JPS6014916Y2 - Fuel tank internal pressure control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel tank internal pressure control device for a fuel system of an internal combustion engine, which has an air chamber formed in the upper part of the fuel tank and discharges fuel vapor in the tank through a canister.

In order to discharge the fuel vapor from the upper part of the fuel tank, from the viewpoint of emission regulations, the fuel vapor is adsorbed in the canister and then discharged.

However, since the filler port of the fuel tank is generally located at a higher position than the canister, when the filler port is filled with fuel, the difference in gravity causes the fuel to flow into the canister.

For this reason, a check valve (usually a one-way valve that opens when the internal pressure of the fuel tank exceeds 300 mAg) has been installed in the middle of the fuel vapor exhaust path connecting the fuel tank and the canister, and a check valve has been installed in the upper part of the fuel tank. form a chamber,
This prevents fuel from flowing into the canister even when the tank is full.

However, by installing such a check valve,
Internal pressure is acting inside the fuel tank and fuel pipe.

If you stop the engine in the summer or after high-load operation when the temperature inside the engine compartment is high, it is often difficult to restart the engine, but this is because fuel from the carburetor float chamber evaporates and the air vent This can also be caused by percolation occurring from within the fuel passage in the carburetor and jumping out into the intake manifold.

However, the biggest factor that makes restartability difficult is that the fuel pipe between the carburetor and the fuel tank gets heated when the engine is stopped, and the fuel vaporizes during this time, and the fuel in the float chamber evaporates, causing the float chamber level to drop. Therefore, the fuel vapor in the fuel pipe or fuel tank is pushed into the float chamber by the pressure caused by the tank internal pressure or the volume change when vaporized, and is sent into the intake manifold through the air vent pipe.

Therefore, the above-mentioned problem can be solved by opening the internal pressure of the fuel tank.

However, if the check valve is removed and the internal pressure of the tank is kept open at all times, fuel will flow into the canister when the tank is filled with refueling.

The present invention solves this problem and aims to improve restartability of the engine at high temperatures by controlling the internal pressure of the fuel tank and to prevent fuel from flowing into the canister.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 is shown as a comparative example, where 1 is a fuel tank, 2 is a fuel tank, and 2 is a fuel tank.
is a fuel vapor discharge path connecting the fuel tank and canister 3, 4 is a carburetor, 5 is a float chamber, 6 is a fuel supply pipe,
7 is a fuel pump, and 8 is a return pipe for returning fuel vapor generated during the fuel vibro to the fuel tank 1.

In the present invention, instead of a conventional check valve, a fuel filler port of the fuel tank 1, that is, a fuel tank cap 1 is installed in the middle of the fuel vapor discharge path 2 connecting the fuel tank 1 and the canister 3.
An on-off valve 9 is provided which opens when the cap 3 is closed and closes when the cap 13 is open.

In the comparative example shown in FIG.
0 is provided in the fuel tank 1, and when the cap 13 is opened, that is, during refueling, the switch 10 is closed and energized, and the solenoid valve 9 cuts off the fuel vapor discharge passage 2 midway.

Of course, the switch 10 needs to have an explosion-proof structure so that sparks from its electrical contacts will not ignite the fuel vapor.

In the comparative example shown in FIG. 1, the switch 10 is constituted by a pivot arm as shown, one end of which can come into contact with the cap 13 inside the fuel tank 1, and the other end extended outside the fuel tank 1. Constructed electrical contacts.

FIG. 2 shows an embodiment of the present invention, which is activated by opening the fuel tank cap 13'.
An example is shown in which an on-off valve 11 that mechanically shuts off is installed near a fuel filler port.

That is, in the embodiment shown in FIG. 2, one end of the pivot arm is attached to the cap 1 within the fuel tank 1, similar to the comparative example shown in FIG.
3', and the other end of the pivot arm outside the tank directly opens and closes the passage 2'.

According to the present invention, during refueling, that is, the fuel tank cap 13.
13' is open, the fuel vapor exhaust paths 2, 2
' is blocked, so even if fuel is filled to the vicinity of the upper end of the fuel filler port, a space air chamber 14 remains in the upper part of the fuel tank 1, and liquid fuel does not flow into the canister 3.

Furthermore, even when the fuel tank cap 13, 13' is closed and the fuel vapor discharge passages 2, 2' are opened, the space air chamber 14 remains in the upper part of the fuel tank 1, as in the conventional case, so that the vehicle Fuel vapor does not flow into the canister 3 even if it is tilted.

Furthermore, at high temperatures, fuel vapor generated from the fuel vibro and fuel return pipe 8 and fuel tank 1
Since the release valves 9 and 11 are open, the fuel vapor generated by the fuel vapor is absorbed into the canister 3 without increasing the pressure in the pipe.

Therefore, even if the engine is stopped in a high temperature state, fuel vapor generated in the fuel pipe or fuel tank 1 will not flow into the engine through the carburetor 4, preventing the mixture from becoming too rich when the engine is restarted. do.

Therefore, engine restartability at high temperatures is improved.

Incidentally, during a high-temperature shutdown, approximately 30% of the fuel vapor that accumulates in the intake manifold comes from the carburetor float chamber.
Approximately 60% of this is due to the fuel tank and tank internal pressure, and the remaining 10% is due to evaporation of liquid fuel in the carburetor passage, so the fuel tank internal pressure control device of this invention is effective in improving restartability at high temperatures. It is shown that it is a thing.

According to the present invention, since the mechanical on-off valve 11 is used, it is not only inexpensive, but also has the problem of ignition of fuel due to sparks generated from electrical contacts, unlike when using electrical means. There is no need to worry about causing this.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a comparative example of the present invention, and FIG. 2 is an embodiment of the present invention, showing only the parts different from the comparative example of FIG. 1. 1...Fuel tank, 2...Fuel vapor exhaust path, 3...Canister, 9, 11...
...Opening/closing valve, 13゜13'...Fuel filler port (cap), 14...Air chamber.

Claims (1)

[Scope of utility model registration request] In the fuel system of an internal combustion engine in which an air chamber 14 is formed in the upper part of the fuel tank 1 and fuel vapor in the tank is discharged through the canister 3, means for detecting opening and closing of the fuel filler port of the fuel tank 1 is provided, In the middle of the fuel vapor discharge path 2' connecting the fuel tank 1 and the canister 3, there is provided an on-off valve 11 which opens when the fuel filler port of the fuel tank is closed and which closes when the filler port is open. The opening/closing detection means is connected to a pivot arm, one end of which can come into contact with the fuel filler cap 13' inside the fuel tank 1, and the other end of which is located outside the fuel tank 1, so that it can be detected by movement of the other end. A fuel tank internal pressure control device characterized in that the fuel vapor discharge path 2' is mechanically opened and closed.