JPH0427754A - Open/close valve for vent pipe of fuel tank - Google Patents

Abstract

PURPOSE:To prevent the back flow of gasoline from a vent pipe by providing a float which floats up with gasoline when the gasoline inside a fuel tank rises above a reference level, to close the opening at one end of the vent pipe. CONSTITUTION:When the gasoline inside a fuel tank 20 rises above a reference level L, a float 90 in an open/close valve 10 floats up with gasoline to close the opening at one end of a vent pipe 40. Consequently, the back flow of gasoline from the vent pipe 40 can be prevented, and also the inflow of vaporized gas of gasoline inside the fuel tank 20 into the vent pipe 40 can be prevented. Thus, at the time of oil supply, the outflow quantity of vaporized gas flowing out into the atmosphere from an oil supplying port through the vent pipe 40 can be reduced. On the other hand, when the gasoline inside the fuel tank 20 falls below the reference level L, the float 90 in the open/close valve 10 descends to open the opening at the one end of the vent pipe 40. Thus, at the time of oil supply, venting can be carried out through the opened vent pipe 40.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an on-off valve for a vent pipe of a fuel tank for an automobile, and in particular prevents backflow of gasoline from the vent pipe and prevents evaporative gas from gasoline. This is an attempt to reduce the amount of fluid pressure into the atmosphere.

[Prior Art] Conventionally, for the purpose of adsorbing evaporative gas from gasoline, activated carbon chambers were provided on the upper surface of the inner wall of the fuel tank and in the middle of the vent pipe. The flow pressure of evaporated gas into the atmosphere was reduced (for example, Utility Model Application Publication No. 62-1484).
Publication No. 23, etc.).

[Problems to be Solved by the Invention] However, in the conventional products using activated carbon as described above, not only is the activated carbon expensive, but the lifespan of the activated carbon is only a relatively short period of about six months to one year. There is a problem.

That is, when activated carbon adsorbs evaporated gas, its adsorption capacity decreases. Therefore, it is necessary to replace or regenerate the activated carbon, and in any case, the activated carbon must be removed from the fuel tank, so the replacement or regeneration work is troublesome and time-consuming.

Furthermore, when an activated carbon chamber is formed within a fuel tank, there is a problem in that the capacity of gasoline within the tank is reduced.

Therefore, the present invention has been made in view of the problems of the above-mentioned conventional technology, and its purpose is to create an on-off valve using a float without using activated carbon.
By attaching it to the vent pipe, it is intended to prevent the backflow of gasoline from the vent pipe and to reduce the amount of gasoline evaporation gas flowing into the atmosphere.

[Means for Solving the Problems] The present invention is for achieving the above-mentioned objects,
The contents will be explained below using examples shown in the drawings.

The opening/closing valve for a vent pipe of a fuel tank according to claim 1 includes: a vent pipe (40) having an opening at one end communicating with the upper part of the fuel tank (20) and an opening at the other end communicating with the fuel filler port (31); ) and an on-off valve (lO) that protrudes into the fuel tank and is attached to the opening at one end of this vent pipe. A float (90) is provided that floats up in contact with gasoline and closes the opening at one end of the vent pipe, and descends to open the opening at one end of the vent pipe when the gasoline drops below a standard level. The on-off valve according to claim 2 is characterized in that the on-off valve according to claim 3 is provided with a return spring (100) that biases the float (90) in a downward direction. The standard level (L) is
It is characterized in that the level is set approximately equal to the level of gasoline in the fuel tank (20) when it is full.

[Function] Therefore, according to the on-off valve according to claim 1, when the gasoline in the fuel tank (20) exceeds the reference level (L), the float (90) of the on-off valve (10) comes into contact with gasoline. It floats up and closes the opening at one end of the vent pipe (40) (see Fig. 1).

Therefore, since the vent pipe is closed, backflow of gasoline from the vent pipe can be prevented.

Further, it is possible to prevent evaporated gas from gasoline in the fuel tank from flowing into the vent pipe. Therefore, during refueling, it is possible to reduce the amount of evaporative gas that flows out into the atmosphere from the refueling port (31) through the vent pipe.

On the other hand, when the gasoline in the fuel tank falls below the standard level, the float of the on-off valve descends, opening one end of the vent pipe (see Figure 7).

Therefore, when refueling, air can be vented through the open vent pipe.

According to the on-off valve according to claim 2, the floating float (
90), the float can be forcibly lowered by the biasing force of the return spring (100) when the gasoline in the fuel tank (20) falls below the reference level (L).

Therefore, the tank internal pressure can prevent the float of the on-off valve from sticking to the opening at one end of the vent pipe (40).

According to the on-off valve according to the third aspect, the reference level (L) is set almost equal to the level of gasoline in the fuel tank (20) when the tank is full, so that the fuel tank is set to the level when the tank is full. It is possible to prevent the on-off valve float from operating until the gasoline in the tank reaches the limit.

Therefore, gasoline can be refilled at once until the gasoline in the fuel tank almost reaches the level when the tank is full.

[Example] The present invention will be described below based on an example shown in the drawings.

Fig. 1 is a longitudinal sectional view of the on-off valve, Fig. 2 is a sectional view of main parts of the fuel tank, Fig. 3 is an exploded sectional view of the on-off valve, and Fig. 4 is a longitudinal sectional view of the on-off valve.
A cross-sectional view along the rV-rV line in the figure, Figure 5 is the ■-- of Figure 1.
6 is a plan view showing an assembled state of the on-off valve, and FIG. 7 is a sectional view showing the on-off valve in an open state.

In FIG. 2, IO is an on-off valve, 20 is a fuel tank for an automobile, 30 is a filler pipe having a fuel filler port 31 at one end and the other end is open to the lower side of the fuel tank 20, and 40 is one end. A vent pipe is shown in which one end communicates with the upper part of the fuel tank 20 and the other end communicates with the filler pipe 30 midway along its length.

As shown in FIGS. 1 and 2, one end of the vent pipe 40 penetrates the upper wall 21 of the fuel tank 20 and partially projects downward and almost vertically into the upper wall 21 of the fuel tank 20. At the tip of this projecting end 41, The above-mentioned on-off valve 10 is installed. Further, as shown in FIG. 2, a fuel tank 20 is located midway along the length of the vent pipe 40.
A check valve 50 and a canister 60 are connected in order from the side.

As shown in FIG. 3, the on-off valve 10 can be roughly divided into a cylindrical case 70, and this case 70 and a vent pipe 40.
a joint 80 that connects the two, a float 90 that is held movably up and down in the hollow interior of the case 70, a return spring 100 that biases the float 90 in the downward direction, and a return spring 100 that is attached to the lower end of the opening of the case 70. It includes a cap 110 that receives and stops the biasing force of the return spring 100 and limits the lowering limit of the float 90, and an O-ring 120 that is interposed between the case 70 and the joint 80.

As shown in FIGS. 1.3 to 5, the case 70 holds the float 90 in a vertically movable manner, and includes a relatively large diameter cylindrical holding cylinder 130 and a narrow constriction extending from the upper end of the holding cylinder HO. an annular neck portion 130 that fits over the vent pipe 40;
The neck part 130 is thickened again from the upper end and extends upward, and is provided with an annular head part 150 that connects the joint 80. For example, an F'OM (
It is integrally molded from thermoplastic resin such as polyoxymethylene).

As shown in FIG. 1.3, inside the holding cylinder 130, an opening rim 131 is formed which is slightly thinner than the neck 140 and hangs in an annular shape. The opening protrusion H1 has an inner diameter set to be approximately equal to the inner diameter of the vent pipe 40, and has an abutment surface 132 formed on the inner surface of the tip thereof to come into contact with and separate from the float 90 that moves up and down within the holding cylinder 130. This abutment surface 132 matches the shape of the tip of the float 90, and here has a substantially truncated conical shape that opens downward and is curved into an arc.

As shown in FIG. 1.3, an annular guide groove 13 with a U-shaped cross section and an open bottom surface is provided on the outside of the opening edge 131.
3 is formed so that the return spring 100 can be fitted into this guide groove 133 from below.

As shown in FIGS. 1 and 3, a plurality of circular through holes 134, here a total of four circular through holes 134, are formed in the peripheral wall of the holding cylinder 130, penetrating the inner and outer peripheries. These through holes 134 act as air flow paths when the float 90 moves up and down.

As shown in FIGS. 1 and 3, a plurality of ribs 13 protrude radially inward on the inner circumference of the peripheral wall of the holding cylinder 130.
Form 5... As shown in FIG. 1, under normal conditions, these ribs 135 face each other at a distance from the outer circumferential surface of the float 90, allowing gasoline to flow downward along each rib 135 to improve gasoline drainage. ing.

Further, at the lower end of the holding cylinder HO, a first. 3. As shown in FIG. 5, a locking means for locking the cap 110 is provided. In this embodiment, as a locking means, one of the concave and convex portions that fit into each other is formed between the holding cylinder 130 and the cap 110, and the cap 110
can be attached to the holding cylinder 130 with one touch.

More specifically, 1. 3. As shown in FIG. 5, on the outer periphery of the lower end of the holding cylinder 130, a plurality of locking claws 136, each having a sawtooth cross-sectional shape with the slope facing downward, are provided as the above-mentioned convex portions.
is installed protrudingly. A total of four of these locking claws 136 are provided on the outer periphery of the lower end of the holding cylinder 130 at 90 degree intervals. Slightly above these locking claws 136, there is a holding cylinder 13.
An annular protrusion 137 is formed annularly protruding from the outer periphery of 0.

Also, among the four locking claws 136, on both sides of one set of locking claws 136 facing away from each other, as shown in FIGS. Protrusion 137
A pair of protrusions 138. extending downward from the ridges 138. 138 are provided. These protrusions 138 are for preventing the cap 110 that fits around the outer periphery of the holding tube 130 from rotating.

The neck portion 140 of the case 70 has a first shape. 3. As shown in FIG. 4, its inner diameter is set to be approximately equal to the outer diameter of the vent pipe 40. An annular stepped portion 141 is formed between the inner periphery of the neck portion 140 and the slightly narrower opening edge portion 131 below the neck portion 140, with which the opening lower end portion of the vent pipe 40 comes into contact.

The head tSO of the case 70 is the first. 3. As shown in FIG. 4, its inner diameter is set larger than the outer diameter of the vent pipe 40, so that the O-ring 120 can be fitted between the inner circumference and the outer circumference of the vent pipe 40.

In the head 150, an upward receiving edge 151 for receiving the O-ring 120 is formed between the head 150 and the slightly narrowed neck 140 below.

Further, on the outer periphery of the head 150, a first. 3. As shown in FIG. 4, a connecting means for connecting the joints 80 is provided. In this embodiment, the head 1 is used as the connecting means.
Between the joint 50 and the joint 80, either one of concave and convex parts that fit into each other is formed, so that the joint 80 can be attached to the head 150 with one touch.

More specifically, 1. 3. As shown in FIG. 4, on the outer periphery of the head 150, a plurality of connecting claws 152 having a sawtooth cross-sectional shape with the slope facing downward are provided as the above-mentioned convex portions. Similar to the locking claws 136 of the case 70, a total of four of these connecting claws 152 are provided on the outer periphery of the head 150 at 90 degree intervals. Of the four connecting claws 152, on both sides of one set of connecting claws 152 facing away from each other, as shown in FIGS. A pair of protrusions 153. 1
53 are provided for each. These protrusions 153 are for preventing the joint 80 that fits around the outer periphery of the head 150 from rotating.

Next, the joint 80 is connected to the first joint 80. 3. As shown in FIG. 4, an outer cylinder 81 fits into the outer periphery of the head 150 of the case 70, forms a concentric circle with the outer cylinder 81, and forms a concentric circle between the outer periphery of the vent pipe 40 and the inner periphery of the head 150 of the case 70. Each has an inner cylinder 82 that fits therein, and a fitting hole 83 as a recess of a connecting means, which is fitted into a connecting claw 152 that extends from the lower edge of the outer cylinder 81 and projects from the outer periphery of the head 150. Plural, in this case, four that matches the number of connecting claws 152.
tongue-shaped connecting pieces 84 . Retaining piece 85・
..., and similarly to the case 70, it is integrally molded from a thermoplastic resin such as POM having appropriate elasticity and rigidity.

As shown in FIGS. 4 and 6, each of the connecting pieces 84 has a width equal to the distance between the pair of protrusions 153 protruding from the outer periphery of the head 150 of the case 70. Each fitting hole 83 is formed in a vertically long rectangular shape at the center of the width of the connecting piece 84, as shown in FIG.

As shown in FIG. 1.3, on the inner surface of the distal end of each of the retaining pieces 85, a check pawl 86 is formed, which protrudes radially inward and has a sawtooth cross-sectional shape with an inclined surface facing upward.

On the other hand, in the middle of the height of the protruding end 41 of the vent pipe 40, as shown in FIG. Futabe 4
form 2.

As shown in FIGS. 1 and 3, the float 90 described above has two
It is composed of a hollow body 91 that has a cylindrical shape with a bottom and an open top surface, and a lid body 92 that seals the open top surface of the hollow body 91. The hollow body 91 and the lid body 92 are , similar to the case 70 and the joint 80, are integrally molded from thermoplastic resin such as POM.

The outer diameter of the hollow body 91 is set to be slightly smaller than the inner diameter at the tip of the rib 135 inside the case 70, as shown in FIG.

The lid body 92 has a hollow body 91 as shown in FIGS.
It consists of an annular flange 93 that rests on the upper edge of the opening, and a spherical tip 94 that swells in a hemispherical shape from the center of the flange 93. An annular, vertically extending inner edge portion 95 is formed on the lower surface of the flange portion 93 and fits into the inner periphery of the opening of the hollow body 91 .

As shown in FIG. 1, the lid 92 has an inner edge 95 fitted into the inner periphery of the opening of the hollow body 91, and a joint surface between the flange 93 of the lid 92 and the upper edge of the opening of the hollow body 91, for example. The float 90 is assembled by ultrasonic welding.

As shown in FIGS. 1 and 3, the return spring 100 is a coil spring, and its inner diameter is set to be slightly larger than the outer diameter of the spherical tip 94 of the float 90.

Then, the return spring 100 is fitted from below with its upper end aligned with the guide groove 133 in the case 70, and the spherical tip 94 of the float 90 is fitted from below into the ring of the return spring 100, and the inner surface of the guide groove 133 is fitted. and the upper surface of the flange 93 of the float 90.

The cap 110 has a first. 3. As shown in FIG. 5, a circular bottom plate 11 that fits into the lower surface of the opening of the case 70
1 and 5 An annular groove 112 with an open upper surface and a U-shaped cross section that falls from the periphery of the bottom plate 111 and fits into the lower edge of the opening of the case 70, and an annular groove 112 that further rises from the periphery of the annular groove 112 and fits into the lower edge of the opening of the case 70. It is provided with a peripheral edge part 113 that extends upward in an annular shape and fits into the outer periphery of the case 70, and is integrally molded from a thermoplastic resin such as POM having appropriate elasticity and rigidity, similarly to the case 70 and the like. .

The bottom plate 111 has a first. 3. As shown in FIG. 5, four circular openings 114 penetrating vertically are opened.

The peripheral portion 113 has a third. 5. As shown in Figure 6, a plurality of slits 115 are formed at predetermined intervals from the upper edge.
A total of four tongue-shaped locking pieces 117 are formed within the interval between adjacent slits 115, each having a locking hole 116 into which the locking claw H6 of the case 70 fits.

The slit 115 has a size in which the protrusion 138 protruding from the outer periphery of the case 70 fits, and the interval between adjacent slits 115 is set to be approximately equal to the interval between the protrusion 138 forming a pair.

The O-ring 120 is made of rubber, for example, and has a diameter of 1.3°4.
As shown in the figure, the outer periphery of the vent pipe 40 and the case 70
and the inner periphery of the head 150 of the head 150.

Next, to explain the assembly procedure of the on-off valve IO having the above configuration, first, the return spring 10 is
0 into the guide groove 133 of the case 70, and then insert the previously assembled float 90 into the case 70 from its spherical tip 94.

After inserting the float 90, at the lower end of the opening of the case 70,
Attach the cap 110.

That is, the cap 110 is fitted from below with its slits 115 aligned with the respective protrusions 138 on the outer periphery of the case 70. When the cap +10 is fitted, the locking piece 117
are engaged with the locking claws 136 of the case 70, and when the cap 110 is strongly pushed in, the locking pieces +17 are pushed by the slopes of the locking claws 136 and are bent radially outward.

When the locking hole 116 of the locking piece 117 advances to the position of the locking claw 136, each locking piece 1
17 is restored with a snap due to the elastic force of the resin, and each locking hole 1
The locking claws 136 fit into each of the caps 11 and 16 .
0 will not come off from the case 70.

Also, in the slit 115 of the cap 110, there is a 5°6
As shown in the figure, each protrusion 138 of the case 70 is fitted into the case 70.

In this way, when the cap 110 is attached, the bottom plate 11
1 closes the bottom surface of the opening of the case 70 Float 90
is held in the case 70 so as to be movable up and down. Further, the return spring 100 elastically contracts between the inner surface of the guide groove 133 in the case 70 and the upper surface of the flange 93 of the float 90. Due to its elastic restoring force, the float 90 is moved as shown in FIG. ,
The cap 110 is biased to a lowered position where its lower surface is still in contact with the upper surface of the bottom plate 111 of the cap 110.

Therefore, as shown in FIG. 7, the spherical tip 94 of the float 90 moves downward away from the opening flange 131 in the case 70, and enters an open state in which the opening flange 131 is opened.

Next, the O-ring 120 is fitted from the open upper surface of the head 150 of the case 70. Thereafter, the joint 80 is attached to the head 150 of the case 70.

That is, the joint 80 is fitted from above so that the connecting piece 84 fits into the space between the pair of protrusions 153 on the outer periphery of the head 150 of the case 70 . joint 80
When the connecting piece 84 is inserted, the connecting piece 84 connects with the connecting claw 1 of the case 70.
52, and when the joint 80 is strongly pushed in, each connecting piece 84 is pushed against the slope of the connecting claw 152,
Deflects radially outward. Then, the insertion hole 8 of the connecting piece 84
3 advances to the position of the connecting pawl 152, each connecting piece 84 snaps back to its original state due to the elastic force of the resin, and the connecting pawl 152 fits into each fitting hole 83, as shown in Fig. 4.6.7. The joint 80 cannot be removed from the case 70.

The thus assembled on-off valve IO is attached to the protruding end 41 of the vent pipe 40 that partially protrudes downward from the upper side into the fuel tank 20.

That is, from inside the fuel tank 20, align the tip of the protruding end 41 of the vent pipe 40 with the inside of the retaining piece 85 of the joint 80 of the on-off valve 10, and fit it upward from below. When inserted from the joint 80, the protruding end 41 passes through the inner cylinder 82 of the joint 80, fits into the O-ring 120, and further advances to the inner periphery of the neck 140 of the case 70.

In this way, while the protruding end 41 of the vent pipe 40 is advancing into the on-off valve 10, the non-return claw 86 of the stopper piece 85
engages with the annular bulge 42 midway in the height of the protruding end 41 . Here, when the on-off valve IO is pushed more forcefully upward than downward, the check claw 86 of the stopper piece 85 is pushed by the annular bulge 42 of the protruding end 41 and deflects radially outward. and,
When the non-return claws 86 of the retaining pieces 85 get over the annular bulge portion 42 of the protruding end portion 41, each retaining piece 8 as shown in FIG.
5 snaps back to its original state due to the elastic force of the resin, and each of its non-return claws 86 is caught on the annular bulging portion 42, so that the on-off valve IO is prevented from coming off downward from the protruding end portion 41 of the vent pipe 40. Also, at this time, the tip of the protruding end portion 41 of the vent pipe 40 abuts against the annular stepped portion 141 of the case 70 .

Next, the operation of the on-off valve 10 mounted on the protruding end portion 41 of the vent pipe 40 will be explained.

First, as shown in FIG. 7, when the gasoline in the fuel tank 20 has not reached the reference level L, the on-off valve 10
The float 90 inside descends due to the biasing force of the return spring +00 and its own weight of the flow 1-90, and the float 90 in the vent pipe 4
The valve is in an open state with the opening flange 131 communicating with 0 being opened. The reference level L is set so that the float 90 operates at approximately 95% of the total capacity of the fuel tank 20 when it is full. Therefore, gasoline can be refilled nonstop until the fuel tank 20 reaches approximately 95% of its full capacity.

That is, during refueling, the on-off valve 10 is in an open state,
Vent pipe 40 is open.

On the other hand, when the supplied gasoline exceeds the reference level L, it flows into the case 70 through the opening 114 of the cap 110 of the on-off valve 10.

When gasoline flows into the case 70, the float 90 floats up and its spherical tip 94 comes into close contact with the contact surface 132 of the opening rim 131 inside the case 70, and the on-off valve 10 closes as shown in FIG. As such, the valve is in a closed state. Therefore, if the vent pipe 40 is blocked, it becomes difficult for gasoline to enter, and although it is possible to refuel until the tank is full, it is possible to indirectly control the full tank state.

In this way, the on-off valve lO is in the closed state, so that backflow of gasoline from the vent pipe 40 can be prevented. This happens not only when the tank is full of gasoline (even when the car is tilted extremely, the gasoline in the fuel tank 20 exceeds the reference level L, and the on-off valve IO operates in the same way. , the gasoline level is tilted and float 9
0 is inclined within the case 70, but since its tip is spherical, it comes into close contact with the abutting surface 132 of the opening flange 131 without any gaps, and can reliably prevent the backflow of gasoline.

Further, by opening the on-off valve lO, it is possible to reduce the amount of gasoline evaporative gas flowing into the atmosphere.

In other words, 5. Evaporative gas is most often generated when the tank is full of gasoline. This generated evaporative gas is transferred to the vent pipe 40.
The fuel flows into the tank, passes through the filler pipe 30, and flows out from the filler port 31 into the atmosphere.

Therefore, by closing the on-off valve 10 when the gasoline tank is full, when the amount of evaporative gas generated is the highest, the vent pipe 40 is closed and the amount of evaporative gas flowing into the vent pipe 40 is effectively reduced. Therefore, the amount of evaporative gas flowing into the atmosphere can be suppressed.

In the embodiment shown in the drawings, the on-off valve 10 is comprised of a case 70, a joint 80, a float 90, and a return spring 10.
The case 70, the joint 80, and the cap 110 may be made up of one member, or the case 70 and the joint 80 may be made into one member. It may be constructed from two members including the cap 110.

Furthermore, the return spring 100 may be omitted and the float 90 may be configured to descend only by its own weight.

[Effects of the Invention] Since the present invention is configured as explained above, it produces the effects as described below.

According to the opening/closing valve for the vent pipe of a fuel tank according to claim 1, it is possible not only to prevent backflow of gasoline from the vent pipe, but also to reduce the amount of gasoline evaporative gas flowing into the atmosphere. .

According to the on-off valve according to the second aspect, the operation of the float of the on-off valve can be ensured.

According to the on-off valve according to the third aspect, gasoline can be refilled smoothly.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a longitudinal sectional view of the on-off valve, FIG. 2 is a sectional view of the main part of the fuel tank, FIG. 3 is an exploded sectional view of the on-off valve, and FIG. 4 is a longitudinal sectional view of the on-off valve. is a sectional view taken along the line IV-IV in Fig. 1, Fig. 5 is a sectional view taken along the line ■-■ in Fig. 1, Fig. 6 is a plan view showing the assembled state of the on-off valve, and Fig. 7 is a sectional view taken on the line IV-IV in Fig. 1. FIG. 3 is a sectional view showing the valve in an open state. 10...Opening/closing valve, 20...Fuel tank length L...Reference level, 30...Filler pipe, 31...Fuel filler port, 40...Bent pipe, 41...Protruding end 90.
...Float, 100...Return spring. Agent Patent Attorney Black 1) Hakudo Diagram Z (Ni'6 αF + Genog Diagram jb Diagram Diagram

Claims (3)

[Claims] (1) A vent pipe whose opening at one end communicates with the upper part of the fuel tank and whose opening at the other end communicates with the fuel filler port, and an on-off valve attached to the opening at one end of the vent pipe and protruding into the fuel tank. The on-off valve is equipped with a valve that, when the gasoline in the fuel tank exceeds the standard level, floats up in contact with the gasoline and blocks the opening at one end of the vent pipe, and when the gasoline falls below the standard level. An on-off valve for a vent pipe of a fuel tank, comprising a float that descends and opens an opening at one end of the vent pipe. (2) The on-off valve for a vent pipe of a fuel tank according to claim 1, wherein the on-off valve is provided with a return spring that biases the float in a downward direction. (3) The on-off valve for a vent pipe of a fuel tank according to claim 1 or 2, wherein the reference level is set approximately equal to the level of gasoline in the fuel tank when the tank is full.