Abstract:
The invention relates to a magnet-retaining spring ( 11 ), to an electric machine ( 10 ) containing such a magnet-retaining spring, and to a method for producing the electric machine ( 10 ), in particular for the motorized adjustment of moving parts in a motor vehicle, wherein the magnet-retaining spring ( 11 ) has a first leg ( 90 ) and a second leg ( 91 ), which are connected to each other by means of a bow ( 92 ), and the first and second legs ( 91, 92 ) span a plane ( 88 ) in space, wherein the bow ( 92 ) protrudes from the spanned plane ( 88 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention proceeds from a magnet-retaining spring, and also an electrical machine containing a magnet-retaining spring of this kind, and also a method for producing the electrical machine. 
         [0002]    U.S. Pat. No. 4,372,035 has disclosed an electric motor in which two permanent magnets which are situated opposite one another and two so-called consequent poles between said two permanent magnets are arranged in a pole housing. In order to form the consequent poles, a contour is formed in the pole housing wall, the arcuate inner face of said contour being at the same distance from the rotor as the shell-like permanent magnets. Magnet-retaining springs which press the permanent magnets against the housing wall by means of a spring force in order to fasten said permanent magnets are known for fastening permanent magnets in the pole housing. DE 102007004873 A1 describes, for example, a magnet-retaining spring of this kind, in which shafts are formed on the two longitudinal limbs in order to stabilize said magnet-retaining spring. The clip between the two longitudinal limbs is of planar design and is arranged in the same plane as the two limbs. If a magnet-retaining spring of this kind is intended to be used for the above-described consequent pole motor, there is a risk of the magnet-retaining spring tilting radially inwardly toward the rotor in the region of the consequent pole contour and touching said rotor. This can lead to destruction of the electric motor. 
       SUMMARY OF THE INVENTION 
       [0003]    In contrast to the above, the magnet-retaining spring according to the invention and the electrical machine containing a magnet-retaining spring of this kind, and the method according to the invention for producing a machine of this kind, have the advantage that the design of the magnet-retaining spring, in particular the clip of said magnet-retaining spring, prevents the magnet-retaining spring from tilting radially inward. This is achieved by the clip not being arranged in the same plane which is formed by the two approximately straight limbs. The clip has at least spatial components which are formed transversely in relation to this plane. Owing to this three-dimensional design of the magnet-retaining spring, the limbs bear securely against the permanent magnets without there being a risk of the magnet-retaining spring touching the rotor. 
         [0004]    It is particularly advantageous when the connecting region between the two limbs is bent. In the assembled state, this connecting region then runs—at least partially—in the manner of an arc through the interior space in the housing starting from the two straight limbs of the housing wall which bear against the permanent magnet. In a preferred embodiment, the clip has, in particular, no straight sections in this case, but rather is curved over its entire longitudinal extent—wherein the bending radius is preferably variable over the longitudinal extent. 
         [0005]    The clip which connects the two approximately straight limbs to one another can also have a straight section which then runs preferably approximately parallel to the plane which is spanned by the two limbs, wherein the straight section is at a certain distance from this plane. In this case, the clip also has two further transition sections which then lead from the straight section to the two limbs in a more or less bent manner. 
         [0006]    If the direction of extent of the clip is broken down (in the mathematical sense) over its entire longitudinal extent into in each case two components which extend in the plane which is spanned by the limbs and a direction perpendicular to said plane, the clip always has at least one section in which the directional component perpendicular to the plane of the limb is different from zero. 
         [0007]    The magnet-retaining spring is produced in a particularly cost-effective manner from a metal wire as a wire bent part in which an integral wire with a round or polygonal cross section is bent into a three-dimensional structure. Owing to the use of spring steel, the magnet-retaining spring is elastically deformed when it is installed, so that said magnet-retaining spring exerts a spring force on the permanent magnets. 
         [0008]    The magnet-retaining spring is preferably manufactured such that the two limbs form an angle in relation to one another before installation, said angle being, for example, 10° to 35°. During installation, the magnet-retaining spring is then deformed such that the two limbs run approximately in parallel. Since the limbs are straight, the deformation during installation takes place in the region of the clip or in the transition regions from the clip to the limbs. 
         [0009]    In order to fix the permanent magnets and the pole housing of the electrical machine in a particularly simple manner, said permanent magnets are pressed against the inner wall by means of magnet-retaining springs. In the process, the free ends of the U-shaped spring bear against side faces, which point in the circumferential direction, of the permanent magnets. Owing to the clamping force which is exerted by means of the magnet-retaining spring between the two permanent magnets, said permanent magnets are fixed in the housing both radially and, in particular, also axially. For improved contact of the free limbs against the side faces, the limbs or the side faces can have a structured surface. The permanent magnets can have—in particular continuous—pole lifting or two different discrete inside radii, as a result of which the side face is at a greater distance from the rotor. The side face is formed radially or obliquely to the radial direction and preferably has a sensor on the outer circumference. It is possible to use, for example, ferrite material for the magnets, or as an alternative also rare-earth magnet materials. 
         [0010]    The consequent poles are preferably expediently realized by integrally forming in each case two beads, which run in the axial direction, in the pole housing wall. As a result, a curved inner contour which interacts with the rotor in a magnetic manner is formed in the circumferential direction. These beads form the edges of the consequent pole in relation to the circumferential direction and at the same time form the boundary for the retaining region of the permanent magnets. Since the consequent poles and the permanent magnets have approximately the same inside diameter, the limbs are arranged between the beads and the side faces of the magnets. 
         [0011]    To this end, a hollow space or gap into which the free limbs engage over the entire axial length is formed between the beads of the consequent pole contour and the side faces of the permanent magnets. In this case, the limbs firstly bear against the side face of the magnet in the circumferential direction and on the opposite side against the lateral inner face of the bead for the purpose of defined positioning. The clip, which connects the two straight limbs, then has radial components which engage over the two edge-side beads of the consequent pole by the clip extending radially inward from the beads. 
         [0012]    The housing is advantageously in the form of a pole pot which has a base—which is preferably integrally formed with the pole pot—on one side, said base having, in particular, a bearing receptacle for a rotor bearing. The opposite open pole pot side has a flange which, after assembly, bears against a corresponding mating flange of a further housing part. In order to prevent the radially inwardly projecting clip colliding with the rotor, the clip is arranged axially between the rotor and the housing base, wherein said clip bears axially against the housing base, in particular for the purpose of unambiguous positioning. 
         [0013]    A receptacle region is formed on the pole housing immediately adjacent to the flange. Said receptacle region can advantageously receive a brush holder component which extends axially over the interface of the flange into the adjacent housing part. By way of example, holes are formed on the flange as receptacles for connecting elements—preferably screws or rivets—to a gear mechanism housing. 
         [0014]    Owing to the production method according to the invention for the pole housing, the consequent pole region with the beads, the retaining region for the magnets and the receptacle region with the flange are formed in a cost-effective and precise manner by means of deep-drawing in one working step. In the process, the design of the specific dimensions of particular components and the wall thickness with minimum material usage can be realized by the selection of the deep-drawing tool. The three-dimensional retaining spring can be used after the insertion of the magnets in accordance with the standard mounting process for customary magnet-retaining springs, wherein the limbs can advantageously be positioned exactly in a simple manner by contact with the side faces of the magnets and with the lateral inner faces of the consequent poles. In the process, the clip of the magnet-retaining spring runs against the housing base radially within the plane between the two limbs, without the clip bearing axially against the rotor. The axial mounting of the rotor and of the brush holder component into the pole housing permits an unambiguously predefinable flange interface which is particularly expediently suitable for a modular construction kit for combining different pole housings and gear mechanism housings. 
         [0015]    The spring-retaining element can optionally also be used in combination with adhesive bonding of the permanent magnets in order to reliably fix said permanent magnets during the adhesive bonding process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Embodiments of the invention are illustrated in the drawings and explained in greater detail in the following description. 
           [0017]    In the drawings 
           [0018]      FIG. 1 : shows an exemplary embodiment of an electrical machine according to the invention, 
           [0019]      FIG. 2 : shows a cross section through  FIG. 1 , 
           [0020]      FIG. 3 : shows an exemplary embodiment of a magnet-retaining spring according to the invention, 
           [0021]      FIG. 4 : shows a further exemplary embodiment of a magnet-retaining spring according to the invention, 
           [0022]      FIG. 5 : shows the magnet-retaining spring according to  FIG. 3  in the state in which it is installed in the housing, 
           [0023]      FIG. 6 : shows a schematic installed arrangement of the magnet-retaining spring according to  FIG. 4 , and 
           [0024]      FIG. 7 : shows the mounting concept according to the invention for the gear mechanism/drive unit. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]      FIG. 1  shows an electrical machine  10  according to the invention which is in the form of an electric motor  11 . The electric motor  11  is, for example, a constituent part of a gear mechanism/drive unit  100 , as is used for adjusting a sliding roof, a window or a seat part in motor vehicles. The electrical machine  10  has a stator  12  in which two permanent magnets  18  are arranged opposite one another in a housing  16  which is in the form of a pole housing  16 . Two consequent poles  22  which are situated opposite one another and are formed by the housing wall  26  of the pole housing  16  are arranged between the two permanent magnets  18  which are situated opposite one another. To this end, in each case two beads  28 , which extend in the axial direction  30 —preferably as far as a housing base  82  of the housing  16 —are formed in flattened regions  20  of the pole housing  16 . The consequent pole  22  is in the form of a curved pole housing wall  26  between the two beads  28  in the circumferential direction  32 , said housing wall forming, together with the beads  28  and a lateral retaining region  34  for the permanent magnets  18 , the flattened region  20  of the pole housing  16 . The pole housing  16  has an axially open side  36  on which a flange  38  for connection to a further housing part  40  is formed. The flange  38  has receptacles  42  for connecting elements which are in the form of, for example, bores  43 . Screws can preferably be screwed into a corresponding mating flange  44  as connecting elements through said bores  43 . A rotor  14  is inserted into the stator  12  in  FIG. 1 , wherein a small radial air gap  46  to the permanent magnets  18  and consequent poles  22  which surround the rotor  14  is formed. 
         [0026]      FIG. 2  shows a section through the stator  12  and the rotor  14  of  FIG. 1  transverse to the axial direction  30 . The permanent magnets  18  bear against the inner wall  17  of the pole housing  16  and are fixed in the pole housing  16  by means of magnet-retaining springs  11 . The two permanent magnets  18  are magnetized in the same sense in the radial direction  31 , and therefore the two permanent magnets form a south pole, for example, on their radially inner face. A magnetic circuit to the consequent poles  22  is produced by means of the pole housing  16  which forms a magnetic return path, said consequent poles then each forming a north pole, for example, on the inner wall  17  of the pole housing  16 . Since no permanent magnets  18  are arranged in the region of the consequent poles  22 , the maximum dimension  25  of the pole housing  16  between the flattened regions  20  is considerably lower than in the direction of the two permanent magnets  18 . The maximum dimension  25  represents a width  24  over flats for the available installation space which is matched in an optimum manner to the corresponding application, in particular to the installation position in the motor vehicle. In  FIG. 2 , the maximum radial dimension  25  is formed at the curved regions of the consequent poles  22  between the beads  28  in the circumferential direction  32 . The wall thickness  54  of the pole housing  16  is optimized in relation to weight, magnetic flux and noise minimization. Since the pole housing  16  is produced as a deep-drawn part, the wall thickness  54  is relatively constant over the entire circumference. The permanent magnets  18  have so-called pole lifting  58 , so that the air gap  46  between the rotor  14  and the permanent magnet  18  widens in the circumferential direction  32 . The rotor  14  has a rotor shaft  60  on which an armature stack  62  for receiving electrical windings  64  is arranged. To this end, the armature stack  64  has rotor teeth  66  which are formed from radial tooth shafts  68  which are terminated by radially outer tooth heads  70 . The electrical windings  64  are wound onto the tooth shafts  68  radially within the tooth heads  70 . The permanent magnets  18  have side faces  99  in the circumferential direction  32 , two free limbs  90 ,  91  of the magnet-retaining spring  11  bearing against said side faces. The free limbs  90 ,  91  are connected to one another at their ends which are not free by means of a clip  92 , so that the magnet-retaining spring  11  between the permanent magnets  18  generates a contact-pressure force which acts transverse to the axial direction  30 . The clip  92  projects out of a plane  88  which is spanned by the two limbs  90 ,  91  and is formed radially into the housing interior in the direction of the rotor shaft  60 . In the upper half of the figure, the magnet-retaining spring  11  has a round cross section  13 , and the clip  92  is curved or in the form of an arc. In this case, the clip  92  has a radial component  96  in the transition sections  87  to the limbs  90 ,  91 , said radial component pointing radially away from the beads  28 , so that the clip  92  runs through the interior of the housing  16  and overlaps the rotor  14 . In this case, the clip  92  runs axially between the rotor  14  and the housing base  82 . In the lower half of  FIG. 2 , the magnet-retaining spring  11  has a polygonal, in particular rectangular or square, cross section  13 . In this case, the clip  92  is formed in an approximately polygonal manner transverse to the axial direction  30 , so that the clip  92  has a straight section  84  which is arranged approximately parallel to the plane  88 . In this case, the transition sections  87  point approximately perpendicularly away from the plane  88 . 
         [0027]      FIG. 3  shows a magnet-retaining spring  11  according to the invention before it is installed into the electrical machine  10 . The two limbs  90 ,  91  are straight and have free ends  95 . The limbs  90 ,  91  are connected to one another by means of the clip  92  at the ends which are situated opposite one another. The two limbs  90 ,  91  form a plane  88 , wherein the clip  92  is arranged outside this plane  88 . As a result, the magnet-retaining spring  11  is three-dimensional. In this case, the clip  92  has a straight section  84  which runs approximately parallel to the plane  88 . The transition sections  87  in the direction of the limbs  90 ,  91  are bent. In this exemplary embodiment, the limbs  90 ,  91  are arranged at an angle in relation to one another within the plane  88 , said angle being, for example, approximately 30°. When it is installed into the housing  16 —as is illustrated in FIG.  5 —the magnet-retaining spring  11  is elastically reshaped, so that the limbs  90 ,  91  then bear against the side faces  99  and are oriented approximately parallel in relation to one another. 
         [0028]      FIG. 4  shows a further exemplary embodiment of a magnet-retaining spring  11  according to the invention, in which the two limbs  90 ,  91  are oriented approximately parallel in relation to one another after installation. The clip  92  again projects out of the plane  88 , wherein the clip  92 —in accordance with the lower half of FIG.  2 —is polygonal transverse to the plane  88 . The straight section  84  of the clip  92  is at a distance  72  from the plane  88 , said distance always being greater than the inwardly directed height of the bead  28 . During installation, the transition sections  87  in particular are elastically deformed in this embodiment, so that the two limbs  90 ,  91  are pressed apart transverse to the axial direction  30 , as is illustrated in  FIG. 6 . 
         [0029]      FIG. 5  shows a plan view of the open side  36  of the stator  12 , in which the permanent magnets  18  are retained in the pole housing  16  by means of magnet-retaining springs  11  according to  FIG. 3 . The magnet-retaining spring  11  has two free limbs  90 ,  91  which are situated opposite one another and which are connected to one another by means of the clip  92 . The free limbs  90 ,  91  bear against the permanent magnets  18  which are situated opposite one another and press said permanent magnets against the inner wall  17  of the pole housing  16  in order to fix said permanent magnets. 
         [0030]    A hollow space  94  into which the limbs  90 ,  91  project is formed between the side face  99  of the permanent magnet  18 , which side face points in the circumferential direction  32 , and an opposite lateral face  27  of the bead  28 . In this case, the free ends  95  of the limbs  90 ,  91  preferably bear both against the side face  99  and also against the lateral face  27  of the bead  28 . In this case, the hollow space  94  in particular is in the form of a wedge in the radial direction  31 . In this exemplary embodiment, the contact face of the limbs  90 ,  91  on the permanent magnets  18  lies within the radially inner half of the radial wall thickness  56  of the permanent magnets  18 . The cross section  13  of the limbs  90 ,  91  is, for example, round, but may also be semicircular, flattened or be in the form of a flat profile or polygonal profile, and/or also have a structured surface which adheres better to the side face  99 . A structure, for example a notch in the axial direction  30 , can likewise be formed on the side face  99 , the limbs  90 ,  91  engaging into said structure. In this case, the contour of the side face  99  can be correspondingly adapted, for example entirely or partially form an angle in relation to the radial direction  31 . Furthermore, the outer or inner magnet edge of the permanent magnet  18  can be correspondingly beveled or have a chamfer  19 . The two adjacent beads  28  each form inner edges  97  which are bridged by the clip  92  which connects the two limbs  90 ,  91  beyond the inner edges  97 . This prevents the magnet-retaining spring  11  tilting radially inward out of the axial direction  30  at the inner edge  97  of the bead  28  which would form a tilting point for a conventional magnet-retaining spring. To this end, the clip  92  has radial components  96  which lead through the interior of the housing  16  radially away from the inner edges  97 . In  FIG. 5 , the clip  92  bears axially against the inner side of the housing base  82  which then forms an axial stop for the magnet-retaining spring  11 . Two magnet-retaining springs  11  are clamped (not illustrated) between the two permanent magnets  18 , the limbs  90 ,  91  of said magnet-retaining springs lying approximately in a plane  88  with the flattened regions  20  of the pole housing  16 . 
         [0031]      FIG. 6  schematically illustrates the magnet-retaining spring  11  according to  FIG. 4  in the installed state without the housing. The clip  92 , which again has a straight section  84  here, is arranged axially between the rotor  14  and the housing base  82 , not illustrated. In this case, the clip  92  overlaps the rotor  14 , so that the clip  92  is arranged radially within the circumferential face  15  of the rotor  14 . A rotor bearing  61  is arranged on the rotor shaft  60 , said rotor bearing being inserted into a bearing receptacle  63  in the housing base  82 . The limbs  90 ,  91  preferably extend over at least half of the axial extent of the permanent magnets  18 , as a result of which said permanent magnets are pressed reliably against the housing  16  over their entire axial extent. 
         [0032]    During the production process for the electrical machine  10 , the pole housing  16  is manufactured as a pole pot with the flange  38  and with the receptacle region  37  as a defined interface by means of deep-drawing, wherein the beads  28  are also integrally formed in one working step. The permanent magnets  18  are then inserted into the pole housing  16 , wherein said permanent magnets can optionally be adhesively bonded to the inner wall  17  of said pole housing. In order to fix the permanent magnets  18 , two magnet-retaining springs  11  are inserted into the pole housing  16  in such a way that the limbs  90 ,  91  bear against the side faces  99  of the permanent magnets  18  and press said permanent magnets against the inner wall  17  of the pole housing  16 . In this case, the clip  92  is arranged at a distance from the plane  88  of the two limbs  90 ,  91  radially within said plane, so that the magnet-retaining springs  11  do not touch the inner edges  97  of the beads  28 . After the permanent magnets  18  are fixed, the rotor  14  and a brush carrier component  86  are inserted axially into the pole housing  16 , so that the brush carrier component  86  is arranged in the receptacle region  37  and projects axially beyond the flange  38 . A further housing part  40  which is in the form of a gear mechanism housing  101  is then mounted onto the brush carrier component  86  axially over the rotor shaft  60 , until the flange  38  bears against the mating flange  44  of the housing part  40 . Connecting elements—preferably screws—are then inserted into the receptacles  42  in the flange  38  and connected to the housing part  40 . This mounting method is shown in  FIG. 7  in which the rotor shaft  60  has a worm  106  and is mounted in the brush holder component  86  by means of a sliding bearing  118 —in particular a spherical bearing. 
         [0033]      FIG. 7  shows a fully mounted gear mechanism/drive unit  100  which, as electrical machine  10 , has an electric motor  9  with consequent poles  22 , which electric motor is flange-connected in a housing part  40  which is in the form of a gear mechanism housing  101  in which a gear mechanism  104  is arranged. The gear mechanism  104  is in the form of, for example, a worm gear mechanism  105  in which the worm  106  which is arranged on the rotor shaft  60  of the electric motor  9  meshes with a worm wheel which is mounted in the gear mechanism housing  101 . The drive torque of the electric motor  9  is passed by the worm wheel to an output drive element  110 —in particular an output drive pinion  112 —which drives, for example, the part—in particular in the motor vehicle—which is to be adjusted. The pole housing  16  of the electric motor  9  is produced from metal and serves as a magnetic return path. In the exemplary embodiment, the gear mechanism housing  101  is produced from plastic, in particular by means of an injection-molding process. The housing part  40  has an electronics housing  102  for accommodating an electronics unit and is in the form of an integral constituent part of the gear mechanism housing  101 . 
         [0034]    It should be noted that various possible combinations of the individual features with one another are possible with regard to the exemplary embodiments which are shown in the figures and described in the description. Therefore, it is possible, for example, for the specific forming of the three-dimensional magnet-retaining spring  11 , in particular the transition sections  87  between the limbs  90 ,  91  and the clip  92 , to be varied and matched to the geometric space conditions in the housing  16 . In the process, it is possible, for example, for the axial length of the two limbs  90 ,  91  to also be of different lengths, or for the limbs  90 ,  91  to have a different angle in relation to the axial axis. Instead of the beads  28 , the consequent pole contour can also be formed in a different way, wherein the clip  92  then radially inwardly bridges the two edge regions of the consequent pole contour. The electrical machine  10  is preferably used for actuating drives in the motor vehicle, for example for adjusting seat parts, window panes, sliding roofs and covers of openings, but is not restricted to applications of this kind