing the upper surface of the front housing. The discharge port is formed on the upper surface of the front housing and on the side close to the cylinder.
Claims 2 to 4 are characterized in that the plurality of openings formed in the second partition plate are formed by a large number of small-diameter through holes and are arranged more on the anti-cylinder side than the central axis of the catalyst unit. The muffler described in any one of the above. The muffler according to any one of claims 2 to 5, wherein the second partition plate is fixed to the first partition plate in a non-contact state between the front housing and the rear housing. The claim is characterized in that the distance d ₂ between the inlet-side opening surface of the catalyst unit and the bottom surface of the rear housing is smaller than the distance d ₁ between the inflow port and the third expansion chamber. The muffler according to any one of Items 2 to 6. Any one of claims 2 to 7, wherein the distance d ₂ between the inlet-side opening surface of the catalyst unit and the bottom surface of the rear housing is smaller than the opening height H ₁ of the exhaust port of the cylinder. The muffler described in. Distance d ₃ between the outlet opening surface and the upper surface of the second partition plate of the catalyst unit, any one of claims 2 to 8, characterized in that it is smaller than the axial length L ₁ of the catalyst unit The muffler described in item 1. The catalyst unit has a cylindrical portion and a honeycomb structure portion that is arranged inside the cylindrical portion and on which a catalyst coat layer containing a catalyst component is formed.
The muffler according to any one of claims 2 to 9, wherein a metal cap portion having a large number of holes is fixed to the outlet side opening of the cylindrical portion. The cap portion is a curved plate-shaped member arranged so as to be separated from the opening on the third expansion chamber side by a predetermined distance, and a large number of through holes are formed in the plate-shaped member. The muffler according to claim 10. The muffler according to claim 10 or 11, wherein in the cap portion, the axial direction of the large number of through holes is widened in a direction of increasing diameter. The inflow port is arranged on the rear side of the catalyst unit in the front-rear direction orthogonal to the axial direction, and exhaust gas is allowed to flow into the catalyst unit from the rear side.
The plurality of openings are arranged including both sides of the catalyst unit in the axial direction and the left-right direction orthogonal to the front-rear direction.
The plurality of openings are characterized in that the opening ratio at a position deviated from the catalyst unit in the left-right direction in the axial direction is larger than the opening ratio at a position overlapping the catalyst unit. The muffler according to any one of claims 1 to 12. Engine working machine having an engine fitted with the muffler according to the cylinder, and a tip tool driving than the driving force of the engine to any one of claims 1 1 3. A muffler in which the first to third expansion chambers are partitioned by arranging the first partition plate and the second partition plate on the dividing surfaces of the front housing and the rear housing, and the rear housing is fixed to the cylinder of the engine. ,
The expansion chamber is arranged so that the inflow direction of the exhaust gas from the first to the third expansion chamber is from the bottom to the top toward the axial direction of the cylinder of the engine.
A columnar catalyst is provided in the passage from the first expansion chamber to the third expansion chamber.
A muffler characterized in that the catalyst is offset so as to be below the exhaust port.

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