Fuel injector with injector nozzle

Description

[0001] The invention relates to an injection nozzle for injecting a fluid, in particular a liquid or gaseous fuel. Furthermore, the invention relates to a fuel injector with an injection nozzle according to the invention. State of the art

[0002] In the prior art, injection nozzles for liquid and / or gaseous fuels are described in a wide variety of designs. They generally comprise a nozzle body and a nozzle needle mounted within the nozzle body for movement. The injection orifices formed in the nozzle body are controlled by the needle's stroke. The nozzle needle is guided along its longitudinal axis by guide surfaces formed in the nozzle body. This guidance is intended to ensure a symmetrical spray pattern and to reduce wear in the area of ​​a sealing seat for the nozzle needle. Sufficiently dimensioned longitudinal grooves or chamfers in the guide area of ​​the nozzle needle ensure that, when the nozzle needle opens, enough fluid at high pressure can reach the seat area and from there, via a blind hole, to the injection orifices.

[0003] To guide the nozzle needle as precisely as possible, longer and / or multiple guides are often provided inside the nozzle body and on the nozzle needle itself. With multiple guides, one is usually positioned as close as possible to the sealing seat to center the nozzle needle relative to the sealing seat. Such a nozzle needle is known, for example, from DE 10 2012 211 156 A1. However, so-called seat-close guides are difficult to manufacture, so that despite the guidance, asymmetrical sliding of the nozzle needle along the sealing seat during closing cannot always be avoided. Furthermore, increasing injection pressure can cause the guide gaps to widen, thus impairing or losing their guiding properties.

[0004] Furthermore, EP 2 642 110 A1 discloses a fuel injection valve comprising a cylindrical nozzle body with a nozzle needle that is longitudinally displaceable within it. The nozzle needle is connected at its end to a sleeve that controls the injection ports and is guided on the outside of the nozzle body.

[0005] In addition to guiding the nozzle needle, the fluid supply to the injection holes must be ensured. Since the fluid flow path runs over the same area or even directly over the guide areas, a compromise must be found between the cross-sectional area through which the fluid can flow and the guiding properties. The cross-sectional area through which the fluid can flow in the guide areas must be dimensioned such that no additional throttling points are created. If possible, throttling points should only be formed by the sealing seat when the nozzle needle opens and by the injection holes at full stroke.

[0006] The present invention is concerned with providing an injection nozzle with an improved guide for a movable nozzle needle. The guide should also have the least possible influence on the fluid flow through the injection nozzle.

[0007] To solve the problem, the injection nozzle with the features of claim 1 is proposed. Advantageous embodiments of the invention are described in the dependent claims. Furthermore, a fuel injector with an injection nozzle according to the invention is specified. Disclosure of the invention

[0008] The proposed injection nozzle for injecting a fluid, in particular a liquid or gaseous fuel, comprises a nozzle body which is at least partially hollow cylindrical and forms a sealing seat over which a flow path for the fluid to be injected leads, a nozzle needle which is movably received in the nozzle body and has a sealing surface that interacts with the sealing seat, and a guide element which is rigidly connected to the nozzle needle and is guided over an external guide of the nozzle body.

[0009] Because the guide element is firmly connected to the nozzle needle, the nozzle needle is guided by the external guide of the nozzle body. The nozzle needle's guidance is thus shifted from the inside to the outside. This allows for guidance at the level of the sealing seat, or at least in close proximity to it, ensuring optimal guidance of the nozzle needle. Asymmetrical sliding of the nozzle needle over the sealing seat during closing is therefore prevented, which in turn reduces wear in the sealing seat area.

[0010] The close proximity of the guide to the valve seat also eliminates the need for additional guides inside the nozzle body, thus providing a larger flow cross-section for the fluid. This improves the fluid flow towards the sealing seat. Furthermore, the guide gaps can narrow with increasing injection pressure, thereby improving their guiding properties.

[0011] By relocating the nozzle needle guide to the outside, a spatial separation between the flow path and the guide is achieved. This means that the fluid no longer flows through the guide. This allows the guide to be designed solely based on its guiding properties, thus simplifying its design. The external arrangement of the guide also offers manufacturing advantages, as the area is easily accessible. Furthermore, the complex undercuts and / or recesses typically required for creating a guide inside the nozzle body are eliminated.

[0012] Preferably, the guide and the flow path through the nozzle body are spatially separated. This means that the nozzle needle is still guided over the nozzle body and the nozzle body limits the flow path, but they are spatially separated from each other, so that the guide does not restrict the flow path.

[0013] Furthermore, the outer guide preferably forms an outer circumferential region of the nozzle body. This can be, in particular, an end section of the nozzle body, which is machined accordingly, for example, by fine grinding. The guide element surrounds this protruding area of ​​the nozzle body. The guide element is preferably designed to be at least partially hollow cylindrical.

[0014] Preferably, the guide element has a central recess in which an end section of the nozzle needle is received. This allows for a secure connection between the guide element and the nozzle needle. The nozzle needle and the guide element thus form a single unit that is guided by the external guide of the nozzle body. This design has the advantage that the nozzle needle and the guide element can be manufactured separately. At the same time, assembly is simplified, as the guide element can be connected to the nozzle needle even after the nozzle needle has been inserted into the nozzle body. This approach has the advantage that any manufacturing tolerances in the area of ​​the sealing surface can still be compensated for during the connection of the guide element to the nozzle needle. The connection of the guide element to the nozzle needle can be made, for example, by welding.

[0015] According to claim 1, the guide element defines a flow chamber and has at least one opening for directing the fluid out of the flow chamber. In this case, the guide element can simultaneously be used to shape the spray pattern, as the at least one opening can be designed as desired. Thus, optimized spray shaping and / or spray direction can be achieved simultaneously with the aid of the guide element.

[0016] Since the flow space defined by the guide element is significantly larger than, for example, a conventional blind hole inside the nozzle body, considerably higher flow rates can be achieved with the proposed injection nozzle. This requires that the opening cross-section of the at least one outlet for the fluid is appropriately dimensioned, which simultaneously prevents the formation of a throttling point downstream of the sealing seat.

[0017] Furthermore, the sealing seat and / or the sealing surface of the nozzle needle interacting with the sealing seat are preferably conically shaped. The conical shape enables the nozzle needle to self-center with respect to the sealing seat during closing, ensuring that the injection nozzle closes securely. If both the sealing seat and the sealing surface of the nozzle needle are conically shaped, they preferably have different cone angles. Preferably, the cone angle of the sealing surface of the nozzle needle is smaller than the cone angle of the sealing seat. In this case, the nozzle needle comes into contact with the sealing seat via a circumferential circular sealing contour, which further increases the sealing tightness of the sealing seat.

[0018] The sealing surface is preferably formed on a part or section of the nozzle needle that has an enlarged outer diameter and is located upstream of the guided end section. This allows for a comparatively large seat diameter and thus high flow rates.

[0019] According to a preferred embodiment of the invention, the nozzle needle opens outwards. This embodiment has the advantage that the sealing seat and the guide can be manufactured from one side in a single clamping operation. This increases the precision of the alignment of the nozzle seat to the guide. In addition, the guide can be arranged at the same level as the sealing seat.

[0020] Alternatively, it is proposed that the nozzle needle open inwards. In this case, the guide element can only be firmly connected to the nozzle needle after it has been inserted into the nozzle body. Here, the pre-assembled design of the nozzle needle proves to be particularly advantageous.

[0021] Furthermore, a fuel injector with an injection nozzle according to the invention is proposed. Since the injection nozzle is suitable for injecting liquid and gaseous fuels, the fuel injector can, for example, be a diesel injector for a common-rail injection system or a gas injector. Because gas injectors generally have to enable high volume flows, the advantages of the injection nozzle according to the invention are particularly evident here.

[0022] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a schematic longitudinal section through a first injection nozzle according to the invention and Fig. 2 a schematic longitudinal section through a second injection nozzle according to the invention. Detailed description of the drawings

[0023] The Figure 1A first preferred embodiment of an injection nozzle 1 according to the invention can be seen in the figure. This nozzle comprises a nozzle body 2 in which a nozzle needle 5 is movably mounted. The nozzle body 2 and the nozzle needle 5 define a flow path 4 for a fluid to be injected. The flow path 4 leads over a sealing seat 3, which is formed by the nozzle body 2. The sealing seat 3 is conically shaped and oriented outwards. In a section 13 with an enlarged outer diameter, the nozzle needle 5 has a conically shaped sealing surface 6, which interacts with the sealing seat 3. The sealing surface 6 is oriented towards the nozzle body 2. The nozzle needle 5 therefore opens outwards (see arrow 15).

[0024] To guide the nozzle needle 5, the nozzle body 2 has a guide 8 in an outer circumferential region. The guide 8 is surrounded by a guide element 7, which is rigidly connected to the nozzle needle 5. For this purpose, a central recess 9 is provided in the guide element 7, in which a pin-like end section 10 of the nozzle needle 5 is received. The guide element 7 delimits a flow chamber 11 downstream of the sealing seat 3, into which the fluid to be injected flows when the nozzle needle 5 is open. To guide the fluid out of the flow chamber 11, the guide element 7 has openings 12, which are shaped in such a way as to simultaneously achieve flow guidance.

[0025] During the Figure 1In the illustrated injection nozzle 1, the nozzle needle 5 is guided on the outside of the nozzle body 2, thus eliminating the need for a guide located near the seat inside the nozzle body 2. The flow cross-section in the flow path 4 can therefore be maximized. In particular, the formation of a throttling point is avoided. Since the guide 8 formed on the outside of the nozzle body 2 is located outside the flow path 4, its guiding properties can be optimized. Furthermore, the guide 8 can be positioned at the level of the sealing seat 3, ensuring optimal guidance of the nozzle needle 5.

[0026] Another preferred embodiment of an injection nozzle 1 according to the invention is described in the Figure 2 This differs from the embodiment of Figure 1 in particular in that the nozzle needle 5 opens inwards (see arrow 16).

[0027] The sealing seat 3 of the nozzle body 2 is therefore oriented inwards. The sealing surface 6 of the nozzle needle 5, which interacts with the sealing seat 3, faces outwards. The nozzle needle 5 is also connected here to a guide element 7, which engages a guide 8 formed on the outer circumference of the nozzle body. The connection is made here by a weld 14 between the nozzle needle 5 and the guide element 7 in the area of ​​a pin-shaped end section 10 of the nozzle needle 5 that engages in a recess 9 of the guide element 7.

[0028] The advantages of the injector nozzle 1 described above are also achieved with an inwardly opening nozzle needle 5, so that the invention can be implemented optionally with an outwardly opening and an inwardly opening nozzle needle 5.

Claims

1. Injection nozzle (1) for injecting a fluid, in particular a liquid or gaseous fuel, comprising: a nozzle body (2) which is of at least sectionally hollow-cylindrical design and forms a sealing seat (3) via which a flow path (4) for the fluid to be injected leads, a nozzle needle (5) which is received, such that it is able to perform stroke movements, in the nozzle body (2) and has a sealing surface (6) which interacts with the sealing seat (3), wherein the nozzle needle (5) is connected fixedly to a guide element (7) which is guided via an outer guide (8) of the nozzle body (2), characterized in that the guide element (7) delimits a flow space (11) and has at least one opening (12) for discharging the fluid from the flow space (11).

2. Injection nozzle (1) according to Claim 1, characterized in that the guide (8) and the flow path (4) are separated spatially by the nozzle body (2).

3. Injection nozzle (1) according to Claim 1 or 2, characterized in that an outer circumferential region of the nozzle body (2) forms the outer guide (8), and the guide element (7) surrounds the outer circumferential region of the nozzle body (2).

4. Injection nozzle (1) according to one of the preceding claims, characterized in that the guide element (7) has a central cutout (9) in which an end portion (10) of the nozzle needle (5) is received, said end portion preferably being of peg-like design.

5. Injection nozzle (1) according to one of the preceding claims, characterized in that the sealing seat (3) and / or the sealing surface (6) interacting with the sealing seat (3) are / is of conical shape.

6. Injection nozzle (1) according to one of the preceding claims, characterized in that the sealing surface (6) is formed on a part or portion (13) of the nozzle needle (5) that has an enlarged outer diameter.

7. Injection nozzle (1) according to one of the preceding claims, characterized in that the nozzle needle (5) opens outwardly.

8. Injection nozzle (1) according to one of Claims 1 to 6, characterized in that the nozzle needle (5) opens inwardly.

9. Fuel injector having an injection nozzle (1) according to one of the preceding claims.