JPH0972258A - Vapor exhaust device of fuel tank for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent outflow of oozed fuel from a cut valve to a canister. SOLUTION: A part 2b on an upper wall 2 of a fuel tank 1 is formed lower than the other part 2a and vapor tubes 4a, 4b are connected to the high/low parts 2a, 2b respectively via cut valves 3a, 3b. Relief valves 5a, 5b are installed in the upper stream side than the merging points of the vapor tube 4 in a vapor exhaust device formed by merging the vapor tubes 4a, 4b on the way and connecting them to a canister. The valve opening value of the relief valve 5a on the upper wall high part 2a side is set to such a value as regulating the filling-up in feeding the fuel oil and the valve opening value of the relief valve 5b on the upper wall low part 2b side is set to rather larger than the valve opening value of the other relief valve 5a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor discharging device for a vehicle fuel tank.

[0002]

2. Description of the Related Art In a fuel tank for automobiles, there is a device disclosed in, for example, Japanese Patent Laid-Open No. 3-246119, for discharging normal vapor. However, due to the layout, as shown in FIG. 4, it may be necessary to form a part of the upper wall (the part indicated by the alternate long and short dash line) one step lower than the other part.

However, when the portion of such a fuel tank which is formed one step lower becomes relatively large, the full liquid level must be set above the portion TL which is formed one step lower in order to secure as much tank capacity as possible. I will have to do it.

In this case, even if the liquid surface inclines in the inclined parking and the space above the liquid surface is divided into left and right, the internal pressure is prevented from rising abnormally due to the occurrence of vapor, so that the high and low portions T of the upper wall are prevented.
Vapor tubes 50H and 50L are connected to H and TL, respectively, and these tubes 50H and 50L are joined in the middle to be connected to a canister (not shown), and when the tank is full or the fuel level is inclined, To prevent fuel from flowing out of the canister through 50L,
The cutoff valves 51H and 51L are installed at the tank side openings of the vapor tubes 50H and 50L, respectively.
It is conceivable to install the relief valve 52 on the downstream side of the merging point of 0H and 50L.

That is, when the tank is full as shown in FIG.
When the cut valve 51L on the lower portion TL side of the upper wall is closed to prevent the fuel from flowing out to the vapor tube 50L and vapor is generated due to the rise in the fuel temperature, and the tank internal pressure exceeds the valve opening pressure Pr of the relief valve 52, Relief valve 5
2 is opened, and the vapor is sent to the canister for adsorption processing. Further, when the liquid surface inclination shown by the chain double-dashed line occurs, the cut valve 51H on the upper wall high portion TH side is closed to prevent the fuel from flowing out to the vapor tube 50L. Incidentally, FIG. 4 schematically shows a fuel tank, and the vapor tubes 50H and 50L are laid out so as to crawl on the upper surface of the tank.

[0006]

Generally, the cut valves 51H and 51L have a structure in which the valve body is pressed against the valve seat by the buoyancy of the float to close the valve.
It is difficult to obtain the molding accuracy of the contact portion between the valve body portion and the valve seat, and there is a limit to ensuring the sealing property in consideration of cost and efficiency.

Therefore, when the tank is full as shown in FIG. 4, the cutoff valve 51L from the lower portion TL of the upper wall to the vapor tube 5 is removed.
It is unavoidable that the fuel oozes out to 0L, and the oozing fuel b
Will accumulate in the tube 50L.

In such a state, when the tank internal pressure Pt rises and exceeds the valve opening pressure Pr of the relief valve 52, the relief valve 52 opens to discharge the vapor, but when the relief valve 52 opens. At the time of vapor relieving, the valve seat opening of the cut valve 50H is an orifice with a small diameter, so pressure loss ΔP occurs at this portion, and the pressure inside the vapor tube 50H is Pt−ΔP (> Pr). become. At this time, on the cut valve 51L side, no pressure loss occurs due to only fuel bleeding, so the oozing fuel b rises by the amount of the head difference corresponding to the pressure loss ΔP on the cut valve 51H. That is, due to the rise in the liquid level of the exuded fuel b, the exuded fuel b may reach the confluence of the tubes 50H and 50L and may flow out to the canister side together with the vapor.

In view of such circumstances, it is an object of the present invention to provide a vapor discharge device for an automobile fuel tank, which can prevent the exuded fuel from flowing out.

[0010]

According to the present invention for solving the above problems, a part of an upper wall of a fuel tank is formed one step lower than the other part, and vapor is provided to each of these high and low parts through a cut valve. In a vapor discharge device in which tubes are connected and these vapor tubes are joined together in the middle to be connected to a canister, a relief valve is installed on each upstream side of the joining point of the vapor tubes, and on the upper wall side of the upper wall. Set the valve opening value of a relief valve to a value that allows full tank control when refueling, and set the valve opening value of the relief valve on the lower side of the upper wall to be larger than the valve opening values of other relief valves. Characterize.

Preferably, the valve opening value of the relief valve on the lower side of the upper wall may be set to be slightly larger than the sum of the valve opening value of the relief valve on the upper side of the upper wall and the pressure loss of the cut valve. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION FIGS. 1 to 3 show a vapor discharging device for an automobile fuel tank according to the present invention, and FIG. 1 is a schematic view of the one shown in FIGS.

In the figure, reference numeral 1 denotes a fuel tank, and a part 2b of an upper wall 2 of the fuel tank is formed to be one step lower than the other part 2a. The cut valve 3 is provided on the high and low portions 2a and 2b of the upper wall 2.
Vapor tubes 4a and 4b are connected via a and 3b, respectively, and these tubes 4a and 4b are merged and connected to a canister (not shown) as one.

Further, relief valves 5a and 5b are installed upstream (tank) of the vapor tube 4 from the confluence. Among these, the valve opening value Pa of the relief valve 5a on the high portion 2a side of the upper wall 2 is set to a value that can sufficiently control the full tank at the time of refueling. That is, it is set to be slightly higher than the tank internal pressure (a value corresponding to the head difference H) at which the fuel is pushed up from the vent tube 6 to the inlet of the filler tube 7.

On the other hand, the valve opening value Pb of the relief valve 5b on the lower portion 2b side of the upper wall 2 is larger than the valve opening value Pa of the other relief valve 5a, preferably the valve opening value Pa of the relief valve 5a. And the orifice 8 of the cut valve 3a
It is set to be slightly larger than the sum of the pressure loss ΔP caused by a. That is, when the tank surface pressure Pt rises when the liquid level is not inclined in the full tank state shown in FIG.
Does not open earlier than the relief valve 5b.
As a matter of course, the tank internal pressure P when the liquid surface is inclined
In order to suppress the rise of t, the valve opening value P of the relief valve 5b
It is preferable that b is not larger than necessary.

The cut valve 3a on the upper wall high portion 2a side
Are installed in consideration of the liquid surface inclination (Figs. 2 to 3).
reference).

Since this embodiment is constructed in this way,
When the tank is full as shown in FIG. 1, the fuel oozes out from the cut valve 3b into the vapor tube 4b, and the oozing fuel b may be accumulated at the same level as the liquid level in the tank body. In this state, the tank internal pressure Pt rises. Relief valve 5a
Of the valve opening value and the pressure loss of the cut valve 4a Pa + ΔP
When it exceeds, the relief valve 5a is opened and the vapor is discharged. At this time, the internal pressure of the vapor tube 4b becomes the same value Pa + ΔP as the internal pressure of the tank, but the relief valve 5b
Since the valve opening pressure Pb is slightly higher than this value, the leaking fuel b does not flow out to the canister side by opening the relief valve 5b.

Further, when the liquid surface inclination shown by the two-dot chain line in the figure occurs, the exuded fuel b in the vapor tube 4b is quickly returned to the tank by opening the cut valve 3b. Even if the tank internal pressure rises, the valve opening pressure Pb of the relief valve 5b is slightly higher than that of the relief valve 5a, so the tank internal pressure Pt does not rise abnormally.

[0019]

According to the invention of claim 1, when the relief valve on the upper portion of the upper wall is opened to discharge the vapor, the relief valve on the lower portion of the upper wall is not opened. It is possible to prevent the fuel that has exuded from the cut valve on the lower side of the upper wall from flowing out to the canister.

Further, by setting the valve opening value of the relief valve on the lower side of the upper wall as in the second aspect, it is not necessary to increase the tank internal pressure when the liquid surface is inclined.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a vapor discharging device of the present invention.

FIG. 2 is a plan view of the device.

FIG. 3 is a front view of the device.

FIG. 4 is a view showing a conventional vapor discharging device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel tank 2 ... Upper wall 2a ... High part of upper wall 2b ... Low part of upper wall 3a ... Cut valve 3b ... Cut valve 4 ... Vapor tube 5a. ..Relief valve 5b ... Relief valve

Claims (2)

[Claims] 1. A canister is formed by forming a part of an upper wall of a fuel tank one step lower than other parts, connecting vapor tubes to respective high and low parts through cut valves, and merging these vapor tubes on the way. In the vapor discharge device connected to, the relief valves are installed on the upstream side of the confluence of the vapor tubes, and the valve opening value of the relief valve on the upper side of the upper wall is regulated for full tank when refueling. A vapor discharge device for a fuel tank for an automobile, wherein the relief valve on the lower side of the upper wall is set to a value that can be set and the opening value of the relief valve is set to be larger than the opening values of other relief valves. 2. The opening value of the relief valve on the lower side of the upper wall is set to be slightly larger than the sum of the opening value of the relief valve on the upper side of the upper wall and the pressure loss of the cut valve. The vapor discharging device for a vehicle fuel tank according to claim 1.