EP1805409A1

EP1805409A1 - Fuel injector actuated by an electromagnetic valve, with a hydraulic overtravel stop

Info

Publication number: EP1805409A1
Application number: EP05801500A
Authority: EP
Inventors: Frieder Buerkle; Ralf Maier; Andreas Rettich; Heiko Seng
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-10-20
Filing date: 2005-10-07
Publication date: 2007-07-11
Anticipated expiration: 2025-10-07
Also published as: DE502005003034D1; DE102004050992A1; WO2006042798A1; EP1805409B1; JP2008517212A; ATE387577T1; JP4495761B2

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

Solenoid-operated fuel injector with hydraulic over-stroke stop

Technical area

Solenoid valves can be used on fuel injection systems for actuating fuel injectors. For this purpose, the solenoid valves comprise an electromagnet which is introduced into the injector body and which cooperates with an armature group which comprises an anchor bolt and an armature plate. The anchor bolt is designed such that a closing body is received on the latter, which closes or releases a drain of a control chamber actuating the nozzle needle of the fuel injector. To achieve a precise lifting movement of the armature group when the electromagnet is energized, a reliable and backlash-free connection of armature plate and anchor bolt in two-part armature assemblies or in armature guide sleeve and anchor bolt in one-piece anchors is required.

State of the art

DE 196 50 865 A1 relates to a solenoid valve. Its armature is in several parts ausgebil¬ det. The armature includes an armature disc and an anchor bolt which is guided in a slider. In order to avoid ringing of the armature disk after closing the solenoid valve, a damping device is provided 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 at a displacement of the first anchor - can partly immerse. 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 part and an annular shoulder is also attached to the first anchor part, between which and the annular shoulder of the anchor bolt a damping space is constantly enclosed, which in turn is enclosed by a Leak gap has a connection to ei¬ nem surrounding relief space.

According to this solution with an actuatable by an electromagnet, two-piece aus¬ formed anchor, a stop ring is ein¬ between the anchor bolt and the anchor plate ein¬ left. The stop ring is designed as an open lock washer and tends to knock out. It may be more severe signs of wear, which can lead to a ein¬-adjusting game between anchor bolt and anchor plate and on the other to complete destruction of the lock washer. A self-adjusting clearance between the anchor bolt and the armature plate adversely affects the quantity tolerances during the injection, so that in particular reproducibility is no longer achieved with injections of very small amounts following each other at short intervals.

From DE 101 33 450 Al a solenoid valve with a plug-in rotary connection is 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 anchor group of the solenoid valve for depressurizing a control chamber can be actuated, so that a nozzle needle assembly present in the injector body 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, one of the anchor parts being encompassed by an armature guide containing a rotation lock.

In today known solenoid valves, which are used in conjunction with fuel injectors in injection systems for fuel supply, the armature stroke is set by adjusting rings, which set the axial position of a corresponding anchor stop fest¬. The opening of a nozzle of the fuel injector and thus the amount of fuel injected are determined via the armature or via the movement of the armature in the axial direction. When assembling a solenoid valve or a fuel injector, the components which determine the armature stroke are measured and based on the measurement results, the required for a given anchor stroke is required dimensioning of a setting ring. A magnet group is then screwed together with the adjusting ring dimensioned according to the calculation in the injector body, and then the armature stroke is measured with a screwed or tensioned state. For use in ultrahigh-pressure injection systems tolerances in the micrometer range are tolerable at most for the armature stroke in order 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 setting of the armature stroke within the narrow tolerance values, the magnet group must be completely disassembled and the armature stroke must be readjusted by selecting an adjusting ring of a different dimensioning. 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, in order to minimize the quantity and the scattering influence in the case of injection events occurring shortly after one another, it is proposed to reduce, if not completely prevent, the impact of an overstroke disc on the anchor bolt. An overrunning spring that has been used for this purpose is being replaced by a hydraulic cushion.

When closing a solenoid valve, the components anchor bolt and An¬ kerplatte a two-piece anchor assembly move together in the direction of 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 range. The separation of Anker¬ bolt and anchor plate during the closing process, the impulse force and thus the "bounce Schließ¬" is reduced.The hitherto used overstroke spring pushes the armature plate before the next injection back to its original position The quality of the injection quantity and the injection scattering deteriorates as a result of the transfer channels designed in the interior of the anchor bolt according to the invention, there is now a hydraulic connection to a stoppered via an outlet throttle The fluid flowing through the transfer passages, that is, the fuel, flows into the further hydraulic space above a stationarily mounted anchor bolt guide g. For this purpose, the outlet opening or the outlet openings open at several overflow channels, in the region between The upper side of the stationarily mounted anchor bolt guide and below a neck region of the anchor plate movably received on the anchor bolt. The fuel emerging from the outlet opening of the one or more transfer ports builds a hydraulic cushion between an upper end face of the stationarily mounted anchor bolt guide and the underside of a neck region of the anchor plate, which dampens the anchor 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. As viewed in the radial direction, the chamfer runs from outside to inside and is bordered by a chamfer edge. Through such a chamfer on the underside of the neck portion of the An¬ kerplatte 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 Anker¬ bolt guide and the bottom of the neck area in the other hydraulic space, from the limited by a conical surface and a chamfer edge arrangement vermie¬ the. 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.

As a result of the solution proposed according to the invention, a restoring force is exerted on the armature plate guided on the anchor bolt, which, however, does not always act permanently on the armature 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 Ventil¬ seat, a restoring force is present, which thus reduces or dampens the impact of the anchor plate on a trained as a sickle stop.

drawing

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

It shows:

1 shows a known from the prior art solenoid valve for controlling a fuel injector, with an overstroke spring, which is received between the An¬ kerplatte and an anchor bolt guide stationary, Figure 2 shows a first embodiment of the invention proposed

Solution with overflow channels formed in the anchor bolt for the hydraulic use of a flow control chamber with a further hydraulic space, and

Figure 3 on the time axis applied movement times of an anchor plate which is acted upon by an overstroke spring and is damped with a hydraulic pad.

variants

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

The solenoid valve 1 shown in Figure 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 can be designed, for example, as a sickle disc and represents the upper stroke limit for the armature plate 7 movably received on the anchor bolt 6. 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 armature plate 7 accommodated movably thereon comprises a spherical cap 12 in which a closing element 13 of spherical design in the illustration according to FIG. 1 is embedded, in which it can, for example, be 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 a not shown in Figure 1 fuel injector is pressure relieved.

With the illustrated in Figure 1, known from the prior art design of a solenoid valve, in particular at short injection intervals of <800 microseconds between pre-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 illustration according to FIG. 2 shows a first embodiment variant of a magnetic armature arrangement proposed according to the invention for a solenoid valve for actuating a fuel injector. The figure 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 outlet throttle space 34 is formed, which has a funnel 33 on its side facing the outlet throttle 14, in which a valve seat 32 is formed. In the illustration according to FIG. 2, the valve seat 32 is closed by a ball-shaped closing element 13, which may be designed, 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 supplied with fuel via an inflow opening 27, which is embodied in the lower section of the anchor bolt 6. The fuel flows with the closing element 13 open via the outlet throttle 14 from the control chamber 15 in the Ablaufdrossel¬ space 34 and from there via the Einströmöffhungen 27 in the at least one overflow channel 26. The or 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 merge into a common outflow opening 24.

The outflow opening 24 is in relation to the anchor bolt 6 so that it opens kerplattenhalters 20 in the region between the end face 23 of the stationary anchor bolt guide 10 and below the An¬. 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 emerging from 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 sized sufficiently large in terms of their diameters. The number of overflow channels 26 which 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 overflow channels 26 has its own outflow opening 24 in order not only to use the static cushion formed in the hydraulic space which surrounds the anchor bolt 6, but also to use an additional dynamic inflow force. A symmetrical arrangement of the overflow channels 26 on the circumference of the anchor bolt 6 is advantageous in order to minimize transverse forces in the guides between the anchor bolt 6 and armature guide 10 as well as the 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 solution proposed according to the invention, impact of the upper plane surface of the anchor plate 7 on the underside of the sickle disk 5 serving as a stop can be considerably damped. Reference number 30 represents 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 exiting from 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 chamfer 21 can quickly reset the anchor plate 7 follow in its original position. As a result of the small amount of leakage that is set, indicated by the arrow 31, the armature plate 7 can impinge on the stop 5 designed as a sickle disk with only a slight impulse and be held there. 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 initial position, so that a wear-causing impact of An¬ kerplatte 7 and stop 5, which can be formed as a sickle disc, can be achieved. The quantity of fuel exiting from the outflow openings 24 is so dimensioned that the anchor plate 7 returns to its original position until the next injection process, i. is returned in contact with the stopper 5. If, however, the next injection process takes place earlier, different lifting behavior results in increased lifting / lifting dispersion of the injection quantities, which is highly undesirable. When closing the valve, which is indicated by the arrow A in FIG. 2, the dynamic flow of the fuel emerging from the outflow openings 24 and the static amount of fuel contained in the annular channel above the anchor bolt guide 10 dampens the through-travel Anchor plate 7. A contact of the anchor plate with the end face 23 of An¬ kerbolzenführung 10 is not required, but possible.

The illustration according to Figure 3, the Hubverläufe an anchor plate can be 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 up to an inflection point 45, at which the curve assumes a second slope 42, which is caused by 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. Due to the spring force building up only slowly, the return movement of an armature plate 7 acted upon by the overstroke spring 8 takes place substantially slower. Reference symbol 44 denotes a self-adjusting overswing, which asymptotically decays over the time axis. By ÜH the entire Ühubbereich is marked, the anchor plate must pass through 7, after a closing operation of the anchor bolt 6, that is, in the valve seat 32 made closing element 13, to reach their original position again, which formed by a system on the sickle disk Stop 5 is characterized.

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

Bezueszeichenliste

1 solenoid valve

2 magnet

3 closing spring

4 valve housing

5 stopper (sickle plate)

6 anchor bolts

7 anchor plate

8 over-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 hole

20 anchor plate neck

21 chamfer

22 symmetry axis

23 face anchor bolt guide

24 outflow opening

25 bevel edge

26 overflow channel

27 inflow opening

28 Overflow channel inclination angle

29 inflow area

30 first return amount

31 second return amount

32 valve seat

33 funnels

34 outlet throttling space

35 Absteuerraum

40 first slope based on tax

42 second Steieune auferund Leckölmenee Gradient due to spring force overshoot inflection point

blowout

Claims

claims

1. Solenoid valve for actuating a fuel injector with a closing element (13) via which an outlet throttle (14) of a control chamber (15) is releasable or closable, an anchor bolt (6) with an armature plate movably received on this

(7), which is secured to the anchor bolt (6) and one of the anchor plate (7) gegenüberlie¬ ing arranged magnets (2), characterized in that in the anchor bolt (6) at least one overflow channel (26) is formed, via which a discharge throttle space (34) and a Absteuerraum (35) hydraulically to the construction of a hydraulic pad below the anchor plate (7) are interconnected.

2. Solenoid valve according to claim 1, characterized in that at least one outlet opening (24) of at least one overflow channel (26) between an end face (23) and an anchor bolt guide (10) and below an anchor plate neck (20) in the Absteuerraum (35). empties.

3. Solenoid valve according to claim 2, characterized in that the anchor plate neck (20) has a chamfer (21).

4. Solenoid valve according to claim 3, characterized in that a cone angle of the chamfer (21) extends radially from outside to inside.

5. Solenoid valve according to claim 3, characterized in that the chamfer (21) is defined to the outside by a chamfer edge (25).

6. Solenoid valve according to claim 1, characterized in that at least one inlet opening (27) of at least one overflow channel (26) is acted upon by fuel contained in the outlet throttling space (34).

7. Solenoid valve according to claim 1, characterized in that overflow channels (26) in the anchor bolt (6) inclined by an inclination angle (28) relative to the axis of symmetry (22) of the anchor bolt (6).

8. Solenoid valve according to claim 1, characterized in that the closing element (13) is designed as a ceramic ball and in a spherical cap (12) of the anchor bolt

(6) is guided.

9. Solenoid valve according to claim 1, characterized in that it is formed with a two-part armature, an anchor plate (7) and an anchor bolt (6) ausge¬ forms and the armature plate (7) is arranged relatively movable to the anchor bolt (6) the armature plate (7) without hydraulic override against a stop (5) zu¬ is reset.

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.