Fuel delivery device

In a fuel delivery device for a motor vehicle a delivery pump (15) is provided in addition to a fuel pump (14). The delivery pump (15) serves to fill a surge baffle (5) and to drive a sucking jet pump (6). The fuel pump (14) draws in fuel from the surge baffle (5) and delivers it to an internal combustion engine (2). For this purpose, the fuel pump (14) is arranged in a feed line (3) in the vicinity of the internal combustion engine (2). A return line (4) leads from the internal combustion engine into the surge baffle (5).

BACKGROUND OF THE INVENTION 
The invention relates to a fuel delivery device for a motor vehicle, having 
a fuel tank, which has a surge baffle, and a fuel pump for delivering fuel 
from the surge baffle to a motor vehicle internal combustion engine via a 
feed line, and having a sucking jet pump arranged in the fuel tank. 
Fuel delivery devices of this type are frequently used in today's motor 
vehicles which have diesel engines or spark ignition engines as the 
internal combustion engine, and are thus known. In these devices the fuel 
pump delivers fuel from the surge baffle into the feed line and to the 
sucking jet pump. The sucking jet pump serves to deliver fuel into the 
surge baffle from a region of the fuel tank which is remote from the surge 
baffle and is generally separated from the region with the surge baffle by 
a saddle. However, the connection of the sucking jet pump to the surge 
baffle is very complicated to install. Furthermore, the surge baffle has 
to be arranged at a very low point within the fuel tank and has to be open 
at the top so that fuel gets into it from above when the fuel tank is 
empty or nearly empty. In the case of diesel fuel, in particular, this 
leads to pronounced foam formation which becomes ever more intensive the 
hotter the fuel is. In addition, when the tank is nearly empty, air is 
drawn in by the sucking jet pump and this likewise leads to a pronounced 
formation of foam. This foam is then drawn in by the fuel pump and leads 
to the fuel delivery being interrupted. Particularly pronounced formation 
of foam occurs in modern diesel engines since in these the fuel flowing 
back into the fuel tank via the return line is at a very high temperature. 
SUMMARY OF THE INVENTION 
The invention is based on the problem of designing a fuel delivery device 
in such a manner that formation of foam in the surge baffle is largely 
avoided even at high fuel temperatures. 
According to the invention, this problem is solved by a delivery pump for 
delivering fuel directly from the fuel tank into the surge baffle and to 
the sucking jet pump, and by the fact that the sucking jet pump is 
arranged to deliver fuel from a region of the fuel tank which is separated 
from the region with the surge baffle, into the region with the surge 
baffle. 
This design enables the fuel delivery device to have a delivery pump which 
is independent of the fuel pump. This delivery pump ensures that the surge 
baffle is continuously filled. Fuel should not therefore slosh into the 
surge baffle from above, which leads to a pronounced reduction in the 
formation of foam in the surge baffle. The delivery pump according to the 
invention makes it possible for the surge baffle to be arranged at any 
desired point in the fuel tank, for example on a sealing cover. Since the 
delivery pump drives the sucking jet pump, the latter receives, as working 
fluid, relatively cool fuel from the fuel tank and not the hot fuel 
flowing back from the internal combustion engine. Since the sucking jet 
pump delivers fuel into that region of the fuel tank which has the surge 
baffle, foam is not directly delivered into the surge baffle by the 
sucking jet pump. The fuel pump is therefore also unable to draw in any 
foam from the surge baffle. 
The surge baffle is always reliably filled under all operating conditions 
if, in accordance with an advantageous development of the invention, the 
amount of fuel delivered by the delivery pump to the sucking jet pump is 
approximately the same as the amount delivered into the surge baffle. 
The fuel delivery device according to the invention is designed in a 
particularly space-saving manner if the delivery pump is arranged in the 
surge baffle and the fuel pump is arranged in the vicinity of the internal 
combustion engine. This design furthermore means that the feed line is not 
under pressure, which reduces the complexity of sealing it. 
In accordance with another advantageous development of the invention, the 
risk of formation of foam in the surge baffle is further reduced if the 
delivery pump, to fill the surge baffle, has a filling line which is 
immersed in the surge baffle and leads almost to its bottom. This means 
that when fuel flows into the surge baffle, air, which would lead to 
pronounced formation of foam, is not entrained. 
In accordance with another advantageous development of the invention, the 
fuel passes into the surge baffle in a particularly steady manner if the 
filling line is surrounded by a stabilizing space which extends from the 
bottom into the upper region of the surge baffle. This design makes it 
possible for any air bubbles present in the fuel to be separated from the 
fuel in this stabilizing space. As a result, the fuel present in the surge 
baffle does not foam up even when the motor vehicle is cornering, during 
which the delivery pump could briefly deliver air or foam. 
In the case of a fuel delivery device having a return line leading from the 
internal combustion engine back into the fuel tank, the return line can be 
led directly into the fuel tank. Since the fuel conducted in the return 
line is basically at a higher temperature than the fuel present in the 
fuel tank, unnecessary heating up of the fuel tank is prevented in a 
simple manner in that the return line opens into the surge baffle. 
The fuel delivered via the return line into the surge baffle is stabilized 
in a simple manner in that the return line is guided to a point directly 
above the bottom of the surge baffle, and is surrounded by a stabilizing 
space which extends from the bottom into the upper region of the surge 
baffle. 
According to another advantageous development of the invention, the 
formation of foam in the fuel tank by air being entrained by the fuel 
flowing out of the surge baffle is reduced in that the surge baffle has an 
overflow pipe which penetrates through the bottom of the surge baffle and 
is guided up to an intended filling height. 
In accordance with an advantageous development of the invention, the 
venting of the surge baffle is designed in a particularly simple manner if 
the surge baffle has, on its upper side, a vent having a filter inserted 
therein. The filter prevents dirt from penetrating into the surge baffle. 
Furthermore, foam produced, for example, by vibration passes out of the 
surge baffle through the filter. 
In accordance with an advantageous development of the invention, noises 
produced by the delivery pump are not transmitted to the fuel tank if the 
delivery pump is held in the surge baffle by an elastomeric part. 
Failure of the delivery pump to deliver fuel is synonymous with an empty 
fuel tank. In accordance with an advantageous development of the 
invention, damage to the delivery pump due to dry running can be avoided 
in a simple manner if means are provided to shut off the internal 
combustion engine in the event of the delivery pump failing to deliver 
fuel. These means, moreover, have the advantage that fuel remains in the 
surge baffle when the fuel tank is empty. When the fuel tank is filled up 
again, this measure prevents air from passing into the feed line and 
interrupting the fuel supply. Dry running of the delivery pump can be 
detected, for example, by the reduction in its power consumption.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a fuel tank 1 and an internal combustion engine 2 which are 
connected to one another via a feed line 3 and a return line 4. A surge 
baffle 5 and a sucking jet pump 6 are arranged in the fuel tank 1. The 
surge baffle 5 is fastened by a retaining arm 7 to a sealing cover 8 which 
is inserted into an opening 9 in the fuel tank 1. 
The sucking jet pump 6 is supplied with fuel via a delivery line 10 and, 
via a line 24, delivers this fuel from a region 11 of the fuel tank 1 into 
the region 12 in which the surge baffle 5 is arranged, The fuel is drawn 
into a delivery pump 15 directly from the bottom region of the fuel tank 1 
via an intake line 13. A fuel pump 14 is arranged in the feed line 3 in 
the vicinity of the internal combustion engine 2. 
FIG. 2 shows the surge baffle 5 from FIG. 1 in a sectional representation. 
A delivery pump 15 is arranged in the surge baffle 5, which delivery pump 
delivers fuel from the intake line 13 into a filling line 16 and into the 
delivery line 10 leading to the sucking jet pump 6. The flow directions of 
the fuel are marked in the drawing by arrows. The filling line 16 and the 
return line 4 are guided to a point directly above the bottom 17 of the 
surge baffle 5 and are in each case surrounded by stabilizing spaces 18, 
19 which extend from the bottom 17 into the upper region of the surge 
baffle 5. As a result, the fuel passes degassed and in a particularly 
steady manner into the surge baffle 5. The feed line 3 is likewise guided 
to a point directly above the bottom 17 of the surge baffle 5 and draws 
fuel off here. The delivery pump 15 is held by an elastomeric part 20 to 
avoid noises being transmitted. As an overflow, use is made of an overflow 
pipe 21 which penetrates through the bottom 17 of the surge baffle 5 and 
extends up to the intended filling height. On the upper side, the surge 
baffle 5 has a vent 22 with a filter 23 inserted therein. To protect the 
fuel pump 14 and delivery pump 15 from dry running, the motor vehicle fuel 
delivery device can be provided with a simple electrical control (not 
shown) to shut off the internal combustion engine 2 when the fuel tank 1 
is empty. The control could, for example, shut off the internal combustion 
engine 2 when it senses a reduction in the power consumption of the 
delivery pump 15. This would ensure that the fuel pump 14, feed line 3 and 
surge baffle 5 contain fuel despite the fuel tank 1 being empty.