EP1554488B1 - Pressure-boosted fuel injection device comprising an internal control line - Google Patents

Description

Technical area

For the introduction of fuel into combustion chambers of self-igniting internal combustion engines, both pressure-controlled and stroke-controlled injection systems can be used. Injection systems with high-pressure accumulators have the advantage that the injection pressure can be adapted to the load and speed of the internal combustion engine. To reduce the resulting emissions and to achieve a high specific power of the internal combustion engine, a high injection pressure is required. Since the achievable by high-pressure fuel pumps in the high-pressure accumulator pressure level is limited for strength reasons, can be used to further increase pressure in fuel injectors with a high-pressure accumulator a pressure booster on the fuel injector.

State of the art

DE 199 10 907 A1 discloses a fuel injector having a pressurizing unit disposed between a pressure accumulating space and a nozzle space. Its pressure chamber is connected via a pressure line to the nozzle chamber. Furthermore, a bypass line connected to the pressure storage space is provided. The bypass line is connected directly to the pressure line. The bypass line is suitable for a pressure injection and is arranged parallel to the pressure chamber, so that the bypass line is independent of the movement and position of a slidably ordered pressure medium of the pressure booster unit.

DE 102 18 904.8 refers to a fuel injector. According to this solution, a fuel injection device for internal combustion engines is proposed with a fuel injector, which can be supplied by a high-pressure fuel source, and a pressure booster device. The closing piston of a fuel injector protrudes into a closing pressure chamber in such a way that the closing piston can be acted upon by fuel pressure to achieve a force acting on the closing piston in the closing direction, whereby the closing pressure space and the rear space of the pressure booster device are formed by a common closing pressure return space. All partial areas of the closing pressure rear space are permanently connected to one another for the purpose of exchanging fuel. From DE 199 10 970 A1 and DE 102 18 904.5 Known pressure booster are actuated via the pressurization or pressure relief of a back space of the booster. A control of a pressure booster via the back space is favorable in terms of the relaxation losses and allows easy control of the pressure booster by means of a 2/2-way valve.

Of disadvantage with the out DE 199 10 970 A1 respectively. DE 102 18 904.8 Known pressure amplifiers is the course of the control bore to relieve the back space of the pressure intensifier. Due to the fact that the control valve for the intensifier is arranged for reasons of space in most internal combustion engines above the pressure booster, it is necessary to lead out with the pressure prevailing in the high pressure accumulator space fuel pressure control line out of the back space of the booster and past the pressure booster. This requires a larger Aussendruchmesser the fuel injector, in which the pressure booster is usually housed in the head area or an eccentric position of the pressure booster arranged in the pressure booster element, which is usually beschaffffen as a piston, Due to this previously required wiring arise Bohrungsverschneidungen on the control line Pressurization or pressure relief of the back space of the pressure booster. Hole intersections usually entail very high material tensions, which require elaborate processing steps and are detrimental to a durable design of a fuel injector.

Out WO 02/092992 A1 Furthermore, a fuel injection device with a pressure booster is known, which has a working space, a differential pressure chamber and a high pressure chamber for pressure boosting. The pressure booster is controlled by controlling the differential pressure chamber by means of a 2/2-way valve, which the differential pressure chamber to a low pressure / return system The filling of the differential pressure chamber takes place via a hydraulically throttled control line, which communicates with the constantly pressurized working space. Less fuel flows through the throttled control line than flows out via the open 2/2 directional valve, so that the differential pressure chamber can be relieved of pressure to control the pressure intensifier.

Presentation of the invention

With the proposed solution according to the invention, an improvement in the high-pressure resistance of a fuel injector with pressure booster can be achieved. The central control line for pressure relief or pressurization of serving for the actuation of the pressure booster differential pressure chamber is substantially coaxial with the axis of symmetry through the pressure booster piston and extends through the pressurized working space of the pressure booster. The control line is sealed against the working space via a high-pressure-tight connection.

The omission of a guided on the outside of the fuel injector with pressure booster control line also reduces the outer dimension of the fuel injector or avoids an eccentric to the fuel injector oriented arrangement of a pressure booster.

A coaxially extending to the axis of symmetry of the fuel injector control line in the booster piston advantageously avoids Bohrungsverschneidungen, as inevitably occur in external lines due to the connection position of high pressure connections and reduces the material stress, which in turn increases the service life of the fuel injector with pressure booster. A seal between the working space and the central control line can be achieved by means of a biased by a spring element sealing sleeve, which advantageously cooperates with a flat seat in the working space. This allows the compensation of production-related tolerances in a running with a plurality of housing parts to be joined fuel injector with pressure booster. The central control line extends through an extension formed on the piston of the pressure booster, which has a guide section for the sealing sleeve movably arranged on the piston shoulder.

In a further embodiment of the idea underlying the invention, a piston extension arranged on the booster piston of the pressure booster can be accommodated in a high-pressure-tight guide, which is embodied in one of the housing parts of the fuel injector with pressure booster. The high pressure-tight guide of the piston extension is designed so that it is effective along the entire stroke of the piston of the pressure booster and the central control line separates from the working space of the pressure booster.

Instead of a central control line receiving piston shoulder on the piston of the pressure booster, in this a piston can be received, which has a continuous channel. According to this embodiment, a sealing point can be designed as a flat seat to seal the central control line against the working space of the pressure booster. On the one hand, this makes it possible to compensate for production-related tolerances between the housing parts and, on the other hand, a production-technically simple production. In a further embodiment variant of a fuel injector with a pressure booster, the pressure booster contains a piston element extending continuously through the piston element with a channel extending continuously through it. The channel is connected depending on the stroke of the pressure booster by a first or by a first and a second flow area with the differential pressure chamber of the pressure booster. Thus, the pressure build-up of the pressure booster can be controlled according to a desired injection pressure curve.

The central control line can be used with all pressure intensifiers that are controlled via a differential pressure chamber.

drawing

Reference to the drawings, the invention will be explained in more detail below.

Figur 1

einen Kraftstoffinjektor mit Druckübersetzer mit hochdruckdichter Ver- bindung am oberen Ende des Arbeitsraumes,

Figur 2

einen Kraftstoffinjektor mit Druckübersetzer, bei dem ein Steuerleitungs- abschnitt in einer hochdruckdichten Führung aufgenommen ist,

Figur 3

eine Ausführungsvariante des Kraftstoffinjektors mit Druckübersetzer mit einem teilweise in den Druckübersetzerkolben eingelassenen, einen Dichtsitz bildenden Kolbenelement und

Figur 4

einen Kraftstoffinjektor mit Druckübersetzer, der über ein servohydrau- lisch unterstützes 3/2-Wege-Ventil angesteuert wird.

It shows:

FIG. 1

a fuel injector with pressure intensifier with high-pressure-tight connection at the upper end of the working space,

FIG. 2

a fuel injector with a pressure booster, in which a control line section is accommodated in a high-pressure-tight guide,

FIG. 3

a variant of the fuel injector with pressure booster with a partially embedded in the pressure booster piston, a sealing seat forming piston element and

FIG. 4

a fuel injector with pressure booster, which is controlled by a servohydraulically assisted 3/2-way valve.

variants

FIG. 1 shows an embodiment of a fuel injector with pressure booster whose piston has a piston neck, which is traversed by a portion of the central control line.

According to the in FIG. 1 illustrated first embodiment of the invention underlying idea, a fuel injection device 1 is acted upon by a high-pressure accumulator 2 (common rail) with fuel under high pressure. The high-pressure fuel contained in the high-pressure accumulator 2 flows to an injector body 4 of the fuel injection device 1 via a high-pressure feed line 3. From the first housing part 8, an inlet 6 to a switching valve 5 extends from the switching valve 5 branches on the one hand a low-pressure side return 7 in a in FIG. 1 Not shown fuel reservoir discharges, and an overflow line 43, which is in communication with a recess 35 within the first housing part 8.

The injector body 4 of the fuel injection device 1 comprises a first housing part 8 and a further, second housing part 9 and an injector housing 10 which encloses an injection valve member 24. The first housing part 8 and the second housing part 9 abut each other along a butt joint 32.

In the injector body 4 of the fuel injection device 1, a pressure booster 11 is received. The pressure booster 11 comprises a working space identified by the reference numeral 12, which can be acted upon by fuel flowing under high pressure via an inlet 13 branching off from the high-pressure line 3. The pressure booster 11 comprises a pressure booster piston 14, which includes a first end face 15, which assigns the working space 12, and a second end face 16, which assigns a differential pressure chamber 17. The pressure booster piston 14 is supported on the second end face 16 by a return spring 18, which in turn is supported on an annular surface within the second housing part 9 of the injector body 4. The pressure booster piston 14 of the pressure booster 11 acts on a high-pressure chamber 19 which is located in the lower region of the second housing part 9. Corresponding to the transmission ratio of the pressure booster 11, the high-pressure space 19 zuweisenden end face of the pressure booster piston 14, the fuel contained in this compressed again and flows on the one hand into a control chamber 20 and on the other hand via a nozzle chamber inlet 22 into a nozzle chamber 23 in the injector 10th is trained. The nozzle chamber 23 encloses the injection valve member 24 of the fuel injection device in a region in which a pressure shoulder is formed on the injection valve member 24. From the nozzle chamber 23, an annular gap extends to the combustion chamber end of the fuel injector 1. About the annular gap injection openings 25 are acted upon at the combustion chamber end of the fuel injection device 1 with fuel. These are released in a vertical movement of the injection valve member 24, so that can be injected via the injection openings 25 under high pressure fuel in a combustion chamber 26 of a self-igniting internal combustion engine.

The pressurization of the control chamber 20 for actuating the injector valve 24, which can be embodied, for example, as a nozzle needle, is effected via a line connecting the nozzle chamber 20 and the high-pressure chamber 19 of the pressure booster 11, in which an inlet throttle 21 is accommodated. Within the Steurraumes 20 a nozzle spring 27 is received, which surrounds a pin 28 of the injection valve member and is supported on an annular surface of the injection valve member 24. Between the differential pressure chamber 17 of the pressure booster 11 and the control chamber 20 extends a discharge throttle 30 receiving relief line 29th

The pressure booster piston 14 of the pressure booster 11 includes a central control line 31. The central control line 31 is connected via a formed in the pressure booster piston 14 transverse opening 41 with the differential pressure chamber 17 of the pressure booster 11 in combination. The transverse opening 41 in turn is connected to a central control line 31 representing channel 40, which passes through the working space 12 and the differential pressure chamber 17 separating portion of the pressure booster piston 14 and through a on the first end face 15 of the pressure booster piston 14 arranged piston extension 34 extends. The piston neck 34 accommodating the channel 40 on the first end face 15 of the pressure-transmitting piston 14 extends into the recess 35 in the first housing part 8 of the injector body 4. A first sealing sleeve 36 can be moved within a guide section 42 on the piston shoulder 34 of the pressure booster piston 14. The first sealing sleeve 36 comprises an annular projection 39, on which a positioning spring 38 is supported. The adjusting spring 38 is supported with its first sealing sleeve 36 opposite end on the first end face 15, the piston neck 34 from surrounding. By the adjusting spring 38, the first sealing sleeve 36 received on the piston shoulder 34 is set with a sealing surface 37 against the lower end face of the first housing part 8 of the injector body 4. This makes it possible to achieve a high-pressure-tight connection 33 which separates the central control line 31 from the working space 12 of the pressure booster 11. According to the in FIG. 1 illustrated embodiment may be formed to compensate for manufacturing tolerances between the first housing part 8 and the second housing part 9 of the fuel injector 4, the high-pressure-tight connection 33 as a flat seat. Furthermore, the protruding into the recess 35 of the first housing part 8 portion of the piston extension 34 can be performed with radial clearance in the recess 35 so that a contact-free guidance between the upper portion of the piston extension 34 and the recess 35 in the first housing part 8 can be achieved.

• Zu Beginn einer Einspritzung wird das Schaltventil 5 von seiner in Figur 1 dargestellten Lage, welche seiner Schließlage entspricht, in eine Öffnungslage geschaltet. In der Öffnungsposition des Schaltventiles 5 stehen der niederdruckseitige Rücklauf 7 und die Überströmleitung 43 in Verbindung miteinander. Während der Arbeitsraum 12 des Druckübersetzers 11 über den Abzweig 13 von der Hochdruckleitung 3 mit dem Hochdruckspeicher 2 verbunden bleibt, strömt vom Differenzdruckraum 17 über die Queröffnung 41, und den die zentrale Steuerleitung 31 bildenden Kanal 40 Kraftstoff durch den Druckübersetzer-Kolben 1 in die Ausnehmung 35 im ersten Gehäuseteil 8 und von dort über die Überströmleitung in den niederungseitigen Rücklauf 7. Aufgrund des im Arbeitsraum 12 des Druckübersetzers 11 nach wie vor herrschenden Hochdruckniveaus fährt der Druckübersetzer-Kolben 14 mit seiner unteren Stirnseite in den Hochdruckraum 19 ein. Von diesem strömt unter einem - im Vergleich zum Druckniveau des Hochdruckspeicherraumes 2 - entsprechend des Übersetzungsverhältnisses des Druckübersetzers 11 erhöhten Druckniveau - Kraftstoff einerseits in den Düsenzulauf 22 im Düsenraum 23 und andererseits über die Zulaufdrossel 21 dem Steuerraum 20 zu. Der in den Düsenraum 23 einschießende und unter hohem Druck stehende Kraftstoff greift an der Druckschulter des Einspritzventilgliedes 24 an und bewirkt eine vertikale Hubbewegung des Einspritzventilgliedes 24 in Öffnungsrichtung entgegen der Wirkung der Düsenfeder 27, die ebenfalls im Steuerraum 20 enthalten ist. Durch die Hubbewegung verdrängtes Absteuervolumen strömt über die Druckentlastungsleitung 29, eine Ablaufdrossel 30 enthaltend, in den Differenzdruckraum 17 des Druckverstärkers 11 ein.

The functioning of the in FIG. 1 illustrated embodiment is as follows:

• At the beginning of an injection, the switching valve 5 of his in FIG. 1 shown, which corresponds to its closed position, switched to an open position. In the opening position of the switching valve 5 are the low-pressure side return 7 and the overflow 43 in communication with each other. While the working space 12 of the pressure booster 11 remains connected to the high-pressure accumulator 2 via the branch 13 from the high-pressure line 3, fuel flows from the differential pressure chamber 17 via the transverse opening 41 and the channel 40 forming the central control line 31 through the pressure booster piston 1 into the recess 35 in the first housing part 8 and from there via the overflow in the low-side return 7. Due to the in the working chamber 12 of the pressure booster 11 still prevailing high pressure levels moves the pressure booster piston 14 with its lower end face in the high-pressure chamber 19 a. From this flows under a - compared to the pressure level of the high-pressure accumulator 2 - corresponding to the transmission ratio of the pressure booster 11 increased pressure level - fuel on the one hand in the nozzle inlet 22 in the nozzle chamber 23 and on the other hand via the inlet throttle 21 to the control chamber 20. The injecting into the nozzle chamber 23 and under high pressure fuel engages the pressure shoulder of the injection valve member 24 and causes a vertical lifting movement of the injection valve member 24 in the opening direction against the action of the nozzle spring 27, which is also contained in the control chamber 20. By the lifting movement displaced Absteuervolumen flows through the pressure relief line 29, containing a discharge throttle 30, in the differential pressure chamber 17 of the booster 11 a.

Due to the vertical lifting movement of the injection valve member 24, the projecting into the combustion chamber 26 of a self-igniting internal combustion engine injection openings 25 are acted upon by high-pressure fuel and inject it into the combustion chamber 26 a.

When the switching valve 5 is switched again, the differential pressure chamber 17 is pressurized by the high-pressure accumulator 2 via the high pressure line 3, the inlet 6 and the overflow line 43 and the recess 35 in the first housing part 8. From there, the fuel flows through the channel 40 forming the central control line 31 and enters via the transverse opening 41 in the differential pressure chamber 17 and acted upon this again with the pressure prevailing in the high-pressure accumulator 2 pressure level. As a result, the high-pressure chamber 19 is relieved, as well as the nozzle chamber 23 surrounding the injection valve member 24 in the injector housing 10. About the nozzle spring 27, the injection valve member 24 is pressed in its combustion chamber side seat, the injection is completed. A refilling of the control chamber 20 via the discharge line 29, which in this case in the opposite direction, the control chamber 20 filling, is flowed through by fuel. A refilling of the high-pressure chamber 19 of the pressure booster 11 takes place by overflowing of fuel from the control chamber 20 via the conduit containing the inlet throttle 21 into the high-pressure chamber 19.

In the in FIG. 1 illustrated embodiment of the idea underlying the invention is arranged on the first end face 15 of the pressure booster piston 11 of the piston extension 34. As a result of this, during the control of the pressure intensifier 11, 1 fuel volume flows either from or into the differential pressure chamber 17. A sealing of the recess 35 within the first housing part 8 is achieved in this embodiment by the piston 34 on the first movably guided first sealing sleeve 36. In manufacturing technology particularly easy to produce way can form a flat seat, with which the high pressure-tight connection 33 between the working chamber 12 and the recess 35 in the first housing part 8, in which the central control line 31 forming channel 40 opens, can be effectively sealed. The guided on the piston shoulder 34 guided first sealing sleeve 36 is supported by an adjusting spring 38 in an advantageous manner. Due to the dimensioning of the adjusting spring 38, the effectiveness of the high-pressure-tight connection 33 at the lower end side of the first Housing parts 8 are ensured over the entire stroke of the pressure booster piston 14 within the second housing part 9 of the injector body 4. The leadership of the central control line 31 substantially coaxially with the line of symmetry of the injector body 4, avoids an additional to be provided on the outside of the injector 4 to the switching valve 5 high-pressure line, which would be required to control the differential pressure chamber 17 of the booster 11. A via the differential pressure chamber 17 (also referred to as the back space) controlled pressure intensifier 11 is particularly favorable in terms of its relaxation losses. With the solution proposed according to the invention, it is possible to arrange a pressure amplifier 11 controlled via its differential pressure chamber 17, which does not adversely affect the external dimensions of the injector body 4, coaxially with the injector housing 10 of the fuel injection device 1. Thus, an eccentric arrangement of the pressure booster 11 with respect to the arranged in the axis of symmetry of the fuel injection device 1 injection valve member 24 can be avoided, which is unfavorable in terms of manufacturing costs and costs.

FIG. 2 shows an embodiment of a fuel injector with pressure booster, wherein the central control line extends through a piston neck, which is guided in a high-pressure-tight guide of the injector body 4.

According to the in FIG. 2 illustrated embodiment, the fuel injection device 1 is supplied via the pressure accumulator 2 (common rail) with fuel under high pressure. From the pressure accumulator 2, fuel flows via the high-pressure line 3 to the first housing part 8 of the injector body 4. The first housing part 8 of the fuel injection device 1 abuts against a butt joint 32 on the second housing part 9 of the injector body 4. The injector body 4 of the fuel injection device 1 further comprises the injector housing 10 in which the injection valve member 24 releasing or closing the injection openings 25, which can be embodied as a nozzle needle, is accommodated.

Via the high-pressure line 3, the first housing part 8 of the injector body 4 of the fuel injection device 1 flows under high pressure fuel. This is passed via the inlet to the switching valve 5. The switching valve 5 comprises a connection to the low-pressure side return 7 and an overflow 43 to the formed in the first housing part 8 recess 35. About the branch 13 of the high-pressure line 3 within the first housing part 8 of the working chamber 12 of the pressure booster 11 is acted upon by high-pressure fuel , The pressure booster 11 comprises a pressure booster piston 14, which separates the working space 12 of the pressure booster 11 from its differential pressure chamber 17. The pressure booster piston 14 comprises the piston extension 34 fastened to the first end face 15. A first washer 51 is arranged on the piston extension 34 passing through the working space 12 in the second housing part 9. Above of the pressure booster piston 14, a further, second disc 52 is disposed on the inside of the working space 12 of the pressure booster 11. Between the first and the second disc 51, 52, a return spring 18 is received, via which the pressure booster piston 14 is returned to its initial position within the second housing part 9.

The lower end face of the pressure booster piston 14 acts on the high pressure chamber 19 formed in the second housing part 9 of the injector body 4. The high pressure level achievable in the high-pressure chamber 19 depends on the transmission ratio of the pressure booster 11 and is higher than the pressure level prevailing in the high-pressure reservoir 2. From the high-pressure chamber 19 of the pressure intensifier 11 under a further increased pressure level stationary fuel flows through the nozzle chamber inlet 22 to the nozzle chamber 23 in the injector 10 to. In the region of the nozzle chamber 23, which surrounds the injector valve 24, which can be embodied as a nozzle needle, for example, the injection valve member 24 comprises a pressure shoulder. From the nozzle chamber 23 within the injector housing 10 extends an annular gap, via which the high-pressure fuel flows from the nozzle chamber 23 to the injection port 25. When the injection valve member 24 is open, fuel injected under very high pressure via the injection openings 25 is injected into the combustion chamber 26 of the self-igniting internal combustion engine.

From the high-pressure chamber 19 further extends a line section to the nozzle chamber 20. In this line section, an inlet throttle 21 is received. The control chamber 20 for the injection valve member 24 includes a nozzle spring 27, on the one hand on an annular surface of the injection valve member 24, a pin 28 surrounding, is supported. On the other hand, the nozzle spring 27 rests against a wall of the second housing part 9 delimiting the nozzle chamber 20. An overflow of control volume from the nozzle chamber 20 in the differential pressure chamber 17 of the pressure booster 11 via the nozzle chamber 20 in the differential pressure chamber 17 connecting discharge line 29, in which a discharge throttle 30 is received.

The pressure booster piston 14 of the pressure booster 11 comprises a central control line 31. The central control line 31 is formed as a both the piston shoulder 34 and the pressure booster piston 14 passing through channel 40, at its lower, opening into the differential pressure chamber 17 end, a Transverse opening 41 comprises. This can be designed as a bore, as a channel or the like in the pressure booster piston 14. From the transverse opening 41 in the pressure booster piston 14, the channel 40 extends into the recess 35 in the first housing part 8 of the injector body 4. In the first housing part 8 of the head portion of the piston extension 34 is received in a high-pressure-tight guide 50. The high pressure-tight guide 50 within the first housing part 8 goes into the Recess 35 and is formed in a the stroke of the pressure booster piston 14 corresponding axial length. This ensures that along the entire stroke of the pressure booster piston 14 of the pressure booster 11, a high-pressure seal between the recess 35 is ensured within the first housing part 8 and the working space 12 of the pressure booster 11.

In the in FIG. 2 shown position is the pressure booster 11 in its rest position. The differential pressure chamber 17 and the working chamber 12 are connected via the switching valve 5 and the inlet 13 to the working chamber 12 and via the inlet 43, 35, 40 to the differential pressure chamber 17 with the pressure accumulator 2 in combination. Therefore prevails in the in FIG. 2 illustrated switching position of the switching valve 5 in the working space 12 and the differential pressure chamber 17 identical pressure. About the branching off from the differential pressure chamber 17 of the pressure booster relief line 29 and the aufgestommone flow restrictor 30 is in the differential pressure chamber 17 prevailing pressure level beyond in the control chamber 20 of the injection valve member 24 at.

Upon actuation of the switching valve 5, ie its transfer from the in FIG. 2 shown switching position in which the overflow line 43 is brought into connection with the low-pressure side return 7, the pressure differential of the differential pressure chamber 17 takes place. The fuel flows from the differential pressure chamber 17 via the formed in the pressure booster piston 14 transverse opening 41 into the central control line 31 forming channel 40 and from this into the recess 35 within the first housing part 8 a. From the recess 35, the fuel flows via the overflow line 43 into the low-pressure side pressure run 7 and from there into an in FIG. 2 Not shown fuel reservoir from. Because of the pressure relief of the differential pressure chamber 17 of the pressure booster piston 14 moves with its lower end side due to the pressure prevailing in the working chamber 12 high pressure levels in the second housing part 9 of the injector body 7 a. In this case, the fuel contained in the high pressure chamber 19 is acted upon by the lower end face of the pressure booster piston 14. The fuel compressed in the high-pressure chamber 19 flows toward the nozzle chamber 23 via the nozzle chamber inlet 22. There, the hydraulic surface of the executed on the injection valve member 24 pressure shoulder is effective, so that the injection valve member 24 against the nozzle chamber 27 received in the control chamber 20 retracts into this and thus the injection openings 25 releases. The displaced during retraction of the injection valve member 24 and the pin 28 in the control chamber 20 fuel volume flows through the discharge line 29 into the differential pressure chamber 17 from. Due to the opening movement of the injection valve member 24, the fuel injected into the nozzle chamber 23 flows to the injection openings 25 along the annular gap surrounding the injection valve member 24 in the injector housing 10, where it is injected into the combustion chamber 26 of the self-igniting internal combustion engine.

If, however, the switching valve 5 in his in FIG. 2 Switched starting position shown, there is a filling of the differential pressure chamber 17 of the pressure booster 11 via the high pressure line 3, the inlet 6 to the switching valve 5, the overflow 43 and the recess 35. From the recess 35 within the first housing part 8 of the fuel flows to the discharge direction of the Differential pressure chamber 17 opposite direction through the channel 40 of the piston extension 34. The differential pressure chamber 17 is refilled by the exiting from the transverse opening 41 in the differential pressure chamber 17 fuel. From the differential pressure chamber 17 from a filling of the control chamber 20 via the discharge line 29. From the control chamber 20, the high-pressure chamber 19 of the pressure booster 11 via the inlet throttle 21 containing line is refilled with fuel.

In the FIG. 2 illustrated variant requires fewer items and is therefore cheaper to manufacture.

FIG. 3 shows an embodiment of the fuel injector with pressure booster with a partially embedded in the pressure booster piston member.

In the FIG. 3 illustrated embodiment of a fuel injector with pressure booster differs from the in FIGS. 1 and 2 illustrated embodiments of a fuel injector with pressure booster in that in the pressure booster piston 14, a piston member 60 is integrated. The piston member 60 is slidably received within the pressure booster piston 14. There is a space 63 between the lower end face of the piston part 60 and the pressure booster piston and the piston part 60 accommodated in the pressure booster piston 14 comprises on its end face opposite the first housing part 8 a sealing seat 61 which compensates for tolerances between the first housing part 8 and the housing second housing part 9 of the injector body 4 is also designed as a flat seat. Via the sealing seat 61, the central control line 31, which extends as a channel 40 through the piston member 60, sealed against the working space 12 of the pressure booster 11. The guide surface for the piston part 60 in the pressure booster piston 14 is designated by reference numeral 64. On the recessed into the pressure booster piston 14 piston member 60, the sealing seat is arranged on a disk-shaped area formed in enlarged diameter. The fuel contained in the working chamber 12 of the pressure booster 11 presses the piston member 60 via this annular surface to the first housing part 8 and thus supports the sealing effect of the sealing seat 61 between the working chamber 12 and the central control line 31 via which the differential pressure chamber 17 of the pressure booster 11 pressure relieved or is pressurizable.

Otherwise this corresponds to in FIG. 3 illustrated embodiment those embodiments, in connection with the FIGS. 1 and 2 already described.

The functioning of the in FIG. 3 illustrated embodiment of a fuel injection device is as follows. In the in FIG. 3 shown position of the switching valve 5, the volume of fuel contained in the high pressure accumulator flows through the high pressure line 3 to the first housing part 8. About the branched off from the high-pressure line 3 inlet 13 of the fuel under high pressure flows into the working space 12 of the pressure booster. Via the inlet 6 to the switching valve 5, the fuel flows via the overflow line 43 to the recessed into the pressure booster piston 14 piston part 60 and passes through the one portion of the central control line 31 forming channel 40. Thereafter, the fuel enters the space 63, from which it flows via the transverse opening 41 in the differential pressure chamber 17 of the pressure booster 11. Thus, this is in the in FIG. 3 shown position of the switching valve 5 under the pressure prevailing in the high-pressure accumulator 2 pressure level. Via the differential pressure chamber 17 of the pressure booster 11, fuel flows via the discharge line 29 into the control chamber 20. The high-pressure chamber 19 of the pressure booster above the control chamber 20 is also supplied with fuel via the control chamber 20, which fuel is present in the nozzle chamber 23 via the nozzle chamber inlet 22. In this switching position of the pressure booster 11, whose deactivated state, the injection valve member 24 remains closed, so no fuel is injected into the combustion chamber 26 of the self-igniting internal combustion engine via the injection openings 25.

A pressure relief of the differential pressure chamber 17 of the pressure booster 11 via an actuation of the switching valve 5. The overflow 43 is brought upon actuation of the switching valve 5 with the low-pressure side return 7 in connection, whereby the differential pressure chamber 17 via the transverse opening 41, the space 63 in the piston part 60 formed central control line 31 (channel 40) is relieved of pressure in the low-pressure side return. Due to the first end face 15 of the pressure booster piston 14 acting on the fuel in the working chamber 12 moves the pressure booster piston 14 with its the high-pressure chamber 19 assigning end face in this.

Upon actuation of the switching valve 5, the overflow 43 and thus the upper piston surface of the piston member 60 is at low pressure. The surface of the piston member 60 in the working space 12 shows a hydraulic sealing force. The piston part 60 is pressed against the housing part 8. In addition, it is also possible to bias the piston part by means of a spring, in order to make this to the lower end face of the housing part 8, which limits the working space 12.

When retracting the lower end face of the pressure booster piston 14 in the high-pressure chamber 19, there is an increase in pressure of the fuel contained therein according to the pressure transmission ratio of the pressure booster 11. The fuel flows from the high-pressure chamber 19 via the nozzle chamber inlet 22 to the nozzle chamber 23. In the region of the nozzle chamber 23, the injector member 24, which can be formed, for example, as a nozzle needle, comprises a pressure shoulder, which causes a vertical movement in the opening direction of the injection valve member 24 into the control chamber 20 due to the high pressure fuel flowing into the nozzle chamber 23. The fuel contained in the nozzle chamber 23 flows via the annular gap surrounding the injection valve member 24 into injection openings 25 and is injected from there into the combustion chamber 26 of the autoignition internal combustion engine. The fuel volume displaced in the nozzle chamber 20 when the nozzle of the injection valve member 24 is displaced flows via the relief line 29 and the throttle point 30 contained therein to the pressure-relieved differential pressure chamber 17. From there, the diverted control volume flows via the transverse opening 41, the space 63, the central control line 31 within the piston part 60 and the overflow line 43 to the switching valve 5 and from there into the low-pressure side return 7.

Both during filling and during the pressure relief of the differential pressure chamber 17 of the pressure booster 11 of the working chamber 12, which is always acted upon by the fuel pressure contained in the high-pressure accumulator 2, effectively against the central control line 31, which passes through the piston member 60 as channel 40, sealed. A compensation of production-related component tolerances between the first housing part 8 and the second housing part 9 on the butt joint 32 can be achieved in an advantageous manner that in the head area, d. H. On the first housing part 8 facing, thickened executed end of the piston member 60, a flat seat 61 is formed.

FIG. 4 is a fuel injector removable with pressure booster, which is controlled by a servohydraulic trained 3/2-way valve.

At the in FIG. 4 The fuel injector shown in Fig. 1 is also controlled by the injector containing a pressure booster 11 via a switching valve 70 arranged on the upper side of the fuel injection device 1, but designed as a servohydraulic 3/2 way valve.

From the high pressure accumulator 2 flows through the high pressure line 3 under high pressure fuel into the working space 12 of the pressure booster 11 a. In this embodiment the servohydraulic switching valve 70 comprises a servo piston (valve body 71) and a control valve arranged at the return 73. The switching valve 70 is connected via a line to the working space 12 of the pressure booster in connection. ND denotes a low-pressure side return, which also branches off from the valve housing of the switching valve 70. In the idle state of the switching valve 70, a control edge designated VQ1 is opened and a control edge designated VQ2 is closed. The control line 31 is thus connected to the working space 12 of the pressure booster. When the valve 70 is switched, the control edge VQ1 is closed and the control edge VQ2 is opened, so that the central control line 31 communicates with the low-pressure side return ND.

From the servohydraulic 3/2-way valve, a low-pressure side return 73 extends to a in FIG. 4 Not shown fuel reservoir, such as the tank of a motor vehicle. The servohydraulic 3/2-way valve comprises a valve body 71, which is traversed by a through hole 72 which receives a throttle point.

The pressure booster piston 14 separates the working space 12 of the pressure booster 11 from the integrated in the injector body 4 differential pressure chamber 17. Within the working space 12 of the pressure booster 11, the return spring 18 is added. This is supported, a sleeve-shaped portion of the pressure booster piston 14 surrounding the first disc 51 and the second disc 52 from. The first disc 51 is attached to the upper end face of the pressure booster piston 14, while the second disc 50 may be introduced into the wall of the injector body 4. The second disc 52 is located above the first end face 15 of the pressure booster piston, while the second end face 16 of the pressure booster piston 14 is a boundary surface of the differential pressure chamber 17 of the pressure booster 11.

In the in FIG. 4 illustrated embodiment of the fuel injection device 1, the control chamber 20 of an injection valve member 80 is integrated into the pressure booster piston 14. Within the control chamber 20, the one end face 79 of the injection valve member 80 acting on nozzle spring 27 is inserted. The injection valve member 80 according to the embodiment in FIG. 4 is surrounded by the high-pressure chamber 19 of the pressure booster 11, that is, in this embodiment, the high-pressure chamber 19 and the nozzle chamber 23 are identical. According to the embodiment according to FIG. 4 the nozzle chamber 23 is formed by the high-pressure chamber 19 of the pressure booster 11. The injection valve member 80 is surrounded below the high-pressure chamber 19 of the pressure booster piston 14 by a sealing sleeve 81. The sealing sleeve 81 is connected via a spring element 82, which in the high-pressure chamber 19 of the pressure booster 11 is inserted, acted upon and sealed against the high pressure chamber 19 of the pressure booster 11 assigning end face, so that the control chamber 20 and a dipping into this coaxial piston 74 are sealed against the high-pressure chamber 19. The injection valve member 80 has a fuel passage 83 which passes through the injection valve 80 in an inclined position and opens at the combustion chamber end of the fuel injection device 1 into an annular gap 84 between injection valve member 80 and injector body 4. Below the annular space 84 in the injector body 4, the combustion chamber-side seat of the injection valve member 80 is closed.

In the pressure booster piston 14 according to the embodiment in FIG. 4 is a coaxial piston 74 is inserted, which is arranged symmetrically to the axis of symmetry of the injector body 4 of the fuel injection device 1 and is received stationary within the injector body 4. For this, the pressure booster piston 14 is relatively movable. The coaxial piston 74 is penetrated by the central control line 31 for pressurizing or pressure relief of the differential pressure chamber 17 serving channel 40. Within the sleeve-shaped region of the pressure booster piston 14, the coaxial piston 74 comprises a support surface 75. On the support surface 75, a biasing spring 76 is supported, which seals the sealing sleeve 36 against the injector body 4. Thus, manufacturing tolerances can be compensated for in multi-part Injektorgehäusen. In this way, the central control line 31 is sealed against the in the working chamber 12 via the high pressure line 3 pending, prevailing in the high pressure accumulator 2 high pressure. At the opposite end of the sealing sleeve 36 of the coaxial piston 74, this is enclosed by the recorded in the control chamber 20 nozzle spring 27. In the area of the control chamber 20 extends the coaxial piston 74 traversing transverse opening 41. Between the differential pressure chamber 17 and the control chamber 20 there is a first connection via a first outflow cross section 77 and a second connection, which is given by the second Abströmquerschnitt 78. The first outflow cross section 77 has a smaller flow cross section compared to the second outflow cross section and is always effective while the second outflow cross section 78 is opened or closed in accordance with the stroke of the pressure booster piston 14 of the pressure booster 11.

In the the in FIG. 4 shown switching position of the servohydraulic 3/2-way valve 70, this is closed. In the working space 12 of the pressure booster 11 is on the high-pressure accumulator 2 from opening into the working space 12 high-pressure line 3 in the working space 12 in the high-pressure accumulator 2 prevailing pressure level. The differential pressure chamber 17 of the pressure booster 11 is above the open control edge VQ1 (valve cross section) and the central control line 31 with fuel pressure corresponding to the prevailing in the working chamber 12 pressure levels. The control chamber 20 is also above the first outflow cross section 77 with the prevailing in the high-pressure accumulator pressure level applied. This pressure level is available via the transverse opening 41 and serving as a central control line 31 channel 40 on the servohydraulic 3/2-way valve 70 at.

By the second sealing sleeve 81 of the control chamber 20 and thus the differential pressure chamber 17 of the pressure booster 11 is separated from acting as a nozzle chamber high-pressure chamber 19 of the pressure booster 11. The sealing effect of the second sealing sleeve 81 is supported by the biasing spring 82, which acts on it and is received in the high-pressure chamber 19.

With the in FIG. 4 In order to achieve an optimum injection pressure curve for the internal combustion engine, a shaping of the pressure build-up or pressure build-up by the pressure booster 11 can be achieved. This is achieved in that a dependent of the stroke of the pressure booster piston 14 flow cross-section is created from the differential pressure chamber. When switching the servohydraulically operated 3/2-way valve 70 used as a switching valve into its open position, the fuel volume contained in the differential pressure chamber 17 flows via the first outflow cross section 77 into the control chamber 20 and via the transverse opening 41 into the central control line 31 designed as channel 40 one. The fuel flows via the overflow line 43 connected to the injector body 4 into the servohydraulic switching valve 70 and via the control edge VQ2 (valve cross-section) into the low-pressure-side return line ND. Due to the pressure reduction in the differential pressure chamber 17 of the pressure booster 11 occurring only slowly over the first outflow cross section 77, a gradual, damped pressure build-up follows in the high-pressure chamber 19 of the pressure booster 11. With increasing stroke of the pressure booster piston 14, ie further retraction into the differential pressure chamber 17, a stroke-dependent successful opening of the second, larger-sized Abströmquerschnittes 78. Is this fully open due to a lack of coverage with the coaxial piston 74, there is a complete pressure reduction in the differential pressure chamber 17, wherein the repelled fuel volume via the central Steuerleitug 31 in the overflow line 43 and from there via the driven from its open position servohydraulic valve 70 in the low-pressure side return to a in FIG. 4 not shown fuel tank flows.

The taking place via the outflow cross sections 77 and 78 pressure relief of the differential pressure chamber 17 causes a corresponding to the transmission ratio of the booster 11 failing pressure increase within the high-pressure chamber 19, in the embodiment according to FIG. 4 acts as a nozzle chamber. The high-pressure chamber 19 and the control chamber 20 are separated from each other via the second sealing sleeve 81 acted upon by the spring 82, so that no overflow of fuel occurs. Due to the increase in pressure in the high-pressure chamber 19 at this retracting pressure booster piston 14, the pressure increases significantly. The increasing fuel pressure acts on one of the injection valve member 80 formed pressure shoulder, which ascends against the force of the nozzle spring 27 in the control chamber 20, ie opens. Via the fuel passage 83 is acted upon by an increased transmission pressure fuel from the high-pressure chamber 19 of the pressure booster 11 in the annular gap 84. The released by the moved from its seat injection valve member 80 injection ports are open, so that from the high-pressure chamber 19 via the fuel passage 83 and the annular gap 84th Fuel can be injected into the combustion chamber 26 of the self-igniting internal combustion engine.

LIST OF REFERENCE NUMBERS

1

Fuel injection system

2

High-pressure accumulator

3

High-pressure line

4

injector

5

switching valve

6

Inlet switching valve

7

low-pressure side return

8th

first housing part

9

second housing part

10

injector

11

Pressure intensifier

12

working space

13

junction

14

Pressure booster piston

15

first end face

16

second end face

17

Differential pressure chamber

18

Return spring

19

High-pressure chamber

20

control room

21

inlet throttle

22

Nozzle chamber inlet

23

nozzle chamber

24

Injection valve member

25

Injection port

26

combustion chamber

27

nozzle spring

28

spigot

29

relief line

30

outlet throttle

31

central control line

32

butt joint

33

High pressure density connection

34

piston extension

35

Recess first housing part

36

sealing sleeve

37

poetry

38

adjusting spring

39

Support surface first sealing sleeve

40

channel

41

transverse opening

42

Guide section (centering 1st sealing sleeve)

43

overflow

50

high pressure-tight guide

51

first disc

52

second disc

60

piston part

61

sealing seat

63

Führupgsraum

64

guide surface

70

Servohydraulic 3/2-way valve

71

valve body

72

Through Hole

73

low-pressure side return

74

Coaxial piston

75

support surface

76

biasing spring

77

first outflow cross section

78

second outflow cross section

79

Front side injection valve member

80

Injection valve member

81

2nd sealing sleeve

82

feather

83

Fuel channel

84

annular gap

V.sub.Q1

first control edge (first valve cross-section)

V Q2

second control edge (second valve cross-section)

ND

low-pressure side return

Claims (16)

1. Fuel injection device (1) which is connected to a high-pressure source (2), having a multi-part injector body (4, 8, 9, 10) in which a pressure booster (11) which can be actuated by means of a differential pressure chamber (17) is held, the pressure booster piston (14) of which pressure booster (11) separates a working chamber (12) from the differential pressure chamber (17), and the fuel injection valve device (1) can be actuated by means of a switching valve (5, 70), with a pressure change in the differential pressure chamber (17) of the pressure booster (11) taking place via a central control line (31) which extends through the pressure booster piston (14), characterized in that the central control line (31) runs substantially coaxially with respect to the axis of symmetry of the pressure booster piston (14) and in that the central control line (31) extends through the working chamber (12) of the pressure booster (11) and is sealed off with respect to said working chamber (12) by means of a high-pressure-tight connection (33, 50, 61).
2. Fuel injection device according to Claim 1, characterized in that the central control line (31) runs substantially coaxially with respect to the axis of symmetry of the injector body (4; 8, 9, 10).
3. Fuel injection device according to Claim 1, characterized in that the pressure booster piston (14) comprises a line section (34, 60, 74) of the central flow line (31), through which line section (34, 60, 74) the duct (40) which constitutes the central control line (31) runs in the working chamber (12) of the pressure booster (11).
4. Fuel injection device according to Claim 1, characterized in that the duct (40) opens out into a recess (35) within a first housing part (8) of the injector body (4; 8, 9, 10), which recess (35) is connected via an overflow line (43) to the switching valve (5, 70).
5. Fuel injection device according to Claim 3, characterized in that the line section of the central control line (31) is formed as a tubular piston extension (34).
6. Fuel injection device according to Claim 3, characterized in that the line section of the central control line (31) is designed as a coaxial piston (74), relative to which the pressure booster piston (14) is movable.
7. Fuel injection device according to Claims 1 and 3, characterized in that a spring-loaded sealing sleeve (36) is held on the line section (34) of the central control line (31), which sealing sleeve (36) is movable relative to said line section (34) and provides a high-pressure sealing (33) of the working chamber (12).
8. Fuel injection device according to Claims 1 and 3, characterized in that the line section (34) comprises a high-pressure-tight guide section (50) which is guided in a first housing part (8) of the injector body (4; 8, 9, 10).
9. Fuel injection device according to Claims 1 and 3, characterized in that a piston part (60) which forms a line section of the central control line (31) is held in a movable fashion in the pressure booster piston (14), which piston part (60) is surrounded by said pressure booster piston (14) and in the head region of which piston part (60) is formed a sealing surface (61) which constitutes a high-pressure-tight connection.
10. Fuel injection device according to Claim 7, characterized in that the sealing sleeve (36) is loaded against the injector body (4; 8, 9, 10) by means of a spring element (38, 76) which is supported either on the line section (74) or on an end side (15) of the pressure booster piston (14).
11. Fuel injection device according to Claim 3, characterized in that the piston part (60), which forms a line section of the central control line (31), has a hydraulically acting surface and is loaded against a delimiting surface of the working chamber (12) of the pressure booster (11), so as to generate a high-pressure-tight connection (61), by the fluid which is held in the working chamber (12).
12. Fuel injection device according to Claim 3, characterized in that outflow cross sections (77, 78) from the differential pressure chamber (17) to the central control line (31) can be controlled in a stroke-dependent fashion.
13. Fuel injection device according to Claim 12, characterized in that the pressure change in the differential pressure chamber (17) takes place via a control chamber (20) into which the first outflow cross section (77) opens out.
14. Fuel injection device according to Claim 12, characterized in that the second outflow cross section (78) exceeds the cross section of the first outflow cross section (77).
15. Fuel injection device according to Claim 1, characterized in that the switching valve (5) is designed as a 3/2 directional valve.
16. Fuel injection device according to Claim 1, characterized in that the switching valve (70) is designed as a servo-hydraulic 3/2 directional valve.

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