1. Field of the Invention
The present invention relates to an electromagnetically actuatable valve.
2. Description of Related Art
Additional variants of guiding a movable armature of an electromagnetically operated fuel injector are also known. For example, published German patent document DE 41 37 994 A1 describes an at least partially circumferential guide lug which may be impressed in a nozzle carrier, this guide lug also being responsible for guiding the armature on its outer periphery. It is also known to provide guide lugs distributed over the periphery in the area of a magnetic restriction of an elongated valve body which guide the armature during its axial movement (see, e.g., published German patent document DE 195 03 820 A1). Published German patent document DE 100 51 016 A1 describes a fuel injector in which guide band segments located in the area of the strongest radial magnetic flux are formed on the outer periphery of the armature.
The electromagnetically actuatable valve according to the present invention has the advantage of a compact design. The valve may be manufactured in a particularly cost-effective way since the armature guide is implemented in a simple and cost-effective manner. According to the present invention, a restoring spring and an internal longitudinal bore hole of the armature are paired in such a way that the armature is guided during its axial movement only along the restoring spring. In addition to its actual function of restoring the valve needle, the restoring spring also assumes the function of guiding the armature, thus implementing an integration of functions in a simple manner. The contact surface used for guiding is advantageously reduced compared to the approaches of the related art. The function is improved by avoiding undesirable radial forces due to the unguided outer periphery of the armature.
It is advantageous in particular to bring the longitudinal bore hole of the armature and optionally the flow bore hole of the internal pole to their exact internal dimensions by friction.
It is advantageous to provide flats on the periphery of the restoring spring along which the armature is guided and which are formed over the entire length or portion of the length of the restoring spring.
The valve has a largely tubular core 2, surrounded by a solenoid 1 and used as an internal pole and partially as a fuel passage. Solenoid 1 is fully surrounded in the peripheral direction by an outer, sleeve-shaped, stepped, for example ferromagnetic, valve jacket 5, which represents an external magnetic circuit component used as an external pole. Solenoid 1, core 2, and valve jacket 5 together form an electrically excitable actuating element.
While solenoid 1 embedded in a bobbin 3 externally surrounds a valve sleeve 6 with a winding 4, core 2 is introduced in an internal opening 11 of valve sleeve 6 running concentrically to a longitudinal valve axis 10. Valve sleeve 6 has an elongated and thin-walled design. Opening 11 is used, among other things, as a guide opening for a valve needle 14 axially movable along longitudinal valve axis 10. Valve sleeve 6 extends in the axial direction approximately over one-half of the total axial length of the fuel injector, for example.
In addition to core 2 and valve needle 14, a valve needle 15, which is attached to valve sleeve 6 by a weld 8, for example, is also situated in opening 11. Valve seat body 15 has a fixed valve seat surface 16 as a valve seat. Valve needle 14 is formed, for example, by a tubular armature 17, an also tubular needle section 18, and a spherical valve closing body 19, valve closing body 19 being fixedly attached to needle section 18 by a weld. On the downstream face of valve seat body 15, a spray hole disk 21, which is pot-shaped, for example, is situated, whose bent, peripheral holding edge 20 is directed upward against the flow direction. Valve seat body 15 is fixedly attached to spray hole disk 21 by a circumferential, airtight weld. One or more transverse openings 22 are provided in needle section 18 of valve needle 14, so that the fuel flowing through armature 17 in an internal longitudinal bore hole 23 may exit and flow along valve closing body 19, for example, flats 24 to valve seat surface 16.
The injector is actuated electromagnetically in the known manner. The electromagnetic circuit having solenoid 1, internal core 2, outer valve jacket 5, and armature 17 is used for axially moving valve needle 14 and thus for opening the injector against the spring force of a restoring spring 25 which engages valve needle 14 or for closing the injector. The end of armature 17 facing away from valve closing body 19 is oriented toward core 2. Instead of core 2, a cover part, which closes the magnetic circuit and is used as an internal pole, may also be provided, for example.
Spherical valve closing body 19 cooperates with valve seat surface 16 of valve seat body 15, which is formed in valve seat body 15 downstream from a guide opening in the axial direction and conically tapers in the direction of flow. Spray hole disk 21 has at least one, for example four, spray opening(s) 27 made by erosion, laser drilling, or punching.
The depth of insertion of core 2 in the injector determines, among other factors, the lift of valve needle 14. One end position of valve needle 14 when solenoid 1 is not excited is determined by valve closing body 19 resting on valve seat surface 16 of valve seat body 15, while the other end position of valve needle 14 when solenoid 1 is excited results from armature 17 resting on the downstream core end. The lift is set by an axial shift of core 2, which is then fixedly attached to valve sleeve 6 according to the desired position.
In addition to restoring spring 25, an adjusting element in the form of an adjusting sleeve 29 is inserted into a flow bore hole 28 of core 2, running concentrically to longitudinal valve axis 10 and used for supplying fuel in the direction of valve seat surface 16. Adjusting sleeve 29 is used for adjusting the spring pre-tension of restoring spring 25 resting on adjusting sleeve 29, whose opposite side is in turn in contact with valve needle 14 in the area of armature 17, the dynamic injection quantity also being adjusted using adjusting sleeve 29. A fuel filter 32 is situated above adjusting sleeve 29 in valve sleeve 6.
The inlet side end of the injector is formed by a metallic fuel inlet nozzle 41, which is surrounded by an extruded plastic sheath 42, which stabilizes, protects, and surrounds it. A flow bore hole 43 of a tube 44 of fuel inlet nozzle 41, running concentrically to longitudinal valve axis 10, is used as a fuel inlet. Extruded plastic sheath 42 is extruded, for example, in such a way that the plastic directly surrounds parts of valve sleeve 6 and valve jacket 5.
Reliable sealing is thus achieved, for example, via a labyrinth seal 46 on the periphery of valve jacket 5. An electrical plug 56 is also sheathed by extruded plastic sheath 42.
However, it is also conceivable to modify restoring spring 25, responsible for the guiding function, on its outer guiding periphery.
Number | Date | Country | Kind |
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10 2007 050 819.2 | Oct 2007 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2008/062923 | 9/26/2008 | WO | 00 | 8/20/2010 |