GB2274435A

GB2274435A - Fuel tank system for motor vehicles.

Info

Publication number: GB2274435A
Application number: GB9400786A
Authority: GB
Inventors: Karl-Heinz Hoffmann; Gunter Kohl; Manfred Muller; Franz Gollner; Dieter Scheurenbrand
Original assignee: Daimler Benz AG; Mercedes Benz AG
Current assignee: Daimler Benz AG
Priority date: 1993-01-23
Filing date: 1994-01-17
Publication date: 1994-07-27
Anticipated expiration: 2014-01-17
Also published as: ES2089964R; GB9400786D0; GB2274435B; FR2702714B1; DE4301762A1; ES2089964A2; FR2702714A1; DE4301762C2; ES2089964B1

Description

2274435 A fuel tank system The invention relates to a fuel tank system f

or liquid fuel of an internal-combustion engine for motor vehicles, with a fuel tank having at least two tank parts connected to one another by means of an overflow, a forwardflow line for supplying fuel from the one tank part to the engine, a return line for returning fuel from the engine to the one tank part, a hydrodynamic suction device arranged on the return line and operated by the fuel flowing back from the engine, suction lines assigned separately to the tank parts and leading to the suction device. and a filling means for supplying fuel to the tank.

A tank system of this type is the subject of EP-B 0,228,176; see especially Figure 1 there.

In internal -combustion engines customary in motor vehicles today, a fuel quantity clearly exceeding the particular consumption is always supplied to the engine via the forward-flow line, so that correspondingly large fuel quantities are conveyed back into the tank system via the return line. Now according to EP-B 0,228,176, this return flow can operate the suction device, mentioned in the introduction, via which, with the engine running, fuel is then constantly introduced from the tank parts additionally into the part of the return line following the suction device in the direction of flow. This ensures that approximately equal fuel levels are present in the tank parts even when the fuel level has already fallen below the level of the overflow. This is because, if the fuel levels in the tank parts were at different heights, and if the suction lines were of identical design. the suction device would suck up fuel to an increased extent from the tank part having the higher fuel level. Moreover. the suction lines (if there is sufficient freedom from air in these lines) form a system of communicating tubes, via which the fuel levels in the tank parts can be -equalized, even when the engine is at a standstill, that is to say when the suction

2 device is inoperative.

However, the system shown in EP-B 0,228,176 cannot bring about any equalization of the fuel levels in the tank parts, should one tank part and the associated suction line be almost completely emptied and the level in the other tank part be below the level of the overflow. In such a case, the suction device could only suck up air from the emptied tank part, and therefore the associated suction line would remain permanently emptied of fuel. In this case, even if the engine were at a standstill. that is to say with the suction device inoperative, it would be completely impossible for fuel to overflow from the filled tank part into the emptied tank part via the suction-line system.

However, a situation of this kind can scarcely occur in the tank system shown in EP-B 0,228,176, because filling lines are arranged in such a way that, during refuelling, fuel always passes into all the tank parts.

Moreover, the tank parts are separated from one another so sharply that, even in the event of very rapid cornering with a tank system partially emptied, the content of one tank part cannot completely slosh over into the other tank part.

Consequently, however, restrictions in construction have to be accepted in the design of a tank system. Besides, a comparatively complicated filling-line system is necessary, another disadvantage being that such a system has a comparatively high flow resistance and therefore makes rapid refuelling at least more difficult.

The present invention seeks, therefore. to provide an improved tank system of the type indicated in the introductory paragraph.

According to the present invention there is provided a fuel tank system for liquid fuel of an internal-combustion engine for motor vehicles, with a fuel tank having at least two tank parts connected to one another by means of an overflow, a forward-flow line for supplying fuel from the one tank part to the engine, a return line for returning 3 f uel f rom the engine to the one tank part, a hydrodynamic suction device arranged on the return line and operated by the fuel flowing back from the engine, suction lines assigned separately to the tank parts and leading to the suction device, and a filling means for supplying fuel to the tank, wherein the filling means opens only into the one tank part and the return line has an outflow opening into the other tank part or outflows opening into the other tank part.

Since the filling means opens only into one tank part, cross-sections of virtually any size or flow resistances virtually as low as desired can be brought about easily, since there is no need to ensure that a sufficient proportion of the refuelled fuel is also supplied to other tank parts. At the same time, a simplification in terms of construction and production is achieved, since the overflow, which regularly has a large cross- section, is utilized for distributing the fuel during filling up to the top with fuel.

By means of the outflows of the return line which open into the other tank parts, an equalization of the fuel levels in the tank parts can be achieved within quite a short time, even when, after a virtually complete emptying of the tank system, only a comparatively small fuel quantity is refuelled and is then received completely by the one tank part. In particular, when the engine is in operation, fuel accordingly passes out of the return line into the other tank parts, so that, after a short time, the suction lines assigned to these tank parts can suck up fuel again and thus form an effectively communicating pipe system between the tank parts.

According to a preferred embodiment of the invention, there is arranged, as a suction device, an injector pump with an injector nozzle through which the fuel flowing back flows. This design of the suction device affords the advantage, in comparison with the use, possible per se, of a Venturi tube arrangement, that the connections 4 of the suction lines can be connected to one another over comparatively large cross-sections. Correspondingly, the suction lines can likewise be designed with larger crosssections and with correspondingly low throttling, in order to allow rapid level equalization between the tank parts.

Moreover, expediently, a plurality of small orifices, for example arranged in a sieve-like manner, are arranged as an inflow orifice at the ends of the respective suction lines located at the tank parts. As a result, in the event that the respective tank part is emptied, an increased formation of small air bubbles, which make it more difficult for the respective suction line to run empty, can occur at the plurality of small orifices. This design is also advantageous when, with the tank system emptied to a relatively great extent, rapid cornering takes place and one suction line or the other temporarily sucks up some air as a result of surging movements of the fuel in the respective tank part. Since a rapid running empty of the respective suction line is prevented in such cases, the latter can subsequently rapidly regain its full suction capacity.

An embodiment of the invention will now be described by way of example with reference to the drawing, in which the single figure shows a diagrammatic sectional representation of the tank system according to the invention.

What is shown is an example of a tank with two tank parts 11 and 111 which are connected to one another by means of a middle region or overflow region V" of large crosssection. The tank can be filled via a filling line 2 opening into one tank part V.

A forward-flow line 3 leads out of the tank part 10 to an engine (not shown), from which the particular fuel not required is predominantly conveyed back into the tank part 11 via a return line 4. only a small part of the fuel flowing back passes into the tank part 111 via an outflow 5, which contains a restriction, of the return line 4.

The outf low orif ice of the return line 4 and the inflow orifice of the forward-flow line 3 are arranged closely adjacent to one another, preferably in an anti-roll vessel 6 which is arranged within the tank part 11 and out of which the f uel f lowing back can f low, only with some delay, into the tank part if, even when the tank is largely emptied. For this purpose, the anti-roll vessel 6 can be designed, f or example, so as to be open at the top and can possess surge walls arranged in a labyrinth-like manner, so that, in the event of surging movements of the fuel in the tank part V, a relatively large quantity of fuel can be intercepted in the anti-roll vessel 6, whereas comparatively little fuel sloshes out of the anti-roll vessel 6.

Arranged on the return line 4 is a suction device 7 which possesses, as an injector pump, an injector nozzle 71, through which the fuel flowing back flows, and a suction zone 711 surrounding the injector nozzle 7' annularly. Connected to the suction zone 711 are suction lines 8 which are each assigned to a tank part 11 and 111 and which possess an inflow orifice on a region of the respective tank part if and 111 which is near the bottom. As mentioned above, the inflow orifices can be formed by a plurality of small orifices.

As long as the levels of the f uel 9 in the tank parts l f and 111 are above the inflow orifices of the suction lines 8, when the engine is in operation the suction device 7, as a result of the returning fuel then f lowing through the injector nozzle 71, sucks up out of the tanks parts 11 and 111 fuel 9 which is then supplied, together with the fuel coming back from the engine, to the anti-roll vessel 6. As a result of an appropriate design of the suction lines 8, during the pumping operation of the suction device 7 level dif f erences of the fuel 9 in the tank parts 1,1 and 111 are equalized, since f uel is sucked up to an increased extent out of the particular tank part having a higher level. Moreover, the suction lines 8 f illed with f uel f orm. a system of communicating tubes, by means of which a level equalization takes place even without a pumping operation of 6 the suction device 7, provided that the suction lines 8 and the return line 4 are essentially free of air and that the fuel levels in the tank parts 11 and 111 are above the inflow orifices of the suction lines 8.

Should only a relatively small quantity of fuel be refuelled after the substantial emptying of the tank, so that only the tank part 11 is partially filled, when the engine is in operation sufficient fuel will pass after a short time, via the return line 4 and the outf low 5, into the tank part 111, so that its level also in the tank part ill is once again above the inflow orifice of the associated suction line 8.

Therefore, in such instances also, a level equalization can take place again within a short time.

A rapid level equalization is desirable because there is then the possibility of determining the filling state of the tank by means of a single measuring transmitter which is assigned to only one tank part, preferably the tank part 111. Costs can thus be saved in this respect too.

If the temporary deviations of the filling-level indicator, which occur as a result of the unavoidable temporary level differences between the individual tank parts, are also to be reduced to an imperceptible amount, then the temporarily incorrect level values measured by the single measuring transmitter can be eliminated by an on-board computer which may be present in any case, since substantial level differences during driving regularly cause level change rates which can differ substantially from those which can occur solely as a result of the fuel consumption of the engine, and which can therefore be used by the on-board computer to identify incorrect level values.

In the tank system illustrated in the drawing, the outf low 5 branches of f from the return line 4 upstream of the suction device 7 in the direction of f low of the fuel conveyed back from the engine. In this case, the outflow 5 should be relatively sharply throttled, in order to guarantee that the main flow of the fuel conveyed back runs 7 via the suction device 7 and the latter can work effectively.

In principle, it is also possible, instead of the outf low 5 upstream of the suction device 7, to have an outflow 51 branch off from the return line 4 downstream of the suction device 7, in order to supply f uel to the tank part ill, as indicated by a broken line in the drawing. This outflow S' can be largely unthrottled.

However, here too, throttling can be expedient, in order always to guide the main flow of fuel into the antiroll vessel 6 or to the forward-flow line 3, primarily when the remaining quantity of fuel in the tank is only small.

8 claims 1. A fuel tank system for liquid fuel of an internalcombustion engine for motor vehicles, with a fuel tank having at least two tank parts connected to one another by means of an overf low, a forward-f low line f or supplying f uel f rom the one tank part to the engine, a return line f or returning fuel from the engine to the one tank part, a hydrodynamic suction device arranged on the return line and operated by the fuel flowing back from the engine, suction lines assigned separately to the tank parts and leading to the suction device, and a filling means for supplying fuel to the tank, wherein the filling means opens only into the one tank part and the return line has an outflow opening into the other tank part or outflows opening into the other tank part.

Claims

2. A fuel tank system according to Claim 1, wherein the suction device

comprises an injector pump with an injector nozzle through which the said fuel flowing back flows.

3. A fuel tank system according to Claim 1 or 2, wherein a plurality of small orifices are arranged on the suction lines on the inflow side.

4. A fuel tank system according to claim 3 wherein the orifices are arranged in a sieve-like manner.

5. A fuel tank system according to any one of Claims 1 to 4, wherein the outflow or outflows are arranged or branch off upstream of the suction device in the direction of flow of the fuel in the return line.

6. A fuel tank system according to Claim 4 or 5, wherein the outflow or outflows are throttled.

7. A fuel tank system according to one of Claims 1 to 9 5, wherein the outf low or outf lows are arranged or branch of f downstream of the suction device in the direction of flow of the fuel in the return line.

8. A fuel tank system for liquid fuel of an internalcombustion engine for motor vehicles, substantially as described herein with reference to and as illustrated in the accompanying drawing.