WO2006114293A1

WO2006114293A1 - Fuel injection system for internal combustion engines

Info

Publication number: WO2006114293A1
Application number: PCT/EP2006/003855
Authority: WO
Inventors: Hans-Joachim Koch; Horst Ressel; Wolfgang Scheibe; Günther SCHRÖDLEN; Holmer Slocinski; Norbert Walter; Thorsten Wolf
Original assignee: L'orange Gmbh
Priority date: 2005-04-27
Filing date: 2006-04-26
Publication date: 2006-11-02
Also published as: EP1875068B1; EP1875068A1; DE502006009350D1; DE102005020012A1; ATE506533T1

Abstract

Disclosed is a fuel injector for internal combustion engines, in which a cross section (21) of an outlet is unblocked to establish a connection between injection pumps (1) and an injection nozzle (2) at the beginning of the pressure reduction process introducing the end of the injection phase such that the compressed fuel volume can be discharged quickly, thus allowing the pressure to be reduced rapidly.

Description

Fuel injection system for internal combustion engines

The invention relates to a fuel injection system for internal combustion engines according to the preamble of claim 1.

Fuel injection systems are widely known and, in particular in connection with very high injection pressures, in principle allow a very fine atomization of the injected fuel, which is aimed at in terms of comfort, performance and emission aspects. In contrast with intermittent pressure build-up, as it results, for example, when using piston pumps, supplied via the injection injectors and pressure-dependent applied with respect to the stroke position of their nozzle needle, the delivery pressure of the injected injector each of the injector fuel varies between one compared to the high Einspritzdruckniveau quite low initial level, and it must be overcome at the beginning and end of an injection each of the pressure difference between the output pressure level and injection pressure level, in this transition region, as soon as a corresponding pressure build-up is reached, the nozzle needle is raised and the injection is released or the Nozzle needle drops and the injection stops. Since the pressure level at the beginning and at the end of the injection is well below the operating injection pressure level, there is also a deterioration in fuel preparation, which is disadvantageous in particular when a respective injection is terminated.

One tries to counter this by using as steep a pressure increase or Pressure drops aimed at, such efforts on the pump side certain limits are already set by the fact that a sudden Absteuerung the fuel delivery at the respective, an injection associated pump stroke is practically impossible.

In order nevertheless to achieve as sudden as possible closing of the pressurized against elastic support in its open position raised nozzle needle at the end of the injection only gradually decreasing discharge pressure, are known from the prior art various solutions, in this phase, still relatively high discharge pressure for additional loading of Use nozzle needle in the closing direction, so as to increase the closing force and the phase of the injection - at the highest possible injection pressure level - to shorten (DE 23 01 419 Al, DE 25 00 644 Al, WO 2004/074671 Al).

DE 27 04 688 C2, and also the DE 27 60 403 C2, provide for this purpose, to provide in the bypass to the nozzle needle seat tapered delivery line working in the manner of a pressure compensator valve assembly having two each connected to the delivery line and throttling interconnected chambers , In the inlet to one of the chambers, which operates as a pressure accumulator, a counter to the inlet spring-loaded blocking check valve is arranged in the counter chamber, a control piston which is spring-loaded on its the throttling connection to the other chamber absteuernden blocking position and in this blocking position also shuts off a branch , which runs over a pressure chamber located at the back to the nozzle needle and throttled to the low pressure side opens. If the pressure in the delivery line drops, then the storage chamber is shut off by pressure against the delivery line via the check valve, whereas in the counter chamber Because of the open connection to the delivery line, the pressure drops, so that the piston - against its resilient support to its locked position - is moved and releases the connection to the branch. This results, in contrast to the still given pressurization of the nozzle needle in the opening direction due to the pending in the delivery line, an additional pressurization of the nozzle needle in the closing direction, with the aim of shortening the closing time and the respective injection, starting from a very high injection pressure level to end abruptly.

Furthermore, a fuel injection system of the type mentioned in the introduction from US Pat. No. 5,647,536 A is known, in which the most immediate possible termination of the respective injection is to be achieved by a rapid reduction of the fuel pressure acting on the nozzle needle in the opening direction. For this purpose, it is provided to release a short-circuit connection of the delivery line discharging onto the nozzle needle seat to an outlet cross-section in the discharge area of the injection when the delivery pressure drops from the injection pressure to an initial level. Starting from a provided with the spray openings, against the delivery line in the closed position of the nozzle needle on the nozzle needle seat demarcated blind hole area of the nozzle needle receiving nozzle body for this purpose, the nozzle needle is provided with an outgoing from its tip central bore. A throttle path connects to this bore, which terminates in the region of a shoulder of the nozzle needle, which limits the opening path of the nozzle needle as a stop shoulder and covers the outlet cross section of the throttle section to the low pressure side in the opening position of the nozzle needle. The outlet cross-section is released only at the end of injection at the beginning of the closing movement of the nozzle needle. The pressure drop at Absteuern the injection pump has a significant delay in such a solution quite apart from the fact that the central, the Düsennadei penetrating bore accommodates a small volume of fuel, although it is discharged on closing the nozzle needle on the blind hole area and thus leads to unwanted dripping.

The invention is also based on the object to quickly lower the nozzle needle acting in the opening direction pressure against the end of injection to end the injection as suddenly as possible.

This is achieved in a fuel injection system by the features of claim 1, which make it possible at the beginning of the injection end initiating pressure reduction from the injection pressure level to the initial level, an outlet cross-section between the injection pump and the injection injector, which quickly drains the compressed fuel volume and thus allows a rapid pressure drop without interfering with the pump structure and / or in the Injektoraufbau as such and without being bound by the relevant, pump-side limits with respect to an almost sudden pressure drop from the injection pressure level to the output pressure level.

The threshold value to be sensed, which is used starting from the injection pressure level in the Absteuerbereich the injection as a trigger for the control of the outlet cross section to the feed line to direct fuel from the feed line, is set in the invention to a size that as a difference to the injection pressure level above is associated with a delivery pressure reduction pressure fluctuations in normal operation, wherein the inventively provided, designed as a valve assembly sensor device designed such that only when pressure is reduced opening of the outflow cross section is possible.

The delivery pressure and spring-loaded admission of the valve member to its locking positions is tuned to the valve member in the opposite direction loading force storage that the storage power only prevails when the threshold is exceeded, this being achieved in that the bias of the energy storage on the Supply pressure is limited to a threshold value corresponding to the threshold value and the bias can only follow the reduced pressure of the valve member by the throttling in a time-delayed manner. The resulting equilibrium disturbance is used to control the outlet cross-section, so that a reversal of the valve member in the shut-off automatically occurs as soon as the biasing force of the energy accumulator is reduced.

In the context of the invention, the energy accumulator can also be formed by a hydraulic spring, since only very small adjustment paths are necessary and since the pressure conditions also make it possible to use the elastic behavior which is compressible at high pressures.

In the context of the invention, in addition, the stroke mobility of the nozzle needle between the closing and the open position can be used to influence the release time of the connection between the delivery line and the valve member or energy storage, which is particularly useful to the pressurization of the fuel storage opposite to initiate the pressurization of the valve member delayed. In a further embodiment of the invention, the fuel flowing through the outlet cross section from the delivery line fuel can be used to additionally apply the nozzle needle in the closing direction, so that according to the invention on the one hand reduces the lifting force dependent on the delivery pressure, acting on the nozzle needle in the opening direction and on the other hand acting in the opposite direction Closing force is increased.

Further details and features of the invention will become apparent from the claims. Furthermore, the invention will be explained in more detail below by exemplary embodiments. Show it:

Fig. 1 to 3

Schematic arrangements of a fuel injection system for internal combustion engines having a fuel injection injector and a connected thereto via a delivery line pressure source, the fuel injector is fed intermittently fuel, wherein the pressure source is formed in the embodiment by a conventional working with control edges reciprocating single-injection pump and wherein can be taken over the pressure curve of the pump side conveyed and fed via the feed line to the injection injector fuel via valve assemblies, which are provided connected to the delivery line and are controllable via the depending on delivery pressure in the delivery line outlet cross-sections to the delivery line,

4 is a schematic sectional view of a first embodiment of such a valve arrangement, Fig. 5 to 7 in turn schematically, a further embodiment of such a valve arrangement, and

8 and 9 an embodiment in which the valve assembly is structurally integrated into the fuel injection injector, wherein as a valve assembly such as is shown, for example, as shown and explained with reference to FIGS. 5 to 7.

1 to 3 illustrate a fuel injection system for internal combustion engines, which is limited to what is essential for understanding elements of the system known in the basic structure, namely an injection pump 1 and an injection injector 2, the fuel from the pump 1 via a feed line 3 fuel is supplied. As a fuel injection pump 1, a known piston pump is provided, which feeds the fuel exceptionally intermittently under high pressure injection injector 2, wherein the funded by the pump at each stroke amount of fuel through the interaction of piston-side control edges 4 provided on the cylinder side supply openings, as in the 5 indicated, controlled. Via the delivery line 3, the high-pressure fuel is supplied to the injector 2, which in turn has a nozzle needle 6 which shuts off injection openings in its closed position and which is elastically supported on its closed position, which is illustrated here via the closing spring 7. From its closed position, the nozzle needle 6 is pressurized in response to the pressure of the supplied via the feed line 3 fuel in a the injection openings releasing opening position against the elastic support via the spring 7 to raise. With a view to the best possible atomization of the fuel to be injected not only worked with very high delivery pressures, ranging up to the range of 1800 bar and beyond, but it is also sought for the injection that it starts as suddenly as possible and ends, what a As steep as possible pressure rise from the given in the system output pressure to the injection pressure and in particular a corresponding steep pressure drop at the injection end conditional. This in order to avoid as far as possible injection phases in the region of the opening and closing stroke of the nozzle needle, in which the full injection pressure is not or no longer available and accordingly also a worse fuel atomization takes place, which is particularly critical in the closing phase, as the combustion conditions due the already low-oxygen combustion chamber atmosphere in this phase are already deteriorated. It is therefore not only important that via the delivery line 3, which extends in the injection injector 2 via the channel 8 to the seat of the nozzle needle 6, the nozzle needle 6 is pressurized as suddenly as possible in the stroke direction in the respective injection cycle, but also that this Pressurization begins and ends as abruptly as possible. On the pump side, this can only be achieved to a limited extent, in particular when the respective delivery stroke is being controlled, since pressure jumps associated therewith are difficult to control, both constructively and from the point of view of the vapor pressure undershooting and resulting cavitation problems. In addition, due to the outgoing from the pump 1 and to the seat of the nozzle needle 6 running conveyor line 3, a storage volume due to the very high pressures, despite the pressure drop towards the end of the injection by closing the nozzle needle, a sudden pressure reduction and a sudden closing of the nozzle needle hardly makes possible. It also exists when closing the nozzle needle because of at Closing pending pressure the risk of uner ^¬ desired post-injections, inter alia, due to pressure fluctuations.

In view of the rudimentary and manifold known problems of such injection systems, the invention provides measures against the injection end to achieve a sudden reduction of the delivery pressure by accessing the delivery line 3 by, upon sensing the taking place at the end of the pressure drop, an outlet cross-section to the delivery line is released, which - in addition to the conventional injection system - allows the realization of the pressure reduction. For this purpose, a valve arrangement 9 is provided, which takes over the function of a sensor valve, is sensed by the connection to the delivery line 3 taking place against the end of the injection pressure drop from the injection pressure level to the initial level, such that when a threshold value is exceeded, an outlet cross-section to the delivery line. 3 is released.

The valve arrangement 9 can switch the connection of the delivery line 3, as indicated in the diagram in FIG. 1, to a tank 10 and / or to a buffer volume, wherein, as indicated in FIG. 2, this also takes place with the interposition of a pressure holding valve 11 can.

3 shows a further solution, by which not only the delivery line 3 removed delivery volume can be reduced via the valve assembly 9, but this volume can also be used via a cross-connection in the valve assembly 9 for injection injector 2, the nozzle needle 6 in addition to load for support via the closing spring 12 in the direction of the closed position by a corresponding, provided on the back of the nozzle needle 6 Pressure chamber is acted upon. The pressure chamber, here marked 13 be ^¬ , may be formed by the spring chamber, which is limited to the nozzle needle 6 through a piston, wherein the closing spring 12 may also be supported against this piston. However, it is also within the scope of the invention to provide the pressure chamber separated from the closing spring 7 and to use the delimitation of the pressure chamber against the closing spring 7 as support for the closing spring, via which the closing dead stress can be varied by way of the pressure, wherein the piston additionally acts against the nozzle needle 6 may be stop limited in its displacement.

4 and 5 to 7, wherein FIGS. 4 and 5 to 7, in addition to the schematic representations according to FIGS. 1 to 3, the valve arrangement 9 in a bypass arrangement connected in parallel to the conveying line 3 show.

Based on the delivery line 3 and indicated by the arrows 17 flow direction, the valve assembly 9 line connections 18 and 19 to the delivery line 3, via the line connection 18, the inlet takes place on a valve member 20 which overrides an outlet cross-section 21 and the closed position to Outlet section 21 spring and delivery pressure is loaded. The spring load is via a spring 22 which is supported against the valve member 20 and against a piston member 23, wherein the piston member 23 forms a receiving chamber for the spring 22 and in turn wegbegrenzt is supported against the valve member 20 in the opening direction, that is against the Spring 22 and the piston member 23 is aufzustoßen. The valve member 20 is designed in the embodiment as a valve with a conical seat, but can also be designed as a plunger and can in turn, be acted upon by a support 24 via a support 24 in the direction of its open position.

The energy accumulator 25 is formed by a lying in a spring chamber 26 spring element 27 as a guard spring, which is designed as a helical spring and end against end pieces 28, 29 is supported, of which the end piece 28, the support 24 acts. The opposite end piece 29 is supported against a piston 30, which runs under delimitation of a pressure chamber 31 in a guide. On the pressure chamber 31 opens opposite to the end piece 29 of the line connection 19 via a throttle 32 and / or, which is not shown here, a blocking in the direction of the delivery line 3 check valve. The supported against the spring element 27 tail

29 is in the direction of compression of the spring element, wegbegrenzt via a stop 33, displaced and is moved with increasing pressure in the direction of the stop 33. Since opposite the valve member 20 is also pressurized and based on an equal pressurization of the piston

30 and the valve member 20 by the design of the surfaces and the vote of the springs, the closed position of the valve member 20 is ensured on the one hand on the stop-limited, pressure-dependent displacement of the piston 30, a threshold for the pressure-dependent increase in the voltage of the spring element 27 given, but on the other hand also defines this threshold, when the valve member 20 is displaced from the energy storage 25 in its open position at pressure drop.

In the context of the invention, if this is to be realized in the respectively desired surface ratios, the end piece 29 is designed and guided such that it assumes the function of the piston 30, in which case the end piece 29 delimits the pressure chamber, onto which the line connection 19, like described above, via the throttle 32 and / or opens in the direction of the feed line 3 blocking check valve.

Although a pressure reduction in the delivery line results in an immediate reduction of the pressurization of the valve member 20, the pressure in the pressure chamber 31 is initially held via the throttle 32 and / or a corresponding non-return valve and can only be adapted to the pressure in the delivery line 3 with a delay. As a result, the valve member 20 is displaced over the support 24 and forced into its open position in which the outlet cross section 21 is controlled, so that a short-circuit connection between the outlet cross-section 21 and the delivery line 3 is briefly connected via the fuel can escape from the delivery line via the outlet cross section 21. After approximation of the pressure applied on both sides, the valve member 20 returns to its original position and it is the outlet section 21 again locked. With regard to the functions mentioned, it should be noted that the travel paths of both the valve member 20 and the piston 30 are very small, for example in the range of one millimeter, and that pressure changes in a closed system can be achieved via only small changes in the volume of the pressure medium , corresponding to the low pressure-dependent compressibility of liquid, incompressible media such as fuel.

Fig. 5 to 7 show a further embodiment of the valve assembly 9, wherein as a force storage 34 now a hydraulic spring is provided. The changes in the construction of the valve arrangement 9 according to FIGS. 5 to 7 are essentially limited to changes which, due to the other type of force accumulator 34, compared to the design according to FIG. are wrong. From the feed line 3 line connections 35, 36 are branched off, of which the line connection 35 opens onto a chamber 37 which can be shut off via the valve member 38 against the outlet cross-section 21. The valve member 38, which in turn may be formed as a diving or seat valve, is acted upon by its illustrated closed position via a arranged in the chamber 37 spring 39 and also pressure-dependent according to the given in line 3 delivery pressure. In the opposite direction, the valve member 38 is supported via a support 40 against the energy accumulator 34, which is designed in a manner not shown as a hydraulic spring. The energy accumulator 34 communicates via a throttle / check valve arrangement 41 with the line connection 36, wherein the inflow to the fuel accumulator 34, as shown in FIG. 6, takes place via a check valve 42 and a throttle bore 43 as a first throttle member. The check valve 42 is formed by a valve plate 45 loaded on the blocking position via a spring 44, which provides a throttle bore 46 as a second throttle member, wherein the first throttle member forming throttle bore 43 has a larger cross-section than the second throttle member forming throttle bore 46 in the valve plate 45, which is loaded via the spring 44 to its blocking position to the line connection 36. Expediently, the spring chamber 47 accommodating the spring 44 forms a through connection between the line connection 36 and the hydraulic spring forming the force accumulator 34, via which the support 40 can be adjusted in dependence on the pressure.

In the illustrated starting position, as in the embodiment according to FIG. 4, the valve member 38 is in its position blocking the passage between the delivery line 3 and the outlet cross section 21. The valve member 38 and the support 40 abut each other, the pressure and spring-dependent Actuation of the valve member 38 in the direction of the closed position is greater than the force exerted on the valve member 38 via the force accumulator 34, wherein the closed position for the valve member 38 at the same time forms its displacement in the direction of the energy storage 34 limiting stop position. If there is a pressure drop with respect to the delivery pressure in the delivery line 3, as occurs in trouble-free operation of the fuel injection system in size, regardless of all pressure fluctuations, only in the Absteuerbereich the injection, a threshold is set on the valve assembly, in which via the valve member 38 a short-circuit connection between the delivery line 3 and the outlet cross section 21 is connected, which runs over the valve member 38. This is due to the fact that the force accumulator 34 is charged with a pressure corresponding to the injection pressure level given in the starting position. The pressure drop to be sensed results in a decrease in the pressure-dependent application force for the valve member 38 in the direction of its closed position. The energy accumulator 34 rushes with respect to the pressure reduction, however, because via the throttle bore 46 as a second throttle member only a delayed pressure reduction is possible, so that the force exerted on the valve member 38 via the force accumulator 34 in the opening direction force is greater than that defined relative to the threshold low pressure, so that the short-circuit connection is briefly pushed open.

FIG. 7 shows an expedient seat configuration for the valve member 38 in the inlet on the outlet cross-section 21 and illustrates that the size of the pressure-side loading surface of the valve member in FIG. 2 is determined by the angle between the closing cone 65 of the valve member 38 and the angle of the housing-side seat cone 66 Ratio can be matched to the energy storage 34. 8 and 9 illustrate a valve arrangement 9, which corresponds in its functional structure that of FIG. 5 to 7, which is why the same reference numerals are used in this regard as in the embodiment of FIG. 5 to 7 and reference is made to the statements there. Due to the integration into the injection injector 2, a division into two mutually parallel bore regions 48, 49 is expedient for space reasons. The nozzle needle 6 is arranged and guided in an end containing the injection holes nozzle neck 64, which is braced via an intermediate plate 50 against the housing part 51, to which a further housing part 53 connects, which receives the nozzle needle 6 acting in the closing direction closing spring 54. Starting from the connection plane of the intermediate plate 50 to the nozzle neck 49, the bores 48 and 49 extend, which are connected at their remote from the intermediate plate 50 end, as indicated only, via a channel 56 and in its the intermediate plate 50 associated portion of the throttle Receive or check assembly 41 and the valve member 38, wherein the intermediate plate 50 in the overlap region to the bores 48 and 49, the line connections 35, 36 in Fig. 5 corresponding line connections 57, 58 open, with the pressure shoulder 59 of the nozzle needle 6 enclosing Pressure chamber 60 are in communication.

Here, the channel 57 opens in the overlap region to the guide 61 for the nozzle needle 6 on the corresponding guide bore 62, based on the closed position of the nozzle needle 6 such that when lifting the nozzle needle 6 of the channel 57 with the pressure chamber 60 in an open Connection passes, which is again deactivated when closing the nozzle needle 6. As a result, it is possible to achieve a delayed application of the energy store 34 in relation to the pressure build-up. which is arranged in the bore 49 opposite to the valve member 38 and cooperates with this in the manner described in FIG. 5 way. About the valve member 38, the outlet cross section 21 is controlled, which is assigned to a channel 63, which opens to a back space to the nozzle needle 6 and in the sense of the embodiment of FIG. 3, the nozzle needle superimposed to the action of the closing spring 54 pressurized in the closing direction. Thus, a delayed pressure build-up in the initial phase of the injection can be achieved for the energy accumulator 34, which may be advantageous to avoid bursting of the valve member by pressure fluctuations in the initial phase of the injection in the construction of the nozzle needle opening pressure.

Claims

claims

1. Fuel injection system for internal combustion engines with a fuel injection injector, the fuel via a delivery line with abstätzendem and in the Absteuerbereich the injection from the injection pressure level to a starting level dropping discharge pressure is supplied and having a nozzle needle in the direction of their Sitzseiti- ge closed position with overlap to at least one injection opening elastically supported and adjustable in the opposite direction, conveying pressure-dependent loading in the injection opening releasing opening position is adjustable, wherein in the Absteuerbereich the injection a decrease in the delivery pressure from the injection pressure level to a predetermined threshold value sensed via a valve assembly and a short End connection is released from the out on the nozzle needle seat delivery line to an outlet cross-section, characterized in that the valve assembly (9) in a bypass to the F is arranged and a on both sides of the delivery pressure dependent acted upon valve member (20; 38) which overrides the outlet cross section (21) and which is delimited to its outlet position in one direction by spring pressure and spring loading and in the opposite direction by an energy accumulator (25, 34), the delivery pressure dependent biased pressure-maintaining with the delivery line (3 ), such that the valve member (20; 38) releases the outlet cross-section (21) when the delivery pressure falls above the threshold value in the discharge region of the injection.

2. Fuel injection system according to claim 1, characterized in that upon release of the outlet cross-section (21) via the valve member (20, 38) via the valve member (20, 38) running short-circuit connection between the feed line (3) and the outlet cross-section (21 ) is connected, which runs under reduction of the delivery pressure and the pressurization of the valve member (20; 38) in the direction of its blocking position via the valve member (20; 38).

3. Fuel injection system according to claim 1 or 2, characterized in that the valve arrangement (9) in the injection injector (2) is integrated.

4. Fuel injection system according to one of claims 1 to 3, characterized in that the valve member (20) designed as a seat valve and the

Locking spring (22) is arranged in a spring chamber.

5. Fuel injection system according to one of claims 1 to 4, characterized in that the energy accumulator (25) is formed by a spring accumulator.

6. Fuel injection system according to claim 5, characterized in that the spring accumulator (25) has a spring element (27) as a pressure spring, which is to be tensioned via a delivery pressure to be acted upon end piece (29).

7. Fuel injection system according to claim 6, characterized in that the end piece (29) is guided in a spring element (27) as a pressure spring receiving spring chamber (26) and that a piston (30), or designed as a piston and guided tail (29), a pressure chamber (31) delimits, which is connected to the delivery line (3) pressure-retaining.

8. Fuel injection system according to claim 7, characterized in that in the supply line from the delivery line (3) to the pressure chamber (31) as a pressure-retaining element, a throttle (32) is provided.

9. Fuel injection system according to claim 7 or 8, characterized in that in the line section (19) from the feed line (3) to the pressure chamber (31) in the direction of the feed line (3) blocking check valve is provided.

10. Fuel injection system according to one of claims 7 to 10, characterized in that the displacement of the pressure piston provided as the end piece (29) in the clamping direction of the spring element (27) provided as a pressure spring is stop-limited.

11. Fuel injection system according to claim 5, characterized in that the energy accumulator (34) is formed by a hydraulic spring.

12. Fuel injection system according to claim 11, characterized in that in that the hydraulic spring has a spring volume which is supported on the valve member.

13. Fuel injection system according to claim 11 or 12, characterized in that the spring volume of the hydraulic spring via an inlet throttle (throttle bore 43) is connected to the delivery line.

14, fuel injection system according to claim 13, characterized in that in the inlet from the feed line (3) to the Zulaufdross- sel (throttle bore 43) against the delivery line (3) blocking check valve (42) is provided.

15. Fuel injection system according to claim 14, characterized in that the check valve (42) with a return throttle (throttle bore 46) is provided.

16. Fuel injection system according to claim 15, characterized in that the return throttle is formed by a in a valve plate (45) provided throttle bore (46) and that the valve plate (45) is resiliently supported on its locking position.

17. Fuel injection system according to one of claims 13 to 16, characterized in that the inlet throttle (throttle bore 43) has a larger cross-section than the return throttle (throttle bore 46).

18. Fuel injection system according to claim 11, characterized in that the connection of the delivery line (3) to the force accumulator (34) of the valve assembly (9) via which the valve member (38) in the direction of the outlet cross-section (21) releasing position resilient is, in dependence on the position of the nozzle needle (6) is controllable.

19. Fuel injection system according to claim 18, characterized in that the connecting line to the energy storage device (34) has a ■ coverage area to the nozzle needle (6) lying line cross section, which is blocked or released depending on the stroke position, the nozzle needle (6).

20. Fuel injection system according to claim 19, characterized in that the delivery line side inlet cross section of the connecting line to the force accumulator (34) of the nozzle needle (3) is overridden and in the stroke direction of the nozzle needle (3) near the pressure shoulder (59) of the nozzle needle (6 ) surrounding pressure chamber (60).

21. Fuel injection system according to claim 1, characterized in that via the outlet cross-section (21) from the feed line (3) flowing off fuel is discharged to a tank (10), in particular to the return of the injection system.

22. Fuel injection system according to claim 21, characterized in that the fuel flowing out of the delivery line (3) via the outlet cross-section (21) is discharged against a pressure-maintaining valve (11).

23. Fuel injection system according to claim 21, characterized in that via the outlet cross-section (21) from the feed line (3) flowing off fuel is discharged against a buffer volume.

24. Fuel injection system according to one of claims 1 to 23, characterized in that the over the outlet cross-section (21) from the feed line (3) flowing fuel, the nozzle needle (6) is discharged acting in the closing direction.