EP1805409B1 - Fuel injector actuated by an electromagnetic valve, with a hydraulic overtravel stop - Google Patents

Abstract

The invention relates to an electromagnetic valve for actuating a fuel injector by means of a closing element (13) via which a discharge throttle (14) of a control chamber (15) can be released or closed. An armature plate (7) is moveably mounted on an armature pin (6) and secured by a stop (5). A magnet (2) is arranged opposite the armature plate (7) and at least one overflow channel (26) is provided inside the armature plate (7), said overflow channel connecting hydraulically the discharge throttle chamber (34) to the control chamber (35), thereby forming a hydraulic cushion underneath the armature plate (7).

Description

Technical area

Solenoid valves can be used on fuel injection systems for actuating fuel injectors. For this purpose, the solenoid valves comprise an electromagnet embedded in the injector body, which cooperates with an armature group comprising an anchor bolt and an armature plate. The anchor bolt is configured such that a closing body is received thereon, which closes or releases an outflow of a control chamber actuating the nozzle needle of the fuel injector. To achieve a precise lifting movement of the armature group upon energization of the electromagnet is a reliable and backlash-free connection of anchor plate and anchor bolts in two-piece anchor assemblies or anchor guide sleeve and anchor bolts in one-piece anchors required.

State of the art

DE 196 50 865 A1 refers to a solenoid valve. Its anchor is designed in several parts. The armature includes an armature disc and an anchor bolt which is guided in a slider. To avoid ringing of the armature disk after closing the solenoid valve, a damping device is designed on the magnet armature. With such a device exactly the required short switching times of the solenoid valve are sustainable and also reproducible. This solenoid valve is intended for use in injection systems, in particular high-pressure injection systems such as those with high-pressure accumulator (common rail).

A damping device, with which a Nachschwingen the first anchor member is attenuated in its dynamic displacement, comprising a first anchor member which includes an axially facing approach, which is complementary to the neck, fixedly arranged recess of a slider in a displacement of the first anchor member can dive. In this case, the recess with the approach includes a damping chamber, which has a leak gap connection with a surrounding relief space.

Alternatively, an annular shoulder can be arranged on the anchor bolt, which is enclosed by a part of the first anchor member and on the first anchor member also an annular shoulder is mounted, between the and the annular shoulder of the anchor bolt constantly a damping space is included, in turn, via a leakage gap to a connection having a discharge space surrounding it.

According to this solution with an actuatable by an electromagnet, two-piece anchor, a stop ring is inserted between the anchor bolt and the anchor plate. The stop ring is designed as an open lock washer and tends to knock out. It can occur more severe signs of wear, which can lead to a self-adjusting game between anchor bolt and anchor plate and the other to complete destruction of the lock washer. A self-adjusting game between anchor bolt and anchor plate affects the quantity tolerances in the injection adversely, so that in particular a reproducibility is no longer given at short intervals successive injections smallest amounts.

Out DE 101 33 450 A1 is a solenoid valve with a plug-in rotary connection known. The solenoid valve is used on a fuel injector for injecting fuel into the combustion chamber of an internal combustion engine, wherein the fuel injector comprises an injector body and an electromagnet. With this an armature assembly of the solenoid valve for depressurizing a control chamber is actuated, so that a present in the injector nozzle needle assembly performs an opening or a closing movement. The anchor group includes a first and a second anchor part. The first anchor part and the second anchor part are joined together by a plug-in rotary connection, wherein one of the anchor parts is encompassed by an armature guide containing a rotation lock.

EP 0 851 114 A2 discloses a solenoid valve with a spring-loaded, slidably received on an anchor bolt anchor plate, wherein a nip under the anchor plate causes a hydraulic damping.

In today known solenoid valves, which are used in connection with fuel injectors in injection systems for fuel supply, the armature stroke is set by adjusting rings which define the axial position of a corresponding anchor stop. About the armature or the movement of the armature in the axial direction, the opening of a nozzle of the fuel injector and thus the injected fuel quantity is set. When assembling a solenoid valve or a fuel injector, the components that determine the armature stroke, measured and based on the results of measurement is required for a given predetermined armature stroke Dimensioning of a setting ring calculated. A magnet group is then screwed together with the adjustment ring dimensioned according to the calculation in the injector body and then the armature stroke is measured with a screwed or braced state. For use in ultrahigh-pressure injection systems tolerances in the micrometer range tolerable at most tolerances for the armature stroke to ensure a reproducible injector behavior. Due to the permitted only slight tolerance deviation, the armature stroke is not always within the tolerance values after a first assembly, as described above. In order to then ensure the adjustment of the armature stroke within the narrow tolerance values, the magnet group must be completely disassembled and be reset by selecting a ring of a different dimensioning of the armature stroke. If necessary, this process must even be repeated several times until an acceptable tolerance compliance of the armature stroke is achieved.

Presentation of the invention

According to the invention it is proposed to reduce, if not completely prevent, the impact of an over-stroke disk on the anchor bolt in order to minimize the influence of quantity and of scattering in injection events occurring shortly after one another. A previously used for this purpose over-stroke spring is replaced by a hydraulic cushion.

When closing a solenoid valve, the components anchor bolt and anchor plate of a two-piece anchor assembly move together towards the valve seat. When the closure member, which may be formed, for example, as a ceramic ball, impacts the valve seat, the anchor plate and anchor bolt separate. The anchor plate can swing through into an overstroke area. Due to the separation of anchor bolt and anchor plate during the closing process, the impulse force and thus the "closing bounce" is reduced. The previously used overstroke spring pushes the armature plate before the next injection back to its original position. Now, if injections take place at short intervals before a previously used overstroke spring has returned the anchor plate to its original position, the quality of injection quantity and injection scattering deteriorates. By inventively proposed, formed in the interior of the anchor bolt overflow channels, there is now a hydraulic connection to initiate a controlled via an outlet throttle amount of fuel from the drain throttle in a hydraulic space. The fluid flowing through the transfer passages, that is to say the fuel, discharges into the additional hydraulic space above a stationarily mounted anchor bolt guide. For this purpose, the outlet opening or the outlet openings open at several overflow channels, in the area between the top of the stationary mounted anchor bolt guide and below a neck portion of the anchor bolt movably received anchor plate. The emerging from the outlet opening of the one or more transfer ports fuel builds between an upper end face of the stationarily mounted anchor bolt guide and the underside of a neck region of the anchor plate on a hydraulic cushion, which dampens the armature plate movably guided on the anchor bolt.

A chamfer is preferably formed on the neck region of the anchor plate on the side of the neck region facing the end face of the stationary anchor bolt guide. The chamfer runs in the radial direction from outside to inside and is bounded by a chamfer edge. By such a chamfer formed on the underside of the neck portion of the anchor plate, the outflow of fuel, which enters via the outlet opening or the outlet openings on the lateral surface of the anchor bolt between the stationary anchor bolt guide and the bottom of the neck area in the other hydraulic space, from the by a Conical surface and a bevel edge limited arrangement avoided. This always leaves a fluid supply in the limited by the conical surface of the chamfer and the chamfer edge and the lateral surface of the anchor bolt space, which then acts on the anchor plate.

By inventively proposed solution, a restoring force is exerted on the armature plate guided on the anchor bolt, which, however, does not always act permanently on the anchor plate. Only in the open state of the ball-shaped closing element and immediately after the closing of the closing element, that is its concerns on the valve seat, a restoring force is present, which thus reduces or dampens the impact of the anchor plate formed on a sickle disk stop.

drawing

With reference to the drawing, the invention will be described below in more detail.

Figur 1

ein aus dem Stand der Technik bekanntes Magnetventil zur Ansteuerung eines Kraftstoffinjektors, mit einer Überhubfeder, die zwischen der Ankerplatte und einer Ankerbolzenführung stationär aufgenommen ist,

Figur 2

eine erste Ausführungsvariante der erfindungsgemäß vorgeschlagenen Lösung mit im Ankerbolzen ausgebildeten Überströmkanälen zur hydraulischen Verwendung eines Ablaufsteuerraumes mit einem weiteren hydraulischen Raum, und

Figur 3

über die Zeitachse aufgetragene Bewegungszeiten einer Ankerplatte, die über eine Überhubfeder beaufschlagt ist sowie mit einem hydraulischen Polster gedämpft wird.

It shows:

FIG. 1

a known from the prior art solenoid valve for controlling a fuel injector, with an overstroke spring, which is received stationary between the anchor plate and an anchor bolt guide,

FIG. 2

a first embodiment of the proposed solution according to the invention with formed in the anchor bolt overflow channels for the hydraulic use of a flow control room with another hydraulic space, and

FIG. 3

Applied over the time axis movement times of an anchor plate, which is acted upon by a Überhubfeder and is damped with a hydraulic pad.

variants

The representation according to FIG. 1 is to be taken from a known from the prior art solenoid valve whose armature plate is acted upon by an overstroke spring, which in turn is supported on a stationary, arranged in the injector anchor bolt guide.

This in FIG. 1 shown solenoid valve 1 comprises a magnet 2, which is accommodated in the valve housing 4. The magnet 2 encloses a closing spring 3, which acts on an upper end face of an anchor bolt 6. Above an anchor plate 7, a mechanical stop 5 is provided, which may be formed for example as a sickle disc and the upper stroke limit for the armature pin 6 movably received anchor plate 7 represents. The anchor plate 7 in turn is acted upon by an overstroke spring 8, which is supported on an anchor bolt guide 10. The anchor bolt guide 10 is fastened in the valve housing 4 via a valve clamping screw 9. In the anchor bolt guide 10, one or more holes 16 may be formed, which allow the overflow of fuel in the leakage region of the fuel injector. About the valve clamping screw 9, the anchor bolt guide 10 is employed on a valve member 11.

The anchor bolt 6 with an armature plate 7, which is held movably thereon, comprises a spherical cap 12, in which, in the illustration according to FIG FIG. 1 Spherically shaped closing element 13 is inserted, which may be, for example, a ceramic ball. The ceramic ball is placed by the anchor bolt 6 in a valve seat and thus closes an outlet throttle 14, via which a control chamber 15 of an in FIG. 1 Not shown fuel injector is pressure relieved.

With the in FIG. 1 illustrated, known from the prior art design of a solenoid valve, in particular at short injection intervals of <800 microseconds between pilot injection and main injection, a significant increases in the absolute quantities and to observe a large increase in the scatters between two main injections when the anchor plate 7 impacts on the stop 5 made as a sickle disk.

The representation according to FIG. 2 is a first embodiment of an inventively proposed Magnetankereinordnung refer to a solenoid valve for actuating a fuel injector. The FIG. 2 removable solenoid valve 1 comprises the magnetic coil 2, which is arranged opposite the top of the anchor plate 7. The armature plate 7 is movably received on the anchor bolt 6 via a stop 5 designed as a sickle disk, whose axis of symmetry is identified by reference numeral 22. The anchor bolt 6 is acted upon by the closing spring 3. The valve housing 4 serves to receive a valve clamping screw 9 provided with an external thread, via which the bolt guide 10 is fastened in the valve housing 4.

The bolt guide 10 rests on an upper plane surface of the valve piece 11, in which the discharge throttle space 34 is formed, which has on its side facing the discharge throttle 14 a funnel 33 in which a valve seat 32 is formed. The valve seat 32 is shown in the illustration FIG. 2 closed by a spherical closure member 13 which may be formed, for example, as a ceramic ball. The closing element 13 is guided in a spherical cap 12 at the lower end of the anchor bolt 6. Below the valve seat 32 is located in the valve piece 11, the outlet throttle 14, via which the control chamber 15 is pressure relieved when the closing element 13 is open. In this case flows via the outlet throttle 14 of the valve housing 4, a Absteuervolumen of fuel from the control chamber 15 in the drain throttle chamber 34 a.

The anchor bolt 6 has at least one overflow channel 26. The at least one overflow channel 26 is acted upon by an inlet opening 27, which is executed in the lower portion of the anchor bolt 6, with fuel. The fuel flows with the closing element 13 open via the outlet throttle 14 from the control chamber 15 into the outlet throttle space 34 and from there via the inlet openings 27 into the at least one overflow channel 26. The or the overflow channels 26 each have an outflow opening 24. However, the overflow channels 26 can however also be formed in the anchor bolt 6 in such a way that all overflow channels 26 open into a common outflow opening 24.

The outflow opening 24 is in relation to the anchor bolt 6 so that it opens in the region between the end face 23 of the stationary anchor bolt guide 10 and below the anchor plate holder 20. This flows out of the overflow 26 exiting Fuel at a point in the Absteuerraum 35, in which advantageously a hydraulic pressure pad can be constructed.

In order to improve the damping properties, the armature plate neck 20 has a chamfer 21 on its end facing the end face 23 of the stationary anchor bolt guide 10. The chamfer 21 extends in a cone angle from outside to inside towards the lateral surface of the anchor bolt 6. The chamfer 21 is delimited by a chamfer edge 25, so that a space formed in accordance with the angle of inclination of the conical surface forms, which can be filled with the fuel volume leaving the outflow openings 24 of the overflow channels 26. Due to the formation of the chamfer 21, premature discharge of fuel from the damping pad is avoided. The number of overflow channels 26 on the anchor bolt 6 can be arbitrary, but is limited by the fact that the overflow 26 should not represent hydraulic throttles and therefore should be sufficiently large in terms of their diameter. The number of overflow channels 26 that can be formed on the anchor bolt 6 depends on the diameter of the anchor bolt 6 and on the production possibilities. Each of the transfer ports 26 has its own discharge port 24 so as not only to utilize the static cushion formed in the hydraulic space surrounding the anchor bolt 6, but also to utilize an additional dynamic upstream force. A symmetrical arrangement of the overflow 26 at the periphery of the anchor bolt 6 is advantageous to minimize lateral forces in the guides between anchor bolt 6 and armature guide 10 and anchor bolt 6 and anchor plate 7.

The hydraulic cushion above the end face 23 of the stationary anchor bolt guide 10 and below the chamfer 21 on the neck portion 20 of the anchor plate 7 is not permanently on, but is effective only in the open state of the closing element 13 and immediately after closing the closing element 13, that is, after this has reached the valve seat 32. With the proposed solution according to the invention, a bouncing of the upper plane of the anchor plate 7 can be significantly attenuated to the underside of the serving as a stopper sickdle 5. Reference number 30 shows the return flow quantities flowing from the outlet throttle control space 34 into the further hydraulic space 35, while reference number 31 designates the fuel volume leaving the discharge opening or openings 24, which serves to dampen the movement of the armature plate 7.

In particular, at short intervals between successive injection operations, the anchor plate 7 can be quickly returned by the emerging from the or the discharge ports 24 fuel back to its original position, wherein the striking of the upper plane of the anchor plate 7 on the executed as a sickle disc stop. 5 with a relatively small pulse. Advantageously, it is utilized that the flow of the Absteuermenge within the discharge throttle chamber 34 is present shortly after the closing of the valve seat 32 by the closing element 13. In contrast, the relatively small leakage quantities of nozzles and valve guide are permanently available.

Due to the fuel flowing through the flow process of the Absteuermenge in the discharge throttle space 34 in the transfer ports 26 and the leakage of fuel through the discharge port 24 between the end face 23 and bevel 21 can quickly return the armature plate 7 in its initial position. Due to the small self-adjusting leakage amount, indicated by the arrow 31, the anchor plate 7 can impinge on the designed as a sickle disk stop 5 and held there with only a small pulse. With reference numeral 31, the second return amount is referred to, which flows from the annular channel above the anchor bolt guide 10. The return movement of the armature plate 7 to the stop 5 takes place with progressive stroke and decreasing axial force in the direction of the starting position, so that a wear-causing impact of anchor plate 7 and stopper 5, which can be formed as a sickle disc, can be achieved. The amount of fuel exiting from the outflow openings 24 is so dimensioned that the armature plate 7 is returned to its initial position, ie in contact with the stop 5, until the next injection process. However, if the next injection process takes place earlier, different opening behavior leads to increased stroke / stroke spread of the injection quantities, which is highly undesirable. When closing the valve, which is indicated by the arrow A in FIG. 2 is indicated, dampens the dynamic flow of the emerging from the exhaust ports 24 fuel and the static amount of fuel contained in the annular channel above the anchor bolt guide 10, the swinging through the armature plate 7. A contact of the armature plate with the end face 23 of the anchor bolt guide 10 is not required but possible.

The representation according to FIG. 3 are the Hubverläufe an anchor plate removed, which is damped with a spring or as proposed by the invention with a hydraulic stop.

The curve identified by reference numeral 40 denotes the slope of a curve which describes the return speed of the armature plate 7 to its starting position. The curve increases with the first slope 40 to a turning point 45, at which the curve assumes a second slope 42, which is caused due to leakage flows 31.

Reference numeral 43 designates a speed which has an armature plate 7 when it is reset by an overstroke spring (compare overstroke spring 8 in the illustration according to FIG FIG. 1 ). Due to the spring force that builds up only slowly, the return movement of an armature plate 7 acted upon by the overstroke spring 8 takes place substantially more slowly. With reference numeral 44 a self-adjusting overswing is characterized, as seen over the time axis, asymptotically decaying. By ÜH the entire overstroke is characterized, the anchor plate must pass through 7, after a closing operation of the anchor bolt 6, that is placed in the valve seat 32 closing element 13, to reach their original position again, characterized by an investment in the form of a sickle disk stop 5 is.

In the provision of the anchor plate 7 by a spring force according to the curve 43 acts over the entire Überhubbereich ÜH the same force on the armature plate 7. The inventively proposed hydraulic reset acts due to the beginning of adjusting overflow and the tight leakage gap between the armature plate 7 and the anchor bolt guide 10 a large restoring force. After the valve closing in the direction of arrow A and after the anchor plate 7 and the anchor bolt guide 10 have moved further apart, only a small force keeps the anchor plate 7 in its initial position. In its initial position, the anchor plate 7 bears against the stop 5 designed as a sickle disk.

LIST OF REFERENCE NUMBERS

1

magnetic valve

2

magnet

3

closing spring

4

valve housing

5

Stopper (sickle plate)

6

anchor bolts

7

anchor plate

8th

travel spring

9

Valve clamping screw

10

Anchor bolt guide

11

valve piece

12

spherical cap

13

Closing element (ceramic ball)

14

outlet throttle

15

control room

16

overflow bore

20

Anchor plate neck

21

chamfer

22

axis of symmetry

23

Face Anchor bolt guide

24

outflow

25

Fasenrand

26

overflow

27

inflow

28

Overflow-tilt angle

29

inflow

30

first return quantity

31

second return amount

32

valve seat

33

funnel

34

Outlet throttle room

35

diversion chamber

40

first slope based on tax amount

42

second slope due to leakage amount

43

Gradient due to spring force

44

overshoots

45

turning point

ÜH

blowout

Claims (10)

1. Solenoid valve for the actuation of a fuel injector, with a closing element (13), via which an outflow throttle (14) of a control space (15) is releasable or closable, with an armature bolt (6) having an armature plate (7) which is received movably on the latter and is secured on the armature bolt (6), and with a magnet (2) arranged opposite the armature plate (7), characterized in that, in the armature bolt (6), at least one overflow duct (26) is formed, via which an outflow-throttle space (34) and a spill space (35) are connected hydraulically to one another for the build-up of a hydraulic cushion beneath the armature plate (7).
2. Solenoid valve according to Claim 1, characterized in that at least one outlet orifice (24) of at least one overflow duct (26) issues into the spill space (35) between one end face (23) and an armature-bolt guide (10) and beneath an armature-plate neck (20).
3. Solenoid valve according to Claim 2, characterized in that the armature-plate neck (20) has a chamfer (21).
4. Solenoid valve according to Claim 3, characterized in that a cone angle of the chamfer (21) runs radially from the outside inwards.
5. Solenoid valve according to Claim 3, characterized in that the chamfer (21) is delimited outwardly by a chamfer edge (25).
6. Solenoid valve according to Claim 1, characterized in that at least one inflow orifice (27) of at least one overflow duct (26) is acted upon by fuel contained in the outflow-throttle space (34).
7. Solenoid valve according to Claim 1, characterized in that overflow ducts (26) in the armature bolt (6) run at an inclination with respect to the axis of symmetry (22) of the armature bolt (6) by the amount of an inclination angle (28).
8. Solenoid valve according to Claim 1, characterized in that the closing element (13) is designed as a ceramic ball and is guided in a spherical cap (12) of the armature bolt (6).
9. Solenoid valve according to Claim 1, characterized in that it is designed with a two-part armature comprising an armature plate (7) and an armature bolt (6), and the armature plate (7) is arranged relatively movably with respect to the armature bolt (6), the armature plate (7) being hydraulically returnable against a stop (5) without an overstroke spring.
10. Use of a solenoid valve according to one or more of the preceding claims in a fuel injector on a common-rail high-pressure injection system.

Images