WO2014002957A1

WO2014002957A1 - Fuel supply device for engine, and portable working machine

Info

Publication number: WO2014002957A1
Application number: PCT/JP2013/067264
Authority: WO
Inventors: 秀夫川嶌
Original assignee: 株式会社マキタ
Priority date: 2012-06-29
Filing date: 2013-06-24
Publication date: 2014-01-03
Also published as: JP2015172330A

Abstract

The present invention is configured from: a fuel tank (98); a carburetor (60) provided with a diaphragm pump which drives by receiving the pressure fluctuation that occurs within a crank case (16); an electric motor (40) connected to a crank shaft (12); and a start-up fuel supply device which creates a pressure fluctuation within the crank case (16) by alternately rotating the crank shaft (12) in the normal rotational direction and the reverse rotational direction by means of the electric motor (40) when the engine is start up and which supplies the fuel stored in the fuel tank (98) to the engine (10) via the carburetor (60). As a consequence, the present invention provides a fuel supply device for an engine wherein it is possible to adequately supply fuel used in starting an engine provided with a diaphragm pump-type carburetor to the engine without causing variations.

Description

Engine fuel supply device and portable work machine

TECHNICAL FIELD The present invention relates to an engine fuel supply device, and more particularly to an engine equipped with a diaphragm pump type carburetor, a technique for supplying fuel used for starting the engine, and a portable work machine using the engine equipped with the fuel supply device as a drive source. About.

Regarding the starting of an engine equipped with a diaphragm pump type carburetor, the following Patent Document 1 discloses the following fuel supply device. The fuel storage part of the carburetor and the inside of the crankcase are always communicated via the starting fuel supply flow path regardless of the vertical position of the piston. Specifically, a pulsation transmission passage is formed to cause pressure fluctuations in the crankcase to act on the diaphragm pump of the carburetor, and a start-up fuel supply passage that branches from the pulsation transmission passage and leads to the fuel storage section is formed. Then, a groove is formed in the inner peripheral wall of the cylinder for communicating the opening on the crankcase side of the pulsation transmission passage with the inside of the crankcase. Here, the opening of the pulsation transmission passage also serves as an opening on the crankcase side of the starting fuel supply passage.

JP 2007-239545 A (paragraph number 0027)

According to the fuel supply device of the above-mentioned Patent Document 1, a starting fuel supply flow path that branches from the pulsation transmission passage is formed, and a groove that communicates the opening of the pulsation transmission passage and the inside of the crankcase with the inner peripheral wall of the cylinder. When the engine is started, the piston is at or near the bottom dead center, and the opening of the pulsation transmission passage (also serving as the opening of the starting fuel supply passage) is blocked by the peripheral side surface of the piston. Even if it is, the fuel storage part of the carburetor and the inside of the crankcase communicate with each other via the groove and the starting fuel supply flow path, so that cranking starts without waiting for the piston to rise and the intake port to be opened. Immediately after that, fuel can be supplied to the engine through the starting fuel supply passage. However, since it is assumed that a sufficient amount of fuel is stored in the fuel storage part of the carburetor, the fuel storage part and the fuel piping between the fuel tank and the carburetor etc. There is a problem that the amount of fuel supplied to the engine may vary.

Therefore, the present invention drives an engine fuel supply device capable of accurately supplying the fuel used for starting the engine with a diaphragm pump type carburetor without variation, and the engine equipped with the fuel supply device. An object is to provide a portable work machine as a source.

In one aspect of the present invention, a fuel tank, a carburetor including a diaphragm pump that is driven by pressure fluctuation generated in an engine crankcase, an electric motor connected to an engine crankshaft, A starting fuel supply that rotates the crankshaft alternately in the forward and reverse directions by a motor to cause pressure fluctuations in the crankcase, and supplies the fuel stored in the fuel tank to the engine via the carburetor A fuel supply device for the engine.

In another embodiment of the present invention, a portable work machine including an engine including the fuel supply device and using the engine as a drive source is configured.

According to the fuel supply device of one aspect of the present invention, the crankshaft is alternately rotated in the normal rotation direction and the reverse rotation direction by the electric motor, thereby causing pressure fluctuation in the crankcase. Thus, when starting the engine, the diaphragm pump provided in the carburetor is operated by this pressure fluctuation, and fuel can be supplied from the fuel tank to the carburetor. Therefore, a sufficient amount of fuel can be secured in the carburetor, and the fuel can be accurately supplied to the engine.

According to a portable work machine of another aspect of the present invention, the portable work machine includes an engine including the fuel supply device, and the engine can be provided as a drive source.

It is sectional drawing which shows the structure of an engine provided with the fuel supply apparatus which concerns on one Embodiment of this invention. It is sectional drawing which shows schematic structure of the carburetor with which an engine same as the above is equipped. It is explanatory drawing which shows the operation | movement (up stroke initial stage) at the time of normal driving | operation of an engine same as the above. It is explanatory drawing which shows the operation | movement (up stroke middle period) at the time of normal driving | operating of an engine same as the above. It is explanatory drawing which shows the operation | movement at the time of a normal driving | operation of an engine same as the above (lower stroke middle stage). It is explanatory drawing which shows the operation | movement (down stroke end stage) at the time of normal driving | operation of an engine same as the above. It is explanatory drawing which shows the operation | movement (at the time of fuel filling) at the time of engine start same as the above. It is explanatory drawing which shows the operation | movement (1st position) at the time of engine start same as the above. It is explanatory drawing which shows the operation | movement (2nd position) at the time of engine start same as the above. It is explanatory drawing which shows the operation | movement (3rd position) at the time of engine start same as the above. It is explanatory drawing which shows the operation | movement (ignition timing) at the time of engine start same as the above. It is sectional drawing which shows the structure of the carburetor with which the fuel supply apparatus which concerns on other embodiment of this invention is equipped.

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine (engine), 12 ... Crankshaft, 14 ... Cylinder, 16 ... Crankcase, 22 ... Piston, 40 ... Electric motor, 42 ... Rotary shaft, 44 ... Electromagnetic coil, 46 ... Permanent magnet, 48 ... Rotor 60 ... carburetor, 68 ... diaphragm, 90 ... priming pump, 98 ... fuel tank, 150 ... control unit, 152 ... ignition circuit, 154 ... motor control circuit, P1 ... intake port, P22 ... scavenging port, P3 ... exhaust port, v1, v2 ... check valves.

FIG. 1 shows a configuration of an internal combustion engine (engine) 10 according to an embodiment of the present invention by a longitudinal section parallel to a central axis Ctr of a crankshaft 12.
An engine (hereinafter simply referred to as “engine”) 10 according to the present embodiment is provided in a horticultural portable work machine, such as a brush cutter, and constitutes a drive source thereof. The output of the engine 10 is transmitted to the rotary blade via the drive shaft of the brush cutter and rotates it. However, it is not limited to brush cutters, but can be provided as a drive source for any portable work machine such as mowers, chainsaws, circular cutters (cut-off saws), sprayers, spreaders, blowers (blowers), and dust collectors. is there.

The engine 10 includes an electric motor 40, and the crankshaft 12 of the engine 10 and the rotating shaft 42 of the electric motor 40 are directly connected, and the output torque of the electric motor 40 is transmitted via the crankshaft 12 to a drive shaft (see FIG. (Not shown), and the output torque of the engine 10 can be transmitted to the rotating shaft 42 of the electric motor 40. The electric motor 40 is not only connected to the crankshaft 12 coaxially with the rotary shaft 42 but also connected via a power transmission medium such as a gear or a chain mechanism, and can be interrupted via a clutch. You may connect to.

The engine 10 is a two-stroke engine. In this embodiment, a single-cylinder small two-stroke engine is adopted.
The engine 10 is roughly divided into a cylinder 14 and a crankcase 16, and the crankshaft 12 is pivotally supported by a bearing 18 with respect to the crankcase 16. An oil seal 20 is installed inside the bearing 18. The piston 22 is inserted into the cylinder 14 so as to be movable up and down, and is connected to the crankshaft 12 via a connecting rod 24.

Specifically, the piston 22 is connected to one end portion of a connecting rod 24 by a piston pin 26, and the connecting rod 24 is connected to a crank pin 28 at the other end portion and cranked via a crank arm 30 that holds the crank pin 28. Connected to the shaft 12. The crank arm 30 includes a counterweight 32 on the side opposite to the holding portion of the crankpin 28.

In the cylinder 14, a combustion chamber C is formed above the piston 22, and an ignition plug 34 is installed so as to face the combustion chamber C. The spark plug 34 operates in response to a command signal from the control unit 150 and ignites the compressed mixture formed in the combustion chamber C. The cylinder 14 has a plurality of heat radiating fins 36 protruding from the outer surface thereof.

The electric motor 40 is a three-phase induction type electric motor (brushless motor), and can function not only as a motor (motor) but also as a generator (generator). In this embodiment, the electromagnetic coil 44 is placed on the stationary side, the permanent magnet 46 is placed on the movable side, and the rotor (rotor) 48 that holds the permanent magnet 46 is placed outside the electromagnetic coil 44. The electromagnetic coil 44 is fixed to the crankcase 16. In the present embodiment, the permanent magnet 46 is fixed to an inner peripheral portion of a rotor 48 formed in a bottomed cylindrical shape, and the rotor 48 is extended to an extended portion of the crankshaft 12 extending outside the crankcase 16. The crankshaft 12 is rotatably mounted on the same axis. In other words, in this embodiment, the extending portion of the crankshaft 12 also functions as the rotating shaft 42 of the electric motor 40. A cooling fan 50 is formed on the outer peripheral surface of the rotor 48.

The control unit 150 includes an ignition circuit 152 and a motor control circuit 154, and also includes an ignition timing detection circuit, a throttle opening detection circuit, and a rotor position detection circuit (not shown) as a configuration for detecting the operating state of the engine 10. .

The ignition circuit 152 calculates an ignition timing Tig corresponding to the operating condition of the engine 10 and outputs a command signal corresponding to the ignition timing Tig to the ignition plug 34.
The motor control circuit 154 calculates an operating condition of the electric motor 40 and outputs a command signal corresponding to the operating condition to the electric motor 40. Specifically, during normal operation of the engine 10, when the output torque of the engine 10 is insufficient with respect to the required torque, a command signal for operating the electric motor 40 as a motor is output, while the output torque of the engine 10 is When there is a margin for the required torque, a command signal for operating this as a generator is output. In addition to this, in the present embodiment, when the engine 10 is started, fuel supply control described later is executed.

When operating the electric motor 40 as a motor, the motor control circuit 154 converts a direct current from the power storage device (for example, a battery or a capacitor) 160 into a three-phase alternating current, and corresponds a current component of each phase. The electromagnetic coil 44 is supplied. On the other hand, when operating as a generator, the three-phase alternating current generated by the electromagnetic coil 44 is converted into a direct current and supplied to the power storage device 160.

FIG. 2 shows a schematic configuration of the carburetor 60 provided in the engine 10 by a longitudinal section parallel to the central axis of the intake passage.
FIG. 3 shows a schematic configuration of the engine 10 by a longitudinal section perpendicular to the central axis Ctr of the crankshaft 12.

The configuration of the engine 10 will be further described with reference to FIG. 3, and then the configuration of the carburetor 60 will be described with reference to FIG.
In FIG. 3, an air supply passage 102, a scavenging passage 104, and an exhaust passage 106 are formed in the engine 10. In the present embodiment, one end of each of these passages 102 to 106 communicates with the inside of the cylinder 14 and is opened and closed by the circumferential side surface according to the reciprocating movement of the piston 22.

The air supply passage 102 communicates with the cylinder 14 at the intake port P1, and the intake port P1 is positioned below the upper surface of the piston 22 whose upper edge is at the bottom dead center, and the lower edge is at the top dead center. It is set so that it may be located below the lower surface of the piston 22 in the above. As a result, the air supply passage 102 is blocked by the peripheral side surface of the piston 22 when the piston 22 is at the bottom dead center, while the supply passage 102 is below the piston 22 in the process of transition from the middle stroke of the piston 22 to the middle stroke of the lower stroke. Opened, the negative pressure generated in the crankcase 16 is introduced, and the air-fuel mixture is sucked into the crankcase 16. This fuel is added to the air taken in from the atmosphere by the carburetor 60 described below. Here, the upward stroke refers to a stroke in which the piston 22 moves from the bottom dead center farthest away from the combustion chamber C to the top dead center closest to the piston 22, and the downward stroke refers to a stroke in which the piston 22 is bottom dead from the top dead center. The process of moving toward a point.

The scavenging passage 104 communicates with the crankcase 16 at the scavenging air inlet P21 at one end, and communicates with the cylinder 14 at the scavenging port P22 at the other end to spatially connect the crankcase 16 and the cylinder 14 with each other. ing. The scavenging port P22 is set such that its upper edge is located above the upper surface of the piston 22 at the bottom dead center and its lower edge is located above the lower surface of the piston 22 at the top dead center. As a result, the scavenging passage 104 allows the scavenging port P22 to open above the piston 22 at the end of the downward stroke of the piston 22 so that the crankcase 16 and the cylinder 14 communicate with each other. A passage for feeding into the cylinder 14 is formed.

The exhaust passage 106 communicates with the inside of the cylinder 14 at the exhaust port P3. The exhaust port P3 is located above the upper surface of the piston 22 whose upper edge is at the bottom dead center, and the lower edge is at the top dead center. It is set to be located above the lower surface of a certain piston 22. As a result, the exhaust passage 106 is closed by the peripheral side surface of the piston 22 when the piston 22 is at the top dead center, while in the cylinder 14 before the scavenging port P22 in the period after the middle of the downward stroke of the piston 22. Opening and exhausting the exhaust gas to lower the pressure in the cylinder 14.

The crankcase 16 is formed with a pressure transmission passage 16a for introducing the pressure fluctuation generated in the crankcase 16 into the pump drive pressure chamber 72 of the carburetor 60 described below. In the present embodiment, the pressure transmission passage 16a is formed so as to penetrate the crankcase 16 in a direction perpendicular to the central axis Ctr of the crankshaft 12, and the inside of the crankcase 16 and the pump drive pressure chamber 72 are connected to this pressure. It communicates via the transmission path 16a.

2, the carburetor 60 is formed with a venturi section 62, and the cylinder 14 of the engine 10 is connected to the carburetor 60 on the downstream side of the venturi section 62. An air cleaner (not shown) is attached on the upstream side of the venturi 62. Inside the main body of the carburetor 60, a choke valve 64 is disposed upstream of the venturi section 62, and an air metering valve 66 is rotatably disposed downstream.

In this embodiment, a pump chamber 70 and a pump drive pressure chamber 72 defined by a diaphragm 68 are formed in the main body wall portion above the venturi portion 62. A fuel storage chamber 76 and an atmospheric chamber 78 defined by a diaphragm 74 are formed in the main body wall portion below the venturi 62, and the pump chamber 70 has an inlet passage 60a in which a check valve v1 is interposed. And communicates with the fuel storage chamber 76 via an intermediate passage 60b in which a check valve v2 is interposed. The pump drive pressure chamber 72 is connected to the pressure transmission passage 16 a of the crankcase 16 through the pressure introduction passage 60 d and communicates with the crankcase 16. The atmospheric chamber 78 is open to the atmosphere.

An inflow restricting valve 80 is interposed in the intermediate passage 60b between the pump chamber 70 and the fuel storage chamber 76. The inflow regulating valve 80 is coupled to one side of a lever member 82 that is supported so as to be rotatable about a shaft 82 a with respect to the main body of the carburetor 60. A spring 84 is interposed between the main body of the carburetor 60 and the lever member 82 in a compressed state, and the lever member 82 is biased by the inflow regulating valve 80 so as to close the intermediate passage 60b. The other side of the lever member 82 is coupled to the central portion of the diaphragm 74.

The fuel storage chamber 76 communicates with the venturi portion 62 via the outlet passage 60c, and a metering hole h1 for regulating the maximum flow rate of the fuel flowing through the passage 60c is formed at the inlet portion of the outlet passage 60c. A jet hole h2 is formed at the outlet. A fuel control valve 86 is installed in the middle of the outlet passage 60c. The fuel adjustment valve 86 is manually operated by an operator and adjusts the amount of fuel supplied to the engine 10 by the carburetor 60.

When the pressure fluctuation in the crankcase 16 is introduced into the pump drive pressure chamber 72 through the

pressure passages

16a and 60d, the diaphragm 68 is operated by this pressure fluctuation, and the fuel is sucked into the pump chamber 70 from the fuel tank 98. The fuel in the fuel storage chamber 76 is sucked out of the fuel storage chamber 76 by the negative pressure generated in the venturi section 62, supplied to the venturi section 62 through the outlet passage 60c, and added to the air that has passed through the air cleaner. Here, the amount of fuel added to the air is adjusted by the fuel adjustment valve 86, and the maximum flow rate is regulated by the metering hole h1. When the fuel stored in the fuel storage chamber 76 decreases, the diaphragm 74 rises accordingly, and the inflow regulating valve 80 is lowered via the lever member 82. As a result, the intermediate passage 60 b is opened, and fuel is supplied from the pump chamber 70 to the fuel storage chamber 76.

In the present embodiment, the “diaphragm pump” of the carburetor 60 includes a main body upper side wall portion of the carburetor 60 that forms the pump chamber 70, the pump drive pressure chamber 72, the inlet passage 60a, the intermediate passage 60b, and the pressure introduction passage 60d, and the diaphragm 68. And check valves v1 and v2.

Here, the operation of the engine 10 will be briefly described.
3 to 6 show the operation of the engine 10 during normal operation in time series.
After the piston 22 passes through the bottom dead center and starts moving toward the top dead center (FIG. 3), when the scavenging port P22 is closed by the peripheral side surface of the piston 22, the inside of the crankcase 16 is exposed to the outside. It becomes a sealed state, and a negative pressure develops in the crankcase 16.

When the middle of the ascending stroke is reached (FIG. 4), the intake port P1 is opened below the piston 22, and the negative pressure in the crankcase 16 is applied to the supply passage 102. As a result, air outside the engine 10 is taken into the carburetor 60, and a mixture of fuel and air added by the carburetor 60 is introduced into the crankcase 16 through the air supply passage 102.

When reaching the end of the ascending stroke, the spark plug 34 operates near the top dead center, and the compressed air-fuel mixture in the combustion chamber C is ignited. When passing through the top dead center and proceeding to the lowering stroke, the piston 22 is pushed down by the volume expansion of the fuel and rotates the crankshaft 12 via the connecting rod 24. The rotational movement of the crankshaft 12 is transmitted to the drive shaft of the portable work machine, and rotates the cutting blade.

When the middle of the lowering stroke is reached (FIG. 5), the exhaust port P3 is opened above the piston 22, and the exhaust gas after combustion is led to the exhaust passage 106. Thereby, the pressure in the cylinder 14 decreases rapidly. The derived exhaust gas passes through a muffler (not shown) and is released into the atmosphere. On the other hand, in the crankcase 16, the air-fuel mixture is compressed by the lowering of the piston 22, and the pressure rises.

When the end of the lowering stroke is reached (FIG. 6), the scavenging port P22 is opened above the piston 22, and the air-fuel mixture in the crankcase 16 flows out into the cylinder 14 through the scavenging passage 104, thereby remaining in the cylinder 14. The exhaust gas is scavenged.

The fuel supply control according to this embodiment will be described below.
7 to 11 show the operation when the engine 10 is started. 7 and 8 show the control for supplying fuel from the fuel tank 98 to the carburetor 60 (hereinafter referred to as “fuel filling control”), and FIGS. 9 and 10 show the fuel supply from the carburetor 60 to the engine 10 to form an air-fuel mixture. FIG. 11 shows the control (hereinafter referred to as “starting fuel supply control”) and the control for igniting the air-fuel mixture and starting the engine 10 (hereinafter referred to as “ignition start control”). A series of controls shown in FIGS. 7 to 11 are executed by the control unit 150 in accordance with the start operation of the portable work machine performed by the worker. Therefore, in this embodiment, the “starting fuel supply device” is configured by the control unit 150.

In the fuel filling control shown in FIGS. 7 and 8, the electric motor 40 that receives the command signal from the control unit 150 rotates the crankshaft 12 alternately in the normal rotation direction and the reverse rotation direction, thereby causing pressure fluctuation in the crankcase 16. The pressure fluctuation is propagated to the pump drive pressure chamber 72 of the carburetor 60, and the diaphragm 68 is operated. As a result, fuel is sucked out of the fuel tank 98 and supplied to the pump chamber 70.

Specifically, the crankshaft 12 is rotated in the forward and reverse directions in the range of crank angles Cr1 to Cr2 in which the scavenging port P22 is closed by the peripheral side surface of the piston 22. In the present embodiment, reciprocation is made between the position of the crank angle Cr1 that brings the piston 22 close to top dead center and the position of the crank angle Cr2 that moves the piston 22 away from top dead center (corresponding to the “first position”). Let Here, at the crank angle Cr2, the crown surface of the piston 22 is located on the top dead center side with respect to the upper edge of the scavenging port P22, and at the crank angle Cr1, the lower surface of the piston 22 is dead with respect to the lower edge of the intake port P1. Located on the point side.

Thus, the diaphragm 68 of the carburetor 60 is operated by the pressure fluctuation in the crankcase 16 by rotating the crankshaft 12 alternately in the forward and reverse directions within the range of the crank angle Cr1 to Cr2 that closes the scavenging port P22. In addition, by generating an air flow in the venturi 62, a negative pressure is applied to the fuel storage chamber 76 through the ejection hole h2, the outlet passage 60c, and the metering hole h1, and the inflow regulating valve 80 is opened. The fuel can be supplied from the fuel tank 98 to the carburetor 60. The supplied fuel is supplied to the fuel storage chamber 76 according to the remaining state of the fuel.

Here, since the closing of the scavenging port P22 is maintained, fuel is not supplied from the carburetor 60 into the combustion chamber of the engine 10 during the fuel filling control, and an excessive supply of fuel to the engine 10 is avoided. Misfire can be prevented.

The number of reciprocations of the crankshaft 12 in the fuel filling control can be appropriately set according to the residual state of fuel in the carburetor 60. For example, it is adapted to the condition in which the remaining amount of fuel is the smallest in the interior of the carburetor 60 (for example, the fuel storage chamber 76) and the fuel piping from the fuel tank 98 to the carburetor 60.

In the present embodiment, when the crankshaft 12 is rotated from the crank angle Cr1 to the position of Cr2, it is rotated until the crown surface of the piston 22 is positioned below the upper edge of the exhaust port P3, and a part of the exhaust port P3 is rotated. Is open. As a result, the reciprocating distance of the piston 22 is increased, a large pressure fluctuation is generated in the crankcase 16, the reaction force action due to compression in the cylinder 14 is reduced, and the load on the electric motor 40 can be reduced. It becomes possible. However, the present invention is not limited to this, and the crankshaft 12 may be rotated in a range up to the crank angle Cr2 'where the crown surface of the piston 22 is located above the upper edge of the exhaust port P3. FIG. 8 shows the piston 22 by a two-dot chain line when the crankshaft 12 is at the crank angle Cr2 '.

In the starting fuel supply control shown in FIGS. 9 and 10, the electric motor 40 rotates the crankshaft 12 alternately in the forward and reverse directions over the range of the crank angles Cr3 to Cr4 wider than the crank angles Cr1 to Cr2. Then, the pressure fluctuation generated in the crankcase 16 is propagated to the pump drive pressure chamber 72 of the carburetor 60 and is also propagated to the intake passage 102. As a result, the air-fuel mixture that has passed through the carburetor 60 is supplied into the crankcase 16.

Specifically, the crankshaft 12 is rotated in the reverse direction to the crank angle Cr3 where the lower surface of the piston 22 is positioned above the lower edge of the intake port P1 and a part of the intake port P1 opens into the crankcase 16. And a forward rotation, and the crown surface of the piston 22 is located below the upper edge of the scavenging port P22, and a crank angle Cr4 at which a part of the scavenging port P22 opens into the cylinder 14 is provided. Rotate in the forward direction to the position. The reciprocating rotation between the crank angles Cr3 and Cr4 is repeated until an ignitable air-fuel mixture is formed in the cylinder 14. In the present embodiment, the position of the crank angle Cr4 that opens the scavenging port P22 corresponds to the “third position”, and brings the piston 22 closer to the bottom dead center than at the crank angle Cr2 (first position). On the other hand, the position of the crank angle Cr3 that opens the intake port P1 corresponds to a “second position”, and brings the piston 22 closer to the top dead center than at the crank angle Cr1.

As described above, the crankshaft 12 is rotated in one direction until the intake port P1 is opened, and then rotated in the opposite direction until the scavenging port P22 is opened, whereby the air-fuel mixture is sucked into the crankcase 16. In addition, the air-fuel mixture can be supplied from the crankcase 16 into the cylinder 14 through the scavenging passage 104.

Here, since a sufficient amount of fuel is secured in the carburetor 60 by the previous fuel filling control, even if the number of reciprocations of the crankshaft 12 in the starting fuel supply control is set to be constant, Variation in the concentration of the compressed air-fuel mixture formed in C can be suppressed, misfire can be prevented, and the engine 10 can be started reliably. In other words, it is possible to suppress variation in the number of reciprocations required to supply an amount of fuel necessary for starting the engine 10.

In FIG. 11, the electric motor 40 rotates the crankshaft 12 in the reverse direction to the position of the crank angle Cr5 at which the piston 22 reaches a predetermined position before the top dead center. In the process in which the crankshaft 12 reaches the crank angle Cr5, the scavenging port P22 and the exhaust port P3 are closed by the peripheral side surface of the piston 22, and a compressed mixture is formed in the combustion chamber C.

In the present embodiment, the crank angle Cr5 is set to an angle that determines the ignition timing at the start of the engine 10, and when the crankshaft 12 reaches the position of the crank angle Cr5, the spark plug 34 is activated, and the combustion chamber Ignition of the C compressed mixture is performed. The electric motor 40 stops the rotational drive of the crankshaft 12 in synchronization with the ignition. As a result, the piston 22 is pushed down from the predetermined position by the volume expansion of the fuel, and the crankshaft 12 starts to rotate forward from the position of the crank angle Cr5 and starts rotating in the forward rotation direction.

If the rotational fluctuation is large and the first top dead center after ignition cannot be satisfactorily passed, the electric motor 40 is driven again before the top dead center, and assist torque in the forward direction is generated with respect to the crankshaft 12. You may make it make it. Thereby, the function of the flywheel can be shared by the electric motor 40.

In the present embodiment, the position Cr5 before the top dead center at which the crankshaft 12 is reached is set in correspondence with the ignition timing, and the rotational drive of the electric motor 40 is stopped in synchronization with the ignition. First, when a configuration (for example, a rotor position detection circuit) for detecting the actual rotational speed of the crankshaft 12 is provided, a position for rotating the crankshaft 12 at the time of ignition is set in advance, and the electric motor 40 causes the crankshaft 12 to rotate. Then, the spark plug 34 may be operated in synchronization with the rotation of the crankshaft 12 being stopped.

Thus, according to the present embodiment, the crankshaft 12 is alternately rotated in the forward and reverse directions by the electric motor 40 to cause pressure fluctuation in the crankcase 16, and this pressure fluctuation is applied to the carburetor 60. By spilling over the pump drive pressure chamber 72, the diaphragm 68 can be operated, and fuel can be supplied from the fuel tank 98 to the carburetor 60. Therefore, a sufficient amount of fuel can be secured in the carburetor 60 when the engine 10 is started.

After the fuel is supplied to the carburetor 60, the air-fuel mixture is supplied into the crankcase 16 through the carburetor 60 by rotating the crankshaft 12 back and forth alternately so that the intake ports P1 and the scavenging ports P22 open alternately. Further, this air-fuel mixture can be supplied into the cylinder 14 through the scavenging passage 104.

Then, the crankshaft 12 is rotated in the reverse direction to compress the air-fuel mixture in the cylinder 14 and ignited when the crankshaft 12 reaches a position before the top dead center. It becomes possible to utilize the volume expansion force. Therefore, the engine 10 can be reliably started, and the cranking that has been performed by the starter motor or the like is unnecessary, so that the electric motor 40 can be reduced in size and labor can be saved.

In the present embodiment, since it is not necessary to pass the top dead center through the piston 22 in the above-described series of controls performed when the engine 10 is started, a smaller and labor-saving electric motor 40 can be employed.

FIG. 12 shows a schematic configuration of a carburetor 60 that constitutes a fuel supply device according to another embodiment of the present invention, in the same longitudinal section as that of FIG.
In the previous embodiment, the supply (filling) of fuel from the fuel tank 98 to the carburetor 60 is realized by the reciprocating rotation of the crankshaft 12, but in the present embodiment, this is realized by the priming pump 90. The configuration other than the priming pump 90 and its periphery is the same as in the previous embodiment.

When the operator crushes the spoid 92 of the priming pump 90 at the time of starting the engine 10 and further restores it, the check valve embodied by the umbrella portion 94a of the umbrella-type valve 94 is inhaled as the volume of the spoid increases. 90a is opened, and the fuel vapor and air in the fuel storage chamber 76 are caused to flow into the spoid 92 through the suction passage 90a. Then, when the operator next crushes the spoid 92, the check valve embodied by the shaft portion 94b of the umbrella valve 94 opens the discharge passage 90b, and the fuel vapor or the like in the spoid 92 is transferred to the fuel tank 98. Reflux. By repeating such an operation, a negative pressure develops in the fuel storage chamber 76, the inflow regulating valve 80 is opened, and fuel is supplied from the fuel tank 98 to the carburetor 60 (fuel storage chamber 76).

The control after filling the carburetor 60 with fuel may be the same as in the previous embodiment (starting fuel supply control, ignition starting control). Specifically, after the crankshaft 12 is reciprocated between the crank angle Cr3 position and the crank angle Cr4 position to supply the air-fuel mixture into the cylinder 14, the crankshaft 12 is moved to a position Cr5 before top dead center. Until the compression mixture in the combustion chamber C is ignited.

According to the present embodiment, when the engine 10 is started, an air-fuel mixture is formed in advance in the cylinder 14 and can be started using the volume expansion force of the fuel. Cranking is not necessary, and the electric motor 40 can be reduced in size and labor.

In the present embodiment, a “diaphragm pump” of the carburetor 60 is configured by the main body upper side wall portion of the carburetor 60, the diaphragm 68, and the check valves v 1 and v 2, and “starting fuel supply” is performed by the control unit 150 and the priming pump 90. Device "is configured.

In the above description, the rotation direction of the crankshaft 12 when the piston 22 is brought close to top dead center is defined as the reverse rotation direction, and the rotation direction when the piston 22 is moved away from it is defined as the normal rotation direction. According to such setting, since the rotation angle when the crankshaft 12 reaches the position before the top dead center at the time of ignition is small, the time required for starting the engine 10 can be shortened. However, the forward / reverse rotation direction may be the forward rotation direction when the piston 22 is brought close to the top dead center, and the reverse rotation direction when the piston 22 is moved away. In this case, for example, with respect to the example shown in FIG. 7, the crankshaft 12 reciprocates at a mirror-symmetrical position with respect to the central axis of the cylinder 14.

∙ A 4-stroke engine can be used as the engine. In this case, when starting the engine, the crankshaft is alternately rotated in the normal rotation direction and the reverse rotation direction in the range of the crank angle (for example, the exhaust stroke) at which the intake valve is closed, and the pressure fluctuation generated in the crankcase is It acts on the diaphragm pump provided in the carburetor. Then, the reciprocating rotation of the crankshaft is continued by changing the reach range of the piston, and after the air-fuel mixture is supplied into the cylinder via the intake port, the crankshaft is reversely rotated to a predetermined position before the compression top dead center. Turn on and ignite.

Claims

A fuel tank,
A carburetor including a diaphragm pump that is driven in response to pressure fluctuations generated in an engine crankcase;
An electric motor connected to the crankshaft of the engine;
When starting the engine, the electric motor alternately rotates the crankshaft in the forward and reverse directions to cause pressure fluctuations in the crankcase, and the fuel stored in the fuel tank is passed through the carburetor. A starting fuel supply device for supplying the engine;
An engine fuel supply device comprising:
The engine is a two-stroke engine;
The starting fuel supply device includes a first position where a crown surface of the piston is on a top dead center side with respect to a scavenging port, a bottom surface of the piston is on a top dead center side with respect to an intake port, and the crown surface of the piston is Supplying fuel to the engine by rotating the crankshaft between a second position closer to top dead center than in the first position;
The engine fuel supply device according to claim 1.
The fuel supply device for an engine according to claim 2, wherein at least a part of the exhaust port is opened when the crankshaft is in the first position.
The starter fuel supply device rotates the crankshaft between the first and second positions, and then the crown surface of the piston comes closer to bottom dead center than in the first position, and the scavenging port Between the third position where at least a part of the intake port is opened and the second position where the crown surface of the piston is on the top dead center side with respect to the scavenging port, and at least a part of the intake port is opened. Supplying fuel to the engine by rotating the crankshaft;
The fuel supply device for an engine according to claim 2.
The engine fuel supply according to claim 4, wherein the crankshaft is rotated between the third and fourth positions, and then the crankshaft is rotated in a reverse direction to a predetermined position before compression top dead center. apparatus.
The engine fuel supply device according to claim 5, wherein the predetermined position corresponds to an ignition timing at the time of starting the engine.
The engine fuel supply device according to claim 5, wherein after the crankshaft is rotated to the predetermined position, an air-fuel mixture of the supplied fuel is ignited in synchronization with the rotation stop of the crankshaft.
The engine is a two-stroke engine;
The starting fuel supply device includes:
A priming pump for supplying the fuel stored in the fuel tank to the carburetor without using the diaphragm pump;
A crown position of the piston is between the upper edge of the scavenging port and an upper edge of the intake port; and a third position where at least a part of the scavenging port is open; and the crown face of the piston is dead from the scavenging port Fuel is supplied to the engine by rotating the crankshaft between a second position on the point side and at least a portion of the intake port opening;
The engine fuel supply device according to claim 1.
9. The fuel supply for an engine according to claim 8, wherein after the crankshaft is rotated between the third and second positions, the crankshaft is rotated in a reverse direction to a predetermined position before the compression top dead center. apparatus.
10. The engine fuel supply apparatus according to claim 9, wherein the predetermined position corresponds to an ignition timing when the engine is started.
The engine fuel supply device according to claim 9, wherein the fuel mixture of the supplied fuel is ignited in synchronization with the rotation of the crankshaft after the crankshaft is rotated to the predetermined position.
A portable work machine including the engine including the fuel supply device according to any one of claims 1 to 11 and using the engine as a drive source.