Abstract:
An arrangement with an electric motor facilitates mounting of the motor, particularly of a miniature or subminiature motor. The motor ( 20 ) has a stator ( 56 ), a rotor ( 24 ), and a support flange ( 36 ) coupled to the motor. A motor mount ( 22 ) is formed with an opening ( 94 ) for engagement with the support flange ( 36 ). The opening has, on its rim, a motor-side shoulder ( 96 ) that has a substantially frustoconical shape and faces axially toward the motor ( 20 ) after mounting. The support flange ( 36 ) is shaped for guidance of a snap-lock element ( 82 ) that extends along at least a portion of the circumference of the support flange ( 36 ) and is resiliently deflectable radially inward, by means of an inwardly directed force. The snap-lock element ( 82 ) is so configured that it snap-locks outward against the motor-side shoulder ( 96 ) of the opening ( 94 ) when the motor is mounted.

Description:
CROSS-REFERENCE 
   This application claims priority from German application DE 10 2004 036 887.2, filed 21 Jul. 2004, the contents of which are incorporated by reference. 
   FIELD OF THE INVENTION 
   The present invention relates generally to an arrangement with an electric motor, and in particular to a mounting arrangement for a so-called miniature or subminiature motor. 
   BACKGROUND 
   Miniature motors of this kind are used for a variety of tasks, for example to drive miniature or subminiature fans; to drive pumps, for example in medical devices; as actuating motors, etc. Such a motor can have a weight, for example, in the range from approximately 50 grams to approximately 250 grams. 
   Because of their relatively low outputs, such motors are sensitive to contamination, such as can often occur, for example, in a washing machine; an effort is therefore made to arrange such motors in a sealed space so that no dirt can reach them. This applies in particular to motors that use a permanent-magnet rotor, since such a rotor attracts iron particles that can block or interfere with rotation of the rotor. 
   Small motors of this kind usually have a flange, which is also referred to as a support flange. It is usual to mount a motor of this kind by bolting its flange in place at the point where the motor is needed, for example, in order to lock a door. This requires, however, the creation of threaded holes or the setting of threaded rivets for bolt-on mounting, which is sometimes undesirable because such holes can result in weakening, and after a while can result in permanent breakage. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to provide a new and improved arrangement with an electric motor. 
   According to the invention, this object is achieved by forming a rim of a mounting recess or cutout with frustoconical surfaces which radially inwardly compress a resilient element on the support flange while the latter is being inserted into the cutout, and having the resilient element radially rebound outward upon full insertion, to thereby snap-lock the motor within the mounting recess or cutout. 
   Such an arrangement makes possible “blind” installation, i.e. such a motor can simply be pushed into the cutout of the associated apparatus, the snap-lock element then snap-locking the motor therein. The snap-locking element is located in the same protected housing or cavity as the motor, so that the snap-locking element, like the motor, is protected from contamination and corrosion and can easily be detached again, if necessary, for example to swap out any failing component. 

   
     BRIEF FIGURE DESCRIPTION 
     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 shown in the drawings. 
       FIG. 1  is a plan view of a miniature motor  20  that is mounted on an apparatus (only symbolically indicated), viewed in the direction of arrow I of  FIG. 2 ; 
       FIG. 2  is a side view looking in the direction of arrow II of  FIG. 1 ;  FIG. 2  shows the motor after it has been mounted on an apparatus (only schematically indicated), and the motor is driving a device  48  (likewise only symbolically indicated), e.g. a water pump or an actuating apparatus; 
       FIG. 3  is a section viewed along line III—III of  FIG. 2 , at greatly enlarged scale; 
       FIG. 4  is a perspective depiction of the stator on the motor according to  FIGS. 1 to 3 , i.e. prior to installation of the external rotor; 
       FIG. 5  is a plan view of the installed motor looking in the direction of arrow V of  FIG. 2 , at a scale greater than in  FIGS. 1 and 2 ; 
       FIG. 6  depicts a detail labeled VI in  FIG. 5 ; 
       FIG. 7  is a section viewed along line VII—VII of  FIG. 5 ; 
       FIG. 8  is an enlarged depiction of the detail labeled X in  FIG. 7 , but (unlike in  FIG. 7 ) before installation; 
       FIG. 9  is an enlarged depiction analogous to  FIG. 8 , but (unlike in  FIGS. 7 and 8 ) during installation; 
       FIG. 10  is an enlarged depiction of the detail labeled X in  FIG. 7 , i.e. after installation is complete; 
       FIG. 11  is a section viewed along line XI—XI of  FIG. 5 ; 
       FIG. 12  is an enlarged depiction of a detail that is labeled XII in  FIG. 11  and shows an embodiment of a defined break point, provided in the support flange, with which an opening can be broken out of the support flange; and 
       FIG. 13  shows a preferred variant of the snap ring that is used. 
   

   DETAILED DESCRIPTION 
     FIGS. 1 and 2  show, at approximately 1:1 scale, an external-rotor miniature motor  20  that is mounted in a generally annular mount or ring  22  which symbolizes an arbitrary apparatus, such as a wall or part of a housing. In this example, motor  20  is a three-phase motor in a star or delta configuration that is supplied for drive purposes, via three lines  19 , with a three-phase current from, for example, an electronic position controller  25 , to which a target value Ssoll for a desired position, and an actual value Sist for a current position, are delivered. 
   Motor  20  has an external rotor  24  having a so-called rotor cup  26  ( FIG. 7 ) made of copper, in which is mounted a magnet ring  28  that is magnetized with, for example, four poles. Such motors are manufactured by the assignee of this application, and are known. 
   As  FIG. 7  shows, there is mounted, on rotor cup  26 , a shaft  30  that is supported in a plain bearing  32 , which in turn is mounted in a bearing tube  34 , by being pressed in. Bearing tube  34  is formed integrally with a support flange  36 . Parts  34 ,  36  are produced from a suitable heat-resistant plastic, for example polypropylene. 
   At its center, support flange  36  has a depression  38  against which shaft  30  rests with its free end  40 . Shaft  30  is pressed by the force of permanent magnets  28  against this depression  38 , thus forming there an axial bearing for external rotor  24 , which bearing is provided with a lubricant (not shown). 
   As  FIG. 1  shows, rotor cup  26  has three elongated cutouts  42 ,  44 ,  46  that extend radially at 120° intervals (see  FIG. 1 ). They serve for coupling with an arbitrary apparatus  48  that is schematically indicated in  FIG. 2  and is to be driven by motor  20 . 
     FIG. 2  also shows a closed housing  50  in which apparatus  48  and most of motor  20  are located. Apparatus  48  supplies, during operation, the value Sist for position controller  25 . 
   This housing  50  is only schematically depicted. What is important is that it keeps dirt away from motor  20  and part  48  that is to be driven, and that motor  20  can be quickly and securely installed in housing  50  (of which ring  22  is a part). The connection is intended to be such that it can also absorb the mechanical forces resulting from the operation of motor  20 . In addition, installation is preferably also intended to create a liquid-tight connection, and that connection should be disengageable in the event of a defect, e.g. in order to replace motor  20  or apparatus  48 . 
     FIG. 7  shows that electrical conductors  54  are embedded in support flange  36 , serving to connect between lines  19  ( FIGS. 1 and 2 ) and an internal stator  56 . The latter has six salient stator poles  58  whose shape may best be gathered from  FIG. 4 . A coil  60  is arranged in known fashion on each pole  58 . These coils  60  are supplied with current via lines  19 . During operation, stator poles  58  coact in known fashion with magnets  28  of rotor  24 , in order to drive rotor  24 . A plane P through opening  94  separates a motor-side space (MS), which is typically enclosed to protect against contamination, from a flange-side space (FS) which is typically not protected. 
   Because the center of the axial extent of rotor magnet  28  is located (in  FIG. 7 ) above the center of the axial extent of stator poles  58  (the ferromagnetic elements of the stator), a continuous magnetic force on rotor  24  is created, which pulls it downward (in  FIG. 7 ) and presses shaft end  40  against depression  38 . In the event of impact, this prevents rotor  24  from moving axially in bearing tube  34  and “rattling.” It is therefore often possible to dispense with axial retention of rotor  24 . 
   Coils  60  project downward (in  FIG. 7 ) into a trough-like depression  62  of support flange  36 . The latter has, at its periphery, a circumferential rim  64  projecting upward with reference to  FIG. 7 . Flange  36  furthermore has a radially outwardly projecting rim segment  66 . 
   Extending between rim  64  and depression  62  are twelve radially extending stiffening ribs  68  which are arranged, as shown in  FIG. 3 , at regular intervals of 30°, and whose shape is clearly evident from  FIG. 7 . They have approximately the profile of an armchair. 
   As  FIGS. 3 and 4  show, electrical connecting elements  70 , on each of which is mounted a connecting line  72  for one of the coils  60 , extend between adjacent reinforcing ribs  68 . A total of three connecting elements  70 , electrically connected to lines  19 , are mounted in flange  36 . 
     FIG. 11  shows the routing of one of connecting elements  54 ,  70  in flange  36 . The result is to prevent, in very simple fashion and without additional cost, infiltration or penetration of liquid into motor  20  in the region of these connecting elements. 
   Stator poles  58  are elements of a stator lamination stack  59  that is pressed, in the manner depicted in  FIG. 7 , onto outer side  74  of bearing tube  34 . Lamination stack  59  is provided, as shown in  FIG. 7 , with an insulating layer  76  that serves as a coil former for coils  60 . 
   Provided on outer periphery  78  of upwardly projecting rim  64  of flange  36  is a recess  80 , similar to an annular groove, in which is arranged a resilient snap-locking element  82  whose shape is best gathered from  FIG. 3 . It is shaped approximately like a C, or like a circle interrupted at one point. It is produced from resilient material, usually steel, and can move, relative to groove  80 , within predetermined limits. A preferred embodiment is a snap ring, but one could also use a conical ring. Various alternatives are known in the leaf spring art. 
     FIG. 13  shows a variant  82 ′ of this snap-lock element that has advantages for many applications. 
   As  FIG. 3  shows, the resilient snap-locking element has two actuation openings  84  into which a tool (not shown) can be introduced, in order to move these actuation openings  84  toward one another, as is necessary when opening the snap-lock system (see description below). 
   Snap-lock element  82 , like snap-lock element  82 ′ of  FIG. 13 , has four enlargements  86  that project radially inward. Annular groove-shaped recess  80  has corresponding depressions  88  into which these enlargements  86  engage, thereby preventing snap-lock element  82  (or  82 ′) from rotating in groove or recess  80 . This is advantageous because special openings must be made through flange  36  for access to actuation openings  84 , and when those openings have been created by the breaking of a defined break point, actuation openings  84  must be located directly behind them, so that a tool can be placed onto them. 
   In  FIG. 13 , snap-lock element  82 ′ additionally has an extension  91  to the right in the region of left opening  84 , and an extension  93  to the left in the region of right opening  84 . Extensions  91 ,  93  are also guided in recess  80 . It has been found that additional guidance of this kind in the region of openings  84  can be advantageous in many cases. 
   As shown in  FIGS. 7–8 , an elastic sealing member  90 , e.g. an O-ring, is arranged on the outer periphery of support flange  36  in an annular groove  89 . Ring or mount  22  also has, on its side facing away from motor  20 , a ramped, frustoconical surface  92  that widens in the direction away from motor  20 . This ramped surface serves as a guide during insertion of motor  20  through opening  94 . In the direction toward motor  20 , this surface  92  transitions into a cylindrical segment  94  ( FIG. 8 ), adjoining which is a second frustoconical surface that forms a diagonally tapered shoulder  96  whose diameter widens toward motor  20 . 
     FIGS. 8 through 10  show the procedure during installation. According to  FIG. 8 , support flange  36 , with motor  20  mounted on it, is inserted, along the direction indicated by arrow  98 , into cylindrical opening  94  of ring  22 . Resilient ring  82  is thereby radially inwardly compressed by contact with frustoconical surface  92  until, as shown in  FIG. 9 , it fits within cylindrical opening  94 , and can be pushed axially through it. 
   Resilient ring  82  ultimately ends up in the position shown in  FIG. 10 . Here, resilient ring  82  can once again partially relax or rebound, and makes contact with a preload against tapered shoulder  96 . At the same time, sealing ring  90  is compressed between annular groove  89  and frustoconical surface  92 , thus forming a secure seal. This keeps contaminants and moisture out of the motor-side space (MS). Flange segment  66  also makes contact against the flat end face  100  of ring  22 , or forms a narrow gap therewith. Clamping ring member  82 , as a result of its spring action, maintains an axial force on elastic sealing member  90 . This axial force also causes immovable retention of flange  36  in opening  94 , and prevents flange  36  from wobbling in opening  94 . 
   An arrangement of this kind thus enables a “blind” installation of motor  20  on ring  22  that proceeds very quickly since, after installation, it is necessary only to connect lines  19 , which is usually done by means of a plug connector (not shown). This type of mounting is very secure and cannot disengage by itself. It also maintains a constant load on sealing ring  90  and is fluid-tight, so that the parts inside housing  50  ( FIG. 2 ) do not become soiled. 
   Contributing to this is the fact that motor  20  has no collector and no carbon brushes. It is also very advantageous that resilient ring  82  or  82 ′ is located inside housing  50  (the protected motor-side space) and therefore cannot corrode. This is desirable because, in many cases, it is necessary to remove motor  20  for repair or even simply for inspection. 
   For that purpose, support flange  36  has, in the region of openings  84  in elastic ring  82 , frangible areas  102 ,  104  ( FIG. 5 ) that can be broken out along defined break lines. The result is to create two openings (not shown) through which a tool can be inserted into openings  84  of elastic ring  82 . Ring  82  is thereby radially compressed in the region of its openings  84 , so that it disengages from frustoconical shoulder  96 , and motor  20  can be pulled out through cylindrical opening  94 . 
   If it is found that motor  20  is OK, the openings that were broken out of flange  36  can be temporarily closed off, and motor  20  can be reinstalled. Motor  20  must then be replaced, when the opportunity arises, with another motor having an intact flange  36 . 
     FIG. 11  and  FIG. 12  show, in flange  36 , two trough-like depressions  106 ,  108  whose location on the flange is apparent from  FIG. 5  and  FIG. 6 . Located between these depressions is a thicker segment  110 , and by pressing on this, segment  110  can be broken out along defined break lines  112 ,  114 , thus creating the above-described opening. 
     FIG. 6  shows the location of areas  102 ,  104  relative to radial stiffening ribs  68  and openings  84  of snap ring  82 . After installation, openings  84  are each located between two stiffening ribs  68 , as are areas  102 ,  104 . 
   Numerous variants and modifications are, of course, possible within the scope of the present invention.