Electromagnetic valve for controlling an injection valve of an internal combustion engine

Abstract

The present invention relates to a solenoid valve (2) for controlling an injection valve (1) of an internal combustion engine, including an electromagnet (34), a movable armature (29), a control valve member (25,26) moved with the armature (29) and cooperating with a valve seat (24) for opening and closing a fuel discharge channel (17) of a control pressure chamber (14) of the injection valve, and a sliding piece (40) guiding the armature (29), which is positioned together with the armature (29) and the control valve member (25,26) in an armature chamber (51,52). For reducing the bounce of the armature, it is proposed that the sliding piece (40) subdivides the armature chamber into a pressure relief chamber (52) connected to a fuel low-pressure connection (10) and an hydraulic damping chamber (51), into which fuel discharge channel (17) opens out, which damping chamber may be pressure-relieved to a pressure relief chamber (52) via at least one connecting channel (44,47) provided with a throttle (43,48), the speed of the control valve member (25,26) being lowered during the closing of solenoid valve (2), before the impact on valve seat (24), by a fuel pressure cushion acting upon the control valve member (25,26) in the damping chamber (51).

Description

BACKGROUND INFORMATION

[0001] The present invention relates to a solenoid valve for controlling a fuel injector of an internal combustion engine according to the generic part of claim 1.

[0002] Such a solenoid valve, as is known, for example, from DE 196 50 865 A1, is used for the control of the fuel pressure in the control pressure chamber of a fuel injector, such as an injector of a common-rail fuel injection system. The fuel pressure in the control pressure chamber controls the movement of a valve plunger by which an injection opening of the fuel injector is opened or closed. The known solenoid valve has an electromagnet positioned in a portion of the housing, a movable armature, and a control valve member moved along with the armature and acted upon by a closing spring, in the closing direction, which cooperates with a valve seat of the solenoid valve and thereby controls the fuel outflow from the control pressure chamber. In the solenoid valve known from DE 196 50 865 A1 the armature is developed in two parts, having an armature bolt and an armature plate supported in a slidingly movable manner on the armature bolt. Beyond that, solenoid valves are also known, having single-part armatures for controlling fuel injectors, in which the armature bolt is firmly connected to the armature plate.

[0003] One disadvantage of the known solenoid valves is the so-called armature bounce. When the magnet is switched off, the armature, and the control valve member along with it, is accelerated toward the valve seat by the closing spring of the solenoid valve, in order to close a fuel outflow channel from the control pressure chamber. The bounce of the control valve member onto the valve seat may result in a disadvantageous vibration and/or bounce of the control valve member onto the valve seat, whereby the control of the fuel injection process is impaired. In the solenoid valve known from DE 196 50 865 A1, therefore, the armature plate is positioned movably on the armature bolt so that, upon the bouncing of the control valve member onto the valve seat, the armature plate moves along further counter to the tension force of a return spring. On account of this measure, it is true that the effectively braked mass, and thus the kinetic energy causing the bounce of the armature hitting the valve seat is diminished, however, the armature plate can post-oscillate on the armature bolt after the closing of the solenoid valve, so that additional measures are required for damping the undesired post-oscillation of the armature plate.

SUMMARY OF THE INVENTION

[0004] In the solenoid valve according to the present invention, having the characterizing features of claim 1, a sliding element guiding the armature is positioned in the armature space of the solenoid valve in such a way that the armature space is subdivided into a pressure relief chamber connected to a fuel low-pressure connection and a hydraulic damping chamber into which the fuel outflow channel opens up from the control pressure chamber. The damping chamber is connected to the pressure relief chamber via at least one connecting channel equipped with a throttle. When the solenoid valve is closed, the control valve member in the damping chamber moves toward the valve seat. The rapid displacement of the fuel in the damping chamber, occurring as a result of this, which cannot immediately escape into the relief chamber through the throttle-equipped connecting channel, has the effect of advantageously forming a fuel pressure cushion which opposes the motion of the control valve member and brakes it together with the armature, so that the impulse transmitted onto the valve seat by the striking of the valve seat by the control valve member is reduced. This premits reducing the armature bounce, or the bouncing movement of the control valve member on the valve seat. Therefore, by the use of the solenoid valve according to the present invention, shorter intervals may advantageously be set between pre-injection, main injection and post-injection, since the armature requires less time for taking up a defined neutral position. This also applies especially for solenoid valves in which the armature plate is formed as one piece with the armature bolt. One-piece armatures may advantageously be manufactured with less effort, and make possible a considerable reduction in cost.

[0005] When the solenoid valve is open, the fuel flowing out of the fuel outflow channel of the control pressure chamber first flows into the damping chamber. Because of the throttling of the fuel flow from the damping chamber into the pressure relief chamber, a defined pressure pattern is ensured in the pressure relief chamber, which has a positive effect on the motion of the armature in the pressure relief chamber, and thus on the course of the injection procedure. A pressure surge coming out of the control pressure chamber when the fuel discharge channel is opened does not directly reach the pressure relief chamber, but first reaches the damping chamber, and only then proceeds into the pressure relief chamber via the connecting channel equipped with the throttle. Quantitative deviations between individual injection processes may be decreased advantageously by the division of the armature chamber.

[0006] Furthermore, the pressure cushion generated in the damping chamber advantageously reduces the seat loading of the valve seat at high closing forces.

[0007] Further developments of the present invention and advantageous embodiments are made possible by the features indicated in the dependent claims.

[0008] It is of advantage to adjust the volume of the damping chamber and the at least one throttle to each other in such a way that, after a relaxation period after the opening of the solenoid valve, an approximately constant fuel pressure is established in the damping chamber.

[0009] Advantageously, the sliding piece includes a sliding sleeve guiding the armature and a flange region, forming a separating wall between the damping chamber and the pressure relief chamber, by which the sliding piece is held stationary in the armature chamber. By this measure, a defined volume of the damping chamber may be set in a simple manner.

[0010] It is particularly advantageous to design the at least one connecting channel by a feed-through opening furnished with a throttle in the flange region of the sliding piece, since producing the connecting channel in the sliding piece may be particularly easy to do from a manufacturing technology point of view. Because the at least one feed-through opening is positioned inside the projection of the armature plate in the direction of motion of the armature, it may be achieved that the fuel flowing from the damping chamber into the pressure relief chamber flows against the armature plate and thereby supports the braking procedure of the armature.

[0011] Because the sliding sleeve guiding the armature projects away from the flange of the sliding piece toward the valve seat, this achieves in a simple manner that a sufficiently dimensioned damping chamber is formed between the sliding sleeve and the housing of the solenoid valve.

[0012] In another exemplary embodiment it is provided that the throttle section of the at least one connecting channel is formed by a slit in an end face, facing the damping chamber and furnished with the valve seat, of a valve piece set into the housing of the fuel injector, the slit being covered by a support part partially bordering on the damping chamber.

[0013] The support part may be, for instance, a screw member holding the valve piece in the housing.

[0014] A section of the connecting channel, which connects the damping chamber to the pressure relief chamber, may advantageously be formed by a leakage channel designed to be inside the housing of the fuel injector.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Exemplary embodiments of the present invention are represented in the drawings and are explained in the description below. The Figures show:

[0016] FIG. 1 a cross section through the upper part of a fuel injector having the solenoid valve according to the present invention,

[0017] FIG. 2 a cross section through a second exemplary embodiment of the solenoid valve according to the present invention,

[0018] FIG. 3 a cross section through a third exemplary embodiment of the solenoid valve according to the present invention,

[0019] FIG. 4 a cross section through a fourth exemplary embodiment of the solenoid valve according to the present invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0020] FIG. 1 shows the upper part of a fuel injector 1 which is intended for use in a fuel injection system which is equipped with a fuel high-pressure reservoir that is continually supplied with high-pressure fuel by a high-pressure booster pump. Fuel injector 1 shown has a valve housing 4 having a longitudinal bore 5, in which a valve punger 6 is positioned which acts with its one end upon a valve needle positioned in a nozzle body (not shown). The valve needle is positioned in a pressure chamber in the lower part (not shown) of fuel injector 1, which is supplied with fuel unter high pressure via a pressure bore 8. When there is an opening lift movement of valve plunger 6, the valve needle is lifted by the fuel high pressure, applied steadily to a pressure shoulder of the valve needle, in the pressure chamber counter to the closing force of a spring (not shown). The injection of the fuel into the combustion chamber of the internal combustion engine takes place through an injection orifice then connected to the pressure chamber. By lowering of valve plunger 6, the valve needle is pressed in the closing direction into the valve seat (not shown) of the fuel injector, and the injection process is ended.

[0021] As may be recognized in FIG. 1, valve plunger 6 is guided in a cylindrical bore 11, at its end facing away from the valve needle, which has been inserted into valve piece 12 which is set into valve housing 4. In cylindrical bore 11, end face 13 of valve plunger 6 closes in a control-pressure chamber 14, which is connected to a fuel high-pressure connection via a supply channel.

[0022] The supply channel is essentially designed in three parts. A bore going radially through the wall of valve piece 12, whose inner walls form a supply throttle 15 along part of their length, is constantly connected to an annular space 16 surrounding valve piece 12 on its outer circumference, which, in turn, is in constant connection to the fuel high-pressure connection of a connecting piece 9 which may be screwed into valve housing 4, via a fuel filter 31 inserted into the supply channel. Annular space 16 is sealed against longitudinal bore 5 by a sealing ring 39. Control pressure chamber 14 is subjected via supply throttle 15 to the high fuel pressure prevailing in the fuel high-pressure reservoir. Coaxially with valve plunger 6, a bore branches off from control pressure chamber 14 running in valve piece 12, which forms a fuel discharge channel 17 provided with a discharge throttle 18. The outlet of fuel discharge channel 17 from valve piece 12 is in the region of a cone-shaped countersunk section 21 of outlying end face 20 of valve piece 12. Valve piece 12 is tightly set into valve housing 4 using a screw element 23 in a flange region 22.

[0023] The opening and closing of the fuel injector is controlled by a solenoid valve which opens and closes fuel discharge channel 17 and thereby controls the pressure in the control pressure chamber. When fuel discharge channel 17 is closed, control pressure chamber 14 is closed toward the discharge side, so that the high pressure which is also present in the fuel high-pressure reservoir builds up rapidly there via the supply channel. Via the surface of end face 13, the pressure in control pressure chamber 14 generates a closing force on valve plunger 6, and thus on the valve needle connected with it, which is greater than the forces acting, on the other hand, in the opening direction as a result of the high pressure present. If control pressure chamber 14 is opened toward the discharge side by opening the solenoid valve, the pressure in the low volume of control pressure chamber 14 goes down very fast, since it is decoupled from the high-pressure side via supply throttle 15. As a result, the force acting on the valve needle in the opening direction outbalances the high fuel pressure present at the valve needle, so that the latter moves upwards, and with that the at least one injection orifice is opened for injection. However, if solenoid valve 30 closes fuel discharge channel 17, the pressure in control pressure chamber 14 may be built up again by fuel that continues to flow via supply channel 15, so that the original closing force is present, and the valve needle of the fuel injector closes.

[0024] In FIG. 1 a preferred exemplary embodiment of solenoid valve 2 is shown, which will be described below. In countersunk section 21 of valve piece 12, a valve seat 24 is formed, with which a control valve member 25,26 of a solenoid valve 2 controlling the injection valve cooperates. The control valve member of solenoid valve 2 includes a ball 25 and a guide piece 26 accommodating the ball, which is coupled to an armature 29 that cooperates with an electromagnet 34 of the solenoid valve. Solenoid valve 2 also includes a housing part 60, containing electromagnet 34, which is firmly connected to valve housing 4 via connecting means 7 which may be screwed together. Armature 29 is formed in one piece with armature plate 28 and an armature bolt 27, and positioned in an armature chamber 51,52 of solenoid valve 2. Armature 29 and control valve member 25,26 coupled to armature bolt 27 are constantly acted upon by a housing-mounted supported closing spring 3 in the closing direction of the solenoid valve, so that control valve member 25,26 normally lies adjacent to valve seat 24 in the closing position, and closes fuel discharge channel 17. As may further be seen in FIG. 1, a sliding piece 40 is positioned in the armature chamber which guides movable armature 29. Sliding piece 40 includes a flange region 42 and a sleeve 41 in which armature bolt 27 of armature 29 is supported in a slidably movable manner. Flange region 42 of sliding piece 40 is firmly held, together with a spacer ring 38 between housing part 60 and a shoulder 32 of housing part 4 of the injection valve. As may be seen in FIG. 1, sliding piece 40 subdivides the armature chamber into a pressure relief chamber 52, which is connected to a fuel low-pressure connection 10 of the injection valve, and an hydraulic damping chamber 51, into which fuel discharge channel 17 opens up. In this context, flange region 42 forms a barrier between damping chamber 51 and pressure relief chamber 52, a first side 45 of flange region 42 facing damping chamber 51, and a second side 46 facing pressure relief chamber 52. Sliding sleeve 41, as it runs closer to valve seat 24, projects away from first side 45 of flange region 42 in such a way that an annular space formed between sliding sleeve 41 and screw member 23 is connected to cone-shaped, countersunk section 21 of valve piece 12. The volume of the annular space is more than twice the inner volume of cone-shaped, countersunk section 21, and includes the major portion of damping chamber 51. Flange region 41 is further provided with two feed-through openings 44, which each have a throttle 43, and which each form a connecting channel between damping chamber 51 and pressure relief chamber 52. Feed-through openings 44 are diametrically opposite each other with respect to armature bolt 27, and are preferably formed as bore holes. The diameter of the two throttle locations 43 is, for instance, 0.6 mm.

[0025] When the solenoid valve is opened, armature plate 28 is attracted by electromagnet 34, and thereby fuel discharge channel 17 leading to armature chambers 51,51 is opened. The fuel flowing from fuel discharge channel 17, provided with throttle 18, first reaches damping chamber 51 and from there goes to pressure relief chamber 52, via feed-through openings 44 provided with throttles 43, which is connected to fuel low-pressure connection 10 which, in turn, is connected to a fuel return flow of injection valve 1, in a manner not shown. The volume of damping chamber 51 and throttles 43 are adjusted to one another in such a way that, when the solenoid valve is open, an approximately constant fuel pressure prevails in damping chamber 51.

[0026] During closing of the solenoid valve, closing spring 3 moves armature bolt 27 along with control valve member 25,26 to valve seat 24. Because of the control valve member's penetrating into the damping chamber, fuel is displaced from the damping chamber which cannot immediately escape completely into pressure relief chamber 52 because of connecting channel 44 being provided with the throttle, so that the pressure goes up in the damping chamber, and the movement of the control valve member is braked by a fuel pressure cushion which engages with control valve member 25,26 and with the lower part of armature bolt 27 counter to the closing direction of the armature bolt. As a result of that, the armature is braked, so that the impulse transmitted of control valve member 25,26 hitting valve seat 24 is diminished. At the same time, the fuel flowing through feed-through openings 44 from damping chamber 51 into pressure relief chamber 52 brakes armature plate 28, which is above the feed-through openings 44, so that armature 29 is additionally braked during the closing motion. The bounce of armature 29 and of control valve member 25,26 at valve seat 24 is clearly reduced by the use of solenoid valve 2 according to the present invention.

[0027] A further exemplary embodiment of solenoid 2 according to the present invention is shown in FIG. 2. The same parts are provided with the same reference numerals. The exemplary embodiment in FIG. 2 differs from the exemplary embodiment in FIG. 1 particularly by the fact that flange region 42 has no feed-through openings. In this exemplary embodiment, the connecting channel between damping chamber 51 and pressure relief chamber 52 is formed by slit 48 in end face 20, having valve seat 24 provided to it, of valve piece 12, an annular space 56 surrounding the valve piece, a transverse bore hole 47 in housing part 4 of the injection valve, a leakage channel 49 and a notch 55 on the second side 46 of flange region 42 of sliding piece 40. Slit 48 is covered by a support part 23 which partially borders damping chamber 51. In the exemplary embodiment shown, the support part is a screw member firmly holding valve piece 12 in housing part 4. Slit 48, covered by screw member 23, which connects countersunk sections 21 at end face 20 of valve piece 12 to annular chamber 56 is designed as a throttle channel. When the solenoid valve is closed, fuel flows through throttle channel 48, annular chamber 56 and transverse bore 47 into leakage channel 49, and gets from there into pressure relief chamber 52. In the exemplary embodiment shown in FIG. 2, the throttle channel, formed by slit 48 and screw member 23, has the same function as throttles 43 in the first exemplary embodiment shown in FIG. 1. Leakage channel 49 is used for flow return of leakage fuel from longitudinal bore hole 5 into the fuel return flow of the injection valve, and is provided anyhow by most injection valves. In the exemplary embodiment as shown in FIG. 2, leakage channel 49, at the same time, advantageously forms a section of the connecting channel between damping chamber 51 and pressure relief chamber 52.

[0028] A third exemplary embodiment is represented in FIG. 3. Armature 29 guided by sliding sleeve 41 is not shown. In differentiation from the exemplary embodiment shown in FIG. 1, sliding piece 40 lies with flange region 42 directly on end face 20 of valve piece 12. In this exemplary embodiment, sliding sleeve 41 for guiding the armature projects away from the flange region on its second side 46 of the flange region facing away from the valve piece. Screw member 23 holds gliding piece 40 together with valve piece 12 in housing part 4. Furthermore, at least one recess 54 is provided at end face 20 of the valve piece, which connects cone-shaped, countersunk section 21 at the end face 20 of valve piece 12 to annular chamber 56. The at least one recess 54 is formed so large that, in contrast to the exemplary embodiment shown in FIG. 2, it does not function as a throttle. Therefore, in the exemplary embodiment shown in FIG. 3, the damping chamber is formed by annular chamber 56, and the cone-shaped volume is formed above countersunk section 21. The volume of annular chamber 56 is, in this case, twice as large as the volume above countersunk section 21. As in the exemplary embodiment as shown in FIG. 1, damping chamber 51 is connected to pressure relief chamber 52 via two feed-through openings 44, which each have one throttle 43.

[0029] A fourth exemplary embodiment of the solenoid valve according to the present invention is shown in FIG. 4. Flange region 42 of sliding piece 40 has no feed-through openings. In the exemplary embodiment shown in FIG. 3, damping chamber 51 is formed by the cone-shaped volume above countersunk section 21 and annular chamber 56, which are connected to each other by at least one recess 54 let into the end face of valve piece 12. The at least one recess 54 is sufficiently large so as not to function as a throttle. A throttle 43 provided in the side wall of housing part 4 connects annular chamber 56 to a leakage channel 49, which, in turn, is connected to pressure relief chamber 52.

Claims

1. A solenoid valve (2) for controlling an injection valve (1) of an internal combustion engine, comprising an electromagnet (34), a movable armature (29), a control valve member (25,26) which is moved by the armature (29) and which cooperates with a valve seat (24) for opening and closing a fuel discharge channel (17) of a control pressure chamber (14) of the injection valve, and a sliding piece (40) guiding the armature (29), which is positioned together with the armature (29) and the control valve member (25,26) in an armature chamber (51,52), wherein the sliding piece (40) subdivides the armature chamber into a pressure relief chamber (52), connected to a fuel low-pressure connection (10), and a hydraulic damping chamber (51) into which the fuel discharge channel (17) opens out, the damping chamber being able to be pressure-relieved toward pressure relief chamber (52) via at least one connecting channel (44,47), provided with a throttle (43,48), the speed of the control valve member (25,26) being reduced at the closing of the solenoid valve (2), before the impact on the valve seat (24), by a fuel pressure cushion acting upon the control valve member (25,26) in the damping chamber (51).

2. The solenoid valve as recited in claim 1, wherein the volume of the damping chamber (51) and the at least one throttle (43) are adjusted to one another in such a way that, when the solenoid valve is open, an approximately constant fuel pressure prevails in damping chamber (51).

3. The solenoid valve as recited in claim 1 or 2, wherein the sliding piece (40) has a sliding sleeve (41) guiding the Armature and a flange region (42) forming a partition between the damping chamber (51) and the pressure relief chamber (52), by which flange region the sliding piece (40) is held in the armature chamber (51,52) in a stationary mount.

4. The solenoid valve as recited in claim 3, wherein, the at least one connecting channel is formed by a feed-through opening (44), provided with a throttle (43), in the flange region (42) of the sliding piece (41). (FIG. 1, FIG. 3)

5. The solenoid valve as recited in claim 4, wherein the at least one feed-through opening (44) is positioned within the projection of the armature plate (28) in the direction of motion of the armature (29).

6. The solenoid valve as recited in claim 3, wherein the sliding sleeve (41) guiding the armature (29) stands away from the flange region (42) in the direction of the valve seat (24).

7. The solenoid valve as recited in one of claims 1 through 3, wherein the throttle section of the at least one connecting channel is formed by a slit (48) in an end face (20), facing the damping chamber (51) and provided with the valve seat (24), of a valve piece (12) set into the housing (4) of the injection valve (1), the slit (48) being covered by a support part (23) which partially borders on damping chamber (51). (FIG. 2)

8. The solenoid valve as recited in claim 7, wherein the support part (23) is a screw member holding the valve piece (12) in the housing (4).

9. The solenoid valve as recited in claim 7 or 8, wherein the slit (48) connects a countersunk section (21), provided with the valve seat (24), of the end face (20) of the valve piece (12) to an annular chamber (56) surrounding the valve piece (12), the annular chamber being connected to the pressure relief chamber (52) via further sections (47,49,55) of the connecting channel.

10. The solenoid valve as recited in claim 9, wherein a section of the connecting channel is formed by a leakage channel (49) developed in the housing (4) of the injection valve (1).