DE19512339B4 - Electromagnetically actuated fuel injection valve - Google Patents

Abstract

Electromagnetically actuated fuel injection valve for fuel injection systems of internal combustion engines having a valve housing, a solenoid, a coil body at least partially surrounding the solenoid, a plastic surrounding the valve housing at least partially and also formed of plastic electrical connector with contact pins, via which the excitation of the solenoid occurs, characterized in that in at least one region in which one end of the plastic encapsulation (50) is present directly on a metal part of the valve housing or on a contact pin (53), a sealing element (56) is arranged which surrounds the metal part of the valve completely radially and is surrounded by the plastic extrusion (50) at least partially radially itself.

Description

State of the art

The invention relates to an electromagnetically actuable fuel injection valve according to the preamble of the main claim. Are already known numerous fuel injection valves, as well as from the EP-PS 0 348 786 , Which have an electrical connector, via which the electrical contacting of a magnetic coil and thus the excitation takes place. The contact itself takes place via metallic contact pins, which extend from the magnetic coil to the actual connector and are largely encapsulated in plastic. The connector is part of a plastic encapsulation, which encloses the valve housing over large parts.

The Connection between the plastic extrusion and the contact pins or the valve housing is not pressure tight. Rather, you can by the shrinkage behavior of the plastic after the encapsulation finest capillary gaps are formed, which is a compound of Coil space with the outside environment represent.

at Operation of the internal combustion engine or the fuel injection valve the coil space of the solenoid is heated. There is a volume compensation the heated, expanding air inside the valve with which the valve surrounding atmosphere.

Becomes the valve is cooled down from operating temperature, so ambient air can into the coil space above the capillary gaps between the plastic extrusion and the contact pins or the valve housing be sucked; the valve interior "breathes". Is the cooling of the Injector by splash water or is on cooling cooling water at the capillaries, the liquid gets into the interior of the Valve, especially in the coil space sucked. The result is one Corrosion on the contact pins and the coil wire, up to a destruction lead the coil wire can.

From the DE 41 20 947 A1 is already known an electromagnetically actuated fuel injection valve for fuel injection systems of internal combustion engines, comprising a valve housing, a solenoid, a coil surrounding the coil body and the valve housing partially surrounding Kunststoffumspritzung and formed of plastic electrical connector with contact pins. In the transition region of the plastic extrusion to the metal components of the fuel injection valve no sealing measures are provided, so that there are no pressure-tight connections. Due to the shrinkage behavior of the plastic after the encapsulation fine capillary gaps can form, which then represent a compound of the coil space with the external environment, so that as a result, a negative and undesirable corrosion at the contact pins and the coil wire of the solenoid is conceivable.

From the DE 34 27 526 C2 a fuel injection valve is already known in which a thin-walled valve seat carrier is sealed as part of a valve housing against a likewise metal valve housing part which surrounds the magnetic coil in the circumferential direction by means of a conventional sealing ring in O-ring shape.

Advantages of the invention

The Fuel injection valve according to the invention with the characterizing features of the main claim has the Advantage that no Moisture penetrates into the interior of the valve, causing corrosion on the contact pins and the coil wire of the solenoid and thus a destruction the same is excluded. This is achieved by the fact that inexpensive tubular sealing elements be arranged in areas on the injection valve, at which ends the plastic encapsulation are present directly on metal parts and otherwise finest capillary gaps could occur.

By in the subclaims listed activities are advantageous developments and improvements of the main claim specified fuel injector possible.

drawing

embodiments of sealing elements on an injection valve according to the invention are in the Drawing simplified and in the following description explained in more detail.

Description of the embodiments

For example, the electromagnetically operable valve in the form of an injection valve for fuel injection systems of mixture-compression spark-ignition internal combustion engines shown in the drawing has one of a solenoid coil 1 surrounded, serving as a fuel inlet nozzle tubular core 2 which has, for example, a constant outer diameter over its entire length. A bobbin stepped in the radial direction 3 takes a coil of the solenoid 1 on and allows in conjunction with the core 2 a compact design of the injector in the field of solenoid 1 ,

With a lower core end 9 of the core 2 is concentric to a valve longitudinal axis 10 tight a tubular metal intermediate part 12 for example, connected by welding and surrounds the core end 9 partially axial. The stepped bobbin 3 overreaches the core 2 and the intermediate part 12 at least partially axially. Downstream of the bobbin 3 and the intermediate part 12 extends a tubular valve seat carrier 16 , for example, fixed to the intermediate part 12 connected is. In the valve seat carrier 16 runs a longitudinal bore 17 that are concentric with the valve longitudinal axis 10 is trained. The valve seat carrier 16 forms together with the core 2 a valve housing. In the longitudinal bore 17 is a z. B. sleeve-shaped valve needle 18 arranged at its downstream end 20 with a spherical valve closing body 24 , on the circumference, for example, five flats 25 are provided for flowing past the fuel, for example, is connected by welding.

The actuation of the injection valve takes place in a known manner, for example, electromagnetically. For the axial movement of the valve needle 18 and thus to open against the spring force of a return spring 26 or closing the injection valve is the electromagnetic circuit with the solenoid 1 the core 2 and an anchor 27 , The anchor 27 is with the valve closing body 24 opposite end of the valve needle 18 connected by a weld and on the core 2 aligned. In the downstream, the core 2 opposite end of the valve seat carrier 16 is in the longitudinal bore 17 a cylindrical valve seat body 29 who has a tight valve seat 30 has, mounted by welding.

For guiding the valve closing body 24 during the axial movement of the valve needle 18 with the anchor 27 along the valve longitudinal axis 10 serves a guide opening 32 of the valve seat body 29 , The spherical valve closing body 24 acts with the valve seat tapering frustoconically in the flow direction 30 of the valve seat body 29 together. At its the valve closing body 24 opposite end face is the valve seat body 29 with an example cup-shaped spray perforated disc 34 concentric and firmly connected. In the spray-disk 34 are at least one, for example four formed by eroding or punching injection orifices 39 intended.

The insertion depth of the valve seat body 29 with the spray perforated disk 34 determines the size of the stroke of the valve needle 18 , Here is the one end position of the valve needle 18 with non-energized magnetic coil 1 through the installation of the valve closing body 24 at the valve seat 30 of the valve seat body 29 set while the other end position of the valve needle 18 with energized solenoid 1 through the attachment of the anchor 27 at the core end 9 results.

The magnetic coil 1 is of at least one, for example, designed as a bracket and serving as a ferromagnetic element guide element 45 Surrounded by the magnetic coil 1 circumferentially at least partially surrounds and with its one end to the core 2 and its other end to the valve seat carrier 16 is present and can be connected to these, for example, by welding, soldering or gluing.

The injection valve is largely with a plastic extrusion 50 enclosed, separate from the core 2 starting in the axial direction via the magnetic coil 1 and that at least one guide element 45 to the valve seat carrier 16 extends, wherein the at least one guide element 45 completely axially and circumferentially covered. To this plastic extrusion 50 For example, includes a mitangespritzter electrical connector 52 ,

About the electrical connector 52 the electrical contacting of the solenoid takes place 1 and thus their excitement. To the connector 52 For example, include two metallic contact pins 53 that are directly related to the winding of the magnetic coil 1 keep in touch. The contact pins 53 protrude from the valve seat 30 opposite direction from the solenoid 1 surrounding bobbin 3 out and are largely encapsulated in plastic. Only at the end of her pencil 54 lie the pins 53 free; They are there so not directly enclosed by plastic, so that a plug connection with a not shown corresponding connector part is possible.

Connections between plastic and metal parts are not always completely sealed. So it is not possible to fuel injection valves, an absolute complete tightness in the area of plastic overmolded pins 53 or in the areas of the ends of the plastic extrusion 50 to ensure. Rather, the finest capillary gaps form between the metal parts, such as the contact pins 53 , and the plastic coating 50 , Especially when exposed to heat, this effect is exacerbated because the different thermal expansion coefficients of plastic and metal lead to material shifts. During operation of the internal combustion engine or the fuel injection valve is just by the internal combustion engine and the heating of the solenoid 1 a temperature increase in the range of magnetic coil 1 and connector 52 which, in turn, increases the likelihood of capillary gap formation. The risk of the entry of liquid into the interior of the fuel injection valve is particularly great when the internal combustion engine high risk of splashing or extreme environmental conditions prevail. Since not only pure water can be sucked into the capillary gaps, but also other particles (eg salts) are taken, the corrosion in the area of the magnetic coil 1 even be accelerated, so that a destruction of the coil wire in the worst case is not excluded.

In a simple manner, this problem is inventively by one or more hose-like sealing elements 56 dissolved, which are arranged above all in areas on the injection valve, at which ends of the plastic extrusion 50 immediately present on metal parts. This therefore applies to the ends of the plastic extrusion 50 at the core 2 (on the inlet side) and on the valve seat carrier 16 (spraying side) as well as on the transition of the molded contact pins 53 to her free endings 54 in the connector 52 to. As materials for the sealing elements 56 are particularly different types of rubber (elastomers) or elastic plastics, as z. B. already known from gaskets to injectors.

In the drawing, five embodiments of the arrangement of the sealing elements are shown on the one injection valve shown 56 represented with additional letters from a to e. It can be both single sealing elements 56 be provided on the injection valve as well as a plurality of sealing elements 56 (eg 56a . 56c and 56e ) on an injection valve. This can be varied according to the installation conditions. The sealing elements 56a and 56b are at the upstream end of the plastic extrusion 50 arranged, in such a way that either the sealing element 56a flush with an upper face 58 the plastic extrusion 50 closes or the sealing element 56b slightly above the upper face 58 protrudes. Depending on the design of this upper sealing element 56a . 56b becomes an upper sealing ring 59 fitting over the end of the plastic extrusion 50 arranged.

Also on the discharge side lower end of the plastic extrusion 50 can be sealing elements 56c and 56d bring in different ways. Both sealing elements 56c . 56d protrude z. B. over a lower end face 60 the plastic extrusion 50 but differ in their radial thickness. While the sealing element 56c z. B. in a circumferential groove 62 on the circumference of the valve seat carrier 16 used and therefore formed more in its radial extent, is the thinner sealing element 56d directly on the outer circumference of the valve seat carrier 16 at. The pins 53 enclosing sealing elements 56e are z. B. mounted so that they are similar to the sealing element 56a flush with the plastic coating 50 to lock. In this case, the sealing elements end 56e So on a face 64 in the connector 52 , at the immediate the free pen ends 54 the contact pins 53 kick off.

Before the encapsulation of the valve housing with plastic at the correspondingly desired locations, the tubular sealing elements 56 already assembled. The sealing elements 56 are arranged so that they are slightly radially pressed by a Umspritzungswerkzeug, not shown. In addition, the Umspritzungswerkzeug surrounds the sealing elements 56 such that they are additionally pressed axially by the Umspritzungsdruck. Upon cooling, the plastic shrinks, causing the radial bias on the sealing elements 56 is further increased, so that a high sealing quality is ensured.

Claims (6)

Electromagnetically actuated fuel injection valve for fuel injection systems of internal combustion engines having a valve housing, a solenoid, a coil body at least partially surrounding the solenoid, a plastic surrounding the valve housing at least partially and also formed of plastic electrical connector with contact pins, via which the excitation of the solenoid occurs, characterized in that in at least one region at which one end of the plastic extrusion coating ( 50 ) directly on a metal part of the valve housing or on a contact pin ( 53 ), a sealing element ( 56 ) is arranged, which surrounds the metal part of the valve completely radially and by the plastic extrusion ( 50 ) is itself at least partially surrounded radially. Fuel injection valve according to claim 1, characterized in that the sealing elements ( 56 ) are formed of rubber. Fuel injection valve according to Claim 1 or 2, characterized in that the sealing elements ( 56 ) are designed hose-shaped. Fuel injection valve according to one of the preceding claims, characterized in that the sealing elements ( 56 ) flush with the respective ends of the plastic extrusion ( 50 ) to lock. Fuel injection valve according to one of claims 1 to 3, characterized in that at least one sealing element ( 56 ) via a respective end of the plastic extrusion ( 50 ) presenting face ( 58 . 60 . 64 protrudes). Fuel injection valve according to one of the preceding claims, characterized in that the sealing element ( 56 ) in a circumferential groove ( 62 ) of the valve housing is inserted.