EP1287254A1 - Accumulator fuel-injection system for an internal combustion engine - Google Patents

Accumulator fuel-injection system for an internal combustion engine

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Publication number
EP1287254A1
EP1287254A1 EP01929262A EP01929262A EP1287254A1 EP 1287254 A1 EP1287254 A1 EP 1287254A1 EP 01929262 A EP01929262 A EP 01929262A EP 01929262 A EP01929262 A EP 01929262A EP 1287254 A1 EP1287254 A1 EP 1287254A1
Authority
EP
European Patent Office
Prior art keywords
fuel
valve
chamber
control chamber
path
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP01929262A
Other languages
German (de)
French (fr)
Other versions
EP1287254B1 (en
Inventor
Wolfgang Stoecklein
Dietmar Schmieder
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of EP1287254A1 publication Critical patent/EP1287254A1/en
Application granted granted Critical
Publication of EP1287254B1 publication Critical patent/EP1287254B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M47/00—Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure
    • F02M47/02—Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure of accumulator-injector type, i.e. having fuel pressure of accumulator tending to open, and fuel pressure in other chamber tending to close, injection valves and having means for periodically releasing that closing pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M47/00—Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure
    • F02M47/02—Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure of accumulator-injector type, i.e. having fuel pressure of accumulator tending to open, and fuel pressure in other chamber tending to close, injection valves and having means for periodically releasing that closing pressure
    • F02M47/027—Electrically actuated valves draining the chamber to release the closing pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M2547/00—Special features for fuel-injection valves actuated by fluid pressure
    • F02M2547/001—Control chambers formed by movable sleeves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/0012—Valves
    • F02M63/0014—Valves characterised by the valve actuating means
    • F02M63/0015—Valves characterised by the valve actuating means electrical, e.g. using solenoid
    • F02M63/0026—Valves characterised by the valve actuating means electrical, e.g. using solenoid using piezoelectric or magnetostrictive actuators

Definitions

  • the invention relates to an injection arrangement for a fuel storage injection system of an internal combustion engine according to the kind defined in the preamble of claim 1.
  • Fuel storage injection systems, common-rail injection systems, for a multi-cylinder internal combustion engine have a high-pressure fuel distributor or rail, from which several high-pressure fuel supply paths each lead to an injection nozzle protruding into one of the cylinder combustion chambers of the internal combustion engine.
  • the fuel injection into the respective combustion chamber is controlled by means of a nozzle needle, which opens and closes the respective injection nozzle depending on the pressure in a control chamber.
  • a nozzle needle which opens and closes the respective injection nozzle depending on the pressure in a control chamber.
  • an always open inlet channel is provided, through which fuel under the rail pressure from the respective fuel supply path into the Control chamber can flow.
  • Fuel can be drained from the control chamber via a separate drainage path and pressure relaxation can thus be brought about in the control chamber.
  • the pressure level in the control chamber and thus the position of the nozzle needle can be influenced by optionally opening and closing a shut-off valve arranged in the discharge path.
  • Tax chamber again. This increase in pressure pushes the nozzle needle back against its seat and closes the injection nozzle.
  • the drainage path and the inlet channel are designed so that when the drain is open, eg the flow rate of the fuel flowing off via the drainage path is greater than the flow rate of the fuel flowing through the inlet channel, so that the fuel volume in the control chamber is effectively smaller.
  • the dosing accuracy of the amount of fuel injected is largely determined by the speed at which the injector can be opened and closed. When the nozzle is closed, it may be due to the comparatively small passage cross section of the inlet channel that the fuel is insufficient Quantity flows to achieve sufficiently fast closing times.
  • the opening of the bypass channel into the discharge path can cause disturbances in the flow behavior of the fuel when it flows out of the control chamber.
  • unavoidable flow edges at the mouth parts can lead to eddies which ultimately prevent the amount of fuel required to open the injection nozzle from flowing out of the control chamber at the desired speed.
  • the delayed opening of the injection nozzle can then have a negative effect on the dosing accuracy.
  • the junction of the bypass channel lies in the drainage path in the area of the valve chamber. It has been shown that this localization of the junction undesirable Disruptions in the flow behavior of the fuel flowing out of the control chamber can be kept very low. Since increased turbulence of the fuel flow must generally be expected anyway in the area of the valve chamber, the additional swirling effect of the flow edges of the confluence point can take a back seat to this turbulence.
  • bypass channel If the bypass channel is open, fuel - if there is a pressure drop - flows from the fuel supply path via the bypass channel into the drain path and increases the pressure there. While this effect is desired when the injection nozzle is closed in order to fill the control chamber more quickly, when the injection nozzle is opened, the fuel flow entering the discharge path via the bypass channel can in some cases considerably hinder the outflow of the fuel from the control chamber and thus result in a delayed opening the injector.
  • the junction of the bypass channel has also proven to be advantageous in this regard.
  • bypass channel In the area of the valve chamber there is sufficient design freedom to allow the bypass channel to open into the drain path in such a way that such obstructions to the fuel drain can be kept as low as possible.
  • the bypass channel can therefore always be open at any time.
  • a discharge throttle will usually be arranged in the discharge path upstream of the valve chamber, by means of which a desired flow of the outflowing fuel can be set.
  • This discharge throttle is preferably at a distance from the valve chamber along the discharge path.
  • the bypass channel opens into the valve chamber and that between the discharge throttle and the
  • the area of the drainage path located in the valve chamber is free of flow edges that arise from the opening of the bypass channel, this area of the drainage path can be optimized in terms of design more easily with regard to a desired flow behavior in the fuel drainage than would be the case if the bypass channel would flow into the discharge path between the discharge throttle and the valve chamber.
  • shut-off element is adjustable in the valve chamber between two opposite valve seats
  • Seat element is designed such that the upstream and downstream sections of the discharge path open into the valve chamber on the two valve seats and that the point of confluence of the bypass channel and the valve chamber — based on the direction in which the fuel drains away — lies between the two valve seats.
  • FIG. 1 shows a schematic, partial representation of an injector assembly of a storage injection system in longitudinal section
  • FIG. 2 schematically shows a quantity map of the injector assembly according to FIG. 1.
  • Rail injection system depicting memory injection system indicated that diesel fuel under a high hen feed pressure of, for example, more than 1500 bar into a distributor pipe or rail 12.
  • the injection nozzle 16 projects in a manner not shown in a cylinder combustion chamber of a multi-cylinder internal combustion engine, for example a motor vehicle internal combustion engine. It is part of an injector assembly, generally designated 18, which can be used as a preassembled unit in a cylinder block of the internal combustion engine.
  • the injector assembly 18 has a housing assembly 20 with a nozzle housing 22 and a valve housing 24.
  • a guide bore 28 is formed which extends along a housing axis 26 and in which an elongated nozzle needle 30 is guided so as to be axially movable.
  • the nozzle needle 30 has a closing surface 34, with which it can be brought into tight contact with a needle seat 36 formed on the nozzle housing 22.
  • Needle seat 36 flows past to nozzle hole arrangement 38. men and there are injected into the combustion chamber essentially under high pressure or rail pressure.
  • the nozzle needle 30 is biased towards its closed position by a biasing spring 42.
  • the biasing spring 42 is accommodated in a spring chamber 44 formed in the nozzle housing 22. It is supported on the one hand by a sleeve 46 sealingly but axially movably receiving the end of the nozzle needle 30 remote from the combustion chamber, with a biting edge biting into the valve housing 24 on the housing assembly 20 and on the other hand by a spring plate 48 attached to the nozzle needle 30 on the nozzle needle 30.
  • the spring plate 48 is supported on a retaining ring 50 inserted into a U groove of the nozzle needle 30.
  • a control chamber 58 is delimited between an end face 56 of the nozzle needle 30, the sleeve 46 and the valve housing 24 which is remote from the combustion chamber and into which an inlet duct 62 with an inlet throttle 60 opens. Fuel from the spring can flow through the inlet channel 62. space 44 flow into the control chamber 58. Fuel can flow out of the control chamber 58 to a relief chamber (not shown in more detail) via an outlet duct 66 designed with an outlet throttle 64.
  • a shut-off valve 70 which can be actuated by means of an electromagnetic or preferably piezoelectric actuator 68, which is only indicated schematically, makes it possible to block the fuel outflow to the relief chamber.
  • a closing force directed axially towards the combustion chamber is exerted on the nozzle needle 30.
  • This closing force axially counteracts an opening force which is exerted on the nozzle needle 30 as a result of the action of the pressure prevailing in the spring chamber 44 or the annular chamber 40 on a step surface 72 formed on the nozzle needle 30. If the shut-off valve 70 is in a closed position and the fuel outflow through the outlet channel 66 is thus blocked, the closing force is greater than the opening force in the stationary state, which is why the nozzle needle 30 then assumes its closed position. If the shut-off valve 70 is then opened, fuel flows out of the control chamber 58.
  • the flow cross-sections of the inlet throttle 60 and the outlet throttle 64 are matched to one another in such a way that the inflow through the inlet duct 62 is weaker than the outflow through the outlet duct 66 and accordingly a net outflow of fuel results.
  • the following Pressure drop in the control chamber 58 causes the closing force to drop below the opening force and the nozzle needle 30 to lift off the needle seat 36.
  • shut-off valve 70 is brought back into a closed position. This blocks the fuel outflow through the outlet channel 64. Fuel continues to flow through the inlet channel 62 from the spring chamber 44 into the control chamber 58, the pressure in the control chamber 58 rising again. As soon as the pressure in the control chamber 58 reaches a level at which the closing force is greater than the opening force, the nozzle needle 30 moves into its closed position, which stops the fuel escaping from the nozzle hole arrangement 38.
  • a bypass duct 74 is therefore provided, by means of which an additional fuel inflow into the control unit 58 can be achieved.
  • the bypass duct 74 branches off from the bore 52 or from the spring chamber 44 and is just like the inlet channel 62 - fed with fuel that is essentially under the rail pressure.
  • bypass duct 74 allows the pressure in the control chamber 58 to rise again to the level required to move the nozzle needle 30 from its open to its closed position faster than when it is filled solely through the inlet duct 62. Ultimately, the amount of fuel injected into the combustion chamber can be metered more finely.
  • Actuator 68 in the sense of keeping the valve 70 open.
  • the ordinate represents the injected fuel quantity M.
  • the solid line L1 shows the relationship between the actuation time and the injection quantity when the bypass channel 74 is present, while the dashed line L2 illustrates this relationship when the bypass channel is missing.
  • the characteristic curve L1 is flatter than the characteristic curve L2. This means that with the same activation time, less fuel emerges from the injection nozzle 16 if the bypass channel 74 is present. The reason for this is that after de-energization of the actuator 68 or after the valve 70 has been closed, the nozzle needle 30, in the absence of a bypass channel 74, takes longer to return from its open position to its closed position than is the case when an additional - rather, fuel flow through the bypass channel 74 accelerates the needle closing.
  • the injection nozzle 16 is thus open for a longer time in the absence of a bypass channel 74 than in the presence of a bypass channel 74. Accordingly, the total fuel output is also greater in the absence of a bypass channel 74.
  • the flatter characteristic curve L1 with the bypass duct 74 present allows the injected fuel quantity to be metered more finely, and thus leads to an injector which is overall less critical.
  • the shut-off valve 70 is designed as a so-called double-switching directional valve, the shut-off element 76 - here a spherical seat element - can be adjusted between two end positions and at least one intermediate position in a valve chamber 78 by means of the actuator 68.
  • the drain channel 66 In the two end positions or valve closing positions, the drain channel 66 is blocked against fuel outflow from the control chamber 58. In the at least one intermediate position or valve opening position, on the other hand, it is released for fuel outflow from the control chamber 58.
  • This configuration of the valve 70 makes it easy to implement a pre-injection and a main injection phase.
  • the shut-off element 76 is moved from a first of the end positions into the second, for the main injection it is moved out of the two ten end position moved back to the first.
  • the time during which the shut-off element 76 is between the two end positions determines the amount of fuel injected for the pre-injection or main injection.
  • the shut-off element 76 can be moved quickly from the first to the second end position for the pre-injection, that is to say without a longer stopover, so that only a little fuel is sprayed out.
  • the shut-off element 76 can be held in the intermediate position for a certain time in order to allow a correspondingly larger amount of fuel to escape.
  • the actuator 68 must be designed as a positioning actuator for this purpose, which also enables the shut-off element 76 to be positioned in the at least one intermediate position.
  • the valve chamber 78 forms a flow connection between an upstream part 66 ′ with respect to the downward direction of the fuel and a downstream part 66 ′′ of the outlet channel 66.
  • a first valve seat 80 for the shut-off element 76 which is designed as a ball or flat seat element, forms a second valve seat 82 at the mouth parts of the upstream part 66 '.
  • the seating of the shut-off element 76 on the first valve seat 80 defines the first of the two end positions mentioned above, the seating on the second valve seat 82 defines the second end position.
  • the shut-off element 76 cannot in FIG be spring-biased in the first end position.
  • the bypass channel 74 also opens into the valve chamber 78.
  • the formation of the valve 70 with two opposite valve seats 80, 82 then has the consequence that in the first end position of the shut-off element 76, i.e. in contact with the first valve seat 80, a fuel flow which accelerates the filling of the control chamber 58 can flow through the bypass channel 74 into the upstream part 66 'of the outlet 66.
  • the outlet channel 66 is designed such that the fuel flowing out of the control chamber 58 cavitates in the outlet throttle 64. This has the advantage that the
  • Fuel flow is independent of the pressure prevailing in the valve chamber 78 and therefore also by a Pressure increase in the valve chamber 78 is not impaired, which can occur when the valve 70 is open due to the inflow of fuel via the bypass channel 74.
  • the outlet throttle 64 is not arranged here directly in front of the valve chamber 78, but at a distance from it.
  • a so-called diffuser 84 is formed between the outlet throttle 64 and the valve chamber 78 and promotes the formation of cavitation in the outlet throttle 64. If the bypass channel 74 would open into the diffuser 84, flow edges at the mouth parts would interfere with, if not prevent, the formation of cavitation. However, because the bypass channel 74 opens into the valve chamber 78 at a distance from the diffuser 84, such disturbances in the cavitation behavior can be avoided.
  • the angle at which the bypass channel 74 opens into the valve chamber 78 can also influence the outflow behavior of the fuel.
  • an acute junction angle of the bypass channel 74 with respect to the drain direction of the fuel can lead to good results.
  • the bypass duct 74 also contains a bypass throttle 86, the design of which is, on the one hand, with regard to the greatest possible fuel flow to the control chamber 58, on the other hand, it is designed with a view to the lowest possible leakage currents that flow unused via the downstream part 66 ′′ of the outlet 66 when the valve 70 is open or the shut-off element 76 abuts the valve seat 82.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fuel-Injection Apparatus (AREA)

Abstract

The invention relates to an injection assembly for an accumulator fuel-injection system comprising an injection nozzle (16) which projects into a combustion chamber and can be supplied with fuel from a high-pressure fuel distributor (10) via a high-pressure fuel supply route (14, 52, 44, 40) and a nozzle needle (30) which opens and closes the nozzle depending on the pressure in a control chamber (58). The fuel is supplied to the control chamber by a supply channel (62), branching off from the fuel supply route and opening into said chamber and the fuel flows out of the control chamber via an outflow route (66, 78) from said chamber. A downstream section (66") of the outflow route can be shut off in relation to an upstream section (66'), using a shut-off valve (70). The downstream and upstream sections of the outflow route open into a valve chamber (78), in which an adjustable shut-off element is positioned (76). A bypass channel (74) which opens into the outflow route branches off from the fuel supply route, for supplying an additional stream of fuel to the control chamber. In order to minimize the interference to the outflow of the fuel, the mouth of the bypass channel opens into the outflow route in the vicinity of the valve chamber.

Description

Einspritzanordnung für ein Kraftstoff- Speichereinspritz-syste einer VerbrennungsmaschineInjection arrangement for a fuel storage injection system of an internal combustion engine
Stand der TechnikState of the art
Die Erfindung betrifft eine Einspritzanordnung für ein Kraftstoff-Speichereinspritzsystem einer Verbrennungsmaschine nach der im Oberbegriff des Patentanspruchs 1 näher definierten Art.The invention relates to an injection arrangement for a fuel storage injection system of an internal combustion engine according to the kind defined in the preamble of claim 1.
Derartige Einspritzanordnungen sind aus der Praxis hinlänglich bekannt. Kraftstoff-Speichereinspritzsysteme, Common-Rail-Einspritzsysteme, für eine mehrzylindrige Verbrennungsmaschine weisen einen Hochdruck- KraftstoffVerteiler bzw. Rail auf, von dem mehrere Hochdruck-Kraftstoffversor-gungswege zu je einer in einen der Zylinderbrennräume der Verbrennungsmaschine ragenden Einspritzdüse führen.Such injection arrangements are well known in practice. Fuel storage injection systems, common-rail injection systems, for a multi-cylinder internal combustion engine have a high-pressure fuel distributor or rail, from which several high-pressure fuel supply paths each lead to an injection nozzle protruding into one of the cylinder combustion chambers of the internal combustion engine.
Die Kraftstoffeinspritzung in den jeweiligen Brennraum wird mittels einer Düsennadel gesteuert, die die jeweilige Einspritzdüse abhängig vom Druck in einer Steuerkammer öffnet und schließt. Zum Druckaufbau in der Steuerkammer ist ein stets offener Zulaufkanal vorgesehen, durch den unter dem Rail-Druck stehender Kraftstoff vom jeweiligen Kraftstoffversorgungsweg in die Steuerkammer strömen kann. Über einen gesonderten Ablaufweg kann Kraftstoff aus der Steuerkammer abgelassen und so eine Druckentspannung in der Steuerkammer herbeigeführt werden. Durch wahlweises Öffnen und Schlie- ßen eines in dem Ablaufweg angeordneten Absperrventils kann das Druckniveau in der Steuerkammer und damit die Position der Düsennadel beeinflußt werden.The fuel injection into the respective combustion chamber is controlled by means of a nozzle needle, which opens and closes the respective injection nozzle depending on the pressure in a control chamber. To build up pressure in the control chamber, an always open inlet channel is provided, through which fuel under the rail pressure from the respective fuel supply path into the Control chamber can flow. Fuel can be drained from the control chamber via a separate drainage path and pressure relaxation can thus be brought about in the control chamber. The pressure level in the control chamber and thus the position of the nozzle needle can be influenced by optionally opening and closing a shut-off valve arranged in the discharge path.
Wird das Ventil geöffnet, fließt Kraftstoff aus der Steuerkammer ab. Der damit einhergehende Druckabfall in der Steuerkammer führt dazu, daß die Düsennadel von einem Sitz an der Einspritzdüse abhebt und es tritt Kraftstoff aus der Einspritzdüse aus. Wird das Ventil wieder geschlossen, erhöht sich durch den über den Zu- laufkanal nachströmenden Kraftstoff der Druck in derWhen the valve is opened, fuel flows out of the control chamber. The associated drop in pressure in the control chamber causes the nozzle needle to lift off a seat on the injection nozzle and fuel emerges from the injection nozzle. If the valve is closed again, the pressure in the increases due to the fuel flowing in via the inlet channel
Steuerkammer wieder. Durch diesen Druckanstieg wird die Düsennadel wieder gegen ihren Sitz gedrückt und verschließt die Einspritzdüse. Der Ablaufweg und der Zulaufkanal sind dabei so gestaltet, daß bei offenem Ablauf eg die Durchflußrate des über den Ablaufweg abfließenden Kraftstoffs größer als die Durchflußrate des durch den Zulaufkanal nachfließenden Kraftstoffs ist, so daß effektiv das Kraftstoffvolumen in der Steuerkammer kleiner wird.Tax chamber again. This increase in pressure pushes the nozzle needle back against its seat and closes the injection nozzle. The drainage path and the inlet channel are designed so that when the drain is open, eg the flow rate of the fuel flowing off via the drainage path is greater than the flow rate of the fuel flowing through the inlet channel, so that the fuel volume in the control chamber is effectively smaller.
Die Dosiergenauigkeit der eingespritzten Kraftstoffmenge wird wesentlich durch die Geschwindigkeit bestimmt, mit der die Einspritzdüse geöffnet und geschlossen werden kann. Beim Schließen der Düse kann es aufgrund des vergleichsweise kleinen Durchlaßquerschnitts des Zulaufkanals sein, daß Kraftstoff nur in ungenügender Menge nachfließt, um ausreichend schnelle Schließzeiten zu erreichen.The dosing accuracy of the amount of fuel injected is largely determined by the speed at which the injector can be opened and closed. When the nozzle is closed, it may be due to the comparatively small passage cross section of the inlet channel that the fuel is insufficient Quantity flows to achieve sufficiently fast closing times.
Um dennoch die erlittenen Kraftstoffverluste in der Steuerkammer hinreichend schnell ausgleichen zu können, ist es bekannt, von dem Kraftstoffversorgungsweg einen Bypasskanal abzuzweigen, der in den Ablaufweg mündet. Sofern das Absperrventil geschlossen ist, kann durch diesen Bypasskanal ein zusätzlicher Kraftstoffström aus dem Kraftstoffversorgungsweg über einen steuerkammerna- hen Teil des Ablaufwegs in die Steuerkammer fließen. Es hat sich gezeigt, daß hierdurch höhere Schließgeschwindigkeiten der Düsennadel erzielbar sind.In order to be able to compensate for the fuel losses suffered in the control chamber sufficiently quickly, it is known to branch off a bypass channel from the fuel supply path, which opens into the drain path. If the shut-off valve is closed, an additional fuel flow from the fuel supply path can flow through this bypass channel into the control chamber via a part of the discharge path close to the control chamber. It has been shown that higher closing speeds of the nozzle needle can be achieved in this way.
Es hat sich allerdings auch gezeigt, daß das Einmünden des Bypasskanals in den Ablaufweg Störungen des Strömungsverhaltens des Kraftstoffs beim Abfließen aus der Steuerkammer hervorrufen kann. Beispielsweise können unvermeidbare Strömungskanten an der Einmündungssteile zu Verwirbelungen führen, die letztlich verhindern, daß die zum Öffnen der Einspritzdüse erforderliche Kraftstoffmenge mit der gewünschten Schnelligkeit aus der Steuerkammer abfließt. Das verzögerte Öffnen der Einspritzdüse kann sich dann nachteilig auf die Dosierge- nauigkeit auswirken.However, it has also been shown that the opening of the bypass channel into the discharge path can cause disturbances in the flow behavior of the fuel when it flows out of the control chamber. For example, unavoidable flow edges at the mouth parts can lead to eddies which ultimately prevent the amount of fuel required to open the injection nozzle from flowing out of the control chamber at the desired speed. The delayed opening of the injection nozzle can then have a negative effect on the dosing accuracy.
Vorteile der ErfindungAdvantages of the invention
Erfindungsgemäß ist es vorgesehen, daß die Einmündungs- stelle des Bypasskanals in den Ablaufweg im Bereich der Ventilkammer liegt. Es hat sich gezeigt, daß durch diese Lokalisierung der Einmündungsstelle unerwünschte Störungen des Strömungsverhaltens des aus der Steuerkammer abfließenden Kraftstoffs sehr gering gehalten werden können. Da im Bereich der Ventilkammer in der Regel ohnehin mit verstärkten Turbulenzen des Kraft- stoffstroms gerechnet werden muß, kann der zusätzliche Verwirbelungseffekt der Strömungskanten der Einmün- dungsstelle gegenüber diesen Turbulenzen in den Hintergrund treten.According to the invention it is provided that the junction of the bypass channel lies in the drainage path in the area of the valve chamber. It has been shown that this localization of the junction undesirable Disruptions in the flow behavior of the fuel flowing out of the control chamber can be kept very low. Since increased turbulence of the fuel flow must generally be expected anyway in the area of the valve chamber, the additional swirling effect of the flow edges of the confluence point can take a back seat to this turbulence.
Ist der Bypasskanal offen, fließt Kraftstoff - sofern ein Druckgefälle besteht - aus dem Kraftstoffversorgungsweg über den Bypasskanal in den Ablaufweg und erhöht dort den Druck. Während dieser Effekt beim Schließen der Einspritzdüse erwünscht ist, um die Steuerkam- mer rascher zu befüllen, kann beim Öffnen der Einspritzdüse der über den Bypasskanal in den Ablaufweg einbiegende Kraftstoffström das Abfließen des Kraftstoffs aus der Steuerkammer zum Teil erheblich behindern und so zu einem verzögerten Öffnen der Einspritz- düse führen. Die erfindungsgemäße Lokalisierung derIf the bypass channel is open, fuel - if there is a pressure drop - flows from the fuel supply path via the bypass channel into the drain path and increases the pressure there. While this effect is desired when the injection nozzle is closed in order to fill the control chamber more quickly, when the injection nozzle is opened, the fuel flow entering the discharge path via the bypass channel can in some cases considerably hinder the outflow of the fuel from the control chamber and thus result in a delayed opening the injector. The localization of the invention
Einmündungsstelle des Bypasskanals hat sich auch diesbezüglich als vorteilhaft erwiesen.The junction of the bypass channel has also proven to be advantageous in this regard.
Im Bereich der Ventilkammer besteht ausreichende kon- struktive Gestaltungsfreiheit, um den Bypasskanal so in den Ablaufweg münden zu lassen, daß derartige Behinderungen des Kraftstoffablaufs möglichst gering gehalten werden können. Der Bypasskanal kann deswegen ohne weiteres stets offen sein.In the area of the valve chamber there is sufficient design freedom to allow the bypass channel to open into the drain path in such a way that such obstructions to the fuel drain can be kept as low as possible. The bypass channel can therefore always be open at any time.
Im Ablaufweg wird stromaufwärts der Ventilkammer in der Regel eine Ablaufdrossel angeordnet sein, mittels der ein gewünschter Durchfluß des ablaufenden Kraftstoffs eingestellt werden kann. Diese Ablaufdrossel weist längs des Ablaufwegs bevorzugt Abstand von der Ventilkammer auf.A discharge throttle will usually be arranged in the discharge path upstream of the valve chamber, by means of which a desired flow of the outflowing fuel can be set. This discharge throttle is preferably at a distance from the valve chamber along the discharge path.
Es hat sich gezeigt, daß die Gestaltung des zwischen der Ablaufdrossel und der Ventilkammer liegenden Bereichs des Ablaufwegs von wesentlicher Bedeutung für das Strömungsverhalten des abfließenden Kraftstoffs sein kann. Insbesondere kann durch geeignete Gestaltung dieses Bereichs des Ablaufwegs Kavitation in der Ablaufdrossel bei Kraftstoffablauf aus der Steuerkammer herbeigeführt werden. Kavitation in der Ablaufdrossel hat den Vorteil, daß der Durchfluß durch die Ablauf- drossel unabhängig vom Druck in der Ventilkammer und damit unabhängig von einem etwaigen Kraftstoffzufluß über den Bypasskanal ist.It has been shown that the design of the region of the discharge path lying between the discharge throttle and the valve chamber can be of essential importance for the flow behavior of the outflowing fuel. In particular, by appropriately designing this region of the discharge path, cavitation in the discharge throttle can be brought about from the control chamber when fuel is discharged. Cavitation in the outlet throttle has the advantage that the flow through the outlet throttle is independent of the pressure in the valve chamber and thus independent of any fuel inflow via the bypass channel.
Indem erfindungsgemäß der Bypasskanal in die Ventilkam- mer mündet und der zwischen der Ablaufdrossel und derIn that, according to the invention, the bypass channel opens into the valve chamber and that between the discharge throttle and the
Ventilkammer liegende Bereich des Ablaufwegs somit frei von Strömungskanten ist, die durch das Einmünden des Bypasskanals entstehen, kann dieser Bereich des Ablauf- wegs gestalterisch leichter im Hinblick auf ein ge- wünschtes Strömungsverhalten beim Kraftstoffablauf optimiert werden, als es der Fall wäre, wenn der Bypasskanal zwischen der Ablaufdrossel und der Ventilkammer in den Ablaufweg münden würde .That is, the area of the drainage path located in the valve chamber is free of flow edges that arise from the opening of the bypass channel, this area of the drainage path can be optimized in terms of design more easily with regard to a desired flow behavior in the fuel drainage than would be the case if the bypass channel would flow into the discharge path between the discharge throttle and the valve chamber.
Eine bevorzugte Weiterbildung der Erfindung sieht vor, daß das Absperrelement als zwischen zwei gegenüberliegenden Ventilsitzen in der Ventilkammer verstellbares Sitzelement ausgebildet ist, daß an den beiden Ventilsitzen der strom-aufwärtige und der stromabwärtige Abschnitt des Ablaufwegs in die Ventilkammer münden und daß die Einmündungsstelle des Bypasskanals in die Ven- tilkammer - bezogen auf die Abiaufrichtung des Kraftstoffs - zwischen den beiden Ventilsitzen liegt.A preferred development of the invention provides that the shut-off element is adjustable in the valve chamber between two opposite valve seats Seat element is designed such that the upstream and downstream sections of the discharge path open into the valve chamber on the two valve seats and that the point of confluence of the bypass channel and the valve chamber — based on the direction in which the fuel drains away — lies between the two valve seats.
Es versteht sich jedoch, daß eine Ausführung des Absperrventils als Kolbenschieberventil oder als Einsitz- Ventil im Rahmen der Erfindung keineswegs ausgeschlossen ist.However, it goes without saying that execution of the shut-off valve as a spool valve or as a single-seat valve is by no means excluded within the scope of the invention.
Weitere Vorteile und vorteilhafte Ausgestaltungen des Gegenstandes der Erfindung sind der Beschreibung, der Zeichnung und den Patentansprüchen entnehmbar.Further advantages and advantageous configurations of the subject matter of the invention can be gathered from the description, the drawing and the patent claims.
Zeichnungdrawing
Ein Ausführungsbeispiel der Erfindung wird nachstehend anhand der beigefügten Zeichnung näher erläutert. Es stellen darAn embodiment of the invention is explained below with reference to the accompanying drawings. It represent
Figur 1 eine schematische, ausschnittsweise Darstellung einer Injektorbaugruppe eines Speichereinspritzsystems im Längsschnitt, und Figur 2 schematisch ein Mengenkennfeld der Injektorbaugruppe nach Figur 1.1 shows a schematic, partial representation of an injector assembly of a storage injection system in longitudinal section, and FIG. 2 schematically shows a quantity map of the injector assembly according to FIG. 1.
Beschreibung des AusführungsbeispielsDescription of the embodiment
In Figur 1 ist eine Druckquelle 10 eines ein Common-In FIG. 1, a pressure source 10 of a common
Rail-Einspritzsystem darstellenden Speichereinspritzsystems angedeutet, die Diesel-Kraftstoff unter einem ho- hen Druck von beispielsweise mehr als 1500 bar in ein Verteilerrohr bzw. Rail 12 einspeist. Von dem Verteilerrohr 12 gehen mehrere Kraftstoffzufuhrleitungen 14 ab, die zur KraftstoffVersorgung je einer Einspritzdüse 16 dienen. Die Einspritzdüse 16 ragt in nicht näher dargestellter Weise in einen Zylinderbrennraum einer mehrzylindrigen Verbrennungsmaschine, beispielsweise eines Kraftfahrzeug-Verbrennungsmotors. Sie ist Teil einer allgemein mit 18 bezeichneten Injektorbaugruppe, welche als vormontierbare Baueinheit in einen Zylinderblock der Verbrennungsmaschine einsetzbar ist.Rail injection system depicting memory injection system indicated that diesel fuel under a high hen feed pressure of, for example, more than 1500 bar into a distributor pipe or rail 12. A plurality of fuel supply lines 14, which serve to supply fuel to one injection nozzle 16 each, branch off from the distributor pipe 12. The injection nozzle 16 projects in a manner not shown in a cylinder combustion chamber of a multi-cylinder internal combustion engine, for example a motor vehicle internal combustion engine. It is part of an injector assembly, generally designated 18, which can be used as a preassembled unit in a cylinder block of the internal combustion engine.
Die Injektorbaugruppe 18 weist eine Gehäusebaugruppe 20 mit einem Düsengehäuse 22 und einem Ventilgehäuse 24 auf. In dem Düsengehäuse 22 ist eine längs einer Gehäuseachse 26 verlaufende Führungsbohrung 28 ausgebildet, in der eine längliche Düsennadel 30 axial beweglich geführt ist. An einer Nadelspitze 32 weist die Düsennadel 30 eine Schließfläche 34 auf, mit welcher sie in dichte Anlage an einen am Düsengehäuse 22 ausgebildeten Nadelsitz 36 bringbar ist.The injector assembly 18 has a housing assembly 20 with a nozzle housing 22 and a valve housing 24. In the nozzle housing 22, a guide bore 28 is formed which extends along a housing axis 26 and in which an elongated nozzle needle 30 is guided so as to be axially movable. At a needle tip 32, the nozzle needle 30 has a closing surface 34, with which it can be brought into tight contact with a needle seat 36 formed on the nozzle housing 22.
Wenn die Düsennadel 30 am Nadelsitz 36 anliegt, d.h. sich in Nadelschließstellung befindet, ist der Kraft- stoffaustritt aus einer Düsenlochanordnung 38 an dem in den Brennraum ragenden Ende des Düsengehäuses 22 gesperrt. Ist sie dagegen vom Nadelsitz 36 abgehoben, d.h. in Nadelöffnungsstellung, kann Kraftstoff aus einem zwischen der Düsennadel 30 und dem Umfangsmantel der Führungsbohrung 28 gebildeten Ringraum 40 an demWhen the nozzle needle 30 abuts the needle seat 36, i.e. is in the needle closed position, the fuel outlet from a nozzle hole arrangement 38 is blocked at the end of the nozzle housing 22 which projects into the combustion chamber. On the other hand, is it lifted off the needle seat 36, i.e. in the needle opening position, fuel can be drawn from an annular space 40 formed between the nozzle needle 30 and the peripheral jacket of the guide bore 28
Nadelsitz 36 vorbei zu der Düsenlochanordnung 38 strö- men und dort im wesentlichen unter dem Hochdruck bzw. Rail-Druck stehend in den Brennraum gespritzt werden.Needle seat 36 flows past to nozzle hole arrangement 38. men and there are injected into the combustion chamber essentially under high pressure or rail pressure.
Die Düsennadel 30 ist durch eine Vorspannfeder 42 in Richtung auf ihre Schließstellung vorgespannt. Die Vorspannfeder 42 ist in einem im Düsengehäuse 22 ausgebildeten Federraum 44 untergebracht. Sie stützt sich einerseits über eine das brennraumferne Ende der Düsennadel 30 dichtend, jedoch axial beweglich aufnehmende, mit einer Beißkante in das Ventilgehäuse 24 beißende Hülse 46 an der Gehäusebaugruppe 20 und andererseits über einen auf die Düsennadel 30 aufgesteckten Federteller 48 an der Düsennadel 30 ab. Der Federteller 48 stützt sich dabei an einem in eine U fangsnut der Dü- sennadel 30 eingesetzten Haltering 50 ab.The nozzle needle 30 is biased towards its closed position by a biasing spring 42. The biasing spring 42 is accommodated in a spring chamber 44 formed in the nozzle housing 22. It is supported on the one hand by a sleeve 46 sealingly but axially movably receiving the end of the nozzle needle 30 remote from the combustion chamber, with a biting edge biting into the valve housing 24 on the housing assembly 20 and on the other hand by a spring plate 48 attached to the nozzle needle 30 on the nozzle needle 30. The spring plate 48 is supported on a retaining ring 50 inserted into a U groove of the nozzle needle 30.
In den Federraum 44 mündet eine in der Gehäusebaugruppe 20 ausgebildete Bohrung 52, in die über die betreffende Kraftstoffzufuhrleitung 14 im wesentlichen unter dem Rail-Druck stehender Kraftstoff eingeleitet wird. Aus dem Federraum 44 gelangt der Kraftstoff über den Ringraum 40 in den Bereich des Nadelsitzes 36. In Axialbereichen, in denen die Düsennadel 30 am Umfangs antel der Führungsbohrung 28 zu Führungszwecken anliegt, strömt der Kraftstoff dabei an einer oder mehreren Abflachungen 54 des Düsennadelumfangs vorbei.A bore 52 formed in the housing assembly 20 opens into the spring chamber 44, into which fuel which is essentially under the rail pressure is introduced via the fuel supply line 14 in question. From the spring space 44, the fuel passes through the annular space 40 into the area of the needle seat 36. In axial areas in which the nozzle needle 30 bears against the circumference of the guide bore 28 for guide purposes, the fuel flows past one or more flats 54 of the circumference of the nozzle needle.
Zwischen einer brennraumfernen Stirnfläche 56 der Düsennadel 30, der Hülse 46 und dem Ventilgehäuse 24 ist eine Steuerkammer 58 begrenzt, in die ein mit einer Zulaufdrossel 60 ausgeführter Zulaufkanal 62 mündet. Durch den Zulaufkanal 62 kann Kraftstoff aus dem Feder- räum 44 in die Steuerkammer 58 einströmen. Über einen mit einer Ablaufdrossel 64 ausgeführten Ablaufkanal 66 kann Kraftstoff aus der Steuerkammer 58 zu einem nicht näher dargestellten Entlastungsraum abfließen.A control chamber 58 is delimited between an end face 56 of the nozzle needle 30, the sleeve 46 and the valve housing 24 which is remote from the combustion chamber and into which an inlet duct 62 with an inlet throttle 60 opens. Fuel from the spring can flow through the inlet channel 62. space 44 flow into the control chamber 58. Fuel can flow out of the control chamber 58 to a relief chamber (not shown in more detail) via an outlet duct 66 designed with an outlet throttle 64.
Ein mittels eines nur schematisch angedeuteten elektromagnetischen oder vorzugsweise piezoelektrischen Stellers 68 betätigbares Absperrventil 70 erlaubt es, den Kraftstoffabfluß zu dem Entlastungsraum zu sperren.A shut-off valve 70, which can be actuated by means of an electromagnetic or preferably piezoelectric actuator 68, which is only indicated schematically, makes it possible to block the fuel outflow to the relief chamber.
Durch die Vorspannfeder 42 und die Einwirkung des in der Steuerkammer 58 herrschenden Drucks auf die Nadelstirnfläche 56 wird eine axial zum Brennraum hin gerichtete Schließkraft auf die Düsennadel 30 ausgeübt. Dieser Schließkraft wirkt axial eine Öffnungskraft entgegen, die infolge der Einwirkung des in dem Federraum 44 bzw. dem Ringraum 40 herrschenden Drucks auf eine an der Düsennadel 30 ausgebildete Stufenfläche 72 auf die Düsennadel 30 ausgeübt wird. Befindet sich das Absperr- ventil 70 in einer geschlossenen Stellung und ist der Kraftstoffabfluß durch den Ablaufkanal 66 somit gesperrt, ist im stationären Zustand die Schließkraft größer als die Öffnungskraft, weshalb die Düsennadel 30 dann ihre Schließstellung einnimmt. Wird das Absperr- ventil 70 daraufhin geöffnet, fließt Kraftstoff aus der Steuerkammer 58 ab.Due to the biasing spring 42 and the action of the pressure prevailing in the control chamber 58 on the needle end face 56, a closing force directed axially towards the combustion chamber is exerted on the nozzle needle 30. This closing force axially counteracts an opening force which is exerted on the nozzle needle 30 as a result of the action of the pressure prevailing in the spring chamber 44 or the annular chamber 40 on a step surface 72 formed on the nozzle needle 30. If the shut-off valve 70 is in a closed position and the fuel outflow through the outlet channel 66 is thus blocked, the closing force is greater than the opening force in the stationary state, which is why the nozzle needle 30 then assumes its closed position. If the shut-off valve 70 is then opened, fuel flows out of the control chamber 58.
Die Durchflußquerschnitte der Zulaufdrossel 60 und der Ablaufdrossel 64 sind dabei so aufeinander abgestimmt, daß der Zufluß durch den Zulaufkanal 62 schwächer als der Abfluß durch den Ablaufkanal 66 ist und demnach ein Nettoabfluß von Kraftstoff resultiert. Der folgende Druckabfall in der Steuerkammer 58 bewirkt, daß die Schließkraft unter die Öffnungskraft sinkt und die Düsennadel 30 vom Nadelsitz 36 abhebt.The flow cross-sections of the inlet throttle 60 and the outlet throttle 64 are matched to one another in such a way that the inflow through the inlet duct 62 is weaker than the outflow through the outlet duct 66 and accordingly a net outflow of fuel results. The following Pressure drop in the control chamber 58 causes the closing force to drop below the opening force and the nozzle needle 30 to lift off the needle seat 36.
Soll die Einspritzung beendet werden, wird das Absperrventil 70 wieder in eine geschlossene Stellung gebracht. Dies sperrt den Kraftstoffabfluß durch den Ablaufkanal 64. Durch den Zulaufkanal 62 fließt weiterhin Kraftstoff aus dem Federraum 44 in die Steuerkammer 58, wobei der Druck in der Steuerkammer 58 wieder ansteigt. Sobald der Druck in der Steuerkammer 58 ein Niveau erreicht, bei dem die Schließkraft größer als die Öffnungskraft ist, geht die Düsennadel 30 in ihre Schließstellung, was den Kraftstoffaustritt aus der Düsenlo- chanordnung 38 stoppt.If the injection is to be ended, the shut-off valve 70 is brought back into a closed position. This blocks the fuel outflow through the outlet channel 64. Fuel continues to flow through the inlet channel 62 from the spring chamber 44 into the control chamber 58, the pressure in the control chamber 58 rising again. As soon as the pressure in the control chamber 58 reaches a level at which the closing force is greater than the opening force, the nozzle needle 30 moves into its closed position, which stops the fuel escaping from the nozzle hole arrangement 38.
Um schnelle Nadelschließgeschwindigkeiten zu erreichen, muß für einen raschen Druckanstieg in der Steuerkammer 58 nach Schließen des Absperrventils 70 gesorgt werden. Der Durchfluß durch den Zulaufkanal 62 ist vergleichsweise gering. Eine Vergrößerung des Durchflußquerschnitts der Zulaufdrossel 60 kommt aber nur in sehr engen Grenzen in Betracht, weil ansonsten die Gefahr besteht, daß bei geöffnetem Absperrventil 70 der Netto- abfluß an Kraftstoff nicht mehr ausreicht, um die Düsennadel 30 zu öffnen.In order to achieve fast needle closing speeds, a rapid increase in pressure in the control chamber 58 after the shut-off valve 70 has been closed must be ensured. The flow through the inlet channel 62 is comparatively low. An increase in the flow cross section of the inlet throttle 60 is only considered within very narrow limits, because there is otherwise the risk that when the shut-off valve 70 is open, the net outflow of fuel is no longer sufficient to open the nozzle needle 30.
Es ist deshalb ein Bypasskanal 74 vorgesehen, mittels dessen ein zusätzlicher KraftstoffZufluß in die Steuer- kam er 58 erzielbar ist. Der Bypasskanal 74 zweigt von der Bohrung 52 oder vom Federraum 44 ab und wird - ge- nauso wie der Zulaufkanal 62 - mit Kraftstoff gespeist, der im wesentlichen unter dem Rail-Druck steht.A bypass duct 74 is therefore provided, by means of which an additional fuel inflow into the control unit 58 can be achieved. The bypass duct 74 branches off from the bore 52 or from the spring chamber 44 and is just like the inlet channel 62 - fed with fuel that is essentially under the rail pressure.
Der zusätzliche Kraftstoffzufluß durch den Bypasskanal 74 läßt den Druck in der Steuerkammer 58 schneller als bei alleiniger Befüllung durch den Zulaufkanal 62 wieder auf das Niveau ansteigen, das nötig ist, um die Düsennadel 30 aus ihrer Offnungs- in ihre Schließstellung zu überführen. Letztlich kann so die in den Brennraum eingespritzte Kraftstoffmenge feiner dosiert werden.The additional fuel flow through the bypass duct 74 allows the pressure in the control chamber 58 to rise again to the level required to move the nozzle needle 30 from its open to its closed position faster than when it is filled solely through the inlet duct 62. Ultimately, the amount of fuel injected into the combustion chamber can be metered more finely.
Dies läßt sich anhand des schematischen Mengenkennfelds der Figur 2 gut erkennen.This can be clearly seen from the schematic quantity map of FIG. 2.
In Figur 2 ist an der Abszisse die Zeitdauer t aufge- tragen, während der eine elektrische Ansteuerung desIn FIG. 2, the time t is plotted on the abscissa during which an electrical control of the
Stellers 68 im Sinne eines Offenhaltens des Ventils 70 erfolgt. Die Ordinate gibt die eingespritzte Kraft- stoffmenge M wieder. Mit durchgezogener Linie Ll ist der Zusammenhang zwischen Ansteuerzeit und Einspritz- menge bei Vorhandensein des Bypasskanals 74 dargestellt, während die gestrichelte Linie L2 diesen Zusammenhang bei fehlendem Bypasskanal veranschaulicht.Actuator 68 in the sense of keeping the valve 70 open. The ordinate represents the injected fuel quantity M. The solid line L1 shows the relationship between the actuation time and the injection quantity when the bypass channel 74 is present, while the dashed line L2 illustrates this relationship when the bypass channel is missing.
Man erkennt, daß die Kennlinie Ll flacher als die Kenn- linie L2 ist. Dies bedeutet, daß bei gleicher Ansteuerzeit weniger Kraftstoff aus der Einspritzdüse 16 austritt, wenn der Bypasskanal 74 vorhanden ist. Der Grund hierfür ist, daß nach Wegnahme der Bestromung des Stellers 68 bzw. nach Schließen des Ventils 70 die Düsenna- del 30 bei fehlendem Bypasskanal 74 länger braucht, um aus ihrer Öffnungsstellung in ihre Schließstellung zurückzukehren, als es der Fall ist, wenn ein zusätzli- eher Kraftstoffström durch den Bypasskanal 74 das Nadelschließen beschleunigt.It can be seen that the characteristic curve L1 is flatter than the characteristic curve L2. This means that with the same activation time, less fuel emerges from the injection nozzle 16 if the bypass channel 74 is present. The reason for this is that after de-energization of the actuator 68 or after the valve 70 has been closed, the nozzle needle 30, in the absence of a bypass channel 74, takes longer to return from its open position to its closed position than is the case when an additional - rather, fuel flow through the bypass channel 74 accelerates the needle closing.
Nach Schließen des Ventils 70 ist die Einspritzdüse 16 bei fehlendem Bypasskanal 74 somit noch für eine längere Zeit offen als bei vorhandenem Bypasskanal 74. Dementsprechend ist auch der Gesamtausstoß an Kraftstoff bei fehlendem Bypasskanal 74 größer. Die flachere Kennlinie Ll bei vorhandenem Bypasskanal 74 erlaubt es, die eingespritzte Kraftstoffmenge feiner zu dosieren, und führt so zu einem insgesamt toleranzunkritischeren Injektor.After the valve 70 has been closed, the injection nozzle 16 is thus open for a longer time in the absence of a bypass channel 74 than in the presence of a bypass channel 74. Accordingly, the total fuel output is also greater in the absence of a bypass channel 74. The flatter characteristic curve L1 with the bypass duct 74 present allows the injected fuel quantity to be metered more finely, and thus leads to an injector which is overall less critical.
Das Absperrventil 70 ist bei dem hier gezeigten Ausfüh- rungsbeispiel als sogenanntes doppeltschaltendes Wegeventil ausgeführt, dessen Absperrelement 76 - hier ein kugelförmiges Sitzelement - mittels des Stellers 68 in einer Ventilkammer 78 zwischen zwei Endstellungen und mindestens einer Zwischenstellung verstellbar ist.In the exemplary embodiment shown here, the shut-off valve 70 is designed as a so-called double-switching directional valve, the shut-off element 76 - here a spherical seat element - can be adjusted between two end positions and at least one intermediate position in a valve chamber 78 by means of the actuator 68.
In den beiden Endstellungen bzw. Ventilschließstellungen ist der Ablaufkanal 66 gegen Kraftstoffabfluß aus der Steuerkammer 58 gesperrt. In der mindestens einen Zwischenstellung bzw. Ventilöffnungsstellung ist er da- gegen für Kraftstoffabfluß aus der Steuerkammer 58 freigegeben.In the two end positions or valve closing positions, the drain channel 66 is blocked against fuel outflow from the control chamber 58. In the at least one intermediate position or valve opening position, on the other hand, it is released for fuel outflow from the control chamber 58.
Diese Ausbildung des Ventils 70 macht es leicht, eine Voreinspritzungs- und eine Haupteinspritzungsphase zu realisieren. Zur Voreinspritzung wird das Absperrelement 76 aus einer ersten der Endstellungen in die zweite bewegt, zur Haupteinspritzung wird es aus der zwei- ten Endstellung in die erste zurückbewegt. Die Zeit, während der sich das Absperrelement 76 dabei jeweils zwischen den beiden Endstellungen aufhält, bestimmt die zur Vor- bzw. Haupteinspritzung eingespritzte Kraft- stoffmenge. Insbesondere kann das Absperrelement 76 zur Voreinspritzung zügig, also ohne längeren Zwischenaufenthalt aus der ersten in die zweite Endstellung bewegt werden, so daß nur wenig Kraftstoff ausgespritzt wird. Zur Haupteinspritzung kann das Absperrelement 76 eine gewisse Zeit in der Zwischenstellung gehalten werden, um den Austritt einer entsprechend größeren Kraftstoffmenge zu ermöglichen.This configuration of the valve 70 makes it easy to implement a pre-injection and a main injection phase. For the pre-injection, the shut-off element 76 is moved from a first of the end positions into the second, for the main injection it is moved out of the two ten end position moved back to the first. The time during which the shut-off element 76 is between the two end positions determines the amount of fuel injected for the pre-injection or main injection. In particular, the shut-off element 76 can be moved quickly from the first to the second end position for the pre-injection, that is to say without a longer stopover, so that only a little fuel is sprayed out. For the main injection, the shut-off element 76 can be held in the intermediate position for a certain time in order to allow a correspondingly larger amount of fuel to escape.
Es versteht sich, daß der Steller 68 hierzu als Posi- tioniersteller ausgelegt sein muß, der eine Positionierung des Absperrelements 76 auch in die mindestens eine Zwischenstellung ermöglicht.It goes without saying that the actuator 68 must be designed as a positioning actuator for this purpose, which also enables the shut-off element 76 to be positioned in the at least one intermediate position.
Die Ventilkammer 78 bildet eine Strömungsverbindung zwischen einem - bezogen auf die Abiaufrichtung des Kraftstoffs - stromaufwärtigen Teil 66' und einem stromabwärtigen Teil 66'' des Ablaufkanals 66. An der Einmündungsstelle des stromabwärtigen Teils 66' ' in die Ventilkammer 78 ist ein erster Ventilsitz 80 für das als Kugel- oder Flachsitzelement ausgebildete Absperrelement 76 gebildet, an der Einmündungssteile des stromaufwärtigen Teils 66' ein zweiter Ventilsitz 82. Die Anlage des Absperrelements 76 am ersten Ventilsitz 80 definiert die erste der beiden oben angesprochenen Endstellungen, die Anlage am zweiten Ventilsitz 82 die zweite Endstellung. Das Absperrelement 76 kann in nicht näher dargestellter Weise in die erste Endstellung federvorgespannt sein.The valve chamber 78 forms a flow connection between an upstream part 66 ′ with respect to the downward direction of the fuel and a downstream part 66 ″ of the outlet channel 66. At the point of entry of the downstream part 66 ″ into the valve chamber 78 there is a first valve seat 80 for the shut-off element 76, which is designed as a ball or flat seat element, forms a second valve seat 82 at the mouth parts of the upstream part 66 '. The seating of the shut-off element 76 on the first valve seat 80 defines the first of the two end positions mentioned above, the seating on the second valve seat 82 defines the second end position. The shut-off element 76 cannot in FIG be spring-biased in the first end position.
Der Bypasskanal 74 mündet ebenfalls in die Ventilkammer 78. Die Ausbildung des Ventils 70 mit zwei gegenüberliegenden Ventilsitzen 80, 82 hat dann zur Folge, daß in der ersten Endstellung des Absperrelements 76, d.h. in Anlage am ersten Ventilsitz 80, ein die Befüllung der Steuerkammer 58 beschleunigender Kraftstoffström durch den Bypasskanal 74 in den stromaufwärtigen Teil 66' des Ablauf anals 66 fließen kann.The bypass channel 74 also opens into the valve chamber 78. The formation of the valve 70 with two opposite valve seats 80, 82 then has the consequence that in the first end position of the shut-off element 76, i.e. in contact with the first valve seat 80, a fuel flow which accelerates the filling of the control chamber 58 can flow through the bypass channel 74 into the upstream part 66 'of the outlet 66.
In der zweiten Endstellung kann ein solcher Kraftstoffström jedoch nicht fließen. Der Zugang zum stro - aufwärtigen Teil 66' des Ablaufkanals 66 wird durch die Anlage des Absperrelements 76 am zweiten Ventilsitz 82 versperrt. Dies muß allerdings nicht problematisch sein, denn wenn das Absperrelement 76 die zweite Endstellung nur nach Voreinspritzungen einnimmt, kann der Kraftstoffzufluß allein durch den Zulaufkanal 62 genügen, um die Kraftstoffverluste der Steuerkammer 58 hinreichend rasch auszugleichen. Während einer Voreinspritzung werden nämlich in der Regel nur geringe Kraftstoffmengen aus der Steuerkammer abfließen. Diese können auch ohne Unterstützung durch den Bypasskanal 74 rasch ersetzt werden.However, such a fuel flow cannot flow in the second end position. Access to the upstream part 66 ′ of the drain channel 66 is blocked by the shutoff element 76 being in contact with the second valve seat 82. However, this does not have to be problematic, because if the shut-off element 76 assumes the second end position only after pre-injections, the fuel inflow through the inlet channel 62 alone is sufficient to compensate for the fuel losses in the control chamber 58 sufficiently quickly. Only small amounts of fuel will generally flow out of the control chamber during a pre-injection. These can be quickly replaced even without the support of the bypass channel 74.
Der Ablaufkanal 66 ist so gestaltet, daß der aus der Steuerkammer 58 abfließende Kraftstoff in der Ablauf- drossel 64 kavitiert. Dies hat den Vorteil, daß derThe outlet channel 66 is designed such that the fuel flowing out of the control chamber 58 cavitates in the outlet throttle 64. This has the advantage that the
Kraftstoffabfluß unabhängig von dem in der Ventilkammer 78 herrschenden Druck ist und deshalb auch durch eine Druckerhöhung in der Ventilkammer 78 nicht beeinträchtigt wird, die sich bei offenem Ventil 70 bedingt durch Kraftstoffzufluß über den Bypasskanal 74 einstellen kann.Fuel flow is independent of the pressure prevailing in the valve chamber 78 and therefore also by a Pressure increase in the valve chamber 78 is not impaired, which can occur when the valve 70 is open due to the inflow of fuel via the bypass channel 74.
Für das Auftreten von Kavitation ist nicht nur die Gestaltung der Ablaufdrossel 64 selbst verantwortlich. Wesentlichen Einfluß hat auch der stromabwärts an die Ablaufdrossel 64 unmittelbar anschließende Kanalab- schnitt. Deshalb ist die Ablaufdrossel 64 hier nicht unmittelbar vor der Ventilkammer 78 angeordnet, sondern im Abstand von dieser. Zwischen der Ablaufdrossel 64 und der Ventilkammer 78 ist ein sogenannter Diffusor 84 ausgebildet, der die Kavitationsentstehung in der Ab- laufdrossel 64 fördert. Würde der Bypasskanal 74 in den Diffusor 84 münden, würden Strömungskanten an der Einmündungssteile die Kavitationsentstehung stören, wenn nicht sogar verhindern. Weil aber der Bypasskanal 74 im Abstand von dem Diffusor 84 in die Ventilkammer 78 mün- det, können solche Störungen des Kavitationsverhaltens vermieden werden.It is not only the design of the outlet throttle 64 itself that is responsible for the occurrence of cavitation. The channel section immediately following downstream of the flow restrictor 64 also has a significant influence. Therefore, the outlet throttle 64 is not arranged here directly in front of the valve chamber 78, but at a distance from it. A so-called diffuser 84 is formed between the outlet throttle 64 and the valve chamber 78 and promotes the formation of cavitation in the outlet throttle 64. If the bypass channel 74 would open into the diffuser 84, flow edges at the mouth parts would interfere with, if not prevent, the formation of cavitation. However, because the bypass channel 74 opens into the valve chamber 78 at a distance from the diffuser 84, such disturbances in the cavitation behavior can be avoided.
Auch der Einmündungswinkel, unter dem der Bypasskanal 74 in die Ventilkammer 78 einmündet, kann das Abfluß- verhalten des Kraftstoffs beeinflussen. Insbesondere ein spitzer Einmündungswinkel des Bypasskanals 74 bezüglich der Abiaufrichtung des Kraftstoffs kann zu guten Ergebnissen führen.The angle at which the bypass channel 74 opens into the valve chamber 78 can also influence the outflow behavior of the fuel. In particular, an acute junction angle of the bypass channel 74 with respect to the drain direction of the fuel can lead to good results.
Der Bypasskanal 74 enthält ferner eine Bypassdrossel 86, deren Gestaltung einerseits im Hinblick auf einen möglichst großen Kraftstoffzufluß zur Steuerkammer 58, andererseits im Hinblick auf möglichst geringe Leckströme ausgelegt ist, die über den stromabwärtigen Teil 66' ' des Ablauf anals 66 ungenutzt abfließen, wenn das Ventil 70 offen ist oder das Absperrelement 76 am Ventilsitz 82 anliegt. The bypass duct 74 also contains a bypass throttle 86, the design of which is, on the one hand, with regard to the greatest possible fuel flow to the control chamber 58, on the other hand, it is designed with a view to the lowest possible leakage currents that flow unused via the downstream part 66 ″ of the outlet 66 when the valve 70 is open or the shut-off element 76 abuts the valve seat 82.

Claims

Ansprüche Expectations
1. Einspritzanordnung für ein Kraftstoff- Speichereinspritz-system einer Verbrennungsmaschine, mit einer in einen Brennraum der Verbrennungsmaschine ragenden, aus einem Hochdruck-KraftstoffVerteiler (10) des Speichereinspritzsystems über einen Hochdruck- Kraftstoffversorgungsweg (14, 52, 44, 40) mit Kraftstoff versorgbaren Einspritzdüse (16) und einer die Einspritzdüse (16) abhängig vom Druck in einer Steuerkammer (58) öffnenden und schließenden Düsennadel (30) , wobei zur Kraftstoffeinleitung in die Steuerkammer (58) ein von dem Kraftstoffversorgungsweg (14, 52, 44, 40) abzweigender Zulaufkanal (62) in die Steuerkammer (58) mündet und ein von der Steuerkammer (58) ausgehender Ablaufweg (66, 78) den Ablauf des Kraftstoffs aus der Steuerkammer (58) ermöglicht, wobei weiter ein Absperrventil (70) vorgesehen ist, mittels welchem ein - bezogen auf die Abiaufrichtung des Kraftstoffs - stromab- wärtiger Abschnitt (66'') des Ablaufwegs (66, 78) gegenüber einem stromaufwärtigen Abschnitt (66') des Ab- laufwegs (66, 78) sperrbar ist, wobei weiter der strom- abwärtige und der stromaufwärtige Abschnitt (66', 66'') des Ablaufwegs (66, 78) in eine Ventilkammer münden (78), in der ein Absperrelement (76) des Absperrventils (70) verstellbar angeordnet ist, und wobei von dem Kraftstoffversorgungsweg (14, 52, 44, 40) ein in den Ablaufweg (66, 78) mündender Bypasskanal (74) zur Einleitung eines zusätzlichen KraftstoffStroms in die Steuerkammer (58) abgezweigt ist, dadurch gekennzeichnet, daß die Einmündungsstelle des Bypasskanals (74) in den Ablaufweg (66, 78) im Bereich der Ventilkammer (78) liegt.1. Injection arrangement for a fuel accumulator injection system of an internal combustion engine, with an injection nozzle projecting into a combustion chamber of the internal combustion engine, from a high-pressure fuel distributor (10) of the accumulator injection system via a high-pressure fuel supply path (14, 52, 44, 40) (16) and a nozzle needle (30) which opens and closes the injection nozzle (16) depending on the pressure in a control chamber (58), a branch branching off from the fuel supply path (14, 52, 44, 40) for fuel introduction into the control chamber (58) Inlet channel (62) opens into the control chamber (58) and an outlet path (66, 78) starting from the control chamber (58) enables the fuel to drain out of the control chamber (58), a shut-off valve (70) being provided, by means of which a downstream section (66 ″) of the outlet path (66, 78) with respect to an upstream outlet, based on the downward direction of the fuel Section (66 ') of the drain path (66, 78) can be blocked, the downstream and the upstream section (66', 66 '') of the drain path (66, 78) lead into a valve chamber (78) in which a shut-off element (76) of the shut-off valve (70) is adjustably arranged, and wherein from the fuel supply path (14, 52, 44, 40) into the drain path ( 66, 78) branching bypass channel (74) for introducing an additional fuel flow into the control chamber (58), characterized in that the junction of the bypass channel (74) in the drainage path (66, 78) in the region of the valve chamber (78) ,
2. Einspritzanordnung nach Anspruch 1, dadurch gekennzeichnet, daß eine im Ablaufweg (66, 78) stromaufwärts der Ventilkammer (78) angeordnete Ablaufdrossel (64) längs des Ablaufwegs (66, 78) im Abstand von der Ventilkammer (78) angeordnet ist.2. Injection arrangement according to claim 1, characterized in that a discharge throttle (64) arranged in the discharge path (66, 78) upstream of the valve chamber (78) is arranged along the discharge path (66, 78) at a distance from the valve chamber (78).
3. Einspritzanordnung nach Anspruch 2, dadurch gekennzeichnet, daß der Ablaufweg (66, 78), insbesondere in seinem zwischen der Ablaufdrossel (64) und der Ventilkammer (78)' liegenden Bereich (84), derart ausgebildet ist, daß bei Kraftstoffablauf aus der Steuerkammer (58) Kavitation in der Ablaufdrossel (64) auftritt.3. Injection arrangement according to claim 2, characterized in that the discharge path (66, 78), in particular in its region between the discharge throttle (64) and the valve chamber (78) ' (84), is designed such that when fuel flows out of the Control chamber (58) cavitation occurs in the outlet throttle (64).
4. Einspritzanordnung nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß der Bypasskanal (74) stets offen ist.4. Injection arrangement according to one of claims 1 to 3, characterized in that the bypass channel (74) is always open.
5. Einspritzanordnung nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß das Absperrelement (76) als zwischen zwei gegenüberliegenden Ventilsitzen (80, 82) in der Ventilkammer (78) verstellbares Sitzelement aus- gebildet ist, daß an den beiden Ventilsitzen (80, 82) der stromaufwärtige und der stromabwärtige Abschnitt (66', 66'') des Ablaufwegs (66, 78) in die Ventilkammer (78) münden und daß die Einmündungssteile des Bypasska- nals (74) in die Ventilkammer (78) - bezogen auf die5. Injection arrangement according to one of claims 1 to 4, characterized in that the shut-off element (76) as between two opposite valve seats (80, 82) in the valve chamber (78) adjustable seat element from It is formed that at the two valve seats (80, 82) the upstream and downstream sections (66 ', 66'') of the drain path (66, 78) open into the valve chamber (78) and that the opening parts of the bypass channel ( 74) in the valve chamber (78) - based on the
Abiaufrichtung des Kraftstoffs - zwischen den beidenDrain direction of the fuel - between the two
Ventilsitzen (80, 82) liegt.Valve seats (80, 82).
6. Einspritzanordnung nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß das Absperrventil (70) piezoelektrisch betätigt ist.6. Injection arrangement according to one of claims 1 to 5, characterized in that the shut-off valve (70) is actuated piezoelectrically.
7. Einspritzanordnung nach einem der Ansprüche 1 bis 6, gekennzeichnet durch seine Verwendung als Bestandteil eines Common-Rail-Injektors . 7. Injection arrangement according to one of claims 1 to 6, characterized by its use as part of a common rail injector.
EP01929262A 2000-05-18 2001-03-24 Accumulator fuel-injection system for an internal combustion engine Expired - Lifetime EP1287254B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10024702A DE10024702A1 (en) 2000-05-18 2000-05-18 Fuel injector for storage injection system includes bypass channel injecting into outlet path at valve chamber
DE10024702 2000-05-18
PCT/DE2001/001159 WO2001088366A1 (en) 2000-05-18 2001-03-24 Accumulator fuel-injection system for an internal combustion engine

Publications (2)

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EP1287254A1 true EP1287254A1 (en) 2003-03-05
EP1287254B1 EP1287254B1 (en) 2006-05-24

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US (1) US6814302B2 (en)
EP (1) EP1287254B1 (en)
JP (1) JP4625228B2 (en)
KR (1) KR20020019539A (en)
CZ (1) CZ298185B6 (en)
DE (2) DE10024702A1 (en)
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WO (1) WO2001088366A1 (en)

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WO2001088366A1 (en) 2001-11-22
DE10024702A1 (en) 2001-11-22
CZ298185B6 (en) 2007-07-18
ES2261403T3 (en) 2006-11-16
US20020134853A1 (en) 2002-09-26
DE50109882D1 (en) 2006-06-29
US6814302B2 (en) 2004-11-09
CZ200282A3 (en) 2003-06-18
KR20020019539A (en) 2002-03-12
JP2003533636A (en) 2003-11-11
EP1287254B1 (en) 2006-05-24
JP4625228B2 (en) 2011-02-02

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