Electromagnetic switching valve

Abstract

Electromagnetic switching valve (10) for a fuel injection system of an internal combustion engine, comprising: - a closing element (20) for closing the switching valve (10) in a closed position; - a movable anchor (24) which is coupled to the locking element (20) for moving the locking element (20) along a movement axis (23) between the closed position and an open position; and - a movement limiting stop (34) that limits movement of the anchor (24); wherein an anchor surface (54) of the anchor (24) and a stop surface (50) of the movement limiting stop (34) are designed such that they meet only at least one linear contact area (56) when they come into contact; and wherein the anchor surface (54) and / or the stop surface (50) is formed from a filament bundle (66), wherein the individual filaments of the filament bundle (66) provide several linear contact areas (56).

Description

[0001] The invention relates to an electromagnetic switching valve for a fuel injection system of an internal combustion engine.

[0002] In fuel injection systems, fuel is usually supplied to the combustion chambers of an internal combustion engine at high pressure. For example, the pressure in gasoline engines ranges from 150 bar to 400 bar, and in diesel engines from 1500 bar to 3000 bar. The high pressure in the respective fuel is generated by a high-pressure fuel pump. The higher the pressure that can be generated in the respective fuel, the lower the emissions generated during fuel combustion in the combustion chambers, which is particularly advantageous given the increasing desire to reduce emissions.

[0003] In order to be able to supply the fuel to the high-pressure fuel pump in a metered manner to pressurize the fuel with high pressure, a controllable inlet valve is usually provided on the high-pressure fuel pump.

[0004] Fast-acting solenoid valves designed as electromagnetic switching valves are often used to control the mass flow of fuel into the high-pressure fuel pump. These valves have an actuator section and a valve section, with a closing element in the valve section interacting with a valve seat to close the switching valve. The actuator section ensures that the closing element can be moved between a closed position and an open position. For this purpose, a movable magnetic component, the so-called armature, is provided. This component is coupled to the closing element and entrains the closing element during movement.

[0005] To limit its movement during operation of the electromagnetic switching valve, the armature strikes a movement limit stop each time the switching valve is actuated, thereby decelerating it. The braking movement of the armature and the impact generate a pulse and thus structure-borne noise in the high-pressure fuel pump.

[0006] Until now, the problem of noise generation during the braking phase of the armature to the movement limit stop has been solved by complex electrical control profiles, in which a force impulse is introduced by the actuator shortly before impact in the opposite closing direction.

[0007] DE 10 2014 212 791 A1 discloses an electromagnetically actuated high-pressure injection valve comprising an armature, a valve needle extending primarily along a closing direction, and a stop element. The valve needle is movable along the closing direction between an open position and a closed position. In the closed position of the valve needle, the armature is movable relative to the valve needle in the direction of the stop element. The stop element has a layer consisting of a viscoelastic material on a side facing the armature.

[0008] DE 10 2017 222 448 A1 describes an actuating device in a fluid pump with a magnet arrangement comprising at least one magnetic coil and an inner pole, and with an axially movable armature, wherein a return spring is arranged between the armature and the inner pole and the armature has an end face which faces an end face of the inner pole, wherein a damping element is arranged in a recess between the end face of the armature and the inner pole and the recess has an undercut.

[0009] The document DE 10 2016 208 956 A1 discloses an electromagnetically controlled suction valve for a high-pressure fuel pump, which comprises an annular solenoid coil for acting on an armature that can be moved between two end stops and coupled to a valve tappet. The armature is accommodated, at least in sections, in a recess of a valve body, with the valve body having an annular collar projecting into the recess.

[0010] Document DE 101 24 747 A1 discloses a fuel injector with a valve needle and an armature engaging the valve needle, which armature has an armature stop surface facing away from the valve seat as a first stop surface. A counter stop surface has an elastic damping element in a recess that projects beyond the armature stop surface or the counter stop surface.

[0011] The document DE 10 2013 220 047 A1 describes a solenoid valve comprising a valve housing with a valve spool comprising an armature plate. An electromagnet is arranged in the valve housing in such a way that it can exert a force on the armature plate to move it from a first end position to a second end position, with the end positions being defined by end stops. A semi-open damping chamber, filled with hydraulic fluid during operation and formed by at least one circumferential edge, is provided at an end stop or on one side of the armature plate.

[0012] The object of the invention is to provide a simplified electromagnetic switching valve in which noise during operation can be reduced to a minimum.

[0013] This object is achieved with an electromagnetic switching valve having the feature combinations of claims 1 and 2.

[0014] Advantageous embodiments of the invention are the subject of the dependent claims.

[0015] An electromagnetic switching valve for a fuel injection system of an internal combustion engine comprises a closing element for closing the switching valve in a closed position and a movable armature coupled to the closing element for moving the closing element along a movement axis between the closed position and an open position. Furthermore, the switching valve comprises a movement-limiting stop that limits the movement of the armature. An armature surface of the armature and a stop surface of the movement-limiting stop are configured such that, upon contact, they only meet at at least one linear contact area. The armature surface and / or the stop surface are formed from a filament bundle.

[0016] The filament bundle can be made of a metallic wire or plastic strands, for example. Because the filament bundle contains gaps, it can yield under slight mechanical resistance when it encounters a moving element, thereby slowing down the moving element. The filament bundle then springs back to its original shape.

[0017] The individual filaments provide several linear contact areas, so that further design of the surface in the form of a special surface structure is not necessary.

[0018] An electromagnetic switching valve for a fuel injection system of an internal combustion engine has a closing element for closing the switching valve in a closed position and a movable armature coupled to the closing element for moving the closing element along a movement axis between the closed position and an open position. Furthermore, the switching valve has a movement-limiting stop that limits movement of the armature. An armature surface of the armature and a stop surface of the movement-limiting stop are configured such that, upon contact, they only meet at at least one linear contact area. The armature surface and / or the stop surface have a surface structure that provides the linear contact area upon contact between the armature surface and the stop surface.The surface structure is formed from an elastic material and has a serrated structure, in particular an irregular serrated structure, in a cross-section arranged perpendicular to the movement axis of the closing element.

[0019] The serrated structure ensures that the surface structure can plastically deform when the armature and the movement limit stop collide, giving way, and thus dampening the collision between the armature and the movement limit stop.

[0020] An electromagnetic switching valve for a fuel injection system of an internal combustion engine has a closing element for closing the switching valve in a closed position and a movable armature coupled to the closing element for moving the closing element along a movement axis between the closed position and an open position. Furthermore, the switching valve has a movement-limiting stop that limits movement of the armature. An armature surface of the armature and a stop surface of the movement-limiting stop are configured such that, upon contact, they only meet at at least one linear contact area. The armature surface and / or the stop surface have a surface structure that provides the linear contact area upon contact between the armature surface and the stop surface.

[0021] The armature surface and the stop surface are the two areas of the armature and the travel limit stop that come into contact during operation of the electromagnetic switching valve, especially during armature deceleration. If the contact area between these two surfaces is kept to a minimum, namely in the form of a line, noise is generated only in this linear contact area, which can be dissipated by the volume of the travel limit stop. This can dampen structure-borne noise.

[0022] If not already provided, both the armature itself and the movement limit stop can have a corresponding surface structure. It is also possible for only one of the two components to have the surface structure that provides the linear contact area.

[0023] In an advantageous embodiment, the surface structure is designed to be elastically deformable. This gives the surface structure spring properties that contribute to dampening structure-borne sound.

[0024] If not already provided, the surface structure is preferably formed from an elastic material and has a serrated structure, in particular an irregular serrated structure, in a cross-section arranged perpendicular to the movement axis of the locking element. The serrated structure ensures that the surface structure can plastically deform and yield when the armature and the movement limit stop collide, thus dampening the impact between the armature and the movement limit stop.

[0025] Preferably, the surface structure is formed from an elastic material and has a convex cross-section perpendicular to the movement axis of the locking element. The convex structure can have a smooth surface structure, but it is also possible for the convex structure to be combined with the serrated structure. Here, too, the surface structure undergoes plastic deformation when the movement limit stop and the armature collide, thus cushioning the impact.

[0026] If not already provided, the surface structure according to an alternative embodiment is formed from an elastic material and is wedge-shaped in a cross-section arranged perpendicular to the movement axis of the closing element.

[0027] In the described embodiments of the surface structure, the surface structure is formed from an elastic material that provides spring and thus damping properties on the material side.

[0028] By changing the basic cross-section of the surface structure, for example, to a serrated, convex, or wedge-shaped structure, the spring rate and thus the damping effect of the surface structure can be adjusted from a design perspective. The respective shape can ensure that the counterforce built up by the braking force increases more slowly, thus resulting in less noise.

[0029] Advantageously, the movement limit stop is designed as an annular disc, which is arranged as a separate component in a guide section of a housing part of the electromagnetic switching valve to guide the armature during its movement. Therefore, the armature strikes a separately formed annular disc for deceleration, which either has the surface structure described above or is designed directly as a filament bundle.

[0030] Preferably, the annular disc has hydraulic compensation grooves. The compensation grooves are formed on the stop surface of the disc and prevent hydraulic sticking of the armature and disc after their contact upon impact.

[0031] Advantageous embodiments of the invention are explained in more detail below with reference to the accompanying drawings, in which: Fig. 1 a schematic sectional view through an electromagnetic switching valve in which a closing element is moved by an armature, the armature being braked in its movement by a movement limiting stop; Fig. 2 a perspective view of the movement limit stop from Fig. 1, which is designed as an annular disc; Fig. 3 a further perspective view of the movement limit stop according to Fig. 2; Fig. 4 a cross-sectional view of the movement limit stop from Fig. 2 and Fig. 3 in a first embodiment; Fig. 5 a cross-sectional view of the movement limit stop from Fig. 2 and Fig. 3 in a second embodiment; Fig. 6 a cross-sectional view of the movement limit stop from Fig. 2 and Fig. 3 in a third embodiment; and Fig. 7 a cross-sectional view of the movement limit stop from Fig. 2 and Fig. 3 in a fourth embodiment.

[0032] Fig. Figure 1 shows a schematic sectional view of an electromagnetic switching valve 10 arranged as an inlet valve 12 on a high-pressure fuel pump 14 of an internal combustion engine. The electromagnetic switching valve 10 has a valve region 16 and an actuator region 18. In the valve region 16, a closing element 20 interacts with a valve seat 22 to close the switching valve 10 in a closed position. When the closing element 20 is lifted from the valve seat 22, the switching valve 10 is in its open position.

[0033] The closing element 20 is moved by the actuator region 18 along a movement axis 23. For this purpose, the closing element 20 is coupled to a movable armature 24. In addition to the armature 24, the actuator region 18 also has a fixed pole piece 26 and a coil 28.

[0034] When the switching valve 10 is in operation, the coil 28 is electrically actuated, i.e., energized, a magnetic field is generated that forms a magnetic circuit. Inside the magnetic circuit are the two magnetic components that are axially movable relative to one another: the movable armature 24 and the stationary pole piece 26. These two components are spaced apart by a compression spring 30 and held apart by this compression spring 30. The resulting magnetic field generates a force that pulls the pole piece 26 and the armature 24 toward each other, overcoming the spring force of the compression spring 30. This sets the armature 24 in motion.

[0035] Since the armature 24 is coupled to the closing element 20, the armature 24 takes the closing element 20 with it as it moves.

[0036] In the present embodiment, the switching valve 10 is designed as a normally open switching valve 10. This means that, when the coil 28 is de-energized, the compression spring 30 keeps the armature 24 spaced from the pole piece 26 and thus the closing element 20 in its open position. Accordingly, if the electrical control of the coil 28 is switched off, the compression spring 30 pushes the armature 24 back into the open position directly or indirectly, for example, via a coupling element 32.

[0037] The design of the electromagnetic switching valve 10 as a normally open switching valve 10 is only an exemplary embodiment; it is also possible to arrange the compression spring 30 differently so that the switching valve 10 is designed as a normally closed switching valve 10.

[0038] In the present embodiment, the armature 24 encounters a movement limiting stop 34 during its movement toward the opening position of the closing element 20. In the present embodiment, the stop is designed as a disc 36, which forms a separate component in a housing part 38 of the switching valve 10 and forms a guide section 40 for guiding the armature 24 during its movement. The movement limiting stop 34, which is thus arranged in the static guide of the armature 24, brakes the downward movement of the armature 24. The braking movement of the armature 24 generates a pulse and thus also structure-borne noise in the high-pressure fuel pump 14.

[0039] The control of the amount of fuel admitted to the high-pressure fuel pump 14 via the electromagnetic switching valve 10 is carried out as follows: The fuel enters the high-pressure fuel pump 14 via an inlet 42. A pump piston 44 oscillates within a pressure chamber 46 of the high-pressure fuel pump 14. A downward movement of the pump piston 44 draws the fuel from the inlet 42 into the pressure chamber 46 when the closing element 20 is in an open position. When the pump piston 44 moves upward, the closing element 20 initially remains in the open position, so that the fuel is pumped back into the inlet 42. This is known as "reflux."

[0040] If the fuel is not to be refluxed back into the inlet 42, but instead to be pumped into a high-pressure region 47, for example, a rail, the closing element 20 is moved into its closed position by the actuator region 18 during the upward movement of the pump piston 44. In the closed position of the switching valve 10, an inlet cross-section is closed. This allows the fuel to be pumped into the high-pressure region 47 via an outlet valve 48 during the remaining upward movement of the pump piston 44.

[0041] If the fuel supply to the high-pressure area 47 is to be terminated, the coil 28 is deactivated again, and the closing element 20 returns to the initial position (open position) together with the armature 24. The armature 24 then strikes the movement limit stop 34 to decelerate its movement, which has been induced by the spring force of the compression spring 30.

[0042] In the present embodiment, the movement limit stop 34 is designed as a separate annular disc 36, which is mounted below the armature 24 in an area below the static guide of the armature 24. The disc 36 has a defined thickness in the unloaded state, so that a defined position of the movement limit stop 34 is available in the starting position.

[0043] In the present embodiment, the movement limiting stop 34 is provided as a separately formed disc 36, but it is also possible to form the movement limiting stop 34 directly in the guide section 40, ie integrally with the housing part 38.

[0044] The movement limit stop 34 formed as an annular disc 36 is in Fig. 2 and Fig. 3 are shown in a perspective view. The disc 36 has hydraulic compensating grooves 52 on a stop surface 50, which prevent hydraulic sticking between the movement limit stop 34 and the armature 24 upon contact.

[0045] To further reduce the structure-borne noise generated when the armature 24 impacts the movement-limiting stop 34, it is proposed to design an armature surface 54, which comes into contact with the stop surface 50 upon impact, and the stop surface 50 such that, upon contact, they only meet at at least one linear contact area 56. This allows the impact forces to be dissipated, and the resulting structure-borne noise is reduced.

[0046] The armature surface 54 or the stop surface 50 may each individually or both have a surface structure 58 that provides the linear contact area 56. Examples of this are shown in cross-sectional views through the disc 36 (position of the cross section shown in Fig. 3) in the Fig. 4 to 6 shown.

[0047] The disc 36 is in the first embodiment according to Fig. 4, the second embodiment according to Fig. 5 and the third embodiment according to Fig. 6 are each formed from an elastic material 60, so that the surface structure 58 is also elastically deformable.

[0048] In the first embodiment, the surface structure 58 is formed as an irregular serrated structure 62. When the armature 24 and the disc 36 come into contact, the serrated structure 62 plastically deforms, thus absorbing and dampening impact forces. After the impact, the serrated structure 62 returns to its original shape. The disc 36 therefore exhibits spring properties and can thus dampen the impact.

[0049] A second embodiment is in Fig. 5, where the disc 36 is also formed from an elastic material 60 and has a convex shape 64. The convex shape 64 alone allows the disc 36 to be plastically deformed at the stop surface 50 and can absorb and dampen the impact forces. It also returns to its original convex shape 64 after impact. The convex shape 64 can be combined with the serrated structure 62 from the first embodiment.

[0050] In an alternative third embodiment, shown in Fig. 6, the disc 36 is wedge-shaped in cross-section and accordingly has a wedge-shaped surface structure 58. The effect of the wedge-shaped surface structure 58 is similar to the surface structure 58 with the convex shape 64 from Fig. 5. The wedge-shaped surface structure 58 can also be combined with the serrated structure 62 from the first embodiment in Fig. 4 can be combined.

[0051] An alternative possibility for forming a linear contact area 56 between stop surface 50 and armature surface 54 is shown in the cross-sectional view of the disc 36 in Fig. 7 as a fourth embodiment.

[0052] Here, the disc 36 is formed as a filament bundle 66 and comprises, for example, simple metallic wires or plastic strands that form the filament bundle 66. The individual filaments of the filament bundle 66 are arranged in such a way that a surface structure 58 is automatically formed, which provides a linear contact area 56 between the stop surface 50 and the armature surface 54.

[0053] The surface structure 58 or the filament bundle 66 can be provided as a single component, for example, in the form of the annular disc 36, in the electromagnetic switching valve 10. However, it is also possible to provide these structures integrally with the armature 24 itself or with the housing part 38 in the guide section 40. The advantage of this structure is that a resilient and damping structure can be easily provided, which is provided for noise reduction.

Claims

[1] Electromagnetic switching valve (10) for a fuel injection system of an internal combustion engine, comprising: - a closing element (20) for closing the switching valve (10) in a closed position; - a movable armature (24) coupled to the closing element (20) for moving the closing element (20) along a movement axis (23) between the closed position and an open position; and - a movement limiting stop (34) which limits a movement of the armature (24); wherein an armature surface (54) of the armature (24) and a stop surface (50) of the movement limiting stop (34) are designed such that, upon contact, they only meet at at least one linear contact region (56); and wherein the armature surface (54) and / or the stop surface (50) is formed from a filament bundle (66), wherein the individual filaments of the filament bundle (66) provide a plurality of linear contact regions (56). [2] Electromagnetic switching valve (10) for a fuel injection system of an internal combustion engine, comprising: - a closing element (20) for closing the switching valve (10) in a closed position; - a movable armature (24) coupled to the closing element (20) for moving the closing element (20) along a movement axis (23) between the closed position and an open position; and - a movement-limiting stop (34) which limits a movement of the armature (24); wherein an armature surface (54) of the armature (24) and a stop surface (50) of the movement-limiting stop (34) are designed such that, upon contact, they only meet at at least one linear contact region (56); wherein the armature surface (54) and / or the stop surface (54) has a surface structure (58) which provides the linear contact region (56) upon contact between the armature surface (54) and the stop surface (50); and wherein the surface structure (58) is formed from an elastic material (60); wherein the movement-limiting stop (34) is designed as an annular disk (36), wherein the disk (36) is wedge-shaped in cross-section, such that the surface structure (58) of the disk (36) is wedge-shaped. [3] Electromagnetic switching valve (10) according to claim 1 or 2,characterized by that the surface structure (58) is elastically deformable. [4] Electromagnetic switching valve (10) according to claim 1, characterized by that the filament bundle (66) is formed from metallic wire or plastic strands. [5] Electromagnetic switching valve (10) according to one of claims 1 to 4, characterized by that the annular disc (36) is arranged as a separate component in a guide section of a housing part (38) of the electromagnetic switching valve (10) for guiding the armature (24) during its movement. [6] Electromagnetic switching valve (10) according to claim 5, characterized by that the annular disc (36) has hydraulic compensating grooves (52).

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