JP2013213414A - Engine work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forced air-cooling engine work machine, in which cooling performance is improved in both of forced air cooling of a muffler during operation of the engine and natural air cooling of the muffler during an engine stop.SOLUTION: A muffler storage chamber is disposed with a heat-shield plate 40 interposed between a muffler 30 and a muffler cover 6. The muffler cover 6 is provided with a cooling air inlet 37a for introducing a part of cooling air generated by a cooling fan into the muffler storage chamber to cool the muffler, and with a discharge outlet for discharging the air after cooling. The inside of the muffler storage chamber is divided into two segments to form: a forced air-cooling chamber 42 that is a space for guiding the cooling air introduced through the cooling air inlet 37a to a cooling air outlet; and a natural air-cooling chamber 43, which is provided with an outside air inlet 40a and guides outside air introduced through the outside air inlet to the discharge outlet. The outside air inlet 40a is formed at a bottom of the heat-shield plate 40; and the discharge outlet is disposed near an upper end of the muffler storage chamber and near an exhaust port 38.

Description

  The present invention mainly relates to an improvement of an engine used as a power source of an engine working machine, and more particularly to an engine working machine having an improved muffler.

  Portable engine working machines such as brush cutters, blowers, hedge trimmers, chain saws, and cutters are often used outdoors. For this reason, noise suppression is often a problem particularly in densely populated areas such as urban areas, and there is a high demand for noise reduction from users. However, since it is an engine working machine, there is a high demand for downsizing. The engine used as the power source of the engine working machine has a high-density design in which a driven device such as a tip tool, a cooling fan, and a manual starter is installed on the drive shaft (crankshaft), and many parts are adjacent to the engine. It is common that Therefore, in order to achieve both a small size and low noise, for example, Patent Document 1 proposes a device on the internal structure and the structure of the exhaust gas exhaust port in the muffler.

Japanese Patent Laid-Open No. 11-156802

  For Patent Document 1, a plurality of exhaust gas exhaust ports are provided and separated by a predetermined distance or more to reduce exhaust noise. However, in the muffler, in addition to the exhaust sound due to the high temperature and high pressure gas being instantaneously ejected from the engine to the muffler, the noise generated by the vibration of the muffler side due to the pressure pulsation caused by the ejection of the high temperature and high pressure gas is generated. Therefore, it has been difficult to obtain further reduction of exhaust noise than before. Furthermore, in order to make the engine output equal to that of the conventional engine, it is necessary to prevent an increase in the back pressure of the exhaust gas. Therefore, the opening area of the exhaust port must be secured to a certain level or more. Normally, in a muffler, the noise source of the exhaust sound is the exhaust port, so it is desirable to reduce the opening area of this exhaust port in order to reduce the exhaust noise. However, it was difficult to obtain a further exhaust noise reduction effect.

  Conventionally, this problem has been addressed by covering the entire muffler with a cover in order to increase the volume of the muffler and reduce noise leaking from the muffler. In the case where the entire muffler is covered with the cover as described above, it is important to effectively cool the muffler when the engine is operating. In recent years, due to the demand for cleaner exhaust gas, a catalyst is often installed in the muffler. However, since the temperature inside the muffler becomes higher due to the use of the catalyst, it remains in the muffler when the engine is stopped. The heat to do becomes a problem, and the device to cool effectively has become important.

  The present invention has been made in view of the above background, and an object thereof is to provide an engine working machine in which the entire muffler is covered with a cover in order to reduce noise generated from the muffler.

  Another object of the present invention is to provide an engine working machine capable of effectively cooling a muffler using a part of cooling air for forced cooling of the engine.

  Still another object of the present invention is to provide an engine working machine capable of effectively cooling a muffler by natural air cooling after the engine is stopped.

  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, a cylinder having a plurality of fins on the outer periphery and forming a combustion chamber, a cooling fan provided at one end of the drive shaft for cooling the cylinder, and a muffler attached to the exhaust port of the cylinder A muffler cover that covers the muffler to form a muffler storage chamber, and has a cooling air inlet that introduces a part of the cooling air generated by the cooling fan into the muffler storage chamber, and a discharge port that discharges the cooled air. The muffler storage chamber is divided into at least two sections, and the cooling air inlet is provided in one section of the muffler storage chamber. The muffler cover is divided into a forced air cooling chamber serving as a space for guiding the cooling air introduced from the cooling air inlet to the outlet and a natural cooling chamber provided with an outside air inlet below the muffler storage chamber. When viewed in the horizontal direction of the muffler, the forced air cooling chamber is formed on the side away from the cylinder, and the natural cooling chamber is formed on the side close to the cylinder.

  According to another aspect of the present invention, the cooling air inlet is provided below the muffler on the side opposite to the exhaust outlet, the outside air inlet is provided below the cooling air inlet, and the outlet is provided on the muffler cover. It is arranged around the exhaust port. In the vicinity of the discharge port, the forced air cooling chamber and the natural cooling chamber are connected, and preferably connected at the upper portion of the surface of the exhaust port. A heat shield plate was interposed between the muffler and the muffler cover, and the muffler storage chamber was constituted by the heat shield plate and the muffler cover. The forced air cooling chamber and the natural cooling chamber are separated at least in the lower half of the space defined by the heat shield and the muffler cover.

  According to still another feature of the present invention, a muffler is formed by forming a partition portion that protrudes in the outer circumferential direction and continues in the circumferential direction outside the housing of the muffler, and that the tip of the partition portion is in contact with the heat shield plate. The storage room was separated into a forced air cooling room and a natural cooling room. This muffler forms a housing by interposing a partition plate between the first housing and the second housing having an opening surface with a partition plate interposed therebetween, and a through hole is formed in the partition plate to form a cylinder. The first expansion chamber into which the exhaust gas from the exhaust port first flows and the second expansion chamber into which the exhaust gas that has flowed in through the through hole is discharged from the exhaust port to the atmosphere are configured. A joining surface protruding outward by caulking joining was used as a partition part. The outside air inlet is formed on the bottom surface of the heat shield, and the outlet is provided near the upper end of the muffler storage chamber. Also, a fan cover that covers the cooling fan is provided, and an introduction passage that guides cooling air to the muffler storage chamber is formed by the fan cover.

According to claim 1, since the muffler storage chamber is divided into at least two sections and the cooling air inlet is provided in one section of the muffler storage chamber, the forced forced cooling air introduced is focused on the place where the temperature rise is high. Therefore, effective muffler cooling can be performed.
According to the second aspect, natural air cooling is promoted by the natural air cooling chamber, and an increase in the temperature of the muffler after the engine is stopped can be suppressed.
According to the third aspect, since the forced air cooling chamber is formed on the side away from the cylinder and the natural cooling chamber is formed on the side close to the cylinder when viewed in the horizontal direction of the muffler, the natural air cooling chamber is provided on the cylinder side. In addition to reducing the influence of the muffler heat transmitted to the cylinder after the engine stops, cooling air (wind after touching the muffler) leaks to the cylinder side by moving the forced air cooling chamber away from the cylinder. Can be suppressed.
According to the fourth aspect, the cooling air inlet is provided below the muffler on the side opposite to the exhaust port, and the outside air inlet is provided below the cooling air inlet, so that the flow direction during forced air cooling and natural air cooling is Similarly, since it is directed from the lower side to the upper side in the direction of gravity, natural air cooling at the time of engine stop is performed without delay in the forced air cooling chamber, and the cooling effect can be enhanced.
According to the fifth aspect, since the forced air cooling chamber and the natural cooling chamber are connected in the vicinity of the discharge port, natural cooling of the forced air cooling chamber can be promoted by the ascending airflow in the natural cooling chamber.
According to the sixth aspect, since the forced air cooling chamber and the natural cooling chamber are connected at the upper portion of the surface of the exhaust port, the waste heat can be discharged to the outside using the common opening portion.

According to the seventh aspect, since the muffler storage chamber is configured by the heat shield plate and the muffler cover with the heat shield plate interposed between the muffler and the muffler cover, the heat shield plate can be used without changing the shape of the muffler itself. It is possible to form two introduction air passages by changing the shape.
According to the eighth aspect, since the forced air cooling chamber and the natural cooling chamber are separated at least in the lower half of the space defined by the heat shield and the muffler cover, the forced air cooling wind leaks to the engine side. It is possible to effectively carry out forced muffler air cooling and natural air cooling without fear of producing the air.
According to the ninth aspect, the muffler storage chamber is separated into the forced air cooling chamber and the natural cooling chamber by arranging the tip of the partition portion so as to be in contact with the heat shield plate, so that the shape of the muffler itself is not changed. Two introduction air paths can be formed by changing the shape of the hot plate.
According to the tenth aspect, since the joint surface of the first housing and the second housing is used as the partitioning portion, the construction of the present invention can be achieved by newly manufacturing only the heat shield without changing the muffler shape used conventionally. Can be realized easily.
According to the eleventh aspect, since the outside air introduction port is formed on the bottom surface of the heat shield plate and the discharge port is provided near the upper end of the muffler storage chamber, the flow direction during natural air cooling is directed upward from below in the direction of gravity. Therefore, natural air cooling when the engine is stopped is performed without delay, and the cooling effect can be enhanced.
According to the twelfth aspect, since the introduction passage for guiding the cooling air generated by the fan cover covering the cooling fan to the muffler storage chamber is formed, it is not necessary to provide a separate fan for forcibly air-cooling the muffler.

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

It is a front view of the engine working machine which concerns on the Example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a left side view of an engine working machine according to an embodiment of the present invention, and a part thereof is shown in a cross-sectional view for explaining the flow of an engine cooling wind. It is a front view of the engine working machine which concerns on the Example of this invention, and one part was shown with sectional drawing in order to demonstrate the flow of the wind for muffler cooling. It is a right view of the engine working machine which concerns on the Example of this invention, and in order to demonstrate the flow of the wind for muffler cooling, a part is shown with sectional drawing. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of an engine working machine according to an embodiment of the present invention, and a part thereof is shown in a sectional view in order to show a state of a muffler during natural air cooling. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of an engine working machine according to an embodiment of the present invention. It is sectional drawing of the AA part of the muffler storage chamber of FIG. It is sectional drawing of the BB part of the muffler storage chamber of FIG.

  FIG. 1 is a side view of an example in which an engine working machine 1 according to an embodiment of the present invention is applied to a brush cutter. The engine working machine 1 accommodates an engine (not shown), and a carburetor 20 is provided on the left side of the engine. The vaporizer 20 sucks combustion air through an air cleaner (not shown) for filtering dust in the air. The air cleaner is accommodated in a cleaner box 22 having a predetermined closed space (air cleaner chamber). Is done. The cleaner box 22 is formed by covering the cleaner body 23 with a cleaner cover 24. A fuel tank 27 for storing fuel for operating the engine is provided in the vicinity of the fan case 4. The fuel tank 27 is manufactured, for example, by integrally molding a polymer resin such as plastic, and is manufactured from a translucent material so that the remaining amount of fuel can be visually observed from the outside. A fuel cap 28 is formed in the opening. Provided. In this embodiment, since a two-cycle engine is used, so-called mixed oil in which oil for lubrication is mixed at a predetermined ratio is stored in the fuel tank 27.

  In an engine (not shown), a cylinder (not shown) is arranged in the vertical direction, and a piston (not shown) reciprocates in the vertical direction in the cylinder. A fan case 4 is attached to a crankcase (not shown) to which the cylinder is attached, and the cylinder portion is covered with a cylinder cover 5. Below the fan case 4 is provided a leg portion 3 that serves as a support when the engine working machine 1 is placed on the floor or the like. A muffler (not shown) is provided on the right side of the cylinder. The muffler is entirely covered by a resin muffler cover 6 except for the exhaust port portion. Here, in order to cool the muffler, a part of the engine cooling air is guided into the muffler cover 6. Therefore, a part of the volute shape formed by the fan case 4 is changed to form a cooling air introduction passage 37 that branches the cooling air, and a cooling air introduction port 37 a is formed inside the muffler cover 6.

  FIG. 2 is a side view of the engine working machine 1 and shows a part thereof in cross section. The engine 10 is a small two-cycle single-cylinder general-purpose engine. A piston 12 is connected to the crankshaft 13 via a connecting rod, and the piston 12 reciprocates up and down inside the cylinder 11. Since the engine intake-compression-explosion-exhaust stroke is the same as that of a known two-cycle engine, a detailed description thereof will be omitted. In the present embodiment, the cylinder 11 is formed by integrally casting a cylinder main body, a head portion, and a heat radiating fin with, for example, an aluminum alloy, and an ignition plug 19 a is attached to the upper portion of the cylinder 11. A high voltage current is supplied from the ignition coil 17 to the spark plug 19a at a predetermined timing. The cylinder cover 5 is a plastic cover, for example, and covers the cylinder 11 that becomes hot during operation so that an operator does not directly touch them. Therefore, a large number of ventilation openings 5 b are formed on the rear side of the cylinder cover 5. A fuel tank 27 is disposed below the crankcase 14.

  A cooling fan 16 is provided at one end of the crankshaft 13 of the engine 10. The cooling fan 16 is rotated by the rotation of the crankshaft 13 and generates cooling air for cooling the cylinder 11 in particular. The cooling fan 16 is covered by a fan case 4 formed integrally with a volute portion formed in the crankcase 14, and an engine cooling air inlet 29 is provided on the surface of the volute portion on the crank chamber side. When the engine 10 is operated, the cooling fan 16 is rotated, so that outside air is taken in from the engine cooling air intake port 29 to generate engine cooling air CA1 to cool each part such as the cylinder 11 and the ignition coil 17, and the ventilation port 5b. By being discharged to the outside of the cylinder cover 5, the engine 10 is cooled around the cylinder 11 portion.

  A manual starter 18 for starting the engine by connecting a reel around which the traction string is wound to a drive shaft of the engine via a clutch and pulling the traction string by a starter knob 18a is attached to the rear of the engine. Although illustration of the internal structure is abbreviate | omitted in FIG. 2, well-known starting devices, such as a recoil starter, can be used, for example.

  FIG. 3 is a front view (partially sectional view) of the engine working machine 1 according to the embodiment of the present invention, and is a view for explaining the flow of wind for cooling the muffler. The muffler 30 of the present embodiment has a substantially rectangular parallelepiped basic shape, and is arranged so that its longitudinal direction is the vertical direction (vertical direction). This is because, in order to effectively reduce exhaust noise in a limited space, the muffler 30 is enlarged in the vertical direction to secure its volume as large as possible. The muffler 30 is fixed to the cylinder 11 or the crankcase 14 by a total of three bolts: two bolts 36a (only one is visible in the figure) for fastening the muffler and the bolt 36b. The muffler 30 is configured to divide a closed space defined by combining the first housing 31 and the second housing 32 into two spaces (a first expansion chamber and a second expansion chamber) by a partition plate 33. . The first housing 31 and the second housing 32 may be manufactured by press working using SPCC (cold rolled steel plate), for example, and heat-resistant coating may be applied to the outer surface.

  The first housing 31 is connected to an exhaust port (not shown) of the engine 10 and has an opening 31b serving as an exhaust gas inflow port. Two bolt insertion pipes for allowing the bolts 36a to pass therethrough are mufflers. It arrange | positions so that it may extend in 30 interior space. The first housing 31 is shaped so that the opening faces the opposite side of the cylinder, and the outer peripheral edge of the opening surface has a U-shaped cross section for sandwiching the lip 31a protruding from the outer periphery of the second housing 32 Ribs 32a are formed, and these are fixed by caulking. At this time, the U-shaped rib 32a is caulked together with the state lip 31a in which the outer edge portion of the cut plate 33 is also sandwiched. Note that these joining methods are not limited to caulking, but adhesion, welding, and other joining techniques may be used. However, in order to have the effect of the present embodiment, a projecting portion projecting outward from the muffler 30 ( It is advantageous if a protruding surface) is provided.

  The second housing 32 is provided on the side away from the engine 10 (not shown), and an exhaust port 38 serving as an outlet (exhaust port) from the muffler 30 is formed. The second housing 32 is shaped so that the opening faces the cylinder side, and a folding rib 32 a for joining to the first housing 31 is formed on the outer peripheral edge of the opening surface. The partition plate 33 serves not only for dividing the inner space of the muffler 30 but also as a holding member for fixing the catalyst 35. The catalyst 35 is fixed to a through hole 33 a formed slightly below the center of the partition plate 33. The partition plate 33 is preferably manufactured from a stainless steel plate.

  The catalyst 35 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 exhaust gas EX indicates the flow of exhaust gas, and the exhaust gas EX flowing from the opening 31b of the muffler 30 flows through the first expansion chamber in the first housing 31 and passes through the catalyst 35 to pass through the second housing 32. It flows through the second expansion chamber and is discharged to the outside through the exhaust port 38.

  The periphery of the muffler 30 configured in this manner is covered with the muffler cover 6 made of synthetic resin, and is configured so that the operator does not touch the muffler 30 that has become hot. A heat shield plate 40 is provided between the muffler cover 6 and the muffler 30. The heat shield plate 40 is formed by pressing a metal plate, for example, and has a size so as to cover the entire muffler 30 and is fixed to the engine 10 together with the muffler 30 by bolts 36a and 36b. The In the present embodiment, the shape of the muffler 30 is a substantially rectangular parallelepiped, and the heat shield plate is configured to cover almost the entire area excluding one surface of the muffler (the surface on the side opposite to the cylinder). The peripheral edge of the opening portion of the heat shield plate 40 facing away from the engine 10 is fitted to ribs 6f and 6g formed on the inner wall of the muffler cover 6, and is a closed space formed by the muffler cover 6 and the heat shield plate 40. (Muffler storage room) is defined. Although not understood in FIG. 3, the front and rear side edges of the heat shield plate 40 are also fitted to ribs (ribs 6 h and 6 i described later in FIGS. 7 and 8) formed on the inner wall of the muffler cover 6. The shape of the heat shield plate 40 is a shape that is slightly larger corresponding to the outer diameter of the muffler 30, and ensures a sufficient space on the outer peripheral side of the muffler 30 to flow the cooling air for the muffler 30. The closed space formed by the muffler cover 6 and the heat shield plate 40 is a partition portion of the muffler 30 (the portion joined by the lip 31a and the rib 32a, the upper and lower edges, the front edge and the rear of the muffler 30). The outer peripheral part of the lower half of the side edge part is formed so as to be in contact with the heat shield plate 40, and the space near the engine becomes the natural air cooling chamber 43, and the space far from the engine becomes the forced air cooling chamber 42.

  On the side of the muffler 30, there is provided a cooling air introduction port 37 a that is an opening of the cooling air introduction passage 37 for introducing a part of the cooling air from the fan case 4 that houses the cooling fan 16. During engine operation, a part of the engine cooling air CA1 (see FIG. 2) is introduced into the forced air cooling chamber 42 from the cooling air inlet 37a, and is discharged as the muffler forced air cooling flow CA2 (opening 6a described later in FIG. 4). It flows toward. Here, the cooling air introduction port 37a is provided below the muffler 30 on the side opposite to the exhaust port (the end opposite to the exhaust gas discharge direction, here the front side). On the other hand, an opening is provided at the lower end surface of the muffler cover 6, and an opening for introducing outside air, that is, a natural air-cooled suction port 40 a is provided at the bottom portion of the heat shield plate 40 above the opening. Thus, the natural air cooling inlet 40a is provided in the lower part of the natural air cooling chamber 43, and the muffler 30 becomes hot during engine operation. Therefore, a muffler natural air cooling flow CA4 is generated due to a temperature difference from the outside air. As the size of the natural air-cooled suction port 40a, the natural air-cooled suction port 40a may be formed to have a width of about the muffler. The natural air-cooled suction port 40a is covered with a gap by the muffler cover 6, and is provided so as to overlap a range where the natural air-cooled suction port 40a is not visible when viewed from the lower surface side. Thereby, when the engine working machine 1 is placed on the ground, it is possible to suppress radiant heat from reaching the ground, and it is possible to prevent grass from entering from the outside.

  FIG. 4 is a side view of the engine work machine 1 as viewed from the right side. In the vicinity of the lower end on the front side of the heat shield plate 40, an opening 40b formed in a convex shape for connection with the cooling air inlet 37a is provided. Through the opening 40b, the cooling air introduced from the cooling air introduction passage 37 is introduced into the forced air cooling chamber 42 at a certain flow rate. In the longitudinal direction (vertical direction) of the muffler 30, the muffler fastening bolt 36a is disposed closer to the plug cap 19 than the engine crankshaft 13 (see FIG. 2) (upper side of the AA cross section). The bolt 36b has the same height as the crankshaft 13 of the engine when viewed in the vertical direction, and is provided at a substantially middle position of the overall height of the muffler.

  In the muffler cover 6, an opening 6 a is provided at the rear and upper part of the muffler storage chamber, and the forced air cooling chamber 42 and the natural air cooling chamber 43 are connected to each other by a communication portion 45 disposed in the vicinity of the opening 6 a below the gravity direction. Is done. The opening 6a also serves as an exhaust port on the muffler cover side for exhaust gas exhausted from the exhaust port 38 of the muffler 30 existing in the past to the outside, and an exhaust gas outlet (exhaust port) In order to also serve as an outlet for cooling air, an opening (discharge port) having an area equal to or larger than the opening area of the conventional exhaust port and the opening area is used. The communication portion 45 is a space that is communicated in the left-right direction in the upper part from about half of the muffler 30 in the up-down direction. On the other hand, the heat shield plate 40 and the rib 32a are in contact portions 44 from about half to the lower part of the muffler 30 in the vertical direction, and the air flows in the forced air cooling chamber 42 and the natural air cooling chamber 43. Are separated to prevent mixing. The muffler natural air cooling flow CA4 directed upward in the gravitational direction merges with the muffler forced air cooling flow CA2 via the communication portion 45, and is discharged to the outside through the opening 6a. Further, the exhaust gas EX discharged from the exhaust port 38 is also discharged to the outside from the opening 6a. Here, the exhaust gas discharged from the exhaust port 38 at a high flow rate effectively discharges the muffler forced air-cooled flow CA2 and the muffler natural air-cooled flow CA4 to the outside.

  Next, the state of natural muffler cooling after the engine is stopped will be described with reference to FIGS. When the engine is stopped, there is no flow of exhaust gas EX as shown in FIG. However, in the natural air cooling chamber 43, outside air flows into the natural air cooling chamber 43 from the natural air cooling inlet 40a on the bottom surface of the heat shield plate 40, and is warmed by the residual heat of the muffler 30. It flows like CA4 and is discharged to the outside from the opening 6a (see FIG. 4). Thus, until the muffler 30 is sufficiently cooled after the engine is stopped, the muffler natural air-cooled flow CA4 continues to be generated as in the case of the engine operation. On the other hand, in the forced air cooling chamber 42, after the muffler forced air cooling flow CA2 from the cooling air inlet 37a stops, the muffler natural air cooling flow CA3 is generated by heat convection. Further, since the communicating portion 45 communicates with the natural air cooling chamber 43 in the upper part, the natural air cooling of the forced air cooling chamber 42 is promoted by the ascending airflow in the natural air cooling chamber 43. Since these flows are all directed upward in the direction of gravity, they are merged through the communication part 45 (see FIG. 4) in the same manner as in the case of forced air cooling of the muffler, and then discharged to the outside from the opening 6a. In the forced air cooling chamber 42, if the muffler forced air cooling is effectively performed, an opening may be provided in addition to the opening 6a. However, if a large number of openings are provided, the muffler cooling air immediately leaks to the outside, so that the forced air cooling effect cannot be obtained sufficiently. Therefore, it is preferable to set the position and number of the openings in consideration of them. Note that CA4 is a schematic illustration of the flow direction from the natural air cooling inlet 40a to the opening 6a. For example, the flow of heat as natural cooling is generated via the side surface of the muffler 30 in the width direction. To do.

  7 is a cross-sectional view of the AA portion of the muffler storage chamber of FIG. In FIG. 7, a natural air cooling chamber 43 is formed by the outer wall of the first housing 31 of the muffler 30 and the inner wall of the heat shield plate 40. A forced air cooling chamber 42 is formed by the outer wall of the second housing 32 of the muffler 30, the heat shield plate 40, and the inner wall of the muffler cover 6. Here, since the caulking portion of the second housing 32 of the first housing 31 is a contact portion 44 that contacts the inner wall of the heat shield plate 40, the natural air cooling chamber 43 close to the engine 10 is separated from the engine 10. It can be seen that the two spaces of the side forced air cooling chamber 42 are separated from each other. In order to separate in this way, the muffler storage chamber has fewer unnecessary openings and gaps, and the opening portion of the heat shield plate 40 has two ribs 6h protruding toward the inner wall side of the muffler cover 6, It fits into the groove between 6i. The state in which the natural air cooling chamber 43 and the forced air cooling chamber 42 are thus separated is maintained at least at the lower half of the muffler 30 and at a position below the vicinity of the bolt 36b in FIG. Further, the caulking portion of the second housing 32 of the first housing 31 has a structure in contact with the inner wall of the heat shield plate 40 also at the lower end portion of the muffler.

  8 is a cross-sectional view of the BB portion of the muffler storage chamber of FIG. The cross section of this BB part is a position included in the upper half of the muffler 30 in the vertical direction, and is a lower part of the opening 6a serving as an outlet for cooling air and exhaust gas from the muffler storage chamber. In the BB portion, a communication portion 45 that connects the two spaces is formed in order to join and discharge the wind flowing through the natural air cooling chamber 43 and the forced air cooling chamber 42. The communication portion 45 is formed so as to be spaced apart from the rib 32a on which the heat shield plate 40 is caulked by changing the shape of the rear wall of the heat shield plate 40. The communication portion 45 is provided to mix the air in the forced air cooling chamber 42 and the natural air cooling chamber 43, so that the introduced cooling air is at least before the outlet, and the introduced cooling air passes from the cooling air introduction passage 37. It is desirable to partition to such an extent that it does not flow into, and in this embodiment, it is provided in the lower part of the opening 6a (FIG. 4).

  As described above, according to the present invention, since a part of the wind of the cooling fan 16 arranged for cooling the engine 10 is introduced into the housing chamber of the muffler 30, the muffler cover 6 substantially covers the muffler 30. The muffler 30 can be cooled effectively. In particular, the forced cooling air generated by the cooling fan 16 is introduced so as to divide a specific area of the muffler housing chamber, so that, for example, the catalyst of the muffler 30 is intensively guided to the surface having the highest temperature to improve the cooling efficiency. It becomes possible to raise. Moreover, it is not necessary to arrange another pump or a blower fan for sending air to the muffler 30, and an increase in manufacturing cost can be suppressed. Further, since the natural air cooling chamber is provided in which the outside air is taken into the muffler storage chamber and the muffler 30 is actively cooled by natural air cooling, the cooling effect of the muffler 30 is effectively improved both when the engine 10 is in operation and when it is stopped. Can be obtained. In particular, when muffler forced air cooling is performed with a cooling system in which the engine cooling air intake port opens to the crankcase side, if exhaust air that has become hot after muffler cooling leaks to the engine side, the air temperature of the engine cooling air However, according to the present invention, the natural air cooling chamber is provided on the engine side so that the forced air cooling air does not leak to the engine side. Therefore, it is possible to effectively perform the muffler forced air cooling and natural air cooling.

  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, in the present specification, the space close to the engine 10 is the natural air cooling chamber 43 and the space on the side away from the engine 10 is the forced air cooling chamber 42, but the two spaces are provided. The arrangement of the natural air cooling chamber and the forced air cooling chamber may be determined in consideration of the shape of the muffler and the portion where the temperature rise is large. Further, the position, size, shape, and the like of the outside air intake provided in the natural air cooling chamber may be appropriately set according to the required cooling capacity. In the above-described embodiment, the brush cutter is used as an example of the engine working machine. However, the general-purpose engine to which the present invention is used is an engine working machine that drives not only the brush cutter but also other working devices. Also good.

DESCRIPTION OF SYMBOLS 1 Engine working machine 3 Leg part 4 Fan case 5 Cylinder cover 5b Ventilation opening 6 Muffler cover 6a Opening part 6f, 6g, 6h, 6i Rib 10 Engine 11 Cylinder 12 Piston 13 Crankshaft 14 Crankcase 16 Cooling fan 17 Ignition coil 18 Starter (Recoil starter)
18a Starter knob 19 Plug cap 19a Spark plug 20 Vaporizer 22 Cleaner box 23 Cleaner body 24 Cleaner cover 27 Fuel tank 28 Fuel cap 29 Engine cooling air inlet 30 Muffler 30a Rib 31 First housing 31a Lip 31b Opening 32 Second housing 32a Rib 33 Partition plate 33a (partition plate) through hole 35 Catalyst 36a, 36b Bolt 37 Cooling air introduction passage 37a Cooling air introduction port 38 Exhaust port 40 Heat shield plate 40a Natural air cooling intake port 40b Opening 42 Forced air cooling chamber 43 Natural Air cooling chamber 44 Contact portion 45 Communication portion CA1 Engine cooling air flow CA2, forced air cooling cooling air flow CA3, CA4 Air flow during natural air cooling EX Exhaust gas flow

Claims (12)

A cylinder having a plurality of fins on the outer periphery and forming a combustion chamber;
A cooling fan provided at one end of the drive shaft for cooling the cylinder;
A muffler attached to the exhaust port of the cylinder;
A muffler cover that covers the muffler and forms a muffler storage chamber is provided.
A cooling air inlet for introducing a part of the cooling air generated by the cooling fan into the muffler storage chamber and a discharge port for discharging the air after cooling are provided, and the muffler storage chamber is divided into at least two sections, An engine working machine, wherein the cooling air inlet is provided in one section of the muffler storage chamber.   The muffler cover may be divided into a forced air cooling chamber serving as a space for guiding the cooling air introduced from the cooling air inlet to the discharge port, and a natural cooling chamber provided with an outside air inlet below the muffler storage chamber. The engine working machine according to claim 1.   The engine work according to claim 2, wherein the forced air cooling chamber is formed on a side away from the cylinder and the natural cooling chamber is formed on a side near the cylinder when viewed in a horizontal direction of the muffler. Machine. The cooling air inlet is provided below the exhaust side of the muffler,
The outside air inlet is provided below the cooling air inlet,
The engine work machine according to claim 2 or 3, wherein the exhaust port is disposed around an exhaust port of the muffler formed in the muffler cover.   The engine working machine according to any one of claims 2 to 4, wherein the forced air cooling chamber and the natural cooling chamber are connected in the vicinity of the discharge port.   The engine working machine according to claim 5, wherein the forced air cooling chamber and the natural cooling chamber are connected at an upper portion of a surface of the exhaust port.   7. The muffler storage chamber is configured by the heat shield plate and the muffler cover with a heat shield plate interposed between the muffler and the muffler cover. 8. Engine working machine.   8. The engine working machine according to claim 7, wherein the forced air cooling chamber and the natural cooling chamber are separated at least at a lower half portion or more in a space defined by the heat shield plate and the muffler cover. . Forming a partition that protrudes in the outer circumferential direction and continues in the circumferential direction outside the housing of the muffler,
The engine work machine according to claim 8, wherein the muffler storage chamber is separated into the forced air cooling chamber and the natural cooling chamber by disposing the leading end of the partition portion so as to be in contact with the heat shield plate. The muffler constitutes a housing by combining the first housing and the second housing having an opening surface with each other through a partition plate,
By forming a through hole in the partition plate, a first expansion chamber into which exhaust gas from the exhaust port of the cylinder first flows, and exhaust gas that has flowed in through the through hole are transferred from the exhaust port to the atmosphere. Constituting the second expansion chamber to be discharged,
The engine work machine according to claim 9, wherein a joint surface between the first housing and the second housing is used as the partition portion. The outside air inlet is formed on the bottom surface of the heat shield plate,
The engine work machine according to any one of claims 8 to 10, wherein the discharge port is provided near an upper end of the muffler storage chamber. The engine working machine according to any one of claims 1 to 11, wherein a fan cover that covers the cooling fan is provided, and an introduction passage that guides the cooling air to the muffler storage chamber is formed by the fan cover. .

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