EP1395745B1 - Fuel injector comprising a damped injector needle - Google Patents

Description

Technical area

In air-compressing internal combustion engines increasingly high-pressure injection systems come used, which include a high-pressure common rail, over which the individual injectors for injecting fuel into the combustion chambers of Internal combustion engine to be fueled. Injection start and injection quantity be set with the electrically controllable fuel injector. The Injectors can be with the help of Spannpratzen in the cylinder head part of the internal combustion engine attach and can either with seat hole or blind hole injection nozzles be equipped. With the fuel injectors, the course of injection can be formed and on adjust the course of combustion in the combustion chamber.

State of the art

The requirements for the pollutant emissions of internal combustion engines are steadily tightened; the forthcoming amendment of the exhaust emission legislation is in the form of the Expected emission standard EURO 4. This makes the requirements for modern internal combustion engines constantly increased so that their fuel injection systems highest be interpreted flexibly.

The accuracy of the injection duration and the amount of fuel injected into the combustion chamber is determined inter alia by the nozzle needle opening or closing speed. On the one hand, the fuel injectors still inject at relatively low pressures of about 250 bar, compared to the system pressure of about 1300 bar inject, on the other hand with the fuel injectors smallest pilot injection amounts from about 0.5 to 1.0 mm ³ / stroke at high pressures be represented by about 1600 bar. These requirements for the fuel injectors represent the conditions under which the nozzle needle opens and closes the injection opening on the combustion chamber. So far, the opening characteristic of the nozzle needle of the fuel injector and the nozzle needle speed is adjusted by a corresponding design of inlet and outlet throttles.

Um geringste Öffnungsdrücke zu erreichen, ist die Ablaufdrossel möglichst groß zu wählen, während die Ablaufdrossel zur Erzielung kleinster Voreinspritzmengen bei höchsten Drücken möglichst klein auszulegen ist. Ziel jeder Injektorauslegung ist es daher, daß den beiden geschilderten Anforderungen Rechnung getragen werden kann.

In order to take into account the described injection conditions with regard to the throttle design, the following design problem arises:

In order to achieve the lowest opening pressures, the outlet throttle is to be as large as possible, while the outlet throttle is to be designed as small as possible to achieve minimum pilot injection quantities at maximum pressures. The aim of each Injektorauslegung it is therefore that the two requirements described can be taken into account.

From DE 199 30 832 A1 a fuel injection valve is known. This will be particular used in diesel engines for the injection of fuel, especially diesel fuel, wherein the diesel fuel through a fuel inlet into the fuel injection valve arrives. This includes a counter in a guide bore of a valve body the force of a closing spring axially displaceable valve member, which at least during the opening stroke a spray hole in the valve body releases, through which the fuel into the combustion chamber can be injected. To provide a fuel injection valve that the same advantages as a 2-spring holder supplies, which nevertheless simple and inexpensive can be made, is counteracting the damping stroke of the valve member Damping volume via a throttle with the fuel inlet in conjunction.

An injector according to the preamble of claim 1 is EP 740068 A2 known.

Presentation of the invention

The advantages of the solution proposed according to the invention are, above all, to be seen in that the solution proposed according to the invention enables nozzle needle damping, which is effective only when opening the nozzle needle on the nozzle seat and the substantially allows two opening speeds of the nozzle. With the invention proposed Solution ensures that the nozzle initially with high opening speed within a Vorhubes opens, whereby the stroke, which within the Vorhubes is returned, is presettable.

Upon further opening of the injector from its seat created by the overlap a control edge of the nozzle needle or the nozzle needle head with a nozzle needle surrounding housing part a leakage gap, so that in a spring chamber within the Injector body absorbed damping volume damping the opening speed the nozzle needle acts and their opening speed within a Partial stroke of the total stroke dampens, i. reduced. From this opening characteristic, essentially by two different opening speeds of the Nozzle needle is stamped in the housing of the fuel injector, the closing behavior of the Nozzle needle, however, not affected. Because of the reduced speed is the integral under the nozzle needle curve at a constant length of the drive signal much lower as without nozzle needle damping. It can thus significantly lower injection quantities without the basic design parameters such as minimum opening pressure and injured smallest pilot injection quantities. It follows that both smallest To achieve opening pressures and also at high pressures, the quantity steepness considerably can be reduced so that the smallest pilot injection quantities in the combustion chambers Internal combustion engine can be injected.

The inventively proposed damping of the nozzle needle allows an insensitive Design of the drain or inlet throttles from or to the control chamber of the nozzle needle in the housing of the fuel injector. The outlet throttle can be compared to known Design variants are designed much larger than before. determining Parameters for the pre-injection quantity are above all the variables pre-stroke and leakage gap. By a larger-sized outlet throttle is an uncritical opening behavior at Small pressure level in the high-pressure collecting space (common rail) possible. this in turn leads to small copy controls in the mass production of high-pressure injection systems.

drawing

The invention will be explained in more detail below with reference to the drawing.

Figur 1

das hydraulische Schaltbild eines erfindungsgemäß gestalteten Injektors zum Einspritzen von Kraftstoff,

Figur 2

einen Injektor im Längsschnitt,

Figur 2.1

eine injektorseitige Düsennadellagerung,

Figur 2.2

eine Darstellung eines Details gemäß Figur 2.1 in vergrößertem Maßstab,

Figur 2.3

den sich einstellenden Leckagespalt am oberen Düsennadellager,

Figur 3

eine weitere Ausführungsvariante einer injektorseitigen Düsennadellagerung,

Figur 3.1

den sich einstellenden Leckagespalt und

Figur 4

den Verlauf der Düsennadelöffnungsgeschwindigkeit mit und ohne Dämpfung eines Ansteuerzyklus.

It shows:

FIG. 1

the hydraulic circuit diagram of an inventively designed injector for injecting fuel,

FIG. 2

an injector in longitudinal section,

Figure 2.1

an injector-side nozzle needle bearing,

Figure 2.2

a representation of a detail according to Figure 2.1 on an enlarged scale,

Figure 2.3

the self-adjusting leakage gap at the upper nozzle needle bearing,

FIG. 3

a further embodiment variant of an injector-side nozzle needle bearing,

Figure 3.1

the self-adjusting leakage gap and

FIG. 4

the course of the nozzle needle opening speed with and without damping of a drive cycle.

variants

The representation according to Figure 1 is the hydraulic circuit diagram of an inventively designed Injector for injecting fuel into the combustion chambers of an internal combustion engine refer to.

Starting from a high-pressure accumulator (not shown here) Rail) 1, a high-pressure line extends in the direction of an injection nozzle 2 of the injector for injecting fuel into the combustion chambers of an internal combustion engine. Branching from the extending between the high-pressure accumulator 1 and the injection nozzle 2 High-pressure line is an inlet throttle 3 is provided, via which a control room 4 is pressurized with high pressure fuel. The control room 4 on the one hand by a boundary wall 5 of the injector housing, not shown here limited; On the other hand, the high-pressure fuel is acted upon Control chamber 4 from a nozzle needle 6, i. whose front cone 7 limited. A pressure relief of the control chamber 4 via a schematically indicated control edge. 8 and a resulting variable size leak oil gap and an outlet throttle 9, the control edge 8 with resulting leakage oil gap in the injector is subordinate. The control of the under high pressure fuel acted upon Control chamber 4 takes place for example via a solenoid valve 10, which a Closed position 10.1 and can accept an open position 10.2. About the solenoid valve is, if this is switched to its open position 10.2, the standing with high pressure Fuel acted upon control room 4 connected to a leak oil outlet 11, so that the control volume can flow to the fuel reservoir of the Kratistoffeinspritzsystems.

In addition to the schematically illustrated in Figure 1 embodiment with solenoid valve 10 can for pressure relief of the control room also a piezoelectric actuator or a magnetic-hydraulic Steller be used.

FIG. 2 shows an injector consisting of several components for injecting Fuel in the combustion chambers of an internal combustion engine shown in longitudinal section.

Through an injector body 20 extends an inlet bore 21, which in the region of Nozzle needle 6 of the injector in a surrounding the nozzle needle 6 in the region of a pressure stage Nozzle space 25 opens. From the nozzle chamber 25, the nozzle needle 6 extends to Nozzle needle tip 26, depending on the vertical stroke movement of the nozzle needle 6 in the injector 20 an injection port 27 in the region of an injection cone releases or closes. Via the injection opening 27 of the injection nozzle 2 passes through the opening or closing movement of the nozzle needle 6 corresponding to certain fuel volume combustion progress into the combustion chamber of an internal combustion engine. In the nozzle needle tip 26 remote from the region of the nozzle needle 6 is a nozzle needle pin 24 formed on the nozzle needle 6, which is surrounded by a spring element. Below the nozzle needle pin 24 of the nozzle needle 6 extends through a portion of the Injector housing a hole that receives the outlet throttle 9 and in the leak oil drain 11 opens.

From the illustration according to FIG. 2.1, the area of the nozzle needle head is on an enlarged scale of the injector as shown in Figure 2 in more detail.

The Figure Z reproducing the detail Z according to Figure 2 shows that the injector body 20 is constructed in several parts and in the direction of the nozzle space, not shown in Figure 2.1 25 is crossed by a high-pressure bore 21. About the high pressure bore 21st is the pressure chamber 4 in the interior of the injector body 20 with the control chamber 4 in connection. In the interior of the control chamber 4, a closing spring element 45 is accommodated, which For example, can be configured as a coil spring. The closing element 45 is supported on the one hand to a nozzle needle head 34 of the nozzle needle 6 and on the other hand to a in the Control chamber 4 recorded shim 23 from. That preferably as a spiral spring trained closing element 45 is penetrated by the nozzle needle pin 24 of the nozzle needle 6; the total stroke, the nozzle needle 6 with appropriate pressure relief of the control room 4 executes, is designated by reference numeral 29.

The locking element 45 accommodated in the control chamber 4 of the injector body 20 is supported at the head portion 34 of the nozzle needle 6 from. The head portion 34 of the nozzle needle 6 in the embodiment as shown in Figure 2.1 is in a nozzle needle head diameter 36 formed, which exceeds the diameter of the nozzle needle 6. On the circumference of the Nozzle needle head 34 open spaces 35 are formed, which in the axial direction of the nozzle needle tip 26 extending are limited by a control edge 28. At the extent of the nozzle needle head 34 may be formed a plurality of free surfaces 35, so for Example three open spaces 35, offset by 120 ° to each other at the periphery of the nozzle needle head 34 are formed.

In the illustration according to Figure 2.1, the nozzle needle 6 is set so that the respective Control edges 28 of the free surfaces 35 above a housing-side control edge in the injector 20 stand. This position corresponds to the closed position of the nozzle needle 6, whose Nozzle needle tip 26 is placed in the nozzle seat, so that the nozzle needle still the entire Hubweg 29 can ascend.

FIG. 2.2 gives an illustration of a detail according to FIG. 2.1 on an enlarged scale again. At the first moment of opening the nozzle needle 6 completes the nozzle needle and the nozzle needle head 34 received thereon has a lifting movement in the direction of the im Control chamber 4 provided shim 23 to, until the control edge 28, the housing side The edge formed in the injector housing 20 is covered. In the first moment of opening the nozzle needle 6 is therefore the leakage gap between the nozzle needle 6 and the Injector 20 is not in use and the nozzle needle 6 can open freely. First after completion of the Vorhubs 31, the control edge 28 is on the housing side on the injector body 20 provided paragraph. Until reaching the Vorhubes 31 can therefore from Control chamber 4 along the free surfaces 35 on the nozzle needle head 34, the nozzle needle head diameter 36 is formed, unimpeded fuel along the control edge 28 in the here not shown outlet throttle 9 and thus reach the leak oil drain 11.

The representation according to Figure 2.3 is the forming leakage gap at further nozzle needle stroke shown.

In the illustration reproduced in Figure 2.3, the nozzle needle 6 has in the nozzle needle head diameter 36 trained nozzle needle head 34 in an upper stop emotional. The force acting on the front side of the nozzle needle head 34 force memory 45th is corresponding to the total stroke 29 - compare illustration according to Figure 2.1 - compressed. The free surface 35 on the nozzle needle head 34 limiting control edge 28 has the corresponding, formed on the injector body 20 control edge in a length a leakage gap 33 defining length covered. The speed of the nozzle needle 6 in the opening direction is now considerably through the existing in the control room 4 Brazed volume, whereby the nozzle needle 6 at a further Auffahrbewegung reduced Speed is imposed until it has reached the top stop. by virtue of the lower nozzle opening speed occurring in the second stroke section of the total stroke 29 is the integral under the nozzle needle curve at constant Length of the drive signal much lower than without nozzle damping. Leave it represent significantly lower injection quantities, without the basic design parameters how to ignore minimum opening pressure and smallest pilot injection quantities.

Depending on the application variant can at the nozzle needle 6 in the region of the nozzle needle head 34th a different number of open spaces 35 with completion by a control edge 28th be educated. In the illustrations according to the figures 2.1, 2.2 and 2.3 can be for Example on the circumference of the nozzle needle head 34 of the nozzle needle 6 three by 120 ° to each other offset offset surfaces 35 form with a conclusion by a control edge 28.

FIG. 3 shows a further embodiment variant of the nozzle needle damping provided on the injector side.

From this representation it is apparent that the head region of the nozzle needle 6 as shown is formed in Figure 3 as a head portion 38 which in to the nozzle needle. 6 corresponding diameter 37 is formed. The integrated nozzle needle 38 of the Nozzle needle 6 as shown in Figure 3 forms a contact surface for a preferred designed as a spiral spring closing element 45, while the opposite end of the Closing element 45 on a recessed in the control chamber 4 of the injector body 20 shim 23 is present. Analogous to the representation according to FIG. 3, the control chamber 4, in FIG which the closing element 45 is received, by an inlet throttle 3 via the Zulaufbohrung 21 to apply pressure, which the injector body 20 substantially runs through parallel to the nozzle needle 6.

In contrast to the representation according to FIG. 2.1, the embodiment of the nozzle needle 6 as shown in Figure 3 at the integrated head portion 38 of the nozzle needle Zuströmflächen 39 formed. The inflow surfaces 39 can, for example, to 180 ° offset at the periphery of the integrated head portion 38 of the nozzle needle 6 may be provided. Seen in the flow direction of the fuel from the control chamber 4, are behind the integrated Head portion 38 of the nozzle needle 6 at the periphery of the nozzle needle open spaces 35 recorded each bounded by a control edge 28. For example, in this area on the nozzle needle 6 three offset by 120 ° to each other at the periphery recorded Open spaces 35 to be received, which in each case from a control edge 28 at the nozzle needle 6 are limited. About the inflow surfaces 39 and the open spaces 35th flows when driving the nozzle needle 6 into the control chamber 4 fuel over the flow restrictor 9 leading hole in the leak oil drain 11 from, so that the nozzle needle 6 via can retract their total stroke 29 in the pressure-relieved control chamber 4.

Analogous to the illustration according to FIG. 2.1, the closing element 45 is preferably configured as a spiral spring - of the boundary wall of the control chamber 4 outside and one supported on the nozzle needle 6 nozzle needle pin 24 so that no kinking can occur.

Figure 3.1 shows the formation of a leakage gap 33 during the Auffahrbewegung the Nozzle needle 6 in a pressure-relieved control chamber.

At a pressure relief of the control chamber 4 via the outlet throttle 9 takes place first an approach of the nozzle needle 6 in the direction of the control chamber 4 inside. Move through it the free surfaces 35 and the control edges 28 delimiting them in the direction of a on the housing side provided control edge in the injector 20 to. As long as the control edge 28 and the housing side provided in the injector body 20 control edge do not overlap, can unimpeded outflow of fuel through the inflow 39 and the free surfaces 35 via the annular drain passage 40 in the direction of the outlet throttle 9 and further from this in the leak oil outlet 11 (not shown here) done. During this one Vorhub 31 corresponding opening movement of the nozzle needle. 6 From her seat, the opening of the nozzle needle 6 takes place with a first not damped opening speed. Cover with further retraction of the nozzle needle 6 in the Control chamber 4, the control edges 28 which provided on the injector body 20 housing side Control edge, the opening speed of the nozzle needle 6 is considerably by the Locked in the control chamber 4 control volume braked, so that the nozzle needle 6 at further movement according to their Gesamthubweges 29 at a reduced speed moved to its upper stop. Depending on the length of the self-adjusting leakage gap 33 between the control edges 28 of the open spaces 35 on the circumference of the nozzle needle 6 and provided in the injector 20 housing side control edge, there is a formed in different lengths leakage gap 33, the inlet to the drainage channel 40 and throttled from there to the outlet throttle 9.

The damping of the opening movement of the nozzle needle 6 to the effect that only when opening the nozzle needle damping is effective, so that two Öfmungsgeschwindigkeiten set according to the total stroke 29 of the nozzles, allows a less sensitive Design of inlet throttle 3 to the control chamber 4 and its outlet throttle 9. The outlet throttle 9 can be much larger according to the proposed invention be designed so far, as the representable with the inventively configured injector Pre-injection quantities mainly by the sizes 2 to 31 and the leakage gap 33 are set. By a larger-sized outlet throttle 9 is a less critical Opening behavior at low pressures in the high-pressure accumulator 1 possible; In particular, this makes it possible to achieve a smaller copy spread in mass production.

From the illustration of Figure 4, the curves of the Düsennadelöffhungsgeschwindigkeit with and without damping.

According to the diagram in Figure 4, the stroke profile 41 of the nozzle needle 6 is denoted by reference numerals 41, during the entire duration of a drive cycle 'with reference numerals 42 is marked.

Opens the nozzle needle 6 in the direction of the recorded in the control chamber 4 shim 3 against the action of the closing spring element 45 and drives it according to the Vorhubweges 31, so can a higher nozzle needle opening speed can be achieved. If, in contrast to the damping effect of the control volume received in the control chamber 4, a braking effect, ie a damping of the nozzle needle opening movement from its nozzle seat in the area of the nozzle needle tip 26 on the nozzle retaining nut 22, the nozzle needle 6 opens according to the course of the curve 44. In contrast, a nozzle needle opening characteristic without damping by the Course of the curve 43 reproduced. Clearly the larger stroke is read, which would take a nozzle needle without damping by a caged control volume. As a result, a much less favorable, as inaccurate injection volume in the combustion chamber of an internal combustion engine. With the inventively proposed variant of a Düsennadelbewegungsdamaging according to the curve 44 can be realized significantly lower injection quantities, so that both the requirement of smallest pilot injection quantities of about 0.5 to 1.0 mm ³ / stroke of the nozzle needle at the highest pressures of about 1600 bar as Even injections at the lowest pressures of about 250 bar bill can be accommodated.

The closing of the nozzle needle 6, be it with executed in enlarged diameter 36 Nozzle needle head 34 or formed with an integrated head 38 with inflow surfaces, so the closing movement is mainly due to the size of the inlet throttle 3 to the control room 4 determined within the injector body and substantially independent of the leakage gap 32 between the nozzle needle 6 and the injector body 20. In view of the less sensitive Design of inlet throttle 3 to the control chamber 4 and this downstream outlet throttle 9 can completely decouple the closing behavior from this design characteristic be so that with respect to the opening of the nozzle needle 6 reaches minimum opening pressures and also at high pressures, the quantity steepness of the in the combustion chamber of a Internal combustion engine to be injected amount of fuel can be significantly reduced can and in particular advantageously realize small pilot injection quantities to let. With regard to the formation of the course of combustion and with regard to the self-adjusting Ignition delay when the flame front spreads inside the cylinder, are the smallest pilot injection quantities in injection phases depending on the application, be it in internal combustion engines for the use of commercial vehicles, rail vehicles or passenger cars really important.

Claims (9)

1. Injector for injecting fuel into the combustion spaces of an internal combustion engine having an injector housing (20) and a nozzle needle (6) for opening and closing injection openings (27), wherein the end of the nozzle needle (6) which faces away from the injection openings (27) opens into a control space (4) in which a spring element (45) is accommodated, the control space (4) is connected via an inflow throttle (3) to a high-pressure line (21) and via an outflow throttle (9) to the leakage oil outflow (11), and wherein the nozzle needle (6) is surrounded by a nozzle space (25) which is acted on via the high-pressure line (21) and which is formed in a nozzle housing which is surrounded by the clamping element (22), characterized in that control edges (28) are formed in the head region (34, 38) of the nozzle needle (6) and when there are stroke movements (29) of the nozzle needle (6) in the control space (4) they form a leakage gap (33) by covering the control edges (28) in the axial direction with a control edge at the housing end.
2. Injector according to Claim 1, characterized in that the nozzle needle (6) is provided on the side facing the control space (4) with a nozzle needle pin (24) which is surrounded by a closing element (45).
3. Injector according to Claim 1, characterized in that the head region (34) of the nozzle needle (6) is embodied with a diameter (36) which exceeds the diameter of the nozzle needle (6).
4. Injector according to Claim 3, characterized in that at least two flow free faces (35), which are bounded by the control edge (28), are formed on the circumference of the head region (34).
5. Injector according to Claim 3, characterized in that three partial faces (35) which are offset by 120° along the circumference are formed on the head region (34) of the nozzle needle (6).
6. Injector according to Claim 1, characterized in that the nozzle needle (6) comprises an integrated head region (38) in which inflow free faces (39) are integrated.
7. Injector according to Claim 6, characterized in that free faces (35), which are bounded by control edges (28), are arranged on the nozzle needle (6) downstream of the inflow free faces (39) viewed in the direction of flow of the fuel.
8. Injector according to Claim 7, characterized in that the free faces (35) are formed offset with respect to one another by 120° along the circumference of the nozzle needle (6).
9. Injector according to Claim 1, characterized in that the leakage gap (33) is set with a length which is dependent on the stroke distance (29, 31) of the nozzle needle (6) in the injector housing (20).

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