EP2105604A2 - Fuel injection system for a combustion engine - Google Patents

Abstract

The invention relates to a fuel injection system for an internal combustion engine, in particular for a diesel engine, with at least one working cylinder and at least one injector per cylinder for injecting fuel into each working cylinder, the injector a quantity valve (20) and one with the flow control valve (20) a first fuel line (40) connected to the injection nozzle (24). In this case, a pressure adjusting valve (22) is additionally provided, which is connected on the one hand to the first fuel line (40) and on the other hand to a fuel return (36), wherein the Standdruckeinstellventil (22) is designed such that this below a first switching pressure in the first fuel line (40), which is smaller than an opening pressure of the injection nozzle (24), in a first working position, the fuel return line (36) from the line (40) separates, at the first switching pressure and above the first switching pressure and below a second switching pressure, which is greater as the first switching pressure and smaller than the opening pressure of the injection nozzle (24), the fuel return (36) fluidly connected to the first fuel line (40) in a second working position, and at and above the second switching pressure in a third working position, the fuel return (36 ) abtre from the first fuel line (40) nnt.

Description

The invention relates to a fuel injection system for an internal combustion engine, in particular for a diesel engine, having at least one working cylinder and at least one injector per cylinder for injecting fuel into each working cylinder, the injector having a quantity valve and an injection nozzle connected to the quantity valve via a first fuel line , according to the preamble of claim 1.

Known injection systems have a strong dependence of the injection quantity on that of the preceding injection, which leads to emission and application problems as well as a reduced efficiency, especially with small injection quantities.

The invention is based on the object, an injection system of o.g. To improve the type of Absteuermengen and the beam conditioning and at the same time to achieve a lower dependence of the injected fuel amount of the pilot injection.

This object is achieved by a fuel injection system o.g. Art solved with the features characterized in claim 1. Advantageous embodiments of the invention are described in the further claims.

For this purpose, it is provided according to the invention in a fuel injection system of the type mentioned above, which is additionally connected to the first fuel line and on the other hand with a fuel return, the Standdruckeinstellventil is designed such that this below a first switching pressure in the first fuel line , which is smaller than an opening pressure of the injection nozzle, in a first working position separates the fuel return line, at the first switching pressure and above the first switching pressure and below a second switching pressure which is greater than the first switching pressure and smaller than the opening pressure of the injection nozzle , the fuel return fluidly connects to the first fuel line in a second working position, as well as at and above the second switching pressure in a third working position the fuel return from the first Kr separating off the fuel line.

This has the advantage that an injection system without Separationszeitempfindlichkeit and with reduced Absteuermengen with better jet preparation by the elimination of a seat throttle is available. The injection system of the invention achieves a lower application cost, a shortened overall length, a smaller Kraftstoffverteilrohrvolumen or rail volume (space) and lower control quantities. As a result, less drive line for the CR (common rail) pump is required and the efficiency improved, which also requires a CO ₂ advantage.

Conveniently, a fuel rail connected to the injector via a line (common rail) or fuel storage and a high-pressure pump connected to the fuel rail is provided, wherein the fuel return is connected to a fuel tank.

In a preferred embodiment, the standard pressure adjustment valve is designed as a 2/3-way valve.

The standard pressure adjusting valve has, for example, an axially displaceable piston depending on the pressure in the line in the three working positions, which abuts in the first and third working position on a sealing surface. Here, the standard pressure adjusting valve preferably has a spring element which acts on the piston in the direction of the first switching position with force.

In a preferred embodiment, an actuator for the flow control valve is designed as an electromagnet or piezoelement or magnetostrictive.

A controlled overflow from the first fuel line into the fuel return is achieved by the fact that the Standdruckeinstellventil connects in the second working position, the fuel return to the first fuel line via a throttle.

In an alternative embodiment, an opposed piston is provided with a pressure chamber axially to the injection nozzle such that the counter-piston exerts an axial force in the direction of the closed position of the injection nozzle at pressure in the pressure chamber. In this case, the pressure chamber of the counter-piston is preferably connected to the injector volume via a second fuel line.

In a preferred embodiment, the quantity valve is designed as a 2/2-way valve.

Conveniently, a fuel cooling device is provided in a fuel tank and / or in the fuel return.

Fig. 1

ein schematisches Schaltbild einer ersten bevorzugten Ausführungsform eines erfindungsgemäßen Kraftstoffeinspritzsystems,

Fig. 2

ein schematisches Schaltbild einer zweiten bevorzugten Ausführungsform eines erfindungsgemäßen Kraftstoffeinspritzsystems,

Fig. 3

ein Standdruckeinstellventil in Form eines 2/3-Wegeventils für ein erfindungsgemäßes Kraftstoffeinspritzsystem in schematischer Schnittansicht in einer Ausgangsstellung (erste Sperrstellung),

Fig. 4

das Standdruckeinstellventil gemäß Fig. 3 in Durchflussstellung mit Drossel,

Fig. 5

das Standdruckeinstellventil gemäß Fig. 3 in zweiter Sperrstellung,

Fig. 6

das Standdruckeinstellventil gemäß Fig. 3 in erster Sperrstellung in vergrößerter Darstellung und

Fig. 7

eine alternative Ausführungsform des Standdruckeinstellventil in schematischer Schnittansicht.

The invention will be explained in more detail below with reference to the drawing. This shows in

Fig. 1

1 is a schematic circuit diagram of a first preferred embodiment of a fuel injection system according to the invention,

Fig. 2

FIG. 2 is a schematic circuit diagram of a second preferred embodiment of a fuel injection system according to the invention, FIG.

Fig. 3

a state pressure adjusting valve in the form of a 2/3-way valve for a fuel injection system according to the invention in a schematic sectional view in an initial position (first blocking position),

Fig. 4

the pressure adjusting valve according to Fig. 3 in flow position with throttle,

Fig. 5

the pressure adjusting valve according to Fig. 3 in the second blocking position,

Fig. 6

the pressure adjusting valve according to Fig. 3 in the first blocking position in an enlarged view and

Fig. 7

an alternative embodiment of the standard pressure adjusting valve in a schematic sectional view.

In the Fig. 1 1, a preferred embodiment of an injection system according to the invention for an internal combustion engine, for example for a diesel engine, comprises a high-pressure pump 10 and a fuel distribution pipe or a rail 12 from which a line 14 with a throttle 16 branches off to an injector or engine cylinder. In the present case, only a 1-cylinder engine is shown for the sake of simplicity of illustration. The injector essentially comprises an injector volume 18, a quantity valve 20 in the form of a 2/2-way valve which is driven, for example, by a piezo element or an electromagnet (not shown), a pressure adjusting valve 22 in the form of a 2/3-way valve and an injection nozzle 24, with nozzle needle spring (passive nozzle). Farther The injection system includes a rail pressure sensor 26 connected to the fuel rail 12, a pressure regulating valve 28 regulating the pressure in the fuel rail 12, a fuel tank 30, and a drain line 28 connected to the pressure regulating valve 28, the fuel tank 30, the stem pressure adjusting valve 22, and the injector 24. Denoted at 34 is an electrical control for the flow control valve 20. A fuel line or return line 36 connects the fuel tank 30 to the pressure adjusting valve 22 and via the pressure control valve 28 to the Kraftstoffverteilrohr 12. For damping the pressure surges generated by the piston of the high-pressure pump 10 is located; between the rail 12 and the injector memory 18 at least one throttle 16. The throttle may be integrated into the injector or into the rail 12. The length of the line 14 between the rail 12 and the injector is the same for all cylinders. The injector memory 18 is formed generated by a hollow of the injector body. The injection quantity release takes place through the 2/2-way valve 20 (flow control valve). The 2/3-way valve 22 stabilizes the positive pressure between the injector 24 and the flow control valve 20. The leak oil flows, possibly through a radiator (not shown), via the leak oil line 32 and the fuel line 36 back to the fuel tank 30. The lines in the injector are as short as possible. A first line 40 connects the injector 24 to the flow control valve 20. A connection of the pressure adjusting valve 22 is connected to the first line 40. The quantity valve is acted upon by a spring 44 in the direction of the closed position with force.

The 2/3-way valve 22 has three positions, which in addition Fig. 3 to 5 are illustrated. In a first switching position according to Fig. 3 the 2/3-way valve 22 is closed. In a second switching position according to Fig. 4 connects the 2/3-way valve 22, the first line 40 to the return line 36 via a formed in the 2/3-way valve 22 throttle 46. In a third switching position according to Fig. 5 this connection between the first line 40 and the return line 36 is disconnected again. The 2/3-way valve 22 is designed such that a pressure applied via the first line 40 in the 2/3-way valve 22 switches between the aforementioned switching positions. Here, the first switching position according to Fig. 3 a starting position of the 2/3-way valve 22 at a pressure in the first line 40 below a first switching pressure. When the first switching pressure is exceeded and below a second switching pressure in the first line 40, the 2/3-way valve 22 changes to the second switching position according to Fig. 4 , wherein fuel flows via the throttle 46 from the line 40 into the return 36. When also the second switching pressure in the first line 40 is exceeded, the 2/3-way valve 22 finally changes in accordance with the third switching position Fig. 5 , so that the connection between the first line 40 and return 36 is closed again. Starting from a pressure above the second switching pressure in the first line 40 changes decreasing pressure accordingly, the 2/3-way valve 22 successively from the third switching position back to the second switching position and finally back to the first switching position. The 2/3-way valve 22 is designed such that the first switching pressure is far below the opening pressure of the injection nozzle 24 and the second switching pressure just below the opening pressure of the injection nozzle 24.

In Fig. 2 a second preferred embodiment of a fuel injection system according to the invention is shown, wherein like reference numerals have functionally identical parts as in Fig. 1 and 3 to 5 so that their explanation in the above description of the Fig. 1 and 3 to 5 is referenced. In addition to the first embodiment according to Fig. 1 includes the second embodiment according to Fig. 2 a counter-piston 38 at the injection nozzle 24. A space for the opposed piston 38 is connected via a second line 42 to the injector volume 18. This counter-piston 38 exerts an additional closing force on the injection nozzle 24.

Hereinafter, the operation of the fuel injection system according to the invention with reference to the first embodiment according to the Fig. 1 explained. However, this explanation applies analogously to the second embodiment according to the Fig. 2 ,

1. 1. Vor der Einspritzung:
   1. a. Die erste Leitung 40 zwischen Mengenventil 20 und Einspritzdüse 24 ist drucklos. Das 2/3-Wegeventil 22 ist geschlossen. Dies ist die Ausgangsstellung des 2/3-Wegeventil 22 gemäß Fig. 3.
   2. b. Das Mengenventil 20 öffnet aufgrund einer Betätigung durch beispielsweise einen Elektromagneten oder ein Piezoelement (nicht dargestellt).
   3. c. Der Druck in der Leitung 40 zwischen Mengenventil 20 und Einspritzdüse 24 steigt, bis er den Öffnungsdruck (erster Schaltdruck) für die 2. Schaltstufe des 2/3-Wegeventils 22 überschreitet und das 2/3-Wegeventils 22 wechselt zur 2. Schaltstellung "Durchfluss mit Drossel 46" (Fig. 4). ,
   4. d. Kraftstoff strömt über die Drossel 46 des 2/3-Wegeventils 22, wie in Fig. 4 dargestellt, in den Rücklauf 36 zum Kraftstofftank 30. Der Druck für die 2. Schaltstufe des 2/3-Wegeventils 22 liegt unter dem Öffnungsdruck der Einspritzdüse 24.
   5. e. Der Druck in der Leitung 40 zwischen Mengenventil 20 und Einspritzdüse 24 steigt weiter. Das 2/3-Wegeventil 22 wechselt bei Überschreiten eines vorbestimmten zweiten Schaltdruckes in der ersten Leitung 40 in die 3. Schaltstufe "zweite Sperrstellung" (Fig. 5). Es sperrt den Durchfluss in die Rücklaufleitung 36 erneut ab. Dieser zweite Schaltdruck ist bevorzugt etwas kleiner als der Öffnungsdruck der Einspritzdüse 24.
2. 2. Einspritzung:
   1. a. Der weiterhin durch das Mengenventil 20 tretende Kraftstoff hebt den Druck in der Leitung 40 zwischen Mengenventil 20 und Einspritzdüse 24 so weit an, dass der Öffnungsdruck der Einspritzdüse 24 überschritten wird und dementsprechend die Einspritzung beginnt.
   2. b. Da der freie Querschnitt des Mengenventils 20 deutlich größer (ca. 4-5 mal) als der der Einspritzdüse 24 ist, tritt keine merkliche Drosselung über das Mengenventil 20 auf. Der Druckverlust ist beispielsweise kleiner als 5% des Druckes in dem Rail 12.
   3. c. Die federbelastete Einspritzdüse 24 "schnappt" auf, d.h. kaum Nadeldrosselung. Die Nadel schaltet quasi digital von zu nach auf.
3. 3. Einspritzende:
   • a. Das Mengenventil 20 wird durch die Feder 44 geschlossen. Der Druck in der Leitung 40 zwischen Mengenventil 20 und Einspritzdüse 24 fällt sehr schnell ab.
   • b. Die Einspritzdüse 24 schließt, sobald ein Schließbeginndruck erreicht bzw. unterschritten wird.
   • c. Das 2/3-Wegeventil 22 bewegt sich in die Mittelstellung (Fig. 4). Über die Drossel 46 in dem 2/3-Wegeventil 22 fließt zusätzlich Kraftstoff aus der Leitung 40 in den Rücklauf 36 ab, so dass der Druckabfall in der Leitung 49 beschleunigt wird.
   • d. Die Einspritzdüse 24 schließt, wobei aufgrund des schnellen Druckabfalls in der ersten Leitung 40 während der Schließphase wenig Kraftstoff austritt. Daraus folgt eine gute Zerstäubung ohne Sitzdrosselung (siehe auch SAE 2003-01-0698). Die zum Mengenventil 20 rücklaufende Druckwelle aufgrund des Schließens der Einspritzdüse 24 wird über die Drossel 46 in dem 2/3-Wegeventil 22 abgebaut. Ein Nachspritzen der Einspritzdüse 24 wird dadurch funktionssicher vermieden.
   • e. Sobald der Standdruck (erster Schaltdruck) in der Leitung 40 zwischen Mengenventil 20 und Einspritzdüse 24 erreicht wird, schließt das 2/3-Wegeventil 22 und es bewegt sich in die Grundstellung zurück (Fig. 3). Der Standdruck bleibt erhalten.
4. 4. Folgende Einspritzungen:
   Wie oben, wobei jedoch die Leitung 40 bereits unter Standdruck steht und nicht mehr so weit vorgespannt werden muss. Das Öffnen des Mengenventils 20 bewirkt sofort ein Überschreiten des ersten Schaltdruckes in der Leitung 40 und dementsprechend ein Schalten des 2/3-Wegeventils 22 in die 2. Schaltstufe. Der restliche Ablauf wie unter Punkten 3. und 4 oben ist analog. Der Standdruck verhindert Kavitation und ein unbekanntes "Luftvolumen" in der Leitung. Weiterhin ergibt sich ein Wirkungsgradvorteil durch vorweggenommene Kraftstoffkompressibilität.

First injection:

1. 1. Before the injection:
   1. a. The first line 40 between flow control valve 20 and injector 24 is depressurized. The 2/3-way valve 22 is closed. This is the starting position of the 2/3-way valve 22 according to Fig. 3 ,
   2. b. The flow control valve 20 opens due to actuation by, for example, an electromagnet or a piezoelectric element (not shown).
   3. c. The pressure in the line 40 between flow control valve 20 and injector 24 increases until it exceeds the opening pressure (first switching pressure) for the 2nd switching stage of the 2/3-way valve 22 and the 2/3-way valve 22 changes to the second switching position "flow with throttle 46 "( Fig. 4 ). .
   4. d. Fuel flows via the throttle 46 of the 2/3-way valve 22, as in Fig. 4 shown, in the return line 36 to the fuel tank 30. The pressure for the 2nd switching stage of the 2/3-way valve 22 is below the opening pressure of the injection nozzle 24th
   5. e. The pressure in line 40 between flow control valve 20 and injector 24 continues to increase. The 2/3-way valve 22 changes when a predetermined second switching pressure in the first line 40 in the third switching stage "second Lock position "( Fig. 5 ). It blocks the flow in the return line 36 again. This second switching pressure is preferably slightly smaller than the opening pressure of the injection nozzle 24.
2. 2nd injection:
   1. a. The further passing through the flow control valve 20 fuel raises the pressure in the line 40 between flow control valve 20 and injector 24 so far that the opening pressure of the injector 24 is exceeded and, accordingly, the injection begins.
   2. b. Since the free cross section of the flow control valve 20 is significantly larger (about 4-5 times) than that of the injection nozzle 24, no appreciable throttling occurs via the flow control valve 20. For example, the pressure loss is less than 5% of the pressure in the rail 12.
   3. c. The spring-loaded injector 24 "snaps" on, ie hardly needle throttling. The needle switches from digital to digital.
3. 3rd injection end:
   • a. The flow control valve 20 is closed by the spring 44. The pressure in the line 40 between flow control valve 20 and injector 24 drops very quickly.
   • b. The injection nozzle 24 closes as soon as a closing start pressure is reached or fallen below.
   • c. The 2/3-way valve 22 moves to the middle position ( Fig. 4 ). In addition, fuel flows from the line 40 into the return line 36 via the throttle 46 in the 2/3-way valve 22, so that the pressure drop in the line 49 is accelerated.
   • d. The injector 24 closes, leaving little fuel due to the rapid pressure drop in the first conduit 40 during the closing phase. This results in a good atomization without seat throttling (see also SAE 2003-01-0698). The return to the flow valve 20 pressure wave due to the closing of the injector 24 is reduced via the throttle 46 in the 2/3-way valve 22. Injection of the injection nozzle 24 is thereby reliably avoided.
   • e. As soon as the stand pressure (first switching pressure) in the line 40 between the quantity valve 20 and the injection nozzle 24 is reached, the 2/3-way valve 22 closes and it moves back into the normal position (FIG. Fig. 3 ). The pressure remains.
4. 4. Following injections:
   As above, but the line 40 is already under pressure and no longer has to be biased so far. The opening of the quantity valve 20 immediately causes an exceeding the first switching pressure in the line 40 and, accordingly, a switching of the 2/3-way valve 22 in the second switching stage. The rest of the procedure as under points 3 and 4 above is analog. The stand pressure prevents cavitation and an unknown "air volume" in the pipe. Furthermore, there is an efficiency advantage through anticipated fuel compressibility.

Small quantities (optional):

In order to influence the course of injection or to improve the metering capability for very small quantities, the actuator which actuates the quantity valve 20 is optionally activated in such a way that the quantity valve 20 executes only a partial stroke. The injection rate is represented by throttling via the flow control valve 20. Since it is a 2/2-way valve 20, this throttling does not lead to a reduction of the volumetric efficiency. Compared to a seat throttling in the injection nozzle, as provided for example in conventional, known CR (common rail) systems, the mixture forming quality is improved. The seat throttling leads to cavitation before and in the nozzle holes and thus to an irregular or uneven distribution of the fuel to the individual injection holes.

In the second embodiment according to Fig. 2 acts a constantly biased by the pressure in the injector memory 18 piston 38 in addition to the back of the nozzle needle 24 a. As a result, the nozzle opening and closing pressure increases with the rail pressure. This allows an additional degree of freedom in the tuning of the injection system. The function corresponds to that of the first embodiment according to FIG Fig. 1 , Like previously described.

The flow control valve 20 is 100% static pressure balanced to minimize the actuating forces. The effective cross section of the flow control valve 20 is, for example 4 times, preferably 4 1/2 times as large as that of the injection nozzle 24, so that no appreciable pressure loss via the flow control valve 20 occurs. The 2/3-way valve 22 is in the starting position ( Fig. 3 ) a seat valve. The 2nd switch position and the 3rd switch position are sealed via gaps (slide valve), as shown 4 and 5 seen. The seat seal in the starting position ( Fig. 3 ) allows a secure holding of the stand pressure, since no leakage occurs over the closed valve 22. The passing through the valve 22 amount can be in the embodiment according to Fig. 6 over the length of a plug 48, which releases a throttle cross-section (throttle edge) set. Alternatively, this can be done by adjusting the (transverse) bore diameter in the valve spool.

An enlargement of the pressure spread between the first switching positions ( Fig. 3 ) and the third switch position ( Fig. 5 ) can be achieved by placing the seat of the poppet valve on a larger diameter than the pusher diameter, as in Fig. 7 shown. With 50, the sealing diameter for the initial position (first switching position) is analog Fig. 3 designated. With 52, the sealing diameter for the third switching position is analog Fig. 5 designated. The pressures, and thus the required spring forces, behave like the diameters associated surfaces on which is sealed. The line pressure acting on the upper face shifts the valve spool. The spring force and the spring stiffness, together with the valve travel determine the pressures for the two switching stages. The connection of the branch line to the 2/3-way valve 22 is located in the immediate vicinity of the flow control valve 20 to "level" or to absorb the returning pressure wave after closing the injector 24 there.

This results in a smaller amount of scatter by direct release of the injection quantity. The injection quantity is metered directly via the quantity valve 20. This eliminates the errors from the timing chain of a conventional injector. In these, a pilot valve is moved via an electromagnet or a piezo actuator. This in turn relieves the back of the injection needle. This lifts off the needle seat and the injection begins. In order to stop the injection, the pilot valve is closed, which leads to a pressure build-up on the back of the injection needle and the initiation of the closing movement.

1. 1. Die gesamte dem System entzogenen Menge (Absteuer- und Einspritzmenge) ist minimiert, da damit die Anregung der Druckwellen minimiert wird.
2. 2. Die Leitungslänge zwischen dem Mengenventil bzw. Vorsteuerventil 20 ist minimiert, damit die Störung möglichst hochfrequent ist. Je größer die Frequenz der Schwingung, desto größer wird die Dämpfung, d.h. die Zeit, nach der die Störung abgeklungen ist, verkürzt sich.
3. 3. Die Druckwelle wird nah am Entstehungspunkt gedämpft. Die Dämpfung erfolgt bei dem erfindungsgemäßen Kraftstoffeinspritzsystem durch die kombinierte Anwendung eines Volumens (Injektorspeicher 18) und der Drossel 46.

Hereinafter, the damping or prevention of the pressure wave effect is explained in more detail on the injection quantity. The feedforward control, which is usually carried out with 2/2-way valves, means that the amount of engine spill is significant. For small injection quantities, for example preinjections of 1 mg, the amount of exhaust is a multiple of the injection quantity. The Absteuermenge is withdrawn, just like the injection quantity, the injector and thus the fuel rail. This loss of volume triggers a strong pressure wave. This pressure wave in turn leads to the effect of the changing injection quantity as a function of the distance between two injections. In order to minimize the effect of the pressure waves, the following measures are taken in the present invention:

1. 1. The total amount withdrawn from the system (spill and injection quantity) is minimized because it minimizes the excitation of the pressure waves.
2. 2. The line length between the quantity valve or pilot valve 20 is minimized, so that the disturbance is as high as possible. The greater the frequency of the oscillation, the greater the attenuation, ie the time after which the disturbance has subsided, is shortened.
3. 3. The pressure wave is damped close to the point of origin. The damping takes place in the fuel injection system according to the invention by the combined use of a volume (injector memory 18) and the throttle 46th

By combining the three aforementioned measures, the pressure wave is effectively calmed, which minimizes the quantity effect on the individual injections.

Furthermore, there are efficiency advantages, ie lower Absteuermengen. The injection quantity corresponds to the amount taken from the reservoir, taking into account the small amount that escapes during pressure build-up and pressure reduction by the 2/3-way valve 22. This Absteuermenge is independent of the injection quantity, it is easily influenced by the accumulator pressure. The Absteuermenge is small (<2mm ³ ).

The operational safety is increased by the 2/3-way valve 22, since small leaks (leaking flow control valve) by shifting the 2/3-way valve 22 in the second switching position ( Fig. 4 ) are intercepted without it comes to a permanent injection.

• a. Innere Leckage über 2/3-Wegeventil
• b. Einspritzdauer bzw. Spritzverzug über Düsennadel bzw. 2/3-Wegeventilsensierung

By a distance / speed measurement of the needle of the 2/3-way valve 22 and / or the nozzle needle 24 can be generated for the OBD useful feedback on the state of the injection system:

• a. Internal leakage via 2/3-way valve
• b. Injection time or spraying delay via nozzle needle or 2/3-way valve sensing

It is further achieved with a length of <130 mm and <100 mm, a length-saving design and in particular for 2-V-engines (inclined installation) and MSV concepts (MSV = M o s v tufen erbrennung). The injector memory 18 is dimensioned large and oriented in the direction of the injector needle axis. The actuator is roughly oriented in the direction of the injector needle axis (on nozzle). The injector memory 18 and the high-pressure port are arranged laterally. The present invention can also be used as injector control for the CRID. In this case, the injector memory 18 is replaced by the pressure booster of the CRID.

LIST OF REFERENCE NUMBERS

10

high pressure pump

12

Fuel distribution pipe or a rail

14

management

16

throttle

18

injector volume

20

Quantity valve / 2/2-way valve

22

Pressure adjusting valve / 3/2-way valve

24

injection

26

Rail pressure sensor

28

Pressure control valve

30

Fuel tank

32

Drain line

34

Control for the quantity valve 20

36

Fuel line / return line

38

opposed piston

40

first fuel line

42

second fuel line

44

feather

46

Throttle in 2/3-way valve 22

48

Plug

50

Sealing diameter for the initial position (first switching position)

52

Sealing diameter for the third switching position

Claims (12)

Fuel injection system for an internal combustion engine, in particular for a diesel engine, having at least one working cylinder and at least one injector per working cylinder for injecting fuel into a respective working cylinder, wherein the injector comprises a quantity valve (20) and one with the quantity valve (20) via a first fuel line ( 40) associated injector (24), characterized in that in addition a Standdruckeinstellventil (22) is provided which is connected on the one hand to the first fuel line (40) and on the other hand with a fuel return (36), wherein the Standdruckeinstellventil (22) is formed is that this below a first switching pressure in the first fuel line (40), which is smaller than an opening pressure of the injection nozzle (24), in a first working position, the fuel return line (36) from the line (40) separates, at the first switching pressure and above the first switching pressure and u nterhalb a second switching pressure, which is greater than the first switching pressure and less than the opening pressure of the injection nozzle (24), the fuel return line (36) fluidly connected to the first fuel line (40) in a second working position, and at and above the second switching pressure in a third working position, the fuel return (36) from the first fuel line (40) separates. Fuel injection system according to claim 1, characterized in that with the injector via a line (14) connected fuel rail (12) (common rail) or fuel storage and a with the fuel rail (12) connected high-pressure pump (10) is provided. Fuel injection system according to at least one of the preceding claims, characterized in that the fuel return (36) is connected to a fuel tank (30). Fuel injection system according to at least one of the preceding claims, characterized in that the foot pressure adjusting valve (22) is designed as a 2/3-way valve. Fuel injection system according to at least one of the preceding claims, characterized in that the standard pressure adjusting valve (22) has an axially displaceable in dependence on the pressure in the line (40) in the three working positions piston which abuts in the first and the third working position on a sealing surface , Fuel injection system according to claim 5, characterized in that the standard pressure adjusting valve (22) has a spring element which acts on the piston in the direction of the first switching position with force. Fuel injection system according to at least one of the preceding claims, characterized in that an actuator for the flow control valve (20) is designed as an electromagnet or piezo element or magnetorestrictive. Fuel injection system according to at least one of the preceding claims, characterized in that in the second working position , the standard pressure adjusting valve (22) connects the fuel return line (36) to the first fuel line (40) via a throttle (46). Fuel injection system according to at least one of the preceding claims, characterized in that an opposed piston (38) with a pressure chamber axially to the injection nozzle (24) is provided such that the counter-piston (38) at pressure in the pressure chamber, an axial force in the direction of the closed position of the injection nozzle ( 24). Fuel injection system according to claim 9, characterized in that the pressure chamber of the counter-piston (38) via a second fuel line (42) with the injector volume (18) is connected. Fuel injection system according to at least one of the preceding claims, characterized in that the flow control valve (20) is designed as a 2/2-way valve. Fuel injection system according to at least one of the preceding claims, characterized in that a fuel cooling device is provided in a fuel tank (30) and / or in the fuel return (36).

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