JP2019052593A - Carburetor and portable working machine - Google Patents

Abstract

To reduce an inflow amount of fuel that unintentionally flows into an air intake passage after operation of an engine is stopped.SOLUTION: A carburetor 30 provided in an air intake system 28 of an engine 1 comprises a fuel chamber 50 capable of storing fuel, an air intake passage 43 in which sucked air in the air intake system 28 and fuel from the fuel chamber 50 are mixed, a first passage 69 for leading fuel from a fuel tank 63 to the fuel chamber 50, a priming pump P2 comprising a suction part 71 and a discharge part 72, and a second passage 73 for connecting the fuel chamber 50 and the suction part 71 of the priming pump P2. A first check valve 80 for restraining a back flow of fuel from the side of the suction part 71 of the priming pump P2 to the side of the fuel chamber 50 is provided in the middle of the second passage 73.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a carburetor (carburetor) provided in an intake system of an engine (internal combustion engine), and a portable work machine using an engine provided with the carburetor in the intake system as a drive source.

  The carburetor provided in the intake system of the engine is, for example, a fuel chamber capable of storing fuel, an intake passage in which intake air in the intake system of the engine and fuel from the fuel chamber are mixed, and fuel from a fuel tank. A first passage leading to the chamber; a priming pump including a suction portion and a discharge portion; and a second passage connecting the fuel chamber and the suction portion of the priming pump. Such a carburetor is disclosed in Patent Document 1. In Patent Document 1, a check valve is provided in the suction portion of the priming pump. This check valve is formed at the peripheral edge of the soot valve.

JP 2001-132545 A

  However, in the technique disclosed in Patent Document 1, fuel has unintentionally flowed into the intake passage after the engine is stopped. Therefore, when the engine is restarted, the fuel concentration in the intake mixture becomes excessively high, and the engine cannot be restarted, or even if the engine can be restarted, the fuel concentration in the subsequent intake mixture rapidly increases. However, there were problems such as engine acceleration failure.

  The present inventors diligently investigated these problems and obtained the following knowledge. Even after the engine is stopped, heat from the hot engine is transmitted to the carburetor, and the temperature of the fuel remaining in the carburetor rises. Therefore, the present inventor has found that the pressure of the fuel remaining in the carburetor has increased, and the fuel has unintentionally flowed into the intake passage due to this pressure increase. The present inventor has also found that most of the fuel that unintentionally flows into the intake passage is the fuel remaining in the second passage and the priming pump. Therefore, after the engine is stopped, the fuel remaining in the second passage and the priming pump has unintentionally flowed into the intake passage via the fuel chamber, that is, the second passage and the priming pump. The present inventor found that the fuel remaining in the fuel was unintentionally flowing back toward the fuel chamber. In addition, due to the back flow of the fuel, the check valve (formed at the peripheral portion of the soot valve) provided in the suction portion of the priming pump does not function sufficiently with respect to this back flow. The present inventor found out.

  The present invention has been made in view of such a situation, and an object of the present invention is to reduce the inflow amount of fuel that unintentionally flows into the intake passage after the engine is stopped.

  Therefore, the carburetor according to the present invention is provided in the intake system of the engine. The carburetor according to the present invention includes a fuel chamber capable of storing fuel, an intake passage in which intake air in the intake system and fuel from the fuel chamber are mixed, and a first passage that guides fuel from the fuel tank to the fuel chamber. And a priming pump having a suction part and a discharge part, and a second passage connecting the fuel chamber and the suction part of the priming pump. Here, in the middle of the second passage, a first check valve that suppresses the back flow of fuel from the suction portion side of the priming pump to the fuel chamber side is provided.

  According to the present invention, the first check valve that suppresses the backflow of fuel from the suction portion side of the priming pump to the fuel chamber side is provided in the middle of the second passage connecting the fuel chamber and the suction portion of the priming pump. It has been. As a result, the back flow of fuel in the second passage is suppressed, so that after the operation of the engine is stopped, the fuel remaining in the second passage and the priming pump flows unintentionally into the intake passage via the fuel chamber. Can be suppressed. Therefore, it is possible to reduce the inflow amount of fuel that unintentionally flows into the intake passage after the engine is stopped.

It is a figure which shows the external appearance of the brush cutter which is an example of the portable working machine in 1st Embodiment of this invention. It is a figure which shows schematic structure of the engine in the said 1st Embodiment. It is front sectional drawing of the carburetor in the said 1st Embodiment. It is a figure which shows an example of the 1st check valve provided in the middle of the 2nd channel | path in the said 1st Embodiment. It is front sectional drawing of the carburetor in 2nd Embodiment of this invention. It is a figure which shows an example of the 1st check valve provided in the middle of the 2nd channel | path in the said 2nd Embodiment. It is front sectional drawing of the carburetor in 3rd Embodiment of this invention.

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

  FIG. 1 is a diagram illustrating an appearance of a brush cutter 100 that is an example of a portable work machine according to the first embodiment of the present invention. FIG. 2 is a diagram showing a schematic configuration of an engine (internal combustion engine) 1 in the present embodiment. Here, FIG. 2 shows the engine 1 when the piston 5 is located at the top dead center. In the present embodiment, the upper side substantially coincides with the vertical upper side when the engine 1 is used for the longest time (upright state).

  As shown in FIG. 1, the brush cutter 100 includes an operating rod 102, a power unit 103 provided at the rear end portion of the operating rod 102, and a work tool portion 104 (gear head 104a) provided at the front end portion of the operating rod 102. And a cutting blade 104b), a handle portion 105 attached to an intermediate portion of the operating rod 102, and a grip portion 106 attached to the operating rod 102 in front of the power unit 103.

  The operating rod 102 has a hollow pipe shape and extends linearly. A drive shaft (not shown) is accommodated in the operation rod 102. The drive shaft transmits the output (rotation and torque) of the power unit 103 (specifically, the engine 1) to the gear head 104a of the work tool unit 104, thereby rotating the cutting blade 104b. The grip portion 106 is provided with a lever 106a that is operated to adjust the rotational speed of the power unit 103 (specifically, the engine 1), and thus the cutting blade 104b. The operator usually operates the brush cutter 100 by holding the handle portion 105 with one hand (mainly the left hand) and holding the grip portion 106 with the other hand (mainly the right hand).

  The power unit 103 includes the engine 1. The engine 1 is an OHV (Over Head Valve) type 4-stroke engine (4-cycle engine) and is air-cooled. The engine 1 constitutes a drive source for the brush cutter 100. That is, the work tool unit 104 (particularly the cutting blade 104b) is driven by the engine 1.

  As shown in FIG. 2, the engine 1 includes a cylinder portion 2, a crankcase 3 attached to the lower portion of the cylinder portion 2, and an oil tank 4 provided below the crankcase 3. The cylinder part 2 has a cylindrical space for sliding the piston 5 in the vertical direction in FIG. In this space, the piston 5 is fitted with a gap slidable in the vertical direction in FIG. That is, the cylinder part 2 accommodates the piston 5 so that reciprocation is possible.

  A crank chamber 7 is formed by the cylinder portion 2, the crankcase 3 and the piston 5. That is, the crank chamber 7 is formed by the side surface of the cylinder portion 2 and the cylindrical space on the crankcase 3 side formed by the piston 5 and the space in the crankcase 3. In the crank chamber 7, the volume of the internal space changes as the piston 5 slides.

  A cylinder head 8 is provided on the upper wall of the cylinder portion 2. A combustion chamber 9 is formed by the cylinder head 8, the cylinder part 2 and the piston 5. The oil tank 4 is provided separately from the crankcase 3 and stores oil for lubricating the engine 1. A check valve 10 is provided between the oil tank 4 and the crankcase 3 to allow only the oil flow from the crankcase 3 (crank chamber 7) to the oil tank 4.

  Here, as the piston 5 moves from the bottom dead center to the top dead center, the pressure in the crank chamber 7 becomes negative. Conversely, as the piston 5 moves from top dead center to bottom dead center, the pressure in the crank chamber 7 becomes positive. Therefore, when the pressure in the crank chamber 7 is positive, the check valve 10 is opened, and liquid or mist-like oil flows from the crank chamber 7 to the oil tank 4. On the other hand, the check valve 10 is closed when the pressure in the crank chamber 7 is negative. Therefore, pulsation pressure can be generated in the crank chamber 7 by repeating the positive pressure and the negative pressure in the crank chamber 7 described above.

  A crank 13 is rotatably supported in the crankcase 3. The crank 13 includes a crankshaft 13a serving as a rotation center, a counterweight, and the like. The piston 5 and the crank 13 are connected by a connecting rod 11. The connecting rod 11 and the piston 5 are rotatably connected. The connecting rod 11 and the crank 13 are rotatably connected. With such a configuration, the piston 5 reciprocates in the cylinder portion 2.

  The cylinder head 8 is provided with an intake port 15 and an exhaust port 16. The intake port 15 communicates with a carburetor (vaporizer) 30 via an insulator 20. An air cleaner 25 is provided on the upstream side of the carburetor 30. A filter 26 is disposed in the air cleaner 25. As air passes through the filter 26, dust in the air is removed. Here, the carburetor 30 is provided in the intake system 28 of the engine 1 including the insulator 20 and the air cleaner 25. Therefore, the intake system 28 of the engine 1 includes the insulator 20, the carburetor 30, and the air cleaner 25. The exhaust port 16 communicates with an exhaust muffler (not shown).

  The cylinder head 8 is provided with an intake valve 17 that opens and closes the intake port 15. The cylinder head 8 is provided with an exhaust valve 18 that opens and closes the exhaust port 16. Here, the intake valve 17 and the exhaust valve 18 open and close the combustion chamber 9.

  The insulator 20 is made of, for example, a cylindrical resin. A passage 21 is formed through the insulator 20. The passage 21 guides the air-fuel mixture from the carburetor 30 to the intake port 15.

  The carburetor 30 is a device that generates an air-fuel mixture (intake air mixture) by mixing fuel with air (intake air) that has passed through the air cleaner 25. The carburetor 30 may vaporize liquid fuel to generate an air-fuel mixture. The carburetor 30 can adjust the mixing ratio of air and fuel. The carburetor 30 can adjust the flow rate of the air-fuel mixture. The carburetor 30 includes a diaphragm fuel pump P1 (see FIG. 3) in order to mix the fuel into the intake air. The carburetor 30 further includes a priming pump P2 for forcibly sending fuel into the fuel flow path from the fuel tank 63 shown in FIG. 3 to the fuel chamber 50 of the carburetor 30 when the engine 1 is started. Here, the fuel tank 63 is included in the power unit 103 shown in FIG.

  FIG. 3 is a front sectional view of the carburetor 30 in the present embodiment.

  In the carburetor 30, a rotary throttle valve 34 having a throttle hole 33 is fitted to a cylindrical portion 32 as a valve chamber of the carburetor body 31 so as to be rotatable and movable up and down. A shaft portion 35 at the upper end of the rotary throttle valve 34 is supported by a cover plate 36 that closes the cylindrical portion 32. The cam surface 38 on the lower surface of the throttle lever 37 coupled to the shaft portion 35 is urged and engaged with a ball 39 supported by the cover plate 36 by the force of the return spring 40. The rod valve 41 screwed and supported by the shaft portion 35 is protruded into the throttle hole 33 of the rotary throttle valve 34 and is fitted into the fuel supply pipe 42. 3 constitutes an intake passage 43 of the carburetor 30. In the intake passage 43 (throttle hole 33), intake air from the intake system 28 of the engine 1 and the fuel chamber 50 Fuel can be mixed.

  When the throttle lever 37 is remotely rotated by the lever 106a (see FIG. 1) of the grip portion 106, the opening degree of the throttle hole 33 with respect to the passage 21 (see FIG. 2) changes, and at the same time, together with the rotary throttle valve 34 Then, the rod valve 41 moves up and down, and the opening area of the fuel injection hole 42a of the fuel supply pipe 42 is adjusted. The fuel supply pipe 42 is fitted and supported by a cylindrical portion 44 provided at the bottom center of the cylindrical portion 32. The fuel supply pipe 42 can communicate with a fuel chamber (constant pressure fuel chamber) 50 via a fuel jet 45 and a check valve 46. Here, the fuel chamber 50 can store fuel and is also referred to as a metering chamber.

  The fuel supply mechanism (constant pressure fuel supply mechanism) Q including the fuel chamber 50 constitutes the carburetor 30 and is formed by sandwiching a diaphragm (membrane) 53 between the intermediate wall body 51 and the cover 52. . The diaphragm 53 partitions the fuel chamber 50 and the atmospheric chamber 54. Therefore, a part of the fuel chamber 50 is formed by the diaphragm 53. In the fuel chamber 50, a lever 56 is supported by a support shaft 55. One end of the lever 56 is urged against the projecting piece of the diaphragm 53 by the force of the spring 57. The poppet type inflow valve 58 supported by the other end of the lever 56 is provided on the downstream side of the discharge passage 59 of the fuel pump P1.

  The fuel pump P <b> 1 is formed by sandwiching a diaphragm (membrane) 60 between the carburetor body 31 and the intermediate wall body 51. The diaphragm 60 partitions the pulsation pressure introduction chamber 61 and the pump chamber 62. Here, in the present embodiment, the pulsation pressure introduction chamber 61 communicates with the crank chamber 7 (see FIG. 2) of the engine 1. Therefore, when the pulsation pressure is introduced into the pulsation pressure introduction chamber 61 during the operation of the engine 1 and the diaphragm 60 vibrates up and down, the fuel in the fuel tank 63 passes through the passage 64, the check valve 65, and the passage 66 to the pump chamber. Then, the air is sucked into 62 and further discharged from the pump chamber 62 to the fuel chamber 50 through the check valve 67, the discharge passage 59, the inlet passage 68, and the inflow valve 58. When the fuel is filled in the fuel chamber 50, the diaphragm 53 is lowered, the inflow valve 58 is pushed up by the lever 56, and the downstream end of the inlet passage 68 is closed. In this way, fuel under a constant pressure can be stored in the fuel chamber 50. Here, the first passage 69 of the carburetor 30 includes a passage 64, a check valve 65, a passage 66, a pump chamber 62, a check valve 67, a discharge passage 59, an inlet passage 68, and an inflow valve 58. The first passage 69 guides the fuel from the fuel tank 63 to the fuel chamber 50.

  The priming pump P2 is generally called a primary pump or a primer pump. The priming pump P <b> 2 is located below the fuel chamber 50. The priming pump P <b> 2 has a hemisphere 70. The hemisphere 70 is formed of, for example, an elastic member made of resin, and is formed in a cup shape with an upper surface opening. The hemisphere 70 is provided on the lower surface of the cover 52. The priming pump P2 includes a suction part 71 and a discharge part 72.

  The second passage 73 of the carburetor 30 connects the fuel chamber 50 and the suction part 71 of the priming pump P2. The second passage 73 has passage portions 73a to 73e. The passage portion 73a is formed in the intermediate wall 51 and extends in the horizontal direction. One end portion of the passage portion 73a is connected to the upper portion of the fuel chamber 50, and the other end portion is connected to the upper end portion of the passage portion 73b. The passage portion 73b is formed in the intermediate wall body 51 and extends in the vertical direction. The lower end portion of the passage portion 73b is connected to the upper end portion of the passage portion 73c. The passage portion 73c is formed in the cover 52 and extends in the vertical direction. The lower end portion of the passage portion 73c is connected to one end portion of the passage portion 73d. The passage portion 73d is formed in the cover 52 and extends in the horizontal direction. The other end portion of the passage portion 73d is connected to the upper end portion of the passage portion 73e. The passage portion 73e is formed in the cover 52 and extends in the vertical direction. The lower end portion of the passage portion 73e is connected to the suction portion 71 of the priming pump P2.

  The carburetor 30 has a third passage 75 for returning the fuel discharged from the discharge portion 72 of the priming pump P <b> 2 to the fuel tank 63. The third passage 75 is formed in the cover 52.

  The discharge part 72 of the priming pump P2 is provided with a check valve 76 that suppresses the backflow of fluid (including fuel) from the third passage 75 side to the discharge part 72 side of the priming pump P2. The check valve 76 is, for example, a so-called duck bill type check valve. However, the form of the check valve 76 is not limited to this.

  A first check valve 80 is provided in the middle of the second passage 73. The first check valve 80 allows the flow of fluid (including fuel) from the fuel chamber 50 side to the suction portion 71 side of the priming pump P2, while it flows from the suction portion 71 side of the priming pump P2 to the fuel chamber 50 side. The back flow of fluid (including fuel) is suppressed. The first check valve 80 is provided in the second passage 73 closer to the fuel chamber 50 than the suction portion 71 of the priming pump P2. In other words, the first check valve 80 is provided in the second passage 73 closer to the fuel chamber 50 than the intermediate position between the fuel chamber 50 and the suction portion 71 of the priming pump P2. The first check valve 80 may be disposed adjacent to the fuel chamber 50 in the second passage 73.

  In the present embodiment, the first check valve 80 is provided at the other end of the passage portion 73 a of the second passage 73. In other words, the first check valve 80 is provided in a portion extending in the horizontal direction in the middle of the second passage 73.

  FIG. 4 is a diagram illustrating an example of the first check valve 80 in the present embodiment. Here, FIG. 4 corresponds to the region α in FIG. FIG. 4 shows the closed state of the first check valve 80.

  A ball 99 is press-fitted into the hole 98 on the outer surface side of the intermediate wall 51 so as to close the hole 98 formed when the passage portion 73a is formed.

  The first check valve 80 provided at the other end of the passage portion 73a is a so-called disc type check valve. The first check valve 80 includes a cylindrical valve casing 81, a disk-shaped (disk-shaped) valve body 85, and an urging member 86. The valve casing 81 has an inlet portion 82, an outlet portion 83, and an annular valve seat 84. The annular valve seat 84 is disposed between the inlet portion 82 and the outlet portion 83. The valve body 85 is disposed on the outlet portion 83 side of the annular valve seat 84. The urging member 86 is disposed on the outlet 83 side of the valve body 85. The biasing member 86 is a spring member, for example, and biases the valve body 85 toward the annular valve seat 84. In other words, the urging member 86 urges the valve body 85 in the valve closing direction. In the first check valve 80, the outer periphery of the valve body 85 is guided in sliding contact with the inner peripheral wall of the valve casing 81. In the first check valve 80, a gap through which fluid (including fuel) can pass is provided between the outer periphery of the valve body 85 and the inner peripheral wall of the valve casing 81.

  4 shows an example in which the first check valve 80 is a so-called disk type check valve, the configuration of the first check valve 80 is not limited to this. The first check valve 80 may be a duckbill type check valve, for example. Alternatively, the first check valve 80 may be a so-called ball check valve having a ball-shaped valve body instead of the disc-shaped valve body 85.

  Returning to FIG. 3, the fuel chamber 50 passes through the second passage 73 provided with the first check valve 80, the inner space 70 a of the hemisphere 70 of the priming pump P <b> 2, the check valve 76, and the third passage 75. The fuel tank 63 communicates.

  When the operator crushes the hemispherical body 70 of the priming pump P2 when the engine 1 is started and further restores it, the first check valve 80 opens the second passage 73 as the volume of the hemispherical body 70 increases. The fluid (including the fuel) in the second passage 73 and the fuel chamber 50 flows into the hemisphere 70. Then, when the operator next crushes the hemisphere 70, the first check valve 80 closes the second passage 73, and the check valve 76 opens the third passage 75, so that the inside of the hemisphere 70 The fluid (including fuel) is returned to the fuel tank 63. By repeating such an operation, a negative pressure develops in the fuel chamber 50, and fuel is supplied from the fuel tank 63 to the fuel chamber 50 through the first passage 69 described above.

  According to the present embodiment, the carburetor 30 provided in the intake system 28 of the engine 1 includes a fuel chamber 50 that can store fuel, and an intake passage in which intake air in the intake system 28 and fuel from the fuel chamber 50 are mixed. 43, the first passage 69 for guiding the fuel from the fuel tank 63 to the fuel chamber 50, the priming pump P2 including the suction portion 71 and the discharge portion 72, and the fuel chamber 50 and the suction portion 71 of the priming pump P2 are connected. A second passage 73. In the middle of the second passage 73, a first check valve 80 that suppresses the backflow of fuel from the suction portion 71 side of the priming pump P2 to the fuel chamber 50 side is provided. As a result, the backflow of fuel in the second passage 73 is suppressed, so that after the operation of the engine 1 is stopped, the fuel remaining in the second passage 73 and the priming pump P2 is intended to the intake passage 43 via the fuel chamber 50. It is possible to suppress inflow without. Accordingly, it is possible to reduce the inflow amount of fuel that unintentionally flows into the intake passage 43 after the operation of the engine 1 is stopped.

  According to the present embodiment, the first check valve 80 is provided in the second passage 73 closer to the fuel chamber 50 than the suction portion 71 of the priming pump P2. Therefore, it is possible to reliably block the fuel from flowing backward from the second passage 73 side to the fuel chamber 50 side at a position relatively close to the fuel chamber 50.

  Further, in the present embodiment, a part of the fuel chamber 50 is formed by a diaphragm 53 (metal ring diaphragm). Thereby, the fuel chamber 50 (metering chamber) can be formed with a simple configuration.

  According to the present embodiment, the engine 1 is a 4-stroke engine. Therefore, in the carburetor 30 that may be hotter than the carburetor provided in the two-stroke engine, it is possible to reduce the inflow amount of the fuel that unintentionally flows into the intake passage 43 after the operation of the engine 1 is stopped.

  Moreover, according to this embodiment, the brush cutter 100 which is an example of a portable work machine includes the carburetor 30. Therefore, in the brush cutter 100, it is possible to reduce the inflow amount of fuel that unintentionally flows into the intake passage 43 of the carburetor 30 after the operation of the engine 1 is stopped.

  FIG. 5 is a front sectional view of the carburetor 30 according to the second embodiment of the present invention. Differences from the first embodiment will be described.

  In the present embodiment, a first check valve 80 ′ is provided in the middle of the second passage 73. The first check valve 80 ′ allows the flow of fluid (including fuel) from the fuel chamber 50 side to the suction portion 71 side of the priming pump P2, while the first check valve 80 ′ from the suction portion 71 side of the priming pump P2 to the fuel chamber 50 side. Prevents backflow of fluid (including fuel) into The first check valve 80 ′ is provided in the second passage 73 closer to the fuel chamber 50 than the suction part 71 of the priming pump P <b> 2. In other words, the first check valve 80 ′ is provided in the second passage 73 closer to the fuel chamber 50 than the intermediate position between the fuel chamber 50 and the suction portion 71 of the priming pump P <b> 2.

  In the present embodiment, the first check valve 80 ′ is provided at the upper end portion of the passage portion 73 c of the second passage 73. In other words, the first check valve 80 ′ is provided in a portion extending in the vertical direction in the middle of the second passage 73.

  FIG. 6 is a diagram illustrating an example of the first check valve 80 ′ in the present embodiment. Here, FIG. 6 corresponds to the region β in FIG. FIG. 6 shows the opened state of the first check valve 80 '.

  The first check valve 80 'provided at the upper end of the passage portion 73c is a so-called disc type check valve. The first check valve 80 ′ has a stopper member 88 instead of the biasing member 86 in the first check valve 80 described above. Therefore, the first check valve 80 ′ includes the valve casing 81 having the inlet portion 82, the outlet portion 83, and the annular valve seat 84, the valve body 85, and the stopper member 88. The stopper member 88 is disposed on the outlet portion 83 side of the valve body 85. In the first check valve 80 ′, the valve body 85 can be raised and lowered between the annular valve seat 84 and the stopper member 88. Here, the valve body 85 is preferably formed of, for example, a resin film in order to reduce its own weight.

  In the first check valve 80 ′, when the pressure of fluid (including oil) that can raise the valve body 85 acts on the valve body 85, the valve body 85 rises and the valve body 85 contacts the annular valve seat 84. Touch. This state is a closed state of the first check valve 80 '. On the other hand, in the first check valve 80 ′, when the pressure of the fluid (including oil) that can raise the valve body 85 does not act on the valve body 85, the valve body 85 moves away from the annular valve seat 84, and the valve The body 85 is lowered by its own weight, or the valve body 85 is placed on the stopper member 88. This state is the open state of the first check valve 80 '.

  In particular, according to the present embodiment, the first check valve 80 ′ is provided in a portion extending in the vertical direction in the middle of the second passage 73. As a result, the valve body 85 of the first check valve 80 ′ can be lowered by its own weight. Therefore, the first check valve 80 having a simple configuration in which the urging member 86 (see FIG. 4) that repeats the expansion and contraction operation is omitted. 'Can be used.

  FIG. 6 shows an example in which the first check valve 80 ′ is a so-called disk type check valve, but the configuration of the first check valve 80 ′ is not limited to this. The first check valve 80 'may be a duckbill type check valve, for example. Alternatively, the first check valve 80 ′ may be a so-called ball type check valve having a ball-shaped valve body instead of the disk-shaped valve body 85. The first check valve 80 ′ may include a biasing member 86 instead of the stopper member 88. That is, the first check valve 80 ′ may have the same configuration as the first check valve 80.

  FIG. 7 is a front sectional view of the carburetor 30 according to the third embodiment of the present invention. Differences from the second embodiment will be described.

  In the present embodiment, the check valve 76 is formed on the shaft portion of the umbrella-type valve (saddle valve) 77. Further, a second check valve 78 is formed at the umbrella portion (peripheral portion) of the umbrella valve 77. Here, the umbrella valve 77 has flexibility.

  The second check valve 78 is provided in the suction part 71 of the priming pump P2. The second check valve 78 allows the flow of fluid (including fuel) from the second passage 73 side to the suction portion 71 side of the priming pump P2, while the second passage 73 from the suction portion 71 side of the priming pump P2. Suppresses backflow of fluid (including fuel) to the side. In the present embodiment, the first check valve 80 ′ has a higher fuel backflow suppression capability than the second check valve 78.

  In particular, according to the present embodiment, the carburetor 30 is provided in the suction portion 71 of the priming pump P2, and the second check that suppresses the backflow of fuel from the suction portion 71 side of the priming pump P2 to the second passage 73 side. It has a valve 78. Thereby, the backflow of fuel in the second passage 73 can be reliably suppressed by the first check valve 80 ′ and the second check valve 78. Further, when the engine 1 is started (when the priming pump P2 is used), the backflow of fuel from the suction portion 71 side of the priming pump P2 to the second passage 73 side is mainly suppressed by the second check valve 78. Therefore, it is possible to reduce the burden on the first check valve 80 ′ when the engine 1 is started (when the priming pump P2 is used), and to achieve a long life.

  In the first embodiment described above, the check valve 76 is formed on the shaft portion of the umbrella-type valve 77 and the second check valve 78 is formed on the umbrella portion of the umbrella-type valve 77 as in the present embodiment. It goes without saying that it may be done.

  In the first to third embodiments described above, the brush cutter is used as an example of the portable work machine in the present invention. However, the portable work machine is not limited to the brush cutter. For example, it may be a portable working machine such as a digging machine, a concrete cutter, a blower working machine, or a sprayer (sprayer).

  As can be seen from the foregoing, the foregoing embodiments are merely illustrative of the present invention, and the present invention is made by those skilled in the art within the scope of the claims in addition to those directly shown by the described embodiments. Needless to say, it includes various improvements and changes.

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder part, 3 ... Crankcase, 4 ... Oil tank, 5 ... Piston, 7 ... Crank chamber, 8 ... Cylinder head, 9 ... Combustion chamber, 10 ... Check valve, 11 ... Connecting rod, 13 ... Crank, 13a ... Crankshaft, 15 ... Intake port, 16 ... Exhaust port, 17 ... Intake valve, 18 ... Exhaust valve, 20 ... Insulator, 21 ... Passage, 25 ... Air cleaner, 26 ... Filter, 28 ... Intake system, 30 Carburetor, 31 carburetor body, 32 cylindrical portion, 33 throttle hole, 34 rotary throttle valve, 35 shaft portion, 36 lid plate, 37 throttle lever, 38 cam surface, 39 ball, 40 Return spring 41 ... Rod valve 42 ... Fuel supply pipe 42a ... Fuel injection hole 43 ... Intake passage 44 ... Cylindrical part 45 ... Fuel jet 46 ... Check , 50 ... Fuel chamber, 51 ... Intermediate wall, 52 ... Cover, 53 ... Diaphragm, 54 ... Air chamber, 55 ... Support shaft, 56 ... Lever, 57 ... Spring, 58 ... Inlet valve, 59 ... Discharge passage, 60 ... Diaphragm, 61 ... Pulsation pressure introduction chamber, 62 ... Pump chamber, 63 ... Fuel tank, 64 ... Passage, 65 ... Check valve, 66 ... Passage, 67 ... Check valve, 68 ... Inlet passage, 69 ... First passage, 70 ... Hemisphere, 70a ... Inner space, 71 ... Suction part, 72 ... Discharge part, 73 ... Second passage, 73a to 73e ... Passage part, 75 ... Third passage, 76 ... Check valve, 77 ... Umbrella type Valve, 78 ... Second check valve, 80, 80 '... First check valve, 81 ... Valve casing, 82 ... Inlet part, 83 ... Outlet part, 84 ... Annular valve seat, 85 ... Valve body, 86 ... With 88 ... Stopper member, 98 ... Hole, 99 ... Ball, 100 ... Brush cutter, 102 ... Operating rod 103 ... power unit, 104 ... power tool unit, 104a ... gearhead, 104b ... cutting blade, 105 ... handle section, 106 ... grip portion, 106a ... lever, P1 ... fuel pump, P2 ... priming pump, Q ... fuel supply mechanism

Claims (6)

A carburetor provided in the intake system of the engine,
A fuel chamber capable of storing fuel;
An intake passage in which intake air in the intake system and fuel from the fuel chamber are mixed;
A first passage for guiding fuel from a fuel tank to the fuel chamber;
A priming pump comprising a suction part and a discharge part;
A second passage connecting the fuel chamber and the suction portion of the priming pump;
Have
A carburetor provided with a first check valve for suppressing a back flow of fuel from the suction portion side of the priming pump to the fuel chamber side in the middle of the second passage.   2. The carburetor according to claim 1, wherein the first check valve is provided in a side closer to the fuel chamber than an inlet of the priming pump in the second passage.   The first check valve according to claim 1, further comprising a second check valve that is provided in the suction portion of the priming pump and suppresses a back flow of fuel from the suction portion side of the priming pump to the second passage side. Carburetor.   The carburetor according to any one of claims 1 to 3, wherein a part of the fuel chamber is formed of a diaphragm.   The carburetor according to any one of claims 1 to 4, wherein the engine is a four-stroke engine.   A portable working machine comprising the carburetor according to any one of claims 1 to 5.