Abstract:
A fluid pump, in particular for the cooling or heating circuit of a motor vehicle, has a claw pole stator and a rotor that is separated from the claw pole stator by a tube, is immersed in a fluid, and has a vane wheel. Claws ( 25 ) of the claw pole stator ( 21 ) are an integral component of the tube ( 11 ), which is part of a motor housing ( 2 ), and the number of mounting steps is thus reduced.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 USC 371 application of PCT/DE 00/04143 filed on Nov. 23, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is based on a fluid pump having a motor housing and on a method for producing a motor housing for a fluid pump useful, for example, as a circulating pump in a heating or cooling system of a motor vehicle. 
     2. Description of the Prior Art 
     The principle of separating the stator inverter with a tube that makes it possible to dispose the rotor in such a way that it is immersed in a coolant is known from German patent DE 37 02 028 C2. 
     A more-detailed description of such a fluid pump can be found in German patent disclosure DE 44 11 960 A1. The fluid pump shown in this reference has a bell-shaped rotor, whose cylindrical interior is engaged by the stator. A tubular or cup-shaped wall extends between the rotor and the stator, and a shaft about which the rotor is rotatably suspended is let into the bottom of a cup. 
     The anchoring of the shaft extends only a slight depth into the interior of the cylindrical hollow chamber, because almost the entire space in this chamber is required for accommodating the stator. The cylindrical wall between the stator and the rotor is very thin, for the sake of attaining a small gap width and thus low magnetic circuit losses. This impairs the stability of the suspension of the rotor. 
     A printed circuit board with a commutation circuit for supplying electric current to the stator can be disposed only in the axial extension of the stator, which thus increases the installation depth of the fluid pump. 
     German patent application 199 34 382 has also proposed using a fluid pump with a motor that has a claw pole stator. This claw pole stator comprises a winding and two claw baffles with claws. The individual parts have to be assembled in a plurality of assembly steps and fixed on the motor housing. Because of tolerance, an air gap is created between the claw pole stator and the motor housing, which makes it more difficult to dissipate a heat loss from the winding to a medium pumped in the fluid pump and makes it harder to achieve low magnetic circuit losses. 
     SUMMARY OF THE INVENTION 
     The fluid pump of the invention having a motor housing, and the method for producing a motor housing for a fluid pump, have the advantage over the prior art that the operating properties are improved and the number of assembly steps is reduced, both in a simple way. 
     By injecting claw baffles, the advantages obtained, because of heat transfer without an air gap, that a heat loss from a winding and claws can be better dissipated to a fluid flowing in a tube. 
     It is especially advantageous to inject or mold the claws or claw baffles into a motor housing, since as a result fewer parts have to be assembled. It is advantageous to inject metal connecting parts into the motor housing, since once again the installation in the motor housing is made unnecessary, and a passage through the connecting parts is simultaneously well sealed off. 
     It is also advantageous to inject a stamped grid into the motor housing; the stamped grid makes an electrical connection from and to a printed circuit board, and as a result it is no longer necessary for electrical connecting lines to be put in place and secured. 
     It is advantageous to spray-coat the claw pole stator in such a way that heat radiation from the winding in the region of the at least one printed circuit board is reduced, since this improves the service life and operating conditions of the printed circuit board. 
     It is advantageous for the winding to be wound directly onto the motor housing, because then no additional winding holder has to be used. 
     A short-circuit ring is advantageously mounted on the motor housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other advantages and features of the invention will become apparent from the detailed description contained below, taken with the drawings, in which: 
     FIG. 1 shows an axial section through a fluid pump of the invention; 
     FIG. 2 shows an axial section through the motor housing with claw poles; and 
     FIG. 3 is a three-dimensional view of claws injected into the motor housing. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The fluid pump  1  can be used for instance as a coolant pump or for a heating circuit in a motor vehicle and has a three-piece pump housing  33 , which comprises a front housing part  30  with an intake stub  4  embodied in it and with a compression stub, not shown, a motor housing  2 , and a rear housing part  3 . The front housing part  30 , intake stub  4 , motor housing  2  and rear housing part  3  are all of plastic, but the intake stub  4  and the rear housing part  3  can also be of some other material, such as metal or ceramic. 
     The parts  30 ,  2 ,  3  are held together by screws, for instance, that keep the motor housing  2  fastened between the front part  30  and rear part  3 . Any other type of connection is also possible, such as rivets and adhesive bonding. A sealing ring  10  is clamped or injected between the front housing part  30  and the motor housing  2 . The motor housing  2  comprises a nonmagnetic material and has a thin-walled portion, in the form of a tube  11  with an inner wall  24 . A rotor  6  is accommodated in the tube  11 , which together with a bottom  12  forms a cup. 
     The rotor  6  is of a plastic-bonded magnetic material, for instance powdered magnetic material embedded in a synthetic resin or plastic matrix, is produced in one piece, for instance by injection molding, and includes an outer cylinder  7  that with slight spacing follows the course of the tube  11 . The rotor  6  is magnetized with two poles or more, depending on the intended use. The rotor  6  rotates about a pivot axis  35 , which also represents a center line of the rotor  6 . The outer cylinder  7 , on its end toward the intake stub  4 , is closed by an end wall  13  that carries a plurality of vanes  14 . 
     A bearing shaft  8  joined integrally to the end wall  13  extends through the interior of the cylinder  7 . The bearing shaft  8 , at least on its two axial ends  8 ′,  8 ″, is supported rotatably about a stationary shaft  9  and surrounds it over essentially the entire length of the stationary shaft. The length of the bearing shaft is as least so great that the center of gravity of the rotor  6  is located between the two ends  8 ′,  8 ″. The shaft  9  is anchored in a manner fixed against relative rotation by knurling on a first end in a recess of the bottom  12 , while its second end is received in hub  15  of a ribbed star embodied integrally with the front housing part  30 , of which only one strut  5  is shown in FIG.  1 . 
     To keep the weight of the rotor  6  low, an annular chamber  16  is provided between the outer cylinder  7  and the bearing shaft  8 ; except for a few thin-walled ribs  17 , the annular chamber is empty. The ribs  17  serve to reinforce the connection between the outer cylinder  7  and the bearing shaft  8 . 
     An encompassing flange  18  is disposed at the transition between the outer cylinder  7  and the end wall  13  of the rotor and engages an annular groove  19  of the motor housing  2 , to prevent the entry of solid contaminants from the coolant flow into the narrow gap  20  between the outer cylinder and the tube  11 . 
     A claw pole stator  21  extends around the tube  11 . At least in part, claw baffles  26  of the claw pole stator  21  with claws  25  are an integral part of the motor housing  2 . For instance, the claw baffles  26  are disposed in the tube  11 . One way to proceed with integral disposition is achieved by providing that the claws  25  or claw baffles  26  are injected at least partly into the plastic motor housing  2 . Another way is made possible by hot-embedding of the claws  25  or claw baffles  26  in the plasticized plastic of the motor housing  2 . Other ways of proceeding are also possible. 
     Located around the claws  25  is a winding  55 , which in turn is surrounded by a short-circuit ring  58 . The winding  55  is wound for instance directly onto the insulating motor housing  2 . However, the winding  55  can also be disposed as a prefabricated part on the motor housing  2 . A winding holder is then not necessary. 
     A supply circuit for the claw pole stator  21  can be mounted for instance on a printed circuit board  38 , which for instance is annular in shape; as a result, it does not increase the axial structure length of the fluid pump  1 . The printed circuit board  38  extends approximately parallel to the pivot axis  35  and is accommodated for instance in the rear housing part  3 . Also located there is a connection point  41  with at least one metal connecting part  44 , which is for instance one part of a stamped grid  47 . The stamped grid  47  connects an external plug to connecting point  41  for instance to the printed circuit board  38 . The printed circuit board  38  is separated from the winding  55  by a radial protective wall  51 , which for instance is injected directly, so that heat radiation of a heat loss from the winding  55  and the claws  25  toward the printed circuit board  38  is reduced. Other ways of fastening the protective wall  51  in the motor housing are also possible. 
     The claws  25  are injected into the motor housing  2 , for instance, and in the same operation the metal connecting parts  44  are injected for instance as stamped grids  47  on the outside and toward the printed circuit board  38 . The stamped grid  47  can for instance also be injected into the rear housing part  3 , which is produced in a separate operation. 
     A winding  55  is then wound around the claws  55 . A short-circuit ring  58  is then installed. 
     A magnetic field generated by the winding  55 , with alternating polarity of the claws  25  of the two claw baffles  26 , reaches radially inward and thus drives the rotor  6 , which is not shown in FIG.  2 . The winding  55  is designed in bifilar fashion; that is, it includes two circuits that can be acted upon separately and independently of one another by an electric current. This makes it possible to generate magnetic fields with alternating polarity. Such a claw pole stator  21  can be operated with simpler power electronics than a unifilar design. 
     A Hall sensor, not shown, assures commutation, for instance, and can be provided as a magnetic field sensor for monitoring the function or speed of the fluid pump  1 , at a location where the sensor is exposed to the varying magnetic field of the rotating rotor  6 . 
     FIG. 2 shows an axial cross section through the motor housing  2  and the claw baffles  26  with the claws  25 . For the same parts or parts functioning the same, the same reference numerals as in FIG. 1 are used. 
     The integral disposition of the claws  25  in the motor housing makes it possible to keep a spacing between the claws  25  and the inner wall  24  and thus a spacing from the cylinder  7  of the rotor  6  very slight, and thus makes it possible to increase an exertion of force between the claw pole stator  21  and the rotor  6 . 
     The heat input of the heat loss of the winding  55  and of the claws into the fluid is also enhanced and thus the cooling is improved, so that the operating temperature and radiation in the direction of the printed circuit board  38  are lowered. 
     FIG. 3 shows a three-dimensional view of claws  25 , which are an integral component of the motor housing  2 . The same reference numerals as in the other drawings are used for the same parts or parts that function the same. Only part of the motor housing  2  is shown, in dashed lines. 
     The claw pole stator  21  includes two claw baffles  26 , each designed identically, with an encompassing outer ring and a plurality of claws  25  on each claw baffle  26 , which claws are bent radially inward, beginning at one edge of the claw baffle  26 , and are then bent in the direction of the opposite edge. The claws  26  extend in the axial direction, tapering trapezoidally, for instance. This improves the efficiency of the motor. The claw baffles  26  are inter-nested in one another in such a way that the claws  25  of one claw baffle  26  protrude into gaps between claws  25  of the other claw baffle  26 , in each case with spacing in the circumferential direction, and the radially extending edges of the claw baffles are spaced apart from one another axially. 
     In the interior toward the inner wall  24 , the claws  25  are covered completely by the plastic of the tube  11 . Farther outward in the radial direction, the claws  25  are also surrounded by plastic, for instance. However, they can also be exposed there. 
     The claw baffles  26  form an annular hollow chamber into which the winding  55  is wound, for instance. 
     The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.