Patent Publication Number: US-9850871-B2

Title: Valve assembly for a fluid injection valve and fluid injection valve

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Stage application of International Application No. PCT/EP2014/055691 filed Mar. 21, 2014, which designates the United States of America, and claims priority to EP Application No. 13161691.4 filed Mar. 28, 2013, the contents of which are hereby incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     Valve assembly for a fluid injection valve and fluid injection valve. 
     BACKGROUND 
     The present disclosure relates to a valve assembly for a fluid injection valve and to a fluid injection valve with a valve assembly. 
     Fluid injection valves are in widespread use for dosing fuel in internal combustion engines. In particular, the fluid injection valve is received in a combustion chamber of the internal combustion engine to dose fuel directly into the combustion chamber. 
     Such fluid injection valves are operated at high pressures of up to 300 bar in the case of gasoline engines and of more than 2000 bar in the case of diesel engines. Often, engines have different operation modes involving a variety of different fuel pressures. 
     SUMMARY 
     One embodiment provides a valve assembly for a fluid injection valve, the valve assembly having a longitudinal axis and comprising a valve seat, a valve disc and a valve stem, wherein the valve seat has an orifice, the orifice being laterally offset from the longitudinal axis, the valve disc has a fluid passage which, in a first angular position of the valve disc, is positioned in such fashion that it overlaps with the orifice at an interface of the valve disc and the valve seat to establish a fluid path through the valve disc and the valve seat for dispensing fluid from the valve assembly, the valve disc is rotatable around the longitudinal axis with respect to the valve seat from the first angular position to a second angular position, the valve seat and the valve disc mechanically interact to seal the orifice in the second angular position, the valve stem mechanically interacts with the valve disc to rotate the valve disc around the longitudinal axis, and the valve stem is axially movable with respect to the valve seat and rotationally fixed with respect to the valve seat and wherein the valve stem is mechanically coupled to the valve disc in such fashion that an axial movement of the valve stem is converted to a rotational movement of the valve disc. 
     In a further embodiment, the valve assembly further comprises a spring for pressing the valve disc against the valve seat. 
     In a further embodiment, the valve stem has a protrusion and the valve disc has a channel or vice versa, the protrusion engaging the channel and moving along the channel when the valve stem is moved in axial direction, wherein the channel is non-parallel to the longitudinal axis so that the valve stem and the valve disc mechanically interact by means of the protrusion and the channel for converting axial movement of the valve stem to rotational movement of the valve disc. 
     In a further embodiment, the valve assembly further comprises a valve body having a cavity extending from a fluid inlet end to a fluid outlet end, wherein the valve seat is arranged at the fluid outlet end and positionally and rotationally fixed with respect to the valve body, the longitudinal axis extends from the fluid inlet end to the fluid outlet end and the valve stem and the valve disc are arranged in the cavity. 
     Another embodiment provides a fluid injection valve comprising the valve assembly discussed above and an actuator assembly. 
     In a further embodiment, the actuator assembly is operable to displace the valve stem in axial direction for rotating the valve disc. 
     Another embodiment provides a fluid injection valve comprising a valve assembly and an actuator assembly, wherein the valve assembly has a longitudinal axis and comprises a valve seat and a valve disc, the valve seat has an orifice, the orifice being laterally offset from the longitudinal axis, the valve disc has a fluid passage which, in a first angular position of the valve disc, is positioned in such fashion that it overlaps with the orifice at an interface of the valve disc and the valve seat to establish a fluid path through the valve disc and the valve seat for dispensing fluid from the valve assembly, the valve disc is rotatable around the longitudinal axis with respect to the valve seat from the first angular position to a second angular position, the valve seat and the valve disc mechanically interact to seal the orifice in the second angular position, the valve assembly comprises a valve stem which mechanically interacts with the valve disc to rotate the valve disc around the longitudinal axis, the valve assembly comprises a valve body having a cavity extending from a fluid inlet end to a fluid outlet end, wherein the valve seat is arranged at the fluid outlet end and positionally and rotationally fixed with respect to the valve body, the longitudinal axis extends from the fluid inlet end to the fluid outlet end and the valve stem and the valve disc are arranged in the cavity, the actuator assembly comprises an armature, the armature being axially displaceable with respect to the valve body and rotationally fixed with respect to the valve body, the valve stem mechanically interacts with the valve disc in such fashion that a rotation of the valve stem around the longitudinal axis effects a rotation of the valve disc around the longitudinal axis, and the armature is mechanically coupled to the valve stem in such fashion that an axial movement of the armature is converted to a rotational movement of the valve stem and the valve disc. 
     In a further embodiment, the valve stem has a protrusion and the armature has a channel or vice versa, the protrusion engaging the channel and moving along the channel when the armature is moved in axial direction, wherein the channel is non-parallel to the longitudinal axis so that the valve stem and the armature mechanically interact by means of the protrusion and the channel for converting axial movement of the armature to rotational movement of the valve stem and the valve disc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Example embodiments are described below in association with schematic figures in which: 
         FIG. 1  shows a schematic sectional view of a valve assembly according to a first example embodiment, 
         FIG. 2  shows a schematic perspective view of the valve stem and the valve disc of the valve assembly according to the first example embodiment, 
         FIG. 3  shows a schematic perspective view of a valve stem of the valve assembly according to the first example embodiment, 
         FIG. 4  shows a schematic perspective view of the valve disc of the valve assembly according to the first example embodiment, 
         FIG. 5  shows a schematic perspective view of the valve seat of the valve assembly according to the first example embodiment, 
         FIG. 6A  shows a schematic top view of the valve disc and the valve seat of the valve assembly according to the first example embodiment in a first angular position, 
         FIG. 6B  shows a schematic top view of the valve disc and the valve seat of the valve assembly according to the first example embodiment in a second angular position, 
         FIG. 7  shows a schematic sectional view of a fluid injection valve with a valve assembly according to the first example embodiment, 
         FIG. 8A  shows a schematic perspective view of the armature of a valve assembly according to a second example embodiment, and 
         FIG. 8B  shows a schematic perspective view of the valve stem and the valve disc of the valve assembly according to the second example embodiment. 
     
    
    
     In the example embodiments and figures, similar, identical or similarly acting elements are provided with the same reference symbols. The figures are not regarded to be true to scale. Rather, individual elements in the figures may be exaggerated in size for a better representability and/or for better understanding. 
     DETAILED DESCRIPTION 
     Embodiments of the present invention provide a valve assembly for a fluid injection valve which is particularly well suited for operation at high fluid pressures and/or for operating at a plurality of different fluid pressures. 
     According to one aspect, a valve assembly for a fluid injection valve is specified. A fluid injection valve comprising the valve assembly is specified according to another aspect. 
     The valve assembly has a longitudinal axis. It comprises a valve seat and a valve disc. The valve seat has an orifice which is laterally offset from longitudinal axis. In particular, the orifice does not overlap with the longitudinal axis in a top view along the longitudinal axis. The valve disc has a fluid passage. The fluid passage extends in particular completely through the valve disc in axial direction. While the description is made with reference to one orifice and one fluid passage, the valve assembly can also comprise a plurality of such orifices and fluid passages, wherein each fluid passage is in particular assigned to one of the orifices. The orifices and fluid passages may, for example, be evenly distributed around the longitudinal axis. 
     The valve disc is rotatable around the longitudinal axis between a first angular position and a second angular position. In the first angular position of the valve disc, the fluid passage is positioned in such fashion that it overlaps with the orifice at an interface of the valve disc and the valve seat to establish a fluid path through the valve disc and the valve disc for dispensing fluid from the valve assembly. In the second angular position, the valve seat and the valve disc mechanically interact to seal the orifice. In particular, the orifice and the fluid passage each have an aperture at the interface of the valve disc and the valve seat, the apertures being laterally displaced with respect to each other when the valve disc is in the second angular position so that they do not overlap in top view along the longitudinal axis. 
     With advantage, the pressure dependency of the force which is needed to rotate the valve disc for sealing and unsealing the orifice has no or only a particularly small dependence from the fluid pressure within the valve assembly. Therefore, the opening movement and the closing movement, i.e. the dynamic behavior of the valve assembly, has a particularly low pressure dependency—for example unlike inward opening needle valves which usually have a pressure imbalance that limits the maximum operating pressure beyond which the needle valve does not open and which leads to a change of the dynamic behavior of the needle valve with the pressure. Due to the small pressure dependency of the dynamic behavior of the present valve assembly, it can be advantageously controlled without electronic mapping of, for example, a fluid flow offset versus operating pressure. In addition, it is possible to manage so-called “overpressure modes” without additional devices or software features. A valve assembly according to the present disclosure is particularly well suited for operating at high operating pressures. 
     According to one embodiment, the axial position of the valve disc is fixed relative to the valve seat. For example, the valve assembly comprises a spring which is operable to press the valve disc against the valve seat. In this way, a particularly good sealing of the orifice is achievable. 
     In a further embodiment, the valve assembly comprises a valve stem which is operable to rotate the valve disc around the longitudinal axis, in particular from the first angular position to the second angular position and/or from the second angular position to the first angular position. In an embodiment, in which the valve stem is only operable to rotate the valve disc from the first to the second angular position or only from the second to the first angular position, but not in the respective opposite angular direction, the valve disc is preferably biased in the respective opposite angular direction, for example by means of an torsion spring. In one development, the spring for pressing the valve disc against the valve seat in axial direction also acts as the torsion spring for rotationally biasing the valve disc. A spring which is a helical spring is, for example, suitable in this case. 
     In one embodiment, the valve stem is axially moveable with respect to the valve seat and rotationally fixed with respect to the valve seat. In this embodiment, the valve stem is mechanically coupled to the valve disc in such fashion that an axial movement of the valve stem is converted to a rotational movement of the valve disc. For example, the valve stem has a protrusion and the valve disc has a channel or vice versa. The protrusion engages the channel and moves along the channel when the valve stem is moved in axial direction for rotating the valve disc. The channel is non-parallel, and in particular also non-perpendicular, to the longitudinal axis. For example it has the general shape of a portion of a helix extending around the longitudinal axis. The valve assembly with such a valve stem is particularly well suited for being actuated by a solenoid actuator assembly or a piezo-electric actuator assembly. In this way, a valve assembly is very well suited for use in internal combustion engines. 
     In one embodiment, the valve assembly further comprises a valve body. The valve body in particular has a cavity which extends from a fluid inlet end to a fluid outlet end. The valve seat is preferably arranged at the fluid outlet end. It is positionally and rotationally fixed with respect to the valve body. It may be formed in one piece with the valve body or the valve seat maybe a separate part which is assembled with the valve body, for example by welding, crimping and/or an interference fit. The longitudinal axis in particular extends from the fluid inlet end to the fluid outlet end of the valve body. The valve stem and the valve disc are preferably arranged in the cavity. A spring may also be arranged in the cavity and, for example, an end of the spring which is remote from the valve disc may bear on a shoulder of the valve body for compressing the spring. 
     The fluid injection valve may comprise an actuator assembly which is operable to move the valve stem for rotating the valve disc. The actuator assembly may, for example, be a solenoid actuator assembly or a piezo-electric actuator assembly. 
     In one embodiment, the actuator assembly is operable to displace the valve stem in axial direction for rotating the valve disc. 
     In another embodiment, the valve stem mechanically interacts with the valve disc in such fashion that a rotation of the valve stem around the longitudinal axis effects a rotation of the valve disc around the longitudinal axis. For example, the valve stem and the valve disc are rigidly fixed to each other. For example in this case, the actuator assembly may comprise an armature, the armature being axially displaceable with respect to the valve body and rotationally fixed with respect to the valve body. The armature is preferably mechanically coupled to the valve stem in such fashion that an axial movement of the armature is converted to a rotational movement of the valve stem and the valve disc. With advantage, conversion between axial and rotational movement may be particularly reliable in this case. Bearing of the valve stem may be particularly simple. 
     In one development, the valve stem has a protrusion and the armature has a channel or vice versa. The protrusion engages the channel and moves along the channel when the armature is moved in axial direction. The channel is non-parallel, and in particular also non-perpendicular, to the longitudinal axis. For example it has the general shape of a portion of a helix extending around the longitudinal axis. In this way, the valve stem and the armature mechanically interact by means of the protrusion and the channel for converting axial movement of the armature to rotational movement of the valve stem and the valve disc. 
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       FIG. 1  shows a cross-sectional view of a valve assembly  1  according to a first example embodiment of the invention. 
       FIG. 7  shows a schematic cross-section of a fluid injection valve  3  comprising the valve assembly  1  of  FIG. 1 . 
     The valve assembly  1  has a longitudinal axis L. It comprises a valve seat  5  and a valve disc  7 . The valve disc  7  is arranged adjacent to the valve seat  5  so that the valve disc  7  and the valve seat  5  have a common interface  6 . Further, the valve assembly  1  comprises a valve stem  11 . 
       FIG. 2  shows a perspective view of the valve disc  7  and the valve stem  11 .  FIG. 3  shows another perspective view of the valve stem  11 .  FIG. 4  shows another perspective view of the valve disc  7 .  FIG. 5  shows a perspective view of the valve seat  5 . 
     The valve seat  5  has a plurality of orifices  51  which a laterally offset from the longitudinal axis L. In the present embodiment, the orifices  51  are arranged in an imaginary region having a cylinder ring shape having the longitudinal axis L as its center axis. For example, the orifices  51  are uniformly distributed around the longitudinal axis L, i.e. the angle which is defined by the centers of gravity of two adjacent orifices  51  and the longitudinal axis L as its vertex in top view along the longitudinal axis L is identical for all pairs of adjacent orifices  51 . 
     The orifices  51  may be of various shapes. In the present embodiment, the orifices  51  extend obliquely through the valve seat  5  with respect to the longitudinal axis L. They are shaped as stepped trough-holes the cross section of which is larger at a side of the orifices  51  facing a fluid outlet end  175  of the valve assembly  1  and then at the end facing a fluid inlet end  173  of the valve assembly  1 . 
     The valve disc  7  has a plurality of fluid passages  71 . Preferably, number of fluid passages  71  equals the number of orifices  51 . In a first angular position P 1 , the valve disc  7  is positioned in such fashion that each of the fluid passages  71  overlaps exactly one of the orifices  51  in the interface region  6  of the valve disc  7  and the valve seat  5 . In this way, a fluid path is established through the valve disc  7  and the valve seat  5  for dispensing fluid from the valve assembly  1 . 
     The valve disc  7  is rotatable around the longitudinal axis L from the first angular position P 1  to a second angular position P 2 . 
       FIG. 6A  shows a top view along the longitudinal axis L of the valve seat  5  and the valve disc  7 , the valve disc  7  being positioned in the first angular position P 1 .  FIG. 6B  shows a top view of the valve seat  5  and the valve disc  7  along the longitudinal axis L with the valve disc  7  being positioned in the second angular position P 2 . In addition,  FIG. 1  also shows the valve assembly with the valve disc being positioned in the second angular position P 2  and  FIG. 7  shows the valve assembly  1  with the valve disc  7  being positioned in the first angular position P 1 . 
     Apertures of the orifices  51  which are positioned at the interface  6  of the valve seat  5  with the valve disc  7  completely overlap with apertures of the fluid passages  71  of the valve disc  7  when the valve disc  7  is in the first angular position P 1 . In the present embodiment, the fluid passages  71  extend trough the valve disc  7  parallel to the direction of the longitudinal axis L, so that the apertures of the orifices  51  which are positioned at the interface  6  of the valve disc  7  with the valve seat  5  are arranged completely within the fluid passages  71  in top view along the longitudinal axis L when the valve disc  7  is in the first angular position P 1 . 
     A rotational movement R of the valve disc  7  with respect to the valve seat  5  from the first angular position P 1  to the second angular position P 2  results in a lateral displacement of each of the fluid passages  71  away from the respectively assigned orifice  51 . When the valve disc  7  is in the second angular position P 2 , the fluid passages  71  are laterally spaced apart from the apertures of the orifices  51  at the interface  6 . In this way, the valve seat  5  and the valve disc  7  mechanically interact to seal the orifices  51  for preventing fluid flow from the valve assembly  1  when the valve disc  7  is in the second angular position P 2 . 
     In this way, the valve disc  7  cooperates with the valve seat  5  for sealing and unsealing the orifices  51 . The second angular position P 2  corresponds to a closing position in which the valve disc  7  is operable to prevent fluid flow through the orifices  51 . The first angular position P 1  corresponds to an opened configuration in which the valve assembly  1  is operable to dispense fluid through the orifices  51 . 
     In the present context, the interface  6  of the valve seat  5  with the valve disc  7  is defined by a sealing surface of the valve seat  5  which comprises the apertures of the orifices  51  which face the valve disc  7  and by a sealing surface of the valve disc  7  which comprises apertures of the fluid passages  71  which face the valve seat  5 . The sealing surfaces of the valve seat  5  and the valve disc  7  may, for example, be in direct contact with each other. The sealing surface of the valve disc  7  preferably faces towards the fluid outlet end  175  and the sealing surface of the valve seat  5  preferably faces towards the fluid inlet end  173 . 
     In the present embodiment, the valve assembly comprises a spring  9  which is operable to press the valve disc  7  against the valve seat  5  for pressing the sealing surface of the valve disc  7  against the sealing surface of the valve seat  5 . The spring retains the valve disc  7  in an axially fixed position with respect to the valve seat  5  during operation of the valve assembly  1 . 
     In order to limit or to prevent linear movement of the valve disc  7  with respect to the valve seat  5  in directions perpendicular to the longitudinal axis L, the valve disc  7  is arranged in a recess of the valve seat  5 . 
     In the present embodiment, the valve assembly  1  comprises a valve body  17  which has a cavity  171  in which the valve disc  7  is arranged. The valve body  17  and its cavity  171  extend from the fluid inlet end  173  to the fluid outlet end  175 . The valve seat  5  is received in the cavity  171  at the fluid outlet end  175 . It is rigidly fixed with the valve body  17 . In this way, it is neither rotatable nor axially moveable with respect to the valve body  17  during operation of the valve assembly  1 . The valve seat  5  may be fixed to the valve body  17  for example by means of at least one of welding, friction fit or crimping. An end of the spring  9  which is remote from the valve disc  7  bears on a shoulder of the valve body  17  which is positioned in such fashion that the spring  9  is pre-compressed when the valve seat  5  and the valve disc  7  are mounted into the valve body  17  during the manufacture of the valve assembly  17 . 
     In the present embodiment, the valve assembly  1  further comprises a valve stem  11  which mechanically interacts with the valve disc  7  to rotate the valve disc  7  around the longitudinal axis L. 
     Specifically the valve stem  11  in the present embodiment is axially moveable with respect to the valve seat  5  and the valve body  17  and rotationally fixed with respect to the valve seat  5  and the valve body  17 . For example, the valve body  17  comprises guide elements which allow axial displacement of the valve stem  11  and block rotational movement of the valve stem  11  with respect to valve body  17 , in particular by means of mechanical interaction with the valve stem  11 . 
     The valve stem  11  is mechanically coupled to the valve disc  7  in such fashion that an axial movement A of the valve stem  11  is converted to a rotational movement R of the valve disc  7 . In the present embodiment, this mechanical coupling is effected by means of a pair of protrusions  13  which are arranged at an outer circumferential surface of the valve stem  11  and a pair of channels in an inner circumferential surface of the valve disc  7 . Specifically, the inner circumferential surface may define a central opening of the valve disc  7  which extends, in longitudinal direction L, into the valve disc  7  or completely through the valve disc  7 . The valve stem  11  may be received in the central opening of the valve disc  7 . The protrusions are in the form of pins or noses in the present embodiment. The channels  15  are non-parallel to the longitudinal axis L and have the shape of a section of the helix which has the longitudinal axis L as central axis. 
     The protrusions  13  are positioned at the valve stem  11  in such fashion that each of the protrusions  13  engages one of the channels  15  and moves along the respective channel  15  when the valve stem  11  is moved in axial direction. In this way, axial movement A of the valve stem  11  causes the protrusions  13  to press against a sidewall of the respective channel  15 . Since the valve stem  11 —and with it the protrusions  13 —is rotationally fix, since the channels  15  extend non-parallel to the longitudinal axis L and since the valve disc  7  is only rotatable but not axially moveable with respect to the longitudinal axis L, interaction of the protrusions  13  of the channels  15  effects a torque on the valve disc  7  which results in a rotational movement R of the valve disc  7 . Shapes and positions of the protrusions  13  and the channels  15  are expediently selected in such fashion that the valve disc  7  is displaceable in angular direction from the first angular position P 1  to the second angular position P 2  and back by means of an axial movement of the valve stem  11 . 
     The fluid valve  3  additionally comprises an actuator assembly  19 . The actuator assembly  19  is operable to displace the valve stem  11  in axial direction for rotating the valve disc  7 . In the present embodiment, the actuator assembly  19  is an electromagnetic actuator assembly comprising an armature  191  which is arranged in the cavity  171  and axially moveable with respect to the valve body  17 . The armature  191  is mechanically coupled to the valve stem  11  in such fashion that it takes the valve stem  11  with it in axial direction when it is displaced axially. In the present embodiment the armature  191  is rigidly coupled to the valve stem  11 . For example, the armature  191  and the valve stem  11  are in one piece. 
     The coil  193 , the valve body  17 , and the armature  191  from an electromagnetic circuit so that the coil  193  is operable to move the armature in a direction away from the valve seat  5  when the coil  193  is energized. The return spring  195  of the actuator assembly  19  biases the armature  191  towards the valve seat  5 , so that the armature  195  is moved towards the valve seat  5  when the coil  193  is de-energized. Alternatively, a piezo-electric actuator assembly  19  can be provided for in the fluid injection valve  3 . Such actuator assemblies  19  are known, in principle, to the skilled person therefore are not explained in greater detail here. 
     Expediently, the valve stem  11  may have an elongated shape, i.e. its extension along the longitudinal axis L is larger—in particular at least twice as large, preferably at least five times as large—as its extension perpendicular to the longitudinal axis L. The valve stem  11  preferably extends in axial direction L from the valve disc  7  to the armature  191 . 
     The valve stem  11  of the present embodiment has the general shape of a hollow cylinder. It may have a sidewall which is perforated so that fluid may flow from the interior of the hollow cylinder to the exterior. For example, fluid may flow from the fluid inlet end  173  of the valve assembly  1  into the interior of the valve stem  11 , further through its perforated sidewall, through the fluid passages  71 , and through the orifices  51  to be dispensed at the fluid outlet end  175 . 
       FIG. 8A  shows the armature  191  of a valve assembly  1  according to a second example embodiment in a schematic perspective view. 
       FIG. 8B  shows the valve stem  11  and the valve disc  7  of the valve assembly  1  according to the second example embodiment in a schematic perspective view. 
     The valve assembly  1  according to the second example embodiment corresponds in general with the valve assembly  1  according to the first example embodiment. 
     In contrast to the valve assembly  1  of the first example embodiment, the valve stem  11  of the valve assembly  1  of the present embodiment is rigidly fixed with the valve disc  7  so that the valve stem  11  and the valve disc  7  are neither axially nor rotationally displaceable with respect to each other. Thus, when the valve stem  11  is rotated around the longitudinal axis L, it interacts with the valve disc  7  so that also the valve disc  7  is rotated around the longitudinal axis L. 
     In the present embodiment, the armature  191  is axially moveable with respect to the valve stem  11 . The armature  191  is also axially displaceable with respect to the valve body  17 , as in the first example embodiment. In one development, the valve body  17  comprises a hard stop (not shown in the figures) which is operable to limit axial displacement of the armature  191  with respect to the valve body  17  in the direction towards the fluid outlet end  175 . 
     Expediently, the armature  191  is rotationally fixed with respect to the valve body  17 . In other words, the armature  191  mechanically interacts with the valve body  17  to block rotational movement of the armature  191  with respect to the valve body  17 , for example by means of at least one guide element  21  of the armature  191  and a corresponding guide element of the valve body  17  (not shown in the figures). The guide element  21  may be, for example, an axially extending bar as in  FIG. 8A , an axially extending groove, a flat side face or the like. Such guide elements can also be used for blocking rotational movement of the valve stem  11  and/or the armature  191  with respect to the valve body  17  in the first example embodiment and other embodiments of the valve assembly  1 . 
     The armature  191  and the valve stem  11  are mechanically coupled in such fashion that axial movement A of the armature  191  is converted into rotational movement R of the valve stem  11  and—since the valve stem  11  is fixed to the valve disc  7 —of the valve disc  7 . The mechanical coupling may be effected in analogous fashion to the mechanical coupling of the valve stem  11  and the valve disc  7  in the first example embodiment. 
     Specifically, the valve stem  11  may be received in a central opening of the armature  191 . The valve stem may have a plurality of protrusions  13  at its outer circumferential surface and an inner circumferential surface of the armature  191  which defines the central opening may have corresponding channels  15 . The protrusions  13  are positioned at the valve stem  11  in such fashion that each of the protrusions  13  engages one of the channels  15  and moves along the respective channel  15  when the armature  191  is moved in axial direction. In this way, axial movement A of the armature  191  causes a sidewall of the respective channel  15  to press against the respective protrusion  14 . Since the armature  191 —and with it the channel  15 —is rotationally fix, since the channels  15  extend non-parallel to the longitudinal axis L and since the valve stem  11  and the valve disc  7  are only rotatable but not axially moveable with respect to the valve body  17 , interaction of the protrusions  13  of the channels  15  effects a torque on the valve stem  11  which results in a rotational movement R of the valve stem  11  and the valve disc  7 . 
     The invention is not limited to specific embodiments by the description on basis on these example embodiments. Rather, it comprises any combination of elements of different embodiments. Moreover, the invention comprises any combination of claims and any combination of features disclosed by the claims.