JPH0148391B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a portable working machine such as a chain saw, a brush cutter, etc., in which fuel in a fuel tank at the bottom of the machine is suctioned and pressure-fed to a vaporizer by a fuel pump. The present invention relates to an internal combustion engine equipped with a diaphragm type carburetor that enables omnidirectional operation by always maintaining a constant negative pressure inside the metering chamber even in the posture.

[Prior Art] In this type of internal combustion engine, the fuel tank is located at the bottom of the working machine, so before the engine starts, the fuel pipe and carburetor at the top of the fuel tank are filled with air and fuel vapor. It is difficult to start the engine unless the fuel vapor is removed.

In addition, for about 10 minutes after the engine stops, the temperature becomes high due to the engine's conduction heat, atmospheric heat, and radiant heat from sunlight, and the fuel in the carburetor evaporates and is filled with fuel vapor, and the engine is still at warm-up temperature. Even in those cases, fuel vapor caused the air-fuel mixture to become too lean, causing problems such as difficulty in starting, difficulty in continuing operation after starting, or even shutdown. To solve these problems, it is required to remove fuel vapor from the carburetor, or to replenish fuel to the carburetor or inject it into the intake pipe when starting the engine.

One technique that meets this demand is disclosed in US Pat. No. 3,494,343. This conventional technology connects a hand pump similar to a dropper and a pair of one-way valves connected upstream and downstream between the fuel tank and the carburetor or intake pipe, and starts the pump with the hand pump. Before or at the same time as starting, fuel is supplied to the intake pipe via a carburetor or directly. However, even if fuel is supplied to the intake pipe in advance, vaporization of the fuel within the intake pipe is not necessarily sufficient if there is no air flow. Although it is desirable to supply fuel at the same time as the engine is started, such an operation is cumbersome and requires skill, and more fuel than necessary may be supplied to the intake pipe, making it difficult to start the engine.

The internal combustion engine disclosed in Japanese Utility Model Publication No. 52-23638 changes the volume of a pump chamber surrounded by a bellows via a leaf spring using a cam provided on a starting pulley at the same time as the engine is started, and the volume of a pump chamber surrounded by a bellows is reversed from a fuel tank. This system sucks fuel into the pump chamber through a stop valve, and then temporarily injects the fuel from a nozzle into the intake pipe through a check valve, exhausts the air in the metering chamber of the carburetor, and replaces it with new fuel. It is different from the one that is refilled from the fuel tank. The bellows is unstable in operation, making it difficult to obtain a large pump capacity, and with the above configuration, when the engine rotates in reverse, the engagement between the cam and the leaf spring becomes unsmooth.

[Problems to be Solved by the Invention] The purpose of the present invention is to forcibly remove air and fuel vapor from the metering chamber of the carburetor,
It helps the diaphragm type fuel pump installed in the carburetor to refuel from the fuel tank,
It is an object of the present invention to provide an internal combustion engine with a diaphragm type carburetor that automatically performs such an operation in conjunction with a starting operation, that is, an operation of a recoil device.

[Means for Solving the Problems] In order to solve the above problems, the present invention has a structure in which a diaphragm-type suction-type starting fuel pump is installed on the side of the fuel tank disposed below the crank chamber. The starting fuel pump is connected to the middle of the pipe connecting the metering chamber of the carburetor and the fuel tank, and the end of the rod connected to the diaphragm of the starting fuel pump is rotated by recoil operation by a spring. It is biased into engagement with the cam on the shaft, and sucks and discharges fuel vapor from the metering chamber into the fuel tank when the engine starts.

[Function] The rotating shaft of the recoil device 30 of the internal combustion engine is configured as a camshaft 34, and the rod 35 reciprocated by the camshaft 34 is connected to the diaphragm 36 of the suction type starting fuel pump 33, and cooperates with the spring 37. The action causes the diaphragm 36 to reciprocate, thereby increasing the metering chamber 1 of the known diaphragm type carburetor 2.
Fuel vapor etc. are sucked out from the fuel tank 6 and returned to the fuel tank 1.

Since fuel vapor and the like in the metering chamber 16 of the diaphragm type carburetor 2 is discharged from the suction port 40 to the fuel tank 1 by the starting fuel pump 33, the inflow valve 10 opens as the pressure in the metering chamber 16 decreases. Diaphragm type fuel pump 50
The fuel is transferred from the fuel tank 1 to the metering chamber 1.
6, and fuel is drawn into the intake pipe from the metering chamber 16 through the low-speed fuel nozzle 21.
The engine can now be started.

[Embodiments of the Invention] FIG. 2 shows a diaphragm type carburetor 2 mounted on an internal combustion engine according to the present invention. In the same figure, 3
is the carburetor main body, 4 is the cover of the fuel pump 50, 5
Reference numeral 6 indicates a pulsating pressure inlet for a crank chamber of an engine (not shown), 6 a diaphragm of the fuel pump 50, and 7 a fuel inlet. Fuel in the fuel tank 1 (FIG. 1) is sucked in by the action of the diaphragm 6 and the check valves 47 and 48 due to the pulsating pressure in the engine's crank chamber, and is forced into the inflow valve 10.

11 is a diaphragm, 12 is a support shaft that rotatably supports the lever 13 on the carburetor main body 3, and 14 is a spring, one end of the lever 13 is biased and engaged with the inflow valve 10, and the other end is biased with the diaphragm 11. are doing. 15 is a cover, which communicates with the outside air. While the engine is operating, the metering chamber 16 is maintained at a low negative pressure by the operation of the diaphragm 11, allowing omnidirectional operation during work.

A bench lily hole 17 and a valve hole 18, which substantially constitute a part of the intake pipe, penetrate the carburetor main body 3 in the front and rear directions. A butterfly-shaped throttle valve 20 is attached to a valve shaft 19 that crosses the valve hole 18, and the valve hole 18 is opened and closed by driving operation. A plurality of low-speed fuel nozzles 21 open in the valve hole 18 corresponding to the idling opening of the throttle valve 20, and fuel metered by the low-speed fuel metering needle valve 22 is injected, allowing idling and low-opening operation.

Reference numeral 23 designates a check valve for preventing backflow of air and fuel from the low-speed fuel nozzle 21 to the metering chamber 16 when a starting fuel pump, which will be described later, is operated. A high-speed fuel jet 24 opens in the bench lily hole 17, and fuel metered by a high-speed fuel metering needle valve 25 is jetted out, allowing high-speed operation. 26 is a high-speed fuel injection port 24 during idling and when the starting fuel pump is activated.
This is a check valve that prevents backflow of air from the metering chamber 16 to the metering chamber 16.

FIG. 1 is a side view showing an internal combustion engine 27 according to the present invention. 28 is an air cleaner, and 29 is an exhaust muffler. 30 is a recoil device for engine starting cranking, 31 is a recoil handle, and pulley 3
By pulling out the recoil handle 31, the pulley 32
rotates and provides starting rotation to the engine crankshaft via the clutch.

33 is a suction type starting fuel pump, and 34 is a camshaft provided at the end of the shaft of the pulley 32. 35 is a rod that responds to the camshaft 34 and supports a roller 43 that slides on the camshaft 34. Rod 35
is the frame 4 of the recoil device 30 fixed to the engine body
5, and one end is fixed to a diaphragm 36, which slides in cooperation with a spring 37 during recoil, and performs a pumping action by two check valves, a suction valve 38 and a discharge valve 39. . The fuel vapor in the metering chamber 16 shown in FIG.
The fuel is sucked in and returned to the fuel tank 1 via the discharge valve 39 and the reflux pipe 42. A fuel pipe 9 connects the filter 8 placed at the bottom of the fuel tank 1 and the fuel inlet 7 of the carburetor.

[Effects of the Invention] As described above, the present invention includes a diaphragm-type suction-type starting fuel pump disposed on the side of the fuel tank disposed below the crank chamber, and the starting fuel pump is connected to the carburetor. The end of the rod connected to the middle of the pipe connecting the metering chamber and the fuel tank and connected to the diaphragm of the starting fuel pump is biased into engagement with the cam of the shaft rotated by the recoil operation by a spring,
When the engine starts, the fuel vapor in the metering chamber is sucked into and discharged into the fuel tank, and has the following effects.

(a) The starting fuel pump operates in conjunction with the engine starting rotation around 5 times by reel operation, which eliminates the need to operate the pump before coil operation as with conventional manual starting fuel pumps, making operation easier. .

(b) Since the end of the rod connected to the diaphragm is biased and engaged with the cam, pump operation is reliable and smooth, and the installation position of the starting fuel pump is away from the high temperature part of the engine and close to the fuel tank. Therefore, the temperature rise of the starting fuel pump is suppressed, the generation of fuel vapor inside the starting fuel pump is reduced, and the operation of the starting fuel pump is ensured.

(c) Therefore, the fuel vapor inside the fuel pipe at the top of the fuel tank and the diaphragm type carburetor is sucked in from the suction port of the metering chamber each time the recoil operation is performed, and is returned to the fuel tank. Startability is improved, and continued operation after startup becomes stable.

(d) Since the starting fuel pump is driven by the recoil operating force that drives the engine, sufficient operating force can be obtained to drive a large capacity starting fuel pump.

(e) Since the capacity of the starting fuel pump can be increased, there is no need to visually check the number of operations of the starting fuel pump or the amount of fuel supplied from the starting fuel pump, and the recoil operation can simply be continued until the engine starts. It is easy to operate.

(f) Even if air is sucked in from the low-speed fuel nozzle during recoil operation, the passage of the low-speed fuel metering needle valve is constricted and the capacity of the starting fuel pump is large, so the fuel is sucked in from the inlet valve. Ru.

[Brief explanation of drawings]

FIG. 1 is a front view of an internal combustion engine with a diaphragm type carburetor according to the present invention, and FIG. 2 is a front sectional view of the same diaphragm type carburetor. 2: Diaphragm type carburetor, 16: Metering chamber, 27: Internal combustion engine, 30: Recoil device, 3
3: Starting fuel pump, 34: Camshaft, 35: Rod, 36: Diaphragm, 38: Suction valve, 3
9: Discharge valve, 40: Suction port, 41: Suction pipe, 4
2: Reflux pipe, 43: Roller, 50: Fuel pump.

Claims (1)

[Claims] 1. A diaphragm-type suction-type starting fuel pump is installed on the side of the fuel tank located below the crank chamber, and the starting fuel pump is installed in the middle of the pipe connecting the metering chamber of the carburetor and the fuel tank. The end of the rod connected to the diaphragm of the starting fuel pump is biased into engagement with the cam of the shaft rotated by the recoil operation by a spring, and when the engine is started, the fuel vapor in the metering chamber is transferred to the fuel tank. An internal combustion engine with a diaphragm type carburetor that features suction and exhaust.