Title of Invention

FUEL INJECTION VALVE AND METHOD FOR MANUFACTURING

Abstract

A fuel injection valve for fuel injection systems of internal combustion engines, with a valve longitudinal axis, with a tubular core, with a magnet coil, with at least one conducting element closing an electromagnetic circuit, characterized in that the plastic injection overmoulding, as a plastic casing, partially surrounds the magnet coil and the one conducting element and, together with these, forms an independently fabricated plastic part, the plastic part has an inner passage orifice and, the independently fabricated valve part is fixedly connected to the plastic part in the passage orifice by means of a catch connection. The method for manufacturing the fuel injection valve comprises the step of producing the independent valve part, producing an independent plastic part with the plastic overmoulding as a plastic casing, with the magnet coil and with the at least one conducting element which are surrounded at least par.tially by the plastic casing and, connecting the valve part firmly to the plastic part in the passage orifice by means of a catch connection. FIGURE 1

Full Text

The invention relates to a fuel injection valve for fuel injection system of internal combustion engines comprising an independently manufactured plastic part and an independently manufactured valve part that are fixedly connected by suitable catch connection. The invention also provides a method for manufacturing the said fuel injection valve. US patent specification 4,946,107 has already disclosed an electromagnetically actuable fuel injection valve which has, inter alia, a non-magnetic sleeve as a connecting part between a core and a valve seat body. The sleeve is fixedly connected at its two axle ends to the core and to the valve seat body. The sleeve extends over its entire axial length with a constant outside diameter and a constant inside diameter. The core and the valve seat body are designed with an outside diameter such that they reach into the sleeve at both ends, so that the sleeve completely surrounds the two components, namely the core and valve seat body, in these inward- projecting regions. A valve needle moves in the axial direction inside the sleeve and has an armature which is led through the sleeve. The fixed connections of the sleeve to the core and to the valve seat body are achieved, for example, by means of welding. The core and the non-magnetic sleeve together delimit relative to the outside an inner valve part which is manufactured and set separately and which later forms the interior of the fuel injection valve. Finally, this inner valve part is surrounded by a plurality of further individual components when the injection valve is in the assembled state, at least one pot-shaped housing part, one magnet coil with a coil former, a bowl-shaped coil housing and one plug part being required. The arrangement and design of the many individual parts surrounding the valve part are relatively complicated in this case. Moreover, a multiplicity of connections has to be made between the outer individual parts and the inner valve part. German Offenlegungsschrift 4,310,819 has likewise disclosed a fuel injection valve which has a non-magnetic thin-walled sleeve as a valve seat carrier. The entire ready-set fuel injection valve, including the sleeve, is largely surrounded by a plastic injection overmoulding which, starting from the core, extends in the axial direction over the magnet coil as far as the downstream termination of the injection valve. The deep-drawn sleeve has only a very small wall thickness ( Advantages of the invention An advantage of the fuel injection valve according to the invention is that it can be mounted cost-effectively in a simple way. According to the invention, this simplified mounting of the fuel injection valve is achieved in that two main components of the injection valve, namely a valve part and a plastic part, are produced and set separately from one another. In this case, the inner valve part is advantageously designed, inter alia, with a non-magnetic thin-walled sleeve, the use of which affords a cost saving in comparison with known valves, since material savings are possible and assembly work for connecting individual components can partly be dispensed with. It is advantageous, moreover, that the outer plastic part has an inner passage orifice, into which the valve part can be inserted very simply and can be fastened by means of a simple and nevertheless secure catch connection. This separation into two main components affords the particular advantage that all the adverse influences occurring during the production of the plastic over- moulding (high overmoulding pressures, generation of heat) are kept away from the components of the valve part which perform the important valve functions. Deformation of the thin-walled sleeve of the valve part by the overmoulding pressure is thus completely ruled out. The relatively dirty overmoulding operation may advantageously be carried out outside the assembly line for the valve part (clean room). Advantageously, the catch connection is made by the engagement, catching or snapping of a catch element on the plastic part into a groove on the outer circumference of the valve part. For this purpose, the catch elements may have the most diverse contours, for example be angular or rounded. Accordingly the present invention provides a fuel injection valve for fuel injection systems of internal combustion engines, with a valve longitudinal axis, with a tubular core, with a magnet coil, with at least one conducting element closing an electromagnetic circuit, with a valve-closing body which is part of a valve needle movable axially along the valve's longitudinal axis and which cooperates with a valve seat provided on a valve seat body, with a thin-walled, axially extending, nonmagnetic sleeve, in which the valve needle moves axially and which is fixedly connected to the core, the core and the sleeve together delimiting a valve part in the outward direction, and with a plastic injection overmoulding which partially surrounds the fuel injection valve, characterized in that the plastic injection overmoulding, as a plastic casing, partially surrounds the magnet coil and the one conducting element and, together with these, forms an independently fabricated plastic part, the plastic part has an inner passage orifice and, the independently fabricated valve part is fixedly connected to the plastic part in the passage orifice by means of a catch connection. Drawing An exemplary embodiment of the invention is illustrated in simplified form in the drawing and is explained in more detail in the following description. Figure 1 shows a fuel injection valve according to the invention, Figure 2 shows an outer tubular plastic part and Figure 3 shows an inner valve part, the parts of Figures 2 and 3, when mounted and connected to one another, producing a fuel injection valve according to Figure 1. Description of the exemplary embodiment The electromagnetically actuable valve, illustrated by way of example in Figure 1 and taking the form of an injection valve for fuel injection systems of mixture-compressing spark-ignition internal combustion engines, has a tubular core 2 surrounded b a magnet coil 1 and serving as a fuel inlet port. A coil former 3 stepped in the radial direction receives a winding of the magnet coil 1 and, in conjunction with the core 2, makes it possible to have a particularly compact design of the injection valve in the region of the magnet coil 1. The magnet coil 1, together with its coil former 3, is surrounded by at least one conducting element 5 which is designed, for example, as a yoke and serves as a ferro magnetic element which at least partially surrounds the magnet coil 1 in the circumferential direction and bears with its upper end 6 upon the core 2. At least one conducting element 5 is made stepped in such a way that an axis-parallel main portion 7 and the upper end 6 are connected by means of a radially extending connecting portion 8. The connecting portion 8 constitutes a cover of the magnet-coil region in the upward direction. To close the magnetic circuit, the conducting element 5 is connected at its lower end 9, for example by means of one or more weld spots, for instance to a conducting ring 9 of L-shaped cross-section which constitutes the limitation of the magnet-coil region in the downward or downstream direction. The parts conducting the magnetic flux, namely the conducting element 5 and the conducting ring 10, surround the magnet coil 1, wound onto the coil former 3, at least partially in a pot-shaped manner. A lower end 15 of the core 2, the said lower end having a somewhat smaller outside diameter than the inflow-side upper end of the core 2 serving as a fuel inlet, has sealingly connected to it, for example by welding, concentrically relative to a valve longitudinal axis 16, a tubular thin-walled sleeve 18 which serves as a connecting part and which, at the same time, surrounds the core end 15 partially axially with an upper sleeve portion 19. The coil former 3 engages at least partially axially over the sleeve portion 19 of the sleeve 18. In particular, the coil former 3 has, over its entire axial extent a larger inside diameter than the diameter of the sleeve 18 in the upper sleeve portion 19 of the latter. The tubular sleeve 18, consisting, for example, of nonmagnetic steel, extends dovmatroaui' with a. lower slcove portion 20 as far as the downstream termination of the fuel injection valve, the lower sleeve portion 20 having a slightly smaller diameter than the diameter of the upper sleeve portion 19. In this case, the reduction in diameter in the form of a small step 23 is located in the upper end region of the conducting ring 10, since the conducting ring 10 has a minimally smaller inside diameter than the inside diameter of the coil former 3. This design contributes to the reliable mounting of the injection valve, this mounting being explained in detail later. The sleeve 18 is therefore designed to be tubular over its entire axial length. At the same time, the sleeve 18 forms, over its entire axial extent, a passage orifice 21 having a diameter which is largely constant, with the exception of the step 23, the said passage orifice running concentrically relative to the valve's longitudinal axis 16. The sleeve 18 surrounds, with its sleeve portion following the step 23 downstream, an armature 24 and, further downstream, a valve seat body 25. A, for example, pot-shaped perforated injection disc 26, fixedly connected to the valve seat body 25 on its downstream end face, is likewise surrounded in the circumferential direction by the sleeve 18, the fixed connection of the valve seat body 25 and the perforated injection disc 26 being made, for example, by means of a peripheral sealing weld seam. The sleeve 18 is thus not only a connecting part, but it also performs holding or carrier functions, in particular for the valve seat body 25, so that the sleeve 18 is actually also a valve seat carrier. Arranged in the passage orifice 21 is a, for example, tubular valve needle 2 8 which is connected, for example by welding, at its downstream end 29 facing the perforated injection disc 26, to a, for example, spherical valve-closing body 30, on the circumference of which are provided, for example, five flattenings 31 for the fuel to be injected to flow past* The injection valve is actuated electro-magnetically in a known way. For the axial xuOv&uiOAit o£ the valve needle 28 and consequently for opening the injection valve counter to the spring force of a return spring 33 and closing the injection valve, there is the electromagnetic circuit having the magnet coil lf the core 2, the at least one conducting element 5, the conducting ring 10 and the armature 24. The armature 24 is connected, for example by means of a weld seam, to that end of the valve needle 28 facing away from the valve-closing body 30 and is aligned with the core 2. A guide orifice 34 of the valve seat body 25 serves for guiding the valve-closing body 3 0 during the axial movement of the valve needle 28, together with armature 24, along the valve's longitudinal axis 16. Moreover, the armature 24 is guided during the axial movement in the sleeve 18. The spherical valve-closing body 30 cooperates with a valve seat face 35 of the valve seat body 25, the said valve seat face tapering frustoconically in the direction of flow and being formed downstream of the guide orifice 34 in the axial direction. The pot-shaped perforated injection disc 24 possesses, in addition to a bottom part 41, to which the valve seat body 25 is fastened and in which at least one, for example four injection orifices 42, shaped out by erosion or punching, extend, a peripheral holding edge 43 which extends downstream. The holding edge 43 is bent conically outwards downstream, so that it bears on the inner wall of the sleeve 18, the said inner wall being defined by the passage orifice 21, radial pressure prevailing at the same time. At its downstream end, the holding edge 43 of the perforated injection disc 26 is connected to the wall of the sleeve 18, for example by means of a peripheral sealing weld seam made, for example, by means of a laser. A direct throughflow of the fuel into an intake pipe of the internal combustion engine outside the injection orifices 42 is avoided by means of the weld seams on the perforated injection disc 26. The push-in depth of the valve seat body 25, together with the perforated injection diac 26, ia the sleeve 18 is critical, inter alia, for the stroke of the valve needle 28. In this case, when the magnet coil 1 is not energized, one end position of the valve needle 28 is determined by the bearing of the valve-closing body 30 on the valve seat face 35 of the valve seat body 25, whilst, with a magnet coil 1 energized, the other end position of the valve needle 28 results from the bearing of the armature 24 on the core end 15. Moreover, stroke setting is carried out by means of the axial displacement of the core 2, pressed in with a slight oversize, in the upper sleeve portion 19 of the sleeve 18. In the appropriately desired position, the core 2 is subsequently connected fixedly to the sleeve 18, laser welding on the circumference of the sleeve 18 being expedient. The assembly oversize of the press fit may also be selected as sufficiently large to ensure that the forces occurring can be absorbed and complete sealing is ensured, with the result that welding may be dispensed with. A setting sleeve 39 is pushed into a stepped flow bore 3 8 of the core 2, the said flow bore running concentrically relative to the valve's longitudinal axis 16 and serving for the supply of fuel in the direction of the valve seat, particularly of the valve seat face 35. The setting sleeve 3 9 serves for setting the spring prestress of the return spring 33 which bears on the setting sleeve 3 9 and which is, in turn, supported on its opposite side on the valve needle 2 8. A fuel filter 40 projects into the flow bore 3 8 of the core 2 at the inflow-side end of the latter and ensures that those fuel constituents which could cause blockages or damage in the injection valve on account of their size are filtered out. The ready-set and mounted injection valve is largely surrounded by a plastic casing 50 which, starting from the core 2, extends in the axial direction over the magnet coil 1 as far as the downstream termination of the sleeve 18, this plastic casing 50 including an electrical junction plug 51 also injection-moulded on. The electrical contacting of the magnet coil 1 and consequently its energization are carried out via the electrical junction plug 51. As shown in Figure 2, the plastic casing 50 is a tubular plastic part which differs considerably from plastic inj ection overmouldings of known fuel injection valves. Figure 2 illustrates an outer tubular plastic part 60 having the magnet-coil subassembly, the said plastic part being formed mainly by the plastic casing 50 together with the junction plug 51. This plastic part 60 consists, in actual fact, of the magnet coil 1, the plastic coil former 3 carrying the windings of the magnet coil 1, the at least one, for example, yoke-shaped conducting element 5, the conducting ring 10 and the plastic casing 50 which completely surrounds in the circumferential direction and outwardly this arrangement which may be referred to as a magnet-coil subassembly. At the same time, the tubular plastic casing 50 surrounds the conventionally designed junction plug 51 which has, for example, two contact pins 52 serving for the electrical energization of the magnet coil 1. These contact pins 52 extend out of the coil former 3 as far as the junction plug 51. The plastic casing 50 is shaped in such a way that an inner passage orifice 54 running axially is formed. In this case, the inner passage orifice 54 of the plastic part 60 is not determined completely by the inside diameter of the plastic casing 50, but also by the inside diameter of the upper end 6 of the conducting element 5, the inside diameter of the coil former 3 and the inside diameter of the conducting ring 10. According to the already described minimal differences in the inside diameters of the components 3, 5 and 10, a plurally slightly stepped passage orifice 54 of the plastic part 60 is obtained. Outside the magnet-coil subassembly, the diameter of the passage orifice 54 is determined by the plastic of the plastic casing 50, the inside diameter of the orifice region 55 located upstream of the magnet coil 1 being greater than the inside diameter of the orifice region 56 located downstream oi the magnet: coxx x. The plastic casing 50 surrounds the magnet-coil subassembly not only in the circumferential direction and in the axial direction, but it also extends in the region of the at least one conducting element 5 between such a conducting element 5 and the magnet coil 1 or the coil former 3. Directly above the coil former 3/ the plastic casing 50 is designed, at the passage orifice 54/ in such a way that a catch element 58 projecting into the passage orifice 54 and extending peripherally, for example through 360°, somewhat reduces the cross-section of the passage orifice 54. This catch element 58 may be designed in the form of a peripheral nose, an inner bead or an inner collar and may have an angular or rounded contour. A plurality of catch noses arranged over the circumference of the passage orifice 54 are likewise conceivable. The outer contour of the plastic casing 50 is adapted to the desired installation conditions, there being provided, for example, at the lower end of the plastic casing 50 an annular groove 59, into which a sealing ring 62 (Figure 1) can be inserted. The design of such a plastic part 60 with the catch element 58 according to Figure 2 allows mounting which is novel and simplified for fuel injection valves. The parts conducting the magnetic flux, namely the conducting element 5 and conducting ring 10, are first connected fixedly, on the coil former 3, to the magnet coil 1, for example by means of a snap connection or weld spots. This magnet-coil subassembly is subsequently overmoulded with plastic, so as to produce the contour of the plastic part 60, the said contour already having been described in detail. At the same time, the inner passage orifice 54 is obtained by providing, in the plastic overmoulding die, a mandrel which simulates an inner valve part 70 illustrated in Figure 3. The valve part 70, shown in Figure 3 and produced and set separately from the plastic part 60, corresponds to the inner subassembly of the fuel injection valve illustrated in Figure 1. The valve part 70 mainly comprises the components, namely cne cgi-«? A, fuel filter 40, setting sleeve 39, return spring 33, valve needle 28 with valve-closing body 30, armature 24, sleeve 18 and valve seat body 25 with perforated injection disc 26 . The individual components cooperate in the above-described way or are connected to one another according to the explanations given previously with regard to Figure 1. The use of the relatively inexpensive sleeve 18 makes it possible to dispense with lathe-turned parts, such as a valve seat carrier or nossle holder, which are conventionally in injection valves and which, on account of their larger outside diameter, are more bulky and more expensive to produce than the sleeve 18. The thin-walled sleeve 18, (wall thickness, for example, 0.3mm) has been made, for example, by deep-drawing, the material used being a non-magnetic material, for example a rust-proof CrNi steel. As already mentioned, the sleeve 18, which is a deep-drawn sheet-metal part, serves, on account of its large extent, for receiving the valve seat body 25, the perforated injection disc 26, the valve needle 28 with the armature 24, the return spring 33 and, at least partially, the core 2 and, consequently, also the stop region of the armature 24 and core 2 for limiting the stroke. The sleeve 18 possesses at its upper axial end, for example, a peripheral edge 64 bent slightly radially outwards. The peripheral edge 64 is obtained by separating the material overflow during deep-drawing and serves for making a secure catch connection in the injection valve. After the stroke setting and the mounting of the individual components to form the valve part 70, the complete valve part 7 0 is pushed into the passage orifice 54 of the plastic part 60 from the upper orifice region 55. The valve part 70 and plastic part 60 make a fixed catch connection at an appropriately desired push-in length. For this purpose, the catch element 58 of the step 65 This may involve engagement, catching or snapping. The groove 66 may also be formed at another location on the circumference of the core 2. At the same time, the geometries of the catch element 58 and of the groove 66 are provided in such a way that an absolutely secure non-slip connection is obtained. It is no longer possible to break the connection without an additional tool. A great advantage of this type of mounting is that the high overmoulding pressure (up to 350 bar) necessary during plastic injection overmoulding cannot lead to deformations of the thin-walled sleeve 18, since the latter is integrated in the plastic part 60 only at a later stage together with the entire valve part 70. WE CLAIM: 1. A fuel injection valve for fuel injection systems of internal combustion engines, with a valve longitudinal axis, with a tubular core, with a magnet coil, with at least one conducting element closing an electromagnetic circuit, with a valve-closing body which is part of a valve needle movable axially along the valve's longitudinal axis and which cooperates with a valve seat provided on a valve seat body, with a thin-walled, axially extending, non-magnetic sleeve, in which the valve needle moves axially and which is fixedly connected to the core, the core and the sleeve together delimiting a valve part in the outward direction, and with a plastic injection overmoulding which partially surrounds the fuel injection valve, characterized in that a) the plastic injection overmoulding, as a plastic casing (50), partially surrounds the magnet coil (1) and the one conducting element (5, 10) and, together with these, forms an independently fabricated plastic part (60), b) the plastic part (60) has an inner passage orifice (54) and, c) the independently fabricated valve part (70) is fixedly connected to the plastic part (60) in the passage orifice (54) by means of a catch connection. 2. The fuel injection valve according to Claim 1, wherein at leas', one catch element (58) is provided in the passage orifice (54) of the plastic part (60). 3. The fuel injection valve according to Claim 1, wherein at least one groove (66) is provided on the circumference of the valve part (70). 4. The fuel injection valve according to Claims 2 and 3, wherein the fixed catch connection can be made by the engagement, catching or snapping of the at least one catch element (58) into the at least one groove (66). 5. The fuel injection valve according to Claim 2 or 4, wherein the catch element (58) is a peripheral catch nose projecting into the passage orifice (54). 6. The fuel injection valve according to Claim 2 or 4, wherein the at least one catch element (58) is a plurality of catch noses arranged over the circumference of the passage orifice (54). 7. The fuel injection valve according to Claim 1 or 3, wherein the sleeve (18) has, at its upper end, a peripheral edge (64) which partially delimits a groove (66) on the outer circumference of the valve part (70). 8. The fuel injection valve according to Claim 1 or 3, wherein the at least one groove (66) is provided on the circumference of the core (2). 9. The fuel injection valve according to Claim 1, wherein the sleeve (18) of the valve part (70) constitutes a deep-drawn sheet-metal part. 10. A method for production of a fuel injection valve for fuel injection systems of internal combustion engines, with a valve longitudinal axis (16) with a tubular core (2), with a magnet coil (1), with at least one conducting element (5, 10) closing an electromagnetic circuit with a valve-closing body (30) which is part of a valve needle (28) movable axially along the valve's longitudinal axis (16) and which cooperates with a valve seat provided on a valve seat body (25), with a thin-walled, axially extending, non-magnetic sleeve (18), in which the valve needle (28) moves axially and which is fixedly connected to the core (2), the core and the sleeve (18) together delimiting a valve part (70) in the outward direction, and with a plastic injection overmoulding (50) which partially surrounds the fuel injection valve according to claims 1 to 9, comprising the step of producing the independent valve part (70) characterized in that producing an independent plastic part (60) with the plastic overmoulding as a plastic casing (50), with the magnet coil (1) and with the at least one conducting element (5, 10) which are surrounded at least partially by the plastic casing (50), the plastic part having an inner passage orifice (54), and, connecting the valve part (70) firmly to the plastic part (60) in the passage orifice (54) by means of a catch connection. 11. The method according to Claim 10, wherein the catch connection is made by the engagement, catching or snapping of the valve part (70) in the plastic part (60). 12. A fuel injection valve for fuel injection systems of internal combustion engines substantially as herein described with reference to the accompanying drawings.

Documents:

1004-mas-1997- abstract.pdf

1004-mas-1997- claims duplicate.pdf

1004-mas-1997- claims original.pdf

1004-mas-1997- correspondence others.pdf

1004-mas-1997- correspondence po.pdf

1004-mas-1997- description complete duplicate.pdf

1004-mas-1997- description complete original.pdf

1004-mas-1997- drawings.pdf

1004-mas-1997- form 1.pdf

1004-mas-1997- form 26.pdf

1004-mas-1997- form 3.pdf

1004-mas-1997- form 4.pdf

1004-mas-1997- pct.pdf