WO2010000514A1 - Solenoid valve for controlling an injection valve of a fuel injector - Google Patents

Abstract

The invention relates to a solenoid valve (1) for controlling an injection valve of a fuel injector, comprising a magnet armature (2) for actuating a valve element, said magnet armature being movable by means of an electromagnet (5) comprising a magnetic core (4), and further comprising a disc (12) arranged axially between the magnetic core (4) and the magnet armature (2). According to the invention, an at least approximately linear contact surface (16) is implemented between the magnetic core (4) and the disc (12) or between the magnet armature (2) and the disc (12).

Description

description

title

Solenoid valve for controlling an injection valve of a fuel injector

State of the art

The invention relates to a solenoid valve for controlling an injection valve of a fuel injector according to the preamble of claim 1.

From DE 10 2004 013 239 Al a designed as a servo valve (control valve) solenoid valve for a fuel injector Inj is known. With the help of the solenoid valve, the fuel pressure is controlled in a control chamber of the fuel injector. Via the fuel pressure in the control chamber, a stroke movement of an injection valve element is controlled, with which an injection opening of the fuel injector is opened or closed. The solenoid valve comprises an electromagnet, a movable armature and a control valve element moved with the armature and acted upon by a valve closing spring in the closing direction, which cooperates with the valve seat of the solenoid valve and thus controls the fuel drain from the control chamber. The force is generated via the air gap field of a pot magnet, the magnetic field via an inner pole, a yoke, an outer pole, which together form a magnetic core, further includes a Außenpolseitigen air gap, a movable armature plate and a innenpolseitigen air gap to the current-carrying coil. In order to produce solenoid valves for common rail injectors as inexpensively as possible, it is known to form the stroke stop of the magnet armature on the magnetic core. In order to reduce the effect of hydraulically bonding the magnet armature to the magnet core, it is known to introduce a stepped step into the inner pole face of the magnet core or into the pole face of the armature in order to reduce the contact area between the magnet armature and the magnet core and thus the hydraulic adhesive effect. The dimensioning of the contact surface is difficult, since on the one hand to minimize the magnetic and hydraulic bonding a small contact surface is required, but this can lead to bouncing of the valve element upon reaching its Hubanschlages. Another problem is to guarantee the durability of the pole faces, especially when the magnetic core is made of a comparatively soft material. Here are often costly additional measures to improve the durability of the stop surfaces necessary.

Another way to ensure a low residual air gap, is the insertion of a non-magnetic disk between the magnetic core and the armature. Such a known solenoid valve is shown in FIG. A section of the cup-shaped magnetic core 100 with its radially inner inner pole 101, its radially outer outer pole 102 and the magnet coil 103 received between inner pole and outer pole can be seen. Between the inner pole 101 and an armature plate 104 of a magnet armature 105, a disc 106 is made of non-magnetic Material that has a residual air gap marked S between a pole face 107 of the outer pole 102 of the magnetic core 100 and a ner opposite, arranged parallel to the pole face 107 pole surface 108 guaranteed.

In the solution shown, it may come at a closing operation of the solenoid valve for adhering the disc 106 on the armature 105 and / or the magnetic core 100, wherein the characteristic of the adhesive refilling the gap between the armature plate 104 and the magnetic core 100 and thus the closing operation of the solenoid valve affected. The result is variable valve dynamics during the closing process from activation to activation and / or from fuel injector to fuel injector and / or over the service life of the fuel injector.

DISCLOSURE OF THE INVENTION Technical Problem

The object of the invention is to propose a solenoid valve, which is improved with regard to the dynamics of the switching processes and designed as a control valve for a fuel injector, in which a disk is provided between its magnetic core and its magnet armature to ensure a residual air gap. Furthermore, the object is to propose a fuel injector with a correspondingly improved solenoid valve.

Technical solution

This object is achieved with regard to the solenoid valve having the features of claim 1 and with regard to the fuel injector having the features of claim 11. Advantageous developments of the invention are specified in the subclaims. Fall within the scope of the invention all combinations of at least two features disclosed in the description, claims and / or figures.

The invention is based on the idea of either forming the contact surface between the magnet armature and the disk or the contact surface between the disk and the magnetic core in a linear manner in order to prevent the disk simultaneously from abutting the magnetic core and the magnet armature over the entire surface. As a result, the adhesion of the disc to the armature or the magnetic core is significantly reduced, whereby a defined, stable dynamic switching behavior of the solenoid valve is obtained. As a linear contact surface is preferably understood a contact surface whose width, ie radial extent less than lmm, preferably less than 0.5mm, preferably less than 0.4mm, more preferably less than 0.3mm, most preferably less than 0.2mm. Of particular advantage is an embodiment in which the radial extent of the linear contact surface is less than 0.1 mm, preferably less than 0.07 mm, particularly preferably less than 0.05 mm. Most preferably, the width of the contact surface is in a range between 0.01 mm and 0.05 mm. In order to minimize the negative effect of Steuerventilelementprellern, the shape of the contact surface forming components should be chosen so that shortly before reaching the stop, so shortly before making contact between the disc and the magnetic core or the disc and the armature a very close Gap formed between the corresponding two components from which the fuel must be displaced, resulting in a reduction the impact speed and thus to a minimization of bouncing leads.

To realize a linear contact surface between see the magnetic core and the magnetic core facing the disc surface, it is preferable to perform the pole face of the magnetic core convex, in particular as an outer cone. In this way it can be achieved that the magnetic core rests with a radially inner region on the, in particular flat disc. Preferably, the convexity of the pole face extends over both an inner pole surface and an outer pole surface. With such a construction, since the distance between the magnetic core and the armature in the region of the outer pole slightly increases as compared with a flat Polflächengeometrie, a slightly increased current is required to hold the solenoid valve against a closing spring force in the open state. An increased power consumption can be avoided if the pole face of the magnetic core is not convex, but concave, preferably designed as an inner cone, so the magnetic core preferably rests in the radially outer disc region on the disc.

In an analogous manner, a linear contact surface between the pole face of the magnet armature, in particular between the armature plate of the magnet armature, and the magnet armature facing surface of the disc can be realized. Either the pole face of the armature is this convex, in particular as an outer cone, or concave, in particular formed as an inner cone, both the geometry of the pole face of the magnetic core and the geometry of the pole face of the magnet armature can be realized by grinding, in particular as the last process step. In the case of the two embodiments with convex or concave magnetic core pole surface or convex or concave magnet armature pole surface described above, it is preferred if the axial slice thickness of the disk is constant over its radius.

To realize a sufficiently narrow hydraulic nip, is displaced from the fuel just before the end of the opening movement of the magnet armature by the adjustment of the armature, it is preferred in the case of forming one of the pole faces as an outer cone or inner cone, the cone angle from a range between about 177 ° to about 179.8 ° to choose.

A convex or concave grinding of the pole face of the magnetic core or the pole face of the magnet armature can alternatively be avoided in that the axial slice thickness increases or decreases in the radial direction from radially inward to radially outward. It is particularly preferred if only one of the flat side surfaces is convex or concave inclined or bent and the respective other flat side surface is formed flat. In one embodiment with changing axial slice thickness over the radius of the disc, both the pole face of the magnetic core and the pole face of the magnet armature can be shaped flat.

Particularly preferred is an embodiment of the Magnetven- tils, in which the pole face of the magnetic core and the pole face of the armature are finally processed by grinding. In other words, preference is given to alternative ve, elaborate processing steps to optimize the pole faces omitted.

In a further development of the invention is advantageously provided that the contact surface is annular, in particular annular contoured.

Preferably, the shape of the magnetic core, the magnet armature or the disc is selected so that the remaining maximum with open solenoid residual air gap between the armature and the magnetic core about 1.05 times to about 3-fold axial extent of the maximum axial slice thickness. This ensures that the obtained nip is sufficiently narrow to ensure a considerable lessening of speed before striking two magnetic components at the end of the opening movement.

In particular, when the armature is not rotationally symmetrical, but is designed with recesses on the outer edge, a circumferentially interrupted broken linear contact surface, whereby the adhesion of the disc on the magnet armature or the disc on the magnetic core is additionally reduced. If the flatness deviation of the pole face of the magnet armature or of the pole face of the magnet core is kept low, shortly before reaching the stop, there is nevertheless a very narrow gap between the magnet core and the disk or magnet armature and the disk from which the fuel must be displaced to avoid control valve element preller.

Preferably, the disc is formed of an amagnetic material. Basically, to reduce the current if necessary, the disc in the inventive design of the magnetic circuit also be made of magnetic material. The reason for this is that now a flat contact of the disc is excluded both on the magnetic core and on the anchor plate.

The invention also leads to a fuel injector, in particular a common rail injector, for injecting fuel into a combustion chamber of an internal combustion engine. According to the invention, the fuel injector has a solenoid valve designed according to the concept of the invention as a control valve for controlling the fuel pressure in a control chamber. By the variation of the fuel pressure in the control chamber, a one-piece or multi-part, consisting for example of a control rod and a nozzle needle injection valve element, between a closed position and the fuel flow from a nozzle hole arrangement releasing opening position can be adjusted.

Brief description of the drawings

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. These show in:

1 is a fragmentary, schematic representation of the basic structure of a possible embodiment of a solenoid valve, wherein the armature has an outer conical surface, Fig. 2: an alternative embodiment of a solenoid valve in which the pole face of the magnet armature is concave and curved, and

Fig. 3: a solenoid valve according to the prior art.

Embodiments of the invention

In the figures, the same components and components with the same function with the same reference numerals.

In Fig. 1, a first embodiment of a control valve designed as a solenoid valve 1 for a fuel injector, not shown, known per se, the basic structure of such a fuel injector results, for example, from DE 10 2004 013 239 Al the It should hereby be disclosed as belonging to the disclosure of the present application with respect to a possible embodiment of the fuel injector.

The solenoid valve 1 comprises an axially adjustable magnet armature 2 with a radially extending armature plate 3. Centric to the magnet armature 2 is not shown, in particular bolt-shaped or sleeve-shaped control valve tilelement can be fixed. Alternatively, an embodiment can be realized in which the armature 2 is integrally connected to a control valve element. By axial displacement of the armature 2 relative to a magnetic core 4th For example, the control valve element, not shown, can be adjusted between an open position and at a closed position adjoining a control valve seat (not shown).

To adjust the armature 2, a solenoid 5 designed as a magnet is provided, comprising a radially inner inner pole 6 and a radially spaced, radially outer pole 7, wherein the inner pole 6 and outer pole 7 are connected to each other via a yoke 8 in the radial direction. Pole 6, yoke 8 and outer pole 7 together form the magnetic core 4 of the solenoid valve 1. In a circumferential groove-shaped recess 10 in the magnetic core 4, an electric solenoid 11 is received. When current flows through the magnetic coil 11, a magnetic field is generated, which via the inner pole 6, the yoke 8, the outer pole 7 via a Außenpolseitigen residual air gap S, the axially adjustable armature 2, a disposed between the inner pole 6 and armature 2 disc 12 of an amagnetic material to the current-carrying solenoid coil 11 (winding) closes. When current is applied to the magnetic coil 11, the armature 2 is moved into the open position shown in the drawing plane. In this, the disc 12 is located with a first, in the drawing level upper, annular surface 13 on also flat inner pole 6 of the magnetic core 4 at. Between a second, in the plane of the drawing lower surface 14 which extends parallel to the first surface 13 and the armature 2, more precisely a magnetic core 4 facing pole face 15 of the anchor plate 3 and the disc 2, an annular contact surface 16 is formed. This is formed on the one hand by an annular, linear portion of the second, in the drawing plane lower, flat surface 14 of the disk 12 and a radially inner edge 17 (minor-shaped contact surface) of the armature 2. From Fig. 1 it follows that the pole face 15 of the armature plate 3 of the magnet armature 2 is convex. Here, due to the ease of manufacture, an outer conical shape is realized. The outer conical contouring of the anchor plate 3 and the pole face 15 was realized by a final grinding process in the manufacture of the magnet armature 2. It can be seen that the contact surface 16 is arranged at a radial spacing radially inward relative to the radially inner edge of the inner pole 6. The cone angle of the outer cone-shaped pole face, which is not denoted by a reference mark, is approximately 179.5 ° in the exemplary embodiment shown, and is chosen such that the nip gap forming between the pole face 15 and the disk 12 when closing is narrow enough to achieve sufficient speed reduction of the armature 2 to achieve before striking by displacing fuel.

In an alternative embodiment, not shown, the pole face 15 of the armature plate 3 of the magnet armature 2 can be formed flat and not convex, in which case the axial thickness D of the disc 12 changes from radially outward to radially inward, namely decreases. Even with such an embodiment, a linear contact surface is formed. Embodiments are also feasible in which not the pole face 15 but an inner pole face 18 and / or an outer pole face 19 are convex or concave in order to realize a linear contact surface between the magnetic core 4 and the pane 12. For ease of manufacture, it is advantageous if the entire pole surface formed by the inner pole surface 18 and the outer pole surface 19 9 is continuously convex or concave in the radial direction.

In a further alternative, also not shown embodiment, the pole face 15 of the armature plate 3 of the magnet armature 2 can be formed flat and not convex, and instead the pole face 9 of the magnetic core 4 are convex and not formed flat, in which case the axial air splitter extension S changed from radially outward to radially inward changes, namely decreases. Even with such an embodiment, a linear contact surface is formed. Embodiments in which not the pole face 15 but an inner pole face 18 and / or an outer pole face 19 are formed convexly or concavely in order to realize a linear contact face between the magnet core 4 and the pane 12 are also possible. To facilitate manufacturability, it is advantageous if the entire pole surface 9 formed by the inner pole surface 18 and the outer pole surface 19 is formed continuously convex or concave in the radial direction.

To close the solenoid valve, the energization of the solenoid 11 is interrupted, whereupon the armature 2 is moved by the closing spring force F _VFK , a closing spring not shown in the drawing _plane , down to the valve seat, not shown, whereby a flow channel, not shown, is closed from a control chamber ,

2, an alternative embodiment of a solenoid valve 1 is shown. The mode of operation corresponds to the exemplary embodiments shown in FIG. 1 and described above, so that in order to avoid repetitions in the case of Reference is made to similarities to the embodiment described above. The only difference with the previously described magnetic valve 1 is that the pole face 15 of the magnet armature 2 is not convex, but concave, so that a line-shaped contact surface 16 is formed between a radially outer edge of the disk 12 and the pole face 15 formed. It can be seen that the pole face 15 has a bent geometry. Alternatively, it is possible to realize the concave pole face 15 by means of an inner cone shape. A similar effect as in the embodiment of FIG. 2 can be achieved when the pole face 15 is made flat, but the axial slice thickness D increases from radially inward to radially outward.

Similarly, a similar effect as in the embodiment of FIG. 2 can be achieved when the pole face 15 is made flat, the disc 12 is designed with a constant thickness D and instead the entire pole face 9 or at least one of the pole faces 18, 19 of the magnetic core 4th is executed concave.

Claims

claims 1. Solenoid valve for controlling an injection valve of a fuel injector, comprising a magnet armature (2) movable by means of an electromagnet (5) comprising a magnet core (4) for actuating a valve element and having an axially between the magnet core (4) and Magnetic armature (2) arranged, disc (12), characterized, in that an at least approximately, linear contact surface (16) is realized between the magnetic core (4) and the disk (12) or between the magnet armature (2) and the disk (12). 2. Solenoid valve according to claim 1, characterized in that a pole face (9) of the magnetic core (4) for realizing a linear contact surface on the disc (12) convex, in particular as an outer cone, or concave, in particular as an inner cone, is formed. 3. Solenoid valve according to one of claims 1 or 2, characterized in that a pole face (15) of the magnet armature (2) for realizing a linear contact surface on the disc (12) convex, in particular as an outer cone, or concave, in particular as an inner cone formed is. 4. Solenoid valve according to one of the preceding claims, characterized in that the axial slice thickness (D) is constant over its radius. 5. Solenoid valve according to one of claims 1 to 3, characterized in that the axial disc thickness (D) decreases from radially inward to radially outward or from radially outward to radially inward. 6. Solenoid valve according to claim 5, characterized in that the pole face (9) of the magnetic core (4) and the pole face (15) of the magnet armature (2) are flat. 7. Solenoid valve according to one of claims 2 to 6, characterized in that the pole face (9) of the magnetic core (4) and the pole face (15) of the magnet armature (2) are finally processed by grinding. 8. Solenoid valve according to one of the preceding claims, characterized in that the contact surface (16) is annular, in particular annular. 9. Solenoid valve according to one of the preceding claims, characterized in that the maximum residual air gap (S) between the armature plate (3) and the magnetic core (4) about 1.05 times to about 3-fold axial extent of the maximum axial slice thickness (D ) having. 10. Solenoid valve according to one of the preceding claims, characterized in that the line-shaped contact surface (16) of mutually circumferentially spaced apart line-shaped partial contact surfaces is formed. 11. Solenoid valve according to one of the preceding claims, characterized in that the disc 12 is made of a non-ferromagnetic material. 12. Fuel Inj ector with a solenoid valve (1) according to one of the preceding claims for pressure relief of a between a closed position and the fuel flow in a combustion chamber of an internal combustion engine releasing opening position adjustable injection valve element.