Fluid handling – Systems – System with plural openings – one a gas vent or access opening
Reexamination Certificate
2000-03-30
2001-01-23
Chambers, A. Michael (Department: 3753)
Fluid handling
Systems
System with plural openings, one a gas vent or access opening
C137S043000, C123S516000, C123S518000, C123S541000, C141S059000
Reexamination Certificate
active
06176259
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a venting system for fuel tanks. More particularly, the present invention relates to such a system comprising at least one canister containing an absorbent for fuel fumes and a connection path for the passage of gases, extending between the fuel tank and the canister.
BACKGROUND OF THE INVENTION
Venting systems of the type described above are used in passenger cars in order to reduce the emission of fuel in gaseous form to the environment. The canister thus functions to absorb fuel fumes which have to be evacuated from the tank when the latter is filled up with gasoline and the free space above the fuel level decreases. Normally, the canister is, in turn, controllably connected with the engine suction or intake system, for emptying the canister of absorbed fuel during engine operation. Such a system is described in the British Patent Application No 2,286,182.
In the system according to the above British Patent Application, the connection path, normally a line in the form of a conventional pipe between the tank and the canister, must be sized so as to be able to evacuate those gas volumes from the tank that are replaced with fuel at the same rate as they are filled with the fuel, in order not to build up a counter-pressure that will shut off the orifice of the gasoline pump prematurely. When filling is then finished, and the car is operated, the fuel is consumed, causing the free volume above the fuel to increase, but the rate of change of the free volume is considerably smaller than during filling up the tank, and the flow of air to the tank needed to avoid a vacuum therein is relatively small. For this flow, the line is thus clearly over-sized. When emptying the canister, a line is normally used (see line No. 15 in British Patent Application No. 2,286,182) between the canister and the open air for replacing the gases being sucked from the canister by the engine, such that substantially no gases are taken from the tank and, in general, no flow is created from or any vacuum in the tank.
When operating vehicles having systems of this kind, fuel fumes are forced into the line and the canister due to e.g. decreasing ambient atmospheric pressure or decreasing exterior temperature, especially when travelling a distance including substantial level changes. As the line between the tank and the canister is sized to allow large flows, a rapid displacement of relatively large quantities of air, in some cases saturated with fuel, may occur, causing fuel to condense in the line and/or in the canister instead of being absorbed by the canister contents. This will cause operational disturbances, in the worst case serious enough to stall the engine due to an incorrect fuel/air mixture (too rich).
An object of the present invention is to provide an improved device for fuel tanks, eliminating the problems described above.
SUMMARY OF THE INVENTION
This and other objects have now been realized by the invention of apparatus for venting a fuel tank comprising a canister containing an absorbent for fuel fumes, a sensor for detecting the filling of the fuel tank and emitting a signal based thereon, a first connection line for connecting the canister with the fuel tank, the first connection line having a size sufficient to permit the free flow of gases from the fuel tank during the filling of the fuel tank with the fuel, the first connection line including a first valve operable between an open position and a closed position, the first valve normally being in the closed position and being actuatable into the open position by the signal, thereby permitting the free flow of the gases from the fuel tank through the first connection line during the filling of the fuel tank, a second connection line for connecting the canister with the fuel tank, the second connection line being connected to the first connection line between the first valve and the canister, the second connection line including a second valve including at least one restrictor for substantially limiting the flow of gases therethrough as compared to the first connection line when the first valve is in the open position, and a condenser for condensing fuel fumes passing through the second connection line whereby the condensed fuel can return to the fuel tank. In a preferred embodiment, the fuel tank includes a filling line. Preferably, the condenser comprises a cooler. In a preferred embodiment, the apparatus includes a pressure equalization line disposed between the interior of the cooler and the filling line.
In accordance with one embodiment of the apparatus of the present invention, the cooler includes an inlet for connection to the fuel tank and an outlet for connection to the first connection line, the outlet from the cooler being located in a vertical position higher than the inlet for the cooler.
In accordance with another embodiment of the apparatus of the present invention, the fuel tank includes a filler cap, and the sensor is adapted to emit the signal when the filler cap is not fitted to the fuel tank.
In accordance with another embodiment of the apparatus of the present invention, the second connection line includes a rollover valve located between the fuel tank and the second valve.
The present invention consists of a venting system comprising a sensing device for detecting and emitting a filling-up signal during filling of the tank. Furthermore, the system is constructed such that the connection path between the tank and the canister is selectively adjustable, through a valve means depending on the sensing device, between at least two modes; a first mode allowing filling-up flow, for enabling the full through flow of gases when a filling-up signal is present; and a second mode allowing a lower flow compared to the filling-up flow, for enabling a restricted through flow of gases, compared to the completely open mode, when no filling-up signal is present.
By means of a system according to the present invention, the risk of amounts of fuel, large enough to disturb the engine during operation, condensing in or at the canister is reduced, whereas the filling-up properties of the system remain unchanged.
In a preferred embodiment of the present invention, the invention comprises the connection path comprising a first line, extending between the tank and the canister and being sized for evacuating the fumes forced out when filling up the tank with fuel, a first valve means arranged in that line, the valve means being adjustable between a completely open and a completely closed position, a second line, extending between the tank and a location on the first line, downstream of the first valve means, towards the canister, and by a second valve means arranged in the second line, containing at least one restriction, allowing a substantially smaller flow than the first valve means in its open position, the first valve means functioning to assume its open position only when a filling-up signal is present, corresponding to the first mode, and otherwise to assume a closed position, whereby a restricted flow may pass through the other line, i.e. the second mode. In such a system, the size of the second line can be selected for a lower flow than that of the first line, and it can also be dimensioned, regarding its length and extension, in such a manner that any condensation required can occur in the line, downstream of the second valve means, towards the tank, at a safe distance from the canister.
In order to further improve the system, the second line may, in accordance with the present invention, comprise a device for condensing passing fuel fumes, the line preferably being arranged to convey fuel condensing therein back to the tank. The condensing device can then preferably consist of a cooler, cooled by the surrounding air.
In order for the system to function, it comprises a sensing device emitting a signal indicative of filling up. According to the present invention, it is suitable that the sensing device functions to sense if the filler cap is on, and to emit a filling-up signal when
Bakir Hussein
Greger Lars
Harde Bo
Chambers A. Michael
Lerner David Littenberg Krumholz & Mentlik LLP
Volvo Personvagnar AB
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