Abstract:
An electromagnetic actuating device comprising a plurality of electromagnetic actuation units ( 10, 12, 14 ), which can be selectively controlled for exerting an actuating force on a corresponding plurality of elongated tappet units ( 22, 24, 26 ) that are supported axially parallel, wherein the actuation units are provided in a common housing ( 18, 20; 78, 82 ) along the actuating direction axially parallel to each other, and form a contact surface that is at least planar in some sections and can be axially moved in the actuating direction at each associated engagement end facing the tappet units. A face ( 34, 36, 38 ) on the engagement side of each of the tappet units interacts with the engagement surface ( 28, 30, 32 ), wherein at least one of the plurality of tappet units sits eccentrically and/or with only a partial surface, with the face thereof on the engagement side, on the engagement surface of the associated actuation unit, particularly adheres to it magnetically.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an electromagnetic actuation device. Devices of this type are generally known from the prior art and are used for manifold actuation tasks, for example in connection with internal combustion engines. 
     On account of limited installation space in an installation location, the requirement often exists to realise a generic actuation device for a respective actuation task sufficiently compactly using a plurality of (typically selectively controllable, that is to say controllable independently of one another) tappet units, so that on the one hand a satisfactory electromagnetic functionality is ensured (for example with regard to the required actuation travel of the tappet units and also reaction or switching time) and on the other hand no undesired reciprocal influencing—mechanical or electromagnetic—is present. 
     It is therefore known from the prior art to realise actuation tasks which require a plurality of actuator units with the aid of individual actuator units, which are fixed or provided independently of one another, wherein this leads to increased configuration and installation outlay and usually the compactness of the overall arrangement is only limited. 
     This problem is aggravated by the fact that the use environment provided for the device, which environment necessitates the engagement of a plurality of tappet units, often predetermines that the tappet units may be closely adjacent to one another and often may only be distanced from one another by a predefined maximum spacing; this is often not achievable or only achievable with restrictions with separate, individually fixed actuator units. 
     The applicant&#39;s German Patent Application 102 40 774 shows an example for a known actuator unit, for example. 
     It is therefore the object of the present invention to create an electromagnetic actuation device with a plurality of electromagnetic actuator units according to the preamble of the main claim, which can be used in particular even in use locations with restricted installation space, as well as in particular beneficially under use conditions which predetermine a limited maximum spacing of the tappet units from one another. 
     SUMMARY OF THE INVENTION 
     The object is achieved by means of the electromagnetic actuation device with a plurality of electromagnetic actuator units, which can be selectively controlled for exerting an actuation force on a corresponding plurality of elongated tappet units, characterised in that the actuator units are provided in a housing along their actuation direction preferably axially parallel to one another, in each case form a working surface which is at least sectionally flat and can be axially moved in the actuation direction at one engagement end facing and in each case assigned one of the tappet units, and interacts with an engagement-side end face of a respective one of the tappet units using the engagement surface, wherein at least one of the plurality of tappet units rests using its engagement-side end face excentrically and/or using only a part surface on the engagement surface of the associated actuator unit, particularly adheres thereto magnetically. 
     In an advantageous manner according to the invention, the plurality of actuator units is first provided (wherein a particularly preferred realisation form of the invention provides at least three actuator units with three tappet units accordingly) in a preferably cylindrical and/or hollow cylindrical housing. According to the invention, the elongated (even preferably cylindrical, even more preferably realised from a metal material) tappet units are driven in that the tappet units rest on an engagement surface of a respective assigned actuator unit (preferably adhere there by means of magnetic action), wherein the engagement surface typically forms the distal end of an armature unit of the relevant actuator unit. 
     According to the invention, the object of an arrangement of the tappet units next to one another which is as compact as possible can then be achieved in that—in the case of adjacent actuator units which are driven parallel to one another—respective tappet units which rest thereon interact with the engagement surfaces excentrically or with their end faces on the engagement side in such a manner that an arrangement which is as compact as possible of the tappet units, which are preferably guided axially parallel to one another takes place, thus—in accordance with the predetermined actuation or use conditions—minimal axial spacings of the tappet units from one another can be realised. 
     In the context of a preferred embodiment of the invention, it is in this case beneficially provided that the common housing which accommodates the actuator units interacts at the end face side with a housing guiding section (guide tube), which offers guides—typically in the form of through holes which run in parallel to one another—for the plurality of the tappet units. 
     According to a preferred embodiment of the invention, at least one of the actuator units is realised in a space-saving manner and at the same time electromagnetically optimised manner by means of a flux-conducting actuator casing unit, which is of bow-shaped construction. In this manner, the packing density of the plurality of actuator units in the common housing can be increased further, particularly on account of the fact that the actuator units are arranged in such a manner that respective actuator casing units of adjacent actuators do not touch one another. 
     In the context of preferred developments of the invention, it is additionally beneficial to create the armature unit from a widened armature section, which armature section has a permanent magnet and at least one armature disc provided thereon (preferably for forming the engagement surface), wherein this widened armature section then merges axially into an elongated armature tappet section, which is guided in a core (preferably a core having a corresponding guide hole). The core (core unit) can then itself preferably accommodate a compression spring provided in accordance with development, which compression spring acts against the armature, and/or have a through hole for fluids (particularly air) for the further movement optimisation by means of pressure equalization. The compression spring provided in accordance with development has proven advantageous, particularly with respect to an optimisation of switching time at low temperatures; in the retracted state of the armature unit, the compression spring is pretensioned by means of the armature tappet section. As soon as current is then applied to the coil unit, the retaining force of the permanent magnet on the core is initially weakened. Additionally, the repelling force acts between coil unit and permanent magnet, as a result of which the armature moves due to the spring force and the repulsion between the permanent magnet and coil unit as soon as the magnetic field has been built up. 
     According to a further preferred embodiment, at least one of the (metallic) tappet units is provided with a plurality of sections in the axial direction: a first, magnetically optimised section of the tappet unit forms the end face on the engagement side, that is to say interacts with the engagement surface of the armature unit, whilst an opposite second tappet section is optimised with respect to hardness and wear properties, more or less for the purpose of interaction with a downstream actuation assembly. A realisation of this type of a plurality of sections of the tappet unit can in this case take place either by means of suitable material influence of a one-piece unit, alternatively in the context of preferred developments, the tappet unit can be assembled in a suitable manner by means of a plurality of individual sections, wherein, in this regard, the disclosure content of the applicant&#39;s German Utility Model Application 20 2006 011 905 should be regarded as belonging to the present invention and as included in the present disclosure. Thus, it is suitable in a beneficial manner in accordance with development to realise the first magnetically optimised section of the tappet unit by means of a soft-magnetic material, wherein ferromagnetic metals (such as iron, cobalt, nickel) are further preferably beneficially suitable for realisation. By contrast, it is preferred in accordance with development in the context of the invention to realise the second tappet unit from austenitic material, wherein here in particular cold forming methods can increase the hardness of the second section further. In this case it is not necessary to realise the tappet unit from two separate workpieces, rather it can be provided within the context of the present invention, for example to form the second, wear-optimised section by means of a hardened (e.g. by a heat treatment) section of an otherwise soft-magnetic material. 
     Whilst the present invention is particularly suitable for realising actuation tasks by means of three tappet units which run axially parallel to one another and in one plane, advantageously for camshaft displacement for an internal combustion engine for example, the present invention is not limited to this. The spacing of two tappet units which are guided towards one another can also advantageously be optimised in particular in the context of the invention, just as realisation forms are conceivable, in which more than three tappet units are driven in a compact and space-saving manner by means of an associated actuator unit in each case. Whilst the axially parallel guiding of the tappet units may additionally be the typical realisation form, the present invention is not limited to this; rather it is sufficient for the realisation of the advantages according to the invention if merely one component of the motion vector of each tappet unit runs in the actuation direction, wherein skew directions of extension of the tappet units or directions of extension of the tappet units which are inclined with respect to one another in some other manner in particular are also comprised by the present invention. The guiding of the tappet units in a common housing is also the typical realisation form, yet variants are conceivable and comprised in the context of the invention, in which variants respective tappet units are guided in separate individual housings which are correspondingly adjacent to one another. 
     As a result, what emerges by means of the present invention in a surprisingly simple and elegant manner is an arrangement which combines a compact design with ease of installation, a high degree of operational reliability and optimal switching-time and magnetic properties. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages, features and details of the invention result from the following description of preferred exemplary embodiments, as well as on the basis of the drawings; in the drawings: 
         FIG. 1  shows a perspective view of the electromagnetic actuation device according to a first preferred embodiment of the invention (with the housing removed); 
         FIG. 2  shows a rear view/plan view onto the arrangement according to  FIG. 1 ; 
         FIG. 3  shows a side view onto the arrangement according to  FIG. 1 ; 
         FIG. 4  shows a sectional view through the exemplary embodiment according to  FIG. 1  to  FIG. 3  (with housing) along a section line B-B in  FIG. 5 ; 
         FIG. 5  shows a longitudinal section through the device according to  FIG. 4  along the section line A-A; 
         FIG. 6  shows a longitudinal section through an actuator unit according to the exemplary embodiment of  FIG. 1  to  FIG. 5 ; 
         FIG. 7 ,  FIG. 8  show detail views turned through 90° of the bow-shaped flux-conduction element (actuator casing unit) for use in the actuator unit according to  FIG. 6 ; 
         FIG. 9 ,  FIG. 10  show a perspective as well as side view to clarify the interaction between an actuator unit ( FIG. 6  to  FIG. 8 ) with a tappet unit which interacts excentrically as well as over part of a surface; 
         FIG. 11  shows a perspective view of the electromagnetic actuation device according to a second embodiment of the present invention with two tappet units; 
         FIG. 12  shows a longitudinal section through the device according to  FIG. 11 ; 
         FIG. 13 ,  FIG. 14  show detail views to clarify the interaction of an actuator unit of the exemplary embodiment of  FIG. 11  and  FIG. 12  with a tappet unit; 
         FIG. 15 ,  FIG. 16  show schematic diagrams to clarify the magnetic interaction of the permanent magnets of two adjacent actuator units in the retracted state ( FIG. 15 ) and in the extended state of an actuator unit ( FIG. 16 ); 
         FIG. 17  shows a longitudinal section analogous to  FIG. 5  to clarify a further embodiment with tappet units which consist of a plurality of functional sections; and 
         FIG. 18 ,  FIG. 19  show a side and perspective view of a variant of the present invention of a tappet unit which is inclined relatively to an actuator movement direction, which tappet unit additionally has a spherically curved end face for interacting with the actuator. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 to 3  for the first exemplary embodiment show how three actuator units  10 ,  12 ,  14  are arranged distributed in a housing (only a circular housing lid  16  is shown as a yoke) in such a manner that the actuator units  10  to  14  bear against a hollow cylindrical inner wall of a housing casing  18  (not shown in the  FIGS. 1 and 3 ). A flat housing section  20  on the engagement side sits on the housing lid (yoke)  16 , which flat housing section has three openings next to one another in an extension plane for guiding three tappet units  22 ,  24 ,  26 , which tappet units are mounted axially parallel in the manner shown and can be driven selectively in a manner to be described below by means of an assigned one of the actuator units  10 ,  12 ,  14 . 
     In the case of a typical external housing diameter of 40 mm, a maximum diameter d ( FIG. 2 ) of one of the actuator units  10  to  14  is approx 17 mm; the arrangement shown can, in the case of an assumed diameter of the elongated cylindrical tappet units  22 ,  24 ,  26  of 5 mm, therefore realise an average axial spacing a of the tappet units of 7 mm in the manner shown in  FIG. 3 , in accordance with the installation and actuation conditions on a downstream assembly, in the present exemplary embodiment a camshaft control for an internal combustion engine, which camshaft control can be actuated (not shown) by the three tappets  22 ,  24 ,  26 . 
     The image views of FIGS.  4  and  5 —(in a deviation from  FIGS. 1 and 3 , the cylindrical housing casing  18  is also shown here) in particular clarify the geometric relationships in the transition between the actuator units  10  to  14  (more precisely the engagement-side engagement surfaces  28 ,  30 ,  32  of the actuator units) and the end faces  34 ,  36  and  38  directed towards them in each case: it emerges, cf. in particular the section view of  FIG. 4 , that the tappet units  22 ,  24 ,  26  in each case rest excentrically on the disc-shaped engagement surfaces  28  to  32 , wherein the likewise circular end faces  34  to  38  partially project beyond a respective outer edge of the engagement surfaces  28  to  32  of the actuator units, in the manner shown in  FIG. 4 . In this manner, the geometry shown can then be achieved, namely tappet units  22  to  26 , which are closely adjacent to one another, nevertheless moveably guided independently of one another, with minimised spacing to one another (in the exemplary embodiment a=7 mm, cf.  FIG. 3 ). In this case, the tappet units have flat end faces in the exemplary embodiment shown, as for example shown in  FIG. 5 . These can have another contouring however, for example a convex (spherical) outer shape, in order to take account of a possible circumstance that in alternative realisation forms, the movement direction of the actuator units does not correspond to the movement direction of the tappet units, rather, for example, the tappet units are inclined (also relatively to one another) with respect to the movement direction of the actuator units (or their engagement surfaces  28  to  32 ). 
     The  FIGS. 6 to 8  clarify constructive details of the three actuator units  10  to  12 : an armature created from an elongated, cylindrical armature tappet section  40  as well as a widened armature section  47 , itself formed in a layered manner from an armature disc  42 , a permanent magnet disc  44  and also a pole disc  46 , forms one of the engagement surfaces  28  to  32  on the outer surface of the pole disc  46  and is guided in an elongated hollow cylindrical core element  48 , which, opposite the armature disc  42 , forms an annular collar section  50  and has a through hole  52  along its axial direction of extension, which, to optimise the fluid flow, enables a free air flow in the arrangement for example and is furthermore constructed to accommodate a compression spring  54 , which, in the stopped state of the armature shown in  FIG. 6 , pretensions the latter in its rightwards-directed movement direction. 
     The yoke element  48  is initially enclosed in turn by a coil unit which has a coil former  56  and also a winding  58  and is itself sectionally enclosed in the circumferential direction by a bow-shaped flux-conduction element  60 , which offers an opening for a narrow end of the yoke element  48  at one end and opens into two free limbs  62 ,  64  at the other end, which limbs delimit the actuation path of the armature (and therefore also of the pole disc  46  with engagement surface). 
     The  FIGS. 7 and 8  show the bow-shaped flux-conduction element  60  in detail; the limbs  62  and  64  are formed in the manner of sections of an elongated cylinder and sit integrally on a bottom section  66 . Variants of this exemplary embodiment additionally provide, in the context of the present invention, that the bow-shaped flux-conduction element  60  has only one limb and another of the limb pair  62  or  64  can be omitted. Although this leads to a reduction of the magnetic properties, it potentially enables the further condensing of a plurality of actuator units formed therewith to a compact structure. 
     The  FIGS. 9 and 10  clarify, as an isolated illustration of an actuator unit with a tappet unit, how—in the case of practically unimpaired electromagnetic functionality—the bow-shaped flux-conduction unit  60  only encloses the arrangement made up of the coil unit, yoke element and armature unit in opposite sections in the circumferential direction, and at the same time establishes the possibility for the part of the end face of the tappet unit  22  shown to project at the edge beyond the engagement surface  28 . 
     The  FIG. 2  clarifies, in this respect, how the elongated-disc-shaped bottom sections  66  and the limbs  62 ,  64  of the respective flux-conduction elements are placed in such a manner that—to minimise the packing density in the hollow-cylindrical housing—no reciprocal influencing of the flux-conduction elements  60  takes place, rather the (lower) external diameter of the coil units can be used effectively for space minimisation. 
     The  FIGS. 11 to 14  show an alternative realisation form of the present invention according to a second exemplary embodiment. This exemplary embodiment provides only two tappet units  70 ,  72 , which are moved by associated actuator units  74  or  76  in each case. The actuator units  74  and  76  correspond constructively to the realisation explained on the basis of  FIGS. 6 to 8  and sit in a common housing  78  in the exemplary embodiment shown, which common housing has a flat contour (the reference number  80  schematically shows a fixing flange for the housing arrangement  78 ). 
     As the section view of  FIG. 12  in particular clarifies, the elongated cylindrical tappet units  70 ,  72  are in turn guided in a front housing section  82  in such a manner that they can be moved parallel to one another while minimising their axial spacing (in turn approx. 7 mm), wherein, as  FIG. 12  allows to be seen, the tappet units  70 ,  72  in each case rest, in the manner according to the invention, excentrically on the outer engagement surfaces formed by a respective pole disc  46  (or adhere there magnetically). 
     In the exemplary embodiment shown it additionally becomes clear that the tappet units  70  and  72  here consist in each case of two sections, a first magnetically optimised section  84  and also a second section  86  seated thereon in the longitudinal direction, which is adapted for optimised interaction with an end-side engagement partner in particular, for example by means of suitable hardening (or other forms of treatment for wear resistance or the like). In the exemplary embodiment shown, a respective one of the tappet units  70 ,  72  is assembled from two suitable metal materials for the sections  84  and  86 ; other alternatives for the realisation of the plurality of sections are conceivable, just as is a use of the two-part tappet units in the context of the first exemplary embodiment of  FIGS. 1 to 10  (to this extent,  FIG. 17  shows this variant as a further exemplary embodiment, wherein identical function components are provided with the same reference numbers and the tappet units  22 ′,  24 ′ and also  26 ′ are accordingly two-part variants). With respect to the realisation of the first section  84  or the second section  86 , reference is made to the applicant&#39;s DE 20 2006 011 905 U1; according to which the use of a soft-magnetic or ferromagnetic material for the first section is particularly beneficially suitable, whilst, for example, an austenitic material is beneficial for the realisation of the second section and both sections are permanently connected to one another by means of suitable bonding methods. Alternatively, for example the second section can, in the context of preferred developments, also be realised by means of hardening, or similar measures, of an otherwise magnetically beneficial (e.g. soft-magnetic) material. 
     For the exemplary embodiment of  FIG. 11  and  FIG. 12 , the detail views of  FIG. 13  and  FIG. 14  in turn clarify the excentric or also laterally projecting resting of the tappet units on a respective engagement surface. 
       FIG. 15  and  FIG. 16  clarify a magnetic interaction between two adjacent actuator units, wherein this applies both for the first exemplary embodiment with three tappet units and for the second exemplary embodiment with two tappet units:  FIG. 15  schematically shows how, in the retracted state of two adjacent actuator units, the respective permanent magnet disc  44  (magnetised in the axial direction) is located at the same height in each case, in other words, and as is shown by the double arrow in  FIG. 15 , a repulsion effect of the respective same magnetic poles from one another results, so that a repulsion force between the respective armature units exists in this operating state. As soon as one of the actuator units is moved out of its rest position (that is to say approximately in accordance with  FIG. 6 ), an attraction (clarified by the long double arrow) results between the south pole of the permanent magnet located on the left and the north pole of the permanent magnet shown on the right, whilst as before, the same-poled permanent magnet sections repel one another (short double arrows). As a result, the dynamic behaviour of the described exemplary embodiments is then improved by this configuration. 
     The present invention was only described in an exemplary manner on the basis of the exemplary embodiments; in the exemplary embodiment shown, an axial spacing of three adjacent cylindrical tappet units (which in each case had a diameter of 5 mm) of only 7 mm was realised in the case of a diameter of the housing casing of approx. 40 mm. With an effective travel of the actuator movement of 4 mm, a switching time of between approx. 20 and 22 ms (12 to 22, up to 100 ms at −35° C.) can be realised. 
     Whilst the previously described exemplary embodiments require that actuator and tappet unit are in each case guided and orientated axially parallel to one another, the present invention is not limited to this; rather it is possible in the context of preferred developments that the tappet units are inclined relatively to the actuators or their movement directions, as the tappet units can also be inclined relatively to one another (that is to say are e.g. guided in a skew manner), just as it is principally not ruled out that the movement directions of the plurality of actuators are also inclined relative to one another.  FIGS. 18 and 19  clarify one such variant as a side or perspective illustration, namely a tappet inclined in its movement direction relatively to the actuator movement direction, which tappet additionally does not, at the end face, have a flat end face in its engagement region for the actuator, but rather has a spherical (concavely curved) end face. 
     A tappet unit  90  definitely rests on the engagement surface  28  of the actuator unit here, analogously to the illustration of  FIGS. 9 and 10  (to this extent, the reference numbers for the actuator unit  60  remain), wherein however, in deviation from the tappet unit  22 , the tappet unit  90  forms a convexly curved spherical end section  92  at the engagement side for interacting with the end face  28 , so that a reliable interaction and a reliable force transmission between the units is ensured in the end region of the disc  28 . The geometry which can be recognised from the illustrations of  FIGS. 18 and 19  additionally clarifies that a movement direction of the tappet unit which runs through the longitudinal axis of the tappet unit  90  (the tappet unit is accordingly guided in an assigned housing—not shown—) is inclined relatively to the longitudinal or axial direction of the actuator unit. In turn, analogously to the embodiment of  FIGS. 9 and 10 , the tappet unit  90  rests on the disc-shaped surface  28  and can be held there e.g. by the action of a permanent magnet in an adhering manner. 
     The present invention is not limited to the configurations shown with two or three tappet units, but rather is also suitable in principle for a larger number of actuators and associated tappet units. Even if a preferred area of application of the present invention lies in the realisation of actuation tasks in the case of internal combustion engines, for example in camshaft displacement, the area of application of the present invention is in principle unlimited and is particularly effective where only a small installation space is available for a plurality of actuator units and yet respective tappets must fulfil their actuation purpose with only a very small spacing from one another at the same time.