Abstract:
An electronically commutated external-rotor motor has an internal stator ( 20 ), having a stator lamination stack ( 64 ) and a winding arrangement ( 66 ) associated therewith. the latter, as well as a central opening ( 149 ) of the stator lamination stack ( 64 ), in which opening a bearing tube ( 56 ) is arranged. The motor further has a permanent-magnet external rotor ( 26 ) separated from the stator lamination stack ( 64 ) by a magnetically effective air gap ( 99 ), which rotor has a shaft ( 42 ) that is journalled in the bearing tube ( 56 ). First and second rolling bearings ( 48, 50 ) are arranged at a distance from one another in the bearing tube ( 56 ). The first rolling bearing ( 48 ), adjacent the rotor hub, is a floating bearing, while the second rolling bearing ( 50 ), near the shaft end ( 70 ) remote from the hub ( 40 ), is braced with one side against a shoulder ( 82 ) provided in the bearing tube ( 56 ). A compression spring ( 78 ) urges the two bearings toward one another, so that they serve as both an axial bearing and a radial bearing for the motor, thereby providing improved durability and longer service life.

Description:
CROSS-REFERENCE 
       [0001]    This application is a section 371 of PCT/EP11/00935, filed 2011-02-25, published 2011-09-22 as WO 2011-1135220-A2, and further claims priority from German application DE 20 2010 003 858.8, filed 2010-03-15, the entire content of which is incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to an external-rotor motor. 
       BACKGROUND 
       [0003]    Such motors have an internal stator, and arranged around the latter is usually a cup-shaped external rotor which has a shaft that is journalled in a bearing tube in the interior of the internal stator. There are various ways of achieving this. 
       SUMMARY OF THE INVENTION 
       [0004]    It is an object of the invention to make available a novel structure for an external-rotor motor with improved durability. 
         [0005]    According to the invention, this object is achieved by arranging first and second rolling bearings, spaced from each other, on the rotor shaft in the bearing tube, the inner ring of the first rolling bearing being displaceable on the rotor shaft, under the influence of a spring force, tending to urge the inner ring away from a free end of the shaft, toward a rotor hub connected to the other end of the shaft. The result thereof is, that the rolling bearings for the shaft of the external rotor can be effective as both radial and axial bearings, yielding a long service life. 
     
    
     
       BRIEF FIGURE DESCRIPTION 
         [0006]    Further details and advantageous refinements of the invention are evident from the exemplifying embodiments, in no way to be understood as a limitation of the invention, that are described below and depicted in the drawings. 
           [0007]      FIG. 1  is a longitudinal section through the basic framework of an external-rotor motor including its internal stator and its fan housing; 
           [0008]      FIG. 2  is a perspective view of the basic structure of  FIG. 1 , viewed approximately in the direction of arrow II of  FIG. 1 ; 
           [0009]      FIG. 3  is a depiction analogous to  FIG. 1 , but in which a circuit board on which electrical components of the motor are located is installed; 
           [0010]      FIG. 4  is an enlarged depiction of detail IV of  FIG. 3 ; 
           [0011]      FIG. 5  is a plan view looking in the direction of arrow V of  FIG. 3 ; 
           [0012]      FIG. 6  is a section looking in the direction of line VI-VI of  FIG. 5 ; 
           [0013]      FIG. 7  is a view analogous to  FIG. 3  but in the closed state; 
           [0014]      FIG. 8  is a variant of  FIG. 7 ; 
           [0015]      FIG. 9  is a depiction analogous to  FIG. 7 , in the context of assembly of the permanent-magnet rotor; 
           [0016]      FIG. 10  is a sectioned depiction of the motor of  FIG. 9  in the assembled state, viewed along line X-X of  FIG. 12 ; 
           [0017]      FIG. 11  is an enlargement of detail XI of  FIG. 10 , in which an installation tool is additionally indicated; 
           [0018]      FIG. 12  is a plan view looking along arrow XII of  FIG. 10 ; 
           [0019]      FIG. 13  shows identical salient poles  140 ,  142 ,  144 ,  146  and a magnetic yoke  148  inside which bearing tube  56  ( FIG. 1 ) is located when the fan is complete; and 
           [0020]      FIG. 14  is a sectioned depiction of a contact pin that serves for connecting the internal stator to the circuit board. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIG. 1  is a longitudinal section through internal stator  20  of an external-rotor motor  22  depicted in  FIG. 10  and its fan housing  24 , in which a fan wheel  26  ( FIG. 9 ) rotates during operation. Said wheel is constituted by an external rotor  28  on whose outer circumference  30  fan blades  32  are implemented. The rotation direction of external rotor  28  is labeled  34  in  FIG. 12 . 
         [0022]    Each fan blade  32  preferably has on its outer periphery an enlargement  36  in order to improve the efficiency of fan wheel  26 . 
         [0023]    As  FIG. 9  shows, external rotor  28  has a cup-shaped magnetic yoke  38  made of soft iron, and the latter is connected at its center to a rotor hub  40 , in which a shaft  42  is secured in the manner depicted. Hub  40  has openings  44  that are utilized during assembly of the fan, and whose function will be further explained below. 
         [0024]    Shaft  42  has two rolling bearings to journal it, namely a first rolling bearing  48  on the side of shaft  42  facing toward rotor  28 , and a second rolling bearing  50  on the side of shaft  42  facing away from rotor  28 . Located between the respective outer rings of rolling bearings  48 ,  50  is an annular spacing member  52  (see  FIG. 9 ), H-shaped in cross-section. This spacing member is guided on shaft  42 . 
         [0025]    A bearing tube  56 , which is depicted in  FIG. 1 , serves to receive rolling bearings  48 ,  50  and spacing member  52 . Said tube has, on its inner circumference, longitudinal ribs  58  whose radially inner ends define a circular enveloping curve. The respective outer rings, of each of the two bearings  48 ,  50 , are guided in ribs  58 . 
         [0026]    Bearing tube  56  transitions to the left into a collar  60  (see  FIG. 1 ). It transitions further into a partly insulating casing  62  of internal stator  20 , whose stator lamination stack, packeted in the usual manner, is labeled  64 , and whose winding arrangement is labeled  66 . 
         [0027]    Provided in this casing  62  as a continuation of bearing tube  56  is a dimple-like recess  68  whose bottom  70  closes off bearing tube  56  in a fluid-tight manner at this location. 
         [0028]    As  FIG. 10  shows, bottom  70  forms an axial tolerance region for free end  74  ( FIG. 9 ) of shaft  42 , i.e. free end  74  does not abut against bottom  70 . A snap ring  76  is provided in the region of free end  74  in a groove of shaft  42 , and provided between said snap ring  76  and the inner ring of second rolling bearing  50  is a compression spring  78  that urges the inner rings of rolling bearings  48 ,  50  toward one another, since a projection  80  ( FIG. 11 ) of hub  40 , which latter is fixedly connected to shaft  42 , abuts against the inner ring of first rolling bearing  48 , while spring  78  urges the inner ring of second rolling bearing  50  to the left in  FIG. 9 , so that the inner rings of rolling bearings  48 ,  50  are urged toward one another. 
         [0029]    As  FIGS. 9 and 10  show, the outer ring of second rolling bearing  50  abuts against a shoulder  82  ( FIGS. 1 and 9 ) of bearing tube  56 , and is secured in that position. The inner ring of first rolling bearing  48  is arranged slidably (floating bearing) on shaft  42 , so that the latter is pressed toward the right in  FIG. 10 . The two rolling bearings  48 ,  50  can thereby serve as both a radial bearing and an axial bearing for external rotor  28 . 
         [0030]    As  FIG. 9  of the assembly process shows, the two rolling bearings  48 ,  50  are pressed in the direction of an arrow  86  into longitudinal ribs  58  of bearing tube  56 . This occurs with the aid of pins  92  that are passed through openings  44  of hub  40 .  FIG. 11  shows only one of said pins  92 , which abut during installation, with their right (in  FIG. 11 ) ends  94 , against a securing member  96  and press it against the outer ring of first rolling bearing  48 , the outer ring of second rolling bearing  50  also being displaced by spacing member  52  ( FIG. 9 ) to the right and being brought into abutment against shoulder  82  of bearing tube  56 . In this manner, the outer rings of both rolling bearings  48 ,  50  are secured within bearing tube  56 . 
         [0031]    Securing member  96  is fastened in collar  60 , in the position that is attained, by the fact that it cuts with its sharp frusto-conical edge  98  ( FIG. 11 ) into inner surface  100  of collar  60  and therefore can no longer be displaced to the left in  FIG. 11 . The result is that secure and zero-clearance installation of rolling bearings  48 ,  50  into bearing tube  56  is achieved, and securing member  96  produces a hooking effect and tilt prevention for rolling bearings  48  and  50 . 
         [0032]    As  FIG. 10  shows, a magnetically effective air gap  99  is located between internal rotor  20  and magnet  37  of rotor  28 . 
         [0033]    Internal stator  20  is completely encased with a plastic  62  in an injection-molding operation. The following, inter alia, are suitable as plastics: 
         [0034]    polyamides, e.g. ULTRAMID® 1  A3X2G5 or polyamide 66 1 ULTRAMID is US TM Reg. # 762,530, issued 1964 to BASF AG of Ludwigshafen, Germany and Florham Park N.J. 07932. 
         [0035]    PBT (PolyButylene Terephthalate), e.g. TECHNYL 2  (PBT-G20FR). These plastics can be reinforced with fibers, e.g. with approximately 20% to approximately 25% glass fillers. These substances can be welded, for example by ultrasonic welding or laser welding. Adhesive connections, seals, or sealing elements are alternatively possible, for example in the form of two-component plastic parts. 2 TECHNYL is US TM Reg. # 2,806,114, issued 2004 to Rhodia Engineering Plastics S.A. of Saint Fons, France &amp; Cranbury N.J. 
         [0036]    As shown, for example, by  FIGS. 1 and 3 , stator lamination stack  64  has a slot insulator  104  which forms a coil former into which is wound stator winding arrangement  66 , whose shape and construction depend on the use of the motor, and which is therefore shown only schematically. 
         [0037]    As  FIG. 4  shows, contact pins  106 , which project to the right in  FIG. 4 , are secured in this slot insulator  104 . ( FIG. 4  shows only one of these contact pins.) One end of a wire  154  ( FIG. 14 ) of stator winding arrangement  66  can be electrically and mechanically secured to these contact pins  106 . In this exemplifying embodiment, a total of four such pins  106  are provided on internal stator  20 . 
         [0038]    In  FIG. 1  and following, pins  106  project into a cavity  108  whose side wall is labeled  109  and in which is located (as shown in  FIG. 3 ) a circuit board  110 , on which electrical components  112  for motor  20  are arranged. As  FIG. 5  shows, strands  114  of a connector cable  116  are attached to circuit board  110 . Pins  106  are also soldered onto conductor paths of circuit board  110  by solder connections  118  (see  FIG. 4 ). Circuit board  110  is held by spacing members  120  ( FIG. 4 ) at a distance from plastic casing  62 , which latter also forms the bottom and side wall  109  of cavity  108 . 
         [0039]    After being fitted with circuit board  110  and after strands  114  are attached ( FIG. 5 ), cavity  108  is closed off with a cover  126  ( FIG. 7 ). The latter can be, for example, welded with ultrasound to side wall  109  at weld joins  128 , or with an adhesive bond. 
         [0040]    It is particularly advantageous here that circuit board  110  having electrical components  112  is arranged in a cavity  108 , so that components  112  are not over-molded with plastic; this might cause components  112  to be torn away from circuit board  110  by the change in volume as the encapsulating material hardens. This risk does not exist here. It is also not precluded in some cases, however, to over-mold components  112  with plastic or provide them with a protective coating. 
         [0041]    Instead of a cover  126 , a closure cap  127  can also be used, as depicted by way of example in  FIG. 8 . Closure cap  127  can be secured, for example, by welding or adhesive bonding. 
         [0042]    As  FIG. 2  shows, wall  109  of cavity  108  is connected via three simple spokes  134  and one channel-shaped spoke  136  to fan housing  24 , which forms an air pass-through aperture  142  similar to a Venturi conduit. Spoke  136  serves for guidance of cable  116  (see  FIG. 5 ). Cable  116  is sealed by means of a rubber seal (not visible). 
         [0043]    Fan housing  24  is thus implemented integrally with a part of the wall of cavity  108  by means of spokes  134 ,  136 , and integrally with the casing of internal stator  20 , so that all these parts can be manufactured in a single working step; this simplifies and speeds up production and moreover reduces costs. Since the assembly of rotor  28  is also greatly simplified, the result is an inexpensive product with outstanding properties and a long service life. 
         [0044]      FIG. 9  depicts, at  37 , the permanent magnet of rotor  28  which is secured in magnetic yoke  38 . Its magnetization can be implemented with two poles, four poles, six poles, etc. 
         [0045]      FIG. 10  shows how blades  32  project into Venturi conduit  142 . 
         [0046]      FIG. 13  is a perspective depiction of a completely wound internal stator  20  that serves, so to speak, as a precursor product in the manufacture of a motor or fan. Its stator lamination stack  64  has, in this example, four identical salient poles  140 ,  142 ,  144 ,  146  and a magnetic yoke  148  having a central opening  149  in which, when the fan is complete, is located bearing tube  56  ( FIG. 1 ) with its longitudinal ribs  158 . 
         [0047]    In this exemplifying embodiment, poles  140  to  146  have different outside diameters on their side facing toward air gap  99  ( FIG. 10 ). In this state, a larger-diameter portion  150  is not yet covered with plastic. A smaller-diameter portion  152  is covered here with insulation made up of two mounted-on half-shells  174 ,  176 . There are various possibilities, known from the existing art, for this covering of the internal stator: for example, as depicted, the use of the two half-shells  174 ,  176 , or over-molding with insulating material, or the use of a special insulating paper. Contact pins  106 , which are depicted e.g. in  FIGS. 1 to 5 , are also attached on upper half-shell  176 .  FIG. 14  shows how a winding wire  154  is secured to pin  106 . For this, the latter is secured in a projection  162  of half-shell  176 , and that projection also serves as a spacing member for circuit board  110  (see  FIG. 3  or  4 ). 
         [0048]    Located on stator poles  140  to  146  in this example are concentrated windings  164 ,  166 ,  168 ,  170  whose terminals are connected in the usual manner to contact pins  106 . The use of a distributed winding and a corresponding lamination stack would of course also be possible. 
         [0049]    As  FIG. 1  shows, the wound internal stator  20  is over-molded on all sides with a plastic  62 , i.e. including at portions  150  of stator lamination stack  64 , only a thin insulation layer (for example, 0.4 mm thick) being produced there. 
         [0050]    As  FIG. 1  shows, upon over-molding the cavities of internal stator  20  are filled up, bearing tube  56 ,  58  with its collar  60  is produced, also wall  109  of cavity  108  and spokes  134 ,  136 , and lastly also fan housing  24 , so that a fan is obtained, so to speak, in a “single shot.” 
         [0051]    After further assembly (circuit board  110 , connector cable  116  (FIG.  5 )), etc., external rotor  20  is installed as depicted in  FIG. 9  and also described there, and lastly an identification plate is attached, etc. 
         [0052]    The number of stator and rotor poles, the shape thereof, etc. are of course a function of the desired properties of the motor, as is known to one skilled in the art of electrical engineering. In some cases, for example, stator lamination stack  64  on the air-gap side can be covered with plastic not at all or only over a smaller area, or a very thin plastic layer is used. 
         [0053]    Many further variants and modifications are possible, within the scope of the present invention.