EP1192352B1 - Fuel injection system for an internal combustion engine - Google Patents

Abstract

The invention relates to a fuel injection system for an internal combustion engine. The inventive fuel injection system comprises a high-pressure pump (1) for delivering the fuel from a fuel reservoir (2) and a number of fuel injectors (5) for injecting the fuel into the combustion chamber of the internal combustion engine. The system is further provided with a high-pressure fuel line (4) that links the high-pressure pump (1) with the fuel injectors (5) and that contains a high-pressure reservoir (3). A fuel return line (11) returns the fuel that was not injected by the fuel injectors (5) and a leakage line (12) returns the leakage amounts that occur at the fuel injectors (5). According to the invention, the high-pressure fuel line (4), the fuel return line (11) and the leakage line (12) are combined in a common fuel line (13) which is characterized by cross-sections of flow that are separated from one another by walls and that correspond to the individual lines (4, 11, 12).

Description

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

Fuel injection systems for internal combustion engines, in particular diesel engines, which have a high-pressure pump for delivering the fuel from a fuel supply, a number of fuel injectors for injecting the fuel into the combustion chamber of the internal combustion engine, and a high-pressure reservoir for connecting the high-pressure pump to the fuel injectors and a high-pressure reservoir for holding the high-pressure pump High-pressure fuel line containing pressure-fed fuel to be injected (common rail systems) are becoming increasingly widespread. A major advantage of fuel injection systems of this type is that the injection process can be adapted very precisely to the respective speed and load condition of the internal combustion engine with respect to the start of injection, injection duration and mass flow rate of the injected fuel per unit of time. In addition to the high-pressure fuel line that conveys the fuel from the high-pressure pump to the fuel injectors and maintains the fuel under high pressure, these fuel injection systems also provide a fuel return line and a leakage line for returning any leakage quantities that occur at the fuel injectors or due to leaks in the sealing points , Providing these additional fuel lines is in itself associated with a great deal of effort and, in particular in the case of large-volume diesel engines, significant vibration problems arise in relation to the attachment of the lines to the engine.

A solution for reducing the effort is known from EP 0 786 593 A1. In the common rail injection system shown, a leakage line surrounds the high-pressure fuel line. The leakage line is designed as an elastomeric sleeve, which is pulled over the corresponding sealing points during assembly.

The object of the present invention is to further simplify the connection of the high-pressure fuel line to the fuel injector in a common rail injection system.

This object is achieved by a fuel injection system with the features of claim 1.

According to the invention, it is provided that the high-pressure fuel line, the fuel return line and the leakage line are combined in a common fuel line with respective flow cross sections separated from one another by walls for each of the lines. To connect the common fuel line to the fuel injector, a connection element is provided according to the invention, which has a screw-on sleeve, an internal connection channel and an external connection channel.

A major advantage of the fuel system according to the invention is that the fastening parts, sealing and connecting elements required for separate attachment of the fuel return line and the leakage line are eliminated. On the one hand, this avoids the risk of a functional failure of such elements and, on the other hand, there are no difficulties with regard to vibration problems of such lines.

A connection is established from the leakage line to a leakage channel mouth of the fuel injector via the internal connecting channel in the connecting element, or a connection is established from the fuel return line to a return channel mouth of the fuel injector via the outer connecting channel.

According to a preferred embodiment of the invention, it is provided that the fuel injectors of the injection system each have a common high-pressure connection provided with a high-pressure channel opening for connecting the high-pressure fuel line, a leakage channel opening for connecting the leakage line, and a return-channel opening for connecting the fuel return line. The advantage of this is that the high-pressure fuel line, the leakage line and the fuel return line are all connected to a common connection directly on the Fuel injector are connected, so that in the cylinder head of the internal combustion engine no channels for discharging return or leakage quantities from the fuel injector must be provided.

A particularly preferred embodiment of the invention provides that the common high-pressure connection has on its front side a centrally arranged high-pressure channel opening for connecting the high-pressure fuel line and on its circumference spaced apart from one another in the axial direction, the leakage channel opening for connecting the leakage line and the return channel opening for connecting the return line the individual mouths are each sealed by sealing elements and separated from the other mouths.

According to a further development of this, it is provided that the sealing element of the high-pressure channel opening is formed by a conical seal which cooperates with a sealing cone formed at the end of the high-pressure fuel line, and that the sealing elements sealing the leakage channel opening and the return channel opening are formed by O-rings which have the inner peripheral surface a screw-on sleeve associated with the leakage line and the fuel return line and having flow cross sections spaced apart from one another in the axial direction interact.

According to a preferred embodiment of the fuel injection system according to the invention, it is provided that the common fuel line is formed by three coaxially arranged, surrounding line pipes, the inner of which forms the high-pressure fuel line, and the high-pressure fuel line is surrounded by an inner and an outer jacket pipe, each of which enclose a flow cross-section and form the fuel return line and the leakage line. One advantage of this is that the high-pressure fuel line, which is very solid due to the required high-pressure strength, forms a stable support for the surrounding jacket pipes. This alleviates the vibration problems.

According to a preferred embodiment, it is provided that the jacket pipes surrounding the high-pressure fuel line are co-located on their inner surface Channels extending in the longitudinal direction are provided, which form the flow cross sections of the fuel return line or leakage line.

It is preferably provided that the jacket pipes surrounding the high-pressure fuel line have webs on their inner surface between the channels forming the flow cross sections of the fuel return line or leakage line, which webs rest on the outer circumference of the respective inner line surrounded by the relevant jacket pipe.

In the following an embodiment of the invention is explained with reference to the drawing.

Figur 1

eine schematische Blockdarstellung eines Kraftstoffeinspritzsystems für eine Brennkraftmaschine nach einem Ausführungsbeispiel der Erfindung;

Figur 2

einen etwas schematisierten Längsschnitt durch einen Kraftstoffinjektor, wie er bei dem beschriebenen Ausführungsbeispiel der Erfindung zur Anwendung kommen kann;

Figur 3

eine Querschnittsansicht, welche den Anschluss einer die Kraftstoffhochdruckleitung, die Kraftstoffrücklaufleitung und die Leckageleitung zusammenfassenden gemeinsamen Kraftstoffleitung an einem Kraftstoffinjektor bei dem beschriebenen Ausführungsbeispiel zeigt;

Figur 4

eine schematische Blockdarstellung eines Kraftstoffeinspritzsystems für eine Brennkraftmaschine mit einem Hochdruckspeicher nach dem Stand der Technik.

Show it:

Figure 1

is a schematic block diagram of a fuel injection system for an internal combustion engine according to an embodiment of the invention;

Figure 2

a somewhat schematic longitudinal section through a fuel injector, as it can be used in the described embodiment of the invention;

Figure 3

a cross-sectional view showing the connection of a common fuel line summarizing the high-pressure fuel line, the fuel return line and the leakage line to a fuel injector in the described exemplary embodiment;

Figure 4

is a schematic block diagram of a fuel injection system for an internal combustion engine with a high pressure accumulator according to the prior art.

4, a fuel injection system for an internal combustion engine with a high-pressure accumulator (common rail system) charged with fuel by a high-pressure pump will first be described. Such a fuel injection system, as is used in particular for a large-volume diesel engine, contains a high-pressure pump 1, which delivers fuel from a Fuel supply 2 to a high pressure accumulator 3 promotes. The high-pressure accumulator 3 is contained in a high-pressure fuel line 4 connecting the high-pressure pump 1 to fuel injectors 5 and operates in the manner of an oil-elastic one High-pressure accumulator. The fuel injectors 5 are intended to inject fuel into the combustion chamber of the internal combustion engine during an injection process that is precisely defined after the start of injection, the end of injection and the course of the injection, and are controlled by a control unit (not shown in the figure) depending on the operating state of the internal combustion engine, in particular the speed, load, temperature and others Parameters controlled. Each fuel injector 5 contains an injection nozzle 7, which is supplied with the fuel to be injected via a fuel channel 6 provided in the fuel injectors 5. The fuel injector 5 is controlled via a control valve 9, which is designed as a 3/2-way valve known per se in the prior art or as a 2/2-way servo valve. A fuel return line 11, which is connected to a corresponding connection of each of the fuel injectors 5, is provided for returning fuel in the form of approximately control quantities, which is delivered via the high-pressure fuel line 4 but not injected by the fuel injectors 5. Furthermore, a leakage line 12 is connected to each fuel injector 5, which is used to return leakage quantities, such as. B. in the event of a line break and non-functional high-pressure sealing points. In a conventional fuel injection system, as shown in FIG. 4, the fuel return line 11 and the leakage line 12 are each provided as separate lines.

Figure 1 shows a schematic block diagram of a fuel injection system with a high-pressure pump acted upon by a high-pressure pump (common rail system) according to an embodiment of the present invention. As in the conventional fuel injection system described in FIG. 4, a high-pressure pump 1 is provided, which delivers fuel from a fuel supply 2 to a high-pressure accumulator 3, which works in the manner of an oil-elastic high-pressure accumulator and in a high-pressure pump 1 with fuel injectors 5 for injecting the fuel into the combustion chamber the internal combustion engine provided fuel high pressure line 4 is included. The fuel injectors 5 each contain an injection nozzle 7, which is supplied with the fuel to be injected in the high-pressure accumulator 3 via a fuel channel 6, the control of the injection being controlled by a control valve 9 provided in the fuel injector 5.

According to the invention, a fuel return line 11 for returning fuel quantities not injected by the fuel injectors 5 and a leakage line 12 for returning leakage quantities occurring in the fuel injectors 5 are combined in a common fuel line 13 together with the high-pressure fuel line 4 containing the high-pressure accumulator 3, as shown in FIG dashed circumferential lines shown. In general terms, the high-pressure fuel line 4, the fuel return line 11 and the leakage line 12 are formed by separate flow cross sections provided in the common fuel line 13. The structure of the common fuel line 13 will be described in more detail later.

Figure 2 shows a somewhat schematic longitudinal section through a fuel injector, as used in the described embodiment of the fuel injection system according to the invention. The fuel injector, designated as a whole by reference number 5, comprises an injector housing 10, in which a nozzle needle 18 is mounted in a longitudinally displaceable manner in a guide sleeve 25 formed in the injector housing 10. The tip of the nozzle needle 18 interacts with an injection nozzle 7 formed at the lower end of the injector housing 10 in the sense of opening and closing an injection opening cross section. A high-pressure duct 19 is formed in the injector housing 10, which leads from a high-pressure connection 26 arranged on the side of the fuel injector 5 to a nozzle antechamber 22 surrounding the nozzle needle 18. Via the high-pressure channel 19, the fuel to be injected is fed from the high-pressure fuel line 4 shown in FIG. 1 to the nozzle chamber 22 under high pressure. The fuel injector 5 is controlled by means of a solenoid 15 arranged at the rear end thereof, which cooperates with a control valve formed by a closing body 16 and a valve body 17. The control valve 16, 17 optionally applies or relieves pressure to fuel supplied under high pressure, which is formed on the back of a needle wedge 23 acting on the nozzle needle 18. A return channel 21 is provided to discharge the control quantities occurring at the control valve 16, 17. A leakage channel 20 serves to discharge any leakage quantities occurring in the fuel injector 5. In this respect, the structure of the fuel injector 5 shown in FIG. 2 corresponds to a fuel injector as is currently used by the applicant.

According to the illustrated exemplary embodiment of the invention, it is provided that the high-pressure connection 26, which serves to connect the high-pressure fuel line 4 shown in FIG. 1, is designed as a common connection which, in addition to a high-pressure channel opening 19a for connecting the high-pressure fuel line 4, has a leakage channel opening 20a for connection of the leakage line 12 shown in Figure 1 and a return channel mouth 21a for connecting the fuel return line 11 shown in Figure 1. The high-pressure channel mouth 19a for connecting the high-pressure fuel line 4 is provided centrally arranged on the front side of the common high-pressure connection 26, the leakage channel mouth 20a for connecting the leakage line 12 and the return channel mouth 21a for connecting the return line 11, return connection 27, are spaced apart from one another in the axial direction on the circumference of the common high-pressure connection 26 is provided. The mentioned mouths 19a, 20a, 21a of the high-pressure duct, leakage duct and return duct are each sealed and separated from one another by associated sealing elements.

The structure of the common fuel line 13 and the manner in which it is connected to the common high-pressure connection 26 of the fuel injector 5 will now be explained in detail with reference to FIGS. 3a) and b) in conjunction with FIG. As FIG. 3b shows, the common fuel line 13 (see FIG. 1) is formed by three coaxially arranged, surrounding line pipes 30, 31, 32. Of these, the inner line pipe 30 forms the high-pressure fuel line 4. The inner line pipe 30 is surrounded by an inner and an outer jacket pipe 31, 32, which each include a flow cross section 31a, 32a and form the fuel line 11 and the leakage line 12 (see FIG. 1). , The inner jacket pipe 31 surrounding the high-pressure fuel line 30 forms the leakage line 12, the outer jacket pipe 32 surrounding the inner jacket pipe 31 forms the fuel return line 11. The jacket pipes 31, 32 are provided on their inner surface with longitudinal channels 31a, 32a, each of which Form flow cross sections for the fuel return line 11 and the leakage line 12. Between these channels 31a, 32a, which form the flow cross sections, webs 31b, 32b are formed which rest on the outer circumference of the inner tube surrounding the respective jacket tube 31, 32, that is to say the webs 31b of the inner tube Jacket tube 31 on the outer circumference of the high-pressure tube 30 and the webs 32b of the outer jacket tube 32 on the outer circumference of the inner jacket tube 31.

As shown in FIG. 3a), at the injector-side end of the common fuel line formed by the three pipes 30, 31, 32, there is provided a connection element, generally designated 28, which connects the flow cross-sections 30a of the high-pressure pipe 30, 31a of the leakage line 12 manufactures the inner casing tube 31 and 32a of the outer casing pipe 32 forming the return line with the associated orifices 19a, 20a and 21a of the high-pressure duct, leakage duct and return duct formed on the common high-pressure connection 26. As can be seen, a sealing cone 37 is formed at the end of the central high-pressure pipe 30, which cooperates with a sealing element in the form of a sealing cone 37 formed on the end face of the common high-pressure connection 26, as is conventional in the field of fuel injectors. The orifices 21a of the return channel 21 and 20a of the leakage channel 20 formed on the circumference of the common high-pressure connection 26 are each sealed by sealing elements 34, 35, 36 in the form of O-rings and separated from one another. A screw-on sleeve 38, which is an essential part of the connection element 28, contains connecting channels 39 and 40, of which an internal connecting channel 39 connects to the flow cross-section 31a of the inner jacket tube 31 and an outer connecting channel 40 connects to the flow cross-section 32a of the produces outer jacket tube 32. The connecting channels 39 and 40 each open in the vicinity of the mouths 20a and 21a of the leakage channel and the return channel, and the sealing elements 33, 34, 35 interact with the inner circumferential surface of the screw-on sleeve 38 such that a flow path from the connecting channel 40 to the return channel mouth 21a and from the connecting channel 39 a flow path to the leakage channel mouth 20a is created.

LIST OF REFERENCE NUMBERS

1

high pressure pump

2

Fuel supply

3

High-pressure accumulator

4

High-pressure fuel line

5

fuel injector

6

Fuel channel

7

injection

9

control valve

10

injector

11

Fuel return line

12

leakage line

13

common fuel line

15

solenoid

16

Control valve closing body

17

valve body

18

nozzle needle

19

High pressure passage

19a

High pressure channel mouth

20

leakage channel

20a

Leakage channel mouth

21

Return channel

21a

Return duct opening

22

nozzle antechamber

23

Nadelstelze

24

control room

25

shell

26

High pressure port

27

Return connection

28

connecting element

30

High-pressure pipe

31

inner casing tube

32

outer jacket tube

30a

channel

31a

channels

32a

channels

31b

Stege

32b

Stege

33

sealing element

34

sealing element

35

sealing element

36

sealing element

37

sealing cone

38

Überschraubhülse

39

connecting channel

40

connecting channel

Claims (9)

1. Fuel injection system for an internal combustion engine, with a high-pressure pump (1) for conveying the fuel out of a fuel storage tank (2), with fuel injectors (5) for injecting the fuel into the combustion space of the internal combustion engine, with a high-pressure fuel line (4) which connects the high-pressure pump (1) to the fuel injectors (5) and contains a high-pressure accumulator (3) for reserving the fuel to be injected which is conveyed under high pressure by the high-pressure pump (1), with a fuel return line (11) for the return of fuel not injected by the fuel injectors (5), and with a leakage line (12) for the return of leakage quantities occurring at the fuel injectors (5), the said leakage line surrounding the high-pressure fuel line (4), characterized in that a connection element (28) for connecting a common fuel line (13) to the fuel injector (5) is provided, the high-pressure fuel line (4), the fuel return line (11) and the leakage line (12) being combined in a common fuel line (13), in each case with, for each of the lines, flow cross sections (30a, 31a, 32a) separated from one another by walls (30, 31, 32), and the connection element (28) having a screw-over sleeve (38), an inner connecting duct (39) and an outer connecting duct (40).
2. Fuel injection system according to Claim 1, characterized in that a connection from the leakage line (12) to a leakage-duct issue (20a) of the fuel injector (5) is made by means of the inner connecting duct (39).
3. Fuel injection system according to Claim 1, characterized in that a connection from the fuel return line (11) to a return-duct issue (21a) of the fuel injector (5) is made by means of the outer connecting duct (40).
4. Fuel injection system according to Claims 2 and 3, characterized in that the fuel injectors (5) of the injection system each have a high-pressure connection (26), in which a high-pressure duct issue (19a) for the connection of the high-pressure fuel line (4), the leakage-duct issue (20a) and the return-duct issue (21a) are jointly arranged.
5. Fuel injection system according to Claim 4, characterized in that, in the case of the high-pressure connection (26), the high-pressure duct issue (19a) is arranged centrally on its end face, and the leakage-duct issue (20a) and the return-duct issue (21a) are arranged, spaced apart from one another in the axial direction, on the circumference of the said high-pressure connection, the individual issues (19a, 20a, 21a) in each case being sealed off and separated from the other issues (19a, 20a, 21a) by means of sealing elements (33, 34, 35, 36).
6. Fuel injection system according to Claim 5, characterized in that the sealing element (33) of the high-pressure duct issue (19a) is formed by a cone seal cooperating with a sealing cone (37) formed at the end of the high-pressure fuel line (4), and in that the sealing elements (34, 35, 36) sealing off the leakage-duct issue (20a) and the return-duct issue (21a) are formed by O-rings.
7. Fuel injection system according to Claim 1, characterized in that the high-pressure fuel line (4) is surrounded coaxially by an inner and an outer casing tube (31, 32) which in each case enclose flow cross sections (31a, 32a) separated from one another by walls and which form the fuel return line (11) and the leakage line (12).
8. Fuel injection system according to Claim 7, characterized in that the casing tubes (31,32) are provided on their inner surface with ducts (32a, 31a) running in the longitudinal direction and forming the flow cross sections of the fuel return line (11) and of the leakage line (12) respectively.
9. Fuel injection system according to Claim 8, characterized in that the casing tubes (31, 32) have on their inner surface, between the ducts (31a, 32a) forming the flow cross sections of the fuel return line (11) and of the leakage line (12) respectively, webs (31b, 32b) which bear against the outer circumference of the in each case inner line surrounded by the respective casing tube (31, 32).