JP2012177336A - Engine, and engine working machine including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine improving operability during engine starting by automatically supplying starting fuel for each cranking during an operation time of a decompressor device, and to provide an engine working machine including the same.SOLUTION: This engine 1 includes a decompression device 28 including a pressure reducing passage communicating with a cylinder bore 4 and a pressure reducing valve 26 communicating the pressure reducing passage with the cylinder bore 4 during valve opening and closing the communication by receiving the pressure in the cylinder bore 4. The decompression device 28 is provided with a pressure transmission pipe 27 transmitting a pressure in the cylinder bore 4. The engine 1 is provided with: a starting fuel supply device 39 increasing fuel concentration of air-fuel mixture to be supplied into the cylinder bore 4 during starting; and a chamber valve connected to the pressure transmission pipe 27 and controlling the supply of starting fuel by the starting fuel supply device 39 in response to a pressure transmitted from the cylinder bore 4.

Description

  The present invention relates to an engine, particularly an engine including a decompression device and a starting fuel supply device, and an engine working machine such as a brush cutter and a chain saw provided with the engine.

  Many portable engine working machines such as a brush cutter and a chain saw start an engine by an operator pulling a starter rope and performing a cranking operation. In such an engine, since the startability when the engine is cold is poor, the operator's cranking operation increases, and the burden on the worker increases. Therefore, for example, as shown in Patent Document 1, a decompression device for reducing the burden on the operator by releasing the pressure in the cylinder bore at the time of cranking, and starting for temporarily increasing the fuel supplied to the cylinder bore There are engines with fuel injection pumps.

JP-A-8-4618

  By the way, in the case of the engine shown in the above-mentioned patent document 1, although the operation of the decompression device and the supply of the starting fuel can be performed simultaneously by one operation, the starting fuel is only supplied once at the time of this operation. . Therefore, when it is necessary to further supply the starting fuel, the operator needs to repeat the starting fuel supply operation again, which causes a problem that the operation becomes complicated and the operability is poor.

  The present invention has been made in view of the above-described problems, and includes an engine in which operability at the time of starting the engine is improved by automatically supplying a starting fuel for each cranking operation of the decompression device. The purpose is to provide an engine working machine.

In order to achieve the above object, an engine according to the first aspect of the present invention provides:
A cylinder block in which a cylinder bore in which a piston slides is formed;
A carburetor for supplying a mixture of fuel and air into the cylinder bore;
A decompression device comprising: a pressure reducing passage communicating with the cylinder bore; and a pressure reducing valve that causes the pressure reducing passage and the cylinder bore to communicate with each other when the valve is opened and closes the communication upon receiving a pressure equal to or higher than a first predetermined value in the cylinder bore;
A pressure transmission path provided in the decompression device for transmitting pressure in the cylinder bore;
A starting fuel supply device for increasing the fuel concentration of the air-fuel mixture supplied into the cylinder bore at the time of starting;
A control device that is connected to the pressure transmission path and controls the supply of the starting fuel by the starting fuel supply device in accordance with the pressure transmitted from the cylinder bore;
It is characterized by that.

The start fuel supply device connects a start fuel storage chamber for storing the start fuel, a start fuel supply nozzle provided in an intake passage of the carburetor, and the start fuel storage chamber. A fuel supply passage for starting,
The control device may include a control valve that opens and closes the starting fuel supply passage in accordance with pressure transmitted from the pressure transmission passage.

A fuel storage section provided in the carburetor for storing fuel supplied from a fuel tank via a fuel supply passage and supplying fuel into the intake passage;
Provided between the fuel storage section and the starting fuel storage chamber, by repeating compression deformation and elastic recovery, the fuel is sucked into the fuel storage section and the sucked fuel is supplied to the starting fuel storage chamber. A priming pump that discharges, and a one-way valve that allows fuel to move from the fuel reservoir to the starting fuel reservoir;
And a return passage for discharging the fuel overflowed from the starting fuel storage chamber to the fuel tank.

  The control valve is preferably opened when the pressure transmitted from the pressure transmission path is equal to or greater than a second predetermined value.

  Furthermore, the starting fuel supply device and the control device may be configured integrally with the carburetor.

An engine work machine according to a second aspect of the present invention includes the above-described engine.
It is characterized by that.

  According to the engine of the present invention, the starting fuel can be automatically supplied for each cranking operation of the decompression device, and the operability when starting the engine can be improved.

The perspective view of the brush cutter carrying the engine which concerns on this invention. Sectional drawing of the engine part of the brush cutter of FIG. Sectional drawing which expanded the carburetor part of the engine of FIG. The figure corresponding to FIG. 3 which shows the state which the chamber valve of the fuel supply apparatus for start-up opened. Sectional drawing which expanded the decompression apparatus part of FIG.

  Embodiments of the present invention will be described below with reference to FIGS. As shown in FIG. 1, a brush cutter 1001 equipped with a two-cycle engine 1 (hereinafter referred to as an engine) has a rotary blade 1003 attached to the front end of the operating rod 1002 and the engine 1 attached to the rear end of the operating rod 1002. . The output of the engine 1 is supplied to the rotary blade 1003 through a drive shaft that is inserted into the operation rod 1002. The operator operates the brush cutter 1001 by holding the handle 1004 attached to the operation rod 1002.

  As shown in FIG. 2, a crankcase 3 is attached to the cylinder block 2 of the engine 1. A piston 5 is accommodated in a cylinder bore 4 formed in the cylinder block 2 so as to be movable up and down (up and down in FIG. 2) between a top dead center and a bottom dead center. In FIG. 2, the piston 5 is located at the top dead center. The cylinder bore 4 is connected to a crank chamber 7 formed in the crankcase 3 below. The piston 5 is connected via a connecting rod 8 to a crankshaft 9 that is rotatably supported by the crankcase 3. The crankshaft 9 is integrally provided with a crank weight 10 accommodated in the crank chamber 7.

  An exhaust opening 11 and an intake opening 13 are formed in the inner peripheral side wall 6 of the cylinder bore 4. The exhaust opening 11 is connected to an exhaust passage 12 formed in the cylinder block 2. A muffler (not shown) communicating with the exhaust passage 12 is attached to the cylinder block 2 on the exhaust passage 12 side. The intake opening 13 is connected to an intake passage 14 formed in the cylinder block 2. An insulator 15 is attached to the cylinder block 2 on the intake passage 14 side, and an insulator-side intake passage 16 of the insulator 15 is connected to the intake passage 14. A diaphragm type carburetor 17 is attached to the side of the insulator 15 opposite to the side where the cylinder block 2 is attached. Connected to the carburetor 17 are a fuel supply pipe (fuel supply passage) 19 for supplying fuel from the fuel tank 18 and a return pipe (return passage) 20 for returning fuel from the carburetor 17.

  At the upper part of the cylinder block 2, a spark plug 25 having an electrode 24 facing a combustion chamber 23 defined by the top wall surface 21 above the cylinder bore 4, the top surface 22 of the piston 5, and the inner peripheral wall 6 of the cylinder bore 4. Is installed. In addition, a pressure reducing valve 26 that can be opened and closed faces the combustion chamber 23 at the upper part of the cylinder block 2, and when the pressure reducing valve 26 is opened, the compressed gas in the combustion chamber 23 is supplied to a pressure transmission pipe (pressure transmission path). ) A decompression device 28 for discharging through 27 is attached. Note that the other end of the pressure transmission pipe 27 whose one end is connected to the decompression device 28 is connected to the vaporizer 17.

  As shown in FIGS. 3 and 4, the carburetor 17 has a first fuel passage 30 having one end connected to the fuel supply pipe 19 and the other end connected to a metering chamber (fuel storage portion) 29 that stores fuel. Have The metering chamber 29 repeats compression deformation and elastic recovery to suck fuel into the fuel suction port 31 while discharging the fuel sucked into the fuel discharge port 32 to the fuel suction port 31 of the priming pump 33. The second fuel passage 34 is connected. A main jet 35 is connected to the metering chamber 29, and fuel in the metering chamber 29 is supplied to the venturi 37 portion of the intake passage of the carburetor 17 through the main nozzle 36 of the main jet 35. Further, the fuel discharge port 32 of the priming pump 31 is provided with a one-way valve (one-way valve) 38 that allows only the movement of fuel from the inside of the priming pump 31 toward the outside of the fuel discharge port 32. The fuel discharge port 32 is connected to a third fuel passage 41 connected to a starting fuel chamber (starting fuel storage chamber) 40 of a starting fuel supply device 39 configured integrally with the carburetor 17. The starting fuel chamber 40 further includes a fourth fuel passage 42 connected to the return pipe 20, and a fifth fuel passage (starting) connected to a starting fuel supply nozzle 43 that opens in the venturi 37 portion of the intake passage of the carburetor 17. The fuel supply passage 44). Further, inside the starting fuel chamber 40, a chamber valve (control device, control valve) 45 that opens and closes communication between the starting fuel chamber 40 and the fifth fuel passage 44, and one end 46 of the chamber valve 45. And a spring 48 that urges the chamber valve 45 in a direction to close the fifth fuel passage 44 by pressing the valve seal 47 against the valve seal 47. The other end 49 of the chamber valve 45 is disposed in the pressure chamber 50 to which the pressure transmission pipe 27 is connected. The chamber valve 45 is provided with an O-ring 51 that keeps the space between the other end 49 of the chamber valve 45 and the pressure chamber 50 during the movement of the chamber valve 45. The urging force of the spring 48 is the chamber valve 45 when the compressed gas pressure (pressure equal to or greater than the second predetermined value) in the cylinder bore 4 (see FIG. 2) is transmitted from the pressure transmission pipe 27 during cranking. 4 is opened (the state shown in FIG. 4 is such that one end 46 of the chamber valve 45 and the valve seal 47 are separated), and the chamber valve 45 is normally closed (one end 46 of the chamber valve 45 contacts the valve seal 47). 3 is in contact).

  As shown in FIG. 5, the decompression device 28 includes an outer cylinder portion 52 having a substantially cylindrical shape that is inserted into and attached to the cylinder block 2, a decompression passage 53 formed inside the outer cylinder portion 52, and a decompression passage 53. The pressure reducing valve 26 is supported so as to be movable in the longitudinal direction (vertical direction in the figure) and opens and closes the pressure reducing opening 57 of the pressure reducing passage 53, and the operation button 54 opens the pressure reducing valve 26. An exhaust chamber 55 is connected to the decompression passage 53. The exhaust chamber 55 communicates with the cylinder bore 4 via the pressure reducing passage 53 when the pressure reducing valve 26 is opened. Further, the exhaust chamber 55 is connected to the pressure transmission pipe 27 via the exhaust passage 56. The pressure reducing valve 26 is held in the open position by pushing the operation button 54, while the pressure in the combustion chamber 23 when the air-fuel mixture is ignited in the combustion chamber 23 (closed position at a pressure equal to or higher than the first predetermined value). Return to.

  According to the engine 1 configured as described above, when an operator starts the engine 1, first, an operation of pushing the plumbing pump 33 several times is performed, and fuel is sucked from the fuel tank 18. The fuel sucked from the fuel supply pipe 19 of the fuel tank 18 flows into the metering chamber 29 of the carburetor 17 through the first fuel passage 30. Then, the fuel exceeding the amount that can be stored in the metering chamber 29 flows into the plumbing pump 33 from the fuel suction port 31 of the plumbing pump 33 through the second fuel passage 34. The fuel flowing into the plumbing pump 33 passes through the one-way valve 38 and flows into the starting fuel chamber 40 from the third fuel passage 41, and the fuel exceeding the amount that can be stored in the starting fuel chamber 40 is the fourth fuel passage 42. To the fuel tank 18 through the return pipe 20. As a result, fuel is stored in the metering chamber 29 and the starting fuel chamber 40, respectively. Next, the operation button 54 of the decompression device 28 is operated to open the pressure reducing valve 26. Then, cranking is performed by operating a recoil starter (not shown). At this time, a choke operation or a half throttle operation may be performed as necessary.

  When the crankshaft 9 rotates, the air-fuel mixture in the cylinder bore 4 is compressed by the piston 5. A part of the compressed air-fuel mixture passes through the decompression opening 57, the decompression passage 53, the exhaust chamber 55, the exhaust passage 56, and the pressure transmission pipe 27 from the opened decompression valve 26 portion of the decompression device 28, and then the starting fuel supply device. The pressure in the pressure chamber 50 of the starting fuel supply device 39 rises. The increase in pressure in the pressure chamber 50 acts on the other end 49 of the chamber valve 45, and the chamber valve 45 opens in the direction in which the chamber valve 45 opens against the spring 48 from the state shown in FIG. ) And the state shown in FIG. 5 is obtained. When the venturi 37 portion of the intake passage of the carburetor 17 becomes negative pressure, fuel is supplied from the metering chamber 29 via the main nozzle, and the starting fuel supply nozzle 43 is connected from the starting fuel chamber 40. After that, the starting fuel is supplied. For this reason, the starting fuel supply device 39 can be operated only by the operation of the decompression device 28 to increase the concentration of fuel in the air-fuel mixture supplied into the cylinder bore 4, thereby improving the startability of the engine 1. In addition, the operability when starting the engine can be improved.

  Further, when the cranking is repeated without starting the engine 1, every time the pressure in the cylinder bore 4 at the time of cranking increases, the starting fuel can be automatically supplied, so that the operator can be supplied with the cranking. This reduces the burden on the engine and improves the operability when starting the engine. When the engine 1 is started, the pressure in the combustion chamber 23 rises and the pressure reducing valve 16 is closed, so that the pressure in the pressure chamber 50 does not rise and the chamber valve 45 is held closed by the spring 48. For this reason, after the engine 1 is started, the supply of the starting fuel from the starting fuel supply device 39 can be automatically stopped. From this point as well, the burden on the operator is reduced and the engine is started. Operability can be improved. Further, since the one-way valve 38 that allows only the flow of fuel from the metering chamber 29 to the start fuel chamber 40 is provided between the metering chamber 29 and the start fuel chamber 40, Even when the starter fuel is supplied to the carburetor 17, it is possible to eliminate pressure fluctuations in the metering chamber 29 due to the starter fuel supply from the starter fuel chamber 40. Fuel can be stably supplied from the ring chamber 29. Moreover, since the starting fuel supply device 39 is configured integrally with the carburetor 17, it can be easily attached to the existing engine 1.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention is not limited to the above-mentioned embodiment, In the range of this invention, it can change suitably. For example, the engine 1 is not limited to being mounted on the brush cutter 1001, and may be mounted on other engine working machines such as a chain saw, a concrete cutter, a hedge trimmer, and the like. The engine 1 is not limited to a two-cycle engine, and may be a four-cycle engine.

1 2-cycle engine (engine)
2 Cylinder block 4 Cylinder bore 5 Piston 9 Crankshaft 17 Vaporizer 18 Fuel tank 19 Fuel supply pipe (fuel supply passage)
20 Return pipe (return passage)
23 Combustion chamber 25 Spark plug 26 Pressure reducing valve 27 Pressure transmission pipe (pressure transmission path)
28 Decompression unit 29 Metering chamber (fuel reservoir)
30 First fuel passage 31 Fuel suction port 32 Fuel discharge port 33 Priming pump 34 Second fuel passage 37 Venturi 38 in intake passage One-way valve (one-way valve)
39 Starting fuel supply device 40 Starting fuel chamber (starting fuel storage chamber)
41 Third fuel passage 42 Fourth fuel passage 43 Starting fuel supply nozzle 44 Fifth fuel passage (starting fuel supply passage)
45 Chamber valve (control device, control valve)
46 One end portion 48 of the chamber valve 48 Spring 49 The other end portion 50 of the chamber valve

Claims (6)

A cylinder block in which a cylinder bore in which a piston slides is formed;
A carburetor for supplying a mixture of fuel and air into the cylinder bore;
A decompression device comprising: a pressure reducing passage communicating with the cylinder bore; and a pressure reducing valve that causes the pressure reducing passage and the cylinder bore to communicate with each other when the valve is opened and closes the communication upon receiving a pressure equal to or higher than a first predetermined value in the cylinder bore;
A pressure transmission path provided in the decompression device for transmitting pressure in the cylinder bore;
A starting fuel supply device for increasing the fuel concentration of the air-fuel mixture supplied into the cylinder bore at the time of starting;
A control device that is connected to the pressure transmission path and controls the supply of the starting fuel by the starting fuel supply device in accordance with the pressure transmitted from the cylinder bore;
An engine characterized by that. The start fuel supply device connects a start fuel storage chamber for storing the start fuel, a start fuel supply nozzle provided in an intake passage of the carburetor, and the start fuel storage chamber. A fuel supply passage,
The control device has a control valve that opens and closes the starting fuel supply passage according to the pressure transmitted from the pressure transmission passage.
The engine according to claim 1. A fuel storage section provided in the carburetor for storing fuel supplied from a fuel tank via a fuel supply passage and supplying the fuel into the intake passage;
Provided between the fuel storage section and the starting fuel storage chamber, by repeating compression deformation and elastic recovery, the fuel is sucked into the fuel storage section and the sucked fuel is supplied to the starting fuel storage chamber. A priming pump that discharges, and a one-way valve that allows fuel to move from the fuel reservoir to the starting fuel reservoir;
A return passage for discharging the fuel overflowed from the starting fuel storage chamber to the fuel tank,
The engine according to claim 2. The control valve opens when a pressure transmitted from the pressure transmission path is equal to or greater than a second predetermined value;
The engine according to claim 2 or 3, characterized in that. The starting fuel supply device and the control device are configured integrally with the carburetor.
The engine according to any one of claims 1 to 4, characterized in that: The engine according to any one of claims 1 to 5, comprising:
An engine working machine characterized by that.

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