DE102012223212B4 - Actuator for operating a fuel injector - Google Patents

Abstract

Fuel injector (10), comprising an actuator (18, 88) for actuating a needle-shaped valve element (30), with an electrical connection (12) for energizing the actuator (18, 88), the actuator (18, 88) with the needle-shaped Valve element (30) is directly connected by means of a connection (50), (78), and wherein when current is supplied, a contraction of the actuator (18) can be converted directly into an opening movement of the valve element (30), characterized in that the actuator (18 , 88) is formed from a stacked arrangement (60) of layered electroactive polymers.

Description

State of the art

Most of the actuators currently used in individual systems for fuel are either piezo actuators or solenoid switching valves. With actuators of this type, needle-shaped valve elements, also referred to as nozzle needles, are controlled and switched directly or indirectly.

US 2009/0250021 A1 relates to a control device for a fluid in which electroactive materials are used. At the off US 2009/0250021 A known solution comprises a fluid control device a valve seat. By means of an actuator made of electroactive polymers, a sleeve-shaped switching element is actuated, which changes a distance between one end of the sleeve and the valve seat.

From the DE 10 2004 043 403 A1 , DE 10 2005 016 960 A1 , DE 10 2005 028 135 A1 and EP 1 046 809 A2 In addition, actuators and devices with these actuators are known which work according to different principles.

Disclosure of the invention

The present invention is based on the object of reducing the manufacturing costs of a fuel injector for injecting fuel on the one hand and realizing longer switching paths for a needle-shaped valve element and possibly shortening the switching times of such an actuating element on the other hand. Furthermore, the course of injection can be shaped in a defined manner.

According to the invention, a fuel injector is proposed which comprises an actuator for actuating a needle-shaped valve element, the actuator having an electrical connection for supplying current and the actuator for actuating the fuel injector being formed from electroactive polymers.

The actuator made of electroactive polymers can either be designed in such a way that a number of electroactive polymers are layered on top of one another in a stack arrangement, or the actuator made of electroactive polymers is formed from a rolled or wound arrangement of electroactive polymers. Among the electroactive polymers are ionic (wet) electroactive polymers, e.g. conductive polymers, ionic metal-polymer composites and ionic gels etc. as well as electronic (dry) electroactive polymers such as e.g. electrostrictive polymers as well as piezoelectric polymers, ferroelectric polymers and dielectric elastomers / polymers etc. to be counted.

In contrast to piezoceramics, which use expensive materials such as e.g. Lead-zirconate-titanate require relatively inexpensive polymers to be used here. When using electroactive polymers to manufacture actuators, long switching paths can be implemented for direct control of the needle-shaped valve element, which is not possible with piezo actuators due to the small size. With a direct activation of the needle-shaped valve element, the course of injection can be shaped. This means that the speed of movement and the direction of movement of the needle-shaped valve element can be controlled directly during the entire movement by regulating the control voltage of the actuator made of electroactive polymers. Furthermore, the use of electroactive polymers enables significantly shorter switching times of fuel injectors in comparison to solenoid switching valves and the resulting very low injection rates. The actuators made of electroactive polymers used according to the invention are soft, in contrast to piezoceramics, which are quite brittle. This property offers enormous advantages in a robust environment. Furthermore, electroactive polymers are very easy to miniaturize and can be switched silently. This eliminates the annoying clicking noises of a piezo or magnetic injector, with which fuel injectors for motor vehicles were previously operated. Due to the fact that the electroactive polymers have elastic properties, the needle-shaped valve element can be pressed into the valve seat without destroying this component.

In a possible embodiment variant of the fuel injector proposed according to the invention, the actuator made of electroactive polymers can be enclosed by a shrink tube, coated in a fuel-resistant manner or inserted into a metal sleeve. The actuator made of electroactive polymers is optionally connected to the actuator base of a fastening point with an injector housing of the fuel injector in a non-positive, material or form-fitting manner.

In the case of the fuel injector proposed according to the invention, the latter extends through a free space on a low-pressure side of the fuel injector which is delimited to the outside by the injector housing. Between the actuator made of electroactive polymers and the needle-shaped valve element, ie the nozzle needle of the fuel injector, there can be a direct connection, for example in the form of a material connection such as a welded connection; on the other hand, it is also possible for the needle-shaped valve element, ie the nozzle needle, to pass through indirectly via a coupler module Pressure change in a control chamber actuates the needle-shaped valve element.

In the first-mentioned alternative, the actuator is firmly connected to the needle-shaped valve element via a coupler piece or the actuator head, the connection being rigid.

The actuator made of electroactive polymers can be supported on the bottom of a cavity of the fuel injector via a spring element.

The needle-shaped valve element itself, or a coupling piece of the coupler module, can be guided in an intermediate disk on which a closing spring is supported, which in turn supports the needle-shaped valve element. the nozzle needle is applied in the closing direction. In an advantageous embodiment variant of the fuel injector proposed according to the invention, the mentioned closing spring can act on an adjusting disk which is provided for adjusting the opening force on the needle-shaped valve element. The actuator made of electroactive polymers can be embedded in a filler which is located in a metal sleeve. This sleeve is closed by a membrane or a bellows, so that the filler or the filler compound remains within the free space between the actuator made of electroactive polymers and the inside of the metal sleeve of the actuator module. The actuator module is located in the injector housing of the fuel injector.

In a further advantageous embodiment of the fuel injector proposed according to the invention, the actuator made of electroactive polymer can be surrounded by a plastic coating, in particular fluorosilicone, fluororubber and / or parylene and / or a shrink tube. The actuator made of electroactive polymers can be rigidly joined at its actuator head at a connection either with an end face of the needle-shaped valve element which is joined directly or with a material fit with an end face of the coupling piece.

Advantages of the invention

The actuator proposed according to the invention is preferably formed from electroactive polymers in a stack arrangement, with several thin layers being arranged one above the other. An advantage of the actuator made of electroactive polymers proposed according to the invention is the fact that the direction of movement of such an actuator in a stack arrangement is the same as the opening direction of the needle-shaped valve element, i.e. the nozzle needle. It is therefore possible to dispense with coupling modules or valves for reversing the direction of movement which would otherwise be necessary. The actuator proposed according to the invention made of electroactive polymers contracts when energized. On the one hand, the solution proposed according to the invention offers the possibility of connecting the needle-shaped nozzle element directly to the actuator module in order to obtain a direct switch. This makes an additional valve for control superfluous. Comparatively large strokes can be implemented with an actuator designed in this way, this having an extremely low level of noise during operation. Furthermore, the actuator proposed according to the invention can be embodied in an encapsulated manner from electroactive polymers; a coating or the use of a shrink tube are also possible. Furthermore, the actuator proposed according to the invention made of electroactive polymers is more elastic than actuators made of piezoceramic; therefore there is no risk of seat damage due to the needle-shaped valve element striking the valve seat.

The actuator proposed according to the invention made of electroactive polymers is controlled by a control device which controls or regulates the voltage and thus the speed of movement of the needle-shaped valve element during the entire opening and closing movement of the needle-shaped valve element. With the electroactive polymer actuator proposed according to the invention, pressures of up to 100 MPa can be generated. An actuator designed as a wound actuator could also be used in systems that exist today, for example actuated by piezo actuators, and replace them, which would result in a cost advantage.

Figure list

The invention is described in more detail below with reference to the drawing.

• 1 die Darstellung Kraftstoffinjektors zum Einspritzen von Kraftstoff, mit gewickeltem Aktor aus elektroaktiven Polymeren im Niederdruckbereich,
• 2 einen Schnitt durch eine weitere Ausführungsvariante des Kraftstoffinjektors mit indirekter Ansteuerung des nadelförmig ausgebildeten Ventilelementes, durch einen hochdruckseitig angeordneten Aktor aus elektroaktiven Polymeren,
• 3 eine weitere Ausführungsvariante des erfindungsgemäß vorgeschlagenen Kraftstoffinjektors, bei dem das nadelförmig ausgebildete Ventilelement durch den im Hochdruck befindlichen Aktor aus elektroaktiven Polymeren direkt angesteuert wird,
• 4 eine weitere Ausführungsvariante eines Kraftstoffinjektors, mit separater Hochdruckbohrung im Injektorgehäuse, bei dem das nadelförmig ausgebildete Ventilelement durch einen im Niederdruck befindlichen Aktor aus elektroaktiven Polymeren direkt betätigt wird,
• 5 eine Ausführungsvariante des erfindungsgemäß vorgeschlagenen Kraftstoffinjektors, bei dem der im Hochdruck befindlichen Aktor aus elektroaktiven Polymeren in einem Freiraum mittels einer Feder abgestützt ist,
• 6 eine Ausführungsvariante des erfindungsgemäß vorgeschlagenen Kraftstoffinjektors, bei dem ein im Niederdruck befindlicher Aktor aus elektroaktiven Polymeren ohne Zwischenschaltung eines stützenden Federelementes direkt mit dem nadelförmig ausgebildeten Ventilelement gekoppelt ist und das Injektorgehäuse von einer Zulaufführung durchzogen ist,
• 7 eine Ausführungsvariante des erfindungsgemäß vorgeschlagenen Kraftstoffinjektors ohne stützendes Federelement analog zu 5, jedoch ohne Stützung des Federelements, mit im Hochdruck befindlichen Aktor aus elektroaktiven Polymeren,
• 8 eine Ausführungsvariante des Aktors aus elektroaktiven Polymeren eingebettet in einen Füllstoff bzw. einer Dichtmasse in einer Metallhülse,
• 9 einen Aktor aus elektroaktiven Polymeren, in aufgewickelter Ausführungsform,
• 10 eine Ausführungsvariante eines Aktors aus elektroaktiven Polymeren in Stapelanordnung mit einer Vielzahl von elektroaktiven Polymer-Elementen, welcher von einer kraftstoffresistenten Beschichtung oder durch einen Schrumpfschlauch umhüllt ist und
• 11 eine gewickelte Anordnung eines Aktors aus elektroaktiven Polymeren, umschlossen von einer kraftstoffresistenten Beschichtung oder einem Schrumpfschlauch.

It shows:

• 1 the representation of the fuel injector for injecting fuel, with a wound actuator made of electroactive polymers in the low-pressure range,
• 2 a section through a further embodiment of the fuel injector with indirect control of the needle-shaped valve element, by an actuator made of electroactive polymers arranged on the high pressure side,
• 3 a further embodiment of the fuel injector proposed according to the invention, in which the needle-shaped valve element is actuated directly by the high-pressure actuator made of electroactive polymers,
• 4th Another variant of a fuel injector, with a separate high-pressure bore in the injector housing, in which the needle-shaped valve element is actuated directly by an actuator made of electroactive polymers at low pressure,
• 5 an embodiment of the fuel injector proposed according to the invention, in which the high pressure actuator made of electroactive polymers is supported in a free space by means of a spring,
• 6th an embodiment of the fuel injector proposed according to the invention, in which an actuator made of electroactive polymers and located at low pressure is coupled directly to the needle-shaped valve element without the interposition of a supporting spring element and the injector housing is traversed by a feed duct,
• 7th an embodiment variant of the fuel injector proposed according to the invention without a supporting spring element analogous to FIG 5 , but without support for the spring element, with an actuator made of electroactive polymers at high pressure,
• 8th a variant of the actuator made of electroactive polymers embedded in a filler or a sealing compound in a metal sleeve,
• 9 an actuator made of electroactive polymers, in a wound embodiment,
• 10 an embodiment variant of an actuator made of electroactive polymers in a stack arrangement with a plurality of electroactive polymer elements, which is encased by a fuel-resistant coating or by a shrink tube and
• 11 a coiled arrangement of an actuator made of electroactive polymers, enclosed by a fuel-resistant coating or a shrink tube.

Design variants

According to the representation 1 a section through a fuel injector can be seen in a schematic view.

The in 1 fuel injector shown 10 includes an electrical connector 12 , with which one in an injector housing 14th arranged actuator made of electroactive polymers 18th is controlled. With the actuator 18th it is, for example, either a rolled or a wound actuator 88 according to one embodiment 9 or 11 . With these actuators 88 they are those that elongate in the axial direction when energized. The injector housing 14th also includes a return connection 16 , through which the return volume is returned to a fuel tank. Furthermore, the in 1 shown fuel injector 10 a high pressure inlet 20th running through the injector housing 14th extends on a coupler module 22nd over to a switching valve 24 . The switching valve 24 is located in a throttle plate 26th . The throttle plate 26th is located above a nozzle module 28 , in which a needle-shaped valve element 30th , ie the nozzle needle is arranged.

The nozzle module 28 is made by means of a nozzle clamping nut 32 via a threaded connection with the injector housing 14th joined.

2 shows a section through a possible embodiment of the fuel injector proposed according to the invention, actuated by an actuator in a stack arrangement made of electroactive polymers, with indirect actuation of a needle-shaped closing element.

Out 2 shows that the fuel injector 10 an electrical connection 12 and an injector housing 14th includes, in which the actuator 18th made of electroactive polymers. This is applied in the in 2 embodiment variant shown a coupler piston 34 . The coupler piston 34 is by a coupler spring 38 supported, which in turn is attached to a coupler sleeve 36 which supports the coupler piston 34 surrounds. Below the coupler sleeve 36 is the washer 26th or the throttle plate, in which a throttle 40 arranged and a high pressure inlet hole are executed. When opening the throttle 40 becomes a control room 42 relieved of pressure so that one face of the enters the control room 42 protruding needle-shaped valve element 30th is relieved of pressure and the needle-shaped valve element, ie the nozzle needle 30th a valve seat on the combustion chamber end of a nozzle body 46 releases and consequently fuel can be injected into the combustion chamber of the internal combustion engine.

Below the washer 26th there is a spring plate 44 . The spring plate 44 limited with the washer 26th the control room 42 . On the spring plate 44 a nozzle closing spring is supported 48 from which the needle-shaped valve element, ie the nozzle needle 30th applied in the closing direction, so that when the actuator is not energized 18th the needle-shaped valve element made of electroactive polymers 30th , ie the nozzle needle remains permanently in its seat, the injection openings consequently remain closed and no fuel is injected into the combustion chamber of the internal combustion engine.

In the variant according to 2 is the needle-shaped valve element 30th in a first needle guide 70 and a second needle guide 72 guided. It is possible to use the needle-shaped valve element 30th also lead only in a single needle guide.

In contrast to 2 shows 3 direct actuation of a needle-shaped valve element by an actuator made of electroactive polymers.

From the representation according to 3 shows that the fuel injector 10 the actuator 18th made of electroactive polymers. In the in 3 The embodiment shown is the actuator 18th made of electroactive polymers from a shrink tube 58 enclosed. The actuator 18th comprises a number of layered elements made of electroactive polymers, which are stacked 60 are arranged. The actuator 18th from the electroactive polymer, here enclosed by a shrink tube 58 , controls the needle-shaped valve element 30th , ie the nozzle needle directly because the actuator 18th made of electroactive polymers 18th via a coupler piece 50 directly with the needle-shaped valve element, ie the nozzle needle 30th is coupled. Instead of the sheathing of the actuator 18th through the hose 58 there is also the option of having this with a fuel-resistant coating 92 to be provided, or to be encapsulated by a metallic component. This means that a longitudinal movement, ie a contraction of the actuator 18th from electroactive polymers when energized directly in the axial direction in an opening movement of the needle-shaped valve element 30th can implement, ie the injection openings at the combustion chamber end of the fuel injector 10 be opened.

As furthermore from the sectional view according to 3 emerges, the actuator extends 18th made of electroactive polymers - here, for example, enclosed by the shrink tubing 58 - through a cavity or free space 76 . Via a fuel connection 20th Fuel under system pressure gets into the free space 76 and flows over into an intermediate disk 26th executed fuel holes 56 a nozzle body 46 to. At the end of the nozzle body on the combustion chamber side 46 are the injection openings through which, when released by the needle-shaped valve element, fuel under system pressure is injected into the combustion chamber of the internal combustion engine.

How out 3 continues, this one is from the shrink tube 58 enclosed actuator 18th made of electroactive polymers at an attachment point 62 with the injector housing 14th of the fuel injector 10 connected. The actuator attachment 62 is rigid so that the actuator 18th made of electroactive polymers with appropriate current supply via the electrical connection 12 executes a contraction movement such that when the actuator is contracted 18th from electroactive polymers that through the coupler 50 in the washer 26th guided needle-shaped valve element 30th opens up in the vertical direction and that at the end of the nozzle body on the combustion chamber side 46 trained injection openings are free. How 3 It can also be seen that the coupling piece is guided 50 through a high-precision bore in the washer 26th is executed. Instead of the shrink tubing 58 can also be a fuel-resistant coating 92 or a metallic encapsulation of the actuator 18th be made. Also in the variant according to 3 is the needle-shaped valve element 30th in a first needle guide 70 and a second needle guide 72 guided. However, there is of course also the possibility of using the needle-shaped valve element 30th only in a needle guide in the nozzle body 46 respectively.

According to the representation 4th an embodiment variant of the fuel injector proposed according to the invention can be seen in which the injector housing has a high-pressure bore formed in the shape of a channel and extending through the injector housing.

Also in the variant according to 4th is the actuator 18th made of electroactive polymers in free space 76 going through the injector housing 14th is limited. Also in the representation according to 4th is the actor 18th made of electroactive polymers in a stacked arrangement 60 formed and in this variant of a shrink tube 58 surround. The energization of the actuator 18th made of electroactive polymers via the electrical connection 12 at the top of the fuel injector 10 . The free space 76 by moving the actuator 18th made of electroactive polymers, it also has a system-related return connection 16 from a low pressure area.

How 4th which can be further removed is the one from the shrink tube 58 enclosed actuator 18th made of electroactive polymers through a spring element 64 supported. The spring element 64 is based on the one hand on the actuator head 66 now and then on the floor of the free space 76 from the injector housing 14th is enclosed. In the variant according to 4th form the actuator 18th made of electroactive polymers, the coupler piece 50 , which is on the actuator head 66 is attached, and the needle-shaped valve element 30th , ie the nozzle needle, an interconnected unit. In the variant according to 4th can do that Coupler piece 50 and the actuator head 66 for example, be joined together in a materially bonded manner, as well as the mutually facing end faces of the coupler piece 50 and the needle-shaped valve element 30th , ie the nozzle needle. The upper area of the needle-shaped valve element 30th is in the washer 68 guided, essentially the washer 26th the variant according to the 2 and 3 corresponds.

The needle-shaped valve element 30th is in the variant according to 4th in a first needle guide 70 and a second needle guide 72 led in 4th are only indicated schematically. The two needle guides 70 or. 72 are in the nozzle body 46 educated. Instead of the in 4th illustrated first needle guide 70 and the second needle guide 72 there is also the possibility here of using the needle-shaped valve element 30th only in one, in the nozzle body 46 to guide provided needle guide. Also in the variant according to 4th has the freedom 76 who is essentially the actuator 18th made of electroactive polymers, via a return connection 16 . The actuator 18th made of electroactive polymers can be used instead of shrink tubing 58 also with a fuel-resistant coating 92 or a metallic component. An actuator base 80 is at a fastening point 63 this variant by a press fit / sealing seat in the injector housing 14th recorded. Although the needle-shaped valve element 30th in this variant in 2 needle guides 70 or. 72 is performed, there is also the possibility that needle-shaped valve element 30th in a single needle guide in the nozzle body 46 respectively.

In contrast to the variant according to 4th , in which the inlet hole is through the injector housing 14th extends, is located in the variant according to 5 the high pressure inlet 20th on the top of the injector housing 14th and flows into the free space 76 . In this is the actor 18th encapsulated from electroactive polymers and possibly also coated, or with a shrink tube 58 Mistake. Also in the variant according to 5 lies on the actuator head 66 the spring element 64 which the actuator 18th based on electroactive polymers. According to the representation 5 is a fastening of the actuator 18th made of electroactive polymers through the compound 63 , for example given a press / seal connection.

The actuator 18th from electroactive polymers is in the embodiment according to 5 exposed to the pressurized fuel entering the cavity 76 through the high pressure inlet 20th flows in.

Also in the variant according to 5 can instead of two needle guides 70 or. 72 , just a needle guide in the nozzle body 46 be provided.

In the variant according to 5 it is an actuator 18th made of electroactive polymers, which are arranged in layers 60 is executed. At the actuator head 66 is the coupler piece 50 materially recorded.
The needle-shaped valve element 30th is in the first needle guide 70 and the second needle guide 72 of the nozzle body 46 at the end of the fuel injector on the combustion chamber side 10 guided. The intermediate disk 68 on which the spring element 64 is supported by one or more fuel through holes 56 Mistake. At the open space 76 of the fuel injector 10 is a return connection 16 provided, via which possibly emerging small amounts of leakage are discharged into the low-pressure part of the fuel injection system, which is not absolutely necessary.

6th shows an embodiment variant of the fuel injector proposed according to the invention in which there is no spring element to support the actuator in the free space.

As shown in the illustration 6th is the actor 18th made of electroactive polymers on the actuator attachment 62 of the injector housing 14th recorded. The actuator 18th made of electroactive polymers extends essentially through the free space 76 , which has a return connection 16 for any small leakages that may occur. The leakage flows through the return connection 16 in the low pressure part of the fuel injection system. The energization of the actuator 18th made of electroactive polymers via the electrical connection 12 . Through the injector housing 14th extends a high pressure inlet channel, which in the washer 68 opens and from there the cavity of the nozzle body 46 pressurized with fuel under system pressure. In the nozzle body 46 is also the closing spring 48 added, located on the underside of the washer 68 and on the other hand on the circumference of the needle-shaped valve element 30th arranged adjusting disk 74 . Analogous to the in 4th and 5 The illustrated embodiment variants of the fuel injector proposed according to the invention is the needle-shaped valve element 30th in the first needle guide 70 or a second needle guide 72 out, both in the nozzle body 46 of the fuel injector 10 are trained.

In the variant according to 6th is the actuator head 66 of the actuator 18th made of electroactive polymers fixed to the coupler piece 50 connected, which in turn have an integral connection with the one on the coupler piece 50 opposite end face of the needle-shaped valve element 30th is coupled. When the actuator is energized 18th made of electroactive polymers in a stacked arrangement 60 via the electrical connection 12 pulls the actuator 18th composed of electroactive polymers, so that following this contraction movement, both the coupler piece 50 and the associated needle-shaped valve element 30th execute an axially upward movement and at the end of the nozzle body on the combustion chamber side 46 release arranged injection openings. The actuator 18th is via a screw connection 62 with the injector housing 14th rigidly connected to that the actuator 18th supporting spring element 64 is not applicable for this reason.

As shown in 7th a variant of the fuel injector is shown, which essentially corresponds to the variant according to FIG 6th corresponds.

In contrast to the representation according to 6th the fuel injector 10 according to the execution in 7th does not have a look through the injector housing 14th continuously up to the intermediate pane 68 extending high pressure inlet 20th . Rather, the high pressure inlet opens 20th in the free space 76 of the fuel injector 10 from the injector housing 14th is formed and enclosed. Via the return connection 16 If necessary, small amounts of leakage are directed to the low-pressure side of the fuel system. Analogous to the representation according to 6th it is missing in the variant according to 7th also on a spring element, which the actuator base 66 of the actuator 18th based on electroactive polymers. In the in 7th The embodiment shown is the actuator 18th made of electroactive polymers not by a spring element 64 but in the upper area of the injector housing 12 either by means of the screw connection 62 attached, or alternatively via a material connection with the injector housing 18th connected. In the event of an energization, the actuator pulls out 18th composed of electroactive polymers, so that with the interposition of the coupler piece 50 the opening of the needle-shaped valve element 30th he follows.

The actuator head 66 is with a coupler piece 50 connected, which in turn with the upper end face of the needle-shaped valve element 30th is connected. In the washer 68 the upper part of the needle-shaped valve element is guided, while its lower part is in the first needle guide 70 and the second needle guide 72 of the nozzle body 76 is led. The composite of actuator 18th made of electroactive polymers, coupler piece 50 and needle-shaped valve element 30th acting closing spring 48 presses the compound into the valve seat at the combustion chamber end of the nozzle body 46 so that injection openings formed there are closed. Only when current is supplied and the actuator contracts accordingly 18th the needle-shaped valve element moves from electroactive polymers 30th from its seat, there are those at the end of the nozzle body on the combustion chamber side 46 formed injection openings free so that fuel can be injected into the combustion chamber of the internal combustion engine. Also in the variant according to 7th can instead of two needle guides 70 or. 72 just a needle guide in the nozzle body 46 be provided.

In the 8th , 9 , 10 and 11 are further design options for the actuator made of electroactive polymers 18th shown without the fuel injector 10 , in which the actuator made of electroactive polymers is used, is shown. Regarding the fuel injector 10 will refer to those already described above 1-7 referenced.

According to the representation 8th a variant of an actuator module made of electroactive polymers is shown, which is surrounded by a metal sleeve and embedded in a filler or a sealing compound, such as silicone.

With reference number 82 is a filler or a sealing compound such as silicone, which is in the free space through the metallic sleeve 84 is limited, is included. The injector housing 14th includes the electrical connection 12 to operate the actuator 18th made of electroactive polymers. The actuator base 80 is with the metal sleeve 84 materially connected, for example welded. On the actuator base 80 opposite end, ie the actuator head 66 , is a membrane or bellows 86 who have favourited the filler 82 or the sealant 82 encapsulates. In the variant according to 8th is the actuator made of electroactive polymers consisting of several thin electrode layers in a stack arrangement 60 built up. The metallic sleeve 84 can be the electrical elastomer and the filler 82 enclose in which the thin electrode layers of the stack arrangement 60 of the actuator 18th are embedded from electroactive polymers. Preferably the membrane is 86 or the bellows 86 with the actuator head 66 and the sleeve 84 firmly connected, for example welded.

9 shows a further embodiment of the actuator proposed according to the invention made from electroactive polymers, the actuator being wound from a dielectric elastomer film and expanding in the longitudinal direction when energized.

A wound or rolled actuator 88 made of electroactive polymers as described in 9 is made of dielectric elastomeric film 90 educated. Also in the variant according to 9 is a lot of a filler 82 or a sealant 82 such as silicone added. The metal sleeve 84 is through the already related 8th mentioned bellows 86 or the membrane 86 capsuled. At the top of the metallic sleeve 84 the electrical connection is located 12 which of the energization of the actuator 18th , 88 of electroactive polymers according to the variant in 9 serves. With the actuator base 80 is the actor 88 made of wound dielectric elastomer film 90 with the metallic sleeve 84 rigidly connected, and can for example in an advantageous manner according to the fuel injector design 1 can be used.

The representations according to the 10 and 11 Actuators made of electroactive polymers, which are wound or stacked and are enclosed by a fuel-resistant coating and / or a shrink tube, can be found.

For example, shows 10 an actuator made of electroactive polymers 18th covered by a fuel-resistant coating 92 and / or a shrink tube 58 can be enclosed. The actuator 18th made of electroactive polymers as shown in 10 is in a stacked arrangement 60 executed. The actuator base 80 opposite is the actuator head 66 . At the upper end, ie at the actuator base 80 of the actuator 18th made of electroactive polymers, the electrical connection is located 12 . When the actuator is energized 18th from electroactive polymers this contracts and actuates - as already explained above - with the interposition of the coupler piece 50 the needle-shaped valve element 30th either directly or indirectly.

11 finally shows the actuator 88 in rolled or coiled training. The rolled or coiled actuator 88 made of electroactive polymers, for example a dielectric elastomer film 90 , can also be a fuel-resistant coating 92 and / or a shrink tube 58 and is also provided by an on the actuator base 80 arranged electrical connection 12 energized. When the actuator is energized 18th made of electroactive polymers in rolled or wound construction 88 the actuator elongates 18th in the axial direction and operated as in connection with 1 already described, a switching valve or a rocker or the like to change the direction of movement in an opening movement of the actuator 18th reverse in a direction opposite to the opening of injection ports.

Claims (11)

Fuel injector (10), comprising an actuator (18, 88) for actuating a needle-shaped valve element (30), with an electrical connection (12) for energizing the actuator (18, 88), the actuator (18, 88) with the needle-shaped Valve element (30) is directly connected by means of a connection (50), (78), and wherein when current is supplied, a contraction of the actuator (18) can be converted directly into an opening movement of the valve element (30), characterized in that the actuator (18 , 88) is formed from a stacked arrangement (60) of layered electroactive polymers. Fuel injector (10) according to Claim 1 , characterized in that electroactive polymers, ionic (wet) electroactive polymers such as conductive polymers, ionic metal-polymer composites and ionic gels, dry electroactive polymers such as electrostrictive polymers, piezoelectric polymers, ferroelectric polymers, dielectric elastomers / polymers. Fuel injector (10) according to one of the preceding claims, characterized in that the actuator (18, 88) made of electroactive polymers on the actuator head (66) or on the actuator base (80) at a first fastening point (62) with an injector housing (14) of the fuel injector (10) is rigidly connected, or is connected to the injector housing (14) at a second fastening point (63) as a press fit, shrink fit or sealing fit. Fuel injector (10) according to one of the preceding claims, characterized in that the actuator (18, 88) extends through a free space (76) on a low-pressure side of the fuel injector (10), the injector housing (14) having a high-pressure inlet ( 20). Fuel injector (10) according to one of the preceding claims, characterized in that the actuator (18, 60, 88) extends through a free space (76) on a high pressure side of the fuel injector (10) and a fuel inlet (20) extends into the free space (76) ) opens. Fuel injector (10) according to one of the preceding claims, characterized in that the actuator (18, 88) is supported on the floor of the free space (76) via a spring element (64). Fuel injector (10) according to one of the preceding claims, characterized in that the needle-shaped valve element (30) or a coupling piece (50) are guided in an intermediate disk (68) on which a closing spring (48) is supported. Fuel injector (10) according to the preceding claim, characterized in that the closing spring (48) acts on an adjusting disk (74) which is provided for adjusting the opening force on the needle-shaped valve element (30). The fuel injector (10) according to any one of the preceding claims, characterized in that the actuator (18, 88) made of electroactive polymers is embedded in a filler (82) which is located in the free space (76) within a metal sleeve (84) which passes through a membrane or a bellows (86) is closed. Fuel injector (10) according to one of the preceding claims, characterized in that the actuator (18, 88) made of electroactive polymers of a fuel-resistant coating (92), in particular made of fluorosilicone, fluororubber and / or parylene, and / or of a shrink tube (58 ) is surrounded. Fuel injector (10) according to one of the preceding claims, characterized in that the actuator (18, 88) on its actuator head (66) at a connection (78) rigidly either with an end face of the needle-shaped valve element (30) or an end face of the coupling piece ( 50) is firmly bonded.

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