JP2623102B2 - Starting fuel supply system for rotary throttle valve type membrane carburetor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a starting fuel supply apparatus for a rotary throttle valve type membrane carburetor of an internal combustion engine mounted on a portable work machine.

[Prior Art] A membrane carburetor of an internal combustion engine mounted on a portable working machine such as a bush cutter can operate the engine in all postures, and supplies an appropriate amount of fuel according to the operating conditions of the engine. Although a supply mechanism is provided, a start-up fuel supply mechanism as disclosed in, for example, Japanese Utility Model Laid-Open No. 62-41955 is separately provided since the range of the concentration of the air-fuel mixture that can be started in cold weather is limited. In this starting fuel supply mechanism, since the starting fuel measured in the starting fuel reservoir is supplied to the porous fuel storage member in the intake passage by a natural head, the starting fuel reservoir is disposed higher than the intake passage. This has the disadvantage that it takes a considerable amount of time to supply the starting fuel to the fuel storage member in the intake passage.

Therefore, according to Japanese Patent Application No. 62-221000, the present applicant holds the fuel in the constant pressure fuel chamber as the starting fuel in the starting fuel chamber by the suction-type primer pump, and starts the engine in the starting fuel chamber by the starting fuel pump. An application has been filed for supplying fuel under pressure to a porous fuel retaining member in an intake passage. But,
In this starting fuel supply device, the fuel in the starting fuel reservoir is supplied to the fuel storage member each time the elastic body of the starting fuel pump is pressed, so that the engine cannot be started by one start (recoil) operation. Excessive starting fuel is supplied to the fuel storage member and eventually overflows into the intake passage, which prevents the engine from starting smoothly. Providing a porous fuel retaining member in the intake passage reduces the intake passage or enlarges the carburetor body.

[Problems to be Solved by the Invention] In view of the above problems, an object of the present invention is to be integrally formed with a carburetor, and to ensure that an appropriate amount of starting fuel is supplied only once from the starting fuel chamber to the vicinity of the intake passage when starting the engine. It is an object of the present invention to provide a starting fuel supply device for a rotary throttle valve type membrane carburetor, which is supplied to a starting fuel storage chamber.

[Means for Solving the Problems] To achieve the above object, the configuration of the present invention is to provide a starting fuel storage chamber at the bottom of a cylindrical portion that traverses the intake passage of a membrane carburetor and that inserts and supports a rotary throttle valve. The starting fuel holding chamber is formed to communicate with the intake passage via a gap between the rotary throttle valve and the cylindrical portion, and the discharge port of the suction-type primer pump communicating with the constant pressure fuel chamber of the membrane carburetor is used for starting fuel. The starting fuel chamber is connected to a fuel tank via a relief valve, and the starting fuel chamber is connected to the starting fuel holding chamber via a fuel release valve which is manually opened when starting the engine. It was made.

[Operation] When the primer pump C is operated before the engine is started, the fuel in the constant pressure fuel chamber 38 is sucked into the pump chamber 43 and the pump chamber 43 is operated.
From the fuel tank 25 through the pressure accumulating mechanism E. When the starting fuel chamber 25 is filled with fuel, excess fuel is released
The gas is discharged to the outside through 26 or returned to the fuel tank 32.
Next, when the fuel discharge valve D is operated, the fuel in the starting fuel chamber 25 passes through the chamber 25a of the fuel discharge valve D and the passage 20, and the starting fuel storage chamber 19 below the throttle valve 8 of the rotary throttle valve type membrane carburetor. Sent to When the engine is started (recoiled), the fuel in the constant pressure fuel chamber 38 is drawn into the intake passage 11 through the fuel jet 46, and the starting fuel in the starting fuel storage chamber 19 is drawn into the intake passage 11 at the same time. The mixture is generated, and the engine is started smoothly.

Once the fuel release valve D is operated, the entire amount of fuel in the starting fuel chamber 25 is supplied to the starting fuel storage chamber 19, and even if the operation is repeated thereafter, no new starting fuel is sent. Therefore, it is possible to avoid a situation in which an abnormally high concentration of the air-fuel mixture is generated due to the repetition of the starting operation, which hinders the starting of the engine.

[Embodiment of the Invention] As shown in Fig. 1, a starting fuel supply device for a rotary throttle valve type membrane carburetor according to the present invention comprises a carburetor body 18, a fuel supply pump A, a fuel supply mechanism B, and a suction device. Type, a pressure pump E, and a fuel discharge valve D are integrally provided. A vertically extending cylindrical portion 2 is formed at the center of a main body 18 having a laterally extending intake passage 11, and the upper end of the cylindrical portion 2 is closed by a lid 12. A rotary throttle valve 8 having a slot hole 8a in the cylindrical portion 2 is fitted so as to be rotatable and slidable in the axial direction. A shaft portion 14 extending upward from the throttle valve 8 is supported by the lid 12, and a follower 16 is supported by a lever 15 coupled to the upper end of the shaft portion 14. The follower is moved between the lid 12 and the throttle valve by the force of a spring 13 surrounding the shaft 14.
16 is urged into engagement with a cam surface 17 provided on the lid 12, and the lever
When the lever 15 is rotated, the throttle valve 8 moves in the axial direction. At this time, the rod valve 3 integrated with the adjustment bolt 14a screwed into the screw hole of the shaft portion 14 also moves in the axial direction together. The spring 5 surrounding the rod valve 3 inside the screw hole facilitates adjustment of the position of the rod valve 3 with respect to the shaft portion 14. The fuel supply pipe 7 whose opening degree of the injection hole 6 is adjusted by the rod valve 3 is fixedly supported on the bottom wall of the main body 18. The fuel supply pipe 7 includes a fuel jet 46 and a check valve 47.
After that, the fuel is communicated to a constant pressure fuel chamber 38 for holding the fuel at a constant pressure.

The fuel supply pump A has a membrane 53 and a
Pulsating pressure introducing chamber having a pulsating pressure introducing port 59 on the upper side
A pump chamber 55 is formed on the lower side, and a pump chamber 55 is formed on the lower side. The pulsating pressure introduction chamber 54 is connected to, for example, a crank chamber of a two-cycle engine, and reciprocates the membrane 53 up and down. Pump room 55 is passage 5
1. Connected to the fuel tank 32 via the check valve 10 and the connection pipe 31. The pump chamber 55 is connected to the constant pressure fuel chamber 38 via the check valve 4, the passage 52, and the fuel inflow valve 9.

The membrane 34 and the cover 28 are coupled to the lower surface of the main body 70, thereby dividing the constant-pressure fuel chamber 38 on the upper side and the atmosphere chamber 36 having the atmosphere port 58 on the lower side. A lever 41 is supported by a support shaft 40 inside the constant pressure fuel chamber 38. The left end of the lever 41 is abutted against the membrane 34 by a spring, while the right end supports the tapered fuel inflow valve 9. The fuel in the fuel tank 32 is
From the fuel inlet valve 9 through a strainer, a check valve 10, a passage 51, a pump chamber 55, a check valve 4, and a passage 52.

The book 33 is joined to the collar 28 with the film 61 interposed therebetween. The film 61 forms a pressurized chamber 64 on the upper side and an air chamber 62 having an air port 49 on the lower side. The membrane 61 is pushed up by the spring 63 of the atmosphere chamber 62 through the backing plate, and the pressurizing chamber 64 and the starting fuel chamber
25 fuels are pressurized. The pressurizing chamber 64 communicates with the starting fuel chamber 25 via the passage 30. The pressurizing chamber 64 has a passage 65 and a check valve.
It is connected to the pump chamber 43 of the primer pump C via 48.

In the primer pump C, a pump chamber 43 is formed by connecting a hemispherical pressing body 42 made of rubber or the like to a main body 33, and a check valve 48 and a check valve 45a are provided inside. The check valve 48 crushes the upper end of the rubber hollow cylinder flat, and the check valve 45a is formed as a lip by expanding the lower end of the cylindrical body radially outward. The pump chamber 43 is communicated with the constant pressure fuel chamber 38 via the check valve 45a and the passage 50.

The fuel discharge valve D includes a cylinder 35 connected to the starting fuel chamber 25 formed in the main body 18. Seal member 22 on cylinder 35
The piston 21 fitted through the valve is pressed against the valve seat 23 by the spring 24. The middle part of the piston 21 has a small diameter,
The lower end has a conical portion that engages the valve seat 23. The chamber 25a of the cylinder 35 communicates with the starting fuel storage chamber 19 integral with the cylindrical part 2 through the passage 20 so as to pivotally and slidably engage the lower end of the throttle valve 8, thereby starting fuel storage. The fuel in the chamber 19 is sucked into the intake passage 11 through a gap between the fitting portion between the cylindrical portion 2 and the throttle valve 8 and a gap between the fitting portion between the throttle valve 8 and the fuel supply pipe 7.

Next, the operation of the starting fuel supply device for the rotary throttle valve type membrane carburetor according to the present invention will be described. When the pressing member 42 of the primer pump C is repeatedly pressed before starting the engine, a negative pressure acts on the pump chamber 43, and the fuel in the constant pressure fuel chamber 38 passes through the passage 50 and the check valve 45a to the pump chamber 43. It is sucked. The fuel in the pump chamber 43 is supplied to the check valve 48, the passage 65, the pressurizing chamber 64, and the passage 30.
Is sent to the starting fuel chamber 25. Excess fuel escape valve 2
6. The gas is discharged outside through the passage 27 and the discharge pipe 29 or returned to the fuel tank 32.

When the fuel in the constant pressure fuel chamber 38 becomes low, the membrane 34 is pushed up, the fuel inflow valve 9 is pulled down via the lever 41, and the passage 52 communicates with the low pressure fuel chamber 38. Fuel tank 32
Is supplied to the low-pressure fuel chamber 38 through the connection pipe 31, the check valve 10, the passage 51, the pump chamber 55, the check valve 4, the passage 52, and the fuel inflow valve 9, and the fuel inflow valve 9 is closed. Next, when the piston 21 of the fuel discharge valve D is pushed down, the starting fuel in the starting fuel chamber 25 is supplied to the starting fuel storage chamber 19 through the chamber 25a and the passage 20.

Next, when the engine is started (recoiled), the starting fuel in the starting fuel storage chamber 19 is sucked by the intake air passing through the intake passage 11, and a high-concentration air-fuel mixture is generated. In addition, the intake air passing through the throttle hole 8a of the throttle valve 8 causes the fuel in the constant-pressure fuel chamber 38 to flow through the check valve 47, the fuel jet 46, and the fuel supply pipe 7.
Through the nozzle hole 6. As a result, a mixture having a higher concentration than that in the normal operation is generated, so that the engine is started smoothly.

[Effects of the Invention] As described above, according to the present invention, a starting fuel storage chamber is formed at the bottom of a cylindrical portion that traverses the intake passage of a membrane carburetor and that supports a rotary throttle valve. Communicating with the intake passage through a gap between the throttle valve and the cylindrical portion,
The discharge port of the suction-type primer pump communicating with the constant-pressure fuel chamber of the membrane-type carburetor is connected to a starting fuel chamber that holds the starting fuel under pressure, and the starting fuel chamber is connected to a fuel tank via a relief valve, and the starting fuel chamber is connected. Is connected to the starting fuel storage chamber via a fuel release valve that is manually opened at the time of engine start, and the starting fuel chamber is formed integrally with the carburetor body, and the starting fuel supplied from the starting fuel chamber is provided. Is stored in the starting fuel storage chamber adjacent to the intake passage below the throttle valve, so that it can be easily provided in the conventional rotary throttle valve type membrane carburetor. Has no effect.

Since the fuel in the constant pressure fuel chamber is supplied to the starting fuel chamber by the primer pump, even if the fuel discharge valve is changed and operated,
Since a fixed amount of starting fuel is sent to the starting fuel storage chamber below the throttle valve, and excess fuel is returned to the fuel tank via the relief valve, the situation of overflowing into the starting fuel intake passage is avoided.

Since the pump chamber and the starting fuel chamber of the primer pump are connected inside the carburetor main body, there is no conduit exposed to the outside, the whole shape is small, and the assembly is easy.

Since the fuel in the starting fuel chamber temporarily stays in the starting fuel storage chamber below the throttle valve, it does not affect the shape of the carburetor body, and even if the engine is slightly inclined, the starting fuel does not overflow into the intake passage. Therefore, there is no need to provide a porous fuel retaining member. At the same time as the operation of the fuel discharge valve, the starting fuel is supplied to the starting fuel storage chamber below the throttle valve and is quickly sucked into the intake passage, so that the engine can be started quickly.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a rotary throttle valve type membrane carburetor provided with a starting fuel supply device according to the present invention. A: fuel supply pump, B: fuel supply mechanism, C: suction-type primer pump, D: fuel release valve, E: pressure accumulator, 6: injection hole, 8: throttle valve, 11: intake passage, 19: starting fuel reserve Chamber, 21: piston, 2
5: Start fuel chamber, 32: Fuel tank, 35: Cylinder, 38: Constant pressure fuel chamber, 42: Pressing body, 43: Pump chamber

Claims (1)

(57) [Claims] 1. A starting fuel storage chamber is formed at the bottom of a cylindrical portion that traverses an intake passage of a membrane type carburetor and that inserts and supports a rotary throttle valve. The starting fuel storage chamber is formed between the rotary throttle valve and the cylindrical portion. The suction port of the suction-type primer pump communicating with the constant pressure fuel chamber of the membrane type carburetor is connected to the starting fuel chamber which holds the starting fuel under pressure, and the starting fuel chamber is provided with a relief valve. Characterized in that the starting fuel chamber is connected to the starting fuel storage chamber via a fuel release valve that is manually opened when the engine is started, the rotary throttle valve type membrane carburetor. Starting fuel supply.