EP3095998B1 - Fuel injector - Google Patents

Description

The invention relates to a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine having the features of the preamble of claim 1.

State of the art

From the publication DE 10 2010 028 835 A1 a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, which comprises a magnetic actuator for direct control of a preferably needle-shaped injection valve member, via the lifting movement at least one injection valve opening of the fuel injector is releasable or closable. The magnetic actuator cooperates with a lifting armature element for controlling the control pressure in a control volume which is limited in the axial direction by a first hydraulic active surface formed on the injection valve member. At the anchor element, a second hydraulic active surface is formed, which is opposite to the hydraulic active surface of the injection valve member on the control volume. A third hydraulic active surface is formed on a hydraulic booster, which limits the control space together with the injection valve member and the anchor element. The area ratio of the hydraulic active surfaces is designed such that during a first stage when opening a force gain and during a second stage, a path gain is achieved. In this way, an adjustment of the actuator force to the changing with the stroke of the injection valve member required opening force. The closing force required for closing is provided by a spring which is supported on the anchor element and the anchor element in the direction of the injection valve member loaded. The spring force causes the armature element strikes on its return to the injection valve member and this returns to its sealing seat.

Another fuel injector is out of the DE 10 2013 221 534 A1 known in which a magnet armature acts on a coupling piston attached thereto to a coupler space for controlling the nozzle needle.

In fuel injectors of the type mentioned above, the closing forces are comparatively low. This has the consequence that the anchor tends to bounce when closing. This means that it swings back after striking the injection valve member and the contact with the injection valve member is lost, so that it is not completely reset. This in turn leads to quantity deviations, which must be avoided. The bouncing of the armature is particularly disadvantageous in the case of multiple injections, that is to say in the case of injections which follow one another at different time intervals.

Based on the above-mentioned prior art, the present invention has the object to provide a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, which has over the prior art, a more stable closing behavior and thus a higher injection accuracy.

To achieve the object of the fuel injector with the features of claim 1 is given. Advantageous developments of the invention can be found in the dependent claims.

Disclosure of the invention

The fuel injector proposed for injecting fuel into a combustion chamber of an internal combustion engine comprises a nozzle needle, which is received in a liftable manner for releasing and closing at least one injection opening in a high-pressure bore of a nozzle body. Furthermore, the fuel injector comprises an annular magnetic coil for acting on a liftable armature, which is hydraulically coupled via an armature shaft with the nozzle needle. According to the invention, a fixedly connected to the armature shaft spring plate or mechanically coupled to the spring plate hubbewegliches damper element on a nozzle needle facing end face, which with a lower stroke stop for the anchor and / or the Damper element serving stop surface cooperating forming a nip.

The nip is formed during closing, and shortly before reaching the serving as a lower stroke stop surface. The formation of the nip leads to a damping of the armature movement, since energy must be expended for displacing the fluid from the nip. The energy expended for displacing the fluid is lost to the kinetic energy, so that the movement of the armature is decelerated. The impact on serving as a lower stroke stop surface occurs with reduced energy, so that the anchor is less prone to bounce. This in particular has the advantage of multiple injections, since the armature has already returned to its starting position before initiating a subsequent injection.

According to a preferred embodiment of the invention serving as a lower stroke stop for the armature and / or the damper element stop surface is formed on a coupler plate. The coupler plate is part of a hydraulic coupling device, via which the armature or the armature shaft with the nozzle needle is preferably hydraulically coupled in such a way that a force transmission or displacement reduction is achieved. Preferably, the coupler plate is axially biased by the spring force of a coupler spring against the nozzle body. In this way, a position fixation of the coupler plate is effected in the axial direction. In the radial direction, alignment of the coupler plate remains possible. Alternatively, the coupler plate can also be clamped between two body components of the fuel injector.

Alternatively or additionally, it is also proposed that the coupler plate, together with the armature shaft, the nozzle needle and a sealing sleeve surrounding the nozzle needle, delimit a coupler space of a hydraulic coupling device for force transmission or travel reduction. In this way, an increase in the actuator force can be effected, so that the opening of the nozzle needle can be achieved with a comparatively small actuator.

If the coupler plate serves as a lower stroke stop for the armature and / or the damper element, the stop surface on the side facing away from the nozzle needle of the Coupler plate formed. This means that the stop surface is outside the coupler space. The abutment surface can be formed by an end face of the coupler plate, which can be designed in particular stepped to adjust the size of the abutment surface to the size of the end face of the spring plate or the damper element, which faces the abutment surface on the nip.

According to an alternative preferred embodiment of the invention serving as a lower stroke stop for the armature and / or the damper element abutment surface is formed on the nozzle body. In this case, the stop surface formed on the nozzle body preferably cooperates with an end face of a liftable damper element that can be mechanically coupled to the spring plate to form a nip gap. The damper element may in particular be a coupler plate of a hydraulic coupler plate accommodated in a liftable manner in the housing. Since the armature shaft passes through the coupler plate in order to effect the hydraulic coupling of the armature with the nozzle needle, the spring plate can be placed so that it comes to rest on the lifting coupler plate when closing and entrains it to serving as a lower stroke stop surface. A separate damper element is therefore dispensable, whereby the number of components can be reduced.

Advantageously, serving as a lower stroke stop for the armature and / or the damper element abutment surface is frusto-conical or spherical. Alternatively or additionally, the end face of the spring plate or of the damper element cooperating with the stop face can also be frusto-conical or spherical. The frusto-conical or spherical configuration of at least one surface involved in the formation of the nip has the consequence that the common contact region is limited to a substantially annular contact line. The limitation or minimization of the common contact region has the advantage that hydraulic adhesive effects can be largely avoided, which has a favorable effect on the opening behavior of the fuel injector. In particular, the nip remains without appreciable influence on the required opening force, so that the energy requirement also remains largely the same.

Alternatively or additionally, it is proposed that the stop surface serving as the lower stroke stop for the armature and / or the damper element and / or the end face cooperating with the stop surface have a hollow cylindrical projection for forming an annular contact surface with the respective other surface. The hollow cylindrical projection can be designed, in particular, as a collar set radially on the inside of the end face of the spring plate or of the damper element, which contacts the stop surface serving as a lower stroke stop when closing. In addition, the hollow cylindrical projection may be formed as a radially inner collar, which is attached to the serving as a lower stroke stop surface. The hollow cylindrical projection on at least one surface involved in the formation of the nip has the consequence that the common contact area is limited to a circular contact surface. Hydraulic adhesive effects are largely avoided in this way, which has a favorable effect on the opening behavior of the fuel injector. In particular, the nip remains without appreciable influence on the required opening force and thus on the energy requirement of the fuel injector.

In a further development of the invention it is proposed that the liftable damper element is axially biased in the direction of serving as an upper stroke stop for the damper element stop surface. The axial preload can be effected in particular by the spring force of a spring, so that it is ensured by the axial prestress that the closing movable over the spring plate carried hubbewegliche damper element is returned to its original position during the subsequent opening. Preferably, the axial bias is effected by the spring force of an existing spring, such as the coupler spring. Alternatively, it is also possible to use a nozzle spring which is supported on the nozzle needle for axial prestressing and which is regularly provided for returning the nozzle needle. As a result, the number of components can be kept low.

In addition, it is proposed as a further development measure that a nozzle needle facing away from the end face of the damper element is frusto-conical or spherical, so that a common contact area is limited to serving as the upper stroke stop surface to a substantially annular contact line. The reduction of the common contact area to an annular Contact line facilitates release of the liftable damper element from the upper travel stop. This ensures that the closing of the fuel injector is not delayed by hydraulic adhesive effects.

In a preferred embodiment of the invention, the liftable damper element is plate-shaped or cup-shaped. The hubbewegliche damper element surrounds the armature shaft of the armature partially. In contrast to the spring plate, which also surrounds the armature shaft partially and is firmly connected to this, the damper element, however, against the armature shaft axially displaceable. The stroke of the damper element can therefore be selected smaller than the stroke of the armature.

The damper element is preferably received in a high-pressure chamber, which is hydraulically connected to the high-pressure bore. The hydraulic connection can be produced, for example, via at least one flow opening formed in the coupler plate. About the high-pressure chamber, the high-pressure bore can be supplied with high-pressure fuel.

Advantageously, the anchor is designed as a plunger anchor. An abutment surface forming the upper stroke stop for the armature is preferably formed on an inner pole body in this case. This embodiment has the advantage that the annular magnet coil can be arranged radially on the outside, so that the magnetic circuit extends over the entire outer diameter of the fuel injector. It can be achieved in this way higher magnetic forces. At the same time you get a compact fuel injector.

• Fig. 1 einen schematischen Längsschnitt durch einen nicht erfindungsgemäßen Kraftstoffinjektor in Schließstellung,
• Fig. 2a einen schematischen Längsschnitt durch einen erfindungsgemäßen Kraftstoffinjektor gemäß einer ersten bevorzugten Ausführungsform beim Öffnen,
• Fig. 2b eine vergrößerte Darstellung der Dämpfungseinrichtung des Kraftstoffinjektors der Fig. 2a,
• Fig. 2c eine vergrößerte Darstellung einer modifizierten Dämpfungseinrichtung für den Kraftstoffinjektor der Fig. 2a und
• Fig. 3 einen schematischen Längsschnitt durch einen erfindungsgemäßen Kraftstoffinjektor gemäß einer zweiten bevorzugten Ausführungsform in Schließstellung.

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

• Fig. 1 a schematic longitudinal section through a non-inventive fuel injector in the closed position,
• Fig. 2a a schematic longitudinal section through a fuel injector according to the invention according to a first preferred embodiment when opening,
• Fig. 2b an enlarged view of the damping device of the fuel injector of Fig. 2a .
• Fig. 2c an enlarged view of a modified damping device for the fuel injector of Fig. 2a and
• Fig. 3 a schematic longitudinal section through a fuel injector according to the invention according to a second preferred embodiment in the closed position.

Detailed description of the drawings

The in the Fig. 1 shown in longitudinal section, not inventive fuel injector comprises a nozzle body 5 with a high-pressure bore 4, in which a nozzle needle 2 for releasing and closing a plurality of injection openings 3 is received in a liftable manner. When the nozzle needle 2 is raised, the injection openings 3 are released, so that fuel under high pressure is injected into a combustion chamber 1.

The actuation of the nozzle needle 2 via a magnetic actuator comprising a magnetic coil 6. In this case, the magnet coil 6 cooperates with an armature 7, which can be coupled hydraulically via an armature shaft 8 to the nozzle needle 2. The nozzle needle 2 facing the end of the armature shaft 8 is guided for this purpose by a supported on the nozzle body 5 coupler plate 16 which defines a coupler space 19 together with the armature shaft 8, the nozzle needle 2 and the nozzle needle 2 end surrounding sealing sleeve. To seal the coupler space 19 with respect to the high-pressure bore 4, the coupler plate 16 is acted upon in the direction of the nozzle body 5 by the spring force of a coupler spring 17. The sealing sleeve 18 is in turn axially biased by the spring force of a nozzle spring 24 against the coupler plate 16.

The coupler plate 16 passing through the end of the armature shaft 8 has an outer diameter D ₁ , which is chosen to be significantly smaller than the outer diameter D _{2 of} the nozzle needle 2. Accordingly, the area ratio of the hydraulic active surfaces lying opposite to the coupler space 19 is selected such that the force transmission is accompanied by a force amplification.

When the magnet coil 6 of the magnet actuator is energized, a magnetic field is formed whose magnetic force F _M pulls the armature 7 in the direction of an inner pole body 30, counter to the spring force F _{A of} an armature spring 32 which is supported on a spring plate 9 pressed onto the armature shaft 8 , The armature shaft 8 retracts from the coupler space 19, so that the volume in the coupler space 19 increases. The increase in volume in turn causes a pressure drop in the coupler space 19. The further the armature 7 moves in the direction of the Innenpolkörpers 30, the more the pressure in the coupler chamber 19 decreases, and as far as the nozzle needle 2 against the spring force of the nozzle spring 24 and the resulting hydraulic closing force moves out of its seat 31. The armature 7 moves maximally up to a stop surface 29 which is formed on the inner pole body 30 and serves as an upper stroke stop for the armature 7. The nozzle needle 2 follows the movement of the armature 7, wherein a path reduction is effected by the predetermined area ratio of the formed on the armature shaft 8 and on the nozzle needle 2 hydraulic active surfaces. The armature stroke A _H is thus greater than the desired nozzle needle stroke DN _H. The injection of fuel into the combustion chamber 1 via the injection openings 3 begins.

The inflow of fuel takes place via a centrally formed inflow channel 36, which is formed in the inner pole body 30 and opens into an armature space 37. The armature space 37 is connected via a laterally arranged connecting channel 38 with a high-pressure chamber 27, in which the coupler plate 16 is received. Via at least one through-flow opening 28 provided in the coupler plate 16, a connection of the high-pressure chamber 27 to the high-pressure bore 4 of the nozzle body 5 is produced, in which the injection openings 3 are formed.

To end the injection, the energization of the solenoid 6 is terminated, so that the magnetic force F _{M is} reduced. The force acting in the closing direction spring force F _{A of} the armature spring 32 is in the sequence the armature 7 back to its original position. In this case, the armature shaft 8 immersed again deeper into the coupler space 19 and reduces the volume, resulting in a pressure increase in the coupler space 19. If the spring force of the nozzle spring 24 acting in the closing direction on the nozzle needle 2 exceeds the resulting hydraulic opening force, the closing movement of the nozzle needle 2 begins. The starting position of the armature 7 is reached when the provided for supporting the armature spring 32 spring plate 9, which is in the present case pressed onto the armature shaft 8, passes over its end face 11 for abutment with a serving as a lower stroke stop surface 13 on the coupler plate 16. Due to the frusto-conical configuration of the stop surface 13 is formed before reaching the lower stroke stop between the end face 11 of the spring plate 9 and the stop surface 13 of the coupler plate 16 from a nip 15, which causes a damping of the movement of the armature 7. Thus, a bouncing of the armature 7 is counteracted. At the same time, the frusto-conical configuration of the stop surface 13 ensures that the common contact region 20 is limited to an annular contact line in order to counteract hydraulic adhesive effects when reopening.

The spring force of the armature spring 32 can be influenced via a Einstellscheibe33, via which the armature spring 32 is indirectly supported on a body member 34 of the fuel injector. The body member 34 also forms the high-pressure chamber 27 and the armature chamber 37, which are hydraulically connected via the connecting channel 38. In the body member 34, a guide bore 35 is further formed, in which the armature shaft 8 of the armature 7 is received in a liftable manner.

A further preferred embodiment of a fuel injector according to the invention is in the Fig. 2a , This is different from the one of Fig. 1 essentially by the fact that not the pressed onto the armature shaft 8 spring plate 9, but with the spring plate 9 mechanically coupled hubbewegliches damper element 10 cooperating with the formed on the coupler plate 16 abutment surface 13 a nip 15 cooperating (see Fig. 2b ). For this purpose, the damper element 10 has an end face 12 facing the coupler plate 16. The end face 12 is flat. In contrast, the stop surface 13 has the shape of a truncated cone, so that the common contact area 20 is again limited to a circular contact line. This ensures, on the one hand, that there is the formation of a nip 15 and, on the other hand, that hydraulic adhesive effects have as little influence as possible on the opening behavior of the fuel injector. In addition, if the spring force of the coupler spring 17 is greater than that of the armature spring 32 selected, the damper element 10 is reset immediately after completion of an injection, so that there is likewise no delay in the subsequent opening due to the nip 15.

The damper element 10 is present cup-shaped and surrounds the spring plate 9; the armature spring 32 and the shim 33. The armature shaft 8 of the armature 7 is guided by the damper element 10, so that the damper element 10 with respect to the armature shaft 8 is liftable. The stroke of the damper element 10 is limited by serving as a lower stroke stop surface 13 of the coupler plate 16, which thus forms the lower stroke stop for both the armature 7 and the damper element 10. The upper stroke stop for limiting the stroke of the damper element 10 is formed by a stop surface 23 of the body member 34. In order to counteract hydraulic adhesive effects on the upper stroke stop, the damper element 10 has a stop face 23 facing the end face 25 is formed on the truncated cone. This leads to a common contact region 26, which is limited to an annular contact line.

When closing the armature 7 moves including the pressed onto the armature shaft 8 spring plate 9 in the direction of the nozzle needle 2. The volume in the coupler chamber 19 decreases as the pressure rises and the nozzle needle 2 is placed back in the seat 31. The armature 7 moves further down, wherein the spring plate 9 passes through a formed on a hollow cylindrical projection 21 contact surface 22 to rest on the damper element 10 and this carries. Shortly before reaching the lower stroke stop, which is formed by the stop surface 13, fluid must be displaced from the nip 15 between the stop surface 13 and the end face 12 of the damper element 10. The energy used in this case reduces the kinetic energy of the armature 7, so that the impact of the end face 12 of the damper element 10 is damped on the stop surface 13.

A modified damping device is in the Fig. 2c shown. This is an alternative to the damping device of Fig. 2b in the fuel injector the Fig. 2a used. Here, the stop surface 13 is not frustoconical, but formed on a hollow cylindrical projection 21 of the coupler plate 16. This measure also serves to form the nip 15 when closing and to reduce hydraulic adhesive effects when opening the injector.

Deviating from the in the Fig. 2a-2c illustrated embodiment of the coupler plate 16, this can also according to the embodiment of Fig. 1 be educated. That is, the coupler plate 16 need not necessarily be clamped between the nozzle body 5 and the body member 34. The coupler spring 17 then serves not only the provision of the hubbeweglichen damper element 10, but also the axial bias of the coupler plate 16 against the nozzle body 5 in order to fix them in their axial position.

A further preferred embodiment of a fuel injector according to the invention is in the Fig. 3 shown. Here, the coupler plate 16 at the same time forms the hubbewegliche damper element 10. The stroke K _{H of} the coupler plate 16 and the damper element 10 is limited on the one hand by a serving as a lower stroke stop surface 14 on the nozzle body 5 and on the other hand by serving as an upper stroke stop surface 23 which is formed by a shoulder of the body member 34. In the direction of the abutment surface 23, the coupler plate 16 - indirectly axially biased by the spring force of the nozzle spring 24 - indirectly via the intermediate sealing sleeve 18. A coupler spring 17 is therefore dispensable.

The common contact region 26 of the coupler plate 16 or of the damper element 10 with the stop surface 23 is reduced to an annular contact surface. Thus, the release of the coupler plate 16 and the damper element 10 can be effected by the upper stroke stop with little force.

The end face 12 of the coupler plate 16 or of the damper element 10 which cooperates with the stop surface 14 serving as the lower stroke stop is designed in the shape of a truncated cone and thus has an annular contact line as a common contact region with the stop surface 14. When closing, this results in the formation of a squeezing gap 15 which damps the movement of the armature 7. During opening, the reduced common contact area counteracts hydraulic adhesive effects. Further, the spring force of the nozzle spring 24 serving to return the damper element 10 is larger than that of the armature spring 32, so that the return is already made upon completion of an injection operation.

Claims (9)

1. Fuel injector for injecting fuel into a combustion chamber (1) of an internal combustion engine, comprising a nozzle needle (2) which, in order to open and close at least one injection opening (3), is accommodated such that it can be lifted in a high-pressure bore (4) of a nozzle body (5), further comprising an annular magnetic coil (6) for acting on an armature (7) that can be lifted counter to the force of an armature spring (32), wherein the armature (7) can be coupled hydraulically to the nozzle needle (2) via an armature shaft (8), and wherein a damper element (10) that can be coupled mechanically to a spring plate (9) such that it can be lifted has an end face (12) facing the nozzle needle (2), the armature spring (32) being supported on the spring plate (9) and the spring plate (9) being connected to the armature shaft (8),
   characterized in that the end face (12) of the damper element (10) interacts with a stop surface (13, 14) serving as a lower stroke stop for the damper element (10) and forming a nip (15) which effects damping of the movement of the armature (7), wherein the damper element (10) that can be lifted is preloaded axially in the direction of a stop surface (23) serving as an upper stroke stop for the damper element (10), wherein the axial preload is preferably effected by the spring force of a coupler spring (17) or a nozzle spring (24), which is supported on the nozzle needle (2).
2. Fuel injector according to Claim 1,
   characterized in that the stop surface (13) serving as a lower stroke stop for the armature (7) and/or the damper element (10) is formed on a coupler plate (16), which is preferably preloaded axially against the nozzle body (5) by the spring force of a coupler spring (17) and/or together with the armature shaft (8), the nozzle needle (2) and a sealing sleeve (18) surrounding the nozzle needle (2) at the end side, delimits a coupler chamber (19).
3. Fuel injector according to Claim 1,
   characterized in that the stop surface (14) serving as a lower stroke stop for the armature (7) and/or the damper element (10) is formed on the nozzle body (5).
4. Fuel injector according to one of the preceding claims,
   characterized in that the stop surface (13, 14) serving as a lower stroke stop for the armature (7) and/or the damper element (10) and/or the end face (11, 12) interacting with the stop surface (13, 14) is or are formed in the shape of a truncated cone or a sphere, so that the common contact region (20) is limited to a substantially circularly annular contact line.
5. Fuel injector according to one of the preceding claims,
   characterized in that the stop surface (13, 14) serving as a lower stroke stop for the armature (7) and/or the damper element (10) and/or the end face (11, 12) interacting with the stop surface (13, 14) has a hollow cylindrical projection (21) for forming a circularly annular contact surface (22) .
6. Fuel injector according to one of the preceding claims,
   characterized in that an end face (25) of the damper element (10) that faces away from the nozzle needle (2) is formed in the shape of a truncated cone or a sphere, so that a common contact region (26) with the stop surface (23) serving as an upper stroke stop is limited to a substantially circularly annular contact line.
7. Fuel injector according to one of the preceding claims,
   characterized in that the damper element (10) is formed in the shape of a plate or a pot and partly surrounds the armature shaft (8) of the armature (7), wherein the damper element (10) can be displaced axially with respect to the armature shaft (8).
8. Fuel injector according to one of the preceding claims,
   characterized in that the damper element (10) is accommodated in a high-pressure chamber (27) which is connected hydraulically to the high-pressure bore (4), preferably via at least one passage opening (28) formed in the coupler plate (16).
9. Fuel injector according to one of the preceding claims,
   characterized in that the armature (7) is designed as a plunger armature, and a stop surface (29) forming the upper stroke stop for the armature (7) is formed on an inner pole body (30).

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