Abstract:
In an electromechanical energy converter having an outer body and an inner body, which are mounted movably relative to one another about an axis of rotation, an outer body according to the invention surrounds an annular structural element, a permanent magnet and a support ring which is received concentrically in the structural element. The support ring comprises a recess to receive the permanent magnet, and the recess has a boundary surface which extends parallel as to a radius of the axis of rotation.

Description:
BACKGROUND OF THE INVENTION 
     An electromagnetic energy converter, which in the form of an electric motor converts an electrical current into a rotational movement or in the form of a generator converts a rotational movement into an electrical current, conventionally comprises two bodies which are arranged so as to be movable relative to one another about an axis of rotation. That body which is static in relation to an observer is referred to as the stator, and the movable body is referred to as the rotor. The stator often comprises a so-called pole pot in which a number of permanent magnets are distributed over a radial inner surface. A rotor which corresponds to the stator comprises a number of electromagnets which interact electromagnetically with the permanent magnets. The permanent magnets are conventionally adhesively bonded in the pole pot and are alternatively or additionally braced by means of elastic elements. The elastic elements are for example spring clips which force adjacent permanent magnets apart in the circumferential direction and lock them on the pole pot. 
     If an adhesive bond is not possible for example from a manufacturing aspect or from a loading aspect, a fastening of the permanent magnets by means of spring clips may be problematic if the dimensions of the permanent magnets and the spacings thereof lie below certain practically manageable thresholds. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to specify a stator for an electromagnetic energy converter, which realizes an improved fastening of the permanent magnets. It is a further object of the invention to specify a method for assembling the stator. 
     In an electromechanical energy converter having an outer body and having an inner body which are mounted so as to be movable relative to one another about an axis of rotation, an outer body according to the invention comprises an annular structural element, a permanent magnet and a support ring which is accommodated concentrically in the structural element, wherein the support ring comprises a cutout for receiving the permanent magnet and the cutout has a delimiting surface which extends parallel to a radius of the axis of rotation. 
     It is advantageously possible for forces between the permanent magnet and the support ring, which may arise for example during the operation of the electromechanical energy converter, to be transmitted by the delimiting surface, such that a fastening of the permanent magnets by means of an adhesive and/or by means of a discrete spring element is not necessary. In this way, the manufacture of the outer body can be simplified and/or the operational reliability of the electromechanical energy converter can be improved. 
     The permanent magnet may be delimited by a surface which extends in a plane which encompasses the axis of rotation. Here, the permanent magnet may be designed to be curved about the axis of rotation. In another embodiment, the surface which delimits the permanent magnet extends in a plane which runs parallel to, but which does not encompass, the axis of rotation. Here, the permanent magnet may be of non-curved form, that is to say it may comprise substantially only planar surfaces, for example by being of cuboidal form. In both cases, the surface of the permanent magnet bears against the delimiting surface of the support ring and the delimiting surface of the support ring extends in a plane parallel to the axis of rotation. 
     The structural element preferably has a radial inner surface for mounting the permanent magnet in the radially outward direction, wherein the inner surface of the structural element extends perpendicular to a radius of the axis of rotation. Form-fitting mounting of the permanent magnet, and rotational locking of the support ring, can be realized by means of the thus at least sectionally polygonal form of the radial inner surface of the structural element. Furthermore, in the specified way, a large-area transmission of force between the permanent magnet or the support ring and the structural element is attained, such that locally highly loaded bearing surfaces, which may lead to damage to the permanent magnet, to the support ring and/or to the structural element, can be avoided. The structural element may be in the form of a magnetic yoke element for the permanent magnet, wherein the described areal contact with the permanent magnet advantageously promotes the transmission of a magnetic field. 
     The permanent magnet may have a planar radial outer surface for engaging with the planar radial inner surface of the structural element; here, the permanent magnet may have an equal thickness and may in particular be cuboidal. The cuboidal form is a standard design for permanent magnets, such that cheap standard permanent magnets can be installed. 
     The permanent magnet may comprise a lanthanoid (a “rare earth”). Particularly powerful permanent magnets can be produced from lanthanoids, in particular in conjunction with neodymium and/or samarium. Such high-power magnets may be of very compact dimensions, and in particular relatively thin in the radial direction. The fastening according to the invention of the permanent magnet with respect to the structural element may be used particularly advantageously in the case of thin permanent magnets, because a fastening of the permanent magnet by means of spring elements, clips or rivets is difficult owing to the small engagement surfaces. 
     The support ring and the structural element may have radial elements, which engage into one another, for securing against relative rotation about the axis of rotation. Such radial elements may comprise for example a lug which extends in the radial direction, and a groove which corresponds to the lug. An additional securing action against rotation of the support ring in the structural element can be attained in this way. Furthermore, an axial insertion of the support ring into the structural element can be facilitated by the radial elements which engage into one another. 
     The support ring may have, in the region of the cutout, a holding element for mounting the permanent magnet in the radially inward direction. By means of the holding element, the permanent magnet can advantageously be prevented from falling into the structural element during assembly and/or during operation of the electromagnetic energy converter. The outer body may comprise an axial closure element for closing off the structural element, wherein the structural element is of pot-shaped form with a base, and the support ring is mounted axially on the base of the structural element and on an inner surface of the closure element. The outer body thus formed, the permanent magnet of which is locked in both axial directions, both radial directions and both circumferential directions, can be assembled easily and quickly. 
     A method for assembling an outer body comprises the steps of providing an annular structural element, a permanent magnet and a support ring which is designed to be accommodated in the structural element concentrically about an axis of rotation, wherein the support ring comprises a cutout for receiving the permanent magnet and the cutout has a delimiting surface which extends parallel to a radius of the axis of rotation. 
     The method according to the invention comprises only a small number of simple steps, with which the elements of the outer body can be joined together in a simple and efficient manner. A multiplicity of outer bodies according to the invention can easily be mass-produced manually, in automated fashion or in combined manual and automated fashion. 
     During the insertion of the permanent magnet, the support ring may be aligned substantially perpendicular to the force of gravity, such that the permanent magnet is inserted perpendicular to the force of gravity. The use of auxiliary devices for temporarily fixing the permanent magnet in the support ring during assembly can thereby be facilitated or eliminated. 
     The method may furthermore comprise the step of axially closing off the structural element in a closure element, wherein the structural element is of pot-shaped form with a base and the support ring is mounted axially between the base of the structural element and an inner surface of the closure element. Said step may precede an insertion of an inner body of the energy converter, such that both the assembly of the outer body and also the assembly of the energy converter can be completed by means of the described step. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in more detail below with reference to the appended drawings, in which: 
         FIG. 1  shows a stator of an electric motor; 
         FIG. 2  shows a detail of the stator from  FIG. 1 ; 
         FIG. 3  shows a further detail of the stator from  FIGS. 1 and 2 ; and 
         FIG. 4  shows a method for assembling the stator from  FIGS. 1 to 3 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a stator  100  of an electric motor in a perspective and partially transparent illustration. The electric motor, as one possible exemplary embodiment of an electromechanical energy converter, comprises an outer body in the form of the stator  100  and an inner body (not illustrated) which, in the illustration of  FIG. 1 , is a rotor. 
     A pole pot  110  with a base  115  and a flange  120  extends along an axis of rotation  105 . The flange  120  extends radially outward at a top end of the pole pot  110  and has two moldings with in each case one fastening hole  125  for fastening the electric motor. In the region of an inner delimitation of the flange  120 , three depressions  130  in the axial and radial direction are formed into the pole pot  110 . Lugs  135  extend in the radially inward direction from a wall of the pole pot  110 . The lugs  135  are formed at different distances from the base  115 . 
     The pole pot  110  comprises a number of planar inner surfaces  145  which interrupt an otherwise circularly curved wall of the pole pot  110  at regular intervals. The lugs  135  are formed in each case on curved portions of the pole pot  110  which are situated between the inner surfaces  145 . In the pole pot  110  there is accommodated a support ring  150 , the radial outer side of which is, in sections, in form-fitting engagement with the radial inner side of the pole pot  110 . The support ring  150  bears against the base  115  of the pole pot  110 . The support ring  150  comprises a row of cutouts in which in each case one cuboidal permanent magnet  155  is accommodated such that the permanent magnet  155  bears areally against one of the inner surfaces  145  of the pole pot  110 . The support ring  150  furthermore comprises grooves  160  which run parallel to the axis of rotation  105  and which are formed so as to correspond with the lugs  135  in such a way that the support ring  150  can be inserted into the pole pot  110  along the axis of rotation  105  from above until said support ring bears against the base  115 . Here, a rotation of the support ring  150  about the axis of rotation  105  is prevented by an engagement, in the circumferential direction, between the lugs  135  and the grooves  160 . 
     The support ring  150  is manufactured from a non-magnetic material, for example from a plastic. Forces exerted on the support ring  150  in the circumferential direction by the permanent magnets  155  are transmitted to the pole pot  110  as a result of the form fit of the support ring  150  with the pole pot  110 . The lugs  135  and the grooves  160  which correspond thereto can likewise transmit forces, which act in the circumferential direction, between the support ring  150  and the pole pot  110 . Flanks of the lugs  135  may bear at one side or at both sides against the corresponding grooves  160  so as to transmit forces, which arise in the event of a rotation of the pole pot  110  relative to the support ring  150  about the axis of rotation  105 , in one or both directions of rotation. 
     The pole pot  110  may be composed of a magnetically soft material, such that it can be used not only for receiving other elements but also for conducting magnetic fields between the permanent magnets  155 . In the illustrated embodiment, an inner diameter of the pole pot  110  is approximately 40-65 mm. The permanent magnets  155  are preferably high-power magnets formed from a neodymium-iron-boron compound or a samarium-cobalt compound. A thickness of the cuboidal permanent magnets  155  in the radial direction is approximately 1.5 mm-2.5 mm. The stator  100  illustrated in  FIG. 1  is part of an electric motor with a power of up to 200 W, preferably of approximately 50-180 W, and is provided for use in an ABS hydraulic system for use in a motor vehicle. 
     The stator  100  can be completed to form an electric motor and/or generator by the insertion of a rotor (not illustrated) along the axis of rotation  105 , and the mounting of a rear cover (likewise not illustrated). The cover may engage into one or more of the depressions  130  and thus be secured against rotation. 
       FIG. 2  shows a detail view of the stator  100  from  FIG. 1  from a different perspective. It can be clearly seen how the permanent magnet  155 , the largest planar outer surface of which points radially outward, bears areally against the planar inner surface  145  of the pole pot  110 . The support ring  150  likewise bears areally against the pole pot  110  in the region of the inner surface  145 . The support ring  150  does not bear areally against a curved portion  210  of the pole pot  110  adjacent to the inner surface  145 , but rather forms a groove  160  for receiving the lug  135  of the pole pot  110 . The support ring  150  can thereby be inserted in the axial direction into the pole pot  160 , and thereafter conducts forces acting in the circumferential direction into the pole pot  110 . In the embodiment illustrated, only one flank of the groove  160  bears against the lug  135  in the circumferential direction. If forces in the circumferential direction between the support ring  150  and the pole pot  110  are to be expected only in one direction, for example because the direction of rotation of the electric motor is invariable, said forces can be transmitted by the one-sided engagement between the lug  135  and the groove  160 . At the same time, the groove  160  is designed to be so wide that a certain clearance remains on that side of the lug  135  which is not in engagement with the groove  160 , such that free axial movement of the support ring  150  is permitted during assembly in the pole pot  110 , without the need for a highly precise fit between the lug  135  and the groove  160 . 
       FIG. 3  shows a further detail of the stator  100  from  FIGS. 1 and 2  from yet another perspective. The support ring  150  and the permanent magnet  155  are shown in an exploded illustration from the outside, with the viewing direction toward the axis of rotation  105 . 
     The support ring  150  has a cutout  310  for receiving the permanent magnet  155 . The cutout  310  is defined by two mutually opposite axial delimitations  320 , and by two mutually opposite delimitations  330  which run in the circumferential direction, of the support ring  150 . The delimitations  330  extend in a plane which runs parallel to the axis of rotation  105  (not illustrated) but which does not encompass the axis of rotation  105 . Said embodiment corresponds to the illustrated cuboidal form of the permanent magnet  155 . In another embodiment, the permanent magnet  155  is formed so as to be curved about the axis of rotation  105  in the manner of a shell, and the delimitations  330  extend in a plane which encompasses the axis of rotation  105 . Two holding elements  340  form axial contact surfaces for the permanent magnets  155 . 
     When the permanent magnet  155  has been inserted into the cutouts  310 , a part of that side of the permanent magnet  155  which faces away from the viewer, said side bearing against the inner surface  145  of the pole pot  110  in  FIGS. 1 and 2 , rests on the holding elements  340  in the radially inward direction, such that the permanent magnet  155  is fixed in the radial direction between the support ring  150  and the pole pot  110 . Fixing of the magnet  155  relative to the support ring  150  in the circumferential direction and in the axial direction is realized by means of a form fit of the outer edges of the permanent magnets  155  with the delimitations  330  and  320  of the cutout  310 . The permanent magnet  155  is thereby fully fixed relative to the pole pot  110  when the support ring  150 , as illustrated in  FIG. 1 , has been pushed axially into the pole pot  110  and secured in the axial direction against displacement in the upward direction. Said securing is conventionally realized, as explained in more detail above with reference to  FIG. 1 , by means of a cover which closes off the pole pot axially. 
       FIG. 4  shows a method  400  for producing the stator  100  from  FIGS. 1 to 3 . In a first step  410 , the method  400  is in a starting state. In a subsequent step  420 , the pole pot  110 , the permanent magnets  155  and the support ring  150  are provided. Then, in a step  430 , the permanent magnets  155  are inserted in the radial direction from the outside into the cutouts  310  of the support ring  155 . For this purpose, the support ring  150  may be aligned substantially perpendicular to the force of gravity, that is to say the axis of rotation  105  runs in the direction of the force of gravity and the permanent magnets are inserted with a movement perpendicular to the force of gravity. Here, the support ring  150  may be arranged on an assembly mandrel in order to fix it in said position and provide additional strength. The permanent magnets  155  may be inserted into the cutouts  310  with a slight force fit, such that no additional securing of the permanent magnets  155  to prevent them from falling out of the support ring  150  is required during the further course of the process  400 . 
     Subsequently, in a step  440 , the support ring  150  with the permanent magnets  155  and possibly the assembly mandrel is inserted axially into the pole pot  110 . Alternatively, the pole pot  110  may also be placed over the support ring  150  with the permanent magnets  155 . The assembly mandrel can thereafter be removed from the support ring  150 . 
     In a subsequent step  445 , which is not necessarily encompassed by the method  400  and which may also be assigned to another method for the final assembly of an electric motor or generator, a rotor is inserted axially into the stator  100 . 
     In a subsequent step  450 , by virtue of a cover being mounted axially, the support ring  150  is secured axially in the pole pot  110 , and at the same time the electric motor is completed. The method  400  terminates in an end state  460 .