EP2307699A1

EP2307699A1 - Solenoid valve for a fuel injector and fuel injector

Info

Publication number: EP2307699A1
Application number: EP09772227A
Authority: EP
Inventors: Friedrich Howey; Dietrich Klauk
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-07-04
Filing date: 2009-05-05
Publication date: 2011-04-13
Anticipated expiration: 2029-05-05
Also published as: EP2307699B1; WO2010000527A1; DE102008040168A1

Abstract

The invention relates to a solenoid valve, especially a servo valve, for a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, comprising a magnet armature (2) which can be adjusted relative to a magnet assembly (3) comprising a magnetic core (6) mounted in a support body (4), said magnetic core comprising in a coil cavity (9) an electric coil (10) having at least two coil contact pins (14, 15), wherein a through-opening (21, 22) axially penetrating the magnetic core (6) is associated with each coil contact pin (14, 15). According to the invention, at least one of the through-openings (21, 22) is designed as a fuel return channel (23, 24). The invention also relates to a fuel injector.

Description

description

title

Solenoid valve for a fuel injector and fuel injector

State of the art

The invention relates to a solenoid valve, in particular a servo valve, for a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine according to the preamble of claim 1 and a fuel injector according to claim 11.

The fuel injector known from DE 10 2004 013 239 A1 comprises a solenoid valve designed as a servo valve for controlling the fuel pressure 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 a magnetic assembly having an electrical coil and a magnet armature which, when the magnet assembly is energized, is adjusted in the direction of the magnet assembly and is spring-loaded in the closing direction when the magnet assembly is not energized by means of a valve closing spring.

When opening the solenoid valve, a liquid volume is expanded and as so-called Absteuermenge over a

Fuel return port drained. The Absteuermenge is receiving a valve closing spring receiving Center bore guided centrally through the magnetic core to injector return port.

In order to minimize magnetic adhesion effects, it has become known to receive a stop disc (residual air disc) axially between the magnet assembly and the magnet armature which can be adjusted relative to the magnet assembly, the axial gap between the magnet assembly and the gap provided in DE 10 2004 013 239 A1 the hydraulic armature closes hydraulically, so that when the solenoid valve is open, the central bore is hydraulically decoupled. For supplying the Absteuermenge to Injektorrücklaufanschluss it is in the applicant as in-house state of the art for the case of providing a stop disc has become known to provide on the outer circumference of the magnetic core one or more, extending in the axial direction groove (s) through which the Absteuermenge can flow to the injector return in the axial direction between the magnetic core and sleeve-shaped carrier body. Due to a given minimum wall thickness of the magnetic core and a required minimum contact surface of the magnetic core on an annular shoulder of a carrier body with limited outer diameter of the magnetic core only a very limited flow is possible, so that diameter tolerances on the carrier body and the magnetic core strongly on the flow cross-section impact the grooves formed. Likewise, the bearing surface of the magnetic core on the carrier body is strongly limited, so that the risk of sinking of the magnetic core is given, which in turn may result in an undesirable change in position of the magnetic core in the carrier body, which would affect the function of the solenoid valve. DISCLOSURE OF THE INVENTION Technical Problem

The invention is therefore based on the object to propose an alternative Native solenoid valve, which is provided in a simple manner at least one fuel return passage with uncritical cross-sectional area. Furthermore, the object is to propose a fuel injector with a correspondingly optimized 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. All combinations of at least two features disclosed in the description, the claims and / or the figures fall within the scope of the invention.

The invention is based on the idea to form at least one of the axial, in the prior art cross-section of each a coil dome filled through holes in the magnetic core for the coil contact pins as fuel return passage through which fuel can flow in the direction of an injector return port with the solenoid valve open. An embodiment is preferred in which both passage openings for the coil contact pins (connecting pins) are designed as fuel return channels, that is to say with a cross-section widened in comparison with the prior art, in order to thus achieve a symmetrical flow pattern. Particularly An embodiment is preferred in which fuel return ducts formed on and in addition to the passage openings are formed by axial grooves formed on the outer circumference of the magnetic core and receive no spin contact pins, so that when the solenoid valve is open the fuel is essentially exclusively supplied by at least one of the in each case one coil contact pin receiving through holes in the magnetic core in the direction injector return port can flow. By forming at least one passage opening receiving a bobbin contact pin as a fuel return passage, fuel return passage cross sections which are sufficiently large and selectable over a wide range can be realized in a surprisingly simple manner which may have a positive effect on the characteristic map and the counterpressure sensitivity of the solenoid valve, in particular because the pressure difference between the pressure above and below the magnetic core can be better controlled. It is particularly advantageous that the diameter-enlarged, fuel return passages forming through holes for the coil contact pins can be introduced into the magnet core at no extra cost, in particular can be pressed into a green compact for a subsequent sintering process. This also has a positive effect on a possibly used for use pressing tool for the magnetic core, since this is more stable due to the larger compared to the prior art, to be produced Durchgangsöffnungsquerschnitte. In addition, in the design of the solenoid valve greater freedom to distribute the fuel return channel cross-section against a support body provided for the magnetic core bearing surface, with the result that the inner circumference of the support body can be narrower, ie designed with a smaller diameter. In a further development of the invention is advantageously provided that at least one of each a coil contact pin receiving through holes, preferably all through holes, either completely disposed in a region radially outside the axial projection surface of the magnet armature, or from a region radially inward to radially outward in extends an area outside the axial projection surface of the armature. In this way, with the solenoid valve open, an optimum fuel inflow path is provided to the corresponding port. In the case of providing a, in particular non-magnetic, stop disc (residual air disc) in a region axially between the magnetic core and the armature, it is preferred if the at least one, a coil contact pin having a fuel return passage and forming a passage opening in a region radially outward of the axial projection surface of the stop disc is arranged or extends at least in a region radially outside this.

A maximum flow cross-section of the at least one fuel return channel can be achieved by the at least one through-hole penetrated by a Spulenkontaktpin is guided radially outward to the outer periphery of the magnetic core, so that of the passage opening partially restricted fuel return passage radially outward of the, in particular sleeve-shaped, carrier body is limited.

In an alternative embodiment, the at least one passage opening forming the fuel return passage does not extend radially to the outer circumference of the magnetic return passage. kerns, so that the passage opening or the fuel return passage is bounded radially outwardly of the magnetic core. The latter embodiment has the advantage that a peripherally closed axial bearing surface for the magnetic core can be provided on the carrier body.

In a further development of the invention is advantageously provided that in addition to the coil contact pin a spool lendom is arranged in the penetrated by a Spulenkontaktpin through holes, in which the associated Spulenkontaktpin is also included in sections. In this case, the coil dome preferably extends from the annular coil receiving in the axial direction and encapsulates the Spulenkontaktpin sections in itself.

An embodiment is preferred in which the maximum circumferential extent of the at least one passage opening forming the fuel return passage corresponds at least approximately to the maximum circumferential extent of a through-hole which passes through the passage opening. In contrast to a solution with provided on the outer circumference of the magnetic core, extending in the circumferential direction Axialnuten hereby a fuel return passage can be achieved with much smaller circumferential extent, whereby a total of a larger contact surface of the magnetic core can be provided on the carrier body. The cross-sectional area of the passageway can be adjusted by the choice of the radial extent of the passageway.

Particularly preferred is an embodiment in which the minimum cross-sectional area of the at least one fuel return channel, ie the cross-sectional area, is closest Range of the fuel return channel at least 8 mm ² , in particular at least 9 mm ² , preferably at least 10 mm ² , more preferably at least 11 mm ² , more preferably at least 12 mm ² , so as to realize a generous outflow volume flow.

As already mentioned, an embodiment of the solenoid valve is preferred in which the armature does not abut directly against the magnet core, but against a stop disk (residual air disk) resting against the magnet core. In particular, in such an embodiment, it makes sense to further divert the Absteuermenge by at least one Spulenkontaktpin passage opening in the axial direction to the injector return, since the stopper plate hydraulically obstructs a central through hole in the magnetic core usually open solenoid valve.

Particularly preferred is an embodiment in which the axial contact surface of the magnetic core on the carrier body is greater than 30 mm ² . Preferably, the carrier surface on which the magnetic core can be supported on the carrier body is formed by an inner annular shoulder of the carrier body. The support surface is preferably greater than 40 mm ² , preferably greater than 50 mm ² , particularly preferably greater than 60 mm ² .

In particular, when the circumferential contour of the fuel return passage is at least approximately rectangular, a comparatively small tolerance dependence of the cross-sectional area of the fuel return passage is obtained.

The invention also relates to a fuel injector for injecting fuel into a combustion chamber of a combustion engine. engine with a, in particular as a servo valve ^¬ nenden, designed according to the concept of the invention solenoid valve. The solenoid valve is characterized in that at least one passage opening receiving a coil contact pin is designed as a fuel return passage. Preferably, both, each a coil contact pin on ^¬ receiving through openings are each formed as a fuel return passage. Very particular preference is given to no further axial fuel return ducts provided for ^¬ additionally to the one through-hole or the two through holes, is allowed to flow in the direction of injector return port through which fuel at geöff ^¬ NetEm solenoid valve from the side facing the magnet armature of the magnet core forth.

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 schematic representation of a trained as a servo valve solenoid valve for a fuel injector,

Fig. 2 is a perspective view of the magnet assembly of the solenoid valve of FIG. 1 and

Fig. 3 shows a magnetic assembly of an alternative magnetic ^¬ valve in a view of the pole faces. Embodiments of the invention

1 shows an incomplete and schematic illustration of a magnetic valve 1 for a fuel injector not shown in any more detail, known per se, for example as described in DE 10 2004 013 239 A1, for injecting fuel into a combustion chamber of an internal combustion engine shown. The solenoid valve 1 serves as a servo valve, with which the fuel pressure in a not shown, limited by an injection valve element control chamber is controllable. With the solenoid valve open, fuel can flow from the control chamber past a magnet armature 2 to an injector return port, not shown, arranged in the plane of the drawing above the solenoid valve 1.

The solenoid valve 1 comprises a magnet assembly 3, which is braced within the fuel injector, not shown. The magnet assembly 3 comprises a sleeve-shaped carrier body 4 made of steel, which has a radially inner annular shoulder 5. Within the carrier body 4, a magnetic core 6 is arranged, which is supported in the axial direction with an annular bearing surface formed by a Außenpolabschnitt 7 on the one support surface for the magnetic core forming annular shoulder 5. With radial distance to the Außenpolabschnitt 7 is an inner pole section 8. Außenpolabschnitt 7 and Innenpolabschnitt 8 are connected via a not visible in the sectional view of FIG. 1, annular yoke portion together. The yoke section, the outer pole section 7 and the inner pole section 8 delimit an annular groove-shaped coil recess 9, which is open in the direction of the magnet armature 2. Within the Spulenausnehmung 9 is an electric coil 10 (magnetic coil), which generates a magnetic field when energized, which causes an adjustment movement of the armature 2 in the direction of the magnet assembly 3.

The electrical coil 10 comprises a winding support 11 which carries a wound winding wire 13 in an axially lower, groove-shaped section 12. Furthermore, two coil contact pins 14, 15 pointing in the axial direction are anchored in the winding support 11 and are electrically contacted with the winding wire 13 in a region axially above the winding support 11. For this purpose, the coil contact pins 14, 15 are partially wrapped by the winding wire 13, wherein the wrapped areas are each surrounded by a copper sleeve 16, 17 (welding sleeves). Each copper sleeve 16, 17 is arranged in a coil mandrel 18, 19, wherein the coil mandrels 18, 19 extend in the axial direction beyond the annular groove-shaped Spulenausnehmung 9 in the direction of the drawing plane up through later to be explained through holes 21, 22 therethrough , As is apparent from Fig. 1, the copper sleeves 16, 17 and the winding wires 13 are received in a Kunststoffvergussmasse 20 which closes the winding wires 13 fuel-tight and forms a main component of the coil mandrels 18, 19.

As is further apparent from FIG. 1, each coil contact pin 14, 15 is associated with an aforementioned axial through opening 21, 22 in the cup-shaped magnet core 6, through which the coil contact pin 14, respectively, passes, in each case through a coil mandrel 18, 19. 15 is led out in the axial direction of the magnetic core 6. Each axial passage opening 21, 22, which extends from an axially lower end side to an axially upper end side of the magnetic core 6, is formed in a radially outer region as a fuel return passage 23, 24, through the fuel with open solenoid valve 1 in the plane of the drawing in the axial direction can flow upward to an injector return not shown.

As can be seen from FIG. 1, the magnet armature 2 with its upper armature plate section 25 in the plane of the drawing can not abut directly on the magnet core 6, more precisely on an inner pole surface 26 or outer pole surface 27 of the magnet core 6, but only on one axially between the armature core 6 Magnetic core 6 and the armature plate portion 25 of the armature 2 arranged stop plate 28 made of an amagnetic material. This closes when the solenoid valve is open, a central passage 29 in the magnetic core 6, which is bounded radially outward by the Innenpolabschnitt 8 of the magnetic core 6. When the solenoid valve 2 is open, the fuel thus flows in the axial direction past the fuel return ducts 23, 24 formed by the passage openings 21, 22, which in the exemplary embodiment shown are radially inward of the electric coil 10 in the circumferential directions of the magnetic core 6, more precisely from the Außenpolabschnitt 7 and radially outside of the carrier body 4, are limited.

In the passage 29, a valve closing spring 30 is accommodated, which is supported in the axial direction, for example, on a Injektordeckel (housing part), not shown, and in the axial direction down the stop plate 28 by itself on the magnet assembly 3 facing end side of the armature 2 is supported. As is further apparent from FIG. 1, the fuel return passages 23, 24 extend from a radially inner region, which lies radially within an axial, not shown projection surface of the armature plate section 25 of the armature 2, into a radially outer region which is radial lies outside the mentioned, axial projection surface of the armature plate portion 25 of the armature.

In Fig. 2, the magnet assembly 3 is shown in FIG. 1 in a perspective view obliquely from below. Evident is the central passage 29, which does not serve here as a fuel return passage. Furthermore, the fuel return passages 23, 24 can be seen, which are bounded radially inward by the electric coil 10 and in the circumferential direction by the outer pole section 7. The fuel return ducts 23, 24 are formed in each case by a passage opening 21, 22 in the magnet core 6 open at the edge. It can be seen that the circumferential extent of the fuel return ducts 23, 24 substantially corresponds to the circumferential extent of the respective coil dome 18, 19. Only in the radial outward direction do the passage openings 21, 22 extend beyond the coil domes 18, 19. Furthermore, it follows from FIG. 2 that the cross-sectional contour of the fuel return ducts 23, 24 is formed substantially rectangular. Alternatively, for example, a pie-shaped (kreissegmentför-mige) formation can be realized.

FIG. 3 shows an alternative embodiment of a magnetic assembly 3 for a solenoid valve 1 of a fuel injector in a view from below. Evident is the central passage 29 of the radially outward of is limited to the Innenpolabschnitt 8, wherein radially between the inner pole portion 8 and a Außenpolabschnitt 7, an annular Spulenausnehmung 9 is formed. FIG. 3 shows that the electrical coil 10 is designed to be thickened at two points offset from one another by 180 °. Here, the coil contact pins 14, 15, not shown in FIG. 3, and the associated coil domes 18, 19 are arranged. It can also be seen that the thickened regions are accommodated in axial passage openings 21, 22 which form a fuel return passage 23, 24 radially outside the electrical coil 10 in each case. It can also be seen from FIG. 3 that the passage openings 21, 22 are not guided to the outer edge of the magnetic core 6, more precisely the outer pole section 7, but that the passage openings 21, 22 and thus the fuel return passages 23, 24 are bounded radially outward of the Außenpolabschnitt 7 of the magnetic core 6. This results in the advantage of a larger, peripheral, annular support surface of the magnetic core 6 on an inner annular shoulder (support surface) of a carrier body shown by way of example in FIG. 1.

Claims

claims

1. Solenoid valve, in particular servo valve, for a

Fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, with a

Magnetic armature (2), which is relative to a magnet assembly

(3) is adjustable, the one in a carrier body

(4) comprises a magnetic core (6) which has in an inductor recess (9) an electrical coil (10) having at least two coil contact pins (14, 15), each coil contact pin (14, 15) having a magnetic core (6). axially passing through opening (21, 22) is assigned,

characterized,

in that at least one of the passage openings (21, 22) is designed as a fuel return passage (23, 24).

2. Solenoid valve according to claim 1, characterized in that at least one of the passage openings (21, 22) is arranged in a region radially outside the axial projection surface of the magnet armature (2), or at least one of the passage openings (21, 22) into a Area extends radially outward of the axial projection surface of the armature (2).

3. Solenoid valve according to one of claims 1 or 2, characterized in that at least one of the passage openings (21, 22) extends radially outward to the outer periphery of the magnetic core (6), such that the fuel back running channel (23, 24) radially outwardly of the carrier body (4) is limited.

4. Solenoid valve according to one of claims 1 or 2, characterized in that at least one passage opening (21, 22) radially outwardly of the magnetic core (6) is limited.

5. Solenoid valve according to one of the preceding claims, characterized in that each coil contact pin (14, 15) in the corresponding passage opening (21, 22) recorded coil dome (18, 19) is assigned.

6. Solenoid valve according to claim 5, characterized in that the maximum circumferential extent of the passage opening (21, 22), at least approximately, corresponds to the maximum circumferential extent of the associated coil dome (18, 19).

7. Solenoid valve according to one of the preceding claims, characterized in that the minimum cross-sectional area of the at least one of the at least one passage opening (21, 22) formed fuel return passage (23, 24) at least 6 mm ² , in particular at least 8 mm ² , preferably at least 10th mm ² , preferably at least 11 mm ² , more preferably at least 12 mm ² .

8. Solenoid valve according to one of the preceding claims, characterized in that in that axially between the magnet assembly (3) and the magnet armature (2) a stop disc (28), preferably of a non-magnetic material, is arranged.

9. Solenoid valve according to one of the preceding claims, characterized in that the axial contact surface of the magnetic core (6) on the support body (4) is greater than 30 mm ² , in particular greater than 40 mm ² , preferably greater than 50 mm ² , more preferably greater than 60 mm ² .

10. Solenoid valve according to one of the preceding claims, characterized in that the inner peripheral contour of the fuel return passage (23, 24) is at least approximately rectangular.

11. Fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, with a, in particular designed as a servo valve, solenoid valve (1) according to one of the preceding claims.