EP2957760B1 - Nozzle assembly for a fuel injector and fuel injector - Google Patents

Description

The invention relates to a nozzle assembly for a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine with the features of the preamble of claim 1. Furthermore, the invention relates to a fuel injector with such a nozzle assembly.

State of the art

From the publication DE 10 2006 021 491 A1 a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine is known, which has an axially displaceably guided in a high-pressure bore of a nozzle body nozzle needle, which is directly actuated by means of an actuator, such as a piezoelectric actuator. The actuator cooperates with a hydraulic coupler, which comprises a coupler piston accommodated in a coupler sleeve for delimiting a coupler space. The coupler chamber is connected to a control chamber, which is delimited in the axial direction by the nozzle needle. Accordingly, the pressure prevailing in the control chamber is at the nozzle needle, which pressure can be controlled via the actuator. Depending on the pressure in the control chamber, the nozzle needle is able to open or is returned to a nozzle needle seat via a hydraulic pressure force to which the spring force of a nozzle spring supported indirectly via a spring plate on the nozzle needle is reset.

The US 5,472,142 A. and the WO 2006/003041 A1 describe a similar fuel injector with a nozzle needle, which is directly actuated by means of an actuator which cooperates with a hydraulic coupler.

In fuel injectors of the aforementioned type, the stroke of the nozzle needle is usually preset and is limited on the one hand by the nozzle needle seat, on the other hand by a stroke stop. However, the default hub may be subject to change. This is especially true when connecting body parts an injector, a nozzle retaining nut is used. Because in the area of screwing the nozzle retaining nut with a body component forces are introduced into the body, which have an influence on the stroke of the nozzle needle. The influence increases with increasing distance of the stroke stop to the seat of the nozzle needle.

The present invention is therefore an object of the invention to provide a nozzle assembly for a fuel injector with a hubbeweglichen nozzle needle whose stroke is limited by a "seat close" stroke stop. This is intended to reduce the risk of changing a nozzle needle stroke preset in production. Furthermore, the stroke stop should be easy and inexpensive to implement.

The object is achieved by the nozzle assembly having the features of claim 1. Advantageous developments of the invention are specified in the subclaims. To solve the problem, the fuel injector is further proposed with the features of claim 8.

Disclosure of the invention

The nozzle assembly proposed for a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine comprises a nozzle body and a nozzle needle which is liftably received for releasing and closing at least one injection opening in a high-pressure bore of the nozzle body and acted upon in the direction of a sealing seat by the spring force of a nozzle spring. The nozzle spring is supported at its end facing the nozzle seat on a spring plate coupled to the nozzle needle. According to the invention, the nozzle spring is supported at its other end on an intermediate plate which is clamped between a nozzle part and a pipe part of the nozzle body. Furthermore, according to the invention, the spring plate interacts with the intermediate plate to form a stroke stop for the nozzle needle.

The nozzle body of a fuel injector according to the invention is thus designed in several parts and comprises at least one nozzle part and a pipe part. The multi-part design allows only the clamping of the intermediate plate, which cooperates with the spring plate hubanschlagbildend.

By clamping the intermediate plate of the stroke stop is fixed immutable in the axial direction. Furthermore, the stroke stop moves further in the direction of the sealing seat, so that a "seat close" stroke stop is formed for the nozzle needle. The axial distance between the intermediate plate and the spring plate gives the maximum opening stroke of the nozzle needle.

A multi-part nozzle body with clamped intermediate plate is simple and inexpensive to produce. The clamping can be done during assembly by means of a nozzle lock nut, which is usually used in fuel injectors for axial clamping of the various body parts. At the same time, an axial force can be applied via the nozzle retaining nut, which causes a high-pressure-proof seal of the high-pressure bore extending over the several parts of the nozzle body.

Furthermore, the spring plate is annular and has a hollow cylindrical projection for forming a stop surface. The stop surface is further preferably formed over an end face of the hollow cylindrical projection which faces the intermediate plate. Due to the coupling of the spring plate with the nozzle needle this is carried by the nozzle needle when it opens. In this case, an axial gap between the stop surface and the intermediate plate defines the maximum opening stroke of the nozzle needle. The nozzle spring is disposed within the hollow cylindrical projection of the spring plate, so that this causes a guide of the nozzle spring.

In addition, the spring plate is supported on a collar of the nozzle needle. The coupling of the spring plate with the nozzle needle is thus carried out by placing on the annular collar, wherein the spring force of the nozzle spring holds the spring plate in contact with the annular collar. To make an adjustment of the stroke of the nozzle needle can be inserted between the collar and the spring plate a shim. A stroke adjustment can alternatively or additionally be made via the height of the hollow cylindrical projection of the spring plate.

Preferably, the intermediate plate has a central recess for the passage of the nozzle needle, wherein the inner diameter of the recess is greater than the outer diameter of the nozzle needle in the region of the implementation. This means that an annular gap remains between the intermediate plate and the nozzle needle, via which fuel is able to flow in the direction of the at least one injection opening.

In order to enable fuel flow in the direction of the at least one injection opening when the nozzle needle is open at maximum, it is further proposed that at least one flow-through opening is formed in the spring plate and / or in the intermediate plate. The flow-through opening may be formed in the intermediate plate, for example, as an eccentrically arranged axially extending channel. In the spring plate, an axially extending channel may be formed, which opens into a radially extending channel to bypass the annular collar of the nozzle needle. Alternatively, the at least one flow-through opening can also be designed to run obliquely. The at least one flow-through opening ensures that the part of the high-pressure bore enclosed by the pipe part of the nozzle body is connected to the part of the high-pressure bore enclosed by the nozzle part, so that fuel to be injected is able to flow in the direction of the at least one injection opening.

Further preferably, the nozzle needle is coupled via a coupling device with an actuator. This may be a mechanical or hydraulic coupling device. About such a coupling device, the actuator can be coupled to the nozzle needle in such a way that a translation of the actuator force or the Aktorhubs and / or a reversal of the effective direction of the actuator takes place. This allows operation of the fuel injector referred to as "direct control". According to a preferred embodiment of the invention, the proposed fuel injector on a hydraulic coupling device for coupling the nozzle needle with an actuator. For this purpose, the coupling device comprises a liftable coupler piston and a coupler plate for guiding the coupler piston. Preferably, the coupler piston and the coupler plate together define a coupler volume that is ideally formed in the coupler plate. In this way, the coupling device can be kept very compact. To guide the coupler piston, the coupler plate may have a hollow cylindrical projection which surrounds the coupler piston at least partially.

It is also proposed that the coupler volume is connected via a connecting channel with a control chamber. The connecting channel is preferably formed in the coupler piston, which is arranged in a liftable manner between the coupler volume and the control chamber. By means of a stroke movement of the coupler piston, an enlargement or reduction of the coupler volume can now be effected, which in turn is accompanied by a pressure drop or a pressure increase in the coupler volume. Due to the hydraulic connection of the coupler volume and the control chamber, a pressure drop or increase in pressure in the control chamber is simultaneously effected. The pressure in the control chamber, which is limited in the axial direction by an end face of the nozzle needle, causes a hydraulic force acting on the nozzle needle in the closing direction. This is to be lowered so far that the nozzle needle is able to open against the spring force of the nozzle spring.

In a further development of the invention it is proposed that the nozzle needle for limiting the control chamber is surrounded at its end remote from the sealing seat by a sleeve which is preferably acted upon in the direction of the coupler piston by the spring force of another spring and this supported on the one hand on the sleeve, on the other hand on the intermediate plate is. The spring force of the other spring holds the sleeve in abutment with the coupler piston, so that the control chamber is separated from the high pressure bore.

In order to couple the coupler piston with the actuator, a pressure pin is preferably guided by the coupler plate. For this purpose, a guide bore is formed in the coupler plate whose guide clearance is chosen to be as small as possible in order to separate the coupler volume from a low-pressure region beyond the coupler plate. In the low-pressure region, the actuator is preferably arranged. The pressure pin transmits the force or the stroke of the actuator to the coupler body.

In addition, a fuel injector is proposed for injecting fuel into the combustion chamber of an internal combustion engine having a nozzle assembly according to the invention and an actuator which is hydraulically and / or mechanically coupled or coupled to the nozzle needle for actuating the nozzle needle. Preferably, the actuator is a piezoelectric actuator or a magnetic actuator, which further preferably in a low pressure region the fuel injector is arranged. The use of a piezoelectric actuator or a magnetic actuator allows direct actuation of the nozzle needle. The actuator is preferably accommodated in a body component of the injector, which is clamped axially via the already mentioned nozzle retaining nut with the parts of the nozzle body, the intermediate plate and the coupler plate.

• Fig. 1 einen schematischen Längsschnitt durch einen Kraftstoffinjektor mit einer erfindungsgemäßen Düsenbaugruppe gemäß einer ersten bevorzugten Ausführungsform und
• Fig. 2 einen schematischen Längsschnitt durch einen Kraftstoffinjektor mit einer erfindungsgemäßen Düsenbaugruppe gemäß einer zweiten bevorzugten Ausführungsform.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. These show:

• Fig. 1 a schematic longitudinal section through a fuel injector with a nozzle assembly according to the invention according to a first preferred embodiment and
• Fig. 2 a schematic longitudinal section through a fuel injector with a nozzle assembly according to the invention according to a second preferred embodiment.

Detailed description of the drawings

The Indian Fig. 1 in longitudinal section shown fuel injector comprises a two-part nozzle body 1 with a nozzle part 1.1 as a first part and a pipe part 1.2 as a second part. Between the two parts 1.1 and 1.2 of the nozzle body 1, an intermediate plate 8 is arranged and clamped together with the two parts 1.1 and 1.2 of the nozzle body 1, a coupler plate 18 and a further body member 26 via a nozzle nut 27 axially. About the screwing of the nozzle retaining nut 27 forces are introduced into the injector, which may be relevant to function. For such forces can lead to a change in a preset stroke h of a nozzle needle 2, which is received in a liftable manner in a high-pressure bore 4 of the nozzle body 1 for releasing and closing at least one injection opening 3. The magnitude of the influence of the forces depends in particular on the distance of a stop surface A for limiting the nozzle needle stroke from a sealing seat 5 of the nozzle needle 2. To reduce the influence, the distance should be as small as possible.

The stop surface A is presently formed on a hollow cylindrical projection 11 of a spring plate 7, which rests on a collar 12 of the nozzle needle 2 and is held by the spring force of a nozzle spring 6 in contact with the annular collar 12. The spring force of the directly adjacent to the spring plate 7 nozzle spring 6 presses the nozzle needle 2 in the sealing seat 5. The nozzle spring 6 is supported by a control pressure in a control chamber 21 which causes a force acting on the nozzle needle 2 hydraulic closing force.

The spring plate 7 is arranged at an axial distance to the aforementioned intermediate plate 8 and cooperates with this a stroke stop 9 training together. The axial distance defines the maximum opening stroke h of the nozzle needle 2. The supported on the spring plate 7 nozzle spring 6 on the other hand supported on the intermediate plate 8, wherein the clamping of the intermediate plate 8 between the nozzle part 1.1 and the tube part 1.2 of the nozzle body 1 a change in position of the intermediate plate 8 prevented. Thus, the stroke stop 9 is set. The default setting of the stroke h via the height of the hollow cylindrical projection 11 of the spring plate. 7

Due to the arrangement of the spring plate 7 and the intermediate plate 8 in the high pressure bore 4, d. H. in a region close to the seat, the axial distance between the stop surface A and the sealing seat 5 is minimized compared to the prior art. This ensures that the influence of the screwing of the nozzle retaining nut 27 on the preset stroke h of the nozzle needle 2 and thus on the function of the injector is minimal. Furthermore, the spring plate 7 and the intermediate plate 8 simple geometries, so that they are inexpensive to produce.

The intermediate plate 8 has a central recess 10 through which the nozzle needle 2 is guided. The inner diameter of the recess 10 is larger than the outer diameter of the nozzle needle 2 selected in this area, so that an annular gap remains as a flow opening for the fuel to be injected. In order to optimize the fuel flow in the direction of the at least one injection port 3, can further - as in the Fig. 1 shown - at least one flow opening 13 may be provided in the form of an axial bore in the intermediate plate 8.

To actuate the nozzle needle 2, an actuator 16 is accommodated in the further body component 26, which is embodied in the present case as a piezoactuator and can be coupled to the nozzle needle 2 via a hydraulic coupling device 15. For this purpose, the hydraulic coupling device 15 comprises a liftable coupler piston 17, which is guided in the coupler plate 18 and defines a coupler volume 19 formed in the coupler plate 18. To guide the coupler piston 17, the coupler plate 18 has a hollow cylindrical projection which surrounds the coupler piston 17 at least in regions. For coupling the coupler plate 17 partially received in the coupler piston 17 with the actuator 16, the coupler plate 18 is penetrated by a pressure pin 24, which transmits the stroke of the actuator 16 to the coupler piston 17.

The coupler volume 19 formed in the coupler plate 18 is connected to the already mentioned control space 21 via a connection channel 20, which in the present case is formed in the coupler piston 17. The limited in the axial direction on the one hand by the nozzle needle 2 control chamber 21 on the other hand limited by the coupler piston 17. In the radial direction, the limitation is effected by a sleeve 22 which surrounds the control-chamber-side end of the nozzle needle 2 and is held in contact with the coupler piston 17 via the spring force of a spring 23. The spring 23 is for this purpose supported on the one hand on the coupler piston 17, on the other hand on the intermediate plate 8.

• Zum Öffnen der Düsennadel 2 und damit zum Freigeben der Einspritzöffnung 3 wird der Aktor 16 aktiviert. Der als Piezoaktor ausgebildete Aktor 16 längt sich daraufhin und drückt - entgegen der Federkraft einer Feder 29 - einen Kolben 28 nach unten. Der Kolben 28 wiederum nimmt den Druckstift 24 mit, der den Aktorhub auf den Kopplerkolben 17 überträgt. Dies hat zur Folge, dass auch der Kopplerkolben 17 nach unten bewegt wird. Die Bewegung des Kopplerkolbens 17 führt zu einer Vergrößerung des Kopplervolumens 19 und damit zu einem Druckabfall im Kopplervolumen 19. Aufgrund der hydraulischen Verbindung des Kopplervolumens 19 mit dem Steuerraum 21 fällt auch dort der Druck ab. Der Druckabfall im Steuerraum 21 entlastet die Düsennadel 2, so dass diese vom Dichtsitz 5 abhebt und die Einspritzöffnung 3 freigibt. Unter hohem Druck stehender Kraftstoff, der einem Hochdruckspeicher 32 entnommen wird, strömt nunmehr über einen im Körperbauteil 26 ausgebildeten seitlichen Zulaufkanal 31, einen in der Kopplerplatte 18 ausgebildeten seitlichen Verbindungskanal 30 und die Hochdruckbohrung 4 in Richtung der wenigstens einen Einspritzöffnung 3. Dabei durchströmt der Kraftstoff ferner die wenigstens eine in der Zwischenplatte 8 ausgebildete Durchströmöffnung 13.

The functioning of the in the Fig. 1 shown fuel injector is as follows:

• To open the nozzle needle 2 and thus to release the injection port 3, the actuator 16 is activated. The trained as a piezoelectric actuator 16 then elongates and pushes - against the spring force of a spring 29 - a piston 28 down. The piston 28 in turn takes the pressure pin 24, which transmits the Aktorhub on the coupler piston 17. This has the consequence that also the coupler piston 17 is moved downward. The movement of the coupler piston 17 leads to an increase in the Kopplervolumens 19 and thus to a pressure drop in the coupler volume 19. Due to the hydraulic connection of the coupler volume 19 with the control chamber 21 also drops the pressure there. The pressure drop in the control chamber 21 relieves the nozzle needle 2, so that it lifts off from the sealing seat 5 and the injection port 3 releases. Under high-pressure fuel, which is taken from a high-pressure accumulator 32, now flows through a formed in the body member 26 side inlet channel 31, formed in the coupler plate 18 side connecting channel 30 and the high-pressure bore 4 in the direction of at least one injection port 3. The fuel also flows through the at least one formed in the intermediate plate 8 through-flow opening 13th

For closing the injection opening 3, the piezoelectric actuator is deactivated. This has the consequence that the piezoelectric actuator contracts again. The spring force of the spring 29 presses the piston 28 upwards. The provision of the coupler piston 17 is effected by the spring force of the spring 23. With the provision of the coupler piston 17, the coupler volume 19 decreases, whereby the pressure in the coupler volume 19 and in the control chamber 21 increases again. On the nozzle needle 2 now acts - in addition to the spring force of the nozzle spring 6 - a hydraulic closing force, which presses the nozzle needle 2 in the sealing seat 5, so that the injection is terminated.

The Indian Fig. 2 illustrated fuel injector differs from that of Fig. 1 only slightly. It has flow-through openings 13, 14 in the spring plate 7, which replace a flow-through opening 13 in the intermediate plate 8. The through-flow opening 13 in the present case is designed as a longitudinal groove in an inner circumferential region of the spring plate 7, into which a radially extending channel serving as a flow-through opening 14 opens. The flow-through opening 14 ensures that the fuel to be injected reaches the annular collar 12 of the nozzle needle 2 in the lower part of the high-pressure bore 4. The functioning of the injector of Fig. 2 the same applies to the Fig. 1 ,

It is noted that the figures represent only preferred embodiments of the invention. Modifications are possible. In particular, may be provided instead of a piezoelectric actuator, a magnetic actuator for controlling the lifting movement of the nozzle needle. Furthermore, the coupler can be designed as a mechanical coupler. In addition, the arrangement of a coupler can also be dispensed with altogether.

Claims (8)

1. Nozzle assembly for a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, comprising a nozzle body (1) and a nozzle needle (2) which is received, such that it can perform stroke movements, in a high-pressure bore (4) of the nozzle body (1) for the purposes of opening up and closing off at least one injection opening (3) and which is forced in the direction of a sealing seat (5) by the spring force of a nozzle spring (6), wherein the nozzle spring (6) is supported, at its end facing toward the nozzle seat (5), on a spring plate (7) coupled to the nozzle needle (2), wherein the nozzle spring (6) is supported, at its other end, on an intermediate plate (8) which is clamped between a nozzle part (1.1) and a tube part (1.2) of the nozzle body (1), and the spring plate (7) interacts with the intermediate plate (8) so as to form a stroke stop (9) for the nozzle needle (2),
   characterized in that the spring plate (7) is of ring-shaped form and has a hollow cylindrical projection (11) for forming a stop surface (A), wherein the nozzle spring (6) is arranged within the hollow cylindrical projection (11), and in that the spring plate (7) is supported on a ring-shaped collar (12) of the nozzle needle (2).
2. Nozzle assembly according to Claim 1,
   characterized in that the intermediate plate (8) has a central recess (10) for the leadthrough of the nozzle needle (2), the inner diameter of which recess is greater than the outer diameter of the nozzle needle (2) in the region of the leadthrough.
3. Nozzle assembly according to one of the preceding claims,
   characterized in that at least one throughflow opening (13, 14) is formed in the spring plate (7) and/or in the intermediate plate (8).
4. Nozzle assembly according to one of the preceding claims,
   characterized in that the nozzle needle (2) is couplable to an actuator (16) by means of a coupling device (15) which preferably comprises a coupler piston (17) which can perform stroke movements and a coupler plate (18) for guiding the coupler piston (17), wherein it is furthermore preferably the case that the coupler piston (17) and the coupler plate (18) together delimit a coupler volume (19).
5. Nozzle assembly according to Claim 4,
   characterized in that the coupler volume (19) is connected to a control chamber (21) via a connecting duct (20) formed preferably in the coupler piston (17).
6. Nozzle assembly according to Claim 4 or 5,
   characterized in that the nozzle needle (2) is, for the purposes of delimiting the control chamber (21), surrounded at its end averted from the sealing seat by a sleeve (22) which is preferably forced in the direction of the coupler piston (17) by the spring force of a further spring (23) and which, for this purpose, is supported at one side on the sleeve (22) and at the other side on the intermediate plate (8).
7. Nozzle assembly according to one of Claims 4 to 6,
   characterized in that a pressure pin (24) for coupling the coupler piston (17) to the actuator (16) is led through the coupler plate (18).
8. Fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, having a nozzle assembly according to one of the preceding claims and having an actuator (16) for actuating the nozzle needle (2), wherein, preferably, the actuator (16) is a piezo actuator or a magnetic actuator, which is furthermore preferably arranged in a low-pressure region (25).

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