VALVE FOR METERING A FLUID

Abstract

A valve for metering a fluid, the valve preferably being designed as a fuel injector for internal combustion engines. The valve includes an electromagnetic actuator and a valve needle that is actuatable by the actuator. The valve needle is used for actuating a valve closing body that cooperates with a valve seat surface to form a sealing seat. An armature of the actuator includes a through opening through which the valve needle extends. An annular gap is formed between an inner wall of a housing part and an outer side of the armature. A movable damping element that may have a partial ring shape is situated on the annular gap. The movable damping element is actuatable by a magnetic field that is generated by the actuator. The dynamics of the armature may thus be advantageously influenced in order to in particular reduce an armature bounce.

Claims

1-10. (canceled)

11. A valve for metering a fluid, comprising: an electromagnetic actuator; a valve needle which is actuatable by the actuator and which actuates a valve closing body that cooperates with a valve seat surface to form a sealing seat, an armature of the actuator including a through opening through which the valve needle extends, and an annular gap being formed between an inner wall of a housing part and an outer side of the armature; and at least one movable damping element situated on the annular gap, the movable damping element being actuatable by a magnetic field that is generated by the actuator.

12. The valve as recited in claim 11, wherein the valve is a fuel injector for an internal combustion engine.

13. The valve as recited in claim 11, wherein the damping element is designed as a damping element that is radially movable.

14. The valve as recited in claim 11, wherein an indentation that is associated with the damping element and at least partially accommodates the damping element is provided in the housing part.

15. The valve as recited in claim 14, further comprising: at least one spring element associated with the damping element, the spring element at least one of: (i) acting on the damping element in a direction of the outer side of the armature, and (ii) is situated in the indentation.

16. The valve as recited in claim 14, wherein at least one of: (i) the indentation is a grooved indentation, (ii) the damping element is radially guided in the indentation, (iii) the indentation is designed in such a way that the damping element is completely accomodatable by the indentation during an actuation by the magnetic field of the actuator.

17. The valve as recited in claim 11, wherein in an unactuated starting position in which the magnetic field that is generatable by the actuator dissipates, the movable damping element reduces the annular gap to the greatest extent possible, and thereby one of: rests against the outer side of the armature, or is situated at a minimum distance from the outer side of the armature.

18. The valve as recited in claim 11, wherein the damping element is made, at least partially, of at least one ferromagnetic material.

19. The valve as recited in claim 11, wherein the damping element is made partially of at least one paramagnetic material that faces the outer side of the armature.

20. The valve as recited in claim 11, wherein the damping element has a partial ring design, and the partial ring-shaped damping element is designed in such a way that the partial ring-shaped damping element spreads apart along its circumference during the actuation by the magnetic field of the actuator.

21. The valve as recited in claim 11, wherein the movable damping element is actuatable in an opening direction by the magnetic field that is generated by the actuator in order to actuate the valve needle, and the damping element damps the armature for a resetting of the valve needle that takes place opposite the opening direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Preferred exemplary embodiments of the present invention are explained in greater detail in the following description with reference to the figures, in which corresponding elements are provided with the same reference numerals.

[0020] FIG. 1 shows a valve in a partial schematic sectional illustration corresponding to a first exemplary embodiment of the present invention.

[0021] FIG. 2 shows the detail of the valve according to the first exemplary embodiment denoted by reference numeral II in FIG. 1, in a detailed illustration in a starting state.

[0022] FIG. 3 shows a flow chart for explaining the operating principle of the valve according to the first exemplary embodiment of the present invention.

[0023] FIG. 4 shows the detail of the valve according to a second exemplary embodiment of the present invention denoted by reference numeral IV in FIG. 1, in a schematic illustration in a starting state.

[0024] FIG. 5 shows a section of the valve according to the second exemplary embodiment, along the section line denoted by reference numeral V in FIG. 4.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0025] FIG. 1 shows a valve 1 for metering a fluid in a partial schematic sectional illustration corresponding to a first exemplary embodiment. Valve 1 may be designed in particular as a fuel injector 1. One preferred application is a fuel injection system in which such fuel injectors 1 are designed as high-pressure injectors 1 and used for direct injection of fuel into associated combustion chambers of the internal combustion engine. Liquid or gaseous fuels may be used as fuel.

[0026] Valve 1 includes an actuator 2 that includes a solenoid 3, a ferromagnetic housing part 4, an armature (solenoid armature) 5, and a ferromagnetic internal pole 6. A valve needle 7 that is in turn used for actuating a valve closing body 8, which in this exemplary embodiment is spherical, is actuatable via actuator 2. Valve closing body 8 cooperates with a valve seat surface 9 to form a sealing seat. For opening valve 1, valve needle 7 is actuated in an opening direction 10 so that the sealing seat is opened, and fuel or some other fluid is injectable or blowable from an inner chamber 11 via spray holes 12, 13 into a suitable chamber 14, in particular a fuel chamber 14. In this exemplary embodiment, an inner chamber 15 in which armature 5 is situated communicates with inner chamber 11. However, in one modified embodiment, inner chamber 15 may also be separate from inner chamber 11 into which the fluid to be injected or blown is provided. This is possible in particular for gaseous fluids in order to fill inner chamber 15 with some other, preferably liquid, fluid for damping.

[0027] Armature 5 of actuator 2 includes a through opening 20 through which valve needle 7 extends. Armature 5 is displaceably situated on valve needle 7. This displaceability is limited by stop elements 21, 22 that are stationarily fastened to valve needle 7. Lower stop 21 in this exemplary embodiment is designed as a stop sleeve 21, and upper stop 22 in this exemplary embodiment is designed as a stop ring 22. The play that is hereby achieved allows an armature free travel path 23. In addition, due to a distance 24 from internal pole 6 that adjoins armature free travel path 23, a lift 24 results, via which a movement of valve needle 7 is possible. In this exemplary embodiment, internal pole 6 forms an end stop during the actuation of armature 5.

[0028] An annular gap 27 is formed between an inner wall 25 of housing part 4 and an outer side 26 of armature 5. A movable damping element 28, which in this exemplary embodiment is acted on by a spring element 29 in the direction of outer side 26 of armature 5, is situated on annular gap 27.

[0029] Movable damping element 28 is actuatable by the magnetic field that is generatable by actuator 2. An actuation of movable damping element 28 in radial direction 30 is thus possible. The design of the valve according to the first exemplary embodiment is explained in greater detail below, also with reference to FIG. 2.

[0030] FIG. 2 shows the detail of valve 1 in the first exemplary embodiment, denoted by reference numeral II in FIG. 1, in a detailed illustration in a starting state. FIG. 2 illustrates opening direction 10 and a radial direction 30, perpendicular to opening direction 10, as one possible reference system for explaining the operating principle. It is understood that radial direction 30 represents a radial direction 30 by way of example. In particular, multiple repetitions of this design in various radial directions 30 that are perpendicular to opening direction 10 are possible. Spring element 29 is pretensioned in such a way that a certain action of damping element 28 opposite to radial direction 30 takes place. This is depicted by a force arrow 31 that is oriented opposite to radial direction 30. When no magnetic field prevails, force 31 presses damping element 28 against outer side 26 of armature 5, thus generating a friction force. In this exemplary embodiment, damping element 28 is formed from two components, namely, partially from a ferromagnetic material 32 and partially from a paramagnetic material 33.

[0031] Ferromagnetic material 32 may be based on a ferritic steel, for example. Paramagnetic material 33 may be based, for example, on an austenitic steel, a plastic, or a ceramic. Paramagnetic material 33 rests against outer side 26 and allows damping due to friction. Ferromagnetic material 32 is separate from outer side 26, so that a magnetic adhesive effect during actuation of damping element 28 is prevented.

[0032] A magnetic field is generated during an energization of solenoid 3. An axial magnetic force 35 that acts on armature 5, and a radial magnetic force 36 that acts on damping element 28, are generated due to this magnetic field, which is depicted by magnetic field lines 34. Radial magnetic force 36 arises due to the action of magnetic field lines 34 on ferromagnetic material 32 of damping element 28. Guiding of damping element 28 in radial direction 30 is ensured by side walls 37, 38 of a grooved indentation 39 in which damping element 28 is at least partially situated.

[0033] When radial magnetic force 36 exceeds elastic force 31 of spring element 29, damping element 28 detaches from outer side 26, thus eliminating the friction force in this regard. This preferably takes place comparatively early during the control, and thus at the beginning of the movement of armature 5 in opening direction 10.

[0034] Inner chamber 15 includes subchambers 40, 41 that are provided on both sides of armature 5. Via a fluid exchange between subchambers 40, 41, hydraulic damping may be achieved in addition to the friction-based damping. For this purpose, a radial extension 42 of annular gap 27 is specified in such a way that, without damping element 28, a fluid exchange that is essentially unthrottled with regard to the dynamics of armature 5 is possible. This may be assisted by one or multiple coaxial through holes 43, of which through hole 43 is denoted by way of example in FIG. 1.

[0035] The free cross section of annular gap 27 is reduced by introducing damping element 28 into annular gap 27, so that the hydraulic throttling effect increases. Taking through holes 43 into account, this results in a coordinated design in such a way that significant throttling of the fluid exchange between subchambers 40, 41 with regard to armature 5 is possible when the free cross section of annular gap 27 is reduced by one or multiple damping elements 28. This also results in hydraulic damping of armature 5.

[0036] In one modified embodiment, instead of direct friction between damping element 28 and outer side 26 of armature 5, an approach up to a minimum distance may be provided, so that sufficient hydraulic damping already takes place due to the viscosity of the fluid, and direct friction may thus be unnecessary.

[0037] The operating principle of valve 1 according to the first exemplary embodiment during an actuation is explained in greater detail below, also with reference to FIG. 3.

[0038] FIG. 3 shows a flow chart for explaining the operating principle of valve 1 according to the first exemplary embodiment. In a state Z1, which preferably occurs shortly after the actuation of armature 5 begins, damping element 28 lifts from outer side 26 of armature 5. As a result, the friction force between damping element 28 and armature 5 ceases, so that a high acceleration of armature 5 is achievable. In a state Z2, damping element 28 is subsequently completely accommodated by grooved indentation 39. An at least essentially unthrottled exchange of the fluid between subchambers 40, 41 is thus possible. This results in high dynamics of armature 5 during the actuation.

[0039] In state Z3 solenoid 3 is de-energized, so that the magnetic field depicted by magnetic lines 34 dissipates preferably quickly, and preferably collapses. As a result, force 31 of spring element 29, which is further tensioned in state Z2, is preferably greater than radial magnetic force 36 at a point preferably early during the resetting. During movement 47 of armature 5 opposite opening direction 10, this results initially in hydraulic damping, and then also the friction-based damping, of the movement of armature 5.

[0040] For the operating principle explained with reference to the flow chart illustrated in FIG. 3, a gap or distance 44 of damping element 28 from a groove base of grooved indentation 39 in the starting position of damping element 28 according to FIG. 2 is at least as large as radial extension 42 of annular gap 27. Grooved indentation 39 may thus completely accommodate damping element 28 within the scope of the sequence in state Z2 depicted with reference to FIG. 3.

[0041] In addition, a material thickness 45 of the paramagnetic material (portion 33) is designed to be greater than distance 44.

[0042] In the unenergized, closed state of valve 1, all damping elements 28 thus rest against outer side 26 of armature 5, designed as an outer lateral surface, and at the same time are pressed on by the particular spring element 29. At the start of the energization of solenoid 3, magnetic field formed in annular gap 27 ensures a continuously increasing radial magnetic force 36 on damping elements 28, since magnetically active gap 44 is smaller than material thickness 45 of paramagnetic material 33. As soon as resulting radial magnetic force 36 exceeds elastic force 31 of spring element 29, damping elements 28 begin to move away from armature 5, as depicted with reference to state Z1, and after some time they disappear completely into their grooved indentations 39 in housing part 4, as depicted with reference to state Z2. Armature 5 may thus be accelerated without mechanical friction or throttling of the fluid flowing past, and may thus build up the maximum opening pulse for rapid, robust opening of the valve needle, which takes place during the movement of armature 5 in opening direction 10.

[0043] The magnetic field once again dissipates after switch-off. Radial magnetic force 36 on damping elements 28 drops below elastic force 31 of spring elements 29 that acts in each case, and damping elements 28 once again move in the direction of outer side 26 of armature 5. Due to damping elements 28 resting against armature 5, on the one hand armature 5 is mechanically decelerated, and on the other hand annular gap 27 is closed, thus greatly throttling the fluid flowing past.

[0044] Significant advantages result from these two effects, as explained above.

[0045] Radial extension 42 and distance 44 are each approximately one-half of sum 46 of armature free travel path 23 and lift 24 depicted in FIG. 1. As depicted in state Z2 on the left side of the flow chart in FIG. 3, paramagnetic material (portion) 33 of damping element 28 may have an end-face side 51 that is curved in the shape of a cylindrical surface, and thus concave, with respect to a longitudinal axis 50 (FIG. 1). The curvature of end-face side 51 is adapted to outer side 26 of armature 5 when end-face side 51 is used as a friction surface 51. In addition, due to the curvature of end-face side 51, annular gap 27 is at least essentially opened up when damping element 28 is situated up to the groove base in grooved indentation 39.

[0046] FIG. 4 shows the detail of valve 1 according to a second exemplary embodiment, denoted by reference numeral IV in FIG. 1, in a schematic illustration in a starting state. In this exemplary embodiment, in contrast to the first exemplary embodiment no spring element 29 is necessary. However, in one modified embodiment, at least one spring element 29 may also be provided, which may then have a correspondingly weaker design. In this exemplary embodiment, damping element 28 is designed as a partial ring-shaped damping element.

[0047] In this regard, FIG. 5 shows a section of valve 1 according to the second exemplary embodiment, along the section line denoted by reference numeral V in FIG. 4. In this exemplary embodiment, partial ring-shaped damping element 28 is designed as a slotted ring with a slot 55. Elastic force 31 is applied by ring-shaped damping element 28, which is spread apart for assembly on armature 5. Radial magnetic force 36 acts against mechanical force 31.

[0048] An actuation by actuator 2 thus causes further spreading of partial ring-shaped damping element 28 via the magnetic field that arises, which eliminates the circumferential contact with outer side 26 of armature 5. In addition, this results in an at least partial sinking of damping element 28 into grooved indentation 39, which is designed as an annular groove 39. This correspondingly enlarges the free cross section of annular gap 27 in the area of damping element 28.

[0049] The present invention is not limited to the described exemplary embodiments.