EP1520101B1 - Fuel injector comprising booster for multiple injection - Google Patents

Description

Technical area

To supply combustion chambers of self-igniting internal combustion engines with Fuel can be used both pressure-controlled and stroke-controlled injection systems become. As fuel injection systems come next to pump-nozzle units, pump-line-nozzle units also storage injection systems are used. accumulator injection (Common rail) allow advantageously the injection pressure at load and adjust the speed of the internal combustion engine. To achieve high specific Achievements and to reduce the emissions of the self-igniting internal combustion engine In general, the highest possible injection pressure is required.

State of the art

For strength reasons, the achievable pressure level in today used storage injection systems currently limited to about 1600 bar. For further pressure increase In accumulator injection systems, pressure intensifiers are used.

EP 0 562 046 B1 discloses an actuation and valve arrangement with damping for an electronically controlled injection unit. The actuation and valve arrangement for a hydraulic unit has an electrically energizable electromagnet with a fixed stator and a movable anchor. The anchor has a first and a second Surface on. The first and second surfaces of the anchor define first and second a second cavity, wherein the first surface of the armature assigns to the stator. It is provided a valve which is connected to the armature. The valve is able to To pass from a sump a hydraulic actuating fluid to the injector. A damping fluid may be with respect to one of the cavities of the solenoid assembly be collected there or be drained from there. By means of a central hole protruding portion of a valve, the flow connection of the damping fluid selectively released or closed in proportion to its viscosity become.

DE 101 23 910.6 relates to a fuel injection device. This is at a Internal combustion engine used. The combustion chambers of the internal combustion engine are supplied with fuel via fuel injectors. The fuel injectors are acted upon by a high pressure source; Furthermore, the fuel injection according to DE 101 23 910.6 a pressure booster, a movable pressure booster piston having a connectable to the high pressure source space of a with the Fuel injector connected high-pressure chamber separates The fuel pressure in the high-pressure chamber can be achieved by filling a back space of the pressure booster with fuel or vary by draining this backspace of fuel.

The fuel injector comprises a movable closing piston for opening or closing the injection ports facing the combustion chamber. The closing piston protrudes a closing pressure chamber, so that it can be acted upon by fuel pressure. Thereby a force acting on the closing piston in the closing direction is achieved. Of the Closing pressure room and another room are shared by a working room formed, with all parts of the working space permanently for the exchange of Fuel are interconnected.

With this solution can be achieved by controlling the pressure booster on the back room be that the drive losses in the high-pressure fuel system compared to a control via a temporarily connected to the high-pressure fuel shaft Working space can be kept small. Furthermore, the high-pressure chamber is only up to the Pressure level of the high-pressure reservoir pressure relieved and not to the leakage pressure level. This improves on the one hand the hydraulic efficiency, on the other hand can a faster pressure build up to the system pressure level so that the between the injection phases lying temporal distances can be shortened.

The later published document DE 101 23 914 shows Common rail injection system with pressure booster.

In pressure-controlled common rail injection systems with pressure booster the problem occurs on that the stability of injected into the combustion chamber injection quantities, especially the representation of very small injection quantities, such as required at pre-injection, is not guaranteed. This is mainly attributed to the fact that the nozzle needle opens very quickly in pressure-controlled injection systems. Therefore, can be very small Scattering in the control period of the control valve strongly affect the injection quantity. An attempt has been made to remedy this problem by providing a separate needle stroke piston, which limits a damping space and in a high pressure tight clearance must be conducted. Although this solution allows a reduction of Needle opening speed, on the other hand, by this solution, the constructive Expenditure and thus the cost of the injection system greatly increased

In view of further increasing demands on emissions and noise self-igniting internal combustion engines are further measures on the injection system necessary to meet the more stringent limits expected in the near future fulfill.

In order to provide the most flexible possible injection, systems with two solenoid valves developed. However, since two solenoid valves are expensive and expensive, it is desirable use only one solenoid valve per injector / booster combination. Such a system was previously controlled via a 3/2-way valve to multiple injections display. These valves are complicated in construction and in mass production due to the required tight tolerances difficult in the required accuracy manufacture.

Presentation of the invention

The inventively proposed fuel injector with pressure booster allows the Execution of multiple injections into the combustion chamber of a self-igniting internal combustion engine by running on a pressure booster piston control sections. These allow for operation in combination with a 2/2-way valve the pressure translator, i. for pressure build-up in a compression chamber and for pressure relief a control room, multiple injections at a high pressure level. The use of one for mass production of injection components rather unsuitable 3/2-way valve, which in the required tolerances difficult and with high Costs connected to manufacture can be avoided.

Control sections on a rotationally symmetric component such as e.g. a pressure booster piston, can be produced cheaper in terms of the required accuracy; In addition, the 2/2-way valve used on the pressure-translated fuel injector has a relatively simple and interference-insensitive construction.

For display during a pre-injection phase into the combustion chamber of the internal combustion engine The smallest pilot injection quantities to be injected can be at the pressure booster piston formed control sections with respect to their axial length, i. in Lifting direction of the pressure booster piston, very narrow. Through the geometry The control sections can be realized another pre-injection phase, which accordingly The design of the control sections may be shorter or longer than a previous first pilot phase, for example. Instead of a further, a first preinjection phase downstream pilot injection phase can by appropriate interpretation of the control sections and a longer main injection phase in the combustion chamber of the internal combustion engine can be realized with little effort.

drawing

With reference to the drawing, the invention will be explained in more detail below.

The single FIGURE shows the hydraulic circuit diagram of an executed according to the invention Kraftstoffinjektors, in which the working space of an upstream pressure booster on a high pressure accumulator (common rail) with high pressure fuel can be acted upon.

variants

The figure shows a device for injecting fuel with a fuel injector, which is preceded by a pressure booster and via a 2/2-way valve trained metering valve is actuated

According to the illustrated in Figure 1 hydraulic circuit diagram of a fuel injector 1, this comprises a high-pressure storage space 2, a pressure booster 5 and a preferred designed as 2/2-way valve metering valve 6. The pressure intensifier 5 is a Downstream of injection valve, the injection valve member 34 via a hydraulic Room 31 and a nozzle chamber 28 can be actuated.

From high-pressure accumulator 2 (common rail) runs a supply line 9, which has an inlet 42 to a working space 10 of the pressure booster 5 has. Next to the workroom 10 the pressure booster 5 comprises a control chamber 11. The working chamber 10 of the pressure booster 5 is separated from the control chamber 11 of the pressure booster 5 by a piston 12, in the embodiment according to Figure 1, a first part piston 13 in enlarged Diameter and a second partial piston 14 in comparison to the first part piston 13th reduced diameter. The first partial piston 13 and the second partial piston 14 may be formed as separate components; in a modification of that shown in Figure 1 Structure of the piston 12, the first part piston 13 and the second part piston 14 also be formed integrally.

The second sub-piston 14 of the piston 12 within the pressure booster 5 is through a preferably acted as a spiral spring spring element 17 acted on the one hand at the bottom of the control chamber 11 of the pressure booster 5 and on the other hand to a spring stop 18 in the upper region of the first piston 14 is supported. The pressure intensifier 5 also includes a trained example as a support ring 16 stop for the upper end side of the first part piston 13 of the piston 12th

The control chamber 11 of the pressure booster 5 is connected via a control line 26 with the preferred designed as a 2/2-way valve metering valve 6 in conjunction, wherein the Circuit from the closed position shown in Figure 1 in the open position a Drukkentlastung the control chamber 11 in a low-pressure side return 8 causes. That as 2/2-way valve formed metering valve 6 can be used both as a solenoid valve and piezoelectric actuator be formed trained. Furthermore, the 2/2-way valve according to the in FIG illustrated embodiment as a servo valve or directly applied valve be formed. The control chamber 11 of the pressure booster is beyond about an overflow line 41 with a compression chamber 15 in the lower region of the pressure booster 5 in connection. From the compression chamber 15 of the pressure booster 5, in which the overflow line 41 opens at an orifice 24, branches at the same height a connecting line 32 from which the compression space 15 of the pressure booster. 5 connects to a hydraulic chamber 31, which can be formed preferably as a nozzle needle Injection valve member 34 acted upon. The compression chamber 15 is connected to the hydraulic Room 31 parallel to the connecting line 32 between the hydraulic space 31st and the compression chamber 15 connected via another line, which is a throttle point 30 contains. The filling of the compression chamber 15 via a branch 29, which is received by the supply line 9 from the high-pressure storage space 2 below one in this Check valve 43 branches off. About the supply line 9, in which to avoid of reactions occurring pressure pulsations or pressure wave reflections in the interior of the high pressure accumulator 2 a pulsation damping this check valve 43, a fuel inlet 27 branches off, which is in a nozzle chamber 28 opens. The nozzle space designated by reference numeral 28 is within one Nozzle body 4 of the fuel injector 1 is formed and encloses the injection valve member 34 annular. In the region of the nozzle chamber 28 is on the outer circumference of the injection valve member 34, a pressure shoulder 38 is formed.

The hydraulic chamber 31 contains a spring element 33 designed as a spiral spring which on the one hand on the ceiling of the hydraulic chamber 31 and on the other hand on the End face 35 of the injection valve member 34 is supported. From the nozzle chamber 28, the injection valve member 34 encloses in the region of a pressure stage 38, runs as an annular gap 26th trained inlet in the direction of the needle tip 37 out. At the needlepoint 37 of the Injection valve member 34 is a combustion chamber side seat of the injection valve member 34 is formed. This configured as a conical seat seat on the needle tip 37 of the Injection valve member 34 opens or closes in a combustion chamber 7 of a self-igniting Internal combustion engine opening injection ports 39, the double as Hole rows or simple hole rows holes can be formed in a circular shape and about which the fuel when entering the combustion chamber 7 of the self-igniting internal combustion engine atomized.

About the supply line 9 is the ruling in the interior of the high-pressure accumulator chamber 2 Pressure on the working space 10 of the booster on. In the ground state, i. at rest of the fuel injector 1 according to the invention is preferably designed as a 2/2-way valve Metering valve 6 is not activated and there is no injection. In this Condition is in the high-pressure reservoir 2 (common rail) applied pressure in the working space 10 of the pressure booster 5 at the metering valve 6 via the working space 10, an im first partial piston 13 formed throttle body 40, via the control chamber 11 and the control line 26 on. Furthermore, the ruling in the interior of the high-pressure accumulator 2 space Pressure via the throttle part 40 formed in the first partial piston 13 in the control chamber 11 of the pressure intensifier 5. Furthermore, the inside of the high pressure accumulator 2 prevailing pressure via a arranged in the supply line 9 check valve 43 via the Fuel inlet 27 in the nozzle chamber 28 of the injector body 4 on; in which the front side 35 of Injection valve member 34 acted upon hydraulic chamber 31 is the inside the pressure accumulator 2 prevailing pressure via the supply line 9, the check valve 43, the inlet 29 to the compression chamber 15 and the line branching off there with throttle 30 on. The compression space 15 of the pressure booster is via the inlet 29, seen in the flow direction of the fuel behind the Check valve 43 branches off from the supply line 9, with high pressure Fuel filled.

In the ground state, i. the rest state of the invention shown in Figure 1 proposed fuel injector are all pressure chambers 10, 11 and 15 of the pressure booster 5 acted upon by the pressure prevailing in the high-pressure accumulator 2 pressure level and the pressure booster 5 is in the pressure-balanced state. In this condition is the end face of the first part of piston 13 on in the injector 3 embedded as Stop element acting support ring 16 at. The pressure booster 5 is in this state deactivated and there is no pressure boost. In this state, the Piston unit 12 of the pressure booster via a via the return spring 17 in the closed Department held when all pressure chambers 10, 11 and 15 of the intensifier with the pressure level prevailing in the high-pressure reservoir 2 (rail pressure) are charged.

By prevailing in the hydraulic chamber 31 in the nozzle body 4 rail pressure is a hydraulic closing force on the end face 35 of the preferred designed as a nozzle needle Injection valve member 34 exerted. In addition to this acts acting in the closing direction Spring force, caused by the coil spring designed as a spring element, for example 33 within the hydraulic chamber 31 on the end face 35 of the injection valve member 34. Therefore, the prevailing inside the high-pressure accumulator 2 space Pressure (rail pressure) constantly in the nozzle chamber 28, the injection valve member 34 in the area a pressure shoulder 38 encloses annular, pending, without the injection valve member 34 by vertical movement in the hydraulic space 31, the injection openings 35 unintentionally releases into the combustion chamber 7 of the self-igniting internal combustion engine.

If an activation of the pressure booster 5, the increase in the compression chamber 15, in the nozzle chamber 28 and in the hydraulic chamber 31 prevailing pressure, as in the control room 11 of the pressure booster 5 prevailing pressure drops because the control line 26th by driving the metering valve 6 with the low-pressure side return 8 in conjunction stands and the control volume contained in the control chamber 11 flows there. This however, does not yet lead to the opening of the injection valve member, which is preferably designed as a nozzle needle 34 within the nozzle body 4, since the pressure difference between the nozzle chamber 28 and the hydraulic chamber 31 is not yet large enough. Only at one active relief of the hydraulic chamber 31 is carried out opening of the injection valve member 34, i. a retraction of its end face 35 in the hydraulic space 31 in the upper Area of the nozzle body 4 of the fuel injector. 1

For realizing an active relief of the hydraulic space 31 in the upper area the nozzle body 4 of the fuel injector 1 are at the compression space 15 of the Pressure translator 5 facing side of the second piston part 14 of the piston 12 control sections 19 and 21 formed. Lie in the embodiment shown in Figure 1 the control sections 19 and 21 in the stroke direction of the first piston part 14 in the Compression space 15 of the pressure booster 5 seen, one behind the other. On the peripheral surface of the second sub-piston 14 is a control portion 19 in a compared to Outside diameter of the first part piston 14 of reduced diameter formed, the seen in the stroke direction of the second part piston 14, in a first axial length 19.1 extends. The further control section 21 is separated from the control section 19 by a collar. The collar which separates the control section 19 from the further control section 21 is in first diameter of the first part piston 14 executed. The axial length 21.1 of the other Control section 21 is compared to the axial length 19.1 of the control section 19th considerably smaller. While the control section 19 is formed as an annular space, is the further control section 21 in comparison to the control section 19, for example as Obtain annular groove.

The control section 19 is on the collar on the first part piston 14 by a control edge 20th limited, while on the opposite side of the covenant on the outer circumference of the first Partial piston 14, a second control edge 22 limits the further control section 21.

Instead of the seen in Figure 1 in the stroke direction of the first piston part 14, two in a row lying control section 19 and 21, according to the intended stroke of the first sub-piston 14 in its immersion movement in the compression space 15 of the pressure booster 5 and three control sections formed one behind the other be corresponding to a number of be made in the context of a multiple injection Injection processes in the combustion chamber. 7

At the compression chamber 15 are the mouth points 24 of the overflow 41 to Control chamber 11 of the pressure booster 5 and the branch point 25 of the connecting line 32 of the compression space 15 with the hydraulic space 31 opposite each other.

The active relief of the hydraulic chamber 31 in the nozzle body 4 of the fuel injector takes place by an immersion movement of the first part piston 14 in the compression space 15. Has the second part piston 14 covered a certain stroke, connects the further control section 21, which may be formed as an annular groove, has a cross section between the hydraulic chamber 31 and the connecting line 32 on the one hand the overflow line 41 into the control chamber 11, the control line 26 to the low pressure side Return 8 on the other hand with each other. Thus, depending on the axial length of 21.1 further Control section 21 of the hydraulic chamber 31 are placed on low pressure, so that the force acting on the end face 35 of the injection valve member 34 decreases, so that the Injection valve member 34 can not be held in its closed position. by virtue of the pending in the nozzle chamber 28, on the pressure shoulder 38 of the injection valve member 34 acting hydraulic force, opens the injection valve member 34 and are the injection ports 39 in the combustion chamber 7 of the self-igniting internal combustion engine opening injection ports. The injection pressure is higher than that in the beginning Interior of the high pressure accumulator 2 prevailing pressure (rail pressure). A high injection pressure has a favorable effect on reducing the emissions of a self-igniting Internal combustion engine and the achievement of high specific performance. The inherent energy of the fuel is best implemented in this way.

To represent a small pilot injection in the context of a multiple injection too can, may the hydraulic chamber 31, the injection valve member 34 at the end face 35 applied, not too long connected to the low-pressure side return 8 stay. The desired pilot injection quantity can be further determined by the axial length 21.1 Control section 21 can be influenced. In the embodiment shown in Figure 1 the axial length 21.1 of the further control section 21 is just dimensioned so that an overflow of fuel from the hydraulic space 31 via the connecting line 32 in the overflow 41 and from there via the control chamber 11 in the control line 26 is possible. Once the further control section 21 at further pressure relief the control chamber 11 enters the compression chamber 15 of the pressure booster 5, interrupts the covenant between the control section 19 and the further control section 21 the Fluid connection between the connecting line 32 and the overflow 41 in the Control room 11. The hydraulic space 31 and the connection line 32 are accordingly through the collar of the overflow 41 the control chamber 11 and the latter of this branching overflow line 26 in the low-pressure side return 8 separately. Out hydraulic reasons is advantageous if the openings of the overflow 41 and the connecting line 32 into the bore into which the piston unit 12 runs open. In the position shown in Figure 1 and in which the piston unit 12 at its upper Stop 16, i. the Abstutzring rests, the openings of the connecting line 32 and the overflow line 41 from the collar between the end face 23 and the control section 21 covered. As a result, in the hydraulic space 31, the translated one builds Pressure on and closes the injection valve member 34, supported by the hydraulic Space 31 arranged spring 33. Since the pressure intensifier 5 remains activated and the End face 23 of the second part piston 14 consequently further into the compression space 15 einfährt, the control section 19 comes into coincidence with the discharge point 24 of Overflow 41 and the branch point 25 of the connecting line 32 to the hydraulic Room 31. Accordingly, one follows according to the axial length 19.1 of the control section 19 longer-lasting pressure relief of the hydraulic chamber 31 in the nozzle body 4, so that a further prolonged injection can take place. ever after dimensioning of the axial lengths 19.1 and 21.1 of the control sections 19 and 20 can this may be another pilot injection or a longer main injection phase. The main injection phase is terminated by either the first control edge 20 of the control section 19 opposite control edge between the fluid connection the mouths 25 and 24 of the lines 41 and 32 closes and this daduch interrupts or otherwise by deactivating the pressure booster. 5

To terminate the injection process, the pressure in the nozzle chamber 28 is in the high-pressure reservoir 2 prevailing pressure level reduced. For this purpose, by the preferably designed as a 2/2-way valve metering valve 6, the control chamber 11 of the pressure booster 5 separated from the low-pressure side return 8. As a result, the control room 11 with the pressure level prevailing in the high-pressure reservoir 2 (common rail) (Rail pressure) applied, which from the working space 10 via the first part piston 13th The throttle 12 provided in the throttle chamber 11 of the pressure booster fifth is effective. In the control room 11 of the pressure booster 5, therefore, rail pressure level builds up aut, since this is no longer on the control line 26 with the low-pressure side return. 8 communicates. In this state, this is preferably designed as a 2/2-way valve Metering valve 6 placed in its closed position shown in Figure 1. The pressure in the compression chamber 15, in the nozzle chamber 28 and in the hydraulic chamber 31 drops to rail pressure level from. As in the hydraulic chamber 31 now also in the high-pressure reservoir 2 prevailing pressure is present, the injection valve member 34 is hydraulically balanced and is acted upon by the force acting on the end face 35 of the injection valve member 34 spring force Spring element 34 is placed in its closed position and closes the injection openings 39 at the needle tip 37 of the injection valve member 34. Thus, the injection of under high pressure fuel into the combustion chamber 7 of the self-igniting internal combustion engine completed

After pressure equalization, the piston 12 of the pressure booster 5 becomes effective the return spring 17, which acts on a stop 18 on the second partial piston 14, again returned to the starting position, wherein the compression chamber 15 by the of the Supply line 9 branching supply line 29 is refilled with fuel. The hydraulic Room 31 is via the supply line 9, in which a pressure pulsations damping Check valve 43 may be included, the inlet 29 to the compression chamber 15th and the branching off this line with throttle point 30, refilled with fuel.

To stabilize the switching sequences with the inventively proposed fuel injector with pressure intensifier 5 additional measures for damping the Vibrations between the high pressure accumulator 2 (common rail) and the fuel injector 1 are taken. The check valve 43 can immediately behind the Mouth point in the high-pressure reservoir 2 or be arranged there. Instead of a check valve 43 may also be arranged there a throttle element. By the Check valve 43 or a throttle element arranged there are actuated the pressure booster 5 of the high-pressure accumulator 2 from the compression chamber 15, of the Lines 29 and 27 and separated from the nozzle chamber 28.

The proposed solution according to the invention combines a simply designed 2/2-way valve, which is designed as a metering valve 6, with a pressure booster piston part, on which the stroke direction of the partial piston seen several control sections are formed lying one behind the other. On the one hand the use of a consuming and costly to be produced bypassed 3/2-way valve, on the other hand can be easily pre-injection, main injection phases and Represents post-injections in the course of an injection molding. Furthermore, with the solution according to the invention instead of two solenoid valves a single metering valve 6 are used. The control sections 19 and 21 in the lower region of the second Partial piston 12 of the pressure booster 5 can be easily produced.

LIST OF REFERENCE NUMBERS

1

fuel injector

2

High-pressure accumulator

3

injector

4

nozzle body

5

Pressure intensifier

6

Metering valve (2/2-way valve)

7

combustion chamber

8th

low-pressure side return

9

supply

10

working space

11

control room

12

piston unit

13

first part piston

14

second partial piston

15

compression chamber

16

support ring

17

Return spring

18

Return spring stop

19

control section

19.1

axial length control section

20

first control edge

21

another control section

21.1

axial length of another control section

22

second control edge

23

Front side second partial piston 14th

24

Mouth connecting line control room

25

Branch line to the hydraulic chamber 31

26

Control line control room 11

27

Fuel inlet nozzle chamber

28

nozzle chamber

29

Inlet compression chamber 15

30

restriction

31

hydraulic room

32

connecting line

33

spring element

34

Injection valve member

35

front

36

annular gap

37

pinpoint

38

pressure shoulder

39

Injection port

40

Throttle first first piston 13th

41

overflow

42

Inlet working space

43

Check valve supply line 9

Claims (16)

1. Device for the injection of fuel into a combustion space (7) of an internal combustion engine, with a high-pressure accumulator space (2), with a pressure intensifier (5) and with a metering valve (6), the pressure intensifier (5) comprising a working space (10) and a control space (11) which are separated from one another by means of an axially movable piston (12; 13, 14), and a pressure change in the control space (11) of the pressure intensifier (5) bringing about a pressure change in a compression space (15) of the pressure intensifier (5), the compression space (15) being connected to a hydraulic space (31) assigned to an injection-valve member (34), characterized in that the piston (12; 13, 14) acting upon the compression space (15) of the pressure intensifier (5) has formed on it control portions (19, 21), via which the hydraulic space (31) of the injection-valve member (34) can be relieved of pressure.
2. Device for the injection of fuel according to Claim 1, characterized in that the hydraulic space (31) can be briefly relieved of pressure.
3. Device for the injection of fuel according to Claim 1, characterized in that the control portions (19, 21) are formed on the circumference of a part-piston (13, 14) of the piston unit (12) one behind the other in the stroke direction of the piston unit (12).
4. Device for the injection of fuel according to Claim 2, characterized in that at least two control portions (19, 21) are formed on the circumference of that part-piston (14) of the piston unit (12) which acts upon the compression space (15).
5. Device for the injection of fuel according to Claim 1, characterized in that an overflow line (41) connected to the control space (11) of the pressure intensifier (5) issues into the bore into which the piston unit (12) runs.
6. Device for the injection of fuel according to Claim 1, characterized in that the bore into which the piston unit (12) runs is connected to the hydraulic space (31) via a connecting line (32).
7. Device for the injection of fuel according to Claims 5 and 6, characterized in that the point of issue (24) of the overflow line (41) and the branch-off point (25) of the connecting line (32) lie opposite one another in the compression space (15).
8. Device for the injection of fuel according to Claim 3, characterized in that the control portions (19, 21) are separated from one another by a collar, as seen in the axial direction of the second part-piston (14).
9. Device for the injection of fuel according to Claim 1, characterized in that that of the control portions (19, 21) which lies nearest to the compression space (15) is designed as an annular groove.
10. Device for the injection of fuel according to Claim 1, characterized in that that of the control portions (19, 21) which lies nearest to the control space (11) of the pressure intensifier (5) is designed as an annular space.
11. Device for the injection of fuel according to Claims 9 and 10, characterized in that the axial lengths (19.1, 21.1) of the control portions (19, 21) are identical, as seen in the stroke direction of the piston unit (12; 13, 14).
12. Device for the injection of fuel according to Claims 9 and 10, characterized in that the axial lengths (19.1; 21.1) of the control portions (19, 21) are different, as seen in the stroke direction of the piston unit (12; 13, 14).
13. Device for the injection of fuel according to Claim 6, characterized in that a line comprising a throttle point (30) is connected in parallel with the connecting line (32) between the compression space (15) and the hydraulic space (31).
14. Device for the injection of fuel according to Claim 1, characterized in that the control space (11) can be relieved of pressure to the low-pressure side (8) via a control line (26) which receives a 2/2-way valve as metering valve (6).
15. Device according to Claim 1, characterized in that the supply line (9, 42, 29, 27) to the working space (10), to the compression space (15) and to the nozzle space (28) receives a non-return valve (43) which separates the high-pressure portion (15, 29, 27, 28) from the high-pressure accumulator space (2) when the pressure intensifier (5) is activated.
16. Device for the injection of fuel according to Claim 1, characterized in that the piston unit (12; 13, 14) of the pressure intensifier (5) comprises a first part-piston (13) which comprises a throttle point (40) connecting the working space (10) to the control space (11) of the pressure intensifier, and the control portions (19, 21) are formed on a second part-piston (14) of the piston unit (12), the end face (23) of the said second part-piston acting upon the compression space (15) of the pressure intensifier (5).

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