JPH04365624A - Fuel cut-off device for fuel tank - Google Patents

Abstract

PURPOSE:To prevent stick without increasing the dimensions of a valve by forming a projection on a valve casing or float valve, elastically holding a sealing part in movable manner on a float body, and forming a sealed space between a sealing part and a float body. CONSTITUTION:A float valve 8 is accommodated in supported state by a spring 10, in a valve accommodation chamber 4 in a valve casing 1 arranged in the upper part B in a tank body. In this case, the float valve 8 is constituted of a flat body 12 having a recessed part 11 at the center on the upper surface, sealing part 13 accommodated in the float body 12, and a sealed space A, and the sealing part 13 is urged upward by a spring 14. While, on the undersurface of the upper wall of the valve casing 1, a projection 18 as stopper is formed. Accordingly, fuel flows into the valve casing 1, and when the fuel liquid level returns to an original state after the closure of the float valve 8, the sealing part 13 is shifted downward by the increase of the pressure difference between the inside of the tank body and the sealed space A, and a valve seat 5 is surely opened.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 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 automobile fuel tanks are known to be equipped with a fuel cutoff device to prevent fuel from flowing out from the evaporative tube due to fluctuations in the fuel level within the tank body. Generally, this fuel cutoff device has a gas exhaust hole that communicates with the evaporative tube in a valve casing disposed at the upper part of the tank body, and a float valve that floats due to the inflow of fuel is housed in the gas exhaust hole. The open end on the inside of the valve housing chamber serves as a valve seat against which the seal portion of the float valve comes into contact. If the fuel level in the tank body fluctuates due to turning or tilting the vehicle and fuel flows into the valve casing, the float valve will rise due to buoyancy and block the valve seat, causing the fuel to pass through the evaporative tube. Prevent leakage to the outside.

However, in the case of such a fuel cutoff device, if the difference in gas pressure between the tank body and the evaporative tube becomes large while the float valve is blocking the valve seat due to buoyancy, the fuel will return from the valve casing into the tank body. The so-called sticking phenomenon, in which the float valve does not separate from the valve seat even after the float valve has been removed, is considered to occur, so countermeasures such as increasing the weight of the float have resulted in problems such as an increase in the weight of the vehicle.

To deal with this problem, conventional methods have been to provide a relief valve in the valve casing, for example as shown in Japanese Utility Model Application Publication No. 62-75278, so that when the float valve closes the valve seat, a relief valve is provided inside the tank body. When the pressure difference between and inside the evaporative tube exceeds the set value,
Fuel cutoff devices have been developed in which a relief valve opens to allow gas in the tank body to escape into the evaporative tube, thereby avoiding a stick.

Problems to be Solved by the Invention In the case of the conventional fuel cutoff device described above, the relief valve is for avoiding stickiness of the float valve, so the opening pressure is lower than that of the tank body where the float valve makes strong contact with the valve seat. Differential pressure between inside and evaporation tube (hereinafter referred to as
It's called stick pressure. ) must be set lower than Therefore, if the stick pressure of the float valve is set low, the opening pressure of the relief valve will also be lowered, and the relief valve will not open when the float valve normally blocks the valve seat due to the inflow of fuel into the valve casing. Therefore, the need to set the stick pressure as high as possible has been dealt with by increasing the weight of the float valve, and there is no drastic solution to the problem of increasing the size and weight of the float valve. is not.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a fuel cutoff device for a fuel tank that can reliably prevent stickiness without increasing the size of the float valve.

Means for Solving the Problems The present invention provides, as means for solving the above-mentioned problems,
A structure in which a float valve is floated by the inflow of fuel into a valve casing disposed in a tank body, and the float valve closes a valve seat to block an external outflow of fuel, wherein the valve casing or A stopper for regulating the closing stroke of the float valve is provided on either side of the float valve, and a seal portion of the float valve is movably and elastically held on the float body, and the interior is sealed between the seal portion and the float body. A possible closed space is provided so that when the pressure difference between the inside of the tank body and the closed space becomes greater than a predetermined value, the seal portion can be moved to a valve open position where it does not come into contact with the valve seat.

Operation When the fuel in the tank body flows into the valve casing due to turning or tilting of the vehicle, the float valve floats and comes into contact with the valve seat, closing the valve seat and blocking the outflow of fuel. At this time, the closing stroke of the float valve is regulated by the stopper. Also,
If the internal pressure of the tank body increases when the float valve is closed, even if fuel returns to the tank body from within the valve casing, the float valve may receive this internal pressure and the valve seat may remain closed. When the internal pressure of the tank body increases, the closing stroke of the float valve is regulated by the stopper, and the pressure difference between the tank body and the closed space increases, and the seal part elastically displaces in the valve opening direction. and move away from the valve seat.

Embodiments Hereinafter, embodiments of the present invention will be described based on FIGS. 1 to 8.

First, a first example will be explained.

In Figs. 1 to 3, 1 is a valve casing made of a resin material, and this valve casing 1 is disposed at an upper part B inside a tank body (not shown), and the upper end of the valve casing 1 is a valve casing made of a resin material. An evaporative tube 2 is connected to guide the evaporated fuel gas to the canister. 3 is an outlet to which the evaporative tube 2 is directly connected;
A communication hole of this outlet 3 opens into a valve housing chamber 4 in the valve casing 1, and this opening portion serves as a valve seat 5. Communication holes 6 and 7 are formed in the lower wall and side wall of the valve casing 1 facing the valve housing chamber 4, respectively, and when the fuel level in the tank body fluctuates when the vehicle turns or tilts, the communication holes 6 and 7 The fuel inside the tank body flows into the valve housing chamber 4 through the valve housing chamber 4.

Reference numeral 8 denotes a float valve installed in the valve housing chamber 4 while being supported by a spring 10. When fuel flows into the valve housing chamber 4, the float valve 8 combines the buoyancy of the fuel with that of the spring 10. It is designed to rise due to force and close the valve seat 5. The float valve 8 also includes a float main body 12 having a recess 11 at the center of the upper surface, a seal part 13 accommodated in the recess 11 so as to be able to rise and fall freely, and a closed space A sandwiched between the seal part 13 and the recess 11. The seal portion 13 is always urged upward by the spring 14. Note that a protrusion 15 is formed at the center of the upper surface of the seal portion 13 to directly close the valve seat 5. An annular flange 16 is formed on the upper edge of the recess 11 and extends in the axial direction, and the flange 13 restricts the upward stroke of the seal portion 13 . An annular projection 17 is formed on the lower surface of the flange 16 over its circumference, and when this annular projection 17 directly contacts the outer peripheral edge of the upper surface of the seal portion 13, the recess 11 and the seal portion 13
The closed space A between the two is completely sealed. Therefore, the seal portion 13 is displaced in the vertical direction due to the differential pressure between the pressure on the upper surface side and the pressure on the lower surface side.

Further, 18 is a protrusion formed on the lower surface of the upper wall of the valve casing 1, and this protrusion 18 comes into contact with the upper end surface of the float body 12 when the float valve 8 is floating, so that the closing stroke relative to the valve seat 5, i.e. , functions as a stopper that restricts the upward stroke of the float valve 8.

Because of the above configuration, under normal conditions where the vehicle does not turn or tilt, as shown in Figure 1,
The float valve 8 inside the valve casing 1 is lowered by its own weight, and the inside of the tank body is communicated with the evaporative tube 2 through the communication holes 6 and 7 and the outlet 3.

In addition, if the fuel level in the tank body fluctuates from this state due to turning or tilting of the vehicle, and the fuel in the tank body flows into the valve casing 1 through the communication holes 6 and 7,
As shown in FIG. 2, the float valve 8 in the valve casing 1 rises due to the buoyancy and the force of the spring 10, and the float body 12 abuts the protrusion 18 as a stopper, and at the same time the protrusion 15 of the seal portion 13 Valve seat 5
occlude. As a result, fuel is prevented from flowing out through the evaporative tube 2.

Furthermore, when the turning or tilting of the vehicle is released from this state, the fuel level in the tank body returns to the original level and the fuel in the valve casing 1 flows out from the communication hole 6. If the pressure difference between the tank body and the evaporative tube 2 is small, the float valve 8 will immediately descend due to its own weight as fuel flows out, but if the pressure difference is large, the float valve 8 will drop as shown in Figure 2. There are times when the valve 8 is attracted to the valve seat 5 and does not descend immediately. Once the float valve 8 is adsorbed in this manner, if it were a conventional general fuel cutoff device, it would become increasingly difficult for the float valve 8 to descend as the gas pressure inside the tank body increased, but this fuel cutoff according to the present invention In the device, the difference between the pressure inside the tank body applied to the upper side of the seal part 13 of the float valve 8 and the pressure in the closed space A applied to the lower side increases as the gas pressure inside the tank body increases. Due to the pressure difference, the seal portion 13 is displaced downward while the float body 12 remains in contact with the protrusion 18, and the valve seat 5 is opened. As a result, the inside of the tank body and the inside of the evaporative tube 2 are communicated with each other, and the float valve 8 falls due to its own weight, so that sticking of the float valve 8 is avoided.

Next, other embodiments of the present invention will be described. still,
The same reference numerals are used for the same parts as in the first embodiment, and the explanation of the overlapping parts will be omitted.

4 to 6 show a second embodiment of the present invention, and this fuel cutoff device is integrally formed of a resin material so that the upper edge of the recess 11 and the seal portion 13 are connected by a thin portion 19. death,
As a result, the closed space A is always sealed, and the seal part 1
3 is movably and elastically held by the float body 12, which is different from the first embodiment. In the case of this fuel cutoff device, when the float valve 8 floats due to the inflow of fuel into the valve casing 1, the seal portion 13 closes the valve seat 5 to prevent the fuel from flowing out, as shown in FIG. In addition, in this state, when the fuel returns from the valve casing 1 into the tank body and the pressure inside the tank body further increases, the thin wall portion 19 is caused by the pressure difference between the inside of the valve casing 1 and the closed space A, as shown in FIG. Upon bending, the end surface of the float body 12 first comes into contact with the protrusion 18 to restrict upward displacement of the float valve 8, and then from this state the seal portion 13 is displaced downward and the valve seat 5 is opened.

FIG. 7 shows a third embodiment of the present invention, and in the case of this fuel cutoff device, as a means for movably and elastically supporting the seal portion 13 on the float body 12, a The only difference from the second embodiment is that a rubber material 20 is interposed therein. With this device as well, substantially the same effects as those of the second embodiment can be obtained.

Further, as other embodiments, for example, as shown in FIG. 8, the entire seal part 13 is made of a rubber material and its outer peripheral edge is fixed to the float main body 12, or as a stopper. It is also possible to adopt an embodiment in which the protrusion 18 is formed on the float body 12.

Effects of the Invention As described above, the present invention provides a stopper for regulating the closing stroke of the float valve on either the valve casing or the float valve, while movably and elastically retaining the seal portion of the float valve on the float body. At the same time, a closed space that can be sealed internally is provided between the seal part and the float body, and when the pressure difference between the tank body and the closed space rises above a predetermined value, the valve opens so that the seal part does not come into contact with the valve seat. As the internal pressure of the tank body increases, the force that pulls the seal part away from the valve seat increases, making it possible to reliably prevent stickiness without increasing the size of the float valve.

[Brief explanation of the drawing]

1, 2, and 3 are cross-sectional views showing the first embodiment of the present invention,
FIG. 4 is a sectional view showing a second embodiment of the invention, FIGS. 5 and 6 are partially enlarged sectional views of the same embodiment, and FIG. 7 is a sectional view showing another embodiment of the invention. DESCRIPTION OF SYMBOLS 1...Valve casing, 5...Valve seat, 8...Float valve, 12...Float body, 13...Seal part, 18
...Protrusion (stopper), A...Closed space.

Claims (1)

[Claims] Claim 1: A float valve is floated by the inflow of fuel into a valve casing disposed in a tank body,
In a structure in which the float valve closes a valve seat to block external outflow of fuel, a stopper is provided on either the valve casing or the float valve for regulating the closing stroke of the float valve, and the float valve is provided with a stopper for regulating the closing stroke of the float valve. A seal portion is movably and elastically held on the float body, and a closed space whose interior can be sealed is provided between the seal portion and the float body, so that the pressure difference between the inside of the tank body and the closed space is equal to or higher than a predetermined value. A fuel cutoff device for a fuel tank, characterized in that when raised, the seal portion can be moved to a valve open position where it does not come into contact with a valve seat.