JPH0226704B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is directed to a paper lock phenomenon in a carburetor-type internal combustion engine, in which engine operating performance is significantly impaired by fuel vapor in the engine fuel supply system in a high-temperature atmosphere. This invention relates to a fuel vapor lock prevention device designed to prevent fuel vapor locking.

[Conventional technology]

As an effective and simple means to eliminate the vapor lock phenomenon that has already been proposed, a check valve is installed in the fuel vapor line that connects the fuel tank and the canister, and the fuel supply line between the fuel tank and the vaporizer is Maintain the pressure higher than the set pressure of
Examples include those designed to suppress the generation of fuel vapor. This means is extremely effective in systems where the fuel supply line is a semi-hermetic circuit, such as an EFI (electronic fuel injection) system. However, in cases where the end of the fuel supply line is open to the atmosphere, such as in a carburetor-type internal combustion engine, a solenoid valve is installed between the carburetor and the fuel tank in order to achieve this effect. After a shutdown, it becomes necessary to shut off the fuel supply line and increase the fuel tank pressure.

[Problem to be solved by the invention]

However, in a carburetor internal combustion engine as shown in Japanese Utility Model Application Publication No. 55-30928, the control valve, that is, the solenoid valve provided between the fuel pump and the float chamber closes at the same time as the engine ignition switch is turned off. , engine ignition switch
In a system where the valve opens as soon as the engine is turned on, the fuel supply line of the engine ignition switch becomes open during a hot start, and as a result, the pressure in the fuel tank drops rapidly and the fuel in the line drains away. Due to the pressure difference, a large amount of fuel flows into the carburetor, causing a problem in that it simultaneously causes a float chamber overflow. As described above, a major problem remains when applying a fuel tank pressurization system to a carburetor internal combustion engine.

SUMMARY OF THE INVENTION An object of the present invention was to prevent the occurrence of vapor lock by maintaining a pressurized state when restarting a carburetor-type internal combustion engine after the engine has been stopped and left unused. An object of the present invention is to provide a fuel vapor lock prevention device that can prevent the fuel vapor lock from occurring and ensure operability equivalent to normal operating conditions even in a high-temperature atmosphere.

[Means to solve the problem]

In order to achieve such an objective, the present invention
In a carburetor internal combustion engine, the fuel supply system between the fuel tank and the carburetor float chamber is equipped with a solenoid valve that opens and closes in conjunction with the disconnection and disconnection of the engine ignition switch. The engine is equipped with a temperature-sensitive pressure regulating valve that can maintain the additional pressure in the fuel supply system according to the fuel temperature, and is designed to prevent the additional pressure from decreasing rapidly when the engine is restarted. It is something.

〔Example〕

Hereinafter, details of the present invention will be explained using examples shown in the drawings.

FIG. 1 is a sectional view showing an embodiment of a fuel vapor lock prevention device for a carburetor internal combustion engine according to the present invention. In the figure, reference numeral 1 indicates a temperature-sensitive pressure regulating valve, and the temperature-sensitive pressure regulating valve 1 is provided with a fuel intake port 2 and a fuel discharge port 3, respectively.
The route of the fuel passing through the communication pipe 4 is cut off by the cutoff valve 5. On the other hand, a diaphragm 7 disposed within the casing 6 is constantly pressed downward by a spring 8 disposed above it, and the upper end of the spring 8 is connected to a thermowax 10 via a spindle 9. Furthermore, the thermowax 10 is the thermowax 10
It is configured so that it is exposed to the fuel through the storage case 11. Therefore, when the engine ignition switch is turned ON to energize the electromagnetic valve 12, the magnetic force exceeds the biasing force of the spring 13, thereby drawing the shutoff valve 5 toward it. Therefore, the path is opened and the fuel flows toward the diaphragm 7 as shown by arrow A. At this time,
The thermowax 10 causes a volume change depending on the fuel temperature, causing the spindle 9 connected to the thermowax 10 to change in the vertical direction, and the elastic force of the spring 8 is adjusted by this change. As a result, the fuel pressure downstream of the diaphragm 7 is regulated.

Next, the actual operation will be explained using FIG. 2.
A fuel vapor line 16 that communicates with the canister 15 is disposed in the fuel tank 14, and a pressure higher than the normal setting pressure of the fuel vapor line determined based on the fuel tank filling head is installed in the middle of the fuel vapor line 16. A check valve 17 is provided, and when the fuel 18 in the fuel tank 14 evaporates, the flow from the fuel tank 14 to the fuel pipe 19, the filter 20, the fuel pump 21, the fuel pipe 22, and even the temperature-sensitive valve 17 is provided. The pressure in the fuel supply line formed by the mold pressure regulating valve 1 will be increased. Here, when the engine stops, the solenoid valve 12 interlocked with the ignition switch 23 shuts off the fuel pipe 26 leading to the float chamber 25 of the carburetor 24 and the fuel pipe 22 leading to the fuel pump 21. This prevents fuel from flowing into the fuel tank, increases the pressure in the fuel supply line, and suppresses vapor generation. Furthermore, when the engine is left unattended, the fuel pump 21 and fuel pipe 22 become extremely hot due to heat radiation from the engine, and the pressure also increases. At this time, when you try to start the engine again, in the conventional case, the solenoid valve turns ON-
Since it only has an OFF action, the solenoid valve opens as soon as the ignition switch is turned ON, and the pressure in the fuel supply line drops rapidly. However, due to the pressure difference, a large amount of fuel in the line flows into the carburetor, overflowing the float chamber and enriching the air-fuel mixture. Furthermore, as shown in FIG. 3, as the pressure decreases, the limit temperature at which vapor lock occurs also decreases, and if the temperature remains the same, vapor lock is extremely likely to occur. Therefore, in a conventional system having only one solenoid valve, vapor lock occurs and the operating performance is significantly deteriorated.

Therefore, the temperature-sensitive pressure regulating valve 1 according to this embodiment becomes an effective means. That is, as already mentioned, when the engine is left unused, the temperature near the fuel pump 21 and fuel pipe 22 becomes high, but at this time the thermowax 10 is also exposed to high temperatures, and as a result, the thermowax 10 increases in volume,
Press the spring 8 downward and remove the diaphragm 7.
Increase the opening pressure. Therefore, even if the ignition switch 23 is turned on and the solenoid valve 12 is opened, the temperature-sensitive pressure regulating valve 1 is removed from the fuel tank 14.
The pressure in the fuel supply line during this period is maintained at a certain level while supplying fuel to the float chamber 25 of the carburetor 24, and vapor lock is suppressed without overflowing the float chamber. Furthermore, as the fuel continues to flow, the temperature of the fuel supply line decreases to 1.
8, which is relatively low. Therefore,
The danger of vapor lock is also reduced, and there is no need to maintain high pressure in the fuel supply line. Therefore, the thermowax 10 performs self-control. That is, as the fuel temperature decreases, the volume of the thermowax 10 decreases, the force applied to the spring 8 decreases, and the opening pressure of the diaphragm 7 decreases. Therefore, the normal fuel pumping pressure is maintained, and smooth fuel supply becomes possible.

FIG. 4 shows another embodiment of the invention. In this embodiment, the spring 8 that determines the opening pressure of the diaphragm 7 of the temperature-sensitive pressure regulating valve 1 is adjusted by a bimetal 27 provided in the fuel passage. The bimetal 2
7 is fixed at one end to the storage case 11 and at the other end to the rotating shaft 28, as shown in FIG. It is configured to rotate counterclockwise. Further, the rotating shaft 28 is connected to a pressure control shaft 29 and is configured to be in contact with a pressure receiving surface 30. Therefore, when high-temperature fuel is near the bimetal 27, the rotating shaft 28 rotates clockwise, causing the pressure control shaft 29 to move downward, increasing the opening pressure of the diaphragm 7 via the spring 8. This means that the occurrence of vapor lock is suppressed. On the other hand, in the case of low temperature, the opposite of the above effect occurs without any explanation. Note that the other configurations are the same as those of the first embodiment described above, so a description thereof will be omitted.

〔Effect of the invention〕

As explained above, according to the fuel vapor lock prevention device for a vaporizer-type internal combustion engine according to the present invention, the temperature-sensitive pressure in the fuel supply line between the fuel tank and the vaporizer can be adjusted according to the fuel temperature. By adopting a configuration equipped with a regulating valve, it is possible to suppress the occurrence of vapor lock by maintaining the additional force using the fuel vapor in the fuel tank, and when the engine is stopped and restarted after being left unused, the additional pressure circuit is opened and the fuel is This provides an excellent effect in that a large amount of fuel in the supply line does not flow into the carburetor, and therefore it is possible to ensure the same operability as normal.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the fuel vapor lock prevention device according to the present invention, Fig. 2 is a system diagram in which the fuel vapor lock prevention device is incorporated into the fuel system of a vehicle, and Fig. 3 shows pressure and vapor lock limit temperature. FIG. 4 is a sectional view showing another embodiment of the fuel vapor lock prevention device according to the present invention;
FIG. 5 is a cross-sectional view of FIG. 4 taken along line V-V. 1...Temperature-sensitive pressure regulating valve, 12...Solenoid valve, 1
4... Fuel tank, 15... Canister, 16...
...fuel vapor line, 17... check valve, 23... ignition switch, 24... carburetor, 25...
...Float chamber.

Claims (1)

[Claims] 1. A check valve set to a predetermined pressure higher than the normal set pressure of the fuel vapor line determined based on the fuel tank filling head is installed in the fuel vapor line connecting the fuel tank and the canister, and the fuel vapor line connects the fuel tank and the canister. Fuel for a carburetor-type internal combustion engine, in which additional pressure is maintained in a fuel supply system between a float chamber of a carburetor, and the fuel supply system is equipped with a solenoid valve that opens or opens in conjunction with the disconnection or disconnection of an engine ignition switch. The vapor lock prevention device includes a temperature-sensitive pressure regulating valve capable of sensing the fuel temperature of the fuel supply system and maintaining an additional pressure of the fuel supply system according to the fuel temperature, and when restarting at a high temperature, A fuel vapor lock prevention device for a carburetor type internal combustion engine, characterized in that the device prevents a sudden decrease in the additional pressure.