JPH0134697Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention provides a fuel supply system for a carburetor in which a negative pressure tank is provided in the fuel passage leading from the fuel tank to the carburetor, and in particular, a fuel storage chamber is provided in order to improve startability. The present invention relates to a fuel supply device having a fuel supply device.

Prior Art Conventionally, this type of fuel supply device is known, for example, as disclosed in Japanese Patent Application Laid-open No. 56-6059. Although the structure includes a fuel reservoir, that is, a fuel storage chamber, the open end of the vent pipe on the atmosphere side and the arrangement of the fuel storage chamber are limited by various conditions, and the negative pressure chamber itself has a built-in fuel storage chamber. Because of this configuration, the cost was high.

Purpose In view of the above points, it is an object of the present invention to provide a fuel supply device for a carburetor that has good startability, has a large degree of freedom in arrangement, and can reduce costs.

Overview This purpose is to provide a fuel supply system for a carburetor that is equipped with a negative pressure tank in the fuel passage leading from the fuel tank to the carburetor. one diaphragm chamber is connected to the fuel passage downstream of the negative pressure socket, and a second diaphragm chamber is connected to the fuel passage or to the fuel tank upstream of the negative pressure socket, This problem is solved by a fuel supply device for a carburetor, characterized in that the diaphragm is urged toward the second diaphragm chamber by a spring.

Furthermore, the tension of the spring is preferably selected to be smaller than the fuel pressure which is exerted on the diaphragm by the fuel pressure introduced into the second diaphragm chamber via the tube 7.

Embodiment The present invention will be described below with reference to an embodiment shown in the drawings. 1 is a fuel tank, 2 is a float chamber of a carburetor, and has a float 2a and a needle valve 2b. Reference numeral 3 indicates a fuel passage leading from the fuel tank 1 to the float chamber 2 of the carburetor, and 4 indicates a negative pressure tank of a known configuration provided in the fuel passage 3, which opens and closes the fuel passage 3 by a fuel shutoff valve 4a connected to a diaphragm. The negative pressure of the engine can be introduced into the negative pressure chamber 4b through the check valve and the leak hole 4c. Reference numeral 5 denotes a fuel reservoir divided into two chambers by a diaphragm 5a, the first diaphragm chamber 5b of which is connected to the fuel passage 3 on the downstream side of the negative pressure tank 4.
The second diaphragm chamber 5c is connected to the fuel passage 3 (or to the fuel tank 1) via a pipe 7 on the upstream side of the negative pressure tank 4. The diaphragm 5a is urged toward the second diaphragm chamber 5c by a spring 8. The tension P _S of the spring 8 is equal to the fuel pressure introduced into the second diaphragm chamber 5c through the pipe 7.
The force (fuel pressure) applied to the diaphragm 5a by P _T is selected to be smaller than the force (fuel pressure) P _T .

Since the present embodiment is configured as described above, when the engine is operating, the negative pressure of the engine is introduced into the negative pressure chamber of the negative pressure tank 4 through the check valve and the leak hole 4c, and the fuel shutoff valve is 4a is open. Therefore, the fuel pressure P _L introduced into the first diaphragm chamber 5b via the pipe 6 becomes substantially equal to the fuel pressure P _T introduced into the second diaphragm chamber 5c via the pipe 7, that is, the fuel pressure P The fuel pressure P _L exerted on the diaphragm 5a by _L is the fuel pressure
Since P _T is approximately equal to P T, the diaphragm 5a is moved into the second diaphragm chamber 5c by the tension P _S of the spring 8.
deviates to the side and is at the position shown by the solid line (P _T < P _L + P _S ).
When the engine stops from this state, the pressure inside the negative pressure chamber gradually increases due to the action of the check valve and the leak hole 4c, and the fuel shutoff valve 4c gradually increases after the engine stops.
a closes. If left in this state for a long time,
When the fuel in the float chamber 2 of the carburetor evaporates and the oil level drops, the float 2a descends and the needle valve 2
b opens, and thus the fuel pressure P _L in the fuel passage 3, pipe 6 and first diaphragm chamber 5b becomes almost zero, so the force acting on the diaphragm 5a is P _T > P _L
+P _S , the diaphragm 5a moves to the first diaphragm chamber 5b side and supplies fuel into the float chamber 2 of the carburetor. Here float chamber 2 of the vaporizer
When the oil level inside returns to the standard level, needle valve 2
b closes, the fuel pressure P _L increases, and the diaphragm 5a
Position where P _T = P _L + P _S (position shown by chain line)
Stop at. In this way, as the diaphragm 5a moves, a volume of fuel (indicated by diagonal lines) corresponding to the movement of the diaphragm 5a is supplied into the float chamber 2 of the carburetor, and the oil level in the float chamber 2 of the carburetor is always maintained constant. Note that when the oil level drops significantly, the diaphragm 5a moves to its upper limit position to supply the maximum volume of fuel, but this maximum volume is smaller than the volume of the float chamber 2 of the carburetor above the oil level. It is preferable from the viewpoint of overflow prevention that this is selected.

When the diaphragm 5a is at the upper limit position, when the engine is started, negative pressure of the engine is introduced into the negative pressure chamber of the negative pressure tank 4 and the fuel shutoff valve 4a is opened, so that fuel flows through the needle valve 2b to the float of the carburetor. At the same time as being supplied into the chamber 2, the diaphragm 5a returns to the position shown by the solid line again by the tension of the spring 8. Note that the flow resistance of the fuel shutoff valve 4a is selected to be smaller than the flow resistance of the needle valve 2b. Float chamber 2 of the carburetor even after one start operation is completed.
If the oil level does not return to the standard level, even if the engine stops, the negative pressure in the negative pressure chamber of the negative pressure tank 4 is maintained for a short time by the action of the check valve and leak hole 4c, and the fuel shutoff valve 4a is opened. Also, after the fuel shutoff valve 4a closes, the fuel pressure P _L becomes almost zero, so the diaphragm 5a is moved to the first diaphragm chamber 5b, and therefore even after the starting operation is completed. Fuel is supplied until the oil level in the float chamber 2 of the carburetor reaches the standard level.

Effects of the Invention As described above, the present invention operates in the same way as a conventional fuel supply device for a carburetor equipped with a fuel storage chamber, and can be operated in a sealed manner without using a vent pipe communicating with the atmosphere. Therefore, the arrangement can be freely performed without any restrictions, and is extremely effective. In addition, the negative pressure cooker itself can be used as is on the market, and can be applied to small to large engines as well as multiple carburetors, which has the effect of reducing costs. It is also possible to configure the fuel tank and the fuel storage unit in one piece.

[Brief explanation of the drawing]

The drawing is a schematic diagram showing an embodiment of a fuel supply device for a carburetor according to the present invention. 1... Fuel tank, 2... Carburetor float chamber, 3... Fuel passage, 4... Negative pressure tank, 5...
Fuel reservoir, 6, 7...tube, 8...spring.

Claims (1)

[Scope of Claim for Utility Model Registration] A fuel supply device for a carburetor in which a negative pressure tank is provided in the fuel passage leading from the fuel tank to the carburetor, which is equipped with a fuel reservoir divided into two chambers by a diaphragm, The first diaphragm chamber is connected to the fuel passage downstream of the negative pressure stock, and the second diaphragm chamber is connected to the fuel passage or to the fuel tank upstream of the negative pressure stock. A fuel supply for a carburetor, characterized in that the diaphragm is pressed toward a second diaphragm chamber by a spring, and the tension of the spring is selected to be smaller than the fuel pressure in the second diaphragm chamber. Device.