Patent Publication Number: US-10763730-B2

Title: Insulating resin coating method and stator

Description:
BACKGROUND 
     The present disclosure relates to insulating resin coating methods and stators. 
     Stator having welded portions at the ends of coil wires being coated with an insulating resin are conventionally known in the art. For example, Japanese Patent Application Publication No. 2012-070515 (JP 2012-070515 A) describes such a stator. 
     The stator described in JP 2012-070515 A includes an annular mold portion formed by performing resin molding on entire coil end portions. The coil end portions have welded portions formed by welding the ends of coil wires together. In JP 2012-070515 A, the entire coil end portions are coated with the mold portion, whereby the welded portions are insulation-coated. 
     The configuration in which resin molding is performed on the entire coil end portions as in JP 2012-070515 A is disadvantageous in that a larger amount of material is required for insulation coating and in that coil cooling efficiency is low because the entire coil end portions are covered with resin. 
     Japanese Patent Application Publication No. 2011-223685 (JP 2011-223685 A) describes another configuration for coating welded portions with an insulating resin. A stator described in JP 2011-223685 A has coils formed by welding the ends of a plurality of conductor segments that are formed by rectangular wires. The stator has many welded portions formed by welding the ends of the conductor segments. Each welded portion is insulation-coated by attaching a cap-shaped insulating resin to each welded portion. 
     Unlike the stator of JP 2012-070515 A in which the portions other than the welded portions are also coated with the insulating resin, only the welded portions can be insulation-coated in the stator described in JP 2011-223685 A. The required amount of material can therefore be reduced in the stator of JP 2011-223685 A. 
     SUMMARY 
     In JP 2011-223685 A, however, the individual welded portions formed by welding do not have the same shape (the welded portions do not have the same shape due to variation among coils etc.). It is therefore necessary to use insulating resin caps having a larger size than the welded portions. Namely, it is necessary to fix the insulating resin caps to the welded portions by an adhesive etc. The step of applying the adhesive is therefore required to insulation-coat the welded portions, which reduces productivity. 
     An exemplary aspect of the disclosure provides an insulating resin coating method and a stator in which an insulating resin can be formed only on portions necessary to insulate welded portions without reducing productivity. 
     An insulating resin coating method according to a first aspect of the present disclosure is an insulating resin coating method for coating with an insulating resin a weld of a stator having a plurality of the welds formed by welding ends of coil wires together. The insulating resin coating method includes the steps of: sandwiching and covering the weld of the coil wires by a pair of resin-molding molds; and injecting the resin into the resin-molding molds by a resin injector. 
     As described above, the insulating resin coating method according to the first aspect of the present disclosure includes: the steps of: sandwiching and covering the weld of the coil wires by the pair of resin-molding molds; and injecting the resin into the resin-molding molds by the resin injector. Each weld can thus be insulation-coated by forming the insulating resin only on a portion necessary to insulation-coat the weld by resin molding using the resin-molding molds. The weld can be coated by merely closing the resin-molding molds with the weld sandwiched therebetween and injecting the resin into the resin-molding molds. Accordingly, unlike the case where a cap-shaped insulating resin is attached to each weld, the plurality of welds can be insulation-coated without requiring the step of applying an adhesive. Productivity is therefore not reduced. As described above, according to the present disclosure, the insulating resin can be formed only on portions necessary to insulate the welds without reducing productivity. 
     A stator according to a second aspect of the present disclosure includes: a stator core having a plurality of slots; a plurality of coils formed by coil wires that are inserted into the plurality of slots; a plurality of welds formed by welding ends of the coil wires; and a plurality of insulating coaters formed by resin molding on the welds of the coil wires and coating the plurality of welds. 
     As described above, the stator according to the second aspect of the present disclosure includes the plurality of insulating coaters formed by resin molding on the welds of the coil wires and coating the plurality of welds. Each weld can thus be insulation-coated by forming an insulating resin only on a portion necessary to insulation-coat the weld by resin molding using resin-molding molds. When forming the insulating coater, the weld can be coated by merely closing the resin-molding molds with the weld sandwiched therebetween and injecting the resin into the resin-molding molds. Accordingly, unlike the case where a cap-shaped insulating resin is attached to each weld, the plurality of welds can be insulation-coated without requiring the step of applying an adhesive. Productivity is therefore not reduced. As described above, according to the present disclosure, the stator in which the insulating resin is formed only on portions necessary to insulate the welds can be obtained without reducing productivity. 
     According to the present disclosure, as described above, an insulating resin can be formed only on portions necessary to insulate welds without reducing productivity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a stator according to a first embodiment. 
         FIG. 2A  is a front view of coils that are placed in a stator, and  FIG. 2B  is a plan view thereof. 
         FIG. 3  is a diagram showing an example of a method for connecting coils. 
         FIG. 4  is an enlarged section showing a welded portion and an insulating coating portion of the stator. 
         FIG. 5  is a plan view showing welded portions and insulating coating portions of the stator. 
         FIG. 6  is a schematic enlarged section illustrating a welded portion and an insulating coating portion. 
         FIG. 7  is a perspective view illustrating an insulating resin coating method according to the first embodiment. 
         FIG. 8  is an enlarged section illustrating the step of covering a welded portion by a resin-molding mold. 
         FIG. 9  is an enlarged section illustrating the step of injecting resin into the resin-molding mold by a resin injection portion. 
         FIG. 10  is a plan view illustrating an insulating resin coating method according to a second embodiment. 
         FIG. 11  is a sectional view illustrating an insulating resin coating method according to a third embodiment. 
         FIG. 12  is a schematic view illustrating an insulating resin coating method according to a fourth embodiment. 
         FIG. 13  is a sectional view illustrating a first modification regarding the step of injecting resin into the resin-molding mold. 
         FIG. 14  is a perspective view of a stator illustrating a second modification regarding the direction in which coil wires extend. 
         FIG. 15  is a schematic sectional view illustrating a third modification regarding the resin-molding mold. 
         FIG. 16  is a schematic sectional view illustrating a fourth modification regarding the resin-molding mold. 
         FIG. 17  is a view showing insulating coating portions formed by the resin-molding mold of the fourth modification. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present disclosure will be described below based on the accompanying drawings. 
     First Embodiment 
     The structure of a stator  100  according to a first embodiment will be described with reference to  FIGS. 1 to 6 . 
     (Overall Configuration of Stator) 
     As shown in  FIG. 1 , the stator  100  includes an annular stator core  1  and a plurality of coils  2  arranged in an annular shape along the inner periphery of the stator core  1 . The stator  100  together with a rotor (not shown) is accommodated in a casing (not shown). For example, the stator  100  is mounted on vehicles such as an automobile. 
     For example, the stator core  1  is formed in an annular shape by stacking electrical steel sheets, and includes a plurality of teeth  11  that form slots  13 , and a back yoke  12 . The stator core  1  has a plurality of slots  13 . The stator core  1  includes axial end faces  14  and a radial outer peripheral surface  15 . 
     The plurality of teeth  11  extend in a radial pattern radially inward (toward a central axis Ax) from the back yoke  12 . The teeth  11  are located at regular intervals in the circumferential direction of the stator core  1 . Each slot  13  holding the coils  2  is formed between adjacent two of the teeth  11 . The plurality of slots  13  are formed in the inner periphery of the stator core  1  along the circumference of the stator core  1  and extend in the radial direction. The back yoke  12  is a portion between the outer peripheral surface  15  of the stator core  1  and the radially outer ends of the slots  13  (the ends on the root side of the teeth  11 ) and extends along the circumference of the stator core  1 . The axial end faces  14  are flat surfaces. 
     Hereinafter, the axial direction of the stator core  1  (the direction in which the central axis Ax extends) is referred to as the A direction. Of the A direction, the A1 direction away from the stator core  1  shown in  FIG. 4  is referred to as toward the outside in the axial direction, and the A2 direction toward the stator core  1  is referred to as toward the inside in the axial direction. The radial direction (the direction of the radius) of the stator core  1  is referred to as the R direction. Of the R direction, the R1 direction shown in  FIG. 4  is referred to as toward the outside in the radial direction, and the R2 direction is referred to as toward the inside in the radial direction. The circumferential direction of the stator core  1  is referred to as the C direction. 
     As shown in  FIG. 2 , each coil  2  is formed by a coil wire  20  that is inserted into a plurality of slots  13 . The coil wire  20  is a rectangular wire having a rectangular section. Each coil  2  is formed in a loop shape (shape of concentric winding) by winding a coil wire  20  a plurality of times (e.g., five times) and forming the resultant winding into a predetermined shape. The coil wire  20  is made of a highly conductive metal such as copper. The coil wire  20  has an insulation-coated surface. 
     Each coil  2  has a pair of slot accommodated portions  21  that are accommodated in the slots  13 , a pair of coil end portions  22  that are placed outside the axial end faces  14  of the stator core  1 , and lead wire portions  23  extending so as to project beyond the slots  13 . 
     The pair of slot accommodated portions  21  are formed substantially linearly and are placed in separate slots  13  so as to extend in the axial direction. An insulating sheet (not shown) is placed along the inner wall surface of each slot  13  so that the stator core  1  is insulated from the coil  2  (slot accommodated portions  21 ) by the insulating sheet. The coil end portions  22  are bent to form a substantially triangular shape. The coil end portions  22  are placed so as to project axially outward beyond the axial end faces  14  on both sides of the stator core  1 . The pair of coil end portions  22  connect the ends of the slot accommodated portions  21  that are separated from each other in the circumferential direction. The lead wire portions  23  are one end (winding start) and the other end (winding end) of the coil wire  20  wound a plurality of times. 
     As shown in  FIG. 1 , the stator  100  includes a plurality of welded portions  25  (i.e., welds) formed by welding ends  24  of the coil wires  20  together. The end  24  of each lead wire portion  23  is connected to another coil  2  or a connection terminal by welding. Each welded portion  25  is formed by welding the end  24  of one coil  2  to the end  24  of another coil  2 . In the first embodiment, the stator  100  includes insulating coating portions  30  (i.e., insulating coaters) that coat the plurality of welded portions  25 . 
     The lead wire portions  23  extend radially outward (in the R1 direction) in a radial pattern. Each lead wire portion  23  is placed at the same radial position as, or radially inside, the outer peripheral surface  15  of the stator core  1 , as viewed in the axial direction (see  FIG. 2 ). The “same radial position as, or radially inside, the outer peripheral surface  15 ” means the same radial position as the outer peripheral surface  15  or a radial position located inside the outer peripheral surface  15 . More specifically, the lead wire portions  23  are placed so that the insulating coating portions  30  coating the welded portions  25  of the ends  24  are located at the same radial position as, or radially inside, the outer peripheral surface  15  of the stator core  1 . The welded portions  25  extend in the radial direction of the stator core  1 . Specifically, the welded portions  25  extend toward the outside in the radial direction of the stator core  1  (in the R1 direction). 
     A plurality of coils  2  are placed in each slot  13  of the stator core  1  in the circumferential direction (C direction). The plurality of coils  2  are arranged along the circumference of the stator core  1  so as to form an annular shape along the inner periphery of the stator core  1 . 
     For example, the coils  2  are mounted, as concentric windings, in the stator core  1  so as to implement (A) to (C) described below. 
     (A) The plurality of coils  2  are placed in the slots  13  so as to be displaced by one slot from each other in the circumferential direction. (B) Two coils  2  that are adjacent to each other in the circumferential direction are mounted so that the coil wires  20  of the two coils  2  are alternately arranged in the direction in which the coils  2  are stacked (the radial direction). (C) Two coils  2  of the same phase which are disposed at a predetermined distance from each other in the circumferential direction are mounted so that the coil wires  20  of the slot accommodated portions  21  of the two coils  2  are alternately arranged in the same slot  13  in the direction in which the coils  2  are stacked (the radial direction). 
     For example, in the case where the stator  100  is a three-phase alternating current (AC) motor, the coils  2  of the same phase mean U-phase coils, V-phase coils, or W-phase coils. In this case, the coils  2  are arranged in a repeated pattern of two U-phase coils, two V-phase coils, and two W-phase coils in the circumferential direction C. 
     For example, the coils  2  of each phase are connected in a Y configuration (star configuration) shown in  FIG. 3 .  FIG. 3  shows a configuration of four parallel coil rows per phase. For example, for U-phase, four rows of a plurality of (e.g., eight) coils  2  connected in series (coil rows L) are connected in parallel. In each coil row L, the ends  24  of the lead wire portions  23  of the eight coils  2  connected in series are welded together to form seven welded portions  25 . 
     The lead wire portion  23  at one end of each coil row L serves as a power line P and is connected to an external circuit. The lead wire portion  23  at the other end of each coil row L serves as a neutral line N and is connected to a neutral point. 
     (Structure of Welded Portion and Insulating Coating Portion) 
     The structure of the welded portion  25  and the insulating coating portion  30  will be described. 
     In the first embodiment, the ends  24  of the lead wire portions  23  (coil wires  20 ) which are welded together are arranged in a radial pattern toward the outside in the radial direction and are placed on top of each other in the axial direction. Specifically, as shown in  FIGS. 4 and 5 , one lead wire portion  23  is extended from the inside in the radial direction toward the outside in the radial direction (in the R1 direction) across the coil end portions  22 . The other lead wire portion  23  stands in the axial direction (the A1 direction) from the slot  13  at an outer position in the radial direction and is bent radially outward. The ends  24  thus placed on top of each other are welded together to form the welded portion  25 . The welded portion  25  is located at a position away from the axial end face  14  toward the outside in the axial direction (in the A1 direction). 
     The insulating coating portion  30  is formed by resin molding so as to cover the welded portion  25  of the coil wires  20  (lead wire portions  23 ). The insulating coating portion  30  is not formed in the coil end portions  22 . As shown in  FIG. 4 , the insulating coating portion  30  (welded portion  25 ) is located at a position away from the axial end face  14  by a distance D 1  toward the outside in the axial direction. The distance D 1  is approximately equal to the amount by which the coil end portions  22  project. 
     As shown in  FIG. 5 , the insulating coating portion  30  is formed on each of the plurality of welded portions  25  located at intervals in the circumferential direction (the C direction). In the first embodiment, the welded portions  25  are arranged in the circumferential direction of the stator  100  along the entire circumference, and the plurality of insulating coating portions  30  are formed on all of the welded portions  25 . The plurality of insulating coating portions  30  are located at intervals in the circumferential direction of the stator core  1 . That is, the insulating coating portions  30  are arranged so as not to contact each other. In the first embodiment, a circumferential interval D 2  between adjacent ones of the insulating coating portions  30  is larger than the circumferential width W of the insulating coating portion  30 . 
     As shown in  FIG. 6 , each lead wire portion  23  (coil wire  20 ) has an end  24  from which an insulating coating  20   a  has been removed, so that a conductor wire in the lead wire portion  23  is exposed at the end  24 , and the welded portion  25  is formed on the exposed part. That is, each lead wire portion  23  (coil wire  20 ) includes an uncoated part  20   b  from which the insulating coating  20   a  has been removed, and a coated part  20   c  covered with the insulating coating  20   a . The uncoated part  20   b  is formed by removing the insulating coating  20   a  of the end  24 . The welded portion  25  is formed on the uncoated parts  20   b.    
     The insulating coating portion  30  is formed by resin molding so as to cover the entire exposed parts of the conductor wires (the entire uncoated parts  20   b ) including the welded portion  25  and a part of the coated parts  20   c  (parts having the insulating coating  20   a  formed thereon) adjoining the uncoated parts  20   b . In other words, the insulating coating portion  30  is formed on the ends  24  of the lead wire portions  23  (coil wires  20 ) so as to surround and cover the outer peripheral surfaces of the welded portion  25 , the uncoated parts  20   b , and a part of the coated parts  20   c . As shown in  FIG. 4 , the insulating coating portion  30  is formed so as to cover the range of a predetermined distance from the ends  24  (welded portion  25 ) of the lead wire portions  23  (coil wires  20 ) to the coil end portions  22 . The insulating coating portion  30  is formed so as to cover a part of the ends  24  of the lead wire portions  23  (coil wires  20 ) which project beyond the coil end portions  22 . 
     The welded portion  25  formed on the ends  24  of the lead wire portions  23  does not have a linear rectangular section but has a roughly spherical shape due to expansion and melting during melting (the shape of the welded portion  25  is shown simplified in  FIG. 5 ). An insulating resin that forms the insulating coating portion  30  is formed so as to surround the welded portion  25  by resin molding. The insulating resin around the welded portion  25  thus engages with the welded portion  25 , thereby functioning as a retainer for the insulating coating portion  30 . The resin thickness (coating thickness) of the insulating coating portion  30  is, e.g., about 0.5 mm. 
     The insulating coating portion  30  is formed so as to cover the welded portion  25  and to fill at least a part of the space between facing surfaces  20   d  of the ends  24  of the pair of coil wires  20  connected by the welded portion  25 . As shown in  FIG. 6 , when placing the pair of coil wires  20  next to each other to weld their ends  24  together, clearance S is created between the facing surfaces  20   d  of the uncoated parts  20   b  because the uncoated parts  20   b  are thinner by an amount corresponding to the removed insulating coating  20   a . Since the insulating coating portion  30  is also formed in the clearance S by resin molding, the insulating coating portion  30  includes an inner coating portion  30   a  that fills at least a part of the space between the facing surfaces  20   d .  FIG. 6  shows an example in which the clearance S is filled with the resin and the resin covers the entire facing surfaces  20   d . However, the insulating coating portion  30  (inner coating portion  30   a ) may cover only a part of the facing surfaces  20   d.    
     A resin material that is used for the insulating coating portion  30  is preferably a resin material having insulation properties and such heat resistance that the insulating coating portion  30  withstand an increase in temperature of the coil wires  20  which occurs when a current is applied to the stator  100 . Examples of the resin material that is used for the insulating coating portion  30  include polyphenylenesulfide (PPS) and liquid crystal polymer (LCP). The insulating coating portion  30  has an injection mark  31  caused by resin molding at a position corresponding to an injection passage (gate) of a resin-molding mold  51  described below (see  FIG. 7 ). Although the first embodiment shows an example in which the outer shape of the insulating coating portion  30  is a prism corresponding to the pair of coil wires  20  formed by rectangular wires, the outer shape of the insulating coating portion  30  may be other than a prism. 
     (Insulating Resin Coating Method) 
     A method for coating the welded portions  25  of the stator  100  with an insulating resin will be described with reference to  FIGS. 7 to 9 . 
     The insulating resin coating method according to the first embodiment is performed with a coating device  50  shown in  FIG. 7 . The coating device  50  includes a resin-molding mold  51 , a resin injection portion  52  (i.e., resin injector), and a support portion  53 . 
     The resin-molding mold  51  is formed by a pair of a first mold (lower mold)  61  and a second mold (upper mold)  62 . As shown in  FIG. 8 , the first mold  61  and the second mold  62  are placed so as to face each other in the axial direction (A direction). The first mold  61  is placed on the inner side in the axial direction (the stator core  1  side), and the second mold  62  is placed on the outer side in the axial direction (the A1 direction side). The first mold  61  and the second mold  62  have, in their facing surfaces (inner surfaces), a cavity (molding recess)  63  corresponding to the shape of the insulating coating portion  30 . The second mold  62  has a positioning recess  64  and an injection passage  65  that allows the positioning recess  64  to communicate with the cavity  63 . The pair of resin-molding molds  51  (the first mold  61  and the second mold  62 ) can sandwich and cover a single welded portion  25 . The first mold  61  and the second mold  62  can independently move in the axial direction to perform a mold closing operation and a mold opening operation. 
     The resin injection portion  52  is placed axially outside (on the A1 direction side of) the second mold  62  and can move in the axial direction. The resin injection portion  52  ejects molten resin from an injection port  52   a  formed at its tip end. With the injection port  52   a  connected to the positioning recess  64  of the second mold  62 , the resin injection portion  52  ejects the molten resin from the injection port  52   a , thereby injecting the molten resin into the cavity  63  through the injection passage  65 . Since the insulating coating portion  30  is thin (e.g., about 0.5 mm), only a small amount of resin need be injected. The molten resin cures quickly because the amount of resin injected is small and the coil wires  20  placed in the cavity  63  are made of a metal material with high thermal conductivity such as copper. 
     The resin-molding mold  51  and the resin injection portion  52  can be moved toward and away from the stator  100  in the radial direction (R direction) by a moving mechanism, not shown. 
     As shown in  FIG. 7 , the support portion  53  is a support base that engages with attachment holes  1   a  of the stator core  1  and holds the stator core  1 . The support portion  53  can be operated by a drive mechanism, not shown, to rotate the stator core  1  about the central axis Ax in the circumferential direction (C direction). 
     Each step of the insulating resin coating method according to the first embodiment is performed by the above configuration. The insulating resin coating method according to the first embodiment roughly includes the steps of sandwiching and covering the welded portion  25  of the coil wires  20  by the pair of resin-molding molds  51  (the first mold  61  and the second mold  62 ) and injecting resin into the resin-molding mold  51  by the resin injection portion  52 . Each of the steps will be described in detail below. 
     &lt;Step of Covering the Welded Portion by the Resin-Molding Mold&gt; 
     As shown in  FIG. 7 , in the step of sandwiching and covering the welded portion  25  of the coil wires  20  by the pair of resin-molding molds  51  (the first mold  61  and the second mold  62 ), the resin-molding mold  51  and the resin injection portion  52  are moved radially inward (in the R2 direction) from a radially outer position with respect to the stator  100  having been subjected to a welding process (having the welded portions  25  formed therein) and having been placed on the support portion  53 . The resin-molding mold  51  and the resin injection portion  52  thus get closer to the stator  100 . At this time, the first mold  61  and the second mold  62  are located away from each other in the axial direction with the first mold  61  being placed axially inside (on the stator core  1  side of) the welded portion  25  and the second mold  62  being placed axially outside the welded portion  25  (see  FIG. 8 ). 
     Thereafter, as shown in  FIG. 9 , the first mold  61  and the second mold  62  are moved toward each other in the axial direction to close the mold. The welded portion  25  is thus accommodated in the cavity  63  of the resin-molding mold  51  and sandwiched and covered by the pair of resin-molding molds  51  (the first mold  61  and the second mold  62 ). 
     In the first embodiment, the step of sandwiching and covering the welded portion  25  of the coil wires  20  by the pair of resin-molding molds  51  is performed by covering by the resin-molding mold  51  the uncoated parts  20   b  of the coil wires  20  which include the welded portion  25  and the parts of the coil wires  20  which adjoin the uncoated parts  20   b  and which have the insulating coating  20   a  formed thereon (a part of the coated parts  20   c ). That is, the welded portion  25 , the uncoated parts  20   b , and a part of the coated parts  20   c  of the ends  24  of the lead wire portions  23  (coil wires  20 ) are accommodated in the cavity  63  of the resin-molding mold  51 . As shown in  FIGS. 8 and 9 , the pair of resin-molding molds  51  (the first mold  61  and the second mold  62 ) cover the range of a predetermined distance from the ends  24  (welded portion  25 ) of the lead wire portions  23  (coil wires  20 ) to the coil end portions  22 . The pair of resin-molding molds  51  (the first mold  61  and the second mold  62 ) also cover a part of the ends  24  of the lead wire portions  23  (coil wires  20 ) which project beyond the coil end portions  22 . 
     &lt;Step of Injecting Resin into the Resin-Molding Mold by the Resin Injection Portion&gt; 
     As shown in  FIG. 9 , in the step of injecting resin, the resin injection portion  52  is moved toward the resin-molding resin  51  (in the A2 direction) so that the injection port  52   a  is connected to the positioning recess  64  of the second mold  62 . The resin injection portion  52  ejects molten resin from the injection port  52   a  to inject the molten resin into the cavity  63  through the injection passage  65 . 
     The step of injecting resin is thus performed by injecting resin into the resin-molding mold  51  in the direction that crosses (is perpendicular to) the direction in which the coil wires  20  extend (the radial direction of the stator  100 ). That is, the resin injection portion  52  injects resin into the resin-molding mold  51  in the axial direction (A direction) from the outside in the axial direction (A1 direction side) of the stator  10 . 
     After the resin is injected into the cavity  63 , the resin injection portion  52  is moved away from the resin-molding mold  51  (in the A1 direction) so that the injection port  52   a  is separated from the positioning recess  64  of the second mold  62 , as shown in  FIG. 8 . The first mold  61  and the second mold  62  are then moved away from each other in the axial direction to open the resin-molding mold  51 . By the time the mold is opened, the resin in the cavity  63  cures to form the insulating coating portion  30 . Insulation coating of a single welded portion  25  (located at one position) is thus completed. 
     &lt;Step of Rotating the Stator and the Resin Injection Portion Relative to Each Other in the Circumferential Direction of the Stator&gt; 
     The insulating resin coating method according to the first embodiment may further include the step of rotating the stator  100  and the resin injection portion  52  relative to each other in the circumferential direction of the stator  100 . In the first embodiment, the step of rotating the stator  100  and the resin injection portion  52  relative to each other is performed by rotating the stator  100  relative to the resin injection portion  52 . 
     That is, as shown in  FIG. 7 , the support portion  53  rotates the stator  100  about the central axis Ax in the circumferential direction (C direction). The support portion  53  rotationally moves the stator  100  in the circumferential direction by an amount corresponding to a single welded portion (hereinafter referred to as incrementally moves the stator  100 ). As a result, the insulation-coated welded portion  25  (insulating coating portion  30 ) is moved from between the first mold  61  and the second mold  62  which are separated from each other in the axial direction, and the subsequent welded portion  25  to be insulation-coated is slid in the circumferential direction to a mold closing position between the first mold  61  and the second mold  62 . 
     Subsequently, the welded portion  25  thus placed between the first mold  61  and the second mold  62  is subjected to the step of covering the welded portion  25  by the resin-molding mold  51  and the step of injecting resin into the resin-molding mold  51 . The insulation coating process is thus performed. 
     Each of the plurality of welded portions  25  is coated with an insulating resin by repeatedly performing the step of covering the welded portion  25  by the resin-molding mold  51  and the step of injecting resin while incrementally moving the stator  100  in the circumferential direction (C direction). The process is completed when the insulation coating process is repeated for all of the welded portions  25  that are to be subjected to the insulation coating process. 
     (Effects of First Embodiment) 
     The first embodiment has the following effects. 
     As described above, the method of the first embodiment includes the step of sandwiching and covering the welded portion  25  of the coil wires  20  by the pair of resin-molding molds  51  (the first mold  61  and the second mold  62 ) and the step of injecting resin into the resin-molding mold  51  by the resin injection portion  52 . Each welded portion  25  can thus be insulation-coated by forming an insulating resin (insulating coating portion  30 ) only on a portion necessary to insulation-coat the welded portion  25  by resin molding using the resin-molding mold  51 . The welded portion  25  can be coated by merely closing the resin-molding mold  51  with the welded portion  25  sandwiched in the middle and injecting resin into the resin-molding mold  51 . Accordingly, unlike the case where a cap-shaped insulating resin is attached to each welded portion  25 , the plurality of welded portions  25  can be insulation-coated without requiring the step of applying an adhesive. Productivity is therefore not reduced. As described above, according to the first embodiment, the insulating resin (insulating coating portion  30 ) can be formed only on portions necessary to insulate the welded portions  25  without reducing productivity. The amount of resin material required and the size (area) of the portion to be coated with resin can thus be reduced as compared to the case where, e.g., the entire coil end portions  22  including the welded portion  25  need be coated with an insulating resin by powder coating. The stator  100  having improved cooling efficiency for the coils  2  when in use can thus be obtained. 
     As described above, in the first embodiment, the step of sandwiching and covering the welded portion  25  by the pair of resin-molding molds  51  (the first mold  61  and the second mold  62 ) may be performed by covering the uncoated parts  20   b  of the coil wires  20  which include the welded portion  25 , and the parts of the coil wires  20  which adjoin the uncoated parts  20   b  and which have the insulating coating  20   a  formed thereon (a part of the coated parts  20   c ), by the resin-molding mold  51 . With this configuration, the insulating resin (insulating coating portion  30 ) can be formed so as to completely coat those regions of the ends  24  of the coil wires  20  from which the insulating coating  20   a  has been removed (the uncoated parts  20   b ). This can more reliably ensure insulation of the welded portions  25 . 
     As described above, in the first embodiment, the step of rotating the stator  100  and the resin injection portion  52  relative to each other in the circumferential direction of the stator  100  may further be included. With this configuration, closing of the resin-molding mold  51  and injection of resin can be sequentially performed for one or more welded portions by rotating the stator  100  and the resin injection portion  52  relative to each other in the circumferential direction of the stator  100 . As a result, the device configuration can be simplified and the insulating resin (insulating coating portion  30 ) can be easily formed as compared to the case where, e.g., the insulating coating portion  30  is formed on all of the welded portions  25  at a time. 
     As described above, in the first embodiment, each of the plurality of welded portions  25  may be coated with the insulating resin (insulating coating portion  30 ) by repeatedly performing the step of sandwiching and covering the welded portion  25  by the pair of resin-molding molds  51  (the first mold  61  and the second mold  62 ) and the step of injecting resin. With this configuration, the plurality of welded portions  25  can be sequentially insulation-coated easily and quickly by merely repeatedly performing the step of covering the welded portion  25  by the resin-molding mold  51  and the step of injecting resin while shifting the welded positions  25  by the step of rotating the stator  100  and the resin injection portion  52  relative to each other in the circumferential direction of the stator  100 . 
     As described above, in the first embodiment, the step of rotating the stator  100  and the resin injection portion  52  relative to each other may be performed by rotating the stator  100  relative to the resin injection portion  52 . With this configuration, the resin-molding mold  51  and the resin injection portion  52  need not be moved in the circumferential direction (C direction) of the stator  100 , whereby the device configuration of the coating device  50  that is used for the insulation coating process can be simplified. 
     As described above, in the first embodiment, the step of injecting resin may be performed by injecting resin into the resin-molding mold  51  in the direction crossing the direction in which the coil wires  20  extend (the radial direction). With this configuration, the surface of the ends  24  of the coil wires  20  which faces the direction crossing the direction in which the coil wires  20  extend can be reliably coated with resin. Of the outer peripheral surfaces of the ends  24  of the coil wires  20  including the welded portion  25 , the outer (axially outer) surface on which an external device etc. is to be placed can be more reliably insulation-coated. 
     As described above, in the first embodiment, the direction in which the coil wires  20  extend may be the radial direction (R direction) of the stator  100  and the resin injection portion  52  may inject resin into the resin-molding mold  51  in the axial direction from the outside in the axial direction (A direction) of the stator  100 . With this configuration, since resin is injected in the axial direction, the installation area of the coating device  50  on a plane in the radial direction of the stator  100  can be reduced. Moreover, the direction in which the stator  100  is rotated relative to the resin injection portion  52  (the circumferential direction) can be made different from the direction in which the resin injection portion  52  is operated to inject resin (the axial direction). The insulation coating process for the plurality of welded portions  25  can be efficiently performed by merely rotating the stator  100  in the circumferential direction while withdrawing the resin-molding mold  51  and the resin injection portion  52  in the axial direction. 
     As described above, in the first embodiment, the welded portions  25  may be formed so as to extend in the radial direction of the stator core  1  and the plurality of insulating coating portions  30  may be located at intervals in the circumferential direction of the stator core  1 . With this configuration, the insulating coating portions  30  for the individual welded portions  25  can be individually formed on necessary portions. Accordingly, insulation can be more effectively ensured. In the case where the welded portions  25  extend in a radial pattern in the radial direction, the circumferential intervals between the welded portions  25  are large. In this case, if all of the plurality of welded portions  25  are coated with a single insulating coating portion  30 , a larger amount of resin material is required because an insulating resin need also be formed in the circumferential spaces between the welded portions  25 . However, since the insulating coating portions  30  are formed at intervals in the circumferential direction, the required amount of resin material can be reduced. 
     As described above, in the first embodiment, the insulating coating portion  30  may be formed so as to fill at least a part of the space (clearance S) between the facing surfaces  20   d  of the ends  24  of the pair of coil wires  20  connected by the welded portion  25 . With this configuration, the insulating resin (inner coating portion  30   a ) formed in the clearance S between the facing surfaces  20   d  can function as a retainer that engages with the welded portion  25 . The insulating coating portion  30  can thus be stably prevented from coming off. 
     In the case where the stator  100  is subjected to vibration such as in the case where the stator  100  is mounted on a vehicle such as an automobile, the pair of coil wires  20  welded together may be subjected to an external force in the direction in which the pair of coil wires  20  are separated from each other along a contact portion  26  therebetween (see  FIG. 6 ). If the coil wires  20  are separated from each other along the contact portion  26 , there is a risk that the facing surfaces  20   d  may be exposed to the outside in the clearance S. However, since the facing surfaces  20   d  are covered with the insulating resin (inner coating portion  30   a ) formed in the clearance S, it is ensured that the facing surfaces  20   d  (uncoated parts  20   b ) are insulated from iron powder etc. that are present around the facing surfaces  20   d  (uncoated parts  20   b ) and on external peripheral members, even if the coil wires  20  are separated from each other along the contact portion  26  due to external factors. 
     Second Embodiment 
     A second embodiment of the present disclosure will be described with reference to  FIG. 10 . Unlike the first embodiment showing an example in which the insulating coating portion  30  is formed on each welded portion  25  by a single resin injection portion  52 , the second embodiment will be described with respect to an example in which formation of insulating coating portions  30  is performed in parallel by a plurality of resin injection portions  52 . Since the configuration of a stator  100  of the second embodiment is similar to the first embodiment, description thereof will be omitted. 
     In an insulating resin coating method according to the second embodiment, the step of injecting resin is performed in parallel for each of a plurality of resin-molding molds  51  by a plurality of resin injection portions  52  arranged in the circumferential direction (C direction) of the stator  100 . 
     Specifically, as shown in  FIG. 10 , a coating device  150  includes a plurality of resin injection portions  52  and resin-molding molds  51  arranged in the circumferential direction (C direction) of the stator  100 . 
       FIG. 10  shows an example in which the coating device  150  includes four sets of resin injection portion  52  and resin-molding mold  51 . The coating device  150  may include a plurality of sets of resin injection portion  52  and resin-molding mold  51  other than four sets, and the number of resin injection portions  52  and resin-molding molds  51  can be determined within the range in which the resin injection portions  52  do not interfere with each other. Since the step of injecting resin is performed in parallel by the resin injection portions  52 , it is preferable in terms of efficiency that the number of resin injection portions  52  be a number that can divide the number of welded portions  25  to be insulation-coated without remainder. For example, in the case where four resin injection portions  52  are provided for a total of 96 welded portions  25 , the step of injecting resin need only be repeated 24 times. However, if the number of welded portions  25  is indivisible by the number of resin injection portions  52  and there is a remainder of the welded portions  25 , the step of injecting resin need be performed the number of times equal to the quotient plus one. 
     It is preferable that the plurality of resin injection portions  52  be arranged at regular angular intervals in the circumferential direction (C direction) of the stator  100 . This allows the same number of welded portions  25  to be assigned to each of the resin injection portions  52  when the stator  100  is incrementally moved in the circumferential direction such that each welded portion  25  is shifted by one. 
     The structures of the resin injection portion  52  and the resin-molding mold  51  are similar to the first embodiment. The configuration of the second embodiment is otherwise similar to the first embodiment. 
     (Effects of Second Embodiment) 
     In the second embodiment, as in the first embodiment, each welded portion  25  can be insulation-coated by forming an insulating resin (insulating coating portion  30 ) only on a portion necessary to insulation-coat the welded portion  25 , and the plurality of welded portions  25  can be insulation-coated by resin molding without requiring the step of applying an adhesive. An insulating resin (insulating coating portion  30 ) can thus be formed only on portions necessary to insulate the welded portions  25  without reducing productivity. 
     As described above, in the second embodiment, the step of injecting resin may be performed in parallel for each of the plurality of resin-molding molds  51  by the plurality of resin injection portions  52  arranged in the circumferential direction of the stator  100 . With this configuration, the insulation coating process can be performed for the plurality of welded portions  25  at a time. The insulation coating process can thus be efficiently performed without reducing productivity, even when the individual welded portions  25  are insulation-coated. 
     In particular, since the direction in which the coil wires  20  extend is the radial direction (R direction) of the stator  100  and the resin injection portions  52  inject resin into the resin-molding molds  51  in the axial direction from the outside in the axial direction (A direction) of the stator  100 , all of the plurality of welded portions  25  can be located at the mold closing positions of the resin-molding molds  51  by merely rotationally moving the stator  100  in the circumferential direction. Since the plurality of resin-molding molds  51  and resin injection portions  52  need not be moved in the circumferential direction, the insulation coating process can be more efficiently performed. 
     Other effects of the second embodiment are similar to the first embodiment. 
     Third Embodiment 
     A third embodiment of the present disclosure will be described with reference to  FIG. 11 . Unlike the first embodiment showing an example in which the insulation coating process is performed for the stator  100  having the welded portions  25  formed in advance (having been subjected to a welding process), the third embodiment will be described with respect to an example in which formation of a welded portion  25  (welding process) and formation of an insulating coating portion  30  (insulation coating process) are performed in parallel. Since the configuration of a stator  100  according to the third embodiment is similar to the first embodiment, description thereof will be omitted. 
     An insulating resin coating method according to the third embodiment includes the step of forming a welded portion  25  by welding ends of coil wires  20  with a welding torch  211  positioned at a position different from a resin injection portion  52  in the circumferential direction of the stator  100 , and the step of forming the welded portion  25  is performed in parallel with the step of injecting resin. 
     Specifically, as shown in  FIG. 11 , a welding device  210  is disposed in addition to a coating device  50 . The welding device  210  includes the welding torch  211 . Since a known configuration can be used for the welding device  210 , description thereof will be omitted. 
     For example, the welding device  210  is placed at a position on the opposite side (the position shifted by 180 degrees) from the resin injection portion  52  and the resin-molding mold  51  in the circumferential direction (C direction). With ends  24  of a pair of coil wires  20  to be welded together being held with a clamp mechanism, not shown, the welding device  210  welds the ends with the welding torch  211 . The welded portion  25  is formed in this manner. 
     In the third embodiment, the stator  100  having not been subjected to the welding process (having no welded portion  25  formed therein) is placed on a support portion  53 . As shown in  FIG. 11 , in the case where the welding torch  211  and the resin injection portion  52  are arranged at positions shifted by 180 degrees from each other, the welding process using the welding torch  211  is first started. After the stator  100  makes half a rotation, the insulation coating process with the resin injection portion  52  and the resin-molding mold  51  is started. After the stator  100  makes half a rotation, formation of the welded portion  25  with the welding torch  211  and insulation coating of the welded portion  25  with the resin injection portion  52  and the resin-molding mold  51  are performed in parallel. 
     As in the second embodiment, a plurality of the welding torches  211  and a plurality of resin injection portions  52  and resin-molding molds  51  may be arranged in the circumferential direction (C direction). In this case, the number of welding torches  211  may be the same as the number of resin injection portions  52  and the number of resin-molding molds  51 , and the welding torches  211  and the resin injection portions  52  and the resin-molding molds  51  may be alternately arranged in the circumferential direction. This arrangement makes a plurality of pairs of welding torch  211  and resin injection portion  52 . Accordingly, after the welded portions  25  are formed with the welding torches  211 , the welded portions  25  can be simultaneously insulation-coated at a plurality of positions with the pairs of resin injection portion  52  and resin-molding mold  51  as the stator  100  is rotated in the circumferential direction. 
     The configuration of the third embodiment is otherwise the same as the first embodiment. 
     (Effects of Third Embodiment) 
     In the third embodiment, as in the first embodiment, each welded portion  25  can be insulation-coated by forming an insulating resin (insulating coating portion  30 ) only on a portion necessary to insulation-coat the welded portion  25 , and the plurality of welded portions  25  can be insulation-coated by resin molding without requiring the step of applying an adhesive. An insulating resin (insulating coating portion  30 ) can thus be formed only on portions necessary to insulate the welded portions  25  without reducing productivity. 
     As described above, in the third embodiment, the insulating resin coating method may include the step of forming the welded portion  25  by welding the ends  24  of the coil wires  20  with the welding torch  211  positioned at a position different from the resin injection portion  52  in the circumferential direction (C direction) of the stator  100 , and the step of forming the welded portion  25  may be performed in parallel with the step of injecting resin. With this configuration, the step of injecting resin (insulation coating process) and the welding step can be performed at the same time without transferring the stator  100  to individual facilities. This can achieve reduction in size of a production facility for the stator  100  and improvement in productivity. 
     Other effects of the third embodiment are similar to the first embodiment. 
     Fourth Embodiment 
     A fourth embodiment of the present disclosure will be described with reference to  FIGS. 8 and 12 . Unlike the first embodiment showing an example in which the insulation coating process is performed with the plurality of welded portions  25  being individually covered by the resin-molding mold  51 , the fourth embodiment will be described with respect to an example in which an insulation coating process is performed with a plurality of welded portions  25  being covered by a common resin-molding mold  351 . Since the configuration of a stator  100  according to the fourth embodiment is similar to the first embodiment, description thereof will be omitted. 
     As shown in  FIG. 12 , in an insulating resin coating method according to the fourth embodiment, the step of sandwiching and covering a welded portion by a pair of resin-molding molds is performed by covering a plurality of welded portions  25  by a common resin-molding mold  351 . In the fourth embodiment as well, the resin-molding mold  351  is formed by a first mold and a second mold, and description of the first mold and the second mold will be omitted. The shape of the welded portions  35  is shown simplified in  FIG. 12  for convenience. 
     In the fourth embodiment, the resin-molding mold  351  can cover a plurality of welded portions  25  at a time.  FIG. 12  shows an example in which the resin-molding mold  351  has five cavities  63  so that the resin-molding mold  351  can cover five welded portions  25 . The resin-molding mold  351  further has five injection passages  65  communicating with the five cavities  63 . The resin-molding mold  351  may be configured to cover a plurality of welded portions  25  more or less than five welded portions. 
     In the fourth embodiment, five resin injection portions  52  (see  FIG. 8 ) may be provided so as to correspond to the five injection passages  65  (cavities  63 ), or the number of resin injection portions  52  may be smaller than the number of injection passages  65 . For example, in the case where only one resin injection portion  52  is provided, the resin injection portion  52  is configured so that the resin injection portion  52  can move with respect to the resin-molding mold  351 . In this case, injection of resin can be performed at the positions of the five injection passages  65  by moving the resin injection portion  52  in the circumferential direction (C direction). Alternatively, the resin-molding mold  351  may be configured so that the resin-molding mold  351  together with the stator  100  is incrementally moved in the circumferential direction to position each injection passage  65  at the injection position of the resin injection portion  52 . 
     The resin-molding mold  351  may have a single injection passage  65  branched to be connected to each cavity  63 . In this case, as in the first embodiment, resin can be injected into all the cavities  63  at a time by a single resin injection portion  52 . 
     The configuration of the fourth embodiment is otherwise similar to the first embodiment. 
     (Effects of Fourth Embodiment) 
     In the fourth embodiment, as in the first embodiment, each welded portion  25  can be insulation-coated by forming an insulating resin (insulating coating portion  30 ) only on a portion necessary to insulation-coat the welded portion  25 , and the plurality of welded portions  25  can be insulation-coated by resin molding without requiring the step of applying an adhesive. An insulating resin (insulating coating portion  30 ) can thus be formed only on portions necessary to insulate the welded portions  25  without reducing productivity. 
     In the fourth embodiment, as described above, the step of sandwiching and covering the welded portion by the pair of resin-molding molds may be performed by covering a plurality of welded portions  25  by the common resin-molding mold  351 . With this configuration, a mold closing operation and a mold opening operation can be performed for a plurality of welded portions  25  at a time. The number of times the mold closing operation and the mold opening operation are performed can thus be reduced as compared to the case where the mold closing operation and the mold opening operation are performed for the individual welded portions  25  one by one. Productivity can therefore be improved. 
     Other effects of the fourth embodiment are similar to the first embodiment. 
     For example, the first to fourth embodiments are described with respect to an example in which the stator  100  is rotated in the circumferential direction in the step of rotating the stator  100  and the resin injection portion  52  relative to each other in the circumferential direction (C direction) of the stator  100 . However, the present disclosure is not limited to this. In the present disclosure, the resin injection portion  52  (and the resin-molding molds  51 ,  351 ) may be rotated (turned) in the circumferential direction, or both the stator  100  and the resin injection portion  52  (and the resin-molding mold  51 ,  351 ) may be rotationally moved in the circumferential direction. 
     The first to fourth embodiments are described with respect to an example in which the resin injection portion  52  injects resin into the resin-molding mold  51  ( 351 ) in the axial direction (A direction) crossing the direction in which the coil wires  20  extend (the radial direction). However, the present disclosure is not limited to this. In the present disclosure, as in a first modification shown in  FIG. 13 , the resin injection portion  52  may inject resin in the direction parallel to the direction in which the coil wires  20  extend (the radial direction). In this case, the resin-molding mold  51  includes a first mold  461  and a second mold  462  according to the direction in which resin is injected. The second mold  462  has an injection passage  65  extending in the radial direction to a radial (R direction) outer end. 
     The first to fourth embodiments are described with respect to an example in which the ends  24  of the coil wires  20  (lead wire portions  23 ) are formed to extend in the radial direction (R direction) of the stator core  1 . However, the present disclosure is not limited to this. As shown in a second modification of  FIG. 14 , the present disclosure may be applied to a stator  500  in which the ends  24  of the coil wires  20  (lead wire portions  23 ) are formed to extend in the axial direction (A direction) of the stator core  1 . In the stator  500 , the end  24  of each coil wire  20  (lead wire portion  23 ) is bent to extend axially outward. 
     The fourth embodiment is described with respect to an example in which an insulating coating process is performed by using the resin-molding mold  351  having five cavities  63 , namely the same number of cavities  63  as the number of (five) welded portions  25  to be insulation-coated at a time. However, the present disclosure is not limited to this. In the present disclosure, as shown in a third modification of  FIG. 15 , the number of cavities may be smaller than the number of welded portions  25 . 
     A resin-molding mold  551  shown in  FIG. 15  has a single cavity  63  for three welded portions  25 . The three welded portions  25  are insulation-coated at a time in the cavity  63  by injection of resin through an injection passage  65 . An insulating coating portion  530  in the example of  FIG. 15  has the shape of a wide plate so as to cover three welded portions  25 . A plurality of welded portions  25  more or less than three may be insulation-coated at a time. The resin-molding mold  551  may have one or more cavities  63 . 
     Alternatively, all of the welded portions  25  (along the entire circumference) of the stator  100  may be subjected to resin molding at a time with a resin-molding mold. In this case, the step of rotating the stator  100  and the resin injection portion  52  relative to each other in the circumferential direction (C direction) of the stator  100  is not required. 
     The configuration in which a plurality of welded portions  25  are insulation-coated at a time as described above is effective in the case where it is difficult to individually place a resin-molding mold due to a small interval D 3  between the ends  24  of adjacent ones of the coil wires  20 . By arranging the ends  24  in groups of one or more (three) so that each group is insulation-coated at a time as shown in  FIG. 15 , an interval for placing a resin-molding mold can be reliably provided between the groups. 
     The fourth embodiment is described with respect to an example in which the injection passages  65  are placed on the upper surfaces of the cavities  63  when a plurality of welded portions  25  are covered by the common resin-molding mold  351  to perform the insulating coating process. However, the present disclosure is not limited to this. As in a fourth modification shown in  FIG. 16 , a resin-molding mold  651  may have a runner (connection passage)  666  connecting adjacent cavities  663 , and an injection passage  665  may be connected to the runner  666 . In this case, it is preferable that the runner  666  be located at a position inside (axially or radially inside) the outer (axially or radially outer) inner wall surfaces of the cavities  663 . 
       FIG. 16  shows an example in which the injection passage  665  extends in the axial direction (A direction) (see  FIG. 8 ). The runner  666  is located at a position axially inside (on the A2 direction side of) axially outer (A1 direction side) upper surfaces  664  of the cavities  663 . That is, the runner  666  is located at a position lower than the upper surfaces  664  of the cavities  663  in the axial direction. It is preferable that an axial distance D 61  between the runner  666  and the upper surface  664  of each cavity  663  be equal to or greater than a length L 61  of the injection passage  665 . 
     In the configuration like the fourth modification, as shown in  FIG. 17 , adjacent insulating coating portions  630  are connected by a bridge portion  631  made of resin injected into the runner  666 . The bridge portion  631  has an injection mark  632  corresponding to the injection passage  665  and facing outward in the axial direction (A1 direction).  FIG. 17  is a side view of the coil end portions  22  of the stator  100  as viewed in the radial direction from the outside in the radial direction (R direction). The A1 direction is toward the outside in the axial direction of the stator  100 , and the A2 direction is toward the inside in the axial direction (the stator core  1  side) of the stator  100 . This configuration prevents the injection mark  632  from projecting axially outward beyond axial upper surfaces  634  of the insulating coating portions  630 . This restrains the stator  100  from having an increased axial dimension due to the injection mark  632 . Similarly, in the case where the injection passage  665  extends in the radial direction (R direction), placing the runner  666  radially inside the radially outer inner wall surfaces of the cavities  663  restrains the stator  100  from having an increased radial dimension due to the injection mark  632 .