JP5621975B2 - Muffler and engine working machine equipped with the muffler - Google Patents

Description

  The present invention relates to an improvement of a muffler of a small engine used as a power unit for various hand-held small working machines such as a brush cutter and a chain saw.

  In recent years, in order to consider the global environment, cleaner exhaust gas has been promoted for power devices with an engine. Two-cycle engines are widely used in portable engine work machines that require small size, light weight, and high output, but it is more difficult to clean exhaust gas than a four-cycle engine, and the catalyst in the muffler is difficult. The exhaust gas is cleaned by reburning unburnt gas contained in the exhaust gas from the cylinder with a catalyst. In Patent Document 1, a catalyst is arranged in a muffler for the purpose of reducing HC, CO, etc. contained in exhaust gas, and unburned gas in exhaust gas is brought into contact with the catalyst and recombusted by an oxidation reaction. Thus, a technique for purifying exhaust gas is disclosed.

  The muffler of a small engine is intended to cause the unburned gas in the exhaust gas to come into contact with the catalyst and cause recombustion due to the oxidation reaction. Therefore, both muffler structures are introduced from the exhaust port of the cylinder. The exhaust gas is brought into contact with the catalyst in a flow path that leads away from a position close to the engine in the muffler, and is then discharged to the outside. As the exhaust gas comes into contact with the catalyst, the catalyst is heated, and as a result, the temperature of the exhaust gas on the downstream side that has passed through the catalyst rises higher than the temperature of the exhaust gas immediately after being introduced from the exhaust port of the cylinder. It will be.

  Thus, since the exhaust gas after contacting the catalyst has a temperature higher than that of the exhaust gas immediately after being introduced from the exhaust port of the cylinder, the exhaust gas flow path in the muffler is close to the engine in the muffler. If it is set in a direction that leads to a position far away from the exhaust gas, the exhaust gas that has been heated in contact with the catalyst flows toward the outside of the muffler, and part of the outer wall of the muffler is partially overheated. The temperature of the cover that covers the cover may rise so that it partially exceeds the regulation value, or if the cover is made of synthetic resin, the cover may melt if the gap between the muffler and the cover is not increased. It was.

  Further, when the exhaust outlet of the muffler is provided at a position close to the catalyst provided in the muffler, the exhaust temperature discharged from the exhaust outlet becomes very high. Therefore, measures such as reducing the influence of heat on the outside by covering the entire outer side of the muffler with a muffler cover as in Patent Document 1.

  However, in a portable engine working machine such as a chainsaw, it may be difficult to cover the entire outside of the muffler with a muffler cover due to restrictions on the overall size. As a countermeasure, a commercially available engine working machine uses a muffler structure as shown in FIG.

  FIG. 7 is a longitudinal sectional view of a known muffler 101, in which an engine cylinder (not shown) is located on the right side in the figure and takes a longitudinal section passing through the exhaust gas discharge direction. The outer portion of the muffler 101 includes a first housing 110 located on the engine side and a second housing 120 located on the side away from the engine. By combining the first housing 110 and the second housing 120, the muffler 101 Is formed.

  A partition plate 130 for holding the catalyst 137 is provided at a joint portion where the first housing 110 and the second housing 120 are joined. The partition plate 130 serves as a holding member for fixing the cylindrical catalyst 137 and also functions to divide the internal space of the muffler 101 into two spaces, a first chamber 151 and a second chamber 152. The catalyst 137 has a plurality of lattice-shaped or honeycomb-shaped cells formed inside a cylindrical outer pipe, and is fixed so that the outer pipe penetrates through the holes of the partition plate 130.

  The catalyst cover 140 is a cover for preventing the exhaust gas that has passed the catalyst 137 from becoming high temperature from directly hitting the second housing 120 that is the outline of the muffler 101 and lengthens the exhaust flow path in the muffler. . The catalyst cover 140 is formed in a substantially S shape with a cross-sectional shape at the cross-sectional position as shown in FIG. 2, and forms a third chamber 153 on the outlet side of the catalyst 137. As an outlet of the third chamber 153, a hole through which exhaust gas passes is formed at a circle 3 of the catalyst cover 140. In the conventional muffler 101, the exhaust gas flowing into the catalyst 137 at the circle 1 passes through the catalyst 137 and then hits the vertical surface 140a of the catalyst cover 140 at the position indicated by the circle 2 so that the flow path is directed downward. It is bent, passes through a hole (not shown) on the horizontal surface 140b of the circle 3, and moves to the space on the second chamber 152 side.

  Below the vertical surface 140a of the catalyst cover 140, a horizontal surface 140b in which a hole is formed, a vertical surface 140c joined to the partition plate 130, and a horizontal surface 140d protruding from the vertical surface to the second chamber 152 side are formed. . The exhaust gas that has passed through the hole of the catalyst cover 140 near the circle 3 hits the horizontal surface 140d near the circle 4, and the direction thereof is bent by about 180 degrees. Thereafter, the exhaust gas is guided by the inner wall of the second housing 120 in the vicinity of the circle 5 and flows to the outside from the opening 127 in the vicinity of the circle 6. In the conventional muffler 101, the inner wall of the second housing 120 near the circle 5 to the circle 6 becomes very hot. As a countermeasure, the heat-resistant cover 145 is fixed to the outer peripheral surface of the second housing 120 with screws 149. .

JP 2000-170518 A

  In the muffler 101 shown in FIG. 7, the exhaust gas after passing through the catalyst 137 is guided to the second chamber 152 through a plurality of holes provided in the catalyst cover 140, so that the high-temperature exhaust gas after passing through the catalyst is outside ( It was guided along the second housing 120) and released from the opening 127 to the atmosphere. Therefore, heat deterioration and red heat of the outer part of the muffler 101 are likely to occur. As a countermeasure, it is necessary to increase the distance between the catalyst cover 140 and the outer portion of the muffler, and the muffler 101 must be enlarged. Further, in order to make the red heat of the outer portion of the muffler 101 invisible to the operator, it is necessary to add a blindfold such as a heat-resistant cover 145.

  This invention is made | formed in view of the said background, The objective is to provide the muffler which can prevent the overheating of the specific location of an outer wall surface, and an engine working machine provided with the same.

  Another object of the present invention is to provide a muffler capable of discharging exhaust gas after sufficiently reducing the temperature of exhaust gas heated by contact with a catalyst, and an engine working machine including the muffler.

  Still another object of the present invention is to provide a muffler suitable for a small engine having excellent assemblability and high durability, and an engine working machine including the muffler.

  The characteristics of representative ones of the inventions disclosed in the present application will be described as follows.

According to one aspect of the present invention, in an muffler of an engine working machine, an inflow port connected to an exhaust port of an engine, a muffler housing having an exhaust port for discharging an inflowing exhaust gas, and an inflow port of the muffler housing And a partition plate that partitions the inside of the muffler housing into a first chamber into which exhaust gas flows from an exhaust port and a second chamber from which exhaust gas is released to the atmosphere and holds the catalyst. When the direction of the exhaust gas after passing through the catalyst from the first chamber be one to convert, has catalytic cover forming a third chamber with a partition plate in the second chamber and the partition plates, the partition plate A depression was provided in the direction of the room. The flow path switching portion is, for example, a convex portion that protrudes to the first chamber provided on the partition plate (a concave shape when viewed from the second chamber side). The exhaust gas that has passed through the catalyst is redirected by the catalyst cover, and the exhaust gas that has been redirected by the flow path switching unit is guided to the second chamber. inflow exhaust gas is discharged to the outside from the discharge port. The muffler housing is configured by matching the opening surfaces of the first housing and the second housing having an opening surface, and the partition plate is fixed so as to be sandwiched between the opening surfaces of the first housing and the second housing. .

According to another feature of the invention, the first housing and the second housing are joined at a split surface substantially perpendicular to the direction of exhaust from the engine exhaust port. In addition, the partition plate is formed with a hole for penetrating and holding the catalyst and a hollow shape that becomes a flow path changing portion .

According to still another feature of the present invention, the catalyst cover is shaped so as to cover a part of the opening of the flow path switching portion and the entire outlet side of the catalyst, and the outer edge of the catalyst cover overlaps the opening. To be fixed to the partition plate. The first and second housings are manufactured, for example, by cold-working steel plate pressing, and the partition plate and the catalyst cover are manufactured, for example, by stainless steel plate pressing.

According to the first aspect of the present invention, the partition plate is provided with the flow path changing portion that is recessed in the direction of the first chamber , and the exhaust gas whose direction is changed by the catalyst cover is guided to the flow path changing portion. Since the exhaust gas that has been redirected to the second chamber is exhausted to the outside through the exhaust port, the temperature of the exhaust gas after passing through the catalyst can be reduced, and when the exhaust gas is released from the muffler to the atmosphere In addition, the risk of ignition of combustible materials such as wood chips can be eliminated. Further, the catalyst cover reverses the traveling direction of the exhaust gas after passing through the catalyst and guides the exhaust gas to the flow path switching portion, and the flow path switching portion reverses the flow of the reversed exhaust gas again, The temperature of the exhaust gas can be effectively reduced by using the region in contact with the low temperature portion for reversing the traveling direction of the exhaust gas.

  According to the invention of claim 2, the muffler housing is configured by matching the opening surfaces of the first housing and the second housing having the opening surfaces, and the partition plate is formed on the opening surfaces of the first housing and the second housing. Since it is fixed so as to be sandwiched, it is possible to realize a muffler with good assemblability and reduced manufacturing cost.

  According to the invention of claim 3, since the first housing and the second housing are joined at a split surface substantially perpendicular to the exhaust direction from the exhaust port of the engine, an inflow port connected to the exhaust port; The exhaust port for discharging the inflowing exhaust gas can be configured separately in the first housing or the second housing, and the first chamber and the second chamber can be easily realized.

  According to the invention of claim 4, since the partition plate is formed with a hole for penetrating and holding the catalyst and a hollow shape that becomes the flow path changing portion, it can be manufactured at a low cost by pressing. .

According to the invention of claim 5 , the catalyst cover is shaped to cover a part of the opening of the flow path changing portion and the entire outlet side of the catalyst, and the outer edge of the catalyst cover is in a position overlapping the opening. Since the exhaust gas immediately after passing through the catalyst is led from the third chamber to the second chamber through the flow path switching portion, the catalyst cover and the partition plate form a third chamber. The exhaust gas, which is hot immediately after passing, does not easily contact the outer part of the muffler housing, can prevent deterioration of the outer part of the muffler, and can effectively prevent red heat due to the high temperature of the outer part, It can be a highly durable muffler that does not cause anxiety to workers.

According to the invention of claim 6 , since the first and second housings are manufactured by pressing a cold-rolled steel plate, and the partition plate and the catalyst cover are manufactured by pressing a stainless steel plate, the temperature is particularly high. Thus, the partition plate and the catalyst cover can be manufactured with a high heat resistance member at low cost, and a highly durable muffler can be realized.

According to the seventh aspect of the present invention, since the muffler of the present invention is fixed to the exhaust port of the engine in the engine working machine that drives the predetermined working means by the engine, red heat due to the high temperature of the muffler housing can be effectively prevented and It is possible to realize an engine work machine that can be used with the heart.

  The above and other objects and novel features of the present invention will become apparent from the following description and drawings.

It is a perspective view which shows the external appearance of the muffler 1 which concerns on the Example of this invention. It is a perspective view which shows an example (chain saw 81) of the engine working machine to which the muffler 1 which concerns on the Example of this invention is applied. FIG. 3 is a longitudinal sectional view of the engine 61 of FIG. 2. It is a disassembled perspective view which shows the assembly structure of the muffler 1 which concerns on the Example of this invention. It is sectional drawing for demonstrating the flow of the exhaust_gas | exhaustion of the muffler 1 which concerns on the Example of this invention. It is the figure which looked at the partition plate 30 and the catalyst cover 40 from the AA cross section of FIG. It is sectional drawing which shows the shape of the muffler 101 which concerns on a prior art example.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view showing an appearance of a muffler 1 according to an embodiment of the present invention. The muffler 1 is directly connected to an exhaust port of a cylinder of a two-cycle engine (not shown) with a bolt or the like, for example, has a predetermined volume, and has one exhaust discharge port 47. The outer casing of the muffler 1 is configured by using two substantially rectangular housings whose one surface is an opening surface, and joining these opening surfaces. The first housing 10 which is one rectangular parallelepiped is disposed on the engine side (not shown). The second housing 20, which is another substantially rectangular parallelepiped, is disposed on the side opposite to the engine, and an exhaust discharge port 47 is formed on the second housing 20 side. Although the outer shape of the first housing 10 is a substantially rectangular parallelepiped, the second housing 20 is not strictly a substantially rectangular parallelepiped, but has a shape in which a part of the rectangular parallelepiped is cut obliquely.

  A plurality of ribs 16 are formed in the bent portion of the first housing 10 by press working or the like for the purpose of reinforcing the surface. One surface of the second housing 20 is exposed to the outside, and an inclined surface 20a for attaching the guide cover 45 in which the exhaust discharge port 47 is formed is formed. A plurality of ribs 26 are formed on the flat surface portion 20b of the second housing 20 by pressing or the like for the purpose of reinforcing the surface.

  The guide cover 45 is a rectifying member that guides exhaust gas in a predetermined direction (exhaust discharge port 47 side) by covering an opening, which will be described later, formed on the inclined surface 20a of the second housing 20. The guide cover 45 prevents exhaust gas from being discharged directly from the inside of the muffler 1 to the outside through an opening that will be described later. A spark arrester (not shown) made of a metal mesh is attached between the guide cover 45 and the second housing 20. The spark arrester is for suppressing sparks from flying from the muffler 1 and is fixed by inserting bolts into bolt holes (described later) and bolt holes 48 formed in the second housing 20 (see FIG. 1 does not show bolts).

  The flat portion 20b of the second housing 20 is provided with bolt insertion holes 24 and 25 for penetrating bolts for attaching the muffler 1 to the engine, and the tip ends of two bolts (not shown) are near the exhaust port of the engine. And screwed into the screw hole formed in. Further, the outer periphery of the muffler 1 is provided with two screw holes 9 (only one is shown in FIG. 1), and screw holes formed in an engine crankcase (not shown) through screws or bolts (not shown). Fixed.

  FIG. 2 is a perspective view showing a state in which the muffler 1 of the present invention is attached to a hand-held small working machine. In FIG. 2, the example used for the chainsaw 81 as an example of a hand-held type small working machine is shown. The chain saw 81 is equipped with a small engine 61 such as a two-cycle engine, and a guide bar around which a saw chain is wound protrudes in front of the main body. In this figure, the saw chain and the guide bar are removed. It is shown.

  The engine 61 is covered with a housing 82 made of a synthetic resin such as plastic, and is guarded so that an operator does not touch the high heat portion of the engine 61. Further, a main handle 83 is formed on the rear side of the housing 82 for the operator to hold with the right hand, and a front handle 86 is provided on the front side of the housing 82 for the operator to hold with the left hand. A safety trigger 90 is provided near the upper portion of the main handle 83, and a throttle lever 91 is provided on the lower side. A hand guard 85 is provided on the front side of the front handle 86. The hand guard 85 serves to protect a worker's hand from being hit by a branch or a cut object.

  A recoil type starter (not shown) for starting the engine is accommodated in the housing 82, and a starter handle 87 is attached. A driving force transmission mechanism (not shown) to the saw chain is attached to the right side of the crankcase 62 of the engine 61, and a gear cover 88 is provided to cover it. The gear cover 88 is provided with two bolts and a nut 92 for fixing a guide bar (not shown). A chain catcher 89 is provided in front of the gear cover 88 and in the vicinity of the housing 82 and the guide bar attachment portion.

  In the chainsaw 81 shown in FIG. 2, the muffler 1 is provided on the front side of the housing 82. This attachment position is located on the front side of the hand guard 85 and a saw chain (not shown) is located on the lower side of the muffler 1, so that it is difficult for the operator to visually check during the work. There is almost no fear of touching. Furthermore, exhaust gas from the muffler 1 is discharged diagonally downward to the right as indicated by an arrow 59, so that it is possible to prevent the exhaust gas from hitting the worker and to directly hit the tree or branch to be cut. Can be prevented. The muffler 1 is directly fixed to the cylinder of the engine 61 by two bolts inserted into the bolt insertion holes 24 and 25 (the bolts are not visible from the position in FIG. 2).

  FIG. 3 is a longitudinal sectional view of the engine 61. The engine 61 is a two-cycle engine, and a piston 64 is disposed in a cylinder 63 attached to an upper part of an engine case 62 so as to be reciprocally movable. The piston 64 is connected to a crankshaft 66 by a connecting rod 65. The crankshaft 66 is rotatably held by the engine case 62 via a bearing mechanism (not shown). A cooling fan (not shown) is attached to one end of the crankshaft 66, and a forced cooling system is employed in which the cylinder 63 is cooled by wind generated by the rotation of the fan. The cylinder 63 is manufactured, for example, by integrally molding an aluminum alloy, and a plurality of heat radiation fins are provided on the outer peripheral side of the head portion and the cylinder portion, and a spark plug 67 is attached to the upper portion of the cylinder 63. An exhaust port (exhaust port) 68 is formed at a portion of the cylinder 63 where the opening is opened and closed by the piston 64, and the muffler 1 is directly attached to the outer opening of the exhaust port 68. A scavenging port (not shown) is formed in the cylinder 63, and a passage from the crank chamber 69 to the cylinder 63 is formed by a scavenging passage (not shown). The cylinder 63 is further provided with an intake port 70, and a carburetor 72 is attached to the intake port 70 via an intake pipe 71. An air cleaner 73 is connected to the vaporizer 72. Since the operating principle of the engine 61 is the same as that of a known two-cycle engine, a detailed description thereof is omitted here.

  Next, the detailed structure of the muffler 1 will be described with reference to FIG. FIG. 4 is an exploded perspective view showing the assembly structure of the muffler 1 according to the embodiment of the present invention. The muffler 1 is configured to divide a closed space defined by combining the first housing 10 and the second housing 20 into two spaces (a first chamber and a second chamber) by a partition plate 30. The first housing 10 and the second housing 20 may be manufactured by press working using, for example, SPCC (cold rolled steel plate), and heat-resistant coating may be applied to the outer surface.

  The first housing 10 is connected to an exhaust port of an engine (not shown) and has an opening 17 serving as an exhaust gas inflow port. Two bolt insertion pipes 14 and 15 for passing bolts (not shown) are formed on both sides of the first housing 10. Is arranged so as to extend into the inner space of the muffler 1. The ends of the two bolt insertion tubes 14 and 15 are connected to the bolt insertion holes 24 and 25 of the second housing 20. On the outer peripheral edge of the opening surface of the first housing 10, a folding rib 11 for joining with the second housing 20 is formed.

  The second housing 20 is provided on a side away from an engine (not shown), and an opening 27 serving as an outlet (exhaust port) from the muffler 1 is formed. The second housing 20 has a basic shape in which one surface of a substantially rectangular shape is an opening surface, and an inclined surface 20a is formed in a part thereof. A lip 21 for joining to the first housing 10 is formed on the outer peripheral edge of the opening surface. Two bolt insertion holes 24 and 25 are formed in the flat surface portion 20b located on the lower side of the inclined surface.

  A part of the second housing 20 is provided with three slit-shaped openings 27 for discharging exhaust gas. The opening 27 is formed by cutting a part of the metal part of the second housing 20 by a cutting and bending process using a press and bending the cut part to the outside so as to have a predetermined angle. The inner region functions as an exhaust gas guide plate. The inclination angle of the inner region is set such that the exhaust gas discharged from the inside through the opening 27 is smoothly guided to the exhaust discharge port 47 formed in the guide cover 45 attached to the inclined surface 20a. The Further, a bolt hole 28 for fixing a bolt is formed in a part of the inclined surface 20a, and a spark arrester (not shown) made of a metal mesh can be attached between the guide cover 45 and the second housing 20. The spark arrester can be fixed by inserting bolts (not shown) into the bolt holes 28 and 48.

  The partition plate 30 serves not only to divide into the internal space of the muffler 1 but also as a holding member for fixing the cylindrical catalyst 37. The catalyst 37 is fixed by being inserted into a through hole 36 formed slightly below the center of the partition plate 30. The partition plate 30 is made of a stainless steel plate, and through holes 31 and 32 for penetrating the bolt insertion tubes 14 and 15 are formed at left and right positions slightly above the center in the vertical direction. On the upper side of the through holes 31 and 32, a recess 33 for changing or reversing the direction in which the exhaust gas flows is formed. The recess 33 is formed by press working. Two through holes 34 and 35 for forming the screw holes 9 (see FIG. 1) are formed around the lower side of the partition plate 30. As described above, the partition plate 30 simply forms the recess 33 and a plurality of holes in the stainless steel plate, and thus can basically be easily manufactured by punching, punching, or the like by pressing.

  The catalyst 37 is for bringing the unburned gas in the exhaust gas into contact with the catalyst and reburning it by an oxidation reaction, and a plurality of lattice-like or honeycomb-like cells are formed inside the cylindrical outer pipe. Catalyst materials such as platinum and rhodium are coated. When the exhaust gas comes into contact with the catalyst material, the exhaust gas is heated (reburning). As a result, the temperature of the downstream exhaust gas that has passed through the catalyst is higher than that of the catalyst immediately after being introduced from the exhaust port of the cylinder. Will also rise significantly.

  The catalyst cover 40 is provided to cover the vicinity of the outlet side opening 38 of the catalyst 37, and is provided to prevent the exhaust gas whose temperature has been increased by the catalyst 37 from directly hitting the inner wall of the second housing 20. . The catalyst cover 40 defines a cylindrical space 41 having an outer diameter larger than the diameter of the cylindrical portion of the catalyst 37 and a space in which a rectangular parallelepiped space 42 is connected to the upper side thereof. The joining surface 43 is formed so that it can be joined with welding. Further, a cut-off portion 44 a for avoiding the bolt insertion tube 14 is formed on the joint surface 43. Although not shown, a cut-off portion 44b (described later) is similarly formed on the bolt insertion tube 15 side.

  The catalyst cover 40 is made of a stainless steel plate made of the same material as the partition plate 30 and is formed by press working. The catalyst cover 40 is welded to the partition plate 30, and the partition plate 30 is configured not to contact the first housing 10 and the second housing 20 after the muffler 1 is assembled. The catalyst cover 40 is preferably not in contact with the bolt insertion tubes 14 and 15. This is because the catalyst cover 40 is considered to have the highest temperature among the constituent members of the muffler 1. By arranging the catalyst cover 40 in this way, it is possible to effectively prevent a phenomenon in which the local region of the second housing 20 becomes hot and becomes red hot.

  The guide cover 45 prevents the opening 27 from being directly exposed to the outside, and guides exhaust gas discharged from the opening 27 in a predetermined direction. The guide cover 45 has a substantially hexagonal projection 46 in a side view, and an exhaust discharge port 47 is formed by cutting out a part of the side of the projection 46. The guide cover 45 is made of SPCC (cold rolled steel plate), which is the same material as the second housing 20, and the protrusion 46 and the exhaust outlet 47 are formed by pressing. The guide cover 45 is attached to the second housing 20 by welding.

  Next, how the exhaust gas discharged from the engine flows through the muffler 1 will be described with reference to FIG. FIG. 5 is a longitudinal sectional view of the muffler 1 shown in FIG. In this figure, the first housing 10 and the second housing 20 are divided by a dividing plane that is substantially perpendicular to the exhaust direction from the exhaust port of the engine. Further, the rib 11 of the first housing 10 is bent about 180 degrees so as to sandwich the outer edge of the partition plate 30 and the lip 21 of the second housing 20, and the first housing 10 and the second housing 20 are bent by this bending. At the same time as the joining, the partition plate 30 is fixed.

  In the figure, the flow of exhaust gas is indicated by a black curve 58 with an arrow. The inner space of the muffler 1 is divided into a first chamber 51 and a second chamber 52 by the partition plate 30. A third chamber 53, which is a small space, is formed between the second chamber 52 and the partition plate 30 by the catalyst cover 40. Exhaust gas discharged from the cylinder of the engine flows into the inside of the muffler 1 from the opening 17 as indicated by a black curve 58 and flows into the inside of the catalyst 37 at the circle 1 portion. The exhaust gas that has passed through the catalyst 37 flows out of the catalyst 37 at the portion of the circle 2 and is bent by about 180 degrees in the direction of the circle 3 by hitting the inner wall 40a of the catalyst cover 40 and is guided to the side wall 40b. As a result, the exhaust gas is directed in the direction opposite to the discharge direction and flows in the direction of the partition plate 30. A recess 33 that is recessed toward the engine is formed in a portion of the partition plate 30 where the exhaust gas is guided.

  The depression 33 is for bending again the flow of the exhaust gas whose direction of flow by the catalyst cover 40 is bent by about 180 degrees, and the direction of the exhaust gas is further increased at the bottom 33a of the depression 33 indicated by a circle 4. Bent approximately 180 degrees and guided by the portion of the slope 33 b of the recess 33, the exhaust gas reaches the guide cover 45 from the opening 27 as indicated by a circle 6.

  Here, there is a difference in the internal temperatures of the first chamber 51, the second chamber 52, and the third chamber 53, and the exhaust gas immediately after exiting the cylinder is about 300 degrees. The temperature of the exhaust gas (temperature around circle 2) reaches about 700 degrees. Therefore, if the exhaust gas immediately after passing through the catalyst 37 is directly applied to the second housing 20 without passing through the catalyst cover 40, the second housing 20 is exposed to a high temperature close to 700 degrees and becomes red hot. Become. Therefore, in this embodiment, the exhaust gas that has passed through the catalyst 37 is applied to the inner wall 40a of the catalyst cover 40, so that even if the catalyst cover 40 is red hot, the red hot state is not visible from the outside. Further, the catalyst cover 40 is not in contact with the second housing 20, and the amount of heat transmitted to the second housing 20 can be greatly reduced because the catalyst cover 40 is separated from the second housing 20 by a predetermined distance.

  The exhaust gas whose direction is changed at the circle 3 hits the recess 33 of the partition plate 30 in the vicinity of the circle 4. Here, the temperature of the exhaust gas from the circle 3 to the circle 4 is slightly lower than 700 degrees, but is significantly higher than the temperature inside the first chamber 51 (at most about 300 degrees). Therefore, the temperature of the exhaust gas can be lowered by using the low temperature of the first chamber 51 by applying the high temperature exhaust gas to the depression 33 that contacts the low temperature first chamber 51 when the direction of the circle 4 is changed. Further, the exhaust gas flowing into the third chamber 53 from around the circle 5 comes into contact with the guide cover 45 through the opening 27, is bent at the circle 6, and is discharged to the outside. Since the outside of the guide cover 45 is the atmosphere and the temperature is sufficiently low, the temperature of the exhaust gas that strikes the guide cover 45 in contact with the atmosphere further decreases.

  The volume relationship between the first chamber 51, the second chamber 52, and the third chamber 53 is closely related to the silencing effect that reduces the noise of the exhaust gas and the exhaust efficiency. The volume of each chamber and the shape of the flow path should be determined so that not only the temperature of the gas is lowered but also a sufficient silencing effect can be obtained.

FIG. 6 is a view of the engine side as seen from the cross section of the AA portion of FIG. In this figure, the upper end position of the catalyst cover 40 and the positional relationship in the vertical direction of the depression 33 that is a flow path changing portion formed in the partition plate 30 can be understood. That is, when viewed from the A-A cross section, the upper end 43 a of the joint surface 43 formed at the outer edge of the catalyst cover 40 is disposed so as to cover the substantially lower half of the substantially rectangular depression 33 in the vertical direction. Further, the height H ₁ of the opening flowing into the depression 33 in the lower half of the depression 33 is reversed in direction by the depression 33 and discharged to the second chamber 52 side through the upper half of the depression 33. Therefore, the height H ₃ of the opening is substantially the same. The relationship with the overall height H of the recess 33 is such that H ₁ = H ₃ , but is not necessarily limited to this ratio, and an optimal ratio may be set in consideration of exhaust resistance and the like. In addition, the size of the opening of the recess 33 is a substantially rectangular shape having a width W and a height H, but it is not always necessary to have a rectangular shape, and may be another recess shape such as a hemispherical shape. Further, the depth of the depression (distance in the exhaust direction) may be appropriately set so as not to impair the exhaust resistance of the exhaust gas as much as possible.

  According to the present embodiment, the exhaust gas flow path that is brought into contact with the catalyst inside the muffler 1 is formed as a relatively long vertical flow path that extends from the lower side to the upper side in the muffler 1. Since a flow path that guides from a distant position to a direction close to the engine is provided to reduce the temperature of the exhaust gas using the temperature difference between the first chamber 51 and the third chamber 53, the exhaust discharged into the atmosphere The temperature of the gas can be sufficiently lowered. As a result, the possibility of ignition can be eliminated even if combustibles such as wood chips are located in the vicinity of the exhaust outlet. In addition, since the exhaust gas having a high temperature immediately after passing through the catalyst does not directly contact the outer portion of the muffler 1, the muffler 1 can be prevented from being deteriorated. Further, since the outer portion does not become red hot due to high temperature, the worker can use the power unit with the engine (engine working machine) with peace of mind.

  As mentioned above, although this invention was demonstrated based on the Example, this invention is not limited to the above-mentioned Example, A various change is possible within the range which does not deviate from the meaning. For example, the muffler of the present invention can be applied not only to a two-cycle engine for a chainsaw but also to other power equipment and an engine for a work tool. Further, the muffler of the present invention is not limited to a two-cycle engine, but can be similarly applied to a four-cycle engine and other internal combustion engines.

DESCRIPTION OF SYMBOLS 1 Muffler 9 Screw hole 10 1st housing 11 Rib 14, 15 Bolt insertion pipe 16 Rib 17 Opening part 20 Second housing 20a Inclined surface 20b Flat part 21 Lip 22 Hole 24, 25 Bolt insertion hole 26 Rib 27 Opening part 28 Bolt hole 30 Partition plate 31 Through hole 33 Dimple 33a Bottom 33b Slope 34, 35 Through hole 36 Through hole 37 Catalyst 38 Outlet side opening 40 Catalyst cover 40a (Catalyst cover) inner wall 40b (Catalyst cover) side wall 41 Cylindrical space 42 Space 43 Joining Surface 43a Upper end 44a, 44b Cut-off portion 45 Guide cover 46 Projection portion 47 Exhaust discharge port 48 Bolt hole 51 First chamber 52 Second chamber 53 Third chamber 58 Black curve 61 Engine 62 Crankcase 63 Cylinder 64 Piston 65 Connecting rod 66 Crank Shaft 7 spark plug 68 exhaust port 69 crankcase 70 intake port 71 intake pipe 72 carburetor 73 air cleaner 81 chain saw 82 housing 83 main handle
85 Hand guard 86 Front handle 87 Starter handle 88 Gear cover 89 Chain catcher 90 Safety trigger 91 Throttle lever 92 Nut 101 Muffler 110 First housing 117 Opening portion 120 Second housing 127 Opening portion 130 Partition plate 137 Catalyst 140 Catalyst cover 140a Vertical surface 140b Horizontal plane 140c Vertical plane 140d Horizontal plane 145 Heat-resistant cover 149 Screw 151 First chamber 152 Second chamber 153 Third chamber

Claims (7)

An inflow port connected to the exhaust port of the engine, a muffler housing having an exhaust port for discharging the inflowing exhaust gas, and
A catalyst provided in a flow path from the inlet to the outlet of the muffler housing;
A partition plate for partitioning the inside of the muffler housing into a first chamber into which exhaust gas flows from the exhaust port and a second chamber for discharging exhaust gas to the atmosphere and holding the catalyst;
Be one to convert the direction of the exhaust gas after passing through the catalyst from the first chamber has a catalyst cover forming a third chamber with said partition plate to the partition plates and the second chamber,
The flow path conversion portion recessed in the direction of the first chamber to the partition plate provided,
The catalyst cover is fixed so as to cover a part of the opening of the flow path switching unit,
Exhaust gas that has passed through the catalyst, the catalytically cover is guided to the flow path changing part in After diverting the exhaust gas is again diverted by the flow path changing part is he guide in the second chamber, muffler exhaust gas flowing into the second chamber, characterized in that the is discharged to the outside from the discharge port. The muffler housing is configured by matching the opening surfaces of the first housing and the second housing having an opening surface,
The muffler according to claim 1, wherein the partition plate is fixed so as to be sandwiched between the opening surfaces of the first housing and the second housing.   3. The muffler according to claim 2, wherein the first housing and the second housing are joined at a split surface substantially perpendicular to a discharge direction from the exhaust port of the engine. Wherein the partition plate, the muffler according to claim 2 or 3, characterized in that a hole for holding by penetrating the catalyst, recess only to be the channel conversion unit is formed. The catalyst cover is shaped so as to cover a part of the opening of the flow path changing portion and the entire outlet side of the catalyst, and the outer edge of the catalyst cover is positioned so as to overlap the opening. The muffler according to claim 4. The first and second housings are manufactured by pressing a cold rolled steel sheet,
The muffler according to any one of claims 2 to 5 , wherein the partition plate and the catalyst cover are manufactured by pressing a stainless plate. A predetermined working means is driven by an engine,
An engine work machine, wherein the muffler according to any one of claims 1 to 6 is fixed to an exhaust port of the engine.

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