JP2009209691A - Carburetor of two-cycle engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carburetor inexpensively reduced in manual operations, and having superior startability and durability. <P>SOLUTION: In this carburetor 12 of a two-cycle engine, a choke valve is installed on the upstream side of an air passage, a fuel is sucked from a fuel tank 16 by a fuel diaphragm valve 23 operated due to the pulsation of the intake air and supplied to a fuel nozzle 22 in the air passage, and the air-fuel mixing ratio is controlled by a throttle valve. The carburetor comprises an air chamber 15a and an air pipe 36 for taking the pulsating pressure in a crankcase into the air chamber 15a and a fuel tank pipe 37 led to a carburetor side passage 35 to the fuel sump chamber 18 side of the carburetor 12 and the fuel tank 16. The carburetor further comprises a fuel pump 15 having a check valve 15b for stopping the return side of the carburetor 12 in the carburetor side passage 35 and a check valve 15c for stopping the return side from the fuel tank 16 in the fuel tank pipe 37 and a means for operating the sub fuel pump 15 only when an engine is started. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a carburetor for a two-cycle engine, and more particularly to a configuration provided with a sub fuel pump that operates by pulsating pressure in a crank chamber in order to fill the carburetor with fuel when the engine is started.

  A conventional two-cycle engine carburetor disclosed in Patent Document 1 is a diaphragm pump that sucks up fuel by using pulsation pressure in the crank chamber during operation, and fuel in the fuel tank in the fuel tank at startup And a manual primer pump that has a combination valve that circulates and flows, and an overflow pipe that returns excess fuel to the fuel tank. During startup, the primer pump is manually crushed to suck up the fuel and fill it into the carburetor. The carburetor is configured to enable the excess fuel and return the fuel to the fuel tank.

In a conventional two-cycle engine carburetor disclosed in Patent Document 2, the above-described primer pump is replaced with a cam provided in a rotating portion of a recoil starter and a fuel pump interlocked with an actuator that operates the cam. . At the time of start-up, an actuator interlocked with the pulling operation of the recoil starter operates the pump to suck up the fuel and fill the carburetor so that it can be started, and the surplus fuel returns to the fuel tank.
Japanese Patent Laid-Open No. 2002-48008 (FIG. 1) JP 2006-275047 A (FIG. 1)

  The carburetor of the two-cycle engine of Patent Document 1 has many manual start operations, and it becomes difficult to start if there is an opportunity for the user to make a mistake in part of the operation or the order. In addition, the vaporizer of Patent Document 2 is often required to have high precision in its component parts, is expensive, and the pump actuator is frequently struck by the starter cam, increasing the tensile force of the recoil starter. However, there are problems such as the start operation being impaired.

  An object of the present invention is to solve a problem in a conventional carburetor for starting a small two-cycle engine, to provide a carburetor excellent in startability and durability by reducing manual operation at low cost. To do.

With respect to the above problems, the present invention aims to solve the problems by the following means.
(1) A carburetor of a two-cycle engine as a first means includes a choke valve upstream of an air passage, and sucks fuel from a fuel tank by a fuel diaphragm valve that is operated by pulsation of intake air to serve as a fuel nozzle in the air passage. In the carburetor of a two-cycle engine that supplies and adjusts the mixing ratio of air fuel by a throttle valve, the carburetor side to the air chamber and the air piping that takes in the pulsation pressure of the crank chamber into the air chamber and the carburetor to the fuel reservoir chamber side A sub fuel having a fuel tank pipe communicating with the passage and the fuel tank, a check valve for stopping the return side to the carburetor on the carburetor side passage, and a check valve for stopping the return side from the fuel tank on the fuel tank pipe The pump and the means for operating the sub fuel pump are performed only when the engine is started.

(2) The two-cycle engine carburetor according to the second means is the above-described two-cycle engine carburetor according to the first means, wherein the sub fuel pump is operated only when the engine is started. It is an on-off valve that opens and closes in conjunction with a choke valve provided in an air pipe that takes in the pulsating pressure of the crank chamber into the air chamber of the sub fuel pump.

(3) The carburetor for the two-cycle engine of the third means is the notch provided in the rotating shaft of the choke valve in the carburetor for the two-cycle engine of the second means. The air passage between the passage port from the pulsation pressure source provided on the bearing boss of the rotating shaft and the passage port to the sub fuel pump is opened and closed by the operation rotation of the choke valve. It is characterized by that.

(4) The means for causing the carburetor for the two-cycle engine of the fourth means to perform the operation of the sub fuel pump only when starting the engine in the carburetor for the two-cycle engine of the first means, When the engine is started by the pull starter, the cam of the pull starter is composed of a cam provided in the rotating part of the pull starter and an on-off valve operated by a cam follower installed in the air piping from the pulsation pressure source to the sub fuel pump. The cam follower that engages with the cam when it rotates rotates the piston valve of the on / off valve so that the on / off valve is opened.

(5) The carburetor for the two-cycle engine of the fifth means is the carburetor for the two-cycle engine of the fourth means, wherein the on-off valve installed in the air piping to the pulsation pressure source and the sub fuel pump is a piston By providing a check valve and a throttle adjusting valve at the closing head of the closing cylinder that guides the valve, the piston valve is maintained in the open position for a while.

  In the invention according to claims 1 to 3, when starting the two-cycle engine, in order to bring the fuel in the carburetor into a state suitable for starting, the opening / closing valve interlocked with the choke valve is opened when starting the engine, The sub fuel pump is operated by the pulsation pressure of the crankcase, and the fuel mixture gas having a mixture ratio suitable for starting is supplied from the fuel nozzle of the carburetor to the engine. In this configuration, since the rotation shaft of the choke valve also serves as the pulsating pressure air on / off valve for driving the sub fuel pump, the number of parts is small, the structure is simple, and the manufacturing cost is low.

  According to a fourth aspect of the present invention, instead of the on-off valve that opens and closes in conjunction with the choke valve at the time of starting the engine according to the first to third aspects, a cam provided on the rotating portion of the pull starter and a cam follower operated by the cam When the engine is started by a pull starter, the cam follower that engages with the cam opens the on-off valve, and the passage (air piping) from the pulsation pressure source to the sub fuel pump leads to the darkness. The fuel mixture of the eyes can be supplied to the engine.

  According to a fifth aspect of the present invention, the cam follower-operated on / off valve according to the fourth aspect is provided with a check valve and a throttle adjusting valve on the closing head (closing head) of the guide cylinder of the piston valve. Since it has a timer structure that keeps the position, the cam follower will not be in contact with the cam even if it rotates several times after the on-off valve is opened by one operation of the cam of the rotating part of the pull starter, The tensile force of the recoil starter is not impaired, and the durability is improved.

(First embodiment)
The configuration of this embodiment will be described with reference to the drawings. FIG. 1 is a side sectional view of a two-cycle engine according to the present embodiment and a schematic diagram showing a means for operating a sub fuel pump for additionally supplying fuel to the carburetor only when the engine is started. FIG. 3 is an enlarged view of a portion A showing the configuration of the gas tank and the sub fuel pump, FIG. 3 is a sectional view taken along the line CC in FIG. 2, FIG. 4 is an enlarged view of the portion B showing the on-off valve also serving as the choke rotation shaft in FIG. It is DD sectional drawing showing the rotation angle position of 4 on-off valves.

  In the figure, a two-cycle engine 10 includes a cylinder 1, a crank chamber 2, a piston 3 sliding in the cylinder 1, a crankshaft 5, a piston pin 7 and a crankpin 6 connected to each other in the cylinder 1. The piston rod 4 that converts the combustion gas pressure into the rotational force of the crankshaft 5, the carburetor 12, the air cleaner 13, a muffler (not shown), and the like.

  Air for combustion gas is sucked from the air supply port of the air cleaner 13, dust is removed by the air filter 14, and sent to the vaporizer 12. Fuel is ejected and vaporized from the fuel nozzle 22 by the negative pressure of the throat of the carburetor 12, and the mixture ratio of the air fuel is adjusted by the throttle valve 12a to become a mixed gas, which passes through the insulator 11 and is cranked in the compression exhaust stroke of the engine 10. In the second half of the exhaust stroke, the air is sucked into the chamber 2 and pushed into the combustion chamber of the cylinder 1 by the back pressure of the piston in the crank chamber 2, compressed and ignited to burn the mixed gas, and the piston 3 is pushed down to drive the engine. Occurs and the crankshaft 5 rotates. The exhaust gas that has been combusted is exhausted from the exhaust port that is opened when the piston 3 moves downward to the outside air through a muffler (not shown).

  Although pulsation pressure is generated in the crank chamber 2 by sliding of the piston 3, the pulsation pressure is transmitted to the carburetor 12 through the air passages 2 a, 1 a, and 21 a connected to the crank chamber 2 and incorporated in the carburetor 12. The diaphragm valve 23 is operated, and the fuel in the fuel tank 16 is sucked into the fuel passage 19 a in the carburetor body 19 through the pipe 17 by the inlet valve 65 and the outlet valve 66. The fuel enters the metering chamber 18c of the fuel reservoir chamber 18 from the fuel passage 19a through the passage 18d in which the inlet needle valve 24 is inserted. Reference numeral 17a denotes a filter.

  A metering diaphragm 28 is attached to the metering chamber 18c with one side opened to atmospheric pressure. The metering lever 25 installed in the metering chamber 18c has a tip 25a engaged with the small diameter portion 24c of the inlet needle valve 24, and the lever plate 25b can be contacted with a contact member 29 of the metaling diaphragm 28. Yes. The metering lever 25 pushes the flange 24b of the inlet needle valve 24 by the metering lever spring 26, and is urged in the direction of closing the fuel passage 19a by the needle 24a at the tip, and in balance with the moving amount of the metering diaphragm 28, The inflow of the fuel is controlled by adjusting the gap with the fuel passage 19a with the needle 24a so that the negative pressure in the ring chamber 18c becomes constant.

  A main check valve 33 is installed in the fuel outlet passage of the metering chamber 18 c, and the amount of fuel that can produce the maximum output from the main check valve 33 at the high speed needle 34 is adjusted and sent to the fuel nozzle 22. The main check valve 33 prevents air from being sucked from the fuel nozzle 22 when the pressure in the metering chamber 18c decreases. 32 is a packing interposed between the carburetor main body 19 and the fuel reservoir chamber 18, and 31 is a packing interposed between the fuel reservoir chamber 18 and the diaphragm cover 27.

  The sub fuel pump 15 provided separately from the carburetor 12 includes an air chamber 15a, an air pipe 36 for taking the pulsation pressure in the crank chamber 2 into the air chamber 15a, and a passage 35 to the metering chamber 18c side of the carburetor 12. A pipe 37 communicating with the fuel tank 16; a check valve 15b for stopping the return side to the metering chamber 18c at the connection with the passage 35; and a connection from the fuel tank 16 to the connection with the pipe 37. And a check valve 15c for stopping the return side, and the operation of the sub fuel pump 15 is performed only when the two-cycle engine 10 is started.

  The air pipe 21 that takes in the pulsating pressure of the crank chamber 2 is coupled to the on-off valve 40 that is linked to the choke valve 41, and the air pipe 36 that is coupled to the on-off valve 40 is coupled to the air chamber 15 a of the sub fuel pump 15.

  The on-off valve 40 that opens and closes in conjunction with the choke valve 41 has a notch 42 a provided in the rotary shaft / rotary valve 42 of the choke valve 41 as an air passage, and the rotary shaft / rotary valve 42 is integrated with the intake pipe 44. The bearing boss 44c is rotatably supported. The bearing boss 44c is formed with a passage 44d that communicates with the air pipe 36 through the passage port 45 and a passage 44e that communicates with the air pipe 21 through the passage port 46. By movement, it leads to the notch 42a. That is, the notch portions 42a and 44d and 44e passages are opened and closed by the operation rotation (rotation angle α) of the choke valve 41, and the pulsation pressure is cut off when the notch portion 42a is in the position of the solid line in FIG. 5, the pulsating pressure acts on the air chamber 15a of the sub fuel pump 15 via the air pipe 21, the passage port 46, the passage 44e, the notch 42a, the passage 44d, the passage port 45, and the air pipe 36. To do. However, the rotation angle α shown in FIG. 5 indicates the rotation angle of the choke operation lever 43 and does not indicate the mounting angle between the air pipe 21 and the air pipe 36.

  The operation of the sub fuel pump 15 and the on-off valve 40 will be described. When starting the two-cycle engine 10, the choke valve 41 is actuated by the manual choke operation lever 43, and the air passage 44b of the air intake port 44a of the carburetor 12 is throttled. The air passage 44b of the carburetor 12 has a large negative pressure, and the fuel suction force is increased. As the choke valve 41 rotates, the notch portion 42a of the rotary shaft / rotary valve 42 rotates, and the air pipe 21 and the air pipe 36 are communicated with each other at the position indicated by the broken line in FIG. The fuel is transmitted to the air chamber 15a, and the function of the fuel pump is generated by the action of the check valves 15b and 15c to suck out the fuel in the metering chamber 18c of the carburetor 12 and promote the circulation of the fuel in the carburetor 12. Thereby, sufficient fuel is ejected from the fuel nozzle 22 without the fuel staying in the vaporizer 12.

(Second Embodiment)
A second embodiment will be described with reference to the drawings. FIG. 6 is a side sectional view of a two-cycle engine according to the present embodiment, and means for sending pulsating air for driving a sub fuel pump for supplying additional fuel to the carburetor only when the engine is started by pulling the pull starter. It is a schematic diagram shown.

  In the first embodiment, the switching of the pulsating air for driving the sub fuel pump is interlocked with the operation of the choke valve. In this embodiment, the switching of the pulsating air for driving the sub fuel pump is performed by the pull starter. Since this mechanism is linked to the pulling operation, the configuration and functions are the same except for this mechanism, including the sub fuel pump.

  In the drawing, an on-off valve 50 is attached to the crank chamber 2 and closed on one side, and provided with air passage ports 53c and 53d symmetrically in the cylindrical portion, and the rotational direction is restricted within the cylinder 53 and slides. A piston valve 54 having a through hole 54a in the radial direction, a piston rod 55 fixed to the piston valve 54, a cam follower 56 rotatably attached to the tip of the piston rod 55, and the piston rod 55 are cams It comprises a compression spring 57 that urges the follower 56 in the pushing direction, a check valve 63 provided at the closing head of the cylinder 53, a throttle adjusting valve 58, and outlets 53a and 53b.

  The means for driving the on-off valve 50 includes a pull starter 60 and a cam 52a provided on the rotating portion 52 of the pull starter 60. When the two-cycle engine 10 is started by pulling the handle 51 of the pull starter 60, the cam of the pull starter 60 is provided. When the valve 52a rotates, the cam follower 56 that engages the cam 52a pushes down the piston valve 54, and thereby the air pipe 61 that sends pulsation pressure, the through hole 54a of the piston valve 54, and the air pipe 62 that communicates with the sub fuel pump 15 are opened. The sub fuel pump 15 is activated.

Even when the cam follower 56 is disengaged from the cam 52a of the pull starter 60, the check valve 63 of the cylinder 53 prevents the return of air into the cylinder 53, and the throttle adjusting valve 58 throttles the air outlet 53b. Can hold the open position for some time. Thus, the operation of the sub fuel pump 15 is performed only when the two-cycle engine 10 is started.
When the two-cycle engine 10 starts rotating and the handle 51 of the pull starter 60 returns to the original position, air enters the cylinder 53 through the throttle adjustment valve 58, and the cam follower 56 also returns to the original position.

FIG. 2 is a side sectional view of the two-cycle engine according to the first embodiment of the present invention and a schematic view showing a means for operating a sub fuel pump for additionally supplying fuel to the carburetor only when the engine is started. It is the A section enlarged view which shows the structure of the vaporizer | carburetor of FIG. 1, and a sub fuel pump. It is CC sectional drawing of FIG. It is the B section enlarged view which shows the on-off valve for choke rotating shafts of FIG. It is DD sectional drawing showing the rotation angle position of the on-off valve of FIG. A side sectional view of a two-cycle engine according to the second embodiment of the present invention, and pulsating air for driving a sub fuel pump for supplying additional fuel to a carburetor only when the engine is started is sent by pulling operation of a pull starter. It is a schematic diagram which shows a means.

Explanation of symbols

Reference Signs List 2 crank chamber 10 two-cycle engine 12 carburetor 12a throttle valve 15 sub fuel pump 15a air chamber 15b, 15c, 63 check valve 16 fuel tank 17 piping 18 fuel reservoir chamber 19 carburetor body 21, 36 air piping 22 fuel nozzle 23 Diaphragm valve (diaphragm valve for fuel)
35 passage (vaporizer side passage)
37 Piping (fuel tank piping)
40, 50 On-off valve 41 Choke valve 42 Rotary shaft and rotary valve (rotary shaft)
42a Notch (air passage)
43 Choke operating lever 44b Air passage 44c Bearing boss 44d, 44e Passage (air passage)
45, 46 Passage port 52 Rotating part 52a Cam 53 Cylinder (closing cylinder)
54 Piston (Piston valve)
56 Cam follower 58 Throttle adjustment valve 60 Pull starter 61, 62 Air piping

Claims (5)

A two-cycle engine equipped with a choke valve upstream of the air passage, sucking up fuel from the fuel tank by a fuel diaphragm valve that operates by the pulsation of intake air, supplying it to the fuel nozzle of the air passage, and adjusting the mixing ratio of air fuel by a throttle valve In the vaporizer of
The air chamber is provided with an air pipe for taking in the pulsation pressure of the crank chamber into the air chamber, a carburetor side passage to the fuel reservoir chamber side of the carburetor, and a fuel tank pipe leading to the fuel tank. A sub fuel pump having a check valve for stopping the return side and a check valve for stopping the return side from the fuel tank in the fuel tank piping, and the operation of the sub fuel pump is performed only when starting the engine. And a carburetor for a two-cycle engine. The carburetor of a two-cycle engine according to claim 1,
The means for performing the operation of the sub fuel pump only when starting the engine is an on-off valve that opens and closes in conjunction with a choke valve provided in an air pipe that takes in the pulsating pressure of the crank chamber into the air chamber of the sub fuel pump A two-cycle engine carburetor characterized by The two-cycle engine carburetor according to claim 2,
The on-off valve interlocked with the choke valve has a notch provided on the rotating shaft of the choke valve as an air passage and a passage port from a pulsation pressure source provided on a bearing boss of the rotating shaft and a passage to the sub fuel pump 2. A carburetor for a two-cycle engine, wherein an air passage with a port is opened and closed by an operation rotation of a choke valve. The carburetor of a two-cycle engine according to claim 1,
The means that the operation of the sub fuel pump is performed only when the engine is started is operated by a cam provided in the rotating portion of the pull starter and a cam follower installed in the air piping from the pulsation pressure source to the sub fuel pump. When the engine is started by the pull starter, when the pull starter cam rotates, the cam follower engaged with the cam pushes the piston valve of the on / off valve to open the on / off valve. Features a two-cycle engine carburetor. The carburetor for a two-cycle engine according to claim 4,
The on-off valve installed in the air piping to the pulsation pressure source and the sub fuel pump is provided with a check valve and a throttle adjusting valve at the closing head of the closing cylinder that guides the piston valve, so that the piston valve opens for a while. A two-cycle engine carburetor characterized by maintaining the position of

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