EP1556605A1

EP1556605A1 - Fuel injection system comprising a pressure intensifier and a delivery rate-reduced low-pressure circuit

Info

Publication number: EP1556605A1
Application number: EP03809691A
Authority: EP
Inventors: Hans-Christoph Magel; Gerhard Geyer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2002-10-17
Filing date: 2003-06-30
Publication date: 2005-07-27
Anticipated expiration: 2023-06-30
Also published as: WO2004040118A1; DE50304388D1; DE10248467A1; US20060042598A1; JP2006503225A; JP4437092B2; US7219659B2; EP1556605B1

Abstract

The invention relates to a fuel injection system for an internal combustion engine comprising a fuel injector (10), which can be supplied with fuel by a fuel high-pressure source (1, 4). Said fuel injector has an injection valve element (37) that opens or closes injection openings (43). The fuel injection system also contains a low-pressure circuit (64) provided with a presupply pump (55) that delivers fuel from a fuel tank (14). The fuel injection system is characterized in that partial quantities of fuel returning from pressure intensifiers (7, 52) or from fuel injectors (10), the pressure of these partial quantities of fuel being reduced to the presupply pressure of the presupply pump (55), are fed to the low-pressure circuit (64) whereby arriving in a feeding section (60) via returns (50, 52; 13, 53).

Description

Fuel injection system with pressure intensifier and low-pressure circuit with reduced delivery rate

Technical field

Both pressure-controlled and stroke-controlled injection systems can be used to supply the combustion chambers of self-igniting internal combustion engines with fuel. In addition to pump injector units (PDE), pump line injector units (PLD), accumulator injection systems are also used as fuel injection systems. Accumulator injection systems (common rail) advantageously make it possible to adapt the injection pressure to the load and speed of the internal combustion engine. A high injection pressure is required to achieve high specific outputs. The higher the achievable injection pressure, the lower the emissions of the internal combustion engine.

State of the art

DE 199 10 970 AI has the object of a fuel injection device. This has a pressure translation unit arranged between a pressure storage chamber and a nozzle chamber, the pressure chamber of which is connected to the nozzle chamber via a pressure line. A bypass line connected to the pressure storage space is also provided. The bypass line is connected directly to the pressure line. The bypass line can be used for a pressure injection and is arranged parallel to the pressure chamber, so that in the bypass line the pressure translation unit is continuous regardless of the movement and position of a displaceable pressure medium. This enables greater flexibility with regard to injection.

DE 101 23 911.4 relates to a fuel injection device with pressure transmission device. A fuel injection device for internal combustion engines also includes a fuel injector that can be supplied by a high-pressure fuel source a pressure transmitter. The pressure intensifying device contains a movable piston which separates a space connected to the high-pressure plastic source from a high-pressure space connected to the injector. The high-pressure space is connected to a rear space via a fuel line, so that the high-pressure space can be filled with fuel via the rear space of the pressure booster. The control of the fuel injection device known from DE 101 23 911.4 with pressure booster device is carried out by depressurizing the rear space of the pressure booster device. According to the solutions known from DE 199 10 970 AI and DE 101 23 911.4, the fuel injection device comprises a stroke-controlled fuel injector. A pressure booster is assigned to each fuel injector in order to increase the injection pressure if necessary. The pressure booster device is controlled by a simple 2/2-way valve and leads to reduced relaxation losses, since the back space of the pressure booster device is relieved of pressure when it is actuated. Furthermore, these solutions allow multiple injections to be carried out and the injection process to be shaped flexibly.

The use of a pressure transmission device in a fuel injection system comprising a high-pressure accumulator leads to a greatly increased quantity requirement per fuel injector within the injection system. For a high-pressure delivery unit, this results in an increased delivery rate at a reduced pressure level. The flow rate also increases for a low pressure pump. However, the pressure level of the low-pressure delivery unit is not reduced, since a good filling of the pump rooms of the high-pressure delivery unit and an exact metering of the delivery rate must be ensured by the metering unit in the fuel system. The design of the pre-pump for the large flow rates required for fuel ejectors with pressure intensifiers is therefore a problem. In a fuel injection system with a high-pressure storage space with an integrated pressure intensifier, high return quantities occur due to the pressure transmission, which are a multiple of the fuel quantity to be injected via the respective fuel injector. This amount of fuel is completely expanded in the systems known from the prior art and fed into the fuel tank which is only exposed to atmospheric pressure. Then the entire volume requirement of the fuel injection system must be compressed by the low-pressure pump to pre-delivery pressure in order to enable the pump rooms of the high-pressure delivery unit to be filled. Presentation of the invention

According to the solution according to the invention, the return of the pressure booster is not completely relaxed and is returned to the fuel tank in order to reduce the amount of feed. According to the proposed solution, an expansion tank can be integrated in the return line of the pressure booster and a return line can open into the low-pressure circuit, for example, directly behind the outlet of the pre-delivery unit on the pressure side. As a result, the amount of fuel returning from the pressure intensifier can only be reduced to the relatively low pressure level of the preliminary pump, i.e. relax the feed pressure. As a result, the quantity to be demanded by the preliminary pump is reduced in accordance with the pressure transmission ratio of the pressure intensifier.

The return flow of the pressure booster can be fed into the low-pressure circuit acted upon by the pre-pump at any point. On the one hand, the return line can be fed in before a fuel filter in order to ensure that the fuel is cleaned, on the other hand it is also possible to feed the pressure booster return flowing back from the pressure intensifier into the low-pressure circuit after the fuel filter in order to reduce the filter size. Furthermore, there is the possibility, after a metering unit connected upstream of the high-pressure delivery unit, to feed the pressure booster return into the low-pressure side circuit in order to reduce the flow cross-section of a metering unit required to regulate the need for the high-pressure delivery unit. Another possible embodiment is to also relax the return of the fuel injector only up to the pressure level that can be built up by the pre-supply and feed it downstream of the feed pump into the low-pressure circuit. This embodiment variant can be used in fuel injection systems with a high-pressure storage chamber without a pressure intensifier to reduce the low-pressure delivery volume, since, depending on the design of the fuel injector and the pressure level prevailing in the high-pressure storage chamber, the return quantity of the fuel injector can represent a significant proportion of the total quantity. However, it is also possible to feed only a subset of the injector return after the pre-pump into the low pressure circuit. As a result, pressure-sensitive spaces of a fuel injector or a pressure intensifier module, e.g. a solenoid valve armature can still be relaxed to a lower pressure level.

drawing

The invention is explained in more detail below with the aid of the drawing. It shows:

FIG. 1 shows the hydraulic construction of the high-pressure and low-pressure circuit on a high-pressure accumulator injection system with a pressure intensifier,

Figure 2 shows the hydraulic functioning of a fuel injection system

High pressure storage space and pressure intensifier and

Figure 3 shows the proposed hydraulic connection of the low pressure circuit of a fuel injection system with pressure intensifier and high pressure storage space according to the invention.

design variants

FIG. 1 shows the hydraulic connection of the components of a fuel injection system with a high-pressure storage space and pressure transmission, as well as the components used therein.

The fuel injection system with a high-pressure storage space 4 and a pressure intensifier 7 connected upstream of a fuel injector 10 comprises a high-pressure delivery unit 1. The high-pressure delivery unit 1 is connected upstream of a metering unit, not shown, by means of which fuel is metered to the high-pressure delivery unit in a demand-controlled manner. From a fuel tank 14, which contains fuel corresponding to the fuel level 15, fuel flows via an inlet 16 to a feed pump upstream of the high-pressure delivery unit 1. There it is compressed to pre-delivery pressure. The compressed fuel then passes through a fuel filter 17 and is metered to the high-pressure delivery unit 1 as required by a metering unit (not shown). Control, flushing and lubrication quantities are returned to the fuel tank 14 via a return line 19.

The fuel compressed to pre-delivery pressure is compressed in the high-pressure delivery unit 1 and stored in the high-pressure storage space 4. The high-pressure delivery unit 1 is connected to the high-pressure storage space 4 via a high-pressure feed line 2. The high-pressure line 2 is received at a high-pressure connection 3 on the high-pressure storage space 4. From the high-pressure storage space 4, fuel standing under the pressure built up by the high-pressure delivery unit 1 flows to the pressure booster 7 via the feed line 6. The high-pressure storage space 4 is connected to the fuel tank 14 via a return line 5 to the fuel tank 14.

From a high-pressure chamber 9 contained in the pressure intensifier 7, fuel which is at a further increased pressure level flows to the fuel injector 10 and can be injected at an injection nozzle 12 of the fuel injector 10 into the combustion chamber (not shown in FIG. 1) of a self-igniting internal combustion engine.

According to the configuration shown in Figure 1, all return quantities occurring in the system, i.e. the return flow of the metering unit and the return flow of the pressure booster 7 as well as the return flow from the fuel injector 10 are completely relaxed and fed back into the fuel tank 14. In the system configuration shown in FIG. 1, the pressure intensifier 7 is procured as a separate component, but can be integrated in the high-pressure storage space 4 as well as in the fuel injector 10.

The leakage or actuation quantities controlled back into the fuel tank 14 under atmospheric pressure all flow back into the fuel tank 14 via the returns 13 from the fuel injector 10, the return line 8 from the pressure booster 7, the return line 5 from the high-pressure storage space 4 and via the return line 19 of the metering unit.

The illustration according to FIG. 2 shows the hydraulic functioning of a fuel injection system which contains a pressure intensifier.

Fuel is supplied via the feed line 6 to the pressure booster 7, which is below the pressure level prevailing in the high-pressure storage space 4 (not shown here). The fuel flows via the feed line 6 into a working space 26 of the pressure booster 7. A first channel 23 and a second channel 24 extend parallel to the feed line which acts on the working space 26 of the pressure booster 7. A filling valve 20 is accommodated within the first channel 23; the second channel 24 comprises a throttle point 21. The first channel 23 and the second channel 24 as well as an overflow line 25 containing a check valve 22 are all connected to a rear space 27 of the pressure booster 7. A return spring 30 is received within the rear space 27 and acts on the lower end face of a booster piston 28 separating the working space 26 from the high pressure space 9. On the booster piston 28 there is an end face 29 which, when the rear space 27 of the pressure booster 7 is relieved of pressure, pressure chamber 9 retracts. The end face 29 which enters the high-pressure chamber 9 when the pressure intensifier 7 is depressurized, brings about a further pressure increase of the fuel contained in the high-pressure chamber 9 in accordance with the transmission ratio of the pressure intensifier 7 within the high-pressure chamber 9. The rear space 27 of the pressure booster 7 is relieved of pressure by activating an actuating valve designated by reference numeral 31. The actuating valve 31 for relieving the pressure in the rear space 27 can be designed, for example, as a 2/2-way valve and is connected to a low-pressure region which is not shown here in FIG.

When the back space 27 is relieved of pressure via the return line 8 after actuation of the valve 31, the fuel under high pressure contained in the high pressure space 9 of the pressure booster 7 is displaced into a high pressure supply line 33 which extends to the fuel injector 10. The check valve 22 contained in the overflow line 25 for refilling the high-pressure chamber 9 prevents fuel volume displaced from the high-pressure chamber 9 from flowing back into the rear chamber 27 of the pressure booster 7.

The high-pressure supply line 33, which extends from the high-pressure chamber 9 of the pressure booster 7 to the fuel injector 10, opens into a nozzle chamber 38 formed in the injector body 11 of the fuel injector 10. Furthermore, a control chamber 34 of the fuel injector 10 is acted on via the inlet throttle 35 via the high-pressure supply line 33. The control chamber 34 is depressurized to actuate an injection valve member 37, which is preferably designed as a nozzle needle, by actuating an actuating valve 32, which can be designed as a 2/2-way valve. Pressure relief of the control chamber 34 takes place via an outlet throttle 36 in the return 13, which connects to the actuating valve 32 for actuating the fuel injector 10.

A nozzle spring chamber 39 is provided in the injector body 11 of the fuel injector 10 as shown in FIG. 2 in addition to a nozzle chamber 38. The nozzle spring chamber 39 receives a nozzle spring 40. Furthermore, a leakage line extends from the nozzle spring chamber 39, via which fuel flowing out of the nozzle chamber 39 during an opening movement of the injection valve member 37 can flow out into the low-pressure region of the fuel injection system.

The fuel compressed in accordance with the transmission ratio of the pressure intensifier 7 flows into the nozzle space 38 via the high-pressure supply line 33. Because of the pressure build-up in the nozzle chamber 38, this translated pressure is applied to a pressure shoulder 42, which is formed on the injection valve member 37 in the region of the nozzle chamber 38 is. The injection valve member 37 is held in its closed position via the nozzle spring 40 and the pressure level prevailing in the control chamber 34.

When the rear space 27 is relieved of pressure via the actuating valve 31, the translator piston 28 moves with its end face 29 into the high-pressure space 9. An increased fuel pressure corresponding to the transmission ratio of the pressure intensifier 7 is achieved in this. In the high-pressure chamber 9, the fuel flows to the nozzle chamber 38 via the high-pressure supply line 33 and acts on the pressure shoulder 42 designed for the injection valve 37. The control chamber 34 is relieved of pressure via the outlet throttle 36 when the actuating valve 32 is switched. The Eirtpritzventilglied 37 opens against the action of the nozzle spring 40, so that there is an injection of fuel into the combustion chamber 44. The control chamber 34 is relieved of pressure via the discharge throttle 36 when the actuating valve 32 is switched, so that fuel is injected into the combustion chamber 44. For the hydraulic function of the pressure transmission, it is irrelevant whether the fuel in the rear space 27 of the pressure intensifier is completely expanded or has a residual pressure which corresponds approximately to the pre-delivery pressure. Maintaining a low residual pressure level within the rear space 27 of the pressure booster is rather advantageous in order to avoid cavitation effects in the rear space 27.

By actuating the switching valve 31 into its closed position, i.e. the interruption of the connection to the return on the low-pressure side fills the back space 27 of the pressure booster 7 via the first channel 23 and the second channel 24. As a result, the booster piston 28, supported by the return spring 30 received in the back space 27, moves back into its rest position, so that the high pressure chamber 9 of the pressure booster 7 is depressurized. As a result, the pressure in the nozzle space 38 drops. The closing movement of the injection valve member 37, which is designed as a nozzle needle, is initiated in that a switching valve 32 which relieves the pressure from the control chamber 34 is switched into its closed position, so that pressure builds up in the control chamber 34 via the inlet throttle 35 branching off from the high-pressure supply line 33.

FIG. 3 shows the circuit proposed according to the invention for a low-pressure area of a fuel injection system with pressure intensifier and high-pressure storage space.

In the fuel injection system shown in FIG. 3, the high-pressure delivery unit 1 delivers fuel into the high-pressure storage space 4 via the high-pressure line 2. Six supply line connections are shown on the high-pressure storage space 4, via which a self-igniting internal combustion engine containing six cylinders is supplied with fuel. Instead of the six high-pressure line connections shown in FIG High-pressure storage space 4, 5, 8, 10 or 12 high-pressure line connections are designed in accordance with the number of cylinders of the combustion engine to be supplied with fuel. The working chamber 26 of the pressure booster 7 is pressurized via the feed line 6 from the high-pressure storage chamber 4. The pressure booster 7 comprises a booster piston 28 which separates the working room 26 from the rear chamber 27. As shown in FIG. 2, a return spring 30 can be accommodated in the rear space 27 of the reverse booster 7, which returns the booster piston 28 to its rest position. The rear chamber 27 of the pressure booster 7 is acted upon by fuel via the feed line 6, which opens into the second channel 24, which contains the throttle point 21. The pressure relief of the rear space 27 takes place via the return line 8, which can be connected by means of the switching valve 31 to a return line 50 assigned to the pressure intensifier and the rear space 27, or can be separated therefrom.

The front side 29 of the booster piston 28 acts on the high-pressure chamber 9 of the pressure booster 7, so that a fuel pressure which is increased in accordance with the pressure booster ratio of the pressure booster 7 can be achieved therein. The check valve 22 connected in parallel to the pressure booster 7 in a bypass line prevents the fuel volume contained in the high-pressure chamber 9 of the pressure booster 7 from flowing back into the feed line 6.

The high-pressure chamber 9 of the pressure booster 7 is connected to the high-pressure supply line 33. From this, a line section, containing an inlet throttle 35, branches off into the control chamber 34; furthermore, via the high-pressure supply line 33, the nozzle chamber 38 within the injector body 11 of the fuel injector 10 is increased, i.e. pressurized fuel under pressure. If the fuel injector 10 is actuated by switching the switching valve 32, fuel flows through the open discharge throttle 36, i.e. the injector control amount, in the return line 13. At the same time, a pressure acting in the opening direction of the injection valve member 37 builds up on the pressure shoulder 42 acting as a hydraulic surface on the injection valve member 37 due to the pressurization of the nozzle chamber 38. The injection valve member 37 moves against the nozzle spring 40 let into the nozzle spring chamber 39, so that the injection openings 43 of the injection nozzle 12 are opened and fuel is injected from the nozzle chamber 38 via the annular gap 45 surrounding the injection valve member 37 into the combustion chamber (not shown in FIG. 3) of a self-igniting internal combustion engine can.

When the switching valve 32 is open, the injector control quantity flows out of the control chamber 34 via the outlet throttle 36. The injector control quantity flows into the unpressurized fuel tank 14 via the return line 13. Via the arrows designated by reference number 53 further return lines 13 of the further fuel injectors 10 for supplying fuel to the self-igniting internal combustion engine are indicated. These also flow into the return 13 into the unpressurized fuel tank 14. However, the return 50 assigned to the pressure booster 7 opens into a compensating tank 51 within a low-pressure circuit 64 of the fuel injection system according to FIG. 3. Arrows denoted by reference symbols 52 indicate further pressure booster 7 assigned pressure booster returns 50 on, which also flow back into the expansion tank 51. For the hydraulic function of the pressure booster 7, it is irrelevant whether the fuel in the rear space 27 of the pressure booster 7 is completely expanded or to a residual pressure which corresponds approximately to the pressure built up by a pre-pump 55. A low residual pressure within the rear space 27 of the pressure booster 7 is rather advantageous in order to avoid cavitation effects.

When the back space 27 is depressurized to a residual pressure which corresponds approximately to the pressure level achievable with a low-pressure precharge pump 55, fuel flows from the expansion tank 51 into a line section 60. The line section 60 comprises a plurality of feed points 61, 62, 63, at which the under pressure standing fuel in the expansion tank 51 back into the low pressure circuit 64, ie can be fed in before the high-pressure conveyor unit 1.

A first possibility is to feed the fuel, which is under residual pressure from the expansion tank 51, into the line section 60 at a first feed point 61, which is arranged behind the pressure-side outlet 56 of the pre-pump 55. For this purpose, a first feed section 66.1 can be provided. The feed points 61, 62 and 63 are all located behind the pressure side 56 of the feed pump 55, so that the fuel volume to be fed by the feed pump 55 is considerably reduced. This is due to the fact that the pressure intensifier 7 produces relatively high return quantities, which result from the transmission ratio multiplied by the injection quantity. In the expansion tank 51, in which the return quantities of the pressure booster 7 are received, pressure vibrations in the return path of the pressure booster 7 can be damped. Furthermore, the expansion tank 51 has a certain cooling effect, which has a favorable influence on the temperature level of the fuel within the low-pressure circuit 64.

To protect the expansion tank 51 is seen in the outflow direction of the fuel contained therein, a pressure relief valve 54 is connected. This pressure relief valve 54 is connected to the unpressurized fuel tank 14 analogously to the return lines 13 running from the fuel injectors 10. The return flow rate, which is determined by the six pressure amplifiers 7 of a six-cylinder self-igniting internal combustion engine, can be fed into the line section 60 at a first feed point 61. If the fuel quantities that are pressure-controlled by the pressure boosters 7 when the working spaces 27 are depressurized are fed in before the fuel filter 17, cleaning of the controlled return flow rates of the pressure intensifiers 7, 52 can be achieved in an advantageous manner. Alternatively, it is possible to feed in the return quantities of the pressure boosters 7 received in the expansion tank 51 at a second feed point 62, which is connected downstream of the fuel filter 17. Feeding the return quantities of the pressure boosters 7 at the second feed point 62 via a second feed section 66.2 offers the advantage that the filter size of the fuel filter 17 can be reduced, which is advantageous in terms of the construction volume.

The return quantities flowing back into the expansion tank 51 from the pressure boosters 7 can finally also be supplied at a third feed point 63 via a third feed section 66.3 into the introduction section 60 in the low-pressure circuit 64. The third infeed point 63 is connected downstream of a metering unit 59, which undertakes the metering of fuel to the high-pressure delivery unit 1 outside the low-pressure circuit 64 in a demand-controlled manner. By means of a third feed point 63 connected downstream of the metering unit 59, the return quantities of the pressure intensifiers 7 downstream of the metering unit 59, upstream of the high-pressure delivery unit 1 outside the low-pressure circuit 64, can be introduced into the inlet section 60, so that the necessary flow cross section of the metering unit 59 is kept small can. By feeding in the return quantity of the pressure booster 7 contained in the expansion tank 51 in the inlet line section 60, the fuel volume flow to be demanded by the preliminary pump 55 can be considerably reduced in all three supply variants, ie positions 61, 62, 63. This allows a smaller dimensioning of the feed pump 55, since the feed pump line to be applied by the feed pump 55 is supplied with respect to the fuel volume flow to the high-pressure feed unit 1 outside the low-pressure circuit 64 in order to supply the feed from the expansion tank 51 within the inlet section 60 to the feed points 61, 62, 63 the pressure boosters 7 controlled return quantities are supplemented. The pressure level prevailing in the low-pressure circuit 64, which is built up by the preliminary pump 55, is preferably in the range between 5 and 7 bar, which corresponds to the residual pressure level, which remains in the work back space 27 when the back space 27 of the pressure booster 7 is relieved when the actuating valve 31 is actuated. Dirt fluctuations within the earth line section 30 can be compensated for by a pressure control valve 57, which is opened in a line section opening into the fuel tank 14. is taken, which branches within the introduction section 60 between the fuel filter 17 and the metering unit 59.

Due to the configuration of the low-pressure circuit 64 of the fuel injection system according to FIG. 3, which is proposed according to the invention, when the fuel volume flowing out of the expansion tank 51 is fed into the second feed point 62 directly behind the fuel filter 17, it can also be achieved that the fuel filter 17, 58 can be designed for smaller fuel volume flows. which has a very favorable influence on the size of delivery components and filter components within the low-pressure circuit 64 of the fuel injection device proposed according to the invention.

A further reduction in the fuel volume flow to be supplied to the high-pressure delivery unit 1 through the pre-supply pump 55, the filter element 17 and the metering unit 59 can be realized in the illustration in FIG. 3 into the fuel tank 14 via the return line 13 assigned to the fuel injectors 10 and a partial quantity return 65 outflowing amount of leakage, likewise to relax only up to the pre-delivery pressure to be applied by the pre-delivery pump 55. This fuel volume flow flowing out of the fuel injector 10 or the fuel injectors 10 via the return line 13 is preferably fed into the low-pressure circuit 64 behind the pressure side 56 on the feed pump 55. As a result, even in the case of fuel injection systems which are designed without a pressure booster, the amount of fuel to be demanded by the pre-charge pump 55 can be reduced. Depending on the injector design of the fuel injectors 10 and the fuel pressure applied in the high-pressure storage chamber 4 by the high-pressure delivery unit 1, the return quantity of the fuel injector (s) 10 can make up a significant proportion of the total fuel quantity. The return flow flowing out of the fuel injector 10 essentially consists of the fuel volume flow that is diverted into the nozzle spring chamber 39 when the injection valve member opens and the control volume that flows out of the control chamber 34 via the outlet throttle 36 when the switching valve is actuated. In the fuel injection system shown in FIG. 3 for supplying a six-cylinder self-igniting internal combustion engine, the returns 53 of further fuel injectors 10, which are not shown here, are indicated by the arrows pointing to the return line 13.

With the configuration of the low-pressure circuit 64 of a fuel injection system proposed according to the invention, complete relaxation of the high return quantity flowing back from the pressure intensifiers 7, which can be a multiple of the injection quantity, to atmospheric pressure can be avoided. With previously known printing This return flow quantity is completely relaxed and returned to the unpressurized fuel tank 14. The total quantity required in this system must then be compressed by the pre-pump 55 to the pre-delivery pressure (5 to 7 bar) in order to ensure that the pump rooms of the high-pressure delivery unit 1 are filled. If, on the other hand, the return flow flowing back from the pressure boosters 7 is not completely relaxed, but is kept at a pressure corresponding to the feed pressure of the feed pump 55 and is fed back to the low pressure circuit 64 at the first feed point 61, the second feed point 62 and the third feed point 63 within the introduction section 60, The structural design of the fuel filter 17 or 58 and the dimensioning of the metering unit 59 and prefeed pump 55 can take place to lower volume flows. Although the lower delivery capacity of the prefeed pump 55 is generally not regulated as required, high overflow quantities occurring in certain map pumps can be avoided, which can contribute to a significant loss of efficiency of the entire fuel injection system.

LIST OF REFERENCE NUMBERS

High pressure pumping unit high pressure line pressure port high-pressure accumulator (common rail) return line to the fuel tank inlet pressure booster return line pressure booster high-pressure chamber pressure booster fuel injector injector injector return fuel injector fuel tank fuel level inlet high pressure feed unit 1 fuel filter bypass line overflow fuel tank filling valve restrictor check valve first channel, second channel overflow working chamber back space booster piston booster piston end face the restoring spring actuating valve pressure intensifier switching valve Fuel injector, high-pressure supply line, fuel injector, control chamber, inlet throttle 36 outlet throttle

37 Injector link

38 nozzle area

39 nozzle spring chamber

40 nozzle spring

41 ring surface of injection valve member

42 pressure shoulder

43 injection port

44 combustion chamber

45 annular gap

46 Combustion chamber seat injection valve member 37

50 intensifier return

51 expansion tank

52 returns of additional pressure translators

53 returns of further fuel injectors 10

54 pressure relief valve

55 pre-feed pump

56 Pressure side of pre-feed pump

57 pressure control valve

59 Metering unit

60 introductory section

61 first entry point

62 second entry point

63 third entry point

64 low pressure circuit

65 Partial return fuel injector

66.1 first feed section

66.2 second feed section

66.3 third feed section

Claims

claims

1. Fuel injection device for an internal combustion engine with a fuel injector (10) which can be supplied with fuel from a fuel pressure source (1, 4) and which comprises an injection valve member (37) which opens or closes injection openings (43) and a low-pressure circuit (64) with a pre-feed pump (55 ), which delivers fuel from a fuel tank (14), characterized in that the low-pressure circuit (64) to the pre-delivery pressure of the pre-delivery pump (55) relaxed partial return quantities of pressure intensifiers (7, 52) or fuel injectors (10) within a feed section (60 ) are fed via returns (50, 52; 13, 53).

2. The fuel injection device according to claim 1, characterized in that the fuel pressure source (1) acts on a high-pressure storage space (4) with fuel under high pressure.

3. Fuel injection device according to claim 1, characterized in that the low-pressure circuit (64) comprises an expansion tank (51) acted upon by the returns (50, 52) from the pressure intensifier (7).

4. Fuel injection device according to claim 1, characterized in that the low-pressure circuit (64) comprises a fuel filter (17) and a metering unit (59).

5. Fuel injection device according to claim 4, characterized in that a first feed section (66.1) runs from the expansion tank (51) to a first feed point (61) in the feed section (60) which is connected upstream of the fuel filter (17).

6. The fuel injection device according to claim 4, characterized in that a second feed section (66.2) runs from the expansion tank (51) to a second feed point (62) in the feed section (60) which is connected downstream of the fuel filter (17).

7. The fuel injection device according to claim 4, characterized in that a third feed section (66.3) runs from the expansion tank (51) to a third feed point (63) in the feed section (60), which is arranged downstream of the metering unit (59).

8. The fuel injection device according to claims 5, 6 and 7, characterized in that the feed sections (66.1, 66.2, 66.3) are secured against the fuel tank (14) via a pressure relief valve (54).

9. The fuel injection device according to claim 1, characterized in that the introduction section (60) extends from the pressure side (56) of the pre-feed pump (55) to the high-pressure delivery unit (1).

10. The fuel injection device according to claim 4, characterized in that the fuel filter (17) and the metering unit (59) for the high-pressure delivery unit (1) are arranged within the feed section (60).

11. A fuel injection device according to claim 1, characterized in that both the injector control quantities and leakage quantities of the fuel injectors (10) are fed to the low-pressure circuit (64) via a return (13, 53) within the feed section (60) behind the prefeed pump (55).

12. Fuel injector according to claim 1, characterized in that the pressure intensifier (7) is integrated in the high-pressure storage space (4).

13. A fuel injection device according to claim 1, characterized in that the pressure intensifier (7) is integrated in the fuel injector (10).

14. Fuel injection device according to claim 1, characterized in that the pre-delivery pressure of the pre-delivery pump (55) is between 4 and 8 bar.

15. Fuel injection device according to claim 1, characterized in that a pressure change in the rear space (27) of the pressure booster (7, 52) causes a pressure change in the high pressure space (9) of the pressure booster (7, 52).