Abstract:
The invention relates to a pump ( 5 ) having an electric motor ( 4 ), more particularly for a motor vehicle, for pumping a fluid, comprising an impeller ( 18 ) that has pumping elements ( 19 ) and can carry out a rotary movement about an axis of rotation ( 27 ); a working chamber around the impeller ( 18 ); an electric motor with a stator ( 13 ) and a rotor ( 16 ), the rotor ( 16 ) being provided with permanent magnets ( 17 ); and preferably a housing ( 8 ); the rotor ( 16 ) and the permanent magnets ( 17 ) being produced by sintering, and the permanent magnets ( 17 ) on the rotor ( 16 ) being integrally bonded to the rotor ( 16 ) by sintering.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a pump with electric motor, a method for producing a rotor with permanent magnets, and a method for producing a pump with electric motor. 
         [0002]    Pumps with electric motor are used for a wide variety of technical applications for the purposes of delivering a fluid. For example, fuel pumps serve for delivering fuel to an internal combustion engine. The electric motor of the pump comprises a stator and a rotor with permanent magnets. In the case of an electric motor with a permanent magnet-excited rotor, permanent magnets are installed or integrated into the rotor. 
         [0003]    The rotor and also the permanent magnets are in this case produced in a separate sintering process. For this purpose, firstly, a green product for the rotor is pressed from a sintering material by way of a molding and pressing tool, and, subsequently, said green product is sintered in a sintering furnace and subjected to reworking after the sintering process. The green products for the permanent magnets are pressed from a different sintering material by way of a molding and pressing tool, and are subsequently sintered in a sintering furnace. In this case, the sintering of the green products for the permanent magnets is performed separately from the sintering of the green product of the rotor. After the sintering of the green products of the permanent magnets, said green products are subjected to reworking. For the arrangement or integration of the sintered permanent magnets, the latter are introduced into recesses on the sintered rotor and are fastened to the rotor by way of adhesive. This disadvantageously necessitates cumbersome cohesive fastening of the sintered permanent magnets to the recesses of the rotor by way of adhesive. 
         [0004]    DE 299 13 367 U1 presents an internal-gear pump having at least one internally toothed internal gear and having an externally toothed impeller, with or without sickle, which meshes with said internal gear, and having an electric drive, which is formed by virtue of the internal gear forming the inner side of a rotor of a brushless electric motor and a stator being arranged adjacent to the rotor, wherein the rotor, which comprises the internal gear, is held rotatably at the outer side by a bearing or a plain bearing, wherein the stator is shielded and sealed off with respect to the rotor and with respect to the interior of the pump such that the bearing or plain bearing situated between the stator and rotor is impermeable to liquid and is sealingly connected, at its two face sides, to in each case one closure cover. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention provides a pump with electric motor, in particular for a motor vehicle, for delivering a fluid, comprising an impeller having delivery elements, which impeller can perform a rotary movement about an axis of rotation, a working chamber provided at the impeller, an electric motor with a stator and a rotor, wherein the rotor is equipped with permanent magnets, preferably a housing, wherein the rotor and the permanent magnets are produced by sintering, wherein the permanent magnets are connected to the rotor by way of a cohesive sintered connection to the rotor. The permanent magnets are connected to the rotor by way of a cohesive sintered connection. The cohesive sintered connection is produced in a common sintering process both of the green product for the rotor and of the green products for the permanent magnets, and it is thus advantageously possible for the cumbersome adhesive connection between the permanent magnets and the rotor to be dispensed with. The production of the pump with electric motor is thereby made much cheaper and easier. 
         [0006]    The impeller with the delivery elements and the electric motor are expediently arranged within the housing. 
         [0007]    In particular, the permanent magnets are arranged in recesses, in particular in blind holes or in through holes, of the rotor, and/or the permanent magnets are connected to the rotor by way of a positively locking connection to the rotor, in particular owing to a corresponding geometry of the recesses and/or geometry of the permanent magnets. In the case of an arrangement of the permanent magnets in the recesses of the rotor, said permanent magnets can be fastened particularly easily to the rotor. Furthermore, the arrangement in the recesses also ensures positively locking fastening of the permanent magnets in the rotor. Furthermore, the recesses have a corresponding geometry, and the permanent magnets have a correspondingly complementarily shaped geometry, such that, in this way, an additional positively locking connection exists between the permanent magnet and the rotor, in particular for example by virtue of the fact that additional grooves are arranged at the recesses, within which grooves a projection of the permanent magnets is arranged. 
         [0008]    In a further refinement, the pump is integrated into the electric motor or vice versa by virtue of the rotor being formed by the impeller, and/or the permanent magnets are connected to the rotor by way of a non-positively locking connection to the rotor. The permanent magnets and the rotor are composed of a different sintering material, such that, in this way, a different change in shape occurs during the sintering process, and thus the permanent magnets on the rotor, in particular on the recesses of the rotor, are connected to the rotor under a preload and thus in non-positively locking fashion. 
         [0009]    In a supplementary embodiment, the rotor with the permanent magnets is produced by way of a method as described in this property right application, and/or the pump is in the form of an internal-gear pump, and/or the electric motor is electronically commutated. 
         [0010]    The invention also provides a method for producing a rotor with permanent magnets for an electric motor, having the steps: molding, in particular pressing or casting, a green product for the rotor from a sintering material, in particular from a sintering powder or a sintering granulate, molding, in particular pressing or casting, green products for the permanent magnets from a sintering material, in particular from a sintering powder or a sintering granulate, sintering the green product of the rotor to form the rotor in a sintering process, sintering the green products for the permanent magnets to form the permanent magnets in a sintering process, connecting the permanent magnets to the rotor, wherein the green product for the rotor and the green products for the permanent magnets are sintered together simultaneously in a common sintering process and are thereby connected to one another, in particular by way of a cohesive sintered connection. The green product for the rotor and the green products for the permanent magnets are sintered simultaneously in a common sintering process, such that, in this way, during the sintering process, the green products of the permanent magnets are connected to the green products of the rotor, in particular by way of the cohesive sintered connection. During the sintering process, the green products of the permanent magnets and the green product of the rotor are heated, in particular to a temperature below the melting temperature, and, here, a reduction in the volume of the green products occurs as a change in shape, with a resulting compaction and surface diffusion between the particles of the sintering materials, such that, in this way, during the sintering process, the green products of the permanent magnets are connected to the green product of the rotor. 
         [0011]    It is preferably the case that the green product for the rotor is molded and pressed from a first sintering material, in particular from a first sintering powder or a first sintering granulate, and the green products for the permanent magnets are molded and pressed from a second sintering material, in particular from a second sintering powder or a second sintering granulate, and the first and second sintering materials are composed of a different material, and/or the green products of the permanent magnets are connected in non-positively locking fashion to the green product of the rotor during the sintering process, and/or the green product for the rotor and the green products for the permanent magnets are sintered in an identical sintering furnace, in particular vacuum furnace. The first and second sintering materials differ, as a different material is required for the rotor than for the permanent magnets. If the first and second sintering materials exhibit a different reduction in volume as a change in shape during the sintering process, and if the reduction in volume of the rotor is less than the reduction in volume of the permanent magnets or of the green products of the permanent magnets, a preload is generated between the green products of the permanent magnets, or the permanent magnets, and the green product of the rotor, or the rotor, such that the permanent magnets are thereby connected in non-positively locking fashion to the rotor. 
         [0012]    In one variant, the second sintering material is introduced into recesses, in particular into blind holes or through holes, of the green product of the rotor, and, subsequently, the second sintering powder within the recesses of the green product of the rotor is molded and pressed, by way of a second molding and pressing tool, to form the green products for the permanent magnets. 
         [0013]    It is expediently provided that the green product for the rotor is molded and pressed by means of a first molding and pressing tool, and the green products for the permanent magnets are molded and pressed by means of the second molding and pressing tool, and, preferably, the first and second molding and pressing tools differ. 
         [0014]    In a further embodiment, firstly, the green product for the rotor is molded, in particular pressed, and, secondly, the green products for the permanent magnets are molded, in particular pressed, and/or the green products of the permanent magnets, or the permanent magnets, are connected in positively locking fashion to the green product of the rotor, or to the rotor, owing to a corresponding geometry of the recesses of the green product of the rotor. Here, the molding and pressing tool for the molding and pressing of the green product of the rotor has a geometry which is such that, at the recesses of the rotor, auxiliary geometries are formed, for example a groove or a bore, such that, subsequently, during the introduction of the second sintering material into the recess after the pressing of the green product of the rotor, the second sintering material for the permanent magnets also fills said auxiliary geometries, and thus an additional positively locking connection between the green product of the rotor, or the rotor, and the green products of the permanent magnets, or the permanent magnets, is produced. The arrangement of the permanent magnets in the recesses also results in a positively locking connection between the permanent magnets and the rotor. 
         [0015]    In particular, the first sintering material, in particular the first sintering powder or the first sintering granulate, is supplied in automated fashion to the molding and pressing tool, in particular to the first molding and pressing tool, for the rotor, and/or the second sintering material, in particular the second sintering powder or the second sintering granulate, is supplied in automated fashion to the molding and pressing tool, in particular to the second molding and pressing tool, for the permanent magnets. 
         [0016]    In a further refinement, the permanent magnets are magnetized after the sintering process, in particular within the recesses of the rotor. After the sintering process, and preferably further method steps, the permanent magnets are magnetized. This is possible because the permanent magnets are formed from a corresponding material. 
         [0017]    In a supplementary variant, the rotor with the permanent magnets is, after the common sintering process, processed by way of at least one further method, in particular sandblasting and/or grinding and/or polishing and/or deburring and/or cleaning and/or clamping and/or packaging. 
         [0018]    The invention also provides a method for producing a pump with electric motor, in particular a pump with electric motor as described in this property right application, for delivering a fluid, having the steps: providing an impeller, which has delivery elements, for the pump, providing a housing, providing an electric motor, which has a stator and a rotor, for driving the pump, wherein the rotor is equipped with permanent magnets, and the rotor and the permanent magnets are produced by sintering, arranging and assembling the impeller with delivery elements and the electric motor with the housing, in particular within the housing, to form the pump with electric motor, wherein the rotor with the permanent magnets is produced by way of a method as described in this property right application. 
         [0019]    In a further variant, the impeller and the rotor are produced such that the impeller with the delivery elements also forms the rotor, and/or an electronically commutated electric motor is provided. 
         [0020]    In a further refinement, the pump is provided as an internal-gear pump with an inner gearwheel and an outer gearwheel, and, in particular, the outer gearwheel is produced such that the outer gearwheel forms the impeller with teeth as delivery elements and the rotor with the permanent magnets. 
         [0021]    In a further embodiment, the rotor, and/or the first sintering material for the rotor, are/is composed at least partially, in particular entirely, of steel, in particular sintering steel, or of magnetically soft iron. 
         [0022]    In a supplementary refinement, the permanent magnets, and/or the second sintering material for the permanent magnets, are/is composed at least partially, in particular entirely, of a mixture of neodymium (Nd), iron (Fe) and boron (B) or of a mixture of samarium (Sm), cobalt (Co) and iron (Fe). 
         [0023]    In a further refinement, the delivery elements are blades or teeth of a gearwheel. 
         [0024]    In a supplementary variant, the pump is a gearwheel pump, in particular an internal-gear pump. 
         [0025]    In a further refinement, the impeller forms the rotor, and/or the permanent magnets are arranged or integrated on or in the impeller, that is to say, preferably, the pump is integrated into the electric motor or vice versa. 
         [0026]    In a further embodiment, the pump is integrated into the electric motor or vice versa; preferably, the pump and the electric motor constitute non-separable structural units. 
         [0027]    In a further variant, the pump with electric motor comprises an inlet opening and an outlet opening for the fluid, which openings issue into the working chamber. 
         [0028]    In a further refinement, the pump is an external-gear pump or a centrifugal pump or a vane-type pump. 
         [0029]    The pump with preferably integrated electric motor expediently comprises a preferably electronic control unit for controlling the energization of the electric magnets. 
         [0030]    The housing of the predelivery pump and/or the housing of the high-pressure pump and/or the inner gearwheel and/or outer gearwheel are/is expediently composed at least partially, in particular entirely, of metal, for example steel or aluminum. 
         [0031]    In particular, the delivery rate of the electric predelivery pump is controllable and/or regulable. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    Below, exemplary embodiments of the invention will be described in more detail with reference to the appended drawings, in which: 
           [0033]      FIG. 1  shows a highly schematized view of a high-pressure injection system, 
           [0034]      FIG. 2  shows a perspective view of a predelivery pump without housing and of a stator, 
           [0035]      FIG. 3  is an exploded illustration of the predelivery pump as per  FIG. 2 , 
           [0036]      FIG. 4  shows a plan view of a green product of the rotor before a sintering process, in a first exemplary embodiment, 
           [0037]      FIG. 5  shows a plan view of the green product of the rotor with the green products of the permanent magnets before the sintering process, in a second exemplary embodiment, 
           [0038]      FIG. 6  shows a section A-A, as per  FIG. 4 , of the green product of the rotor, 
           [0039]      FIG. 7  shows a section B-B, as per  FIG. 5 , of the green product of the rotor with a green product of a permanent magnet, and 
           [0040]      FIG. 8  shows a flow diagram of a method for producing a rotor with permanent magnets. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]      FIG. 1  illustrates a pump arrangement  1  of a high-pressure injection system  2 . An electric predelivery pump  3  delivers fuel out of a fuel tank  41  through a fuel line  35 . Subsequently, the fuel is delivered by the electric predelivery pump  3  to a high-pressure pump  7 . The high-pressure pump  7  is driven by an internal combustion engine  39  by means of a drive shaft  44 . 
         [0042]    The electric predelivery pump  3  has an electric motor  4  and a pump  5  ( FIGS. 2 and 3 ). Here, the electric motor  4  of the pump  5  is integrated into the pump  5 , and, furthermore, the electric predelivery pump  3  is arranged directly on the high-pressure pump  7 . The high-pressure pump  7  delivers fuel at high pressure, for example a pressure of 1000, 3000 or 4000 bar, through a high-pressure fuel line  36  to a high-pressure rail  42 . From the high-pressure rail  42 , the fuel is supplied at high pressure to a combustion chamber (not illustrated) of the internal combustion engine  39  by an injector  43 . The fuel not required for the combustion is returned to the fuel tank  41  again via a fuel return line  37 . The porting openings  28  ( FIG. 2 ) of the electric predelivery pump  3  are connected, without an external connection, to the high-pressure pump  7 . Here, the mounting position of the electric predelivery pump  3  on the high-pressure pump  7  is selected such that the fuel can be conducted from the pressure side of the predelivery pump  3  to the suction side of the high-pressure pump  7  through short hydraulic connections. A fuel filter  38  is installed in the fuel line  35  from the fuel tank  41  to the electric predelivery pump  3 . In this way, it is advantageously possible for the fuel line  35  from the fuel tank  41  to the electric predelivery pump  3  to be of inexpensive design, as it does not need to withstand positive pressure. The electric motor  4  ( FIGS. 2 and 3 ) of the electric predelivery pump  3  is operated with three-phase current or alternating current and is controllable and/or regulable in terms of power. The three-phase current or alternating current for the electric motor  4  is provided by power electronics (not illustrated) from a direct-current voltage network of an on-board electrical system of a motor vehicle. The electric predelivery pump  3  is thus an electronically commutated predelivery pump  3 . 
         [0043]    The electric predelivery pump  3  has a housing  8  with a housing pot  10  and a housing cover  9  ( FIG. 3 ). The pump  5 , in the form of an internal-gear pump  6  or gearwheel pump  26 , and the electric motor  4  are arranged within the housing  8  of the predelivery pump  3 . The housing pot  10  is equipped with a recess  56 . The electric motor  4  has a stator  13  with windings  14  as electromagnets  15 , and has a soft iron core  45  as a magnetically soft core  32 , which is in the form of a laminated core  33 . Positioned within the stator  13  is the pump  5 , which is in the form of an internal-gear pump  6  with an inner gearwheel  22  with an inner toothed ring  23  and an outer gearwheel  24  with an outer toothed ring  25 . The inner and outer gearwheels  22 ,  24  thus constitute a gearwheel  20  and an impeller  18 , and the inner and outer toothed rings  23 ,  25  have teeth  21  as delivery elements  19 . A working chamber  47  is formed between the inner and outer gearwheels  22 ,  24 . Into the outer gearwheel  24  there are installed permanent magnets  17 , such that the outer gearwheel  24  also forms a rotor  16  of the electric motor  4 . The electric motor  4  is thus integrated into the pump  5 , or vice versa. The electromagnets  15  of the stator  13  are energized in alternating fashion, such that, owing to the magnetic field generated at the electromagnets  15 , the rotor  16  or the outer gearwheel  24  is set in rotational motion about an axis of rotation  27 . On the stator  13  there are arranged electrical contact elements  34  which serve for the energization of the electromagnets  15 . The contact elements  34  are, after the assembly process, arranged in the recess  56  of the housing pot  10 . 
         [0044]    The housing cover  9  serves as a bearing  11  or axial bearing  11  or plain bearing  11  for the inner and outer gearwheels  22 ,  24 . Furthermore, in the housing cover  9 , there are formed a suction porting opening  29  and a pressure porting opening  30 , which are each in the form of porting openings  28 . The fluid to be delivered, specifically fuel, flows through the suction porting opening  29  into the predelivery pump  3 , and the fuel flows out of the predelivery pump  3  again from the pressure porting opening  30 . Furthermore, the housing pot  10  and the housing cover  9  each have three bores  46  in which there are positioned screws (not illustrated) for screwing the housing pot  10  and the housing cover  9  together. 
         [0045]    A green product  51  for the rotor  16  and the green products  52  for the permanent magnets  17  are produced by sintering.  FIGS. 4 and 6  illustrate a first exemplary embodiment of the green product  51  for the rotor  16 . The green product  51  for the rotor  16  is pressed or molded from a first sintering material, for example a sintering powder, by way of a first molding and pressing tool  58 . Here, the green product  51  has six recesses  48  in the form of blind holes  49 . After the pressing of the green product  51  for the rotor  16 , a second sintering material, for example a sintering powder, is introduced into the six recesses  48  in the form of blind holes  49 , and the second sintering material in the six blind holes  49  is pressed by way of a second molding and pressing tool  59 . During the pressing process, additional compaction of the second sintering material is performed. Here, the first molding and pressing tool  58  has a corresponding geometry, such that the green product  51  of the rotor  16  is formed with the six recesses  48  as blind holes  49  and with the outer toothed ring  25  with teeth  21 . As permanent magnets  17 , use may be made either of sintered permanent magnets  17  without magnetic characteristics or of magnetic permanent magnets  17  after the magnetization by way of a magnetic field. 
         [0046]      FIGS. 5 and 7  illustrate a second exemplary embodiment of the green product  51  for the rotor  16 . Substantially only the differences in relation to the first exemplary embodiment as per  FIGS. 4 and 6  will be described below. The recesses  48  are formed not as blind holes  49  but as through holes  50 . In  FIGS. 5 and 7 , the second sintering material has already been introduced into the through holes  50 , and the second sintering material in the through holes  50  has subsequently been compacted and compressed by means of the second molding and pressing tool  59 . 
         [0047]      FIG. 8  illustrates a flow diagram for the production of the rotor  16 . Firstly, the first sintering material is supplied  53  to the first molding and pressing tool  58 . Here, the first sintering material is composed for example of sintering steel. After the pressing of the first sintering material in the first molding and pressing tool  58  to form the green product  51  of the rotor  16  with the recesses  48 , the second sintering material, composed of neodymium (Nd), iron (Fe) and boron (B) is supplied  54 . Here, the second sintering material is introduced into the recesses  48  of the green product  51  of the rotor  16 , and, subsequently, the green products  52  of the permanent magnets  17  within the recesses  48  are pressed  57  by way of the second molding and pressing tool  59 . Subsequently, the green product  51  of the rotor  16  is, together with the already-pressed green products  52  of the permanent magnets  17  within the recesses  48 , placed into a vacuum furnace  61  as a sintering furnace, and, subsequently, sintering  60  or a sintering process  60  is performed here, such that the green product  51  of the rotor  16  and the green product  52  of the permanent magnets  17  are sintered and heated jointly and simultaneously in the vacuum furnace  61 . After the removal of the sintered rotor  16  with the sintered permanent magnets  17  and the cooling process, transportation  64  and subsequent reworking by sandblasting  62  are thereupon performed. After further transportation  64 , placement  65  into a clamping cavity is performed. Furthermore, a material inspection  31  is performed between the sandblasting  62  and packaging  63  processes. After the placement  65  into the clamping cavity (not illustrated), clamping  66  is performed, followed by reworking by grinding  67  of the two flat surfaces of the rotor  16 . This is followed by polishing  68  and placement  70  into a deburring apparatus (not illustrated). Between the polishing  68  and the placement  70  into the deburring apparatus, a sampling inspection  69  of the external dimensions of the rotor  16  is additionally performed. This is followed by a deburring process  71  and a cleaning process  72 . Further transportation  64  is performed between the deburring process  71  and the cleaning process  72 . After the cleaning process  72 , magnetization  74  of the permanent magnets  17  or of the sintered permanent magnets  17  is performed, which after the sintering process do not yet have magnetic characteristics or a magnetic field. Between the cleaning process  72  and the magnetization  74 , a visual inspection  73  is performed. After the magnetization of the sintered permanent magnets  17  to form the permanent magnets  17 , an inspection  75  of the magnetic field of the magnetic permanent magnets  17  is performed. At the end of the production process, the rotors  16  with the permanent magnets  17  are supplied to the method step of packaging  63 . 
         [0048]    Viewed overall, the method according to the invention for producing the rotor  16  with the permanent magnets  17  is associated with major advantages. The green product  51  of the rotor  16  without the permanent magnets  17 , or without the green products  52  of the permanent magnets  17 , is pressed separately from the green products  52  for the permanent magnets  17 , and, subsequently, the green product  51  for the rotor  16  and the green products  52  for the permanent magnets  17  are sintered jointly and simultaneously in the vacuum furnace  61 , such that, in this way, the green products  52  for the permanent magnets  17  are cohesively connected, by way of a sintered connection, to the green product  51  for the rotor  16 . In this way, it is advantageously the case that only one sintering process is required to produce the rotor  16  with the permanent magnets  17 , and an additional and cumbersome adhesive connection between the sintered permanent magnets  17  and the sintered rotor  16  using an adhesive is no longer required. In this way, it is advantageously possible for the costs for the production of the rotor  16  with the permanent magnets  17  to be considerably reduced, and a particularly reliable and permanent cohesive sintered connection between the permanent magnets  17  and the rotor  16  can be produced.