EP2470771B1 - Fuel injection valve - Google Patents

Description

The invention relates to a fuel injection valve 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 2006 012 242 A1 shows a fuel injection valve for an internal combustion engine forth, which has a valve body in which a fuel-filled under high pressure pressure space is formed, from which emanates at least one injection port. In the pressure chamber, a longitudinally displaceable valve needle is arranged, which cooperates with a sealing surface with a conical valve seat formed in the pressure chamber for opening and closing the at least one injection opening. In order for sufficient fuel to flow between the sealing surface of the valve needle and the valve seat to the injection openings in order to achieve a corresponding injection rate, the valve needle must pass through a certain minimum stroke. For only the area must be overcome, in which the gap between the sealing surface and the valve seat throttles and the pressure applied to the injection openings injection pressure is reduced. With a large minimum stroke to reach the full injection pressure, however, no rapid successive injections can be realized. In the aforementioned publication, therefore, a conical valve seat is proposed with an opening angle between 75 ° and 100 °. Opposite fuel injection valves, which have a conical valve seat with a common opening angle of about 60 °, the proposed fuel injection valve the advantage that to overcome the seat throttling area a lesser stroke of the valve needle is required, so that rapid successive injections are possible with a high injection pressure. In addition, the larger opening angle of the valve seat should reduce flow-related disturbing forces on the valve needle, which can result in a desalination of the valve needle.

Out DE 20 2006 007 883 41 For example, a fuel injector is known having a seat-proximate guide portion for the needle and a blind-hole nozzle.

In view of steadily rising injection pressures, strength aspects, especially in the area of the valve seat, are in the foreground in the development of modern fuel injection valves today. Where the selected seat geometry has great influence on the function of the fuel injector.

The object of the present invention is therefore to provide a fuel injector which has a high strength, in particular in the region of the valve seat.

The object is achieved by a fuel injection valve having the features of claim 1. Advantageous developments of the invention are specified in the dependent claims directly or indirectly to claim 1.

Disclosure of the invention

The proposed to solve the problem fuel injector has a nozzle needle, which is guided in a central bore of a nozzle body for releasing or closing at least one injection port hubbeweglich, wherein the nozzle needle formed on its combustion chamber end end, circumferential sealing area with a combustion chamber end of the Nozzle body trained conical seal seat cooperates. According to the conical sealing seat has an opening angle α ₁ between 40 ° and 50 °. The advantage of such a seat geometry is that due to the smaller opening angle, which is far below the usual 60 °, significant voltage reductions in the region of the sealing seat at the combustion chamber end of the nozzle body can be achieved. Due to the achieved voltage reduction or the lower load, for example, the injection pressure can be increased by corresponding values. Alternatively or additionally, the nozzle body in the region of the injection openings have a smaller wall thickness, so that the injection openings have a shorter length, which in turn has a favorable effect on the coking sensitivity. Although a greater strength or robustness of the Dichtsitzbereiches is also achievable by making other strength-increasing measures, such as a higher material quality, greater wall thicknesses or stiffeners, these measures are usually more expensive and usually not without influence on the function of the fuel injector.

Since there is the danger of a desalination of the nozzle needle, it is also provided to form a seat-near guide region for guiding the nozzle needle in the central bore. In the present case, a "guide fitment" is defined as a "guide fit" which is formed within a region of the central bore whose length amounts to a maximum of 40% of the total length of the nozzle body starting from the combustion chamber end of the nozzle body. By a seat near leadership can be counteracted a desalination or misalignment of the nozzle needle. Thus, a good beam symmetry and thus a uniform distribution of the injected fuel in the combustion chamber of the internal combustion engine is ensured, which is otherwise not guaranteed in particular with seat hole nozzles due to the possible desalination of the nozzle needle. For this purpose, the central bore has an area of reduced diameter for the formation of the seat-near guide area.

The proposed seat geometry requires a larger Düsennadelhub Sitzentdrosselung. Accordingly, find in the proposed fuel injection valve preferably quick-switching valves use. These enable the stroke range above the seat throttle to be reached more quickly so that the full injection pressure is applied to the injection openings in a short time. To increase the speed of the nozzle needle, for example, a large ratio of drain and inlet throttle can be selected. Thus, larger needle strokes are compensated by a "fast" needle. On the other hand, a targeted utilization of the needle throttle area and a reduced needle force for small needle strokes allow smaller and smallest injection quantities to be more accurately metered. Because compared to fuel injection valves with a 60 ° opening angle of the valve seat has a fuel injection valve according to the invention for small needle strokes a lower needle force. Such also leads to the fact that when using a servo valve for nozzle needle control of the control room is relieved faster, whereby the nozzle needle in turn experiences an acceleration.

The at least one injection opening opens in the region of the sealing seat in the central bore of the nozzle body. Accordingly, the fuel injection valve has a so-called seat hole nozzle. Seat hole nozzles have blind hole nozzles, in which the injection openings open below the sealing seat in a blind hole, among other things, the advantage that the harmful volume can be reduced by up to 50%. Due to the lower harmful emissions, HC emissions are also significantly reduced. Since the requirements with respect to the emission values steadily increase, another object of the present invention can be seen in the reduction of such. In that regard, the proposed seat geometry of a fuel injection valve according to the invention proves to be particularly advantageous in connection with the training as a seat hole nozzle. Due to the injection openings formed in the seat portion, a seat hole nozzle has a lower strength compared to a blind hole nozzle, but this is compensated by the fact that stresses due to the proposed smaller opening angle of the sealing seat can be significantly reduced.

Preferably, the seat-near guide area is formed immediately adjacent to the sealing seat. On the one hand, an optimal guidance of the nozzle needle can be achieved on the other hand, the production of the guide area within the central bore is simplified. The central bore has a reduced diameter for forming the guide region, so that only on one side of the guide region, that is on the seat remote side, a region of the central bore with a larger diameter connects, so that it can be easily prepared by exposure ,

Preferably, the peripheral sealing area formed on the nozzle needle has at least one cone-shaped partial area. The cone angle α _{2 of} this partial area is preferably selected to be at least slightly larger than the opening angle α _{1 of} the sealing seat. The nozzle needle thus essentially abuts with a line-shaped sealing contour on the sealing seat. To form a sealing edge of the circumferential sealing area be composed of two cone-shaped portions with different cone angles.

According to a preferred embodiment, the circumferential sealing area formed on the nozzle needle has a pressure stage with hydraulic active surfaces which can be acted on with fuel pressure in the axial and / or radial direction. Such a pressure stage may for example also have the shape of a circumferential groove. An adjoining, in the radial direction effective hydraulic pressure can also contribute to the leadership of the nozzle needle and thus prevent the risk of Ausachsierung.

Due to the above properties, a fuel injection valve according to the invention is particularly suitable for modern combustion processes with a high proportion of premixed combustion in the partial load range, which generate significantly increased HC emissions. The commonly chosen nozzle designs add to the increased levels. Because the injection nozzle is usually designed as a blind hole nozzle with a seat angle of about 60 °. The presently proposed nozzle design, however, can significantly reduce the HC emissions, to ensure good spray symmetry and to achieve a strength of the nozzle area, which allows high injection pressures. Furthermore, ballistic fuel injection valves without stroke stop are widely used. A fuel injection valve according to the invention can also be designed in this way.

• Fig. 1 schematische Teilschnitte im Bereich des Dichtsitzes, die eine erfindungsgemäße 45°-Düse einer bekannten 60°-Düse gegenüberstellen und
• Fig. 2 schematische Teilschnitte, die eine Sitzlochdüse einer Sacklochdüse gegenüberstellen.

The invention will be explained in more detail with reference to FIGS. These show:

• Fig. 1 schematic partial sections in the region of the sealing seat, which contrast a 45 ° nozzle according to the invention of a known 60 ° nozzle and
• Fig. 2 schematic partial sections, which face a Sitzlochdüse a blind hole nozzle.

The juxtaposition of Fig. 1 is on the left side according to the invention and to remove a known nozzle construction on the right side. Both nozzle designs comprise a nozzle needle 1, which in a central bore 2 of a Nozzle body 3 is guided in a liftable manner. For this purpose, the nozzle construction according to the invention has a seat-near guide region 7 with a reduced diameter. About the lifting movement of the nozzle needle 1, at least one injection port 4 is released or closed. Both nozzles are constructed as seat hole nozzles, that is to say that the at least one injection opening 4 open into the central bore 2 in the region of a sealing seat 6 formed within the central bore 2 in each case. The sealing seat 6 in each case has a conical shape, which essentially corresponds to a conically extending partial region 8 of the nozzle needle 1 and forms a sealing region 5. At the conical portion 8 of the nozzle needle 1, a cylindrical portion and thereafter joins again a conical portion, so that at the nozzle needle 1, a pressure stage 9 and between the nozzle needle 1 and sealing seat 6, an annular space is formed as a pressure chamber, which in the operation of the injection valve with is filled under high pressure fuel. The pressure chamber is in communication with a formed between the nozzle needle 1 and the central bore 2 annular gap, which also serves as a pressure chamber. Combustion chamber side (in the Fig. 1 below), the central bore 2 in each case runs out into a blind hole 10. Differences essentially exist only with regard to the selected opening angle α _{1 of} the conical sealing seat 6, which is 60 ° in the left-hand illustration and 60 ° in the right-hand illustration, and the cone angle α _{2 of} the conical sub-region 8 of the nozzle needle 1, respectively is designed accordingly.

Fig. 2 shows a seat hole nozzle (left side) and a blind hole nozzle (right side) in a juxtaposition. In the seat-hole nozzle, the at least one injection opening 4 opens in the region of the sealing seat 6 into the central bore 2 of the nozzle body, while in the blind-hole nozzle the at least one injection opening 4 opens into the blind hole 10. Even with the seat hole nozzle remains when injecting fuel into the combustion chamber of an internal combustion engine, a dead volume in the blind hole 10. As the illustrations of Fig. 2 it can be seen, however, this is significantly, that is reduced by about 50%. The HC emissions can therefore also be significantly reduced when using a seat hole nozzle, which represents a further advantage.

Claims (4)

1. Fuel injection valve for injecting fuel into a combustion chamber of an internal combustion engine, having a nozzle needle (1) which is guided, such that it can perform a stroke motion, in a central bore (2) of a nozzle body (3) in order to open or close at least one injection opening (4), wherein the nozzle needle (1) interacts, by means of an encircling sealing region (5) formed on the combustion-chamber end thereof, with a conically extending sealing seat (6), which is formed on the combustion-chamber end of the nozzle body (3), characterized in that the conically extending sealing seat (6) has an opening angle (α₁) of between 40° and 50° the at least one injection opening (4) opens into the central bore (2) in the region of the sealing seat (6), and the central bore (2) has a guiding region (7) of reduced diameter, close to the seat, for guiding the nozzle needle (1), wherein the guiding region (7) is formed within a region of the central bore (2), the length of which is no more than 40% of the total length of the nozzle body (3), starting from the combustion-chamber end of the nozzle body (3).
2. Fuel injection valve according to Claim 1, characterized in that the guiding region (7) close to the seat is formed immediately adjacent to the sealing seat (6).
3. Fuel injection valve according to one of the preceding claims, characterized in that the encircling sealing region (5) formed on the nozzle needle (1) has at least one conical partial region (8), wherein the cone angle (α₂) of the partial region (8) is preferably at least slightly larger than the opening angle (α₁) of the sealing seat (6).
4. The fuel injection valve according to one of the preceding claims, characterized in that the encircling sealing region (5) formed on the nozzle needle (1) has a pressure step (9) with hydraulic effective surfaces which can be subjected to fuel pressure in an axial and/or a radial direction.

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