Abstract:
In a stator of a vehicle ac generator, a slot insulator has a portion closing the opening of a slot. Therefore, portions of the stator winding disposed in the slot can be retained in the slot without an additional member, and water or the like can be shut out.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is based on and claims priority from Japanese Patent Application Hei 10-180755, filed on Jun. 26, 1998, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ac generator&#39;s stator for a passenger car or a truck and a method of manufacturing the same. 
     2. Description of the Related Art 
     An insulating structure between a stator core and a stator winding of an ac generator&#39;s stator for a vehicle is disclosed in JP-A-8-80001, in which insulation film sheets are disposed between slot walls and the stator winding. Each slot has an opening formed at the inner periphery of the stator core, which is closed by a separate press-fitted wedge member to retain in-slot portions of the stator winding inside the slot. 
     Because the insulation film member and the press-fitted insulation member are separate in such a stator core, small gaps are necessarily formed between the two members. When a rotor rotates inside the stator, pressure near the slot openings rises. As a result, snow mixed with salt or salt water may be introduced into the slots through the small gaps by the cooling air blowing on the stator winding. This causes electrolyzation of the in-slot portions of the stator winding thereby resulting in insulation failure of the stator winding. 
     On the other hand, the space factor of the in-slot portions of the stator winding has been increased to satisfy recent demand for increasing output power of the vehicle ac generator. The separate wedge member has become an obstacle to increasing in the space factor. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the invention is to provide an ac generator&#39;s stator for a vehicle that has improved insulation structure formed between the stator winding and the stator core and a method of manufacturing such a stator. 
     In a stator of a vehicle ac generator according to a preferred embodiment of the invention, each of slot insulators has a closing portion closing the opening of slot. Therefore, electric conductors can be held within the slots without additional retaining members. In addition, the closing portion can shut out salt water or other electrolyte easily. 
     As a result, the insulation coating of the stator winding is free from damage otherwise caused by some of the wedge members being press-fitted into the slots. 
     Each of the insulators can be a roll of a rectangular sheet with opposite sides overlapping with each other to fit to the inner periphery of the slot. The insulators can be formed in a tubular fashion. 
     In a method of manufacturing the stator according to a preferred embodiment of the invention, a bundle of the in-slot portions is enclosed by an insulator sheet. Then, bundles of in-slot-portions are inserted into all the slots, and connecting portions extending from the bundles are connected to one another to form the stator winding. 
     Each of the insulators can be inserted into one of the slots and disposed to fit the entire peripheral surface of the slot and to close the opening of the slot before the conductors are inserted into the slot from one axial end of the stator core. 
     Thus, the ac generator&#39;s stator for a vehicle according to an embodiment of the invention can be manufactured easily. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and characteristics of the present invention as well as the functions of related parts of the present invention will become clear from a study of the following detailed description, the appended claims and the drawings. In the drawings: 
     FIG. 1 is a cross-sectional view of an ac generator for a vehicle having a stator according to an embodiment of the invention; 
     FIG. 2 is a fragmentary cross-sectional view of the stator according to a first embodiment of the invention; 
     FIG. 3 is a perspective schematic diagram of a segment inserted into a stator core according to the first embodiment of the invention; 
     FIG. 4 is a perspective diagram illustrating the segment according to the first embodiment being inserted into a slot; and 
     FIG. 5 is a fragmentary cross-sectional view of a stator according to a second embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A stator according to a first embodiment of the invention is described with reference to FIGS. 1-4. Vehicle ac generator  1  includes stator  2 , rotor  3 , front housing  4   a  and rear housing  4   b  and ac-dc converting rectifier  5 . Front and rear housings  4   a  and  4   b  support stator  2  and rotor therebetween by a plurality of bolts  4   c.    
     Rotor  3  has shaft  6 , pole core  7 , field coil  8 , slip rings  9 ,  10 , and mix-flow fan  11  and centrifugal fan  12 . Shaft  6  is fixed to pulley  20  to be driven by an engine (not shown) mounted in a vehicle. 
     Pole core  7  has a pair of pole core members, each of which has boss portions  71 , disk portions  72  and six claw-pole-pieces  73 . 
     Front housing  4   a  and rear housing  4   b  respectively have air inlets  41  at the axial ends thereof and air outlets  42  at the outer periphery thereof around coil ends  31   a ,  31   b.    
     Stator  2  has annular stator core  32  and a three-phase ac stator winding. 
     Stator core  32  is a lamination of thin steel sheets having thirty six parallel-sided slots  30  formed at the inner periphery thereof, a plurality of yoke portions  32   a  and a plurality of tooth-edges  32   b.    
     As shown in FIG. 2, each slot  30  accommodates a plurality of conductor segments therein, which are insulated from stator core  32  by insulators  34 . 
     The stator winding is composed of a plurality of U-shaped conductor segments  33  made of round copper wire connected in a prescribed pattern. As shown in FIG. 3, each conductor segment  33  has a continuous U-shaped crossing portion  33   b , a pair of in-slot portions  33   a  and a pair of connecting portions  33   c . U-shaped portion  33   b  is disposed at an axial end of stator core  32  and continuously connecting one of the pair of in-slot portion  33   a  disposed in one slot  30  and the other in-slot portion  33   a  disposed in another slot  30 . Each of the pair of connecting portions  33   c  extends from one of the above in-slot portions  33   a  and is disposed at the other axial end of stator core  32  to be respectively welded to another connecting portion of another segment  33  extending from different one of slots  30 . 
     As shown in FIG. 4, insulator  34  is made of a generally rectangular insulation sheet that has axially extending sides overlapped with each other at overlap portion  34   a  to form an axially extending cylinder. Insulators  34  are inserted from one axial end of stator core  32  into slots  30  with overlap portions  34   a  being at radially outer wall of slots  30 , so that slot openings  35  are respectively closed by closing portions  34   b . Overlap portions  34   a  can be disposed anywhere other than slot openings  35  to have the same effect as the above. 
     Thereafter, segments  33  are inserted into slots  30  from one end of stator core  32  so that two in-slot portions  33   a  thereof are respectively inserted into two slots  30  spaced apart a prescribed pole pitch from each other. 
     Then, connecting portions  33   c  are bent oppositely in the circumferential direction as shown by broken lines in FIG.  3 . Each end of connecting portions  33   c  is welded to an end of connecting portion  33   c  of another segment  33  to form a three-phase ac winding. 
     Thus, slot openings  35  are closed without gaps, and segments  33  are retained inside slots  30  without using specific retainer members. Because it is not necessary to press-fit separate wedge members into slots  30 , any damage on segments  33  such as scratches or problems in inserting such members can be avoided. Moreover, the space factor of conductor segments  33  in slots can be increased. 
     Segments  33  and insulators  34  can be easily inserted into slots  30  from the same axial end of stator core  32  jointly or separately. Therefore, it is possible to put segments  33  in slots  30  in proper order to increase the space factor, resulting in reduction in resistance of the stator winding and higher output power of the ac generator. 
     As shown in FIG. 5, U-shaped segment  33  can be made of a conductor wire having a rectangular shape in cross-section fitted to slot  30 . If insulators having overlap portion  34   a  are used, overlap portions  34   a  are preferably position on the radial line to which segments  33  are aligned, as shown in FIG. 2, because the overlap portion  33   a  is surely pressed down by the aligned segments  33 . Instead of the insulator  34  having overlap portions  34   a , seamless tubular insulator  34  can be also used. Smooth tubular insulator  34  can be made by bonding opposite edges of a rectangular insulation film or nonwoven sheet. 
     The size and shape of tubular insulators  34  and rectangular segments  33  correspond to those of slots  30 , thereby reducing unnecessary gaps. 
     Because segments  33  are held by friction force via insulators  34 , vibration resistance can be improved. 
     Insulators  34  can be inserted into slots  30  from slot openings  35  instead of the axial end of the stator core. Segments  33  together with insulators  34  can be also inserted from slot openings  35 . 
     A plurality of in-slot portions  33   a  can be wrapped by a sheet of insulator  34  or inserted into tubular insulator  34  beforehand. The stator winding can be formed of continuous wire in a well-known manner. In this case, a prescribed number of turns are formed and wrapped by sheet insulators  34  beforehand. Thereafter, they are inserted into slots  30  from slot openings  35 . Insulators  34  are rotated so that overlap portions  34   a  can be disposed at radially outer portion of slots  30 . 
     Rod-like segments can be also used instead of U-shaped segments. 
     In the foregoing description of the present invention, the invention has been disclosed with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made to the specific embodiments of the present invention without departing from the broader spirit and scope of the invention as set forth in the appended claims. Accordingly, the description of the present invention in this document is to be regarded in an illustrative, rather than restrictive, sense.