Abstract:
In order, in an electric motor having a housing including a housing sleeve and a housing cover disposed at the end of the housing sleeve, a rotor mounted rotatably about a rotor axis in the housing, a stator disposed in the housing and having a least one motor winding and having an electrical connection unit disposed on the housing, to lead a feed line to the motor winding in the most favorable way possible in terms of assembly, it is proposed that at least one feed line leading from the electrical connection unit to the motor winding runs within the housing sleeve.

Description:
[0001]    The present disclosure relates to the subject matter disclosed in European application No. 02 025 777.0 of Nov. 16, 2002, which is incorporated herein by reference in its entirety and for all purposes.  
         BACKGROUND OF THE INVENTION  
         [0002]    The invention relates to an electric motor, in particular a micro-motor, comprising a housing including a housing sleeve and a housing cover disposed at the end of the housing sleeve, comprising a rotor mounted rotatably about a rotor axis in the housing, comprising a stator disposed in the housing with a least one motor winding and with an electrical connection unit disposed on the housing.  
           [0003]    Such electric motors are known in the prior art. The problem here is to lead a feed line to the motor winding in the most favorable way possible in terms of assembly.  
         SUMMARY OF THE INVENTION  
         [0004]    This object has been achieved for an electric motor of the type described in the opening paragraph in accordance with the invention in that at least one feed line leading from the electrical connection unit to the motor runs in the housing sleeve.  
           [0005]    A particularly simple solution is achieved in this manner and avoids the need to lead the at least one feed line to the motor winding through the housing interior which would then require special protective measures to ensure its safe passage.  
           [0006]    When the feed line runs in the housing sleeve, it is particularly favorable if the housing sleeve is made of an insulating material since this makes extra insulating measures for the at least one feed line unnecessary.  
           [0007]    It is particularly favorable if the housing sleeve is made of plastics.  
           [0008]    To enable the housing sleeve to be made of plastics at low cost, it has proven favourable if the housing sleeve is made by means of injection molding.  
           [0009]    So far, no precise details have been given concerning the form of the housing sleeve. A particularly suitable solution provides that the housing sleeve has a sleeve body and at least one rib and that the at least one feed line runs in the housing sleeve in the region of this rib. This makes it possible to use the build-up of material present in the rib to have the at least one feed line run in this without detracting from the stability of the housing sleeve.  
           [0010]    The rib is then suitably formed in such a way that it extends on the housing sleeve in a direction approximately parallel to the rotor axis.  
           [0011]    The feed line is located in a particularly advantageous manner in the housing sleeve when the rib stabilizes the regions of the sleeve body lying on either side of the feed line in relation to each other, in particular connects them, so that the feed line running in the housing sleeve does not weaken the housing sleeve along its course.  
           [0012]    It is favourable if the rib is arranged in such a way that it lies on an inner side of the sleeve body.  
           [0013]    So far, in relation to the above description of the individual embodiments, no precise details have been given concerning the arrangement of the connection unit.  
           [0014]    The connection unit can be disposed, for example, on the housing sleeve. It is particularly advantageous if the connection unit is disposed on a first of the housing covers.  
           [0015]    It is even more preferable for the connection unit to be mounted on the first housing cover.  
           [0016]    Here, the connection unit is preferably formed as a connection board which carries conductor tracks so that external connections for the electric motor can be connected to the feed lines leading to the winding in a suitable way.  
           [0017]    The electric motor is suitably formed in such a way that the stator has a first stator unit facing the housing cover and a second stator unit disposed on a side of the first stator unit lying opposite the first housing cover and that the at least one feed line running in the housing sleeve leads to the second stator unit.  
           [0018]    The advantage of this solution can be seen in the fact that it provides a simple means of leading a feed line to the stator unit which is not connected to the first housing cover carrying the connection unit, but is located at a distance from it.  
           [0019]    An advantageous embodiment of the electric motor according to the invention particularly provides that the first stator unit and the second stator unit are disposed on opposite sides of the rotor and the feed line thus leads from the first housing cover over the first stator unit and the rotor to the second stator unit.  
           [0020]    So far, no precise details have been given concerning the way in which the feed lines are to run in the housing sleeve. A preferred embodiment provides that the housing sleeve has at least one groove which accommodates the feed line so that the at least one feed line running in the housing sleeve is located in this groove.  
           [0021]    Here, it is preferable if the groove runs in the housing sleeve in a direction approximately parallel to the rotor axis.  
           [0022]    The groove can be located on an inner side of the housing which means a side facing the stator and the rotor. In terms of assembly, it is particularly advantageous if the groove, starting at an outer surface of the housing sleeve, extends into the housing sleeve.  
           [0023]    A particularly favourable solution provides that the groove runs in the region of the at least one rib of the housing sleeve.  
           [0024]    The groove is preferably located such that it penetrates into the body of the housing sleeve and that the respective rib ensures that the regions of the sleeve body lying on either side of the groove remain stable and connected to each other.  
           [0025]    To mount the feed line running in the groove in a particularly simple way, it is provided that the groove substantially penetrates through the sleeve body so that if the rib has a shorter length than the sleeve body, an opening is automatically provided to lead the feed line out from the interior of the housing.  
           [0026]    To prevent the feed line from working free of the groove, it is preferable for the feed line to be fixed in the groove.  
           [0027]    This can suitably be effected by fixing the feed line into the groove by means of a bonding compound.  
           [0028]    The bonding compound is preferably formed as a sealing compound which seals the groove.  
           [0029]    To make it even easier to lay the feed line during the assembly of the electric motor according to the invention, it is preferable for a groove in the first housing cover to adjoin a groove in the housing sleeve, so that the feed line can be led both through the first housing cover as well as the housing sleeve, in each case through a groove.  
           [0030]    So far, no precise details have been given concerning the type of feed line which is to run in the groove. It would, for example, be conceivable to lay a conducting wire in the groove which is then connected near the stator unit to a winding wire of the motor winding, in particular a stator winding.  
           [0031]    However, to avoid in particular an extra line connection of lines, it is especially favourable if the feed line is a winding wire which continues from the motor winding, in particular the stator winding, so that no additional connection between an extra line and the winding wire of the stator winding has to be made.  
           [0032]    As an alternative or in addition to providing a groove through which the at least one feed line can be led, another embodiment provides that the at least one feed line is embedded in the material forming the housing sleeve. This solution has the advantage that the feed line need not be laid at a later date and thus makes it possible to lay the feed line in the housing sleeve at the same time as the housing sleeve is manufactured.  
           [0033]    A variety of different possibilities are conceivable for embedding the feed line in the housing sleeve. An advantageous solution provides that the at least one feed line is molded into the housing sleeve.  
           [0034]    When the housing sleeve is manufactured by means of injection molding, it is advantageous if the at least one feed line is injection molded into the housing sleeve at the same time.  
           [0035]    If the housing sleeve is provided with a rib, it has proved particularly advantageous if the at least one feed line is embedded in the rib and thus lies in the region of a build-up of material, which prevents any weakening of the stability of the housing sleeve.  
           [0036]    To lead the feed line to the connection unit in a favourable way, it is preferably provided that the feed line enters through an opening in the housing cover and can thus be led in a simple way to the connection unit, in particular to the connection board.  
           [0037]    The feed line embedded in the housing sleeve could, for example, be a flexible wire. However, for ease of handling and embedding the feed line when the housing sleeve is being manufactured, it is provided that the feed line is formed as a rigid line section.  
           [0038]    Further characteristics and advantages of the invention form the subject matter of the description below as well as the illustration in drawings of a member of embodiments. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0039]    [0039]FIG. 1 a section along line  1 - 1  in FIG. 3 through a first embodiment of an electric motor according to the invention;  
         [0040]    [0040]FIG. 2 an enlarged perspective view of a stator unit of the first embodiment of the electric motor according to the invention;  
         [0041]    [0041]FIG. 3 a view of the first embodiment of the electric motor according to the invention in the direction of the arrow A in FIG. 1 and  
         [0042]    [0042]FIG. 4 a perspective view of a housing sleeve of the first embodiment of the electric motor according to the invention;  
         [0043]    [0043]FIG. 5 a section similar to FIG. 1 through a second embodiment of the electric motor according to the invention and  
         [0044]    [0044]FIG. 6 a perspective view of a half-section through a housing sleeve of the second embodiment of the electric motor according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0045]    A first embodiment of a brushless electric motor according to the invention, illustrated in FIG. 1 to  4 , preferably a stepper motor, includes a housing, denoted in its entirety by  10 , with a housing sleeve  12 , which is preferably formed as a cylindrical sleeve, and housing covers  14  and  16 , which close off the housing sleeve  12  at opposite ends and which are connected to the housing sleeve  12 . Each of the housing covers  14 ,  16  is preferably provided with recesses  18 ,  20  running around the housing covers  14 ,  16 , into which recesses end regions  22 ,  24  of the housing sleeve engage, so that the housing covers  14 ,  16  are held by the housing sleeve  12  centered with respect to an axis  26 .  
         [0046]    The housing covers  14  and  16  are preferably at the same time also formed as bearing supports for rotary bearings  28 ,  30 , in which a shaft, denoted in its entirety by  32 , is rotatably mounted coaxially with the axis  26 .  
         [0047]    Here, the rotary bearings  28 ,  30  are inserted into bearing receptacles  34 ,  36  which are formed by retaining rings  38 ,  40  which are mounted on a supporting plate  42 ,  44  of the respective housing cover  14 ,  16  and are preferably formed integrally with the supporting plate.  
         [0048]    The housing covers  14 ,  16  formed as bearing supports are moreover provided with receiving sleeves  46 ,  48  protruding from the supporting plates  42 ,  44  into the interior of the housing  10 , which sleeves are used as a bearing mounting for the stator, denoted in its entirety by  50 , which includes two stator units  52 ,  54 , the stator unit  52  being held on housing cover  14  and the stator unit  54  on housing cover  16  and thus fixed in the housing  10  by this.  
         [0049]    Each stator unit  52 ,  54  includes, as particularly illustrated in FIG. 2 with reference to stator unit  54 , a first pole shoe element  60  which includes first pole shoes  62 , formed as claw poles, as well as a pole shoe carrier  64  which preferably extends in a plane approximately perpendicular to the axis  26 .  
         [0050]    In addition, each stator unit  52 ,  54  includes a second pole shoe element  70  which includes second pole shoes  72 , formed as claw poles, which are also held by a pole shoe carrier  74  which extends approximately perpendicular to the axis  26 .  
         [0051]    The two pole shoe carriers  64  and  74  extend approximately parallel to each other and are kept at a distance from each other by means of a connecting element  78  which is mounted on the receiving sleeve, in this case the receiving sleeve  48  of the housing cover  14 , and is held by this.  
         [0052]    The connecting element  78  creates a magnetic circuit between the first pole shoe element  60  and the second pole shoe element  70 .  
         [0053]    In addition, a toroidal coil  80 , representing a stator winding, is also mounted on the connecting element  78 , which coil is located between the pole shoe carriers  64  and  74  and in addition lies within the second pole shoes  62  which extend beyond the toroidal coil  80 .  
         [0054]    The first pole shoes  62  and the second pole shoes  72  preferably lie on a common, cylindrical enveloping surface  82  disposed concentrically with respect to the axis  26  and have a width in an azimuthal direction with respect to the axis  26  extending over an angular distance WB which is identical for all the pole shoes  62 ,  72 .  
         [0055]    Moreover, each of the second pole shoes  72  is positioned between two successive first pole shoes  62 , so that the first pole shoes  62  and the second pole shoes  72  are staggered relative to each other.  
         [0056]    This results in an angular distance WA existing between the respective successive pole shoes  62 ,  72  which is identical between all pole shoes  62 ,  72 .  
         [0057]    The first and second pole shoes  62 ,  72  thus overlap a space  84  enclosed by them in order to accommodate a rotor  90  which can rotate about the axis  26  representing the rotor axis.  
         [0058]    Moreover, the stator units  52  and  54  have an identical construction and are arranged in mirror image to each other in the housing  10  so that respective ends  63 ,  73  of the pole shoes face each other and so that the spaces  84  substantially follow one another directly in the direction of the axis  26 .  
         [0059]    The rotor  90  is disposed in the spaces  84  of the stator units  52 ,  54  and includes rotor units  92 ,  94 , rotor unit  92  being associated with stator unit  52  and rotor unit  94  being associated with stator unit  54 , both rotor units  92 ,  94  being seated fixedly on the shaft  32  and each of the rotor units  92 ,  94  having magnetized regions which interact with the pole shoes  62 ,  72 .  
         [0060]    To supply current to the two toroidal coils  80  of the stator units  52 ,  54 , one of the housing covers  14 ,  16 , the first housing cover  14  in the case illustrated, is provided with an electrical connection unit  100  which preferably includes a connection board  102  which carries conductor tracks  104  and has a recess  106  which engages around the retaining ring  38  so that the connection board  102  encircles the retaining ring  38 , engages against the supporting plate  42  and is preferably connected to this, for example, by bonding.  
         [0061]    The connection of the connection board  102  to the housing cover  14  allows the toroidal coil  80  held on the housing cover  14  to be supplied with current in simple manner via the connection board  102  by lines penetrating through the housing cover  14 .  
         [0062]    For this purpose, coil connections  108   a, b , for example, are provided on the connection board  102  to which, for example, a winding wire is led from the toroidal coil  80  seated on the housing cover  14 .  
         [0063]    On the other hand, supplying the coil  80  which is held on the second housing cover  16  lying opposite the first housing cover  14 , is problematic to the extent that the supply has to be led on the outside around the rotor  90 .  
         [0064]    For this purpose, as illustrated in FIG. 3 and FIG. 4, the housing sleeve  12  is provided with grooves  110 , for example, longitudinal grooves  110   a, b , which run in a longitudinal direction  112 , preferably approximately parallel to the axis  26 , extending from the one end region  22  to the other end region  24  of the housing sleeve  12  and penetrate into the housing sleeve  12  from an outer surface  114 .  
         [0065]    The housing sleeve  12  is preferably made of plastics and has a sleeve body  116  which is formed, for example, by a circular-cylindrical wall extending around the axis  26  so that the grooves  110  penetrate into the sleeve body  116  from the outer surface  114 .  
         [0066]    Moreover, the housing sleeve  12  includes ribs  118  disposed on an inner side  117  of the sleeve body  116  which also run approximately parallel to the longitudinal direction  112  and, in relation to the axis  26 , are disposed at a constant angular spacing WS from each other.  
         [0067]    In the assembled electric motor, the ribs  118  lie in intermediate spaces  120  between successive pole shoes  62 ,  72 , which spaces are produced as a result of a clearance with an angular distance WA existing between the successive pole shoes  62 ,  72 .  
         [0068]    As a result, the pole shoes  62 ,  72  of both stator units  52 ,  54  are by necessity arranged coaxially and aligned with each other in the housing sleeve  12  and fixed in this position by the ribs  118  on the housing  10 .  
         [0069]    At the same time, the ribs  118  are used to reinforce the housing sleeve  12  in the region of the longitudinal grooves  110   a, b , in that the longitudinal grooves  110   a, b  have a lesser width in an azimuthal direction  122  than the ribs  118  and in addition the longitudinal grooves  110   a, b  run in the middle of the respective ribs  118 , so that even if the longitudinal grooves  110   a, b  penetrate completely through the sleeve body  116  in a radial direction with respect to the axis  26 , the ribs  118  would still bridge over the longitudinal grooves  110   a, b  and connect the regions  123   a, b  of the sleeve body  116  lying on either side of the longitudinal grooves  110   a, b  and thus ensure overall the rigidity of the housing sleeve  112 .  
         [0070]    Moreover, the longitudinal grooves  110   a, b  penetrate through the housing sleeve  12  at least at the end regions  22  and  24 , so that, as illustrated in FIGS. 1 and 4, at the end region  24  a winding wire  124  of the toroidal coil  80  can be led out of the interior of the housing  10  via the groove  110 , for example, the longitudinal groove  110   a , and can be led within the groove  110  and within a following groove  126  in the housing cover  14  to a terminal  128  on the connection board  102 , it being then possible to lay the winding wire  124  from the outside into the grooves  110  and  126  of the housing sleeve  12  and the housing cover  14 .  
         [0071]    The winding wire  124  is preferably fixed by a sealing compound  130  with which the groove  110  is filled and at the same time the groove  110  is sealed along its entire length by means of the sealing compound  130  so that the housing  10  in the region of the housing sleeve  12  is thus also sealed against media penetrating from the outside.  
         [0072]    This solution enables the electric feed line  124  to be led in particularly simple manner from the toroidal coil  80  disposed in the stator unit  54  mounted on the second housing cover  16  to the connection unit  100 , which coil is disposed at an end of the housing  10  which is located opposite the end carrying the connection unit  100 .  
         [0073]    In a second embodiment of an electric motor according to the invention, illustrated in FIGS. 5 and 6, the elements which are identical with those of the first embodiment, are provided with the same references which means that where the explanation of the second embodiment is concerned, full reference can be made to the comments applying to the first embodiment.  
         [0074]    In contrast to the first embodiment, in the second embodiment no groove is provided in the sleeve body  116  of the housing sleeve  12 ′, but rather, feed lines  132  are embedded in the housing sleeve  12 ′ in the region of the ribs  118  which lead from the coil  80  of the stator unit  54 , which is mounted on the second housing cover  16 , and thus from the end region  24  to the connection board  102 , so that a connection with the appropriate conductor tracks of the connection board  102  can be made.  
         [0075]    The feed lines  132  are then in particular embedded in the region of one of the ribs  118  and penetrate substantially through the middle of the respective rib  118 , so that the feed line  132  preferably runs in the region of an inner side of the sleeve body  116 .  
         [0076]    This means that in the region of the coil  80  of the stator unit  54 , it is possible to connect the winding wire of the toroidal coil  80  to the feed line  132 , for example, by soldering one end  134  of the feed line  132  to a winding wire of the coil  80 .  
         [0077]    Another end  136  of the feed line  132  projects from the housing sleeve  12  at the end region  22  and can be pushed through an opening  138  in the housing cover  14  to reach a terminal  140  of the connection board  102 .  
         [0078]    A particularly advantageous embodiment of the feed line  132  provides that the feed line is formed as a rod or rib and can thus be laid in the mold when the housing sleeve  12  is injection molded and can thus be injection molded along with the housing sleeve  12 .