JPH04201717A - Fuel cut-off of fuel tank - Google Patents

Abstract

PURPOSE:To ensure a smooth elevating operation of a valve seat which makes blocking action by floating of a float stored in a casing by projectingly providing, on the casing a guide shaft which is slidably fitted to the shaft core portion of the valve seat. CONSTITUTION:In a fuel cut-off on which a casing 3 having a gas discharging hole 2 is provided on the upper portion of the inside of a tank main body 4, and a float 5 for blocking a valve seat 2a is stored in the casing 3, a stopper 18 is projectingly provided on the lower surface of the upper wall of the room 10b of a casing 10 to regulate an upward displacement of the float 5. A valve seat 15 is stored in the room 10b, but this valve seat 15 is formed into its external shape having small diameter portions 15b, 15c on both upper and lower sides of a large diameter portion 15a, and a through hole 21 is formed in its shaft core portion. A guide shaft 23 is projectingly provided downward on an upper wall of a room 10a, and the tip portion of the guide shaft 23 is slidably fitted in the through hole 21 to smooth the elevating operation of the valve seat 15.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a fuel cutoff device for a fuel tank mounted on a vehicle such as an automobile.

BACKGROUND OF THE INVENTION Some fuel tanks for automobiles are equipped with a fuel cutoff device to prevent the fuel inside the tank body from flowing out due to the tilting of the automobile or the like. Generally, as shown in FIG. 4, this fuel cutoff device has a casing 3 equipped with a gas discharge hole 2 that communicates with an evaporative tube 1 and is disposed in the upper part of a tank body 4. It has a structure in which a float 5 is housed to close the valve seat 2a at the end of the discharge hole 2, and fuel A flows into the casing 3 due to fluctuations in the fuel liquid level as shown by E and F in the figure. Sometimes, the floating of the float 5 causes the valve seat 2 to
a to prevent fuel A from flowing out through the evaporative tube 1.

However, in the case of such a fuel cutoff device, when the float 5 closes the valve seat 2a due to fluctuations in the fuel level in the tank body 4, and the gas pressure in the tank body 4 increases in this state, gas leaks from inside the casing 3. Even after the fuel A flows out, there is a possibility that the float 5 will stick to the valve seat 2a and not be able to separate from it, which is a so-called stick phenomenon, so this is dealt with by increasing the weight of the float.

For this reason, conventionally, as shown in FIG.
is movably and elastically held via a cylindrical valve seat guide 8, while a stopper 9 is protrudingly provided on the lower surface of the upper wall of the casing 3 or on the upper surface of the float 5 to restrict the closing stroke of the float 5, When the gas pressure inside the tank body increases with the float 5 blocking the valve seat 6, the float 5 will strike, and the valve seat 6 will move to the valve open position under the gas pressure inside the tank body while the float 5 is in a loaf-regulated state. A fuel cut-off device has been devised in which the displacement and thereby the sticking of the float 5 is avoided.

This similar structure is shown in, for example, Japanese Patent Application No. 1-96658.

Problem to be Solved by the Invention In the case of the fuel cutoff device shown in FIG. 5, the float 5 and the valve seat 6 are guided by the inner peripheral surfaces of the casing 3 and the valve seat guide 8, respectively, so that their relative positions are always maintained. However, if the gap between the valve seat guide 8 and the valve seat 6 is narrowed beyond a certain range in order to improve the relative positional accuracy between the valve seat 6 and the float 5, the valve seat 6 There is a concern that even if the valve seat 6 is slightly tilted when it is raised, the outer corner of the valve seat 6 will interfere with the valve seat guide 8 and the smooth operation of the valve seat 6 will be hindered, so the manufacturing process is extremely expensive. This is done with great precision, leading to an increase in manufacturing costs.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a fuel cutoff device for a fuel tank that can improve the relative positional accuracy of the valve seat and the float without interfering with the smooth lifting and lowering movement of the valve seat.

Means for Solving the Problems As a means for solving the above-mentioned problems, the present invention provides a method of blocking a portion of the casing provided in the tank body facing the gas discharge hole by the floating of a float housed in the casing. While the valve seat is movably and elastically held, a stopper is provided on the casing or the float to restrict the closing stroke of the float, and when the internal pressure of the tank body rises above a predetermined value, the valve seat does not come into contact with the float. In the fuel cutoff device for a fuel tank, the casing includes:
A guide shaft is provided that protrudes and is slidably fitted into the shaft core of the valve seat.

If the internal pressure of the tank body increases with the float floating and blocking the valve seat, the float may remain adsorbed to the valve seat even after the fuel has flowed out from the casing. When the internal pressure further increases and reaches the set value, the valve seat receives the internal pressure of the tank body while the closing stroke of the float is restricted by the stopper, and is displaced to the valve opening position while sliding on the guide shaft. Further, since the valve seat is guided by the guide shaft at its axial center, the vertical movement is not hindered due to the inclination of the valve seat.

EXAMPLE Hereinafter, an example of the present invention will be described based on FIGS. 1 to 3.

In FIG. 1, reference numeral 10 denotes a casing of a fuel cutoff device made of a resin material. is extended to guide the evaporated fuel gas generated within the tank body 4 from the gas discharge hole 2 of the outlet 11 via the evaporative tube 1 to a canister (not shown).

Further, communication holes 12 are provided in the side wall and the lower wall of the casing 10, respectively.
．． 1. ．． 3 is formed, and when the fuel level in the tank body 4 changes when the vehicle turns or tilts, this communication hole 12.1
The fuel in the tank body 4 flows into the casing 10 through the casing 10.

Further, the inside of the casing 10 is divided into two upper and lower chambers by a wall provided with an opening 14, with the valve seat 15 in the upper chamber 10a and the float 5 carrying springs 16 and 17 in the lower chamber 10b. It is housed in a state where it can be elastically displaced through the housing.

The valve seat 15 is movably and elastically held in the casing 10 in the upper chamber 10a facing the gas discharge hole 2. In addition, 18 is a stopper provided protrudingly provided on the lower surface of the upper wall of the chamber 10b of the casing 0, and this stopper 18 controls the amount of upward displacement of the float 5 by coming into contact with the upper surface of the float 5, that is, its closing. It is designed to regulate the dynamic stroke.

The float 5 is provided with a protruding seal portion 19 at the center of its upper surface, and when fuel flows into the casing 10, it rises by its own buoyancy while being guided by the side wall of the casing 10 (of the chamber 10b), and seals. The opening 20 of the valve seat 15 is closed by the portion 19 .

Further, as shown in FIGS. 2 and 3, the valve seat 15 has small diameter portions 15b on both upper and lower sides of the large diameter portion 15a.

15c, and the lower small diameter part 1
5C loosely inserted into the opening 14 to open the chamber 10a of the casing 10.
In the set state, the spring 16 comes into contact with the upper surface of the large diameter portion 15a. and,
This valve seat 15 has a through hole 21 formed in its axial center, and a horizontal passage 22 is formed perpendicularly to the middle part of the through hole 21. The upper surface of the diameter portion 15a is communicated with the horizontal passage 22. Note that the lower end of the through hole 21 serves as the opening 20 that is closed by the float 5.

On the other hand, on the upper wall of the chamber 10a of the casing 10, a guide shaft 23 of a predetermined length is provided to protrude downward. A hole 21 is slidably fitted therein. The guide shaft 23 and the through hole 21 are formed with almost no clearance within the range in which they can slide relative to each other, so that the valve seat 15 can be moved up and down with high precision and without inclination. Further, the tip of the guide shaft 23 is located above the horizontal passage 22 when the valve seat 15 is in its lowest position, but when the valve seat 15 is raised, it lowers relative to the horizontal passage 22 and opens. 20 and the horizontal passage 22 are cut off from communicating with each other.

Due to the above structure, in a normal state where the fuel level in the tank body 4 does not fluctuate, the float 5 is lowered by its own weight, so the evaporated fuel gas generated in the tank body 4 is transferred to the valve seat 15. , the gas discharge hole 2, and the evaporative tube 1, and are discharged to the outside.

When fuel flows into the casing 10 from this state due to fluctuations in the fuel level within the tank body 4, the float 5 floats and its seal portion 19 closes to the valve seat 1.
The opening 20 of No. 5 is closed.

As a result, fuel is prevented from flowing out through the gas exhaust hole 2.

In this state, when the gas pressure inside the tank body 4 increases,
Even after the fuel returns to the tank body 4 from inside the casing 10, the float 5 may remain adsorbed to the valve seat 15, but the gas pressure inside the tank body 4 is transferred to the large diameter of the valve seat 15 through the opening 14. Since it acts on the lower surface of the section 15a, when the gas pressure in the tank body 4 becomes higher than the set value, the valve seat 15 is raised by the gas pressure while being regulated by the upward displacement of the float 5 or the stopper 18, and this causes the valve seat 15 openings 20 are opened and flow 1
-5 stick is avoided. At this time, the valve seat 15 is guided by the guide shaft 23 and rises, or if the valve seat 15 rises to a certain extent, the guide shaft 23
Since the tip of the guide shaft 23 is located below the horizontal passage 22 to block communication between the opening 20 and the horizontal passage, the The pressure in space B gradually increases as the valve seat 15 rises. Therefore, the difference between the gas pressure in the tank body 4 and the pressure in the space B gradually becomes smaller, and the stick of the float 5 becomes easier to release.

In the fuel cutoff device according to the present invention, since the valve seat 15 is accurately positioned on the guide shaft 23 at its axial center, the relative position of the float 5 positioned on the side wall of the float 10 and the valve seat 15 is Accuracy is greatly improved. Therefore, the valve seat 15 can operate smoothly without getting caught, and it is possible to keep the valve seat 15 and the float 5 in stable contact at all times.

Effects of the Invention As described above, according to the present invention, since the casing is provided with a protruding guide shaft that is slidably fitted to the shaft core of the valve seat, smooth lifting and lowering movement of the valve seat is ensured. It becomes possible to perform strict positioning of the valve seat, and it becomes possible to greatly improve the relative positional accuracy of the valve seat and float.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is an enlarged sectional view of the main parts of the same embodiment, Fig. 3 is an exploded perspective view of the main parts of the embodiment, and Fig. 4 is a conventional FIG. 5 is a sectional view showing another conventional technique. 2... Gas discharge hole, 4... Tank body, 5... Float, 10... Casing, 15... Valve seat, 18... Stopper, 23... Guide shaft. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) The valve seat, which is blocked by the floating of the float housed in the casing, is movably and elastically held in the part facing the gas discharge hole of the casing disposed inside the tank body, while , a fuel cutoff device for a fuel tank, which is provided with a stopper that regulates the closing stroke of the float, and when the internal pressure of the tank body rises above a predetermined value, the valve seat is displaced to a valve open position where it does not come into contact with the float. A fuel cutoff device for a fuel tank, characterized in that the casing has a guide shaft protruding from the casing that is slidably fitted into the shaft core of the valve seat.