DE102005058079A1 - Fuel injector for internal combustion engine, has valve arrangement with switching condition, in which arrangement hydraulically couples reset path with high pressure system and couples operating path with low pressure system - Google Patents

Abstract

The injector has a nozzle needle (3), where a needle assembly of the needle has an injecting piston (10) which separates an injecting area (9) from a nozzle area (12). A valve arrangement (17) has a switching condition, in which the arrangement hydraulically couples an operating path with a fuel guided high pressure system and couples a reset path with a low pressure system or with a high pressure system. The arrangement has another switching condition, in which the arrangement couples the reset path with the high pressure system and couples the operating path with the low pressure system. An independent claim is also included for a method for operating an injector.

Description

injector

State of the art

The The present invention relates to an injector for fuel injection in an internal combustion engine, in particular in a motor vehicle is arranged.

Out WO 02/093001 A1 discloses an injector which has a nozzle needle for controlling at least one injection hole and a separate booster piston having. A control valve generates to initiate an injection process a pressure drop in corresponding control chambers of the nozzle needle and the booster piston. Then leads the translator piston a pressure stroke, the pressure in a pressure chamber to an injection pressure elevated, the above the already relatively high pressure of a high-pressure system lies. At the same time leads the nozzle needle an opening stroke through, leaving the nozzle needle the at least one spray hole releases and under injection pressure standing fuel can be injected into an injection space. The known injector thus operates with a pressure-controlled nozzle needle and with a pressure intensifier.

To the Controlling the at least one injection hole acts a needle point the nozzle needle with a needle seat of the nozzle body together, which is arranged upstream of the at least one injection hole. During one Initial phase of the opening stroke the nozzle needle the needle point is in the immediate vicinity of the needle seat, so that there only a very small flow cross-section prevails. this leads to to the fact that under injection pressure fuel throttled only the area of the needle seat can flow through, so-called seat throttling. As long as the seat throttling prevails, the fuel can not with the injection pressure, but only with a more or less strongly throttled pressure to be injected into the injection space. It has been shown that during the the initial phase of the injection process only throttled injected Fuel quantity increased Pollutant emissions can.

Advantages of invention

Of the Inventive injector with the features of claim 1 has the advantage that a Seat throttling does not occur at the beginning of the injection process. Much more can at the beginning of the injection process, the injection pressure on at least to build up a spray hole unthrottled. For this purpose, the nozzle needle or a nozzle needle needle assembly having an injection piston having an injection space, in which there is at least one spray hole, from a nozzle chamber separates. To prepare for an injection process raises the nozzle needle with its needle tip from the needle seat, at the same time the injection piston Fuel from the nozzle chamber via a corresponding connection path displaced into the injection space. As soon as In the injection chamber, the desired injection quantity is present, the actual injection process is carried out in the nozzle needle again in the closing direction is driven. As a result, the injection piston builds in the in Injection space located fuel to the injection pressure, with the fuel through the at least one injection hole the injection space leaves and enters the injection room. At the beginning of the injection process the needle point has a relatively large, regularly their greatest distance from the needle seat. At the beginning of the injection process can thus no seat throttling occur, which improves the emissions of the combustion process.

Especially an embodiment is advantageous in which the connection path, through the fuel from the nozzle chamber can get into the injection space, in the form of at least one hole is integrated in the injection piston.

Further important features and advantages of the injector according to the invention arise from the dependent claims, from the drawings and from the associated description of the figures the drawings.

drawings

embodiments of the injector according to the invention are shown in the drawings and are explained in more detail below, wherein the same reference numerals to the same or similar or functionally identical Refer to components. Show, in each case schematically,

1a to 1c simplified schematic diagrams of an injector in three different operating phases,

2a to 2c Views of the injector at different operating phases as in the 1a to 1c but in another embodiment,

3 to 5 greatly simplified schematic diagram of the injector in further different embodiments.

According to the 1 to 5 comprises an injector according to the invention 1 that uses fuel in an injection room 2 an internal combustion engine, not shown, are injected can, a nozzle needle 3 in a nozzle body 4 is arranged adjustable in stroke. The nozzle needle 3 can be part of a needle assembly 5 be, which consists of several components that a common stroke adjustable unit, namely the needle bandage 5 form. In this case, at least two of these components may lie loosely in the stroke direction or be fastened to each other or be made of one piece. The internal combustion engine usually has such an injector for each cylinder 1 and may preferably be arranged in a motor vehicle.

The nozzle body 4 has at least one spray hole 6 by the fuel in the injection space during an injection process 2 is injected. Usually, several, star-shaped injection ports are 6 intended. For controlling the at least one injection hole 6 has the nozzle needle 3 or the needle bandage 5 a needle point 7 on the one with the nozzle body 4 trained needle seat 8th interacts. In a closed state of the nozzle needle 3 the needle tip sits 7 in the needle seat 8th and thereby separates the at least one spray hole 6 from an injection room 9 from.

The nozzle needle 3 or the needle bandage 5 has an injection piston 10 on, concerning the nozzle needle 3 is arranged stationary. The injection piston 10 separates in an injection cylinder 11 the injection space 9 from a nozzle room 12 ,

The nozzle needle 3 or the needle bandage 5 also has a control piston 13 on, also with respect to the nozzle needle 3 is arranged stationary. The control piston 13 separates in a control cylinder 14 a workroom 15 from a recovery room 16 , Here is relative to the control piston 13 the recovery room 16 the needle tip 7 facing, while the workroom 15 from the needle point 7 turned away.

The injector 1 is also with a valve assembly 17 equipped, over which the individual rooms 9 . 12 . 15 . 16 of the injector 1 with a low-pressure fuel system 18 or with a fuel-carrying high-pressure system 19 hydraulically connectable. The high pressure system 19 usually includes a fuel only high pressure line shown symbolically 20 about the injector 1 the fuel is provided under a relatively high pressure. If several injectors 1 to a common high-pressure fuel line 20 are connected, it is a so-called common rail system. In the low pressure system 18 There is a reduced pressure. The low pressure system 18 is used to return unneeded fuel to a fuel reservoir or fuel tank. The pressure prevailing in the low-pressure system may be higher than the ambient pressure.

The injector 1 has a connection path 21 on, over which the injection space 9 with the nozzle space 12 hydraulically coupled. Where is the connection path 21 be configured so that fuel from the nozzle chamber 12 to the injection room 9 can flow, but not in the opposite direction. For this, the connection path 21 for example, with a non-return valve 22 be equipped that towards the nozzle chamber 12 locks out. In the embodiments shown here, the connection path is 21 through at least one hole 23 formed, which the injection piston 10 penetrates in the axial direction.

Furthermore, a nozzle path 24 provided over the nozzle space 12 with the low pressure system 18 hydraulically coupled. In this nozzle path 24 can be a check valve 25 be arranged. The check valve 25 can be biased in its blocking position by means of a spring not specified. In the embodiment of the 1a to 1c is the non-return valve 25 so in the nozzle path 24 built it in the direction of the low pressure system 18 locks. This is the nozzle path 24 designed so that fuel only from the low pressure system 18 to the nozzle room 12 can flow, but not in the opposite direction. By the bias of the non-return valve 25 in its blocking position is also achieved that only fuel from the low pressure system 18 to the nozzle room 12 can flow when the fuel pressure in the nozzle chamber 12 falls below a predetermined holding pressure.

In the embodiments of the 2 to 5 is the non-return valve 25 so in the nozzle path 24 built it in the direction of the nozzle space 12 locks. The result is the nozzle path 24 in these embodiments designed so that fuel only from the nozzle chamber 12 to the low pressure system 18 can flow and not in the opposite direction. By the bias of the non-return valve 25 in its blocking position is also achieved that only fuel from the nozzle chamber 12 to the low pressure system 18 can drain when the fuel pressure in the nozzle chamber 12 rises above a predetermined holding pressure.

There is also a reset path 26 and a work path 27 intended. About the reset path 26 is the recovery room 16 with the valve assembly 17 hydraulically coupled. The work path 27 couples the workspace 15 with the valve assembly 17 hydraulically. The reset path 26 and the work path 27 may be throttled, which in the figures by symbolized throttles 28 is indicated.

Furthermore - but need not - the injector 1 with a compression spring 29 be equipped. This pressure spring 29 can according to the Ausfüh forms of the 1 . 3 . 4 and 5 in the workroom 15 be arranged to the control piston 13 in the direction of the recovery room 16 drive. Alternatively, the compression spring 29 according to the embodiment of the 2 also in the recovery room 16 be arranged to the control piston 13 in the direction of the workroom 15 drive.

The valve arrangement 17 is designed such that it has at least two or exactly two switching states. In a first switching state, in the 1a . 1c . 2a . 2c and 3 to 5 is shown, the valve assembly couples 17 hydraulically the return path 26 with the low pressure system 18 and the work path 27 with the high pressure system 19 , In one in the 1b and 2 B shown second switching state couples the valve assembly 17 hydraulically the return path 26 with the high pressure system 19 and the work path 27 with the low pressure system 18 ,

In the in the 1a to 1c embodiment shown, the valve assembly comprises 17 a 4/2-way valve 30 which has four terminals and two switch positions. A first connection 31 is to a return line 32 of the return path 26 connected. A second connection 33 is to a work management 34 of the work path 27 connected. A third connection 35 is via a low pressure line 36 to the low pressure system 18 connected. A fourth connection 37 is finally over a high pressure line 38 to the high pressure system 19 connected. In a first switching position I connects the 4/2-way valve 30 the first connection 31 with the third connection 35 so the reset path 26 with the low pressure system 18 connected, and the second port 33 with the fourth connection 37 so the work path 27 with the high pressure system 19 connected is. In a second switching position II connects the 4/2-way valve 30 the first connection 31 with the fourth connection 37 so the reset path 26 with the high pressure system 19 connected, and the second port 33 with the third connection 35 so the work path 27 with the low pressure system 18 connected is.

The in the 1a to 1c The embodiment shown operates as follows:

1a shows a resting phase of the injector 1 , This resting phase is present after the completion of an injection process. In the resting phase, the valve assembly decreases 17 their first switching state, which is achieved here in that the 4/2-way valve 30 his first shift position I occupies. In the resting phase, the needle tip sits 7 in the needle seat 8th and thus blocks the at least one spray hole 6 , In the resting phase prevails thus in the work space 15 the high pressure of the high pressure system 19 and in the recovery room 16 the low pressure of the low pressure system 18 , In the nozzle room 12 the holding pressure is the same or greater than the low pressure. In the injection room 9 the pressure of the injection room prevails 2 , The connection path 21 , in particular its non-return valve 22 can be designed so that in the resting phase, no fuel from the nozzle chamber 12 in the injection room 9 passes, or so that of the injector 2 over the injection space 9 during a compression stroke or intake stroke of the internal combustion engine no gas in the nozzle chamber 12 is pressed.

This is achieved for example by a corresponding bias of the non-return valve 22 in its locked position.

In 1b is the injector 1 in a reset phase This reset phase is used to prepare an injection process. In the reset phase is the valve assembly 17 switched to its second switching state, which is achieved here in that the 4/2-way valve 30 its second switching position Π occupies. The result is now the workspace 15 with the low pressure system 18 connected, so in the workroom 15 the pressure drops. At the same time, the recovery room 16 with the high pressure system 19 connected, so that there the pressure rises. As a result, the nozzle needle 3 or the needle bandage 5 perform an opening stroke, according to an arrow 39 , This raises the needle point 7 from the needle seat 8th off and the injection piston 10 reduces the volume of the nozzle space 12 and displaces the fuel from the nozzle chamber 12 in the injection room 9 , This reset phase is carried out until it is in the injection chamber 9 exactly the amount of fuel that has accumulated during the subsequent injection process in the injection chamber 2 to be injected. Suitably, the reset phase is performed during a period of time at which the pressure in the injection chamber 2 is greater than the fuel pressure in the injection chamber 9 , In this way it is prevented that during the reset phase already fuel from the injection chamber 9 through the at least one spray hole 6 in the injection room 2 arrives.

1c now shows the injector 1 during an injection phase. This injection phase follows immediately after the reset phase. During the injection phase, the actual fuel injection takes place in the injection space 2 instead of. For this purpose, the valve assembly 17 again transferred to its first switching state; in the present case, therefore, takes the 4/2-way valve 30 his first shift position I again. As a result, the pressure in the working space increases 15 while at the same time in the recovery room 16 drops. This causes the nozzle needle 3 or the needle bandage 5 now moved in the opposite direction and one by an arrow 40 indicated Closing stroke performs. During this closing stroke 40 compresses the injection piston 10 the fuel in the injection chamber 9 where it builds up the injection pressure with which the fuel from the injection chamber 9 expelled and into the injection room 2 is injected. At the same time while the nozzle chamber 12 over the nozzle path from the low pressure system 18 refilled.

Thus, the needle tip 7 at the beginning of the actual injection process from the needle seat 8th relatively far away, so that a seat throttling does not occur at the beginning of the injection process. The injection pressure can be in the injection chamber 9 build up unthrottled at the beginning of the injection phase. In this case, the injection pressure may be greater than the high pressure. A corresponding pressure ratio is achieved in that the cross section of the injection piston 10 is smaller than the cross section of the control piston 13 ,

During the reset path 26 in the embodiment according to 1 only a single return line 32 are in the embodiments of the 2 to 5 in each case two return lines provided, namely a return low pressure line 41 and a return high pressure line 42 , Accordingly, in the embodiments of the 2 to 5 also two working lines, namely a working low pressure line 43 and a working high pressure line 44 provided while the embodiment according to 1 only a single management 34 having. The return low pressure line 41 is in the embodiments of 2 and 3 to the low pressure system 18 or to a low-pressure line coupled thereto 45 connected. In the embodiments of the 4 and 5 is the return low pressure line 41 over the valve assembly 17 with the low pressure system 18 connectable. The return high pressure line 42 is in the embodiments of 2 and 3 over the valve assembly 17 to the high pressure system 19 connected. In the embodiments of the 4 and 5 is the return high-pressure line 42 directly to the high pressure system 19 connected. The low pressure line 43 is in the embodiments of 2 and 3 over the valve assembly 17 with the low pressure system 18 connectable. In the embodiments of the 4 and 5 is the working low pressure line 43 also via the valve arrangement 17 with the low pressure system 18 connectable. The working high pressure line 44 is in the embodiments of 2 and 3 over the valve assembly 17 with the high pressure system 19 connectable. In the embodiments of the 4 and 5 is the working high pressure line 44 permanently with the high pressure system 19 connected.

In the embodiments of the 2 and 3 includes the valve assembly 17 a 2/2-way valve 46 and a servo valve 47 , The 2/2-way valve 46 has two ports and two switch positions. A first connection 48 is doing to a connection line 49 connected while a second connection 50 over the low pressure line 36 to the low pressure system 18 connected. In a first switching position I of the 2/2-way valve 46 are both connections 48 . 50 blocked. In a second switching position II, the two terminals 48 . 50 connected with each other.

The servo valve 47 has five connections and two switching positions. A first connection 51 is also connected to the connection line 49 connected. A second connection 52 is to the working low pressure line 43 connected. A third connection 53 is to the working high pressure line 44 connected. A fourth connection 54 is to the return high pressure line 42 connected. Finally, there is a fifth connection 55 over the high pressure line 38 to the high pressure system 19 connected. In one in the 2a . 2c and 3 shown first switching position of the servo valve 47 is the first connection 51 with the second connection 52 connected. Besides, the third port is 53 with the fifth connection 55 connected while at the same time the fourth connection 54 Is blocked. In the in 2 B shown second switching position II are also the first connection 51 and the second connection 52 connected with each other. At the same time, the third connection 53 locked while the fourth port 54 with the fifth connection 55 connected is.

The in the 2 and 3 The embodiments shown operate as follows:

In 2a is the resting phase of the injector 1 before, so the valve assembly 17 shows her first switching state. These are the 2/2-way valve 46 and the servo valve 47 each adjusted in their first switching position I. Accordingly prevails in the work space 15 the high pressure while in the recovery room 16 the low pressure prevails. In the nozzle room 12 the maximum is the low pressure. In the injection room 9 is the pressure of the injection room 2 in front.

2 B shows the reset phase while the nozzle needle 3 or the needle bandage 5 the opening stroke 39 performs. The valve arrangement 17 has its second switching state, which is realized in that both the 2/2-way valve 46 as well as the servo valve 47 each occupy their second switching position II. As a result, the working space prevails 15 the low pressure while in the recovery room 16 the high pressure prevails. The injection room 9 can fill with the amount of fuel to be injected.

In 2c is the injector 1 in its injection phase, realized by the first switching state of the valve arrangement 17 , so the nozzle needle 3 or the needle bandage 5 the closing stroke 40 performs. The fuel gets out of the injection room 9 under injection pressure in the injection chamber 2 expelled.

In the 3 The embodiment shown differs from that shown 2 only by the arrangement of the compression spring 29 ,

At the in 4 embodiment shown, the valve assembly comprises 17 two 2/2-way valves, each with two connections and two switching positions. A left illustrated first 2/2-way valve 56 is with its first connection 58 to the working low pressure line 43 connected and with its second connection 59 over the low pressure line 36 with the low pressure system 18 connected. In the reproduced first switching position I, the two terminals 58 . 59 locked while they are connected together in a second switching position. In a second 2/2-way valve 57 is a first connection 60 with the return low-pressure line 41 connected while a second connection 61 over the low pressure line 36 with the low pressure system 18 connected is. In a first switching position I shown, the two terminals 60 . 61 locked while in a second position 1 connected to each other. For the first switching state of the valve arrangement 17 has the first 2/2-way valve 56 its first switching position I and the second 2/2-way valve 57 also has its first switching position I on. As a result, both the workspace prevails 15 as well as in the recovery room 16 the high pressure. In the second switching state of the valve arrangement 17 has the first 2/2-way valve 56 its second switching position II, while the second 2/2-way valve 57 maintains its first switching position I. As a result, the pressure falls in the workspace 15 while he is in the recovery room 16 stays high, so the nozzle needle 3 opens. In a third switching state of the valve arrangement 17 then points the first 2/2-way valve 56 again its first shift position I on, while then the second 2/2-way valve 57 its second switching position II occupies. Consequently, the pressure falls in the recovery room 16 and takes off in the workroom 15 too, leaving the nozzle needle 3 closes again.

At the in 5 embodiment shown, the valve assembly comprises 17 only a single 3/2-way valve 62 , which has three connections and two switching positions. A first connection 63 is to the working low pressure line 43 connected while a second connection 64 to the return low-pressure line 41 connected. A third connection 65 is via the low pressure line 36 to the low pressure system 18 connected. In an in 5 active first switching position I is the first port 63 with the third connection 65 connected while the second port 64 Is blocked. In a second switching position II then the first port 63 locked while the second port 64 with the third connection 65 connected is.

In the first switching state of the valve arrangement 17 by adjusting the 3/2-way valve 62 is set in the second switching position II, prevails in the working space 15 the high pressure while in the recovery room 16 the low pressure is present. In the second switching state of the valve arrangement 17 has the 3/2-way valve 62 his first shift position I on, as a result, the pressure drops in the working space 15 while he is in the recovery room 16 increases.

1

injector

2

injection room

3

nozzle needle

4

nozzle body

5

needle unit

6

spiracle

7

pinpoint

8th

needle seat

9

Injection room

10

Injection piston

11

Injection cylinder

12

nozzle chamber

13

spool

14

control cylinder

15

working space

16

Restoring chamber

17

valve assembly

18

Low pressure system

19

High pressure system

20

High pressure fuel line

21

connection path

22

Return check valve of 21

23

drilling

24

nozzle path

25

Return check valve of 24

26

Return path

27

work path

28

throttle

29

compression spring

30

4/2-way valve

31

first connection of 30

32

Reset line

33

second connection of 30

34

working line

35

third connection from 30

36

Low-pressure line

37

fourth connection from 30

38

High-pressure line

39

opening stroke

40

Closing

41

Restoring low-pressure line

42

Reset high pressure line

43

Working low pressure line

44

Working high-pressure line

45

Low-pressure line

46

2/2 way valve

47

servo valve

48

first connection of 46

49

connecting line

50

second connection of 46

51

first connection of 47

52

second connection of 47

53

third connection from 47

54

fourth connection from 47

55

fifth connection of 47

56

first 2/2 way valve

57

second 2/2 way valve

58

first connection of 56

59

second connection of 56

60

first connection of 57

61

second connection of 57

62

3/2-way valve

63

first connection of 62

64

second connection of 62

65

third connection from 62

Claims (12)

Injector for fuel injection in an internal combustion engine, in particular in a motor vehicle, - with one in a nozzle body ( 4 ) Hubverstellbar arranged nozzle needle ( 3 ) whose needle tip ( 7 ) for controlling at least one injection hole ( 6 ) in an injection space ( 9 ) with a needle seat ( 8th ), - wherein the nozzle needle ( 3 ) or a nozzle needle ( 3 ) having needle dressing ( 5 ) an injection piston ( 10 ), the injection space ( 9 ) from a nozzle space ( 12 ), wherein - the nozzle space ( 12 ) via a connection path ( 21 ) with the injection space ( 9 ) is hydraulically coupled, such that fuel from the nozzle chamber ( 12 ) to the injection space ( 9 ), but not back, - wherein the nozzle chamber ( 12 ) via a nozzle path ( 24 ) with a low-pressure fuel system ( 18 ) is hydraulically coupled, - wherein the nozzle needle ( 3 ) or the needle bandage ( 5 ) a control piston ( 13 ) having a working space ( 15 ) from a recovery room ( 16 ), - the recovery room ( 16 ) via a reset path ( 26 ) with a valve arrangement ( 17 ) is hydraulically coupled, - wherein the working space ( 15 ) via a work path ( 27 ) with the valve arrangement ( 17 ) is hydraulically coupled, - wherein the valve arrangement ( 17 ) has a first switching state, in which the working path ( 27 ) with a high-pressure fuel system ( 19 ) and the reset path ( 26 ) with the low pressure system ( 18 ) or with the high-pressure system ( 19 ) hydraulically coupled, - wherein the valve assembly ( 17 ) has a second switching state in which the reset path ( 26 ) with the high pressure system ( 19 ) and the work path ( 27 ) with the low pressure system ( 18 ) hydraulically coupled. Injector according to claim 1, characterized in that - the connection path ( 21 ) at least one check valve ( 22 ), which in the direction of the injection space ( 9 ) to the nozzle space ( 12 ) locks, and / or - that the connection path ( 21 ) at least one of the injection piston ( 10 ) penetrating bore ( 23 ) having. Injector according to claim 1 or 2, characterized in that - the nozzle path ( 24 ) is designed so that fuel from the low pressure system ( 18 ) to the nozzle space ( 12 ), but not back, and / or - that the nozzle path ( 24 ) is designed so that only fuel from the low pressure system ( 18 ) to the nozzle space ( 12 ) flows when the pressure in the nozzle chamber ( 12 ) is below a predetermined holding pressure, and / or - that the nozzle path ( 24 ) a check valve ( 25 ), which in the direction of the nozzle chamber ( 12 ) to the low-pressure system ( 18 ) locks. Injector according to one of claims 1 to 3, characterized in that - the valve arrangement ( 17 ) a 4/2-way valve ( 30 ) with four connections ( 31 . 33 . 35 . 37 ) and two switching position (I, II), - that the first connection ( 31 ) to the reset path ( 26 ), that the second connection ( 33 ) to the work path ( 27 ) - that the third connection ( 35 ) to the low pressure system ( 18 ), that the fourth connection ( 37 ) to the high pressure system ( 19 ) is connected, - that in the first switching position (I) of the first port ( 31 ) with the third connection ( 35 ) and the second connection ( 33 ) with the fourth connection ( 37 ) are connected, - that in the second switching position (II) of the first terminal ( 31 ) with the fourth connection ( 37 ) and the second connection ( 33 ) with the third connection ( 35 ) are connected. Injector according to claim 1 or 2, characterized in that - the reset path ( 26 ) a return low-pressure line ( 41 ) connected to the low-pressure system ( 18 ) is connected or via the valve assembly ( 17 ) with the low pressure system ( 18 ) is connectable, and a return high-pressure line ( 42 ) connected to the high-pressure system ( 19 ) or via the valve arrangement ( 17 ) with the high pressure system ( 19 ), and / or - that the work path ( 27 ) a working low pressure line ( 43 ) connected to the low-pressure system ( 18 ) or via the valve arrangement ( 17 ) with the low pressure system ( 18 ) is connectable, and a working high pressure line ( 44 ) connected to the high-pressure system ( 19 ) or via the valve arrangement ( 17 ) with the high pressure system ( 19 ) is connectable. Injector according to claim 5, characterized in that - the valve arrangement ( 17 ) a 2/2-way valve ( 46 ) with two connections ( 48 . 50 ) and two switching position (I, II) and a servo valve ( 47 ) with five connections ( 51 . 52 . 53 . 54 . 55 ) and two switch positions (I, II), - that the 2/2-way valve ( 46 ) with its first connection ( 48 ) to a connecting line ( 49 ) and with its second connection ( 50 ) to the low pressure system ( 18 ) is connected, in its first switching position (I) the first terminal ( 48 ) locks and in its second switching position (II) the first port ( 48 ) with the second connection ( 50 ), - that the servo valve ( 47 ) with its first connection ( 51 ) to the connecting line ( 49 ), with its second connection ( 52 ) to the working low pressure line ( 43 ), with its third connection ( 53 ) to the working high pressure line ( 44 ), with its fourth connection ( 54 ) to the return high-pressure line ( 42 ) and with its fifth connection ( 55 ) to the high pressure system ( 19 ) is connected, in its first switching position (I) the first terminal ( 51 ) with the second connection ( 52 ) connects the third port ( 53 ) with the fifth connection ( 55 ) and the fourth port ( 54 ) locks and in its second switching position (II) the first port ( 51 ) with the second connection ( 52 ) connects the third port ( 53 ) and the fourth port ( 54 ) with the fifth connection ( 55 ) connects. Injector according to claim 5, characterized in that - the valve arrangement ( 2 ) two 2/2-way valves ( 56 . 57 ) with two connections ( 58 . 59 ; 60 . 61 ) and each two switching position (I, II), - that the first 2/2-way valve ( 56 ) with its first connection ( 58 ) to the working low pressure line ( 43 ) and with its second connection ( 59 ) to the low pressure system ( 18 ) is connected, in its first switching position (I) the first terminal ( 58 ) locks and in its second switching position (II) the first port ( 58 ) with the second connection ( 59 ), - that the second 2/2-way valve ( 57 ) with its first connection ( 60 ) to the return low-pressure line ( 41 ) and with its second connection ( 61 ) to the low pressure system ( 18 ) is connected, in its first switching position (I) the first terminal ( 60 ) locks and in its second switching position (II) the first port ( 60 ) with the second connection ( 61 ) connects. Injector according to claim 5, characterized in that - the valve arrangement ( 17 ) a 3/2-way valve ( 62 ) with three connections ( 63 . 64 . 65 ) and two switching position (I, II), - that the 3/2-way valve ( 62 ) with its first connection ( 63 ) to the working low pressure line ( 43 ), with its second connection ( 64 ) to the return low-pressure line ( 41 ) and with its third connection ( 65 ) to the low pressure system ( 18 ) is connected, in its first switching position (I) the first terminal ( 63 ) with the third connection ( 65 ) and the second port ( 64 ) locks and in its second switching position (II) the first port ( 63 ) and the second port ( 64 ) with the third connection ( 65 ) connects. Injector according to one of claims 6 to 8, characterized in that - the nozzle path ( 24 ) is configured so that fuel from the nozzle chamber ( 12 ) to the low pressure system ( 18 ), but not back, and / or - that the nozzle path ( 24 ) is designed so that only fuel from the nozzle chamber ( 12 ) to the low-pressure system ( 18 ) flows when the pressure in the nozzle chamber ( 12 ) is above a predetermined holding pressure, and / or - that the nozzle path ( 24 ) a check valve ( 25 ) directed in the direction of the low pressure system ( 18 ) to the nozzle space ( 12 ) locks. Injector according to one of claims 1 to 9, characterized in that - a compression spring ( 29 ), which in the recovery room ( 16 ) for driving the control piston ( 13 ) in the direction of the working space ( 15 ) or in the workroom ( 15 ) for driving the control piston ( 13 ) in the direction of the recovery room ( 16 ), and / or - that the control piston ( 13 ) has a larger cross section than the injection piston ( 10 ). Method for operating an injector ( 1 ) according to one of claims 1 to 10, - in which in a rest phase, which is present after an injection process, the valve arrangement ( 17 ) assumes its first switching state and the needle tip ( 7 ) in the needle seat ( 8th ) sits and that at least one injection hole ( 6 ) locks, - in which in a reset phase in preparation for an injection process, the valve assembly ( 17 ih ren second switching state assumes, so that the needle tip ( 7 ) from the needle seat ( 8th ) takes off and the at least one injection hole ( 6 ) and the injection piston ( 10 ) Fuel from the nozzle chamber ( 12 ) over the connection path ( 21 ) into the injection space ( 9 ), in which, in an injection phase immediately following the reset phase, the valve arrangement ( 17 ) assumes its first switching state, so that the injection piston ( 10 ) in the injection space ( 9 ) contained fuel through the at least one injection hole ( 6 ) from the injection space ( 9 ) drives out. A method according to claim 11, characterized in that the reset phase is carried out during a period of time in which the pressure in an injection space ( 2 ) into which the injector ( 1 ) injects the fuel is greater than one in the injection space ( 9 ) prevailing pressure.