Fuel tank

Details Fuel tank Fuel tank

2001-11-08

2003-08-19

Rivell, John (Department: 3753)

Fluid handling

Systems

Plural tanks or compartments connected for serial flow

C137S142000, C137S147000, C137S587000, C137S565220, C123S510000, C123S514000

Reexamination Certificate

active

06607005

ABSTRACT:

FIELD OF THE INVENTION
The invention concerns generally a fuel tank and more particularly a fuel tank for a motor vehicle.
BACKGROUND OF THE INVENTION
One form of fuel tank, generally referred to as a saddle tank, is formed by at least first and second tank regions of relatively large cross-section which form respective communicating sub-volumes of the tank. Those tank regions are in communication with each other by way of a further tank region of smaller cross-section. When considered in the position of installation of the tank, the tank region of smaller cross-section is formed by the bottom of the tank being displaced upwardly, whereby the bottom of the tank in the area of the tank region of smaller cross-section forms an inverted generally U-shaped configuration, whence the name saddle tank. The tank has at least one fuel delivery unit in the first tank region, and it also has means for venting the tank. There is at least one compensating or equalising line which intercommunicates the first and second tank regions on the basis of the principle of communicating tubes. The compensating line also has means for venting thereof.
By virtue of their saddle configuration such tanks are used primarily in relation to rear wheel drive motor vehicles where the tanks can be appropriately arranged over drive components, for example a universally joined shaft, or over parts of the exhaust system of the vehicle. For that purpose, in the region of the bottom, as indicated above the fuel tank has a recess extending upwardly into the tank which generally subdivides the tank into first and second tank regions of relatively large cross-section, constituting thus first and second tank chambers. For structural reasons and also for reasons which are relevant in terms of safety, those tank chambers do not have any communicating lines forming a communication therebetween, at a low level relative to the tank. In general, one of the first and second tank regions of relatively large cross-section accommodates the fuel delivery unit which comprises an electric fuel pump arranged in a reservoir which is also referred to as a surge pot or swirl pot. The reservoir ensures that the fuel pump is always supplied with fuel in all possible travel conditions and attitudes of the motor vehicle. As therefore fuel is conveyed to the engine only from a part of the fuel tank, namely the first tank region in which the fuel delivery unit is disposed, it is necessary to ensure that the fuel in the other regions of the fuel tank are also appropriately fed to the fuel pump. In general that is implemented by means of one or more suction jet pumps which are driven by way of a partial flow of fuel which is branched off the delivery flow of fuel to the engine or by a fuel return flow from the engine. Such suction jet pumps in which a jet of fuel, also referred to as the drive jet, in a branching from a fuel line produces a delivery suction action, are known units and can be found for example in DE 39 40 060 C2 to which reference may be made for a more detailed description of such a pump and the disclosure of which is thereby incorporated into this specification. In that way, by means of one or more suction jet pumps, fuel at other levels or in other sub-volumes of the fuel tank is continuously fed to the reservoir of the fuel delivery unit so that in terms of emptying the fuel tank it is possible to ensure that no unused fuel remains in parts of the fuel tank.
When the vehicle in which the tank is fitted is an inclined position or in different conditions of acceleration, particularly when the vehicle is subjected to transverse acceleration forces in bends, the design configuration of such a saddle tank in which the upwardly extending recess configuration in the bottom of the tank forms the saddle-shaped raised configuration in the interior of the tank means that it is quite possible for fuel to flow over from one tank chamber into the other, thereby resulting in different filling levels in the tank chambers. Such differences in level are generally not critical in regard to an adequate supply of fuel to the fuel pump in operation of the motor vehicle, but nonetheless it would still be desirable if the level of fuel in that region of the tank in which the fuel pump is disposed were higher than in the second tank region which is generally in opposite relationship to the first tank region transversely with respect to the longitudinal axis of the vehicle in which the tank is fitted.
It will further be noted that differences in level between the first and second tank regions of the tank, that is to say the two tank chambers defined thereby, can give rise to problems when refuelling the motor vehicle, particularly when the fuel in one chamber of the tank reaches a level at which a refuelling vent valve provided therein responds, although the maximum filling level has not yet been reached in the respective other chamber of the tank. In that case, the automatic shut-off valve in the refuelling gun shuts off prematurely in the refuelling procedure, with the consequence that the tank cannot be completely filled. That problem can occur in particular if the saddle configuration provided in the tank between the first and second tank regions is particularly pronounced and the refuelling vent valve shut-off level in at least one tank chamber is below the level of the top surface of the saddle configuration, so that equalisation of the levels in the chambers by virtue of fuel flowing across from one chamber into the other could occur only after the refuelling vent valve has responded.
It would be possible to avoid that by the provision of a refuelling vent valve in each chamber of the tank, so that the automatic shut-off valve in the refuelling gun will shut off only when both refuelling vent valves in the tank respond. That however involves the disadvantage that, in a situation in which the first refuelling vent valve to respond in a refuelling procedure is that which is disposed in the chamber into which the filler pipe of the tank does not open, there is the possibility of the tank chamber in question being overfilled so that the tank no longer has a sufficient expansion volume therein for possible expansion of the fuel. The other situation in which the refuelling vent valve in the chamber with the tank filling pipe responds first is not critical for the fuel can flow across from that chamber into the other chamber. It will be seen therefore that, with such a tank design configuration, it is not always possible to guarantee that the shut-off valve in the refuelling gun shuts off at the same filling level in the tank chambers.
For the purposes of equalising the filling levels in various chambers in a tank system, for example EP 0 228 167 involves a system wherein various chambers of a tank are in communication with each other by way of a compensating line or conduit, based on the principle of communicating vessels. It will be noted however that this involves ensuring the same filling level in the different volumes of the tank, both when the vehicle is stationary and also when it is in operation, although, as indicated above, that may not always be desirable.
A comparable arrangement for the purposes of equalising the levels of fuel in different volumes of a tank is to be found in DE 44 00 919 A1 describing a saddle tank of the general configuration referred to hereinbefore. In this case, the levels of fuel in the two chambers of the saddle tank are also equalised by means of a compensating line which is in the form of a siphon. The compensating line is communicated by way of a branch therefrom to a vacuum chamber of a suction jet pump which is operated by the return flow of fuel from the engine back to the tank. That arrangement ensures that any air or gas which has accumulated in the compensating line can be removed therefrom so that equalisation of the levels of fuel in the tank chambers can take place irrespective of fuel being removed by suction from the compensating line, which can happen in that situation.
That design is disadvantag

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