Abstract:
An electric centrifugal pump having a motor housing, a pump head, a containment shell, and a rotor assembly consisting of a pump impeller and a permanent magnet rotor, wherein the pump head with the containment shell defines a wet chamber, in which the rotor assembly is arranged rotationally around a longitudinal motor axis, the containment shell with the motor housing defines a dry chamber, in which a wound stator is arranged, and the permanent magnet rotor is arranged within the stator and a hollow-cylindrical region of the containment shell. Particle accumulations in the region between the containment shell and the permanent magnet rotor cannot occur or can only occur to a very minor extent and that the consequences of impurities in the wet chamber are reduced in order to prevent premature wear or a blockage of the centrifugal pump.

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
       [0001]    The invention relates to electric centrifugal pumps having a structure to remove contaminations in cooling circuits. 
       (2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
       [0002]    In combustion engines in the field of motor vehicles, mechanical pumps driven by a crankshaft via a gear belt are generally provided as a main cooling water pump. As a support or an alternative in a turned-off combustion engine, electric centrifugal pumps are used as ancillary cooling water pumps, which generally make use an electronically commutated direct-current motor. Main cooling water pumps can also be run electrically. Cooling water pumps are likewise used in hybrid and electric vehicles, primarily in the cooling circuit of an accumulator cooling system. 
         [0003]    Sand grains and other dirt particles are also conveyed in cooling circuits. Particles of quartz sand (SiO 2 ) or metal chips can occur in dimensions of up to 1.6 mm. The impurities can occur during assembly of an engine block for a vehicle, e.g. by residues of molding sand in the production of aluminum die-cast components. The gap between the outer contour of the rotor and the stator or the containment shell is generally significantly below 1 mm. A smaller gap is required for sufficient engine efficiency. Contaminations with particles larger than the gap between the rotor and the stator or the containment shell can result in premature wear or jamming up resulting in blockage of the centrifugal pump. Smaller particles can also accumulate in the region of the rotor mount and significantly reduce its service life. 
         [0004]    In order to exclude this condition, the task of the present invention is to provide an electric centrifugal pump in such a way that particle accumulations in the region between the containment shell and the permanent magnet rotor cannot occur or can only occur to a very minor extent and that the consequences of impurities in the wet chamber are reduced in order to prevent premature wear or a blockage of the centrifugal pump. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The invention relates to an electric centrifugal pump with a motor housing, a pump head, a containment shell, and a rotor assembly consisting of a pump impeller and a permanent magnet rotor, whereby the pump head with the containment shell defines a wet chamber, in which the rotor assembly is arranged rotational around a longitudinal motor axis, the containment shell with the motor housing defines a dry chamber, in which a wound stator is arranged, and the permanent magnet rotor is arranged within the stator and a hollow-cylindrical region of the containment shell. 
         [0006]    In order to reliably remove small particles which have entered the gap between the rotor and the containment shell, containment shell grooves parallel to the axis and/or parallel to pole gaps are provided, which extend radially into pole gaps of the stator. The depth of the containment shell groove is dimensioned in such a way that the largest particles to be expected can be accommodated therein. When contaminations, such as metal chips or grains of quartz, arrive in the gap region between the rotor and the containment shell, the motor is not immediately blocked but is decelerated as a result of the mass inertia of the rotor. As a result of the rotational momentum, the contaminations search for an escape path and thereby enter into the free space provided by the containment shell grooves. As a result of the frictional forces caused by the rotational movement of the rotor, it is ensured that the foreign body remains in the recess, adheres to other impurity particles or is worn down with time to even smaller particles by the rotational movement of the rotor. 
         [0007]    In order to avoid a wedge effect, it is preferable to design the containment shell grooves asymmetrically. In this way, particles can be securely held in the direction of rotation of the permanent magnet rotor if the containment shell grooves are correspondingly designed. Particularly suitable for solving the task are containment shell groove cross sections with undercuts, wherein the width of the containment shell grooves increases with increasing groove depth at least in sections. 
         [0008]    An easier transporting away of the dirt particles initially trapped in the containment shell grooves in the direction of rotation of the permanent magnet rotor can be achieved by groove cross sections that change over the groove length of the containment shell grooves. In this respect, it is provided that the cross-sectional area of the groove is smallest in the groove center (in the axial direction) and largest at its ends. 
         [0009]    An annular protrusion largely prevents larger particles from arriving at the region between the permanent magnet rotor and the containment shell. Smaller articles can be flushed out of this region again without causing damage. The containment shell grooves can be in the shape of a semicircular disk (semicircular) or have a rectangular, triangular, or trapezoidal cross section. 
         [0010]    Since the containment shell grooves only have sufficient space in pole gaps, they must be shaped correspondingly to the shape of the pole gaps, in particular with respect to an angle of inclination or a pitch angle. 
         [0011]    When applied to claw pole stators with pitch of the poles engaging with one another, only every second pole gap can accommodate a containment shell groove for manufacturing reasons. Since the pitch angles of adjacent pole gaps are not parallel, the containment shell could otherwise not be taken out of an injection molding tool. Alternatively, a very complex injection molding tool would have to be used. 
         [0012]    The depth of the containment shell grooves should be between 0.3 and 1 mm. In this design, most of the particles could be made harmless when using the centrifugal pump as a cooling water pump in the vehicle. It is preferred to design the edges of the containment shell grooves to be sharp-edged. In this way, wedge effects are avoided. 
         [0013]    In order to limit the size of particles that arrive in the gap between the permanent magnet rotor and the containment shell in the first place, it is provided that an annular protrusion extends coaxially to the longitudinal motor axis from the pump impeller into a chamber region within the containment shell and the outer diameter of the annular protrusion is smaller than the inner diameter of the containment shell in the region of the protrusion. 
         [0014]    In addition to the annular protrusion, a protruding ring collar can extend from the containment shell toward the pump impeller and the outer diameter of the annular protrusion can under all tolerance conditions be slightly smaller than the inner diameter of the protruding ring collar, and the annular protrusion and the protruding annular collar can be arranged concentrically to one another and to the longitudinal motor axis. By means of the protruding ring collar, a defined sealing gap geometry can be achieved, in which the gap distance is consistently small under all tolerance conditions. 
         [0015]    Advantageously, the outer diameter of the annular protrusion is selected to be larger than or equal to the outer diameter of the permanent magnet rotor. With a smaller diameter, the radial gap between the annular protrusion and the protruding ring collar would become too large for a sealing effect, because the inner diameter of the protruding ring collar cannot be smaller than the outer diameter of the rotor. In order to not impair hydraulic efficiency, the protruding ring collar of the containment shell is to indeed have a very minor distance from the pump impeller but not touch it. 
         [0016]    The permanent magnet rotor is also provided on its outer shell surface with several rotor grooves. The permanent magnet rotor is thereby able to move a portion of the conveyed medium in an annular direction within the gap between the permanent magnet rotor and the containment shell. In order to also bring about an axial component of this forced flow movement of the conveyed medium, a pitch angle of the rotor grooves relative to straight lines parallel to the axis is provided. In this case, the rotor grooves still extend on the outer surface of the permanent magnet rotor. 
         [0017]    An optimal distance of the annular protrusion from the protruding ring collar can be achieved by the outer diameter of the annular protrusion being smaller than the inner diameter of the containment shell in the region of the permanent magnet rotor. This results in a minimum friction radius, which has an advantageous effect on the hydraulic efficiency. 
         [0018]    The hydraulic resistance is further reduced by a containment shell flange comprising a recess radially outside the protruding ring collar, which recess enlarges the distance to an impeller disk of the pump impeller. A larger distance to the containment shell flange is thereby ensured precisely in the region of larger diameters of the pump impeller in order to reduce the drag torque. For the same reason, the protruding ring collar is designed such that it tapers in the axial direction toward the pump impeller. As a result, the annular surfaces, which are located opposite each other and which bring about the sealing effect with respect to coarse particles, are as small as possible. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0019]    The invention is better understood by reading the following Detailed Description of the Preferred Embodiments with reference to the accompanying drawing figures, in which like reference numerals refer to like elements throughout, and in which: 
           [0020]      FIG. 1  illustrates a section of a stator with a containment shell with a containment shell groove, 
           [0021]      FIG. 2  is a spatial representation of a claw pole stator, 
           [0022]      FIG. 3  illustrates a section of a containment shell with a first variant of the containment shell groove, 
           [0023]      FIG. 4  illustrates a section of a containment shell with a second variant of the containment shell groove, 
           [0024]      FIG. 5  illustrates a section of a containment shell with a third variant of the containment shell groove, 
           [0025]      FIG. 6  illustrates a containment shell with pitched containment shell grooves, 
           [0026]      FIG. 7  illustrates a containment shell with a direction of pitch opposite  FIG. 6 . 
           [0027]      FIG. 8  is a sectional view through a centrifugal pump according to the invention, 
           [0028]      FIG. 9  illustrates an enlarged section A of  FIG. 8 , 
           [0029]      FIG. 10  is a spatial representation of a rotor assembly, 
           [0030]      FIG. 11  is a front view of the rotor assembly, 
           [0031]      FIG. 12  illustrates an enlarged section A of  FIG. 11 , 
           [0032]      FIG. 13  is a top view of the rotor assembly, 
           [0033]      FIG. 14  is a sectional view of the rotor assembly of  FIG. 13 , 
           [0034]      FIG. 15  is a schematic representation of a containment shell, and 
           [0035]      FIG. 16  is a sectional view of the containment shell. 
       
    
    
       [0036]    Note: The reference symbols with apostrophe/index and the corresponding reference symbols without apostrophe/index refer to details with the same name in the drawings and the drawing description. This reflects use in another embodiment or the prior art, and/or the detail is a variant. For the sake of simplicity, the claims, the description introduction, the reference symbol list and the abstract contain only reference symbols without apostrophe/index. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0037]    In describing preferred embodiments of the present invention illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. 
         [0038]      FIG. 1  shows a section of a stator  4 ′ with pronounced poles, into which a containment shell  3 ′ is inserted. The containment shell  3 ′ comprises a containment shell groove  35 ′ and a cooling rib  38 ′, which is accommodated in a pole gap  51 ′. The cooling rib  38 ′ enlarges the surface of the containment shell  3 ′ and therefore improves the heat transfer from the stator winding (not shown) to the conveyed medium within the containment shell  3 ′. The containment shell groove  35 ′ extends in the region of the pole gap  51 ′ and has in this case a cross section in the shape of a semicircular disk. 
         [0039]      FIG. 2  shows a spatial representation of a claw pole stator  52  with claw poles  53 , containment shell grooves  35 , and a winding intake space  54 . The containment shell  3  has in this case been produced by injection molding around the claw poles  53 , as a result of which the claw poles  53  partially form the containment shell  3 . In every second pole gap  51 , a containment shell groove  35  is formed. The illustrated containment shell grooves  35  are pitched parallelly to one another. The removal from the injection molding tool takes place by unscrewing. The cross section of the containment shell grooves  35  comprises a minimal surface at a first end of the axial extent and a maximal surface at its other end. 
         [0040]      FIG. 3  shows a section of a containment shell  3 ″ with a first variant of the containment shell groove  35 ″ and the cooling rib  38 ″, where the cross section of the containment shell groove  35 ″ is substantially rectangular. 
         [0041]      FIG. 4  shows a section of a containment shell  3 ′″ with a second variant of the containment shell groove  35 ′″ and the cooling rib  38 ′″, where the cross section of the containment shell groove  35 ′″ is substantially triangular. The cross section of the containment shell groove  35 ′″ is thus asymmetrical and largely holds particles in the preferential direction of rotation. 
         [0042]      FIG. 5  shows a section of a containment shell  3 ″ with a third variant of the containment shell groove  35 ′″ and the cooling rib  38 ″, where the cross section of the containment shell groove  35 ′″ is substantially trapezoidal with an undercut. In this case, particles are largely held independently of the direction of rotation. 
         [0043]      FIG. 6  shows a containment shell  3   a  with pitched containment shell grooves  35   a , a containment shell flange  22   a , screw holes  27   a , and a mount  34   a  for an axis component. The containment shell grooves  35   a  have a cross section, the cross-sectional area of which changes in the direction of extent. At a first end of the containment shell groove  35   a , the cross-sectional area is smallest and at the other end of the containment shell groove  35   a , it is at largest. 
         [0044]      FIG. 7  shows a containment shell  3   b  with pitched containment shell grooves  35   b , a containment shell flange  22   b , screw holes  27   b , and a mound  34   b . The containment shell grooves  35   a  have a cross section, the cross-sectional area of which changes in the direction of extent. At a first end of the containment shell groove  35   a , the cross-sectional area is at smallest and at the other end of the containment shell groove, it is at largest. The direction of pitch is opposite the direction of pitch of  FIG. 6 . The containment shell according to  FIG. 6  or according to  FIG. 7  can be used for both claw pole stators and stators with pronounced poles. 
         [0045]      FIG. 8  shows a sectional view through an electric centrifugal pump  1 ′ according to the invention, having a motor housing  10 ′, a pump head  11 ′, a containment shell  3 ′, a stator  4 ′, and a rotor assembly  2 ′. The rotor assembly  2 ′ consists of a permanent magnet rotor  20 ′ and a pump impeller  16 ′. The pump head  11 ′ and the containment shell  3 ′ constitute the delimitation of a wet chamber  26 ′. The containment shell  3 ′ and the motor housing  10 ′ constitute the delimitation of a dry chamber  25 ′. The permanent magnet rotor  20 ′ comprises a permanent magnet  15 ′, a hollow shaft  12 ′, and a fixed bearing  42 ′. The pump impeller  16 ′ comprises a portion of the hollow shaft  12 ′, an impeller disk  41 ′, pump vanes  40 ′, an annular protrusion  7 ′, a spherical bearing  43 ′, and a cover plate  19 ′ (see  FIG. 9 ). 
         [0046]    The rotor assembly  2 ′ is mounted rotationally around a longitudinal motor axis  21 ′ and an axis component  39 ′, which are mounted in an axis mount sleeve  13 ′ as a component of the containment shell  3 ′ and in a mount  34 ′ as a component of the pump head  11 ′. The spherical bearing  43 ′ can be supported on a spherical counter bearing  44 ′, which is fixed in the mount  34 ′. The mount  34 ′ is integral with the pump head  11 ′ via spokes  33 ; said pump head comprising a suction nozzle  31 ′, a discharge nozzle  32 ′, and a pump head flange  23 ′. The containment shell  3 ′ comprises a containment shell bottom  17 ′, containment shell grooves  35 ′, a containment shell casing  45 ′, a containment shell flange  22 ′, and a protruding ring collar  8 ′ in the transition region between the containment shell casing  45 ′ and the containment shell flange  22 ′. The motor housing  10 ′ comprises a housing bottom  46 ′, a connector shaft  29 ′, a housing cover  47 ′, and a housing flange  24 ′. The containment shell flange  22 ′ is respectively connected to the pump head flange  23 ′ and the housing flange  24 ′ via an O-ring  30 ′. For mounting, the pump head  11 ′, the containment shell  3 ′, and the motor housing  10 ′ are provided with screw holes  27 ′ and connected to one another via screws  28 ′. The stator  4 ′, a circuit board  37 ′, and a supporting plate  14 ′ are arranged in the dry chamber  25 ′. The stator consists of a stator lamination  9 ′, a first insulating element  5 ′, and a second insulating element  6 ′, and a winding (not shown here). 
         [0047]      FIG. 9  shows an enlarged section A of  FIG. 8  with the pump head  11 ′, the containment shell  3 ′, and the pump impeller  16 ′. The pump impeller  16 ′ consists of the impeller disk  41 ′, the pump vanes  40 ′, the cover plate  19 ′, and the annular protrusion  7 ′. The containment shell  3 ′ comprises a containment shell flange  22 ′, a protruding annular collar  8 ′, and a recess  18 ′, which is adjacent to the annular collar  8 ′ and forms a recess for the impeller disk  41 ′. 
         [0048]      FIG. 10  shows a spatial representation of the rotor assembly  2 ′ consisting of the permanent magnet rotor  20 ′ and the pump impeller  16 ′, with a hollow shaft  12 ′, the permanent magnet  15 ′, the impeller disk  41 ′, the annular protrusion  7 ′, the cover plate  19 ′, and with rotor grooves  36 ′. The rotor grooves  36 ′ extend in a first approximation parallel to the axis along an outer surface  48 ′ of the permanent magnet rotor  20 ′ but deviate in relation to straight lines parallel to the axis by a small angle. The fixed bearing  42 ′ can be seen inside the permanent magnet  15 ′. 
         [0049]      FIG. 11  shows a front view of the rotor assembly  2 ′ with the permanent magnet  15 ′, the hollow shaft  12 ′, the pump impeller  16 ′, and the impeller disk  41 ′. The rotor grooves  36 ′ in the permanent magnet  15 ′ can be seen at its periphery. In this case, the rotor assembly  2 ′ is shown without fixed bearing. 
         [0050]      FIG. 12  shows an enlarged section B of  FIG. 11  with the permanent magnet  15 ′, a rotor groove  36 ′, and the impeller disk  41 ′. The rotor groove  36 ′ is designed in the shape of a circular segment. 
         [0051]      FIG. 13  shows a top view of the rotor assembly  2 ′ with the permanent magnet rotor  20 ′ and the pump impeller  16 ′, which are connected to one another via the hollow shaft  12 ′. The permanent magnet  15 ′, the rotor grooves  36 ′, the impeller disk  41 ′, the annular protrusion  7 ′, and the cover plate  19 ′ can also be seen. 
         [0052]      FIG. 14  shows a sectional view of the rotor assembly  2 ′ of  FIG. 13 , with the permanent magnet rotor  20 ′, the pump impeller  16 ′, the permanent magnet  15 ′, the hollow shaft  12 ′, the impeller disk  41 ′, the annular protrusion  7 ′, the pump vanes  40 ′, and the cover plate  19 ′. The impeller disk  41 ′, the cover plate  19 ′, and the pump vanes  40 ′ enclose conveyor channels  49 ′, through which the liquid to be conveyed is transported. In the hollow shaft  12 ′, a recessed connecting contour  50 ′ is provided, which allows for a positive connection to the permanent magnet  15 ′. 
         [0053]      FIG. 15  shows a spatial representation of the containment shell  3 ′, with the containment shell casing  45 ′, the containment shell flange  22 ′, the mounting holes  27 ′, the protruding ring collar  8 ′, and the recess  18 ′. Containment shell grooves  35 ′ are present on the inner circumference of the containment shell casing  45 ′ and cooling ribs  38 ′ are present on the outer circumference of the containment shell casing  45 ′. 
         [0054]      FIG. 16  shows a sectional view of the containment shell  3 ′, with the containment shell casing  45 ′, the containment shell flange  22 ′, the mounting eyes  27 ′, the protruding ring collar  8 ′, the recess  18 ′, the containment shell grooves  35 ′, the cooling ribs  38 ′, the containment shell bottom  17 ′, and the axis mount sleeve  13 ′. As can be seen in this case, the containment shell grooves  35 ′ are aligned parallel to the longitudinal motor axis  21 ′. 
         [0055]    It is to be understood that the present invention is not limited to the illustrated embodiments described herein. Various types and styles of user interfaces may be used in accordance with the present invention without limitation. Modifications and variations of the above-described embodiments of the present invention are possible, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described. 
         [0000]    
       
         
               
             
               
               
             
           
               
                   
               
               
                 LIST OF REFERENCE SYMBOLS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 Centrifugal pump 
               
               
                 2 
                 Rotor assembly 
               
               
                 3 
                 Containment shell 
               
               
                 4 
                 Stator 
               
               
                 5 
                 First insulating element 
               
               
                 6 
                 Second insulating element 
               
               
                 7 
                 Annular protrusion 
               
               
                 8 
                 Protruding ring collar 
               
               
                 9 
                 Stator sheet package 
               
               
                 10 
                 Motor housing 
               
               
                 11 
                 Pump head 
               
               
                 12 
                 Hollow shaft 
               
               
                 13 
                 Axis mounting sleeve 
               
               
                 14 
                 Support plate 
               
               
                 15 
                 Permanent magnet 
               
               
                 16 
                 Pump impeller 
               
               
                 17 
                 Containment shell bottom 
               
               
                 18 
                 Recess 
               
               
                 19 
                 Cover plate 
               
               
                 20 
                 Permanent magnet rotor 
               
               
                 21 
                 Longitudinal motor axis 
               
               
                 22 
                 Containment shell flange 
               
               
                 23 
                 Pump head flange 
               
               
                 24 
                 Housing flange 
               
               
                 25 
                 Dry chamber 
               
               
                 26 
                 Wet chamber 
               
               
                 27 
                 Screw hole 
               
               
                 28 
                 Screw 
               
               
                 29 
                 Connector shaft 
               
               
                 30 
                 O-ring 
               
               
                 31 
                 Suction nozzle 
               
               
                 32 
                 Discharge nozzle 
               
               
                 33 
                 Spoke 
               
               
                 34 
                 Mount 
               
               
                 35 
                 Containment shell groove 
               
               
                 36 
                 Rotor groove 
               
               
                 37 
                 Circuit board 
               
               
                 38 
                 Cooling rib 
               
               
                 39 
                 Axis component 
               
               
                 40 
                 Pump vane 
               
               
                 41 
                 Impeller disk 
               
               
                 42 
                 Fixed bearing 
               
               
                 43 
                 Spherical bearing 
               
               
                 44 
                 Spherical counter bearing 
               
               
                 45 
                 Containment shell casing 
               
               
                 46 
                 Housing bottom 
               
               
                 47 
                 Housing cover 
               
               
                 48 
                 Outer surface 
               
               
                 49 
                 Conveyor channel 
               
               
                 50 
                 Connecting contour 
               
               
                 51 
                 Pole gap 
               
               
                 52 
                 Claw pole stator 
               
               
                 53 
                 Claw pole 
               
               
                 54 
                 Winding mounting space