Abstract:
A centrifugal pump impeller in an electromotive centrifugal pump, the impeller including a base body having a bearing to which is attached, on a first end, a permanent-magnetic rotor and, on a second end, a cover disk that is mounted on the base body; and a plurality of pump blades made of first and second parts, the first part being a base blade segment attached to the base body thus forming a first unitary piece and a cover disk blade segment attached to the cover disk thus forming a second unitary piece.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present patent application claims priority from German Application No. 102014201487.5, filed Jan. 28, 2014, which is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    (1) Field of the Invention 
         [0003]    The invention relates to a centrifugal pump impeller having pump blades made of a plastic material processed by injection molding technology for an electromotive centrifugal pump consisting of a base body having a bearing to which is attached, at one end, a permanent-magnetic rotor and, at the other end, a cover disk that is mounted on the base body. 
         [0004]    (2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
         [0005]    Centrifugal pumps are frequently used as auxiliary water pumps in motor vehicles and mostly assist belt-driven main cooling water pumps. Thanks to their superb controllability, centrifugal pumps are generally also integrated into brushless DC motors. These motors possess a wound stator and a permanent-magnetic rotor that form a compact assembly with a centrifugal pump impeller. The rotors can be configured both as internal rotors and as external rotors. The centrifugal pump impeller is located in a wet chamber, which is sealed off by a partition wall from a dry chamber that includes the stator. Centrifugal pump impellers generally consist of a permanent-magnetic area and a hydraulic area. The hydraulic area comprises a disk and pump blades attached to it that project the pumping medium radially outward, thereby generating a pump pressure. Open centrifugal pump impellers and closed ones that have a cover disk are known. Centrifugal pump impellers with cover disks are more efficient but are more difficult to manufacture. In the case of centrifugal pump impellers manufactured using injection molding technology, especially problematic is the demolding process of the relatively complicated mold. That is why the cover disks are often manufactured separately and then installed. 
         [0006]    A generic centrifugal pump impeller with a cover disk is known from WO 2011/131251 A1. It consists of plastic material processed by injection molding technology, the base body forming one piece with the permanent-magnetic rotor and consisting throughout of a plastic-bonded magnet material. The impellers form one piece with the cover disk and consist of a plastic material without permanent-magnetic components. The separation into two parts enables the mechanical and permanent-magnetic properties of the function to be correspondingly optimized. However, since the base body also contains permanent-magnetic material, the cost of materials is higher. This is especially true when higher-quality permanent-magnetic materials are used. In the known centrifugal pump impeller, the pump blades always have a width that corresponds to the distance from the base body up to the cover disk, so that there is no gap between them. However, studies have shown that from a flow technology point of view, it is more desirable if the pump blades have a lead-in chamfer on the inside. However, in the case of the known pumps, for manufacturing technology reasons this cannot be realized or can be realized only at great expense. 
         [0007]    Therefore, the problem solved by the present invention is to ensure that a centrifugal pump rotor of the kind mentioned at the outset has a simple design, is more efficient and can be manufactured economically. 
       SUMMARY OF THE INVENTION 
       [0008]    According to the invention, this problem is solved by a plurality of pump blades made of two parts and formed, having a base blade segment that with a base body forms the first part and a cover disk blade segment that with a cover disk forms the second part. Because the pump blades are formed in two pieces, base blade segments forming one piece with the base body and cover disk blade segments forming one piece with the cover disk, there are design possibilities that allow for an optimized blade geometry and thus are more efficient, making it possible to use simple tools. 
         [0009]    Pump impellers mostly have flow surfaces that are curved. If such parts consist of two pieces and are supposed to be mounted in such curved areas, significant problems result because such contours are difficult to calculate, especially if shrinkage problems must be taken into account. That is why one especially preferred embodiment of the invention provides that essentially all axial boundary surfaces of the cover disk blade segments adjacent to the base body lie on the same plane. When these axial boundary surfaces also serve as contact surfaces, there are defined and calculable conditions. 
         [0010]    High mechanical strength and a precise arrangement of the junction between the cover disk and the base body can be achieved by engagement of the cover disk blade segments into grooves defined in the base body. 
         [0011]    If such parts that fit into the grooves are welded or glued together, it is possible that excess material will accumulate in the grooves and not make it into the area of the flow contour. In that case, ultrasonic welding is the preferred welding method. 
         [0012]    Alternatively, however, there is also the possibility that the cover disk blade segments are connected to the base body by hot stamping connecting pins that preferably extend from the cover disk blade segments through recesses provided in the base body adapted to them. 
         [0013]    Due to the flow contour, a very deep groove is necessary in the area near the axis of rotation in order to exploit the advantages cited above. Moreover, studies have shown that lead-in chamfers significantly increase pump efficiency. For these reasons, it is advantageous if the base blade segments are arranged radially inside the cover disk blade segments to which they are attached. At the same time, the lead-in chamfers are designed so that the wingspan of the base blade segments extends through the lead-in chamfers from a minimum value radially inward up to a maximum value radially outward. At the same time, it is also provided that the maximum value of the wingspan of the base blade segments corresponds to a wingspan of the cover disk blade segments in a radial inner section attached to the base blade segments. 
         [0014]    Due to the lead-in chamfers, between the base blade segments and the cover disk is a free space that narrows radially outward towards the cover disk blade segments. 
         [0015]    Especially high efficiency results if the base body has a flow surface that passes continuously from a cylinder ring surface originating from a suction port to a ring surface, the flow surface being limited radially by the pump blades and always self-contained in a spiral-shaped course. 
     
    
     
       DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0016]    One exemplary embodiment of the invention is explained in detail below by means of an example: 
           [0017]      FIG. 1  is a cross section view of a centrifugal pump impeller according to the invention: 
           [0018]      FIG. 2  is an enlarged section A from  FIG. 1 ; 
           [0019]      FIG. 3  is a perspective view a cover disk of the centrifugal pump impeller; 
           [0020]      FIG. 4  is a perspective view of a base body of the centrifugal pump impeller; 
           [0021]      FIG. 5  is a cross section view of a centrifugal pump motor incorporating the present invention: 
           [0022]      FIG. 6  is a perspective view of the inventive centrifugal pump; 
           [0023]      FIG. 7  is a cross section view of a further embodiment of the centrifugal pump impeller incorporating the present invention; 
           [0024]      FIG. 8  is an enlarged section from  FIG. 7 ; 
           [0025]      FIG. 9  is a perspective view of a cover disk found in the present invention; 
           [0026]      FIG. 10  shows a cross section of another variant of the centrifugal pump impeller incorporating the present invention; 
           [0027]      FIG. 11  is an enlarged section from  FIG. 10 ; 
           [0028]      FIG. 12  is a perspective view of a variant of the cover disk in accordance with the present invention; and 
           [0029]      FIG. 13  is an enlarged section from  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    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. 
         [0031]      FIG. 1  shows a cross section of a centrifugal pump impeller  1  according to the invention, having a base body  3 , a permanent-magnetic rotor  4  and a cover disk  5 . The base body  3  has a supporting tube  17  into which two bearings  10  are incorporated, which in this case are configured as plastic plain bearings—alternatively, a ceramic plain bearing can be used. The plastic plain bearings are press-fit into the supporting tube. The supporting tube  17  forms one piece with the base body  3 . The base body  3  also has a flow surface  14  that expands out continuously from a cylinder ring surface  15  in the diameter and extends up to a ring surface  16 . The flow surface  14  is limited radially by pump blades  2 . A plurality of pump blades  2  are formed in two pieces, each with a base blade segment  6  that foams one piece with the base body  3  and a cover disk blade segment  7  that forms one piece with the cover disk  5 . 
         [0032]    The cover disk blade segments  7  each go into mating grooves  20  that extend out from the flow surface  14  up to a plane  9  in the material of the base body  3 . Axial boundary surfaces  8  of the cover disk blade segments  7  lie on the same plane  9 . The base blade segments  6  have a lead-in chamfer  11  that extends from an area near the center with a reduced wingspan to the cover disk blade segments  7  with a maximum wingspan. To prevent accumulations of material, a recess  18  is molded in on the side of the base body  3  opposite the base blade segments  6 . The permanent-magnetic rotor  4  consists in this case of a plastic-bonded magnetic body that is primary molded around an area  19  of the base body  3  that in cross section is L-shaped. This results in a form fit that has additional torsion protection (not shown here) in the form of recesses or protrusions. Also shown in  FIG. 1  is an annular suction opening  23 , a bearing recess  21  and a pivot  26 . 
         [0033]      FIG. 2  shows an enlarged section A from  FIG. 1 , with the base body  3 , the pump blades  2 , the cover disk  5 , the base blade segment  6 , the cover disk blade segments  7 , the groove  20 , the boundary surface  8 , the plane  9 , the suction opening  23  and the lead-in chamfer  11 , which as a result has a recess  12  between the cover disk  5  and the base blade segment  6 . 
         [0034]      FIG. 3  shows the cover disk  5  of the centrifugal pump impeller as an individual part with the cover disk blade segments  7  and the suction opening  23  that corresponds to a suction port  13  (see  FIG. 6 ). The cover disk blade segments  7  have on their radial inner ends limits  22  that correspond to contact surfaces  24  (see  FIG. 4 ) of the base body  3 . 
         [0035]      FIG. 4  shows the cylindrically shaped base body  3  of the centrifugal pump impeller, having the cylindrically shaped permanent-magnetic rotor  4 , the spiral grooves  20 , the base blade segments  6 , the lead-in chamfers  11 , the contact surfaces  24 , the bearing recess  21  and the contact surface  24 , along with the cylinder ring surface  15  and the ring surface  16 . The groove depth of the grooves  20  increases in the direction of the base blade segments  6 . 
         [0036]      FIG. 5  shows a cross section of a centrifugal pump motor  27 , having the centrifugal pump impeller  1 , with the permanent-magnetic rotor  4 , the base body  3 , the cover disk  5  and the pump blades  2 , a shaft  30 , a partition wall  29  that forms one piece with a motor casing  31 , a casing cover  32  that is provided with a connector plug  34  and a circuit board  33 . A face-side pump casing  35  is shown in  FIG. 6 . 
         [0037]      FIG. 6  is a three-dimensional view of a centrifugal pump  38 , having a pump casing  35 , a suction port  13 , the motor casing  31 , the casing cover  32 , the connector plug  34  and a plurality of screw-on eyes  37 . The screw-on eyes also help attach casing cover  32  and pump casing  35  to the motor casing  31 . 
         [0038]      FIG. 7  shows a cross section of a second embodiment of the centrifugal pump impeller  1 , having the base body  3 , the cover disk  5 , the base blade segments  6 , the cover disk blade segments  7 , the permanent-magnetic rotor  4  and the supporting tube  17 . The variant is characterized by connecting pins  39 , which extend axially from the cover disk blade segments  7  through connecting recesses  40 . 
         [0039]      FIG. 8  shows an enlarged section from  FIG. 7 , making it easier to see the connecting pin  39  that extends from the cover disk blade segment  7  and the connection recess  40 . The drawing shows an end section  42  of the connecting pin  39  compressed by hot shaping into a conical extension  41 . To that end, the connecting pin is dimensioned so that it protrudes from the connecting recess  40  prior to reshaping. The protruding material is then forced into the conical extensions  41  as it is subjected to heat. A slightly enlarged in diameter inserter  43  at the start of the connecting recess  40  makes it easier to join the cover disk  5  to the base body  3 , in particular the connecting pin  39  to the connecting recesses  40 . 
         [0040]      FIG. 9  is a three-dimensional drawing of a cover disk  5 , having the connecting pins  39  that extend axially from the cover disk blade segments  7 . In this case, each cover disk blade segment  7  supports two connecting pins  39 . The number of connecting pins  39  depends on the size of the cover disk and the mechanical requirements. 
         [0041]      FIG. 10  shows a cross section of a third embodiment of the centrifugal pump impeller  1 , having the base body  3 , the cover disk  5 , the base blade segments  6 , the cover disk blade segments  7 , the permanent-magnetic rotor  4  and the supporting tube  17 . The third embodiment is characterized by V-shaped ribs  44  acting as energy directors that extend from the cover disk blade segments  7  axially into corresponding non-continuous grooves  45  (see  FIG. 11 ). This type of connection is chosen if an ultrasonic welded joint is used. The V-shaped ribs  44  (see  FIG. 11 ) help concentrate the oscillation energy, so that the material of the ribs  44  is fused at the neck and bonds to the surrounding material of the base body  3 . 
         [0042]      FIG. 11  shows an enlarged section from  FIG. 10 . Visible in it is one of the cover disk blade segments  7  having a narrow rectangular base rib  46  attached to the cover disk blade segment  7  and the V-shaped rib  44  attached in turn to it. The rib extends into the groove  45 . 
         [0043]      FIG. 12  is a three-dimensional drawing of a fourth embodiment of the cover disk  5 , having the cover disk blade segments  7  and the ribs  44 . 
         [0044]    In  FIG. 13 , which shows an enlarged section from  FIG. 12 , the geometry of the ribs  44  is more clearly visible. Next to the V-shaped rib  44  is the rib base  46  and a slope  47  which are provided with radial blade ends on the outside. 
         [0045]    In all configurations, the cover disk  5 , the base body  3  and the partition wall are made of a PPS material (polyphenylene sulfide), in particular PPS-GF40. The basic material of the plastic-bonded permanent magnets is also made of PPS. Ferrite serves as the magmet material. The casing cover  32  and the pump casing  35  are made of PPA-GF40 (polyphthalamide). 
         [0046]    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 NUMERALS: 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 Centrifugal pump impeller 
               
               
                 2 
                 Pump blades 
               
               
                 3 
                 Base body 
               
               
                 4 
                 Permanent-magnetic rotor 
               
               
                 5 
                 Cover disk 
               
               
                 6 
                 Base blade segment 
               
               
                 7 
                 Cover disk blade segment 
               
               
                 8 
                 Boundary surface 
               
               
                 9 
                 Common plane 
               
               
                 10 
                 Bearing 
               
               
                 11 
                 Lead-in chamfer 
               
               
                 12 
                 Free space 
               
               
                 13 
                 Suction port 
               
               
                 14 
                 Flow surface 
               
               
                 15 
                 Cylinder ring surface 
               
               
                 16 
                 Ring surface 
               
               
                 17 
                 Supporting tube 
               
               
                 18 
                 Recess 
               
               
                 19 
                 L-shaped area 
               
               
                 20 
                 Groove 
               
               
                 21 
                 Bearing recess 
               
               
                 22 
                 Limit 
               
               
                 23 
                 Suction opening 
               
               
                 24 
                 Contact surface 
               
               
                 26 
                 Pivot 
               
               
                 27 
                 Centrifugal pump motor 
               
               
                 28 
                 Stator 
               
               
                 29 
                 Partition wall 
               
               
                 30 
                 Shaft 
               
               
                 31 
                 Motor casing 
               
               
                 32 
                 Casing cover 
               
               
                 33 
                 Circuit board 
               
               
                 34 
                 Connector plug 
               
               
                 35 
                 Pump casing 
               
               
                 36 
                 Pressure ports 
               
               
                 37 
                 Screw-on eyes 
               
               
                 38 
                 Centrifugal pump 
               
               
                 39 
                 Connecting pins 
               
               
                 40 
                 Connecting passageways 
               
               
                 41 
                 Conical extension 
               
               
                 42 
                 End section 
               
               
                 43 
                 Inserter 
               
               
                 44 
                 Rib 
               
               
                 45 
                 Groove 
               
               
                 46 
                 Base rib 
               
               
                 47 
                 Slope