JPH0826815B2 - 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 No. 5 is provided. However, in this starting fuel supply device, since the starting fuel amount is uniquely determined by the capacity of the starting fuel chamber, it is not possible to supply the starting fuel amount suitable for the starting conditions such as the ambient temperature and the engine temperature. In particular, when the engine temperature is high immediately after the engine operation is stopped or when the ambient temperature is high, the starting fuel amount is small and sufficient.In such a case, if excessive starting fuel is supplied to the intake passage, On the contrary, it hinders the smooth start of the engine.

[Problems to be Solved by the Invention] An object of the present invention is to provide a starting fuel supply device for a carburetor capable of supplying a starting fuel amount suitable for engine temperature and ambient temperature conditions.

[Means for Solving the Problem] In order to achieve the above object, in the configuration of the present invention, the fuel in the metering chamber is sent to the starting fuel chamber through the pressure accumulator by the suction type primer pump, and the fuel is opened by opening the starting valve. In the case of pressure feeding to the intake passage, the stroke of the pressure accumulator is regulated by the temperature sensitive member.

[Operation] Since the temperature sensitive member 66, which is provided as a stroke limiting member in the atmosphere chamber on the opposite side of the pressure accumulator chamber 64 of the pressure accumulator E, is deformed to be convex upward when the ambient temperature or the engine temperature is high. The amount of fuel sent from the primer pump C to the starting fuel chamber 25 via the pressure accumulating chamber 64 is small. Therefore, when the diaphragm 61 is lifted by the spring 63 when the starting valve D is opened, the starting fuel chamber 25
The amount of starting fuel supplied from the intake passage 11 to the intake passage 11 is suppressed.

On the other hand, when the engine temperature or the ambient temperature is low, the temperature sensitive member 66 deforms convexly downward. Therefore, the diaphragm 61 defining the pressure accumulating chamber 64 can make a large stroke against the spring 63. This means that the amount of fuel stored in the starting fuel chamber 25 from the primer pump C via the pressure accumulating chamber 64 increases. As a result, when the start valve D is pressed during cold weather, a large amount of fuel is supplied from the start fuel chamber 25 to the fuel holding chamber 19, a high-concentration air-fuel mixture suitable for low temperatures is generated, and the engine is easily started. It

[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 its upper end 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 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
Are fixedly supported on the bottom wall of the main body 18. The fuel supply pipe 7 is connected to a metering 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 passes through the passage 51, the check valve 10 and the connecting pipe 31,
It is connected to the fuel tank 32. The pump chamber 55 communicates with the metering 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 metering chamber 38 is defined on the upper side and the atmospheric chamber 36 having the atmospheric opening 58 is defined on the lower side. A lever 41 is supported by a spindle 40 inside the metering chamber 38. The left end of the lever 41 abuts the diaphragm 34 by a spring, while the right end locks the tapered fuel inflow valve 9. The fuel in the fuel tank 32 is sent from the connecting pipe 31 to the inlet side of the fuel inflow valve 9 through the strainer, the check valve 10, 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 to the lower side of the cover 28 with the diaphragm 61 interposed therebetween. 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. The spring 63 is the bottom wall of the atmosphere chamber and the diaphragm 61.
It is interposed between the plate 67 and the lower plate.

According to the present invention, the peripheral portion of the temperature sensitive member 66, which is preferably dish-shaped, is fixed to the bottom wall of the atmosphere chamber 62. This temperature sensitive member 66
Is composed of a bimetal or a shape memory alloy, and is deformed upwardly at room temperature or higher, but is deformed downwardly at low temperature (see FIG. 2). Due to the deformed state of the temperature sensitive member 66, the vertical movement of the diaphragm 61 that partitions the pressure accumulating chamber 64 is restricted. The accumulator chamber 64 communicates with the starting fuel chamber 25 via the passage 30. Further, the accumulator chamber 64 has a passage 65 and a check valve 48.
Through the pump chamber 43 of the primer pump C.

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 communicates with the metering 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.
It has a conical portion that engages with 23. Cylinder 35 chamber 25a
Through the passage 20 is communicated with the fuel storage chamber 19 that is integral with the cylindrical portion 2 that engages the lower end portion 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 the engine is started, a negative pressure acts on the pump chamber 43, and the fuel in the metering chamber 38 passes through the passage 50 and the check valve 45.
It is sucked into the pump chamber 43 via a. The fuel in the pump chamber 43 passes through the check valve 48, the passage 65, the pressure accumulating chamber 64, and the passage 30, and then the starting fuel chamber.
Sent to 25. Excess fuel is used as relief valve 26, passage 27, and exhaust pipe.
It is discharged to the outside via 29 or returned to the fuel tank 32.

When the fuel in the metering chamber 38 is low, 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 metering chamber 38.
The fuel in the fuel tank 32 is replenished to the metering chamber 38 via the connecting 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 eventually the fuel inflow valve 9 is replaced. close.

Next, when the valve body 21 of the starting valve D is pushed down, the pressure accumulator E
The diaphragm 61 is pushed up by the force of the spring 63, and the starting fuel in the starting fuel chamber 25 is pumped to the fuel holding chamber 19 through the chamber 25a and the passage 20.

Next, when the engine is started (recoil), the starting fuel in the 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 throttle valve 8
Due to the intake air passing through the throttle hole 8a, the fuel in the metering chamber 38 is transferred to the check valve 47, the fuel jet 46, and the fuel supply pipe 7.
Through the nozzle hole 6. In this way, as a result of producing the air-fuel mixture having a higher concentration than in the normal operation, the engine is smoothly started.

[Advantages of the Invention] As described above, the present invention is one in which the fuel in the metering chamber is sent to the starting fuel chamber via the pressure accumulator by the suction type primer pump, and the fuel is pumped to the intake passage by opening the starting valve. Since the stroke of the pressure regulator is regulated by the temperature sensitive member, the stroke (operating range) of the diaphragm of the pressure accumulator is limited by the temperature sensitive member, the volume of the starting fuel chamber is small at high temperature, and the volume of the starting fuel chamber decreases at low temperature. Since the volume of the engine is large, the amount of starting fuel suitable for the temperature condition is supplied from the starting fuel chamber to the fuel holding chamber adjacent to the intake passage of the carburetor, and a very smooth starting of the engine is obtained.
Especially, the starting fuel is supplied to the intake passage side more than necessary at a high temperature, and the problem that the smooth starting of the engine is hindered is eliminated.

Since the amount of starting fuel corresponding to the temperature condition is held by the primer pump in the starting fuel chamber through the pressure accumulator, excessive fuel will not overflow into the intake passage even if the starting valve is repeatedly operated. .

Since the fuel storage chamber is arranged below the throttle valve, it can be easily implemented in the conventional carburetor without changing the dimensions of the intake passage. Since the pump chamber of the primer pump, the pressure accumulator, and the starting fuel chamber are connected inside the carburetor body, there is no conduit exposed to the outside, the overall shape is small, and assembly is easy.

Since the fuel from the starting fuel chamber temporarily accumulates in the fuel holding chamber below the throttle valve, it does not affect the shape of the carburetor body, and the starting fuel overflows into the intake passage even when the engine is slightly tilted. Therefore, it is not necessary to provide a porous fuel retaining member. This means that at the same time as the starting operation, the starting fuel in the starting fuel chamber is sucked into the intake passage through the fuel holding chamber below the throttle valve, so that the engine can be quickly started.

[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 is a perspective view showing a state of a temperature sensitive member at a low temperature. 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: Metering chamber, 42: Pressing body, 43: Pump chamber, 61: Diaphragm, 63: Spring, 64: Accumulation chamber, 65: Sensation Temperature member

Claims (3)

[Claims] Claim: What is claimed is: 1. In a fuel pump, the fuel of a metering chamber is sent to a starting fuel chamber by a suction type primer pump through a pressure accumulator, and the fuel is pressure-fed to an intake passage by opening a starting valve. A starting fuel supply device for a carburetor, which is regulated. 2. A starting fuel supply device for a carburetor according to claim 1, wherein the temperature sensitive member is a bimetal. 3. The starter fuel supply device for a carburetor according to claim 1, wherein the temperature sensitive member is a shape memory alloy.