EP1904741B1 - Accumulator injection system for an internal combustion engine - Google Patents

Abstract

Disclosed is a high-pressure accumulator injection system (10) for an internal combustion engine, preferably a diesel engine. Said injection system (10) comprises a number of injection valves (18) which are connected to a high-pressure conveying device (12) via fuel pipes (16, 14). A reservoir (22) and a check valve encompassing a bypass throttle (24) that is connected in parallel are assigned to each injection valve (18). Said check valve which is assigned to each injection valve (18) and encompasses a bypass throttle (24) that is connected in parallel allows the accumulator injection system (10) to perform stable and reproducible injection processes with a favorable pressure curve during each injection process even when the discrete reservoirs (22) are provided with an unusually low volume. The reservoirs (22) can be integrated in the housing of the injection valves (18). The inventive injection system dispenses with the need for a complex common rail.

Description

The present invention relates to a storage injection system for the intermittent injection of high-pressure fuel into combustion chambers of an internal combustion engine according to the preamble of claim 1.

A storage injection system of this kind is known from DE 102 10 282 A1 or from the EP 0 657 642 A2 known. Delivery units promote fuel from a fuel reservoir for supplying at least one high pressure line to the cylinders of the internal combustion engine. A number of fuel injectors are supplied via the at least one high-pressure line, each of which contains a combustion chamber of the internal combustion engine with fuel injector nozzles. The at least one high-pressure line comprises line sections with which the individual fuel injectors are connected to one another. The injector bodies of the fuel injectors comprise an integrated storage space. The storage spaces are used instead of a common rail component and each storage space has a volume which corresponds to 50 times to 80 times the maximum injection quantity of a fuel injector per injection process. Each storage space is acted upon by a supply throttle with high-pressure fuel. These inlet throttles are designed in such a way that injection processes connected in series one after the other are possible without pressure pulsations occurring in the line sections. The influence of other fuel injectors is avoided.

In one in the DE 32 27 742 disclosed fuel injection system injectors are used which are equipped with a storage room. During the injection process, the fuel under high pressure in the storage space is partially released while the pressure in the storage space drops. As a result, the injection law, that is, the time course of the injection process, a falling from the beginning to the end characteristic, which has a negative effect on the combustion process of the internal combustion engine. Each storage space communicates with the high pressure fuel delivery line via a restricted orifice or restrictor passage. Due to the small flow cross-sectional area, the throttle passage prevents the formation of appreciable pressure waves in the fuel delivery lines during each injection event. Such pressure waves would unduly influence the uniform fuel distribution in a multi-cylinder engine and the stability of the injection processes of a single injection valve from cycle to cycle.

In the EP 0 228 578 A be similar fuel injectors as in the DE 32 27 742 proposed. In one embodiment variant of these injection valves, a spring-loaded check valve is located between an annular bore around a guide element of the injection valve member and the storage space of the injection valve. The annular bore is connected to the fuel supply bore of the injection valve and a bore connects the storage space with the back of the check valve, ie in the flow direction talseitig the check valve seat. Thus, the pressure in the storage space is constantly lower than the pressure in the fuel supply hole, especially at the beginning of each injection process. As a result, in accordance with the injection valve of the EP 0 228 578 A the injection valve member are closed reliably even with small injection quantity.

The storage spaces of the DE 32 27 742 as well as from the EP 0 228 578 A known injection valves are located below a guide piston and a hydraulic control chamber of the injection valve member. The guide piston and the control chamber belong to a hydraulic control device for controlling the movement of the injection valve member and it is necessary in most operating states of the injection valve that during the injection or even at the beginning of the injection, the pressure below the guide piston is lower than the pressure in the fuel supply hole, to ensure a sufficiently rapid closing of the injection valve member. In many cases, this has the consequence that the injection valve member is very long and expensive production. In addition, this arrangement severely limits the freedom to construct the storage chamber.

In the EP 0 264 640 A It is shown how the total system volume can be optimized by laying the volume of each individual injector reservoir into the piping system and the disadvantages of the DE 32 27 742 and the EP 0 228 578 A known fuel injection systems can be overcome while maintaining the stability of the injection operations. In practice, according to the EP 0 264 640 A a line section, which is upstream of all injectors, designed with a larger internal cross section than the cross section of the remaining lines, so that this section has a higher storage effect than the remaining lines. This line section was called Common Rail and consequently the Injection system called "common rail injection system". For example, compare the article "The common rail injection system - a new chapter in diesel injection technology" from the Motortechnische Zeitschrift MTZ No. 58, October 1997 ,

In the DE 31 19 050 an injection valve is shown with a likewise integrated in the housing storage chamber. The storage chamber is unthrottled connected to a feed pressure line which communicates with a fuel pump. This system, in which each an injection valve with pressure line and pump is shown as a unit, is suitable for very large diesel engines.

The injection systems according to the DE 102 10 282 A1 and the DE 32 27 742 have the major disadvantage of the falling injection characteristic. To mitigate this, a rather large storage chamber could be integrated in the injection valve, but this has the disadvantage that the injection valve is bulky.

Injectors both in accordance with DE 32 27 742 as well as the EP 0 228 578 A have the significant disadvantages of a long injection valve member and the strong limitation in the spatial arrangement of the storage space.

The practical implementation of the system according to EP 0 264 640 A has the line section with a larger cross section. For example, in engines of the power class above about 350 kW and up to 20,000 kW and more, this line section is also quite bulky and expensive. Furthermore, in many applications for safety reasons common rail and Pressure lines are executed in the case of a crack double-walled. This further increases the effort and costs for the common rail. When this is attached to the engine block, there is also the problem that the different thermal expansion between the engine and common rail causes undesirable mechanical stresses. In part, therefore, the line section is divided into several shorter sections, which are executed up to the design of individual memory with a short line, each to an injection valve. These individual memories are not housed in the housing of the injection valve, since the space available in the engine cylinder head mostly allow only the placement of a too small Injektorspeichers. about the commercial design of such a system, for example, in the technical article "The accumulator common rail injection system for the MTU series 8000 with 1800 bar system pressure", published in the Motortechnische Zeitschrift MTZ No. 61, October 2000 , to read.

The embodiment according to DE 31 19 050 allows only the unit of an injector with integrated storage chamber together with a pump and the associated connection line, as occur in the connection of several injectors with a sub-sized storage chamber via a relatively thin pressure line to a multi-cylinder pump too large and not to be brought in phase with the injections dynamic pressure fluctuations , which influence the accuracy of injection processes inadmissible.

Object of the present invention is to further develop a storage injection system of the type mentioned so that even with smaller storage chambers an optimal injection process is possible.

This object is achieved with a storage injection system having the features of claim 1.

A known as a common rail line section with a larger cross section is not present. It is possible to use discrete storage chambers of such a small volume that they can be integrated into the installation space of the injection valve housing when required. Each injector of the storage injection system is associated with such a discrete storage chamber. The spatial arrangement of the discrete storage chambers can be optimally chosen with great freedom of design, since the storage chambers, not as in the DE 32 27 742 and the EP 0 228 578 A disclosed, must be located below the guide piston of the injection valve. Furthermore, these discrete storage chamber are connected exclusively with pressure lines of relatively small cross-section with each other and with a high-pressure conveying device common to all injection valves. The cross-section of these lines is such that they form a total of a volume of too low storage effect to make alone the required, reproducible same injection operations of the injectors. These power cross sections may be equal or unequal.

Thanks to the assignment of a throttling device according to claim 1 to each injection unit, it is possible, despite the possibly small, discrete storage chambers, on the one hand, the pressure curve during the injection process for all injectors of an internal combustion engine to control exactly and without disturbing pressure drop, what the effect of dynamic pressure waves is used. On the other hand, it is also possible to dampen the dynamic pressure waves from one injection process of an injection valve to the injection process of the next injection valve as far as equal or equal for each injector that all injection events take place under virtually the same conditions. Therefore, the exact arrangement of the hydraulic line means - pressure lines - in the injection system does not play a major role and this arrangement can be designed with great freedom geometric and cost optimal.

The inventive storage injection system is particularly suitable for diesel engines - preferably medium to large power - suitable. However, it can also be used in smaller diesel engines, such as those used in the automotive industry.

Fig. 1

eine schematische Darstellung eines Speichereinspritzsystems gemäss der vorliegenden Erfindung mit sechs Einspritzeinheiten mit je einem Einspritzventil, einer Speicherkammer und einer Drosselungsvorrichtung, geeignet für einen Sechszylindermotor, wobei die hydraulischen Leitungsmittel, wie Brennstoffspeiseleitung und Brennstoffleitungen, sowie die Einspritz- einheiten im Längsschnitt gezeigt sind;

Fig. 2

ein Längsschnitt durch eines der sechs in Fig. 1 gezeigten Einspritzventile mit zugeordneter diskreter Speicherkammer und einer als Einweg- Rückschlagventil mit parallelgeschalteter Bypassdrossel ausgestalteten Drosselungs- vorrichtung in vergrösserten Massstab gegenüber Fig. 1, wobei die dem Einspritzventil zugeordnete Speicherkammer vom Brennstoff durchflossen wird (= Durchfluss-Speicherkammer);

Fig. 3

eine gegenüber Fig. 2 nochmals vergrösserte, partielle Schnittdarstellung des Rückschlag- ventils mit Parallelschaltung der Bypassdrossel;

Fig. 4

eine Schnittzeichnung einer unterschiedlichen Ausführungsform des Rückschlagventils mit Parallelschaltung der Bypassdrossel, wo die Bypassdrossel im Körper des Rückschlagventils hergestellt ist;

Fig. 5

in gleicher Darstellung wie in Fig. 2 eine zweite Ausführungsform der Einspritzeinheit mit Anordnung des Rückschlagventils mit Bypassdrossel zwischen Speicherkammer und Einspritzventil oberhalb des Hochdruckzulaufs, wobei der Hochdruckzulauf seitlich angeordnet ist, und die Speicherkammer vom Brennstoff nicht durchflossen wird (= Sackgasse-Speicherkammer);

Fig. 6

in gleicher Darstellung wie Fig. 2 und 5 eine dritte Ausführungsform der Einspritzeinheit mit Anordnung des Rückschlagventils mit Bypassdrossel zwischen Speicherkammer und Einspritzventil unterhalb des Hochdruckzulaufs, wobei die Speicherkammer des Einspritzventils eine Sackgasse-Speicherkammer ist (vom Brennstoff nicht durchflossen);

Fig. 7

in gleicher Darstellung wie Fig. 1 eine Variante des Speichereinspritzsystems, wobei die Leitungsmittel einen Verteilerblock aufweisen;

Fig. 8

eine gegenüber Fig. 7 vergrössert dargestellte alternative Konstruktion des Verteilerblocks mit doppelwirkenden Überlast-Durchflussbegrenzungs- ventilen;

Fig. 9

in gleicher Darstellung wie Fig. 8 eine zweite alternative Konstruktion des Verteilerblocks mit einfachwirkenden Überlast-Durchflussbegrenzungs- ventilen;

Fig. 10

in gleicher Darstellung wie Fig. 1 und 7 eine Ausführungsform des erfindungsgemässen Speicher- einspritzsystems mit einer Hochdruckförderpumpe pro Einspritzeinheit;

Fig. 11

ein Diagramm mit den zeitabhängigen Druckverläufen in den Speicherkammern und somit am Eingang des Einspritzventils eines Speichereinspritzsystems gemäss Fig. 1 mit acht Einspritzeinheiten;

Fig. 12

ein Diagramm in gleichem Massstab wie Fig. 11 mit den zeitabhängigen Druckverläufen am Eingang der Einspritzventile eines Einspritzsystems wie es der Fig. 11 zugrunde liegt, wobei den Einspritzventilen jedoch keine diskreten Speicherkammern mit Drosselungsvorrichtung zugeordnet sind, sondern die Brennstoff- speiseleitung als Common Rail mit entsprechenden Speichervolumen ausgebildet ist;

Fig. 13

einen Ausschnitt aus dem Diagramm von Fig. 12 mit dem Druckverlauf in der Speicherkammer und somit am Eingang des Einspritzventils während eines Einspritzvorgangs dieses Einspritzventils;

Fig. 14

in gleicher Darstellung wie Fig. 13 einen entsprechenden Zeitausschnitt aus dem Diagramm der Fig. 12;

Fig. 15

ein Diagramm mit dem zeitabhängigen Verlauf des Brennstoffflusses durch die Düse eines Einspritzventils und des Brennstoffflusses in die betreffende Speicherkammer bei einem Einspritzvorgang gemäss Fig. 11 und 13; und

Fig. 16

in gleicher Darstellung wie Fig. 15 den zeitabhängigen Verlauf des Brennstoffflusses durch die Düse eines Einspritzventils und des Brennstoffflusses am Eingang des Einspritz- ventils bei einem Einspritzvorgang gemäss Fig. 12 und 14.

The present invention will be explained in more detail with reference to preferred embodiments, which are illustrated in the drawings and described below. It shows purely schematically:

Fig. 1

a schematic representation of a storage injection system according to the present invention with six injection units each having an injection valve, a storage chamber and a throttle device, suitable for a six-cylinder engine, wherein the hydraulic line means, such as fuel supply line and fuel lines, and the injection units are shown in longitudinal section;

Fig. 2

a longitudinal section through one of the six in Fig. 1 shown injection valves with associated discrete storage chamber and designed as a one-way check valve with parallel-connected bypass throttle throttling device on an enlarged scale compared Fig. 1 , wherein the fuel chamber is passed through the fuel chamber associated with the injection valve (= flow storage chamber);

Fig. 3

one opposite Fig. 2 again enlarged, partial sectional view of the check valve with parallel connection of the bypass throttle;

Fig. 4

a sectional view of a different embodiment of the check valve with parallel connection of the bypass throttle, where the bypass throttle is made in the body of the check valve;

Fig. 5

in the same representation as in Fig. 2 a second embodiment of the injection unit with arrangement of the check valve with bypass throttle between the storage chamber and injector above the high-pressure inlet, the high-pressure inlet is arranged laterally, and the storage chamber is not traversed by the fuel (= dead end storage chamber);

Fig. 6

in the same representation as Fig. 2 and 5 a third embodiment of the injection unit with arrangement of the check valve with bypass throttle between the storage chamber and injection valve below the high-pressure inlet, wherein the storage chamber of the injection valve is a dead end storage chamber (from Fuel did not flow through);

Fig. 7

in the same representation as Fig. 1 a variant of the storage injection system, wherein the conduit means comprise a manifold block;

Fig. 8

one opposite Fig. 7 enlarged illustrated alternative design of manifold block with double acting overload flow relief valves;

Fig. 9

in the same representation as Fig. 8 a second alternative construction of the manifold block with single acting overload flow relief valves;

Fig. 10

in the same representation as Fig. 1 and 7 an embodiment of the inventive storage injection system with a high-pressure feed pump per injection unit;

Fig. 11

a diagram with the time-dependent pressure curves in the storage chambers and thus at the entrance of the injector of a storage injection system according to Fig. 1 with eight injection units;

Fig. 12

a diagram on the same scale as Fig. 11 with the time-dependent pressure curves at the entrance of the injection valves of an injection system like the Fig. 11 However, the injection valves are not associated with discrete storage chambers with throttling device, but the fuel supply line as common rail with corresponding Storage volume is formed;

Fig. 13

a section of the diagram of Fig. 12 with the pressure gradient in the storage chamber and thus at the inlet of the injection valve during an injection process of this injection valve;

Fig. 14

in the same representation as Fig. 13 a corresponding time excerpt from the diagram of Fig. 12 ;

Fig. 15

a diagram with the time-dependent course of the fuel flow through the nozzle of an injection valve and the fuel flow into the relevant storage chamber in an injection process according to Fig. 11 and 13 ; and

Fig. 16

in the same representation as Fig. 15 the time-dependent course of the fuel flow through the nozzle of an injection valve and the fuel flow at the entrance of the injection valve in an injection process according to Fig. 12 and 14 ,

FIG. 1 shows a storage injection system 10, in which a high-pressure conveyor 12 is shown schematically. In general, the high pressure conveyor 12 is a high pressure pump 12 ', which is driven by the internal combustion engine mechanically and at a fixed speed ratio. Within the high-pressure pump 12 'may be a high pressure compensating volume and additionally a pressure sensor for detecting and regulating the system high pressure, which is in Fig. 1 not shown. On the outlet side of the high pressure pump 12 'or high pressure conveyor 12 closes, usually with a High pressure fitting attached, a high pressure piping system. The piping system constructed of hydraulic line means 13 consists of a longitudinally extending fuel feed line 14 (which normally consists of a plurality of longitudinally connected line pieces 14 ') and of one fuel line 16 per injection valve 18, of which a total of six are present. The illustrated storage injection system 10 is thus suitable for a six-cylinder engine. It can also be used other than six-cylinder engines, which are used in all possible, common cylinder numbers. The six fuel lines 16 are fluidly connected to the fuel feed line 14 at the branching points 26. Although the fuel feed line 14 and the fuel lines 16 of Fig. 1 drawn with the same cross section, these cross sections may be different in size (the diameter of the fuel lines 16 may, for example, by half the diameter of the fuel feed line 14 amount to). However, the total volume of the fuel lines 14 and 16 is in the sum of too low storage effect in order to realize the required, reproducible same injection processes of the injectors 18 alone.

Depending on a fuel line 16 opens at each injection valve 18, in the direction of the longitudinal axis 20 of the respective injection valve, in a the injection valve 18 associated storage chamber 22 (see also Fig. 2 ). The fuel lines 16 could also open laterally into the storage chambers 22. Between each fuel line 16 and each storage chamber 22 is in the immediate vicinity of the storage chamber 22, a one-way check valve 24a arranged with parallel connection of a bypass throttle 24b. For simplicity, this arrangement is called a check valve with bypass throttle 24 and it forms a throttling device 25. The check valve with bypass throttle 24 could also be located somewhere in the fuel line 16 between the associated storage chamber 22 and the branch point 26, or in the branch point 26, as hydraulic T-piece with screw connections can be executed, integrated. In this case, the flow direction for the check valve with bypass throttle 24 plays an important role, and especially the fact that each injector 18, both a check valve with bypass throttle 24 and a storage chamber 22 are assigned. Each injection valve 18 with the associated storage chamber 22 and the associated check valve with bypass throttle 24 form an injection unit 27.

In the description of the in the Figures 2 - 10 In the embodiments shown, the same reference numerals are used for the corresponding parts, as described above in connection with the description of FIG FIG. 1 Further, in the following, only the differences to in the FIG. 1 shown storage injection system 10 or already previously described embodiments set forth.

In the longitudinal section of the injection valve 18 of FIG. 2 connects a bore 28 in an injection valve housing 30, in which also the storage chamber 22 is formed, the storage chamber 22 with a further bore 32 in a nozzle 34 of the injection valve 18. The bore 28 and the further bore 32 forming a connecting channel 33. Further, the injection valve 18 has an injection valve member 36 with a control piston 35, the underside of which is designated 35a, a guide sleeve 37 for the injection valve member 36, an injection valve member spring 38, a control chamber 39, a hydraulic control device 40, a nozzle vestibule 41, into which the connecting channel 33 opens, and a solenoid valve actuator assembly 42 (it could also be a piezo actuator).

The mode of operation of the injection valve 18 is summarized as follows: when the actuator arrangement 42 is energized, the hydraulic control device 40 responds. This causes a movement of the injection valve member 36 away from a nozzle seat 44 of the nozzle 34, whereby fuel flows under high pressure from the storage chamber 22 via the bore 28 and further bore 32 to the nozzle spray openings 46 of the nozzle 34 and the injection process begins. If the actuator assembly 42 is de-energized, the injection valve member 36 is moved in the direction of the nozzle seat 44 via the hydraulic control device 40 until the injection process is interrupted. For a detailed description of the structure and the mode of operation, reference is made to the prior art, for example to the Swiss Patent Application 00676/05 and the corresponding WO application PCT / CH2006 / 000191 which describe this part of the injection valve 18 exactly. The actuator arrangement 42, which is shown in a salient manner with respect to the longitudinal axis 20, could also be arranged on the longitudinal axis 20.

The underside 35a of the control piston 35 of the injection valve member 36, the guide sleeve 37 and the control chamber 39 are located below the storage chamber 22. The storage chamber 22 of the injection valve 18 is connected via the bore 28 and further bore 32 hydraulically practically without resistance to the nozzle vestibule 41. Also, the passages not shown in detail (for details, turn on the Swiss Patent Application 00676/05 and the WO application PCT / CH2006 / 000191 referenced) for the fuel flow from the nozzle vestibule 41 to the region 43 immediately in front of the nozzle seat 44 are dimensioned such that the smallest possible pressure drop occurs between the nozzle front chamber 41 and the region 43 during the injection process.

By way of illustration, reference is made to the volume content of the storage chamber 22, which in accordance with the injection unit 27 Fig. 1 and 2 , designed for an engine full load injection quantity of 2500 mm ³ per injection can be between 50 and 100 cm ³ . For comparison, in an injection system, as described in the technical article "The accumulator common rail injection system for the MTU 8000 series with 1800 before system pressure" at a full load injection quantity of 3300 mm ³ per injection, a single memory of 400 cm ^{3 is} used that is 3 to 6 times more memory. It will be appreciated that it is much easier to integrate a reservoir such as that to injector 18 into injector housing 30.

With each injection of an injection valve 18, the high pressure fuel flows from the fuel line 16 through the storage chamber 22 to pass through the bore 28 and further bore 32 to the nozzle antechamber 41 and consequently to the nozzle 34. The storage chamber 22 is traversed by the fuel flow, so it is a flow-storage chamber 22 '. By way of illustration, the Diameter of the fuel lines 14 and 16 ( Fig. 1 ), again designed for a full-load injection quantity of 2500 mm ³ per injection, two 3 and 9 mm, for example 6 mm.

According to FIG. 3 the check valve with bypass throttle 24, the check valve 24a with a ball 50, a check valve seat 52 and a check valve spring 54, a bypass throttle 56 and an input of the fuel line 16 and an output 58 in the storage chamber 22. In the in FIG. 3 shown position, the ball 50 is on the check valve seat 52 in abutment; there is no flow through the check valve 24a. 48, the flow direction of the high-pressure fuel is shown when the injection valve member 36 of the injection valve 18 is open and the injection process takes place.

It is known that the kinetic energy of the flow through a throttle is largely lost and converted into heat, which is the case with the bypass throttle 56. The bypass throttle 56 has an effective flow area, which is preferably slightly smaller than the total effective flow area of the nozzle spray openings 46 (the design range varies between 0.3 and 3 times, depending on the specific design and the number of injection valves 18 of the injection system 10). , The check valve spring 54 is preferably not very strong and allows opening of the check valve 24a, that is the movement of the ball 50 in the flow direction 48 away from the check valve seat 52, at a pressure difference of, for example, 20 bar (the design range moves depending on the bias Spring 54 between about 2 to just over 50 bar).

In an alternative design variant of the storage injection system 10 of Fig. 1 For example, the fuel lines 16 to the injection units 27 are omitted and the fuel line pieces 14 'arranged to connect the injection units 18 in series. This can be realized so that a T-piece with integrated check valve with bypass throttle 24, a first line section 14 ', which leads to the side of the high-pressure pump 12', with a second line section 14 ', which leads to the next injection valve 18 connects, and the third T connection via the check valve with bypass throttle 24 to the storage chamber 22 of the injection valve 18 leads. In the last injection valve 18 of this chain, the free line connection is either blind or else it is led back to the high-pressure pump 12 'or to the first injection valve 18 of the series. In this last case, a circumferential, circular shape-like arrangement of the line pieces 14 'is formed. The pipe sections 14 'may be straight or curved, as well as the same or not equal, with an arrangement in which the length of the pipe sections 14' is the same length or only slightly unequal, mostly useful.

• Zu Beginn des Einspritzvorgangs fliess bei zunächst geschlossenem Rückschlagventil 24a Brennstoff aus der Speicherkammer 22 durch die Bohrung 28 und weitere Bohrung 32 und wird durch die Düsen-Spritzöffnungen 46 in den Brennraum der Brennkraftmaschine eingespritzt (Brennraum und Brennkraftmaschine sind nicht gezeigt). Dadurch entspannt sich der Brennstoff unter leichtem Druckabfall in der Speicherkammer 22. Die Bypassdrossel 56 kann nicht genügend Brennstoff nachfördern, was zum Abheben der Kugel 50 ab dem Rückschlagventilsitz 52 in Richtung der Strömung 48 führt, womit der Nachschub von Kraftstoff aus der Brennstoffleitung 16 in die vom Brennstoff durchflossene Speicherkammer 22 beginnt. Dieser Vorgang bewirkt eine dynamische Druckabsenkung in der Brennstoffleitung 16, die sich mit Schallgeschwindigkeit in das Brennstoffleitungssystem fortpflanzt. In der Fortsetzung des Einspritzvorgangs sinkt der Druck in der Speicherkammer 22 weiter ab. Diese Druckabsenkung kann wegen der reduzierten Dimensionen der Speicherkammer 22 bei einem Anfangsdruck von beispielsweise 1600 bar bis zu einigen hundert bar (beispielsweise 100-400 bar) betragen, und sie propagiert sich wiederum dynamisch in die Brennstoffleitung 16 und in das Brennstoffleitungssystem. Dadurch, dass die Brennstoffleitung 16 über das offene Rückschlagventil 24a mit der Speicherkammer 22 kommuniziert, ist die Druckabsenkung in der Speicherkammer 22 jedoch kleiner, als wenn bei gleichem Speicherkammervolumen nur die Bypassdrossel 56 dazwischen geschaltet wäre, also kleiner als beispielsweise bei einem Einspritzsystem gemäss der DE 32 27 742 . Dadurch, dass die Speicherkammer 22 nahe dem Düsensitz 44, aber mittels der Bohrung 28 und weitere Bohrung 32 oberhalb des Steuerkolbens 35 des Einspritzventilgliedes 36 vorgelagert ist, ist ferner die Amplitude der dynamischen Druckabsenkung in der Brennstoffleitung 16 geringer als in einem der EP 0 264 640 A offenbarten Einspritzsystem, wo es keine jedem Einspritzventil 18 zugeordnete Speicherkammer 22 hat.

The operation of the fuel storage injection system 10 of FIG. 1 together with the injection valves 18 according to FIG. 2 , the check valve with bypass throttle 24 according FIG. 3 and the storage chamber 22 is as follows:

• At the beginning of the injection process, when the check valve 24a is initially closed, fuel flows out of the storage chamber 22 through the bore 28 and further bore 32 and through the nozzle spray openings 46 into the Combustion chamber of the internal combustion engine injected (combustion chamber and internal combustion engine are not shown). As a result, the fuel relaxes with slight pressure drop in the storage chamber 22. The bypass throttle 56 can not nachfördern enough fuel, resulting in the lifting of the ball 50 from the check valve seat 52 in the direction of the flow 48, whereby the supply of fuel from the fuel line 16 in the from the fuel flowing through the storage chamber 22 begins. This process causes a dynamic pressure reduction in the fuel line 16, which propagates at the speed of sound in the fuel line system. In the continuation of the injection process, the pressure in the storage chamber 22 continues to drop. This pressure reduction can be due to the reduced dimensions of the storage chamber 22 at an initial pressure of for example 1600 bar up to several hundred bar (for example, 100-400 bar), and it propagates itself dynamically in the fuel line 16 and in the fuel line system. Due to the fact that the fuel line 16 communicates with the storage chamber 22 via the open check valve 24a, the pressure reduction in the storage chamber 22 is smaller than if only the bypass throttle 56 were interposed with the same storage chamber volume, ie smaller than, for example, an injection system according to FIG DE 32 27 742 , The fact that the storage chamber 22 near the nozzle seat 44, but by means of the bore 28 and further bore 32 upstream of the control piston 35 of the injection valve member 36, the amplitude of the dynamic pressure reduction in the fuel line 16 is also lower than in one of EP 0 264 640 A disclosed injection system where there is no each injector 18 associated storage chamber 22nd Has.

In an injection process which corresponds to a full-load injection of the associated internal combustion engine, the phase of the pressure reduction in the storage chamber 22 continues until approximately half of the total injection duration. This information is purely indicative and may vary up or down depending on the application. The dynamic pressure reduction in the fuel line 16 now also detects the fuel feed line 14, the fuel lines 16 of the other, in particular adjacent fuel injection valves 18 and the bypass throttles 56 and the respective storage chambers 22. All these elements with high-pressure fuel have a storage effect. However, the flow direction from the storage chambers 22 of the adjacent and possibly further fuel injection valves 18 is opposite to the flow direction 48 of the injection valve 18, where the injection takes place. Therefore, the check valves 52 of the adjacent and possibly further injectors 18 remain closed and the fuel replenishment from the associated storage chambers 22 takes place solely by the bypass throttles 56, which in the adjacent and possibly further storage chambers 22 only a lower pressure drop than in the storage chamber 22 of the currently operating Injector 18 caused.

However, since a plurality of storage chambers 22 can supply high-pressure fuel via their bypass throttles 56, the supply of fuel in the fuel line 16 and in the storage chamber 22 of the fuel storage system takes place overall Injecting injection valve 18 an advantageous recovery of the injection pressure in the second half of the injection process, which continues until the end of Volllasteinspritzdauer. The injection pressure in this phase increases at the nozzle spray openings 46 and reaches towards the end of the injection process a desired high value; see also Fig. 13 with the corresponding description.

If now the injection process is completed quickly, takes place in the bore 28 and further bore 32 because of the abrupt deceleration of the liquid column at the nozzle seat 44, a dynamic pressure increase. This propagates to the associated storage chamber 22 and is attenuated by the storage chamber volume. Furthermore, the remaining pressure increase from the storage chamber 22 out, also only muted, propagate through the bypass throttle 56 and against the flow direction 48 in the remaining part of the storage injection system 10, since the check valve 52 does not allow flow counter to the flow direction 48. The bypass throttle 56 destroys a substantial portion of the entrained by the flow through the bypass throttle 56 and energy can not difficult to control pressure amplitudes in the storage injection system 10 arise.

• sie dämpft die Druckschwankung in den Speicherkammern 22 von nicht einspritzenden Brennstoffeinspritzventilen 18 während der Einspritzung eines beliebigen Einspritzventils 18,
• sie dämpft die Druckschwankung zwischen dem einspritzenden Einspritzventil 18 und dem Rest des Speichereinspritzsystems 10 am Ende der Einspritzung, und
• sie bewirkt eine vorteilhaft ansteigende Charakteristik des Einspritzdruckes in der zweiten Hälfte eines Volllasteinspritzvorgangs eines beliebigen Einspritzventils 18.

The arrangement of the check valve with bypass throttle 24 of the storage injection system 10 of FIG. 1 and the injection valve 18 with storage chamber 22 of FIG. 2 has the following advantages:

• it dampens the pressure fluctuation in the storage chambers 22 of non-injecting fuel injectors 18 during the injection of any one Injector 18,
• it dampens the pressure fluctuation between the injecting injector 18 and the remainder of the accumulator injection system 10 at the end of the injection, and
• it causes an advantageously increasing characteristic of the injection pressure in the second half of a Volllasteinspritzvorgangs any injection valve 18th

After the end of any injection process remain in the accumulator injection system 10 pressure differences in the storage chambers 22 and residual vibrations in the fuel feed line 14 and fuel lines 16 left. By suitable design of the volume of the storage chambers 22, the characteristics of the check valves with bypass throttles 24 (as mentioned above) and the fuel feed line 14 and the fuel lines 16 of a particular injection system 10 is generated therein for all injectors 18 always repeating, practically the same wave pattern, so that all injection valves 18 of the injection system 10, viewed from the pressure curve forth, receive virtually equal conditions for the injection (see Fig. 11 ). This allows the arrangement of a number of injectors 18 in the storage injection system 10 with the simple arrangement of Fig. 1 , usually up to 8 injectors 18 and in some cases more. The complex and expensive common rail is replaced by simple hydraulic line 13 - fuel supply line 14 and fuel lines 16 -. These can all be essentially the same Have flow cross-section.

FIG. 4 shows another constructive design of the check valve with bypass throttle 24, which is associated with each injector 18. In this embodiment, a needle-shaped closure member 60 cooperates with the check valve seat 52. At the front and in the direction of the longitudinal axis 20, the closure member 60, the bypass throttle 56, which opens into a bore 62 and then into a recess 64 in the closure member 60. The recess 64 receives the check valve spring 54. The needle-shaped closure member 60 has radially outward a guide 66, which reliably guides the closure member 60, and also at least one passage 68 on the periphery of the closure member 60 (it may also be two or three passages 68). The total cross section of the passage 68 is sufficiently large to represent only a very small flow resistance. The operation of this throttling device 25 is the same as that according to Fig. 3 , In all embodiments, the check valve with bypass throttle according Fig. 4 be educated.

In FIG. 5 is the injection valve 78 associated check valve with bypass throttle 24 between the storage chamber 22 and the nozzle 34, wherein the high-pressure inlet 70 is arranged to the injection valve 78 side in the injection valve housing 30 below the check valve with bypass throttle 24. The high-pressure inlet 70 connected to the fuel line 16 branches down into the bore 28 and up into the short bore 72, which leads to the check valve with bypass throttle 24. The check valve with Bypass throttle 24 is thus arranged in the connecting channel 33, which - connects through the holes 28, 32 and 72 - the storage space 22 with the injection valve 78. The high pressure inlet 70 could also be vertical and parallel to the longitudinal axis 20, or at an angle thereto. Important in this example is that the check valve with bypass throttle 24 between the high-pressure inlet 70 and the storage chamber 22 is located. As a result, the storage chamber 22 of the injection valve 78 is not traversed by the fuel during an injection process and it partially empties into the bore 72. The dead-end storage chamber 22 "acting storage chamber 22 is located above the control piston 35 of the injection valve member 36 and is here these elements upstream.

• Zu Beginn des Einspritzvorgangs wird der Brennstoff mehrheitlich aus der Brennstoffleitung 16 durch die Bohrungen 70, 28 und 32 zu den Düsen-Spritzöffnungen 46 fliessen. Mit der Auslegung des Querschnitts der Bypassdrossel 56 und der Kraft der Feder 54 (siehe Fig. 3) kann bestimmt werden, wie viel Brennstoff anteilmässig zu Beginn der Einspritzung von der Speicherkammer 22 zu den Düsen-Spritzöffnungen 46 fliesst und wann das Rückschlagventil 52 öffnet. Bis etwa zur Hälfte eines Volllasteinspritzvorgangs sind die Verhältnisse ansonsten ähnlich zu jenen der Anordnung gemäss der Figuren 1 und 2.

This arrangement leads to a relative to the injection unit 27 according to Fig. 2 different behavior of the injection valve 78 in the entire storage injection system 10, as follows:

• At the beginning of the injection process, the majority of fuel from the fuel line 16 through the holes 70, 28 and 32 to the nozzle-injection ports 46 flow. With the design of the cross section of the bypass throttle 56 and the force of the spring 54 (see Fig. 3 ), it can be determined how much fuel proportionally flows at the beginning of the injection from the storage chamber 22 to the nozzle-injection ports 46 and when the check valve 52 opens. Up to about half of a Volllasteinspritzvorgangs the conditions are otherwise similar to those of the arrangement according to the FIGS. 1 and 2 ,

Now comes the dynamic pressure reduction in one Injection valve 78 via the fuel feed line 14 and fuel line 16 to the check valve with bypass throttle 24 of an adjacent injection valve 78, can also open its check valve 24a and in addition to the associated bypass throttle 56 fuel from the storage chamber 22 dynamically to the injecting injection unit 27 nachschieben. If the dynamic pressure recovery shaft reaches the injecting injection valve 78, the check valve 24a of this injecting injection valve 78 will block the passage of the pressure recovery shaft to the storage chamber 22 of this injecting injection valve 78 upon arrival of the pressure recovery shaft on the closing side of the check valve 24a and almost the entire pressure wave amplitude thus becomes practical unattenuated as an increase in pressure to the nozzle-injection ports 46 (reduced by that proportion which can pass through the bypass throttle 24b in the storage chamber 22 of this injecting injection valve 78).

That opposite the arrangement of FIG. 2 different switching behavior of the check valves 24a in the second half of the injection process forms a first significant difference. This dynamic process can produce a more powerful pressure recovery in the second half of the full load injection event than in the arrangement of FIGS FIGS. 1 and 2 ,

Even with only two injection valves 78 with two associated storage chambers 22, two associated check valves with bypass throttles 24 and the associated fuel supply and fuel lines 14, 16, this arrangement is very effective. In fuel injection systems 10 with more than two injectors 78 is compared to the arrangement of FIGS. 1 and 2 an additional reduction of the total volume of stored high-pressure fuel can be achieved. The arrangement of the check valve with bypass throttle 24 of the injection valve 78 of Fig. 5 Thus, in terms of the dynamic pressure recovery wave in the second part of the injection process offers more advantages than those according to the Fig. 1 and 2 ,

The second major difference to the arrangement of FIG. 2 If the injection process is terminated quickly, a dynamic pressure increase takes place again in the bores 28 and 32 because of the abrupt deceleration of the liquid column at the nozzle seat 44. This propagates itself stronger in the pipe system than in the arrangement of Fig. 1 and 2 because it can only pass through the bypass throttle 56 to the storage chamber 22 of the injection valve 78, which has just completed the injection process, and consequently the storage chamber volume is not traversed by this dynamic pressure increase and the pressure increase is less damped.

In an embodiment of an injector not shown according to the present invention, the injection valve has a dead-end accumulator chamber 22 "and the check valve with bypass throttle 24 is located at the inlet of the high-pressure side inlet 70 of the injector FIG. 2 ,

An in Fig. 5 a first dividing line 74 shown by a dashed line refers to a first alternative embodiment in which the storage chamber 22 with its own storage chamber housing 80 is to be understood as a separate unit from the injection valve 78. The storage chamber housing 80 is then connected either with a short line or by screwing with the injection valve housing 30, but in any case remains associated with the injection valve 78. The check valve with bypass throttle 24 is further arranged in the section of the connecting channel 33 of the injection valve 30. A second separation line 76 shows a second alternative embodiment in which the check valve with bypass throttle 24 is integrated in the storage chamber housing 80. Also in this second alternative, the connection with the injection valve housing 30 can be realized either with a short line or by screwing and the assignment to the injection valve 78 remains. These alternative embodiments allow a greater creative freedom and can also at the injection valve 18 ( FIG. 1 ) and injector 88 (described below) FIG. 6 ) and also in the variant with series connection between the line pieces 14 'are used together with the injection valves 18, 78 and 88.

In a further, not shown alternative embodiment of the injection valves 18, 78, 88, the storage chamber 22 is arranged laterally, either parallel to the longitudinal axis 20 desachsiert or at an angle (for example 90 °) to the longitudinal axis 20. Again, the housing of the storage chamber 22 integrally with the injection valve housing 30 (for example, this unit is manufactured as a forged), or be designed as two components screwed together.

In FIG. 6 is the check valve with bypass throttle 24 of the injection valve 88 in the connecting channel 33 between the storage chamber 22 and the nozzle 34 below the lateral high-pressure inlet 70. Otherwise, the injection unit 27 is according to Fig. 6 the same as those according to Fig. 5 , The high-pressure fuel can freely circulate here via the fuel feed line 14 and fuel lines 16 in all storage chambers 22 of the storage injection system 10, wherein the supply and return to and from the nozzle 34 is controlled by the check valve with bypass throttle 24. In the first and second part of a Volllasteinspritzvorgangs the injection curve represents a hybrid form of what is the case in the storage injection system 10 when using the injectors 18 or 78. The advantage of this arrangement lies in the particularly short path with a small volume between nozzle spray openings 46 and check valve with bypass throttle 24. As a result, the rapid termination of the injection process overpressure vibration, which has a high oscillation frequency, attenuated very quickly.

However, in a storage injection system 10 with the execution of the injection units 27 according to Fig. 6 the ripple of the dynamic pressure oscillations, which have a lower oscillation frequency, special attention to be paid, since these pressure oscillations between the storage chambers 22 of the storage injection system 10 are only slightly attenuated and can lead to overly unequal injection operations of the injectors 88. The arrangement of the check valve with bypass throttle 24 of the injector 88 may be problematic in more than four unimpeded interconnected injectors 88. Solutions to this problem are in the Connection with the storage injection system 90 according to FIG. 7 and the FIGS. 8 and 9 described.

At the in Fig. 7 shown embodiment of the inventive storage injection system 90, the high-pressure conveyor 12 and the injection valve units 27 are formed as in connection with the Fig. 1 and 2 disclosed. However, the hydraulic line means 13 have a manifold block 96 to which the fuel feed line 92 and all the fuel lines 94a to 94f are routed and connected to, for example, high pressure fittings (not shown in detail). Manifold block 96 is provided with bores 98 which hydraulically interconnect fuel feed line 92 and all fuel lines 94a-94f. In the arrangement of Fig. 7 with six injectors 18, the fuel lines 94a and 94f, 94b and 94e, and 94c and 94d shown in pairs the same length. Alternatively, all the fuel lines 94a to 94f can be made the same length so that the shaft transit times from each injection valve 18 to the distributor block 96 last the same length. Also different cable lengths that are not the same in pairs, are conceivable. The advantage of the manifold block assembly 96 is in the central position thereof, which unites all high pressure fittings in this manifold block 96. Here, too, the conduit means 13 have too little storage action to allow the required, reproducible same injection operations of the injectors alone.

For the sake of completeness it should be mentioned that also injection units as in the Fig. 5 and 6 shown in the storage injection system 90 can be used as well this also applies to the storage injection system 10.

In one design variant, the distribution block 96 is assigned a storage chamber 97, as shown in FIG FIG. 7 indicated by dashed lines. This storage chamber 97 preferably has approximately the same volume as each of the storage chambers 22. However, the volume can also be greater, for example two to six times as large. This is a single additional storage chamber 97. If the storage chamber 97 with a throttle 93 or with a check valve with bypass throttle 24, connected to the manifold block 96, this storage chamber 97 can firstly positively influence the individual injections, and secondly the ripple those dynamic pressure oscillations, which have a lower oscillation frequency, advantageously attenuate, which is mainly when using injection units 88 according to Fig. 6 positively affects. The disadvantage is the additional construction cost of the storage chamber 97th

FIG. 8 FIG. 12 shows a construction of the manifold block 99 equipped with double acting overload flow restricting valves 104. Flow control valves are disclosed, for example, in the publication SAE-Paper 910 184 (1991). Their purpose is to preserve the engine from overload in the event that the injector member of an injector unintentionally remains open for too long.

The high-pressure fuel passes via the fuel feed line 100 in a symmetrical to an axis 101 manifold block 99 and fuel lines 102a, 102b, 102c and 102d to four Injection units 27. With 102 'are further dashed lines possible fuel lines indicated by dashed lines with extension 116 of the manifold block 99. The valve body 106 of each flow restricting valve 104 is double-acting. During each injection operation, the valve body 106 moves in the direction of the fuel line 102, which leads to the injection unit 27 with the injecting injection valve. During normal operation of the storage injection system 90, the valve body 106 does not move so far that the conical end 110 reaches the shut-off seat 112. In the rest periods between injection operations, the valve body 106 is brought by the force of a spring 108 in its central rest position. If too much fuel is inadvertently required in the case of too long an injection process, on the other hand, the conical end 110 reaches the shut-off seat 112 and closes off the further fuel flow. Denoted at 114 are slightly throttling annular passage areas between the valve body 106 and the body of the manifold block 99. They lie between the fuel inlet through the fuel feed line 100 and an antechamber 116 to a fuel line 102. Further, the valve bodies 106 have a tapered region 118 in the center to allow unrestricted fuel flow from the fuel line 100 and through a bore 120 to all of the flow restriction valves 104 guarantee.

The advantage of this solution is that a double-acting flow control valve 104 serves at least two injectors 18 and thereby at least halves the number of restrictors 104 for a particular engine over the prior art.

In design variants, a throttle 121a is arranged in the fuel supply to the manifold block 99, as shown in dashed lines. Instead of this throttle 121a, a throttle 121b may be present in the fuel inflow section between two chambers 124 each receiving a double-acting flow-limiting valve 104. However, it is also conceivable to install both throttles 121a and 121b. Furthermore, the manifold block 99, analogous to the manifold block 96, a storage chamber 97 be assigned. The purpose of these elements is the same as described in connection with the construction variant of the manifold block 96. Also in this case, the construction costs increase.

FIG. 9 FIG. 12 shows another alternative construction of manifold block 128, which in turn is symmetrical about axis 101, having two single-acting overload flow restricting valves 122. Only the lower part of manifold block 128 will be described which is symmetrically equal to the upper part. Similar to the example described above Fig. 8 The fuel in the chamber 124 flows through annular flow areas 114 to the antechamber 116 and from here into a respective passage 132 with three outlets for three fuel lines 130d, 130e and 130f, which each lead to an injection unit 27. The two valve bodies 126 are single acting here. If the injection duration is excessively long, the conical end 110 of the respective valve body 126 will once again enter the shut-off seat 112 and interrupt the fuel flow at three injection units 27. The engine can then still be operated at reduced load, but three cylinders fail instead of just one cylinder as in the construction of Fig. 8 , This is the number of flow control valves smaller.

Fig. 10 shows a further embodiment of an inventive storage injection system 152, which according to that Fig. 1 is very similar. The only difference is that the high-pressure conveying device 12 per injection unit 27 has a high-pressure pump 12 ', which are each connected via a fuel pump line 14 "to the fuel feed line 14 or line sections 14' FIGS. 1 and 2 , However, all other described embodiments may be used.

When in the Fig. 10 In the embodiment shown, the high-pressure pumps 12 'are equipped with short-conveying cams, as is customary in injection systems with a high-pressure feed pump 12' per injection valve 18. However, it is also possible to form the cams 154 as a harmonic eccentric. Will, as in Fig. 10 1, using a short conveying cam per injection unit 27, the volume of the storage chambers 22 of each injection unit 27 can be made particularly small; a volume which is about 10 times as large as the injection quantity for a Volllasteinspritzvorgang may be sufficient, since the just injecting injector 18 associated and at the same time or shortly before the injection process starting and taking place fuel delivery shock a significant proportion of the injected quantity directly into the respective storage chamber 22 promotes. In a preferred manner, the pumping operation of each high-pressure delivery pump 12 'overlaps at least partially, preferably completely, with the injection process of the assigned injection unit 27.

Such a storage injection system is particularly suitable for a retro-fit on an existing internal combustion engine, wherein the high pressure pumps 12 'of the original conventional injection system can be maintained and thus only new injection units 27 and new hydraulic line 13 must be retrofitted.

In all embodiments shown, the storage chambers 22 and the check valve with bypass throttle 24 - the throttling device 25 - and the mouth of the bore 32 above the bottom 35a of the control piston 35 of the injection valve member 36 are mounted, which allows a particularly compact design of the functional elements in the nozzle 34. The storage chamber 22 and / or the check valve with bypass throttle 24 can also be installed so that they find space below the bottom 35 a of the control piston 35, analogous to known Einspritzventilausführungen and possibly accepting a long injection valve member. Also, the embodiment could be such that only the bore 32 opens below the bottom 35a of the control piston 35 of the injection valve member 36.

In all embodiments, the storage injection system has no - common to all injectors - storage space in the manner of a common rail. This is expressed by the fact that the hydraulic connection means of a storage injection system according to the invention have too little storage effect in order to design solely the required, reproducibly identical injection processes of the injection valves. The connecting means can - in a preferred manner - all at least approximately the same cross-section. Any small chambers or rooms, as they are necessary for example for flow control valves, or any chokes should be included. It is important, however, that during each Volllasteinspritzvorgang fuel is also supplied from other storage chambers than the injection valve currently associated injection chamber and from the high-pressure conveyor.

The throttling device 25 may for example also be designed as a "hydraulic circular diode".

An inventive storage injection system preferably has at least three injection units 27.

For diesel engines with a power of the order of 250 KW per cylinder, flow cross sections in the fuel line system corresponding to a diameter of about 6 mm are recommended. For outputs of about 50 - 100 KW diameters of 2 - 4 mm are recommended.

An inventive storage injection system 10 as in Fig. 1 shown for an eight-cylinder diesel engine with a power of 250 kW per cylinder has been analyzed by means of a computer-aided simulation. The injection quantity per injection operation under full load was set at 2000 mm ³ and the diameter of the fuel feed line 14 and fuel lines 16 was 6 mm. The system high pressure was 1500 bar and each of the storage chambers 22 had a storage volume of 100 cm ³ . The diagrams of Figures 11 . 13 and 15 show results of this simulation.

For comparison, a storage injection system with common rail was simulated. The exact same specifications were taken into account. The only difference was that the fuel was supplied directly to the injection valves 18 by means of the fuel lines 16 and that a volume corresponding to the eight storage chambers 22 of 800 cm ³ - in the manner of a common rail - was laid in the line pieces 14 'by their Cross section was increased correspondingly enlarged. The injection valves 18 was thus assigned no individual storage chamber 22 and no throttling device 25. Results of this simulation show the diagrams of the Fig. 12 . 14 and 16 ,

In all diagrams, the abscissa is the time axis, with the time in seconds. On the ordinate are in the Fig. 11 to 14 the pressure in units of 1000 bar and in the FIGS. 15 and 16 the flow rate of the fuel is plotted in liters per minute.

Fig. 11 shows the pressure curves in all eight injection units 27 at the mouth of the bore 28 in the storage chamber 22 (see Fig. 2 ). With Te the good five milliseconds long duration of the injection process of one of the injectors 18 is designated. The broken down in this interval down to about 1400 bar and back up, dashed line shows the pressure at the active injection injector 18, whereas the superimposition of the pressure curves of the remaining seven injectors 18 in this time interval form the lying at about 1500 bar thick line , Subsequent to this time interval Te, the pressure at the inlet of the injection valve 18, which has just finished the injection process, according to the above the thick line running dashed line. In a corresponding manner, the eight consecutive injection operations of the eight injectors 18 are shown.

Of the Fig. 11 It can be seen that for all injection processes approximately the same pressure conditions prevail and that in a first part of an injection process, during about half the time of Te, the pressure drops by about 100 bar and he returns to about the original in a second part of the injection process Pressure of 1500 bar recovered.

Fig. 12 shows at the same scale the pressure gradients at the same location - at the entrance of the bore 28 - each of the eight injectors 18, but in the injection system with common rail and without the injectors 18 associated storage chambers 22 and throttling devices 25. As can be easily seen from this, are the pressure fluctuations At the entrance of the injectors 18 much larger and much higher frequency than in the inventive storage injection system 10. It is readily apparent that the latter reliably ensure better injection conditions.

Fig. 13 shows the pressure curve of during the in Fig. 11 time period injecting injector 18 highlighted with Te during one millisecond prior to the injection event, during the five millisecond injection process, and during nearly four milliseconds after completion of the injection event. As also mentioned above in connection with the functional description of the storage injection system 10 Fig. 1 and 2 already executed takes during a first part of a Volllasteinspritzvorgangs, the About half as long as the entire injection process takes at the entrance of the active injection valve 18, the pressure from here about 100 bar and then increases in the subsequent second part of the injection process again. This pressure increase is caused by the flow of fuel from other, in particular adjacent storage chambers 22 and the high-pressure conveyor device 12. With the dashed straight 156 of the pressure curve is indicated without flow of fuel. The pressure gain until the end of the injection process is thus well 250 bar in the inventive storage injection system 10. The time profile Te subsequent pressure curve with a vibrating pressure increase is caused by the abrupt stopping of the moving fuel column when closing the injector 18. The pressure quickly returns to the system high pressure of 1500 bar.

Fig. 14 shows the pressure curve at the same injection valve 18 as this Fig. 13 shows, however, in the injection system with common rail. The duration of the injection process is again highlighted with Te. The strong and rapid pressure drop at the beginning of the injection process is caused by the lack of a storage chamber 22 at the injection valve 18. The make-up from the common rail then causes a strong pressure increase up to about 1700 bar. Again Fig. 14 can be removed, this vibration is slightly attenuated again within the injection interval Te. The even greater pressure fluctuations after completion of the injection process are caused by the return end, virtually unattenuated pressure wave.

Fig. 15 shows in the solid line the flow of fuel through the nozzle 34 of the injecting Injector 18 and the dashed line shows the flow of fuel into the respective storage chamber at the entrance of this storage chamber 22 (at 58 in Fig. 2 ) of the inventive storage injection system 10. This representation shows that in the first part of the injection process up to the time designated X thanks to the relevant storage chamber 22 and then, thanks to the refilling of this storage chamber 22 with fuel from other storage chambers 22, in particular adjacent injection units 27, and from the high-pressure conveyor 12 ago, a very regular injection of fuel over the entire injection interval Te is achieved. In particular, part of the injection quantity originates from the storage chamber 22 of the currently operating injection valve 18 until time X, and at the same time the pressure in the storage chamber 22 drops (FIG. Fig. 13 ). At time X there is equilibrium between fuel extraction and Nachförderstrom from the adjacent storage chambers 22 and from the high-pressure conveyor 12. The pressure curve is at this time, see Fig. 13 , horizontal. After time X, the supply is greater than the fuel extraction, the pressure in the storage chamber 22 of the currently operating injection valve 18 rises again. If, at the end of the injection, the pressure in this storage chamber 22 is again equal to the initial pressure at the beginning of the injection, then the total amount flowed in is equal to the amount injected.

In comparison, is - like this Fig. 16 shows - in the injection system with common rail, the flow rate through the nozzle of the injection valve 18 - solid line - irregular and is also the flow of fuel at the entrance of the injector 18 with associated with great unrest. There are at the nozzle changing undersupply and oversupply, the entire injection process is much more dynamic and uncontrollable than the inventive storage injection system.

Claims (16)

1. Accumulator injection system for the intermittent injection of high-pressure fuel into combustion spaces of an internal combustion engine, with a high-pressure conveying device (12) which feeds high-pressure fuel to a number of injection units (27) having in each case an injection valve (18, 78, 88), a discrete accumulator chamber (22) assigned to this and a throttling device (25), the injection units (27) being connected to one another and to the high-pressure conveying device (12) by means of hydraulic line means (13), and each injection valve (18, 78, 88) having an injection valve member (35), actuated by means of an actuator arrangement (42) and a hydraulic control device (40), for controlling the operation of injecting high-pressure fuel through nozzle injection orifices (46) of a nozzle (34) of the injection valve (18, 78, 88), characterized in that the hydraulic line means (13) have too low an accumulator action to ensure the required, reproducibly identical injection operations of the injection valves (18, 78, 88), and the throttling device (25) permits, at least approximately unimpeded, the flow of the high-pressure fuel in the direction of the injection valve (18, 78, 88) and throttles said flow in the opposite direction, in such a way that high-pressure fuel flows to each injection valve (18, 78, 88) during its injection operation both from the assigned accumulator chamber (22) and from the accumulator chamber (22) of other injection units (27) and from the high-pressure conveying device (12).
2. Accumulator injection system according to Claim 1, characterized in that each throttling device (25) has a nonreturn valve (24a) and, preferably in a parallel connection, a bypass throttle (24b).
3. Accumulator injection system according to Claim 1, characterized in that the throttling device (25) is arranged between the line means (13) and the accumulator chamber (22), and the accumulator chamber (22) is connected to the injection valve (18) via a connecting duct (33).
4. Accumulator injection system according to Claim 3, characterized in that the throttling device (25) has a nonreturn valve (24a) with bypass throttle (24b), the nonreturn valve opening in the direction of the accumulator chamber (22).
5. Accumulator injection system according to Claim 1, characterized in that the accumulator chamber (22) and the injection valve (88) are connected to one another via a connecting duct (33), the throttling device (25) is connected into the connecting duct (33), and the line means (13) issue into the connecting duct (33) between the throttling device (25) and the accumulator chamber (22).
6. Accumulator injection system according to Claim 1, characterized in that the accumulator chamber (22) and the injection valve (78) are connected to one another via a connecting duct (33), the throttling device (25) is connected into the connecting duct (33), and the line means (13) issue into the connecting duct (33) between the throttling device (25) and the injection valve (78).
7. Accumulator injection system according to Claim 5 or 6, characterized in that the throttling device (25) has a nonreturn valve (24a) with bypass throttle (24b), the nonreturn valve (24a) opening in the direction of the injection valve (78).
8. Accumulator injection system according to one of Claims 1, 4 or 7, characterized in that the nonreturn valve (24a) has a needle-shaped closing member (60), loaded in the closing direction by a spring (54), for closing and opening the nonreturn valve, and in that the bypass throttle (56) is manufactured in the closing member (60).
9. Accumulator injection system according to one of Claims 1 to 8, characterized in that the line means (13) have a fuel feedline (14) leading away from the high-pressure conveying device (12) and, per injection valve (18, 78, 88), a fuel line (16), the fuel lines (16) issuing into the fuel feedline (14).
10. Accumulator injection system according to one of Claims 1 to 8, characterized in that the line means (13) have a fuel feedline (14) leading away from the high-pressure conveying device (12), at least one distributor block (96, 99, 128) and, per injection valve (18, 78, 88), a fuel line (94a, 94b, 94c, 94d, 94e, 94f, 102a, 102b, 102c, 102d, 102', 130a, 130b, 130c, 130d, 130e, 130f), the fuel lines and the fuel feedline (92, 100) issuing into the distributor block (96, 99, 128) and being flow-connected to one another there.
11. Accumulator injection system according to Claim 10, characterized in that, in the distributor block (99), at least one double-acting throughflow limiting valve (104) is installed, which interrupts the inflow to one of two fuel lines (102a, 102b, 102c, 102d, 102') when the injection valve member (36) of the respective injection valve (18, 78, 88) unintentionally remains in the open position for too long a time.
12. Accumulator injection system according to Claim 10, characterized in that, in a distributor block (128), at least one single-acting throughflow limiting valve (122) is installed, which interrupts the inflow to at least two fuel lines (130a, 130b, 130c, 130d, 130e, 130f) when the injection valve member (36) of at least one of the respective at least two injection valves (18, 78, 88) unintentionally remains in the open position for too long a time.
13. Accumulator injection system according to one of Claims 10 to 12, characterized in that the distributor block (96, 99, 128) is assigned an additional accumulator chamber (97), the accumulator volume of which corresponds preferably at least approximately to that of an accumulator chamber (22) of an injection unit (27).
14. Accumulator injection system according to one of Claims 1 to 8, characterized in that the high-pressure conveying device (12) has a plurality of high-pressure conveying pumps (12'), preferably a high-pressure conveying pump (12') per injection unit, and the line means (13) have a fuel pump line (14") leading away from each high-pressure conveying pump (12'), a fuel feedline (14) and, per injection valve (18, 78, 88), a fuel line (16), the fuel pump lines (14") and the fuel lines (16) issuing into the fuel feedline (14).
15. Accumulator injection system according to Claim 14, characterized in that the high-pressure conveying pumps (12') have short-conveying cams (154).
16. Accumulator injection system according to Claim 14 or 15, characterized in that the pumping operation of each high-pressure conveying pump (12') overlaps at least partially with the injection operation of the assigned injection unit (27).

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