WO2008138800A1

WO2008138800A1 - Injector with piezo actuator

Info

Publication number: WO2008138800A1
Application number: PCT/EP2008/055512
Authority: WO
Inventors: Stefan Schuerg
Original assignee: Robert Bosch Gmbh
Priority date: 2007-05-15
Filing date: 2008-05-06
Publication date: 2008-11-20
Also published as: DE102007047426A1

Abstract

The invention relates to an injector (1) for injecting fuel into the combustion chamber of an internal combustion engine, in particular a common rail injector, with a valve element (2) which can be adjusted in the axial direction between a closed position and an open position in which the fuel flow is released from a nozzle orifice arrangement into the combustion chamber, and with a piezo actuator (19) with which a valve piston (15) of a control valve (14) can be actuated. When the control valve (14) is open, fuel can flow out of a valve chamber (13) of the control valve (14) into a low pressure region of the injector. According to the invention, the valve piston (15) simultaneously forms the boundary of the valve chamber (13) in two opposite axial directions.

Description

description

title

Injector with piezo actuator

State of the art

The invention relates to an injector for injecting fuel into the combustion chamber of an internal combustion engine, in particular a common rail injector according to the preamble of claim 1.

DE 103 53 169 A1 shows a piezo-controlled common-rail injector with a control valve actuated by means of a piezoactuator and designed as a 3/2-way valve. When the control valve is open, a control chamber bounded by an end face of a valve element is hydraulically connected to a low-pressure region of the injector, so that a net discharge into the low-pressure region results from the control chamber, which is supplied with high-pressure fuel via an inlet throttle. As a result, the pressure in the control chamber decreases, which in turn has an opening movement of the valve element and thus the release of a nozzle hole arrangement result. The piezoelectric actuator does not act directly on a valve piston of the control valve, but only indirectly via a coupler piston of a hydraulic coupler, in particular to compensate for temperature-induced length fluctuations of the piezoelectric actuator. The valve piston is adjustably arranged in the axial direction in a valve chamber which is delimited by a throttle plate in an axial direction. To adjust the valve piston must be expended by the piezoelectric actuator large adjustment forces, since the valve piston from under high pressure standing fuel is pressurized in the direction of its upper valve seat. Due to the large opening force to be applied, the demands on the performance and the stability of the piezoelectric actuator and the entire switching chain are high.

DISCLOSURE OF THE INVENTION Technical Problem

The invention is therefore based on the object to propose a piezo-controlled injector, in which the applied by the piezoelectric actuator opening force is reduced.

Technical solution

This object is achieved with the features of claim 1. Advantageous developments of the invention are specified in the subclaims. All combinations of at least two features specified in the description, the claims and / or the figures also fall within the scope of the invention.

The invention is based on the idea not to arrange the valve piston axially displaceable in a valve chamber, but to form the valve chamber on the valve piston, in particular such that the valve chamber, at least partially, is mitverstellt in adjusting the valve piston in the axial direction. In other words, the valve chamber is arranged at least partially on the outer circumference of the valve piston, such that the valve piston delimits the valve chamber at any time in two opposite axial directions, that is to say from the valve piston two pressure application surfaces acting in opposite axial directions to be provided. By choosing the size of the effective pressure application surfaces, the magnitude of the resultant compressive force acting in an axial direction can be determined, which is due to the pressurization of the pressure surfaces of the valve piston acting in the opposite axial directions by the high pressure fuel in the valve chamber , By means of the invention, the opening force to be applied by the piezoactuator can be reduced, as a result of which piezoactuators with lower power and thus with a smaller overall volume and lower power consumption can be used. In addition, the stability requirements are reduced to the entire switching chain.

In an embodiment of the invention is advantageously provided that the acting in opposite axial directions effective pressure application surfaces (projection surfaces) are at least approximately, preferably exactly the same size. As a result, the compressive force components cancel in the opposite axial directions, as a result of which no closing force which is to be overcome by the piezoactuator acts on the valve piston from the fuel located in the valve chamber. In other words, in this case, the control valve is a pressure-balanced valve in the axial direction. The formation of equal pressure application surfaces can be realized in a simple manner that the valve piston diameter, ie the diameter of the valve piston, with which the valve piston rests against its valve piston seat and the valve piston guide diameter, ie the diameter of the valve piston in its adjacent to the valve chamber guide portion, at least approximately , preferably exactly the same size. If the control valve is designed as a slide valve should, the two with axial distance adjacent to the valve chamber guide diameter of the valve piston are advantageously the same size to choose.

Particularly preferred is an embodiment in which the valve piston is formed by a coupler piston of a hydraulic coupler. In other words, it is possible to dispense with a separate valve piston or a separate coupler piston, whereby the construction of the injector can be substantially simplified and at least one component can be dispensed with. The coupler piston preferably acts in a force-transmitting manner directly or with another coupler piston, in particular permanently connected to the piezoactuator, in a coupler body.

The simultaneous at least partially, preferably complete limitation of the valve chamber by the valve piston in the opposite axial directions and the concomitant minimization of the opening force applied by the piezo actuator allows an embodiment of the hydraulic coupler with a transmission ratio of 1. Such a coupler is relatively easy to implement , For example, in that the coupling piston fixedly connected to the piezoelectric actuator is formed as a sleeve closed on one side, is guided in the other coupler piston, in particular the valve piston.

In an embodiment of the invention is advantageously provided that the valve chamber is limited by a diameter-reduced portion of the valve piston. This embodiment enables a design in which the guide bore accommodating the valve piston, at least in the region of the valve tilkammer can be designed as a simple cylinder bore.

Preferably, the valve piston sealing diameter is formed by a radially inwardly tapering conical surface (conical surface), which cooperates sealingly with a valve piston seat on a guide member accommodating the valve piston. Alternatively, it is conceivable to design the control valve as a slide valve, in which case the valve piston diameter is formed by a guide section of the valve piston.

When the control valve is open, the valve chamber is preferably connected to a discharge chamber, in which a free end of the valve piston protrudes. The discharge chamber is in turn connected to the injector return, in particular via a low pressure piezoelectric actuator space which receives the piezoelectric actuator.

Since no closing force acts on the valve piston from the fuel within the valve chamber, in the development of the invention at least one closing spring is provided with which the valve piston is spring-loaded in the direction of its valve piston seat.

In particular, in order to enable the use of closing springs with a small diameter, the closing spring engages in an end blind bore of the valve piston.

In terms of production, it is advantageous if an axial stop, which is opposite the valve piston seat, for the valve pistons is formed by a throttle plate, in which Preferably, the outlet throttle of the control chamber and / or the inlet throttle is integrated to the control chamber.

In order to minimize the installation space of the injector in the axial direction, an embodiment is advantageous in which the closing spring acting on the valve piston is not (completely) arranged at axial distance from the spring element which acts on the piezoactuator and / or the coupler, but instead in which the spring element and the closing spring (at least in sections) nested in the radial direction, ie is arranged radially in one another. Preferred is an arrangement of the spring element and the closing spring, wherein the closing spring does not project beyond the spring element in the axial direction. This can be realized, for example, in that the spring element and the closing spring are supported on a common support plane in the axial direction. In addition, an embodiment can be realized in which the closing spring projects beyond the spring element in the axial direction, in particular when the support surface for the closing spring is axially spaced from the support surface for the spring element. Likewise, an embodiment can be realized in which the spring element projects beyond the closing spring in two axial directions. By an at least partially radial interleaving of the spring element and the closing spring, the installation space length is optimized in the axial direction, since not two spaced apart in the axial direction spring chambers for receiving the closing spring and the spring element must be provided.

To act on the valve piston in the closing direction with a spring force, an embodiment is advantageous in which the closing spring either on a is integrally formed with the valve piston formed circumferential collar or on a fixed to the valve piston retaining ring in the axial direction. For securing the securing ring, which is preferably designed as a shaft-sealing ring, a circumferential groove is preferably introduced into the valve piston.

For maximum space reduction in the axial direction, it is advantageous if the closing spring is arranged completely radially within the spring element for the piezoelectric actuator and / or the hydraulic coupler, ie the closing spring does not project beyond the spring element in the axial direction. In this case, the closing spring and the spring element are jointly supported on a valve member receiving the guide member in the axial direction.

In a development of the invention, it is advantageously provided that an outer boundary of the coupler space accommodating a coupler volume is not made in one piece, but rather in several parts, preferably in two parts. In this case, the boundary of the coupler space as a radially outer circumferential boundary preferably comprises a sleeve part, which cooperates in a sealing manner with a separate cover part from the sleeve part. In this embodiment, can be dispensed with a need for a one-piece design of the boundary of the coupler space grinding spout at the axial end of a blind hole, whereby the coupler space volume minimized and thereby the rigidity of the hydraulic coupler is increased. In the described embodiment can also be dispensed with the introduction of a blind hole with leadership quality for the coupler piston, which is preferably formed by the valve piston. To seal the sleeve part relative to the cover part is provided in a further development of the invention that the sleeve part is spring-loaded against the cover part. For this purpose, the spring element biasing the piezoactuator in the axial direction is preferably provided, which is advantageously supported on a (lower) side facing away from the cover part, annular end face of the sleeve part. In this case, a biasing force must be realized with the spring element, which is greater than the product of the maximum fuel pressure within the coupler space and the inner cross-sectional area of the sleeve part.

Of particular advantage is an embodiment in which the sleeve part serves as an external guide for guiding the coupler piston, in particular the valve piston. In this case, the inner diameter of the sleeve part, which corresponds to the Kopplerkolbendurchmesser plus a minimum clearance, due to the formation of a separate component can be made particularly accurate and easy.

In order to ensure the tightness of the coupler space in a region between the sleeve part and the cover part also occurring during operation pressure surges, an embodiment is advantageous in which the sleeve part has on its cover part facing the end face a biting edge, preferably with a flat surface on the cover part cooperates sealingly. The provision of a biting edge ensures a sufficient, the tightness of the coupler space ensuring surface pressure.

There are various possibilities for forming the cover part. Preferred is an embodiment in which the cover part on the actual piezoelectric actuator, in particular positive fit, is fixed. It is also a one-piece design of the cover part and piezoelectric actuator feasible. Furthermore, it is conceivable that, due to the spring loading of the sleeve part in the mounted state, the cover part bears only on one end face of the piezoactuator and is pressed against the sleeve part against it.

Particularly preferred is an embodiment of the injector in which the cover part is designed as adjusting piece, can be compensated with the manufacturing tolerances of the hydraulic actuator and / or a housing part of the injector. It is also conceivable to provide a separate adjusting piece between the actuator and the hydraulic coupler.

In order to increase the closing speed of the one-part or multi-part valve element, an embodiment is advantageous in which the control chamber, which can be connected via the control valve to the low-pressure region, not only via an inlet throttle, which opens directly into the control chamber, with high pressure stagnant fuel is refillable, but in addition to the inlet throttle a Fülldrossel is provided, can flow through the high-pressure fuel with the control valve closed in the control chamber, resulting in a faster refilling of the control chamber and thus in a faster pressure increase within the control chamber and thus in turn results in a faster closing behavior of the valve element. The filling throttle, which is permanently hydraulically connected to the high-pressure region of the injector, is preferably arranged in such a way that it first flows via this fuel to an outflow throttle, via which the control chamber communicates with the valve chamber of the Control valve is connected and then flows through the outlet throttle into the control chamber. The filling throttle and the outlet throttle are thus connected in series. It is conceivable to arrange the filling throttle such that the fuel can flow directly to the outlet throttle. Alternatively, an embodiment can be realized in which the filling throttle or a filling channel having these opens into the valve chamber and flows out of this outflowing fuel from the valve chamber to the outlet throttle and via this into the control chamber.

Of particular advantage is an embodiment in which the filling throttle is arranged in a filling channel, which is branched off from a fuel supply line for supplying the injector with fuel under high pressure. Preferably, a flow channel discharging out of the control chamber opens into this filling channel with an outlet throttle, so that both the valve chamber of the control valve and the control chamber are directly refilled when the control valve is closed via the filling throttle. Alternatively, it is conceivable that the filling channel opens out of a pressure chamber of the injector.

Brief description of the drawings

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and the drawings. These show in:

1 is a schematic partial view of a piezo-controlled injector, 2 shows a schematic partial view of an alternative embodiment of a piezo-controlled injector, in which a spring element for the piezoelectric actuator and a closing spring for the valve piston, which are arranged nested in the radial direction,

Fig. 3 is a schematic representation of an alternately formed coupler space and

4 shows a schematic partial view of a piezo-controlled injector, in which a

Valve chamber of a control valve via an outlet throttle and a Fülldrossel with

Fuel is supplied.

Embodiment of the invention

In Fig. 1 a section of a common rail injector designed as an injector 1 for injecting fuel into the combustion chamber of an internal combustion engine is shown. The injector 1 comprises a one-piece or multi-part valve element 2, which is adjustable between an open position and a closed position. In its open position, the valve element 2 releases the fuel flow from a nozzle hole arrangement (not shown) into the combustion chamber of an internal combustion engine.

With an upper end face 3, the valve element 2 defines a control chamber 4. The control chamber 4 is arranged radially inside a sleeve 5, which by means of a helical spring 6, which held on a valve element 2 Circlip 7 is supported, spring-loaded in the axial direction on a throttle plate 8.

In the control chamber 4 opens an introduced into the throttle plate 8 inlet throttle 9, which is hydraulically connected to a fuel supply line 10. The fuel supply line 10 connects a pressure chamber 11 which surrounds the control chamber 4 radially on the outside with fuel under high pressure from a fuel high-pressure accumulator (rail) (not shown). When the valve element 2 is open, the fuel flows from the pressure chamber 11 through the nozzle hole arrangement (not shown) into the combustion chamber of the internal combustion engine.

The control chamber 4 is hydraulically connected to a valve chamber 13 of a control valve 14 (servo valve) via an outlet throttle 12, which is also introduced into the throttle plate 8.

The control valve 14 comprises a valve piston 15, which is guided in an axially displaceable manner in a guide bore 16 of a guide part 17. The valve piston 15 of the control valve 14 is formed by a coupler piston of a hydraulic coupler 18, via which an adjusting movement of a piezoelectric actuator 19 is transmitted. This is the piezoelectric actuator

19 fixedly connected to a further coupler piston 20 which simultaneously forms a coupler body 21, in which a fuel-coupler volume 22 is received. The further coupler piston 20 of the coupler 18 is designed as a closed end sleeve, in which the valve piston 15 is guided axially displaceable. The other coupler piston

20 is connected via a spring element 23, which is connected to the guide Part 17 supported, in the direction of the piezoelectric actuator 21 spring loaded.

The valve chamber 13 is bounded radially on the outside by a peripheral wall 24 of the guide bore 16. In both axial directions, the valve chamber 13 is limited exclusively by the valve piston 15. A valve piston sealing diameter D ₁ , with which the valve piston 15 in its closed position rests against a valve piston seat 25, which is formed by the guide part 17, is just as large as a valve piston guide diameter D ₂ in a guide region 26 of the valve piston 15, so that two effective in opposite axial directions pressure application surfaces 27, 28 (projection surfaces) of the valve piston 15 are equal. The actual effective pressure application surfaces (projection surfaces) are drawn with dashed lines. Radially inside, the valve chamber 15 is bounded by a diameter-reduced portion 29 of the valve piston 15. By thus constructed valve chamber 13, the force acting in opposite directions Axialkraftkomponenten, which are due to the located within the valve chamber 13, pressurized fuel cancel each other, so that no resultant axial force acts on the valve piston 15. The control valve 14 is thus a pressure balanced in the axial direction valve.

To open the valve piston 15, only the closing force generated by a closing spring 30 must be overcome by the piezoelectric actuator 19. The closing spring 30 is disposed within a Absteuerraums 31 which is bounded radially outwardly of the guide member 17. More specifically, the Absteuerraum 31 is limited by a bore in the guide member 17 whose diameter is greater than the diameter the guide bore 16. The closing spring 30 is based on one nenenden on the throttle plate 8, which forms an axial stop 32 for the valve piston 15 and the other end at the bottom of an end blind hole 33 in the valve piston 15th

The Absteuerraum 31 is hydraulically connected via a connecting line 34 with a piezoelectric actuator space 35, which in turn is connected to the injector return, not shown. Thus, the piezoelectric actuator chamber 35 and the exhaust chamber 31 form a low-pressure region 36 of the injector 1.

To open the valve element 2, the piezoelectric actuator 19 is energized in a conventional manner, causing the other coupler piston 21 moves in the drawing plane down. Via the coupler volume 22, an axial force is transmitted to the valve piston 15, which thus likewise moves downwards into the discharge chamber 31 in the plane of the drawing, whereby fuel from the valve chamber 13 and thus via the outlet throttle 12 from the control chamber 4 into the exhaust chamber 31 and can flow to the Injektorrücklauf via the connecting line 34 and the piezoelectric actuator space 35. The flow cross sections of the inlet throttle 9 and the outlet throttle 12 are matched to one another such that when the control valve 14 is open, a net outflow from the control chamber 4 results, which in turn reduces the pressure in the control chamber 4. This raises the valve element 2 (preferably control rod plus nozzle needle) from its seat and it is the fuel flow released from the pressure chamber 11 into the combustion chamber of an internal combustion engine. To close the valve element 2, the energization of the piezoelectric actuator 19 is interrupted, whereby the coupler piston 21, in particular due to the spring force of the spring element 23 moves in the drawing plane upwards. Due to the Due to the spring force of the closing spring 30, the valve piston 15 moves upwards in the drawing plane in the axial direction, whereby the valve piston 15 with a conical surface 37 (valve piston diameter Di) rests against the valve piston seat 25 and the valve piston 15 thus abuts the valve chamber 13 closes. Due to the fuel flowing in via the inlet throttle 9, the pressure in the control chamber 4 increases, as a result of which the valve element 2 in the drawing plane is moved downwards onto its valve seat, which in turn terminates the injection process.

In the following, the embodiment of FIG. 2 will be explained. This corresponds essentially to the exemplary embodiment according to FIG. 1, so that essentially only the differences from the exemplary embodiment according to FIG. 1 are discussed in order to avoid repetition. With regard to the similarities, reference is made to the preceding description of the figures and to FIG. 1.

In contrast to the exemplary embodiment according to FIG. 1, in the exemplary embodiment according to FIG. 2, the closing spring 30 is not arranged within the discharge chamber 31, but within the piezoelectric actuator chamber 35. The closing spring 30 is located radially between the valve piston 15 of the control valve 14 and the spring element 23, which is supported in the axial direction on the hydraulic coupler 18.

Both the spring element 23 and the closing spring 30 are supported in the axial direction on an upper plane 38, which is flat in the plane of the drawing, of the guide part 17. The closing spring 30 lies at the other end with its front side facing away from the guide part 17 at a securing point. ring 39 (shaft lock ring), which is fixed in a circumferential groove 40 within the valve piston 15. As a result, the closing spring 30 urges the valve piston 15 in the closing direction, in the drawing plane upwards. It is the task of the closing spring 30, the valve piston 15 to move in the direction of the valve piston seat 15 when the energization of the piezoelectric actuator 19 is interrupted.

By the arrangement of the closing spring 30 shown radially in FIG. 2 radially inside the spring element 23, the installation space of the injector 1 can be minimized compared with the exemplary embodiment according to FIG. 1, in particular in the event that larger valve piston seat diameters are to be realized and consequently in comparison to FIG the embodiment of FIG. 1 larger closing springs must be used with a larger clamping force. As is apparent from Fig. 2, the closing spring 30 does not project beyond the spring element 23 in the axial direction.

In Fig. 3, only a section of another embodiment of an injector 1 is shown. The illustrated hydraulic coupler 18 can be realized both in the embodiment of FIG. 1 and in the embodiment of FIG. 2.

3, the coupler space 41 surrounding the coupler volume 22 is not realized as a blind hole within the coupler piston 20. In the embodiment according to FIG. 3, the coupler space 41 is bounded radially on the outside by a sleeve part 42. In the axial direction in the plane of the drawing, the coupler space 41 is bounded by a cover part 43 which is fixed to the piezoactuator 19. In the opposite axial direction the coupler space 41 bounded by a plane in the drawing upper end face 44 of the valve piston 15, which serves as a coupler piston in the embodiment shown. Alternatively, it is conceivable to provide a separate coupler piston, which in turn forces the valve piston 15. The sleeve part 42 is spring-loaded in the axial direction in the plane of the drawing upwards by the spring element 23, wherein the spring element 23 on the one hand on a lower, annular end face of the sleeve part 42 in the drawing plane and at the end face 38 of the guide part 17th for the valve piston 15 is supported.

The essential difference from the embodiment of FIG. 1 is that the coupler body 21 shown there is formed in two parts in the embodiment of FIG. consists of the lid part 43 and the sleeve part 42.

At its front side facing the cover part 43, the sleeve part 42 has a circumferential biting edge 45, which is formed directly on the inner circumference of the sleeve part 42 to avoid a pressure step. The biting edge 45 is realized by a slightly conical bevel at the upper end face of the sleeve part 42 in the drawing plane. The spring force (biasing force) with which the spring element 23 biases the sleeve part 42 and thus the piezoelectric actuator 19 is dimensioned so that the sleeve part 42 is not in the axial direction down from the cover part even with a maximum pressurization of the coupler volume 22 during operation of the injector 1 43 can be moved away. The fixed to the piezoelectric actuator 19 cover part 43 has in addition to the sealing of the coupler space 41 in the axial direction in the drawing plane up the task of Einstellstücks. By an appropriate choice of Axialerstre- cover (thickness) of the cover part 43 manufacturing tolerances of the piezoelectric actuator 19 and other components of the injector 1 are compensated.

The embodiment of an injector 1 shown in FIG. 4 essentially corresponds to the embodiment according to FIG

Fig. 1, so that with respect to the similarities to

Avoiding repetition to the description of the figures to Fig. 1 is referenced. The following are in the

Essentially, only the differences from the embodiment of FIG. 1 explained.

In contrast to the embodiment of FIG. 1, in which a refilling of the control chamber 4 takes place with the control valve 14 closed only via the inlet throttle 9, in the embodiment of an injector 1 shown in FIG. 4 in addition to the inlet throttle 9, a Fülldrossel 46 is provided. The Fülldrossel 46 is disposed in a filling channel 47 within the guide member 17, wherein the filling channel 47 is permanently connected to the fuel supply line 10. The fuel supply line 10 and the pressure chamber 11 belong to the high pressure region of the injector 1. In this prevails substantially rail pressure. The filling channel 47 with the filling throttle 46 opens directly into the valve chamber 13. In the flow direction behind the Fülldrossel 46 opens into the filling channel 47, a drain channel 48, which opens out of the control chamber 4 and is integrated into the outlet throttle 12. Since the filling throttle 46 and the outlet throttle 48 are connected in series, with the control valve 14 closed, not only does fuel flow via the inlet throttle from the high-pressure region of the injector into the control chamber 4, but also via the filling throttle 46 and the outlet throttle 12 Fuel over the Fülldrossel 46 into the valve chamber 13 of the control valve 14. Overall, a faster refilling of the valve chamber 13 and the control chamber 4 is achieved hereby, resulting in an increased closing speed of the valve element 2.

Claims

claims

1. injector for injecting fuel into the combustion chamber of an internal combustion engine, in particular common rail Inj ector, with a in the axial direction between a closed position and a fuel flow in the combustion chamber releasing opening position adjustable valve element (2), and with a piezoelectric actuator (19 ), with which a valve piston (15) of a control valve (14) can be actuated, with open control valve (14) from a valve chamber (13) of the control valve (14) fuel in a low pressure region (36) of the injector (1) can flow,

characterized,

the valve piston (15) limits the valve chamber (13) simultaneously in two opposite axial directions.

2. An injector according to claim 1, characterized in that a valve piston sealing diameter (Di) at least approximately, preferably exactly, a valve piston benführungsdurchmesser (D ₂ ) corresponds.

3. Injector according to one of claims 1 or 2, characterized in that the valve piston (15) is pressure-balanced in the axial direction.

4. Injector according to one of the preceding claims, characterized in that the valve piston (15) is a coupler piston of a hydraulic coupler (18).

5. An injector according to claim 4, characterized in that the transmission ratio of the hydraulic coupler (18) at least approximately, preferably exactly, one.

6. Injector according to one of the preceding claims, characterized in that the valve chamber (13) is designed as an annular space, which is preferably bounded radially inwardly by a diameter-reduced portion (29) of the valve piston (15).

7. An injector according to one of the preceding claims, characterized in that the valve piston sealing diameter (Di) is formed by a conical surface which cooperates sealingly with a valve piston (15) axially displaceable receiving guide member (17).

8. Injector according to one of the preceding claims, characterized in that one of the piezoelectric actuator (19) facing away end face of the valve piston (15) in a Absteu- erraum (31) is arranged, which hydraulically with a lying on low pressure Piezoaktorraum (35) connected is.

9. Injector according to one of the preceding claims, characterized in that an axial stop for the valve piston (15) by a throttle plate (8) is formed.

10. Injector according to one of the preceding claims, characterized in that the valve piston (15) in the direction of its closed position by means of a closing spring (30) is loaded feherkraftkraft.

11. An injector according to claim 9, characterized in that the closing spring (30) engages in an end-side blind hole (33) of the valve piston (15).

12. An injector according to claim 10, characterized in that the closing spring (30) is arranged radially within a spring element (23) which acts on the piezoelectric actuator (19) and / or the hydraulic coupler (18) in the axial direction Federkraftschlagt.

13. An injector according to claim 12, characterized in that the closing spring (30) in the axial direction on a peripheral collar of the valve piston (15) or on a valve piston (15) fixed securing ring (39), in particular a shaft securing ring, is supported.

14. Injector according to one of claims 12 or 13, characterized in that the closing spring (30) and / or the spring element (23) on a valve piston (15) leading guide member (17) is supported / supported.

15. Injector according to one of the preceding claims, characterized in that the hydraulic coupler (18) has a coupler volume bounding a coupler space (41), at least partially, preferably completely, formed in one of a cover part (43) separate sleeve part (42) is.

16. An injector according to claim 15, characterized in that the sleeve part (42) axially against the cover part (43), in particular by means of the spring element (23), is spring-loaded.

17. Injector according to one of claims 15 or 16, characterized in that the sleeve part (42) is designed as an external guide for the valve piston.

18. An injector according to claim 15 to 17, characterized in that on the cover part (43) facing the front side of the sleeve part (42) has a biting edge (45) is formed.

19. Injector according to one of claims 15 to 18, characterized in that the cover part (43) is fixed to the piezoelectric actuator (19) or formed integrally therewith.

20. Injector according to one of claims 15 to 19, characterized in that the cover part (43) is designed as a setting piece to compensate for manufacturing tolerances, or that an adjusting piece between the cover part (43) and the piezoelectric actuator (19) is provided.

21. Injector according to one of the preceding claims, characterized in that in addition to an inlet throttle (46) with the high-pressure region of the injector (1) connected Fülldrossel (46) is provided by the fuel at high pressure with the control valve (14) in closed the control chamber (4) can flow.

22. An injector according to claim 21, characterized in that the filling throttle (46) and an outlet throttle (12) are connected in series.

23. An injector according to any one of claims 21 or 22, characterized in that the Fülldrossel (46) is arranged in a filling channel (47) which is branched off from a fuel supply line (10).