JP2527983B2 - Vaporizer starting fuel supply device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a starting fuel supply device for a diaphragm type carburetor of an internal combustion engine mounted on a portable working machine such as a brush cutter.

[Prior Art] This type of diaphragm type carburetor is capable of operating the engine in all postures and is provided with a fuel supply mechanism for supplying a fuel amount suitable for the operating conditions of the engine. However, when starting the engine in cold weather, the range of the air-fuel mixture concentration is limited, and the startability is poor with an ordinary fuel supply mechanism.
A starting fuel supply device as disclosed in Japanese Patent Publication No. 5 is provided. However, in this starting fuel supply device, since the starting fuel measured in the starting fuel storage chamber is supplied to the porous fuel holding member in the intake passage due to a natural drop, the starting fuel storage chamber is placed above the intake passage. However, there is a problem in that it takes a considerable time to supply the starting fuel to the fuel holding member in the intake passage.

Therefore, the applicant supplies the fuel in the constant pressure fuel chamber to the starting fuel chamber through the pressure accumulator by the suction type primer pump and opens the starting valve at the time of starting the engine to supply the starting fuel in the starting fuel chamber to the intake passage. Patent application for a starting fuel supply device for a carburetor. According to this starting fuel supply device, as soon as the starting valve is opened, the fuel in the starting fuel chamber is supplied to the fuel holding chamber arranged below the throttle valve by the pressure of the pressure accumulator, and further the intake negative pressure causes the intake passage to move. And a high-concentration air-fuel mixture is generated, and a smooth start of the engine is obtained.

However, if the accumulator formed relatively flat for the convenience of mounting on the engine is kept substantially horizontal, there is no problem in starting the engine, but the accumulator E is tilted and the primer pump The inlet passage 65 from C to the accumulator chamber 64 is
When the temperature is lower than the outlet passage 30 from the fuel cell to the starting fuel chamber, the fuel sent from the primer pump C to the pressure accumulating chamber 64 is
The air can be discharged from the outlet passage 30 and the pressure accumulating chamber 64 can be filled with fuel. However, as shown in FIG. 3, when the inlet passage 65 is higher than the outlet passage 30, the fuel is accumulated from the primer pump C. Even if it is sent to the chamber 64, the air in the pressure accumulating chamber 64 may not be completely exhausted. This air changes the reserved fuel amount, and the starting fuel amount sent to the intake passage at the time of engine start is not constant,
The startability of the engine is impaired.

[Problems to be Solved by the Invention] In view of the above problems, the object of the present invention is to prevent the air from accumulating inside the accumulator even when the engine is tilted, and the accumulator is filled with fuel to start the engine. It is an object of the present invention to provide a starting fuel supply device for a carburetor, in which a specified amount of starting fuel is supplied to the intake passage.

[Means for Solving the Problem] In order to achieve the above-mentioned object, the structure of the present invention is that the fuel in the constant pressure fuel chamber is sent to the starting fuel chamber via the pressure accumulator by the suction type primer pump, and the starting fuel is opened by opening the starting valve. In the case of supplying the fuel in the chamber to the intake passage, a circumferential passage is provided in an upper end wall portion of the pressure accumulator chamber, and the circumferential passage is connected to the pressure accumulation chamber and the starting fuel chamber by a plurality of small holes. It is a thing.

[Operation] For example, even if the pressure accumulating chamber 64 is inclined so that the inlet passage 65 communicating with the primer pump C is higher than the outlet passage 30 communicating with the starting fuel chamber 25, the air in the pressure accumulating chamber 64 flows into the inlet passage 65. From the small hole 71 near to the circumferential passage 72 of the upper end wall of the pressure accumulating chamber 64, to the outlet passage 30 through the small hole 71 near the outlet passage 30, the outlet passage 30
Is sent to the starting fuel chamber 25 from. The air in the starting fuel chamber 25 passes through the relief valve 26 and is discharged to the outside together with the surplus fuel. The small hole 71 that connects the circumferential passage 72 and the accumulator chamber 64 has a small passage area, and therefore has a small resistance to the flow of air, but exhibits a large fluid resistance to the flow of fuel. Therefore, the fuel in the pressure accumulating chamber 64 tries to flow into the small hole 71 near the outlet passage 30.
As the fuel is supplied to 64, the air in the pressure accumulating chamber 64 is pressurized earlier than this fuel, enters the circumferential passage 72 from the small hole 71 near the inlet passage 65, and further flows to the outlet passage 30 via the passage 74. . In this way, the fuel from the primer pump C is stored in the pressure chamber.
As it is supplied to 64, the air in the accumulator 64 is first expelled to the outlet passage 30.

[Embodiment of the Invention] As shown in FIG. 1, a carburetor starting fuel supply apparatus according to the present invention includes a carburetor body 18, a fuel supply pump A, a fuel supply mechanism B, and a suction type primer pump C. , Accumulator E
And a starting valve D are integrally provided. Lateral intake passage
A vertical cylindrical portion 2 is formed in the center of a main body 18 having 11 and an upper end portion of the cylindrical portion 2 is closed by a lid 12.

A rotary type throttle valve 8 having a slot hole 8a is fitted in the cylindrical portion 2 so as to be rotatable and axially movable. A shaft portion 14 extending upward from the throttle valve 8 is supported by the lid 12, and the shaft portion 14
A follower 16 is supported by a lever 15 coupled to the upper end of the.
A spring 13 surrounding the shaft portion 14 between the lid 12 and the throttle valve 8.
The force of the force causes the follower 16 to be urged and engaged with the cam surface 17 provided on the lid 12, and 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 is
Facilitates the adjustment of the position of the rod valve 3 with respect to.

Fuel supply pipe 7 whose opening degree of injection hole 6 is adjusted by rod valve 3
Is fixedly supported on the bottom wall of the main body 18. The fuel supply pipe 7 is connected to a constant pressure fuel chamber 38 that holds the fuel at a constant pressure via a fuel jet 46 and a check valve 47.

The fuel supply pump A has a pulsating pressure introducing chamber 54 having a pulsating pressure introducing port 59 on the upper side, which is formed by connecting the diaphragm 53 and the main body 70 on the lower surface of the main body 18, and a pump chamber 55 on the lower side. The pulsating pressure introducing chamber 54 is connected to, for example, the crank chamber of a two-cycle engine, and reciprocates the diaphragm 53 up and down. The pump chamber 55 is connected to the fuel tank 32 via the passage 51, the check valve 10 and the connecting pipe 31. The pump chamber 55 is communicated with the constant pressure fuel chamber 38 via the check valve 4, the passage 52, and the fuel inflow valve 9.

The diaphragm 34 and the cover 28 are joined to the lower surface of the main body 70, whereby the constant pressure fuel chamber 38 is on the upper side and the atmosphere port is on the lower side.
Atmospheric chambers 36 each having 58 are partitioned. Constant pressure fuel chamber
A lever 41 is supported inside the shaft 38 by a support shaft 40. lever
The left end of 41 is abutted against the diaphragm 34 by a spring, while the right end is locked to the tapered fuel inflow valve 9. The fuel in the fuel tank 32 is straight from the connecting pipe 31, the check valve 10,
It is sent to the inlet side of the fuel inflow valve 9 through the passage 51, the pump chamber 55, the check valve 4, and the passage 52.

The pressure accumulator E is configured by connecting the main body 33 with the diaphragm 61 sandwiched under the cover 28. A pressure accumulation chamber 64 is formed on the upper side of the diaphragm 61, and an atmosphere chamber 62 having an atmosphere port 49 is formed on the lower side. A spring 63 is interposed between the bottom wall of the atmosphere chamber and a plate 67 that is pressed against the lower side of the diaphragm 61. The accumulator chamber 64 communicates with the starting fuel chamber 25 via the outlet passage 30. Also, the accumulator
64 communicates with the pump chamber 43 of the primer pump C via the inlet passage 65 and the check valve 48.

The pressure accumulator E is provided with an air removing means including a passage for guiding the air in the pressure accumulation chamber 64 to the outlet passage 30. Therefore, the atmosphere chamber 36 and the pressure accumulation chamber 64 of the fuel supply mechanism B are liquid-tightly partitioned by the cover plate 73 fitted in the atmosphere chamber 36. A circumferential passage 72 is provided on the upper wall of the pressure accumulating chamber 64, and the circumferential passage 72 and the accumulating chamber 64 are communicated with each other by a plurality of small holes 71 arranged at intervals in the circumferential direction. Preferably, the small holes 71 are provided adjacent to the inlet passage 65 and the outlet passage 30, respectively, in preparation for the left and right inclination in the figure of the carburetor, and further in preparation for the front and rear inclination of the carburetor, the passages 65, 30 are provided.
It is also installed in the middle part of. The circumferential passage 72 is connected to the outlet passage 30 by a passage 74.

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, as shown in FIG. 2, a small diameter portion having a small outer diameter is provided on the upper end side and a plurality of upper end surfaces are provided. Radial groove
The stepped annular member 77 including 71a may be formed by fitting the upper end portion of the pressure accumulating chamber 64. That is, a radial groove instead of the small hole 71 is formed on the upper end surface of the stepped annular member 77 having a different outer diameter.
71a is provided, while the radial groove 6 connecting to the inlet passage 65 is provided on the lower surface.
After fitting the one provided with 5a to the cylindrical accumulator 64,
If the lid plate 73 is fitted on the upper side, the stepped portion 72a of the stepped annular member 77
A circumferential passage 72 is formed in the small diameter portion on the upper side. The circumferential passage 72 is connected to the pressure accumulating chamber 64 by the radial groove 71a.

In the primer pump C, a hemispherical pressing body 42 made of rubber or the like (a pressed state is shown in FIG. 1) is connected to the main body 33 to form a pump chamber 43, and a check valve 48 and a check valve are formed inside. 45a
Are arranged integrally. The check valve 48 flatly crushes the upper end of the rubber hollow cylinder, 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 constant pressure fuel chamber 38 via the check valve 45a and the passage 50.

The starting valve D includes a cylinder 35 that is connected to a starting 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 part of the valve body 21 has a small diameter, and the lower end part has a valve seat.
A cone is formed that engages 23. Cylinder 35 chamber 25a
Is communicated via a passage 20 to a fuel storage chamber 19 which is integral with the cylindrical portion 2 which engages the lower end of the throttle valve 8 in a rotatable and slidable manner. Therefore, the fuel in the fuel reserve 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 throttle valve 8 and the fuel supply pipe 7.

Next, the operation of the starting fuel supply device for the carburetor according to the present invention will be described. When the pressing body 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 is sucked into the pump chamber 43 through the passage 50 and the check valve 45a. It The fuel in the pump chamber 43 is sent to the starting fuel chamber 25 via the check valve 48, the inlet passage 65, the pressure accumulating chamber 64, and the outlet passage 30. Excess fuel is discharged to the outside through the relief valve 26, the passage 27, and the discharge pipe 29, or returned to the fuel tank 32.

When the carburetor or accumulator 64 is inclined, since the passage area of the small hole 71 is small, air having a fluid passage resistance smaller than that of the fuel enters the circumferential passage 72 from the small hole 71 at a higher position first, and then the passage.
It is discharged to the exit passage 30 via 74. Of course, the fuel also tries to flow from the small hole 71 at the lower position to the circumferential passage 72, but since the passage resistance is large, the pressure accumulating chamber for the fuel that is instantaneously supplied in large amount from the primer pump C to the accumulating chamber 64. 64 air is expelled to the exit passage 30 first.

When the constant pressure fuel chamber 38 runs low on fuel, the diaphragm 34
Is pushed up, the fuel inflow valve 9 is pulled down via the lever 41, and the passage 52 communicates with the constant pressure fuel chamber 38. The fuel in the fuel tank 32 is the connection pipe 31, the check valve 10, the passage 51, the pump chamber 5
5, the check valve 4, the passage 52, the fuel inlet valve 9 and the constant pressure fuel chamber 3
8 is replenished, and eventually the fuel inflow valve 9 is closed.

Then, when the valve body 21 of the starting valve D is pushed down, the starting fuel chamber 25 communicates with the chamber 25a, the diaphragm 61 is pushed up by the force of the spring 63 of the pressure accumulator E, and the starting fuel in the starting fuel chamber 25 is transferred to the chamber 25a, It is supplied to the fuel reserve chamber 19 via the passage 20. Next, when the engine is started (recoil), the intake passage 11
The starting fuel in the fuel storage chamber 19 is sucked into the intake passage 11 due to the negative pressure of the intake air passing through the intake passage 11 to generate a high-concentration mixture.
Further, due to the negative pressure of the intake air passing through the throttle hole 8a of the throttle valve 8, the fuel in the constant pressure fuel chamber 38 is forced to flow in the check valve 47 and the fuel jet.
46, it is sucked into the injection hole 6 through the fuel supply pipe 7. As a result, a mixture having a higher concentration than that in the normal operation is generated, so that the engine is started smoothly.

As described above, the present invention sends the fuel in the constant pressure fuel chamber to the starting fuel chamber through the pressure accumulator by the suction type primer pump, and supplies the fuel in the starting fuel chamber to the intake passage by opening the starting valve. In this case, since a circumferential passage is provided in the upper end wall portion of the pressure accumulating chamber of the pressure accumulator, and the circumferential passage is connected to the pressure accumulating chamber and the starting fuel chamber by a plurality of small holes, the posture of the engine is inclined. Even when the outlet passage of the accumulator is located below the inlet passage, the air with a small flow resistance enters the circumferential passage through the small holes before the fuel, and then the small passage and the outlet passage. After that, it is discharged to the starting fuel chamber. Therefore, by operating the primer pump, the fuel is completely filled in the pressure accumulating chamber, and at the same time, the air discharged to the starting fuel chamber is discharged to the outside from the relief valve together with the excess fuel. This allows
When the engine is started, the specified amount of starting fuel is retained in the accumulator chamber and the 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 the engine is started reliably. To be done.

[Brief description of drawings]

FIG. 1 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 relates to a partially modified embodiment of the starting fuel supply device, which is mounted in a pressure accumulating chamber. FIG. 3 is a side cross-sectional view showing a tilted state of the starting fuel supply system which is not provided with the air removing means. A: Fuel supply pump, B: Fuel supply mechanism, C: Primer pump, D: Start valve, E: Accumulator, 6: Injection hole, 8: Throttle valve, 11: Intake passage, 19: Fuel reserve chamber, 21: Valve body, 25: Starting fuel chamber, 32: Fuel tank, 35: Cylinder, 38: Constant pressure fuel chamber, 42: Pressing body, 4
3: Pump chamber, 61: Diaphragm, 63: Spring, 64: Accumulation chamber, 7
1: Small hole, 72: Circumferential passage, 73: Lid plate, 77: Annular member

Claims (2)

(57) [Claims] 1. A pressure accumulating chamber of a pressure accumulator, wherein fuel in a constant pressure fuel chamber is sent to a starting fuel chamber through a pressure accumulator by a suction type primer pump, and fuel in the starting fuel chamber is supplied to an intake passage by opening a starting valve. A starting fuel supply device for a carburetor, characterized in that a circumferential passage is provided in an upper end wall portion of the fuel cell, and the circumferential passage is connected to the pressure accumulating chamber and the starting fuel chamber by a plurality of small holes. 2. A stepped annular member having a small diameter portion having a small outer diameter on the upper end side and a plurality of radial grooves on the upper end surface of the circumferential passage and the small hole is fitted to the upper end portion of the pressure accumulating chamber. A starting fuel supply device for a carburetor according to claim 1, which is formed by combining the two.