EP1605157A1 - Fuel injector with multipiece injection valve member and with pressure amplifier - Google Patents

Abstract

The fuel injector (3) has a multipart injector unit (18) with two needle parts (18.1,18.2). A control area (43) is fixed on the second needle part (18.2). The injector is connected with high pressure accumulator (1) for fuel, and operated by a control valve (32). The injector unit is biased by a spring (20) in closing direction. A movable damper (49) is arranged on the injector unit to limit damping area (42).

Description

Technical area

For supplying combustion chambers of self-igniting internal combustion engines with fuel Both pressure-controlled and stroke-controlled injection systems can be used become. As fuel injection system 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 to load and Adjust the speed of the internal combustion engine. To achieve high specific Achievements and to reduce the emissions of the internal combustion engine is general to aim for the highest possible injection pressure.

State of the art

For reasons of material strength, the achievable pressure level is used today Storage injection systems currently limited to about 1800 bar. For further pressure control In accumulator injection systems, pressure boosters are used on common-rail systems for use.

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 second cavity, wherein the first surface of the armature assigns to the stator. It is a Valve provided, which is connected to the armature. The valve is able to out To pass a hydraulic actuating fluid to the injection device to a sump. One Attenuation fluid may be there with respect to one of the cavities of the solenoid assembly be collected or be discharged from there again. By means of one in one Central bore projecting portion of a valve, the flow connection of the Damping fluids in proportion to its viscosity selectively released or closed become.

From DE 102 22 106 A1 a fuel injection valve for internal combustion engines is known. The fuel injection valve for internal combustion engines comprises a housing in which in one Bore a longitudinally displaceable outer valve needle and in turn this longitudinally slidable inner valve needle are arranged. These control with their combustion chamber side End ever at least one injection port. Furthermore, a control room is provided, the is connected via an inlet throttle with a high-pressure chamber and by the pressure at least indirectly a closing force is exerted on the outer valve needle. Further is a control pressure chamber provided by the pressure at least indirectly a closing force is exerted on the inner valve needle; Furthermore, a leakage oil space is provided in the always a low fuel pressure prevails. In the housing, a control valve is arranged, the one Valve chamber and a valve member disposed therein, wherein the valve space a Connection to the leakage oil chamber, an always open connection to the control room and a connection having the control pressure chamber. The valve member is in the valve space between two End positions movable, wherein in the first end position the connection to the leakage oil space closed and opened the connection to the control pressure chamber and in the second end position closed the connection to the control pressure chamber and the connection to the leakage oil chamber is open.

From DE 102 29 415 A1 discloses a device for Nadelhubdämpfung pressure-controlled Fuel injectors known. The device for injecting fuel comprises a Fuel injector, which via a high-pressure shaft with high-pressure fuel can be acted upon and actuated via a metering valve. In the injection valve member is a assigned by these independently movable damping element, which has a damping chamber limited. The damping element has at least one overflow channel to Connection of the damping chamber with another hydraulic space. at Fuel injectors comprising a multi-part injection valve member can be the opening pressure of the internal injection valve member part, for example, spring assist to a constant level or with the help of an additional assistant pressure (like e.g. the system pressure in the high-pressure accumulator) to a specific ratio of closing pressure to set the opening pressure. This is an adaptation of the hydraulic flow possible at the respective load point of the internal combustion engine. It turned out that the inner needle part only at relatively high pressures in the area of over 1500 bar may open to good emissions even at partial load operation to reach. It has been found that the setting of the opening pressure of the inside part of a multipart injection valve member is very sensitive to tolerances. This is due to the fact that with the opening of the inner needle part Quantity jump with respect to the in the combustion chamber of a self-igniting internal combustion engine associated fuel volume. Thus, specimen spreads, which occur in the mass production of fuel injectors, disadvantageous noticeable.

Presentation of the invention

With the solution proposed according to the invention, a control of a fuel injector, which contains a pressure booster, in the context of a high-pressure system for injection provided by fuel, which is the use of a multi-part Injection valve member for improving emissions with an active or passive switchable Injector valve member permitted. The inventive solution is achievable that a internally arranged nozzle needle-shaped part of the multi-part injection valve member only opens at full load and in partial load operation of the internal combustion engine Injection of fuel into the combustion chamber of the internal combustion engine only over that external part of the nozzle needle formed injection valve member is made.

The proposed solution also allows very short drive times of the internal Part of the multi-part injection valve member, which in turn short injection periods allows full-load operation of the self-igniting internal combustion engine. In the partial load range the internal combustion engine, however, can be an injection with small Nozzle flow, d. H. with only one open row of holes in the combustion chamber over any take long injection durations without opening another, second row of holes. By the in the partial load range opened first row of holes can be a small nozzle flow and a corresponding injection course shaping can be achieved while at a large Nozzle flow, given by the open first row of holes and the opened second Hole row an injection course shaping in the full load range of the self-igniting internal combustion engine can be achieved. A larger hydraulic flow through the opened first row of holes and the opened second row of holes in the combustion chamber of the self-igniting Internal combustion engine and an early, d. H. simultaneous in this case Opening the second needle, allow the introduction of a larger injection quantity at a given, motor-related constant injection duration, which is dependent on degrees crank angle and thus a higher performance.

With the inventively proposed solution of the control of a multi-part trained injection valve member having, and a pressure amplifier comprehensive Fuel injector is ensured that the multi-part injection valve member formed in other map areas no adverse effect on the hydraulic behavior of Fuel injector has. By simultaneously opening both needle parts of the multi-part Einspritzventilgliedes a shorter injection duration can be achieved, whereby the disadvantage of previously used, multi-part injection valve members avoided in which one of the needle parts only opens when the other needle part has an upper one Has reached stop, creating a time-delayed release of the additional, further Injection cross-section occurs in the combustion chamber, whereby its filling improvement only can be achieved to a limited extent.

drawing

With reference to the drawing, the proposed solution according to the invention is described in more detail below described.

Figur 1

den Hydraulikschaltplan eines aus dem Stand der Technik bekannten Kraftstoffinjektors mit einem Druckübersetzer,

Figur 2

eine erste Ausführungsvariante eines erfindungsgemäß ausgebildeten Kraftstoffinjektors mit Druckübersetzer und mehrteilig ausgebildetem Einspritzventilglied,

Figur 3

eine weitere Ausführungsmöglichkeit des erfindungsgemäß vorgeschlagenen Kraftstoffinjektors mit Druckverstärker und ansteuerbarem Servoventil und

Figur 4

eine weitere Ausführungsvariante eines erfindungsgemäß ausgebildeten Kraftstoffinjektors mit Druckverstärker und mehrteilig ausgebildetem Einspritzventilglied.

It shows:

FIG. 1

the hydraulic circuit diagram of a known from the prior art fuel injector with a pressure booster,

FIG. 2

a first embodiment of an inventively designed fuel injector with pressure booster and multipart injection valve member trained,

FIG. 3

a further embodiment of the present invention proposed fuel injector with pressure booster and controllable servo valve and

FIG. 4

a further embodiment of an inventively designed fuel injector with pressure booster and multipart trained injection valve member.

variants

In the illustration according to FIG. 1, an embodiment variant already known from the prior art is shown a fuel injector illustrated by its hydraulic circuit diagram.

A shown in Fig. 1 fuel injector 3 is a high-pressure accumulator 1 (common rail) supplied with high pressure fuel. The high-pressure accumulator 1 is via a high-pressure pump, which compresses the fuel and the high-pressure accumulator 1 supplies, fueled. The in the high-pressure accumulator 1, (common rail) prevailing fuel pressure is thus at each fuel injector 3 of the internal combustion engine to disposal. The fuel injector 3 comprises a control valve 32, a Pressure booster 4 and an injection valve member 18, which may be designed in several parts.

The pressure booster 4 is formed as axially displaceable stepped piston 9, wherein the Stepped piston 9 a acted upon via a high-pressure line 5 working space 6 of a pressure loadable differential pressure chamber 7 (back space) separates. The stepped piston 9 is acted upon by a return spring 8, which the stepped piston 9 in its upper position emotional. The stepped piston 9 acts upon pressure relief of the differential pressure chamber. 7 a compression chamber 10. In the idle state of the pressure booster 4 is the control valve 32 not activated, no injection takes place. In this case, it is located in the high-pressure accumulator 1 stored system pressure via the high pressure line 5, which is a throttle or may have a check valve 2, in the working space 6 of the pressure booster 4 at. Furthermore, the system pressure is applied to the control valve 32 via a high-pressure branch 34. about this and the likewise pressurized with system pressure control line 11 prevails system pressure also in the differential pressure chamber 7. Since the differential pressure chamber 7 via a connecting line is connected to a pressure chamber 12, in which a first spring element 20 and a second spring element 21 are received, there is also in the pressure chamber 12th System pressure. About a filling line 14 and an open refill valve 15 is System pressure in the compression chamber 10 and the high pressure line 16 in the nozzle chamber 17 of the fuel injector 3 as shown in Fig. 1 at. This means you are at rest the pressure booster 4, the hydraulic chambers on the pressure booster 4 with system pressure acted upon, so that the stepped piston 9 is pressure balanced. In this condition is the stepped piston 9 via the arranged in the differential pressure chamber 7 (back space) Restored spring 8 applied.

Due to the pressure prevailing in the pressure chamber 12 system pressure is the e.g. multi-part trained Injection valve member 18 is acted upon in the closing direction. The multipart injection valve member 18 includes a first, external needle part 18.1 and a second needle part 18.2, which is arranged on the inside and within the first needle part 18.1 is guided. Each of the two needle parts 18.1 or 18.2 is arranged in the pressure chamber 12 Associated spring element 20 and 21, respectively on the end faces of the first needle part 18.1 and the second needle part 18.2 act in the closing direction. Due to the effect the two spring elements 20 and 21 in the closing direction, the can in the nozzle chamber 17 pending, and at a pressure stage 25 of the first needle portion 18.1 attacking system pressure, the first needle part 18.1 not open. Only when the pressure in the nozzle chamber 17 via the system pressure rises, which is achieved by activating the pressure booster 4, opens the first needle portion 18.1 of the multi-part injection valve member 18 against the effect of this acting on its end face first spring element 20th

The metering of the fuel is carried out by pressure relief of the differential pressure chamber. 7 of the pressure booster 4. If the control valve 32 is actuated, which is the differential pressure chamber 7 (working space) with a pressure-side return 33 connecting control line 11 released and separated from the high pressure line 5. As a result, the pressure drops in the Differential pressure chamber 7 (working space) from, whereby the pressure around the compression space 10th rises due to the retracting in this stepped piston 9. As a result, over the High pressure line 16 and the pressure in the nozzle chamber 17. This increases in the opening direction the first needle part 18.1 at the compression stage 25 acting pressure force and the first needle part 18.1 opens. When opening a first row of holes 26 is released, so that at the combustion chamber end of the fuel injector 3 via this fuel in the Combustion chamber of the self-igniting internal combustion engine can be injected.

As long as the differential pressure chamber 7 (working space) of the pressure booster 4 depressurized remains, the pressure booster 4 remains activated and compresses the fuel in the compression chamber 10. The pressure chamber 12 remains pressure relieved. At the top of the combustion chamber of the second needle part 18.2 is now also on injection pressure level.

On a pressure surface A ₁ at the combustion chamber end of the second needle part 18.2 acts on this in the opening direction acting pressure force. Since the pressure chamber 12 is relieved of pressure, acting in the closing direction on the second needle member 18.2 second spring element 21 in the pressure chamber 12. About the dimensioning of the pressure surface A ₁ and the second spring element 21, an opening pressure can be adjusted, in which the second, inner needle part 18.2 of multi-part injection valve member 18 opens. At a lower injection pressure, for example in the partial load range of an internal combustion engine below the opening pressure with respect to the second needle part 18.2, only the first needle part 18.1 opens, the second needle part 18.2 remains closed so that only one injection of fuel takes place via the first row of holes 26.

On the other hand, the injection pressure is above the opening pressure of the second needle part 18.2, both needle parts 18.1 and 18.2 are opened, so that an injection of Fuel in the combustion chamber of the self-igniting internal combustion engine both over the first row of holes 26 as well as the second row of holes 27 can be made.

To end the injection by the control valve 32 of the differential pressure chamber. 7 (Working space) and the pressure chamber 12 separated from the low-pressure side return 33 and with the system pressure source, i. the high-pressure accumulator (common rail) connected. by virtue of whose builds up in the differential pressure chamber 7 (back space) of the pressure booster 4 of the System pressure on. The pressure in the compression chamber 10 now drops to system pressure level. Since system pressure is now also present in the pressure chamber 12, both needle parts 18.1 and 18.2 hydraulically balanced and are acted upon by the spring elements 20 or pressed 21 in its closed position. This completes the injection. The Closing speed can via the pressure chamber 12 upstream inlet throttle 13th to be influenced.

To avoid leakage currents at the guides of the two in each other Needle parts 18.1 and 18.2 of the multipart injection valve member can circulating grooves Be provided 28 and 29, and a bore 30 in the first needle part 18.1, so that the leakage are passed directly into a low-pressure side return 31 can.

Fig. 2 is a first embodiment of the proposed solution according to the invention a fuel injector with pressure booster and multi-part injection valve member refer to.

The illustration according to FIG. 2 shows that the fuel injector shown there 3 is controlled via a servo valve 40, which in turn via the control valve 32nd is pressed.

From the high-pressure accumulator 1 (common rail) extends according to this solution, the High-pressure line 5, in which a throttle point or a check valve 2 may be included can, to the working space 6 of the pressure booster 4 of the fuel injector 3. The return spring 8 is - in contrast to the illustration of FIG. 1 - according to this embodiment recorded in the working space 6. The working space 6 and the differential pressure space 7 (working space) the pressure booster 4 are separated from each other by the stepped piston 9, the the compression space 10 is applied. From the compression chamber 10 extends from High-pressure line 16 to the pressure chamber 12, which is the multipart injection valve member encloses. The multi-part injection valve member 18 comprises a first, outer needle part 18.1 and guided in this, the second inner needle part 18.2.

In the de-energized state of the control valve 32 prevails both in the control line 11 as also in the high pressure line 16 to the pressure chamber 12 system pressure. Im not energized State of the control valve 32 is the servo valve piston of a servo valve 40 with its Sealing edge a placed in his seat. At the same time, a slide edge b gives the connection between the working space 6 and the control line 11 free, so that the differential pressure space 7 can be applied to system pressure. Due to the closed sealing edge a of Servo valve piston of the servo valve 40 is a discharge of the system pressure in the low-pressure side Return 31 avoided.

From the control line 11 branches off from a damper chamber throttle 48, which in a damper chamber 42 opens. Thus system pressure prevails also in the damper space 42, as well as in a control chamber 43 in which via a check valve 47 in the opening direction fuel nachströmt. The in the control chamber 43 for the second needle part 18.2 incoming Fuel passes through a formed in the control piston 49 channel 53 in a hydraulic Room 54, which is bounded by the control piston 49 and the second needle part 18.2.

Upon actuation of the control valve 32, an energization of the magnet of the control valve 32 below the system pressure level, which is provided for the full load range, a pressure relief of the control line 11 in the low-pressure side return 31. This results in a pressure relief of the differential pressure chamber 7, so that the stepped piston 9 with his facing the compression space 10 end face in this einfährt and the high-pressure line 16 to the pressure chamber 12 subjected to high pressure. In this case, a branch leading from the high-pressure line 16 to the multipart injection valve member 18 is closed by a non-return valve 46 received therein, which is acted upon in the shooting direction. The check valve 47 connected upstream of the control chamber 43 for the second needle part 18.2, on the other hand, remains closed so that the control chamber 43 for the second needle part 18.2 remains pressureless. In a damper chamber 42 above the multi-part injection valve member 18 falls due to the outflow of fuel through the damper chamber throttle 48 in the pressure-relieved control line 11, the pressure, so that the damper chamber 42 limiting control piston 49 moves against the first spring element 20 acting on this upward. Now opens the outer needle part 18.2. During the upward movement of the control piston 49 with decreasing pressure in the damper chamber 42, the second spring element 21 which is provided in the spring chamber 44, although relieved, but the spring force is still large enough to hold the second needle part 18.2 in his seat 23. This results from the fact that no pressure surface A ₁ (see illustration according to FIG.

During the closing process takes place by relieving the control valve 32, an admission of the Control line 11 with system pressure, i. in the high-pressure accumulator 1 (common rail) prevailing Pressure level. The multipart injection valve member 18 and the control piston 49 are filled by the damper space 42 via the damper space choke 48 again in the direction of their seat.

In the full load range of the internal combustion engine increases by actuation of the control valve 32 and operatively connected to this servo valve 40, the pressure in the high-pressure line 16 to the pressure chamber 12 exceeds the prevailing in the high-pressure line 16 Pressure the opening pressure of the check valve 47 in the supply line to the control chamber 42nd for the second needle part 18.2, so this opens, so that the control chamber 43 for the second Needle part 18.2 loaded with a considerably above the low pressure level pressure becomes. The fuel volume, which with the control chamber 43 in direct Connection is as small as possible to high pressure losses in the high pressure part of the fuel injector 3 to limit.

Upon application of the annular control space 43 for the second needle part 18.2 flows fuel via a channel 53 in the hydraulic chamber 54 a. Thereby the second needle part 18.2 is pressed against a stop 50 on the control piston 49. There at this time, the first needle part 18.1 is no longer in his seat 22 builds under the second needle part 18.2 a pressure. The second needle part 18.2 opens due the pressure difference between the hydraulic chamber 54 and the spring chamber 44 for the second needle part 18.2; on the other needle part 18.2, however, no force acts in the closed Status.

Since the first needle part 18.1 due to the decreasing pressure in the damper chamber 42 has already opened, the stopper 50 shifts for the internally arranged second Needle part 18.2 also upwards, so now fuel through the two, for example formed as concentric hole circles rows of holes 26 and 27 in the combustion chamber the self-igniting internal combustion engine can be injected.

During the closing process, a pressure relief of the high pressure line 16, so that the previously opened check valve 47 in the supply line to the control chamber 43 for the second Needle part 18.2 closes again. As with pressure relief of the high-pressure line 16, the control line 11 is again pressurized with system pressure, flows over the damper chamber throttle 48th Fuel in the damper chamber 42 a. Due to this, the spool 49 moves downwards, so that the inner, second needle part 18.2 on the stop 50 of the damper piston 49 is applied and is returned to his seat 23. Through the channel 52 flows at the downward movement of the control piston 49 fuel in the low-pressure side return 31, if in the control chamber 43, a greater pressure than the low pressure level prevails. This ensures that in the control chamber 43 for the second needle part 18.2 a pressure relief is brought about. Through the channel 52 is leakage and fuel from the hydraulic space 54, if the second needle part 18.2 is activated or the check valve 47 is opened, regardless of the momentary movement of the control piston 49th

By illustrated in Fig. 2 embodiment of the present invention proposed Solution is an exact opening time of the inner, second needle part 18.2 guaranteed, because the pressure gradient of the increasing system pressure is very steep. In spite of small time differences between the opening of the outer first needle portion 18.1 and the opening of the inner second needle part 18.2 of a multi-part injection valve member, is the injection of small quantities over the first row of holes 26 on the combustion chamber side end of the fuel injector 3, e.g. in the context of pilot injections possible.

The illustration according to FIG. 3 is a further embodiment of the invention proposed fuel injector with pressure booster and multipart trained injection valve refer to.

In contrast to the embodiment variant shown in Fig. 2 is in the illustrated in Fig. 3 Execution variant, the check valve 47, which the control chamber 43 for the second needle part 18.2 is assigned, from the high pressure area in the low pressure area relocated. The attachment point of the check valve 47 for the control chamber 43 for the second needle part 18.2 is not in this embodiment to the high-pressure line 16, but to the control line 11 for pressure relief of the differential pressure chamber 7 (back space) integrated pressure intensifier 4.

From a certain achievable system pressure opens the check valve 47, so that the Control chamber 43 charged for the second needle part 18.2 according to the applied pressure levels becomes. As a result, the inner, second needle part 18.2 against the stop 50 on the Bottom of the control piston 49 is set. This is accompanied by an upward movement of the inside, second needle part 18.2, so that its seat 23 is released. About the Throttle 45, which is formed in the inner, second needle part 18.2 escapes fuel, whereby the pressure level in the control chamber 43 for the second needle part 18.2 decreases. by virtue of this opens the check valve 47 again to bring about pressure equalization. The throttle 45 within the second needle portion 18.2, which is the hydraulic space 54 and the spring chamber 44 for the second needle part 18.2 connects to each other, the second Needle part 18.2 acted upon spring 21 and the check valve 47 are to be interpreted as that the inner, second needle part 18.2 at system pressures that for full load areas the internal combustion engine, always to the stop 50 at the bottom located in the damper chamber 42 movable control piston 49 is located.

The inner, second needle part 18.2 of the multipart injection valve member 18 is therefore no longer in front of the pressure relief of the control line 11 its seat 23, resulting in that immediately after lifting the needle tip of the outer first needle part 18.1, the cross sections of both rows of holes 26 and 27 on the combustion chamber side end of the fuel injector 3 are released, so that the injection of fuel into the combustion chamber of the self-igniting internal combustion engine both concentrically to each other trainable rows of holes 26 and 27 can be made.

The throttle 45 in the upper region of the second needle part 18.2 the hydraulic Room 54 and the spring chamber 44 connects to each other, is with a very small throttle cross-section designed. As a result, the prevailing pressure in the hydraulic chamber 54 pressure level be kept as long as possible so that the inner, second needle part 18.2 acting spring force of the second spring element 21 is overcome. Within of 720 ° KW of the internal combustion engine should prevail in the hydraulic space 54 Pressure level to be reduced.

As the illustration in FIG. 3 can be seen, is at the connection 60 of Check valve 47, the connection to the control line 11 shown. In contrast to Representation of FIG. 3 is the junction of the check valve 47 on the other Side of the fuel injector 3.

The illustration according to FIG. 4 is a further, third embodiment of the invention to be taken from the proposed solution.

The embodiment differs from that shown in Figures 2 and 3 embodiments according to the invention characterized in that on the one hand the check valve 47, which is assigned to the control chamber 43 for the second needle part 18.2, to the control line 11 for pressure relief of the differential pressure chamber (working space) of the pressure booster 4 is connected and that in the check valve 47 further another check valve in opposite directions and in the second check valve 71 acting line a throttle point 72 is formed.

As a result, according to the embodiment variant shown in FIG. 4, there is no direct connection of the second, inner needle part 18.2 acted upon control chamber 43 for Low pressure area. The filling of the control chamber 43 according to the embodiment in Fig. 4 takes place as already shown in connection with the embodiment in Fig. 3. The realizable according to this embodiment stroke, the internal, second needle part 18.2 executes until reaching the stop 50, but is sized so that this is sufficient that under the seat 23 of the inner, second needle part 18.2 of the metallic injection valve member 18 can build a pressure, according to the embodiments shown in Figures 2 and 3.

When pressure relief of the control line 11 according to this embodiment opens first the second check valve 71 at pressure relief of the control line 11th Die Pressure relief of the control line 11 is effected by activation of the control valve 32, whereby the servo valve 40 is actuated. The servo valve piston of the servo valve 40 contains a through-passage 41, so that in the pressure chambers of the servo valve 40 equal pressure, However, different effective hydraulic surfaces act.

When opening by means of another check valve 71 escapes fuel into the control line 11, so that the pressure level in the control chamber 43 for the second needle part 18.2 decreases. The check valve 47 opens only from a certain pressure (system pressure) and charged the control chamber 43 for the second needle part 18.2 and the hydraulic chamber 54. At lower Press system, the check valve 47 is not opened, so that the control room 43 and the hydraulic chamber 54 remain at low pressure level. When opening the check valve 47 is a pressure build-up in the second control chamber 53 and im hydraulic space 54, so that the second needle part 18.2 of the multipart injection valve is raised. With a discharge of the control line 11 opens the other Check valve 71, wherein the pressure reduction in the control chamber 43 for the second needle part 18.2 delayed or slowed down by the throttle point 72. Through the throttle point 72 is ensures that the second needle part 18.2 when opening the first needle part 18.1 is still on the stop 50 and rests against this with its control surface 51. As long as the Control line 11 is relieved, the pressure during injection in the control room 43 for the second needle part 18.2 or in the hydraulic chamber 54 at low pressure level dismantle.

When the pressure relief of the control line 11, so therefore during the closing movement of the both needle parts 18.1 and 18.2 of the metallic injection valve member 18 is located the inner, second needle part 18.2 always on the upper stop 50, the through the underside of the movable in the damping chamber 42 control piston 49 is formed. After this the outer, first needle part 18.1 has reached its seat 22, the inner, second needle part 18.2 still a stroke. This stroke, i. that to achieve the seat 23 of the inner, second needle part 18.1 required stroke is very small, since the control chamber 43 of the second needle part 18.2 on the in its closed position located check valve 47 is separated from the control line 11 and therefore no Can escape fuel.

In the embodiment of the invention proposed in FIG. 4 Fuel injector with pressure booster 4 and multipart trained injection valve member 11 is the spring force of the inner, second needle part 18.2 acting second Design spring element 21 slightly higher. Due to the closed check valve 47 is to ensure that in the control chamber 43 for the second needle part 18.2 still prevailing Residual pressure level with closed impact valve 47 in the control line 11 still can be overcome to the inner, second needle part 18.2 in his seat 23rd to move the combustion chamber side end of the fuel injector 3.

As a result, according to the embodiment variant shown in FIG. 2, no pressure stage in FIG Area of the needle seat 23 of the second needle part 18.2 is formed, the assets in high-frequency oscillations occurring during a fuel injection system, the needle during not to open the injection.

According to the embodiments shown in Figures 3 and 4 can be a damped Open the inner, second needle part realize 18.2, so that no Quantity jumps in the core field can occur. Through the connection to the control line 11 is ensured in an advantageous manner that no pressure increase during the injections may occur. Due to the reduction of pressure oscillations in the system is a more accurate vote of the opening pressure of the inner, second needle part 18.2 given, so that reproducible injections are ensured.

LIST OF REFERENCE NUMBERS

1

High-pressure accumulator (common rail)

2

Throttle / non-return valve

3

Kraftstoffmjektor

4

Pressure intensifier

5

High-pressure line

6

working space

7

Differential pressure chamber (backspace)

8th

Return spring

9

stepped piston

10

compression chamber

11

control line

12

pressure chamber

13

inlet throttle

14

filling line

15

Refill valve (RSV)

16

High-pressure line

17

nozzle chamber

18

multi-part injection valve member

18.1

1. first needle part (outboard)

18.2

2. second needle part (inside)

19

Stop for first needle part

20

first spring element

21

second spring element

22

Seat first needle part 18.1

23

Seat second needle part 18.2

24

annular gap

25

Pressure stage first needle part 18.1

26

first row of holes

27

second row of holes

28

first circumferential groove

29

second circulation groove

30

drilling

31

low-pressure side return

32

control valve

33

Return control amount

34

High pressure branch

A ₁

print area

40

servo valve

41

Through-channel with throttle point

42

damper space

43

Control room 2. Needle part 18.2

44

Spring chamber 2. Needle part 18.2

45

throttle

46

check valve

47

Check valve for control room 43

48

Damper chamber throttle

49

spool

50

inner stop on the control piston 42 for second needle part 18.2

51

Control surface second needle part 18.2

52

drain channel

53

channel

54

hydraulic room

60

RSV connection to control line 11

70

opposite RSV arrangement

71

another check valve

72

restriction

Claims (14)

Fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, wherein the fuel injector (3) communicates with a high-pressure accumulator (1) for fuel and comprises a pressure booster (4) and can be actuated via a control valve (32) and an injection valve member (18). which is acted upon in the closing direction by at least one spring element (20) and the injection valve member (18) is associated with one of these independently movable damping element (49) which limits a damping chamber (42), characterized in that the injection valve member (18) a first needle part (18.1) and a second needle part (18.2), wherein the second needle part (18.2) is associated with a system-pressure-side or high-pressure side connected control chamber (43). Fuel injector according to claim 1, characterized in that the control chamber (43) for the second needle part (18.2) is associated with a check valve (47). Fuel injector according to claim 1, characterized in that the injection valve member (18) is associated with a control piston (49) in which a spring element (44) for the second needle part (18.2) acting on spring element (21) is accommodated. Fuel injector according to claim 2, characterized in that the damping element (49) has a stop surface (50) for the second needle part (18.2). Fuel injector according to claim 3, characterized in that the spring chamber (44) via a throttle channel (52) with the low-pressure side region (31) of the fuel injector (3) is connected. Fuel injector according to claim 3, characterized in that the second needle part (18.2) includes a throttle channel (45) extending between the spring chamber (44) and the control chamber (43). Fuel injector according to claim 1, characterized in that a damper chamber throttle (48) is associated with a damping chamber (42) connected to a control line (11) of the pressure booster (4). Fuel injector according to claim 1, characterized in that the second needle part (18.2) on its combustion chamber-side seat (23) is formed free of pressure surface. Fuel injector according to claim 3, characterized in that a via the spring chamber (43) pressurizable or druckentlastbare hydraulic space (54) by the second needle part (18.2) and the damping element (49) is limited. Fuel injector according to claim 2, characterized in that the non-return valve (47) associated with the control chamber (43) is connected to the maximum pressure connection (16) between a compression chamber 10 of the pressure booster (4) and a pressure chamber (12). Fuel injector according to claim 2, characterized in that the non-return valve (47) associated with the control chamber (43) is connected to the control line (11) for actuating the pressure booster (4). Fuel injector according to claim 11, characterized in that the check valve (47), a further check valve (71) is connected in parallel. Fuel injector according to claim 12, characterized in that the check valves (47, 71) are arranged in opposite directions to each other. Fuel injector according to claim 12, characterized in that the check valve (71) upstream of a throttle point (72).

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