ARRANGEMENT FOR A VEHICLE FUEL TANK

Abstract: An ejector (6) is arranged in a fuel tank (1) in order to transfer fuel from the fuel tank (1) to a fuel chamber (2) arranged in the tank (1). The ejector (6) comprises a housing section (8) with an opening (10) leading to the fuel tank (1). Connected to the housing section (7) is an inlet channel (26) for the engine's surplus fuel and an evacuation channel (17) which is connected to the fuel chamber (2).

Description: The present invention relates to an arrangement for a vehicle fuel tank, in which fuel tank an ejector is arranged which utilises the kinetic energy of the surplus fuel of a vehicle engine in order to transfer fuel from the fuel tank to a fuel chamber arranged in the fuel tank, in which fuel chamber a fuel pump is accommodated, which ejector pump comprises a housing section which is connected to an inlet channel through which the surplus fuel is supplied to the ejector and an evacuation channel which is connected to the fuel chamber and which housing section is designed with at least one opening leading to the fuel tank. In order to ensure that air does not enter the fuel system of a vehicle, it is known to arrange a special fuel chamber inside the fuel tank. The fuel chamber is supplied with fuel by a separate ejector. The actual fuel pump is accommodated in the fuel chamber in order to pump fuel further in the fuel system. The fuel pump is designed to pump more fuel to the vehicle engine than is consumed in the combustion process in the engine. The resulting surplus fuel is returned to the fuel chamber while its kinetic energy is utilised in order to suck fuel, using the ejector, from the fuel tank to the fuel chamber. Ejector arrangements for vehicle fuel tanks are previously well known through patent applications DE-A-36 15 214, DE-A 36 02 155 and DE-A-24 01 728. Known ejector arrangements have a number of disadvantages. For example, in German Patent Application DE-A-36 15 214, the surplus fuel is allowed to flow in a more or less uncontrolled manner past the inlet opening of an ejector at such low kinetic energy that the surplus fuel can barely give rise to a sufficiently great suction effect for the fuel chamber to be supplied with a sufficient amount of fuel. In another ejector according to the German application DE-A 3 02 155 the fuel splashing around in the fuel tank is allowed to flow in an uncontrolled manner to and fro an opening around an intake pipe and impair the suction capacity of the ejector. In German Patent Application DE-A-21 01 728 there is a space between the nozzle of an ejector and an intake pipe. The effect of the ejector is impaired in this arrangement since the fuel splashing around in the fuel tank is allowed to penetrate into the said space and impair the suction capacity of the ejector. The object of the present invention is to eliminate the above mentioned disadvantages. For this purpose the invention is characterised by the fact that the evacuation channel in the fuel flow direction is separate from the inlet channel and has a first part positioned outside the fuel chamber and a second part positioned inside the fuel chamber, which second part extends into a free space in the fuel chamber between the fuel pump and the wall of the fuel chamber, and in that the opening leading to the fuel tank is directed downwardly toward a bottom part of the fuel tank. The arrangement according to the invention comprises relatively simple and inexpensive parts which ensure that the fuel chamber is constantly supplied with a sufficient amount of fuel from the fuel tank and which ensure that the fuel splashing around does not impair the suction capacity of the ejector. Other features characterising the invention emerge from the subsequent patent claims and from the following description of an embodiment illustrating the invention. In the description reference is made to the attached figures of which Figure 1 shows a schematic side view of the fuel tank in which an arrangement according to the invention is arranged, Figure 2 shows a side view of the arrangement according to the invention, and Figure 3 shows a plan view of the arrangement according to the invention when assembled in a fuel chamber. Figure 1 shows schematically a fuel tank 1 in which a fuel chamber 2 is arranged. A fuel pump 3 is accommodated in the fuel chamber 2 in order to pump fuel via a fuel line form 4 to an internal combustion engine (not shown). The fuel pump 3 is designed to pump more fuel to the internal combustion engine than is consumed in the combustion process in the engine. The resulting surplus fuel is pumped back to the fuel chamber 2 via a fuel return line 5 and an ejector 6. The ejector 6 comprises an ejector housing 7 which consists of two parts, 8, 9. The first part 8 of the ejector housing 7 is cylindrical and designed with a channel 10 of rectangular cross section leading to the fuel tank 1. The open end 11 of the channel 10 is designed with downwardly-directed pin-shaped spacing elements 12 which bear against the bottom of the fuel tank 1 and define a gap 13 through which fuel is supplied to the ejector 6. That opening of the channel 10 which is directed towards the ejector housing 7 is provided with a filter 14, preferable of fine-meshed wire net, for preventing any free particles in the fuel from being sucked into the ejector 6. The second part 9 of the ejector housing 7 is conical and its diametrically larger end 15 is connected to the cylindrical part 8, while its diametrically smaller end 16 is connected to a tubular evacuation channel 17. Both the transition between the cylindrical part 8 and the conical part 9 and the transition between the conical part 9 and the evacuation channel 17 are rounded off in order to avoid flow losses in the ejector 6. The evacuation channel 17 passes through a collar section 18, which is arranged in an outer recess 19 in the wall of the fuel chamber 2, and it extends by more than half its length into the fuel chamber essentially tangentially in relation to the fuel pump 3. The evacuation channel 17 leads into a free space between the fuel pump 3 and the cylindrical outer wall of the fuel chamber 2. The nozzle 21 of the evacuation channel 17 is in this connection designed with a conical expansion space 22 whose length L1 is at least 1/10 of the length L2 of the evacuation channels 17. In addition, the length L2 of the evacuation channel 17 is at least greater than about five times the inner diameter D1 of the evacuation channel 17 and is advantageously greater than or equal to seven and less than ten, times the said inner diameter D1. A sealing ring 23 bears against the evacuation channel 17 and against the collar section 18. The sealing ring 23 is axially fixed between two radially outwardly directed flanges 24 on the evacuation channel 17. The evacuation channel 17 is designed with a number of connecting elements 25 by means of which the ejector 6 is fixed to the fuel chamber 2. The connecting elements 25 are made up of locking heads (not described in detail) which interact in a locking manner with heads on the collar section 18 which correspond to the locking heads. The ejector also comprises an inlet channel 26, one end 27 of which is connected to the fuel return line 5 and the other end of which is provided with a throttling 28. The inlet channel 26 is advantageously a tubular element which, at its one end is designed with a converging section having a nozzle orifice 30. The outer conicity of the converging section is less than the conicity of the conical inner part 9 on the ejector housing 7 and the diameter D2 of the nozzle orifice 30 is advantageously 0.3-0.6 times the diameter D1 of the evacuation channel 17 and preferably about 0.4 times the said diameter D1. The inlet channel 26 and evacuation channel 17 are arranged in series in the longitudinal direction of the ejector 6. The inlet channel 26 thus passes through an opening 31 in a wall 32, which delimit the ejector housing 7 towards the rear, and is introduced so far into the ejector housing 7 that its throttling 28 empties between the nozzle over the evacuation channel and the opening 10 leading to the fuel tank 1. The distance L3 between the throttling 28 and the evacuation channel 17 is about 0.8-3.5 times the diameter D2 of the nozzle orifice 30 of the throttling 28 and is advantageously about 2.0 times the said diameter D2. The arrangement described according to the invention operates as follows. The fuel pump 3 pumps fuel from the fuel chamber 2 via the fuel line 4 to the internal combustion engine (not shown). The surplus fuel from the internal combustion engine flows through the fuel return line 5, the inlet channel 26 and out through the nozzle orifice 30 over the throttling 28 as a controlled jet of fuel. At the same time, due to the ejector action resulting from the flow of fuel, fuel is sucked from the fuel tank 1 via the channel 10 and into the ejector housing 7. The surplus fuel and the fuel from the fuel tank 1 are then fed to the fuel chamber 2 via the evacuation channel 17.

Claims: 1. Arrangement for a vehicle fuel tank (1), in which fuel tank (1) an ejector (6) is arranged which utilises the kinetic energy of the surplus fuel of the vehicle engine in order to transfer fuel from the fuel tank (1) to a fuel chamber (2) arranged in the fuel tank (1), in which fuel chamber (2) a fuel pump (3) is accommodated, which ejector (6) comprises a housing section (7) which is connected to an inlet channel (26) through which the surplus fuel is supplied to the ejector (6) and an evacuation channel (17) which is connected to the fuel chamber (2) and which housing section is designed with at least one opening leading to the fuel tank (1), characterised in that the evacuation channel (17) in the fuel flow direction is separate from the inlet channel and has a first part positioned outside the fuel chamber (2) and a second part positioned inside the fuel chamber (2), which second part extends into a free space in the fuel chamber (2) between the fuel pump (3) and the wall of the fuel chamber (2), and in that the opening leading to the fuel tank (1) is directed downwardly toward a bottom part of the fuel tank (1). 2. Arrangement according to claim 1, characterised in that the evacuation channel (17) extends into the fuel chamber (2) essentially tangentially in relation to the fuel pump (3). 3. Arrangement according to claim 2, characterised in that the evacuation channel (17) extends by more than half its length into the fuel chamber (2). 4. Arrangement according to claim 1, characterised in that the evacuation channel (17) passes through a collar section (18) in the wall of the fuel chamber (2). 5. Arrangement according to claim 4, characterised in that the collar section (18) is arranged in a recess (19) in the wall of the fuel chamber (2). 6. Arrangement according to Claim 4, characterised in that the evacuation channel (17) is designed with a conical expansion space (22) the length of which is greater than or equal to 0.1 times the length of the evacuation channel (17) and in that the length of the evacuation channel (17) is greater than or equal to seven times the inner diameter of the evacuation channel (17). 7. Arrangement according to claim 1, characterised in that the opening (10) leading to the fuel tank (1) is designed as a channel which is covered by a filter. 8. Arrangement according to Claim 2 or 5, characterised in that the conical part (9) of the housing section (7) has a conicity which is greater than the conicity of the converging section of the inlet channel (26). 9. Arrangement according to Claim 1, characterised in that the evacuation channel (17) is designed with a conical expansion space (22) the length of which is greater than or equal to 0.1 times the length of the evacuation channel (17). 10. Arrangement according to any one of the preceding claims, characterised in that the length of the evacuation channel (17) is greater than or equal to seven times the inner diameter of the evacuation channel (17).

Inventors: OLSSON, GOERAN, Olsson, Göran
Applicants: SAAB AUTOMOBILE AKTIEBOLAG
Application year: 1988
Main classification: B60K15
IPC codes: F02M37, B60K15