Abstract:
The invention relates to a primary part ( 1 ) or secondary part ( 31 ) of an electric motor ( 2 ), having a core ( 3 ) of a magnetically conductive material, which forms slots ( 4 ) for the windings ( 5 ), and at least one cooling tube ( 6 ), through which a coolant fluid ( 7 ) can flow, is inserted into the slots ( 4 ) under the windings ( 5 ). To assure that a primary part ( 1 ) or secondary part ( 31 ) of this kind is comparatively simple to produce and assemble and has increased cooling performance or increased cooling efficiency compared to the prior art, it is proposed that the effective slot cross section has an at least local retaining constriction ( 10, 11 ) relative to the cooling tube ( 6 ), so that the cooling tube is fixed by the retaining constriction ( 10, 11 ) in its seat in a receptacle region ( 12 ) of the slot ( 4 ), and the slot cross section in the receptacle region ( 12 ) has a contour ( 13 ) corresponding to the outer contour ( 14 ) of the cooling tube ( 6 ) in such a way that the cooling tube ( 6 ) has a surface contact ( 18 ) extending substantially over its length with the inner wall ( 19 ) of the receptacle region ( 12 ), the surface contact being at least local with respect to its outer circumference ( 17 ).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a primary part or secondary part to a method for producing such a primary part or secondary part, and to a forming die for performing the aforementioned method, 
     In synchronous motors, it is the primary part with the windings that is cooled; in asynchronous motors, both the primary part and the secondary part can be cooled. The invention also pertains to rotary motors, but preferably to linear motors. 
     In such a motor, there are slots into which the windings for the coils are inserted. This applies to all types of windings, such as pole windings or windings for generating a migrating field. 
     As electrical current flows through the applicable windings, heat is generated, which—depending on the power of the motor—must be dissipated by means of suitable provisions for cooling. In the electric motors involved in the subject of the invention, the heat is dissipated by means of cooling tubes which are inserted into the slots below the windings. 
     For that purpose, it is known to insert a cooling tube into the slots—through the slot opening—before the windings are inserted. Depending on the cross section of the slot, the cooling tube is dimensioned such that it can be simply inserted into the slot and comes to rest on the slot bottom. 
     The core of the primary part or secondary part comprises a magnetically conductive material, such as stacked laminations, or a solid material in which the appropriate slots are made. In the case of stacked laminations, the laminations are stamped out individually and then joined together into a lamination packet, forming the slots in the process. In the case of solid material, the slots can be milled out, for instance. 
     Because the cooling tubes are inserted into the slots, the geometry of the slot and the cooling tube is predetermined in such a way that in their installed position, the cooling tubes are disposed on the slot bottom with air between them and the slot wall. Because of the undefined position of the cooling tubes, the windings located above them can contact the cooling tubes only linearly rather than uninterruptedly. This makes the overall cooling performance or cooling efficiency comparatively poor. 
     SUMMARY OF THE INVENTION 
     It is therefore the object of the present invention to disclose a primary part or secondary part of the type defined at the outset which is comparatively simple to produce and install and which has increased cooling performance or efficiency compared to the prior art. 
     The invention offers the advantage of increased cooling performance/efficiency along with simple manufacture and easy installation of a primary part or secondary part. 
     This advantage is attained by providing that by means of an at least local retaining constriction of the effective slot cross section relative to the cooling tube to be inserted, the cooling tube is fixed in its seat in a receptacle region of the slot. The slot cross section in the receptacle region has a contour that corresponds at least locally—viewed in the circumferential direction—with the outer contour of the cooling tube. These corresponding contours extend substantially over the length of the cooling tube, that is, over that length of the cooling tube to which the cooling tube is placed in a corresponding slot. The result, viewed over the aforementioned longitudinal length, is an at least local surface contact, circumferentially, with the inner wall of the receptacle region. 
     The cooling tube assumes a predetermined defined position in the receptacle region of the slot, in which the aforementioned surface contact exists. As a result, on the one hand the heat transfer resistance between the magnetically conductive material to be cooled and the wall of the cooling tube is reduced. The air gap between the outer wall of the cooling tube and the inner wall of the receptacle region is reduced substantially or even avoided entirely. In contrast to the prior art, a surface contact exists; that is, if the cooling tube—as in the prior art—rests relatively loosely in the receptacle region, then it is surrounded on practically all sides in terms of its circumference by an air gap, which forms a strong barrier to heat conduction. By comparison, in the surface contact of the invention, there is substantially better coupling with regard to heat conduction. This already substantially increases the cooling performance or efficiency. Because the seat of the cooling tube is defined exactly by the slot geometry, it is possible, for instance by using lines that have a larger cross section, to achieve a higher copper fill factor. 
     A further factor is that the cooling tube rests in a defined position in the receptacle region, so that the windings can be inserted in such a way that a preferably large-area contact also exists between the underside of the cooling windings and the top face of the introduced cooling tube. This will be addressed in further detail hereinafter. 
     For producing the at least local surface contact, the shape of the outer wall of the cooling tube corresponds to that of the wall of the receptacle region. This means that the curvatures involved—viewed over the circumference of the cooling tube—correspond locally to one another, resulting in an at least local areal contact. To assure uniform heat dissipation over the length of the cooling tube, the surface contact or surface contact zone extends circumferentially over practically the length of the cooling tube to which the cooling tube is inserted into the slot. The creation of hot spots is thus avoided, and homogeneous cooling is achieved. 
     The invention has recognized that a defined heat dissipation of this kind can be effected via a defined position of the cooling tube in the receptacle region. As a result, for each portion of the cooling tube or cooling tubes—even over a plurality of slots—homogeneous heat dissipation is assured; conversely, in the prior art, a largely undefined position of the cooling tube occurs, so that—depending on the random disposition of cooling tubes—heat nests can occur between adjacent slots, for instance, while other regions are more strongly cooled. In the prior art, because of these nonhomogeneities, the cooling tubes must be comparatively large, to assure always-adequate cooling even in the unpredictable terminal positions of the cooling tubes in the receptacle regions. This problem is eliminated completely by the invention. As a result, with the invention, the cooling flow can be made less and/or the cooling tubes can be made smaller, yet nevertheless, uniform and above all adequate cooling can still be assured. Thus with the invention the resultant cooling can be calculated, or calculated in advance, substantially more precisely and simply. As noted above, in the prior art there is always uncertainty in terms of the design. In the invention, this uncertainty is eliminated, since the clearly defined position of the cooling tubes means that their cooling efficiency is defined directly as well. The dimensioning can therefore be accomplished substantially more efficiently, accurately, and simply. 
     The retaining constriction can be merely local and for instance can extend over only a certain portion in the depthwise direction of the slot; and upon insertion, for instance at a press-fitting force to be exerted, it is possible to move past this portion, so that the cooling tube practically snaps into place. This too will be addressed in further detail hereinafter. The retaining constriction can also extend over practically a majority of the slot depth or the entire depth of the slot. Then the slot has a width, over a majority of its depth or over its entire depth, that is slightly less than the corresponding outside diameter of the cooling tube. As a result, the cooling tube is seated with a quasi-press-fit in the receptacle region and is to be thrust into its seat in the installed position through the retaining constriction at the press-fitting force. As a result of this provision as well, the advantage of the invention, which is that the cooling tube is disposed in a defined seat in the receptacle region and has the surface contact that is required for heat conduction, is already achieved. 
     Preferred features of the present invention are described in the dependent claims. 
     Since the cooling tube is fixed in its seat in the receptacle region and has a local surface contact with the wall of the receptacle region, a certain frictional engagement exists between the cooling tube and the receptacle region. In order therefore to minimize the force that is required to insert the cooling tube into the receptacle region, it is proposed that the cooling tube, upon insertion at the press-fitting force, can move past the local retaining constriction. As a result, the cooling tube can readily be inserted into its receptacle region from above through the slot opening in the depthwise direction of the slot, and the force of friction that has to be overcome is relatively slight; in fact, the force of friction has to be overcome only in the region of the retaining constriction, i.e., preferably merely locally—in terms of the depthwise direction of the slot. The result attained is that the cooling tube has to be pressed in or press-fitted over only a comparatively short distance while it is overcoming the force of friction. 
     It is proposed that the cooling tube be inserted laterally, that is, in the longitudinal direction of the slot, into the receptacle region. What is essential for the invention is that the cooling tube is fixed and has the required surface contact. Thus, without losing the aforementioned advantages, it can readily also be thrust inward laterally. That has the disadvantage that the retaining constriction can also be smaller than the outside diameter of the cooling tube, so that the cooling tube does not have to be able to move past the retaining constriction. This provides corresponding flexibility in dimensioning the retaining constriction and the slot cross section. 
     However, it already suffices if a local retaining constriction is provided only above the receptacle region. In that case, the retaining constriction is merely local, and the cooling tube can move past it preferably in the depthwise direction of the slot. Once again, this has an advantage in terms of the degree of freedom in dimensioning the slot geometry: The slot width can be equal to or greater than the definitive cross section of the cooling tube, so that more space for the windings can for instance be provided. 
     The retaining constriction can be embodied as a retaining protrusion. In that case it is preferred that the cooling tube virtually snaps into its seat and is held/fixed/pressed by the retaining protrusion, so that the surface contact is assured. The retaining protrusion can be formed by one retaining strut each and/or one or more retaining lugs of one or both slot walls. Preferably, opposed retaining struts of the slot walls are provided, which form a detent lock for the cooling tube. The aforementioned features have the advantage that the slot width can be greater than the effective slot cross section in the region of the retaining protrusions/retaining struts, so that the cooling tube can be placed in the slot very easily up to the retaining protrusions, and merely a greater contact-pressure/press-fitting force has to be brought to bear to overcome the detent force. 
     The cooling tube in its seat in the receptacle region may be pressed at least locally, in terms of its outer circumference, against the inner wall of the receptacle region by the retaining constriction. In that case, a detent lock is for instance provided that presses the cooling tube in its seat against the applicable zones of the wall of the receptacle region. At the same time, however, the cooling tube is seated, firmly held by positive engagement, in its seat. 
     To prevent local damage to or deformation of the cooling tube in its seat, it is proposed that the cooling tube, in its seat in the receptacle region, rests on the underside of the retaining constriction, and that the retaining constriction has a contour there that corresponds with the contacting part of the outer circumference of the cooling tube. Then on the one hand the cooling tube is retained by positive engagement and pressed in its seat against the wall of the receptacle region, but on the other hand, it is assured that practically no zones of increased stress are created in the region of contact on the retaining constriction. Moreover, the surface contact is enlarged still further as a result, namely by the applicable portion of contact of the retaining constriction or of the cooling tube. 
     In order to assure effective overall heat dissipation, it is proposed that a surface shape which forms a practically areal support for the windings located above it is embossed on the cooling tube on its top face. The surface shape can be embossed before the cooling tube is inserted. Preferably, however, the cooling tube is deformed in the appropriate way in the insertion operation or at the conclusion of the insertion operation. This will be addressed in further detail hereinafter. The result is an improvement in heat dissipation, since the heat source—namely the windings—themselves rest partly on the cooling tube, and there is thus a direct transfer of heat between the heat source and the cooling tube. 
     It suffices if the contact is only over a partial area relative to the slot width, but preferably it is over practically a full area across the slot width. 
     The invention also relates to a method for producing a primary part or secondary part of one of claims  1 - 12 . This method, too, attains the object stated above and offers a simple, effective method for producing such a device. It can be provided that the cooling tube is inserted laterally, that is, in the longitudinal direction of the slot, into the receptacle region. This has the aforementioned advantages of the lateral insertion. 
     Preferably, it is proposed that the cooling tube is pressed into the slot by a forming die corresponding with the slot geometry, and the local retaining constriction is embodied in such a way, taking the cooling tube geometry and the cooling tube material into account, that the cooling tube can move past it with solely elastic deformation. The forming die corresponds with the slot geometry in such a way that on the one hand it is to be inserted into the slot opening and can be introduced far enough that the cooling tube can be displaced into its seat and optionally snaps into place. To that end, the forming die protrudes with a foot of the die as far as necessary into the slot opening. The at least local retaining constriction is embodied such that the cooling tube is only elastically deformed upon insertion, and practically no permanent deformations remain after the insertion. Then the cooling tube in its seat is completely undamaged. 
     In its seat in the receptacle region, the cooling tube is preferably given an embossed surface form of claim  12  by the forming die, by means of plastic deformation. As a result, a corresponding deformation of the cooling tube before the insertion is unnecessary. The deformation and insertion are then practically a single work step, thus considerably reducing the overall effort and expense of installation. As a result, specifically, some of the production—namely making the embossing of the surface shape—is accomplished simultaneously with the installation. To that end, the forming die is embodied such that on its underside, it has a shape that is essentially a negative of the surface shape. 
     To minimize or preclude stress on the forming die, or on the—preferably only local—retaining constriction, it is proposed that the forming die, on its underside, has a geometry that deviates laterally from the retaining constriction, so that on being press-fitted, the retaining constriction is not touched/damaged by the forming die. 
     The cooling tubes can be embodied in the form of a cooling coil. In that case, the forming die can be dimensioned such that it has only one plunger rib corresponding to the slot geometry with respect to the operation of press-fitting the cooling tube. This is readily practicable in a cooling coil with a cooling tube made of a material that is not overly brittle. Specifically, in that case the cooling coil is merely maximally deflected—in the individual press-fitting insertion of the cooling distances—by the cooling tube diameter relative to adjacent cooling distances, which diameter for conventional cooling coils is located in the region of the solely elastic deformation. This is true for the case where the cooling distance that is next to the cooling distance of the cooling coil in the receptacle region is at least inserted into the slot and rests on the retaining struts. 
     Alternatively, it can also be provided that the forming die has a plurality of plunger ribs corresponding to the slot geometry with respect to the operation of press-fitting the cooling tube. Then for the press-fitting/pressing-in, fewer work steps are needed. The press-fitting can be accomplished in only a single work step, if the number and/or disposition and/or geometry of the plunger ribs corresponds to the number and/or disposition and/or geometry of those slots in each of whose receptacle regions a respective cooling tube is provided. This tube can be used in a conventional cooling coil, or can also be used in the form or radiator in which the cooling distances branch off into the slots at right angles from a primary cooling line, and deformation in the region of the branching points must therefore be avoided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in further detail in terms of exemplary embodiments shown in the drawing. Shown are: 
         FIG. 1 , a schematic cross section through a secondary part and a primary part of a linear motor; 
         FIG. 2 , an enlarged detail from  FIG. 1 ; 
         FIG. 3 , a cross-sectional view of a detail of a slot in the primary part of FIG.  1  and  FIG. 2  without the cooling tube and without windings; 
         FIG. 4 , a schematic cross section through a primary part, while the cooling tube or tubes are about to be press-fitted in/pressed in with a forming die; 
         FIG. 5 , a schematic cross section through a multiple forming die; 
         FIG. 6 , a schematic cross section through a single forming die. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Unless otherwise noted below, all the reference numerals always apply to all the drawing figures. 
       FIG. 1  schematically shows a cross section through a linear motor  2  with a primary part  1  and a secondary part  31 . The secondary part  31  substantially comprises a secondary part magnet holder  33 , to which permanent magnets  32  are glued adjacent one another in the longitudinal direction and in the transverse direction. These permanent magnets  32  interact with the windings, through which current flows in a predetermined way, of the primary part  1 . To that end, the windings  5  rest in slots  4  that are present in the core  3 . Under the windings  5 , there are cooling tubes  6  in each of the slots  4 , or one cooling tube  6 , through which a coolant fluid  7  flows. The coolant fluid  7  can for instance be water, oil, or a coolant gas. 
     The heat that occurs from the current in the windings  5  is so high—particularly in linear motors, but also in high-power rotary motors—that the primary part  1  is actively cooled. 
     The detail view in  FIG. 2  shows the design of the slot  4 , winding  5  and cooling tube  6  in detail: 
     The effective slot cross section  8  (see the description of  FIG. 3  below) is formed by a retaining constriction, in the form of two opposed retaining struts  10 ,  11 , opposite one another at the same point in a retaining constriction region  9  in the depthwise direction  16  of the slot, in the respective slot walls  20 ,  21 . The retaining struts  10 ,  11  continue—although not shown here—without interruption in the longitudinal direction  15  of the slots  4 . The result is a receptacle region  12  which is undercut with respect to each of the slots  4  and in which the cooling tube  6  is seated. Because of the undercutting of the retaining struts  10 ,  11 , the cooling tube is fixed there in such a way, specifically taking its outer contour  14  and the contour  13  of the slot cross section in the receptacle region  12  into account, that it has an at least local surface contact  18 , in terms of its outer circumference  17 , with the inner wall  19  of the receptacle region  12  (in this respect see also FIG.  3 ), which contact extends essentially over its length (viewed in the longitudinal direction  15 ). 
     The surface contact extends in cross section over practically the entire portion  17  of the outer circumference  17  shown. For the sake of simplicity in the drawing, only one reference numeral  17  was selected. However, it can readily be seen that on the one hand, this means the general outer circumference  17  of the cooling tube  6 , and on the other, it means the circumferential zone over which the surface contact is assured. It is also possible for the surface contact to be present over only part of the outer circumference  17  shown. 
     The retaining struts  10 ,  11  are below—as defined here, in terms of the depthwise direction  16 —the windings  5 . In the installed configuration, they are practically “buried” under the windings  5 . As a result, the cooling tube  6  is seated overall in a defined and predetermined way in the receptacle region  12 . The cooling tube  6  rests with the corresponding contact zones  23  of its outer circumference on the underside of the retaining struts  10 ,  11 . The geometry and disposition of the retaining struts  10 ,  11  are selected such that the cooling tube in this seat is pressed against the inner wall  19  of the receptacle region  12 . This means that the cooling tube  6  is retained with slight pressure in the undercut receptacle region  12 . Taking the cooling tube geometry and the cooling tube material into account, the pressure is selected by way of the appropriate dimensioning and disposition of the retaining struts  10 ,  11 . 
     In the contact zone  23 , the retaining struts  10 ,  11  have a contour that corresponds locally with the outer circumference  17  of the cooling tube  6 , so that the appropriate pressure is exerted without excessively deforming or damaging the cooling tube  6 . The retaining struts  10 ,  11 , viewed over the course of their depth, have a practically rounded contour, so that even in the process of press-fitting/pressing-in through this bottleneck, the cooling tube  6  is indeed deformed only elastically, but is not plastically deformed, scratched, or damaged. This will be addressed in further detail hereinafter. 
     In  FIG. 2  it can be seen clearly that the cooling tube  6  has a flattened, practically level shape on its top face  24 . This shape is practically equivalent to a flattening  25  of the top face  24  of the cooling tube  6  over the longitudinal length of the cooling tube  6  (viewed in the longitudinal direction  15  of the slots  4 ), so that a practically homogeneous contact is assured over the longitudinal length as well. Specifically, in the installed configuration, the windings  5  rest with their underside directly on this flattening  25  of the top face  24  of the cooling tube  6 ; in the exemplary embodiment shown, this means that they rest there with their slot insulation  34 ; if there is no such slot insulation  34 , then the windings rest there directly with their conductor insulation. 
     As a rule, the slot insulation  34  is so thin that heat conduction is impaired by it only slightly, if at all. Because of the areal, partial-areal or full-areal contact, very good heat-transfer contact and thus very low heat-transfer resistance between the flattening  25  and the support  26  of the windings  5  are achieved. 
     The slot geometry is shown in detail in FIG.  3 . One slot width d 2 , plus the width of an adjacent tooth, corresponds to a slot pitch τ n . The slot pitch τ n  can be predetermined by the motor parameters, so that the slot geometry according to the invention is to be designed in accordance with the requisite motor parameters. This means that—for a predetermined or restricted slot width d 2 —there should be an effective slot cross section  8  adapted to this and to the cooling tube. The diameter d 1  of the receptacle region  12  is predetermined essentially by the needs of the corresponding contacting faces of the cooling tube  6  and inner wall  19  of the receptacle region  12 . 
     The total height h ges  is composed essentially of the height of the receptacle region  12 , plus the portion of the slot depth that remains for the windings  5 . 
     As an example, in  FIG. 3  a radius of curvature R d  in the region of the retaining struts  10 ,  11  is shown; the critical factor here is that these retaining struts  10 ,  11 —to assure nondamaging press-fitting of the cooling tube  6 —are rounded in the region above (that is, below in the drawing) the highest point of the retaining struts  10 ,  11 , and in the region of the tips of the retaining struts  10 ,  11 . 
       FIG. 4  shows a schematic cross section through a primary part  1  which is just now being equipped with the cooling tube  6 . The cooling tube  6  is inserted partway into the slot  4 , in the depthwise direction  16  of the slot, and has not yet reached the retaining struts  10 ,  11 . Above it is a forming die—in this case a multiple die  27 —that has as many plunger ribs  37  as there are slots  4  with cooling tubes  6  placed in them. This means that in one work step, with one forming die  27 , one cooling tube  6  or a plurality of cooling tubes  6  can be pressed/press-fitted into their inserted position  35  into all the slots  4 , or into many slots  4 . 
     The forming die  27  comprises the aforementioned plunger ribs  37 , which correspond to the slot geometry to the extent that they are somewhat narrower than the slot width d 2 . However, they are preferably at least as high as the slot depth up to the position of the retaining struts  10 ,  11 . They are elongated in the longitudinal direction  15  and extend over practically the entire length of the inserted portions of the cooling tubes  6 . This prevents the cooling tubes from being inserted unevenly or even canted. 
     The cooling tubes  6  can move past the retaining constriction  10 ,  11  in the depthwise direction  16  of the slot and can virtually snap into place in their receptacle region  12 , if a sufficient press-fitting/pressing-in force is exerted by the forming die  27 . 
     In  FIG. 5 , a multiple die  27  is schematically shown, which—as in all the exemplary embodiments shown, including the primary part  1  and secondary part  31  of the linear motor  2 —is shown interrupted. On the underside  29  of the forming die  27 , the plunger ribs  37  have a shape  30  that is essentially a negative shape  30  of the surface shape  25 —which in the exemplary embodiment shown is a level shape. This shape  30  is accordingly likewise plane. However, this is true only for the central part of the underside  22  or of the shape  30 . 
     The rib width  41  is at least slightly less than the slot width d 2 , so that the plunger ribs  37  can plunge into the slots  4  without becoming canted and without inhibition. To attain a practically uncanted/uninhibited insertion, the forming die can be introduced with at least one plunger rib into the slot, and the plunger rib narrows at least in some portions, and in particular toward a base of the die. The rib width  41  is furthermore dimensioned such that—precisely in the case of a multiple die  27 —even taking into account possible changes in position with regard to parallelism between the base  36  of the die and the primary part  1 , or its relative tilting, an essentially uninhibited plunging inward of the plunger ribs is still always assured. To that end, the material comprising the plunger ribs  37  or the entire forming die  27  can be selected accordingly to have a low coefficient of friction. Steel such as St37 or a high-strength steel can be used, including steel with a teflon coating. However, it should be noted that the force to be exerted by the forming die  27  and thus the stability of the material must be assured. Analogously, the width  42  of the interstice  43  is at least slightly greater than the tooth width. 
     In  FIG. 6 , a single die  28  is shown, which is capable of pressing in individual cooling tubes  6 , or portions of cooling tubes  6  individually, into a slot  4  intended for it. Besides the base  36  of the die, only a single plunger rib  37  is provided, which can plunge successively into a given slot  4  in order to press-fit the cooling tube  6 . However, a plurality of single dies  28  may also be provided, which simultaneously equip various slots  4  with the cooling tube  6 . 
     As an example of a multiple die  27  as in  FIG. 5 ,  FIG. 6  because of its larger view also illustrates the precise contour of the shape  30  of the underside  29  of the plunger rib  37  in more detail. At the edge of the underside  29  of the plunger rib  37 , lateral struts  38  are provided, whose respective outer edges spring back laterally at the outside  39  and thus are embodied as “deviating”, upon the press-fitting in of the retaining constriction  10 ,  11 , in such a way that the retaining constriction  10 ,  11  and/or the plunger rib  37  on being pressed in do not touch one another and cannot damage one another. By comparison, the lateral struts  38  on the respective inside  40  drop away rapidly toward the center of the plunger rib  37 , so that the remaining space for the surface shape  30  for embossing the shape of claim  12  is as large as possible and can be utilized to a great proportion for embossing the shape.