EP1780406A1 - Injector for a fuel injection system and fuel injection system with such injector - Google Patents

Abstract

The injector (20) has a nozzle needle (26) configured to be hydraulically actuated by an actuating mechanism (19) arranged at the upper end of the injector housing (18). The actuating mechanism opens and closes an injection valve (22) depending on the axial position of the injection valve. Two separate high-pressure junction (24,25) are situated within the injector housing, and configured to provide external access to an internal high-pressure space (23). The high-pressure junctions are connected to a high-pressure line. The nozzle needle runs through the high-pressure space in axial direction. The injection valve is situated at the lower end of the injector housing and connected to the high-pressure space. The injector housing is extended along an axis (45), and surrounds the high-pressure space for receiving fuel under high pressure.

Description

TECHNICAL AREA

The present invention relates to the field of internal combustion engines with fuel injection. It relates to an injector for a fuel injection system according to the preamble of claim 1 and a fuel injection system with such an injector.

STATE OF THE ART

In common-rail fuel injection systems, the fuel delivered by a high-pressure pump is usually pumped into the storage volume of a common rail extending along the row of injectors, from which individual branch lines are supplied to each of them individually go off the controlled injectors. Such an arrangement with a separate common rail has various disadvantages: The separate common rail, which must be designed for the high fuel pressures, requires considerable manufacturing effort. This applies in particular also to the screw connections and connections of the branch lines to the injectors, as well as the supply and return lines from and to the high-pressure pump. Each of these connections poses a risk in terms of tightness. In addition, the common rail in the engine compartment, in which more and more auxiliary units must be accommodated, takes up a considerable space.

It is in the EP-A1-1 469 188 in the context of a planned for common rail systems coaxial double line, are combined in the Hochdruckzu- and low-pressure return line for the fuel, has been proposed, the injectors of the common rail system on the upper side with two opposite combined high and low pressure connections equip. The injectors can then be connected in series within the fuel injection system on the high and low pressure side, wherein the connecting lines between adjacent injectors with their high-pressure line volumes together form the common rail.

Such a configuration is shown schematically in Fig. 1, wherein only two injectors 11 and 12 are shown. Each of the injectors 11, 12 has an internal high pressure chamber 14, which opens down to an injection nozzle 13, which can be opened and closed by means of a nozzle needle 16. The high-pressure chamber 14 is connected in the manner of a T-piece through a narrow connection channel 15 with a line section of the high-pressure line 17 extending between two high-pressure connections A. The high-pressure line 17 forms the common rail and determines its storage volume. The high-pressure spaces 14 in the injectors 11, 12 are fluid-dynamically decoupled from the high-pressure line 17 by the narrow connection channels 15, so that they do not play any role in the common-rail function. In order to obtain a sufficient storage volume, therefore, the high-pressure line 17 must be designed accordingly. At the same time, the storage volume changes significantly with the distance of the injectors from each other.

PRESENTATION OF THE INVENTION

It is therefore an object of the invention to provide an injector for a fuel injection system according to the common rail principle, which allows a simplification of the injection system, without having the disadvantages of known solutions, and to specify a working with such injectors fuel injection system.

The object is solved by the totality of the features of claims 1 and 9. The injector according to the invention is characterized in that at least two separate high-pressure ports are provided in the injector housing, which allow access from the outside to the high-pressure chamber and are each designed to connect a high-pressure line. In the fuel injection system according to the invention, the injectors are arranged with their high pressure ports in the high pressure line in series such that the high pressure line passes through the high pressure chamber of each injector.

An embodiment of the injector according to the invention is characterized in that the high-pressure connections are arranged at the upper end of the high-pressure chamber, and that the high-pressure connections are arranged in the axial direction at the same height. This results in good accessibility and ease of manufacture and connection. This applies in particular if, according to a further development, two high-pressure connections are provided, and the two high-pressure connections are arranged opposite one another with respect to the axis and are aligned with one another.

A further simplification results when the high-pressure connections in configuration and dimensions, in particular with respect to the passage cross-section, are equal to each other.

The high pressure ports preferably have a thread for releasably screwing the high pressure line, in particular, the thread is formed as an internal thread.

The injector becomes particularly simple if the high-pressure chamber is arranged coaxially with the axis of the injector.

The core idea of the inventive fuel injection system is to use injectors with a high-pressure chamber, from which the fuel required for the injection is removed, the volume of the high-pressure chamber is chosen so large that the sum of the volumes of the high-pressure chambers of several similar injectors in a common rail Injection system sufficient to form the storage volume required for the common rail, and to insert these injectors with their high-pressure chambers in a row in the high-pressure line, so that the high-pressure chambers together with the high-pressure line connecting them form a common rail with a corresponding storage volume. As a result, a space-saving fuel injection system according to the common rail principle can be realized in a particularly simple and effective manner.

For the fuel injection system, the injectors according to the invention can be used with advantage.

An embodiment of the fuel injection system according to the invention is characterized in that a return line to the high-pressure pump is returned from the last of the injectors in series. As a result, a kind of loop is formed, which is advantageous for the compensation of pressure fluctuations in the storage volume formed.

BRIEF EXPLANATION OF THE FIGURES

Fig. 1

die schematisierte Darstellung von entlang einer Hochdruckleitung angeordneten Injektoren mit zwei Hochdruckanschlüssen nach dem Stand der Technik;

Fig. 2

in einer zu Fig. 1 vergleichbaren Darstellung das Prinzip der Kraftstoffeinspritzanlage nach der Erfindung;

Fig. 3

im Längsschnitt ein bevorzugtes Ausführungsbeispiel eines Injektors nach der Erfindung mit einem grossvolumigen Hochdruckraum, der durch zwei separate Hochdruckanschlüsse von aussen zugänglich ist; und

Fig. 4

ein Ausführungsbeispiel einer Kraftstoffeinspritzanlage nach der Erfindung mit in Serie liegenden, durch Hochdruckverbindungsleitungen untereinander verbundenen Injektoren gemäss Fig. 2 und einer Rückleitung zur Hochdruckpumpe.

The invention will be explained in more detail with reference to embodiments in conjunction with the drawings. Show it

Fig. 1

the schematic representation of arranged along a high-pressure line injectors with two high-pressure ports according to the prior art;

Fig. 2

in a comparable to Figure 1 representation of the principle of the fuel injection system according to the invention.

Fig. 3

in longitudinal section, a preferred embodiment of an injector according to the invention with a large-volume high-pressure chamber, which is accessible through two separate high-pressure connections from the outside; and

Fig. 4

an embodiment of a fuel injection system according to the invention with lying in series, interconnected by high-pressure connection lines injectors according to FIG. 2 and a return line to the high-pressure pump.

WAYS FOR CARRYING OUT THE INVENTION

2, the principle of the fuel injection system according to the invention is shown in a representation comparable to FIG. 1 representation. Of the fuel injection system 10 'again only two injectors 11' and 12 'are shown by several. Each of the injectors 11 ', 12' has an internal one High-pressure chamber 14 'is injected from the high-pressure fuel through the injector 13 and the nozzle needle 16 formed injection valve into the combustion chamber. At the high-pressure chambers 14 'of the injectors 11', 12 ', two high-pressure connections A' are arranged laterally and oppositely, with which the injectors 11 ', 12' can be inserted into the high-pressure line 17 'coming from the high-pressure pump in series so that the High-pressure chambers 14 'and the connecting portion of the high-pressure line form a continuous storage volume in the manner of a common rail. The prerequisite for this is that the volume of the individual high-pressure chamber 14 'is large enough so that the sum of the volumes of all in-line injectors is sufficient as a common rail storage volume.

To meet these requirements, a novel injector is proposed. In Fig. 3 is a longitudinal section of a preferred embodiment of such an injector according to the invention reproduced. The injector 20 is intended for the direct injection of fuel, preferably for diesel engines, based on the common rail principle.

The injector 20 has within a Injektorgehäuses 18 in the longitudinal direction (along the axis 45) extending, coaxial high-pressure chamber 23, in which, for example, the nozzle needle 26 of the injector 20 is located. At the lower end of the injector housing 18, the actual injection valve 22 is screwed by means of a union nut 37. At the lower end of the injection valve 22 are injection holes 38 which communicate with the high-pressure chamber 23 and can be opened or closed with the nozzle needle 26. Such an arrangement of the nozzle needle 26 with its needle shaft 21 is particularly advantageous for the invention because this high-pressure chamber 23 has a significantly larger volume compared to conventional injectors. So runs in a standard common rail injector, such as in the EP-A1-584 815 is shown, a high pressure leading bore approximately parallel to the nozzle. However, this thin bore has insignificant volume, so a designed injector is unlikely to be used to form a common rail can. By contrast, in the space surrounding the nozzle needle shaft of the conventional injector, low pressure prevails.

At the center of the invention is - as already mentioned above - the idea to omit the common rail, which forms the storage volume in the prior art corresponding common rail systems. As a substitute, the sum of the individual volumes of the high-pressure spaces 23 in the injectors is used by connecting them to one another via simple high-pressure lines in a type of series connection (FIG. 4).

For this purpose, the high-pressure chamber 23 of the injector 20 must have at least two separate high-pressure ports 24 and 25 (FIG. 3). These high-pressure ports 24, 25 are laterally mounted in the radial direction on the injector housing 18 and each open into the high-pressure chamber 23, thus creating a connection of the high-pressure chamber 23 to the high pressure connecting lines (43 in Fig. 4), which the series-connected injectors 20.1 ,. .., 20.4 connect with each other (Fig.4). The high-pressure pump 41 likewise has two high-pressure connections and, together with the high-pressure feed line 42, the injectors 20.1,..., 20.4, the high-pressure connection lines 43 and the return line 44, forms a kind of ring line, which is advantageous for the compensation of pressure fluctuations in the storage volume formed.

The high-pressure connections 24, 25 on the injector housing 18 are preferably arranged at the same height in the axial direction. They are arranged opposite each other with respect to the axis 45 and are aligned with each other. In addition, they are identical in design and dimensions, in particular with regard to the passage cross-section. The high-pressure connections 24, 25 have, for example, an internal thread (not shown in FIG. 3) which serves as mating thread for a high-pressure screw connection (not shown) for pressure-tight connection to the high-pressure line 42, 43, 44 (FIG. 4). Similarly, the connection points on the high-pressure pump 41 (Fig. 4) are executed.

The injector 20 shown in Fig. 3 has in detail the following structure:

At the top of the injector 20, an actuating mechanism 19 for controlling the injection valve 22 is shown schematically. The adjusting mechanism 19 has e.g. an electromagnet 30, which, when acted upon by an excitation pulse fed in via the connection 28, attracts an associated armature 31 and thereby releases a control bore 32 (the electromagnet 30 itself is firmly connected to the injector housing 18). By opening the control bore 32, the pressure drops in a control chamber 34 arranged therebelow. A in the control chamber 34 in the axial direction slidably movable control piston 35 and the adjoining needle shaft 21 are raised together with the nozzle needle 26 against the pressure of a closing spring 36, the arranged at the lower tip of the injector 22 injection holes 38 are released, and the fuel is from the High-pressure chamber 23 injected into the combustion chamber 39 surrounding the tip of the injection valve 22.

If the excitation of the electromagnet 30 is interrupted, the spring 29 pushes the armature 31 downwards, and the control bore 32 is closed. Through leading to the control chamber 34 smaller bore 33 fuel flows into the control chamber 34 after. The acting on the control piston 35 pressure difference is canceled, the closing spring 36 presses the needle shaft 21 with the nozzle needle 26 down, and the injection through the injection holes 38 is interrupted.

The flowing during the open control bore 32 (energized electromagnet 30) amount of fuel flows through the hollow armature 31 up through a return nipple 27 via a collecting hose, not shown, in the (also not shown) fuel tank back.

An exemplary fuel injection system 40 according to the invention for four cylinders is shown in simplified form in FIG. From a high-pressure pump 41 for the fuel, a high pressure supply line 42 goes to the four in series and with each other with high pressure connection lines 43 connected injectors 20.1 to 20.4. From the last injector 20.1 from the row of four injectors, a return line 44 goes back to the high pressure pump 41. The injectors 20.1 to 20.4 preferably have the internal structure, as shown in Fig. 3 on the basis of the injector 20. They are inserted with their high-pressure chambers 23 directly into the ring line formed from the lines 42, 43 and 44. The sum of the volumes of the four high-pressure chambers 23 and the interposed high-pressure connection lines 43 forms a storage volume for the fuel under high pressure in the manner of a common rail, which can completely replace the conventional external common rail. It goes without saying that the principle of the invention can be used not only for four cylinders, but in an analogous manner for other numbers of cylinders such as 3, 5, 6 or 8.

LIST OF REFERENCE NUMBERS

10,10 ', 40

Fuel injection system

11.11 '12.12'

injector

13

injection

14.14 '

High-pressure chamber

15

connecting channel

16

nozzle needle

17,17 '

High-pressure line

18

injector

19

mechanism

20

injector

20.1 .. 20.4

injector

21

needle shaft

22

Injector

23

High-pressure chamber

24.25

High pressure port

26

nozzle needle

27

Backflow nipples

28

Connection (electromagnet)

29

feather

30

electromagnet

31

anchor

32

control bore

33

Bore (small)

34

control room

35

spool

36

closing spring

37

Nut

38

Injection hole

39

combustion chamber

41

high pressure pump

42

High pressure supply line

43rd

A high pressure line

44

return

45

axis

A, A '

High pressure port

Claims (11)

An injector (11 ', 12', 20) for a fuel injection system (10 ', 40), comprising an injector housing (18) extending along an axis (45), having an internal high pressure space (14', 23) for receiving high pressure enclosed fuel, at the lower end of the injector (18) an injection valve (13, 16, 22) which is in communication with the high-pressure chamber (14 ', 23), as well as in the axial direction through the high-pressure chamber (14', 23) extending nozzle needle (13, 21, 26) which is hydraulically actuated by means of a at the upper end of the injector (18) arranged adjusting mechanism (19) and depending on the axial position, the injection valve (13, 16, 22) opens or closes, characterized in that at least two separate high-pressure ports (A ', 24, 25) are provided in the injector housing (18), which allow access from the outside to the high-pressure chamber (14', 23) and in each case for connecting a high-pressure line (17 ', 42, 43, 44) are formed. Injector according to claim 1, characterized in that the high pressure ports (A ', 24, 25) at the upper end of the high-pressure chamber (14', 23) are arranged. Injector according to claim 1 or 2, characterized in that the high-pressure connections (A ', 24, 25) are arranged in the axial direction at the same height. Injector according to one of claims 1 to 3, characterized in that two high pressure ports (A ', 24, 25) are provided, and that the two high pressure ports (A', 24, 25) are arranged opposite each other with respect to the axis and with each other aligned. Injector according to one of claims 1 to 5, characterized in that the high-pressure connections (A ', 24, 25) in configuration and dimensions, in particular with respect to the passage cross-section, are equal to each other. Injector according to one of claims 1 to 5, characterized in that the high-pressure connections (A ', 24, 25) have a thread for releasably screwing on the high-pressure line (17', 42, 43, 44). Injector according to claim 6, characterized in that the thread is formed as an internal thread. Injector according to one of claims 1 to 7, characterized in that the high-pressure chamber (14 ', 23) coaxial with the axis (45) of the injector (11', 12 ', 20) is arranged. Fuel injection system (40) with a high pressure pump (41) and a plurality of injectors (11 ', 12', 20.1, ..., 20.4), which of the high pressure pump (41) via a high pressure line (17 ', 42, 43) supplied under high pressure fuel, characterized in that the injectors (11 ', 12', 20.1, ..., 20.4) each have a high-pressure chamber (14 ', 23), from which the fuel required for the injection is taken, the volume of the high-pressure chamber (14 ', 23) is selected to be so large that the sum of the volumes of the high-pressure chambers (14', 23) of several similar injectors in a common rail injection system is sufficient to form the storage volume necessary for the common rail, and that the injectors (11 ', 12', 20.1, ..., 20.4) with their high-pressure chambers (14 ', 23) are inserted successively into the high-pressure line (17', 42, 43). Fuel injection system according to claim 9, characterized in that injectors (11 ', 12', 20.1, ..., 20.4) according to one of claims 1 to 8 are used. Fuel injection system according to claim 9 or 10, characterized in that from the last of the series injectors (11 ', 12' 20.1, ..., 20.4) a return line (44) to the high-pressure pump (41) is returned.

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