Patent Publication Number: US-2003227230-A1

Title: Exterior winding strategy for salient pole brushless motor for fuel pump application

Description:
BACKGROUND OF THE INVENTION  
       [0001] A multi-phase salient motor is often used in vehicle systems, most often in the fuel pump. The multi-phase salient pole motor includes a rotor having magnets positioned at the ends of arms and a stator comprising a plurality of electromagnets. The electromagnets on the stator are on spokes of the stator. The stator spokes are wound with wire, and electricity run through the wire to create a magnetic field.  
       [0002] The winding of the spokes has been difficult to accomplish in a manner conducive to mass production. The stator must be wound tightly and each spoke has only a small open space between them. Winding the spokes in the assembled stator increases manufacturing cost as well as the manufacturing time, which is ineffective for mass production of the motor.  
       BRIEF SUMMARY OF THE INVENTION  
       [0003] According to one embodiment of the present invention, there is provided a stator for a motor. The stator includes a plurality of spokes, at least one of the spokes each having a first end and a second end, where the first end is engaged with an inner stator frame and the second end is engaged with an outer stator frame. The spokes are wound with wire external to the two stator frames. A stator housing is mounted over the outer stator frame.  
       [0004] According to another embodiment of the present invention, there is provided a method for production of a stator for a motor including providing a plurality of spokes and winding each spoke individually with a wire. The spokes are inserted into an inner stator frame and attached to an outer stator frame.  
       [0005] Other aspects of the present invention will become apparent in connection with the following description of the present invention.  
     
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS  
     [0006]FIG. 1 is a view of an assembled stator according to one embodiment of the present invention, with a portion of the stator housing removed;  
     [0007]FIG. 2 is a view of multiple spokes of the embodiment of FIG. 1 being wound according to the present invention;  
     [0008]FIG. 3 is a flow diagram of a preferred embodiment of the present invention; and  
     [0009]FIG. 4 is a magnified view of the outer stator frame of the embodiment of FIG. 1 depicting one preferred geometry of crimping according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0010] An assembled stator according to one embodiment of the present invention is depicted in FIG. 1. The stator includes a plurality of spokes  10 , an inner stator frame  12 , an outer stator frame  14 , and a stator housing  16 . The stator components are preferably made of metal, such as a silicon steel, and more preferably M49 silicon steel or M19 silicon steel. Other materials having good magnetic properties may also be used.  
     [0011] The spokes  10  are preferably of identical or similar geometry, but may differ from each other. Preferably, the spokes  10  have a rectangular prism shape, such as a rectangular prism with a square base and cross-section. Cylindrical or other cross-section geometries may also be used for the spokes  10 . Each spoke  10  has a first end at one base and a second end directly opposite the first end.  
     [0012] Both the inner stator frame  12  and the outer stator frame  14  are preferably circular, and the inner stator frame  12  has a smaller radius than the outer stator frame  14 . Other shapes may be used. In a preferred embodiment, the difference between the radius of the outer stator frame  14  and the inner stator frame  12  is about the length of a spoke  10 . Preferably, the inner stator frame  12  comprises a number of indentations  19 . These indentations  19  are designed to snugly hold one of the ends of the spoke  10 .  
     [0013] The winding process is shown in FIG. 2. The spokes  10  are individually wound external to the stator. Winding of the spokes  10  before installation into the stator allows for faster and more efficient production. Instead of requiring special equipment to thread through the spaces between spokes  10  in an assembled stator, a more conventional winding apparatus as known to those of skill in the art may be used. Further, the winding may be done more precisely, tightly, and uniformly. Precise and uniform winding of the wire  18  on the spokes  10  produces more reliable stators.  
     [0014] The wire  18  is made of any electrically conductive material, such as copper. At the time of winding, any additional wire modification to improve the conductivity can be performed. For example, wire ends may be fitted with connectors, or insulation taken off the ends.  
     [0015]FIG. 3 shows a flow diagram of a preferred embodiment of the present invention. The spokes  10  are first wound with wire  18  before insertion into the stator at Box  110 . The spokes  10  wound with wire  18  are then inserted into the inner stator frame  12  at Box  120 . Preferably, the inner stator frame  12  comprises indentations  19  to hold the first ends of the spokes  10  in place. According to one preferred embodiment of the present invention, the spokes  10  are additionally secured to the inner stator frame  12  by an adhesive or by  20  welding. The adhesive used may be any one known to promote metal-to-metal bonding. A snap fit, latch, or other connection may be used, on its own or in connection with welding or an adhesive. The spokes  10  are preferably arranged at equidistant intervals circumferentially around the inner stator. Wires  18  may also be connected to the inner stator frame  12  or to wires  18  on other spokes  10 .  
     [0016] The spokes  10  wound with wire  18  and mounted on the inner stator frame  12  are then pressed into the outer stator frame  14  at Box  130 . Preferably, the outer stator frame  14  comprises indentations to hold the second ends of said spokes  10  in place. For example, the outer stator frame  14  has crimpings  20 , as shown in FIG. 4, allowing the spokes  10  and inner stator frame  12  to be easily pressed into the outer stator frame  14 . These crimpings  20  are indentations designed to allow the spoke  10  to be easily inserted while stabilizing and securing the spoke  10 . FIG. 4 illustrates one preferred embodiment of these crimpings  20 . Spokes  10  as mounted in a finished stator frame are depicted in FIG. 1. Other crimping geometries that also facilitate the joining of the spokes  10  to the outer stator frame  14  are possible. Preferably, these crimpings  20  are arranged on the outer stator frame  14  so as to be equidistant from each other along the circumference and to align with the spokes  10 . In one preferred embodiment, the connection between the spokes  10  and the outer stator frame  14  at the crimping  20  is strengthened by welding the two parts together or by using an adhesive. The adhesive used may be any one known in the art to promote metal-to-metal bonding. Wires  18  may also be connected to the outer stator frame  14  or to wires  18  on other spokes  10 .  
     [0017] Alternatively, the spokes  10  may be pressed into the outer stator frame  14  at Box  130  before being pressed into the inner stator frame  12  at Box  120 . In such a method, the crimpings  20  may remain on the outer stator  14 , or be placed on the inner stator frame  12 .  
     [0018] In a second embodiment, an additional stator housing  16  is mounted over the assembled stator, as shown in FIG. 1. The stator housing  16  is a cover for the stator, and is mounted on top of the outer stator frame  14 . The stator housing  16  may then be pressed, crimped, welded, or otherwise attached to the outer stator frame  14 . An adhesive may also be used. The adhesive used may be any type known to promote metal-to-metal bonding. Further, a snap fit, latch, or other connection may be used, on its own or in connection with welding or an adhesive.  
     [0019] The embodiments shown in the present invention are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the following claims.