Abstract:
A method of molding a resin casing covering a stator of a motor may include preparing first and second molds; disposing the stator in the first mold; combining the molds; pouring a resin into the cavity; curing the resin; separating the molds; and taking the stator and resin casing from the mold. The stator may include a core, an insulator, and a coil. The core may include a core back surrounding and teeth that extend inward from the core back. The insulator may include wall portions inside the coil. The wall portions may be provided around the teeth and extend toward one side in an axial direction. One of the molds may include cylindrical surfaces contacting inner end faces of the teeth. The first mold may include wall supporting surfaces contacting or facing the inner surfaces of the wall portions. The wall supporting surfaces may be outside the cylindrical surfaces.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present invention claims priority under 35 U.S.C. §119 to Japanese Application No. 2014-023978 filed Feb. 12, 2014, the entire content of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method of molding a resin casing that partially covers at least a stator of a motor, and a motor. 
         [0004]    2. Description of the Related Art 
         [0005]    A molded motor has been known in the past. The molded motor includes a housing in which a stator is embedded and which is made of a resin. A rotor is disposed in the housing. The molded motor is excellent in terms of the waterproof property of the stator and vibration resistance and a sound insulating property when the motor is driven. 
         [0006]    For example, Japanese Unexamined Patent Application Publication No. 2001-268862 discloses a molded motor in the related art. Japanese Unexamined Patent Application Publication No. 2001-268862 discloses a method that holds a core by stepped portions formed at the center core of a mold and performs molding (Paragraph No. [0004] and FIG. 3). 
         [0007]    In FIG. 3 of Japanese Unexamined Patent Application Publication No. 2001-268862, inner end faces of teeth protrude inward from an insulator. Further, the portions, which protrude inward from the insulator, of the teeth are placed on stepped surfaces of the center core of the mold. Further, to facilitate the insertion of the stator into the mold, a small gap is formed between an outer peripheral surface, which is present below the stepped portions of the center core of the mold, and the insulator. 
         [0008]    However, the thickness of a resin formed between the center core of the mold and the insulator is small in this structure. In particular, if the insulator is inclined toward the center core of the mold due to the pressure of the resin that is in a flowing state when molding is performed, the resin between the center core of the mold and the insulator becomes thinner. The thinner resin is likely to peel from the insulator. Further, if the resin peels from the insulator, the peeled resin comes into contact with the rotor and noise or failure may be caused. 
         [0009]    At least an embodiment of the invention provides a molding method and the structure of a motor that can suppress inward inclination of wall portions of an insulator in a radial direction during the molding of a resin casing. 
       SUMMARY 
       [0010]    According to at least an embodiment of the present invention, there is provided a method of molding a resin casing that partially covers at least a stator of a motor. The method includes steps of: a) preparing first and second molds in which a cavity is formed when the first and second molds are combined with each other; b) disposing the stator in the first mold; c) combining the first and second molds so that the stator is received in the cavity; d) pouring a resin, which is in a flow state, into the cavity; e) obtaining the resin casing by curing the resin that is in a flow state; f) separating the first mold from the second mold; and g) taking the stator and the resin casing out of the first mold. The stator includes a stator core, an insulator, and a coil. The stator core includes an annular core back that surrounds a center axis and a plurality of teeth that extend inward from the core back in a radial direction. The insulator is mounted on at least the teeth. The coil is formed of a conducting wire that is wound on the insulator. The insulator includes wall portions that are positioned inside the coil in the radial direction. The wall portions are provided around the teeth and extend toward at least one side in an axial direction. Radially inner end portions of the teeth protrude inward from radially inner surfaces of the wall portions in the radial direction. At least one of the first and second molds includes cylindrical surfaces that come into contact with radially inner end faces of the teeth. The first mold includes wall supporting surfaces that come into contact with or face the radially inner surfaces of the wall portions in the radial direction. The wall supporting surfaces are positioned outside the cylindrical surfaces in the radial direction. 
         [0011]    According to at least an embodiment of the present invention, there is provided a motor comprising: a stator; and a resin casing that partially covers at least the stator. The stator includes a stator core, an insulator, and a coil. The stator core includes an annular core back that surrounds a center axis and a plurality of teeth that extend inward from the core back in a radial direction. The insulator is mounted on at least the teeth. The coil is formed of a conducting wire that is wound on the insulator. The insulator includes wall portions that are positioned inside the coil in the radial direction. The wall portions are provided around the teeth and extend toward at least one side in an axial direction. Radially inner end portions of the teeth protrude inward from radially inner surfaces of the wall portions in the radial direction. The resin casing includes wall covering portions that cover the radially inner surfaces of the wall portions. The wall covering portions include mold marks that are recessed from radially inner surfaces thereof toward the outside in the radial direction. The mold marks reach the outside of at least radially inner end faces of the teeth in the radial direction. 
         [0012]    According to at least an embodiment of the present invention, since the wall portions come into contact with the wall supporting surfaces even though the wall portions of the insulator are to collapse inward in the radial direction due to the pressure of the resin that is in a flowing state, the inward inclination of the wall portions in the radial direction is suppressed. 
         [0013]    According to at least an embodiment of the present invention, it is possible to suppress the inward inclination of the wall portions in the radial direction during the molding of the resin casing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several Figures, in which: 
           [0015]      FIG. 1  is a partial sectional view showing an aspect when a resin casing according to a first embodiment is molded. 
           [0016]      FIG. 2  is a side view of a motor according to a second embodiment. 
           [0017]      FIG. 3  is a longitudinal sectional view of the motor according to the second embodiment. 
           [0018]      FIG. 4  is a perspective view of a part of a stator according to the second embodiment that is seen from the inside in a radial direction and the lower side in an axial direction. 
           [0019]      FIG. 5  is a bottom view of a resin casing according to the second embodiment. 
           [0020]      FIG. 6  is a perspective view of the resin casing according to the second embodiment that is obliquely seen from below. 
           [0021]      FIG. 7  is a view showing a part of an inner peripheral surface of the resin casing according to the second embodiment from the inside in the radial direction. 
           [0022]      FIG. 8  is a flowchart illustrating a procedure for molding the resin casing according to the second embodiment. 
           [0023]      FIG. 9  is a sectional view showing an aspect when insert molding according to the second embodiment is performed. 
           [0024]      FIG. 10  is a bottom view of a center mold, a plurality of first auxiliary molds, and a plurality of second auxiliary molds according to the second embodiment. 
           [0025]      FIG. 11  is a sectional view showing an aspect when insert molding according to the second embodiment is performed. 
           [0026]      FIG. 12  is a sectional view showing an aspect when insert molding according to the second embodiment is performed. 
           [0027]      FIG. 13  is a sectional view showing an aspect when insert molding according to the second embodiment is performed. 
           [0028]      FIG. 14  is a partial sectional view of a first mold, a stator, and a resin casing according to a modification when molding is performed. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0029]    Exemplary embodiments of the invention will be described below with reference to the drawings. Meanwhile, in this specification, a direction parallel to a center axis of a motor is referred to as an “axial direction”, a direction orthogonal to the center axis of the motor is referred to as a “radial direction”, and a direction along a circular arc having a center on the center axis of the motor is referred to as a “circumferential direction”. 
       1. First Embodiment 
       [0030]      FIG. 1  is a partial sectional view showing an aspect when a resin casing  23 A according to a first embodiment is molded. As shown in  FIG. 1 , the motor includes a stator  21 A and a resin casing  23 A that partially covers at least the stator  21 A. 
         [0031]    The stator  21 A includes a stator core  211 A, an insulator  212 A, and coils  213 A. The stator core  211 A includes an annular core back  41 A that surrounds a center axis  9 A and a plurality of teeth  42 A. Each of the plurality of teeth  42 A extends inward from the core back  41 A in the radial direction. The insulator  212 A is mounted on at least the plurality of teeth  42 A of the stator core  211 A. The coils  213 A are formed of conducting wires that are wound on the insulator  212 A. 
         [0032]    As shown in  FIG. 1 , the insulator  212 A includes wall portions  52 A. The wall portions  52 A are positioned inside the coils  213 A in the radial direction. Further, the wall portions  52 A are provided around the teeth  42 A and extend toward one side in the axial direction and the other side in the axial direction. Radially inner end portions of the teeth  42 A protrude inward from radially inner surfaces of the wall portions  52 A in the radial direction. 
         [0033]    When the resin casing  23 A is to be molded, first and second molds  81 A and  82 A for injection molding are prepared first. Further, the stator  21 A is disposed in the first mold  81 A. After that, the first and second molds  81 A and  82 A are combined with each other. When the first and second molds  81 A and  82 A are combined with each other, a cavity  83 A is formed in the molds. The stator  21 A is received in the cavity  83 A. 
         [0034]    Next, a resin, which is in a flowing state, is poured into the cavity  83 A. Further, after the resin, which is in a flowing state, spreads into the cavity  83 A, the resin is cured by heating and cooling. Accordingly, the resin casing  23 A is obtained. After that, the first and second molds  81 A and  82 A are separated from each other. Then, the stator  21 A and the resin casing  23 A are taken out of the first mold  81 A. 
         [0035]    In this embodiment, the first mold  81 A and the second mold  82 A includes cylindrical surfaces  91 A as shown in  FIG. 1 . The radially inner end faces of the teeth  42 A come into contact with the cylindrical surfaces  91 A. However, gaps, which are small enough that the resin cannot flow into the gaps, may be formed between the radially inner end faces of the teeth  42 A and the cylindrical surfaces  91 A. Further, the first mold  81 A includes a wall supporting surface  951 A on one side of the cylindrical surface  91 A in the axial direction. Furthermore, the second mold  82 A includes a wall supporting surface  952 A on the other side of the cylindrical surface  91 A in the axial direction. These wall supporting surfaces  951 A and  952 A are positioned outside the cylindrical surfaces  91 A in the radial direction. When the stator  21 A is disposed in the cavity  83 A, the radially inner surfaces of the wall portions  52 A come into contact with or face the wall supporting surfaces  951 A and  952 A in the radial direction. 
         [0036]    The resin casing  23 A, which has been molded, includes wall covering portions  64 A that cover the radially inner surfaces of the wall portions  52 A. A mold mark  63 A, which is recessed from the radially inner surface of the wall covering portion  64 A toward the outside in the radial direction, remains on the wall covering portion  64 A. The mold mark  63 A is a mark of the above-mentioned wall supporting surface  951 A. Accordingly, the mold mark  63 A reaches the outside of at least the radially inner end face of the tooth  42 A in the radial direction. 
         [0037]    In the step of pouring the resin, which is in a flowing state, into the cavity  83 A, pressure, which is caused by the flow of the resin, is applied to the wall portions  52 A of the insulator  212 A. However, since the wall portions  52 A come into contact with the wall supporting surfaces  951 A even though the wall portions  52 A are to collapse inward in the radial direction due to the pressure, the inward inclination of the wall portions  52 A in the radial direction is limited. For this reason, excessive reduction in the thickness of the wall covering portion  64 A is prevented. Accordingly, it is possible to suppress the occurrence of the peeling of the resin from the wall covering portions  64 A after molding. 
       2. Second Embodiment 
     2-1. Entire Structure of Motor 
       [0038]    Subsequently, a second embodiment of the invention will be described. While an axial direction is defined as a vertical direction and the side corresponding to a top plate portion  232  of a resin casing  23  relative to a rotor  32  is defined as an upper side, the shape and positional relationship of each portion will be described below. Meanwhile, “a lower side in the axial direction” in the following description corresponds to “one side in the axial direction.” However, there is no intention to limit the direction at the time of manufacture and use of a motor according to at least an embodiment of the present invention by this definition of the vertical direction. 
         [0039]      FIG. 2  is a side view of a motor  1  according to the second embodiment.  FIG. 3  is a longitudinal sectional view of the motor  1 . The motor  1  of this embodiment is used in home appliances such as an air conditioner. However, the motor may be used for a purpose other than in home appliances. For example, the motor may be mounted in transport machines, such as automobiles and trains, OA equipment, medical equipment, tools, large-sized industrial facilities, and the like to generate various driving forces. 
         [0040]    As shown in  FIGS. 2 and 3 , the motor  1  includes a stationary unit  2  and a rotary unit  3 . The stationary unit  2  is fixed to a frame of a home appliance. The rotary unit  3  is supported so as to be rotatable relative to the stationary unit  2 . 
         [0041]    The stationary unit  2  of this embodiment includes a stator  21 , a circuit board  22 , a resin casing  23 , a lower bearing  24 , and an upper bearing  25 . 
         [0042]    The stator  21  is an armature that generates a magnetic flux according to driving current. The stator  21  includes a stator core  211 , an insulator  212 , and a plurality of coils  213 . The stator core  211  is formed of a laminated steel plate in which electromagnetic steel plates are laminated in the axial direction. The stator core  211  includes an annular core back  41  and a plurality of teeth  42 . The core back  41  surrounds a center axis  9  and is disposed substantially coaxially with the center axis  9 . 
         [0043]    The stator core  211  of this embodiment is so-called split cores. That is, the core back  41  of the stator core  211  includes a plurality of core pieces that are arranged in the circumferential direction. The plurality of teeth extend inward from the core pieces in the radial direction, respectively. Further, the plurality of teeth  42  are arranged at substantially regular intervals in the circumferential direction. However, a single annular stator core may be used instead of the split cores. 
         [0044]    The insulator  212  is mounted on the stator core  211 . A resin, which is an insulating material, is used as the material of the insulator  212 . The insulator  212  includes teeth insulating portions  51  that cover at least both axial end faces and both circumferential faces of the respective teeth  42 . The coils  213  are formed of conducting wires that are wound on the teeth insulating portions  51 . 
         [0045]      FIG. 4  is a perspective view of a part of the stator  21  that is seen from the inside in the radial direction and the lower side in an axial direction. The resin casing  23  is not shown in  FIG. 4 . As shown in  FIGS. 3  and  4 , the insulator  212  includes wall portions  52  that are positioned inside the coils  213  in the radial direction. The wall portions  52  extend from radially inner end portions of the teeth insulating portions  51  toward the upper side and the lower side in the axial direction. The wall portions  52  suppress the collapse of the coils  213 , and prevent the conducting wires, which form the coils  213 , from protruding inward in the radial direction. 
         [0046]    Further, as shown in  FIGS. 3 and 4 , radially inner end portions of the teeth  42  protrude inward from radially inner surfaces of the wall portions  52  in the radial direction. Accordingly, a part of radially inner portions of lower surfaces of the teeth  42  in the axial direction are positioned inside the radially inner surfaces of the wall portions  52  in the radial direction. 
         [0047]    The circuit board  22  is positioned above the stator  21  in the axial direction, and is disposed substantially perpendicular to the center axis  9 . The circuit board  22  is fixed to upper end portions of the wall portions  52  of the insulator  212  by, for example, welding. An electrical circuit, which supplies driving current to the coils  213 , is mounted on the circuit board  22 . End portions of the conducting wires, which form the coils  213 , are electrically connected to the electrical circuit mounted on the circuit board  22 . Current, which is supplied from an external power source, flows to the coils  213  through the circuit board  22 . 
         [0048]    The resin casing  23  is a member that holds the stator  21  and the circuit board  22  and is made of a resin. The resin casing  23  is obtained by pouring a resin into a cavity of a mold in which the stator  21  and the circuit board  22  are received. That is, the resin casing  23  is a resin molded article that uses the stator  21  and the circuit board  22  as insert components. Accordingly, the stator  21  and the circuit board  22  are at least partially covered with the resin casing  23 . 
         [0049]    The resin casing  23  of this embodiment includes a cylindrical portion  231  and a top plate portion  232 . The cylindrical portion  231  extends in the axial direction so as to have a substantially cylindrical shape. At least the core back  41  of the stator  21  is covered with a resin that forms the cylindrical portion  231 . Further, a rotor  32  to be described below is disposed at a radially inner portion of the cylindrical portion  231 . The top plate portion  232  is provided above the stator core  211  and the rotor  32  in the axial direction, and extends inward from the cylindrical portion  231  in the radial direction. A circular hole  233  into which a shaft  31  to be described below is inserted is formed at the center of the top plate portion  232 . 
         [0050]    The lower bearing  24  is provided below the rotor  32  in the axial direction and supports the shaft  31  so as to allow the shaft  31  to be rotatable. The upper bearing  25  is provided above the rotor  32  in the axial direction and supports the shaft  31  so as to allow the shaft  31  to be rotatable. A ball bearing, which rotates an inner race through spherical bodies, is used as each of the lower and upper bearings  24  and  25  of this embodiment. An outer race of the lower bearing  24  is fixed to the cylindrical portion  231  of the resin casing  23  through a lower cover member  241  made of metal. An outer race of the upper bearing  25  is fixed to the top plate portion  232  of the resin casing  23  through an upper cover member  251  made of metal. However, other types of bearings, such as a sliding bearing and a fluid bearing, may be used instead of the ball bearing. 
         [0051]    The rotary unit  3  of this embodiment includes a shaft  31  and a rotor  32 . 
         [0052]    The shaft  31  is a columnar member that extends in the axial direction. The shaft  31  is supported by the lower and upper bearings  24  and  25  and is rotated about the center axis  9 . An upper end portion of the shaft  31  protrudes upward from an upper surface of the resin casing  23  in the axial direction. For example, a fan for an air conditioner is mounted on the upper end portion of the shaft  31 . However, the shaft  31  may be connected to a drive unit other than the fan through a power transmission mechanism such as a gear. 
         [0053]    Meanwhile, the shaft  31  of this embodiment protrudes upward from the resin casing  23  in the axial direction, but the invention is not limited thereto. The shaft  31  may protrude downward from the resin casing  23  in the axial direction and a lower end portion of the shaft  31  may be connected to a drive unit. Further, the shaft  31  may protrude upward and downward from the resin casing  23  in the axial direction, and both the upper and lower end portions of the shaft  31  may be connected to a drive unit. 
         [0054]    The rotor  32  is fixed to the shaft  31 , and is rotated together with the shaft  31 . The rotor  32  includes a rotor core  321  and a plurality of magnets  322 . The rotor core  321  is formed of a laminated steel plate in which electromagnetic steel plates are laminated in the axial direction. The plurality of magnets  322  are disposed on the outer peripheral surface of the rotor core  321 . Radially outer surfaces of the respective magnets  322  form magnetic pole faces that face radially inner end faces of the teeth  42  in the radial direction. The plurality of magnets  322  are arranged at regular intervals in the circumferential direction so that magnetic pole faces corresponding to an N pole and magnetic pole faces corresponding to an S pole are alternately arranged. 
         [0055]    Meanwhile, a single annular magnet may be used instead of the plurality of magnets  322 . When an annular magnet is used, N poles and S poles have only to be alternately magnetized on the outer peripheral surface of the magnet. Further, the magnet may be embedded in the rotor core. Furthermore, the magnet may be molded from a resin with which magnetic material powder is mixed, and may be connected to the shaft  31 . 
         [0056]    When the motor  1  is driven, driving current is supplied to the coils  213  through the circuit board  22 . In that case, a magnetic flux is generated in the plurality of teeth  42  of the stator core  211 . Further, torque in the circumferential direction is generated by the action of the magnetic flux that is generated between the teeth  42  and the magnets  322 . As a result, the rotary unit  3  is rotated about the center axis  9 . 
       2-2. Regarding the Shape of the Resin Casing Near the Wall Portions 
       [0057]    Subsequently, the shape of the resin casing  23  near the wall portions  52  will be described in more detail.  FIG. 5  is a bottom view of the resin casing  23 .  FIG. 6  is a perspective view of the resin casing  23  that is obliquely seen from below.  FIG. 7  is a view showing a part of an inner peripheral surface of the resin casing  23  from the inside in the radial direction. Meanwhile, the section of the resin casing  23  in  FIG. 3  corresponds to the section taken along line A-A of  FIG. 5 . 
         [0058]    As shown in  FIGS. 3 and 5  to  7 , the resin casing  23  includes an inner resin portion  60  and an outer resin portion  70 . The inner resin portion  60  means an annular portion of the resin casing  23  that is positioned inside the wall portions  52  in the radial direction. The outer resin portion  70  means the entire portion of the resin casing  23  that is positioned outside the wall portions  52  in the radial direction. The inner and outer resin portions  60  and  70  are connected to each other. Accordingly, since the strength of the inner and outer resin portions  60  and  70  is increased overall, peeling of the inner resin portion  60  is suppressed. 
         [0059]    The inner resin portion  60  includes a plurality of protruding portions  61  and a plurality of recessed portions  62  adjacent to the respective protruding portions  61  below the teeth  42  in the axial direction. Radially inner surfaces of the recessed portions  62  are positioned outside radially inner surfaces of the protruding portions  61  in the radial direction. In this embodiment, the protruding portions  61  and the recessed portions  62  are alternately arranged in the circumferential direction. Further, the plurality of protruding portions  61  and the plurality of recessed portions  62  are disposed at substantially regular angular intervals in the circumferential direction, respectively. 
         [0060]    The number of the teeth  42 , the number of the protruding portions  61 , and the number of the recessed portions  62  are equal to each other (each of which is twelve in this embodiment). The plurality of protruding portions  61  and the wall portions  52  of the insulator  212  correspond to each other one to one. At least a part of each protruding portion  61  overlaps with the wall portion  52  in the radial direction. However, as shown in  FIG. 7 , a circumferential width w 1  of the protruding portion  61  is smaller than the maximum circumferential width w 2  of the wall portion  52 . In this embodiment, the position of the middle of each wall portion  52  in the circumferential direction corresponds to the position of the middle of each protruding portion  61  in the circumferential direction. The protruding portions  61  and a part of the recessed portions  62 , which are positioned on both sides of the protruding portions  61  in the circumferential direction, form wall covering portions that cover the radially inner surfaces of the wall portions  52 . 
         [0061]    As described above, in this embodiment, the protruding portion  61  is disposed inside each wall portion in the radial direction. Accordingly, the radial thickness of the inner resin portion  60  inside the wall portion  52  in the radial direction is increased. As a result, the peeling of a resin, which is caused by degradation over time or the like, is suppressed inside the wall portion  52  in the radial direction. 
         [0062]    In terms of the suppression of the peeling of a resin, it is preferable that the radial thickness of the protruding portion  61  be large. However, if the protruding portions  61  protrude inward from the radially inner end faces of the teeth  42  in the radial direction, there is a concern that the protruding portions  61  come into contact with the rotor  32 . In this embodiment, as shown in a right enlarged view in  FIG. 3 , the radial positions of the radially inner end faces of the teeth  42  substantially correspond to the radial positions of the radially inner surfaces of the upper end portions of the protruding portions  61  coming into contact with the teeth  42 . That is, the radially inner end faces of the teeth  42  are smoothly connected to the radially inner end faces of the protruding portions  61 . Accordingly, while the protruding portions  61  are thick in the radial direction, the contact between the protruding portions  61  and the rotor  32  is prevented. 
         [0063]    Further, mold marks  63 , which are recessed from the radially inner surfaces of the protruding portions  61  toward the outside in the radial direction, are formed in the middle of the protruding portions  61  in the circumferential direction. The mold marks  63  are formed during a step of molding the resin casing  23  to be described below by support protrusions  95  of a first mold  81 . Accordingly, the mold marks  63  are evidence that the inward inclination of the wall portions  52  in the radial direction is limited by the support protrusions  95  when the resin casing  23  is molded. The mold mark  63  of this embodiment reaches the outside of a radially outer end edge of an exposed surface  421 , which will be described below, of the tooth  42  in the radial direction. However, the mold mark  63  has only to reach the outside of at least the radially inner end face of the tooth  42  in the radial direction. 
         [0064]    The plurality of recessed portions  62  are disposed in a portion of the circumference extending over the adjacent teeth  42 . That is, as shown in  FIG. 7 , a circumferential width w 3  of each recessed portion  62  is larger than a circumferential width w 4  of a gap between the adjacent teeth  42 . Further, as shown in  FIGS. 3 and 5  to  7 , a lower end face of the tooth  42  in the axial direction is positioned inside the wall portion  52  in the radial direction and includes exposed surfaces  421  exposed from the inner resin portion  60 . The exposed surface  421  is exposed in a space that is formed between the protruding portions  61  adjacent to each other in the circumferential direction and is present inside the recessed portion  62  in the radial direction. When the injection molding of the resin casing  23  to be described below is performed, stepped surfaces  92  of the first mold  81  come into contact with the exposed surfaces  421  of the teeth  42 . Accordingly, the position of the stator  21  relative to the first mold  81  in the axial direction is determined. 
         [0065]    Furthermore, the resin casing  23  includes slot-resin portions  71  and a lower end face-resin portion  72  in addition to the above-mentioned inner and outer resin portions  60  and  70 . The slot-resin portion  71  means a portion of the resin casing  23  that is interposed between the wall portions  52  adjacent to each other in the circumferential direction. The lower end face-resin portion  72  means an annular portion of the resin casing  23  that is positioned below the wall portions  52  in the axial direction. The inner and outer resin portions  60  and  70  are connected to each other through the slot-resin portions  71  and the lower end face-resin portion  72 . 
         [0066]    In particular, in this embodiment, the slot-resin portions  71  are positioned outside the plurality of recessed portions  62  in the radial direction. Accordingly, a part of the recessed portions  62 , a part of the slot-resin portions  71 , and a part of the outer resin portion  70  are connected to each other in the radial direction. Therefore, the isolation of the recessed portion  62  is reduced, so that the peeling of a resin from the recessed portion  62  is further suppressed. 
         [0067]    Further, in this embodiment, a part of lower portions of the plurality of protruding portions  61  and the plurality of recessed portions  62  in the axial direction, the lower end face-resin portion  72 , and a part of the lower portion of the outer resin portion  70  in the axial direction are connected to each other in the radial direction. Accordingly, the isolation of the protruding portion  61  and the recessed portion  62  is further reduced, so that the peeling of a resin from the protruding portion  61  and the recessed portion  62  is further suppressed. 
         [0068]    Furthermore, the wall portion  52  of this embodiment includes a converging portion  521  that is provided below the tooth  42  in the axial direction. The converging portion  521  is a portion that is shown in  FIG. 7  by the hatching of a broken line. The converging portion  521  of this embodiment has a substantially trapezoidal shape when seen in the radial direction. The circumferential width of the converging portion  521  is gradually reduced toward the lower side in the axial direction. For this reason, the surface area of the wall portion  52  is smaller than that of a wall portion  52  of which the circumferential width is constant between the vicinity of the lower surface of the tooth  42  and the lower end portion of the wall portion  52 . Further, the area of a portion of the wall portion  52 , which protrudes from the coils  213  when seen in the radial direction, is reduced. Accordingly, the pressure of a resin, which is applied to the wall portion  52  when insert molding to be described below is performed, is reduced. Furthermore, since the converging portion  521  is formed, the amount of a resin material used to form the wall portion  52  is reduced. 
         [0069]    As shown in  FIG. 7 , in this embodiment, both end sides of the protruding portion  61  in the circumferential direction cross both end sides of the converging portion  521  in the circumferential direction when seen in the radial direction. Further, the protruding portion  61  is connected to the outer resin portion  70  through portions of the slot-resin portions  71  that are positioned on both sides of the converging portion  521  in the circumferential direction. Accordingly, the peeling of a resin from the protruding portion  61  is further suppressed. 
         [0070]    Furthermore, as shown in  FIG. 7 , in this embodiment, both end sides of the recessed portion  62  in the circumferential direction cross both end sides of the converging portion  521  in the circumferential direction when seen in the radial direction. Moreover, the recessed portion  62  is connected to the outer resin portion  70  through portions of the slot-resin portions  71  that are positioned on both sides of the converging portion  521  in the circumferential direction. Accordingly, the peeling of a resin from the recessed portion  62  is further suppressed. 
       2-3. Regarding a Method of Molding the Resin Casing 
       [0071]    Subsequently, a method of molding the resin casing  23  will be described.  FIG. 8  is a flowchart illustrating a procedure for molding the resin casing  23 .  FIGS. 9 and 11  to  13  are sectional views showing an aspect when insert molding is performed. 
         [0072]    When the resin casing  23  is to be molded, the first and second molds  81  and  82  for injection molding are prepared first (Step S 1 ). A cavity  83 , which corresponds to the shape of the resin casing  23  and is formed in the first and second molds  81  and  82  when the first and second molds  81  and  82  are combined with each other, is used. In this embodiment, the first and second molds  81  and  82  are disposed so as to face each other in the vertical direction as shown in  FIG. 9 . However, the first and second molds  81  and  82  may be disposed so as to face each other in a horizontal direction. 
         [0073]    Next, the stator  21  and the circuit board  22  are disposed in the first mold  81  (Step S 2 ). The circuit board  22  is fixed above the insulator  212  in advance. In Step S 2 , a unit, which includes the stator  21  and the circuit board  22 , is inserted into the first mold  81 . 
         [0074]    Here, the structure of the first mold  81  will be described in detail. As shown in  FIG. 9 , the first mold  81  includes a base mold  811 , a center mold  812 , a plurality of first auxiliary molds  813 , and a plurality of second auxiliary molds  814 . The base mold  811  is a bottomed substantially cylindrical mold that is opened to the upper side in the axial direction. At least a part of the axially lower end face and the outer peripheral surface of the resin casing  23  are molded using the base mold  811 . The center mold  812  is a substantially columnar mold that is disposed on the upper surface of the bottom of the base mold  811  so as to be substantially coaxial with the center axis  9 . The plurality of first auxiliary molds  813  and the plurality of second auxiliary molds  814  are molds smaller than the center mold  812  and are mounted on the center mold  812 . Meanwhile, the base mold  811  and the center mold  812  may be one continuous mold. 
         [0075]      FIG. 10  is a bottom view of the center mold  812 , the plurality of first auxiliary molds  813 , and the plurality of second auxiliary molds  814 . The sections of the center mold  812 , the plurality of first auxiliary molds  813 , and the plurality of second auxiliary molds  814  shown in  FIGS. 9 and 11  to  13  correspond to a section taken along line B-B of  FIG. 10 . As shown in  FIG. 10 , the first and second auxiliary molds  813  and  814  are fitted to grooves that are formed on the outer peripheral surface of the center mold  812 . In this embodiment, the first and second auxiliary molds  813  and  814  are alternately arranged along the outer peripheral surface of the center mold  812  in the circumferential direction. Further, the plurality of first auxiliary molds  813  and the plurality of second auxiliary molds  814  are disposed at substantially regular angular intervals in the circumferential direction, respectively. 
         [0076]    When the center mold  812 , the plurality of first auxiliary molds  813 , and the plurality of second auxiliary molds  814  are combined with each other, cylindrical surfaces  91 , a plurality of stepped surfaces  92 , a plurality of first opposite surfaces  93 , a plurality of second opposite surfaces  94 , and support protrusions  95  are formed on the outer peripheral surface of a mold group of these molds. 
         [0077]    The cylindrical surfaces  91  are substantially cylindrical surfaces that face the radially inner end faces of the teeth  42  after the completion of Step S 2 . In Step S 2 , the radially inner end faces of the plurality of teeth  42  come into contact with the cylindrical surfaces  91 . Accordingly, in the first mold  81 , the stator  21  is positioned substantially coaxially with the center axis  9 . In this embodiment, the cylindrical surfaces  91 , which are continuous in the circumferential direction, are formed by the center mold  812 , the plurality of first auxiliary molds  813 , and the plurality of second auxiliary molds  814 . 
         [0078]    The plurality of stepped surfaces  92  are surfaces that slightly protrude from the lower end portions of the cylindrical surfaces  91  toward the outside in the radial direction. The plurality of stepped surfaces  92  are disposed at substantially regular angular intervals in the circumferential direction. In Step S 2 , an axially lower end face of a portion, which protrudes inward from the wall portion  52  in the radial direction, of each of the teeth  42  comes into contact with each of the plurality of stepped surfaces  92 . Accordingly, the stator  21  is positioned relative to the first mold  81  in the axial direction. 
         [0079]    Particularly, in this embodiment, the plurality of stepped surfaces  92  are equally disposed around the center axis  9 . For this reason, the inclination of the stator  21  is suppressed as compared to a case in which the plurality of stepped surfaces  92  are not equally disposed around the center axis  9 . Accordingly, it is possible to further suppress excessive reduction in the thickness of a part of the inner resin portion  60  after molding. 
         [0080]    The plurality of first opposite surfaces  93  extend downward from the radially outer end edges of the stepped surfaces  92  in the axial direction. Accordingly, the first opposite surfaces  93  are positioned outside the cylindrical surfaces  91  in the radial direction. The plurality of first opposite surfaces  93  are disposed at substantially regular angular intervals in the circumferential direction. In Step S 2 , the radially inner surfaces of the wall portions  52  and the first opposite surfaces  93  partially face each other in the radial direction. After the completion of Step S 2 , the first opposite surfaces  93  are disposed in a portion of the circumference extending over the adjacent teeth  42 . That is, the circumferential width of each of the first opposite surfaces  93  is larger than the circumferential width of the gap between the adjacent teeth  42 . 
         [0081]    The plurality of second opposite surfaces  94  are disposed adjacent to both sides of the first opposite surfaces  93  in the circumferential direction. In this embodiment, the first and second opposite surfaces  93  and  94  are alternately arranged in the circumferential direction. The respective second opposite surfaces  94  are positioned inside the first opposite surfaces  93  in the radial direction. In this embodiment, the cylindrical surfaces  91  and the second opposite surfaces  94  are disposed at the same positions in the radial direction. After the completion of Step S 2 , the radially inner surfaces of the wall portions  52  and the second opposite surfaces  94  partially overlap with each other in the radial direction. However, the circumferential width of the second opposite surface  94  is smaller than the maximum circumferential width of the wall portion  52 . 
         [0082]    The support protrusions  95  protrude outward from the second opposite surface  94  in the radial direction. The support protrusion  95  includes a wall supporting surface  951  at an outer portion thereof in the radial direction. The wall supporting surface  951  is positioned outside the cylindrical surface  91  in the radial direction. In Step S 2 , the radially inner surfaces of the wall portions  52  and the wall supporting surfaces  951  come into contact with each other or face each other in the radial direction. 
         [0083]    In this embodiment, the wall supporting surfaces  951  are inclined in a direction away from the center axis toward the lower side in the axial direction as shown in a right enlarged view in  FIG. 9 . In this case, when the stator  21  is inserted into the first mold  81 , the wall supporting surfaces  951  do not easily cause insertion resistance. Further, when lower end portions of some wall portions  52  are moved down along the wall supporting surfaces  951 , the wall supporting surfaces  951  and the wall portions  52  are positioned coaxially. That is, work for inserting the stator  21  into the first mold  81  becomes easy. Furthermore, since the wall supporting surfaces  951  are inclined, releasing work in Step S 7  to be described below also becomes easy. 
         [0084]    Particularly, inclined surfaces  522  are also formed on the radially inner surfaces of the wall portions  52  in this embodiment. The inclined surfaces  522  of the wall portions  52  are inclined in a direction away from the center axis  9  toward the lower side in the axial direction. In Step S 2 , the wall supporting surfaces  951  of the support protrusions  95  and the inclined surfaces  522  of the wall portions  52  come into contact with each other or face each other. Since the inclined surfaces  522  are also formed on the wall portions  52  as described above, work for inserting the stator  21  in Step S 2  and releasing work in Step S 7  become easier. 
         [0085]    In this embodiment, the stepped surfaces  92  and the first opposite surfaces  93  do not belong to the center mold  812  and belong to the first auxiliary mold  813  which is smaller than the center mold  812 . For this reason, each of the stepped surfaces  92  and each of the first opposite surfaces  93  are accurately formed as compared to a case in which the stepped surfaces  92  and the first opposite surfaces  93  are formed on the center mold  812  itself. Further, in this embodiment, the support protrusions  95  including the wall supporting surfaces  951  belong to the second auxiliary mold  814 . For this reason, each of the support protrusions  95  is accurately formed as compared to a case in which the support protrusions  95  are formed on the center mold  812  itself. Accordingly, portions, which are molded by these portions, are more accurately molded. 
         [0086]    After the stator  21  and the circuit board  22  are completely disposed in the first mold  81 , the first and second molds  81  and  82  are combined with each other (Step S 3 ). That is, the second mold  82  approaches the first mold  81  from the upper side of the first mold  81  in the axial direction, and the upper portion of the first mold  81  is closed with the second mold  82 . Accordingly, the cavity  83  is formed between the first and second molds  81  and  82  and the stator  21  and the circuit board  22  are received in the cavity  83  as shown in  FIG. 9 . 
         [0087]    In this case, as shown in the right enlarged view in  FIG. 9 , the axially lower end face of the tooth  42  is spaced apart from the axially upper end portion of the support protrusion  95  in the axial direction. That is, the support protrusion  95  does not come into contact with the tooth  42 . Accordingly, an axially lower end face of a portion, which protrudes inward from the wall portion  52  in the radial direction, of the tooth  42  comes into contact with only the stepped surface  92 . For this reason, the positional deviation of the stator  21 , which is caused by contact with the support protrusion  95 , does not occur. 
         [0088]    Subsequently, a resin  230 , which is in a flowing state, is poured into the cavity  83  (Step S 4 ). Here, as shown in  FIG. 11 , the resin  230 , which is in a flowing state, is poured into the cavity  83  from a gate  84  that is formed near a contact surface between the first and second molds  81  and  82 . The poured resin  230  spreads into the entire cavity  83 . At this time, radially inward pressure is applied to the wall portion  52  by the force of the flow of the resin  230 . However, when a portion of the wall portion  52 , which is present below the tooth  42  in the axial direction, is to collapse inward in the radial direction, the inclined surface  522  of the wall portion  52  comes into contact with the wall supporting surface  951  of the first mold  81 . Accordingly, the inward inclination of the wall portion  52  in the radial direction is suppressed. 
         [0089]    A portion, which is displaced most when receiving pressure from the resin  230 , of the wall portion  52  below the tooth  42  in the axial direction is an axially lower end edge of the converging portion  521 . In this embodiment, at least the axially lower end edge of the converging portion  521  overlaps with the wall supporting surface  951  in the radial direction after the completion of the above-mentioned Step S 2 . Accordingly, the inward displacement of the end edge in the radial direction is suppressed by the contact between the wall supporting surface  951  and the wall converging portion  521 . Accordingly, the inward inclination of the wall portion  52  in the radial direction is further suppressed. 
         [0090]    Further, in this embodiment, the support protrusion  95  protrudes so as to have a substantially rectangular shape in top view or bottom view. For this reason, a contact portion between the wall supporting surface  951  and the inclined surface  522  of the wall portion  52  extends in the circumferential direction. That is, the wall supporting surface  951  and the inclined surface  522  come into surface contact with each other. Accordingly, the contact area between the wall supporting surface  951  and the inclined surface  522  is increased. Therefore, the inward inclination of the wall portion  52  in the radial direction is further suppressed. 
         [0091]    When the resin  230 , which is in a flowing state, spreads into the cavity  83  as shown in  FIG. 12 , the resin  230  present in the cavity  83  is subsequently cured (Step S 5 ). For example, when a thermosetting resin is used, the resin present in the cavity  83  is cured by being heated. Further, when a thermoplastic resin is used, the resin present in the cavity  83  is cured by being cooled. The resin  230  present in the cavity  83  forms the resin casing  23  by being cured. 
         [0092]    A portion of the axially lower end face of the tooth  42 , which comes into contact with the stepped surface  92  of the first mold  81 , forms the exposed surface  421  after the resin  230  is cured. Further, the first opposite surfaces  93 , the second opposite surfaces  94 , and the support protrusions  95  of the first mold  81  mold the recessed portions  62 , the protruding portions  61 , and the mold marks  63  of the resin casing  23 , respectively. 
         [0093]    As described above, in the molding method of this embodiment, the wall supporting surface  951  of the first mold  81  suppresses the inward inclination of the wall portion  52  in the radial direction. When the inward inclination of the wall portion  52  in the radial direction is suppressed, it is possible to ensure the radial thickness of a resin inside the wall portion  52 . That is, it is possible to suppress reduction in the radial thickness of the inner resin portion  60  after molding. In particular, the radial thickness of the recessed portion  62 , which is molded between the first opposite surface  93  and the wall portion  52 , is originally smaller than the radial thickness of the protruding portion  61 , but it is possible to suppress excessive reduction in the radial thickness of the recessed portion  62 . As a result, it is possible to further suppress the peeling of a molded resin from the radially inner surface of the wall portion  52 . 
         [0094]    Further, the protruding portion  61  of which the radial thickness is larger than the radial thickness of the recessed portion  62  is molded between the wall portion  52  and the second opposite surface  94 . Accordingly, it is possible to further suppress the peeling of a molded resin from the radially inner surface of the wall portion  52 . 
         [0095]    When the resin  230  is completely cured, the first and second molds  81  and  82  are then separated (Step S 6 ). Specifically, the second mold  82  is moved up, so that the second mold  82  is separated from the first mold  81  and the upper portion of the first mold  81  is opened. After that, the resin casing  23 , which covers the stator  21  and the circuit board  22 , is taken out of the first mold  81  as shown in  FIG. 13  (Step S 7 ). 
         [0096]    Meanwhile, in Step S 6 , pins protrude downward from the second mold  82  so as to facilitate the release of the resin casing  23  from the second mold  82 . Further, in Step S 7 , pins protrude upward from the first mold  81  so as to facilitate the release of the resin casing  23  from the first mold  81 . 
       3. Modification 
       [0097]    The exemplary embodiments of the invention have been described above, but the invention is not limited thereto. 
         [0098]      FIG. 14  is a partial sectional view of a first mold  81 B, a stator  21 B, and a resin casing  23 B according to a modification when molding is performed. In the example of  FIG. 14 , a second opposite surface  94 B of the first mold  81 B is inclined in a direction away from a center axis toward the lower side in the axial direction. Accordingly, a radially inner surface of a protruding portion  61 B of the resin casing  23 B, which has been molded, is inclined in a direction away from the center axis toward the lower side in the axial direction. When the second opposite surface  94 B is formed in a tapered shape as described above, the resin casing  23 B is easily released from the first mold  81 B after the resin is cured. Meanwhile, the first opposite surface may also be formed in a tapered shape likewise. 
         [0099]    Further, in the second embodiment, both the stator and the circuit board have been covered with the resin casing. However, the circuit board may be disposed outside the resin casing. For example, the circuit board may be fixed to an upper portion of the resin casing in the axial direction after the resin casing is molded. 
         [0100]    Furthermore, the cylindrical surfaces have been formed on the first mold in the second embodiment. However, the cylindrical surfaces may be formed on the second mold, and may be formed on both the first and second molds. That is, the cylindrical surfaces, which come into contact with the radially inner end faces of the teeth, may be formed on at least one of the first and second molds. 
         [0101]    Moreover, in the second embodiment, the position of the first mold has been fixed and the second mold has been adapted to be moved relative to the first mold so that the mold is opened and closed. However, the position of the second mold may be fixed and the first mold may be adapted to be moved relative to the second mold. 
         [0102]    Further, in the second embodiment, the plurality of protruding portions, the plurality of recessed portions, and the mold marks have been formed on only a portion of the inner resin portion that is present below the teeth in the axial direction. However, the same plurality of protruding portions, the same plurality of recessed portions, and the same mold marks may also be formed on a portion of the inner resin portion that is present above the teeth in the axial direction. 
         [0103]    Furthermore, the detailed shapes of the respective member may be different from the shapes shown in the respective drawings of this specification. Moreover, the respective elements shown in the embodiments and the modification may be appropriately combined with each other so that contradiction does not occur. 
         [0104]    At least an embodiment of the present invention can be used in a method of molding a resin casing that partially covers at least a stator of a motor and the motor. 
         [0105]    While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention. 
         [0106]    The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.