JP2015094256A - Work machine equipped with two-cycle internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size of a drive part including a loop scavenging type two-cycle internal combustion engine.SOLUTION: A bush cutter 100 has a single cylinder two-cycle internal combustion engine 20 mounted in an upright position. In the engine 20, an intake port 26 is opened forward and an exhaust port 30 is opened rearward. The intake port 26 and the exhaust port 30 are opened and closed by a piston 42. A centrifugal clutch 50 is arranged at the front end of a crankshaft 46. A carburetor 28 is arranged in front of the engine 20. An air cleaner case 60 is arranged above the carburetor 28. A cooling fan 58 is arranged at the rear end of the crankshaft 46. A recoil starter 66 is arranged behind the cooling fan 58.

Description

  The present invention relates to a working machine having a two-cycle internal combustion engine, which is generally an air-cooled single cylinder.

  Air-cooled small two-cycle internal combustion engines are used in various portable work machines such as brush cutters, power blowers, hedge trimmers, chainsaws, debranching machines, and spreaders. In this industry, dealing with exhaust gas regulations that are becoming more severe has become a major issue. Patent Documents 1 and 2 disclose typical examples of engine structures effective for exhaust gas purification.

  The two-cycle internal combustion engine disclosed in Patent Document 1 is a so-called reverse scavenging engine. In a reverse scavenging engine, the scavenging is performed by an air-fuel mixture. It has an intake port and an exhaust port which are arranged facing each other in the diameter direction of the cylinder. That is, when the engine is viewed in plan, the intake port and the exhaust port are disposed approximately 180 degrees apart. The intake port communicates with the crank chamber. In this engine, scavenging ports are arranged on both sides of an imaginary line passing through the intake port and the exhaust port. These intake port, exhaust port, and scavenging port are opened and closed by a piston. That is, the engine disclosed in Patent Document 1 is a piston valve type engine. Since Patent Document 1 describes in detail the structure of an inverted scavenging engine, the entire text of Patent Document 1 is incorporated herein by reference.

  The two-cycle internal combustion engine disclosed in Patent Document 2 is a so-called stratified scavenging engine. In a stratified scavenging engine, fresh air (leading air) containing no fuel is first put into the combustion chamber, and then the air-fuel mixture is put into the combustion chamber at the beginning of the scavenging stroke. The engine disclosed in FIG. 2 is also a piston valve type engine, similar to the reverse scavenging type engine. Since Patent Document 2 describes the structure of the layered scavenging in detail, the entire text of Patent Document 2 is incorporated herein.

  In addition, various inventions relating to a two-cycle internal combustion engine for a portable work machine and a work machine equipped with the same have been proposed. The invention disclosed in Patent Document 3 has a technical problem that the hot air around the cylinder head of an upright engine is easily transmitted to an operator. Here, “upright” means a state in which the crank chamber is down and the cylinder head is up. In order to achieve the above technical problem, the invention of Patent Document 3 arranges the engine in an inverted state, opens the exhaust port toward the rear, and arranges the exhaust system behind the engine. is suggesting. Here, “inverted” refers to a state in which the crank chamber is up and the cylinder head is down. An example disclosed in Patent Document 3 is a brush cutter. In the engine of the embodiment, the carburetor is mounted on the inverted engine, that is, on the crank chamber, and the air cleaner is positioned on the carburetor. A fuel tank is disposed around the centrifugal clutch device.

  Patent Document 4 proposes an improved invention for suppressing vibration of a brush cutter provided with a flexible linear cutting blade (nylon cord). The brush cutter disclosed as an example in Patent Document 4 has a two-cycle internal combustion engine, and this engine is mounted in an inverted state. The silencer, which is an exhaust system component, is arranged behind the engine. A carburetor is disposed behind the crank chamber of the inverted engine, and an air cleaner is disposed behind the carburetor. That is, in this engine, both the intake port and the exhaust port are opened rearward.

  In the brush cutter disclosed in Patent Document 4, the fuel tank is positioned above the crank chamber. A fan housing surrounding the cooling fan is disposed in front of the engine, and the centrifugal clutch device is positioned in front of the fan housing.

  Patent Document 5 proposes an improved invention relating to a throttle mechanism of a small internal combustion engine such as a brush cutter or a spreader. The brush cutter disclosed as an example in Patent Document 5 has a two-cycle internal combustion engine, and this engine is mounted in an upright state. When the extension direction of the engine output shaft, that is, the extension direction of the operating rod of the brush cutter is referred to as the “front-rear direction”, the carburetor is arranged on the left side of the engine and the exhaust system parts are arranged on the right side of the engine. The invention disclosed in Patent Document 5 proposes that a swingable relay arm is interposed between a throttle lever operated by an operator and an output control valve of an intake system.

  Patent Document 6 proposes a two-cycle internal combustion engine that can be reduced in size while maintaining the exhaust gas purification effect of the above-described reverse scavenging engine (Patent Document 1). Describing the engine proposed in Patent Document 6, the intake port and the exhaust port are arranged approximately 90 ° apart from each other about the longitudinal axis of the cylinder. The scavenging port is arranged in a 90 ° region sandwiched between the intake port and the exhaust port and a 270 ° region that opposes the 90 ° region. An example disclosed in Patent Document 6 is a chainsaw. The engine is mounted horizontally on this chainsaw. Specifically, the engine is mounted on the chainsaw with the intake port opened upward and the exhaust port opened laterally.

  Patent Document 7 discloses a two-cycle internal combustion engine. This engine is a reverse scavenging engine as in Patent Document 1. That is, the engine disclosed in Patent Document 7 has an intake port and an exhaust port that are arranged to face each other in the diameter direction of the cylinder. When the engine is viewed in plan, scavenging ports are arranged on both sides of a virtual line connecting the intake port and the exhaust port. Further, this engine is a piston valve type as in Patent Document 1. In Patent Document 7, the angle between the axis of the exhaust port and the axis of the crankshaft is smaller than 90 ° for the purpose of increasing the degree of design freedom for installing exhaust system parts (exhaust muffler). In the example, it is proposed to be mounted on the work machine so as to be 15 ° to 85 °.

JP JP 09-280053 A WO 98/57053 JP Utility Model Publication No. 1-166235 JP 1-171407 A JP Utility Model Publication No. 2-63041 JP JP 2009-299605 A USP 7,131,406

  The engine disclosed in Patent Document 1 is a typical example of a reverse scavenging engine. This engine is mounted on the brush cutter in an upright state. Here, “upright” means a state in which the crank chamber is down and the cylinder head (ignition plug) is up. The cylinder is mounted on the brush cutter such that its intake port and exhaust port are opened in the lateral direction of the brush cutter, and the scavenging port is located opposite to the longitudinal direction of the brush cutter. That is, the engine mounted on the brush cutter has an intake port and an exhaust port opened in a direction perpendicular to the axis of the crankshaft. Of course, a carburetor which is an intake system component is connected to the intake port, and an air cleaner is connected to the carburetor. A silencer, which is an exhaust system component, is connected to the exhaust port.

  As can be seen from the above description, in a working machine such as a brush cutter, an intake system component and an exhaust system component are arranged to oppose a direction orthogonal to the axis of the crankshaft, that is, a lateral direction.

  As is well known, a working machine such as a brush cutter has a working tool (cutlery) at the front end and a drive unit (engine and its auxiliary equipment and fuel tank) at the rear end. Manufacturers are always required to make efforts to improve workability of work machines.

  Miniaturization of the drive unit is effective in improving workability and safety of the work machine. The downsizing of the drive unit in the work machine has two meanings. One is to reduce the longitudinal dimension of the drive unit. The other one is to reduce the width dimension of the drive unit. Here, the “front-rear direction” refers to the extending direction of the crankshaft. The “width direction” refers to a direction orthogonal to the crankshaft.

  Typical examples of working machines equipped with cutting tools are brush cutters and lawn edges that form the boundary between the sidewalk and the lawn. Such a working machine has a handle in the middle of the operating rod in the longitudinal direction, and a throttle lever is disposed on the handle. Thus, in the working machine in which the throttle lever is arranged in front of the drive unit, the throttle lever is mechanically connected to the output control valve (butterfly valve or rotary valve) of the intake system by the throttle cable. The operator can control the engine output by operating the throttle lever. As described above, Patent Document 5 proposes that a swingable relay arm is interposed between the throttle lever and the output control valve. However, if such a relay arm is provided, the number of parts increases. This deteriorates maintainability and makes it difficult to manage the dimensions of the throttle wire. Ideally, the distance between the throttle lever and the output control valve should be short and linear for a simpler construction.

  The inventor of the present invention has come up with the present invention in the process of pursuing a working machine that should be based on the viewpoint of workability and safety, with exhaust gas regulations in mind.

  The objective of this invention is providing the working machine which can reduce the size of the drive part containing the 2 cycle internal combustion engine of a reverse scavenging system.

  A further object of the present invention is to provide a working machine capable of reducing the size of a drive unit including a two-cycle internal combustion engine of a stratified scavenging system.

  It is a further object of the present invention to provide a working machine capable of reducing the size of a drive unit including a piston valve type two-cycle internal combustion engine.

  A further object of the present invention is to provide a working machine capable of reducing the size of a drive unit including a two-cycle internal combustion engine having a cylinder in which a scavenging passage is integrally formed.

According to the present invention, the above technical problem is
A working machine comprising a drive unit including a two-cycle internal combustion engine, wherein the two-cycle internal combustion engine is mounted in an upright posture,
The drive unit is
A centrifugal clutch device connected to a tip of a crankshaft of the engine;
An intake port positioned at the front of a cylinder of the engine when the working machine is viewed in plan,
A carburetor disposed above the centrifugal clutch device, the carburetor connected to the intake port;
An air cleaner disposed in front of or above the vaporizer;
An exhaust port positioned at the rear of the cylinder when the working machine is viewed in plan;
An exhaust system component connected to the exhaust port;
This is achieved by providing a working machine including scavenging ports arranged on the left and right of the axis of the crankshaft when the engine is viewed in plan.

  A typical example of the working machine is a working machine having an operating rod at the front end of the driving unit and a working unit at the front end of the operating rod, such as a brush cutter or a lawn edger.

In preferable embodiment of this invention, it is a working machine provided with the operating rod extended ahead from a drive part. This work machine
The drive unit is
A centrifugal clutch device connected to a tip of a crankshaft of the engine;
An intake port positioned at the front of a cylinder of the engine when the working machine is viewed in plan,
A carburetor disposed above the centrifugal clutch device, the carburetor connected to the intake port;
An air cleaner disposed in front of or above the vaporizer;
An exhaust port positioned at the rear of the cylinder when the working machine is viewed in plan;
An exhaust system component connected to the exhaust port;
A scavenging port disposed on the left and right of the axis of the crankshaft when the engine is viewed in plan,
The power of the engine is transmitted to the working unit disposed at the tip of the operating rod via the centrifugal clutch device and a power transmission shaft connected to the centrifugal clutch device.

  The intake port and the exhaust port may be located on the axis of the crankshaft when the cylinder is viewed in plan. In addition, either or both of the intake port and the exhaust port may be offset left and right from the axis of the crankshaft. In the two-cycle internal combustion engine included in the present invention, typically, the intake port, the exhaust port, and the scavenging port are opened and closed by a piston.

  In a preferred embodiment of the present invention, the drive unit further includes a cooling fan, and the cooling fan is assembled to a rear end portion of the crankshaft.

  Moreover, in preferable embodiment of this invention, a fuel tank is arrange | positioned at the side of the said carburetor and the said centrifugal clutch apparatus located in the downward direction, and this fuel tank is extended in the up-down direction.

  Other objects and effects of the present invention will become apparent from the detailed description of the embodiments of the present invention described below.

It is a perspective view of the rear part of the brush cutter of 1st Example. It is a longitudinal cross-sectional view of the two-cycle internal combustion engine mounted on the brush cutter of the first embodiment, and is a view cut along a vertical plane that passes through the crankshaft and extends in the front-rear direction of the brush cutter. It is the longitudinal cross-sectional view of the 2-cycle internal combustion engine mounted in the brush cutter of 1st Example, Comprising: It is the figure cut | disconnected by the vertical surface which crosses a crankshaft. It is the perspective view which looked at the drive part (illustration of the fuel tank was omitted) of the brush cutter of 1st Example from diagonally forward. It is the longitudinal cross-sectional view of the drive part of the brush cutter of 1st Example, Comprising: It is the figure cut | disconnected by the vertical surface which passes a crankshaft and spreads in the front-back direction of a brush cutter. It is the perspective view which looked at the drive part (a fuel tank is included) of the brush cutter of 1st Example from diagonally forward. It is the perspective view which looked at the drive part (illustration of the fuel tank was omitted) of the brush cutter of 1st Example from diagonally forward. It is the perspective view which looked at the drive part of the brush cutter of 1st Example from diagonally forward from the fuel tank side, and is a figure for demonstrating the modification of the shape of a fuel tank. It is a conceptual block diagram of the drive part of the brush cutter shown in FIG. It is a conceptual block diagram of the drive part of the brush cutter of 2nd Example. It is a conceptual block diagram of the drive part of the brush cutter of 3rd Example. It is a conceptual block diagram of the drive part of the brush cutter of 4th Example. It is a conceptual block diagram of the drive part of the brush cutter of 5th Example. It is a conceptual block diagram of the drive part of the brush cutter of 6th Example.

  Hereinafter, preferred embodiments will be described with reference to the accompanying drawings, taking a brush cutter to which the present invention is applied as an example.

  FIG. 1 is a perspective view of a rear end portion of the brush cutter according to the embodiment. Referring to FIG. 1, the brush cutter 100 has a drive unit 2 at its rear end, and the drive unit 2 is covered with a case 4. The case 4 is made by combining a plurality of plastic molded products and lightweight metal parts such as magnesium. In the figure, reference numeral 6 is a primary pump, and 8 is a choke knob. A recoil starter grip 10 is positioned at the rear end of the drive unit 2. The operator can start the engine by pulling the grip 10 by a predetermined amount.

  The case 4 extends forward and constitutes a part of the operation rod 54. A cutting blade is disposed at the front end of the operation rod 54 as in the conventional case. The cutting blade is rotated by the power generated by the drive unit 2. A handle (not shown) is provided between the cutting blade and the drive unit 2 as in the prior art, and a throttle lever (not shown) is attached to the handle. The power generated by the drive unit 2 can be controlled by operating the throttle lever.

  Reference numeral 12 shown in FIG. 1 is a fuel tank. Reference numeral 14 indicates a cap of the fuel tank 12. As will be described later, the fuel tank 12 is disposed in the front portion of the side portion of the drive unit 2.

  A cover 16 that constitutes a part of the top surface of the case 4 is positioned at the front end portion of the portion 4 a surrounding the drive unit 2 in the case 4. This cover 16 constitutes a part of a case of an air cleaner (described later).

  2 and 3 show a single-cylinder two-cycle internal combustion engine mounted on the brush cutter 100 in an upright state. FIG. 2 is a cross-sectional view taken along a vertical plane extending in the front-rear direction of the brush cutter 100. FIG. 3 is a cross-sectional view taken along a vertical plane extending in the width direction of the brush cutter 100. Here, the “front-rear direction” refers to the extending direction of the operating rod, that is, the axial direction of the crankshaft. The “width direction” refers to a direction orthogonal to the crankshaft.

  The illustrated engine 20 is typically an air-cooled two-cycle internal combustion engine, and the engine 20 is a single cylinder. The engine 20 is mounted on the brush cutter 100 in an upright state as described above. That is, the engine 20 is mounted on the brush cutter 100 with the crank chamber 22 facing down and the spark plug 24 facing up.

  Referring to FIG. 2, when the cylinder 34 is viewed in plan, the intake port 26 is positioned at the front portion of the cylinder 34, and the intake port 26 is opened forward. A carburetor 28 (FIGS. 4 and 5) described later is connected to the intake port 26. The intake port 26 communicates with the crank chamber 22.

  The exhaust port 30 is positioned at the rear portion of the cylinder 34. In this embodiment, the exhaust port 30 is opened rearward, but may be opened sideways. An exhaust system part 32 (FIG. 5) such as a silencer described later is connected to the exhaust port 30.

  A scavenging port 36 located on the circumferential surface of the cylinder 34 is open to the combustion chamber 38. The scavenging port 36 is arranged on the left and right sides of an imaginary line connecting the intake port 26 and the exhaust port 30. The left and right scavenging ports 36 are each composed of two scavenging ports 36A and 36B on the right and left sides, respectively, and the engine 20 has a total of four scavenging ports 36. The scavenging port 36 is typically directed toward the intake port 26 side.

  The scavenging port 36 communicates with the crank chamber 22 through a scavenging passage 40 formed integrally with the cylinder block. That is, the scavenging passage 40 extends in the vertical direction, the upper end thereof communicates with the scavenging port 36, and the lower end communicates with the crank chamber 22. In the scavenging stroke, the air-fuel mixture in the crank chamber 22 is introduced into the combustion chamber through the scavenging port 36.

  The scavenging port 36 and the exhaust port 30 are opened and closed by a piston 42. That is, the two-cycle internal combustion engine 20 is a piston valve type engine. The piston 42 is connected to the crankshaft 46 via a connecting rod 44. The reciprocating motion of the piston 42 up and down is converted into a rotational motion by the crankshaft 46 and output by the crankshaft 46.

  The above configuration is a basic configuration of a so-called reverse scavenging engine. Since the reverse scavenging engine is described in detail in the cited reference 1, the detailed description of the reverse scavenging engine 20 is omitted by using the entire text of the cited reference 1. As a modified example of the engine 20, a so-called laminar scavenging engine in which scavenging is performed first with fresh air containing no air-fuel mixture, and then with air-fuel mixture, may be used.

  4 to 7 show the drive unit 2 of the brush cutter 100. The drive unit 2 is manufactured by attaching an operating rod, a power transmission shaft inserted into the operating rod, a cutting blade, and the like in an attachment manner. When the cutting blade is called a working unit, a plurality of types of working units are prepared. The working unit may be a cutting blade that rotates like a brush cutter, or may be a member that reciprocates like a shaft hedge trimmer.

  FIG. 4 is a perspective view of the drive unit 2 as viewed obliquely from the front, and illustration of the fuel tank 12 is omitted. FIG. 5 is a longitudinal sectional view of the drive unit 2 cut along a vertical plane passing through the axis of the crankshaft 46. FIG. 6 is a perspective view of the drive unit 2 as viewed obliquely from the front.

  2 and 5, a centrifugal clutch device 50 is connected to the front end of the crankshaft 46. The centrifugal clutch device 50 includes a centrifugal clutch and a drum surrounding the centrifugal clutch, as in the conventional art. Reference numeral 52 in FIG. 2 indicates a clutch case surrounding the centrifugal clutch device 50. The output of the engine 20 is transmitted to a power transmission shaft (not shown) through the centrifugal clutch device 50, and then transmitted to a cutting blade (not shown) at the tip of the power transmission shaft. This power transmission shaft is inserted into the operation rod 54.

  As best seen in FIG. 5, a cooling fan 58 is attached to the rear end of the crankshaft 46. The engine 20 is forcibly cooled by the cooling fan 58. A recoil starter 66 is assembled behind the cooling fan 58. The recoil starter 66 operates by pulling the grip 10 (FIG. 1) described above by a predetermined amount to start the engine 20. The engine 20 may be a reverse scavenging engine or a stratified scavenging engine.

  4 and 5, the carburetor 28 is positioned in front of the engine 20. Specifically, the intake port 26 of the engine 20 is open forward as described above. A carburetor 28 is disposed in front of the intake port 26 and above the centrifugal clutch device 50.

  Reference numeral 60 in FIG. 6 denotes an air cleaner case. The air cleaner case 60 is installed above the carburetor 28 in an open state. An air cleaner element (not shown) is assembled to the air cleaner case 60 and covered with a cover 16 (FIG. 1). The air cleaner case 60, the air cleaner element, and the cover 16 are elements constituting the air cleaner. The air cleaner and vaporizer 28 are intake system components. The air purified by the air cleaner is supplied to the vaporizer 28.

  As a modification, an air cleaner may be disposed in front of the vaporizer 28.

  Referring to FIG. 5 again, an exhaust system part 32 such as a silencer connected to the exhaust port 30 is positioned behind the engine 20. The exhaust system component 32 is disposed above the cooling fan 58 as best seen in FIG. FIG. 7 is a perspective view of the drive unit 2 as viewed obliquely from the front, and shows the fuel tank 12 removed. As can be seen from FIG. 7, the exhaust system component 32 has a shape extending laterally from the rear of the engine 20. That is, the exhaust system part 32 has a shape extending rearward and laterally of the cylinder 34.

  Referring to FIG. 6 again, the shape of the fuel tank 12 will be described. The fuel tank 12 has an L-shape when viewed from the front, and extends laterally from the centrifugal clutch device 50 and the carburetor 28 in the vertical direction. It has a main body 12A and a lower end portion 12B that extends laterally from the lower end of the main body 12A and approaches the centrifugal clutch device 50.

  FIG. 8 is a view for explaining a modification of the shape of the fuel tank 12. As shown in FIG. 8, the fuel tank 12 may have a shape in which a lower portion extends rearward.

  As can be understood from the above description, the drive unit 2 of the brush cutter 100 includes the reverse scavenging and piston valve type engine 20, the carburetor 28 and the air cleaner constituting the intake system, the exhaust system component 32, the cooling A fan 58 and a centrifugal clutch device 50 are included. The engine 20 mounted on the brush cutter 100 is front intake and rear exhaust.

  As best seen in FIG. 5, the height level of the carburetor 28 disposed in the vicinity of the intake port 26 of the front intake engine 20 is the same even if the carburetor 28 is disposed above the centrifugal clutch device 50. The height level does not interfere with 50. In other words, the centrifugal clutch device 50 can be assembled close to the engine 20 without worrying about interference with the carburetor 28.

  Further, the exhaust port 30 of the rear exhaust engine 20 has a height level higher than that of the intake port 26. Therefore, the cooling fan 58 assembled to the rear end of the crankshaft 46 can employ a large-diameter cooling fan. That is, the cooling fan 58 can be increased in diameter although it is assumed that the cooling fan 58 does not interfere with the exhaust port 30 and the exhaust system component 32 directly connected thereto.

  As a comparison, when it is assumed that the cooling fan 58 and the centrifugal clutch device 50 are disposed in front of the engine 20, the cooling fan 58 is different from the intake port 26 positioned at a relatively lower height level than the exhaust port 30. In order to avoid this interference, the cooling fan 58 cannot be brought close to the center of the engine 20 unless a small-diameter cooling fan is employed. In other words, if the large-diameter cooling fan 58 is employed, it is necessary to keep the cooling fan 58 away from the center of the engine 20. This also leads to an increase in the axial length (length in the front-rear direction) of the drive unit 2.

  As can be seen from the description of this comparative example, even if a large-diameter cooling fan 58 is employed, the cooling fan 58 is disposed behind the front intake and rear exhaust engine 20 without increasing the longitudinal length of the drive unit 2. Can be placed. Further, since the intake port 26 and the carburetor 28 are located at a relatively high level, the centrifugal clutch device 50 can be assembled in a state of being close to the center of the engine 20. That is, the vaporizer 28 and the large-diameter cooling fan 58 can be arranged while the length of the driving unit 2 in the front-rear direction is minimized.

  In other words, in the conventional layout, that is, in the side intake and side exhaust engines, the lower area of the intake port and the exhaust port becomes a dead space, but by adopting the layout of the front intake and the rear exhaust as in the embodiment, In addition, it is possible to minimize the length in the front-rear direction of the drive unit 2 while utilizing the area below the intake port 26 and the exhaust port 30 as an installation space for the centrifugal clutch device 50 and the cooling fan 58.

  Further, by arranging the air cleaner in the space above the vaporizer 28 arranged adjacent to and above the centrifugal clutch device 50, a relatively large capacity air cleaner can be arranged without difficulty.

  Reference numeral 34A shown in FIGS. 3, 4, 6, and 7 indicates a bulging portion from which the cylinder 34 protrudes sideward, and the scavenging passage 40 is formed by the bulging portion 34A. Although the cylinder 34 is a die-cast product, when the cylinder 34 is formed, a scavenging passage 40 opened downward is integrally formed. In order to allow the scavenging passage 40 to communicate with the crank chamber 22, it is preferable that the bulging portion 34 </ b> A that defines the scavenging passage 40 exists up to the lower end of the cylinder 34. As can be seen from FIG. 3 and the like, the bulging portion 34A of the cylinder 34 is located not in the front-rear direction of the engine 20 but in the width direction. Therefore, there is no need to design the lower end portion of the bulging portion 34A with the interference with the centrifugal clutch device 50 and the cooling fan 58 in mind. As can be seen from FIG. 3 and the like, the bulging portion 34A (scavenging passage 40) of the cylinder 34 included in the embodiment has substantially the same shape and extends straight up and down. In other words, the scavenging passage 40 extending in the vertical direction has substantially the same cross-sectional shape from the upper end to the lower end. The shape of the scavenging passage 40 can be easily removed when the cylinder 34 is die-cast. Further, when applied to a stratified scavenging engine, it is possible to increase the amount of air introduced into the scavenging passage 40 by forming the bulging portion 34A larger, and the degree of freedom in designing the scavenging passage shape is also increased.

  FIG. 9 is a schematic configuration diagram of the drive unit 2 included in the brush cutter 100 according to the embodiment. When the drive unit 2 is viewed in plan, the engine 20 mounted on the brush cutter 100 in an upright posture is positioned so as to be front intake and rear exhaust. The axis of the crankshaft 46 is indicated by reference sign CL. The axis CL of the crankshaft 46 is coaxial with the axis of the power transmission shaft connected in series to the crankshaft 46 via the centrifugal clutch device 50. In the figure, reference numeral 66 denotes a recoil starter.

  With continued reference to FIG. 9, the engine 20 included in the brush cutter 100 according to the embodiment has the intake port 26 and the exhaust port 30 positioned on the axis CL of the crankshaft 46 when viewed in plan. The intake port 26 extends forward along the axis CL of the crankshaft 46 and is connected to a carburetor 28 disposed on the axis CL. The vaporizer 28 is connected to an air cleaner (air cleaner case 60) disposed on the axis CL. Similarly, the exhaust port 30 extends rearward along the axis CL of the crankshaft 46 and is connected to the exhaust system component 32.

  10 to 14 show various embodiments of the drive unit 2. In the description of these embodiments, the same elements as those in the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 10 shows the driving unit 120 of the brush cutter according to the second embodiment. Referring to FIG. 10, the driving unit 120 of the brush cutter according to the second embodiment arranges the intake port 26 and the exhaust port 30 offset from the axis CL to the left and right, and the carburetor 28 is the same as the intake port 26. 5 shows an example in which positioning is performed by offsetting to the left from the axis CL, and the exhaust system component 32 is also positioned by being offset to the right from the axis CL in the same manner as the exhaust port 30. Of course, the intake port 26 is located above the centrifugal clutch device 50, and the exhaust port 30 is located above the cooling fan 58. As a modification of the second embodiment, the intake port 26 and the carburetor 28 are offset to the right from the axis CL as in the driving unit 130 of the brush cutter of the third embodiment shown in FIG. The exhaust system component 32 may be offset to the left from the axis CL.

  In these second and third embodiments, the exhaust port 30 is opened rearward, but the exhaust port 30 may be opened sideways.

  FIG. 12 shows the driving unit 140 of the brush cutter according to the fourth embodiment. Referring to FIG. 12, in drive unit 140 of the brush cutter according to the fourth embodiment, exhaust port 30 located above cooling fan 58 is opened sideways. As a result, the exhaust system component 32 is positioned at a position offset laterally from the axis CL of the crankshaft 46.

  FIG. 13 shows a driving unit 150 of the brush cutter according to the fifth embodiment. Referring to FIG. 13, the driving unit 150 of the bush cutter of the fifth embodiment is such that the exhaust port 30 located above the cooling fan 58 is offset laterally (rightward in the illustrated example) from the axis CL of the crankshaft 46. Is positioned. Then, one of the left and right scavenging passages 40, 40 is set at a predetermined distance from the exhaust port 30 in relation to the fact that the exhaust port 30 is offset laterally (rightward in the illustrated example) from the axis CL. The left and right scavenging passages 40, 40 are positioned so that the scavenging passage 40 on the right side in the example approaches the intake port 26 and the scavenging passage 40 on the other side (left side in the illustrated example) moves away from the intake port 26.

  In the brush cutter drive unit 150 of the fifth embodiment, the exhaust port 30 is opened sideways, but the exhaust port 30 may be opened rearward.

  FIG. 14 shows a drive unit 160 of a brush cutter according to the sixth embodiment. The drive unit 160 of the sixth embodiment is also a modification of the drive unit 150 of the fifth embodiment described above. Referring to FIG. 14, the driving unit 160 of the brush cutter of the sixth embodiment is such that the intake port 26 located above the centrifugal clutch device 50 is laterally (leftward in the illustrated example) from the axis CL of the crankshaft 46. Positioned offset.

  The present invention can be suitably applied to a working machine having an operation rod extending forward from a drive unit such as a brush cutter, a shaft hedge trimmer, a power pruner, and a lawn edger. The working part arranged at the tip of the operation rod may be a cutter that rotates like a brush cutter, or may be a cutter that reciprocates like a shaft hedge trimmer, or a tip like a power pruner. A working machine with a chain saw attached thereto may be used.

DESCRIPTION OF SYMBOLS 100 Brush cutter of embodiment 2 Drive unit 10 Grip (recoil starter)
12 Fuel tank 16 Cover (part of the air cleaner case)
20 2-cycle internal combustion engine 22 Crank chamber 24 Spark plug 26 Intake port 28 Vaporizer 30 Exhaust port 32 Exhaust system parts such as silencer 34 Cylinder 34A Swelling part (scavenging passage)
36 Scavenging port 38 Combustion chamber 40 Scavenging passage 42 Piston 46 Crankshaft CL Crankshaft axis (axis of power transmission shaft)
50 Centrifugal Clutch Device 52 Clutch Case 54 Operation Rod 58 Cooling Fan 60 Air Cleaner Case 66 Recoil Starter

Claims (10)

A working machine comprising a drive unit including a two-cycle internal combustion engine, wherein the two-cycle internal combustion engine is mounted in an upright posture,
The drive unit is
A centrifugal clutch device connected to a tip of a crankshaft of the engine;
An intake port positioned at the front of a cylinder of the engine when the working machine is viewed in plan,
A carburetor disposed above the centrifugal clutch device, the carburetor connected to the intake port;
An air cleaner disposed in front of or above the vaporizer;
An exhaust port positioned at the rear of the cylinder when the working machine is viewed in plan;
An exhaust system component connected to the exhaust port;
And a scavenging port arranged on the left and right of the axis of the crankshaft when the engine is viewed in plan.   The working machine according to claim 1, wherein the engine is configured such that the intake port, the exhaust port, and the scavenging port are opened and closed by a piston of the engine.   The working machine according to claim 1 or 2, wherein the exhaust port is opened rearward.   The work machine according to claim 1 or 2, wherein the exhaust port is open toward a side.   The work machine according to any one of claims 1 to 4, wherein the engine is a reverse scavenging engine.   2. The engine is a stratified scavenging engine in which fresh air containing no fuel component is first introduced into a combustion chamber of the engine and then an air-fuel mixture is introduced into the combustion chamber in a scavenging stroke. The working machine as described in any one of -4. An operating rod extending forward from the drive unit;
The working machine according to any one of claims 1 to 6, wherein a working unit is disposed at a tip of the operating rod.   The working machine according to claim 7, wherein the working unit is a rotating blade or a reciprocating blade. The driving unit further includes a cooling fan;
The work machine according to any one of claims 1 to 8, wherein the cooling fan is assembled to a rear end portion of the crankshaft.   The working machine according to claim 9, wherein a recoil starter is attached to the rear of the cooling fan.

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