JP2007315254A - Fuel-air mixture generating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel-air mixture generating device which is able to unfailingly supply the required amount of fuel at a time of starting even in an engine which has small manifold vacuum, keeping the cost of the device low and without complicating the device configuration. <P>SOLUTION: The fuel-air mixture generating device comprises diaphragm-type fuel pump 14, which intakes fuel in response to the pressure change in a crankcase of internal-combustion engine and discharges it to fuel path 25, fuel injection valve 30 for injecting and supplying fuel in the fuel path 25 at a prescribed timing to air intake system of the internal-combustion engine, and manual fuel pump 40 for supplying and filling fuel to the fuel path 25 when the diaphragm-type fuel pump 14 is not operated. Valve opening pressure of either the manual pump inlet valve 44 or discharge valve 43 is set higher than the injection pressure required at a time of starting and a needle valve 85 is disposed on a downstream side of the fuel injection valve 30 in the fuel path 25 as a means to limit the amount of fuel returning to fuel tank 81. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an air-fuel mixture generating apparatus including a diaphragm fuel pump, a fuel injection valve, and a manual fuel pump, and more particularly, a crankcase precompression air-cooled two-cycle gasoline engine mounted on a portable work machine or the like. The present invention relates to an air-fuel mixture generating apparatus suitable for use in an intake system.

  In place of a conventional general carburetor in the intake system of a crankcase precompression type small air-cooled two-cycle gasoline engine (hereinafter simply referred to as an engine) mounted on a portable work machine such as a chainsaw or a brush cutter, It is known to incorporate an air-fuel mixture generator that includes a diaphragm fuel pump, a fuel injection valve, and a manual fuel pump.

  An example of such an air-fuel mixture generator will be briefly described below with reference to FIGS. 3 and 4 (see also Patent Document 1 below).

  The illustrated example of the air-fuel mixture generating apparatus 10 ′ is a diaphragm type fuel that draws fuel and discharges it to the fuel passage section 25 in response to a pressure change in the crank chamber 56 of the crankcase precompression type small air-cooled two-cycle internal combustion engine 50. A fuel injection valve 30 for injecting and supplying the fuel in the fuel passage 25 to the intake system 5 of the internal combustion engine 50 at a predetermined timing into the main body 12 having the pump 14, and the non-diaphragm type fuel pump 14. A manual fuel pump 40 for supplying and filling fuel to the fuel passage portion 25 during driving is provided. The fuel passage portion 25 communicates with the suction port 42 of the manual fuel pump 40, and the suction port 42 is connected to the suction port 42. When the manual fuel pump 40 is operated, it functions as an intake valve. When the fuel pressure in the fuel passage 25 is equal to or higher than a predetermined pressure, the fuel in the fuel passage 25 is manually removed. Pressure regulating valve 44 acts as a relief valve for releasing the manual pump chamber 40A of the fuel pump 40 'is arranged.

  The diaphragm fuel pump 14 includes a diaphragm 15 disposed in the main body 12, a pulse pressure chamber 21 provided on one surface side of the diaphragm 15 to which a pulse pressure of the crank chamber 56 is transmitted, a fuel And a pulse pressure pump chamber 22 provided on the other surface side of the diaphragm 15.

  Further, the suction valve 16 and the discharge are respectively provided at a boundary portion between the pulse pressure pump chamber 22 and the fuel suction passage portion 24 and a boundary portion between the pulse pressure pump chamber 22 and the fuel passage portion 25 in the diaphragm fuel pump 14. A valve 17 is provided, and the relief port 43 of the manual fuel pump 40 is closed when the pressure in the manual pump chamber 40A is lower than a predetermined pressure, and is opened when the pressure is higher than the low pressure. 'Is arranged.

  An injection port 36 of the fuel injection valve 30 is disposed in a throat portion 13 a provided on the downstream side of the throttle valve 18 of the intake passage 13 in the internal combustion engine 50.

  In the air-fuel mixture generating apparatus 10 configured as described above, the manual pump chamber 40A of the manual fuel pump 40 is used as a start preparation operation before starting the internal combustion engine 50 in which the diaphragm fuel pump 14 is not driven. The pump is operated several times by pressing it with your fingers and releasing it to restore it. By the pump operation, the pressure regulating valve 44 'and the relief valve 43' act as a suction valve and a discharge valve, respectively, and perform a pump function.

  That is, when the manual pump chamber 40A is pressed, the internal volume of the manual pump chamber 40A is compressed, the pressure regulating valve 44 'closes the suction port 42 (the upper opening 42a thereof), and the relief valve 43'. Opens the relief port 41 (lower opening 41a), and air A and fuel F in the manual pump chamber 40A are returned from the relief port 41 to the fuel tank 81 through the relief passage portion 49 and released. When this occurs, the manual pump chamber 40A is restored to its original hemispherical shape by its own elastic force. At this time, the relief valve 43 'closes the relief port 41 (lower opening 41a). The pressure valve 44 'opens the suction port 42 (the upper opening 42a thereof).

  At that time, due to the suction force (negative pressure) generated when the manual pump chamber 40A is restored, the fuel F in the fuel tank 81 is allowed to flow into the fuel suction passage 24, the pulse pressure pump chamber 22, and the discharge side flap valve 17. The fuel passage portion 25 (26 to 29) is supplied and filled through the fuel tank 25 and the plunger 37 of the fuel injection valve 30 is also filled.

  In this state, when the internal combustion engine 50 is started by operating a recoil starter or the like, the fuel injection valve 30 opens at a predetermined timing (for example, at the start of the intake stroke), and the fuel in the fuel passage portion 25 passes through the intake passage 13. The fuel F is mixed in the intake air A and is supplied from the injection port 36 disposed in the throat portion 13a on the downstream side of the throttle valve 18, and the crank chamber 56 and the combustion are mixed. The air-fuel mixture is supplied to the working chamber 53, and the air-fuel mixture is ignited by the spark plug 59, explosively burned, and enters a normal operation state in which it can rotate by itself.

  During normal operation after start-up, the pressure change (pulse pressure) in the crank chamber 56, that is, the pressure change that is reduced when the piston 54 is raised and pressurized when the piston 55 is lowered is the pressure change of the diaphragm fuel pump 14. This is transmitted to the pulse pressure chamber 21, whereby the diaphragm 15 reciprocates (up and down), and the fuel F is sucked into the pulse pressure pump chamber 22 from the fuel tank 81 by the pumping action caused by the vertical movement of the diaphragm 15. At the same time, the fuel F is sent from the pulse pressure pump chamber 22 to the fuel passage portion 25 (26 to 29), and the fuel F in the fuel passage portion 25 is added while the injection port 36 is closed. Pressed. During this normal operation, the fuel injection valve 30 is opened for a predetermined period of time (for example, 1 to 3 milliseconds) according to the operating state such as the intake air amount of the engine 50, thereby increasing the pressure in the fuel passage portion 25. The pressurized fuel F is injected and supplied to the downstream side of the throttle valve 18 of the intake passage 13, and the fuel F is mixed with the intake air A.

  In this case, when the internal combustion engine 50 is in a high-speed rotation state, the fuel discharge amount of the diaphragm fuel pump 14 increases and the pressure of the fuel F in the fuel passage portion 25 increases, but the fuel passage portion When the pressure of the fuel F in the fuel tank 25 becomes equal to or higher than a predetermined pressure (for example, 0.05 MPa), the pressure regulating valve 44 disposed in the suction port 42 of the manual fuel pump 40 opens the upper opening 42a. The fuel F in the fuel passage portion 25 is released to the manual pump chamber 40A of the manual fuel pump 40 via the pump side communication portion 27b, and the pressure in the manual pump chamber 40A is equal to or higher than a predetermined pressure. Then, the relief valve 43 disposed in the relief port 41 opens the lower opening 41a, and the fuel F in the manual pump chamber 40A is returned to the fuel tank 81.

As a result, the pressure (maximum value) of the fuel F in the fuel passage portion 25 is suppressed to approximately the predetermined pressure or less, and as a result, the fuel F is excessively injected from the fuel injection valve 30. Thus, it is possible to prevent a situation in which a rich air-fuel mixture is supplied to the combustion operation chamber 53 of the internal combustion engine 50.
JP 2001-193610 A

  However, it has been clarified that the conventional air-fuel mixture generating apparatus 10 'has the following problems.

  That is, in the air-fuel mixture generating apparatus 10 ′, the manual fuel pump 40 is disposed on the fuel return side (downstream from the fuel injection valve 30), so that the pressure regulating valve (manual pump intake valve) 44 ′ is opened. The valve pressure (negative pressure) substantially becomes the injection pressure (pressure of fuel in the fuel passage portion 25). That is, even if the pump operation by the manual fuel pump 40 is performed several times as a start preparation operation, the fuel sucked into the manual pump chamber 40A through the pressure regulating valve 44 ′ is supplied to the fuel tank 81 through the relief valve 43 ′. Since the pressure is returned, the injection pressure becomes atmospheric pressure or less. Therefore, even if an attempt is made to start the internal combustion engine 50 by operating a recoil starter or the like after the start preparation operation, only an amount of fuel corresponding to the intake negative pressure of the engine is injected from the fuel injection valve 30. Since the intake negative pressure of the engine is small, as a result, the fuel supply amount tends to be insufficient at the time of starting, and the engine cannot be started smoothly.

  The present invention has been made in view of the above-described problems, and its object is to provide a diaphragm fuel pump, a fuel injection valve, and a manual fuel pump without complicating the device configuration. An object of the present invention is to provide an air-fuel mixture generating device that can reliably supply a required amount of fuel at the start without depending on the negative suction pressure of the engine while keeping the device cost low.

  In order to achieve the above object, an air-fuel mixture generating apparatus according to the present invention basically includes a diaphragm type fuel pump that sucks fuel and discharges it to a fuel passage in response to a pressure change in a crank chamber of an internal combustion engine. A fuel injection valve for injecting and supplying fuel in the fuel passage portion to the intake system of the internal combustion engine at a predetermined timing, and for supplying and filling the fuel passage portion with fuel when the diaphragm fuel pump is not driven Equipped with a manual fuel pump.

  In addition, a suction port provided with a manual pump suction valve and a discharge port provided with a manual pump discharge valve communicate with the pulse pressure pump chamber of the diaphragm fuel pump, and the manual pump suction valve and the discharge port are provided. The opening pressure of any one of the valves is set higher than the injection pressure required at the time of starting, and the return that limits the amount of fuel returned to the fuel tank downstream from the fuel injection valve in the fuel passage portion It is characterized in that a quantity limiting means is provided.

  The return amount limiting means is preferably constituted by a throttle member such as a needle valve that narrows the effective passage cross-sectional area of the fuel passage portion.

  In a preferred aspect of the present invention, a suction valve and a discharge valve are respectively provided at a boundary portion between the pulse pressure pump chamber and the fuel suction passage portion and a boundary portion between the pulse pressure pump chamber and the fuel passage portion in the diaphragm fuel pump. Is disposed.

  In another preferred embodiment, the internal combustion engine is a crankcase precompression air-cooled two-cycle gasoline engine, and an intake throttle portion provided downstream of the throttle valve in the intake passage of the internal combustion engine is provided with the fuel injection valve. An injection port is distributed.

  In a preferable aspect of the air-fuel mixture generating apparatus according to the present invention having such a configuration, when the manual fuel pump is operated before starting, the manual pump suction valve and the discharge valve are respectively opened and closed in opposite phases, and the fuel is generated. The fuel in the tank is sucked into the manual pump chamber through the fuel suction passage, the pulse pressure pump chamber of the diaphragm fuel pump, and the manual pump suction valve, and the fuel in the manual pump chamber is pulsed through the manual pump discharge valve. It is discharged into the pressure pump chamber.

  In this case, the valve opening pressure of either the manual pump suction valve or the discharge valve is set higher than the injection pressure required at the time of start-up, and the fuel tank is provided downstream of the fuel injection valve to the fuel tank. Since the return amount limiting means for limiting the fuel return amount is provided, by operating the manual fuel pump, the pressure on the upstream side of the portion where the return amount limiting means is provided in the fuel passage, that is, The injection pressure is increased and adjusted to the injection pressure value required at the start.

  In this state, when the internal combustion engine is started by operating a recoil starter or the like, the fuel injection valve is opened at a predetermined timing (for example, at the start of the intake stroke), and the fuel in the fuel passage portion is taken into the intake system (for example, the intake passage). The fuel is mixed into the intake air at an appropriate ratio and supplied to the crank chamber and the combustion working chamber of the internal combustion engine. It is ignited by the spark plug and burned explosively, and enters a normal operation state in which autonomous rotation is possible.

  During normal operation after startup, the crank chamber pressure change (pulse pressure), that is, the pressure change is reduced when the piston is raised, and the pressure change when the piston is lowered is transmitted to the pulse pressure chamber of the diaphragm fuel pump. The diaphragm is driven (reciprocating), and fuel is sucked into the pulse pressure pump chamber from the fuel tank and pumped into the fuel passage portion from the fuel tank by the pump action by the vertical movement of the diaphragm. Thus, the fuel in the fuel passage is pressurized. During this normal operation, the fuel injection valve is opened for a predetermined period (for example, 1 to 3 milliseconds) according to the operation state such as the intake air amount of the engine, whereby the pressurized fuel in the fuel passage section is opened. Is injected into the intake system, and fuel is mixed with the intake air.

  In the air-fuel mixture generating apparatus according to the present invention, the valve opening pressure of either the manual pump suction valve or the discharge valve is set higher than the injection pressure required at the start, and more than the fuel injection valve in the fuel passage section. Since the return amount limiting means for limiting the fuel return amount to the fuel tank is provided on the downstream side, the operation of the manual fuel pump causes the upstream of the portion where the return amount limiting means is provided in the fuel passage portion. Side pressure, that is, the injection pressure is gradually increased and is eventually adjusted to the injection pressure value required at the time of starting, so that the required amount of fuel can be reliably supplied at the time of starting without depending on the negative suction pressure of the engine. .

  In addition, when fuel is supplied by a diaphragm fuel pump and a fuel injection valve, the opening pressure of any of the suction valve and the discharge valve that is always provided in the essential manual fuel pump is set higher than the required injection pressure. Since the return amount limiting means only needs to be constituted by an inexpensive member such as a needle valve, it is not necessary to newly incorporate a pressure regulating valve, a fuel pressure regulator, etc., and no other modification is required. Therefore, the apparatus configuration is not complicated and the apparatus cost can be suppressed.

  Further, since the fuel supply amount is adjusted by the fuel injection valve, it is possible to control the fuel supply amount with respect to the intake air with higher accuracy than the conventional diaphragm type carburetor. In addition to the advantages that the gasification action, responsiveness, etc. can be improved, and it is possible to effectively take measures for exhaust gas purification, etc., it is structurally a diaphragm except that the fuel supply part is a fuel injection valve. Since it can be made substantially the same as the type carburetor, it can be easily incorporated in a conventional internal combustion engine instead of the carburetor.

  Hereinafter, an embodiment of an air-fuel mixture generator of the present invention will be described with reference to the drawings.

  FIG. 1 is a longitudinal sectional view showing an embodiment of an air-fuel mixture generating apparatus according to the present invention.

  The air-fuel mixture generating apparatus 10 of the illustrated embodiment is incorporated into the intake system 5 of the engine 50 shown in FIG. 3 in the same manner as the conventional air-fuel mixture generating apparatus 10 ′ shown in FIG. 4 described above. In the air-fuel mixture generating apparatus 10 shown in FIG. 1, the same reference numerals are given to the parts having the same constituent functions as those of the conventional air-fuel mixture generating apparatus 10 ′ shown in FIG. .

  The engine 50 is a crank chamber pre-compression type small air-cooled two-cycle gasoline engine mounted on a portable work machine such as a brush cutter, and its structure is well known. To do.

  The engine 50 includes a cylinder 52 in which a piston 54 is slidably inserted in a vertical direction, and a crankcase 55 connected to the lower side of the cylinder 52 to form a crank chamber 56 therein. A number of cooling fins 58 are formed on the outer periphery of 52, and a spark plug 59 is attached to the top (combustion chamber 53 a) of the combustion working chamber 53 above the piston 54 in the cylinder 52.

  The crank chamber 56 has a sealed short cylindrical shape, and a crankshaft 60 is pivotally supported at the center of its left and right ends. The piston 54 is connected to the crankpin 71 of the crankshaft 60 via a connecting rod 72. A crank web 74 is fixed to the left and right of the crank pin 71 so as to be pivotally connected and sandwich the connecting rod 72.

  An exhaust port 62 is formed in the cylinder 52 in a direction perpendicular to the axis of the crankshaft 60, and an intake port 63 is formed in a step-down state facing the exhaust port 62 (position shifted by 180 degrees). Then, a pair of scavenging scavenging ports 65, 65 are formed at the left and right side positions shifted 90 degrees from the exhaust port 62 and the intake port 63, and the pair of scavenging ports 65, 65 are connected to the cylinder 52. It is formed at the upper end of a scavenging passage 64 that extends downward and communicates with the crank chamber 56.

  In addition, an intake system 5 that forms an intake passage 13 in which the air-fuel mixture generator 10 and the air cleaner 6 according to an embodiment of the present invention are incorporated is disposed on the intake port 63 side via a heat insulator 67. A muffler 69 with an exhaust gas purification function is disposed on the exhaust port 62 side. The intake passage 13 includes a throttle passage portion 13A of the air-fuel mixture generating device 10 portion and a passage portion 13B of the heat insulator 67 portion, and is upstream of the throttle passage portion 13A in the air-fuel mixture generating device 10. On the side, an idle automatic return type throttle valve 18 is arranged. 3 is an adjusting screw for regulating the idle speed of the engine 50 by regulating the minimum opening of the throttle valve 18.

  The air-fuel mixture generation apparatus 10 of the present embodiment draws fuel F from a fuel tank 81 with a breather 82 in response to a pressure change (pulse pressure) in the crank chamber 56 of the internal combustion engine 50 and enters the fuel passage portion 25. It has a main body portion 12 having a diaphragm-type fuel pump 14 for discharging and having an appearance similar to that of a conventional diaphragm type carburetor. The fuel passage is provided in the throat portion 13a of the throttle passage portion 13A in the main body portion 12. A fuel injection valve 30 is provided for injecting and supplying the fuel F supplied and filled in the portion 25 to the downstream side of the throttle valve 18 in the intake passage 13 at a predetermined timing. Contrary to the conventional one, a manual fuel pump 40 is provided for sucking and filling the fuel F into the fuel passage 25 when the diaphragm fuel pump 14 is not driven. It has been.

  The diaphragm fuel pump 14 is made of nylon (trade name), which is held and fixed between a pulse pressure pump chamber forming member 14A, and the pulse pressure pump chamber forming member 14A and the upper end surface of the main body 12. Or the diaphragm 15 of the structure which affixed the rubber | gum on the sheet | seat made from a Teflon (trade name), and the pulse pressure of the said crank chamber 56 including the conduit | pipe 20A (refer also FIG. 3) was installed in the said main-body part 12 sideways. The fuel F is sucked from the fuel tank 81 through the fuel suction passage 24 including the suction conduit 24A and the pulse pressure chamber 21 provided on the lower surface side of the diaphragm 15 and transmitted through the passage 20. It comprises a pulse pressure pump chamber 22 provided on the upper surface side of the diaphragm 15 that is discharged to the fuel passage portion 25.

  The diaphragm 15 has a boundary portion between the pulse pressure pump chamber 22 and the fuel suction passage portion 24 and a boundary portion between the pulse pressure pump chamber 22 and the fuel passage portion 25 (passage portion 26) in the diaphragm 15, respectively. A flap valve 16 serving as a suction valve and a flap valve 17 serving as a discharge valve, which are formed by making a U-shaped cut into the valve, are provided.

  The fuel injection valve 30 is of an electromagnetic drive type, and includes a cylindrical housing 31, a field coil 32, a stator (attractor) 33, and a stepped plunger (valve element) having a conical surface at the tip (lower end). 37), a valve seat 35 having an injection port 36 opened and closed by the plunger 37, a compression coil spring 38 interposed between the stator 33 and the plunger 37, etc. In the intake passage 13, the throttle passage portion 13 </ b> A is opened to the throat portion 13 a on the downstream side of the throttle valve 18.

  In the fuel injection valve 30, a pulse signal having a pulse width (duty ratio) corresponding to an operating state such as the rotational speed, load, vibration, temperature, etc. of the internal combustion engine 50 is applied to the field coil 32. A period corresponding to the pulse width (energization excitation period) is supplied from an automatic control device (MP) 80 such as a microprocessor with predetermined timing (for example, at the start of the suction stroke) to energize and excite the field coil 32. Therefore, the fuel injection amount is adjusted by lifting the plunger 37 against the biasing force of the coil spring 38 and opening the injection port 36. For example, during the intake stroke, the fuel injection amount can also be adjusted by supplying constant width pulses in the number corresponding to the operating state of the internal combustion engine 50 at a predetermined interval.

  The fuel passage portion 25 communicates with the pulse pressure pump chamber 22 via the discharge side flap valve 17 and communicates with the upstream passage portion 26 via the communication portion 26a. An annular fuel reservoir 28 formed around the valve seat 35 of the fuel injection valve 30 communicated with the injection port 36 via the injection valve side communication portion 29 and the plunger 37, and communicated with the fuel reservoir 28 It consists of a downstream passage portion 27 and the like communicating with each other via a portion 27a. Further, the downstream passage portion 27 and the fuel tank 81 are connected by a return passage portion 84 including a nipple 86, a conduit 87, and the like.

  In the present embodiment, as the return amount limiting means for limiting the fuel return amount to the fuel tank 81 in the downstream passage portion 27 downstream of the fuel injection valve 30 in the fuel passage portion 25, the downstream side A needle valve 85 is disposed so as to narrow the effective passage sectional area of the passage portion 27. The needle valve 85 has an adjustment male thread portion 85a and a conical end portion 85b, and the main body portion 12 is formed so as to form a predetermined throttle portion (orifice) in cooperation with the end conical opening 86a of the nipple 86. Is screwed sideways from the side opposite to the return passage portion 84, and by adjusting the screwing amount, the fuel return amount to the fuel tank 81, in other words, the injection pressure (the fuel injection in the fuel passage portion 25) The pressure of the fuel upstream of the valve 30 is adjusted.

  The manual fuel pump 40 is provided because the fuel passage portion 25 needs to be manually filled with fuel when the diaphragm fuel pump 14 is not driven, that is, before the internal combustion engine 50 is started. A manual pump chamber 40A having a U-shaped or hemispherical cross section made of an elastic material such as rubber, and a closing base 40B. A manual pump suction valve 44 is arranged on the closing base 40B. A suction port 41 provided with a provided suction port 42 and a manual pump discharge valve 43 is provided, and the suction port 42 and the discharge port 41 communicate with the pulse pressure pump chamber 22. The manual pump chamber 40A is crushed when pressed with a finger, and restored to its original hemisphere by its own elastic force when released.

  The manual pump suction valve 44 disposed in the suction port 42 includes a circular plate-shaped valve body 47 that opens and closes a lower opening of the suction port 42, and a direction in which the valve body 47 closes the upper opening 42a (downward direction). And a manual pump discharge valve 43 disposed in the discharge port 41 includes a circular plate-shaped valve body 45 that opens and closes the upper opening of the discharge port 41, and It comprises a compression coil spring 46 that urges the valve body 45 in a direction (upward) for closing the upper opening, and the opening pressure of the manual pump suction valve 44 is higher than the injection pressure required at the time of starting. It is set high. The valve opening pressure is set by adjusting the spring load (initial set load) of the compression coil springs 47 and 46. Needless to say, the valve opening pressures of the flap valve 16 as the main body side intake valve and the flap valve 17 as the main body side discharge valve are set lower than that of the manual fuel pump 40.

  In the air-fuel mixture generating apparatus 10 of the present embodiment having such a configuration, when the manual fuel pump 40 is operated before starting, the manual pump suction valve 44 and the discharge valve 43 are opened and closed in opposite phases, respectively. The fuel in the fuel tank 81 is sucked into the manual pump chamber 40A via the fuel suction passage 24, the pulse pressure pump chamber 22 of the diaphragm fuel pump 14, and the manual pump suction valve 44, and the fuel in the manual pump chamber 40A. Fuel is discharged into the pulse pressure pump chamber 22 via the manual pump discharge valve 43.

  In this case, the valve opening pressure of the manual pump suction valve 44 is set higher than the injection pressure required at the start, and the fuel returns to the fuel tank 81 downstream of the fuel injection valve 30 in the fuel passage portion 25. Since the needle valve 85 is provided as a return amount limiting means for limiting the amount, a portion (downstream side passage) where the needle valve 85 is provided in the fuel passage portion 25 by operating the manual fuel pump 40. The pressure upstream from the part 27), that is, the injection pressure is increased and adjusted to the injection pressure value required at the time of starting.

  In this state, when the engine 50 is started by operating a recoil starter or the like, the fuel injection valve 30 opens at a predetermined timing (for example, at the start of the intake stroke), and the fuel in the fuel passage portion 25 is allowed to flow into the intake passage 13. The fuel is mixed with the intake air A so that the fuel F is sucked out from the injection port 36 disposed in the throat portion 13 a downstream of the throttle valve 18. The air-fuel mixture is supplied to the crank chamber 56 and the combustion operation chamber 53, and the air-fuel mixture is ignited by the spark plug 59, explosively burns, and enters a normal operation state where it can rotate by itself.

  During normal operation after startup, the pressure change (pulse pressure) in the crank chamber 56, that is, the pressure change that is reduced when the piston 54 is raised and pressurized when the piston 55 is lowered is the pressure of the diaphragm fuel pump 14. This is transmitted to the pulse pressure chamber 21, whereby the diaphragm 15 reciprocates (vertically moves), and the fuel F from the fuel tank 81 enters the pulse pressure pump chamber 22 by the pump action caused by the vertical movement of the diaphragm 15. While being sucked, the fuel F is sent from the pulse pressure pump chamber 22 to the fuel passage portion 25, and the fuel F in the fuel passage portion 25 is pressurized while the injection port 36 is closed. During this normal operation, the fuel injection valve 30 is opened for a predetermined period (for example, 1 to 3 milliseconds) according to the operation state such as the intake air amount of the internal combustion engine 50, thereby the fuel passage portion 25. The pressurized fuel F is injected and supplied to a portion of the intake passage 13 downstream of the throttle valve 18, and the fuel F is mixed with the intake air A.

  Thus, in the air-fuel mixture generating apparatus 10 of the present embodiment, the valve opening pressure of the manual pump suction valve 44 is set higher than the injection pressure required at the start, and the fuel injection valve in the fuel passage portion 25 is set. Since the needle valve 85 as a return amount restricting means for restricting the fuel return amount to the fuel tank 81 is provided downstream of the fuel tank 81, the needle valve in the fuel passage portion 25 is operated by operating the manual fuel pump 40. The pressure upstream of the part where the engine is installed, that is, the injection pressure, is increased and adjusted to the injection pressure value required at the time of starting. Can be supplied to.

  Further, when the fuel is supplied by the diaphragm fuel pump 14 and the fuel injection valve 30, the opening pressure of the suction valve 44 which is always provided in the essential manual fuel pump 40 is made higher than the required injection pressure, and the needle Since it is only necessary to configure the return amount limiting means with an inexpensive member such as a valve, there is no need to newly install a pressure regulating valve, a fuel pressure regulator, etc., and no other modification is required. Therefore, the apparatus configuration is not complicated and the apparatus cost can be suppressed.

  Further, since the fuel supply amount is adjusted by the fuel injection valve 30, the fuel supply amount can be controlled with high accuracy with respect to the intake air as compared with the conventional diaphragm type carburetor. Atomization action, responsiveness, etc. are improved, and it is possible to obtain advantages such as being able to effectively take measures for exhaust gas purification, and structurally, except that the fuel supply part is a fuel injection valve Since it can be made substantially the same as the diaphragm type carburetor, it can be easily incorporated in a conventional internal combustion engine in place of the carburetor.

  FIG. 2 is a longitudinal sectional view showing another embodiment of the air-fuel mixture generator according to the present invention.

  The air-fuel mixture generating apparatus 10S of the illustrated embodiment is configured by separating the manual fuel pump 40 integrally attached to the main body 12 from the main body 12 in the embodiment shown in FIG. It can be attached to. In the air-fuel mixture generating apparatus 10 shown in FIG. 2, the same reference numerals are given to portions having the same configuration functions as those of the air-fuel mixture generating apparatus 10 shown in FIG. 1 described above.

  The manual fuel pump 40 of the present embodiment includes a manual pump chamber 40A and a closing base 40B similar to those shown in FIG. 1, and a connection base on the lower side of the closing base 40B via a mounting plate 40C. A table 40D is provided. The closing base 40B, the mounting plate 40C, and the connection base 40D are provided with a suction port 42 provided with a manual pump suction valve 44 and a discharge port 41 provided with a manual pump discharge valve 43. The port 42 and the discharge port 41 are connected to the pulse pressure pump chamber 22 of the diaphragm fuel pump 14 through a joint / conduit 88 or the like.

  Also in the air-fuel mixture generating apparatus 10S configured as described above, the valve opening pressure of the manual pump suction valve 44 is set higher than the injection pressure required at the start, and the fuel passage, as in the above embodiment. Since the needle valve 85 as a return amount limiting means for limiting the fuel return amount to the fuel tank 81 is provided downstream of the fuel injection valve 30 in the portion 25, the manual fuel separated from the main body portion 12 is provided. By operating the pump 40, the pressure upstream of the portion (downstream passage portion 27) where the needle valve 85 is provided in the fuel passage portion 25, that is, the injection pressure, is gradually increased, and is eventually required at the time of starting. The injection pressure value is adjusted.

  In any of the embodiments, instead of setting the valve opening pressure of the manual pump suction valve 44 higher than the injection pressure required at the time of starting, the same effect can be obtained even if the valve opening pressure of the discharge valve 43 is set high. In this case, a residual pressure is generated in the manual pump chamber 40A. Therefore, it is preferable to set the valve opening pressure of the suction valve 44 high.

The longitudinal cross-sectional view which shows one Embodiment of the air-fuel | gaseous mixture production apparatus which concerns on this invention. The longitudinal cross-sectional view which shows other embodiment of the air-fuel | gaseous mixture production | generation apparatus which concerns on this invention. Sectional drawing which shows the prior art example of an air-fuel | gaseous mixture production apparatus with the engine in which it was integrated. The expanded sectional view of the air-fuel | gaseous mixture production | generation apparatus shown by FIG.

Explanation of symbols

5 Intake System 10, 10S Mixture Generation Device 12 Main Body 13 Intake Passage 13a Throttle 14 Diaphragm Fuel Pump 15 Diaphragm 16 Suction Side Flap Valve (Suction Valve)
17 Discharge flap valve (discharge valve)
18 Throttle valve 21 Pulse pressure chamber 22 Pulse pressure pump chamber 24 Fuel intake passage 25 Fuel passage 27 Downstream passage 30 Fuel injection valve 36 Injection port 40 Manual fuel pump 40A Manual pump chamber 41 Manual pump discharge port 42 Manual pump Suction port 43 Manual pump discharge valve 44 Manual pump suction valve 50 Air-cooled two-cycle gasoline engine 56 Crank chamber 84 Return passage 85 Needle valve (return amount limiting means)

Claims (4)

A diaphragm fuel pump (14) that sucks fuel in response to a pressure change in the crank chamber (56) of the internal combustion engine (50) and discharges the fuel to the fuel passage portion (25), and fuel in the fuel passage portion (25) Is injected into the intake system (5) of the internal combustion engine (50) at a predetermined timing, and when the diaphragm fuel pump (14) is not driven, fuel is supplied to the fuel passage portion ( 25) an air-fuel mixture generator (10) comprising a manual fuel pump (40) for feeding and filling 25)
A suction port (42) provided with a manual pump suction valve (44) and a discharge port provided with a manual pump discharge valve (43) in the pulse pressure pump chamber (22) of the diaphragm fuel pump (14). (41) is communicated, and the valve opening pressure of either the manual pump suction valve (44) or the discharge valve (43) is set higher than the injection pressure required at the start, and the fuel passage An air-fuel mixture generation characterized in that return amount limiting means (85) for limiting the amount of fuel return to the fuel tank (81) is provided downstream of the fuel injection valve (30) in the section (25). apparatus.   2. The air-fuel mixture generation according to claim 1, wherein the return amount limiting means is constituted by a throttle member such as a needle valve (85) that narrows an effective passage cross-sectional area of the fuel passage portion (25). apparatus.   A boundary portion between the pulse pressure pump chamber (22) and the fuel suction passage portion (24) and a boundary portion between the pulse pressure pump chamber (22) and the fuel passage portion (25) in the diaphragm fuel pump (14). An air-fuel mixture generating device according to claim 1 or 2, wherein a suction valve (16) and a discharge valve (17) are respectively provided.   The internal combustion engine is a crankcase precompression air-cooled two-cycle gasoline engine (50), and a throat portion (13a) provided downstream of the throttle valve (18) of the intake passage (13) in the internal combustion engine (50). ), The fuel injection valve (30) is provided with an injection port (36). 4. The air-fuel mixture generation device according to claim 1, wherein the fuel injection valve (30) is provided with an injection port (36).

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