EP1152142B1 - Fuel supply system for combustion engine with direct fuel injection - Google Patents

Description

The invention relates to a fuel supply system for a direct fuel injection working internal combustion engine, near which one High pressure fuel pump is arranged by a a fuel tank assigned feed pump is supplied with fuel and being from the high-pressure section between the high-pressure pump and the internal combustion engine of the fuel supply system a fuel leak and / or fuel flush quantity is branched off. For technical For example, the environment is referred to DE 198 10 867 A1.

Both with self-igniting diesel engines, in particular those with common rail technology, as well as with spark-ignited, with direct fuel injection Otto internal combustion engines working in the combustion chambers high-pressure fuel pumps are used, which the Fuel must already be provided with a certain excess pressure, i.e. Fuel should already be on the so-called flow side of a high-pressure pump an increased pressure level. This minimum pressure, in particular of outstanding importance for starting the internal combustion engine is by an electric fuel pump, which is usually arranged in the fuel tank which generates the fuel from the tank to the high pressure pump promotes and is therefore referred to as a feed pump.

Under different operating conditions of the internal combustion engine Of course, different amounts of fuel are required, depending on the operating point also the fuel pressure level on the so-called flow side (or suction side) of the high pressure pump mentioned can. Now becomes the mentioned feed pump, that of a high-pressure fuel pump upstream and is assigned to the fuel tank designed the most critical operating point, i.e. to the point with maximum Throughput or maximum delivery rate with maximum required pressure level, is an extremely powerful and therefore not only expensive, but also large-volume and heavy-duty electric fuel pump required, which is also an expensive, suitable Electronic power control must be assigned.

To point out a simplified fuel supply system according to the preamble of claim 1 is the object of the present invention.
The solution to this problem is characterized in that at least a part of the leakage quantity or flushing quantity is returned to the feed side of the high-pressure pump by means of a further fuel pump. The leakage quantity and / or flushing quantity is preferably limited via a suitable throttle point and / or a pressure limiting valve or pressure control valve.

The invention is explained in more detail with reference to two preferred exemplary embodiments, of which the attached FIGS. 1 and 2 each show a schematic structure. 1 shows a fuel supply system according to the invention, preferably for a diesel internal combustion engine with common rail technology, while FIG. 2 shows that of a spark-ignited internal combustion engine with gasoline direct injection.

In both figures, the same components are designated with the same reference numbers. A fuel tank 1 is always provided, in which a feed pump 2 assigned to it is provided in the form of an electric fuel pump. At the opposite end of the fuel supply system there are fuel injection valves 4, which are shown only symbolically and branch off from an injection rail 3 and via which fuel can be injected into the individual cylinders of a multi-cylinder internal combustion engine. This fuel rail 3 is always preceded by a high-pressure fuel pump 5, which brings the fuel (essentially) supplied by the feed pump 2 to the feed side of the high-pressure pump 5 to the required pressure level or builds up the required fuel pressure level in the fuel rail 3. In the embodiment according to FIG . 2, a pressure relief valve 6 is also provided in the injection bar 3 upstream of the injection valves 4 for safety.

In both exemplary embodiments (FIGS. 1 and 2) , a fuel filter 8 is arranged in the fuel delivery line 7 leading from the delivery pump 2 to the high-pressure pump 5. 2 there is a pressure regulator 9 downstream of the same in the exemplary embodiment according to FIG , As is known, in addition to the fuel quantity brought to the required high pressure level, a leakage quantity fuel flow is also discharged from the high-pressure pump 5, specifically via a so-called leak line 11a. A so-called fuel flushing quantity can also be discharged from the high-pressure pump 5 and / or from the injection valves 4, specifically via a so-called flushing line 11b. Both the leakage line 11a and the flushing line 11b are in the so-called high-pressure section of the fuel supply system, but these two lines 11a and 11b themselves only have a relatively low fuel pressure in the order of magnitude of approximately 0.5 bar to approximately 1.5 bar should be loaded.

According to the invention (in both preferred exemplary embodiments according to FIGS. 1 and 2 ), the leakage fuel flow and / or the fuel flushing amount mentioned is at least partially fed back to the feed side of the high pressure pump 5. For this purpose, the mentioned leakage line 11a and the mentioned flushing line 11b unite to form a leak and flushing line 11 ultimately opening in the delivery line 7 downstream of the filter 8. This quantity of fuel thus supplied to the feed side of the high-pressure pump 5 has already been delivered by the delivery pump 2 transported to the high pressure pump 5, so that it would be energetically or efficiency analytically unfavorable to return this amount of fuel to the tank 1 and to feed it from there again by means of the feed pump 2 to the high pressure pump 5. Therefore, the quasi-excess amount of fuel coming from the so-called high-pressure section of the fuel supply system is fed directly back to this high-pressure section starting with the high-pressure pump 5 without being returned to the tank 1 beforehand.

However, the mentioned leakage quantity fuel flow and / or the mentioned flushing quantity of fuel, which are fed back via the leakage and flushing line 11 to the feed side of the high-pressure pump 5, are initially not below that required or required on this side by the high-pressure pump 5 Pressure level before. For this reason, a further fuel pump 12 is provided in the leak and flush line 11, which brings the amount of fuel carried in this line 11 to the required pressure level. Downstream of this further fuel pump 12 - by the way, the direction of flow of the fuel in the individual lines, some of which are also not shown in more detail by arrows - a fuel filter 8 'is provided in both exemplary embodiments for safety reasons, since both the fuel leakage flow and the so-called fuel flushing quantity added dirt particles or also abrasion (from the additional fuel pump 12) can contain. In the arrangement according to FIG. 1, deviating from the introduction shown upstream of the high-pressure pump 5 and downstream of the fuel filter 8, the introduction can also alternatively take place upstream of this fuel filter 8, so that of course no further fuel filter 8 'is then required ,

In the exemplary embodiment according to FIG. 1, a non-return valve 13 is also provided in the leakage and flushing line 11 downstream of the filter 8 'and upstream of the mouth into the delivery line 7 - that is, blocking the further fuel pump 12. In the exemplary embodiment according to FIG. 2 , this is not necessary due to the pressure regulator 9 present there in the delivery line 7, since the pressure downstream thereof is lower than the pressure generated by the further fuel pump 12. For this purpose, in the exemplary embodiment according to FIG . 1, there is a pressure relief valve 6 ′ in the leak and flush line 11 upstream of the further fuel pump 12, which branches off an excess portion of fuel into a return line 10 that ultimately ends in the tank 1. This pressure limiting valve 6 ', which can alternatively also be designed as a pressure control valve, thus regulates the fuel pressure in the leak and flush line 11. In the exemplary embodiment according to FIG. 2 , in which the high-pressure fuel pump 5 is flushed itself, that is to say a fuel flushing quantity this is passed through, a throttle point 14 is provided in the flushing line 11b, which limits the quantity of fuel flushing quantity in order to limit the delivery losses to an acceptable level. In the exemplary embodiment according to FIG. 1 , this throttle function is taken over by a pressure regulator 9 ′, which is preferably built in the high-pressure pump 5.

The particular advantage of the fuel supply system according to the invention consists in using the inevitable amount of fuel leakage as well as the fuel purge flow in the further fuel pump 12 suitably compressed and then the flow side of the high pressure pump 5 is supplied so that the total assigned to the tank 1 Delivery pump 2 provide a correspondingly lower delivery rate got to. This feed pump 2 can therefore advantageously accordingly smaller, lighter and less expensive. advantageously, none or essentially none comes close to the internal combustion engine heated amount of fuel back into the fuel tank 1.

The further fuel pump 12 can also be driven mechanically or electrically. Both exemplary embodiments also have in common that the fuel tank 1 is a so-called saddle construction. Since the only feed pump 2 can only be located in two halves (here in the right half of the tank) of the tank 1, a suction jet pump 15 is provided in the other half of the tank as usual, which supplies fuel from the left half of the tank in the right half of the tank. While in the embodiment according to FIG. 2 this suction jet pump 15 is fed via the return line 10 mentioned, in the embodiment according to FIG. 1 it is fed from the delivery line 7, however this and a large number of further details, in particular of a constructive nature, may deviate from the exemplary embodiments shown be designed without leaving the content of the claims.

LIST OF REFERENCE NUMBERS

1

Fuel Tank

2

Feed pump (electric fuel pump)

3

Fuel rail

4

Injector

5

High-pressure fuel pump

6.6 '

Pressure relief valve

7

Fuel delivery line (between 2 and 5)

8,8 '

Fuel filter

9, 9 '

pressure regulator

10

Return line

11

Leak and flush line

11a

leakage line

11b

flushing line

12

(further) fuel pump

13

check valve

14

restriction

15

eductor

Claims (3)

1. A fuel supply pump for an internal combustion engine with direct fuel injection, a high-pressure fuel pump (5) being disposed near the fuel supply system and supplied with fuel by a delivery pump (2) associated with a fuel tank (1), wherein an amount of leakage or overflow fuel and/or an amount of flushing fuel is branched off the high-pressure portion of the fuel supply system between the high-pressure pump (5) and the engine,
   characterised in that at least a part of the leakage or flushing fuel is supplied by an additional fuel pump (12) to the outflow side of the high-pressure pump (5).
2. A fuel supply system according to claim 1, characterised in that the amount of leakage and/or flushing fuel is limited by a suitable restrictor (14) and/or by a pressure-limiting valve (6') or a pressure-regulating valve.
3. A fuel supply system according to claim 1 or 2, characterised in that the additional fuel pump (12) is mechanically or electrically operated.

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