JPH01151758A - Starting fuel feeder for carburetor - Google Patents

Abstract

PURPOSE:To improve starting performance of engine, in a system where fuel is fed from a metering chamber through a suction primer pump and an accumulator into a starting fuel chamber, by providing a circumferential path in the upper wall section of an accumulation chamber in the accumulator and communicating the path through a group of small holes with the accumulation chamber. CONSTITUTION:In a starting fuel feeder, a carburetor body 18 comprises a fuel feed pump A, a fuel feed mechanism B, a suction primary pump C, an accumulator E and a starting valve D integrally. A rotary throttle valve 8 is fitted rotatably and movably in axial direction to a cylindrical section 2 formed vertically in the center of the body 18 having a suction path 11. Atmospheric chamber 36 of the fuel feed mechanism B and accumulation chamber 64 of the accumulator E are partitioned liquid-tightly through a cover board 73 so as to form a circumferential path 72 in the upper wall of the accumulation chamber 64. The circumferential path 72 is communicated through a plurality of small holes 64 arranged with interval in circumferential direction with the accumulation chamber 64 thus providing an air discharging means for leading the air from the accumulation chamber 64 to an outlet path 30.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a starting fuel supply device for a diaphragm type carburetor of an internal combustion engine used in a portable working machine such as a brush cutter.

C. Prior Art 1 This type of diaphragm carburetor allows the engine to be operated in all positions, and is equipped with a fuel supply mechanism that supplies an amount of fuel suitable for the operating conditions of the engine. However, when starting an engine in cold weather, the range of air-fuel mixture concentration is limited and the normal fuel supply mechanism has poor starting performance.
A starting fuel supply system as disclosed in Japanese Patent No. 955 is provided. However, in this starting fuel supply system, the starting fuel measured in the starting fuel reservoir is supplied to the porous fuel storage member in the intake passage due to natural head, so the starting fuel reservoir is arranged above the intake passage. There are also disadvantages in that it takes a considerable amount of time for the starting fuel to be supplied to the fuel storage member in the intake passage.

Therefore, by using a suction type primer pump to send the fuel in the metering chamber through the pressure accumulator to the starting fuel chamber, and opening the starting valve when starting the engine, the starting fuel in the starting fuel chamber is transferred to the intake passage. The application is for a starting fuel supply device for a pressure-fed carburetor. According to this starting fuel supply device, as soon as the starting valve is opened, the starting fuel amount is pressure-fed by the pressure of the pressure accumulator to the fuel storage space arranged below the throttle valve, and then the intake air is further pumped by the intake i pressure. The air is drawn into the passage, creating a highly concentrated air-fuel mixture that allows the engine to start smoothly.

However, if the pressure accumulator, which is relatively flat due to mounting on the engine, is kept almost horizontal, there will be no problem in starting the engine, but if the pressure accumulator E is tilted, the primary When the inlet passage 65 from the pump C to the pressure accumulation chamber 64 is lower than the outlet passage 30 from the pressure accumulation chamber 64 to the starting fuel Flv, the fuel sent from the primer pump C to the pressure accumulation chamber 64 is mixed with the air in the pressure accumulation chamber 64. can be discharged from the outlet passage 30 to fill the pressure accumulation chamber 64 with fuel. However, as shown in FIG. Even if the air is sent to the pressure storage chamber 64, the air may not be completely removed. This air causes a change in the stored fuel, and the amount of starting fuel sent to the intake passage when starting the engine is not constant, impairing the startability of the e1 engine.

[Problems to be Solved by the Invention] Therefore, the purpose of the present invention is to prevent air from accumulating inside the pressure accumulator even when the engine is tilted, to fill the pressure accumulator with fuel, and to prevent the engine from starting within a specified period of time when starting the engine. An object of the present invention is to provide a starting fuel supply device for a carburetor, in which fuel is supplied to an intake passage.

Means for Solving Problem c] In order to achieve the above object, the configuration of the present invention is to send fuel from the metering base to the starting fuel chamber via a pressure accumulator using a suction type primer pump, and to release the fuel by opening the starting valve. In the case of pressure-feeding air intake passages, a circumferential passage is provided in the earthen wall of the pressure accumulator chamber of the pressure accumulator. ! It communicated with the pressure accumulation chamber through a small hole.

[Function] For example, even if the pressure accumulation chamber 64 is inclined and the inlet passage 65 connected to the primer pump C is located at a higher level than the outlet passage 30 connected to the starting fuel chamber 25, the air in the pressure accumulation chamber 64 will not flow into the inlet passage 65. The fuel flows from the nearby small hole 71 through the circumferential passage 72 in the earthen wall of the pressure accumulating chamber 64 to the outlet passage 30, and is sent from the outlet passage 30 to the starting fuel chamber 25. Starting fuel flv25 is relief valve 2
6 and is discharged to the outside together with excess fuel. Since the small hole 71 that communicates the circumferential passage 72 and the pressure accumulation chamber 64 has a narrow passage area, resistance to the flow of air is small, but it presents a large fluid resistance to the flow of fuel. Therefore, pressure accumulates in the small hole 71 near the outlet passage 30! 64 tries to flow in, but as the fuel is supplied to the pressure storage v64, the air in the pressure storage chamber 64 is pressurized faster than this fuel, and it enters the circumferential passage 72 from the small hole 71 near the inlet passage 65. , Zarani passage 74
and then flows to the outlet passage 30. In this way, as fuel is supplied from the primer pump C to the pressure accumulation chamber 64, the air in the pressure accumulation chamber 64 is first expelled to the outlet passage 30.

[Embodiments of the Invention] As shown in FIG. 1, a starting fuel supply device for a carburetor according to the present invention includes a fuel supply pump A, a fuel supply titlB, a suction type primer pump C, and a carburetor main body 18. It is integrally equipped with a pressure accumulator E and a starting valve. A vertical cylindrical part 2 is formed in the center of a main body 18 having a horizontal intake passage 11, and the upper end of this part is closed by a lid 12.

A rotary throttle valve 8 having a throttle hole 8a is fitted into the cylindrical portion 2 so as to be rotatable and movable in the axial direction. A shaft portion 14 extending upward from the calibration 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 16 is moved between the lid 12 and the valve 8 by the force of the spring 13 that surrounds the shaft 14.
When the lever 15 is rotated, the 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. A spring 5 surrounding the rod valve 3 inside the threaded hole facilitates adjustment of the position of the rod valve 3 with respect to the shaft 14.

A fuel supply pipe 7 whose opening degree of the nozzle 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 passes through a fuel jet 46 and a check valve 47, and is metered to hold the fuel at a constant pressure! 38.

The fuel supply pump △ has a diaphragm 53 on the bottom surface of the main body 18.
The main body 70 is combined to form a pulsating pressure introduction chamber 54 having a vibrating pressure introduction port 59 on the upper side and a pump 55 on the lower side. The pulsating pressure introduction chamber 54 is connected to, for example, a crank chamber of a two-stroke engine, and causes the diaphragm 53 to reciprocate up and down. The pump chamber 55 has a passage 51 and a check valve 10.
．． It is connected to a fuel tank 32 via a connecting pipe 31. In addition, the pump chamber 55 includes a check valve 4, a passage 52, a fuel inflow valve 9
The metering room 38 is communicated through the metering room 38.

A diaphragm 34 and a cover 28 are coupled to the lower surface of the main body 70, thereby defining a metering chamber 38 on the upper side and an atmospheric chamber 36 having an atmospheric air port 58 on the lower side. A lever 41 is supported by a support shaft 40 inside the metering chamber 38 .

The left end of the lever 41 is brought into contact with the diaphragm 34 by a spring, while the right end is locked with a taber-shaped fuel inlet valve 9. The fuel in the fuel tank 32 is supplied through the connecting pipe 31] Lena, the check valve 10, the passage 51, the pump chamber 55, the check valve 4,
The fuel F4 is sent to the inlet side of the F4 inlet valve 9 through the passage 52.

The pressure accumulator E is constructed by connecting a main body 33 with a diaphragm 61 sandwiched between the cover 28 and the lower side. An atmospheric chamber 6 having a pressure accumulation chamber 64 on the upper side of the diaphragm 61 and four atmospheric ports on the lower side.
2 are formed respectively.

A spring 63 is interposed between the bottom wall of the atmospheric chamber and a plate 67 placed against the underside of the diaphragm 61. Accumulator chamber 64 communicates with starting fuel chamber 25 via outlet passage 30 . Further, the pressure accumulation chamber 64 is communicated with the pump chamber 43 of the primer pump C via an inlet passage 65 and a check valve 48.

The pressure accumulator E is provided with air removal means consisting of a passage that guides the air in the pressure accumulation chamber 64 to the outlet passage 30. Therefore, the atmospheric chamber 36 and the pressure accumulating chamber 64 of the fuel supply mechanism B are liquid-tightly partitioned off by the lid plate 73 fitted into the atmospheric chamber 36. A circumferential passage 72 is provided in the upper wall of the pressure accumulating chamber 64, and the circumferential passage 72 and the pressure accumulating chamber 64 communicate with each other through a plurality of small holes 71 arranged at intervals in the circumferential direction. Preferably, the small holes 71 are arranged adjacent to the inlet passage 65 and the outlet passage 30, respectively, in order to prepare for the left and right inclinations in the carburetor diagram, and are arranged adjacent to the passages 65. It is also arranged in the middle part of 30. Circumferential passage 72 is connected to outlet passage 30 by passage 74.
will be communicated with. Instead of providing the above-mentioned circumferential passage 72 and small hole 71 in the cover 28 which is the main body of the pressure accumulator E, a groove in place of the small hole 71 is provided on the upper end surface of the stepped annular member 77 having a different outer diameter as shown in FIG. 718, and a radial groove 65a continuous to the inlet passage 65 may be provided on the lower surface. When the annular member 77 is fitted into the cylindrical pressure accumulation chamber 64 and the lid plate 73 is fitted on the upper side, a circumferential passage 72 is formed in the small diameter portion above the stepped portion 72a of the annular member 77. be done. This circumferential passage is communicated with the pressure accumulation chamber 64 through the groove 71a.

In the primer pump C, a pump chamber 43 is formed by combining a hemispherical pressing body 42 (shown in a pressed state in FIG. 1) made of rubber or the like with a main body 33, and a check valve 48 and a check valve are installed inside. A valve 45a is integrally provided. The check valve 48 is formed by flattening the upper end of a hollow cylinder made of rubber, and the check valve 45a is formed as a lip by expanding the lower end of the cylinder radially outward. The pump chamber 43 is communicated with the metering seedling 38 via a check valve 45a and a passage 50.

The starter valve includes a cylinder 35 that communicates with a starter fuel chamber 25 formed in the main body 18. The valve body 21 fitted into the cylinder 35 via the seal member 22 is pressed against the valve seat 23 by the spring 24 . The middle portion of the valve body 21 has a small diameter, and the lower end portion is formed into a conical portion that engages with the valve seat 23.

The end 25a of the cylinder 35 communicates via the passage 20 with a fuel storage chamber 19 that is integrated with the cylindrical portion 2 that rotatably and slidably engages the lower end of the comparison valve 8. Therefore, the fuel in the fuel storage chamber 19 is sucked into the intake passage 11 through the gap between the cylindrical portion 2 and the fitting portion of the throttle valve 8 and the gap between the fitting portion of the comparison valve 8 and the fuel supply pipe 7.

Next, the operation of the carburetor starting fuel supply system according to the present invention will be explained. Primer pump C before starting the engine
When the pressing body 42 is repeatedly pressed, a negative pressure acts on the pump chamber 43, and the fuel in the metering v38 is sucked into the pump chamber 43 through the passage 50 and the check valve 45a. The fuel in the pump chamber 43 is supplied to the check valve 48, the inlet passage 65, the pressure accumulation chamber G4,
Exit passage 308! and is sent to the starting combustion chamber 25. Excess fuel is discharged to the outside through the relief valve 2G, the passage 27, and the discharge pipe 29, or is returned to the fuel tank 32.

If the vaporizer or pressure accumulation chamber 64 is inclined, the small hole 71
Since the passage area is narrow, air, which has a lower fluid passage resistance than the fuel, first enters the circumferential passage 72 through the small holes 71 at a higher level, and is discharged to the outlet passage 30 via the passage 74. Of course, the fuel also tries to flow from the lower small hole 71 to the circumferential passage 72, but this passage resistance is large, so the primer pump C
In contrast to the fuel that is instantaneously supplied to the pressure accumulation chamber 64 in a lengthwise manner, the air in the pressure accumulation W 64 is expelled to the outlet passage 30 first.

When the fuel in the metering chamber 38 becomes low, the diaphragm 34 is pushed up, the fuel inlet valve 9 is pulled down via the lever 41, and the passage 52 communicates with the metering chamber 38. The fuel in the fuel tank 32 is connected to the connecting pipe 31, the check valve 10, the passage 51, the pump chamber 55, the check valve 4, the passage 52,
The metering chamber 38 is replenished via the fuel inflow valve 9, and the fuel inflow valve 9 is eventually closed.

Next, when the valve element 21 of the starting valve is pushed down, the starting fuel chamber 25 communicates with the seedling 25a, the diaphragm 61 is pushed up by the force of the spring 63 of the pressure accumulator E, and the starting fuel chamber 25
The starting fuel passes through the chamber 25a1 passage 20 and enters the fuel storage chamber 19.
is pumped to.

Next, when the engine is started (recoiled), the starting fuel in the fuel storage chamber 19 is drawn into the intake passage 11 by the intake negative pressure passing through the intake passage 11, and a mixture of high l1r1 is generated. Further, due to the intake negative pressure passing through the throttle hole 8a of the throttle valve 8, the fuel in the metering chamber 38 is sucked into the nozzle hole 6 via the check valve 47, the fuel jet 46, and the fuel supply pipe 7.

In this way, a mixture with a higher concentration than during normal operation is generated, and as a result, the engine can be started smoothly.

[Effect of R Light] As described above, the present invention sends fuel in the metering chamber to the starting fuel chamber via the pressure accumulator using the suction type primer pump,
Above the pressure accumulation chamber of the pressure accumulator in a device that pumps fuel through the intake passage by opening the starter valve! A circumferential passage is provided in the section, and the circumferential passage is communicated with the pressure accumulator through a plurality of small holes, so even when the pressure chamber is tilted, especially when the outlet passage of the pressure accumulator is located below the inlet passage, Since the pressure accumulation chamber encounters the circumferential passage through the small hole, air with lower flow resistance than the FY6 fuel first enters the circumferential passage through the small hole, and then passes through the outlet passage to the starting fuel chamber. It is discharged.

Therefore, by operating the primer pump, the pressure accumulation chamber is completely filled with fuel, and at the same time, the air discharged into the first combustion chamber is discharged to the outside from the relief valve together with excess fuel. As a result, when starting the engine, the current amount of starting fuel is reserved in the pressure accumulation chamber and starting fuel chamber by operating the primer pump, so there is no variation in the amount of starting fuel sent to the intake passage by operating the starting valve, and it is reliable. The engine is started.

[Brief explanation of the drawing]

? Fig. 141 is a side sectional view of a diaphragm type carburetor equipped with a starting fuel supply device for a carburetor according to the present invention, and Fig. 2 is a partially modified embodiment of the starting fuel supply device, which is installed in a pressure accumulation chamber. FIG. 3 is a perspective view of the annular member, and FIG. 3 is a side sectional view showing the starting fuel supply device in an inclined state without air removal means. A: Fuel supply pump B: Fuel supply machine ill c Nibrima pump D = Start valve E: Pressure accumulator 6: Nozzle hole 8
: Throttle valve 11: Intake passage 19: Fuel storage chamber 21:
Valve body 25: Starting fuel chamber 32: Fuel tank 35 Niji cylinder 38: Metering chamber 42: Pressing body 43:
Pump chamber 61: Diaphragm 63: Spring 64: Accumulator chamber 71: Small hole 72: Circumferential passage 73: Cover plate 77
: if-shaped member

Claims (2)

[Claims] (1) In a system in which the fuel in the metering chamber is sent to the starting fuel chamber via the pressure accumulator using a suction type primer pump, and the fuel is pumped through the intake passage when the starting valve is opened, there is a circle on the upper wall of the pressure accumulator of the pressure accumulator. 1. A starting fuel supply device for a carburetor, characterized in that a circumferential passage is provided, and the circumferential passage is communicated with a pressure accumulation chamber through a plurality of small holes. (2) Claims in which the circumferential passage and the small hole are formed by fitting an annular member having a small diameter part on the upper outer periphery side and a radial groove on the upper edge part into the upper part of the pressure accumulation chamber. The starting fuel supply device for a carburetor according to (1).