Liquid fuel storage device

A liquid fuel storage device is provided for use with an automobile system including an engine, a fuel tank, and a canister for absorbing fuel vapor during refueling. The device includes an air bag disposed in the fuel tank and constructed and arranged to inflate to occupy a space in the fuel tank in accordance with an amount fuel remaining in the fuel tank. Piping structure communicates the fuel tank with the engine for inflating the air bag by reducing pressure in the fuel tank when the engine is started. An air introduction pipe communicates with the atmosphere and includes a first valve mechanism for introducing air into the air bag and prevents air from escaping from the air bag after inflation thereof. An air emission pipe includes a second valve mechanism, which is opened only in refueling to emit air in the air bag during refueling. The air emission pipe is connected to the canister.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a liquid fuel storage device including a 
fuel tank and a canister for use with a vehicle. 
2. Description of Related Art 
In order to fill-up a fuel tank with fuel smoothly, it is necessary that 
fuel vapor in the fuel tank be instantly emitted to the outside of the 
fuel tank to enable the fuel vapor to be replaced with the fuel without 
resistance. Further, since the fuel is vigorously ejected from a fuel gun 
inserted into a fuel port of the fuel tank in refueling, a lot of fuel 
mist is produced. Since the emission of fuel vapor and mist (hereinafter, 
referred to as "fuel gas") to the atmosphere causes an environmental 
problem, the fuel gas is generally introduced to a canister and adsorbed 
and captured thereby as in U.S. Pat. No. 5,090,459. 
When refueling is necessary, since a fuel tank is usually almost entirely 
filled with a fuel gas, a large canister must be designed, taking the 
capacity of the fuel tank into consideration. 
However, a large canister is not preferable to satisfy a trade-off request 
to increase the capacity of a fuel tank as well as the space in a vehicle. 
To cope with this problem, a liquid fuel storage device for a vehicle has 
been proposed having a mechanism for inflating and deflating an air bag 
disposed in a tank according to a surplus space produced by an amount of 
storage fuel. This type of storage device has been disclosed, for example, 
in Japanese Patent Unexamined Publication No. 64-16426 (1989) wherein the 
space in a fuel tank filled with fuel gas (i.e., the space obtained by 
subtracting the amount of remaining fuel from the total capacity of the 
tank) can be reduced in refueling. 
The fuel storage device arranged as described above usually requires 
pressurizing means (a pressurizing pump or the like) for pressurizing the 
air bag (by which the space occupied by the fuel storage unit as a whole 
is increased). Further, since the air bag communicates directly with the 
atmosphere to emit air in refueling, a fuel gas in the air bag which 
passes through an air bag film is simultaneously emitted. 
SUMMARY OF THE INVENTION 
In view of the above problem, an object of the present invention is to 
provide a liquid fuel storage device including a mechanism for inflating 
and deflating an air bag disposed in a fuel tank according to an amount of 
stored fuel, the liquid fuel storage device being arranged such that it 
does not need pressurizing means and does not raise the possibility of a 
fuel gas passing though the air bag being emitted to the atmosphere 
simultaneously with the emission of air to the atmosphere. 
To solve the above problem, in accordance with the present invention, a 
liquid fuel storage device is provided which comprising: 
a fuel tank; 
a canister for absorbing fuel vapor as the fuel tank is refilled with fuel; 
an air bag disposed in the fuel tank and constructed and arranged to 
inflate to occupy a space in the fuel tank according an amount of 
remaining fuel; 
piping structure communicating the fuel tank with the engine for inflating 
the bag by reducing the pressure in the fuel tank; 
an air introduction pipe communicating with the atmosphere and provided 
with a first valve mechanism for introducing air into the air bag and 
preventing air from flowing out of the air bag after the air bag is 
inflated; and 
an air emission pipe provided with a second valve mechanism which is opened 
only in refueling to emit the air in the air bag in refueling and which is 
connected to the canister.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention will be described below in detail with reference to 
an embodiment shown in FIGS. 1 and 2. 
The liquid fuel storage device of the invention includes a fuel tank 12 and 
a canister 14. 
Although the present invention is described with reference to a liquid fuel 
storage device provided with a mechanism for keeping an interior of a fuel 
tank at a predetermined, reduced pressure state for a predetermined time 
when an engine starts, so as to check for abnormal leakage of the fuel 
tank, the present invention is not limited thereto. Note, the fuel tank 
leakage check mechanism is one of the mechanisms developed for an 
on-board-diagnosis system established by the United States Government for 
controlling air pollution generated by vehicles. The system will be 
described below in detail. 
A fuel tank 12 having a fuel filler pipe 16 stores liquid fuel 18 and feeds 
the fuel 18 to the engine of a vehicle (not shown). The fuel filler pipe 
16 includes a filler neck 22 provided with a fuel cap 20. A seal member 26 
provided with a trap door 24 and a protective cylindrical member 28 for 
protecting the seal member 26 are attached to the filler neck 22. Further, 
a bleeder pipe 30 serving as a bleeder port in refueling is disposed in 
the vicinity of the extreme end of the fuel filler pipe 16 above the upper 
wall of the fuel tank 12 and a fuel shut-off valve 34 to which a float 32 
is assembled is disposed at position apart from the extreme end of the 
fuel filler pipe 16, respectively. A baffle 38 for preventing an abrupt 
back flow of the liquid fuel in the fuel tank 12 is attached to the 
downstream end of the fuel filler pipe 16. Note, numeral 39 denotes a fuel 
return pipe. 
A canister 14 temporarily adsorbs and captures fuel gas produced in the 
fuel tank 12. An air inlet port 14a is formed at a bottom the canister 14 
and is connected to an air cleaner 44 through an air inlet pipe 42, 
provided with a two-position switching valve (solenoid operation type) 40. 
The two-position switching valve 40 is opened and closed in response to a 
signal (electric signal) sent by an engine controller unit (hereinafter, 
abbreviated as "ECU"). 
A fuel gas emission port 14b and a fuel gas introduction port 14c are 
formed at an upper wall of the canister 14. The fuel gas emission port 14b 
is connected to an air inlet pipe 48 through a fuel gas emission pipe 46 
provided with a flow rate/pressure reduction control valve 
(electromagnetic valve) 45. The air inlet pipe 48 defines a reduced 
pressure generation chamber communicating with the engine. The flow 
rate/pressure reduction control valve 45 has two roles: (a) it controls a 
flow rate of fuel gas separated from the canister 14; and (b) it controls 
pressure in the fuel tank in such a manner that the control valve 45 is 
opened and closed in response to a sensing signal from a pressure sensor 
50 attached to an inside of the seal member 26 of the filler neck 22 by a 
signal sent from the ECU 62, in order to check for leakage of the fuel 
tank 12. 
The fuel tank 12 and the fuel gas introduction port 14c of the canister 14 
are connected to the fuel shut-off valve 34 of the fuel tank 12 through a 
fuel vapor pipe 66 provided with a positive/negative pressure control 
valve (spring-biased two-way valve) 64. A gas introduction valve 
(electromagnetic valve) 68 is connected to the fuel vapor pipe 66 in 
parallel with the positive/negative pressure control valve 64. The gas 
introduction pipe 68 is also opened and closed in response to a signal 
sent from the ECU 62 (opened when the engine is in operation). 
The bleeder pipe 30 of the fuel tank 12 is connected to the fuel 
introduction port 14c of the canister 14 through a bleeder pipe 72 
provided with a gas shut-off valve 70 which is normally closed and only 
opened during refueling. Since only one fuel gas introduction port 14c is 
provided with the canister 14 in the illustrated example, the port 14c 
joins the fuel vapor pipe 66 on the canister 14 side. However, two sets of 
fuel gas introduction ports may be provided and connected to completely 
different pipes. 
The gas shut-off valve 70 may be of any construction, in the illustrated 
embodiment, the valve 70 is opened and closed in such a manner that a 
valve plug driving lever 76, which is biased in a valve plug closing 
direction by a circular cam 74 fixed to the rotary shaft 24a of the trap 
door 24, moves a seal valve plug 78 upwardly and downwardly. In the 
illustrated embodiment, numeral 77 denotes a coil spring for easing the 
bias and impact on the seal valve plug 76. 
In the illustrated embodiment, the gas shut-off valve 70 is provided with a 
fuel check valve 82 accommodating a float 80 so that fuel does not flow 
out to the canister 14 when the vehicle turns sideways, or the like. 
In the liquid fuel storage device arranged as described above, the 
embodiment is characterized in the following arrangement. 
The storage device includes an air bag 36 disposed in the fuel tank 12, the 
pressure reduction pipe (fuel vapor pipe) 66 for reducing pressure in the 
fuel tank 12 to inflate the air bag 36, an air introduction pipe 84 
communicating with the atmosphere to introduce air into the air bag 36, 
and an air emission pipe 86 for emitting the air in the air bag only 
during refueling. 
The air bag 36 is preferably made of a resin film of polyvinyl fluoride, 
polyamide, polyethylene, polyvinyl chloride etc. A synthetic fiber cloth 
of polyamide, polyester etc. having a resistance to fuel, with the inside 
thereof coated with fuel resistant rubber may also be used. 
In this embodiment, the pressure reduction pipe need not be provided, since 
the aforesaid fuel vapor pipe 66 can serve as the pressure reduction pipe. 
The air introduction pipe 84 is connected to the air inlet pipe 42 between 
the air cleaner 44 and the two-position switching valve 40. The air inlet 
pipe 84 is provided with a valve mechanism for preventing the air bag 36 
to be deflated after the air bag has been inflated. The valve mechanism is 
in the form of a spring-biased one way valve (check valve) 88. 
The air emission pipe 86 is connected to the bleeder pipe 72 through an air 
emission valve 78b, wherein a seal valve plug 78, a bleeder valve plug 78a 
and an air emission valve plug 78b of the shut-off valve 70 connected to 
the bleeder pipe 72 are formed in parallel with each other on a single 
valve sheet 79. 
As described above, although the gas shut-off valve 70 is mechanically 
opened and closed by the circular cam 74 associated with the rotary shaft 
24a of the trap door 24, the gas shut-off valve 70 is not particularly 
limited to this arrangement and may be opened and closed by an 
electromagnetic mechanism or the like. 
Next, operation of the embodiment will be described. 
When the engine is started, the two-position switching valve 40 in the air 
inlet pipe 42 of the canister 14 is closed in response to a signal sent 
from the ECU 62, the flow rate/pressure reduction control valve 45 
communicating with the fuel gas pipe 46 is opened, and the gas 
introduction pipe 68 disposed in the fuel vapor pipe 66 connecting the 
fuel gas introduction port 14c of the canister 14 to the fuel shut-off 
valve 34 of the fuel tank 12, is opened. As a result, the air inlet pipe 
48 exposed to a reduced pressure is caused to communicate with the fuel 
tank 12 so that the pressure in the fuel tank 12 is reduced (lower than 
the atmospheric pressure) defining a reduced pressure state. When the ECU 
62 receives a sensing signal from the pressure sensor 50 to check the 
presence of abnormal leakage of the fuel tank 62, the ECU 62 controls the 
reduced pressure state by inputting a command signal to the flow 
rate/pressure reduction control valve 45 as well as determines a change of 
the reduced pressure state for a predetermined time, and when leakage 
arises, the ECU 62 issues warning through a warning lamp or the like. 
Since the reduced pressure state in the fuel tank 12 is maintained for a 
predetermined time as described above, the air bag 36 will inflate so that 
pressure in the air bag 36 is also reduced. Thus, the one-way valve 88 is 
automatically opened against a spring force so that the atmosphere flows 
into the air bag 36 through the air cleaner 44 to inflate the air bag 36 
according to an amount of remaining fuel in the fuel tank. 
Then, after the reduced pressure state is maintained for a predetermined 
time, that is, in response to a signal sent from the ECU 62 which 
indicates that the predetermined time has elapsed after starting the 
engine, the two-position switching valve 40 in the air inlet pipe 42 is 
opened. Thus, the air inlet pipe 42 communicates with the air inlet pipe 
48 so that the pressure in the air introduction pipe 84 for the air bag 36 
connected to the air inlet pipe 42 is also reduced. As a result, in the 
air introduction pipe 84, the one-way valve 88 is also automatically 
closed by a spring force due to the above reduced pressure state, and even 
if fuel gas is produced while the vehicle travels, parks or stops (except 
a time of refueling) and the pressure in the fuel tank 12 is made 
positive, air in the air bag 36 does not escape. Naturally, the gas 
shut-off valve 70 of the air emission pipe 86 communicating with the air 
bag 36 is closed (refer to FIG. 1). 
When fuel is consumed as the vehicle travels and a space is created in the 
fuel tank 12 to permit the air bag 36 to inflate, the air bag is inflated 
by a pressure difference between the inside and the outside of the air bag 
36 each time the engine is started and the space in the fuel tank 12 in 
which fuel can evaporate, is greatly reduced. When fuel violently 
evaporates and the pressure in the tank is increased excessively, a 
positive/negative pressure control valve 64 in the fuel vapor pipe 66 is 
operated and fuel vapor is emitted into the canister 14 through the fuel 
gas introduction port 14c and adsorbed and captured by the canister 14. 
Next, when the fuel cap 20 is removed for refueling and a fuel gun 90 is 
inserted into the fuel filler 16, the protective cylindrical member 28 
advances to push and open the trap door 24. At this time, since the 
circular cam 74 is rotated in association with the rotation of the rotary 
shaft 24a of the trap door 24, the valve plug driving lever 76 lifts the 
seal valve plug 78 upwardly through locking means by the long diameter 
portion of the circular cam 74. Therefore, the bleeder valve plug 78a and 
the air emission valve plug 78b are in open positions and the fuel tank 12 
and the air bag 36 are caused to communicate with the canister 14 through 
the bleeder pipe 72 (refer to FIG. 2). 
When refueling is started, fuel vapor in the fuel tank 12 and mist produced 
in refueling are introduced into the canister 14 through the bleeder pipe 
30, the shut-off valve, in an open state, and the bleeder pipe 72. On the 
other hand, the air bag 36 is deflated by a refueling pressure and air in 
the air bag 36 is introduced into the canister 14 through the air emission 
pipe 86, the gas shut-off valve 70 and the bleeder pipe 72. 
Consequently, even if air in the air bag 36 is mixed with fuel gas, since 
the fuel gas is introduced into the canister 14 and adsorbed and captured 
by the canister 14, the emission of fuel gas into the atmosphere can be 
minimized. 
Since the liquid fuel storage device according to the present invention is 
arranged as described above, the device achieves the following meritorious 
effects. 
Since the air bag is inflated in such a manner that pressure in the fuel 
tank is reduced by making use of the pressure reduction pipe through which 
the fuel tank is connected to the pressure reduction chamber and the 
engine, a special pressurizing unit is not required. 
The fuel vapor pipe for connecting the fuel tank to the canister can be 
used as the pressure reduction pipe and the bleeder pipe connected to the 
canister can be used as the air emission pipe for emitting air in the air 
bag during refueling. Consequently, when the fuel storage unit is mounted 
on a vehicle, any additional space is not fully occupied. 
Since the valve mechanism, opened only during refueling is provided and air 
in the air bag is emitted during refueling through the air emission pipe 
connected to the canister, fuel gas passing through the air bag is 
captured by the canister. Thus, there is not a possibility that fuel gas 
is emitted to the atmosphere when air is emitted from the air bag. 
The size of the canister can be reduced by the reduction of an amount of 
fuel gas in the fuel tank. 
While the invention has been described in connection with what is presently 
considered to be the most practical and preferred embodiment, it is to be 
understood that the invention is not limited to the disclosed embodiment, 
but, on the contrary, is intended to cover various modifications and 
equivalent arrangements included within the spirit and scope of the 
appended claims.