Abstract:
A method of manufacturing a stator of an electric rotating machine is provided. The stator includes a plurality of teeth radially extended from a yoke portion formed by stacking steel sheets, a stator core having an insulating film on a surface of the teeth, and a winding portion including a plurality of layers of a power generating coil wound around each of the plurality of teeth. The method includes: a step of forming an insulating coating film by impregnating the power generating coil in a lower layer portion of the winding portion with a varnish using a liquid-type thermosetting resin, thereafter covering the power generating coil in a surface portion of the winding portion with a thermally meltable powder resin, and melt-bonding and thereafter curing the powder resin; and a step of curing the varnish that is performed simultaneously with the step of forming an insulating coating film.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention relates to a method of manufacturing a stator of an electric rotating machine mounted to, for example, vehicles. 
     Description of the Related Art 
     An electric rotating machine that is mounted to a vehicle and used as a power generator or a motor, such as a magnet generator, has a multipolar stator. This multipolar stator has a stator core, which has radially-arranged teeth provided on the outer circumference of an annular yoke portion. Around the outer circumference of each of the teeth of this stator core, a stator coil is wound with an insulating material interposed therebetween. Because the stator coils of such a multipolar stator are affected by vibrations from the engine, a bonding process of bonding the coiled wires of the stator coils to each other with a resin such as a varnish is essential. 
     A conventionally known method of bonding the coiled wires of the stator coil of the electric rotating machine to be mounted in a vehicle is disclosed in, for example, JP-A-11-150923 (Patent Document 1), in which a varnish resin in liquid form is impregnated between the coiled wires and cured to bond the coiled wires to each other. 
     Another method of bonding the coiled wires is also known, as disclosed in JP-A-58-26552 (Patent Document 2). In this method, the coiled wires are bonded by bringing thermally meltable powder such as an epoxy resin into contact with the coiled wire surface of the stator coil that has been pre-heated so as to melt the thermally meltable powder, and then curing the thermally meltable powder. 
     Patent Document 1: JP-A-11-150923 
     Patent Document 2: JP-A-58-26552 
     However, conventional coil bonding methods have the following problems, because of circumstances such as an increase of engine vibration that is associated with higher vehicle output performance, a voltage increase in vehicle&#39;s power supply system, and maintenance of the coiled wire quality that is commensurate with these. 
     According to the method disclosed in Patent Document 1 above, it is possible to cause the varnish resin to permeate between the coiled wires and into the coiled wire lower layer portion because of its low viscosity. However, if the bonding of the coil end portion is insufficient and the engine vibration is large, it may be possible that the coil end portion can move and undergo fatigue failure. 
     In view of the problem, the coil end portion is conventionally bonded in the following manner. In order to bond the coil end portion sufficiently, the above-described bonding process with the varnish resin is performed, and thereafter, the coil end portion is bonded again with a high-viscosity liquid-type varnish resin. 
     According to the method disclosed in the foregoing Patent Document 2, bonding of the stator coil winding portion exterior, including the coil end portion, is sufficient, but insulation failure may occur between the coiled wires. The reason is as follows. The thermally meltable powder such as epoxy resin does not easily permeate between the coiled wires or into the coiled wire lower layer portion. For this reason, when the engine vibration is large, the coiled wires in the lower layer portion in particular move mutually, and because of the friction between the coiled wires, the insulating coating film on the coil surface wears out. 
     In addition, since the thermally meltable powder such as epoxy resin does not easily permeate between the coiled wires or into the coiled wire lower layer portion, an insulation failure may occur between the coils and between the coils and the stator core because of pin holes in the coil insulating coating film and pin holes in the core insulating film. The probability of this insulation failure between the coils and between the coils and the stator core becomes higher due to an increase in the voltage of the vehicle electric power supply system. 
     Furthermore, when merely both the bonding by the impregnation of the liquid-type varnish resin and the bonding by melting and curing the powdered resin are employed, there is a problem of extremely low productivity. 
     SUMMARY OF THE INVENTION 
     This invention has been accomplished in view of the foregoing circumstances, and the invention provides a method of manufacturing a stator of an electric rotating machine that can achieve both good productivity and assurance of the coiled wire quality and bonding strength between the coiled wires and in the coiled wire lower layer portion as well as in the coiled wire surface portion including the coil end portion. 
     This invention provides a method of manufacturing a stator of an electric rotating machine, the stator including a plurality of teeth radially extended from a yoke portion formed by stacking steel sheets, a stator core having an insulating film on a surface of the teeth, and a winding portion comprising a plurality of layers of a coil wound around each of the plurality of teeth, the method including: a step of forming an insulating coating film by impregnating the coil in a lower layer portion of the winding portion with a varnish using a liquid-type thermosetting resin, thereafter covering the coil in a surface portion of the winding portion with a thermally meltable powder resin, and melt-bonding and thereafter curing the powder resin; and a step of curing the varnish that is performed simultaneously with the step of forming an insulating coating film. 
     The method of manufacturing a stator of an electric rotating machine according to this invention makes it possible to ensure the coiled wire quality and the bonding strength between the coiled wires and in the lower layer portion of the coil winding portion as well as in the coiled wire surface portion including the coil end portion, and to improve the productivity at the same time. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a magnet generator according to a first embodiment of this invention; 
         FIG. 2  is a side cross-sectional view of the magnet generator according to the first embodiment of this invention; 
         FIG. 3  is a detail view of a power generating coil winding portion of the magnet generator according to the first embodiment of this invention; 
         FIGS. 4A, 4B and 4C  are views illustrating the power generating coil winding portion shown in  FIG. 3 , viewed from the right side, wherein each of  FIGS. 4A, 4B and 4C  shows a different example of the bent shape portion; 
         FIG. 5A  shows a flow-chart for illustrating a bonding process of power generating coils according to the invention, and  FIG. 5B  shows a comparative techniques known by the inventor; 
         FIG. 6  is a detail view of a power generating coil winding portion of the magnet generator according to a second embodiment of this invention; and 
         FIG. 7  is a detail view of a power generating coil winding portion of the magnet generator according to a third embodiment of this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinbelow, preferred embodiments of the method of manufacturing a stator of an electric rotating machine according to this invention will be described with reference to the drawings. It should be noted that, in the drawings, the same or corresponding component parts are designated by the same reference numerals. 
     First Embodiment 
       FIG. 1  is a front view showing a magnet generator according to a first embodiment of this invention, and  FIG. 2  is a side cross-sectional view thereof.  FIG. 3  is a detail view showing a power generating coil winding portion of the magnet generator, and  FIG. 4  is a view thereof from its right side. 
     Referring to  FIGS. 1 and 2 , a magnet generator  20  has a rotor  1  coupled to an internal combustion engine (not shown), and a stator  2  that is an armature provided inside the rotor  1 . The rotor  1  has a bowl-shaped flywheel  3  and a plurality of permanent magnets  4  secured to an inner wall surface of the flywheel  3 . The rotor  1  is configured so as to rotate about a rotational axis line A-A as the center. 
     The permanent magnets  4  are secured to the inner circumferential surface of a cylindrical portion  3   a  of the flywheel  3  by a mold material  5  (see  FIG. 2 ) so as to have regular angular intervals around the rotational axis line A-A. The plurality of permanent magnets  4  are magnetized in such a manner that adjacent permanent magnets  4  have opposite polarities to each other, so that a magnetic field in which its directions change alternately is produced in the space inward of the permanent magnets  4 . 
     The stator  2  has a stator core  6  and a power generating coil  7 . The stator core  6  has a circular ring-shaped yoke portion  6   a  and a plurality of teeth  6   b  protruding radially outward from the yoke portion  6   a  at circumferentially regular intervals. The surface of each of the teeth  6   b  is covered by an insulating film  8  made of a thermoplastic resin material. 
     In the stator core  6 , a plurality of through-holes  9  are formed at circumferential intervals. Mounting bolts (not shown) are allowed to penetrate through the through-holes  9  so as to screw-fasten the stator  2  to a bracket (not shown) that is a non-rotating body, whereby the stator  2  is secured thereto. 
     The stator core  6  has a laminated body  10  and end plates  11 . The laminated body  10  is formed by laminating a multiplicity of layers of circular ring-shaped magnetic steel sheet (for example, cold rolled steel sheet such as SPCC) along the direction of the rotational axis line A-A. The end plates  11  are overlapped respectively on both side faces of the laminated body  10  so as to be in intimate contact therewith. 
     As shown in  FIG. 3 , the power generating coil  7  is wound around each of the teeth  6   b  of the stator core  6  to form a plurality of layers. A lower layer portion of the winding portion is impregnated with a varnish  12  that uses a liquid-type thermosetting resin, and an insulating coating film is formed on a surface of the winding portion by melt-bonding a powder resin  13  such as epoxy resin onto the surface. The thickness T of the varnish  12  in the undermost layer of the winding portion that has been impregnated with the varnish  12  is formed so as to be equal to or greater than the thickness of the insulating coating film formed by the powder resin  13 . A bent shape portion  11   a , which is bent outward substantially at a right angle, is formed at a tip end portion of the end plate  11 . As illustrated in  FIG. 4 , the bent size of the bent shape portion  11   a  is set to be equal to or greater than the winding width of the winding portion on the tooth  6   b.    
     By forming the bent shape portion  11   a  at the tip end portion of the end plate  11  so as to have a bent size equal to or greater than the winding width of the winding portion of the tooth  6   b  in this way, it becomes possible to prevent the uncured varnish  12  from leaking out to the radially outward side at the time of the electrical heating for melt-bonding the powder resin  13 . It should be noted that  FIGS. 4A through 4C  illustrate different examples of the bent shape portion  11   a.    
     Next, the bonding process of the power generating coil  7  is described with reference to  FIG. 5 .  FIG. 5  shows block diagrams for illustrating the bonding process of the power generating coil in comparison with techniques known by the inventor.  FIG. 5A  shows a bonding process of the power generating coil according to the first embodiment, and  FIG. 5B  shows techniques known by the inventor. 
     Referring to  FIG. 5A , the stator  2  is preliminarily heated (step S 1 ), and thereafter, the varnish  12  that uses a liquid-type thermosetting resin is supplied to the power generating coil  7  (step S 2 ). Thereafter, in order to melt-bond the powder resin  13 , the winding portion of the power generating coil  7  is heated in a thermostatic chamber (step S 3 ). At this time, the varnish  12  supplied at step S 2  is gelled. The reason why the stator  2  is preliminarily heated at step S 1  is to make the permeability of the varnish  12  better. 
     After the winding portion of the power generating coil  7  has been heated at step S 3 , the stator  2  is immersed in a powder resin bath in which the powder resin  13  is accommodated, so as to melt-bond the powder resin  13  on the surface of the stator  2  (step S 4 ). Thereafter, the stator  2  is heated in the thermostatic chamber, then the powder resin  13  is gelled, and a curing step of the varnish  12  and the powder resin  13  is performed (step S 5 ). 
     Thus, in the method of manufacturing a stator of an electric rotating machine according to the first embodiment, the curing step for the varnish  12  in the bonding process of the power generating coil  7  is performed simultaneously with the heating, melt-bonding, and curing step for the powder resin  13 . As a result, productivity can be remarkably improved. In contrast, in techniques known by the inventor, a gelling and curing step for the varnish  12  (step S 2   a ) is performed after the process of step S 2  of supplying the varnish  12  that uses the liquid-type thermosetting resin to the power generating coil  7 , as shown in  FIG. 5B . That is, the varnish  12  is impregnated and bonded, and thereafter, the winding portion of the power generating coil  7  is heated to melt-bond the powder resin  13 , so that the powder resin  13  is melt-bonded to the surface of the stator  2 . Consequently, productivity is reduced. It should be noted that, according to an experiment by the inventors, a more than 30% time reduction from the conventional method is made possible by simultaneously performing the heat-curing step of the impregnated varnish  12  and the melt-bonding step and curing process of the powder resin  13 , which results in a thermal history corresponding to the curing condition for the varnish  12 . 
     The method of manufacturing a stator of an electric rotating machine according to the first embodiment makes it possible to ensure the coiled wire quality and bonding strength between the coiled wires of the power generating coil  7  and in the winding portion lower layer portion of the power generating coil  7  as well as in the coiled wire surface portion including the coil end portion, and to improve the productivity at the same time. 
     Second Embodiment 
     Next, a method of manufacturing a stator of electric rotating machine according to a second embodiment of this invention will be described below.  FIG. 6  is a detail view of a power generating coil winding portion of a magnet generator according to the second embodiment. 
     The second embodiment is characterized in that, as shown in  FIG. 6 , the film thickness of the insulating film  8  at a radially inward region of the stator core  2  is formed to be thicker than the film thickness thereof at a radially outward region thereof. Specifically, referring to  FIG. 6 , the relationship of the film thickness of the insulating film  8  is set to be T2&gt;T1, where the film thickness at the radially outward region of the stator core  2  is T1 and the film thickness at the radially inward region of the stator core  2  is T2. The other configurations are identical to those in the first embodiment, so the same or corresponding parts are designated by the same reference numerals and the explanations thereof are omitted. 
     When the film thickness of the insulating film  8  at a radially inward region of the stator core  2  is formed to be thicker than the film thickness thereof at a radially outward region thereof as in the second embodiment, the advantageous effects of the first embodiment can be obtained, and also, the varnish  12  can be prevented from leaking out to the radially inward side of the stator core  2  at the time of heating for melt-bonding the powder resin  13 . 
     Third Embodiment 
     Next, a method of manufacturing a stator of electric rotating machine according to a third embodiment of this invention will be described below.  FIG. 7  is a detail view of a power generating coil winding portion of a magnet generator according to the third embodiment. 
     In the third embodiment, an inner circumferential wall  8   a  is formed at a region of the insulating film  8  that is radially inward of the stator core  2  by molding a thermoplastic resin material, as shown in  FIG. 7 . This inner circumferential wall  8   a  is integrally formed with the insulating film  8 . However, it is also possible that the inner circumferential wall  8   a  may be formed separately from the insulating film  8  and then integrated with the insulating film  8 . The other configurations are identical to those in the first embodiment, so the same or corresponding parts are designated by the same reference numerals and the explanations thereof are omitted. 
     When the inner circumferential wall  8   a  is formed at a region of the insulating film  8  that is radially inward of the stator core  2  as in the third embodiment, the advantageous effects of the first embodiment can be obtained, and also, the varnish  12  can be prevented from leaking out to the radially inward side of the stator core  2  during the heating for melt-bonding the powder resin  13 . 
     The first to third embodiments of this invention have been described hereinabove. However, various modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention is not limited to the illustrative embodiments set forth herein.