Abstract:
In a method for constructing a linear motor, each tooth of a plurality of teeth is provided with two separate tooth halves with removable tooth tips. After removing the tooth tips to expose an open end of the tooth halves, a prewound coil is pushed over the open end of the two tooth halves of each tooth up to an end position, and a magnet is inserted between the two tooth halves of each tooth. The tooth halves have a thickness between the open end and the end position which does not exceed a thickness of the tooth halves at the end position.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a method for constructing an electrical machine, in particular a linear motor. The invention also relates to tooth halves for a tooth of an electrical machine which make it possible to implement the method according to the invention. 
     In more recent linear motors, both coils and magnets are provided on a primary part (which corresponds to a stator), while the secondary part (which corresponds to the rotor) does not have any separate magnets. 
     The coils surround in each case two tooth halves, which each have a so-called tooth tip, which is used for guiding the magnetic flux. 
     In the prior art it is not possible to apply prewound coils onto the tooth halves since the tooth tip is so wide on the tooth tip side that coils are prevented from being plugged on, while the side remote from the tooth tip does not have a free end, with the result that it would be possible for a coil to be plugged on. This makes assembly more difficult when using tooth halves with tooth tips. 
     A linear motor with such tooth halves is generally fitted in such a way that first the magnets are positioned between the tooth halves. Then the coils are wound around the tooth halves. 
     This type of fitting is laborious. As a result of the permanent magnets being introduced early, component parts can be magnetized, which results in problems during fitting, and may even bring about a risk of injury for the fitter. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to simplify the fitting of a linear motor when using tooth halves with tooth tips. 
     According to one aspect of the present invention, the object is achieved by a method for constructing an electrical machine, in particular a linear motor, having the steps of providing a plurality of teeth, which each comprise two separate tooth halves with tooth tips, wherein the tooth halves are shaped or capable of being modified in such a way that the following steps are made possible: pushing in each case one prewound coil over an open end of the two tooth halves of a tooth up to an end position, inserting a magnet ( 22 ;  46 ;  70 ) in each case between the two tooth halves of a tooth. 
     According to another aspect of the present invention, the object is achieved by a tooth half for a tooth of an electrical machine, in particular a linear motor, with a tooth tip, which has a free end, and on which a desired position for a coil surrounding in each case two identical such tooth halves is defined, wherein the tooth half is shaped in such a way that its thickness from the free end up to the desired position does not exceed the thickness of a desired position, with the result that, when the electrical machine is fitted on two identical such tooth halves, a prewound coil can be pushed on from the free end up to the desired position. 
     According to yet another aspect of the present invention, the object is achieved by a tooth half for a tooth of an electrical machine, in particular a linear motor, with a removable tooth tip. 
     According to the invention, a plurality of teeth, which each comprise two separate tooth halves with tooth tips, is therefore provided, the tooth halves being shaped or being capable of being modified in such a way that the following steps are made possible: pushing in each case one prewound coil over an open end of the two tooth halves of a tooth up to an end position, and inserting a magnet in each case between the two tooth halves of a tooth. In particular, it is now possible to implement the steps in the described sequence, with the result that the magnets do not need to be inserted until right at the end. The fitting speed is also increased and fitting is overall facilitated by virtue of the fact that the coil can be prewound. This is enabled by the shape or capability of the tooth halves to be modified. 
     In a preferred embodiment, the shape of the tooth halves is such that they have an open end, and that the tooth halves have a thickness between the open end and the end position which does not exceed the thickness of the tooth halves at the end position. The term thickness in this case relates to the extent of the tooth half in that dimension of the three dimensions provided in which the tooth half extends the least. This is particularly evident in the case of a plate-shaped basic body of the tooth half in which the thickness is naturally defined. 
     The capability of the tooth halves to be modified can also be such that the tooth halves have a removable tooth tip. When modifying the tooth halves by removing the tooth tip, in each case an open end is provided on the tooth halves, the tooth halves having a thickness between the open end and the end position which does not exceed the thickness of the tooth halves at the end position. 
     Even when the same terms are used here, the two preferred embodiments differ in the position of the open end. Firstly, the open end is positioned on that side of the respective tooth half which is remote from the tooth tip since the tooth half is shaped from the beginning in such a way that the open end is available. 
     With the embodiment with the removable tooth tip, however, the open end is produced by means of the removal of the tooth tip, i.e. on the tooth tip side. Both embodiments can each have an advantage. If the component parts of the electrical machine (the linear motor) are fitted in a housing, it may be dependent on the shape of the housing from which side it is desirable to push on the prewound coil. The shape of the tooth half or the capability of modifying said tooth half (by removing the tooth tip) can then be selected depending on this. 
     The separation of the teeth into tooth halves is preferably at least partially counteractive again in the fitted electrical machine. Thus, an embodiment is possible in which in each case two tooth halves of the same tooth are connected to one another via a connecting element (yoke). It is likewise possible, once coils have been pushed on and magnets have been inserted, for in each case adjacent tooth halves, which belong to different teeth, to be connected to one another via a connecting element. In this embodiment, it is preferable for the connecting element to conduct the magnetic flux. A yoke conducting the magnetic flux can comprise, for example, a stack of laminates (by means of the use of baked enamel, which acts as an adhesive once the stack has been baked in an oven). Such a stacked element also makes it possible for threaded bores to be set. Then, it is particularly possible to fix the yoke in the housing of the electrical machine. 
     Irrespective of whether the yoke produces a connection between two tooth halves of the same tooth or of adjacent teeth, it can be held in slots of the tooth halves, with, in the first case, the slots naturally needing to be provided in an inner side of the tooth halves, with the inner side pointing in the direction of the magnet pushed between the tooth halves, while in the second case the slots need to be provided in an outer side of the tooth halves, with the outer side being the side facing the coil. 
     If the yoke is held in slots of the tooth halves and a yoke is used which has been produced by baking laminate parts by means of baked enamel, it is thus possible for threaded bores to be set into the yoke, as a result of which the yoke can be fixed on the housing and then fixing of the tooth halves takes place indirectly via the slot. In this case, the yoke (which can also be referred to as a sliding block in the case of guidance in the slots) absorbs many forces. 
     Instead of yokes between in each case two adjacent tooth halves, a plate may also be provided which bridges a plurality of teeth. Preferably, the plate is then fastened on the tooth halves. In order to produce a fastening option, the tooth halves should then likewise be produced by baking laminate parts by means of baked enamel in order that a threaded bore can be set. 
     The invention also includes a specially shaped tooth half. This tooth half has a free end, a desired position for a coil surrounding in each case two identical such tooth halves being defined on the tooth half. The tooth half is shaped in such a way that its thickness from the free end up to the desired position does not exceed the thickness at the desired position, with the result that, when the electrical machine is fitted on two identical such tooth halves, a prewound coil can be pushed on from the free end up to the desired position. 
     The embodiment of the tooth half with a removable tooth tip is also part of the invention. When the tooth tip is removed, an open end is then provided, the tooth half being shaped, when the tooth tip is removed, in such a way that it is nevertheless possible for a prewound coil to be pushed on from the open end up to a desired position during fitting of the electrical machine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Preferred embodiments of the invention will be described below with reference to the drawing, in which: 
         FIG. 1A  shows a first embodiment of the method according to the invention in a perspective view in partial section, with the perspective view illustrating the steps of the method starting from the provision of tooth halves according to the invention; 
         FIG. 1B  in comparison with  FIG. 1A , illustrates the assembled state; 
         FIG. 2A  shows an alternative embodiment of the invention in partial section, with parts of the diagram illustrating the assembly and other parts of the diagram illustrating the assembled state; 
         FIG. 2B  shows a rear yoke which can be used in the embodiment shown in  FIG. 2A ; 
         FIG. 2C  shows a sliding block which can be used in the embodiment shown in  FIG. 2A ; and 
         FIG. 3  shows an alternative embodiment of the invention in section. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1A  shows a tooth, which comprises two tooth halves  10 . The tooth halves  10  are substantially plate-shaped, in each case widening of the plate shape occurring at the lower end in  FIG. 1A , as a result of which tooth tips  12  are formed. In the assembled state, the tooth tips  12  are located on the side on which the interaction of the primary part with the secondary part takes place. 
     Owing to the plate shape of the tooth halves  10 , a free end  14  is provided. The plate shape has the same thickness at the free end  14  as in a lower region (still above the tooth tips  12 ), where a coil is intended to be fitted. As a result of the fact that the tooth halves  10 , in contrast to the prior art, for example, do not extend in the region of the free end  14  beyond a plane which is defined by the outer side  16  of the plate, it is now possible for a prewound annular coil  18  (shown in section) to be pushed on corresponding to the arrows  20  until the coil  18  has reached a desired position, which is illustrated in  FIG. 1B . (The desired position of the coil defines a desired position on the tooth half.) Once the coil  18  has been pushed onto the tooth halves  10 , which are already located at the correct distance from one another when the electrical machine is fitted, a permanent magnet can be inserted between the two tooth halves  10 . In the present case, three permanent magnets  22  are illustrated, and these permanent magnets are pushed between the two tooth halves  10  (arrows  24 ). In contrast to the prior art, tooth halves  10  with tooth tips  12  are therefore provided, it being possible for a prewound coil  18  to be pushed on and magnets  22  then to be inserted. 
     In order to provide a termination, a plate  26  bridging all of the teeth is provided on the free ends  14  of the tooth halves when a large number of teeth is provided. The positioning takes place corresponding to the arrows  28 , the fitted state being illustrated in  FIG. 1B . The plate  26  may be a purely mechanical way of ensuring stability, but it can in addition also be designed to conduct the magnetic flux which originates from the magnets  22  or else the coil  18  during operation. 
     In order that the plate  26  can be fastened on the tooth halves  10 , threads  30  for screws  32  are provided in the plate  26 . Likewise, threads  34  for the screws  32  are provided in the tooth halves  10 . 
     In order to make it possible to drill threads  30  and  34 , both the plate  26  and the tooth halves  10  are produced by baking laminate parts by means of baked enamel. In this case, baked enamel is applied to the individual laminate layers. When introducing the apparatus into an oven, the baked enamel changes its properties and in the process produces adhesive joints. 
       FIG. 2A  illustrates an alternative embodiment of the tooth halves. The tooth halves  36  shown in  FIG. 2A  likewise comprise tooth tips  38 , which represent a widening in comparison with the basic body of the tooth halves. The actual basic body of the tooth halves  36  is still plate-shaped. In contrast to the embodiment shown in  FIG. 1A , however, a slot  40  is provided in the plate shape. The free end  42  of the tooth halves  36  is no thicker than the actual plate-shaped basic body. The thickness d 2  illustrated is in particular equal to the thickness d 1 . The outer side of the tooth halves, which is partially covered by a coil  44  (shown in section) in the representation shown in  FIG. 2A , therefore forms a plane, with the exception of the slot  40 . In other words, the outer plane of the plate-shaped basic body continues beyond the slot  40  towards the free end  42 . The free end  42  is therefore not widened or also does not protrude beyond the outer side of the tooth halves  36 . 
     Correspondingly, it is also possible here to push a coil  44  onto the two tooth halves during fitting when there is at the same time a fitting spacing between the tooth halves  36 . The assembled state is shown on the right-hand side in  FIG. 2A . Once the coil  44  has been pushed on, it is possible for a magnet  46  to be inserted between two tooth halves of a tooth. In this case,  FIG. 2A  likewise shows the assembled state in the center of the diagram. 
     In the embodiment shown in  FIG. 2A , there is no termination of the tooth halves  36  by means of a plate bridging all of the teeth in the manner of the plate  26  ( FIG. 1A ). Instead, the slots  40  are used for holding connecting elements  48  ( FIG. 2B ) or  50  ( FIG. 2C  or  FIG. 2A , right-hand part of the diagram). Since the slots  40  are provided on the outer side of the tooth halves  36 , the connecting elements  48  and  50  each provide a connection between two tooth halves  36 , which belong to different teeth. 
     A rear yoke  48  can be inserted into the slots  40 . The rear yoke can serve the purpose of conducting the magnetic flux. The rear yoke at  48 , as is shown in  FIG. 2B , has substantially the shape of an (inverted) “T” in cross section, with for its part a horizontal T-shaped slot  54  being let into the base  52  of the “T”. 
     The slot  54  can be used for accommodating a sliding block in the manner of the sliding block  50 , as is shown in  FIG. 2C , which likewise has a T-shaped cross section. The sliding block is produced by baking laminate parts by means of baked enamel and can therefore have threaded bores  56 . If the rear yoke  48  is inserted into the slots  40  and the sliding block  50  into the slot  54  of the rear yoke  48 , firstly a magnetic connection between the two tooth halves  36  which provide the slots  40  which hold the rear yoke  48  is produced. Secondly, fastening of the entire apparatus on a housing of the electrical machine is ensured via the threaded bore  56 . The sliding block  50  can absorb in particular severe forces which act during operation of the machine and can transfer them to the housing. In an alternative embodiment, the sliding block  50  is designed to be slightly larger and is guided directly in the slots  40  (cf.  FIG. 2A ). In this case, too, it is used for fastening purposes via the threaded screws  56 . 
       FIG. 3  illustrates an alternative embodiment of the invention. In this case, tooth halves  58  are provided which have tooth tips  60 . The basic shape of the tooth halves  58  corresponds to the prior art with the following exception: The tooth tips  60  are removable. 
     The tooth tips  60  and  60 ′ are connected to the body of the tooth halves  58  and  58 ′, respectively, via plug-type connections  62  and  62 ′, respectively. A first embodiment is shown on the left-hand side in  FIG. 3 : The plug-type connections  62  are inserted on the inner side of the respective tooth half  58 . In the alternative in accordance with the central tooth in  FIG. 3 , the plug-type connection  62 ′ of the tooth tip  60  extends into the solid body of the tooth half  58 ′. 
     The two mentioned embodiments have the removability of the tooth tips  60  and  60 ′, respectively, in common. When the tooth tips  60  and  60 ′ are removed, an open end of the tooth halves  64 , now on the side of the tooth tips  60  and  60 ′, respectively, is provided. (It is merely necessary to imagine that the tooth tips  60  and  60 ′, respectively, are not there for this purpose.) The open end  64  has a thickness which is no wider than the rest of the body of the tooth half  58  up to a half-slot  66 , which can be used to hold a coil  68 . It is thus possible to plug a completely wound coil  68  onto the two tooth halves  58  which are located in the fitted position from the free end  64  when the tooth tip  60  (or  60 ′) is removed, until the prewound coil  68  finds a hold in the half-slot  66 . Then, a permanent magnet  70  can be inserted into a gap between the two tooth halves  58 . 
     The embodiment according to the invention with a removable tooth tip therefore likewise makes the method according to the invention possible, with in this case the coil being pushed on from the tooth tip side because the tooth tip is indeed removable. Slots  72  are also provided in the tooth halves  58 , but this time on the inner side of the tooth halves  58 , which inner side faces the magnet  70 , to be precise directly above the magnet  70 . In this case, too, the slots  72  make it possible to insert a rear yoke in accordance with the rear yoke  48  in  FIG. 2B , or a sliding block  50 , as is shown in  FIG. 2C . 
     The three different embodiments of the invention each provide the possibility of pushing prewound coils as a whole onto tooth tip halves. Magnets can then comfortably be inserted into a corresponding gap between the tooth tip halves.