Abstract:
To provide a circulation pump comprising a housing, in which a pump space is arranged, a pump impeller, which can be rotated about a rotational axis, and an electric motor to drive the pump impeller, that can be produced simply and economically, it is proposed that the housing have a receiving space for the electric motor.

Description:
[0001]     This application is a continuation of international application number PCT/EP2005/011860 filed on Nov. 5, 2005.  
         [0002]     The present disclosure relates to the subject matter disclosed in international application number PCT/EP2005/011860 of Nov. 5, 2005 and German application number 10 2004 058 591.1 of Nov. 26, 2004, which are incorporated herein by reference in their entirety and for all purposes. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     The invention relates to a circulation pump, comprising a housing, in which a pump space is arranged, a pump impeller which can be rotated about a rotational axis and an electric motor to drive the pump impeller.  
         [0004]     The invention also relates to a method for producing a circulation pump.  
         [0005]     A circulation pump is known from U.S. Pat. No. 6,082,976 A, which has a pump housing with a pump space and which has a motor with a motor housing, which borders the pump housing. The motor is pressed against one side of the pump housing, the pump housing being clamped between a distributor pipe and the motor.  
       SUMMARY OF THE INVENTION  
       [0006]     In accordance with the present invention, a circulation pump is provided, which can be produced simply and economically.  
         [0007]     In accordance with an embodiment of said circulation pump the housing has a receiving space for the electric motor.  
         [0008]     The circulation pump in accordance with the invention can be produced in a simple manner: no separate housings have to be provided for the pump space and to receive the electric motor, but a single interconnected housing may form the pump space and the receiving space for the electric motor. The electric motor can be fixed in a simple manner.  
         [0009]     The solution according to the invention is, in particular, advantageous in connection with electric motors with a low axial overall height, the overall height of the electric motor being substantially determined by a rotor. In an electric motor of this type with a low axial overall height, the heat can be removed, in particular from a stator to a liquid to be pumped. No separate part housing then has to be provided for the electric motor, which has to be fixed (externally) to the pump housing.  
         [0010]     The electric motor may be braced between at least two opposing contact faces. No screws or bolts or the like thus have to be provided to fix the electric motor in the housing. Thus, the housing configuration is simplified, on the one hand, as no engagement regions have to be provided for screws or the like. On the other hand, production is simplified.  
         [0011]     In a production of the housing from plastics material, an optimised shaping can be provided for it.  
         [0012]     In particular, the housing has an axial extent with respect to the rotational axis of the electric motor to form the receiving space for the electric motor. A receiving space can thus be provided to receive the electric motor.  
         [0013]     It is quite particularly advantageous if the housing is produced from a plastics material. Possible materials are, for example, PPS or PA6.6. The housing can thus be produced integrally, for example by an injection moulding method. Plastics materials can easily be shaped. Thus, the design required for a high degree of efficiency can be adjusted, in particular for the pump space.  
         [0014]     The housing is advantageously configured in one piece. The production of the components for the pump is thus simplified and assembly is simplified.  
         [0015]     In particular, the pump space and the receiving space for the electric motor are axially arranged one after the other in the housing. The circulation pump can thus be configured in a space-saving manner and the pump impeller can be driven directly by the electric motor.  
         [0016]     It is quite particularly advantageous if a fixing device is provided at least for axially fixing the electric motor in the housing. The fixing device ensures a substantially play-free fixing of the electric motor in the housing.  
         [0017]     In particular, the electric motor is fixed by means of the fixing device to the housing by bracing.  
         [0018]     It is favourable if the fixing device has one or more holding elements, which are fixed to the housing and by means of which the electric motor is held in position. The electric motor may be axially positioned and fixed and/or, if necessary at all, radially positioned and fixed by means of the at least one holding element. The at least one holding element provides one or more contact faces, which block an axial mobility of the electric motor at least in an axial direction. The electric motor can thus be held clamped or braced in the housing. The at least one holding element can absorb the static pressure of the system and the dynamic pressure, caused by the pumping function.  
         [0019]     It is quite particularly advantageous if the at least one holding element is fixed on the housing by means of a housing periphery or at least one interconnected part region of a housing periphery. The pressure acting on the housing can thus be absorbed in a structurally simple manner. This fixing can be achieved, for example, by a thread connection of the at least one holding element to the housing, by a clamping device, for example with snap closure connections or by a bayonet lock connection. No receiving space region for screws or bolts thus has to be provided in the housing. Corresponding housing walls can be configured so as to be thin-walled. The housing can thus be produced in a manner “suitable for plastics material”, in other words, plastics material can be used to produce the housing. With regard to an axial fixing, no substantial shear stresses occur in the housing when the holding element is fixed by means of a housing periphery. This in turn makes it possible to use a plastics material to produce the housing.  
         [0020]     In one embodiment, it is provided that the at least one holding element is fixed to the housing along the entire periphery. This fixing takes place, for example, by means of a thread connection, in that, for example, a holding element is screwed directly into the housing or a retainer nut as the holding element fixes the electric motor.  
         [0021]     In one embodiment, the at least one holding element is provided with a thread and the housing is provided with a corresponding thread. The holding element can thus be screwed to the housing by means of a screw connection, the holding element itself forming the screw, for example, and the housing the counter piece.  
         [0022]     For example, the at least one holding element is provided with an external thread and the housing is provided with an internal thread. The holding element is then configured as a type of plug, which can be fixed to the housing in order to close it by means of a thread connection.  
         [0023]     It may be provided that the at least one holding element projects into the housing. For example, the holding element may be configured in the manner of a plug, the plug projecting into the housing and thus acting on the electric motor in order to brace it axially. It is also possible for the holding element to be part of the electric motor and, in particular, formed by means of the motor housing of the electric motor. The holding element itself is then in turn configured in such a way that it fixes the electric motor in the housing “from within”, for example by means of recess/tongue connections or groove/pin connections.  
         [0024]     It is also possible for the at least one holding element to have an internal thread and the housing to have an external thread. A holding element can thus be formed as a retainer nut, for example, by means of which the electric motor is axially fixed.  
         [0025]     It is particularly advantageous when the electric motor has one or more contact faces for the at least one holding element. The holding element may act on a corresponding contact face in order to thus hold the electric motor axially fixed in the housing. In particular, the electric motor can be held clamped in the housing.  
         [0026]     In one embodiment, it is provided that the at least one contact face projects over the housing. A holding element may then be used, which does not project into the housing. For example, a holding element can be configured as a retainer nut.  
         [0027]     It is basically possible for the at least one holding element to be a separate component from the electric motor. For example, the holding element is configured as a type of plug, which is screwed into the housing, so the plug acts on the electric motor, and in particular a motor housing of the electric motor in order to fix the latter in the housing of the circulation pump. (The motor housing of the electric motor then has no fixing function apart from providing contact faces for the at least one holding element. The motor housing of the electric motor is substantially used to “hold together” the motor components, in order to be able to handle the electric motor as a unit.)  
         [0028]     Alternatively, it is possible for the at least one holding element to be arranged on the electric motor. No additional component is then necessary for fixing the electric motor in the housing.  
         [0029]     In particular, the at least one holding element is then formed by means of a motor housing of the electric motor.  
         [0030]     It may be provided that the at least one holding element is fixed by means of a clamping device in the housing. In particular, the clamping device comprises one or more snap closure connections. In this manner, for example, a circulation pump may be provided, in which a housing cover, which is formed by means of a holding element, can no longer be detached without destruction.  
         [0031]     It may be provided that the clamping device has at least one tongue, which is arranged on the at least one holding element and/or the housing, and at least one adapted recess, which is arranged on the housing and/or the at least one holding element, so by projection of the at least one tongue into the associated recess, the at least one holding element is fixed on the housing at least axially. A snap closure connection can thus be provided. In particular, a tongue of this type is elastically arranged and configured in such a way that the holding element can be inserted into the housing. When the tongue reaches into the region of the associated recess, it is pressed into the recess because of the elastic force and projects thereinto. This projecting in blocks the further movement of the holding element such that the holding element is positioned and fixed by the “automatic” production of the snap closure connection on insertion of the holding element and thus the electric motor is also positioned and fixed.  
         [0032]     It may also be provided that the at least one holding element is fixed by means of a bayonet connection to the housing. In a bayonet connection, a pin/groove device is provided, one or more pins being arranged on the housing and/or a holding element and one or more adapted grooves being provided on the holding element and/or the housing. The grooves provide, when the pins are inserted, the movement capabilities for the holding element and also its end position.  
         [0033]     It may be provided that one or more seals are arranged between the at least one holding element and the housing. The housing interior on the holding element, which is also used as a cover to close the housing, can thus be protected before the entry of liquids into the housing interior. A corresponding circulation pump can be used, in particular, as an immersion pump.  
         [0034]     It is quite particularly advantageous if a contact face is arranged on the housing to support the electric motor. Between a contact face of this type and a holding element, the electric motor may be held braced in the housing. A contact face of this type forms a counter bearing for the electric motor.  
         [0035]     A corresponding circulation pump can be produced in a simple manner when the contact face is formed on a shoulder in an interior of the housing. This shoulder can be integrally co-produced during production of the housing.  
         [0036]     It is favourable if the receiving space of the housing is adapted to the electric motor in such a way that it is radially positioned and fixed by resting on interior housing wall regions. No screw connections or the like are required, in particular, for a radial fixing of this type. It is basically also possible for an insert to be provided for an intermediate space between the electric motor and the housing, by means of which the electric motor is radially positioned. An insert of this type is, in particular, produced from a plastics material.  
         [0037]     It is favourable if the electric motor has a spherically mounted rotor. A corresponding electric motor has a high degree of quiet running. It can be configured with a low axial overall height.  
         [0038]     In this connection, it is also favourable if the rotor is configured to generate a magnetic field. A corresponding electric motor is described in DE 102 45 015 A1, US 2003/0222527 A1, EP 1 416 607 A2 and US 2004/0119371 A, to which reference is expressly made.  
         [0039]     In particular, it is advantageous if the rotor is spherically configured facing a stator. An electric motor with a low axial overall height can thus be constructed, the axial overall height thereof being substantially determined by the height of the rotor.  
         [0040]     For the same reason, it is favourable if the stator is spherically configured facing the rotor.  
         [0041]     A low axial overall height can be achieved when a magnetic return body of the stator annularly surrounds the rotor. The stator can thus be positioned completely adjacent to the pumping space. This in turn allows heat to be also removed from the stator directly by means of the liquid flowing through the circulation pump. This in turn means that the housing is thermally less loaded in the region of the electric motor. A plastics material can thus be used to produce the housing in the region of the electric motor. This in turn allows an integral housing for the circulation pump (which also receives the electric motor) to be produced from a plastics material.  
         [0042]     The magnetic return body may be produced from a pressed powder material. A corresponding electric motor is disclosed in EP 1 416 607 A2 and US 2004/0119371 A1, to which reference is expressly made.  
         [0043]     It is favourable if a height of the stator substantially corresponds to the height of the rotor or has a smaller height than the height of the rotor. The height of the electric motor is then substantially determined by the height of the rotor. The advantages described above, that, for example, heat can be removed from the stator by means of the pumping liquid, are thus produced.  
         [0044]     In particular, it is favourable if a rotor and a stator of the electric motor are configured adapted in such a way that an axial magnetic holding force, which holds the rotor on a spherical bearing, is greater than a maximum axial counterforce. It can be achieved by means of the corresponding adjustment of the magnetic holding forces that, even when the motor is switched off, the rotor is held magnetically on the spherical bearing, in other words does not lift up therefrom. A corresponding electric motor is described in DE 102 45 015 A1 and US 2003/0222527 A1, to which reference is expressly made.  
         [0045]     It is quite particularly advantageous if the electric motor is arranged and configured in such a way that heat can be removed from it by means of the liquid to be pumped. The thermal loading of the housing in the region of the electric motor is thus sharply reduced. A plastics material can thus in turn be used to produce the housing.  
         [0046]     In particular, a stator of the electric motor is in thermal contact with the pump space in order to be able to remove heat by means of the pumping liquid.  
         [0047]     In accordance with the present invention, a method for producing a circulation pump is provided, which can be implemented in a simple and economical manner.  
         [0048]     In accordance with an embodiment of the invention, a housing with a pump space and a receiving space for an electric motor is produced and the electric motor is inserted into this housing.  
         [0049]     The method according to the invention already has the advantages described in conjunction with the circulation pump according to the invention.  
         [0050]     Further advantageous configurations have also already been described in conjunction with the circulation pump according to the invention.  
         [0051]     In particular, the housing is produced from a plastics material. A “total housing”, which has a pump space part and a receiving space part, can thus be integrally produced. The housing can be produced in such a way that it is optimised with respect to its properties. For example, the pump space is integrally produced in the housing in such a way that a high degree of efficiency is produced. For example, contact faces are also produced in the housing, on which an electric motor can be supported for the clamping or braced holding thereof in the housing.  
         [0052]     It is favourable if the electric motor is axially fixed by means of one or more holding elements, the at least one holding element being fixed to the housing. The corresponding electric motor can thus be produced in a simple manner. A holding element for fixing the electric motor can thus also be configured, for example, as a cover to close a housing interior.  
         [0053]     In one embodiment, the housing is closed by means of the at least one holding element, i.e. the receiving space is closed relative to the outer space. The holding element, which is configured, for example, as a stopper, then forms a housing cover.  
         [0054]     It is quite particularly advantageous if the at least one holding element is fixed to the housing by means of a peripheral region of the housing. An axial positioning and fixing of the holding element and therefore of the electric motor in the housing can thus be achieved in a simple manner. However, with the fixing around a peripheral region, the shear stresses may be kept low or no shear stresses occur. This in turn makes it possible for the housing in the fixing region to be configured with relatively thin walls, which in turn allows the use of plastics materials.  
         [0055]     It may be provided that the electric motor is radially positioned in the housing by resting on the housing. In particular, a simultaneous radial fixing then also takes place. The corresponding circulation pump can then be produced in a simple manner as, when inserting the electric motor, automatic alignment, positioning and fixing of the electric motor in the radial direction are ensured.  
         [0056]     The following description of preferred embodiments is used in conjunction with the drawings for a closer description of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0057]      FIG. 1  shows a sectional view of a first embodiment of a circulation pump according to the invention;  
         [0058]      FIG. 2  shows a sectional view of a second embodiment of a circulation pump according to the invention;  
         [0059]      FIG. 3  shows an enlarged view of the region A in  FIG. 2 ;  
         [0060]      FIG. 4  shows a sectional view of a third embodiment of a circulation pump according to the invention;  
         [0061]      FIG. 5  shows an enlarged view of the region B according to  FIG. 4 ;  
         [0062]      FIG. 6  shows a sectional view of a fourth embodiment of a circulation pump according to the invention; and  
         [0063]      FIG. 7  shows a sectional view along the line  7 - 7  according to  FIG. 6 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0064]     A first embodiment of a circulation pump according to the invention, which is shown in  FIG. 1  and designated  10  there, comprises a housing  12 , in which a pump space  14  is formed.  
         [0065]     A pump impeller  16  is rotatably arranged in the pump space  14 . The pump impeller  16  is non-rotationally connected to a rotor  18  of an electric motor  20 .  
         [0066]     The pump space  14  is in fluid connection with an inlet connector  22  and a pressure connector  24 . Liquid is introduced into the pump space  14  by means of the inlet connector  22  and liquid guided through the pump space  14  can be removed by means of the pressure connector  24 .  
         [0067]     The housing  12  has a pump space part  26  and an electric motor part  28 . The pump space part  26  of the housing  12  comprises a connecting piece  30 , on which the inlet connector  22  is formed. The connecting piece  30  extends, for example, in parallel or coaxially to a rotational axis  32  of the electric motor  20 .  
         [0068]     In the embodiment shown, the connecting piece  30  is connected by means of a dome-shaped region  34  to a cross-sectionally substantially rectangular housing region  36 .  
         [0069]     A connecting piece  38  is also provided and extends in a transverse direction  40  to the rotational axis  32 ; the transverse direction  40  is perpendicular to the rotational axis  32 , for example. The pressure connector  24  is arranged or formed on the connecting piece  38 . The pressure connector  24  and the inlet connector  22 , are, in particular, offset with respect to one another such that their axes do not intersect (centreline-offset arrangement).  
         [0070]     The connecting piece  38 , the dome-shaped region  34  and the connecting piece  30  are, in particular, connected to one another in one piece.  
         [0071]     In the housing  12 , a receiving space  42  for the electric motor  20 , with respect to the rotational axis  32 , axially follows the pump space  14 . The electric motor  20  is largely arranged in this receiving space  42 .  
         [0072]     To form the receiving space  42 , the housing  12  in the electric motor part  28 , comprises a wall  44 . This wall  44  is, in particular, cylindrical with an axis coaxial to the rotational axis  82 . The receiving space  42  for the electric motor  20  therefore has a cylindrical design.  
         [0073]     The wall  44  is connected in one piece to the pump region  26  of the housing  12 . The housing  12  is thus configured in one piece, the pump space  14  being arranged and the electric motor  20  being received therein.  
         [0074]     A wall thickness of the wall  44  is smaller than a corresponding wall thickness of the housing  12  in the pump region  26 . A step-shaped shoulder  46  is thus formed at the transition from the pump space  14  to the receiving space  42 . An in particular annular contact face  48  is provided by this shoulder  46 . The electric motor  20  can be placed directly or via a seal  50  on this contact face  48 .  
         [0075]     The electric motor  20  is configured with a motor housing  52  in such a way that it can be positioned radially in the receiving space  42 . The motor housing  52  is used to hold together the motor components, so the electric motor  20  can be handled as a unit. It is, for example, produced from a plastics material. It has, for example, a cylindrical side wall  54 , which protrudes over a base  56 . The side wall  54  surrounds the stator  88  laterally. The base  56  rests, at least partially, by means of one or more contact elements  58  on a stator  86 .  
         [0076]     It may be provided that a circuit board  59  is held, for example, by means of one or more snap pin connections  60  on the base  56  and therefore on the motor housing  52 . Electronic components are arranged on the circuit board  59 .  
         [0077]     The circuit board  59  can be fixed to the motor housing  52  by means of the at least one snap pin connection  60 .  
         [0078]     The electric motor  20  with its motor housing  52  has a cross-sectional diameter transverse to the rotational axis  32 , which corresponds substantially to the internal diameter of the receiving space  42 .  
         [0079]     During production of the circulation pump  10 , the electric motor  20  with its motor housing is pushed from an open end of the housing  12  into the receiving space  42 . The displaceability into the pump space  14  is blocked by the shoulder  46 : when the electric motor  20  rests on the contact face  48  of the shoulder  46 , it cannot be displaced further in the direction of the pump space  14 . The motor housing  52  thus ensures a radial positioning and therefore a radial fixing of the electric motor  20  in the receiving space  42 .  
         [0080]     To fix the electric motor  20  in the housing  12 , a fixing device  61  is provided. This is used for the axial positioning and fixing of the electric motor  20  in the housing  12 . It can also be used for radial positioning and fixing; in the circulation pump  10  the motor housing  52  takes on the task of the radial positioning and fixing of the electric motor  20 .  
         [0081]     For the axial fixing of the electric motor  20  with respect to the end of the housing  12 , which is open during the insertion of the electric motor  20 , a holding element  62  is provided, which is fixed on the housing  12 . The holding element  62  blocks a movement of the electric motor  20  away from the pump space  14 , so the electric motor is also axially fixed in the housing  12 . The holding element  62  thus acts on the electric motor  20  in order to hold it braced or clamped in the axial direction in the housing  12 .  
         [0082]     In the circulation pump  10 , the holding element  62  is configured in the manner of a stopper with an external thread  64 , which is adapted to an internal thread  66  of the housing  12  in the electric motor region  28 . The holding element  62  can thus be screwed in the housing  12 .  
         [0083]     The holding element  62  is also used as a cover for closing the housing  12  on the receiving space  42 .  
         [0084]     The external thread  64  of the holding element  62  is configured on an annular holding region  68 . This holding region  68  has an end annular face  70 . By means of this annular face  70 , the holding element  62  acts on the motor housing  52  and therefore in turn on the electric motor  20 . The electric motor  20  can be pushed against the contact face  48  of the shoulder  46  by means of the annular face  70  and can therefore be held braced.  
         [0085]     The holding element  62  may have an annular flange  72 , an external diameter of this flange  72  being greater than an internal diameter of the receiving space  42 . The flange  72  can thus overlap an end face  74  of the housing  12  in the electric motor part  28  (which is annular), to ensure a seal.  
         [0086]     The electric motor  20  has a spherical bearing  76 , by means of which the rotor  18  is spherically mounted. The spherical bearing  76  comprises a holding column  78 , on which a spherical sliding body  80  is seated. The sliding body  80  is, in particular, produced from a ceramic material.  
         [0087]     A bearing shell  82  adapted to the spherical sliding body  80  is non-rotationally seated on the rotor  18 .This bearing shell slides on the sliding body  80  on rotation of the rotor  18 .  
         [0088]     In one embodiment, the rotor  18  generates a magnetic field. One or more permanent magnets  84  are arranged thereon. The rotor  18  is spherically configured facing a stator  86 . The stator  86  is also spherically configured facing the rotor  18 .  
         [0089]     A magnetic return body  88  of the stator  86  surrounds the rotor  18  annularly, it being possible for this return body  88  to be configured, in particular, closed. An axial height of the stator  86  substantially corresponds to the height of the rotor  18  or is smaller.  
         [0090]     In particular, the rotor  18  and the stator  86  are configured adapted in such a way that an axial magnetic holding force, which holds the rotor  18  on the spherical bearing  76 , is greater than a maximum axial counterforce. It is thus achieved that even when the motor is switched off, the rotor  18  is held magnetically on the spherical bearing  76 , in other words does not lift off from it. In particular, the configuration of rotor  18  and the stator  86  is adapted in such a way that a magnetic force at one end of the rotor  18  is greater than at an opposing end, so a holding force results which, even in the event of a maximum counterforce, such as, for example, in the event of a hydraulic counterforce, presses the rotor  18  against the sliding body  80  of the spherical bearing  76 . The electric motor  20  can thus be configured with a low overall height.  
         [0091]     An electric motor of this type is described in DE 102 45 015 A1 and US 2003/0222527 A1, to which reference is expressly made.  
         [0092]     The return body  88  is configured spherically, at least in segments, facing the rotor  18  for the spherical configuration of the stator  86 . For example, the magnetic return body  88  is produced from a pressed powder material.  
         [0093]     A corresponding electric motor is disclosed in EP 1 416 607 A2 or US 2004/0119371 A1, to which reference is expressly made.  
         [0094]     The stator  86  has a region  90 , which borders on the pump space  14  or is at least in thermal contact therewith. Additional heat from the electric motor  20  can thus be removed by means of the liquid flowing through the pump space  14 . (A relatively large part of the heat flow goes from the stator  88  into the rotor region.)  
         [0095]     The circulation pump  10  according to the invention functions as follows:  
         [0096]     The housing  12  is a common housing for the pump part of the circulation pump  10  and the electric motor part of the circulation pump  10 ; the housing  12  forms the pump space  14  and the receiving space  42  for the electric motor  20 . The housing  12  is, in particular, produced in one piece. It is preferably produced from a plastics material. A simple and economical producibility thus results.  
         [0097]     The electric motor  20  is fixed in the housing  12  axially by means of the shoulder  46  and the holding element  62 . The holding element  62  with its external thread engages in the internal thread  66  of the housing  12 . A complete fixing is therefore achieved between the holding element  62  and the housing  12 . The holding element  62  absorbs the axial bracing force to brace the electric motor  20  and the static and dynamic force in the receiving space  42 .  
         [0098]     The housing  12  can thus be configured so as to be thin-walled and plastics material can therefore be used as the housing material. As the holding element  62  also has to ensure an axial fixing, no, or only small, shear stresses occur.  
         [0099]     The electric motor is radially fixed in the receiving space  42  by the motor housing  52 .  
         [0100]     By using a plastics material for the housing  12 , substantially any shaping is possible for the housing  12 ; this is in contrast to cast iron housings. A housing shape can thus be used, by means of which an optimised degree of efficiency of the circulation pump  10  can be achieved.  
         [0101]     The electric motor  20  has a low axial height, this axial height being substantially determined by the height of the rotor. Stator heat can thus be removed to the liquid to be pumped. This, in turn, sharply reduces the thermal load for a motor housing. A plastics material can thus be used for the housing for the electric motor  20 , namely for the electric motor part  28  of the housing  12 .  
         [0102]     A circulation pump, which can be produced in a simple and economical manner and in which the degree of efficiency can be optimised by the housing shaping, is provided by the solution according to the invention.  
         [0103]     The circulation pump  10  is produced according to the invention as follows:  
         [0104]     The housing  12  is produced, in particular, from a plastics material, for example by an injection moulding method.  
         [0105]     The electric motor  20  is produced separately and the pump impeller  16  is connected to the rotor  18  of the electric motor  20 .  
         [0106]     The electric motor  20  is then pushed by means of the open end  60  of the housing  12  into the housing  12 . The electric motor  20  is automatically correctly positioned radially by means of its motor housing  52 .  
         [0107]     The stopper-like holding element  62  is then screwed on. This ensures the axial fixing of the electric motor  20  in connection with the shoulder  46  in the housing  12  and closes the housing  12 .  
         [0108]     The holding element  62 , in this case, also closes the open end  60  of the housing  12 , so a housing interior is closed toward the outer chamber.  
         [0109]     A second embodiment of a circulation pump according to the invention, which is shown in  FIG. 2  and designated  92  there, comprises a housing  94 , which is configured substantially the same as the housing  12  of the circulation pump  10 . A difference of the housing  94  from the housing  12  is that an internal thread  66  is not provided. Otherwise, reference is made to the description of the housing  12 .  
         [0110]     An electric motor  95 , which is basically configured the same with respect to its functional components as the electric motor  20  in the first embodiment  10 , is arranged in the housing  94 . The same reference numerals are therefore used for the same functional motor components as in the first embodiment  10 .  
         [0111]     A motor housing  96 , on which a holding element  98  acts, is used to fix the electric motor  95  in the housing  94 . The motor housing  96  (which holds the components of the electric motor together) has a cylindrical wall  100 , by means of which a radial positioning and fixing of the electric motor  95  in the housing  94  is ensured.  
         [0112]     The wall  100  is connected in one piece to an annular region  102 , on which a further cylindrical region  104  is seated in one piece. When the electric motor  20  is fixed, an intermediate space  107  is formed between the electric motor  20  and a base  106  of the cylindrical region  104 . This space may, for example, receive a control circuit for the circulation pump  92 .  
         [0113]     The annular region  102  projects over the housing  94  to such an extent that the holding element  98  can act on it; the electric motor  95  can thus be axially fixed.  
         [0114]     One or more pins  108  are arranged, for example, on the annular region  102 , by means of which pins a circuit board  110  is held ( FIG. 3 ). In particular, the pin  108  is configured in relation to the circuit board  110  in such a way that the circuit board  110  can be fixed in the manner of a snap connection on the motor housing  96 .  
         [0115]     The motor housing  96  of the electric motor  95  is cup-shaped to ensure a radial positioning and fixing of the electric motor  95  in a corresponding receiving space of the housing  94  for the electric motor  95 .  
         [0116]     The motor housing  96 , which is used to close the housing  94 , is held on the housing  94  by the holding element  98 . A holding element  98  is, for example, configured as a retainer nut. For this purpose, it has an internal thread  112 . The housing  94 , close to its end face end  114  has an external thread  116 , which is adapted to the internal thread. 112 .  
         [0117]     In cross-section, the holding element  98  is L-shaped ( FIG. 3 ). The internal thread  112  is formed on a first holding element part  118 . A second holding element part  120 , which extends perpendicularly to the first holding element part  118 , is used for resting the holding element  98  on an outer side of the annular region  102 . The electric motor  95  can thus be axially fixed by means of the holding element  98  by its second holding element part  120 . The motor housing  96  may be pressed, in particular, by means of the holding element  98  in the direction of a pump space of the housing  94 , to thus brace the electric motor  95  in the housing  94  and to axially fix it.  
         [0118]     The second holding element  120  of the holding element  98  overlaps the end face end  114  of the housing  94 . This also ensures a seal, and specifically in the same manner as the flange  72  of the holding element  62  in the circulation pump  10  overlaps an end face of the housing  12 .  
         [0119]     The holding element  98  is in particular annular, with it surrounding the region  104 . It acts as a retainer nut for axially fixing the electric motor  95 .  
         [0120]     In a variant of the circulation pump  92 , a seal  121 , for example in the form of an O-ring, is arranged between the annular region  102  and a housing wall  119 , which forms the receiving space for the electric motor  95 . This seal  121  is used to prevent the penetration of liquid into the receiving space. The corresponding circulation pump can then be used, for example, as an immersion pump.  
         [0121]     Otherwise, the circulation pump  92  functions like the circulation pump  10  and can be produced in basically the same manner.  
         [0122]     In a third embodiment, which is shown in  FIG. 4  and designated  122 , a housing  124  is provided, in which a pump space  126  is formed and which has a receiving space  128  for an electric motor  129 . The electric motor  129  is basically configured the same with respect to its functional components as described with the aid of the embodiment. The same reference numerals are therefore used for the same functional components.  
         [0123]     The housing  124  is basically configured the same as the housing  12 , no internal thread  66  being provided.  
         [0124]     The housing  124  is provided, in particular in the region of the receiving space  128 , with a plurality of recesses  130  ( FIG. 5 ).  
         [0125]     The recesses  130  may be through recesses or only arranged as a depression on an inner side  132  of a housing wall of the housing  124 , which forms the receiving space  128 .  
         [0126]     In the case of a plurality of recesses  130 , they are located, in particular at the same axial height.  
         [0127]     To fix the electric motor  129  in the housing  124 , a correspondingly configured motor housing  134  is provided. The motor housing  134  forms a holding element  134 . It comprises a cylindrical wall  136 , which surrounds the electric motor  129  and, when the electric motor  129  is fixed, projects into an intermediate space between the electric motor  129  and the inner side  132  of the housing  124 . The wall  136  is consequently used for the radial positioning and fixing of the electric motor  129  in the receiving space  128 .  
         [0128]     The cylindrical wall  136  is connected, in particular in one piece, to an annular region  138 . A dome-like region  140  with a cylindrical inner space projects over the annular region  138 . The motor housing  134  is basically configured the same here as the motor housing  96  in the second embodiment  92 .  
         [0129]     A plurality of pins  142  may be provided, which are immersed in corresponding recesses on a circuit board  144  and hold this circuit board  144  on the motor housing  134 . The motor housing  134  is fixed in the associated electric motor  129  by means of pin/recess connections.  
         [0130]     The motor housing  134  is provided with a plurality of tongues  146  as “intrinsic” holding elements, which, when the electric motor  129  is fixed, project into the corresponding recesses  130 . The tongues  146  project over an outer face  148  of the cylindrical wall  136 . They are elastically configured in such a way that the electric motor  129  with its motor housing  134  can be inserted into the receiving space  128 . For this purpose, a force is necessary to hold the tongues  146  out of their basic position in the direction of the rotational axis  32 . When the tongues  146  reach their associated recesses  130 , they snap into the respective recesses  130 . An axial fixing of the electric motor  129  in the receiving space  128  is thus achieved. A radial positioning and fixing takes place simultaneously owing to the cylindrical wall  136 .  
         [0131]     The tongue/recess combinations, for example, form a snap connection. The snap connection is thus configured, in particular, in such a way that after the fixing of the electric motor  129 , the circulation pump  122  can no longer be disassembled, in other words the motor housing  134  can no longer be detached from the housing  124  without destruction. In the embodiments  10  and  92 , on the other hand, the corresponding housing  12  and  94  can also be opened without destruction after assembly, in that the corresponding holding element  62  or  98  is released.  
         [0132]     The tongues  146  and the recesses  130  form a clamping device  149  for clamping the electric motor  129  directly on the housing  124 . It is thus basically also possible for the tongues to be arranged on the housing and the recesses on the electric motor  129 .  
         [0133]     In a fourth embodiment, which is shown in  FIGS. 6 and 7  and designated  150  there, a housing  152  is provided, which is substantially configured the same as the housing  12  of the circulation pump  10 .  
         [0134]     The housing  152  forms a pump space  154  and a receiving space  156  for an electric motor  157 . The electric motor  157  is basically configured the same with respect to its functional components as described above with the aid of the first embodiment  10 . The same reference numerals are therefore used for the corresponding functional components.  
         [0135]     The housing  152 , unlike the housing  12 , has no internal thread. Furthermore, one or more groove-shaped recesses  160  are arranged on a cylindrical housing wall  158 , which forms the receiving space  156 . This recess or recesses  160  are used to form a bayonet connection with a holding element  162 . The holding element  162  is formed here by a motor housing of the electric motor  157 .  
         [0136]     The electric motor  129  can be fixed and positioned axially and radially in the housing  152  by means of its holding element  162 . For this purpose, the motor housing  162  has a cylindrical wall  164 , which, when the electric motor  157  is fixed, at least in part regions, rests on an inner side of the wall  158  of the housing  152 .  
         [0137]     The wall  158  is formed on a base  166 , which is used to close the housing  152  at an end remote from the pump space  154 . In the base  166 , a free space  168  may be formed, in order, for example, to receive an electronic control circuit for the circulation pump  150 .  
         [0138]     One or more groove pins  170 , which may project into the associated recesses  160 , are seated on the base  166 , and adapted to the recess or recesses  160 .  
         [0139]     The groove-shaped recesses  160  and the groove pins  170  are arranged and configured adapted to one another in such a way that the groove pins  170 , when the holding element  162  with the electric motor  157  (on which it is fixed by means of one or more pins) is inserted into the housing  152 , can project into the recesses  160  and an axial displacement of the electric motor  157  up to its desired end position is possible. This axial displacement is brought about here by a rotation of the holding element  162 . During this rotation, the groove pins  170  are guided in their recesses  160  in such a way that a fixing of the electric motor  157  in its desired axial position is made possible.  
         [0140]     In order to be able to insert the groove pins  170 , the associated recesses  160  have an aperture region  172  ( FIG. 7 ), which leads to an end face end of the housing  152 . This aperture region  172  is substantially aligned parallel to the rotational axis  32 . Adjoining this aperture region  172  is a transverse region  174 , which is located at an angle to the rotational axis  32  to allow a rotation and thus an axial displacement of the holding element  162 .  
         [0141]     The groove pin/recess connection is configured in the manner of a bayonet connection. The electric motor  157  can thus be inserted and fixed in the housing.  
         [0142]     Otherwise the circulation pump  150  functions as described above.